11 ms·

Lithium-Sulfur Battery Project Aims to Double the Range of Electric Airplanes

95 points by pross356 7y ago

adammunich 7y ago
Have they solved the problems of 1. sulfur plating the anode? 2. The cathode swelling during charge and mechanically damaging the cell? If so, I'm excited! But last I checked thier solution to #2 was to clamp the cell between metal plates, which nullified the gains in energy density when considering the mass of the clamps.
- chrisdwyer 7y ago
  1 & 2. Not really and not really. Curious, have you ever heard of Boron-Nitride Nanotubes (BNNT)? Basically a new nanomaterial that is similar to carbon nanotubes except it has the rare property of being a high energy band-width semiconductor whilst having excellent thermal conductivity (basically solves problems 1. and 2.). Only problem is that its really hard to produce in mass quantity... well maybe... have a look at the company PPK
philipkglass 7y ago
No lithium-sulfur battery (so far) survives enough charge-discharge cycles to be attractive for portable electronics or electric cars. But higher energy density makes it potentially attractive over lithium ion batteries for aircraft. Even if you have to replace the batteries after e.g. only 100 cycles, that could enable multi-month missions for solar powered high altitude UAVs. The Airbus Zephyr was using lithium-sulfur batteries back in 2015: https://cosmosmagazine.com/technology/lighter-cheaper-satellite https://cosmosmagazine.com/technology/lighter-cheaper-satell...
RcouF1uZ4gsC 7y ago
> They said the Oxis battery would provide “in excess” of 500 Wh/kg, a number which appears to apply to the individual cells, rather than the battery pack, with all its packaging, power electronics, and other paraphernalia. For comparison the energy density of gasoline is 12,200 Wh/kg https://xtronics.com/wiki/Energy_density.html https://xtronics.com/wiki/Energy_density.html
- scotchmi_st 7y ago
  Although it's more complicated than that, because IC engines are only have about 15% efficiency, whereas electric motors are up at about 80%.
  - nradov 7y ago
    Real world efficiency for modern gasoline engines is closer to 20%. In hybrid applications they can get up to 35%.
    - djaychela 7y ago
      >In hybrid applications they can get up to 35%. But surely that is largely due to the electric element of the combined powertrain? The ICE part hasn't magically become more efficent?
      - tasty_freeze 7y ago
        The whole point of a hybrid is to run the ICE only in its most efficient region. At low loads the electric battery drives the car. If the battery gets too low, then the ICE runs, but rather than running at a low (and inefficient) load, it runs at its sweet spot and the excess power it generates charges the battery. When the demand is high, rather than running the ICE hard, it is kept at its sweet spot and the electric motor boosts power instead. So yes, the ICE part is more efficient in a hybrid, though it isn't magic.
      - aidenn0 7y ago
        The ICE is more efficient because the design constraints have changed. Here's a single example with the Prius: 1. The intake valve stays open for part of the compression stroke. 2. (1) means that the compression ratio for the compression stroke is lower than the compression ratio for the power stroke. 3. The efficiency of the engine is limited by the compression ratio of the power stroke 4. The compression ratio of the compression stroke is limited by engine knocking (if you compress a mixture of fuel and air too much, it will spontaneously combust) 5. So this engine can be made more efficient than an engine that closes the valve for the entire compression stroke 6. Some (non-hybrid) engines have variable valve timing and can do (1) some of the time, to a small extent. 7. Doing (1) to a larger extent makes the low-RPM torque very poor. 8. Electric motors have excellent low-RPM torque, so (7) is compensated for by having an electric motor run at low speeds.
aazaa 7y ago
See also lithium-air (aka lithium oxygen) battery: https://en.wikipedia.org/wiki/Lithium–air_battery https://en.wikipedia.org/wiki/Lithium–air_battery
svara 7y ago
Electric aviation always strikes me as an odd idea, given the low power densities that batteries achieve. By contrast, biofuels are available today and can be made from agricultural waste products (2nd gen), in bioreactors using salt water algae (3rd gen) or electrochemically (4th gen). They're potentially a drop in replacement for regular fuel - for planes, but also for cars. Due to the lower energy requirements for building ICE cars versus batteries, a biofuel powered car will be much better for CO2 emissions than an electric one, which you need to drive for many years before it beats a similar sized gasoline fueled car on sum CO2 emissions. So why are we not heavily investing in biofuel infrastructure? Why are electric motors and batteries hyped up as being the tech of the future? That's an honest question, since I've yet to hear a well-founded physical or engineering argument against it.
- jeffreyrogers 7y ago
  Don't biofuels take up way too much land to be economical? A large portion of US crop area is for corn and soybeans for ethanol and biodiesel. I can see the reasoning behind biofuels for aircraft, but I don't think biofuels are sustainable if people continue driving as much as they do now.
  - JumpCrisscross 7y ago
    > Don't biofuels take up way too much land to be economical? Can we turn solar energy into hydrocarbons? (Water and CO2 are total feedstocks.)
    - philipkglass 7y ago
      Yes. Hydrogenate CO2 to methanol with electrolytic hydrogen produced from clean electricity [1]. Reform methanol to hydrocarbons [2] that can burn in existing engines. (Or burn methanol itself in slightly modified engines. This offers somewhat lower energy density per tankful of fuel, higher total efficiency from electricity-to-motion.) Synthetic fuel makes sense for fueling aircraft, rockets, long distance shipping, collectible historic cars, and other niches. It doesn't make sense for fueling everyday ground transportation. Too much of the original energy is lost in the chain of chemical transformations and the chemical processing requires facilities on the scale of conventional oil refineries. The total cost is lower to electrify ground transportation and supply it with clean electricity than to transform clean electricity into liquid fuels for equivalent legacy vehicles. [1] https://www.frontiersin.org/articles/10.3389/fchem.2018.00446/full https://www.frontiersin.org/articles/10.3389/fchem.2018.0044... [2] https://en.wikipedia.org/wiki/Gas_to_liquids https://en.wikipedia.org/wiki/Gas_to_liquids
