JP2007273127A - Non-aqueous secondary battery - Google Patents

Abstract

[Problem] By interposing a thermally expandable microcapsule capable of thermal expansion with quick response, it is possible to suppress the loss of insulation of a separator even when a sudden exothermic reaction occurs due to an internal short circuit or the like. An object of the present invention is to provide a non-aqueous secondary battery capable of avoiding a situation that causes explosion, ignition and the like.
A heat-expandable microcapsule is included in at least an interface between a separator 9 or a positive electrode plate 5 or a negative electrode plate 7 and a separator 9 of an electrode group 4 constituting a non-aqueous secondary battery. is there.
[Selection] Figure 1

Description

  The present invention relates to a non-aqueous secondary battery represented by a lithium ion battery, and more particularly to a non-aqueous secondary battery with improved safety.

In recent years, lithium secondary batteries, which are widely used as power sources for portable electronic devices, use a carbonaceous material capable of occluding and releasing lithium for the negative electrode and a composite oxidation of transition metal such as LiCoO ₂ and lithium for the positive electrode. In this way, secondary batteries with high potential and high discharge capacity have been realized. However, with the recent increase in functionality of electronic devices and communication devices, higher capacities are desired. ing. In these lithium secondary batteries, while increasing capacity, importance should be given to safety measures, and in particular, it is extremely important to suppress rapid temperature rise due to internal short circuit between the positive electrode plate and the negative electrode plate. .
Conventionally, as a countermeasure, a separator is generally formed using an olefin polymer such as polyethylene (PE) or polypropylene (PP), and this is interposed between a positive electrode plate and a negative electrode plate. Safety is ensured by closing the micropores of the separator (shutdown function) by heat generated by excessive current flowing in the secondary battery. However, when a polymer with a melting point of 120-170 ° C. such as polyethylene (PE) or polypropylene (PP) is used for the separator, if the temperature continues to rise even after shutdown, the separator itself melts, and the current interruption function There is a problem that disappears.
As a means for chemically suppressing the battery reaction, the alkali metal or alkaline earth metal anhydrous salt is enclosed in an electrolyte-resistant microcapsule and stored in the battery as a means for chemically suppressing the battery reaction. It has been proposed to reduce the activity of fire and to provide fire extinguishing power against ignition (see, for example, Patent Document 1).
Next, as another chemical suppression means, the microcapsules that release a chemical substance having a hydroxyl group or a chemical substance that is a polymerization initiator are dispersed in the electrolyte or separator to solidify the electrolyte when the temperature rises. Has been proposed (see, for example, Patent Document 2).

  In addition, as another chemical suppression means, heat-denatured polymer or electropolymerizable monomer that cures by overcharge, overdischarge, or temperature rise is sealed in microcapsules and added to the electrolyte, increasing the temperature. Sometimes it has been proposed to cure the electrolyte (see, for example, Patent Document 3).

  Furthermore, as another chemical suppression means, as shown in FIG. 5, the surface of the positive electrode active material layer 32 formed on the positive electrode current collector 31 or the surface of the negative electrode active material layer 35 formed on the negative electrode current collector 34 is used. On at least one surface, a thermoplastic or thermosetting resin 36, a solvent A that dissolves the thermoplastic or thermosetting resin, a solvent B that does not dissolve the thermoplastic or thermosetting resin, a flame retardant, It has been proposed to use a separator 33 in which a porous film is formed by applying a solution containing porous microcapsules 37 encapsulating an anti-inflammatory agent and drying (see, for example, Patent Document 4).

  On the other hand, as shown in FIG. 6, as a means for interrupting current in the event of an abnormality, on the surface of a hollow balloon formed of a thermoplastic resin partition wall having a melting point in the range of 120 to 170 ° C. on a thermosensitive resistor (not shown). After forming the heat sensitive resistor layer 43 composed of conductive microbeads coated with nickel or copper on the surface of the positive electrode current collector 41, the positive electrode active material layer 44 is formed, and the surface of the negative electrode current collector 42 is also formed. It is proposed that the negative electrode active material layer 45 is formed after the heat sensitive resistor layer 43 is formed, and the resistance value is increased when the temperature rises by winding it in a spiral shape via the separator 46 therebetween. (For example, refer to Patent Document 5).

