Stanford developed streaming batteries operating at room temperature.

Sodium-potassium melt is in stream batteries at room temperature, allowing you to get devices with high operating voltage. Source: Antonio Baclig

As we know, in recent years, the renewable energy sector has been rapidly developing, and therefore additional storage capacity, cheap and capacious, withstanding many recharge cycles and capable of quickly and efficiently delivering energy back to the network, are constantly required. Researchers at Stanford University believe that they can solve this problem by using a new application of several widely used materials.

Stream batteries are known for a relatively long time and have been repeatedly considered as a candidate for creating large capacity storage facilities, but the electrolytes used in them either have voltage limitations or require high temperatures to maintain a liquid state, or they are very expensive or extremely toxic components.

However, Stanford Associate Professor William Chewy, together with his graduate students Antonio Backlig and Jason Ragolo, developed for the “cathode” flow an alloy of sodium with potassium, which remains in the liquid phase at room temperature, and theoretically makes it possible to store 10 times more energy per gram of mass than any another electrolyte.

“Of course, there is still much to be done,” says Bucklig, “But we hope that thanks to this project, people will more often prefer solar panels and wind turbines, as they will receive a battery based on the elements present in the earth’s crust in abundance.”

We divide the parties

Also in the process of experiments, a ceramic membrane of sodium and aluminum oxide was developed, which does not interfere with the ion exchange between the “electrodes” and at the same time quite reliably separates the anodic and cathodic streams. As a result, the operating voltage doubled compared with the known samples (3.1–3.4 V vs. 1.5 V), and the parameters of the prototype remained stable even after several thousand hours of tests; in addition, increased operating voltage means the ability to store more energy.

“Of course, our work has yet to be assessed by a variety of parameters - cost, efficiency, number of operating cycles, dimensions, safety,” explains Bucklig. “Nevertheless, we believe that we will surpass existing stream batteries in all respects and therefore we look to the future. with enthusiasm. "

Real progress is still ahead

At the moment, the team of graduate students - Bucklig, Ragolo, as well as Jeff MacConaughey and Andrei Poletaev - continues to work on the membrane because it does not sufficiently prevent potassium from diffusing into the anode flow, and this is very critical for normal battery operation; in addition, the original part functioned best at about 200 degrees Celsius, which is unacceptable. In an attempt to maintain the desired properties at room temperature, the researchers tried thinner variants (∼330 µm) and achieved quite acceptable results, while also increasing the output power; Thus, further experiments will be conducted in the field of selection of the most suitable membrane.

You also have to choose the appropriate anodic electrolyte - unfortunately, water-based mixtures quickly bring the membrane down, so you will need to use some other liquid to further increase battery performance.

The final study was published in an article in ScienceDirect on July 18.