Unraveling the reaction mechanism of low dose Mn dopant in Ni(OH)2 supercapacitor electrode

Mn doping is deemed as a promising strategy to improve the electrochemical performance of the alpha-Ni (OH)(2) battery-type supercapacitor electrode. However, the internal structure evolution, the pathways and the dynamics of the proton/intercalated anion migration, as well as the functioning mechanism of Mn dopant to stabilize the layered structure during cycles remain unclear. Here, we unveil that irreversible oxidization of Mn3+ at the initial CV cycles, which will remain as Mn4+ in the NiO2 slabs after the first oxidization to effectively suppress the phase transformation from alpha-Ni(OH)(2)/gamma-NiOOH to beta-Ni (OH)(2)/beta-NiOOH and further maintain the structural integrity of electrode. With a synergistic combination of theoretical calculations and various structural probes including XRD and H-2 MAS solid state NMR, we decode the structure evolution and dynamics in the initial CV (cyclic voltammetry) cycles, including the absorption/desorption of hydrogen containing species, migration of intercalated anions/water molecules and the change of interlayer space. This present work elucidates a close relationship between doping chemistry and structural reliability, paving a novel way of reengineering supercapacitor electrode materials. (C) 2021 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.

Automated summary

This study elucidates the role of Mn doping in enhancing the performance of supercapacitor electrodes, revealing the mechanisms through which Mn dopants stabilize the layered structure and maintain structural integrity during cycling. By decoding the structural evolution and dynamics, the research provides insights into the relationship between doping chemistry and structural reliability, paving the way for the reengineering of supercapacitor electrode materials.