KR102304346B1 - Electrode for lithium ion secondary battery, and lithium ion secondary battery - Google Patents

Abstract

An electrode for a lithium ion secondary battery comprising an electrode active material layer and a porous layer containing organic particles formed directly on the electrode active material layer, wherein the organic particles include a core portion and a shell portion partially covering the outer surface of the core portion has a core-shell structure, wherein the core part consists of a polymer having a swelling degree of 5 times or more and 30 times or less with respect to the electrolyte, and the shell part is made of a polymer having a swelling degree of more than 1 time and 4 times or less with respect to the electrolyte solution, An electrode for a lithium ion secondary battery.

Description

Electrode for lithium ion secondary batteries and lithium ion secondary batteries TECHNICAL FIELD

This invention relates to the electrode for lithium ion secondary batteries, and the lithium ion secondary battery provided with the same.

In recent years, the spread of portable terminals, such as a notebook computer, a mobile phone, and a PDA (Personal Digital Assistant), is remarkable. Lithium ion secondary batteries are often used for secondary batteries used as power sources for these portable terminals.

A lithium ion secondary battery is generally equipped with a positive electrode, a negative electrode, and electrolyte solution. Moreover, in order to prevent the short circuit between a positive electrode and a negative electrode in a lithium ion secondary battery, a separator is normally provided (refer patent documents 1 and 2).

International Publication No. 2005/029614 International Publication No. 2011/040474

Generally, a lithium ion secondary battery reduces battery capacity by repeating charging/discharging. In order to implement|achieve a lithium ion secondary battery with a long life, it is calculated|required that the battery capacity is hard to fall even if it repeats charging/discharging. From such a viewpoint, the development of a technology capable of realizing a lithium ion secondary battery having excellent high-temperature cycle characteristics is demanded.

The present invention was devised in view of the above problems, an electrode for a lithium ion secondary battery capable of producing a lithium ion secondary battery excellent in high temperature cycle characteristics; And, to provide a lithium ion secondary battery excellent in high temperature cycle characteristics do.

As a result of intensive studies in order to solve the above problems, the present inventors have found a core formed of a polymer that can swell with a predetermined degree of swelling with respect to an electrolytic solution and provided with a core portion and a shell portion partially covering the outer surface of the core portion. By forming the porous layer containing the organic particle|grains which has a shell structure directly on the electrode active material layer of an electrode, it discovered that the lithium ion secondary battery excellent in high temperature cycling characteristics could be implement|achieved, and completed this invention.

That is, the present invention is as follows.

[1] An electrode for a lithium ion secondary battery comprising an electrode active material layer and a porous layer containing organic particles formed directly on the electrode active material layer,

The organic particles have a core-shell structure including a core portion and a shell portion partially covering the outer surface of the core portion,

The core part is made of a polymer having a swelling degree of 5 times or more and 30 times or less with respect to the electrolyte,

The said shell part, the swelling degree with respect to electrolyte solution is larger than 1 time, and consists of a polymer of 4 times or less, The electrode for lithium ion secondary batteries.

[2] The glass transition temperature of the polymer of the core portion is 0 ° C. or more and 150 ° C. or less,

The electrode for a lithium ion secondary battery according to [1], wherein a glass transition temperature of the polymer in the shell portion is 50°C or more and 200°C or less.

[3] A lithium ion secondary battery comprising the electrode for a lithium ion secondary battery according to [1] or [2] and an electrolyte.

[4] The lithium ion secondary battery according to [3], wherein a counter electrode is provided on the porous layer side of the electrode for a lithium ion secondary battery directly or through a member having no shutdown function.

[5] The lithium ion secondary battery according to [3] or [4], wherein the electrode has a flat shape.

ADVANTAGE OF THE INVENTION According to the electrode for lithium ion secondary batteries which concerns on this invention, the lithium ion secondary battery excellent in high temperature cycling characteristics can be manufactured.

The lithium ion secondary battery which concerns on this invention is excellent in high temperature cycling characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows typically an example of the organic particle which a porous layer contains.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail by showing embodiments and examples. However, the present invention is not limited to the embodiments and examples described below, and can be arbitrarily changed and implemented without departing from the scope of the claims of the present invention and its equivalents.

In the following description, (meth)acrylic acid includes acrylic acid and methacrylic acid. In addition, (meth)acrylate includes an acrylate and a methacrylate. In addition, (meth)acrylonitrile includes acrylonitrile and methacrylonitrile. In addition, (meth)acrylamide includes acrylamide and methacrylamide.

In addition, that a certain substance is water-soluble means that an insoluble content is less than 1.0 weight%, when the substance 0.5g is melt|dissolved in 100 g of water at 25 degreeC. In addition, that a certain substance is water-insoluble means that an insoluble content is 90 weight% or more, when the substance 0.5g is melt|dissolved in 100 g of water at 25 degreeC.

In addition, when solubility in water changes with the pH of water, if there exists a water-soluble area|region, the substance is included as a water-soluble thing.

Moreover, in the polymer produced by copolymerizing a plurality of types of monomers, the ratio in the polymer of the structural unit formed by polymerization of a certain monomer is the total ratio usually used for polymerization of the polymer, unless otherwise specified. It coincides with the ratio (injection ratio) of the said any monomer to a monomer.

In addition, the "electrode plate" includes not only a rigid plate-shaped member, but also a flexible sheet and film.

In addition, a "monomer composition" is used also as a term which points out not only the composition containing two or more types of monomers but one type of monomer.

[One. Outline of electrode for lithium ion secondary battery]

The electrode for lithium ion secondary batteries of this invention (Hereinafter, it may call an "electrode" suitably.) is equipped with an electrode active material layer and the porous layer directly formed in the electrode active material layer. Moreover, normally, the electrode of this invention is equipped with a collector. When providing an electrical power collector, an electrode is normally equipped with an electrical power collector, an electrode active material layer, and a porous layer in this order.

A porous layer contains the organic particle which has a core-shell structure provided with a core part and the shell part which partially covers the outer surface of this core part. And the core part and the shell part of organic particle|grains consist of a polymer which has swelling degree of predetermined range with respect to electrolyte solution, respectively.

When the electrode has such a configuration, the following advantages can be obtained.

i. High-temperature cycle characteristics of the lithium ion secondary battery can be improved.

ii. Usually, the swelling of the battery cell accompanying charging/discharging can be suppressed.

iii. Usually, the low-temperature output characteristic of a lithium ion secondary battery can be made favorable.

iv. Usually, even if it does not provide the organic separator which has a shutdown function in a lithium ion secondary battery, this lithium ion secondary battery can be equipped with a shutdown function.

Although the reason such an excellent advantage is acquired is not necessarily certain, according to examination of this inventor, it is guessed as follows. However, this invention is not restrict|limited by the reason guessed below.

i. High-temperature cycle characteristics:

Generally, in a lithium ion secondary battery, when charging/discharging is repeated, gas may be generated by decomposition|disassembly of electrolyte solution. Such decomposition of the electrolytic solution usually tends to occur in the vicinity of the electrode active material layer of the electrode. When electrolyte solution decomposes|disassembles and gas is generated, since the electrode active material and electrolyte solution cannot contact in the part where the electrolyte solution was decomposed|disassembled, battery capacity may fall.

On the other hand, in the electrode of this invention, the porous layer formed directly in the electrode active material layer contains the organic particle which has a core-shell structure, and the core part has a high swelling degree with respect to electrolyte solution. Since it has a high degree of swelling, this core part has excellent liquid retention, and can store a lot of electrolyte. Therefore, when electrolyte solution runs short in the vicinity of an electrode active material by decomposition|disassembly of electrolyte solution, electrolyte solution can be replenished from the core part to the part where the electrolyte solution runs out. Therefore, in the lithium ion secondary battery provided with the electrode of this invention, even if it repeats charging/discharging, since the contact of an electrode active material and electrolyte solution is hard to be inhibited, the fall of battery capacity can be suppressed.

Moreover, since the gap between molecules of a polymer becomes large in the state which swelled greatly in electrolyte solution, ions become easy to pass through the intermolecular. Further, since the shell part covers the outer surface of the core part not entirely, but partially, the movement of ions is hardly stopped by the shell part, and the ions can easily enter the core part. Therefore, ions can easily permeate|transmit the core part of organic particle|grains in electrolyte solution. Therefore, since lithium ions easily pass through a porous layer, precipitation of lithium in electrolyte solution can be prevented normally. Therefore, in the lithium ion secondary battery provided with the electrode of this invention, even if it repeats charging/discharging, since it is hard to generate|occur|produce the increase in resistance by lithium precipitation, it can suppress the increase in resistance by repetition of charging/discharging.

Moreover, the lithium ion secondary battery provided with the electrode of this invention can suppress the swelling of the battery cell accompanying charging/discharging normally. Therefore, even if charging and discharging are repeated, the distance between the positive electrode and the negative electrode is difficult to increase, so that a decrease in the battery capacity can be suppressed also by this.

By combining these factors, it is guessed that the electrode of this invention can improve the high temperature cycling characteristics of a lithium ion secondary battery.

ii. Inhibition of swelling of battery cells:

In a lithium ion secondary battery, in general, when charging and discharging are repeated, the battery cell swells due to, for example, generation of gas due to decomposition of electrolyte and additives, and generation of voids due to expansion and contraction of the electrode active material. there was a case

However, the polymer constituting the shell portion of the organic particles has high binding properties in the electrolytic solution. It is presumed that this high binding property is caused by, for example, activation of a functional group of the polymer of the swollen shell part to cause chemical or electrical interaction with a functional group on the surface of the electrode active material layer. Since the members in the battery are bound to each other by the organic particles having such high binding properties, it is presumed that the swelling of the battery is suppressed.

iii. Low temperature output characteristics:

As mentioned above, since lithium ion passes easily through a porous layer in electrolyte solution, the lithium ion secondary battery provided with the electrode of this invention can make resistance low. Moreover, according to the electrode of this invention, since precipitation of lithium can be prevented as mentioned above, in the lithium ion secondary battery provided with the electrode of this invention, the raise of resistance by lithium precipitation can be suppressed. Therefore, it is estimated that the low-temperature output characteristic can be improved. Moreover, if the electrode of this invention is used, the lithium secondary battery which does not have a separator can be implement|achieved. Thus, since the lithium ion secondary battery which does not have a separator does not have resistance by the separator, resistance can be made small. Therefore, it is thought that the lithium ion secondary battery which does not have a separator can further improve low-temperature output characteristics.

iv. Shutdown function：

The organic particles of the present invention can be melted when heat is generated. Therefore, when the temperature inside the battery becomes high, the organic particles can be melted and the pores can be blocked, so that the movement of lithium ions can be prevented and the electric current can be cut off. Thus, since the organic particle itself contained in the porous layer melts and can exhibit the shutdown function, it is guessed that the shutdown function can be provided in the lithium ion secondary battery without separately forming the organic separator which has a shutdown function. The shutdown function refers to a function of blocking a current by blocking the pores when a member having pores formed between electrodes of a battery increases in temperature and reaches a predetermined temperature range (typically 130°C ± 5°C).

[2. current collector]

As the current collector, a material that has electrical conductivity and is electrochemically durable can be used. Usually, a metal material is used as a material of this electrical power collector. Examples thereof include iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, and platinum. Especially, as a collector used for a positive electrode, aluminum is preferable, and copper is preferable as an electrical power collector used for a negative electrode. Moreover, said material may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

Although the shape in particular of a collector is not restrict|limited, A sheet-like thing with a thickness of about 0.001 mm - 0.5 mm is preferable.

In order that an electrical power collector may raise the binding strength with an electrode active material layer, it is preferable to use it by roughening previously on the surface. As a roughening method, a mechanical polishing method, an electrolytic polishing method, a chemical polishing method etc. are mentioned, for example. In the mechanical polishing method, for example, abrasive paper to which abrasive particles are adhered, a grindstone, an emery buff, a wire brush provided with a steel wire, etc. are used. Moreover, in order to improve the binding strength and electroconductivity of an electrode active material layer, you may form an intermediate|middle layer on the surface of an electrical power collector.

[3. electrode active material layer]

An electrode active material layer is a layer containing an electrode active material, and is normally formed on an electrical power collector.

The electrode active material of a lithium ion secondary battery can use what can intercalate or discharge|release lithium ion reversibly by applying an electric potential in electrolyte solution.

As the positive electrode active material, for example, a lithium-containing composite metal oxide such as _{LiCoO 2} , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiFePO ₄ , LiFeVO ₄ , LiNi _1/3 Mn _1/3 Co _1/3 O ₂ can be heard

Moreover, you may use the positive electrode active material which consists of a composite material which combined the inorganic compound and the organic compound.

