JP6959015B2 - Non-aqueous electrolyte secondary battery - Google Patents

Description

The present invention relates to a non-aqueous electrolyte secondary battery.

Lithium-ion secondary batteries are characterized by higher energy density and electromotive force than lead-acid batteries and nickel-metal hydride batteries, and are therefore widely used as power sources for mobile phones and laptop computers that require smaller size and lighter weight. ing. Most of these lithium ion secondary batteries use a non-aqueous electrolyte solution in which a lithium salt is dissolved in an organic solvent as an electrolyte.
In the lithium ion secondary battery, for example, a positive electrode having a positive electrode active material layer provided on a positive electrode current collector and a negative electrode having a negative electrode active material layer provided on a negative electrode current collector are laminated via a separator. It is manufactured by accommodating the laminate inside the exterior, filling it with a non-aqueous electrolyte solution, and sealing it.

It is also known that a porous insulating layer is provided on the surface of the electrode.
For example, in the examples of Patent Document 1, an inorganic particle, 1 part by mass of a polycarboxylic acid salt with respect to 100 parts by mass of the inorganic particle as a dispersant, and a binder for a total of 100 parts by mass of the inorganic particle and the dispersant. Described is a non-aqueous electrolyte secondary battery in which an aqueous slurry containing 3 parts by mass of a certain styrene butadiene rubber is applied on the surface of a positive electrode, and water as a solvent is dried and removed to form a particle layer having a thickness of 2 μm. ..
Such a particle layer functions as a filter for trapping decomposition products of non-aqueous electrolyte generated by the reaction at the positive electrode and elements (elements other than lithium) eluted from the positive electrode active material, and these are precipitated on the surface of the negative electrode and the separator. It is formed for the purpose of preventing.

Japanese Patent No. 5213534

According to the findings of the present inventor, the non-aqueous electrolyte secondary battery described in Patent Document 1 does not have sufficient peel strength of the particle layer.
An object of the present invention is to provide a non-aqueous electrolyte secondary battery having a particle layer on the surface of an electrode and having excellent peel strength of the particle layer.

The present invention has the following aspects.
[1] A positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, a separator provided between the positive electrode and the negative electrode, a non-aqueous electrolyte solution containing lithium ions, and the positive electrode and the negative electrode. A non-aqueous electrolyte secondary battery including a particle layer provided on at least one surface, wherein the particle layer contains particles and a binder, and the particles do not store and release lithium ions, and the binder. However, a non-aqueous electrolyte secondary battery containing a resin having an amide bond.
[2] The non-aqueous electrolyte secondary battery according to [1], wherein the content of the resin having an amide bond in the particle layer is 1.5 to 18 parts by mass with respect to 100 parts by mass of the particles.
[3] The non-aqueous electrolyte secondary battery according to [1] or [2], wherein the particles contain inorganic particles.
[4] The non-aqueous electrolyte secondary battery according to [3], wherein the inorganic particles are at least one selected from the group consisting of magnesia particles, titania particles, and alumina particles.
[5] The non-aqueous electrolyte secondary battery according to [3] or [4], wherein the average particle size of the inorganic particles is 1 μm or less.
[6] Any of [1] to [5], wherein the particles include organic particles made of a thermoplastic resin having a melting point of more than 150 ° C. or a glass transition point of more than 150 ° C. or a thermosetting resin. The non-aqueous electrolyte secondary battery according to item 1.
[7] The non-aqueous electrolyte secondary battery according to any one of [1] to [6], wherein the particle layer has a thickness of 1.5 to 18 μm.
[8] The positive electrode has a positive electrode current collector and a positive electrode active material layer containing the positive electrode active material provided on the surface of the positive electrode current collector, and the positive electrode active material layer is the positive electrode collector. Any one of [1] to [7], which is provided on a part of the surface of the electric body, and the particle layer exists on the positive electrode active material layer and on the surface of the positive electrode current collector. The non-aqueous electrolyte secondary battery described in the section.
[9] The negative electrode has a negative electrode current collector and a negative electrode active material layer containing the negative electrode active material provided on the surface of the negative electrode current collector, and the negative electrode active material layer is the negative electrode collector. Any one of [1] to [8], which is provided on a part of the surface of the electric body, and the particle layer exists on the negative electrode active material layer and on the surface of the negative electrode current collector. The non-aqueous electrolyte secondary battery described in the section.

