I was watching Jim El-Khalili's series on Netflix & there was an interesting section on using Graphene for power storage in electric cars. As far as I could see it uses the graphene as a type of distributed capacitor rather than a traditional battery (it talked about building the body from graphene rather than having a separate power storage compartment).
I can't see too much about it elsewhere and obviously shows on Netflix need to be taken with a large grain of salt (though I do like El-Khalili as a presenter) - is this a real development direction or just a dead-end?
Graphene for electric cars
I did my PhD in this stuff. Thesis title was literally "Investigation into nanostructured carbon-based materials for electrochemical applications"
Graphene is cool, but not really the saviour of the world just yet, and probably won't be outside of niche applications. Will always be of interest in research, though.
The attraction of graphene is that it's theoretical specific surface per unit mass area is absurdly high. It's literally all surface, no bulk.
A simple parallel plate capacitor has C=εA/d. You want to maximise capacitance (C), so that you're getting the best bang for your buck. More C, less mass to achieve cetain performance, lower material costs, etc.
Permittivity (ε) is hard to change, so you make the separation (d) really small, or massively increase the area (A), to maximise C. Electrochemical capacitors do both. One plate is the electrode with an applied bias, the other is the layer of oppositely charged molecules which arrange themselves next to the electrode. This creates the electrochemical double layer which behaves like a parellel plate capacitor, where d is of the order of the Helmholtz layers, like 1 nm. Add in an electrode material with very high specific sufrace area and you've maximised capacitance.
This is where graphene comes in. Literally no other material has better theoretical stats. It's themally, electrically, and chemically stable, thermally and electrically conductive, high surface area etc. Problem is, to make actual monolayer graphene is difficult. Any process which does, it thoroughly unsuited to mass production of electrodes in any economically viable manner. Chemical Vapour Deposition works well, but it's better suited to CMOS type processing*, than how battery type electrodes are mass produced. (*Except that it uses copper as a growth substrate, which is utterly incompatible with CMOS processes. Si-carbides are not your friend when making semiconductors).
Other bulk production processes exfoliate graphite powder in appropriate liquid media, resultilng in a stable dispersion of graphene flakes. This can be spray-coated, filtered etc to form a graphene layer on your current collector to increase the surface area. Issues arise in that the flakes tend to agglomerate a fair bit on drying, which means lots of the "surface" is not longer actually at the surface and accesible to the electrolyte.
Decorating a surface with graphene (or carbon nanotubes) absolutey increases surface area, but a reality is that other forms of activated carbon work just as well at a much lower overall cost. CVD of graphene requires hydrocarbons, elevated temperature, metal catalysts. Liquid Phase Exfoliation (LPE) requires highly crystalline graphite powder to start with, plus a load of sonic energy. While this isn't the most expensive raw material, it still requires elevated temperatures and pressures to synthesise highly crystalline samples.
It's just easier to make activated carbon (aC) powder by pyrolysing some banana plant leaves and then treating the resultant carbon black powder it with hot carbon monoxide to chemically activate the surface. This hives you almost identical chemical properties to graphene and CNTs, with much simpler manufacturing and processing costs. Actual performance of aC-based supercaps probably isn't that far off graphene ones, especially when you do a full life-cycle analysis which takes into account all costs.
TL;DR: graphene unlikely to be used in place of other carbon materials for supercap electrodes in the vast majority of consumer applications. For all the superlatives used to describe it, other (possibly inferior) materials are just easier to work with.
Graphene is cool, but not really the saviour of the world just yet, and probably won't be outside of niche applications. Will always be of interest in research, though.
The attraction of graphene is that it's theoretical specific surface per unit mass area is absurdly high. It's literally all surface, no bulk.
A simple parallel plate capacitor has C=εA/d. You want to maximise capacitance (C), so that you're getting the best bang for your buck. More C, less mass to achieve cetain performance, lower material costs, etc.
Permittivity (ε) is hard to change, so you make the separation (d) really small, or massively increase the area (A), to maximise C. Electrochemical capacitors do both. One plate is the electrode with an applied bias, the other is the layer of oppositely charged molecules which arrange themselves next to the electrode. This creates the electrochemical double layer which behaves like a parellel plate capacitor, where d is of the order of the Helmholtz layers, like 1 nm. Add in an electrode material with very high specific sufrace area and you've maximised capacitance.
This is where graphene comes in. Literally no other material has better theoretical stats. It's themally, electrically, and chemically stable, thermally and electrically conductive, high surface area etc. Problem is, to make actual monolayer graphene is difficult. Any process which does, it thoroughly unsuited to mass production of electrodes in any economically viable manner. Chemical Vapour Deposition works well, but it's better suited to CMOS type processing*, than how battery type electrodes are mass produced. (*Except that it uses copper as a growth substrate, which is utterly incompatible with CMOS processes. Si-carbides are not your friend when making semiconductors).
Other bulk production processes exfoliate graphite powder in appropriate liquid media, resultilng in a stable dispersion of graphene flakes. This can be spray-coated, filtered etc to form a graphene layer on your current collector to increase the surface area. Issues arise in that the flakes tend to agglomerate a fair bit on drying, which means lots of the "surface" is not longer actually at the surface and accesible to the electrolyte.
