Carbon-Encapsulated\nBimetallic Fe–W-Based Selenides\nwith Abundant Heterogeneous Conductive Network for Superior Potassium\nIon Storage

Potassium-ion batteries (KIBs) are one of the most promising\nalternatives\nto lithium-ion batteries (LIBs) due to their high ion mobility, abundant\nresources, and low cost. However, the problems of low capacity and\npoor cycling stability of KIBs remain unsolved; therefore, it is crucial\nto explore alternative electrode materials suitable for reversible\ninsertion and extraction of K<sup>+</sup>. Herein, carbon-encapsulated\nFe<sub>3</sub>Se<sub>4</sub>/WSe<sub>2</sub> microsphere material\nassembled from nanosheets with abundant heterogeneous interfaces and\nexpanded interlayer spacing (denoted as FWSC) is designed as an anode\nmaterial for superior potassium ion storage. The microspheres assembled\nfrom nanosheets, the outer carbon coating, and the expanded layer\nspacing can expose more active sites and improve the electronic conductivity\nand structural stability of the material. The abundant heterogeneous\nconductive network not only improves the conductivity of the material\nbut also enhances the reversibility of the electrochemical reaction.\nAs a result, the FWSC exhibits outstanding cycling stability, excellent\nrate performance (the capacity retention is 53% when the current density\nis from 0.5 to 1.0 A g<sup>–1</sup>), and stable long-term\ncycle performance (a capacity of 209 mAh g<sup>–1</sup> at\n1.0 A g<sup>–1</sup> over 1000 cycles).