is 21700 battery better than 18650?

While there have been rumors that Tesla will use the 21700 battery in newer vehicles, many of these have been dismissed by Tesla, which is said now to favor an even larger format, the 4416 battery.

Originally, it was claimed that the 21700 was not necessarily more powerful, but provided up to 20% higher energy density… which is a lot. Increasing the density would allow component and weight decrease by around 10%.

However, in our tests so far, the mass-market 21700 cells becoming available now have a higher energy density than some 18650 cells, but not all. They also do not have good availability and procurement is still not mature for this new format.

At the current moment, we recommend 18650 cells over larger, newer formats like the 21700.
It is possible within 6 months to 1 year, we may change this recommendation as the technology matures. It may be possible we will start recommending even larger format cells too. But at the current moment, the 18650 is still the best choice for electric bikes.