Mechanically rechargeable zinc-air batteries for two- and three-wheeler electric vehicles in emerging markets | Communications Materials

Communications Materials volume 5, Article number: 244 (2024) Cite this article

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Mechanically rechargeable zinc-air batteries are considered promising for powering electric vehicles due to their high theoretical energy density, but a few practical hurdles impede their implementation. Understanding the key technical blockades that restrict their implementation will enable quick deployment of these batteries in electric vehicles. This Review analyzes the performance of various on-road electric vehicle segments powered by lithium-ion batteries and compares this with the current rechargeable zinc-air battery development. We discuss the theoretical limits and vehicle-specific blockades involved in achieving the performance of mechanically rechargeable zinc-air battery-powered electric vehicles, equivalent to those powered by lithium-ion batteries. Based on the identified blockades, we present ideas on future research direction on positive and negative electrodes, and battery operation and architecture. Finally, we discuss the conditions under which these batteries can be implemented in various electric vehicle segments.

Electric vehicles (EVs) are gaining importance over internal combustion engine (ICE) vehicles to curb carbon emissions caused by the transportation sector. Globally, the share of electric light-duty vehicle sales increased from 9 % in 2021 to 14 % in 2022, and an estimated 18 % in 2023, with China leading the market1. The penetration of EVs in emerging markets like China and India is led by 2- and 3-wheelers, predominantly. In 2022–23, ~75% of the total vehicle units sold in India were 2-wheelers with a total sales of over 16 million units and over 0.77 million units of 3-wheelers2. Among the total units sold, the share of EVs is increasing, with 2-wheelers leading the numbers. In India, electric 2-wheeler share is 5 % of total 2-wheeler sales with 800000 units in 2023. In the 3-wheeler segment, the corresponding number is ~51 % with 400,000 units. The share in four-wheeler segments is fairly low with electric passenger vehicles accounting for 4.2 %, with 40000 units3. Also, within ICE 2-wheelers, over 70 % of the vehicles are low to medium powered with less than 125 cc engines. The same proportion can be expected to continue with electric 2-wheelers also, indicating the huge market for low to medium powered electric vehicles in emerging large markets like China and India.

Currently, almost all the EVs are powered by lithium-ion (Li-ion) batteries owing to favorable performance parameters. Li-ion batteries achieved high energy density of 800 Wh l−14, specific energy of greater than 400 Wh.kg−15, and specific power of over 500 W kg−16, combined with charge–discharge energy efficiency of above 90 %5. However, all the above parameters are not achieved in a single battery configuration yet. The high energy density and specific power of a battery, offer long range and required acceleration/speed, respectively. With the combination of fast rechargeability and high cycle life, the battery lifetime is equivalent to that of the vehicle itself. A lot of research is carried out to recycle the elements from batteries at the end of life to enable sustainability. Despite all these advantages, wide penetration of EVs is challenged for two key reasons. First, the scarce availability of essential raw materials like lithium, and cobalt7. For the cost of electric vehicles to be competitive with ICE vehicles without any government subsidies, battery pack costs should fall below 100 $/kWh8. The material costs account for 75 % of the battery manufacturing costs. The cathode material alone, which majorly constitutes lithium and cobalt, accounts for 50 % of the material cost or 37 % of battery manufacturing cost9. This indicates that the insufficient supply of these elements can have a significant effect on battery costs. Various cost estimation calculations were conducted by considering the combination of multiple factors like demand for energy storage, scale of production, innovations in material science, and material costs10,11,12,13,14,15. According to these estimations, the costs can fall anywhere in between 100 and 200 $/kWh by the year 2030 and the accuracy of the estimates depends on the assumptions made, factors considered and calculation model used. Though there is a significant drop in Li-ion battery prices in the past decade16, the price increased to 151 $/kWh in 202217, which is primarily due to lithium supply chain. Hence, the drop in prices to below 100 $/kWh by 2030 may be constrained due to supply chain issues and inadequate battery recycling technologies/facilities.

Secondly, thermal hazard posed by Li-ion batteries is a matter of concern, specifically in countries where the ambient temperature is higher. These batteries can catch fire due to mechanical abuses like crash, electrical abuses like fast charging-discharging or over charging, and thermal abuse like operating batteries at high ambient temperature18,19,20,21,22,23.

The EVs are operated in various conditions like extreme cold below −10 °C to extreme hot conditions of above 50 °C. Li-ion battery can achieve high specific energy of ~300 Wh kg−1, but the capacity and power can reduce significantly at low temperatures24,25,26,27,28. On the other hand, the combination of high temperature, fast charging and discharging, over charging and discharging can lead to thermal runaway. To overcome the challenges of raw material scarcity, poor low-temperature performance, and thermal runaway, various solutions are proposed. One such example is a combination of Li-ion and Na-ion batteries. Na-ion batteries have a comparatively low specific energy of ~150 Wh.kg−1, but delivers almost constant capacity and power in the temperature range of −20 °C to 80 °C29,30,31,32,33,34. Hence, a battery pack with combination of Li-ion and Na-ion battery can be operated safely in wide temperature range with sufficient specific energy, power, and recharging time. Also, sodium is available abundantly offsetting the scarcity of lithium35. Similarly, various EV segments are operated in different environmental conditions and have different combinations of range, speed, recharging time and cost requirements.

For example, last mile transport by 2, 3-wheelers or public buses in India typically operates around 8 to 15 h a day, traveling around 200–300 kms, and they should be extremely safe under drastic climatic conditions36,37. As the range required is high, either the energy stored should be high or it can be a low-energy battery with ability to safely recharge in a few minutes. The speed and acceleration of these vehicles need not be too high which gives some allowance for low to medium power batteries. They should be economical for an average three-wheeler auto-rickshaw owner to afford it, as these are primary commuting modes in many town and cities in emerging economies. While many excellent initiatives to lower the price and increase the safety of state-of-the-art lithium-ion batteries are being taken, it is worthwhile looking at alternate battery technology to selectively cover the low- to medium-power vehicle market, specifically 2- and 3-wheelers for Asian countries.

In addition to Na-ion batteries, metal–air batteries are potential contenders for this race and their prospects to offer low price and ultimate safety for this segment of electric vehicles, are high. The practical energy density of zinc– or aluminum–air batteries are higher than theoretical energy density of Li-ion batteries. The power density of these batteries is lower than that of Li-ion batteries, but it is sufficient for low-power EVs. For peak/transient high-power demand or to store regenerative braking energy, these alternate batteries can be coupled to a small Li-ion battery. The cost of zinc and aluminum metals is ten times lower compared to lithium carbonate, cobalt and nickel metals38. In addition, the fabrication of metal–air batteries does not require expensive dry rooms like Li-/Na-ion batteries, due to which the metal–air battery cost can be 3-5 times less, when the production scales. Discussions by some researchers suggested that metal–air batteries have the potential to be a side-by-side technology and co-exist in the market with Li-ion technology8,39. The durability and effective operation of metal–air batteries are influenced by a complex interplay of factors within their electrochemical framework40. A primary factor contributing to reduced battery lifespan is the occurrence of dendrites or needle-like structures capable of causing internal short circuit41. The complexities extend to corrosion and additional reactions between the metal anode and electrolyte, leading to passivation resulting in the formation of obstructive insulating layers, impeding electrochemical processes, and the undesired dissolution of metal into the electrolyte42. Furthermore, the presence of impurities in the material significantly affects electrochemical performance43, while the composition of the electrolyte plays a crucial role in the stability of the anode44. Ongoing research efforts are actively directed towards enhancing battery efficiency and lifespan through various strategies45,46. These strategies include inhibiting dendrite growth47, developing corrosion-resistant materials48, minimizing passivation49, controlling zinc dissolution50, and customizing the composition of the electrolyte51.

Although the electrically rechargeable metal–air batteries show good potential for EVs, fast recharging is not tested yet and this may affect the last mile connectivity vehicles. Options of mechanical refueling of metal cassettes in metal–air batteries offer distinct advantages compared to electrically rechargeable. The system consists of two distinct units, a discharge only unit where metal is converted to metal oxide and another unit which independently converts metal oxide back to metal. This system is analogous to fuel cell and water electrolyzer, respectively, except that the fuel is metallic in the former case. The charge/discharge decoupled mechanical refueling system can enable faster charging52. In particular, mechanically rechargeable zinc–air battery (MR-ZAB) is a matured technology for EVs owing to their high specific energy, safety and low recharging time. A bus powered by this battery was demonstrated by Israel-based Electric Fuel Limited in late 1990s52,53,54,55,56,57,58,59. Vehicles based on Al–air has also been recently demonstrated by Phinergy60,61,62,63,64. Various other companies have proven the technical and economic viability of metal–air batteries for EVs65,66,67,68,69,70,71,72. These mechanically rechargeable batteries have phenomenal prospects in potentially powering low- to medium-power EVs, specifically in low power last-mile-connectivity vehicles. It is important to understand the technical capabilities offered by lithium-ion battery in this vehicle segment and eventually target these benchmark numbers in metal–air systems. A careful analysis of gaps in product-market fit is required to identify key challenges that are restricting the wide implementation of this technology.

In this perspective, we first provide a thorough analysis of Li-ion battery parameters collected from research papers, battery OEMs (Original Equipment Manufacturers) and commercial EVs, to map battery specifications with vehicle performance. To define the specification or the requirement of LIBs for a given vehicle segment, no standard benchmarking numbers are defined. This makes the next-generation battery technology development devoid of design/performance parameters for comparison. Benchmarking evolves over time, and as a first step, we made an attempt by compiling and comparing specifications of batteries in various segments to vehicle parameters. This unified information is obtained by comparing 76 EVs from 34 different manufacturers (31 two-wheeler models from 15 manufacturers, 16 three-wheeler models from 7 manufacturers, and 29 four-wheeler models from 12 manufacturers). This led us to develop a correlation between (i) energy of batteries (kWh) and vehicle range (km) and, (ii) power of batteries (kW) and speed (kmph), for a given kerb weight of the vehicle. This information can be generalized to any EVs irrespective of battery chemistry. With this benchmarking numbers, we identified the gap between research and practical (commercially achieved) power/energy numbers in the next-generation battery technologies (Na–ion, Li–air, Li–S, Al–air, and Zn–air). This information led us to believe that zinc–air batteries possess a significant gap between research and industrially achieved values, albeit phenomenal achievements have been made in the academic/research labs. Many of the challenges in zinc–air batteries have been addressed independently in various device configurations. Here, we review (i) the solutions proposed for the problems in zinc–air batteries, followed by (ii) bringing a set of these solutions together to achieve the benchmarked kW/kWh numbers. This latter provides roadmap to both academic/industry R&D towards focussing on targeted strategies to potentially employ zinc–air batteries in electric vehicles.

The cell-level theoretical specific energies of various battery chemistries were calculated. The calculation procedure and assumptions made are given below. The theoretical specific energy (Eth-sp, in Wh kg−1) of a cell is calculated using the equation:

where Ccell is the cell capacity (in Ah), Vcell is the cell voltage (in V) and Wcell is the total cell weight (in kg). Here, Ccell is fixed at 1 Ah for all battery chemistries and the weight of anode and cathode active materials required to provide 1 Ah capacity is calculated as follows:

Taking a case of Li(Ni0.6Mn0.2Co0.2)O2 | |graphite chemistry,

Where n is the number of electrons provided by one Li(Ni0.6Mn0.2Co0.2)O2 unit in case of cathode and by graphite (C6) in the case of an anode and MW is the molecular weight of the anode or cathode.

