Power bank battery dismantled and reviewed

Power bank battery dismantled and reviewed
(backup battery for iPhone produced in China)

Before we start some explanation and disclaimer.
Here is a short review, based on observations and simple calculation of one of "power bank" or backup battery for iPhone, which may be found in any shop. I did not intend to do this review simply because I did not buy that device and not going to buy such things in a future (near future). This example device I have got from my friend after its stoped working and actually the plastic shell become opened (Fig. 2).

This is not a denunciation or exposure for certain product or certain manufacturer or certain country.
I hope this review will make you more skeptical and realistic about what you see and what you get.

All dismantle and photos, as well calculation and conclusions done by me.
 
Although I dismantle Li-ion batteries (LIB) of any shape and size many times for many years since I have work with it for the last 15 years. I have to say, please do not try to repeat it at home, its may be  harmful.

Here are some pictures of how this "power bank" is looks like (may be looks familiar to someone?)

Fig. 1 (front)

Fig. 1(back)

On the spec (Fig. 1 (back)) it shows 1000 mAh (1Ah). Which is about a half of iPhone`s battery. I don`t have a package so there is no much information.

And here is how it looks like after it stopped produce a juice:

Fig. 2

Fig. 3

Fig. 4

 Very easy to open plastic box, in fact its already opened

Fig. 5

 As you may see (Fig. 5), Al bag of LIB is bloated with a lot of gas inside. This was the reason of the shell become opened.
Some other views of the "power bank" on Fig. 6 a-c:

Fig. 6a

Fig. 6b

Fig. 6c

After brief inspection of the battery I have found a possible source for battery failure. On the next pictures (Fig. 7 a-b) you will see defected sealing of Al bag, which caused electrolyte leakage and moisture penetration inside battery. Which happened first it is difficult to say now. From my experience, it is more likely that last one will happened first. As we know, when "polymer battery" sealed in Al bag, it is more likely happened at low or middle vacuum environment. However, each maker/factory will use its own way.

Fig. 7a

Fig. 7b

 As a result of chemical reactions between moisture (H2O) and electrolyte/electrode (anode/graphite) and Li (on an anode/graphite surface) LIB will release a lot of gaseous products inside of Al bag, as well as slowly decline a power of LIB.
It can be seen by observing electrode (anode/graphite) surface;

Fig. 8

Fig. 9

Fig.10

Fig.11

 Surface of the anode/graphite electrode shows serious Li plating and transformation it to inactive form (Fig. 11, 12).

Fig. 12

Now, about quality:
As you can see on above pictures, electrode quality is quite poor. On the pictures below, I will show that it is even more poor:

Fig. 13

 On this (Fig. 13) you will see some tape on the cathode (right side) electrode surface. This hilarious battery makers don`t want to waste any peace of electrode, so even it was broken during some assembling process, they will "fix" it with anything can be glued to surface. Like this piece of tape (Fig. 14)

Fig. 14 (front)

Fig. 15 (back side of Fig. 14)

Although they use quite strong separator (~ 20 um thickness), to prevent possible soft-shorting (Fig. 16).

Fig. 16b

Fig. 16 a

 Now, after we get our hands inside of this battery, we can get actual numbers (at least some of them) of battery design. That would be (a) electrode surface area, (b) thickness, (c) current collector (Al and Cu) quality/thickness etc. Which will give as (at least rough) understanding of real battery capacity.
After some measurements we have:

Cathode area: 164 cm2
Al current collector thickness: 25 um
Cathode loading: ~ 0.021 mg/cm2

Anode area: 164 cm2
Cu current collector thickness: 30 um
Anode loading: ~ 0.01 mg/cm2

Now we have to assume something to be able to calculate real battery capacity. Since we do not use any fancy tools (XPS, X-ray, NMR etc.) to detect for sure what kind of material this particular maker used in this particular battery. We will use common sense and assume (with a bit fair) that:

Cathode: LiCoO2 (145 mAh/g) with 90% of active and 10% binder/conductive
Anode: Graphite (330 mAh/g) with 90% of active and 10% binder/conductive

Now, we can calculate that actual capacity for this device (which is  labeled as 1000 mAh) it is just about 900 mAh (with relatively fair assumptions).

This means, well you know what is that.....


Full size pictures are available here

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