JP2011071109A - Battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery increasing an energy density by housing more flat-type electrode groups in an outer can and having structure for efficiently collecting current by decreasing resistance in the connecting part of a positive electrode lead and that of a negative electrode lead. <P>SOLUTION: The battery is equipped with: positive and negative current collecting tabs 8a, 9a spirally projected from both end surfaces of a flat electrode group 2; a positive electrode nipping member 12 having first and second nipping sections 12a, 12b nipping each bundle of two bundles laminated in the thickness direction of the electrode group, the positive current collecting tab being separated into the two bundles; a negative electrode nipping member 11 having first and second nipping sections 11a, 11b nipping each bundle of two bundles laminated in the thickness direction of the electrode group the negative current collecting tabs being separated into the two bundles; the positive electrode lead 3 having current collecting parts 3c, 3d bifurcating from a connection part electrically connected to a positive terminal 6 and nipping the positive electrode nipping member; and the negative electrode lead 4 having current collecting parts 4c, 4d bifurcating from a connection part electrically connected to a negative terminal 7 and nipping the negative electrode nipping member. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  An embodiment of the present invention relates to a battery, and in particular, a sealed square two-piece having a flat electrode group wound in a flat shape, a lead for collecting electric energy from the electrode group, and a sandwiching plate. Next battery.

  In recent years, with the advancement of electronic devices such as mobile phones and personal computers, secondary batteries used in these devices have been required to be smaller and lighter. As a secondary battery having a high energy density that can respond to this, a lithium ion secondary battery can be given. On the other hand, secondary batteries such as lead-acid batteries and nickel-metal hydride batteries are used as large-scale, large-capacity power sources such as electric vehicles, hybrid vehicles, electric motorcycles, and forklifts. Recently, lithium ions with high energy density are used. Development toward the adoption of secondary batteries is thriving. Lithium-ion secondary batteries that can respond to these demands have been developed for larger sizes and larger capacities while taking into consideration the long life and safety.

  As the shape of the sealed secondary battery, a cylindrical shape or a rectangular shape is generally used. In particular, the rectangular sealed secondary battery is attracting attention because it is excellent in space efficiency when mounted on a device.

  In a sealed secondary battery, for example, a flat electrode group in which a belt-like positive electrode and a negative electrode having electrode active material layers formed on both surfaces of a metal foil are wound into a flat shape via a belt-like separator is used. In order to extract the electric energy generated by the flat electrode group to the outside, a metal foil on which the electrode active material layer of the flat electrode group is not formed is formed on both the positive electrode and the negative electrode. It is known to extract energy. Further, for example, Patent Documents 1 and 2 disclose that in order to further improve the current collection efficiency, the metal foils are joined in a state of being stacked and bundled, and welding of leads and the like is performed.

  By the way, in order to increase the energy density of the battery, it is necessary to accommodate more flat electrode groups in the outer can. In addition, a large current flows through the leads and joints that collect electrical energy, and heat is likely to be generated. In the worst case, there is a risk of overheating and burning.

  However, the batteries described in Patent Documents 1 and 2 do not sufficiently satisfy these requirements.

Japanese Patent No. 4134521 JP 2003-197174 A

  Embodiments of the present invention provide a battery having a structure capable of efficiently collecting electricity by increasing the energy density by storing a larger number of flat electrode groups in an outer can and suppressing the resistance of the joints of positive and negative electrode leads. Is.

A battery according to an embodiment of the present invention includes a positive electrode including a positive electrode current collector, and a flat electrode group in which a negative electrode including a negative electrode current collector is wound into a flat shape via a separator,
A positive electrode current collector tab comprising the positive electrode current collector projecting spirally from one end face of the electrode group;
A negative electrode current collector tab comprising the negative electrode current collector projecting spirally from the other end face of the electrode group;
The positive electrode current collecting tab is divided into two bundles stacked in the thickness direction of the electrode group, and first and second sandwiching portions for sandwiching each bundle, the first sandwiching portion, and the second sandwiching portion. A conductive positive electrode clamping member having a coupling portion for electrically connecting the clamping portion;
The negative electrode current collecting tab is divided into two bundles stacked in the thickness direction of the electrode group, and first and second sandwiching portions for sandwiching each bundle, the first sandwiching portion, and the second sandwiching portion. A conductive negative electrode clamping member having a coupling part for electrically connecting the clamping part;
An outer can in which the electrode group is stored;
A lid attached to the opening of the outer can and having a positive terminal and a negative terminal;
A connecting portion electrically connected to the positive electrode terminal; and a bifurcated branch from the connecting portion to sandwich the positive electrode holding member; one of the positive electrode holding members is joined to an outer surface of the first holding portion; And a positive electrode lead having a current collector joined to the outer surface of the second sandwiching part on the other side,
A connecting portion that is electrically connected to the negative electrode terminal, and bifurcated from the connecting portion to sandwich the negative electrode holding member, and one of them is joined to the outer surface of the first holding portion of the negative electrode holding member And a negative electrode lead having a current collector joined to the outer surface of the second clamping part.

  According to the embodiment of the present invention, a battery having a structure capable of collecting more flat type electrode groups in an outer can and increasing the energy density, and efficiently collecting current while suppressing resistance such as a junction of positive and negative electrode leads. Can be provided.

FIG. 2 is an exploded perspective view showing the prismatic secondary battery according to the first embodiment. The perspective view which shows the external appearance of the battery of FIG. The expansion | deployment perspective view of the electrode group used for the battery of FIG. The expanded sectional view which looked at the cross section along the IV-IV line of FIG. 1 from the arrow direction. The schematic diagram which shows the lamination | stacking state of the positive / negative electrode current collection tab in an electrode group. The schematic diagram for comparing the ultrasonic welding in the battery of FIG. 1 with the conventional battery. The partial exploded perspective view of the battery of a 2nd embodiment. The conceptual diagram which shows the program of a pulse charging / discharging test. The graph which shows the time-dependent change of the temperature of the thermostat in the pulse charge / discharge of STEP4, a positive electrode terminal, a negative electrode terminal, and an outer can center part. The graph which shows the time-dependent change of the electric current and voltage of a cell in the pulse charge / discharge of STEP4. The graph which shows the time-dependent change of the temperature of the thermostat in the pulse charge / discharge of STEP5, a positive electrode terminal, a negative electrode terminal, and an outer can center part. The graph which shows the time-dependent change of the electric current and voltage of a cell in the pulse charge / discharge of STEP5.

