High-performance graphene films for thermal management and electromagnetic shielding prepared through high-temperature annealing

Graphene films have been considered excellent candidates for thermal management and electromagnetic interference (EMI) shielding materials due to their outstanding flexibility, exceptional thermal conductivity, and electrical conductivity. In this study, lignin, a biomass carbon precursor, was added as a welding agent to graphene oxide (GO), and the graphene composite films with enhanced performance were obtained through multi-step high-temperature annealing. Lignin assisted the assembly of GO through hydrogen bonds and covalent bonds, resulting in more compact and ordered precursor films. During the annealing process, lignin played a welding role by synergistically crystallizing with GO, which not only repaired the defects in the graphene sheets but also connected adjacent graphene sheets to form larger sheets. As a result, the graphene composite film achieved a 30.3% improvement in thermal conductivity (1462   W   m −1 K −1 ), a 50.0% increase in electrical conductivity (1.49 × 10 6 S m −1 ), and an excellent EMI shielding effectiveness of up to 70.3   dB. Moreover, the composite film exhibited excellent flexibility, with almost no decrease in electrical conductivity after 100,000 folding cycles. This dual-functional graphene film offers a new solution to the heat dissipation challenges and electromagnetic pollution issues posed by the integrated development of electronics, with potential applications in advanced devices, portable equipment, and aerospace fields.