Metal-ion exsolution effect to accelerate the reaction kinetics in Li–S batteries

Abstract

Sluggish reaction kinetics in lithium–sulfur (Li–S) batteries has seriously hindered their practical application. Herein, a three-dimensional (3D) granular carbon skeleton decorated with nickel-rich NCM materials (NCM@3D-SP) is prepared as a cathode host for Li–S batteries, where the carbon matrix is rich in pore channels, can provide good conductivity and electrolyte diffusion, and NCM811 particles contribute abundant metal sulfides active sites through metal-ion exsolution. The different metal sulfides (NiS, Ni₃S₂, Ni₇S₆, and CoS) in heterogeneous structures exhibit outstanding catalytic and adsorption effects on polysulfides during cycling, where the ion diffusion coefficient is increased by approximately 2.5 times compared to the cathode without catalytic active sites (3D-SP). A Li metal battery using NCM@3D-SP/S as the cathode exhibits a capacity decay of only 0.051% per cycle at 2C after 500 cycles. Even at an ultra-high current density of 10C and a sulfur-loading of 6 mg cm⁻², the cells maintain a stable reversible discharge capacity of 453.1 mA h g⁻¹ after 500 cycles and 4 mA h cm⁻². The incorporation of nickel-rich cathode materials and 3D sulfur host structure presents a novel strategy for high-catalytic activity cathodes of Li–S batteries.