JP2011141997A - Flat-type nonaqueous secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flat-type nonaqueous secondary battery with excellent productivity. <P>SOLUTION: The flat-type nonaqueous secondary battery includes nonaqueous electrolyte and an electrode group with a plurality of cathodes and anodes laminated through a separator in a space formed by caulking and sealing a cathode case and an anode case through an insulation gasket. Each of the cathode and the anode includes a body and a collector tab part protruded from the body, all collector tab parts of the cathodes and the anodes are brought together and folded to an external surface of the electrode group jointed with each other and adhered with the external surface, and electrically connected with the cathode case or the anode case. <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 a 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. Welding with the inner surface of the sealing case may be difficult, and battery productivity 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.

  In the flat non-aqueous secondary battery of the present invention that can achieve the above object, a positive electrode case that also serves as a positive electrode terminal and a negative electrode case that also serves as a negative electrode terminal are caulked and sealed 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 collecting tab portion of the positive electrode, a positive electrode mixture layer is not formed on the current collector, and the negative electrode protrudes from the main body portion in plan view with the main body portion. And a current collecting tab portion narrower than the main body portion, and the book of the negative electrode In the part, a negative electrode agent layer containing a negative electrode active material is formed on one side or both sides of the current collector, and in the current collector tab portion of the negative electrode, the negative electrode agent layer is not formed on the current collector, At least on both sides of the positive electrode facing both sides of the negative electrode, separators made of a microporous film made of a thermoplastic resin are arranged, and the two separators are main portions that cover the entire body of the positive electrode And a projecting portion that protrudes from the main portion and covers at least a portion of the current collecting tab portion of the positive electrode that includes a boundary portion with the main body portion, and the two separators are provided on the main portion. At least a part of the peripheral edge has a welded portion that is welded to each other, and the electrode group is joined together by collecting current collecting tabs of the positive electrode, on the outer surface of the electrode group on the positive electrode case side Folded to adhere to the outer surface, Are electrically connected to the positive electrode case and / or the current collecting tab portions of the negative electrode are collectively welded to each other, folded back onto the outer surface of the electrode group on the negative electrode case side, and adhered to the outer surface. And it is electrically connected with the negative electrode case.

  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 (a positive electrode case 2 and a negative electrode 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. Type electrode group and non-aqueous electrolyte (not shown) are a positive electrode case (exterior case in FIGS. 1 and 2) 2 serving as a positive electrode terminal, and a negative electrode case (sealing case in FIGS. 1 and 2) also serving as a negative electrode terminal 3) and a space formed by the insulating gasket 4 (sealed space). The negative electrode case 3 is fitted in the opening of the positive electrode case 2 via an insulating gasket 4, and the opening end of the positive electrode case 2 is tightened inward, whereby the insulating gasket 4 contacts the negative electrode case 3. Thus, the opening of the positive electrode case 2 is sealed, and the inside of the battery has a sealed structure. The positive electrode case 2 and the negative electrode 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.

  The negative electrode also has a main body portion and a current collecting tab that protrudes from the main body portion in a plan view and is narrower than the main body portion, as in the positive electrode 5, and is shown in FIGS. 1 and 2. As described above, the negative electrode agent layer 61 is formed on one or both surfaces of the current collector 62 in the main body 6 a of the negative electrode 6. Further, in the current collecting tab portion 6 b of the negative electrode 6, the negative electrode agent layer is not formed on the surface of the current collector 62, and the current collector 62 is exposed.

  In the battery shown in FIG. 1 and FIG. 2, the upper and lower ends of the electrode group are negative electrodes 6B and 6B, and these negative electrodes 6B and 6B are provided on only one side of the current collector 62 (the inner surface of the battery). A layer 61 is provided. 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, all the negative electrodes 6 (the negative electrode 6 </ b> A in which the negative electrode layer 61 is formed on both surfaces of the current collector 62 and the negative electrode layer 61 on one surface of the current collector 62). The current collecting tab portions 6b according to the negative electrode 6B) formed on the electrode group are collected, and the current collecting tab portions 6b are welded to each other, and then on the outer surface of the electrode group on the negative electrode case 3 side (FIG. 1). 2 and is bonded to the outer surface and directly connected without being joined to the negative electrode case 3 to be electrically connected.

