JP2013164903A - Square secondary battery and module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a square secondary battery capable of reducing variation in expansion of a battery can.SOLUTION: A square secondary battery 1 includes a flat power generation element 3 housed in a square battery can 11. One turn or more of an insulating protective film 41 is wound around the outer periphery of the power generation element 3. Total thickness Dt of the power generation element 3 and the insulating protective film 41 is adjusted to a preset thickness, by adjusting the length of the insulating protective film 41 wound around the power generation element 3.

Description

  The present invention relates to a prismatic secondary battery and a module having a plurality of the prismatic secondary batteries.

  In recent years, lithium ion secondary batteries with high energy density have been developed as power sources for electric vehicles and the like. For in-vehicle use, a square secondary battery with good volume efficiency is used. For example, Patent Document 1 discloses a structure in which a group of electrodes wound in a flat shape is housed in a deep-drawn battery can with a winding axis being sideways. Is disclosed. In this structure, an insulating bag is provided between the electrode group and the inner wall of the battery can.

JP 2011-100591 A

  In a rectangular secondary battery in which a flatly wound electrode group is housed in a rectangular battery can, the electrode group may swell due to charging, and the battery can be deformed in a bulging direction. Therefore, if the variation in the thickness dimension of the electrode group or the variation in the dimensional shape of the battery can is large among a plurality of batteries, the gap between the electrode group and the battery can varies, resulting in a variation in the expansion of the battery can. Becomes larger.

  For example, in a vehicle-mounted application or the like, since a plurality of prismatic secondary batteries are used as a module (assembled battery) that is arranged side by side in the thickness direction of the electrode group, the variation in expansion of the battery can between the prismatic secondary batteries is small. Is preferable.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a prismatic secondary battery that can reduce variation in expansion of a battery can.

  The present application includes a plurality of means for solving the above-described problems. To give an example, a rectangular secondary battery in which a flat battery element is accommodated in a prismatic battery can, The insulation protective film is wound around the outer periphery of the power generation element more than once, and the insulation protective film has a preset total thickness of the power generation element and the insulation protective film by adjusting the winding length wound around the power generation element It is characterized by being adjusted to thickness.

  According to the prismatic secondary battery of the present invention, it is possible to reduce the variation in expansion of the battery can among the plurality of prismatic secondary batteries and to make the expansion uniform. Problems, configurations, and effects other than those described above will be clarified by the following description of the embodiments.

1 is an external perspective view of a prismatic secondary battery according to a first embodiment. The disassembled perspective view of the square secondary battery shown by FIG. The external appearance perspective view of the state which showed the detail of the winding electrode group shown by FIG. 2, and expanded one part. The figure explaining the winding method of an insulation protective film. The perspective view which shows the state which wound the insulation protective film. FIG. 5B is a cross-sectional view taken along the line X2-X2 in FIG. The X2-X2 sectional view taken on the line of FIG. 5A which shows the state which wound the insulating protective film 1 round. The figure explaining an example of the method of closing the protrusion edge part of an insulating protective film. FIG. 7 is a cross-sectional view taken along line X3-X3 in FIG. The figure explaining another example of the method of closing the protrusion edge part of an insulating protective film. FIG. 9 is a cross-sectional view taken along line X4-X4 in FIG. Sectional drawing which shows the state which has arrange | positioned the winding electrode group and insulation protective film which were shown to FIG. 5B in the battery can. Sectional drawing which shows the state arrange | positioned in the battery can in the winding electrode group and insulation protective film which were shown in FIG. 5C. Sectional drawing explaining the other structural example of the square secondary battery concerning 1st Embodiment. The figure explaining the structure of the module concerning 1st Embodiment. The disassembled perspective view of the square secondary battery concerning 2nd Embodiment. Sectional drawing of the square secondary battery which has the structure shown in FIG. Sectional drawing of the square secondary battery which has the structure shown in FIG.

Next, embodiments of the present invention will be described with reference to the drawings.
The prismatic secondary battery of the present invention is a prismatic secondary battery in which a flat power generation element is accommodated in a prismatic battery can, and the power generation element has an insulating protective film wound around the outer periphery of the power generation element at least once. The insulating protective film has a structure in which the total thickness of the power generating element and the insulating protective film is adjusted to a preset thickness by adjusting the winding length wound around the power generating element.

<First embodiment>
1 is an external perspective view of the prismatic secondary battery according to the first embodiment, FIG. 2 is an exploded perspective view of the prismatic secondary battery shown in FIG. 1, and FIG. 3 is a winding shown in FIG. It is the external appearance perspective view of the state which showed the detail of the electrode group and expanded one part.

