Ni0.85Se/NiSe2-C electrocatalyst with defect engineering and heterostructure for the multifunctional acceleration of lithium polysulfide conversion

Reasonably designed sulfur cathode materials are one of the effective ways to solve the shuttle effect of lithium polysulfide (LiPSs) and the sluggish electrochemical reaction kinetics of lithium-sulfur batteries (LSBs), in which the defect engineering and multi-component heterostructures design has received extensive attention. In this work, a composite material of Ni0.85Se/NiSe2 decorating carbon tubes (N0.85S/NS2-C) with cation vacancy and heterostructure was successfully constructed. The experimental results confirm that the Ni0.85Se cation vacancies and Ni0.85Se/NiSe2 heterostructure enhance the intrinsic catalytic activity and the chemisorption capacity toward LiPSs, reduce the nucleation barrier of Li2S, and accelerate the electrochemical reaction kinetics. Simultaneously, the carbon tubes improve the electronic conductivity of the sulfur electrode and inhibit the agglomeration of Ni0.85Se/NiSe2 nanoparticles. By incorporating both heterostructure and cation vacancy, efficient multifunctional coupling of adsorption-catalysis-conversion toward LiPSs is achieved. The N0.85S/NS2-C/S electrode exhibited satisfactory electrochemical performance, it delivered a low-capacity attenuation of 0.083 % per cycle during 450 cycles at 1 C. Under a sulfur loading of 2.9 mg cm -2, a high initial specific discharge capacity of 1126 mA h g-1 can be obtained at 0.1 C rate. This work will provide a feasible scheme and new ideas for the designing of multifunctional coupling sulfur host materials for efficient LSBs.