High-capacity binderless supercapacitor electrode obtained from sulfidation large interlayer spacing of NiMn-LDH

Abstract

Layered double hydroxide (LDH) is a promising pseudocapacitive electrode material with adjustable interlayer spacing, good electrochemical properties, and ion exchange ability. However, low conductivity and low exposure of electrochemically active sites limit its application in electrode materials. In the paper, NiMn-LDH nanoarrays with large interlayer spacing were synthesized on nickel foam (NF) by hydrothermal and modified by different degrees of incomplete sulfidation by controlling the times. The results show that NiMn-LDH/Ni3S2 is obtained when the sulfidation time is 3, 5, and 7 h. The best electrochemical performance is obtained at 3 h, with a specific capacity of 682 mA h g–1 at a current density of 5 mA cm–2 and maximum multiplicative performance of 59% (at 100 mA cm–2). The assembled hybrid supercapacitor obtains an energy density of 49 Wh kg–1 at a power density of 815 W kg–1 and capacity retention of 102% after 10,000 cycles (74 F g–1 at 10 A g–1). This is because the expanded interlayer spacing decreases the diffusion resistance between the interlayers, making it easier for OH– to enter the interlayers to improve the interaction with LDH. The sulfidation enhances the interfacial interaction by enhancing the electrical conductivity, while the conductive substrate provides additional electrical conductivity to the electrodes, leading to improved electrochemical performance.