Disclosed is a cell with a power-generating element and an outer package. The power-generating element includes a unit cell layer including a first electrode, a second electrode and an electrolyte layer disposed between the first and second electrodes. In the first electrode, a first collector is provided with one of a positive electrode active material layer and a negative electrode active material layer. In the second electrode, a second collector is provided with the other one of the positive and negative electrode active material layers. The first and second collectors have thicknesses such that when a conductor from outside penetrates at least two cells and a short circuit is formed between two cells via the conductor, shorted portions of the first and second collectors are fused by the heat generated by the current before the temperature of the cells reaches a predetermined value so that the short circuit is blocked.