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 delta-MnO2 cathodes. The results demonstrate the attractive potential of the GCF substrate in the application of the rechargeable batteries.