applications to enhance its mechanical strength, but alloying is detrimental for high electrical conductivity because of more electron scattering centers. [3,4] Therefore, achieving electrical conductivity at a level beyond that of pure aluminum in practical applications is a major challenge.Composite fabrication by incorporating ultrahigh conductive reinforcement with a metal matrix is considered a possible approach to improve the electrical conductivity of metals. [5] Graphene has excellent intrinsic electrical properties and is one of the most promising candidates for such purposes. [6,7] An electron mobility (µ) of ≈2.0 × 10 5 cm 2 V −1 s −1 was measured in a suspended graphene with a carrier density (n) of ≈10 12 cm --2 at room temperature, [8,9] exceeding the record of ≈7.7 × 10 4 cm 2 V −1 s −1 reported for InSb. [10] According to the equation σ = enµ (e is the electron charge, ≈1.6021766209 × 10 −19 C), the electrical conductivity (σ) of the graphene is calculated to be 96 × 10 6 S m −1 , [11] which is ≈170% higher than that of aluminum. Therefore, it is possible to improve the electrical conductivity of aluminum by incorporating graphene.However, such improvement is not easy to achieve in practical graphene/aluminum matrix composites. [12,13] The challenges lie in the following factors. First, the forementioned intrinsically high electrical conductivity of a single graphene layer strongly depends on its fabrication method, structural integrity, [14][15][16] intrinsic defects, [17][18][19][20] chemical contamination, [21][22][23][24] and the substrates used to support graphene. [25][26][27][28][29] Second, to exert the intrinsic electrical properties of graphene at macroscopic level (such as in bulk graphene/aluminum matrix composites), fabrication methods have to be developed for achieving homogenous dispersion of graphene in metals without damage and good electrical contact between graphene and metals. Because of these complex prerequisites, the electrical conductivity of almost all the reported graphene/metal matrix composites does not exceed that of the pure matrix. As an exception, Pan et al. [30] reported conductivity enhancement in graphene/copper matrix composites based on highquality graphene. The quality of reduced graphene oxide (GO) was improved by heat treatment at high temperature and high pressure, and then high-quality graphene was incorporated in a copper matrix by a ball-milling process. As a result, an Graphene is considered a promising reinforcement to improve the electrical conductivity of metals because of its excellent intrinsic electrical conductivity. However, graphene/Al matrix composites with enhanced electrical conductivity have not yet been reported. In this work, it is attempted to understand the factors influencing the electrical conductivity of graphene embedded in an Al matrix by adjusting the interfacial structure and composition. By sandwiching graphene (Gr) or graphene oxide (GO) with either pristine or passivated Al foils, three kinds of typical composite interfaces ar...