Constructing Cation-Coupled MoSe₂/FeSe/C Heterostructures for Rapid and Efficient Sodium Ion Transport

Low electron conductivity and slow ion dynamics are the two key barriers limiting the use of transition-metal selenide (TMSe) anodes for high-power energy storage device applications. A rational structural design for TMSe can effectively promote the rapid transfer of Na⁺ on the surface and bulk phase. Presently, a cation-coupled MoSe₂/FeSe/C heterostructure is developed by a facile two-step reaction and applied to sodium ion batteries/capacitors (SIBs/SICs). Wherein, a unique edge mixed phase (1T/2H-MoSe₂) is generated under Fe induction. Additionally, the metal–organic framework-derived carbon guarantees structural stability and provides support for the rapid adsorption and transport of Na⁺ on the surface and bulk. Significantly, density functional theory (DFT) calculations verify that the constructed MoSe₂/FeSe heterogeneous interface has a strong metallic property that can facilitate the rapid transfer of electrons and ions within the bulk phase. As a result, the prepared MoSe₂/FeSe/C can deliver a high specific capacity of 597.2 mA h g^–1 (after 1000 cycles) at a current density of 2 A g^–1 when applied as the anode of SIBs. Impressively, 3000 cycles can be stabilized, even at a high current density of 10 A g^–1. When applied to SIC anodes, a capacity retention of 80.4% can be achieved at 2 A g^–1 after 8000 cycles. The strategy of combining cation-coupled induced phase transitions with heterostructure design can serve as a reference for exploring the potential of TMSe in high-power energy storage devices.