液相燃烧法制备锂离子电池负极材料钛酸锂的研究
发布时间：2018-07-23 11:22
【摘要】：随着全球电子产业的迅猛发展,新一代的电子设备逐步向着更加小型化与智能化的方向迈进。这种发展趋势对下一代的锂离子电池提出了一系列新的应用条件。高能量密度、高电势、良好的循环性能、良好的高倍率充放电性能以及无污染性成为了研发新型锂离子电池电极材料的基本要求。尖晶石结构的钛酸锂是近年来被开发出的一种新型锂离子电池负极材料。它除了满足上述性能之外,还具有充放电电压平稳,可逆容量高(175mAhg~(-1))等特点。此外,尖晶石钛酸锂作为一种“零应变”材料,具有极好的理论循环性能。所有这些优点使其成为锂离子电池领域中极具发展前景的电极材料,有着巨大的研究价值和商业应用价值。 然而,制备尖晶石钛酸锂材料一般采用固相法。固相法的合成步骤相对简单,但是缺点也很明显,即耗能高以及纯度低。此外,Li_4Ti_5O_(12)材料的本征电子导电能力(电导率10~(-1)3Scm~(-1))和离子导电能力(锂离子扩散系数约为2×10~(-8)cm2s~(-1))不高,因此Li_4Ti_5O_(12)在大电流充放电时容量衰减快、倍率性能较差,限制了其在动力锂离子电池中的应用。本文针对以上问题,以钛酸四丁酯,硝酸锂等为原材料,采用液相燃烧法合成了纳米级纯相钛酸锂以及钛酸锂/碳复合材料,并通过对实验方法以及实验条件的探索,大大改善了燃烧法合成钛酸锂的生产工艺,从而促进了尖晶石型钛酸锂材料在锂离子电池产业中的实际应用。其中获得的主要成果与结论如下: 1.通过采用以P123为表面活性剂的燃烧法能够合成具有多孔结构的钛酸锂材料。多孔结构能有效提高钛酸锂材料的电化学性能。 2.恰当的热处理能有效改善钛酸锂样品的各项特征。在不同的热处理条件下,能得到具有不同晶粒大小、不同晶粒分散性已经不同纯度的样品。在空气中热处理的样品具有较好的纯度和分散性,但是晶粒尺寸较大;在氩气中热处理的样品具有较小的晶粒尺寸,但是晶粒分散性和纯度较差。 3.考虑到在长时间以及高温度的热处理条件下锂元素会因为蒸发而损失,所以在合成之初在原材料中加入适量额外的锂原料是必要的。实验证明,5%~10%的额外锂源能有效改善最终产物的纯度。 4.在空气中和氩气中对燃烧产物进行热处理,具有5%额外锂源含量的样品均具有最高的首次充放电容量,分别达到了160.7 mAhg~(-1)和163.6 mAhg~(-1) (0.5C),约为理论容量的93.5%。说明产物的纯度越高,分散性越好,其电化学性能越好。 5.不同锂源含量的钛酸锂材料均具有较好的循环性能,在不同的充放电速率下经过30次循环,容量保持率均能保持在96%以上。这是由钛酸锂材料的固有性质决定的。 6.对于在氩气中热处理的样品来说,残余碳的存在增强了合成产物的导电性,进而提高了其在高倍率下的充放电。
[Abstract]:With the rapid development of the global electronics industry, the new generation of electronic equipment is gradually moving towards a more miniaturized and intelligent direction. This development trend puts forward a series of new application conditions for the next generation lithium ion battery. High energy density, high potential, good cycling performance, high rate charge and discharge performance and no pollution have become the basic requirements for the development of new lithium ion battery electrode materials. Lithium titanate with spinel structure is a new type of anode material for lithium ion batteries developed in recent years. It not only meets the above performance, but also has the characteristics of steady charge-discharge voltage and high reversible capacity (175mAhg-1). In addition, lithium spinel titanate, as a "zero strain" material, has excellent theoretical cycling performance. All these advantages make it a promising electrode material in the field of lithium-ion batteries, which has great research value and commercial application value. However, the preparation of lithium spinel titanate materials is usually by solid state method. The synthesis procedure of solid-phase method is relatively simple, but the disadvantages are also obvious, that is, high energy consumption and low purity. In addition, the intrinsic electronic conductivity (conductivity 10-1) and ionic conductivity (ion diffusion coefficient about 2 脳 10 ~ (-8) cm ~ (-2) s ~ (-1) of Li4Ti5O _ (12) are not high. Its application in power lithium ion battery is limited. In order to solve the above problems, nanometer pure lithium titanate and lithium titanate / carbon composites were synthesized by liquid-phase combustion using tetrabutyl titanate and lithium nitrate as raw materials. The production process of lithium titanate synthesized by combustion method has been greatly improved, thus promoting the practical application of spinel lithium titanate material in lithium ion battery industry. The main results and conclusions are as follows: 1. Lithium titanate with porous structure can be synthesized by combustion method with P123 as surfactant. Porous structure can effectively improve the electrochemical performance of lithium titanate. 2. Proper heat treatment can effectively improve the characteristics of lithium titanate samples. Under different heat treatment conditions, samples with different grain size and different grain dispersity have been obtained with different purity. The samples heat treated in air have better purity and dispersity, but larger grain size, while the samples treated in argon have smaller grain size, but the dispersity and purity of grains are poor. 3. In view of the loss of lithium element due to evaporation under the condition of long time and high temperature heat treatment, it is necessary to add a proper amount of additional lithium raw material to the raw material at the beginning of synthesis. Experiments show that 10% extra lithium source can effectively improve the purity of the final product. When the combustion products were heat treated in air and argon, the samples with 5% extra lithium content had the highest initial charge and discharge capacities, reaching 160.7 mAhg-1 and 163.6 mAhg-1 (0.5C), respectively, which was about 93.5C of the theoretical capacity. The higher the purity and the better the dispersity, the better the electrochemical performance of the product. The lithium titanate materials with different lithium content have better cycling performance. After 30 cycles at different charge and discharge rates, the capacity retention rate can be kept above 96%. This is determined by the inherent properties of lithium titanate. 6. 6. For the samples heat treated in argon, the existence of residual carbon enhances the electrical conductivity of the synthesized products, and thus improves their charge and discharge at high rate.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2011
