7 ms·

Conspicuously missing is any mention of energy density. Who cares about power density. That's juste how fast it can discharge. We don't need capacitors that can

Conspicuously missing is any mention of energy density. Who cares about power density. That's juste how fast it can discharge. We don't need capacitors that can discharge faster. All capacitors are already much better than batteries with respect to power. We need capacitors that can store more energy. Capacitors typically suck at that and this article doesn't give any indication that these new ones are better.

akandiah 14y ago
Here's a page which provides a bit more information than the OP: http://www.engineer.ucla.edu/newsroom/more-news/archive/2012/researchers-develop-graphene-supercapacitor-holding-promise-for-portable-electronics http://www.engineer.ucla.edu/newsroom/more-news/archive/2012... And here's a paper on the subject: http://evmc2.files.wordpress.com/2013/02/laser-scribing-of-high-performance-and-flexible-graphene-based-electrochemical-capacitors.pdf http://evmc2.files.wordpress.com/2013/02/laser-scribing-of-h...
- BenoitEssiambre 14y ago
  ok so here is the only real data I could find. At the end of the paper: "The LSG-EC can exhibit energy densities of up to 1.36 mWh/cm3 , a value that is approximately two times higher than that of the AC-EC" 1.36 mWh/cm3 = 1.36 Wh/L If we assume that 1 L of it weights very roughly 1kg. We get 1.36 Wh/kg. From wikipedia: "The amount of energy stored per unit weight [in ultracapacitors] is generally lower than that of electrochemical batteries (3 to 5 W·h/kg, although 85 W·h/kg has been achieved in the lab[12] as of 2010 compared to 30 to 40 W·h/kg for a lead acid battery, 100 to 250 W·h/kg for a lithium-ion battery and about 0.1% of the volumetric energy density of gasoline." This is still less than 1% of the energy density of lithium ion batteries.
  - buster 14y ago
    There is a big miscalculation: Graphene seems to be extremely light weight. 1 liter of graphene will definitely not weight 1kg. Wikipedia [1] only gives measures for m²: Graphene is very light, weighing only about 0.77 milligrams per square meter. [1] https://en.wikipedia.org/wiki/Graphene https://en.wikipedia.org/wiki/Graphene
    - claudius 14y ago
      Graphene is also very thin. If you created a box of graphene, it would naturally have about the same weight as diamond or coal (plus or minus 100%, maybe, but certainly not orders of magnitude less).
      - homeomorphic 14y ago
        Probably not minus 100% :-)
    - sherjilozair 14y ago
      Here[1], the density is said to be as low as 0.03 gm/cc which is the same as kg/liter. That gives a multiplicative factor of 33 over the above calculations, i.e. this could be 33% of the energy density of lithium ion batteries. Not bad. [1]: http://www.strem.com/uploads/resources/documents/graphene_nanoplatelets.pdf http://www.strem.com/uploads/resources/documents/graphene_na...
      - Someone 14y ago
        Energy per liter also is an important factor. Your mobile would float, but it also would be the size of your lower arm. Maybe, you should wear your battery as a jacket or a pair of trousers?
    - mapt 14y ago
      A square meter of a single-atom-thick layer of graphene isn't very relevant. Expect the final product to have a volumetric density in the neighborhood of graphite or diamond.
      - sliverstorm 14y ago
        Probably closer to graphite, as to my knowledge graphite is literally just layers of graphene.
        Retric 14y ago
dmethvin 14y ago
In the comments they mention about 1/4 the energy density of a lithium ion battery, so yes they don't compete on that measure. But full charging can happen in a minute or two, and you could top up a charge in seconds. Perhaps public areas would have inductive chargers on the wall; you'd just walk over and hold your phone or tablet up to it for a few seconds. Airline tray tables could have an inductive charger built in. Higher energy densities aren't without issues, as Boeing found out with their 787. A battery like that is basically an explosive and it can be tricky to manage.
- deleted 14y ago
  [deleted]
- brokenparser 14y ago
  Your inductive charging tray tables are terrible for my magnetic tapes and floppy disks. Also, where does it get its energy from? It's much more efficient to walk around with wearable solar panels or to embed them directly into the devices. It may not work well on the north pole half the time but batteries aren't very conductive in those environments, anyway.
  - samstave 14y ago
    When was the last time you walked around with a magnetic tape or floppy disc? Now - what happens if you put your wallet full of credit cards on it?
    - Tomdarkness 14y ago
      To be honest, magnetic strips on credit cards are redundant in a fair proportion of the world as well, especially Europe, although with a notable exception of the US which seems to be seriously lagging behind in this area. I live in the UK and it has easily been over 6 years since I have been anywhere where the magnetic strip has been read rather than using chip & pin (EMV).
      - philwelch 14y ago
sliverstorm 14y ago
Who cares about power density. Well, cars do. As evidenced by the use of lead-acid batteries, power density > energy density for automobiles. Of course, better power density is probably not the main obstacle to using capacitors in a car to replace the battery.
solistice 14y ago
I have the article printed out somewhere, the energy density is in there, about 10 times that of conventional activated carbon supercapacitors and 3 times that of a comparable thin film lithium polymer battery off the top of my head, but I could be wrong. You can find the original paper at the AAAS (American Association for Advancement of Science) website, but its behind a registration wall, and they do mad data mining, so registering might take a while. Also, I have to remind you that this is an article on io9, not in the Scientific American. There are several other articles about this which likely came prior to io9 picking up on the story, and im pretty sure they provide some additional numbers which you so or so will find in the original paper on the subject. Here's the Kady paper that is referred to by the way. http://www.sciencemag.org/content/335/6074/1326.abstract http://www.sciencemag.org/content/335/6074/1326.abstract
ChuckMcM 14y ago
Excuse me? This from the linked article (and in the paper abstract): "These micro-supercapacitors demonstrate a power density of ~200 W cm−3, which is among the highest values achieved for any supercapacitor." Granted its not a legitimate energy density (wrong units) but lets guess it is 200 Ws per cubic centimeter. I make that guess based on the comment in the video that they ran an LED for 5 minutes. So an LED is like 15mA and with a forward drop of a couple of volts so 30 mW. For 5 minutes your looking at 9000 mW-seconds, or 9 Ws for the small capacitor they showed in their video which could have been about a cm ^ 2. So if the cell they had made was 1/2 mm thick then a stack of 20 of them would be 1 cm^3 and 180 W-seconds (in the ball park of the abstract). There is a fun presentation on Supercaps [1] that was given to DoE in 2011. This computation does suggest that 200 Ws for this material would be a decent jump in capacity. That said, I immediately dug an old LightScribe CD recorder out of my junk bin to start playing around with making graphene sheets :-) [1] http://www1.eere.energy.gov/vehiclesandfuels/pdfs/merit_review_2011/electrochemical_storage/es038_smith_2011_p.pdf http://www1.eere.energy.gov/vehiclesandfuels/pdfs/merit_revi...
- wamatt 14y ago
  >That said, I immediately dug an old LightScribe CD recorder out of my junk bin to start playing around with making graphene sheets :-) You serious? Sounds interesting, do tell us more.
  - deleted 14y ago
    [deleted]
  - ChuckMcM 14y ago
    Of course I am serious! Still trying to figure out what they used as a 'base' graphite oxide slurry (pencil lead in solution it isn't)
- lambdasquirrel 14y ago
  That's still power density. Power is Watts. Total energy is joules. You haven't addressed the parent's concern. We are interested in how long it can keep up that wattage, ie. joules/sec.

