JP5483587B2 - Battery and manufacturing method thereof - Google Patents

Description

  The present invention relates to a battery having high reliability and good productivity, and a manufacturing method thereof.

  As a battery having an electrode group configured by alternately laminating a plurality of positive electrodes and a plurality of negative electrodes, for example, it has a battery container composed of an outer case, a sealing case and a gasket, and is generally a coin-type battery or a button type A flat battery called a battery is known.

  In the flat battery as described above, a positive electrode mixture layer or a negative electrode mixture layer is formed on one or both sides of the current collector on the positive electrode and the negative electrode, and a part of the current collector is formed on the positive electrode mixture layer or the negative electrode. Some are used for electrical connection with exterior cases and sealing cases that also serve as terminals by exposing the mixture layer without forming it, using it as a current collecting tab, and bending the current collecting tab. .

  A flat battery having an electrode group in which the positive electrode as described above is inserted into a bag-shaped separator and laminated with the negative electrode is also known (Patent Documents 1 and 2). In these batteries, in forming a bag-shaped separator, an insulating polymer film such as a polyester resin film is disposed between two separators, and an adhesive component provided on the surface of the film allows the film and the separator to be separated from each other. Are bonded together (Patent Document 1), or two separators are welded together (Patent Document 2).

JP-T-2004-509443 JP 2008-91100 A

  By the way, as the positive electrode accommodated in the bag-shaped separator, for example, a wide positive electrode that is obtained through a process of punching it with a punch and a die is generally used. In this case, the outer peripheral portion of the current collector that is relatively difficult to cut and easily deforms is likely to remain as a burr in a form protruding from the outer edge of the positive electrode mixture layer that can be easily cut.

  When the battery is formed by accommodating the positive electrode having such burrs in a bag-like separator, the separator may be damaged by the burrs, causing a short circuit, which may cause a decrease in battery reliability.

  Therefore, it is necessary to develop a technique that avoids the above-described problems caused by burrs remaining on the positive electrode, ensures the reliability of the battery, and increases its productivity.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a battery having high reliability and good productivity, and a manufacturing method thereof.

  The battery of the present invention that has achieved the above object is a battery having an electrode group in which a plurality of positive electrodes and a plurality of negative electrodes are alternately laminated via separators, and an electrolyte solution, and the positive electrode includes a main body portion. And a current collecting tab portion having a narrower width than the main body portion that protrudes from the main body portion in plan view, and the positive electrode main body portion has a positive electrode active material on one or both sides of the current collector. A positive electrode material mixture layer is formed, and the outer peripheral portion of the current collector protrudes from the outer edge of the positive electrode material mixture layer in a plan view. No separator layer is formed, and at least on both sides of the positive electrode facing both sides of the negative electrode, separators made of a microporous film made of a thermoplastic resin are disposed, and the two separators are A main body covering the entire surface of the main body of the positive electrode, and protruding from the main body, The electric tab portion has an overhang portion covering at least a portion including the boundary portion with the main body portion, and the two separators are bonded to each other at least at a part of the peripheral edge portion of the main portion. The main body of one separator is substantially parallel to the positive electrode surface, and the outer peripheral portion of the current collector protruding from the outer edge of the positive electrode mixture layer in the main body of the positive electrode is Of the two separators arranged on both sides, the main body portion is bent toward the separator side substantially parallel to the positive electrode surface.

  Further, the battery manufacturing method of the present invention is a method of manufacturing a battery having an electrode group in which a plurality of positive electrodes and a plurality of negative electrodes are alternately stacked via separators, and an electrolyte solution, A sheet-like positive electrode having a positive electrode mixture layer on a part of both sides is punched out using a punch and a die, and a main body part having a positive electrode mixture layer on both sides of a current collector, and protruding from the main body part in plan view A positive electrode manufacturing step of manufacturing a positive electrode having a current collecting tab portion that is narrower than the main body portion and in which a positive electrode mixture layer is not formed on the current collector; and a thermoplastic resin on both sides of the positive electrode A separator made of a microporous membrane is arranged, and these two separators are welded together to form a joint, or two separators made of a thermoplastic microporous membrane are stacked, Bags welded together to form a joint And by inserting the positive electrode into the bag-like separator, a boundary between the main body portion covering the entire main body portion of the positive electrode and the current collecting tab portion of the positive electrode and at least the main body portion. A projecting portion covering a portion including the portion, and having the joint portion at least at a part of the peripheral portion of the main portion, and the main portion of one separator being substantially parallel to the positive electrode surface A positive electrode housing step of housing the positive electrode in a separator, an electrode group formed by alternately laminating a plurality of positive electrodes including at least the positive electrode housed in a bag-shaped separator, and a plurality of negative electrodes, and an electrolyte solution A battery assembly process for accommodating the battery in a battery container, wherein in the positive electrode accommodation process, the surface of the positive electrode is in contact with the punch in the positive electrode production process, and the main part of the bag-shaped separator is the positive electrode surface. Almost parallel It characterized in that it arranged to be side separator.

  According to the present invention, it is possible to provide a battery having high reliability and good productivity, and a manufacturing method thereof.

It is a longitudinal cross-sectional view which represents typically an example of the battery of this invention. It is a principal part cross-sectional enlarged view of FIG. It is a top view which represents typically an example of the positive electrode which concerns on the battery of this invention. It is a top view which represents typically an example of the separator which concerns on the battery of this invention. It is a figure which represents typically the principal part cross section of the positive electrode which concerns on the battery shown in FIG. 1 and FIG. 2, and the separator arrange | positioned on both surfaces. It is a principal part enlarged view of FIG.

  1 and 2 schematically show an example of the battery of the present invention. In the battery shown in FIGS. 1 and 2, an electrode group and an electrolyte solution are accommodated in a space formed by caulking and sealing an outer case 2 and a sealing case 3 constituting a battery container via an insulating gasket 4. This is an example of a battery having a different structure, that is, a flat battery. FIG. 1 is a longitudinal sectional view showing a section of the battery container and the insulating gasket 4 in the battery. FIG. 2 is an enlarged view of the main part of FIG.

