Electrical Conductivity of Copper-Graphene (Cu-Gr) Composites: The Underlying Mechanisms of Ultrahigh Conductivity

Copper-graphene composite (CGC) conductors are widely considered as a potential alternative to pure copper (Cu). Yet, the effect of graphene (Gr) on the electrical conductivity of CGCs remains elusive, and their electrical performance is still controversial. This work addresses these unresolved questions by unambiguously quantifying how the electrical properties of CGCs depend on the characteristics of Gr and Cu. Gr is synthesized on Cu foils, foams, and wires by utilizing a wide range of chemical vapor deposition conditions to independently control their characteristics. Then the Gr-enhanced electrical conductivity (Δσ) is characterized for CGCs with different Cu geometries and Gr qualities. This study confirms that unprecedented electrical conductivity (Δσ = 17.1%) can be achieved only when both Gr and Cu are carefully optimized. Specifically, the study reveals three key factors: (1) Δσ is positively correlated with continuity of Gr; (2) CGCs with a continuous monolayer Gr exhibit a strong Δσ - A_s linear relation where A_s is the specific surface area of a CGC; and (3) Δσ becomes more pronounced when a Cu matrix has a curved cross-section. This work reveals the fundamental mechanisms of how Gr influences the overall electrical conductivity of CGCs and, therefore, is a crucial step toward designing and manufacturing high-performance CGC conductors for emerging applications.