I remember in a solid state chemistry MOOC I took, from a professor who was a lithium battery researcher, the professor did mention in passing that we actually don't have a really good understanding of lithium batteries.
Of course he was talking about a much lower level than you need to understand when it comes to actually using them.
There are actually a lot of things we know how to deal with when it comes to engineering but have a poor grasp of the low level details. There was a great example in the Feynman Lectures where he says this about friction (Volume 1, section 12-2):
> It is quite difficult to do accurate quantitative experiments in friction, and the laws of friction are still not analyzed very well, in spite of the enormous engineering value of an accurate analysis. Although the law F=μN is fairly accurate once the surfaces are standardized, the reason for this form of the law is not really understood. To show that the coefficient μ is nearly independent of velocity requires some delicate experimentation, because the apparent friction is much reduced if the lower surface vibrates very fast. When the experiment is done at very high speed, care must be taken that the objects do not vibrate relative to one another, since apparent decreases of the friction at high speed are often due to vibrations. At any rate, this friction law is another of those semiempirical laws that are not thoroughly understood, and in view of all the work that has been done it is surprising that more understanding of this phenomenon has not come about. At the present time, in fact, it is impossible even to estimate the coefficient of friction between two substances.
That was written around 60 years ago. Anyone here happen to know if it still holds?
At some point, scale-wise, friction problems become electrochemical rate problems, I suppose. See this recently published research article on lithium iron phosphate batteries, opening:
> "Reaction rates at spatially heterogeneous, unstable interfaces are notoriously difficult to quantify, yet are essential in engineering many chemical systems, such as batteries and electrocatalysts..."
It's a much harder problem than working with pure crystals or gas-phase molecules or similar, which makes sense, as a half-discharged battery is a very messy system at the molecular-atomic level. See also news story on the above article:
> “We discovered at the nano scale that variation of the carbon coating thickness directly controls the rate, which is something you could never figure out if you didn't have all of this modeling and image analysis,” Bazant says.
> That was written around 60 years ago. Anyone here happen to know if it still holds?
Not really the same question but I attended a talk by some top tribologists at my uni and I asked them if friction really was independent of contact area (as F=μN would suggest), their reply was that it roughly was, but not really if you were very precise or varying parameters. It would appear that the equation is a good approximation, like classical Newtonian physics.
It depends on what kind of friction you’re talking about too. Eg it is well known that for some fluid (air for example), the friction can be proportional to the speed instead, to a certain extend of course, and can be proved in an idealized situation.
Apparently even solubility of compounds in various solvents is empirically derived because there's no reliable theoretical model of this in chemistry/physics. (AIUI anyway)
not to get too leaky, and this is a bit dated, but…
the math produces results that are understood but not, because the math is calculating with some implicit inclusions, and things get weird when you start explicitly including.
the answers make sense, but not quite for the questions being asked. (but the answers are valid for a question, and more importantly, immediately useful for making dollars.)
unfortunately the vagueness of this will likely irritate a doctor. it certainly did years ago.
Lfp chemistry is not that innovative -- it's in use in homes for sure and I think also tesla uses them. Given the breathlessness of the article I expected sodium batteries or something
The last of the patents on LFP expired last year. Up until then, the patent holders made a deal where Chinese companies could produce the cells, but not export them.
So that appears to be the reason for so much investment in the space in recent times.
>> The last of the patents on LFP expired last year. Up until then, the patent holders made a deal where Chinese companies could produce the cells, but not export them <<
China did negotiate a deal with a patent consortium in Suisse to license LFP royalty-free for all domestic use. But then I wonder what the point was, since all foreign battery makers/patent holders such as LG (NCM), Panasonic (NCA) were required to give up their IP Rights in order to acces China's NEV market, or China would have ignored their IP Rights anyway.
>> So that appears to be the reason for so much investment in the space in recent times. <<
Sure, there has been some improvement, but LFP is still mostly limited to entry-level, low-range EVs. The recent rise of LFP is largely attributable to the various COVID related auto component shortages and price spike in battery raw materials past few years. The average price of lithium however plunged by some 80% since last November and once 400+GWh new production capacity come up in the US, I suspect that LFP won't be as competitive.
