Molecularly Engineered Alternating Carbonate-Ether Solid Polymer Electrolytes via In Situ Ring-Opening Polymerization for Sustainable High-Voltage Lithium Metal Batteries

The development of all-solid-state lithium metal batteries (LMBs) demands solid polymer electrolytes (SPEs) that harmonize high ionic conductivity, electrochemical stability, and environmental sustainability. Herein, we present a molecularly engineered polycarbonate-based solid electrolyte (PCE) network synthesized via in situ ring-opening polymerization (ROP), featuring a unique cross-linked network structure of alternating carbonate-ether chemical bonds. This “rigid-flexible” architecture effectively utilizes the characteristic hierarchical structures of polymers, establishing continuous Li+ conduction pathways while suppressing crystallization. The carbonate groups enhance Li+ dissociation through weak coordination interactions, whereas the ether pendants facilitate rapid ion transport, endowing PCEs with an exceptional room-temperature ionic conductivity of 1.37 × 10–4 S cm–1 (30 °C) and an ultrawide electrochemical stability window up to 5.9 V vs Li+/Li. Furthermore, the cross-linked framework ensures mechanical robustness and dendrite suppression, enabling stable Li plating/stripping for over 5500 h. The assembled LFP/PCE-3/Li cell delivers remarkable cycling stability, maintaining a capacity retention rate of 85.8% after 1200 cycles. The cycling performance of LCO/PCE-3/Li and NCM622/PCE-3/Li cells demonstrates the potential applicability of PCE for sustainable, high-energy-density energy storage systems. Notably, the PCEs exhibit full degradation into nontoxic small molecules within 35 days under ambient conditions via hydrolysis of the carbonate backbone, addressing critical environmental challenges.