Ultrahigh-ratio drawing during spinning achieves graphene fibres with high strength and thermal conductivity.

The demand for materials combining high strength with exceptional thermal conductivity is growing across aerospace, automotive, thermal management and energy applications. Graphene offers an ideal building block, but multiscale defects such as disordered stacking and voids prevent macroscopic assemblies from realizing its intrinsic properties. Here we show that ultrahigh-ratio draw spinning, enabled by the polymer-like viscoelasticity of two-dimensional sheets in viscous solvents, produces graphene fibres with a tensile strength of 5.9 GPa, a Young modulus of 963 GPa, a thermal conductivity of up to 1,720 W m-1 K-1 and an electrical conductivity of 1.3 MS m-1. A high-ratio draw spinning up to 11, combined with high-temperature annealing, efficiently removes defects and produces densely packed, highly ordered graphene fibres. These properties surpass most existing strong and thermally conductive fibres. This work provides a versatile route for assembling two-dimensional materials into high-performance macroscopic structures and expands opportunities for multifunctional materials.