KR102276260B1 - Microcapsule for rechargeable lithium battery, separator layer for rechargeable lithium battery, electrod for rechargeable lithium battery, electrod active material layer for rechargeable lithium battery, rechargeable lithium battery - Google Patents

Abstract

Provided is a microcapsule for a lithium secondary battery comprising a core part comprising a polymer of a foaming monomer, and a shell part covering the core part and having higher stability in the non-aqueous electrolyte secondary battery than the core part.

Description

A microcapsule for a lithium secondary battery, a separator layer for a lithium secondary battery comprising the same, an electrode for a lithium secondary battery, an electrode active material layer for a lithium secondary battery, and a lithium secondary battery ELECTROD ACTIVE MATERIAL LAYER FOR RECHARGEABLE LITHIUM BATTERY, RECHARGEABLE LITHIUM BATTERY}

It relates to a microcapsule for a lithium secondary battery, a separator for a lithium secondary battery including the same, an electrode for a lithium secondary battery, an electrode active material layer for a lithium secondary battery, and a lithium secondary battery.

For example, as disclosed in Japanese Patent Application Laid-Open No. 2007-273127, by containing thermally expandable microcapsules capable of thermal expansion in a nonwoven fabric using heat-resistant organic fibers, even when a rapid exothermic reaction due to an internal short circuit or the like occurs, the insulation of the separator It is known that a non-aqueous secondary battery capable of suppressing the loss can be provided. Thermally expandable microcapsules are often made of polystyrene or polyolefin (such as polyethylene or polypropylene).

However, conventional thermally expandable microcapsules have a problem that the particle diameter is large. For this reason, a lithium ion secondary battery in which thermally expansible microcapsules are disposed on an electrode or a separator has a problem in that the film thickness is increased.

Further, the thermally expansible microcapsules made of polystyrene are easily soluble in an electrolyte solution, and therefore, application to batteries has been difficult. On the other hand, polyolefins such as polyethylene and polypropylene have no problem in terms of electrolyte resistance, but since they are produced by extrusion molding after melt-kneading a foaming agent and polyolefin, it is difficult to produce sub-micron particles. there was

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to thin a non-aqueous electrolyte secondary battery, stably exist in the non-aqueous electrolyte secondary battery, and at the same time, when abnormal heat generation of the non-aqueous electrolyte secondary battery To provide a novel and simultaneously improved microcapsule for a nonaqueous electrolyte secondary battery, a separator for a nonaqueous electrolyte secondary battery, an electrode for a nonaqueous electrolyte secondary battery, an electrode active material layer for a nonaqueous electrolyte secondary battery, and a nonaqueous electrolyte secondary battery capable of ensuring insulation between electrodes .

According to one embodiment, a core portion comprising a polymer of a foamable monomer, and

Provided is a microcapsule for a lithium secondary battery covering the core part and including a shell part having higher stability in the non-aqueous electrolyte secondary battery than the core part.

The foamable monomer may include a diazo compound.

The diazo compound may be represented by the following formula (I).

[Formula Ⅰ]

In the above formula (I),

R1 is a hydrogen atom or a methyl group,

R2 is a hydrogen atom or a C1 to C6 alkyl group,

R3 is a hydrogen atom or a C1 to C6 alkyl group,

R4 is a hydrogen atom, a methyl group, an acryl group, a methacryl group or a glycidyl group,

X is a direct bond or a C1 to C6 alkylene group.

The diazo compound may be represented by the following Chemical Formula II.

[Formula II]

In the above formula (II),

R1 is a hydrogen atom or a methyl group,

R2 is a hydrogen atom or a C1 to C6 alkyl group,

A is a methylene group or a carbonyl group,

Q is a methylene group or a methine group,

T is a direct bond, a double bond, a methylene group, oxygen, or an NH group.

The foaming temperature of the microcapsule for a lithium secondary battery may be 120 °C or more and 250 °C or less.

The average particle diameter of the microcapsules for a lithium secondary battery may be 0.05 μm to 0.5 μm.

According to another embodiment, there is provided a separator layer for a lithium secondary battery comprising a separator and a microcapsule layer positioned on the separator, wherein the microcapsules are dispersed in the microcapsule layer.

The separator may be a heat-resistant separator.

The separator may include a nonwoven fabric, an amide-based compound, or a combination thereof.

According to another embodiment, there is provided an electrode for a lithium secondary battery comprising an electrode active material layer, and a microcapsule layer positioned on the electrode active material layer, wherein the microcapsules are dispersed in the microcapsule layer.

According to another embodiment, there is provided an electrode active material layer for a lithium secondary battery comprising an electrode active material and the microcapsules described above.

According to another embodiment, a lithium secondary comprising a core part including a positive electrode and a negative electrode, comprising a polymer of a foamable monomer, and a shell part covering the core part and having higher stability in the nonaqueous electrolyte secondary battery than the core part It provides an electrode assembly for a lithium secondary battery in which the battery microcapsule is present on the electrode plate of the positive electrode or the negative electrode.

According to another embodiment, a lithium secondary battery including the above-described separator layer is provided.

According to another embodiment, there is provided a lithium secondary battery including the above-described electrode for a lithium secondary battery.

According to another embodiment, there is provided a lithium secondary battery including the electrode active material layer for a lithium secondary battery described above.

According to another embodiment, there is provided a lithium secondary battery including the above-described electrode assembly for a lithium secondary battery.

As described above, the microcapsule according to the present invention thins the non-aqueous electrolyte secondary battery and stably exists in the non-aqueous electrolyte secondary battery, and at the same time, it is possible to secure the insulation between the electrodes during abnormal heat generation of the non-aqueous electrolyte secondary battery.

1 is a side cross-sectional view showing the configuration of a lithium ion secondary battery according to a first embodiment of the present invention.
2 is a side cross-sectional view showing the configuration of a lithium ion secondary battery according to the second embodiment.
3 is a side cross-sectional view showing the configuration of a lithium ion secondary battery according to the third embodiment.

Hereinafter, embodiments of the present invention will be described in detail. However, this is provided as an example, and the present invention is not limited thereto, and the present invention is only defined by the scope of the claims to be described later.

In addition, in this specification and drawings, the same code|symbol is attached|subjected to the component which has substantially the same functional structure, and the duplicate description is abbreviate|omitted.

(First embodiment)

(Composition of lithium ion secondary battery)

First, the configuration of the lithium ion secondary battery 10 according to the first embodiment will be described with reference to FIG. 1 .

The lithium ion secondary battery 10 includes a positive electrode 20 , a negative electrode 30 , and a separator layer 40 . The charging arrival voltage (oxidation-reduction potential) of the lithium ion secondary battery 10 is, for example, 4.3 V (vs.Li/Li +) or more and 5.0 V or less, and particularly 4.5 V or more and 5.0 V or less. The form of the lithium ion secondary battery 10 is not specifically limited. In other words, the lithium ion secondary battery 10 may be of a cylindrical shape, a prismatic shape, a laminate type, a button type, or the like.

The positive electrode 20 includes a current collector 21 and a positive electrode active material layer 22 . The current collector 21 may be any conductor as long as it is a conductor, and is made of, for example, aluminum, stainless steel, or nickel-coated steel.

