JP2018101624A - Electrode for lithium-ion battery and lithium-ion battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode for a lithium-ion battery and a lithium-ion battery, which are excellent in energy density and cycle characteristics.SOLUTION: An electrode for a lithium-ion battery includes an electrode current collector and an electrode active material layer, and is characterized in that: the electrode active material layer comprises a non-bound body of an electrode active material composition containing an electrode active material; a pressure relieving layer formed from a conductive carbon filler is arranged between the electrode current collector and the electrode active material layer; and the electrode active material is present near the surface of the pressure relieving layer, the surface being on an electrode active material layer side.SELECTED DRAWING: Figure 1

Description

The present invention relates to an electrode for a lithium ion battery and a lithium ion battery.

In recent years, reduction of carbon dioxide emissions has been strongly desired for environmental protection. In the automobile industry, there are high expectations for reducing carbon dioxide emissions by introducing electric vehicles (EVs) and hybrid electric vehicles (HEVs), and we are eager to develop secondary batteries for motor drives that hold the key to their practical application. Has been done. As a secondary battery, attention is focused on a lithium ion battery that can achieve a high energy density and a high output density.

In order to increase the energy density of a lithium ion battery, an active material having a larger theoretical capacity, that is, a material that can occlude more lithium ions per unit volume has attracted attention. However, as the amount of lithium ions that can be occluded per unit volume increases, the volume change associated with insertion / extraction of lithium ions also increases. Therefore, there is a case where the material self-destructs due to the volume change, and the active material layer is easily peeled off from the current collector surface, so that it is difficult to improve cycle characteristics.

For example, Patent Document 1 discloses a lithium ion battery that suppresses expansion of a negative electrode by adjusting a mixing ratio of at least one of silicon and a silicon compound and carbon and a particle diameter thereof to a predetermined range. ing.

Japanese Patent Laid-Open No. 2006-103337

However, since the negative electrode described in Patent Document 1 uses a binder, there is a problem that the negative electrode active material is peeled off from the surface of the negative electrode current collector when the electrode thickness is excessively increased. In addition, the binder may restrict the expansion and contraction of silicon and the silicon compound, and may easily break. Furthermore, the effect of suppressing the expansion of the negative electrode is not sufficient, and there is room for further improvement.

This invention is made | formed in view of the said subject, and it aims at providing the electrode for lithium ion batteries excellent in energy density and cycling characteristics, and a lithium ion battery.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have reached the present invention.
That is, the present invention is an electrode for a lithium ion battery comprising an electrode current collector and an electrode active material layer, wherein the electrode active material layer is a non-binding electrode active material composition containing an electrode active material. A pressure relaxation layer made of a conductive carbon filler is disposed between the electrode current collector and the electrode active material layer, and in the vicinity of the surface on the electrode active material layer side of the pressure relaxation layer The present invention relates to an electrode for a lithium ion battery, characterized in that the electrode active material is present; and relates to a lithium ion battery provided with the electrode.

The electrode for a lithium ion battery of the present invention is excellent in cycle characteristics.

FIG. 1 is a cross-sectional view schematically showing an example of an electrode for a lithium ion battery of the present invention. 2 (a) and 2 (b) are cross-sectional views schematically showing the state before and after charge / discharge of the electrode active material layer and the pressure relaxation layer constituting the electrode for a lithium ion battery of the present invention.

Hereinafter, the present invention will be described in detail.
The electrode for a lithium ion battery of the present invention is an electrode for a lithium ion battery comprising an electrode current collector and an electrode active material layer, and the electrode active material layer comprises an electrode active material composition containing an electrode active material A pressure relaxation layer made of a conductive carbon filler is disposed between the electrode current collector and the electrode active material layer, and the electrode active material layer of the pressure relaxation layer The electrode active material is present in the vicinity of the surface on the side.

The structure of the lithium ion battery electrode of the present invention will be described with reference to FIG.
FIG. 1 is a cross-sectional view schematically showing an example of an electrode for a lithium ion battery of the present invention.
As shown in FIG. 1, the electrode 1 for a lithium ion battery includes an electrode current collector 10 and an electrode active material layer 30, and is electrically conductive between the electrode current collector 10 and the electrode active material layer 30. A pressure relaxation layer 20 made of a carbon filler is disposed.
The electrode active material layer 30 is a non-binding body of an electrode active material composition containing an electrode active material.

In the electrode for a lithium ion battery of the present invention, a pressure relaxation layer is provided between the electrode current collector and the electrode active material layer. When the electrode active material layer expands due to either charging or discharging, the pressure relaxation layer contracts, whereby the volume change of the entire electrode can be suppressed. On the other hand, when the electrode active material layer contracts due to either charging or discharging, the pressure relaxation layer expands, whereby the volume change of the entire electrode can be suppressed. Therefore, peeling of the electrode active material layer accompanying charge / discharge can be suppressed and cycle characteristics can be improved.

Furthermore, in the electrode for a lithium ion battery of the present invention, the electrode active material layer is a non-binding body of an electrode active material composition containing an electrode active material. The non-binding body means that the positions of the electrode active materials constituting the electrode active material layer are not fixed by a binder (also referred to as a binder).
An electrode active material layer in a conventional lithium ion battery is manufactured by applying a slurry in which an electrode active material and a binder are dispersed in a solvent to the surface of an electrode current collector, etc., and heating and drying. The electrode active material layer is in a state of being hardened by a binder. At this time, the electrode active materials are fixed to each other by the binder, and the positions of the electrode active materials are fixed. When the electrode active material layer is hardened with a binder, excessive stress is applied to the electrode active material due to expansion / contraction at the time of charge / discharge, and the electrode active material layer is easily broken.
Further, since the electrode active material layer is fixed to the surface of the electrode current collector by the binder, the electrode active material layer solidified by the binder due to expansion / contraction during charge / discharge of the electrode active material is cracked. May occur, or the electrode active material layer may be peeled off from the surface of the electrode current collector.

On the other hand, in the electrode active material layer constituting the lithium ion battery electrode of the present invention, the components in the electrode active material layer (electrode active material and optional components added as necessary) are not bound to each other. Also, the position is not fixed. Therefore, self-destruction caused by expansion / contraction during charging / discharging of the electrode active material can be suppressed. Furthermore, since the electrode active material layer constituting the lithium ion battery electrode of the present invention is not fixed to the surface of the electrode current collector by a binder, the electrode active material may be expanded or contracted during charging / discharging. Since the electrode active material layer is not cracked or peeled off, deterioration of cycle characteristics can be suppressed.
Therefore, the lithium ion battery electrode of the present invention can provide a lithium ion battery excellent in energy density and cycle characteristics.

Hereinafter, each structure of the electrode for lithium ion batteries of this invention is demonstrated.

In the electrode for a lithium ion battery of the present invention, a pressure relaxation layer made of a conductive carbon filler is disposed between the electrode current collector and the electrode active material layer. The electrical resistivity of the conductive carbon filler constituting the pressure relaxation layer is preferably 50 μΩ · m or less.
In addition, since the pressure relaxation layer is composed of a conductive filler, the pressure relaxation layer has a void. When the electrode active material enters the void, the pressure relaxation layer has an electrode in the vicinity of the surface on the electrode active material layer side. Active material is present.

The bulk density of the conductive carbon filler constituting the pressure relaxation layer is not particularly limited, but is 0.01 to 0.7 g / cm ³ from the viewpoint of ease of absorption of expansion and contraction of the electrode active material layer. Is preferred. The bulk density of the conductive carbon filler is measured according to JIS K5101-12-1 Pigment test method-Part 12: Apparent density or apparent specific volume-Section 1: Standing method.

The pressure relaxation layer may contain components other than the conductive carbon filler.
As components other than the said conductive carbon filler, a well-known metal filler etc. are mentioned, for example.

Although the thickness of a pressure relaxation layer is not specifically limited, Although it can adjust according to the thickness of an electrode, it is preferable that it is 2-500 micrometers, and it is more preferable that it is 30-100 micrometers.
When the thickness of the pressure relaxation layer is within this range, it becomes easy to achieve both absorption of expansion and contraction of the electrode active material layer and improvement of energy density.
The electrode active material is present near the surface on the electrode active material layer side of the pressure relaxation layer, but the thickness of the thickest portion of the pressure relaxation layer is the thickness of the pressure relaxation layer. To do. The thickness of the pressure relaxation layer is measured, for example, by observing the cut surface of the lithium ion battery electrode cut perpendicularly to the thickness direction with a digital microscope [VHX-5000, manufactured by Keyence Corporation]. Can do.

The pressure relaxation layer disposed between the electrode current collector and the electrode active material layer forms a substantially sponge-like porous layer having a skeleton made of conductive carbon filler and voids. It is thought to form.
Therefore, the expansion of the active material layer caused by lithium ions being taken into the active material generates a force that expands from the inside to the outside of the battery outer body. Therefore, it is possible to suppress the occurrence of defects such as cracks and peeling in the electrode active material layer, so that a lithium ion battery having excellent cycle characteristics can be obtained.

The reason why the lithium ion battery electrode of the present invention can suppress the expansion of the electrode active material layer will be described with reference to FIG. 2A and FIG.
2 (a) and 2 (b) are cross-sectional views schematically showing the state before and after charge / discharge of the electrode active material layer and the pressure relaxation layer constituting the electrode for a lithium ion battery of the present invention.
Note that the lithium ion battery electrode 1 shown in FIGS. 2A and 2B is housed in an exterior body 40. This does not show the actual usage of the lithium ion battery electrode of the present invention, and the negative electrode and the positive electrode, which are electrodes in the lithium ion battery, are covered with a battery outer package, so that free volume expansion is limited. It is for showing that it is being done.
2A schematically shows a state before the volume expansion of the electrode active material, and FIG. 2B schematically shows a state after the volume expansion of the electrode active material.
As shown in FIGS. 2A and 2B, the lithium ion battery electrode 1 including the electrode current collector 10, the pressure relaxation layer 20, and the electrode active material layer 30 is accommodated in an exterior body 40. Yes. When occlusion reaction of lithium ions in the lithium ion battery electrode 1 occurs, the thickness of the electrode active material layer 30 is increased from b ₁ to b _2. This increase in volume is considered to be largely due to the expansion of the electrode active material contained in the electrode active material layer 30. At this time, since the outer package 40 is present, the electrode active material layer expands toward the pressure relaxation layer, and the thickness of the pressure relaxation layer 20 decreases from a ₁ to a ₂ . That is, the volume reduction of the electrode active material layer 30 is offset by the volume reduction of the pressure relaxation layer 20, and the volume expansion of the entire electrode can be suppressed.
In FIGS. 2 (a) and 2 (b), the electrode total thickness of the electrode active material layer and the pressure relief layer before and after the volume expansion of the active material (for a ₁ and b ₁ in FIGS. 2 (a) The total, the sum of a ₂ and b ₂ in FIG.

In FIG. 2A and FIG. 2B, the boundary between the pressure relaxation layer 20 and the electrode active material layer 30 is indicated by a wavy line, but the boundary between the pressure relaxation layer 20 and the electrode active material layer 30 is It is not configured to be wavy. In the lithium ion battery electrode of the present invention, the electrode active material constituting the electrode active material layer is present in the vicinity of the surface of the pressure relaxation layer on the electrode active material layer side. 2A and 2B, the wavy lines indicate that the boundary between the pressure relaxation layer 20 and the electrode active material layer 30 is not clear due to the above reason.

The pressure relaxation layer is preferably composed of a conductive carbon filler having an electrical resistivity of 50 μΩ · m or less. It is preferable that the electrical resistivity of the conductive carbon filler is in the above range because the current generated by the battery reaction of the electrode active material can be transmitted to the negative electrode current collector.

Examples of the conductive carbon filler include carbon [graphite and carbon black (acetylene black, ketjen black, furnace black, channel black, thermal lamp black, etc.)], PAN-based carbon fiber, pitch-based carbon fiber, and other carbon fibers. , Carbon nanofibers and carbon nanotubes.

The conductive carbon filler constituting the pressure relaxation layer is at least one selected from the group consisting of carbon fiber, carbon nanofiber, and carbon nanotube from the viewpoint of absorbing the volume expansion of the active material layer and from the viewpoint of conductivity. Is more preferable.
The aspect ratio of the conductive carbon filler constituting the pressure relaxation layer is not particularly limited, but is preferably 20 to 10,000.
The aspect ratio of the conductive carbon filler can be measured by observing the conductive carbon filler with a scanning electron microscope (hereinafter also referred to as SEM).

In the lithium ion battery electrode of the present invention, a positive electrode active material or a negative electrode active material can be used as the electrode active material.
An electrode current collector when a positive electrode active material is used as the electrode active material is also referred to as a positive electrode current collector, and an electrode current collector when a negative electrode active material is used as the electrode active material is also referred to as a negative electrode current collector. An electrode active material layer when a positive electrode active material is used as an electrode active material is also called a positive electrode active material layer, and an electrode active material layer when a negative electrode active material is used as an electrode active material is also called a negative electrode active material layer. Pressure relief layer constituting a lithium ion battery electrode using a positive electrode active material as a positive electrode pressure relief layer, and pressure relief layer constituting a lithium ion battery electrode using a negative electrode active material as an electrode active material Also called a layer.

