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TomT
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Re: Why do lithium batteries die and how to improve them?

Sat Feb 15, 2014 7:49 pm

+10,001

TimLee wrote:
drees wrote:No, it's simple. Just do these steps:

1. Give realistic expectations on how fast you might expect the battery to lose capacity based on use and climate. Provide an upper and lower bound that one might see based on various usage habits. Make sure the car tracks operating conditions accurately to help improve future expectations.

Really, all the magic is in #1. Provide realistic expectations and err on the side of under promising and over delivering.

Do that and people will be able to make their own educated decisions in terms of what is and is not acceptable.

+10,000
False marketing will accomplish nothing other than complete total destruction of your BRAND!!!!
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71,770 miles/12 bars/256 Gids/59.04 AHr/88% SOH/87.92% Hx 3Mar16 at lease return.

Now driving a 2016 Volt Premier.

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keydiver
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Re: Why do lithium batteries die and how to improve them?

Thu Jun 18, 2015 12:02 pm

Great news:
Tesla Motor's Co-founder and Chief Technology Officer JB Straubel signed a research agreement with Dalhousie University's Jeff Dahn, Li-ion battery researcher with the Faculty of Science and his group of students, postdoctoral researchers and technical staff.

http://www.powerpulse.net/story.php?sto ... =061820151
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mbender
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Re: Why do lithium batteries die and how to improve them?

Thu Jun 18, 2015 1:58 pm

See also TSLA stock price discussion thread <-- Link jumps to the appropriate post of June 17, 2015.

keydiver wrote:Great news:
Tesla Motor's Co-founder and Chief Technology Officer JB Straubel signed a research agreement with Dalhousie University's Jeff Dahn, Li-ion battery researcher with the Faculty of Science and his group of students, postdoctoral researchers and technical staff.

http://www.powerpulse.net/story.php?sto ... =061820151
I think I just felt my paradigm shift.

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gadyamit
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Re: Why do lithium batteries die and how to improve them?

Wed Jul 27, 2016 9:22 am

Can we say that from what we know now about the Leaf battery pack, Elon Musk was right?
Tesla Motors (s TSLA) CEO Elon Musk has derided Nissan’s battery pack, which uses an air cooling system, as “primitive” compared with the sophistication of even Tesla’s first prototype, which uses liquid cooling. As a result, the LEAF pack will have temperatures “all over the place,” claimed Musk, causing it to suffer “huge degradation”

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RegGuheert
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Re: Why do lithium batteries die and how to improve them?

Tue Nov 01, 2016 1:41 pm

keydiver wrote:Great news:
Tesla Motor's Co-founder and Chief Technology Officer JB Straubel signed a research agreement with Dalhousie University's Jeff Dahn, Li-ion battery researcher with the Faculty of Science and his group of students, postdoctoral researchers and technical staff.

http://www.powerpulse.net/story.php?sto ... =061820151" onclick="window.open(this.href);return false;
It seems this arrangement will pay off rather quickly. According to this article, Dahn and his team have already published a paper which should help pave the way to operation of Li-ion batteries at higher voltages, thus increasing the energy density:
electrek wrote:The paper states that ethylene carbonate (EC), an organic compound until now thought to be an essential electrolyte component for Li-ion cells, is “actually detrimental for cells at high voltages” – 4.5 V and above. Tesla/Panasonic’s current cells are believed to be around 4.2 V, but the upcoming cells to be produced at the Gigafactory are expected to have a higher voltage.

In order to replace EC in the electrolytes, the group developed “EC-free linear alkyl carbonate electrolytes” and tested them in pouch cells. They report “excellent charge-discharge cycling and storage properties” and better cyclability of cells than cells with EC.

The researchers are hopeful that it could lead to better high-voltage battery cells:

“Further optimizing these linear alkyl carbonate electrolytes with appropriate co-additives may represent a viable path to the successful commercial utilization of NMC/graphite Li-ion cells operated to 4.5 V and above.”
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RegGuheert
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Re: Why do lithium batteries die and how to improve them?

Tue Nov 01, 2016 2:31 pm

This two-year-old article in Quartz gives a good overview of the issue with operation of NMC at high voltages that Dahn is trying to address:
Quartz wrote:The key to the second-generation cathode is an unusual jolt of voltage that unlocks the higher performance. The best current lithium-ion batteries operate at an average of 3.7 volts or so. The idea with the NMC formulation was to operate it at 4.7 volts. The resulting leap in energy is what got the licensees so excited.

But researchers began to notice a problem with the cathode at the higher voltage, which was an unexplained fast and steep loss of energy as the battery went through charge-and-discharge cycles. They called the malady “voltage fade.” Until it was fixed, they said, the second-generation material could not be used commercially.
If the average operating voltage of NMC Li-ion cells could be increased from 3.85V to something like 4.3V, that would result in a significant boost in capacity. In addition, it would allow the same operating voltage to be achieved with a smaller number of cells.

I have to give Dr. Dahn a lot of credit here: he has had faith in his invention of 16 years ago based on its promise and has worked to eliminate the problems with its commercialization. He is a significant contibutor to the BEV revolution which is currently ongoing.
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ydnas7
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Re: Why do lithium batteries die and how to improve them?

Tue Nov 01, 2016 5:49 pm

RegGuheert wrote:This two-year-old article in Quartz gives a good overview of the issue with operation of NMC at high voltages that Dahn is trying to address:
Quartz wrote:The key to the second-generation cathode is an unusual jolt of voltage that unlocks the higher performance. The best current lithium-ion batteries operate at an average of 3.7 volts or so. The idea with the NMC formulation was to operate it at 4.7 volts. The resulting leap in energy is what got the licensees so excited.

