Interface-stabilized gel polymer electrolyte for high-performance lithium metal batteries

Lithium metal batteries demand electrolytes that combine high ionic conductivity with mechanical robustness and interfacial stability. This study presents a novel composite gel polymer electrolyte (GPE) engineered by integrating a cyano-functionalized polysiloxane (PCMS) frameworks, diethylene glycol dimethyl ether (DEGDME) plasticizers, and electrospun polyacrylonitrile (PAN) nanofiber scaffolds. The optimized GPE system achieves an exceptional combination of properties: high ionic conductivity (3.3 × 10^-3 S cm^-1 at 30 °C), outstanding Li⁺ transference number (0.79), and remarkable mechanical strength (3.9 MPa). Theoretical calculations and experimental analyses collectively confirm that the -CN groups competitively coordinate with Li⁺, restructuring the solvation environment to favor TFSI^- anion participation, thereby facilitating the formation of a robust solid electrolyte interphase (SEI) enriched with LiF and Li₃N. As a result, the GPE demonstrates a wide electrochemical stability window (5.3 V vs. Li⁺/Li) and stable lithium plating/stripping for 1000 h at 0.1 mA cm^-2. Additionally, LiFePO₄/GPE/Li full cells achieve 94.9% capacity retention after 500 cycles at 0.5C, while NCM811/GPE/Li cells deliver a high discharge capacity of 153.8 mAh g^-1 with 86.5% retention after 150 cycles. This work establishes a scalable and promising strategy for the development of high-performance lithium metal batteries.