Experimental investigation on a novel phase change material composites coupled with graphite film used for thermal management of lithium-ion batteries

Thermal management system is a key component to maintain the performance of lithium-ion batteries in electric vehicles. Cooling technology based on phase change materials with single-phase transition range has been proposed by many researchers but the temperature control of batteries is not ideal for high charge/discharge rates and cycle tests. Herein, we designed a novel phase change material consisting of paraffin with dual-phase transition ranges (around 34 degrees C and 48 degrees C), expanded graphite (thermal conductivity = 40 W/m K), and epoxy resin with a mass ratio of 5:2:3. This material was combined with graphite film (in-plane thermal conductivity of 1400 W/m K) to prepare a thermal management module. Graphite film and expanded graphite form an excellent heat conduction structure. Epoxy resin endows this composite with satisfactory mechanical properties, even at 70 degrees C. The paraffin provides a double buffer effect that minimizes the temperature increase of the batteries and the temperature differences between the batteries in the pack due to the broad phase transition range. As a result, the maximum temperature of the batteries is 33 degrees C and the maximum temperature difference between the batteries is only 1.4 degrees C, even at the highest 4C discharge rate. In addition, the maximum temperature of the batteries is only 44.8 degrees C after six extreme cycles. (c) 2019 Elsevier Ltd. All rights reserved.