Research On Low-temperature Heating And Healthy Charging Strategy For Lithium-ion Batteries Based On A Thermal Coupling Model

As the most widely used green high-energy rechargeable battery,lithium-ion battery has many advantages such as high voltage,energy density,good cycle performance,no memory effect and other prominent merits.Lithium-ion batteries are used as the core components of energy storage in portable electronic products,electric vehicles and aerospace fields.Therefore,it is very important to study the external characteristics and management strategy of lithium-ion battery under different temperature environment.Based on the thermal coupling model,the simulation of the temperature and terminal voltage of the lithium-ion battery at normal temperatures and low temperatures was realized.Moreover,the research on the health preheating strategy of the battery at low temperature and the battery health charging strategy at normal temperature were implemented and verified through experiments.The details are as follows:Firstly,considering the effect of temperature on the performance of lithium-ion batteries,the parameters of the thermal coupling model for lithium-ion batteries were corrected.The parameters in the thermally coupled model of the Li-ion battery were reduced from the parameters of P2 D model.Then,the relationship between temperature-sensitive parameters and temperature was established according to the relationship of the parameters.Based on the different electrochemical reaction mechanism and the excitation response analysis method,current excitation condition was designed to decouple different reaction process in battery.Hereafter,parameters of different equations were accurately identified by the least squares method.Secondly,the preheating strategy of high-frequency charging and discharging current was studied based on the improved thermal coupling model of lithium-ion battery for preheating system in-15℃ low temperature environment.In preheating process,the amplitude of heating current was controlled to satisfy the condition that the internal negative reaction polarization over-potential value was less than the equilibrium potential,according to the battery’s temperature and state of charge.Experimental verification showed that the strategy can efficiently preheat the battery and avoid lithium deposition and other side effects of battery.Finally,the characteristics of over-potential of two type battery were analyzed by the thermal coupling mechanism model.It was proposed that the charging process of lithium iron phosphate battery can save time when constant voltage charging process wasn’t included.In order to reduce the influence of high internal temperature in battery,a new charging strategy based on the controlling of battery internal temperature during constant current charging was proposed.The feasibility of the control strategy is verified by model simulation and experiment.Experiments showed that the charging strategy can not only fully charge the battery but also delay the attenuation of lithium-ion battery’s capacity.