A electrochemical battery including: a battery module including one or more metal air cells which use oxygen gas as a positive electrode active material; an air supply configured to supply air to the battery module and to adjust an oxygen concentration in air supplied to the battery module; and a control unit configured to control an oxygen concentration adjusting operation of the air supply unit. Also a method of operating the electrochemical battery including: supplying air to a battery module using an air supply unit, the battery module including one or more metal air cells which use oxygen in air as a positive electrode active material; and controlling the air supply unit to adjust an oxygen concentration in the air supplied to the battery module.