Further, as another means for interrupting current, as shown in FIG. 7, a positive electrode mixture layer 56 made of a positive electrode active material (not shown) is sandwiched between a positive electrode current collector 57 and a separator 55, and The negative electrode mixture layer 52 containing the thermally expandable microcapsule 34 in the negative electrode mixture layer 52 or at the interface between the negative electrode mixture layer 52 and the negative electrode current collector 53 is interposed between the negative electrode current collector 53 and the separator 55. It has been proposed that the current is interrupted by sudden resistance increase when the temperature rises (see, for example, Patent Document 6).
JP-A-63-86355 JP-A-6-283206 Japanese Patent Laid-Open No. 9-45369 JP 2004-119132 A Japanese Patent Laid-Open No. 10-50294 JP 2001-332245 A

  However, in the above-described conventional technology that chemically suppresses the battery reaction or cuts off the current when there is an abnormality, when the temperature of the battery rises due to an internal short circuit, etc., it responds to the temperature rise at a fast response speed and is effective in thermal runaway of the battery reaction. It had the problem that it was difficult to prevent it.

  More specifically, in the conventional techniques for chemically suppressing the battery reaction in Patent Documents 1 to 4 described above, the inclusion material of the microcapsule is not effectively released or included when the battery temperature rises due to an internal short circuit or the like. Even if the release of the substance does not catch up with the temperature rise of the battery, or if the encapsulated substance is released, it is difficult to exert the battery reaction suppression effect caused by this suddenly. Effective deterrence is difficult.

  Moreover, in the prior art which physically inhibits the conductive state in the battery in Patent Documents 5 to 6 described above, the adhesion between the active material mixture and the current collector in the electrode plate is increased while the charge / discharge reaction is repeated. There is a concern that the electrical conductivity in the active material mixture may be reduced, or as a result, battery characteristics such as cycle characteristics may be deteriorated.

  The present invention has been made in view of the above-described conventional problems. Even when a sudden exothermic reaction occurs due to an internal short circuit or the like by interposing a thermally expandable microcapsule at the interface between the separator or the electrode plate and the separator. This microcapsule is capable of thermal expansion with quick response to heat generation, prevents the separator from losing its insulating properties, and can prevent the occurrence of explosion, ignition, etc. A non-aqueous secondary battery is provided.

  In order to solve the above-described conventional problems, the non-aqueous secondary battery of the present invention is obtained by kneading and dispersing at least an active material composed of a lithium-containing composite oxide, a conductive material, and a water-insoluble polymer binder. A positive electrode plate formed by applying a positive electrode mixture paint on a positive electrode current collector, an active material made of a material capable of holding at least lithium, and a water-insoluble polymer binder were kneaded and dispersed in a dispersion medium. A non-aqueous secondary battery comprising a negative electrode plate formed by applying a negative electrode mixture paint on a negative electrode current collector, a separator, and an electrolyte comprising a non-aqueous solvent, comprising at least a separator or a positive electrode plate or It is characterized by containing thermally expandable microcapsules at the interface between the negative electrode plate and the separator.

According to the non-aqueous secondary battery of the present invention, the microcapsule can be used even when a sudden exothermic reaction due to an internal short circuit occurs by interposing a thermally expandable microcapsule at the interface between the separator or the electrode plate and the separator. Thermal expansion can be achieved with fast response to heat generation, and the loss of the insulating properties of the separator can be suppressed, and a situation that causes explosion, ignition, etc. can be avoided.

  In the first invention of the present invention, a positive electrode current collector is prepared by mixing a positive electrode mixture paint obtained by kneading and dispersing an active material composed of at least a lithium-containing composite oxide, a conductive material, and a water-insoluble polymer binder in a dispersion medium. A negative electrode current collector comprising a positive electrode plate formed by coating on top thereof, and a negative electrode mixture paint obtained by kneading and dispersing an active material made of a material capable of holding at least lithium and a water-insoluble polymer binder in a dispersion medium A non-aqueous secondary battery comprising a negative electrode plate formed by coating on top, a separator, and an electrolyte comprising a non-aqueous solvent, wherein at least the separator, the positive electrode plate, or the interface between the negative electrode plate and the separator is heated. By containing the expandable microcapsules, even when a sudden exothermic reaction occurs due to an internal short circuit or the like, the microcapsules can be thermally expanded with a quick response to the heat generation. Suppress the insulating data is lost, explosion, it is possible to avoid a situation that causes ignition and the like.

