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

Abstract: 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 Cu₂O 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 Cu₂O 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 Cu₂O 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. [ABSTRACT FROM AUTHOR]