JP2009134915A - Non-aqueous secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-aqueous secondary battery which can maintain a high capacity and good life characteristics by suppressing cutting of an electrode plate at the time of winding while suppressing internal short circuit of the non-aqueous secondary battery, since as a factor of internal short circuit, four short circuit modes are considered consisting of an exposed part of a positive electrode current collector of a positive electrode plate and the surface of a negative electrode mixture layer of a negative electrode plate, the exposed part of the positive electrode current collector and the exposed part of the negative electrode current collector, the surface of the positive electrode mixture layer of the positive electrode plate and the surface of the negative electrode mixture of the negative electrode plate, and the surface of the positive electrode mixture layer of the positive electrode plate and the exposed part of the negative electrode current collector. <P>SOLUTION: The positive electrode plate 5 and the negative electrode plate 9 have portions on which an electrode mixture paint is not coated on the electrode current collector. An insulator layer 4 having flexibility is formed at a boundary portion of an exposed part of the positive electrode current collector 1 and a coated part of the positive electrode mixture layer 2 opposed to the negative electrode mixture layer 7, and thereby, internal short circuit is restrained and cutting at the time of winding is suppressed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a non-aqueous secondary battery represented by a lithium ion secondary battery.

2. Description of the Related Art Conventionally, lithium ion secondary batteries, which are widely used as power sources for portable electronic devices, use a carbonaceous material or the like capable of occluding and releasing lithium for a negative electrode plate, and lithium cobalt oxide (LiCoO ₂ ) for a positive electrode plate. As the active material, a lithium-ion secondary battery with a high potential and a high discharge capacity has been realized. However, in recent years, electronic devices and communication devices have become multifunctional. Along with this, the demand for safety of lithium ion secondary batteries is increasing as the capacity increases.

  If the chargeable / dischargeable secondary battery is accidentally subjected to an external physical shock or is charged by an excessive current, the separator inside the lithium ion secondary battery may be damaged, etc. An internal short circuit may occur due to contact with the negative electrode plate.

  When an internal short circuit occurs, current concentrates on that part and heat is generated, and when the heat generation is large, gas generation due to decomposition of the material of the positive electrode plate and the negative electrode plate or boiling and decomposition of the electrolyte may occur. Thus, an electrode reaction due to an internal short circuit is considered as one of the causes of rapid heat generation of the secondary battery.

  First, as a highly safe lithium ion secondary battery that can prevent an internal short circuit, as shown in FIG. 7, from the vicinity of the end of the active material mixture layer 32 of the positive electrode plate or the negative electrode plate to the exposed portion of the current collector 31. A method has been proposed in which an insulating tape 33 formed so that the thickness of the end portion having a predetermined width is reduced is adhered, and the contact with the counter electrode is prevented at a portion where the occurrence rate of the internal short circuit is large. (For example, refer to Patent Document 1).

In addition, as shown in FIG. 8, an insulating tape 36 having a predetermined width is pasted across the boundary between the active material mixture layer 35 of the positive electrode plate or the negative electrode plate and the current collector 34. When the battery is heated to a high temperature or when the lithium ion secondary battery is heated to a high temperature by receiving heat from the outside, the insulating tape 36 is contracted to expose the boundary portion, and as a result, the inside In contrast to causing a short circuit, a method has been proposed in which the easy contraction direction of the insulating tape 36 is the length direction of the positive electrode plate or the negative electrode plate so that the boundary portion is not exposed even when contracted by heat (for example, see Patent Document 2). ).
JP 2005-235414 A JP 2006-19199 A

  However, both methods of Patent Document 1 and Patent Document 2 are methods for sticking an insulating tape to avoid an internal short circuit. Compressive stress applied to the inner circumference of the winding to prevent the movement of the paint cannot be dispersed, causing the positive plate or negative plate to break, or due to a steep step between the edge of the insulating tape and the positive plate or negative plate The curvature at the time of winding becomes small and it bends at an acute angle, and stress is generated on the positive electrode plate or the negative electrode plate, causing the positive electrode plate or the negative electrode plate to be cut at the time of winding.

Moreover, in the method of sticking such an insulating tape, there exists a possibility that the insulating tape may be displaced at the time of sticking, and the positive electrode plate and the negative electrode plate are short-circuited. Further, since the insulating tape does not follow the sheet during winding, the insulating tape cannot be wound in a spiral shape and swells occur, and the swells cause wrinkles of the positive electrode plate and the negative electrode plate or the separator, thereby causing an internal short circuit.

  Further, as disclosed in Patent Document 1 of the prior art described above, in the method of reducing the thickness of the end portion of the insulating tape, the stress applied to the positive electrode plate or the negative electrode plate is reduced and the positive electrode plate or the negative electrode plate is cut off. Although it can suppress, there exists a limit which can make thickness thin, and it cannot be said that it can suppress the cutting | disconnection of all the positive electrode plates or negative electrode plates.

