【作者】 段文升；

【导师】 朱继平；

【作者基本信息】 合肥工业大学 ， 材料物理与化学， 2010， 硕士

【摘要】 目前商业化的锂离子电池负极材料广泛采用石墨,但石墨电极的不可逆容量损失较大,而且存在安全隐患等问题。尖晶石型Li₄Ti₅O₁₂作为新的锂离子电池负极材料,具有在充放电时晶体结构几乎不发生变化的特点,因而被称为“零应变”材料。与石墨电极相比,Li₄Ti₅O₁₂具有优良的循环性能和平稳的放电电压平台等优点,其安全性和使用寿命都大大提高。本文采用固相合成法对尖晶石型Li₄Ti₅O₁₂负极材料的掺杂改性和电化学性能进行了详细研究。目的旨在通过掺杂Mg、Al和包覆Cu来改善Li₄Ti₅O₁₂的电化学性能,考察了不同掺杂元素和不同掺杂比例对Li₄Ti₅O₁₂负极材料的性能影响,并对它们的最佳掺杂工艺进行了探讨。实验中采用XRD表征了Li₄Ti₅O₁₂材料的结构特征,采用激光粒度分析仪对产物进行了粒度分析。此外,还用充放电性能曲线和循环次数考察了产物的电化学性能。实验结果表明,固相反应合成的Li₄Ti₅O₁₂在700-900℃煅烧,并处理15-24h时可以提高产物的倍率性能,但如果处理时间过长或煅烧温度太高,则易导致颗粒团聚,从而降低产物的电化学性能。对于掺杂镁离子而言,产物的倍率性能比较优越,Li_4-xMg_xTi₅O₁₂ （x=0.1）具有良好的电化学性能和粒度分布,在0.5C, 1C, 5C, 10C倍率下放电时,首次放电比容量依次为175.8,151.5,140.3,121.3mAh/g。结果表明掺杂镁的Li₄Ti₅O₁₂,其高倍率性能得到了改善。在0.1C的倍率下放电时,Li_4-xAl_xTi₅O₁₂,（x = 0.05,0.1,0.2,0.3）的首次放电容量分别为135.5mAh/g,138.8mAh/g,141.2mAh/g和150.6mAh/g。掺杂Al的Li₄Ti₅O₁₂,其容量并没有得到改善,但是在一定程度上增加了循环稳定性。对于Li₄Ti₅O₁₂/CuO,在0.5C、1C、5C和10C倍率下放电时,放电比容量依次为228.7、173.3、159.8、144.3 mAh/g。铜添加剂极大地改善了纯钛酸锂的电化学性能和循环稳定性。更多还原

【Abstract】 The graphite-type carbon anode material has been widely used in the commercial lithium ion batteries, but its irreversible capacity loss is high and there is a potential safety problem. Spinel Li₄Ti₅O₁₂ as a new anode material for lithium-ion battery almost has no changes in the structure when charged and discharged and it has been called as "zero strain" material.Li₄Ti₅O₁₂ has excellent cycle performance and plateau voltage and so on.The safety and reliability of the material are improved greatly as compared with carbon electrode.In this thesis, the solid-state method and doping modification of spinel Li₄Ti₅O₁₂ anode materials were researched. The thesis focused on the improvement of the electrochemical properties of the Li₄Ti₅O₁₂ material doped by elements such as Mg、Al and Cu,the influences to Li₄Ti₅O₁₂ were studied with different doping ratio and doping elements, and their optimal synthetic process was studied. The samples were characterized and researched by XRD and laser particle size analyzer to get the images of their crystal structures and the particle size distribution. Moreover, the electrochemical properties of the doped products were studied by charge-discharge curves and cycle number. The experiment result indicated that Li₄Ti₅O₁₂ material synthesized at 700-900℃for 15-24h could enhance the electrode rate capabilities. However, overlong heat treatment and higher calcination temperature would result in the aggregation of particles and lead to a poor electrochemistry performance.As far as Li_4-xMg_xTi₅O₁₂ was concerned, it was found that the x=0.1 has a good electrochemistry performance and size distribution,the first discharge special capacity was 175.8, 151.5, 140.3, 121.3mAh/g at 0.5C, 1C, 5C, 10C rate, respectively. It was found that the high rate capability of Li₄Ti₅O₁₂ doped by magnesium had been improved.At 0.1C discharging rate, the first discharge specific capacities of Li4-xAlxTi5O12（x=0.05, 0.1, 0.2 and 0.3） were found to be 135.5mAh/g ,138.8mAh/g, 141.2mAh/g and 150.6mAh/g respectively. The capacity of the Li₄Ti₅O₁₂ doped by Al had not been improved, but cycle stability was enhanced, compared to the pristine Li₄Ti₅O₁₂. For Li₄Ti₅O₁₂/CuO, the discharge special capacity was 228.7, 173.3, 159.8, 144.3 mAh/g at 0.5C, 1C, 5C, 10C rate, respectively. The Cu additive effectively improved the cycle stability and electrochemical performance of the pristine Li₄Ti₅O₁₂.更多还原