Why 40kWh Leaf doesn't have active cooling? Because it can only charge at 50kW rate (exactly the same as 30kWh Leaf), it can only discharge at averaged 45kW rate (top speed limitation) and it's still not suitable for long distance driving. Aka battery will not heat up enough and passive cooling is absolutely fine.
Except that it has NOT proven "absolutely fine" in the 30kwh Leaf outside of cool climates. Given that the 40kwh Leaf uses the same pack structure, with a higher energy density, we have to hope that Nissan has both increased energy density again, and at the same time solved the 'warm degradation' problem that ruins the 30kwh Leaf for most people. At this point that seems to me a lot like Magical Thinking. I'll be leasing a 2018 Leaf with the expectation that it will lose 20-40% capacity in three years - probably closer to 40%. I only need about 70 miles of Winter range and 100 miles of Summer range, so that isn't crazy of me, but I pity those who lease (or especially BUY) one with 100+ mile long term range needs.