  The present invention has been made in view of the above-described conventional problems, and supplies a group of electrodes having high safety and stable quality by suppressing breakage of the positive electrode plate or the negative electrode plate during winding while suppressing internal short circuit. However, it is an object of the present invention to provide a non-aqueous secondary battery that has little battery capacity variation and exhibits good life characteristics.

  In order to achieve the above object, the non-aqueous secondary battery of the present invention is obtained by applying and drying a positive electrode mixture paint composed of at least an active material, a conductive agent and a binder on a positive electrode current collector. A negative electrode plate composed of a positive electrode plate and at least an active material and a binder are coated and dried on a negative electrode current collector, and the negative electrode plate and a separator are wound in a spiral shape. A non-aqueous secondary battery comprising an electrode group and an electrolyte mainly composed of a non-aqueous solvent, and a positive electrode mixture paint or a negative electrode mixture paint is applied to a part of the positive electrode current collector or the negative electrode current collector The exposed portion of the positive electrode current collector or negative electrode current collector of at least one of the positive electrode plate and the negative electrode plate and at least the boundary portion between the application portion of the positive electrode mixture paint or the negative electrode mixture paint. Characterized in that an insulating layer is formed It is.

  According to the present invention, the insulating layer having at least flexibility is formed at the boundary portion between the exposed portion of the current collector of at least one of the positive electrode plate and the negative electrode plate and the application portion of the electrode mixture paint. In addition, it suppresses the short-circuiting of the positive electrode plate or negative electrode plate while suppressing internal short-circuiting, thereby providing an electrode group with high safety, stable quality, low battery capacity variation, and good life characteristics. A secondary battery can be provided.

  In the first invention of the present invention, a positive electrode plate formed by applying and drying a positive electrode mixture paint comprising at least an active material, a conductive agent and a binder on a positive electrode current collector, and at least the active material and A negative electrode plate made of a binder and a negative electrode plate formed by applying and drying a negative electrode mixture paint on a negative electrode current collector and a separator wound in a spiral shape, and a non-aqueous solvent as a main component A non-aqueous secondary battery composed of an electrolyte solution, wherein a positive electrode current collector or a negative electrode current collector is provided with an exposed portion on which a positive electrode mixture paint or a negative electrode mixture paint is not applied, and a positive electrode plate or a negative electrode An insulating layer having at least flexibility is formed at a boundary portion between the exposed portion of the positive electrode current collector or negative electrode current collector on at least one of the plates and the application portion of the positive electrode mixture paint or negative electrode mixture paint. To collect positive or negative electrode plates that are easily short-circuited. The surface of the electrode mixture layer of the positive electrode plate or the negative electrode plate facing the exposed portion of the body can be protected with an insulator layer, and it is possible to provide a non-aqueous secondary battery having high safety. A non-aqueous system that can suppress breakage of the positive electrode plate or the negative electrode plate during winding of the positive electrode plate or the negative electrode plate, supplies an electrode group with stable quality, has a small battery capacity variation, and exhibits good life characteristics. A secondary battery can be provided.

In the second aspect of the present invention, by forming the insulator layer on the positive electrode plate, it is possible to protect the exposed portion of the positive electrode current collector that is particularly short-circuited and the surface of the negative electrode mixture layer with the insulator layer. In addition to having high safety, it is possible to suppress the breakage of the positive electrode plate, which is particularly easily cut when the positive electrode plate or the negative electrode plate is wound, and to supply a group of electrodes with stable quality, with less battery capacity variation. In addition, it is possible to provide a non-aqueous secondary battery that exhibits good life characteristics.

In the third invention of the present invention, since the insulator layer is made of a rubber-like elastic body, the positive electrode plate and the negative electrode plate current collector are likely to break when forming the electrode group. By imparting flexibility to the boundary portion between the exposed portion and the coating portion of the electrode mixture paint, it is possible to prevent the positive electrode plate or the negative electrode plate from being cut.
In the fourth invention of the present invention, by adjusting the flexibility by adding an inorganic additive to the rubber-like elastic body, the flexibility suitable for the positive electrode plate and the negative electrode plate can be imparted. When the plate or the negative electrode plate is wound, cutting of the positive electrode plate or the negative electrode plate can be suppressed.

In the fifth aspect of the present invention, the inorganic additive is a silica material and / or an alumina material, so that the exposed portion of the current collector and the surface of the electrode mixture layer are protected by an insulating layer having a high insulating property. Thus, a non-aqueous secondary battery having excellent safety can be provided.
In the sixth aspect of the present invention, the rubber-like elastic body is a styrene-butadiene copolymer rubber particle and / or a rubber particle binder having an acrylate unit, whereby the exposed portion of the current collector and the electrode mixture The surface of the layer can be protected with a highly flexible insulator layer, and a highly reliable non-aqueous secondary battery can be provided.

