水热法制备锂离子二次电池用球形Li4Ti5O12负极材料及其电化学性能

Hydrothermal Synthesis and Electrochemical Performance of Spherical Li_4Ti_5O_(12) as Anode Material for Lithium-ion Secondary Battery

以LiOH溶液和不同粒径的自制球形TiO2为反应物,通过水热法快速地合成了尖晶石型结构的球形Li4Ti5O12,并考察了材料合成的水热反应机理和电化学性能。TiO2在100℃、5 mol/L Li OH溶液中经水热反应20 h得到前驱体,再经800℃热处理2 h便可得到粒径大小不同（0.5-1.5μm）且分布均匀的球形尖晶石Li4Ti5O12材料。Li OH在水热反应条件下扩散到球形TiO2内部,得到在分子水平混合均匀的Li-Ti-O中间体,利于高温下生成纯相的尖晶石Li4Ti5O12。所得粒径大小不同的Li4Ti5O12材料均表现出稳定的电化学循环充放电性能,其中,粒径为0.5μm的Li4Ti5O12材料的电化学性能最好：室温下,以0.2 C的倍率进行充放电,其可逆容量达到158 m Ah/g,70周后容量保持率高于99%;同时还表现出优异的高温循环稳定性,55℃下以0.2 C的倍率进行充放电,50次循环后其可逆放电比容量仍能达到125 m Ah/g。

Self-made TiO2 with different particle sizes was adopted to react in LiOH solution via a fast hydrothermal process, from which spherical spinel lithium titanium oxide Li4Ti5O12 was efficiently prepared. In detail, precursor was obtained from hydrothermal reaction between TiO2 with 5 mol/L LiOH solution at 100℃ for 20 h, and Li4Ti5O12 was synthesized by calcining the precursor at 800℃ for 2 h. The mechanism of the hydrothermal process discussed show that an even Li-Ti-O mixture is formed during Li cation diffusing into the TiO2, resulting in the structure conversion to pure Li4Ti5O12 fast at high temperature. While all the obtained Li4Ti5O12 with different particle sizes show stable electrochemical cycling ability, the 0.5 μm Li4TisO12 exhibits optimal electrochemical performance. Its initial discharge capacity reaches 158 mAh/g at 0.2 C and more than 99% of capacity is retained after 70 cycles, while the reversible capability readily exceeds 125 mAh/g after 50 cycles at 0.2 C at 50℃.