The most important tool of an electrochemist is a potentiostat. The group uses modular potentiostats from the company BioLogic. These enable fairly uncomplicated integration of the devices into the measurement setups and software developed by the group. Their ability to be integrated into a network makes them accessible from several computers simultaneously. In addition, the parameter settings can be freely changed during running measurements making experimental protocols highly flexible.
Many non-aqueous systems are highly sensitive to atmospheric components like O2, CO2, H2O or even N2. It is therefore very important to eliminate these contaminants. Furthermore, to achieve controlled water concentrations it is necessary to avoid water in the atmosphere. Hence all the measurements and their preparations are carried out in a glovebox having water and oxygen concentration below 0.1 ppm. Moreover, our glovebox (MBraun glovebox cluster composed of two modular boxes with four pairs of gloves each, solvent filter and 2 heatable antechambers) is equipped with a nitrogen filter which has its relevance especially when working with metallic lithium.
This analytical method is coupled to an electrochemical scanning flow cell in order to analyse traces of metals in the electrolytes dissolved during the electrochemical experiments. ICP-MS is the most sensitive tool to analyze metal ions in liquid samples at very low concentrations (ppt levels). Coupled to an electrochemical cell this technique offers a very effective method to study the stability of electrode materials and catalysts in organic systems. Carrying out ICP-MS measurements with organic electrolytes is not a trivial problem and requires the tedious optimization of the instrument settings. The group has a Nexion2000 ICP-MS from the company Perkin-Elmer.
Quadrupole mass spectrometry with electron impact ionization coupled to electrochemistry is a well-known technique to analyze gaseous reaction products. We use the MS together with the scanning flow cell to analyze gas formation in electroorganic synthetic processes. The group has a HiQuad QMA410 quadrupole mass spectrometer of the company Pfeiffer Vacuum GmbH.
Gas thight RDE
Rotating disk electrode setups are used routinely in classical electrochemistry laboratories to characterize electrodes under well-defined electrochemical and hydrodynamic conditions. However, their use in a glovebox is not straightforward, because it is difficult to make the cells tight due to the rotating shaft. A completely gas tight RDE setup has been developed in the group enabling the use of gases like O2, CO2, CO or H2 in the glovebox. The gas exchange and rotation rate is controlled via a home-made control box and a software developed in the group, thus a long series of measurements can be carried out without any problem in a completely automated sequence of experiments.
This classical titration method of analytical chemistry is used to determine trace amounts of water in samples. We prefer coulometric titration, because this method enables the detection of water levels down to 1 ppm from small amounts of samples. The group uses a Metrohm 917 Coulometer for this purpose, which is installed in the glovebox.
For routine tests on battery materials the group has a small battery tester from BioLogic (BCS 810) consisting of eight channels. Each channel has a built in impedance option for the frequency range 10 mHz – 10 kHz and the maximum applicable charge/discharge currents are 1.5 A per channel. Therefore, the preferred cell types to test are CR2032 coin cells. We also have all equipment to make the coin cells on our own.
The purity of electrolytes plays an essential role in basic research, especially if working with well-defined metal surfaces. Even high purity products on the market contain contaminants in several ten ppm concentrations and anhydrous, dry solvents still have water levels usually above 30 ppm. In order to get rid of the impurities it is essential to purify the solvents with classical methods, like distillation, under inert atmosphere or a certain pressure (vacuum).
To dry solids, like electrolyte salts or equipment and consumables that are used in the glovebox, the application of vacuum ovens is necessary. They substantially decrease the drying time and increase the efficiency.