The non-aqueous electrolyte secondary battery of the present invention has a particle layer on the surface of the electrode and is excellent in peel strength of the particle layer.

It is sectional drawing which schematically explains an example of the non-aqueous electrolyte secondary battery which concerns on this invention. It is a schematic block diagram which schematically explains the measuring method of the piercing strength.

Hereinafter, embodiments of the lithium ion secondary battery according to the present invention will be described with reference to the drawings. In addition, in the drawings used in the following description, in order to make the features easy to understand, the featured parts may be enlarged and shown, and the dimensional ratios of each component may differ from the actual ones. There is. Further, the materials, dimensions, etc. exemplified in the following description are examples, and the present invention is not limited thereto, and the present invention can be appropriately modified without changing the gist thereof.

[Non-aqueous electrolyte secondary battery]
FIG. 1 is a cross-sectional view schematically showing an embodiment of the non-aqueous electrolyte secondary battery of the present invention (hereinafter, may be simply referred to as a secondary battery). In the figure, reference numeral 1 is a positive electrode, 2 is a separator, 3 is a negative electrode, 4 is a particle layer, 5 is an exterior body, and 10 is a secondary battery.
The positive electrode 1 has a plate-shaped positive electrode current collector 11 and positive electrode active material layers 12 provided on both surfaces thereof. The positive electrode active material layer 12 is provided on a part of the surface of the positive electrode current collector 11, and the positive electrode current collector exposed portion 13 in which the positive electrode active material layer 12 does not exist at the edge of the surface of the positive electrode current collector 11 Is provided. An outlet wiring (tab) (not shown) is provided at an arbitrary portion of the exposed edge portion so as to conduct with the positive electrode current collector 11. The particle layer 4 is provided so as to cover the positive electrode active material layer 12, and a part of the particle layer 4 extends on the surface of the positive electrode current collector exposed portion 13.
The negative electrode 3 has a plate-shaped negative electrode current collector 31 and a negative electrode active material layer 32 provided on both surfaces thereof. The negative electrode active material layer 32 is provided on a part of the surface of the negative electrode current collector 31, and the negative electrode current collector exposed portion 33 in which the negative electrode active material layer 32 does not exist at the edge of the surface of the negative electrode current collector 31. Is provided. An drawer wiring (tab) (not shown) is provided at an arbitrary portion of the exposed edge portion so as to be conductive with the negative electrode current collector 31.
The secondary battery 10 of the present embodiment has an exterior body in which one positive electrode 1, two negative electrodes 3, and two separators 2 are laminated in the order of negative electrode / separator / positive electrode / separator / negative electrode. It is housed in 5 and is filled with a non-aqueous electrolytic solution (not shown) and sealed. In the present embodiment, the positive electrode 1, the negative electrode 3, and the separator 2 each have a rectangular shape in a plan view.

<Particle layer>
The particle layer contains particles and a binder. The particles in the particle layer are particles that do not occlude and release lithium ions. The binder in the particle layer contains a resin having an amide bond.
It is preferable that the particle layer 4 in the secondary battery 10 is formed with some gaps. When this gap is formed, lithium ions and the like can pass through the particle layer 4. The gap is preferably formed between the particles, between the binder and the particles, and the like.

The particles that do not occlude and release lithium ions may be either inorganic particles or organic particles, or both may be used in combination. It is preferable to contain inorganic particles in terms of higher peel strength and piercing strength. When organic particles are contained, the internal resistance can be further reduced.

The inorganic particles may be particles made of an inorganic material that does not occlude and release lithium ions. The number of inorganic particles in the particle layer may be one, or two or more may be used in combination.
As the inorganic particles, for example, inorganic oxide particles are preferable. Specifically, one or more selected from the group consisting of magnesia (magnesium oxide) particles, titania (titanium oxide) particles, and alumina (aluminum oxide) particles is preferable.
The average particle size of the inorganic particles is preferably 1.2 μm or less. 1.0 μm or less is more preferable from the viewpoint of being more excellent in the piercing strength of the particle layer. The lower limit of the average particle size of the inorganic particles is not particularly limited, but from the viewpoint of dispersibility in the coating liquid, 0.1 μm or more is preferable, and 0.3 μm or more is more preferable.

