SnO2-Li4Ti5O12复合材料的溶胶-凝胶法制备与表征

Preparation and characterization of SnO2-Li4Ti5O12 composite by sol-gel technique

以SnCl4·5H2O、CH3COOLi·2H2O、（CH3（CH2）3O）4Ti和NH3·H2O为原料，采用溶胶-凝胶法制备SnO2-Li4Ti5O12复合材料粉末。采用热重和差热分析、X射线衍射、红外光谱、透射电镜和电化学测试等手段对复合材料的结构、表面形貌和电化学性能进行表征。结果表明：采用溶胶-凝胶法制备的复合材料是一种核-壳结构的纳米复合材料。在复合材料中，Li4Ti5O12以无定形态包覆在SnO2颗粒的表面，其包覆层的厚度为20-40nm。电化学研究表明，0．1C放电时SnO2-Li4Ti5O12复合材料粉末的可逆容量达到688．7mA·h／g，0．2C放电时经60次循环后复合材料的容量保持率达到93．4％。由于复合材料中Li4Ti5O12能够有效吸收SnO2电极的体积变化，有效阻止循环过程中Sn颗粒的聚集，大大改善了SnO2的循环稳定性。

SnO2-Li4Ti5O12 was prepared by sol-gel method using tin tetrachloride, lithium acetate, tetrabutylorthotitanate and aqueous ammonia as starting materials. The structure, morphology and electrochemical performance of composite were characterized by thermogravimertric （TG） analysis and differential thermal analysis （DTA）, X-ray diffractometry （XRD）, infrared （IR） spectroscopy, transmission electron microscopy （TEM） and electrochemical tests. The results show that SnO2-Li4Ti5O12 composite derived by sol-gel technique is a nanocomposite with core-shell structure, where the amorphous Li4Ti5O12 layer with 20-40 nm in thickness is coated on the surface of SnO2 particles. Electrochemical tests show that SnO2-Li4Ti5O12 composite delivers a reversible capacity of 688.7 mA·h/g at 0.1C and 93.4% of that is retained after cycling 60 times at 0.2C. The amorphous Li4Ti5O12 in composite can accommodate the volume change of SnO2 electrode and prevent the small and active Sn particles aggregating into larger and inactive Sn clusters during cycling effectively, and enhance the cycling stability of SnO2 electrode significantly.