The present disclosure is directed to 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. The single-cell battery further includes a current interruption device mounted on the battery post. The current interruption device is in communication with gas inside the case. The current interruption device has a conductive member and a flipping member connected to the conductive member for mutual electrical connection. The flipping member and the conductive member are electrically disconnected from each other under action of air pressure. The conductive member is connected to the battery post for mutual electrical connection.