Closed-Loop Recyclable Solid-State Polymer Electrolytes Enabled by Reversible Lithium Salt Catalysis

The rapid expansion in lithium battery production and disposal presents considerable sustainability challenges, emphasizing the critical need for recycling. However, current methods predominantly focus on metals from cathodes, while electrolytes have rarely been recycled. Here, we propose an innovative closed-loop design for solid polymer electrolytes (SPEs), enabled by reversible catalysis of lithium bis(trifluoromethane) sulfonimide (LiTFSI) in both polymerization and depolymerization. The formation of a hydrogen-bonded adduct between TFSI^- and alcohol initiates the in situ ring-opening polymerization of Li⁺-activated trimethylene carbonate (TMC), generating well-defined SPEs. With delicate structural optimization, the SPE achieves an outstanding ionic conductivity of 1.62 × 10^-3 S cm^-1 at room temperature with robust high-voltage stability up to 4.7 V. The assembled Li||NCM811 demonstrates promising cycling stability with 88% capacity retention over 100 cycles. Upon end-of-life, LiTFSI facilitates selective depolymerization of the polycarbonate-based SPE at 180 °C without introducing external catalysts, recovering both TMC monomer (>90%) and LiTFSI (>98%) for reuse. This work highlights a significant advance in closed-loop recyclable SPEs and a vital step toward sustainable lithium battery technology.