不同温度下锂离子电池正极材料LiCoO_(2)的第一性原理研究  

First principles study of LiCoO_(2) cathode material for lithium ion batteries at different temperatures

作　　者：陈志强[1] 崔磊[1] 杨丽娟[1] CHEN Zhiqiang;CUI Lei;YANG Lijuan(School of Information Engineering,Suqian University,Suqian 223800,China)

机构地区：[1]宿迁学院信息工程学院,江苏宿迁223800

出　　处：《功能材料》2021年第7期7046-7051,共6页Journal of Functional Materials

基　　金：国家自然科学基金资助项目(11504418);江苏省六大人才高峰资助项目(XCL227);宿迁市科技计划资助项目(Z2019097)。

摘　　要：对电极材料在固定温度下热力学性质的评价,有助于准确描述锂离子电池(LIBs)的性能。为了全面了解层状锂LiMO_(2)(M=Co、Ni、Mn)的特性,大量理论计算被用来预测该类材料的各种物理、化学性质,包括嵌入电压、Li空位有序化、Li扩散、复杂过渡金属有序化以及电子迁移路径等。然而,在高功率下,电池由于高速运转产生了更多的热量,导致一系列热力学问题出现。目前,大多数基于密度泛函理论(DFT)的研究只考虑了0 K下的热力学性能,而忽略了高温下晶格振动对性能的影响。基于此,在DFT的基础上,通过精确地模拟Li、LiCoO_(2)及Li□CoO_(2)声子谱和晶格振动等热力学参数,计算并绘制了关于Li、LiCoO_(2)及Li□CoO_(2)的温度与赫姆霍兹自由能的关系图;并根据不同温度的相关影响对脱锂电势进行了修正处理,发现随着温度的不断升高,晶格振动会进一步造成脱锂电势的逐步降低,从而导致正极材料的容量减小。The evaluation of the thermodynamic properties of electrode materials at a fixed temperature is helpful to accurately describe the performance of lithium ion batteries(LIBS).In order to fully understand the characteristics of layered lithium LiMO_(2)(M=Co,Ni,Mn),a large number of theoretical calculations has been used to predict the physical and chemical properties of these materials,such as insertion voltage,Li vacancy ordering,Li diffusion,complex transition metal ordering and electron migration path.However,at high power,the battery generates more heat due to high-speed operation,which leads to a series of thermodynamic problems.At present,most studies based on density functional theory(DFT)only consider the thermodynamic properties at 0 K,but ignore the effect of lattice vibration on the properties at high temperature.On the basis of DFT,the relationship between the temperature and the Helmholtz free energy of Li,LiCoO_(2) and Li□CoO_(2) is calculated and plotted by accurately simulating the phonon spectrum and lattice vibration of Li,LiCoO_(2) and Li□CoO_(2).Accorded to the influence of different temperature,the delithiation potential is modified.It is found that with the increase of temperature,lattice vibration would further cause the decrease of the delithiation potential,which leads to the decrease of the capacity of the cathode material.

关 键 词：锂离子电池 正极材料 DFT LiCoO_(2) 晶格振动 

分 类 号：TM201[一般工业技术—材料科学与工程] O64[电气工程—电工理论与新技术]