Thermal Management System For Lithium-Ion Batteries Based On MXene/Paraffin Composite Phase Change Material

In recent years,the safety accidents of electric vehicles caused by the Thermal runaway of lithium-ion batteries have occurred frequently.Therefore,it is necessary to develop an efficient,complete and stable battery thermal management system(BTMS)to ensure that the batteries can operate safely and smoothly within the appropriate temperature range during operation.BTMS based on phase change materials can balance the temperature of the system through the heat change in the process of endothermic and Exothermic process,greatly reducing the possibility of Thermal runaway of the battery.Phase change material(PCM)cooling is a relatively new cooling method in BTMS,which has a simple structure,high cooling efficiency,no additional energy consumption,and better temperature balance performance.Moreover,PCM cooling coupled with active cooling methods(air cooling and liquid cooling used in this article)can be used to charge and discharge high-density high-power batteries.Therefore,PCM cooling would have been separately applied to Design and study the square lithium-ion battery pack model from three aspects:PCM cooling coupled with air cooling and PCM cooling coupled with liquid cooling.Paraffin,as the most commonly used phase change material,has characteristics such as high latent heat,low cost,and chemical compatibility with most metals.However,its low thermal conductivity can affect the rate at which heat is stored and released during the phase change process in batteries.In order to make up for this defect,researchers increased the thermal conductivity of composite phase change materials(CPCM)by adding materials such as Graphene,expanded graphite and metal foam to paraffin,so as to improve the heat dissipation performance of the whole system.However,there is still some room for improvement in its cooling efficiency and heat dissipation effect.This article proposes for the first time to composite MXene with paraffin phase change materials in response to existing problems,and constructs a BTMS based on MXene/paraffin CPCM,MXene/paraffin CPCM coupled air cooling BTMS,and MXene/paraffin CPCM coupled liquid cooling BTMS.The heat dissipation performance is studied and analyzed,and the impact mechanisms of MXene’s mass fraction,convective heat transfer coefficient,and system structure design on the temperature field of the battery pack are explored.The best heat dissipation effect is selected The coupled cooling system with the best temperature uniformity provides reference ideas for the practical application of phase change materials in lithium-ion battery BTMS.In COMSOL Multiphysics software,Graphene,expanded graphite,MXene,foam aluminum and phase change material paraffin are respectively compounded.The results show that when the CPCM is MXene/paraffin,the maximum temperature of the lithium-ion battery pack is the lowest and the heat dissipation performance is the best.The high thermal conductivity of MXene enhances the thermal conductivity of paraffin based composite phase change materials,enhancing their ability to absorb and release heat,allowing for faster and more heat transfer to the external environment,reducing the heat dissipation pressure of the battery pack.When the mass fraction ratio of MXene to paraffin is 1:1,the battery spacing lengths in the X-axis and Y-axis directions are 20 mm and 10 mm,respectively,and the ambient temperature and convective heat transfer coefficient are controlled within 34℃and 4 W/(m~2·K),the lithium-ion battery can operate within a suitable temperature range.At this time,the highest temperature of the battery pack is the lowest,the maximum temperature difference is the smallest,and the heat dissipation effect and temperature uniformity are the best.Due to the inability of a single CPCM thermal management method to meet the charging and discharging behavior of high-power density lithium-ion batteries,this article couples air cooling on the basis of MXene/paraffin CPCM and constructs an MXene/paraffin CPCM coupled air cooling system.From the perspectives of MXene mass fraction,height and length of the air cooling box,and air flow rate,temperature characteristics,cost,and energy consumption are comprehensively considered,Optimize the design of the heat dissipation system for lithium-ion battery packs.Considering the material cost of batteries in practical applications and the overall energy consumption of the thermal management system,the heat dissipation performance of the system is optimal when the mass fraction of MXene is 50%,the height and length of the air cooling box are 608 mm and 1154mm,respectively,and the air flow rate is 0.1 m/s.Coupling air cooling with MXene/paraffin CPCM can accelerate the internal heat dissipation of CPCM,slow down the melting rate of CPCM,meet the temperature requirements of the battery,and effectively reduce the heat dissipation cost of BTMS by utilizing latent heat.Therefore,coupling MXene/paraffin CPCM with air cooling can achieve better heat dissipation effect than single CPCM cooling.In order to obtain better cooling efficiency and heat dissipation effect,this paper constructs MXene/paraffin CPCM coupled liquid cooling BTMS,analyzes the heat dissipation characteristics of the battery pack during the charging and discharging process,explores the influence mechanism of the mass fraction of MXene,the number of liquid channels,the channel radius,and the liquid flow rate on the Degree distribution of the battery pack temperature,and studies the temperature characteristics of the battery pack under different discharge rates,And compare and analyze the heat dissipation effects of different thermal management systems based on PCM cooling.When the mass fraction of MXene is 50%,the number of liquid channels is 6,the radius of liquid channels is 3 mm,and the liquid flow rate is less than 0.8 m/s,the system has the best heat dissipation performance.The highest temperatures are 21.776,14.255,and 8.133℃lower than pure paraffin PCM cooling,MXene/paraffin CPCM cooling,and MXene/paraffin CPCM coupled air-cooled BTMS,respectively.Compared with air cooling,the liquid in liquid cooled BTMS has a higher Specific heat capacity and thermal conductivity,which will make the liquid have a stronger ability to take away heat than air,so that it can absorb more and faster the heat generated by the battery and be more efficient.Therefore,MXene/paraffin CPC coupled liquid cooled BTMS has a better heat dissipation performance than coupled air cooling.