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Author: Subject: The Robert Murray-Smith Battery
aga
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[*] posted on 21-11-2016 at 14:01
The Robert Murray-Smith Battery


Bob does a whole load of videos documenting a battery design using graphene-type material on utooob, such as this one :
https://www.youtube.com/watch?v=ggLFG_dRDoc&t=8s

Not found out how to view his videos in sequence, nor how to even find the first in that sequence.

Somehow i feel that the toasted bread experiments done by violet sin et al are kind of in a place to replicate Bob's experiments.

Call it Lizard Alien tech if you will.

It still looks like a very promising avenue worthy of research.

Going from Toasted Bread to Battery ?

That would be amazing.




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[*] posted on 21-11-2016 at 15:20


Another battery referenced from the Robert Murray-Smith video comment section.
https://news.vanderbilt.edu/2016/11/02/making-high-performan...

From the Vanderbilt article comment section
"Don't know why my last post was removed by vanderbilt, but lets suppose
it was accidential. The supplement with all the practical details is
available for free from:"
http://pubs.acs.org/doi/suppl/10.1021/acsenergylett.6b00295/...

[Edited on 21-11-2016 by Morgan]
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[*] posted on 7-12-2016 at 15:58
RMS EESD Work Outline


Hello - been following RMS for a while - thought I'd post a rough outline here and with some of this forums collaboration / agreement send it to Rob for posting on his sight if he pleases.....intent is to try and organize his work so that others spend less time coming up to speed and together can better understand and experiment on our own in this 'fun' space.

1. Initial EESD work based on a symmetric super cap made from Aluminum foil or grafoil current collectors, coated with electrode materials either Activated Carbon ink, AC, or graphene oxide ink. Rob's simple inks consist of a carrier like water if PVA is the binder or Acetone if ABS is the binder. Current collectors are dipped or sprayed with electrode material. These form a sandwich with separator material in the middle 'soaked' with electrolyte. Electrolytes are water based (1.2V charge limits) or other (ionic liquid?) typically in the 2.5 to 2.7V charge range. Typical of his original separator materials were paper based. Others such as polypropylene (from lead acid battery salvage) or his proprietary recipe for a cast and calendared poly???
2. Original demo cells were as much as 4F with the AC electrodes, 1cm>2.
3. Next came larger versions with preproduction of a major modification where the electrode material was printed not on the current conductors but onto one or both sides of a paper separator. Stated that separator was 'soaked' with electrolyte via porosity of electrode ink. Nice video of about 600 sheets of printer paper EESD powering an electric scooter. I believe these were Graphene ink coated. Electrolyte ?? but 2.5V/cell.
4. There then there were a few videos on other materials to make graphene besides graphite - like hemp. Not sure where that fits in with the latest EESD work.
5. Rob is now showing a new EESD he calls a 'battery' that eliminates the grafoil current collectors - mixes up a magic electrode that is highly conductive so it becomes its own current collector - printed ? onto substrate ? - that is highly flexible and strong. Rob showed a 'plan' to make rolls of same fit into form factor of Type27 battery case. For this battery I think he still has a water based neutral (NaCl?) electrolyte. Not sure if there are more or less power from a double layer cap or some Faraday type reaction.
6. Note how things have progressed back and forth relative to the electrodes- carbon material bonded to current collectors, carbon material bonded to separator, and now a unitized current collector/electrode material. Great work.
edit here:
7. Please add something here on how his reference to a type B or type C design match up to any of the above - must have misted that in the vids somewhere.




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[*] posted on 8-12-2016 at 01:00


Hi Geekineer, and thanks for that list which puts RMS's battery videos into some kind of order.

Hopefully soon there will be a simple-to-follow write-up, as/when time allows.

That will enable anyone to replicate RMS's experiments.




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[*] posted on 8-12-2016 at 14:59


OK. Re-watched three RMS videos relating to his battery/capacitor series and made some notes.

The idea is to put his videos into some kind of write-up so anyone can actually have a go at making batteries/super-capacitors according to some starting recipe/documented and tested procedure.

