Battery Chemistry

Can anyone confirm the battery chemistry of the i3? Tom posted in his blog 3 years ago that it was to be NMC (LiNiMnCoO2 or Nickel-Manganese-Cobalt), but does anyone know of a source that can confirm what BMW ended up using?

I'm pretty sure Tom's right that it's NMC.

Here's another report backing him up (ironically, from the National Petroleum Council... lot's of good info, though):

http://www.npc.org/reports/FTF-report-080112/Chapter_13-Electric.pdf

Sweet. That makes it the BMW of battery technology, spanking the LMO technology of the Tesla Model S, Chevy Volt, and Nissan Leaf in Specific Energy, Performance, and Life Span, while maintaining parity in Specific Power, Safety and Cost. From Battery University (http://batteryuniversity.com/learn/article/types_of_lithium_ion):

BMW NMC Technology:


Tesla, Volt, Leaf LMO Technology:

ok , thx for the info!

Let us go through what we know about the BMW i3 battery specs, maybe we can get to the bottom of it based on other batteries used in other cars. Also the Tesla Roadster is lithium cobalt oxide and the Model S is Nickel Cobalt Aluminum oxide

Here's what we know:
Lithium Cobalt Oxide- used in the Tesla Roadster
Nickel Cobalt Aluminum Oxide- used in the Model S
NMC- not used in any EV's; maybe the I3 and i8
Manganese spinel- used in the Leaf, Focus EV, Volt
Iron Phosphate- used in the Fisker and the Spark
Lithium Titanate- used in the MiEV

Cobalt oxide it out- that is just a bad chemistry for model EVs right off the bat- it is touchy, limited cycle life, needs massive cooling, even Tesla doesn't use it any more.

Now we have some detective work:
Here's what we know about the i3 battery
Capacity of lithium-ion battery in kWh 18.8
Fast charging, e.g. at DC fast-charging station: DC; 125 A; 50 kW (80 %) Under 30 min.
Battery weight is 230 kg
http://www.asymcar.com/graphics/14/i3/bmwi3b.pdf

So that puts it at 81.7 Whr per Kg AND it has fast charging capabilities

Now NMC and NCA are close for whr per Kg
So let us check to see the Tesla Model S since it uses NCA
The Tesla pack weighs in 600 kg and has 85 kwhr, that turns out to be 141 Whr per kg, NMC should have 130-120 whr/kg, lower, but not by much.

Can't be NMC or NCA, the density is too low for the i3

Now let us look at Manganese Spinel- Nissan Leaf, well known, no cooling- that is 24 kwhr and 300 kg
That is 80 Whr per kg; possible, BUT remember the Leaf lacks a cooling system for the battery- so that may not be accurate

Iron phosphate- Spark is 254 kg for a 21.4 kwhr battery- 84 kwhr per kg

Lithium Titanate- could be also- green car congress reports 80 kwhr per kg also

Currently we narrowed it down to 3 potential ones based one energy density.
Now let us look at the behavior of each battery and let us also assume the i8 will have the same type.
Quick charge 80% in 30 minutes- That is pretty rough in the battery world, but all three can handle it to varying degrees.

We have some comment in 2012 from Kate Middletown, an apparent BMW employee, that A123 was the supplier (comments section)
http://www.autosavant.com/2012/10/16/ev-battery-maker-a123-systems-files-for-bankruptcy-protection/

It makes sense, BYD does use iron phosphates and quick charges them already so not a stretch, Could be one of the other 2 candidates too, they are so close on a Whr/kg.

A123 is not the supplier. BMW showed us that it was Bosch. The ActiveE was SB LiMotive (Bosch/Samsung JV), and Bosch retained the rights when the JV was disolved.

http://www.bmwblog.com/2011/04/19/innovation-days-%E2%80%93-electrification/

--Woof!

Yeah, I didn't really believe the iron phosphate either. A123 likes to confuse people, i remember they were saying they were the Volt supplier or something years ago.

So that narrows it down to either Manganese oxide or lithium titanate since they fit the battery energy density.

Dan5 said:

Capacity of lithium-ion battery in kWh 18.8

Click to expand...

Capacity of the i3 battery is 21.6 kWh, of which 18.8 is useable: http://www.bmwusa.com/Standard/Cont...3/Features_and_Specs/BMWi3Specifications.aspx

That would be 93.9 Wh/kg assuming 230 kg is an accurate number. There is a difference between weight of the cells and weight of the battery pack assembly.

