Experimental Study of Dual-PCM Gradient Thermal Management for Lithium-Ion Batteries with Wide Temperature Ranges

In this study， a new method for passive thermal management of lithium-ion batteries based on paraffin/expanded graphite/bamboo charcoal composite bilayer phase-change materials is proposed. To solve the problem of the limited temperature-control range of existing phase-change materials， a dual phase-change temperature （30 ℃/50 ℃） gradient structure is constructed， and a composite phase-change system with dual phase-change temperature regulation is developed by combining the high thermal conductivity of expanded graphite with the porous adsorption properties of bamboo charcoal. Based on these results， at 40 ℃ ambient temperature and under 5 C large multiplication rate， the temperature increase of the battery constructed using the double-layer phase-change material was 37.8% lower than that of the non-phase-change material group （43.3 ℃ vs. 69.6 ℃， respectively）； at low ambient temperatures （-10 ℃ and 0 ℃）， the double-layer phase-change material extended the battery's effective working temperature range through the synergistic effects of the latent heat release of the phase change materials and the heat storage in the pores. The composite phase-change system realized intelligent thermal management across a broad temperature spectrum （-10 - 40 ℃） via the dual-phase-change mechanism， providing an innovative solution for the thermal safety regulation of batteries， which has significant engineering application value.