Si/Li_4Ti_5O_(12)复合锂离子电池负极材料的制备、结构和电化学性能

Fabrication,Structure and Electrochemical Properties of Si/Li_4Ti_5O_(12) Nanocomposites as Anode Materials for Lithium Ion Batteries

本文以纳米Si为原料,通过溶胶-凝胶法,采用不同的煅烧温度,合成了在Si颗粒表面包覆Li4Ti5O12的复合结构材料作为锂离子电池负极材料。结合采用XRD、SEM、TEM、HRTEM和EDS等材料结构分析方法和对合成材料的首次库仑效率、循环稳定性及CV曲线的测试分析,研究了凝胶煅烧温度对合成材料的结构和电化学性能的影响,探讨了Li4Ti5O12的引入对改善Si负极材料循环性能的作用。研究结果表明,在600-800℃的煅烧温度下,溶胶-凝胶过程的产物主要为Li4Ti5O12,产物中Si保持其初始的晶体结构和颗粒特征。提高煅烧温度至1000℃,产物中出现相当量的杂相,大大降低了材料的容量。Si/Li4Ti5O12材料的首次充放电容量随煅烧温度的升高呈现先升高后又下降的变化,并在700℃获得最大值。Li4Ti5O12的引入较明显地改善了Si负极材料的循环稳定性。

A sol-gel method has been used to fabricate Li_4Ti_5O_（12） and coated it on the surfaces of nano-Si particles forming Si/Li_4Ti_5O_（12） composites as anode materials for lithium ion batteries.Different calcination temperatures were used.The structures of the products are analyzed by X-ray diffractometry（XRD）,scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,high resolution TEM（HRTEM） as well as energy dispersive spectrometry（EDS）.Combing the electrochemical properties testing including galvanostatic charge-discharge and cyclic voltammetry（CV） measurement,the effects of the calcination temperature on the structure and electrochemical properties of the Si/Li_4Ti_5O_（12） materials are studied.The action of the Li_4Ti_5O_（12） on the cycle performance of the Si/Li_4Ti_5O_（12） anode is discussed.The results show that in the calcination temperature range of 600 to 800℃,Li_4Ti_5O_（12） is the main phase formed from the gel precursor,and the Si in the products preserved its crystal structure and nano size.When the calcination temperature is increased to 1000℃,considerable impurity forms in the products,lowering the capacity greatly.The first discharge/charge capacities of Si/Li_4Ti_5O_（12） increase at first and then decrease with increasing the calcination temperature,displaying a maximum value for the calcination temperature of 700℃.The introduction of Li_4Ti_5O_（12） improves effectively the cyclic stability of the Si/Li_4Ti_5O_（12） nanocomposites.