  In the battery industry, a flat battery with a diameter larger than the height is called a coin-type battery or a button-type battery, but there is a clear gap between the coin-type battery and the button-type battery. There is no difference, and the flat battery referred to in this specification includes both coin-type batteries and button-type batteries.

  The battery shown in FIGS. 1 and 2 includes a stacked electrode group in which a positive electrode 5 and a negative electrode 6 are stacked so that their planes are substantially parallel (including parallel) to the flat surface of the battery, and an electrolytic solution (illustrated). Is not accommodated in a space (sealed space) formed by the outer case 2, the sealing case 3, and the insulating gasket 4. The sealing case 3 is fitted to the opening of the outer case 2 via an insulating gasket 4, and the opening end of the outer case 2 is tightened inward, whereby the insulating gasket 4 contacts the sealing case 3. Thereby, the opening part of the exterior case 2 is sealed, and the inside of the battery has a sealed structure. The outer case 2 and the sealing case 3 are made of a metal such as stainless steel, and the insulating gasket 4 is made of an insulating resin such as nylon.

  FIG. 3 schematically shows a plan view of the positive electrode 5. The positive electrode 5 has a main body 5a and a width larger than that of the main body 5a projecting from the main body 5a in plan view (in the vertical direction in FIG. 3). And a current collecting tab portion 5b having a narrow length.

  In the main body 5 a of the positive electrode 5, a positive electrode mixture layer 51 is formed on one side or both sides of a current collector 52. In the current collecting tab portion 5b of the positive electrode 5, the positive electrode mixture layer is not formed on the surface of the current collector 52, and the current collector 52 is exposed.

  In the main body portion 5 a of the positive electrode 5, the outer peripheral portion of the current collector 52 protrudes from the outer edge of the positive electrode mixture layer 51 as a burr remaining when the positive electrode 5 is manufactured (when punched from a wide positive electrode).

  Further, for the negative electrode, similarly to the positive electrode 5, for example, it can have a structure having a main body part and a current collecting tab that protrudes from the main body part in a plan view and is narrower than the main body part. As shown in FIGS. 1 and 2, the negative electrode agent layer 61 is formed on one or both surfaces of the current collector 62 in the main body 6 a of the negative electrode 6. Further, in the current collecting tab portion 6 b of the negative electrode 6, the negative electrode agent layer is not formed on the surface of the current collector 62, and the current collector 62 is exposed.

  In the battery shown in FIG. 1 and FIG. 2, the upper and lower ends of the electrode group are negative electrodes 6B and 6B, and these negative electrodes 6B and 6B are provided on only one side of the current collector 62 (the inner surface of the battery). A layer 61 is provided. In addition, the exposed surface of the current collector 62 of the negative electrode 6B on the upper side in the drawing in the electrode group is welded to the inner surface of the sealing case 3 or is directly connected without being welded. That is, in the battery shown in FIGS. 1 and 2, the sealing case 3 also serves as the negative electrode terminal.

  And all the negative electrodes 6 (the negative electrode 6A in which the negative electrode agent layer 61 is formed on both surfaces of the current collector 62 and the negative electrode 6B in which the negative electrode agent layer 61 is formed on one surface of the current collector 62) included in the electrode group, Are electrically connected to each other through the current collecting tab portion 6b. In addition, the connection of the current collection tab part 6b of each negative electrode 6 can be performed by welding, for example.

  Further, in the battery shown in FIGS. 1 and 2, the current collecting tab portions 5b of the respective positive electrodes 5 are electrically connected to each other and are welded to the inner surface of the outer case 2 or directly contacted without being welded. Are electrically connected. That is, in the battery shown in FIGS. 1 and 2, the outer case 2 also serves as a positive electrode terminal. In the battery shown in FIGS. 1 and 2, for the purpose of insulating the negative electrode 6B located at the lowermost part of the electrode group from the outer case 2 also serving as the positive electrode terminal, polyethylene terephthalate (PET), polyimide, etc. An insulating seal 8 made of tape or the like is disposed.

  FIG. 4 schematically shows a plan view of the separator according to the battery of the present invention. In FIG. 4, assuming the case of a stacked electrode group in which the positive electrode, the negative electrode, and the separator are stacked together with the separator 7, the positive electrode 5 disposed below the separator 7 is indicated by a dotted line, A current collecting tab portion 6b related to the negative electrode disposed on the lower side is indicated by a one-dot chain line, and a binding tape 9 for suppressing positional deviation of each component related to the electrode group is indicated by a two-dot chain line. Further, the positive electrode 5 shown in FIG. 4 has an electrode group in which both sides (both sides) face the negative electrode. Although not shown in FIG. 4, when the electrode group is used, the upper side of the separator 7 (in the drawing) In the forward direction), at least a negative electrode is arranged.

  As shown in FIG. 4, the separator 7 and other separators disposed below (in the depth direction in the figure) via the positive electrode 5 (indicated by a dotted line in the figure) were welded to each other at the peripheral edge. It has a joint 7c (indicated by a lattice pattern in the figure). That is, the separator 7 and the separator disposed below the separator 7 are welded to each other at the peripheral edge to form a bag shape, and the positive electrode 5 is accommodated therein.

  The separator 7 protrudes from the main body part 7a (that is, the main body part 7a having a larger area in plan view than the main body part 5a of the positive electrode 5) covering the entire surface of the main body part 5a of the positive electrode 5 and the main body part 7a. The electric tab portion 5b has an overhang portion 7b that covers at least a portion including a boundary portion with the main body portion 5a. Then, two separators (the separator 7 and the separator disposed below the positive electrode 5) disposed on both surfaces of the positive electrode 5 were welded to at least a part of the peripheral portion of the main body portion 7 a of the separator 7. A joint 7c is provided.

