Self‐Templated Synthesis of Cuprous Oxide Nanofiber‐Assembled Hollow Spheres for High‐Performance Electrochemical Energy Storage

Hollow structures are considered as promising electrode materials. Their enhanced surface‐to‐volume ratio results in an increased contact area between the electrolyte and electrode and, thereby, a higher accessibility of active material. Here, a facile hydrothermal method is applied to synthesize hollow Cu 2 O spheres, assembled by well‐aligned nanofibers. Based on the investigation of the samples at different reaction times, a growing mechanism is proposed. Nano building‐blocks create porous channels within the shell, which could facilitate the transfer and shorten the transportation pathway for both ions and charge. The Cu 2 O with its unique structure displays a high specific capacitance of 1075 F g −1 at a current density of 5 mA cm −2 , a remarkable rate capability of 82 %, and an excellent cycling property of nearly 100 % of the initial value remaining after 5000 charge‐discharge cycles. Moreover, the hollow Cu 2 O spheres are first used for the preparation of a positive electrode in an asymmetric supercapacitor, using carbon as a negative electrode. The device exhibits a high energy density of 44.7 Wh kg −1 at a power density of 420.2 W kg −1 , and when the power density reaches values as high as 4201.7 W kg −1 , an energy density of 16 Wh kg −1 is still attained.