But researchers began to notice a problem with the cathode at the higher voltage, which was an unexplained fast and steep loss of energy as the battery went through charge-and-discharge cycles. They called the malady “voltage fade.” Until it was fixed, they said, the second-generation material could not be used commercially.
If the average operating voltage of NMC Li-ion cells could be increased from 3.85V to something like 4.3V, that would result in a significant boost in capacity. In addition, it would allow the same operating voltage to be achieved with a smaller number of cells.

I have to give Dr. Dahn a lot of credit here: he has had faith in his invention of 16 years ago based on its promise and has worked to eliminate the problems with its commercialization. He is a significant contibutor to the BEV revolution which is currently ongoing.



voltage fade and electrolyte degradation are 2 separate issues. A high voltage spinel like Ni.5Mn1.5O4 has nil voltage fade, but suffers from electrolyte degradation (and resulting cathode leaching). Similarly, high voltage bland NMC has nil voltage fade but still has the same electrolyte degradation (but less cathode leaching). Mn rich, Li rich NMC has voltage fade + electrolyte degradation. That class of cathode probably exhibits voltage fade even at conventional voltages levels, its related to how its high capacity Mn transitions to a high stability Mn during use.

recently it seems the Chinese have also cracked the higher voltage EC free electrolyte challenge, and using only conventional ingredients. This is massive news as it ushers in both a new class of cathode (high voltage Mn Spinel, cheap and safe) as well as promotes higher capacity in conventional NCA and NMC.

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RegGuheert
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Re: Why do lithium batteries die and how to improve them?

Wed Nov 02, 2016 6:00 am

Just for reference so that we can try to use similar terminology, here is a link to a transcript a blogger made to Professor Dahn's lecture on Li-ion battery degradation.
ydnas7 wrote:voltage fade and electrolyte degradation are 2 separate issues.
This is where I am getting a bit confused. In the lecture, Professor Dahn describes two mechanism that are degrading the batteries: one on the anode and one on the cathode. At the anode, he describes the formation of a film which he calls solid electrolyte interphase (SEI), which apparently is a reaction between the graphite and the electrolyte. That causes a slippage of the voltage curve to the RIGHT. At the cathode, he describes an oxidation of the electrolyte which occurs due to the high voltages present. This results in additional reactions which ALSO causes a shift in the voltage curves to the RIGHT.

So the question is: What are you referring to as "voltage fade" and what are you referring to as "electrolyte degradation"? I'll guess that electrolyte degradation is the oxidation of the electrolyte at high voltages that appear at the cathode. But the slippage of the voltages to the right can hardly be described as "voltage fade" since they are increases in voltages. Perhaps it is considered "fade" because most battery chargers (like the one in the LEAF) use a constant voltage to determine when to terminate the charge cycle and this shifting of the voltage curve to the right results in an increasing inability to fully charge the battery?
ydnas7 wrote:A high voltage spinel like Ni.5Mn1.5O4 has nil voltage fade, but suffers from electrolyte degradation (and resulting cathode leaching). Similarly, high voltage bland NMC has nil voltage fade but still has the same electrolyte degradation (but less cathode leaching). Mn rich, Li rich NMC has voltage fade + electrolyte degradation. That class of cathode probably exhibits voltage fade even at conventional voltages levels, its related to how its high capacity Mn transitions to a high stability Mn during use.
Am I correct in assuming that it is this last class of Mn-rich, Li-rich NMC that is being discussed in the recent Dahn paper and the Quartz article?
ydnas7 wrote:recently it seems the Chinese have also cracked the higher voltage EC free electrolyte challenge, and using only conventional ingredients. This is massive news as it ushers in both a new class of cathode (high voltage Mn Spinel, cheap and safe) as well as promotes higher capacity in conventional NCA and NMC.
Unfortunately, the state-of-the-art in the world of computer modelling of chemistry is NOWHERE near having the ability to model something as complex as the electrodes in a Li-ion battery, so it seems that the work is still proceeding emperically. The good news with Li-ion is that there are so many eyes on the problem now and advancements such as Professor Dahn's extremely-accurate Coulomb counter GREATLY speed up the time between experiment and result.
RegGuheert
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Re: Why do lithium batteries die and how to improve them?

Wed Nov 02, 2016 8:40 am

Here are a couple more articles which reference Dr. Dahn's new paper:

Green Plug District: Ethylene Carbonate-free Electrolytes Promise Less Oxidation and Better-performing Li-ion Cells

Green Car Congress: Dahn team develops ethylene-carbonate-free electrolytes for better-performing high-voltage Li-ion cells

The Green Car Congress article contains the following results of testing various additives to 4.5V from the paper:

Image

Quote from the paper (from the article):
Xia et al. wrote:The work in this paper suggests that EC itself is the root cause of many issues associated with the operation of NMC/graphite cells to high potential. Electrolyte oxidation reactions at high voltages cause gas evolution and impedance growth, leading to cell failure. These parasitic reactions become very problematic at 4.5 V even with state of the art electrolyte additives PES211 in EC:EMC electrolyte. … This work demonstrates that cyclic carbonates such as VC, FEC and DiFEC can act as the enablers for EMC-based electrolytes which function well in NMC442/graphite cells tested up to 4.4 or 4.5 V.
Interestingly, the article indicates that this work was NOT funded by Tesla, but rather by 3M:
Green Car Congress wrote:3M has filed a patent on this work.
RegGuheert
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palmermd
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Re: Why do lithium batteries die and how to improve them?

Wed Nov 02, 2016 9:37 am

RegGuheert wrote:...Interestingly, the article indicates that this work was NOT funded by Tesla, but rather by 3M...


He's only been working for Tesla since June, so not much time to do enough work to publish a paper. His announced move was about 18 months or so before then, and he had a contract with 3M to complete before he moved over to Tesla.
Michael

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