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A new application for your post-omelette waste

Illustration for article titled A new application for your post-omelette waste

I have a real weakness for papers that use standard consumer products in cutting edge research. Maybe this is because I work with graphene in my day job, and that is made with graphite + Scotch Tape. Anyway, this paper is a prime example, with the authors repurposing eggshell membranes in battery cathodes.


Rechargable batteries are useful things. They're in cameras and smart phones, they save us money, they keep batteries out of landfills, and so on and so forth. They also have the potential to be even more useful if we can advance them enough for use in electric vehicles. (I know we already have electric vehicles, but people are pretty hesitant about the short range of today's batteries.) So it's not hard to see both the financial and environmental incentives behind battery research.

One material that has been considered for next-generation battery cathodes is sulfur. Sulfur has high theoretical capacity and energy density, is abundant, environmentally friendly, low cost and light weight. Which all sounds pretty perfect, but of course there's always the "but...", and in this case there are two. First, sulfur and it's discharge products are poorly conducting, which is clearly not ideal for an electrode, and second, sulfur-based batteries tend to have a short lifecycle due to soluble polysulfides which can diffuse away from the active layer. This research looks to address both challenges.


Luckily for the researchers, both birds can be killed with one stone. Or more accurately, one egg. If the active sulfur is absorbed onto a conductive porous mesh, it will both improve electrical conductivity and stabilize the soluble materials. The challenge is in finding a uniformly microporous substrate that doesn't negate the benefits of using sulfur in the first place, ie: is still environmentally friendly, low cost, etc. Hence using eggshell membrane, a waste product that just happens to have a perfectly microporous structure. To make the membrane more conductive, the authors first coated it in sucrose and then carbonized it. The addition of sucrose was not arbitrary, it actually improved conductivity of plain old carbonized eggshell membrane by an order of magnitude. The result was a cell with "high discharge capacity, excellent cycle stability, and high sulfur loading". Not a bad use for the thing that I mostly just use for cursing at when peeling a hard-boiled egg.

Check out the orginal paper, "Carbonized Eggshell Membrane as a Natural Polysulfide Reservoir for Highly Reversible Li-S Batteries" in Advanced Materials.

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