JP2016081629A - Battery pack and square secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery pack that can prevent short-circuiting between a lid member of a square secondary battery and a power generation element.SOLUTION: A battery pack 200 has plural square secondary batteries 100 which are alternately laminated with battery holders 210, and a restraining member for restraining the battery holders 210 and the square secondary batteries 100. The square secondary battery 100 has a power generation element 70 configured by rolling a positive electrode and a negative electrode which are arranged to confront each other through a separator, a battery can 11 in which the power generation element 70 is mounted, and a lid member 12 for sealing the upper opening of the battery can 11. The lid member 12 has end portions 12a confronting the battery holder 210, and an intermediate portion 12b between the end portions 12a. The center Cb in the thickness direction of the intermediate portion 12b is located above the center Ca in the thickness direction of the end portions 12a.SELECTED DRAWING: Figure 9

Description

  The present invention relates to an assembled battery including a plurality of prismatic secondary batteries and a prismatic secondary battery used for the assembled battery.

  For example, a secondary battery having a large capacity (Wh) has been developed as a power source for a hybrid electric vehicle or a pure electric vehicle, and among them, a prismatic lithium ion secondary battery having a high energy density (Wh / kg). Is attracting attention. A prismatic lithium ion secondary battery generally includes a prismatic battery case having an opening formed on the upper side, a lid member fitted into the opening of the battery case, and a power generation element accommodated in the battery case. (For example, refer to Patent Document 1 below).

  A rectangular secondary battery described in Patent Document 1 includes a positive terminal and a negative terminal protruding from a battery case cover, a positive current collecting terminal that electrically connects the positive terminal to a power generating element, and a negative terminal serving as a power generating element. And a negative electrode current collecting terminal electrically connected to. The power generation element is formed by winding a positive electrode including a positive electrode current collector, a negative electrode including a negative electrode current collector, and a separator. The positive electrode current collector terminal is connected to the positive electrode current collector, and the negative electrode current collector terminal is connected to the negative electrode current collector.

  In addition, the rectangular secondary battery described in Patent Document 1 includes a welded portion formed by wobbling and welding the end portion of the lid member and the end portion of the battery case. And the cover material contains the protruding part which protrudes outside a battery case rather than a welding part. In patent document 1, it is possible to suppress that the height position of a lid | cover material varies for every battery with the battery provided with such a structure.

JP 2014-38812 A

  A square secondary battery is usually used as an assembled battery in which a plurality of batteries are connected. The assembled battery includes a plurality of prismatic secondary batteries stacked alternately with the battery holder, and a restraining member that restrains the plurality of prismatic secondary batteries disposed between the battery holders from both sides in the stacking direction. ing. When the rectangular secondary battery constrained between the battery holders expands with charging, it receives a reaction force that limits expansion from the battery holder.

  In the prismatic secondary battery described in Patent Document 1, the end of the lid is fitted inside the opening of the battery case, and the end of the lid and the end of the battery case are welded together. Therefore, when an assembled battery is constituted by the prismatic secondary battery described in Patent Document 1, when the prismatic secondary battery expands between the battery holders, the inner side lower side of the battery case is formed at both ends of the lid member facing the battery holder. The force that faces is applied. When such a force acts on the lid member, the entire lid member is deformed so as to bend inward and downward of the battery case, and the lid member and the power generation element may be short-circuited.

  The present invention has been made in view of the above problems, and provides an assembled battery capable of preventing a short circuit between a lid member of a rectangular secondary battery and a power generation element, and a rectangular secondary battery used for the assembled battery. For the purpose.

  In order to achieve the above object, an assembled battery of the present invention is an assembled battery including a plurality of prismatic secondary batteries stacked alternately with a battery holder, and a restraining member that restrains the battery holder and the prismatic secondary battery. The prismatic secondary battery includes a power generation element in which a positive electrode and a negative electrode are opposed to each other with a separator interposed therebetween, a battery can that houses the power generation element, and an upper opening of the battery can. A lid member that stops, and the lid member has an end facing the battery holder and an intermediate portion between the ends, and the center of the thickness of the intermediate portion is the thickness of the end portion. It is characterized by being located above the center of.

  In the assembled battery of the present invention, when the prismatic secondary battery is charged, the prismatic secondary battery is disposed between the battery holders and expands while being restrained by the restraining member. Then, with respect to the end portion of the lid member that seals the upper opening of the battery can of the rectangular secondary battery, a force directed from the battery holder facing the end portion toward the intermediate portion of the lid member acts.

  In the lid member, the center of the thickness of the intermediate part is located above the center of the thickness of the end part. Therefore, when a force directed to the intermediate portion acts on the end portion of the lid member, an upward force acts on the intermediate portion from the end portion, and the entire lid member is deformed so as to bend upward. Thus, when the prismatic secondary battery is expanded, the lid member that seals the upper opening of the battery can is deformed upward from the upper opening of the battery can and is deformed toward the outside of the battery can.

  Therefore, according to the assembled battery of the present invention, when the prismatic secondary battery is expanded, the lid member is prevented from being deformed toward the power generation element inside the battery can, and a short circuit between the lid member and the power generation element is prevented. Can do.

The perspective view which shows one Embodiment of the assembled battery of this invention. The perspective view which cut | disconnected a part of assembled battery shown in FIG. The exploded perspective view of the assembled battery shown in FIG. The perspective view of the square secondary battery which comprises the assembled battery shown in FIG. The disassembled perspective view of the square secondary battery shown in FIG. The disassembled perspective view which expand | deployed some electric power generation elements of the square secondary battery shown in FIG. FIG. 7 is a cross-sectional view taken along the line VII-VII of the prismatic secondary battery shown in FIG. 4. The expanded sectional view of VIII part of the square secondary battery shown in FIG. The expanded sectional view of the state which the square secondary battery of the assembled battery shown in FIG. 1 expanded. The expanded sectional view which shows the modification 1 of the square secondary battery shown in FIG. The expanded sectional view which shows the modification 2 of the square secondary battery shown in FIG. The expanded sectional view which shows the modification 3 of the square secondary battery shown in FIG. The expanded sectional view which shows the modification 4 of the square secondary battery shown in FIG. The expanded sectional view which shows the modification 5 of the square secondary battery shown in FIG.

  Hereinafter, embodiments of the assembled battery and the prismatic secondary battery of the present invention will be described in detail with reference to the drawings.

