【作者】 张娜；

【导师】 唐致远；

【作者基本信息】 天津大学 ， 应用化学， 2005， 博士

【摘要】 本论文的主要工作是通过高温固相法合成改性的动力锂离子电池正极材料尖晶石型锰酸锂,并将所研制的材料进行中试研究。主要采用阴阳离子复合掺杂和碳包覆以及钴酸锂改性的方式来提高锰酸锂的性能,并采用自制材料研制了性能良好的18650S型动力电池。研究工作主要从以下几个方面展开:系统地研究了几种阳离子单元掺杂时,不同掺杂浓度对合成产物的物相结构和电化学性能的影响。采用离子半径比Mn³⁺大,但有着比Mn-O键强很多的M-O键的元素Zr和稀土元素La、Ce和Nd对尖晶石锰酸锂进行单元掺杂改性,取得了很好的效果,稀土元素的掺杂可改善材料的高温（55℃）循环性能。对尖晶石锰酸锂进行了二元阳离子组合掺杂,进一步改善了材料的电化学性能。对尖晶石锰酸锂进行了阴阳离子的多元复合掺杂改性,通过筛选掺杂元素的组合方案和控制掺杂的量,制备出了既具有高的初始容量又有良好的常温和高温循环性能的尖晶石型锰酸锂正极材料LiCo_0.02La_0.01Mn_1.97O_3.98Cl_0.02。并初步研究了5V锰酸锂材料的性能。研究了锰酸锂正极材料的中试制备工艺,并研究了粒径对正极材料性能的影响,所制备的材料性能达到小试时的水平。首次利用葡萄糖和聚乙烯醇为碳源,合成了碳包覆的掺杂型锰酸锂复合材料,提高了材料的放电平台和放电容量;制备出性能优良的钴酸锂,利用直接混合和高温处理混合的方式进一步改善了锰酸锂的性能,当锰酸锂和钴酸锂以90 : 10的质量比混合时,可以发挥二者共同的优势,当二者以90 : 5的质量比混合并通过高温处理后的材料,具有较高的比容量和最佳的常温和高温循环稳定性。研究自制产品为正极材料的电动工具用动力18650S-1300mAh电池的制作工艺,所制作的电池具有良好的倍率性能和常温及高温循环性能,并通过了一系列的安全测试。最后探讨了动力锂离子电池中的不安全因素、爆炸机理和防爆措施,并从机理上解释了锰酸锂材料的安全性和实用性,指出研究开发性能更稳定的正极材料是解决动力电池安全性问题的重要方向。更多还原

【Abstract】 The spinel lithium manganese oxide cathode materials for lithium-ion power batteries were synthesized by solid-state method, and the 18650S cells using the as-prepared cathode materials were prepared. The lithium manganese oxide with better electrochemical performance was prepared by multidoping. The pilot-scale production of modified LiMn₂O₄ was performed. The modification effects of coated-carbon and mixing lithium cobalt oxide on the spinel lithium manganese were studied respectively. The power batteries with good performances were developed. The main contents of this dissertation are as follows:The effects of doping concentration on the phase structure and electrochemical performance of the produced cathode were systematically investigated with several kinds of cations mono-doped separately. Attempts were made in choosing the doping ions Zr and rare earth elements La, Ce and Nd for the spinel lithium manganese modification, which have larger ionic radius than Mn³⁺ while have much stronger M-O bond energy. It was proved that their doping is propitious to the produced spinel cathode and rare earth elements have greatly improved the cycle performance at elevated temperatre（55℃）. The binary-cation doping has much better effects on improving the electrochemical performance. The modified spinel cathode with two cations and one anion multiplex doped were synthesized. By choosing the doping ions combination scheme and controlling the doping quantum, perfect spinel lithium manganese cathode LiCo_0.02La_0.01Mn_1.97O_3.98Cl_0.02 was produced for the first time, which has high initial capacity as well as good cycle performances at both room temperature and high temperature. The properties of 5V spinel material were also characterized.The pilot-scale production technics of modified LiMn₂O₄ were investigated and the role of particle size in the cathode performance was also studied. So the pilot-scale samples have nearly good performance as that made in the lab. The coated-carbon composite cathode materials were made with glucose and polyvinyl alcohol as carbon additive, which has higher dischargeplateau and higher capacity. The well performed lithium cobalt oxide cathode was synthesized to modify the as-prepared spinel by directly mixing and by solid-state reactions using the mixture as precursors. The best mixing mass proportion of the two kinds of cathode materials was got from the experiments. When the direct mixing mass proportion of LiMn₂O₄ and LiCoO₂ was 90 : 10, the sample exhibits the superiority of the both kinds of materials. The mixture of the two with the mass proportion of 90 : 5 after heat treatment shows the best cycle stability with acceptable capacity.18650S-1300mAh cells used for powered tools were made with the self-productive materials as cathode. The power batteries had good high-rate discharge performance and good cycleability at room and high temperature. The cells also had passed some safety tests. In the end the factors influencing the cell safety were also evaluated and methods which could improve the safety of the lithium-ion batteries were also put forward. The safety of the lithium manganese oxide cathode was explained from the energy states. It is concluded that stable electrode material is the most important essential to the cell safety.更多还原