ELECTRICITY STORAGE DEVICE

An electricity storage device includes: an electrode group including first and second electrodes; a case accommodating the electrode group therein, the case having an opening provided therein; and a sealing body covering the opening of the case. The case includes a tubular part, a curved part connected to one end of the tubular part, and a bottom part closing another end of the tubular part. The curved part includes an opening rim, a crimp part connected to the opening rim, and a groove part connected to the crimp part, the crimp part being located outward from the opening rim along a radial direction of the tubular part, the groove part being recessed to protrude inward in the radial direction of the tubular part and having an annular shape. The sealing body includes: a sealing plate having conductivity; and a gasket having electric insulation, the gasket being compressed between the sealing plate and a portion of the crimp part facing the groove part and between the sealing plate and an inner surface of the groove part. The case is electrically connected to the first electrode. The sealing plate is electrically connected to the second electrode. The opening rim does not contact the gasket.

TECHNICAL FIELD

The present disclosure relates to an electricity storage device.

BACKGROUND ART

Electricity storage devices have been broadly used as driving sources typically in vehicles and electronic apparatuses. In general, an electricity storage device includes a case accommodating therein an electrode group including a first electrode and a second electrode and having an opening, and a sealing body covering the opening of the case. In the case that the first electrode is electrically connected to the case, the second electrode is provided on the sealing body and connected to a terminal electrically insulated from the case.

To prepare a module of plural electricity storage devices, from the viewpoint of simplifying a collector structure, a first collector member electrically connected to the first electrode and a second collector member electrically connected to the second electrode are preferably arranged toward the opening of the electricity storage device. In this case, the first collector member is preferably welded onto a rim of the opening of the case and the second collector member is preferably welded onto a terminal of the sealing body.

PTL 1 discloses a cylindrical battery as a rechargeable battery. The cylindrical battery includes an electrode body, a cylindrical external can, and a sealing body crimped and fixed to an opening of the external can via a gasket. The sealing body is crimped and fixed with the gasket in the cylindrical battery.

CITATION LIST

Patent Literature

SUMMARY OF THE INVENTION

Technical Problem

In PTL 1, a rim of the opening of the case is crimped to an outer periphery of a sealing lid via the gasket. Therefore, the rim of the opening is pressed onto the gasket and securely contacts the gasket. When the first collector member is welded onto the rim of the opening of the case in this structure, the gasket may deteriorate due to heat at the welding. Upon deteriorating, the gasket may cause a sealing property achieved by crimping to degrade.

An object of the present disclosure is to suppress deterioration of a gasket provided in a sealing body of an electricity storage device.

Solution to Problem

An electricity storage device in accordance with one aspect of the present disclosure includes: an electrode group including first and second electrodes; a case accommodating the electrode group therein, the case having an opening provided therein; and a sealing body covering the opening of the case. The case includes a tubular part, a curved part connected to one end of the tubular part, and a bottom part closing another end of the tubular part. The curved part includes an opening rim, a crimp part connected to the opening rim, and a groove part connected to the crimp part, the crimp part being located outward from the opening rim along a radial direction of the tubular part, the groove part being recessed to protrude inward in the radial direction of the tubular part and having an annular shape. The sealing body includes: a sealing plate having conductivity; and a gasket having electric insulation, the gasket being compressed between the sealing plate and a portion of the crimp part facing the groove part and between the sealing plate and an inner surface of the groove part. The case is electrically connected to the first electrode. The sealing plate is electrically connected to the second electrode. The opening rim does not contact the gasket.

Advantageous Effect of Invention

In the present disclosure, a collector member can be bonded onto a portion of the crimp part of the case which does not contact the gasket, providing an electricity storage device that suppresses deterioration of the gasket in the sealing body.

DESCRIPTION OF EMBODIMENT

An electricity storage device in accordance with one aspect of the present disclosure includes: an electrode group including a first electrode and a second electrode; a case accommodating the electrode group therein, the case having an opening provided therein; and a sealing body covering the opening of the case. The case includes a tubular part, a curved part connected to one end of the tubular part, and a bottom part closing another end of the tubular part. The curved part includes an opening rim, a crimp part connected to the opening rim, and a groove part connected to the crimp part, the crimp part being located outward from the opening rim along a radial direction of the tubular part, the groove part being recessed to protrude inward in the radial direction of the tubular part and having an annular shape. The sealing body includes: a sealing plate having conductivity; and a gasket having electric insulation, the gasket being compressed between the sealing plate and a portion of the crimp part facing the groove part and between the sealing plate and an inner surface of the groove part. The case is electrically connected to the first electrode. The sealing plate is electrically connected to the second electrode. The opening rim does not contact the gasket.

