All-climate thermal management structure for batteries based on expanded graphite/polymer composite phase change material with a high thermal and electrical conductivity

With the large-scale application of lithium battery technology, a thermal management system is required to ensure battery performance and safety in all climates. This study reports an all-climate battery thermal management structure based on an expanded graphite/polymer/paraffin wax ternary composite phase change material with high thermal (19.3 Wm−2/K) and electrical (1590.5 S/m) conductivity. The thermal management structure adopts a double-layer structure, an inter phase change material with high thermal and electrical conductivity, and an outer phase change material with low thermal conductivity as a heat preservation and insulation medium. The thermal management structure innovation uses the phase change material and the battery to form a preheating circuit to generate Joule heat to warm up the battery at low temperatures. This heating method uses the energy of the battery to greatly improve the adaptability of the thermal management system. The preheating speed reaches 20.5 °C/min at –20 °C. The phase change material can continue to generate heat during the discharge process of the battery to ensure normal operation. At a discharge rate of 1C and at –20 °C, the discharge energy increased by 35.5% compared with the case without preheating. In addition to acting as a heating element, phase change materials also act as heat dissipation media in high temperature environments, the structure exhibited a good heat dissipation capacity. At 35 °C, the temperature of the battery was controlled at 42.2 °C after the battery was discharged at a rate of 2C.