SECONDARY BATTERY AND METHOD OF MANUFACTURING SAME

A first electrode assembly has a first electrode tab and a second electrode tab. A second electrode assembly has a third electrode tab and a fourth electrode tab. The first electrode tab is joined to a first current collector. The second electrode tab is joined to a second current collector. The third electrode tab is joined to a third current collector. The fourth electrode tab is joined to a fourth current collector. The first current collector and the third current collector are constituted of separate components. The second current collector and the fourth current collector are constituted of separate components.

CROSS REFERENCE TO RELATED APPLICATIONS

This nonprovisional application is based on Japanese Patent Application No. 2023-147005 filed on Sep. 11, 2023 with the Japan Patent Office, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present technology relates to a secondary battery and a method of manufacturing the secondary battery.

Description of the Background Art

Japanese Patent No. 4537353 discloses a prismatic secondary battery in which an electrode group (25) is accommodated in a case (14) provided with openings (14a,14b) at both ends thereof and electrode terminals (21,23) are respectively attached to cap plates (33,33′) that seal the openings (14a,14b).

SUMMARY OF THE INVENTION

In the secondary battery described in Japanese Patent No. 4537353, there is room for attaining improved energy density and stable manufacturing of the secondary battery.

The present technology has been made to solve the above-described problem, and has an object to provide a method of manufacturing a secondary battery and the secondary battery so as to attain improved energy density and stable manufacturing thereof.

A secondary battery according to the present technology comprises a first electrode assembly, a second electrode assembly, and a case. Each of the first electrode assembly and the second electrode assembly includes a first electrode and a second electrode having a polarity different from a polarity of the first electrode. The case accommodates the first electrode assembly and the second electrode assembly. The case includes a case main body having a tubular shape, a first sealing plate, and a second sealing plate. The case main body is provided with a first opening located at an end portion of the case main body on a first side, and is provided with a second opening located at an end portion of the case main body on a second side opposite to the end portion on the first side. The first sealing plate seals the first opening. The second sealing plate seals the second opening. The first sealing plate is provided with a first electrode terminal electrically connected to the first electrode. The second sealing plate is provided with a second electrode terminal electrically connected to the second electrode. The first electrode assembly has a first electrode tab located at an end portion of the first electrode assembly on the first sealing plate side and a second electrode tab located at an end portion of the first electrode assembly on the second sealing plate side, the first electrode tab being electrically connected to the first electrode, the second electrode tab being electrically connected to the second electrode. The second electrode assembly has a third electrode tab located at an end portion of the second electrode assembly on the first sealing plate side, and a fourth electrode tab located at an end portion of the second electrode assembly on the second sealing plate side, the third electrode tab being electrically connected to the first electrode, the fourth electrode tab being electrically connected to the second electrode. The first electrode tab is joined to a first current collector. The second electrode tab is joined to a second current collector. The third electrode tab is joined to a third current collector. The fourth electrode tab is joined to a fourth current collector. The first current collector and the third current collector are constituted of separate components. The second current collector and the fourth current collector are constituted of separate components. Each of the first current collector and the third current collector is connected to a fifth current collector electrically connected to the first electrode terminal. Each of the second current collector and the fourth current collector is connected to a sixth current collector electrically connected to the second electrode terminal.

A secondary battery in a method of manufacturing the secondary battery according to the present technology comprises a first electrode assembly, a second electrode assembly, and a case. Each of the first electrode assembly and the second electrode assembly includes a first electrode and a second electrode having a polarity different from a polarity of the first electrode. The case accommodates the first electrode assembly and the second electrode assembly. The case includes a case main body having a tubular shape, a first sealing plate, and a second sealing plate. The case main body is provided with a first opening located at an end portion of the case main body on a first side, and is provided with a second opening located at an end portion of the case main body on a second side opposite to the end portion on the first side. The first sealing plate seals the first opening. The second sealing plate seals the second opening. The first sealing plate is provided with a first electrode terminal electrically connected to the first electrode. The second sealing plate is provided with a second electrode terminal electrically connected to the second electrode. The first electrode assembly has a first electrode tab located at an end portion of the first electrode assembly on the first sealing plate side and a second electrode tab located at an end portion of the first electrode assembly on the second sealing plate side, the first electrode tab being electrically connected to the first electrode, the second electrode tab being electrically connected to the second electrode. The second electrode assembly has a third electrode tab located at an end portion of the second electrode assembly on the first sealing plate side, and a fourth electrode tab located at an end portion of the second electrode assembly on the second sealing plate side, the third electrode tab being electrically connected to the first electrode, the fourth electrode tab being electrically connected to the second electrode. The first electrode tab is joined to a first current collector. The second electrode tab is joined to a second current collector. The third electrode tab is joined to a third current collector. The fourth electrode tab is joined to a fourth current collector. The first current collector and the third current collector are constituted of separate components. The second current collector and the fourth current collector are constituted of separate components. Each of the first current collector and the third current collector is connected to a fifth current collector electrically connected to the first electrode terminal. Each of the second current collector and the fourth current collector is connected to a sixth current collector electrically connected to the second electrode terminal. The method of manufacturing the secondary battery comprises: producing the first electrode assembly and the second electrode assembly; joining the first electrode tab to the first current collector after producing the first electrode assembly and the second electrode assembly; joining the second electrode tab to the second current collector after producing the first electrode assembly and the second electrode assembly; joining the third electrode tab to the third current collector after producing the first electrode assembly and the second electrode assembly; joining the fourth electrode tab to the fourth current collector after producing the first electrode assembly and the second electrode assembly; overlapping the first electrode assembly and the second electrode assembly with each other in a thickness direction of each of the first electrode assembly and the second electrode assembly; connecting the first current collector and the third current collector to the fifth current collector after overlapping the first electrode assembly and the second electrode assembly with each other; after connecting the first current collector and the third current collector to the fifth current collector, inserting the first electrode assembly and the second electrode assembly into the case main body via the first opening with each of the second electrode tab side and the fourth electrode tab side being inserted first; and after inserting the first electrode assembly and the second electrode assembly into the case main body, connecting, to the sixth current collector, the second current collector and the fourth current collector each protruding from the second opening.

Regarding the expression “overlapping the first electrode assembly and the second electrode assembly with each other”, the first electrode assembly and the second electrode assembly may be overlapped with each other directly, or another member may be disposed between the first electrode assembly and the second electrode assembly. Further, the first electrode assembly and the second electrode assembly may or may not be fixed by a tape or the like.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present technology will be described. It should be noted that the same or corresponding portions are denoted by the same reference characters, and may not be described repeatedly.

It should be noted that in the embodiments described below, when reference is made to number, amount, and the like, the scope of the present technology is not necessarily limited to the number, amount, and the like unless otherwise stated particularly. Further, in the embodiments described below, each component is not necessarily essential to the present technology unless otherwise stated particularly. Further, the present technology is not limited to one that necessarily exhibits all the functions and effects stated in the present embodiment.

It should be noted that in the present specification, the terms “comprise”, “include”, and “have” are open-end terms. That is, when a certain configuration is included, a configuration other than the foregoing configuration may or may not be included.

