LiNiO2正极材料的量子化学研究.doc

LiNiO2正极材料的量子化学研究 摘 要 锂离子电池以电压高、比容量大等优点倍受世人关注，其性能主要受制于正极材料。现在研究最多的三种正极材料有LiCoO2、LiNiO2LiMn2O4，LiNiO2的性价比最高，有希望替代LiCoO2实现产业化。 为了从微观上认识镍系正极材料的结构和电化学性能之间的关系，我们将量子化学的理论计算方法引入电化学过程的研究，对过程中涉及的微观粒子的真实行为做出理论解释。 本论文应用Materials Studio软件的基于密度泛函理论的CASTEP模块，构建并优化了具有α-NaFeO2型层状结构的LiNiO2及其掺杂化合物的晶体结构模型，重点研究了材料的电子结构，通过对结构模型的计算，得到了各个原子体系的能带结构、态密度（总态密度和部分态密度）、体系总能量。 研究结果表明：镍酸锂正极材料是电子的良导体，电子容易嵌入和脱出，且在充放电过程中具有良好的稳定性，适合作为正极材料。在LiNiO2晶体中主要是氧和镍之间成键，镍离子和氧离子的相互作用比较强，锂在嵌入层状结构材料后部分失去电子，以离子状态存在。通过对掺杂材料的计算可见掺杂后电子更容易跃迁或转移，增强了材料的导电性能，其中掺锰和掺铝的材料稳定性更强，电离能降低，说明失去最外层电子更容易，也就是说锂离子在材料中嵌入和脱出更加容易；掺钴之后材料的放电电压降低，电解液氧化的可能性减小，循环性能得到改善。 关键词：锂离子电池；LiNiO2；掺杂；量子化学计算 The Quantum Chemistry Study on LiNiO2 Cathode Materials Abstract The investigation and developing of lithium-ion batteries have attracted worldwide attention due to their excellent properties such as high cell voltage and specific capacity, and so on. LiCoO2, LiNiO2 and LiMn2O4 are three kinds of cathode materials which are studied widely at present. LiNiO2 has a crystal structure same to LiCoO2 and excellent electrochemical properties close to also. It is a very good material to replace LiCoO2 and realize industrialization. In order to understand the relation between the structure and the electrochemistry properties of LiNiO2 cathode materials from microcosm, the quantum chemistry theoretical calculation method was introduced to the investigation of electrochemistry performances. CASTEP board of Materials Studio software which is based on density functional theory (DFT) was used in the study to construct and optimize the crystal structure model of LiNiO2 and its doping compounds, which have α-NaFeO2 layered structure. Stress of this thesis was the studies on electronic structures of materials. By calculating the model, each system’s band structure, density of states (DOS and PDOS) and total energy were obtained. The results indicate that LiNiO2 cathode material is good conductor for electrons and has good stability in the progress of charge an