导　　师： 刘业翔;胡国荣

学科专业： 080603

授予学位： 博士

作　　者： ;

机构地区： 中南大学

摘　　要： 提高电池性能和降低电极材料的成本一直是锂离子电池的主要研发方向。目前已大规模商业化的正极材料还只有LiCoO/_2,但因其存在价格昂贵和有毒性等问题,故研发者一直致力于寻找其替代材料。本文在详细考查了锂离子电池正极材料研究进展的基础上,选取了性能优良的层状LiNi/_/(1//3/)Co/_/(1//3/)Mn/_/(1//3/)O/_2材料为研究重点,对其合成、掺杂、性能和嵌//脱锂动力学过程开展了深入系统的研究;还对廉价的尖晶石LiMn/_2O/_4进行了体相掺杂和表面改性研究。 研究了合成方法和沉淀剂选取、前驱体处理、热处理制度和配锂量合成条件对层状LiNi/_/(1//3/)Co/_/(1//3/)Mn/_/(1//3/)O/_2材料的表面形貌、晶格常数、比表面积、粒度分布和电化学性能的影响规律,确定其最佳合成工艺为:采用NH/_4HCO/_3+Na/_2CO/_3为沉淀剂制备三元共沉淀前驱体,然后与Li/_2CO/_3均匀混合,锂配比为1.05,在950℃下热处理20h。 在上述工艺条件下合成的层状LiNi/_/(1//3/)Co/_/(1//3/)Mn/_/(1//3/)O/_2材料,在2.5-4.6V、0.1C下的首次放电比容量为190.29mAh//g/(以Li为负极/);在2.75-4.2V、1C下的初始放电比容量为145.5mAh//g,循环100次容量保持率为98.41/%/(以C为负极/)。其性能已接近美国能源部BATT计划所报道的同类产品,是一种很有发展前景的锂离子电池正极材料。 X光电子能谱/(XPS/)分析表明LiNi/_/(1//3/)Co/_/(1//3/)Mn/_/(1//3/)O/_2中Co,Ni,Mn的主要氧化态分别为+3,+2,+4价,还有少量的Ni~/(3+/)和Mn~/(3+/),并从晶体场理论解释了其氧化态分布机制。而LiNi/_/(1//3/)Co/_/(1//3/)Mn/_/(1//3/)O/_2的循环伏安曲线上主要存在3.95V氧化峰和3.69V还原峰,分别对应于Ni~/(2+/)//Ni~/(4+/)的氧化还原反应。 采用共沉淀法制备了掺杂型层状LiNi/_/(1//3/)Co/_/(1//3/)Mn/_/(1///(3-x/)/)M/_xO/_2/(M=Cr、Al、Mg/)材料。结果表明,以掺杂Al~/(3+/)、Mg~/( Intensive research and development work is being conducted to further improve the performance of lithium ion batteries and reduce the cost of electrode materials. LiCoO/_2 has been widely used as a cathode material in commercial lithium ion battery production. But, due to the high cost and toxicity of LiCoO/_2, many efforts have been made to replace it. On the base of reviewing the development of cathode materials for lithium ion batteries, this dissertation emphasizes on layered LiNi/_1//3Co/_1//3Mn/_1//3O/_2 cathode materials possessed superior performance. The synthesis, doping, electrochemical behavior and kinetics of lithium insertion-extraction process of layered LiNi/_1//3Co/_1//3Mn/_1//3O/_2 cathode materials were studied in detail. Then the doping and surface modification of spinel LiMn/_2O/_4 were studied, too.The effect of synthesis method and synthesis conditions, such as precipitating agent, precursors synthesis, heat treatment and Li//M/(M=Ni+Co+Mn/) molar ration, on morphology, lattice parameter, specific surface area, particle distribution and electrochemical performance of layered LiNi/_1//3Co/_1//3Mn/_1//3O/_2 were studied. On this basis, the optimized flowsheet was obtained, i.e. triple carbonate of nickel-cobalt-manganese precursor was prepared by co-precipitation method with NH/_4HCO/_3+Na/_2CO/_3 as precipitating agent, and mixed with Li/_2CO/_3 /( Li//M ration of 1.05/), then the mixture powders were calcined at 950℃ for 20h. The results showed that the initial discharge capacity of Li//LiNi/_1//3Co/_1//3Mn/_1//3O/_2 cell was 190.29 mAh//g in 2.5-4.6V and at 0.1C rate. And initial discharge capacity of C//LiNi/_1//3Co/_1//3Mn/_1//3cell was 145.5mAh//g in the voltage window 2.75-4.2V and at 1C rate, its capacity retained 98.41/% after 100 cycles. Its performance was close to that of the material reported by BATT program of the U.S. Development of Energy /(DOE/). So this material is determined to be a promising cathode material for lithium ion batteries.Furthermore, X-ray photoelectron spec

关 键 词： 锂离子电池 层状 尖晶石 掺杂改性 表面包覆

领　　域： [电气工程]