Patent ID: 12230843

DESCRIPTION OF EMBODIMENTS

The structure of a rectangular secondary battery20, which is a secondary battery according to an embodiment, will now be described. The present invention is not limited to the embodiment.

FIG.1is a perspective view of the rectangular secondary battery20.FIG.2is a sectional view taken along line II-II inFIG.1. As illustrated inFIGS.1and2, the rectangular secondary battery20includes a battery case100constituted by a rectangular exterior body1having the shape of a rectangular tube with an opening and a bottom and a sealing plate2that seals the opening in the rectangular exterior body1. The rectangular exterior body1and the sealing plate2are each preferably made of a metal, for example, aluminum or an aluminum alloy. The rectangular exterior body1contains an electrode assembly3together with an electrolyte. The electrode assembly3has a stacked structure in which positive electrode plates and negative electrode plates are stacked together with separators interposed therebetween. An insulating sheet14made of a resin is disposed between the electrode assembly3and the rectangular exterior body1.

Positive-electrode tabs40and negative-electrode tabs50are provided at an end of the electrode assembly3that is adjacent to the sealing plate2. The positive-electrode tabs40are electrically connected to a positive electrode terminal7via a second positive-electrode current collector6band a first positive-electrode current collector6a. The negative-electrode tabs50are electrically connected to a negative electrode terminal9via a second negative-electrode current collector8band a first negative-electrode current collector8a. The first positive-electrode current collector6aand the second positive-electrode current collector6bconstitute a positive-electrode current collecting member6. The first negative-electrode current collector8aand the second negative-electrode current collector8bconstitute a negative-electrode current collecting member8. The positive-electrode current collecting member6may instead be constituted by a single component. Also, the negative-electrode current collecting member8may instead be constituted by a single component.

The positive electrode terminal7is fixed to the sealing plate2with an outer insulating member11made of a resin interposed therebetween. The negative electrode terminal9is fixed to the sealing plate2with an outer insulating member13made of a resin interposed therebetween. The positive electrode terminal7is preferably made of a metal, more preferably aluminum or an aluminum alloy. The negative electrode terminal9is preferably made of a metal, more preferably copper or a copper alloy.

A conductive path between the positive electrode terminal7and the positive electrode plates is preferably provided with a current interruption mechanism60that is activated to break the conductive path between the positive electrode terminal7and the positive electrode plates when a pressure in the battery case100reaches or exceeds a predetermined value. A conductive path between the negative electrode terminal9and the negative electrode plates may also be provided with a current interruption mechanism.

The sealing plate2is provided with a gas discharge valve17that breaks to enable gas in the battery case100to be discharged out of the battery case100when the pressure in the battery case100reaches or exceeds a predetermined value. The activating pressure of the gas discharge valve17is set to a pressure higher than the activating pressure of the current interruption mechanism60.

The sealing plate2has an electrolyte introduction hole15. The electrolyte introduction hole15is sealed by a sealing plug16after the electrolyte is introduced into the battery case100through the electrolyte introduction hole15. The sealing plug16is preferably a blind rivet.

A method for manufacturing the rectangular secondary battery20and components of the rectangular secondary battery20will now be described in detail.

[Production of Positive Electrode Plate]

A positive electrode slurry containing a lithium nickel cobalt manganese composite oxide as a positive electrode active material, polyvinylidene fluoride (PVdF) as a binder, a carbon material as a conductive agent, and N-methyl-2-pyrrolidone (NMP) as a dispersion medium is prepared. The positive electrode slurry is applied to both sides of a rectangular piece of aluminum foil having a thickness of 15 μm that serves as a positive electrode core. Then, the positive electrode slurry is dried to remove NMP contained therein so that positive electrode active material mixture layers are formed on the positive electrode core. After that, a compression process is performed so that the thickness of the positive electrode active material mixture layers is reduced to a predetermined thickness. The thus-obtained positive electrode plate is cut into a predetermined shape.

FIG.3is a plan view of a positive electrode plate4produced by the above-described method. As illustrated inFIG.3, the positive electrode plate4includes a main portion in which positive electrode active material mixture layers4bare formed on both sides of a positive electrode core4ahaving a rectangular shape. The positive electrode core4aprojects from an edge of the main portion, and the projecting portion of the positive electrode core4aconstitutes the positive-electrode tab40. The positive-electrode tab40may either be a portion of the positive electrode core4a, as illustrated inFIG.3, or be constituted by another member that is connected to the positive electrode core4a. The positive-electrode tab40preferably includes positive-electrode protecting layers4dhaving an electrical resistance higher than that of the positive electrode active material mixture layers4bin regions adjacent to the positive electrode active material mixture layers4b.

[Production of Negative Electrode Plate]

A negative electrode slurry containing graphite as a negative electrode active material, styrene-butadiene rubber (SBR) as a binder, carboxymethyl cellulose (CMC) as a thickener, and water is prepared. The negative electrode slurry is applied to both sides of a rectangular piece of copper foil having a thickness of 8 μm that serves as a negative electrode core. Then, the negative electrode slurry is dried to remove water contained therein so that negative electrode active material mixture layers are formed on the negative electrode core. After that, a compression process is performed so that the thickness of the negative electrode active material mixture layers is reduced to a predetermined thickness. The thus-obtained negative electrode plate is cut into a predetermined shape.

FIG.4is a plan view of a negative electrode plate5produced by the above-described method. As illustrated inFIG.4, the negative electrode plate5includes a main portion in which negative electrode active material mixture layers5bare formed on both sides of a negative electrode core5ahaving a rectangular shape. The negative electrode core5aprojects from an edge of the main portion, and the projecting portion of the negative electrode core5aconstitutes the negative-electrode tab50. The negative-electrode tab50may either be a portion of the negative electrode core5a, as illustrated inFIG.4, or be constituted by another member that is connected to the negative electrode core5a.

[Production of Electrode Assembly Unit]

Electrode assembly units (3aand3b) having a stacked structure are each produced by preparing50positive electrode plates4and51negative electrode plates5produced by the above-described method and stacking them together with rectangular separators made of polyolefin interposed therebetween. As illustrated inFIG.5, each electrode assembly element (3a,3b) having a stacked structure is formed so that the positive-electrode tabs40of the positive electrode plates4and the negative-electrode tabs50of the negative electrode plates5are stacked together at one end thereof. Each electrode assembly element (3a,3b) has separators at the outer sides thereof, and the electrode plates and the separators may be fastened together in the stacked state with a piece of tape or the like. Alternatively, the separators may be provided with adhesive layers so that the separators are bonded to the positive electrode plates4and to the negative electrode plates5.

The size of the separators in plan view is preferably greater than or equal to that of the negative electrode plates5. The positive electrode plates4and the negative electrode plates5may be stacked together after placing each of the positive electrode plates4between two separators and thermally welding the separators at the peripheral edge thereof. Each electrode assembly element (3a,3b) may instead be produced by using an elongated separator and stacking the positive electrode plates4and the negative electrode plates5while fan-folding the elongated separator, or by using an elongated separator and stacking the positive electrode plates4and the negative electrode plates5while winding the elongated separator.

