8 ms·

I have two questions regarding batteries I often wonder about. Maybe the wisdom of the HN crowd can answer one or both of them: Is there a theoretical limit on

I have two questions regarding batteries I often wonder about. Maybe the wisdom of the HN crowd can answer one or both of them: Is there a theoretical limit on how much energy a rechargeable battery of, say, 1 kg mass can hold? Can a rechargeable battery be discharged and recharged and afterwards be in the same state it was before the cycle? Or is degradation inevitable? Again, I am asking for the theoretical possibility. Not real life challenges to implement it.

vincnetas 7y ago
if by battery you mean box with two wires, then for the first one answer is yes. for example batery storing energy in fast spinning mater. for second one i assume theoretical energy dencity limit is much greater than anything that we might need. but for chemical bateries i would also like to find out answers to your questions.
- founderling 7y ago
  I mean for batteries in general. Independent of the technology. For the spinning matter battery, the limit might be when the whole matter of 1 kg spins at the speed of light. I wonder if it matters how big the radius is with which it spins around the center? For a non-rechargeable battery, I guess the limit is 1kg * c^2. As Einstein postulated that e=mc^2. And that guy was right more often then not. Is that also the upper limit for rechargeable batteries? How long could a Tesla drive on 1kg * c^2?
  - Faaak 7y ago
    1kg * c² = 24 TWh. Supposing a Tesla averages 200Wh/km, then it would drive ~ 10¹¹ km (4 light-days, or around 600 times the earth-sun distance... which is a lot)
    - founderling 7y ago
      If Wolfram Alpha is right, then 10^11 km is 2 million times around the earth: https://www.wolframalpha.com/input/?i=10%5E11km+%2F+earth+circumference https://www.wolframalpha.com/input/?i=10%5E11km+%2F+earth+ci... Shows the potential of batteries. Charge your one kilo batttery to drive around the planet two million times.
      - mensetmanusman 7y ago
        It would be a misnomer in common parlance to describe nuclear fuel as a battery (mass > energy conversion). The broader language to describe this is ‘energy storage.’ E.g. oil is stored solar energy over millions of years, batters are stored electrochemical energy, flywheels are stored mechanical energy, etc.
    - nielsole 7y ago
      At least in the medium-term future we would at most be able to use is Hydrogen->Helium which would yield 6.45 x 10^14 Joules [1] which is equivalent to 179 GWh which at 200Wh/km would be 8.95*10^8 km. That's still enough to go 20.000 times around the globe and longer than any car is known to have lasted so far[2] [1] https://www.phys.ksu.edu/personal/wysin/astro/review9/p4.html https://www.phys.ksu.edu/personal/wysin/astro/review9/p4.htm... [2] https://en.wikipedia.org/wiki/Car_longevity https://en.wikipedia.org/wiki/Car_longevity
  - andyljones 7y ago
    Yeah, the absolute limit is c^2 if you've got 50-50 matter-antimatter. The efficiency however is brought down by the difficulty of _producing_ antimatter in the first place. A more popular hard-sci-fi concept is black hole engines; a 600kt black hole sprays out a hundred petawatts of Hawking radiation, and the fuel is whatever you've got lying around. That still has issues around energy _capture_, since the radiation is going to be ridiculously high-frequency. The best way I've heard of to dodge those issues is the 'Penrose process', where the fuel is the black hole's rotation and you get good ol' kinetic energy out. That can at most get you 20% of the mass-energy though, and there's a bunch more small print.
    - ThomasBHickey 7y ago
      20% is the energy gain of particles involved in each energy transfer, total energy available is 29% of the black hole's rotational energy according to Wikipedia.
  - the8472 7y ago
    > For a non-rechargeable battery, I guess the limit is 1kg * c^2. Assuming it is antimatter-based you can double that capacity by consuming air. But that just turns it into a fuel tank for an internal annihilation engine and hardly qualifies as battery anymore.
    - microtherion 7y ago
      This is Tesla we’re talking about. They’d probably ship this with a footnote in the owners’ manual: “Any use of this doomsday device for purposes other than a battery is prohibited. Do not operate outside containment field.’
    - founderling 7y ago
      Aha! So the most efficient mass based rechargeable battery would be one that while loading creates antimatter and while being used burns that antimatter with air (or other stuff) it takes from the environment.
    - JshWright 7y ago
