- Joint project
- Partner: Helmholtz-Zentrum Berlin für Materialien und Energie
- Funding organization: DFG
- Project duration: 2017 - 2022
The three-dimensional structural and morphological processes which take place in lithium-air batteries have been insufficiently studied and understood. This represents a major obstacle in the development of innovative electrode structures. The aim of the proposed project is to provide a detailed picture of the inside of a lithium-air accumulator through a combination of innovative experimental in-operando methods (three-dimensional X-ray phase-contrast tomography and impedance-based analysis methods) during cycling as well as the structural and morphological processes. This information will be used to to create a chemical-physical 3D-structure model of the electrodes which correlates with the real microstructural properties. With (synchrotron) X-ray tomography, the three-dimensional distribution of the different reaction products and deposits during loading and unloading is quantitatively recorded and described, depending on the structure of the electrodes, and combined with the impedance data. This will provide a better understanding of the basic processes of cycling. Simulation models based on the developed model will then serve to develop and predict battery behavior under different operating parameters and will ultimately be used to optimize electrode structures.
In summary, we are focused on the following:
- Assembly of lithium-air coin cells from self-synthesized materials
- Tomography experiments to elucidate reaction processes/aging
- Cell characterization using impedance spectroscopy
- Creation of a simulation model
Fabrication of suitable electrode materials
Our focus here is synthesizing several high porous carbon materials with an active surface area of more than 100 m²/g for optimal adsorption of oxygen, which is required for the battery reaction.
Furthermore, we will also investigate the impact of several transition metal compounds (e.g. metal oxides, metal cluster, etc.) which act as catalysts for the cell chemistry (ORR/OER). This can lead to a better understanding of the cell processes and also help increase the power density.
By using scanning electron microscopy (SEM), the size of the synthesized graphite structures and the distribution of the catalytic centers can be detected and characterized.
Manufacturing of battery electrodes
The primary focus here is the fabrication of gas diffusion electrodes. We are currently testing a method to attain comparable battery electrodes. Atomic force microscopy (AFM) is used to achieve this.
Manufacturing lithium-air accumulator cells
CR2032 button cells are assembled under a protective gas atmosphere. Many factors during the manufacturing process directly influence cell performance (for example adjusting the correct crimping pressure for the battery materials, stamping size of the separator foil, etc.). In addition to the mechanical impacts on battery performance, we are also investigating the influence of different battery electrolytes.
The manufactured lithium-air cells are cycled under different gas atmospheres. Varying analytical methods are used to characterize the influence of the battery modifications (for example different electrolyte compositions, electrode thickness, etc.) on capacity and power density.