Comprehensive evaluation of battery cooling mechanisms including two-phase immersion with 3 M™ NOVEC™-7000 and 7100

• Comprehensive comparison of all battery thermal management methods was performed. • Single- and two-phase immersion cooling reduced peak cell temperatures by 28 % and 42 %, respectively. • Porous media enhanced immersion cooling performance by an additional 15 % in peak temperature reduction. • Immersion cooling offers strong temperature uniformity but faces flow control and leakage risks. Effective thermal management is critical for ensuring the safety, performance, and lifespan of lithium-ion batteries (LIBs), particularly in high-demand applications such as electric vehicles. This study presents a comparative experimental evaluation of five battery thermal management strategies—natural and forced air convection, cold plate cooling, and single-phase (3 M™ NOVEC™ 7100) and two-phase (3 M™ NOVEC™ 7000) immersion cooling, each tested without and with porous structures to enhance coolant distribution and boiling behaviour. A distinguishing feature of this work is the use of a realistic 24-cell (12S2P) battery pack, significantly larger than typical laboratory-scale tests, enabling a more practical assessment of intra-pack thermal gradients. Temperatures were recorded from seven spatially distributed locations to capture nonuniformities within the pack during operation. A key innovation is the integration of porous compression pads within immersion-cooled configurations. These structures enhance fluid transport, improve capillary liquid retention, and promote vapor venting, resulting in marked improvements in thermal uniformity. Among the methods tested, natural convection resulted in excessive peak temperatures (>60 °C) and poor distribution, while forced convection provided only marginal gains. Cold plates showed localized cooling but failed to address internal localised thermal gradients effectively. Single-phase immersion cooling with porous media improved uniformity but showed elevated surface temperatures due to limited conductive pathways through the porous layer. In contrast, two-phase immersion cooling, enhanced by latent heat effects and porous structures, achieved the lowest maximum temperatures (<36 °C) and the most uniform thermal profile. These findings establish two-phase immersion cooling with porous enhancement as a scalable, effective, and safety-oriented solution for next-generation battery systems, offering improved performance, lifespan, and integration potential for real-world applications.