Also, in the present specification, when geometric terms and terms representing positional/directional relations are used, for example, when terms such as “parallel”, “orthogonal”, “obliquely at 45°”, “coaxial”, and “along” are used, these terms permit manufacturing errors or slight fluctuations. In the present specification, when terms representing relative positional relations such as “upper side” and “lower side” are used, each of these terms is used to indicate a relative positional relation in one state, and the relative positional relation may be reversed or turned at any angle in accordance with an installation direction of each mechanism (for example, the entire mechanism is reversed upside down).

In the present specification, the term “secondary battery” is not limited to a lithium ion battery, and may include other secondary batteries such as a nickel-metal hydride battery and a sodium-ion battery. In the present specification, the term “electrode” may collectively represents a positive electrode and a negative electrode. It should be noted that in each of the figures, the X direction is defined to represent a direction along a winding axis of an electrode assembly included in the secondary battery, the Y direction is defined to represent a short-side direction of the electrode assembly when viewed in the X direction, and the Z direction is defined to represent a long-side direction of the electrode assembly when viewed in the X direction. Further, in order to facilitate understanding of the invention, the size of each configuration in the figures may be illustrated to be changed from its actual size. In the specification of the present application, the X direction may be referred to as a “width direction” of the secondary battery or the case main body, the Y direction may be referred to as a “thickness direction” of the secondary battery or the case main body, and the Z direction may be referred to as a “height direction” of the secondary battery or the case main body.

First Embodiment

(Overall Configuration of Battery)

FIG.1is a front view of a secondary battery1according to the present embodiment.FIGS.2to5are diagrams showing states of secondary battery1shown inFIG.1when viewed in directions of arrows II, III, IV, and V respectively.FIG.6is a front cross sectional view of secondary battery1shown inFIG.1.

Secondary battery1can be mounted on a battery electric vehicle (BEV), a plug-in hybrid electric vehicle (PHEV), a hybrid electric vehicle (HEV), or the like. It should be noted that the purpose of use of secondary battery1is not limited to the use on a vehicle.

As shown inFIGS.1to6, secondary battery1includes a case100, an electrode assembly200, electrode terminals300, and current collectors400. Case100includes a case main body110, a first sealing plate120, and a second sealing plate130.

When forming a battery assembly including secondary battery1, a plurality of secondary batteries1are stacked in the thickness direction of each of the plurality of secondary batteries1. Secondary batteries1stacked may be restrained in the stacking direction (Y direction) by a restraint member to form a battery module, or the battery assembly may be directly supported by a side surface of a case of a battery pack without using the restraint member.

Case main body110is constituted of a member having a tubular shape, preferably, a prismatic tubular shape. Thus, secondary battery1having a prismatic shape is obtained. Case main body110is composed of a metal. Specifically, case main body110is composed of aluminum, an aluminum alloy, iron, an iron alloy, or the like.

As shown inFIGS.1and2, first sealing plate120and second sealing plate130are provided at respective end portions of the case main body. Case main body110can be formed to have a prismatic tubular shape in, for example, the following manner: end sides of a plate-shaped member having been bent are brought into abutment with each other (joining portion115illustrated inFIG.2) and are joined together (for example, laser welding). Each of the corners of the “prismatic tubular shape” may have a shape with a curvature.

In the present embodiment, case main body110is formed to be longer in the width direction (X direction) of secondary battery1than in each of the thickness direction (Y direction) and the height direction (Z direction) of secondary battery1. The size (width) of case main body110in the X direction is preferably about 30 cm or more. In this way, secondary battery1can be formed to have a relatively large size (high capacity). The size (height) of case main body110in the Z direction is preferably about 20 cm or less, more preferably about 15 cm or less, and further preferably about 10 cm or less. Thus, (low-height) secondary battery1having a relatively low height can be formed, thus resulting in improved ease of mounting on a vehicle, for example.

Case main body110includes a pair of first side surface portions111and a pair of second side surface portions112. The pair of first side surface portions111constitute parts of the side surfaces of case100. The pair of second side surface portions112constitute the bottom surface portion and upper surface portion of case100. The pair of first side surface portions111and the pair of second side surface portions112are provided to intersect each other. The pair of first side surface portions111and the pair of second side surface portions112are connected at their respective end portions. Each of the pair of first side surface portions111desirably has an area larger than that of each of the pair of second side surface portions112.

As shown inFIG.5, a gas-discharge valve150is provided in one second side surface portion112A of the pair of second side surface portions112. Gas-discharge valve150extends in the width direction (X direction) of secondary battery1. Gas-discharge valve150extends from the center of case main body110in the X direction to such an extent that gas-discharge valve150does not reach both ends of case main body110in the X direction. Gas-discharge valve150can be changed appropriately.

The thickness of the plate-shaped member in gas-discharge valve150is thinner than the thickness of the plate-shaped member of case main body110other than gas-discharge valve150. Thus, when the pressure in case100becomes equal to or more than a predetermined value, gas-discharge valve150is fractured prior to the other portions of case main body110, thereby discharging the gas in case100to the outside.

As shown inFIG.2, a joining portion115is formed at the other second side surface portion112B of the pair of second side surface portions112. Joining portion115extends in the width direction (X direction) of secondary battery1. At joining portion115, the end sides of the plate-shaped member of case main body110are joined to each other.

As shown inFIG.3, a first opening113is provided at an end portion of case main body110on a first side in the first direction (X direction). First opening113is sealed by first sealing plate120. Joining portion115is formed at first opening113so as to seal first opening113. Each of first opening113and first sealing plate120has a substantially rectangular shape having a long-side direction and a short-side direction in a direction intersecting the first direction (X direction) in which first opening113and second opening114are arranged side by side. Each of first opening113and first sealing plate120in the present embodiment has a substantially rectangular shape in which the Y direction corresponds to its short-side direction and the Z direction corresponds to its long-side direction. It should be noted that the substantially rectangular shape includes a rectangular shape or a generally rectangular shape such as a shape having corners each with a curvature.

A negative electrode terminal301(first electrode terminal) is provided on first sealing plate120. The position of negative electrode terminal301can be appropriately changed.

As shown inFIG.4, a second opening114is provided at an end portion of case main body110on a second side opposite to the first side in the first direction (X direction). That is, second opening114is located at the end portion opposite to first opening113. Second opening114is sealed by second sealing plate130. Joining portion115is formed at second opening114so as to seal second opening114. Each of second opening114and second sealing plate130has a substantially rectangular shape having a long-side direction and a short-side direction in the direction intersecting the first direction (X direction) in which first opening113and second opening114are arranged side by side. Each of second opening114and second sealing plate130in the present embodiment has a substantially rectangular shape in which the Y direction corresponds to its short-side direction and the Z direction corresponds to its long-side direction.

Second sealing plate130is provided with a positive electrode terminal302(second electrode terminal) and an injection hole134. The positions of positive electrode terminal302and injection hole134can be appropriately changed.

Each of first sealing plate120and second sealing plate130is composed of a metal. Specifically, each of first sealing plate120and second sealing plate130is composed of aluminum, an aluminum alloy, iron, an iron alloy, or the like.

Negative electrode terminal301is electrically connected to a negative electrode (first electrode) of electrode assembly200. Negative electrode terminal301is attached to first sealing plate120, i.e., case100.

Positive electrode terminal302is electrically connected to a positive electrode (second electrode) of electrode assembly200. Positive electrode terminal302is attached to second sealing plate130, i.e., case100.

