Research On Li-ion Power Battery Cycle Life Prediction Based On The Driving Condition

Cycle life prediction of power battery is one of the key technologies to ensure the efficient and safe operation of electric vehicles.However,the current power battery for electric vehicles cycle life prediction method is based on the battery’s electrochemical properties,ignoring the characteristics that the power battery discharge rate and depth of discharge changing with the driving conditions and the driver’s intentions,which leads to difficulty to predict the driving conditions of the electric vehicle battery cycle life correctly and fast.To this end,the paper takes a typical lithium iron phosphate power battery of electric vehicles,hereinafter referred to as lithium power battery,as the research object in order to predict its cycle life and shorten the forecast time,and study the cycle life prediction method of Li FePO4 power battery based on driving condition.In this paper,the principle and method of cycle life prediction for lithium power battery based on the electrochemical properties were studied.Then,using this method to a single lithium battery life cycle prediction experiment on the different driving conditions,finding it is difficult to predict the lithium power battery cycle life under the different driving conditions.Next,according to the definition of cycle life,the formation of lithium power battery and its decay mechanism with driving conditions were studied.The internal and external factors influencing the decay and cycle life of lithium battery were analyzed.The behavior of the lithium power battery was discussed in terms of its electrochemical performance and the micro-morphology of its plates and diaphragms.On the basis of this,according to the principles of battery electrochemical and digital X-ray computed tomography,the cycle life prediction method of Li FePO4 power battery was proposed based on driving condition.The mechanism of predicting the cycle life of Li-ion power battery was analyzed by using characteristic tomography image,abbreviated as morphological feature image,of electrochemical characteristics and geometrical and physical characteristics.A prediction model of cycle life of lithium battery was designed,composed of electrochemical performance prediction model and morphological prediction correction model.Then,a certain type of electric vehicle lithium power battery was taken as the object.It was set up that the experimental system of cyclic life prediction of lithium-ion battery composed of tomography measurement system,electrochemical characteristic measurement system,charge-discharge controller and battery life prediction system.And the experiment on the prediction of cycle life of lithium battery under different driving conditions was carried out,studying the relationship between electrochemical characteristics and morphological characteristics of Li-ion power battery under different driving conditions to establish the prediction model of electrochemical performance of lithium power battery by using electrochemical characteristics and multiple nonlinear regression method and modifying the morphological prediction and correction model of lithium battery by morphological feature image.Based on this,an experimental model of cycling life prediction of lithium battery based on driving conditions was established.Finally,in order to validate the feasibility of predicting cycle life of lithium battery based on driving condition,a real-car experiment to predict the cycle life of a typical lithium-powered battery was carried out.