Li-ion Battery Charge And State-of-health Prediction Based On Electrochemical Model

Electric vehicles(EVs)have become effective measures to alleviate the pressure of environmental pollution at home and abroad.As a key EV component,which bears the major cost,the safety performance of the battery directly determines the safety performance of the vehicle.While the amount of remaining energy of the battery directly determines the distance that the EV can travel,the degree of aging determines the endurance of the EV and whether the battery needs to be replaced.The ratio of the remaining energy to the rated capacity is defined as the state of charge(SOC)of batteries,and the rated capacity of the battery is closely related to the degree of aging and state of health(SOH).The more accurate prediction of battery SOC and SOH the EV manufacturer can provide to the users,the better the user can arrange the trip.The battery SOC and SOH,however,cannot be directly measured.They can only be estimated through measurable parameters,such as the voltage,current,and temperature,etc.Therefore,the development of accurate models for predicting SOC and SOH has important research significance.In this dissertation,an electrochemical model of lithium-ion batteries is established firstly based on the internal reaction mechanism of charging and discharging,and then based on the electrochemical model,accurate models are derived for predicting the SOC and SOH of lithium-ion batteries.The constructed lithium-ion battery SOC estimation model is verified by comparing the predicted with the actual values for three cases:(a)the initial SOC given by the model is equal to the actual initial SOC of the battery;(b)the initial SOC given by the model is not equal to the actual initial SOC of the battery;and(c)the SOC under dynamic charging and discharging conditions.The SOH estimation model of the battery is verified in two cases,and the comparison chart with the reference value and error chart are given:(a)the battery is discharged from full charge or charged from full discharge under the condition that the initial SOH of the battery is not equal SOH estimation,and(b)the battery is discharged or discharged from an SOC value between full charge and full discharge under the condition that the initial SOH of the battery is not equal.The comparison between the model predicted results and the actual values shows that the estimation errors of the SOC and SOH models proposed in this dissertation are within the engineering acceptable range,i.e.the estimation models proposed in this article is effective and accurate.This provides a solid basis for further research in the future to further estimate the SOC and SOH when both the initial SOC and SOH are not equal to the actual values.