Occasionally I do this when I need battery materials: Crack open a D cell battery and pull out the anode.
The anode is a gooey cylinder at the center of the battery. In the second picture I’ve peeled off one layer of cellophane and one layer of paper from the anode. Inside it’s just a shiny jelly of zinc particles. Zinc is a high energy material, so by dissolving it you can get power. That’s how a battery works, basically.
There’s a cathode too, which is made of manganese oxide. It’s a black powder caked around the inside of the cell. You can also see the nail or pin sticking up at the center. This is the electrical contact to the zinc jelly.
Karl Kordesch, the chemist who invented the alkaline battery, died in 2011.