These have no battery. They "wake up" only when they enter the radio field of an RFID reader, drawing just enough power from the reader's signal to send back their information. They are incredibly cheap (often costing less than $0.10) and are used for retail items, library books, and event wristbands.
The base material, like paper or plastic, that holds the chip and antenna together. Active vs. Passive: How They Power Up rfid chip
At its core, an RFID chip (or tag) is a simple yet sophisticated device consisting of three main parts: These have no battery