The Design And Electrochemical Performance Of LiVO₃ Anode Material

As a new insertion type electrode material for lithium-ion batteries,LiVO₃ has attracted much research attention due to its high specific capacity,high initial coulombic efficiency（ICE）and high electron/ion conductivity.However,LiVO₃ has mainly been studied as a positive electrode material due to its relatively-high discharge platform.The synthesis and electrochemical behavior of LiVO₃-based materials as anode for lithium-ion batteries is still in its infancy.This paper aims to design and prepare LiVO₃ based anode materials via optimized annealing,carbon coating strategy and template aided method,and to study the electrochemical performance of these materials.Specific research contents are as follows:LiVO₃ precursor was firstly prepared by a simple hydrothermal method.High purity LiVO₃ was successfully prepared by annealing the precursor in N₂ atmosphere and air atmosphere（named LiVO₃-N₂,LiVO₃-Air）.The LiVO₃-N₂ shows particle-like morphology with mean size less than 1μm,and the LiVO₃-Air consists of nanoneedles.The electrochemical properties of the LiVO₃-N₂ and LiVO₃-Air as anode materials for lithium ion batteries are studied.It is found that the LiVO₃-N₂induces a higher contribution of pseudocapacitance and improves the reaction kinetics,thus showing better electrochemical performance of lithium storage.The specific capacity of the LiVO₃-N₂ anode is 715 m Ah g^-1 after 300 cycles at a current density of0.2 A g^-1.After 6 periods rate property testing,when the current density is restored to0.2 A g^-1,the specific capacity is 520 m Ah g^-1;After 3000 cycles with a current density of 5 A g^-1,the specific capacity is still 120 m Ah g^-1.The synthesis of LiVO₃anode material by annealing in N₂ atmosphere may be referential for the synthesis of LiVO₃/C material.LiVO₃/C composite with core/shell structure was successfully synthesized by a simple hydrothermal-annealing two-step synthesis method using carbon cladding strategy.The uniform conducting carbon layer and the unique shell structure could promote the penetration of electrolyte and provide more lithium storage sites,thus inducing a high contribution of pseudocapacitance and realizing fast reaction kinetics.The LiVO₃/C composite exhibits excellent lithium storage electrochemical performance as anode for lithium ion battery:high discharge specific capacity of776.0 m Ah g^-1 at 0.2 A g^-1;excellent rate performance with an average capacity of365.8 m Ah g^-1 at 5.0 A g^-1 and high discharge capacity of 569.0 m Ah g^-1 after 5periods rate performance test from 0.2 to 5.0 A g^-1.The LiVO₃/C also demonstrates unprecedented long cycle performance,maintaining a specific capacity of 205.0 m Ah g^-1 after 2000 cycles at 10.0 A g^-1.This work proves that carbon coating is a viable to improve the performance of LiVO₃,which is referential for the design of high performance LiVO₃-based anode materials.Li₃VO₄/C hollow porous microsphere with high purity,stable structure,good crystallizability and cycle stability was prepared by a spray drying method.Then,LiVO₃/C hollow porous microsphere was synthesized by mixing the Li₃VO₄/C（acts as template）and additional vanadium source and annealing in air at low temperature.Its unique hollow structure and porous characteristics facilitate the penetration of electrolyte,shorten the transmission distance of lithium ions and provide more lithium storage sites,thereby inducing high pseudocapacitance contribution and displaying fast reaction kinetics.The LiVO₃/C hollow porous microsphere was used as anode of lithium ion battery,and it showed excellent rate performance and cycle stability.The discharge capacity of the LiVO₃/C electrode was restored to 526.5 m Ah g^-1 when reverting current density to 0.5 A g^-1 after 5 periods rate property testing from 0.5 to10.0 A g^-1.This simple template method provides a feasible idea for the morphology design of LiVO₃/C anode materials,and will promote the application of LiVO₃ anode materials in lithium ion batteries.