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Nanocomposite Perfluorosulfonic Acid/Montmorillonite-Na+ Polymer Membrane as Gel Electrolyte in Hybrid Supercapacitors
Solid-state supercapacitors with gel electrolytes have emerged as a promising field for various energy storage applications, including electronic devices, electric vehicles, and mobile phones. In this study, nanocomposite gel membranes were fabricated using the solution casting method with perfluorosulfonic acid (PFSA) ionomer dispersion, both with and without the incorporation of 10 wt.% montmorillonite (MMT). MMT, a natural clay known for its high surface area and layered structure, is expected to enhance the properties of supercapacitor systems. Manganese oxide, selected for its pseudocapacitive behavior in a neutral electrolyte, was synthesized via direct coprecipitation. The materials underwent structural and morphological characterization. For electrochemical evaluation, a two-electrode Swagelok cell was employed, featuring a carbon xerogel negative electrode, a manganese dioxide positive electrode, and a PFSA polymer membrane serving as both the electrolyte and separator. The membrane was immersed in a 1 M Na2SO4 solution before testing. A comprehensive electrochemical analysis of the hybrid cells was conducted and compared with a symmetric carbon/carbon supercapacitor. Cyclic voltammetric curves were recorded, and galvanostatic charge–discharge tests were conducted at various temperatures (20, 40, 60 °C). The hybrid cell with the PFSA/MMT 10 wt.% exhibited the highest specific capacitance and maintained its hybrid profile after prolonged cycling at elevated temperatures, highlighting the potential of the newly developed membrane.
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Electrochemical Performance of Symmetric Solid-State Supercapacitors Based on Carbon Xerogel Electrodes and Solid Polymer Electrolytes
For the development and optimization of solid-state symmetrical supercapacitors, herein, we propose using carbon-based electrodes and sodium- and lithium-form Aquivion electrolyte membranes, which serve as the separator and electrolyte. Carbon xerogels, synthesized using microwave-assisted sol-gel methodology, with designed and controlled properties were obtained as electrode materials. Commercial activated carbon (YP-50F, “Kuraray Europe” GmbH) was used as the active material for comparison. Notably, the developed solid-state symmetrical supercapacitors provide sufficiently high specific capacitances of 105–110 F g−1 at 0.2 A g−1, along with an energy density of 4.5 Wh kg−1 at 300 W kg−1, and a voltage window of 0–1.2 V in aqueous environments, also demonstrating an excellent cycling stability for up to 10,000 charge/discharge cycles. These results can demonstrate the potential applications of carbon xerogel as the active electrode material and cation exchange membrane as the electrolyte in the development of solid-state supercapacitor devices.
Electrochemical testing of zeolite‑based gas‑diffusion electrodes for secondary metal air batteries—in memory of Prof. A. Milchev
The oxidation of carbon in conventional gas diffusion electrodes is a limiting factor for the life of secondary metal-air batteries. Replacement of carbon with zeolite is a possible solution to avoid its oxidation in the gas-diffusion electrodes (GDE) and thus to increase the battery lifetime. Due to the fact that the technology provides the required number of charge/discharge cycles, it is applicable for solar energy storage. Zeolites are a large group of natural or synthetic porous aluminosilicate minerals. Their porous structure provides good gas permeability. The gas diffusion layer of the electrode must also have good hydrophobicity. To prevent leakage of electrolyte from the battery, the zeolite was mixed with an appropriate amount of polytetrafluoroethylene, and the electrode was subjected to hot pressing according to a specially developed procedure. The experiments were performed in a specially designed test cell. Its construction ensures measurements of the bifunctional gas-diffusion electrode in a half-cell configuration applying a reference hydrogen electrode. The stationary volt-ampere characteristics and impedance tests were performed on the zeolite electrodes at certain operating points. The cell was subjected to cycling at charge/discharge current ± 2 mA/cm2, respectively. The obtained experimental results show that zeolite is a suitable material for carbon substitution in secondary metal air batteries. The zeolite/polytetrafluoroethylene (PTFE) ratio needs to be optimised in order to improve the gas permeability of the gas diffusion layer without compromising hydrophobicity.
Anodic oxidation of tungsten under illumination - multi-method characterization and modeling at the molecular level
Tungsten oxide has received considerable attention as photo-anode in photo-assisted water splitting due to its considerable advantages such as significant light absorption in the visible region, good catalytic properties, and stability in acidic and oxidative conditions. The present paper is a first step in a detailed study of the mechanism of porous WO3 growth via anodic oxidation. In-situ electrochemical impedance spectroscopy (EIS) and intensity modulated photocurrent spectroscopy (IMPS) during oxidation of W illuminated with UV and visible light are employed to study the ionic and electronic processes in slightly acidic sulfate-fluoride electrolytes and a range of potentials 4–10 V. The respective responses are discussed in terms of the influence of fluoride addition on ionic and electronic process rates. A kinetic model is proposed and parameterized via regression of experimental data to the EIS and IMPS transfer functions.
In Situ Electron Paramagnetic Resonance Monitoring of Predegradation Radical Generation in a Lithium Electrolyte
Herein we present an innovative in situ EPR spectroscopy approach complemented with computational modeling as a methodology for assessing a nonaqueous electrolyte behavior just before its massive degradation. As a proof of concept, we use the conventional lithium electrolyte (1 M LiPF6 in EC/DMC), which is utilized in current lithium-ion batteries. Through in situ EPR, long-lived EC•– associates in amounts of 10–250 ppm were detected in a broad potential window (>2.0 V) prior to the electrolyte oxidation or reduction. The pathways of radical formation are discussed in terms of the imperfection in the electron flow across the electrolyte–electrode interface and of the strong affinity of EC to electron trapping. The radical amount could be amplified markedly (above 1000 ppm) by addition of vinylene carbonate (VC) to the electrolyte, while the added CeO2 has a moderate effect. The proposed in situ EPR methodology could be transferred to other electrolyte solutions to become a universal approach.