Australian researchers make water battery breakthrough

Researchers at RMIT University have found a way to replace the electrolyte in lithium-ion batteries with water, an innovation that could remove the fire risk from the devices entirely. 

So far, the team has created button-sized batteries that have achieved an energy density of 75 watt-hours per kilogram (Wh kg-1), or 30 per cent of the latest Tesla car batteries.

“We use materials such as magnesium and zinc that are abundant in nature, inexpensive and less toxic than alternatives used in other kinds of batteries, which helps to lower manufacturing costs and reduces risks to human health and the environment,” says lead researcher, distinguished professor Tianyi Ma.

“What we design and manufacture are called aqueous metal-ion batteries – or we can call them water batteries.

“Addressing end-of-life disposal challenges that consumers, industry and governments globally face with current energy storage technology, our batteries can be safely disassembled and the materials can be reused or recycled.”

The RMIT team isn’t the only Australian group looking at aqueous batteries. 

In January, UNSW researchers made a breakthrough with aqueous rechargeable zinc battery (AZB) technology, after they too found a way to solve the dendrite problem. 

Lithium-ion batteries have long dominated the market, from the tiny devices that run the smallest electronics right up to grid-scale energy storage systems. 

But for all of the pros, which include excellent energy density and known, mature chemistry, they used expensive materials and when they catch fire can create a thermal runaway, which is where the heat from the flames creates a chemical reaction that creates even more heat and ever more chemical reactions in a disastrous spiral.  

Ma says the so-called water batteries are at the cutting edge of an emerging field of aqueous energy storage devices, with breakthroughs that significantly improve the technology’s performance and lifespan.

Water replaces the usual organic electrolytes in metal-ion batteries, a process that came with its own challenges including the formation of dendrites, or spiky crystal growths on, in the case of this particular research, the zinc anode. 

Dendrites can cause batteries to short circuit.

To cure this problem, the team coated affected battery parts with a metal called bismuth and its oxide (otherwise known as rust) as a protective layer to prevent dendrite formation.

“Our batteries now last significantly longer – comparable to the commercial lithium-ion batteries in the market – making them ideal for high-speed and intensive use in real-world applications,” Ma says.

“With impressive capacity and extended lifespan, we’ve not only advanced battery technology but also successfully integrated our design with solar panels, showcasing efficient and stable renewable energy storage.

“The next step is to increase the energy density of our water batteries by developing new nano materials as the electrode materials.”

Ma believes that magnesium-based water batteries could replace lead-acid storage in the space of one to three years, and give lithium-ion a new rival within five to 10 years, for applications from the smallest to the largest version of energy storage.