  In the battery of the present invention, as described above, the joint portion for joining the two separators arranged on both surfaces of the positive electrode is provided on the peripheral portion of the main portion of the separator, but the peripheral portion ( You may provide a junction part also in the peripheral part of the protrusion part of a separator along the protrusion direction from a main-body part.

  The joining portion 7c may be formed by directly welding the peripheral portions of the two separators, but a layer made of a thermoplastic resin is interposed between the two separators, and 2 You may form by welding the separator of a sheet. However, in the latter case, depending on the type of thermoplastic resin that constitutes the layer interposed between the separators and the type of thermoplastic resin that constitutes the separator, the strength of the joint may be reduced. It is preferable to use the layer made of the same kind of resin as the thermoplastic resin constituting the separator. That is, when the separators are welded directly, or when the separators are welded via a layer composed of the same type of resin as the thermoplastic resin that constitutes the separator, the strength of the joint is determined by the strength of the separator itself. Since they are almost the same, for example, separation at a joint portion that may occur due to vibration or the like when the battery is used can be satisfactorily suppressed, and a battery with higher reliability can be obtained.

  In addition, although all the peripheral parts which concern on the main part of a separator may be a junction part, as shown in FIG. 4, for example, as shown in FIG. You may leave as 7d and 7d. After the two separators are welded to form a bag, the positive electrode is accommodated therein, the positive electrode is disposed on one separator, and the separator is further disposed on the positive electrode. When the positive electrode is housed in a separator that is welded to form a bag, air may remain in the separator. However, when manufacturing a battery using such a positive electrode, when the outer case and the sealing case are caulked, the residual air is well discharged outside the separator through the non-welded portions 7d and 7d. Occurrence of problems due to residual air in the separator (problems such as non-uniform reaction during power generation and reduced capacity) can be prevented.

  When providing a non-welding part in the peripheral part of a separator, it is preferable that the number shall be about 1-5 from a viewpoint of suppressing the productivity fall of a battery. Moreover, when providing a non-welding part in the peripheral part of a separator, the length of the outer edge of the non-welding part related to the main part of the separator is the total length of the outer edge related to the main part of the separator (the total length of the outer edge excluding the overhanging part) Is preferably about 15 to 60%. That is, in the main part of the separator, it is preferable that 40% or more (preferably 70% or more) of the entire length of the outer edge is a joined part, thereby ensuring good joining strength between the separators. Can do.

  FIG. 5 schematically shows a cross section of the main part of the positive electrode (the main body of the positive electrode) according to the battery shown in FIGS. 1 and 2 and the separator (the main part of the separator) arranged on both surfaces thereof. Note that the cross section shown in FIG. 5 corresponds to, for example, a part of the cross section taken along the line II in FIG.

  In the battery of the present invention, the main part of one of the two separators 7, 7 arranged on both surfaces of the positive electrode 5 (the lower separator 7 in the figure) is approximately on the surface of the positive electrode 5 (the plane of the positive electrode 5). Parallel (including parallel, the same shall apply hereinafter).

  When the positive electrode is accommodated in a bag-shaped separator formed by joining two separators 7 and 7, the inner surface of the separator 7 comes into contact with the corner of the positive electrode mixture layer 51 related to the positive electrode [FIG. The contact points are circled]. In this case, for example, an angle (inner angle) directed downward in the left part of the figure from the outer edge of the positive electrode 5 (the outer edge of the main body of the positive electrode 5) of the upper separator 7 in the figure, and the lower separator 7 in the figure. The angle (inner angle) directed upward in the left part of the figure from the outer edge of the positive electrode 5 (outer edge of the main body of the positive electrode 5) is smaller than in the case shown in FIG. 5, and the positive electrode in the part indicated by a circle in the figure If the inner angle of the inner surfaces of the separators 7 and 7 that come into contact with the corners of the mixture layers 51 and 51 becomes smaller, the inner surfaces of the separators 7 and 7 are damaged at the contact points, causing an internal short circuit. There is a possibility that the reliability may be lowered, or the corner portions of the positive electrode mixture layers 51 and 51 may be lost, resulting in a reduction in capacity. In particular, when the positive electrode is placed on one separator, the separator is further stacked thereon, and the peripheral portions of both separators are welded by heating press or the like to form a joint portion, the inner surface of the separator 7 is the positive electrode. Since it is strongly pressed against the corner portion of the mixture layer 51, the above problem is likely to occur.

  However, of the two separators 7 and 7 arranged on both surfaces of the positive electrode 5, the separator 7 whose main portion is substantially parallel to the surface of the positive electrode 5 (the lower separator 7 in the figure) is attached to the positive electrode mixture layer 51. At the place where the separator 7 comes into contact (the place surrounded by a circle in the figure), the inner angle of the separator 7 that comes into contact with the corner of the positive electrode mixture layer 51 becomes very large. Therefore, it is possible to satisfactorily suppress damage to the inner surface of the separator 7 due to these contacts and missing corner portions of the positive electrode mixture layer 51, thereby improving the reliability of the battery.

  In the battery of the present invention, the outer peripheral portion (that is, burr) of the current collector 52 protruding from the outer edge of the positive electrode mixture layer 51 in the main body portion of the positive electrode 5 is disposed on both surfaces of the positive electrode 5. Among the separators 7 and 7, the positive electrode 5 and the two separators 7 and 7 are arranged so that the main body bends toward the separator 7 that is substantially parallel to the surface of the positive electrode 5 (the lower separator in FIG. 5). To do.

  For example, when a flat positive electrode 5 as shown in FIG. 3 is punched from a wide positive electrode by using a punch and a die, the outer peripheral portion of the current collector 52 remaining as a burr is usually formed by punching at the time of punching. It tends to bend toward the opposite side of the moving direction (hereinafter referred to as “punching direction”).

