In-situ electronic modulation of ultra-high-capacity S-modified Cu/Cu2O electrodes for energy storage applications

Due to the modification of anions, an electron redistribution occurs at the metal ions can affect the electronic structure, and induce excellent specific capacity. Herein, we report an effective and low time-consuming method by in-situ wet chemical reduction at room temperature to construct S-modified Cu/Cu 2 O negative electrode material. Moreover, the sulfur can occupy partial O sites in Cu 2 O to play a crucial role in the electronic structure of the material, demonstrated by DFT calculation, XRD, XPS and XAS measurements. The prepared S-Cu/Cu 2 O samples exhibit excellent electrochemical performance with high specific capacity of 669 mAh·g −1 at 1 A·g −1 , even 450 mAh·g −1 at 10 A·g −1 . When the materials are composed as pseudo capacity-type cathode//battery-like anode (MnO 2 //S-Cu/Cu 2 O), and (+) battery-type//battery-type (-) (Ni-Cu hydroxide/Cu(OH) 2 /CF//S-Cu/Cu 2 O) hybrid capacitors, they show the energy density of 47.7 and 147.3 Wh·kg −1 at the power density of 636.2 and 800 kW·kg −1 , respectively. Otherwise, the flexible MnO 2 //S-Cu/Cu 2 O hybrid capacitor is assembled, which also exhibits good performance at different bending conditions. This work can provide a simple method to prepare the electrode materials via in situ anion modification for high-energy density battery-like energy storage systems.