Multilayered bimetallic selenide heterointerfaces embedded in gradient-doped hollow carbon scaffold for advanced sodium-ion batteries and hybrid capacitors

In this work, hollow bimetallic selenide nanocages featuring multilayered heterointerfaces have been rationally constructed via nucleation kinetics-guided MOF-on-MOF growth coupled with gradient heteroatom doping strategies. The resulting gradient-doped hollow carbon scaffold serves as robust and conductive matrix to alleviate volume changes during cycling. DFT calculations confirm the generated multi-interfacial built-in electric fields decrease Na + adsorption energy, promoting Na + capture and facilitating subsequent reaction kinetics. In situ XRD verifies a highly reversible intercalation-conversion-alloying mechanism. The resulting electrode exhibits superior reversible capacity of 712 mA h g −1 at 0.1 A g −1 after 200 cycles, 517 mA h g −1 at 1 A g −1 after 1000 cycles and 449 mA h g −1 at 10 A g −1 , highlighting outstanding long-term cycling stability and rate capability for sodium-ion batteries. The constructed ZnSe/CoSe@NC@NSC//AC sodium-ion hybrid capacitor exhibits superior energy density of 169 W h kg −1 and power density of 17,000 W kg −1 . Our findings pave the way for fabricating advanced anodes for sodium storage and can be extended to other electrode materials.