A surfactant-modified composite separator for high safe lithium ion battery

Separators have been gaining increasing attention to improve the performance of lithium ion batteries (LIBs), especially for high safe and long cycle life. However, commercial polyolefin separators still face the problems of rapid capacity decay and safety issues due to the poor wettability with electrolytes and low thermal stability. Herein, a novel composite separator is proposed by introducing a surfactant of sodium dodecyl thiosulfate (SDS) into the polytetrafluoroethylene (PTFE) substrate with the binder of polyacrylic acid (PAA) through the suction filtration method. The introduction of PAA/SDS enhances the adsorption energy between PTFE substrate and electrolyte through density functional theory calculations, which improves wettability and electrolyte uptake of the separator significantly. The as-achieved composite separator enables the LIBs to own high Li⁺ conductivity (0.64 × 10^-3 S cm⁻¹) and Li⁺ transference number (0.63), further leading to a high capacity retention of 93.50% after 500 cycles at 1 C. In addition, the uniform and smooth surface morphology of Li metal employed the composite separator after cycling indicates that the lithium dendrites can be successfully inhibited. This work indicates a promising route for the preparation of a novel composite separator for high safe LIBs.