The positive electrode active material layer 22 contains at least a positive electrode active material, and may further contain a conductive agent and a binder. The positive electrode active material is, for example, a solid solution oxide containing lithium, but is not particularly limited as long as it is a material capable of electrochemically occluding and releasing lithium ions. The solid solution oxide is, for example, Li a Mn x Co y Ni z O 2 (1.150≤a≤1.430, 0.45≤x≤0.6, 0.10≤y≤0.15, 0.20≤z≤0.28), LiMnxCo y Ni z O 2 (0.3≤x≤0.85, 0.10≤y≤0.3, 0.10≤z≤0.3), LiMn 1.5 Ni 0.5 O 4 .

The conductive agent is, for example, carbon black such as Ketjenblack and acetylene black, natural graphite, artificial graphite, and the like, but is not particularly limited as long as it is intended to increase the conductivity of the anode.

The binder is, for example, polyvinylidene fluoride, ethylene-propylene-diene terpolymer, styrene-butadiene rubber, acrylonitrile-butadiene rubber. , fluororubber, polyvinyl acetate, polymethylmethacrylate, polyethylene, nitrocellulose, etc., but the positive electrode active material and the conductive agent are placed on the current collector 21 It is not particularly limited as long as it can be bound. The positive electrode active material layer 22 is produced, for example, by the following manufacturing method. In other words, first, a positive electrode mixture is prepared by dry-mixing a positive electrode active material, a conductive agent, and a binder. Next, a positive electrode mixture slurry is formed by dispersing the positive electrode mixture in an appropriate organic solvent, and the positive electrode mixture slurry is applied on the current collector 21 , dried and rolled to form a positive electrode active material layer.

The negative electrode 30 includes a current collector 31 and a negative electrode active material layer 32 . The current collector 31 may be any conductor as long as it is a conductor, and is made of, for example, aluminum, stainless steel, and nickel-plated steel. The negative electrode active material layer 32 may be any as long as it is used as a negative electrode active material layer of a lithium ion secondary battery. For example, the negative electrode active material layer 32 contains a negative electrode active material, and may further contain a binder. The negative electrode active material is, for example, a graphite active material (artificial graphite, natural graphite, a mixture of artificial graphite and natural graphite, natural graphite coated with artificial graphite, etc.), a mixture of fine particles of silicon or tin or their oxides and a graphite active material , fine particles of silicon or tin, alloys based on silicon or tin, and Li ₄ Ti ₅ O ₁₂ Titanium oxide type compounds, such as these, etc. are considered. The oxide of silicon is represented by SiOx (0≤x≤2). Examples of the negative electrode active material other than these include metallic lithium. The binder is also the same as the binder constituting the positive electrode active material layer 22 . The mass ratio between the positive electrode active material and the binder is not particularly limited, and the mass ratio employed in the conventional lithium ion secondary battery is applicable in this embodiment.

The negative electrode active material layer 32 is produced, for example, by the following manufacturing method. In other words, first, a negative electrode mixture is prepared by dry-mixing the negative electrode active material and the binder. Next, a negative electrode mixture slurry is formed by dispersing the negative electrode mixture in a suitable solvent, and the negative electrode mixture slurry is applied on the current collector 31 , dried and rolled to form the negative electrode active material layer 32 .

The separator layer 40 includes a separator 40a, microcapsule layers 40b and 40c, and a non-aqueous electrolyte. The separator in particular is not restrict|limited, As long as it is used as a separator of a lithium ion secondary battery, what kind may be sufficient. As a separator, it is preferable to use individually or together a porous film, a nonwoven fabric, etc. which show the outstanding high rate discharge performance. As a resin constituting the separator, for example, a polyolefin-based resin represented by polyethylene, polypropylene, etc., polyethylene terephthalate, polybutylene terephthalate, etc. Representative polyester resins, PVDF, vinylidene fluoride (VDF)-hexafluoropropylene (HFP) copolymer, vinylidene fluoride-perfluorovinyl ether (par fluorovinyl ether) copolymer, vinylidene fluoride- Tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-fluoroethylene copolymer, vinylidene fluoride-hexafluoroacetone copolymer , vinylidene fluoride-ethylene copolymer, vinylidene fluoride-propylene copolymer, vinylidene fluoride-trifluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene- and a hexafluoropropylene copolymer, a vinylidene fluoride-ethylene (ethylene)-tetrafluoroethylene copolymer, and the like. The separator may be a heat-resistant separator, and may include, for example, a nonwoven fabric, an amide-based compound, or a combination thereof.

The microcapsule layer 40b is formed on the surface of the separator 40a opposite to the positive electrode active material layer 22 . The microcapsule layer 40c is formed on the surface of the separator 40a opposite to the negative electrode active material layer 32 . The microcapsule layers 40b and 40c include microcapsules and a binder.

The microcapsule is a core-shell type thermally expansible microcapsule, and has a core portion and a shell portion. The core portion comprises a polymer of foamable monomers. Therefore, the core part has a function of thermal expansion. The foamable monomer can be used without particular limitation as long as it is a resin that foams when heated, but a low volatility monomer is preferable. This is because, when microcapsules containing a highly volatile foaming monomer are put into the electrolyte, volatile components may elute into the electrolyte.

It is preferable to foam a foamable monomer between 120 degreeC - 250 degreeC. This is because the lithium ion secondary battery 10 may rapidly heat up to a temperature within this temperature range. The foaming monomer preferably comprises a diazo compound I. Diazo compounds are decomposed by heating. And, the diazo compound is foamed by nitrogen gas, which is a decomposition product. The diazo compound preferably has a structure represented by the following formula (I) or (II).

[Formula Ⅰ]

(In Formula I,

R1 is a hydrogen atom or a methyl group,

R2 is a hydrogen atom or a C1 to C6 alkyl group,

R3 is a hydrogen atom or a C1 to C6 alkyl group,

R4 is a hydrogen atom, a methyl group, an acryl group, a methacryl group or a glycidyl group,

X is a direct bond or a C1 to C6 alkylene group.)

[Formula II]

(In Formula II,

R1 is a hydrogen atom or a methyl group,

R2 is a hydrogen atom or a C1 to C6 alkyl group,

A is a methylene group or a carbonyl group,

Q is a methylene group or a methine group,

T is a direct bond, a double bond, a methylene group, oxygen, or an NH group.)

In particular, when the core portion is composed of a polymer of a diazo compound, it tends to react with the electrode active material and, at the same time, tends to swell in the electrolyte solution. Therefore, when only the core part is injected|thrown-in to electrolyte solution, the core part reacts with an electrode and swells with electrolyte solution. As a result, problems such as an increase in the internal resistance of the lithium ion secondary battery 10 and a decrease in cycle life may occur.

Therefore, in this embodiment, the core part is covered with the shell part. The shell part has higher stability in the lithium ion secondary battery 10 than the core part. Specifically, the shell portion is more difficult to swell in the electrolyte than the core portion. Moreover, the shell part is more difficult to react with the electrode active material than the core part. Examples of the material constituting the shell portion include a copolymer of acrylonitrile and acrylic acid.

The average particle diameter of the microcapsules is 0.05 to 0.5 μm. Here, the average particle diameter is the D50 value of the diameter when the microcapsule is regarded as a sphere. The average particle diameter is, for example, a laser diffraction scattering particle diameter particle size distribution measuring device (for example, Microtrac MT3000 manufactured by Nikkiso Co., Ltd.) When the average particle diameter is less than 0.05 µm, the microcapsules thermally expand Even if it does not become a sufficient magnitude|size, as a result, there is a possibility that the insulation between electrodes cannot be ensured at the time of abnormal heat_generation|fever of the lithium ion secondary battery 10. On the other hand, when the average particle diameter of the microcapsules becomes larger than 0.5 μm, the lithium ion secondary battery 10 becomes thick, and at the same time, the internal resistance increases.