  The prismatic secondary battery 1 is a prismatic lithium ion secondary battery and has a configuration in which a power generation element 3 is accommodated in a battery container 2. The battery container 2 includes a battery can 11 having an opening 11 a and a battery lid 21 that closes the opening 11 a of the battery can 11. The power generating element 3 includes a wound electrode group 31 wound in a flat shape in a state where the separators 33 and 35 are interposed between the positive electrode 34 and the negative electrode 32 so as to overlap each other. The wound electrode group 31 is accommodated in the battery can 11 of the battery container 2 in a state in which a sheet-like insulating protective film 41 is wound around the wound electrode group 31.

  The battery can 11 and the battery lid 21 are both made of an aluminum alloy, and the battery lid 21 is welded to the battery can 11 by laser welding. In the battery container 2, the battery can 11 and the battery lid 21 constitute a rectangular parallelepiped flat rectangular container. The battery can 11 has a pair of wide side surfaces PW, a pair of narrow side surfaces PN, and a bottom surface PB.

  The battery lid 21 is provided with a positive electrode terminal 51 and a negative electrode terminal 61 (a pair of electrode terminals) via an insulating member, and constitutes the lid assembly 4. In addition to the positive electrode terminal 51 and the negative electrode terminal 61, the battery lid 21 has a gas discharge valve 71 that is opened when the pressure in the battery container 2 rises above a predetermined value and discharges the gas in the battery container 2; A liquid injection port 72 for injecting an electrolytic solution into the battery container 2 is disposed.

  The positive electrode terminal 51 and the negative electrode terminal 61 are disposed at positions separated from each other on one side and the other side in the longitudinal direction of the battery lid 21. The positive terminal 51 and the negative terminal 61 include external terminals 52 and 62 arranged outside the battery lid 21 and connection terminals 53 and 63 arranged inside the battery lid 21 and electrically connected to the external terminals 52 and 62. Have. The positive external terminal 52 and the connection terminal 53 are made of an aluminum alloy, and the negative external terminal 62 and the connection terminal 63 are made of a copper alloy.

  Insulating members (not shown) are interposed between the connection terminals 53 and 63 and the external terminals 52 and 62, respectively, and are electrically insulated from the battery lid 21. The connection terminals 53 and 63 have current collection terminals 54 and 64 that extend from the inside of the battery lid 21 toward the bottom of the battery can 11 and are conductively connected to the wound electrode group 31. The wound electrode group 31 is disposed and supported between the current collecting terminal 54 of the positive electrode terminal 51 and the current collecting terminal 64 of the negative electrode terminal 61. A power generation element assembly 5 is configured by the power generation element 3 and the lid assembly 4 described above.

  As shown in FIG. 3, the wound electrode group 31 is configured by winding a separator 33, a negative electrode 32, a separator 35, and a positive electrode 34 in this order and winding them in a flat shape. In the wound electrode group 31, the outermost electrode plate is the negative electrode 32, and at least one of the separators 33 and 35 is wound outside. 3 indicates the thickness direction of the wound electrode group 31, and the Y-axis direction is a direction parallel to the wide surface of the wound electrode group 31 and orthogonal to the wound axis direction. The Z-axis direction is a direction parallel to the wide surface of the wound electrode group 31 and a direction parallel to the wound axis direction.

  The separators 33 and 35 are interposed between the positive electrode 34 and the negative electrode 32 and have a role of insulating between the positive electrode 34 and the negative electrode 32. The negative electrode coating portion 32a of the negative electrode 32 is larger in the width direction than the positive electrode coating portion 34a of the positive electrode 34, whereby the positive electrode coating portion 34a is always sandwiched between the negative electrode coating portion 32a. Yes.

  The positive electrode uncoated portion 34b and the negative electrode uncoated portion 32b are bundled in the thickness direction at the wide surface portion of the wound electrode group 31 and connected to the current collecting terminals 54 and 64 of each electrode by welding or the like. In addition, although the separators 33 and 35 are wider than the negative electrode coating part 32a in the width direction, they are wound to a position where the metal foil surface at the end is exposed in the positive electrode uncoated part 34b and the negative electrode uncoated part 32b. Therefore, it does not hinder the welding when bundled.

  The positive electrode 34 has a positive electrode coating portion 34a in which a positive electrode active material mixture is applied to both surfaces of a positive electrode metal foil that is a positive electrode current collector, and a positive electrode active portion 34 is provided at one end in the width direction of the positive electrode metal foil. A positive electrode uncoated portion (positive metal foil exposed portion) 34b to which no material mixture is applied is provided.

