Battery cell, battery, and electrical device

Embodiments of this application provide a battery cell, which includes a housing and an electrode assembly. The electrode assembly is accommodated in the housing. A film structure is arranged at a position located on an inner wall of the housing and opposite to the electrode assembly. The film structure combines with the inner wall of the housing to form a capsule structure. An accommodation cavity is formed inside the capsule structure. In this way, the capsule structure is more space-efficient, and the battery cell is more structurally compact.