Potential difference-induced electrodeposition of defect-rich α-cobalt hydroxide on porous copper (PCu): High-voltage performance of supercapacitor

Abstract

Designing electrode materials for aqueous battery-type supercapacitors to extend the operating voltage window remains a significant challenge to increase the energy density of aqueous supercapacitors. In this work, a directional electrodeposition method without any additives was employed to deposit alpha-Co(OH)(2) onto a porous copper (PCu) current collector substrate, which involves the fabrication of a supercapacitor electrode material with a cross-linked network structure named alpha-Co(OH)(2)@PCu900. The potential difference between copper and cobalt facilitated the formation of a larger interlayer spacing for alpha-Co(OH)(2). In addition, crystals of alpha-Co(OH)(2) with different orientations exert stress on one another, leading to lattice distortion and vacancy formation. The morphology and microstructure of materials were analyzed through techniques such as SEM, HRTEM, XRD, and XPS, confirming the validity of the experimental design. This defect-rich, large interlayer spacing structure facilitates ion intercalation and deintercalation during the charge-discharge process, thereby expanding the operating voltage window. In a three-electrode system, alpha-Co(OH)(2)@PCu900 exhibited a potential range from -0.45 V to 0.55 V and demonstrated an areal capacitance of 2580 mF cm(-2) and specific capacitance of 600 A g(-1) at 2 mA cm(-2). The alpha-Co(OH)(2)@PCu900 was used as the cathode material and commercial reduced graphene oxide (rGO) was used as the anode material in an asymmetric supercapacitor, and the ASC device exhibited an areal capacitance of 295.3 mF cm(-2) and a specific capacitance of 87.89 F g(-1). Notably, it retained a high energy density of 0.12 mW h cm(-2) (35.27 Wh kg(-1)) at a power density of 1.7 mW cm(-2) (505.95 W kg(-1)). This method established alpha-Co(OH)(2)@PCu900 as a promising supercapacitor electrode material, providing a viable strategy for designing and fabricating functional electrode materials.