Porous Lithium-Doped ZnO Nanosheets with Abundant Oxygen Vacancies for Accelerating Li<sup>+</sup> Transport in Solid-State Composite Electrolyte

The flexible Li‐ion conducting solid polymer electrolyte (SPE) endows a stable long‐term cycling to Li‐metal anode to significantly improve the energy density of solid‐state lithium batteries; however, the practical application of the SPE is limited by its low ionic conductivity and small critical current density for dendrite nucleation. Herein, Li+‐doped porous ZnO (LZO) nanosheets are introduced into the poly(ethylene oxide) (PEO)‐based SPE, releasing more mobile Li ions for faster Li‐ion transport due to the enhanced interaction between abundant oxygen vacancies and anions of Li‐salt. As a result, the optimized LZO/PEO composite polymer electrolyte exhibits a high Li‐ion conductivity of 3.3 × 10−4 S cm−1 at 50 °C, 4 times higher than the pure PEO electrolyte. The solid‐state LiFePO4/Li cell shows extraordinarily long‐term stable cycling, up to 1500 cycles with a high average Coulombic efficiency of 99.8%. In addition, the cycling stability of the high‐voltage LiNi0.8Mn0.1Co0.1O2 (NMC811)/Li cell was also obviously improved compared to the nondoped pure PEO electrolyte, indicating the positive contribution of the LZO on interfacial stability.