First, the negative electrode active material will be described.
When the electrode active material constituting the electrode for the lithium ion battery of the present invention is a negative electrode active material, the negative electrode active material layer is a non-binding body of a mixture containing silicon and / or a silicon compound and a carbon-based negative electrode active material. Preferably, it is a non-binding body of a mixture comprising silicon and / or a silicon compound, a carbon-based negative electrode active material, and an electrolytic solution.
When silicon and / or a silicon compound having a large theoretical capacity is used for the negative electrode active material layer, the energy density is excellent. Furthermore, since it is a non-binding body and does not contain a binder, it is possible to suppress deterioration of cycle characteristics as described above.
As the electrolytic solution, an electrolytic solution containing an electrolyte and a non-aqueous solvent used for manufacturing a lithium ion battery can be used.

The mass mixing ratio of the total of silicon and silicon compounds contained in the mixture constituting the negative electrode active material layer and the carbon-based negative electrode active material is preferably 5:95 to 35:65.
When the mass mixing ratio is in the above range, the effect of improving the energy density by silicon and / or silicon compound is sufficient. Moreover, the volume expansion at the time of charge of a negative electrode active material layer does not become large too much.
When the carbon-based negative electrode active material is a carbon-based coated negative electrode active material, which will be described later, when calculating the mass mixing ratio, the mass of the electrode coating layer constituting the carbon-based coated negative electrode active material is also taken into account.

Although the thickness of a negative electrode active material layer is not specifically limited, It is preferable that it is 100-2500 micrometers, It is more preferable that it is 150-2000 micrometers, It is further more preferable that it is 200-1500 micrometers.
By setting the thickness of the negative electrode active material layer in the above range, the electrode can be thicker than the conventional negative electrode, and the amount of the active material contained in the electrode is increased. Furthermore, since the energy density is increased by including silicon and / or a silicon compound in the negative electrode active material layer, an electrode having a high energy density and a high capacity can be obtained.
The thickness of the negative electrode active material layer is obtained by subtracting the thickness of the negative electrode pressure relaxation layer from the total thickness of the negative electrode active material layer and the negative electrode pressure relaxation layer.
In addition, the thickness of the negative electrode active material layer and the thickness of the negative electrode pressure relaxation layer are determined before the negative electrode active material layer is charged, or the negative electrode active material layer is subjected to an electrode potential value +0.05 V (vs. Li / Li ⁺ ) The thickness when discharged to below.

The relationship between the thickness of the negative electrode active material layer and the thickness of the negative electrode pressure relaxation layer is not particularly limited, but the thickness of the negative electrode pressure relaxation layer is preferably 0.3 to 25% of the thickness of the negative electrode active material layer. 2 to 15% is more preferable.
By setting the relationship between the thickness of the negative electrode active material layer and the thickness of the negative electrode pressure relaxation layer in the above range, the expansion of the negative electrode active material layer during charging can be absorbed more without lowering the energy density.

The silicon may be crystalline silicon, amorphous silicon, or a mixture thereof.

Examples of the silicon compound include silicon oxide (SiO _x ), Si—C composite, Si—Al alloy, Si—Li alloy, Si—Ni alloy, Si—Fe alloy, Si—Ti alloy, Si—Mn alloy, It is preferably at least one selected from the group consisting of Si—Cu alloys and Si—Sn alloys.
Examples of the Si-C composite include silicon carbide, carbon particles whose surfaces are coated with silicon and / or silicon carbide, and silicon particles and silicon oxide particles whose surfaces are coated with carbon and / or silicon carbide. included.
Even if silicon and / or silicon compound particles are single particles (also referred to as primary particles), composite particles obtained by agglomeration of primary particles (that is, primary particles made of silicon and / or silicon compound agglomerate). Secondary particles) may be formed. The composite particles may be agglomerated when primary particles of silicon and / or silicon compound particles are aggregated due to the adsorbing force, or when the primary particles are adsorbed via another material. As a method of forming composite particles by binding primary particles through another material, for example, primary particles of silicon and / or silicon compound particles and a polymer compound constituting an electrode coating layer described later are mixed. The method of doing is mentioned.

The silicon-based negative electrode active material may be the silicon-based negative electrode active material itself, or a silicon-based coating in which part or all of the surface of the silicon-based negative electrode active material is coated with an electrode coating layer containing a polymer compound. Although it may be a negative electrode active material, it is preferably a silicon-based negative electrode active material.
In addition, the electrode coating layer which coat | covers part or all of the surface of a silicon-type negative electrode active material is also called negative electrode coating layer. The volume average particle diameter when the silicon-based negative electrode active material is a silicon-based coated negative electrode active material is the volume average particle diameter of the silicon-based negative electrode active material before the electrode coating layer is formed.

The volume average particle diameter of silicon and silicon compounds is not particularly limited, but is preferably 0.2 to 30 μm from the viewpoint of electrical characteristics. In particular, when composite particles are formed, the volume average particle size of the composite particles The diameter (also referred to as secondary particle diameter) is more preferably 10 to 30 μm.

Examples of the carbon-based negative electrode active material include carbon-based materials [for example, graphite, non-graphitizable carbon, amorphous carbon, resin fired bodies (for example, those obtained by firing and carbonizing phenol resin, furan resin, etc.), cokes (for example, pitch) Coke, needle coke, petroleum coke, etc.)], or conductive polymers (such as polyacetylene and polypyrrole), metal oxides (titanium oxide and lithium / titanium oxide), and metal alloys (lithium-tin alloys, lithium- A mixture of an aluminum alloy, an aluminum-manganese alloy, etc.) and a carbon-based material. Among the above carbon-based negative electrode active materials, those that do not contain lithium or lithium ions may be subjected to a pre-doping treatment in which some or all of the inside contains lithium or lithium ions.

The volume average particle diameter of the carbon-based negative electrode active material is preferably 0.01 to 50 μm, more preferably 0.1 to 25 μm, and more preferably 2 to 20 μm, from the viewpoint of the electrical characteristics of the negative electrode for a lithium ion battery. Is more preferable.

In this specification, the volume average particle size of silicon, silicon compound and carbon-based negative electrode active material is the particle size (Dv50) at an integrated value of 50% in the particle size distribution determined by the microtrack method (laser diffraction / scattering method). means. The microtrack method is a method for obtaining a particle size distribution using scattered light obtained by irradiating particles with laser light. In addition, Nikkiso Co., Ltd. microtrack etc. can be used for the measurement of a volume average particle diameter.

The carbon-based negative electrode active material may be the carbon-based negative electrode active material itself, and a carbon-based coating in which a part or all of the surface of the carbon-based negative electrode active material is coated with an electrode coating layer containing a polymer compound. Although it may be a negative electrode active material, it is preferably a carbon-based coated negative electrode active material. In addition, the electrode coating layer which coat | covers a part or all of the surface of a carbon-type negative electrode active material is also called a negative electrode coating layer.
The volume average particle size when the carbon-based negative electrode active material is a carbon-based coated negative electrode active material is the volume average particle size of the carbon-based negative electrode active material before the electrode coating layer is formed.

When the negative electrode active material layer contains silicon and / or a silicon compound and a carbon-based negative electrode active material, particles composed of silicon and / or a silicon compound and particles composed of a carbon-based negative electrode active material may be mixed and used. Granulated particles containing both silicon and / or a silicon compound and a carbon-based negative electrode active material may be used. When using granulated particles containing both silicon and / or a silicon compound and a carbon-based negative electrode active material, granulation in which silicon and / or a silicon compound is fixed to the surface of the carbon-based negative electrode active material via a negative electrode coating layer It may be a particle.

Subsequently, the positive electrode active material will be described.
When the electrode active material which comprises the electrode for lithium ion batteries of this invention is a positive electrode active material, it is preferable that a positive electrode active material layer is a non-binding body of the positive electrode active material composition containing a positive electrode active material. The positive electrode active material composition may be only the positive electrode active material, but is more preferably a non-binding body of a mixture of the positive electrode active material and the electrolytic solution.
If the positive electrode active material layer is a non-binder of the positive electrode active material composition containing the positive electrode active material, the positive electrode active material layer does not contain the binder, and as described above, the deterioration of cycle characteristics is suppressed. Can do.
As the electrolytic solution, an electrolytic solution containing an electrolyte and a non-aqueous solvent used for manufacturing a lithium ion battery can be used.

As the positive electrode active material, a conventionally known material can be suitably used, which is a compound that can insert and desorb lithium ions by applying a certain potential, and has a higher potential than the negative electrode active material used for the counter electrode. A compound capable of inserting and desorbing lithium ions can be used.

As the positive electrode active material, a composite oxide of lithium and a transition metal (a composite oxide having one kind of transition metal (such as LiCoO ₂ , LiNiO ₂ , LiAlMnO ₄ , LiMnO _2, and LiMn ₂ O ₄ ), a transition metal element is used. Two kinds of complex oxides (for example, LiFeMnO ₄ , LiNi _1-x Co _x O ₂ , LiMn _1-y Co _y O ₂ , LiNi _1/3 Co _1/3 Al _1/3 O ₂ and LiNi _0.8 Co _0.15 Al _0.05 O ₂ ) and a composite oxide having three or more metal elements [for example, LiMaM′bM ″ cO ₂ (M, M ′, and M ″ are different transition metal elements, and a + b + c = 1, for example, LiNi _1/3 Mn _1/3 Co _1/3 O ₂ ) etc.], lithium-containing transition metal phosphates (eg LiFePO ₄ , LiCoPO ₄ , LiMnPO ₄ and LiNiPO ₄ ), transition metal oxides (eg MnO ₂ and V ₂ O ₅ ), transition metal sulfides (eg MoS ₂ and TiS ₂ ) and conductive polymers (eg polyaniline, polypyrrole, polythiophene, polyacetylene). And poly-p-phenylene and polyvinylcarbazole) and the like may be used in combination.
The lithium-containing transition metal phosphate may be one in which a part of the transition metal site is substituted with another transition metal.

The volume average particle size of the positive electrode active material is preferably 0.01 to 100 μm, more preferably 0.1 to 35 μm, and further preferably 2 to 30 μm from the viewpoint of battery characteristics.
The volume average particle diameter of the positive electrode active material means the particle diameter (Dv50) at an integrated value of 50% in the particle size distribution obtained by the microtrack method (laser diffraction / scattering method).

The positive electrode active material layer may further contain a conductive additive as necessary.
As a conductive support agent, the thing similar to the conductive material which is an arbitrary component of a negative electrode coating layer can be used suitably.

The positive electrode active material may be the positive electrode active material itself, or may be a coated positive electrode active material in which part or all of the surface of the positive electrode active material is coated with an electrode coating layer containing a polymer compound. Is preferably a coated positive electrode active material. In addition, the electrode coating layer which coat | covers part or all of the surface of a positive electrode active material is also called positive electrode coating layer.

Although the thickness of a positive electrode active material layer is not specifically limited, It is preferable that it is 100-2500 micrometers, It is more preferable that it is 150-2000 micrometers, It is further more preferable that it is 200-1500 micrometers.
By setting the thickness of the positive electrode active material layer in the above range, the electrode can be thicker than the conventional electrode, and the amount of the active material contained in the electrode is increased.
The thickness of the positive electrode active material layer is obtained by subtracting the thickness of the positive electrode pressure relaxation layer from the total thickness of the positive electrode active material layer and the positive electrode pressure relaxation layer.
In addition, the thickness of the positive electrode active material layer and the thickness of the positive electrode pressure relaxation layer are determined before the discharge of the positive electrode active material layer or when the positive electrode active material layer has an electrode potential value +4.20 V (vs. Li / Li ⁺ ) and the thickness when charged to above.

The relationship between the thickness of the positive electrode active material layer and the thickness of the positive electrode pressure relaxation layer is not particularly limited, but the thickness of the positive electrode pressure relaxation layer is preferably 0.3 to 25% of the thickness of the positive electrode active material layer. 1 to 20% is more preferable, and 5 to 10% is still more preferable.
By setting the relationship between the thickness of the positive electrode active material layer and the thickness of the positive electrode pressure relaxation layer in the above range, the expansion during charging of the positive electrode active material layer can be absorbed more without lowering the energy density.

Subsequently, an electrode coating layer that may cover part or all of the surface of the electrode active material will be described.
The electrode coating layer includes a polymer compound, and may further include a conductive material as necessary.
The coated electrode active material is one in which part or all of the surface of the electrode active material is coated with an electrode coating layer containing a polymer compound. In the electrode active material layer, for example, the coated electrode active material Even if the substances contact each other, the electrode coating layers do not irreversibly adhere to each other on the contact surface, and the adhesion is temporary and can be easily loosened by hand. They are not fixed by the electrode coating layer. Therefore, in the electrode active material layer containing the coated electrode active material, the electrode active materials are not bound to each other.
More specifically, whether or not the electrode active material layer contains a binder is to observe whether or not the electrode active material layer collapses when the electrode active material layer is completely impregnated in the electrolytic solution. It can be confirmed with. When the electrode active material layer is a binder containing a binder, the shape can be maintained for one minute or longer, but the electrode active material layer is a non-binder containing no binder. The shape collapses in less than a minute.