The notes posted below are simply what i wrote down while watching each video.

If you wish to assist by watching a video in that series and noting down anything, then posting those notes, please do.

--------------------------------------------------------------

How To Make A SuperCapacitor - Step By Step

Published on 18 Feb 2016

https://www.youtube.com/watch?v=1Ce2au3PWnI

3 parts. One a graphene super-capacitor, the other an activated carbon super-capacitor.

Coconut fibre said to be good for activated carbon.

Activated carbon generally used due to huge surface area.

Separators tried : bog roll, kitchen towel, paper, others.

Electrolytes: sodium sulphate, phosphoric acid, sulphuric acid,
lithium hydroxide, potassium hydroxide, sodium hydroxide, sodium chloride, others.

Build scene :

3 jars:-
One with graphene oxide. (? says a video exists)
One has activated carbon, ground, acetone carrier.
Graphoil/Graphoyl ?

Dip-coat X in the AC. Allow to dry.
(MnO2 possible for other side)

Scrapes off some graphene oxide from X.

Small slice of X, kitchen towel, some sodium sulphate, small slice of the AC material.

Charge at 1.2V, 1 min

Outputs 45mA briefly.

Cell area is 1cm<sup>2</sup>

AC version measures 0.144 Farad

Graphene version measures 3.95 Farad

--------------------------------------------------------------

Graphene - A Simple Method For Mass Production

Published on 23 Jul 2016

https://www.youtube.com/watch?v=gcwCGRXVHzQ

PSU
0.5M sodium sulphate
Electrodes : SS, Graphite
SS -ve
Graphite +ve
2v for 2 mins
then increase to 10v. Can see graphene peeling off, and gas formation.

Graphene 'worms' come off the anode. Leave for 30-60 mins

"Intercolating the suphate, then exploding it" is said (?)

Filter then wash the graphene nanoplatelets (not done in video)

Zap in ultrasound cleaner for 1hr-1hr 30 mins.

This Breaks the nanoplatelets into 80% 1 to 3 layer graphene flakes.

Result is a beaker of black graphene mush.

This process is considered 'gentle' resulting in a solution of relatively large graphene flakes.

--------------------------------------------------------------

Structured Carbon Battery - An Update

Published on 18 Nov 2016

https://www.youtube.com/watch?v=ggLFG_dRDoc

Button cells.

Previously used current-collector -> active material -> separator -> active material -> current collector.

Decided to change the binder system, which is poly vinyl acrylate or or poly vinyl alcohol (based on wood glue).

In LiPO batts they use a 70/30 mix of carboxymethyl cellulose / styrene butadene rubber.

CMS = wallpaper paste).
SBR = concrete additive.

"After we 'calend' it (@5:44) we got a tough material" ?

Now using active material, separator, active material, no current collectors, but he says there is one on the top ?

--------------------------------------------------------------

[Edited on 9-12-2016 by aga]




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[*] posted on 8-12-2016 at 22:29


Weeee!

This is my second post here...and you can thank (or curse) RMS.
Since I found his videos I've been going like a madman...now with a garage full of chems, and reading papers on DES everyday! I have pretty much all the chems/equip now to at least get started on his supercapacitors and hopefully around the 1st of the year I can get started and make some vids myself. Then go into making DES!

Anyway...so you've found the newset making Graphene video via electrochem (Tour) method.

The making GO video is here
https://www.youtube.com/watch?v=c17ePPuEaAk
Then you disperse the GO in distilled water using a sonicator.
(Or you can find GO solutions on ebay to get started as I did)

The Activated carbon active material "paint" is (I am pretty sure), just powdered AC (got mine at Walmart in the pet section), 3% (by weight) of Polyvinylpyrrolidone (again..ebay is mah friend). You'll find that info in the 1700F cap video https://www.youtube.com/watch?v=iD2rVGjG2HQ&list=PLbQqm4...

Oh he also mentioned Celgard separators which I decided to get. Since I'm more interested in playing with different electrolyte/active materials just using a consistent separator eliminates one variable.

