JP2008041581A - Rolled electrode group, rectangular secondary battery, and laminated type secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rectangular secondary battery and a laminated type secondary battery excellent in reliability and safety, as well as a rolled electrode group capable of structuring these secondary batteries. <P>SOLUTION: The rolled electrode group for a secondary battery is made to be wound in spiral with a laminate made of a cathode having an active material containing layer on both sides of a collector and an anode having an active material containing layer on both sides of a collector laminated through a separator containing thermal resistance particles with electric insulation, or, made to be wound in spiral with a laminate made of a cathode having an active material containing layer on both sides of a collector, an anode having an active material containing layer on both sides of a collector, and a separator integrally formed on a surface of the cathode and/or the anode, laminated through the above separator. The rolled electrode group is flat, and does not involve in a charge/discharge reaction of a facing part on the innermost peripheral side among facing parts facing the layers containing the active materials of the cathode and the anode respectively in at least one side of a curving part, and the battery includes above the electrode group. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a flat wound electrode group suitable for constituting a rectangular secondary battery and a laminated secondary battery, and a secondary battery having the wound electrode group.

  Lithium ion batteries, which are a type of non-aqueous battery, are widely used as power sources for portable devices such as mobile phones and notebook personal computers because of their high energy density. As the performance of portable devices increases, the capacity of lithium ion batteries tends to increase further, and ensuring safety is important.

  In the current lithium ion battery, as a separator interposed between a positive electrode and a negative electrode, for example, a polyolefin-based porous film having a thickness of about 20 to 30 μm is used. In addition, as separator material, the constituent resin of the separator is melted below the thermal runaway temperature of the battery to close the pores, thereby increasing the internal resistance of the battery and improving the safety of the battery in the event of a short circuit. In order to ensure the so-called shutdown effect, polyethylene having a low melting point may be applied.

  By the way, as such a separator, for example, a uniaxially stretched film or a biaxially stretched film is used for increasing the porosity and improving the strength. Since such a separator is supplied as a single film, a certain strength is required in terms of workability and the like, and this is ensured by the above stretching. However, with such a stretched film, the degree of crystallinity has increased, and the shutdown temperature has increased to a temperature close to the thermal runaway temperature of the battery. Therefore, it can be said that the margin for ensuring the safety of the battery is sufficient. hard.

  Further, the film is distorted by the stretching, and there is a problem that when this is exposed to high temperature, shrinkage occurs due to residual stress. The shrinkage temperature is very close to the melting point, ie the shutdown temperature. For this reason, when a polyolefin-based porous film separator is used, when the battery temperature reaches the shutdown temperature in the case of abnormal charging, the current must be immediately decreased to prevent the battery temperature from rising. This is because if the pores are not sufficiently closed and the current cannot be reduced immediately, the battery temperature easily rises to the shrinkage temperature of the separator, and there is a risk of heat generation due to an internal short circuit.

  As described above, it is difficult to achieve the necessary strength for the constituent film of the separator and to avoid the problem of thermal shrinkage at high temperatures with a single polyolefin film.

  Various techniques have been proposed in order to prevent a short circuit due to thermal contraction of the separator as described above. For example, Patent Document 1 discloses a method in which a porous layer mainly composed of inorganic fine particles is applied to a substrate and peeled off, and this is used as a separator. Patent Document 2 discloses a heat-resistant fine particle such as an inorganic oxide. There is a technique in which a porous layer formed by binding together with a binder is formed on an electrode and used as a separator.

JP 2005-276503 A International Publication No. 97/8863

  According to the techniques disclosed in Patent Document 1 and Patent Document 2, there is a certain effect in preventing the occurrence of a short circuit due to the thermal contraction of the separator. However, recent secondary batteries such as lithium-ion batteries use rectangular outer cans and laminated film outer packaging materials. Particularly, secondary batteries used for consumer portable devices are extremely small and thin. Because of the shape, when the above separator is used, the following problems may occur.

  That is, in a secondary battery, it is common to stack a positive electrode and a negative electrode with a separator interposed between them, and then wind this to use as a wound body electrode group. When applied, the separator is bent with a very small diameter because the wound electrode group is crushed flat. Therefore, the separator is required to have high flexibility. However, the separator mainly composed of inorganic fine particles as described in Patent Document 1 lacks flexibility, and particularly the inorganic fine particles in the curved portion of the wound electrode group. Are likely to fall off, and it is difficult to completely prevent a short circuit.

  Further, when the wound body electrode group is crushed flat, cracks are likely to occur in the active material-containing layer of the positive electrode or the negative electrode at the curved portion (particularly the innermost curved portion), but this is disclosed in Patent Document 2. Since the separator is integrated with the electrode, the separator easily breaks along with the cracking of the active material-containing layer. Again, it is difficult to completely prevent the short circuit. Occurrence is difficult to prevent.

  The present invention has been made in view of the above circumstances, and its object is to provide a prismatic secondary battery and a laminated secondary battery excellent in reliability and safety, and a wound body that can constitute these secondary batteries. It is to provide an electrode group.

  The wound body electrode group of the present invention that has achieved the above object is characterized by having the following aspect (1), (2), or (3).

(1) A positive electrode having an active material-containing layer on both sides of a current collector and a negative electrode having an active material-containing layer on both sides of the current collector are laminated via a separator containing at least electrically insulating heat-resistant particles. The laminated body is a wound body electrode group for a secondary battery wound in a spiral shape, and the wound body electrode group is flat and is provided at both ends in the major axis direction. At least one of the curved portions, among the facing portions where the positive electrode active material-containing layer and the negative electrode active material-containing layer face each other, the innermost facing portion does not participate in the charge / discharge reaction. .

(2) A positive electrode having an active material-containing layer on both sides of a current collector, a negative electrode having an active material-containing layer on both sides of the current collector, and a separator integrally formed on the surface of the positive electrode and / or the negative electrode And a laminated body in which the positive electrode and the negative electrode are laminated via the separator is a wound body electrode group for a secondary battery wound in a spiral shape, and the wound body electrode The group has a flat shape, and in at least one of the curved portions at both ends in the major axis direction, the active material-containing layer of the positive electrode and the active material-containing layer of the negative electrode are opposed to each other. The opposed portion on the innermost peripheral side does not participate in the charge / discharge reaction.

(3) A positive electrode having an active material containing layer on both sides of a current collector and a negative electrode having an active material containing layer on both sides of the current collector are laminated via a separator containing at least electrically insulating heat-resistant particles. The laminated body is a wound body electrode group for a secondary battery wound in a spiral shape, and the wound body electrode group is flat and is provided at both ends in the major axis direction. In at least one of the curved portions, the portion where the positive electrode and the negative electrode face each other on the innermost peripheral side has a plain portion where at least the positive electrode active material-containing layer is not present, On the side, the active material-containing layer of the positive electrode and the active material-containing layer of the negative electrode are opposed to each other so as to allow a charge / discharge reaction.

  In the wound body electrode group of the present invention, the separator has a specific configuration according to (1) or (2) to prevent occurrence of a short circuit due to thermal contraction of the separator, and (1) and (2) In both of these aspects, in at least one of the curved portions where a short circuit is likely to occur, a facing portion in which the active material-containing layer of the positive electrode and the active material-containing layer of the negative electrode face each other (hereinafter simply referred to as “facing portion”). )), The opposite innermost part is configured not to be involved in the charge / discharge reaction, thereby preventing the occurrence of a short circuit at the above-mentioned location and improving the safety and reliability of the battery. .

  Moreover, in the wound body electrode group of this invention, by making a separator into the specific structure which concerns on (3), generation | occurrence | production of the short circuit by the thermal contraction of a separator is prevented, and also the curved part which a short circuit is easy to generate | occur | produce. In at least one of the above-mentioned locations, by providing a solid portion where at least the active material-containing layer of the positive electrode does not exist in a portion where the positive electrode and the negative electrode face each other on the innermost peripheral side, It prevents the occurrence of short circuit and enhances battery safety and reliability. In addition, a charging / discharging reaction is provided on the inner terminal side from the plain portion by providing a facing portion in which the active material-containing layer of the positive electrode and the active material-containing layer of the negative electrode face each other and are capable of charge / discharge reaction. Therefore, the area of the opposing portion that can be increased can be increased to increase the capacity.

  That is, a rectangular secondary battery in which the wound electrode group of the present invention is enclosed in a rectangular outer can, and a laminate type battery in which the wound electrode group of the present invention is enclosed in a bag-like laminate film. Secondary batteries are also included in the present invention.

  According to the present invention, it is possible to provide a prismatic secondary battery and a laminated secondary battery that are excellent in safety and reliability, and a wound electrode group that can constitute these secondary batteries.

  The wound body electrode group of the present invention is flat in any of the aspects (1), (2), and (3), and the aspects (1) and (2) In at least one of the curved portions, the innermost facing portion does not participate in charging / discharging. In the aspect of (3), in at least one of the curved portions, in the portion where the positive electrode and the negative electrode are opposed to each other on the innermost side, at least the plain portion (the current collector of the current collector is not present). Thus, the above-described portion is not involved in charging / discharging. Furthermore, in the aspect of (3), the active material-containing layer of the positive electrode and the active material-containing layer of the negative electrode are opposed to each other on the inner terminal side from the plain portion so that a charge / discharge reaction is possible. As a result, the area of the facing portion capable of charge / discharge reaction is increased, and the capacity can be increased.

  A partial cross-sectional view of the wound body electrode group is shown in FIG. In FIG. 1, 10 is a wound body electrode group, 20 is a positive electrode, 21 is a positive electrode active material containing layer, 22 is a positive electrode current collector, 23 is a positive electrode tab, 30 is a negative electrode, 31 is a negative electrode active material containing layer, 32 is A negative electrode current collector, 33 is a negative electrode current collector tab, 40 is a separator, and 100 is a curved portion. The “curved portion” of the wound body electrode group is a region (lattice line portion) existing between the straight line B and the straight line C shown in FIG. The straight line B passes through a point that is orthogonal to the maximum diameter in the direction in which the wound body electrode group is flattened and has the maximum distance from the intersection with the maximum diameter to the innermost inner circumference of the wound body electrode group. A straight line that is orthogonal to the straight line A and passes through the intersection of the innermost inner circumference of the wound electrode group and the straight line A, and the straight line C is orthogonal to the straight line A, and the outermost outer periphery of the wound electrode group It is a straight line that passes through the intersection with the straight line A.