The organic particles may be particles made of an organic material that does not occlude and release lithium ions. The number of organic particles in the particle layer may be one, or two or more may be used in combination.
Examples of organic particles include polyethylene particles, polypropylene particles, vinyl chloride resin particles, acrylic resin particles, polyamide (nylon) particles, polyester particles and the like.
When heat resistance is required for the particle layer, it is preferable to use organic particles made of a thermoplastic resin or a thermosetting resin that satisfies at least one of a melting point of more than 150 ° C. and a glass transition point of more than 150 ° C. Such organic particles are stable at a temperature of 150 ° C. or lower, and have excellent heat resistance at an operating temperature of 150 ° C. or lower, which is lower than the boiling point of the non-aqueous electrolytic solution.
Examples of the thermoplastic resin, which is a thermoplastic resin having a melting point of more than 150 ° C. or a glass transition point of more than 150 ° C., include polypropylene, polyamide, polyphenylene sulfide, and fluororesin. Examples of the thermosetting resin include melamine resin, epoxy resin, unsaturated polyester, silicone resin and the like.
The upper limit of the average particle size of the organic particles is preferably 2 μm or less, more preferably 1 μm or less, from the viewpoint of balance with the thickness of the particle layer. The lower limit is preferably 0.01 μm or more, and more preferably 0.1 μm or more from the viewpoint of dispersibility in the coating liquid.

The "average particle size" of the inorganic particles and the organic particles is a number-based number average particle size. For the average particle size of the inorganic particles and organic particles, 50 particles to be measured were randomly selected, observed with an electron microscope or an optical microscope, and the major axis of each particle (the longest transfer length) was measured. , Calculate the average value of them. Further, it may be simply obtained by a laser diffraction type particle size distribution measuring device.

The content of the particles in the particle layer is preferably 70 to 99% by mass, more preferably 88 to 96% by mass, based on the total mass (100% by mass) of the particle layer. When it is not more than the upper limit of the above range, both the particle binding property and the ion permeability are excellent.

When both inorganic particles and organic particles are used as the particles in the particle layer, the amount of the inorganic particles is preferably 50 to 95% by mass, preferably 80 to 95% of the total of the inorganic particles / organic particles (100% by mass). More preferably by mass. When the proportion of the inorganic particles is at least the lower limit of the above range, the peel strength and the piercing strength of the particle layer are more excellent. When it is not more than the upper limit value, the effect of reducing the internal resistance of the secondary battery by containing the organic particles is more excellent.

The resin having an amide bond used as a binder is preferably polyamide, polyimide, or polyamideimide. Polyimide or polyamide-imide is more preferable in that the peel strength and the piercing strength of the particle layer are more excellent.
The resin having an amide bond may be one kind or two or more kinds may be used in combination.

The resin having an amide bond preferably has a Tg of 250 ° C. or higher or a tensile strength (measurement method: JIS K6251) of 100 MPa or higher, and more preferably a Tg of 250 ° C. or higher and a tensile strength of 100 MPa or higher.
Examples of polyimides satisfying Tg of 250 ° C. or higher and tensile strength of 100 MPa or higher include Yupia (registered trademark) -AT and Yupia (registered trademark) LB (both product names, manufactured by Ube Industries, Ltd.).
Examples of the polyamide-imide having a Tg of 250 ° C. or higher and a tensile strength of 100 MPa or higher include Vilomax HR-11NN and HR-16NN (both product names, manufactured by Toyobo Co., Ltd.).

The content of the resin having an amide bond is preferably 1.5 to 18 parts by mass, more preferably 2 to 15 parts by mass with respect to 100 parts by mass of the particles in the particle layer.
When the content of the resin having an amide bond is within the above range, the effect of improving the peel strength and the piercing strength is excellent while suppressing the increase in the internal resistance.

