Tag Archive for: batteries

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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Scientific publication

Unraveling the two-phase lithiation process in TiS2 by using the combination of operando EQCM and Electrochemical Dilatometry techniques

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Authors: Jeronimo Miranda, Giovanna Franklin, Tyler S. Mathis, Pierre-Louis Taberna, Patrice Simon

Journal: Energy Storage Materials

Abstract

A combination of operando Electrochemical Quartz Microbalance (EQCM) and Electrochemical Dilatometer (ECD) techniques have been used to study Li-ion intercalation into TiS2. Confirmation of two distinct Li-ion intercalation regions was achieved, showing different diffusion kinetics and interlayer space parameters. Starting from Li0TiS2, a first lithiation zone exhibits diffusion limited (battery-like) behavior, which is associated with a significant electrode volume expansion. Conversely, once a maximum interlayer distance is attained, subsequent lithiation results in non-diffusion limited (capacitive-like) behavior, with no further evolution of the volume of the material. EQCM motional resistance analysis shows that the TiS2 under consideration undergoes a reversible transformation, while keeping the rigid properties of the film unchanged. This study sheds light on the mass transport and deformation analysis of a model material such as TiS2. Finally, a correlation analysis between two operando techniques such as ECD and EQCM to explain charge storage mechanism is for the first time reported.

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Scientific publication

Robust battery interphases from dilute fluorinated cations

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Authors: Chulgi Nathan Hong, Mengwen Yan, Oleg Borodin, Travis P. Pollard, Langyuan Wu, Manuel Reiter, Dario Gomez Vazquez, Katharina Trapp , Ji Mun Yoo, Netanel Shpigel, Jeremy I. Feldblyum and Maria R. Lukatskaya

Journal: Energy Environ. Sci.

Abstract

Controlling solid electrolyte interphase (SEI) in batteries is crucial for their efficient cycling. Herein, we demonstrate an approach to enable robust battery performance that does not rely on high fractions of fluorinated species in electrolytes, thus substantially decreasing the environmental footprint and cost of high-energy batteries. In this approach, we use very low fractions of readily reducible fluorinated cations in electrolyte (∼0.1 wt%) and employ electrostatic attraction to generate a substantial population of these cations at the anode surface. As a result, we can form a robust fluorine-rich SEI that allows for dendrite-free deposition of dense Li and stable cycling of Li-metal full cells with high-voltage cathodes. Our approach represents a general strategy for delivering desired chemical species to battery anodes through electrostatic attraction while using minute amounts of additive.

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Dynamic Resolution of Ion Transfer in Electrochemically Reduced Graphene Oxides Revealed by Electrogravimetric Impedance

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Authors: Hamza Goubaa, Freddy Escobar-Teran, Ibtissam Ressam, Wanli Gao, Abdelkrim el Kadib, Ivan T. Lucas, Mustapha Raihane, Mohammed Lahcini, Hubert Perrot, Ozlem Sel. Sorbonne Université, UPMC, Univ Paris 06, CNRS, France. Laboratoire Interfaces et Systèmes Électroquimiques; Université Cadi Ayyad, Faculté des Sciences et Techniques, Laboratoire de Chimie Organométallique et Macromoléculaire Matériaux composites, Marrakech, Morocco.

Journal:  The Journal of Physical Chemistry (2017)

To accompany the search for optimal materials in electrochemical supercapacitors, appropriate characterization tools to assess key parameters of newly developed electrodes are required. Here we demonstrate the capabilities of ac-mode electrogravimetry to study in details the capacitive charge storage mechanisms in electrochemically reduced graphene oxide (ERGO) thin films electrodes. The coupling of electrochemical impedance spectroscopy (EIS) with fast quartz crystal microbalance (QCM) complements classical electrochemical quartz crystal microbalance (EQCM) by capturing here the dynamics of the electroadsorption process, identifying charged moieties and detecting solvation effects. We evidenced the co-electroadsorption of two types of cationic species (fully and partially hydrated cations) in the potential range studied and the indirect intervention of free solvent molecules. Further kinetic information on electroadsorption is also obtained which leads to a full deconvolution of the global EQCM response at both gravimetric and temporal level. Through a fine analysis of the interactions of different cations of period one elements, Li+, Na+ and K+ with ERGO, we evidenced the critical role of solvation processes on the kinetics of electroadsorption, and provided an experimental proof to the phenomena that smaller ions are more tightly bound to their water molecules such that an inverse relationship exists between the dehydration energy and the ion size. Such gravimetric and dynamic subleties are unreachable with classical tools and with EQCM method alone which permits us to suggest the ac-mode electrogravimetry as a baseline diagnostic tool to explore charge transfer mechanisms at the nanoscale.