Preparation Of Paraffin/Epoxy Composite Phase Change Material And Its Application In Battery Thermal Management

Paraffin?PA?,as a typical phase change material for Battery Thermal Management?BTM?,has many advantages such as high latent heat,non-supercooling and low price.However,the poor thermal conductivity,strong fluidity and flammability of PA seriously affecte its practical application.Conventional strategy to enhance the thermal conductivity of the composite phase change material?CPCM?may raise another neglected safety issue in practical applications of BTM:the electrical conductivity of the CPCM module is significantly increased due to the addition of the conductive carbonaceous or metallic component,reducing its insulating properties.To address this issue,we develop a new kind of CPCM herein by introducing a silicon carbide?SiC?/expanded graphite?EG?thermal conductive skeleton,and thus the obtained CPCM presents a high thermal conductivity but low electrical conductivity.On the other hand,in order to improve the flame-retardant properties of the phase change materials,a series of flame-retardant CPCMs are prepared by using flame-retardant ammonium polyphosphate?APP?and red phosphorus?RP?to form an expansion-condensation flame retardant.Vertical burner and and cone calorimeter?CONE?are used to study their thermal and flame-retardant properties.The main contents and conclusions are as follows:?1?A new CPCM is successfully fabricated by introducing SiC/EG skeleton to substitute conventional EG or metal skeleton for ensuring high thermal conductivity and volume resistivity of CPCM.The test results show that the thermal conductivity of the CPCM increases with the increase of SiC content,and the volume resistivity increases first and then decreases.After adding 15wt%of SiC,the volume resistivity of CPCM-4 is up to12.5×10¹¹?cm,and a higher thermal conductivity of 2.0 W m^-1 K^-1 is obtained.The DSC test shows that the prepared CPCM obtains a high latent heat value of about 100 J g^-1,and the precipitation test also shows that the prepared CPCM has a very low precipitation rate,which is less than 2%.In addition,the mechanical properties test shows that when the SiC content is 15%,the tensile strength and flexural strength of the CPCM reach the maximum value.?2?A series of flame-retardant composite phase change materials?RPCMs?are prepared by adding APP/RP expansion-condensation flame retardant.And their thermal and flame-retardant properties are studied.The DSC test shows that the phase change temperature of the RPCM is very close to that of paraffin.The latent heat of RPCM is also similar to the theoretical value of paraffin(about 88 J g^-1),which indicates that no chemical reaction between appears the components of RPCM.The UL-94 vertical burning test shows that the sample RPCM-6 with a content of 23%APP and 10%RP passed the UL-94 V-0rating and the LOI value reach the maximum value of 27.4%.The TGA test shows that RPCM-6 has higher thermal stability and amount of carbon residue.Furthermore,it is confirmed by cone calorimeter?CONE?that RPCM-6 can reduce the PHRR value of paraffin/epoxy composite phase change material more effectively,from 870.9 kW m^-2 to313.1 kW m^-2,and reduce the smoke release rate.It can be seen that APP/RP has a better flame-retardant effect than APP or RP alone.Finally,it is confirmed by SEM that in the RPCM-6 sample with an APP and RP mass ratio of 23/10,a denser and uniform carbon layer can be obtained,which effectively blocks the transfer of the heat and oxygen.?3?The prepared CPCM is applied to the heat dissipation research of the battery module.18650 single cells are used as the thermal management research objects.Compares their temperature variations of the constructed CPCM-based and nature air cooling?NAC?-based battery modules during the discharge rate at 2.5 C and 3.5 C.The results show that the battery module based on CPCM-4 provides superior cooling performance,especially under high-rate discharge conditions.For example,during the discharge process of 3.5 C,the maximum temperature of the CPCM-1 modules and NAC modules without SiC reach47.4? and 62.6?,respectively,while the temperature of CPCM-4 module reduces to43.5?.The temperature difference is reduced from 3.4? to 1.7?,indicating that CPCM-4has an outstanding performance in cooling and temperature uniformity.In addition,the prepared RPCM-6 is applied to the battery module.The results show that the maximum temperature of the RPCM-6 module and NAC module under the 2 C discharge process reach49.1? and 61.5?,respectively.The temperature difference of the battery module with RPCM-6 reachs 1.1?,indicating that RPCM-6 has good temperature-controlling capability and temperature-uniformed performance.