Electrochemical -thermal Coupled Modeling and Thermal Management of High-energy-density Lithium-ion Batteries

Abstract

The rising demand for electric vehicles (EVs) is driven by the need to reduce dependence on fossil fuels and mitigate climate change. The transportation sector consumes more than half of global oil production and contributes nearly 30% of global CO₂ emissions, with road transport accounting for the majority share. Lithium-ion batteries (LIBs), with their high energy density and efficiency, are central to EV adoption but face challenges related to heat generation, performance degradation, and safety risks such as thermal runaway. Effective battery thermal management systems (BTMS) are therefore critical for ensuring reliability and extending cycle life. This work develops an electrochemical–thermal coupled modeling framework to analyze transient heat generation in LIBs under varying conditions. A Doyle-Fuller-Newman (DFN) electrochemical model integrated with a 3D thermal model is applied to a 5Ah, 21700 cylindrical cell. Contributions from different heat sources are quantified for LIB across discharge rates from 1C to 5C and ambient temperatures from 5 °C to 45 °C. Results show that irreversible heat dominates at higher C-rates and temperatures, while reversible heat is more significant at the positive electrode and mixing heat at the negative electrode. Two BTMS strategies are proposed for effective thermal management. An active serpentine-shaped cooling channel (SSCC) for a 7S4P, 0.5 kW battery pack demonstrates strong heat dissipation, reducing maximum cell temperature from 107 °C to 61 °C at 5C while maintaining uniform distribution. A passive system using composite phase change materials (CPCMs) is also evaluated. Expanded graphite (EG)-enhanced CPCMs outperform paraffin and MWCNT-based composites, achieving up to 4.2 W/mK thermal conductivity and lowering maximum temperature by 11% under a 3C discharge. The research highlights a dual approach of advanced modeling with active and passive BTMS for safe, efficient, and long-life operation of high-energy-density LIBs in EVs.