Large-scale synthesis of few-layered copper antimony sulfide nanosheets as electrode materials for high-rate potassium-ion storage

Metal chalcogenides (MCs) have received widespread attentions in potassium ion storage, due to their high theoretical specific capacity and low cost. However, practical applications are still a challenge because of the slow diffusion rate and large ionic radius, leading to dramatic volume expansion and slow rate performance. Herein, we introduce a simple and large scale solvothermal method to synthesize high-quality two-dimensional (2D) layered CuSbS ₂ nanosheets with a thickness of about 5 nm. The thin 2D layered structure has a weak van der Waals gap and a large exposed surface area to contact the electrolyte and promotes rapid K ⁺ diffusion kinetics. In addition, the in-situ copper exsolution during potassiation process enhances the rate capability of K ⁺ storage. CuSbS ₂ half cells exhibited excellent rate performance, delivering specific capacities of 573, 505, 476, 230, 177 mAh g ⁻¹ at current densities of 0.1, 0.5, 1, 5, 10 A g ⁻¹ , respectively. The unique K ⁺ electrochemical storage mechanism and resistance change during reaction process was revealed in detail by operando XRD, XPS and TEM. Finally, potassium ion hybrid capacitors (PIHCs) with CuSbS ₂ nanosheets as anode and AC as cathode demonstrated excellent performances with the maximum energy density of 127 W h kg ⁻¹ and the power density of 2415 W kg ⁻¹ , providing an example of rationally design a high rate battery-type PIHC anode.