His start-up, Gelion, wants to bring zinc bromide batteries—and more-reliable power—to remote regions
Remote communities in the Australian outback often rely on solar power—and on batteries that can reliably store that electricity, should anything go wrong with their solar panels. But temperatures in this region can exceed a sweltering 40 °C, which saps the efficiency of traditional battery chemistries such as lithium ion and lead acid.
Thomas Maschmeyer, a chemist at the University of Sydney, was awarded the 2021 David Craig Medal by the Australian Academy of Science in recognition of his work honing the chemistry of a zinc bromide battery that uses a gel electrolyte rather than a liquid one. The result is a hardier, safer, and more heat-tolerant battery. Shares of his company, Gelion Technologies, were floated on the London Stock Exchange late last year and are worth about £120 million (US$164 million) once listed, as reported by the Daily Telegraph.
Benjamin Plackett spoke with Maschmeyer about the science behind his invention and getting the batteries to market by repurposing existing battery factories. This interview was edited for length and clarity.
What is a zinc bromide battery?
OK, let me start by first explaining what’s normally in a battery. A battery basically consists of two electrodes. A chemical reaction occurs inside the battery, and electrons are transferred from one reactant to the other by oxidation at one electrode and reduction at the other.
However, when the reactants donate or accept electrons, you get a local charge imbalance. That’s called polarization, and it diminishes the battery’s driving force. So something needs to try and stop it. That’s the job of the electrolytes, which facilitate charge equalization. They are usually liquids or gels containing ions that support the redox chemistry.
In addition to electrolyte ions like chloride, sodium, and potassium, our group’s batteries also contain zinc metal and bromine. If you were to put those two chemicals into a beaker, they would spontaneously and vigorously turn into zinc bromide. They don’t want to be separate; they want to be together. That’s where our battery gets its power from. By conducting this spontaneous reaction using the two electrodes, with the electrons flowing through an outside circuit rather than directly between the chemicals inside the battery, chemical energy is converted into electrical energy.
Then, when the battery is being recharged, the opposite happens: we put electrical power into the battery to oxidize the bromide back into bromine on one electrode and then convert the zinc ions back into zinc metal on the other electrode.
So what does the gel have to do with it? What chemistry is going on in there?
Bromine is a heavy liquid, so it can sink to the bottom of the battery. This process is called stratification, and frankly, it’s an issue with this type of battery. This is where the gel comes in. It creates a three-dimensional aspect to the electrolyte’s matrix. The gel helps keep conditions homogeneous across the whole battery—up, down, left, and right.
What are the pros and cons to your approach? Why choose a zinc bromide battery over lithium, for example?
The negative, as I say, is that bromide is heavy, so our batteries are heavy too. They’re not going to be used to power mobile devices like laptops. Instead, our batteries are for stationary energy storage.
We’re also not as small as a lithium-ion battery. We’re about the same size as—maybe even a bit smaller than—traditional lead-acid batteries. That comes with something of an advantage, though: we’re constructing our product to look like a lead battery, which is an older technology. This means we can go into lead-acid factories and say, “Rather than staying in a no-growth or low-growth situation, we can repurpose this.” We estimate it would cost about $16 million to do this. By comparison, it would be about $75 million to build a brand-new factory.
We’ve partnered with a lead-acid battery firm in Sydney, and we’re building a pilot line inside their factory. Things have been delayed by COVID because we couldn’t get electricians and contractors into the factory, but we expect to start putting that together in early 2022. Then after some fine-tuning, it will be a cookie-cutter process.
Also, the zinc bromide redox chemistry isn’t strongly affected by temperature. In fact, it works well at 35 °C, and then we lose only about a percent or two of efficiency at 55 °C, which is amazing. This makes our technology particularly relevant for off-grid remote communities that experience very hot summers, such as the Australian outback, where the batteries could be hooked up to solar panels.
How far have you tested this heat tolerance?
We’ve put the battery on a 600 °C hot plate to see what happens. We know what would happen with lithium batteries: they’d blow up. The plastic casing of our battery of course melted, and then it started to smoke a bit and got close to catching fire. Then the electrolytes swelled out, and that stopped any fire from happening, and the smoke reduced. There was no explosion, no large release of bromine vapors. It was all very contained. No other battery can do that.
The brominated components in our batteries suppress fire—unlike the organic solvents in lithium-ion batteries. If there were a fire, we have the stuff inside the battery to put it out.
These robust properties are important because in truth the real cost of batteries isn’t really in the hardware itself; it’s the maintenance. If you’re in the middle of the desert, it costs a lot and takes a long time to get someone to come out and service or repair it.
Source: acs
