Energy storage is already accelerating the transition to wind and solar energy, and things are about to get a little more interesting. Scientists at the Energy Department’s Lawrence Berkeley National Laboratory have come up with a new bijel that could have some interesting energy storage applications. They’re still trying to find the right adjectives to describe it, but “weirdly exciting” seems to fit the bill for now.
So … what’s a bijel?
What, Exactly, Is A Bijel?
Bijel is short for “bicontinuous jammed emulsion gels.” If that sounds somewhat mysterious, it’s really not. You can almost DIY your own bijel right at the dinner table. Here’s the explainer from Berkeley Lab:
Bijels are typically made of immiscible, or non-mixing, liquids. People who shake their bottle of vinaigrette before pouring the dressing on their salad are familiar with such liquids. As soon as the shaking stops, the liquids start to separate again, with the lower density liquid – often oil – rising to the top.
The key word is almost. Those spherical droplets in your vinaigrette bottle are as close to true bijellery as you can get.
The unique feature of bijels is that the two liquids can’t separate. The particles are “jammed” at the interface where they meet. Instead of distinct droplets, they form a web of channels.
That feature provides bijels with a wide range of applications in energy storage and other areas involving catalysis, conductivity, and energy conversion — potentially, that is.
In addition to issues involving the fabrication of bijels, the main catch is that the fluid channels are too wide to be of much use in energy conversion applications.
Cracking The Bijel Conundrum For More And Better Energy Storage
That’s where Berkeley Lab comes in. You can get all the details from the journal Nature Nanotechnology under the title, “Bicontinuous structured liquids with sub-micrometre domains using nanoparticle surfactants.” For those of you on the go, here’s a snippet from the abstract:
A wealth of applications has been proposed for bijels in catalysis, energy storage and molecular encapsulation 3, 4, 5, but large domain sizes (on the order of 5 µm or larger) and difficulty in fabrication pose major barriers to their use 6, 7, 8. Here, we show that bijels with sub-micrometre domains can be formed via homogenization, rather than spinodal decomposition.
Got all that? Lead author Caili Huang provides the plain-language rundown:
Bijels have long been of interest as next-generation materials for energy applications and chemical synthesis. The problem has been making enough of them, and with features of the right size. In this work, we crack that problem.
Spinodal decomposition refers to the separation of a solution into two phases, each with a distinct chemical composition. For whatever reasons, that method typically produces useless bijels.
The Berkeley Lab team went another route, opting for a homogenization process. Referring back to that salad dressing analogy, if you could put your bottle of salad dressing in a vortex and spin it at 3,200 revolutions per minute, you will finally get your bijel. The lab’s Joe Forth explains:
This extreme shaking creates a whole bunch of new places where these particles and polymers can meet each other. You’re synthesizing a lot of this material, which is in effect a thin, 2-D coating of the liquid surfaces in the system.
The Berkeley Lab team also went against the grain with a formula based on nanoparticles of silica.
The particle-based pathway was previously not take seriously because of the difficulty in getting nanoscale bits of matter to stay in position at the interface. For a solution to that problem, the research team introduced water to the formula. In effect, they created a “nanoscale supersoap” in which the particles to form ligands, or bonds. The result was a stable shape resembling an octopus with its legs “jammed” at the interface.
Next steps include getting the bonds to hold up for long periods of time. So far about one week appears to be the limit, which is a promising start.
Yes, You Can DIY Your Own Next-Generation Bijel Energy Storage Device…Maybe
Berkeley Lab is awfully excited about the new formula. Staff scientist Brett Helms enthuses:
Bijels are really a new material, and also excitingly weird in that they are kinetically arrested in these unusual configurations. The discovery that you can make these bijels with simple ingredients is a surprise. We all have access to oils and water and nanocrystals, allowing broad tunability in bijel properties…
This is the first time that bijels have crossed the CleanTechnica radar, so stay tuned for more on that topic.
Meanwhile, the bijel field has a lot of catching up to do when it comes to next-generation energy storage, especially when it comes to cracking into the highly competitive mobile energy storage (aka electric vehicle battery) marketplace.
Other recent energy storage developments that are edging closer to commercial development include a “water battery” being pursued by the US Army, and an “air battery” supported by Toyota.
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Image: “Illustration shows key stages of bijel formation. Clockwise from top left, two non-mixing liquids are shown. Ligands (shown in yellow) with amine groups are dispersed throughout the oil or solvent, and nanoparticles coated with carboxylic acids (shown as blue dots) are scattered in the water. With vigorous shaking, the nanoparticles and ligands form a “supersoap” that gets trapped at the interface of the two liquids. The bottom panel is a magnified view of the jammed nanoparticle supersoap,” by Caili Huang/ORNL.
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