The invention relates to an end cover
assembly, a single battery, a battery and an electric device, and a plugging
assembly is plugged in an operation hole so as to
cut off communication between the interior of the single battery and the outside. In the plugging
assembly, when the elastic body bears force in the direction from the first surface to the second surface, at least part of the elastic body can be separated from the end cover, so that an overflowing opening communicated with the operation hole is formed. In the exhaust or
liquid injection process, force can be applied to the elastic body in the direction from the first surface to the second surface to push the elastic body open, so that an overflowing opening communicated with the outside is formed between the elastic body and the end cover, and an
electrolyte can be injected into the battery
monomer; or, the gas in the battery
monomer can be exhausted outwards during baking, so that effective gas exhaust or
liquid injection is realized. The elastic body can be wholly discharged from the operation hole when being subjected to the force from the second surface to the first surface, so that the elastic body is discharged from the operation hole after the
internal pressure of the battery
monomer is increased to a certain value, and effective pressure relief can be realized.