  In the seventh aspect of the present invention, by setting the thickness of the insulator layer to 2 μm or more and 25 μm or less, a high-capacity secondary battery excellent in safety can be obtained while suppressing an internal short circuit.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a non-aqueous secondary battery of the present invention. After preparing the electrode group 14 which wound the positive electrode plate 5 which uses a composite lithium oxide as an active material, and the negative electrode plate 9 which uses the material which can hold | maintain lithium as an active material through the separator 10, it produces electrode group 14 is housed in the bottomed cylindrical battery case 11 together with the insulating plate 15, the negative electrode lead 8 led out from the lower part of the electrode group 14 is welded to the bottom part of the battery case 11, and then led out from the upper part of the electrode group 14. After the positive electrode lead 3 is welded to the sealing plate 12 and a predetermined amount of non-aqueous electrolyte (not shown) is injected into the battery case 11, a sealing gasket 13 is attached to the periphery of the opening of the battery case 11. The sealing plate 12 is inserted, and the opening of the battery case 11 is folded inward to seal it by caulking.

  Next, an example of a method for producing an electrode plate according to the present invention will be described. When the positive electrode plate or the negative electrode plate applied to the present invention is wound to form an electrode group, it is necessary to have toughness that does not cause the active material layer to crack or fall off. The prescription of the positive electrode plate or the negative electrode plate is not limited to the following method as long as the toughness can be exhibited.

  First, the positive electrode plate 5 is not particularly limited, but a positive electrode active material, a conductive agent, a foil or a foil made of aluminum or an aluminum alloy, a positive electrode current collector 1 having a thickness of 10 μm to 60 μm that has been processed or etched, It is produced by applying a positive electrode mixture paint in which a binder is kneaded and dispersed in a dispersion medium, drying, and rolling to form a positive electrode active material layer.

  Examples of the positive electrode active material include lithium-containing composite oxides such as lithium cobaltate and modified products thereof (eutectic crystals of aluminum and magnesium), lithium nickelate and modified products thereof (partially nickel was substituted with cobalt) ), Lithium manganate and modified products thereof.

  As the conductive agent, carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black and thermal black, and various graphites may be used alone or in combination.

  Examples of the binder for the positive electrode include polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), styrene-butadiene (SBR) copolymer rubber particles, and a rubber particle binder having an acrylate (AN) unit. be able to.

  Next, the negative electrode plate 9 is not particularly limited, but the negative electrode active material is formed on one or both sides of a negative electrode current collector 6 having a thickness of 10 μm to 50 μm made of rolled copper foil, electrolytic copper foil, lath processed or etched copper foil. It is prepared by applying a negative electrode mixture paint in which a binder and, if necessary, a conductive agent and a thickener are kneaded and dispersed in a dispersion medium, drying and rolling to form a layer of the negative electrode active material Is done.

  As the negative electrode active material, various natural graphites, artificial graphite, silicon-based composite materials such as silicide, and various alloy composition materials can be used.

  As the binder for the negative electrode, various binders such as PVdF and modified products thereof can be used, and SBR and modified products thereof can also be mentioned from the viewpoint of improving the lithium ion acceptability.

  The thickener is not particularly limited as long as it is a material having viscosity as an aqueous solution such as polyethylene oxide (PEO) or polyvinyl alcohol (PVA), but methylcellulose and its modified product are thickened by the mixture, and dispersible by the mixture. From the viewpoint of

  Furthermore, as separators, polyethylene, polypropylene, PVdF, polyvinylidene chloride, polyacrylonitrile, polyacrylamide, PTFE, polysulfone, polyethersulfone, polycarbonate, polyamide, polyimide, polyether (PEO and polypropylene oxide), cellulose (carboxymethylcellulose, A microporous film made of a polymer such as hydroxypropylcellulose), poly (meth) acrylic acid, poly (meth) acrylic acid ester or the like is preferably used.

  A multilayer film in which these microporous films are superposed can also be used. Among these, a microporous film made of polyethylene, polypropylene, PVdF, or the like is suitable, and the thickness is preferably 10 μm to 25 μm.

  As the battery case 11, a bottomed cylindrical or rectangular battery case having an open top can be used. As the material, a steel plate with nickel plating or an aluminum alloy can be used.

  The non-aqueous electrolyte is composed of a non-aqueous solvent and a solute, and the non-aqueous solvent contains a cyclic carbonate and a chain carbonate as main components. The cyclic carbonate is preferably at least one selected from ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC). The chain carbonate is preferably at least one selected from dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and the like.

As the solute, a lithium salt having a strong electron-withdrawing property is used. For example, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiC (SO ₂ CF ₃ ) _{3 and the} like. These electrolytes may be used alone or in combination of two or more. These solutes are preferably dissolved at a concentration of 0.5 to 1.5 M in the non-aqueous solvent.

  In addition, vinylene carbonate (VC), cyclohexylbenzene (CHB), and modified products thereof are added to form a good film on the positive electrode mixture layer 2 and the negative electrode mixture layer 7 and to ensure stability during overcharge. It is also possible to do.