  As described above, in the battery of the present invention, when the two separators arranged on both sides of the positive electrode are formed into a bag shape, one separator is made substantially parallel to the positive electrode surface, so that it is outside the positive electrode outer edge of the other separator. This portion is bent toward the one separator as shown in FIG. Therefore, if the direction of burr bending in the positive electrode is on the other separator side (the separator that is not substantially parallel to the positive electrode surface), the distance between the burr and the separator becomes close, and the separator is easily damaged by the burr. There is a risk that the reliability and productivity of the battery may decrease, such as an internal short circuit of the battery.

  On the other hand, in the battery of the present invention, as shown in FIG. 5, the bent direction of the burr (the outer peripheral portion of the current collector 52) in the positive electrode 5 is the separator 7 side substantially parallel to the positive electrode surface. Thereby, the distance between the burr and the separator is made longer, and the damage of the separator due to the burr is suppressed well, thereby improving the reliability and productivity of the battery.

  The length of the burr in the positive electrode varies depending on the clearance between the punch and die used for punching the positive electrode. For example, the burr does not occur on the positive electrode due to the clearance between the unused punch and the die. Even if it is adjusted to the extent, if these punches and dies are used repeatedly, the clearance increases due to wear, and the burr in the positive electrode gradually punched out becomes longer. Therefore, the life of punches and dies used for punching positive electrodes is affected by the allowable length of burrs of positive electrodes in batteries. For example, punches and dies for punching positive electrodes used for batteries with short allowable burrs are used. Then, the service life is shortened. However, in the present invention, since the distance between the burr of the positive electrode and the separator can be made relatively long, the allowable length of the burr becomes long, so that it is possible to extend the service life of the punch and die for punching the positive electrode. This also increases battery productivity.

  In the battery of the present invention, the length of the burr (the outer peripheral portion of the current collector protruding from the outer edge of the positive electrode mixture layer) in the main body portion of the positive electrode is the length of the burr and the separator (the lower separator 7 in FIG. 5). From the viewpoint of more reliably preventing contact with the positive electrode, for example, the inner end of the joint portion of the two separators arranged on both sides of the positive electrode and the positive electrode joint in the main body portion of the positive electrode existing between the two separators. The distance is preferably equal to or shorter than the shortest distance from the outer edge of the agent layer (A in FIG. 5).

  In the battery of the present invention, the shortest distance between the inner end of the joint 7c of the two separators 7 and 7 and the outer edge of the main body of the positive electrode 5 existing between the two separators 7 and 7 is A ( μm), where the thickness of the positive electrode is B (μm), the ratio A / B between A and B is preferably 1 or more, more preferably 1.7 or more.

  By setting the A / B value to preferably 1 or more, more preferably 1.7 or more, as shown in FIG. 5, a separator 7 (a lower separator in the figure) arranged substantially parallel to the positive electrode 5 surface. 7) In addition to the other separator 7 (upper separator 7 in the figure), the inner angle of the inner surface at the contact point with the corner of the positive electrode mixture layer 51 is reduced to reduce the inner surface of the other separator 7. Can also be brought into gentle contact with the corners of the positive electrode mixture layer 51. Therefore, the occurrence of scratches on the inner surface of the separator 7 of the other method and the lack of corners of the positive electrode mixture layer 51 in contact with the separator 7 can be further suppressed, and the reliability of the battery can be further improved. it can.

  However, if the A / B value becomes too large, the area of the main body of the separator that is not in contact with the main body of the positive electrode becomes large, the volume occupied by the separator in the battery increases, and the capacity of the battery decreases. There is a risk of doing. Therefore, the A / B value is preferably 5 or less, and more preferably 2.7 or less.

6 shows a further enlarged view of the main part of the cross section of the positive electrode 5 shown in FIG. 5 and the separators 7 and 7 arranged on both sides thereof. In such a cross section, as shown in FIG. Furthermore, a triangle (side a connecting both corners of the outer edge of the main body portion of the positive electrode 5, a main body portion of the positive electrode 5 by both corner portions of the outer edge of the main body portion of the positive electrode 5 and the inner ends of the joint portions of the two separators 7 and 7 Among the corners of the outer edge of the figure, the side b connecting the upper corner of the figure and the inner ends of the joints of the two separators 7 and 7, and the lower side of the corner of the outer edge of the main body of the positive electrode 5 ) And a triangle having a side c connecting the inner ends of the joint portions of the two separators 7 and 7 are formed. In FIG. 6, each side of the triangle is indicated by a dotted line, and the surfaces of the separators 7 and 7 and the outer edge of the positive electrode 5 existing in the portion are omitted. In the triangle, the inner angle C ₁ formed by the sides a and side b is preferably 45 ° or more, and more preferably 60 ° or more.

In the battery of the present invention, one separator (the lower separator 7 in the figure) of the two separators 7 and 7 disposed on both surfaces of the positive electrode 5 is substantially parallel to the surface of the positive electrode 5. side a shown in 6, in the triangle formed by sides b and side c, the interior angle C ₂ formed by the side a and the side c becomes 90 °, at the apex formed by the side a and the side c The lower separator 7 in the drawing gently abuts on the corners of the positive electrode mixture layer 51. Then, by setting the inner angle C ₁ to the above value, the upper separator 7 in the figure also hits the corner of the positive electrode mixture layer 51 relatively gently at the apex formed by the sides a and b. Therefore, the damage of the upper separator 7 in the figure and the lack of the corners of the positive electrode mixture layer 51 in contact with the separator 7 can be suppressed more favorably. However, it becomes possible to secure better.

  Further, from the viewpoint of better ensuring the reliability improvement effect and the capacity reduction suppression effect, in the triangle, the interior angle D formed by the side b and the side c is 45 ° or less. Is preferably 30 ° or less, more preferably 10 ° or more, and even more preferably 20 ° or more.

The A / B value, the inner angle C ₁ , the inner angle C ₂ and the inner angle D can be controlled by adjusting the thicknesses of the A and the positive electrode (that is, the B). The A can be adjusted by adjusting the size of the separator and the positive electrode.