The binder included in the electrode active material layer in the conventional lithium ion battery also includes polymer compounds such as starch, polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, and styrene-butadiene rubber. The binder is used by being dissolved or dispersed in water or an organic solvent, and is dried and solidified by volatilizing the solvent component (or dispersion medium component) to form electrode active materials, electrode active material particles, and a current collector. Is firmly fixed to form a negative electrode active material layer. On the other hand, the electrode coating layer covers a part or all of the surface of the electrode active material. As described above, even in the negative electrode active material layer, even if the coated electrode active materials are in contact with each other, The coating layers are not firmly bonded and fixed, and the electrode coating layer and the binder are different members.

Examples of the polymer compound constituting the electrode coating layer include thermoplastic resins and thermosetting resins. For example, fluororesins, acrylic resins, urethane resins, polyester resins, polyether resins, polyamide resins, epoxy resins, polyimides Examples thereof include resins, silicone resins, phenol resins, melamine resins, urea resins, aniline resins, ionomer resins, polycarbonates, polysaccharides (such as sodium alginate), and mixtures thereof. Among these, acrylic resins, urethane resins, polyester resins and polyamide resins are preferable, and acrylic resins are more preferable.
Among these, a polymer compound having a liquid absorption rate of 10% or more when immersed in an electrolytic solution and a tensile elongation at break in a saturated liquid absorption state of 10% or more is more preferable.

The liquid absorption rate when dipped in the electrolytic solution is obtained by the following formula by measuring the weight of the polymer compound before dipping in the electrolytic solution and after dipping.
Absorption rate (%) = [(weight of polymer compound after immersion in electrolyte−weight of polymer compound before immersion in electrolyte) / weight of polymer compound before immersion in electrolyte] × 100
As an electrolytic solution for obtaining the liquid absorption rate, LiPF ₆ is preferably added at 1 mol / liter as an electrolyte in a mixed solvent in which ethylene carbonate (EC) and propylene carbonate (PC) are mixed at a volume ratio of EC: PC = 1: 1. An electrolytic solution dissolved to a concentration of L is used.
The immersion in the electrolytic solution for determining the liquid absorption rate is performed at 50 ° C. for 3 days. By immersing at 50 ° C. for 3 days, the polymer compound becomes saturated. The saturated liquid absorption state refers to a state in which the weight of the polymer compound does not increase even when immersed in the electrolytic solution.
In addition, the electrolyte solution used when manufacturing a lithium ion battery using the electrode for lithium ion batteries of this invention is not limited to the said electrolyte solution, You may use another electrolyte solution.

When the liquid absorption rate is 10% or more, lithium ions can easily permeate the polymer compound, so that the ionic resistance in the electrode active material layer can be kept low. When the liquid absorption is less than 10%, the lithium ion conductivity is lowered, and the performance as a lithium ion battery may not be sufficiently exhibited.
The liquid absorption is preferably 20% or more, and more preferably 30% or more.
Moreover, as a preferable upper limit of a liquid absorption rate, it is 400%, and as a more preferable upper limit, it is 300%.

The tensile elongation at break in the saturated liquid absorption state was determined by punching the polymer compound into a dumbbell shape and immersing it in an electrolytic solution at 50 ° C. for 3 days in the same manner as the measurement of the liquid absorption rate. The state can be measured according to ASTM D683 (test piece shape Type II). The tensile elongation at break is a value obtained by calculating the elongation until the test piece breaks in the tensile test according to the following formula.
Tensile elongation at break (%) = [(length of specimen at break−length of specimen before test) / length of specimen before test] × 100

When the tensile elongation at break in the saturated liquid absorption state of the polymer compound is 10% or more, the polymer compound has an appropriate flexibility, so that the electrode coating layer peels off due to the volume change of the electrode active material during charge / discharge It becomes easy to suppress.
The tensile elongation at break is preferably 20% or more, and more preferably 30% or more.
Further, the preferable upper limit value of the tensile elongation at break is 400%, and the more preferable upper limit value is 300%.

The acrylic resin is preferably a resin comprising a polymer (A1) having an acrylic monomer (a) as an essential constituent monomer.
The polymer (A1) is a monomer composition comprising a monomer (a1) having a carboxyl group or an acid anhydride group as the acrylic monomer (a) and a monomer (a2) represented by the following general formula (1). A polymer is preferred.
CH ₂ = C (R ¹ ) COOR ² (1)
[In Formula (1), R ¹ is a hydrogen atom or a methyl group, and R ² is a linear alkyl group having 4 to 12 carbon atoms or a branched alkyl group having 3 to 36 carbon atoms. ]

As the monomer (a1) having a carboxyl group or an acid anhydride group, monocarboxylic acids having 3 to 15 carbon atoms such as (meth) acrylic acid (a11), crotonic acid and cinnamic acid; (anhydrous) maleic acid and fumaric acid (Anhydrous) dicarboxylic acids having 4 to 24 carbon atoms such as itaconic acid, citraconic acid and mesaconic acid; trivalent to tetravalent or higher valent polycarboxylic acids having 6 to 24 carbon atoms such as aconitic acid, etc. Can be mentioned. Among these, (meth) acrylic acid (a11) is preferable, and methacrylic acid is more preferable.

In the monomer (a2) represented by the general formula (1), R ¹ represents a hydrogen atom or a methyl group. R ¹ is preferably a methyl group.
R ² is preferably a linear or branched alkyl group having 4 to 12 carbon atoms or a branched alkyl group having 13 to 36 carbon atoms.

(A21) Ester compound in which R ² is a linear or branched alkyl group having 4 to 12 carbon atoms As the linear alkyl group having 4 to 12 carbon atoms, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, Nonyl group, decyl group, undecyl group, dodecyl group can be mentioned.
Examples of the branched alkyl group having 4 to 12 carbon atoms include 1-methylpropyl group (sec-butyl group), 2-methylpropyl group, 1,1-dimethylethyl group (tert-butyl group), 1-methylbutyl group, 1 , 1-dimethylpropyl group, 1,2-dimethylpropyl group, 2,2-dimethylpropyl group (neopentyl group), 1-methylpentyl group, 2-methylpentyl group, 3-methylpentyl group, 4-methylpentyl group 1,1-dimethylbutyl group, 1,2-dimethylbutyl group, 1,3-dimethylbutyl group, 2,2-dimethylbutyl group, 2,3-dimethylbutyl group, 1-ethylbutyl group, 2-ethylbutyl group 1-methylhexyl group, 2-methylhexyl group, 2-methylhexyl group, 4-methylhexyl group, 5-methylhexyl group, 1-ethylpentyl group, 2 Ethylpentyl group, 3-ethylpentyl group, 1,1-dimethylpentyl group, 1,2-dimethylpentyl group, 1,3-dimethylpentyl group, 2,2-dimethylpentyl group, 2,3-dimethylpentyl group, 2-ethylpentyl group, 1-methylheptyl group, 2-methylheptyl group, 3-methylheptyl group, 4-methylheptyl group, 5-methylheptyl group, 6-methylheptyl group, 1,1-dimethylhexyl group, 1,2-dimethylhexyl group, 1,3-dimethylhexyl group, 1,4-dimethylhexyl group, 1,5-dimethylhexyl group, 1-ethylhexyl group, 2-ethylhexyl group, 1-methyloctyl group, 2- Methyloctyl group, 3-methyloctyl group, 4-methyloctyl group, 5-methyloctyl group, 6-methyloctyl group, 7-methyloctyl Group, 1,1-dimethylheptyl group, 1,2-dimethylheptyl group, 1,3-dimethylheptyl group, 1,4-dimethylheptyl group, 1,5-dimethylheptyl group, 1,6-dimethylheptyl group 1-ethylheptyl group, 2-ethylheptyl group, 1-methylnonyl group, 2-methylnonyl group, 3-methylnonyl group, 4-methylnonyl group, 5-methylnonyl group, 6-methylnonyl group, 7-methylnonyl group, 8- Methylnonyl group, 1,1-dimethyloctyl group, 1,2-dimethyloctyl group, 1,3-dimethyloctyl group, 1,4-dimethyloctyl group, 1,5-dimethyloctyl group, 1,6-dimethyloctyl group 1,7-dimethyloctyl group, 1-ethyloctyl group, 2-ethyloctyl group, 1-methyldecyl group, 2-methyldecyl group, 3-methyl Rudecyl group, 4-methyldecyl group, 5-methyldecyl group, 6-methyldecyl group, 7-methyldecyl group, 8-methyldecyl group, 9-methyldecyl group, 1,1-dimethylnonyl group, 1,2-dimethylnonyl group, 1 , 3-dimethylnonyl group, 1,4-dimethylnonyl group, 1,5-dimethylnonyl group, 1,6-dimethylnonyl group, 1,7-dimethylnonyl group, 1,8-dimethylnonyl group, 1-ethylnonyl Group, 2-ethylnonyl group, 1-methylundecyl group, 2-methylundecyl group, 3-methylundecyl group, 4-methylundecyl group, 5-methylundecyl group, 6-methylundecyl group, 7 -Methylundecyl group, 8-methylundecyl group, 9-methylundecyl group, 10-methylundecyl group, 1,1-dimethyldecyl group, 1,2-dimethyldecyl group Group, 1,3-dimethyldecyl group, 1,4-dimethyldecyl group, 1,5-dimethyldecyl group, 1,6-dimethyldecyl group, 1,7-dimethyldecyl group, 1,8-dimethyldecyl group 1,9-dimethyldecyl group, 1-ethyldecyl group, 2-ethyldecyl group and the like. Of these, a 2-ethylhexyl group is particularly preferable.

(A22) R ² is a branched alkyl group having 13 to 36 carbon atoms. Examples of the branched alkyl group having 13 to 36 carbon atoms include a 1-alkylalkyl group [1-methyldodecyl group, 1-butyleicosyl group, 1-hexyloctadecyl group, 1-octylhexadecyl group, 1-decyltetradecyl group, 1-undecyltridecyl group, etc.], 2-alkylalkyl group [2-methyldodecyl group, 2-hexyloctadecyl group, 2- Octylhexadecyl group, 2-decyltetradecyl group, 2-undecyltridecyl group, 2-dodecylhexadecyl group, 2-tridecylpentadecyl group, 2-decyloctadecyl group, 2-tetradecyloctadecyl group, 2- Hexadecyl octadecyl group, 2-tetradecyl eicosyl group, 2-hexadecyl eicosyl group, etc.], 3 34-alkylalkyl groups (3-alkylalkyl groups, 4-alkylalkyl groups, 5-alkylalkyl groups, 32-alkylalkyl groups, 33-alkylalkyl groups, 34-alkylalkyl groups, etc.), and propylene oligomers (7 To 11-mer), ethylene / propylene (molar ratio 16/1 to 1/11) oligomer, isobutylene oligomer (7 to 8-mer), and α-olefin (carbon number 5 to 20) oligomer (4 to 8-mer). And a mixed alkyl group containing one or more branched alkyl groups such as a residue obtained by removing a hydroxyl group from an oxo alcohol obtained from the above.

The polymer (A1) preferably further contains an ester compound (a3) of a monovalent aliphatic alcohol having 1 to 3 carbon atoms and (meth) acrylic acid.
Examples of the monovalent aliphatic alcohol having 1 to 3 carbon atoms constituting the ester compound (a3) include methanol, ethanol, 1-propanol, and 2-propanol.

The content of the ester compound (a3) is preferably 10 to 60% by weight based on the total weight of the polymer (A1) from the viewpoint of suppressing the volume change of the electrode active material, and 15 to 55% by weight. More preferably, it is more preferably 20 to 50% by weight.

The polymer (A1) may further contain an anionic monomer salt (a4) having a polymerizable unsaturated double bond and an anionic group.
Examples of the structure having a polymerizable unsaturated double bond include a vinyl group, an allyl group, a styryl group, and a (meth) acryloyl group.
Examples of the anionic group include a sulfonic acid group and a carboxyl group.
An anionic monomer having a polymerizable unsaturated double bond and an anionic group is a compound obtained by a combination thereof, such as vinyl sulfonic acid, allyl sulfonic acid, styrene sulfonic acid and (meth) acrylic acid. It is done.
The (meth) acryloyl group means an acryloyl group and / or a methacryloyl group.
Examples of the cation constituting the salt (a4) of the anionic monomer include lithium ion, sodium ion, potassium ion and ammonium ion.

When the salt (a4) of the anionic monomer is contained, the content thereof is preferably 0.1 to 15% by weight based on the total weight of the polymer compound from the viewpoint of internal resistance and the like. It is more preferably ˜15% by weight, and further preferably 2 to 10% by weight.

The polymer (A1) preferably contains (meth) acrylic acid (a11) and an ester compound (a21), and more preferably contains an ester compound (a3).
Particularly preferably, methacrylic acid is used as (meth) acrylic acid (a11), 2-ethylhexyl methacrylate is used as ester compound (a21), and methyl methacrylate is used as ester compound (a3). Methacrylic acid, 2-ethylhexyl A copolymer of methacrylate and methyl methacrylate.

