Because lithium ions are so tiny, it's very difficult to see them using experiment alone.
So as a chemist, I'm lucky that my research can use more than supercomputers-- and to
model what's happening inside batteries at the atomic level.
In fact, at parties-- when I get invited, that is--
when people ask me, what do I do?
I sometimes say, I model.
And this is a computer model of the atomic structure of a lithium battery matrix.
So this is a lithium cobalt oxide electrode.
The cobalts are in purple.
The oxygens are in red.
But you can see the lithium ions zipping through between the channels.
So it's a very sheet-like structure.
And the important stuff is happening between the sheets.
So you can see the lithium ion just zipping through.
So they just indicate very fast ion motion.
So when you charge up your phone tonight, probably Snapchatting too, late in the evening--
when you see those red and green symbols, they just indicate that tiny lithium ions
are moving through a battery mattoo.
Those tiny lithium ions are moving through those sheets.
But, as you may have seen in the news recently, batteries sometimes go wrong.
They overheat and it's usually due to short circuiting.
And I should stress that this is a very rare event, considering the billions of cells that
have being sold practically every week.
So we've set up a demonstration.
And this one is so dangerous, that we couldn't actually do it in the lecture theatre.
So we're doing outside, and we're doing it-- we've set it up on the roof.
So what you see there is a lithium battery pack.
It's within a perspex box.
And right above it, you can just about see a tube.
And at the top of the tube, you'll see a giant nail.
And it's gonna go straight down into that lithium-ion battery.
And this is a serious point.
Do not attempt this at home.
OK?
It's gonna be pulled by that small string there.
That's gonna release the rod, and that nail is gonna go straight down.
So I think we need a countdown here.
All right?
Another countdown-- 3, 2, 1.
So what you're seeing there is the reaction, right on that lithium-ion battery.
So, as you can see, that is an intense reaction.
Just from that nail going right through that lithium-ion battery.
So what's happening there?
So what's happening is that the nail connects the two electrodes and short circuits the
battery.
Which makes it overheat.
And this mimics the short-circuiting caused by bad battery design.
But it's not the lithium that explodes.
It's actually something else.
It's the liquid electrolyte that sits between the two electrodes.
And that electrolyte is made up of a lithium salt in the solvent.
And that solvent is highly flammable.
And get it too hot-- and it simply erupts out of the casing.
So we're gonna see a demonstration of this, right now.
I think, Natasha-- I think we're ready, so give us a demonstration.
Great!