Batteries
Solid-state batteries with ceramic ion conductors as the electrolyte promise very high power densities. On the one hand, these can be lithium ion conductors, on the other hand, oxygen ion conductors can also be used in a so-called metal/metal oxide battery.
New solid electrolytes with high ionic conductivity need to be developed for the Li-ion conductors. The task of electrochemistry is to research and characterize the corresponding electrodes for these new electrolytes for the oxidation and reduction processes when charging and discharging the battery.
The materials in a metal/metal oxide battery are very similar to those in the solid oxide fuel cell. The task here is to design the electrolyte/electrode interface so that the oxidation and reduction reactions that take place alternately at the interfaces during charging and discharging are permanently reversible.
Metal-Air Batteries
Improving the energy density of energy storage systems by optimizing the lithium storage material has reached its limits for use in real systems. The use of lithium/air cells can further increase the energy density of lithium battery systems.
Figure: Schematic representation of a lithium-air cell with Li metal as anode and MnO2 on carbon fibers as porous cathode.
Primary cells with an air cathode are used (Zn-O2 hearing aid batteries) in order to minimize the costs of storing electrical energy and still achieve high energy densities. The reversibility of these battery systems is currently little researched.
The development of air cathodes for use in various metal/air batteries (Fe, Si, Al, Mg, Li) is one of the goals of current research activities at IET-1.
Methods such as the production of aerogels and the electrospinning process are used to produce highly porous carbon membranes as air cathodes.
In order to achieve this goal, a detailed understanding of the deactivation processes of these batteries is necessary, and novel methods of in-operando spectroscopy are used at IET-1 for this purpose. The development of these methods on MAS-NMR, EPR and Raman basis is an additional pillar of the institute.
The new research in the field of silicon-oxygen batteries shows that reversibility can be achieved for a wide variety of metal-air cells.
- P. Jakes, G. Cohn, Y. Ein-Eli, F. Scheiba, H. Ehrenberg, R.-A. Eichel: “Limitation of Discharge Capacity and Mechanisms of Air-Electrode Deactivation in Silicon–Air Batteries“, Chem. Sus. Chem. 5 (2012) 2278-2285
- G. Cohn, R.-A. Eichel, Y. Ein-Eli: “New insight into the discharge mechanism of silicon–air batteries using electrochemical impedance spectroscopy”, Phys. Chem. Chem. Phys. 15 (2013) 3256-3263