关键词: 弛豫/
耦合/
固相扩散/
液相扩散
English Abstract
Relaxation behavior simulation of power lithium-ion battery in high-rate charging-discharging process
Tang Yi-Wei1,Ai Liang2,
Cheng Yun1,
Wang An-An2,
Li Shu-Guo1,
Jia Ming1
1.School of Metallurgy and Environment, Central South University, Changsha 410083, China;
2.Hunan Aihua Group Co., LTD, Yiyang 413002, China
Fund Project:Project supported by the National Natural Science Foundation of China (Grant Nos. 51204211, 51222403), the Fundamental Research Funds for Central Universities of Central South University, China (Grant No. 2014zzts029), and the Special Foundation for Industrial Upgrading Transformation and Strengthen the Foundation of Ministry of Industry and Information Technology, China (Grant No. 0714-EMTC02-5271/6).Received Date:12 October 2015
Accepted Date:08 December 2015
Published Online:05 March 2016
Abstract:The relaxation behaviors of a power lithium-ion battery significantly affect its performance, and these properties are greatly affected by temperature. This study presents a validated electrochemical-thermal model battery model covering the conservations of charge, mass, and energy and the electrochemical reaction kinetics, and considering the effect of heat on electrochemical performance of a battery. Using this battery model, the relaxation behavior of power lithium-ion battery in high-rate charging-discharging process and the effect of difference among charge-discharge systems are investigated. It is found that ohmic polarization is the main reason for voltage change in charging-discharging process. Constant-current-constant-voltage charging mode can effectively remit ohmic polarization and then avoid changing the voltage rapidly. In the shelving process after constant-current-constant-voltage charging, voltage change is smaller and the time for it to take to reach open circuit potential is shorter than in the shelving process after constant-current charging. In charging-discharging process, the values of polarization at positive and negative electrode are almost the same. Power lithium-ion battery can be charged into more energy by constant-current-constant-voltage charging modes, meaning that it is beneficial to battery performance. Because active material particles in electrodes have certain sizes, in discharging process, there is some gradient between the surface and center of solid particle, and the electrodes each have a certain thickness, different place of electrode has a different lithium-ion concentration. In the shelving process after discharging, there is no outer current, so the gradient of lithium-ion concentration disappears due to the effect of diffusion process. The relaxation time of lithium-ion concentration in solid phase is longer than in liquid phase. The ratio between characteristic time of solid diffusion and that of liquid diffusion increases constantly near the end of the discharge, thus the polarization due to solid diffusion cannot be neglected in the whole discharging process.
Keywords: relaxation/
coupling/
solid diffusion/
liquid diffusion
