Interesting article. What are your thoughts?

[Jesse Walker]

https://thedriven.io/2021/01/19/warmed-up-electric-car-batteries-could-be-cheaper-safer-and-last-two-million-miles/

[Dacian Todea]

Jesse,

Not sure how they came up with the +60C LiFePO4 as typical LiFePO4 will degrade way faster at this elevated temperatures. Maybe this can work for some commercial applications but I do not think this is a solution for consumer vehicles.

Yes LiFePO4 internal resistance drops with increased temperature but LiFePO4 already has a very low internal resistance to start with.

If a very good LiFePO4 will degrade at a rate of 1 to 2% per year (not used just the calendar aging) at +25C then I expect this calendar aging to be at least 3 if not 4x higher at +60C so 4 to 8% degradation per year meaning even if not used almost at all the battery will be at the end of life in around 3 to 5 years while consumer vehicles usually have at least a 8 year warranty on battery.

Typical NMC batteries with rated cycle life of around 500 cycles come with an 8 year and 160000km warranty and since this vehicles have around a 400km range you can get 160000km/400km = 400 cycles (100% DOD equivalent) the difference being made up by the calendar aging.

Now a LiFePO4 may be 3000 to 5000 cycles depending on brand and quality so it can be up to an order of magnitude more and in commercial applications (Taxi, buses, self driving vehicles used for commercial purposes) may be able to get 1.6 million miles with a LiFePO4 as it is not sure if heating the battery will be able to double this number but if it does then those km will need to be done in around 3 years meaning just commercial type applications as average personal car is not driven more than 20000km/year so the current NMC battery is more than sufficient for that and that is why it was selected as it offered better range compared with LiFePO4 that has lower energy density so for same weight lower range.

It is a good thing that Tesla will use LiFePO4 as it will be a good type of battery for second life in solar energy storage but this will only happen in China so for us in North America and Europe it will not be of much help.

China seems to own all LiFePO4 IP as they understood the advantage and things over longer therm than others and likely the use of LiFePO4 was imposed on Tesla as a condition to be allowed to manufacture and sell EV's in China.

[Chris Card]

It’s hard to make sense of that article. It says by warming the cells up, you don’t need to have a battery cooling system....  Also like Dacian said, warmer LFP cells are know for last less time rather than more as the researcher speculates. 

A lot of research is only a very small part of the overall answer.  They look at particular conditions and test just those, so extrapolating results and making conclusions on the likely effects of this test on the overall EV battery market is likely to fail.

Tesla may not be taking the LFP route in N America and Europe, but in Sweden, Northvolt is building a huge production plant for LFP EV cells. They are taking the prismatic rather than cylindrical cell route, so while the name Northvolt isn’t known today, it could become a good source of second hand off grid solar cells in 10+ years time.  But there I go extrapolating! :)