Further, for example, by reducing and firing an iron-based oxide in the presence of a carbon source material, a composite material covered with a carbon material may be produced, and this composite material may be used as a positive electrode active material. Although the iron-based oxide tends to be poor in electrical conductivity, it can be used as a high-performance positive electrode active material by using the composite material as described above.

Moreover, what carried out the element substitution of the said compound partially may be used as a positive electrode active material.

These positive electrode active materials may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios. Moreover, you may use the mixture of an inorganic compound and an organic compound as a positive electrode active material.

The particle diameter of the positive electrode active material may be selected in balance with other structural requirements of the lithium ion secondary battery. From the viewpoint of improving battery characteristics such as load characteristics and cycle characteristics, the volume average particle diameter of the positive electrode active material is preferably 0.1 µm or more, more preferably 1 µm or more, preferably 50 µm or less, more preferably 20 μm or less. When the volume average particle diameter of a positive electrode active material is this range, a battery with a large charge/discharge capacity can be obtained, and the handling at the time of manufacturing the slurry for electrodes and an electrode is easy. Here, the slurry for electrodes is a fluid composition for manufacturing an electrode, and contains an electrode active material and a solvent normally. In addition, the volume average particle diameter of particle|grains represents the particle diameter at which the cumulative volume calculated from the small-diameter side becomes 50 % in the particle-size distribution measured by the laser diffraction method.

The ratio of the positive electrode active material in the electrode active material layer is preferably 90% by weight or more, more preferably 95% by weight or more, and preferably 99.9% by weight or less, and more preferably 99% by weight or less. By making the quantity of a positive electrode active material into the said range, the capacity|capacitance of a lithium ion secondary battery can be made high, and the flexibility of a positive electrode and binding property of an electrical power collector and a positive electrode active material layer can be improved.

Examples of the negative electrode active material include carbonaceous materials such as amorphous carbon, graphite, natural graphite, mesocarbon microbeads, and pitch-based carbon fibers; and conductive polymers such as polyacene. Moreover, metals, such as silicon, tin, zinc, manganese, iron, and nickel, and alloys thereof; Oxides of the said metals or alloys; Sulfates of the said metals or alloys, etc. are mentioned. Moreover, metallic lithium; Lithium alloys, such as Li-Al, Li-Bi-Cd, and Li-Sn-Cd; Lithium transition metal nitride; Silicon, etc. may be used.

Among them, for example, _{it is preferable to use an active material containing silicon such as SiO, SiO 2} , SiOx (0.01 ≤ x < 2), SiC, or SiOC, and SiOx, SiC and SiOC are particularly preferable. By using the active material containing a silicon, the battery capacity of a lithium ion secondary battery can be enlarged. In addition, the active material containing silicon usually greatly expands or contracts by charging and discharging. In the active material that causes such large expansion and contraction, the fluctuation of the electrolyte solution becomes large, so that a place where the electrode active material and the electrolyte solution cannot contact easily occurs, and the high-temperature cycle characteristic tends to be low in the prior art. However, since the electrode of the present invention supplies an electrolyte solution from the core portion to make it difficult to form a place where the electrode active material and the electrolyte solution cannot contact, the capacity of the lithium ion secondary battery can be increased without impairing high-temperature cycle characteristics. have.

Among the active materials containing silicon, it is particularly preferable to use SiOx as the active material containing silicon from the viewpoint that the swelling of the negative electrode active material itself is suppressed. SiOx can be formed by a one or both metal silicon and of SiO and SiO ₂ as raw materials. The SiOx may, for example, a silicon monoxide gas is generated by heating a mixture of SiO ₂ and silicon metal, by cooling and precipitation, it can be produced.

A negative electrode active material may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios. Therefore, you may use it in combination of 2 or more types among said negative electrode active materials. Especially, it is preferable to use the negative electrode active material which contains carbon and the active material containing silicon in combination. In the negative electrode active material containing carbon and the active material containing silicon in combination, it is estimated that insertion and desorption of Li into the active material containing silicon occur at high potential, and insertion and desorption of Li into carbon at low potential occur. . For this reason, since expansion and contraction|shrinkage as the whole negative electrode active material are suppressed, the cycling characteristics of a lithium ion secondary battery can be improved further.

The particle diameter of a negative electrode active material is suitably selected from the balance with other structural requirements of a lithium ion secondary battery. From the viewpoint of improving battery characteristics such as initial efficiency, load characteristics, and cycle characteristics, the volume average particle diameter of the negative electrode active material is preferably 0.1 µm or more, more preferably 1 µm or more, still more preferably 5 µm or more, Preferably it is 100 micrometers or less, More preferably, it is 50 micrometers or less, More preferably, it is 20 micrometers or less.

The specific surface area of the negative electrode active material is preferably 2 m 2 /g or more, more preferably 3 m 2 /g or more, still more preferably 5 m 2 /g or more, and preferably 20 m 2 /g or less, more preferably 15 m 2 /g or less, still more preferably 10 m 2 /g or less. The specific surface area of the negative electrode active material can be measured, for example, by the BET method.

The ratio of the negative electrode active material in the electrode active material layer is preferably 85% by weight or more, more preferably 88% by weight or more, and preferably 99% by weight or less, and more preferably 97% by weight or less. By making the amount of the negative electrode active material within the above range, it is possible to realize a negative electrode exhibiting excellent flexibility and binding property while exhibiting a high capacity.

Moreover, you may use what made the electrically conductive material adhere to the surface by the mechanical modification method as an electrode active material.

It is preferable that an electrode active material layer contains the binder for electrodes other than an electrode active material. By containing the binder for an electrode, the binding property of an electrode active material layer can improve, and the tolerance with respect to the mechanical force of an electrode can be improved. Moreover, since it becomes difficult for an electrode active material layer to peel from an electrical power collector and a porous layer, the possibility of the short circuit by the detached material which peeled can be made low.

As a binder for electrodes, a polymer can be used, for example. As a polymer which can be used as a binder for electrodes, the following soft polymer is mentioned, for example. As a soft polymer, for example,

(i) polybutyl acrylate, polybutyl methacrylate, polyhydroxyethyl methacrylate, polyacrylamide, polyacrylonitrile, butyl acrylate styrene copolymer, butyl acrylate acrylonitrile copolymer, butyl Acrylic soft polymers which are homopolymers of acrylic acid or a methacrylic acid derivative, such as an acrylate acrylonitrile glycidyl methacrylate copolymer, or a copolymer of it and the monomer copolymerizable;

(ii) isobutylene-based soft polymers such as polyisobutylene, isobutylene/isoprene rubber, and isobutylene/styrene copolymer;

(iii) polybutadiene, polyisoprene, butadiene styrene random copolymer, isoprene styrene random copolymer, acrylonitrile butadiene copolymer, acrylonitrile butadiene styrene copolymer, butadiene styrene block copolymer, styrene - diene type soft polymers, such as a butadiene styrene block copolymer, an isoprene styrene block copolymer, and a styrene isoprene styrene block copolymer;

(iv) silicon-containing soft polymers such as dimethylpolysiloxane, diphenylpolysiloxane, and dihydroxypolysiloxane;

(v) liquid polyethylene, polypropylene, poly-1-butene, ethylene/α-olefin copolymer, propylene/α-olefin copolymer, ethylene/propylene/diene copolymer (EPDM), ethylene/propylene/styrene copolymer, etc. of olefinic soft polymers;

(vi) vinyl-based soft polymers such as polyvinyl alcohol, polyvinyl acetate, polyvinyl stearate, and vinyl acetate/styrene copolymer;

(vii) epoxy-based soft polymers such as polyethylene oxide, polypropylene oxide, and epichlorohydrin rubber;

(viii) fluorine-containing soft polymers such as vinylidene fluoride rubber and tetrafluoroethylene-propylene rubber;

and (ix) other soft polymers such as natural rubber, polypeptide, protein, polyester thermoplastic elastomer, vinyl chloride thermoplastic elastomer, and polyamide thermoplastic elastomer.

Among these, a diene type soft polymer and an acrylic type soft polymer are preferable.

Moreover, what has a crosslinked structure may be sufficient as these soft polymers, and what introduce|transduced the functional group by modification|denaturation may be sufficient as them.

In addition, a particulate form may be sufficient as the binder for electrodes, and a non-particulate form may be sufficient as it.

Moreover, the binder for electrodes may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

The amount of the binder for electrodes in the electrode active material layer is preferably 0.1 parts by weight or more, more preferably 0.2 parts by weight or more, preferably 10 parts by weight or less, more preferably, with respect to 100 parts by weight of the electrode active material. 5 parts by weight or less. By making the quantity of the binder for electrodes more than the lower limit of the said range, binding property of an electrical power collector and an electrode active material layer can be improved. Moreover, by setting it as below an upper limit, the low-temperature output characteristic of a battery can be made favorable.

Moreover, it is preferable that an electrode active material layer contains a thickener. As thickeners, it is possible to use, for example, water-soluble polymers. Examples of the water-soluble polymer that can be used as the thickener include: cellulosic polymers such as carboxymethylcellulose, methylcellulose, and hydroxypropylcellulose, ammonium salts and alkali metal salts thereof; (modified) poly(meth)acrylic acid and ammonium salts and alkali metal salts thereof; Modified) polyvinyl alcohol compounds such as polyvinyl alcohol, a copolymer of acrylic acid or acrylate and vinyl alcohol, maleic anhydride or a copolymer of maleic acid or fumaric acid and vinyl alcohol; polyethylene glycol, polyethylene oxide, polyvinyl pyrrolidone, and modified polyacrylic acid, starch oxide, starch phosphate, casein, and various modified starches. Especially, it is preferable to use the salt of carboxymethylcellulose. Here, "(modified) poly" means "unmodified poly" and "modified poly". Moreover, a thickener may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

By using a thickener, the viscosity of the slurry for electrodes used in order to manufacture an electrode active material layer can be adjusted. Moreover, a thickener normally functions as a binder in an electrode active material layer, and can bind|conclude binders.

The amount of the thickener is preferably 0.1 parts by weight or more, more preferably 0.2 parts by weight or more, preferably 5 parts by weight or less, and more preferably 3 parts by weight or less with respect to 100 parts by weight of the electrode active material. By making the quantity of a thickener more than the lower limit of the said range, binding property of an electrical power collector and an electrode active material layer can be improved. Moreover, by setting it as below an upper limit, the low-temperature output characteristic of a battery can be made favorable.

The electrode active material layer may contain any component other than the electrode active material, the binder for the electrode, and the thickener as long as the effects of the present invention are not significantly impaired. For example, an electrically conductive material, a reinforcing material, etc. are mentioned. Moreover, arbitrary components may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

Examples of the conductive material include conductive carbons such as acetylene black, Ketjen black, carbon black, graphite, vapor-grown carbon fibers and carbon nanotubes; carbon powders such as graphite; and various metal fibers and foils. By using a conductive material, since the electrical contact between electrode active materials can be improved, battery characteristics, such as cycling characteristics, can be improved.

The conductive material has a specific surface area of preferably 50 m 2 /g or more, more preferably 60 m 2 /g or more, particularly preferably 70 m 2 /g or more, preferably 1500 m 2 /g or less, more preferably 1200 m 2 /g or more. m 2 /g or less, particularly preferably 1000 m 2 /g or less. By making the specific surface area of a conductive material more than the lower limit of the said range, the low-temperature output characteristic of a lithium ion secondary battery can be improved. Moreover, binding property of an electrode active material layer and an electrical power collector can be improved by using below an upper limit.

As a reinforcing material, various inorganic and organic spherical, plate-shaped, rod-shaped, or fibrous fillers can be used, for example. By using the reinforcing material, a tough and flexible electrode can be obtained, and excellent long-term cycle characteristics can be obtained.

The amount of the conductive material and the reinforcing material used is usually 0 parts by weight or more, preferably 1 part by weight or more, preferably 20 parts by weight or less, more preferably 10 parts by weight or less, with respect to 100 parts by weight of the electrode active material. am.

The thickness of the electrode active material layer is both the positive electrode and the negative electrode, preferably 5 µm or more, more preferably 10 µm or more, preferably 300 µm or less, and more preferably 250 µm or less.

The manufacturing method in particular of an electrode active material layer is not restrict|limited. The electrode active material layer may be prepared by, for example, applying a slurry for an electrode containing an electrode active material and a solvent, and, if necessary, a binder for an electrode, a thickener, and an optional component on a current collector, and drying. As the solvent, both water and an organic solvent can be used.

