Metal–Organic Coaxial Nanowire Array Electrodes Combining Large Energy Capacity and High Rate Capability

Pseudocapacitors have been widely studied in the context of their potential applications in portable electronics and energy regeneration. However, the internal resistance within these devices hampers charge transport and limits their performance. As a result, maximum charge/discharge rates are typically limited to a few hundred mV s−1 for pseudocapacitors. Beyond this limit, capacitance rapidly decreases and devices become incapable of storing energy. Here, we design electrodes in which coaxial nanowires made of highly conductive metal cores and pseudocapacitive organic shells are fabricated into a seamless, monolithic, and vertically aligned structure. The design of this structure reduces its internal resistance, and devices fabricated using these electrodes exhibit excellent energy capacity even when charged/discharged at high rates of more than a few hundred mV s−1. The energy density obtained in these devices corresponds to the maximum energy density predicted by the Trasatti method, and the coaxial‐nanowire structure of the electrodes enhances the charge storage capacity and rate capability simultaneously. Inside the wire: Metal–organic coaxial nanowire array electrodes exhibit a large capacity of 62.2 mF cm−2 and 11.6 F cm−3 at a fast charge/discharge rate of 5080 mA cm−3. The design of the nanowire electrodes imparts excellent rate capability to pseudocapacitors, and their energy density can be increased to a maximum value while maintaining a high‐level power density.