Silicon Air Battery

Jülich researchers claim to have made a silicon-air battery that actually works.

German language article

Promising 5 times higher charge density ( I guess per weight, unfortunately the journalist omitted the “5 times per WHAT” – but weight is the only category that is important)…

…they still got some problems – the silicon electrode gets depleted over time; but at least they made it actually  recharge which was a problem up to now…

Besides the high density (due to the air electrode, air-anything batteries are sought after because one of the electrodes just becomes ordinary surrounding air therefore adding nothing to the weight) – it promises the advantage of using only very cheap materials. Nothing scarse like Lithium.

We are looking at least at 5 more years of research I guess before any kind of product will be possible.

But. A breakthrough of this magnitude could actually make battery cars work economically – which they can’t now, without the market distorting power of the Total State by virtue of taxes and subsidies.

 

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19 thoughts on “Silicon Air Battery”

    1. Hell if I know. The linked article has a nice drawing. A metal mesh exposed to air on one side forms one electrode, electrolytic solution in between, and a silicon electrode on the other side.

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      1. What it looks like to me, based on that very nice drawing and some online review (not done yet, but maybe enough for now) and what I remember of the principles involved:

        The Silicon electrode (the cathode) is the electron source. The electrolyte is probably alkaline (or neutral?), since silicon isn’t soluble in acid (Strong bases etch glass). Connect the terminals to initiate the reaction, and then Si loses electrons, is oxidized to Si+4 which dissolves in the (alkaline?) electrolyte. The porous (to air) Nickel doped Carbon electrode (the anode) accepts the electrons, allowing Oxygen from the air to enter and to be reduced to 2O-2, which then reacts with the Si+4 to produce SiO2, which I think then precipitates out on the porous anode (probably ultimately clogging it up?).

        I’m guessing that the half reactions involved are something like this:

        Si –> Si+4 + 4e-
        O2 + 4e- –> 2O-2

        Sorry I can’t do better, but I haven’t access to the journals the relevant papers might be in, and haven’t done that chemistry since my prehistoric college days. So, as best I can recall that’s it. It’s pretty std electrochemistry, once a clever fellow figured out how to build a device to capitalize on it.

        Wouldn’t work in a vacuum, though. Probably won’t be selling many of those to NASA.

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      2. @ yonason,
        Common glass is silica based. That is, it is crystalline silicon dioxide plus other stuff that was melted and cooled in a manner that didn’t allow recrystallization. A silicon electrode wouldn’t necessarily be silica.

        Hmm, I wonder if the white stuff you see was silica precipitated from silicic acid (SiOH4), now that would make some sense of the silicon electrode side.

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      3. Thanks, yonason.

        I think we have something to work with now. Silicon anode of some kind, an alkaline electrolyte of some kind, and an oxygen cathode open to the air.

        Too bad that I lost my CRC Handbook of Chemistry and Physics that I purchased about 40 years ago. I wonder if that reference is available to the public.

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      4. Update: The CRC Handbook of Chemistry and Physics is still available in print form. Only about $200 US, and that’s about twice what I paid for it in 1978 or 1979.

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  1. That was the question that I asked myself. I had to memorize a bunch of redox potentials and I’d not recalled one for silicon. A search didn’t turn up anything useful.

    @yonason,
    I don’t see your first guesses as useful, for you have to consider the electrolyte. From what I could gather, the oxygen electrode would be O2 + 4H+ + 4e- -> 2H2O giving 0.4V potential, but then things like pH, temperature, molality, purity, and more come into the picture. If the quoted 1.1V (from memory) is correct, what is the silicon side’s chemistry and what is the electrolyte doing?

    Metal-air batteries are old, think zinc-air batteries for hearing aids. Sure, lacking the need of a heavy cathode (oxygen electrode open to the air), you can get high weight specific energy densities. I don’t recall those being rechargeable and that is another design consideration. Then again, electrochemical batteries are very old (living cells being the most ubiquitous examples of these). Their properties are fixed by chemistry. Many of these systems have been evaluated for over a century and some for two to three centuries. The best ones, economically, are the ones we have had in use because they were cheap to make and use.

    I suspect the real breakthrough, to the extent there is one, is the electrolyte.

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    1. @cdquarles

      ERRATA
      1. I transposed “Anode” and “Cathode.” (It’s discharging, not charging)
      2. My guesses for the half-reactions were based on that figure in the article Dirk give, and while I’ve seen them written similarly for Zn in one other case, you are correct that I was off on those, thanks. However, yours looks like it’s for an acidic environment and the potential appears to be incorrect – see here.