Two other good RMS videos are
Making High Performance Supercapacitor Materials - 1 & 2.
https://www.youtube.com/watch?v=GSDSUFvLOEo
https://www.youtube.com/watch?v=ftAPXujssr8

His newer videos seem to be on a "Hemp" battery which (if I'm not mistaken) he has rebranded as "Structured Carbon" :P
I dont think there is an explicate video where he makes the Hemp carbon, but he did make a vid or two on hydrothermal carbonization. That plus a little Google shows that the cool kids are carbonizing hemp "bast," which allegedly has greater surface area/m^2 than graphene!

I've got a huge spreadsheet of video links, research paper links, chem suppliers,etc. related to Supercaps, Deep Eutectic Solvents, graphene quantum dots, making/doping graphene....






[Edited on 9-12-2016 by Aztral]
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[*] posted on 9-12-2016 at 01:27


Thanks Aztral !

RMS has so many videos (250+) that it is hard to sift through them for the relevant info without being led off on other interesting avenues.

Your spreadsheet sounds very useful.

Have you constructed a battery/supercap yet ?




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[*] posted on 10-12-2016 at 08:05


Hi aga.

I haven't built a supercapacitor or battery yet.
Been "preparing" to get started though.
I have all the supplies to build multiple versions, and beyond, and I "almost" have little workspace cleaned out in my garage.

Around the first of the year I'll start-out trying to replicate the RMS supercaps - and share some videos. :)

I DID try a quick test of coating glass with GO, but instead of using a "laser" (like UCLA did) or xenon flash I used a 250W infrared heat lamp! I didn't think it produced a conductive sheet until I noticed my multimeter max ohms is around 2Mohms. But then I setup a setup a simple circuit which ran current over the glass and lit a light :)

And..yes...the RMS videos are great!
I've been reading on various things for years, but have never taken action until watching RMS. Dye Sensitized Solar Cells caught my interest, but I didn't do squat. I've also had a desire to play with fuel cells/water splitting but again...nada. But (if nothing else) the RMS videos have really put a" fire under my rear" and have me taking action :)

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[*] posted on 10-12-2016 at 08:21


For me it's the Carbon angle that caught my attention/imagination.

With any joy i'll get time tomorrow to do his sugar & Zn(NO3)2 route to a good activated carbon, which i can then test alongside some commercial AC.

If that works out OK, onwards to a supercap with all haste !

... besides making 100ml benzene for Congo Red thing, rubbing bits of metal with sandpaper ... etc - basically all the Other stuff on my list.




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[*] posted on 10-12-2016 at 08:34


Yay!

There are definitely some good vids by RMS and others on making various "nanoparticles"

And OH I forgot to mention that there are actually TWO search bars on youtube...one to search all youtube, but if if you click on RMSs "videos" (not "playlists") you can search through ALL his videos. I find this very useful to find other "related" video by RMS

(I mention this only in the off-chance you're a youtube newbie like me.)
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[*] posted on 10-12-2016 at 08:43


Maybe the spreadsheet is the best way to keep track of videos, recipes, suppliers etc.

I've made several caps - all simple formulas.
Best so far is 2" aluminum foil duct tape, with sprinkled activated carbon after coffee grinding and using what passes through 80 mesh screen. 3M NaCl solution soaked into regular copy paper for membrane/electrolyte. 10cm sq. ran phone vibrator motor for 3 minutes after charge to 1.2V.

Next step is working on an activated carbon ink, with a binder of either an ABS (LEGO chips) or PLA (3D printer filament) dissolved in Acetone. Binder to AC ratio of 1/20 (5%) by weight.

I tried for a membrane salvaged from Lithium 18650 cells (Robs idea) It worked OK but need better data to say better / worse than soaked copy paper.

I'm investigating the several options to build a cheap 2 wire potentiostat (google Ardustat) to be able to make better A, B, C, choices of components.
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[*] posted on 10-12-2016 at 08:45


Been watching stuff on utoob for years, but certainly did not know about that feature, so i guess i'm not a Qualified utoober !