(Battery)
FIG. 1 is a perspective view showing an embodiment of an assembled battery 200 of the present invention. FIG. 2 is a perspective view in which a part of the assembled battery 200 shown in FIG. 1 is cut. FIG. 3 is an exploded perspective view of the assembled battery 200 shown in FIG.

  The assembled battery 200 of the present embodiment includes a plurality of prismatic secondary batteries 100 that are alternately stacked with a battery holder 210, and a restraining member 220 that restrains the battery holder 210 and the prismatic secondary battery 100. More specifically, the assembled battery 200 of this embodiment includes a plurality of prismatic secondary batteries 100, a battery holder 210 that holds each prismatic secondary battery 100, and a prismatic secondary battery that is held by the battery holder 210. A restraining member 220 that restrains 100, and a top plate 230 and a cover 240 that are arranged so as to cover the upper portions thereof are provided.

  The prismatic secondary battery 100 includes a battery container 10 formed in a rectangular parallelepiped flat square shape. The battery container 10 includes a bottomed rectangular tube-shaped battery can 11 having an open top, a rectangular plate-shaped lid member 12 that seals the upper opening of the battery can 11, and a positive electrode disposed on the top surface of the lid member 12. An external terminal 20A and a negative external terminal 20B are provided. The lid member 12 has a gas discharge valve 13 at the center in the longitudinal direction. The gas discharge valve 13 is provided by, for example, thinning a part of the lid member 12 to form a cleavage groove, and the gas discharge valve 13 is opened when the internal pressure of the battery container 10 rises above a predetermined pressure. The internal pressure of the battery container 10 is reduced by releasing gas or the like inside the container 10.

  The battery holder 210 is a plate-like member disposed on both sides in the thickness direction of the battery container 10 so as to face the wide side surface 10 a having the largest area among the side surfaces of the battery container 10 of the square secondary battery 100. The battery holder 210 is, for example, a resin material such as glass epoxy resin, polypropylene, polybutylene terephthalate, polycarbonate, nylon resin, or a composite resin material, aluminum, an aluminum alloy, copper, a copper alloy, a magnesium alloy, a metal material such as stainless steel, or the like. It is made of a composite material of resin and metal.

  The battery holder 210 has holding portions 212 having L-shaped cross sections at the four corners of the rectangular plate-shaped main body portion 211. By fitting the corners of the four corners of the wide side surface 10a of the battery case 10 inside the four holding portions 212 of the battery holder 210, the prismatic secondary battery 100 and the battery in a direction parallel to the wide side surface 10a of the battery case 10 can be obtained. The relative position with respect to the holder 210 is defined, and one side of the rectangular secondary battery 100 in the thickness direction is held by the battery holder 210. A plurality of concave grooves 213 are provided in the body portion 211 of the battery holder 210 facing the wide side surface 10 a of the battery container 10 along the width direction of the battery container 10, and the width direction of the battery container 10 is between the concave grooves 213. A contact portion 214 extending along the line is provided. The battery holder 210 has a symmetrical shape in a cross section passing through the center of the thickness of the main body 211 and is disposed between the two rectangular secondary batteries 100.

  The restraining member 220 includes a pair of end plates 221, four shafts 222, and nuts not shown. The end plate 221 is a rectangular plate-like member having through holes 221a at the four corners. The end plate 221 has a concave groove 213 similar to that of the battery holder 210 and a contact hole on the surface facing the wide side surface 10a of the battery case 10 of the rectangular secondary battery 100. The contact portion 214 and the holding portion 212 that holds the corner portion of the battery case 10 are provided. That is, the portion of the end plate 221 that faces the prismatic secondary battery 100 can be regarded as a battery holder 210 that holds the prismatic secondary battery 100. The end plate 221 can be manufactured by the same material as the battery holder 210, for example.

  The shaft 222 of the restraining member 220 is provided with male screws at both ends 222a formed in a round bar shape. An intermediate portion 222b of the shaft 222 is provided by a plate material bent into an L-shaped cross-sectional shape. The shape of the intermediate portion 222 b of the shaft 222 corresponds to the shape of the holding portions 212 at the four corners of the battery holder 210, and the holding portions 212 at the four corners of the battery holder 210 are held by the intermediate portions 222 b of the four shafts 222. On both sides of the intermediate portion 222b of the shaft 222, flange portions 222c bent toward the outer side in the width direction of the rectangular secondary battery 100 are provided, and both end portions 222a having a round bar shape are provided on the flange portion 222c.

  In order to place the plurality of prismatic secondary batteries 100 alternately with the battery holders 210 and restrain them by the restraining member 220, first, the plurality of prismatic secondary batteries 100 are stacked in the thickness direction with the battery holder 210 interposed therebetween. At this time, the prismatic secondary batteries 100 are stacked by alternately reversing 180 ° so that the positions of the positive electrode external terminals 20A and the negative electrode external terminals 20B of the prismatic secondary batteries 100 adjacent in the stacking direction are reversed. And the battery holder 210 is arrange | positioned between the square secondary batteries 100, and the wide case of the battery container 10 of the square secondary battery 100 of the both ends of a lamination direction is arrange | positioned at the both ends of the lamination direction. A pair of end plates 221 are arranged facing the side surface 10a.

  Next, the L-shaped intermediate portion 222b of the shaft 222 in cross-section is aligned with the position of the holding portion 212 of the battery holder 210, and the round bar-shaped end portions 222a of the shaft 222 are passed through the through holes 221a of the end plate 221, The flange portions 222c on both sides of the intermediate portion 222b are brought into contact with the surface of the end plate 221 facing the rectangular secondary battery 100. Then, by fastening nuts to the male screws at both ends 222a of the shaft 222, the interval between the pair of end plates 221 is defined by the intermediate portion 222b of the shaft 222, and a plurality of rectangular secondary plates are between the pair of end plates 221. The battery 100 is held and restrained by the battery holder 210.

  The prismatic secondary battery 100 is compressed between the two battery holders 210 or between the end plate 221 and the battery holder 210, and the wide side surface 10 a of the battery container 10 is in contact with the contact portion 214 of the battery holder 210 or the end plate 221. It is pressed against the upper and lower parts of the main body 211. Although details will be described later, both ends of the lid member 12 of the rectangular secondary battery 100 in the short direction and the battery holder 210 or the end plate 221 are in contact with each other. However, for example, before charging / discharging the square secondary battery 100, there may be a gap between both ends in the short direction of the lid member 12 and the battery holder 210 or the end plate 221.