[4. porous layer]

A porous layer is a film|membrane containing organic particle|grains. Usually, the clearance gap between organic particle|grains comprises the pore of a porous layer.

〔4. 1. Organic Particles]

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows typically an example of the organic particle which a porous layer contains. As shown in FIG. 1 , the organic particle 100 has a core-shell structure including a core portion 110 and a shell portion 120 . Here, the core part 110 is a part inside the shell part 120 in this organic particle|grain 100. Moreover, the shell part 120 is a part which covers the outer surface 110S of the core part 110, and is the part which is the outermost part in the organic particle|grains 100 normally. However, the shell part 120 does not cover the whole outer surface 110S of the core part 110, but covers the outer surface 110S of the core part 110 partially.

(4.1. 1. Core part)

The core part is made of a polymer having a predetermined degree of swelling with respect to the electrolytic solution. Specifically, the swelling degree of the polymer of the core portion with respect to the electrolyte solution is usually 5 times or more, preferably 6 times or more, more preferably 7 times or more, and usually 30 times or less, preferably 25 times or less, more Preferably it is 20 times or less. By accommodating the swelling degree of the polymer of a core part in the said range, since the liquid retention property of the electrolyte solution in a core part can be improved, high temperature cycling characteristics of a lithium ion secondary battery can be improved. Moreover, by making the swelling degree of the polymer of a core part more than the lower limit of the said range, the low-temperature output characteristic of a lithium ion secondary battery can be improved normally, Moreover, by setting it as below an upper limit, porosity in electrolyte solution normally. It is possible to effectively increase the binding properties of the layers.

As the electrolyte solution used for measuring the swelling degree of the polymer of the core part, a mixed solvent of ethylene carbonate, diethyl carbonate, and vinylene carbonate (volume mixing ratio ethylene carbonate/diethyl carbonate/vinylene carbonate = 68.5/30/1.5; SP value 12.7 (cal/cm 3 ) ^1/2 _{), a solution in which LiPF 6} as a supporting electrolyte is dissolved at a concentration of 1 mol/liter with respect to a solvent is used.

The swelling degree of the polymer of a core part can be specifically, measured as follows.

First, the polymer of the core part of the organic particle is prepared. For example, in the manufacturing method of organic particle|grains, the polymer obtained by implementing the same process as that implemented in order to manufacture a core part is prepared.

Then, a film is produced with the prepared polymer. For example, if a polymer is a solid, after drying a polymer on the conditions of 25 degreeC and 48 hours, the polymer is shape|molded into a film form, and the film of thickness 0.5mm is produced. For example, when the polymer is a solution or dispersion such as latex, the solution or dispersion is placed in a polytetrafluoroethylene petri dish, dried at 25° C. for 48 hours, and has a thickness of 0.5 mm make a film

Thus, the produced film is cut to 1 cm in width and length, and the test piece is obtained. The weight of this test piece is measured and it is set as W0.

Moreover, this test piece is immersed in electrolyte solution at 60 degreeC for 72 hours, and the test piece is taken out from electrolyte solution. The electrolytic solution on the surface of the taken out test piece is wiped off, and the weight W1 of the test piece after the immersion test is measured.

And using these weights W0 and W1, swelling degree S (fold) is calculated by S = W1/W0.

As a method of adjusting the swelling degree of the polymer of a core part, for example, considering the SP value of electrolyte solution, selecting appropriately the kind and quantity of the monomer for manufacturing the polymer of the said core part is mentioned. In general, when the SP value of the polymer is close to the SP value of the electrolytic solution, the polymer tends to swell in the electrolytic solution. On the other hand, if the SP value of the polymer is away from the SP value of the electrolyte, the polymer tends to be difficult to swell in the electrolyte.

The SP value means a solubility parameter.

The SP value may be calculated using the method introduced in Hansen Solubility Parameters A User's Handbook, 2nd Ed (CRCPress).

Moreover, the SP value of an organic compound can be estimated from the molecular structure of the organic compound. Specifically, it can be calculated using the simulation software (for example, "HSPiP" (http://www.hansen-solubility.com)) which can calculate the SP value from the expression of SMILE. Moreover, in this simulation software, it is calculated|required based on the theory described in Hansen SOLUBILITY PARAMETERS A User's Handbook Second Edition, Charles M. Hansen.

As a monomer used in order to manufacture the polymer of a core part, what becomes the swelling degree of the polymer in the said range can be used. Examples of such a monomer include: vinyl chloride monomers such as vinyl chloride and vinylidene chloride; vinyl acetate monomers such as vinyl acetate; aromatic vinyls such as styrene, α-methylstyrene, styrenesulfonic acid, butoxystyrene, and vinylnaphthalene Monomers; Vinylamine-based monomers such as vinylamine; Vinylamide-based monomers such as N-vinylformamide and N-vinylacetamide; (meth)acrylic acid derivatives such as 2-hydroxyethyl methacrylate; methyl acrylate, ethyl acrylate (meth)acrylic acid ester monomers such as methyl methacrylate, ethyl methacrylate, and 2-ethylhexyl acrylate; (meth)acrylamide monomers such as acrylamide and methacrylamide; acrylonitrile, methacrylonitrile, etc. of (meth)acrylonitrile monomers; fluorine-containing acrylate monomers such as 2-(perfluorohexyl)ethyl methacrylate and 2-(perfluorobutyl)ethyl acrylate; maleimide; maleimide such as phenylmaleimide Mid derivative; diene monomers, such as 1, 3- butadiene and isoprene, etc. are mentioned. Moreover, these may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

Among said monomers, a (meth)acrylic acid ester monomer and a (meth)acrylonitrile monomer are preferable, and a (meth)acrylic acid ester monomer is more preferable. That is, it is preferable to contain a (meth)acrylic acid ester monomeric unit or a (meth)acrylonitrile monomeric unit, and, as for the polymer of a core part, it is more preferable to contain a (meth)acrylic acid ester monomeric unit. Here, a (meth)acrylic acid ester monomeric unit represents the structural unit which has a structure formed by superposing|polymerizing a (meth)acrylic acid ester monomer. Moreover, a (meth)acrylonitrile monomeric unit shows the structural unit which has a structure formed by superposing|polymerizing (meth)acrylonitrile. Thereby, control of the swelling degree of a polymer can be performed easily. Moreover, the ion diffusivity of a porous layer can be improved further.

The ratio of the total of the (meth)acrylic acid ester monomer unit and the (meth)acrylonitrile monomer unit in the polymer of the core part is preferably 50% by weight or more, more preferably 55% by weight or more, still more preferably 60% by weight or more, particularly preferably 70% by weight or more, preferably 99% by weight or less, more preferably 95% by weight or less, particularly preferably 90% by weight or less. By accommodating the ratio of a (meth)acrylic acid ester monomeric unit and a (meth)acrylonitrile monomeric unit in the said range, it is easy to control a swelling degree in the said range. Moreover, the ion diffusivity of a porous layer can be improved. In addition, it is possible to improve the low-temperature output characteristics of the lithium ion secondary battery.

In addition, said "sum of (meth)acrylic acid ester monomeric unit and (meth)acrylonitrile monomeric unit" may contain only (meth)acrylic acid ester monomeric unit, and contains only (meth)acrylonitrile monomeric unit, It may exist, and it means that you may contain combining the (meth)acrylic acid ester monomeric unit and the (meth)acrylonitrile monomeric unit.

Moreover, the polymer of a core part can contain an acidic radical containing monomeric unit. As an acidic radical containing monomer, the thing similar to the acidic radical containing monomer which can be contained in a shell part is used. Among these, as an acidic radical containing monomer, an unsaturated carboxylic acid monomer is preferable, Among these, monocarboxylic acid is preferable and (meth)acrylic acid is more preferable.

Moreover, an acidic radical containing monomer may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

Moreover, the ratio of the acidic radical content body unit in the polymer of a core part becomes like this. Preferably it is 0.1 weight% or more, More preferably, it is 1 weight% or more, More preferably, it is 3 weight% or more, Preferably it is 20 weight% or less. , More preferably, it is 10 weight% or less, More preferably, it is 7 weight% or less. By accommodating the proportion of the acid group-containing unit within the above range, the dispersibility of the polymer of the core part is improved, and it is easy to form a shell part that partially covers the outer surface of the core part with respect to the outer surface of the polymer of the core part.

Moreover, it is preferable that the polymer of a core part contains the crosslinkable monomer unit. A crosslinkable monomeric unit is a structural unit which has a structure formed by superposing|polymerizing a crosslinkable monomer. Moreover, a crosslinkable monomer is a monomer which can form a crosslinked structure during superposition|polymerization or after superposition|polymerization by heating or irradiation of an energy ray. By containing a crosslinkable monomer unit, the swelling degree of a polymer can be accommodated easily in said range.

As a crosslinkable monomer, the polyfunctional monomer which has 2 or more polymerization reactive groups in the said monomer is mentioned, for example. As such a polyfunctional monomer, For example, divinyl compounds, such as divinylbenzene; ethylene dimethacrylate, diethylene glycol dimethacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, 1; Di(meth)acrylic acid ester compounds such as 3-butylene glycol diacrylate; Tri(meth)acrylic acid ester compounds such as trimethylolpropane trimethacrylate and trimethylolpropane triacrylate; Allylglycidyl ether, glycy Ethylenically unsaturated monomers containing an epoxy group, such as dilmethacrylate; Polyfunctional monomers which have 2 or more olefinic double bonds, such as allyl (meth)acrylate, etc. are mentioned. Among these, a dimethacrylic acid ester compound and the ethylenically unsaturated monomer containing an epoxy group are preferable from a viewpoint of controlling the swelling degree of the polymer of a core part easily, and a dimethacrylic acid ester compound is more preferable. Moreover, these may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

Generally, when the ratio of the crosslinkable monomer unit in a polymer increases, the degree of swelling of the polymer with respect to the electrolyte solution tends to become small. Therefore, it is preferable to determine the ratio of the crosslinkable monomer unit in consideration of the type and amount of the monomer to be used. The specific ratio of the crosslinkable monomer unit in the polymer of the core part is preferably 0.1% by weight or more, more preferably 0.2% by weight or more, particularly preferably 0.5% by weight or more, preferably 5% by weight or less, More preferably, it is 4 weight% or less, Especially preferably, it is 3 weight% or less. By making the ratio of a crosslinkable monomer unit more than the lower limit of the said range, binding property of the porous layer in electrolyte solution can be improved. Moreover, the lifetime of a lithium ion secondary battery can be lengthened by using below an upper limit.

The glass transition temperature of the polymer of the core portion is preferably 0°C or higher, more preferably 5°C or higher, still more preferably 10°C or higher, still more preferably 20°C or higher, particularly preferably 30°C or higher, more It is particularly preferably 60°C or higher, preferably 150°C or lower, more preferably 130°C or lower, still more preferably 110°C or lower, still more preferably 100°C or lower, particularly preferably 90°C or lower, more Especially preferably, it is 80 degrees C or less. By accommodating the glass transition temperature of the polymer of the core in the above range, expansion of the cell of the battery due to charging and discharging can be suppressed, so that the shape of the cell of the battery can be maintained over a long period of time. Moreover, when the glass transition temperature of the polymer of a core part exists in the said range, the temperature at which the organic particle|grains express a shutdown function WHEREIN: The fusion|melting of organic particle|grains can be implemented effectively. A glass transition temperature can be measured according to JISK7121.

The diameter of the core part is preferably 50% or more, more preferably 60% or more, still more preferably 70% or more, particularly preferably 80% or more, with respect to 100% of the volume average particle diameter of the organic particles. Preferably it is 99 % or less, More preferably, it is 98.5 % or less, Especially preferably, it is 98 % or less. By making the diameter of a core part more than the lower limit of the said range, the ionic conductivity of a porous layer can be raised. Moreover, binding property of the porous layer in electrolyte solution can be improved by using below an upper limit.

The diameter of a core part can be measured as a volume average particle diameter of the particulate-form polymer before forming the shell part obtained in the manufacturing process of organic particle|grains. The particulate polymer before forming such a shell part is, ie, a particulate polymer constituting the core part.