  Furthermore, in the battery shown in FIG. 1 and FIG. 2, the current collecting tab portions 5b related to all the positive electrodes 5 included in the electrode group are collected, and the current collecting tab portions 5b are welded to each other. Folded on the outer surface of the electrode group on the positive electrode case 2 side (on the outer surface on the lower side in FIGS. 1 and 2), adhered to the outer surface, and directly contacted without being joined to the positive electrode case 2 Is electrically connected.

  In a normal flat non-aqueous secondary battery having a stacked electrode group, current collecting tab portions related to the positive electrode are joined together by welding or the like, and this is joined to the inner surface of the positive electrode case (where the electrode group is not disposed). Or the like, and the current collecting tab portions related to the negative electrode are joined together by welding or the like, and this is joined to each other by welding or the like, and this is connected to the inner surface of the negative electrode case (no electrode group is disposed) It is electrically connected by welding to the inner surface). 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 positive electrode case or the negative electrode 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 and the current collecting tab portions related to all the negative electrodes are collected and folded on the outer surface of the electrode group to form a positive electrode case. Or the negative electrode case, the inner surface of the positive electrode case or the negative electrode case where the electrode group is arranged is used for current collection, and the current collecting tab of each electrode in the positive electrode case or the negative electrode case The area for welding with the part is unnecessary. For this reason, in the battery of the present invention, for example, the opening area of the insulating gasket is made very small, so that the connection between the positive and negative electrodes and the positive electrode case or the negative electrode case is difficult by the conventional method. In this way, the productivity is increased.

  As described above, in the battery of the present invention, the current collecting tab portions related to all the collected positive electrodes and the current collecting tab portions related to all the collected negative electrodes are joined to each other. When the collected current collector tab portion is folded back on the outer surface of the electrode group, the bent tab portion (curved portion) requires a shorter current collector tab portion, and the outer side. The current collecting tab part located in the needs to be longer. However, when the current collecting tab portions related to the positive electrode and the negative electrode are welded together, due to the problem of workability, welding is performed before folding back on the outer surface of the electrode group. The current collecting tab portion located on the outer side and the current collecting tab portion located on the outer side are fixed to each other. Therefore, in the bent portion, the current collecting tab portion located on the inner side is excessively bent. End up. For this reason, the current collecting tab portion folded back on the outer surface of the electrode group returns to the original state before being loaded into the positive electrode case or the negative electrode case, and the productivity of the battery is impaired.

  Therefore, in the battery of the present invention, the current collecting tab portions related to all the collected positive electrodes and the current collecting tab portions related to all the collected negative electrodes are welded to each other and then folded on the outer surface of the electrode group. In such a case, the outer surface and the current collecting tab portion are bonded. Thereby, since the return of the current collection tab part after folding on the outer surface of an electrode group is suppressed, the productivity of a battery can be improved.

  In the battery shown in FIGS. 1 and 2, polyethylene terephthalate (between the negative electrode 6B located at the top of the electrode group and the negative electrode case 3 and between the negative electrode 6B located at the bottom of the electrode group and the positive electrode case ( An insulating seal 8 made of tape or the like formed of PET or polyimide is disposed. The insulating seal 8 is mainly for insulating the negative electrode 6B located at the lowermost part of the electrode group and the positive electrode case 2. The insulating seal 8 includes each component (positive electrode) related to the electrode group. , Negative electrode and separator) can be used, and in that case, as shown in FIG. 1 and FIG. 2, between the negative electrode 6B located at the top of the electrode group and the negative electrode case 3 Also, the insulating seal 8 is arranged.

  In the battery of the present invention, for at least one of the positive electrode and the negative electrode of the electrode group, all the current collecting tab portions are gathered together and welded together, folded back on the outer surface of the electrode group, and adhered to the outer surface In addition, as long as it is electrically connected to the positive electrode case or the negative electrode case, both the positive electrode and the negative electrode may have the above-described mode as shown in FIGS.

  Note that, for any one of the positive electrode and the negative electrode in the electrode group, all the current collecting tab portions are collected and welded together, folded back on the outer surface of the electrode group, and adhered to the outer surface, and the positive electrode When it is set as the aspect electrically connected to the case or the negative electrode case, the other electrode can be electrically connected to the battery case, for example, as described in (1) or (2) below.

