Hybrid single-phase immersion cooling structure for battery thermal management under fast-charging conditions

•Immersion cooling structure with one pass partition and graphite fins are proposed.•The hydrofluoroethers fluid is selected as a dielectric fluid with an upward flow design.•The proposed design reduces the pressure drop by 45% and power consumption by 61%.•It can reduce the maximum temperature by 6.7 °C and temperature difference by 3 K. Immersion cooling technology shows the potential for high-energy–density battery thermal management under extreme charging/discharging conditions. In this study, a hybrid immersion cooling structure is proposed for overcoming challenges of conventional indirect liquid cooling methods. A simulation model for the hybrid immersion cooling design is developed based on experiments. The performance of the proposed design is investigated with variations in key design parameters, such as the flow directions, gaps between the batteries, pass partitions, and heat transfer materials. Ultimately, a hybrid immersion structure with one pass partition and graphite fins shows the best performance regarding the overall weight and temperature uniformity. This hybrid structure reduces the pressure drop and power consumption by 45.4% and 61.0%, respectively, thereby reaching a preferred battery temperature condition relative to a baseline structure under a 3C charging condition. In addition, the hybrid immersion structure provides a 6.7 °C lower maximum temperature and 3.0 K lower temperature difference relative to those of a conventional structure with a nearly identical weight. This structure can also reduce the battery temperature effectively under thermal abuse conditions; thus, it can be regarded as more reliable in terms of safety.