Those early Leafs had some bad battery fails. I'm pretty sure they were air cooled only, not liquid cooled. Also, their battery management system was rubbish.
It seems Tesla had it right from the get go with the S model. Liquid cooled, better cell layout and a better BMS. Their battery performance speaks for itself. Everyone else is copying them now.
Temperature management is also super important. There's plenty of info about this out there now.