  The battery of this invention can be manufactured with the manufacturing method of this invention which has the following positive electrode preparation processes, a positive electrode accommodation process, and a battery assembly process.

  In the positive electrode production process of the present invention, a sheet-like positive electrode (wide sheet-like positive electrode) having a positive electrode mixture layer on part of both surfaces of the current collector is punched out using a punch and a die, and the main body portion and the collector are collected. A positive electrode having an electric tab portion is prepared.

  The sheet-like positive electrode includes, for example, a positive electrode mixture-containing composition prepared by dispersing a positive electrode mixture containing a positive electrode active material, a conductive additive, a binder, and the like in a solvent (the binder may be dissolved) ( (Slurry, paste, etc.) can be produced by applying and drying both sides of the current collector, but may be produced by other methods.

  In the positive electrode housing step, separators (separators made of a microporous film of thermoplastic resin) are arranged on both sides of the positive electrode obtained in the positive electrode preparation step, and these two separators are welded directly to each other, A method may be adopted in which a layer composed of the same kind of resin as the constituent resin is interposed and welded to form a joint, and two separators made of a microporous film made of a thermoplastic resin are stacked. Two separators are welded directly to each other, or a layer made of the same kind of resin as the constituent resin of the separator is interposed to form a joint by forming a bag, and the positive electrode is placed in the bag-like separator. You may employ | adopt the method of inserting.

  In the case where a layer composed of the same type of resin as the constituent resin of the separator is interposed between the two separators and these are welded to form a joint, for example, the joint on one separator It is possible to employ a method in which a film serving as the layer is placed at a place where it is planned to be arranged, a positive electrode is disposed on this separator, and a separator is further stacked thereon, and then the peripheral portions of these separators are welded. In addition, a film to be the layer is placed in a place where it is planned to become a joint portion on one separator, and the separator and the film are previously welded. Adopting a method of laminating the peripheral portion by overlapping, or a method of inserting a positive electrode between these separators after forming a joined portion by interposing a film serving as the layer between two separators. You can also.

  For example, the peripheral edge of the separator can be welded by a hot press. In this case, the heating temperature may be a temperature higher than the melting point of the thermoplastic resin constituting the separator, but for example, the heating temperature is preferably 10 to 50 ° C. higher than the melting point. Moreover, about the time of a hot press, if a junction part can be formed satisfactorily, there will be no restriction | limiting, However, Usually, it shall be about 1 to 10 second.

  Moreover, in a positive electrode accommodation process, you may punch out to the required size, after forming a junction part using a separator larger than the required size.

  In the positive electrode housing step, the positive electrode is disposed such that the surface opposite to the surface in contact with the punch in the positive electrode manufacturing step is such that the main portion of the bag-like separator is on the separator side substantially parallel to the positive electrode surface. As described above, in the positive electrode manufactured by punching using a punch and a die, when a burr (outer peripheral portion of the current collector protruding from the outer edge of the positive electrode mixture layer in the main body portion of the positive electrode) occurs, the punching direction The burr tends to bend in the direction opposite to the side, that is, in the direction of the surface in contact with the punch. Therefore, the surface of the positive electrode in contact with the punch at the time of punching is disposed on the side of the separator of the bag-shaped separator whose main part is substantially parallel to the positive electrode surface, so that the direction of bending of the burr can be the side of the separator. it can. Therefore, even if burrs occur in the positive electrode in the positive electrode manufacturing step, it is possible to suppress a decrease in battery reliability due to this.

  In the battery assembly process, a plurality of positive electrodes including at least a positive electrode housed in a bag-shaped separator and a plurality of negative electrodes are alternately stacked to form an electrode group, and the electrode group and the electrolyte solution are placed in the battery container. To house.

  Although there is no restriction | limiting in particular about the manufacturing method of a negative electrode, It can produce by the method similar to a positive electrode. That is, for example, a sheet-like negative electrode (wide sheet-like negative electrode) having a negative electrode mixture layer on one side or a part of both sides of a current collector is punched using a punch and a die, and a main body portion and a current collecting tab portion are formed. The negative electrode which has can be produced. The sheet-like negative electrode is prepared by, for example, preparing a negative electrode mixture containing a negative electrode active material, a binder and, if necessary, a conductive additive in a solvent (the binder may be dissolved). A mixture-containing composition (slurry, paste, etc.) can be produced by applying it on one or both sides of a current collector and drying it. Further, when the negative electrode active material is lithium or a lithium alloy (details will be described later), a sheet-like negative electrode is produced by forming a negative electrode layer by pressing the lithium or lithium alloy foil to a current collector. can do. The sheet-like negative electrode may be produced by other methods.

  In the electrode group, as shown in FIGS. 1 and 2, the upper and lower electrodes are usually negative electrodes. The negative electrodes at the upper and lower ends may have a negative electrode mixture layer on both sides of the current collector, or may have a negative electrode mixture layer only on one side of the current collector. For example, as shown in FIGS. 1 and 2, when using a metal outer case and a metal sealing case for the battery container, as described above, the negative electrodes at the upper and lower ends of the electrode group are connected to the current collector. And having the negative electrode mixture layer only on one side of the electrode, the inner surface of the outer case or sealing case also serving as the negative electrode terminal and the surface not having the negative electrode mixture layer related to the negative electrode (exposed surface of the current collector) are brought into direct contact with each other Or welding, it can be used for electrical connection between the negative electrode terminal and the negative electrode of the electrode group.