  Next, as shown in FIG. 2, in the positive electrode plate or the negative electrode plate of the nonaqueous secondary battery of the present invention, the inside of the positive electrode current collector 1 of the positive electrode plate 5 and the negative electrode mixture layer 7 of the negative electrode plate 9. In order to suppress a short circuit, as a method of providing the insulator layer 4 at the boundary between the positive electrode current collector 1 and the positive electrode mixture layer 2, a rubber-like elastic body obtained by applying and drying a paint of a flexible rubber-like elastic body Layer 4 was formed.

  In general, in order to form the insulator layer 4, there is a method of sticking an insulating tape, but the curvature at the time of winding due to a steep step between the edge of the insulating tape and the positive electrode plate 5 or the negative electrode plate 9. The positive electrode plate 5 and the negative electrode plate are bent in a sharp angle, causing stress on the positive electrode plate 5 or the negative electrode plate 9 and inhibiting the movement of the electrode mixture layer under the insulating tape. The compression stress at the time of winding when the electrode group 14 is formed with the separator 10 interposed between the positive electrode plate 9 and the positive electrode plate 5 or the negative electrode plate 9 is cut off.

  The insulator layer 4 according to the present invention relieves the compressive stress at the time of winding without forming a step that becomes a stress at the time of winding while ensuring the original insulating function, and the positive electrode plate 5 or the negative electrode This suppresses the breakage of the plate 9.

  Next, a state where the positive electrode plate or the negative electrode plate is cut when the positive electrode plate, the negative electrode plate, and the separator are actually wound to form the electrode group will be described with reference to FIG. FIG. 3 is a schematic diagram of a winding device that forms the electrode group 14 by winding the positive electrode plate 5, the negative electrode plate 9, and the separator 10.

  In FIG. 3, a positive plate conveying device 25 having a plurality of roller portions for conveying the positive plate 5, a negative plate conveying device 26 having a plurality of roller portions for conveying the negative plate 9, the positive plate 5 and the negative plate 9. And a separator 27 for winding the separator 10 together. Winding is performed by applying tension while rotating and pulling the winding portion 27 so that the positive electrode plate 5, the negative electrode plate 9, and the separator 10 are not bent.

  The cause of the breakage of the positive electrode plate 5 or the negative electrode plate 9 that occurs when the electrode group 14 is configured using the winding device is roughly divided into the following two. First, the positive electrode plate 5 is generated by receiving bending stress due to the curvature of the roller portion when the positive electrode plate 5 is wound around the plurality of roller portions of the conveying device 25 and conveyed. When being wound around the roller portion and being conveyed, the positive electrode plate 5 or the negative electrode plate 9 is cut by receiving bending stress due to the curvature of the roller portion. Next, the positive electrode plate 5 or the negative electrode plate 9 is cut off due to the bending stress due to the curvature at the time of winding at the winding portion 27 and the tensile stress due to the tension applied to the positive electrode plate 5 or the negative electrode plate 9.

  Further, the cause of the breakage of the positive electrode plate 5 or the negative electrode plate 9 in the winding part 27 of the winding device will be described in more detail with reference to FIG. FIG. 4 shows a cross-sectional view of the cylindrical electrode group 14, in which the positive electrode plate 5, the negative electrode plate 9 and the separator 10 are wound. In the drawing, in the positive electrode plate 5a and the negative electrode plate 9a in the vicinity of the winding center where the curvature is reduced, the tensile stress at the time of winding is concentrated, so that the positive electrode plate 5 or the negative electrode plate 9 is easily cut.

In order to suppress the disconnection of the positive electrode plate 5 or the negative electrode plate 9 that occurs when the electrode group 14 is configured as described above, the positive electrode plate 5 or the negative electrode plate 9 is disposed at a winding position where the radius of curvature of the electrode group 14 is reduced. It is important to alleviate the bending stress applied to the material. As a result of sincere consideration from this viewpoint, the bending stress is reduced by forming the insulator layer 4 for ensuring safety with a rubber-like elastic body having flexibility. It has been newly found that it is possible to absorb and prevent the positive electrode plate 5 or the negative electrode plate 9 from being cut.

  Hereinafter, specific examples will be described in more detail with reference to the drawings, but these do not limit the present invention.

  First, in the positive electrode mixture coating material, as a positive electrode active material, 3 parts by weight of acetylene black as a conductive agent and 3 parts by weight of PVdF as a binder with respect to 100 parts by weight of lithium cobaltate and 100 parts by weight of the active material. Was mixed with an appropriate amount of N-methyl-2-pyrrolidone with a double-arm kneader to obtain a positive electrode mixture paint. Next, this positive electrode mixture paint is continuously applied in an intermittent manner in which a portion of the aluminum foil having a thickness of 15 μm is not applied on the positive electrode current collector 1 and dried, so that the total thickness becomes 150 to 180 μm. The positive electrode mixture layer 2 was pressed to form a positive electrode plate 5.

