多孔钛基氧化物锂离子电池负极材料制备及其电化学性能

发布时间：2018-06-09 13:46

本文选题：锂离子电池 + 二氧化钛　；参考：《浙江大学》2016年博士论文

【摘要】：锂离子电池作为新一代绿色能量储存和转化装置,被广泛应用于通信设备、便携式电子设备、静态储能系统、电动汽车等领域。目前,碳材料因其价格低廉、资源丰富等优点被广泛用作商业化锂离子电池的负极材料。但碳负极材料在放电至较低电压时,会产生锂枝晶,导致电池短路,易造成严重的安全问题；同时,在不断的充放电过程中,碳负极的表面不可避免地形成一层不稳定的电子绝缘固体电解质界面膜(SEI),导致容量的快速衰减和性能的恶化,制约着碳负极材料的发展和应用。钛基氧化物材料(TiO2和Li4Ti5O12相对于传统碳负极材料具有较高的电压平台、充放电过程中体积变化小等优点,具有很好的安全性和循环稳定性,被认为是一种非常有应用前景、可替代碳的新型负极材料。然而,钛基氧化物负极材料较低的电子传导率和锂离子扩散速率导致倍率性能不佳,从而限制其实际应用。提高电子的传导和锂离子的传输,已成为钛基氧化物材料的主要研究方向之一。本文在综合论述了锂离子电池负极材料、TiO2负极材料、Li4Ti5O12负极材料研究现状的基础上,以钛基氧化物材料TiO2和Li4Ti5O12为研究对象,设计阶层多孔、微纳结构、多相复合结构,采用溶胶-凝胶技术,分别制备了阶层多孔二氧化钛／碳(TiO2/C)复合材料、椭球形微纳结构钛酸锂-二氧化钛(Li4Ti5O12-TiO2)复合材料、钛酸锂/二氧化钛/碳(Li4Ti5O12/TiO2/C)纳米晶复合材料、多孔TiO2气凝胶材料等材料体系,分析了钛基氧化物材料的溶胶-凝胶制备机理,探索尺寸、形貌、以及材料复合对电极材料的电化学性能影响,揭示了纳米化、多孔结构、微纳结构、多相复合的作用机制,借助形貌和微结构的调控来改善钛基氧化物材料的倍率性能和循环稳定性,为钛基氧化物负极材料的实际应用奠定重要基础。主要研究结果如下：(1)开展了阶层多孔二氧化钛/碳(TiO2/C)复合材料的制备及其储锂性能研究。以硫酸氧钛为钛源,聚乙烯吡咯烷酮(PVP)为相分离诱导剂和碳源,采用溶胶-凝胶伴随相分离法制备了TiO2/C复合材料。所制备的复合材料具有独特的阶层多孔结构,其大孔呈三维共连续贯通,孔径为1-3 μm,骨架由10～30 nm的纳米晶集聚而成；PVP在惰性气氛中裂解为碳,与Ti02材料进行原位复合。所制备的阶层多孔TiO2/C复合材料表现出优越的电化学性能,在1 C下循环100次容量保持在132 mAh g-1,30 C大倍率下可逆容量仍达96 mAh g-1。阶层多孔、高比表面积、碳原位复合是TiO2/C复合材料具有优异循环性能和高倍率性能的主要原因。(2)开展了椭球形微纳结构钛酸锂-二氧化钛(Li4Ti5O12-TiO2)复合材料的制备及其储锂性能研究。以钛酸四丁酯为钛源,二水合醋酸锂为锂源,冰醋酸为凝胶促进剂,采用溶胶-凝胶法制备了椭球形微纳结构Li4Ti5O12-TiO2复合材料。所制备的材料是具有微纳结构的多相复合材料,相组成为Li4Ti50O12、锐钛矿和金红石,尺寸为30-80 nm的纳米晶单元构成了椭球形微米颗粒,其颗粒尺寸为3-5 μm。微纳结构多相复合材料拥有大量的相界,有效提高锂离子的传输速度,显示出优异的储锂性能,在10 C下循环100次后可逆容量保持为92mAhg-1,即使在30 C大倍率下,其容量依旧有89 mAh g-1。研究表明微纳多孔结构和多相复合能有效改善Li4Ti5O12材料的电化学性能。(3)开展了钛酸锂/二氧化钛/碳(Li4Ti5O12/TiO2/C纳米晶复合材料的制备及其储锂性能研究。以钛酸四丁酯为钛源、二水合醋酸锂为锂源、冰醋酸为凝胶促进剂,采用溶胶-凝胶法制备了Li4Ti5O12/TiO2/C纳米晶复合材料。所制备Li4Ti5O12/TiO2/C纳米晶的物相组成为Li4Ti5O12和锐钛矿型TiO2,尺寸分布在50-100 m。相对Li4Ti5O12与Li4Ti5O12/TiO2, Li4Ti5O12/TiO2/C纳米晶复合材料表现出更好的倍率性能和循环稳定性,30 C高倍率下,其可逆容量仍达88 mAh g-1,在1 C倍率下100次循环后可逆容量保持在102 mAh g-1,为初始容量的80%。Li4Ti5O12/TiO2/C纳米晶的优越电化学性能主要来源于纳米晶、多相复合和原位生成碳的综合作用。(4)开展了多孔TiO2气凝胶材料的制备及其储锂性能的研究。以钛酸四丁酯(TBOT)为钛源、F127为表面改性剂,采用溶胶-凝胶法结合表面改性,常压干燥制备了TiO2气凝胶材料,并首次将TiO2气凝胶材料应用于锂离子电池负极材料。所制备的气凝胶具有高孔隙率,其比表面积高达431 m2·g-1.900℃热处理得到结晶完全的锐钛矿TiO2气凝胶,其比表面积减小至131m2·g-1。 800℃热处理的TiO2气凝胶表现出最优的电化学性能,其初始的放电和充电容量分别为180和135 mAh g-1,首次库伦效率为75%,100次循环后其可逆容量能保持在114mAh g-1,较好的电化学性能得益于均匀的孔结构、较高的比表面积和较好的结晶性。
[Abstract]:As a new generation of green energy storage and conversion device, lithium ion battery is widely used in the fields of communication equipment, portable electronic equipment, static energy storage system, electric vehicle and other fields. At present, carbon materials are widely used as negative materials for commercial lithium ion batteries because of their low price and rich resources. At the lower voltage, the lithium dendrite will lead to the short circuit of the battery and cause the serious safety problems. At the same time, the surface of the carbon negative electrode inevitably forms a layer of unstable electronic insulating solid electrolyte mask (SEI) on the surface of the carbon negative electrode during the continuous charging and discharging process, which leads to the rapid attenuation of the capacity and the deterioration of the performance, which