I would rule out Lithium Titanate. That doesn`t need any heating in cold temperatures, as it has almost full capacity at -30°C. So why would BMW bother with conditioning the battery in the winter?
Also, with Lithium Titanate you can use almost all capacity down to very low voltage and still have an extremely high cycle life. With Titanate, one would use more that 18,8 out of 22 kWh.

Frank
Germany

That is why I used other EVs and packs as comparisons.
See my Tesla comment, that was also at the pack level, as were all the other calculations.

So essentially what we have at the pack level is below 100 Whr per kg.

That eliminates most of the high energy ones, cobalt oxide, nickel aluminum cobalt, and nickel manganese oxide.

Since Bosch is the supplier that eliminates iron phosphate

It is most likely manganese spinel doped with some NCM to bring up the energy density.

Yes, titanate does not need that level of cooling.

What does concern me is the charge/discharge cycles, but I guess if it fine with the Leaf and Energi it should not affect it too much.

If BMW would give a cost per kwhr, charge/discharge degradation, or an MSDS we would know for certain.

Hi DanS,

afaik, Bosch and/or the Bosch/Samsung colaboration was dropped as battery supplier. It looks like Samsung is the sole battery supplier, see for instance this link on Reuters: http://www.reuters.com/article/2014/01/23/samsung-sdi-idUSL3N0KX0YZ20140123

I think Tom's blog posting about the battery states Samsung as supplier as well. But do correct me if I'm wrong.

Regards, Steven

Dan5 said:

That is why I used other EVs and packs as comparisons.

Click to expand...

Dan, thanks for all of the information. I learned a lot attempting to track down sources. Understandably, manufacturers are very tight-lipped about battery chemistry, and all we really find is a tremendous amount of unsourced conjecture from inquisitive folks like us.

I don't agree that one can infer the comparative energy density of a battery cell technology based on the energy density of a battery pack:

• - First there are differences of scale. The BMW i3 battery pack has roughly 1/4 the capacity of the 85kWh Tesla Model S, so considering some fixed components that do not scale, it is highly probable that a pack of 1/4 identical cells will be more than 1/4 the weight
  - There is volumetric efficiency. A 1' x 1' x 1' empty cardboard box weighs more than 1/4 the weight of a 1.6' x 1.6' x 1.6' empty cardboard box, but has 1/4 the volume.
  - There are varying design objectives for a given battery pack. For instance, to make cooling highly efficient, and the battery pack less explody, BMW chose to use a freon refrigerant cooling system in the pack, which surely must add some weight. (see http://darrenortiz.com/website_pdfs/BMWi3PG.pdf)

Back to the original question - does anyone have a source indicating the i3's battery chemistry? I can only find two (thanks, Buskraut!), and neither is from a manufacturer. They both point to NMC:

• http://bmwi3.blogspot.mx/2011/03/bmw-i3-light-weight-means-less-energy.html
  Table 13-4 of http://www.npc.org/reports/FTF-report-080112/Chapter_13-Electric.pdf

I have been unable to find any source that suggests otherwise.

ultraturtle said:

Dan5 said:

That is why I used other EVs and packs as comparisons.

Click to expand...

Dan, thanks for all of the information. I learned a lot attempting to track down sources. Understandably, manufacturers are very tight-lipped about battery chemistry, and all we really find is a tremendous amount of unsourced conjecture from inquisitive folks like us.

I don't agree that one can infer the comparative energy density of a battery cell technology based on the energy density of a battery pack:

• - First there are differences of scale. The BMW i3 battery pack has roughly 1/4 the capacity of the 85kWh Tesla Model S, so considering some fixed components that do not scale, it is highly probable that a pack of 1/4 identical cells will be more than 1/4 the weight
  - There is volumetric efficiency. A 1' x 1' x 1' empty cardboard box weighs more than 1/4 the weight of a 1.6' x 1.6' x 1.6' empty cardboard box, but has 1/4 the volume.
  - There are varying design objectives for a given battery pack. For instance, to make cooling highly efficient, and the battery pack less explody, BMW chose to use a freon refrigerant cooling system in the pack, which surely must add some weight. (see http://darrenortiz.com/website_pdfs/BMWi3PG.pdf)

Back to the original question - does anyone have a source indicating the i3's battery chemistry? I can only find two (thanks, Buskraut!), and neither is from a manufacturer. They both point to NMC:

• http://bmwi3.blogspot.mx/2011/03/bmw-i3-light-weight-means-less-energy.html
  Table 13-4 of http://www.npc.org/reports/FTF-report-080112/Chapter_13-Electric.pdf

I have been unable to find any source that suggests otherwise.

