Batteries in space, chemical batteries used in outer space. What this is listing are devices that store electrical power using chemicals, typically two different ones combine in a certain way to create an electrical potential difference that results voltage and current flow. Each combination of chemicals has different properties, and with some electricity can be sent to the device and stored there (a reverse reaction). What is special here, is its specially about batteries used in orbit, outer space, and deep space, really anything above about 100 thousand meters above the surface of the Earth.