JP2011187266A - Flat nonaqueous secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flat nonaqueous secondary battery having an excellent reliability. <P>SOLUTION: The flat nonaqueous secondary battery is provided with an electrode group in which a plurality of positive electrodes and a plurality of negative electrodes are laminated with a separator interposed and a nonaqueous electrolyte solution in a space formed of an outer case and a sealing case caulking-sealed via an insulation gasket interposed. The positive electrode and the negative electrode have body parts and current collector tab parts protruded from the body parts, respectively. An area of the body part of the negative electrode is larger than an area of the body part of the positive electrode in a plan view, and at least one out of the electrodes located at an outermost part of the electrode group is connected electrically with the outer case or the inner surface of the sealing case with a metal-made spacer interposed, and an area of the metal-made spacer is smaller than an area of the body part of the positive electrode in a plan view and moreover the metal-made spacer is arranged at a position corresponding to an inner side than an outer edge of the positive electrode. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a flat non-aqueous secondary battery having good 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 (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. Exposed without forming a layer or negative electrode agent layer, which is used as a current collecting tab, and is used for electrical connection with an outer case or sealing case that also serves as a terminal by bending this current collecting tab There is. Further, the current collector is exposed without forming the positive electrode mixture layer or the negative electrode agent layer on the outermost surface of the electrode group in the electrode that is the outermost electrode group, and this is used as the inner surface of the outer case or the sealing case. In some cases, electrical connection is made by contact.

JP 2003-142161 A

  For flat non-aqueous secondary batteries, for example, an electrode group is inserted into an outer case, and this is covered with a sealing case into which a non-aqueous electrolyte is injected and an insulating gasket is attached, or an insulating gasket is attached. It is manufactured by, for example, a method in which an outer case is covered and crimped on a sealing case that contains an electrode group and a non-aqueous electrolyte.

  For this reason, the flat surfaces of the exterior case and the sealing case may not be kept flat by caulking, and in particular, the vicinity of the center may be curved toward the outside of the battery. When electrical connection is made by bringing the current collector of the outermost electrode in the electrode group into contact with the inner surface of the outer case or sealing case, depending on the degree of curvature of the outer case or sealing case, good electrical Connection may not be achieved.

  For this reason, a metal spacer is interposed between the electrode group and the outer case or the sealing case, and the electrical connection between the electrode according to the electrode group and the outer case or the sealing case is good using this. Technology to make it is also being studied.

  However, in the battery using the spacer as described above, it is clear from the examination of the present inventors that the separator is easily scratched as compared with the battery not using the spacer, and there is a possibility that the reliability may be impaired thereby. became.

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

  The flat non-aqueous secondary battery of the present invention that has achieved the above-described object has a plurality of positive electrodes and a plurality of negative electrodes in a space formed by caulking and sealing an outer case and a sealing case via an insulating gasket. Is a flat non-aqueous secondary battery having electrode groups and non-aqueous electrolytes alternately stacked via separators, and the positive electrode protrudes from the main body portion in a plan view. And a positive electrode mixture layer containing a positive electrode active material is formed on one or both sides of the current collector, and the positive electrode current collecting tab portion. Then, a positive electrode mixture layer is not formed on the current collector, and the negative electrode has a main body portion and a current collecting tab portion protruding from the main body portion in plan view. In the main body portion, a negative electrode agent layer containing a negative electrode active material is formed on one side or both sides of a current collector, In the current collecting tab portion of the electrode, a negative electrode agent layer is not formed on the current collector, and the area of the main body portion of the negative electrode in plan view is larger than the area of the main body portion of the positive electrode in plan view At least one of the two electrodes located on the outermost part of the electrode group is exposed at the outermost surface of the electrode group in the main body, and the current collector is exposed inside the battery of the outer case. A surface or a battery inner surface of the sealing case is electrically connected via a metal spacer, and the area of the metal spacer in plan view is the area of the positive electrode main body in plan view The metal spacer is arranged at a position corresponding to the inner side of the outer edge of the positive electrode in the electrode group in plan view.

  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 reliability.

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 schematic diagram showing an example of the metal spacer which concerns on the flat nonaqueous secondary battery of this invention. It is a longitudinal cross-sectional view which represents typically the other example of the flat nonaqueous secondary battery of this invention. FIG. 5 is an enlarged sectional view of a main part of FIG. 4. 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 nylon.