  In the second invention of the present invention, as a means for containing the thermally expandable microcapsules in the separator, the microcapsules in the separator are obtained by dispersing and containing the thermally expandable microcapsules in heat-resistant organic fibers. However, it is possible to prevent the insulating property of the separator itself from being lost due to heat generation because the heat expands with quick response to heat generation.

  In the third invention of the present invention, the heat-resistant organic fiber is made of at least one resin selected from the group consisting of wholly aromatic polyamide, wholly aromatic polyester, aromatic polyetheramide, polyamideimide, and polybenzimidazole. By configuring, it is possible to further improve the heat resistance of the nonwoven fabric separator itself, in which heat-expandable microcapsules are dispersed in heat-resistant organic fibers, and it is more effective that the insulating property of the separator itself is lost due to heat generation. It can be deterred.

  In the fourth aspect of the present invention, as a means for containing thermally expandable microcapsules at the interface between the positive electrode plate or negative electrode plate and the separator, an insulator layer comprising at least the thermally expandable microcapsules and a binder is used. By coating and forming on the surface of the plate, the microcapsules in the insulator layer thermally expand with quick response to heat generation, and thus it is possible to prevent the insulation of the separator itself from being lost due to heat generation. .

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. For example, as shown in FIG. 1, in the non-aqueous secondary battery of the present invention, a separator 9 includes a positive electrode plate 5 using a composite lithium oxide as an active material and a negative electrode plate 7 using a material capable of holding lithium as an active material. After the electrode group 4 wound in a spiral shape is produced via the electrode, the electrode group 4 is housed in the bottomed cylindrical battery case 1 together with the insulating plate 15 and is led out from the lower part of the electrode group 4. 8 is connected to the bottom of the battery case 1, then the positive electrode lead 6 led out from the upper part of the electrode group 4 is connected to the sealing plate 2, and the battery case 1 has an electrolyte solution (not shown) made of a predetermined amount of nonaqueous solvent. Then, a sealing plate 2 having a sealing gasket 3 attached to the periphery is inserted into the opening of the battery case 1, and the opening of the battery case 1 is bent inward to seal it.

As shown in FIG. 2, in the separator 25 of the present invention, a positive electrode plate 21 composed of a positive electrode active material layer 21b formed on a counter positive electrode current collector 21a and a negative electrode active material layer 22b formed on a negative electrode current collector 22a. In order to suppress an internal short circuit with the negative electrode plate 22 made of the above, the separator 25 includes a thermally expandable microcapsule 23. The separator 25 includes the heat resistant organic fiber 24 and the thermally expandable microcapsule 23. If necessary, a dilute aqueous slurry having a concentration of 0.01 to 0.5% by weight containing a hot-melt resin (not shown) is prepared, and a web obtained by wet-making this slurry is used alone or laminated. Then, after drying, it can be produced by hot pressing.

  As shown in FIG. 3 and FIG. 4, as means for containing the thermally expandable microcapsule 23 at the interface between the positive electrode plate 21 or the negative electrode plate 22 and the separator 25, as shown in FIG. An insulator layer 27 made of a binder 26 containing the thermally expandable microcapsule 23 is formed on the surface of the material layer 21b, or as shown in FIG. 4, the thermally expandable microcapsule 23 is formed on the surface of the negative electrode active material layer 22b. It can be produced by applying and forming an insulator layer 27 made of a binder 26 containing bismuth.

  Here, the thermally expandable microcapsule 23 is constituted by an outer shell made of a thermoplastic resin in which an expansion agent is encapsulated. The heat-expandable microcapsule 23 has a temperature rise inside the battery for some reason. When the temperature reaches the softening temperature of the outer shell (hereinafter referred to as the shell wall softening point), the thermal expansion microcapsule 23 rapidly expands and has a volume of several. It will increase tenfold.

  Next, a method for producing the positive electrode plate 21 and the negative electrode plate 22 will be specifically described. First, the positive electrode plate 21 is not particularly limited, but a positive electrode active material, a conductive material, an aluminum or aluminum alloy foil or a positive electrode current collector 21a having a thickness of 5 μm to 30 μm subjected to lath processing or etching treatment, The positive electrode active material layer 21b is formed by applying, drying, and rolling a positive electrode mixture paint obtained by mixing and dispersing a binder with a dispersing machine such as a planetary mixer in a dispersion medium.

  Examples of the positive electrode active material include lithium cobaltate and modified products thereof (such as lithium cobaltate in which aluminum or magnesium is dissolved), lithium nickelate and modified products thereof (such as those obtained by partially replacing nickel with cobalt). And composite oxides such as lithium manganate and modified products thereof.

