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Abstract The application of solid polymer electrolytes (SPEs) in all‐solid‐state(ASS) batteries is hindered by lower Li + ‐conductivity and narrower electrochemical window. Here, three families of ester‐based F‐modified SPEs of poly‐carbonate (PCE), poly‐oxalate (POE) and poly‐malonate (PME) were investigated. The Li + ‐conductivity of these SPEs prepared from pentanediol are all higher than the counterparts made of butanediol, owing to the enhanced asymmetry and flexibility. Because of stronger chelating coordination with Li + , the Li + ‐conductivity of PME and POE is around 10 and 5 times of PCE. The trifluoroacetyl‐units are observed more effective than −O−CH 2 −CF 2 −CF 2 −CH 2 −O− during the in situ passivation of Li‐metal. Using trifluoroacetyl terminated POE and PCE as SPE, the interfaces with Li‐metal and high‐voltage‐cathode are stabilized simultaneously, endowing stable cycling of ASS Li/LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622) cells. Owing to an enol isomerization of malonate, the cycling stability of Li/PME/NCM622 is deteriorated, which is recovered with the introduce of dimethyl‐group in malonate and the suppression of enol isomerization. The coordinating capability with Li + , molecular asymmetry and existing modes of elemental F, are all critical for the molecular design of SPEs.
Xie et al. (Mon,) studied this question.