Modified graphene film powder scraps for re-preparation of highly thermally conductive flexible graphite heat spreaders

Graphene film (GF) is widely used for heat dissipation in portable electronic devices by virtue of its lightweight and high thermal conductivity (K). However, in practical applications, mold-cutting GF inevitably generates plenty of scraps with high K, so it is worthwhile to investigate the secondary utilization of scraps. This contribution first used polydopamine (PDA) to surface-modify the crushed large-sized graphite nanosheets (GNs) powder scraps to obtain GNs@PDA. Then the GNs@PDA was mixed with graphene oxide (GO) sheets to prepare graphene/GNs@PDA (G/PG) composite films via self-assembly. After graphitization, the graphitized PDA "welded" the GNs to the derived graphene through covalent bonds. The resulting long-range ordered defect-free lamellar stacking structures effectively facilitated the transfer of phonons and electrons, thus significantly enhancing the K and electrical conductivity of the G/PG film. The in-plane K and electrical conductivity of the G/ PG film are up to 1301.8 W/mK and 5939.0 S/cm, respectively. Furthermore, G/PG films also exhibit superior mechanical properties, foldability, and electromagnetic shielding performance. This work provides ideas for the preparation of flexible heat spreaders and realizes the reuse of GF scraps.