Method and apparatus for protecting battery member, secondary battery, battery module, battery pack, and electric device

The invention relates to a protection method of a battery component, the battery component comprises an electrode assembly and a top cover assembly, the method comprises the following steps: step (1): placing the battery component in a cavity, and vacuumizing the cavity to be within 100kPa, optionally within 100Pa; (2) a first reactant is introduced into the cavity until the pressure is increased by 1 Pa or above, optionally increased by 1 kPa or above, and kept for 1 ms or above, optionally 0.1 s to 600 s; and optionally, step (3), vacuumizing the cavity to be within 100 kPa, and optionally, vacuumizing the cavity to be within 100 Pa; and (4) introducing a second reactant into the cavity until the pressure is increased by more than 1Pa, optionally increased by more than 1kPa, and kept for more than 1ms, optionally 0.1-600s, thus, a protective layer is formed on the surface of the battery member. The invention also relates to a protection device of the battery member, a secondary battery, a battery module, a battery pack and an electric device.