摘要：近些年出于对新型能源的需求，人们把目光投向了开发储锂能力更高，循环寿命更长的硅基锂离子电池。然而，锂原子进入硅后会引起硅产生近400%的巨大体积膨胀，这一问题不仅缩减了电池的使用寿命更带来了严重的安全隐患。在硅产生巨大形变的过程中往往伴随着各种形式位错的产生。因此，本文采用耦合了第一性原理（DFT）和分子动力学（MD）的QM/MM多尺度计算方法来模拟锂原子在硅中shuffle型60°位错中及周边的稳定结构以及在位错芯中的扩散特性。

本文的主要工作：

一、模拟锂在硅中shuffle型60°位错中的稳定构型。

二、模拟锂在位错芯周边的稳定构型，比较锂在位错芯周边结合能和在晶体硅中结合能，证明shuffle型60°位错对锂原子的吸引力。

三、模拟锂由位错周边位置进入位错芯的扩散路径。

四、模拟锂在位错芯中的扩散路径，通过扩散势垒的变化证明shuffle型60°位错对锂原子运动的加速作用。

关键词：锂离子电池；硅；位错；多尺度方法；锂的扩散

Abstract：In recent years, due to the demand for new energy sources, people have turned their attention to the development of lithium ion batteries with higher lithium storage capacity and longer cycle life. However, the lithium atoms into silicon will cause silicon to produce nearly 400% of the huge volume expansion, this problem not only reduces the battery life and has brought serious security risks. In the process of huge deformation of silicon, there are many kinds of dislocations. Therefore, we use a multiscale computational method for QM/MM based on first principles (DFT) and molecular dynamics (MD) to simulate the lithium atom in silicon shuffle 60 degrees dislocation and the dislocation core diffusion characteristics.

The main work of this paper:

1.Simulate the stable configuration of lithium in shuffle type 60 degree dislocation in silicon.

2.Simulate the stable configuration of lithium in the vicinity of the dislocation core . The binding energy of lithium in the core and the binding energy in the crystal silicon are compared, and the attraction of the shuffle type 60 degree dislocation to the lithium atom is proved.

3.Simulate the diffusion path of lithium from dislocation position to dislocation core.

4.The diffusion path of lithium in the dislocation core is simulated, and the acceleration of the shuffle type 60 degree dislocation to the lithium atom is proved by the change of diffusion barrier.

Keywords: Lithium-ion battery; Si; dislocation; multi-scale method; diffusion of Li

目录

第一章绪论 1

1.1课题背景及研究意义 1

1.2锂离子电池的电极材料 1

1.3硅基锂离子电池负极材料 4

1.4位错简介 6

1.4.1位错的基本类型 7

1.4.2晶体硅中的位错类型 8

1.5主要研究内容 8

第二章多尺度计算方法 10

2.1引言 10

2.2不同空间尺度所对应的计算方法 10

2.3常用多尺度方法的分类及简介 11

2.3.1空间尺度耦合方法 12

2.3.2准连续方法 13

2.3.3粗粒化分子动力学方法(CGMD) 13

2.4本文使用的多尺度计算方法