JP5528305B2 - Flat non-aqueous secondary battery - Google Patents

Description

  The present invention relates to a flat non-aqueous secondary battery having excellent reliability.

  In a flat non-aqueous secondary battery generally referred to as a coin-type battery or a button-type battery, an electrode group in which a positive electrode and a negative electrode are opposed to each other with a separator interposed therebetween, and a non-aqueous electrolyte solution are provided in an outer case. And a structure accommodated in a space formed by a sealing case and an insulating gasket.

  In the flat non-aqueous secondary battery as described above, a positive electrode mixture layer or a negative electrode agent layer is formed on one or both surfaces of the current collector on the positive electrode and the negative electrode, and a part of the current collector is mixed with the positive electrode mixture. It is exposed without forming a layer or a negative electrode agent layer, and this is used as a current collecting tab. The current collecting tabs of each positive electrode and each negative electrode are welded together, and these collected current collecting tabs are connected to terminals. There are some which are electrically connected by welding or the like to the inner surface of the outer case or the sealing case that also serves as a material (for example, Patent Document 1).

JP 2003-142161 A

  By the way, in the flat type non-aqueous secondary battery having the above-described configuration, for example, due to dropping, a crack is formed at the end portion of the current collecting tab related to the electrode in the vicinity of welding with the inner surface of the outer case or the sealing case. It is easy to be damaged. Such scratches on the current collecting tabs often do not immediately make the battery unusable, but they can be a factor that impairs the reliability of the battery. Is preferred.

  Recently, with the expansion of applications of flat non-aqueous secondary batteries, for example, the possibility of falling from a very high position as well as falling from a height that humans use for hands has increased. Therefore, in preparation for such a case, development of a technique for improving the reliability of the battery by highly suppressing damage on the current collecting tab of the electrode is required.

  This invention is made | formed in view of the said situation, The objective is to provide the flat non-aqueous secondary battery excellent in reliability.

  The flat type non-aqueous secondary battery of the present invention that has achieved the above object has a positive electrode and a negative electrode with a separator in a space formed by caulking and sealing the outer case and the sealing case via an insulating gasket. And an electrode group in which the total number of positive and negative electrodes is three or more, and a flat non-aqueous electrolyte solution. A water secondary battery, wherein either one of the outer case and the sealing case serves as a positive electrode terminal and the other serves as a negative electrode terminal, and has the following aspect (1) or (2): To do.

(1) The positive electrode has a main body portion and a current collecting tab portion that protrudes from the main body portion in a plan view and is narrower than the main body portion. A positive electrode mixture layer containing a positive electrode active material is formed on one side or both sides of the current collector, and in the current collector tab portion of the positive electrode, a positive electrode mixture layer is not formed on the current collector, and the electrode group is , Having at least two positive electrodes, collecting current tab portions of each positive electrode, being welded together and integrated, and the integrated current collecting tab portions of each positive electrode also serve as a positive electrode terminal The portion that is welded to the inner surface of the exterior case or the sealing case, and the portion of the integrated current collecting tab portion of each positive electrode that is closest to the main body portion of the positive electrode among the portions where the current collecting tab portions of each positive electrode are welded to each other Is a portion other than the end portion in the width direction of the current collecting tab portion of each integrated positive electrode. It is present in.

(2) The negative electrode includes a main body portion and a current collecting tab portion that protrudes from the main body portion in a plan view and is narrower than the main body portion. A negative electrode layer containing a negative electrode active material is formed on one side or both sides of a current collector. In the current collector tab portion of the negative electrode, a negative electrode layer is not formed on the current collector. An outer case having at least two negative electrodes, in which the current collecting tab portions of the respective negative electrodes are integrated and welded together, and the integrated current collecting tab portions of the respective negative electrodes also serve as negative electrode terminals Or it is welded to the inner surface of the sealing case, and the portion closest to the main body portion of the negative electrode among the portions where the negative electrode current collecting tab portions of the integrated negative electrode current collecting tab portions are welded to each other, Locations other than the end in the width direction in the current collecting tab portion of each integrated negative electrode It is present.

  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 non-aqueous secondary battery of the present invention includes both coin-type batteries and button-type batteries.

  ADVANTAGE OF THE INVENTION According to this invention, the flat nonaqueous secondary battery excellent in reliability can be provided.

It is a longitudinal cross-sectional view which represents typically an example of the flat non-aqueous secondary battery of this invention. It is a top view which represents typically an example of the positive electrode which concerns on the flat nonaqueous secondary battery of this invention. It is a top view which represents typically an example of the negative electrode which concerns on the flat nonaqueous secondary battery of this invention. FIG. 2 is a plan view illustrating an example of a welded location between an inner surface of an exterior case in the flat nonaqueous secondary battery of FIG. 1 and a current collecting tab portion of each positive electrode integrated by welding and the vicinity thereof. It is a top view showing the welding location of the inner surface of the exterior case in the flat type non-aqueous secondary battery of FIG. 1, and the current collection tab part of each positive electrode integrated with each other, and other examples of the vicinity. It is a longitudinal cross-sectional view which represents typically the other example of the flat nonaqueous secondary battery of this invention. FIG. 7 is an enlarged cross-sectional view of a main part of the flat nonaqueous secondary battery in FIG. 6. It is a top view which represents typically an example of the separator which concerns on the flat nonaqueous secondary battery of this invention.

