Energy

Liquid metal feeds Stanford's new high-voltage flow battery

Liquid metal feeds Stanford's ...
Engineers at Stanford have developed a new type of flow battery using a metal mixture that remains liquid at room temperature
Engineers at Stanford have developed a new type of flow battery using a metal mixture that remains liquid at room temperature
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A diagram demonstrating how the Stanford team's new liquid metal flow battery works
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A diagram demonstrating how the Stanford team's new liquid metal flow battery works
Researchers on the new battery design team, from left: Geoff McConohy, Antonio Baclig and Andrey Poletayev
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Researchers on the new battery design team, from left: Geoff McConohy, Antonio Baclig and Andrey Poletayev
Engineers at Stanford have developed a new type of flow battery using a metal mixture that remains liquid at room temperature
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Engineers at Stanford have developed a new type of flow battery using a metal mixture that remains liquid at room temperature

Flow batteries have the potential to help store energy on a large scale, and might be particularly useful to back up renewable energy sources, but there are a few issues still to overcome. Engineers at Stanford have developed a new type of flow battery that might be scalable, safe, efficient and inexpensive, using a metal mixture that remains liquid at room temperature.

In a flow battery, the cathode and anode are in fluid form and are kept in external tanks, to be pumped into the main cell of the battery when needed. There, the two liquids are separated by a membrane that selectively allows them to exchange electrons to either charge or discharge the energy.

These devices may be able to store huge amounts of energy in future, but the chemicals used are often toxic, expensive, and difficult to handle. The Stanford team designed the new flow battery to overcome those problems, using a unique combination of materials.

A diagram demonstrating how the Stanford team's new liquid metal flow battery works
A diagram demonstrating how the Stanford team's new liquid metal flow battery works

First and foremost, the fluid used as the negative side of the battery is an alloy of sodium and potassium. This mixture remains a liquid metal at room temperature, and theoretically packs at least 10 times the energy density of other fluids previously suggested for the role. On the positive side of the cell, the team tested four different water-based liquids.

The second new material is in the membrane used inside the cell. The team made a ceramic membrane out of potassium and aluminum oxide, which keeps the positive and negative fluids separate while still allowing current to flow between them.

The combination of the new anolyte and the new membrane, reportedly produces twice the maximum voltage of other flow batteries, which means a better overall energy density and lower production cost. The prototype the team developed also proved its stability over thousands of hours of operation.

"A new battery technology has so many different performance metrics to meet: cost, efficiency, size, lifetime, safety, etc.," says Antonio Baclig, co-author of the study. "We think this sort of technology has the possibility, with more work, to meet them all, which is why we are excited about it."

To further improve the battery design, the researchers say in future they could tweak the membrane thickness, or use a non-watery liquid for the positive side of the cell.

The research was published in the journal Joule.

Source: Stanford University

5 comments
MD
Liquid Sodium and potasium.. should go well with an aqueous solution in the event of a fuel cell failure... BOOOM... anyone ??
Kpar
Hey MD, they SAID it was safe, right?
ljaques
"We think" + "with more work" ? Higher voltage density, but what about current? What is the actual power density? Why is this being released before you've had a chance to tweak it and give some actual figures for power density, folks? Oh, it's an overture to induce angels to throw money at them. I get it.
Don Duncan
Over the last 35 years I have read about 100s of battery or PV break throughs. Not one panned out. I used to go to all the energy fairs and listen to the pitches for funding by guys in white coats/black horn-rimmed glasses and I almost fell for their con a few times. I offered to invest in a flying car and a new BEV in Sacramento about 30 years ago. I later met people who did and lost everything. I listened to my inner voice and backed out. Guess what? I still want a BEV + a PV array to charge it up and power my house + a house battery so I won't need the grid. Yea, I dream on but my love of math keeps me grounded, keeps me from throwing away money.
Ralf Biernacki
If metallic sodium and potassium are so much less "toxic, expensive, and difficult to handle" than the previous materials, then I shudder to think what they used to use.