context: Lithium–sulphur (Li–S) batteries with high theoretical capacity, cost-effectiveness and environmental sustainability have attracted tremendous interest as the next generation rechargeable batteries. However, the performance of Li–S batteries is constrained by sulphur's low conductivity and large volume change during lithiation/delithiation. As the cathode matrix for the sulphur cathode, h-BNNS with nitrogen vacancies (v-BN) were found to improve the cycling performance of Li–S batteries. Compared with the pristine h-BN electrode, the v-BN electrode demonstrated significantly improved capacity. The engineered vacancies were believed to improve the kinetics of polysulphide conversion, lithium-ion diffusion rate, and protection of the Li anode from corrosion.
answer: sulphur 