(4.1. 2. Shell part)

The shell portion is made of a polymer having a predetermined swelling degree smaller than the swelling degree of the core portion with respect to the electrolytic solution. Specifically, the swelling degree of the polymer of the shell portion with respect to the electrolyte solution is usually greater than 1 times, preferably 1.1 times or more, more preferably 1.2 times or more, and is usually 4 times or less, preferably 3.5 times or less. Hereinafter, more preferably, it is 3.0 times or less. By accommodating the swelling degree of the polymer of the shell part in the above range, the mechanical strength of the shell part when swollen in the electrolytic solution can be increased, so that external force is not easily transmitted to the core part. Therefore, since the unintentional discharge of the electrolyte solution from the core part by an external force can be suppressed when electrolyte solution is not running out, the liquid retention property of the electrolyte solution in a core part can be improved. Therefore, it is possible to improve the high-temperature cycle characteristics of the lithium ion secondary battery. Moreover, by accommodating the swelling degree of the polymer of a shell part in the said range, the binding property in the electrolyte solution of an organic particle can normally be improved, and by extension, the binding property in the electrolyte solution of a porous layer can be improved.

As an electrolyte solution used in order to measure the swelling degree of the polymer of a shell part, the thing similar to the electrolyte solution used in order to measure the swelling degree of the polymer of a core part is used.

The swelling degree of the polymer of the shell part can be specifically measured as follows.

First, the polymer of the shell part of organic particle|grains is prepared. For example, in the manufacturing method of organic particle|grains, using the monomer composition used for manufacture of a shell part instead of the monomer composition used for manufacture of a core part, it carries out similarly to the manufacturing method of a core part, and manufactures a polymer.

Then, by the method similar to the measuring method of the swelling degree of the polymer of a core part, a film is produced with the polymer of a shell part, a test piece is obtained from the film, and swelling degree S is measured.

As a method of adjusting the swelling degree of the polymer of a shell part, for example, considering the SP value of electrolyte solution, selecting appropriately the kind and quantity of the monomer for manufacturing the polymer of the said shell part is mentioned.

As a monomer used in order to manufacture the polymer of a shell part, what becomes the swelling degree of the polymer within the said range can be used. As such a monomer, the example similar to the monomer illustrated as a monomer which can be used in order to manufacture the polymer of a core part is mentioned, for example. Moreover, such a monomer may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

Among these monomers, an aromatic vinyl monomer is preferable. That is, it is preferable that the polymer of a shell part contains an aromatic vinyl monomeric unit. Here, an aromatic vinyl monomeric unit shows the structural unit which has a structure formed by superposing|polymerizing an aromatic vinyl monomer. Moreover, styrene derivatives, such as styrene and styrenesulfonic acid, are more preferable among aromatic vinyl monomers. When an aromatic vinyl monomer is used, it is easy to control the swelling degree of a polymer. Moreover, binding property of the porous layer in electrolyte solution can be improved.

The proportion of the aromatic vinyl monomer unit in the polymer of the shell part is preferably 20% by weight or more, more preferably 40% by weight or more, still more preferably 50% by weight or more, still more preferably 60% by weight or more, Especially preferably, it is 80 weight% or more, Preferably it is 100 weight% or less, More preferably, it is 99.5 weight% or less, More preferably, it is 99 weight% or less. By accommodating the ratio of an aromatic vinyl monomeric unit in the said range, it is easy to control swelling degree to the said range. Moreover, the binding force in the electrolyte solution of a porous layer can be raised more.

Moreover, the polymer of a shell part may contain an acidic radical containing monomeric unit. An acidic radical containing monomeric unit is a structural unit which has a structure formed by superposing|polymerizing the monomer which has an acidic radical. Examples of the acid group-containing monomer include an unsaturated carboxylic acid monomer, a monomer having a sulfonic acid group, a monomer having a phosphoric acid group, and a monomer having a hydroxyl group.

As an unsaturated carboxylic acid monomer, monocarboxylic acid, dicarboxylic acid, etc. are mentioned, for example. As monocarboxylic acid, acrylic acid, methacrylic acid, a crotonic acid, etc. are mentioned, for example. Moreover, as dicarboxylic acid, a maleic acid, a fumaric acid, itaconic acid etc. are mentioned, for example.

Examples of the monomer having a sulfonic acid group include vinylsulfonic acid, methylvinylsulfonic acid, (meth)allylsulfonic acid, (meth)acrylic acid-2-sulfonate ethyl, 2-acrylamide-2-methylpropanesulfonic acid, 3-aryloxy-2 -Hydroxypropanesulfonic acid etc. are mentioned.

As the monomer having a phosphoric acid group, for example, phosphoric acid-2-(meth)acryloyloxyethyl, phosphoric acid methyl-2-(meth)acryloyloxyethyl, phosphoric acid ethyl-(meth)acryloyloxyethyl, etc. can be heard

As a monomer which has a hydroxyl group, acrylic acid 2-hydroxyethyl, acrylic acid 2-hydroxypropyl, methacrylic acid 2-hydroxyethyl, methacrylic acid 2-hydroxypropyl, etc. are mentioned, for example. .

Among these, an unsaturated carboxylic acid monomer is preferable, monocarboxylic acid is especially preferable, and (meth)acrylic acid is especially preferable.

Moreover, an acidic radical containing monomer may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

The proportion of the acid group-containing monomer unit in the polymer of the shell part is preferably 0.1% by weight or more, more preferably 1% by weight or more, still more preferably 3% by weight or more, preferably 20% by weight or less, more Preferably it is 10 weight% or less, More preferably, it is 7 weight% or less. By accommodating the ratio of an acidic radical containing monomeric unit in the said range, the dispersibility of the organic particle|grains in a porous layer can be improved, and favorable binding property can be expressed over the whole porous layer.

Moreover, the polymer of a shell part may contain a crosslinkable monomer unit. As a crosslinkable monomer, the example similar to what was illustrated as a crosslinkable monomer which can be used for the polymer of a core part is mentioned, for example. Moreover, a crosslinkable monomer may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

The proportion of the crosslinkable monomer unit in the polymer of the shell part is preferably 0.1% by weight or more, more preferably 0.2% by weight or more, particularly preferably 0.5% by weight or more, preferably 5% by weight or less, more Preferably it is 4 weight% or less, Especially preferably, it is 3 weight% or less.

The glass transition temperature of the polymer of the shell part is preferably 50°C or higher, more preferably 80°C or higher, particularly preferably 100°C or higher, and preferably 200°C or lower, more preferably 180°C or lower, More preferably, it is 150 degrees C or less, Especially preferably, it is 120 degrees C or less. By accommodating the glass transition temperature of the polymer of the shell part in the above range, the expansion of the battery cell by charging and discharging can be suppressed, so that the shape of the battery cell can be maintained over a long period of time. Moreover, when the glass transition temperature of the polymer of a shell part exists in the said range, below the temperature at which the organic particle|grains express a shutdown function, WHEREIN: The shape of organic particle|grains can be maintained effectively.

The shell part partially covers the outer surface of the core part. That is, the shell portion covers the outer surface of the core portion, but does not cover the entire outer surface of the core portion. Even when it appears that the outer surface of the core part is completely covered by the shell part from the outside, if a hole communicating the inside and the outside of the shell part is formed, the shell part is a shell part according to the present invention that partially covers the outer surface of the core part. Accordingly, for example, organic particles having a shell portion having pores communicating from the outer surface of the shell portion to the outer surface of the core portion are included in the organic particles according to the present invention. Here, the outer surface of the shell part is usually the peripheral surface of the organic particle.

The average ratio of the outer surface of the core part covered by the shell part is preferably 10% or more, more preferably 30% or more, still more preferably 40% or more, particularly preferably 60% or more, and preferably It is 99.9 % or less, More preferably, it is 98 % or less, More preferably, it is 95 % or less, More preferably, it is 90 % or less, Especially preferably, it is 85 % or less. By accommodating the average ratio in which the outer surface of the core part is covered by the shell part in the above range, the balance between the diffusibility of ions in the electrolytic solution and the binding property of the porous layer can be improved.

The average ratio in which the outer surface of the core part is covered by the shell part can be measured from the observation result of the cross-sectional structure of organic particle|grains. Specifically, it can measure by the method demonstrated below.

First, after fully disperse|distributing organic particle|grains in the epoxy resin of room temperature curability, it embed|builds and produces the block piece containing organic particle|grains. Next, with a microtome equipped with a diamond blade, it cuts out from a block piece into thin slices with a thickness of 80 nm - 200 nm, and the sample for a measurement is produced. After that, if necessary, the sample for measurement is subjected to a dyeing treatment using, for example, ruthenium tetraoxide or osmium tetraoxide.

Next, this sample for a measurement is set in a transmission electron microscope (TEM), and the cross-sectional structure of organic particle|grains is photographed. As for the magnification of an electron microscope, the magnification into which the cross section of one organic particle|grain enters a visual field is preferable, and, specifically, about 10,000 times is preferable.

In the cross-sectional structure of the photographed organic particles, the length D1 of the circumference corresponding to the outer surface of the core portion and the length D2 of the portion where the outer surface of the core portion and the shell portion contact are measured. And using the measured length D1 and length D2, the ratio Rc in which the outer surface of the core part of the organic particle|grains is covered by a shell part is computed by following (1) Formula.

Coverage ratio Rc (%) = D2/D1 × 100 (1)

Said coverage ratio Rc is measured about 20 or more organic particle|grains, the average value is calculated, and let it be the average ratio in which the outer surface of a core part is covered by a shell part.

Although the said coverage ratio Rc can also be calculated manually from a cross-sectional structure, it can also be calculated using commercially available image analysis software. As commercially available image analysis software, "AnalySIS Pro" (manufactured by Olympus Corporation) can be used, for example.

It is preferable that the shell part has an average thickness which falls within a predetermined range with respect to the volume average particle diameter of organic particle|grains. Specifically, the average thickness of the shell portion with respect to the volume average particle diameter of the organic particles is preferably 1% or more, more preferably 2% or more, particularly preferably 5% or more, preferably 30% or less, more Preferably it is 25 % or less, Especially preferably, it is 20 % or less. By making the average thickness of a shell part more than the lower limit of the said range, the low temperature output characteristic of a lithium ion secondary battery can be improved further. Moreover, the binding property of the porous layer in electrolyte solution can further be improved by using below an upper limit.

The average thickness of a shell part is calculated|required by observing the cross-sectional structure of organic particle|grains by a transmission electron microscope (TEM). Specifically, the maximum thickness of the shell portion in the cross-sectional structure of the organic particles is measured, and the average value of the maximum thickness of the shell portions of 20 or more arbitrarily selected organic particles is defined as the average thickness of the shell portion. However, when the shell portion is composed of polymer particles, and the particles constituting the shell portion do not overlap each other in the radial direction of the organic particles, and the polymer particles constitute the shell portion in a single layer, the shell portion Let the number average particle diameter of the particle|grains which comprise it be the average thickness of a shell part.

Although the shape in particular of a shell part is not restrict|limited, It is preferable that the shell part is comprised by the particle|grains of a polymer. When the shell portion is constituted by polymer particles, a plurality of particles constituting the shell portion may overlap each other in the radial direction of the organic particles. However, in the radial direction of organic particle|grains, it is preferable that the particle|grains which comprise a shell part do not overlap with each other, and that the particle|grains of these polymers comprise a shell part in a single layer.

The number average particle diameter of the particles constituting the shell part is preferably 10 nm or more, more preferably 20 nm or more, particularly preferably 30 nm or more, preferably 200 nm or less, more preferably 150 nm or less, Especially preferably, it is 100 nm or less. By accommodating a number average particle diameter in the said range, the balance of the diffusivity of the ion in electrolyte solution, and the binding property of a porous layer can be made favorable.

The number average particle diameter of the particle|grains which comprise a shell part is calculated|required by observing the cross-sectional structure of organic particle|grains with a transmission electron microscope (TEM). Specifically, the longest diameter of the particles constituting the shell portion in the cross-sectional structure of the organic particles is measured, and the average value of the longest diameters of the particles constituting the shell portion of 20 or more arbitrarily selected organic particles is calculated as that of the particles constituting the shell portion. Let it be a number average particle diameter.

(4. 1. 3. Random Components)

As long as the effect of this invention is not impaired remarkably, organic particle|grains may be equipped with arbitrary components other than the above-mentioned core part and shell part.

For example, you may have a part formed with the polymer different from the core part in the inside of a core part. When a specific example is given, the seed particle used when manufacturing organic particle|grains by the seed polymerization method may remain in the inside of a core part.

However, from a viewpoint of exhibiting the effect of this invention remarkably, it is preferable that organic particle|grains are equipped with only a core part and a shell part.

