Video-New Lithium Battery Research,Jeff Dahn,Dalhousie-Tesla

okashira said:

Thx for posting. I learned alot from Dahn's prior research.
This was a pita to watch but this is what I gleaned.

--Alot of testing done on individual electrodes - ie graphite alone or nmc/nca alone is hugely invalid due to interactions between the electrodes and electrolyte in a complete cell. This is a big DUH for me. But if you are reviewing published research, be sure to note of data gained from testing on isolated electrodes.
--Note: the limits of their research. They are limited to what their suppliers can supply economically - Chinese made electrodes, pouches
--POSITIVE electrode seems to produce much of the calendar degradation of cells. This is great info, but also not surprising. This confirms why positive electrode changes seem to produce such remarkable differences in cell durability - ie NCA is great for high temp long term , NCM is also good, but really depends on electrolyte composition, LiMnO "spinel" is terrible for high temp, FePO4 is also inferior, but better then LiMnO
--impedance growth can be correlated with cell degradation, and again, negative electrode usually does not exhibit degradation,,,, the positive electrode exhibits most of the change.
--electrolyte composition can have a remarkable effect on cell durability in storage/high temp/high voltage. Should assume competent manufacturers have this right. (Lg, SS, Pana, etc..)
--degradation of both the positive electrode as well as the electrolyte can be masked by the negative electrode - gasses are absorbed by the negative electrode and negative byproducts of the electrolyte oxidation is absorbed by the negative electrode. what could this mean, for low and high density negative electrode cells? how about cells with silicon in the negative electode?
--There is probably lots here not presented and kept secret by Tesla and Panasonic
--99.9% of folks here won't learn much nor benefit from info here. This is a paid speech for researchers.

more:
fluorinated solvents ... still gas production but preserve low resistance. Much better for higher voltage and cycle life. blah blah.
coatings on the positive electrode can make huge differences. blah blah.

This was a whole bunch of trying to verify why certain electrolytes and positive electrodes perform better, something manufacturers have figured out for over 5 years using trial and error. This research just tries to look more closely at what is going on, but it does not quite reach an end result or conclusion that has not already been obtained.
This is exactly why I did not go into academia. :-( I am too good at picking out the bs.

Click to expand...

AfdhalAtiffTan said:

okashira said:

Thx for posting. I learned alot from Dahn's prior research.
This was a pita to watch but this is what I gleaned.

--Alot of testing done on individual electrodes - ie graphite alone or nmc/nca alone is hugely invalid due to interactions between the electrodes and electrolyte in a complete cell. This is a big DUH for me. But if you are reviewing published research, be sure to note of data gained from testing on isolated electrodes.
--Note: the limits of their research. They are limited to what their suppliers can supply economically - Chinese made electrodes, pouches
--POSITIVE electrode seems to produce much of the calendar degradation of cells. This is great info, but also not surprising. This confirms why positive electrode changes seem to produce such remarkable differences in cell durability - ie NCA is great for high temp long term , NCM is also good, but really depends on electrolyte composition, LiMnO "spinel" is terrible for high temp, FePO4 is also inferior, but better then LiMnO
--impedance growth can be correlated with cell degradation, and again, negative electrode usually does not exhibit degradation,,,, the positive electrode exhibits most of the change.
--electrolyte composition can have a remarkable effect on cell durability in storage/high temp/high voltage. Should assume competent manufacturers have this right. (Lg, SS, Pana, etc..)
--degradation of both the positive electrode as well as the electrolyte can be masked by the negative electrode - gasses are absorbed by the negative electrode and negative byproducts of the electrolyte oxidation is absorbed by the negative electrode. what could this mean, for low and high density negative electrode cells? how about cells with silicon in the negative electode?
--There is probably lots here not presented and kept secret by Tesla and Panasonic
--99.9% of folks here won't learn much nor benefit from info here. This is a paid speech for researchers.

more:
fluorinated solvents ... still gas production but preserve low resistance. Much better for higher voltage and cycle life. blah blah.
coatings on the positive electrode can make huge differences. blah blah.

This was a whole bunch of trying to verify why certain electrolytes and positive electrodes perform better, something manufacturers have figured out for over 5 years using trial and error. This research just tries to look more closely at what is going on, but it does not quite reach an end result or conclusion that has not already been obtained.
This is exactly why I did not go into academia. :-( I am too good at picking out the bs.

Click to expand...

Thank you for your summary, I really appreciate it.
Do you know if the degradation can be electrically reversed by any chance?

I was hoping for it to behave almost like sulphation in lead acid battery technology.
I had some successes desulphating it by feeding high voltage pulses before.

Click to expand...

okashira said:

Thx for posting. I learned alot from Dahn's prior research.
This was a pita to watch but this is what I gleaned.

Click to expand...

