【作者】 张丽；

【导师】 文衍宣；

【作者基本信息】 广西大学 ， 化学工艺， 2008， 硕士

【摘要】 LiCoO₂是目前商品锂离子电池的主流正极材料,其替代材料的研究一直是锂离子电池的研究重点。在众多的替代材料中,LiNi_0.5Mn_1.5O₄具有4.7V电压、较高的比容量和优良的循环性能,是一种性能优良的高电位正极材料。通常LiNi_0.5Mn_1.5O₄用固相反应法制备,但性能较差。尽管溶胶—凝胶、共沉淀法、乳液干燥法、熔盐合成法和液相燃烧法可以制备性能优良的LiNi_0.5Mn_1.5O₄,但这些方法有的需要消耗大量的柠檬酸、乙二醇、聚乙烯醇、氯化锂等有机和无机化合物,工艺复杂、成本高。为了克服这些缺点,本文以尿素燃烧合成法和碳燃烧合成法制备LiNi_0.5Mn_1.5O₄。用X射线衍射（XRD）、扫描电镜（SEM）及电化学测试等方法研究了合成工艺对LiNi_0.5Mn_1.5O₄的结构、微观形貌和电化学性能的影响。研究表明尿素燃烧或碳燃烧释放的热量所形成的高温环境能够促进LiNi_0.5Mn_1.5O₄（Fd3m）尖晶石结构的形成。尿素燃烧合成LiNi_0.5Mn_1.5O₄的工艺条件为:预置炉温500℃,尿素与锂摩尔比0.57、热处理温度900℃、热处理时间4h。除预置炉温为800℃,碳与锂摩尔比为0.25外,碳燃烧合成LiNi_0.5Mn_1.5O₄的其它工艺条件与尿素燃烧合成相似。尿素燃烧合成LiNi_0.5Mn_1.5O₄的放电比容量达133.6mAh·g^-1,循环20次后容量保持率为99.6%。而碳燃烧合成LiNi_0.5Mn_1.5O₄的放电比容量达131.7mAh·g^-1,循环20次后容量保持率为99.3%。与现有的合成方法相比,尿素燃烧合成法和碳燃烧合成法可在较短时间内制备性能优良的锂离子电池正极材料LiNi_0.5Mn_1.5O₄。本文的研究可为进一步开发简单、高效的LiNi_0.5Mn_1.5O₄制备技术提供基础数据。更多还原

【Abstract】 There are intensive efforts to develop new cathodes for Li-ion batteries.A major impetus is to find cheaper cathode materials than LiCoO₂ which is the main cathode material used in commercial Li-ion batteries.Among those materials,LiNi_0.5Mn_1.5O₄ received great attentions for it showed the higher discharge capacity with stable cycle-ability at around 4.7V potential.In general,LiNi_0.5Mn_1.5O₄ prepared by a conventional solid-state reaction method,has poor electrochemical behaviors.Sol-gel,co-precipitation,emulsion drying,composite carbonate process,molten salt synthesis,and solution combustion synthesis can obtain high-quality LiNi_0.5Mn_1.5O₄.However,these methods are yet too complicated involving large quantities of solvent,molten salt and organic materials such as citric acid,ethylene glycol, polyvinyl alcohol,lithium chloride,etc.To overcome these disadvantages,Urea combustion synthesis（UCS）method and carbon combustion Synthesis（CCS）were employed for the preparation of LiNi_0.5Mn_1.5O₄.Synthetic variables on the character and performance of LiNi_0.5Mn_1.5O₄ were investigated by X-ray diffraction（XRD）,scanning electron microscopy（SEM）and electrochemical method.The results showed that the heat generated by carbon combustion or urea combustion could accelerate the formation of spinel LiNi_0.5Mn_1.5O₄（Fd3m）from Li₂CO₃,NiO and Mn₃O₄.The optimal synthesis conditions of LiNi_0.5Mn_1.5O₄ prepared by UCS were found to be a preheating temperature 500℃,the mole ratio of urea/Li 0.57,annealing temperature 900℃and annealing time 4h.The material synthesized using the optimal conditions provided an initial discharge capacity of 133mAh·g^-1and capacity retention of 99.6%after 20 cycles at 25℃.The preheating temperature 800℃,and the mole ratio of carbon/Li is 0.25 in the CCS. Other conditions were similar with the UCS.The material prepared by CCS delivered a discharge capacity of 131.7 mAh·g^-1and capacity retention of 99.3%after 20 cycles at 25℃.Compared with the solid reaction method and the wet method,LiNi_0.5Mn_1.5O₄ can be prepared by UCS and CCS at the shorter time.The research provided here can be considered as the base for developing the simple and effective route to prepare high performance LiNi_0.5Mn_1.5O₄.更多还原