A battery cell includes a housing. A dimension of the housing along a length direction of the battery cell is greater than a dimension of the housing along a thickness direction of the battery cell and a dimension of the housing along a width direction of the battery cell. The housing includes a board extending along the length direction and an accommodation space opened from at least one end of the accommodation space. The battery cell further includes an electrode assembly disposed in the accommodation space and a cover configured to cover the opening. A pressure relief mechanism is disposed at the board and configured to be actuated, in response to an internal pressure or temperature of the housing reaching a threshold, to relieve the internal pressure. In the length direction, an extension dimension of the pressure relief mechanism is greater than or equal to ¼ of an extension dimension of the board.