  In addition, the normal wound body electrode group has a substantially oval cross section, and the above-mentioned “maximum diameter in the direction in which the wound body electrode group is flattened flat” is a straight line on the minor axis of the ellipse. A corresponds to the major axis of an oval (however, in FIG. 2 and later described below, cross-sectional views showing the entire wound body electrode group are shown, but in these drawings, the structure of the wound body electrode group is shown. In order to facilitate understanding, the thickness of the positive electrode, the negative electrode, the separator, etc. with respect to the size of the wound electrode group is shown larger than the actual one, so that the minor axis and the major axis are not orthogonal. .

  In the curved part of the wound body electrode group of the present invention, there is no particular limitation on the method of configuring the opposing positive electrode and negative electrode not to participate in the charge / discharge reaction. Specifically, the following (i) or ( The method ii) is preferred.

  (I) The surface of the positive electrode and / or the negative electrode in the facing portion is covered with an electrically insulating material.

  FIG. 2 is a schematic cross-sectional view of a wound body electrode group employing the method (i). In FIG. 2, elements having the same functions as those of the wound body electrode group in FIG. 1 are denoted by the same reference numerals (the same applies to the drawings described later). The wound body electrode group 11 shown in FIG. 2 uses a positive electrode, a negative electrode, and two separators 40, which are laminated to form a laminated body, and further wound in a spiral shape and then flattened. In addition, an insulating layer 50 made of an electrically insulating material is disposed on the innermost facing portion of the curved portion on the right side in the drawing among the curved portions at both ends in the major axis direction. The negative electrode of the wound body electrode group 11 is provided with the active material-containing layer 33 only on one surface of the current collector 32 from the inner peripheral end to a predetermined location, and the inside of the electrode body 11 is the current collector. 32 is exposed.

  FIG. 3 shows an enlarged view of the main part of FIG. 2. Among the curved parts at both ends in the major axis direction, the innermost facing part of the right curved part according to FIG. The surface of the positive electrode active material-containing layer 21 on the opposite side is covered with an insulating layer 50 (hereinafter sometimes simply referred to as “insulating layer”) made of an electrically insulating material. In the above portion, the surface of the negative electrode active material-containing layer 31 may be covered with an insulating layer, or both the surface of the positive electrode active material-containing layer 21 and the surface of the negative electrode active material-containing layer 31 may be covered with an insulating layer. Good.

  (Ii) An insulating layer made of an electrically insulating material is disposed between the positive electrode and / or negative electrode current collector and the active material-containing layer in the facing portion.

  In FIG. 4, the cross-sectional schematic of the wound body electrode group which employ | adopted the method of (ii) is shown. In the wound body electrode group 12 in FIG. 4, the insulating layer 50 is disposed at the innermost facing portion of the curved portion on the right side in the drawing among the curved portions at both ends in the major axis direction.

  FIG. 5 shows an enlarged view of the main part of FIG. 4. Among the curved parts at both ends in the major axis direction, the innermost facing part of the right curved part according to FIG. An insulating layer 50 is provided between the positive electrode active material containing layer 21 and the positive electrode current collector 22 on the opposite side. In the above portion, an insulating layer may be provided between the negative electrode active material-containing layer 31 and the negative electrode current collector 32 in the negative electrode, between the positive electrode active material-containing layer 21 and the positive electrode current collector 22, and the negative electrode An insulating layer may be provided between the active material-containing layer 31 and the negative electrode current collector 32.

  (Iii) At least the positive electrode is provided with a plain portion where no active material-containing layer exists.

  FIG. 6 shows a schematic cross-sectional view of a wound electrode group employing the method (iii). In the wound body electrode group 13 in FIG. 6, the plain portion 60 is provided on the innermost peripheral side of the curved portion on the right side in the drawing among the curved portions at both ends in the major axis direction.

  FIG. 7 shows an enlarged view of the main part of FIG. Of the curved portions at both ends in the major axis direction, the positive electrode active material-containing layer 21 does not exist in the plain portion 60 on the innermost side of the right curved portion according to FIG. 6, and the positive electrode current collector 22 is exposed. ing. 6 and 7 show an example in which a solid portion is provided on the positive electrode in the portion where the positive electrode and the negative electrode face each other on the innermost peripheral side of the curved portion, but the negative electrode active material-containing layer is provided only on the negative electrode. If a non-existing plain part is provided, lithium dendrite may be deposited, so the plain part is provided at least on the positive electrode. Moreover, in the said part, you may provide a plain part in both a positive electrode and a negative electrode.

  6 and 7, the positive electrode active material-containing layer 21 of the positive electrode and the negative electrode active material-containing layer 31 of the negative electrode are disposed closer to the inner peripheral end than the portion where the plain portion 60 is provided. Are opposed to each other and can be charged and discharged.

  Moreover, you may comprise a wound body electrode group combining 2 or 3 methods among the methods of said (i), (ii), and (iii).

  Furthermore, in the wound body electrode group of the present invention, the portions that are not involved in the charge / discharge reaction by the method (i) or (ii) are curved portions at both ends in the major axis direction of the wound body electrode group. Of the facing portions in at least one of the above, the innermost facing portion may be used, but since it is more likely to be a short-circuit occurrence location, the facing portion with the larger curvature is not involved in the charge / discharge reaction. It is preferable to have. Usually, the curvature of the facing portion on the inner peripheral end side among the facing portions on the innermost peripheral side is larger.

  Of the opposing parts of the curved part at both ends in the major axis direction, the opposing parts other than the innermost opposing part are not as far as the innermost opposing part, but may be short-circuit occurrence points. In these locations, it is also preferable to adopt a configuration that does not participate in the charge / discharge reaction. In this case, for the facing portion other than the facing portion on the innermost side, for example, the above (i) Alternatively, the method (ii) may be configured not to participate in the charge / discharge reaction.

  Further, in the wound body electrode group of the present invention, the location that is not involved in the charge / discharge reaction by the method (iii) is at least one of the curved portions at both ends in the major axis direction of the wound body electrode group. It is sufficient that the positive electrode and the negative electrode are opposed to each other on the innermost peripheral side, but the above-mentioned portion in the curved portion having the larger curvature is more likely to be charged / discharged because it tends to be a short-circuit occurrence location. It is preferable to have a configuration that is not involved.

  The electrically insulating material used in the method (i) and the method (ii) is stable against a non-aqueous electrolyte (hereinafter abbreviated as “electrolyte”) in the battery, There is no particular limitation as long as it is electrochemically stable with respect to the charge / discharge reaction, and examples thereof include films and fine particles composed of the following inorganic and organic materials. As used herein, “electrochemically stable” means that no chemical change occurs during charging / discharging of the battery.

Examples of the inorganic material (inorganic fine particles) include oxide fine particles such as iron oxide, SiO ₂ , Al ₂ O ₃ , TiO ₂ , BaTiO ₂ , and ZrO; nitride fine particles such as aluminum nitride and silicon nitride; calcium fluoride, Slightly soluble ionic crystal materials such as barium fluoride and barium sulfate; Covalent crystalline materials such as silicon and diamond; Clay such as talc and montmorillonite; Boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine, sericite And materials derived from mineral resources such as bentonite or artificial products thereof. Further, the surface of conductive fine particles such as metal fine particles; oxide fine particles such as SnO ₂ and tin-indium oxide (ITO); carbon fine particles such as carbon black and graphite; It may be fine particles that have been electrically insulated by surface treatment with the above-mentioned materials constituting non-electrically conductive inorganic fine particles or materials constituting crosslinked polymer fine particles described later.

  Organic materials include cross-linked polymethyl methacrylate, cross-linked polystyrene, polydivinylbenzene, styrene-divinylbenzene copolymer cross-linked product, polyimide, polyurethane, epoxy resin, melamine resin, phenol resin, benzoguanamine-formaldehyde condensate, etc. Molecular compounds, cellulose and derivatives thereof, PVDF, PVDF-HFP and derivatives thereof, polytetrafluoroethylene, polypropylene, polysulfone, polyethersulfone, polycycloolefin, polyvinyl alcohol, polyacrylonitrile, polyester [polyethylene terephthalate (PET), polyethylene Naphthalate (PEN), polybutylene terephthalate (PBT), etc.], polyamideimide, polyetherimide, polyaramid Which organic resin can be exemplified. The organic resin (polymer) may be a mixture, a modified body, a derivative, or a copolymer (random copolymer, alternating copolymer, block copolymer, graft copolymer).

  When an electrically insulating material is used as a film, it may be formed directly on the active material-containing layer or current collector by a method such as sputtering, vapor deposition, casting, or coating, or an adhesive layer is formed on the film. You may affix in the form of an adhesive tape (insulating tape).

  In the case where the electrically insulating material is in the form of particles, the particles can be used together by using a binder, or the particles and the active material-containing layer or current collector can be bound to form a layer. Further, in the case of particles having binding properties, the particles themselves can also serve as a binder.

  Moreover, in order to improve the reliability of a battery, it is preferable that the wound body electrode group of this invention has the following aspect (4) or (5).

  In the wound electrode group according to the aspect (4), a plain portion (exposed portion of the current collector) in which no active material-containing layer is present is provided inside the positive electrode or the negative electrode located on the innermost inner periphery side. A wound body electrode group having a structure in which a portion facing the positive electrode or the negative electrode located on the innermost inner periphery in the terminal part of the negative electrode or the positive electrode located on the outermost inner periphery is covered with an electrically insulating material It is.

  Moreover, the winding body electrode group which concerns on the aspect of (5) is provided with the plain part which does not have an active material content layer in the outer side of the positive electrode or negative electrode located in the outermost outer periphery side, and is located in the outermost outer periphery side. In the terminal part of the negative electrode or the positive electrode, a wound electrode group having a structure in which a portion facing the positive electrode or the negative electrode located on the outermost outer periphery is coated with an electrically insulating material.

  FIG. 8 shows a schematic cross-sectional view of the wound electrode group having the aspects (4) and (5). In FIG. 8, in order to facilitate understanding of the characteristics of the wound body electrode group described with reference to this drawing, the hatched lines indicating the cross section are omitted except for the elements of the characteristic portions.

