JP2011154784A - Flat nonaqueous secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flat nonaqueous secondary battery superior in productivity. <P>SOLUTION: In the flat nonaqueous secondary battery provided with an electrode group in which a plurality of positive electrodes and a plurality of negative electrodes are laminated with separators interposed and a nonaqueous electrolyte solution arranged in a space formed by caulking-sealing with an outer case also serving as a positive electrode terminal and a negative electrode case also serving as a negative electrode terminal via an insulation gasket, the positive electrode has a main body and a current collector tab projecting from the main body, and the current collector tabs of all of the positive electrodes are collected together and are folded on an outer surface of the electrode group on the outer case side to be connected electrically to the positive electrode case, and the insulation gasket has a projected part toward a battery inside on its inner wall on the outer case side. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a flat non-aqueous secondary battery with good productivity.

  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 (Patent Document 1, etc.).

  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. Some of them are electrically connected by welding or the like to the inner surface of the outer case or the sealing case.

JP 2003-142161 A

  Incidentally, in recent years, as the application range of flat non-aqueous secondary batteries has expanded, there has been a demand for, for example, downsizing. However, in the flat non-aqueous secondary battery, depending on the shape of the battery, such as a small one, the inside of the battery is very narrow. For example, the collected current collecting tab of the positive electrode related to the electrode group and the positive terminal It may be difficult to weld the inner surface of the outer case that also serves as a battery, and the productivity of the battery may be impaired.

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

  The flat non-aqueous secondary battery of the present invention that can achieve the above object is a space formed by caulking and sealing an exterior case that also serves as a positive electrode terminal and a sealing case that also serves as a negative electrode terminal through an insulating gasket, A flat non-aqueous secondary battery having a non-aqueous electrolyte and an electrode group in which a plurality of positive electrodes and a plurality of negative electrodes are alternately stacked via separators, the positive electrode in a main body part and in plan view, A positive electrode mixture that includes a positive electrode active material on one or both sides of the current collector, the current collector having a current collecting tab that protrudes from the main body and narrower than the main body. In the current collector tab portion of the positive electrode, a positive electrode mixture layer is not formed on the current collector, and at least both sides of the positive electrode facing the negative electrode are thermoplastic. A separator made of a microporous membrane made of resin is disposed, The separator includes a main body that covers the entire surface of the main body of the positive electrode, and a projecting portion that protrudes from the main body and covers a portion of the current collecting tab of the positive electrode that includes at least a boundary with the main body. And the two separators have a welded portion welded to each other at least at a part of the peripheral edge of the main portion, and the electrode group includes the current collecting tab portions of the positive electrode. The electrode assembly is folded on the outer surface of the outer case side and is electrically connected to the outer case, and the insulating gasket has a protruding portion toward the inside of the battery on the outer case side of the inner wall. It is characterized by.

  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.

  According to the present invention, it is possible to provide a flat non-aqueous secondary battery with good productivity.

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 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 flat nonaqueous secondary battery of this invention. It is a top view which represents typically an example of the separator which concerns on the flat nonaqueous secondary battery of this invention.

  1 and 2 schematically show an example of the flat non-aqueous secondary battery of the present invention. FIG. 1 is a longitudinal sectional view showing a cross section of a battery case (outer case 2 and sealing case 3) and an insulating gasket 4 part of a flat non-aqueous secondary battery. FIG. 2 is an enlarged view of the main part of FIG. Furthermore, the electrode group is shown in cross section. As shown in FIGS. 1 and 2, the flat non-aqueous secondary battery 1 is formed by laminating a positive electrode 5 and a negative electrode 6 so that their planes are substantially parallel (including parallel) to the flat plane of the battery. A type electrode group and a non-aqueous electrolyte (not shown) are accommodated in a space (sealed space) formed by an exterior case 2 also serving as a positive electrode terminal, a sealing case 3 also serving as a negative electrode terminal, and an insulating gasket 4. Yes. 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.

  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.

  As for the main-body part 5a of the positive electrode 5, the positive mix layer 51 is formed in the single side | surface or both surfaces of a collector (52 in FIG. 2). 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.

  Similarly to the positive electrode 5, the negative electrode also 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. As shown, a negative electrode agent layer 61 is formed on one side or both sides of a 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. On the other hand, the negative electrode 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.

  In the battery shown in FIGS. 1 and 2, polyethylene terephthalate (between the negative electrode 6B positioned at the uppermost part of the electrode group and the sealing case 3 and between the negative electrode 6B positioned at the lowermost part of the electrode group and the outer case) An insulating seal 8 made of tape or the like formed of PET or polyimide is disposed. This insulating seal 8 mainly serves to insulate the negative electrode 6B located at the bottom of the electrode group and the outer case 2 (the positive current collecting tab portion 5b electrically connected to the outer case 2). However, the insulating seal 8 can use a binding tape for suppressing misalignment of each component (positive electrode, negative electrode, and separator) related to the electrode group. As shown, the insulating seal 8 is also disposed between the negative electrode 6B located at the top of the electrode group and the sealing case 3.

