Effects of nickel-doping on the microstructure and electrochemical performances of electrospun Li₃V₂(PO₄)₃/C fiber membrane cathode

Metal ion-doping and fibrosis treatment are important ways to improve the conductivity of lithium vanadium phosphate (Li₃V₂(PO₄)₃) electrode materials. However, the traditional casting preparation method could reduce the electronic and ionic conductivities of Li₃V₂(PO₄)₃ electrodes. In this work, the nickel (Ni)-doped Li₃V₂(PO₄)₃/C nanofiber membrane with a three-dimensional network structure was prepared by an electrospinning technique, which was directly used for self-standing cathodes in lithium-ion batteries. The effects of Ni-doping on the morphology, structure, and electrochemical properties of Li₃V₂(PO₄)₃/C nanofiber membrane were studied. The results show that the Ni-doping not only changes the crystal structure and morphology of Li₃V₂(PO₄)₃/C fibers, but also affects the electrochemical performances of the Li₃V₂(PO₄)₃/C electrodes. 1‰ Ni-doping has slightest effect on the crystal structure compared with other ratios, and the catalytic effect of Ni nanoparticles makes Li₃V₂(PO₄)₃/C grow directionally to form a hybrid membrane containing Li₃V₂(PO₄)₃/C nanofibers and Li₃V₂(PO₄)₃/C nanowires. The hybrid membrane electrode possesses good electrochemical performances at the current densities of 1C and 5C owing to the long-range continuous electron conductive networks, high porosity to favor the electrolyte permeation and Li-ion transport, and stable integrated-electrode structure to enhance the redox reaction. This self-standing Li₃V₂(PO₄)₃/C nanofiber membrane cathode is expected to be used in high-energy lithium-ion batteries.