Tag Archive for: Aqueous electrolytes

Publication on AWSensors technology

Operando Tracking of Resistance, Thickness, and Mass of Ti3C2Tx MXene in Water-in-Salt Electrolyte

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Authors: Audrey Perju, Danzhen Zhang, Ruocun John Wang, Pierre-Louis Taberna, Yury Gogotsi, Patrice Simon

Journal:  Adv. Energy Mater.

Abstract: MXenes are among the fastest-growing families of 2D materials, promising for high-rate, high-energy energy storage applications due to their high electronic and ionic conductivity, large surface area, and reversible surface redox ability. The Ti3C2Tx MXene shows a capacitive charge storage mechanism in diluted aqueous LiCl electrolyte while achieving abnormal redox-like features in the water-in-salt LiCl electrolyte. Herein, various operando techniques are used to investigate changes in resistance, mass, and electrode thickness of Ti3C2Tx during cycling in salt-in-water and water-in-salt LiCl electrolytes. Significant resistance variations due to interlayer space changes are recorded in the water-in-salt LiCl electrolyte. In both electrolytes, conductivity variations attributed to charge carrier density changes or varied inter-sheet electron hopping barriers are detected in the capacitive areas, where no thickness variations are observed. Overall, combining those operando techniques enhances the understanding of charge storage mechanisms and facilitates the development of MXene-based energy storage devices.

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Publication on AWSensors technology

Unlocking self-discharge: Unveiling the mysteries of electrode-free Zn-MnO2 batteries with advanced in situ techniques in mild acid aqueous electrolytes

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Authors: Arvinder Singh, Lamia Ouassi, Keho Allemang, Jean-François Lemineur, Ozlem Sel, Frédéric Kanoufi, Christel Laberty-Robert

Journal: Journal of Power Sources 2025

Abstract: We introduce a novel approach to Zinc-MnO2 battery architecture utilizing a 3D network of carbon nanofibers as both current collector and electrode material, promising enhanced performance and longevity for large-scale energy storage. Employing mild aqueous electrolytes, we address the challenge of managing self-discharge, crucial for short-term energy storage. Advanced coupled characterization techniques, including in-situ EQCM (Electrochemical Quartz Crystal Microbalance) and high-resolution optical microscopy, elucidate self-discharge mechanisms across over multiple length scales. Findings reveal that the self-discharge is mainly at the zinc electrode due to concomitant dissolution of Zinc (corrosion) and HER (Hydrogen Evolution Reaction) phenomena. Interestingly, the corrosion current was estimated irrespective of charging protocol and remains consistent, indicating the independence of zinc corrosion kinetics from the length scale. Finally, the morphology of the zinc layer appears to be critical, suggesting that self-discharge is primarily a chemical process. This innovative design strategy offers the potential for high-performance Zinc-MnO2 batteries with extended cycle life to meet the requirements of large-scale energy storage applications.

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Publication on AWSensors technology

Revisiting the Charging Mechanism of α-MnO2 in Mildly Acidic Aqueous Zinc Electrolytes

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Authors: Lang Yuan Wu, ZhiWei Li, YuXuan Xiang, WenDi Dong, XiaoDong Qi, ZhenXiao Ling, YingHong Xu, HaiYang Wu, Mikhael D. Levi, Netanel Shpigel, XiaoGang Zhang

Journal: Small 

Abstract: In recent years, there have been extensive debates regarding the charging mechanism of MnO2 cathodes in aqueous Zn electrolytes. The discussion centered on several key aspects including the identity of the charge carriers contributing to the overall capacity, the nature of the electrochemical process, and the role of the zinc hydroxy films that are reversibly formed during the charging/discharging. Intense studies are also devoted to understanding the effect of the Mn2+ additive on the performance of the cathodes. Nevertheless, it seems that a consistent explanation of the α-MnO2 charging mechanism is still lacking. To address this, a step-by-step analysis of the MnO2 cathodes is conducted. Valuable information is obtained by using in situ electrochemical quartz crystal microbalance with dissipation (EQCM-D) monitoring, supplemented by solid-state nuclear magnetic resonance (NMR), X-ray diffraction (XRD) in Characterization of Materials, and pH measurements. The findings indicate that the charging mechanism is dominated by the insertion of H3O+ ions, while no evidence of Zn2+ intercalation is found. The role of the Mn2+ additive in promoting the generation of protons by forming MnOOH, enhancing the stability of Zn/α-MnO2 batteries is thoroughly investigated. This work provides a comprehensive overview on the electrochemical and the chemical reactions associated with the α-MnO2 electrodes, and will pave the way for further development of aqueous cathodes for Zn-ion batteries.

 

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