Some embodiments of this application disclose a battery and an electrical device. The battery includes: a battery cell, where a pressure relief mechanism is disposed on a first wall of the battery cell; and a protection plate, where the protection plate is disposed opposite to the pressure relief mechanism. The protection plate is a polymer-based composite fiberboard. The technical solution provided in this application can protect a box of the battery from airflow impact and high-temperature melting arising from thermal runaway of the battery, thereby enhancing safety performance of the battery.