  The positive external terminal 20A and the negative external terminal 20B of the prismatic secondary battery 100 adjacent to each other in the stacking direction are connected by a metal bus bar 250 having conductivity, and a plurality of prismatic secondary batteries 100 are connected in series. The bus bar 250 has a through hole 250a through which the bolts 21 of the positive external terminal 20A and the negative external terminal 20B pass, and a nut (not shown) is fastened to the through hole 250a through the bolt 21 of the positive external terminal 20A and the negative external terminal 20B. Thus, the positive electrode external terminal 20A and the negative electrode external terminal 20B are fixed.

  The top plate 230 is a rectangular plate-like member disposed above the prismatic secondary battery 100 that is restrained by the restraining member 220 and the battery holder 210. The top plate 230 has through holes 230a and 230b having an elongated round shape at a position corresponding to the gas discharge valve 13 of the rectangular secondary battery 100 and a position corresponding to the bus bar 250 connecting the adjacent rectangular secondary batteries 100. Is provided. A ring-shaped seal member 231 is fitted in the through hole 230a corresponding to the gas discharge valve 13.

  The seal member 231 seals the gap between the top plate 230 and the lid member 12. The top plate 230 is maintained at a predetermined distance from the lid member 12 of the rectangular secondary battery 100 by having both ends in the width direction of the rectangular secondary battery 100 abut on the upper surface of the holding portion 212 of the battery holder 210. Has been. As a result, the seal member 231 is compressed to a predetermined height between the top plate 230 and the lid member 12 of the rectangular secondary battery 100, and the sealing performance of the seal member 231 is ensured.

  The cover 240 is a rectangular plate-like member that is disposed on the top plate 230 and covers the top plate 230, and has a recess 240 a on the surface facing the top plate 230. The recess 240 a is continuously provided in the stacking direction of the rectangular secondary battery 100 at a position overlapping the through hole 230 a of the top plate 230 corresponding to the gas discharge valve 13 of the rectangular secondary battery 100, and between the top plate 230. A duct D is formed in The gas discharged from the gas discharge valve 13 of the prismatic secondary battery 100 is discharged to the outside through the through hole 230a of the top plate 230 and the duct D.

  A part of the cover 240 and the top plate 230 protrudes from both ends of the prismatic secondary battery 100 in the stacking direction, and tubular connection portions Dc are formed at both ends of the duct D. The connection part Dc of the duct D is connected to the connection part Dc of the duct D of another adjacent assembled battery 200 or connected to a hose for guiding discharged gas or the like to the outside of the vehicle or a pan for gas supplementation. The The cover 240 and the top plate 230 have a through hole 230c through which the bolt B is passed, and the bolt B passed through the through hole 230c is fastened to a screw hole 222d provided in an intermediate portion 222b of the shaft 222 of the restraining member 220. , Fixed to the restraining member 220.

(Square secondary battery)
The assembled battery 200 of this embodiment has technical features in the configuration of the lid member 12 of the prismatic secondary battery 100 described later. Hereinafter, an example of the configuration of the prismatic secondary battery 100 used in the assembled battery 200 of the present embodiment will be described in detail.

  FIG. 4 is a perspective view of the prismatic secondary battery 100 constituting the assembled battery 200 shown in FIG. FIG. 5 is an exploded perspective view of the prismatic secondary battery 100 shown in FIG.

  The prismatic secondary battery 100 includes a battery container 10 formed in a rectangular box shape. The battery container 10 is arranged on the bottomed rectangular tube-shaped battery can 11 having an open top, a rectangular plate-shaped lid member 12 that seals the upper opening 11 a of the battery can 11, and an upper surface of the lid member 12. A positive external terminal 20A and a negative external terminal 20B are provided. The battery can 11 is manufactured, for example, by subjecting a metal material such as aluminum or aluminum alloy to deep drawing. The lid member 12 is manufactured, for example, by pressing a metal material similar to that of the battery can 11. The configuration of the lid member 12 of the prismatic secondary battery 100, which is a characteristic part of the assembled battery 200 of the present embodiment, will be described in detail later using an enlarged view.

  The battery case 10 is formed in a substantially rectangular parallelepiped shape, and has a wide side surface 10a having a maximum area along the width direction of the battery case 10, a narrow side surface 10b along the thickness direction of the battery case 10, and a long width direction of the battery case 10. It has a rectangular bottom surface 10c with the side direction and the thickness direction of the battery case 10 as the short side direction. A positive electrode external terminal 20A and a negative electrode external terminal 20B made of different materials are provided on the upper surface of the lid member 12 outside the battery container 10 at both ends in the width direction of the battery container 10, that is, in the longitudinal direction of the lid member 12. .

  The positive external terminal 20A and the negative external terminal 20B are generally formed in a rectangular flat plate shape. The positive external terminal 20A is made of, for example, aluminum or an aluminum alloy, and the negative external terminal 20B is made of, for example, copper or a copper alloy. The shapes of the positive electrode external terminal 20A and the negative electrode external terminal 20B are not limited to a plate shape, and may be formed in, for example, a substantially rectangular parallelepiped block shape or a column shape. Each of the positive external terminal 20 </ b> A and the negative external terminal 20 </ b> B includes a bolt 21 for fastening the bus bar 250.

  A gasket 30 as an insulating member is disposed between the positive electrode external terminal 20A and the negative electrode external terminal 20B and the lid member 12, and the positive electrode external terminal 20A and the negative electrode external terminal 20B are electrically insulated from the lid member 12. Has been. The gasket 30 is made of, for example, an insulating resin material such as polypropylene (PP).

  The lid member 12 has a gas discharge valve 13 and a liquid injection port 14 between the positive electrode external terminal 20A and the negative electrode external terminal 20B. The gas discharge valve 13 is provided by, for example, thinning a part of the lid member 12 to form a cleavage groove, and the gas discharge valve 13 is opened when the internal pressure of the battery container 10 rises above a predetermined pressure. The internal pressure of the battery container 10 is reduced by releasing the gas inside the container 10. The liquid injection port 14 is used for injecting an electrolytic solution into the battery container 10, and the liquid injection plug 15 is welded and sealed by laser welding, for example.

