Researchers at the Chinese Academy of Sciences said they developed a solid-state lithium-metal battery that achieved an energy density of 451.5 Wh/kg while operating under ultra-fast charging conditions equivalent to roughly three-minute charge and discharge cycles.

The team reported that the battery maintained stable cycling for 700 cycles with 81.9 percent capacity retention when paired with a 4.7V high-nickel cathode under a 20C charging rate.

Researchers focused on improving polymer electrolytes based on polyvinylidene fluoride, or PVDF, a material widely studied for solid-state batteries because of its oxidation stability and ionic conductivity.

According to the researchers, conventional plasticizers used in PVDF electrolytes often suffer from poor electrochemical stability, leading to side reactions that reduce compatibility with lithium-metal anodes and high-voltage cathodes.

Fixing unstable electrolytes

To solve the issue, the team developed what it described as a “compatibilizing-solvent plasticization” strategy. The approach uses a temporary volatile solvent during electrolyte preparation to improve compatibility between the polymer and stable plasticizers. As the solvent evaporates during film formation, the plasticizer remains trapped inside the polymer network.

The researchers said the method enabled the formation of a lithium fluoride-rich interfacial layer while suppressing unwanted side reactions at both electrodes.

The study abstract also reported an average lithium plating and stripping Coulombic efficiency of 99.1 percent over 1,400 cycles.

Researchers used sulfolane as the representative plasticizer in the electrolyte system. According to the study, interactions between the polymer and sulfolane suppressed plasticizer migration and stabilized the electrolyte structure during battery operation.

The team also demonstrated an ampere-hour-level pouch cell using a thin lithium-metal anode with an N/P ratio of 1.1. The pouch cell achieved an energy density of 451.5 Wh/kg, more than double the energy density typically associated with many commercial lithium iron phosphate EV battery cells.

Racing toward commercialization

The pouch cell also passed a nail-penetration test, which researchers described as evidence of strong intrinsic safety performance.

The latest findings arrive as battery makers and research institutes push to commercialize solid-state battery systems capable of delivering higher energy density, faster charging, and improved safety compared to conventional lithium-ion batteries.

Several Chinese battery developers are targeting commercial solid-state battery systems in the 400 Wh/kg to 500 Wh/kg range between 2026 and 2027 while continuing work on lithium-metal and semi-solid-state technologies.

Despite accelerating investment in next-generation battery systems, lithium iron phosphate chemistry continues to dominate China’s EV battery market because of lower costs and large-scale manufacturing maturity.

The researchers said the work could expand the design space for PVDF-based polymer electrolytes and provide a potential pathway toward practical lithium-metal batteries with both high energy density and fast charging capability.

The study was published in the Journal of the American Chemical Society.