Ni3S2 Anchored into N/S co-doped Reduced Graphene Oxide with Highly Pleated Structure as a Sulfur Host for Lithium-Sulfur Batteries
Reported herein is investigation of a unique cathode candidate for Li-S batteries, i.e. Ni3S2/(N, S)-RGO type hybrid materials, which are expected to optimize battery performance by elevating utilization of sulfur and chemically confining adsorption/diffusion of polysulfide. Versatile structural and compositional characterizations confirm uniform growth and strong chemical coupling of nanostructured Ni3S2 on N/S co-doped RGO matrix. Rich physical and chemical properties were revealed: large specific surface area and pore volume being beneficial for polysulfide capture; 3D conductive network supporting rapid charge transfer to the Ni3S2-polysulfide interface to improve intrinsic equilibrium of polysulfide. Specifically, integration of ~ 28.2 wt% of Ni3S2 produced a highly pleated composite with the largest BET specific surface area (618 m2 g-1) and pore volume (1.73 cm3 g−1) among the hybrids studied. This typical material also performs the best in the following battery test, recording ultra-high cycling stability over 1000 cycles at current density of 3 C with capacity decay as 0.023% per cycle. As sulfur loading per areal reached as dense as 5.8 mg cm-2, specific capacities were measured as 6.72 mAh cm-2 (at 0.05 C), while capacity retention for 200-cycle test (at 1 C) was still preserved above 72.5%.