restricts the carbon negative electrode material. Titanium based oxide materials (TiO2 and Li4Ti5O12) have the advantages of high voltage platform and small volume change in charge discharge process compared with traditional carbon negative electrode materials. It has good safety and cyclic stability. It is considered to be a new negative electrode for replacing carbon. However, the negative titanium oxide negative material is negative. The low electronic conductivity and lithium ion diffusion rate of polar materials lead to poor multiplying performance, thus limiting their practical applications. Improving the conduction of electrons and the transmission of lithium ions has become one of the main research directions of titanium based oxide materials. In this paper, lithium ion battery negative electrode, TiO2 negative electrode, Li4Ti5O12 negative electrode have been discussed in this paper. On the basis of the research status, TiO2 and Li4Ti5O12 were used as the research object. The porous, micro nano structure and multiphase composite structure were designed. The stratum porous titanium dioxide / carbon (TiO2/C) composite and the ellipsoidal micro nano structure lithium titanate titanium dioxide (Li4Ti5O12-TiO2) composite were prepared by the sol-gel technique. Lithium titanate / titanium dioxide / carbon (Li4Ti5O12/TiO2/C) nanocrystalline composites and porous TiO2 aerogel materials are used to analyze the preparation mechanism of the sol-gel of titanium based oxide materials, explore the size, morphology, and the electrochemical properties of the electrode materials, and reveal the nanoscale, porous structure, micro nano structure and multiphase complex. The synthesis of titanium based oxide materials can be improved by the combination of morphology and microstructures. The main results are as follows: (1) the preparation of stratum porous titanium dioxide / carbon (TiO2/C) composite and its lithium storage performance With titanium sulfate as the titanium source and polyvinylpyrrolidone (PVP) as the phase separation inducer and carbon source, the TiO2/C composite was prepared by the sol-gel accompanying phase separation method. The composite material has a unique stratum porous structure, its large pore is three dimensional continuous penetration, the pore size is 1-3 u m, and the framework of the skeleton is 10~30 nm nanocrystalline. In addition, PVP is cracked into carbon in the inert atmosphere and in situ composite with Ti02 material. The prepared stratum porous TiO2/C composite exhibits excellent electrochemical performance, and the reversible capacity remains 96 mAh g-1. stratum porous, high specific surface area, and carbon in situ composite is TiO2/C under 1 C at 1 C. The main reasons for the excellent cycling properties and high ratio properties of the composites are obtained. (2) the preparation of the lithium titanate titanate (Li4Ti5O12-TiO2) composite with ellipsoidal micro nano structure and the study of its lithium storage properties are carried out. The preparation of the composite with four butyl titanate as the