In Situ Formed Poly(ester-alt-acetal) Electrolytes with High Oxidation Potential and Electrode–Electrolyte Interface Stability

The advancement of polymer electrolytes (PEs) for reliable lithium metal batteries (LMBs) is highly desired but is limited by the lack of polymers that have satisfied stability for lithium metal anodes and high-voltage cathodes. This work reports a poly(ester-alt-acetal) (PEA) electrolyte, in situ formed by the cationic copolymerization of 1,3-dioxolane and glutaric anhydride in the presence of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). The PEA-based PE presents stable lithium plating/stripping behaviors in symmetric lithium cells for up to 2000 h and a high oxidation potential of 5.2 V versus Li/Li⁺. The ester-alt-ether structure can form multiple coordination configurations with Li⁺ and suppress concentration polarization through interactions with TFSI^–. The density functional theory calculations reveal that the intermolecular interaction between PEA and dissociated LiTFSI governs the highest occupied molecular orbital–lowest unoccupied molecular orbital energy levels, thereby promoting favorable compatibility between PEA and electrodes. This work provides a new PE to construct LMBs with improved electrode–electrolyte stability.