The military uses some pretty exotic batteries that I think are supposed to have near-forever shelf-life (well, 20 years, anyway.) In missiles and fuzes and things. They're essentially solid and inert at room temperature and need to be activated by a pyrotechnic charge to melt the relevant parts. After which they produce plenty of power, for long enough for the device to reach the target. Molten-salt battery - Wikipedia
Come to think of it, there's a slightly similar class of water-activated batteries, and a near equivalent in the zinc-air batteries commonly used in hearing aids. I suspect that if you can build a storage container that will hold vacuum for 100 years, a circuit with OTS Zinc-air batteries might still work after 100 years once you let air (and moisture) in.