锂离子电池用钛基负极材料合成及电化学性能研究

发布时间：2018-03-16 10:51

本文选题：锂离子电池　切入点：高电压　出处：《南开大学》2014年博士论文　论文类型：学位论文

【摘要】：锂离子电池在消费类电子中得到了广泛的应用,在纯电驱动汽车和混合动力汽车中处于规模应用阶段,在电网储能领域则处于性能考核及验证阶段,而汽车和储能行业对所采用电池体系的寿命、安全性和成本等提出了更高的要求。目前应用于消费类电子的产业化锂离子电池负极材料均采用石墨类材料,其具有离子和电子传导性好、结构稳定和嵌锂电位低等优点；但在反复充放电过程中,锂离子易在石墨负极沉积产生锂枝晶,进而刺穿电池隔膜而导致安全隐患或事故。因此,寻找安全型负极材料是电动汽车和储能行业用锂离子电池的重要研究方向之一。在安全型负极材料中,尖晶石结构的钛酸锂材料由于其独特的性能和结构优势而备受关注,成为安全型锂离子电池的首选负极材料之一。钛酸锂材料相对于金属锂的电位高(1.5V, vs Li/Li+),因此采用钛酸锂做负极材料的锂离子电池的工作电压和能量密度较低。本论文重点研究以钠离子取代锂离子制备纳米结构的钛酸锂材料,以期构筑钛酸锂材料的新结构,降低电位平台；采用商业化的微米级高电压LiNi0.5Mn1.5O4正极材料与研制的具有低电势的钛基负极材料配对制备软包装锂离子电池,开展电池性能研究与评价,以期提升电池的电压。本论文在以下三个方面开展了相关研究工作：一、Li4-xNaxTi5O12负极材料的合成及电化学性能研究将二氧化钛、无水碳酸锂和无水碳酸钠混合,采用高温烧结的方法,钠离子逐步取代锂离子,制备出Li4-xNaxTi5O12材料。可以明显地看出,随着Li4-xNaxTi5O12材料中钠离子和锂离子摩尔比例的逐渐提升,所制备材料的相结构由立方结构转变为斜方晶结构(LiNaTi3O7),最后转变为六方结构(Na4Ti5O12)。同时随着钠离子取代量的增加,所制备样品的晶体尺寸增大。钠离子取代锂离子后,所制备样品的放电容量有所降低,但材料的电势平台降低。尤其是Li2Na2Ti5O12材料样品,具有单一相结构,电位平台低且倾斜。因此,通过适量的钠离子取代钛酸锂材料中的锂离子,可提升所制备材料的电化学性能,如电势平台、放电容量和高倍率能力等。二、Li2-xNaxTi3O7负极材料的合成与电化学性能研究以Li2Ti307为基,采用钠离子替代的方式制备了Li2-xNaxTi3O7负极材料,研究了钠离子逐步替代对材料的电化学性能影响。研究显示,随着钠离子掺杂量的增加,晶体从斜方锰矿型的Li2Ti3O7相逐渐转变为斜方晶结构的LiNaTi3O7相。适量钠离子取代可实现材料的低电势及倾斜的电势平台。同时,钠离子的引入可节省锂资源,降低材料成本。三、Li2Na2Ti5O12/LiNi0.5Mn1.5O4软包装锂离子电池性能研究采用钠离子部分替代锂离子制备的Li2Na2Ti5O12材料和商业化的Li4Ti5O12材料,与商业化的高电压尖晶石LiNi0.5Mn1.5O4材料匹配,组装成软包装锂离子电池。电池测试性能表明,采用具有低电势的Li2Na2Ti5O12负极材料的确可以提升电池体系的放电电压,实现了本论文的预期设计思路。其中,在0.05C放电条件和相同比例放电容量(30%)下,采用Li2Na2Ti5O12负极的电池放电电压比采用Li4Ti5O12负极的电池高出约0.25V。综上所述,通过钠离子替代锂离子制备了纳米结构钛酸锂材料,适宜的替代量提升了材料的电化学性能,如电势平台、放电容量和高倍率能力等。制备的Li2Na2Ti5O12样品具有单一相,电位平台低且倾斜,具有良好的放电容量和倍率性能,同时降低了工作电势,可提高锂离子电池的工作电压；所采用的商业化微米级高电压镍锰酸锂(LiNi0.5M1.5O4)材料具有良好的电化学性能,采用研制的Li2Na2Ti5O12材料与之匹配制备软包装锂离子电池,提升了锂离子电池的工作电压,这为现有高性能材料改性研究和新型高性能材料研发提供了新思路。
[Abstract]:Lithium ion battery has been widely used in consumer electronics, in pure electric drive in the stage of large-scale application and hybrid vehicles, in the performance appraisal and field verification stage in grid storage, and storage of the car and battery life system industry, put forward higher requirements for safety and cost. At present, in the consumer electronics industry of lithium ion battery anode materials are used graphite materials with ionic and electronic conductivity, stable structure and intercalation potential advantages; but in repeated charge and discharge process of lithium ion, easy to produce lithium dendrite in graphite anode deposition, and then pierce the battery the diaphragm and lead to safety problems or accidents. Therefore, looking for safe type anode materials for electric vehicles and energy storage industry is an important research direction for lithium ion batteries. In safety type cathode material, spinel The lithium titanate material structure has attracted much attention because of its unique structure and performance advantages, become one of the safety type lithium ion battery cathode material lithium titanate. The preferred material relative to the potential of lithium metal (1.5V, vs, Li/Li+) high, so using lithium titanate as the cathode material of lithium from the work voltage and energy density than batteries low. This paper focuses on the study on sodium ion substituted lithium ion preparation of lithium titanate nano structural material, in order to build a new structure of lithium titanate material, reducing the potential platform; a micron high voltage LiNi0.5Mn1.5O4 cathode material and the development of the commercial material has a low potential of titanium based anode materials for preparation of soft package lithium pairing ion battery, carry out research and evaluation in order to improve the performance of the battery voltage, battery.
This paper has carried out relevant research work in the following three aspects:
Synthesis and electrochemical properties of Li4-xNaxTi5O12 negative electrode
The titanium dioxide, anhydrous lithium carbonate and anhydrous sodium carbonate mixed by high temperature sintering method, the sodium ion gradually replace the lithium ion, the preparation of Li4-xNaxTi5O12 materials. It can be clearly seen, with the gradually enhanced Li4-xNaxTi5O12 materials of sodium ion and lithium ion molar ratio, phase structure of the prepared materials changed from cubic structure for cable square crystal structure (LiNaTi3O7), and finally into the six party structure (Na4Ti5O12). At the same time, with the increasing amount of sodium ion substitution, the crystal size of the sample increases. The sodium ion substituted lithium ion, the discharge capacity of the sample decreased, but the potential platform material especially Li2Na2Ti5O12 material samples decreased. That has a single phase structure, and low potential platform tilt. Therefore, lithium ion lithium titanate material to replace the sodium ions through proper, can improve the electrochemical performance of as prepared materials, such as potential platform, Discharge capacity and high rate capacity and so on.
Study on the synthesis and electrochemical properties of two, Li2-xNaxTi3O7 negative electrode
Based on Li2Ti307, Li2-xNaxTi3O7 cathode materials were synthesized by sodium ion substitution method was studied, the sodium ion gradually replace the influence the electrochemical performance of the composites. The results show that with the increase of sodium ion doping, Li2Ti3O7 crystal from the ramsdellite type phase gradually transforms to the orthorhombic structure of the LiNaTi3O7 phase. The amount of sodium ion replace the potential platform can realize the low potential and inclined material. At the same time, the introduction of sodium ions can save lithium resources, reduce the material cost.
Study on the performance of three, Li2Na2Ti5O12/LiNi0.5Mn1.5O4 soft packed lithium ion battery
The sodium ion substitution of lithium ion Li2Na2Ti5O12 materials prepared and commercial Li4Ti5O12 materials, and high voltage spinel LiNi0.5Mn1.5O4 material business, assembled into a soft package lithium ion battery. The battery test showed that the performance of using Li2Na2Ti5O12 cathode materials with low potential can indeed enhance the discharge voltage of the battery system, to achieve the desired design ideas of this paper. Among them, in the same proportion and discharge conditions of 0.05C discharge capacity (30%), the battery discharge voltage of Li2Na2Ti5O12 electrode than the Li4Ti5O12 negative cells higher than about 0.25V.
In summary, the structure of lithium titanate nano materials were prepared by sodium lithium ion ion substitution, substitution amount to enhance the electrochemical performance of the material, such as potential platform, discharge capacity and high rate capability. The Li2Na2Ti5O12 samples prepared with a single phase, and has low potential platform tilt, discharge capacity and good rate capability. At the same time reduce the working potential, can improve the working voltage of the lithium ion battery; commercial micron high voltage lithium nickel manganese oxide used (LiNi0.5M1.5O4) material has good electrochemical performance, the development of the Li2Na2Ti5O12 material matched with the preparation of soft packaging lithium ion battery, improve the working voltage of the lithium ion battery, which provides a new idea for the existing high performance materials R & D research and new materials of high performance.

【学位授予单位】：南开大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM912

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