The binder binds the microcapsules together and fixes the microcapsule layers 40b and 40c to the separator 40a. There is no restriction|limiting in particular as long as a binder is used as a binder of the lithium ion secondary battery 10, For example, carboxymethylcellulose (CMC) etc. are mentioned.

The microcapsule layers 40b and 40c are prepared by coating a slurry containing microcapsules and a binder on the separator 40a and drying. On the other hand, the lithium ion secondary battery 10 may not have any one of the microcapsule layers 40b and 40c (modified example).

The above-mentioned microcapsules thin the nonaqueous electrolyte secondary battery and stably exist in the nonaqueous electrolyte secondary battery, and at the same time, it is possible to secure insulation between electrodes in the case of abnormal heat generation of the nonaqueous electrolyte secondary battery. In addition, the microcapsule can suppress the thermal contraction of the separator during abnormal heat generation of the non-aqueous electrolyte secondary battery.

As the non-aqueous electrolyte, the same non-aqueous electrolyte used in the conventional lithium secondary battery may be used without particular limitation. The non-aqueous electrolyte has a composition in which an electrolyte salt is contained in a non-aqueous solvent. Examples of the non-aqueous solvent include cyclic carbonate esters such as propylene carbonate, ethylene carbonate, butylene carbonate, chloroethylene carbonate, and vinylene carbonate. (ester); cyclic esters such as γ-butyrolactone and γ-valerolactone; Chain carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate; methyl formate, methyl acetate, butyric acid methyl chain esters such as; Tetrahydrofuran or a derivative thereof; 1,3-dioxane, 1,4-dioxane, 1,2-dimethoxyethane, 1,4 -Ethers such as dibutoxyethane and methyl diglyme; nitriles such as acetonitrile and benzonitrile; Dioxolane or its derivatives ; ethylene sulfide (ethylene sulfide), sulfolane (sulfolane), sultone (sultone) or a derivative thereof alone or a mixture of two or more thereof, but is not limited thereto.

Further, as the electrolyte salt, for example, LiClO 4 , LiBF 4 , LiAsF 6 , LiPF 6 , LiPF 6-x (C n F 2n+1) x [provided that 1 <x <6, n=1or2], LiSCN , LiBr, LII, Li 2 SO 4, Li 2 B 10 Cl 10, NaClO 4, NaI, NaSCN, NaBr, KClO 4, KSCN, etc. Lithium (Li), sodium (Na), or potassium (K) an inorganic ion salt _{include, LiCF 3 SO 3, LiN (} CF 3 SO 2) 2, LiN (C 2 F 5 SO 2) 2, LiN (CF 3 SO 2) (C 4 F 9 SO 2), LiC (CF _{3 SO 2) 3, LiC (} C 2 F 5 SO 2) 3, (CH 3) 4 NBF 4, (CH 3) 4 NBr, (C 2 H 5) 4 NClO 4, (C 2 H 5) 4 NI _{, (C 3 H 7) 4} NBr, (n-C 4 H 9) 4 NClO 4, (n-C 4 H 9) 4 NI, (C 2 H 5) 4 N-maleate, (C 2 H 5) ４ Ｎ－ｂｅｎｚｏａｔｅ，（C ₂ H _５ ） ４ N -phtalate, lithium stearyl sulfonic acid, lithium octyl sulfonic acid, benzene sulphonate of dodecyl benzene sulfonic acid, etc. An ionic salt etc. are mentioned, These ionic compounds can be used individually or in mixture of 2 or more types. On the other hand, the concentration of the electrolyte salt may be the same as the non-aqueous electrolyte used in the conventional lithium secondary battery, and there is no particular limitation. In this embodiment, a non-aqueous electrolyte containing a suitable lithium compound (electrolyte salt) at a concentration of 0.8 to 1.5 mol/L may be used.

Meanwhile, various additives may be added to the non-aqueous electrolyte. Such additives include anode action additives, anode action additives, ester additives, carbonate ester additives, sulfuric acid ester additives, phosphoric acid ester additives, boric acid ester additives, acid anhydride additives, and electrolytes. of additives. Any one of these may be added to the non-aqueous electrolyte, or a plurality of types of additives may be added to the non-aqueous electrolyte.

(Manufacturing method of lithium ion secondary battery)

Next, the manufacturing method of the lithium ion secondary battery 10 is demonstrated. The anode 20 is manufactured as follows. First, a slurry is formed by dispersing a mixture of a positive electrode active material, a conductive agent, and a binder in a solvent (eg, N-methyl-2-pyrrolidone). Next, the slurry is formed (eg, applied) on the current collector 21 and dried to form the positive electrode active material layer 22 . In addition, the method of application|coating is not specifically limited. As a method of application|coating, the knife coater method, the gravure coater method, etc. are considered, for example. Each of the following application|coating processes is also performed by the same method. Next, the positive electrode active material layer 22 is pressed by a press machine. Accordingly, the anode 20 is manufactured.

The negative electrode 30 is also manufactured in the same manner as the positive electrode 20 . First, a slurry is formed by dispersing a mixture of a negative electrode active material and a binder in a solvent (eg, N-methyl-2-pyrrolidone, water). Then, the slurry is formed on the current collector 31 ( coating) and drying to form the negative electrode active material layer 32. Next, the negative electrode active material layer 32 is pressed with a press machine. Thereby, the negative electrode 30 is produced.

The microcapsule layers 40b and 40c are manufactured by the following method. In other words, a slurry is formed by dispersing a mixture of microcapsules and a binder in a solvent (for example, water). Then, the slurry is coated on both sides of the separator 40a and dried. Accordingly, the microcapsule layer ( 40b, 40c) are fabricated.

Next, by placing the separator 40a on which the microcapsule layers 40b and 40c is formed between the positive electrode 20 and the negative electrode 30, an electrode structure is manufactured. Then, the electrode structure is processed into a desired shape (eg, cylindrical, prismatic, laminated, buttoned, etc.) and inserted into a container of the corresponding shape. Next, by injecting the electrolyte solution having the above composition into the container, the pores in the separator are impregnated with the electrolyte solution. Accordingly, a lithium ion secondary battery is manufactured.

(Second embodiment)

(Composition of lithium ion secondary battery)

Next, the configuration of the lithium ion secondary battery 10a according to the second embodiment will be described with reference to FIG. 2 . The lithium ion secondary battery 10a according to the first modification also includes a positive electrode 20 , a negative electrode 30 , and a separator layer 40 .

The positive electrode 20 includes a current collector 21 , a positive electrode active material layer 22 , and a microcapsule layer 23 . The current collector 21 and the positive electrode active material layer 22 are the same as in the first embodiment. The microcapsule layer 23 is provided on the surface of the positive electrode active material layer 22 , that is, the surface in contact with the separator layer 40 . The configuration of the microcapsule layer 23 itself is the same as that of the first embodiment.

The negative electrode 30 includes a current collector 31 , an anode active material layer 32 , and a microcapsule layer 33 . The current collector 31 and the anode active material layer 32 are the same as in the first embodiment. The microcapsule layer 33 is provided on the surface of the negative electrode active material layer 32 , that is, the surface in contact with the separator layer 40 . The configuration of the microcapsule layer 33 itself is the same as that of the first embodiment. The lithium ion secondary battery 10a may not have any one of the microcapsule layers 22 and 32 . The microcapsule layers 22 and 23 are manufactured by coating and drying the slurry described in the first embodiment on the surface of the positive active material layer 22 or the negative active material layer 23 .

