Thin film, li-polymer, and nanowire battery question.

Hey I got a bunch of questions because I have been “thinking” again. I would like to get some info on some topics I am curious about. I have been typing them into a word file as they come up since I keep forgetting them before I get a chance to post ^^…blasted memory -_- So here we go and I got links to the other topics below.

5.) Battery technology question.

Nanowire, li-polymer, thin film batteries.

I know nanowire is supposed to be 8x better than “current li-ion cell” I assume that is li-ion and or li-polymer. Also there is thin film and I was reading this company’s site and it said these numbers.

See picture.


So if li-polymer has 380 density and thin film has 959 and 1,041. Does that mean that in a same size square battery thin film would hold ~2.5 and 2.7 times the energy respectively? Though it would be significantly heavy? Since the energy density is a higher factor than its energy weight?

The other question is that nanowire batteries are able to have 8 times the capacity because they use silicon so if thin film used silicon would it also grant much larger capacity? I would think that thin film would use silicon since it is only .05-2 microns thick. I wonder if the expansion of the silicon would not be an issue with this design.

I looked at the sizes and thickness and the density doesn’t seem to add up to me. Do they not include the substrate in the math?


Excellatron - the Company

As always I appreciate the advice!

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5.) Thin film, li-polymer, and nanowire battery question.
http://forum.notebookreview.com/har...er-nanowire-battery-question.html#post9014931

 

i am not too sure what the question is, but i doubt you can use silicon as material for thin film, because it simplify isnt conductive enough for that purpose, although i think its properties may change when its in form of a nanowire/tube. to get silicon to be conductive enough for this application, you would have to dope it with a large amount of other metals which probably defeats the purpose of using silicon in the first place.

edit: after looking at that diagram, i think its because silicon does not have enough electrons and holes to serve as material for your PN junctions, also the band gap for Si would be too wide for electrons to jump from valence band to conduction band, espeically at lower temperatures

edit 2: i am assuming they are fucntionalizing these nanowires do give it a surface charge, and with the shear amount of nanowires, it is possible to store large amount of power (also, Si being very stable will allow a large number of charge/discharge cycles). This isnt possible with films because the suface area of a film is too small compared to trillions of nanowires.

 

Good Website to ask your battery technology questions.

Flashlight Electronics - Batteries Included

John.

 

dont think that forum will help too much, since he's asking the theoretical stuff about batteries, that forum discuss batteries on the market

 

btw reason why before silicon couldn't be used before nanowire batteries was because when it filled up with a charge they would explain and deteriorate.

wikipedia

 

skimmed through a lot of the Li Cui published articles and i guess they have tried multiply types of nano tech batteries and other types of nano tech research.

Yi Cui Group - Stanford University

i skimmed about 20-30 articles on nanowire batteries and what not. They found that hollow spheres and nanowires worked best from what i could tell. They use a lot of terms and explain things must more difference than i am used to. I see that they use mah in turns of capacity and not the terms of density or volume which is hard to understand their research in terms of wh total and wh density. I am wondering which one worked best and they are using for developement. They formed a company with some verture capitalists called Amprius and i called to see if i could get any details......still waiting for a return call. (obviously i doubt they will call back but worth a 2 min shot ^^)

 

capacitance increases with surface area, thats why hollow nanowires/tubes have higher capcitance. I have a professor who's last name is also Cui, but he teaches nanolithography

 

did they ever try hollow nanowires? Also wouldn't hollow ones take up more space though and have less surface area per square inch? It is like putting a bunch of .'s and o's together.


Delete....realized what i said was wrong....forgot a couple things. What is confusing is they test using mah per g (i think/forget weight) Though i know mah is kind of a bad measurement because it ignores voltage. Not all li batteries carry the same voltage. LiFePO4 cells have different voltages compared to li-ion and some li-ion and polymers can vary a couple .x voltage depending on how they are used. If i remember correctly the "ultra high capcity" li cells at battery space are not actually any higher besides you just charge them to a higher voltage at the cost of cycles....though i may be wrong. Several batteries they made in the pubs have wide ranging voltage and it is hard to tell what voltage would be the standard for them. Anyways, it is odd how they calculate capacity in their articles and makes it really hard to figure out and follow. Maybe in the science field mah per g is norm but odd in the tech/consumer world. I just don't get why everyone just doesn't use the simple wh measurement *shrugs*

 

no, hollow would have a lot more surface per squre inch. the diameter of the wires is just a few nanometers, so it doesnt really take up any space for it to be hollow. i personally tried multiwall carbon nanotubes functionalized with polypyrrole as a supercapacitance material. the problem with that is the reversibility isnt very good

source: i major in nanotechnology engineering

 

Interesting....i am very interested in how they know these things ^^ Like how to make a nano tube in their process. I thought it had to due with a bath in something with a current but so damn random lol. Also did you see my update

 

i think the most popular way of making nanotubes is by CVD (chemical vapour deposition). i am not too familiar with all the battery stuff, but the way i calculated capacitance was by cyclic voltammetry, where i use the formula C=I/(v*m), I is the average current over the swept voltage range ν is the potential sweep rate (V/s), and m is the mass loading of the sample over the surface of the electrode (g).

 

.....don't quite understand that....oh well...my interest doesn't go that far ^^ I'll just wait and see i guess and stick with the easy AxV=Wh ^^