烧结方式对LiFePO4/C复合正极材料电化学性能的影响

对LiFePO4/C复合前驱体,分别采用静态氮气气氛,动态氮气气氛及静态真空三种烧结方式进行碳热还原合成LiFePO4/C复合正极材料.采用XRD、SEM、CV和充放电循环测试等方法分析和表征材料的结构、形貌和电化学性能.结果表明,烧结方式对所得材料的结晶度、晶粒大小、碳含量、合成温度以及电化学性能均有显著影响.真空烧结所得材料结晶度高,而动态气氛烧结对材料颗粒细化及均匀化都有积极影响,同时也能有效促进锂离子扩散动力学.动态气氛烧结可将材料的烧结温度降低到500℃,且所得材料表现出优异的电化学性能.0.5C倍率下循环首次放电比容量达到163.4 mAh/g,50次循环后容量保持率为99.02%.

Effect of Sintering-method on Electrochemical Performance of LiFePO4/C Cathode Material

Static nitrogen atmospheres(SA),dynamic nitrogen atmosphere(DA) and static vacuum(SV) sintering methods were adopted to synthesize LiFePO4/C cathode material.The crystalline structure,morphology and electrochemical performances of the products were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM) and galvanostatic charge/discharge test.Effects of sintering method on crystallinity,particle size,carbon content,reaction temperature and electrochemical performance of the as-obtained LiFePO4/C cathode material are remarkable.SV-sintered LiFePO4/C has better crystalline,but DA-sintering is helpful to obtain LiFePO4/C particles with smaller particle size and narrower particle size distribution,kinetics of Li+ diffusion is also improved.For the DA-sintered sample,sintering temperature can be reduced to 500℃ with excellent electrochemical performance.Specific discharge capacity for the first cycle reaches 163.4 mAh/g at 0.5C rate,and up to 99.02% of discharge capacity can be kept after 50 cycles.