The separator layer 40 has a separator and a non-aqueous electrolyte. The separator and the non-aqueous electrolyte are the same as in the first embodiment. In other words, the lithium ion secondary battery 10a is different from the first embodiment in that a microcapsule layer is formed on each electrode.

(Manufacturing method of lithium ion secondary battery)

The manufacturing method of the lithium ion secondary battery 10a according to the second embodiment is almost the same as that of the first embodiment. The anode 20 is manufactured as follows. First, the positive electrode active material layer 22 is manufactured by the same method as in the first embodiment. Meanwhile, a slurry is formed by dispersing a mixture of microcapsules and a binder in a solvent (for example, water). Then, the slurry is coated on the positive electrode active material layer 22 and dried. Accordingly, the microcapsule layer 23 ) is produced.

The cathode 30 is also manufactured by the same method. First, the anode active material layer 32 is manufactured by the same method as in the first embodiment. On the other hand, a slurry is formed by dispersing a mixture of microcapsules and a binder in a solvent (eg, water). Then, the slurry is coated on the negative electrode active material layer 32 and dried. Accordingly, the microcapsule layer 33 is Next, an electrode structure is manufactured by placing the separator 40a between the positive electrode 20 and the negative electrode 30. After that, the same treatment as in the first embodiment is performed, and the lithium ion secondary battery 10a is produced

(3rd embodiment)

(Composition of lithium ion secondary battery)

Next, the configuration of the lithium ion secondary battery 10a according to the third embodiment will be described with reference to FIG. 3 . The lithium ion secondary battery 10b according to the first modification also includes a positive electrode 20 , a negative electrode 30 , and a separator layer 40 .

The positive electrode 20 is the same as in the first embodiment, and the separator 40 is the same as in the second embodiment. The negative electrode 30 includes a current collector 31 and a negative electrode active material layer 32a. The current collector 31 is the same as in the first embodiment.

The negative electrode active material layer 32a contains a negative electrode active material and microcapsules, and may further contain a binder. In other words, in the third embodiment, microcapsules are incorporated in the anode active material layer 32a. Each material is the same as in the first embodiment.

(Manufacturing method of lithium ion secondary battery)

The manufacturing method of the lithium ion secondary battery 10b according to the third embodiment is almost the same as that of the first embodiment. The anode 20 is fabricated by the same processing as in the first embodiment. The cathode 30 is produced by the following process. In other words, a slurry is formed by dispersing a mixture of a negative active material and a binder in a solvent (eg, N-methyl-2-pyrrolidone, water). Then, the slurry is formed on the current collector 31 . (For example, coating) and drying, the negative electrode active material layer 32 is formed. Next, the negative electrode active material layer 32 is pressed with a press machine. Thereby, the negative electrode 30 is produced. The lithium ion secondary battery 10b is manufactured by the same process as in the second embodiment, and according to the third embodiment, the trouble of forming the microcapsule layer can be omitted.

Meanwhile, the first to third embodiments may be arbitrarily combined. For example, the separator layer 40 of the second or third embodiment may be replaced with the separator layer 40 of the first embodiment. In addition, the negative electrode 30 of the first or second embodiment may be substituted with the negative electrode 30 of the third embodiment.

Hereinafter, specific embodiments of the present invention are presented. However, the examples described below are only for specifically illustrating or explaining the present invention, and the present invention is not limited thereto. In addition, since the content not described here can be sufficiently technically inferred by a person skilled in the art, the description thereof will be omitted.

(Synthesis Example 1 of Effervescent Monomer)

First, the synthesis example of the foaming monomer used in this Example is demonstrated. In Synthesis Example 1, N-monoacryl azodicarbonamide was synthesized as a foaming monomer by the following method.

50 g (0.43 mol, 1 equivalent) of azodicarbonamide, 500 g of anhydrous N, N-dimethylformamide (DMF), 500 g of anhydrous N, N-dimethylformamide (DMF), in a 1-liter 3-neck flask equipped with a cooling tube, thermometer, and dropping funnel under nitrogen atmosphere. 500 g (6.32 mol, 14.7 equivalents) of pyridine was added, and the mixture was cooled to 5°C with an ice bath while stirring with a magnetic stirrer.

Then, 39 g (0.43 mol, 1.0 equivalent) of acrylic acid chloride was added to the dropping funnel, and acrylic acid chloride was added dropwise to the mixed solution while maintaining the temperature of the mixed solution at 30°C or less. After completion of the dropwise addition, the ice bath was replaced with an oil bath, and the mixture was heated and stirred at 40°C for 2 hours. Then, after cooling the reaction solution to room temperature, the reaction solution was poured into 1000 ml of water and stirred. This solution was transferred to a 3000 ml separatory funnel, and extracted three times with 300 ml of ethyl acetate. All organic layers were collected, and the collected material was washed twice with 500 ml of water and once with 300 ml of saturated brine, and dried by adding anhydrous magnesium sulfate. Anhydrous magnesium sulfate was removed from the dried collection by suction filtration, and then concentrated by a rotary evaporator (bath temperature: 40°C). The concentrate was further dried with a vacuum dryer (40 DEG C/133 Pa) for 6 hours. Thus, 55 g of N-monoacryl azodicarbonamide (yield 75%) was obtained.

(Synthesis Example 2 of Effervescent Monomer)

Except for using 45 g (0.43 mol, 1.0 equivalent) of methacrylic acid chloride instead of acrylic acid chloride, the same treatment as in Synthesis Example 1 of the foaming monomer was performed. Accordingly, 58 g (yield 73%) of N-monoacrylic azodicarbonamide was obtained.

(Synthesis Example 3 of Effervescent Monomer)

Except for using 80 g (0.88 mol, 2.05 equivalent) of acrylic acid chloride, the same treatment as in Synthesis Example 1 of the foaming monomer was performed.

Accordingly, 78 g (yield 81%) of N,N'-diacrylic azodicarbonamide was obtained.

(Synthesis Example 4 of Effervescent Monomer)

The same treatment as in Synthesis Example 4 of the foaming monomer was performed except that 92.3 g (0.88 mol, 2.05 equivalent) of methacrylic acid chloride was used instead of the acrylic acid chloride. Accordingly, 85 g (yield 78%) of N,N'-dimethacrylic azodicarbonamide was obtained.

(Synthesis Example 1 of microcapsules)

Next, a synthesis example of the microcapsules used in this example will be described. In Synthesis Example 1, microcapsules having an average particle diameter of 98 nm were produced by the following treatment. In a 0.5 liter 3-neck flask equipped with a stirrer, thermometer, cooling tube, and a liquid pump, 240 g of water, sodium dodecylbenzenesulfonate (SDBS) as a surfactant 300 mg (0.861 mmol, micro The 1st liquid mixture was produced by adding 0.001 mass part (external water, external water) with respect to the monomer gross mass of a capsule.

