Porous <i>g</i>‐C₃N₄ Microspheres Wrapped by Garnet Nanoparticles Enable Solid Composite Electrolytes with Improved Ionic Conduction and Interfacial Stability

Abstract Solid composite electrolytes composed of poly(vinylidene fluoride) (PVDF) and Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 (LLZTO) hold promise for realizing practically applied solid lithium batteries (SLBs) with high safety and energy density. However, they face the issues of the LLZTO agglomeration in polymers and the dehydrofluorination of PVDF at the anode interface. To overcome these issues, porous g ‐C 3 N 4 microspheres are wrapped homogeneously by LLZTO nanoparticles via the metal‐nitrogen bonding between Li atoms in LLZTO and N atoms in g ‐C 3 N 4 and then incorporated into the composite electrolytes. The achieved LLZTO network with 3D structures provides continuous and fast ionic transport channels inside electrolytes. Additionally, g ‐C 3 N 4 with abundant N can endow the construction of a stable solid electrolyte interface (SEI) consisting of rich Li 3 N, separating PVDF from Li‐metal and suppressing the PVDF dehydrofluorination at the anode interface. Consequently, the obtained composite electrolytes with the ionic conductivity of 7.56 × 10 −4 S cm −1 at 30 °C undergo stable stripping‐plating cycles over 2000 h. The SLBs using LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622) and LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) achieve superior cycle stability with the capacity retention of 88.65% for 300 cycles and 88.22% for 150 cycles at 0.5 C, respectively. This work provides a universal strategy for constructing PVDF‐based composite electrolytes with high conductivity and interface compatibility.