I was under the impression this chemistry is a lot more unstable but denser and lighter. Isn’t it what is used in drones and you have to charge them inside a firebox because they’re more prone to thermal runaway?
Eh, people have to charge drone batteries carefully not because of chemistry, but because of sketchy industry norms.
Almost every other industry making lithium-battery-powered products insists on 'genuine' batteries and tells people buying third-party replacements is taking your life into your own hands. Drone enthusiasts, on the other hand? Ordering batteries from unknown suppliers on ebay or aliexpress isn't unusual.
And even reputable drone battery brands face the temptation to advertise a spec without any safety margin, to stay competitive. If all your competitors advertise '90C discharge' on the assumption they get the cooling of the drone's fans, you gotta follow suit to stay competitive.
At the same time, can you think of any other application that takes a battery from full to empty in 15 minutes? Or an application that runs its batteries without a BMS, fuse, or battery temperature monitoring?
(Of course, in a sense that's a reasonable state of affairs - shutting down because the battery's overheated isn't exactly a safety feature for a drone, unlike for a battery drill or vacuum cleaner)
LiFePO₄? Drones probably use LiCoO2. It has a much higher energy density and higher C-rate than LiFePO₄. LiFePO₄ has a much higher thermal runaway temperature than NMC (and other chemistries).
I found this article with a short summation:
https://www.newcastlesys.com/blog/lithium-ion-vs-lithium-iro...
The drones you're thinking of here (FPV stunt drones, racing drones) have the most demanding discharge profile of any use for lithium batteries.
The whole drone is built around draining current from the smallest possible battery, as fast as possible, right up to the limit of safety. Charging is also a faster-is-better thing, from a pilot's perspective.
This kind of maximum discharge raises the risk of dendrite shorts considerably, which are what pops a lithium battery usually. So a firebox is a good idea for this case, it's just inherently dangerous to be right at the limit of energy-per-gram and discharge capacity all the time.
The chemistry is also never LiFePo, which is too heavy.
