Coupling the fast electron transportation of cobalt diselenide-based anode via cationic modulation for high rate Na+ storage

The sodium-ion batteries (SIBs), as compelling candidate for partially replacing lithium-ion batteries (LIBs) in relevant application scenarios, is gaining increasing attention. The development of high-rate performance anode materials for sodium-ion batteries is exceptionally crucial. Here, a ZIF (zeolitic imidazolate framework) compound targeting bimetallic cations has applied through a pyrolysis-induced in-situ selenization strategy. This resulted in a nitrogen-doped porous carbon-encapsulated Fe-ion-modified CoSe ₂ material with a rhombic dodecahedron morphology (Fe-CoSe ₂ @NC). The architecture not only effectively alleviates the bulk stress induced by the insertion/extraction of sodium ions, but also enhances the migration and transport of electrons/ions. Additionally, Fe doping enhances the material`s conductivity and expedites reaction kinetics. Consequently, the Fe-CoSe ₂@NC exhibits outstanding rate performance and cycling stability (362.54 mAh g ^-1 after 1000 cycles at a current density of 10.0 A g ^-1) when utilized as an anode for SIBs in a coin-type half-cell. The Fe-CoSe ₂ @NC also delivers a high initial coulombic efficiency (ICE) of 70.14%. This is substantiated by diffusion analysis and in-situ electrochemical impedance spectroscopy (EIS) characterization. The charging and discharging mechanisms of Fe-CoSe ₂ @NC were verified through XRD and TEM characterizations during the electrochemical processes. When coupled with Na ₃V ₂(PO ₄) ₃ as the cathode material to form a full cell, the Fe-CoSe ₂@NC// Na ₃V ₂(PO ₄) ₃ battery system achieves a high energy density of 112.05 Wh kg ^-1 . In this study, the successful construction of a transition metal selenide anode material for SIBs characterized by a stable structure and facilitation of rapid ion migration was demonstrated.