(Invited) Distinguishing High-Rate Electrochemical Mechanisms Via Advanced Impedance Spectroscopy Analysis (2022)

The electrochemical kinetics of advanced materials are metered mechanistically by how charge transfer or accumulation occurs at the electrode/electrolyte interface. Fundamental insights garnered from traditional voltammetric techniques superimpose information on charge-storage mechanisms, but impedance spectroscopy can provide deeper insight into charge-storage kinetics beyond the electrode/electrolyte interface. Mirroring the work of Bai and Conway, which tracked pseudoinductive effects as a function of both frequency and potential, 1,2 we similarly track the colors of capacitance in a protocol we designate ‘3D Bode Analysis.’ This impedance variant can distinguish double-layer response, pseudocapacitance, and battery-like faradaic reactions at device-relevant electrodes. 3–7 For &lt;10 nm coatings of lithium manganese oxide on a 3D aperiodic carbon architecture, we could identify the respective potential windows for pseudocapacitance and battery-like reactions. 4 Mapping the respective impedance signatures of electroprecipitated zinc hydroxide sulfate in Zn 2+ -containing electrolytes provides insight into complex electrodeposition processes. 7 In addition to deconvolving distinct charge-storing processes, we also use 3D Bode analysis to understand the positive effects of carbothermal shock on improving the double-layer response of graphene oxide–carbon nanotube composites. 6 Analyzing impedance in the form of 2D color-mapped surface plots reveals that the characteristic relaxation time of these electrodes is 70% faster than activated carbon. These studies highlight an exciting direction to garner key mechanistic information regarding the complex electrochemical response of advanced electrochemical materials. References [1] L. Bai and B. E. Conway, AC impedance of faradaic reactions involving electrosorbed intermediates: Examination of conditions leading to pseudoinductive behavior represented in three-dimensional impedance spectroscopy diagrams. J. Electrochem. Soc ., 138 , 2897–2907 (2019). [2] L. Bai and B. E. Conway, Three-dimensional impedance spectroscopy diagrams for processes involving electrosorbed intermediates, introducing the third electrode-potential variable—Examination of conditions leading to pseudo-inductive behavior. Electrochim. Acta , 38 , 1803–1815 (1993). [3] J. S. Ko, M. B. Sassin, J. F. Parker, D. R. Rolison, and J. W. Long, Combining battery-like and pseudocapacitive charge storage in 3D MnO x @carbon electrode architectures for zinc-ion cells. Sustain. Energy Fuels 2 , 626–636 (2018). [4] J. S. Ko, M. B. Sassin, D. R. Rolison, and J. W. Long, Deconvolving double-layer, pseudocapacitance, and battery-like charge-storage mechanisms in nanoscale LiMn 2 O 4 at 3D carbon architectures. Electrochim. Acta , 275 ,225–235 (2018). [5] J. S. Ko, C.-H. Lai, J. W. Long, D. R. Rolison, B. Dunn, and J. Nelson Weker, Differentiating double-layer, pseudocapacitance, and battery-like mechanisms by analyzing impedance measurements in three dimensions. ACS Appl. Mater. Interfaces , 12 , 14071–14078 (2020). [6] J. S. Ko, P. Y. Meng, H. Elazar-Mittelman, J. K. Johnson, Z. Xia, and S. Holdren, Rapid carbothermal shock enhances the double-layer response of graphene oxide–carbon nanotube electrodes. Energy Fuels , 35 , 17919–17929 (2021). [7] J. S. Ko, M. D. Donakowski, M. B. Sassin, J. F. Parker, D. R. Rolison, and J. W. Long, Deciphering charge-storage mechanisms in 3D MnO x @carbon electrode nanoarchitectures for rechargeable zinc-ion cells. MRS Commun ., 9 , 99–106 (2019).