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Wednesday, August 4, 2021

Metal-Free, Completely Organic, Fully Biodegradable Batteries

Batteries that don't have metal electrodes, that are completely organic and fully biodegradable exist.  They're still somewhat of a laboratory curiosity in that I can't tell you a name that's on the market.  They're even worse at energy density than batteries that don't check all those squares in your game of Buzzword Bingo.  

I should point out that when they use the term organic, it's in sense that chemistry formally recognizes: it means that they're based on carbon compounds, not that they're grown on hippie farms.  As always, the common word biodegradable translates into normal-speak as "they will rot."

The article I'll refer to first appeared in the June Electronic Design magazine and focuses on work carried out by a team at Texas A&M University headed by Jodie Lutkenhaus, Professor of Chemical Engineering and Materials Science & Engineering.  In place of inorganic elements or compounds, like Lead and Sulfuric acid or Nickel and Cadmium terminals with a conducting paste, they created a battery using positively and negatively chargeable polypeptides.  Polypeptides are combinations of amino acids by what are referred to as peptide bonds.  The biggest and best known polypeptides are the proteins every living tissue is made from.  The battery polypeptides are only similar to those bigger proteins in the organic chemistry sense.


The process begins with an amino acid called L-Glutamic Acid (L meaning it rotates polarized light to the left; "levorotary").  L-Glutamic Acid is common in foods but not one of the "essential amino acids" that we can't synthesize and thus need to eat.  

Here I'll mercilessly grab part of the original article.  

In basic chemical terms, they started with l-glutamic acid polypeptide chains, then attached 2,2,6,6-tetramethyl-4-piperidine-1-oxyl (biTEMPO) to make the cathode and 4,4′-bipyridine derivatives (viologen) to make the anode (Fig. 2). A radical-based chemical mechanism “shuttled” electrons between the two structures.


Of course, as anyone doing research on batteries will tell you: a battery is more than just making this glop and pouring it somewhere, it has to be packaged properly, too. The packaging is shown in the Electronic Design article, but looks much like (well...) a battery.  Anode and cathode separated (by some filter paper in this case) and connected positive to anode and negative to cathode.  

The big question I had when I first saw this was how the energy density compared to other batteries, assuming it would be lower than existing batteries at this point in development.  

The storage density of this battery, with a terminal voltage between 1.1 and 1.6 V, is about 38 mA-hr/gm and 60 mW-hr/gm, which about one-third that of lithium-based sources. Furthermore, according to their detailed, fully referenced comparison table, it’s in the mid-range of “organic” cells that are non-degradable.

Unless I've gotten too out of practice at converting units, milliWatt*hour/gram are numerically the same as Watt*Hour/kilogram.  60 W*H/kg seems lower than the stated 1/3 of lithium batteries, but not terribly low.  I've read of electric car batteries doing over 400 W*H/kg and some claims of twice that being seen in some lab somewhere.  Gasoline offers 12,000 W*H/kg.

Given that, it's reasonable to ask "so what?  Why should I care about a low capacity battery that doesn't seem to offer any improvements?"  

The standard arguments against Lithium Ion batteries center on their not being recycled as much as people want (it costs too much), and that they use cobalt in their chemistries, a toxic metal that has become the target of human rights protesters - undoubtedly you've seen the pictures of children forced to work in the cobalt mines in horrible conditions.  Both of these objections are being raised in several places and everyone in the battery business is trying to come up with better solutions.    

 

 

16 comments:

  1. In some uses energy density isn't as important. Low cost, nontoxic recyclable have uses. Storage for home solar/wind generation would be a possibility where you had some leeway for weight and size. Lots of questions still to answer but we simply MUST find better ways to store energy if we are no remain a technological society.

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    1. In the home storage situation, I supposed it depends on a few factors, but weight seems secondary. Personally, since I replace my single AGM lead-acid battery far more than I use it, I'd rather see better battery lifetimes.

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  2. If the woke eat Tide Pods, they'll love these.

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  3. So "The Matrix" is the future...

    As to 'Organic,' I love telling people that gasoline is organic. So are many toxins, poisons, venoms and other chemicals that will kill you.

    Benzene is organic, for God's sake.

    If it's composed of Carbon, Hydrogen, Oxygen, Nitrogen or a mix of them it's organic, as long as Carbon is part of it all.

    Carbon monoxide is organic.

    Carbon dioxide is organic.

    It's all Organic! (waves hands in air, runs screaming into the distance.)

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  4. Replies
    1. Neither the Electronic Design or linked articles mention weight at all, so it's apparently not something they're designing for.

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  5. Electric eels and rays had this figured out millennia ago.

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    1. They didn't say where the idea came from for the polypeptides they used, but it makes me wonder if they took them from one of these electric critters.

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  6. Funny how a lot of science fiction has all the alien tech based on organic processes. Control panels are organic. Power suits are organic. Heck, in Farscape the entire spaceship was a living creature. We seem to be headed in that direction.

    One of these days we'll put together a lawn mower that makes cloth and looks a lot like ... a sheep.

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  7. You would think there would be a market for long-life batteries. If they're heavy, that would reduce (but not eliminate) the market.

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    1. And Borepatch nails it again.

      Over the last 100 years the biggest jump in battery technology has been the Lithium Ion battery. Technology is behind the curve on power storage. We need a smaller/lighter but higher energy storage batteries that are economically and ecologically feasible to produce and recycle.

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  8. Batteries, like solar panels, are very mature products. Smart people have been trying to improve them for decades, without much real change. Perhaps there's a revolutionary breakthrough right around the corner, but maybe not. In some cases we've simply reached the limit of the materials that are available on this planet, like with the compressor blades on jet engines (steel melts, ceramics are too brittle, etc.) or physical limits like the aerodynamic effect on the forward speed of a helicopter.

    Now, sometimes we find a clever way around the problem, like a tilt-rotor aircraft. So here's hoping. But I'm not holding my breath.

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  9. Let's hope it scales up, judging by the various lithium fires in the news of late, the last thing we need is the large battery banks of lithium battery banks aka bombs here in the windbelt. We burn every year anyway due to our natural climate but no need to give mother nature a supercharger.

    Forgive my ignorance on lithium recycling, but what specifically makes it nonviable? Too much plastic vs metal?

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    1. Afraid I can't be much help. I never really saw anything specific about why they say lithium recycling is too expensive. I can guess that lithium's high reactivity makes it want to bond to everything and harder to separate out, but that's not saying much.

      The fire issue has a few factors, but basically comes down to packaging. As I understand it. If you expose lithium metal, it's going to react with things. Put water on it, and you get a constant fuel source. Lithium batteries (and there's a few types) tend to have a flammable electrolyte solution and are really on the edge of trouble all the time. Still, lithium batteries store less than 5% of the energy per pound as gasoline, and that's stored rather reliably. Which argues it's the packaging.

      There was a big issue with Samsung Galaxy phones catching fire back in '16-'17 that was caused by the phone design pinching a corner of the battery. I've never seen a cause listed for cylindrical, metal-celled Lithium batteries catching fire.

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    2. Thanks for the info!! I've never looked into the chemistry aspect of this, never had a need to. Its not my field, so I have some studying to do on lithium's reactivity.

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  10. Better batteries are not and never were the answer. The answer is better small scale energy generation. Get it small enough and you just take your generator with you...like a brain piloting a meat suit that is powered by widely available material.

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