akandiah 14y ago

Here's a page which provides a bit more information than the OP: http://www.engineer.ucla.edu/newsroom/more-news/archive/2012/researchers-develop-graphene-supercapacitor-holding-promise-for-portable-electronics http://www.engineer.ucla.edu/newsroom/more-news/archive/2012... And here's a paper on the subject: http://evmc2.files.wordpress.com/2013/02/laser-scribing-of-high-performance-and-flexible-graphene-based-electrochemical-capacitors.pdf http://evmc2.files.wordpress.com/2013/02/laser-scribing-of-h...

BenoitEssiambre 14y ago
ok so here is the only real data I could find. At the end of the paper: "The LSG-EC can exhibit energy densities of up to 1.36 mWh/cm3 , a value that is approximately two times higher than that of the AC-EC" 1.36 mWh/cm3 = 1.36 Wh/L If we assume that 1 L of it weights very roughly 1kg. We get 1.36 Wh/kg. From wikipedia: "The amount of energy stored per unit weight [in ultracapacitors] is generally lower than that of electrochemical batteries (3 to 5 W·h/kg, although 85 W·h/kg has been achieved in the lab[12] as of 2010 compared to 30 to 40 W·h/kg for a lead acid battery, 100 to 250 W·h/kg for a lithium-ion battery and about 0.1% of the volumetric energy density of gasoline." This is still less than 1% of the energy density of lithium ion batteries.
- buster 14y ago
  There is a big miscalculation: Graphene seems to be extremely light weight. 1 liter of graphene will definitely not weight 1kg. Wikipedia [1] only gives measures for m²: Graphene is very light, weighing only about 0.77 milligrams per square meter. [1] https://en.wikipedia.org/wiki/Graphene https://en.wikipedia.org/wiki/Graphene
  - claudius 14y ago
    Graphene is also very thin. If you created a box of graphene, it would naturally have about the same weight as diamond or coal (plus or minus 100%, maybe, but certainly not orders of magnitude less).
    - homeomorphic 14y ago
      Probably not minus 100% :-)
  - sherjilozair 14y ago
    Here[1], the density is said to be as low as 0.03 gm/cc which is the same as kg/liter. That gives a multiplicative factor of 33 over the above calculations, i.e. this could be 33% of the energy density of lithium ion batteries. Not bad. [1]: http://www.strem.com/uploads/resources/documents/graphene_nanoplatelets.pdf http://www.strem.com/uploads/resources/documents/graphene_na...
    - Someone 14y ago
      Energy per liter also is an important factor. Your mobile would float, but it also would be the size of your lower arm. Maybe, you should wear your battery as a jacket or a pair of trousers?
  - mapt 14y ago
    A square meter of a single-atom-thick layer of graphene isn't very relevant. Expect the final product to have a volumetric density in the neighborhood of graphite or diamond.
    - sliverstorm 14y ago
      Probably closer to graphite, as to my knowledge graphite is literally just layers of graphene.
      - Retric 14y ago

