Numerical Research on Electrochemical Behavior, Thermal Characteristics, and Aging Formation of Lithium-Ion Cell at Different Ambient Temperatures and Charge/Discharge Rates

Lithium-ion battery is an efficient and environmentally friendly energy storage device. Electrochemical reaction, heat generation, and aging formation in battery cells interplay with each other, which is currently insufficiently considered and studied under various conditions. A dynamic electrochemical-thermal-aging coupling model was developed to study the effects of ambient temperature and charge/discharge rate on a lithium-ion cell under natural convection condition. Evolution of heat generation power and cell temperature and dynamic distribution of electrochemical and aging parameters during charge/discharge were studied. If charge/discharge rate increases or ambient temperature decreases, the polarization effect or internal resistance of the lithium-ion cell increases to increase the polarization heat and ohmic heat; however, the reversible heat changes little. Peaks of current density and lithium-ion concentration difference of electrode particles caused by potential plateaus of the negative electrode were discovered. The main reasons for lithium-ion cell aging are high total strain energy density in electrode particle, solid electrolyte interface (SEI) film, and lithium metal deposition (lithium plating). The low ambient temperature can cause the total strain energy density peak of electrode particle at the beginning of charge or discharge, and the potential plateaus of negative electrode also cause the total strain energy density peaks. SEI film mainly forms during charge; the increase of ambient temperature or charge rate increases SEI reaction rate to accelerate the SEI film growth. Kinetics difficulty of lithium-ion intercalation on the negative electrode is increased by the decrease of ambient temperature or increase of charge rate, which causes the lithium plating overpotential less than 0 V to appear earlier to accelerate the deposited lithium metal growth.