Metal sulfides are promising anodes for potassium-ion batteries (PIBs) due to their high theoretical capacity and abundant active sites; however, their intrinsic low conductivity and poor cycling stability hampered their practical applications. Given this, the rational design of hybrid structures with high stability and fast charge transfer is a critical approach. Herein, CoS2/ZnS@rGO hybrid nanocomposites were demonstrated with stable cubic phases. The synergistic effect of the obtained bimetallic sulfide nanoparticles and highly conductive 2D rGO nanosheets facilitated excellent long-term cyclability for potassium ion storage. Such hybrid nanocomposites delivered remarkable ultrastable cycling performances in PIBs of 159, 106, and 80 mA h g-1 at 1, 1.5, and 2 A g-1 after 1800, 2100, and 3000 cycles, respectively. Moreover, the full-cell configuration with a perylene tetracarboxylic dianhydride organic cathode (CoS2/ZnS@rGO∥PTCDA) exhibited a better electrochemical performance. Besides, when the CoS2/ZnS@rGO nanocomposites were applied as an anode for sodium-ion batteries, the electrode demonstrated a reversible charge capacity of 259 mA h g-1 after 600 cycles at 2 A g-1. In situ X-ray diffraction and ex situ high-resolution transmission electron microscopy characterizations further confirmed the conversion reactions of CoS2/ZnS during insertion/desertion processes. Our synthesis strategy is also a general route to other bimetallic sulfide hybrid nanocomposites. This strategy opens up a new roadmap for exploring hybrid nanocomposites with feasible phase engineering for achieving excellent electrochemical performances in energy storage applications.
Keywords: CoS2/ZnS nanoparticles; full cell; graphene sheets; in situ XRD; potassium ion battery.