锂离子负极材料Li_4Ti_5O_(12)新工艺的合成及其掺杂改性

Synthesis and doping modification with new technology of cathode material Li_4Ti_5O_(12) for li-ion batteries

通过运用机械法-固相两步法工艺与机械法-喷雾造粒-固相三步法工艺合成了负极材料Li4Ti5O12,并对其进行掺杂改性研究(Li4Ti4.95Nb0.05O12),采用XRD、SEM、循环伏安(CV)、电化学阻抗谱(EIS)及充放电测试探讨了材料颗粒形貌及Nb的掺杂对产品结构和电化学性能的影响。XRD和SEM测试表明产品相纯度及颗粒形貌主要受工艺的影响。电化学性能测试结果显示,机械法-喷雾造粒-高温固相三步法制备的掺杂Nb产品的电化学性能有明显提升,其具有更小的韦伯阻抗系数σ和大的锂离子扩散系数D,表现出较高的比容量和循环稳定性,0.2C的放电容量接近理论容量175mAh·g-1,5C的放电容量达106.14mAh·g-1,50圈后的容量仍高达101.71mAh·g-1。

The cathode material Li4Ti5O12 for Li-ion batteries were prepared via two-step of mechanical-solid phase method ,three-step of mechanical-spray-dried-solid phase method and Nb-doping modification. Effects of the morphology and Nb-doping on structure and properties of the products were investigated by using XRD,SEM, cyclic vohammetry（CV）, electrochemical imprdence spectra（EIS）and charge-discharge tests. XRD and SEM results indicated that the phase purity, crystallinity and morphology mainly depend on synthetic technology. The electrochemical tests showed that the sample that Nb-doping was prepared via three-step exhibited better electrochemical performance with much smaller Warburg impedance coefficient（o）and higher lithium ion diffusion coefficient（D）, and showed higher capacity and good cycling stability. Its dis- charge capacity at 0. 2C reached the theoretical capacity175mAh · g^-1, the discharge capacity at 5C extended 106. 14mAh · g^-1 ,and retained 101.71mAh · g^-1after 50 cycles.