Magnesium battery patents
Date: Wednesday, August 25, 2004 @ 21:47:08 GMT
Topic: Devices


Stefan (overunity2001) writes: Have a look at this:
http://www.visforvoltage.com/forums/index.php?act=ST&f=31&t=594 (or: http://tinyurl.com/683cr)

A cell with 4 Volts ! Amazing !
Regards, Stefan.

From AeroneousB's post: OK. Let me separate these two magnesium battery patents and clear things up.
The first one from Dr. Aurbach is about the magnesium battery that lasts practically forever.
The first patent on that was #6,316,141.
It however doesn't try to show a way to make a solid electrolyte.
This is the patent and the technology that the recent news item was written about and is the source of the pdf file that was posted here by Ken as a news item.


Since then he has found/developed a "binder" (so to speak) that he can put the electrolyte in so that it is no longer a liquid electrolyte, but a gel which removes the need to have a separator.
And it does not diminish his previous results.
That is patent number 6,713,212.
He is focusing on extreme lifetime and non-toxicity with this particular project.

The other patent #6,713,213.
Is from some Asian or Oriental guys for Matsushita Electric Industrial Co. Ltd..
That is a parent company that owns hundreds of other companies that you all buy stuff from all the time so good luck on trying to find out what company if/will make these batteries.

Quickly I'll compare the two here.
Aurbach's electrolyte provides a window of 2.3volts and the cell only produces 1.8volts so you have about a half volt margin to keep from electrolyzing the electrolyte into hydrogen gas and stuff.
So that's a good safety margin.
I think he gets something like 70mAh/g.
The Matsushita patent shows trial runs of various electrolytes and mixes in combination with various salts and doesn't state what the window voltage is for all of them as an average but clearly it is way up there because they are getting FOUR VOLTS out of the cells. And towards the end of the patent they show only an average decline of 20mAh in capacity per cell after 50 cycles.
They get a supercalifragilistic 420mAh/g!

Now let's compare how easy they are to reproduce in your garage.
Straight from their example items.

Aurbach's
------------
Cathode --> A chevrel compound called Cu2Mo6S8.
You need to buy the powders of each copper, molybdenum, and elemrntal sulfur.
Probably from Alfa Aesar.
You need an adjustable oven that you can leave on for a week that can reach 1050 degrees celsius and stay there. and a quartz crystal that you can vaccuum seal. Then when it's done you need to mill it into a fine powder and mix it with Teflon-loaded carbon black and then you need to spread it onto SS mesh and press it and dry it under vaccuum at room temp. for 24hrs.
Then you need to do a couple more things to trick some of the copper ions out and then clean it again and dry it again.

Anode ----> Magnesium film.
You need to clean the oxygen off first if you want to have it last a really long time. Otherwise you can just be lazy and wait a while to let the electrolyte take off most of the oxygen coating. Or just discharge it and charge it one time and don't count the first cycle like the Matsushita guys did.

Electrolyte -------> Mg(AlCl2 BuEt)2 salt and tetraglyme in a PVdF matrix.



Matsushita's
----------------
Cathode ------> Silver Oxide powder mixed with 5 parts by weight each of a polyethylene (PE) powder and acetylene black (AB) and press mold it into your desired shape.
Or if you want to get 4 volts per cell you can use vanadium oxide but you get less energy density overall.

Separator ----->polypropylene

Anode-------> Magnesium film.

Electrolyte ------> You have many choices.
Picking one of the top three performers for AgO and magnesium elctrodes.
di-ethyl-ether with the salt C2H5MgPF6 in it.

I think the Matsushitas are easier to reproduce except that the voltage windows for each of these electrolyte/ salt combinations are not clearly defined so we really don't know how easy it is to over volt them and hence start elctrolyzing the electrolytes. Furthermore we don't know what the gas is that would be produced if/when that happens. We don't know that for Aurbach's either but atleast he clearly defines that the voltage window exceeds the voltage produced by the cell and so we have a safety margin.
So Aurbach's is realiable,
Matsushitas seem more powerful and might possibly be just as reliable if they precleaned their darn Magnesium foil and they have a .2 or .3 volt safety margin.
AironeousB

Post Script: Obviously I made a mistake on the Matsushita patent in my prior posting. The 4 volts is for the lesser 130mAh/g range batteries using Vanadium oxide as the cathode. The main cathode used in the patent (silver oxide) get's only 3 volts but still...... 420mAh/g. That's a lot of energy even at 3 volts.





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