Both renewable energies in general and electric cars, in particular, have an Achilles heel —electricity storage. Even devices such as cell phones suffer from battery life issues due to increasing computational needs. Heavy investments in a new generation of batteries give grounds for optimism, but solar and wind farms will require a quantum leap to provide a stable supply. One area of research is the transition from lithium batteries to sodium batteries, with the latter being a much more affordable material. However, the development of sodium cathodes is proving a challenge for researchers. Fortunately, it seems that the answer could lie in a new lesson in biomimicry, i.e., the application of processes and structures from nature. In this case, the solution lies in the bones of mammals.
This innovative technology project is the outcome from a collaboration between the universities of Texas (USA) and Sungkyunkwan (South Korea), and Brookhaven National Laboratory. To develop more robust and stable sodium cathodes, they have closely examined the bone structures of mammals. Mammalian bones consist of a hard exterior and a spongy interior that stores and transports the marrow. This morphology gives them a tremendous mechanical strength that resists great pressure. Under these premises, the international team has created porous structures, known as NVP, coated with a layer of reduced graphene oxide (rGO). NVP offers excellent conductive qualities for sodium ions, but it is a very fragile structure.
By combining it with the graphene coating as if the cathode were a bone, they have succeeded in significantly improving the structural integrity, which reduces deterioration due to mechanical and electrochemical stress. Among the significant advantages of these new sodium batteries are their ultra-fast charging speed and high resistance, since they maintain a capacity of 90% after 10,000 charge cycles. However, there is still a lot of testing to be done before they reach a commercial version.
From bones to muscles
Another example of biomimetic batteries is a project at MIT in the United States. Instead of using bone structures, it has drawn inspiration from the characteristics of muscles. In collaboration with Southwest University, the researchers have explored how muscle fibers transport blood, oxygen, and nutrients to develop a new electrode type. Instead of muscle cells, the team used microscopic spheres of tellurium-loaded carbon. Besides, they used carbon nanotubes that act as an electrically conductive material, which would be the equivalent of blood flow. The carbon spheres, in turn, operate as electrical storage cells.
Research shows that the prototype can withstand five hundred charge cycles, which is still far from having commercial applications. However, the study published a few years ago already pointed to the potential of bio-inspired systems for energy storage.
If you want to learn more about the new generation of alternative batteries currently in development around the world, we recommend this article on batteries based on eggshells or this one exploring the use of wood waste. Another example would be the technology enabling paper-based batteries.