Electrochemically Derived Graphene‐Like Carbon Film as a Superb Substrate for High‐Performance Aqueous Zn‐Ion Batteries

3D graphene, as a light substrate for active loadings, is essential to achieve high energy density for aqueous Zn‐ion batteries, yet traditional synthesis routes are inefficient with high energy consumption. Reported here is a simplified procedure to transform the raw graphite paper directly into the graphene‐like carbon film (GCF). The electrochemically derived GCF contains a 2D–3D hybrid network with interconnected graphene sheets, and offers a highly porous structure. To realize high energy density, the Na:MnO2/GCF cathode and Zn/GCF anode are fabricated by electrochemical deposition. The GCF‐based Zn‐ion batteries deliver a high initial discharge capacity of 381.8 mA h g−1 at 100 mA g−1 and a reversible capacity of 188.0 mA h g−1 after 1000 cycles at 1000 mA g−1. Moreover, a recorded energy density of 511.9 Wh kg−1 is obtained at a power density of 137 W kg−1. The electrochemical kinetics measurement reveals the high capacitive contribution of the GCF and a co‐insertion/desertion mechanism of H+ and Zn2+ ions. First‐principles calculations are also carried out to investigate the effect of Na+ doping on the electrochemical performance of layered δ‐MnO2 cathodes. The results demonstrate the attractive potential of the GCF substrate in the application of the rechargeable batteries. A simplified procedure is developed to transform raw graphite paper directly into graphene‐like carbon film (GCF). The highly porous GCF contains a 2D–3D hybrid network with interconnected graphene sheets. The GCF‐based Zn‐ion batteries deliver a high capacity of 381.8 mA h g−1 at 100 mA g−1 and a record energy density of 511.9 Wh kg−1.