Anion‐Trapping Induced Solvation Optimization for High‐Performance Polyester‐Based Quasi‐Solid‐State Lithium Metal Batteries

Abstract Compared with conventional solid polymer electrolytes (SPEs), polyester‐based quasi‐solid‐state electrolytes exhibit a wider electrochemical window and higher ionic conductivity but suffer from poor interfacial compatibility with lithium metal anodes. Here, an anion‐trapping strategy is described to design polyester‐based copolymer electrolytes (PECEs) with moderate Li⁺‐polyester (PVPT) interactions via molecular engineering of the polymer backbone, achieving excellent interfacial stability and electrochemical performance. In particular, incorporation of the fluorinated monomer 2,2,3,3‐tetrafluoropropyl methacrylate (TFMA) regulates the solvation environment via an electron withdrawing group anion trapping (EWGAT) effect, effectively traps the bis(trifluoromethanesulfonyl)imide anions (TFSI − ) through hydrogen bond interaction, promotes a solvation structure transition from ionic aggregates (AGGs) to contact ion pairs (CIPs), and balances anion‐reinforced solvation structure and ionic conductivity. As a result, the PVPT electrolyte delivers high ionic conductivity of 1.7 mS cm −1 , high Li + transference number of 0.75, and extended electrochemical window up to 5.3 V. Through an in situ polymerization approach, the PVPT electrolyte enables lithium metal batteries (LMBs) with LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathodes to achieve a high capacity retention of 85.64% over 400 cycles. This molecular design of PVPT offers a distinctive, promising strategy for developing high‐performance PECEs toward advanced quasi‐solid‐state lithium batteries with high energy density and long cycle life.