Long-cycling and high-loading lithium-sulfur battery enabled by free-standing three-dimensional porous NiCo2O4 nanosheets

The lithium-sulfur (Li-S) battery is a promising electrochemical energy storage system with ultrahigh theoretical energy density and abundant raw material, however, issues of "shuttle effect", low sulfur utilization and dendrite of lithium anode restrict its wide applications. Herein, hierarchical porous NiCo2O4 nanosheets anchored on carbon cloth framework (NCO-CC) have been prepared and applied as highly efficient sulfur host for Li-S battery. NiCo2O4 nanosheets are composed of interconnected nanoparticles and mesopores of about 300-600 nm. The porous NCO-CC can offer adequate space to increase sulfur loading and relieve the volumetric change during charge/discharge processes, and provide strong chemisorption for trapping lithium polysulfides, to effectively increase utilization and redox kinetics. The three-dimensional conductive carbon cloth substrate can be directly used as current collector, and the free-standing cathode without any carbon black and binder displays high specific capacities of 1275.1 and 732.1 mAh/g at respectively 0.1 and 5 C, and a low capacity decay rate (similar to 0.022 %/cycle) over 1500 cycles at 2 C. The novel porous NiCo2O4 nanosheet based sulfur cathode is promising to construct highly efficient and long cycling Li-S battery, and the rational design of flexible CC based hierarchical porous composites might be extended for various applications of energy and catalysis.