Batteries are a key element in electric vehicles (EVs), and there has been a lot of development in solid-state and other EV battery chemistry. This FAQ will highlight the promising materials that align with solid-state and other EV batteries, making them suitable for EV batteries.
Material advances in solid-state batteries
In solid-state batteries, sulfide, oxide, and polymer-based materials have gained traction for EV battery production. These materials have different ionic conductivity, mechanical properties, and operating temperature ranges, offering a variety of choices for EV makers.
Sulfide-based solid electrolytes
Sulfide-based solid electrolytes are characterized by high ionic conductivity, a high operating temperature range, and lower cost, as shown in Figure 1. At room temperature, sulfide electrolytes such as Li6PS5Cl and Li3PS4 have high ionic conductivity, indicating faster charging. However, this theoretical benefit is limited by several other properties that require specific charging design considerations.

Figure 1. Radar plot showing the properties of sulfide-based solid-state electrolytes. (Image: Wiley)
The thermal stability up to 450 °C gives a wide operating window. However, the charging system must still carefully control heat generation during fast charging to stay below this limit. To do this, the charging infrastructure needs to include advanced thermal control systems.
The conditions for stack pressure make designing a charging system very difficult. A research study found that a pressure of 25 MPa led to Li+ ions passing into the pores of the electrolyte. Any pressure less than or more than this proved counterproductive. This means that both charging stations and vehicles need pressure monitoring systems to ensure contact is maintained during the charging process.
The narrow electrochemical voltage window and air stability limitations directly impact charging protocols. Charging systems must operate within tighter voltage constraints than traditional liquid electrolyte batteries, requiring more precise voltage control mechanisms.
Perhaps most critically, the risk of lithium dendrite formation, especially at higher pressures, requires charging protocols that carefully balance speed with safety.
Oxide-based electrolytes
Oxide-based electrolytes, such as Garnet, Perovskite, and NA/LISICON, have various variants for making EV batteries. In Figure 2, NA/LISICON has better air stability, Garnet is cost-effective, and Perovskite has a better operating temperature range.

Figure 2. Radar plot showing the properties of oxide-based solid-state electrolytes. (Image: Wiley)
The air stability of oxide electrolytes (NA/LISICON) represents a significant advantage for charging system design. Unlike sulfide-based systems, charging infrastructure for oxide-based batteries does not need to incorporate extensive protective measures against air exposure. This simplifies the charging connector design and reduces the complexity of the charging interface between the vehicle and the charging station.
Due to their large band gaps, oxide electrolytes have high voltage stability. This enables charging system designs to operate at higher voltages without degrading the electrolyte. Provided other components can handle these elevated voltages, this allows for more efficient power transfer during charging and faster charging rates.
However, the sintering process at temperatures above 700 °C creates a fundamental manufacturing constraint that impacts the overall battery design and, consequently, the charging system requirements.
Polymer-based electrolytes
Polymer electrolytes’ non-flammable nature enhances charging safety, allowing for charging system designs with simplified safety mechanisms compared to liquid electrolyte systems. They also have a favorable combination of air stability, ionic conductivity, and cost (Figure 3).

Figure 3. Radar plot showing the properties of polymer-based solid-state electrolytes. (Image: Wiley)
The dendrite suppression capability of gel-based polymer electrolytes is particularly advantageous for charging system design. This characteristic allows for more flexible charging protocols that prioritize charging speed without the same level of concern for dendrite formation that exists with other electrolyte types.
The physical properties of polymer electrolytes, including their flexibility and efficient electrode contact, impact charging system design in several ways. Maintaining consistent electrode-electrolyte contact during charging, even with thermal expansion and physical stress, means charging systems can operate more reliably across various temperature conditions.
Solid polymer electrolytes’ thin-film casting capability and direct coating possibility influence the physical interface requirements of charging systems. The uniform electrolyte layer formation enables more consistent charging behavior across the battery surface, requiring charging systems to maintain even current distribution.
However, the lower mechanical properties and ionic conductivity compared to liquid electrolytes present a significant constraint for the charging system design. This limitation necessitates charging protocols that carefully balance charging speed against the electrolyte’s inherent conductivity limitations.
Figure 4 summarizes the properties of sulfide, oxide, and polymer-based solid-state batteries to give a comprehensive picture of their suitability for EV battery production.

