A Multifunctional Inorganic Composite Separator for Stable High-Safety Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries attract great attention as next-generation rechargeable batteries with high energy density owing to their high theoretical energy density. However, the dissolution issue of sulfur cathodes and the dendrite growth of lithium anodes impede their practical application. In addition, the potential safety risks of Li–S batteries might be more serious than those of lithium-ion batteries because of the use of lithium-metal anodes. In this work, a multifunctional inorganic composite separator composed of a hydroxyapatite (HAP) framework and a Mn3O4/carbon nanotube (CNT) interlayer (H@CM) is fabricated for solving the abovementioned problems. The thermally inert HAP shows a superior stability at elevated temperatures and helps suppress electrolyte combustion, leading to enhanced cell safety. At the anode side, the polar and porous HAP framework promotes uniform lithium plating. At the same time, the Mn3O4/CNT interlayer at the cathode side effectively suppresses the dissolution of polysulfides. As a result, the Li–S battery assembled with the H@CM separator exhibits an initial capacity of 1319 mAh g–1 at 0.1 C and maintains 1000 mAh g–1 after 150 cycles, and it even achieves a capacity as high as 607 mAh g–1 at 4 C (8.7 A g–1).