An ion conducting ZIF-8 coating protected PEO based polymer electrolyte for high voltage lithium metal batteries

Solid polymer electrolyte with broad electrochemical stability window is regarded as the most promising candidate for high-voltage lithium metal batteries enabling high specific energy density. However, solid polymer electrolyte without particular protection is not facile to realize stable cycle of LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) cathode at high voltage because of the strong oxidizing property from the direct contact between cathode and electrolyte. Herein, an ion conducting asymmetric poly(ethylene oxide) (PEO) based electrolyte composed of zeolitic imidazolate framework (ZIF-8)@ionic liquid protective coating on NCM811 cathode surface and PEO-based electrolyte with ZIF-8 nanofillers on lithium metal anode is prepared in order to construct high-performance solid-state lithium metal batteries. The as-prepared asymmetric composite electrolyte exhibits a high ionic conductivity of 9.02 × 10 -4 S/cm at 60 °C and broad electrochemical stability window of above 4.9 V. Notably, the as-prepared cells exhibit the highest discharge capacity of 150 mAh/g at 0.2C under 60 °C. It is found that the ZIF-8@ionic liquid protective coating effectively prevents the oxidative decomposition of PEO based electrolyte at high voltage and the transition metal dissolution from the cathode. Meanwhile, the growth and penetration of lithium dendrites are also restrained, which shows significant potential for boosting the commercialization of high-voltage lithium metal batteries.