Progress to lithium-oxygen batteries with up to four times the energy density of lithium-ion

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University of Waterloo Chemists are the first to achieve four-electron conversion, which doubles the electron storage of lithium-oxygen, also known as lithium-air, batteries.

The high theoretical-energy density of lithium-oxygen (Li-O2) batteries and their relatively light weight have made them the Holy Grail of rechargeable battery systems. But long-standing issues with the battery’s chemistry and stability have kept them a purely academic curiosity.

Two of the more serious issues involve the intermediate of the cell chemistry (superoxide, LiO2) and the peroxide product (Li2O2) reacting with the porous carbon cathode, degrading the cell from within. In addition, the superoxide consumes the organic electrolyte in the process, which greatly limits the cycle life.

Science – A high-energy-density lithium-oxygen battery based on a reversible four-electron conversion to lithium oxide [C. Xia, C. Y. Kwok, L. F. Nazar, Science 24 Aug 2018: Vol. 361, Issue 6404, pp. 777-781, DOI: 10.1126/science.aas9343]

Nazar and her colleagues switched the organic electrolyte to a more stable inorganic molten salt and the porous carbon cathode to a bifunctional metal oxide catalyst. Then by operating the battery at 150 C, they found that the more stable product Li2O is formed instead of Li2O2. This results in a highly reversible Li-oxygen battery with coulombic efficiency approaching 100%.

By storing O2 as lithium oxide (Li2O) instead of lithium peroxide (Li2O2), the battery not only maintained excellent charging characteristics, it achieved the maximum four-electron transfer in the system, thereby increasing the theoretical energy storage by 50%.

“By swapping out the electrolyte and the electrode host and raising the temperature, we show the system performs remarkably well,” said Nazar, who is also a University Research Professor in the Department of Chemistry at Waterloo.

Science – Hot lithium-oxygen batteries charge ahead [Shuting Feng, Jaclyn R. Lunger, Jeremiah A. Johnson, Yang Shao-Horn Science 24 Aug 2018: Vol. 361, Issue 6404, pp. 758 DOI: 10.1126/science.aau4792]

The need to increase the energy storage per unit mass or volume and to decrease stored-energy cost from solar and wind has motivated research efforts toward developing alternative battery chemistries. In particular, lithium-oxygen (Li-O2) batteries offer great promise. During discharge, oxygen can be reduced to form either peroxide (Li2O2 in a two-electron pathway) or oxide (Li2O in a four-electron pathway). The estimated energy densities of lithium-oxygen batteries based on peroxide and oxide are two and four times higher than that of lithium-ion batteries, respectively, but degradation of organic electrolytes and of oxygen electrodes (typically made of carbon) by these reactive oxygen species has limited the reversibility of these systems. On page 777 of this issue, Xia et al address these issues by using inorganic components—a molten salt electrolyte and a nickel-based oxide supported by stainless steel mesh for the oxygen electrode—and demonstrate reversible operation for the four-electron–pathway Li-O2 battery at 150°C.

An elevated lithium battery

Batteries based on lithium metal and oxygen could offer energy densities an order of magnitude larger than that of lithium ion cells. But, under normal operation conditions, the lithium oxidizes to form peroxide or superoxide. Xia et al. show that, at increased temperatures, the formation of lithium oxide is favored, through a process in which four electrons are transferred for each oxygen molecule (see the Perspective by Feng et al.). Reversible cycling is achieved through the use of a thermally stable inorganic electrolyte and a bifunctional catalyst for both oxygen reduction and evolution reactions.

Abstract

Lithium-oxygen (Li-O2) batteries have attracted much attention owing to the high theoretical energy density afforded by the two-electron reduction of O2 to lithium peroxide (Li2O2). We report an inorganic-electrolyte Li-O2 cell that cycles at an elevated temperature via highly reversible four-electron redox to form crystalline lithium oxide (Li2O). It relies on a bifunctional metal oxide host that catalyzes O–O bond cleavage on discharge, yielding a high capacity of 11 milliampere-hours per square centimeter, and O2 evolution on charge with very low overpotential. Online mass spectrometry and chemical quantification confirm that oxidation of Li2O involves transfer of exactly 4 e–/O2. This work shows that Li-O2 electrochemistry is not intrinsically limited once problems of electrolyte, superoxide, and cathode host are overcome and that coulombic efficiency close to 100% can be achieved.

30 thoughts on “Progress to lithium-oxygen batteries with up to four times the energy density of lithium-ion”

  1. Great! 150 deg-C battery sounds super practical! Gonna create a big side business for adiabatic enclosures; I hear asbestos is a great insulator.

  2. Great! 150 deg-C battery sounds super practical! Gonna create a big side business for adiabatic enclosures; I hear asbestos is a great insulator.

