The invention relates to the technical field of battery cells, and discloses a protection device and a battery. The protection device comprises a first connecting piece, a second connecting piece, a first element, and an elastic sheet. The elastic sheet is connected with at least one of the first connecting piece and the second connecting piece when the temperature of the elastic sheet is lower than the first temperature, and the elastic sheet deforms to enable the first connecting piece, the second connecting piece, the elastic sheet and the first element to form a series circuit when the temperature of the elastic sheet is equal to the first temperature. When the protection device is not triggered, the temperature of the elastic sheet is less than the first temperature, the elastic pieceis connected with at least one of the first connecting piece and the second connecting piece, and external heat can be rapidly conducted to the elastic piece through at least one of the first connecting piece or the second connecting piece, therefore, the elastic piece can reach the first temperature in time, the protection device can be triggered timely to cut off or reduce current, and the protection effect is achieved. Therefore, the trigger sensitivity of the protection device is high, and the protection effect is good.