Activating Redox Kinetics of LiS via Cu, I Co-Doping Toward High-Performance All-Solid-State Lithium Sulfide-Based Batteries.

All-solid-state lithium sulfide-based batteries (ASSLSBs) have drawn much attention due to their intrinsic safety and excellent performance in overcoming the polysulfide shuttle effect. However, the sluggish kinetics of LiS cathode severely impede commercial utilization. Here, a Cu, I co-doping strategy is employed to activate the kinetics of LiS to construct high-performance ASSLSBs. The electronic conductivity and Li-ion diffusion coefficient of the co-doped LiS are increased by five and two orders of magnitude, respectively. Cu as a redox medium greatly improves the reaction kinetics, which is supported by ex situ X-ray photoelectron spectroscopy. Density functional theory calculation (DFT) shows that Cu, I co-doping reduces the Li-ions diffusion energy barrier. The co-doped LiS exhibits a remarkable improvement in capacity (1165.23 mAh g (6.65 times that of pristine LiS) at 0.02 C and 592.75 mAh g at 2 C), and excellent cycling stability (84.58% capacity retention after 6200 cycles at 2 C) at room temperature. Moreover, an ASSLSB, fabricated with a lithium-free (Si─C) anode, obtains a high specific capacity of 1082.7 mAh g at 0.05 C and 97% capacity retention after 400 cycles at 0.5 C. This work provides a broad prospect for the development of ASSLSBs with practical energy density exceeding that of traditional lithium-ion batteries.