  In the negative electrode mixture paint, 100 parts by weight of artificial graphite as an active material and 100 parts by weight of an active material, and a styrene-butadiene copolymer rubber particle dispersion (solid content 40% by weight) as a binder are used. 5 parts by weight (1 part by weight in terms of solid content of the binder), 1 part by weight of carboxymethyl cellulose as a thickener and an appropriate amount of water are stirred and kneaded in a double-arm kneader, whereby a negative electrode mixture Paint was used. Next, this negative electrode mixture paint is continuously applied in an intermittent manner in which a part of the copper foil negative electrode current collector 6 having a thickness of 10 μm is not applied, and dried, so that the total thickness becomes 180 to 220 μm. The negative electrode mixture layer 7 was pressed to form a negative electrode plate 9.

  In the insulator layer 4, an aqueous dispersion of SBR copolymer rubber particles styrene-butadiene copolymer rubber particles (solid content 40 wt%) is used as an insulator paint, and the positive electrode mixture layer 2 and the positive electrode of the positive electrode plate 5. The boundary of the exposed portion of the current collector 1 is detected, and the insulator paint is applied to the front and back surfaces of the boundary portion of the exposed portion of the positive electrode current collector 1 facing the negative electrode mixture layer 7 as shown in FIG. The insulating layer 4 was formed by coating and drying.

  Next, a positive electrode plate 5 on which an insulating layer 4 made of a rubber-like elastic body composed of an aqueous dispersion (solid content 40% by weight) of the SBR copolymer rubber particles styrene-butadiene copolymer rubber particles is formed. And the negative electrode plate 9 are slit to a width defined in a cylindrical 18650 lithium ion secondary battery, and a 20 μm thick polyethylene microporous film is wound as a separator 10 in the direction of the arrow shown in FIG. The group 14 was formed, cut to a predetermined length, inserted into the battery case 11, and the internal resistance was measured with a tester to confirm that there was no internal short circuit.

Thereafter, 5.5 g of an electrolytic solution in which 1 part of LiPF ₆ and 3 parts by weight of VC were dissolved in an EC / DMC / MEC mixed solvent was added and sealed. A non-aqueous secondary battery produced as an ion secondary battery was taken as Example 1.

  In the non-aqueous secondary battery of Example 2, in the insulator layer 4, a dispersion of 2-ethylhexyl acrylate, acrylic acid, and acrylonitrile copolymer with an appropriate amount of N-methyl-2-pyrrolidone is used as the insulator coating. The boundary between the positive electrode mixture layer 2 of the positive electrode plate 5 produced in Example 1 and the exposed portion of the positive electrode current collector 1 is detected, and the positive electrode current collector facing the negative electrode mixture layer 7 as shown in FIG. The insulator paint was applied to the front and back surfaces of the boundary portion of the exposed portion 1 and dried to form the insulator layer 4.

Next, the positive electrode plate 5 and the negative electrode plate prepared in Example 1 were prepared by dispersing the copolymer of 2-ethylhexyl acrylate, acrylic acid and acrylonitrile with an appropriate amount of N-methyl-2-pyrrolidone as an insulator layer 4. A non-aqueous secondary battery produced by the same production method as in Example 1 using the same polyethylene microporous film as in Example 9 and Example 1 as separator 10 was designated as Example 2.

In the non-aqueous secondary battery of Example 3, in the insulator layer 4, 100 parts by weight of alumina (Al ₂ O ₃ ) powder having an average particle size of 1.0 μm, styrene-butadiene copolymer rubber particle dispersion (solid Insulating paint was obtained by dispersing 2.5 parts by weight of 40% by weight) together with an appropriate amount of water. Further, the boundary between the positive electrode mixture layer 2 and the positive electrode current collector 1 of the positive electrode plate 5 produced in Example 1 was detected, and the positive electrode current collector 1 facing the negative electrode mixture layer 7 as shown in FIG. An insulating coating was applied to the front and back surfaces of the exposed portion and dried to form an insulating layer 4 made of a rubber-like elastic body.

  Next, the positive electrode plate 5 on which the insulator layer 4 composed of the alumina material and the styrene-butadiene copolymer rubber particle dispersion is formed, the negative electrode plate 9 produced in Example 1, and the same polyethylene as in Example 1. A non-aqueous secondary battery produced by the same production method as in Example 1 using the microporous film as the separator 10 was taken as Example 3.

In the non-aqueous secondary battery of Example 4, in the insulator layer 4, 100 parts by weight of alumina (Al ₂ O ₃ ) powder having an average particle diameter of 1.0 μm, the co-weight of 2-ethylhexyl acrylate, acrylic acid and acrylonitrile 10 parts by weight of the coalescence with 100 parts by weight of Al ₂ O ₃ powder was mixed with an appropriate amount of N-methyl-2-pyrrolidone using a disper stirrer to make an insulating coating.

  Further, the boundary between the positive electrode mixture layer 2 and the positive electrode current collector 1 of the positive electrode plate 5 produced in Example 1 is detected, and the positive electrode current collector 1 facing the negative electrode mixture layer 7 as shown in FIG. The insulating layer 4 was formed by applying and drying an insulating paint on the front and back surfaces of the boundary portion of the exposed portion. As the inorganic additive, the positive electrode plate 5 on which the insulator layer 4 composed of an alumina material, a copolymer of 2-ethylhexyl acrylate, acrylic acid and acrylonitrile was formed, and the negative electrode plate 9 produced in Example 1 and the implementation. A non-aqueous secondary battery produced by the same production method as in Example 1 using the same polyethylene microporous film as in Example 1 as separator 10 was designated as Example 4.