When the thickness of the particle layer is a certain thickness, the peel strength increases as the thickness increases. The internal resistance increases as the particle layer becomes thicker. The piercing strength also increases as the particle layer becomes thicker.
The thickness of the particle layer is preferably 1.5 to 18 μm, more preferably 2 to 15 μm, and even more preferably 2 to 5 μm.
Here, the thickness of the particle layer in the present invention is a value obtained as a value obtained by observing the thickness of an arbitrary 10 points on the cross section of the particle layer with an SEM and calculating the average thereof.

As a relationship between the thickness T of the particle layer and the average particle size D of the particles, the ratio (D / T) represented by (average particle size D) / (thickness T of the particle layer) is, for example, 0.5 / 100 to 80/100 is preferable, 1/100 to 40/100 is more preferable, and 5/100 to 20/100 is even more preferable.
When the ratio (D / T) is at least the lower limit of the above range, the ionic conductivity of the particle layer is further enhanced, and the increase in internal resistance can be further suppressed.
When the ratio (D / T) is not more than the upper limit of the above range, the mechanical strength of the particle layer tends to be further increased, and the peel strength and the piercing strength tend to be further improved.

In addition to the particles and the resin having an amide bond, the particle layer may contain other components as long as the effects of the present invention are not impaired. Examples of other components include binders other than resins having an amide bond (polyvinylidene fluoride, polymethyl methacrylate, etc.).
The total content of the other components in the particle layer is preferably 0 to 10% by mass, more preferably 0 to 5% by mass, based on the total mass (100% by mass) of the particle layer.

[How to create a particle layer]
The particle layer is prepared by applying a coating liquid (slurry) containing particles, a resin having an amide bond, a diluting solvent, and any other component on at least one surface of a positive electrode and a negative electrode, and then drying the solvent. Can be formed by a method of removing.
The diluting solvent may be any one capable of dissolving or dispersing the resin having an amide bond. The amount of the diluting solvent used can be appropriately adjusted according to the coating workability and the like.
The resin having an amide bond can be used in the form of a commercially available varnish.

<Positive electrode>
The positive electrode current collector and the positive electrode active material layer are not particularly limited, and known materials can be used.
A conductive metal foil is used as the positive electrode current collector, and for example, aluminum, stainless steel, nickel, titanium, or an alloy thereof is used.
The positive electrode active material layer is formed, for example, by applying a positive electrode slurry obtained by dispersing a positive electrode active material, a conductive auxiliary agent, and a binder in a solvent on the surface of a positive electrode current collector.
Examples of the positive electrode active material include transition metal oxides such as lithium cobalt oxide, lithium nickel oxide, lithium manganate, and lithium olivine-type iron phosphate, and one or more selected from the group consisting of these materials is preferable.
As the conductive auxiliary agent, for example, acetylene black, carbon nanofiber or the like is used, and as the binder, for example, polyvinylidene fluoride or the like is used.

<Negative electrode>
The negative electrode current collector and the negative electrode active material layer are not particularly limited, and known materials can be used.
As the negative electrode current collector, a conductive metal foil is used, and for example, copper, stainless steel, nickel, titanium or an alloy thereof is used.
The negative electrode active material layer is formed by, for example, applying a negative electrode slurry prepared by dispersing a negative electrode active material, a binder, and a conductive additive added as needed in a solvent on the surface of the negative electrode current collector. It is formed.
Examples of the negative electrode active material include metallic lithium, lithium alloys, carbon-based materials capable of occluding and releasing lithium ions (carbon powder, graphite powder, etc.), metal oxides, etc., and one or more selected from the group consisting of these materials. Is preferable.
As the binder, for example, polyvinylidene fluoride, styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose salt (CMC) and the like can be used, and as the conductive auxiliary agent, for example, acetylene black, carbon nanotubes and the like can be used. Can be done.

<Separator>
The material of the separator is not particularly limited, and for example, a microporous polymer film or non-woven fabric made of an olefin resin (polyethylene, polypropylene, etc.) or a cellulosic material; a woven cloth or a non-woven fabric made of glass fiber, etc. Can be mentioned.

