Synthesis And Electrochemical Modification Of The Cathode Material Na₃V₂?PO₄?₃ For High Performance Sodium Ion Batteries

At present,lithium ion batteries have been widely used in a variety of portable electronic products.However,conventional lithium resources are scarce and unevenly distributed,so our attention has been focused on sodium,which is cheap,widely distributed and has electrochemical properties similar to lithium.Sodium ion battery has become an important new force in the future development of energy storage battery because of its lower cost,richer resources and can be used for large-scale energy storage.Among the many anode materials for sodium ion batteries,Na₃V₂?PO₄?₃cathode materials with NASICON structure have attracted much attention due to their advantages of stable structure,high voltage platform and good thermal stability.In this paper,Na₃V₂?PO₄?₃anode materials were prepared by sol-gel method,and the optimal synthesis conditions were explored.The materials were doped with metal Ru ion and metal La ion,and the influence of different doping amounts on the electrochemical properties of Na₃V₂?PO₄?₃/C materials was investigated.The doping mechanism of different materials was explored and studied.Na₃V₂?PO₄?₃/C anode materials were prepared by sol-gel method.The effects of different proportions of Na and citric acid,different calcination temperatures and different calcination time on the structural morphology and electrochemical properties of the materials were studied,and the optimal preparation conditions were determined by comparing the results under different conditions.XRD and SEM results showed that the samples prepared at the ratio of Na to citric acid was 3:2,the calcination temperature was 800?,and the calcination time was 10h.The samples have the most regular morphology and the best crystal structure.The electrochemical performance test showed that the specific discharge capacity,coulombic efficiency and cyclic performance of the first cycle of the sample prepared under the above comprehensive conditions are the best.Na₃V₂?PO₄?₃/C anode material was prepared under the optimal synthesis process.and Na₃V₂?PO₄?₃/C was doped with Ru using Ru Cl₃as the source of ruthenium,to synthesize Na₃V_2-xRu_x?PO₄?₃/C?x=0.1,0.15,0.2?composite material.To explore the influence of different doping amount on electrochemical properties of materials.The results show that the doping of ruthenium ions is beneficial to increase the discharge capacity of the material.With the increase of Ru doping amount,the discharge specific capacity of the sample first increased and then decreased,but it was higher than that of Na₃V₂?PO₄?₃/C.Na₃V_1.85Ru_0.15?PO₄?₃/C has the best cycling performance and rate performance,the discharge specific capacity after 100 cycles is 92.28 m Ah/g,capacity retention rate reaches 89.55%.Na₃V_2-xLa_x?PO₄?₃/C?x=0.1,0.15,0.2?samples were prepared by sol-gel method with lanthanum nitrate as lanthanum source.To explore the influence of different doping amount on electrochemical properties of materials.The results show that lanthanum ion doping is beneficial to improve the electrochemical properties of materials.At x=0.15,Na₃V_1.85La_0.15?PO₄?₃/C sample has the best cycling performance and rate performance.CV and EIS results showed that lanthanum ion doping inhibited the increase of material impedance to a large extent,resulting in decreased polarization,which was beneficial to improve the electrochemical properties of materials.