Multifunctional NiCo2O4 Nanosheet Assembled Hollow Nanoflower as a Highly Efficient Sulfur Host for Lithium-Sulfur Batteries

Here, a simple approach is developed to fabricate the novel NiCo2O4 hollow nanoflowers (NCOHF), which is explored as sulfur carrier materials of lithium-sulfur (Li-S) batteries. Remarkably, the capacity of the NCOHF/S composite electrodes was ~666.8 mA h g-1 in the fourth cycle and maintained at ~432.9 mA h g-1 in the 400th cycle under the current density of 1.0C, with a low decay rate of 0.087% per cycle. The overall outstanding properties of NCOHF/S composite should be attributed to the success of a new strategy of structure design by in situ and ex situ experiments. Firstly, NCOHF with bifunctional catalytic activities and chemical adsorption can efficiently promote the lithium polysulfides (LiPSs) redox reactions and suppress the diffusion of polysulfide. Secondly, NCOHF with inherently high electronic conductivity acts as a conduit to accelerate the transport of electrons and ions. Thirdly, the flower-like NiCo2O4 nanosheets are anchored tightly to conductive carbon and binder during the Li+ insertion and extraction processes, which can effectively suppress the aggregation of NCOHF/S composite during cycling. Finally, the hollow space inside NCOHF/S composite provides sufficient free space for the expansion of encapsulated pure sulfur.