The present disclosure discloses a single-cell battery, a battery module, a power battery, and an electric vehicle. The single-cell battery includes a case, a battery cell accommodated in the case, an electrode terminal electrically connected to the battery cell, and a cover plate for sealing the case. The electrode terminal is disposed on the cover plate. The electrode terminal includes a battery post passing through the cover plate and electrically connected to the battery cell with an internal guide member. The single-cell battery further includes a current interruption device mounted on the battery post. The current interruption device includes a flipping member in communication with gas inside the case. The flipping member is connected to an outer end surface of the battery post with a connection point. The connection point is configured to be disconnected under action of air pressure.