  FIG. 1 schematically shows an example of a flat non-aqueous secondary battery of the present invention. FIG. 1 is a longitudinal sectional view of a flat non-aqueous secondary battery. As shown in FIG. 1, the flat non-aqueous secondary battery 1 includes a plurality of positive electrodes 5 and a plurality of negative electrodes 6 with separators 7 interposed therebetween. The laminated electrode group laminated so that the planes are substantially parallel (including parallel) to the flat surface of the battery, and the non-aqueous electrolyte (not shown) are the outer case 2, the sealing case 3, and It is accommodated in a space (sealed space) formed by 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 polypropylene.

  In the battery of FIG. 1, the outer case 2 also serves as the positive electrode terminal, and the sealing case 3 also serves as the negative electrode terminal. However, in the battery of the present invention, for example, the outer case has the negative electrode terminal depending on the configuration of the electrode group. The sealing case may also serve as the positive electrode terminal.

  FIG. 2 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. 2). And a current collecting tab portion 5b having a narrow length.

  In the main body 5a of the positive electrode 5, a positive electrode mixture layer 51 containing a positive electrode active material or the like is formed on both surfaces of a current collector (52 in FIG. 1). 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 battery shown in FIG. 1, since the outermost electrodes in the electrode group are all negative electrodes, the positive electrode mixture layers 51 are formed on both surfaces of the current collector 52 in the main body 5a of all the positive electrodes 5. For example, one of the outermost electrodes in the electrode group (more specifically, the electrode on the exterior case side or the sealing case side that also serves as the positive electrode terminal) or both can be used as the positive electrode. In this case, the positive electrode on the outermost side in the electrode group may have a positive electrode mixture layer only on one surface (surface inside the battery) of the current collector in the main body.

  3 schematically shows a plan view of the negative electrode 6. The negative electrode 6 has a width that is larger than the main body 6a and the main body 6a protruding from the main body 6a in plan view (upper and lower in FIG. 3). Current collecting tab portion 6b having a narrow direction length).

  As for the main-body part 6a of the negative electrode 6, the negative electrode agent layer 61 containing a negative electrode active material etc. is formed in the single side | surface or both surfaces of a collector (62 in FIG. 1). And the current collection tab part 6b of the negative electrode 6 does not have the negative electrode agent layer formed in the surface of the electrical power collector 62, and the electrical power collector 62 is exposed.

  In the battery shown in FIG. 1, the upper and lower ends of the electrode group are negative electrodes 6B and 6B. The negative electrodes 6B and 6B are provided with a negative electrode agent layer 61 only on one side (the inner surface of the battery) of the current collector 62. Have. On the other hand, the negative electrode 6 </ b> A arranged on the electrode group other than the upper and lower ends has negative electrode agent layers 61 and 61 on both surfaces of the current collector 62.

  Further, in the battery shown in FIG. 1, the current collecting tab portions 5b of all the positive electrodes 5 constituting the electrode group are collected, and these are welded and integrated, and the end portions of the electrode group are viewed in plan view. It is bent to face outward (left side in the figure). And the current collection tab part 5b of each positive electrode 5 integrated by welding and integrated is welded to the inner surface of the outer case 2.

  FIG. 4 is a plan view showing an example of a welded portion between the inner surface of the outer case 2 and the current collecting tab portion of each integrated positive electrode 5 in the battery of FIG. 1 and the vicinity thereof. In FIG. 4, in the integrated current collecting tab portion 500 of each positive electrode, a dot is added to a location 500 a where the current collecting tab portions are welded to each other. That is, in the integrated current collecting tab portion 500 of each positive electrode, a portion (in the figure, 500b) where dots are not attached is a portion where the current collecting tab portions are not welded to each other. In FIG. 4, reference numeral 501 denotes a welding mark with the inner surface of the outer case 2 in the integrated current collecting tab portion 500 of each positive electrode. Furthermore, in FIG. 4, 100 is an electrode group, In the figure, the upper surface (surface by the side of the sealing case 3) is represented.

  In the battery shown in FIG. 4, the positive electrode body portion (lower side in FIG. 4) of the portions 500 a where the positive electrode current collector tab portions of the integrated positive electrode current collector tab portions 500 are welded to each other. The nearest part exists inside the end part of the width direction of the current collection tab part 500 of each integrated positive electrode.

  FIG. 5 is a plan view showing another example of a welding location between the inner surface of the outer case 2 and the integrated current collecting tab portion of each positive electrode 5 in the battery of FIG. 1 and the vicinity thereof. In the battery shown in FIG. 5, the current collecting tab portions of the respective positive electrodes are not welded to each other at the end portions in the width direction of the current collecting tab portions 500 of the respective positive electrodes (that is, the current collecting tab portions of the respective positive electrodes are not welded). The place 500a welded to each other is not formed).

  Thus, in the battery of the present invention, the portion closest to the main body portion of the positive electrode among the portions where the current collecting tab portions of the respective positive electrode current collecting tab portions are welded to each other is integrated. It is made to become places other than the edge part of the width direction in the current collection tab part of each positive electrode. Or, in the battery of the present invention, the portions closest to the main body of the negative electrode among the portions where the current collecting tab portions of the negative electrodes in the integrated current collecting tab portions of the negative electrodes are welded to each other are integrated. It is made to become places other than the edge part of the width direction in the current collection tab part of a negative electrode.