[Attachment of Components to Sealing Plate (Positive Electrode Side)]

A method for attaching the positive electrode terminal7, the first positive-electrode current collector6a, and other components to the sealing plate2and the structure of a part including the positive electrode terminal7will be described with reference toFIGS.2and6to8.FIG.6is a perspective view illustrating the positive electrode terminal7, the outer insulating member11, the sealing plate2, a first insulating member10, and a conductive member61before assembly.FIG.7illustrates the sealing plate2to which the components are attached when viewed from the inside of the battery.FIG.7does not illustrate the positive-electrode tabs40and the negative-electrode tabs50.FIG.8Ais a sectional view of the part including the positive electrode terminal7taken along line VIIIA-VIIIA inFIG.7.FIG.8Bis a sectional view of the part including the positive electrode terminal7taken along line VIIIB-VIIIB inFIG.7.FIG.8Cis a sectional view of the part including the positive electrode terminal7taken along line VIIIC-VIIIC inFIG.7.

The outer insulating member11is placed on a surface of the sealing plate2that faces the outside of the battery in a region including a positive-electrode-terminal attachment hole2a. The first insulating member10and the conductive member61are placed on a surface of the sealing plate2that faces the inside of the battery in the region including the positive-electrode-terminal attachment hole2a. Next, an inserting portion7bprovided on one side of a flange7aof the positive electrode terminal7is inserted through a first terminal-receiving hole11ain the outer insulating member11, the positive-electrode-terminal attachment hole2ain the sealing plate2, a second terminal-receiving hole10din the first insulating member10, and a third terminal-receiving hole61cin the conductive member61. Then, the inserting portion7bis crimped onto the conductive member61at the end thereof. Thus, the positive electrode terminal7, the outer insulating member11, the sealing plate2, the first insulating member10, and the conductive member61are fixed together. When the inserting portion7bof the positive electrode terminal7is crimped, a large-diameter portion having an outer diameter greater than the inner diameter of the third terminal-receiving hole61cin the conductive member61is formed at the end of the inserting portion7b. The crimped portion of the inserting portion7bof the positive electrode terminal7is preferably welded to the conductive member61by, for example, laser welding. The first insulating member10and the outer insulating member11are each preferably made of a resin.

As illustrated inFIGS.6and8, the first insulating member10includes a first-insulating-member main portion10aarranged to face the sealing plate2. A pair of first side walls10bare provided at both ends of the first-insulating-member main portion10ain a long-side direction of the sealing plate2. A pair of second side walls10care provided at both ends of the first-insulating-member main portion10ain a short-side direction of the sealing plate2. The second terminal-receiving hole10dis formed in the first-insulating-member main portion10a. First connecting portions10eare provided on the outer surfaces of the second side walls10c. The first connecting portions10eare preferably provided at the centers of the second side walls10cin the long-side direction of the sealing plate2. Second connecting portions10fare also provided on the outer surfaces of the second side walls10c. The second connecting portions10fare preferably provided at ends of the second side walls10cin the long-side direction of the sealing plate2. A first groove10xis formed in a surface of the first-insulating-member main portion10athat faces the sealing plate2. A second groove10yis formed in a surface of the first-insulating-member main portion10athat faces the conductive member61. The second groove10yis disposed outside the first groove10x. The surface of the first-insulating-member main portion10athat faces the sealing plate2has recesses10gat four corners thereof.

As illustrated inFIGS.6and8, the conductive member61includes a conductive-member base portion61aarranged to face the first-insulating-member main portion10aand a tubular portion61bthat extends toward the electrode assembly3from an edge portion of the conductive-member base portion61a. The cross sectional shape of the tubular portion61balong a plane parallel to the sealing plate2may be either circular or polygonal. The tubular portion61bhas a flange61dat an end thereof adjacent to the electrode assembly3. A conductive-member opening portion61fis provided at the end of the tubular portion61bthat is adjacent to the electrode assembly3. A pressing projection61eis provided on a surface of the conductive-member base portion61athat faces the first insulating member10. The pressing projection61epresses the first insulating member10against the sealing plate2. The pressing projection61eis preferably provided at or near an edge portion around the third terminal-receiving hole61c.

Next, the deformation plate62is placed to cover the conductive-member opening portion61fof the conductive member61, and is welded to the conductive member61at the peripheral edge thereof by, for example, laser welding. Thus, the conductive-member opening portion61fof the conductive member61is sealed by the deformation plate62. The conductive member61and the deformation plate62are each preferably made of a metal, more preferably aluminum or an aluminum alloy.

FIG.9is a perspective view of the deformation plate62. InFIG.9, the electrode assembly3is at the upper side and the sealing plate2is at the lower side. As illustrated inFIG.9, the deformation plate62includes a stepped projection62athat projects toward the electrode assembly3at the center thereof. The stepped projection62aincludes a first projecting portion62a1and a second projecting portion62a2that has an outer diameter less than that of the first projecting portion62a1and that projects toward the electrode assembly3from the first projecting portion62a1. The deformation plate62has an annular rib62bthat projects toward the electrode assembly3at the peripheral edge thereof. An annular thin portion62chaving an annular shape is provided on a surface of the deformation plate62that faces the electrode assembly3. The deformation plate62may have any shape as long as the deformation plate62is capable of sealing the conductive-member opening portion61fof the conductive member61.

A method for fixing the second insulating member63and the first positive-electrode current collector6awill now be described with reference toFIG.10. InFIG.10, surfaces that face the electrode assembly3in the rectangular secondary battery20are at the upper side, and surfaces that face the sealing plate2are at the lower side.

As illustrated inFIG.10A, the first positive-electrode current collector6ahas a connection hole6c. An edge portion around the connection hole6cis connected to the deformation plate62by welding. The first positive-electrode current collector6aalso has four fixing holes6daround the connection hole6c. Although the number of fixing holes6dmay instead be one, two or more fixing holes6dare preferably provided. The first positive-electrode current collector6aalso has displacement prevention holes6earound the connection hole6c. Although the number of displacement prevention holes6emay be one, at least two displacement prevention holes6eare preferably provided. The displacement prevention holes6eare preferably disposed between the fixing holes6d. Each fixing hole6dpreferably includes a small diameter portion6d1and a large diameter portion6d2having an inner diameter greater than that of the small diameter portion6d1. The large diameter portion6d2is preferably closer to the electrode assembly3than the small diameter portion6d1is.

As illustrated inFIGS.8and10A, the second insulating member63includes an insulating-member first region63xarranged to face the deformation plate62, an insulating-member second region63yarranged to face the sealing plate2, and an insulating-member third region63zthat connects the insulating-member first region63xand the insulating-member second region63yto each other. The insulating-member first region63xhas an insulating-member first opening63aat the center thereof. A third wall portion63bis provided at an end of the insulating-member first region63xin the long-side direction of the sealing plate2. A third connecting portion63dis provided on the third wall portion63b. Fourth wall portions63care provided at both ends of the insulating-member first region63xin the short-side direction of the sealing plate2. Fourth connecting portions63eare provided on the fourth wall portions63c. In addition, four fixing projections63fare provided on a surface of the insulating-member first region63xthat faces the electrode assembly3. In addition, two displacement prevention projections63gare also provided. Four lug portions63hare provided on a surface of the insulating-member first region63xthat faces the sealing plate2. The insulating-member second region63yis located closer to the sealing plate2than the insulating-member first region63xis. The insulating-member second region63yhas an insulating-member second opening63ithat is located to face the electrolyte introduction hole15in the sealing plate2. An insulating-member annular rib63kthat extends toward the electrode assembly3is provided at an edge portion around the insulating-member second opening63i.

