Experimental Investigation and Machine Learning Modelling of Shape Stabilized Composite Phase Change Materials for Thermal Management of Lithium Ion Batteries

Abstract

The usage of electric vehicles has substantially increased worldwide to reduce greenhouse gas emissions and decrease the dependence on crude oil. Li-ion batteries have a promising future due to their lightweight, high-energy-density (230 Wh/kg), stable charge cycles, and relatively long lifespan. However, the lifespan and performance of these batteries depend dominantly on their operating temperature, with the desired operating temperature range being 15-40oC. Hence, thermal management strategies for Li-ion battery packs are critical for better lifespan, safety, and performance. newlinePhase change material (PCM) based battery thermal management system (BTMS) can be an attractive solution due to the high latent heat of fusion of PCM and isothermal energy exchange. However, pure PCM has some drawbacks, like low thermal conductivity, leakage due to volume expansion during phase change, etc. Thus, the development of novel shape stable composite PCMs (SSCPCMs) is necessary to resolve the leakage and thermal conductivity issues of pure PCMs. In the present work, two porous structured matrix materials are selected: expanded graphite (EG) and biochar (BC) for preparing the SSCPCMs. The prepared composite PCMs are characterized to understand the chemical compatibility, thermal properties variations and shape stability. The selected PCM in the present study is Myristyl alcohol, a non-paraffinic organic PCM with several advantages over paraffin PCMs and phase transition temperature ideally suitable for Li-ion battery thermal management. newlineIn the present study, newline(i) composite PCMs are developed by adding EG at various loadings (5,10, and 15%) to Myristyl alcohol. The minimum EG quantity required to achieve shape stability is 15% (PCM-EG15, called SSCPCM), in which case the Myristyl alcohol PCM is found to be completely absorbed in the EG pores. The thermophysical properties and kinetics behaviour of developed composite PCMs are investigated. The thermal conductivity of SSCPCM is 17.6 times higher than that of pure PCM.