  As the conductive material at this time, for example, carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black and thermal black, and various graphites may be used alone or in combination.

  As the binder for the positive electrode at this time, for example, polyvinylidene fluoride (PVdF), a modified polyvinylidene fluoride, polytetrafluoroethylene (PTFE), a rubber particle binder having an acrylate unit, and the like can be used. At this time, an acrylate monomer or an acrylate oligomer into which a reactive functional group is introduced can be mixed in the binder.

  On the other hand, the negative electrode plate 22 is not particularly limited, but the negative electrode active material is formed on one or both sides of a negative electrode current collector 22a having a thickness of 5 μm to 25 μm made of rolled copper foil, electrolytic copper foil, lath processed or etched copper foil. The negative electrode active material layer is formed by applying, drying and rolling a negative electrode mixture 22b in which a binder, and if necessary, a conductive material and a thickener are mixed and dispersed in a dispersion medium by a dispersing machine such as a planetary mixer. It is produced by forming.

As the negative electrode active material, various natural graphites, artificial graphite, silicon-based composite materials such as silicide, and various alloy composition materials can be used.
Various binders such as PVDF and modified products thereof can be used as the binder for the negative electrode at this time. From the viewpoint of improving lithium ion acceptability, styrene-butadiene copolymer rubber particles (SBR) and modified products thereof are used. Etc. can also be used.
The thickener is not particularly limited as long as it is a material having viscosity as an aqueous solution such as polyethylene oxide (PEO) or polyvinyl alcohol (PVA), but cellulosic resins such as carboxymethyl cellulose (CMC) and modified products thereof may be used. From the viewpoint of dispersibility and thickening of the paint mixture, it is preferable.

Further, for the electrolytic solution, various lithium compounds such as LiPF ₆ and LIBF ₄ can be used as the electrolyte salt. Further, ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and methyl ethyl carbonate (MEC) can be used alone or in combination as a solvent. It is also preferable to use vinylene carbonate (VC), cyclohexylbenzene (CHB), and modified products thereof in order to form a good film on the positive and negative electrode plates and to ensure stability during overcharge.
An embodiment of the present invention will be described with reference to the drawings and tables.

  First, 100 parts by weight of lithium cobaltate as a positive electrode active material, 2 parts by weight of acetylene black as a conductive agent with respect to 100 parts by weight of the active material, and 2 parts by weight of polyvinylidene fluoride as a binder with respect to 100 parts by weight of the active material The mixture was stirred and kneaded with a suitable amount of N-methyl-2-pyrrolidone with a double-arm kneader to prepare a positive electrode mixture paint.

  Next, as shown in FIG. 2, this paint was applied to a 15 μm thick aluminum foil current collector 21a, and a positive electrode plate 21 having a single-sided mixture thickness of 100 μm after drying was produced. Further, by pressing the positive electrode plate 21 so as to have a total thickness of 165 μm, the positive electrode active material layer 21b is formed on the current collector 21a made of aluminum foil so that the thickness of one side of the mixture becomes 75 μm. The positive electrode plate 21 was produced by slitting to the specified width of the cylindrical battery shown in FIG.

  On the other hand, 100 parts by weight of artificial graphite as the negative electrode active material and 2.5 parts by weight (consolidated) of styrene-butadiene copolymer rubber particle dispersion (solid content 40% by weight) as the binder with respect to 100 parts by weight of the active material. 1 part by weight in terms of solid content of the adhesive), 1 part by weight of carboxymethyl cellulose as a thickener with respect to 100 parts by weight of the active material, and an appropriate amount of water, agitated in a double-arm kneader, A paint was made.

  Next, as shown in FIG. 2, this paint was applied to a 10 μm thick copper foil current collector 22 a, and a negative electrode plate 22 having a single-sided mixture thickness of 110 μm after drying was produced. Further, by pressing the negative electrode plate 22 so that the total thickness becomes 180 μm, the negative electrode active material layer 22b is formed on the copper foil current collector 22a so that the single-sided thickness of the mixture is 85 μm. The negative electrode plate 22 was manufactured by slitting to a specified width of the cylindrical lithium secondary battery shown in FIG.

