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题名: 层状锰系正极材料制备及性能研究
作者: 王欢欢
答辩日期: 2014-05-28
导师: 康雪雅
专业: 材料物理与化学
授予单位: 中国科学院大学
授予地点: 北京
学位: 硕士
关键词: 正极材料 ; 富锂锰基 ; 离子交换法 ; 化学计量比 ; Li2MnO3相
摘要: 化石能源的广泛使用让我们享受现代化生活的同时,也在积聚了百余年之后爆发它的另一面——环境污染、能源匮乏等问题。人类越来越陷入这种便利舒适的生活不能自拔,同时对环境也提出了更高的要求。我们既要享受汽车、便携式电子设备带来的现代化社会,又要保持人与自然和谐相处,这就需要依赖二次电池技术的应用和发展,其中锂离子二次电池技术因为长寿命、高安全、大容量、轻质化和绿色环保等诸多优势成为最理想可靠的二次电池技术。 锂离子电池由正极材料、负极材料、隔膜、电解质以及其它关联部件组成,其中正极材料是锂离子电池技术发展的最大瓶颈。常用的大规模商业化的正极材料包括钴酸锂(LiCoO2)、磷酸铁锂(LiFePO4)、锰酸锂(LiMn2O4)、三元材料(Li[Ni,Co,Mn]O2)等。考虑到材料中部分元素的毒性和成本问题,锰基材料脱颖而出,成为锂电子电池研究领域的热点,富锂锰基材料因自身较高的容量、稳定的循环性能成为下一代商用锂离子电池的理想选择。本论文采用高温固相法和共沉淀法合成富锂锰基材料0.5Li2MnO3·0.5Li[Ni1/3Co1/3Mn1/3]O2。运用X射线衍射(XRD)确定产物是包含有Li2MnO3相的富锂材料,恒电流充放电曲线测试表明共沉淀法相较于高温固相法合成的最终产物具有更优异的电化学性能,高温固相法产物在25 mA/g(0.1 C)电流密度下首次充电比容量为288 mAh/g,首次库仑效率63%,平均放电容量约为175 mAh/g;而共沉淀法产物首次充电比容量达到322 mAh/g,首次库仑效率也有82%,平均放电容量更是高达260 mAh/g。部分研究者通过离子交换法合成具有优异电化学性能的层状LiMnO2,本论文在此基础上通过离子交换法合成具有化学计量比的最终产物LixLi’1-xNa0.06MnO2(变量x取0,0.1,0.2,0.25,0.35),控制合成过程两个阶段锂源添加量调整最终产物中变量x值。产物通过X射线衍射(XRD)表征和电化学循环测试发现最终产物中包含有Li2MnO3相,单斜Li2MnO3相和层状LiyNa0.06MnO2的比例与最终产物中变量x值相关联。这一成果拓展了对富锂相的认知,通过扫描电镜(SEM)、比表面积分析(BET)和恒电流充放电测试表明Li0.25Li’0.75Na0.06MnO2和Li0.35Li’0.65Na0.06MnO2表现出优异的电化学性能,Li0.25Li’0.75Na0.06MnO2在10 mA/g(0.04 C)的测试条件下首次充电容量达到206 mAh/g,Li0.35Li’0.65Na0.06MnO2显示出更优异的循环稳定性,平均放电容量达到150mAh/g。各个样品不同的电化学性能主要归因于含有的单斜Li2MnO3相的比例,优异的电化学性能使LixLi’1-xNa0.06MnO2材料成为那些含有毒性和价格高昂元素的电极材料可选的替代。
英文摘要: On the one hand, the widespread use of fossil fuels had brought us to enjoy modern society life, on the other hand, it showed the other side of fossil fuels over a hundred years later---- environmental pollution and energy shortages. Human being was stuck in this convenient and comfortable life which brought by automobiles and portable electronic devices, and required more healthful living environment. In order to meet these requirements, we must rely on the application and development of the secondary battery technologies. The lithium-ion rechargeable battery technology with long life, high safety, high-capacity, lightweight, and environmental protection was the ideal and reliable secondary battery technology. The lithium-ion battery was consisted of the cathode material, anode material, separator, electrolyte and other related components, among them, the cathode material was the biggest bottleneck in the development of the lithium-ion battery. The commercial cathode materials include lithium cobalt oxide (LiCoO2), lithium iron phosphate (LiFePO4), lithium manganese oxide spinel (LiMn2O4) and nickel cobalt manganese ternary material (Li[Ni,Co,Mn]O2). Taking into account the toxicity and cost of some elements in the cathode materials, the lithium-rich manganese-based cathode material which with high capacity and stable cycle performance was the ideal option for the next generation of commercial lithium-ion batteries. In this thesis, we synthesized the lithium-rich manganese-based material written as 0.5Li2MnO3?0.5Li[Ni1/3Co1/3Mn1/3]O2 by the high temperature solid state method and coprecipitation method. We confirmed the Li2MnO3 phase in the obtained material by X-ray diffraction (XRD) method. The products were characterized by the galvanostatic charge-discharge cycling technique in order to investigate the electrochemical properties. The first charge capacity of the product obtained by the high temperature solid state method was 288 mAh/g and the first coulomb efficiency was 63%, the average discharge capacity was 175 mAh/g, by contrast, The first charge capacity of the product obtained by the coprecipitation method was 322 mAh/g and its first coulomb efficiency reached up to 82%, the average discharge capacity was 260 mAh/g. Using ion-exchange method, previous researchers have successfully synthesized cathode materials with excellent electrochemical properties. In this paper, the stoichiometrical LixLi’1-xNa0.06MnO2 containing Li2MnO3 phase was synthesized depending on the two stages which was the characteristic of the ion-exchange route. The additive proportion of Li in the first and second steps of the ion exchange process was changed in the purpose of regulating the proportional relation of the layered LiyNa0.06MnO2 and the monoclinic Li2MnO3 (m-Li2MnO3) phases. The exist of the Li2MnO3 phases was confirmed by the X-ray diffraction (XRD) and the electrochemical testing. The LixLi’1-xNa0.06MnO2 cathode material was characterized by scanning electron microscopy (SEM), surface area analysis method (BET) and galvanostatic charge-discharge cycling technique in order to investigate the crystalline structure, surface morphology and electrochemical property. Through our experiments, Li0.25Li’0.75Na0.06MnO2 and Li0.35Li’0.65Na0.06MnO2 behaved the excellent electrochemical performance. Li0.25Li’0.75Na0.06MnO2 could deliver the capacity of 206 mAh/g at 10 mA/g in the first charge process, and Li0.35Li’0.65Na0.06MnO2 showed outstanding cycle stability. Its average discharge specific capacity reached 150 mAh/g. The improved performance might arise from the existence of the optimal proportion of m-Li2MnO3 phase. This stoichiometrical LixLi’1-xNa0.06MnO2 might be a good substitute for the cathodes containing poisonous or expensive metals.
内容类型: 学位论文
URI标识: http://ir.xjipc.cas.cn/handle/365002/3433
Appears in Collections:材料物理与化学研究室_学位论文

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作者单位: 中国科学院新疆理化技术研究所

Recommended Citation:
王欢欢. 层状锰系正极材料制备及性能研究[D]. 北京. 中国科学院大学. 2014.
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