New eco-friendly electrolyte design boosts lithium metal battery performance

The newly-developed method uses fluorinated cations as a vehicle to transport fluorine to the protective layer. As a result, the protective layer remains stable, fluorine use is minimized, production costs are reduced, and the battery is rendered more sustainable. Credit: ETH Zurich / Chulgi Nathan Hong.

Researchers at ETH Zurich have made a significant breakthrough in lithium metal battery technology that could dramatically increase the range of electric vehicles and reduce the frequency of recharging for devices like smartphones.

This new development focuses on creating a more environmentally friendly electrolyte that requires far less harmful fluorine.

Lithium metal batteries are seen as the future of high-energy batteries because they can store at least twice as much energy as the commonly used lithium-ion batteries.

This means electric cars could travel twice as far on a single charge, and smartphones wouldn’t need to be recharged as often.

However, lithium metal batteries have a major drawback: they need large amounts of fluorinated solvents and salts in their liquid electrolyte to function properly.

Fluorine is harmful to the environment, making these batteries less eco-friendly.

Without fluorine, the batteries would be unstable, stop working after a few charges, and be prone to short circuits, overheating, and even catching fire.

Professor Maria Lukatskaya and her research team at ETH Zurich have developed a new method that drastically reduces the amount of fluorine needed in lithium metal batteries.

This new approach not only makes the batteries more environmentally friendly but also enhances their stability and cost-effectiveness.

Their work has been published in the journal Energy & Environmental Science, and they have applied for a patent.

The fluorine in the electrolyte helps form a protective layer around the metallic lithium at the battery’s negative electrode.

This layer is crucial because it prevents continuous reactions between the lithium and the electrolyte, which would otherwise deplete the electrolyte and cause the battery to fail.

Without a stable layer, lithium metal whiskers called dendrites can form during recharging, potentially causing short circuits and fires.

The researchers’ new method uses electrostatic attraction to bring fluorine to the protective layer. This technique requires only 0.1% by weight of fluorine in the electrolyte, which is 20 times less than previous methods.

One of the main challenges was finding the right molecule that could carry the fluorine and then break down under the right conditions once it reached the lithium metal. The advantage of this method is that it can be easily integrated into existing battery production processes without additional costs.

The team tested their method on coin-sized batteries in the lab. The next step is to scale up the process and test it on larger pouch cells, like those used in smartphones. If successful, this new electrolyte design could lead to greener, more efficient lithium metal batteries, benefiting both the environment and consumers.

This breakthrough brings us closer to a future where electric vehicles can travel further on a single charge and our devices need less frequent recharging, all while being kinder to the planet.