For 1 Ah, the weight of active materials required are:

To calculate the weight of the cell, the weight of all components including anode and cathode active materials, conductive carbon, binder, current collectors, and electrolyte are considered. The cell casing and terminals are not considered as they may vary based on the form factor of the cell. The composition of the anode and cathode layers is taken as 96:02:02 of active material, conductive carbon, and binder, respectively. The maximum amount of active material in the mixture provides maximum specific energy.

Hence, the total weight of the cathode layer is calculated as,

The total weight of the anode layer is

To calculate the weight of current collectors, cathode areal loading of 25 mg cm−2 on one side of current collector is considered. Typical loadings reported in literature are between 3 − 15 mg cm−2 (references provided in the excel Supporting Information) and 25 mg cm−2 is considered as the higher side of the loading. In commercial cells, material coating will be done on both sides of the current collector. Hence area of cathode current collector required for 1 Ah capacity is calculated as

Area of cathode current collector

where factor of 2 in the denominator takes into account of two-sided coating.

The area of an anode current collector will be the same as that of a cathode current collector and anode loading will be adjusted accordingly. Here, we considered 12 µm thick aluminum foil as cathode current collector and 6 µm thick copper foil as an anode current collector.

Hence, the weight of the cathode current collector is

Weight of the anode current collector is

For all lithium-ion battery chemistries, 1 M LiPF6 in EC-DEC 1:1 v/v (EC - ethylene carbonate, DEC – diethyl carbonate) is considered as an electrolyte with an electrolyte areal loading of 0.01 ml cm−2. Using molecular weights, weight of 1 ml of electrolyte is calculated to be 1.3 grams as shown in the excel Supporting Information.

Hence, the weight of electrolyte (in g) in 1 Ah cell is

Polypropylene separator of 25 µm thickness, and porosity of 0.55 is considered as separator in all the batteries. Hence the weight of separator will be

Hence, total weight of a 1 Ah Li(Ni0.6Mn0.2Co0.2)O2 | |graphite cell is

Vcell is the average discharge voltage of the cell, which is 3.9 V for Li(Ni0.6Mn0.2Co0.2)O2|| graphite chemistry. Hence the theoretical specific energy for this chemistry is,

In the case of metal–air batteries, cathode (oxygen) is assumed to come from the atmosphere and is not included in the total weight. The positive electrode contains a nickel current collector whose one side is coated with a catalyst layer containing catalyst, conducting carbon, and hydrophobic binder in the ratio of 1:3:1 and other side is coated with a PTFE hydrophobic layer. Accordingly, electrode weight is calculated as shown in the excel Supporting Information. Anode is considered to be pure metal without any current collector. All the data relevant to the calculation are provided in Section 4 of Supplementary Information.

Figure 1 illustrates the gravimetric/volumetric energy density, and specific power of battery chemistries that can power electric vehicles. Lithium-ion battery chemistries based on lithium nickel manganese cobalt oxide (NMC), lithium iron phosphate (LFP), lithium nickel cobalt aluminum oxide (NCA) and lithium titanium oxide (LTO) are currently being used in EVs. We have also considered other battery chemistries like sodium–ion, lithium–sulfur, lithium–air, aluminum–air, zinc–air, and lithium–metal that have the potential to power EVs in the future. For a given battery chemistry, its performance parameter data is collected from research articles (denoted as ‘Research’) and battery OEM data sheets (denoted as ‘Practical’). The data from research articles is the currently achieved state-of-the-art lab-scale data. The practical data is reported by battery OEM in their data sheet. The list is appended in Supplementary Information.

A Specific energy (gravimetric), (B) energy density (volumetric), and (C) specific power of various battery chemistries. Theoretical values are calculated, and the details are given in Methods section. Research and practical data are collected from research articles and battery OEMs, respectively.

Figure 1A shows theoretical, practical, and research data of specific energy of various battery chemistries. The theoretical values are calculated using the formula given in the Methods section. The theoretical calculation considers all the active and inactive materials that go into cell making, excluding cell casing. In these calculations, maximum active material loading is chosen from values reported in multiple research articles. A small number of research articles report very high material loading and are not considered in our calculations. The plot shows that for NMC, LFP, NCA, LTO, Na–ion, and Li–metal, the numbers reached close to theoretical limit in lab-scale. Practical numbers are also close to theoretical limit and have minimum scope for improvement. Lab-scale specific energy of Li–S and Li–air is still lower than theoretical limit and have scope for improvements. Al–air and Zn–air batteries are bit far from the theoretical limit and have lots of scope for improvement. The highest zinc–air specific energy values of ~400 Wh.kg−1 reported in research articles belongs to coin cell and primary pouch cell configuration73. However, configurations are not suitable for EV applications. The practical specific energy values of zinc–air are slightly above 250 Wh.kg−1 in compact batteries used for portable electronic applications73. On the other hand, the mechanically rechargeable zinc–air batteries used for EV applications have specific energies below 200 Wh.kg−1 and have significant potential to reach close to theoretical limit55,74,75. The practically achieved specific energy of Al/Zn–air batteries is already similar to theoretical value for Li-ion chemistries. Hence, these batteries hold great potential in electric vehicles. Figure 1B shows the research and practical volumetric energy densities of various battery chemistries. This data infers that the practical energy density of NMC, LFP, NCA, LTO, Na-ion, and Li-metal have almost reached the lab-scale values with a little scope for improvement. Whereas for Al–air and Zn–air batteries, the gap between the peak values of research and practical energy densities is high, indicating a potential scope for significant improvement. Research and practical specific power data are shown in Fig. 1C. For Li-ion, the pulse or short-duration discharge as high as 10 C-rate is reported for lab-scale devices indicating their high-power capabilities. In practical situation, maximum discharge rates are typically in between 1 C and 2 C, to avoid heating issues and faster capacity fading6. For Al/Zn–air batteries, the specific power is very low compared to Li-ion batteries76. Li-S batteries possess high specific energy but needed more scientific breakthroughs to achieve the lifetime required for practical applications. While metal–air batteries have shown modest specific energy and reasonable cycle life, further improvements on both the parameters are required to become suitable for EVs. More information on the comparison of Li-S and the metal–air batteries are provided in the Supplementary Information. From these gap-analysis data, it can be inferred that efforts towards alternate battery segments will yield step advancements compared to the benchmark lithium-ion systems.

Figure 2A, C, E shows the relation between the total energy (kWh) of batteries and range (km) for different 2-, 3- and 4-wheeler EVs. The general trend for all the EVs indicates the obvious increase in range with increase in energy. But a closer look reveals that range is also dependent on weight of the vehicle. In each vehicle category, the data is grouped based on their kerb weight. In two-wheeler segment with ~3 kWh batteries, the range delivered by 90–101 kg kerb weight EV (shown in red dots) is higher than the 104–130 kg kerb weight EV (shown in blue dots). This data quantitatively shows the variation of range with energy and weight of the EVs. Similar trends can be seen in three- and four-wheeler EVs. Figure 2B, D, F shows the relation between peak power and maximum speed of 2-, 3- and 4-wheeler EVs. The EV speed also increased with increase in power, but it is also dependent on the weight. The data provided in Fig. 2 are replotted in Fig. 3 to understand the energy consumed by vehicles as a function of kerb weight and segment. The energy consumed per km, ranges from 25 to 50 Wh, 40 to 100 Wh, and 75 to 300 Wh for 2-, 3- and 4-wheelers, respectively. In every segment the energy requirement is nearly linearly proportional to the kerb weight of the vehicle and as expected the energy consumed by bigger vehicle is higher. Another interesting observation is that the Wh consumed per km per unit weight is higher for 2-wheelers followed by 3- and 4-wheelers. Most of the 2-wheelers consume between 0.24 and 0.38 Wh km−1 kg−1 whereas 3-wheelers consume 0.15 to 0.19 Wh km−1 kg−1, with 4-wheelers around 0.07 to 0.13 Wh km−1 kg−1.

A, C, E Range versus total energy stored and (B, D, F) maximum speed versus peak power in (A, B) two-wheeler, (C, D) three wheeler, and (E, F) four-wheeler electric vehicles. The vehicles are categorized based on their kerb weight (numbers in legends). For each data point, corresponding vehicle OEM name and vehicle model are mentioned.

Top panel provides information on Wh consumed per km whereas the bottom panel provides Wh consumed per km for every kg of vehicle.

Assuming the vehicle has a kerb weight of 100 kg that should run for 80 km range, we would need around 1.92 to 3.04 kWh. For the same kerb weight of vehicles, from Fig. 2, we can find that the power required is around 2 to 4 kW. This leads to a requirement of 1 C discharge rate at peak for 2-wheelers. Similarly, for 3-wheelers, calculations assuming 100 km range and 500 kg kerb weight yields battery requirement of 7.5 to 9.5 kWh. The power required is around 6 to 10 kW. The power requirement in 3-W is similar to 2-W with around 1 C requirement. Taking 1600 kg kerb weight and 300 km range for 4-wheelers, the battery requirement would be between 33 and 62 kWh, with power > 100-200 kW (>2 C). This comparison between different vehicle segments, enable us to tentatively conclude that low power batteries shall fit for 2- and 3-wheelers.

A typical zinc–air battery consists of a zinc plate (negative electrode) and catalyst coated over gas diffusion layer for oxygen reduction reaction (ORR) or oxygen evolution reaction (OER) (positive electrode), separated by aqueous potassium hydroxide electrolyte. At positive electrode, oxygen from atmosphere enter into the battery through air breathing gas diffusion electrode (GDE). A triple phase boundary is formed where oxygen comes in contact with aqueous alkaline electrolyte and electrons on the surface of the catalyst, and reduces to hydroxyl ion. The relevant chemical reactions during cell discharge are shown below.

Positive electrode reaction:

Negative electrode reactions:

Overall discharge cell reaction:

The data shown in Fig. 1, shows that electrically rechargeable zinc–air batteries (ER-ZAB) have comparable or better energy densities with respect to lithium-ion systems, however the values for mechanically rechargeable zinc–air (MR-ZAB) batteries are low. Hence in the first part, the options reported for ER-ZAB literature to improve the energy density is reviewed and provide perspective on implementing these options for MR-ZAB. Similar efforts were focused on reviewing and providing recommendations on power and lifetime. These options combined with benefits like fast recharging and storing the energy as solid fuel, will enable later to be implemented in EVs. Additional information on the comparison of ER-ZAB and MR-ZAB is provided in the Supplementary Information.

