A Nanocrystallite CuS/Nitrogen-Doped Carbon Host Improves Redox Kinetics in All-Solid-State Li2S Batteries

All-solid-state Li-S batteries are a promising energy storage system that can solve the shuttle effects of polysulfides in liquid Li-S batteries. However, sluggish solid-state reaction kinetics and the low conductivity of cathode materials have impeded their development. Here, a N-doped carbon embedded with CuS nanoparticles (CuSNC) is reported as a host for Li2S in all-solid-state batteries that addresses some of these issues. Electrochemical studies, supported by a combination of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), electron microscopy, and density functional theory (DFT) calculations reveal that CuSNC provides good affinity to Li2S. This lowers the activation barrier for the conversion of Li2S to sulfur on the charge, suggesting an electrocatalytic effect on the CuS surface. Li+ diffusion in the cathode and the reaction kinetics are enhanced compared to N-doped graphene. The CuSNC/Li2S cathode reaches an areal capacity of 1.8 mAh cm(-2) and a retention rate of 94% after 100 cycles. At a 1.0 mA cm(-2) current density, CuSNC/Li2S maintains stable performance over 500 cycles with a low decay rate (0.05% per cycle); at a higher Li2S loading, delivers a capacity of 9.6 mAh cm(-2), albeit with more limited cycling. This study provides a promising way to design Li2S cathodes to achieve improved reaction kinetics and better electrochemical performance.