Carbon-Encapsulated Bimetallic Fe–W-Based Selenides with Abundant Heterogeneous Conductive Network for Superior Potassium Ion Storage

Potassium-ion batteries (KIBs) are one of the most promising alternatives to lithium-ion batteries (LIBs) due to their high ion mobility, abundant resources, and low cost. However, the problems of low capacity and poor cycling stability of KIBs remain unsolved; therefore, it is crucial to explore alternative electrode materials suitable for reversible insertion and extraction of K⁺. Herein, carbon-encapsulated Fe₃Se₄/WSe₂ microsphere material assembled from nanosheets with abundant heterogeneous interfaces and expanded interlayer spacing (denoted as FWSC) is designed as an anode material for superior potassium ion storage. The microspheres assembled from nanosheets, the outer carbon coating, and the expanded layer spacing can expose more active sites and improve the electronic conductivity and structural stability of the material. The abundant heterogeneous conductive network not only improves the conductivity of the material but also enhances the reversibility of the electrochemical reaction. As a result, the FWSC exhibits outstanding cycling stability, excellent rate performance (the capacity retention is 53% when the current density is from 0.5 to 1.0 A g^-1), and stable long-term cycle performance (a capacity of 209 mAh g^-1 at 1.0 A g^-1 over 1000 cycles).