      > hardly qualifies as battery anymore Why not? There are plenty of battery technologies that use air as an oxidizer.
      - slavik81 7y ago
        It follows from the definitions of a battery and a cell: > battery: a container consisting of one or more cells, in which chemical energy is converted into electricity and used as a source of power. > cell: a device containing electrodes immersed in an electrolyte, used for current-generation or electrolysis. An antimatter reactor would not be a battery because it would not contain any cells. Additionally, because it converts nuclear energy into useful power, not chemical energy.
    - zaroth 7y ago
      You all really took this question and ran with it in a way that totally avoids answering the practical question at the core — how good are these batteries going to get over the next 20 years? The answer is really, really good. Fast charging, long rang, 1 million mile lifespans. Add on top of that the ability to connect into a smart grid and earn money by buying energy off-peak and selling on-peak, and the ability to double as an emergency generator for your home.
  - deleted 7y ago
    [deleted]
  - saagarjha 7y ago
    > For the spinning matter battery, the limit might be when the whole matter of 1 kg spins at the speed of light. Of course, it's theoretically impossible for the matter to spin at the speed of light, and any actual material will tear itself apart at speeds far below c.
morley 7y ago
Another tangential question I've been struggling with is: is there a human limit to a power density we'll tolerate? Any sufficiently powerful battery is a defect or bad actor away from becoming a weapon. We already see defects in lithium batteries shaping airline policy, and the devices we're talking about are peanuts if we want to enable all our sci-fi dreams.
- deleted 7y ago
  [deleted]
- the8472 7y ago
  It depends on how easy it is to release the energy. A full petrol tank already contains a scary amount of energy, but you can't release it instantanously since it is bottlenecked by oxygen intake for combustion. Explosives bring their own compact oxidizer to get around that problem. A chunk of uranium-238 contains a lot of energy but it is only fissionable but not fissile, so you need an external fast neutron source to extract that energy. Comparatively it is a fairly safe energy source for its density. Similarly there are some metastable nuclear isomers that can theoretically be stimulated to release their energy with high energy photons with a precise frequency and would otherwise release their energy relatively slowly through their natural decay modes. And I think the difficulty of turning a hypothetical portable fusion power plant into an explosive device should be evident from the difficulties of keeping current experiments running for even a few minutes.
  - baybal2 7y ago
    I just though of an interesting twist on subcritical reactor. What about smelting a californium neutron source together with the fuel? We get a much cheaper RTG alternative with near no need for regulation. Any nuclear scientists here?
- ChuckNorris89 7y ago
  There is a power limit already in place for batteries you can carry on airlines and IIRC it's 100 Wh. As for weaponizing batteries, pretty sure bad actors have been able to cook dangerous bombs at home for decades that can inflict magnitudes more damage than a battery could ever do. So battery based bombs won't be a thing for the near future.
deleted 7y ago
[deleted]
jacquesm 7y ago
> I am asking for the theoretical possibility. That's a nonsense question then. Theoretical limits on power density will revolve around unobtanium and matter-anti-matter explosions; it's off topic as far as I'm concerned in a thread about Tesla acquiring a Canadian Battery Specialist, a company that is engineering batteries in the real world where practical limitations of materials science and chemistry are the ingredients, not your fantasy of what amount of energy one could theoretically store in a given volume if all of natures laws would be lifted. For reference, just the kinetic energy of a couple of liters of Neutron star alone should also figure into such discussions as well as a whole bunch of other nonsense.
- JshWright 7y ago
  > just the kinetic energy of a couple of liters of Neutron star alone should also figure into such discussions That would have a mass _substantially_ higher than 1kg...
fulafel 7y ago
An efficient (power density within factor of ~ 1e6 of the ideal mc^2 power source) EV battery doesn't need to be rechargeable, because the battery capacity will outlast the vehicle. Approximately same goes for stuff we already know how to build, vehicle applications of nuclear batteries and reactors. Although IIRC for practical reasons nuclear refueling is done ever 10 years or so in terrestial applications.