Negative electrode terminal301is composed of a conductive material (more specifically, a metal), and can be composed of copper, a copper alloy, or the like, for example. A portion or layer composed of aluminum or an aluminum alloy may be provided at a portion of an outer surface of negative electrode terminal301.

Positive electrode terminal302is composed of a conductive material (more specifically, a metal), and can be composed of aluminum, an aluminum alloy, or the like, for example.

Injection hole134is sealed with a sealing member (not shown). As the sealing member, for example, a blind rivet or another metal member can be used.

Electrode assembly200is an electrode assembly having a flat shape and having a below-described positive electrode plate and a below-described negative electrode plate. Specifically, electrode assembly200is a wound type electrode assembly in which a strip-shaped positive electrode plate and a strip-shaped negative electrode plate are both wound with a strip-shaped separator (not shown) being interposed therebetween. It should be noted that in the present specification, the “electrode assembly” is not limited to the wound type electrode assembly, and may be a stacked type electrode assembly in which a plurality of positive electrode plates and a plurality of negative electrode plates are alternately stacked. The strip-shaped separator can be constituted of, for example, a microporous membrane composed of polyolefin. The electrode assembly may include a plurality of positive electrode plates and a plurality of negative electrode plates, respective positive electrode tabs provided in the positive electrode plates may be stacked to form a positive electrode tab group, and respective negative electrode tabs provided in the negative electrode plates may be stacked to form a negative electrode tab group. It should be noted that electrode assembly200may include a plurality of wound type electrode assemblies or may include a plurality of stacked type electrode assemblies.

As shown inFIG.6, case100accommodates electrode assembly200.FIG.6illustrates a first electrode assembly201described below. First electrode assembly201is accommodated in case100such that the winding axis thereof is parallel to the X direction.

Specifically, one or a plurality of the wound type electrode assemblies and an electrolyte solution (electrolyte) (not shown) are accommodated inside a below-described insulating sheet700disposed in case100. As the electrolyte solution (non-aqueous electrolyte solution), it is possible to use, for example, a solution obtained by dissolving LiPF6at a concentration of 1.2 mol/L in a non-aqueous solvent obtained by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) at a volume ratio (25° C.) of 30:30:40. It should be noted that instead of the electrolyte solution, a solid electrolyte may be used.

First electrode assembly201includes: a main body portion (portion in which a positive electrode plate and a negative electrode plate are stacked with a separator being interposed therebetween); a first tab220(negative electrode tab group); and a second electrode tab250(positive electrode tab group).

The main body portion is constituted of a below-described negative electrode plate210and a below-described positive electrode plate240. First electrode tab220is located at an end portion of first electrode assembly201on the first side with respect to the main body portion in the first direction (X direction). The first side in the present embodiment is the first sealing plate120side. Second electrode tab250is located at an end portion of first electrode assembly201on the second side with respect to the main body portion in the first direction (X direction). The second side in the present embodiment is the second sealing plate130side.

Each of first electrode tab220and second electrode tab250is formed to protrude from a central portion of electrode assembly200toward first sealing plate120or second sealing plate130.

Current collectors400include a negative electrode current collector400A and a positive electrode current collector400B. Each of negative electrode current collector400A and positive electrode current collector400B is constituted of a plate-shaped member. Electrode assembly200is electrically connected to negative electrode terminal301and positive electrode terminal302through current collectors400.

Negative electrode current collector400A is disposed on first sealing plate120with an insulating member composed of a resin being interposed therebetween. Negative electrode current collector400A is electrically connected to first electrode tab220and negative electrode terminal301. Negative electrode current collector400A is composed of a conductive material (more specifically, a metal), and can be composed of copper, a copper alloy, or the like, for example. It should be noted that details of negative electrode current collector400A will be described later.

Positive electrode current collector400B is disposed on second sealing plate130with an insulating member composed of a resin being interposed therebetween. Positive electrode current collector400B is electrically connected to second electrode tab250and positive electrode terminal302. Positive electrode current collector400B is composed of a conductive material (more specifically, a metal), and can be composed of aluminum, an aluminum alloy, or the like, for example. It should be noted that second electrode tab250may be electrically connected to second sealing plate130directly or via positive electrode current collector400B. In this case, second sealing plate130may serve as positive electrode terminal302. Moreover, details of positive electrode current collector400B will be described later.

FIG.7is a front view showing a negative electrode raw plate210S before negative electrode plate210(first electrode) is formed,FIG.8is a cross sectional view of negative electrode raw plate210S shown inFIG.7along VIII-VIII, andFIG.9is a front view showing negative electrode plate210formed from negative electrode raw plate210S.

Negative electrode plate210is manufactured by processing negative electrode raw plate210S. As shown inFIGS.7and8, negative electrode raw plate210S includes a negative electrode core body211and a negative electrode active material layer212. Negative electrode core body211is a copper foil or a copper alloy foil.

Negative electrode active material layer212is formed on negative electrode core body211except for each of end portions of both surfaces of negative electrode core body211on one side. Negative electrode active material layer212is formed by applying a negative electrode active material layer slurry using a die coater.

The negative electrode active material layer slurry is produced by kneading graphite serving as a negative electrode active material, styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) each serving as a binder, and water serving as a dispersion medium such that the mass ratio of the graphite, the SBR, and the CMC is about 98:1:1.

Negative electrode core body211having the negative electrode active material layer slurry applied thereon is dried to remove the water included in the negative electrode active material layer slurry, thereby forming negative electrode active material layer212. Further, by compressing negative electrode active material layer212, negative electrode raw plate210S including negative electrode core body211and negative electrode active material layer212is formed. Negative electrode raw plate210S is cut into a predetermined shape, thereby forming negative electrode plate210. Negative electrode raw plate210S can be cut by laser processing with application of an energy ray, die processing, cutter processing, or the like.

As shown inFIG.9, a plurality of negative electrode tabs230each constituted of negative electrode core body211are provided at one end portion, in the width direction, of negative electrode plate210formed from negative electrode raw plate210S. When negative electrode plate210is wound, the plurality of negative electrode tabs230are stacked to form first electrode tab220. Thus, first electrode tab220is connected to negative electrode plate210(first electrode). The position of each of the plurality of negative electrode tabs230and the length thereof in the protruding direction are appropriately adjusted in consideration of the state in which first electrode tab220is connected to negative electrode current collector400A. It should be noted that the shape of negative electrode tab230is not limited to the one shown inFIG.8.

FIG.10is a front view showing a positive electrode raw plate240S before positive electrode plate240(second electrode) is formed,FIG.11is a cross sectional view of positive electrode raw plate240S shown inFIG.10along XI-XI, andFIG.12is a front view showing positive electrode plate240formed from positive electrode raw plate240S.

Positive electrode plate240serving as the second electrode has a polarity different from a polarity of negative electrode plate210serving as the first electrode. Positive electrode plate240is manufactured by processing positive electrode raw plate240S. As shown inFIGS.10and11, positive electrode raw plate240S includes a positive electrode core body241, a positive electrode active material layer242, and a positive electrode protective layer243. Positive electrode core body241is an aluminum foil or an aluminum alloy foil.

