State Parameters' Estimation Of Power Lithium Battery Cascade Utilization

With the utilization and exploitation of traditional fossil energy,the accompanying problems of environmental pollution and energy shortage are urgent to be solved.To this end,scientists around the world are studying how to efficiently develop and utilize new energy technologies which leads to the emergence of electric vehicles.Electric vehicles are being promoted worldwide and power lithium batteries as the source of electric vehicles power also draw great attentions.Power lithium battery has a huge yield but if the value of lithium battery performance decay to 80% of initial state,it will be sifted out from electric vehicle and the corresponding decommissioning battery processing technology has become one of the key technologies for the healthy development of the electric vehicle industry.Power lithium battery cascade utilization is an excellent solution for improving the utilization rate of power lithium batteries.The advantage of power lithium battery cascade utilization is that the decommissioned lithium batteries with stable performance can be screened out by battery parameters and these batteries can be used in energy storage or other occasions which greatly extends battery life.The battery parameters required by the cascade utilization process are the main research contents of this paper.The details are as follows:1?Power lithium battery state of health(SOH)estimation.Firstly,the concepts of power lithium battery cascade utilization and SOH are introduced,and the significance of selecting SOH as a sorting parameter for cascade utilization is clearly shown.Next,the frontier estimation strategy called electrochemical impedance spectrum is used to estimate SOH: The data acquisition is achieved by 18650 lithium battery charge and discharge equipment,capacity measurement equipment and the impedance spectrum measurement platform built by this article;The second-order equivalent circuit model of the battery is selected to fit the electrochemical impedance spectroscopy to obtain estimation equation of SOH after the analysis of battery electrochemical impedance spectroscopy.Finally,the accuracy of the estimation equation is verified by experimental data.2?Power lithium battery state of function(SOF)estimation.Firstly,the definition of SOF is given and the physical meaning of SOF is explained.Then,the status of battery SOF in the cascade utilization of power lithium batteries is analyzed,variables and parameters related to SOF are further explained through experiments and theories.Next,three variables called SOC?SOH and C-rate related to SOF are selected for SOF fuzzy prediction which is optimized by fuzzy c-means(FCM)algorithm.A derivation model is established and its membership functions and fuzzy rules are optimized to estimate SOF.The prediction algorithm closely combines the SOF with other parameters and can be corrected and adjusted,which reduces the errors caused by neglecting other variables in SOF estimation process.Finally,experimental data is used to analyze the SOF estimation results.3?Based on the estimation results of SOH and SOF,the recommendations for the cascade utilization of power lithium batteries are offered,and a hierarchical structure is proposed to evaluate the comprehensive performance of power lithium battery.