【作者】 刘瑶；

【导师】 陈猛；

【作者基本信息】 哈尔滨工程大学 ， 应用化学， 2009， 硕士

【摘要】 本文分别采用高温固相法和溶胶-凝胶法合成了尖晶石型Li4Ti5O12,并对其进行了阳离子一元掺杂,考察了不同掺杂比例和不同掺杂元素对锂离子电池负极材料的影响。根据离子半径与Ti4+相近原则,选取以下掺杂方案：对高温固相法合成的尖晶石型Li4Ti5O12进行Sn4+、Zr4+的一元掺杂和溶胶-凝胶法合成的尖晶石型Li4Ti5O12进行Sn4+一元掺杂。采用XRD和SEM测试了材料的晶体结构和表面形貌,采用恒流充放电测试、电化学阻抗测试、循环伏安测试分析了材料作为锂离子电池负极材料的综合电化学性能。XRD和SEM测试分析表明,采用传统的高温固相法和溶胶-凝胶法都成功合成了尖晶石型Li4Ti5O12材料晶体结构的特征峰与尖晶石型钛酸锂的标准图谱(26-1198)相吻合,只是峰强度和峰宽与标准图谱有所不同。阳离子掺杂并未改变材料的尖晶石结构,只是当掺杂量较大时,材料中有微量杂质相出现,但主体材料仍为尖晶石型锂钛氧化物。高温固相法合成的尖晶石型Li4Ti5O12进行Sn4+、Zr4+掺杂后,样品的放电平台平坦,集中在2.4 V左右,且放电平台范围较宽,首次放电容量较大。样品Sn：Ti=1：9(原子比)的综合性能最好,50次循环后,比容量仍保持在111 mAh.g-1以上,容量保持率为81%。Zr4+掺杂对提高材料的比容量效果不明显,且当掺杂量较大时,样品的容量保持率降低。其中以样品Zr：Ti=1：24(原子比)循环性能最为理想,其50次循环后容量仍保持在119 mAh·g-1以上,容量保持率为87.35%。采用溶胶-凝胶法制备的尖晶石型Li4Ti5O12进行Sn4+掺杂后,样品的放电平台更加平坦,首次放电容量更大。其中以样品Sn：Ti=1：4(原子比)所得的材料性能最好。其首次放电容量达到144.21 mAh.g-1以上,经过50次充放电循环后,容量保持在137.58mAh.g-1,容量保持率为95.34%。更多还原

【Abstract】 The lithium titanate composites were synthesized respectively by high temperature solid-state method and sol-gel method and doped with cations, and then the influences to the samples as the anode materials for lithium ion battery were studied with different doping ratio and doping elements. According to the ion diameter, the following doping plans were chose:Sn4+、Zr4+cations doping in the lithium titanate composites were synthesized respectively by high temperature solid-state method and Sn4+cations doping in the lithium titanate composites were synthesized respectively by high temperature sol-gel method dibasic doping. The crystalline structure of the samples was analyzed by X-ray diffraction analysis, and SEM exterior analysis and the electrochemical proprieties of the samples were tested by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and galvanostatic cycling tests. The results were listed as follows:The XRD and SEM test indicated that, the spinel lithium titanate composite Li4Ti5O12 was successfully synthesized by the traditional solid-state method and sol-gel method.The peaks of the sample were identical with that of the standard chart (26-1198) with some differences of the intensity and width of the peaks. Cation doping did not change the spinel structure of the sample, but when with larger doping amount, the spinel lithium titanate samples were not very pure.Sn4+、Zr4+cations doping in the lithium titanate composites were synthesized respectively by high temperature solid-state method:The doped samples had a wide and flat discharge platform around 2.4 V, and the initial discharge capacity of the doped samples was large. The performance of sample Sn:Ti=1:9(molar ratio) is the best, which obtained a capacity of 111 mAh-g-1 with a capacity retention of 81% after 50 cycles. The Zr4+doping increased the capacity of the material, but when with a larger doping amount, the capacity retention of the sample decreased; The cycle performance of sample Zr:Ti=1:24 (molar ratio) is the best, which obtained a capacity of 119 mAh·g-1 with a capacity retention of 87.35% after 50 cycles.Sn4+cations doping in the lithium titanate composites were synthesized respectively by high temperature sol-gel method:The doped samples had a wider flat discharge platform and the initial discharge capacity of the doped samples was large. The performance of sample Sn:Ti=1:4(molar ratio) is the best, and the sample as the anode material for lithium ion battery had an initial capacity of 144.2 mAh-g-1,obtained a capacity of 137.58 mAh-g-1 with a capacity retention of 95.34%after 50 cycles.更多还原