- zaroth 7y ago
  Wait, what? It sounds like you’re saying if cars had fusion reactors for engines then we wouldn’t need rechargeable batteries?
  - fulafel 7y ago
    Yes, we just need to restart DeLorean production... I'm not sure how far we have studied the miniaturization of reactors. There were some designs for airplanes and cruise missiles in the 50s. And there's the current Russian missile (https://en.wikipedia.org/wiki/9M730_Burevestnik https://en.wikipedia.org/wiki/9M730_Burevestnik). A paper at https://aip.scitation.org/doi/abs/10.1063/1.1358022 https://aip.scitation.org/doi/abs/10.1063/1.1358022 claims that 60-80 kg reactors might be possible.
petra 7y ago
The theoretical maximum is higher than gasoline(1700Wh/Kg[2]), and that's what matters: rechargable Li/CuCl2 could offer 1166.4 Wh/kg[1], while recyclable, non-rechargeable aluminum-air could offer 5200Wh/Kg[1]. Some batteries may have 200K recharge cycles[3]. Innolith is talking about a battery with 50K recharge cycles[4], but for the grid. They also talk abuot building a 1000Wh/Kg battery for cars. But who knows , they're a startup, so we'll need to wait and see. And phinergy, another startup working on recyclable aluminum-air battery - is planning to open a factory in India in 2020. [1]https://electronics.stackexchange.com/questions/4328/whats-the-highest-theoretical-energy-density-for-a-chemical-battery https://electronics.stackexchange.com/questions/4328/whats-t... [2]https://phys.org/news/2018-10-catalyst-high-energy-aluminum-air-batteries.html https://phys.org/news/2018-10-catalyst-high-energy-aluminum-... [3]https://www.pcmag.com/news/343967/researchers-stumble-on-a-200-000-cycle-battery https://www.pcmag.com/news/343967/researchers-stumble-on-a-2... [4]https://www.pv-magazine.com/2018/10/10/innolith-launches-inflammable-battery-with-50000-charging-cycles/ https://www.pv-magazine.com/2018/10/10/innolith-launches-inf...
- geogra4 7y ago
  That wouldn't be a huge problem, and probably much better for the world if we "gased up" with aluminum
  - Klinky 7y ago
    Aluminum requires huge amounts of electricity to produce. Hopefully that electricity isn't coming from fossil fuels. However it does appear to be highly recyclable, at a fraction of the energy cost.
    - mrfusion 7y ago
      The beauty of electricity is that it can come from anywhere. And you don’t have to change anything in your process to change source of electricity.
      - chongli 7y ago
jiggawatts 7y ago
It helps to simplify the problem into a more fundamental thing instead of focusing specifically on batteries. Essentially, all practical energy storage can be thought of as putting some sort of strain on chemical bonds. That is, you're taking things away from a low-energy configuration to a high-energy configuration and back to store and retrieve the energy. The insightful part is that all energy storage systems (aside from Nuclear) are fundamentally this! They're all made of matter, and they all "strain" chemical bonds of one type or another. People think of "batteries" as something special, but they're fundamentally the same as explosives, compressed gas cylinder, superconducting magnetic storage, flywheels, or whatever. All of them are limited by chemical bond strengths and start going BOOM if you push them too far. Explosives... explode if the stored chemical potential energy is too great. A lot of research goes into finding novel compounds that approach such limits as close as possible without actually going bang. Compressed gas cylinders can store energy, but explode when the pressure ruptures the walls -- which have a tensile strength dependent on the chemical bonds of the material used to make them. Magnetic storage is an exotic approach, but used in MRIs and some power stations. The ultimate storage limit is that strong magnetic fields produce significant forces that can rip even steel apart. Flyweels are typically made of materials with high tensile strengths to allow them to be spun up to higher RPMs. Again, the tensile strength depends on the internal chemical bonds of the material. In all cases, the upper limit is ultimately bounded by the available chemical bond strengths of the known elements, one way or another. There are only very few ways past this limit. Anti-matter storage is probably the most "practical" energy storage method currently known that significantly exceeds chemical bond strength limits. In practice, separating chemicals helps a lot. Liquid fuels can store much more energy than explosives. People think a stick of TNT has a lot of energy, but