As illustrated inFIG.10B, the first positive-electrode current collector6ais placed on the second insulating member63such that the fixing projections63fof the second insulating member63are inserted in the fixing holes6din the first positive-electrode current collector6aand that the displacement prevention projections63gof the second insulating member63are inserted in the displacement prevention holes6ein the first positive-electrode current collector6a. Then, end portions of the fixing projections63fof the second insulating member63are deformed by, for example, heat crimping. Thus, as illustrated inFIGS.8C and10C, large-diameter portions63f1are formed at the ends of the fixing projections63fof the second insulating member63, and the second insulating member63and the first positive-electrode current collector6aare fixed together.

As illustrated inFIG.8C, the large-diameter portions63f1formed at the ends of the fixing projections63fof the second insulating member63are preferably disposed in the large diameter portions6d2of the fixing holes6d.

Unlike the fixing projections63f, the displacement prevention projections63gof the second insulating member63are not subjected to heat crimping.

The outer diameter of the fixing projections63fis preferably greater than the outer diameter of the displacement prevention projections63g. The inner diameter of the small diameter portions6d1of the fixing holes6din the first positive-electrode current collector6ais preferably greater than the inner diameter of the displacement prevention holes6ein the first positive-electrode current collector6a.

Next, as illustrated inFIGS.8A to8C, the second insulating member63to which the first positive-electrode current collector6ais fixed is connected to the first insulating member10and the conductive member61.

As illustrated inFIG.8B, the fourth connecting portions63eof the second insulating member63are connected to the first connecting portions10eof the first insulating member10. In addition, as illustrated inFIG.8C, the lug portions63hof the second insulating member63are connected to the flange61dof the conductive member61. Thus, the second insulating member63is connected to the first insulating member10and the conductive member61. The second insulating member63is not necessarily connected to both the first insulating member10and the conductive member61. The second insulating member63is preferably connected to at least one of the first insulating member10and the conductive member61. Thus, even when the rectangular secondary battery20is strongly impacted or vibrated, load applied to weak portions of the first positive-electrode current collector6acan be reduced. Accordingly, the risk of damage or breakage of the weak portions of the first positive-electrode current collector6acan be reduced.

The deformation plate62is connected to the first positive-electrode current collector6aby welding.FIG.11is an enlarged view of a part ofFIG.8Aincluding the connecting portion between the deformation plate62and the first positive-electrode current collector6a. As illustrated inFIG.11, the second projecting portion62a2of the deformation plate62is placed in the connection hole6cin the first positive-electrode current collector6a. Then, the second projecting portion62a2of the deformation plate62and the edge portion around the connection hole6cin the first positive-electrode current collector6aare welded and connected together by, for example, laser welding. The connecting portion between the deformation plate62and the first positive-electrode current collector6ais formed at a position corresponding to the position of the insulating-member first opening63ain the second insulating member63.

The first positive-electrode current collector6ahas a thin portion6fin a region around the connection hole6c. The thin portion6fhas an annular notch6gthat surrounds the connection hole6c. An annular connection rib6his formed along the edge portion around the connection hole6c. The connection rib6his connected to the deformation plate62by welding. The first positive-electrode current collector6aand the deformation plate62may be welded either in an annular region over the entire circumference around the connection hole6cor in a non-annular region having unwelded portions. The first positive-electrode current collector6aand the deformation plate62may be welded at multiple locations that are separated from each other along the edge portion around the connection hole6c.

The operation of the current interruption mechanism60will now be described. When the pressure in the battery case100increases, the deformation plate62is deformed such that a central portion thereof moves toward the sealing plate2. When the pressure in the battery case100reaches or exceeds a predetermined value, the notch6gin the thin portion6fof the first positive-electrode current collector6abreaks due to the deformation of the deformation plate62. Accordingly, the conductive path from the positive electrode plates4to the positive electrode terminal7is broken. Thus, the current interruption mechanism60includes the first positive-electrode current collector6a, the deformation plate62, and the conductive member61. When the rectangular secondary battery20is overcharged and the pressure in the battery case100is increased, the current interruption mechanism60is activated and breaks the conductive path from the positive electrode plates4to the positive electrode terminal7. As a result, further overcharging is prevented. The activation pressure at which the current interruption mechanism60is activated may be determined as appropriate.

A leakage test for a welding portion between the conductive member61and the deformation plate62may be performed before welding the deformation plate62and the first positive-electrode current collector6atogether by introducing gas into the space inside the conductive member61through a terminal through hole7cformed in the positive electrode terminal7. The terminal through hole7cis sealed by a terminal sealing member7x. The terminal sealing member7xpreferably includes a metal member7yand a rubber member7z.

FIG.12is a perspective view of the sealing plate2to which the first insulating member10, the conductive member61, the deformation plate62, the second insulating member63, and the first positive-electrode current collector6aare attached. As illustrated inFIG.12, the third connecting portion63dis provided at an end of the second insulating member63in the long-side direction of the sealing plate2. In addition, the second connecting portions10fare provided at both ends of the first insulating member10in the short-side direction of the short-side direction.

[Attachment of Components to Sealing Plate (Negative Electrode Side)]

A method for attaching the negative electrode terminal9and the first negative-electrode current collector8ato the sealing plate2will now be described with reference toFIGS.2and13. The outer insulating member13is placed on a surface of the sealing plate2that faces the outside of the battery in a region including a negative-electrode-terminal attachment hole2b. An inner insulating member12and the first negative-electrode current collector8aare placed on a surface of the sealing plate2that faces the inside of the battery in the region including the negative-electrode-terminal attachment hole2b. Next, the negative electrode terminal9is inserted through a through hole in the outer insulating member13, the negative-electrode-terminal attachment hole2bin the sealing plate2, a through hole in the inner insulating member12, and a through hole in the first negative-electrode current collector8a. Then, an end portion of the negative electrode terminal9is crimped onto the first negative-electrode current collector8a. Thus, the outer insulating member13, the sealing plate2, the inner insulating member12, and the first negative-electrode current collector8aare fixed together. The crimped portion of the negative electrode terminal9is preferably welded and connected to the first negative-electrode current collector8aby, for example, laser welding. The inner insulating member12and the outer insulating member13are each preferably made of a resin.

[Connection Between Current Collectors and Tabs]

FIG.14illustrates a method for connecting the positive-electrode tabs40to the second positive-electrode current collector6band the negative-electrode tabs50to the second negative-electrode current collector8b. Two electrode assembly elements are produced by the above-described method, and are referred to as a first electrode assembly element3aand a second electrode assembly element3b. The first electrode assembly element3aand the second electrode assembly element3bmay have completely the same structure or different structures. The positive-electrode tabs40of the first electrode assembly element3aform a first positive-electrode tab group40a. The negative-electrode tabs50of the first electrode assembly element3aform a first negative-electrode tab group50a. The positive-electrode tabs40of the second electrode assembly element3bform a second positive-electrode tab group40b. The negative-electrode tabs50of the second electrode assembly element3bform a second negative-electrode tab group50b.

