Impedance Characteristics and Detection Method of Lithium-ion Battery Under Overcharge Condition Based on Electrochemical Impedance Spectroscopy
Currently,electrochemical energy storage units and systems utilizing lithium-ion batteries are increasingly popular,however,lithium-ion batteries frequently fail due to overcharge abuse in practical use.Therefore,accurate detection of actual battery overcharge status is always a difficult and bottleneck problem in this field.In view of this,the electrochemical impedance spectroscopy technology is used to detect and study the overcharging behavior and process of single batteries.The battery overcharging simulation cycle experiment is designed and developed in the laboratory,and the relaxation time distribution method is used to analyze the impedance characteristics of lithium battery.On the basis of obtaining the impedance characteristics of the cell,the relaxation time distribution curve of the cell is analyzed.Finally,the impedance characteristic parameter is selected as the model input,and the support vector machine model is constructed to detect the battery overcharge.The results show that the polarization peak P1 in the relaxation time distribution curve corresponds to the diffusion process of lithium ions in SEI film,peak P2 corresponds to the diffusion process of electrons in the positive electrode material,and peak P3 corresponds to the redox reaction of lithium ions at the electrode interface.Overcharging results in the growth rate of ohmic resistance,SEI film resistance and charge transfer resistance of the battery are 266%,360%and 182%of the normal cycle,in which the SEI film resistance is the main factor.The impedance characteristic parameters of electrochemical impedance spectroscopy and the support vector machine model can be used to detect the overcharge of lithium batteries,and the estimated accuracy is 93.24%.It can not only master the running state of the battery,but also effectively identify the overcharge.
lithium-ion batteriesdistribution of relaxation timeselectrochemical impedance spectroscopyoverchargesupport vector machine
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