Thanks for the info.

Right now i cannot watch any more of his videos or i'll get side-tracked again and end up in front of the laptop all day instead of actually Doing things.




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[*] posted on 10-12-2016 at 08:50


Quote: Originally posted by Geekineer  
I've made several caps - all simple formulas.
Best so far is 2" aluminum foil duct tape, with sprinkled activated carbon

Excellent !

Photos ! Photos !

How long was the charge time ?

I will certainly characterise the batteries made (IF i manage to make one work) so the charge/discharge voltage, current, time all need measuring to get relevant data.

Naturally material composition/area/volume/weight will also be important.

Temperature too i guess.




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[*] posted on 10-12-2016 at 09:15


GJ Geekineer!

Yes..I find the spreadsheet useful.
I also keep track of free science docs of interest, but sometimes even just an abstract provides enough info too. Worthy pdfs get downloaded.
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[*] posted on 10-12-2016 at 09:20


Quote: Originally posted by Aztral  
Yes..I find the spreadsheet useful.

We're trying to Hint that we want you to share the spreadsheet by uploading it here ;)




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[*] posted on 10-12-2016 at 09:49


Here's what I have on strictly supercaps.

I also posted what I have on deep eutectic solvents here http://www.sciencemadness.org/talk/viewthread.php?tid=62263#...
(*All files were save as tabbed delimited)

Includes little "thought bubbles" that may only make sense to me :)

Also in the near term, please take anything I post with a grain of salt - in solution of course ;) Although I was physics major, I got offered a really good software dev job 3rd year and left UCLA before I finished chemistry. I am still catching-up on even basic chemistry and may not know completely what I'm talking about - lol.


Code:
1700F Supercapacitor https://www.youtube.com/watch?v=iD2rVGjG2HQ&list=PLbQqm4rNo625Etz4INo2wP2X4sxgwDyNN&index=32 3-Apr-15 1cm^2 = 2.3 Farads printer's paper (aluminized polypropalene) aluminum ~100micrometer coating "0.08g, 4microns thick" etch aluminum copper sulfate/sodium cloride 50/50 in 1liter water graphene paint (Not GO) Polyvinylpyrrolidone 3% by weight of graphene PVA 10% by weight of graphene polypropalene separator (previous vids on making) used salt water in vid..but could be an ionic fluid (deep eutectic solvent) "A World First - A 10 kiloFarad Capacitor (10,000 F)" https://www.youtube.com/watch?v=9hLeydni7Ks&index=33&list=PLbQqm4rNo625Etz4INo2wP2X4sxgwDyNN&spfreload=1 electrolyte Acetonitrile-amonium salt 2.2V + alum electrodes commercial paper separator "sealed in latex dip-coated, because this electrolyte will eat through anything" conductive ink #1 https://www.youtube.com/watch?v=WR7SHPGGQ34#t=138.254467 100g of gum arabic 500mL of water 300g of flake graphite powder Homemade conductive inks https://www.youtube.com/watch?v=mOr3ZdyqgCk ceramic paint for induction heating waterproof binder sodium silcate Making High Performance Supercapacitor Materials - 1 https://www.youtube.com/watch?v=GSDSUFvLOEo Making High Performance Supercapacitor Materials - 2 https://www.youtube.com/watch?v=ftAPXujssr8 GO on graphfoil flame reduced - best method 8-Mar-16 coat grafoil with GO 1cm^2=1.5 farads flame reduce Eric Goeken https://www.youtube.com/watch?v=uujf5tpkm8M thought on making hydrogen - separate electrodes with Kiln paper! RMS on Deep Eutectic solvents https://www.youtube.com/watch?v=EDoCDM5vuwY deep eutectic (red rake) https://www.youtube.com/watch?v=nVHEYQCcuMI Home Made Ionic Liquids (Robert Murray-Smith) https://www.youtube.com/watch?v=vF0T8EaEE50&index=24&list=PLbQqm4rNo625Etz4INo2wP2X4sxgwDyNN Gel Electrolyte For Supercapacitors 2 (good for G & MnO2) asym https://www.youtube.com/watch?v=aWDol9CTjpQ&t=8s making PV Alcohol for solid separator https://www.youtube.com/watch?v=Ogpeaklho_M how to build a supercapacitor step by step https://www.youtube.com/watch?v=1Ce2au3PWnI Super Cap A activated carbon (fish tank carbon) activated carbon 3000m^2 per g grafoil current collector (dip coated) acetone Polyvinylpyrrolidone 3% by weight of carbon Super Cap B GO graphene 2630m^2 per g grafoil current collector (heat reduce GO ~50C) water hemp super capacitor http://newatlas.com/hemp-high-performance-supercapacitor/33435/ hemp buy http://www.hemptraders.com/product-p/f-l2.htm 100ml hydrothermic reactor http://www.ebay.com/itm/100-mL-Teflon-Lined-Hydrothermal-Synthesis-Autoclave-Acid-Digestion-Reactor-/371497847881?hash=item567eff4c49:g:Ru8AAOSwL7VWl1xs Aluminum should have acid electrolyte sodium sulfate Nickle could stand alkaline electrolyte separator company https://www.celgard.com/battery-innovation laser inscribe graphene https://www.youtube.com/watch?v=M0-0fbpARQg used the Kapton method Graphitic Carbon Nitride https://www.youtube.com/watch?v=Jj-nuTSjCBc&t=525s use as a hydrogen evolution catalyst? large scale graphene oxide production https://www.youtube.com/watch?v=w0jo9OmD84U Making a PVA Separator (MFCTechnology) https://www.youtube.com/watch?v=JFrEq3dMAfQ 8% PVAlc solution http://pubs.acs.org/doi/abs/10.1021/am302301t https://en.wikipedia.org/wiki/Tetramethylammonium_chloride adds porousity http://inhabitat.com/rice-universitys-carbon-nanotube-paint-turns-any-surface-into-a-solar-battery/


