Study On Synthesis And Characteristics Of Cathode Materials For Sodium-ion Batteries

Since Sony’s commercialization of lithium batteries in 1991,owing to its advantages such as light weight,high capacity and efficient,lithium battery is being widely used in portable electronic devices.In these years,with the booming development of electric vehicles(EVs),the demand of lithium batteries is becoming huger and huger.Meanwhie,the expansion of renewable energy has also raised the demand of energy storage systems with high safety,high energy density and low cost.As a result,the limitied lithium resources will be a big problem,which will increase the price of lithium batteries accordingly.Sodium batteries have attracted a lot of attention for its similar properties with lithium batteries and the abundance of sodium resources.Among the candidates of sodium battery cathode materials,NASICON Na3V2(PO4)3 is considered as a promising cathode material for its high energy density and stable three-dimensional NASICON structure.In addition,carbon coating and reducing particle size are usually adopted to enhance its poor electronic conductivity.In this paper,we mainly focus on the preparation of carbon coated Na3V2(PO4)3.In the following,we will discuss the morphology and electrochemical properties of Na3V2(PO4)3/C under different synthetic strategies.In the first part,we employed H2C2O4 as the reductive agent to reduce the V5+ to V3+.Then we applied spray drying method to synthesize Na3V2(PO4)3/C hollow spheres.And we used grapheme oxides as the additive agent in order to enhance electronic conductivity.The former Na3V2(PO4)3/C hollow spheres became porous and rate performance was improved greatly.In the second part,we combined ultrasonic spray with freeze drying to synthesize Na3V2(PO4)3/C cathode materials.And we found the morphology of Na3V2(PO4)3/C varies with experiment operations.80-120nm Na3V2(PO4)3/C nanoflakes were prepared due to the impact of the additional liquid nitrogen.The half cell made with the Na3V2(PO4)3/C nanoflakes demonstrated a good electrochemical performance and renderd an initial capacity of 108.5 mAh g-1 at 0.1 C and an excellent capacity retention of 81.4%after 100 cycles at 1C.