Researchers from Carnegie Mellon University have reported on a battery they developed that can be swallowed and later degraded safely by the GI system.
The battery consists of safe and well known materials including pectin, melanin, and already widely used PLGA copolymer.
Although the battery is expected to be excreted, if it does get stuck inside the body it will break up into small pieces and exit the body safely anyways.
One interesting aspect of the device is its ability to pass safely through the stomach where hydrochloric acid is aplenty. This is done thanks to melanin, which is actually produced in an acidic environment and so handles the stomach’s juices pretty well. And because melanin has a high affinity for metal ions, it works well as either an anode or cathode.