I have other tabs in my spreadsheet on chem suppliers, making graphene oxide, DES, etc. - lemme know :)
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[*] posted on 10-12-2016 at 09:59


Cool !

Many thanks Aztral.




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[*] posted on 10-12-2016 at 10:15


Here's some info on making graphene oxide too.
Hemp hydro-thermally carbonized may have greater surface area, but may still be of interest to supercap builders...
Code:
Tour Method graphene oxide https://www.youtube.com/watch?v=c17ePPuEaAk 3g graphite EXPLODES ABOVE 55C !! 18g Potassium Permanganate PP is an oxidizing agent mix powders 360ml Sulfuric acid 96-98% 40ml phosphoric acid 75% mix acids SLOWLY STIR/ADD ACIDS HEATER STIRRER AT 50C for 12hrs let sit to room temperature pour over 400ml deionized water ice "400ml deionized water frozen,chunks" add 3ml 35% hydrogen peroxide (or 9ml 12% hydrogen peroxide ) Cleaning let mixture settle pour through 45micron filter GO pours through refilter thru polyester fiber "wash with water, 30% hydrocloric acid, ethanol" result from3g graphite = 5.6g GO Improved Faster Method for Making Graphene Oxide https://www.youtube.com/watch?v=aQcMYTiUPqA r-Go from GO in DES @100C http://pubs.rsc.org/en/content/articlelanding/2013/ra/c3ra41485j#!divAbstract making high quality graphene http://m.phys.org/news/2016-09-microwaves-high-quality-graphene.html fixing defective graphene http://m.phys.org/news/2016-08-route-scalable-production-highly-crystalline.html http://www.nature.com/articles/srep28936
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[*] posted on 10-12-2016 at 12:29


Reading your notes is a bit like reading some of mine !

The research references you're posting are Exactly what i hoped this thread would be about.

With any joy, we can come up with a 'distilled' version soon so people can follow a simple, proven recipe to get started with these materials.