  The negative electrode 32 has a negative electrode coating part 32a in which a negative electrode active material mixture is applied to both surfaces of a negative electrode metal foil that is a negative electrode current collector, and a negative electrode active part is provided at the other end in the width direction of the positive electrode metal foil. A negative electrode uncoated portion (negative electrode metal foil exposed portion) 32b where no material mixture is applied is provided. The positive electrode uncoated portion 34b and the negative electrode uncoated portion 32b are regions where the metal surface of the metal foil is exposed. As shown in FIG. 3, the winding electrode group 31 has one end on one side in the winding axis direction. It arrange | positions mutually apart at the edge part of the other side.

  In the negative electrode 32, 10 parts by weight of polyvinylidene fluoride (hereinafter referred to as PVDF) is added as a binder to 100 parts by weight of amorphous carbon powder as a negative electrode active material, and N as a dispersion solvent. -A negative electrode mixture in which methyl bilolidon (hereinafter referred to as NMP) was added and kneaded was prepared. This negative electrode mixture was applied to both surfaces of a 10 μm thick copper foil (negative electrode metal foil) leaving the current collecting portion (negative electrode uncoated portion). Thereafter, drying, pressing, and cutting were performed to obtain a negative electrode with a negative electrode active material coating portion thickness of 70 μm that did not contain copper foil.

  In this embodiment, the case where amorphous carbon is used as the negative electrode active material is exemplified, but the present invention is not limited to this, and natural graphite capable of inserting and removing lithium ions and various artificial graphites are not limited thereto. The material may be a carbonaceous material such as a material or coke, and the particle shape is not particularly limited to a scale shape, a spherical shape, a fiber shape, a lump shape, or the like.

Regarding the positive electrode 34, 10 parts by weight of flaky graphite as a conductive material and 10 parts by weight of PVDF as a binder are added to 100 parts by weight of lithium manganate (chemical formula LiMn ₂ O ₄ ) as a positive electrode active material. A positive electrode mixture was prepared by adding and kneading NMP as a dispersion solvent. This positive electrode mixture was applied on both sides of an aluminum foil (positive metal foil) having a thickness of 20 μm, leaving a solid current collecting part (positive electrode uncoated part). Thereafter, drying, pressing, and cutting were performed to obtain a positive electrode having a thickness of 90 μm, which does not include an aluminum foil.

  Further, in the present embodiment, the case where lithium manganate is used as the positive electrode active material is exemplified, but other lithium manganate having a spinel crystal structure or a lithium manganese composite oxide partially substituted or doped with a metal element or A lithium cobalt oxide or lithium titanate having a layered crystal structure, or a lithium-metal composite oxide in which a part thereof is substituted or doped with a metal element may be used.

  In the present embodiment, the case where PVDF is used as the binder of the coating part in the positive electrode and the negative electrode is exemplified, but polytetrafluoroethylene (PTFE), polyethylene, polystyrene, polybutadiene, butyl rubber, nitrile rubber, Use polymers such as styrene butadiene rubber, polysulfide rubber, nitrocellulose, cyanoethyl cellulose, various latexes, acrylonitrile, vinyl fluoride, vinylidene fluoride, propylene fluoride, chloroprene, acrylic resins, and mixtures thereof. be able to.

  Next, the structure of the insulating protective film 41 wound around the outer periphery of the wound electrode group 31 will be described with reference to FIGS. In addition, although the insulating protective film 41 is shown as a transparent member for convenience of explanation, it is not limited to being transparent, and may be opaque. 5B, FIG. 5C, FIG. 7, and FIG. 9 are interposed between the positive electrode 34 and the negative electrode 32 constituting the wound electrode group 31 and between the positive electrode 34 and the negative electrode 32. The separators 33 and 35 are not shown, and only the outer shape of the wound electrode group 31 is shown.

  A conventional lithium ion secondary battery is formed in a box shape by intricately bending an insulating sheet, and a wound electrode group is accommodated therein to achieve insulation from the battery can. However, since the thickness of the positive electrode or the negative electrode varies within manufacturing tolerances, the wound electrode group is formed when the positive electrode and the negative electrode are wound with a separator interposed therebetween. The thickness (thickness in the direction orthogonal to the wide surface) also changes. Therefore, the gap between the wide surface of the wound electrode group in the battery can and the inner wall surface of the battery can facing the wide surface fluctuated, and the variation in expansion of the battery can was large.

