Big jump in battery tech - Tabless cells are here
Big jump in battery tech - Tabless cells are here
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Joelonghair

Original Poster:

266 posts

90 months

Friday 5th September
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Not sure if many of the readers of this area of PH are also interested in the evolution of the cells that power EV's but it seems to me a quiet evolution of cell technology has gone mostly unnoticed.

I have a casual interest in cell technology from a tangential hobby and up to now the king of the hill 21700 cell was the Molicel P50B - as used in the McMurtry Speirling. This was the best of the best, and has only been widley available over the past year.

THis cell is at the pinnacle of what is achievable - it features circa 5000mAh capacity, continuous discharge of 60A and 5C fast charging. Impressive.

But tabless cells have landed. This new tech reduces internal resistance of the cell enabling faster discharge, faster charging, and better thermal performance. I have an example on hand now, the EVE 50PL which boasts the same 5000mAh capacity of the previous state of the art Molicel, but with over double the continuous discharge rate at 125A, and faster charging. Voltage drop and heating also appear superior over the P50B from the tests I have seen.

Molicel have yet to adopt this new technology but have teased 21700 cells with a 20%-30% increase in capacity (6/6.5mAh) whilst still sustaining resonably high discharge rates.

To me a doubling of discharge rates (read power), faster charging, and a significant improvement in capacity needs to be talked about more.

uktrailmonster

7,007 posts

218 months

Friday 5th September
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Tesla has been developing tabless cells for some time and already using them in their CT.

JonnyVTEC

3,202 posts

193 months

Friday 5th September
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U wot m8

PetrolHeadInRecovery

335 posts

33 months

Saturday 6th September
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Joelonghair said:
THis cell is at the pinnacle of what is achievable - it features circa 5000mAh capacity, continuous discharge of 60A and 5C fast charging. Impressive.

But tabless cells have landed. This new tech reduces internal resistance of the cell enabling faster discharge, faster charging, and better thermal performance. I have an example on hand now, the EVE 50PL which boasts the same 5000mAh capacity of the previous state of the art Molicel, but with over double the continuous discharge rate at 125A, and faster charging. Voltage drop and heating also appear superior over the P50B from the tests I have seen.

Molicel have yet to adopt this new technology but have teased 21700 cells with a 20%-30% increase in capacity (6/6.5mAh) whilst still sustaining resonably high discharge rates.

To me a doubling of discharge rates (read power), faster charging, and a significant improvement in capacity needs to be talked about more.
Nice step forward in general! It should also get us closer to lightweight EV sports cars. If I'm not mistaken, 125A would correspond to 25C discharge rate. So you wouldn't need a big battery to support high power.

A 40kWh battery (roughly 250kg?) could support1000kW (over 1300hp) for almost 2.5 minutes. Combining this with high-power, lightweight motors (like this:https://insideevs.com/news/766621/yasa-axial-flux-electric-motor/) would add ~13kg and extend the "full power" time to close to 5 minutes. Recharging with a 600kW charger (fastest European COTS solution) would typically take the same ~5 minutes.

The combination should be able to take a few kg off this https://caterhamcars.com/en/models/evseven (smaller gross capacity to get to 40kW net, lower cooling needs, probably lighter motor) and triple the power (~1000bhp per ton).

Niche of a niche (Caterham sold 550 cars total in 2024), but could be a nice halo model/tech demonstrator.

Edited by PetrolHeadInRecovery on Saturday 6th September 10:02

Cristio Nasser

362 posts

11 months

Saturday 6th September
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Seems thermal management is still the main limiting factor. In that vein, seems the obvious next step is to make the positive terminal an internally finned tube that runs through the center of the cell that coolant can flow through. This would dramatically increase the area available for cooling, particularly in the core of the cell.

Not sure why it’s not been done yet tbh as it seems an obvious step. Unless I’m missing something as to why it can’t be done.

PetrolHeadInRecovery

335 posts

33 months

Saturday 6th September
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Cristio Nasser said:
Seems thermal management is still the main limiting factor.
But where do we encounter the limitations?

Seems that the higher voltage systems do already quite well in most scenarios even with older cell technology. Ioniq 5N capable of a couple of laps around the Nordschleife, 10C charging demo by BYD and a couple of record runs (production and prototype) by MB at Nardo.

Cristio Nasser

362 posts

11 months

Saturday 6th September
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PetrolHeadInRecovery said:
Cristio Nasser said:
Seems thermal management is still the main limiting factor.
But where do we encounter the limitations?

Seems that the higher voltage systems do already quite well in most scenarios even with older cell technology. Ioniq 5N capable of a couple of laps around the Nordschleife, 10C charging demo by BYD and a couple of record runs (production and prototype) by MB at Nardo.
Yea, but it hammers the longevity, particularly when trying to fast charge an already hot battery. That’s where the thermal management piece is super important .

