Thermal performance enhancement of lithium-ion battery modules through coolant selection and cold plate structural optimisation

Effective thermal management is critical to ensuring the safety, performance, and lifetime of lithium-ion battery modules used in electric vehicles. This study investigates two complementary strategies for enhancing indirect liquid-cooled battery thermal management systems: the use of environmentally benign coolants and the optimisation of practical cold-plate geometries. First, propylene glycol–water (PG–W) mixtures are evaluated as non-toxic alternatives to conventional ethylene glycol–water (EG–W) coolants using a validated three-dimensional computational fluid dynamics (CFD) framework incorporating a multi-scale multi-domain (MSMD) electrochemical battery model. The results demonstrate that PG–W mixtures with different volume ratios provide thermal performance comparable to EG–W solutions, with a 40/60 PG–W mixture offering the most balanced compromise between peak cell temperature, pressure drop, freeze protection, and environmental safety. Second, the influence of cooling-plate architecture is examined at the module scale using a thirty-cell CFD model driven by heat-generation data extracted from the MSMD simulations. Three cooling configurations are analysed: a baseline serpentine channel, a double-row vertical cold-plate design, and a triple-row vertical cold-plate design. The results show that structural optimisation has a dominant impact on reducing peak temperature and improving temperature uniformity, particularly under high discharge rates. Among the configurations studied, the double-row vertical cold-plate design delivers substantial thermal improvement while maintaining moderate mass and structural complexity. The study highlights the combined importance of safe coolant substitution and manufacturable geometric optimisation for the development of efficient, scalable, and environmentally responsible battery thermal management systems.