  As described above, when an impact such as dropping is applied to the flat non-aqueous secondary battery, the current collecting tab portion of each integrated electrode (each positive electrode or each negative electrode) welded to the inner surface of the outer case or the sealing case The end of the battery is likely to crack, which may impair the reliability of the battery.

  However, of the portions where the current collecting tab portions of each electrode (each positive electrode or each negative electrode) in the integrated current collecting tab portion are welded together, the portion closest to the main body portion of the electrode is integrated. If the current collecting tab portion of each electrode is other than the end portion in the width direction, the end portion of the current collecting tab portion of each integrated electrode when an impact such as dropping is applied to the battery Generation of cracks can be satisfactorily suppressed, and the reliability of the battery can be improved.

  In addition, as shown in FIG. 4, the location where the current collection tab parts of each electrode in the current collection tab part of each integrated electrode (each positive electrode or each negative electrode) are welded together is the current collection of each integrated electrode. When it is provided up to the end in the width direction of the tab portion, at least the welded portion at the end in the width direction is prevented from being the closest to the main body portion of the electrode. In this case, at the end of the electrode main body portion side at the welding location of the end portion in the width direction of the current collecting tab portion of each integrated electrode and at the end portion in the width direction of the current collecting tab portion of each integrated electrode The distance (the length of x in FIG. 4) between the position corresponding to the welded portion closest to the main body of the electrode is preferably 0.1 mm or more, and 0.5 mm or more. Is more preferable.

  Moreover, in FIG. 4, the shape of the part nearest to the main-body part of an electrode among the places where the current collection tab part of each electrode in the current collection tab part of each electrode integrated is mutually integrated. In the battery of the present invention, the shape of the location where the current collecting tab portions of each electrode are welded to each other is such a shape. It is not limited. For example, the shortest distance from the end in the width direction of the current collecting tab portion at the portion where the current collecting tab portions of each electrode are welded to each other (the length y in FIG. 4) Is preferably 0.4 mm or more, and more preferably 0.6 mm or more. In addition, among the locations where the current collecting tabs of each electrode are welded to each other, the shape of the portion closest to the main body of the electrode has a plurality of vertices such as, for example, a linear shape or a U-shape. The shape may be a shape having a curve (for example, a semicircular shape), and even in such a shape, the same effect as that in the shape shown in FIG. 4 can be ensured.

  Furthermore, when the current collecting tab portions of the respective electrodes (each positive electrode or each negative electrode) in the width direction of the current collecting tab portions are not welded to each other, the current collecting tab portions of the respective electrodes are welded to each other. The shortest distance from the end in the width direction of the current collecting tab portion (the length of y in FIG. 5) of the portion closest to the main body portion of the electrode in the place where it is made is preferably 0.4 mm or more, More preferably, it is 0.6 mm or more. Further, the shape of the portion closest to the main body of the electrode where the current collecting tabs of each electrode are welded to each other is not particularly limited, and there are a plurality of vertices such as a U-shape as shown in FIG. In addition to the shape, for example, a shape having one vertex or a shape having a curve (for example, a semicircular shape) can be used. Even in such a shape, the shape shown in FIG. The effect of can be ensured. Further, the shape of the portion other than the portion closest to the main body portion of the electrode among the portions where the current collecting tab portions of the electrodes are welded to each other is not particularly limited, and in addition to the rectangular shape shown in FIG. It may be a shape having a trapezoidal shape, a triangular shape, a gourd shape, or the like.

  In addition, the width | variety (namely, width | variety of the current collection tab part of a positive electrode or a negative electrode) of the current collection tab part of each electrode (each positive electrode or each negative electrode) is 1.2-6.0 mm, for example. preferable.

  FIG. 1 shows a mode in which the current collecting tab portion 5b of each integrated positive electrode 5 is welded to the inner surface of the outer case 2, as described above. The current collecting tab portion may be welded to the inner surface of the sealing case (sealing case that also serves as the positive electrode terminal). Also in this case, of the locations where the current collecting tab portions of the positive electrode current collecting tab portions are welded to each other, the portion closest to the main body portion of the positive electrode is the current collecting portion of the integrated positive electrodes. What is necessary is just to make it become places other than the edge part of the width direction in an electric tab part.

  In addition, in the battery in a mode in which the integrated current collecting tab portion of each positive electrode is welded to the inner surface of the outer case or the sealing case, as shown in FIG. In general, both electrodes are negative electrodes. In that case, for the electrical connection between the negative electrode related to the electrode group and the outer case or sealing case that also serves as the negative electrode terminal, for example, as shown in FIG. The negative electrode on the outermost side of the electrode group, which is integrated by welding or the like, and the negative electrode closer to the outer case or sealing case that also serves as the negative electrode terminal, has one surface of the current collector (the outermost surface of the electrode group). The current collector may be exposed without forming a negative electrode agent layer, and the exposed surface of the current collector may be brought into contact with or welded to the inner surface of the outer case or sealing case that also serves as the negative electrode terminal.

