Abstract: To ensure the safe and stable operation of lithium-ion batteries in electric vehicles across a broad temperature range of -30℃ to 40℃, highly efficient battery thermal management systems (BTMS) are essential for precise temperature regulation. These systems mitigate capacity degradation at low temperatures and thermal runaway risks at high temperatures. Microencapsulated phase change material slurry (MPCMS) has emerged as a promising working fluid for battery thermal management. While recent research has primarily explored its application at low concentrations, this study proposes a comprehensive all-climate BTMS utilizing MPCMS at high mass fraction (5-30%). The thermal management performance was systematically evaluated under three characteristic operational modes—thermal insulation and storage at low temperatures, cold storage and heat absorption at moderate temperatures, and heat dissipation and cooling at high temperatures—using electrically heated rods to simulate battery thermal loads. Experimental findings demonstrate that under a low-temperature condition of -30℃, compared to a system without MPCMS, the mass fraction of 5%, 15%, and 30% MPCMS, synergistically working with an insulation layer, extended the thermal preservation time by 8.1%, 18.2%, and 24%, respectively. At a moderate ambient temperature (23℃, below the phase change point of the microcapsules), MPCMS effectively absorbed the heat generated during battery discharge. Under 1C, 2C, and 3C discharge rate scenarios, the maximum temperature reductions achieved were 2.6℃, 4.7℃, and 5.2℃, respectively, compared to the system without MPCMS. Notably, the mass fraction 15% MPCMS formulation demonstrated an optimal balance between latent heat absorption capacity and convective heat transfer performance. Under a high-temperature environment of 40℃, even when the heating rod simulated a 3C discharge thermal load within the mass fraction 30% MPCMS, the system temperature was successfully stabilized below 40℃ by maintaining a 10℃ temperature difference between the cooling water inlet and the ambient environment. This study underscores the significant potential of high-concentration MPCMS as an efficient thermal management medium for lithium-ion batteries, enabling effective thermal regulation across diverse and challenging climatic conditions.

Key words: battery thermal management, All-weather temperature, Phase-change microcapsule suspension, heat preservation, heat transfer