a candle the same size releases vastly more when it burns. There are grid-scale battery systems that rely on this approach, using tanks of chemicals to keep things apart. Still though, the maximum energy you can recover from a fuel and an oxidizer is limited by the difference in chemical bond strengths between the reagents and the end product. I'm not quite sure what the maximum possible energy release is, but chances are that it's whatever the Caesium-Fluorine reaction produces, or close to it. PS: This is why I chuckle when people are shocked to hear about exploding phone batteries. Well... duh. That's literally what a "high capacity battery is", it's a chemical system that's packed full of energy. Literally ready to explode, held back from the brink only through careful arrangement of its constituent parts.
magicalhippo 7y ago
> Is there a theoretical limit on how much energy a rechargeable battery of, say, 1 kg mass can hold? As with most things, you can find some fairly irrelevant theoretical maximum. It's fairly irrelevant because real life implementations will invariably involve compromises. It can be nice to know the limit, but it's not terribly useful for making an actual device. For rechargeable batteries, it's not just about how much energy the battery can store, but how fast can you charge and discharge, what's the recharge efficiency like, does it degrade when recharged, can it be deep cycled without adverse effects, how sensitive it is to physical and electrical disturbances, does it have high or low self-discharge and so on. Different applications have different demands and so there's usually not a single optimal battery technology.
mrfusion 7y ago
I’ve always wondered what the energy density of superconducting rings is? I guess no one has ever tried to optimize one for weight or size.
andrewtbham 7y ago
"It is not feasible to get much more energy into a material than 1 eV per atom. Most solids have atomic weights of 30 GeV/c^2 [*] which yields E/m = 3x10^-11 c^2. When you convert this into the more human Watt-hour/kg, you get 850 W-hr/kg. " https://www.quora.com/Is-it-true-that-battery-energy-density-improves-5-8-per-year-Does-this-represent-an-average-or-is-it-a-consistent-trend-each-year-Do-these-improvements-increase-the-cost-What-has-been-the-trend-if-any-regarding-energy-to-weight-ratio https://www.quora.com/Is-it-true-that-battery-energy-density... I believe.. this is true, but not 100% sure. However the limit is higher with air batteries... as stated in another answer. The energy density of gasoline is high because it uses air intake for oxidation. Also... part of why rockets are so big is because they also don't use oxygen from the atmosphere, they carry their oxidizer in the rocket.
- marcosdumay 7y ago
  This is an orders of magnitude approximation.
- alexis_fr 7y ago
  Tesla Model 3’s batteries are 207 Wh/kg. It strikes me as so close to the limit, whereas we usually are an order of magnitude under, in physics. At one point the only improvement beyond the physical barrier will be to throw electrons into a void sphere and call that a battery.
andrewtbham 7y ago
Interestingly your two questions point towards a trade off in battery design. Current research is adding more silicon to the batteries to increase energy density but doing so makes the battery degrade. https://phys.org/news/2019-01-tiny-silicon-particles-power-lithium.html https://phys.org/news/2019-01-tiny-silicon-particles-power-l... "Silicon shows promise for building much higher-capacity batteries because it's abundant and can absorb much more lithium than the graphite used in current lithium ion batteries. The problem is that silicon is prone to fracturing and breaking after numerous charge-and-discharge cycles, because it expands and contracts as it absorbs and releases lithium ions."
naasking 7y ago
> Is there a theoretical limit on how much energy a rechargeable battery of, say, 1 kg mass can hold A sufficiently high energy density will collapse into a black hole, so a theoretical limit on ordinary energy storage definitely exists. But it might still be possible to use black holes since they radiate energy as Hawking radiation: https://en.wikipedia.org/wiki/Black_hole_starship https://en.wikipedia.org/wiki/Black_hole_starship
- founderling 7y ago
  A battery with 1 kg of mass would only collapse into into a black hole if it is very small. A bottle of water is 1 kg and I never saw one collapsing.
  - naasking 7y ago
    Hence why I said energy density.
kleton 7y ago
A lithium/air battery is 40.1 MJ/kg. There are people working on aprotic liquid electrolytes that could be used with secondary (rechargeable) cells with a metallic lithium anode.

