Large-area high thermal conductivity graphite-carboxymethylcellulose film easily produced by mechanical exfoliation of natural graphite using a three-roll mill

• Thermally conductive films with high in-plane thermal conductivity are produced using exfoliated graphite • The proposed method is simple, scalable and environmentally friendly. • A mixed structure of large graphite and thin graphite sheets provides high thermal conductivity With the rapid development of the electronics industry, the demand for superior heat dissipation materials is increasing. Although many studies have been conducted on graphene films with high thermal conductivity, most of them are processed at high temperatures (∼3000°C) using graphene oxide, which is environmentally harmful and consumes large amounts of energy. This paper reports a simple, low-cost, low-energy, high-efficiency method for the preparation of graphite films using only environmentally friendly materials. Composite films with a thermal conductivity of 298.5 Wm -1 K -1 were successfully produced by simply dispersing and exfoliating natural graphite and carboxymethylcellulose in a roll mill and depositing by blade coating. Conventional films fabricated using graphene nanoplates (GNP) exhibited a thermal conductivity of 94.6 Wm -1 K -1 , which is significantly lower than the graphite film produced by roll-milling. Experimental and theoretical investigations reveal the reason for this is that the mixed structure of large graphite and small graphite/GNP reduces the interfacial thermal resistance while forming a denser network of heat conduction paths.