Does a battery's ability to supply high current mainly depend on its internal resistance?
Short answer, yes you are right. The Ri of a battery limits the current it can supply, but the Ri is not the real cause, more a symptom. The design and characteristics of the electrodes, chemical processes, temperature, etc. all kinds of internal and external parameters interact when current is &quot;requested&quot; and Ri is just your way to put all these influences into one handy value. And we need to mention: Ri changes while the battery operates.
For example, my 50km/h RC car does not move a mm when the LiPos are 0°C or below. Temperature is a huge influence on Ri. In the summer 2 of these packs should start my car easily.