  On the other hand, in the rectangular secondary battery 1 of the present embodiment, the sheet-like insulating protective film 41 made of PP or the like is rubbed against the wound electrode group 31, and the inner dimension (thickness direction) of the battery can 11 is ) To a predetermined thickness. That is, the rectangular secondary battery 1 of the present embodiment has a winding length in which the insulating protective film 41 is wound around the outer periphery of the wound electrode group 31 at least once and the insulating protective film 41 is wound around the wound electrode group 31. The total thickness Dt (see FIGS. 5B and 5C) of the wound electrode group 31 and the insulating protective film 41 is adjusted to a preset set thickness.

  And in this Embodiment, since the battery can 11 is shape | molded by the deep drawing process using a metal mold | die, the variation in the shape dimension of the battery can 11 is very few. Therefore, when the wound electrode group 31 is inserted into the battery can 11 by adjusting the total thickness Dt of the wound electrode group 31 and the insulating protective film 41 to the set thickness, the wide side surface PW of the battery can 11 is increased. The gap in the thickness direction of the wound electrode group 31 formed between the inner wall surface and the outer peripheral surface of the insulating protective film 41 can be set to a predetermined dimension (preset value). Therefore, when the wound electrode group 31 expands due to charging / discharging, the variation in expansion of the battery cans 11 can be reduced in the plurality of rectangular secondary batteries 1.

  The gap between the inner wall surface of the wide side surface PW of the battery can 11 and the outer peripheral surface of the insulating protective film 41 is for facilitating the work of inserting the wound electrode group 31 into the battery can 11. From the viewpoint of reducing the size of the can 11, it is preferably as small as possible, and is preferably smaller than the thickness of one insulating protective film 41.

  5A is a perspective view showing a state in which an insulating protective film is wound, FIG. 5B is a sectional view taken along the line X2-X2 in FIG. 5A showing a state in which the insulating protective film is wound three times, and FIG. 5C is an insulating protective film. It is the X2-X2 sectional view taken on the line of FIG. 5A which shows the state which wound 1 round.

  As a result of measuring the thickness D1, the wound electrode group 31A shown in FIG. 5B was found to be thinner in the tolerance range than the design value. Therefore, by adjusting the winding length of the insulating protective film 41 according to the thickness and winding the insulating protective film 41 three times, the total thickness Dt of the insulating protective film 41 and the wound electrode group 31A is set. Adjusted to set thickness.

  As a result of measuring the thickness D2, the wound electrode group 31B shown in FIG. 5C was found to be thicker in the tolerance range than the design value. Therefore, by adjusting the winding length of the insulating protective film 41 according to the thickness and winding the insulating protective film 41 once, the total thickness Dt of the insulating protective film 41 and the wound electrode group 31B is set. Adjusted to thickness.

  The insulating protective film 41 also serves to insulate the power generating element assembly 5 from the battery can 11 and therefore needs to be wound at least once. Further, in the present embodiment, the case where the insulating film 41 is wound three times or one time has been described as an example. However, the present invention is not limited to this, and the winding length depends on the thickness of the wound electrode group 31. It is desired to adjust the total thickness Dt of the insulating protection film 41 and the wound electrode group 31 to the set thickness by adjusting the thickness and changing the circumference.

  The insulating protective film 41 can be attached by winding the insulating protective film 41 around the outer periphery of the wound electrode group 31 and can be attached to the wound electrode group 31 in a state in which displacement is prevented. . Therefore, the total thickness Dt of the insulating protective film 41 and the wound electrode group 31 can be easily adjusted as compared with the conventional case.

  The insulating protective film 41 is made of a single sheet member made of synthetic resin such as PP (polypropylene), for example, and is in a direction parallel to the wide surface of the wound electrode group 31 and perpendicular to the winding axis direction (FIG. 4). The Y-axis direction) is a length that can be wound one or more times around the winding center, and an end portion (protruding end portion 42) on one side in the width direction of the insulating protective film 41 that is disposed on the bottom side of the battery can 11 in the wound state. However, it has a width projecting in a cylindrical shape on the bottom side of the battery can 11 with respect to the wound electrode group 31.

  In this embodiment, after covering the outer periphery of the wound electrode group 31 with the connection terminals 53, 63 several times so as to cover the wide surface of the wound electrode group 31, both ends of the insulating protective film 41 are overlapped with each other. And heat welding for sealing by projecting further downward from the position of the curved surface portion 31a of the wound electrode group 31 disposed from the battery lid 21 to the bottom of the battery can 11 Alternatively, the width is set in consideration of the folding allowance for bending. The thickness of the insulating protective film is preferably 0.01 mm to 0.50 mm, and more preferably 0.05 mm to 0.10 mm.

  The gap between the inner wall surface of the wide side surface PW of the battery can 11 and the outer peripheral surface of the insulating protective film 41 is preferably equal to or less than the thickness of one insulating protective film 41. In consideration of the property and expansion of the wound electrode group 31, the gap may be set to a predetermined value.