<Non-aqueous electrolyte>
A known non-aqueous electrolyte solution can be used in the non-aqueous electrolyte secondary battery.
The non-aqueous electrolyte solution may be in the form of a mixture of an electrolyte and a non-aqueous solvent, or may be in the form of a mixture of an electrolyte, a polymer and a non-aqueous solvent.
As the electrolyte, those used in known lithium ion secondary batteries can be applied, for example, lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoride (LiBF ₄ ), lithium bisfluorosulfonylimide. Known lithium salts such as (LiFSI), bis (trifluoromethanesulfonyl) imidelithium (LiN (SO ₂ CF ₃ ) ₂ , LiTFSI) and the like can be mentioned. One type of electrolyte may be used alone, or two or more types may be used in combination.

As the non-aqueous solvent, for example, carbonates, esters, ethers, lactones, nitriles, amides, sulfones and the like can be used. As the non-aqueous solvent, one kind may be used alone, or two or more kinds of mixed solvents may be used.
Specific examples include propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, dimethoxyethane, acetonitrile, propionitrile, tetrahydrofuran, 2-methyltetrahydrofuran, dioxane, nitromethane, N, N-dimethylformamide, and dimethylsulfoxide. , Sulfolane, γ-butyrolactone and the like.

<Action / effect>
Since the secondary battery of the present embodiment is provided with a particle layer on the surface of the positive electrode, decomposition products of the non-aqueous electrolyte solution generated by the reaction at the positive electrode and elements (other than lithium) eluted from the positive electrode active material. Elements) are trapped in the particle layer, preventing them from depositing on the negative electrode surface and separator.
Further, by using a resin having an amide bond as a binder of the particle layer, it is possible to improve the peel strength of the particle layer while suppressing an increase in internal resistance as much as possible.
Further, by using a resin having an amide bond as a binder of the particle layer, it is possible to improve the piercing strength of the particle layer while suppressing an increase in internal resistance as much as possible. For example, when the lithium ion secondary battery is repeatedly charged and discharged, needle-like crystals (dendrites) of lithium metal are deposited on the negative electrode side, and when the dendrites are elongated, they penetrate the separator and reach the positive electrode, causing an internal short circuit. be. By providing a particle layer having excellent piercing strength on the surface of the positive electrode, it is possible to prevent foreign matter such as dendrite from reaching the positive electrode.

Further, the resin having an amide bond has excellent heat resistance, and by using a resin having high heat resistance as the particles of the particle layer, a secondary battery having excellent heat resistance can be obtained. Specifically, by using only inorganic particles as particles in the particle layer, or by using organic particles made of a thermoplastic resin or a thermosetting resin having a melting point of more than 150 ° C., a particle layer having excellent heat resistance can be obtained. Can be formed.

Further, in the secondary battery of the present embodiment, the particle layer is not only on the positive electrode active material layer but also on the surface of the positive electrode current collector on the surface of the positive electrode current collector on which the positive electrode active material layer is provided. exist. That is, as shown in FIG. 1, a part of the particle layer 4 exists on the surface of the positive electrode current collector exposed portion 13. Therefore, when the separator does not exist between the negative electrode active material layer 32 and the positive electrode current collector exposed portion 13 facing each other due to thermal shrinkage or misalignment of the separator, the negative electrode active material layer 32 and the positive electrode collection The particle layer 4 existing between them can prevent the electric body exposed portion 13 from coming into contact with each other and causing a short circuit.
The larger the region of the surface of the positive electrode current collector exposed portion 13 where the particle layer 4 exists, the higher the effect of preventing the short circuit. For example, the distance from the edge of the positive electrode active material layer 12 to the edge of the particle layer 4 (indicated by x in the figure) is preferably 2 mm or more, and more preferably 5 mm or more.

