Yolk-shell porous carbon spheres@CoSe2 nanosheets as multilayer defenses system of polysulfide for advanced Li-S batteries

Abstract

Restraining the shuttle effect and improving the cycling durability of lithium-sulfur (Li-S) batteries are the basic premise to realize its large-scale application, while the adsorption and catalytic capacities of the host to polysulfide lithium (Li2Sn, 4 ≤ n ≤ 8) is the key to affect those performances. Therefore, in this work, yolk-shell porous carbon spheres loaded with CoSe2 nanosheets (THC-CoSe2) are synthesized as hosts for Li-S batteries. Due to the unique microstructure, as-constructed S@THC-CoSe2 cathode not only can relieve the volume expansion of active substance, but also offer a “multilayer defensive system” to prevent the outward diffusion of Li2Sn through physical and chemical interactions simultaneously. In addition, the outermost CoSe2 nanosheets with excellent electronic conductivity is able to catalyze the transformation of Li2Sn anchored on its surface, finally accelerating the elimination of soluble intermediates and weakening the shuttle phenomenon. Based on above advantages, the initial discharge capacity of the Li-S battery assembled by S@THC-CoSe2 cathode is as high as 1230.0 mAh g−1 at the current rate of 0.1C, and the capacity attenuation of each cycle is as low as 0.034% in 1000cycles at 1.0C.