Non-flammable rechargeable batteries for electric bicycles - LiNiMnCoO2?

[e100]

When I looked at electric bike conversion kits a couple of years ago it seemed like everyone was using LiFePO4 batteries. These are essentially non-flammable (unlike the LiCoO2 battery typically used in mobile phones), so storing and charging a large bike battery in your house or workplace was unlikely to set it on fire.

However, since then things have changed. It looks like LiFePO4 is being displaced by LiNiMnCoO2 (NMC) batteries.
I tried searching for information about the safety of these types of battery but couldn't find much.
Can anyone comment on the failure modes of this type of cell and whether they contain a flammable electrolyte or solid?

[MagicSmoker]

The solvent for the electrolyte in all lithium ion chemistries is a combination of various carbonate esters which are themselves very flammable, unlike pretty much every other type of battery chemistry in which water is the solvent for the electrolyte.

The reason LFP (LiFePO4) is considered (relatively) safe is because it is practically immune to auto-ignition from thermal runaway, while LCO is inordinately prone to it; NMC and NCA are in between those two extremes, though closer to the LFP end of the scale. Note, however, that LFP still has a considerable advantage in both charge and discharge rate compared to all the other Li-ion cell types except the rather rare Titanate kind. That may or may not be relevant in an electric bike application - a 500W drive system with a 48V/10Ah battery will only be stressed at a little over 1C, and the typical NMC or NCA cell can handle at least a 2C discharge (the >10C discharge rating of a LFP cell is hardly an advantage, then, as I imagine an e-bike that can only run for 6 minutes wouldn't be a big seller).

[exmadscientist]

It's a few years old now, but this NREL report has more information than you could ever want on lithium-ion chemistries. Short version: yep, they're flammable... but so are all the others.

[grifftech]

The solvent for the electrolyte in all lithium ion chemistries is a combination of various carbonate esters which are themselves very flammable, unlike pretty much every other type of battery chemistry in which water is the solvent for the electrolyte.

The reason LFP (LiFePO4) is considered (relatively) safe is because it is practically immune to auto-ignition from thermal runaway, while LCO is inordinately prone to it; NMC and NCA are in between those two extremes, though closer to the LFP end of the scale. Note, however, that LFP still has a considerable advantage in both charge and discharge rate compared to all the other Li-ion cell types except the rather rare Titanate kind. That may or may not be relevant in an electric bike application - a 500W drive system with a 48V/10Ah battery will only be stressed at a little over 1C, and the typical NMC or NCA cell can handle at least a 2C discharge (the >10C discharge rating of a LFP cell is hardly an advantage, then, as I imagine an e-bike that can only run for 6 minutes wouldn't be a big seller).

one that only takes 6 minutes to charge would be