【分类号】：TM912
[Abstract]:With the rapid development of the global electronics industry, the new generation of electronic equipment is gradually moving towards a more miniaturized and intelligent direction. This development trend puts forward a series of new application conditions for the next generation lithium ion battery. High energy density, high potential, good cycling performance, high rate charge and discharge performance and no pollution have become the basic requirements for the development of new lithium ion battery electrode materials. Lithium titanate with spinel structure is a new type of anode material for lithium ion batteries developed in recent years. It not only meets the above performance, but also has the characteristics of steady charge-discharge voltage and high reversible capacity (175mAhg-1). In addition, lithium spinel titanate, as a "zero strain" material, has excellent theoretical cycling performance. All these advantages make it a promising electrode material in the field of lithium-ion batteries, which has great research value and commercial application value. However, the preparation of lithium spinel titanate materials is usually by solid state method. The synthesis procedure of solid-phase method is relatively simple, but the disadvantages are also obvious, that is, high energy consumption and low purity. In addition, the intrinsic electronic conductivity (conductivity 10-1) and ionic conductivity (ion diffusion coefficient about 2 脳 10 ~ (-8) cm ~ (-2) s ~ (-1) of Li4Ti5O _ (12) are not high. Its application in power lithium ion battery is limited. In order to solve the above problems, nanometer pure lithium titanate and lithium titanate / carbon composites were synthesized by liquid-phase combustion using tetrabutyl titanate and lithium nitrate as raw materials. The production process of lithium titanate synthesized by combustion method has been greatly improved, thus promoting the practical application of spinel lithium titanate material in lithium ion battery industry. The main results and conclusions are as follows: 1. Lithium titanate with porous structure can be synthesized by combustion method with P123 as surfactant. Porous structure can effectively improve the electrochemical performance of lithium titanate. 2. Proper heat treatment can effectively improve the characteristics of lithium titanate samples. Under different heat treatment conditions, samples with different grain size and different grain dispersity have been obtained with different purity. The samples heat treated in air have better purity and dispersity, but larger grain size, while the samples treated in argon have smaller grain size, but the dispersity and purity of grains are poor. 3. In view of the loss of lithium element due to evaporation under the condition of long time and high temperature heat treatment, it is necessary to add a proper amount of additional lithium raw material to the raw material at the beginning of synthesis. Experiments show that 10% extra lithium source can effectively improve the purity of the final product. When the combustion products were heat treated in air and argon, the samples with 5% extra lithium content had the highest initial charge and discharge capacities, reaching 160.7 mAhg-1 and 163.6 mAhg-1 (0.5C), respectively, which was about 93.5C of the theoretical capacity. The higher the purity and the better the dispersity, the better the electrochemical performance of the product. The lithium titanate materials with different lithium content have better cycling performance. After 30 cycles at different charge and discharge rates, the capacity retention rate can be kept above 96%. This is determined by the inherent properties of lithium titanate. 6. 6. For the samples heat treated in argon, the existence of residual carbon enhances the electrical conductivity of the synthesized products, and thus improves their charge and discharge at high rate.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2011
【分类号】：TM912
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