ctocoder 7y ago
Whoever creates a better battery, which moves us away from Li, will be a trillionaire. I do not think lithium or a chemical battery is the right solution. Too expensive and polluting. I am hoping for a silicon battery that will take over the world.
- ghgfhgfhn 7y ago
  It's all about the super capacitors.
- rvz 7y ago
  > Whoever creates a better battery, which moves us away from Li, will be a trillionaire. So now it should be a golden age to be a chemical engineer or a physicist specialising in battery technology research I suppose. > I am hoping for a silicon battery that will take over the world. Chemical Engineers and Battery Technologists will be the new 'Software Engineers'.
  - Xcelerate 7y ago
    As a chemical engineer who did my Ph.D in Li-ion battery anodes, I switched to data science immediately afterward. So I wish you were right, but I wouldn’t count on it any time soon.
    - cagenut 7y ago
      uh... unless that data science is on like cancer research or something please go back
- adammunich 7y ago
  Lithium is here to stay for a while because it has the best ion mobility of any reactive metal. Sodium is much fatter and slower, but might be good for grid storage.
PowerfulWizard 7y ago
This reminded me of a graph I thought was really interesting from a thesis on a solar powered UAV that shows energy density and power per weight for different sources of energy, I've highlighted the 500wh/kg line which is being claimed in the article: https://i.imgur.com/nZSWpW1.png https://i.imgur.com/nZSWpW1.png Should be very interesting if they can deliver that level of performance. The source document for that graph is here: https://ethz.ch/content/dam/ethz/special-interest/mavt/robotics-n-intelligent-systems/asl-dam/documents/phd_thesis/Andre_Noth_Design_of_Solar_Powered_Airplanes_for_Continuous_Flight.pdf https://ethz.ch/content/dam/ethz/special-interest/mavt/robot... And described here: https://spie.org/news/1649-designing-solar-airplanes-for-continuous-flight?SSO=1 https://spie.org/news/1649-designing-solar-airplanes-for-con...
- m463 7y ago
  24,965,421,631,578 wh/kg (antimatter) 23,222,915,000 wh/kg (plutonium 239) https://en.wikipedia.org/wiki/Energy_density#Table_of_energy_content https://en.wikipedia.org/wiki/Energy_density#Table_of_energy...
  - the8472 7y ago
    If your goal is to use exciting power sources then those two have a flaw, they can be scaled down to fit the power needs of the plane, which would limit the spectacle you could achieve. The penrose process may be a better choice since there's a miniaturization limit.
    - xyzzyz 7y ago
      You can, in fact, put a functional nuclear reactor on a plane: https://en.wikipedia.org/wiki/Tupolev_Tu-95LAL https://en.wikipedia.org/wiki/Tupolev_Tu-95LAL . Of course, it's a terrible idea, but it is feasible.
      - m463 7y ago
        The holy grail would be to put antimatter on a spaceship. Instead of the pyramid of fuel mass needed to escape a gravity well, the capsule would basically be constant mass. An antimatter-powered spaceship could conquer the solar system or even the universe.
joshfraser 7y ago
Flying at higher altitudes reduces drag and increases efficiency due to the thinner air. Ideally, we'd be flying planes a lot higher than we do today. The problem is combustion engines need oxygen and the higher you go, the less oxygen you have available. Electric planes don't have that problem which could be the secret to faster global travel.
- Scramblejams 7y ago
  The SR-71 and U-2 flew plenty high and had enough oxygen. When you’re high enough that there’s no oxygen, you have no atmosphere, and then your wings and turbines don’t do anything useful. That means it’s rocket time. Also, depressurization happens, and the risks and complexity of workarounds increase with altitude.
  - namirez 7y ago
    > The SR-71 and U-2 flew plenty high and had enough oxygen Actually none those two planes had fully pressurized cockpits. I guess they were pressurized at 26k feet altitude pressure. That's why the pilots were literally wearing spacesuits. https://images.app.goo.gl/KjqGARoyiddhDxAE6 https://images.app.goo.gl/KjqGARoyiddhDxAE6
    - Scramblejams 7y ago
      GP was referencing oxygen in regards to combustion, not the cockpit. The space suits weren't because of the cockpit altitude (when the cockpit was pressurized), they were because the crew were operating well above the Armstrong Limit and no amount of oxygen could keep them awake in the event of depressurization without the suit.
- ohazi 7y ago
  Unless you're thinking supersonic travel, the "coffin corner" (difference between stall speed and Mach 1 (or Vne)) also narrows as you get higher. In an extreme case, the U-2 cruises at 70,000 ft, and at that altitude the stall speed is about 10 knots below the maximum speed.
taf2 7y ago
I can imagine two really amazing effects from electric airplanes 1. Noise pollution could be significantly reduced . So many flight paths over homes. 2. Cost efficiencies could be amazing with fuel anywhere from 25% - 35% fluctuations, https://www.statista.com/statistics/591285/aviation-industry-fuel-cost/ https://www.statista.com/statistics/591285/aviation-industry... I imagine the operating cost of electric would be even less due to the simpler design of engines for electric vs gas In my dreams airplanes could be designed to be more comfortable due to fixed operating costs... that would be nice
Tade0 7y ago
I've been following this company since their announcement of "300Wh/kg soon" a few years ago. The pace of their progress is not jaw-dropping, but if anyone has a shot at bringing this chemistry to the market, it's them.

