Yi Ting-Feng, Fang Zi-Kui, Xie Ying, Zhu Yan-Rong, Yang Shuang-Yuan
School of Chemistry and Chemical Engineering, Anhui University of Technology , Maanshan, Anhui 243002, People's Republic of China.
ACS Appl Mater Interfaces. 2014 Nov 26;6(22):20205-13. doi: 10.1021/am5057568. Epub 2014 Oct 31.
Well-defined Li4Ti5O12-TiO2 nanosheet and nanotube composites have been synthesized by a solvothermal process. The combination of in situ generated rutile-TiO2 in Li4Ti5O12 nanosheets or nanotubes is favorable for reducing the electrode polarization, and Li4Ti5O12-TiO2 nanocomposites show faster lithium insertion/extraction kinetics than that of pristine Li4Ti5O12 during cycling. Li4Ti5O12-TiO2 electrodes also display lower charge-transfer resistance and higher lithium diffusion coefficients than pristine Li4Ti5O12. Therefore, Li4Ti5O12-TiO2 electrodes display lower charge-transfer resistance and higher lithium diffusion coefficients. This reveals that the in situ TiO2 modification improves the electronic conductivity and electrochemical activity of the electrode in the local environment, resulting in its relatively higher capacity at high charge-discharge rate. Li4Ti5O12-TiO2 nanocomposite with a Li/Ti ratio of 3.8:5 exhibits the lowest charge-transfer resistance and the highest lithium diffusion coefficient among all samples, and it shows a much improved rate capability and specific capacity in comparison with pristine Li4Ti5O12 when charging and discharging at a 10 C rate. The improved high-rate capability, cycling stability, and fast charge-discharge performance of Li4Ti5O12-TiO2 nanocomposites can be ascribed to the improvement of electrochemical reversibility, lithium ion diffusion, and conductivity by in situ TiO2 modification.
通过溶剂热法合成了结构明确的Li4Ti5O12-TiO2纳米片和纳米管复合材料。在Li4Ti5O12纳米片或纳米管中原位生成的金红石型TiO2的结合有利于降低电极极化，并且Li4Ti5O12-TiO2纳米复合材料在循环过程中显示出比原始Li4Ti5O12更快的锂嵌入/脱出动力学。Li4Ti5O12-TiO2电极还显示出比原始Li4Ti5O12更低的电荷转移电阻和更高的锂扩散系数。因此，Li4Ti5O12-TiO2电极显示出更低的电荷转移电阻和更高的锂扩散系数。这表明原位TiO2改性提高了电极在局部环境中的电子导电性和电化学活性，从而使其在高充放电速率下具有相对较高的容量。Li/Ti比为3.8:5的Li4Ti5O12-TiO2纳米复合材料在所有样品中表现出最低的电荷转移电阻和最高的锂扩散系数，并且与原始Li4Ti5O12相比，在10 C倍率下充放电时显示出大大提高的倍率性能和比容量。Li4Ti5O12-TiO2纳米复合材料的倍率性能、循环稳定性和快速充放电性能的提高可归因于原位TiO2改性对电化学可逆性、锂离子扩散和导电性的改善。
