A new study has taken a lesson from biology to show how the performance of lithium ion (Li-ion) batteries can be improved. A team from the University of Maryland, Baltimore County, borrowed a technique that organisms use to build the mineralized tissues that comprise bones, teeth and shell to show how biological molecules can latch onto nanoscale components, locking them into position to help produce high-performing Li-ion battery electrodes.

The development of mineralized tissues is helped by specialized peptides, organic molecules made by the cells of living things. These peptides can bind to the particular inorganic molecules required to create that tissue and hold them in place, but can also help create very fine structures with fabricated materials. In this study, presented at the 59th annual meeting of the Biophysical Society held recently in Baltimore, a bi-functional peptide that binds strongly to lithium manganese nickel oxide (LMNO) – used in the manufacture of cathodes in high-performance batteries – was isolated. The peptide locked onto nanosized particles of LMNO, connecting them to conductive components of a battery electrode, improving both its potential power and stability.

Images on the left show no specific interactions between cathode material LiNi0.5Mn1.5O4 and MWCNTs, observe formation of CNTs bundles that attached to material non-specifically during water evaporation from the TEM grid. Images on the right indicate that presence of multifunctional 24-mer peptide with two binding domains, one for LMNO and another for CNTs, allows to form dispersed CNTs conjugated to LMNO particles at the nanoscale.
Images on the left show no specific interactions between cathode material LiNi0.5Mn1.5O4 and MWCNTs, observe formation of CNTs bundles that attached to material non-specifically during water evaporation from the TEM grid. Images on the right indicate that presence of multifunctional 24-mer peptide with two binding domains, one for LMNO and another for CNTs, allows to form dispersed CNTs conjugated to LMNO particles at the nanoscale.

Using the “phage display” approach, more than a billion potential peptides were screened to find one that would adhere strongly enough to LMNO. The new peptide was then combined with a previously isolated peptide that binds to carbon nanotubes, which can act as conductive nanowires. When these two specialized peptides are combined, they can form a “nanobridge” between the two components of the cathode, keeping them near one another to maintain a connection through multiple charging cycles. As researcher Evgenia Barannikova said, this helps to “prevent disaggregation of electroactive and conductive material, which currently results in loss of conductivity and low performance of some batteries”.

Nanostructured electrodes in Li-ion batteries offer advantages over bulk material electrodes, such as shorter distances for charge-carrying particles to travel and a high surface area, providing more active sites for electrochemical reactions to occur, potentially leading to lighter and longer-lasting batteries.

Studies into the surface interactions between solid-binding peptides and inorganic materials are also important for applications such as biomedicine, electronics, data storage, sensors, optics and catalysis. The team is now testing the efficiency of the new cathodes, and aim to produce an anode using similar techniques and integrate the two components, offering new ways of developing devices based on the assembly of materials at the nanoscale.