The polymer compound includes (meth) acrylic acid (a11), the monomer (a2), an ester compound (a3) of a monovalent aliphatic alcohol having 1 to 3 carbon atoms and (meth) acrylic acid, and polymerization used as necessary. A monomer composition comprising a salt (a4) of an anionic monomer having a polymerizable unsaturated double bond and an anionic group, and the monomer (a2) and the (meth) acrylic acid The weight ratio of (a11) [the monomer (a2) / (meth) acrylic acid (a11)] is preferably 10/90 to 90/10.
When the weight ratio of the monomer (a2) and the (meth) acrylic acid (a11) is 10/90 to 90/10, the polymer obtained by polymerizing the monomer has good adhesion to the electrode active material and peels off. It becomes difficult.
The weight ratio is preferably 30/70 to 85/15, and more preferably 40/60 to 70/30.

Moreover, the monomer which comprises a polymer (A1) includes the monomer (a1) which has a carboxyl group or an acid anhydride group, the monomer (a2) represented by the said General formula (1), C1-C3 In addition to the ester compound (a3) of a monovalent aliphatic alcohol of (meth) acrylic acid and an anionic monomer salt (a4) having a polymerizable unsaturated double bond and an anionic group, As long as the physical properties of the combined (A1) are not impaired, the monomer (a1), the monomer (a2) represented by the general formula (1), a monovalent aliphatic alcohol having 1 to 3 carbon atoms, and (meth) acrylic A radical polymerizable monomer (a5) that can be copolymerized with an ester compound (a3) with an acid may be contained.
As the radical polymerizable monomer (a5), a monomer containing no active hydrogen is preferable, and the following monomers (a51) to (a58) can be used.
(A51) Hydro formed from a linear aliphatic monool having 13 to 20 carbon atoms, an alicyclic monool having 5 to 20 carbon atoms or an araliphatic monool having 7 to 20 carbon atoms and (meth) acrylic acid Carbyl (meth) acrylate As the monool,
(I) linear aliphatic monool (tridecyl alcohol, myristyl alcohol, pentadecyl alcohol, cetyl alcohol, heptadecyl alcohol, stearyl alcohol, nonadecyl alcohol, arachidyl alcohol, etc.)
(Ii) alicyclic monool (cyclopentyl alcohol, cyclohexyl alcohol, cycloheptyl alcohol, cyclooctyl alcohol, etc.)
(Iii) aromatic aliphatic monools (such as benzyl alcohol) and mixtures of two or more thereof.

(A52) poly (n = 2 to 30) oxyalkylene (2 to 4 carbon atoms) alkyl (1 to 18 carbon atoms) ether (meth) acrylate [methanol ethylene oxide (hereinafter abbreviated as EO) 10 mol adduct (meta ) Propylene oxide of acrylate, methanol (hereinafter abbreviated as PO), 10 mol adduct (meth) acrylate, etc.]

(A53) nitrogen-containing vinyl compound (a53-1) amide group-containing vinyl compound (i) (meth) acrylamide compound having 3 to 30 carbon atoms such as N, N-dialkyl (1 to 6 carbon atoms) or diaralkyl (carbon number) 7-15) (meth) acrylamide (N, N-dimethylacrylamide, N, N-dibenzylacrylamide, etc.), diacetone acrylamide (ii) amide group containing 4-20 carbon atoms excluding the above (meth) acrylamide compound Vinyl compounds such as N-methyl-N-vinylacetamide, cyclic amides [pyrrolidone compounds (having 6 to 13 carbon atoms, such as N-vinylpyrrolidone)]

(A53-2) (meth) acrylate compound (i) dialkyl (1 to 4 carbon atoms) aminoalkyl (1 to 4 carbon atoms) (meth) acrylate [N, N-dimethylaminoethyl (meth) acrylate, N, N -Diethylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate, morpholinoethyl (meth) acrylate, etc.]
(Ii) Quaternary ammonium group-containing (meth) acrylate {quaternary amino group-containing (meth) acrylate [N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, etc.] quaternary] (Quaternized with a quaternizing agent such as methyl chloride, dimethyl sulfate, benzyl chloride, dimethyl carbonate, etc.)}

(A53-3) Heterocycle-containing vinyl compound pyridine compound (carbon number 7 to 14, for example, 2- or 4-vinylpyridine), imidazole compound (carbon number 5 to 12, for example, N-vinylimidazole), pyrrole compound (carbon number) 6 to 13, for example, N-vinylpyrrole), pyrrolidone compound (6 to 13 carbon atoms, for example, N-vinyl-2-pyrrolidone)

(A53-4) Nitrile group-containing vinyl compound A nitrile group-containing vinyl compound having 3 to 15 carbon atoms such as (meth) acrylonitrile, cyanostyrene, cyanoalkyl (1 to 4 carbon atoms) acrylate

(A53-5) Other nitrogen-containing vinyl compounds Nitro group-containing vinyl compounds (8 to 16, for example, nitrostyrene), etc.

(A54) Vinyl hydrocarbon (a54-1) Aliphatic vinyl hydrocarbon olefin having 2 to 18 or more carbon atoms (ethylene, propylene, butene, isobutylene, pentene, heptene, diisobutylene, octene, dodecene, octadecene, etc.), Diene having 4 to 10 or more carbon atoms (butadiene, isoprene, 1,4-pentadiene, 1,5-hexadiene, 1,7-octadiene, etc.), etc.

(A54-2) Alicyclic vinyl hydrocarbon cyclic unsaturated compounds having 4 to 18 or more carbon atoms, such as cycloalkene (for example, cyclohexene), (di) cycloalkadiene [for example, (di) cyclopentadiene], terpene ( For example, pinene and limonene), indene

(A54-3) Aromatic vinyl hydrocarbon aromatic unsaturated compound having 8 to 20 or more carbon atoms, such as styrene, α-methylstyrene, vinyltoluene, 2,4-dimethylstyrene, ethylstyrene, isopropylstyrene, butyl Styrene, phenyl styrene, cyclohexyl styrene, benzyl styrene

(A55) vinyl ester aliphatic vinyl ester [carbon number 4-15, for example, alkenyl ester of aliphatic carboxylic acid (mono- or dicarboxylic acid) (for example, vinyl acetate, vinyl propionate, vinyl butyrate, diallyl adipate, isopropenyl acetate, Vinyl methoxyacetate)]
Aromatic vinyl ester [carbon number 9-20, for example, alkenyl ester of aromatic carboxylic acid (mono- or dicarboxylic acid) (for example, vinyl benzoate, diallyl phthalate, methyl-4-vinyl benzoate), containing aromatic ring of aliphatic carboxylic acid Ester (eg acetoxystyrene)]

(A56) vinyl ether aliphatic vinyl ether [carbon number 3 to 15, for example, vinyl alkyl (carbon number 1 to 10) ether (vinyl methyl ether, vinyl butyl ether, vinyl 2-ethylhexyl ether, etc.), vinyl alkoxy (carbon number 1 to 6) Alkyl (C1-C4) ether (vinyl-2-methoxyethyl ether, methoxybutadiene, 3,4-dihydro-1,2-pyran, 2-butoxy-2'-vinyloxydiethyl ether, vinyl-2-ethyl Mercaptoethyl ether, etc.), poly (2-4) (meth) allyloxyalkanes (2-6 carbon atoms) (diallyloxyethane, triaryloxyethane, tetraallyloxybutane, tetrametaallyloxyethane, etc.)], Aromatic vinyl ether (carbon number 8-20, for example, vinyl phenyl ether , Phenoxystyrene)

(A57) Vinyl ketone aliphatic vinyl ketone (4 to 25 carbon atoms such as vinyl methyl ketone, vinyl ethyl ketone), aromatic vinyl ketone (9 to 21 carbon atoms such as vinyl phenyl ketone)

(A58) Unsaturated dicarboxylic acid diester An unsaturated dicarboxylic acid diester having 4 to 34 carbon atoms, such as a dialkyl fumarate (two alkyl groups are linear, branched or alicyclic groups having 1 to 22 carbon atoms) ), Dialkyl maleate (two alkyl groups are linear, branched or alicyclic groups having 1 to 22 carbon atoms)

Of those exemplified as (a5) above, (a51), (a52) and (a53) are preferable from the viewpoint of withstand voltage.

In the polymer (A1), a monomer (a1) having a carboxyl group or an acid anhydride group, a monomer (a2) represented by the general formula (1), a monovalent aliphatic alcohol having 1 to 3 carbon atoms and ( The content of the ester compound (a3) with meth) acrylic acid, the salt (a4) of the anionic monomer having a polymerizable unsaturated double bond and an anionic group, and the radical polymerizable monomer (a5) Based on the weight of the combined (A1), (a1) is 0.1 to 80% by weight, (a2) is 0.1 to 99.9% by weight, (a3) is 0 to 60% by weight, and (a4) is It is preferable that 0 to 15% by weight and (a5) is 0 to 99.8% by weight.
When the content of the monomer is within the above range, the liquid absorptivity to the electrolytic solution is good.

The preferable lower limit of the number average molecular weight of the polymer (A1) is 3,000, more preferably 50,000, still more preferably 100,000, particularly preferably 200,000, and the preferable upper limit is 2,000,000. It is preferably 1,500,000, more preferably 1,000,000, and particularly preferably 800,000.

The number average molecular weight of the polymer (A1) can be determined by gel permeation chromatography (hereinafter abbreviated as GPC) measurement under the following conditions.
Apparatus: Alliance GPC V2000 (manufactured by Waters)
Solvent: Orthodichlorobenzene Reference material: Polystyrene detector: RI
Sample concentration: 3 mg / ml
Column stationary phase: PLgel 10 μm, MIXED-B 2 in series (manufactured by Polymer Laboratories)
Column temperature: 135 ° C

The polymer (A1) is a known polymerization initiator {azo initiator [2,2′-azobis (2-methylpropionitrile), 2,2′-azobis (2,4-dimethylvaleronitrile, etc.)]. , Peroxide initiators (benzoyl peroxide, di-t-butyl peroxide, lauryl peroxide, etc.)} by a known polymerization method (bulk polymerization, solution polymerization, emulsion polymerization, suspension polymerization, etc.) Can be manufactured.
The amount of the polymerization initiator used is preferably 0.01 to 5% by weight, more preferably 0.05 to 2% by weight, based on the total weight of the monomers, from the viewpoint of adjusting the number average molecular weight to a preferable range. More preferably, it is 0.1 to 1.5% by weight, and the polymerization temperature and polymerization time are adjusted according to the type of polymerization initiator, etc., but the polymerization temperature is preferably -5 to 150 ° C (more preferably 30 to 120 ° C.) and the reaction time is preferably 0.1 to 50 hours (more preferably 2 to 24 hours).

Examples of the solvent used in the solution polymerization include esters (having 2 to 8 carbon atoms such as ethyl acetate and butyl acetate), alcohol (having 1 to 8 carbon atoms such as methanol, ethanol and octanol), and hydrocarbons (having carbon atoms). 4 to 8, for example, n-butane, cyclohexane and toluene) and ketones (having 3 to 9 carbon atoms, for example, methyl ethyl ketone) are used. From the viewpoint of adjusting the number average molecular weight to a preferable range, the amount used is the sum of the monomers. Based on the weight, it is preferably 5 to 900% by weight, more preferably 10 to 400% by weight, still more preferably 30 to 300% by weight, and the monomer concentration is preferably 10 to 95% by weight, more preferably 20 to 90% by weight, more preferably 30 to 80% by weight.

Examples of the dispersion medium in the emulsion polymerization and the suspension polymerization include water, alcohol (for example, ethanol), ester (for example, ethyl propionate), light naphtha and the like, and the emulsifier includes a higher fatty acid (having 10 to 24 carbon atoms) metal salt. (For example, sodium oleate and sodium stearate), higher alcohols (10 to 24 carbon atoms) sulfate metal salts (for example, sodium lauryl sulfate), ethoxylated tetramethyldecynediol, sulfoethyl sodium methacrylate, dimethylaminomethyl methacrylate, etc. Is mentioned. Furthermore, you may add polyvinyl alcohol, polyvinylpyrrolidone, etc. as a stabilizer.
The monomer concentration of the solution or dispersion is preferably 5 to 95% by weight, more preferably 10 to 90% by weight, and still more preferably 15 to 85% by weight. The amount of the polymerization initiator used is based on the total weight of the monomers. It is preferably 0.01 to 5% by weight, more preferably 0.05 to 2% by weight.
In the polymerization, known chain transfer agents such as mercapto compounds (such as dodecyl mercaptan and n-butyl mercaptan) and / or halogenated hydrocarbons (such as carbon tetrachloride, carbon tetrabromide and benzyl chloride) can be used. .

The polymer (A1) contained in the acrylic resin is a crosslinking agent (A ′) having a reactive functional group that reacts the polymer (A1) with a carboxyl group {preferably a polyepoxy compound (a′1) [polyglycidyl ether]. (Bisphenol A diglycidyl ether, propylene glycol diglycidyl ether, glycerin triglycidyl ether, etc.) and polyglycidylamine (N, N-diglycidylaniline and 1,3-bis (N, N-diglycidylaminomethyl)), etc.] And / or a crosslinked polymer formed by crosslinking with a polyol compound (a′2) (ethylene glycol or the like)}.