From the wikipedia article, it's all about the form factor:
> The space utilization of the battery pack is increased by over 50% compared to most conventional lithium iron phosphate block batteries.
> BYD claims that, in the nail penetration test, the Blade Battery emitted no smoke or fire after being penetrated, and its surface temperature reached only 30 to 60 °C (86 to 140 °F). It is currently the only power battery in the world that can safely pass the test.
Reducing volume by 33% and mostly eliminating fire risks are both huge wins, if true. Doing it in a standard form factor that can be reused across future vehicle platforms is an even bigger deal.
This is a lithium iron phosphate battery. Safer chemistry than lithium-ion, but heavier. There's a lot be said for lithium iron phosphate. Once we have millions of old, badly maintained electric cars on the road, it's better if they're not using a battery technology prone to fire.
This is mostly a packaging and cooling innovation. Round cells are inefficient from a density standpoint, but the empty space between cylinders allows heat to escape.
BYD's approach to electric cars in China is modest range and lots of charging stations. Average distance driven per day in the US is 60 km. Current BYD vehicles all have a range over 200km.
Same niche as Chevrolet, or what Chevy used to be - a seller of basic transportation.
It's a worry that, in the last few years, US manufacturers have gone way overboard on too much car per car, to the point that most American workers can't afford current vehicles.
>It's a worry that, in the last few years, US manufacturers have gone way overboard on too much car per car, to the point that most American workers can't afford current vehicles.
Things like the Nissan Leaf have been widely available in the US for nearly a decade now, with battery sizes from 20-40kWh. There's a market for it, but it's niche. The reality is just that EVs will never truly become mainstream in the US until there's a >60kWh budget vehicle that sells out the door under $25k. The distances are simply too much for anything less to be viable for people outside of a major metro area.
I share your opinion. Everything <60 kWh has no real winter range. 60 kWh battery brings me 150 miles in winter (Autobahn in Germany, not saving energy) since the regular battery shouldn’t be charged to 100% and discharged bellow 10%. That’s 2 days of commuting without charging for me.
I believe that is one of the benefit of the LFP chemistry that it is not harmed by sustained charges to 100%. That should help offset the range downside sometimes listed for LFP batteries.
However, IIRC it has other problems in cold weather. With charging, I think? I know I’ve seen reports that regenerative braking is essentially completely disabled while the LFP batteries are cold.
> The space utilization of the battery pack is increased by over 50% compared to most conventional lithium iron phosphate block batteries.
> BYD claims that, in the nail penetration test, the Blade Battery emitted no smoke or fire after being penetrated, and its surface temperature reached only 30 to 60 °C (86 to 140 °F). It is currently the only power battery in the world that can safely pass the test.
> In addition, it successfully passed an extreme safety test that saw it being rolled over by a 46-tonne heavy-duty truck[citation needed].
> The Blade Battery also passed other extreme test conditions, such as being crushed, bent, being heated in a furnace to 300 °C (572 °F) and overcharged by 260%. None of these resulted in a fire or explosion.
None of that sounds like big leaps of progress to you?
More on-topic, I wonder if the battery is fully functional with that 260% overcharge. Could be interesting if you can tell the battery (controller) “yes I accept the 1% point extra wear, please enable overcharge mode” for a really long trip that won’t have charging stations.
> More on-topic, I wonder if the battery is fully functional with that 260% overcharge. Could be interesting if you can tell the battery (controller) “yes I accept the 1% point extra wear, please enable overcharge mode” for a really long trip that won’t have charging stations.
Overcharge doesn't mean that the battery can store additional capacity beyond its design limits. It just means that the battery won't be damaged or catch on fire if you continue to put electricity in it after it is already full.
>Lfp chemistry is not that innovative -- it's in use in homes for sure and I think also tesla uses them. Given the breathlessness of the article I expected sodium batteries or something
Cell chemistry is just one part of the equation. Better (lighter) pack designs are equally important to increasing overall energy density, safety, and reliability.
Tesla uses LFP cells in cars as part of a requirement to use locally sourced materials at Giga Shanghai. Before opening a factory in China, Tesla only used NMC/NCA cells.