  A positive electrode current collector plate 50 </ b> A and a negative electrode current collector plate 50 </ b> B are fixed to the lower surface of the cover member 12, which is the inside of the battery container 10, at both ends in the longitudinal direction of the cover member 12 via insulating members 40. The positive electrode current collector plate 50A is made of, for example, aluminum or an aluminum alloy, and the negative electrode current collector plate 50B is made of, for example, copper or a copper alloy. Each of the positive electrode current collector plate 50A and the negative electrode current collector plate 50B has a plate-like base portion 51 substantially parallel to the lid member 12 and a plate-like terminal portion 52 extending from the base portion 51 toward the bottom surface 10c of the battery container 10. doing.

  The base 51 of the positive electrode current collector plate 50A is connected to the positive electrode external terminal 20A by the positive electrode connection terminal 60A passing through the insulating member 40, the lid member 12 and the through hole of the positive electrode external terminal 20A, and the base 51 of the negative electrode current collector plate 50B is In addition, the insulating member 40, the lid member 12, and the negative electrode external terminal 20B are connected to the negative electrode external terminal 20B through the negative electrode connection terminal 60B that penetrates the through hole of the negative electrode external terminal 20B. The positive electrode connection terminal 60A and the negative electrode connection terminal 60B are made of the same material as the positive electrode current collector plate 50A and the negative electrode current collector plate 50B, respectively. The positive electrode connection terminal 60 </ b> A and the negative electrode connection terminal 60 </ b> B are electrically insulated from each other by the gasket 30.

  The positive electrode connection terminal 60A and the negative electrode connection terminal 60B have base ends connected to the base portions 51 of the positive electrode current collector plate 50A and the negative electrode current collector plate 50B, respectively, and cylindrical tip portions respectively have a positive electrode external terminal 20A and a negative electrode external terminal 20B. The diameter is expanded on the upper surface of the plate and plastically deformed into a disk shape. Thereby, the caulking portions 61 of the positive electrode connection terminal 60A and the negative electrode connection terminal 60B are formed on the upper surfaces of the positive electrode external terminal 20A and the negative electrode external terminal 20B, respectively. By forming the caulking portion 61 at the tips of the positive electrode connection terminal 60A and the negative electrode connection terminal 60B, the positive electrode external terminal 20A and the positive electrode current collector plate 50A are connected via the positive electrode connection terminal 60A, and the negative electrode external terminal 20B and the negative electrode current collector are connected. The electric plate 50B is connected via the negative electrode connection terminal 60B. The positive electrode external terminal 20A and the negative electrode external terminal 20B, the gasket 30, the insulating member 40, and the positive electrode current collector plate 50A and the negative electrode current collector plate 50B are caulked and fixed integrally to the lid member 12, and the lid assembly 110 is assembled. Is configured.

  The terminal portions 52 extending downward from the base portions 51 of the positive electrode current collector plate 50A and the negative electrode current collector plate 50B are respectively exposed to the positive electrode foil exposed portion 71c of the power generation element 70 accommodated in the battery can 11 by ultrasonic pressure welding or resistance welding, for example. And the negative electrode foil exposed portion 72c. Accordingly, the power generation element 70 is electrically connected to the terminal portions 52 of the positive current collector plate 50A and the negative current collector plate 50B, and is fixed between the positive current collector plate 50A and the terminal portions 52 of the negative current collector plate 50B. , Held by the lid assembly 110. The power generation element 70 is accommodated in the battery can 11 with the insulating case 80 interposed so as to cover the periphery of the power generation element 70 while being held by the lid assembly 110. The insulating case 80 is made of, for example, a sheet of an insulating resin material such as polypropylene (PP), and electrically insulates the battery can 11 from the power generation element 70. The power generation element 70 is arranged such that the winding center axis R (see FIG. 6) is along the long side direction of the lid member 12.

When assembling the prismatic secondary battery 100, the power generation element 70 held by the lid assembly 110 is accommodated in the battery can 11, and the lower end surface of the peripheral portion of the lid member 12 is placed around the upper opening 11 a of the battery can 11. The lid member 12 is joined to the upper end portion of the battery can 11 over the entire circumference by, for example, laser welding. Thereby, the upper opening 11 a of the battery can 11 is sealed by the lid member 12. Thereafter, a non-aqueous electrolyte is injected into the battery container 10 through the liquid injection port 14 of the lid member 12, and the liquid injection plug 15 is joined to the liquid injection port 14 by laser welding, for example, and sealed. The battery container 10 is sealed. Examples of the non-aqueous electrolyte injected into the battery container 10 include a non-aqueous electrolyte in which a lithium salt such as lithium hexafluorophosphate (LiPF ₆ ) is dissolved in a carbonic acid ester-based organic solvent such as ethylene carbonate. Can be used.

  FIG. 6 is an exploded perspective view in which a part of the power generation element 70 of the rectangular secondary battery 100 shown in FIG. 5 is developed.

  The power generation element 70 is a wound electrode group in which a positive electrode 71 and a negative electrode 72 opposed to each other with separators 73 and 74 interposed therebetween are wound around an axis parallel to the winding center axis R and formed into a flat shape. is there. The power generation element 70 is formed into a flat shape having a flat portion 70 a facing the wide side surface 10 a of the battery case 10 and a curved portion 70 b facing the bottom surface of the lid member 12 and the battery can 11. The flat portion 70a is a portion where the electrodes 71, 72 and the separators 73, 74 are laminated flat, and the curved portion 70b is a portion where the electrodes 71, 72 and the separators 73, 74 are bent and laminated in a semi-cylindrical shape. It is.

  The positive electrode 71 includes a positive electrode metal foil 71a that is a positive electrode current collector, and a positive electrode mixture layer 71b made of a positive electrode active material mixture applied to both surfaces of the positive electrode metal foil 71a. One side in the width direction of the long strip-like positive electrode 71 is a foil exposed portion 71c where the positive electrode mixture layer 71b is not formed and the positive metal foil 71a is exposed. The positive electrode 71 is wound around the winding center axis R such that the foil exposed portion 71 c is disposed on the opposite side of the winding exposed portion 72 c of the negative electrode 72 in the winding central axis R direction.