dmethvin 14y ago

In the comments they mention about 1/4 the energy density of a lithium ion battery, so yes they don't compete on that measure. But full charging can happen in a minute or two, and you could top up a charge in seconds. Perhaps public areas would have inductive chargers on the wall; you'd just walk over and hold your phone or tablet up to it for a few seconds. Airline tray tables could have an inductive charger built in. Higher energy densities aren't without issues, as Boeing found out with their 787. A battery like that is basically an explosive and it can be tricky to manage.

deleted 14y ago
[deleted]
brokenparser 14y ago
Your inductive charging tray tables are terrible for my magnetic tapes and floppy disks. Also, where does it get its energy from? It's much more efficient to walk around with wearable solar panels or to embed them directly into the devices. It may not work well on the north pole half the time but batteries aren't very conductive in those environments, anyway.
- samstave 14y ago
  When was the last time you walked around with a magnetic tape or floppy disc? Now - what happens if you put your wallet full of credit cards on it?
  - Tomdarkness 14y ago
    To be honest, magnetic strips on credit cards are redundant in a fair proportion of the world as well, especially Europe, although with a notable exception of the US which seems to be seriously lagging behind in this area. I live in the UK and it has easily been over 6 years since I have been anywhere where the magnetic strip has been read rather than using chip & pin (EMV).
    - philwelch 14y ago

sliverstorm 14y ago

Who cares about power density. Well, cars do. As evidenced by the use of lead-acid batteries, power density > energy density for automobiles. Of course, better power density is probably not the main obstacle to using capacitors in a car to replace the battery.

solistice 14y ago

I have the article printed out somewhere, the energy density is in there, about 10 times that of conventional activated carbon supercapacitors and 3 times that of a comparable thin film lithium polymer battery off the top of my head, but I could be wrong. You can find the original paper at the AAAS (American Association for Advancement of Science) website, but its behind a registration wall, and they do mad data mining, so registering might take a while. Also, I have to remind you that this is an article on io9, not in the Scientific American. There are several other articles about this which likely came prior to io9 picking up on the story, and im pretty sure they provide some additional numbers which you so or so will find in the original paper on the subject. Here's the Kady paper that is referred to by the way. http://www.sciencemag.org/content/335/6074/1326.abstract http://www.sciencemag.org/content/335/6074/1326.abstract

ChuckMcM 14y ago

Excuse me? This from the linked article (and in the paper abstract): "These micro-supercapacitors demonstrate a power density of ~200 W cm−3, which is among the highest values achieved for any supercapacitor." Granted its not a legitimate energy density (wrong units) but lets guess it is 200 Ws per cubic centimeter. I make that guess based on the comment in the video that they ran an LED for 5 minutes. So an LED is like 15mA and with a forward drop of a couple of volts so 30 mW. For 5 minutes your looking at 9000 mW-seconds, or 9 Ws for the small capacitor they showed in their video which could have been about a cm ^ 2. So if the cell they had made was 1/2 mm thick then a stack of 20 of them would be 1 cm^3 and 180 W-seconds (in the ball park of the abstract). There is a fun presentation on Supercaps [1] that was given to DoE in 2011. This computation does suggest that 200 Ws for this material would be a decent jump in capacity. That said, I immediately dug an old LightScribe CD recorder out of my junk bin to start playing around with making graphene sheets :-) [1] http://www1.eere.energy.gov/vehiclesandfuels/pdfs/merit_review_2011/electrochemical_storage/es038_smith_2011_p.pdf http://www1.eere.energy.gov/vehiclesandfuels/pdfs/merit_revi...

wamatt 14y ago
>That said, I immediately dug an old LightScribe CD recorder out of my junk bin to start playing around with making graphene sheets :-) You serious? Sounds interesting, do tell us more.
- deleted 14y ago
  [deleted]
- ChuckMcM 14y ago
  Of course I am serious! Still trying to figure out what they used as a 'base' graphite oxide slurry (pencil lead in solution it isn't)
lambdasquirrel 14y ago
That's still power density. Power is Watts. Total energy is joules. You haven't addressed the parent's concern. We are interested in how long it can keep up that wattage, ie. joules/sec.