Research On Electrochemical Modeling,Estimation And Aging For EV Battery

With the rapid development of EVs and the advantages compared with other storage batteries,lithium batteries are widely used in EVs field.At the same time,the extensive application of lithium-ion battery also makes people more and more demanding on the accuracy of battery management system(BMS).People pay more attention to the accuracy of battery model,estimation of state of charge(SOC)and the effect of battery aging.In order to realize the efficient and safe management of batteries in BMS,it is necessary to study the accuracy of battery model and the influence of aging on battery.The main research work of this paper is the modeling of the EV lithiumion battery with electrochemical mechanism.And more detailed research work can be described as the following three aspects:Firstly,starting from the electrochemical reaction mechanism of lithium batteries,this paper builds an electrochemical transfer function model through the simplification of partial differential equations.In this model,the relationship between the cell voltage and the current can be represented by a transfer function which has a rational polynomial expression.Meanwhile,this paper proposes an equivalent circuit model based on electrochemical mechanism by combining the electrochemical model and the equivalent circuit model.With this model,this paper realizes the parameter identification and the SOC estimation by the recursive least squares(RLS)algorithm and the Extended Kalman Filter(EKF)algorithm.On the other hand,in order to study the effect of battery aging,this paper builds a battery aging model from the side reactions take place at the negative electrode.The relationship between capacity fade and cycle life was studied by the battery aging cycle experiment.And after the aging experiment,the batteries were opened and the SEM?TEM and XPS experiments were conducted to observe the microstructure and analyze the components of the deposit layer.The model proposed by this paper combines the electrochemical model and the equivalent circuit model,which is possible for the application of electrochemical model.And the aging model based on the side reactions provides a basis for further research on battery aging in the future,and provides a technical support for incorporating the effects of battery aging into BMS.