95 points by pross356 7y ago

Have they solved the problems of 1. sulfur plating the anode? 2. The cathode swelling during charge and mechanically damaging the cell? If so, I'm excited! But last I checked thier solution to #2 was to clamp the cell between metal plates, which nullified the gains in energy density when considering the mass of the clamps.

chrisdwyer 7y ago
1 & 2. Not really and not really. Curious, have you ever heard of Boron-Nitride Nanotubes (BNNT)? Basically a new nanomaterial that is similar to carbon nanotubes except it has the rare property of being a high energy band-width semiconductor whilst having excellent thermal conductivity (basically solves problems 1. and 2.). Only problem is that its really hard to produce in mass quantity... well maybe... have a look at the company PPK

philipkglass 7y ago

No lithium-sulfur battery (so far) survives enough charge-discharge cycles to be attractive for portable electronics or electric cars. But higher energy density makes it potentially attractive over lithium ion batteries for aircraft. Even if you have to replace the batteries after e.g. only 100 cycles, that could enable multi-month missions for solar powered high altitude UAVs. The Airbus Zephyr was using lithium-sulfur batteries back in 2015: https://cosmosmagazine.com/technology/lighter-cheaper-satellite https://cosmosmagazine.com/technology/lighter-cheaper-satell...

RcouF1uZ4gsC 7y ago

> They said the Oxis battery would provide “in excess” of 500 Wh/kg, a number which appears to apply to the individual cells, rather than the battery pack, with all its packaging, power electronics, and other paraphernalia. For comparison the energy density of gasoline is 12,200 Wh/kg https://xtronics.com/wiki/Energy_density.html https://xtronics.com/wiki/Energy_density.html

