Need help modding ETWOW 33v 6.5ah electric scooter

Battery: 190-243; Li-Po
Total weight: 10.8 kg
Max load: 125kg
Charger: 3.5A
Voltage 33v 6.5 ah
Motor rated output max. power: 500W
Motor type: DC Brushless motor
Charging time: 1.5h-2h (4A charger) or 3h-3.5h (2A charger)
Charger input voltage: 220V/110V

33v vs 36v
Someone did a mod of 36v 10ah

These are the specs I can gather. My goal is to build a more powerful battery without having to change the controller so that I can still use the scooter as normal but just get a boost in performance and endurance. It does pretty good but it feels a bit weak going up hills although it can top out at around 18mph on flatter surfaces.

Other scooter owners have told me about Panasonic 18650 cells. I’ve tried to do a little research on this, some cells seem more dense, lighter weight with more energy.

If anyone here knows, please feel free.