So everyone should start carrying external spare batteries.
I've seen a 22400 mAh portable Li-ion battery for less than $50. Imagine a whole plane full of those. And no, consumer grade Li-ion batteries never explode.
Up to two spare Li-ion batteries up to 300 Wh ("large batteries") are allowed in the carry-on baggage. So external USB chargers/accumulators up to 60 mAh should be OK.