The second positive-electrode current collector6band the second negative-electrode current collector8bare disposed between the first electrode assembly element3aand the second electrode assembly element3b. The first positive-electrode tab group40a, which is formed of the positive-electrode tabs40in a stacked state that project from the first electrode assembly element3a, is placed on the second positive-electrode current collector6b, and the first negative-electrode tab group50a, which is formed of the negative-electrode tabs50in a stacked state that project from the first electrode assembly element3a, is placed on the second negative-electrode current collector8b. The second positive-electrode tab group40b, which is formed of the positive-electrode tabs40in a stacked state that project from the second electrode assembly element3b, is placed on the second positive-electrode current collector6b, and the second negative-electrode tab group50b, which is formed of the negative-electrode tabs50in a stacked state that project from the second electrode assembly element3b, is placed on the second negative-electrode current collector8b. The first positive-electrode tab group40aand the second positive-electrode tab group40bare connected to the second positive-electrode current collector6bby welding to form welded connecting portions90. The first negative-electrode tab group50aand the second negative-electrode tab group50bare connected to the second negative-electrode current collector8bby welding to form welded connecting portions90. The welding and connecting process may be performed as described below.

The tabs in a stacked state (the first positive-electrode tab group40a, the second positive-electrode tab group40b, the first negative-electrode tab group50a, and the second negative-electrode tab group50b) and the current collectors (the second positive-electrode current collector6band the second negative-electrode current collector8b) are clamped by a pair of welding jigs from above and below and are welded together. The welding method is preferably ultrasonic welding or resistance welding. The pair of welding jigs are a pair of resistance welding electrodes for resistance welding, and are a horn and an anvil for ultrasonic welding. The tabs (the first positive-electrode tab group40a, the second positive-electrode tab group40b, the first negative-electrode tab group50a, and the second negative-electrode tab group50b) and the current collectors (the second positive-electrode current collector6band the second negative-electrode current collector8b) may instead be connected by laser welding.

As illustrated inFIG.14, the second positive-electrode current collector6bincludes a current-collector first region6b1and a current-collector second region6b2. The positive-electrode tabs40are connected to the current-collector first region6b1. A current-collector second opening6zis formed in the current-collector first region6b1. The current-collector first region6b1and the current-collector second region6b2are connected to each other by a current-collector third region6b3. When the second positive-electrode current collector6bis connected to the first positive-electrode current collector6a, the current-collector second opening6zis at a position corresponding to the position of the electrolyte introduction hole15in the sealing plate2. A current-collector first opening6yis formed in the current-collector second region6b2. A current-collector first recess6mis formed around the current-collector first opening6y. Target holes6kare formed on both sides of the current-collector first opening6yin the short-side direction of the sealing plate2.

As illustrated inFIG.14, the second negative-electrode current collector8bincludes a current-collector first region8b1and a current-collector second region8b2. The negative-electrode tabs50are connected to the current-collector first region8b1. A current-collector first opening8yis formed in the current-collector second region8b2. A current-collector first recess8fis formed around the current-collector first opening8y. Target holes8eare formed on both sides of the current-collector first opening8yin the short-side direction of the sealing plate2.

[Connection Between First Positive-Electrode Current Collector and Second Positive-Electrode Current Collector]

As illustrated inFIGS.2,7, and8and other drawings, the second positive-electrode current collector6bis placed on the second insulating member63such that a current-collector projection6xon the first positive-electrode current collector6ais inserted in the current-collector first opening6yin the second positive-electrode current collector6b. Then, the current-collector projection6xon the first positive-electrode current collector6ais welded to an edge portion around the current-collector first opening6yin the second positive-electrode current collector6bby irradiation with an energy ray, such as a laser beam. Thus, the first positive-electrode current collector6aand the second positive-electrode current collector6bare connected together. The first positive-electrode current collector6aand the second positive-electrode current collector6bare preferably welded together in the current-collector first recess6m.

As illustrated inFIGS.2and8, the distance between the sealing plate2and the current-collector first region6b1is less than the distance between the sealing plate2and the current-collector second region6b2in the direction perpendicular to the sealing plate2. According to this structure, the space occupied by the current collecting unit can be reduced, and the volume energy density of the rectangular secondary battery can be increased.

When the first positive-electrode current collector6aand the second positive-electrode current collector6bare welded together by irradiation with an energy ray, such as a laser beam, the target holes6kare preferably used as image correction targets.

As illustrated inFIG.8A, the first positive-electrode current collector6ahas a current-collector second recess6win a surface thereof that faces the second insulating member63at a position behind the current-collector projection6x. Accordingly, a larger welded connecting portion can be more easily formed between the first positive-electrode current collector6aand the second positive-electrode current collector6b. In addition, the current-collector second recess6wreduces the risk that the second insulating member63will be damaged by heat generated in the welding process when the first positive-electrode current collector6aand the second positive-electrode current collector6bare connected together by welding.

[Connection Between First Negative-Electrode Current Collector and Second Negative-Electrode Current Collector]

As illustrated inFIG.13, the second negative-electrode current collector8bincludes the current-collector first region8b1and the current-collector second region8b2. The negative-electrode tabs50are connected to the current-collector first region8b1. The current-collector first opening8yis formed in the current-collector second region8b2. The current-collector first region8b1and the current-collector second region8b2are connected to each other by a current-collector third region8b3.

As illustrated inFIG.13, the second negative-electrode current collector8bis placed on the inner insulating member12such that a current-collector projection8xon the first negative-electrode current collector8ais inserted in the current-collector first opening8yin the second negative-electrode current collector8b. Then, the current-collector projection8xon the first negative-electrode current collector8ais welded to an edge portion around the current-collector first opening8yin the second negative-electrode current collector8bby irradiation with an energy ray, such as a laser beam. Thus, the first negative-electrode current collector8aand the second negative-electrode current collector8bare connected together. The first negative-electrode current collector8aand the second negative-electrode current collector8bare preferably welded together in the current-collector first recess8f. Similar to the second positive-electrode current collector6b, the second negative-electrode current collector8bhas the target holes8e. The distance between the sealing plate2and the current-collector first region8b1is less than the distance between the sealing plate2and the current-collector second region8b2in the direction perpendicular to the sealing plate2. The first negative-electrode current collector8amay be omitted, and the second negative-electrode current collector8bmay be connected to the negative electrode terminal9.

As illustrated inFIG.13, the first negative-electrode current collector8ahas a current-collector second recess8win a surface thereof that faces the inner insulating member12at a position behind the current-collector projection8x. Accordingly, a larger welded connecting portion can be more easily formed between the first negative-electrode current collector8aand the second negative-electrode current collector8b. In addition, the current-collector second recess8wreduces the risk that the inner insulating member12will be damaged by heat generated in the welding process when the first negative-electrode current collector8aand the second negative-electrode current collector8bare connected together by welding.

The current-collector projection6xand the current-collector projection8xare preferably not circular, and are preferably rectangular, elliptical, or track-shaped in plan view.

