Salt batteries: The fireproof battery

In 1997, the Mercedes-Benz A-Class famously tipped out of a bend throughout the elk check. One of many causes of the notorious incident: The automobile was initially designed to be electrical. Switching to a combustion engine eradicated the heavy battery, ensuing within the heart of gravity shifting too far upwards.

The battery that ought to have been put in within the A-Class was a so-called salt battery. In distinction to most different batteries, during which the cathode and anode are immersed in a shared pool of liquid electrolyte, the electrolyte in a salt battery is a strong, specifically a ceramic ion conductor primarily based on sodium aluminum oxide.

The strong electrolyte is non-flammable and permits the anode and cathode to be separated, which will increase the service lifetime of the battery. The cathode of a salt battery is predicated on granules of frequent salt and nickel powder; the sodium steel anode is just fashioned throughout charging.

For electromobility, this battery expertise has not confirmed to be the most effective answer. At present’s electrical vehicles run on lithium-ion batteries, that are lighter and faster to cost. Nevertheless, for different purposes, salt batteries are superior to their lithium-ion rivals. Because of this, they’re the topic of ongoing analysis—at Empa, amongst different websites.

Secure and sturdy

The analysis collaboration started in 2016 when the Ticino-based salt battery producer HORIEN Salt Battery Options, previously referred to as FZSoNick, approached Empa. The corporate needed to enhance the ceramic electrolyte consisting of sodium aluminum oxide, often known as beta-alumina, in its battery cells as a part of an Innosuisse challenge. This led to additional initiatives on the cell geometry and electrochemistry of the salt battery, because it differs significantly from different battery sorts.

“The assembly of salt battery cells for research purposes is very complex and there are hardly any studies on their exact mechanisms of action. That’s what makes these projects so interesting for us: We can learn a lot and develop our understanding together with our industrial partner,” says Empa researcher Meike Heinz from the Supplies for Vitality Conversion laboratory, headed by Corsin Battaglia.

This totally different cell construction provides salt batteries some benefits over lithium-ion batteries, for instance by way of security. Though salt batteries want an operating temperature of about 300°C, they will neither burn nor explode. That is why they’re additionally utilized in locations the place lithium-ion batteries should not even permitted, resembling in mining and tunnel development and on offshore oil and gasoline manufacturing platforms.

Because of their excessive working temperature, salt batteries are additionally a lot much less delicate to temperature than their lithium-ion counterparts. This makes them ideally suited emergency energy storage techniques for critical infrastructureresembling cell phone antennas. Even in distant and uncovered areas, the long-lasting and maintenance-free salt batteries can do their job reliably for many years.

Nevertheless, the working temperature can be a drawback of this battery expertise: Salt batteries want energetic heating to be prepared to be used. How can a battery that wants electrical energy be in any respect cost-effective?

“Depending on the application, it is more efficient to keep a battery warm than to cool it,” explains Heinz. “Heat is generated during charging and discharging due to the cell’s resistance. In an optimal system, a large battery can heat itself,” provides Empa researcher Enea Svaluto-Ferro.

Cell chemistry for the longer term

As supplies scientists, Heinz and her workforce give attention to cell chemistry. Many of the raw materials for salt batteries are cheap and accessible in giant portions. The structure of the cell additionally makes it straightforward to recycle.

Nevertheless, because the cathode materials, nickel, is more and more being labeled as essential, HORIEN and Empa set about lowering the nickel content material of the cells as a part of the challenge HiPerSoNick. This was no straightforward job, because the composition and microstructure of the cell should be very exactly coordinated to make sure an environment friendly and long-lasting salt battery.

As a part of the EU challenge SOLSTICE, which runs till mid-2025, HORIEN and Empa, along with different challenge companions, are investigating whether or not the nickel in molten salt batteries may even get replaced totally by zinc. “The low melting point of zinc is a challenge at the current operating temperature,” says Heinz. Nonetheless, the researchers have already discovered promising approaches to stabilize the cathode microstructure.

Extra follow-up initiatives during which the Empa workforce will try and additional enhance—and scale up—nickel-free salt batteries are already in planning. In any case, their security, lengthy service life and avoidance of essential uncooked supplies would make salt batteries ideally suited for stationary storage. If salt batteries could be produced cheaply and in giant portions, they might sooner or later present electrical energy not solely to cell phone antennas however to total residential areas.