(4. 1. 4. Organic particle size)

The volume average particle diameter of the organic particles is preferably 0.01 µm or more, more preferably 0.1 µm or more, particularly preferably 0.3 µm or more, preferably 10 µm or less, more preferably 5 µm or less, particularly preferably is 1 μm or less. By making the volume average particle diameter of organic particle|grains more than the lower limit of the said range, since expansion of the cell of a battery by charging/discharging can be suppressed, the shape of the cell of a battery can be maintained over a long period of time. Moreover, the low-temperature output characteristic of a lithium ion secondary battery can be made favorable by using below an upper limit.

(4. 1.5. Amount of organic particles)

It is preferable to set the quantity of organic particle|grains so that the ratio of the organic particle|grains in a porous layer may enter into a predetermined range. Specifically, the proportion of organic particles in the porous layer is preferably 50% by weight or more, more preferably 60% by weight or more, still more preferably 70% by weight or more, particularly preferably 80% by weight or more. , preferably 99.9% by weight or less, more preferably 99% by weight or less, still more preferably 98% by weight or less, particularly preferably 96% by weight or less. By making the quantity of organic particle|grains into the said range, binding property of the porous layer in electrolyte solution can be improved, and ion diffusivity can be improved.

(4.1. 6. Method for producing organic particles)

Organic particles can be produced, for example, by using a monomer of a polymer of a core part and a monomer of a polymer of a shell part, changing the ratio of those monomers over time and polymerizing in stages. Specifically, it can be obtained by a continuous multi-step emulsion polymerization method and a multi-step suspension polymerization method in which the polymer in the previous step is sequentially coated with the polymer in the subsequent step.

An example in the case of obtaining the organic particle|grains which has a core-shell structure by the multistep emulsion polymerization method is shown.

In polymerization, according to a conventional method, as an emulsifier, for example, anionic surfactants such as sodium dodecylbenzenesulfonate and sodium dodecylsulfate, polyoxyethylene nonylphenyl ether, and nonionic interfaces such as sorbitan monolaurate An activator or cationic surfactant, such as octadecylamine acetate, can be used. Further, as the polymerization initiator, for example, peroxides such as t-butylperoxy-2-ethylhexanoate, potassium persulfate and cumene peroxide, 2,2'-azobis(2-methyl-N-(2-) Azo compounds such as hydroxyethyl)-propionamide) and 2,2'-azobis(2-amidinopropane) hydrochloride can be used. These emulsifiers and polymerization initiators may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

As a polymerization procedure, the monomer and emulsifier which form a core part are mixed with water which is a solvent first, and the particulate-form polymer which comprises a core part is obtained by putting a polymerization initiator and emulsion-polymerizing after that. Further, organic particles having a core-shell structure can be obtained by performing polymerization of a monomer forming a shell portion in the presence of the particulate polymer constituting the core portion.

At this time, from the viewpoint of partially covering the outer surface of the core part with the shell part, it is preferable that the monomer of the polymer of the shell part is divided into a plurality of times or continuously supplied to the polymerization system. By supplying the polymer monomers of the shell part to the polymerization system in a divided or continuous manner rather than collectively supplying the polymerization system, the polymer constituting the shell part is usually formed in particulate form, and these particles bind to the core part, A shell portion partially covering the core portion may be formed.

When the monomer of the polymer of the shell part is divided into a plurality of times and supplied, it is possible to control the particle diameter of the particles constituting the shell part and the average thickness of the shell part according to the ratio of dividing the monomer. Moreover, when the monomer of the polymer of the shell part is continuously supplied, it is possible to control the particle size of the particles constituting the shell part and the average thickness of the shell part by adjusting the amount of the monomer supplied per unit time.

Moreover, when a monomer with low affinity to the polymerization solvent is used as the monomer forming the polymer of the shell part, it tends to easily form the shell part which partially covers the core part. When the polymerization solvent is water, the monomer forming the polymer of the shell part preferably contains a hydrophobic monomer, and particularly preferably contains an aromatic vinyl monomer.

Moreover, when the amount of the emulsifier used is reduced, it tends to become easy to form the shell part which partially covers the core part, and by appropriately adjusting the amount of the emulsifier, the shell part which partially covers the core part can be formed.

In addition, the volume average particle diameter of the particulate polymer constituting the core part, the volume average particle diameter of the organic particles after forming the shell part, and the number average particle diameter of the particles constituting the shell part are, for example, the amount of the emulsifier and the amount of the monomer. It can be set as a desired range by adjusting etc.

In addition, the average ratio that the outer surface of the core part is covered by the shell part corresponds to the volume average particle diameter of the particulate polymer constituting the core part, for example, the amount of the emulsifier and the amount of the monomer of the polymer of the shell part. By adjusting, it can be set as a desired range.

〔4. 2. Binder for porous layer]

It is preferable that a porous layer contains the binder for porous layers. By using this binder for porous layers, organic particle|grains can be made to bind|conclude with the binder for porous layers, and the mechanical strength of a porous layer can be raised. Moreover, since the binder for porous layers exhibits the effect|action which binds a porous layer to an electrode active material layer, the binding property of a porous layer and an electrode active material layer can be improved.

As a binder for porous layers, a polymer is used normally. Although a non-particulate polymer may be used as a binder for porous layers, it is preferable to use a particulate-form polymer from a viewpoint of enlarging the hole of a porous layer and improving ion permeability. As such a particulate polymer, a water-insoluble polymer is usually used. Since the slurry for a porous layer, which is a composition for producing a porous layer, often contains water as a solvent, by using a water-insoluble polymer as a binder for the porous layer, the binder for the porous layer in the porous layer can be easily made into particles. have.

As a water-insoluble polymer, it is preferable to use thermoplastic elastomers, such as a styrene-butadiene copolymer, a styrene-acrylonitrile copolymer, and a (meth)acrylic acid ester polymer, for example. Among these, as a binder for porous layers, a (meth)acrylic acid ester polymer is preferable. A (meth)acrylic acid ester polymer means the polymer containing a (meth)acrylic acid ester monomeric unit. By using a (meth)acrylic acid ester polymer as a binder for porous layers, since the ion conductivity of a porous layer can be made high, the rate characteristic of a lithium ion secondary battery can be improved. Moreover, since the (meth)acrylic acid ester monomeric unit is electrochemically stable, the high temperature cycling characteristic of a lithium ion secondary battery can further be improved.

As a (meth)acrylic acid ester monomer corresponding to a (meth)acrylic acid ester monomeric unit, For example, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl Acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, n-tetradecyl acrylate, stearyl acrylate Acrylic acid alkyl esters, such as; And methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, pentyl methacrylate, hexyl Methacrylate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, lauryl methacrylate, n-tetradecyl methacrylate, stearyl methacrylate Alkyl methacrylic acid, such as a rate, is mentioned. Moreover, these may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios. Among them, n-butyl acrylate and 2-ethylhexyl acrylate are preferable from the viewpoint of excellent flexibility.

The ratio of the (meth)acrylic acid ester monomer unit in the binder for a porous layer becomes like this. Preferably it is 50 weight% or more, More preferably, it is 70 weight% or more, Especially preferably, it is 90 weight% or more, Preferably it is 99 weight%. Hereinafter, more preferably, it is 98 weight% or less, Especially preferably, it is 97 weight% or less. By making the ratio of a (meth)acrylic acid ester monomeric unit more than the said lower limit, the softness|flexibility of a porous layer can be improved and binding property of a porous layer can be improved. Moreover, the rigidity of a porous layer can be improved by making the ratio of a (meth)acrylic acid ester monomeric unit below the said upper limit, and binding property of a porous layer can be improved also by this.

Moreover, it is preferable that the binder for porous layers contains an amide monomer unit. The amide monomer unit is a structural unit having a structure formed by polymerization of an amide monomer. In addition, an amide monomer is a monomer which has an amide group, and includes not only an amide compound but an imide compound.

By having an amide monomer unit, the binder for porous layers can capture|acquire the halide ion in electrolyte solution. Therefore, since decomposition|disassembly of the electrolyte solution and SEI (Solid Electrolyte Interphase) caused by halide ions can be suppressed, generation|occurrence|production of the gas accompanying charging/discharging can be suppressed. Moreover, the binder for porous layers can capture|acquire the transition metal ion in electrolyte solution. For example, metal ions eluted from the positive electrode can be captured by the binder for a porous layer. Therefore, precipitation of the transition metal in the negative electrode accompanying charging and discharging can be suppressed effectively. Therefore, when the binder for porous layers is used, since the grade of the fall of the battery capacity accompanying charging/discharging can be made small, the cycling characteristics of a lithium ion secondary battery can be improved further.

Moreover, since generation|occurrence|production of the gas accompanying charging/discharging can be suppressed as mentioned above when the binder for porous layers is used, generation|occurrence|production of the space|gap by the gas can be suppressed. Accordingly, it is possible to further improve the low-temperature output characteristics of the lithium ion secondary battery. The generation amount of such a gas can be evaluated by the volume change of the cell of a lithium ion secondary battery when charging/discharging is repeated.

As an amide monomer, a carboxylic acid amide monomer, a sulfonic acid amide monomer, a phosphoric acid amide monomer, etc. are mentioned, for example.

The carboxylic acid amide monomer is a monomer having an amide group bonded to a carboxylic acid group. Examples of the carboxylic acid amide monomer include (meth)acrylamide, α-chloroacrylamide, N,N'-methylenebis(meth)acrylamide, N,N'-ethylenebis(meth)acrylamide, N -Hydroxymethyl (meth) acrylamide, N-2-hydroxyethyl (meth) acrylamide, N-2-hydroxypropyl (meth) acrylamide, N-3-hydroxypropyl (meth) acrylamide, croton Unsaturated carboxylic acid amide compounds, such as acid amide, maleic acid diamide, fumaric acid diamide, and diacetone acrylamide; N-dimethylaminomethyl (meth)acrylamide, N-2-aminoethyl (meth)acrylamide, N- 2-methylaminoethyl (meth)acrylamide, N-2-ethylaminoethyl (meth)acrylamide, N-2-dimethylaminoethyl (meth)acrylamide, N-2-diethylaminoethyl (meth)acrylamide N-amino of unsaturated carboxylic acid amides, such as N-3-aminopropyl (meth)acrylamide, N-3-methylaminopropyl (meth)acrylamide, and N-3-dimethylaminopropyl (meth)acrylamide alkyl derivatives; and the like.

The sulfonic acid amide monomer is a monomer having an amide group bonded to a sulfonic acid group. Examples of the sulfonic acid amide monomer include 2-acrylamide-2-methylpropanesulfonic acid and N-t-butylacrylamidesulfonic acid.

The phosphoric acid amide monomer is a monomer having an amide group bonded to a phosphoric acid group. Examples of the phosphoric acid amide monomer include acrylamide phosphonic acid and acrylamide phosphonic acid derivatives.

Among these amide monomers, from a viewpoint of improving the durability of a porous layer, a carboxylic acid amide monomer is preferable, an unsaturated carboxylic acid amide compound is more preferable, (meth)acrylamide and N-hydroxymethyl (meth)acryl Amides are particularly preferred.

Moreover, an amide monomer and an amide monomer unit may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

The proportion of the amide monomer unit in the binder for the porous layer is preferably 0.1% by weight or more, more preferably 0.2% by weight or more, particularly preferably 0.5% by weight or more, preferably 20% by weight or less, more preferably preferably 15% by weight or less, particularly preferably 10% by weight or less. By making the ratio of an amide monomer unit more than the lower limit of the said range, generation|occurrence|production of the gas in a lithium ion secondary battery can be suppressed effectively, and the transition metal ion in electrolyte solution can be captured effectively. Moreover, the cycling characteristics of a lithium ion secondary battery can be improved by setting it as below an upper limit.

Moreover, the binder for porous layers can contain an acidic radical containing monomeric unit. As an acidic radical containing monomeric unit, what is selected from the range similar to what was demonstrated as what can be used for organic particle|grains can be used, for example. Moreover, an acidic radical containing monomeric unit may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

The proportion of the acid group-containing monomer unit in the binder for the porous layer is preferably 0.2% by weight or more, more preferably 0.4% by weight or more, particularly preferably 0.6% by weight or more, preferably 10.0% by weight or less, more Preferably it is 6.0 weight% or less, Especially preferably, it is 4.0 weight% or less. By making the ratio of an acidic radical containing monomeric unit into the said range, the cohesive failure of a porous layer can be suppressed and the binding property of the porous layer in electrolyte solution can be improved.

