Porous CAP/PVDF Polymer Electrolyte with Rapid Ion Transport Pathways for High-Performance Lithium-Ion Batteries

The rapid development of high-performance lithium-ion batteries (LIBs) has driven intensive research on electrolytes, which serve as a key component in governing battery performance and safety. Among the diverse electrolyte systems available for LIBs, gel polymer electrolytes (GPEs) have emerged as a research focus, owing to the superior ionic conductivity and enhanced safety characteristics. However, developing a gel polymer electrolyte combining high lithium-ion transport efficiency and structural stability remains a challenge in the field. Herein, a gel polymer electrolyte membrane composed of poly(vinylidene fluoride) (PVDF) and cellulose acetate propionate (CAP) was fabricated via the phase inversion method. CAP significantly improved electrolyte wettability while refining the porous structure of the membrane through the addition of the nonsolvent glycerol as a porogen. The PVDF/CAP composite electrolyte membrane (PCBG2) exhibited an excellent porosity of 74.54% and an electrolyte uptake of 513.33%, showing unique gel-like properties. The PCBG2 demonstrated a high ionic conductivity (1.71 mS cm^–1), a lithium-ion transference number of 0.56, and a substantial electrochemical stability window up to 4.45 V. Furthermore, the PCBG2 combined excellent flexibility with robust thermal stability, exhibiting negligible thermal shrinkage after exposure to 180 °C for 0.5 h, which effectively ensured battery operational safety under extreme conditions. The LiFePO₄||Li with PCBG2 as the electrolyte presented an initial capacity of 146.28 mAh g^–1at 0.2 C. The LiFePO₄|PCBG2|Li also exhibited exceptional capacity retention (89.02%) after 120 cycles, which was significantly superior to that of LiFePO₄|PVDF|Li. The experimental results demonstrated that PCBG2 exhibited substantial practical potential for LIBs.