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  1. 30 Oct '15 07:23 / 3 edits
    http://phys.org/news/2015-10-path-ultimate-battery.html

    "...Scientists have developed a working laboratory demonstrator of a lithium-oxygen battery which has very high energy density, is more than 90% efficient, and, to date, can be recharged more than 2000 times, showing how several of the problems holding back the development of these devices could be solved.


    Lithium-oxygen, or lithium-air, batteries have been touted as the 'ultimate' battery due to their theoretical energy density, which is ten times that of a lithium-ion battery. Such a high energy density would be comparable to that of gasoline - and would enable an electric car with a battery that is a fifth the cost and a fifth the weight of those currently on the market to drive from London to Edinburgh on a single charge.
    ..."

    Impressive. And I hope this comes to something practical on the market soon.

    However, energy density isn't everything here and, although this would be less energy dense, I predict magnesium-sulfer batteries will probably be the batteries of choice in the far future. One reason for this is that they should be cheaper. Another reason is because metal-air batteries have the disadvantage of not being air-tight and things like water and water vapor and other contaminants can work their way into them interfering with their functionality and so make them less reliable.
  2. 30 Oct '15 15:31
    Originally posted by humy
    http://phys.org/news/2015-10-path-ultimate-battery.html

    "...Scientists have developed a working laboratory demonstrator of a lithium-oxygen battery which has very high energy density, is more than 90% efficient, and, to date, can be recharged more than 2000 times, showing how several of the problems holding back the development of these devices could be solv ...[text shortened]... an work their way into them interfering with their functionality and so make them less reliable.
    Impressive. And I hope this comes to something practical on the market soon.


    That depends, if you allow 'soon' to mean at least a decade away, then sure.

    http://arstechnica.co.uk/science/2015/10/lithium-air-battery-research-shows-potential-paths-to-next-gen-batteries/
  3. Standard member sonhouse
    Fast and Curious
    30 Oct '15 15:59
    Originally posted by humy
    http://phys.org/news/2015-10-path-ultimate-battery.html

    "...Scientists have developed a working laboratory demonstrator of a lithium-oxygen battery which has very high energy density, is more than 90% efficient, and, to date, can be recharged more than 2000 times, showing how several of the problems holding back the development of these devices could be solv ...[text shortened]... an work their way into them interfering with their functionality and so make them less reliable.
    It says the energy density equals gasoline. Is it theoretically possible for a battery to exceed gasoline in energy density? Even equaling petrol would really put electric cars on the map. You have cars with 300 Km range now, that would approach 3000 Km with such a battery.
  4. Standard member DeepThought
    Losing the Thread
    30 Oct '15 17:31
    Originally posted by sonhouse
    It says the energy density equals gasoline. Is it theoretically possible for a battery to exceed gasoline in energy density? Even equaling petrol would really put electric cars on the map. You have cars with 300 Km range now, that would approach 3000 Km with such a battery.
    I don't see why not. The way a battery works you have oxidation at one terminal and reduction at the other, so it depends on chemistry, but I don't have any intuition as to what the limitations on energy density are. While looking at the relevant Wikipedia pages I came across this, which I'd never heard of before, as humy noted power density isn't the only consideration, longevity is also important and if it's that you want:

    https://en.wikipedia.org/wiki/Oxford_Electric_Bell
  5. 31 Oct '15 05:51
    Originally posted by sonhouse
    Even equaling petrol would really put electric cars on the map.
    Electric cars are already on the map, and price more than range is the main factor at present. Find me an electric car I can afford and I will buy one today.
  6. 31 Oct '15 07:04 / 2 edits
    Originally posted by sonhouse
    It says the energy density equals gasoline. Is it theoretically possible for a battery to exceed gasoline in energy density?
    No, I don't think so. They vaguely said "Such a high energy density would be comparable to that of gasoline" without defining what they mean by "comparable" but it certainly doesn't mean "equal"!

    I once have worked out that the absolute theoretical maximum energy density for a lithium-sulfur battery, which isn't the same thing as a lithium-oxygen battery, is 9.6MJ/kg which is 24% of that of octane (which will have almost the same energy density as that of gasoline ).
    The absolute theoretical maximum energy density for a lithium-oxygen battery will be higher than that and, although I haven’t worked out how much higher, I guess it probably wouldn't in effect be higher than octane if you take into account the weight of not only the lithium but also the oxygen in the lithium oxide on discharge.
  7. Standard member sonhouse
    Fast and Curious
    31 Oct '15 16:57
    Originally posted by humy
    No, I don't think so. They vaguely said "Such a high energy density would be [b]comparable to that of gasoline" without defining what they mean by "comparable" but it certainly doesn't mean "equal"!

    I once have worked out that the absolute theoretical maximum energy density for a lithium-sulfur battery, which isn't the same thing as a lithium-oxygen batt ...[text shortened]... ccount the weight of not only the lithium but also the oxygen in the lithium oxide on discharge.[/b]
    But doesn't the O2 come from just atmosphere? That would reduce the weight right there.
  8. 31 Oct '15 18:32
    Originally posted by sonhouse
    But doesn't the O2 come from just atmosphere? That would reduce the weight right there.
    Or add to it.
    Would these batteries get heavier as they loose charge?

    The big advantage of fuel is it is used up during the journey so if you are measuring weight that needs to be transported you should really divide it in half. This may be irrelevant for a car, but when it comes to an aeroplane it is critical. A battery powered plane must provide enough power to carry the full weight of the batteries for the whole flight.
  9. 01 Nov '15 07:05
    Originally posted by twhitehead

    Would these batteries get heavier as they loose charge?
    .
    Yes, exactly.
  10. 01 Nov '15 08:09
    With cars, although reduced size and weight are desirable, that is not a limiting factor right now. If batteries were exactly the same size and weight as now but either cost half the price or lasted twice as long (in terms of time to replacement) then it would make electric cars much more desirable. Cut the costs even more and electric cars will beat fossil fuel cars in just about every way.
  11. 01 Nov '15 12:56 / 8 edits
    Originally posted by twhitehead
    With cars, although reduced size and weight are desirable, that is not a limiting factor right now. If batteries were exactly the same size and weight as now but either cost half the price ... then it would make electric cars much more desirable. ....
    That is one of the reasons why I think Mg-S batteries are the long term future; unlike lithium, magnesium is relatively cheap because it is very abundant ( + the theoretical maximum limit to the energy density of Mg-S batteries is far greater than that of, say, lithium-ion batteries, which are often used today + magnesium metal is far less of a hazard if the battery ruptures and the metal is suddenly exposed to air/moisture than lithium -although both Mg and lithium can easily burn, Mg less fiercely so and lithium can much more easily explode! ) .