Moreover, the binder for porous layers can contain a (meth)acrylonitrile monomeric unit. At this time, as the (meth)acrylonitrile monomer corresponding to the (meth)acrylonitrile monomer unit, acrylonitrile may be used, methacrylonitrile may be used, or acrylonitrile and methacrylonitrile are combined you can use it.

The ratio of the (meth)acrylonitrile monomer unit in the binder for a porous layer becomes like this. Preferably it is 0.2 weight% or more, More preferably, it is 0.5 weight% or more, Especially preferably, it is 1.0 weight% or more, Preferably it is 20.0 weight%. % or less, more preferably 10.0 wt% or less, particularly preferably 5.0 wt% or less. By making the ratio of a (meth)acrylonitrile monomeric unit more than the said lower limit, the life of a lithium ion secondary battery can be lengthened especially. Moreover, the mechanical strength of a porous layer can be raised by making the ratio of a (meth)acrylonitrile monomeric unit below the said upper limit.

Moreover, the binder for porous layers can contain a crosslinkable monomer unit. Examples of the crosslinkable monomer corresponding to the crosslinkable monomer unit include the same examples as those exemplified in the description of the organic particles. In addition, since N-hydroxymethyl (meth)acrylamide exemplified as a carboxylic acid amide monomer can act as both an amide monomer and a crosslinkable monomer, this N-hydroxymethyl (meth)acrylamide is used as a crosslinkable monomer. may be used as A crosslinkable monomer may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

The proportion of the crosslinkable monomer unit in the binder for the porous layer is preferably 0.2% by weight or more, more preferably 0.6% by weight or more, particularly preferably 1.0% by weight or more, preferably 5.0% by weight or less, more Preferably it is 4.0 weight% or less, Especially preferably, it is 3.0 weight% or less. By making the ratio of a crosslinkable monomer unit more than the said lower limit, the mechanical strength of a porous layer can be raised. Moreover, it can prevent that the softness|flexibility of a porous layer is impaired and becomes brittle by using below an upper limit.

The binder for porous layers can further contain arbitrary structural units other than the above. Examples of the optional structural unit include a structural unit having a structure formed by polymerization of styrene (styrene unit), a structural unit having a structure formed by polymerization of butadiene (butadiene unit), and the like. Moreover, these arbitrary structural units may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

The glass transition temperature of the binder for a porous layer is preferably -100°C or higher, more preferably -90°C or higher, particularly preferably -80°C or higher, preferably 0°C or lower, more preferably -5°C or higher. Hereinafter, particularly preferably, it is -10°C or less. By making the glass transition temperature of the binder for porous layers more than the lower limit of the said range, binding property of a porous layer can be improved. Moreover, the softness|flexibility of a porous layer can be improved by using below an upper limit.

When the binder for porous layer is a particulate polymer, the volume average particle diameter of the particles of the binder for porous layer is preferably 0.01 µm or more, more preferably 0.02 µm or more, particularly preferably 0.05 µm or more, and preferably 1 µm. Below, more preferably, it is 0.9 micrometer or less, Especially preferably, it is 0.8 micrometer or less. By making the volume average particle diameter of the binder for porous layers more than the lower limit of the said range, the dispersibility of the binder for porous layers can be improved. Moreover, binding property of a porous layer can be improved by using below an upper limit.

As a manufacturing method of the binder for porous layers, the solution polymerization method, the suspension polymerization method, the emulsion polymerization method etc. are mentioned, for example. Especially, since it can superpose|polymerize in water and can use it suitably as a material of the slurry for porous layers as it is, the emulsion polymerization method and the suspension polymerization method are preferable. Moreover, when manufacturing the binder for porous layers, it is preferable that the reaction system contains a dispersing agent. Although the binder for porous layers is normally formed with the polymer which comprises it substantially, you may be accompanied by arbitrary components, such as the additive used in superposition|polymerization.

The amount of the binder for the porous layer is preferably 0.1 parts by weight or more, more preferably 0.2 parts by weight or more, preferably 30 parts by weight or less, more preferably 25 parts by weight or less with respect to 100 parts by weight of the organic particles. By carrying out quantity of the binder for porous layers more than the lower limit of the said range, since expansion of the cell of the battery by charging/discharging can be suppressed, the shape of the cell of a battery can be maintained over a long period of time. Moreover, the low-temperature output characteristic of a lithium ion secondary battery can be made favorable by using below an upper limit.

〔4. 3. Optional Ingredients]

A porous layer can contain arbitrary components other than the organic particle|grains mentioned above and the binder for porous layers. As such optional components, those which do not have an excessively undesirable influence on the cell reaction can be used. For example, the porous layer is a non-conductive particle, a water-soluble polymer, an isothiazoline-based compound, a chelate compound, a pyrithione compound, a dispersing agent, a leveling agent, a wetting agent, an antioxidant, a thickener, an antifoaming agent, a wetting agent, and an electrolyte solution decomposition inhibition You may contain the electrolyte solution additive etc. which have the function of. These arbitrary components may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

〔4. 4. Position of porous layer]

The porous layer is directly formed in the electrode active material layer. That is, the porous layer is in direct contact with the electrode active material layer, and there is no other layer between the porous layer and the electrode active material layer. As a result, since the organic particles contained in the porous layer are in the immediate vicinity of the electrode active material layer, when the electrolyte is decomposed and voids are formed in the vicinity of the electrode active material layer, the electrolyte is rapidly supplied from the core of the organic particles to close the voids. can be filled For this reason, in a lithium ion secondary battery, since the fall of the battery capacity by decomposition|disassembly of electrolyte solution can be suppressed, high high temperature cycling characteristics can be implement|achieved.

〔4. 5. Thickness of porous layer]

The thickness of the porous layer is preferably 0.1 µm or more, more preferably 0.2 µm or more, particularly preferably 0.5 µm or more, preferably 30 µm or less, more preferably 25 µm or less, particularly preferably 20 µm or less. μm or less. By carrying out the thickness of a porous layer more than the lower limit of the said range, since expansion of the cell of the battery by charging/discharging can be suppressed, the shape of the cell of a battery can be maintained over a long period of time. Moreover, the low temperature output characteristic of a lithium ion secondary battery can be made favorable by using below an upper limit.

〔4. 6. Action by the porous layer]

As described above, when the electrolytic solution is decomposed along with charging and discharging, the porous layer supplies an amount of the electrolytic solution lost due to the decomposition from the core portion, thereby exhibiting the effect of suppressing a decrease in the battery capacity. Moreover, this porous layer can also express the following effect|actions, for example.

Usually, when the shell part of organic particle|grains swells in electrolyte solution, high binding property will be expressed. For this reason, the porous layer containing this organic particle|grain can have high binding property in electrolyte solution. Moreover, even if it is the state which is not swollen in electrolyte solution, organic particle|grains can express binding property by heating to a fixed temperature or more (for example, 60 degreeC or more).

Since a porous layer contains organic particle|grains, it is easy to form a hole in a porous layer. Therefore, normally, a porous layer has porosity and can express the outstanding ion diffusivity. Moreover, normally, the core part of organic particle|grains has high ion diffusivity. Therefore, since lithium ion can permeate|transmit a porous layer easily, resistance of a lithium ion secondary battery can be made small.

Usually, since the shell part of organic particle|grains does not swell large enough to impair the rigidity too much, organic particle|grains have moderate rigidity. Therefore, the porous layer is excellent in mechanical strength. Thus, since the porous layer excellent in mechanical strength is formed directly on the electrode active material layer, detachment of particles, such as an electrode active material, from an electrode active material layer, and peeling of an electrode active material layer from a collector can be prevented.

〔4. 7. Method of forming porous layer]

The porous layer is, for example, a step of applying the slurry for the porous layer on the electrode active material layer to obtain a film of the slurry for the porous layer, and, if necessary, a step of removing a solvent such as water from the film by drying. method can be formed. Here, the slurry for porous layers is a fluid composition containing the component contained in a porous layer, a solvent, and arbitrary components as needed.

As a solvent, it is preferable to use water. Since organic particles and the binder for a porous layer are normally water-insoluble, when water is used as a solvent, the organic particle|grains and the binder for porous layers become particulates and are disperse|distributed in water.

As the solvent, a solvent other than water may be used in combination with water. Examples of the solvent that can be used in combination with water include cyclic aliphatic hydrocarbons such as cyclopentane and cyclohexane; aromatic hydrocarbons such as toluene and xylene; ketones such as ethylmethyl ketone and cyclohexanone; ethyl acetate , esters such as butyl acetate, γ-butyrolactone, and ε-caprolactone; nitriles such as acetonitrile and propionitrile; ethers such as tetrahydrofuran and ethylene glycol diethyl ether: methanol, ethanol, isopropanol, Alcohols, such as ethylene glycol and ethylene glycol monomethyl ether; Amides, such as N-methylpyrrolidone (NMP) and N,N- dimethylformamide, etc. are mentioned. These may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios. However, it is preferable to use water independently as a solvent.

It is preferable to set the quantity of the solvent in the slurry for porous layers so that solid content concentration of the slurry for porous layers may enter a desired range. The solid content concentration of the specific porous layer slurry is preferably 10% by weight or more, more preferably 15% by weight or more, particularly preferably 20% by weight or more, preferably 80% by weight or less, more preferably 75% by weight or more. % or less, particularly preferably 70% by weight or less. Here, the solid content of a certain composition means the substance which remains after drying the composition.

Each component contained in the slurry for porous layers has high dispersibility normally. Therefore, the viscosity of the slurry for porous layers can be made low normally easily. As for the specific viscosity of the slurry for porous layers, 10 mPa*s - 2000 mPa*s are preferable from a viewpoint of making the applicability|paintability at the time of manufacturing a porous layer favorable. Said viscosity is a value when it measures at 25 degreeC and rotation speed 60 rpm using an E-type viscometer.

The slurry for porous layers can be manufactured by mixing each component mentioned above, for example. There is no restriction|limiting in particular in the mixing order of each component. Moreover, there is no restriction|limiting in particular also in the mixing method. Usually, in order to disperse|distribute the particle|grains quickly, mixing is performed using a disperser as a mixing device. The disperser is preferably a device capable of uniformly dispersing and mixing the components. For example, a ball mill, a sand mill, a pigment disperser, a brain crusher, an ultrasonic disperser, a homogenizer, a planetary mixer, etc. are mentioned. Among them, high dispersion devices such as bead mills, roll mills, and fill mixes are particularly preferable from the viewpoint that high dispersion shear can be applied.

As a coating method of the slurry for porous layers, methods, such as the doctor blade method, the dip method, the reverse roll method, the direct roll method, the gravure method, the extrusion method, the brush application method, are mentioned, for example. Especially, a dip method and the gravure method are preferable at the point from which a uniform porous layer is obtained.

As a drying method of the film|membrane of the slurry for porous layers, For example, drying by winds, such as a warm air, a hot air, and a low humidity wind; vacuum drying; The drying method by irradiation of infrared rays, far infrared rays, and electron beams, etc. are mentioned.

The drying temperature is preferably 40°C or higher, more preferably 45°C or higher, particularly preferably 50°C or higher, preferably 90°C or lower, more preferably 80°C or lower, particularly preferably 70°C or lower. ℃ or less. By carrying out drying temperature more than the lower limit of the said range, the solvent and low molecular weight compound from the film|membrane of the slurry for porous layers can be removed efficiently. Moreover, by setting it as below an upper limit, the deformation|transformation by the heat|fever of the electrode active material layer as a base material can be suppressed.

The drying time is preferably 5 seconds or more, more preferably 10 seconds or more, particularly preferably 15 seconds or more, preferably 3 minutes or less, more preferably 2 minutes or less, particularly preferably 1 minute or less. am. By carrying out drying time more than the lower limit of the said range, since a solvent can fully be removed from the slurry for porous layers, the output characteristic of a battery can be improved. Moreover, manufacturing efficiency can be raised by setting it as below an upper limit.

In the manufacturing method of a porous layer, you may perform arbitrary operations other than what was mentioned above.

For example, you may pressurize a porous layer with press methods, such as a metal mold|die press and roll press. By performing a pressurization process, the binding property of an electrode active material layer and a porous layer can be improved. However, from a viewpoint of maintaining the porosity of a porous layer in a preferable range, it is preferable to control suitably so that a pressure and pressurization time may not become large too much.

Moreover, in order to remove residual water|moisture content, it is preferable to dry in vacuum drying or a dry room, for example.

Moreover, it is also preferable to heat-process, for example. Thereby, the thermal crosslinking group contained in a polymer component can be bridge|crosslinked, and the binding property of a porous layer can be improved.