Positive electrode active material layer242is formed on positive electrode core body241except for each of end portions of both surfaces of positive electrode core body241on one side. Positive electrode active material layer242is formed on positive electrode core body241by applying a positive electrode active material layer slurry using a die coater.

The positive electrode active material layer slurry is produced by kneading a lithium-nickel-cobalt-manganese composite oxide serving as a positive electrode active material, polyvinylidene difluoride (PVdF) serving as a binder, a carbon material serving as a conductive material, and N-methyl-2-pyrrolidone (NMP) serving as a dispersion medium such that the mass ratio of the lithium-nickel-cobalt-manganese composite oxide, the PVdF, and the carbon material is about 97.5:1:1.5.

Positive electrode protective layer243is formed in contact with positive electrode core body241at an end portion of positive electrode active material layer242on the one side in the width direction. Positive electrode protective layer243is formed on positive electrode core body241by applying a positive electrode protective layer slurry using a die coater. Positive electrode protective layer243has an electrical resistance larger than that of positive electrode active material layer242.

The positive electrode protective layer slurry is produced by kneading alumina powder, a carbon material serving as a conductive material, PVdF serving as a binder, and NMP serving as a dispersion medium such that the mass ratio of the alumina powder, the carbon material, and the PVdF is about 83:3:14.

Positive electrode core body241having the positive electrode active material layer slurry and the positive electrode protective layer slurry applied thereon is dried to remove the NMP included in the positive electrode active material layer slurry and the positive electrode protective layer slurry, thereby forming positive electrode active material layer242and positive electrode protective layer243. Further, by compressing positive electrode active material layer242, positive electrode raw plate240S including positive electrode core body241, positive electrode active material layer242, and positive electrode protective layer243is formed. Positive electrode raw plate240S is cut into a predetermined shape, thereby forming positive electrode plate240. Positive electrode raw plate240S can be cut by laser processing with application of an energy ray, die processing, cutter processing, or the like.

As shown inFIG.12, a plurality of positive electrode tabs260each constituted of positive electrode core body241are provided at one end portion, in the width direction, of positive electrode plate240formed from positive electrode raw plate240S. When positive electrode plate240is wound, the plurality of positive electrode tabs260are stacked to form second electrode tab250. Thus, second electrode tab250is connected to positive electrode plate240(second electrode). The position of each of the plurality of positive electrode tabs260and the length thereof in the protruding direction are appropriately adjusted in consideration of the state in which second electrode tab250is connected to positive electrode current collector400B. It should be noted that the shape of positive electrode tab260is not limited to the one shown inFIG.12.

Positive electrode protective layer243is provided at the root of each of the plurality of positive electrode tabs260. Positive electrode protective layer243may not necessarily be provided at the root of positive electrode tab260.

In a typical example, the thickness of (one) negative electrode tab230is smaller than the thickness of (one) positive electrode tab260. In this case, the thickness of first electrode tab220is smaller than the thickness of second electrode tab250.

FIG.13is a cross sectional view of the secondary battery shown inFIG.1along XIII-XIII. As shown inFIG.13, electrode assembly200includes first electrode assembly201and a second electrode assembly202. Each of first electrode assembly201and second electrode assembly202includes a first electrode (negative electrode) and a second electrode (positive electrode). It should be noted that electrode assembly200may be constituted of three or more electrode assemblies.

Electrode assembly200is formed by overlapping first electrode assembly201and second electrode assembly202with each other. First electrode assembly201and second electrode assembly202are arranged side by side in the thickness direction (Y direction) of each of first electrode assembly201and second electrode assembly202.

First electrode assembly201includes first electrode tab220. First electrode tab220is electrically connected to the first electrode at its first end portion205on the first sealing plate120side in the X direction. Second electrode assembly202includes a third electrode tab270. Third electrode tab270is electrically connected to the first electrode at its third end portion207on the first sealing plate120side in the X direction.

First electrode tab220has a curved portion221and a tip portion222. Curved portion221is a portion at which first electrode tab220is curved on the side, on which the first electrode is connected, with respect to tip portion222. Tip portion222is a portion located at an end portion of first electrode tab220on the side opposite to the side on which the first electrode is connected.

Third electrode tab270has a curved portion271and a tip portion272. Curved portion271is a portion at which third electrode tab270is curved on the side, on which the first electrode is connected, with respect to tip portion272. Tip portion272is a portion located at an end portion of third electrode tab270on the side opposite to the side on which the first electrode is connected.

First electrode tab220and third electrode tab270are curved in opposite directions such that tip portions222,272are close to each other. It should be noted that tip portions222,272are separated from each other in the present embodiment; however, it is not limited to this configuration, and tip portions222,272may be in contact with each other.

Negative electrode current collector400A electrically connects negative electrode terminal301to first electrode tab220and third electrode tab270. Negative electrode current collector400A in the present embodiment is connected to negative electrode terminal301between electrode assembly200and first sealing plate120.

Negative electrode current collector400A includes a first current collector410, a third current collector430, and a fifth current collector450.

First current collector410is a plate-shaped member. First current collector410has a long-side direction in the Z direction and a short-side direction in the Y direction. Third current collector430is a plate-shaped member. Third current collector430has a long-side direction in the Z direction and a short-side direction in the Y direction. First current collector410and third current collector430are arranged side by side in parallel in the Y direction. In this way, first current collector410and third current collector430are constituted of separate components.

First electrode tab220is joined to first current collector410at a joining location411described later. Third electrode tab270is joined to third current collector430at a joining location431described later. Joining locations411,431can be formed by, for example, ultrasonic welding, resistance welding, laser welding, swaging, or the like. In the present embodiment, first electrode tab220and first current collector410are joined by ultrasonic joining, and third electrode tab270and third current collector430are joined by ultrasonic joining, for example.

Fifth current collector450is electrically connected to each of first current collector410and third current collector430at a joining location located at a below-described end portion in the Z direction. Fifth current collector450is electrically connected to negative electrode terminal301. The connection between fifth current collector450and negative electrode terminal301can be formed by swaging and/or welding, for example.

Negative electrode terminal301is provided to be exposed to the outside of first sealing plate120and reach fifth current collector450of negative electrode current collector400A provided on the inner surface side of first sealing plate120. Negative electrode terminal301is connected to a first plate portion303.

First plate portion303is located on the outer side with respect to first sealing plate120. First plate portion303is disposed along first sealing plate120. First plate portion303has electric conductivity. First plate portion303is disposed to secure an area of connection with a bus bar or the like that electrically connects secondary battery1and another secondary battery adjacent thereto. The connection between negative electrode terminal301and first plate portion303can be formed by, for example, laser welding.

A first insulating member510is disposed between first plate portion303and first sealing plate120. A second insulating member520is disposed between negative electrode terminal301and first sealing plate120. A third insulating member530is disposed between fifth current collector450and first sealing plate120.

It should be noted that negative electrode terminal301may be electrically connected to first sealing plate120. Further, first sealing plate120may serve as negative electrode terminal301.

A spacer600is disposed between first sealing plate120and electrode assembly200. Spacer600is composed of a resin member having an insulating property. Spacer600includes a first component610and a second component620. First component610and second component620are engaged with each other at engagement portions (not shown) at both ends in the Z direction.

Each of first component610and second component620protrudes in the Y direction at its end portion side on the electrode assembly200side in the X direction. Thus, spacer600functions as a guide to facilitate curving of curved portions221,271when forming curved portions221,271.

