Abstract: An electrochemical cell has a container having a main surface and a cavity containing therein a positive electrode, a negative electrode, a separator separating the positive and negative electrodes from one another, and an electrolyte. A sealing plate that seals the cavity of the container is bonded to the main surface of the container with an unoxidized weld.

Abstract: In an electrochemical cell in which a container is bonded to a cap, observation of liquid leakage has been needed in directions from four sides of the container, therefore much time and high cost have been required. The outer circumference of the cap is made to be smaller than that of the container, whereby surfaces for observing liquid leakage can be made to be only one surface in a direction from an upside of the cap, consequently an electrochemical cell can be provided at low cost.

Abstract: In a conventional electrochemical cell, since a welding between a container and a sealing plate is performed in the atmospheric air, a weld zone is oxidized and a corrosion resistance decreases. For this reason, impurities are eluted from the weld zone into an electrolyte, and this causes an internal resistance increase and a capacity decrease of the electrochemical cell. Further, there is a possibility that an organic solvent in the electrolyte is oxidized by the welding. According to the invention, in order to solve the above problems, the seal welding between the container and the sealing plate of the electrochemical cell is performed under an inert atmosphere.