Bimetallic Hexagonal Layered Ni-Co Sulfides with High Electrochemical Performance for All-Solid-State Lithium Batteries

All-solid-state lithium (Li) batteries have been emerging as attractive technologies for energy storage systems due to their benefits in safety. However, the electrochemical performance of all-solid-state Li batteries is limited by the interfacial problems resulting from the solid-solid contact between electrolytes and electrodes. Here, a binary transition-metal sulfide NixCo3-xS4 with a special hexagonal layered structure is synthesized and introduced into all-solid-state Li batteries based on sulfide electrolytes. By freely adjusting the Ni/Co ratio, components with optimal performance can be easily obtained. In addition, the well-designed interfacial structure is favorable for ion transport and interfacial stability because the sulfide electrolyte particles can rivet on the hexagonal platelets which can maximally reduce the contact resistance between the solid electrolytes and cathodes. As a result, the all-solid-state Li battery employing the Ni0.3Co2.7S4@Li7P3S11 composite cathode exhibits enhanced rate capability and cycling stability. At a current density of 0.1 A g(-1), it delivers a specific capacity as high as 1216 mA h g(-1). Even under a large current of 1 A g(-1), a large capacity of 510 mA h g(-1) can be retained after 100 cycles.