Cobalt sulfide quantum dot embedded in nitrogen/sulfur-doped carbon nanosheets as a polysulfide barrier in Li-S batteries

Abstract

Abstract Lithium-sulfur (Li-S) batteries are considered to be one of the most promising next-generation energy storage systems, due to their low cost and high theoretical energy density (2600 W h kg −1). However, the shuttle effect seriously limits the practical use of Li-S batteries. In this work, we demonstrate cobalt sulfide quantum dot embedded nitrogen/sulfur-doped carbon nanosheets composite material (CoSx QD-NSC) as coating material for commercial polypropylene (PP) separator (celgard 2400) in Li-S batteries. It is able to act as an efficient barrier for the blocking of polysulfides in Li-S batteries. The cell with modified separator, at the sulfur loading of 1.6 mg cm−2, can exhibit a high initial specific capacity of 1250 mAh g −1 at 500 mA g−1, with a capacity retention of 73.6% after 100 cycles. When cycled at 1 C (1675 mA g−1), the cell can deliver a high initial specific capacity of 874 mAh g−1 and a reversible specific capacity of nearly 500 mAh g −1 after 1000 cycles, exhibiting an average capacity fading of only 0.05% per cycle. The excellent performance is ascribed to the efficient adsorption of the CoSx QD-NSC to polysulfides, which inhibits the shuttle effect in Li-S batteries. The CoSx QD-NSC modified separator in this work provides new insights and opportunities for the development of advanced Li-S batteries.