Examples of the method of crosslinking the polymer (A1) using the crosslinking agent (A ′) include a method of crosslinking after coating the electrode active material with the polymer (A1). Specifically, the electrode active material is mixed with a resin solution containing the polymer (A1) and the solvent is removed to produce a coated electrode active material in which the electrode active material is coated with the polymer (A1). The solution containing the agent (A ′) is mixed with the coated electrode active material and heated to cause solvent removal and a crosslinking reaction, and the polymer (A1) is crosslinked by the crosslinking agent (A ′). A method of causing a reaction to be a molecular compound on the surface of the electrode active material is mentioned.
The heating temperature is adjusted according to the type of the crosslinking agent, but when the polyepoxy compound (a′1) is used as the crosslinking agent, it is preferably 70 ° C. or higher, and when the polyol compound (a′2) is used. Preferably it is 120 degreeC or more.

The electrode coating layer may contain a conductive material.
The conductive material is selected from conductive materials. Specifically, in addition to the conductive carbon filler described above, a metal [nickel, aluminum, stainless steel (SUS), silver, copper, titanium, etc.] is used. it can.
These conductive materials may be used alone or in combination of two or more. Further, these alloys or metal oxides may be used. From the viewpoint of electrical stability, preferably aluminum, stainless steel, conductive carbon filler, silver, copper, titanium and a mixture thereof, more preferably silver, aluminum, stainless steel and conductive carbon filler, still more preferably. It is a conductive carbon filler. Moreover, as these electrically conductive materials, what coated the electroconductive material (metal thing among the above-mentioned electrically conductive materials) by plating etc. around the particulate ceramic material or the resin material may be used. A polypropylene resin kneaded with graphene is also preferable as the conductive material.
The conductive carbon filler used for the conductive material is preferably carbon [graphite and carbon black (acetylene black, ketjen black, furnace black, channel black, thermal lamp black, etc.)].
The aspect ratio of the conductive carbon filler used for the conductive material is preferably 1 or more and less than 100. As the conductive carbon filler used for the conductive material, the same conductive carbon filler used for the pressure relaxant can be suitably used.
Note that the conductive carbon filler constituting the pressure relaxation layer and the conductive carbon filler contained in the electrode coating layer are different in location, and therefore can be distinguished by performing an enlarged observation of the electrode.

The average particle size of the conductive material is not particularly limited, but is preferably 0.01 to 10 μm and more preferably 0.02 to 5 μm from the viewpoint of the electrical characteristics of the electrode for a lithium ion battery. Preferably, it is 0.03 to 1 μm. In the present specification, “particle diameter” means the maximum distance L among the distances between any two points on the particle outline. As the value of “average particle diameter”, the average value of the particle diameter of particles observed in several to several tens of fields using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). The calculated value shall be adopted.

The shape (form) of the conductive material is not limited to the particle form, and may be a form other than the particle form, for example, a fibrous conductive material.
Fibrous conductive materials include conductive fibers made by uniformly dispersing highly conductive metal and graphite in synthetic fibers, metal fibers made from metal such as stainless steel, and the surface of organic fibers as metal. Among the conductive fibers coated with, the conductive fibers whose surfaces of organic substances are coated with a resin containing a conductive substance, and conductive carbon fillers, those having an aspect ratio of 1 to less than 100 are preferable.
The average fiber diameter of the fibrous conductive material is preferably 0.1 to 20 μm.

The ratio of the total weight of the polymer compound and the conductive material contained in the electrode coating layer is not particularly limited, but is preferably 25% by weight or less with respect to the weight of the electrode active material.

The ratio of the weight of the polymer compound to the weight of the electrode active material is not particularly limited, but is preferably 0.1 to 20% by weight.
The ratio of the weight of the conductive material to the weight of the electrode active material is not particularly limited, but is preferably 10% by weight or less.

The electrode active material layer may further contain a conductive additive.
In addition, a conductive support agent is an arbitrary component which may be added to an electrode active material composition, and is distinguished from the conductive material which is an arbitrary component of an electrode coating layer.
As a conductive support agent, the same thing as the conductive material which is an arbitrary component of an electrode coating layer can be used suitably.

Next, the electrode current collector will be described.
Examples of the material constituting the electrode current collector include metal materials such as copper, aluminum, titanium, stainless steel, nickel, and alloys thereof, and calcined carbon, conductive polymer, conductive glass, and the like. Of these, aluminum and copper are more preferable from the viewpoint of weight reduction, corrosion resistance, and high conductivity, and aluminum is preferably used on the positive electrode side and copper is used on the negative electrode side. The electrode current collector may be a resin current collector made of a conductive polymer material.
The shape of the electrode current collector is not particularly limited, and may be a sheet-shaped current collector made of the above material and a deposited layer made of fine particles made of the above material.
The thickness of the electrode current collector is not particularly limited, but is preferably 50 to 500 μm.

As the conductive polymer material constituting the resin current collector, for example, a conductive polymer or a material obtained by adding a conductive agent to the resin as necessary can be used.
As the conductive agent constituting the conductive polymer material, the same conductive material as the conductive material that is an optional component of the electrode coating layer can be suitably used.
Examples of the resin constituting the conductive polymer material include polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), polycycloolefin (PCO), polyethylene terephthalate (PET), polyether nitrile (PEN), poly Tetrafluoroethylene (PTFE), styrene butadiene rubber (SBR), polyacrylonitrile (PAN), polymethyl acrylate (PMA), polymethyl methacrylate (PMMA), polyvinylidene fluoride (PVdF), epoxy resin, silicone resin or mixtures thereof Etc.
From the viewpoint of electrical stability, polyethylene (PE), polypropylene (PP), polymethylpentene (PMP) and polycycloolefin (PCO) are preferable, and polyethylene (PE), polypropylene (PP) and polymethylpentene are more preferable. (PMP).

Hereinafter, the method for producing the lithium ion battery electrode of the present invention will be described.
In the lithium ion battery electrode of the present invention, for example, after a pressure relaxation layer is formed on an electrode current collector, an electrode active material layer is formed on the pressure relaxation layer, and pressure is applied as necessary. Can be manufactured.

As a method for forming the pressure relaxation layer on the electrode current collector, for example, a dispersion in which a conductive carbon filler serving as the pressure relaxation layer is dispersed in a solvent at a concentration of 5 to 60% by weight based on the weight of the solvent. Is applied to the electrode current collector with a coating device such as a bar coater, then dried to remove the solvent, and if necessary, pressed with a press machine, and a conductive material that becomes a pressure relaxation layer on the electrode current collector. There is a method in which the porous carbon filler is sprayed in a solid state and pressed with a press if necessary.
By applying a dispersion liquid containing an electrode active material on the pressure relaxation layer having voids, the electrode active material enters the voids of the pressure relaxation layer. It can be in a state where an active material exists.
When the pressure relaxation layer is formed by these methods, an infinite number of voids can exist in the pressure relaxation layer, and the volume of the pressure relaxation layer contracts / expands according to the volume expansion / contraction during charging / discharging of the electrode active material layer. Can be easily done.
Moreover, as a method of forming an electrode active material layer on a pressure relaxation layer, for example, a dispersion liquid in which an electrode active material is dispersed at a concentration of 30 to 60% by weight based on the weight of a solvent is formed on the pressure relaxation layer. Examples of the method include a method of drying with a coating machine such as a bar coater, drying to remove the solvent, and pressing with a press if necessary.
The pressure relaxation layer obtained by drying the dispersion serving as the pressure relaxation layer and the electrode active material layer obtained by drying the dispersion serving as the electrode active material layer are respectively formed on the electrode current collector and the pressure relaxation layer. It is not necessary to form directly on the surface of the electrode current collector, for example, by laminating layered products (pressure relaxation layer and electrode active material layer) obtained by applying the above dispersion on the surface of an aramid separator or the like and drying it on the electrode current collector. The electrode for lithium ion batteries of this invention can be manufactured. In addition, as a method of drying the dispersion liquid applied on the aramid separator, the solvent may be removed by suction from the back surface of the surface on which the dispersion liquid is applied. At this time, it is only necessary to remove the solvent in the dispersion to such an extent that it can be separated from the aramid separator while maintaining the shape of the layered product, and it is not necessary to completely remove the solvent in the dispersion.
When the pressure relief layer and the electrode active material layer respectively produced on the aramid separator are laminated, an electrode active material in the pressure relief layer is formed by a part of the surface of the electrode active material layer entering the void of the pressure relief layer at the interface. An electrode active material can be present in the vicinity of the surface on the layer side.
You may add well-known binders mentioned above, such as a polyvinylidene fluoride (PVdF), to the dispersion liquid used as a pressure relaxation layer as needed.

When using a coated electrode active material as the electrode active material, for example, in a state where the electrode active material is put in a universal mixer and stirred at 30 to 50 rpm, the polymer solution containing the polymer compound is taken for 1 to 90 minutes. It can be obtained by dropping and mixing, further mixing conductive materials as necessary, raising the temperature to 50 to 200 ° C. with stirring, reducing the pressure to 0.007 to 0.04 MPa, and holding for 10 to 150 minutes. .

The mixing ratio of the electrode active material and the polymer compound is not particularly limited, but it is preferable that the electrode active material: polymer compound = 1: 0.001 to 0.1 by weight ratio.

Examples of the solvent include 1-methyl-2-pyrrolidone, methyl ethyl ketone, N, N-dimethylformamide (hereinafter also referred to as DMF), dimethylacetamide, N, N-dimethylaminopropylamine, and tetrahydrofuran.
Examples of the binder used in the dispersion that becomes the pressure relaxation layer include starch, polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, styrene-butadiene rubber, polyethylene, and polypropylene.

The lithium ion battery of the present invention includes the lithium ion battery electrode of the present invention.

When producing the lithium ion battery of the present invention using the electrode for the lithium ion battery of the present invention, the counter electrode is combined, accommodated in a cell container together with a separator, and an electrolyte is injected as necessary. It can be manufactured by a method of sealing the cell container.
Further, a bipolar electrode is formed by forming an electrode active material layer made of an active material constituting a counter electrode on the other surface of the electrode current collector in which the pressure relaxation layer and the electrode active material layer are formed on one surface of the electrode current collector. The bipolar electrode is laminated with a separator and accommodated in a cell container, and an electrolytic solution is injected as necessary to seal the cell container.

Examples of separators include polyethylene or polypropylene porous films, laminated films of porous polyethylene films and porous polypropylene, non-woven fabrics made of synthetic fibers (such as polyester fibers and aramid fibers) or glass fibers, and silica on the surfaces thereof. In addition, known separators for lithium ion batteries, such as those to which ceramic fine particles such as alumina and titania are attached, may be mentioned.

As the electrolytic solution, an electrolytic solution containing an electrolyte and a non-aqueous solvent used for manufacturing a lithium ion battery can be used.

As the electrolyte, those used in known electrolyte solutions can be used, and preferable examples include lithium salt electrolytes of inorganic acids such as LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ and LiClO ₄ , A sulfonylimide-based electrolyte having fluorine atoms such as LiN (FSO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ and LiN (C ₂ F ₅ SO ₂ ) _{2, and} a fluorine atom such as LiC (CF ₃ SO ₂ ) ₃ are used. Examples thereof include a sulfonylmethide-based electrolyte.

Although it does not specifically limit as electrolyte concentration of electrolyte solution, From a viewpoint of the handleability of electrolyte solution and battery capacity, it is preferable that it is 0.5-5 mol / L, and it is more preferable that it is 0.8-3 mol / L. It is more preferably 1 to 2 mol / L.

As the non-aqueous solvent, those used in known electrolytic solutions can be used, for example, lactone compounds, cyclic or chain carbonates, chain carboxylates, cyclic or chain ethers, phosphates, nitriles. Compounds, amide compounds, sulfones and the like and mixtures thereof can be used.

Examples of the lactone compound include a 5-membered ring (γ-butyrolactone, γ-valerolactone, etc.) and a 6-membered lactone compound (δ-valerolactone, etc.).

Examples of the cyclic carbonate include propylene carbonate, ethylene carbonate and butylene carbonate.
Examples of the chain carbonate include dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl-n-propyl carbonate, ethyl-n-propyl carbonate, and di-n-propyl carbonate.

Examples of chain carboxylic acid esters include methyl acetate, ethyl acetate, propyl acetate, and methyl propionate.
Examples of the cyclic ether include tetrahydrofuran, tetrahydropyran, 1,3-dioxolane, 1,4-dioxane and the like.
Examples of the chain ether include dimethoxymethane and 1,2-dimethoxyethane.

Examples of phosphate esters include trimethyl phosphate, triethyl phosphate, ethyl dimethyl phosphate, diethyl methyl phosphate, tripropyl phosphate, tributyl phosphate, tri (trifluoromethyl) phosphate, tri (trichloromethyl) phosphate, Tri (trifluoroethyl) phosphate, tri (triperfluoroethyl) phosphate, 2-ethoxy-1,3,2-dioxaphospholan-2-one, 2-trifluoroethoxy-1,3,2- Examples include dioxaphospholan-2-one and 2-methoxyethoxy-1,3,2-dioxaphosphoran-2-one.
Examples of the nitrile compound include acetonitrile.
Examples of the amide compound include DMF.
Examples of the sulfone include chain sulfones such as dimethyl sulfone and diethyl sulfone, and cyclic sulfones such as sulfolane.
A non-aqueous solvent may be used individually by 1 type, and may use 2 or more types together.