Since the opening rim does not contact the gasket, heat of welding is hardly transferred to the gasket even when a first collector member is welded to the opening rim. Accordingly, deterioration of the gasket is suppressed. For example, a first collector lead having the same polarity as the first electrode and led out from the first collector member is welded onto an outer surface of the opening rim. On the other hand, a second collector lead having the same polarity as the second electrode and led out from a second collector member is welded to an outer surface of the sealing plate. A material of the gasket is, for example, polypropylene (PP), polyphenylene sulfide (PPS), polybutylene terephthalate (PBT), perfluoroalkoxy alkane (PFA), and polyether ether ketone (PEEK).

The curved part may include a step at a boundary between the opening rim and the crimp part, such that a distance D1between the opening rim and the groove part in an axial direction of the tubular part is larger than a distance D2between the crimp part and the groove part in the axial direction. Distance D1is the shortest distance between the opening rim and the groove part in the axial direction. Distance D2is the shortest distance between the crimp part and the groove part in the axial direction. A height of the groove part that constitutes a reference of D1and D2is a height of the groove part at the deepest point of the groove part (which is closest to an axis of the tubular part). The heat of welding is hardly transferred to the gasket due to the relation of D1>D2, and therefore the deterioration of the gasket can be further suppressed.

To easily achieve the relation of D1>D2, the curved part may include a first bending portion at a boundary between the opening rim and the crimp part. The first bending portion is directed opposite to a bending direction of the crimp part. The first bending portion can be easily formed on the case before forming the crimp part. The gasket is most strongly compressed by the first bending portion. In other words, the first bending portion allows the crimp part to easily increase a compression rate of the gasket. In the electricity storage device of the present disclosure, the first bending portion may not most strongly compress the gasket. A flat portion is formed in the crimp part, and this flat portion may most strongly compress the gasket. Still more, an inclining surface descending outward in the radial direction of the electricity storage device may most strongly compress the gasket.

The curved part may include a second bending portion between the first bending portion and a tip of the opening rim. The second bending portion is directed toward in the bending direction of the crimp part. The second bending portion prevents the tip of the opening rim from excessively protrude away from the sealing body in the axial direction of the tubular part. An angle formed between the opening rim and the radial direction of the tubular part becomes close to 0° by controlling an inner angle of the second bending portion. In other words, the opening rim may include a flat portion in the radial direction of the tubular part. This flat portion facilitates welding to the first collector member. The first collector lead having the same polarity as the first electrode and led out from the first collector member can be easily welded onto an outer surface of the flat portion of the opening rim.

At least a part of the opening rim may include a thin portion thinner than the crimp part. A notch may be formed in a surface of the curved part facing the gasket. The notch is demarcated to include the thin portion. This configuration may provide a space between the thin portion and the gasket, similarly to the configuration in which the opening rim is bent from the crimp part. This space suppresses transferring, to the gasket, of heat generated when the thin portion is bonded to the collector member. The thin portion provides the space between the gasket and the opening rim without bending the crimp part or the opening rim away from the case. This configuration suppresses an increase of dimension of the electricity storage device in a height direction. The entire opening rim may be the thin portion thinner than the crimp part or a part of the opening rim may be the thin portion. In the curved part, the stepped surface or the inclining surface may be formed on the crimp part or an inner surface (surface facing the gasket) of the thin portion of the opening rim.

Types of the electricity storage device are not particularly limited, and include primary batteries, rechargeable batteries, lithium ion capacitors, electric double layer capacitors, and solid electrolyte capacitors. In particular, nonaqueous electrolyte capacitors (including total solid batteries) such as lithium ion rechargeable batteries that have high energy density are preferably applicable.

The electricity storage device in accordance with an exemplary embodiment of the present disclosure will detailed below with reference to the drawings. However, the present disclosure is not limited thereto.