  In the non-aqueous secondary battery of Example 5, 100 parts by weight of silica powder having an average particle size of 1.0 μm and a styrene-butadiene copolymer rubber particle dispersion (solid content: 40% by weight) in the insulator layer 4 were used. 2.5 parts by weight were dispersed together with an appropriate amount of water to obtain an insulating paint. Further, the boundary between the positive electrode mixture layer 2 of the positive electrode plate 5 produced in Example 1 and the exposed portion of the positive electrode current collector 1 is detected, and the positive electrode current collector facing the negative electrode mixture layer 7 as shown in FIG. An insulating paint was applied and dried on the front and back surfaces of the boundary portion of the exposed portion of the body 1 to form an insulating layer 4 made of a rubber-like elastic body.

  The negative electrode produced in Example 1 and the positive electrode plate 5 on which the insulator layer 4 composed of a silica material and a styrene-butadiene copolymer rubber particle dispersion (solid content 40% by weight) was formed as the inorganic additive. A non-aqueous secondary battery produced by the same production method as in Example 1 was used as Example 5 using the same microporous polyethylene film as that in Example 9 as the separator 9.

  In the non-aqueous secondary battery of Example 6, in the insulator layer 4, 100 parts by weight of silica powder having an average particle size of 1.0 μm, and a copolymer of 2-ethylhexyl acrylate, acrylic acid and acrylonitrile with respect to the silica powder. An appropriate amount of N-methyl-2-pyrrolidone was mixed with 10 parts by weight with a disper stirrer to obtain a coating material for the insulator layer 4.

  Further, the boundary between the positive electrode mixture layer 2 of the positive electrode plate 5 produced in Example 1 and the exposed portion of the positive electrode current collector 1 is detected, and the positive electrode current collector facing the negative electrode mixture layer 7 as shown in FIG. An insulator paint was applied to the front and back surfaces of the boundary portion of the exposed portion of the body 1 and dried to form the insulator layer 4. As the inorganic additive, a positive electrode plate 5 formed with an insulating layer 4 composed of a silica material, a copolymer of 2-ethylhexyl acrylate, acrylic acid and acrylonitrile, and a negative electrode plate 9 produced in Example 1 and an implementation A non-aqueous secondary battery produced by the same manufacturing method as in Example 1 using the same polyethylene microporous film as in Example 1 as separator 10 was designated as Example 6.

(Comparative Example 1)
In the same manner as in Example 1, in the positive electrode mixture paint, 3 parts by weight of acetylene black as a conductive agent and 3 PVdF as a binder with respect to 100 parts by weight of lithium cobaltate as an active material and 100 parts by weight of the active material. A positive electrode mixture paint is prepared by stirring and kneading a part by weight with an appropriate amount of N-methyl-2-pyrrolidone in a double-arm kneader, and this positive electrode mixture paint is made of a positive electrode current collector made of 15 μm thick aluminum foil. A positive electrode plate 5 is formed by forming a positive electrode mixture layer 2 by continuously applying and drying in an intermittent manner in which a part of the body 1 is not applied on the body 1 and drying, and pressing to a total thickness of 150 to 180 μm. did.

  Similarly to Example 1, in the negative electrode mixture paint, 100 parts by weight of artificial graphite as an active material and 100 parts by weight of the active material, a styrene-butadiene copolymer rubber particle dispersion (as a binder) Stir in a double-arm kneader with 2.5 parts by weight (solid content 40% by weight) (1 part by weight in terms of solid content of binder) and 1 part by weight of carboxymethylcellulose as a thickener and an appropriate amount of water. And kneading to form a negative electrode mixture paint, and this negative electrode mixture paint is continuously applied and dried in an intermittent manner in which a part of the copper foil negative electrode current collector 6 of 10 μm thickness is not applied, The negative electrode plate 9 was formed by pressing the negative electrode mixture layer 7 so as to have a total thickness of 180 to 220 μm.

  Next, as in Example 1, these positive electrode plate 5 and negative electrode plate 9 were slit to a width defined in a cylindrical 18650 lithium ion secondary battery, and a polyethylene microporous film having a thickness of 20 μm was used as separator 10. A spiral electrode group was formed by winding in the direction of the arrow shown in FIG. 5, cut into a predetermined length, inserted into the battery case 11, and the internal resistance was measured with a tester to confirm that there was no internal short circuit. .

Then, 5.5 g of an electrolytic solution in which 1 part of LiPF ₆ and 3 parts by weight of VC were dissolved in an EC / DMC / MEC mixed solvent was added and sealed. A non-aqueous secondary battery produced as an ion secondary battery was referred to as Comparative Example 1.