The specific energy of metal–air batteries is decided only by the metal anode as oxygen required for cathodic reaction is not stored within the battery. It is directly received from the atmosphere through air-breathing positive electrode77,78,79. Theoretically, a compact metal plate will possess high energy density for a given battery dimension. Metals like Mg, Al, Fe, Li, and Zn offer specific energy of 5238, 5779, 1080, 5928, and 1218 Wh kg−1, respectively80,81. While Mg- and Al-based air batteries rival lithium in energy storage capabilities, their electrochemical performance presents a challenge. Their significantly low reduction potentials (−2.69 V vs. SHE for Mg, and −2.31 V vs. SHE for Al) make these batteries susceptible to rapid self-discharge, resulting in low coulombic efficiency80. This limitation impedes their viability as dependable energy storage solutions. However, zinc showcases notable advantages. Aside from its impressive energy density, Zn is widely abundant in the earth crust, rendering it a sustainable option than lithium79. Moreover, Zn-based batteries exhibit superior round-trip energy efficiency compared to Al- and Mg-based batteries during the charge-discharge process, especially when employing aqueous electrolytes. These favorable environmental, economic, and electrochemical characteristics collectively position zinc as the most promising contender among various metal–air batteries44,80,82.

The mechanically rechargeable metal–air batteries83, were first implemented in electric vehicles and they typically consist of stagnant electrolyte which results in technical issues like surface passivation and corrosion, resulting in very low-capacity utilization77. In ER-ZAB, various approaches like anode alloying84, introducing porous anode architectures85, adding additives to electrolyte and electrolyte flow were employed, to avoid those issues86. Porous anode architectures through 3D porous casting87, powder metallurgy88, and electrodeposition43, were developed to reduce surface passivation and increase anode current density, simultaneously. But the increase in surface area increases corrosion rate due to which net capacity utilization didn’t improve significantly89, The porous anode used in static electrolyte battery typically consists of a slurry of metal, potassium hydroxide, binder, and additives pressed on a current collector. Such anodes will have a metal density almost half to that compared to pure compact metal, thus reducing energy density. Among the various efforts being made towards increasing practical specific energy, equal attention should be given to the removal of anode discharged product from the cells as it forms. The metal anode oxidizes to metal oxide during discharge and gets dissolved/dispersed in the electrolyte. For a fixed amount of stagnant electrolyte in the cell, the electrolyte gets saturated quickly and excess metal oxide will remain as precipitate. This precipitate results in anode passivation and increasing electrolyte resistance which leads to low anode depth of discharge and low power output, respectively90. Metal–air battery with electrolyte flow system has proven to reduce the effects of anode passivation91. As shown in Table 1, electrolyte flow increased energy efficiency by avoiding passivation. Among these options reported for ER-ZAB, electrolyte flow and additives along with anode alloying may be transferred to MR-ZAB to increase the performance, while retaining high energy density.

In MR-ZAB, another important aspect of metal oxide is its complete recovery from the cell after discharge cycle. When implemented on a large scale, the operating costs of metal–air batteries can be kept low only if the metal oxide by-product from the battery is completely recovered and reduced back to metal using renewable energy sources and reused instead of depending on metal mining. Though state-of-the-art technologies are available to convert metal oxide to metal with high efficiency, the ability to recover metal oxide from the battery will decide the overall recycling efficiency. Electric Fuel Limited. implemented a separator bag mechanism to recover metal oxide from individual cells where each anode is placed in a non-woven cloth separator bag before being mechanically inserted in the cell52. After discharge, the anode is mechanically removed from the cell along with a separator bag, which contains metal oxide precipitates. The bags can be washed and reused multiple times. However, we believe that this is not a complete solution as it cannot avoid anode passivation and increased electrolyte resistance. Also, this separator bag being a poor hydroxyl ion conductor, will add more resistance in the cell. In addition, washing, checking for holes in the bag, and reinserting anode in it may become cumbersome work when implemented on a large scale. A better solution like electrolyte flow shall simultaneously avoid passivation and recover metal oxide efficiently will help increase energy efficiency and quick implementation of metal air batteries in EVs on a large scale.

To achieve electrolyte flow, extra accessories like electrolyte storage tank, pump, and pipes are required which will reduce specific energy. But this can be compensated by using compact anode plates with some alloying to avoid corrosion, instead of porous plates with low metal density. As the electrolyte flow can avoid passivation, there is no need for porous electrodes, which in turn will reduce the corrosion rate due to the reduced electrode-electrolyte interface. It is claimed that the increased surface area in porous anode will also help to increase cell current output, but a detailed analysis needs to be done to understand if anode is really the current limiting electrode when put together with a positive electrode. It is widely known that oxygen reduction reaction is very sluggish compared to metal oxidation92. So, if the positive electrode is current limiting, increasing the surface area of the negative electrode will not result in improved cell current. In such cases, a compact metal anode will help in increasing the specific energy of the battery. In addition, with electrolyte flow, there is no need to store more electrolyte within the cell, resulting in less distance between positive and negative electrodes and reduced ion diffusion resistance. Also, developing a mechanism to remove metal oxide precipitates from the electrolyte flowing out of the battery and pumping it back into the battery will allow the battery to operate with a minimal amount of electrolyte stored in the system thus reducing the overall volume of the battery. As the electrolyte is stripped off the precipitates continuously outside the battery, passivation can be completely suppressed and increase anode utilization. The precipitates can be stored outside the battery and recovered during mechanical refueling.

The maximum power of a battery primarily depends on the practical working voltage limit of the cell and the maximum C rate that can be obtained.

The practical cell potential that can be obtained is less than the theoretical potential due to kinetic overpotential or activation losses and transport resistances93. The losses can be reduced by developing (i) better catalysts to reduce reaction activation losses, and (ii) appropriate electrode fabrication techniques, membranes, efficient contacts and cell design to reduce ohmic and mass transfer resistances94,95.

In any aqueous metal–air battery, a cathodic reaction is an oxygen reduction reaction (ORR) which occurs at an ORR catalyst coated on a gas diffusion layer (GDL). GDL is a porous positive electrode containing a current collector, hydrophobic layer coating on the air side, and ORR catalyst coating on the electrolyte side. The hydrophobic layer allows atmospheric air to enter the cell but stops electrolytes from leaking through pores. Hence, the positive electrode potential is fixed, and the theoretical cell potential depends on the metal used. Generally, the potential drop at the negative electrode is due to anode activation potential which is either small as in the case of zinc or high as in the case of aluminum96. However, the potential drop at the positive electrode can vary and is dependent on the type of catalyst used. Hence, most of the research is focused on developing suitable ORR catalyst with improved reaction kinetics. For electrically recharging metal–air batteries, the oxygen evolution reaction (OER) is also important, however since it is not relevant to MR-ZAB, the OER part of the reaction is not discussed.

Theoretically, ORR occurs at 1.23 V vs. RHE, but with the Pt/C catalyst which is considered to be the best, the current onset starts at ~1 V vs RHE and 0.23 V is lost as kinetic overpotential97. Under working conditions, potential will drop further due to mass transfer, membrane and interfacial contact resistances. While a lot of research is being conducted to reduce the kinetic activation potential of ORR, ohmic resistances, like membrane resistance and catalyst-current collector interfacial resistance, should be investigated to understand the magnitude of impact created by each of these parameters.

The key parameters for EV battery selection are energy and power densities. Especially for a two-wheeler, the volume available to place the battery is less, and the number of metal–air cells in series required to provide sufficient voltage won’t fit in the available volume. In such case, instead of obtaining full voltage from battery pack, only a half or a quarter of the required voltage can be provided by the battery at high current, and a compact boost converter (DC-DC converter or high-frequency step-up transformer) will boost the voltage to required levels at the cost of current98,99. An illustrative example is given in Table 2, where a two-wheeler with peak power requirement is considered. To provide 48 V output from the battery pack alone, 48 cells need to be connected in series with each cell operating at 1 V. If a boost converter that can boost voltage by 5 times is used along with battery, the number of cells connected in series can be reduced by 5 times, but each cell should be discharged at 5 times higher C-rate. On the other hand, if research is focused only on improving cell voltage, the maximum value will be limited by theoretical cell potential. So, the reduction in a number of cells connected in series to obtain the required voltage in this case will be negligible compared to that in the case of using a boost converter, and the volume constraint cannot be overcome. Hence, while focusing on reducing potential losses, it is mandatory to focus on improving C-rate at a given potential simultaneously to achieve EV requirements.

The C-rate of a metal–air battery is primarily limited by ORR. ORR is a sluggish reaction as it is a four-electron process and the catalyst need to be highly selective to OH- formation. Also, the solubility of oxygen in aqueous KOH electrolyte is poor, limiting the oxygen availability at catalyst active sites. Multiple strategies are implemented to overcome these challenges and improve the current density at a given voltage in a diffusion-limited regime. Broadly, these strategies can be divided into two categories, (i) increasing the surface area of the catalyst and (ii) increasing triple phase boundaries and substrate surface area.

Catalyst surface area can be improved by employing 3D carbon aero gel substrate100, self-sacrificial high surface area template101, hard template102, and soft template103. Various doped porous carbon catalysts were made from MOF104, and ZIF105, based high surface area self-sacrificial templates with uniformly distributed micropores. Freeze-drying have recently attracted as a crucial method for creating porous electrodes in Zn–air batteries106. This process involves freezing the electrode material and then removing the frozen solvent through sublimation, resulting in a porous structure with interconnected channels and voids107. The significance of this approach lies in its ability to increase the electrode's surface area, which eventually improves mass transfer for efficient electrochemical reactions and enhances the deposition/dissolution of zinc in the anode. The porous structure also reduces polarization effects, leading to a more efficient and stable Zn–air battery with improved overall performance108,109. Though such catalysts have surface area, the active sites in the bulk cannot be efficiently utilized due to high mass transfer resistance in micro pores110, To overcome mass transfer limitations, hierarchical macro-meso-micro pores were created by using hard or soft templates111. The widely used hard template is silicon dioxide spheres with size in the order of 500 nm. They can give better control on the pores, but the removal process involves etching with harmful hydrofluoric acid. If this process has to be implemented on a large scale, better handling is required which can increase costs significantly112. On the other hand, control over pores is difficult with soft templates and their removal process can involve heating at high temperature or etching or both113. While the surface area of the catalyst is improved significantly using hierarchical pores engineering, the current is not increased in the same order as shown in Table 3. This mismatch can happen if all the active sites are not accessible to the reactants in the electrolyte due to diffusion and charge transport limitations which will not be included in BET surface area analysis114. Electrochemical surface area (ECSA) can provide insight into the fraction of total surface area (hence the number of active sites) accessible for electrochemical reactions. ECSA of catalyst film coated on a substrate is dependent on the catalyst surface area, pore volume, pore diameter, and diffusion path lengths of the reactants involved115,116,117, which in turn depends on the catalyst ink composition and coating procedure118. Yuanhui Cheng et al.119 synthesized a N,S-doped porous carbon catalyst with and without hierarchical pores with BET surface area, ECSA and pore volume of (1261 m2 g−1, 429 m2 g−1, 1.05 cm3 g−1) and (446 m2 g−1, 122 m2 g−1, 0.31 cm3 g−1) respectively. The increment of ECSA is contributed by meso- and macropores. The maximum diffusion-limited current at 1600 rpm is 5.2 and 4.6 mA cm−2, respectively. They found that the uniform distribution and abundance of active sites in accessible pores can increase current density. Jianing Guo et al.120 synthesized Fe-, Ni- bimetallic doped covalent organic polymer with (CCOPTDP-FeNi-SiO2) and without (CCOPTDP-FeNi) pore-forming templates. BET surface area of CCOPTDP-FeNi-SiO2 is 435.5 m2 g−1 and CCOPTDP-FeNi is not given, but ECSA is 126.3 and 46.2 m2 g−1, respectively. However, the maximum diffusion-limited current at 1600 rpm is ~3.3 and 2.8 mA cm−2, respectively. Though the ECSA increased significantly in both cases, current density increment is not proportional. Hence, a combined analysis of BET surface area, pore volume, pore diameter and ECSA of catalyst synthesized with and without pore forming templates is recommended to understand if the hierarchical pore structure helps improving C-rate sufficiently.

