Comparative analysis of the SOH estimation based on various resistance parameters for LiCoO2 cells

摘要

State of charge (SOC) and state of health (SOH) are the most important part of the battery management system (BMS). Typical parameters for implementing the SOH of the cell are the equivalent resistance R and capacitance C. Cell resistances in equivalent circuit model (ECM) are divided into internal ohmic resistance Ri and diffusion resistance Rdiff by the electrochemical dynamic characteristics. This paper introduces a detailed comparison of the SOH estimation based on various resistance parameters for lithium-ion, especially LiCoO2 cells. Firstly, two resistances such as Ri and Rdiff of 1.3Ah LiCoO2 cells are extracted according to the aging levels. Secondly, real experimental data is utilized for determination of the optimal resistance that can expect an improved performance on SOH estimation of LiCoO2 cells. Finally, this work proposes the simple method using the capacity and various resistance information according to the charging and discharging current duration for SOH.