A power storage device includes a case, a power storage element disposed in the case, a lead connected to an electrode of the power storage element, a sealing member sealing an opening of the case. The sealing member includes a gasket and a sealing plate having conductivity. The gasket includes a base having a disk shape. The base is disposed between the sealing plate and the power storage element. The base has a through-hole formed therein. The sealing plate includes a protrusion inserted in the through-hole. The protrusion of the sealing plate is connected to the lead. The protrusion is configured to be displaced in a direction away from the lead in accordance with an increase of an internal pressure of the case so as to be disconnected from the lead.

An energy storage device includes a current collector (negative electrode current collector), electrode body that includes a body portion and a tab projecting from the body portion, and a leading plate (negative electrode leading plate) that connects the current collector and the tab. In the leading plate, first and second plates and facing each other are continuously connected at end portions thereof in the first plate, the current collector is fixed to a first principal surface on the opposite side to the second plate. In the second plate, the tab is fixed to a second principal surface on the opposite side to the first plate.

An energy storage device includes a current collector (negative electrode current collector), electrode body that includes a body portion and a tab projecting from the body portion, and a leading plate (negative electrode leading plate) that connects the current collector and the tab. In the leading plate, first and second plates and facing each other are continuously connected at end portions thereof in the first plate, the current collector is fixed to a first principal surface on the opposite side to the second plate. In the second plate, the tab is fixed to a second principal surface on the opposite side to the first plate.

An energy storage device includes: an external terminal having any one of positive and negative polarities and including a protrusion and a first terminal; a case having a polarity opposite to the external terminal and including an extension; a substrate disposed to surround an outer circumference of the protrusion of the external terminal through a hole formed at a center thereof; and a connection member located at an upper surface of the substrate and coupled to the first terminal of the external terminal, wherein the first terminal and the substrate are connected by means of the connection member, and the extension is connected to the substrate. Since positive and negative electrodes of the energy storage device are electrically connected to a substrate having a cell balancing function without a harness or any other member, it is possible to improve the economic feasibility and productivity of the energy storage device module.

An energy storage device includes: an external terminal having any one of positive and negative polarities and including a protrusion and a first terminal; a case having a polarity opposite to the external terminal and including an extension; a substrate disposed to surround an outer circumference of the protrusion of the external terminal through a hole formed at a center thereof; and a connection member located at an upper surface of the substrate and coupled to the first terminal of the external terminal, wherein the first terminal and the substrate are connected by means of the connection member, and the extension is connected to the substrate. Since positive and negative electrodes of the energy storage device are electrically connected to a substrate having a cell balancing function without a harness or any other member, it is possible to improve the economic feasibility and productivity of the energy storage device module.

An energy storage device includes: an electrode assembly; a positive electrode current collector and a negative electrode current collector connected to the electrode assembly; and a container configured to house the electrode assembly and the positive electrode current collector and the negative electrode current collector, wherein the container has recessed portions, a connecting portion of the positive electrode current collector and a connecting portion of the negative electrode current collector respectively connected to the electrode assembly are housed in the recessed portions, respectively, the electrode assembly has a tab portion which includes a connecting portion connected to the positive electrode current collector and a tab portion which includes a connecting portion connected to the negative electrode current collector, and the tab portions have a bent portion respectively.

A sealing film which seals between a metal first base and a second base, the sealing film including: a first adhesive layer that mainly contains an acid-modified polyolefin and adheres to the first base; a second adhesive layer that mainly contains a polyolefin and adheres to the second base; and a base material layer provided between the first adhesive layer and the second adhesive layer, in which the base material layer contains (A), (B), and (C), a ratio [(A)/(B)+(C)] is 90/10 to 20/80, a content percentage of (B) with respect to a total amount of (A), (B), and (C) is 5% by mass or more and 70% by mass or less, and a content percentage of (C) with respect to the total amount of (A), (B), and (C) is 5% by mass or more and 70% by mass or less.

A sealing member containing a copolymer containing tetrafluoroethylene unit and a perfluoro(propyl vinyl ether) unit, wherein the copolymer has a content of the perfluoro (propyl vinyl ether) unit of 4.0 to 6.0% by mass with respect to the whole of the monomer units, a melt flow rate of 26 to 37 g/10 min, and the number of functional groups of —CF═CF.sub.2, —CF.sub.2H, —COF, —COOH, —COOCH.sub.3, —CONH.sub.2 and —CH.sub.2OH of more than 50 per 10.sup.6 main-chain carbon atoms, wherein the sealing member has a thickness of 0.5 to 2.5 mm and a sealing area of 0.5 to 50 cm.sup.2, and wherein the sealing member is in a state of being compressed at a compression deformation rate of 20 to 60%. Also disclosed is a power storage assembly including the sealing member.

An ultracapacitor that is capable of exhibiting good properties even after being subjected to high temperatures, such as experienced during solder reflow, is provided. The ultracapacitor contains a housing having sidewalls that extend in a direction generally perpendicular to a base. An interior cavity is defined between an inner surface of the base and the sidewalls within which an electrode assembly can be positioned. To attach the electrode assembly, first and second conductive members are disposed on the inner surface of the base. The electrode assembly likewise contains first and second leads that extend outwardly therefrom and are electrically connected to the first and second conductive members, respectively. The first and second conductive members are, in turn, electrically connected to first and second external terminations, respectively, which are provided on an outer surface of the base.

An ultracapacitor that is capable of exhibiting good properties even after being subjected to high temperatures, such as experienced during solder reflow, is provided. The ultracapacitor contains a housing having sidewalls that extend in a direction generally perpendicular to a base. An interior cavity is defined between an inner surface of the base and the sidewalls within which an electrode assembly can be positioned. To attach the electrode assembly, first and second conductive members are disposed on the inner surface of the base. The electrode assembly likewise contains first and second leads that extend outwardly therefrom and are electrically connected to the first and second conductive members, respectively. The first and second conductive members are, in turn, electrically connected to first and second external terminations, respectively, which are provided on an outer surface of the base.