Next, the dissolved oxygen in the first mixed solution was removed by repeating the operation of reducing the pressure in the three-necked flask to 2600 Pa with a diaphragm pump and returning it to normal pressure with nitrogen three times. Then, maintaining the inside of the flask in a nitrogen atmosphere, and heating the temperature in the flask to 65 degrees in an oil bath while stirring the first mixture, 0.102 g of ammonium persulfate (0.447 mmol, microcapsule monomer) 0.05 mol% (external water)) with respect to the number of moles (mol) of the total mass was added to the first liquid mixture. Immediately after adding ammonium persulfate, 15 g of N-monoacryl azodicarbonamide (Synthesis Example 1) (88.2 mmol, 25.0 parts by mass relative to the total mass of the monomer of the microcapsule), acrylonitrile (Wako Pure Chemical Industries, Ltd.) (manufactured by Wako Pure Chemical Industries, Ltd.) 15 g (282.7 mmol, 25.0 parts by mass based on the total mass of the monomer of the microcapsule), butyl acrylate (manufactured by Wako Pure Chemical Industries, Ltd.) 3 g (23.4 mmol, the monomer of the microcapsule) Each monomer was emulsion-polymerized by dripping the mixture (2nd liquid mixture) of 5.0 mass parts with respect to the total mass to the 1st liquid mixture over 1 hour with a liquid feeding pump. Accordingly, the core portion of the microcapsule was synthesized.

Subsequently, 25 g of acrylonitrile (manufactured by Wako Pure Chemical Industries, Ltd.) (471.2 mmol, 41.7 parts by mass relative to the total mass of the monomer of the microcapsule), 2 g of acrylic acid (manufactured by Wako Pure Chemical Industries, Ltd.) (27.8 mmol, 3.3 with respect to the total mass of the monomer of the microcapsule) parts by mass) was added dropwise to the dispersion liquid of the core part with a liquid feeding pump over 1 hour, whereby the monomer was emulsion-polymerized on the surface of the core part. Thereby, the shell part was formed on the surface of the core part. After completion of the dropwise addition, the microcapsule dispersion was stirred for another 1 hour, and then the temperature of the microcapsule dispersion was raised to 80 DEG C and stirring was continued for 1 hour. After cooling the microcapsule dispersion to room temperature, the microcapsule dispersion was filtered with a 100 mesh filter, and aggregates were excluded. Thus, a microcapsule dispersion was obtained. About 1 ml of the microcapsule dispersion was measured in an aluminum pan and dried for 15 minutes on a hot plate heated to 160 degrees. The non-volatile content was calculated from the weight of the residue, 19.6 based on the total mass of the microcapsule dispersion. It was mass % (yield 98%). Further, the average particle diameter (D50) of the microcapsules was measured using a laser diffraction scattering particle diameter particle size distribution analyzer (Microtrac MT3000 manufactured by Nikiso Corporation) and found to be 98 nm.

(Synthesis Example 2 of microcapsules)

The same treatment as in Synthesis Example 1 of the microcapsules was performed except that 150 mg of sodium dodecylbenzenesulfonate (0.43 mmol, 0.0025 parts by mass (external water) relative to the total mass of the monomers of the microcapsules) was used. Accordingly, microcapsules according to Synthesis Example 2 were obtained. The nonvolatile matter was 19.5 mass % (yield 98%). Moreover, the average particle diameter was 150 nm.

(Synthesis Example 3 of microcapsules)

The same treatment as in Synthesis Example 1 of the microcapsules was performed except for using 190 g of water and 60 mg of sodium dodecylbenzenesulfonate (0.17 mmol, 0.001 parts by mass relative to the total mass of the monomer (external water)). Accordingly, microcapsules according to Synthesis Example 3 were obtained. The nonvolatile matter was 23.7 mass % (yield 99%). In addition, the average particle diameter of the microcapsules was 300 nm.

(Synthesis Example 4 of microcapsules)

Except for using 30 g (162.9 mmol, 50.0 parts by mass relative to the total mass of the monomer of the microcapsule) of N-monomethacrylic azodicarbonamide (Synthesis Example 2 of the foaming monomer) instead of N-monoacryl azodicarbonamide, the microcapsules were The same treatment as in Synthesis Example 1 was performed. Accordingly, microcapsules according to Synthesis Example 4 were obtained. The nonvolatile matter was 19.5 mass % (yield 98%). In addition, the average particle diameter of the microcapsules was 100 nm.

(Synthesis Example 5 of microcapsules)

Instead of N-monoacryl azodicarbonamide, N-monomethacrylic azodicarbonamide (Synthesis Example 2 of effervescent monomer) 30 g (162.9 mmol, 50.0 parts by mass based on the total mass of the monomer of the microcapsule), sodium dodecylbenzenesulfonate 150 mg The same treatment as in Synthesis Example 1 of the microcapsules was performed except that (0.43 mmol, 0.0025 parts by mass (external water) relative to the total mass of the monomer of the microcapsules) was used. Accordingly, microcapsules according to Synthesis Example 5 were obtained. The nonvolatile matter was 19.5 mass % (yield 98%). In addition, the average particle diameter of the microcapsules was 160 nm.

(Synthesis Example 6 of microcapsules)

190 g of water was used, and 30 g (162.9 mmol, 50.0 parts by mass based on the total mass of the monomer of the microcapsule) was used instead of N-monoacryl azodicarbonamide. and 60 mg of sodium dodecylbenzenesulfonate (0.17 mmol, 0.001 parts by mass (external water) relative to the total mass of the monomer of the microcapsule) was used, and the same treatment as in Synthesis Example 1 of the microcapsule was performed. Accordingly, microcapsules according to Synthesis Example 6 were obtained. The nonvolatile matter was 23.5 mass % (yield 98%). In addition, the average particle diameter of the microcapsules was 305 nm.

(Synthesis Example 7 of microcapsules)

Instead of N-monoacryl azodicarbonamide, 30 g (133.8 mmol, 50.0 parts by mass relative to the total mass of the monomer of the microcapsule) of N,N'-diaryl azodicarbonamide (Synthesis Example 3 of the foaming monomer) was used, and dode The same treatment as in Synthesis Example 1 of the microcapsules was performed except that 150 mg of sodium methylbenzenesulfonate (0.43 mmol, 0.0025 parts by mass (external water) relative to the total mass of the monomers of the microcapsules) was used. Accordingly, microcapsules according to Synthesis Example 7 were obtained. The nonvolatile matter was 19.5 mass % (yield 98%). In addition, the average particle diameter of the microcapsules was 110 nm.

(Synthesis Example 8 of microcapsules)

Instead of N-monoacryl azodicarbonamide, N,N'-dimethacryl azodicarbonamide (Synthesis Example 4 of foaming monomer) 30 g (118.9 mmol, 50.0 parts by mass based on the total mass of the monomer of the microcapsule) was used, The same treatment as in Synthesis Example 1 of the microcapsule was performed except that 150 mg of sodium dodecylbenzenesulfonate (0.43 mmol, 0.0025 parts by mass relative to the total mass of the monomer (external water)) was used. Accordingly, microcapsules according to Synthesis Example 8 were obtained. The nonvolatile matter was 19.6 mass % (yield 98%). In addition, the average particle diameter of the microcapsules was 105 nm.

(Preparation example 1 of negative electrode mixture slurry)

Next, an example of the preparation of the negative electrode mixture slurry will be described.

By mixing 95 mass % of artificial graphite, 2 mass % of acetylene black, 2 mass % of styrene butadiene copolymer (SBR), and 1 mass % of carboxymethyl cellulose (CMC), and adding water for viscosity adjustment A negative electrode mixture slurry was prepared. On the other hand, the non-volatile content in the negative electrode mixture slurry was 48 mass % with respect to the total mass of the slurry.

(Production Example 2 of negative electrode mixture slurry)

Synthetic graphite 95 mass %, acetylene black 2 mass %, styrene butadiene copolymer (SBR) 1 mass %, carboxymethyl cellulose (CMC) 1 mass %, microcapsule dispersion prepared in Synthesis Example 1 of microcapsule 1 in terms of solid content A negative electrode mixture was produced by mixing in mass %. Next, by adding water to the negative electrode mixture for viscosity adjustment, a negative electrode mixture slurry was prepared. On the other hand, the nonvolatile matter in the negative electrode mixture slurry was 48 mass % with respect to the total mass of the slurry.

