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Li-ion is a very big umbrella of battery chemistries, and within can have broadly different safety and stability profiles.

More important is that Li-ion cells are no joke, and are not equivalent to ‘AA’ or ‘AAA’ battery formats. You can NCM, NCA, LFP, Cobalt chemistries and blends within - not even accounting for differing mAH and charge/discharge capacities. 18650 is simply a form factor.

Better labeling, specing, regulated and certified repair processes are just a start for solutions as it is currently a Wild West.

However, statements like ‘Li-ion should be replaced ASAP’ do not factor in that… lithium ion as a platform is not going anywhere and has essentially won at least the next half century for 18650 type form factors and applications. Moving away is not a reasonable solution.

Lithium Ion without further designation refers to Lithium Polymer or plain Lithium Ion cells such as this one: https://eu.nkon.nl/products/sony-murata-us18650-vtc6.html

Other chemistries are usually indicated by a different designation, such as LiFePO4, LTO and so on.

Sorry but that just isn't right. The battery you listed is an just an NMC battery , the listing pages are just lazy and don't list it. There isn't just a plain lithium ion cell. Also lithium polymer just means that a polymer electrolyte is used instead of a liquid electrolyte.

https://en.wikipedia.org/wiki/Lithium-ion_battery

That's pedantic. They're sold that way by the truck load and anybody that buys them for DIY purposes knows that this is how they are designated. People are buying based on the working voltage nominally 3.6V, Lithium Ion chemistry, battery capacity, form factor. Not on the internal details of the battery, which are not normally listed in sales documentation on consumer oriented outlets anyway.

Yes, you can go into the details of the exact chemistry, the packaging, the manufacturers specs and so on but for bulk DIY purposes this is the reality. The detailed chemistry obviously has some implications for safety but because you will have no idea what is in a pack unless you open it (and plenty of times the cells are unmarked) you just have to assume the worst. That's the safest.

> People are buying based on the working voltage nominally 3.6V, Lithium Ion chemistry, battery capacity, form factor. Not on the internal details of the battery, which are not normally listed in sales documentation on consumer oriented outlets anyway.

Lithium Ion chemistry is the internal details of the battery. Which denotes the type of lithium ion battery, there is no generic lithium ion battery. It will fall under a certain category (Ex LFP, NMC, NCA).

The same battery you linked on other websites is called out as NMC: https://voltaplex.com/sony-vtc6-18650-battery-us18650vtc6

Sure you can go buy unmarked cells on ebay but any reputable website should list the battery chemistry on their website or have a link to the datasheet. It is no different than buying any other electronic component.

I've refurbished many packs and built my own, for cameras, e-bikes and laptops. I've yet to find anybody other than myself to be interested in the exact chemistry of the batteries involved. What they're interested in at the highest level is whether it works, and second to that how much it will cost them. I'd be happy to bet that most people that use these batteries would not be able to figure out what exact composition a cell has nor would they care.

It is very clear to me that there is a vast gulf between DIY and professional application, and for the latter I'm 100% sure that everybody there would be able (and should be able) to make the distinction. The number of hobbyists that can do so is going to be very low.

For maximum cringe, have a look at this youtube video and spot the potential problems:

https://www.youtube.com/watch?v=DAoCK3QNLng

And that's one of the very best.

> Lithium Ion should be replaces ASAP by safer chemistries so we can sidestep this issue completely

That would be nice, but so far there are no good candidates that have anywhere near the energy density of Li-based cells. As far as I understand it, besides material degradation and overcharge/overdraw, the energy density itself poses a risk. So even if we had that miracle cell chemistry it would be still pose a fire hazard when subjected to mechanical stress. The stored energy has to go somewhere.

That's true, there are some inherent risks that are hard to mitigate. But those are roughly equivalent to say a gasoline fire or something like that. They are not due to handling the stuff or working on it. Though in fairness: working on an ICE car, especially the fuel supply system is not without risk.

> Lithium Ion should be replaces ASAP by safer chemistries so we can sidestep this issue completely. As far as I'm concerned this should have never gotten as far as it did and manufacturers that produce crap batteries (of which there are plenty!) should be held responsible.

What should they be replaced with? I'm curious to know what alternate chemistry you're proposing for my e-bike battery.

Usually, the safer replacement for Lithium Ion would be LiFePO4. Although I don't know how good performs in e-bikes (I guess it should be fine, as they're used in cars and other stuff...)

It works just fine for that application. But: it is a little bit more expensive for the same capacity, and unfortunately the voltage is a little bit lower so it isn't a drop-in replacement.

Isn't it also quite a bit heavier?

Yes, about 50%. So for the same amount of energy you need a larger and heavier battery. Typically the largest capacity Lithium Ion in 18650 format is roughly comparable to a 26650 LIFEPO4. And then there is still the voltage difference (nominally 3.2 for LIFEPO4 and 3.6 for Li-ion).

50% heavier is kind of a problem for E-Bike applications, although maybe not on the low end.

Yes, it is, otoh on the weight of the whole bike it isn't a huge problem.

> otoh on the weight of the whole bike it isn't a huge problem.

Why do you say this? Non-ebikes can be sub-16 lbs; ebike battery packs can weigh, like, on the order of 50 lbs. Ebike users sometimes need to lift the bikes (up stairs at home, or on/off transit).

Battery pack weight absolutely dominates the design and utility of ebikes; any double-digit percent factor is very relevant (IMO).

> on the order of 50 lbs

A really large e-bike battery is 4kg. Nobody is riding an e-bike with 50 pounds of batteries. Even the battery pack on a Zero FX, an electric motorcycle, is only 42 pounds.

Huh, you're right. I wonder why the hell people are building 75 lb ebikes if even the large batteries are so light.

That's because the motors are pretty heavy as well, and once you have that much torque available you'll need a frame and rear hub that can handle it too. My biggest e-bike is about 30Kg including a 2.2 KWh battery. Not quite 75 lb but getting there. The basic machine is a Riese&Mueller charger with a Bosch speed pedelec motor and the usual complement of brakes, gearing and bunch of bags. I don't mind the weight, but I've yet to find someone else that likes that bike. It's a bit of a pain to move around with the motor off but once you're on it and riding it's just like any other bike only more powerful and it lasts for a really long time on a single charge.

I don't know either. I think part of it is that some e-bike customers are not otherwise bike buyers and go for the niche of huge-wheeled quasimotorcycle. I recommend keeping e-bike weight under 50 pounds because it is the design limit of the bike carriers on American buses and on Amtrak. There are plenty of e-bikes under 40 pounds even.

I mean: relative to the total weight of an e-bike using one chemistry or another.

A bigger issue is that batteries are often placed in very bad spots (such as riding high on the rear pannier).

The 50% or so difference is when both batteries are new. From what I've read Li-ion degrade faster than LiFePO4, so the difference becomes smaller over time (and might even reverse, but I don't have actual data).

Interesting!