Investigating the NH<sub>4</sub><sup>+</sup> Preintercalation and Surface Coordination Effects on MnO<sub>2</sub> for Ammonium-Ion Supercapacitors
Ting Xiao, Can Tang, Hongxiang Lin, Xiuru Li, Yuting Mei, Can Xu, Lin Gao, Lihua Jiang, Peng Xiang, Shibing Ni, Yequan Xiao, Xinyu Tan
Abstract
Ion preintercalation is an effective method for fine-tuning the electrochemical characteristics of electrode materials, thereby enhancing the performance of aqueous ammonium-ion hybrid supercapacitors (A-HSCs). However, much of the current research on ion preintercalation lacks controllability, and the underlying mechanisms remain unclear. In this study, we employ a two-step electrochemical activation approach, involving galvanostatic charge–discharge and cyclic voltammetry, to modulate the preintercalation of NH 4 + in MnO 2 . An in-depth analysis of the electrochemical activation mechanism is presented. This two-step electrochemical activation approach endows the final MnO 2 /AC electrode with a high capacitance of 917.4 F g –1, approximately 2.4 times higher than that of original MnO 2 . Furthermore, the MnO 2 /AC electrode retains approximately 93.4% of its capacitance after 10 000 cycles at a current density of 25 mA cm –2 . Additionally, aqueous A-HSC, comprising MnO 2 /AC and P-MoO 3, achieves a maximum energy density of 87.6 Wh kg –1 . This study offers novel insights into the controllable ion preintercalation approach via electrochemical activation.