LiCo LiPoly cell dissection pics! Very cool!

[liveforphysics]

This little guy was the weak cell in a string, and I ended up giving him a 6v REVERSE charge! It didn't like that much, and it puffed and hot warm and vented, sitting right in the living room at home. Didn't smell too bad, no flames, just some white smoke that seemed to quickly fade from the air in the living room.


So, I decided he would be a perfect choice to cut apart and get some pics.

This is a 20C rated 700mAh LiCo chemistry Lithium Polymer cell.

I enjoyed seeing the design, I hope you guys do too!

 

[liveforphysics]

I had heard from a guy who was an Air-soft nut that you could pinch a 30c pack between a couple of boards with screws to provide big clamping force, and then safely draw +60c from the pack. Now I can see how some additional mechanical pressure on the layers could directly effect cell performance from lower resistance connections at the plate/polymer connections. Fortunately, when I build my large LiPo E-bike pack, I was careful to put about 100lbs of clamping force on the cell stacks, so hopefully that is helping my pack.

My lesson from this was that the heat-shrink on a pack is not just to insulate and make a neat package. That pressure is critical to cell performance and durability, and likely changes Ri as well.

I'm going to try some experiments now measureing Ri on cells to see if it changes depending on clamping tension, as well as test to see what levels of pressure it takes before the clamping force causes a failure.

Very cool stuff if you happen to be a battery geek!

Best Wishes,
-Luke

 

[dak664]

Great pictures, I can smell the solvent (I hope it's imagination and not my laptop battery). How thick is the copper foil, and how easy to clean without tearing?

 

[liveforphysics]

Tissue paper thin for both the copper and aluminum foil layers. It took very gentle pressure with the blade to keep from tearing it.

 

[kfong]

Wouldn't a simple vacuum bagging process do the same. I assume these cells were created in a vacuum. Interesting that pressure can increase the C ratings. I will have to play around with some of my old packs for RC use.