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 °C and 48 °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 °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 °C and the maximum temperature difference between the batteries is only 1.4 °C, even at the highest 4C discharge rate. In addition, the maximum temperature of the batteries is only 44.8 °C after six extreme cycles.