The operating conditions of RDE where oxygen reactant is supplied through purging are different from actual battery operating conditions where oxygen is to be obtained directly from the atmosphere. This led to the development of triple phase boundaries on gas diffusion layer. A triple phase boundary is where oxygen from the gas phase, water and solid catalyst active site come together and resulting in ORR. Oxygen solubility and diffusivity in water is very low due to which it is preferred to obtain from gas phase and triple phase boundary serves the purpose. Hence, the key to increasing C- rate of battery is to increase triple phase boundaries and decrease oxygen diffusion path lengths within the electrolyte. Triple phase boundaries are formed by adding hydrophobic material polytetrafluoroethylene (PTFE) to catalyst ink. Optimization of catalyst ink composition is necessary as high PTFE composition can lead to more active sites being away from electrolyte. In contrast, low PTFE composition will increase oxygen diffusion path length121,122.

Another way to increase triple phase boundaries is to use substrates with high specific surface area (surface-to-volume ratio) like nickel foam (~5000 m−1)123, and carbon felt (~22,000 m−1)124. The efficient utilization of complete surface area is dependent on coating techniques implemented for catalyst and hydrophobic gas diffusion layers. Conventional GDL fabrication procedure involves coating of catalyst/hydrophobic layer on substrate followed by simultaneous pressing and sintering process to achieve uniform distribution and good adhesion of coated layer on the substrate. But pressing porous substrates like nickel foam will destroy the porosity and the complete surface area may not be accessible to electrolyte. Soraya Hosseini et al.125 fabricated GDL by first applying a hydrophobic paste containing PTFE, carbon and D-glucose mixture on one side of nickel foam and pressing it at 350 °C on hot press. Then the mixture of MnO2 and carbon as catalyst layer is applied on another side and pressed at 150 °C. A current density of 100 mA cm−2 at 1 V is obtained from a tubular zinc air battery at 100 mL min−1 electrolyte flow rate. Xiaofei Gong et al.126 fabricated GDL where the catalyst layer is coated by simply loading catalyst ink -containing mixture of Fe/N-CNR (carbon nanorods) catalyst, acetylene black, activated carbon and NafionTM dispersed in isopropyl alcohol (IPA) on Ni foam and drying at 60 °C for 12 h. They obtained a current density of 100 mA cm−2 at 1 V from a primary zinc–air battery. Zhihao Wang et al.127 fabricated GDL by simply dispersing catalyst on hydrophobic carbon paper and obtained 75 mA cm−2 at 1 V from primary zinc–air battery. In most of the research papers, the GDLs are prepared only to understand the catalyst performance in zinc–air batteries and hence conventional fabrication procedure is employed. However, the battery and catalyst performance characteristics cannot be compared because of the different substrates and coating techniques used. Gyutae Nam et al.128 suggested the use of volumetric power density (W.cm−3GDL) instead of areal power density (W.cm−2GDL) to consider the variations in substrates.

They fabricated GDLs with nitrogen and sulfur co-doped porous carbon as ORR catalyst and carbon paper, carbon felt and nickel foam as substrates. For carbon paper and felt, catalyst ink is simply dropped on the substrate and dried in oven at 60 °C. For nickel foam, the catalyst paste is cast on the foam and calendared to a thickness of 700 μm. The catalyst loading is maintained constant on all substrates. The nickel foam, carbon felt and carbon paper as substrates delivered maximum volumetric power density of 5070, 3410 and 1243 mW.cm−3 of substrate respectively. Zinc–air battery discharge current with nickel foam substrate at 1 V operating potential is shown to be 4500 mA.cm−3 (324 mA.cm−2 with GDL thickness of 721 μm) which is reasonably high compared to other reported values given in Table 4. Though the actual reasons for this varied power density are not explained clearly in the paper, the following conclusion can be drawn from the results. With a given catalyst, power density can be significantly increased by using the right coating technique and high surface area substrate with good electrical conductivity and mechanical stability.

Though mechanically refuellable metal–air batteries have high theoretical energy density and have proven to be suitable for electric vehicles, they are still not implemented on a large scale due to failure of battery earlier than the expected lifetime and inefficiency in utilizing total energy stored. The lifetime of the mechanically refuellable metal–air batteries primarily depend only on the air electrode and separator. Electrolyte degradation, evaporation and dendrite growth on metal anode won’t play any role as they will be replaced frequently during mechanical refueling. The critical modes of air electrode failure reported in the literature are pore blocking on the gas diffusion layer by carbonate precipitates129, wetting of the gas diffusion layer by electrolyte130,131, flooding of electrolyte due to erosion of the gas diffusion layer132, catalyst layer erosion and degradation of catalytic active sites133,134. Another mode of battery failure occurs due to separator degradation which leads to settling of anode discharge product on air electrode135,136. Companies like Yardney Electric Corporation and Electric Fuel Limited have attributed this premature failure of mechanically rechargeable metal–air batteries to pore blocking in the gas diffusion layer137. Carbon dioxide in air reacts with highly alkaline electrolyte in battery to form carbonate precipitates, thus blocking the pores and restricting the flow of oxygen reactant into battery leading to failure138. This indicates that the battery failure can occur by the fastest mode and the remaining modes which take longer time to occur will not be identified. As it is time consuming and costly affair to monitor the battery for thousands of hours and identifying all possible failure modes, Keliang Wang et al.139 used a mathematical model of a rechargeable zinc–air battery which take all real time operating conditions into account. The simulation of 2 h of charge & discharge each with 2A.dm−2air-electrode current density, found that the discharge potential drop starts at the 7th cycle and the drop increases exponentially after 10th cycle. This is attributed to wetting of the gas diffusion layer resulting oxygen depletion at active sites. Under same operating conditions, the catalyst layer erosion led to potential drop from 17th cycle and the drop continued linearly with time. To understand the effect of carbon dioxide dissolution in electrolyte and pore blocking by carbonate precipitates, CO2 partial pressures of 1, 30 and 100 Pa were considered and battery model is simulated with current density of 2 A.dm−2air-electrode and charge/discharge for 3 h each and a voltage drop of 0.2 V is considered as cut-off voltage. To reach cut-off voltage, it took 10, and 27 cycles with CO2 partial pressures of 100, and 30 Pa respectively. With 1 Pa, cut-off voltage is not reached even after 50 cycles indicating the use of CO2 filter will help increasing the lifetime. Though these results provide insights into the chronological order of failure modes, more experimental validation is needed to understand actual battery lifetime.

Several research groups are working on various technologies to filter carbon dioxide from the air feed to increase the battery life. Out of the widely known CO2 removal methods like adsorption, absorption, membrane and cryogenic gas cleaning techniques140,141,142, adsorption has been considered to be a promising method to remove low concentrations of CO2 from air143,144. Amunátegui et al.145 tested a pilot scale electrically rechargeable metal–air flow battery where they used adsorption drying technology to remove carbon dioxide from ambient air. They achieved maximum of 2000 charge-discharge cycles (760 h) in an accelerated durability test. The failure of battery after 2000 cycles occurred due to electrolyte flooding. Though the removal of CO2 has increased lifetime of battery, the filtration equipment is too big to implement in an electric vehicle. Israel-based company, Phinergy, claimed that they developed a compact gas diffusion layer structure that can block CO2 entering into the battery and hence increased the battery life to a few thousands of hours. But the detailed technology is not available in the public domain. The CO2 adsorption on high surface area specialized materials is gaining lot of attention. Shih-Cheng et al.146 constructed a sorption-type air filter impregnated with MgO and CaO which adsorbed >95 % of the inlet CO2, at low air flow rates. As flow rate increases, CO2 adsorption efficiency fell below 88 %. The maximum surface area available in these materials for adsorption is found to be 957 m2 g−1. But the amount of CO2 adsorbed per unit mass of material is not specified, which is a critical parameter to understand the durability. Mehrdad Asgari et al147. developed sodalite-type metal-organic framework (MOF) with maximum surface area of 2050 m2 g−1. This material is shown to selectively adsorb CO2 in very less time with high efficiency. Once this material is saturated with CO2, it can be regenerated by mild heating. The compact, lightweight, cheap and durable nature of MOF, makes this filter highly suitable for CO2 filtration in electric vehicles.

Though CO2 free air feed has the potential to significantly increase the lifetime of the battery, this alone is not sufficient to achieve competitive lifetime compared to that of lithium-ion batteries. Other failure mechanisms also need to be eliminated for large scale implementation of metal–air batteries. Keliang Wang et al.139 identified that the loss of the catalyst layer is due to the synergistic effect of carbon decomposition due to high polarization and oxygen bubble formation during charging. Hence, as mentioned in previous section, the air electrode fabrication parameters should be optimized to achieve high adhesion of catalyst layer and air diffusion layer to the substrate to avoid erosion while maintaining surface area for high current density.

Performance loss of battery over time can also happen due to degradation of catalytic active sites. George et al.148 used transmission electron microscopy and in situ flow cell coupled with inductively coupled plasma optical emission spectrometer to monitor the performance of PtNiMo/C ORR catalyst in ionic liquid. They observed that the ionic liquid selectively accelerated Mo dissolution resulting in severe catalyst degradation. Zehui Yang et al.149 tested the durability of Pt-based electrocatalysts following the protocol from the Fuel Cell Conference of Japan150,151 in which carbon corrosion is accelerated. They found that the ECSA of carbon black/Pt and poly[2,2′-(2,6-pyridine)−5,5′-bibenzimidazole]-wrapped multi-walled carbon nanotubes, on which Pt nanoparticles have been deposited (MWNT/PyPBI/Pt) catalysts reduced by ~46 % and ~10 % after 10,000 cycles respectively. They coated poly(vinylphosphonic acid) (PVPA) on MWNT/PyPBI/Pt and reduced the loss of ECSA significantly as PVPA reduced carbon corrosion and Pt agglomeration. The polymer coated catalyst showed increase in ORR activity and methanol resistance leading to increased durability of the catalyst. Xue Wang et al.152 developed a Pd@Pt core−shell concave decahedra catalyst whose mass activity is reduced from 1.6 to 0.69 A mg−1Pt after 10,000 cycles after an accelerated durability test which is 2.2 times better than the pristine Pt/C catalyst. They observed that the reduction of mass activity is due to reduction in specific ECSA. Recently, nonprecious metal doped porous carbon attracted a lot of attention for their high ORR activity equivalent to that of commercial Pt/C catalyst. But their durability is not clearly understood for them to be considered for commercial applications. Dustin Banham et al.153 made a review on durability status of these catalysts, highlighted their failure modes and made future recommendations for half-cell testing methods to understand and compare the catalyst durability. Once the catalyst is proven to be sufficiently stable for acceptable duration in half cell testing under carefully designed accelerated stress tests, it can be used in an actual battery for further durability testing. Especially when the target application is to power EVs, durability tests must be conducted under the actual EV power profile. Most of the research work present the durability data of catalyst implemented in metal air battery at very low and constant current discharge rates, as shown in Table 4, which is far from the EV operating conditions. Also, dynamic in situ analysis of metal and air electrodes while discharging the battery will help in understanding the catalyst related failure mechanisms.

