熔盐法制备锂离子电池正极材料的影响因素与性能

发布时间：2018-03-30 21:45

  本文选题：熔盐法　切入点：锂离子电池　出处：《武汉理工大学》2010年博士论文

【摘要】： 锂离子电池作为清洁高效的能源已经广泛应用于照相机、手机、笔记本电脑等便携式移动设备,并逐渐应用于电动汽车。一直以来,昂贵的价格制约着锂离子电池大规模车用化的发展。降低锂离子电池成本的关键是研究开发价格低廉的新材料以及采用简单易行的低成本制备方法。新材料的开发到最终应用往往需要数十年的时间,而制备工艺的优化通常能应用于多种材料的合成。 熔盐合成法是一种工艺简单的制备多元复合氧化物的方法,目前已经应用于个别电池材料的研究,但研究熔盐种类有限,缺乏系统性。本论文选择了层状结构材料Li(Ni0.5Mn0.5)O2、Li(Ni0.2Mn0.2Co0.6)O2和尖晶石结构LiMn2O4作为研究对象,系统研究了熔盐种类以及反应条件在熔盐法合成中对这些材料结构、形貌和电化学性能的影响。探索了熔盐法在合成层状和尖晶石状结构材料时,熔盐的选择规律。 在对Li(Ni0.5M0.5)O2材料的研究中,发现LiCl熔盐易造成最终产物的缺锂。LiNO3和Li2CO3作为熔盐均能合成出Li(Ni0.5Mn0.5)O2层状材料。LiNO3作为熔盐制备的材料循环稳定性好,其放电比容量大于Li2CO3熔盐制备的材料,但Li2CO3熔盐制备的材料放电比容量随循环有增大的趋势。将LiNO3和Li2CO3按不同比例组合所得熔盐对制备的Li(Ni0.5Mn0.5)O2形貌影响很大。当用0.9LiNO3-0.05Li2CO3作熔盐时,Li(Ni0.5Mn0.5)O2颗粒尺寸均匀,表面光滑,在恒流模式下充放电,放电比容量为150 mAh g-1,恒流恒压模式下为200 mAh g-1。 0.9LiNO3-0.05Li2CO3和0.38LiOH-0.62LiNO3均能作为熔盐制备Li(Ni0.2Mn0.2Co0.6)O2材料,但因为熔盐熔点不同,材料颗粒形貌不同,且放电比容量均不高。高温下的二次热处理能有效提高材料的放电比容量,以0.38LiOH-0.62LiNO3为熔盐,经二次处理过的Li(Ni0.2Mn0.2Co0.6)O2材料放电比容量达150 mAh g-1此外,氯化物和硫酸盐实验证明不适合制备层状Li(Ni0.2Mn0.2Co0.6)O2材料。 氯化物在制备尖晶石结构材料时优势明显。0.5NaCl-0.5KCl和0.6LiCl-0.4KCl都能制备出LiMn2O4材料。以0.5NaCl-0.5KCl作为熔盐制备的LiMn2O4材料具有一次纳米颗粒团聚成二次微米颗粒的形貌。具有该形貌的LiMn2O4,能达到124 mAh g-1的放电比容量,且循环性能优异。 最后,在上述材料的研究基础上,本论文总结了熔盐法合成锂离子电池正极材料的熔盐选择规律以及制备工艺影响。用熔盐法制备的锂离子电池材料均具有较好的循环性能。除氯化物和硫酸盐外,其它含锂单组分盐或者复合熔盐均能用于制备层状结构材料。熔盐的熔点对合成材料的形貌影响很大,进而影响材料的电化学性能。氯化物可优先选为制备尖晶石结构材料所用熔盐。熔盐法合成在高温(800℃左右)加热5-6小时就能制备出结构、形貌和电化学性能良好的电池材料。
[Abstract]:Lithium-ion batteries have been widely used in portable mobile devices such as cameras, mobile phones, laptops and other portable devices as clean and efficient energy sources, and have gradually been used in electric vehicles. The key to reducing the cost of lithium-ion batteries lies in the research and development of low-cost new materials and the simple and easy low-cost preparation method. It often takes decades to get to the end of the application, The optimization of the preparation process can be used in the synthesis of many materials. The method of molten salt synthesis is a simple method for the preparation of multicomponent composite oxides, which has been applied to the study of individual battery materials, but the kinds of molten salts are limited. In this paper, the layered structure material Li Li Ni 0.5 mn 0. 2 O 2 Li Li Li Ni 0. 2 mn 0. 2 Co 0. 6 O 2 and spinel structure LiMn2O4 were selected as the research objects. The types of molten salts and reaction conditions were systematically studied in the synthesis of these materials by molten salt method. The influence of morphology and electrochemical properties on the selection of molten salts in the synthesis of layered and spinel structure materials by molten salt method was investigated. In the study of Li(Ni0.5M0.5)O2 materials, it was found that the lithium-deficient Li-LiNo3 and Li2CO3 as the molten salts, which were the final products of LiCl, could be used as molten salts to synthesize Li(Ni0.5Mn0.5)O2 layered materials, which had good cycling stability, and their specific discharge capacity was higher than that prepared by Li2CO3 molten salts. However, the specific discharge capacity of the materials prepared by Li2CO3 melts increases with the cycle. The morphology of Li(Ni0.5Mn0.5)O2 is greatly affected by the combination of LiNO3 and Li2CO3 in different proportions. When 0.9LiNO3-0.05Li2CO3 is used as the molten salt, the size of Li(Ni0.5Mn0.5)O2 particles is uniform and the surface is smooth. The specific discharge capacity is 150 mAh g -1 in constant current mode and 200 mAh g -1 in constant current and constant voltage mode. Both 0.9LiNO3-0.05Li2CO3 and 0.38LiOH-0.62LiNO3 can be used as molten salts to prepare Li(Ni0.2Mn0.2Co0.6)O2 materials. However, because of the different melting points, the morphology of the materials is different, and the discharge specific capacity is not high. The secondary heat treatment at high temperature can effectively improve the discharge specific capacity of the materials, with 0.38LiOH-0.62LiNO3 as the molten salt. The specific discharge capacity of the secondary treated Li(Ni0.2Mn0.2Co0.6)O2 material is 150 mAh g ~ (-1). Furthermore, the chloride and sulfate experiments show that it is not suitable for the preparation of layered Li(Ni0.2Mn0.2Co0.6)O2 material. The advantages of chlorides in the preparation of spinel structure materials are obvious. 0.5NaCl-0.5KCl and 0.6LiCl-0.4KCl can both produce LiMn2O4 materials. The LiMn2O4 materials prepared with 0.5NaCl-0.5KCl as molten salt have the morphology of first order agglomeration of nanocrystalline particles into secondary micron particles. Limn _ 2O _ 4 can reach the discharge specific capacity of 124 mAh g ~ (-1). And the cycle performance is excellent. Finally, based on the research of the above materials, In this paper, the selection rule of molten salt and the influence of preparation process on the cathode materials of lithium-ion batteries synthesized by molten salt method are summarized. All the materials prepared by molten salt method have good cycling performance, except for chlorides and sulphates. Other lithium-containing monocomponent salts or composite melts can be used to prepare layered structure materials. The melting point of the molten salt has a great influence on the morphology of the synthesized materials. Chloride can be selected as the preferred molten salt for the preparation of spinel structure materials. The structure, morphology and electrochemical properties of the battery materials can be prepared by molten salt synthesis at about 800 鈩，

本文编号：1687771