锂离子电池负极材料Li_(4-x)K_xTi_5O_(12)结构和电化学性能

采用固相反应的方法制备了尖晶石型Li4Ti5O12和K掺杂Li4-xKxTi5O12(x=0.02,0.04,0.06)。通过XRD、SEM、BET等对制备材料进行了分析。结果表明,K掺杂没有影响立方尖晶石型Li4Ti5O12的合成,同时也没有改变Li4Ti5O12的电化学反应过程。K掺杂Li4-xKxTi5O12具有比Li4Ti5O12小的颗粒粒径和比Li4Ti5O12大的比表面积、孔容积。适量的K掺杂能够明显改善Li4Ti5O12的电化学性能,尤其是倍率性能,但是过多的K掺杂却不利于材料电化学性能的提高。研究表明,Li3.96K0.04Ti5O12体现了相对较好的倍率性能和循环稳定性。0.5C下,首次放电比容量为161mAh·g-1,3.0和5.0C下,容量保持分别为138和121mAh·g-1。3.0C下,200次循环后容量保持为137mAh·g-1。

Structural and Electrochemical Characteristics of Li4-xKxTi5O12 as Anode Material for Lithium-Ion Batteries

The spinel Li₄Ti₅O₁₂ and K-doped Li_4-xK_xTi₅O₁₂(x=0.02, 0.04, 0.06) were prepared by a solid state reaction. X-ray powder diffraction (XRD), scanning electronic microscopy (SEM) and Brunau-Emmertt-Teller (BET) were employed to characterize the synthesized materials. The results indicated that K-doping did not affect the synthesis of the cubic spinel Li₄Ti₅O₁₂. Furthermore, the K-doping did not change the electrochemical reaction process of Li₄Ti₅O₁₂. The K-doped Li_4-xK_xTi₅O₁₂(x=0.02, 0.04, 0.06) had smaller particle size, larger specific surface area and hole cubage than the pristine Li₄Ti₅O₁₂ without K doping. An appropriate amount of K doping was favorable to the electrochemical performances, and in particular the rate capability of Li₄Ti₅O₁₂. However, a high amount of Zr-doping was adverse. The research suggested that Li_3.96K_0.04Ti₅O₁₂ exhibited a relatively good rate capability and cycling stability. At the charge-discharge rate of 0.5C, 3.0C and 5.0C, its discharge capacities were 161, 138 and 121 mAh·g^-1, respectively. After 200 cycles at 3.0C, its discharge capacity remained at 137 mAh·g^-1.