Insulating sheet700(electrode assembly holder) composed of a resin is disposed between electrode assembly200and case main body110. Insulating sheet700may be composed of, for example, a resin. More specifically, the material of insulating sheet700is, for example, polypropylene (PP), polyethylene terephthalate (PET), polyphenylene sulfide (PPS), polyimide (PI), or polyolefin (PO).

FIG.14is a cross sectional view of the secondary battery shown inFIG.1along XIV-XIV. First electrode assembly201includes second electrode tab250. Second electrode tab250is electrically connected to the second electrode at its second end portion206on the second sealing plate130side in the X direction. Second electrode assembly202includes a fourth electrode tab280. Fourth electrode tab280is electrically connected to the second electrode at its fourth end portion208on the second sealing plate130side in the X direction.

Second electrode tab250has a curved portion251and a tip portion252. Curved portion251is a portion at which second electrode tab250is curved on the side, on which the second electrode is connected, with respect to tip portion252. Tip portion252is a portion located at an end portion of second electrode tab250on the side opposite to the side on which the second electrode is connected.

Fourth electrode tab280has a curved portion281and a tip portion282. Curved portion281is a portion at which fourth electrode tab280is curved on the side, on which the second electrode is connected, with respect to tip portion282. Tip portion282is a portion located at an end portion of fourth electrode tab280on the side opposite to the side on which the second electrode is connected.

Second electrode tab250and fourth electrode tab280are curved in opposite directions such that tip portions252,282are close to each other. It should be noted that tip portions252,282are separated from each other in the present embodiment; however, it is not limited to this configuration, and tip portions252,282may be in contact with each other.

Positive electrode current collector400B electrically connects positive electrode terminal302to second electrode tab250and fourth electrode tab280. Positive electrode current collector400B in the present embodiment is connected to positive electrode terminal302between electrode assembly200and second sealing plate130.

Positive electrode current collector400B includes a second current collector420, a fourth current collector440, and a sixth current collector460.

Second current collector420is a plate-shaped member. Second current collector420has a long-side direction in the Z direction and a short-side direction in the Y direction. Fourth current collector440is a plate-shaped member. Fourth current collector440has a long-side direction in the Z direction and a short-side direction in the Y direction. Second current collector420and fourth current collector440are arranged side by side in parallel in the Y direction. In this way, second current collector420and fourth current collector440are constituted of separate components.

Second electrode tab250is joined to second current collector420at a joining location421described later. Fourth electrode tab280is joined to fourth current collector440at a joining location441described later. Joining locations421,441can be formed by, for example, ultrasonic welding, resistance welding, laser welding, swaging, or the like. In the present embodiment, second electrode tab250and second current collector420are joined by ultrasonic joining, and fourth electrode tab280and fourth current collector440are joined by ultrasonic joining, for example.

Sixth current collector460is electrically connected to each of second current collector420and fourth current collector440at a joining location located at a below-described end portion in the Z direction. Sixth current collector460is electrically connected to positive electrode terminal302. The connection between sixth current collector460and positive electrode terminal302may be formed by swaging and/or welding, for example.

Positive electrode terminal302is provided to be exposed to the outside of second sealing plate130and reach sixth current collector460of positive electrode current collector400B provided on the inner surface side of second sealing plate130. Positive electrode terminal302is connected to a second plate portion304.

Second plate portion304is located on the outer side with respect to second sealing plate130. Second plate portion304is disposed along second sealing plate130. Second plate portion304has electric conductivity. Second plate portion304is disposed to secure an area of connection with a bus bar or the like that electrically connects secondary battery1and another secondary battery adjacent thereto. The connection between positive electrode terminal302and second plate portion304may be formed by, for example, laser welding.

A first insulating member510is disposed between second plate portion304and second sealing plate130. A second insulating member520is disposed between positive electrode terminal302and second sealing plate130. A third insulating member530is disposed between sixth current collector460and second sealing plate130.

It should be noted that positive electrode terminal302may be electrically connected to second sealing plate130. Further, second sealing plate130may serve as positive electrode terminal302.

A spacer600is disposed between second sealing plate130and electrode assembly200. Spacer600is composed of a resin member having an insulating property. Spacer600includes a first component610and a second component620. First component610and second component620are engaged with each other at engagement portions (not shown) at both ends in the Z direction.

Each of first component610and second component620protrudes in the Y direction at its end portion side on the electrode assembly200side in the X direction. Thus, spacer600functions as a guide to facilitate curving of curved portions251,281when forming curved portions251,281.

Insulating sheet700(electrode assembly holder) composed of a resin is disposed between electrode assembly200and case main body110.

(Manufacturing Process for Secondary Battery1)

Hereinafter, a method of manufacturing the secondary battery according to the present embodiment will be described.FIG.15is a flowchart showing the method of manufacturing the secondary battery according to the first embodiment.FIG.16is a perspective view showing a state before the two electrode assemblies included in the secondary battery according to the first embodiment are overlapped with each other.

As shown inFIG.15, in the method of manufacturing the secondary battery according to the present embodiment, first, first electrode assembly201and second electrode assembly202are produced (step S1). Part of the tips of first electrode tab220, second electrode tab250, third electrode tab270, and fourth electrode tab280are cut such that they have the same tip length when bundled.

As shown inFIGS.15and16, after producing first electrode assembly201and second electrode assembly202, first electrode tab220is joined to first current collector410(step S2). First electrode tab220is joined to first current collector410at joining location411. Next, second electrode tab250is joined to second current collector420(step S3). Second electrode tab250is joined to second current collector420at joining location421. Next, third electrode tab270is joined to third current collector430(step S4). Third electrode tab270is joined to third current collector430at joining location431. Next, fourth electrode tab280is joined to fourth current collector440(step S5). Fourth electrode tab280is joined to fourth current collector440at joining location441.

In the height direction of each of first electrode assembly201and second electrode assembly202, each of first current collector410, second current collector420, third current collector430, and fourth current collector440is disposed on one side with respect to the center of a corresponding one of first electrode assembly201and second electrode assembly202. Thus, each of the current collectors can be formed to be short, thereby reducing the size of the current collector.

It should be noted that each of first current collector410, second current collector420, third current collector430, and fourth current collector440is not limited to this configuration. In the height direction of each of first electrode assembly201and second electrode assembly202, each of first current collector410, second current collector420, third current collector430, and fourth current collector440may be disposed at the center of a corresponding one of first electrode assembly201and second electrode assembly202. In this case, in the height direction of each of first electrode assembly201and second electrode assembly202, each of first electrode tab220, second electrode tab250, third electrode tab270, and fourth electrode tab280is disposed at the center of a corresponding one of first electrode assembly201and second electrode assembly202so as to correspond to a corresponding one of first current collector410, second current collector420, third current collector430, and fourth current collector440.

The order of the steps of joining first current collector410, second current collector420, third current collector430, and fourth current collector440to first electrode assembly201and second electrode assembly202is not limited to the one described above, and the order may be changed.

FIG.17is a cross sectional view showing a state of bending the electrode tabs. As shown inFIGS.15to17, next, first electrode assembly201and second electrode assembly202are overlapped with each other in the thickness direction of each of first electrode assembly201and second electrode assembly202(step S6). First electrode assembly201and second electrode assembly202are overlapped with each other along directions of arrows inFIG.16. That is, first electrode assembly201and second electrode assembly202are collected into one.