Figure 4. Properties of key materials leading the advancement of SSBs. (Image: MDPI)
Other EV battery chemistries
Beyond solid-state electrolytes and lithium-ion batteries, a few more battery chemistries have regularly caught the attention of EV battery makers. The technologies worth mentioning are metal-air batteries, sodium-beta batteries, zinc-ion batteries, and magnesium-ion batteries.
Metal-air batteries
These batteries use a metal (such as aluminum, zinc, or lithium) as the anode and oxygen from the air as the cathode, creating a unique power source. Metal-air batteries are substantially lighter and more compact than traditional lithium-ion batteries. The batteries hold a high energy density and specific energy, respectively, making them promising for EV applications (Figure 5).

Figure 5. Theoretical energy density and specific energy of various metal-air batteries. (Image: MDPI)
Companies like Phinergy are developing metal-air batteries as range extenders for EVs. These batteries can provide additional miles of power when the primary battery is depleted, helping drivers reach a charging station.
However, traditional metal-air batteries also have serious drawbacks. They cannot be easily turned off and on, and the only way to stop the reaction is to drain the electrolyte, which can cause corrosion.
Sodium-beta batteries
Sodium-beta batteries have two promising variants: sodium/metal chloride and sodium/sulfur batteries, known for their high energy density. The sodium/metal (NA/NiCl2) can operate at a wide temperature range and has a higher power density. It is also less prone to metallic material corrosion. In a typical Na-NiCl2 cell, nickel makes up most of the cell components, which helps achieve a decent specific energy of 120-140 Wh/kg (Figure 6).

Figure 6. Weight distribution of components in a typical ZEBRA (Na-NiCl2) cell. (Image: MDPI)
However, sodium/sulfur batteries suffer from degradation and increasing internal resistance. The incremental depth of discharge further aggravates the problem. Therefore, further research is necessary to scale up for EV applications.
Zinc-ion batteries
Zinc-ion batteries have a reasonable energy density, improved safety, and are environmentally friendly. They are also economical, which makes them compelling for large-scale EV use cases. However, suitable cathode materials are being researched to ensure the proper intercalation of zinc ions, making them viable for EV battery production.
Magnesium-ion batteries
Magnesium-ion batteries have high specific energy and specific power. Magnesium is more abundant than lithium and has better safety and environmental friendliness. However, at this point, the technology needs to mature further to make any real use case in EVs.
Summary
Battery chemistries will continue to play a key role in EV battery production. At this point, solid-state batteries are promising, and more specifically, sulfide-based solid electrolytes have suitable characteristics for EV battery making. The NA/LISICON variant of oxide-based electrolytes has the best air stability characteristics and can be integrated with other oxide-based electrolyte variants. Polymer-based electrolytes are best for safety reasons because they are non-flammable.
However, while the other battery chemistries, such as metal-air, sodium-beta, zinc-ion, and magnesium-ion batteries, are promising, they require a technological breakthrough for large-scale practical applications in EVs.
References
On the Current and Future Outlook of Battery Chemistries for Electric Vehicles—Mini Review, Batteries, MDPI
Sulfide and Oxide Inorganic Solid Electrolytes for All-Solid-State Li Batteries: A Review, Nanomaterials, MDPI
Review article Overview of batteries and battery management for electric vehicles, ScienceDirect
Applications of Polymer Electrolytes in Lithium-Ion Batteries: A Review, Polymers, MDPI
A Review of Sodium-Metal Chloride Batteries: Materials and Cell Design, Batteries, MDPI
New Metal-Air Battery Design Offers a Potential Boost to Electric Vehicles, Tech Briefs
A Review of Model-Based Design Tools for Metal-Air Batteries, Batteries, MDPI
A Review on Lithium Phosphorus Oxynitride, ACS Publications
Homepage, Phinergy
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