Enhancing potassium-ion storage through nanostructure engineering and ion-doped : a case study of Cu²⁺-doped Co₀.₈₅Se with yolk-shell structure

Abstract

Fabricating transition metal selenide (TMSe) anode materials with rapid K⁺ diffusion and high-rate performance is crucial for the advancement of potassium-ion batteries (PIBs), yet it remains a challenge. In this study, a Cu²⁺-doped Co₀.₈₅Se@N-doped carbon anode with an optimal concentration of Cu²⁺-doped and yolk-shell structure (denoted as Cu-Co₀.₈₅Se@NC-2) is developed to enhance the reaction kinetics and cycling life. The Cu²⁺-doped modulates the electronic structure of the Co₀.₈₅Se interface, improves the diffusion and adsorption of K⁺, and further promotes the charge transport efficiency, as demonstrated by theoretical calculations and experimental results. In addition, an optimal Cu²⁺-doped content is identified that is conducive to achieving the best structure and electrochemical performance. Moreover, the N-doped carbon shell effectively enhances the conductivity of the electrode and alleviates the volume change of Co₀.₈₅Se yolk during cycling. Benefiting from the above advantages, the obtained Cu-Co₀.₈₅Se@NC-2 anode exhibits excellent rate performance (208.1 mA h g⁻¹ at 10 A g⁻¹) and cycling stability (239.7 mA h g⁻¹ at 2 A g⁻¹ after 500 cycles, the capacity retention rate is up to 80.4%). This work integrates nanostructure engineering and ion-doped to provide a straightforward and effective strategy for designing advanced high-rate TMSe anodes for next-generation PIBs.