  In the present invention, in order to solve the above-described problem, the positive electrode current collecting tab is protruded spirally from one end face of the electrode group, and the negative electrode current collecting tab is protruded spirally from the other end face. Each of the current collecting tabs is divided into two bundles stacked in the thickness direction of the electrode group, one bundle is sandwiched by the first sandwiching portion of the sandwiching member, and the other bundle is sandwiched by the second sandwiching member of the sandwiching member Hold between the parts. The positive and negative electrode current collector tab uses a current collector portion on which no active material layer is formed, but with the above configuration, the length in the width direction protruding from the separator of the positive and negative electrode current collector tab can be kept short. .

  The positive and negative electrode leads electrically connected to the positive and negative electrode terminals provided on the lid have a connection portion with the positive and negative electrode terminals, and a current collecting portion that branches into two branches from the connection portion and sandwiches a holding member therebetween. One of the current collectors is joined to the outer surface of the first clamping part of the clamping member, and the other is joined to the outer surface of the second clamping part. The positive and negative electrode leads having such a structure can be disposed within the thickness range of the flat electrode group.

  From the above, the space inside the outer can can be used efficiently, and a wider application width of the electrode part coated with the active material layer of the positive electrode and the negative electrode of the flat electrode group can be secured inside the outer can. Can do. Thereby, the energy density of a square-type secondary battery can be improved.

  In addition, since the first clamping portion and the second clamping portion of the clamping member are electrically connected by the connecting portion, and the positive and negative electrode leads are joined to the first and second clamping portions, respectively, By providing two joints with leads at equal positions in the thickness direction with respect to the mold electrode group, a state of good current collection balance can be formed.

  Further, since the first clamping part and the second clamping part of the clamping member are connected by the connecting part, a space can be secured between the first clamping part and the second clamping part, Even when the negative electrode lead, the clamping member, and the positive and negative current collecting tabs are ultrasonically welded, the ultrasonic welding horn or anvil is securely inserted and arranged in the space between the first clamping portion and the second clamping portion. And ultrasonic welding can be easily performed. In the space, either an ultrasonic welding horn or an anvil may be arranged depending on welding conditions.

(First embodiment)
Hereinafter, a battery according to an embodiment of the present invention will be described with reference to the drawings. Note that the present invention is not limited to these embodiments.

  The battery 20 shown in FIGS. 1 and 2 is a sealed prismatic non-aqueous electrolyte secondary battery. The battery 20 includes an outer can 1, a flat electrode group 2 housed in the outer can 1, positive and negative leads 3 and 4 positioned in the outer can 1, and a lid attached to the opening of the outer can 1. 5 and positive and negative terminals 6 and 7 provided on the lid 5.

  The outer can 1 has a bottomed rectangular tube shape, and is formed of a metal such as aluminum, an aluminum alloy, iron, or stainless steel, for example. An electrolytic solution (not shown) is accommodated in the outer can 1 and impregnated in the flat electrode group 2.

  As shown in FIG. 3, the flat electrode group 2 includes a positive electrode 8 and a negative electrode 9 wound in a flat shape with a separator 10 therebetween. The positive electrode 8 includes a strip-shaped positive electrode collector made of, for example, metal foil, a positive electrode current collector tab 8a formed of one end parallel to the long side of the positive electrode current collector, and at least the positive electrode current collector tab 8a. And a positive electrode active material layer 8b formed on the current collector. On the other hand, the negative electrode 9 excludes, for example, a strip-shaped negative electrode current collector made of a metal foil, a negative electrode current collection tab 9a composed of one end parallel to the long side of the negative electrode current collector, and at least a portion of the negative electrode current collection tab 9a. And a negative electrode active material layer 9b formed on the negative electrode current collector.

  In the positive electrode 8, the separator 10, and the negative electrode 9, the positive electrode current collecting tab 8 a protrudes from the separator 10 in the winding axis direction of the electrode group, and the negative electrode current collecting tab 9 a protrudes from the separator 10 in the opposite direction. Thus, the positive electrode 8 and the negative electrode 9 are wound with the positions shifted. As a result of such winding, as shown in FIG. 1, the electrode group 2 has the positive electrode current collecting tab 8a wound in a spiral shape from one end face, and is wound in a spiral form from the other end face. The negative electrode current collection tab 9a protrudes.

  As shown in FIG. 4, the negative electrode current collecting tab 9 a is divided into two bundles stacked in the thickness direction T of the electrode group. Specifically, two halves of the negative electrode current collecting tabs 9a are formed by laminating the halves on one side in the thickness direction with the core space near the center of the electrode group 2 as a boundary. The electroconductive negative electrode clamping member 11 is a connection that electrically connects the first and second clamping parts 11a and 11b, which are substantially U-shaped, and the first clamping part 11a and the second clamping part 11b. Part 11c. The connecting part 11c is located between the first holding part 11a and the second holding part 11b, and the first holding part 11a and the second holding part 11b are connected to each other in the thickness direction of the electrode group 2. The 1 clamping part 11a and the 2nd clamping part 11b are connected.

  One bundle of the negative electrode current collecting tabs 9a is sandwiched between the first sandwiching portions 11a and held by the first sandwiching portions 11a. The other bundle of the negative electrode current collecting tabs 9a is sandwiched between the second sandwiching portions 11b and held by the second sandwiching portions 11b. Although the joining method of the negative electrode current collection tab 9a and the 1st, 2nd clamping parts 11a and 11b is not specifically limited, For example, ultrasonic welding is mentioned.

  On the other hand, the positive electrode current collecting tab 8a is divided into two bundles stacked in the thickness direction T of the electrode group in the same manner as the case of the negative electrode current collecting tab 9a. As shown in FIG. 1, the conductive positive electrode clamping member 12 includes first and second clamping parts 12a and 12b (12a not shown) having a substantially U-shape, a first clamping part 12a, It has a connection part (not shown) which electrically connects the 2nd clamping part 12b. The connecting portion is located between the first sandwiching portion 12a and the second sandwiching portion 12b, and the first sandwiching portion 12a and the second sandwiching portion 12b are connected to each other in the thickness direction of the electrode group 2. The clamping part 12a and the second clamping part 12b are connected.

