08/04/2015: Energy from salmon sperm?

Ioannis Zabetakis, Assistant Professor of Food Chemistry, University of Athens, Athens, Greece.

First published in International Aquafeed, March-April 2015

In aquaculture, we are looking at issues of functionality and sustainability in order to produce more fish at affordable prices to feed the World. But there are some other applications that are promising and fascinating.

For example, have you ever thought how fish and batteries are connected?

A research group in China have turned to nature to help overcome one of the key challenges facing the most probable successor to the lithium ion (Li-ion) battery by using salmon sperm!

Today, lithium–sulphur (Li–S) batteries are cheaper, more sustainable and already capable of delivering up to three times the energy density of most Li-ion cells. However, they are not stable and this is a major problem for further development.

Li–S cells typically consist of a lithium metal anode and a carbon–sulphur cathode separated by a liquid electrolyte. Lithium ions dissolve from the anode during discharge, reacting with sulphur to form lithium polysulfides (Li2Sx) at the cathode, while the reverse occurs on charging. Some of the polysulfide intermediates are unfortunately soluble in the electrolyte and their dissolution from the cathode leads to irreversible loss of the active sulphur, adversely affecting cell performance.

Several strategies have been tested to reduce the Li2Sx dissolution problem, which often involve coating the cathode to isolate sulphur from the electrolyte, or hybridising it with third party materials that can help to anchor Li2Sx to the cathode surface through electrostatic interaction with the lithium ions. The drawback with these approaches is that there is substitution of the active materials that can increase internal resistance or reduce capacity.

In a important development, though, Chenggang Zhou and his colleagues at the China University of Geosciences, Wuhan, have been looking for an additive that was molecularly lightweight, dispersible on the carbon–sulphur cathode material, and rich in sulphur-loving functional groups, they thought of DNA.

Computational chemistry verified that functional groups common in all four of the nucleobases that comprise DNA were sulphur-loving, with phosphate groups exhibiting the strongest adsorption. Having confirmed their suspicion, the team then observed experimentally a three-fold enhancement in capacity retention after 200 discharge cycles by dispersing a small amount of DNA derived from salmon sperm onto the carbon–sulphur surface.

This development is quite exciting in terms of crossing species barriers but also on joining forces of material scientists with bioscientists.

The future is definitely holistic and 'salmony'!

Further reading

High-performance lithium/sulfur batteries by decorating CMK-3/S cathodes with DNA

http://pubs.rsc.org/en/Content/ArticleLanding/2015/TA/c4ta06083k#!divAbstract

izabet@chem.uoa.gr@yanzabet

Read the magazine HERE.

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