>> Before opening a factory in China, Tesla only used NMC/NCA cells. <<
Tesla has been primarily working with Panasonic's NCA for over a decade now. LG's NCM was added only after 2020 for their Long Range models in China/EU.
Panasonic canned battery production is highly efficient and semi flow based, long lengths of materials can be assembled like lasagne and then rolled up into cigars and well.. canned. It's a centuries old model since leclanche cells.
If this one is amenable to a mass production model it's great.
This efficiency doesn't translate to EV battery packs. They require thousands of welds, the pack contains ends up with plenty of empty space and it's impractical to replace parts of it.
For LFP you can supposedly pack the cells very tight, as they require less thermal management if I understand correctly. And you’re HAVE to do this optimisation for LFP to have decent pack level energy density.
For Li-ion cells, you need that empty space for cooling of the battery cells anyway.
And Tesla has demonstrated that cylindrical cells can contribute to the structure in a structural battery pack.
So for Li-ion I don’t think cylindrical cells are worse. There’s just different trade-offs.
But yeah, one of downsides it can be hard or impossible to replace individual cells if they have problems.
Panasonic used to be called Matsushita and they pioneered the non-cylindrical "prismatic" nickel metal hydride battery when they were working with Toyota on the Prius. It did not go this far, it was more like 6 pouch-cells aligned in a blade shape, but still not alien to them I bet. Also they transferred a lot of that tech to China over time so it is quite possible BYD grew off the Panasonic tradition. I'm betting Panasonic could do a Blade in mass production if they wanted.
Offering awards for things is kind of self-serving for a publication.
Bet it drives up click rates.
I remember reading something once, where famous people should carefully vet who they accept awards from. An award might just be a sneak way of getting some relevant person to speak at an event for free or a nominal cost.
would love to be corrected here but if i understand they basically did away with the idea of "modules of cells" and just have the entire pack made of hundreds of cells directly attached to the bus.
which ironically is more like the Prius battery (28 'prisms') than the Tesla battery (cylndrical).
also seems to me like, they maybe dont have to flood the entire thing with disgusting pink foam, maybe you could have a halfway chance of replacing a single cell if it went bad.
Longer. My M3 RWD delivered in December 2022 has a third-gen LFP pack with 60 kWh capacity, in the years before they used first a 50 and then a 55 kWh packs before going to the current 60 kWh variant.
Isn't the Cybertruck using regular lithium ion? That shows how immature the 4680 production process is, if they can barely compete with LFP, though some of the weight is contributing to the structure of the vehicle.
But personally it just seems so worth it. LFP has far greater cycle count than Li-ion. That the battery is going to last 4x longer or more is a huge factor for me. The net-energy (across the usable battery lifetime)/$ is so much vastly better that I'm happy in most applications dealing with the weight.
>> LFP has far greater cycle count than Li-ion. That the battery is going to last 4x longer or more is a huge factor for me. <<
Sure, that's true in individual cell studies in lab, or stationary energy storage (aka, ESS), but not necessarily in moving vehicles, ie, EVs. CATL's cheap, inferior LFP would probably make more sense in storage.
Preemptively posting what is people's biggest confusion:
Battery cell energy density is not the same as the whole battery pack energy density.
Western battery cell manufacturers chased the specific energy density figure, and in the process they decided to save weight on the casing, and electrodes as much as possible, resulting in very fragile battery cells.
To avoid 18650 cells being crushed, you will need a lot of structural reinforcements added to the battery pack, consuming weight.
Even with all of that, tiny, individually 18650 cells waste a lot of weight on the cell casing, on things like welds, terminals, relief valves, thermal interface material etc.
Bigger cells invariably have better casing to active material ratio, but the casing mass is still "useless.
Blade battery reverses all of above, and intentionally uses very strong, and thermally conductive case, to make the casing weight to contribute to battery pack mechanical strength.
LFP cathode feels very well at high temperatures, and has very high resistance to mechanical expansion during charge. This allows to make LFP cells much bigger than cells with other chemistries, and removes the need for liquid cooling system inside the battery pack, greatly saving weight.
https://en.m.wikipedia.org/wiki/Blade_Battery