Mechanical refueling of metal–air battery involves replacing discharged metal anode plates with fresh metal plates, complete recovery of electrolyte and precipitates of metal discharge products if any and refilling of fresh electrolyte. The whole process should be completed safely within 15 to 20 min for four-wheelers and less than 10 min for two- and three-wheelers to be competitive. To achieve such low refueling times, battery design plays an important role. Jonathan Goldstein et al.55 developed a large-scale zinc–air battery with stagnant electrolyte and the zinc anodes can be mechanically refueled within minutes. These anodes are placed in a separator envelop before inserting in the battery to avoid anode discharge product being settled on air electrode and to collect the complete discharge product while refueling. But then the separator bags are prone to punctures due to frequent removal and can lead to battery failure. Hence, they should be thoroughly cleaned and inspected for punctures before reusing. Zequan Zhao et al.154 provided a detailed compact battery design that enables electrolyte flow and can be assembled easily without bolts. But in this design, anode plates are fixed to the cell frame using bolts. They assembled these cells into packs which is very compact, while electric connections were made using metal connectors connected to terminals using bolts155. A close inspection of the design reveals that at least three bolts per cell should be unscrewed to remove discharged anodes and the same bolts should be tightened to fix the fresh anodes. This screwing and unscrewing of the bolts can increase refueling time significantly. However, this design can be readily implemented for laboratory experiments to understand metal–air battery performance under electrolyte flow conditions.

There are additional engineering challenges that might arise during the implementation of this technology as a complete energy storage unit. The challenges include:

Recovery of zinc oxide from battery pack after discharge and the auxiliaries required to achieve it.

Maintenance/refilling of electrolyte is required due to parasitic hydrogen evolution reaction.

Arrangement of pack in the EV for easy access of anodes for replacement

Balancing the state-of-charge (SoC) of all the cells in the pack. This particularly is a challenge as the cell voltage profile is almost flat and we cannot monitor SoC with voltage. Relevant battery management system needs to be developed to monitor SoC by coulomb counting.

Zinc–air pack are extremely safe in any environmental conditions. As they use aqueous electrolyte, the fire hazard is less or zero, unlike devices with non-aqueous and flammable solvents. Hence the thermal management system can be very minimal or eliminated in zinc–air batteries.

Based on the practical zinc–air battery performance data from electric vehicles, the specific energy and specific power are found to be in the range of 140–200 Wh kg−1 and 20–60 W kg−1 respectively54,74. To understand the zinc–air battery’s fit in EV, we have done high-level calculations where the existing lithium-ion battery of a given weight replaced with zinc–air battery of same weight. The calculation procedure is provided below.

The objective of this calculation is to estimate the energy and power of the zinc–air battery, if it were to replace Li-ion battery in EVs with same weight and volume. Hence, the weight of the Li-ion battery in each EV segment is calculated based on the data given in excel Supplementary Information.

An example calculation for a 2-wheeler EV is given below.

Considering a scooter which uses 2.9 kWh NMC battery chemistry (2.6 kWh usable), the total battery weight can be around 12 kg at a pack specific energy of 240 Wh kg−1. The kerb weight of this EV is 108 kg. Hence, the weight percentage of battery compared to vehicle kerb weight is 11.1%. Similarly, this percentage is calculated for all EV segments and the weight percentage is estimated. The maximum weight percentage of battery compared to vehicle kerb weight is found to be 15% for 2-, 3-wheelers and buses. It is around 30% for cars. Hence these numbers were used to estimate total energy and power of zinc–air battery with ~200 Wh kg−1 specific energy and 50 W kg−1 specific power.

Then, for the same vehicle mentioned above, if Li-ion battery is to be replaced with zinc–air battery of same weight with specific energy and specific power of 200 Wh kg−1 and 50 W kg−1, its total energy and power will be 2.4 kWh, and 0.6 kW. Comparing these numbers with Fig. 2, the same vehicle with zinc–air battery is expected to achieve ~80 km range and ~30 kmph top speed. These calculations were made for all the vehicle’ data provided in excel Supplementary Information, and possible maximum numbers are provided in Table 5. It is to be noted that, for more realistic estimation, both weight and volume of the battery need to be taken into account as EVs have volume constraint. Also, the numbers provided in Table 5 are only indicative and can vary slightly, depending on the vehicle and battery design.

Based on the calculated battery weight, the zinc–air battery energy will be maximum of 3, 10, 350, and 100 kWh for 2, 3- wheelers, buses and cars respectively. The battery peak power will be maximum of 0.9, 3, 100 and 36 kW for 2, 3- wheelers, buses and cars respectively. By comparing these numbers with benchmark values provided in Fig. 2, zinc–air batteries will offer a range and speed of vehicles as shown in the Table 5. These data indicates that if zinc–air batteries can be made with ~200 Wh kg−1 specific energy and 30–50 W kg−1 specific power, they will be suitable for long range and low speed 2-wheelers, 3-wheelers and city buses. But they are not suitable for cars as the speed requirement is high.

For the wide adoption of EVs, new battery technologies should have a high energy density, low cost and be extremely safe. In the quest to identify the next potential battery technology, we made an attempt to critically compare potential future battery technologies that can power EVs. A comparison based on specific energy revealed that lithium-ion batteries have reached their theoretical potential and there is little scope for improvement without compromising on safety. It also revealed that there is a lot of room for improvement of metal–air batteries. But then again, there is a need to identify research and implementation gaps that are restricting their wide implementation in EVs. Till date, to the best of authors’ knowledge, there is no benchmark on EV battery requirements. An in-depth analysis on comparison of battery parameters to the vehicle specifications was done, on various vehicle segments. This comparison led to the benchmarking of the energy (kWh) versus range (km), and power (kW) versus speed (kmph).

With these benchmark specifications or parameters, we have analyzed the potential of alternate battery technologies for mobility applications. The metal–air batteries are identified as potential contenders because of their high specific energy, and more specifically, the mechanically rechargeable zinc–air battery which will enable ultrafast recharging. With the detailed analysis on state-of-the-art zinc–air battery research, we have provided future research paths that can increase practical specific energy, specific power and lifetime. Battery design aspects are discussed to achieve fast mechanical refuellability of zinc anodes. Based on the analysis and theoretical limits, we believe that zinc–air batteries hold great potential as a safe and low-cost alternative to cover low to medium powered EVs, with high range. In high power EVs powered by high power batteries, zinc–air batteries can be used as range extenders.

International Energy Agency. Global EV Outlook 2023, Catching up with climate ambitions. Geo. 9–10 (2023).

Indian vehicle registration data, Vahan dashboard. https://vahan.parivahan.gov.in/vahan4dashboard/.

Analytics, J. R. and. India E. V. market, Annual Report Card 2023. 60 (2023).

Baasner, A. et al. The role of balancing nanostructured silicon anodes and nmc cathodes in lithium-ion full-cells with high volumetric energy density. J. Electrochem. Soc. 167, 020516 (2020).

Article CAS Google Scholar

Bloi, L. M. et al. Mechanistic insights into the reversible lithium storage in an open porous carbon via metal cluster formation in all solid-state batteries. Carbon N. Y 188, 325–335 (2022).

Article CAS Google Scholar

Ren, D. et al. Ultrahigh rate performance of a robust lithium nickel manganese cobalt oxide cathode with preferentially orientated lI-diffusing channels. ACS Appl. Mater. Interfaces 11, 41178–41187 (2019).

Article CAS PubMed Google Scholar

World Economic Forum; Global Battery Alliance. A Vision for a Sustainable Battery Value Chain in 2030. 10–11 (2019).

Baes, K., Carlot, F., Ito, Y., Kolk, M. & Merhaba, A. Future of batteries: Winner takes all? Arthur D Little 24 (2018). https://www.adlittle.com/sites/default/files/viewpoints/adl_future_of_batteries-min.pdf.

Kwade, A. et al. Current status and challenges for automotive battery production technologies. Nat. Energy 3, 290–300 (2018). This work focuses on challenges involved in Li-ion battery manufacturing by comparing production process, quality, performance, and impact of materials and process on scale and cost.

Article Google Scholar

Schmidt, O., Hawkes, A., Gambhir, A. & Staffell, I. The future cost of electrical energy storage based on experience rates. Nat. Energy 2, 17110 (2017).

Article Google Scholar

Kittner, N., Lill, F. & Kammen, D. M. Energy storage deployment and innovation for the clean energy transition. Nat. Energy 2, 17125 (2017).

Article Google Scholar

Nykvist, B. & Nilsson, M. Rapidly falling costs of battery packs for electric vehicles. Nat. Clim. Chang 5, 329–332 (2015).

Article Google Scholar

Berckmans, G. et al. Cost projection of state of the art lithium-ion batteries for electric vehicles up to 2030. Energ. (Basel) 10, 1314 (2017).

Google Scholar

Hsieh, I. Y. L., Pan, M. S., Chiang, Y. M. & Green, W. H. Learning only buys you so much: Practical limits on battery price reduction. Appl Energy 239, 218–224 (2019).

Article Google Scholar

Penisa, X. N. et al. Projecting the price of lithium-ion NMC battery packs using a multifactor learning curve model. Energ. (Basel) 13, 5276 (2020).

CAS Google Scholar

NAtional Blueprint for Lithium Batteries 2021–2030. 1–24 (2021). https://www.energy.gov/sites/default/files/2021-06/FCAB%20National%20Blueprint%20Lithium%20Batteries%200621_0.pdf.

BloombergNEF. Lithium-ion Battery Pack Prices Rise for First Time to an Average of $151/kWh. https://about.bnef.com/blog/lithium-ion-battery-pack-prices-rise-for-first-time-to-an-average-of-151-kwh/.

Ouyang, D. et al. A Review on the thermal hazards of the lithium-ion battery and the corresponding countermeasures. Appl. Sci. (Switz.) 9, 2483 (2019).

Article CAS Google Scholar

Jiang, J. & Dahn, J. R. ARC studies of the thermal stability of three different cathode materials: LiCoO2; Li[Ni0.1Co0.8Mn0.1]O2; and LiFePO4, in LiPF6 and LiBoB EC/DEC electrolytes. Electrochem. Commun. 6, 39–43 (2004). This work analyses the self-sustained exothermic reactions of different Li-ion battery cathode materials in presence of different electrolytes under thermal abuse using ARC, and provides suggestions on best anode-cathode-electrolyte combination which is abuse-tolerant.

