【作者】 郑少伟；

【导师】 徐云龙；

【作者基本信息】 华东理工大学 ， 材料科学与工程， 2012， 硕士

【摘要】 Li4Ti5O12是一种理想的锂离子电池负极材料,充放电的过程中材料的晶体结构几乎不发生变化,Li+的嵌入和脱嵌对材料的晶体结构几乎没有影响,也就是所谓的“零应变”特性；嵌锂电位较高(1.55V vs. Li+/Li),充放电过程中不会引起金属锂的析出,能够在大多数有机电解液中使用；理论放电比容量为175mAh/g,实际放电比容量可高达150～160mAh/g;锂离子扩散系数比碳材料高一个数量级；库伦效率高、原材料来源广清洁环保。钛酸锂具备了下一代锂离子电池所必需的充放电次数多、充放电过程快、安全性好的特性。本文采用高温固相法,以锐钛矿型TiO2和Li2CO3为原料,按照锂钛摩尔比n(Li)/n(Ti)=0.84来取料,以去离子水作为分散剂,采用行星式高能球磨机球磨混料,研究了反应温度和反应时间对Li4Ti5O12合成的影响,得到该条件下制备Li4Ti5O12的最佳工艺条件为800℃下反应12h,产物在0.5C倍率下首次放电比容量为135.8mAh/g。采用上述的最佳合成工艺条件,以TiO2为钛源、Li2CO3为部分锂源、柠檬酸锂为碳源和部分锂源,制备得到Li4Ti5O12/C复合物,产物的一次粒子的平均粒径为70nm(同等条件下合成的纯Li4Ti5O12的颗粒的粒径为600nm),粒子表面包覆了一层厚约1nm的碳膜；Li4Ti5O12/C复合物具有优异的电化学性能,尤其是高倍率性能,20C倍率下首次放电比容量为121.1mAh/g,循环100次后比容量仍有106.1mAh/g,容量保持率高达87.6%。用恒电位间歇滴定法(PITT)测定了Li4Ti5012电极材料在充放电不同阶段的锂离子扩散系数DLi+,并在此基础上研究了Li4Ti5012的充放电过程。实验测得的锂离子在活性材料中的扩散系数为10-12-10-10cm2s-1数量级,主要集中在10-11cm2s-1附近；Li4Ti5O12在充放电过程中形成了核／壳结构。更多还原

【Abstract】 Spinel Li4Ti5O12 is a promising lithium ion battery anode material. It has some evident advantages:there is negligible volume change during charge/discharge process (the so-called "zero-strain insertion material"), so it possesses excellent reversibility; its Li-insertion potential is at about 1.55V vs. Li+/Li, which is high than the reduction voltage of common electrolyte; the diffusion coefficient is 2×10-11 cm2/s, so it has excellent lithium ion mobility that promising for high-rate battery applications. Furthermore, this material accommodates Li+ with theoretical capacity of 175 mAh/g. Compared with graphite anode material, Li4Ti5O12 is considered to be of better rate performance and safety.Anatase TiO2 and Li2CO3 were used as raw material to synthesize Li4Ti5O12 by solid-state method to study the optimal synthesis conditions of Li4Ti5O12. The moral ratio of n(Li)/n(Ti) was 0.84. Water was used as dispersant and ball-milling was used as mixing method. The result showed that the optimal synthesis conditions of Li4Ti5O12 were sintering 12h under 800℃. The initial discharge capacity at 0.5C was 135.8 mAh/g.Li4Ti5O12/C composite was prepared with the optimal synthesis conditions above and Li-citrate was used as carbon source and part of lithium source. The average particle size of as-prepared material was 70nm, while that of virgin Li4Ti5O12 synthesized under the same conditions was 600nm. The material showed excellent electrochemical performances, especially high-rate performances. The initial discharge capacity at 20C was 121.1 mAh/g, and after 100 cycles, it was still 106.1 mAh/g.PITT method was used to measure Li+ diffusion coefficient of Li4Ti5O12. The result showed that DLi+, ranged from 10-12 to 10-10cm2s-1 at various electrode potentials; core/shell structure was formed during charging/discharging process.更多还原