Fiber-Based Composite Separator with Stable Interface and High Ionic Transport Capacity for Lithium Batteries

Fiber-based separators are generally designed with particle composites to address the internal shorts brought by the oversized pores of the fiber layer, which typically results in high resistance due to poor interfacial compatibility and high thickness and is detrimental to the lithium battery performance. Herein, we proposed a fibrous composite separator by easily coating a nonwoven fabric with a mixture of cross-linked poly(vinyl alcohol) and silica nanoparticles. Owing to the interlaced fiber network and abundant polar groups, the prepared separator exhibits excellent electrolyte wettability, low internal resistance, and great interfacial compatibility and stability. The fiber-based separator performs better than the polyolefin separator in terms of ionic conductivity, lithium-ion transference number, and lithium dendrite inhibition. Consequently, the fiber-based separator enables the LiFePO₄//Li battery to cycle steadily with a capacity retention rate of 99.1% after 100 cycles and 82.2% after 500 cycles and also helps the Li//Li symmetrical cell to cycle stably for 800 h at 0.5 mA cm^-2. Therefore, the fibrous composite separator that can be scaled up might be a competitive substitute for lithium separators that are already on the market.