  Further, as shown in FIG. 2, para-type wholly aromatic polyamide fiber having a pulp shape as heat-resistant organic fiber 24 is 90 weight, and high-density polyethylene pulp is 9.5 weight as hot-melt resin (not shown). Part, the thermal expansion microcapsule 23 having a shell wall softening point of 135 to 140 ° C. is mixed at a ratio of 0.5 wt. To prepare a dilute aqueous slurry having a concentration of 0.01 to 0.5 wt. A paint was made.

  Next, after the web obtained by wet papermaking of this separator mixture paint is dried alone or laminated, it is formed into a thickness of 20 μm by heating and pressing at a temperature that does not reach the shell wall softening point. The separator 25 was manufactured by slitting to a specified width of the cylindrical lithium secondary battery shown in FIG.

These positive electrode plate 21, negative electrode plate 22 and separator 25 are wound, cut to a predetermined length, inserted into a battery case, and 3 weights of 1M and VC of LiPF ₆ in an EC / DMC / MEC mixed solvent. A partially dissolved electrolyte solution was added and sealed to produce a cylindrical lithium ion secondary battery as shown in FIG.

  In the lithium secondary battery, in the event of abnormal heat generation of the battery, the shutdown function of the separator 25 works first at the melting temperature of the polyerylene, and then when the temperature becomes higher than that, the thermally expandable microcapsules 23 in the separator 25 become the shell wall softening point. And the structure is held by the heat-resistant organic fiber 24 in the separator 25, so that the positive electrode plate 21 and the negative electrode plate 22 can be kept in an insulating state, and after the heat generation A thermal runaway reaction in which the electrode plates are short-circuited is suppressed. The heat-resistant organic fiber 24 is selected from the group consisting of wholly aromatic polyamides, wholly aromatic polyesters, aromatic polyether amides, polyamide imides, and polybenzimidazoles in order to enhance the structure retention function when the temperature rises. More preferably, it is composed of at least one kind of resin.

  First, the positive electrode active material layer 21b was formed on the current collector 21a made of aluminum foil by the same method as in Example 1 using the positive electrode mixture paint similar to that in Example 1, and the positive electrode plate 21 was produced.

  Next, as shown in FIG. 3, as the insulator layer 27, 100 parts by weight of silica powder (not shown) having an average particle size of 1.0 μm and polyvinylidene fluoride (PVdF) 26 are added to 100 parts by weight of silica powder. 10 parts by weight, 1 part by weight of heat-expandable microcapsule 23 having a shell wall softening point of 135 to 140 ° C. with respect to 100 parts by weight of silica powder, together with an appropriate amount of N-methyl-2-pyrrolidone in a double arm kneader The insulating layer mixture paint was prepared by stirring and kneading. Furthermore, the insulator layer mixture paint was applied to and dried on the surface of the positive electrode plate 21 that had been subjected to pressing, thereby forming an insulator layer 27 having a thickness of 6 μm on the surface of the positive electrode plate 21.

  On the other hand, the negative electrode active material layer 22b was formed on the copper foil current collector 22a by the same method as in Example 1 using the negative electrode mixture paint similar to that in Example 1, thereby preparing the negative electrode plate 22. Here, as the separator 28, a polyethylene (PE) porous film having a thickness of 15 μm was used. The positive electrode plate 21, the negative electrode plate 22, and the separator 28 on which the insulator layer 27 was formed were wound, and a cylindrical lithium ion secondary battery as shown in FIG. .

  In the lithium secondary battery, when the battery is abnormally heated, the shutdown function of the separator 28 works first at the melting temperature of the polyerylene, and then when the temperature becomes higher than that, the thermally expandable microcapsules 23 in the insulator layer 27 form the shell wall. Since the structure expands rapidly at the softening point and the silica powder in the insulator layer 27 holds the structure, the positive electrode plate 21 and the negative electrode plate 22 can be kept in an insulating state. In addition, the thermal runaway reaction in which the electrode plates are short-circuited is suppressed.

  First, the positive electrode active material layer 21b was formed on the current collector 21a made of aluminum foil by the same method as in Example 1 using the positive electrode mixture paint similar to that in Example 1, and the positive electrode plate 21 was produced. On the other hand, the negative electrode active material layer 22b was formed on the copper foil current collector 22a by the same method as in Example 1 using the negative electrode mixture paint similar to that in Example 1, and the negative electrode plate 22 was produced.

