I saw a Prius Prime the other day in the Phoenix area. It winter here so only 70-80F most days. I hope a few members of our Phoenix Electric Auto Association 501C3 non profit will get one so we can see how they do in 110F during summer. I have a prius 10K conversion by Plugin Supply . It would drop back to only hybrid at 100F exactly. It never got improved so I sold it and for got a 100% LEAF. It's batteries wilted so bad I dumped it and got a 2013 Lizard LEAF that also wilted so I gave it back at the end of the lease. I then got a 2015 SOUL EV that also dropped in capacity so bad it went back for warranty fixing along with all the 10 other SOUL EV in our HOT area. Only liquid cooling like Chevy SPARK EV/Bolt, FORD FOCUS EV ,BMW i3 and Tesla have works in the heat. Even is cooler areas the batteries last twice as long. 20-30 years at 80% or better.
Toyota has 20 years of dealing with air cooled battery heat from the first Japanese Prius through all of the current models. Granted the first ones were NiMH but having owned a Gen-1 Prius, heat was (and remains) the enemy. One problem is we don't have a battery temperature gauge, yet. Living in Dixie, we get tolerable night temperatures. But we are seeing some cool weather, <50F (10C) temperature related, performance issues. Bob Wilson
the Prius uses the Air conditioning from the passenger compartment and pulls it with a fan in the back seat to blow over the battery in the rear trunk area. I'm not sure how they cool the prius prime with the larger battery. On line everyone thinks the Prime is the same design with just air vents. see below.
When i had the Prime, I recall it actually asking me on the screen if I would let it run the AC to keep the battery cool.