Few-Layer Boron Nitride with Engineered Nitrogen Vacancies for Promoting Conversion of Polysulfide as a Cathode Matrix for Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries have become one of the most promising candidates as the next generation batteries, due to their high specific capacity, low-cost, and environmental benignity. Although lots of strategies have been proposed to restrain the shuttle of lithium polysulfides (LiPSs) through physical trapping and chemical binding, the sluggish kinetics of PS conversion still degrade the capacity, rate and cycling performance of Li-S batteries. Herein, a novel kind of few-layer BN with engineered nitrogen vacancies (v-BN) has been developed as a cathode matrix for Li-S batteries. The positive vacancies existing in BN nanosheets not only promote the immobilization and conversion of LiPSs, but also accelerate the lithium ion diffusion in cathode electrodes. Compared with pristine BN, the v-BN cathodes exhibit higher initial capacities from 775 mAh g-1 to 1262 mAh g-1 at 0.1 C and a high average coulombic efficiency over 98% during 150 cycles. While increasing the current density to 1 C, the cell still preserved capacity of 406 mAh g-1 after 500 cycles, exhibiting a capacity decay of only 0.084% per cycle. The new vacancy-engineered material provides a promising method for excellent performance in Li-S batteries.