Solder-free electrical Joule welding of macroscopic graphene assemblies

Welding is an important convenient methodology to realize robust coalescence of individual metallic or polymeric objects through local melting of contact boundaries. However, how to firmly conjoin the refractory graphene-based materials via conventional welding remains an open question because of their non-melting nature. In this work, we report an efficient solder-free approach to weld individual macroscopic graphene assemblies via electrical Joule heating. Graphene-based materials with different architectures, including graphene fibers, films, and foams, are covalently welded together with high joint strength. The welding mechanism was studied by in situ transmission electron microscope and molecular dynamic simulations. We attributed the unique welding behavior to the defect-facilitated cross-linking between graphene layers at contact interface. The facile electrical Joule welding strategy provides a new reliable connection method for carbon materials, enabling the direct assembling of macroscopic graphene materials to sophisticated three-dimensional configurations.