  The wound body electrode group 14 in FIG. 8 is a plain part in which the negative electrode current collector 32 is exposed inside the negative electrode located on the innermost inner periphery side (the side not facing the positive electrode) and no active material-containing layer is present. Is provided. A portion of the terminal end portion of the positive electrode located on the outermost inner periphery facing the negative electrode located on the innermost inner periphery is covered with an insulating layer 50 made of an electrically insulating material. When the current collector of the electrode located on the innermost inner periphery is in direct contact with the counter electrode located on the outermost inner periphery, a large current may flow to cause deterioration or ignition of the battery, but the insulating layer 50 By covering the portion of the counter electrode by the contact between the current collector of the electrode and the counter electrode, the reliability of the battery can be improved.

  Further, in the wound body electrode group 14 in FIG. 8, the positive electrode current collector 22 is exposed outside the positive electrode located on the outermost outer periphery side, and a plain portion where no active material-containing layer is present is provided. And the part which opposes the positive electrode located in the outermost periphery outer side in the terminal part of the negative electrode located in the outermost periphery inner side is coat | covered with the insulating layer 50 comprised with the electrically insulating material. Even when the current collector of the electrode located on the outermost outer periphery is in direct contact with the counter electrode located on the innermost outer periphery, the battery may be deteriorated or ignited. Since the contact between the current collector of the electrode and the counter electrode can be prevented, the reliability of the battery can be improved.

  Further, in the wound body electrode group 14 in FIG. 8, the surface of the active material-containing layer 21 on the inner side of the positive electrode is the insulating layer 50 at the two innermost opposing portions of both curved portions at both ends in the major axis direction. , 50.

  In the aspect of (4), in the aspect of (5), in the aspect of (5), the electrically insulating material that covers the portion facing the counter electrode located on the innermost inner circumference at the terminal end of the electrode located on the outermost innermost circumference The electrical insulation material that covers the portion of the terminal portion of the electrode located inside the outer periphery that faces the counter electrode located outside the outermost circumference is the electrical insulation that can be used in the methods (i) and (ii). Various materials exemplified above can be used as the material having the property.

  In the wound electrode group of the present invention, from the viewpoint of preventing the precipitation of lithium metal, the width of the negative electrode is preferably equal to or greater than the width of the positive electrode, and in particular, a separator integrated with the electrode is used. In the embodiment, it is desirable that the positive and negative electrode widths have such a relationship. In the aspect (2), when the width of the negative electrode is larger than the width of the positive electrode, the separator is preferably integrated with the negative electrode. In this way, the positive and negative electrodes are more reliably separated. can do.

  In the wound electrode group of the present invention, the separator according to the embodiments (1) and (3) contains the electrically insulating heat-resistant particles (A). On the other hand, the separator according to the embodiment (2) of the wound electrode group of the present invention may be integrated with the positive electrode and / or the negative electrode, and may contain the heat-resistant particles (A) [that is, It may be the same configuration as the separator according to the embodiments of (1) and (3)], and may not be contained.

  The heat-resistant particles (A) have electrical insulating properties, are electrochemically stable, and are stable to an electrolyte solution described later and a solvent used in a liquid composition used in the production of a separator. If it does not melt | dissolve in electrolyte solution in a state, there will be no restriction | limiting in particular. The high temperature state is specifically a temperature of 150 ° C. or higher, and the heat-resistant particles (A) may be stable particles that do not deform or undergo chemical composition changes in the electrolytic solution at such temperatures. .

Specific examples of such heat-resistant particles (A) include the following inorganic fine particles and organic fine particles, and these can be used alone or in combination of two or more. Examples of the inorganic fine particles (inorganic powder) include oxide fine particles such as iron oxide, SiO ₂ , Al ₂ O ₃ , TiO ₂ , BaTiO ₂ , and ZrO; nitride fine particles such as aluminum nitride and silicon nitride; calcium fluoride, Slightly soluble ionic crystal particles such as barium fluoride and barium sulfate; Covalent crystal particles such as silicon and diamond; Clay particles such as talc and montmorillonite; Boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine, sericite And materials derived from mineral resources such as bentonite or artificial products thereof. Further, the surface of conductive fine particles such as metal fine particles; oxide fine particles such as SnO ₂ and tin-indium oxide (ITO); carbonaceous fine particles such as carbon black and graphite; Surface treatment with a material constituting the above non-electrically conductive inorganic fine particles or a material constituting particles not corresponding to the swellable particles (D) among the crosslinked polymer fine particles described later] Fine particles provided with may be used.

  Organic fine particles (organic powder) include crosslinked polymethyl methacrylate, crosslinked polystyrene, polydivinylbenzene, styrene-divinylbenzene copolymer crosslinked product, polyimide, polyurethane, epoxy resin, melamine resin, phenol resin, benzoguanamine-formaldehyde. Various crosslinked polymer fine particles such as condensates, cellulose and derivatives thereof, polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) and derivatives thereof, and organic resin particles such as polytetrafluoroethylene Can be illustrated. The organic resin (polymer) constituting these organic fine particles is a mixture, modified body, derivative, or copolymer (random copolymer, alternating copolymer, block copolymer, graft copolymer) of the materials exemplified above. Polymer).

  The heat resistant particles (A) may contain two or more materials constituting the above exemplified particles.

  The particle diameter of the heat-resistant particles (A) is 0.001 μm or more, more preferably 0.1 μm or more, and 15 μm or less, more preferably 1 μm or less is recommended.

  The shape of the heat-resistant particles (A) may be, for example, a so-called spherical shape, or may be a plate shape or a needle shape. More preferably, it is a plate-like particle. When the heat-resistant particles (A) are plate-like, further improvement in the effect of preventing a short circuit caused by lithium dendrite can be expected.

  As the form of the plate-like heat resistant particles (A), it is desirable that the aspect ratio is 5 or more, more preferably 10 or more, and 100 or less, more preferably 50 or less. Moreover, the average value of the ratio of the length in the major axis direction to the length in the minor axis direction of the flat plate surface of the plate-like heat resistant particles (A) is 0.3 or more, more preferably 0.5 or more, and 3 or less. More preferably, it is 2 or less.

  The average particle diameter of the heat-resistant particles (A) is dispersed in a medium (for example, water) in which the heat-resistant particles (A) do not swell using a laser scattering particle size distribution meter (“LA-920” manufactured by HORIBA). The measured number average particle diameter. The average value of the ratio of the long axis direction length to the short axis direction length of the flat plate surface when the heat-resistant particles (A) are plate-like is, for example, an image taken with a scanning electron microscope (SEM). Can be obtained by image analysis. Furthermore, the above aspect ratio in the case where the heat resistant particles (A) are plate-like can also be obtained by image analysis of an image taken by SEM.

  Moreover, when the heat resistant particles (A) are plate-shaped, the heat resistant particles (A) are preferably oriented in the separator. As a specific form of existence, the flat surface of the plate-like heat-resistant particles (A) is preferably substantially parallel to the surface of the separator, and the average angle near the surface of the separator is 30 ° or less. Is preferred. Here, “near the surface” means a region within 10% of the total thickness from the surface of the separator. When the form of presence of the plate-like heat-resistant particles (A) in the separator is as described above, the heat-resistant particles (A) are arranged substantially in parallel when the battery is formed, Since the formation of so-called through holes between the negative electrodes can be prevented, it is possible to more effectively prevent a short circuit caused by lithium dendrite.

  As the plate-like heat-resistant particles (A), various commercially available products can be used as they are or after being appropriately pulverized.

Among the above, an AlOOH or Al 2 _{O 3} · _H 2 _O principal component a compound represented by (e.g. more than 80 wt%) to good practice to use a plate-like particles, particularly preferable to use boehmite.

  When inorganic particles are used as the heat-resistant particles (A), surface treatment can be performed in order to improve adhesion with a binder described later. As a surface treatment method, a conventionally known method, that is, a method using a coupling agent, a method using a surfactant, or a method using a polar resin can be applied. Among these, treatment using various coupling agents such as a silane coupling agent, a titanate coupling agent, an alumina coupling agent, and a zirconia coupling agent is desirable.

  The separator which concerns on the wound body electrode group of the aspect of (1) and (3) may contain the fibrous material (B) with the heat resistant particle | grains (A). Moreover, the separator which concerns on the wound body electrode group of the aspect of (2) WHEREIN: In any case of not containing a heat resistant particle (A), when containing a heat resistant particle (A), a fibrous material (B) May be contained.

  The fibrous material (B) has an electrical insulating property, is electrochemically stable, and further includes an electrolyte solution described in detail below, heat-resistant particles (A) used in the production of the separator, and the like. As long as the solvent used for the contained liquid composition is stable, there is no particular limitation, but it is preferable that the solvent does not substantially deform at 150 ° C. The “fibrous material” in the present specification means that having an aspect ratio [length in the longitudinal direction / width (diameter) in a direction perpendicular to the longitudinal direction] of 4 or more. The aspect ratio of the fibrous material (B) is preferably 10 or more.

  Specific constituent materials of the fibrous material (B) include, for example, cellulose, modified cellulose (such as carboxymethyl cellulose), polypropylene (PP), polyester [polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene. Terephthalate (PBT), etc.], polyacrylonitrile (PAN), polyvinyl alcohol (PVA), polyaramid, polyamideimide, polyimide and other resins; glass, alumina, silica and other inorganic materials (inorganic oxides); and the like. The fibrous material (B) may contain one kind of these constituent materials, or may contain two or more kinds. Further, the fibrous material (B) contains, as necessary, various known additives (for example, an antioxidant in the case of a resin) in addition to the above-described constituent materials. It doesn't matter.

  Although the diameter of a fibrous material (B) should just be below the thickness of a separator, it is preferable that it is 0.01-5 micrometers, for example. If the diameter is too large, the entanglement between the fibrous materials may be insufficient, and the strength of the sheet-like material constituted by these, and consequently the strength of the separator may be reduced, making it difficult to handle. On the other hand, if the diameter is too small, the gap of the separator becomes too small, and the ion permeability tends to be lowered, and the load characteristics of the battery may be lowered.

  For example, the state of the fibrous material (B) in the separator (sheet-like material) is preferably such that the angle of the long axis (axis in the longitudinal direction) with respect to the separator surface is 30 ° or less on average, 20 More preferably, it is not more than 0 °.

  In addition, the wound body electrode group can be provided with a shutdown function in order to increase the resistance of the battery and ensure safety at a high temperature.

