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Abstract 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. 

Abstract Aqueous zinc metal batteries (AZMB) are emerging as a promising alternative to the prevailing existing Lithium‐ion battery technology. However, the development of AZMBs is hindered due to challenges including dendrite formation, hydrogen evolution reaction (HER), and ZnO passivation on the anode. Here, a tetraalkylsulfonamide (TAS) additive for suppressing HER, dendrite formation, and enhancing cyclability is rationally designed. Only 1 mmTAS is found that can effectively displace water molecules from the Zn²⁺solvation shell, thereby altering the solvation matrix of Zn²⁺and disrupting the hydrogen bond network of free water, as demonstrated through⁶⁷ Zn and¹H nuclear magnetic resonance spectroscopy, high‐resolution mass spectrometry (HRMS), and density functional theory (DFT) studies. Voltammetry synchronized with in situ monitoring of the electrode surface reveals suppressed dendritic growth and HER in the presence of TAS. Electrochemical mass spectrometry (ECMS) captures real‐time HER suppression during Zn electrodeposition, revealing the ability of TAS to suppress the HER by an order of magnitude. A ≈25‐fold cycle life improvement from ≈100 h to over 2500 h in coin cells cycled in the presence of TAS. Furthermore, by suppressing passivation product formation, it is demonstrated that strategy robustly maximizes the stability of Zn metal anodes. 

Abstract Despite the advantages of aqueous zinc (Zn) metal batteries (AZMB) like high specific capacity (820 mAh g⁻¹and 5,854 mAh cm⁻³), low redox potential (−0.76 V vs. the standard hydrogen electrode), low cost, water compatibility, and safety, the development of practically relevant batteries is plagued by several issues like unwanted hydrogen evolution reaction (HER), corrosion of Zn substrate (insulating ZnO, Zn(OH)₂, Zn(SO₄)_x(OH)_y, Zn(ClO₄)_x(OH)_yetc. passivation layer), and dendrite growth. Controlling and suppressing HER activity strongly correlates with the long‐term cyclability of AZMBs. Therefore, a precise quantitative technique is needed to monitor the real‐time dynamics of hydrogen evolution during Zn electrodeposition. In this study, we quantify hydrogen evolution using in situ electrochemical mass spectrometry (ECMS). This methodology enables us to determine a correction factor for the faradaic efficiency of this system with unmatched precision. For instance, during the electrodeposition of zinc on a copper substrate at a current density of 1.5 mA/cm²for 600 seconds, 0.3 % of the total charge is attributed to HER, while the rest contributes to zinc electrodeposition. At first glance, this may seem like a small fraction, but it can be detrimental to the long‐term cycling performance of AZMBs. Furthermore, our results provide insights into the correlation between HER and the porous morphology of the electrodeposited zinc, unravelling the presence of trapped H₂and Zn corrosion during the charging process. Overall, this study sets a platform to accurately determine the faradaic efficiency of Zn electrodeposition and provides a powerful tool for evaluating electrolyte additives, salts, and electrode modifications aimed at enhancing long‐term stability and suppressing the HER in aqueous Zn batteries. 

Nanoparticles are an indispensable part of our lives. From electronic devices to drug delivery to catalysis and energy storage, nanoparticles have found various important applications. Out of the many synthetic strategies to generate nanoparticles, electrodeposition has stood out due to its cost effectiveness, low time consumption and simplicity. However, traditional electrodeposition techniques have suffered from controlling the size, shape, morphology and microstructure of nanoparticles. Here, we use a technique called nanodroplet‐mediated electrodeposition, where nanodroplets carrying the metal salt precursor collide with a negatively‐biased electrode. In this work, we use this nanodroplet‐mediated electrodeposition technique along with transmission electron microscopy, selected‐area electron diffraction and high‐angle‐annular dark‐field scanning transmission electron microscopy to show control over the microstructure of single nanoparticles. Along with that, we use X‐ray photoelectron spectroscopy to get mechanistic insights behind the alteration of microstructure observed. Having achieved a control over the microstructure, we show the application by synthesising polycrystalline alloys at room temperature and evaluating the electrocatalytic behavior of the different microstructures towards the hydrogen evolution reaction. This fundamental work of controlling microstructures of single nanoparticles and its applications in alloy synthesis and electrocatalysis opens a new avenue of tuning nanoparticles for various applications.