Fe-cation Doping in NiSe2 as an Effective Method of Electronic Structure Modulation towards High-Performance Lithium-Sulfur Batteries

Graphical Doping for batteries : Fe-doped NiSe 2 nanosheets grown on activated carbon cloth substrates provide elevated performance as Li−S free-standing cathodes. Fe-doping in NiSe 2 enables improved charge transfer and stronger interactions with the adsorbed sulfur species, as well as higher electrical conductivity. The transformation of Li 2 S 2 /Li 2 S growth from conventional 2D films to 3D particles eliminates the barriers of phase transitions during the cathode redox processes. The commercialization of Li−S batteries is hindered by the shuttling of lithium polysulfides (LiPSs), the sluggish sulfur redox kinetics as well as the low sulfur utilization during charge/discharge processes. Herein, a free-standing cathode material was developed, based on Fe-doped NiSe 2 nanosheets grown on activated carbon cloth substrates (Fe-NiSe 2 /ACC) for high-performance Li−S batteries. Fe-doping in NiSe 2 plays a key role in the electronic structure modulation of NiSe 2 , enabling improved charge transfer with the adsorbed LiPSs molecules, stronger interactions with the active sulfur species and higher electrical conductivity. Effective promotion of the sulfur redox kinetics and enhanced sulfur utilization were achieved under high areal sulfur loadings. The stronger interactions with LiPSs together with the unique 3D structure of Fe-NiSe 2 /ACC also induced the transformation of Li 2 S 2 /Li 2 S growth from conventional 2D films to 3D particles, significantly eliminating the barriers of solid nucleation and growth during the phase transition of liquid LiPSs to solid Li 2 S 2 /Li 2 S. With a high sulfur loading of 9.9 mg cm −2 , the Fe-NiSe 2 /ACC cathode enabled a high area capacity of 9.14 mAh cm −2 with a low average decay of 0.11 % per cycle over 200 cycles at 0.1 C.