Metal-injection and interface density engineering induced nickel diselenide with rapid kinetics for high-energy...

The key to the innovation of sodium-ion batteries (SIBs) is to find efficient sodium-storage electrode. Here, metal Mo doping of NiSe₂ is proposed by modified electrospinning strategy followed by in situ conversion process. The Mo-NiSe₂ anchoring on hollow carbon nanofibers (HCNFs) would make full use of the multi-channel HCNFs in the inner layer and the active sites of Mo-NiSe₂ in the outer layer, which plays an important role in buffering the volume stress of Na⁺ (de)insertion and reducing the adsorption energy barrier of Na⁺. Innovatively, it is proposed to jointly regulate the SIBs performance of NiSe₂ by both metal atom doping and interface effects, thereby adjusting the sodium ion adsorption barrier of NiSe₂. The Mo-NiSe₂@HCNFs exhibits remarkable performance in SIBs, demonstrating a high specific capacity of 396 mAh/g after 100 cycles at 1 A/g. Moreover, it maintains outstanding cycling stability, retaining 77.6 % of its capacity (211 mAh/g) even after 1000 cycles at 10 A/g. This comprehensive electrochemical performances are due to the structural stability and outstanding electronic conductance of the Mo-NiSe₂@HCNFs, as evidenced by the diffusion analysis and ex situ charge-discharge process characterization. Furthermore, coupled with the Na₃V₂(PO₄)₂O₂F cathodes, the full cell also achieves a high energy density of 123 Wh kg^-1. The theoretical calculation of the hypervalent Mo doing further proves the benefit of its Na⁺ adsorption and denser conduction band distribution. This study provides a reference for the construction of transition metal selenide via doping and interface engineering in sodium storage.