Preparation And Electrochemical Performance Of Li₃VO₄ Electrode Material

In this paper,Li₃VO₄/C electrode materials were synthesized by sol-gel method using ammonium metavanadate,lithium acetate dihydrate,citric acid monohydrate,oxalic acid dihydrate,glucose monohydrate and soluble starch as raw materials,and the reaction conditions?carbon source type,carbon content,sintering temperature,etc.?were optimized and explored.Studies have shown that the electrochemical performance of Li₃VO₄/C synthesized using different carbon sources?citric acid monohydrate,oxalic acid dihydrate,glucose monohydrate,and soluble starch?is better than Li₃VO₄.Comparing Li₃VO₄/C synthesized from different carbon sources,it was found that Li₃VO₄/C synthesized using citric acid monohydrate as the carbon source had the best electrochemical performance.Further investigation showed that the electrochemical performance of the sample prepared when the ratio of ammonium metavanadate and citric acid monohydrate was 1:1 and the sintering temperature was 650?.When used as a negative electrode material for lithium-ion batteries,the first discharge specific capacity is 771.32 mAh·g^-1 and the first charge specific capacity is 524.27 mAh·g^-1 at a current density of 0.1 A·g^-1;After 200 cycles of charge and discharge at a current density of 1.0 A·g^-1,the specific discharge capacity can still reach412.54 mAh·g^-1,and the capacity retention rate is as high as 95.13%.Through kinetic analysis,it is found that most of the charge storage in the electrode is a fast and reversible interfacial reaction,which is conducive to the fast storage and long-term cycle of charge.In addition,the electrochemical performance of Li₃VO₄/C synthesized as the negative electrode material of hybrid supercapacitors under the optimal conditions was also investigated.When the current density was 0.1 A·g^-1,the discharge specific capacity reached47.17 mAh·g^-1(?158.35 F·g^-1),after 90 charge and discharge cycles at a current density of0.2 A·g^-1,the capacity retention rate is about 81.88%;81.68 Wh·kg^-1 energy is provided at a power density of 166.51 W·kg^-1 Density,with a high power density of 2823.35 W·kg^-1?full charge and discharge in 40 seconds?,the energy density can still reach 15.68 W·kg^-1.In order to further improve its electrochemical performance,in this thesis,vanadium neodymium ion doping modification of Li₃VO₄/C was performed using neodymium acetate.Li₃V_1-x-x Nd_xO₄/C?x=0,x=0.001,x=0.003,x=0.005 and x=0.008?electrode materials.The electrochemical performance analysis of Li₃V_1-xNd_xO₄/C electrode materials found that although the doping of neodymium ions had little effect on the material's first charge-discharge specific capacity as a negative electrode material for lithium ion batteries,a proper amount of neodymium ion doping Improve the rate and cycle performance of materials.The performance of the material is the best at x=0.005.When the current density is 5.0 A·g^-1,the discharge specific capacity reaches 300.75 mAh·g^-1.After 200 charge and discharge cycles at a current density of 1.0 A·g^-1,the capacity retention rate reaches 97.55%;In addition,proper doping of neodymium ions can increase the lithium ion diffusion coefficient of the material.Finally,using Li₃V_0.995Nd_0.005O₄/C as the anode material for hybrid supercapacitors has better performance?compared to Li₃VO₄/C?.When the current density is 0.1 A·g^-1,its discharge specific capacity reaches 46.79 mAh·g^-1(?157.04 F·g^-1).After 90 charge and discharge cycles at a current density of 0.2 A·g^-1,the capacity retention rate was about91.06%.With a power density of 221.41 W·kg^-1,it provides an energy density of 81.27Wh·kg^-1.At an ultra-high power density of 3387.12 W·kg^-1?full charge and discharge in 30seconds?,the energy density can still reach 16.00 Wh·kg^-1.