vincnetas 7y ago

if by battery you mean box with two wires, then for the first one answer is yes. for example batery storing energy in fast spinning mater. for second one i assume theoretical energy dencity limit is much greater than anything that we might need. but for chemical bateries i would also like to find out answers to your questions.

founderling 7y ago
I mean for batteries in general. Independent of the technology. For the spinning matter battery, the limit might be when the whole matter of 1 kg spins at the speed of light. I wonder if it matters how big the radius is with which it spins around the center? For a non-rechargeable battery, I guess the limit is 1kg * c^2. As Einstein postulated that e=mc^2. And that guy was right more often then not. Is that also the upper limit for rechargeable batteries? How long could a Tesla drive on 1kg * c^2?
- Faaak 7y ago
  1kg * c² = 24 TWh. Supposing a Tesla averages 200Wh/km, then it would drive ~ 10¹¹ km (4 light-days, or around 600 times the earth-sun distance... which is a lot)
  - founderling 7y ago
    If Wolfram Alpha is right, then 10^11 km is 2 million times around the earth: https://www.wolframalpha.com/input/?i=10%5E11km+%2F+earth+circumference https://www.wolframalpha.com/input/?i=10%5E11km+%2F+earth+ci... Shows the potential of batteries. Charge your one kilo batttery to drive around the planet two million times.
    - mensetmanusman 7y ago
      It would be a misnomer in common parlance to describe nuclear fuel as a battery (mass > energy conversion). The broader language to describe this is ‘energy storage.’ E.g. oil is stored solar energy over millions of years, batters are stored electrochemical energy, flywheels are stored mechanical energy, etc.
  - nielsole 7y ago
    At least in the medium-term future we would at most be able to use is Hydrogen->Helium which would yield 6.45 x 10^14 Joules [1] which is equivalent to 179 GWh which at 200Wh/km would be 8.95*10^8 km. That's still enough to go 20.000 times around the globe and longer than any car is known to have lasted so far[2] [1] https://www.phys.ksu.edu/personal/wysin/astro/review9/p4.html https://www.phys.ksu.edu/personal/wysin/astro/review9/p4.htm... [2] https://en.wikipedia.org/wiki/Car_longevity https://en.wikipedia.org/wiki/Car_longevity
- andyljones 7y ago
  Yeah, the absolute limit is c^2 if you've got 50-50 matter-antimatter. The efficiency however is brought down by the difficulty of _producing_ antimatter in the first place. A more popular hard-sci-fi concept is black hole engines; a 600kt black hole sprays out a hundred petawatts of Hawking radiation, and the fuel is whatever you've got lying around. That still has issues around energy _capture_, since the radiation is going to be ridiculously high-frequency. The best way I've heard of to dodge those issues is the 'Penrose process', where the fuel is the black hole's rotation and you get good ol' kinetic energy out. That can at most get you 20% of the mass-energy though, and there's a bunch more small print.
  - ThomasBHickey 7y ago
    20% is the energy gain of particles involved in each energy transfer, total energy available is 29% of the black hole's rotational energy according to Wikipedia.
- the8472 7y ago
  > For a non-rechargeable battery, I guess the limit is 1kg * c^2. Assuming it is antimatter-based you can double that capacity by consuming air. But that just turns it into a fuel tank for an internal annihilation engine and hardly qualifies as battery anymore.
  - microtherion 7y ago
    This is Tesla we’re talking about. They’d probably ship this with a footnote in the owners’ manual: “Any use of this doomsday device for purposes other than a battery is prohibited. Do not operate outside containment field.’
  - founderling 7y ago
    Aha! So the most efficient mass based rechargeable battery would be one that while loading creates antimatter and while being used burns that antimatter with air (or other stuff) it takes from the environment.
  - JshWright 7y ago
    > hardly qualifies as battery anymore Why not? There are plenty of battery technologies that use air as an oxidizer.
    - slavik81 7y ago
      It follows from the definitions of a battery and a cell: > battery: a container consisting of one or more cells, in which chemical energy is converted into electricity and used as a source of power. > cell: a device containing electrodes immersed in an electrolyte, used for current-generation or electrolysis. An antimatter reactor would not be a battery because it would not contain any cells. Additionally, because it converts nuclear energy into useful power, not chemical energy.
  - zaroth 7y ago
    You all really took this question and ran with it in a way that totally avoids answering the practical question at the core — how good are these batteries going to get over the next 20 years? The answer is really, really good. Fast charging, long rang, 1 million mile lifespans. Add on top of that the ability to connect into a smart grid and earn money by buying energy off-peak and selling on-peak, and the ability to double as an emergency generator for your home.
- deleted 7y ago
  [deleted]
- saagarjha 7y ago
  > For the spinning matter battery, the limit might be when the whole matter of 1 kg spins at the speed of light. Of course, it's theoretically impossible for the matter to spin at the speed of light, and any actual material will tear itself apart at speeds far below c.

