A domestic research team has developed a film-type electrolyte for solid state batteries. (Ulsan National Institute of Science and Technology)

By Koh Hyunjeong

A domestic research team has extended the lifespan of a non-explosive and all-solid state battery through a simple process of "stretching" a film-shaped electrolyte.

The team announced on Nov. 17 that it developed an electrolyte that can create all-solid state batteries that last long. Leading the research were professors Kang Seokju of the Department of Energy and Chemical Engineering at Ulsan National Institute of Science and Technology and Joo Se Hun of Sookmyung Women's University's Department of Chemical and Biological Engineering.

Electrolytes are a key material that allows lithium ions to move between a battery's anodes and cathodes.

Solid electrolytes are far safer than their liquid counterparts due to lower risk of explosion and fire. But their relatively low ionic conductivity has limits, as repeated charging and discharging increases internal resistance and reduces capacity.

The researchers developed their film-type electrolyte based on a fluorinated polymer (PVDF-TrFE-CFE) that greatly enhances lithium ion mobility.

The principle is that the stretching process straightens the internal winding polymer chains, something that opens a pathway for lithium ions to move.

Experiments showed that the rate of lithium ion diffusion of the pure polymer electrolyte that underwent stretching skyrocketed 4.8 times than that of the unstretched electrolyte, with ionic conductivity also rising 72%.

"Polymer electrolytes are more flexible and easier to mass produce than inorganic solid electrolytes," Kang said. "This will help speed up the commercial application of safer and longer-lasting solid state batteries."

hjkoh@korea.kr