Guan Dongsheng, Cai Chuan, Wang Ying
Mechanical Engineering Department, Louisiana State University, Baton Rouge, LA 70803, USA.
J Nanosci Nanotechnol. 2011 Apr;11(4):3641-50. doi: 10.1166/jnn.2011.3765.
We have employed a simple process of anodizing Ti foils to prepare TiO2 nanotube arrays which show enhanced electrochemical properties for applications as Li-ion battery electrode materials. The lengths and pore diameters of TiO2 nanotubes can be finely tuned by varying voltage, electrolyte composition, or anodization time. The as-prepared nanotubes are amorphous and can be converted into anatase nanotubes with heat treatment at 480 degrees C. Rutile crystallites emerge in the anatase nanotube when the annealing temperature is increased to 580 degrees C, resulting in TiO2 nanotubes of mixed phases. The morphological features of nanotubes remain unchanged after annealing. Li-ion insertion performance has been studied for amorphous and crystalline TiO2 nanotube arrays. Amorphous nanotubes with a length of 3.0 microm and an outer diameter of 125 nm deliver a capacity of 91.2 microA h cm(-2) at a current density of 400 microA cm(-2), while those with a length of 25 microm and an outer diameter of 158 nm display a capacity of 533 microA h cm-2. When the 3-microm long nanotubes become crystalline, they deliver lower capacities: the anatase nanotubes and nanotubes of mixed phases show capacities of 53.8 microA h cm-2 and 63.1 microA h cm(-2), respectively at the same current density. The amorphous nanotubes show excellent capacity retention ability over 50 cycles. The cycled nanotubes show little change in morphology compared to the nanotubes before electrochemical cycling. All the TiO2 nanotubes demonstrate higher capacities than amorphous TiO2 compact layer reported in literature. The amorphous TiO2 nanotubes with a length of 1.9 microm exhibit a capacity five times higher than that of TiO2 compact layer even when the nanotube array is cycled at a current density 80 times higher than that for the compact layer. These results suggest that anodic TiO2 nanotube arrays are promising electrode materials for rechargeable Li-ion batteries.
我们采用了一种简单的钛箔阳极氧化工艺来制备二氧化钛纳米管阵列，该阵列在用作锂离子电池电极材料时表现出增强的电化学性能。通过改变电压、电解质成分或阳极氧化时间，可以精细调节二氧化钛纳米管的长度和孔径。制备出的纳米管为非晶态，在480℃进行热处理可将其转化为锐钛矿型纳米管。当退火温度升至580℃时，锐钛矿型纳米管中会出现金红石微晶，从而形成混合相的二氧化钛纳米管。退火后纳米管的形态特征保持不变。已对非晶态和晶态二氧化钛纳米管阵列的锂离子嵌入性能进行了研究。长度为3.0微米、外径为125纳米的非晶态纳米管在电流密度为400微安/平方厘米时的容量为91.2微安·时/平方厘米，而长度为25微米、外径为158纳米的纳米管容量为533微安·时/平方厘米。当3微米长的纳米管变为晶态时，其容量较低：在相同电流密度下，锐钛矿型纳米管和混合相纳米管的容量分别为53.8微安·时/平方厘米和63.1微安·时/平方厘米。非晶态纳米管在50次循环中表现出优异的容量保持能力。与电化学循环前的纳米管相比，循环后的纳米管形态变化很小。所有二氧化钛纳米管的容量均高于文献报道的非晶态二氧化钛致密层。即使纳米管阵列在比致密层高80倍的电流密度下循环，长度为1.9微米的非晶态二氧化钛纳米管的容量仍比二氧化钛致密层高五倍。这些结果表明，阳极氧化二氧化钛纳米管阵列是有前景的可充电锂离子电池电极材料。