(Preparation examples 3 to 9 of negative electrode mixture slurry)

Except for using the microcapsule dispersion prepared in Synthesis Examples 2 to 8 of the microcapsules, all were treated in the same manner as in Production Example 2 of the negative electrode mixture slurry to prepare negative electrode mixture slurries according to Preparation Examples 3 to 9.

(Cathode Production Example 1)

Next, a manufacturing example of the negative electrode will be described. The gap of the bar coater was adjusted so that the mixture application amount (area density) after drying was set to 9.55 mg/cm ^{2 .} Next, the negative electrode mixture slurry prepared in Production Example 1 was uniformly applied to a copper foil (current collector, 10 µm) with this bar coater. Next, the negative electrode mixture slurry was dried for 15 minutes with a blow dryer set at 80°C. Then, the negative electrode mixture after drying was pressed by a roll press machine so that the density of the mixture was 1.65 g/cm ³ . Then, the negative electrode mixture was vacuum dried at 150° C. for 6 hours to prepare a sheet-type negative electrode comprising a negative electrode current collector and a negative electrode active material layer. This negative electrode corresponds to the first embodiment.

(Cathode Production Example 2)

100 parts by mass of the microcapsule dispersion prepared in Synthesis Example 1 of microcapsules and 25 parts by mass of a 1 mass % aqueous solution of carboxymethyl cellulose (containing 1 mass % of carboxymethyl cellulose with respect to the total mass of the aqueous solution. The same applies hereinafter) A mixed solution was prepared. Next, this mixed solution was applied to the sheet-shaped negative electrode produced in Negative Electrode Production Example 1 with a bar coater adjusted so that the thickness of the coating layer after drying was 2 μm, and then dried with a blow dryer at 80° C. for 15 minutes. Then, the coating layer was vacuum dried at 80° C. for 6 hours to prepare a sheet-shaped negative electrode comprising a negative electrode current collector, a negative electrode active material layer, and a microcapsule layer. This negative electrode corresponds to the second embodiment.

(Cathode Production Examples 3 to 9)

The same treatment as in Example 2 of the negative electrode was performed except that the microcapsule dispersions prepared in Synthesis Examples 2 to 8 of the microcapsules were used. Accordingly, negative electrodes according to negative electrode preparation examples 3 to 9 were prepared. These negative electrodes also correspond to the second embodiment.

(Cathode Production Examples 10 to 17)

Negative electrode mixture slurry Preparation Examples 2 to 9, except for using the slurry prepared in the negative electrode Preparation Example 1 was processed in the same manner to prepare a negative electrode according to the negative electrode Preparation Examples 10 to 17. These negative electrodes correspond to the third embodiment.

(Example of production of positive electrode mixture slurry)

Next, an example of the preparation of the positive electrode mixture slurry will be described. By dispersing 296 mass % of solid solution oxide Li 1.20 Mn 0.55 Co 0.10 Ni 0.15 O, 2 mass % of Ketjenblack, and 2 mass % of polyvinylidene fluoride (PVDF) in N-methyl-2-pyrrolidone, a positive electrode mixture A slurry was formed. On the other hand, the non-volatile content in the positive electrode mixture slurry was 50 mass %.

(Anode Production Example 1)

Next, a positive electrode fabrication example will be described. The gap of the bar coater was adjusted so that the mixture coating amount (area density) after drying was 22.7 mg/cm ^{2 .} Next, the positive electrode mixture slurry was applied onto an aluminum current collector foil serving as a current collector by this bar coater and dried to prepare a positive electrode active material layer. The dried positive electrode mixture was pressed with a roll press so that the mixture density was 3.9 g/cm ³ . Then, the positive electrode mixture was vacuum dried at 80° C. for 6 hours to prepare a sheet-shaped positive electrode comprising a positive electrode current collector and a positive electrode active material layer. This anode corresponds to the first embodiment.

(Anode Production Example 2)

A mixed solution of 100 parts by mass of the microcapsule dispersion prepared in Microcapsule Synthesis Example 1 and 25 parts by mass of a 1 mass % carboxymethyl cellulose aqueous solution was prepared. Next, this mixed solution was applied to the sheet-shaped positive electrode produced in the positive electrode production example 1 with a bar coater adjusted so that the thickness of the coating layer after drying was 2 μm, and then dried with a blow dryer at 80° C. for 15 minutes. Then, the coating layer was vacuum dried at 80° C. for 6 hours to prepare a sheet-shaped positive electrode comprising a positive electrode current collector, a positive electrode active material layer, and a microcapsule layer. This anode corresponds to the second embodiment.

(Anode Production Examples 3 to 9)

Except for using the microcapsule dispersion prepared in Microcapsule Synthesis Examples 2 to 8, all were treated in the same manner as in Positive Electrode Preparation Example 2 to prepare positive electrodes according to positive electrode Preparation Examples 3 to 9. These anodes correspond to the second embodiment.

(Separator Production Example 1)

A polyethylene porous membrane having a thickness of 16 µm was prepared. Moreover, the gap of the applicator was adjusted so that the film thickness of the whole polyethylene porous film|membrane after drying might be set to 18 micrometers (the thickness of an application layer becomes 2 micrometers in both surfaces total). Further, a mixed solution of 100 parts by mass of the microcapsule dispersion prepared in Microcapsule Synthesis Example 1 and 25 parts by mass of a 1% carboxymethylcellulose aqueous solution was prepared. Next, using the above applicator, the mixture was applied to both surfaces of the polyethylene porous membrane and dried (drying furnace temperature: 80°C). Then, the coating layer was vacuum-dried at 80° C. for 6 hours to prepare a polyethylene porous membrane separator having microcapsule layers on both surfaces. This separator corresponds to the first embodiment.

(Separator Preparation Examples 2 to 8)

Separators according to Separator Production Examples 2 to 8 were prepared in the same manner as in Separator Production Example 1 except that the microcapsule dispersions prepared in Microcapsule Synthesis Examples 2 to 8 were used. These separators also correspond to the first embodiment.

(Separator Production Example 9)

A polyethylene porous membrane having a thickness of 16 µm was prepared. Moreover, the gap of the applicator was adjusted so that the film thickness of the whole polyethylene porous membrane after drying might be set to 18 micrometers (the thickness of an application layer becomes 2 micrometers). Further, a mixed solution of 100 parts by mass of the microcapsule dispersion prepared in Microcapsule Synthesis Example 1 and 25 parts by mass of a 1% carboxymethylcellulose aqueous solution was prepared. Next, using the above-mentioned applicator, the mixed solution was applied to one side of the polyethylene porous membrane, and dried for 15 minutes with a blow dryer at 80°C. Then, the coating layer was vacuum-dried at 80° C. for 6 hours to prepare a polyethylene porous membrane separator having a microcapsule layer on one side. This separator corresponds to a modification of the first embodiment.

(Separator Production Examples 10 and 11)

Separators according to Separator Production Examples 10 and 11 were prepared in the same manner as in Separator Production Example 9 except that the microcapsule dispersions prepared in Microcapsule Synthesis Examples 2 and 3 were used. These separators also correspond to modifications of the first embodiment.