Click to expand...

Actually that was the reason I used the Model S as a comparable vehicle, it also has a water cooling system to keep the batteries cool. I think Tesla and BMW are both capable of designing a cooling system that is lightweight, but still provides adequate cooling.

The Tesla is a very conservative number and one would assume that the "plate design" that BMW uses actually decreases the weight.

Remember Tesla is using a bunch of these cells called 18650's (essentially the orientation of the cells you find in laptops) and as such have about 11% of the weight that is coverings.

The only odd balls would be the leaf- air cooled and the MiEV.

I think we did narrow it down, Altair is not the supplier, neither is Toshiba- means it is not lithium titanate
A123 is not the supplier- means it is not iron phosphate
Panasonic is not the supplier that means it is not NCA
The criteria for cobalt oxide does not fit.

The Volt is like 83 Whr/kg and has liquid cooling (We all know about the crash test where the coolant leaked 2 weeks later and short circuited the battery) and that is manganese oxide

So it's 12% more than manganese oxide (pure) battery, but not quite as much as a pure NCM battery.
I found this paper, this may be something that they did- doping with Cobalt
http://www.electrochem.org/dl/ma/206/pdfs/0416.pdf

Makes sense, Samsung works with NCM and NCA
Also I narrowed down one of the authors.
Atsuo Yamada is involved in the Samsung group
http://www.researchgate.net/publication/44579586_Tailoring_the_electrochemical_properties_of_composite_electrodes_by_introducing_surface_redox-active_oxide_film_VO%28x%29-impregnated_LiFePO4_electrode

If only we could link him further...

Dan,

Thanks for the additional sources.

According to page 17 of this document - http://darrenortiz.com/website_pdfs/BMWi3PG.pdf, the i3 utilizes 8 modules weighing 25 kg each, which would make the pack level energy density 108 kWh/kg. While I still do not generally agree that pack level energy densities are useful for sleuthing cell chemistry, I think being in the same order of magnitude might be of some use. Volumetric efficiency alone might account for differences, as the 85 kWh Tesla Model S module has 31.5 times the capacity of a single 2.7 kWh i3 module.

I was unable to locate a source for the Tesla Model S battery pack weight. Could you steer me in the right direction?

ultraturtle

Here's the car and driver article
http://www.caranddriver.com/reviews/2013-tesla-model-s-test-review

Graph with the battery pack comparison with a leaf.
1323 lbs/601 kg for 85 kwhr pack ~ 140 Whr/kg

Plus when that article Dec 2012 was written only 85 kwhr packs were being delivered

Now if you take out the modules themselves and weight out the batteries
There are around 7104 batteries each weighing 45 grams = 320 kg, or roughly half is the cells, other half is controllers, fluid, dividers, etc.
http://lygte-info.dk/review/batteries2012/Common18650Summary%20UK.html

16 modules * 6 groups * 74 cells per group = 7104 cells

You can also back calculate, easy since they are 18650s
85000 whr / (3.4 Ah *3.6 V) = ~6950 cells
Or if you use 3.1 Ah (older cells) you get ~ 7600 cells

As the i3 batteries are changing , from 94h to 120h, the nickel content keeps increasing and cobalt and other content for stability keeps reducing. NMC111, to NMW622 to may be NMC 811
While of course, the total capacity increases, what is it coming against ? What are the Cons ?
I guess reduced stability means , reduce temperature operating range, reduced safety and what else ?
Will it also reduce battery c rate ? The books says, the c rates also in increase always, but at least for the Bolt with NMC622 the c rate looks less.
The battery cycle rates will also reduce, but may balance out with less cycles needed.

https://goo.gl/images/Cv2cKW

Here are some battery specs:

https://insideevs.com/lets-look-at-the-specs-of-the-samsung-sdi-94-ah-battery/