  In the battery shown in FIGS. 1 and 2, the current collecting tab portions 5b of all the positive electrodes 5 of the electrode group are collected, and the current collecting tab portions 5b are welded or welded. Without being joined to each other, the electrode group is folded back on the outer surface of the outer case 2 side (on the lower outer surface in FIG. 1 and FIG. 2) and directly contacts the outer case 2 without being joined. Is electrically connected.

  In a normal flat non-aqueous secondary battery having a stacked electrode group, the electrical connection between the positive electrode and the outer case that also serves as the positive electrode terminal is joined by, for example, welding the current collecting tabs related to the positive electrode together. And the method of welding this etc. to the inner surface (the inner surface of the location where the electrode group is not arrange | positioned) of the exterior case is employ | adopted. However, for example, in a flat battery having a very small opening area of the insulating gasket, it is difficult to secure a region for welding with the current collecting tab portion in the outer case.

  On the other hand, in the flat non-aqueous secondary battery of the present invention, the current collecting tab portions related to all the positive electrodes are gathered, and these are folded back on the outer surface of the electrode group and brought into contact with the outer case, whereby the electrode in the outer case The inner surface of the place where the group is arranged is used for current collection, and an area for welding with the current collecting tab portion of each positive electrode in the outer case is unnecessary. Therefore, in the battery of the present invention, for example, by making the opening area of the insulating gasket very small, even if the conventional method makes it difficult to connect the positive electrode and the outer case, such connection is facilitated. Increases productivity.

  In the battery of the present invention, the current collecting tab portions of all the collected positive electrodes may be welded to each other or may not be joined by welding or the like. From this point, welding is performed before turning back onto the outer surface of the electrode group. Once welded, the positions of the current collecting tab portion located on the inner side and the current collecting tab portion located on the outer side are fixed. Will be. However, when the collected current collecting tab portion is folded back on the outer surface of the electrode group, the current collecting tab portion positioned on the inner side is short in the bent portion (curved portion) and positioned on the outer side. The current collecting tab portion needs to be longer. Therefore, in the bent part of the folded current collecting tab part, the current collecting tab part located on the inner side is excessively bent. Therefore, the current collecting tab portion of the positive electrode folded back on the outer surface of the electrode group returns to the original state when loaded into the outer case, and the productivity of the battery is impaired.

  Therefore, in the battery of the present invention, as shown in FIGS. 1 and 2, the insulating gasket 4 having a protruding portion 4a toward the inside of the battery on the outer case side of the inner wall is used. The positive current collecting tab portion 5b folded on the outer surface of the electrode group hits the protruding portion 4a of the insulating gasket when the electrode group is mounted on the outer case 2, and the return is suppressed. The battery of the present invention enhances productivity by such action.

  Regarding the height of the projecting portion (height from the contact surface with the outer case) and the projecting length in the battery inner direction (the length in the lateral direction in FIG. 1) of the insulating gasket, Although it can be appropriately changed according to the size and the like, it is usually preferable that the height is 0.05 to 0.3 mm, and the protrusion length is 0.05 to 0.3 mm. Is preferred.

  In addition, about the electrical connection of the negative electrode which concerns on the electrode group which the battery of this invention has, and the sealing case which serves as a negative electrode terminal, the method of following (1)-(3) is employable, for example.

(1) Either one of the outermost electrodes in the electrode group is a negative electrode, and the negative electrode at the outermost part is formed by forming a negative electrode agent layer only on one side of the current collector. The exposed surface is used as the outer surface of the electrode group, and is brought into direct contact with the sealing case for electrical connection. In addition, what is necessary is just to join the negative electrode arrange | positioned at the outermost part which concerns on an electrode group, and the other negative electrode which an electrode group has, such as welding each current collection tab part collectively.

(2) As shown in FIG. 1, for the negative electrode associated with the electrode group, all the current collecting tabs are gathered and folded back onto the outer surface of the electrode group on the sealing case side without joining them together by welding or the like. Electrically connected to the inner surface of the case. In this case, since the current collecting tab portions of the collected negative electrodes are not joined to each other, when folded on the outer surface of the electrode group, the current collecting tab portions located on the inner side and the outer side are located on the bent portion. Misalignment occurs with the current collecting tab portion. Therefore, it is possible to suppress the deflection of the current collecting tab portion located on the inside as described above, and to suppress the return of the current collecting tab portion after being folded back on the outer surface of the electrode group.

