This is the conclusion reached by an international team including scientists from the Helmholtz Institute Ulm (HIU) founded by the Karlsruhe Institute of Technology (KIT). Chicken eggs are used in large quantities worldwide: in the food, pharmaceutical, and manufacturing industries. After the eggs have been used, the shells are thrown away and disposed of as biowaste in landfills. The shell consists of a composite material that consists of calcium carbonate (CaCO3) and a protein-rich fiber 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 chicken egg shells that are able to store lithium well due 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 1000 charge and discharge cycles, the test cell maintained a capacity of 92 percent. Both the calcified shell and the inner and outer shell membranes of the eggshells were used. The researchers washed, dried, and crushed the shells into a powder, creating a conductive material.
So far, egg shell waste has been used in a number of applications, including bioceramics, cosmetics, and the dyestuff industry. The protein-rich, fibrous egg shell membrane also served as a separator in supercapacitors. However, biowaste was used as an electrode for the first time worldwide. According to the research team, further research and a detailed understanding of the electrochemical and physical behavior of the material are now required in order to improve the performance of the material and enable it to be used widely.