【作者】 王希敏；

【导师】 王先友；

【作者基本信息】 湘潭大学 ， 无机化学， 2007， 硕士

【摘要】 近年来,以嵌锂化合物作为正极材料的锂离子蓄电池由于具有电压高、质量轻、比能量密度高等优点,成为便携式摄像机、手机、蜂窝电话、笔记本电脑等移动电子器件的主要能源,并逐步向电动汽车、混合型电动汽车和高效储能系统等领域拓展。目前,LiCoO₂由于容量高,可逆性和倍率性好成为商业化锂离子电池的主要正极材料,但由于其成本、容量以及安全性方面等问题,人们正努力试图寻找一种可替换材料。本文采用氨配合氢氧化物共沉淀法制备出粒径均匀的球形(Ni_0.8Co_0.1Mn_0.1)（OH）₂粒子作为前驱体。考察了反应时间、溶液的pH值、加氨量对前驱体(Ni_0.8Co_0.1Mn_0.1)（OH）₂物理和化学性能的影响,发现制备球形前驱体(Ni_0.8Co_0.1Mn_0.1)（OH）₂的最佳工艺条件为:pH=11.5,NH₃/M=2.5,反应时间t=16 h。以球形(Ni_0.8Co_0.1Mn_0.1)（OH）₂为前驱体,用固相合成技术制备了高密度球形LiNi_0.8Co_0.1Mn_0.1O₂正极材料。探讨了固相反应条件,如烧结温度,烧结时间以及Li/（Ni+Mn+Co）等对材料性能的影响,发现最佳制备工艺为:Li/（Ni+Mn+Co）=1.07,材料造粒后在480℃预热5 h,再于650℃预热9 h,然后在750℃锻烧16 h。最后,本论文对所制备的LiNi_0.8Co_0.1Mn_0.1O₂电极材料形貌、密度和结构进行了表征,并重点探讨了LiNi_0.8Co_0.1Mn_0.1O₂材料的电化学性能。最优条件下合成的LiNi_0.8Co_0.1Mn_0.1O₂粉末保持了原前驱体形貌,仍为二次球形粒子,发现该粒子是由直径500-800 nm的一次粒子堆积形成的类球形二次粒子。一次粒子的晶体发育完全,结晶度较高,所得样品的振实密度为2.3-2.5g·cm^-3,接近于商业化LiCoO₂。电化学测试表明,其首次放电容量和库仑效率分别为168.6 mA·h/g和90.5%,20次循环后容量为161.7 mA·h/g,保持率达到95.9%,是一种很有前景的新型锂离子电池正极材料。更多还原

【Abstract】 Lithium-ion batteries （LIB） with high energy density, power capability and long cycle life are used to power portable electronic devices such as cellular phones and laptop computers and have long been considered as possible power source for electric vehicle （EV）, hybrid electric vehicle （HEV） and high efficiency energy-storage systems. Layered LiCoO₂ is the most widely used cathode material in the present-day commercial Li-ion batteries. However, due to its high cost and toxicity, considerable effort has been expended over the past decade to find possible alternatives to LiCoO₂.Recently, LiNi_0.8Co_0.1Mn_0.1O₂ as a special case among the Li[Ni1-2xCoxMnx]O₂ series which x is 0.1 has attracted a great deal of interest in the investigation of cathode materials of LIB to replace the presently popular LiCoO₂ because the combination of Ni, Co, Mn can provide advantages such as high reversible capacity, stable cycling performance, good thermal stability, excellent rate capability and low cost. It is considered to be one of the best candidates of positive electrode material for hybrid electric vehicle （HEV） power source system. In this dissertation,the studies on the synthesis, morphology, structure and electrochemical performance of LiNi_0.8Co_0.1Mn_0.1O₂ as cathode materials for lithium ion batteries were carried out systemically and in detail.In this paper, the uniform spherical metal hydroxide (Ni_0.8Co_0.1Mn_0.1)（OH）₂ was prepared via hydroxide co-precipitation as precursor. This paper represents details of the optimized spherical (Ni_0.8Co_0.1Mn_0.1)（OH）₂ formation process by control reaction time, pH, amount of chelating agent, etc., during co-precipitation reaction. The results indicated that the optimum conditions for spherical (Ni_0.8Co_0.1Mn_0.1)（OH）₂ were that the pH of the aqueous solution was 11.5, the NH₃/M was 2.5 and the reaction time was 16h.Layered spherical LiNi_0.8Co_0.1Mn_0.1O₂ powders with high tap-density were successfully synthesized by mixing uniform co-precipitated spherical (Ni_0.8Co_0.1Mn_0.1)（OH）₂ with LiOH?H2O followed by heat-treatment. The mixture was pre-heated at 480℃and kept in this temperature for 5h, then kept at 650℃for 9h. The effects of calcination temperature, time and Li/（Ni+Mn+Co） ratio on electrochemical properties of the LiNi_0.8Co_0.1Mn_0.1O₂ were studied intensively. The results showed that the sample of LiNi_0.8Co_0.1Mn_0.1O₂ which were sintered for 16h at 750℃in a flowing oxygen atmosphere exhibited the best electrochemical performance.In this study, the morphology, tap-density, structure and electrochemical performance of the sample LiNi_0.8Co_0.1Mn_0.1O₂ obtained at optimal conditions have been further studied. The particle shape is still spherical, which is the same as the precursor (Ni_0.8Co_0.1Mn_0.1)（OH）₂. The SEM micrograph of LiNi_0.8Co_0.1Mn_0.1O₂ showed that a large number of spherical primary particles with an average size of about 500-800 nm pilled loosely to form quasi-spherical secondary particle. The corresponding tap-density was about 2.3-2.5 g·cm^-3, of which the value is close to that of commercialized LiCoO₂. Electrochemical measurement showed that it delivers an initial discharge capacity of 168.6 mA·h/g during the first charge and discharge cycle and the first coulombic efficiency is 90.5%, and the discharge capacity at the 20th cycle was 161.7 mA·h/g. The material will be potential cathode material for Li-ion battery.更多还原