FIG.1is a sectional view of electricity storage device100in accordance with the exemplary embodiment for illustrating an example of a structure thereof.FIG.2is a sectional view of the electricity storage device shown inFIG.1for illustrating a structure before processing a case of the electricity storage device. Electricity storage device100includes electrode group120including a first electrode and a second electrode, case110accommodating therein electrode group120and having opening101, and sealing body130covering opening101of case110. Case110includes tubular part111having a cylindrical shape, curved part112connected to one end of tubular part111, and bottom part113closing another end of tubular part111.

Curved part112includes opening rim1121, crimp part1122connected to opening rim1121and located outward from opening rim1121in the radial direction of tubular part111, and groove part1123having connected to crimp part1122. Groove part1123has an annular shape, and is recessed to protrude inward in the radial direction of tubular part111.

Sealing body130includes sealing plate131having conductivity and gasket133having electric insulation. Gasket133is compressed between sealing plate131and a portion of crimp part1122facing groove part1123and between sealing plate131and an inner surface of groove part1123.

Case110is electrically connected to the first electrode. Sealing plate131is electrically connected to the second electrode. Opening rim1121does not contact gasket133, and a space is provided between opening rim1121and gasket133, thereby preventing heat applied to opening rim1121from being transferred to gasket133.

Internal insulating plate140is disposed between electrode group120and sealing body130, and prevents electrode group120from contacting sealing body130. Predetermined lead hole141is formed in internal insulating plate140. The first electrode constituting electrode group120is electrically connected to case110. Therefore, case110has the same polarity as the first electrode. Lead122led out from the second electrode passes through lead hole141and electrically connected to an inner surface of sealing plate131. Therefore, sealing plate131has the same polarity as the second electrode.

First collector lead301having the same polarity as the first electrode is led out from the first collector member and welded to an outer surface of opening rim1121. On the other hand, second collector lead401having the same polarity as the second electrode is led out from the second collector member and welded to an outer surface of sealing plate131.

FIG.3illustrates a thermal impact on gasket133provided in sealing body130. As illustrated inFIG.3(a), in the case that opening rim1121is not different from crimp part1122and in contact with gasket133, the heat applied to opening rim1121is directly transferred to gasket133at a most compressed portion where a load is applied, resulting in deteriorating gasket133. On the other hand, as illustrated inFIG.3(b), in the case that opening rim1121is different from crimp part1122and does not contact gasket133, the heat applied to opening rim1121is hardly transferred to gasket133, resulting in suppressing the deterioration of gasket133.

A boundary between opening rim1121and crimp part1122is stepped so that distance D1between opening rim1121and groove part1123in the axial direction of tubular part111becomes larger than distance D2between crimp part1122and groove part1123in the axial direction. Distance D1is the shortest distance between an inner surface of opening rim1121and groove part1123in the axial direction. Distance D2is the shortest distance between an inner surface of crimp part1122and groove part1123in the axial direction. A height of the groove part constituting a reference of D1and D2is a height of the groove part at the deepest point of the groove part which is closest to the axis of the tubular part (indicated by point P inFIG.1).

Curved part112includes first bending portion112A at the boundary between opening rim1121and crimp part1122. First bending portion112A is bent in a direction opposite to a bending direction of crimp part1122. Gasket133is most strongly compressed by first bending portion112A.

Curved part112includes second bending portion112B between first bending portion112A and tip1121T of opening rim1121. Second bending portion112B is bent toward the same side as the bending direction of crimp part1122. Second bending portion112B prevents tip1121T of opening rim1121from excessively protruding away from sealing body130in the axial direction of tubular part111. An angle formed by opening rim1121and tubular part111in the radial direction (horizontal direction perpendicular to the axial direction) is substantially 0°. Accordingly, first collector lead301is easily welded to opening rim1121.

At least a part of opening rim1121may have a thin portion thinner than crimp part1122. A notch demarcated to include the thin portion may be provided in a surface of curved part112facing gasket133.

Next, a method of manufacturing the electricity storage device in accordance with the exemplary embodiment will be described below.FIGS.4A to4Jillustrate first to tenth steps of a manufacturing process of the electricity storage device. To facilitate understanding, each diagram illustrates case110, sealing plate131, gasket133, and outer shapes of predetermined dies, but other components are generally omitted from illustration.

First Step

First, electrode group120, a precursor (case precursor110X) of case110, and sealing body130are prepared. Electrode group120is accommodated in case precursor110X, and internal insulating plate140is disposed. Then, a lead (not illustrated) led out from the first electrode is electrically connected to case110, and lead122led out from the second electrode is electrically connected to the inner surface of sealing plate131(FIG.4A). Then, groove part1123having the annular shape is formed in case precursor110X at a position which is slightly above internal insulating plate140toward opening101.

