Electrical Energy Storage

The research focus in the area lies on electrochemical and electrophysical energy storage. Electrochemical cells are a key technology of the electrification of mobile drivetrains.

Research objective

To achieve the assertion of electrical energy storage it is important to reach a high power and energy density (>> 300 Wh/kg) with simultaneous functional reliability and durability as well as reduced costs (< 300€/kWh). This aim can be reached by li/air- und zinc/air cells. This new generation of batteries allows a high energy density and it combines low specific costs with a better availability of necessary materials.

Topics

The research topics within the post graduate program will be concerned with both the above significantly different electrochemical concepts:

Within li/air batteries, lithium ions are produced at the anode and then transported to the cathode via an acid electrolyte. There they take part in the oxygen reduction reaction.

In contrast to that, in zinc/air batteries, the hydroxil ions are produced at the cathode and then transported via an alkaline electrolyte to the anode.

The resulting voltage is limited by the slow electrochemical reactions of the oxygen reduction at the cathode in both cases. For this purpose new catalytic materials, combining a high activity with good stability properties must be explored.
The catalytic materials, their structure, the carrier material and geometry have a significant influence on the capability of the cell. The electrode material can be existent in different forms with fundamental differences in surface properties as well as in the electrochemical structure, for example in the form of nanoparticles, nanotubes or even quantum dots. The cathode in rechargeable batteries must consist of a bifunctional material suitable for charging and discharging.

Procedure

Efficiency and power of the electrochemical cell will be predicted by a consistent, computer aided process. Special attention is paid to the prediciotn of the activity of the catalytic materials depending on material properties and geometry.
The process is based on ASIMOV (“Ab-initio Simulations for Identifying Materials with Optimal catalytic actiVity“) which is an approach developed by Prof. Pitsch. ASIMOV consists of a combination of quantum mechanical and Monte Carlo simulations, which are specially developed for computer assisted checking of catalytic electrode material and is validated for oxygen reduction in different platinum and palladium based alloys. In the process reaction kinetic parameters are generated by quantum chemical simulation and the cluster expansion method taking account of electrode and electrolyte structure. These data are used in a combination of the Metropolis and the thermal dynamic Monte Carlo simulation to calculate the current density. Electrode materials and catalytic converter geometry can be investigated experimentally and theoretically in cooperation with the other projects.

Combining the high energy density of metal air cells (1000 Wh/kg) with a simplified separation process it is possible to use reactivatable primary cells in the integrated energy supply module. The research will focus on the cell layout in order to be able to use a large amout of active material for efficient discharging.

This field is in charge of the Professors Pitsch, Simon and Sauer.