Li-ion Battery Research Moves Ahead at Snail’s Pace

Inspired by the way snails control the growth of their shells, researchers are using biology to improve the properties of lithium-ion batteries.

Biological molecules can latch onto nanoscale components and lock them into position to make high-performing Li-ion battery electrodes, according to new research presented at the 59th annual meeting of the Biophysical Society in Baltimore.

The University of Maryland researchers tell attendees they have isolated a peptide, a type of biological molecule, which binds strongly to lithium-manganese nickel oxide (LMNO), the material that can be used to make the cathode in high-performance batteries.

The peptide can latch onto nano-sized particles of LMNO and connect them to conductive components of a battery electrode, improving the potential power and stability of the electrode.

Graduate student Evgenia Barannikova says one of the inspirations for her research is the way organisms such as mollusks use peptides to control the growth of their shells. She says they demonstrate remarkable control to build intricate nano- and macrostructures from inorganic materials such as calcium carbonate.

“Biology provides several tools for us to solve important problems,” says Barannikova, who is studying how biological molecules in general can improve the properties of inorganic materials in batteries. “By mimicking biological processes we can find the better solution.”

While the researchers borrowed the general approach of the mollusks, they had to employ some lab-bench wizardry to find the appropriate peptide because snails, of course, do not make their shells from lithium manganese nickel oxide.

One of the problems now facing battery researchers is the difficulty of working with nanoscale materials, which due to their extra-tiny size can be hard to control and hold in place.

Nanostructured electrodes in Li-ion batteries have several advantages over bulk material electrodes, including shorter distances for charge-carrying particles to travel and a high surface area that provides more active sites for electrochemical reactions to occur – all of which translate to batteries that are lighter and longer-lasting.

Barannikova turned to peptides to take on the challenge of manufacturing on the nano-scale.

Made up from strings of molecules known as amino acids, peptides are naturally occurring and bind to many different types of organic and inorganic materials, depending on their sequence of the amino acids. They play many roles in the human body, from signaling in the brain to regulating blood sugar, and some drugs, such as insulin, are made up of peptides.

Barannikova and her colleagues used a procedure called Phage Display to screen more than 1 billion possible peptides in search of one that would stick strongly to lithium-manganese nickel oxide.

The “peptide library” contains a vast number of randomly combined amino acid sequences incorporated into a protein made by a virus called the M13 bacteriophage.

Barannikova isolated a peptide that binds to LMNO by combining the library with a sample of the metal oxide and then repeatedly washing away the peptides that didn’t stick to it. She then combined the newly discovered peptide with a previously isolated peptide that binds to carbon nanotubes that can serve as conductive nanowires in Li-ion electrodes.

The resulting peptide then could form a bridge, binding to both the LMNO nanoparticles and the carbon nanotubes and keeping them close to each other so they can maintain a connection through multiple charging cycles.

By helping maintain a highly organized architecture at the nanoscale, the researchers expect their peptides will improve the power and cycling stability of future Li-ion batteries, allowing them to be smaller and maintain longer lifetimes.

The research team now is testing how well the new cathodes perform.

Barannikova plans to make an anode with similar techniques and to integrate the two components.