[Attachment of Cover]

FIG.15is a perspective view of the sealing plate2to which the components are attached and a cover80. The positive-electrode tabs40are not illustrated inFIG.15. The cover80includes a cover main portion80aarranged to face the first positive-electrode current collector6aand a pair of arm portions80bthat extend toward the sealing plate2from both ends of the cover main portion80ain the short-side direction of the sealing plate2. The cover80also includes a cover wall portion80ethat extends toward the sealing plate2from an end of the cover main portion80ain the long-side direction of the sealing plate2. Connecting projections80care provided on inner surfaces of the arm portions80b. The cover main portion80ahas base openings80dat positions near the base ends of the arm portions80b. The cover wall portion80ehas a wall portion opening80f.

As illustrated inFIGS.16A and16B, the cover80is connected to the first insulating member10and the second insulating member63so that the cover main portion80aof the cover80faces the first positive-electrode current collector6a. The connecting projections80con the pair of arm portions80bof the cover80are connected to the second connecting portions10fof the first insulating member10. The cover wall portion80eof the cover80is connected to the third connecting portion63dof the second insulating member63.

As illustrated inFIG.17A, the third connecting portion63dis a projection provided on the third wall portion63b. The third connecting portion63dis fitted to the wall portion opening80fin the cover wall portion80eso that the first insulating member10and the cover80are connected together. As illustrated inFIG.17B, the connecting projections80con the arm portions80bof the cover80are connected to the second connecting portions10fof the first insulating member10by being engaged therewith.

The cover80is preferably made of resin. In addition, the cover80is preferably composed of an insulating member.

As illustrated inFIGS.17A and17B, a gap is preferably provided between the first positive-electrode current collector6aand the top surface of the cover main portion80aof the cover80. Such a structure allows gas to smoothly flow along the bottom surface of the deformation plate62, so that the deformation plate62is smoothly deformed when the pressure in the battery case100reaches or exceeds the predetermined value. However, it is not necessary that the above-described gap be provided.

As illustrated inFIG.17B, the cover main portion80aof the cover80preferably has the base openings80d. In such a case, gas smoothly flows along the bottom surface of the deformation plate62, so that the deformation plate62is smoothly deformed when the pressure in the battery case100reaches or exceeds the predetermined value. However, it is not necessary that the base openings80dbe provided.

[Production of Electrode Assembly]

The first positive-electrode tab group40a, the second positive-electrode tab group40b, the first negative-electrode tab group50a, and the second negative-electrode tab group50bare bent so that the top surfaces of the first electrode assembly element3aand the second electrode assembly element3billustrated inFIG.14are in contact with each other directly or with another component interposed therebetween. Thus, the first electrode assembly element3aand the second electrode assembly element3bare combined together to form a single electrode assembly3. The first electrode assembly element3aand the second electrode assembly element3bare preferably combined together by using a piece of tape or the like. Alternatively, the first electrode assembly element3aand the second electrode assembly element3bare preferably combined together by placing the first electrode assembly element3aand the second electrode assembly element3bin the insulating sheet14formed in a box shape or a bag shape.

[Assembly of Rectangular Secondary Battery]

The electrode assembly3attached to the sealing plate2is covered with the insulating sheet14, and is inserted into the rectangular exterior body1. The insulating sheet14is preferably flat sheet shaped, and is folded into a box shape or a bag shape. Then, the sealing plate2and the rectangular exterior body1are joined together by, for example, laser welding to seal the opening in the rectangular exterior body1. After that, a nonaqueous electrolyte containing an electrolyte solvent and an electrolyte salt is introduced into the battery case100through the electrolyte introduction hole15in the sealing plate2. Then, the electrolyte introduction hole15is sealed with the sealing plug16. Thus, the rectangular secondary battery20is produced.

[Regarding Rectangular Secondary Battery20]

As illustrated inFIGS.8,17, and18, the conductive member61includes a pressing projection61ethat projects toward the first insulating member10in a region where the conductive member61faces the first insulating member10. Accordingly, the pressing projection61estrongly presses the first insulating member10against the sealing plate2. Therefore, gas around the electrode assembly3does not flow through a gap between the sealing plate2and the first insulating member10or a gap between the first insulating member10and the conductive member61toward the connecting portion between the conductive member61and the positive electrode terminal7. As a result, gas does not flow into the space defined by the conductive member61and the deformation plate62through a gap between the conductive member61and the positive electrode terminal7. This ensures reliable activation of the current interruption mechanism60when the pressure in the rectangular exterior body1increases in case of abnormal operation of the rectangular secondary battery20. Thus, the reliability of the rectangular secondary battery20is increased.

The pressing projection61eis formed on a surface of the conductive-member base portion61aof the conductive member61that faces the sealing plate2. When the conductive member61and the positive electrode terminal7are viewed in the direction perpendicular to the sealing plate2, the pressing projection61epreferably overlaps a crimped portion7d(large diameter portion) of the inserting portion7bof the positive electrode terminal7. In addition, the pressing projection61eis preferably formed along the edge of the third terminal-receiving hole61cin the conductive member61. However, the pressing projection61emay instead be formed at a position separated from the edge of the third terminal-receiving hole61cin the conductive member61. The pressing projection61epreferably has an annular shape in plan view. However, the shape of the pressing projection61ein plan view is not limited to an annular shape, and may instead be a shape obtained by partially cutting an annular shape. For example, the length of the pressing projection61emay be 70% or more of that in the case where the pressing projection61ehas an annular shape. When the pressing projection61eis formed on the conductive member61, the pressing projection61ecan be easily formed in a desired shape.

When the first insulating member10pressed by the pressing projection61eis deformed to move in the horizontal direction (direction parallel to the sealing plate2, leftward inFIG.18), there is a risk that a gap will be formed between the sealing plate2and the first insulating member10or between the first insulating member10and the conductive member61due to the deformation of the first insulating member10. Such a risk can be reduced by forming a groove in a portion of the first insulating member10that is disposed between the sealing plate2and the conductive member61and that is on the outer side of the pressing projection61ein the radial direction of the second terminal-receiving hole10din the first insulating member10. For example, a first groove10xis preferably formed in a surface of the first insulating member10that faces the sealing plate2. Also, a second groove10yis preferably formed in a surface of the first insulating member10that faces the conductive member61in addition to or in place of the first groove10x. The first insulating member10may have only one of the first groove10xand the second groove10y. Alternatively, the first insulating member10may have the second groove10yin the surface thereof facing the sealing plate2, and the first groove10xin the surface thereof facing the conductive member61. The first groove10xand the second groove10yare not essential.

The first groove10xpreferably has an annular shape in plan view. The second groove10ypreferably also has an annular shape in plan view. However, the shape of the first groove10xand the second groove10yin plan view is not limited to an annular shape, and may instead be a shape obtained by partially cutting an annular shape. For example, the length of the first groove10xand the second groove10ymay be 70% or more of that in the case where the first groove10xand the second groove10yhave an annular shape.

When grooves are formed in both surfaces of the first insulating member10, the grooves are preferably arranged such that one of the grooves is on the outer side the other groove in the radial direction of the second terminal-receiving hole10din the first insulating member10. In other words, when the grooves are formed in both surfaces of the first insulating member10, the distance from the second terminal-receiving hole10din the first insulating member10to one of the grooves is preferably greater than the distance from the second terminal-receiving hole10din the first insulating member10to the other groove.

In addition, the distance between the center of one of the grooves and the center of the other groove in the radial direction of the second terminal-receiving hole10din the first insulating member10(distance D inFIG.18) is preferably 0.5 mm to 10 mm, and more preferably 0.5 mm to 5 mm.