(Cell Preparation Example 1)

Cut the positive electrode prepared in Positive Preparation Example 1 into a circle with a diameter of 1.3 cm, the negative electrode prepared in Preparation Example 2 into a circle with a diameter of 1.55 cm, and as a separator, a porous polyethylene film with a thickness of 16 μm into a circle with a diameter of 1.9 cm. did. Next, in a stainless steel coin outer container having a diameter of 2.0 cm, a positive electrode with a diameter of 1.3 cm, a separator with a diameter of 1.9 cm, a negative electrode with a diameter of 1.55 cm, and a spacer with a diameter of 1.5 as a spacer A copper plate having a thickness of 200 μm cut in a circle of cm was overlapped in this order. Then, the electrolytic solution (1.5 M LiPF6 ethylene carbonate (EC)/diethyl carbonate (DEC)/fluoroethylene carbonate (FEC)=10/70/20 mixed solution (volume ratio)) was poured into the container so as not to overflow. Next, a polypropylene packing was interposed, and a stainless steel cap was put on the container, and the container was sealed with an adhesive for coin battery production. Accordingly, a lithium ion secondary battery was produced.

(Cell Preparation Examples 2 to 38)

Lithium ion secondary batteries according to Cell Preparation Examples 2 to 38 were prepared in the same manner as in Cell Preparation Example 1 except that the positive electrode, negative electrode, and separator shown in Table 2 were used.

(foaming test)

Next, in order to confirm that each of the microcapsules produced in this example foams at a temperature between 120°C and 250°C, the following foaming test was performed. Specifically, the separators produced in Separator Production Examples 1 to 8 were heated to 160°C on a hot plate, and left to stand at that temperature for 3 minutes. Then, the temperature of the separator was returned to room temperature, and the film thickness of the separator was measured. Next, the thickness (film thickness) of the microcapsule layer after heating was measured by reducing the thickness (=16 µm) of the polyethylene porous membrane from the measured value. Table 1 shows the measurement results.

Production example Film thickness after foaming (um) Production Example 1 7.4 Production Example 2 7.3 Production example 3 7.4 Production example 4 7.3 Production example 5 7.4 Production example 6 4.4 Production example 7 6.5 Production example 8 6.4

In both microcapsule layers, the film thickness is increased by heating to 160°C. Therefore, it was confirmed that both microcapsules foamed within a temperature range of 120°C to 250°C.

(Evaluation method of cell resistance value)

The lithium ion secondary battery manufactured in each production example was charged to 4.2V and 0.04mA at a constant current-constant voltage of 0.1C at 25°C, and then one cycle was performed under the condition of discharging to 2.5V at a constant current of 0.1C. The cell resistance (internal resistance of a lithium ion secondary battery) was measured for this using the AC 4-terminal method of the low resistance meter (Tsuruga Electric Corporation MODEL3566). Further, the lithium ion secondary battery was heated to 160°C on a hot plate, left at that temperature for 3 minutes, cooled to room temperature, and the cell resistance was measured again. The results are shown in Table 2.

Cell production example cathode anode separator cell resistance
(before heating) cell resistance
(After heating at 160℃) Cell Preparation Example 1 Cathode Production Example 2 Anode Production Example 1 Polyethylene porous membrane with a thickness of 16 μm 4.3 249 Cell Production Example 2 Cathode Production Example 3 Anode Production Example 1 Polyethylene porous membrane with a thickness of 16 μm 4.4 250 Cell Production Example 3 Cathode Production Example 4 Anode Production Example 1 Polyethylene porous membrane with a thickness of 16 μm 4.6 255 Cell Production Example 4 Anode Preparation Example 5 Anode Production Example 1 Polyethylene porous membrane with a thickness of 16 μm 4.5 246 Cell Production Example 5 Cathode Production Example 6 Anode Production Example 1 Polyethylene porous membrane with a thickness of 16 μm 4.4 252 Cell Production Example 6 Cathode Production Example 7 Anode Production Example 1 Polyethylene porous membrane with a thickness of 16 μm 4.7 258 Cell Production Example 7 Cathode Production Example 8 Anode Production Example 1 Polyethylene porous membrane with a thickness of 16 μm 4.4 218 Cell Production Example 8 Cathode Production Example 9 Anode Production Example 1 Polyethylene porous membrane with a thickness of 16 μm 4.2 216 Cell Production Example 9 Cathode Production Example 10 Anode Production Example 1 Polyethylene porous membrane with a thickness of 16 μm 4.5 212 Cell Production Example 10 Cathode Preparation Example 11 Anode Production Example 1 Polyethylene porous membrane with a thickness of 16 μm 4.4 205 Cell Production Example 11 Cathode Production Example 12 Anode Production Example 1 Polyethylene porous membrane with a thickness of 16 μm 4.6 212 Cell Production Example 12 Anode Preparation Example 13 Anode Production Example 1 Polyethylene porous membrane with a thickness of 16 μm 4.6 209 Cell Production Example 13 Anode Preparation Example 14 Anode Production Example 1 Polyethylene porous membrane with a thickness of 16 μm 4.5 213 Cell Production Example 14 Cathode Production Example 15 Anode Production Example 1 Polyethylene porous membrane with a thickness of 16 μm 4.7 215 Cell Production Example 15 Cathode Production Example 16 Anode Production Example 1 Polyethylene porous membrane with a thickness of 16 μm 4.2 186 Cell Production Example 16 Cathode Production Example 17 Anode Production Example 1 Polyethylene porous membrane with a thickness of 16 μm 4.3 184 Cell Production Example 17 Cathode Preparation Example 1 Anode Production Example 2 Polyethylene porous membrane with a thickness of 16 μm 4.5 281 Cell Production Example 18 Cathode Preparation Example 1 Anode Production Example 3 Polyethylene porous membrane with a thickness of 16 μm 4.5 285 Cell Production Example 19 Cathode Preparation Example 1 Anode Production Example 4 Polyethylene porous membrane with a thickness of 16 μm 4.3 300 Cell Production Example 20 Cathode Preparation Example 1 Anode Production Example 5 Polyethylene porous membrane with a thickness of 16 μm 4.5 277 Cell Preparation Example 21 Cathode Preparation Example 1 Anode Production Example 6 Polyethylene porous membrane with a thickness of 16 μm 4.3 280 Cell Production Example 22 Cathode Preparation Example 1 Anode Manufacturing Example 7 Polyethylene porous membrane with a thickness of 16 μm 4.5 295 Cell Production Example 23 Cathode Preparation Example 1 Anode Production Example 8 Polyethylene porous membrane with a thickness of 16 μm 4.2 246 Cell Production Example 24 Cathode Preparation Example 1 Anode Production Example 9 Polyethylene porous membrane with a thickness of 16 μm 4.3 244 Cell Production Example 25 Cathode Preparation Example 1 Anode Production Example 1 Separator Production Example 1 6.3 373 Cell Production Example 26 Cathode Preparation Example 1 Anode Production Example 1 Separator Production Example 2 6.5 380 Cell Production Example 27 Cathode Preparation Example 1 Anode Production Example 1 Separator Production Example 3 6.6 385 Cell Production Example 28 Cathode Preparation Example 1 Anode Production Example 1 Separator Production Example 4 6.4 368 Cell production example 29 Cathode Preparation Example 1 Anode Production Example 1 Separator Production Example 5 6.5 370 Cell Production Example 30 Cathode Preparation Example 1 Anode Production Example 1 Separator Production Example 6 6.7 375 Cell Production Example 31 Cathode Preparation Example 1 Anode Production Example 1 Separator Production Example 7 6.4 327 Cell Production Example 32 Cathode Preparation Example 1 Anode Production Example 1 Separator Production Example 8 6.5 324 Cell Production Example 33 Cathode Preparation Example 1 Anode Production Example 1 Separator Production Example 9 6.6 476 Cell Production Example 34 Cathode Preparation Example 1 Anode Production Example 1 Separator Production Example 10 6.5 449 Cell Production Example 35 Cathode Preparation Example 1 Anode Production Example 1 Separator Production Example 11 6.4 460 Cell Production Example 36 Cathode Production Example 2 Anode Production Example 2 Polyethylene porous membrane with a thickness of 16 μm 10.5 705 Cell Production Example 37 Cathode Production Example 3 Anode Production Example 3 Polyethylene porous membrane with a thickness of 16 μm 10.3 665 Cell Production Example 38 Cathode Production Example 4 Anode Production Example 4 Polyethylene porous membrane with a thickness of 16 μm 11.1 681

