Recyclable Batteries on the Horizon Replacing Organic Electrolytes with Water

Water Batteries & Fire Safety

For years now, Lithium-ion batteries have been the dominant form of battery on the market, both for electronics and for EVs. This is thanks to their exceptional profile in terms of energy density, and overall safety. But when they fail, they tend to do so in a spectacular fashion, with very intense fires that are hard to put out. This is also an issue when the batteries are at the end of their life and need recycling.

A worst-case scenario is when one battery failure causes a cascade of fire on adjacent batteries, a very real concern when it comes to building battery parks with lithium-ion for large utility-scale systems. The fire risk in lithium batteries mostly comes from the flammable organic electrolytes used to connect the anode and cathode of the battery.

Researchers at the RMIT in Australia might have found a solution by replacing the electrolytes with water. The team is led by Prof. Tianyi Ma (left), who worked on the project with Dr. Lingfeng Zhu (right).

Source: RMIT

The so-called water batteries, or aqueous metal-ion batteries, are unable to start a fire or blow up. They are also very low in toxicity for both humans and the environment.

Water Battery Promises

The design of water batteries relies on simple elements like zinc and magnesium, which are abundant and with low toxicity, reducing manufacturing costs and making them easy to mass produce.

In practice, this means that water batteries can come in several forms. For example, it is in the shape of a magnesium-ion battery or ammonia-ion.

And Prof. Tianyi's team is working on making these batteries commercially viable by solving the details that have hindered their adoption so far.

One example is the improvement of a manganese electrode, creating capacitors using Magnesium and manganese and achieving “a 128.39 Wh/kg with an ultra-long cycling capability, giving 85 % capacitance retention after 6000 cycles“

The outstanding electrochemical properties, and the critical safety implications of an aqueous electrolyte, make this aqueous MIC promising for large-scale energy storage applications. Moreover, the strategy of the cation-anion dual defects construction concept should provide essential insights into fabricating rechargeable metal-ion-based batteries.

Source: Energy Storage Material

Solving Dendrites

Another issue experienced by most batteries is the progressive growth of dendrites in the batter. Dendrites are spiky metal structures that can, over time, create shortcuts (and fire in the case of lithium-ion). Water batteries are also vulnerable to the issue of dendrites.

By coating the metal parts of the battery in bismuth, it creates a protective layer blocking the formation of dendrites.

This makes the new batteries significantly more durable than lithium-ion batteries, making them fit for intensive use like utility-scale battery packs, or maybe even commercial vehicles. Especially as they are much safer, they are resultingly a good candidate for growing the selection of alternative chemistries to lithium-ion, especially for utility-scale (something we explored further in our article “The Future Of Energy Storage – Utility-Scale Batteries Tech”, including which companies are working on making them at a commercial scale).

“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.”

Pr Tianyi Ma

Are Water Batteries the Way Forward?

Utility-scale batteries will likely be radically different from EV batteries, as the two do not operate under the same constraints:

• EV batteries must be light and small, very energy-dense, and charge quickly.
• Utility-scale batteries must be cheap, very durable, stable/safe, and rely on abundant materials that can be sourced in massive amounts.

And even in the field of utility-scale batteries, several chemistries will likely share the market for years, if not decades.

This is because each will have its own advantages and use cases, like different timeframes, storing energy for the night/day cycle or for weeks at a time.

And because in any case, mass adoption of renewables means mass adoption of batteries, and diversifying materials will avoid a price shock on metals that are not rare, but not in massive oversupply either, like:

• Zinc (zinc batteries)
• Magnesium (magnesium-ion)
• Manganese (metal hydrogen batteries)
• Vanadium (redox flow batteries)
• Antimony (molten metal batteries)
• Sulfur (sodium-sulfur batteries)

There are currently no companies working on bringing magnesium-ion batteries to the market. But this might change soon, considering the various other chemistry combinations that are progressing toward mass production.