  For example, the melting temperature measured using a differential scanning calorimeter (DSC) is 80 to 130 ° C. according to the provisions of JIS K 7121. A shutdown function can be provided by configuring the wound body electrode group using a separator containing particles. When the wound electrode group having the separator containing the heat-melting particles (C) is exposed to 80 to 130 ° C. (or higher temperature), the heat-melting particles (C) are melted and the voids of the separator Therefore, a shutdown phenomenon that suppresses ion permeation in the separator appears.

  The shutdown function of the separator can be evaluated by an increase in the internal resistance of the battery. However, the temperature at which the void blocking phenomenon occurs in the wound electrode group having the separator containing the heat-meltable particles (C) (the internal resistance value is before heating). The temperature which is 5 times or higher) is not lower than the melting point of the heat-meltable particles (C) and not higher than 130 ° C.

  Specific examples of the heat-meltable particles (C) include polyethylene (PE), copolymerized polyolefin having a structural unit derived from ethylene of 85 mol% or more, polypropylene (PP), or polyolefin derivative (chlorinated polyethylene, chlorinated polypropylene, etc. ), Polyolefin wax, petroleum wax, carnauba wax and the like. Examples of the copolymer polyolefin include an ethylene-vinyl monomer copolymer, more specifically, an ethylene-vinyl acetate copolymer (EVA), an ethylene-methyl acrylate copolymer, or an ethylene-ethyl acrylate copolymer. it can. Moreover, polycycloolefin etc. can also be used. The heat-meltable particles (C) may have only one kind of these constituent materials, or may have two or more kinds. Among these, PE, polyolefin wax, or EVA having a structural unit derived from ethylene of 85 mol% or more is preferable. The heat-meltable particles (C) may contain, as a constituent component, various known additives (for example, antioxidants) that are added to the resin as necessary in addition to the constituent materials described above. I do not care.

  The particle diameter of the heat-meltable particles (C) is an average particle diameter measured by the same measurement method as that of the inorganic particles (A), for example, 0.001 μm or more, more preferably 0.1 μm or more, and 15 μm. Hereinafter, it is recommended that the thickness is 1 μm or less.

  Moreover, the shutdown function can be imparted to the wound electrode group by using the swellable particles (D) that can swell in the non-aqueous electrolyte and increase in the degree of swelling as the temperature rises.

  As a part to contain the swellable particles (D), a separator or an active material containing layer of positive and negative electrodes is preferable. Further, the swellable particles (D) may be contained in the battery electrolyte. In this case, the wound electrode group does not have a shutdown function, but the battery has a shutdown function. To have.

  In a battery using a wound electrode group containing swellable particles (D) or containing swellable particles (D) in an electrolyte, the swellable particles (D) are exposed to high temperatures. The swellable particles (D) absorb the electrolyte and expand greatly due to the property that the degree of swelling increases with increasing temperature (hereinafter referred to as “thermal swellability”). At this time, a so-called “liquid withering” state in which the amount of the electrolyte present in the gap of the separator is insufficient, and the lithium ion conductivity in the battery is remarkably reduced, so that the internal resistance of the battery increases and the shutdown phenomenon occurs. It comes to express.

  As the swellable particles (D), the temperature exhibiting the above-mentioned heat swellability is preferably 75 to 125 ° C. If the temperature exhibiting thermal swellability is too high, the thermal runaway reaction of the active material in the battery may not be sufficiently suppressed, and the battery safety improvement effect may not be sufficiently ensured. Moreover, when the temperature which shows heat swelling property is too low, the conductivity of the lithium ion in the battery in a normal use temperature range will become low too much, and it may cause trouble in use of an apparatus. That is, in the wound electrode group of the present invention, it is desirable that the temperature at which the lithium ion conductivity in the battery is remarkably reduced (so-called shutdown temperature) is in the range of about 80 to 130 ° C. ) Starts to show thermal swellability as the temperature rises, it is preferably in the range of 75 to 125 ° C.

The swellable particles (D) are preferably those having a degree of swelling B as defined by the following formula measured at 120 ° C. of 1 or more.
_{B = (V 1 / V 0} ) -1 (1)
[In the above formula (1), V ₀ is the volume of fine particles (cm ³ ) 24 hours after being introduced into the non-aqueous electrolyte at 25 ° C., and V ₁ is introduced into the non-aqueous electrolyte at 25 ° C. 24 hours later, the temperature of the non-aqueous electrolyte is raised to 120 ° C., and the volume of fine particles (cm ³ ) after 1 hour at 120 ° C.]

  Specific measurement of the swellable particles (D) defined by the above formula (1) can be performed by the following method. The swellable particles (D) are added to a binder resin solution or emulsion in which the degree of swelling when immersed in an electrolytic solution at room temperature for 24 hours in advance and the degree of swelling defined by the above formula (1) at 120 ° C. is known. An emulsion is mixed to prepare a slurry, which is cast on a substrate such as a PET sheet or a glass plate to produce a film, and its mass is measured. Next, the film was immersed in an electrolytic solution at room temperature (25 ° C.) for 24 hours, and the mass was measured. Further, the electrolytic solution was heated to 120 ° C., and the mass after 1 hour was measured at the temperature. The degree of swelling B is calculated by the formulas (2) to (8). [In the following formulas (2) to (8), the volume increase of components other than the electrolyte due to the temperature rise from room temperature to 120 ° C. can be ignored. It is said].

V _i = M _i × W / P _A (2)
V _B = (M ₀ −M _i ) / P _B (3)
_{V C = M 1 / P c} -M 0 / P B (4)
V _V = M _i × (1−W) / P _V (5)
V ₀ = V _i + V _B −V _V × (B _B +1) (6)
V _D = V _V × (B _B +1) (7)
B = [{V ₀ + V _C −V _D × (B _C +1)} / V ₀ ] −1 (8)

Here, in the above formulas (2) to (8),
V _i : volume (cm ³ ) of the swellable particles (D) before being immersed in the electrolytic solution,
V ₀ : volume (cm ³ ) of the swellable particles (D) after being immersed in the electrolyte at room temperature for 24 hours,
V _B : volume of the electrolyte solution (cm ³ ) absorbed in the film after being immersed in the electrolyte solution at room temperature for 24 hours,
V _c : The volume of the electrolyte solution absorbed by the film (cm) during the period from when the electrolyte solution was immersed in the electrolyte solution at room temperature for 24 hours until the electrolyte solution was heated to 120 ° C. and further passed at 120 ° C. for 1 hour. ³ ),
V _V : volume (cm ³ ) of the binder resin before being immersed in the electrolytic solution,
V _D : volume of the binder resin (cm ³ ) after being immersed in the electrolytic solution at room temperature for 24 hours,
M _i : mass (g) of the film before being immersed in the electrolytic solution,
M ₀ : mass (g) of the film after being immersed in the electrolytic solution at room temperature for 24 hours,
M _l : After immersing in the electrolytic solution at room temperature for 24 hours, the temperature of the electrolytic solution was raised to 120 ° C., and the mass (g) of the film after 1 hour at 120 ° C.
W: Mass ratio of the swellable particles (D) in the film before being immersed in the electrolytic solution,
P _A : specific gravity (g / cm ³ ) of the swellable particles (D) before being immersed in the electrolytic solution,
P _B : Specific gravity of electrolyte at room temperature (g / cm ³ ),
P _C: specific gravity of the electrolyte at a predetermined temperature (g / ^cm 3),
P _V : Specific gravity (g / cm ³ ) of the binder resin before being immersed in the electrolytic solution,
B _B : degree of swelling of the binder resin after being immersed in the electrolyte at room temperature for 24 hours,
B _C : Swelling degree of the binder resin at the time of temperature rise defined by the above formula (1).

Also, swellable particles (D) is the swelling degree B _R at room temperature (25 ° C.) which is defined by the following equation (9) is preferably 0 or more and 1 or less.
B _R = (V ₀ / V _i ) -1 (9)
In the above formula (9), V ₀ and V _i are the same as those described for the above formulas (2) to (8).

That is, the swellable particles (D) may be those that do not absorb the electrolytic solution (B _R = 0) at room temperature, or those that absorb some of the electrolytic solution. In the range (for example, 70 ° C. or less), the absorption amount of the electrolytic solution does not change so much regardless of the temperature, and thus the degree of swelling does not change so much. It only needs to increase.

The swellable particles (D), and preferably has satisfied the swelling degree B or B _R, also has an electrically insulating, electrochemically stable, further described below electrolyte, separator There is no particular limitation as long as it is stable to the solvent used in the liquid composition containing the heat-resistant particles (A) and the like used in the production and does not dissolve in the electrolytic solution at a high temperature.

  Specific examples of the swellable particles (D) include polystyrene (PS), acrylic resin, styrene-acrylic resin, polyalkylene oxide, fluororesin, styrene butadiene rubber (SBR), and their derivatives and crosslinked products thereof; Examples include urea resin; polyurethane; The swellable particles (D) may contain the above-mentioned constituent materials singly or in combination of two or more. Furthermore, the swellable particles (D) contain, as a constituent component, various known additives (for example, antioxidants) that are added to the resin as necessary in addition to the constituent materials described above. It doesn't matter.

  In the above-mentioned resin cross-linked body, even if it expands due to a temperature rise once, the volume change accompanying the temperature change is reversible such that it shrinks again by lowering the temperature. In a so-called dry state that does not contain water, it is stable up to a temperature higher than the temperature of thermal expansion. Therefore, in the separator using the swellable particles (D) composed of the above crosslinked resin, the swellable particles (D) are thermally swollen even through a heating process such as drying of the separator or drying of the electrode group during battery production. Therefore, the handling in such a heating process becomes easy. Furthermore, by having the above reversibility, even if the shutdown function is activated once due to the temperature rise, it can be made to function as a separator again when safety is ensured by the temperature drop in the battery. is there.

  Among the above constituent materials, crosslinked PS, crosslinked acrylic resin [for example, crosslinked polymethyl methacrylate (PMMA)], crosslinked styrene-acrylic resin, and crosslinked fluororesin [for example, crosslinked PVDF] are preferable, and crosslinked PMMA is particularly preferable.

  Although the details of the mechanism by which the fine particles of these resin crosslinked bodies swell due to temperature rise are not clear, for example, in crosslinked PMMA, the glass transition point (Tg) of PMMA, which is the main component of the particles, is around 100 ° C. It is conceivable that the cross-linked PMMA particles become flexible near Tg and absorb more electrolyte and swell. Therefore, it is considered desirable that the glass transition point of the swellable resin (D) is in the range of about 75 to 125 ° C.