  As shown in FIG. 1, when the two electrodes on the outermost side of the electrode group are both negative electrodes, an outer case or a sealing case (external case 2 in FIG. 1) that also serves as a positive electrode terminal, and an electrode group (the outermost part thereof) An insulating seal (8 in FIG. 1) made of, for example, a tape formed of polyethylene terephthalate (PET), polyimide, or the like may be disposed between it and the negative electrode on the side.

  In the battery of the present invention, for example, the two electrodes on the outermost side of the electrode group may both be positive electrodes. In that case, the electrical connection between the negative electrode and the outer case or the sealing case serving as the negative electrode terminal of the electrode group may be used. The current collecting tabs of the negative electrodes are integrated together by welding together, and the integrated current collecting tabs of the negative electrodes and the inner surface of the outer case or sealing case that also serves as the negative electrode terminal are welded. To do. And in the case of this aspect, among the places where the current collecting tab portions of the negative electrodes in the integrated negative current collecting tab portions are welded together, the portion closest to the main body portion of the negative electrode is the integrated negative electrode What is necessary is just to make it become places other than the edge part of the width direction in the current collection tab part.

  Further, for example, when the two electrodes on the outermost side of the electrode group are both positive electrodes, the electrical connection between the positive electrode related to the electrode group and the outer case or the sealing case that also serves as the positive electrode terminal is, for example, to the electrode group. The current collecting tabs of the respective positive electrodes are integrated by welding or the like, and among the positive electrodes on the outermost side of the electrode group, the current collector is used for the positive electrode closer to the outer case or the sealing case that also serves as the positive electrode terminal. The current collector is exposed without forming a positive electrode mixture layer on one side (the outermost surface of the electrode group), and the exposed surface of the current collector and the inner surface of the outer case or sealing case that also serves as the positive electrode terminal Can be contacted or welded.

  When the two outermost electrodes in the electrode group are both positive electrodes, for example, PET or polyimide is used between the outer case or sealing case that also serves as the negative electrode terminal and the electrode group (the outermost positive electrode). What is necessary is just to arrange | position the insulation seal | sticker which consists of tapes etc. which were formed by.

  Further, in the battery of the present invention, depending on the laminated configuration of the electrode group, the current collecting tab portions of the positive electrode are integrated and welded together, and this is welded to an outer case or a sealing case that also serves as a positive electrode terminal, and each negative electrode The current collecting tab portions can be collectively welded and integrated, and this can be welded to an outer case or a sealing case that also serves as a negative electrode terminal. In the case of this aspect, among the portions where the current collecting tab portions of each positive electrode in the integrated current collecting tab portion are welded to each other, the portion closest to the main body portion of the positive electrode is the integrated positive electrode. Among the locations where the current collecting tabs of the negative electrodes in the current collecting tab portions of the current collecting tab portions are welded to each other. What is necessary is just to make it the part nearest to a main-body part become places other than the edge part of the width direction in the current collection tab part of each integrated negative electrode.

  The welding of the integrated electrode (each positive electrode or each negative electrode) to the inner surface of the outer case or the sealing case in the current collecting tab portion is preferably performed by, for example, ultrasonic welding. Further, in the ultrasonic welding, it is preferable that a square-shaped welding trace having a side of 0.1 to 0.6 mm is formed, but the shape of the welding trace is not limited, and is 0.1 to 0.6 mm. It may be a welding mark having an area corresponding to a circle having a diameter. And it is preferable to perform ultrasonic welding so that about 2 to 10 welding marks of such a size are formed.

  Further, in the battery shown in FIG. 4 and FIG. 5, the welding trace 501 with the inner surface of the outer case or the sealing case in the current collecting tab portion 500 of each positive electrode is welded to the current collecting tab portion of each positive electrode. It exists in the location 500a and the location 500b where the current collection tab part of each positive electrode is not welded mutually. As described above, in the battery of the present invention, the welding traces with the inner surface of the outer case or the sealing case in the current collecting tab portion of each integrated electrode (each positive electrode or each negative electrode) are in contact with each other. It is preferable that the welding tabs and the current collecting tab portions of the respective electrodes exist at locations where they are not welded to each other. In this case, the joining by the welding of the current collection tab part of each integrated electrode and the inner surface of an exterior case or a sealing case becomes better.

  In addition, the welding trace with the inner surface of the exterior case or the sealing case in the current collecting tab portion of each integrated electrode is welded to each other because the current collecting tab portion of each electrode is present at a location where they are not welded to each other. Since the smoothness of the surface of the current collecting tab portion is higher than that of the location, it is easy to perform stable welding.

  In the battery of the present invention, the two separators arranged on both surfaces of the positive electrode can be welded to each other at at least a part of their peripheral portions to form a joint portion.

  6 and 7 schematically show another example of the flat non-aqueous secondary battery of the present invention. The battery shown in FIGS. 6 and 7 has a group of electrodes formed by forming joints at the peripheral edges of the two separators 7 and 7 arranged on both surfaces of the positive electrode 5, and FIG. FIG. 7 is a longitudinal sectional view showing a cross section of the outer case 2, the sealing case 3, and the insulating gasket 4 of FIG. 7. FIG. 7 is an enlarged view of the main part of FIG.

  FIG. 8 schematically shows a plan view of a separator in which a joining portion is formed on a part of the peripheral edge. In FIG. 8, 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 under 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. 8 is one in which both sides (both sides) of the electrode group are opposed to the negative electrode. Although not shown in FIG. In the forward direction), at least a negative electrode is arranged.

