The electrochemical device includes a first stack of solid thin layers formed on a substrate, the first stack forming a battery and including: a first electrode and a second electrode separated by a first electrolyte layer, a first current collector in contact with the first electrode, a second current collector in contact with the second electrode. The device includes a second stack forming a thermometer. The second stack includes a third current collector and a fourth current collector separated by a second electrolyte layer forming a resistive layer, the second electrolyte layer being ionically dissociated from the first electrolyte layer. The device includes a control circuit configured to measure the resistance of the resistive layer.