<Modification example>
In the present embodiment, the particle layer 4 is provided on the surface of the positive electrode 1, but a similar particle layer may be provided on the surface of the negative electrode 3, or both on the surface of the positive electrode 1 and on the surface of the negative electrode 3. The same effect can be obtained.
The secondary battery 10 of the present embodiment has one positive electrode 1, two negative electrodes 3, and two separators 2 laminated as shown in FIG. 1, but has a unit composed of a negative electrode / separator / positive electrode. The number of the units can be changed arbitrarily.
In the secondary battery 10 of the present embodiment, the positive electrode active material layer 12 and the particle layer 4 are provided on both sides of the positive electrode current collector 11, but may be provided only on one side of the positive electrode current collector 11. When the particle layer is provided on the surface of the negative electrode, the negative electrode active material layer and the particle layer may be provided on both sides of the negative electrode current collector, or may be provided on only one side of the negative electrode current collector.
In general, the positive electrode has a rate-determining conductivity, and the negative electrode has an ionic conductivity that determines the rate. Therefore, from the viewpoint of smoothly advancing the electrochemical reaction of the secondary battery and suppressing an increase in internal resistance, it is preferable to provide the particle layer on the surface of the positive electrode rather than the surface of the negative electrode.
The shape of the secondary battery is not limited to the shape of the present embodiment, and can be adjusted to various shapes such as a cylindrical type, a square type, a coin type, and a sheet type.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

[Manufacturing Example 1: Manufacture of positive electrode]
100 parts by mass of a solid component containing a positive electrode active material, 5 parts by mass of a conductive auxiliary agent (acetylene black), 5 parts by mass of a binder (vinylidene fluoride, hereinafter also referred to as PVdF), and a solvent (N-methyl-). A mixture (slurry) composed of 2-pyrrolidone (hereinafter, also referred to as NMP) is adjusted to a solid content of 45% by mass, applied to both sides of an aluminum foil, pre-dried, vacuum dried at 120 ° C., and at 4 kN. A positive electrode was prepared by pressurizing and punching to a 40 mm square electrode size.
Lithium iron olivine was used as the positive electrode active material, and the following mixing ratio (mass ratio) was used.
Positive electrode active material: Binder (PVdF): Conductive aid = 90: 5: 5

[Manufacturing example 2: Manufacture of negative electrode]
A mixture (slurry) consisting of 100 parts by mass of a solid component containing a negative electrode active material, 1.5 parts by mass of a binder (SBR), 1.5 parts by mass of a binder (CMC), and an aqueous solvent is solidified. After adjusting to 50% by mass, the mixture was applied to both sides of the copper foil, vacuum dried at 100 ° C., pressure-pressed at 2 kN, and further punched to an electrode size of 42 mm square to prepare a negative electrode.
Graphite was used as the negative electrode active material, and the following mixing ratio (mass ratio) was used.
Negative electrode active material: Binder (CMC): Binder (SBR) = 98: 1: 1

[Production Example 3: Preparation of non-aqueous electrolyte solution]
A non-aqueous electrolyte solution was prepared by dissolving _{LiPF 6} as an electrolyte in a solvent in which ethylene carbonate (EC): diethyl carbonate (DEC) was mixed at a volume ratio of 3: 7 so as to be 1 mol / liter.

[Example 1]
(Formation of particle layer)
Alumina particles (manufactured by Nippon Light Metal Co., Ltd., product name: AHP200, average particle diameter 0.4 μm) are used as inorganic particles, and silicone resin particles (manufactured by Shin-Etsu Chemical Co., Ltd., product name: X-52-854, average) are used as organic particles. Particle size 0.7 μm) was used. Inorganic particles account for 90% by mass with respect to the total of inorganic particles / organic particles.
Polyimide varnish (manufactured by Ube Industries, Ltd., product name: Yupia (registered trademark) -AT, solvent: NMP) was used as the binder.

A coating solution was prepared by uniformly mixing NMP as an inorganic particle, an organic particle, a binder, and a diluting solvent with the formulations shown in Table 1.
The obtained coating liquid was applied on both sides of the positive electrode obtained in Production Example 1 and dried to remove the diluting solvent, and a particle layer was formed on both sides of the positive electrode. The thickness of each particle layer after drying was 5 μm. The content of the particles was 95.2% by mass with respect to the total mass of the particle layer.
As shown in FIG. 1, the particle layer 4 was continuously formed on the positive electrode active material layer 12 of the positive electrode and on the positive electrode current collector exposed portion 13 adjacent thereto. The distance (x) from the edge of the positive electrode active material layer 12 to the edge of the particle layer 4 was 5 mm.

