Lithium-ion batteries (LIBs) are key devices for energy storage in modern day life. However, conventional LIBs suffer from several safety issues caused by the organic liquid electrolytes. Replacing the organic component with a piece of lithium-ion conductive ceramic, i.e., solid electrolyte, can in general solve the problem. Garnet-based oxide Li7La3Zr2O12(LLZO) is known to have good conductivity and stability when doped with proper dopants such as Ta, making it a promising solid electrolyte. However, due to the solid-solid contact problem with electrodes, the performance of solid-state batteries are not satisfactory.
We developed a modified plastic-crystal material based on succinonitrile that could be used as a deformable interlayer between electrodes and the solid electrolyte. The high lithium conductivity and the plasticity of the interlayer enables a good performance of the solid-state Li|LLZO|LiFePO4 battery even at room temperature. By adding a stabilizer to succinonitrile, we were able to use the interlayer at both LiFePO4|LLZO and Li|LLZO interface. The battery could be stably cycled at room temperature with a capacity of 140mAh/g.