For example, the first insulating member10is formed such that the second groove10yis on the outer side of the first groove10xin the radial direction of the second terminal-receiving hole10din the first insulating member10. Referring toFIG.18, the distance D between the center of the first groove10xin the width direction and the center of the second groove10yin the width direction is preferably 0.5 mm to 10 mm, and more preferably 0.5 mm to 5 mm. The width of the first groove10xand the second groove10y(width in the left-right direction inFIG.18) is preferably 0.5 mm to 2 mm.

Preferably, the first groove10xand the second groove10ypartially overlap in plan view of the first insulating member10. However, preferably, the first groove10xand the second groove10ydo not completely overlap in plan view of the first insulating member10. According to such a structure, deformation of the first insulating member10can be more effectively reduced.

The width of the pressing projection61ein the radial direction of the third terminal-receiving hole61cin the conductive member61is preferably 5 mm or less, and more preferably 2 mm. The distance between the pressing projection61eand the first groove10xin the radial direction of the third terminal-receiving hole61cin the conductive member61is preferably 0.5 mm to 5 mm, more preferably 0.5 mm to 2 mm, and still more preferably 0.5 mm to 1 mm.

The above configuration is particularly effective when the first insulating member10is made of a relatively soft material, such as perfluoroalkoxy alkane (PFA) or polytetrafluoroethylene (PTFE).

As illustrated inFIG.18, an edge portion around the third terminal-receiving hole61cin the conductive member61preferably includes a tapered portion61gon a side thereof facing the electrode assembly3. According to such a structure, a gap is not easily formed between the positive electrode terminal7and the conductive member61, and the risk that gas will flow through the gap between the positive electrode terminal7and the conductive member61can be effectively reduced.

The conductive member61is preferably made of aluminum or an aluminum alloy. The positive electrode terminal7is also preferably made of aluminum or an aluminum alloy.

As illustrated inFIG.10, the second insulating member63and the first positive-electrode current collector6aare fixed together by inserting the fixing projections63fof the second insulating member63into the fixing holes6din the first positive-electrode current collector6aand forming the large-diameter portions63f1by increasing the diameter of the end portions of the fixing projections63f. According to this structure, load applied to weak portions of the first positive-electrode current collector6a, such as the thin portion6fand the notch6g, can be reduced when the rectangular secondary battery20is strongly impacted or vibrated. The second insulating member63is preferably connected to at least one of the first insulating member10and the conductive member61.

In the case where the second insulating member63is made of resin, there is a risk that gaps will be formed between side surfaces of the fixing projections63fof the second insulating member63and the inner surfaces of the fixing holes6din the first positive-electrode current collector6adue to distortion or contraction of the fixing projections63fwhen the diameter of the end portions of the fixing projections63fis increased after inserting the fixing projections63finto the fixing holes6d. Such gaps may cause a displacement of the first positive-electrode current collector6awith respect to the second insulating member63in a direction parallel to the sealing plate2when the rectangular secondary battery20is strongly impacted or vibrated. In the case where the end portions of the fixing projections63fare increased in diameter while being heated, the above-described gaps are easily formed due to thermal contraction of portions of the fixing projections63fin the fixing holes6d.

The rectangular secondary battery20is configured such that the second insulating member63includes the displacement prevention projections63gand that the displacement prevention projections63gare disposed in the displacement prevention holes6ein the first positive-electrode current collector6a. Unlike the fixing projections63f, the displacement prevention projections63gare not increased in diameter. Therefore, even when gaps are formed between the fixing projections63fand the fixing holes6d, since the displacement prevention projections63gare fitted to the displacement prevention holes6e, displacement of the first positive-electrode current collector6awith respect to the second insulating member63can be effectively reduced.

Preferably, a plurality of fixing projections63fare provided around the connecting portion between the deformation plate62and the first positive-electrode current collector6a. In particular, the fixing projections63fare preferably provided at four or more locations. The displacement prevention projections63gare preferably provided on both sides of the connecting portion between the deformation plate62and the first positive-electrode current collector6a. In addition, the displacement prevention projections63gare preferably disposed between the fixing projections63f.

The diameter of the fixing projections63fis preferably greater than the diameter of the displacement prevention projections63g.

When the displacement prevention holes6eare provided at two locations, the inner diameter of one displacement prevention hole6emay be greater than that of the other. In addition, when the displacement prevention projections63gare provided at two locations, the outer diameter of one displacement prevention projection63gmay be greater than that of the other.

The ratio of the outer diameter of the displacement prevention projections63gto the inner diameter of the displacement prevention holes6eis preferably 0.95 to 1. The difference between the inner diameter of the displacement prevention holes6eand the outer diameter of the displacement prevention projections63gis preferably less than or equal to 0.1 mm.

When a plurality of fitting portions at which the displacement prevention projections63gare fitted to the displacement prevention holes6eare provided, the difference between the inner diameter of the displacement prevention hole6eand the outer diameter of the displacement prevention projection63gat one of the fitting portions may differ from the difference between the inner diameter of the displacement prevention hole6eand the outer diameter of the displacement prevention projection63gat another one of the fitting portions.

Preferably, each displacement prevention hole6eis not a notch formed in an edge portion of the first positive-electrode current collector6a, but is formed such that an edge portion therearound has an annular shape. In other words, the side surface of each displacement prevention projection63gis preferably surrounded by the first positive-electrode current collector6aover the entire circumference thereof. In such a case, displacement can be more effectively reduced.

Preferably, the displacement prevention holes6eare provided on both sides of the connecting portion between the deformation plate62and the first positive-electrode current collector6ain the short-side direction of the sealing plate2. In addition, preferably, the connecting portion between the deformation plate62and the first positive-electrode current collector6ais disposed between two displacement prevention holes6eon a straight line connecting the two displacement prevention holes6e. Accordingly, load applied to the connecting portion between the deformation plate62and the first positive-electrode current collector6a, the thin portion6f, and the notch6gcan be reliably reduced.

The end portions of the fixing projections63fpreferably have recesses before the diameter thereof is increased. In such a case, load applied to the base ends of the fixing projections63fwhen the end portions of the fixing projections63fare increased in diameter can be reduced.

As illustrated inFIGS.16and17, the cover80is disposed between the first positive-electrode current collector6aand the electrode assembly3. According to this structure, even when the rectangular secondary battery20is strongly impacted or vibrated and the electrode assembly3is moved toward the sealing plate2, the electrode assembly3can be prevented from coming into contact with the first positive-electrode current collector6aand causing damage or breakage of, for example, the weak portions of the first positive-electrode current collector6a, such as the thin portion6fand the notch6g, and the connecting portion between the deformation plate62and the first positive-electrode current collector6a. Accordingly, a secondary battery with increased reliability can be provided. The cover80is preferably made of resin. In addition, the cover80is preferably electrically insulative.

The cover80is preferably formed as a component separate from the first insulating member10and the second insulating member63. When, for example, the cover80is a component separate from the first insulating member10and the second insulating member63, the secondary battery can be easily assembled. In addition, when the cover80and the second insulating member63are separate components, a projection may be formed on a surface of the second insulating member63that faces the first positive-electrode current collector6a, and the second insulating member63and the first positive-electrode current collector6acan be strongly connected together by using the projection.