  One bundle of the positive electrode current collecting tabs 8a is sandwiched between the first sandwiching portions 12a and held by the first sandwiching portions 12a. The other bundle of the positive electrode current collecting tabs 8a is sandwiched between the second sandwiching portions 12b and held by the second sandwiching portions 12b. Although the joining method of the negative electrode current collection tab 9a and the 1st, 2nd clamping parts 12a and 12b is not specifically limited, For example, ultrasonic welding is mentioned.

  As shown in FIG. 1, the negative electrode lead 4 has a connection plate 4a for electrical connection with the negative electrode terminal 7, a through hole 4b opened in the connection plate 4a, and a bifurcated branch from the connection plate 4a. Strip-shaped current collectors 4c and 4d. On the other hand, the positive electrode lead 3 has a connection plate 3a for electrical connection with the positive electrode terminal 6, a through hole 3b opened in the connection plate 3a, and a strip that branches off from the connection plate 3a and extends downward. Current collectors 3c and 3d.

  As shown in FIGS. 1 and 4, the negative electrode lead 4 sandwiches the negative electrode clamping member 11 between the current collectors 4 c and 4 d. The current collector 4 c is disposed on the outer surface of the first clamping part 11 a of the negative electrode clamping member 11. On the other hand, the current collector 4d is disposed on the outer surface of the second clamping unit 11b. Here, the outer surfaces of the first and second holding portions 11a and 11b are the outermost surfaces of the bundle of the negative electrode current collecting tabs 9a. Between the negative electrode current collecting tabs 9a held between the first holding parts 11a, a bundle of the negative electrode current collecting tabs 9a and the first holding parts 11a, the first holding part 11a and the current collecting part 4c are, for example, ultrasonic welding. Joined by. On the other hand, between the negative electrode current collecting tabs 9a held between the second holding parts 11b, a bundle of the negative electrode current collecting tabs 9a, the second holding part 11b, the second holding part 11b, and the current collecting part 4d are, for example, super Joined by sonic welding. Thereby, the negative electrode 9 and the negative electrode lead 4 of the electrode group 2 are electrically connected via the negative electrode current collection tab 9a.

  As in the case of the negative electrode lead 4, the positive electrode lead 3 sandwiches the positive electrode clamping member 12 between the current collectors 3 c and 3 d. The current collector 3 c is disposed on the outer surface of the first clamping part 12 a of the positive electrode clamping member 12. The current collector 3d is disposed on the outer surface of the second clamping unit 12b. Here, the outer surfaces of the first and second holding portions 12a and 12b are the outermost surfaces of the bundle of the positive electrode current collecting tabs 8a. Between the positive electrode current collecting tabs 8a held between the first holding parts 12a, a bundle of the positive electrode current collecting tabs 8a and the first holding parts 12a, and the first holding part 12a and the current collecting part 3c are, for example, ultrasonic welding. Joined by. On the other hand, between the positive electrode current collector tabs 8a sandwiched between the second sandwiching parts 12b, a bundle of the positive electrode current collector tabs 8a and the second sandwiching part 12b, the second sandwiching part 12b and the current collector part 3d are, for example, super Joined by sonic welding. Thereby, the positive electrode 8 and the positive electrode lead 3 of the electrode group 2 are electrically connected via the positive electrode current collection tab 8a.

  The positive and negative electrode clamping members 11 and 12 can be formed of a conductive material such as metal, for example.

  The thickness of the first and second clamping portions 12a and 12b of the positive electrode clamping member 12 is thinner than the thickness of the positive electrode lead 3, and the thickness of the first and second clamping portions 11a and 11b of the negative electrode clamping member 11 is as follows. It is desirable that the thickness of the negative electrode lead 4 is smaller. As a result, the bundle of current collecting tabs can be easily clamped and welded by the first and second clamping portions, so that the resistance of the joint portion between the first and second clamping portions and the current collecting tab is lowered. be able to.

  By the way, as shown in FIG. 1, the negative electrode terminal 7 is attached to the lid 5 via an insulating gasket 13 by, for example, caulking. The negative electrode terminal 7 is also electrically connected to the through hole 4b of the negative electrode lead 4 by caulking. As a result, the negative electrode terminal 7 is electrically connected to the negative electrode 9 of the electrode group 2 via the negative electrode lead 4. On the other hand, the positive electrode terminal 6 is attached to the lid 5 through an insulating gasket 14 by, for example, caulking. The positive electrode terminal 6 is also electrically connected to the through hole 3b of the positive electrode lead 3 by caulking. Thereby, the positive electrode terminal 6 is electrically connected to the positive electrode 8 of the electrode group 2 through the positive electrode lead 3.

  As shown in FIG. 2, the lid 5 is attached to the opening of the outer can 1 by, for example, laser seam welding. The lid 5 is made of, for example, a metal such as aluminum, an aluminum alloy, iron, or stainless steel. The lid 5 and the outer can 1 are preferably formed from the same type of metal.

  As shown in FIG. 5, when a current collecting tab 8a (9a) made of metal foil is bonded to a laminated surface A in which a plurality of current collecting tabs 8a (9a) are bundled, a current collecting tab laminated surface A is joined. Although it is ideal that only the plane portion A2 is formed, the deviation A1 between the outermost current collecting tab 8a (9a) and the innermost current collecting tab 8a (9a) is reduced by bundling and stacking. appear. For example, when a current collecting lead or the like is to be joined in a state where all of the current collecting tabs 8a (9a) of the flat electrode group 2 are bundled at a time, the deviation A1 between the current collecting tabs is the current collecting tab 8a ( As the thickness C of the flat electrode group 2 is larger than the length B of 9a), the ratio of the deviation A1 between the current collecting tabs is increased, and the stacked end portions of the bundled current collecting tabs are stepped. The plane portion A2 can hardly be formed, and a good laminated surface A cannot be formed. In order to avoid this, for example, it is possible to increase the proportion of the plane portion A2 by increasing the length B of the current collecting tab 8a (9a), but the length B of the current collecting tab 8a (9a) is If it becomes longer, the space occupied by the inside of the outer can 1 must be secured, and the proportion occupied by the flat electrode group 2 decreases, resulting in poor space efficiency and a decrease in energy density.