--Alot of testing done on individual electrodes - ie graphite alone or nmc/nca alone is hugely invalid due to interactions between the electrodes and electrolyte in a complete cell. This is a big DUH for me. But if you are reviewing published research, be sure to note of data gained from testing on isolated electrodes.
--Note: the limits of their research. They are limited to what their suppliers can supply economically - Chinese made electrodes, pouches
--POSITIVE electrode seems to produce much of the calendar degradation of cells. This is great info, but also not surprising. This confirms why positive electrode changes seem to produce such remarkable differences in cell durability - ie NCA is great for high temp long term , NCM is also good, but really depends on electrolyte composition, LiMnO "spinel" is terrible for high temp, FePO4 is also inferior, but better then LiMnO
--impedance growth can be correlated with cell degradation, and again, negative electrode usually does not exhibit degradation,,,, the positive electrode exhibits most of the change.
--electrolyte composition can have a remarkable effect on cell durability in storage/high temp/high voltage. Should assume competent manufacturers have this right. (Lg, SS, Pana, etc..)
--degradation of both the positive electrode as well as the electrolyte can be masked by the negative electrode - gasses are absorbed by the negative electrode and negative byproducts of the electrolyte oxidation is absorbed by the negative electrode. what could this mean, for low and high density negative electrode cells? how about cells with silicon in the negative electode?
--There is probably lots here not presented and kept secret by Tesla and Panasonic
--99.9% of folks here won't learn much nor benefit from info here. This is a paid speech for researchers.

more:
fluorinated solvents ... still gas production but preserve low resistance. Much better for higher voltage and cycle life. blah blah.
coatings on the positive electrode can make huge differences. blah blah.

This was a whole bunch of trying to verify why certain electrolytes and positive electrodes perform better, something manufacturers have figured out for over 5 years using trial and error. This research just tries to look more closely at what is going on, but it does not quite reach an end result or conclusion that has not already been obtained.
This is exactly why I did not go into academia. :-( I am too good at picking out the bs.

Click to expand...

MitchJi said:

He started by trying to increase the energy density by increasing the voltage. (Ah = v x a)

Click to expand...

Punx0r said:

MitchJi said:

He started [his project with Tesla] by trying to increase the energy density by increasing the voltage. (Ah = v x a)

Click to expand...

lol, nope

Click to expand...

August 24th, 2016
<snip>
Jeff Dahn’s battery technology research team at Dalhousie University in Canada has developed a new means of improving high-voltage, lithium-ion battery cell performance through the use of cyclic carbonates as the enablers for ethylmethyl carbonate (EMC)-based electrolytes, rather than conventional options, according to recent reports.
<snip>
The research showed that the cyclic carbonates in question — VC (vinylene carbonate), FEC (fluoroethylene carbonate), and DiFEC ((4R,5S)-4,5-Difluoro-1,3-dioxolan-2-one) — reportedly worked well as the enablers for the aforementioned EMC-based electrolytes when used in NMC442/graphite battery cells tested at high voltages (up to 4.4 V or 4.5 V).
<snip>
As an example, the combo of EMC with specific amounts of some of the enablers mentioned above resulted in battery cells with improved performance as compared to battery cells with EC-containing electrolytes with additives, when tested up to 4.5 V.

The paper provides more: “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.”
<snip>

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May. 4th 2017
<snip>
Dahn is considered a pioneer in li-ion battery cells since he has been working on the batteries pretty much since they were invented. He is credited for having help increase the life cycle of the cells, which helped their commercialization. His work now focuses mainly on a potential increase in energy density and durability.
<snip>
Last year, Dahn transitioned the group from their 20-year research agreement with 3M to a new association with Tesla under the newly formed ‘NSERC/Tesla Canada Industrial Research’.
<snip>
At the International Battery Seminar & Exhibit in March, Dahn presented his new research to improve the chemistry of NMC Li-ion in order to limit the gasses generated by the cells when operating at high voltage.

The improved cells that they created from their research have performed exceptionally well after over 1,200 cycles:

<snip>
If made into a car battery pack, 1,200 cycles would translate to roughly 300,000 miles (480,000 km) – meaning that a battery pack could still retain about 95% of its original energy capacity after ~300,000 miles – or 25 years at the average 12,000 miles per year.

Those results are truly impressive – especially since Dahn said that his team’s research is already “going into the company’s products“.

In his presentation – embedded below, Dahn demonstrates how they virtually removed the harmful reactions in the positive electrode – leading to what they describe as “superb NMC Li-ion cells that can operate at high potential.”
<snip>

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<snip>
Dahn's focus won't just be cost, nor will his research apply only to the lithium-ion batteries used in Tesla's electric cars. His research team aims to increase both the energy density — or the amount of energy that can be stored in a battery per its volume — and the lifetime of lithium-ion cells, which could, in turn, help drive down costs in automotive and grid energy storage applications.
<snip>
Conceptually, it's easy to increase energy density. You can store more energy—about another 25%—in a lithium-ion cell simply by charging it to a higher voltage. However, that comes with a major downside.

"The problem is when you do that [charge it to a higher voltage] the lifetime is compromised," Dahn said in an interview with Fortune. "So it's always a trade off between lifetime and energy density."

If Dahn can crack this problem—a technically difficult task that requires improving or changing the materials of a lithium-ion cell—he could help Tesla produce cheaper, longer lasting, more powerful batteries. That could have huge financial implications beyond Tesla's electric cars, and could be used in the company's new energy storage products, the Powerwall and Powerpack.
<snip>

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