Research On Performance Of Sodiumion Battery For Electric Vehicle Based On Sodium Super-Ionic Materials

For electric vehicles,batteries are one of the key factors affecting their development.Lithium-ion batteries are the most successful secondary batteries currently being developed.They have the advantages of high capacity,high voltage,long life,and no memory effect,and are regarded as one of the most promising chemical power sources.However,the reserves of lithium resources in the world are very limited,which greatly limits the large-scale application of lithium batteries in the future.Sodium,as the active metal element with the main group of lithium,has physical and chemical properties very similar to that of lithium.Moreover,sodium is abundant in the earth’s crust.However,there are relatively few studies on sodium ion batteries,and the radius of sodium ions is greater than that of sodium.Lithium ion,which makes the sodium ion battery has a certain limit on the selection.Firstly,Na Ti₂（PO₄）₃ is coated with liquid carbon and pure Na Ti₂（PO₄）₃is synthesized through high-speed mechanical mixing with sucrose and then carbothermal reduction at high temperature.In order to further improve the conductive properties of the material,a conductive network was constructed,and Na Ti₂（PO₄）₃ was carbon-coated again by decomposition of acetylene gas at a high temperature.Next,polyaniline-coated Na₃V₂（PO₄）₃ and Na Ti₂（PO₄）₃ were assembled into a full cell.Finally,a Ni Fe-PBA/Na Ti₂（PO₄）₃ full cell was assembled and circulated at a current density of 4C in a p H=13 oxygen-scavenging electrolyte,and the capacity of the sodium ion battery was tested to reveal the cause of capacity decay of the aqueous sodium ion battery.The results show that the full battery has a very obvious charging and discharging platform around 1.3 V,and this full battery system is very stable.Charge and discharge at 1C current density,the first discharge specific capacity was 95.8 m A h g-1,capacity retention was 81.4%after 150 cycles,and Na₃V₂（PO₄）₃ was synthesized by hydrothermal method to study its sodium storage performance..However,the hydrothermally coated carbon layer is of different thickness and affects its electrochemical performance.In addition,Na₃V₂（PO₄）₃ before and after coating with polyaniline was used as a working electrode,and cyclic voltammetry（CV）and cycling tests were performed in a three-electrode manner.It was found that the volume decay of Na₃V₂（PO₄）₃ before coating and after coating was relatively fast;the side reactions of aqueous batteries were complicated,leading to poor cycle performance.