A power storage device includes a lid of a case housing an electrode body and a stopper welded to a liquid inlet circumferential portion of the lid by energy-beam welding to seal the liquid inlet. An annular solidified molten portion made of metal, which has been once molten and then solidified, is positioned on a lid thickwise inside than a lid outer plane of the lid over the entire circumference, and has a surface which continues to an outer annular step surface and a peripheral outward surface and fomes a convex shape toward a lid thickwise outside.

A power storage device includes a lid of a case housing an electrode body and a stopper welded to a liquid inlet circumferential portion of the lid by energy-beam welding to seal the liquid inlet. An annular solidified molten portion made of metal, which has been once molten and then solidified, is positioned on a lid thickwise inside than a lid outer plane of the lid over the entire circumference, and has a surface which continues to an outer annular step surface and a peripheral outward surface and fomes a convex shape toward a lid thickwise outside.

A cathode-active material for a proton-conducting secondary battery, the cathode-active material being for use in a proton-conducting secondary battery, the cathode-active material comprising a compound that is a solid solution that has a composition containing Mn.

A separator which is permeable to hydroxide ion, and which contains at least one Dendrite Stopping Substance such as Ni(OH).sub.2, or its precursor.

A separator which is permeable to hydroxide ion, and which contains at least one Dendrite Stopping Substance such as Ni(OH).sub.2, or its precursor.

A method for producing a button cell includes providing a cell cup, the cell cup having a flat bottom area and a cell cup casing; providing a cell top, the cell top having a flat top area and a cell top casing having a first height; and providing an electrode-separator assembly winding. The cell top casing and the cell cup casing form an overlap area extending in a direction parallel to the axis of the winding and having a second height, the second height being between 20% and 99% of the first height. The method includes applying, in a radial direction perpendicular to the axis of the winding, a pressure on the cell cup casing so as to seal the housing, wherein a portion of the cell top casing that is cylindrical forms at least a part of the overlap area.

A method for producing a button cell includes providing a cell cup, the cell cup having a flat bottom area and a cell cup casing; providing a cell top, the cell top having a flat top area and a cell top casing having a first height; and providing an electrode-separator assembly winding. The cell top casing and the cell cup casing form an overlap area extending in a direction parallel to the axis of the winding and having a second height, the second height being between 20% and 99% of the first height. The method includes applying, in a radial direction perpendicular to the axis of the winding, a pressure on the cell cup casing so as to seal the housing, wherein a portion of the cell top casing that is cylindrical forms at least a part of the overlap area.

Energy storage devices, battery cells, and rechargeable batteries of the present technology may include an anode and a cathode. The battery cells may include a separator positioned between the anode and the cathode. The battery cells may include an electrolyte incorporated with the anode and the cathode. The battery cells may also include a pseudo-reference electrode at least partially in contact with the electrolyte. The pseudo-reference electrode may be electrically isolated from the anode and the cathode.

A metal porous body is a metal porous body mainly composed of nickel and having a framework of a three-dimensional network structure, Ni(OH).sub.2 being present in a surface of the framework, when the metal porous body is subjected to at least 30 potential scans between a lower limit potential of −0.10 V and an upper limit potential of +0.65 V with respect to a hydrogen standard potential in not less than 10% by mass and not more than 35% by mass of a potassium hydroxide aqueous solution, at least oxygen being detected within a depth of 5 nm from the surface, and hydrogen being detected at least in the surface.

A rechargeable button cell including a housing half-parts comprising a housing cup and a housing top separated from one another by an electrically insulating seal or film seal is disclosed. The button cell includes an electrode-separator assembly within the housing having a positive and a negative electrode in the form of flat layers connected to one another by a porous plastic film separator. The electrodes each include a metallic film or mesh embedded in a respective electrode material as a current collector, which acts as an output conductor that connects the electrodes to one of the flat bottom or flat top areas of the housing.