Enhancing Potassium‐Ion Storage through Nanostructure Engineering and Ion‐Doped: A Case Study of Cu ²⁺ ‐Doped Co _0.85 Se 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 Cu ²⁺ ‐doped Co _0.85 Se@N‐doped carbon anode with an optimal concentration of Cu ²⁺ ‐doped and yolk‐shell structure (denoted as Cu‐Co _0.85 Se@NC‐2) is developed to enhance the reaction kinetics and cycling life. The Cu ²⁺ ‐doped modulates the electronic structure of the Co _0.85 Se 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 Cu ²⁺ ‐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 Co _0.85 Se yolk during cycling. Benefiting from the above advantages, the obtained Cu‐Co _0.85 Se@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.