  Then, in order to form the same state with the length B of the current collecting tab 8a (9a) as short as possible, the current collecting tabs 8a (9a) are not bundled all at once, for example, as shown in FIG. In this way, the current collecting tabs 8a (9a) are divided into a plurality of sheets and bundled, thereby suppressing the deviation A1 between the current collecting tabs and forming a large proportion of the plane portion A2 so that the bonding surface has a good state. Can be formed. That is, as the number of places to be bundled increases, the deviation A1 between the bundled current collecting tabs decreases. However, if several places to be bundled are provided, the current collecting lead or the like may actually be joined to that part. In many cases, it becomes difficult. The number of parts increases, the joining method becomes complicated, and the assemblability is lacking. In addition, space is secured, and space efficiency becomes unusable, and the cost increases.

  In view of these matters, the current collecting tabs 8a (9a) of the flat-type electrode group 2 are provided at two locations each of the positive electrode and the negative electrode in view of the efficiency of current collection, ease of assembly, simplification of component shape, etc. It can be said that the most convenient and favorable state is formed.

  Each of the positive and negative electrode current collecting tabs 8a and 9a is bundled in one half of the flat electrode group 2 in the thickness direction, and two bundles are formed for each of the positive and negative electrodes. A space can be secured within the thickness range of the flat electrode group 2 by sandwiching and holding these bundles by the first and second clamping portions of the positive and negative electrode clamping members. By effectively using this space and arranging the positive electrode lead 3 and the negative electrode lead 4 in the thickness direction of the electrode group 2 along the bundled current collecting tabs, it is possible to separately route the current collecting leads. It is not necessary to secure a space, and as a result, the volume ratio of the flat electrode group 2 in the outer can 1 can be increased. For example, there is a secondary battery having a structure in which current collecting leads and the like are arranged on the side surface in the width direction of the flat electrode group. Naturally, in that case, for collecting the current collecting leads etc. at both ends of the flat electrode group Space must be secured. Compared to these, it is clear that the arrangement of the positive and negative electrode leads 3 and 4 according to the present invention is also effective in terms of space.

If the width and thickness of the positive and negative electrode leads 3 and 4 are dimensions that can be accommodated in a space secured within the thickness range of the flat electrode group 2, the electrical and mechanical functions can be sufficiently achieved. be able to.

  Further, the positive and negative electrode current collecting tabs 8 a and 9 a are divided into a half on one side in the thickness direction of the flat electrode group 2, and are bundled so that the positive and negative electrode current collector tabs protruding from the separators 10 on both end faces of the electrode group 2 are collected. The length B of the electric tabs 8a and 9a can be kept shorter than the state where all of the positive and negative electrode current collecting tabs 8a and 9a are bundled at a time for the above-described reason. By minimizing the length B of the positive and negative electrode current collecting tabs 8a and 9a necessary for bonding the positive and negative electrode leads 3 and 4, etc., the electrode active material layers of the positive electrode 8 and the negative electrode 9 of the flat electrode group 2 The width direction of the electrode part coated with can be expanded.

  Furthermore, the current collecting portions 3c and 3d of the positive electrode lead 3 are disposed on the surface located outside the laminated surface of the positive electrode current collecting tabs 8a in the first and second holding portions 12a and 12b of the positive electrode holding member 12, and The current collecting portions 4c and 4d of the negative electrode lead 4 are arranged on the surface located outside the laminated surface of the negative electrode current collecting tabs 9a in the first and second holding portions 11a and 11b of the negative electrode holding member 11. With this arrangement, the positive and negative electrode leads 3 and 4 can be arranged within the thickness range of the flat electrode group 2. In addition, the positive and negative leads 3 and 4 having such a structure are not wound at one place in the thickness direction of the flat electrode group 2, and have a joint portion with two sandwiching members, so that the wound state can be obtained. With respect to the positive and negative electrode portions (portions where the active material is held) of a flat electrode group 2, the current collection balance is reduced by having joints at equal positions on a semicircular basis and by reducing the current collection distance accordingly. It will be in good condition.

  In addition, the current collector of the lead is split into two for each of the positive and negative electrodes, and is dispersed at two locations and joined to the clamping member, so that each joint and lead can be protected against heat generation when a large current is passed. It has a structure in which heat is difficult to concentrate on itself, and can maintain a good electrical property. Further, the positive and negative leads 3 and 4 are formed in an integrated shape including a bifurcated portion, and are connected to the clamping members 11 and 12 from the joint with the positive terminal 6 or the negative terminal 7. Since no other joints are provided between the joints, it can be said that the structure is electrically and mechanically reliable.

  Further, the first clamping member 11a, 12a and the second clamping member 11b, 12b in the positive and negative electrode clamping members 11, 12 are connected to each other in a substantially U-shape by the connecting portion. 11a, 12a and the second clamping member 11b, 12b can be secured between the positive and negative leads 3 and 4, and the ultrasonic welding horn or anvil is securely attached to the space. Therefore, ultrasonic welding can be easily performed. In addition, by sandwiching a plurality of current collecting tabs by the first and second clamping portions and performing ultrasonic welding, the current collecting tabs directly receive the amplitude energy of ultrasonic waves so that the melted current collecting tabs are torn and scattered. A good joint can be formed without any problems.

  Here, the ultrasonic welding is to perform welding by accurately transmitting vibration energy from the horn by pressurizing the bonding interface between materials, removing the oxide film, and bringing the bonding interface close to the interatomic distance. Therefore, it is important that the vibration energy is accurately transmitted to the joint interface without slipping and slipping on the contact surface with the horn or anvil, and the shape of the contact surface of the horn or anvil is anti-slip or gripping. In order to maintain force, it is common to provide mountain-shaped irregularities.

  FIG. 6A shows an embodiment of ultrasonic welding between the current collecting part 3c (4c) of the positive and negative electrode leads 3 and 4 and the first clamping parts 11a and 12a in the battery of FIG. The horn and the anvil may be arranged either inside or outside, but in FIG. 6A, the horn 21 is arranged inside and the anvil 22 is arranged outside. On the other hand, FIG. 6B shows a plate surface of the sandwich plate 26 in which the lead 23 and a plurality of current collecting metal foils 25 protruding from the end surface of the power generation element 24 are overlapped as in Patent Document 2. Shows a case where is sandwiched between facing parts facing each other.

