Efficient polysulfides anchoring for Li-S batteries: Combined physical adsorption and chemical conversion in V2O5 hollow spheres wrapped in nitrogen-doped graphene network

Lithium-sulfur (Li-S) batteries are attracting intense attention due to its high specific capacity and low cost. However, serious lithium polysulfides (LiPS) shuttle effect and the insulating property of sulfur restrict the practical application of Li-S batteries. In this work, we put forward an efficient strategy to anchor soluble LiPS through a combination of physical adsorption and chemical conversion, which is accomplished by using a heterostructure of V2O5 hollow spheres wrapped in nitrogen-doped graphene network (VOHS/NG) as the sulfur host. The nitrogen-doped graphene (NG) network not only provides excellent conductivity but also traps the LiPS rapidly with high specific surface area. The initially adsorbed LiPS chemically react with V2O5 hollow spheres (VOHS) to form thiosulfate intermediates. These intermediates convert the soluble high-order LiPS to insoluble low-order LiPS. Hence, the shuttle effect can be restrained efficiently. Owing to the physical and chemical synergy of the two components, the VOHS/NG heterostructure with 71 wt% sulfur can deliver superior rate performance and excellent cycling stability. A high specific capacity of 970 mAh g(-1) can be obtained after 100 cycles at 0.2 C. Even cycled at 2 C for 1000 times, a reversible capability of 623 mAh g(-1) can still be achieved with the decay rate as low as 0.017% per cycle.