Among the nonaqueous solvents, lactone compounds, cyclic carbonates, chain carbonates, and phosphates are preferable from the viewpoint of battery output and charge / discharge cycle characteristics. More preferred are lactone compounds, cyclic carbonates and chain carbonates, and particularly preferred are cyclic carbonates or a mixture of cyclic carbonates and chain carbonates. Most preferred is a mixture of ethylene carbonate (EC) and propylene carbonate (PC), a mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC), or a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC). It is.

EXAMPLES Next, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the examples without departing from the gist of the present invention. Unless otherwise specified, “part” means “part by weight” and “%” means “% by weight”.

<Production Example 1: Production of conductive carbon filler>
Conductive carbon fillers, Eiichi Yasuda, Asao Oya, Shinya Komura, Shigeki Tomonoh, Takashi Nishizawa, Shinsuke Nagata, Takashi Akatsu, CARBON, 50,2012,1432-1434 and Eiichi Yasuda, Takashi Akatsu, Yasuhiro Tanabe, Kazumasa Nakamura, Yasuto It was produced with reference to the production method of Hoshikawa, Naoya Miyajima, TANSO, 255, 2012, pages 254 to 265.
10 parts by weight of synthetic mesophase pitch AR · MPH [manufactured by Mitsubishi Gas Chemical Co., Ltd.] and 90 parts by weight of polymethylpentene TPX RT18 [manufactured by Mitsui Chemicals, Ltd.] as a carbon precursor under a barrel temperature of 310 ° C. under a nitrogen atmosphere A resin composition was prepared by melt-kneading using a single screw extruder. Subsequently, the resin composition was melt-extruded and spun at 390 ° C. The spun resin composition was placed in an electric furnace and held at 270 ° C. for 3 hours under a nitrogen atmosphere to stabilize the carbon precursor. Next, the electric furnace was heated to 500 ° C. over 1 hour and held at 500 ° C. for 1 hour to decompose and remove polymethylpentene. The electric furnace was heated up to 1000 ° C. over 2 hours and held at 1000 ° C. for 30 minutes. Of the remaining carbon fiber precursor, 90 parts by weight together with 500 parts by weight of water and 1000 parts by weight of zirconia balls having a diameter of 0.1 mm were pot milled. Placed in a container and ground for 5 minutes. After classification of the zirconia balls, the zirconia balls were dried at 100 ° C. to obtain a carbon fiber as the conductive carbon filler A1.
From the measurement results with SEM, the average fiber diameter of the carbon fiber was 0.3 μm, and the average fiber length was 26 μm (the aspect ratio was about 87). Moreover, the electrical resistivity of the carbon fiber was 50 μΩ · m, and the bulk density measured according to JIS K 5101-12-1 was 0.5 g / cm ³ .

<Production Example 2: Production of polymer compound solution 1 for coating>
A four-necked flask equipped with a stirrer, thermometer, reflux condenser, dropping funnel and nitrogen gas inlet tube was charged with 83 parts of ethyl acetate and 17 parts of methanol, and the temperature was raised to 68 ° C.
Next, a monomer compounded liquid in which 242.8 parts of methacrylic acid, 97.1 parts of methyl methacrylate, 242.8 parts of 2-ethylhexyl methacrylate, 52.1 parts of ethyl acetate and 10.7 parts of methanol were blended, and 2,2′- An initiator solution prepared by dissolving 0.263 parts of azobis (2,4-dimethylvaleronitrile) in 34.2 parts of ethyl acetate and stirring with a dropping funnel over 4 hours while blowing nitrogen into a four-necked flask. The radical polymerization was carried out by dropping continuously.
After the completion of dropping, an initiator solution prepared by dissolving 0.583 parts of 2,2′-azobis (2,4-dimethylvaleronitrile) in 26 parts of ethyl acetate was continuously added using a dropping funnel over 2 hours. Furthermore, the polymerization was continued for 4 hours at the boiling point. After removing the solvent to obtain 582 parts of polymer, 1,360 parts of isopropanol was added to obtain a coating polymer compound solution 1 having a resin solid content concentration of 30% by weight.

<Production Example 3: Production of silicon-coated negative electrode active material particles (N-24)>
69 parts of silicon oxide particles [Sigma Aldrich Japan, volume average particle diameter 2.0 μm] 69 parts are put into a universal mixer high speed mixer FS25 [Earth Technica Co., Ltd.] and stirred at room temperature at 720 rpm. 33.3 parts of the coating polymer compound solution (1) prepared in Example 2 was added dropwise over 10 minutes, and the mixture was further stirred for 5 minutes. Thereafter, the pressure is reduced to 0.01 MPa while maintaining the stirring, and then the temperature is raised to 140 ° C. while maintaining the stirring and the degree of vacuum, and the volatile matter is distilled off by maintaining the stirring, the pressure and the temperature for 8 hours. Then, silicon-based coated negative electrode active material particles (N-24) were obtained.

<Production Example 4: Production of polymer compound solution 2 for coating>
A 4-necked flask equipped with a stirrer, thermometer, reflux condenser, dropping funnel and nitrogen gas inlet tube was charged with 407.9 parts of DMF and heated to 75 ° C. Next, a monomer liquid mixture containing 242.8 parts of methacrylic acid, 97.1 parts of methyl methacrylate, 242.8 parts of 2-ethylhexyl methacrylate, and 116.5 parts of DMF, and 2,2′-azobis (2,4-dimethyl) (Valeronitrile) 1.7 parts and 2,2′-azobis (2-methylbutyronitrile) 4.7 parts dissolved in 58.3 parts of DMF and an initiator solution while blowing nitrogen into a four-necked flask, Under stirring, radical polymerization was carried out by continuously dropping with a dropping funnel over 2 hours. After completion of dropping, the reaction was continued at 75 ° C. for 3 hours. Subsequently, the temperature was raised to 80 ° C. and the reaction was continued for 3 hours to obtain a copolymer solution having a resin solid content concentration of 50% by weight. To this, 789.8 parts of DMF was added to obtain a coating polymer compound solution 2 having a resin solid content concentration of 30% by weight.

<Production Example 5: Production of carbon-based coated negative electrode active material particles (N-11)>
Non-graphitizable carbon powder [Carbotron (registered trademark) manufactured by Kureha Battery Materials Japan Co., Ltd., volume average particle size 20 μm] 69 parts in universal mixer high speed mixer FS25 [manufactured by Earth Technica Co., Ltd.] Then, 33.3 parts of the coating polymer compound solution (2) prepared in Production Example 4 was added dropwise over 10 minutes while stirring at room temperature and 720 rpm, and the mixture was further stirred for 5 minutes. Then, the pressure is reduced to 0.01 MPa while maintaining the stirring, and then the temperature is raised to 140 ° C. while maintaining the stirring and the degree of vacuum, and the volatile matter is distilled off by maintaining the stirring, the pressure and the temperature for 8 hours. Carbon-based coated negative electrode active material particles (volume average particle diameter 20 μm) (N-11) were obtained.

<Production Example 6: Production of carbon-based coated negative electrode active material particles (N-12)>
Carbon-based coated negative electrode active material particles (N-12) were obtained in the same manner as in Production Example 5 except that the volume average particle size of the non-graphitizable carbon powder was changed to 2 μm.

<Production Example 7: Production of carbon-based coated negative electrode active material particles (N-13)>
Carbon-based coated negative electrode active material particles (N-13) were obtained in the same manner as in Production Example 5 except that the volume average particle diameter of the non-graphitizable carbon powder was changed to 18 μm.

<Production Example 8: Production of silicon oxide particles (N-25) whose surface is coated with carbon>
Silicon oxide particles (manufactured by Sigma-Aldrich Japan, volume average particle size 2.0 μm) are placed in a horizontal heating furnace, and a chemical vapor deposition operation of 1100 ° C./1000 Pa and average residence time of about 2 hours is performed while aeration of methane gas is performed. Silicon-based negative electrode active material particles (volume average particle diameter of 2.0 μm) (N-25), which are silicon oxide particles having a carbon content of 2% by weight and a surface coated with carbon, were obtained.

<Production Example 9: Production of composite particles (N-26)>
In a state where 3 parts of silicon particles [manufactured by Sigma-Aldrich Japan, volume average particle diameter 5 μm] (N-21) are put into a universal mixer high speed mixer FS25 [manufactured by Earth Technica Co., Ltd.] and stirred at room temperature at 720 rpm, 10 parts of a polyacrylic acid resin solution (solvent: ultrapure water, solid content concentration 10%) was added dropwise over 2 minutes, and the mixture was further stirred for 5 minutes. Next, 1 part of acetylene black [Denka Co., Ltd., Denka Black (registered trademark)] was added while stirring, and stirring was continued for 30 minutes. Thereafter, the pressure was reduced to 0.01 MPa while maintaining the stirring, and then the temperature was raised to 140 ° C. while maintaining the stirring and the degree of vacuum, and the volatile matter was distilled off by maintaining the stirring, the degree of vacuum and the temperature for 8 hours. . The obtained powder was classified with a sieve having an opening of 20 μm to obtain composite particles (volume average particle diameter 30 μm) (N-26).

<Example 1>
[Preparation of negative pressure relief layer]
It was prepared by dissolving LiPF ₆ at a ratio of 1 mol / L in 5 parts of carbon fiber obtained in Production Example 1 and a mixed solvent of ethylene carbonate (EC) and propylene carbonate (PC) (volume ratio 1: 1). 95 parts of the electrolyte (X) was put into a universal mixer high speed mixer FS25 [manufactured by Earth Technica Co., Ltd.] and stirred at room temperature and 2000 rpm for 5 minutes to obtain a pressure relaxation layer raw material paste.
The reverse side of the surface where 174 mg of this pressure relaxation layer raw material paste was dropped on the surface of a 23 mm aramid nonwoven fabric (manufactured by Japan Vilene Co., Ltd.), which was a butyl rubber sheet with a hole of φ15 mm (hereinafter referred to as a mask) overlapped. The negative electrode pressure relaxation layer was produced on the aramid separator by removing a part of the electrolytic solution (X).

[Preparation of laminate of negative electrode pressure relaxation layer and negative electrode active material layer]
9.5 parts by weight of carbon-based coated negative electrode active material particles (N-11) obtained in Production Example 5, silicon particles [manufactured by Sigma-Aldrich Japan, volume average particle diameter 5 μm] (N-21) 0.5 parts by weight Electrolytic solution (X) prepared by dissolving 1 part by weight of carbon fiber as a conductive material in a mixed solvent of ethylene carbonate (EC) and propylene carbonate (volume ratio 1: 1) at a rate of 1 mol / L LiPF ₆ Parts were mixed to prepare a negative electrode active material slurry.
On the negative electrode pressure relaxation layer produced on the aramid nonwoven fabric, the negative electrode active material slurry is dropped so as to have a weight per unit area of 47 mg / cm ^2, and suction filtration (reduced pressure) is performed so that voids on the surface of the negative electrode pressure relaxation layer A negative electrode active material layer is laminated on a negative electrode pressure relaxation layer while a part of the negative electrode active material is put in, and further pressed at a pressure of 5 MPa, whereby the negative active material layer and the negative electrode pressure relaxation layer are integrated on the aramid nonwoven fabric. Thus, a laminate 1 of the negative electrode pressure relaxation layer and the negative electrode active material layer was produced.
The thickness of the negative electrode pressure relaxation layer and the negative electrode active material layer was 50 μm and 550 μm, respectively.
In addition, the thickness of each layer was measured using a contact-type film thickness meter [ABS Digimatic Indicator ID-CX manufactured by Mitutoyo Corporation].

[Preparation of Positive Electrode Pressure Relaxation Layer and Laminate of Positive Electrode Pressure Relaxation Layer and Positive Electrode Active Material Layer]
5 parts of the carbon fiber obtained by the above [Preparation of conductive carbon filler] and 95 parts of the electrolytic solution (X) are put into a universal mixer high speed mixer FS25 [manufactured by Earth Technica Co., Ltd.] at room temperature and 2000 rpm. It stirred for 5 minutes and the positive electrode pressure relaxation layer raw material paste was obtained.
0.2 part of carbon fiber, 9.8 parts of LiNi _0.8 Co _0.15 Al _0.05 O ₂ powder (volume average particle diameter 15 μm) which is a positive electrode active material, and 90 parts of the electrolytic solution (X) Were mixed for 5 minutes at 2000 rpm using a planetary agitation type mixing and kneading apparatus {Awatori Netaro [manufactured by Shinky Co., Ltd.]} to prepare a positive electrode active material slurry.
A mask is placed on a 2300 mesh stainless steel wire mesh of 23 mm in diameter [manufactured by Sunnet Kogyo Co., Ltd.], 174 mg of positive electrode pressure relaxation layer raw material paste is dropped, sucked from the back side of the dropped surface, and is on the surface of the positive electrode pressure relaxation layer By laminating the positive electrode active material on the positive electrode pressure relaxation layer while putting a part of the positive electrode active material in the gap, a part of the electrolyte solution (X) was removed, and a positive electrode pressure relaxation layer was produced on the stainless steel wire mesh. .
The positive electrode active material slurry is dropped onto the positive electrode pressure relaxation layer prepared on the stainless steel wire mesh so that the basis weight is 78.0 mg / cm ² and is sucked from the back surface. The material layer and the positive electrode pressure relaxation layer were integrated to produce a laminate 1 of the positive electrode pressure relaxation layer and the positive electrode active material layer. The thicknesses of the positive electrode pressure relaxation layer and the positive electrode active material layer were 50 μm and 580 μm, respectively.