(Comparative Example 2)
As shown in FIG. 6, the positive electrode plate 5 of the comparative example 1 detects the boundary between the positive electrode mixture layer 2 of the positive electrode plate 5 and the exposed portion of the positive electrode current collector 1 and faces the negative electrode mixture layer 7. A positive electrode plate of Comparative Example 2 was prepared by attaching an insulating tape (made of PP) 16 having a width of 16 mm and a thickness of 25 μm to the front and back surfaces of the boundary portion of the exposed portion of the current collector 1. A non-aqueous secondary battery produced by the same manufacturing method as in Comparative Example 1 using the positive electrode plate 5 thus obtained, the negative electrode plate 9 of Comparative Example 1 and the separator 10 used in Comparative Example 1 was compared with Comparative Example 2. It was.

  The said Example and a comparative example are shown in (Table 1).

  In the non-aqueous secondary battery prototyped under the conditions of (Table 1), evaluation was performed with the following contents. Regarding the breakage of the electrode plate, the number of breaks that occurred when the electrode group was wound was measured, and the occurrence rate is shown in Table 2 as the number of breaks in n = 30.

  The initial capacity was a discharge capacity at 0.2 C at room temperature (25 ° C.), and n = 5 variations were obtained. For the cycle life, the ratio of the remaining capacity to the initial capacity at the end of 500 cycles was taken as the capacity retention rate, and an average value of n = 5 was obtained. These results are shown in (Table 2).

  For non-aqueous secondary batteries to be evaluated for safety, an applied voltage of 250 V is applied between the positive electrode terminal and the negative electrode terminal for all the non-aqueous secondary batteries in order to improve reliability. The internal resistance was measured with a tester, and a non-aqueous secondary battery of 100 MΩ or less was omitted as a poorly insulated battery.

For the drop test, the non-aqueous secondary battery subjected to the insulation resistance test was charged for 2 hours under the conditions of an upper limit voltage of 4.2 V and a current of 2 A. A drop test is performed 10 times on three surfaces of the water-based secondary battery, and the exothermic temperatures of n = 3 non-aqueous secondary batteries are measured at room temperature (25 ° C.), and the average value of n = 3 is obtained. The results are shown in (Table 2).
Table 2 shows the results of confirming the presence or absence of an internal short circuit for n = 100 nonaqueous secondary batteries after the drop test.

  For the round bar crushing test, the non-aqueous secondary battery subjected to the insulation resistance test was charged for 2 hours under the conditions of an upper limit voltage of 4.2 V and a current of 2 A, and then the longitudinal direction of the non-aqueous secondary battery was compared. In the vertical direction, a crush test was performed with a round bar having a diameter of 10 mm, and the heat generation temperature of n = 3 non-aqueous secondary batteries was measured at room temperature (25 ° C.), and the average value of n = 3 was obtained. The results are shown in (Table 2).

  For the 150 ° C. heating test, the non-aqueous secondary battery subjected to the insulation resistance test was charged for 2 hours under the conditions of an upper limit voltage of 4.2 V and a current of 2 A, and then the non-aqueous secondary battery was inserted into the constant temperature layer. Then, the temperature of the thermostatic chamber was raised to 150 ° C. under the condition that the temperature rose from room temperature to 5 ° C. per minute, the battery heat generation temperature at that time was measured, and the result of obtaining the average value of n = 3 ( Table 2).

  As shown in Table 2, when the insulator layer 4 is applied with a rubber-like elastic body in Examples 1 to 6, there is little variation in the occurrence rate of cuts and initial capacity during winding, and the capacity is maintained. The rate was high, and it was found to be equivalent to Comparative Example 1 without the insulator layer 4. Since there are few breaks at the time of winding, the current collection performance is good, so the variation in initial capacity is small, and even if the electrode plate expands or contracts during the charge / discharge cycle, the positive electrode plate 5 and the negative electrode plate 9 It was found that there was little cycle deterioration because the balance was not lost locally.

  On the other hand, it was found that in the conventional example 2 to which the conventional insulating tape 16 was applied, the occurrence rate of cuts and variations in initial capacity were large, and the capacity maintenance rate was low. This is because there are many cuts at the time of winding, so the current collection performance is poor, so there is a large variation in the initial capacity, and because of the expansion and contraction of the electrode plate that occurs during the charge / discharge cycle, the positive electrode plate 5 and the negative electrode plate 9 It was found that the balance may be locally broken, resulting in a decrease in capacity retention rate.

  Further, in the non-aqueous secondary battery in which the insulator layer 4 is formed in Examples 1 to 6 and Comparative Example 2, the positive electrode current collector 1 is formed by the insulator layer 4 even when a physical impact is applied from the outside. Since it was not exposed, the contact between the positive electrode plate 5 and the negative electrode plate 9 did not occur, so that the internal short circuit did not occur and the safety was good.

