Published on December 10th, 2014 | by Tina Casey12
Flakey New “Foam Party” Graphene Battery Breakthrough
December 10th, 2014 by Tina Casey
Boy, does this look like fun. You got your flakes, your foam, your sheets of Kapton plastic, your laser, and you wake up in the morning with a hangover and a new type of super graphene battery. This interesting mashup comes to us by way of that dynamic duo of graphene, Rice University and the US Air Force (more on that later), so you know it’s got to be good.
For those of you new to the graphene topic, before we discovered nanocellulose fibers we were calling graphene the nanomaterial of the new millennium. Graphene is a sheet of carbon only one atom thick. This nano-slim frame provides it with exceptional strength and conductivity, dovetailing perfectly with new clean technology.
The problem is how to actually use something that is only one atom thick, and that’s where the graphene battery — the graphene supercapacitor, to be more precise — comes in.
The Rice University Graphene Battery
A supercapacitor is a type of battery that charges and discharges rapidly, so we’re going to just simplify things by calling it a battery most of the time.
The Rice team made their new graphene microsupercapacitor (same thing as a supercapacitor but smaller) using a process they call LIG, for laser induced graphene.
They solved the first problem — how to use something that is only one atom thick — by creating their graphene battery on a base of plastic film. That took some doing, as it turned out that not all plastic film is equal when it comes to graphene batteries.
They finally nailed it when they got to polyimide, a heat-resistant plastic film that’s been around for about 50 years or so.
The rest of the setup is relatively simple. Instead of trying to layer single-atom sheets of graphene onto the plastic, the team applied a porous foam of graphene flakes.
This graphene “jumble” was carefully engineered to consist of flakes with five-, six-, and seven-atom rings. If you’re familiar with the six-sided chickenwire structure of graphene sheets, the inclusion of five-and-seven atom flakes may seem like a mistake, and it is a mistake, but it is a deliberate mistake.
The five-and-seven atom rings are considered defects, but these so-called defects can be deployed as desirable, performance-enhancing features.
While not nearly as slim as a single-atom graphene sheet, the 20-micron layer of foam still possesses some of its superior qualities.
Once you plaster your graphene foam onto the plastic base, then you run down the hall to the university’s Oshman Engineering Design Kitchen and ask them if you can borrow one of their shop lasers to etch a supercapacitor into it. Calling Julia Child!
The process exposes the foam while leaving the base intact. Here’s an actual image of the end result, with that white bar in the lower right-hand corner showing the scale of one millimeter:
As for performance, here’s the rundown from Rice:
The best results showed capacitance of more than 4 millifarads per square centimeter and power density of about 9 milliwatts per square centimeter, comparable to other carbon-based microsupercapacitors, and negligible degradation after as many as 9,000 charge/discharge cycles.
Next Steps For A Graphene Battery
So, now that you have a usable form of graphene. The next question is whether or not you can scale the process up to commercial size, and then after that you have to worry about hitting a price point that will enable your new graphene battery to compete in the market.
The Rice team is pretty confident on those point. In terms of scalability, the etching is a one-step laser writing process commonly used in modern industry.
As for price, the plastic in question is inexpensive polyimide in the form of flexible sheets, which you can get under the brand name Kapton (thanks, DuPont!). The flexible base also translates into ease of handling, shipping, and application.
As an aside, the petro-plastic angle isn’t particularly sustainable but some time in the sparkly green future you could be looking at a graphene battery based on bioplastic.
Where were we? Oh, right. The whole process can take place at room temperature in a relatively relaxed environment, which cuts down on expensive furnaces and workplace controls.
Don’t hold your breath for that EV battery based on foam graphene. Rice has another graphene battery approach that seems like a more likely pathway, and then of course Tesla is eyeballing the EV graphene battery, too.
The best results so far indicate that the flexible foam battery could be used for inexpensive wearable electronic devices but stay tuned, the Tour Group is already setting its sights on some improvements.
As for that Air Force thing, the Air Force is all over graphene, partly because light + strong = perfect for flight, so it’s no surprise that the Air Force chipped in for the new Rice research along with the US Navy and other agencies.