液相燃燒法制備鋰離子電池負極材料鈦酸鋰的研究
發(fā)布時間：2018-07-23 11:22
【摘要】：隨著全球電子產(chǎn)業(yè)的迅猛發(fā)展,新一代的電子設備逐步向著更加小型化與智能化的方向邁進。這種發(fā)展趨勢對下一代的鋰離子電池提出了一系列新的應用條件。高能量密度、高電勢、良好的循環(huán)性能、良好的高倍率充放電性能以及無污染性成為了研發(fā)新型鋰離子電池電極材料的基本要求。尖晶石結(jié)構(gòu)的鈦酸鋰是近年來被開發(fā)出的一種新型鋰離子電池負極材料。它除了滿足上述性能之外,還具有充放電電壓平穩(wěn),可逆容量高(175mAhg~(-1))等特點。此外,尖晶石鈦酸鋰作為一種“零應變”材料,具有極好的理論循環(huán)性能。所有這些優(yōu)點使其成為鋰離子電池領(lǐng)域中極具發(fā)展前景的電極材料,有著巨大的研究價值和商業(yè)應用價值。 然而,制備尖晶石鈦酸鋰材料一般采用固相法。固相法的合成步驟相對簡單,但是缺點也很明顯,即耗能高以及純度低。此外,Li_4Ti_5O_(12)材料的本征電子導電能力(電導率10~(-1)3Scm~(-1))和離子導電能力(鋰離子擴散系數(shù)約為2×10~(-8)cm2s~(-1))不高,因此Li_4Ti_5O_(12)在大電流充放電時容量衰減快、倍率性能較差,限制了其在動力鋰離子電池中的應用。本文針對以上問題,以鈦酸四丁酯,硝酸鋰等為原材料,采用液相燃燒法合成了納米級純相鈦酸鋰以及鈦酸鋰/碳復合材料,并通過對實驗方法以及實驗條件的探索,大大改善了燃燒法合成鈦酸鋰的生產(chǎn)工藝,從而促進了尖晶石型鈦酸鋰材料在鋰離子電池產(chǎn)業(yè)中的實際應用。其中獲得的主要成果與結(jié)論如下: 1.通過采用以P123為表面活性劑的燃燒法能夠合成具有多孔結(jié)構(gòu)的鈦酸鋰材料。多孔結(jié)構(gòu)能有效提高鈦酸鋰材料的電化學性能。 2.恰當?shù)臒崽幚砟苡行Ц纳柒佀徜嚇悠返母黜椞卣�。在不同的熱處理條件下,能得到具有不同晶粒大小、不同晶粒分散性已經(jīng)不同純度的樣品。在空氣中熱處理的樣品具有較好的純度和分散性,但是晶粒尺寸較大;在氬氣中熱處理的樣品具有較小的晶粒尺寸,但是晶粒分散性和純度較差。 3.考慮到在長時間以及高溫度的熱處理條件下鋰元素會因為蒸發(fā)而損失,所以在合成之初在原材料中加入適量額外的鋰原料是必要的。實驗證明,5%~10%的額外鋰源能有效改善最終產(chǎn)物的純度。 4.在空氣中和氬氣中對燃燒產(chǎn)物進行熱處理,具有5%額外鋰源含量的樣品均具有最高的首次充放電容量,分別達到了160.7 mAhg~(-1)和163.6 mAhg~(-1) (0.5C),約為理論容量的93.5%。說明產(chǎn)物的純度越高,分散性越好,其電化學性能越好。 5.不同鋰源含量的鈦酸鋰材料均具有較好的循環(huán)性能,在不同的充放電速率下經(jīng)過30次循環(huán),容量保持率均能保持在96%以上。這是由鈦酸鋰材料的固有性質(zhì)決定的。 6.對于在氬氣中熱處理的樣品來說,殘余碳的存在增強了合成產(chǎn)物的導電性,進而提高了其在高倍率下的充放電。
[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.
【學位授予單位】：哈爾濱工業(yè)大學
【學位級別】：碩士
【學位授予年份】：2011
【分類號】：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.
【學位授予單位】：哈爾濱工業(yè)大學
【學位級別】：碩士
【學位授予年份】：2011
【分類號】：TM912
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