Potassium is very abundant in granitic rocks, but it is not extracted from them as that would require too much energy.

However, potassium is also a major component of sea water and that is the main source for it.

The amount of potassium in sea water is almost four hundred times more than lithium by number of atoms (which is what counts for the capacity of batteries) and by almost 2200 times more than lithium by mass.

Absolutely. Potassium is more abundant than lithium by a factor of 200x or more. A quick google will show that the annual production of potassium is more than 40 million tons while the annual production of lithium is less than 200k tons.

From Wikipedia "Heavy crop production rapidly depletes the soil of potassium, and this can be remedied with agricultural fertilizers containing potassium, accounting for 95% of global potassium chemical production". ---For this to replace lipo yeah there would need to be a BIG a shift