  In this embodiment, the case where PP is used as the material of the insulating protective film 41 is shown as an example. However, the present invention is not limited to this. For example, PFA (polytetrafluoroethylene), PPS (polyphenylene sulfide) is used. ), PET (polyethylene terephthalate), or any synthetic resin that does not react or change quality due to the electrolyte.

  The insulating protective film 41 is wound so that the end of one side in the width direction of the insulating protective film 41 is disposed at a position close to the side of the battery lid 21 so as not to overlap. In this Embodiment, it winds so that the separation distance of about 0.5 mm may be formed between the upper end part of an insulating protective film, and a battery cover.

  The insulating protective film 41 covers the outer periphery of the wound electrode group 31 of the power generation element assembly 5 together with the connection terminals 53 and 63, and then the overlapping portions of the insulating protective film 41 are fixed with an adhesive tape (not shown). The As a fixing method, in addition to the method of fastening with an adhesive tape, it may be fastened with an adhesive.

  As a method of winding the insulating protective film 41, for example, as shown in FIG. 4, a part of the wound electrode group 31 or the connection terminals 53, 63 is brought into close contact with the end portion of the insulating protective film and applied in one direction while applying tension. It is possible to take a method of wrapping around and covering. The winding direction is not limited to the clockwise direction shown in FIG. 4 and may be counterclockwise.

  FIG. 6 is a diagram for explaining an example of a method for closing the tip of the insulating protective film, and FIG. 7 is a cross-sectional view taken along line X3-X3 in FIG.

  As shown in FIGS. 5A to 5C, the insulating protective film 41 protrudes further downward than the position of the curved surface portion 31 a of the wound electrode group 31 disposed at the bottom of the battery can 11 when wound. The part 42 protrudes and opens in a cylindrical shape. As shown in FIGS. 6 and 7, the projecting end portion 42 is sealed by thermal welding and is in a closed state, covers the curved surface portion 31 a of the wound electrode group 31, and includes the wound electrode group. It is made into a bag shape. The heat welding part (sealing part) 43 of the insulating protective film 41 is formed by being sandwiched and heated by a heat welding machine (not shown), and is welded over the length direction of the protruding end part 42.

  In addition, although heat welding was demonstrated as an example of the method of sealing the protrusion end part 42 of the insulation protective film 41, the method of sealing is not limited to heat welding. For example, as shown in FIG. 8 and FIG. 9, the folded end portion 42 is folded from the state in which the projecting end portion 42 is opened in a cylindrical shape to the state where the opposite ends of the projecting end portion 42 are closed together and wound from the tip. You may seal by (sealing part) 44. Moreover, after heat welding, it may be bent and sealed, and for example, it may be sealed using a tape or the like. Further, in the present embodiment, the case where heat welding is performed over the length direction of the protruding end portion 42 has been described as an example. However, a part of the protruding end portion 42 may be partially heat welded.

  However, even if the projecting end portion 42 is sealed by any method, the curved projecting end portion 42 of the wound electrode group 31 and the sealed projecting end portion 42 are not overlapped with the wide surface of the wound electrode group 31. It is necessary to be positioned between the battery can 11. Thereby, the total thickness Dt of the wound electrode group 31 and the insulating protective film 41 can be set to a predetermined dimension.

  In the configuration of the prismatic secondary battery 1 described above, the winding length of the insulating protective film 41 is adjusted so that the total thickness Dt of the wound electrode group 31 and the insulating protective film 41 becomes the set thickness. For example, when a material having a high expansion coefficient that expands by charging is used as the material of the negative electrode 32, the battery can 11 and the wound electrode group are considered in consideration of the battery thickness after charging. It is also possible to change the circumference of the insulating protective film 41 so that the gap between the insulating protective film 41 and the 31 has a predetermined dimension.

  10A is a cross-sectional view showing a state where the wound electrode group and the insulating protective film shown in FIG. 5B are arranged in the battery can, and FIG. 10B shows the battery can on the wound electrode group and the insulating protective film shown in FIG. 5C. It is sectional drawing which shows the state arrange | positioned in the inside.

  The square secondary battery 1A in FIG. 10A has a wound electrode group 31A that is thinner in the range of tolerance than the design value, and the square secondary battery 1B in FIG. 10B is thicker in the range of tolerance than the design value. A rotating electrode group 31B is provided.

  Both the rectangular secondary battery 1A of FIG. 10A and the rectangular secondary battery 1B of FIG. 10B change the winding frequency of the insulating protective film 41 according to the thickness of the wound electrode group 31, and the wound electrode group 31 Since the total thickness Dt of the insulating protection film 41 is the set thickness, the gap Dc between the battery can 11 and the insulating protection film 41 is constant.

