Ultrathin Layered Double Hydroxide Nanosheets Enabling Composite Polymer Electrolyte for All‐Solid‐State Lithium Batteries at Room Temperature

Abstract Solid electrolytes are the most promising substitutes for liquid electrolytes to construct high‐safety and high‐energy‐density energy storage devices. Nevertheless, the poor lithium ion mobility and ionic conductivity at room temperature (RT) have seriously hindered their practical usage. Herein, single‐layer layered‐double‐hydroxide nanosheets (SLN) reinforced poly(vinylidene fluoride‐ co ‐hexafluoropropylene) (PVDF‐HFP) composite polymer electrolyte is designed, which delivers an exceptionally high ionic conductivity of 2.2 × 10 −4 S cm −1 (25 ° C), superior Li + transfer number ( ≈ 0.78) and wide electrochemical window ( ≈ 4.9 V) with a low SLN loading ( ≈ 1 wt%). The Li symmetric cells demonstrate ultra‐long lifespan stable cycling over ≈ 900 h at 0.1 mA cm −2 , RT. Moreover, the all‐solid‐state Li|LiFePO 4 cells can run stably with a high capacity retention of 98.6% over 190 cycles at 0.1 C, RT. Moreover, using LiCoO 2 /LiNi 0.8 Co 0.1 Mn 0.1 O 2 , the all‐solid‐state lithium metal batteries also demonstrate excellent cycling at RT. Density functional theory calculations are performed to elucidate the working mechanism of SLN in the polymer matrix. This is the first report of all‐solid‐state lithium batteries working at RT with PVDF‐HFP based solid electrolyte, providing a novel strategy and significant step toward cost‐effective and scalable solid electrolytes for practical usage at RT.