Multi-interface Combination of Bimetallic Selenide and VCT MXene for High-Rate and Ultrastable Sodium Storage Devices.

Sodium-ion batteries (SIBs) have great potential as electrochemical energy storage systems; however, their commercial viability is limited by the lack of anode materials with fast charge/discharge rates and long lifetimes. These challenges were addressed by developing a multi-interface design strategy using FCSe (FeSe/CoSe) nanoparticles on VCT MXene nanosheets as conductive substrates. The heterogeneous interface created between the two materials provided high-speed transport of sodium ions, suppressed the chalking-off of nanoparticles, and improved the cycling stability. Additionally, the Fe-Co bonds generated at the interface effectively relieved mechanical stress, further enhancing the electrode durability. The C@FCSe@VC electrode exhibited high-speed charging and discharging characteristics, and maintained a high specific capacity of 260.5 mAh g even after 15,000 cycles at 10 A g, with a capacity retention rate of 50.2% at an ultrahigh current density of 20 A g. Furthermore, the composite displayed a good cycling capability in the fast discharge and slow charge mode. This demonstrates its promising commercial potential. This multi-interface design strategy provides insights and guidance for solving the reversibility and cycling problems of transformed selenide anode materials.