As others said, energy density. Batteries are roughly four times less energy dense than fuel.
But that’s not all! As the fuel gets used, the plane becomes lighter, needing less fuel. Fuel requirements are calculated per flight and the planes are filled with just enough fuel, so that it doesn’t lug extra weight around. This is not something that’s possible with an empty battery.
As for speed, air resistance increases at a cubed rate. What this means is that for every doubling in speed, air resistance increases eight times. However, this applies even to smaller factors. So a plane flying at 800km/h, if it were to fly just 10% faster, the air resistance would increase by 33%. Now couple the increased energy demands with the lower energy density of batteries.
It’s not the fuel limiting the speed (for common use cases, at least), but rather the laws of physics making it unfeasible.
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