Metallically conductive TiB₂ as a multi-functional separator modifier for improved lithium sulfur batteries

A metallically conductive TiB₂ is developed to construct multifunctional separator toward improved lithium-sulfur (Li–S) battery performance. Coupled with two-dimensional graphene, the obtained TiB₂@G separator fulfills a synergistic combination of strong physical and chemical sulfur immobilization as well as a high-efficiency sulfur reutilization, thus establishing a robust barrier against the polysulfide shuttling and enabling a fast and durable sulfur electrochemistry. As a result, cells based on TiB₂@G separator exhibit a high sulfur utilization with 1350 mA h g⁻¹ capacity at 0.05C, superb rate capability up to 5.0C, and excellent cyclability with a high capacity retention over 85% after 300 cycles at 0.5C. Moreover, significantly mitigated self-discharge and considerably high areal capacity of 5.8 mA h cm⁻² can be also achieved, indicating the great promise of this separator design for the development of high-performance Li–S batteries.