Scalable High-Performance Graphene Films Over Hundreds Micrometer Thickness via Sheargraphy

High-performance graphene films with hundreds of micron thicknesses are promising to solve severe thermal management demands owing to higher heat-carrying capacity. However, thick graphene films exhibit limited thermal conductivity below 1000 W m^-1 K^-1, caused by internal wrinkle defects of sheets. Here, a sheargraphy strategy is proposed to precisely regulate the sheet arrangement of liquid crystals and achieve the 215 µm thick graphene films with a record in-plane thermal conductivity of 1380 W m^-1 K^-1. Microscale shearing fields of 5 µm generated by horizontally moved wire array flatten sheet wrinkles and eliminate polycrystallinity of graphene oxide liquid crystals. The uniform liquid crystals impart condensed solid films with high ordering, thereby forming densified and flat stacked graphitic crystallites. The highest thermal flux, defined as thickness multiplied by thermal conductivity, reaches up to 0.3 W K^-1, endowing thick film with long-distance rapid heat spreading capability and designability for heat transfer pathways. This work provides a valid methodology to regulate the ordering of 2D sheets and produce high heat-flux graphene films to solve growing thermal management challenges.