  When the clamping members 11 and 12 are arranged inside the positive and negative electrode leads 3 and 4 as shown in FIG. 6A, the joining interface by ultrasonic welding is connected to the current collecting part 3c (4c) of the positive and negative electrode leads 3 and 4. It becomes a contact surface with the holding members 11, 12 and a contact surface with the positive and negative current collecting tabs 8 a, 9 a held between the holding members 11, 12 and the holding members 11, 12. On the other hand, in the case of FIG. 6B, the joining interface by ultrasonic welding is the contact surface between the lead 23 and the current collector metal foil 25, the contact between the stacked current collector metal foils 25 and the sandwiching plate 26. It becomes a surface. The most suitable arrangement for the horn or anvil is to directly contact and grip the horn or anvil on the surface opposite to the bonding interface of the material to be provided with the bonding interface. When the sandwiching plate 26 is arranged outside the lead 23 as shown in FIG. 6B, the lead 23 itself may be displaced inside because the horn or anvil cannot directly contact and hold the lead 23. It cannot be said that proper energy transfer to the bonding interface is possible. Compared with the case where the holding members 11 and 12 are arranged inside the positive and negative leads 3 and 4 as shown in FIG.

  In addition, when the sandwiching plate 26 is disposed outside the lead 23, it is necessary to perform alignment work with the lead 23 while bundling the current collector metal foil 25 in one process, and the difficulty of the work increases. The possibility of the displacement of the current collector metal foil 25 is increased. Also, the ultrasonic welding work must be performed within the same process, and the work time of the process is long. The difference in working time with the preceding and following processes becomes large, and the line balance also deteriorates.

  When the clamping members 11 and 12 are arranged inside the positive and negative electrode leads 3 and 4 as shown in FIG. 6A, the bundling work, alignment and ultrasonic welding work of the positive and negative current collecting tabs 8a and 9a are divided. Therefore, it can be said that it is a reasonable shape considering the assembly.

  Here, typical positive and negative electrode terminal materials will be described. In the case of a lithium ion secondary battery using a carbon-based material for the negative electrode active material, the positive electrode terminal is generally made of aluminum or an aluminum alloy, and the negative electrode terminal is made of a metal such as copper, nickel, or nickel-plated iron. used. When lithium titanate is used as the negative electrode active material, in addition to the above, aluminum or an aluminum alloy may be used for the negative electrode terminal. When aluminum or an aluminum alloy is used for the positive and negative electrode terminals, the positive and negative current collecting tabs, the positive and negative electrode holding members, and the positive and negative electrode leads are preferably formed from aluminum or an aluminum alloy.

  Hereinafter, the positive electrode, the negative electrode, the separator, and the electrolytic solution used in the above-described prismatic nonaqueous electrolyte secondary battery in FIG. 1 will be described.

  The positive electrode is produced, for example, by applying a slurry containing a positive electrode active material to a current collector made of an aluminum foil or an aluminum alloy foil. Although it does not specifically limit as a positive electrode active material, The oxide, sulfide, polymer, etc. which can occlude / release lithium can be used. Preferable active materials include lithium manganese composite oxide, lithium nickel composite oxide, lithium cobalt composite oxide, lithium iron phosphate, and the like that can obtain a high positive electrode potential. The negative electrode is produced by applying a slurry containing a negative electrode active material to a current collector made of an aluminum foil or an aluminum alloy foil. The negative electrode active material is not particularly limited, and metal oxides, metal sulfides, metal nitrides, alloys, and the like that can occlude and release lithium can be used. Preferably, the lithium ion occlusion and release potential is metal lithium. It is a substance that becomes noble 0.4V or more with respect to the potential. Since the negative electrode active material having such a lithium ion storage / release potential can suppress the alloy reaction between aluminum or an aluminum alloy and lithium, it is possible to use aluminum or an aluminum alloy for a negative electrode current collector and a negative electrode related component. And For example, there are titanium oxide, lithium titanium composite oxide such as lithium titanate, tungsten oxide, amorphous tin oxide, tin silicon oxide, silicon oxide, etc. Among them, lithium titanium composite oxide is preferable. As the separator, a microporous film, a woven fabric, a non-woven fabric, a laminate of the same material or different materials among these can be used. Examples of the material for forming the separator include polyethylene, polypropylene, ethylene-propylene copolymer, and ethylene-butene copolymer.

As the electrolytic solution, a nonaqueous electrolytic solution prepared by dissolving an electrolyte (for example, lithium salt) in a nonaqueous solvent is used. Examples of the non-aqueous solvent include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), γ-butyrolactone (γ -BL), sulfolane, acetonitrile, 1,2-dimethoxyethane, 1,3-dimethoxypropane, dimethyl ether, tetrahydrofuran (THF), 2-methyltetrahydrofuran and the like. Nonaqueous solvents may be used alone or in combination of two or more. Examples of the electrolyte include lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium arsenic hexafluoride (LiAsF ₆ ), and trifluorometa. A lithium salt such as lithium sulfonate (LiCF ₃ SO ₃ ) can be given. The electrolyte may be used alone or in combination of two or more. The amount of electrolyte dissolved in the non-aqueous solvent is desirably 0.2 mol / L to 3 mol / L.

  As described above, according to the present invention, the flat and negative electrode leads are formed in a bifurcated shape, and they are arranged in a space efficient manner inside the outer can so that the flat electrode group can be placed in the outer can. A large amount of energy can be stored and the energy density can be increased. By splitting the positive and negative electrode leads and dispersing the joints to the flat electrode group in two places, heat is concentrated even when heat is generated when a large current is applied. It is a difficult structure and can have a structure with a good current collection balance by having joints at equal positions with respect to the electrode portions of the flat electrode group. Furthermore, a good joint can be formed by sandwiching the positive and negative current collecting tabs of the flat electrode group by the sandwiching member, and ultrasonic welding which is the joining method can be easily performed.

(Second Embodiment)
One form of the battery according to the second embodiment is shown in FIG. In addition, about the member similar to having described in FIGS. 1-6, the same code | symbol is attached | subjected and the overlapping description is abbreviate | omitted.

  A battery 50 shown in FIG. 7 is a sealed prismatic nonaqueous electrolyte secondary battery. The battery 50 includes an outer can 1, a flat electrode group 2 accommodated in the outer can 1, positive and negative electrode leads 3 and 4 located in the outer can 1, and an insulating tape that covers the outermost periphery of the electrode group 2. 35, the first insulating cover 36, the second insulating cover 37, the insulating cover fixing tape 38, the lid 5 attached to the opening of the outer can 1, and the positive and negative terminals 6 provided on the lid 5. , 7. An electrolytic solution (not shown) is impregnated in the electrode group 2.

