Can Chicken Eggshells Replace Graphite in Li-Ion Battery Electrodes?
One challenge to making lithium-ion batteries safe, cost-effective, and high-performance is perfecting the components. A recent study found the calcium carbonate in chicken egg shells can be used to create the electrode in lithium-ion batteries, capitalizing on an abundant natural material to aid performance and reduce costs.
As renewable energy continues to develop, so does the demand for lithium-ion batteries (Li-ions) to power this growth. But Li-ions are not simple battery systems with a green and clean guarantee—lithium extraction, producing graphite for electrodes, and disposal of these batteries all compromise the renewable value. Now, a study has found chicken eggshells can actually be treated and used to build electrodes, creating an innovative option for a novel and unlikely conductor of electricity.
Typical lithium-ion battery used in electric vehicles. Image used courtesy of the Renault Group
The electric vehicle (EV) market has grown substantially in recent years, but problems emerge as the pace of EV production picks up. While the infrastructure to produce the vehicles is robust, charging station infrastructure lags. Algorithms and software need improvement, and engineers are still working on the safety and performance of Li-ions.
The EV market boom will impact reducing carbon footprints, but important labor must be done to ensure that all facets of this market are optimized.
Electrodes, Graphite, and Fossil Fuel Use
Graphite is commonly used in commercial Li-ions because of its high conductivity, but there are various drawbacks associated with its use as a material for electrodes and anodes. One major issue is its energy density and capacity for storage. Graphite is only capable of holding one lithium atom for every six carbon atoms.
In addition to energy storage limitations, some might forget that fossil fuels are used in graphite production. Flake graphite mined from the ground can be used in Li-ion production, but synthetic graphite is, in many ways, a superior option. Not only does synthetic graphite have fewer impurities, but it also has a higher rate of thermal conductivity, which is key for the performance of lithium-ion batteries. While synthetic graphite has a thermal conductivity of 700-1500 W, the natural option is notably less, with a thermal conductivity of 300-700 W.
Graphite production from carbon ore. Image used courtesy of Department of Energy
The problem with the synthetic option, then, is not a performance issue but the necessity of fossil fuel use in its production. Oil byproducts are essential in producing synthetic graphite, and some commonly used byproducts include coal tar pitch and petroleum coke. The production process also involves much heat as temperatures up to 3,000 degrees Celsius are generated from coal-powered furnaces.
While the EVs powered by Li-ions are often framed as the green answer to the combustion engine, Li-ions still need significant fine-tuning to minimize environmental impacts and maximize performance.
Chicken Eggshells and the Conductivity of Calcium Carbonate
Researchers led by Manickam Minakshi Sundaram, an associate professor from Murdoch University in Perth, Australia, are pioneering a natural direction for lithium-ion component production that might make the need for synthetic graphite a thing of the past.
Minakshi has developed a method of treating and baking chicken eggshells that increases their conductivity, creating a substance that holds promise as a material that can replace the graphite used for Li-ions components. Calcium carbonate is found in significant amounts in chicken eggshells, and the treatment process Minakshi has developed helps maximize its utility. Commercial Li-ions use electrolyte solutions that include organic solvents, many of which are carbonates, so this calcium carbonate supply would be an excellent source for this battery component.
Cheaper, Safer, More Sustainable Li-ions
The potential impact of finding an abundant natural material like chicken eggshells to replace graphite in Li-ion production would not only help make the batteries safer and more sustainable, but battery production costs would also be significantly reduced.
The graphite market is projected to reach hundreds of billions of dollars in the coming years.
Yearly graphite market projections up to 2027. Image used courtesy of Digital Journal
In Australia, where this study was conducted, annual egg production approaches 6.2 billion eggs. Most of these chicken eggshells become a waste product, so this new use case could transform Li-ions production and reduce a significant source of natural waste from the global food market.
As engineers develop the technologies that support the shift toward electric vehicles, they are finding surprising and unlikely materials to advance Li-ions production, maximize performance, and improve the sustainability of EV infrastructure.