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Tesla battery researcher unveils new cell that could last 1M miles

electrek.co

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Re: Tesla battery researcher unveils new cell that could last 1M miles

#21

Post by Osiris30 »

zaroth wrote: post #10

Post of the actual paper; https://news.ycombinator.com/item?id=20908726 For those commenting that the discharge rate is too slow in the test, or the depth of discharge was fudged... the tests were run with a high discharge rate combined with 100% charge at storage. > Figure 23 shows the projected fractional capacity of these NMC532/graphite cells as a function of time in years in a scenario where the cells are cycled…

Would this be a correct summary of the paper?

1) eliminates Cobalt

2) improves energy density (more range)

3) faster charge rate

4) less SOC (state of charge) swing, meaning less cost & weight

4) 5x longer lifespan

Re: Tesla battery researcher unveils new cell that could last 1M miles

#22

Post by manmal »

miketery wrote: post #13
sandworm101 wrote: post #8

>> The new battery tested is a Li-Ion battery cell with a next-generation “single crystal” NMC cathode and a new advanced electrolyte. If this is anything like growing single-crystal parts for aircraft, it won't be cheap. The real question should be whether these new battery modules will last twice as long while remaining less than twice as expensive. >> Controlling the charge to less than 100% state-of-charge also h…

> >> Controlling the charge to less than 100% state-of-charge also helps push the longevity. > Um, that is cheating. Running any battery at less than capacity will extend its life. You could put two batteries in the car, run them at 50% or alternate between them, and get double the life. No prizes for that. I imagine the idea is that by going to X% instead of 100% fill, you extend by more than 1/X. So at 95%, perhaps…

Exactly. And this practice is widely followed by basically every BEV car manufacturer. Most of the more recent models even have a bigger battery than specified, and charge only up to 90-95% capacity while providing the specified range.

Re: Tesla battery researcher unveils new cell that could last 1M miles

#24

Post by manmal »

This is very exciting. BEVs that were made before 2016 (I think that was when the last breakthrough trickled down to BEVs in the market) typically had a battery lifetime of about 70k miles or maybe a bit more before reaching 70% capacity. Fast-charging regularly might reduce capacity by several percent points within a few hot summer months. Basically, you bought a car for €30k and it might become useless 5-7 years later. Within a couple of years, we have gone from "I don't know, it's a bit risky to buy" to "My grandkids might be able to use this battery in their static storage system in a few decades".

Re: Tesla battery researcher unveils new cell that could last 1M miles

#25

Post by Reason077 »

falcolas wrote: post #20
zaroth wrote: post #10

Post of the actual paper; https://news.ycombinator.com/item?id=20908726 For those commenting that the discharge rate is too slow in the test, or the depth of discharge was fudged... the tests were run with a high discharge rate combined with 100% charge at storage. > Figure 23 shows the projected fractional capacity of these NMC532/graphite cells as a function of time in years in a scenario where the cells are cycled…

Nothing here indicates a discharge rate. I'm having trouble finding the actual wattage produced by these cells over the 6 hour discharge time. Also, 6 hours is a longer than the current Tesla will run full charge at highway speeds (350 mile range, 75 mph ~= 4.5 hours). Plus, the current tesla can be re-charged and continue to operate, conditions I don't see mentioned. If it is similar to existing batteries though...…

"Nothing here indicates a discharge rate."

In battery terminology, and this paper, charge/discharge rate is referred to as "C". Charging or discharging at 1C means a battery would be fully charged/discharged in 1 hour. A 100 Wh cell discharging at 1C would produce 100 W. Likewise, at 3C it would take 20 minutes and produce 300 W. At C/3, it would take 3 hours.

Re: Tesla battery researcher unveils new cell that could last 1M miles

#26

Post by alanh »

Osiris30 wrote: post #21
zaroth wrote: post #10

Post of the actual paper; https://news.ycombinator.com/item?id=20908726 For those commenting that the discharge rate is too slow in the test, or the depth of discharge was fudged... the tests were run with a high discharge rate combined with 100% charge at storage. > Figure 23 shows the projected fractional capacity of these NMC532/graphite cells as a function of time in years in a scenario where the cells are cycled…

Would this be a correct summary of the paper? 1) eliminates Cobalt 2) improves energy density (more range) 3) faster charge rate 4) less SOC (state of charge) swing, meaning less cost & weight 4) 5x longer lifespan

what is 'state of charge swing'?

Re: Tesla battery researcher unveils new cell that could last 1M miles

#28

Post by hwillis »

Osiris30 wrote: post #21
zaroth wrote: post #10

Post of the actual paper; https://news.ycombinator.com/item?id=20908726 For those commenting that the discharge rate is too slow in the test, or the depth of discharge was fudged... the tests were run with a high discharge rate combined with 100% charge at storage. > Figure 23 shows the projected fractional capacity of these NMC532/graphite cells as a function of time in years in a scenario where the cells are cycled…

Would this be a correct summary of the paper? 1) eliminates Cobalt 2) improves energy density (more range) 3) faster charge rate 4) less SOC (state of charge) swing, meaning less cost & weight 4) 5x longer lifespan

1) 532 is not a new chemistry. It's not even the lowest cobalt chemistry; there's 511 and 811 beyond that (811, or 80% nickel, 10% manganese, and 10% cobalt, is not yet technically feasible).

2) Range is decreased. 532 has lower energy density.

3) Maybe..? But nothing truly significant. The additives in this chemistry mean a lot of heat gets generated during charge/discharge. Heat is the limiting factor during charge, so swapping directly to this would mean lower top charging speed. However with better cooling... maybe? It can sustain high charge current for longer, but not as high overall.

4) The buffer for EVs is ~10%. It's not a big factor in cost or weight.

5) Yes, 5x longer lifespan. The caveat is that they havent actually tested >3 years, but IMO this is probably a 50 year battery. The paper is more conservative and gives it 20 years.

This will be pretty enormous for grid storage, since a battery that lasts 5x as long costs 5x less. It may be important for trucks and buses, since they are much higher mileage and will want to run at 100% depth of discharge. Cars on the other hand run closer to 20%, where normal batteries will also last for many thousands of cycles.

Re: Tesla battery researcher unveils new cell that could last 1M miles

#29

Post by guerby »

Two things missed by the electrek piece:

- The article is CC-BY and downloable without scribd horrible UI: http://jes.ecsdl.org/content/166/13/A3031 PDF direct http://jes.ecsdl.org/content/166/13/A3031.full.pdf HTML direct http://jes.ecsdl.org/content/166/13/A3031.full.html

- In the conclusion the authors mention: Full details of these cells including electrode compositions, electrode loadings, electrolyte compositions, additives used, etc. have been provided in contrast to literature reports using commercial cells. This has been done so that others can re-create these cells and use them as benchmarks for their own R+D efforts be they in the spaces of Li-ion cells or “beyond Li-ion cells”.

So it's science as it should be!

Re: Tesla battery researcher unveils new cell that could last 1M miles

#30

Post by hwillis »

ianai wrote: post #27

Can anyone tell whether this is a solid state electrolyte? I’m still hooked on what I saw in that Netflix documentary where the guy was able to cut and puncture the battery without combustion. Also seemed capable of being much more dense.

It is not. This is a fairly conventional cell, with a different crystal structure for one of the ingredients, and a tweaked mix of liquid electrolytes.

The most important part of this paper is that they actually prove that optimizing for cycle and calendar life can have such incredible effects.

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