New battery with inbuilt fire extinguisher
You may remember the stories last year about the Galaxy Note 7 catching fire. Although unconfirmed by Samsung, many suspect that an overheating battery was at fault. Now a group of researchers from Stanford University might be able to help. They’ve released a design for a battery that comes complete with a fire-extinguisher! Peter Cowley and Graihagh Jackson discuss how common these batteries are...
Peter - Batteries are very common and have been for many years. But these are lithium-ion batteries and these are probably about one per head of population on the globe per year, so many, many billions per year are manufactured and sold.
Graihagh - So it’s not just in your smartphone then?
Peter - No. It’s in cars, it’s in tools, it’s in laptops. It’s a great energy density for a rechargeable battery.
Graihagh - Why is it that they’re so vulnerable to catching fire?
Peter - Mainly because we’re wanting the devices to have greater and greater energy density, so we want our phones to be small, we want them to last longer, etc. And because of that you end up with the potential of manufacturing tolerances going wrong - materials being too small or geometry being wrong. The other thing, if you get the charging wrong, you can overcharge one of these devices and they can go wrong and potentially catch fire.
Graihagh - When you say ‘overcharge’ you mean literally leave your phone plugged in for too long?
Peter - No, no. It’s to do with the charging process.
Graihagh - So it’s nothing that the user’s done?
Peter - No, no, don’t worry about that. It’s not a problem there. It’s to do with something happening in there which will lead to more gases being produced than it should. Obviously pressure will build up and that could cause some sort of explosion. This is very, very uncommon, we must make absolutely certain that it doesn’t happen often. We’re all carrying these around - I’ve got two in my pocket at the moment and I’m not worried about that at all.
Graihagh - How does this fire extinguisher work?
Peter - It’s really cunning actually. It’s not…
Graihagh - I’m imagining it’s not like - I’m thinking about a fire extinguisher like those carbon ones.
Peter - It’s actually automatic as well so you don’t have to catch fire and you press a button or something, or an app that switches it on. No it’s nothing like that, it’s actually a material called triphenyl phosphate, which is used for fire suppression anyway, embedded in a little capsule inside the battery. When that reaches 150 degrees Centigrade then it breaks open, releases this TTP material, and it will put it out within half a second or so.
Graihagh - It sounds so simple...
Peter - It is, but there’s a big, big downside because this takes up quite a lot of space. So this energy density we’re all wanting will be reduced by this fire extinguisher. Now I’ve got no clue what the proportion is, but it may be something like a third.
Graihagh - Okay. So it’s quite a trade off then?
Peter. Exactly, yeah.
Graihagh - Do you envisage this sort of technology going beyond mobile phones - into your laptop, things like that?
Peter - Yeah. If we look at cars. Obviously, more and more cars will be electric. There are videos of Tessler catching fire on YouTube. But what they’re doing is they’re much lower energy density, it’s not so important to do that. Also they use individual cells, so if one cells goes it won’t take the whole lot out. There are 150 thousand car fires per year in the States in normal petrol and diesel cars.
Graihagh - That’s high.
Peter - That’s very high. It works out because it's a billion miles a year driven. About one fire per 20 million miles for a car and, apparently, it’s five times less than an electric vehicle. So it’s actually safer than an electric vehicle.
Graihagh - I guess these things just get publicised a bit more?
Peter - Exactly, yeah. We’ll wait and see.
Graihagh - So moving forward, are there any alternative batteries that we could be thinking about?
Peter - Well, there are of course things like nuclear power fuel cells of various sorts. The one that I think we probably ought to talk about is ‘energy harvesting.’ This is a concept of taking energy from the air, or from movements. So this is heat from the body, movements of the body. It’s stepping on paving slabs etc.
Graihagh - Piezo electrics. That’s what they call that moving around.
Peter - This rather cunning piece of technology I’ve got her in front of me which collects radio frequencies from the air. This is from routers, it’s from mobile phones, it’s from the screens we’ve got around us. Even the microphone, my watch, will collect that and will power things with it. It’s quite a big device I’ve got in front of me but it won’t last very long with the amount of energy, but this is the start of energy harvesting generally.
Graihagh - So let’s have a look at this. This is what, about the size of the smartphone except it’s very, very thin isn’t it?
Peter - It’s a gas sensing device and I can tell you it’s called Cleanspace - It’s a UK company. There are probably thousands of those around the place, particularly inside the M25 monitoring the pollution in the air. There is a battery in there in case it’s not picking up much RF. It will last say for five to ten years, partly charged by the radio frequency in the air.
Graihagh - Could we charge our smartphones with things like this?
Peter - It would take a very long time. In fact, I’ve worked it out that the energy from this from the manufacturer's data sheet to charge that battery would take 185 thousand years. Now, maybe my calculations wrong. It’s wearables, taking energy from our movement. Another figure I’ve worked out actually - if you were to be powered personally by AA cells - 650 AA cells would run you for a day - that’s a human being.
Graihagh - Wow!
Peter - Now some of that’s going as heat, some of it’s going as movement, some of it’s going as thought, possibly. I don’t know how much energy that takes. But you can imagine that being captured…
Graihagh - Lots Peter… to power my brain.
Peter - Let’s talk to Chris about that. Who’s got the PhD in this room? I haven’t. Collecting energy you wouldn’t miss is the thing. You would miss it of course because you still having to use it but you wouldn’t generally miss it.