scotchmi_st 7y ago
Although it's more complicated than that, because IC engines are only have about 15% efficiency, whereas electric motors are up at about 80%.
- nradov 7y ago
  Real world efficiency for modern gasoline engines is closer to 20%. In hybrid applications they can get up to 35%.
  - djaychela 7y ago
    >In hybrid applications they can get up to 35%. But surely that is largely due to the electric element of the combined powertrain? The ICE part hasn't magically become more efficent?
    - tasty_freeze 7y ago
      The whole point of a hybrid is to run the ICE only in its most efficient region. At low loads the electric battery drives the car. If the battery gets too low, then the ICE runs, but rather than running at a low (and inefficient) load, it runs at its sweet spot and the excess power it generates charges the battery. When the demand is high, rather than running the ICE hard, it is kept at its sweet spot and the electric motor boosts power instead. So yes, the ICE part is more efficient in a hybrid, though it isn't magic.
    - aidenn0 7y ago
      The ICE is more efficient because the design constraints have changed. Here's a single example with the Prius: 1. The intake valve stays open for part of the compression stroke. 2. (1) means that the compression ratio for the compression stroke is lower than the compression ratio for the power stroke. 3. The efficiency of the engine is limited by the compression ratio of the power stroke 4. The compression ratio of the compression stroke is limited by engine knocking (if you compress a mixture of fuel and air too much, it will spontaneously combust) 5. So this engine can be made more efficient than an engine that closes the valve for the entire compression stroke 6. Some (non-hybrid) engines have variable valve timing and can do (1) some of the time, to a small extent. 7. Doing (1) to a larger extent makes the low-RPM torque very poor. 8. Electric motors have excellent low-RPM torque, so (7) is compensated for by having an electric motor run at low speeds.

aazaa 7y ago

See also lithium-air (aka lithium oxygen) battery: https://en.wikipedia.org/wiki/Lithium–air_battery https://en.wikipedia.org/wiki/Lithium–air_battery

svara 7y ago

Electric aviation always strikes me as an odd idea, given the low power densities that batteries achieve. By contrast, biofuels are available today and can be made from agricultural waste products (2nd gen), in bioreactors using salt water algae (3rd gen) or electrochemically (4th gen). They're potentially a drop in replacement for regular fuel - for planes, but also for cars. Due to the lower energy requirements for building ICE cars versus batteries, a biofuel powered car will be much better for CO2 emissions than an electric one, which you need to drive for many years before it beats a similar sized gasoline fueled car on sum CO2 emissions. So why are we not heavily investing in biofuel infrastructure? Why are electric motors and batteries hyped up as being the tech of the future? That's an honest question, since I've yet to hear a well-founded physical or engineering argument against it.

jeffreyrogers 7y ago
Don't biofuels take up way too much land to be economical? A large portion of US crop area is for corn and soybeans for ethanol and biodiesel. I can see the reasoning behind biofuels for aircraft, but I don't think biofuels are sustainable if people continue driving as much as they do now.
- JumpCrisscross 7y ago
  > Don't biofuels take up way too much land to be economical? Can we turn solar energy into hydrocarbons? (Water and CO2 are total feedstocks.)
  - philipkglass 7y ago
    Yes. Hydrogenate CO2 to methanol with electrolytic hydrogen produced from clean electricity [1]. Reform methanol to hydrocarbons [2] that can burn in existing engines. (Or burn methanol itself in slightly modified engines. This offers somewhat lower energy density per tankful of fuel, higher total efficiency from electricity-to-motion.) Synthetic fuel makes sense for fueling aircraft, rockets, long distance shipping, collectible historic cars, and other niches. It doesn't make sense for fueling everyday ground transportation. Too much of the original energy is lost in the chain of chemical transformations and the chemical processing requires facilities on the scale of conventional oil refineries. The total cost is lower to electrify ground transportation and supply it with clean electricity than to transform clean electricity into liquid fuels for equivalent legacy vehicles. [1] https://www.frontiersin.org/articles/10.3389/fchem.2018.00446/full https://www.frontiersin.org/articles/10.3389/fchem.2018.0044... [2] https://en.wikipedia.org/wiki/Gas_to_liquids https://en.wikipedia.org/wiki/Gas_to_liquids

ctocoder 7y ago

Whoever creates a better battery, which moves us away from Li, will be a trillionaire. I do not think lithium or a chemical battery is the right solution. Too expensive and polluting. I am hoping for a silicon battery that will take over the world.

ghgfhgfhn 7y ago
It's all about the super capacitors.
rvz 7y ago
> Whoever creates a better battery, which moves us away from Li, will be a trillionaire. So now it should be a golden age to be a chemical engineer or a physicist specialising in battery technology research I suppose. > I am hoping for a silicon battery that will take over the world. Chemical Engineers and Battery Technologists will be the new 'Software Engineers'.
- Xcelerate 7y ago
  As a chemical engineer who did my Ph.D in Li-ion battery anodes, I switched to data science immediately afterward. So I wish you were right, but I wouldn’t count on it any time soon.
  - cagenut 7y ago
    uh... unless that data science is on like cancer research or something please go back
adammunich 7y ago
Lithium is here to stay for a while because it has the best ion mobility of any reactive metal. Sodium is much fatter and slower, but might be good for grid storage.

