项目名称: 磷酸铁锂离子动力学及微观结构的计算机模拟研究
项目编号: No.50874074
项目类型: 面上项目
立项/批准年度: 2009
项目学科: 金属学与金属工艺
项目作者: 张培新
作者单位: 深圳大学
项目金额: 38万元
中文摘要: LiFePO4被认为是下一代锂离子电池的首选正极材料,具有广阔的应用前景。本项目通过高温固相法合成了锂离子电池正极材料LiFePO4以及离子掺杂和碳包覆的LiFePO4。采用第一性原理结合XRD、HRTEM、EPR、PALS、恒流充放电等技术研究了离子掺杂和碳包覆LiFePO4的晶体结构、微观缺陷结构、电子结构与电化学性能关系,从微观、介观和宏观三个层次阐明了离子掺杂和碳包覆提高材料离子及电子电导率、充放电性能和循环性能的原因,解决了长期处于争论的离子掺杂和碳包覆改变导电机制的问题,同时也为掺杂离子的选择提供了理论依据,丰富了离子掺杂理论。研究表明,离子掺杂不仅改变了正极材料内部的微观缺陷,同时也改变了晶格中阳离子外层电子能量的排布,从而提高晶格内部电导率的机理,因此改善了LiFePO4正极材料的电化学性能。采用分子动力学方法研究了LiFePO4中离子的结构及传递性质,建立了Li离子的扩散与LiFePO4的微观结构关系,结果表明,LiFePO4沿ac面生长排列,更有利于Li扩散,从而具有更优异的电化学性能。这些研究工作对加速LiFePO4产业化的发展,具有重要的科学指导意义。
中文关键词: LiFePO4;离子掺杂;碳包覆;微观结构;计算机模拟
英文摘要: LiFePO4, considered as the most promising cathode materials for the lithium-ion battery, has a broad application prospects. In this project, carbon-coated and doped LiFePO4 were synthesized by high temperature solid-state method and the relationship between their crystal structure, defect, electronic structure and the electrochemical property was investigated by first-principles method combined with XRD, HRTEM, EPR, PALS, etc. The reason about improving the electronic conductivity, charge-discharge performance and cycle performance of LiFePO4 after ion doping and carbon-coating was clarified in the micro, meso and macro levels, thus, the long period debate about the conductive mechanism of the carbon coating and ion-doping was solved. The results have shown that doping not only changes the microscopic defects within the cathode material, but also changes the arrangement of the outer electrons energy of the cation within lattice. Therefore, the internal conductivity mechanism of the lattice is enhanced and the electrochemical property of LiFePO4 is improved. The structure and transport property of ion within LiFePO4 was studied using molecular dynamics and the relationship between Li ion diffusion and micro-structure of LiFePO4 was established. The results show that LiFePO4 arranging along the ac plane is beneficial to Li diffusion, which has more excellent electrochemical performance. These conclusions have an important scientific significance on LiFePO4 industrialization.
英文关键词: LiFePO4; ion doping; carbon coating; microstructure; computer simulation