[5. lithium ion secondary battery]

The lithium ion secondary battery of this invention is equipped with the electrode of this invention, and electrolyte solution. Specifically, the lithium ion secondary battery of this invention is equipped with a positive electrode, a negative electrode, and electrolyte solution, and is equipped with the electrode of this invention as at least one of said positive electrode and a negative electrode. Since the electrode of this invention is provided, the lithium ion secondary battery of this invention is excellent in high temperature cycling characteristics.

Moreover, in the lithium ion secondary battery of this invention, the electrode of this invention may have a flat shape, without folding or bending. Thus, since the lithium ion secondary battery provided with the electrode which has a flat shape has the structure in which the electrode which has the flat shape was laminated|stacked, it is called a laminated type battery. Since stacked batteries are manufactured without high pressure processes such as bending and winding, in general, the distance between electrodes tends to be widened by charging and discharging, and battery characteristics such as cycle characteristics and output characteristics This tends to be inferior. By the way, in the electrode of this invention, since a porous layer has high binding property in electrolyte solution, a positive electrode and a negative electrode can be strongly bound by this porous layer. Therefore, even if the lithium ion secondary battery provided with the electrode of this invention is laminated|stacked type, since the distance between electrodes does not increase easily, battery characteristics can be made favorable.

As electrolyte solution, what swells the polymer of the core part and the polymer of the shell part of organic particle|grains to the swelling degree of the predetermined range mentioned above can be used. As such an electrolytic solution, an organic electrolytic solution containing an organic solvent and a supporting electrolyte dissolved in the organic solvent can be preferably used.

As a supporting electrolyte, lithium salt is used, for example. Examples of the lithium salt include LiPF ₆ , LiAsF ₆ , LiBF ₄ , LiSbF _{6 , LiAlCl 4} , LiClO ₄ , CF ₃ SO ₃ Li, C ₄ F ₉ SO ₃ Li, CF ₃ COOLi, (CF ₃ CO) ₂ NLi, (CF ₃ SO ₂ ) ₂ NLi, (C ₂ F ₅ SO ₂ )NLi, and the like. _{Among them, LiPF 6} , LiClO ₄ and CF ₃ SO ₃ Li are preferable from the viewpoint of being easy to dissolve in a solvent and exhibiting a high degree of dissociation. Moreover, a supporting electrolyte may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios. As the supporting electrolyte having a high degree of dissociation is used, the lithium ion conductivity tends to increase, so that the lithium ion conductivity can be adjusted according to the type of the supporting electrolyte.

The concentration of the supporting electrolyte in the electrolytic solution is preferably 1% by weight or more, more preferably 5% by weight or more, preferably 30% by weight or less, and more preferably 20% by weight or less. Further, depending on the type of the supporting electrolyte, the supporting electrolyte is preferably used at a concentration of 0.5 mol/liter to 2.5 mol/liter. By accommodating the quantity of a supporting electrolyte in this range, since ion conductivity can be made high, the charging characteristic and discharge characteristic of a lithium ion secondary battery can be made favorable.

As an organic solvent used for electrolyte solution, what can melt|dissolve a supporting electrolyte can be used. Examples of the organic solvent include dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene carbonate (BC), methylethyl carbonate (MEC), vinylene carbonate carbonate compounds such as (VC); ester compounds such as γ-butyrolactone and methyl formate; ether compounds such as 1,2-dimethoxyethane and tetrahydrofuran; sulfur-containing compounds such as sulfolane and dimethyl sulfoxide are preferred can be heard Moreover, these may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios. Among them, a carbonate compound is preferable because it has a high dielectric constant and has a stable potential region over a wide range. Moreover, since the lithium ion conductivity tends to become high, so that the viscosity of the solvent to be used is low, lithium ion conductivity can be adjusted according to the kind of solvent.

Moreover, electrolyte solution can contain an additive as needed. An additive may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

It is preferable to use what has a desired SP value as a solvent of electrolyte solution from a viewpoint of being easy to control the swelling degree of the polymer of the core part of organic particle|grains, and the polymer of a shell part among the electrolyte solutions mentioned above. The specific SP value of the solvent of the electrolytic solution is preferably 8 (cal/cm 3 ) ^1/2 or more, more preferably 9 (cal/cm 3 ) ^1/2 or more, and preferably 15 (cal/cm 3 ). ^1/2 or less, More preferably, it is 14 (cal/cm ^{<3>) 1/2} or less. Examples of the solvent having an SP value falling within the above range include cyclic ester compounds such as ethylene carbonate and propylene carbonate; and chain ester compounds such as ethylmethyl carbonate and diethyl carbonate.

The lithium ion secondary battery of this invention WHEREIN: It is not necessary to provide a separator between the electrode of this invention and its counter electrode. Therefore, you may provide a counter electrode directly in the porous layer side of the electrode of this invention. Directly forming the counter electrode here means that there is no separate member between the electrode of the present invention and the counter electrode on the porous layer side of the electrode of the present invention. Since the porous layer is an insulating layer, the short circuit between the positive electrode and the negative electrode can be prevented without providing a separator as a separate member from the porous layer. Moreover, also in this case, since a porous layer normally has a shutdown function, the safety|security of a lithium ion secondary battery is favorable. In addition, since the resistance can be reduced by not forming the separator, the low-temperature output characteristics of the battery can be improved.

Moreover, in the lithium ion secondary battery of this invention, even when forming arbitrary members between electrodes, it is not necessary to form the member which has a shutdown function between the electrode of this invention and its counter electrode. Therefore, on the porous layer side of the electrode of this invention, you may form a counter electrode through the member which does not have a shutdown function. Thus, even if it does not form the member which has a shutdown function between electrodes, since the porous layer with which the electrode of this invention is equipped normally has a shutdown function, the safety|security of a lithium ion secondary battery is favorable. Moreover, even when a separator is formed as an arbitrary member between electrodes, since the separator does not need to have a shutdown function, the selection width|variety of the material of a separator can be expanded. Therefore, the range of separators that can be selected can be broadened, and by extension, a wide range of actions corresponding to the separator can be imparted to the battery. Moreover, you may provide components other than a separator which do not have a shutdown function, such as a heat-resistant layer, between electrodes, for example.

The manufacturing method of the lithium ion secondary battery of this invention is not specifically limited. For example, the above-mentioned negative electrode and positive electrode may be overlapped, this may be put in a battery container, and electrolyte solution may be inject|poured into a battery container, and it may seal. In addition, if necessary, an expanded metal; an overcurrent preventing element such as a fuse or a PTC element; The shape of the battery may be, for example, a laminate cell type, a coin type, a button type, a sheet type, a cylindrical shape, a square shape, a flat shape, or the like.

Example

Hereinafter, the present invention will be specifically described with reference to Examples. However, this invention is not limited to the Example shown below, In the range which does not deviate from the Claim of this invention and its equivalent range, it can change arbitrarily and implement it.

In the following description, "%" and "part" indicating a quantity are based on weight unless otherwise specified. In addition, the operation demonstrated below was performed on conditions of normal temperature and normal pressure, unless otherwise indicated.

[Assessment Methods]

(1) Measurement method of cell volume change before and after high temperature cycle test

The 1000 mAh stacked lithium ion secondary battery manufactured in the Example and the comparative example was left still in the environment of 25 degreeC for 24 hours. Then, in a 25 degreeC environment, charging and discharging were performed at 0.1C to 4.35V, and discharge to 2.75V at 0.1C was performed. The cell of this battery was immersed in liquid paraffin, and the volume X0 of the cell was measured.

In addition, in a 60 degreeC environment, the operation of charging/discharging was repeated 1000 cycles on the conditions similar to the above. The cell of the battery after 1000 cycles was immersed in liquid paraffin, and the volume X1 of the cell was measured.

The volume change ΔX of the cell of the battery before and after repeating charging and discharging for 1000 cycles was calculated as “ΔX (%) = (X1 - X0)/X0×100”. It shows that the battery is excellent in cell swelling suppression, so that the value of this volume change (DELTA)X is small.

(2) HOT-ER test (evaluation method of shutdown property)

The 1000 mAh laminated lithium ion secondary battery manufactured by the Example and the comparative example was made to stand still in 25 degreeC environment for 24 hours. Then, in a 25 degreeC environment, charging and discharging were performed at 0.1C to 4.35V, and discharge to 2.75V at 0.1C was performed. Next, while the cell of this battery was pressed by the pressure of 500 kgf, the temperature was raised to 200 degreeC, and the cell resistance R was measured with the resistance measuring instrument ("Loresta MCP-TP06P" manufactured by Mitsubishi Chemical Anaritek Co., Ltd.). The value of the measured cell resistance R was evaluated by the following evaluation criteria. It shows that the shutdown property is excellent, so that the value of the cell resistance R is large.

(Evaluation criteria for shutdown properties)

E: R = 0 (Ω)

D: 0 (Ω) ＜ R ≤ 1 (Ω)

C : 1 (Ω) ＜ R ＜ 10 (Ω)

B: 10 (Ω) ≤ R ＜ 100 (Ω)

A: 100 (Ω) ≤ R (Ω)

(3) Evaluation method of high temperature cycle characteristics

The 1000 mAh laminated lithium ion secondary battery manufactured by the Example and the comparative example was left still in 25 degreeC environment for 24 hours. Then, in a 25 degreeC environment, charging and discharging were performed at 0.1C to 4.35V, and discharge to 2.75V at 0.1C was performed, and initial stage capacity|capacitance C0 was measured.

Moreover, in a 60 degreeC environment, 1000 cycles of charging/discharging were repeated under the same conditions as the above, and the capacity|capacitance C1 after 1000 cycles was measured.

The capacity retention rate ΔC was calculated as “ΔC = C1/C0×100 (%)”. It shows that it is excellent in the high temperature cycling characteristics of a lithium ion secondary battery, and a battery has a long life, so that this capacity retention rate (DELTA)C is high.

(4) Evaluation method of low-temperature output characteristics

The 1000 mAh laminated lithium ion secondary battery manufactured by the Example and the comparative example was left still in 25 degreeC environment for 24 hours. Then, in a 25 degreeC environment, the charging operation for 5 hours was performed at the charging rate of 0.1C, and the voltage V0 at that time was measured. Then, in a -10 degreeC environment, discharge operation was performed at the discharge rate of 1 C, and the voltage V1 15 second after the start of discharge was measured.

The voltage change ΔV was calculated as “ΔV = V0 - V1”. It shows that it is excellent in low-temperature output characteristics, so that the value of this voltage change (DELTA)V is small.

(5) Measuring method of metal lithium precipitation amount in negative electrode

The 1000 mAh laminated lithium ion secondary battery manufactured by the Example and the comparative example was left still in 25 degreeC environment for 24 hours. Then, in a -10 degreeC environment, operation of charging to 4.35V over 1 hour at a charging rate of 1C was performed. Thereafter, the negative electrode was taken out from the battery in an argon environment at room temperature. The taken out negative electrode was observed, and the area Ws (cm<2>) in which lithium metal was deposited was measured. The measured area was evaluated by the following evaluation criteria. It shows that there is little precipitation of lithium metal by charging/discharging, so that the area in which lithium metal is precipitated is small, and it is possible for a negative electrode to take in lithium ion in electrolyte solution smoothly. Thus, it is said that it is excellent in low-temperature accommodation characteristics that a negative electrode can take in lithium ion in electrolyte solution smoothly.

(Evaluation criteria for the amount of precipitation of lithium metal)

A: 0 (cm2) ≤ Ws < 1 (cm2)

B: 1 (cm2) ≤ Ws < 5 (cm2)

C: 5 (cm2) ≤ Ws < 10 (cm2)

D: 10 (cm2) ≤ Ws < 15 (cm2)

E: 15 (cm2) ≤ Ws < 20 (cm2)

F: 20 (cm2) ≤ Ws ≤ 25 (cm2)

(6) Method for measuring the swelling degree of the polymer in the core part

In the same manner as in the method for preparing an aqueous dispersion containing the polymer constituting the core portion in Examples and Comparative Examples, an aqueous dispersion containing the polymer constituting the core portion of the organic particles was prepared. This aqueous dispersion was placed in a petri dish made of polytetrafluoroethylene and dried at 25°C for 48 hours to prepare a film having a thickness of 0.5 mm.

This film was cut out to 1 cm in width and length, and the test piece was obtained. The weight of this test piece was measured and it was set as W0.

Moreover, the said test piece was immersed in electrolyte solution at 60 degreeC for 72 hours. Then, the test piece was taken out from the electrolytic solution, the electrolytic solution on the surface of the test piece was wiped off, and the weight W1 of the test piece after the immersion test was measured.

