Positively-charged graphene mediate the crystal growth and microstructure to achieve ultrahigh mechanical properties of electrodeposited copper foils

To meet the stringent requirements of electrodeposited copper foil, graphene (Gr) has been recognized for its potential as an outstanding reinforcement agent, capable of significantly improving the mechanical and functional characteristics of copper foils. However, the effectiveness of Gr is often hindered by its poor dispersion and the weak interfacial bond strength with the metal matrix. In this study, we present a novel strategy that utilizes ionic liquid (IL) as a functionalizing agent to stabilize Gr for enhancing its reinforcement capabilities. This method has been demonstrated to successfully prepare copper foils with superior mechanical properties. Firstly, the impact of IL-functionalization on the dispersion, stability, morphology, and charge state of Gr was investigated. Subsequently, the IL-functionalized Gr (IL-Gr), serving as a reinforcement, was co-deposited with Cu2+ ions to fabricate copper foil. The results revealed that the surface functionalization resulted in a well-dispersed and positively-charged Gr in solution. Under optimized conditions, the copper foil exhibited remarkable improvements compared to those prepared without IL-Gr. Specifically, the surface roughness decreased from 3.582 to 2.834 μm, while the tensile strength and elongation values of the copper foil increased from 253.7 MPa to 2.29% to 471.5 MPa and 7.19%, respectively. Further characterizations indicated that this simultaneous enhancement in both tensile strength and elongation could be ascribed to the refining grains (0.23 μm) and an increase in the density of Σ3 twin boundaries (23.4%), resulting from the cathode polarization of IL-Gr. Overall, our innovative and facile approach provides an effective method for fabricating high-performance electrodeposited copper foils.