  In addition, the electrode group used for the battery in the method of the present invention and the electrode group according to the battery of the present invention may have one or both of the upper and lower electrodes (the two outermost electrodes) as a positive electrode. In addition, when a metal outer case and a metal sealing case are used for the battery container, of the outermost electrodes of the electrode group, the electrode closer to the battery container (for example, the outer case) that also serves as the positive electrode terminal is positive. In this case, the positive electrode may have a positive electrode mixture layer on both sides of the current collector, and may be in contact with a battery container (for example, an outer case) that also serves as a positive electrode terminal only at the current collecting tab portion. The positive electrode mixture layer is provided only on one side (the inner surface of the battery), and the exposed surface of the current collector is welded or not welded to the inner surface of a battery container (for example, an outer case) that also serves as the positive electrode terminal. It may be electrically connected by direct contact.

  When a battery case and a metal sealing case are used for the battery container and both the upper and lower electrodes (the two outermost electrodes) of the electrode group are used as positive electrodes, the battery that also serves as the negative electrode terminal The connection between the container (for example, the sealing case) and the negative electrode is made by electrically connecting the current collecting tab portions of each negative electrode and welding them to the inner surface of the battery container (for example, the sealing case) that also serves as the negative electrode terminal. Or it can carry out by the method of making it contact directly, without welding.

  Further, in the battery manufactured by the method of the present invention and the battery of the present invention, separators are disposed on both sides of the positive electrode facing at least both sides to the negative electrode, but the positive electrode disposed on the outermost side of the electrode group, that is, one side As for the positive electrode in which only (one side) is opposed to the negative electrode, separators may be disposed on both sides (a junction part may be formed on these two separators), or the surface facing the negative electrode You may arrange | position a separator only to. Furthermore, when both the outermost electrodes related to the electrode group are set as positive electrodes, and separators are not arranged on both surfaces of these positive electrodes, between the battery container that also serves as the negative electrode terminal and the outermost positive electrode of the electrode group, An insulator such as an insulating seal made of a tape formed of polyethylene terephthalate (PET) or polyimide is disposed.

  The positive electrode having the positive electrode mixture layer only on one side of the current collector is the same as the method described in the positive electrode preparation step of the present invention except that the positive electrode mixture layer is formed only on one side of the current collector. Can be produced by a method.

  In the electrode group, the current collecting tab portion of each positive electrode is arranged so as to face the same direction in a plan view of the electrode group, and the current collecting tab portion of each negative electrode has the same direction in the plan view of the electrode group. It is preferable to arrange so as to face. Thereby, current collection of the positive electrode and the negative electrode becomes easier.

  Furthermore, the current collecting tab portion of each positive electrode and the current collecting tab portion of each negative electrode only need to be arranged so as not to contact each other in a plan view of the electrode group, but these contacts are better suppressed, And from the viewpoint of making the production of the battery better, as shown in FIG. 4, the current collecting tab portion 5b of each positive electrode and the current collecting tab portion 6b of each negative electrode face each other in a plan view of the electrode group. More preferably, it is arranged at a position where

  In addition, as shown in FIG. 4, the electrode group formed by laminating the positive electrode, the negative electrode, and the separator is bound to the outer periphery with a binding tape 9 made of polypropylene having chemical resistance, etc. It is preferable to suppress misalignment of the positive electrode and the negative electrode wrapped in the separator.

  There are a plurality of positive electrodes and negative electrodes in the electrode group, and the total number of layers of the electrode is at least 4, but it is also possible to make it more (5 layers, 6 layers, 7 layers, 8 layers, etc.) It is. However, if the number of stacked positive and negative electrodes is increased too much, the merit as a flat battery may be reduced. Therefore, it is usually preferable to have 40 layers or less.

  1 and 2 show a battery container in which the outer case and the sealing case are caulked and sealed with an insulating gasket. In addition to this, for example, a laminated film outer case constituted by a metal laminated film The battery container of the type which welds a body, an exterior case, and a sealing case can also be used.

  It should be noted that the current collecting tab portion of each positive electrode and the battery positive electrode terminal (for example, an exterior case or sealing case that also serves as the positive electrode terminal) are electrically connected, and the current collecting tab portion of each negative electrode and the negative electrode terminal of the battery (for example, negative electrode) The electrical connection with the outer case or the sealing case that also serves as a terminal may be made via a lead body (lead body made of metal foil or the like) that is separate from the positive electrode and the negative electrode.

  The planar shape of the battery is not particularly limited. For example, in the case of a flat battery, a polygonal shape such as a square (quadrangle) may be used in addition to a circular shape that is the mainstream of conventionally known flat batteries. In addition, the polygon such as a square as the planar shape of the battery in this specification includes a shape in which the corner is cut off and a shape in which the corner is curved. Moreover, the planar shape of the main body part of the positive electrode and the negative electrode may be a shape corresponding to the planar shape of the battery, and may be a substantially circular shape or a polygon such as a rectangle such as a rectangle or a square. In the case of a substantially circular shape, the portion corresponding to the location where the current collecting tab portion of the counter electrode is disposed is cut off as shown in FIG. 3 in order to prevent contact with the current collecting tab portion of the counter electrode. It is preferable to keep it.

  1 and 2 show an example in which the outer case is a positive electrode case and the sealing case is a negative electrode case, but the battery of the present invention and the battery manufactured by the method of the present invention are not limited to this, and may be used as necessary. Thus, the outer case can be a negative electrode case, and the sealing case can be a positive electrode case.

  The type of the battery of the present invention and the battery produced by the method of the present invention is not particularly limited. For example, a non-aqueous primary battery (such as a lithium ion primary battery) or a non-aqueous secondary battery (such as a lithium ion secondary battery). Is included. Below, the case of the non-aqueous secondary battery which is a main aspect among the batteries of this invention and the battery obtained by this invention method is demonstrated in detail.

