Preparation And Application Of Composite Phase Change Energy Storage Materials In Lithium Battery Thermal Management System

Lithium-ion batteries have become the power source of a new generation of electric vehicles due to their excellent performance such as high specific energy,specific power and discharge voltage.However,the thermal runaway seriously affected the safe use of lithium battteries.The thermal storage system based on phase change energy storage materials has become a key material that can effectively solve the safe use of lithium batteries.Based on this,two high-performance composite phase change energy storage materials was prepared in this paper,and analyzed their temperature control effects on batteries.1.A ternary low eutectic fatty acid(LMP)with a mass ratio of LA/MA/PA=0.52:0.30:0.18 was prepared from lauric acid,myristic acid,palmitic acid and stearic acid based on the principle of minimum eutectic.The melting temperature and melting enthalpy were 33.7 ℃ and153.23 J/g.The solidification temperature and solidification enthalpy were 32.56 ℃ and 151.46J/g.The results indicate that no chemical reaction occurred during the preparation of LMP.The good thermal properties and stability of LMP contribute to its application in the thermal management system of lithium batteries.2.The silver particles/expanded graphite/ternary low eutectic fatty acid composite phase change materials(Ag/EG/LMP)with different silver particle contents were prepared by vacuum impregnation using LMP as the core material and silver particle-modified expanded graphite as the carrier.The results of thermal properties and thermal conductivity showed that the composite phase change material with 3% of silver particles in the carrier was the best choice.The melting temperature and melting enthalpy were 30.57 ℃ and 117.02 J/g.The solidification temperature and solidification enthalpy were 30.61 ℃ and 110.50 J/g.The phase change temperature meeted the requirements of the thermal management system of lithium battery.The analysis revealed that the silver particles and phase change materials were uniformly distributed in the expanded graphite flake layer.Ag/EG/LMP exhibited good thermal storage properties,chemical stability and high thermal conductivity.3.The silver nanowires/expanded graphite/ternary low eutectic fatty acid composite phase change material(Ag NWs/EG/LMP)was prepared with LMP as the core material and silver nanowires modified expanded graphite as the carrier.The melting temperature and melting enthalpy were 30.64 ℃ and 118.41 J/g.The solidification temperature and solidification enthalpy were 31.15 ℃ and 113.71 J/g.The analysis revealed that the silver nanowires and LMP were uniformly distributed in the expanded graphite flake layer.Ag NWs/EG/LMP exhibited good stability below 250 ℃.And the composite Ag NWs/EG/LMP exhibited high thermal conductivity of 4.23 W/(m·K).In addition,the feasibility of the two composite phase change materials Ag/EG/LMP and Ag NWs/EG/LMP prepared in this paper was verified by theoretical calculations for application in the thermal management system of lithium batteries.It is proved that both of the two shaped composite phase change materials can effectively control the battery temperature in the safe range.