Defect-Rich g-C3N4 Nanosheets Catalyze PEO-Based Electrolytes to Create Fluorine-Rich Interfaces for High-Rate All-Solid-State Lithium-Metal Batteries

Although poly(ethylene oxide) (PEO) based electrolytes have attracted significant interest in all-solid-state lithium-metal batteries, the inferior ionic conductivity and poor interfacial incompatibility with lithium-metal have limited their practical application. Herein, nitrogen-defect-abundant g-C₃N₄ (V_N-CN) nanosheets are introduced into PEO to form composite solid electrolytes (V_N-CN-PEO). The rich defects act as "electron traps" that effectively weaken Li⁺ coordination with the anions and facilitate the decomposition of lithium salt, thus forming a LiF-rich interface with the Li anode. Therefore, the V_N-CN-PEO exhibits reduced interfacial resistance with electrodes, improved Li⁺ conductivity, and high mechanical strength. As a result, the Li symmetrical cells exhibit ultralong plating/stripping cycling for 3600 h at 0.1 mA cm^-2. The Li/V_N-CN-PEO/LiFePO₄ cells deliver a capacity retention of 90% after 300 cycles at 0.2 C under 30 °C. Even the pouch cells show 81% capacity retention after 300 cycles at 0.1 C under 60 °C.