New recyclable water batteries stay cool under pressure

A global team of researchers  led by RMIT University have invented recyclable ‘water batteries’ that won’t catch fire or explode.

Lithium-ion energy storage dominates the market due to its technological maturity, but its suitability for large-scale grid energy storage is limited by safety concerns with the volatile materials inside.

Lead researcher Distinguished Professor Tianyi Ma acknowledged the other and equally important benefit of these water batteries is the ability to be recycled.

“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,”

Ma said their batteries were at the cutting edge of an emerging field of aqueous energy storage devices, with breakthroughs that significantly improve the technology’s performance and lifespan.

“What we design and manufacture are called aqueous metal-ion batteries, or we can call them water batteries,” he said.

Ma said the team’s batteries were well suited for large-scale applications, making them ideal for grid storage and renewable energy integration, especially in terms of safety considerations.

“As our technology advances, other kinds of smaller-scale energy storage applications such as powering people’s homes and entertainment devices could become a reality.”

The team enables the flow of electric current between the positive and negative terminals by using water to replace organic electrolytes, meaning their batteries can’t start a fire or blow up.

Ma explained that the simplicity of manufacturing processes for their water batteries helped make mass production feasible.

“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,” he said.

The team has made a series of small-scale trial batteries  to tackle various technological challenges, including boosting energy storage capacity and the lifespan.

T hey’ve triumphed over  the growth of disruptive dendrites which can lead to short circuits and other serious faults, through coating affected battery parts with a metal called bismuth and its oxide (otherwise known as rust).

Ma said this method resulted in a significant breakthrough.

“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,” he said.

“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 team’s water battery is closing the gap with lithium-ion technology in terms of energy density, with the aim of using as little space per unit of power as possible.

“We recently made a magnesium-ion water battery that has an energy density of 75 watt-hours per kilogram (Wh kg-1) – up to 30% that of the latest Tesla car batteries,” Ma said.

Ma conveyed the large potential of the water batteries and why his team’s future plans with these batteries includes magnesium.

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

“Magnesium-ion water batteries have the potential to replace lead-acid battery in the short term, like one to three years, and to replace potentially lithium-ion battery in the long term, 5 to 10 years from now.”

“Magnesium is lighter than the alternative metals, including zinc and nickel, has a greater potential energy density and will enable batteries with faster charging times and better capability to support power-hungry devices and applications.”

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