Lithium Battery Cooling Structure Design And Performance Evaluation

Lithium battery has demonstrated high energy density,long life,the environment pollution-free and so on,so it is widely used in various fields,particularly for the electric car as the most ideal power.To adapt to the demand,lithium battery must achieve the fast charging,however,which can produce a mass of heat in a short time.So internal temperature of lithium battery rise very quickly.The high temperature not only reduces the performance of lithium battery but also may cause burning or explosion in lithium battery.To solve these problems,the thermal characteristics and reasonable cooling structure should be further studied for lithium battery.In this article,we built an effective thermal conductivity numerical model and a theoretical model for the lithium battery winding structure,considering the influence of radial and spiral heat transfer and thermal contact resistance in the lithium battery winding structure.And study the influence of winding structure’s thickness and winding tension on the effective thermal conductivity by the effective thermal conductivity model.Then we compare the numerical calculation results with the theoretical calculation results to verify the accuracy of the theoretical model.Second,basing on the characteristics of temperature distribution in the lithium batteries,we design a new type of cooling structure for lithium battery by heat pipe.To evaluate the performance of cooling structure for lithium battery by comparing the temperature of lithium battery,we build a threedimensional electrochemical-thermal coupling model for lithium battery with the air cooling and phase change cooling.And we also optimize the fin by comparing the performance of cooling structure in different fin thicknesses,number and radius.The results show that: 1)with the increase of winding thickness,the effective thermal conductivity of winding structure decreases gradually.However,the change of the effective thermal conductivity gradually flatten out.And with the increase of winding tension,effective thermal conductivity of winding structure increases gradually.But the change is quite gentle for larger winding structure.The results of numerical simulation have good conformity degree with the theoretical calculation result,therefore the accuracy of the theoretical simulation is verified.2)When couple the cooling structure with air cooling,the lithium battery with cooling structure can effectively reduce the internal temperature of the lithium battery,and improve uniformity of the internal temperature distribution.However,this method does not make the temperature uniformity of lithium-ion batteries into a reasonable range in larger charging ratio conditions.3)When coupling the cooling structure with phase change cooling,it can quickly and effectively reduce the internal temperature of the lithium battery to a reasonable temperature range.And the uniformity of temperature in lithium battery can meet the requirements.The temperature of lithium battery pack is also controlled in a reasonable range.4)Results of fin optimization: the fin thickness is 0.4 mm,number is 5 and radius is 6 mm.In this paper,the study about the effective thermal conductivity of the lithium-ion batteries can provide more accurate parameters for the lithium battery thermal model.Using the new cooling structure,coupling with the phase change cooling,can effectively keep the lithium battery in a reasonable working temperature range,which is a rapid and effective cooling method.