Article CAS Google Scholar

Zhang, G. et al. Comprehensive investigation of a slight overcharge on degradation and thermal runaway behavior of lithium-ion batteries. ACS Appl Mater. Interfaces 13, 35054–35068 (2021).

Article CAS PubMed Google Scholar

Archibald, E., Kennedy, R., Marr, K., Jeevarajan, J. & Ezekoye, O. Characterization of thermally induced runaway in pouch cells for propagation. Fire Technol. 56, 2467–2490 (2020).

Article Google Scholar

Stephens, D. et al. Lithium-Ion Battery Safety Issues for Electric and Plug-in Hybrid Vehicles. Report No. DOT HS 812 418 (National Highway Traffic Safety Administration, Washington, DC, 2017).

Feng, X. et al. Thermal runaway mechanism of lithium ion battery for electric vehicles: a review. Energy Storage Mater. 10, 246–267 (2018).

Article Google Scholar

Rodrigues, M.-T. F. et al. A materials perspective on Li-ion batteries at extreme temperatures. Nat. Energy 2, 17108 (2017).

Article CAS Google Scholar

Zhang, S. S., Xu, K. & Jow, T. R. The low temperature performance of Li-ion batteries. J. Power Sources 115, 137–140 (2003).

Article CAS Google Scholar

Ouyang, D. et al. Influence of low temperature conditions on lithium-ion batteries and the application of an insulation material. RSC Adv. 9, 9053–9066 (2019).

Article CAS PubMed Google Scholar

Luo, H. et al. Lithium-ion batteries under low-temperature environment: challenges and prospects. Materials 15, 8166 (2022).

Article CAS PubMed Google Scholar

Ma, S. et al. Temperature effect and thermal impact in lithium-ion batteries: a review. Prog. Nat. Sci.: Mater. Int. 28, 653–666 (2018).

Article CAS Google Scholar

You, Y. et al. Subzero-temperature cathode for a sodium-ion battery. Adv. Mater. 28, 7243–7248 (2016).

Article CAS PubMed Google Scholar

Li, Z. et al. Sodium-ion battery with a wide operation-temperature range from −70 to 100 °C. Angew. Chem. - Int. Ed. 61, e202116930 (2022).

Article CAS Google Scholar

Wang, C. et al. Extending the low-temperature operation of sodium metal batteries combining linear and cyclic ether-based electrolyte solutions. Nat. Commun. 13, 4934 (2022).

Article CAS PubMed Google Scholar

Rui, X. et al. A low-temperature sodium-ion full battery: superb kinetics and cycling stability. Adv. Funct. Mater. 31, 2009458 (2021).

Article CAS Google Scholar

Yang, C. et al. Entropy-driven solvation toward low-temperature sodium-ion batteries with temperature-adaptive feature. Adv. Mater. 35, 2301817 (2023).

Article CAS Google Scholar

Li, P., Hu, N., Wang, J., Wang, S. & Deng, W. Recent progress and perspective: na ion batteries used at low temperatures. Nanomaterials 12, 3529 (2022).

Article CAS PubMed Google Scholar

Scott, A. Sodium comes to the battery world. CEN Glob. Enterp. 100, 16–18 (2022).

Article Google Scholar

Ltd, M. T. C. (Chennai). Performance Indicators. https://mtcbus.tn.gov.in/Home/performance.

Hyderabad City Bus and Routes. http://www.hyderabadcitybus.com/.

Economics, T. Commodity Prices. https://tradingeconomics.com/commodity/zinc.

Durmus, Y. E. et al. Side by side battery technologies with lithium-ion based batteries. Adv. Energy Mater. 10, 2000089 (2020).

Article CAS Google Scholar

Shan, X. et al. High-performance anodes for aqueous Zn-iodine batteries from spent Zn-air batteries. Mater. Adv. 4, 1623–1627 (2023).

Article CAS Google Scholar

Wang, K. et al. Dendrite growth in the recharging process of zinc-air batteries. J. Mater. Chem. A Mater. 3, 22648–22655 (2015).

Article CAS Google Scholar

Zhao, Z. et al. Challenges in zinc electrodes for alkaline zinc-air batteries: obstacles to commercialization. ACS Energy Lett. 4, 2259–2270 (2019).

Article CAS Google Scholar

Liu, P. et al. Porous zinc anode design for Zn-air chemistry. Front. Chem. 7, 656 (2019).

Article CAS PubMed Google Scholar

Wei, Y., Shi, Y., Chen, Y., Xiao, C. & Ding, S. Development of solid electrolytes in Zn-air and Al-air batteries: From material selection to performance improvement strategies. J. Mater. Chem. A Mater. 9, 4415–4453 (2021).

Article CAS Google Scholar

Yi, J. et al. Challenges, mitigation strategies and perspectives in development of zinc-electrode materials and fabrication for rechargeable zinc-air batteries. Energy Environ. Sci. 11, 3075–3095 (2018).

Article CAS Google Scholar

Lee, C. W., Sathiyanarayanan, K., Eom, S. W. & Yun, M. S. Novel alloys to improve the electrochemical behavior of zinc anodes for zinc/air battery. J. Power Sources 160, 1436–1441 (2006).

Article CAS Google Scholar

Lu, W., Xie, C., Zhang, H. & Li, X. Inhibition of zinc dendrite growth in zinc-based batteries. ChemSusChem 11, 3996–4006 (2018).

Article CAS PubMed Google Scholar

Li, Q., Han, L., Luo, Q., Liu, X. & Yi, J. Towards understanding the corrosion behavior of zinc-metal anode in aqueous systems: from fundamentals to strategies. Batter Supercaps 5, e202100417 (2022).

Article CAS Google Scholar

Liu, S., Lin, H., Song, Q., Zhu, J. & Zhu, C. Anti-corrosion and reconstruction of surface crystal plane for zn anodes by an advanced metal passivation technique. Energy Environ. Mater. 6, e12405 (2023).

Article CAS Google Scholar

Xie, W., Zhu, K., Yang, H. & Yang, W. Advancements in achieving high reversibility of zinc anode for alkaline zinc-based batteries. Adv. Mater. 36, 2306154 (2023).

Article Google Scholar

Clark, S. et al. Designing aqueous organic electrolytes for zinc–air batteries: method, simulation, and validation. Adv. Energy Mater. 10, 1903470 (2020).

Article CAS Google Scholar

Koretz, B. & Goldstein, J. R. Regeneration of zinc anodes for the electric fuel zinc-air refuelable EV battery system. Proc. Intersoc. Energy Convers. Eng. Conf. 2, 877–882 (1997).

Google Scholar

Goldman, A. J. et al. Mechanically rechargeable electric batteries and anodes for use therein. United States Patent, US5360680A (1994).

Goldstein, J. R., Koretz, B. & Harats, Y. Field test of the Electric Fuel zinc-air refuelable battery system for electric vehicles. Proc. Intersoc. Energy Convers. Eng. Conf. 3, 1925–1929 (1996).

Google Scholar

Goldstein, J., Brown, I. & Koretz, B. New developments in the Electric Fuel Ltd. zinc/air system. J. Power Sources 80, 171–179 (1999).

Article CAS Google Scholar

Goldstein, J., Meitav, A., Lezion, R.& Kravitz, M. Method for inhibiting corrosion in particulate zinc. United States Patent US5232798A (1993).

Alexander, G. Process and device for cleaning an anode bag. European Patent Office EP0697748A1 (1996).

Naimer, N. & Goldstein, J. R. Process for the preparation of gas diffusion electrodes. United States Patent US5441823A (1995).

Goldstein Jonathan R., Gektin, Inna., G. M. Preparation and regeneration of slurries for use in zinc-air batteries. European Patent Office EP0564664B1 (1997).

Arbel, A. & Goldstein, J. R. Metal-air fuel cells and methods of removing spent fuel therefrom. United States Patent US20150118583 (2018).

Tzidon, A. et al. Methods for regenaration of aqueous alkaline solution. European Patent Office EP3132491B1 (2020).

Tzidon, D. & Mellman, A. Electrolyte system and method of preparation thereof. World Intellectual Property Organization WO2013/150521 (2018).

Yadgar, A., Miller, Y. & Tzidon, D. Protected anode structure suitable for use in metal-air batteries. United States Patent US20160013529 (2016).

Khasin, E. Electrolyte system for metal-air batteries and method of use thereof. United States Patent US20130034781A1 (2015).

Vivek Singhal, A., Kumar Sharma, A., Jain, A., Raina, A. & Charaya, H. System and method for extending a range of an electric vehicle. World Intellectual Property Organization WO2020/121337-A1 (2020).

Chireau, R. F. New Mechanically Rechargeable Zinc/Air Battery Design—Final Report. Defense Technical Information Center AD0762573 (1973). https://apps.dtic.mil/sti/citations/AD0762573.

Almerini, A. L. & Bartosh, S. J. Simulated field tests on zinc-air batteries. In: Annual Proceedings Power Sources Conference Vol. 4 (1974). https://apps.dtic.mil/sti/tr/pdf/ADA037702.pdf.

Putt, R. A., & Merry, G. W.,. Zinc air battery development for electric vehicles. National Technical Information Service, LBL-31184. https://doi.org/10.2172/5558985 (1991).

Rudd, E. J. & Lott, S. Development of Aluminum-Air Batteries for Application in Electric Vehicles Final Report. National Technical Information Service SAND-91-7066 (1990). https://trid.trb.org/View/363148.

Sierra Alcazar, H. B., Nguyen, P. D. & Pinoli, A. A. Technology Base Research on Zinc/Air Battery Systems: Final Report. National Technical Information Service LBL-23960 (1987). https://trid.trb.org/View/286312.

Sen, R. K., Van Voorhees, S. L. & Ferrel, T. Metal-Air Battery Assessment. UNT Digital Library (1988). https://digital.library.unt.edu/ark:/67531/metadc1450455/m1/1/.

Cooper, J. F. et al. Demonstration of zinc/air fuel battery to enhance the range and mission of fleet electric vehicles: preliminary results in the refueling of a multicell module. (1994). Presented at the 29th Intersociety Energy Conversion Engineering Conference, Monterey, CA, 7-12 Aug. 1994.

Naimer, N., Koretz, B. & Putt, R. Zinc-Air Batteries for UAVs and MAVs. 1–4 (2002). Report from 'Electric Fuel Corporation'. https://www.efbpower.com/userfiles/UVS02.pdf.

Cooper, J. F., Fleming, D., Hargrove, D., Koopman, R. & Peterman, K. A Refuelable zinc/air battery for fleet electric vehicle propulsion. SAE Technical Paper Series Vol. 1 (2010).

Powerzinc. Products & applications, dynamic quick-refuel fuel cell (DQFC). https://powerzinc.com/en/index-2-c1-3.html.

Xu, N. et al. Self-Assembly formation of Bi-functional Co 3 O 4 /MnO 2-CNTs hybrid catalysts for achieving both high energy/power density and cyclic ability of rechargeable zinc-Air battery. Sci. Rep. 6, 33590 (2016).

Article CAS PubMed Google Scholar

Zhang, X., Wang, X. G., Xie, Z. & Zhou, Z. Recent progress in rechargeable alkali metal–air batteries. Green. Energy Environ. 1, 4–17 (2016).

