SoylentNews is people
SoylentNews
Arndt Remhof's team has developed a solid electrolyte that facilitates good mobility of sodium ions at 20 degrees. This last point is crucial: ions require a source of heat in order to move, and inducing a reaction at room temperature poses a technical challenge. The electrolyte is also non-flammable and is chemically stable up to 300 degrees, which addresses the various safety concerns associated with lithium-ion batteries. Hans Hagemann's team at the University of Geneva has been working in parallel to develop cheaper technology for the production of this new solid electrolyte.
Unlike lithium, there are huge reserves of sodium: it's one of the two components of table salt. "Availability is our key argument", says Léo Duchêne of Empa and first author of the research paper. "However, it stores less energy than the equivalent mass of lithium and thus could prove to be a good solution if the size of the battery isn't a factor for its application."
Magnesium: the perfect but complex material
The same team has also developed a solid magnesium-based electrolyte. Until now, very little research had been done in this field. The fact that it is much more difficult to set this element in motion doesn't mean that it is any less attractive: it's available in abundance, it's light, and there's no risk of it exploding. But more importantly, a magnesium ion has two positive charges, whereas lithium only has one. Essentially, this means that it stores almost twice as much energy in the same volume.
Some experimental electrolytes have already been used to stimulate magnesium ions to move, but at temperatures in excess of 400 degrees. The electrolytes used by the Swiss scientists have already recorded similar conductivities at 70 degrees. "This is pioneering research and a proof of concept," says Elsa Roedern of Empa, who led the experiments. "We are still a long way from having a complete and functional prototype, but we have taken the first important step towards achieving our goal."
The energy density of a magnesium electrolyte would solve the EV range problem, if it is double lithium's.
(Score: 2) by physicsmajor on Wednesday May 03 2017, @11:16AM (4 children)
The quote from the research group is a little baffling. When they talk about energy storage vs. mass, I'm not surprised at all - the same number of atoms of sodium will weigh more than triple as much as a molar equivalent of lithium. Just look at the atomic weights. However, they then say this has volume implications. It's the same number of atoms, and that does not necessarily follow. These batteries are not a super dense bar of metal; the actual packing may vary. And, while the atomic weight is quite different, the space each takes is not. The mass will definitely matter for applications like EVs, but in consumer electronics a more proper comparison would be energy storage vs. volume - not energy storage vs. mass.
(Score: 3, Touché) by iwoloschin on Wednesday May 03 2017, @11:22AM
Mass is important too though, because at some point Apple will run out of physical thickness to shave off (you can't have negative thickness after all) and then they'll need another ridiculous claim to fame.
(Score: 2) by VLM on Wednesday May 03 2017, @12:47PM (2 children)
However, they then say this has volume implications.
Sigh. Physics Majors meddling in Chemistry Major topics....
There's a classic graph of elemental density vs atomic mass and yes its wiggly as all heck but the slope is about 5 grams/cc per 33 or so mass. So you can guess the density of lithium is less than 5 g/cc (plus or minus 50% or so) whereas a nice bar of wolfram (name just to annoy the phosphoroni pizza poster) is gonna score somewhere close to 20 grams/cc just based on atomic mass.
Meanwhile the number of electrons to F with as a battery goes up with atomic number.
So that brings up all the graphs of atomic mass vs atomic number.
When you mush it all together I don't remember the average slope (and the error bars are getting really big) but in electrochemistry it boils down to the higher the atomic number is, if you want 100 electrons (plating some metal, perhaps, or electrorefining) then the heavier those soon to be ions are gonna be and the physically larger the object.
So like lead is atomic number 82 and atomic weight 207 or so and density 12 g/cc or so vs lithium number 3 and weight 7 and 0.5g/cc
Its a simplification, like all chemistry, but 6.022e23 atoms is a mole of atoms and it weighs the atomic weight of that element.
So you want a pure lithium metal battery to push 6e23 electrons, implying 6e23 atoms of lithium change ionization state, that many is gonna weigh 3 grams, and at room temp thats about 1.5 cc which (handwave) is about 1.5 mL which is about one or two water droplets.
Meanwhile the pure lead metal plate battery in your car wants to push 6e23 electrons, implying 6e23 atoms of lead change ionization state, that many is gonna weigh 207 or so grams, and at room temp thats a fat 17 cc of lead. Thats enormously bigger than an infantry rifle bullet but only a third or so the mass of a 50 cal bullet.
So metal of a battery that can push 6e23 of electrons made of lithium resembles a fat single drop of water or if made of lead it looks like a slightly growth stunted but close enough to visually fool normies 50 cal bullet.
(Score: 2) by Immerman on Wednesday May 03 2017, @05:27PM (1 child)
As it happens, lithium atoms are actually somewhat *larger* than the heavier magnesium atoms, 182pm versus 173pm for magnesium. Include the fact that you get twice as many ionizable electrons per atom, and you might naively expect magnesium-based batteries to be only about 43% (= (173/182)³/2) the size of their lithium-based cousins (though 171% the mass)
Obviously, the discrepancies likely lie in the supporting chemistry - batteries are far more complicated than ionized metal bricks.
(Score: 2) by VLM on Wednesday May 03 2017, @06:01PM
Obviously, the discrepancies likely lie in the supporting chemistry - batteries are far more complicated than ionized metal bricks.
Oh agreed totally. Just in context of why would the chemist have a hand-wavy most of the time generally thing going on about atomic numbers vs volume of a mole (mole as in 6e23-somethings not the garden variety).
In one line without any explanation is summarizes to as atomic number goes up the mass of a mole goes up like two orders of magnitude while the density only goes up one order of magnitude so the ratio being the volume, generally speaking a mole of higher atomic number stuff will be both denser and physically larger than lighter stuff. Or the density IS increasing, but at a slower rate than the mass is increasing.
This comes up in those daydreams or sci fi movie plots about "sure atomic numbers immediately above 90 or have been radioactive, but what if there was an island of stability for super atoms with atomic number 200 or whatever" Well you can predict based on trends if there were a stable atom with a number of a couple hundred a gram-molecular-weight or whatever the cool kids call a mole today would be the size of a construction brick and it would probably have a density of like 100 g/cc which would certainly be mildly impressive. Picking up a little sugar cube of it would be like picking up a supermagnet stuck to a fridge, I can't get a grip did someone superglue this Fing thing to the lab bench?