Decorating a surface with graphene (or carbon nanotubes) absolutey increases surface area, but a reality is that other forms of activated carbon work just as well at a much lower overall cost. CVD of graphene requires hydrocarbons, elevated temperature, metal catalysts. Liquid Phase Exfoliation (LPE) requires highly crystalline graphite powder to start with, plus a load of sonic energy. While this isn't the most expensive raw material, it still requires elevated temperatures and pressures to synthesise highly crystalline samples.
It's just easier to make activated carbon (aC) powder by pyrolysing some banana plant leaves and then treating the resultant carbon black powder it with hot carbon monoxide to chemically activate the surface. This hives you almost identical chemical properties to graphene and CNTs, with much simpler manufacturing and processing costs. Actual performance of aC-based supercaps probably isn't that far off graphene ones, especially when you do a full life-cycle analysis which takes into account all costs.
TL;DR: graphene unlikely to be used in place of other carbon materials for supercap electrodes in the vast majority of consumer applications. For all the superlatives used to describe it, other (possibly inferior) materials are just easier to work with.
WRT, actually using the body of the car as a power storage medium, that sounds absolutely mental, TBH. I'm not an engineer, though, so happy to be proved wrong.
It's certainly an out-there idea, but unique solutions are required to solve some problems.
It's certainly an out-there idea, but unique solutions are required to solve some problems.
Oh, I like that. Combine it with a car alarm: "Touch my car, get 10k volt charge up your arse"Nols wrote: Mon Jul 13, 2020 3:16 pm WRT, actually using the body of the car as a power storage medium, that sounds absolutely mental, TBH. I'm not an engineer, though, so happy to be proved wrong.
It's certainly an out-there idea, but unique solutions are required to solve some problems.
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ScarfaceClaw
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Is that you Elon?Munch wrote: Mon Jul 13, 2020 8:41 pm I've read they've shown graphene can turn lead to gold, they just can't make it economically viable yet but 5 years time it'll be on the market.
A friend works at an Australian graphite mine in Mozambique.
They extract flake and fine grafite, the fine grafite is used to make spherical grafite which is stuff used in EVs, so I'm told.
It's the new gold apparently.
There's a battle for exploration rights in Africa. Chinese companies have a head start but Western outfits have more experience and are more efficient.
At the moment only China makes the spherical grafite for EVs but they're building a plant in Louisiana, with some Trump subsidies, to compete.
Strangely it's not something the Trump administration publicises.
They extract flake and fine grafite, the fine grafite is used to make spherical grafite which is stuff used in EVs, so I'm told.
It's the new gold apparently.
There's a battle for exploration rights in Africa. Chinese companies have a head start but Western outfits have more experience and are more efficient.
At the moment only China makes the spherical grafite for EVs but they're building a plant in Louisiana, with some Trump subsidies, to compete.
Strangely it's not something the Trump administration publicises.
These things always seem to be 5 years awayScarfaceClaw wrote: Tue Jul 14, 2020 6:54 amIs that you Elon?Munch wrote: Mon Jul 13, 2020 8:41 pm I've read they've shown graphene can turn lead to gold, they just can't make it economically viable yet but 5 years time it'll be on the market.
Fusion power has been twenty years away for at least fifty years now.sturginho wrote: Tue Jul 14, 2020 8:03 amThese things always seem to be 5 years awayScarfaceClaw wrote: Tue Jul 14, 2020 6:54 amIs that you Elon?Munch wrote: Mon Jul 13, 2020 8:41 pm I've read they've shown graphene can turn lead to gold, they just can't make it economically viable yet but 5 years time it'll be on the market.
And are there two g’s in Bugger Off?
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HighKingLeinster
- Posts: 254
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The most surprising thing on this thread is that Nols is a doctor 
So were silicon semiconductors at one point. Applications will come.
And are there two g’s in Bugger Off?
So is Ross GellerHighKingLeinster wrote: Tue Jul 14, 2020 8:55 am The most surprising thing on this thread is that Nols is a doctor
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HighKingLeinster
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- Joined: Mon Jun 29, 2020 7:19 pm
i have always imagined Nols to be more like Sheldon from Big bang theorySandstorm wrote: Tue Jul 14, 2020 3:35 pmSo is Ross GellerHighKingLeinster wrote: Tue Jul 14, 2020 8:55 am The most surprising thing on this thread is that Nols is a doctor
Metals needed for Li batteries, fuel cells, electrolysers etc are often sourced in central Africa, too. That's the next resource battleground. The areas around the Congo basin already have hideous records with human rights and exploitation driven by profit.Zig wrote: Tue Jul 14, 2020 7:55 am A friend works at an Australian graphite mine in Mozambique.
They extract flake and fine grafite, the fine grafite is used to make spherical grafite which is stuff used in EVs, so I'm told.
It's the new gold apparently.
There's a battle for exploration rights in Africa. Chinese companies have a head start but Western outfits have more experience and are more efficient.
At the moment only China makes the spherical grafite for EVs but they're building a plant in Louisiana, with some Trump subsidies, to compete.
Strangely it's not something the Trump administration publicises.
I just hope the developed world doesn't prop up scummy regimes like in the ME.
As if I've ever used a whiteboard for a calculation in my life. Pffff.HighKingLeinster wrote: Tue Jul 14, 2020 3:40 pmi have always imagined Nols to be more like Sheldon from Big bang theorySandstorm wrote: Tue Jul 14, 2020 3:35 pmSo is Ross GellerHighKingLeinster wrote: Tue Jul 14, 2020 8:55 am The most surprising thing on this thread is that Nols is a doctor