PowerfulWizard 7y ago

This reminded me of a graph I thought was really interesting from a thesis on a solar powered UAV that shows energy density and power per weight for different sources of energy, I've highlighted the 500wh/kg line which is being claimed in the article: https://i.imgur.com/nZSWpW1.png https://i.imgur.com/nZSWpW1.png Should be very interesting if they can deliver that level of performance. The source document for that graph is here: https://ethz.ch/content/dam/ethz/special-interest/mavt/robotics-n-intelligent-systems/asl-dam/documents/phd_thesis/Andre_Noth_Design_of_Solar_Powered_Airplanes_for_Continuous_Flight.pdf https://ethz.ch/content/dam/ethz/special-interest/mavt/robot... And described here: https://spie.org/news/1649-designing-solar-airplanes-for-continuous-flight?SSO=1 https://spie.org/news/1649-designing-solar-airplanes-for-con...

m463 7y ago
24,965,421,631,578 wh/kg (antimatter) 23,222,915,000 wh/kg (plutonium 239) https://en.wikipedia.org/wiki/Energy_density#Table_of_energy_content https://en.wikipedia.org/wiki/Energy_density#Table_of_energy...
- the8472 7y ago
  If your goal is to use exciting power sources then those two have a flaw, they can be scaled down to fit the power needs of the plane, which would limit the spectacle you could achieve. The penrose process may be a better choice since there's a miniaturization limit.
  - xyzzyz 7y ago
    You can, in fact, put a functional nuclear reactor on a plane: https://en.wikipedia.org/wiki/Tupolev_Tu-95LAL https://en.wikipedia.org/wiki/Tupolev_Tu-95LAL . Of course, it's a terrible idea, but it is feasible.
    - m463 7y ago
      The holy grail would be to put antimatter on a spaceship. Instead of the pyramid of fuel mass needed to escape a gravity well, the capsule would basically be constant mass. An antimatter-powered spaceship could conquer the solar system or even the universe.

joshfraser 7y ago

Flying at higher altitudes reduces drag and increases efficiency due to the thinner air. Ideally, we'd be flying planes a lot higher than we do today. The problem is combustion engines need oxygen and the higher you go, the less oxygen you have available. Electric planes don't have that problem which could be the secret to faster global travel.

Scramblejams 7y ago
The SR-71 and U-2 flew plenty high and had enough oxygen. When you’re high enough that there’s no oxygen, you have no atmosphere, and then your wings and turbines don’t do anything useful. That means it’s rocket time. Also, depressurization happens, and the risks and complexity of workarounds increase with altitude.
- namirez 7y ago
  > The SR-71 and U-2 flew plenty high and had enough oxygen Actually none those two planes had fully pressurized cockpits. I guess they were pressurized at 26k feet altitude pressure. That's why the pilots were literally wearing spacesuits. https://images.app.goo.gl/KjqGARoyiddhDxAE6 https://images.app.goo.gl/KjqGARoyiddhDxAE6
  - Scramblejams 7y ago
    GP was referencing oxygen in regards to combustion, not the cockpit. The space suits weren't because of the cockpit altitude (when the cockpit was pressurized), they were because the crew were operating well above the Armstrong Limit and no amount of oxygen could keep them awake in the event of depressurization without the suit.
ohazi 7y ago
Unless you're thinking supersonic travel, the "coffin corner" (difference between stall speed and Mach 1 (or Vne)) also narrows as you get higher. In an extreme case, the U-2 cruises at 70,000 ft, and at that altitude the stall speed is about 10 knots below the maximum speed.

taf2 7y ago

I can imagine two really amazing effects from electric airplanes 1. Noise pollution could be significantly reduced . So many flight paths over homes. 2. Cost efficiencies could be amazing with fuel anywhere from 25% - 35% fluctuations, https://www.statista.com/statistics/591285/aviation-industry-fuel-cost/ https://www.statista.com/statistics/591285/aviation-industry... I imagine the operating cost of electric would be even less due to the simpler design of engines for electric vs gas In my dreams airplanes could be designed to be more comfortable due to fixed operating costs... that would be nice

Tade0 7y ago

I've been following this company since their announcement of "300Wh/kg soon" a few years ago. The pace of their progress is not jaw-dropping, but if anyone has a shot at bringing this chemistry to the market, it's them.