  The particle size of the swellable particles (D) is an average particle size obtained by the same method as the heat resistant particles (A), and is preferably 0.1 to 20 μm.

  In the wound electrode group, the heat-meltable particles (C) and the swellable particles (D) can be used in combination, and the particles obtained by combining the heat-meltable particles (C) and the swellable particles (D) are combined. It is also possible to use it.

  Furthermore, the composite particles (E) in which the heat-resistant particles (A) and the constituent resins of the heat-meltable particles (C) and the constituent resins of the swellable particles (D) are combined are used for the wound electrode group. You can also As the composite particles (E) of the constituent resin of the heat-resistant particles (A) and the heat-meltable particles (C), the heat-meltable particles (C) were used in the same manner of use as the heat-meltable particles (C). The same effect as the case can be exhibited. Moreover, the composite particle (E) of the constituent resin of the heat-resistant particle (A) and the swellable particle (D) is a case where the swellable particle (D) is used in the same usage form as the swellable particle (D). Can exhibit the same effect. That is, the composite particles (E) of the heat-resistant particles (A) and the constituent resins of the swellable particles (D) are not only used for the wound electrode group, but also by being contained in the battery electrolyte, A shutdown function can be imparted to the battery.

  The form of the composite particles (E) is not particularly limited, and can take any structure such as a core-shell structure, a sea-island structure, or a partially covered structure, but the form of the heat-resistant particles (A) is maintained as much as possible. In particular, when the heat-resistant particles (A) are plate-like particles, it is desirable to hold the plate-like structure in order to maintain the characteristics due to the use of the plate-like particles. .

  By using the composite particles (E), it is possible to improve the filling properties of the particles when forming the separator, and it is possible to form a more uniform separator while providing a shutdown function. Among them, when plate-like particles are used as the heat-resistant particles (A), it is possible to provide a shutdown function while maintaining the effect of the plate-like particles being oriented, so the composite particles (E) The effect to use is remarkable. As the presence state of the composite particles (E) [plate-like composite particles (E)] composed of the plate-like heat resistant particles (A) in the separator, the plate-like heat resistant particles (A) have been described. It is preferable to be the same as the existing state. In this case, the effect of using the plate-like composite particles (E) becomes more remarkable.

  Further, the ratio of the heat-resistant particles (A) in the composite particles (E) is preferably 50% or more, more preferably 60% or more, and preferably 90% or less by volume.

  The composite particles (E) are prepared by a conventionally known physically heat-resistant particle (A) and resin [a constituent resin of a hot-melt particle (C) or a constituent resin of a swellable particle (D), a composite particle (E The same applies hereinafter in the description of the manufacturing method. ] Or a chemical method in which the heat-resistant particles (A) and the resin are combined by chemical bonding.

  As a physical method, a method in which heat-resistant particles (A) and resin powder are combined by mechanical alloying; a slurry in which heat-resistant particles (A) are dispersed in a dispersion medium; and a resin is dispersed in the dispersion medium. A method of coating the surface of the heat-resistant particles (A) with a resin by spray drying using a slurry and a solution dissolved in a solvent; immersing and dispersing the heat-resistant particles (A) in the resin solution; And a method of coating the heat-resistant particles (A) with a resin after drying. Moreover, as a chemical method, the method of carrying out the graft polymerization of the resin molecule | numerator on the surface of a heat resistant particle (A), and coating the surface of a heat resistant particle (A) with resin by this etc. is mentioned.

  Among the various methods described above, the mechanical alloying method and the spray drying method are preferable. Commercially available devices such as a planetary ball mill, mechanofusion (manufactured by Hosokawa Micron), and a hybridizer (manufactured by Nara Machinery Co., Ltd.) can be used as the device used for mechanical alloying.

  Of the preparation methods of the composite particles (E), according to the chemical method described above, even if the resin alone has a property of being dissolved in an organic solvent such as an electrolyte, As long as the resin is stable, it can be used as a constituent resin of the composite particles (E) having heat swellability.

  The degree of swelling of the composite particles (E) having thermal swellability can be measured using the composite particles by the same method as the method for measuring the degree of swelling of the above-mentioned swellable particles (D).

  The particle diameter of the composite particles (E) is an average particle diameter measured by the same method as that for the heat-resistant particles (A), and is, for example, 0.002 μm or more, more preferably 0.2 μm or more, and 15 μm or less. More preferably, it is 3 μm or less.

  As above-mentioned, the separator which concerns on the wound body electrode group of the aspect of (1) and (3) makes a heat-resistant particle | grain (A) an essential structural component, and other components [fibrous material (B ), Heat-fusible particles (C), swellable particles (D), composite particles (E), etc.], which are related to the wound electrode group of aspects (1) and (3). Since the separator is an independent film that is not integrated with the electrode, it is preferable to have the fibrous material (B) as a reinforcing material in order to ensure the strength necessary for the independent film.

  On the other hand, the separator according to the wound electrode group of the aspect (2) is not particularly limited as long as it is integrated with the positive electrode and / or the negative electrode. For example, similarly to the separator according to the embodiments of (1) and (3), it contains the heat-resistant particles (A) and, if necessary, other components [fibrous matter (B), hot-melt particles ( C), swellable particles (D), composite particles (E), etc.] may be included, and the fibrous material (B) described above without containing the heat-resistant particles (A), A separator having a configuration containing the heat-meltable particles (C), the swellable particles (D), the composite particles (E), or the like may be used. More specifically, for example, a separator composed of a sheet-like material such as a woven fabric or a non-woven fabric composed of the fibrous material (B) may be used. (C), the separator of the structure containing one or more types of materials among the swellable particles (D) and the composite particles (E) may be used.

  Further, in any of the wound body electrode group of the aspect (1), the wound body electrode group of the aspect (2), and the wound body electrode group of the aspect (3), the constituent components of the separator are bound together. For this purpose, the separator may contain a binder (F). The binder (F) is not particularly limited as long as it is electrochemically stable and stable with respect to the electrolyte solution, and can satisfactorily adhere each component of the separator. For example, EVA (a structural unit derived from vinyl acetate is 20 ˜35 mol%), ethylene-acrylate copolymers such as ethylene-ethyl acrylate copolymer, various rubbers and derivatives thereof [styrene-butadiene rubber (SBR), fluoro rubber, urethane rubber, ethylene-propylene-diene rubber ( EPDM)], cellulose derivatives [carboxymethyl cellulose (CMC), hydroxyethyl cellulose, hydroxypropyl cellulose, etc.], polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyvinyl pyrrolidone (PVP), polyurethane, epoxy resin, PVDF, PV F-HFP copolymer, and the like, these can be used alone, or two or more thereof. When these binders (F) are used, they can be used in the form of an emulsion dissolved or dispersed in a solvent of a liquid composition for forming a separator described later.

  In addition, when a hot-melt particle (C) and a swellable particle (D) have adhesiveness independently, these particle | grains can serve as a binder (F). Therefore, specific examples of the binder (F) include those having adhesiveness among the constituent resins of the hot-melt particles (C) and the swellable particles (D).

  The thickness of the separator according to the wound electrode group of aspects (1) and (3), which are independent films, is 3 μm or more, more preferably 5 μm or more, and 50 μm or less, more preferably 30 μm or less. desirable. If the separator is too thin, it may be difficult to completely prevent a short circuit, or the separator may be insufficient in strength and difficult to handle. On the other hand, if it is too thick, the energy density of the battery is small. Tend to be.

  Also, in the case of the separator according to the wound electrode group of the aspect (2) integrated with the electrode, in order to completely prevent a short circuit, a certain thickness or more is required, for example, 1 μm or more. More preferably, it has a thickness of 3 μm or more. In order to increase the energy density, it is desirable not to make the separator too thick. For example, it is preferably 20 μm or less, and more preferably 10 μm or less.

The porosity of the separator is desirably 15% or more, more preferably 20% or more, and 70% or less, more preferably 60% or less in a dry state. If the porosity of the separator is too small, the ion permeability may be reduced, and if the porosity is too large, the strength of the separator may be insufficient. The porosity of the separator: P (%) can be calculated by calculating the sum of each component i from the thickness of the separator, the mass per area, and the density of the constituent components using the following formula.
_{P = Σ a i ρ i /} (m / t)
Here, in the above formula, a _i : ratio of component i expressed by mass%, ρ _i : density of component i (g / cm ³ ), m: mass per unit area of separator (g / cm ² ), t: thickness of separator (cm).

Further, the air permeability of the separator, which is carried out by a method according to JIS P 8117 and indicated by the Gurley value indicated by the number of seconds in which 100 ml of air passes through the membrane under a pressure of 0.879 g / mm ² , is 10 to 10. It is desirable to be 300 sec. If the air permeability is too high, the ion permeability is reduced, whereas if it is too low, the strength of the separator may be reduced. Further, the strength of the separator is desirably 50 g or more in terms of piercing strength using a needle having a diameter of 1 mm. If the piercing strength is too low, a short circuit may occur due to the breakthrough of the separator when lithium dendrite crystals are generated.

  In the case where the electrode and the separator are integrated, the Gurley value and piercing strength of the separator can be measured by, for example, separating a liquid composition (slurry or the like) for manufacturing a separator, which will be described later, such as a PET film. It can be applied to form a separator film, peeled off from the film, and used for measurement.

  In any of the wound body electrode group of the aspect of (1), the wound body electrode group of the aspect of (2), and the wound body electrode group of the aspect of (3), the heat resistant particles (A) were contained. In the separator, the content of the heat-resistant particles (A) in the total volume of the constituent components of the separator is preferably 20% by volume or more, more preferably 30% by volume or more. By setting the volume ratio of the heat-resistant particles (A) to the above value, it is possible to provide a separator that can more effectively exhibit the function of the heat-resistant particles (A) and can prevent the occurrence of a short circuit. In addition, even if the volume ratio of the heat-resistant particles (A) in the separator is too large, the function of preventing the short circuit of the separator may be lowered, so the upper limit of the volume ratio of the heat-resistant particles (A) in the separator is For example, it is preferably 80% by volume.

  Moreover, in the separator using a fibrous material (B), it is preferable that the content rate of the fibrous material (B) in the whole volume of the structural component of a separator shall be 30-80 volume%. Furthermore, in the separator using one or more of the heat-meltable particles (C), the swellable particles (D), and the composite particles (E), the total content of these particles in the total volume of the constituent components of the separator is 10 to 10. It is preferable to set it as 50 volume%. And it is preferable that the content rate of the binder (F) in the whole volume of the structural component of a separator is 1-10 volume%.

