Research On The Characteristics And Influence Of Lithium Plating In Lithium-ion Batteries At Low Temperature

In the use of lithium-ion batteries,low-temperature charging will have a great negative impact on the battery.On the one hand,low-temperature charging will cause lithium plating in the negative electrode,and the battery capacity will decline rapidly,which increases the cost of use;on the other hand,the lithium-plating caused by lowtemperature charging will form lithium dendrites.If the lithium dendrites pierce the separator,they will cause a short circuit in the battery.It may cause thermal runaway problems and threaten personal and property safety.This dissertation focuses on the low-temperature lithium plating characteristics of lithium-ion batteries.This work is mainly divided into two parts.The first part is the non-destructive testing method for lithium plating,and the second part is the change of battery model parameters under low-temperature lithium plating and the effect of subsequent room temperature aging.The research content is as follows:(1)Research the performance changes of lithium-ion batteries under different temperature stresses,especially the low-temperature characteristics.The battery characteristic test experiment was completed on the built experimental platform,and the influence of low temperature environment on the change of the charging voltage curve,open circuit voltage,coulomb efficiency,energy efficiency and capacity decay rate of lithium-ion battery was analyzed.(2)Analyzed the mechanism of lithium plating caused by low-temperature charging,and studied two non-destructive lithium-plating detection methods.The first detection method is based on the voltage relaxation curve,and its temperature and rate sensitivity are measured.Analyze and get the applicable scope of the voltage relaxation curve detection method.The second part is the lithium plating detection method based on the differential curve,and the traditional differential curve drawing method is improved to obtain a higher-precision differential curve to analyze the battery state after the lithium plating analysis.(3)A low-temperature SOC interval stress experiment was designed to study the SOC dependence of lithium analysis.The characteristic parameters of the differential curve were used to analyze the difference in low-temperature lithium plating analysis in different SOC intervals.Under the environment of minus 20 degrees,the experimental results showed that the loss of active lithium ions is the main cause of capacity loss,and the amount of lithium plating presents the characteristics of the SOC interval.The low SOC interval has the largest amount of lithium plating,and the high SOC interval has the smallest amount of lithium plating.The production of lithium is also accompanied by the loss of electrode active materials,and the low SOC In the interval capacity loss,the electrode active material accounts for the largest proportion of the capacity loss,and the high SOC interval electrode active material loses the smallest proportion.(4)In order to analyze the changes in the equivalent circuit model and electrochemical model parameters of the low-temperature cycling battery in different SOC intervals after lithium plating analysis,the equivalent circuit model and the electrochemical model were built respectively,and a set of model parameter automatic models were compiled for the equivalent circuit model.The identification program can quickly and easily complete the model parameter identification.Aiming at the problem of many amount of electrochemical model parameters and strong nonlinearity,a parameter identification method based on simulated annealing algorithm is designed,and the battery state change after lithium is analyzed through the equivalent circuit model obtained by the identification and the change of electrochemical parameters.(5)The subsequent room temperature aging of the low temperature lithium battery is studied,and the aging of the battery without low temperature lithium is compared and analyzed.It is found that the reversible lithium plating caused by the low temperature charging at high SOC interval accounts for less of the lithium plating,and it will cause the subsequent increase in the rate of capacity decline at room temperature.