  In order to manufacture the positive electrode 71, for example, a positive electrode active material mixture obtained by adding a conductive material, a binder and a dispersion solvent to a positive electrode active material and kneading is mixed on both surfaces of the positive electrode metal foil 71a except for one side in the width direction. Apply, dry, press and cut. As the positive electrode metal foil 71a, for example, an aluminum foil having a thickness of about 20 μm to 30 μm can be used. The thickness of the positive electrode mixture layer 71b not including the thickness of the positive electrode metal foil 71a is, for example, about 90 μm.

As a material of the positive electrode active material mixture, for example, 100 parts by weight of lithium manganate (chemical formula LiMn ₂ O ₄ ) is used as the positive electrode active material, 10 parts by weight of flaky graphite as the conductive material, and 10% by weight as the binder. Part of polyvinylidene fluoride (hereinafter referred to as PVDF) and N-methylpyrrolidone (hereinafter referred to as NMP) can be used as a dispersion solvent.

  The positive electrode active material is not limited to the above-described lithium manganate. For example, another lithium manganate having a spinel crystal structure, or a lithium manganese composite oxide partially substituted or doped with a metal element may be used. Further, as the positive electrode active material, lithium cobaltate or lithium titanate having a layered crystal structure, and a lithium-metal composite oxide obtained by substituting or doping a part thereof with a metal element may be used.

  The negative electrode 72 includes a negative electrode metal foil 72a that is a negative electrode current collector, and a negative electrode mixture layer 72b made of a negative electrode active material mixture applied to both surfaces of the negative electrode metal foil 72a. One side in the width direction of the long strip-shaped negative electrode 72 is a foil exposed portion 72c where the negative electrode mixture layer 72b is not formed and the negative metal foil 72a is exposed. The negative electrode electrode 72 is wound around the winding center axis R such that the foil exposed portion 72 c is disposed on the opposite side of the foil exposed portion 71 c of the positive electrode 71 in the winding central axis R direction.

  In order to manufacture the negative electrode 72, for example, a negative electrode active material mixture kneaded by adding a binder and a dispersion solvent to the negative electrode active material is applied to both surfaces of the negative electrode metal foil 72a except for one side in the width direction. , Dry, press, cut. As the negative electrode metal foil 72a, for example, a copper foil having a thickness of about 10 μm to 20 μm can be used. The thickness of the negative electrode mixture layer 72b not including the thickness of the negative electrode metal foil 72a is, for example, about 70 μm.

As a material for the negative electrode active material mixture, for example, 100 parts by weight of amorphous carbon powder as the negative electrode active material, 10 parts by weight of PVDF as the binder, and NMP as the dispersion solvent can be used. The negative electrode active material is not limited to the above-mentioned amorphous carbon, and natural graphite capable of inserting and removing lithium ions, various artificial graphite materials, carbonaceous materials such as coke, and compounds such as Si and Sn (for example, , SiO, TiSi ₂ or the like), or a composite material thereof. The particle shape of the negative electrode active material is not particularly limited, and a particle shape such as a scale shape, a spherical shape, a fiber shape, or a lump shape can be appropriately selected.

  Note that the binder used for the mixture layer of the positive electrode and the negative electrode is not limited to PVDF. Examples of the binder include polytetrafluoroethylene (PTFE), polyethylene, polystyrene, polybutadiene, butyl rubber, nitrile rubber, styrene butadiene rubber, polysulfide rubber, nitrocellulose, cyanoethyl cellulose, various latexes, acrylonitrile, and vinyl fluoride. Polymers such as vinylidene fluoride, propylene fluoride, chloroprene fluoride, and acrylic resins, and mixtures thereof may be used.

  The separators 73 and 74 insulate the positive electrode 71 and the negative electrode 72 from each other, and the separator 74 is wound around the outer periphery of the negative electrode 72 wound around the outermost periphery of the power generation element 70. The separators 73 and 74 are made of, for example, a microporous polyethylene resin through which lithium ions can pass.

  The power generation element 70 includes a positive electrode foil exposed portion 71c of the positive electrode 71 laminated at one end in the winding center axis R direction and a negative electrode foil exposed portion 72c of the negative electrode 72 laminated at the other end in the winding central axis R direction. 5 are bundled so as to be divided into two in the thickness direction of the battery container 10 as shown in FIG. The positive electrode foil exposed portion 71c and the negative electrode foil exposed portion 72c are joined to the terminal portions 52 of the positive electrode current collector plate 50A and the negative electrode current collector plate 50B, respectively, by, for example, ultrasonic welding or resistance welding. Accordingly, the positive electrode 71 and the negative electrode 72 are connected to the positive external terminal 20A and the negative external terminal 20B via the positive current collector plate 50A and the negative current collector plate 50B, respectively.

  Based on the above configuration, the prismatic secondary battery 100 shown in FIGS. 4 and 5 uses, for example, power supplied from an external power generation device or the like to supply the positive external terminal 20A, the negative external terminal 20B, the positive collector plate 50A, Charging is performed by accumulating between the mixture layers 71b and 72b of the positive electrode 71 of the power generation element 70 and the negative electrode 72 via the negative electrode current collecting plate 50B. In addition, the prismatic secondary battery 100 is configured such that power charged between the mixture layers 71b and 72b of the positive electrode 71 and the negative electrode 72 of the power generation element 70 is supplied to the positive current collector plate 50A, the negative current collector plate 50B, and the positive electrode external terminal 20A. For example, electric power is supplied to an external load such as a motor via the negative electrode external terminal 20B.

  Hereinafter, the configuration of the lid member 12 that is a characteristic part of the assembled battery 200 and the prismatic secondary battery 100 of the present embodiment will be described in detail.

  FIG. 7 is an enlarged sectional view taken along line VII-VII of the prismatic secondary battery 100 shown in FIG. FIG. 8 is an enlarged cross-sectional view of a VIII portion of the prismatic secondary battery 100 shown in FIG.

  The assembled battery 200 and the prismatic secondary battery 100 according to the present embodiment are such that the lid member 12 of the prismatic secondary battery 100 is between the end 12a facing the battery holder 210 shown in FIGS. 2 and 3 and the end 12a. And the center Cb of the thickness Tb of the intermediate part 12b is located above the center Ca of the thickness Ta of the end part 12a. Here, the end portion 12 a of the lid member 12 means both end portions 12 a in the thickness direction of the battery container 10, that is, the short direction of the lid member 12. Further, the end portion 12a of the lid member 12 is a portion including a welded portion WP of the lid member 12 joined to the upper end portion of the battery can 11 by welding. Moreover, upward means the direction which faces the outer side of the battery can 11 further from the position of the upper opening 11a of the battery can 11, and does not necessarily mean the upper direction of the vertical direction.

