# Same Chemistry, Different Density?



## PhantomPholly (Aug 20, 2008)

A spinoff of A123 called "24m" (for "24 Molar") intends to start production on a new type of battery based on LiIon chemistries. According to their press, "...it combines the best attributes of conventional batteries, fuel cells, and something called flow batteries, while avoiding some of the disadvantages of these technologies."

Goal is to cut production costs as much as 85% (shooting for half initially) while doubling or even tripling energy density.


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## EscapeVelocity (Nov 12, 2010)

Currently, in a single Thunder Sky or CALB cell, there may be hundreds of individual layers of anodes, cathodes, and electrolyte sandwiched together. Each of these layers needs to be chemically isolated from one another, and this contributes to the thickness of the cell.

This new design mandates that each cell only has one single anode, cathode, and electrolyte layer. Rather than having the reactive pastes on the anode and cathode glued into place, there would be a storage tank (like a gas tank) that would continually pump fresh liquid form of the chemicals through the battery cell.

There are numerous advantages I can see to this approach:
1) Your range is determined by the size of your storage tank, not the volume of your battery cells
2) Battery balancing would no longer be an issue, because the tank's energy-storing chemicals would be evenly distributed among all the cells.
3) This would open up the possibility of 30-second refueling stations. Forget replacing the entire battery pack, just exchange your chemical mix.

However, it is not without disadvantages:
1) Although pumps can be designed to be very durable, it introduces a point of failure.
2) We may still need the large sized cells for their surface area (power density)
3) This opens up the market to exploitation again by potential "oil companies of lithium", meaning that you can't simply charge at home but that you would need to visit a service station.


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## PhantomPholly (Aug 20, 2008)

EscapeVelocity said:


> However, it is without disadvantages:


Think you meant, "...not without disadvantages..." 



> 1) Although pumps can be designed to be very durable, it introduces a point of failure.


Yeah, first thing I thought of (always thinking airplanes). Of course, if they are small there is no reason you can't have more than one "converter" unit. I have to believe that each unit has an upper limit on how much goo it can process per minute (max instantaneous Kw output). Why not have several smaller ones?



> 2) We may still need the large sized cells for their surface area (power density)


Err, I think the whole point was that these already exceed the power density of the regular cells. You may be right for instantaneous output, though, but they don't give enough info to know for sure.



> 3) This opens up the market to exploitation again by potential "oil companies of lithium", meaning that you can't simply charge at home but that you would need to visit a service station.


That's not what the article said - it said battery and rechargeable, and described the process as reversible. That implies home charging. Of course, until solar power gets cheaper we're still tied to the grid.


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## PhantomPholly (Aug 20, 2008)

Something else I didn't think about with these. If current can be controlled by variable-speed pumps, then we won't need motor controllers any more for DC motors. Just a primary contactor and a reverser for the motor.

Now THAT's simplicity....


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## JRoque (Mar 9, 2010)

Hi. Great article Phantom. It's really amazing how quickly we're moving to improve battery technology now that we're merely looking into it. Imagine what can be done with a well funded project.

Did I read somewhere their ETA is somewhere close to the end of the decade? Yes, here: http://www.boston.com/business/technology/innoeco/2010/08/a123_systems_spawns_another_al.html

JR


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## Beemer (Jun 2, 2011)

I'm glad they have a clue but I'm stumped how they can foist the electrolyte between those tightly fitting anode/separator/cathode foils.

This idea will also end under/overheating issues thus higher C rates.

The last thought.. The electrolyte is the most expensive part of these cells and very little is needed. You can't simply pump more through and expect more miles like a car because you will need to recharge the cells to restore the chemistry on the plates.


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## PhantomPholly (Aug 20, 2008)

JRoque said:


> Hi. Great article Phantom. It's really amazing how quickly we're moving to improve battery technology now that we're merely looking into it. Imagine what can be done with a well funded project.
> 
> Did I read somewhere their ETA is somewhere close to the end of the decade? Yes, here: http://www.boston.com/business/technology/innoeco/2010/08/a123_systems_spawns_another_al.html
> 
> JR


I think he indicated that that was more at the outside:



> A123 chief executive David Vieau said it could take the better part of the decade to turn it into a product.


Of course, given that he is a spokesman that should always be taken with a grain of salt. It may be delivered "just as soon as EEStor..."


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## PhantomPholly (Aug 20, 2008)

Beemer said:


> The last thought.. The electrolyte is the most expensive part of these cells and very little is needed. You can't simply pump more through and expect more miles like a car because you will need to recharge the cells to restore the chemistry on the plates.


Thought the lithium was in the cathodes/anodes? They talked about two fluids with a permeable membrane - perhaps they've made the fluid into cathode / anode with the ion exchange across the membrane, changing the makeup of the fluid (like a fuel cell, just reversible).

I guess it really doesn't matter to us in the end, only whether they deliver. But, I really like the idea of a fixed volume fluid circulating through a converter. Makes weight and balance for airplanes simple when you aren't burning off gas changing the handling.


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## valerun (Nov 12, 2010)

super-awesome. The scientific article at http://onlinelibrary.wiley.com/doi/10.1002/aenm.201100152/full

it is the future. Imagine repurposing old gas stations installing pumps of lithium goo! I am also sure that we will have a [DIY first] opportunity to build pumping / charging units at home. We are talking about a couple of gallons of liquid here.

EDIT: some quotes from the scientific paper:
* A 20 vol% suspension of the high-voltage spinel LiNi0.5Mn1.5O4 exhibited the expected capacity (120 mAh g−1) and voltage (4.7 V average). This means ~550Wh/kg. Even if you have the same amount of weight in the supporting components, this still means a 20kWhr pack weighing <200lbs!
* The mixes were tested up to 2.5C so far, with 25% capacity loss at 2.5C (relative to 1C capacity). Not bad for the first lab results.
* they expect costs of automotive - scale systems to be at ~$250 / kWhr (given CURRENT prices of active materials etc!), which is half of the cost of current lithium cell packs (once you factor in casing, protection, mounting).

great stuff

V


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## Beemer (Jun 2, 2011)

PhantomPholly said:


> Thought the lithium was in the cathodes/anodes? They talked about two fluids with a permeable membrane - perhaps they've made the fluid into cathode / anode with the ion exchange across the membrane, changing the makeup of the fluid (like a fuel cell, just reversible).
> 
> I guess it really doesn't matter to us in the end, only whether they deliver. But, I really like the idea of a fixed volume fluid circulating through a converter. Makes weight and balance for airplanes simple when you aren't burning off gas changing the handling.


There is a pre-plate of lithium onto the plates to condition them. Done like a 'controlled abuse' scheme to force all the cells have the same electrical qualities. The ionically active lithium is in the electrolyte.

Once each plate is loaded, its loaded. Thats your lot. No amount of extra electrolyte will give you more charge.

Also anybody who imagines you can simply shove the fluid past the plates. Good luck to them. The more you force the plates apart. the more you destabilise the cells from a matched set by hydraulically pumping apart the plates. Volume/charge density depends on the proximity of opposing plates.
=============================================​I do recall as a young lad in a motorbike shop. One irate punter phoned me up having an angry word why we only put a diluted sulphuric acid/water mix in the battery. He said if we put pure acid in, it will be far stronger. Took me over 10minutes to get it into his head the water was the chemical reaction and the acid was simply the enabler.


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