Article Google Scholar

Rahman, Md. A., Wang, X. & Wen, C. High energy density metal-air batteries: a review. J. Electrochem Soc. 160, A1759–A1771 (2013).

Article CAS Google Scholar

Lee, J. S. et al. Metal-air batteries with high energy density: Li-air versus Zn-air. Adv. Energy Mater. 1, 34–50 (2011).

Article CAS Google Scholar

Fu, J. et al. Electrically rechargeable zinc–air batteries: progress, challenges, and perspectives. Adv. Mater. 29, 1604685 (2017).

Article Google Scholar

Iqbal, A., El-Kadri, O. M. & Hamdan, N. M. Insights into rechargeable Zn-air batteries for future advancements in energy storing technology. J. Energy Storage 62, 106926 (2023).

Article Google Scholar

Chen, X. et al. Recent advances in materials and design of electrochemically rechargeable zinc–air batteries. Small 14, 1801929 (2018).

Article Google Scholar

Blurton, K. F. & Sammells, A. F. Metal/air batteries: their status and potential—a review. J. Power Sources 4, 263–279 (1979).

Article CAS Google Scholar

Peng, M. et al. Alloy-type anodes for high-performance rechargeable batteries. Angew. Chem.—Int. Ed. 61, e202206770 (2022).

Article CAS Google Scholar

Pan, J. et al. Advanced architectures and relatives of air electrodes in Zn–Air batteries. Adv. Sci. 5, 1700691 (2018).

Article Google Scholar

Rajagopalan, K. et al. Organo-metallic electrolyte additive for regulating hydrogen evolution and self-discharge in Mg-air aqueous battery. N. J. Chem. 46, 19950–19962 (2022).

Article CAS Google Scholar

Kahveci, O. Preparation of a 3-D porous pure Al electrode for Al-air battery anode and comparison of its electrochemical performance with a smooth surface electrode. ChemElectroChem 202300221, 1–11 (2023).

Google Scholar

Pan, Y. et al. High capacity porous VB2/Ni anodes for VB2/air batteries. J. Alloy. Compd. 771, 565–570 (2019).

Article CAS Google Scholar

Linjee, S., Moonngam, S., Klomjit, P., Pålsson, N. S. & Banjongprasert, C. Corrosion behaviour improvement from the ultrafine-grained Al–Zn–In alloys in Al–air battery. Energy Rep. 8, 5117–5128 (2022).

Article Google Scholar

Wang, C. et al. Recent progress of metal-air batteries—a mini review. Appl. Sci. (Switz.) 9, 1–22 (2019).

Google Scholar

Hosseini, S. et al. Discharge performance of zinc-air flow batteries under the effects of sodium dodecyl sulfate and pluronic F-127. Sci. Rep. 8, 1–13 (2018).

Article Google Scholar

Lee, J. S. et al. Ketjenblack carbon supported amorphous manganese oxides nanowires as highly efficient electrocatalyst for oxygen reduction reaction in alkaline solutions. Nano Lett. 11, 5362–5366 (2011).

Article CAS PubMed Google Scholar

Bhosale, A. C. & Rengaswamy, R. Interfacial contact resistance in polymer electrolyte membrane fuel cells: recent developments and challenges. Renew. Sustain. Energy Rev. 115, 109351 (2019).

Article CAS Google Scholar

Park, S. et al. Polarization losses under accelerated stress test using multiwalled carbon nanotube supported Pt catalyst in PEM fuel cells. J. Electrochem Soc. 158, B297 (2011).

Article CAS Google Scholar

Bednarek, T. & Tsotridis, G. Issues associated with modelling of proton exchange membrane fuel cell by computational fluid dynamics. J. Power Sources 343, 550–563 (2017).

Article CAS Google Scholar

Chen, L. D., Nørskov, J. K. & Luntz, A. C. Al-air batteries: fundamental thermodynamic limitations from first-principles theory. J. Phys. Chem. Lett. 6, 175–179 (2015).

Article CAS PubMed Google Scholar

Xu, G. et al. Strategies for improving stability of Pt-based catalysts for oxygen reduction reaction. Adv. Sens. Energy Mater. 2, 100058 (2023).

Article Google Scholar

González-Castaño, C., Restrepo, C., Kouro, S., Vidal-Idiarte, E. & Calvente, J. A bidirectional versatile buck–boost converter driver for electric vehicle applications. Sensors 21, 5712 (2021).

Article PubMed Google Scholar

Rahimi, T., Islam, M. R., Gholizadeh, H., Mahdizadeh, S. & Afjei, E. Design and implementation of a high step-up dc-dc converter based on the conventional boost and buck-boost converters with high value of the efficiency suitable for renewable application. Sustainability (Switz.) 13, 10699 (2021).

Article Google Scholar

Persky, Y. et al. Biomimetic Fe-Cu porphyrrole aerogel electrocatalyst for oxygen reduction reaction. ACS Catal. 13, 11012–11022 (2023).

Article CAS Google Scholar

Yang, L. et al. Self-sacrificial template synthesis of a nitrogen-doped microstructured carbon tube as electrocatalyst for oxygen reduction. ChemElectroChem 5, 3731–3740 (2018).

Article CAS Google Scholar

Sun, F., Liu, T., Huang, M. & Guan, L. High specific surface area Fe–N–C electrocatalysts for the oxygen reduction reaction synthesized by a hard-template-assisted ball milling strategy. Sustain Energy Fuels 7, 3675–3683 (2023).

Article CAS Google Scholar

Kang, Y. et al. Soft template-based synthesis of mesoporous phosphorus- and boron-codoped nife-based alloys for efficient oxygen evolution reaction. Small 18, 2203411 (2022).

Article CAS Google Scholar

Liu, T. et al. Self-sacrificial template-directed vapor-phase growth of MOF assemblies and surface vulcanization for efficient water splitting. Adv. Mater. 31, 1806672 (2019).

Article Google Scholar

Li, J. et al. ZIF-67 as continuous self-sacrifice template derived NiCO2O4/Co,N-CNTs nanocages as efficient bifunctional electrocatalysts for rechargeable Zn-Air batteries. ACS Sustain Chem. Eng. 6, 10021–10029 (2018).

Article CAS Google Scholar

Kurian, M. et al. Influence of ice templating on oxygen reduction catalytic activity of metal-free heteroatom-doped mesoporous carbon derived from polypyrrole for zinc–air batteries. Energy Technol. 10, 2200840 (2022).

Article CAS Google Scholar

Cai, S. et al. Ice-template-induced highly interconnected porous polymer gel electrolytes for dendrite-free flexible zinc-air batteries. J. Phys. Chem. Lett. 14, 7445–7453 (2023).

Article CAS PubMed Google Scholar

Zong, L. et al. Metal-free, active nitrogen-enriched, efficient bifunctional oxygen electrocatalyst for ultrastable zinc-air batteries. Energy Storage Mater. 27, 514–521 (2020).

Article Google Scholar

Cai, X., Lai, L., Lin, J. & Shen, Z. Recent advances in air electrodes for Zn-air batteries: Electrocatalysis and structural design. Mater. Horiz. 4, 945–976 (2017).

Article CAS Google Scholar

Wang, X. et al. Balancing mass transfer and active sites to improve electrocatalytic oxygen reduction by B,N codoped C nanoreactors. Nano Lett. 23, 4699–4707 (2023).

Article CAS PubMed Google Scholar

Xiang, Y., Lu, L., Kottapalli, A. G. P. & Pei, Y. Status and perspectives of hierarchical porous carbon materials in terms of high-performance lithium–sulfur batteries. Carbon Energy 4, 346–398 (2022).

Article CAS Google Scholar

Xie, Y. et al. Dual-template strategy synthesis of hierarchically porous electrocatalysts for oxygen reduction reaction. Adv. Sens. Energy Mater. 1, 100006 (2022).

Article Google Scholar

Vazhayil, A., Vazhayal, L., Thomas, J., Ashok C, S. & Thomas, N. A comprehensive review on the recent developments in transition metal-based electrocatalysts for oxygen evolution reaction. Appl. Surf. Sci. Adv. 6, 100184 (2021).

Article Google Scholar

Ehelebe, K., Escalera-López, D. & Cherevko, S. Limitations of aqueous model systems in the stability assessment of electrocatalysts for oxygen reactions in fuel cell and electrolyzers. Curr. Opin. Electrochem 29, 100832 (2021).

Article CAS Google Scholar

Zhu, P. & Zhao, Y. Effects of electrochemical reaction and surface morphology on electroactive surface area of porous copper manufactured by Lost Carbonate Sintering. RSC Adv. 7, 26392–26400 (2017).

Article CAS Google Scholar

Ma, C. et al. Ion accumulation and diffusion behavior in micro-/meso-pores of carbon nanofibers. J. Electrochem. Soc. 161, A1330–A1337 (2014).

Article CAS Google Scholar

Wang, D. W., Li, F., Liu, M., Lu, G. Q. & Cheng, H. M. Mesopore-aspect-ratio dependence of ion transport in rodtype ordered mesoporous carbon. J. Phys. Chem. C. 112, 9950–9955 (2008).

Article CAS Google Scholar

Sassin, M. B., Garsany, Y., Gould, B. D. & Swider-Lyons, K. E. Fabrication method for laboratory-scale high-performance membrane electrode assemblies for fuel cells. Anal. Chem. 89, 511–518 (2017).

Article CAS PubMed Google Scholar

Cheng, Y. et al. Hierarchically porous metal-free carbon with record high mass activity for oxygen reduction and Zn-air batteries. J. Mater. Chem. A: Mater. 7, 9831–9836 (2019).

Article CAS Google Scholar

Guo, J. et al. Superior oxygen electrocatalysts derived from predesigned covalent organic polymers for zinc-air flow batteries. Nanoscale 11, 211–218 (2019).

Article CAS Google Scholar

Li, Y. & Dai, H. Recent advances in zinc–air batteries. Chem. Soc. Rev. 43, 5257–5275 (2014).

Article CAS PubMed Google Scholar

Fei, Y., Wang, L., Fang, Y., Deng, J. & Hu, Y. H. Highly efficient thin zinc air batteries. J. Electrochem Soc. 166, A2879–A2286 (2019).

Article CAS Google Scholar

Duan, D. L., Zhang, R. L., Ding, X. J. & Li, S. Calculation of specific surface area of foam metals using dodecahedron model. Mater. Sci. Technol. 22, 1364–1368 (2006).

Article CAS Google Scholar

González-García, J. et al. Characterization of a carbon felt electrode: structural and physical properties. J. Mater. Chem. 9, 419–426 (1999).

Article Google Scholar

Hosseini, S. et al. The influence of dimethyl sulfoxide as electrolyte additive on anodic dissolution of alkaline zinc-air flow battery. Sci. Rep. 9, 14958 (2019).

Article PubMed Google Scholar

Gong, X. et al. Self-templated hierarchically porous carbon nanorods embedded with atomic fe-n4 active sites as efficient oxygen reduction electrocatalysts in Zn-Air batteries. Adv. Funct. Mater. 31, 2008085 (2020).