  3. If this works out it is important for battery powered vehicles. Not so much for stationary storage applications. In vehicles high energy per unit mass & volume is the most important factor. For stationary applications high energy per unit cost is the most important, which is why grid energy storage is currently almost all pumped hydro. High energy density *might* also turn out to be cheap, but not necessarily.

  4. Your snarky criticism is silly and unwarranted. 150C is not extreme and thermal management is nothing new to batteries.

  5. You probably don’t want a 150 deg battery in your phone, but it isn’t as silly as it sounds for say a car. Existing petrol cars function with a few hundred kg lump of metal that has to heat up to over 100 deg before you can get full performance. So it’s not completely ridiculous for your battery pack to have multiple types of cell in it. A more normal low temp cell to start off with, and then as the standard heat of operation warms up the rest of the pack you can kick over to the high capacity LiO2 cells. The battery pack would be a bit more sophisticated, with an insulated main section, heat transfer mechanisms designed to heat up and maintain a high temp region. But this could well be worth it for quote “energy densities an order of magnitude larger than that of lithium ion cells” For something like electric aircraft it’s even more applicable. You recharge on the ground which heats up your battery pack (well insulated) and it’s at operating temperature as you unhook the charging leads and begin to taxi. You probably never have to start from cold without external power anyway. Big EV trucks would partway between those cases.

  6. Your snarky criticism is silly and unwarranted. 150C is not extreme and thermal management is nothing new to batteries. Bringing up asbestos is particularly ridiculous. We have lots of materials for thermal insulation and vacuum. Hell even plain PUR sprayfoam can take a meager 150°C temperature.

  7. If this works out it is important for battery powered vehicles. Not so much for stationary storage applications.In vehicles high energy per unit mass & volume is the most important factor. For stationary applications high energy per unit cost is the most important which is why grid energy storage is currently almost all pumped hydro.High energy density *might* also turn out to be cheap but not necessarily.

  8. Your snarky criticism is silly and unwarranted. 150C is not extreme and thermal management is nothing new to batteries. “” “””

  9. You probably don’t want a 150 deg battery in your phone but it isn’t as silly as it sounds for say a car.Existing petrol cars function with a few hundred kg lump of metal that has to heat up to over 100 deg before you can get full performance. So it’s not completely ridiculous for your battery pack to have multiple types of cell in it. A more normal low temp cell to start off with and then as the standard heat of operation warms up the rest of the pack you can kick over to the high capacity LiO2 cells.The battery pack would be a bit more sophisticated with an insulated main section heat transfer mechanisms designed to heat up and maintain a high temp region. But this could well be worth it for quote energy densities an order of magnitude larger than that of lithium ion cells””For something like electric aircraft it’s even more applicable. You recharge on the ground which heats up your battery pack (well insulated) and it’s at operating temperature as you unhook the charging leads and begin to taxi. You probably never have to start from cold without external power anyway.Big EV trucks would partway between those cases.”””

  10. Your snarky criticism is silly and unwarranted. 150C is not extreme and thermal management is nothing new to batteries.Bringing up asbestos is particularly ridiculous. We have lots of materials for thermal insulation and vacuum. Hell even plain PUR sprayfoam can take a meager 150°C temperature.

  11. So this is not a viable battery type for your cell phone. Cars maybe but most likely only in industrial use where the high temperature can be handled. I’ll wait until they get that temperature down about 100 degrees.

  12. What I expect as more of a challenge is preventing the cold oxygen from cooling down the battery, particularly since the battery’s “coulombic efficiency is approaching 100%”. It might have a rather significant negative impact on efficiency, particularly in winter conditions, or airplane usage as you mentioned.

  13. So, this is not a viable battery type for your cell phone. Cars, maybe, but most likely only in industrial use where the high temperature can be handled. I’ll wait until they get that temperature down about 100 degrees.

  14. What I expect as more of a challenge is preventing the cold oxygen from cooling down the battery particularly since the battery’s coulombic efficiency is approaching 100{22800fc54956079738b58e74e4dcd846757aa319aad70fcf90c97a58f3119a12}””. It might have a rather significant negative impact on efficiency”” particularly in winter conditions”” or airplane usage as you mentioned.”””

  15. While not giving off as much heat as IC vehicles, EVs still generate some serious heat output. I couldn’t find an authoritative source, but numbers like 85% get mentioned for the total electricity to wheel efficiency of a Tesla. That’s pretty good by IC car standards, but it still means that just cruising down the highway at 10 kW is giving off 1.5 kW, just above an electric room radiator on half strength. An electric aeroplane could well run at 5 or 10 times that. Now this heat is not (mostly) from the battery itself. The motor controller is probably the worst culprit, and the motor isn’t that good either. So you’d want some way to move heat from these components to your LiO battery. Made difficult by not wanting them to be anywhere near 150 deg. Maybe a heat pump would help??

