Uniform α-Ni(OH)2 hollow spheres constructed from ultrathin nanosheets as efficient polysulfide mediator for long-term lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries are of great importance as promising electrochemical-energy storage systems in view of their overwhelming advantage of energy density . However, their commercial applications are still far away mainly due to fast capacity decay in a high sulfur content caused by low utilization of active material and severe polysulfide dissolution during electrochemical cycling. Here we have designed and prepared uniform α-Ni(OH) 2 hollow spheres constructed from ultrathin nanosheets with the thickness of ~3.5   nm as a hollow sulfur nanosphere host for Li-S batteries. Specifically, the synthesized hierarchical hollow spheres not only manifest the advantages of hollow structure and robust protective shell to encapsulate a very high content of sulfur up to 81   wt%, but also offer sufficient functionalized surfaces to directly bond and entrap polysulfides in hollow sphere. When used as cathode materials for Li-S batteries, the S@Ni(OH) 2 double-shell hollow hybrids exhibit a highly stable cycle life over 1000 cycles at 1   C with a very small capacity decay rate of only ~0.04% per cycle.