N,S co-doped V₃Nb₁₇O₅₀@C fibers used for lithium-ion storage

Bimetallic oxides deliver high specific capacity in energy storage, but their disadvantages, such as poor electrical conductivity, low ion diffusion rate and interatomic instability, limit their application. In this work, lattice defects (N,S co-doping) and carbon interfaces are introduced into S-V₃Nb₁₇O₅₀@NC nanofibers to improve the electron/ion kinetic stability, electrical conductivity and electrochemical activity. Firstly, the lattice defects constructed by N,S co-doping produce more unmatched electrons, widen the lattice channels of S-V₃Nb₁₇O₅₀@NC, provide more active sites, improve the material affinity to the electrolyte and enhance its electron/ion transport kinetics. Secondly, the carbon interfacial layer protects the lattice defects, inhibits the adverse reactions between the bimetal oxides and electrolyte, and boosts the stability and uniformity of ion transport. In addition, the volume effect of S-V₃Nb₁₇O₅₀@NC is alleviated under the synergistic effect of the carbon layer and carbon fiber network, thus improving the cycling performance of the electrode material. In general, benefitting from N,S co-doping and interface protection, S-V₃Nb₁₇O₅₀@NC nanofibers show good electrochemical performance in lithium-ion hybrid capacitors.