Could Zinc Gel Chemistry Outperform Flow Batteries?

Australian startup's new stationary storage tech nods to the time-tested, lead-acid cell

4 min read
Researchers at the Gelion Technologies Laboratory

Researchers at the Gelion Technologies Laboratory and Testing Facility in Sydney, Australia, working on the “gel-ion” (non-flow) zinc-bromine Gelion Endure battery

Gelion Technologies

Maybe flow batteries aren't always everything they're cracked up to be. A new technology from Australia is certainly raising this prospect, offering a novel approach to stationary energy storage—whose packaging at least harkens back to the old, familiar car battery.

Flow batteries use liquid electrolytes held externally in tanks and which circulate through the cells using pumps and piping. Their capacity is proportional to the size of the tanks, making them easily scalable. In theory, they should be a good choice for applications, such as storing surplus energy from renewables. But their reliance on mechanical components and intricate design presents drawbacks, including highly specialized maintenance needs, while flow batteries' electrolytes can be costly, corrosive or toxic. This has inhibited flow batteries from gaining widespread deployment, despite increasing improvements.

Now, Gelion Technologies, a startup based in Sydney, Australia, has found a way to dispense with the pumps and plumbing, and to eliminate other drawbacks common with conventional flow batteries by creating a non-flow zinc-bromine battery. Gelion founder and inventor of the new technology, Professor Thomas Maschmeyer at the University of Sydney, describes how it works.

"Instead of circulating fluids, the battery uses a proprietary gel, hence the company name gel plus ion." The gel enables molecular encapsulation of the bromine in a manner that is reversible, so that the bromine is still available for electrochemistry. To explain, he uses the analogy of Velcro. The “Velcro"-like gel sticks to the bromine, yet it can separate from it with a little pull when needed. "That pull in the battery is a little bit of its potential," he says.

Gel batteries, say its advocates, deliver robust, durable, non-flammable storage made from materials that are inexpensive, readily sourced, and recyclable.

Equally important, the gel ensures the bromine, which is heavy, stays well-distributed throughout the battery, reducing stratification and the formation of undesirable zinc plating called dendrites, which can cause short-circuits. In turn, fewer dendrites reduce gassing and pH drift (unwanted change in the acidity or alkalinity in the electrolyte).

"By keeping everything homogenous within the gel, it's basically dealing with all the issues addressed by flow so that they don't really arise," says Maschmeyer. Or if they arise, "they can be dealt with in the existing paradigms of battery technology. This makes for a super safe battery."

The downside of the technology compared to flow batteries is that whereas every component of the latter is serviceable or replaceable, the Gelion battery has to be entirely replaced with a new one, should it break down.

Another general disadvantage is that it is heavier and larger than lithium-ion batteries. On the other hand, lithium-ion is temperature sensitive and state-of-charge sensitive. Zinc-bromide, by contrast, "is much more robust," says Maschmeyer. "From -15 degrees to 50 degrees Celsius, no problem. Zero state of charge is also no problem, so we serve a completely different market to that of lithium-ion."

Yet Gelion's very inventiveness may make some potential customers hesitate. "The energy sector is very conservative," says Jens Noack of the Redox-Flow-Battery-Group, Fraunhofer-Institute for Chemical Technology, Germany. "New technologies generally have a hard time entering. However, they can be accepted if the lifetime price is right." He adds that non-flow technologies likely "have lower investment cost but the energy throughput is lower. So we will have to see."

“What we are good at is energy shifting. Our aim is to firm renewables, making solar and wind into baseload generation."
—Thomas Maschmeyer, Gelion Technologies

As for applications, with a charging rate sweet spot of 4 hours and a discharge rate of between 2 to 36 hours, the Gelion Endure is not suitable for quick bursts of high power, as is needed in electric vehicles or to stabilize the voltage in an electric grid.

"What we are good at is energy shifting," says Maschmeyer. "Our aim is to firm renewables, making solar and wind into base load generation." He gives the example of running a solar electrolyzer for producing green hydrogen. The Gelion battery recharges during the day, then takes over when the sun doesn't shine. "We can run electrolyzers so they operate at peak performance 24/7 with our batteries running day in day out at full charge-discharge in high temperatures. Any other battery would break down under such conditions."

"There is a need for inexpensive storage to cover the gaps caused by fluctuating renewable energies," says Noack, who is also an adjunct associate professor at UNSW Sydney. "Zinc-bromine technologies can do well due to the low cost of materials."

To commercialize the technology, the company is preparing to list on the London Stock Exchange to raise 16 million pounds sterling (US$22 million). The Gelion Endure battery will go into pilot production next year with the help of two partners, Battery Energy Power Solutions, based in Sydney, and a second larger-scale partner in India. After customer trials around the world in 2022, commercial production is expected to start in 2023. Initially, the battery is expected to have a usable energy density of at least 47 Wh/L with a specific energy of at least 37 Wh/kg. The company is also forecasting these metrics could double with further optimization.

To enable a fast ramp-up in production, Maschmeyer hit on the idea of going with a sealed lead-acid battery format that has been established for over 30 years. "It means we are able to have the zinc-bromide chemical advantages within the advantages of lead-acid packaging. Meaning our battery is made and looks like a lead-acid battery—a non-flow solid block of energy."

A major benefit of this decision is that Gelion can use existing manufacturing lines for lead-acid batteries by converting them at relatively low cost to zinc-bromine manufacturing lines, Maschmeyer points out. Gelion is also able to utilize a factory's materials handling, production operations, and the way batteries are stored and shipped, etc.

He says that their partner in India expects that with around a $16 million investment in CapEx, Gelion can change a gigawatt hour a year of the existing lead-acid production capability to the equivalent zinc-bromide production capability. That compares well, he says, to the $135 million it costs to build a greenfield gigawatt hour per year lithium-ion factory.

As for Gelion's prospects, Noack says there are many competitors with different technologies in the stationary storage sector. At the same time, the need for storage is growing exponentially. "No one technology will be able to cover all needs. I think that if the [Gelion] technology can achieve low lifetime costs, and considering its safety and environmental friendliness, then it will be able to take a share of the market."

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