Research On Detection Method For Capacity Degradation Of Lithium Iron Phosphate Battery For Vehicle

Battery capacity is one of the key control parameters for pure electric vehicle power system,and the detection of it directly affects the performance and the life cycle of the electric vehicle,however,because the detection methods of battery capacity based on the electrochemical performance ignore the characteristics that the discharge rate and discharge depth of the power battery of the electric vehicle vary with the driving condition and driver's intention,and it is difficult to accurately detect the battery capacity and its attenuation,which become one of the bottleneck of the popularization and application of electric vehicles.This paper takes a typical lithium iron phosphate battery of pure electric car as the object,with the comprehensive utilization of image features of the geometry shape and physical properties form and the electrochemical properties,this paper studies the detection method of lithium iron phosphate power battery capacity attenuation based on morphology and properties,in order to solve the capacity dynamic decay detection problem in battery under the condition of different discharge rate,the depth of discharge and the discharge time.In this paper,the working principle of the lithium iron phosphate power battery and the formation mechanism of its capacitance are analyzed firstly,and the influence factors of the capacity decay are analyzed from two aspects of the internal and external of the lithium battery.Based on this,the frequently-used methods for detecting the capacity attenuation of lithium battery is discussed and it is difficult to detect the capacity degradation state of lithium battery in a correct and nondestructive way,and its behavior performance of Lithium power battery capacity attenuation on electrochemical performance and the micro-morphology images was analyzed.On this basis,according to the battery electrochemistry and digital X ray computed tomography image measurement principle,the method of capacity attenuation of lithium iron phosphate battery for vehicle was proposed based on morphology and properties,and the mechanism of detecting the capacity attenuation state of lithium battery by the method of detecting the electrochemical performance parameters and the digital X-ray computer tomography technology for material attenuation coefficient is discussed in this paper.Then,with the power battery of an electric vehicle as the object,a test system of lithium battery capacity attenuatio based on morphology and performance is established,and the battery capacity attenuation state is detected by image measurement data of geometry shape and physical properties shapes and electrochemical properties and the relationship between the chromatography structure and the electrochemical performance of lithium iron phosphate battery and the battery capacity attenuation are studied,and the feasibility of the method based on morphology and performance of lithium iron phosphate power battery capacity attenuation test is verified.