Thermally conductive silicone composites modified by graphene-oxide aerogel beads loaded with phase change materials as efficient heat sinks

Abstract

Electrically insulating phase change composite materials (PCCMs) with lightweight, good thermal management performance, high stability and high mechanical strength are strongly desired for lithium-ion battery (LIB) thermal management. This research study presents a group of PCCMs based on the integration of reduced graphene-oxide aerogel beads (rGOAB), phase change materials (PCMs) and thermally conductive silicone rubbers (SRs). To demonstrate the thermal management performance, a 3 × 3 square 18650 LIB module was inserted into a SR pack. The temperature reduction (temperature reduction of the battery cells at the hottest point in the SR pack compared with in air) reached 8.6 °C, 13.0 °C and 14.7 °C at 1C, 2C and 3C discharge rate, respectively, at a concentration of 20 wt% PCM beads in SR with thermal conductivity of 0.5 W/mK. The specific energy reduction of above-mentioned pack is only 15.8%, substantially lower than the commercial level (above 30% to 40%). The lowest specific energy reduction in SR pack with thermal conductivity of 0.3 W/mK goes down to 13.4%, indicating its remarkable lightweight and high energy density features. The effects of PCM-encapsulant type, SR matrix thermal conductivity and bead size on LIB temperature reduction were also discussed. The heat transfer mechanism between the matrixes and rGOAB/PCM was thoroughly explained. Mechanical properties and battery thermal management performance of the composites were systematically examined. The rGOAB/PCM@SR composites exhibited more than 10 times of impact strength compared with expanded graphite-based PCCMs and higher compressive toughness above the phase transition point.