Electrospun Li3V2(PO4)3 nanocubes/carbon nanofibers as free-standing cathodes for high-performance lithium-ion batteries

Abstract

Lithium vanadium phosphate Li₃V₂(PO₄)₃ (LVP)-based cathodes have attracted much attention in pursuit of high-performance lithium-ion batteries (LIBs). In this study, an ionic liquid (IL) has been introduced into the electrospinning process for the first time, successfully leading to the formation of free-standing cathodes built up of LVP nanocubes embedded in N-doped carbon nanofibers (LVP-NC/NCNF). In particular, the IL plays multiple roles in the resulting free-standing cathodes: (i) the IL improves the feasibility of the PAN-based electrospinning system for preparing electrode materials due to its good solubility, resulting in a self-supporting substrate conductive network with good mechanical properties and electrical conductivity; (ii) the IL can act as a structure-directing agent to induce the formation of (100) facet-oriented LVP nanocubes, giving rise to a convenient lithium-ion transport path; and (iii) the IL adsorbed on the surface of LVP nanocubes can form a N-doped dual-phase carbon coating layer during the heat-treatment process, further enhancing the electronic conductivity of the entire electrode. As a result, LVP-NC/NCNF free-standing electrodes exhibit an outstanding electrochemical performance including a high specific capacity, stable cycling performance and superior rate capability. Specially, the LVP-NC/NCNF free-standing cathodes deliver a high discharge capacity of 143.6 mA h g⁻¹ at 5C for a prolonged cycling life of over 1000 cycles. It is highly expected that this facile IL-assisted electrospinning method can be expanded to other polyanion-based cathodes, thus presenting new opportunities for the design and fabrication of high-performance free-standing electrodes for LIBs.