  Next, as shown in FIG. 3, 100 parts by weight of alumina powder (not shown) having an average particle diameter of 1.0 μm and 10 parts by weight of polyvinylidene fluoride (PVdF) 26 are used as the insulator layer 27 with respect to 100 parts by weight of the alumina powder. 1 part by weight of heat-expandable microcapsule 23 having a shell wall softening point of 140 to 145 ° C. with 100 parts by weight of alumina powder and an appropriate amount of N-methyl-2-pyrrolidone is stirred in a double-arm kneader. The insulating layer mixture paint was prepared by kneading. Furthermore, the insulating layer mixture paint was applied to the surface of the negative electrode plate 22 that had been pressed and dried to form an insulating layer 27 having a thickness of 6 μm on the surface of the negative electrode plate 22. Here, as the separator 28, a polypropylene (PP) porous film having a thickness of 15 μm was used.

  The positive electrode plate 21, the negative electrode plate 22 on which the insulator layer 27 was formed, and the separator 28 were wound, and a cylindrical lithium ion secondary battery as shown in FIG.

  In the lithium secondary battery, when the battery is abnormally heated, the shutdown function of the separator 28 works first at the melting temperature of the polypropylene, and then when the temperature becomes higher than that, the thermally expandable microcapsules 23 in the insulator layer 27 soften the shell wall. Since the structure expands rapidly at the point and the structure is maintained with the alumina powder in the insulator layer 27, the positive electrode plate 21 and the negative electrode plate 22 can be kept in an insulating state. A thermal runaway reaction in which the electrode plates are short-circuited is suppressed.

  The non-aqueous secondary battery according to the present invention has this thermal expansibility even when a sudden exothermic reaction due to an internal short circuit occurs by interposing a thermal expansible microcapsule at the interface between the separator or the electrode plate and the separator. Microcapsules are capable of thermal expansion with quick response to heat generation, preventing the loss of separator insulation, avoiding the occurrence of explosions, fires, etc., and excellent safety Therefore, it is useful as a portable power source or the like for which a higher capacity is desired in accordance with the multifunctionalization of electronic devices and communication devices.

1 is an exploded cross-sectional view of a cylindrical secondary battery according to an embodiment of the present invention. The fragmentary sectional view which shows the electrode plate in one Embodiment of this invention The fragmentary sectional view which shows the electrode plate in another one Embodiment of this invention. The fragmentary sectional view which shows the electrode plate in another one Embodiment of this invention. Partial sectional view showing an electrode plate in a conventional example Exploded sectional view showing electrode group in conventional example Partial sectional view showing an electrode plate in a conventional example

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Battery case 2 Sealing plate 3 Gasket 4 Electrode group 5 Positive electrode plate 6 Positive electrode lead 7 Negative electrode plate 8 Negative electrode lead 9 Separator 15 Insulating plate 21 Positive electrode plate 21a Positive electrode collector 21b Positive electrode active material layer 22 Negative electrode plate 22a Negative electrode collector 22b Negative electrode active material layer 23 Thermally expandable microcapsule 24 Heat resistant organic fiber 25 Separator 26 Binder 27 Insulator layer 28 Separator

Claims (4)

  A positive electrode plate formed by applying a positive electrode mixture paint obtained by kneading and dispersing an active material composed of at least a lithium-containing composite oxide, a conductive material, and a water-insoluble polymer binder in a dispersion medium onto a positive electrode current collector And a negative electrode plate formed by coating a negative electrode current collector with a negative electrode mixture paint obtained by kneading and dispersing an active material made of a material capable of holding lithium and a water-insoluble polymer binder in a dispersion medium And a non-aqueous secondary battery comprising an electrolyte comprising a separator and a non-aqueous solvent, comprising at least a thermal-expandable microcapsule at an interface between the separator or the positive electrode plate or the negative electrode plate and the separator A non-aqueous secondary battery characterized by being made.   2. The non-aqueous secondary battery according to claim 1, wherein as the means for containing the thermally expandable microcapsules in the separator, the thermally expandable microcapsules are dispersed and contained in heat-resistant organic fibers to form a nonwoven fabric.   The heat-resistant organic fiber is composed of at least one resin selected from the group consisting of wholly aromatic polyamide, wholly aromatic polyester, aromatic polyetheramide, polyamideimide, and polybenzimidazole. Non-aqueous secondary battery. As a means for containing a thermally expandable microcapsule at the interface between the positive electrode plate or the negative electrode plate and the separator, an insulator layer composed of at least a thermally expandable microcapsule and a binder is applied and formed on the surface of the positive electrode plate or the negative electrode plate. The non-aqueous secondary battery according to claim 1.

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