Almost 20 billion eggs are consumed in Germany every year. And of course, everyone wants the yellow of the egg. The eggshells also offer quite interesting potential: They are suitable as an effective, sustainable storage material and thus for the construction of a cost-effective and at the same time good lithium-ion capacitor. The idea of meaningfully recycling biowaste is an exciting topic. Professor Maximilian Fichtner of the Helmholtz Institute Ulm (HIU): “Surprisingly, there are always new examples in which natural substances bring good to very good preconditions for producing materials for electrochemical storage.”
For example, chicken eggshells are made of a composite with calcium carbonate (CaCO3) and a protein-rich fiber membrane. Thanks to the high proportion of CaCO3, they offer excellent electrochemical properties that enable them to store lithium well. This is the result of an international team that includes scientists from HIU. The researchers used eggshell powder as an electrode against a metallic lithium anode in a nonaqueous electrolyte. With over 1000 charge and discharge cycles, the test cell maintained a capacity of 92 percent.
For their investigations, the researchers used both the calcified shell and the inner and outer shell membrane. To do this, they washed, dried and shredded the shells to a powder and obtained the conductive material. Improving the performance of the material and enabling it to be widely used requires further research and a detailed understanding of the electrochemical and physical behavior of the material, according to the research team.
Cost-Effective And Good
So far, eggshell waste has been used in a number of applications. They are used in bioceramics, in cosmetics or the dye industry. The protein-rich, fibrous eggshell membrane also acted as a separator in supercapacitors. Now the egg shells were used for the first time worldwide as an electrode. In addition to the areas of application mentioned above, they could thus be used in the future as the sustainable storage material. The Research Group recently presented the findings in the journal Dalton Transactions of the Royal Society of Chemistry (DOI: 10.1039 / c8dt03252a).
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