The Preparation And Properties Of Li₃VO₄ Anode

Lithium vanadate（Li₃VO₄）has been regarded as a potential anode material for lithium ion batteries owing to its ideal discharge potential（～0.5-1.0 V vs.Li⁺/Li）and high theoretical capacity(592 m Ah g^-1,with three Li⁺intercalation).However,the poor conductivity of Li₃VO₄and the difficulty in adjusting its morphology and structure due to hydrophilia restrict its electrochemical performance.Vanadium oxides exhibit diverse morphologies and facile synthesis methods,and has been studied as a raw material for synthesizing Li₃VO₄.Herein,vanadium oxides with special morphologies are used as templates to regulate the morphology of Li₃VO₄.Moreover,the electronic conductivity and electrochemical performance of Li₃VO₄is further improved via carbon combination.As a result,Li₃VO₄/C composite with high capacity and long cycle stability are obtained.The specific research contents and results are as follows:V₂O₅ microspheres were used as templates to tune the morphology of Li₃VO₄,and polyvinylpyrrolidone（PVP）was used as carbon source.After pyrolysis at high temperature,Li₃VO₄/C microspheres with high conductivity could be obtained.The microsphere structure can effectively shorten the diffusion path of lithium ions,thus enhancing the electrochemical performance of Li₃VO₄/C microspheres.The discharge capacity of the Li₃VO₄/C microspheres can maintain at 488 m Ah g^-1 after 200 cycles at a current density of 0.2 A g^-1.The capacity of the Li₃VO₄/C microspheres can be completely recovered after four periods of ratecapability testing.The microsphere structure induces high pseudocapacitive charge storage,which significantly improves the reaction kinetics of the Li₃VO₄/C microspheres.Carbon-coated Li₃VO₄/C nanorods were prepared by morphology inheritance approach,using VO₂ nanorods as templates.The uniform size and the specific rod-like morphology of the Li₃VO₄/C nanorods significantly improve the electron and Li⁺transport in the composites.The Li₃VO₄/C nanorods exhibit high pseudocapacitive charge storage capacity and excellent rate performance.The discharge/charge capacities of the Li₃VO₄/C nanorods are 562/559 m Ah g^-1after 200 cycles at a current density of 0.2 A g^-1.The rate performance of the Li₃VO₄/C nanorods was tested at various current densities of 0.2,0.5,1.0,2.0 and 5.0 A g^-1.After four periods of rate capability testing,the discharge capacity could be restored to 518 m Ah g^-1.Stable cycling could also be achieved over 1000 cycles at a high current density of 2.0 A g^-1.By using V₂O₃/C fiber obtained via electrospinning as template,mixing with lithium source and sintering,Li₃VO₄/C nanofibers were successfully prepared.The long distance and continuous electron transport path and the large specific surface area of the nanofibers provide fast paths for charge transfer in electrochemical process.Pores among fibers can alleviate the volume vatiation upon lithium ion intercalation/deintercalation,thus obtaining stable mechanical properties and long cycle life.The initial discharge/charge capacity of the Li₃VO₄/C nanofiber is 801.5/553.4 m Ah g^-1 at a current density of 0.2 A g^-1,maintaining of 558.9/563.2m Ah g^-1 after 200 cycles.After five periods rate capability testing from 0.2 to 4.0 A g^-1,the capacity of the Li₃VO₄/C nanofibers can be completely recovered.The synthesis of Li₃VO₄/C composites from the lithiation of vanadium oxides and carbon combination provide are viable for the design of Li₃VO₄ with special morphology.This method is expandable and referential for the synthesis of Li₃VO₄ anode materials with special morphology.