Yes, its likely the battery isn't powerful enough.
Look for a 7.4v LiPo with the highest mAh (How long it lasts) and C (Max burst power) rating you can find that will fit in the battery space.
All the usual places I would look (Turnigy/HobbyKing/ComponentShop) seem to be out of stock 🙄
But remember you'll also need a decent charger to make sure charge is optimal.
Do a search on the forum as chargers have been discussed before.
Also consider changing connectors to DEANS (T-plugs) for best current flow.
EDIT
THIS battery should work (check size)
THIS charger (or similar) is the most basic
THIS charger is good and a good price but note that it needs the DEANS connector on the battery.