  The minimum value of the width Wa of the end portion 12a of the lid member 12 in the thickness direction of the battery container 10 is, for example, at least an intermediate portion when the end portion 12a of the lid member 12 is pressed against the battery holder 210 or the end plate 221. 12b is set to a width Wa that does not contact the battery holder 210 or the end plate 221. Further, the maximum value of the width W of the end portion 12a of the lid member 12 is such that, for example, the lower surface of the gasket 30 between the positive electrode external terminal 20A and the negative electrode external terminal 20B and the lid member 12 becomes the end portion 12a of the lid member 12. The width Wa is set so as not to overlap. That is, the positive external terminal 20 </ b> A and the negative external terminal 20 </ b> B are not disposed at the end 12 a of the lid member 12 but are disposed at the intermediate portion 12 b of the lid member 12.

  In the present embodiment, the lid member 12 has a thickness Ta of the end portion 12a that is thinner than a thickness Tb of the intermediate portion 12b. A step 12c is formed on the upper surface of the lid member 12 between the end 12a and the intermediate portion 12b. In the prismatic secondary battery 100 of the present embodiment, the stepped portion 12c of the lid member 12 is provided over the entire circumference of the lid member 12, as shown in FIGS. Note that the stepped portion 12c of the lid member 12 only needs to be provided at least between the end portion 12a and the intermediate portion 12b of the lid member 12 facing the battery holder 210 or the end plate 221. In other words, the stepped portion 12c along the stacking direction of the rectangular secondary battery 100, that is, the short direction of the lid member 12, can be omitted.

  At the end portion 12 a of the lid member 12, the lower end surface of the lid member 12 is in contact with the upper end portion of the battery can 11. Then, when the lid member 12 and the battery can 11 are joined by laser welding, a laser is irradiated to the contact portion between the lower end surface of the lid member 12 and the upper end portion of the battery can 11. Thereby, a part of the lower end surface of the lid member 12 and a part of the upper end portion of the battery can 11 are melted and fused, and the weld metal is formed between the lower end surface of the lid member 12 and the upper end portion of the battery can 11. A solidified weld WP is formed, and the battery can 11 is sealed by the lid member 12.

  Hereinafter, the operation of the assembled battery 200 and the square secondary battery 100 of the present embodiment will be described.

  FIG. 9 is a schematic cross-sectional view showing an enlarged cross section of the assembled battery 200 shown in FIG. In FIG. 9, in order to easily understand the operation of the assembled battery 200 and the prismatic secondary battery 100 of the present embodiment, the configuration other than one prismatic secondary battery 100 and the battery holders 210 on both sides thereof is omitted. In addition, the deformation of the lid member 12 is exaggerated and the scale of each part is appropriately changed.

  In the assembled battery 200 and the prismatic secondary battery 100 of the present embodiment, the power generation element 70 accommodated in the battery container 10 expands as the prismatic secondary battery 100 is charged and discharged, and the wide side surface 10a of the battery container 10 is the battery. It tries to deform so as to bulge out of the container 10. However, the wide side surface 10 a of the battery container 10 comes into contact with the upper and lower ends and the contact portion 214 of the main body portion 211 (or the end plate 221, the same applies hereinafter) of the opposite battery holder 210 and expands from the battery holder 210. Receives reaction force in the compression direction to be regulated. Further, the end 12a of the lid member 12 facing the battery holder 210 abuts on the battery holder 210 after the battery container 10 expands even if the end 12a does not contact the battery holder 210 before the battery container 10 expands. A force F in a direction from 210 toward the intermediate portion 12b of the lid member 12 is received.

  Here, as shown in FIG. 8, the assembled battery 200 and the prismatic secondary battery 100 according to the present embodiment have a center Cb of the thickness Tb of the intermediate portion 12b of the lid member 12 of the prismatic secondary battery 100 at the end 12a. It is located above the center Ca of the thickness Ta. Therefore, as shown in FIG. 9, an upward force f acts on the intermediate portion 12b from the end 12a of the lid member 12, and the entire lid member 12 is deformed so as to bend upward. Accordingly, when the rectangular secondary battery 100 is expanded, the lid member 12 that seals the upper opening of the battery can 11 is deformed upward from the upper opening 11 a of the battery can 11 and is directed toward the outside of the battery can 11. Deform.

  Therefore, according to the assembled battery 200 and the prismatic secondary battery 100 of the present embodiment, unlike the conventional prismatic secondary battery described in Patent Document 1, the lid member 12 faces the inner lower side of the battery can 11. The deformation is prevented, and a short circuit between the lid member 12 and the power generation element 70 can be prevented.

  Further, as shown in FIG. 8, the lid member 12 has a thickness Ta of the end portion 12a smaller than a thickness Tb of the intermediate portion 12b. By changing the position of the center Cb of the thickness Tb, the center Cb of the thickness Tb of the intermediate portion 12b can be positioned above the center Ca of the thickness Ta of the end portion 12a.

  Further, since the lid member 12 has the step portion 12c between the end portion 12a and the intermediate portion 12b, the end portion 12a faces the outer side of the battery can 11 from the end portion 12a to the intermediate portion 12b in the step portion 12c. A force f can be applied. Further, by forming the stepped portion 12 c over the entire circumference of the lid member 12, the end in the width direction of the battery container 10, that is, the longitudinal direction of the lid member 12 abuts on the battery holder 210, and the length of the lid member 12 is increased. Even when a force directed toward the intermediate portion 12b in the longitudinal direction of the lid member 12 acts on the end portion in the direction, a force f directed toward the outside of the battery can 11 acts on the intermediate portion from the end portion in the stepped portion 12c. Can be made.

  The lower end surface of the lid member 12 is in contact with the upper end portion of the battery can 11. Therefore, unlike the prayer welding of the end portion of the lid member of the rectangular secondary battery described in Patent Document 1, when the central portion of the wide side surface 10a of the battery container 10 is expanded most, the upper end portion of the wide side surface 10a It is possible to prevent the force directed toward the lower inside of the battery can 11 from acting on the end 12 a of the lid member 12.