Examples of the positive electrode active material include Li _x CoO ₂ , Li _x NiO ₂ , Li _x MnO ₂ , Li _x Co _y Ni _1-y O ₂ , Li _x Co _y M _1-y O ₂ , and Li _x Ni _1-1. like _{y M y O 2, Li x} Mn y Ni z Co 1-y-z O 2, Li x Mn 2 O 4, Li x Mn 2-y M y O 4 lithium-transition metal composite oxides such as (However, in each of the lithium transition metal composite oxides, M is at least one metal element selected from the group consisting of Mg, Mn, Fe, Co, Ni, Cu, Zn, Al, and Cr; ≦ x ≦ 1.1, 0 <y <1.0, 2.0 ≦ z ≦ 2.2.) These positive electrode active materials may be used individually by 1 type, and may use 2 or more types together.

  Moreover, as a conductive support agent of a positive electrode, carbon black, scale-like graphite, ketjen black, acetylene black, fibrous carbon etc. are mentioned, for example. Furthermore, examples of the binder for the positive electrode include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), carboxymethyl cellulose, and styrene butadiene rubber.

  As a composition of the positive electrode, for example, in 100% by mass of the positive electrode mixture constituting the positive electrode, the positive electrode active material is 75 to 90% by mass, the conductive additive is 5 to 20% by mass, and the binder is 3 to 15% by mass. Is preferred. Moreover, it is preferable that the thickness of a positive mix layer is 30-200 micrometers, for example.

  Examples of the current collector for the positive electrode include a metal foil made of aluminum or an aluminum alloy, an expanded metal, and a plain weave wire mesh. In addition, by reducing the total thickness of the positive electrode and increasing the number of stacked positive and negative electrodes in the battery, the positive electrode mixture layer and the negative electrode agent layer (including the negative electrode mixture layer. The same applies hereinafter unless otherwise specified). From the viewpoint of increasing the facing area and improving the load characteristics of the battery, it is preferable to use a metal foil for the current collector. Moreover, it is preferable that the thickness of a collector is 8-20 micrometers, for example.

  Examples of the negative electrode active material include lithium, a lithium alloy, a carbon material capable of occluding and releasing lithium ions, and lithium titanate.

  Examples of the lithium alloy that can be used for the negative electrode active material include lithium alloys that reversibly alloy with lithium, such as lithium-aluminum and lithium-gallium, and the lithium content is, for example, 1 to 15 atomic%. Is preferred. Examples of the carbon material that can be used for the negative electrode active material include artificial graphite, natural graphite, low crystalline carbon, coke, and anthracite.

The lithium titanate that can be used for the negative electrode active material is represented by the general formula Li _x Ti _y O ₄ , and x and y are 0.8 ≦ x ≦ 1.4 and 1.6 ≦ y ≦ 2.2, respectively. Lithium titanate having a stoichiometric number is preferable, and lithium titanate having a stoichiometric number of x = 1.33 and y = 1.67 is particularly preferable. The lithium titanate represented by the general formula Li _x Ti _y O ₄ can be obtained, for example, by heat-treating titanium oxide and a lithium compound at 760 to 1100 ° C. As the titanium oxide, either anatase type or rutile type can be used, and examples of the lithium compound include lithium hydroxide, lithium carbonate, and lithium oxide.

  As the binder and the conductive auxiliary agent related to the negative electrode, various binders and conductive auxiliary agents exemplified above as those that can be used for the positive electrode can be used.

  The composition of the negative electrode when a carbon material is used as the negative electrode active material is, for example, that the carbon material is 80 to 95% by mass and the binder is 3 to 15% by mass in 100% by mass of the negative electrode mixture constituting the negative electrode. Moreover, when using together a conductive support agent, it is preferable that a conductive support agent shall be 5-20 mass%. On the other hand, the composition of the negative electrode when lithium titanate is used as the negative electrode active material is, for example, 75 to 90% by mass of lithium titanate and 3 to 15% by mass of the binder in 100% by mass of the negative electrode mixture constituting the negative electrode. In addition, when a conductive auxiliary is used in combination, the conductive auxiliary is preferably 5 to 20% by mass.

  The thickness of the negative electrode agent layer in the negative electrode is preferably 40 to 200 μm, for example.

  Examples of the current collector for the negative electrode include a metal foil made of copper or a copper alloy, an expanded metal, and a plain weave wire mesh. From the viewpoint of reducing the total thickness of the negative electrode and increasing the number of layers of the positive electrode and negative electrode in the battery to increase the facing area between the positive electrode mixture layer and the negative electrode agent layer, and improving the load characteristics of the battery, It is preferable to use a metal foil for the current collector. Moreover, it is preferable that the thickness of a collector is 5-30 micrometers, for example.

  A separator made of a microporous film made of a thermoplastic resin is used. As the thermoplastic resin constituting the separator, for example, polyolefins such as polyethylene (PE), polypropylene (PP), ethylene-propylene copolymer, polymethylpentene, and the like are preferable. From the viewpoint of arranging and welding the same type of resin as the constituent resin, the melting point, that is, the melting temperature measured using a differential scanning calorimeter (DSC) in accordance with the provisions of JIS K 7121 is 100. A polyolefin of ˜180 ° C. is more preferable.

  The form of the microporous film made of the thermoplastic resin constituting the separator may be any form as long as it has an ionic conductivity sufficient to obtain the required battery characteristics, but is a conventionally known solvent. An ion-permeable microporous film (a microporous film that is widely used as a battery separator) having a large number of pores formed by an extraction method, a dry method or a wet stretching method is preferable.

  The thickness of the separator is preferably, for example, 5 to 25 μm, and the porosity is preferably, for example, 30 to 70%.

  Examples of non-aqueous electrolytes for batteries include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate, butylene carbonate, and vinylene carbonate; chain carbonate esters such as dimethyl carbonate, diethyl carbonate (DEC), and methyl ethyl carbonate. 1,2-dimethoxyethane, diglyme (diethylene glycol methyl ether), triglyme (triethylene glycol dimethyl ether), tetraglyme (tetraethylene glycol dimethyl ether), 1,2-dimethoxyethane, 1,2-diethoxymethane, tetrahydrofuran, etc. It is possible to use an electrolytic solution prepared by dissolving an electrolyte (lithium salt) in a concentration of about 0.3 to 2.0 mol / L in an organic solvent such as ether; That. The above organic solvents may be used alone or in combination of two or more.