A gap is preferably provided between the first positive-electrode current collector6aand the cover main portion80aof the cover80. The distance between a surface of the first positive-electrode current collector6athat faces the electrode assembly and a surface of the cover main portion80athat faces the sealing plate is preferably 0.1 mm to 5 mm, and more preferably 0.5 to 2 mm.

Preferably, a portion of the cover80that extends toward the sealing plate2from the cover main portion80ais connected to at least one of the first insulating member10and the second insulating member63so that a gap is provided between the first positive-electrode current collector6aand the cover main portion80a. According to this structure, even when the electrode assembly3moves toward the sealing plate2and comes into contact with the cover80, the cover80absorbs the impact to some extent and thereby prevents the electrode assembly3from being damaged.

Preferably, the cover80is connected to at least one of the first insulating member10and the second insulating member63. More preferably, the cover80is connected to each of the first insulating member10and the second insulating member63. For example, preferably, the cover80includes the cover main portion80aand the pair of arm portions80bthat extend from the cover main portion80atoward the sealing plate2, and the arm portions80bare connected to the first insulating member10. In addition, preferably, the cover main portion80ais provided with the cover wall portion80e, and the cover wall portion80eis connected to the second insulating member63.

The cover main portion80apreferably has through holes. Such a structure enables gas to smoothly flow below the deformation plate62. The base openings80dformed in the cover main portion80aat positions near the base ends of the arm portions80bpreferably serve as the through holes.

When the positive-electrode current collecting member includes the first positive-electrode current collector6aand the second positive-electrode current collector6b, the cover80is preferably disposed between the electrode assembly3and the connecting portion between the first positive-electrode current collector6aand the second positive-electrode current collector6b. According to this structure, even when the rectangular secondary battery20is strongly vibrated or impacted and the electrode assembly3is moved toward the sealing plate2, the electrode assembly3can be prevented from coming into contact with the connecting portion between the first positive-electrode current collector6aand the second positive-electrode current collector6band causing damage or breakage of the connecting portion between the first positive-electrode current collector6aand the second positive-electrode6bcurrent collector. A surface of the cover main portion80athat faces the first positive-electrode current collector6ais preferably formed such that a portion thereof that faces the connecting portion between the first positive-electrode current collector6aand the second positive-electrode current collector6bis recessed from a portion thereof that faces the connecting portion between the deformation plate62and the first positive-electrode current collector6a.

The cover80is preferably connected to at least one of the first insulating member10and the second insulating member63after the second positive-electrode current collector6bto which the positive-electrode tabs40are connected is connected to the first positive-electrode current collector6ato which the deformation plate62is connected.

As illustrated inFIGS.8and9, the deformation plate62includes the annular rib62bthat projects toward the electrode assembly3(upward inFIG.9) at the outer peripheral edge thereof. The annular rib62bis fitted to an end portion of the tubular portion61bof the conductive member61that is adjacent to the electrode assembly3, and is connected to the conductive member61by welding. The deformation plate62also includes the annular thin portion62cin a region closer to the center than the annular rib62bis. According to this structure, even if the thickness of the deformation plate62is increased, the deformation plate62can be smoothly deformed when the pressure in the rectangular exterior body1reaches or exceeds the predetermined value. The thermal capacity of the deformation plate62can be increased by increasing the thickness of the deformation plate62. Therefore, even when the weak portions of the first positive-electrode current collector6a, such as the thin portion6fand the notch6g, are heated, the generated heat is transferred to the deformation plate62, and fusion breakage of the weak portions of the first positive-electrode current collector6a, such as the thin portion6fand the notch6g, can be prevented. The annular connection rib6his preferably provided along the edge portion around the connection hole6cin the first positive-electrode current collector6a. Accordingly, the thermal capacity of the first positive-electrode current collector6acan be increased in regions around the weak portions thereof, such as the thin portion6fand the notch6g. As a result, fusion breakage of the weak portions of the first positive-electrode current collector6a, such as the thin portion6fand the notch6g, can be more effectively prevented.

The deformation plate62is preferably inclined toward the sealing plate2in the direction from the outer peripheral edge toward the center thereof. The annular thin portion62cis preferably formed by forming a recess in a surface of the deformation plate62that faces the electrode assembly3. Such a configuration enables a smooth deformation of the deformation plate62. The width of the annular thin portion62cin plan view is preferably 1 mm to 3 mm, and more preferably 1.5 mm to 2 mm.

After the gas discharge valve17breaks and gas in the battery case100is discharged to the outside of the battery case100, the deformation plate62remains unbroken and the conductive-member opening portion61fin the conductive member61is sealed by the deformation plate62.

As illustrated inFIGS.9and11, the deformation plate62includes the stepped projection62aincluding the first projecting portion62a1and the second projecting portion62a2in a central region thereof. The second projecting portion62a2is fitted to the connection hole6cin the first positive-electrode current collector6a. The outer diameter of the first projecting portion62a1is greater than the inner diameter of the connection hole6c, so that a surface of the first projecting portion62a1that faces the electrode assembly3is in contact with a top surface6iof the first positive-electrode current collector6a. According to this structure, when the connecting portion between the second projecting portion62a2of the deformation plate62and the connection hole6cin the first positive-electrode current collector6ais irradiated with an energy ray, such as a laser beam, the energy ray is prevented from passing through a gap between the first projecting portion62a1and a side wall of the connection hole6cin the first positive-electrode current collector6aand being scattered in a region above the first positive-electrode current collector6a. Accordingly, damage or breakage of components due to the energy ray can be reliably prevented. The stepped projection62apreferably has a stepped recess in a surface thereof that faces the sealing plate2. The stepped recess preferably has a bottom portion62dthat is closer to the sealing plate2than the top surface6iof the first positive-electrode current collector6ais.

<<First Modification>>

A rectangular secondary battery according to a first modification has a structure similar to that of the rectangular secondary battery20according to the embodiment except for the shape of the cover. As illustrated inFIGS.19A and19B, a cover81according to the first modification includes a cover main portion81aarranged to face the first positive-electrode current collector6aand a pair of arm portions81bthat extend toward the sealing plate2from both ends of the cover main portion81ain the short-side direction of the sealing plate2. The cover81also includes a cover wall portion81ethat extends toward the sealing plate2from an end of the cover main portion81ain the long-side direction of the sealing plate2. Connecting projections are provided on inner surfaces of the arm portions81b. The connecting projections are connected to the second connecting portions10fof the first insulating member10.

The cover main portion81ahas base openings81dat positions near the base ends of the arm portions81b. The cover wall portion81ehas a wall portion opening81f. The cover81of the rectangular secondary battery according to the first modification has a cover opening81xin the cover main portion81a. The cover opening81xis located such that the cover opening81xfaces the connecting portion between the deformation plate62and the first positive-electrode current collector6a. Accordingly, the current interruption mechanism can be more smoothly activated.

<<Second Modification>>

The rectangular secondary battery20according to the above-described embodiment is configured such that the conductive member61includes the pressing projection61ein the region where the conductive member61faces the first insulating member10. A rectangular secondary battery according to a second modification has a structure similar to that of the rectangular secondary battery20according to the above-described embodiment except that a pressing projection is provided not on the conductive member but on a portion of the sealing plate that faces the first insulating member10.