morley 7y ago

Another tangential question I've been struggling with is: is there a human limit to a power density we'll tolerate? Any sufficiently powerful battery is a defect or bad actor away from becoming a weapon. We already see defects in lithium batteries shaping airline policy, and the devices we're talking about are peanuts if we want to enable all our sci-fi dreams.

deleted 7y ago
[deleted]
the8472 7y ago
It depends on how easy it is to release the energy. A full petrol tank already contains a scary amount of energy, but you can't release it instantanously since it is bottlenecked by oxygen intake for combustion. Explosives bring their own compact oxidizer to get around that problem. A chunk of uranium-238 contains a lot of energy but it is only fissionable but not fissile, so you need an external fast neutron source to extract that energy. Comparatively it is a fairly safe energy source for its density. Similarly there are some metastable nuclear isomers that can theoretically be stimulated to release their energy with high energy photons with a precise frequency and would otherwise release their energy relatively slowly through their natural decay modes. And I think the difficulty of turning a hypothetical portable fusion power plant into an explosive device should be evident from the difficulties of keeping current experiments running for even a few minutes.
- baybal2 7y ago
  I just though of an interesting twist on subcritical reactor. What about smelting a californium neutron source together with the fuel? We get a much cheaper RTG alternative with near no need for regulation. Any nuclear scientists here?
ChuckNorris89 7y ago
There is a power limit already in place for batteries you can carry on airlines and IIRC it's 100 Wh. As for weaponizing batteries, pretty sure bad actors have been able to cook dangerous bombs at home for decades that can inflict magnitudes more damage than a battery could ever do. So battery based bombs won't be a thing for the near future.

deleted 7y ago

[deleted]

jacquesm 7y ago

> I am asking for the theoretical possibility. That's a nonsense question then. Theoretical limits on power density will revolve around unobtanium and matter-anti-matter explosions; it's off topic as far as I'm concerned in a thread about Tesla acquiring a Canadian Battery Specialist, a company that is engineering batteries in the real world where practical limitations of materials science and chemistry are the ingredients, not your fantasy of what amount of energy one could theoretically store in a given volume if all of natures laws would be lifted. For reference, just the kinetic energy of a couple of liters of Neutron star alone should also figure into such discussions as well as a whole bunch of other nonsense.

JshWright 7y ago
> just the kinetic energy of a couple of liters of Neutron star alone should also figure into such discussions That would have a mass _substantially_ higher than 1kg...

fulafel 7y ago

An efficient (power density within factor of ~ 1e6 of the ideal mc^2 power source) EV battery doesn't need to be rechargeable, because the battery capacity will outlast the vehicle. Approximately same goes for stuff we already know how to build, vehicle applications of nuclear batteries and reactors. Although IIRC for practical reasons nuclear refueling is done ever 10 years or so in terrestial applications.