Regarding the expression “overlapping the first electrode assembly and the second electrode assembly with each other”, the first electrode assembly and the second electrode assembly may be overlapped with each other directly, or another member may be disposed between the first electrode assembly and the second electrode assembly. Further, the first electrode assembly and the second electrode assembly may or may not be fixed by a tape or the like.

First electrode tab220, second electrode tab250, third electrode tab270, and fourth electrode tab280are bent in respective directions of arrows inFIG.17. Thus, tip portions of first electrode tab220and third electrode tab270are disposed to face each other. Further, the tip portions of second electrode tab250and fourth electrode tab280are disposed to face each other.

It should be noted that the step of overlapping first electrode assembly201and second electrode assembly202with each other is preferably performed before the steps of joining first current collector410, second current collector420, third current collector430, and fourth current collector440to first electrode assembly201and second electrode assembly202. The step of overlapping first electrode assembly201and second electrode assembly202with each other may be performed during each of the steps of joining first current collector410, second current collector420, third current collector430, and fourth current collector440.

FIG.18is a perspective view showing a state of attaching the holder and the spacer to the electrode assembly. As shown inFIGS.15and18, next, spacer600and insulating sheet700are assembled to electrode assembly200(step S7).

It should be noted that insulating sheet700does not necessarily need to cover a whole of the surfaces of electrode assembly200. Insulating sheet700preferably covers an area of about 50% or more, more preferably about 70% or more, of the outer surfaces of the electrode assembly. Insulating sheet700preferably covers a whole of at least four surfaces of the six surfaces of electrode assembly200having a substantially rectangular parallelepiped shape (flat shape) other than the two surfaces thereof on which first electrode tab220and second electrode tab250are formed respectively.

FIG.19is a perspective view showing a state of attaching the first sealing plate to the first current collector.FIG.20is a cross sectional view of each of the electrode assemblies and the current collectors shown inFIG.19along XX-XX.

As shown inFIGS.15,19, and20, after overlapping first electrode assembly201and second electrode assembly202with each other, first current collector410and third current collector430are connected to fifth current collector450(step S8).

It should be noted that step S8can be performed before step S7. By performing step S8before step S7, negative electrode terminal301and each of first electrode tab220and third electrode tab270can be more stably connected to each other when electrically connecting them. Further, a configuration with a smaller space between first sealing plate120and the main body portion of electrode assembly200can be readily attained.

First electrode tab220and third electrode tab270are bent such that tip portions222,272face each other.

Each of negative electrode terminal301and fifth current collector450is attached to first sealing plate120with an insulating member being interposed therebetween. Fifth current collector450is brought into abutment with first current collector410and third current collector430in the X direction. Fifth current collector450is joined to first current collector410and third current collector430by laser welding from between first sealing plate120and insulating sheet700. It should be noted that the connecting of first plate portion303to negative electrode terminal301may be performed at any timing.

The connecting of each of first current collector410, third current collector430, and fifth current collector450is performed through welding in the same manner as in the connecting of each of second current collector420, fourth current collector440, and sixth current collector460as described later.

Specifically, when viewed in the long-side direction (Y direction) of first sealing plate120, a third overlapping region is defined in which first current collector410and fifth current collector450overlap with each other on the end portion side (upper end portion in the Z direction) in the long-side direction of first sealing plate120. Further, when viewed in the long-side direction (Y direction) of first sealing plate120, a fourth overlapping region is defined in which third current collector430and fifth current collector450overlap with each other on the end portion side (upper end portion in the Z direction) in the long-side direction of first sealing plate120.

In the third overlapping region, first current collector410and fifth current collector450are connected to each other by welding. In the fourth overlapping region, third current collector430and fifth current collector450are connected to each other by welding.

FIG.21is a perspective view showing a state of inserting the electrode assemblies into the case main body. Next, as shown inFIGS.15and21, after connecting first current collector410and third current collector430to fifth current collector450, first electrode assembly201and second electrode assembly202are inserted into case main body110via first opening113with each of the second electrode tab250side and the fourth electrode tab280side being inserted first (step S9).

First sealing plate120is brought into abutment with case main body110. Thus, first electrode tab220and third electrode tab270are curved. As shown inFIG.13, first electrode tab220and third electrode tab270are curved along the shape of spacer600such that the folded portions of curved portions221,271are close to case main body110in the Y direction.

Thereafter, first sealing plate120is temporarily joined to case main body110. By the temporary joining, first sealing plate120is partially joined to first opening113of case main body110. Thus, first sealing plate120is positioned with respect to case main body110.

When inserting electrode assembly200into case main body110, electrode assembly200may be pulled from each of the second current collector420side and the fourth current collector440side, or may be pushed from each of the first current collector410side and the third current collector430side. When electrode assembly200is pressed from each of the first current collector410side and the third current collector430side, first electrode tab220and third electrode tab270can be curved at the same time.

FIG.22is a perspective view showing a state of attaching the second sealing plate to the second current collector.FIG.23is a cross sectional view of each of the electrode assemblies and the current collectors shown inFIG.22along XXIII-XXIII.FIG.24is a diagram showing a state in which the current collectors shown inFIG.22are viewed in a direction of arrow XXIV.FIG.25is a cross sectional view of the current collectors shown inFIG.24along XXV-XXV. It should be noted that inFIG.23, case main body110is not shown.

Next, as shown inFIG.15andFIGS.22to25, after inserting first electrode assembly201and second electrode assembly202into case main body110, second current collector420and fourth current collector440each protruding from second opening114are connected to sixth current collector460(step S10).

Specifically, each of positive electrode terminal302and sixth current collector460is attached to second sealing plate130with an insulating member being interposed therebetween. Sixth current collector460is brought into abutment with second current collector420in the X direction. It should be noted that the connecting of second plate portion304to positive electrode terminal302may be performed at any timing.

As shown inFIGS.24and25, each of second current collector420, fourth current collector440, and sixth current collector460in the present embodiment has a folded portion F at its end portion in the Z direction. Folded portion F is along the X direction. Since folded portion F is along the X direction, high-energy ray2can be applied in a direction parallel to the Z direction, with the result that high-energy ray2is less likely to interfere with case main body110or second sealing plate130. The high-energy ray is, for example, laser light.

When viewed in the long-side direction (Y direction) of second sealing plate130, a first overlapping region R11is formed in which second current collector420and sixth current collector460overlap with each other on the end portion side of second sealing plate130in the long-side direction. First overlapping region R11is formed by arranging folded portions F side by side in the Z direction.

Further, when viewed in the long-side direction (Y direction) of second sealing plate130, a second overlapping region R12is formed in which fourth current collector440and sixth current collector460overlap with each other on the end portion side of second sealing plate130in the long-side direction. Second overlapping region R12is formed by arranging folded portions F side by side in the Z direction.

When connecting second current collector420and fourth current collector440to sixth current collector460, high-energy ray2is applied to at least one of second current collector420and sixth current collector460from between second sealing plate130and the end portion of case main body110on the second opening114side so as to weld second current collector420and sixth current collector460. Further, high-energy ray2is applied to at least one of fourth current collector440and sixth current collector460from between second sealing plate130and the end portion of case main body110on the second opening114side so as to weld fourth current collector440and sixth current collector460.

