Facile Fabrication of High‐Performance Hybrid Supercapacitor by One-Step, Self‐Grown Copper Nanopillar Forest Anchored with Fe₃O₄ Anode

Hybrid supercapacitors are considered as one of the most promising next-generation energy storage devices, owing to high-energy, high-power density, and long-cycle life. In this work, a simple and low-cost fabrication method of the nanostructured anode with a high capacity and power is proposed for fabrication of high-performance hybrid supercapacitors. This is achieved by a one-step in-situ growth of numerous copper nanopillars on a commercially available copper foil though the galvanic displacement reaction in an aqueous ionic solution. The copper nanopillar forest-based structure with a high surface area, ion accessibility, and electron transportability provides excellent current collecting characteristics for the anode of a lithium-ion battery. The electrochemical performance of a Li half-cell incorporating the copper nanopillar-based current collector exhibits a high capacity (880 mAh g^{− 1} at 0.2 °C), excellent rate capability, and extremely high durability (97% after 1000 cycles). These results show that the fabricated anode structure can improve the electrochemical performance of the hybrid supercapacitors. To demonstrate the feasibility of an alternative power source, the full cell was fabricated by combining the copper nanopillar anode and an activated carbon cathode. This device provided a high energy density (98.9 Wh kg^{− 1} at 248 W kg^{− 1}), high power density (7018 W kg^{− 1}), and long-cycle life (> 1000 cycles).