FIG.20is a sectional view of a part of the secondary battery according to the second modification, the part including a current interruption mechanism. The sectional view ofFIG.20corresponds toFIG.8B. As illustrated inFIG.20, a pressing projection102xis provided on a portion of a sealing plate102that faces the first insulating member10. According to this structure, the first insulating member10is strongly pressed by the pressing projection102x, so that gas does not flow toward the connecting portion between a conductive member161and the positive electrode terminal7. Accordingly, gas in the region around the electrode assembly does not leak into the space defined by the conductive member161and the deformation plate62. As a result, a delay in the activation of the current interruption mechanism can be prevented. In addition, when the sealing plate102includes the pressing projection102x, the first insulating member10can be easily prevented from being warped such that a peripheral portion thereof approaches the electrode assembly3. The pressing projection102xpreferably has an annular shape in plan view.

When the sealing plate102and the positive electrode terminal7are viewed in the direction perpendicular to the sealing plate102, the pressing projection102xpreferably overlaps the crimped portion7d(large diameter portion) of the inserting portion7bof the positive electrode terminal7.

The rectangular secondary battery according to the second modification is configured such that the conductive member161has no pressing projection. However, the conductive member161may also have a pressing projection.

<Others>

Portions expected to break in response to a deformation of the deformation plate are preferably the weak portions of the current collecting member, the connecting portion between the current collecting member and the deformation plate, or the weak portions of the deformation plate. Preferred examples of the weak portions include thin portions and notches.

The first insulating member, the second insulating member, and the cover are preferably made of a resin. For example, polypropylene, polyethylene, perfluoroalkoxy alkane (PFA), polytetrafluoroethylene (PTFE), or ethylene tetrafluoroethylene copolymer (ETFE) may be used.

In the above-described embodiment, the electrode assembly3is formed of two electrode assembly elements (3aand3b). However, the electrode assembly3is not limited to this. The electrode assembly3may instead be a single stacked electrode assembly. Alternatively, the electrode assembly3may be a single wound electrode assembly in which an elongated positive electrode plate and an elongated negative electrode plate are wound with a separator interposed therebetween. Also, each of the electrode assembly elements (3aand3b) is not limited to a stacked electrode assembly, and may instead be a wound electrode assembly in which an elongated positive electrode plate and an elongated negative electrode plate are wound with a separator interposed therebetween.

When the electrode assembly is a stacked electrode assembly including a plurality of positive electrode plates and a plurality of negative electrode plates or when the electrode assembly is a wound electrode assembly having a winding axis extending in a direction perpendicular to the sealing plate, the electrode assembly is preferably configured such that end portions of the positive electrode plates, end portions of the negative electrode plates, and end portions of the separators are adjacent to the sealing plate. According to this structure, when the sealing plate has the electrolyte introduction hole, the electrolyte can be easily introduced into the electrode assembly. In this case, the end portions of the separators that are adjacent to the sealing plate preferably project toward the sealing plate2beyond the end portions of the negative electrode active material mixture layers of the negative electrode plates that are adjacent to the sealing plate. In addition, the electrode assembly is preferably configured such that the end portions of the separators that are adjacent to the sealing plate project toward the sealing plate beyond the end portions of the positive electrode active material mixture layers of the positive electrode plates that are adjacent to the sealing plate. In addition, preferably, the positive electrode plates and the separators are bonded together by adhesive layers, and the negative electrode plates and the separators are bonded together by adhesive layers. According to this structure, the risk that the positive electrode active material mixture layers and the negative electrode active material mixture layers will come into contact with the second insulating member and the positive electrode active material layers or the negative electrode active material layers will be damaged can be reliably eliminated.

REFERENCE SIGNS LIST

20. . . rectangular secondary battery1. . . rectangular exterior body2. . . sealing plate2a. . . positive-electrode-terminal attachment hole2b. . . negative-electrode-terminal attachment hole100. . . battery case3. . . electrode assembly3a. . . first electrode assembly element3b. . . second electrode assembly element4. . . positive electrode plate4a. . . positive electrode core4b. . . positive electrode active material mixture layer4d. . . positive-electrode protecting layer40. . . positive-electrode tab40a. . . first positive-electrode tab group40b. . . second positive-electrode tab group5. . . negative electrode plate5a. . . negative electrode core5b. . . negative electrode active material mixture layer50. . . negative-electrode tab50a. . . first negative-electrode tab group50b. . . second negative-electrode tab group6. . . positive-electrode current collecting member6a. . . first positive-electrode current collector6c. . . connection hole6d. . . fixing hole6d1. . . small diameter portion6d2. . . large diameter portion6e. . . displacement prevention hole6f. . . thin portion6g. . . notch6h. . . connection rib6i. . . top surface6x. . . current-collector projection6w. . . current-collector second recess6b. . . second positive-electrode current collector6b1. . . current-collector first region6b2. . . current-collector second region6b3. . . current-collector third region6k. . . target hole6m. . . current-collector first recess6y. . . current-collector first opening6z. . . current-collector second opening7. . . positive electrode terminal7a. . . flange7b. . . inserting portion7c. . . terminal through hole7d. . . crimped portion7x. . . terminal sealing member7y. . . metal member7z. . . rubber member8. . . negative-electrode current collecting member8a. . . first negative-electrode current collector8x. . . current-collector projection8w. . . current-collector second recess8b. . . second negative-electrode current collector8b1. . . current-collector first region8b2. . . current-collector second region8b3. . . current-collector third region8e. . . target hole8f. . . current-collector first recess8y. . . current-collector first opening9. . . negative electrode terminal10. . . first insulating member10a. . . first-insulating-member main portion10b. . . first side wall10c. . . second side wall10d. . . second terminal-receiving hole10e. . . first connecting portion10f. . . second connecting portion10g. . . recess10x. . . first groove10y. . . second groove11. . . outer insulating member11a. . . first terminal-receiving hole12. . . inner insulating member13. . . outer insulating member14. . . insulating sheet15. . . electrolyte introduction hole16. . . sealing plug17. . . gas discharge valve60. . . current interruption mechanism61. . . conductive member61a. . . conductive-member base portion61b. . . tubular portion61c. . . third terminal-receiving hole61d. . . flange61e. . . pressing projection61f. . . conductive-member opening portion61g. . . tapered portion62. . . deformation plate62a. . . stepped projection62a1. . . first projecting portion62a2. . . second projecting portion62b. . . annular rib62c. . . annular thin portion62d. . . bottom portion of stepped recess63. . . second insulating member63x. . . insulating-member first region63a. . . insulating-member first opening63b. . . third wall portion63c. . . fourth wall portion63d. . . third connecting portion63e. . . fourth connecting portion63f. . . fixing projection63f1. . . large-diameter portion63g. . . displacement prevention projection63h. . . lug portion63y. . . insulating-member second region63i. . . insulating-member second opening63k. . . insulating-member annular rib63z. . . insulating-member third region80. . . cover80a. . . cover main portion80b. . . arm portion80c. . . connecting projection80d. . . base opening8e. . . cover wall portion80f. . . wall portion opening81. . . cover81a. . . cover main portion81b. . . arm portion81d. . . base opening81e. . . cover wall portion81f. . . wall portion opening81x. . . cover opening90. . . welded connecting portion102. . . sealing plate102x. . . pressing projection161. . . conductive member