In first overlapping region R11, second current collector420and sixth current collector460are connected to each other by welding. In the present embodiment, second current collector420and sixth current collector460are connected to each other by welding at a welding position P1of first overlapping region R11.

In second overlapping region R12, fourth current collector440and sixth current collector460are connected to each other by welding. In the present embodiment, fourth current collector440and sixth current collector460are connected by welding at a welding position P2of second overlapping region R12.

A method of welding second current collector420or fourth current collector440to sixth current collector460is, for example, piercing welding. Sixth current collector460may be provided with a thin portion, and the current collectors may be welded to each other at the thin portion, or sixth current collector460may be provided with a through hole, and the current collectors may be welded to each other at a position away from the through hole.

Second electrode tab250and fourth electrode tab280are bent such that tip portions252,282face each other. Second sealing plate130is brought into abutment with case main body110. Thus, second electrode tab250and fourth electrode tab280are curved. As shown inFIG.14, second electrode tab250and fourth electrode tab280are curved along the shape of spacer600such that the folded portions of curved portions251,281are close to case main body110in the Y direction.

Thereafter, second sealing plate130is temporarily welded to case main body110. By the temporary joining, second sealing plate130is partially joined to second opening114of case main body110. Thus, second sealing plate130is positioned with respect to case main body110.

FIG.26is a perspective view showing a configuration of the secondary battery according to the first embodiment. As shown inFIGS.15and26, next, first sealing plate120and second sealing plate130are joined to case main body110(step S11). First sealing plate120seals first opening113of case main body110, and second sealing plate130seals second opening114of case main body110. Thus, first electrode assembly201and second electrode assembly202are accommodated in case100.

After the above-described steps, an inspection such as a leakage inspection is performed (step S12). After the leakage inspection, secondary battery1is dried to remove moisture in case100. Then, the electrolyte solution is injected into case100through injection hole134. When injecting the electrolyte solution, case100is inclined with second sealing plate130facing upward and first sealing plate120facing downward, thereby injecting the electrolyte solution into case100via injection hole134of second sealing plate130. Thereafter, charging is performed to result in release of gas. For performing the charging to result in release of gas, injection hole134may be temporarily sealed. Thereafter, the injection hole is sealed, thereby completing secondary battery1.

In each of secondary battery1and the method of manufacturing the same according to the first embodiment of the present technology, since first electrode assembly201is provided with first electrode tab220and second electrode tab250and second electrode assembly202is provided with third electrode tab270and fourth electrode tab280, first electrode assembly201and second electrode assembly202can be configured to have separate electrode tabs. With this configuration, the electrode tabs can be shortened as compared with a case where one collective electrode tab is formed by first electrode assembly201and second electrode assembly202and the electrode tab is bent. As a result, the occupied volume of the electrode tabs can be reduced, thereby improving the energy density of secondary battery1. Further, in the configuration in which the separate electrode tabs are respectively provided for first electrode assembly201and second electrode assembly202, the electrode tabs are readily bent and the electrode tabs and the current collectors can be therefore readily joined as compared with the case where one collective electrode tab is formed by first electrode assembly201and second electrode assembly202, with the result that the secondary battery can be stably manufactured. In particular, since secondary battery1can be stably manufactured, reliability of the connection portion between each of the electrode tabs and each of the current collectors can be increased.

In each of secondary battery1and the method of manufacturing the same according to the first embodiment of the present technology, by providing each of first overlapping region R11in which second current collector420and sixth current collector460overlap with each other and second overlapping region R12in which fourth current collector440and sixth current collector460overlap with each other, it is possible to secure a region in which the current collectors can be joined to each other, with the result that the current collectors can be stably connected to each other. When connecting the current collectors to each other by applying high-energy ray2from between second opening114and second sealing plate130of case main body110, a range in which the current collectors can be welded can be readily secured for the application of high-energy ray2in the second direction (Z direction) intersecting the first direction in which first opening113and second opening114are arranged side by side.

In each of secondary battery1and the method of manufacturing the same according to the first embodiment of the present technology, by providing each of the third overlapping region in which first current collector410and fifth current collector450overlap with each other and the fourth overlapping region in which third current collector430and fifth current collector450overlap with each other, it is possible to secure a region in which the current collectors can be joined to each other, with the result that the current collectors can be stably connected to each other. When connecting the current collectors to each other by applying a high-energy ray from between first opening113and first sealing plate120of case main body110, a range in which the current collectors can be welded can be readily secured for the application of the high-energy ray in the second direction (Z direction) intersecting the first direction in which first opening113and second opening114are arranged side by side.

In the method of manufacturing secondary battery1according to the first embodiment of the present technology, since second current collector420and sixth current collector460are welded by applying high-energy ray2to at least one of second current collector420and sixth current collector460from between second sealing plate130and the end portion of case main body110on the second opening114side and fourth current collector440and sixth current collector460are welded by applying high-energy ray2to at least one of fourth current collector440and sixth current collector460from between second sealing plate130and the end portion of case main body110on the second opening114side, the current collectors on the second opening114side can be stably connected to each other after electrode assembly200is inserted into case main body110.

Hereinafter, a secondary battery according to a second embodiment will be described. Since the secondary battery according to the second embodiment is different from secondary battery1according to the first embodiment of the present technology in terms of the connection structure between the electrode assembly and the current collector, the same configurations as those of secondary battery1according to the first embodiment of the present technology will not be described repeatedly.

Second Embodiment

FIG.27is a cross sectional view showing a configuration of the secondary battery according to the second embodiment. As shown inFIG.27, in the secondary battery according to the second embodiment, tip portions222A,272A of a first electrode tab220A and a third electrode tab270A are bent in the same direction in the Y direction.

Thereafter, a first electrode assembly201A and a second electrode assembly202A are inserted into the case main body, and first sealing plate120is brought into abutment with the case main body. Thus, first electrode tab220A and third electrode tab270A are curved in the same direction such that tip portions222A,272A located at the end portions thereof on the side opposite to the side on which the first electrode is connected are oriented in the same direction. In order to facilitate curving of tip portions222A,272A in the same direction, a third component630A of a spacer600A is provided between first electrode tab220A and third electrode tab270A.

Since tip portions222A,272A of first electrode tab220A and third electrode tab270A are curved in the same direction in the Y direction and the tip portions of the second electrode tab and the fourth electrode tab are curved in the same direction in the Y direction, first electrode assembly201A to which first current collector410and second current collector420are attached and second electrode assembly202A to which third current collector430and fourth current collector440are attached can be prepared to have the same configuration. Thus, first electrode assembly201A to which first current collector410and second current collector420are attached and second electrode assembly202A to which third current collector430and fourth current collector440are attached can be formed as electrode assemblies of one type and therefore can be readily manufactured.

Hereinafter, secondary batteries according to third to seventh embodiments will be described. Since each of the secondary batteries according to the third to seventh embodiments is different from secondary battery1according to the first embodiment of the present technology in terms of the connection structure between the current collectors, the same configurations as those of secondary battery1according to the first embodiment of the present technology will not be described repeatedly and the same configurations among the third to seventh embodiments will not be described repeatedly.