  The separator 7 shown in FIG. 8 is joined to another separator disposed on the lower side (in the depth direction in the drawing) via the positive electrode 5 (indicated by a dotted line in the drawing), and a joint 7c (FIG. Middle). 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 shown in FIG. 8 includes a main body part 7a (that is, a main body part 7a having a larger area in plan view than the main body part 5a of the positive electrode 5) and the main body part 7a. It has a protruding portion 7b that protrudes and covers at least a portion of the current collecting tab portion 5b of the positive electrode 5 that includes 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.

  As separators for non-aqueous secondary batteries, a microporous film made of a thermoplastic resin that is easily heat-shrinkable at high temperatures is generally used. In this way, two sheets arranged on both sides of the positive electrode are used. In this separator, the peripheral portions are welded to each other to form a joint portion, so that, for example, even if the inside of the battery becomes high temperature, the thermal contraction of the separator is suppressed, so that a safer battery is configured. be able to.

  In addition, as shown in FIG. 8, when using the separator which has a main-body part and an overhang | projection part, the junction part for joining two separators arrange | positioned on both surfaces of a positive electrode is a peripheral part of the main-body part of a separator However, a joining portion may also be provided at the peripheral portion of the separator overhanging portion (the portion of the peripheral edge portion of the separator overhanging portion along the protruding direction from the main body portion).

  The joining portion 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 two sheets are interposed via this layer. The separator may be formed by welding. 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, when using the separator which has a main-body part and an overhang | projection part as shown in FIG. 8, all the peripheral parts which concern on the main-body part of a separator may be a junction part, For example, it shows in FIG. Thus, you may leave a part of peripheral part as the non-welding parts 7d and 7d, without welding separators. 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.

  In order to form a joint part at the peripheral part of two separators and to accommodate a positive electrode between these separators, when two separators are directly welded together to form a joint part, for example, one sheet It is possible to employ a method in which the positive electrode is overlaid on the separator, the separator is further overlaid thereon, and then the peripheral portions of these separators are welded. It is also possible to adopt a method in which two separators are stacked, the peripheral portions thereof are welded to join the separators, and then the positive electrode is inserted between these separators.

  On the other hand, when a layer composed of the same kind 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 adopt a method in which a film to be the layer is placed at a place where the layer is expected to be placed, a positive electrode is disposed on the 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.

  In addition, the planar shape of the separator used for the battery of the present invention is, for example, at least a part of the peripheral part of the separator as described above at least at the joint part (at least the peripheral part of the two separators arranged on both surfaces of the positive electrode). In the case of forming a joint part formed by welding a part of each other, the shape shown in FIG. 7 is preferable. However, even when the joint part is not formed, the shape shown in FIG. Is preferred.

  In the battery of the present invention, when forming the electrode group, separators are disposed on both sides of the positive electrode at least on both sides facing the negative electrode. As for the positive electrode facing the negative electrode, separators may be disposed on both sides thereof (joint portions may be formed on these two separators), or only on the surface facing the negative electrode. You may arrange. Furthermore, when all the outermost electrodes in the electrode group are positive electrodes, and no separator is disposed on both surfaces of these positive electrodes, the battery case that also serves as the negative electrode terminal and the outermost positive electrode of the electrode group are between As described above, an insulator such as an insulating seal made of tape or the like made of PET or polyimide is disposed.

  The positive electrode mixture layer of the positive electrode according to the battery of the present invention is a layer containing a positive electrode active material, a conductive additive, a binder and the like.

Examples of the positive electrode active material according to the battery of the present invention include Li _x CoO ₂ , Li _x NiO ₂ , Li _x MnO ₂ , Li _x Co _y Ni _1-y O ₂ , and Li _x Co _y M _1-y O _2. lithium transition metal composite such as _{Li x Ni 1-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 (However, in each of the above lithium transition metal composite oxides, M is at least one selected from the group consisting of Mg, Mn, Fe, Co, Ni, Cu, Zn, Al, and Cr.) It is a metal element, and 0 ≦ x ≦ 1.1, 0 <y <1.0, and 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.

  For the positive electrode, for example, a positive electrode mixture obtained by mixing a positive electrode active material, a conductive additive, and a binder is dispersed in water or an organic solvent to prepare a positive electrode mixture-containing paste (in this case, the binder is preliminarily mixed with water or It may be dissolved or dispersed in a solvent and mixed with a positive electrode active material or the like to prepare a positive electrode mixture-containing paste), and the positive electrode mixture-containing paste is made of metal foil, expanded metal, plain weave metal mesh, etc. It is manufactured by forming a positive electrode mixture layer by applying it to one or both sides of a current collector, drying it, and then press-molding it. However, the method for manufacturing the positive electrode is not limited to the above-described method, and other methods may be used.

  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.

  The material for the current collector of the positive electrode is preferably aluminum or an aluminum alloy. From the viewpoint of reducing the total thickness of the positive electrode and increasing the number of layers of the positive electrode and the 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 8-20 micrometers, for example.

  Examples of the negative electrode according to the battery of the present invention include a negative electrode having lithium, a lithium alloy, a carbon material capable of occluding and releasing lithium ions, lithium titanate, and the like as an active material.

  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.

