Understanding the enhancement of electrochemical properties of NiCo layered double hydroxides via functional pillared effect: An insight into dual charge storage mechanisms

In terms of the charge storage mechanism of supercapacitors, there are three types, including electrical double layer (EDL), surface redox reaction and intercalation reaction. The surface redox mechanism of transition metal-layered double hydroxides (TM-LDH) supercapacitor had been previously revealed. A dual charge storage mechanism integrated with surface redox and ion intercalation for LDH-based supercapacitors, however, is seldom reported before. For this purpose, here, we synthesized NiCo layered double hydroxide nanosheets via the intrinsic pillar effect of sodium dodecylbenzene sulfonate (NiCoSDBS-LDH), and found that the surface redox and intercalation behaviors take effect simultaneously in NiCo-SDBS-LDH via electrochemical analysis. The NiCo-SDBS-LDH electrode having a relatively low specific surface area (15.28m(2) g (1)) still exhibited a remarkable specific capacitance of 1094 F g (1) at a scan rate of 5 A g (1), and super long cycle life of 81% retention over 3000 cycles. A dual charge storage mechanism is subsequently proposed based on the analysis of our results to explain the excellent properties of NiCo-SDBS-LDH. We believe that the enhancements should mainly be ascribed to the structural feature of the SDBS stabilized NiCo-LDH and the expanded interlayer space of NiCo-SDBS-LDH. These findings open new doors to functional pillared effect to control the electrochemical behaviors of TM-LDH-based materials. (C) 2017 Elsevier Ltd. All rights reserved.