In an ongoing effort to improve the performance of lithium-ion batteries, scientists have looked to the techniques that snails use to control the growth of their shells. This biological inspiration, combined with a peptide found to bind very effectively with materials used to make cathodes, has potential for making lighter and longer-lasting batteries.

What pointed the battery researchers from the University of Maryland, Baltimore County (UMBC) toward the slithering slugs was the inherent obstacles in dealing with materials at the nanoscale. Working with objects between one and 100 nanometers in size, chemical reactions are different and can be somewhat unpredictable, due in part to an increase in surface area for nanostructured materials

In terms of battery technology, nanostructured electrodes with greater surface area compared to conventional bulk material electrodes offer more active sites for electrochemical reactions to occur, with the particles that carry the charge also traveling shorter distances.

The team looked to the way mollusks are able to use peptides, strings of amino acids, to dictate the growth of their shells. Using inorganic materials such as calcium carbonate, the creatures display a high amount of control in forming nanoscale structures, something the researchers believed could be used as a blueprint in battery chemistry and lead to lithium-ion batteries that are both lighter and have longer lifetimes.

In applying the technique to their research, the scientists needed to identify a peptide that could bind with lithium manganese nickel oxide (LMNO), a material used to make cathodes in high performance batteries. They were able to do so using a procedure called Phage Display, which allowed them to screen more than one billion possible peptides contained in a commercially-available "peptide library" with the LMNO and washing off those that didn't stick.

Once the sticky peptide had been identified, the team combined it with another peptide known to stick to carbon nanotubes, devices that can act as conductive nanowires in lithium-ion electrodes. The outcome was a peptide capable of latching onto the LMNO as well as the carbon nanotubes. Binding the two materials close to one another served to provide a better connection through the charging cycles.

By providing a new nanoscale architecture for lithium-ion batteries, the researchers say that the approach could improve the power and cycling stability of lithium-ion batteries. At present, they are investigating how the cathodes perform, with a view to employing the same method to develop more efficient anodes and build an entire biology-inspired battery.

The team presented its research at the 59th annual meeting of the Biophysical Society and published its findings in Biophysical Journal.

Source: Biophysical Society (PDF)

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