  When the negative electrode active material is lithium or a lithium alloy, the negative electrode is formed by bonding the lithium or lithium alloy to a current collector such as a metal network to form a negative electrode layer made of lithium or lithium alloy on the surface of the current collector. Can be obtained. On the other hand, when a carbon material or lithium titanate is used as the negative electrode active material, for example, a negative electrode composite obtained by mixing a carbon material or lithium titanate with a binder as the negative electrode active material and, if necessary, a conductive additive. The negative electrode mixture-containing paste is prepared by dispersing the agent in water or an organic solvent (in this case, the binder is previously dissolved or dispersed in water or solvent, and mixed with the negative electrode active material or the like to contain the negative electrode mixture) The paste containing the negative electrode mixture may be applied to a current collector made of metal foil, expanded metal, plain weave metal mesh, etc., dried, and then pressed to form a negative electrode layer (negative electrode composite). The negative electrode can be produced by forming an agent layer. However, the manufacturing method of the negative electrode is not limited to the above-described method, and other methods may be used.

  In addition, as a binder and conductive support agent which concern on a negative electrode, the various binders and conductive support agent which were illustrated previously as what can be used for a 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 layer (including the negative electrode mixture layer) in the negative electrode is preferably 40 to 200 μm, for example.

  The material for the current collector of the negative electrode is preferably copper or a copper alloy. 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.

  As the form of the microporous film made of the thermoplastic resin constituting the separator, any form may be used as long as it has an ionic conductivity sufficient to obtain the required battery characteristics. Or the ion-permeable microporous film (microporous film currently used widely as a battery separator) which has many holes formed by the wet extending | stretching method etc. 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%.

  The positive electrode, the negative electrode, and the separator are stacked and used as a stacked electrode group as shown in FIGS. 1, 6, and 7. At this time, the current collecting tab portion of each positive electrode is a plane of the electrode group. It is preferable that they are arranged so as to face the same direction as viewed, and the current collecting tab portions of the respective negative electrodes are arranged so as to face the same direction when seen in a plan view of the electrode group. 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. 8, 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

  Further, as shown in FIG. 8, 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.

  The total number of positive electrodes and negative electrodes in the electrode group is at least 3, but it is also possible to increase the number (4, 5, 6, 7, 8, etc.). 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 that the number is 40 or less.

  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.

  The planar shape of the flat non-aqueous secondary battery of the present invention is not particularly limited, and may be a polygonal shape such as a square (quadrangle) in addition to the 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 FIGS. 2 and 3 in order to prevent contact with the current collecting tab portion of the counter electrode. It is preferable to use a different shape.

  The flat non-aqueous secondary battery of the present invention can be applied to the same use as a conventionally known flat non-aqueous secondary battery.

  Hereinafter, the present invention will be described in detail based on examples. However, the following examples do not limit the present invention.

Example 1
<Preparation of positive electrode>
A positive electrode was prepared using LiCoO ₂ as a positive electrode active material, carbon black as a conductive additive, and PVDF as a binder. First, LiCoO ₂ : 93 parts by mass and carbon black: 3 parts by mass were mixed, and the resulting mixture and PVDF: 4 parts by mass were previously dissolved in N-methyl-2-pyrrolidone (NMP). Were mixed to prepare a positive electrode mixture-containing paste. The obtained positive electrode mixture-containing paste was applied to both surfaces of a positive electrode current collector made of an aluminum foil having a thickness of 15 μm by an applicator. When applying the positive electrode mixture-containing paste, the application part and the non-application part were continuously arranged every 5 cm, and the part that was the application part on the front surface was also the application part on the back surface. Subsequently, the applied positive electrode mixture-containing paste was dried to form a positive electrode mixture layer, and then roll-pressed and cut into a predetermined size to obtain a belt-like positive electrode. The positive electrode had a width of 40 mm, and the positive electrode mixture layer forming portion had a thickness of 140 μm.

  The belt-like positive electrode is such that the positive electrode mixture layer forming portion is the main body portion (arc portion diameter 15.1 mm), and the positive electrode mixture layer non-forming portion is the current collecting tab portion (width 3.5 mm). 2 was punched into the shape shown in FIG. 2 to obtain a positive electrode for a battery.

<Integration of battery positive electrode and separator>
A PE microporous membrane separator (thickness 16 μm) having the shape shown in FIG. 7 is arranged on both surfaces of the battery positive electrode, and the portion shown in FIG. 7 is welded by a hot press (temperature 170 ° C., press time 2 seconds). A joining part was formed in a part of the peripheral part of the main part and a part of the peripheral part of the overhanging part related to the two separators, and the battery positive electrode and the separator were integrated. Note that the width of the joint portion relating to the two separators was 0.3 mm for both the main portion and the overhang portion, and the length in the protruding direction from the main portion at the peripheral portion of the overhang portion was 0.5 mm. Of the outer edges of the main parts of the two separators, 90% of the length was used as the joint.