[Production of lithium-ion batteries]
First, a copper foil (3 cm × 3 cm, thickness 17 μm) with a terminal (5 mm × 3 cm) serving as a current collector and an aluminum foil (3 cm × 3 cm, thickness 21 μm) with a terminal (5 mm × 3 cm) were used as two terminals Is laminated in the same direction, and is sandwiched between two commercially available heat-bonding aluminum laminate films (10cm x 8cm). Was made.
The laminate 1 of the negative electrode pressure relaxation layer and the negative electrode active material layer was peeled off from the aramid nonwoven fabric, and the negative electrode active material layer was stacked on the copper foil.
Next, 100 μL of the electrolytic solution (X) is dropped on the negative electrode active material layer, and a separator (Celgard 2500, manufactured by Polypore International, polypropylene separator with a thickness of 23 μm) is placed on the negative electrode active material layer. 100 μL of the electrolytic solution (X) was dropped from above.
The laminate 1 of the positive electrode pressure relaxation layer and the positive electrode active material layer was peeled off from the stainless steel metal mesh, and the positive electrode active material layer was laminated on the separator placed on the negative electrode active material.
Further, 100 μL of the electrolytic solution (X) was dropped, and then the laminate cell was closed so that the aluminum foil in the laminate cell was covered thereon, and two sides orthogonal to one side heat-sealed first were heat sealed.
Furthermore, the laminate cell was sealed by heat-sealing the remaining one side while evacuating the inside of the cell using a vacuum sealer, and the positive electrode for the lithium ion battery according to Example 1 and the negative electrode for the lithium ion battery according to Example 1 were prepared. A lithium ion battery according to Example 1 was prepared.

<Example 2>
[Preparation of laminate of negative electrode pressure relaxation layer and negative electrode active material layer]
A negative electrode pressure relaxation layer was produced in the same procedure as in Example 1 except that the amount of the negative electrode pressure relaxation layer raw material paste was changed to 104 mg. Subsequently, 9.5 parts by weight of the carbon-based coated negative electrode active material particles (N-11) was changed to 3.4 parts by weight of the carbon-based coated negative electrode active material particles (N-12) obtained in Production Example 6, Silicon particles (volume average particle diameter 5 μm) (N-21) 0.5 parts by weight were changed to silicon particles (volume average particle diameter 0.2 μm) (N-22) 1.6 parts by weight, and the total amount was 100 parts by weight. A negative electrode active material slurry was prepared in the same procedure as in Example 1 except that the amount of the electrolytic solution (X) was adjusted so that A laminate 2 of a negative electrode pressure relaxation layer and a negative electrode active material layer was produced in the same procedure as in Example 1 except that the basis weight of the negative electrode active material slurry was changed to 19 mg / cm ² .
The thicknesses of the negative electrode pressure relaxation layer and the negative electrode active material layer were 30 μm and 200 μm, respectively.

[Preparation of laminate of positive electrode pressure relaxation layer and positive electrode active material layer]
A mask is layered on a 2300 mesh stainless steel wire mesh with a diameter of 23 mm, 104 mg of the positive electrode pressure relaxation layer raw material paste used in Example 1 is dropped, and a part of the electrolyte solution (X) is sucked from the back side of the dropped surface. The positive electrode pressure relaxation layer was produced on the stainless steel wire mesh by removing.
Lamination of the positive electrode pressure relaxation layer and the positive electrode active material layer in the same procedure as in Example 1 except that the basis weight of the positive electrode active material slurry was changed to 74.0 mg / cm ² and dropped onto the positive electrode pressure relaxation layer. Body 2 was produced.
The thickness of the positive electrode pressure relaxation layer and the positive electrode active material layer was 30 μm and 550 μm, respectively.
[Production of lithium-ion batteries]
The laminate 1 of the negative electrode pressure relaxation layer and the negative electrode active material layer and the laminate 1 of the positive electrode pressure relaxation layer and the positive electrode active material layer are respectively laminated with the laminate 2 of the negative electrode pressure relaxation layer and the negative electrode active material layer and the positive electrode pressure. For a lithium ion battery according to Example 2, except that the layered body 2 of the relaxation layer and the positive electrode active material layer was changed and the injection amount of the electrolytic solution (X) was changed to 60 μL. A lithium ion battery according to Example 2 including a positive electrode and a negative electrode for a lithium ion battery according to Example 2 was produced.

<Example 3>
[Preparation of laminate of negative electrode pressure relaxation layer and negative electrode active material layer]
Acetylene black [Denka Co., Ltd. Denka Black (registered trademark)] (aspect ratio: 1, average particle size: 35 nm, electrical resistivity: 60 μΩ · m), the same amount of conductive carbon filler A1 as conductive carbon filler A2 , Bulk density: 0.04 g / cm ³ )], the dripping amount of the negative electrode pressure relaxation layer raw material paste was changed to 7.0 mg, and carbon-based coated negative electrode active material particles (N-11) 9.5 parts by weight Was changed to 3.3 parts by weight of the carbon-based coated negative electrode active material particles (N-13) obtained in Production Example 7, and 0.5 parts by weight of silicon particles (volume average particle diameter 5 μm) (N-21) were added. Silicon particles (volume average particle diameter 1.5 μm) (N-23) was changed to 1.7 parts by weight, the amount of the electrolyte (X) was adjusted so that the total amount was 100 parts by weight, and the negative electrode active material slurry except that the basis weight was changed to 10 mg / cm ² from example 1 To, to produce a laminate 3 of the negative electrode pressure relief layer and the anode active material layer-like.
The thicknesses of the negative electrode pressure relaxation layer and the negative electrode active material layer were 2 μm and 100 μm, respectively.
[Preparation of laminate of positive electrode pressure relaxation layer and positive electrode active material layer]
A mask is layered on a 2300 mesh stainless steel wire mesh with a diameter of 23 mm, 7.0 mg of the positive electrode pressure relaxation layer raw material paste used in Example 1 is dropped, and sucked from the back side of the dropped surface, whereby one electrolyte solution (X) is obtained. The portion was removed, and a positive electrode pressure relaxation layer was produced on a stainless steel wire mesh.
A laminate 3 of the positive electrode pressure relaxation layer and the positive electrode active material layer was obtained in the same manner as in Example 1 except that the basis weight of the positive electrode active material slurry was changed to 40.3 mg / cm ² and dropped onto the positive electrode pressure relaxation layer. Was made.
The thicknesses of the positive electrode pressure relaxation layer and the positive electrode active material layer were 2 μm and 300 μm, respectively.
[Production of lithium-ion batteries]
The laminate 1 of the negative electrode pressure relaxation layer and the negative electrode active material layer and the laminate 1 of the positive electrode pressure relaxation layer and the positive electrode active material layer are combined with the laminate 3 of the negative electrode pressure relaxation layer and the negative electrode active material layer and the positive electrode pressure relaxation layer. The positive electrode for a lithium ion battery according to Example 3 and the positive electrode active material layer according to the same procedure as in Example 1 except that the amount of injection of the electrolyte (X) was changed to 20 μL. The lithium ion battery which concerns on Example 3 containing the negative electrode for lithium ion batteries which concerns on Example 3 was produced.

<Example 4>
[Preparation of laminate of negative electrode pressure relaxation layer and negative electrode active material layer]
The conductive carbon filler A1 is changed to the same amount of conductive carbon filler A2, and the electrolytic solution (X) is replaced with the same amount of electrolytic solution (Y) [mixed solvent of ethylene carbonate (EC) and propylene carbonate (PC) (volume ratio The electrolytic solution prepared by dissolving LiN (FSO ₂ ) ₂ at a ratio of 2 mol / L in 1: 1)] and changing the silicon particles (N-21) in Production Example 3 A laminate 4 of a negative electrode pressure relaxing layer and a negative electrode active material layer in the same procedure as in Example 1 except that the particle (N-24) was changed and the basis weight of the negative electrode active material slurry was changed to 46 mg / cm ^2. Was made. The thickness of the negative electrode pressure relaxation layer and the negative electrode active material layer was 50 μm and 540 μm, respectively.
[Preparation of laminate of positive electrode pressure relaxation layer and positive electrode active material layer]
The positive electrode pressure relaxation layer is the same procedure as in Example 1 except that the conductive carbon filler A1 is changed to the same amount of conductive carbon filler A2 and the electrolytic solution (X) is changed to the same amount of electrolytic solution (Y). Was made.
The positive electrode pressure relaxation layer was the same as in Example 1 except that the electrolyte solution (X) was changed to the same amount of electrolyte solution (Y) and the basis weight of the positive electrode active material slurry was changed to 67.2 mg / cm ^2. And a laminate 4 of the positive electrode active material layer.
The thicknesses of the positive electrode pressure relaxation layer and the positive electrode active material layer were 50 μm and 500 μm, respectively.
[Production of lithium-ion batteries]
The laminate 1 of the negative electrode pressure relaxation layer and the negative electrode active material layer and the laminate 1 of the positive electrode pressure relaxation layer and the positive electrode active material layer are combined with the laminate 4 of the negative electrode pressure relaxation layer and the negative electrode active material layer and the positive electrode pressure relaxation layer. The positive electrode for a lithium ion battery according to Example 4 and the positive electrode active material layer according to the same procedure as in Example 1 except that the electrolyte solution (X) is changed to the electrolyte solution (Y). The lithium ion battery which concerns on Example 4 containing the negative electrode for lithium ion batteries which concerns on Example 4 was produced.

<Example 5>
[Preparation of laminate of negative electrode pressure relaxation layer and negative electrode active material layer]
The conductive carbon filler A1 was changed to the same amount of conductive carbon filler A2, the electrolytic solution (X) was changed to the same amount of electrolytic solution (Y), and silicon particles (N-21) were produced in Production Example 8. Except that it was changed to silicon-based negative electrode active material particles (N-25), the dropping amount of the negative electrode pressure relaxation layer raw material paste was changed to 348 mg, and the basis weight of the negative electrode active material slurry was changed to 46 mg / cm ^2. 1 to prepare a laminate 5 of a negative electrode pressure relaxation layer and a negative electrode active material layer. The thicknesses of the negative electrode pressure relaxation layer and the negative electrode active material layer were 100 μm and 540 μm, respectively.
[Preparation of laminate of positive electrode pressure relaxation layer and positive electrode active material layer]
A positive electrode pressure relaxation layer was produced on a stainless steel wire mesh in the same procedure as in Example 1 except that the electrolytic solution (X) was changed to the same amount of electrolytic solution (Y).
The positive electrode pressure relaxation was carried out in the same manner as in Example 1 except that the basis weight of the positive electrode active material slurry was changed to 67.2 mg / cm ² on the positive electrode pressure relaxation layer and dropped onto the positive pressure relief layer. A laminate 5 of the layer and the positive electrode active material layer was produced.
The thicknesses of the positive electrode pressure relaxation layer and the positive electrode active material layer were 50 μm and 500 μm, respectively.
[Production of lithium-ion batteries]
A laminate 1 of a negative electrode pressure relaxation layer and a negative electrode active material layer and a laminate 1 of a positive electrode pressure relaxation layer and a positive electrode active material layer are combined with a laminate 5 of a negative electrode pressure relaxation layer and a negative electrode active material layer and a positive electrode pressure relaxation layer. A lithium ion battery according to Example 5 in the same procedure as in Example 1 except that the laminate 5 is made of a positive electrode active material layer and the electrolyte solution (X) is changed to the same amount of electrolyte solution (Y). A lithium ion battery according to Example 5 including a positive electrode for use and a negative electrode for a lithium ion battery according to Example 5 was produced.

