Synthesis And Modification Of Lithium Vanadium Phosphate For Lithium-ion Battery Cathode Material

In the current energy and environmental issues under the great challenge,efficient energy-saving,low-emission electric vehicle development by the world's attention.As a power supply for electric vehicles,the performance of power cells plays a key role in the safe and reliable operation of electric vehicles.Li₃V₂?PO₄?₃ has high specific capacity,stable cycle performance,high potential platform,good safety and price Low and other advantages make it very commercial application potential of lithium-ion battery cathode material.However,due to the low electrical conductivity of materials,a serious impact on the material of the practical process.Based on the sol-gel method,the effects of different reaction conditions on the structure,morphology and electrochemical energy of Li₃V₂?PO₄?₃ Li-ion battery were studied.The effects of different reaction conditions on the structure,morphology and electrochemical energy of Li₃V₂?PO₄?₃,the cathode materials were coated with carbon and fluorinated coatings and modified with rare earth ions.The effects of different doping amounts of Gd³⁺ and La³⁺ rare earth elements on the structure and electrochemical properties of Li₃V₂?PO₄?₃/C were studied on the basis of sol-gel method.The results show that the electrochemical properties are reduced after rare earth doping,and the rare earth Gd³⁺ is the best electrochemical performance at x=0.03.At room temperature 3-4.3 V charge and discharge platform,The first discharge capacity of 0.1 C to reach 120.3m Ah/g,the 50 th cycle discharge capacity is still 100.9m Ah/g,capacity retention rate of 83.8%.The Li₃V₂?PO₄?₃/C cathode material coated with Mg F₂ and Al F₃ coatings has been studied.The electrochemical properties of Mg F₂-LVP/C 4.3V voltage range,thedischarge capacity of 0.1 C rate,the first discharge capacity of materials reached 121.4m Ah/g,50 times after the capacity is still maintained at 109.2m Ah/g,the retention rate of 89.9%.In the higher 3-4.7 V voltage range,the material's first discharge capacity reached 165.7 m Ah/g,while the LVP/C discharge capacity was only 158.4 m Ah/g.we synthesized Li₃V₂?PO₄?₃/C composite cathode materials with different reducing agents and different surfactants.The results showed that citric acid could be used as a reducing agent to control the morphology of the particles,enhance the dispersibility of the particles,the smaller the particle size and the morphology of the products.Li₃V₂?PO₄?₃/C prepared by ascorbic acid and oxalic acid as reducing agent,composite material particle size is relatively large.And PVP as a surfactant,the regulation of particle performance is better than SDBS;citric acid as a reducing agent,PVP for the synthesis of Li₃V₂?PO₄?₃/C has the best electrochemical performance,0.1 C rate,The first charge and discharge capacity of 122.2 m Ah/g,50 times after the cycle,the capacity remains at 98.1 m Ah/g,even when the magnification of 5 C,the first discharge capacity is still 60.2 m Ah/g.we studied the electrochemical properties of p H to Li₃V₂?PO₄?₃/C composites under optimized conditions.The p H value of the precursor was adjusted with ammonia and nitric acid,and the morphologies of the materials were changed by changing the electrochemical performance.When the p H is 4,the morphology of the material is better,the first discharge capacity in the range of 3-4.3 V reaches 123.6 m Ah/g,and the first discharge capacity in the range of 3-4.7 V is 159.8 m Ah/g,After 50 weeks,the capacity is still 140.2 m Ah/g,capacity retention rate of 87.7%.