Separator engineering toward practical Li-S batteries: Targeted electrocatalytic sulfur conversion, lithium plating regulation, and thermal tolerance

Rechargeable Li-S batteries (LSBs) have aroused wide research interest due to their high energy density, yet still have many intractable challenges such as the sluggish sulfur electrochemistry, polysulfide shuttling, as well as hazardous Li corrosion/dendrites issues to be addressed. Here, we have simultaneously addressed these challenges by developing a multifunctional PP separator covered by functional layers to regulate the interfacial electrochemistry in LSBs. The functional layer consisting of VS4 and tannin acid can synergistically work as redox mediators to catalyze the sulfur conversion and a buffer layer to regulate Li ions stripping/deposition behaviors. The LSBs with the as-designed multifunctional separator can deliver a considerable capacity of more than 3 mA h cm−2 after 400 cycles, realize a stable cycling performance for 1200 cycles, and show excellent thermal tolerance even at a high temperature of 130 °C. By combining with the feasible manufacturing process, this separator engineering strategy bridges the electrode reactions initially and demonstrates safe LSBs for practical application.