<Production of negative electrode>
A negative electrode was prepared using graphite as the negative electrode active material and PVDF as the binder. The graphite: 94 parts by mass, PVDF: 6 parts by mass, and a binder solution previously dissolved in NMP were mixed to prepare a negative electrode mixture-containing paste. The obtained negative electrode mixture-containing paste was applied to one or both sides of a negative electrode current collector made of a copper foil having a thickness of 10 μm by an applicator. In addition, when applying the negative electrode mixture-containing paste, when the coated part and the non-coated part are continuously applied every 5 cm and are applied to both sides of the current collector, the place where the coated part is the surface is the back side However, it was made to become an application part. Subsequently, the applied negative electrode mixture-containing paste was dried to form a negative electrode mixture layer, and then roll-pressed and cut into a predetermined size to obtain a strip-shaped negative electrode. The negative electrode had a width of 40 mm, and the negative electrode mixture layer forming portion had a thickness of 190 μm when formed on both sides of the current collector and 100 μm when formed on one side of the current collector.

  The strip-shaped negative electrode has the shape shown in FIG. 3 such that the negative electrode mixture layer forming portion is a main body portion (arc portion diameter 16.3 mm) and the negative electrode mixture layer non-forming portion is a current collecting tab portion. The negative electrode for a battery having a negative electrode mixture layer on one side of the current collector and the negative electrode for a battery having a negative electrode mixture layer on both sides of the current collector were obtained. A part of the negative electrode for a battery having the negative electrode mixture layer on one side of the current collector was punched after a PET film having a thickness of 100 μm was attached to the exposed surface of the current collector of the strip-shaped negative electrode. .

<Battery assembly>
7 positive electrodes for a battery integrated with the separator, 6 negative electrodes for a battery in which a negative electrode mixture layer is formed on both sides of the current collector, and a negative electrode for a battery in which a negative electrode mixture layer is formed on one side of the current collector The battery negative electrode with a negative electrode mixture layer formed on one side of the current collector was used as the outermost electrode using two sheets (one of which was a PET film affixed to the exposed surface of the current collector) The battery positive electrode and the battery negative electrode were alternately stacked. And the current collection tab part of each battery positive electrode was integrated and welded together, and the current collection tab part of each battery negative electrode was welded together and integrated, and the electrode group was formed. When welding the current collecting tab portions of the positive electrodes for each battery, the planar shape of the location where the current collecting tab portions are welded to each other is the shape shown in FIG. 4 (the apex that is the portion closest to the main body portion). The inner angle of the two sides connected to this apex is 120 ° at the center position in the width direction of the current collecting tab portion.

  The electrode group was placed in the outer case so that the PET film faced the inner surface of the outer case, and the integrated current collecting tab portion of each battery positive electrode was welded to the inner surface of the outer case. In addition, welding to the outer case inner surface of the current collecting tab portion of each integrated battery positive electrode is performed by ultrasonic welding, and as shown in FIG. 4, four square welding marks each having a side of 0.4 mm are formed. It was to so. Of the four welding marks, two are at the locations where the current collector tab portions of the battery positive electrodes are welded together (location 500a in FIG. 4), and the remaining two are the current collector tab portions of the battery positive electrodes. Is formed at a location where the two are not welded to each other (location 500b in FIG. 4), and the shortest distance (in FIG. 4) from the end in the width direction of the current collecting tab portion of each battery positive electrode integrated with these welding marks. The length of z) was set to 1.0 mm.

In addition, an insulating gasket was attached to the sealing case, and a non-aqueous electrolyte (LiPF ₆ dissolved in a mixed solvent of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 1: 2 at a concentration of 1.2 mol / l) 200 mg 5A and 5B except that the outer case containing the electrode group is covered and the periphery is caulked, the diameter is 20 mm, the thickness is 3.2 mm, and the number of battery positive electrodes and battery negative electrodes according to the electrode group is different. A flat non-aqueous secondary battery having the same structure as that shown in FIG. 6 was obtained. The flat non-aqueous secondary battery is designed to discharge at a current value of 14 mA and a discharge capacity of 70 mAh.

Example 2
When welding the current collecting tab portions of the positive electrodes for each battery, the planar shape of the location where the current collecting tab portions are welded to each other is the shape shown in FIG. 5 (the welding width in the horizontal direction in FIG. A flat nonaqueous secondary battery was produced in the same manner as in Example 1 except that the length y in FIG. 5 was 1.15 mm.

Comparative Example 1
When welding the current collecting tabs of each battery positive electrode to each other, the end portions in the width direction of the current collecting tab portions of the respective battery positive electrodes, which are welded in parallel to the width direction of the current collecting tab portions, and the others A flat non-aqueous secondary battery was produced in the same manner as in Example 1 except that the shortest distance from the main part of the positive electrode for the battery was the same.

  Thirty batteries (not charged) of Examples and Comparative Examples were prepared, and the following 1.5 m drop test and 1.9 m drop test were performed.

<1.5m drop test>
The test of dropping 15 batteries of each of the example and the comparative example from a height of 1.5 m onto a concrete floor with their side faces down was repeated 5 times.

<1.9m drop test>
For each of the 15 batteries of the examples and comparative examples (batteries different from those for which the 1.5 m drop test was performed), the above 1.5 m drop test was performed except that the dropped height was changed to 1.9 m. The test was conducted in the same way.

  Each battery immediately after performing each drop test was disassembled, and the presence or absence of cracks in the widthwise end of the current collecting tab portion of the positive electrode was examined. The results are shown in Table 1.