  Although the top view of the positive electrode 5 is typically shown in FIG. 2, the positive electrode 5 has the main-body part 5a and the current collection tab part 5b which protruded from the main-body part 5a by planar view. As shown in FIG. 2, the current collecting tab portion 5b usually has a width (length in the vertical direction in FIG. 2) narrower than that of the main body portion 5a.

  In the battery 1 shown in FIG. 1, the body portion 5 a of the positive electrode 5 has a positive electrode mixture layer 51 formed on both surfaces of a current collector 52. In the current collecting tab portion 5 b of the positive electrode 5, the positive electrode mixture layer 51 is not formed on the surface of the current collector 52, and the current collector 52 is exposed. In the electrode group according to the battery 1 shown in FIG. 1, the outermost electrodes (upper and lower ends in the figure) are all negative electrodes (negative electrode 6B), and the positive electrodes 5 are all on both sides (both sides) with separators 7 interposed therebetween. Therefore, when the outermost electrode of the electrode group is a positive electrode, for example, when the outermost electrode of the electrode group is a positive electrode, the outermost electrode The positive electrode may have a structure having a positive electrode mixture layer only on one side of the current collector (the surface inside the battery).

  The negative electrode also has a main body portion and a current collecting tab protruding from the main body portion in plan view, like the positive electrode 5. The current collecting tab portion of the negative electrode is usually narrower than the width of the main body portion. As shown in FIG. 1, the main body 6a of the negative electrode 6B located at the outermost part of the electrode group has a negative electrode agent layer 61 formed only on one surface (surface inside the battery) of the current collector 62. A negative electrode layer is formed on both surfaces of the current collector 62 in the main body 6a of the negative electrode 6A other than the negative electrode 6A. Further, in the current collecting tab portion 6b of the negative electrodes 6A and 6B, the negative electrode agent layer 61 is not formed on the surface of the current collector 62, and the current collector is exposed.

  In the battery 1 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 to the inner surface of the outer case 2 or directly contacted without being welded. So that they are electrically connected. That is, in the battery 1 shown in FIG. 1, the outer case also serves as the positive electrode terminal. The current collecting tab portions 5b of the collected positive electrodes 5 may or may not be welded to each other, but the collected current collecting tab portions 5b are separated at the time of manufacturing the battery. It is preferable that the current collecting tab portions 5b are welded to each other in that they can be suppressed.

  In the battery 1 shown in FIG. 1, the outermost electrode (upper and lower ends) of the electrode group is the negative electrodes 6B and 6B having the negative electrode agent layer only on one side of the current collector (the inner surface of the battery). The exposed surface of the current collector of the upper negative electrode 6 </ b> B in the figure is electrically connected to the sealing case 3 via a metal spacer 9. That is, in the battery 1 shown in FIG. 1, the sealing case 3 also serves as the negative electrode terminal.

  The battery 1 shown in FIG. 1 is formed of polyethylene terephthalate (PET), polyimide, or the like between them for the purpose of insulating the negative electrode 6B located at the lowermost part of the electrode group and the outer case 2 also serving as the positive electrode terminal. An insulating seal 8 made of tape or the like is disposed.

  In the battery of the present invention, unlike the embodiment shown in FIG. 1, one or both of the outermost two electrodes (upper and lower electrodes) of the electrode group may be used as the positive electrode. In addition, when the electrode on the side close to the battery case (for example, the outer case) that also serves as the positive electrode terminal is used as the positive electrode among the outermost electrodes of the electrode group, this positive electrode has a positive electrode mixture layer on both sides of the current collector. However, it may be in contact with a battery case (for example, an exterior case) that also serves as a positive electrode terminal only at the current collecting tab portion, and has a positive electrode mixture layer only on one side of the current collector (the surface inside the battery). The exposed surface of the body is electrically connected to the inner surface of a battery case (for example, an outer case) that also serves as a positive electrode terminal via a metal spacer.

  In addition, when both of the outermost two electrodes (upper and lower electrodes) of the electrode group are positive electrodes, the connection between the negative electrode terminal and the battery case (for example, a sealing case) and the negative electrode is connected to the current collecting tab of each negative electrode. The parts can be electrically connected to each other, and these can be welded to the inner surface of a battery case (for example, a sealing case) that also serves as the negative electrode terminal, or directly contacted without welding.