zaroth 7y ago
Wait, what? It sounds like you’re saying if cars had fusion reactors for engines then we wouldn’t need rechargeable batteries?
- fulafel 7y ago
  Yes, we just need to restart DeLorean production... I'm not sure how far we have studied the miniaturization of reactors. There were some designs for airplanes and cruise missiles in the 50s. And there's the current Russian missile (https://en.wikipedia.org/wiki/9M730_Burevestnik https://en.wikipedia.org/wiki/9M730_Burevestnik). A paper at https://aip.scitation.org/doi/abs/10.1063/1.1358022 https://aip.scitation.org/doi/abs/10.1063/1.1358022 claims that 60-80 kg reactors might be possible.

petra 7y ago

The theoretical maximum is higher than gasoline(1700Wh/Kg[2]), and that's what matters: rechargable Li/CuCl2 could offer 1166.4 Wh/kg[1], while recyclable, non-rechargeable aluminum-air could offer 5200Wh/Kg[1]. Some batteries may have 200K recharge cycles[3]. Innolith is talking about a battery with 50K recharge cycles[4], but for the grid. They also talk abuot building a 1000Wh/Kg battery for cars. But who knows , they're a startup, so we'll need to wait and see. And phinergy, another startup working on recyclable aluminum-air battery - is planning to open a factory in India in 2020. [1]https://electronics.stackexchange.com/questions/4328/whats-the-highest-theoretical-energy-density-for-a-chemical-battery https://electronics.stackexchange.com/questions/4328/whats-t... [2]https://phys.org/news/2018-10-catalyst-high-energy-aluminum-air-batteries.html https://phys.org/news/2018-10-catalyst-high-energy-aluminum-... [3]https://www.pcmag.com/news/343967/researchers-stumble-on-a-200-000-cycle-battery https://www.pcmag.com/news/343967/researchers-stumble-on-a-2... [4]https://www.pv-magazine.com/2018/10/10/innolith-launches-inflammable-battery-with-50000-charging-cycles/ https://www.pv-magazine.com/2018/10/10/innolith-launches-inf...

geogra4 7y ago
That wouldn't be a huge problem, and probably much better for the world if we "gased up" with aluminum
- Klinky 7y ago
  Aluminum requires huge amounts of electricity to produce. Hopefully that electricity isn't coming from fossil fuels. However it does appear to be highly recyclable, at a fraction of the energy cost.
  - mrfusion 7y ago
    The beauty of electricity is that it can come from anywhere. And you don’t have to change anything in your process to change source of electricity.
    - chongli 7y ago

jiggawatts 7y ago

It helps to simplify the problem into a more fundamental thing instead of focusing specifically on batteries. Essentially, all practical energy storage can be thought of as putting some sort of strain on chemical bonds. That is, you're taking things away from a low-energy configuration to a high-energy configuration and back to store and retrieve the energy. The insightful part is that all energy storage systems (aside from Nuclear) are fundamentally this! They're all made of matter, and they all "strain" chemical bonds of one type or another. People think of "batteries" as something special, but they're fundamentally the same as explosives, compressed gas cylinder, superconducting magnetic storage, flywheels, or whatever. All of them are limited by chemical bond strengths and start going BOOM if you push them too far. Explosives... explode if the stored chemical potential energy is too great. A lot of research goes into finding novel compounds that approach such limits as close as possible without actually going bang. Compressed gas cylinders can store energy, but explode when the pressure ruptures the walls -- which have a tensile strength dependent on the chemical bonds of the material used to make them. Magnetic storage is an exotic approach, but used in MRIs and some power stations. The ultimate storage limit is that strong magnetic fields produce significant forces that can rip even steel apart. Flyweels are typically made of materials with high tensile strengths to allow them to be spun up to higher RPMs. Again, the tensile strength depends on the internal chemical bonds of the material. In all cases, the upper limit is ultimately bounded by the available chemical bond strengths of the known elements, one way or another. There are only very few ways past this limit. Anti-matter storage is probably the most "practical" energy storage method currently known that significantly exceeds chemical bond strength limits. In practice, separating chemicals helps a lot. Liquid fuels can store much more energy than explosives. People think a stick of TNT has a lot of energy, but a candle the same size releases vastly more when it burns. There are grid-scale battery systems that rely on this approach, using tanks of chemicals to keep things apart. Still though, the maximum energy you can recover from a fuel and an oxidizer is limited by the difference in chemical bond strengths between the reagents and the end product. I'm not quite sure what the maximum possible energy release is, but chances are that it's whatever the Caesium-Fluorine reaction produces, or close to it. PS: This is why I chuckle when people are shocked to hear about exploding phone batteries. Well... duh. That's literally what a "high capacity battery is", it's a chemical system that's packed full of energy. Literally ready to explode, held back from the brink only through careful arrangement of its constituent parts.

