Research On Prediction Mechanism Of Cycle Life Of Power Battery For Electric Vehicle By Tomography

The prediction of the power battery’s cycle life is one of the most critical technologies of the energy management methods of electric vehicles.However,conventional cycle life prediction methods neglect the structural properties of batteries and are not be able to detect the change of these properties so that the prediction results are not reliable even though incorrect in some situations.And this issue restricts the application and development of the electric vehicles’ energy management methods.So,the thesis took the iron phosphate-lithium power battery as the object,and studied the computed tomographic image prediction mechanism and application to the power batteries of the electric vehicle.Firstly,the cycle life degration mechanism of power batteries in different operating conditions has been discussed,the relationship between the variation of the battery’s inner structural parameters including the anode and cathode active material,electrolyte,current collector and the different operating conditions including environmental temperature,current,and the depth of discharge hace been analysed.With this wizard,this thesis studied the relationship among electrochemistry properties,inner structural properties and cycle life.Then,according to the basic electrochemistry principle and the computed tomographic image detection method,the thesis analyzed the behavior law among electrochemistry performance,inner structure and computed tomographic images.Then,applying the computed tomography image processing method,the different morphology properties in computed tomography images of battery which can represent its inner structural properties have been obtained by histogram characters and material distribution moments.And the morphology properties in computed tomography images changes with the cycle times have been analyzed.The relationship between electrochemistry properties and morphology properties in computed tomography images has been discussed.Based on the analyzation,this thesis submmited the prediction mechanism of the cycle life of electrica vehicle’s battery by computed tomography images and set up a cycle lfe prediction model based on morphology properties in computed tomography images.Finally,a type of iron phosphate-lithium power batteris was taken as the reseach object,and the feasibility experiments were carried out.Experiments verified the relationship between morphology properties in computed tomography images and cycle life of the power battery in the experimental operating mode.And experiments also compared the novel method with the conventional cycle life prediction method.The result showed that the cycle life of the power battery not only depended on the external reasons including environmental temperature,discharge rate and the depth of discharge but also related to the variation of the morphology properties of inner structure such as the active material of anode and cathode,electrolyte,and current collector.