  In addition, the square secondary battery 100 includes a positive electrode external terminal 20A and a negative electrode external terminal 20B on the upper surface of the lid member 12, and the positive electrode external terminal 20A and the negative electrode external terminal 20B are disposed in the intermediate portion 12b of the lid member 12. Yes. Therefore, when the positive electrode external terminal 20A and the negative electrode external terminal 20B are arranged on the upper surface of the lid member 12, the positive electrode external terminal 20A and the negative electrode external terminal 20B are not affected by the step portion 12c provided on the lid member 12 and can be stably arranged. .

  Further, in the rectangular secondary battery 100, the battery can 11 is formed in a flat rectangular shape, and the battery holder 210 is alternately stacked in the thickness direction of the battery can 11. The lid member 12 is formed in a rectangular plate shape, the battery holders 210 are arranged on both sides in the short side direction, and the power generation element 70 is arranged so that the winding center axis R is along the long side direction of the lid member 12. Has been. In the prismatic secondary battery 100 having such a configuration, the expansion of the central portion in the height direction of the wide side surface 10a having the maximum area of the battery can 11 facing the short side direction of the lid member 12 at the time of charging / discharging becomes the largest. Therefore, the tendency that the upper end portion of the battery can 11 tends to be deformed toward the inner lower side of the battery can 11 becomes strong. However, according to the assembled battery 200 and the secondary battery of the present embodiment, based on the above-described configuration, the lid member 12 is prevented from being deformed toward the inner lower side of the battery case, and the lid member 12 and the power generation element 70 are Can be prevented.

  As described above, according to the assembled battery 200 and the secondary battery of the present embodiment, the assembled battery 200 that can prevent a short circuit between the lid member 12 of the rectangular secondary battery 100 and the power generation element 70 and the assembled battery. The prismatic secondary battery 100 used in the apparatus 200 can be provided.

(Modifications 1 and 2)
Hereinafter, modifications 1 and 2 of the prismatic secondary battery 100 of the above-described embodiment will be described with reference to FIGS. 10 and 11 with reference to FIGS. 1 to 7 and FIG. 9. 10 and 11 are enlarged cross-sectional views of the prismatic secondary batteries 100A and 100B of Modifications 1 and 2 corresponding to FIG. 8 of the above-described embodiment.

  The prismatic secondary batteries 100A and 100B of Modifications 1 and 2 have the prisms described in the above-described embodiment in that the intermediate portion 12b of the lid member 12 has a convex portion 12P that fits into the upper opening 11a of the battery can 11. Different from the secondary battery 100. The other points of the rectangular secondary batteries 100A and 100B of the first and second modified examples are the same as those of the rectangular secondary battery 100 described in the above-described embodiment, and thus the same portions are denoted by the same reference numerals. Is omitted.

  In the prismatic secondary battery 100 </ b> A of Modification 1 shown in FIG. 10, the protrusion 12 </ b> P protruding from the lower end surface of the cover member 12 toward the inside of the battery can 11 is adjacent to the end 12 a of the cover member 12. Is provided at the end of the intermediate portion 12b. The convex portion 12 </ b> P extends in a ring shape along the inner wall of the upper end portion of the battery can 11, and fits inside the upper opening 11 a of the battery can 11 to position the lid member 12. The center Cb1 of the thickness Tb1 of the portion where the convex portion 12P of the intermediate portion 12b of the lid member 12 is not provided and the center Cb2 of the thickness Tb2 of the portion where the convex portion 12P is provided are of the end portion 12a of the lid member 12 It is located above the center Ca of the thickness Ta.

  In the prismatic secondary battery 100B of Modification 2 shown in FIG. 11, a convex portion 12P protruding from the lower end surface of the lid member 12 toward the inside of the battery can 11 is provided over the entire intermediate portion 12b of the lid member 12. The lid member 12 is positioned by being fitted inside the upper opening 11 a of the battery can 11. The center Cb2 of the thickness Tb2 of the intermediate portion 12b of the lid member 12 provided with the convex portion 12P is located above the center Ca of the thickness Ta of the end portion 12a of the lid member 12.

  According to the prismatic secondary batteries 100A and 100B of Modifications 1 and 2, and the assembled battery 200 including the prismatic secondary batteries 100A and 100B, the centers Cb1 and Cb2 of the thickness Tb1 and Tb2 of the intermediate portion 12b are the center Ca of the thickness Ta of the end portion 12a. Therefore, the same effect as that of the assembled battery 200 and the prismatic secondary battery 100 described in the above embodiment can be obtained. Moreover, when the convex part 12P is provided along the inner side wall of the upper end part of the battery can 11, when joining the lower end surface of the cover member 12 and the upper end part of the battery can 11 by laser welding, of the battery can 11 Debris and the like generated during welding are prevented from entering the inside. Moreover, the mechanical strength of the cover member 12 can be improved by providing the convex part 12P.

(Modification 3)
Hereinafter, Modification 3 of the prismatic secondary battery 100 of the above-described embodiment will be described with reference to FIGS. FIG. 12 is an enlarged cross-sectional view of a prismatic secondary battery 100C of Modification 3 corresponding to FIG. 8 of the above-described embodiment.

  The prismatic secondary battery 100C of Modification 3 is described in the above embodiment in that it does not have the step 12c between the end 12a and the intermediate part 12b of the lid member 12 but has the inclined part 12d. This is different from the prismatic secondary battery 100. The other points of the prismatic secondary battery 100C of the modification 3 are the same as those of the prismatic secondary battery 100 described in the above embodiment, and therefore, the same portions are denoted by the same reference numerals and description thereof is omitted.

  In the prismatic secondary battery 100C of this modification, the center portion Cb of the thickness Tb of the intermediate portion 12b is the thickness of the end portion 12a by having the inclined portion 12d between the end portion 12a and the intermediate portion 12b of the lid member 12. It is located above the center Ca of the length Ta. Therefore, when a force F from the battery holder 210 toward the intermediate portion 12b of the lid member 12 acts on the end portion 12a of the lid member 12, the inclination from the end portion 12a of the lid member 12 to the intermediate portion 12b of the lid member 12 is inclined. A force f directed outwardly from the battery can 11 acts through the portion 12d. Therefore, according to the prismatic secondary battery 100C of this modification and the assembled battery 200 including the same, the same effects as those of the assembled battery 200 and the prismatic secondary battery 100 described in the above embodiment can be obtained. The inclined surface of the inclined portion 12d may be flat or curved.