Examples of the electrolyte include LiBF ₄ , LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) Lithium salts such as ₂ are mentioned.

In addition, the positive electrode having the shape shown in FIG. 3 and the separator having the shape shown in FIG. 4 are used, and A is 300 μm and B (the thickness of the positive electrode) is 140 μm (that is, A / B value is 2.14). As shown in FIG. 4, the peripheral portions of two separators having the structure shown in FIG. 5 with the positive electrode sandwiched therebetween are welded and joined, and this positive electrode (the positive electrode accommodated in the two separators) is used to and flat-shaped nonaqueous secondary battery having the structure shown in FIG. 2 (inner angle C ₁ is 65 ° shown in FIG. 6, the inner angle C ₂ is 90 °, the interior angle D is 25 °) was prepared. The positive electrode was produced by punching a wide sheet-shaped positive electrode with a punch and a die, and the burr heading in the direction opposite to the punching direction (the outer peripheral portion of the current collector protruding from the outer edge of the positive electrode mixture layer) Had. Then, the positive electrode was punched out so that the direction of bending of the burr was toward the side of the separator substantially parallel to the positive electrode surface of the two separators (bag-shaped separator) as shown in FIG. In this case, the surface in contact with the punch was disposed so as to contact a separator substantially parallel to the positive electrode surface.

  As a result, a flat non-aqueous secondary battery excellent in reliability was successfully produced. Further, when this flat non-aqueous secondary battery was disassembled, no damage was observed on the inner surface of the separator in the circled portion shown in FIG. 5, and no corners of the positive electrode mixture layer were observed. The separator was not damaged by burrs.

  The battery of the present invention can be applied to the same applications as conventionally known batteries such as a non-aqueous primary battery and a non-aqueous secondary battery.

DESCRIPTION OF SYMBOLS 1 Battery 2 Exterior case 3 Sealing case 4 Insulating gasket 5 Positive electrode 5a Positive electrode main body 5b Positive electrode current collecting tab 6 Negative electrode 6a Negative electrode main body 6b Negative current collecting tab 7 Separator 7a Separator main part 7b Separation of separator Part 7c Junction 52 Positive electrode current collector

Claims (5)

A battery having an electrode group in which a plurality of positive electrodes and a plurality of negative electrodes are alternately laminated via separators, and an electrolyte solution,
The positive electrode has a main body part, and a current collecting tab part that protrudes from the main body part in a plan view and is narrower than the main body part,
In the main body of the positive electrode, a positive electrode mixture layer containing a positive electrode active material is formed on one side or both sides of the current collector, and the outer peripheral portion of the current collector protrudes from the outer edge of the positive electrode mixture layer in plan view. And
In the current collector tab portion of the positive electrode, a positive electrode mixture layer is not formed on the current collector,
At least a separator made of a microporous film made of a thermoplastic resin is disposed on both sides of the positive electrode facing both sides of the negative electrode,
The two separators include a main body that covers the entire surface of the main body of the positive electrode, and an overhang that protrudes from the main body and covers at least a portion of the current collecting tab of the positive electrode that includes a boundary with the main body. The two separators have a welded portion welded to each other at least at a part of the peripheral edge of the main body, and the main body of one separator is substantially parallel to the positive electrode surface. ,
In the main body of the positive electrode, the outer peripheral portion of the current collector protruding from the outer edge of the positive electrode mixture layer is the one in which the main portion is substantially parallel to the positive electrode surface among the two separators arranged on both surfaces of the positive electrode Batteries characterized by being bent toward the separator side.   A (μm) is the shortest distance between the inner end of the joint of the two separators arranged on both sides of the positive electrode and the outer edge of the positive electrode mixture layer in the main body of the positive electrode existing between the two separators. 2. The battery according to claim 1, wherein the ratio A / B of A to B is 1 to 5 when the thickness of the positive electrode is B (μm).   3. The battery according to claim 1, wherein the battery is a flat battery in which an electrode group and an electrolytic solution are accommodated in a space formed by caulking and sealing an exterior case and a sealing case via an insulating gasket.   The battery according to claim 1, wherein the electrolytic solution is a non-aqueous electrolytic solution. A method of manufacturing a battery having an electrode group in which a plurality of positive electrodes and a plurality of negative electrodes are alternately laminated via separators, and an electrolyte solution,
A sheet-like positive electrode having a positive electrode mixture layer on part of both surfaces of the current collector is punched out using a punch and a die, and the main body having a positive electrode mixture layer on both surfaces of the current collector, and the main body in plan view A positive electrode production step of producing a positive electrode having a current collecting tab portion protruding from the portion, having a width narrower than that of the main body portion, and having no positive electrode mixture layer formed on the current collector,
A separator made of a microporous film made of a thermoplastic resin is arranged on both surfaces of the positive electrode, and these two separators are welded together to form a joint, or from a microporous film made of a thermoplastic resin A main body that covers the entire body of the positive electrode by inserting the positive electrode into the bag-like separator, A projecting portion that protrudes from the main body portion and covers at least a part of the current collecting tab portion of the positive electrode that includes a boundary portion with the main body portion, and the joint portion is provided on at least a part of the peripheral portion of the main body portion. A positive electrode housing step of housing the positive electrode in a bag-shaped separator having a main body of one separator substantially parallel to the positive electrode surface;
A plurality of positive electrodes including at least the positive electrode accommodated in the bag-shaped separator, an electrode group formed by alternately laminating a plurality of negative electrodes, and a battery assembly process for accommodating the electrolytic solution in the battery container. And
In the positive electrode housing step, the positive electrode is arranged so that a surface in contact with the punch in the positive electrode preparation step is such that a main part of the bag-shaped separator is on a side of the separator substantially parallel to the positive electrode surface. Battery manufacturing method.