This might seem a very naive question. Maybe the comparison of electric vehicle to aircraft is hugely inappropriate. But I couldn't find a clear answer in web search.
Lithium-ion batteries have a high power-to-weight ratio, high energy efficiency and good high-temperature performance. Even then they are not preferred to be used in aircraft.
If safety is the concern, aren't there enough protection mechanisms which have enabled their widespread proliferation in electric vehicle market.
Why is the weight to power-to-weight advantage not being exploited by aerospace industry? What are the other aspects to be considered- extreme environmental conditions or so?
EDIT: OP has added in comments (but not here) that "I am referring to the regular usage of batteries in aircraft. Not for propulsion".