  16. While not giving off as much heat as IC vehicles EVs still generate some serious heat output.I couldn’t find an authoritative source but numbers like 85{22800fc54956079738b58e74e4dcd846757aa319aad70fcf90c97a58f3119a12} get mentioned for the total electricity to wheel efficiency of a Tesla. That’s pretty good by IC car standards but it still means that just cruising down the highway at 10 kW is giving off 1.5 kW just above an electric room radiator on half strength.An electric aeroplane could well run at 5 or 10 times that.Now this heat is not (mostly) from the battery itself. The motor controller is probably the worst culprit and the motor isn’t that good either. So you’d want some way to move heat from these components to your LiO battery. Made difficult by not wanting them to be anywhere near 150 deg. Maybe a heat pump would help??

  17. Indeed. Though it might not be easy to collect. The motor and electronics tend to be away from the batteries even in cars (especially if more practical in-wheel motors take off sometime) in aircraft it’s even more of a problem.Maybe a heat pump would help??””Perhaps. But it feels too convoluted. Maybe they’d sooner put a heating filament inside the pack. It’s supposedly only for startup anyway.”””

  18. Indeed. Though it might not be easy to collect. The motor and electronics tend to be away from the batteries even in cars (especially if more practical in-wheel motors take off sometime), in aircraft it’s even more of a problem. “Maybe a heat pump would help??” Perhaps. But it feels too convoluted. Maybe they’d sooner put a heating filament inside the pack. It’s supposedly only for startup anyway.

  19. Fortunately, it’s easy to reach and maintain 150 degrees C – on Venus. What’s the energy cost of running the thermostat on 150?

  20. Fortunately it’s easy to reach and maintain 150 degrees C – on Venus. What’s the energy cost of running the thermostat on 150?

  22. Indeed. Though it might not be easy to collect. The motor and electronics tend to be away from the batteries even in cars (especially if more practical in-wheel motors take off sometime), in aircraft it’s even more of a problem.

    “Maybe a heat pump would help??”

    Perhaps. But it feels too convoluted. Maybe they’d sooner put a heating filament inside the pack. It’s supposedly only for startup anyway.

  23. While not giving off as much heat as IC vehicles, EVs still generate some serious heat output.
    I couldn’t find an authoritative source, but numbers like 85% get mentioned for the total electricity to wheel efficiency of a Tesla. That’s pretty good by IC car standards, but it still means that just cruising down the highway at 10 kW is giving off 1.5 kW, just above an electric room radiator on half strength.

    An electric aeroplane could well run at 5 or 10 times that.

    Now this heat is not (mostly) from the battery itself. The motor controller is probably the worst culprit, and the motor isn’t that good either. So you’d want some way to move heat from these components to your LiO battery. Made difficult by not wanting them to be anywhere near 150 deg. Maybe a heat pump would help??

  24. What I expect as more of a challenge is preventing the cold oxygen from cooling down the battery, particularly since the battery’s “coulombic efficiency is approaching 100%”. It might have a rather significant negative impact on efficiency, particularly in winter conditions, or airplane usage as you mentioned.

  25. So, this is not a viable battery type for your cell phone. Cars, maybe, but most likely only in industrial use where the high temperature can be handled. I’ll wait until they get that temperature down about 100 degrees.

  26. If this works out it is important for battery powered vehicles. Not so much for stationary storage applications.
    In vehicles high energy per unit mass & volume is the most important factor. For stationary applications high energy per unit cost is the most important, which is why grid energy storage is currently almost all pumped hydro.
    High energy density *might* also turn out to be cheap, but not necessarily.

  27. ” Your snarky criticism is silly and unwarranted. 150C is not extreme and thermal management is nothing new to batteries. ” <-- It's not new to cars. ScaryJello has a particularly severe case of pathological skepticism. It's not that this battery tech is guaranteed to pan out, it's that he's always sure nothing can improve.

  28. You probably don’t want a 150 deg battery in your phone, but it isn’t as silly as it sounds for say a car.

    Existing petrol cars function with a few hundred kg lump of metal that has to heat up to over 100 deg before you can get full performance. So it’s not completely ridiculous for your battery pack to have multiple types of cell in it. A more normal low temp cell to start off with, and then as the standard heat of operation warms up the rest of the pack you can kick over to the high capacity LiO2 cells.
    The battery pack would be a bit more sophisticated, with an insulated main section, heat transfer mechanisms designed to heat up and maintain a high temp region. But this could well be worth it for quote “energy densities an order of magnitude larger than that of lithium ion cells”

    For something like electric aircraft it’s even more applicable. You recharge on the ground which heats up your battery pack (well insulated) and it’s at operating temperature as you unhook the charging leads and begin to taxi. You probably never have to start from cold without external power anyway.

    Big EV trucks would partway between those cases.

  29. Your snarky criticism is silly and unwarranted. 150C is not extreme and thermal management is nothing new to batteries.
    Bringing up asbestos is particularly ridiculous. We have lots of materials for thermal insulation and vacuum. Hell even plain PUR sprayfoam can take a meager 150°C temperature.

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