Controlled Preparation And Electrochemical Properties Of M=（Li、Na）V₃O₈ Cathode Materials

The current social energy shortage and environmental crisis bring great pressure to people,and new energy technology can effectively alleviate the pressure.President Xi Jinping made clear at the seventy-fifth session of the United Nations General Assembly that our country needs to further accelerate energy change,mainly because,on the one hand,human demand for energy is growing.On the other hand,the continuous consumption of natural energy such as oil has brought great damage to the environment.So it is imperative to develop better new energy.Since the birth of lithium ion batteries in the last century has been in line with the development of the times,major enterprises and universities research and development in full swing,never stop.Among them,the cathode material Li_1+xV₃O₈ is cheaper and less polluting than other materials.What’s more,it has high theoretical specific capacity and can adapt to a wider temperature change.In order to improve the cycling stability of lithium vanadate and sodium vanadate,lithium vanadate and sodium vanadate were prepared by different synthetic methods in this paper,and carbon plating by magnetron sputtering was improved.The main research contents and experimental results are as follows:1.Li_1.2V₃O₈ material can be controlled and prepared based on sol-gel method.The optimal calcination temperature and time were determined by the fixed variable comparison experiment.The results show that 450°C/8h is the best preparation condition.Under this condition,the first discharge specific capacity reaches 292 m Ah/g,the first charge and discharge efficiency is 98.6%,and the capacity retention rate is 75.3%after 100 cycles.2.Na V₃O₈ material was prepared by sol-gel method.Different temperatures and time were explored,and finally it was concluded that Na V₃O₈ had the best performance at300°C/10h,and the Na V₃O₈ obtained under this condition had good rate and cycle performance.The initial discharge specific capacity of Na V₃O₈ material was as high as 248 m Ah/g.After the rate test,the discharge specific capacity was 213 m Ah/g and the recovery rate was 86.2%when it returned to 0.1C and was stable.After 100 weeks of cyclic test,the capacity retention rate was 53.2%.3.Li_1.2V₃O₈ material was prepared by spray drying method.By fixing a single variable to explore,the results show that the best condition of Li_1.2V₃O₈ material obtained by spray drying is 450°C/8h.The precursor of this material is spherical with smooth surface,and it is still spherical after calcination.The material reached 266m Ah/g in the first week,and the stable value was 221 m Ah/g after 100 weeks.The capacity retention rate was 83.1%.The capacity was significantly improved at the rate performance of 3C,and the cycle and rate performance were higher than those of the sol Li1.2V3O8.4.Na V₃O₈ material was prepared by spray drying method.The effects of different temperatures and time on the material were explored,and finally 300°C/10h was the optimal condition.The material obtained by this method was spherical,and it was also spherical after calcination.The specific charge-discharge capacity in the first week was 221 m Ah/g,and the charge-discharge efficiency was 100%.The material retained 128 m Ah/g after 100 cycles,and the capacity retention rate was 57.9%.The rate performance,especially at 1C,was greatly improved compared with that of the Na V₃O₈ material obtained by the sol method,and the recovery rate was 88.2%.5.The sol-gel Li_1.2V₃O₈ material was coated by magnetron sputtering.The carbon deposition on Li_1.2V₃O₈ material under the optimal conditions of 450°C/8h was studied by magnetron sputtering,and the effect of carbon deposition time on the performance of Li_1.2V₃O₈ material was explored.The experimental results show that the carbonized 20s material has the best performance.The first discharge specific capacity is 274 m Ah/g.When the rate performance is returned from 3C to 0.1C and remains stable,the discharge specific capacity is 233 m Ah/g and the recovery rate is83.8%.After 100 weeks,the discharge specific capacity of LVO-450-8-20s material was finally reduced to 226 m Ah/g,and the capacity retention rate was 82.5%.The cycle and rate performance were better than those of Li_1.2V₃O₈ material prepared by sol-gel method,and the cycle performance was improved significantly.