      FURTHER COMMENTS
      Here’s a very detailed survey of several air-battery types, with the correct half-reactions for the electrolytes used, and sketching out the actual reactions that occur. The downside is they don’t give refs., but there may be sufficient information (the authors names for one, and major centers where research is being done) to find all one might want that’s available on the subject.

      And from what I’ve found, you are probably also correct about the importance of the electrolyte (though it doesn’t look like they are playing around with that). There may be other things that might be done (if they haven’t been already), like tinkering with what catalyst it’s best to dope the porous carbon with, etc.

      Look forward to any comments/corrections you may have.

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  2. Oh yes, the key is the electrolyte. I searched for room temperature ionic liquids. In concept, consider a detergent solution. Chemically engineer these to have a low vapor pressure and they’d be an excellent addition to the polycarbonate gel lithium salt electrolytes that helped make lithium ion batteries economical, with a much less likelihood of explosive decomposition.

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    1. Apparently in the case of Si, a “protic ionic liquid” is used as an electrolyte. Sorry for the age of that paper, but at least it describes what was known about them in 2007. There’s more recent stuff, but unless I can find a good review or two to start with, I’m not going to spend any more time on that, for now anyway.

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    1. Thanks, but for some reason I can’t access the 2n’d page, probably due to some protective software I’m running. But I saw a similar article elsewhere, so it’s probably a lot of the same stuff. At that other site it mentioned that the AL was “consumed” in generating the current, and one commenter I found amusing said that in his lexicon a device that consumed a component was a “fuel cell” not a “battery.” (Not same words, but same gist)

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      1. Here is one chemistry based definition: http://glossary.periodni.com/glossary.php?en=fuel+cell. A fuel cell, by this definition, requires a continuous flow of both the oxidizer and the reducer. Non-rechargeable batteries consume reactants within each cell, with the battery being the collection of the cells, yet these are not considered fuel cells. Given that the battery is the collection and is mute concerning the question of the chemical processes, you can have a battery of fuel cells.

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      2. @@cdquarles

        So, you aren’t posting to your blog anymore? Looks like some interesting stuff. You’re in computer programing, or related?

        Oh, wait, you’re on Facebook. I have an account I’ve never used, but should probably get around to it, since a lot of people I know use it. On the other hand, I’m already otherwise in touch with most of those I know who use it, so it would just be redundant. Some day. Maybe.

        Anyway, I think we’ve teased out enough on the battery for me to realize it’s way too specialized for a hacker like myself. I have a friend who’s an emeritus prof., at USF who’s working on new batteries. I’ll have to ask him about it when I see him next (not often lately). If I get to, I’ll pass it on.

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  3. Yeah, that was something that I did while recovering from a bad illness and was in physical therapy. I went back to work, but got too sick to keep it and then my mom’s health slowly ebbed away. From 2007 on, and especially from 2010 to March of this year, her care became my job. My mom passed away almost 5 months ago now. Writing for a blog is a lot of work with little recompense. Reading other’s blogs and commenting is much less work and much more rewarding ;).

    I have an eclectic set of interests. I read a lot and try to keep up with things going on in chemistry, physics, medicine and computers. Nature fascinates me. I loved hunting, fishing and hiking in my youth. Weather fascinates me. Languages fascinate me, whether natural human languages or various codes, including the artificial languages used to code computer programs. Economics also fascinates me, where I’ve read much more than was needed for the basic introduction courses.

    I have a bachelor’s degree in chemistry and hold a doctorate, though not in chemistry. Most of my working life was in and around human physiology and pathology. While at the University, I took a couple of programming classes. I also took a preceptorship in medical information technology. Almost 19 years ago now, I developed the illness that eventually put me in and out of work chronically. I currently am working on a business plan to attempt to open a research institute. The brain still works but much of the rest of me doesn’t work as well as it used to.

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    1. First things first. Sorry to hear about your mom. That’s a tough one. I can relate to that, and to personal health issues.

      I have a bachelor’s degree in chemistry and hold a doctorate, though not in chemistry.

      My BS is in chemistry as well, with a masters (doctorate cut short for health reasons) in something else, and career in something else. Funny how that all works out.

      “Reading other’s blogs and commenting is much less work and much more rewarding”

      Only slight disagreement there, I would have written “satisfying” rather than “rewarding.”. But, it does help one focus one’s ideas, so I guess it is “rewarding” at times, as well. And one does get to meet some interesting people one wouldn’t otherwise, so that’s also good. 🙂

      Here’s a mildly informative low tech article on battery market realities.
      https://www.technologyreview.com/s/602245/why-we-still-dont-have-better-batteries/

      Again, I hope you can have a good recovery, and success in your business endeavors.

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