All well and good hot lapping and then blasting it with 350kW, but it really does a number on the longevity. Very tight thermal management is needed to keep the cells within the optimum temperature range throughout both discharge and recharge cycles. Cell temperature is the primary factor the BMS monitors to determine the maximum safe charge and discharge rates, and derating to suit.

PetrolHeadInRecovery

335 posts

33 months

Sunday 7th September
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Cristio Nasser said:
PetrolHeadInRecovery said:
Cristio Nasser said:
Seems thermal management is still the main limiting factor.
But where do we encounter the limitations?

Seems that the higher voltage systems do already quite well in most scenarios even with older cell technology. Ioniq 5N capable of a couple of laps around the Nordschleife, 10C charging demo by BYD and a couple of record runs (production and prototype) by MB at Nardo.
Yea, but it hammers the longevity, particularly when trying to fast charge an already hot battery. That’s where the thermal management piece is super important .

All well and good hot lapping and then blasting it with 350kW, but it really does a number on the longevity. Very tight thermal management is needed to keep the cells within the optimum temperature range throughout both discharge and recharge cycles. Cell temperature is the primary factor the BMS monitors to determine the maximum safe charge and discharge rates, and derating to suit.
Sure, but it seems thermal management... manages.

IIRC, the Mercedes concept was charged at around 850kW and when not charging was driven flat out for 40,000km. The battery SoH at the end was reportedly 90%.

Anecdotally, more mundane cars seem to do well enough. Two Ioniq 5 data points I'm aware of:
  • 580,000km (~360,000 miles) with SoH of 87% when Hyundai offered a battery swap to study the old one. South Korea, sales representative.
  • 400,000km (250,000 miles) with SoH just under 90%, the majority of charging on HPC chargers (often charging to 90 - 95%). California, Lyft driver.
This is with pouch cells that the industry is moving away from, but even they seem to be good enough.

With ours, it is still very early days (72,000km/45,000 miles), but any impact of frequent high-speed charging (often in 30+ degree temperatures, arriving straight from the motorway) is more than compensated for by the lower rolling resistance of partially worn tyres.

OutInTheShed

12,265 posts

44 months

Sunday 7th September
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The reality seems to be that cell life is adequate for sensible BEV cars, enough power for highway use, charge and discharge rates are not a huge issue with a battery size which give good range?
If you've got a 50kWh battery, it's not too stressed by a 50kW motor or 50kW charging and you get 150 mile range.
150,000 miles is the equivalent of 1000 cycles and that's all adequate.

Where batteries are showing issues is in hybrids, where a 10kWh battery gets a very hard life from a 50kW motor because that's a 5C charge rate which is high stress, and 1000 high stress cycles is only 30,000 miles. This is an areas where Mercedes and others would appear to have issues?

But even these issues would be negated if a new battery at say 50k miles was a sensible price, which would be achievable if cars were not designed by wkers. A 10kwh battery should cost a few hundred pounds and be easy to change. Recycling the battery 3 or 4 times in the life of the car could just be one of those things like tyres or clutches and batteries in Morris Minors.

There may be more significant gains from cell developments in markets other than ordinary passenger cars.

PetrolHeadInRecovery

335 posts

33 months

Sunday 7th September
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OutInTheShed said:
Where batteries are showing issues is in hybrids, where a 10kWh battery gets a very hard life from a 50kW motor because that's a 5C charge rate which is high stress, and 1000 high stress cycles is only 30,000 miles. This is an areas where Mercedes and others would appear to have issues?

But even these issues would be negated if a new battery at say 50k miles was a sensible price, which would be achievable if cars were not designed by wkers. A 10kwh battery should cost a few hundred pounds and be easy to change. Recycling the battery 3 or 4 times in the life of the car could just be one of those things like tyres or clutches and batteries in Morris Minors.

There may be more significant gains from cell developments in markets other than ordinary passenger cars.
Good point re. hybrids! Reminded me of this: https://evclinic.eu/2025/07/11/ferrari-laferrari-h...

Regarding changing the battery: being a conservative late adopter, I checked the prices of second-hand battery packs (under 10k€ with shipping at the time) and the difficulty of swapping one out (six bolts and a few connectors) before choosing the Ioniq 5. I guestimated that the worst-case battery-related costs would be roughly in the same ballpark as filling up once at a wrong station in a Euro 6 car.

Regarding normal wear, third-party batteries should be available with higher capacities and lower weights than the original ones when needed (more than 10 years into the future). Nissan Leaf upgrades seem to be getting common already.

Ten years from now, Lithium-Sulphur cells might be the standard solution. I found and skimmed through a paper that summarised the state of the art (included a literature review of over 800 articles...!) and concluded that 500Wh/kg cells should be feasible soon (roughly double the LFP and almost 1.5 times the best NMC ones). Might not be as robust as LFP, but the price might end up being low enough to make it a non-issue.

