Safety of Lithium-ion Batteries - Battery University

The info below is from the following link: 

Myth-buster: Lithium-ion Battery Chemistries and Safety — Part 1 | by Nikhilesh Mishra | Grinntech | Medium

It deals with explicit information regarding the differences in fire safety from one type of lithium-ion battery to another.  It is important to distinguish these differences because they exclude from accuracy the common journalistic erroneous  practice of lumping all lithium-ion battery chemistries into the same basket in regards to their ability to degrade via thermal decomposition.  

The "Devil" may be in the details, but the "Truth" is also in the details and it takes a little bit more effort to get to that level than most "Journalists" are willing to expend.

The original article I posted in this series delt with how fire blankets may be of more value in extinguishing lithium-ion  battery fires once they have occurred.  Any quick search on the internet today reveals a myriad of different companies that market these devices and in a wide array of sizes, some more effective than others.  Rather than pour seemingly unlimited volumes of water continuously onto such a fire for hours and hours these blankets can help to extinguish such a fire, sometimes in a manner of a fraction of the time.  I have no doubt that as the number of lithium-ion EVs increasing dramatically on the roadways that the market for such simple devices that can be used should someone have the rare eperience of their own EV lithium-ion fire occur will be an opportunity for investment in these easily transportable fire blankets that may someday be a ubiquitous presence in the trunks of EV owners.

I predict that such an item to invest in might be just a lucrative 20 years from now, or less, as will be the future everpresent "Tatoo Removal" business that has an unlimited promise of ROI during that same time.  JMO, obviously!!

Okiedo

As can be seen, the LCO and NCA are having lowest thermal runaway temperature of 150 degrees centigrade. When a cell starts heating, (either because of thermal runaway of nearby cells or any external heat source or high current draw), these chemistries will be the first to start disintegrating and going into a state of thermal runaway. On the other hand, LFP has the highest thermal runaway temperature of 270 degrees centigrade. This makes it the safest Cathode material. LMO and NMC are midway at 250 degrees and 210 degrees centigrade, respectively.

This is the reason, why LFP is advertised to be the most safe Lithium-ion chemistry but it overlooks a lot of important factors. Let us understand what those are.

Factors overlooked

Safety of LTO Battery: LTO batteries are considered to be the safest of all Li-ion batteries. LTO batteries have NMC for their Cathode material and LTO is the Anode material. Even with NMC in place these batteries are extremely safe. This tells us that most accidents with Li-ion batteries are not related to Cathode material. Instead the stability of the Anode material, plays a much bigger role, and here LTO makes it much safer than Graphite.

Energy density: Energy density plays a big role in the safety of the battery. It is not hard to understand that more energy is released, from these high energy density cells, in the event of a thermal runaway. This high amount of energy increases the probability of a nearby cell reaching their thermal runaway temperature threshold. This can be understood from the fact that any cell chemistry, which fails the “nail penetration test” at full charge condition, passes the same test in a partially charged state. Partially charging a cell, in a way, is making it a low energy density cell. This is the reason why LTO and LFP are so safe, as they have much lower energy density of 70Wh/kg and 120Wh/kg respectively, when compared to 250+Wh/kg for NMC and others.