(Battery manufacturing)
A polyethylene porous film (melting point 128 ° C.) was used as the separator.
As shown in FIG. 1, the two negative electrodes obtained in Production Example 2, the one positive electrode having the particle layer formed above, and the two separators were laminated in the order of negative electrode / separator / positive electrode / separator / negative electrode. A terminal tab is electrically connected to each of the positive electrode current collector exposed portion and the negative electrode current collector exposed portion, and the laminate is sandwiched between aluminum laminate films so that the terminal tab protrudes to the outside, and the three sides are sandwiched. Sealed by laminating. A secondary battery (laminated battery) was manufactured by injecting the electrolytic solution obtained in Production Example 3 from one side left unsealed and vacuum-sealing. When the battery was evaluated, the initial discharge capacity was 50 mAh.

(evaluation)
(1) Internal resistance The internal resistance (impedance) of the secondary battery manufactured above was measured at room temperature (25 ° C.) using a battery high tester BT3562 (product name, manufactured by Hioki Electric Co., Ltd.). The results are shown in Table 1.
(2) Peeling Strength The positive electrode having the particle layer formed as described above was immersed in the electrolytic solution (60 ° C.) obtained in Production Example 3 for 2 hours as a sample. From the sample, the part where the particle layer is provided on the positive electrode active material layer is cut out in a strip shape with a width of 1 cm, a strong adhesive tape is attached to the particle layer with a roller, and a peeling test in the 180 ° direction is performed using an autograph. rice field. The test was carried out at room temperature (25 ° C.), and the peeling test speed was 10 mm / sec. The results are shown in Table 1.

(3) Puncture strength The piercing strength was measured using the device configured as shown in FIG. In the figure, reference numeral 41 indicates a negative electrode obtained in Production Example 2, 42 indicates a separator used in Example 1, 43 indicates a nickel piece, 44 indicates a particle layer, and 45 indicates an aluminum foil used in Production Example 1. The particle layer 44 is formed on the aluminum foil 45 under the same conditions as in Example 1. Reference numeral 51 is a pressing jig that applies pressure in a direction in which the negative electrode 41 and the aluminum foil 45 (positive electrode) approach each other, and this pressure is measured by an autograph. Reference numeral 52 is a backing plate made of SUS304. As the nickel small piece 43, the one described in the JIS C 8714 forced internal short circuit test was used. When the pressing jig 51 is lowered to increase the pressure for pressing the negative electrode 41 against the aluminum foil 45 (positive electrode), the nickel small pieces 43 penetrate the separator 42 and the particle layer 44 to cause conduction (short circuit).
In the test, 2V is applied between the negative electrode 41 and the aluminum foil 45 (positive electrode), the resistance value between the positive electrode and the negative electrode is measured while lowering the pressing jig 51, and when the resistance value becomes 10Ω or less. It was judged that the particles were conducting, and the pressure at that time was taken as the piercing strength of the particle layer. The results are shown in Table 1.

(4) Heat resistance test When the secondary battery manufactured above is charged to 3.8 V and then stored in a constant temperature bath at 130 ° C. for 3 hours, a voltage drop of 1 V or more is observed. The case where the voltage was less than 0 to 1 V was evaluated as 〇. The results are shown in Table 1.

[Comparative Examples 1 to 3]
In Example 1, the binder of the particle layer was changed to the following. Other than that, the secondary battery was manufactured and evaluated in the same manner as in Example 1.
Binder of Comparative Example 1: PMMA (manufactured by Wako Pure Chemical Industries, Ltd., Poly (methyl polypolylate), MW to 12,000).
Binder of Comparative Example 2: PVdF (manufactured by Kureha Corporation, product name: # 7300, solvent: NMP, solid content concentration: 5% by mass).
Binder of Comparative Example 3: CMC (manufactured by Daicel Corporation, product name: # 2200) and SBR (manufactured by JSR, product name: TRD-104) mixture (CMC solid content concentration 1% by mass, SBR solid content concentration 1 mass) %).

[Example 2]
In Example 1, the binder of the particle layer was changed to a polyamide-imide varnish (manufactured by Toyobo Co., Ltd., product name: Vilomax HR-11NN, solvent: NMP, solid content concentration: 15% by mass). Other than that, the secondary battery was manufactured and evaluated in the same manner as in Example 1.

