New Manufacturing Method For Graphene-Based Capacitors

While a couple months old; I have neither seen mention of this nor found it via search (famous last words...).

I must admit, the prospect of this is very interesting to someone with hobby projects in electronics - such as myself.

For those who don't know what a capacitor is: A capacitor works in mysterious, magical ways (for all intents and purposes) that make them nearly identical to a battery in function. The only real difference between the two is that a capacitor's voltage will drop linearly through its discharge cycle (well, it's actually a hyperbolic function... but that's more than most of you care about).

Anyway - the principle is that it stores power so that it can be used later. You can charge them very quickly - hundreds to thousands of times faster than a battery, and recharge them indefinitely (some of the solid state capacitors out there outlive the children of the people who made them). However, the key restriction has been that of total power storage (and the very rapid rate of self-discharge by comparison to batteries - though in a world where we recharge our cellular phones daily - that's an academic distinction). Capacitors, while they can provide absolutely massive amounts of power almost instantly, cannot provide much in terms of total energy - being able to hold only a fraction of what a battery can for the same size and weight.

Enter the savior of seemingly everything electronic - graphene. It's the new silicon, steel, and kevlar, for the respective industries; the Jesus of materials science (or so one gets the impression when reading about it).

Graphene, or forms of it, has the distinct advantage of being able to form very small structures capable of boosting the surface area of capacitors by unimaginable proportions. Since capacitors operate on electrostatic principles largely tied in to surface area - graphene has been demonstrated to have very, very powerful ramifications for the world of capacitors that would make the chemical battery, as we know it, a niche application.

But graphene, while cheap in material - is expensive in manufacturing. It's difficult to produce pure graphene.

Some researchers at UCLA have, apparently, found a method of producing crude - yet functional and industrially viable graphene.... using a once-was technology known as Light Scribe and a DVD burner. Yeah - that was my reaction, too.

www.sciencedaily.com...

The process is based on coating a DVD disc with a film of graphite oxide that is then laser treated inside a LightScribe DVD drive to produce graphene electrodes.

Additionally, LSG electrodes are mechanically robust and show high conductivity (>1700 S/m) compared to activated carbons (10-100 S/m). This means that LSG electrodes can be directly used as supercapacitor electrodes without the need for binders or current collectors as is the case for conventional activated carbon ECs. Furthermore, these properties allow LSG to act as both the active material and current collector in the EC. The combination of both functions in a single layer leads to a simplified architecture and makes LSG supercapacitors cost-effective devices.

And to think... I scoffed at Light Scribe as being gimmicky and faddish.

wow Aim that is truly amazing.... so what are the implications for this? It says they can create the graphene electrodes what about other parts of the capacitor? or do you only really need electrodes to make a capacitor? If this technology takes off will it result in super capacitors to run cars and etc?

reply to post by roguetechie


You know they could always thin-film them on a web process. Convert during the process and wrap the thin film graphene sheets onto a semiconductor thin film layer with the entire thickness around 100nm. Then they could roll that up into a battery shape with all the electrode connections at the top and bottom of column. If they wanted to make it even better, they could use a selective process to increase the porosity of the graphene, filling the sheet with tiny holes and valleys which would increase the surface area and therefore for the energy storage density by 10 to 1000 times.

Cheers - Dave

reply to post by roguetechie

so what are the implications for this?

It's a mixed bag. Currently, there aren't any similar industrial setups to simply merge these types of advances into. ... For example - a lot of the upgrades in technology have been very linear in terms of manufacturing. Robotic machines can be more accurate and perform more complex tasks - reducing time, improving reliability, etc - but you can, basically, drop a robotic machine into a shop that used to be primarily operated by hand presses without having to completely rethink your industry.

In that respect - several things have to come together. First - while the use of Light Scribe burners is interesting and of importance to the hobbyist; it is hard to envision a cost-effective super-capacitor industry being built around masses of Light Scribe burners. More dedicated laser lithography devices need to be developed for this purpose and applied to large sheets of graphite oxide before such a scheme would be viable.

The next would be a cost effective packaging. Personally - I see the flexible trait as gimmicky in light of current battery uses. A solid battery (like the Lithium-Ion in your cell phone) with a very strong dielectric material (as opposed to a flexible one - though that may not be exclusive) would be far more useful and offer higher nominal voltages with better capacitance. Flexible is cool - but doesn't have much of a market at present.

In either case - they are going to have to stack hundreds - even thousands of these layers together to create a viable battery-replacing capacitor. Alternatively - they can bind it to flexible substrates while winding it around a spool (which will be the more likely solution). Both solutions will provide a functioning capacitor, but may not necessarily be cost-effective. Some serious process engineering will have to go into developing it into a cost effective solution.

The real implication, for the time being, at least - is that for those who can put forth the time, effort, and a little money (graphite oxide is not all that expensive) can potentially build some very capable energy storage devices.

It says they can create the graphene electrodes what about other parts of the capacitor?

They are talking a little above their audience, in many regards. Usually, in other capacitors, a metal conductor of some kind must be used to interconnect the activated carbon used in electrolytic capacitors. That's because activated carbon doesn't have much in terms of conductivity (but it does have a lot of surface area - more than metal films do). This graphene material, however, is quite conductive - so much so that no other support materials are required. Basically - a simple metal lead can be connected to the graphene - and the capacitor will work just fine.

Or... so I interpret.

If this technology takes off will it result in super capacitors to run cars and etc?

In a simple word - yes.

Keep in mind - this is still being developed - but one of their top preliminary designs (in terms of power storage) was able to store 276 Farads per gram at a nominal 4 volts. Roughly speaking - that's about 5 times the energy density of the top Lithium Ion technologies available. Realistically - it would be reduced to 3 or 4 times by time you incorporated thermal management and other support materials - but that beats the absolute piss out of everything else out there.

Even if they were to be on a one-for-one with Lithium Ion - or slightly below... the longevity and quick charge/discharge aspects make them ideal for high power applications (where their 1-3% self-discharge per day is not much of an issue).

There would be some specifics to work out - such as the less than desirable voltage drop-off that comes with capacitor discharge - but that would be managed with support circuitry that is no more complex or costly than the current circuitry used to manage the very temperamental lithium batteries currently in use.

So - basically - yes. Give this ten years (... I know - "But it's right there, Aim!") to make it through the industrial hurdles and the approval of the three government agencies who have a death-grip on the auto industry... and we'll have practical electric cars.... tentatively.

A better article I found:

www.gizmag.com...

That is pretty amazing... here's hoping we see this on store shelves ten years from now.... At that rate they'll beat EEStor to the punch LOL.

reply to post by roguetechie


Personally, I found myself a new hobby project.

I'll have to research the patents before I get any crazy ideas to start trying to sell capacitors produced in that method, though. That's one of the little 'secrets' to UCLA's funding... they hold a #-ton of patents and collect royalties.

I prefer dealing with lawyers on my terms, not other people's.

For graphene mass production you'll be looking for something like this
www.niu.edu...

for large sheets
blog.case.edu...

But yeah pretty exciting stuff graphene is.