A battery material helps batteries work in cold and hot conditions, supports higher charging voltages, and maintains performance during repeated charging and discharging.
Lithium metal batteries could operate at temperatures from -40°C to 55°C while maintaining performance at high voltages, according to new research from South China Normal University. The researchers developed a solid-state polymer electrolyte that remained stable over hundreds of charge-discharge cycles and supported battery operation at voltages up to 4.5 V.
The electrolyte was tested in lithium metal batteries paired with nickel-rich NCM811 and lithium cobalt oxide cathodes. The batteries showed limited capacity loss during cycling, suggesting the material could help address some of the durability and performance challenges facing next-generation battery technologies.
The work targets several limitations of solid-state batteries. While these batteries replace flammable liquid electrolytes with solid materials, many solid-state polymer electrolytes suffer from low ionic conductivity, poor contact with electrodes, and limited stability when used with high-voltage cathodes.
To address these issues, the researchers developed a cross-linked poly(tetrahydrofuran) (poly-THF) electrolyte that forms directly inside the battery through an in-situ polymerization process. Because the material begins as a liquid before solidifying, it can spread across electrode surfaces and create close contact while remaining compatible with existing battery manufacturing methods.
A key part of the design was replacing the commonly used monomer 1,3-dioxolane with tetrahydrofuran. According to the researchers, this improved oxidation stability and allowed the electrolyte to withstand voltages of up to 4.9 V.
The team also introduced ethylene glycol diglycidyl ether as a cross-linking agent. This created a three-dimensional polymer structure that improved lithium-ion transport, increasing ionic conductivity to 3.3 mS/cm at room temperature.
Another component, lithium difluoro(oxalato)borate (LiDFOB), served several functions. Along with acting as a lithium salt and polymerization initiator, it helped form a protective interphase on both electrodes. The resulting layer reduced side reactions during battery operation and contributed to stable cycling performance.
The researchers say the combination of voltage stability, ion transport, and electrode protection could be useful for applications such as electric vehicles, electric vertical take-off and landing aircraft, and grid-scale energy storage systems. They also believe the same design strategy could be adapted for other battery chemistries, including sodium-ion and lithium-sulfur batteries.
