[kennyb]

I was talking to a battery expert about Lithium Sulfer and he didn't seem hopeful, here is what he said: (he's Russian)
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SION is a new name of Moltech company that have been promoting
the Li/Sulfur-organic technology for over 10 year now. Until now
they were not able to solve several serious problems with this
idea, which are:

- solubility of Li poly-sulfides in organic electrolytes, so it diffuses to
opposite electrode and causes high self-discharge.

- need to use metalic Li in assembly, which make technology inherently more
expensive then traditional Li-ion using only passive materials in assembly

- bed cycleability of metallic Li electrode

- need for slow charging (also associated with use of Li-metall)

- regulatory problems with using Li-metall. Basically you are not allowed to have
Li-metall on airoplane, and I doubt it is going to change. Tadiran battery
(having leading researchers in Li-metall anodes, Aurbach and Levi) succseded
in making a working Li/LiMn2O4 battery, but then were forced to limit the
production to serving amateour avia-modelers, I suspect because of still
bad cycleability and regulatory problems.

SION are continuing working on it, magicaly finding more funding after so
many years, and I am curious to see what will come out of it, but
considering above inherent problems, I would not bet my money on it.

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Do you think they will have a lithium based hybrid battery soon? I think lithium is supposed to be much more efficient than NiMH, but I don't know about how many deep cycles it can do.

 

[clett]

Hi Kenny,

Thanks for your interest! I've been following this story for a while now. Yes your friend is right, SION, Polyplus and Newturn have all struggled to overcome these problems associated with using lithium sulphur. But, all three companies have persevered because the potential rewards are enormous - up to 5 times the Gibbs energy of the LiS reaction versus todays typical lithium ion.

As far as I am aware, most of the past obstacles your friend has mentioned have now been overcome...

- solubility of Li poly-sulfides in organic electrolytes, so it diffuses to opposite electrode and causes high self-discharge.

With a new anode protection technology, self discharge of SION cells is now only ~10% per month, on a par with NiMH and entirely acceptable (see here).

- need to use metalic Li in assembly, which make technology inherently more expensive then traditional Li-ion using only passive materials in assembly

All three companies predict LiS will be cheaper than LiIon because of cheaper raw materials.

- bed cycleability of metallic Li electrode

Yes, this problem has only partly been solved - SION are seeing cycle life of 300 charge/discharge cycles, but I think Polyplus in particular are making more progress on this front by using different electrode protection. Some progress yet to come here I think!

need for slow charging (also associated with use of Li-metall)

I hadn't heard this one, but I'd be surprised as the discharge rate is phenomenal - up to 2kilowatts per kilogram. One major benefit of LiS, however, is the ability to both charge and discharge at down to -60oC!

- regulatory problems with using Li-metall.

Yes this is a problem. All three companies need to demonstrate the safety of LiS before regulators will accept the presence of metallic lithium. One company has done a lot of "nail testing", where they drive a nail right through a fully charged LiS battery and they've not yet caught fire, though there was some smoke. Your friend is right, safety is still the biggest issue that needs to be adressed, though SION are close to marketing a battery for laptops, so they can't be that far off.

I would not bet my money on it.

Let me put it this way, if you had your money in fuel cells (like GM) and SION or Polyplus cracked the LiS problems, you'd cry your eyes out!
It may have taken them 10 years of research to get this far, but I reckon they can't be too far off now!

:wink: