Catalytic Co₉S₈ decorated carbon nanoboxes as efficient cathode host for long-life lithium-sulfur batteries

Lithium sulfur (Li-S) batteries with high specific capacity and energy density can bring enormous opportunities for the next-generation energy storage systems. However, the severe dissolution and shuttle effect of lithium polysulfides (LiPSs) is still the key issue that seriously impedes the development of practical Li-S batteries. Here, polar Co₉S₈ inlaid carbon nanoboxes (Co₉S₈@C NBs) have been investigated as cathode host for high-performance Li-S batteries. In this integrated structure, Co₉S₈ nanocrystals not only provide strong chemisorptive capability for polar LiPSs, but also act as a catalyst to accelerate polysulfide redox reactions; while carbon nanobox with large inner space can offer enough space to relieve the volume expansion and physically confine LiPSs’ dissolution. As a result, the S/Co₉S₈@C NBs cathode exhibits high specific capacity at 1C and the capacity retention was ~ 83% after 400 cycles, corresponding to an average decay rate of only ~ 0.043% per cycle.