  In the battery of the present invention, the current collector is exposed on the outermost surface of the electrode group in the main body portion of at least one of the electrodes positioned on the outermost side of the electrode group (that is, only one surface of the current collector). And a metallic spacer is interposed between the exposed surface of the current collector in the main body and the inner surface of the battery case (exterior case or sealing case). By doing so, the electrode which concerns on an electrode group, and the battery case are electrically connected favorably.

  However, by using a metal spacer, the positive electrode and the negative electrode are pressed against the separator existing between the positive and negative electrodes. In particular, in the separator, the portion where the corner of the outer edge of the positive electrode or the negative electrode is pressed is liable to cause defects such as scratches, which may cause a short circuit, thereby reducing the reliability of the battery.

  Therefore, in the battery of the present invention, the metal spacer is arranged at a position corresponding to the inner side of the outer edge of the positive electrode in the electrode group in plan view. That is, as shown in FIG. 1, the end of metal spacer 9 (the left and right ends in the figure) is arranged to be inside the end (outer edge) of positive electrode 5 of the electrode group. In the battery of the present invention, in order to make the area of the negative electrode main body in plan view larger than the area of the positive electrode main body in plan view, the metal spacer is inward of the positive electrode outer edge in plan view. If it is disposed at a position corresponding to the side, it is also disposed at a position corresponding to the inner side of the outer edge of the negative electrode. Therefore, even if the positive electrode and the negative electrode are pressed against the separator due to the presence of the metal spacer, the force with which the corners of the positive electrode and the negative electrode are pressed against the separator can be reduced.

  Thereby, in this invention, since the electrical connection of an electrode group and a battery case can be made favorable, suppressing the defect of the separator by use of metal spacers, it can be set as a reliable battery.

  Examples of the metal spacer include a metal plate, a metal net, and a metal spring, but a metal net or spring is used in that the electrical connection between the electrode group and the battery case can be improved. preferable. In addition, as a metal spring, the thing of the shape shown in FIG. 3 is mentioned, for example. 3A is a plan view and FIG. 3B is a side view.

  In order to improve the electrical connection between the electrode group and the battery case, the size of the metal spacer is, for example, such that the area in plan view is 5 to 95% of the area in plan view of the positive electrode main body. Preferably. In addition, the thickness of the metal spacer is preferably thinner than the outermost electrode of the electrode group in contact with the metal spacer, thereby preventing the metal spacer from breaking through the outermost electrode of the electrode group. Is desirable.

  Examples of the metal constituting the metal spacer include stainless steel such as SUS430, SUS316, and SUS304, and iron.

  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.

  4 and 5 schematically show other examples of the flat non-aqueous secondary battery of the present invention. The battery 1 shown in FIG. 4 and FIG. 5 has an electrode group formed by forming joints on the peripheral portions of the two separators 7 and 7 arranged on both surfaces of the positive electrode 5. FIG. 5 is a longitudinal sectional view showing a section of the battery case (the outer case 2 and the sealing case 3) and the insulating gasket 4 part of the battery, and FIG. 5 is an enlarged view of the main part of FIG. It is.

  Moreover, the top view of the separator which formed the junction part in a part of peripheral part in FIG. 6 is shown typically. In FIG. 6, assuming the case of a stacked electrode group in which the positive electrode, the negative electrode, and the separator are stacked together with the separator 7, the positive electrode 5 disposed below the separator 7 is indicated by a dotted line, A current collecting tab portion 6b related to the negative electrode disposed on the lower side is indicated by a one-dot chain line, and a binding tape 10 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. 6 has both sides (both sides) opposed to the negative electrode in the electrode group. Although not shown in FIG. 6, 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.