  As shown in Table 1, in the batteries of Example 1 and Example 2, no crack occurred at the end of the current collecting tab portion of the positive electrode in any of the 1.5 m drop test and the 1.9 m drop test. On the other hand, in the battery of Comparative Example 1, in the 1.5 m drop test, the end of the current collector tab portion of the positive electrode is not cracked, but in the 1.9 m drop test, the current collector tab portion of the positive electrode is not cracked. There are cracks at the edges.

DESCRIPTION OF SYMBOLS 1 Flat type non-aqueous secondary battery 2 Exterior case 3 Sealing case 4 Insulating gasket 5 Positive electrode 5a Positive electrode main body 5b Positive electrode current collecting tab portion 6, 6A, 6B Negative electrode 6a Negative electrode main body portion 6b Negative electrode current collecting tab portion 7 Separator 7c Joint 8 Insulating material 500 Current collecting tab 501 of each integrated positive electrode Welding trace

Claims (8)

In the space formed by crimping the outer case and the sealing case via an insulating gasket, the positive electrode and the negative electrode are alternately interposed via a separator, and substantially parallel to the flat surface of the outer case and the sealing case. A flat non-aqueous secondary battery having a non-aqueous electrolyte and an electrode group in which the total number of positive and negative electrodes is 3 or more,
Either one of the outer case and the sealing case serves as a positive electrode terminal, and the other serves as a negative electrode terminal,
The positive electrode has a main body portion and a current collecting tab portion that protrudes from the main body portion in a plan view and is narrower than the main body portion. The main body portion of the positive electrode includes a current collector. A positive electrode mixture layer containing a positive electrode active material is formed on one side or both sides, and in the current collector tab portion of the positive electrode, a positive electrode mixture layer is not formed on the current collector,
The electrode group has at least two positive electrodes, the current collecting tabs of the positive electrodes are gathered together, and are welded and integrated with each other.
The integrated current collecting tab portion of each positive electrode is welded to the inner surface of an outer case or a sealing case that also serves as a positive electrode terminal,
The location where the current collecting tab portions of each positive electrode in the integrated current collecting tab portion are welded to each other is provided up to the end in the width direction of the current collecting tab portion of each integrated positive electrode. And the portion of the integrated current collecting tab portion of each positive electrode, where the current collecting tab portions of each positive electrode are welded to each other, is the portion closest to the main body portion of the positive electrode. A flat non-aqueous secondary battery, which is present in a portion other than the end portion in the width direction of the electric tab portion.   In the integrated current collecting tab portion of each positive electrode, the welding mark with the inner surface of the exterior case or sealing case that also serves as the positive electrode terminal, the location where the current collecting tab portions of each positive electrode are welded to each other, and the current collecting tab of each positive electrode The flat nonaqueous secondary battery according to claim 1, wherein the portions are present at locations where the portions are not welded to each other. In the space formed by crimping the outer case and the sealing case via an insulating gasket, the positive electrode and the negative electrode are alternately interposed via a separator, and substantially parallel to the flat surface of the outer case and the sealing case. A flat non-aqueous secondary battery having a non-aqueous electrolyte and an electrode group in which the total number of positive and negative electrodes is 3 or more,
Either one of the outer case and the sealing case serves as a positive electrode terminal, and the other serves as a negative electrode terminal,
The negative electrode has a main body portion and a current collecting tab portion that protrudes from the main body portion in a plan view and is narrower than the main body portion. The main body portion of the negative electrode includes a current collector. A negative electrode layer containing a negative electrode active material is formed on one side or both sides, and in the current collector tab portion of the negative electrode, the negative electrode layer is not formed on the current collector,
The electrode group has at least two negative electrodes, the current collecting tabs of the negative electrodes are gathered together, and are welded together to be integrated,
The integrated current collecting tab portion of each negative electrode is welded to the inner surface of the outer case or sealing case that also serves as the negative electrode terminal,
The locations where the negative electrode current collecting tab portions of the integrated negative electrode current collecting tab portions are welded to each other are provided up to the end in the width direction of the integrated negative electrode current collecting tab portions. And the portion of the negative electrode current collecting tab portion of the negative electrode current collecting tab portion welded to each other is the portion closest to the negative electrode main body portion is the current collector of the integrated negative electrode. A flat non-aqueous secondary battery, which is present in a portion other than the end portion in the width direction of the electric tab portion.   In the integrated current collecting tab portion of each negative electrode, the welding trace with the inner surface of the outer case or sealing case that also serves as the negative electrode terminal, the location where the current collecting tab portions of each negative electrode are welded to each other, and the current collecting tab of each negative electrode The flat nonaqueous secondary battery according to claim 3, wherein the portions are present at locations where the portions are not welded to each other. At least on both sides of the positive electrode facing the negative electrode, separators made of a microporous film made of thermoplastic resin are arranged,
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 flat separator according to any one of claims 1 to 4, wherein the two separators have joint portions welded to each other at least at a part of a peripheral edge portion of the main body portion. Water secondary battery.   The flat non-aqueous secondary battery according to claim 5, wherein a joint portion between two separators disposed on both surfaces of the positive electrode is formed by directly welding the two separators.   The joining portion of the two separators arranged on both surfaces of the positive electrode is formed by welding through a layer made of the same kind of resin as the thermoplastic resin constituting the two separators. The flat non-aqueous secondary battery described.   The flat non-aqueous secondary battery according to any one of claims 5 to 7, wherein the thermoplastic resin constituting the separator is a polyolefin.