<Example 6>
[Preparation of laminate of negative electrode pressure relaxation layer and negative electrode active material layer]
The silicon particle (volume average particle diameter 5 μm) (N-21) 0.5 part by weight is changed to the composite particle (volume average particle diameter 30 μm) (N-26) 0.5 part by weight, and the basis weight of the negative electrode active material slurry A laminate 6 of a negative electrode pressure relaxation layer and a negative electrode active material layer was produced in the same procedure as in Example 1 except that was changed to 46 mg / cm ² . The thickness of the negative electrode pressure relaxation layer and the negative electrode active material layer was 50 μm and 550 μm, respectively.
[Preparation of laminate of positive electrode pressure relaxation layer and positive electrode active material layer]
A positive electrode pressure relaxation layer was prepared in the same procedure as in Example 1 except that the electrolytic solution (X) was changed to the same amount of electrolytic solution (Y).
The electrolytic solution (X) was changed to the electrolytic solution (Y), the basis weight of the positive electrode active material slurry was changed to 63.9 mg / cm ² , and the solution was dropped onto the positive electrode pressure relaxation layer as in Example 1. The laminated body 6 of the positive electrode pressure relaxation layer and the positive electrode active material layer was produced integrally. The thicknesses of the positive electrode pressure relaxation layer and the positive electrode active material layer were 50 μm and 475 μm, respectively.
[Production of lithium-ion batteries]
The laminate 1 of the negative electrode pressure relaxation layer and the negative electrode active material layer and the laminate 1 of the positive electrode pressure relaxation layer and the positive electrode active material layer are combined with the laminate 6 of the negative electrode pressure relaxation layer and the negative electrode active material layer and the positive electrode pressure relaxation layer. A lithium ion battery according to Example 6 in the same procedure as in Example 1 except that the laminate 6 and the positive electrode active material layer were respectively changed and the electrolytic solution (X) was changed to the same amount of electrolytic solution (Y). A lithium ion battery according to Example 6 including a positive electrode for use and a negative electrode for a lithium ion battery according to Example 6 was produced.

<Example 7>
[Preparation of laminate of negative electrode pressure relaxation layer and negative electrode active material layer]
A negative electrode pressure relaxation layer was produced in the same procedure as in Example 1 except that the amount of the negative electrode pressure relaxation layer raw material paste was changed to 104 mg. Subsequently, 9.5 parts by weight of the carbon-based coated negative electrode active material particles (N-11) are changed to 8 parts by weight, and 0.5 parts by weight of silicon particles (volume average particle diameter 5 μm) (N-21) are combined. Change the particle (N-26) to 2 parts by weight, change the electrolyte (X) to the same amount of electrolyte (Y), and adjust the amount of the electrolyte (Y) so that the total amount becomes 100 parts by weight. A laminate 7 of a negative electrode pressure relaxation layer and a negative electrode active material layer was produced in the same procedure as in Example 1 except that the basis weight of the negative electrode active material slurry was changed to 29 mg / cm ² . The thickness of the negative electrode pressure relaxation layer and the negative electrode active material layer was 30 μm and 350 μm, respectively.
[Preparation of positive electrode active material layer]
A positive electrode active material layer 7 is formed on the stainless steel wire mesh by overlaying a mask on a 2300 mesh stainless steel wire mesh with a diameter of 23 mm, dropping the positive electrode active material slurry used in Example 1 on the mask and sucking it from the back surface. did. At this time, the basis weight of the positive electrode active material slurry to be dropped was set to 49.1 mg / cm ² . The thickness of the positive electrode active material layer was 365 μm.
[Production of lithium-ion batteries]
The laminate 1 of the negative electrode pressure relaxation layer and the negative electrode active material layer and the laminate 1 of the positive electrode pressure relaxation layer and the positive electrode active material layer are combined with the laminate 7 of the negative electrode pressure relaxation layer and the negative electrode active material layer and the positive electrode active material layer. The positive electrode for a lithium ion battery according to Example 7 and Example 7 are the same as Example 1, except that the electrolyte solution (X) is changed to the same amount of electrolyte solution (Y). A lithium ion battery according to Example 7 including a negative electrode for a lithium ion battery was produced.

<Example 8>
[Preparation of laminate of negative electrode pressure relaxation layer and negative electrode active material layer]
The negative electrode pressure relaxation layer and the negative electrode active material layer were processed in the same manner as in Example 1, except that the amount of the negative electrode pressure relaxation layer raw material drop was changed to 348 mg and the basis weight of the negative electrode active material slurry was changed to 43 mg / cm ^2. A laminate 8 was prepared. The thickness of the negative electrode pressure relaxation layer and the negative electrode active material layer was 100 μm and 550 μm, respectively.
[Preparation of positive electrode active material layer]
A positive electrode active material layer 8 is produced on a stainless steel wire mesh by overlaying a mask on a 2300 mesh stainless steel wire mesh with a diameter of 23 mm, dropping the positive electrode active material slurry used in Example 1 on the mask and sucking it from the back surface. did. At this time, the basis weight of the positive electrode active material slurry to be dropped was set to 71.3 mg / cm ² . The thickness of the positive electrode active material layer was 530 μm.
[Production of lithium-ion batteries]
Implementation was performed except that the laminate 7 and the positive electrode active material layer 7 of the negative electrode pressure relaxation layer and the negative electrode active material layer were changed to the laminate 8 and the positive electrode active material layer 8 of the negative electrode pressure relaxation layer and the negative electrode active material layer, respectively. A lithium ion battery according to Example 8 including the positive electrode for lithium ion batteries according to Example 8 and the negative electrode for lithium ion batteries according to Example 8 was produced in the same procedure as Example 7.

<Comparative Example 1>
[Preparation of negative electrode active material layer]
In 85 parts of the electrolytic solution (X) used in Example 1, 3.3 parts by weight of carbon-based coated negative electrode active material particles (N-13), silicon particles [manufactured by Sigma-Aldrich Japan, volume average particle diameter 1.5 μm] ( N-23) After adding 1.7 parts by weight and 1 part by weight of the above-mentioned carbon fiber as conductive carbon filler A1, 10 parts of an N-methylpyrrolidone solution containing 5% by weight of polyvinylidene fluoride from which moisture has been removed is added. Then, using a planetary agitation type mixing and kneading apparatus {Awatori Netaro (manufactured by Shinky Co., Ltd.)}, mixing was performed at 2000 rpm for 1.5 minutes to prepare a negative electrode active material slurry.
The obtained negative electrode active material slurry was dropped onto a φ23 mm aramid nonwoven fabric equipped with a φ15 mm mask so that the weight per unit area was 9 mg / cm ^2, and the electrolyte solution (X) was sucked from the back side of the dropped surface A part of was removed to prepare a negative electrode active material layer. Thereafter, pressing was performed at a pressure of 5 MPa for about 10 seconds, followed by drying at 100 ° C. for 15 minutes to obtain a negative electrode active material layer 1 ′. The thickness of the negative electrode active material layer 1 ′ was 100 μm.
[Preparation of positive electrode active material layer]
A mask is placed on a 2300 mesh stainless steel wire mesh with a diameter of 23 mm, and the positive electrode active material slurry used in Example 1 is dropped on the mask and sucked from the back surface. Produced. At this time, the basis weight of the dropped positive electrode active material slurry was set to 36.3 mg / cm ² .
The thickness of the positive electrode active material layer 1 ′ was 270 μm.
[Production of lithium-ion batteries]
The laminate 1 of the negative electrode pressure relaxation layer and the negative electrode active material layer and the laminate 1 of the positive electrode pressure relaxation layer and the positive electrode active material layer were changed to the negative electrode active material layer 1 ′ and the positive electrode active material layer 1 ′, respectively. A lithium ion battery according to Comparative Example 1 including the positive electrode for lithium ion batteries according to Comparative Example 1 and the negative electrode for lithium ion batteries according to Comparative Example 1 was prepared in the same procedure as in Example 1.

<Comparative example 2>
[Preparation of negative electrode active material layer]
The electrolytic solution (X) was changed to the same amount of electrolytic solution (Y), and 0.5 part by weight of the silicon particles (N-21) was changed to the same amount of silicon-based negative electrode active material particles (N-25). A negative electrode active material slurry was prepared in the same procedure as in Comparative Example 1.
Part of the electrolyte (Y) by dropping the negative electrode active material slurry onto a φ23 mm aramid nonwoven fabric equipped with a φ15 mm mask so that the basis weight is 46 mg / cm ² and sucking it from the back side of the dropped surface. Then, a negative electrode active material layer was produced. Thereafter, pressing was performed at a pressure of 5 MPa for about 10 seconds, followed by drying at 100 ° C. for 15 minutes to obtain a negative electrode active material layer 2 ′. The thickness of the negative electrode active material layer 2 ′ was 540 μm.
[Preparation of positive electrode active material layer]
A mask is layered on a 2300 mesh stainless steel wire mesh with a diameter of 23 mm, and the positive electrode active material slurry used in Example 1 is dropped on the mask and sucked from the back surface, whereby the positive electrode active material layer 2 ′ is formed on the stainless steel wire mesh. Produced. At this time, the basis weight of the positive electrode active material slurry to be dropped was set to 67.2 mg / cm ² .
The thickness of the positive electrode active material layer 2 ′ was 500 μm.
[Production of lithium-ion batteries]
The laminated body 1 of the negative electrode pressure relaxation layer and the negative electrode active material layer and the laminated body 1 of the positive electrode pressure relaxation layer and the positive electrode active material layer are changed to the negative electrode active material layer 2 ′ and the positive electrode active material layer 2 ′, respectively, and an electrolyte solution The lithium ion battery positive electrode according to Comparative Example 2 and the lithium ion battery negative electrode according to Comparative Example 2 are included in the same procedure as in Example 1 except that (X) is changed to the same amount of the electrolytic solution (Y). A lithium ion battery according to Comparative Example 2 was produced.

[Measurement of battery characteristics]
About the produced lithium ion battery, a charge / discharge test was conducted by the following method using a charge / discharge measurement apparatus “HJ0501SM8A” [manufactured by Hokuto Denko Co., Ltd.]. The ratio of the discharge capacity at the 50th cycle to the discharge capacity (also referred to as the capacity retention rate after 50 cycles) was determined. The results are shown in Table 1.
In addition, the lithium ion battery used when calculating | requiring the expansion coefficient of the negative electrode after the first charge and the lithium ion battery which evaluated the capacity maintenance rate after 50 cycles was used. That is, the following 50 charging / discharging processes in the evaluation of the capacity maintenance rate after 50 cycles are continuously performed, and the charging / discharging process for measuring the expansion coefficient of the negative electrode is not interrupted.
[Capacity maintenance rate after 50 cycles]
Charging / discharging in which the lithium ion battery for battery characteristic evaluation is charged to 4.2 V with a current of 0.1 C under a condition of 45 ° C., and discharged to 2.5 V with a current of 0.05 C after 10 minutes of rest. The process was repeated 50 times with a 10 minute pause. The 50th discharge capacity was compared with the initial discharge capacity, and the capacity retention rate after 50 cycles was determined.
[Expansion coefficient of negative electrode]
The expansion coefficient of the negative electrode during the first charge was calculated by the following formula (2) using the thickness of the negative electrode before the first charge and the thickness of the negative electrode after the first charge.
Expansion rate of negative electrode after first charge (%) = [((Thickness of negative electrode after first charge) − (Thickness of negative electrode before first charge)) / (Thickness of negative electrode before first charge)] × 100 (2)
(Negative electrode thickness) in the above calculation is the sum of (Negative electrode active material layer thickness) and (Negative electrode pressure relaxation layer thickness), and does not cause volume expansion / contraction during charging / discharging (Negative electrode current collector) Thickness) was not considered.

From the results in Table 1, it can be seen that the electrode for a lithium ion battery of the present invention suppresses expansion of the electrode and is excellent in cycle characteristics.

The electrode for lithium ion batteries of the present invention is particularly useful as an electrode for bipolar secondary batteries and lithium ion batteries used for mobile phones, personal computers, hybrid vehicles, and electric vehicles.

DESCRIPTION OF SYMBOLS 1 Electrode for lithium ion batteries 10 Electrode current collector 20 Pressure relaxation layer 30 Electrode active material layer 40 Exterior body

Claims (9)

An electrode for a lithium ion battery comprising an electrode current collector and an electrode active material layer,
The electrode active material layer is composed of a non-binding body of an electrode active material composition containing an electrode active material,
Between the electrode current collector and the electrode active material layer, a pressure relaxation layer made of a conductive carbon filler is disposed,
The electrode for a lithium ion battery, wherein the electrode active material exists in the vicinity of the surface on the electrode active material layer side in the pressure relaxation layer. The lithium ion battery electrode according to claim 1, wherein the pressure relaxation layer has a thickness of 2 to 500 μm. The electrode for a lithium ion battery according to claim 1 or 2, wherein a ratio of the thickness of the pressure relaxation layer to the thickness of the electrode active material layer is 0.3 to 25%. The electrode for a lithium ion battery according to claim 1, wherein the conductive carbon filler constituting the pressure relaxation layer is at least one selected from the group consisting of carbon nanofibers, carbon fibers, and carbon nanotubes. . The electrode for a lithium ion battery according to claim 1, wherein the electrode active material layer is a non-binding body of an electrode active material composition including the electrode active material and an electrolytic solution. The electrode for a lithium ion battery according to claim 1, wherein the electrode active material is a positive electrode active material. The electrode for a lithium ion battery according to any one of claims 1 to 5, wherein the electrode active material is a mixture containing silicon and / or a silicon compound and a carbon-based negative electrode active material. The electrode for a lithium ion battery according to any one of claims 1 to 7, wherein the electrode active material is a coated electrode active material in which part or all of the surface thereof is coated with an electrode coating layer containing a polymer compound. . A lithium ion battery comprising the electrode for a lithium ion battery according to claim 1.

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