AIST team developing Li-air capacitor-battery targeted for EVs
05 November 2011
A team from Japan’s AIST (National Institute of Advanced Industrial Science and Technology) reports on the development of a “lithium–air capacitor–battery based on a hybrid electrolyte” in a paper in the RSC journal Energy & Environmental Science.
The team had earlier investigated a hybrid electrolyte lithium–air battery, in which a lithium anode in a non-aqueous electrolyte and an air-catalytic cathode in an aqueous electrolyte solution were separated by a ceramic LISICON film. (Earlier post.)
As reported then, the lithium-air cell showed a continuous cathode discharge capacity of 50,000 mAh g-1 (per unit mass of the carbon, catalyst and binder). By comparison, conventional Li-ion batteries offer 120-150 mAh g-1 (active material + conduction assisting carbon + binder), and conventional lithium-air cells offer 700-3,000 mAh g-1.
In the present work, a capacitor electrode was put in the non-aqueous electrolyte solution as an additional cathode in parallel with the air catalytic cathode. The proposed lithium–air batteries with an additional capacitor cathode can successfully unite capacitor character and lithium–air battery character in one device which is now nominated as a “lithium–air capacitor–battery based on a hybrid electrolyte”.
When high power is needed, the capacitor cathode would play the main role of peak power output; when high energy is demanded, the air catalytic cathode would display its high energy character. The adjustability of power output and energy output demonstrate that the proposed lithium–air capacitor–battery should be a promising power system for future electric vehicles.
—Wang et al.
Resources
Yonggang Wang, Ping He and Haoshen Zhou (2011) A lithium–air capacitor–battery based on a hybrid electrolyte. Energy Environ. Sci., DOI: 10.1039/C1EE02121D
That sounds almost like science fiction. I'm sure it is only a lab curiosity at this point but maybe something will come of it.
Posted by: DaveD | 05 November 2011 at 10:04 AM
If a commercial product can get a fifth of that performance in the field, it'll revolutionize everything from cell phones on up.
Posted by: Engineer-Poet | 05 November 2011 at 11:25 AM
Two cathodes better than one. How about cycle time? Cost of materials? Safety?
Posted by: Reel$$ | 05 November 2011 at 11:47 AM
Hello, flash charge!
I'm thinking these kind of discharge properties would allow for 500 miles < 1 minute charging and make EVs workable for all street parkers.
Posted by: drivin98 | 05 November 2011 at 01:45 PM
"the lithium-air cell showed a continuous cathode discharge capacity of 50,000 mAh g-1"
It's only for the cathode. You still have to precipitate Li ions into the lithium anode, which has a theoretical capacity of 3,800 mAh/g. That would limit the capacity of the cell. A practical battery might get 30-40% of theoretical. With packaging, you could have a battery with 2,500 wh/kg. Probably would be cheaper than Li-Ion too.
Posted by: Zhukova | 05 November 2011 at 08:26 PM
This article doesn't add anything to the one from 2009, except that they shunted a capacitor across the cathode. The capacitor isn't going to help the charging time. It's only for short bursts of power, which would be good for car acceleration. Charging would still take three or four days for a 500 mile battery, certainly not less than a minute.
Posted by: Zhukova | 05 November 2011 at 09:07 PM
The battery cannot be charged and it is low power the reson the capacitor is added. It is not relevant for the auto industry and it is still a law experiment.
Posted by: Account Deleted | 06 November 2011 at 02:36 AM
@ DaveD:
No, it's not just a lab curiosity. The researchers at AIST have been working diligently on this subject since 2009 and apparently are making headway. Hopefully they'll be succesful (the sooner the better). Here's the initial report:
http://www.aist.go.jp/aist_e/latest_research/2009/20090727/20090727.html
Posted by: yoatmon | 06 November 2011 at 02:49 AM
@Henrik
From the 2009 article (click on the Earlier post link in this article) "AIST says that the new lithium-air battery needs further technical improvement toward practical use. Generally, there are two directions in this new lithium-air battery research, one is for a rechargeable lithium air battery and the other is for a lithium fuel cell."
automotive application is a primary goal.
So this new cathode is to be used in a rechargeable battery or a fuel cell where the lithium is quickly replaced at a service station, in some kind of cassette. The electrolyte would also be replaced. This would presumably take only a few minutes. But the density of energy storage is so great, you would only need to do it once in two months for a 200 kg battery giving 2000 miles of driving range at an average 15 horsepower.
Since you could get only 15 hp average from a 200 kg Li-Air battery, which is good enough for most passenger car driving, you would need the capacitor for acceleration. That's why they added it. Charging a battery this size would take about a week, so the fuel cell with Li cassettes looks attractive.
Posted by: Zhukova | 06 November 2011 at 07:24 AM
The battery application is also attractive. Most people never drive 2,000 miles in one day. Most people drive only 40 miles per day. So a Li-air battery with this cathode could probably have 40 miles of charge, about 8-10 kWhs, put into it in about 4 hours. The deep discharge cycle life is only 50. But that's 50 times 2,000 miles. If you drive for two months and then charge it for a week, which would be the extreme, it would last about 8 years. Charging only 10 kwhs per day would allow it to last 10-20 years.
However, you would have to keep it charged. If you didn't charge it for a week of normal driving, it would take 8 hours each night for a week to top off the charge. Not charging for a month would require 8 hours per night for a month.
Posted by: Zhukova | 06 November 2011 at 07:44 AM
Zhu...this type of very large capacity, slow charge, battery/super cap combo would effectively give the users the choice to re-charge it daily for an average of about 4 to 6 hours or after 500+ Km on weekends.
Eventually, ways will be found to arrive to quick charge equivalent.
The game changer would be an extended range storage unit with quick acceleration possibilities, ideal for future BEVs.
Another interesting avenue.
Posted by: HarveyD | 06 November 2011 at 09:31 AM
This "lithium–air capacitor–battery" could allow people fly like birds as in the most unbelievable science fiction story.
Posted by: Juan Carlos Zuleta | 06 November 2011 at 09:53 AM
Assuming this cathode in a battery would provide low current output per gram, which is what other Li-air batteries can do, the same low current input for charging can be assumed. The low current capacity is what requires a big battery. If you make it big enough, you could get 15 hp average output. But this is going to take a 200 kg battery = 440 lbs. It's not so heavy, but you have to carry around a lot of effectively dead weight in the car because you only need less than 100 miles range 95% of the year and your getting 2,000. I'll be glad to drive with all that dead weight.
If you don't charge it for four days during the week, you'll need 16 hours of charging time to make up for the lost charging time on the four weekdays. Not so bad if you like to sleep late on the weekends. Improving the charging time? It would take a real scientific breakthrough.
Posted by: Zhukova | 06 November 2011 at 06:46 PM