magicalhippo 7y ago

> Is there a theoretical limit on how much energy a rechargeable battery of, say, 1 kg mass can hold? As with most things, you can find some fairly irrelevant theoretical maximum. It's fairly irrelevant because real life implementations will invariably involve compromises. It can be nice to know the limit, but it's not terribly useful for making an actual device. For rechargeable batteries, it's not just about how much energy the battery can store, but how fast can you charge and discharge, what's the recharge efficiency like, does it degrade when recharged, can it be deep cycled without adverse effects, how sensitive it is to physical and electrical disturbances, does it have high or low self-discharge and so on. Different applications have different demands and so there's usually not a single optimal battery technology.

mrfusion 7y ago

I’ve always wondered what the energy density of superconducting rings is? I guess no one has ever tried to optimize one for weight or size.

andrewtbham 7y ago

"It is not feasible to get much more energy into a material than 1 eV per atom. Most solids have atomic weights of 30 GeV/c^2 [*] which yields E/m = 3x10^-11 c^2. When you convert this into the more human Watt-hour/kg, you get 850 W-hr/kg. " https://www.quora.com/Is-it-true-that-battery-energy-density-improves-5-8-per-year-Does-this-represent-an-average-or-is-it-a-consistent-trend-each-year-Do-these-improvements-increase-the-cost-What-has-been-the-trend-if-any-regarding-energy-to-weight-ratio https://www.quora.com/Is-it-true-that-battery-energy-density... I believe.. this is true, but not 100% sure. However the limit is higher with air batteries... as stated in another answer. The energy density of gasoline is high because it uses air intake for oxidation. Also... part of why rockets are so big is because they also don't use oxygen from the atmosphere, they carry their oxidizer in the rocket.

marcosdumay 7y ago
This is an orders of magnitude approximation.
alexis_fr 7y ago
Tesla Model 3’s batteries are 207 Wh/kg. It strikes me as so close to the limit, whereas we usually are an order of magnitude under, in physics. At one point the only improvement beyond the physical barrier will be to throw electrons into a void sphere and call that a battery.

andrewtbham 7y ago

Interestingly your two questions point towards a trade off in battery design. Current research is adding more silicon to the batteries to increase energy density but doing so makes the battery degrade. https://phys.org/news/2019-01-tiny-silicon-particles-power-lithium.html https://phys.org/news/2019-01-tiny-silicon-particles-power-l... "Silicon shows promise for building much higher-capacity batteries because it's abundant and can absorb much more lithium than the graphite used in current lithium ion batteries. The problem is that silicon is prone to fracturing and breaking after numerous charge-and-discharge cycles, because it expands and contracts as it absorbs and releases lithium ions."

naasking 7y ago

> Is there a theoretical limit on how much energy a rechargeable battery of, say, 1 kg mass can hold A sufficiently high energy density will collapse into a black hole, so a theoretical limit on ordinary energy storage definitely exists. But it might still be possible to use black holes since they radiate energy as Hawking radiation: https://en.wikipedia.org/wiki/Black_hole_starship https://en.wikipedia.org/wiki/Black_hole_starship

founderling 7y ago
A battery with 1 kg of mass would only collapse into into a black hole if it is very small. A bottle of water is 1 kg and I never saw one collapsing.
- naasking 7y ago
  Hence why I said energy density.

kleton 7y ago

A lithium/air battery is 40.1 MJ/kg. There are people working on aprotic liquid electrolytes that could be used with secondary (rechargeable) cells with a metallic lithium anode.