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The detailed mechanistic understanding of the electrochemical reactions occurring in lithium-ion battery electrodes is fundamental for their further improvement. Conversion/alloying materials (CAMs), such as Zn0.9Fe0.1O, one of the most recent alternatives for classic graphite anodes, offer superior specific capacity and rate capability. However, despite fast kinetics, CAMs suffer from a large voltage hysteresis upon de-/lithiation and improvable Coulombic efficiencies when cycled in a large voltage window. Here, we use isothermal microcalorimetry together with operando X-ray diffraction as well as ex situ 7Li NMR and 57Fe Mössbauer spectroscopies to investigate the asymmetric reaction mechanism of the lithiation and delithiation of Zn0.9Fe0.1O during electrochemical cycling. We demonstrate that the measured heat flow is correlated with compositional changes of the electrode material. This combination of highly complementary techniques allows us to propose a new nucleation site model for the initial lithiation of Zn0.9Fe0.1O. Modeling the heat flow provides concrete evidence for the deleterious impact of high anodic cutoff potentials (>2 V), resulting in a continuous quasireversible solid electrolyte interphase formation. The presented methodology is suggested to provide improved insights into the reaction mechanism of conversion- and alloying-type energy-storage materials.

A series of vanadium redox‐flow battery (VRFB) electrolytes at 1.55 M vanadium and 4.5 M total sulfate concentration is prepared from vanadyl sulfate solution and tested under conditions of appearance of ""power drop"" effect (discharge at high current density from high state‐of‐charge). A correlation between the initial electrolyte composition, the thermal stability of catholyte and the susceptibility of VRFB to exhibit a ""power drop"" effect is derived. The increase of total acidity to 3 M, expressed as concentration of sulphuric acid in precursor vanadyl sulfate solution, enables ""power drop"" free operation of VRFB at least at 75 mA cm‐2. Thermally‐induced degradation of electrolyte was evaluated based on decrease in vanadium concentration in the electrolyte series after exposure to the temperature of 45°C and based on chacterization of catholytes series using 51V, 17O, 1H nuclear magnetic resonance spectroscopy.

Supercapacitors are usually used as energy storage devices that work at a high current rate. This operating mode is often accompanied by the production of large amounts of heat inside the cell. Therefore, health monitoring of supercapacitors is still needed to avoid overheating and subsequent destruction. This paper presents a new method to determine the heat generation and the resulting temperature development of an aqueous hybrid capacitor based on extensive measurement data. We concentrate not only on the Ohmic power loss but also on heat phenomenon originating from side and overcharge reactions as well as entropy effects. The bearing of the final state of charge and the charging current on the temperature development is demonstrated. Finally, the temperature parameters of air and water cooled capacitors are simulated. The temperature distribution within the cell as a function of time is presented and discussed. The great advantage of the developed evaluation method is that it is an inexpensive method which can be realised in most test laboratories and that the measurements and simulations consider all crucial origins of power loss. The results obtained can be used to evaluate appropriate cooling systems. The method can be applied to capacitors and batteries.

Insufficient wetting of Na on Na-beta"-alumina is responsible for an increased interfacial polarization in Na-batteries if the operating temperature is below 270-300 A degrees C. In this study, Na alloys (Na-Sn, Na-Bi and Na-In) on the ceramic surface are examined on their capability to improve the wetting with molten sodium at medium temperatures and thereby enabling operation of the cell at temperatures in the range of 105 to 150 A degrees C. Metallic coatings with Bi or Sn confirm this improvement at a temperature of 115 A degrees C. The overpotential of a symmetrical Naa",Na-beta"-aluminaa",Na cell is determined by galvanostatic cycling and electrochemical impedance spectroscopy and then associated to contact angle measurements. As a result, both the alloys and the metallic coatings have a positive impact on wetting and reduction of the overpotential during galvanostatic cycling.

Since PEM-water electrolysis (PEMWE) produces very pure H2, reacts fast and well to dynamic load conditions and is technologically simple, it could play a large role in a future hydrogen economy. One way to alleviate the drawback of expensive noble metal catalysts is to disperse the active component on a support. Tungsten oxide and tungsten carbide were investigated here comparing different synthesis routes. Adam's fusion and hydrolysis route with the addition of support during different stages of the synthesis and mechanical mixing of catalyst and support were investigated and compared. Rotating Disk Electrode (RDE) measurements show high currents for mechanically mixed samples and samples obtained via hydrolysis with a WO3 precursor. Single cell tests confirm catalyst activity and stability. Further studies are needed to completely understand catalyst behavior, especially fast activity loss during RDE.

A hydrogen economy is one of the most promising concepts for the future energy infrastructure. The conversion of sunlight into hydrogen (H-2) using directly coupled photovoltaics (PV) and a proton exchange membrane (PEM) water electrolysis cell could compliment the required hydrogen production by using excess renewable electricity. It has many advantages such as producing pure hydrogen at high photon-tochemical energy efficiency and simple technical operation, but it suffers from the high cost of the catalyst. Here we show single-cell tests using commercial membranes and an in-house synthesized WO3-supported IrxRu1-xO2 anode catalyst. The catalyst was synthesized by Adam's Fusion protocol and loaded onto the support using an annealing procedure. Membrane electrode assemblies (MEAs) were prepared using an airbrush spraying technique. The electrolysis activity was greatly increased by adding tungsten carbide (WC) to the support, leading to a higher current density than commercial MEAs; however it also showed very fast degradation, losing most of the activity in minutes. The biggest issue in terms of stability seems to be on the cathode side of the cell.