  As a manufacturing method of the separator used for the wound body electrode group of this invention, the method of following (I), (II) and (III) is mentioned, for example. The method (I) is a production method in which a liquid composition (slurry or the like) containing the heat-resistant particles (A) is applied to or impregnated into an ion-permeable sheet material and then dried at a predetermined temperature. By this method, the separator which can be used for the wound body electrode group of the aspects of (1) and (3) can be manufactured.

  The “sheet-like product” in the method (I) corresponds to a sheet-like product (woven fabric, non-woven fabric, etc.) composed of the fibrous product (B). Specifically, a porous sheet such as a non-woven fabric having a structure in which at least one of the above-exemplified materials is included as a constituent component and the fibrous materials are entangled with each other can be used. More specifically, non-woven fabrics such as paper, PP non-woven fabric, polyester non-woven fabric (PET non-woven fabric, PEN non-woven fabric, PBT non-woven fabric, etc.), PAN non-woven fabric, and PVA non-woven fabric can be exemplified.

The thickness of the woven fabric or nonwoven fabric used for the separator is preferably 20 μm or less, and more preferably 16 μm or less. The basis weight is preferably 15 g / m ² or less, and more preferably 10 g / m ² or less. The lower limit of the thickness is preferably 5 μm, and the lower limit of the basis weight is preferably 2 g / m ² . As a method for producing the nonwoven fabric, conventionally known methods can be used, and specifically, methods such as wet, dry, melt blow, spun bond, and charge melt spinning can be used.

  The liquid composition for forming the separator is composed of heat-resistant particles (A) and, if necessary, heat-meltable particles (C), swellable particles (D), composite particles (E), and binders (F). And these are dispersed or dissolved in a solvent (including a dispersion medium, the same applies hereinafter). The solvent used in the liquid composition can uniformly disperse the heat-resistant particles (A), the hot-melt particles (C), the swellable particles (D), the composite particles (E), etc. Organic solvents such as aromatic hydrocarbons such as toluene; furans such as tetrahydrofuran; ketones such as methyl ethyl ketone and methyl isobutyl ketone; are suitable as long as they can be dissolved or dispersed uniformly. In addition, for the purpose of controlling the interfacial tension, alcohols (ethylene glycol, propylene glycol, etc.) or various propylene oxide glycol ethers such as monomethyl acetate may be appropriately added to these solvents. In addition, when the binder (F) is water-soluble or used as an emulsion, water may be used as a solvent. In this case, alcohols (methyl alcohol, ethyl alcohol, isopropyl alcohol, ethylene glycol, etc.) are appropriately used. In addition, the interfacial tension can be controlled.

  In the liquid composition, the solid content including the heat-resistant particles (A), the heat-meltable particles (C), the swellable particles (D), the composite particles (E), and the binder (F) is, for example, 10 to 40 mass. % Is preferable.

  The sheet-like material composed of the fibrous material (B) is composed of a fibrous material, such as a nonwoven fabric such as paper, PP nonwoven fabric, and polyester nonwoven fabric. When it is large (for example, when the opening diameter of the gap is 5 μm or more), this tends to cause a short circuit of the battery. Therefore, in this case, it is preferable to have a structure in which part or all of the heat-resistant particles (A) are present in the voids of the sheet-like material, whereby the occurrence of a short circuit can be further suppressed. In addition, when using the heat-meltable particles (C), the swellable particles (D), or the composite particles (E), a structure in which some or all of these particles are present in the voids of the sheet-like material. It is preferable, and thereby, the function of each particle can be exhibited more effectively.

  In order to allow the heat-resistant particles (A) and the like to be present in the voids of the sheet-like material, for example, after impregnating the above-mentioned liquid composition into the sheet, the excess liquid composition is removed through a certain gap. A process such as drying may be used. In addition, in the case where plate-like particles [heat-resistant particles (A), composite particles (E), etc.] are contained in the separator, the liquid composition is used in order to enhance the orientation and to effectively function the function. In the impregnated substrate, a method of applying a shear or a magnetic field to the liquid composition may be used. For example, as described above, the liquid composition can be sheared by impregnating the liquid composition into a sheet and then passing through a certain gap.

  The separator (II) is produced by adding the fibrous material (B) to the separator-producing liquid composition described in the method (I), and applying this to a substrate such as a film or metal foil. It is a method of peeling from the substrate after coating and drying at a predetermined temperature. That is, this is a method of simultaneously performing sheeting of the fibrous material (B) and adding heat-resistant particles (A) and the like. Also by this method, the separator which can be used for the wound body electrode group of the aspect of (1) and (3) can be manufactured similarly to the method of (I).

  The liquid composition used in the method (II) is the same as the liquid composition used in the method (I) except that it is essential to contain the fibrous material (B). In the separator obtained by the method (II), the heat-resistant particles (A) and other particles [heat-meltable particles (C ), Swellable particles (D), composite particles (E), and the like].

  The method for producing (III) of the separator includes, for example, a liquid composition for producing a separator described in the method (I) and a liquid composition for producing a separator described in the method (II), using an electrode (positive electrode and (Or negative electrode), and a separator is formed while drying and integrating with an electrode. By this method, a separator that can be used for the wound electrode group according to the embodiment (2) can be produced.

  Application | coating of the liquid composition on an electrode can be performed with the application | coating method using conventionally well-known coating apparatuses, such as a blade coater, a roll coater, a die coater, a spray coater, for example.

  In addition, the separator used for the wound body electrode group of this invention is not limited to said structure. For example, in a separator having a structure containing the heat-resistant particles (A), the heat-resistant particles (A) may not be present independently, and some of the heat-resistant particles (A) or the fibrous material (B) are partially present. May be fused.

  The separator produced by the above method (I), (II) or (III) is preferably subjected to a heat treatment after drying to remove volatile components such as moisture and solvent (dispersion medium) contained therein. . By removing these volatile components, the secondary battery can be prevented from being deteriorated in battery characteristics when charging and discharging are repeated, so that a secondary battery having excellent long-term reliability can be provided. The residual amount of moisture and solvent is desirably 100 ppm or less with respect to the separator.

  The temperature of the heat treatment is set to a temperature lower than the shutdown temperature of the separator when the heat-meltable particles (C) are contained in the separator. When heat treatment is performed at a temperature equal to or higher than the shutdown temperature, the pores of the separator are clogged. Therefore, the secondary battery using the wound electrode group provided with such a separator has inferior characteristics. If the separator does not contain heat-meltable particles (C), for example, if the shutdown function is ensured with the swellable particles (D), the shutdown characteristics are affected even if heat treatment is performed in a dry state, as described above. Therefore, the heat treatment temperature is not particularly limited as long as it is not higher than the thermal decomposition temperature of the resin.

  The specific heat treatment temperature is, for example, 70 to 140 ° C., and the heat treatment time is, for example, 1 hour or more, more preferably 3 hours or more, and 72 hours or less, more preferably 24 hours or less. It is desirable to do. Such heat treatment can be performed, for example, in a warm air circulation type thermostatic bath. Moreover, you may dry under reduced pressure using a vacuum dryer as needed.

  In any of the aspects (1), (2), and (3), the positive electrode and the negative electrode in the wound electrode group of the present invention are the above (i), (ii) or (iii) There is no particular limitation except that the specific portion is not involved in the charge / discharge reaction by a method such as the above, and the positive electrode and the negative electrode employed in a conventionally known secondary battery (lithium secondary battery) can be used. .

As the positive electrode, for example, as an active material, Li _{1 + x} MO ₂ (−0.1 <x <0.1, M: Co, Ni, Mn, etc.), a lithium-containing transition metal oxide; LiMn ₂ O Lithium manganese oxide such as ₄ ; LiMn _x M _(1-x) O _{2 in} which part of Mn of LiMn ₂ O ₄ is substituted with another element; olivine type LiMPO ₄ (M: Co, Ni, Mn, Fe); _{LiMn 0.5 Ni 0.5 O 2; Li} (1 + a) Mn x Ni y Co (1-x-y) O 2 (-0.1 <a <0.1,0 <x <0.5,0 <Y <0.5); can be applied, and a known conductive additive (carbon material such as carbon black) or a binder such as PVDF is appropriately added to these positive electrode active materials. The positive electrode material mixture is formed on both sides of the current collector as the core material (positive electrode active material). The material finished in the quality layer) can be used.

  As the current collector of the positive electrode, a metal foil such as aluminum, a punching metal, a net, an expanded metal, or the like can be used. Usually, an aluminum foil having a thickness of 10 to 30 μm is preferably used.

  The lead portion on the positive electrode side is usually provided by leaving the exposed portion of the current collector without forming the positive electrode active material layer on a part of the current collector and forming the lead portion at the time of producing the positive electrode. However, the lead portion is not necessarily integrated with the current collector from the beginning, and may be provided by connecting an aluminum foil or the like to the current collector later.

  As the negative electrode, for example, as active material, graphite, pyrolytic carbons, cokes, glassy carbons, organic polymer compound fired bodies, mesocarbon microbeads (MCMB), carbon fibers, etc., occlude lithium, One or a mixture of two or more releasable carbon-based materials is used. In addition, elements such as Si, Sn, Ge, Bi, Sb, In and their alloys, lithium-containing nitrides, oxides and other compounds that can be charged and discharged at a low voltage close to lithium metal, or lithium metals and lithium / aluminum alloys Can also be used as a negative electrode active material. A negative electrode mixture obtained by appropriately adding a conductive additive (carbon material such as carbon black) or a binder such as PVDF to these negative electrode active materials is formed on both surfaces of the current collector as a core material (negative electrode active material). In addition to the finished material-containing layer, a material obtained by forming the above-described various alloys or lithium metal foils (which become the negative electrode active material-containing layer) on both surfaces of the current collector may be used.

  As the current collector for the negative electrode, a foil made of copper or nickel, a punching metal, a net, an expanded metal, or the like can be used, but a copper foil is usually used. In the negative electrode current collector, when the thickness of the entire negative electrode is reduced in order to obtain a battery having a high energy density, the upper limit of the thickness is preferably 30 μm, and the lower limit is preferably 5 μm.

