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Mie University team working on aqueous li-air batteries; 300 Wh/kg

16 March 2014

Researchers at Mie University in Japan have developed a new protected lithium electrode for aqueous lithium/air rechargeable batteries. Lead researcher Nobuyuki Imanishi said that the system has a practical energy density of more than 300 Wh/kg, about twice that of many commercial lithium-ion batteries. They presented their work at the 247th National Meeting & Exposition of the American Chemical Society (ACS) in Dallas.

Lithium/air rechargeable batteries are attracting great attention, because of a possibility to achieve energy density which is comparable to combustion engines. Most of the studies recently reported focus on the non-aqueous system in which the reaction product Li2O2 is deposited at the surface of the air electrode. In the aqueous Li-air system, the reaction product (LiOH•H2O) is soluble into the electrolyte solution.

A key challenge of the aqueous system is the low output power of the protected lithium electrode. In 2004, a research team developed a composite lithium anode with a three-layered structure to overcome this problem. The Mie team used this approach, and adopted a lamination of NASICON-type lithium conducting solid electrolyte (LATP) and PEO-based polymer electrolyte as the protective layers which cover and isolate lithium metal from contacting directly with aqueous electrolytes.

The researchers also used ether-oligomer electrolyte additives, e.g., tetraethylene glycol dimethyl ether (TEGDME) to PEO18LiTFSI. The electrode/electrolyte interface resistance was decreased and maximum current density of 4 mA cm-2 can be applied. A Li/PEO18LiTFSI- 2TEGDME/LATP/saturated LiCl aqueous solution/Pt, air cell showed stable cyclability up to 100 cycles at 2.0 mAh cm-2 of capacity.

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Could this become the foundation for one type of future 3-3-3 rechargeable batteries?

PEO-based polymer electrolyte as the protective layers which cover and isolate lithium metal from contacting directly with aqueous electrolytes.

hmmm

I was hoping that the 4-7-5 system would win out.
But then again I am unable to write comprehensible English and so resort to jargon.

As a long-time lurker here before some recent comments, I have noticed the frequent use of a numeric figure of merit for perceived battery “advancement”. I’m referring to what I will call the “p-c-t” metric in which

p = multiple of a baseline power density
c = multiple of cost per kwh improvement
t = time in years from the baseline.

To be a bit more specific: the first use of “5-5-5” in a more or less “official”, authoritative quote that I can find was used by the Argonne Lab Director Eric Isaacs in Dec 2012. He stated it in reference to the $120M grant forming the Joint Center for Energy Storage Research (JCSER), making the public commitment to the Team’s BHAG. Unless there’s a disagreement, since the Project really kicked off in earnest with the Battery Science and Characterization Workshop on 20 May 2013, we are still in year 1 until May 20 of this year. So anything new available as an actual “battery” until then is an “x-x-1”. Okay?

As for the baselines: when Dr. George Crabtree, who is leading the project, announced target metrics last year, he showed the following objectives for transportation applications (I am citing them verbatim; you can find his presentation on the JCSER site):

$100/kwh
400 Wh/kg, 400 Wh/l
800 W/kg, 800 W/l
1000 cycles 80% DoD C/5
15 yr calendar life

Those are targets. By inference, if $100/kwh is a “five times cost improvement”, then he is working from a PERCEIVED baseline of $500/kwh. I emphasize PERCEIVED because there is some considerable belief that Tesla has achieved production costs as low as $300/kwh. If so then we might assume the Tesla value for “c” is already 1.67.

As for “p”: again, if 800 Wh/kg is the target at “five times the energy density”, then Dr. Crabtree is working from a PERCEIVED baseline of 160 Wh/kg. I’m not sure where the measurement of “battery” begins and ends (e.g., cooling loop, BMS?), but as best I know I’ll quote Tesla’s number as provided to Car and Driver for an 85kwh ESS at 601kg, yielding about 140 Wh/kg. Close enough for reasonable comparison.

So, using the most advanced automotive propulsion battery in production from the Model S, the best you can get today is a “1-1.67-1”. If you read what’s posted at the JCSER site, you will not find progress toward the first two “fives” to be very promising. The third “five” merely marks the passage of time. As for Mie U.’s work: Dr. Imanishi is NOWHERE close to a practical, producible configuration. I think Tesla’s Gigafactory achieving perhaps “2-2.5-5” in 2017 is the very best we are likely to see, but might be enough to make a genuinely marketable mid-range offering.

BTW: just to amplify the JCSER targets just a bit… if you watch this presentation by Dr. Crabtree from last year’s Argonne Out Loud lectures

http://www.youtube.com/watch?v=PEHs3X75IDo

you’ll see this key point made at about 12:35: the second of JCSER’s desired “Legacies” is to build “two prototypes, one for transportation and one for the electric grid, that, when scaled up to manufacturing, have the potential to meet JCSER’s 5-5-5 goals”.

Once more, with appropriate skepticism: “when scaled up to manufacturing, HAVE THE POTENTIAL TO MEET JCSER’s 5-5-5 goals”. So in 2017 (the fifth and final year of this phase of the program), they will produce a prototype that by their estimation could meet the targets.

Remember that Tesla's “Gigafactory” will be building Li Ion cells that are fundamentally quite similar to today’s technology, though certainly with significant process improvement, raw material scale and leverage, and improved assembly/integration for the completed ESS. Tesla’s team has stated cost improvement targets of 30%, perhaps more. Clearly it’s an industry leader. But with nowhere near as great a leap as JCSER’s explicit target of moving “beyond Li Ion”, the Gigafactory doesn’t achieve rate production until 2017, or year “5”.

If JCSER achieves its prototype energy and cost targets (and with no clear choice of chemistry or configuration yet chosen, I’d be shocked if they do), industry will need at least another 5 years to achieve true industrial capability.

So I think the best you’ll get is a “5-5-10”, if that. By no means is this an EV killer, but it’s short of the optimism in our typical comments.

Thanks for breaking down the jargon, Herman.

AFAIK there are no claims at all that initially at least the Gigafactory will be producing batteries which have any technical improvements other than reduced costs over current practise.

Musk has specifically stated that he does not see major improvements in the next 4-5 years, which covers the build time of the factory.

It is easy to believe that battery break through science is right around the corner when you read all the research announcements, but those have to be put into perspective.

They have gone from lithium ion batteries in laptops that could be safer to lithium ion batteries in cars that are safer over about 10 years. At that rate you could expect more capacity, more safety but not much lower cost over then next 5 years.

I know people want to believe, but belief and science are different. I counted about 12 models of EV for sale in the U.S. as of 2014. Al together they might sell 100,000 units in the U.S. this year, that is less than 1% of the vehicles sold. It will take a while, that is why I am for synthetic and bio synthetic fuels for the next few decades.

Electrified vehicles (HEVs-PHEVs-BEVs-FCEVs) sales in Japan are already close to 25% and increasing at a fast rate.

Norway, Holland, S-Korea, China, Germany and a few other EU countries will follow Japan's lead soon.

By 2020 or so, most countries will get on board and try to catch up with Japan with 2, 3, 4 and 4+ wheels electrified vehicles.

Norway seems to be the only country leading with electrified vehicles but with lots of Oil and NG?

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