Two-Dimensional Fluorinated Graphene Reinforced Solid Polymer Electrolytes for High-Performance Solid-State Lithium Batteries

Solid polymer electrolytes (SPEs) hold a great promise in the application of solid-state lithium batteries, but suffer from poor mechanical properties and uncontrolled electrode/electrolyte interfacial reaction, which restrict their overall electrochemical performance. Herein, the design of 2D fluorinated graphene-reinforced PVDF-HFP-LiTFSI (FPH-Li) polymer electrolytes to address these challenges is reported. Uniformly dispersed fluorinated graphene induces a unique grain refinement effect, which effectively improves the mechanical properties without excessively increasing the thickness of the polymer electrolyte. Significant reduction in polymer grain size enhances interfacial lithium ion (Li-ion) transport and homogenizes Li-ion flux, thereby improving Li-ion conductivity and promoting uniform Li plating/stripping. Furthermore, extensive characterizations show that fluorinated graphene is involved in the construction of a stable artificial interface, which effectively prevents the side reactions between the lithium metal anode and solvated molecules. As a result, the use of thin FPH-Li polymer electrolytes (thickness of ≈45 µm) enables long-term Li plating/stripping with a small overpotential in Li/Li symmetrical cells and stable cycling of Li/LiNi_0.6Co_0.2Mn_0.2O₂ full cells with a high average Coulombic efficiency of 99.5% at 1.0 C. This work verifies the effectiveness of 2D materials in improving the comprehensive properties of polymer electrolytes and promotes the applications of SPEs in high-performance solid-state lithium batteries.