  The lead part on the negative electrode side, like the lead part on the positive electrode side, usually leaves an exposed part of the current collector without forming a negative electrode active material-containing layer on a part of the current collector during the preparation of the negative electrode. The lead portion is provided. However, the lead portion on the negative electrode side is not necessarily integrated with the current collector from the beginning, and may be provided by connecting a copper foil or the like to the current collector later.

  In any of the aspects (1), (2), and (3), a positive electrode and a negative electrode are laminated through a separator in accordance with a conventional method to form a laminate, which is then wound in a spiral shape. Then, it is crushed flat to form a wound body electrode group having a structure shown in FIG. In the wound electrode group of the present invention, even if the bending diameter at the innermost peripheral portion is as high as 0.1 to 0.5 mm, a short circuit that can occur at the innermost facing portion of the bending portion. Thus, a secondary battery having excellent reliability can be configured.

  The battery of the present invention is a prismatic secondary battery (rectangular lithium secondary battery) having a structure in which the wound electrode group of the present invention is enclosed in an outer can such as a square steel can or an aluminum can together with an electrolytic solution, Alternatively, a laminate type secondary battery (laminated lithium secondary battery) having a structure in which the wound electrode group of the present invention is encapsulated in an exterior material configured by laminating a metal-deposited laminate sheet in the form of a bag. It is.

  In addition, as an outer can in the case of a square secondary battery, the ratio of width to thickness is about 5 to 10 with respect to the thickness 1, and the wound body electrode group of the present invention is like this. Even when applied to a thin prismatic battery having a large width to thickness ratio, it is possible to prevent occurrence of a short circuit due to lithium dendrite in the innermost curved portion, and it is possible to configure a battery with excellent reliability.

As described above, a solution obtained by dissolving a lithium salt in an organic solvent is used as the nonaqueous electrolytic solution. The lithium salt is not particularly limited as long as it dissociates in a solvent to form Li ⁺ ions and does not cause a side reaction such as decomposition in a voltage range used as a battery. For example, inorganic lithium salts such as LiClO ₄ , LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiSbF ₆ ; LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , Li ₂ C ₂ F ₄ (SO ₃ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiC _n F _{2n + 1} SO ₃ (n ≧ 2), LiN (RfOSO ₂ ) ₂ [where Rf is a fluoroalkyl group]; it can.

  The organic solvent used in the electrolytic solution is not particularly limited as long as it dissolves the above lithium salt and does not cause side reactions such as decomposition in the voltage range used as a battery. For example, cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate and vinylene carbonate; chain carbonates such as dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate; chain esters such as methyl propionate; cyclic esters such as γ-butyrolactone; Chain ethers such as ethane, diethyl ether, 1,3-dioxolane, diglyme, triglyme and tetraglyme; cyclic ethers such as dioxane, tetrahydrofuran and 2-methyltetrahydrofuran; nitriles such as acetonitrile, propionitrile and methoxypropionitrile; Sulfites such as ethylene glycol sulfite; and the like, and these may be used alone. , It may be used in combination of two or more thereof. In order to obtain a battery with better characteristics, it is desirable to use a combination that can obtain high conductivity, such as a mixed solvent of ethylene carbonate and chain carbonate. In addition, for the purpose of improving the safety, charge / discharge cycleability, and high-temperature storage properties of these electrolytes, vinylene carbonates, 1,3-propane sultone, diphenyl disulfide, cyclohexane, biphenyl, fluorobenzene, t- Additives such as butylbenzene can also be added as appropriate.

  The concentration of the lithium salt in the electrolytic solution is preferably 0.5 to 1.5 mol / l, and more preferably 0.9 to 1.25 mol / l.

  In addition, instead of the above organic solvent, melting at room temperature such as ethyl-methylimidazolium trifluoromethylsulfonium imide, heptyl-trimethylammonium trifluoromethylsulfonium imide, pyridinium trifluoromethylsulfonium imide, guanidinium trifluoromethylsulfonium imide A salt can also be used.

  Furthermore, a polymer material that contains the above non-aqueous electrolyte and gels may be added, and the non-aqueous electrolyte may be gelled and used for a battery. Polymer materials for making the non-aqueous electrolyte into a gel include PVDF, PVDF-HFP, PAN, polyethylene oxide, polypropylene oxide, ethylene oxide-propylene oxide copolymer, crosslink having ethylene oxide chain in the main chain or side chain Known host polymers capable of forming a gel electrolyte, such as polymers and cross-linked poly (meth) acrylates, can be mentioned.

  The prismatic secondary battery and the laminated secondary battery of the present invention can be applied to the same applications as those in which conventionally known lithium secondary batteries are used.

  Hereinafter, the present invention will be described in detail based on examples. However, the following examples are not intended to limit the present invention, and all modifications made without departing from the spirit of the preceding and following descriptions are included in the technical scope of the present invention.

Production Example 1
<Production of negative electrode>
Graphite as negative electrode active material: Latex mainly composed of SBR is dispersed in a slurry in which 95 parts by mass and an aqueous solution in which CMC is dissolved, and adjusted so that the solid content of CMC and SBR is 5 parts by mass, respectively. Thus, a negative electrode mixture-containing paste was prepared. This negative electrode mixture-containing paste was intermittently applied to both sides of a 10 μm thick current collector made of copper foil so that the active material application length was 320 mm on the front surface and 260 mm on the back surface, dried, and then subjected to calendar treatment. The thickness of the negative electrode active material-containing layer was adjusted so that the total thickness was 142 μm, and the negative electrode was cut to have a width of 45 mm to produce a negative electrode having a length of 330 mm and a width of 45 mm. Further, a tab was welded to the exposed portion of the copper foil of the negative electrode to form a lead portion.

Production Example 2
<Preparation of positive electrode>
85 parts by mass of LiCoO _{2 as a} positive electrode active material, 10 parts by mass of acetylene black as a conductive additive, and 5 parts by mass of PVDF as a binder are uniformly mixed with N-methyl-2-pyrrolidone (NMP) as a solvent. It mixed so that positive electrode mixture containing paste might be prepared. This paste was intermittently applied on both sides of a 15 μm thick aluminum foil serving as a current collector so that the active material application length was 319 to 320 mm on the front surface and 258 to 260 mm on the back surface, dried, and then subjected to calendar treatment. The thickness of the positive electrode mixture layer was adjusted so that the total thickness was 150 μm, and the positive electrode mixture layer was cut to a width of 43 mm to produce a positive electrode having a length of 330 mm and a width of 43 mm. Further, a tab was welded to the exposed portion of the aluminum foil of the positive electrode to form a lead portion.

Production Example 3
<Preparation of separator>
Alumina (Al ₂ O ₃ ) fine particles (average particle size 1.5 μm) as heat-resistant particles (A): 1000 g, water: 800 g, isopropyl alcohol (IPA): 200 g, and PVB [Sekisui Chemical Co., Ltd.] as binder (F) “S Lek KX-5 (trade name)” manufactured by the company: 375 g was put in a container and dispersed by stirring for 1 hour with a three-one motor to form a uniform slurry. In this slurry, a PP meltblown nonwoven fabric with a thickness of 15 μm was placed. The slurry was applied by pulling up and then dried to obtain a separator having a thickness of 20 μm.

Production Example 4
<Preparation of separator>
Plate boehmite (average particle diameter 1 μm, aspect ratio 10): 1000 g, water: 800 g, isopropyl alcohol (IPA) 200 g, and PVB [Sekisui Chemical Co., Ltd. KX-5 (trade name)]]: 375 g was put in a container, and stirred and dispersed with a three-one motor for 1 hour to obtain a uniform slurry. Into this slurry, 800 g of an emulsion containing PE as a heat-meltable particle (C) (average particle size 1 μm, melting point 125 ° C.) was added, and a PP meltblown nonwoven fabric with a thickness of 15 μm was passed through this slurry, and then pulled up. After applying the slurry, the gap was passed through a gap having a predetermined interval and then dried to obtain a separator having a thickness of 20 μm.

Production Example 5
<Preparation of separator>
SBR latex [JSR “TRD-2001 (trade name)”]: 100 g and CMC (Daicel Chemical “2200”): 30 g and water: 4000 g are uniformly dissolved in a container (F). Stir until room temperature. Further, as a swellable particle (D), an aqueous dispersion of crosslinked PMMA (average particle size 0.3 μm, B _R = 0.5, B = 4): 2500 g was added, and the mixture was stirred with a disper at 2800 rpm for 1 hour. And dispersed. To this, 3000 g of plate boehmite (average particle size 1 μm, aspect ratio 10): 3000 g was added as heat-resistant particles (A), and stirred with a disper at 2800 rpm for 3 hours to obtain a uniform slurry. Using an applicator, this slurry was applied onto a wet PP nonwoven fabric having a gap of 50 μm and a thickness of 23 μm, and dried to obtain a separator having a thickness of 30 μm.

Production Example 6
<Preparation of separator integrated with negative electrode>
EVA as a binder (F) (structural unit derived from vinyl acetate is 15 mol%): 100 g and 6000 g of toluene were placed in a container and stirred at room temperature until evenly dissolved. Further, 3000 g of PE powder (average particle size 5 μm, melting point 105 ° C.): 3000 g was added as hot-melt particles (C) and dispersed with a disper at 2800 rpm for 1 hour. Thereafter, 300 g of alumina (Al ₂ O ₃ ) fine particles (average particle size 0.4 μm) as heat-resistant particles (A) was added, and the mixture was stirred with a disper at 2800 rpm for 3 hours to prepare a uniform slurry. After applying this slurry on the negative electrode produced in Production Example 1 using a die coater, toluene was removed to obtain a negative electrode in which a separator having a thickness of 15 μm was integrally formed.

Production Example 7
<Preparation of Positive Electrode Having Insulating Layer in Part Between Current Collector and Positive Electrode Active Material Containing Layer>
In the case where the wound body electrode group is used, a portion having a width of 5 mm is preliminarily placed on the current collector at a position where it is planned to be located inside the innermost facing portion (the facing portion on the inner peripheral end side) of the curved portion. A positive electrode was produced in the same manner as in Production Example 2, except that an insulating layer was formed. The insulating layer on the current collector is coated with the slurry prepared for manufacturing the separator in Production Example 3 on the current collector using the applicator and dried to obtain a size of 5 mm in width and 5 μm in thickness. Formed.