  FIG. 11 is a cross-sectional view illustrating another configuration example of the prismatic secondary battery according to this embodiment. In FIG. 11, regarding the wound electrode group 31 and the insulating protective film 41, the state before the wound electrode group 31 expands is indicated by a solid line, and the expanded state is indicated by a two-dot chain line.

  The prismatic secondary battery 1 is provided with a space S between the insulating protective film 41 and the battery can 11. 10A and 10B, the gap between the rectangular secondary batteries 1 is narrow enough to facilitate insertion of the wound electrode group 31 around which the insulating protective film 41 is wound into the battery can 11. Thus, the gap S of the prismatic secondary battery 1 shown in FIG. 11 has a relatively wide interval in consideration of the swollenness of the wound electrode group 31 due to charging. Therefore, when the wound electrode group 31 expands due to charging, as shown by a two-dot chain line in FIG. 11, the amount that expands in the gap S and causes the battery can 11 to expand and deform can be reduced. Therefore, the thickness variation of the battery after charging can be reduced.

Next, a method for manufacturing the prismatic secondary battery 1 having the above configuration will be described.
First, the positive electrode 34 and the negative electrode 32 are overlapped with separators 33 and 35 interposed therebetween, and wound in a flat shape, whereby the wound electrode group 31 that is the power generation element 3 is manufactured. Next, the positive electrode terminal 51 and the negative electrode terminal 61 are attached to the battery lid 21 via an insulating member to produce the lid assembly 4. Then, the positive electrode uncoated portion 34 b and the negative electrode uncoated portion 32 b of the wound electrode group 31 are ultrasonically joined to the positive electrode terminal 51 and the negative electrode terminal 61 of the lid assembly 4 and conductively connected, thereby generating the power generation element assembly 5. Is made.

  Then, the insulating protective film 41 is wound around the wound electrode group 31 of the power generation element assembly 5 to cover the connection terminals 53 and 63 together. The insulating protective film 41 is wound around the outer periphery of the wound electrode group 31 at least once, and the total thickness Dt of the wound electrode group 31 and the insulating protective film 41 is set by adjusting the winding length. Adjust it. And the edge part of the insulation protective film 41 is fastened with an adhesive tape so that it may not be unwound. Then, the protruding end portion 42 of the insulating protective film 41 is thermally welded and sealed to form a bag shape including the wound electrode group 31 (see FIGS. 6 and 7). Then, the wound electrode group 31 with the insulating protective film 41 wound around the outer periphery is inserted from the opening 11a of the battery can 11, and the battery lid 21 and the battery can 11 are welded by laser welding. Then, an electrolytic solution is injected into the battery container 2 from the liquid injection port 72 of the battery lid 21, and the liquid injection port 72 is closed by the liquid injection plug 73.

The electrolyte is, for example, 1 mol / L of LiPF ₆ (lithium hexafluorophosphate) in a mixed solution of ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) in a volume ratio of 1: 1: 1. What was melt | dissolved so that it might become.

Incidentally, the electrolyte, an example of using LiPF _6, is not limited thereto, for _{example, LiClO 4, LiAsF 6, LiBF} 4, LiB (C 6 H 5) 4, CH 3 SO 3 Li , CF ₃ SOLi, or a mixture thereof can be used. Moreover, in this embodiment, although the example which used the mixed solvent of EC and DMC was shown as the solvent of nonaqueous electrolyte solution, propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, 1, 2- dimethoxyethane, , 2-diethoxyethane, γ-butyllactone, tetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, diethyl ether, sulfolane, methylsulfolane, acetonitrile, propionitrile, propionitrile, etc. A mixed solvent of seeds or more may be used, and the mixing ratio is not limited.

  Then, electric power is supplied from the wound electrode group 31 to the external load via the external terminals 52 and 62, or external generated power is charged to the wound electrode group 31 via the external terminals 52 and 62.

  The technology for continuously covering films and sheets and the technology for sealing by thermal welding are widely used in addition to batteries, so automation is relatively easy and the cost of equipment installation can be reduced. . Furthermore, since it is not necessary to bend the insulating protective sheet in a complicated manner as in the prior art, the cost of the insulating protective film 41 can be suppressed.

  12A and 12B are diagrams for explaining a configuration of a module using a plurality of prismatic secondary batteries according to the present embodiment. FIG. 12A is a perspective view, and FIG. 12B is a diagram of FIG. (B) It is a direction arrow directional view.