  On the other hand, the non-aqueous secondary battery of Comparative Example 1 in which the insulator layer 4 is not formed is in contact with the positive electrode plate and the negative electrode plate because the battery temperature is high in any of the tests of dropping, round bar crushing, and heating at 150 ° C. In other words, the insulator layer 4 is provided so that the positive electrode current collector 1 and the negative electrode mixture layer 7 generate heat and the positive electrode current collector 1 and the negative electrode mixture layer 7 do not contact each other. This has a great effect of preventing the occurrence of minute short circuits and internal short circuits.

  In addition, with respect to safety, in Example 1 to Example 6, the rubber-like elastic insulator layer 4 was formed in comparison with Comparative Example 2 in which the conventional insulating tape 16 was adhered. It was possible to secure enough safety.

That is, by forming the insulator layer 4 from a rubber-like elastic body, the breakage at the time of winding is equivalent to the case without the insulator layer 4, and with respect to safety, the insulating tape 16 which is a conventional insulator layer and It turns out that it satisfies the equivalent function.

  Note that the formation of the insulator layer 4 is not limited to the positive electrode plate 5, and may be formed on the negative electrode plate 9, and it goes without saying that both may be applied to the entire surface of the electrode plate.

  The non-aqueous secondary battery according to the present invention is provided on at least one of the surface of the negative electrode mixture layer facing the exposed portion of the positive electrode current collector and the exposed portion of the positive electrode current collector facing the negative electrode mixture layer. Applying an insulating coating composed of at least an inorganic additive and a water-insoluble polymer binder to form an insulating layer that is dried to coat the exposed portion, thereby making it more physical than a conventional non-aqueous secondary battery. Can suppress the short circuit between the positive electrode plate and the negative electrode plate due to mechanical shock, etc., and can maintain high capacity and good life characteristics with excellent safety. It is useful as a portable power source for communication equipment.

1 is a partially cutaway perspective view of a cylindrical non-aqueous secondary battery according to an embodiment of the present invention. Schematic which shows the insulator layer and negative electrode plate of the boundary surface of the positive electrode plate which concerns on the Example, positive mix layer, and positive electrode collector exposed part Sectional drawing which shows the outline of the winding apparatus of the electrode group which concerns on the Example Schematic diagram showing a cross section of the non-aqueous secondary battery according to the same example Schematic showing a positive electrode plate and a negative electrode plate according to a conventional example Schematic which shows the insulator layer and negative electrode plate of the boundary part of the positive electrode plate which concerns on another prior art example, and positive mix, and a positive electrode collector exposed part The schematic diagram which showed the cross section which stuck the insulating tape shape | molded so that the thickness of the edge part in a prior art example might become thin on the positive electrode plate. Schematic diagram showing that the insulating tape was attached with the liquid shrinkage direction in the conventional example set to the length direction of the positive electrode plate or negative electrode plate

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Positive electrode collector 2 Positive electrode mixture layer 3 Positive electrode lead 4 Insulator layer 5 Positive electrode plate 5a Positive electrode plate of winding center part 6 Negative electrode collector 7 Negative electrode mixture layer 8 Negative electrode lead 9 Negative electrode plate 9a of winding center part Negative electrode plate 10 Separator 11 Battery case 12 Sealing plate 13 Sealing gasket 14 Electrode group 15 Insulating plate 16 Insulating tape 21 Positive electrode plate 22 Negative electrode plate 23, 24 Separator 25 Positive electrode plate conveying device 26 Negative electrode plate conveying device 27 Winding part

Claims (7)

  A positive electrode plate constituted by applying and drying a positive electrode mixture paint comprising at least an active material, a conductive agent and a binder on a positive electrode current collector, and a negative electrode mixture comprising at least the active material and the binder A non-aqueous two-layered electrode composed of a negative electrode plate formed by coating and drying a paint on a negative electrode current collector and an electrode group formed by spirally winding a separator and an electrolyte mainly composed of a non-aqueous solvent. In the secondary battery, an exposed portion where no positive electrode mixture paint or negative electrode mixture paint is applied is provided on a part of the positive electrode current collector or the negative electrode current collector, and at least one of the positive electrode plate or the negative electrode plate A non-aqueous system characterized in that an insulating layer having at least flexibility is formed at a boundary portion between an exposed part of a positive electrode current collector or a negative electrode current collector and an application part of the positive electrode mixture paint or the negative electrode mixture paint. Secondary battery.   The non-aqueous secondary battery according to claim 1, wherein the insulator layer is formed on a positive electrode plate.   The non-aqueous secondary battery according to claim 1, wherein the insulator layer is made of a rubber-like elastic body.   The non-aqueous secondary battery according to claim 3, wherein an inorganic additive is added to the rubber-like elastic body.   The non-aqueous secondary battery according to claim 4, wherein the inorganic additive is a silica material and / or an alumina material.   The non-aqueous secondary battery according to claim 3, wherein the rubber-like elastic body is a rubber particle binder having styrene-butadiene copolymer rubber particles and / or acrylate units.   The non-aqueous secondary battery according to claim 1, wherein the thickness of the insulator layer is 2 μm or more and 25 μm or less.

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