Example 1
The negative electrode produced in Production Example 1 and the positive electrode produced in Production Example 2 were laminated via the separator produced in Production Example 4, wound in a spiral shape, then crushed into a flat shape, and flattened winding A body electrode group was prepared. At that time, a polyimide tape having a width of 5 mm is pasted as an insulating layer inside the facing portion (the facing portion on the inner peripheral end side) with the larger curvature among the facing portions on the innermost peripheral side in the curved portion of the positive electrode. As shown in FIGS. 2 and 3, the positive electrode active material-containing layer does not directly face the negative electrode (only through the separator) at the opposite curvature portion of the innermost circumferential facing portion. The structure. The obtained wound body electrode group was loaded in a laminate film exterior material, and an electrolyte (LiPF ₆ was added at a concentration of 1.2 mol / l in a solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 1: 2). The solution was dissolved in and vacuum-sealed to produce a laminated secondary battery.

Example 2
The negative electrode produced in Production Example 1 and the positive electrode produced in Production Example 7 are laminated via the separator produced in Production Example 5, wound in a spiral shape, and then crushed into a flat shape, as shown in FIGS. A wound electrode group having the structure shown in FIG. Using the obtained wound electrode group, a laminated secondary battery was produced in the same manner as in Example 1.

Example 3
The separator side of the negative electrode having the separator produced in Production Example 6 and the positive electrode produced in Production Example 2 are laminated, wound in a spiral shape, and then crushed into a flat shape to form a flat wound electrode group. Produced. At that time, as shown in FIG. 6, the active material-containing layer surface inside the positive electrode, the inner peripheral end portion of the positive electrode, and the outer peripheral end portion of the negative electrode at the two innermost opposing portions of the curved portions, A polyimide tape was applied. Using the obtained wound electrode group, a laminated secondary battery was produced in the same manner as in Example 1.

Example 4
The negative electrode produced in Production Example 1 and the positive electrode produced in Production Example 2 were laminated via the separator produced in Production Example 3, wound in a spiral shape, then crushed into a flat shape, and flattened winding A body electrode group was prepared. At that time, a solid portion having a width of 5 mm is provided by removing the active material-containing layer of the positive electrode in a portion where the positive electrode and the negative electrode on the innermost side of the curved portion face each other, as shown in FIGS. A wound electrode group having a structure was obtained. Using the obtained wound electrode group, a laminated secondary battery was produced in the same manner as in Example 1.

Comparative Example 1
Among the opposed parts on the most inner peripheral side in the curved part of the positive electrode, except that the polyimide tape that becomes the insulating layer is not affixed inside the opposed part (opposed part on the inner peripheral end side) with the larger curvature, A laminated secondary battery was produced in the same manner as in Example 1.

Comparative Example 2
The polyimide tape was not applied to the active material-containing layer surface inside the positive electrode, the inner peripheral edge of the positive electrode, and the outer peripheral edge of the negative electrode at the two innermost peripheral portions of both curved portions. A laminated secondary battery was produced in the same manner as in Example 3 except for the above.

Comparative Example 3
A laminated secondary battery was produced in the same manner as in Example 1 except that a polyethylene microporous film having a thickness of 20 μm was used as the separator.

  The following evaluation was performed about the laminated secondary battery of Examples 1-4 and Comparative Examples 1-3. The results are shown in Table 1.

<Charge / discharge efficiency>
About each battery of Examples 1-4 and Comparative Examples 1-3, constant current charging at 0.2 C (up to 4.2 V) and charging by constant voltage charging at 4.2 V (constant current charging and constant voltage charging) After a total time of 15 hours), the battery was discharged at 0.2 C up to 3.0 V, and charge / discharge efficiency (ratio of discharge capacity to charge capacity) was determined. In addition, charging / discharging efficiency was calculated | required as an average value of 10 batteries, respectively.

<Reliability test>
The batteries of Examples 1 to 4 and Comparative Examples 1 to 3 were left in a high-temperature layer at 150 ° C., the time until the function of the battery was lost was measured, and a reliability test at a high temperature was performed.

  As can be seen from Table 1, in the laminated secondary batteries of Examples 1 to 4, the charge / discharge efficiency was good and at a practical level. On the other hand, the batteries of Comparative Examples 1 and 2 had low charge / discharge efficiency, did not reach a practical level, and had insufficient reliability. Further, when the batteries of Examples 1 to 4 were left at 150 ° C., the time until the function of the battery was lost due to heat generation or the like was longer than that of the battery of Comparative Example 3 corresponding to the conventionally known battery, and the temperature was high. Reliability and safety in the environment were improved.

It is a principal part cross-sectional enlarged view of a wound body electrode group. It is a cross-sectional schematic diagram which shows an example of the wound body electrode group of this invention. FIG. 3 is an enlarged view of a main part of FIG. 2. It is a cross-sectional schematic diagram which shows the other example of the wound body electrode group of this invention. It is a principal part enlarged view of FIG. It is a cross-sectional schematic diagram which shows the other example of the wound body electrode group of this invention. It is a principal part enlarged view of FIG. It is a cross-sectional schematic diagram which shows the other example of the wound body electrode group of this invention.

Explanation of symbols

10, 11, 12, 13, 14 Rolled electrode group 20 Positive electrode 21 Positive electrode active material-containing layer 22 Positive electrode current collector 30 Negative electrode 31 Negative electrode active material-containing layer 32 Negative electrode current collector 40 Separator 50 Insulating layer (insulating tape)
60 Solid part 100 Curved part

Claims (18)

A positive electrode having an active material-containing layer on both sides of a current collector and a negative electrode having an active material-containing layer on both sides of the current collector are laminated via a separator containing at least electrically insulating heat-resistant particles. The laminated body is a wound body electrode group for a secondary battery wound in a spiral shape,
The wound body electrode group is flat,
And in at least one of the curved portions at both ends in the major axis direction, the most innermost facing portion of the facing portions where the active material-containing layer of the positive electrode and the active material-containing layer of the negative electrode face each other A wound electrode group, wherein the part does not participate in the charge / discharge reaction. A positive electrode having an active material-containing layer on both sides of the current collector, a negative electrode having an active material-containing layer on both sides of the current collector, and a separator formed integrally on the surface of the positive electrode and / or the negative electrode; A laminated body in which the positive electrode and the negative electrode are laminated via the separator is a wound battery electrode group for a secondary battery wound in a spiral shape,
The wound body electrode group is flat,
And in at least one of the curved portions at both ends in the major axis direction, the most innermost facing portion of the facing portions where the active material-containing layer of the positive electrode and the active material-containing layer of the negative electrode face each other A wound electrode group, wherein the part does not participate in the charge / discharge reaction.   The wound body electrode group according to claim 1 or 2, wherein at least the facing portion having the larger curvature among the facing portions on the innermost side does not participate in the charge / discharge reaction.   The wound body electrode group according to any one of claims 1 to 3, wherein a surface of the positive electrode and / or the negative electrode is coated with an electrically insulating material at the facing portion not involved in the charge / discharge reaction.   The positive electrode and / or the negative electrode have an insulating layer made of an electrically insulating material between the current collector and the active material-containing layer in the facing portion that does not participate in charging / discharging. The wound body electrode group in any one. A positive electrode having an active material-containing layer on both sides of a current collector and a negative electrode having an active material-containing layer on both sides of the current collector are laminated via a separator containing at least electrically insulating heat-resistant particles. The laminated body is a wound body electrode group for a secondary battery wound in a spiral shape,
The wound body electrode group is flat,
And in at least one of the curved portions at both ends in the major axis direction, the portion where the positive electrode and the negative electrode face each other on the innermost peripheral side has at least a plain portion where no active material-containing layer of the positive electrode exists. ,
The wound body electrode, characterized in that the positive electrode active material-containing layer and the negative electrode active material-containing layer are opposed to each other on the inner terminal side from the plain portion and have a facing portion capable of charge / discharge reaction. group.   A plain part without an active material-containing layer is provided on the inner side of the positive or negative electrode located on the innermost inner circumference, and is located on the innermost inner circumference in the terminal part of the negative or positive electrode located on the outermost inner circumference. The wound body electrode group according to claim 1, wherein a portion facing the positive electrode or the negative electrode is coated with an electrically insulating material.   The positive electrode located outside the outermost periphery is provided with a solid portion outside the active material-containing layer on the outer side of the positive electrode or negative electrode, and the positive electrode located outside the outermost periphery in the negative electrode located at the outermost outer periphery or the terminal portion of the positive electrode The wound body electrode group according to any one of claims 1 to 7, wherein a portion facing the negative electrode is coated with an electrically insulating material.   The wound body electrode group according to any one of claims 1 to 8, wherein the width of the negative electrode is equal to or greater than the width of the positive electrode.   The wound body electrode group according to any one of claims 2 to 5 and 7 to 9, wherein a separator is integrally formed on at least the negative electrode surface.   The wound body electrode group according to any one of claims 1 to 10, wherein the separator has a sheet-like material composed of a fibrous material.   The wound electrode group according to claim 11, wherein the sheet-like material composed of the fibrous material is a woven or non-woven fabric of fibers.   The wound body electrode group according to claim 11 or 12, wherein some or all of the heat-resistant particles are present in the voids of the sheet-like material composed of the fibrous material.   The wound body electrode group according to any one of claims 1 to 13, wherein the separator contains particles that melt at 80 to 130 ° C.   The wound body electrode group according to any one of claims 1 to 14, wherein the separator contains particles that can swell in a non-aqueous electrolyte and whose degree of swelling increases with an increase in temperature. The wound electrode group according to claim 15, wherein particles that can swell with a non-aqueous electrolyte and have a degree of swelling increased by an increase in temperature have a degree of swelling B defined by the following formula of 1 or more.
_{B = (V 1 / V 0} ) -1
[In the above formula, V ₀ is the volume of particles (cm ³ ) 24 hours after being introduced into the non-aqueous electrolyte at 25 ° C., and V ₁ is 24 after being introduced into the non-aqueous electrolyte at 25 ° C. The temperature of the non-aqueous electrolyte is raised to 120 ° C. after time, and the volume (cm ³ ) of the particles after 1 hour at 120 ° C. is meant. ]   A prismatic secondary battery, wherein the wound electrode group according to any one of claims 1 to 16 is enclosed in a prismatic outer can. A laminated secondary battery, wherein the wound electrode group according to any one of claims 1 to 16 is enclosed in a bag-like laminate sheet.

Images