The 2016 invention of a short-term, self-destructing battery definitely made waves. Iowa State University mechanical engineering professor Reza Montazami lead a team of researchers in creating what they called the first practical transient battery.
The battery is tiny—just 5x6 mm, and 1 mm thick. It contains an anode, a cathode, and an electrolyte separator, like most batteries, and is sandwiched between two layers of polyvinyl alcohol-based polymer. When you drop the battery in water, that polymer casing swells, causing the electrodes to break apart and dissolve completely except for a certain quantity of nanoparticles, which don't degrade. This also happens when the battery is exposed to heat or light. The entire process takes about a half-hour.