(Modifications 4 and 5)
Hereinafter, modifications 4 and 5 of the prismatic secondary battery 100 of the above-described embodiment will be described with reference to FIGS. 13 and 14 with reference to FIGS. 1 to 7 and FIG. 9. 13 and 14 are enlarged cross-sectional views of prismatic secondary batteries 100D and 100E of Modifications 4 and 5 corresponding to FIG. 8 of the above-described embodiment.

  In the square secondary batteries 100D and 100E of Modifications 4 and 5, the thickness Ta of the end 12a of the lid member 12 and the thickness Tb of the intermediate portion 12b are equal, and the gap between the end 12a and the intermediate portion 12b is the same. The present embodiment is different from the prismatic secondary battery 100 described in the above-described embodiment in that the connection portions 12e and 12f are provided. Since the other points of the rectangular secondary batteries 100D and 100E of the modified examples 4 and 5 are the same as those of the rectangular secondary battery 100 described in the above-described embodiment, the same portions are denoted by the same reference numerals. Is omitted.

  In the prismatic secondary battery 100D shown in FIG. 13, the connecting portion 12e formed between the end portion 12a and the intermediate portion 12b of the lid member 12 is substantially perpendicular to the end portion 12a and the intermediate portion 12b of the lid member 12. The lid member 12 has a predetermined height H in the thickness direction, that is, in the height direction of the battery case 10. Thereby, the center Cb of the thickness Tb of the intermediate part 12b of the lid member 12 is located above the center Ca of the thickness Ta of the end part 12a.

  In the prismatic secondary battery 100E shown in FIG. 14, the connecting portion 12f formed between the end portion 12a and the intermediate portion 12b of the lid member 12 is 90 ° with respect to the end portion 12a and the intermediate portion 12b of the lid member 12. By being bent at a smaller angle α, the lid member 12 has a predetermined height H in the thickness direction, that is, in the height direction of the battery case 10. Thereby, the connection part 12f of the cover member 12 inclines with respect to the edge part 12a and the intermediate part 12b of the cover member 12, and the center Cb of the thickness Tb of the intermediate part 12b of the cover member 12 is the thickness of the edge part 12a. It is located above the center Ca of the length Ta.

  In the square secondary batteries 100D and 100E of this modification, connecting portions 12e and 12f having a height H in the thickness direction of the lid member 12 are provided between the end 12a and the intermediate portion 12b of the lid member 12. Thereby, the center Cb of the thickness Tb of the intermediate part 12b is located above the center Ca of the thickness Ta of the end part 12a. Therefore, when a force F directed from the battery holder 210 toward the intermediate portion 12b of the lid member 12 acts on the end portion 12a of the lid member 12, the end portion 12a of the lid member 12 is connected to the intermediate portion 12b of the lid member 12. A force f directed outward and upward of the battery can 11 acts through the portions 12e and 12f. Therefore, according to the prismatic secondary batteries 100D and 100E of this modification and the assembled battery 200 including the same, the same effects as those of the assembled battery 200 and the prismatic secondary battery 100 described in the above embodiment can be obtained. .

  The embodiment of the present invention has been described in detail with reference to the drawings, but the specific configuration is not limited to this embodiment, and there are design changes and the like without departing from the gist of the present invention. They are also included in the present invention.

11 battery can, 11a top opening, 12 lid member, 12a end, 12b middle part, 12c stepped part, 12d inclined part, 12e connecting part, 12f connecting part, 12P convex part, 20A positive electrode external terminal, 20B negative electrode external terminal, 70 power generation element, 71 positive electrode, 72 negative electrode, 73 separator, 74 separator, 100 prismatic secondary battery, 100A-100E prismatic secondary battery, 200 assembled battery, 210 battery holder, 220 restraining member, thickness of Ca end Center, thickness center of Cb middle part, height of H connection part, R winding center axis, thickness of Ta end part, thickness of Tb middle part

Claims (10)

A battery pack comprising a plurality of prismatic secondary batteries stacked alternately with a battery holder, and a restraining member that restrains the battery holder and the prismatic secondary battery,
The prismatic secondary battery includes a power generation element wound with a positive electrode and a negative electrode facing each other with a separator interposed therebetween, a battery can that houses the power generation element, and a lid member that seals an upper opening of the battery can With
The lid member has an end portion facing the battery holder and an intermediate portion between the end portions, and the center of the thickness of the intermediate portion is positioned above the center of the thickness of the end portion. A battery pack characterized by that.   The assembled battery according to claim 1, wherein the lid member has a thickness of the end portion thinner than a thickness of the intermediate portion.   The assembled battery according to claim 2, wherein the lid member has a step portion between the end portion and the intermediate portion.   The assembled battery according to claim 2, wherein the lid member has an inclined portion between the end portion and the intermediate portion. The lid member has a connection portion between the end portion and the intermediate portion,
The assembled battery according to claim 1, wherein the connection portion has a height in a thickness direction of the lid member.   The assembled battery according to any one of claims 1 to 5, wherein a lower end surface of the lid member is in contact with an upper end portion of the battery can.   The assembled battery according to claim 6, wherein the lid member has a convex portion that fits into the upper opening of the battery can at the intermediate portion. The prismatic secondary battery includes a positive electrode external terminal and a negative electrode external terminal on an upper surface of the lid member,
The assembled battery according to any one of claims 2 to 5, wherein the positive external terminal and the negative external terminal are disposed in an intermediate portion of the lid member. In the prismatic secondary battery, the battery can is formed into a flat rectangular shape, and alternately stacked with the battery holder in the thickness direction of the battery can,
The lid member is formed in a rectangular plate shape, the battery holder is disposed on both sides in the short side direction,
The assembled battery according to claim 1, wherein the power generation element is arranged such that a winding center axis is along a long side direction of the lid member. A prismatic secondary battery used as an assembled battery by stacking alternately with a battery holder and restraining by a restraining member,
A power generation element wound with a positive electrode and a negative electrode facing each other with a separator interposed therebetween, a battery can that houses the power generation element, and a lid member that seals an upper opening of the battery can,
The lid member has an end portion facing the battery holder and an intermediate portion between the end portions, and the center of the thickness of the intermediate portion is positioned above the center of the thickness of the end portion. A prismatic secondary battery characterized by:

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