  The positive electrode lead 3 has a connection plate 3a for electrical connection with the positive electrode terminal 6, a through hole 3b opened in the connection plate 3a, a bifurcated branch from the connection plate 3a, and a strip-like shape extending downward. Current collectors 3c and 3d. The negative electrode lead 4 includes a connection plate 4a for electrical connection with the negative electrode terminal 7, a through hole 4b opened in the connection plate 4a, and a strip that branches off from the connection plate 4a and extends downward. Current collectors 4c and 4d.

  The positive electrode current collecting tab 8 a is divided into two bundles stacked in the thickness direction of the electrode group 2. The conductive positive electrode holding member 12 holds each bundle of the positive electrode current collecting tabs 8a. The negative electrode current collecting tab 9 a is divided into two bundles stacked in the thickness direction of the electrode group 2. The conductive negative electrode holding member 11 holds each bundle of the negative electrode current collecting tabs 9a.

  The positive electrode lead 3 sandwiches the positive electrode clamping member 12 between the current collecting portions 3c and 3d. The current collector 3 c is disposed on the outer surface of the first clamping part 12 a of the positive electrode clamping member 12. The current collector 3d is disposed on the outer surface of the second clamping unit 12b. The 1st, 2nd clamping parts 12a and 12b, the positive electrode current collection tab 8a, and the current collection parts 3c and 3d are joined, for example by ultrasonic welding. Thereby, the positive electrode 8 and the positive electrode lead 3 of the electrode group 2 are electrically connected via the positive electrode current collection tab 8a.

  The negative electrode lead 4 sandwiches the negative electrode clamping member 11 between the current collecting portions 4c and 4d. The current collector 4 c is disposed on the outer surface of the first clamping part 11 a of the negative electrode clamping member 11. On the other hand, the current collector 4d is disposed on the outer surface of the second clamping unit 11b. The 1st, 2nd clamping parts 11a and 11b, the negative electrode current collection tab 9a, and the current collection parts 4c and 4d are joined by ultrasonic welding, for example. Thereby, the negative electrode 9 and the negative electrode lead 4 of the electrode group 2 are electrically connected via the negative electrode current collection tab 9a.

  The adhesive insulating tape 35 insulates the outermost periphery of the electrode group 2 from the outer can 1. In FIG. 7, the insulating tape 35 is in close contact with the outermost periphery of the electrode group 2 and covers the outermost periphery. This combines the winding function of the wound electrode group 2 and the insulating function between the electrode group 2 and the outer can 1. It also contributes to cost reduction by reducing the number of parts. Further, no new insulating material other than the insulating cover is required, and the insertion into the outer can 1 is facilitated, and the electrode group dimensions can be secured up to the inner dimensions of the outer can 1, thereby contributing to the improvement of volume efficiency. Further, since the positive and negative electrode current collecting tabs 8a and 9a at both ends of the electrode group 2 are not covered with the insulating tape 35, the insulating tape 35 does not hinder the impregnation of the electrolytic solution. The number of turns of the insulating tape 35 can be one or more. In the embodiment, the electrode group 2 is wound into a flat shape, but the present invention can also be applied to a stacked electrode group.

  Examples of the resin that can be used for the base material of the insulating tape 35 include polyester (PET), polyimide, polyphenylene sulfide (PPS), and polypropylene.

  The first insulating cover 36 is made of a resin molded product having a shape that covers portions of the positive electrode lead 3, the positive electrode holding member 12, and the positive electrode current collecting tab 8 a that face the inner surface of the outer can 1. Specifically, the first insulating cover 36 covers the opening 36a facing the inner surface of the lid 5, the side plate 36b covering the end face of the positive current collecting tab 8a, and the outermost periphery of the positive current collecting tab 8a. And a side plate 36c curved in a U-shape.

  The second insulating cover 37 is made of a resin molded product having a shape that covers portions of the negative electrode lead 4, the negative electrode holding member 11, and the negative electrode current collecting tab 9 a that face the inner surface of the outer can 1. Specifically, the second insulating cover 37 covers the opening 37a facing the inner surface of the lid 5, the side plate 37b covering the end face of the negative current collecting tab 9a, and the outermost periphery of the negative current collecting tab 9a. And a side plate 37c curved in a U-shape.

  The first insulating cover 36 has a function of protecting the ultrasonic welding portion of the positive electrode lead 3, the positive electrode holding member 12, and the positive electrode current collecting tab 8 a from vibration and impact, and the positive electrode lead 3, the positive electrode holding member 12, and the positive electrode collector. A function of insulating the electric tab 8a from the outer can can also be used, which contributes to cost reduction by reducing the number of parts. Further, the second insulating cover 37 has a function of protecting the ultrasonic welding portion of the negative electrode lead 4, the negative electrode holding member 11 and the negative electrode current collecting tab 9a from vibration and impact, and the negative electrode lead 4, the negative electrode holding member 11 and The negative electrode current collecting tab 9a can also serve as a function of insulating the outer can 1 from the outer can 1 and contributes to cost reduction by reducing the number of parts. Further, by protecting the ultrasonic welded portions with the first and second insulating covers 36 and 37, the insertability of the electrode group 2 into the outer can 1 is also improved.

  The first insulating cover 36 is inserted into the end face from which the positive electrode current collecting tab 8 a of the electrode group 2 protrudes, a U-shaped side plate 36 c is overlaid on the insulating tape 35, and the insulating tape 35 is covered with the insulating cover fixing tape 38. Fixed on top. The second insulating cover 37 is inserted into the end face from which the negative electrode current collecting tab 9 a of the electrode group 2 protrudes, and a U-shaped side plate 37 c is overlaid on the insulating tape 35 and insulated by the insulating cover fixing tape 38. It is fixed on the tape 35. With this configuration, the electrode group 2, the positive and negative current collecting tabs 8 a and 9 a, the positive and negative electrode holding members 11 and 12, and the positive and negative electrode leads 3 and 4 can be completely insulated from the outer can 1. The insulating tape 35 and the first and second insulating covers 36 and 37 may be overlapped and the insulating cover fixing tape 38 may not be used.

  Examples of the resin that can be used for the first and second insulating covers 36 and 37 include polypropylene, polyimide, polyphenylene sulfide (PPS), and polyester (PET). Among these, polypropylene is desirable from the viewpoints of heat resistance, insulation, and cost.

