Mesoporous hierarchical NiCoSe2-NiO composite self-supported on carbon nanoarrays as synergistic electrocatalyst for flexible lithium-sulfur batteries.

ABSTRACT

Lithium-sulfur batteries (LSBs) have enormous application potential in the flexible energy storage field due to their large theoretical specific capacities and high energy densities. However, lithium-sulfur batteries face a notorious shuttle effect problem. To address this challenge, this work reports a three-dimensional (3D) structure of binary transition metal selenides (B-TMSe) hierarchical composites (CC/NiCoSe2-NiO) on carbon cloth as a self-supporting sulfur host for flexible LSBs. According to the density functional theory (DFT) calculations, NiCoSe2can exert a synergetic effect of high affinity with Lithium polysulfides (LiPSs) and electrocatalytic activity to lower the adsorption energy barrier and accelerate the sluggish reaction kinetics of polysulfides. Consequently, the CC/NiCoSe2-NiO-based electrodes realize a large specific capacity of approximately 1363 mAh/g at a current density of 0.1C, excellent rate performance (454.66 mAh/g at 5C) and a reversible specific capacity of 978.9 mAh/g at 1C, along with impressive cycling stability with an attenuation rate of 0.038% per cycle for 1000 cycles. They also achieve a large reversible cycle capacity of 919.43 mAh/g at 0.2C even at a high sulfur loading (3.5 mg/cm2). With a lean electrolyte (E/S ratio 10 µL/mg) and a high sulfur loading of 2.65 mg/cm2, a large capacity of 934.1 mAh/g is retained after 150 cycles at 0.5C. The assembled pouch cells from S@CC/NiCoSe2-NiO electrodes show a high initial discharge capacity of 1039.5 mAh/g at 1C at a sulfur loading of 2.65 mg/cm2 and maintain strong stability under high twisting and buckling.