What does a battery contain?

Answer 1

All batteries will have some kind of cathode (positive element), anode (negative element), and some type of electrolyte.

Often there will be several sets of cathodes, anodes, and electrolytes configured in series to increase the voltage. For example in a car battery, there are 6 cells, each having roughly 2.1 volts arranged in series to produce a total of 12 volts. The acid used in car batteries is sulfuric acid.

I've linked a good diagram of a battery below.

Lead acid batteries use a lead anode (-) plate, a lead dioxide cathode (+) plate, and a sulfuric acid electrolyte. These are usually arranged in sets of plates next to each other in a car battery.

A fun science project might be to make a "lemon battery." The lemon becomes the acid electrolyte. You can drive a galvanized nail into the lemon for the negative anode, and bare copper electrical wire for the positive cathode. A copper penny will also work, but keep in mind that from 1982 and later the pennies were copper plated zinc, so you should find a pre-1981 penny.