There’s so much good energy flowing through the renewables revolution that it’s tempting to be hopeful about every new piece of technology because, you know, we’re all excited about the air getting clean. But with new stuff being announced almost every day it’s easy to get behind.
That’s why if you ever get the chance to collar a scientist who’s come up with a new type of battery you should jump at it. Not that it happens every day, of course.
Professor Thomas Maschmeyer of the University of Sydney has been cooking away at the secret ingredient that gives life to the Gelion Endure battery for years, and was happy to welcome EcoGeneration into his den in the School of Chemistry to explain the how it works.
The cell on the table in front of us looks like a low-profile ice hockey puck. Maschmeyer wedges the cell apart with his house key and starts to explain. The two halves are made of your everyday milk bottle plastic, with a special carbon laminate to make them conductive. To make these bits of plastic into a battery cell you simply squeeze in special gel, add a spacer, squeeze in some more gel, stick them together and that’s it. “The manufacturing process is incredibly easy,” says Maschmeyer.
Next, you stack the cells in an aluminium cylinder – 24 volts or 48 – write “+” on the top and “–” on the bottom, arrange them in series or parallel and you’re away.
So far, so good. But it’s time for a deeper explanation and the chemistry professor heads to the whiteboard. He draws two electrodes with electrons whizzing overhead. “I start off with an empty battery with zinc ion, with two positive charges on it, plus two bromide ions, so that’s electrically neutral – that’s your zinc-bromide salt,” he says.
That salt is dissolved in water to make an electrolyte. “I now transfer electrons,” he says. “The salt, when you add electrons to it, becomes zinc metal, which deposits on the shiny black electrode as a zinc mirror – very flat, very shiny.” The electrons come from the other reaction side – EcoGeneration is following so far – but after a short pause Maschmeyer anticipates our first question.
“The big question is, why, if I now have bromine here, why doesn’t that go and eat that?” he says, indicating the elemental deposits on the two charged electrodes. “Why does a battery work? It should just self-discharge.” One secret ingredient in the Gelion cell, it turns out, is the “spacer” Maschmeyer mentioned placing between the two squirts of gel. It’s actually a porous film that hinders the bromine’s short journey to the other side. The second important feature is that the bromine is tempered by a special gel. “Think of it like a special toothpaste,” he says, where the bromine is happier to stay in its local environment than yield to electrostatic instinct and react with the zinc. “We have it in an embrace, but not too tight.”
But is there still a membrane? “Not really, no.” So there are two squirts of gel with nothing in between? “Well,” he pauses, “this is now getting into IP, how we do it…”
All we can say about the gel is that it’s cheap, non-flammable and contains some organics and a special soap which helps locate the bromine. “That’s our main IP – it took years to develop”
The cell’s evolution is a fine example of how great ideas sometimes start as failed experiments. In this case Maschmeyer concedes it started when a Dutch exchange student was set the task to make a membrane from an ionic liquid, which would selectively allow some things through and block others. “Conceptually it was wonderful, it just didn’t work,” he says. The challenge for the student was then downgraded to separating two dyes. Lo and behold, it worked … a bit. “It had only conducted certain dyes which had certain charges – like ions in a battery.”
That sounds like it could be useful one day.
The student wrote up his report and got a mark – and the university had some more research for its bottom drawer. But failed experiments have a way of following circuitous routes as they bubble through the corridors of academia. And so it was for Maschmeyer one day when he was looking into flow batteries, which contain liquid electrolytes, and he saw “what you need is selective control over the transport of these ions, and then you don’t need all this flow stuff…”
He raises his eyebrows and claps his hands.
“Maybe if I make a gel out of an ionic liquid, that will do the job?”
The idea was patented and the research powered ahead.
Somewhere back in Holland, meanwhile, a graduate is missing out on the glory. But that’s the way it goes, as patents are only granted to those who have made an intellectual contribution and have “novelty”. The student didn’t look at his results and say: Why don’t we use that in a battery? That’s how it is in the world of R&D. But no hard feelings.
“It was a high-quality fail, and that’s the key,” Maschmeyer says. “When you have a high-quality fail you learn something. We knew increasingly well why it failed. I was then able to eliminate potential uses for it, knowing why it did fail. It meant I was focusing more and more on an area where it would succeed. All the dross went away.”
The bottom drawers at universities are filled with this sort of stuff, Maschmeyer says, and at any time he says between five and 10 “failed ideas” are prominent in his grey matter. When they bubble to the surface, spurred by an apparently intractable problem, students and peers turn in wonder – not knowing it’s the ol’ bottom drawer that’s been accessed.
The Gelion technology is in its early stages, with arrays of cells being tested on a couple of lighting rigs in Sydney and further applications in the works. Maschmeyer says it can be put to work from 1kWh up to utility scale, fully containerised. “That’s the beauty of it,” says Maschmeyer, who is founding director of the Australian Institute for Nanoscale Science and Technology. “With a flow battery you have to engineer for every size a different solution, because you have tanks and pumps…”
It’s too early to talk about performance statistics, such as depth of discharge, but he says the technology can manage more than 3,000 cycles at full daily discharge. Based on his faith in the chemistry, however, he hints at a much higher figure. Insurance covers seven years.
At the end of its life each cell is fully recyclable. Just throw it into a shredder, wash out soluble stuff – a salty aqueous solution containing some special soap – and recycle the rest.
An energy management system is designed to hold the battery at an excess load once every 30-40 cycles so the bromine strips all the zinc back to a virgin surface, he says, to overcome the possibility of residual build-up causing a short circuit.
“That’s why lithium batteries blow up.”