  The module (assembled battery) 81 has a configuration in which a plurality of the rectangular secondary batteries 1 described above are assembled in the thickness direction of the wound electrode group 31. In the example shown in FIG. 12, six rectangular secondary batteries 1 of # 1 to # 6 are assembled side by side so that the positions of the positive electrode terminal 51 and the negative electrode terminal 61 are alternately switched from the left side to the right side in the drawing. . Spacers 102 are provided between the adjacent square secondary batteries 1, and the plurality of square secondary batteries 1 are kept in a fixed state while keeping the distance between them constant and allowing the cooling medium to pass therethrough. A cooling passage is formed. And between the positive electrode terminals 51 and 51 of the adjacent square secondary battery 1 and between the negative electrode terminals 61 and 61 are electrically connected by the bus bar 82.

  In the module 81, the thickness of each rectangular secondary battery 1 becomes a predetermined dimension due to external pressure by a securing means (not shown). In each square secondary battery 1, the winding number of the insulating protective film 41 is changed according to the thickness of the wound electrode group 31.

  In the present embodiment, the square secondary batteries 1 of # 1, # 3 to # 6 have the wound electrode group 31A that is thinner in the tolerance range than the design value, and only the square secondary battery 1 of # 2 is used. Has a wound electrode group 31B that is thicker in the crossing range than the design value.

  In the square secondary batteries 1 of # 1 to # 6, the total thickness of the wound electrode group 31 and the insulating protective film 41 is adjusted by adjusting the winding length for winding the insulating protective film 41 around the wound electrode group 31. All the thicknesses Dt are adjusted to the same set thickness. Therefore, the variation in expansion of the battery can 11 is prevented from increasing between the square secondary batteries 1 of # 1, # 3 to # 6 and the square secondary battery 1 of # 2, and # 1 to # 6. The variation in expansion of the battery can 11 among all the rectangular secondary batteries 1 can be reduced and the expansion can be made uniform.

  Therefore, in the square secondary batteries 1 of # 1 to # 6, the surface pressure between the wound electrode group 31 and the battery can 11 is always a predetermined value, and the positive electrode metal of the positive electrode 34 in the wound electrode group 31. The distance between the foil and the negative electrode metal foil of the negative electrode 32 can always be a predetermined dimension. Therefore, the variation in the characteristics of the square secondary batteries 1 of # 1 to # 6 can be reduced.

  The configuration of the present invention is not limited to the configuration of the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, the case where the power generation element 3 has the wound electrode group 31 has been described as an example, but instead of the wound electrode group 31, a plate-like positive electrode and negative electrode are used. You may use the planar-shaped electrode group laminated | stacked through the separator between.

<Second Embodiment>
FIG. 13 is an exploded perspective view of the prismatic secondary battery according to the second embodiment. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  What is characteristic in the present embodiment is that the thickness of the wound electrode group 311 is adjusted by adjusting the winding length of the separator 33 that extends from the end portion of the negative electrode and winds around the outer periphery of the negative electrode. That is, the thickness is adjusted to a preset thickness.

  As shown in FIG. 13, the rectangular secondary battery 101 has a configuration in which the power generation element 3 is accommodated in the battery container 2. The power generation element 3 includes a wound electrode group 311 wound in a flat shape in a state where separators 33 and 35 are interposed between the positive electrode 34 and the negative electrode 32 and overlapped with each other.

  The wound electrode group 311 is accommodated in the battery can 11 with the periphery thereof covered with the insulating protective film 411. The insulating protective film 411 is configured by bending a sheet-like film into a bag shape, and is inserted into the battery can 11 by covering the wound electrode group 311 of the power generation element assembly 5, thereby winding the wound electrode group 311. In addition, it is interposed between the connection terminals 53 and 63 and the battery can 11.

  14 and 15 are cross-sectional views of the prismatic secondary battery having the configuration shown in FIG. 14 and 15, for convenience of explanation, the positive electrode 34 and the negative electrode 32 constituting the wound electrode group 311, and the separators 33 and 35 interposed between the positive electrode 34 and the negative electrode 32 are shown. Only the cross-sectional outline of the wound electrode group 311 up to the winding end end of the negative electrode 32 and the separator 33 wound around the outer periphery of the outermost negative electrode 32 of the wound electrode group 311 are illustrated.

  As shown in FIG. 14B and FIG. 15B, the thickness of the wound electrode group 311 to the winding end of the negative electrode 32 is D3, D4, the thickness of the wound electrode group 311 is Db, The total thickness of the wound electrode group 311 and the insulating protective film 411 is Dt, and the gap between the battery can 11 and the insulating protective film 411 is Dc.

