Yes, you can. The ONE+ system is designed for that.
Any Ryobi ONE+ 18V Lithium+ battery is compatible with your P215K1 drill. The 9.0Ah battery will physically fit and will work. It will provide significantly longer run time compared to a smaller battery.
A couple of things to note: The tool might feel a bit heavier and more front-heavy with a large battery. Also, while the 9.0Ah battery is listed for use with other tools like the R18DD5, it is fully compatible across the ONE+ 18V line.
Heads up: The performance and run time always depend on the specific tool and the task you're doing. A bigger battery gives you more work time, not necessarily more peak power, as that's managed by the tool's electronics.