Enhancing Rapid Li<sup>+</sup>/Na<sup>+</sup> Storage\nPerformance via Interface Engineering of Reduced Graphene Oxide-Wrapped\nBimetallic Sulfide Nanocages

Transition-metal sulfide is considered to be an admirable\ntransformational\nelectrode material due to low cost, large specific capacity, and good\nreversibility in lithium-ion batteries (LIBs) and sodium-ion batteries\n(SIBs). Herein, the reduced graphene oxide-wrapped open bimetallic\nsulfide (NiS<sub>2</sub>–Co<sub>3</sub>S<sub>4</sub>@rGO) nanocage,\nderived from nickel–cobalt Prussian blue, was obtained by two-step\ncalcination. There are luxuriant pore structures in the nanocage composite\nwith a specific surface area of 85.28 m<sup>2</sup> g<sup>–1</sup>, which provides plentiful paths for rapid transmission of Li<sup>+</sup>/Na<sup>+</sup> and alleviates the volume stress caused by\ninsertion and extraction of alkali metal ions. The excellent interface\ncombination of bimetallic sulfide wrapped in reduced graphene oxide\nimproves the conductivity and overall performance of the battery.\nThanks to the special interface engineering, the open NiS<sub>2</sub>–Co<sub>3</sub>S<sub>4</sub>@rGO nanocage composite displays\nrapid lithium storage properties with an average diffusion coefficient\nof 8.5 × 10<sup>–13</sup> cm<sup>2</sup> s<sup>–1</sup>. Moreover, after 300 cycles, the reversible capacity of the composite\nis 1113.2 mAh g<sup>–1</sup> at 1 A g<sup>–1</sup>.\nIn SIBs, the capacity of the open NiS<sub>2</sub>–Co<sub>3</sub>S<sub>4</sub>@rGO composite is 487.9 mAh g<sup>–1</sup> when\nthe current density is 5 A g<sup>–1</sup>. These preeminent\nperformances demonstrate the enormous development prospects of bimetallic\nsulfide nanocage as anode material in LIBs and SIBs.