(3) As shown in FIG. 1, after collecting all the current collecting tab portions of the negative electrode of the electrode group and welding them together, they are folded back onto the outer surface of the electrode group on the sealing case side, Connect. As will be described in detail later, since the current collecting tab portion of the positive electrode is partially covered by the protruding portion of the separator, when the current collecting tab portion of the positive electrode is folded, the protruding portion of the separator is also folded together. The current collecting tab portion is likely to return. On the other hand, since the current collecting tab portion of the negative electrode does not have to be covered by the protruding portion of the separator, even if the current collecting tab portion of the negative electrode is folded, the influence of the separator is affected. There are few, and it is hard to return compared with a current collection tab part. Therefore, for the current collector tab portion of the negative electrode, even if all of them are gathered together and then folded back onto the outer surface on the sealing case side of the electrode group, the occurrence of return can be suppressed compared to the current collector tab portion of the positive electrode. it can. Further, in this case, since the current collecting tab portions of the negative electrode are welded to each other, it is possible to suppress a decrease in battery productivity due to variations in the current collecting tab portions of the negative electrode during battery assembly. .

  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, The current collection tab part 6b which concerns on the negative electrode arrange | positioned below is shown with the dashed-dotted 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 flat non-aqueous secondary battery of the present invention, as described above, the joint for joining the two separators arranged on both sides of the positive electrode is provided on the peripheral edge of the main body of the separator. You may provide a junction part also in the peripheral part of the overhang | projection part (part along the protrusion direction from a main-body part among the peripheral parts of the overhang | projection part of a separator).

  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, peeling at the joint 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.

  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 the battery shown in FIG. 1 and FIG. 2, both the upper and lower electrodes (the two outermost electrodes) in the electrode group are negative electrodes. In the battery of the present invention, the embodiment shown in FIG. 1 and FIG. In contrast, one or both of the upper and lower electrodes (the two outermost electrodes) in the electrode group may be used as a positive electrode.

  Further, in the battery of the present invention, separators are disposed on both surfaces of the positive electrode at least on both sides facing the negative electrode, but only the positive electrode disposed on the outermost part of the electrode group, that is, one side (one surface) is opposed to the negative electrode. With respect to the positive electrode, separators may be disposed on both surfaces thereof (joint portions may be formed on these two separators), or the separator may be disposed only on the surface facing the negative electrode. Absent.

The size of the battery of the present invention is not particularly limited, but the effect of the present invention is particularly remarkable when the opening area of the insulating gasket is very small, for example, 100 mm ² or less. However, since the battery having a very small opening area of the insulating gasket itself tends to be difficult to produce, the opening area of the insulating gasket according to the battery of the present invention is preferably 20 mm ² or more, for example.

  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.

  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%.

  The positive electrode, the negative electrode, and the separator are stacked and used as a stacked electrode group as shown in FIG. 1 and FIG. 2, and the current collecting tab portion of each positive electrode is the same in a plan view of the electrode group. When the negative electrode has a current collecting tab portion, the negative electrode current collecting tab portions are preferably arranged so as to face the same direction 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. 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 described above, 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 made of chemical-resistant polypropylene or the like, and each component (wrapped in the separator). It is preferable to suppress misalignment between the positive electrode and the negative electrode).

  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.

  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 FIG. 3 in order to prevent contact with the current collecting tab portion of the counter electrode. It is preferable to keep it.

A positive electrode having the shape shown in FIG. 3, a separator having the shape shown in FIG. 4, and an insulating gasket having a shape shown in FIGS. 1 and 2 (the height of the protruding portion is 0.2 mm and the protruding length is 0.15 mm). 1 and FIG. 2, the flat non-aqueous secondary battery (the outer diameter is 10 mm, the height is 2.5 mm, the opening area of the insulating gasket is 47.8 mm ² , and each current collecting tab of the positive electrode 5 is used. The current collecting tabs 6b of the part 5b and the negative electrode 6 were collected and joined to each other by ultrasonic welding), and when the electrode group was inserted into the sealing case, the collected positive electrode currents were collected. As the tab hits the protruding part of the insulating gasket, no return occurred, and it was confirmed that the production with good productivity was possible.

  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.

DESCRIPTION OF SYMBOLS 1 Flat type non-aqueous secondary battery 2 Exterior case 3 Sealing case 4 Insulating gasket 4a Protrusion part 5 Positive electrode 5a Positive electrode main body part 5b Positive electrode current collection tab part 6A, 6B Negative electrode 6a Negative electrode main body part 6b Negative electrode current collection tab part 7 Separator 7a Separator body 7b Separator overhang 7c Joint 8 Insulation seal

Claims (2)

An electrode in which a plurality of positive electrodes and a plurality of negative electrodes are alternately stacked via separators in a space formed by caulking and sealing an exterior case that also functions as a positive electrode terminal and a sealing case that also functions as a negative electrode terminal A flat non-aqueous secondary battery having a group and a non-aqueous electrolyte,
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,
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. And the two separators have a joint part welded to each other at least at a part of the peripheral part of the main part,
In the electrode group, the current collecting tab portions of the positive electrode are gathered, folded back on the outer surface of the outer case side in the electrode group and electrically connected to the outer case,
2. The flat non-aqueous secondary battery according to claim 1, wherein the insulating gasket has a protruding portion toward the inside of the battery on the outer case side of the inner wall.   The flat nonaqueous secondary battery according to claim 1, wherein the thermoplastic resin constituting the separator is polyolefin.

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