What's the Target ? a GigaFarad capacitor made from toenails ? ;)




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[*] posted on 11-12-2016 at 10:05


Lol.

So https://www.youtube.com/watch?v=iD2rVGjG2HQ&list=PLbQqm4...
is a pretty good blueprint for making a supercapacitor with 3x the capacitance of commercially available supercaps (as RMS said).
That's a 0.08g, 1cm^2, 2.3F supercapacitor. To the best of my knowledge this the highest rated supercapacitor made by RMS in his videos (in terms of F/cm^2).

In that video he made a graphene paint (not GO, not AC).
He shows how to make graphene here
https://www.youtube.com/watch?v=gcwCGRXVHzQ&t=38s

As it happens, my sodium sulfate order came in yesterday and I couldn't contain my inner-nerd so I headed out to the garage and made graphene (as per the video above) :o

Next I'll mix-up graphene paint with acetone and 3% by weight PVP binder.

Really, the only slightly difficult part of this whole process is right there - making the graphene paint. After that you choose the electrolyte you want to use, which will dictate the current collector material. In the RMS video he just used salt water and aluminum. RMS also used polypropylene separator. I found some 25micron commercial Celgard on ebay, so I'll roll with that.

That's about as "distilled" of a version as they come :)

Going forward, I've been extremely interested in deep eutectic solvents as supercap/battery electrolytes. For supercaps, the capacitance goes up as the square of the voltage. Aqueous electrolytes break-down at 1.2V, and even nasty acetenitrile breaks down @2.2V. I heard reference of some DES having potential windows around 6V. That's 5 times the potential window, or 25 times the capacitance of an equally prepared, aqueous solution supercap! (Assuming of course the DES was suitable as this kind of electrolyte).

Although I do have ChCl on hand, Ialso have ZnCl ordered so I wait for that to come in before I play with DES as electrolyte. And then of course Dot 3 brake fluid, antifreeze and glycerin are the easy store purchases I've already made. These may not be the absolute best (other HBDs might be better...I'm still reading) for our purpose, but they're a start :)



[Edited on 11-12-2016 by Aztral]
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[*] posted on 11-12-2016 at 11:20


Today i did lots of things while waiting for a batch of zinc nitrate to finish reacting.

Turns out that what i thought was pure zinc powder is pure crap, so started again with a freshly-cast bar of zinc instead.

First base (for me) is some home-made AC to test against the commercial stuff, hopefully coming out with an I.N. of > 500. (this will also serve as a verification of what RMS is saying)

When that is done, empirically test it in a cell and see what we get, hopefully setting some kind of benchmark for future materials.

I love love to shove random things into pots, boil/zap/pulverise them and then go 'woohoo!' but experience tells me that way rapidly leads to disappointment.

My gut feeling is that this tech is worth exploring properly.




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[*] posted on 11-12-2016 at 13:27


I'm typing on a tiny smartphone, so please bear with me. The electrochemical window of a solvent or electrolyte depends also on the electrode materials. An ionic liquid with an EC window of 6V on platinum or glassy carbon electrodes will normally only work to 2.5-3.5V on graphene electrodes made from flake graphite precursor. The edges of the flakes are electro chemically more active than the basal plane, so it's possible that a flat, non-porous sheet of graphene would work at these high voltages, but then such an electrode would be useless in a capacitor.

This also means that acqueous cells do not really work over about 0.6V, unless asymmetrically-sized electrodes are used. The anode gets oxidized over this potential (on the flake edges). This oxidation is partly reversible, and this can give the appearance that the cell capacitance is gradually increasing. This is a faradaic effect, much like what happens in a battery. If allowed to charge continually over about 0.6V, however, the anode pores gradually clog with functional groups, and cell capacity drops.

Leakage current and short life at usable operating voltages are the bane of graphene supercapacitors. All of this information can be found in the literature, if one reads in between the lines. In most cases, however, the journal articles are written to generate more research dollars, so in many cases such candidness isn't forthcoming. After a while one develops a critical eye, and can immediately spot "weasel words", omissions, intellectual sloppiness, and other annoying things that pop out in graphene research.

