Electrochemical-Structural Coupled Multi-Scale Modeling And Stress Analysis Of Ternary Lithium-ion Battery

Since it can effectively improve the air quality and reduce the noise pollution in the urban,new energy vehicles,especially pure electric vehicles,have achieved rapid development in recent years.However,the capacity and life of lithium-ion battery pack commonly used in electric vehicles is still difficult to meet people's expectations.The reduction in the life of lithium-ion batteries is closely related to the battery stress,and the larger stress will cause the destruction of the internal structure of the battery at the level of active particles,electrode level and the battery level,resulting in the reduction of the capacity,battery life,and capacity.However,at this stage,the model of battery stress mainly stays on the particles and the electrode level,and there are few models that can reflect the interaction of stress inside the battery.Therefore,building a higher accuracy battery stress model has very important meanings to study the failure mechanism and estimate the life of the battery.It can provide the idea of relieving stress and guide the design and use of battery.A commercial pouch lithium-ion battery is taken as the research object,and a battery charging and discharging stress test platform using battery charging and discharging test equipment is built.Under different external pressures and charging and discharging rates,the external pressure change and charging and discharging performance of the battery are tested to get validation data for building the electrochemical-structure coupled multi-scale model of the battery.Aiming at finding ways to reduce the battery stress and improve the charging performance,the effects of the e initial external compressive stress on the battery performance at different charging and discharging rates are analyzed.The multi-scale electrochemical-structure coupling model was established by COMSOL Multiphysics software with the same battery as the object.Firstly,the simulation operation is carried out under the experimental conditions to verify the accuracy of the battery model and calibrate the model.After obtaining a higher accuracy model,the model was used to further study the effect of the initial external stress and charging mode on the battery stress.At the same time,the layered characteristics of the obtained model can be used to study the stress distribution law inside the battery.Through analysis of experimental and simulation data,it can be found that a larger current will increase the polarization phenomenon inside the battery and internal stress of the battery.When the initial stress on the large surface of the battery is increased,the increase range in the internal stress of the battery will increase.Therefore,in the process of battery assembly,the surface pressure of the clamp on the battery needs to be carefully controlled to prevent premature damage to the internal structure of the battery caused by excessive internal stress.Meanwhile,in order to make the battery have enough time to relieve the internal stress,the battery pack should be avoided to be in high current condition for a long time.In addition,the charging mode should be selected according to the actual situation.