Negative electrode production examples 2 to 17, positive electrode production examples 2 to 9, and separator production examples 1 to 11 contain the microcapsules according to the present embodiment, and therefore correspond to the examples of this embodiment. In addition, since the lithium ion secondary battery according to Production Examples 1 to 38 includes a microcapsule in any one or more components of the positive electrode, the negative electrode, and the separator, it corresponds to the embodiment of the present embodiment.

According to Table 2, all of the lithium ion secondary batteries before heating have low internal resistance. Accordingly, it can be seen that the microcapsules hardly adversely affect the reaction in the lithium ion secondary battery (for example, the core portion swells, etc.). In addition, by heating the lithium ion secondary battery to 160 ℃, the internal resistance of the lithium ion secondary battery is greatly increased. Therefore, it can be seen that the lithium ion secondary battery of the present embodiment increases internal resistance when abnormal heat is generated.

As described above, the microcapsules according to the first to third embodiments are stably present in the lithium ion secondary batteries 10, 10a, and 10b, and at the same time foam (expand) when abnormal heat is generated. In addition, the average particle diameter of the microcapsules is very small in the range of 0.05 μm to 0.5 μm.

Therefore, the microcapsule thins the lithium ion secondary battery and stably exists in the lithium ion secondary battery, and at the same time, it is possible to secure the insulation between the electrodes during abnormal heat generation of the lithium ion secondary battery. In addition, the microcapsule can suppress the thermal contraction of the separator during abnormal heat generation of the lithium ion secondary battery.

Here, the foamable monomer constituting the core portion of the microcapsule may contain a diazo compound, and in this case, it can foam rapidly during abnormal heat generation.

In addition, the diazo compound may have a structure represented by the above formula (I) or formula (|), and in this case, it can foam rapidly at the time of abnormal heat generation.

In addition, since the foaming temperature of the microcapsule is 120°C or higher and 250°C or lower, it can be reliably foamed by abnormal heat generation of the lithium ion secondary battery.

In addition, by applying the separator layer according to one embodiment to the non-aqueous electrolyte secondary battery, the non-aqueous electrolyte secondary battery can be thinned and, at the same time, insulation between the electrodes can be ensured when the non-aqueous electrolyte secondary battery generates abnormal heat. In addition, the microcapsules are stably present in the non-aqueous electrolyte secondary battery, and can suppress thermal contraction of the separator during abnormal heat generation of the non-aqueous electrolyte secondary battery.

In addition, an electrode for a lithium secondary battery according to another embodiment includes an electrode active material layer; and a microcapsule layer positioned on the electrode active material layer, wherein the microcapsules are dispersed in the microcapsule layer, and by applying the electrode to the non-aqueous electrolyte secondary battery, the non-aqueous electrolyte secondary battery is thinned, and at the same time, the non-aqueous Insulation between electrodes can be ensured when the electrolyte secondary battery generates abnormal heat.

In addition, by applying the electrode active material layer for a lithium secondary battery according to another embodiment to the non-aqueous electrolyte secondary battery, the non-aqueous electrolyte secondary battery is thinned and, at the same time, insulation between the electrodes can be ensured during abnormal heat generation of the non-aqueous electrolyte secondary battery. In addition, the microcapsules are stably present in the non-aqueous electrolyte secondary battery, and can suppress thermal contraction of the separator during abnormal heat generation of the non-aqueous electrolyte secondary battery.

In addition, the lithium secondary battery according to another embodiment can be thinned, and at the same time, insulation between electrodes can be ensured when abnormal heat is generated.

As mentioned above, although this invention was demonstrated in detail about preferred embodiment, referring an accompanying drawing, this invention is not limited to this example.

It is clear that various changes or modifications can be made within the scope of the technical idea described in the claims by those having ordinary knowledge in the field of technology to which the present invention belongs. It is understood to be within the technical scope of the present invention. For example, although the present invention is applied to a lithium ion secondary battery in the above embodiment, it goes without saying that it may be applied to other nonaqueous electrolyte secondary batteries.

10, 10a, 10b lithium ion secondary battery
20 anode
21 current collector
22 cathode active material layer
23 microcapsule layer
30 cathode
31 current collector
32 Anode active material layer
33 microcapsule layer
40 separator layer
40a separator
40b, 40c microcapsule layer

Claims (13)

a core portion comprising a polymer of a foamable monomer; and
A microcapsule for a lithium secondary battery covering the core part and including a shell part having higher stability in the non-aqueous electrolyte secondary battery than the core part,
The foamable monomer is a microcapsule for a lithium secondary battery comprising at least one of a compound represented by the following formula (I) and a compound represented by the following formula (II):
[Formula I]

In the above formula (I),
R1 is a hydrogen atom or a methyl group,
R2 is a hydrogen atom or a C1 to C6 alkyl group,
R3 is a hydrogen atom or a C1 to C6 alkyl group,
R4 is a hydrogen atom, a methyl group, an acryl group, a methacryl group or a glycidyl group,
X is a direct bond or a C1 to C6 alkylene group,
[Formula II]

In the above formula (II),
R1 is a hydrogen atom or a methyl group,
R2 is a hydrogen atom or a C1 to C6 alkyl group,
X is a direct bond or a C1 to C6 alkylene group,
A is a methylene group or a carbonyl group,
Q is a methylene group or a methine group,
T is a direct bond, a double bond, a methylene group, oxygen, or an NH group. delete delete delete In claim 1,
Microcapsules for lithium secondary batteries having a foaming temperature of 120°C or higher and 250°C or lower. In claim 1,
Microcapsules for lithium secondary batteries having an average particle diameter of 0.05 μm to 0.5 μm. separator; and
a microcapsule layer positioned on the separator;
A separator layer for a lithium secondary battery in which the microcapsules of any one of claims 1, 5 and 6 are dispersed in the microcapsule layer. In claim 7,
The separator is a separator layer for a lithium secondary battery that is a heat-resistant separator. In claim 8,
The separator is a separator layer for a lithium secondary battery comprising a nonwoven fabric, an amide compound, or a combination thereof. electrode active material layer; and
It includes a microcapsule layer positioned on the electrode active material layer,
An electrode for a lithium secondary battery in which the microcapsules of any one of claims 1, 5 and 6 are dispersed in the microcapsule layer. electrode active material; and
The microcapsule of any one of claims 1, 5 and 6
An electrode active material layer for a lithium secondary battery comprising a. comprising an anode and a cathode;
The electrode assembly for a lithium secondary battery in which the microcapsule of any one of claims 1, 5 and 6 is present on the electrode plate of the positive electrode or the negative electrode. A lithium secondary battery comprising the separator layer according to claim 7 .

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