Research On Synthesis And Performance Of Lithium Vanadium Phosphate Cathode For Li-ion Batteries

Peer work about lithium-ion battery cathode materials had been reviewed at the beginning, then the microwave (MW) method and the carbothermal reduction (CTR) was introduced to prepare lithium vanadium phosphate cathode material. The assembly process of the experimental button cell was introduced too. The evaluating methods of cathode material, such as X-ray diffraction (XRD), scanning electron microscope (SEM), cyclic voltammetry (CV) and charge-discharge method had been used to evaluate the performance of the as-prepared materials.The influence of microwave heating time on the performance of lithium vanadium phosphate was studied. The results showed that at the microwave oven output of 800W,6 min is the appropriate heating time to synthesize Li3V2(PO4)3/C. The XRD patterns showed that the as-prepared Li3V2(PO4)3/C is monoclinic crystal, and the excessive C didn't influence the crystal structure of Li3V2(PO4)3. The SEM pictures indicated that the as-prepared materials were mainly constituted of spherical particles with the diameter less than 100nm. At the current densities of 2C, there were 3 charging plateaus at about 3.65, 3.7 and 4.1V. The corresponding discharging plateaus were at about 3.6,3.65 and 4.05V respectively. The discharging capacity of the sample heated for 6 min was 118.3mAh/g. After 40 cycles, the discharging specific capacities of the sample dropped to 91.9%. At the current of 2C, it could give out 72.2% of the capacity at 0.2C. These numbers indicated that the material had high specific capacity, good cycling stability and the capability of high rate discharging. These good properties were attributed to the nano-sized particles and the carbon electronic conductor.The performance of Li3V2(PO4)3/C and Li3V2(PO4)3 was compared. The results showed that, the specific capacity of the Li3V2(PO4)3/C was a little lower than that of the Li3V2(PO4)3, because the doped carbon had no capacity, but the cycle performance and the high rate capability were much better than that of the Li3V2(PO4)3. Those good properties were attributed to that the doped carbon acted as the electronic conductor and could hinder the growth of the particle size.The performance of Li3V2(PO4)3/C prepared by MW and CTR was compared. The results showed that, the specific capacity, the cycle performance and the high rate capability of the Li3V2(PO4)3/C prepared by MW were all better than that prepared by CTR. These good properties were attributed to the nano-sized particles prepared by MW. However, the Coulomb efficiency of the Li3V2(PO4)3/C prepared by MW was a little lower than that prepared by and CTR, it was assumed that the large surface area of the nanometer particles was responsible to this.