Fe2O3 Nanoneedles on Ultrafine Nickel Nanotube Arrays as Efficient Anode for High‐Performance Asymmetric Supercapacitors

High performance of electrochemical energy storage devices depends on the smart structure engineering of electrodes, including the tailored nanoarchitectures of current collectors and subtle hybridization of active materials. To improve the anode supercapacitive performance of Fe 2 O 3 for high‐voltage asymmetric supercapacitors, here, a hybrid core‐branch nanoarchitecture is proposed by integrating Fe 2 O 3 nanoneedles on ultrafine Ni nanotube arrays (NiNTAs@Fe 2 O 3 nanoneedles). The fabrication process employs a bottom‐up strategy via a modified template‐assisted method starting from ultrafine ZnO nanorod arrays, ensuring the formation of ultrafine Ni nanotube arrays with ultrathin tube walls. The novel developed NiNTAs@Fe 2 O 3 nanoneedle electrode is demonstrated to be a highly capacitive anode (418.7 F g −1 at 10 mV s −1 ), matching well with the similarly built NiNTAs@MnO 2 nanosheet cathode. Contributed by the efficient electron collection paths and short ion diffusion paths in the uniquely designed anode and cathode, the asymmetric supercapacitors exhibit an excellent maximum energy density of 34.1 Wh kg −1 at the power density of 3197.7 W kg −1 in aqueous electrolyte and 32.2 Wh kg −1 at the power density of 3199.5 W kg −1 in quasi‐solid‐state gel electrolyte.