I've built an aqueous cell that works up to about 0.6-0.65V. The leakage current at that voltage was good enough that its self discharge time constant was over a month (Measured). With ionic liquids I found that leakage currents became a significant problem over about 2.5-3V, even with very dry electrolytes under a vacuum. In other words, the operating voltages aren't any better than Maxwell supercaps, which have excellent cycle life and low leakage current.




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[*] posted on 11-12-2016 at 14:33


All material published so far should be regarded as 'weasel words'.

Empirical testing and experimentation will provide hard data to be analysed.

Personally i have the idea that the capacitor/battery chemistries can be somehow mixed or drastically altered to be Something Else.

It's just Electrons after all ...

No idea yet. Time will tell.

[Edited on 11-12-2016 by aga]




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[*] posted on 11-12-2016 at 15:36
RMS latest video


In Robs latest vid - about 2 weeks ago - he seems to abandon his graphene ink on grafoil electrodes, or ink on both sides of copy paper membrane (used in his 600sheet bat/cap for the electric moped). He's now happy with a magic mix that forms both the current collector and electrode - looks like some form of conductive poly???. About 1.5" wide strips will sandwich a poly? membrane and maybe (rolled?) and inserted into the Type 27 repurposed battery case as a demo?

PS - forgive my ignorance but in this forum how do I reply to a specific message vs. just replying to the newest post?

Also I'm not getting any email notifications if messages are replied ?????

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Morgan
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[*] posted on 11-12-2016 at 15:42


Quote: Originally posted by aga  
All material published so far should be reagarded as 'weasel words'.

Empirical testing and experimentation will provide hard data to be analysed.

Personally i have the idea that the capacitor/battery chemistries can be somehow mixed or drastically altered to be Something Else.

It's just Electrons after all ...

No idea yet. Time will tell.


I recall reading this comment on the Towards a 1 MegaFarad video.


WGTR1 year ago
That's an interesting project, Robert. Might I suggest hooking the cell up to a stable voltage for 72 hours, and then measuring the charging current? Bonus points if the following test measures self-discharge, with voltage charted against # of days. Those are pretty easy tests to do. Only connect the meter when actively measuring voltage, to avoid having the voltmeter continually load the cell.

The leakage current test is a good measure of cell quality. Ideally the current should be zero, but impurities in the electrodes and electrolyte, choice of collector material, and ohmic paths through the separator will cause it to be greater than this.

The self discharge test is probably the most important one, if the supercapacitor as an energy storage device is considered. For example, even if a cell has an energy density rivaling Li-ion chemistry, it won't be useful if it self-discharges in 15 minutes. Also, the shape of the discharge curve indicates if there are faradaic reactions occurring, if there is moisture contamination, etc.

Cell lifetime is related closely to the previous test results. A cell with high leakage current will usually have a short lifetime at rated voltage. There are other tests that measure quality, but I think the first two are the most important and practical for a home hobbyist. For reference, my own aqueous cells lose half their stored energy after about 3 weeks. The self-discharge time constant is > 2 months. The ionic liquid-based ones currently self-discharge more quickly. Those lose half their energy after 5-7 days. By contrast, cells from the "Big Boys" like Maxwell may lose only 10% of their voltage after a month.

Finally, as you've already mentioned earlier, I'd suggest measuring capacitance by calculating the voltage drop vs. time with a fixed load. The load should be > 10x the leakage current, small enough that internal resistance is insignificant, and small enough that the discharge takes place over 10-60 seconds (to improve measurement accuracy).

Standard capacitance meters are useless for measuring EDLCs, as measured EDLC capacitance depends on test frequency (a graphene electrode is similar to a transmission line of sorts, with distributed resistance and capacitance).

Hopefully some of this information will be useful to some people. I think if testing methods are standardized a bit more in the hobbyist world, it may be easier to compare the results different people are getting.
https://www.youtube.com/watch?v=MfEroyS6Ix0

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