Case precursor110X includes tubular part111having a cylindrical shape, curved part112connected to one end of tubular part111, and bottom part113closing another end of tubular part111(seeFIG.2). Curved part112includes crimp region1122X connected to opening rim1121and groove part1123connected to crimp region1122X.

Groove part1123has an annular shape. Opening rim1121includes first bending portion112A that expands a diameter of opening101outward along the radial direction of tubular part111and second bending portion112B that returns the diameter of opening101inward along the radial direction of tubular part111.

Sealing body130includes sealing plate131and gasket133. Sealing plate131has a disk shape. Gasket133includes wall1331having a tubular shape and annular base part1332having an inner flange shape supporting an inner surface of a periphery of sealing plate131, thus having a tubular shape.

Second Step

Next, first die510including annular protrusion511on an inner peripheral surface of the die is fitted into groove part1123from outside along the radial direction of tubular part111. Still more, annular second die520is pressed onto the outer surface of sealing plate131to press sealing plate131along the axial direction of tubular part111(FIG.4B). This step allows sealing body130to be supported on groove part1123.

Third Step

Next, third die530that is rotatable contacts the outer surface of opening rim1121(FIG.4C). Third die530has a tapered surface with plural steps in a circumferential surface of the third die such that a diameter of the case gradually decreases from opening101toward bottom part113along the axial direction of tubular part111.

Fourth Step

Next, while third die530is rotated, opening rim1121is pushed in from the outside to inside in the radial direction to bend opening rim1121inward (FIG.4D).

Fifth Step

Next, annular fourth die540contacts crimp region1122X (FIG.4E). Crimp region1122X is located between first bending portion112A and groove part1123in curved part112, and is to be crimp part1122. Fourth die540has a tubular concave surface configured to contact crimp region1122X. An inner diameter of the concave surface decreases toward a portion of the die configured to contact first bending portion112A. Crimp region1122X, a peripheral portion of sealing plate131, and gasket133are arranged between this concave surface and annular protrusion511of first die510.

Sixth Step

Next, fourth die540is pressed onto the outer surface of crimp region1122X to press crimp region1122X together with gasket133along the axial direction of tubular part111between fourth die540and annular protrusion511of first die510(FIG.4F).

Seventh Step

Next, fifth die550having a concave surface with radius of curvature smaller than the concave surface of fourth die540is prepared. The radius of curvature is defined as a minimum radius of curvature of a concave surface of the die provided by cutting the die along a plane including the axis of the tubular part (FIG.4G).

Eighth Step

Next, fifth die550is strongly pressed onto the outer surface of crimp region1122X to further press crimp region1122X together with gasket133along the axial direction of tubular part111between fifth die550and annular protrusion511of first die510(FIG.4H).

The concave surface of fifth die550presses crimp region1122X along the axial direction to just contacting opening rim1121. Therefore, almost no stress is applied to opening rim1121. On the other hand, crimp region1122X receives a pressing force from the concave surface of fifth die550, and strongly compresses gasket133More specifically, gasket133is compressed between sealing plate131and crimp part1122(particularly a portion of the gasket facing groove part1123of crimp part1122) and between sealing plate131and the inner surface of groove part1123. First bending portion112A bites gasket133.

Ninth Step

Next, first die510is removed away from groove part1123, and a circumferential surface of tubular part111is fixed by tubular sixth die560having an inner circumferential surface facing the circumferential surface of tubular part111. Then, a pressing surface of annular seventh die570contacts, along the axial direction, crimp part1122formed by previous steps (FIG.4I)

Tenth Step

Next, seventh die570further strongly presses crimp part1122along the axial direction (FIG.4J). As a result, groove part1123is compressed along the axial direction to increase sealing property of crimp part1122.

The above describes an example of a cylindrical electricity storage device. However, the present disclosure is applicable to various shapes (e.g., rectangular shape) of electricity storage devices.

INDUSTRIAL APPLICABILITY

The electricity storage device according to the present disclosure is effectively applicable, in particular, to a power source of vehicles such as hybrid vehicles and electric vehicles.

REFERENCE MARKS IN THE DRAWINGS