Abstract
Poly(ethylene oxide)(PEO)polymer electrolytes(PEs)have been commercially applied in LiFePO4||Li solid-state lithium batteries(SSLBs).However,it remains challenging to develop PEO-based PEs appli-cable to the high-voltage SSLBs with higher energy density,owing to the poor electrochemical stabil-ity of PEO.Herein,we report a scalable strategy for fabricating PEO-based PEs with high-voltage com-patibility,by exploiting a new mechanism to stabilize the cathode-electrolyte interface in the high-voltage SSLBs.The protocol only involves a one-pot synthesis procedure to covalently crosslink the PEO chains,in the presence of high-content lithium bis(trifluoromethylsulphonyl)imide(LiTFSI)salts and N,N-dimethylformamide(DMF).LiTFSI-DMF supramolecular aggregates are formed and firmly embedded in the polymer network,endowing the PE with high room-temperature ionic conductivity.The dissociated and highly concentrated TFSI-anions can enter the Helmholtz layer close to the high-voltage cathode,leading to the formation of a thin and homogeneous cathode electrolyte interface(CEI),mainly com-posed of LiF,on the cathode.The CEI with high electrochemical stability can effectively stabilize the cathode-electrolyte interface,enabling long-term stable cycling of the high-voltage LiCoO2||Li and nickel-rich NCM622||Li batteries at room temperature.The simplicity and scalability of the strategy makes the reported PEO-based PE potentially applicable in high-voltage SSLBs in practice.
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