Non-Newtonian Batteries

Batteries placed in harm’s way need to be protected. A battery placed where a breakdown could endanger a life needs to be protected. Lithium-ion batteries on the bottoms of electric cars are subject to accidental damage and they are bathed in flame-retardant epoxy inside a metal sled. Phone batteries are hidden behind something that will shatter or snap before the battery suffers and warrant inspection. Hoverboard batteries are placed behind cheap plastic, and we have all seen how well that works. Batteries contain chemicals with a high density of energy, so the less exploding they do, the better.

Researchers at Oak Ridge National Laboratory have added a new ingredient to batteries that makes them armored but from the inside. The ingredient is silica spheres so fine it is safe to call it powder. The effect of this dust is that the electrolyte in every battery will harden like cornstarch/water then go right back to being a liquid. This non-Newtonian fluid works on the principal principle of shear-thickening which, in this case, says that the suspension will become harder as shear force is applied. So, batteries get rock hard when struck, then go back to being batteries when it is safe.

Non-Newtonian fluids are much fun, but we’re also happy to see them put to use. The same principle works in special speed bumps to allow safe drivers to continue driving but jolts speeders. Micromachines can swim in non-Newtonian fluids better than water in some cases.

43 thoughts on “Non-Newtonian Batteries

      1. Or something that when heated undergoes a reaction that releases something.

        From Wikipedia: “Mixtures of huntite and hydromagnesite work in a similar manner. They endothermically decompose releasing both water and carbon dioxide,[4][5] giving fire retardant properties[6][7][8] to the materials in which they are incorporated.”

        Except I’d guess water and CO2 might not be as effective with a lithium battery fire, so something else would be necessary.

          1. 2 NaHCO3 → Na2CO3 + H2O + CO2

            Sodium bicarbonate releases water on thermal breakdown, which is a a terrible way to put out a lithium battery fire because the water then instantly reacts to create hydrogen.

    1. They don’t need to be *intentionally* flexible. A solid steel chassis will bend with enough force, everything’s flexible in a car crash. This makes the batteries intrinsically tougher, without having to clad them in things, although they’ll work fine alongside armour too.

  1. Excellent idea, but how much energy density does adding these spheres take away from the cell? Manufacturers are contstanty trying to increase energy density, and adding a filler (no matter what form the filler takes) will reduce that.

    1. Unless you can find an non-newtonian mix where the “filler” is part of the battery chemistry ;)
      But then you would still end up with a race between: Superior chemistry + passive filler vs inferior chemistry with “active filler”. I can see this as an growing research area considering the development and deployment of electric cars and planes.

    2. Time for an car analogy ;) Many if not most car buyers consider it more important with safety ratings/features and comfort rather then the motor effect and efficiency. The car with the best motor / drive train will not be the best seller.

      Its all LiCoO_2 vs LiNiMnCoO_2, that is, do you want efficiency and a risk of Boom Boom, or “good enough” and a good nights sleep. cost might also be a big factor, economy of scale will always be limited by the cost of the raw materials.

      1. True story: economist hired by GM runs big fancy regression on what consumers like using all manner of car characteristics. Horsepower, luggage room, safety, mileage… and the most influential factor is? Cupholders.

        I’d bet that “non-explodiness” is a ridiculously desirable feature in batteries for most people.

        1. >”and the most influential factor is? Cupholders.”

          These sort of “focus on the irrelevant” effects happen in market research all the time. It’s certainly true that when a consumer is presented with nearly identical options, or a vast variety of incomparable differences which makes it difficult to pick, they tend to focus on some small detail, but that’s a problem of inadequate product differentiation rather than the cupholders being the most important factor to consumers.

          1. I dunno. It’s an example of either “statistics are sometimes stupid” or “people are stupid”. Could go either way, and statistics have a better track record.

          2. A couple of decades ago my friends were looking for a mini-van for their new family. The Dodge Caravan salesman pointed out it had the most cup holders in its class. (It had more cupholders than it could carry in passengers!)

        2. I built a small test jig for cups that fits in my pocket, to make it possible to shop for a car cup. The cup holder itself is well-engineered, (Nissan) but the range of sizes it can hold is rather narrow compared to the wide range of available cup sizes and shapes.

          1. That is sort of what I’m getting at: put some non-newtonian filler in which reduces capacity (let’s say for arguments sake it halves it), then effectively the weight per watt-hour is doubled. Price?
            And safety is still not as good. Just because you can hit it hard and it survives, doesn’t mean that a puncture will automatically become a ‘safe event’.

      2. The uptake of electric cars aready sufferes (needlessly I would say) from ‘range anxiety’ and reducing range (by increasing weight or reducing capacity) would only add to that problem.

        Safety is an interesting aspect. People seem to be paranoid about some aspects of safety (don’t want a litre of hydrocarbon refrigerant gas in a sealed system, but a tank with 50 plus liters behind the back seat is fine?).
        And hackers that make ‘power walls’ from second hand Li batteries to put in their basements, out of sight…

        1. I did a little anecdotal research, and it seems like some people in the industry think that electric vehicle fires will be comparable in number to fuel vehicle fires, we just hear about the electric ones more at the moment.

      1. If using law makes things safer overall, that’s not a bad thing. Patents expire. And quickly enough that the system is useful, unlike the Disneyright system, that drags all creative works out forever, if they were created after the birth of Mickey Mouse.

        Who was a ripoff of a rabbit Fleischer drew, but I’m not a billion-quid company, who cares what I think?

        1. What? Are you talking about Oswald Rabbit? Disney drew that but he was working for Universal who therefore owned the copyrights. When they had their falling out he drew Mickey for himself. I could definitely see one making a point though that Mickey looks too much like the original version of Oswald. It’s kind of late for Universal to sue though since they already sold Oswald to the Disney corporation.

          The only Fleischer I could find associated with a cartoon rabbit was the voice of Roger Rabbit and nearly 70 years too late to be a prototype for Mickey.

          So.. what are you talking about?!?!

    3. 30% of the mass of a typical large battery is support structures and protective covers to stop anything from poking into it.

      If you make a poke-safe battery, you can shed some of that excess weight.

    4. If it reduces the capacity, you can just make the batteries bigger and heavier. To compensate for that, you don’t need as much protective structure around them. It might work out as an advantage overall, where you can have the same capacity but better damage resistance.

  2. Having lived in Knoxville for a few years, and meeting many of the ORNL scientists, I’m always amazed at what comes out of their labs.

    Obviously, the best stuff is always kept secret, so it’s awesome to see things like this make the light of day.

  3. The fuel tank of any car has the energy of a fuel to explode and burn more than an electric battery of the size or mass of a similar electric vehicle. Why is no one indignant and does not try to improve or ban it? I’m funny and sad ….

    1. Because its only explosive together with oxygen.
      It wont burn unless it escapes the tank.

      The fuel tank is designed to take some beating and even change shape without bursting.

      LiPo cells generate their own oxygen if overheated or exposed to water.

  4. I’d be very interested if the solidification of the electrodes during strain causes significant current drop. This could be particularly problematic in high vibration environments like impact wrenches or tools or even off-road applications.

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