  The wound electrode group 311 is configured by winding the separator 33, the negative electrode 32, the separator 35, and the positive electrode 34 in this order in the same manner as the wound electrode group 31 of the first embodiment and winding them in a flat shape. Yes. Further, the wound electrode group 311 extends from the end of the winding end of the negative electrode 32 so that the gap between the wound electrode group 311 and the battery can 11 always has a predetermined dimension, and the negative electrode 32 at the outermost periphery. The number of windings of the separator 33 wound around at least one round is changed.

  Specifically, the thicknesses D3 and D4 of the wound electrode group 311 to the end of the negative electrode 32 are measured, and the gap Dc formed between the battery can 11 and the insulating protective film 411 is determined. The winding length of the separator 33 extending from the end of the winding end of the negative electrode 32 is adjusted so that the thickness Db of the wound electrode group 311 is adjusted to the set thickness so as to have a predetermined dimension. .

  For example, in the example shown in FIG. 14, based on the thickness D of the wound electrode group 311, the winding length of the separator 33 wound around the outermost negative electrode 32 is further increased from one essential round to one. Only the circumference is added, and it is wound as a total of 2 laps.

  In the example shown in FIG. 15B, since the thickness D4 of the wound electrode group 311 is the lower limit within the design tolerance, the winding length of the separator 33 wound around the outermost negative electrode 32 is wound. Is added from the essential one lap for two more laps, and is wound as a total of three laps.

  Thereby, each square secondary battery 101 shown in FIG. 14 and FIG. 15 can make the space | interval space | interval Dc into a fixed magnitude | size mutually. Therefore, the total thickness Dt of the wound electrode group 311 and the insulating protective film 411 becomes a predetermined set thickness in relation to the inner dimension (thickness direction) of the battery can 11, and the variation in the expansion of the battery can is reduced. Can be reduced.

  In the second embodiment, the length of the separator 33 is adjusted to set the total thickness Dt of the wound electrode group 311 and the insulating protective film 411 to a predetermined set thickness. However, the present invention is not limited to this. For example, there is no problem even if the length of the separator 35 is adjusted, and there is no problem even if the lengths of both the separator 33 and the separator 35 are adjusted.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various designs can be made without departing from the spirit of the present invention described in the claims. It can be changed. For example, the above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to one having all the configurations described. Further, a part of the configuration of an embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of an embodiment. Furthermore, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

DESCRIPTION OF SYMBOLS 1 Lithium ion secondary battery 2 Battery container 3 Power generation element 4 Lid assembly 5 Power generation element assembly 11 Battery can 21 Battery cover 31 Winding electrode group 41 Insulating protective film 42 Projection end part 43 Thermal welding part 44 Folding part 51 Positive electrode terminal (Electrode terminal)
52, 62 External terminals 53, 63 Connection terminals 54, 64 Current collecting terminal 61 Negative terminal (electrode terminal)

Claims (6)

A prismatic secondary battery in which a flat power generation element is housed in a prismatic battery can,
In the power generation element, an insulating protective film is wound around the outer periphery of the power generation element at least once,
The insulating protective film is characterized in that a total thickness of the power generating element and the insulating protective film is adjusted to a preset thickness by adjusting a winding length wound around the power generating element. Square secondary battery.   The set thickness is a thickness in which a gap in a thickness direction of the power generation element formed between the battery can and the power generation element is set to a preset value. Item 2. The prismatic secondary battery according to item 1. The power generation element has a wound electrode group wound with a separator interposed between a positive electrode and a negative electrode,
The insulating protective film is wound around a direction parallel to the wide surface of the wound electrode group and perpendicular to the winding axis direction, and the insulating protective film protrudes from the power generation element. The prismatic secondary battery according to claim 1 or 2, wherein the prismatic secondary battery is formed in a bag shape by closing a protruding end portion on one side in the width direction. The insulating protective film has a sealing part in which the protruding end part is sealed by at least one of heat welding and folding,
The prismatic secondary battery according to claim 3, wherein the sealing portion is disposed between the curved portion of the wound electrode group and the battery can.   A plurality of the prismatic secondary batteries according to any one of claims 1 to 4, wherein the plurality of prismatic secondary batteries are arranged in the thickness direction of the power generation element. Module. A prismatic secondary battery in which a flat power generation element is housed in a prismatic battery can,
The power generating element has a wound electrode group wound with a separator interposed between a positive electrode and a negative electrode, and extends from a winding end end of the negative electrode, A prismatic secondary battery, wherein a thickness of the wound electrode group is adjusted to a preset thickness by adjusting a length of the separator wound around an outer periphery.

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