Green and continuous preparation of poly(vinylidene fluoride)/SiO2 composite membrane with interpenetrating bicontinuous porous architecture

As a critical component in lithium-ion batteries (LIBs), the separator significantly influences the electrochemical performance and safety of the batteries. However, conventional polyolefin separators suffer from poor ionic conductivity and limited thermal stability, hindering further improvements in battery charge–discharge property. This study introduces a poly(vinylidene fluoride)/nano-silica (PVDF/SiO 2 ) composite microporous membrane with interpenetrating dual-continuous pore structures, fabricated via a green and efficient thermally induced phase separation (TIPS) process using environmentally friendly diluents. The resulting membrane,with a thickness of 14 μm, incorporates uniformly dispersed nano-silica (nmSiO₂) particles, which significantly enhance electrolyte wettability and thermal stability. The composite membrane exhibits an impressive ionic conductivity of 1.35 mS/cm, thermal shrinkage of only 3.58% at 160 °C, and excellent structural integrity at 200 °C. Electrochemical tests using Li||LiFePO 4 (12 mg/cm −2 ) cells demonstrate that the PVDF/SiO 2 composite membrane delivers superior cycling stability (> 200 cycles) and a higher capacity retention rate (86.9%) compared to commercial polyolefin membranes. These findings underscore the developed membrane,s exceptional properties and highlight the success of a green and efficient process for fabricating PVDF/SiO 2 composite microporous membranes, paving the way for their application in high-performance LIBs. Graphical abstract