  The rectangular plate-shaped lid 5 is seam welded to the opening of the outer can 1 by, for example, a laser. An electrolyte solution injection port (not shown) is opened in the lid 5 and sealed with a sealing lid 51 after the electrolyte solution is injected. Two rectangular recesses 5 a are provided on the outer surface of the lid 5. The positive electrode terminal 6 is accommodated in one recess 5a, and the negative electrode terminal 7 is accommodated in the other recess 5a. Each recess 5a is provided with one through hole 5b. The safety valve 52 is disposed between the recesses 5 a on the outer surface of the lid 5. The safety valve 52 has a rectangular recess and a groove formed in the recess. When the pressure in the outer can 1 becomes equal to or higher than the reference value, the groove is broken by the pressure, and gas is discharged to the outside from the broken portion, thereby preventing the battery from being ruptured.

  An internal insulator 53 is disposed on the back surface of the lid 5. The internal insulator 53 includes a through hole 53a provided at a position facing the through hole 5b of the lid 5, a gas vent hole 53b provided at a position facing the safety valve 52, and a liquid injection port 53c. A spacer 53 d is provided on the back surface of the internal insulator 53, that is, the surface facing the electrode group 2. The spacer 53 d can prevent the electrode group 2 from moving in the direction approaching the lid 5.

  The positive electrode insulating gasket 14 includes a cylindrical tube portion 14a and a flange portion 14b formed in a bowl shape at one opening end of the tube portion 14a. The negative electrode insulating gasket 13 includes a cylindrical tube portion 13a and a flange portion 13b formed in a bowl shape at one opening end of the tube portion 13a. The cylindrical portions 13 a and 14 a are each inserted into the through hole 5 b in the recess 5 a of the lid 5, and the respective lower opening ends are inserted into the through holes 53 a of the internal insulator 53. The flange portions 13b and 14b cover the periphery of the through hole 5b in the recess 5a of the lid 5, respectively.

  The positive electrode terminal 6 has a head portion 6a and a shaft portion 6b extending downward from the head portion 6a. The head portion 6 a of the positive electrode terminal 6 is accommodated in the flange portion 14 b of the insulating gasket 14. Moreover, the negative electrode terminal 7 has the head part 7a and the axial part 7b extended below from the head part 7a. The head portion 7 a of the negative electrode terminal 7 is accommodated in the flange portion 13 b of the insulating gasket 13.

  The shaft portion 6 b of the positive electrode terminal 6 is inserted into the through hole 5 b of the lid 5 and the through hole 53 a of the internal insulator 53 while being inserted into the cylindrical portion 14 a of the insulating gasket 14, and the tip is a through hole of the positive electrode lead 3. It is inserted in 3b. The shaft portion 6 b is deformed by caulking and is fixed to the lid 5, the internal insulator 53 and the positive electrode lead 3 by caulking. On the other hand, the shaft portion 7 b of the negative electrode terminal 7 is inserted into the through hole 5 b of the lid 5 and the through hole 53 a of the internal insulator 53 while being inserted into the cylindrical portion 13 a of the insulating gasket 13, and the tip of the negative electrode lead 4. It is inserted into the through hole 4b. The shaft portion 7 b is deformed by caulking and is fixed to the lid 5, the internal insulator 53 and the negative electrode lead 4 by caulking. As a result, the positive and negative terminals 6 and 7 and the lid 5 are fixed in a state where insulation and airtightness are ensured, and further, the positive and negative terminals 6 and 7 and the positive and negative leads 3 and 4 are electrically connected. It is fixed in the state.

  The insulating cover 54 has a through hole 54 a at a location facing the positive and negative terminals 6 and 7. The insulating cover 54 is disposed on the lid 5 so that the heads 6a and 7a of the positive and negative electrode terminals 6 and 7 protrude from the through hole 54a.

Regarding the nonaqueous electrolyte secondary battery having the structure shown in FIG. 7, when the current-carrying limit during pulse charge / discharge was confirmed, the following results were obtained. Note that lithium cobalt oxide (LiCoO ₂ ) was used as the positive electrode active material, and a negative electrode active material having an open circuit potential of 0.4 V or higher with respect to the open circuit potential of lithium metal was used as the negative electrode active material. A non-aqueous electrolyte was used as the electrolyte. Aluminum alloy was used for the outer can 1, the lid 5, the positive and negative electrode terminals 6 and 7, the positive and negative electrode current collecting tabs 8 a and 9 a, the positive and negative electrode leads 3 and 4, and the positive and negative electrode holding members 11 and 12. Polypropylene molded products were used for the first and second insulating covers 36 and 37, and polyester was used for the base material of the insulating tape 35.

  Charging / discharging was repeated with a pulse current, and the cell temperature at that time was measured. The energization current started from 100 A, and the current was increased stepwise until the cell temperature exceeded 100 ° C. or until the set voltage (1.5 V to 2.95 V) was removed. A specific evaluation method will be described below.

A pulse charge / discharge test was conducted as shown in FIG. That is, this is a test method in which pulse charging / discharging is performed a plurality of times while increasing the current value stepwise, and a certain rest period is provided between the pulse charging / discharging. Pulse charge / discharge was performed every 10 seconds under the initial condition of SOC 50%. Pulse charge / discharge was performed while increasing the current value stepwise from STEP1 to STEP5. Table 1 shows the current values of STEP1 to STEP5. As for the current value of each STEP in Table 1, the value displayed in A units and the value converted into the C rate are shown in parentheses. Moreover, the pulse charge / discharge of each STEP was set to a fixed time of 40 to 60 minutes. There was a pause between each STEP. When the cell temperature reaches 100 ° C or exceeds the set voltage (1.5V to 2.95V), charging / discharging is stopped. After that, when the cell temperature decreases and settles at the ambient temperature, pulse at the current value one step higher. Charging / discharging was repeated. Moreover, at the time of pulse charge / discharge, current, voltage, time, and temperature were measured at 4 points (a constant temperature bath, a positive electrode terminal, a negative electrode terminal, and an outer can center). Table 2 and FIGS. 9 to 12 show the test results when STEP1 to STEP5, that is, the pulse charge / discharge test at the time of energization of 100A to 250A at maximum. FIG. 9 shows changes over time in the temperature of the constant temperature bath, the positive electrode terminal, the negative electrode terminal, and the outer can center in the pulse charge / discharge of STEP 4 (200A). FIG. 10 shows time-dependent changes in cell current and voltage during pulse charge / discharge of STEP 4 (200A). FIG. 11 shows changes over time in the temperature of the constant temperature bath, the positive electrode terminal, the negative electrode terminal, and the central portion of the outer can in the pulse charge / discharge of STEP 5 (250A). FIG. 12 shows time-dependent changes in cell current and voltage during pulse charge / discharge of STEP 5 (250 A). 9 and 11, the temperature of the thermostatic chamber is indicated by T ₁ , the temperature of the positive terminal is T ₂ , the temperature of the negative terminal is T ₃ , and the temperature of the central portion of the outer can is indicated by T ₄ . FIG. 2 shows the measurement points α, β, and γ for the temperature T _{2 of} the positive electrode terminal, the temperature T ₃ of the negative electrode terminal, and the temperature T _{4 of the} central portion of the outer can.