Cristio Nasser

362 posts

11 months

Tuesday 9th September
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I’ve said it elsewhere, and I’m with you on hybrid vehicle batteries. I think that’s going to be the next big scandal in the automotive world. Cars being mechanically totaled by a failed hybrid battery at relatively low miles because of insane replacement costs. Compared to a full BEV, hybrid batteries are worked so much harder and cycled so many more times over the same mileage that comparatively early failure is unavoidable. And it’s not like you can still use the car without the hybrid battery. Even the most basic hybrid has an integrated starter/motor/generator setup that won’t work without the hybrid battery.

Edited by Cristio Nasser on Tuesday 9th September 08:14

Peterpetrole

1,054 posts

15 months

Tuesday 9th September
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Interesting info, love seeing how this stuff gets productionised

Mikehig

912 posts

79 months

Tuesday 9th September
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Cristio Nasser said:
I ve said it elsewhere, and I m with you on hybrid vehicle batteries. I think that s going to be the next big scandal in the automotive world. Cars being mechanically totaled by a failed hybrid battery at relatively low miles because of insane replacement costs. Compared to a full BEV, hybrid batteries are worked so much harder and cycled so many more times over the same mileage that comparatively early failure is unavoidable. And it s not like you can still use the car without the hybrid battery. Even the most basic hybrid has an integrated starter/motor/generator setup that won t work without the hybrid battery.

Edited by Cristio Nasser on Tuesday 9th September 08:14
Exactly! To top it off there's the rich irony of people buying PHEVs rather than pure EVs because of concerns over battery life and degradation. A number of friends have PHEVs and are fond of remarking how they hardly ever need to refuel...

What about "mild" hybrids, the ones with relatively small batteries and no plug-in charging facility? Are they prone to similar problems or are their batteries managed better (we don't hear anything about problems with Prius batteries)?

PetrolHeadInRecovery

335 posts

33 months

Tuesday 9th September
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Mikehig said:
Cristio Nasser said:
I ve said it elsewhere, and I m with you on hybrid vehicle batteries. I think that s going to be the next big scandal in the automotive world. Cars being mechanically totaled by a failed hybrid battery at relatively low miles because of insane replacement costs. Compared to a full BEV, hybrid batteries are worked so much harder and cycled so many more times over the same mileage that comparatively early failure is unavoidable. And it s not like you can still use the car without the hybrid battery. Even the most basic hybrid has an integrated starter/motor/generator setup that won t work without the hybrid battery.

Edited by Cristio Nasser on Tuesday 9th September 08:14
Exactly! To top it off there's the rich irony of people buying PHEVs rather than pure EVs because of concerns over battery life and degradation. A number of friends have PHEVs and are fond of remarking how they hardly ever need to refuel...

What about "mild" hybrids, the ones with relatively small batteries and no plug-in charging facility? Are they prone to similar problems or are their batteries managed better (we don't hear anything about problems with Prius batteries)?
EVClinic has a few mild hybrid horror stories, too. However, it seems Toyotas are relatively cost-effective to repair:

https://evclinic.eu/2024/09/05/toyota-huge-battery...

A more recent article (Lexus-branded hybrid, not sure if it was a plug-in) mentioned that it is possible to clear the faults using an OBD tool, and I'd imagine the engine compensates using the variable timing intake (more often at max ICE power, worse fuel economy).

OutInTheShed

12,265 posts

44 months

Tuesday 9th September
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Cristio Nasser said:
I ve said it elsewhere, and I m with you on hybrid vehicle batteries. I think that s going to be the next big scandal in the automotive world. Cars being mechanically totaled by a failed hybrid battery at relatively low miles because of insane replacement costs. Compared to a full BEV, hybrid batteries are worked so much harder and cycled so many more times over the same mileage that comparatively early failure is unavoidable. And it s not like you can still use the car without the hybrid battery. Even the most basic hybrid has an integrated starter/motor/generator setup that won t work without the hybrid battery.

Edited by Cristio Nasser on Tuesday 9th September 08:14
It generally doesn't affect the first owner (lease customer), so manufacturers are not exposed much to the problem.

Some hybrid and PHEV cars last OK, which may be a combination of the right people buying them for the right use pattern and better battery management. The characteristics of batteries are pretty well known, a good car design won't allow the user to destroy the battery too quickly.

The problem is, some of us expect cars to last 20 years and 200k miles, without major bits being replaced, which only really happened for a short halcyon era of IC cars, even then there were failures.
Many E91 BMW 320D estates were scrapped with the engine still running OK at high mileages for instance, but others had various BER failures beofre 150k miles.
Many cars are worth small change before they reach 100k miles, because by then they are over 10 years old.

It's not 2005 any more, cars are designed to last 100k miles then get recycled.

P675

532 posts

50 months

Monday 15th September
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What is a tab and why don't I want it in my EV battery?

RobbyJ

1,744 posts

240 months

Monday 15th September
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P675 said:
What is a tab and why don't I want it in my EV battery?
This