Article Google Scholar

Wang, Z. et al. Fe, Cu-coordinated ZIF-derived carbon framework for efficient oxygen reduction reaction and zinc–air batteries. Adv. Funct. Mater. 28, 1802596 (2018).

Article Google Scholar

Nam, G. et al. Evaluation of the volumetric activity of the air electrode in a zinc-air battery using a nitrogen and sulfur co-doped metal-free electrocatalyst. ACS Appl Mater. Interfaces 12, 57064–57070 (2020).

Article CAS PubMed Google Scholar

Ma, Z. et al. Degradation characteristics of air cathode in zinc air fuel cells. J. Power Sources 274, 56–64 (2015).

Article CAS Google Scholar

Philips, M. F., Gruter, G. J. M., Koper, M. T. M. & Schouten, K. J. P. Production of gas diffusion layers with tunable characteristics. ACS Omega 7, 23041–23049 (2022).

Article CAS PubMed Google Scholar

Danner, T., Eswara, S., Schulz, V. P. & Latz, A. Characterization of gas diffusion electrodes for metal-air batteries. J. Power Sources 324, 646–656 (2016).

Article CAS Google Scholar

Marini, E. et al. Mapping of the degradation processes at bifunctional O2 gas diffusion electrode for aqueous alkaline metal-air batteries. J. Power Sources 546, 231879 (2022).

Article CAS Google Scholar

Li, M. et al. Relating catalysis between fuel cell and metal-Air batteries. Matter 2, 32–49 (2020).

Article Google Scholar

Lu, Q. et al. What matters in engineering next-generation rechargeable Zn-air batteries? Energy 1, 100025 (2023).

Google Scholar

Zhang, W. et al. Design principles of functional polymer separators for high-energy, metal-based batteries. Small 14, 1703001 (2018).

Article Google Scholar

Tsehaye, M. T. et al. Membranes for zinc-air batteries: Recent progress, challenges and perspectives. J. Power Sources 475, 228689 (2020).

Article CAS Google Scholar

Y. Harats, Y., Sharon, Y. & Neal Naimer, J. G. Coated absorbent particles for a carbon dioxide scrubber system, UK Patent, GB2305139A (1997).

Wang, T. et al. Carbonate formation on carbon electrode in rechargeable zinc-air battery revealed by in-situ Raman measurements. J. Power Sources 533, 231237 (2022).

Article CAS Google Scholar

Wang, K. & Yu, J. Lifetime simulation of rechargeable zinc-air battery based on electrode aging. J. Energy Storage 28, 101191 (2020).

Article Google Scholar

Ogawa, M. & Nakano, Y. Separation of CO2/CH4 mixture through carbonized membrane prepared by gel modification. J. Memb. Sci. 173, 123–132 (2000).

Article CAS Google Scholar

Horng, S. Y. & Li, M. H. Kinetics of absorption of carbon dioxide into aqueous solutions of monoethanolamine + triethanolamine. Ind. Eng. Chem. Res. 41, 257–266 (2002).

Article CAS Google Scholar

Cornelissen, R. L. & Hirs, G. G. Exergy analysis of cryogenic air separation. Energy Convers. Manag. 39, 1821–1826 (1998).

Article CAS Google Scholar

Sarkar, S. C. & Bose, A. Role of activated carbon pellets in carbon dioxide removal. Energy Convers. Manag. 38, 105–110 (1997).

Article Google Scholar

Shin, D. H., Cheigh, H. S. & Lee, D. S. The use of Na2CO3-based CO2 absorbent systems to alleviate pressure buildup and volume expansion of kimchi packages. J. Food Eng. 53, 229–235 (2002).

Article Google Scholar

Amunátegui, B., Ibáñez, A., Sierra, M. & Pérez, M. Electrochemical energy storage for renewable energy integration: zinc-air flow batteries. J. Appl Electrochem 48, 627–637 (2018).

Article Google Scholar

Hu, S. C. et al. Removal of carbon dioxide in the indoor environment with sorption-type air filters. Int. J. Low.-Carbon Technol. 12, 330–334 (2017).

CAS Google Scholar

Asgari, M. et al. An experimental and computational study of CO2 adsorption in the sodalite-type M-BTT (M = Cr, Mn, Fe, Cu) metal-organic frameworks featuring open metal sites. Chem. Sci. 9, 4579–4588 (2018).

Article CAS PubMed Google Scholar

George, M. et al. Effect of ionic liquid modification on the ORR performance and degradation mechanism of trimetallic PtNiMo/C catalysts. ACS Catal. 9, 8682–8692 (2019).

Article CAS PubMed Google Scholar

Yang, Z. & Nakashima, N. A simple preparation of very high methanol tolerant cathode electrocatalyst for direct methanol fuel cell based on polymer-coated carbon nanotube/platinum. Sci. Rep. 5, 12236 (2015).

Article CAS PubMed Google Scholar

Pizzutilo, E. et al. On the need of improved accelerated degradation protocols (ADPs): examination of platinum dissolution and carbon corrosion in half-cell tests. J. Electrochem Soc. 163, F1510–F1514 (2016).

Article CAS Google Scholar

Shinohara, K., Ohma, A., Iiyama, A., Yoshida, T. & Daimaru, A. Membrane and catalyst performance targets for automotive fuel cells by FCCJ membrane, catalyst, MEA WG. ECS Trans. 41, 775–784 (2011).

Article Google Scholar

Wang, X. et al. Pd@Pt core-shell concave decahedra: a class of catalysts for the oxygen reduction reaction with enhanced activity and durability. J. Am. Chem. Soc. 137, 15036–15042 (2015).

Article CAS PubMed Google Scholar

Banham, D. et al. A review of the stability and durability of non-precious metal catalysts for the oxygen reduction reaction in proton exchange membrane fuel cells. J. Power Sources 285, 334–348 (2015).

Article CAS Google Scholar

Zhao, Z. et al. Methods for producing an easily assembled zinc-air battery. MethodsX 7, 100973 (2020).

Article CAS PubMed Google Scholar

Zhao, Z. et al. An easily assembled boltless zinc–air battery configuration for power systems. J. Power Sources 458, 228061 (2020).

Article CAS Google Scholar

Yin, X. et al. Influence of rolling processing on discharge performance of Al-0.5Mg-0.1Sn-0.05Ga-0.05In alloy as anode for al-air battery. Int J. Electrochem. Sci. 12, 4150–4163 (2017).

Article CAS Google Scholar

Wen, H. et al. High energy efficiency and high power density aluminum-air flow battery. Int J. Energy Res. 44, 7568–7579 (2020).

Article CAS Google Scholar

Wang, Z. et al. Defect-rich nitrogen doped CO3O4/C porous nanocubes enable high-efficiency bifunctional oxygen electrocatalysis. Adv. Funct. Mater. 29, 1902875 (2019).

Article Google Scholar

Guo, X. et al. Tuning the bifunctional oxygen electrocatalytic properties of core-shell CO3O4@NiFe LDH catalysts for Zn-air batteries: effects of interfacial cation valences. ACS Appl Mater. Interfaces 11, 21506–21514 (2019).

Article CAS PubMed Google Scholar

Liu, J. et al. Confining ultrasmall bimetallic alloys in porous N-carbon for use as scalable and sustainable electrocatalysts for rechargeable Zn-air batteries. J. Mater. Chem. A: Mater. 7, 12451–12456 (2019).

Article CAS Google Scholar

Wang, P., Wan, L., Lin, Y. & Wang, B. Construction of mass-transfer channel in air electrode with bifunctional catalyst for rechargeable zinc-air battery. Electrochim. Acta 320, 134564 (2019).

Article CAS Google Scholar

Chen, J. et al. Dual single-atomic Ni-N4 and Fe-N4 sites constructing Janus hollow graphene for selective oxygen electrocatalysis. Adv. Mater. 32, 1–11 (2020).

Google Scholar

Pan, J. et al. Preliminary study of alkaline single flowing Zn-O2 battery. Electrochem commun. 11, 2191–2194 (2009).

Article CAS Google Scholar

Chen, G., Wang, X., Yang, C., Liang, H. P. & Wang, Z. NaCl-promoted hierarchically porous carbon self-co-doped with iron and nitrogen for efficient oxygen reduction. ChemistrySelect 5, 13703–13710 (2020).

Article CAS Google Scholar

Luo, Y. et al. Dual-template construction of iron-nitrogen-codoped hierarchically porous carbon electrocatalyst for oxygen reduction reaction. Energy Fuels 34, 16720–16728 (2020).

Article CAS Google Scholar

Gao, J., Liu, S., Zhu, P., Zhao, X. & Wang, G. Fe-N4engineering of S and N co-doped hierarchical porous carbon-based electrocatalysts for enhanced oxygen reduction in Zn-air batteries. Dalton Trans. 49, 14847–14853 (2020).

Article CAS PubMed Google Scholar

Chen, Y. et al. Enhanced oxygen reduction with single-atomic-site iron catalysts for a zinc-air battery and hydrogen-air fuel cell. Nat. Commun. 9, 5422 (2018).

Article CAS PubMed Google Scholar

Yang, L., Feng, S., Xu, G., Wei, B. & Zhang, L. Electrospun MOF-based FeCo nanoparticles embedded in nitrogen-doped mesoporous carbon nanofibers as an efficient bifunctional catalyst for oxygen reduction and oxygen evolution reactions in zinc-air batteries. ACS Sustain Chem. Eng. 7, 5462–5475 (2019).

Article CAS Google Scholar

Jin, H. et al. ZIF-8/LiFePO4 derived Fe-N-P Co-doped carbon nanotube encapsulated Fe2P nanoparticles for efficient oxygen reduction and Zn-air batteries. Nano Res. 13, 818–823 (2020).

Article CAS Google Scholar

Li, Y. et al. Advanced zinc-air batteries based on high-performance hybrid electrocatalysts. Nat. Commun. 4, 1805 (2013).

Article PubMed Google Scholar

Lee, J. S., Lee, T., Song, H. K., Cho, J. & Kim, B. S. Ionic liquid modified graphene nanosheets anchoring manganese oxide nanoparticles as efficient electrocatalysts for Zn-air batteries. Energy Environ. Sci. 4, 4148–4154 (2011).

Article CAS Google Scholar

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The authors acknowledge the project funding from Government of India under Institute of Eminence programme (Sanction no. SP22231245CPETWOEGYHOC).

Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai, 600036, Tamil Nadu, India

Akhil Kongara, Arun Kumar Samuel, Gunjan Kapadia & Aravind Kumar Chandiran

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A.K. and A.K.C. conceptualized the idea and created a work plan. A.K. collected all the data related to electric vehicles parameters and zinc–air batteries. A.K., A.K.S., G.K. and A.K. analyzed the data and created the plan for the first draft. A.K. wrote the first draft. All the authors contributed to reviewing the draft and subsequent revisions.

Correspondence to Aravind Kumar Chandiran.

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Kongara, A., Samuel, A.K., Kapadia, G. et al. Mechanically rechargeable zinc-air batteries for two- and three-wheeler electric vehicles in emerging markets. Commun Mater 5, 244 (2024). https://doi.org/10.1038/s43246-024-00662-6

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Received: 22 November 2023

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DOI: https://doi.org/10.1038/s43246-024-00662-6

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