Third Embodiment

FIG.28is a perspective view showing a configuration of each of current collectors included in the secondary battery according to the third embodiment.FIG.29is a cross sectional view of the current collectors shown inFIG.28along XXIX-XXIX.

As shown inFIGS.28and29, each of a second current collector420B, a fourth current collector440B, and a sixth current collector460B in the present embodiment has a folded portion F on its end portion side in the Z direction. Folded portion F is inclined with respect to the YZ plane and is folded to have a protruding shape toward case main body110.

There is a clearance G1at a flat plate portion of each of second current collector420B, fourth current collector440B, and sixth current collector460B other than folded portion F. Thus, the current collectors are facilitated to be in contact with each other at folded portion F. Further, a reaction force due to bending of each electrode tab is applied toward the current collector. Thus, the current collectors can be brought into close contact with each other.

In each of the secondary battery and the method of manufacturing the same according to the third embodiment of the present technology, by providing each of a first overlapping region R31in which second current collector420B and sixth current collector460B overlap with each other and a second overlapping region R32in which fourth current collector440B and sixth current collector460B overlap with each other, it is possible to secure a region in which the current collectors can be joined to each other, with the result that the current collectors can be stably connected to each other. When connecting the current collectors to each other by applying high-energy ray2from between second opening114and second sealing plate130of case main body110, a range in which the current collectors can be welded can be readily secured for the application of high-energy ray2in the direction intersecting the first direction in which first opening113and second opening114are arranged side by side.

Fourth Embodiment

FIG.30is a perspective view showing a configuration of each of current collectors included in the secondary battery according to the fourth embodiment.FIG.31is a cross sectional view of the current collectors shown inFIG.30along XXXI-XXXI.

As shown inFIGS.30and31, each current collector in the present embodiment has a folded portion F on its end portion side in the Z direction. An extension portion E extending in the Z direction is provided at the tip of folded portion F.

There is a clearance G2at extension portion E of sixth current collector460C. As a result, a distance between the current collector and the insulating member can be provided, with the result that heat generated when joining the current collectors to each other using the high-energy ray is less likely to be transmitted to the insulating member.

By bringing extension portions E of second current collector420C and sixth current collector460C into abutment with each other, a first abutment region R41is formed to extend in the directions (Y and Z directions) intersecting the first direction (X direction) in which first opening113and second opening114are arranged side by side, first abutment region R41being a region in which second current collector420C and sixth current collector460C are in abutment with each other in the first direction (X direction). First abutment region R41includes an abutment plane between second current collector420C and sixth current collector460C. First abutment region R41expands on a plane intersecting the first direction (X direction). First abutment region R41extends in the Y direction and the Z direction. First abutment region R41is preferably disposed along second sealing plate130.

By bringing extension portions E of fourth current collector440C and sixth current collector460C into abutment with each other, a second abutment region R42is formed to extend in the directions (Y and Z directions) intersecting the first direction (X direction), second abutment region R42being a region in which fourth current collector440C and sixth current collector460C are in abutment with each other in the first direction (X direction).

At the end portion of first abutment region R41, second current collector420C and sixth current collector460C are connected by welding. At the end portion of second abutment region R42, fourth current collector440C and sixth current collector460C are connected by welding.

The connection between the current collectors on the first sealing plate120side of the secondary battery is configured in the same manner as the connection between the current collectors on the second sealing plate130side.

Specifically, a third abutment region is formed to extend in the direction intersecting the first direction, the third abutment region being a region in which the first current collector and the fifth current collector are in abutment with each other in the first direction (X direction). A fourth abutment region is formed to extend in the direction intersecting the first direction, the fourth abutment region being a region in which the third current collector and the fifth current collector are in abutment with each other in the first direction. The first current collector and the fifth current collector are connected to each other by welding at an end portion of the third abutment region. The third current collector and the fifth current collector are connected by welding at an end portion of the fourth abutment region.

In each of the secondary battery and the method of manufacturing the same according to the fourth embodiment of the present technology, by providing each of first abutment region R41and second abutment region R42, it is possible to secure a region in which the current collectors can be joined to each other, with the result that the current collectors can be readily stably connected to each other. In particular, a joining location can be secured between the current collectors without highly precisely positioning the current collectors to be joined to each other.

In each of the secondary battery and the method of manufacturing the same according to the fourth embodiment of the present technology, by providing each of the third abutment region and the fourth abutment region, it is possible to secure a region in which the first current collector or the third current collector and the fifth current collector can be joined to each other, with the result that the current collectors can be readily stably connected to each other.

Fifth Embodiment

FIG.32is a perspective view showing a configuration of each of current collectors included in the secondary battery according to the fifth embodiment.FIG.33is a cross sectional view of the current collectors shown inFIG.32along XXXIII-XXXIII.

As shown inFIGS.32and33, each of a second current collector420D, a fourth current collector440D, and a sixth current collector460D in the present embodiment has a folded portion F on its end portion side in the Z direction. An extension portion E extending in the Z direction is provided at the tip of folded portion F. The tips of extension portions E are bent in directions in which the current collectors joined are separated from each other. Since a contact portion of each extension portion E is located on the inner side with respect to the tip of extension portion E, dripping of weld is less likely to occur.

Sixth Embodiment

FIG.34is a perspective view showing a configuration of each of current collectors included in the secondary battery according to the sixth embodiment.FIG.35is a cross sectional view of the current collectors shown inFIG.34along XXXV-XXXV.

As shown inFIG.34andFIG.35, a sixth current collector460E in the present embodiment has a thicker thickness in the X direction than that of each of a second current collector420E and a fourth current collector440E. Thus, a large permissible amount of heat when joining the current collectors to each other using high-energy ray2can be secured in sixth current collector460E, with the result that the heat when joining the current collectors to each other using the high-energy ray can be less likely to be transmitted to the insulating member.

Each of second current collector420E and fourth current collector440E is provided with a fuse portion422E. When the current collector generates an excessive amount of heat, the current collector is melted first at fuse portion422E of the positive electrode current collector that is located as far as possible from the insulating member.

Seventh Embodiment

FIG.36is a cross sectional view showing a configuration of each of current collectors included in the secondary battery according to the seventh embodiment.

As shown inFIG.36, a sixth current collector460F in the present embodiment has a thicker thickness in the X direction than that of each of a second current collector420F and a fourth current collector. There is a clearance G3at extension portion E of sixth current collector460F located on the tip side of folded portion F. Thus, a distance between the current collector and the insulating member can be provided, with the result that heat generated when joining the current collectors to each other using high-energy ray2can be less likely to be transmitted to the insulating member.

In each of the secondary battery and the method of manufacturing the same according to each of the fifth to seventh embodiments of the present technology, by providing each of first abutment region R51, R61, R71and second abutment region R52, R62, it is possible to secure a region in which the current collectors can be joined to each other, with the result that the current collectors can be readily stably connected to each other. In particular, a joining location between the current collectors can be secured without highly precisely positioning the current collectors to be joined to each other.

Each of first sealing plate120and second sealing plate130preferably has a pair of long end sides disposed in parallel to each other and short end sides disposed in parallel to each other and shorter than the pair of long end sides. In this case, a direction in which the pair of long end sides extends is the long-side direction thereof.

Although the embodiments of the present invention have been described and shown in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.