Realizing the Kinetic Origin of Hydrogen Evolution for Aqueous Zinc Metal Batteries

• Published in: Advanced energy materials 2024-11, Vol.14 (43), p.n/a
• Main Authors: Rana, Ashutosh, Roy, Kingshuk, Heil, Joseph N, Nguyen, James H., Renault, Christophe, Tackett, Brian M., Dick, Jeffrey E.
• Format: Article
• Language: English
• Subjects: Commercialization; electrochemical mass spectrometry; Electrodeposition; hydrogen evolution reaction; Hydrogen evolution reactions; in situ electrochemistry; Mass spectrometry; scanning electrochemical microscopy; Water chemistry; Zinc; Zn metal batteries
• ISSN: 1614-6832; 1614-6840
• DOI: 10.1002/aenm.202402521

The commercialization of zinc metal batteries (ZMBs) for large‐scale energy storage is hindered by challenges such as dendrite formation, the hydrogen evolution reaction (HER), and passivation/corrosion, which lead to poor stability of zinc metal anodes. HER is a primary contributor to this instability, and despite efforts to enhance ZMB cyclability, a significant knowledge gap remains regarding the origin of HER in these systems. Prior works, based primarily on theoretical calculations with minimal experimental support, suggest that HER originates from Zn2⁺‐solvated water. For the first time, by employing scanning electrochemical microscopy (SECM), and electrochemical mass spectrometry (ECMS), in real‐time the inherently intertwined nature of Zn electrodeposition and H₂ liberation is revealed, both exhibiting the same onset potential in voltammetry. The findings show that water molecules surrounding Zn2⁺ ions undergo reduction simultaneously during Zn2⁺ deposition. Additionally, ECMS conducted under chronopotentiometric/galvanostatic conditions at battery‐relevant current densities elucidates why elevated electrolyte concentrations enhance the prolonged cyclability of ZMBs. Understanding the origin of HER opens avenues for developing high‐performance, reliable aqueous ZMBs, addressing key challenges in their commercialization and advancing their technological capabilities. For the first time, the origin of HER is shown to occur at the same onset potential as zinc electrodeposition using scanning electrochemical microscopy and electrochemical mass spectrometry. Mechanistic insights into charge distribution during zinc plating under galvanostatic conditions are provided. This understanding is utilized to address the superior performance of water‐in‐salt electrolytes.