titanium source, two lithium acetate as the lithium source, the glacial acetic acid as the gel promoter, and the sol-gel method are prepared. The ellipsoidal micro nano structure Li4Ti5O12-TiO2 composite has been prepared. The material is a multiphase composite with micronano structure. The phase group becomes Li4Ti50O12, anatase and Jin Hongshi, and the nanocrystalline element with a size of 30-80 nm consists of ellipsoidal microparticles. The particle size of the composite material with a particle size of 3-5 mu m. has a large number of phases. Boundary, effectively improving the transmission speed of lithium ion, showing excellent lithium storage performance, the reversible capacity is 92mAhg-1 after 100 cycles under 10 C. Even at 30 C large ratio, the capacity still has 89 mAh g-1. studies showing that microporous structure and multiphase composite can effectively improve the electrochemical properties of Li4Ti5O12 materials. (3) lithium titanate / The preparation of titanium dioxide / carbon (Li4Ti5O12/TiO2/C nanocrystalline composite and its lithium storage properties), Li4Ti5O12/TiO2/C nanocrystalline composite was prepared by sol-gel method with four butyl titanate as titanium source, two lithium acetate as lithium source and glacial acetic acid as gel promoter. The phase group of preparation of Li4Ti5O12/TiO2/C nanocrystals became Li4Ti5 O12 and anatase TiO2, with a size distribution at 50-100 M. relative to Li4Ti5O12 and Li4Ti5O12/TiO2, Li4Ti5O12/TiO2/C nanocrystalline composites exhibit better multiplication and cyclic stability. The reversible capacity of the composite is still 88 mAh g-1 under the high rate of 30 C, and the reversible capacity is kept at 102 mAh g-1 after 100 cycles of 1 C multiplier, which is 80 of the initial capacity. The superior electrochemical properties of%.Li4Ti5O12/TiO2/C nanocrystals are mainly derived from the synthesis of nanocrystalline, polyphase composite and in situ formation of carbon. (4) the preparation of porous TiO2 aerogels and their lithium storage properties were studied. The titanium titanate (TBOT) was used as the titanium source and F127 as the surface modifier. The sol-gel method combined with surface modification was used. TiO2 aerogels were prepared by compression drying, and TiO2 aerogels were applied to lithium ion batteries for the first time. The aerogels prepared have high porosity, and their specific surface area is up to 431 m2. G-1.900 C. The crystalline anatase TiO2 aerogels are obtained, and their specific surface area is reduced to TiO2 gas treated by 131m2. G-1. 800 C. The gel shows the best electrochemical performance, its initial discharge capacity and charge capacity are 180 and 135 mAh g-1 respectively, the first Kulun efficiency is 75%, and the reversible capacity can be kept at 114mAh g-1 after the 100 cycle. The better electrochemical properties benefit from the uniform pore structure, the higher specific surface area and better crystallinity.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TM912;TQ134.11

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