Strictly speaking - a battery is stored potential energy
A common battery for grid level storage is pumped hydro - that is, use the peak power during the day(s) to push water from the bottom of an elevation to the top, and hold it there - bonus points if it captures water delivered from other solar processes (evaporation -> rain)
There are about 90 billion battery solutions - none of them are very efficient, cheap to manufacture, easy to manufacture/acquire materials for, and long-lasting all at the same time.
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