  The separator 7 shown in FIG. 6 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 portion 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. 6 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. 6, when using the separator which has a main-body part and an overhang | projection part, the junction part for joining the two separators arrange | positioned on both surfaces of a positive electrode is a peripheral part of the main 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. 6, 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 the battery of the present invention, in forming the electrode group, separators are disposed on both sides of the positive electrode at least on both sides facing the negative electrode, but only the positive electrode disposed on the outermost side of the electrode group, that is, only one side (one side). As for the positive electrode facing the negative electrode, separators may be arranged on both sides thereof (joint portions may be formed on these two separators), and the separator is arranged only on the surface facing the negative electrode. It doesn't matter. However, the outer surface of the outermost positive electrode group on the outer case or sealing case side that also serves as the positive electrode terminal exposes the current collector and is electrically connected to the outer case or the sealing case through a metal spacer. Therefore, the separator is disposed only on the surface facing the negative electrode. Furthermore, when both the outermost electrodes related to the electrode group are positive electrodes, and separators are not arranged on both surfaces of these positive electrodes, the battery case serving also as the negative electrode terminal and the outermost positive electrode of the electrode group, An insulator such as an insulating seal made of a tape formed of polyethylene terephthalate (PET) or polyimide is disposed.

  The positive electrode 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, 4, and 5. 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. 6, the current collecting tab portion 5b of each positive electrode and the current collecting tab portion 6b of each negative electrode face each other in a plan view of the electrode group. More preferably, it is arranged at a position where

  In addition, as shown in FIG. 6, the electrode group configured by laminating the positive electrode, the negative electrode, and the separator is bound to the outer periphery with a binding tape 10 made of chemical-resistant polypropylene or the like. It is preferable to suppress misalignment of the positive electrode and the negative electrode wrapped in the separator.

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

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

  1, 4, and 5 show examples in which the outer case is a positive electrode case and the sealing case is a negative electrode case, but the battery of the present invention is not limited to this, and the outer case may be a negative electrode as necessary. A case and a sealing case can be used as a positive electrode case.

  4 and FIG. 4 using a SUS430-made spring shown in FIG. 3 or a SUS430-made net for the positive electrode having the shape shown in FIG. 2, the separator having the shape shown in FIG. 6, and a metal spacer. When the flat non-aqueous secondary battery having the structure shown in FIG. 5 was produced, it was confirmed that the battery had good discharge characteristics even when any spacer was used, and was excellent in reliability. When these batteries were disassembled, the separator was not scratched by the corners of the positive electrode.

  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 5 Positive electrode 5a Positive electrode main body 5b Positive electrode current collecting tab 6 Negative electrode 6a Negative electrode main body 6b Negative electrode current collecting tab 7 Separator 7a Main part 7b Overhang part of separator 7c Joint part 9 Metal spacer

Claims (4)

In a space formed by caulking and sealing the outer case and the sealing case via an insulating gasket, there is an electrode group in which a plurality of positive electrodes and a plurality of negative electrodes are alternately stacked via a separator and a non-aqueous electrolyte. A flat non-aqueous secondary battery,
The positive electrode has a main body portion and a current collecting tab portion protruding from the main body portion in plan view, and the main body portion of the positive electrode includes a positive electrode active material on one or both sides of the current collector. A positive electrode mixture layer is formed, 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 protruding from the main body portion in plan view. The main body portion of the negative electrode includes a negative electrode active material on one or both sides of the current collector. A negative electrode agent layer is formed, and in the current collector tab portion of the negative electrode, a negative electrode agent layer is not formed on the current collector, and an area of the negative electrode main body in plan view is Larger than the area of the main body in plan view,
At least one of the two electrodes located at the outermost part of the electrode group has a current collector exposed at the outermost surface of the electrode group in the main body, and the inner surface of the battery of the outer case or It is electrically connected to the inner surface of the battery in the sealing case via a metal spacer,
The area in plan view of the metal spacer is smaller than the area in plan view of the main body of the positive electrode,
The flat non-aqueous secondary battery, wherein the metal spacer is arranged at a position corresponding to an inner side of the outer edge of the positive electrode in the electrode group in plan view.   The flat non-aqueous secondary battery according to claim 1, wherein the metal spacer is a mesh or a spring.   At least both sides of the positive electrode facing the negative electrode are provided with separators made of a microporous film made of a thermoplastic resin, and the two separators are mutually connected at least at a part of their peripheral portions. The flat non-aqueous secondary battery according to claim 1, wherein the flat non-aqueous secondary battery has a welded joint.   The flat non-aqueous secondary battery according to claim 3, wherein the thermoplastic resin constituting the separator is polyolefin.

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