Egg shells as electrodes for energy storage devices
Egg shells consist of porous calcium carbonate, which is very suitable for electrochemical storage. This is the conclusion reached by an international team of scientists from the Helmholtz Institute Ulm (HIU) founded by the Karlsruhe Institute of Technology (KIT).
The research group recently presented this sustainable storage material, which could make a low-cost lithium ion capacitor possible. It is known that chicken eggs are used worldwide in large quantities in the food, pharmaceutical and manufacturing industries. The shells are discarded after use and disposed of as biowaste in landfills. The shell consists of a composite of calcium carbonate (CaCO3) and a protein-rich fibre membrane. "Surprisingly, there are always new examples in which natural substances have good to very good prerequisites for producing materials for electrochemical storage," explains Professor Maximilian Fichtner from the Helmholtz Institute Ulm, a KIT-supported institution.
Together with his Australian colleagues, Fichtner discovered the promising electrochemical properties of egg shells that can store lithium well thanks to their high CaCO3 content. The eggshell powder was used as an electrode against a metallic lithium anode in a non-aqueous electrolyte. With over 1,000 charge and discharge cycles, the test cell maintained a capacity of 92 %. Both the calcified shell and the inner and outer shell membranes were used.
Further research and a detailed understanding of the electrochemical and physical behaviour of the material were now required to improve the performance of the material and enable its widespread use.