(1) Either one of the outermost electrodes in the electrode group is used as the other electrode, and the other electrode at the outermost portion is provided with an electrode agent layer (positive electrode mixture layer or negative electrode only on one side of the current collector) An agent layer) is formed, and the exposed surface of the current collector is used as the outer surface of the electrode group, and is brought into direct contact with and electrically connected to the battery case (positive electrode case or negative electrode case). The other electrode disposed on the outermost part of the electrode group and the other electrode having the same polarity as the other electrode may be joined together by welding the current collecting tab portions together. .

(2) For the other electrode of the electrode group, all the current collecting tab portions are gathered, and these are joined to each other by welding or the like, and on the outer surface on the battery case side having the same polarity as the other electrode in the electrode group And is electrically connected to the inner surface of the battery case of the same polarity. In this case, since the collected current collecting tab portions 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 current collecting tab portions located on the outer side at the bent portion Misalignment occurs with the 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.

  Adhesion between the current collecting tab portion related to the electrode and the outer surface of the electrode group can be performed, for example, by hot pressing through a hot melt material such as ethylene-vinyl acetate copolymer (EVA). Is preferable in that it becomes favorable. In addition to the hot melt material described above, the current collecting tab portion and the outer surface of the electrode group are bonded with an adhesive such as an acrylic resin-based, cyanoacrylate-based, epoxy-based adhesive, or an ionomer resin adhesive. It can also be glued.

  In FIGS. 1 and 2, hot melt material or adhesive interposed between the folded portion of the current collecting tab 5 b of the positive electrode 5 or the current collecting tab portion 6 b of the negative electrode 6 and the insulating seal 8 corresponding to the outer surface of the electrode group. The agent is not shown.

  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. For example, the effect of the present invention is particularly remarkable when the opening area of the insulating gasket is very small such as 80 mm ² or less. However, since the battery having a very small opening area of the insulating gasket tends to be difficult to produce, the opening area of the insulating gasket according to the battery of the present invention is preferably 15 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. It is preferable that the current collecting tabs of the negative electrodes are arranged so as to face in the same direction in the 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.

  In FIG. 1 and FIG. 2, an example in which the positive electrode case is an outer case and the negative electrode case is a sealing case is shown. However, the battery of the present invention is not limited thereto, and if necessary, the negative electrode case is an outer case. The positive electrode case can be a sealing case.

In addition, 5 positive electrodes having the shape shown in FIG. 3, 6 negative electrodes having the same shape as the positive electrode, and a separator having the shape shown in FIG. 4 were used, and the current collecting tab portions 6b of the negative electrode 6 were not joined to each other. Folded on the outer surface of the electrode group (on the outer surface on the negative electrode case 3 side), and the current collecting tab portions 5a of the positive electrode 5 were welded together and folded on the outer surface of the electrode group (outer surface on the positive electrode case 2 side). Above, the EVA which is a hot-melt material is arranged between the insulating seals 8 and heated to bond the current collecting tab portion 5a and the insulating seal 8, and then the positive and negative electrode layers related to the electrode group are laminated. A flat non-aqueous secondary battery having a design capacity of 7 mAh (size: outer diameter 10 mm, thickness 2.5 mm, opening area of insulating gasket) except that the number is changed. 47mm ²⁾ was prepared and there is no problem in productivity, good It was confirmed that it is possible to manufacture in.

  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 Positive electrode case 3 Negative electrode case 4 Insulation gasket 5 Positive electrode 5a Main body part of positive electrode 5b Positive electrode current collection tab part 6 Negative electrode 6a Negative electrode body part 6b Negative electrode current collection tab part 7 Separator 7a Main part 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 a positive electrode case serving also as a positive electrode terminal and a negative electrode case serving also 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,
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 agent 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 agent 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 tabs of the positive electrode are gathered and welded together, folded back onto the outer surface of the electrode group on the positive electrode case side, adhered to the outer surface, and electrically connected to the positive electrode case. And / or the current collecting tabs of the negative electrode are gathered and welded together, folded back onto the outer surface of the electrode group on the negative electrode case side, adhered to the outer surface, and electrically connected to the negative electrode case A flat non-aqueous secondary battery characterized by comprising:   The flat nonaqueous secondary battery according to claim 1, wherein the thermoplastic resin constituting the separator is polyolefin.

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