[Examples 3 to 5]
In Example 1, the blending amount of the binder was changed as shown in Table 1. A secondary battery was manufactured in the same manner as in Example 1 except for the above, and evaluated (internal resistance, peel strength, piercing strength) by the above method (hereinafter, the same applies).

[Examples 6 to 8]
In Example 1, the inorganic particles were changed as follows.
Inorganic particles of Example 6: Alumina particles (average particle size 1.2 μm).
Inorganic particles of Example 7: Titania particles (average particle size 0.4 μm).
Inorganic particles of Example 8: magnesia particles (average particle size 0.7 μm).

[Examples 9 to 12]
When forming the particle layer, the same coating liquid as in Example 1 was used, the coating amount was changed, and the film thickness of the particle layer was changed as shown in Table 1.

[Example 13]
Example 13 is a reference example.
In Example 1, the organic particles were not used, and instead the content of the inorganic particles was changed as shown in Table 1.

As shown in the results in Table 1, the secondary batteries of Examples 1 to 13 are excellent in peel strength and piercing strength. In addition, the increase in internal resistance was suppressed, and specifically, the internal resistance (impedance) was less than 300 mΩ and the peel strength was 0.5 N / cm or more.
Further, as compared with Comparative Examples 1 to 3 in which the binder is a resin having no amide bond, Examples 1 and 2 are excellent in heat resistance.

1 Positive electrode 2 Separator 3 Negative electrode 4 Particle layer 5 Exterior body 10 Secondary battery 11 Positive electrode current collector 12 Positive electrode active material layer 13 Positive electrode current collector exposed part 31 Negative electrode current collector 32 Negative electrode active material layer 33 Negative electrode current collector exposed part 41 Negative electrode 42 Separator 43 Nickel small piece 44 Particle layer 45 Aluminum foil 51 Pressing jig 52 Receiving plate

Claims (9)

A positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, a separator provided between the positive electrode and the negative electrode (excluding those having a layer containing particles), and a non-containing lithium ion. A non-aqueous electrolyte secondary battery comprising a water electrolyte and a particle layer fixed on the surface of at least one of the positive electrode and the negative electrode.
The particle layer contains particles and a binder and contains
The particles are inorganic particles that do not occlude and release lithium ions, and organic particles that do not occlude and release lithium ions.
The amount of the inorganic particles is 50 to 95% by mass with respect to the total of the inorganic particles and the organic particles.
A non-aqueous electrolyte secondary battery in which the binder contains a resin having an amide bond. The non-aqueous electrolyte secondary battery according to claim 1, wherein the content of the resin having an amide bond in the particle layer is 1.5 to 18 parts by mass with respect to 100 parts by mass of the particles. The non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the inorganic particles are at least one selected from the group consisting of magnesia particles, titania particles, and alumina particles. The non-aqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the average particle size of the inorganic particles is 1 μm or less. The non-aqueous electrolyte secondary battery according to any one of claims 1 to 4, wherein the average particle size of the organic particles is 2 μm or less. The invention according to any one of claims 1 to 5, wherein the organic particles include organic particles made of a thermoplastic resin having a melting point of more than 150 ° C. or a glass transition point of more than 150 ° C. or a thermosetting resin. The non-aqueous electrolyte secondary battery described. The non-aqueous electrolyte secondary battery according to any one of claims 1 to 6, wherein the particle layer has a thickness of 1.5 to 18 μm. The positive electrode has a positive electrode current collector and a positive electrode active material layer containing the positive electrode active material provided on the surface of the positive electrode current collector.
The claim that the positive electrode active material layer is provided on a part of the surface of the positive electrode current collector, and the particle layer exists on the positive electrode active material layer and on the surface of the positive electrode current collector. The non-aqueous electrolyte secondary battery according to any one of 1 to 7. The negative electrode has a negative electrode current collector and a negative electrode active material layer containing the negative electrode active material provided on the surface of the negative electrode current collector.
The claim that the negative electrode active material layer is provided on a part of the surface of the negative electrode current collector, and the particle layer exists on the negative electrode active material layer and on the surface of the negative electrode current collector. The non-aqueous electrolyte secondary battery according to any one of 1 to 8.

Images