Experimental Research on the LiNi_xCo_yMn_zO_2 Lithium-ion Battery Characteristics for Model Modification of SOC Estimation

摘要

The Kalman Filter (KF) known as an optimum adaptive algorithm based on recursive estimation, has been widely used to estimate the State Of Charge (SOC) of the lithium-ion batteries. To improve the performance of SOC estimation, the parameters of battery model in the KF method should be chosen correctly. Nevertheless, the battery parameters, such as the OCV-SOC, capacity and resistance are significantly depended on the battery SOC, temperature, current and ageing. In this study, these dependencies and their variation over the temperature, current and ageing are investigated on a Samsung ICR18650-22P-typed lithium-ion battery with LiNi_xCo_yMn_zO_2 cathode which offers guidance to model modification of SOC estimation. The experimental results show that the OCV-SOC relationship are strong consistent under the conditions of 0～60℃ but it varies when the temperature remains below zero degrees Celsius. The capacity varies considerably with the temperature and cycles and slightly with the current of below 3C. The Ohmic resistance varies slightly with charge current but considerably with discharge current and SOC. Based on the experimental results, some suggestion for model modification of SOC estimation is put forward.