2D perovskite Enabling Super‐Fluorinated Interphasial Chemistry in Solid Polymer Electrolyte for Lithium‐metal Batteries

Abstract Solid polymers with large‐scale processability are regard as the promising electrolytes for lithium metal batteries. However, their applications simultaneously face several difficulties, including low ionic conductivity, poor interfacial stability and the incompatibility with high‐voltage cathodes. Composite solid‐state electrolytes (CSEs) capable of generating LiF‐containing interphase can alleviate these difficulties, but the low LiF content of current LiF‐containing interphase hinders the service life of lithium metal batteries. Herein, this study designs a 2D perovskite‐based CSE based on Li x TiNbO 5 nanosheets and PEO polymer. The large 2D active area and oxygen vacancies of Li x TiNbO 5 nanosheets jointly create a TFSI − ‐rich interface with electron delocalization, which then forms a super‐fluorinated interphase with ultra‐high average LiF content (≈55.3 at.%), significantly suppressing the lithium dendrites and enabling Li||Li cell to exhibit long cycling life ≈3300 h. Furthermore, this super‐fluorinated interphase, coupled with the high electrochemical stability and high ionic conductivity of 2D perovskite‐based CSE, endow LiFePO 4 || Li cell and NCM811 || Li cell to achieve a cycle life of 2350 cycles and 800 cycles at 1 C and 0.5 C, respectively. This 2D perovskite not only inspires the design of stable interphase beyond lithium systems, but expands the potential application areas of 2D nanomaterials.