  As is clear from Table 2, in the pulse current 100A, the temperature difference between the temperature before the start of evaluation and the maximum temperature was the largest in the central portion of the outer can, and was 11.6 ° C. In the pulse current 130A, the temperature difference between the temperature before the start of evaluation and the maximum temperature was 18.0 ° C., which was the largest in the central portion of the outer can. In the pulse current 160A, the temperature difference between the temperature before the start of evaluation and the maximum temperature was 27.2 ° C., which was the largest in the central portion of the outer can.

  As is clear from FIGS. 9 and 10, the battery according to the second embodiment was able to be energized for 60 minutes or more at a pulse current of 200A. As shown in Table 2, the temperature difference between the temperature before the start of evaluation and the maximum temperature was the largest in the central portion of the outer can, and was 40.4 ° C. Further, as is clear from FIGS. 11 and 12, at the time of 250 A energization, 25 minutes after the start of the evaluation, the lower limit value of the set voltage end condition was 1.5 V. For this reason, the evaluation was forcibly terminated at this point. Regarding the temperature rise at the measurement point, as shown in Table 2, the temperature difference between the temperature before the start of evaluation and the maximum temperature was 66.2 ° C., which was the largest at the positive electrode terminal. Further, no problem of heat generation occurred even when a large current of 250 A was applied to the battery. Furthermore, in the set voltage range (1.5 V to 2.95 V), it was possible to energize with a pulse current of 250 A for 25 minutes.

  According to the second embodiment described above, the flat electrode group is accommodated more in the outer can to increase the energy density, and the structure that can efficiently collect current while suppressing the resistance of the joint portion of the positive and negative electrode leads is provided. Batteries can be provided. Moreover, the volume efficiency of the battery of the structure which insulates an electrode group, a current collection tab, and a lead from an exterior can can be improved.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

  DESCRIPTION OF SYMBOLS 1 ... Exterior can, 2 ... Electrode group, 3 ... Positive electrode lead, 4 ... Negative electrode lead, 3a, 4a ... Connection part, 3c, 3d, 4c, 4d ... Current collecting part, 5 ... Cover, 6 ... Positive electrode terminal, 7 ... Negative terminal, 8a ... Positive current collecting tab, 9a ... Negative current collecting tab, 10 ... Separator, 11 ... Negative electrode holding member, 11a, 11b ... First and second holding portions, 12 ... Positive electrode holding member, 12a, 12b ... 1st and 2nd clamping part, 13 and 14 ... insulation gasket, 20 ... battery, 21 ... horn, 22 ... anvil, 23 ... lead, 24 ... power generation element, 25 ... current collecting metal foil, 26 ... clamping plate, 35 ... insulating tapes 36, 37 ... first and second insulating covers.

Claims (7)

A flat electrode group in which a positive electrode including a positive electrode current collector and a negative electrode including a negative electrode current collector are wound into a flat shape via a separator;
A positive electrode current collector tab comprising the positive electrode current collector projecting spirally from one end face of the electrode group;
A negative electrode current collector tab comprising the negative electrode current collector projecting spirally from the other end face of the electrode group;
The positive electrode current collecting tab is divided into two bundles stacked in the thickness direction of the electrode group, and first and second sandwiching portions for sandwiching each bundle, the first sandwiching portion, and the second sandwiching portion. A conductive positive electrode clamping member having a coupling portion for electrically connecting the clamping portion;
The negative electrode current collecting tab is divided into two bundles stacked in the thickness direction of the electrode group, and first and second sandwiching portions for sandwiching each bundle, the first sandwiching portion, and the second sandwiching portion. A conductive negative electrode clamping member having a coupling part for electrically connecting the clamping part;
An outer can in which the electrode group is stored;
A lid attached to the opening of the outer can and having a positive terminal and a negative terminal;
A connecting portion electrically connected to the positive electrode terminal; and a bifurcated branch from the connecting portion to sandwich the positive electrode holding member; one of the positive electrode holding members is joined to an outer surface of the first holding portion; And a positive electrode lead having a current collector joined to the outer surface of the second sandwiching part on the other side,
A connecting portion that is electrically connected to the negative electrode terminal, and bifurcated from the connecting portion to sandwich the negative electrode holding member, and one of them is joined to the outer surface of the first holding portion of the negative electrode holding member And a negative electrode lead having a current collector joined to the outer surface of the second clamping part.   The positive electrode current collecting tab, the first and second holding parts of the positive electrode holding member, and the current collecting part of the positive electrode lead are joined by ultrasonic welding, and the negative electrode current collecting tab; 2. The battery according to claim 1, wherein the first and second holding portions of the negative electrode holding member and the current collecting portion of the negative electrode lead are joined by ultrasonic welding.   The thickness of the first and second clamping portions of the positive electrode clamping member is thinner than the thickness of the positive electrode lead, and the thickness of the first and second clamping portions of the negative electrode clamping member is the thickness of the negative electrode lead. The battery according to claim 1, wherein the battery is thinner than the thickness.   A portion of the positive electrode lead, the positive electrode holding member and the positive electrode current collecting tab facing the inner surface of the outer can, or a portion of the negative electrode lead, the negative electrode holding member and the negative electrode current collecting tab facing the inner surface of the outer can The battery according to claim 1, further comprising an insulating cover made of a resin molded product having a shape covering the battery.   The battery according to claim 4, wherein the insulating cover has a hole serving as a flow path between the outer can and the electrode group.   6. The battery according to claim 4, wherein the insulating cover has a convex portion projecting inwardly on a side plate facing an end face of the positive current collecting tab or the negative current collecting tab.   The battery according to claim 4, further comprising an insulating tape for insulating the outermost periphery of the electrode group.

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