Using these weights W0 and W1, the swelling degree S (fold) was calculated as S = W1/W0.

At this time, as the electrolyte solution, in a mixed solvent of ethylene carbonate, diethyl carbonate, and vinylene carbonate (volume mixing ratio EC/DEC/VC = 68.5/30/1.5; SP value 12.7 (cal/cm 3 ) ^1/2 ), a supporting electrolyte As the solution, LiPF ₆ dissolved in a solvent at a concentration of 1 mol/liter was used.

(7) Method for measuring the swelling degree of the polymer of the shell part

In the same manner as in the method for preparing an aqueous dispersion containing organic particles in Examples and Comparative Examples, except that the monomer composition used for the production of the shell part was used instead of the monomer composition used for the production of the core part, the shell part was formed An aqueous dispersion containing the polymer was prepared. The swelling degree S of the polymer of the shell part was measured in the same manner as in the method for measuring the swelling degree of the polymer of the core part except that an aqueous dispersion containing the polymer constituting the shell part was used as the aqueous dispersion for producing the test piece.

(8) Measuring method of the average ratio that the outer surface of the core part is covered by the shell part

After fully disperse|distributing organic particle|grains to visible light curable resin ("D-800" by Nippon Electronics Co., Ltd.), it embedded and produced the block piece containing organic particle|grains. Next, it cut into thin 100 nm-thick shape with the microtome provided with the diamond blade, and produced the sample for a measurement. Then, the dyeing process was performed to the sample for a measurement using ruthenium tetraoxide.

Next, the dyed|stained sample for measurement was set in the transmission electron microscope ("JEM-3100F" by Nippon Electronics Co., Ltd.), and the cross-sectional structure of organic particle|grains was photographed by 80 kV of acceleration voltages. The magnification of the electron microscope was set so that the cross section of one organic particle|grain might enter into a visual field.

In the cross-sectional structure of the photographed organic particles, the length D1 of the periphery of the core portion and the length D2 of the portion in contact with the outer surface of the core portion and the shell portion are measured, and the outside of the core portion of the organic particles is measured by the following formula (1) The ratio Rc in which the surface was covered by the shell part was computed.

Coverage ratio Rc (%) = D2/D1 × 100 (1)

Said coverage ratio Rc was measured about 20 arbitrarily selected organic particle|grains, the average value was calculated, and it was set as the average ratio in which the outer surface of a core part was covered with a shell part.

(9) Method for measuring the volume average particle diameter of particles

The particle size distribution of the particle|grains used as a sample was measured with the laser diffraction type particle size distribution analyzer ("SALD-3100" by Shimadzu Corporation). In the measured particle size distribution, the particle size at which the cumulative volume calculated from the small-diameter side becomes 50% was determined as the volume average particle size.

(10) Measuring method of core-shell ratio

The average thickness of the shell part of organic particle|grains was measured by the following procedure.

When the shell portion is composed of polymer particles, the cross-sectional structure of the organic particles is observed with a transmission electron microscope in the same manner as described in the section of the method for measuring the average ratio of the outer surface of the core portion covered by the shell portion. did. From the cross-sectional structure of the observed organic particle|grains, the longest diameter of the particle|grains of the polymer which comprises a shell part was measured. For 20 arbitrarily selected organic particles, the longest diameter of the polymer particles constituting the shell part was measured by the above method, and the average value of the longest diameter was taken as the average thickness of the shell part.

In the case where the shell portion has a shape other than particles, the cross-sectional structure of the organic particles was measured by a transmission electron microscope in the same manner as described in the section of the method for measuring the average ratio of the outer surface of the core portion covered by the shell portion. observed. From the cross-sectional structure of the observed organic particles, the maximum thickness of the shell portion was measured. For 20 arbitrarily selected organic particles, the maximum thickness of the shell portion was measured by the above method, and the average value of the maximum thickness was taken as the average thickness of the shell portion.

And the core-shell ratio was calculated by dividing the average thickness of the measured shell part by the volume average particle diameter of organic particle|grains.

[Example 1]

(1-1. Preparation of binder for porous layer)

To a reactor equipped with a stirrer, 70 parts of ion-exchanged water, 0.15 parts of sodium lauryl sulfate ("Emar 2F" manufactured by Kao Chemical Co., Ltd.) as an emulsifier, and 0.5 parts of ammonium persulfate were respectively supplied, and the gas phase part was replaced with nitrogen gas, , the temperature was raised to 60°C.

Meanwhile, in another container, 50 parts of ion-exchanged water, 0.5 parts of sodium dodecylbenzenesulfonate as a dispersant, and 94 parts of butyl acrylate, 2 parts of acrylonitrile, 2 parts of methacrylic acid, allylmethacrylic as a polymerizable monomer 1 part of the rate and 1 part of acrylamide were mixed to obtain a monomer mixture. This monomer mixture was continuously added to the above reactor over 4 hours to conduct polymerization. During addition, it reacted at 60 degreeC. After completion|finish of addition, it stirred at 70 degreeC again for 3 hours, the reaction was complete|finished, and the aqueous dispersion containing the (meth)acrylic polymer as a particulate-form binder for porous layers was manufactured.

The volume average particle diameter D50 of the obtained (meth)acrylic polymer particle|grains was 0.36 micrometer, and the glass transition temperature was -45 degreeC.

(1-2. Preparation of organic particles)

In a 5 MPa pressure vessel equipped with a stirrer, as a monomer composition used for manufacturing the core part, 75 parts of methyl methacrylate, 4 parts of methacrylic acid, and 1 part of ethylenedimethacrylate; 1 part of sodium dodecylbenzenesulfonate as an emulsifier ; 150 parts of ion-exchanged water; And 0.5 parts of potassium persulfate was put as a polymerization initiator, and it fully stirred. Then, it heated to 60 degreeC and started superposition|polymerization. By continuing superposition|polymerization until the polymerization conversion ratio became 96 %, the aqueous dispersion containing the particulate-form polymer which comprises a core part was obtained.

Then, 19 parts of styrene and 1 part of methacrylic acid were continuously added to this aqueous dispersion as a monomer composition used for manufacture of a shell part, and it heated to 70 degreeC, and superposition|polymerization was continued. The aqueous dispersion containing organic particle|grains was manufactured by cooling and stopping reaction when the polymerization conversion ratio became 96%. The volume average particle diameter D50 of the obtained organic particle|grains was 0.45 micrometer. About the obtained organic particle|grains, by the method mentioned above, the average ratio in which the core-shell ratio and the surface of a core part were covered by the shell part was measured.

(1-3. Preparation of slurry for porous layer)

100 parts of the aqueous dispersion containing the organic particles in the amount of organic particles, 6 parts of the aqueous dispersion containing the (meth)acrylic polymer in the amount of (meth)acrylic polymer, and a polyethylene glycol type surfactant ( 0.2 parts of "SN wet 366" by Sanno Fuco Co., Ltd.) were mixed, and the slurry for porous layers was manufactured.

(1-4. Preparation of binder for negative electrode)

In a 5 MPa pressure vessel equipped with a stirrer, 33 parts of 1,3-butadiene, 3.5 parts of itaconic acid, 63.5 parts of styrene, 0.4 parts of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of ion-exchanged water and 0.5 parts of potassium persulfate as a polymerization initiator After adding parts and fully stirring, it heated to 50 degreeC and started superposition|polymerization. When the polymerization conversion ratio became 96%, it cooled, reaction was stopped, and the mixture containing the particulate-form binder for negative electrodes (SBR) was obtained. 5% sodium hydroxide aqueous solution was added to the mixture containing the said binder for negative electrodes, and it adjusted to pH 8. Then, the unreacted monomer was removed by heating and reduced pressure distillation, and it cooled to 30 degrees C or less, and obtained the aqueous dispersion containing the particulate-form binder for negative electrodes.

(1-5. Preparation of slurry for negative electrode)

90 parts of artificial graphite (volume average particle diameter of 15.6 µm), 10 parts of SiOx particles (volume average particle diameter of 5 µm), and a 2% aqueous solution of carboxymethylcellulose sodium salt ("MAC350HC" manufactured by Nippon Paper Co., Ltd.) as a thickener as a solid content equivalent After mixing 1.0 part and adding ion-exchange water and adjusting solid content concentration to 68%, it mixed for 60 minutes at 25 degreeC. Furthermore, after adding ion-exchange water and adjusting solid content concentration to 62 %, it mixed again for 15 minutes at 25 degreeC. 1.5 parts of the aqueous dispersion containing the binder for negative electrodes mentioned above was put into the liquid mixture obtained in this way, and ion-exchange water was further added, and it adjusted so that the final solid content concentration might be 52%, and it mixed for 10 minutes again. This was degassed under reduced pressure to obtain a slurry for negative electrodes with good fluidity.

(1-6. Manufacture of electrode plate for negative electrode)

The slurry for negative electrodes obtained above was apply|coated on the single side|surface of the 20-micrometer-thick copper foil which is an electrical power collector with a comma coater so that the film thickness after drying might be set to about 150 micrometers, and it dried. This drying was performed by conveying the inside of 60 degreeC oven over 2 minutes for copper foil at the speed|rate of 0.5 m/min. Then, it heat-processed at 120 degreeC for 2 minute(s), and the electrode plate raw material before press provided with a negative electrode active material layer on one side was obtained. This electrode plate original fabric was rolled by a roll press, and the electrode plate for negative electrodes which has an 80-micrometer-thick negative electrode active material layer on one side of an electrical power collector was obtained.

In addition, after applying and drying the negative electrode slurry on one side of the current collector in the same manner as in the process of manufacturing the electrode plate fabric before pressing, the negative electrode slurry is applied and dried on the other side of the current collector in the same manner. Then, it heat-processed again at 120 degreeC for 2 minute(s), and the electrode plate raw material before press provided with a negative electrode active material layer on both surfaces was obtained. This electrode plate original fabric was rolled by a roll press, and the electrode plate for negative electrodes which has 80-micrometer-thick negative electrode active material layer, respectively on both surfaces of an electrical power collector was obtained.

(1-7. Preparation of negative electrode)

On each negative electrode active material layer of the electrode plate for negative electrodes obtained above, the slurry for porous layers was apply|coated with the comma coater so that dry thickness might be set to 12 micrometers, and it was dried. Drying was performed by conveying the inside of 60 degreeC oven over 1 minute for an electrode plate at a speed|rate of 0.5 m/min. Thereby, a negative electrode having a negative electrode active material layer and a porous layer on one side of the current collector (hereinafter, may be appropriately referred to as a "single side negative electrode"), and a negative electrode having a negative electrode active material layer and a porous layer on both surfaces of the current collector (hereinafter referred to as "one side negative electrode") , which may be appropriately referred to as "double-sided negative electrode") was obtained.

(1-8. Preparation of slurry for positive electrode)

_{100 parts of LiCoO 2} having a volume average particle diameter of 12 µm as a positive electrode active material, 2 parts of acetylene black ("HS-100" manufactured by Denki Chemical Industries, Ltd.) as a conductive material, and polyvinylidene fluoride (manufactured by Kureha Corporation, #7208) as a positive electrode binder ) was mixed in 2 parts corresponding to solid content, N-methylpyrrolidone was added to this, and total solid content concentration was adjusted to 70 %. This was mixed with the planetary mixer, and the slurry for positive electrodes was obtained.

(1-9. Preparation of positive electrode)

The above slurry for positive electrodes was applied with a comma coater on an aluminum foil having a thickness of 20 µm as a current collector so that the film thickness after drying was set to about 150 µm, and dried. This drying was performed by conveying the inside of 60 degreeC oven over 2 minutes for aluminum foil at the speed|rate of 0.5 m/min. Then, it heat-processed at 120 degreeC for 2 minute(s), and the positive electrode raw material before press provided with a positive electrode active material layer on one side was obtained. This positive electrode raw material was rolled by a roll press, and the positive electrode which has a positive electrode active material layer with a thickness of 80 micrometers on the single side|surface of an electrical power collector (Hereinafter, it may call a "single-sided positive electrode" suitably.) was obtained.

In addition, after applying and drying the positive electrode slurry on one side of the current collector in the same manner as in the process of manufacturing the positive electrode raw material before pressing, the positive electrode slurry is applied and dried on the other side of the current collector in the same manner. It carried out and heat-processed again at 120 degreeC for 2 minute(s), and the positive electrode raw material before press provided with a positive electrode active material layer on both surfaces was obtained. This positive electrode raw material was rolled by a roll press, and the positive electrode which has 80-micrometer-thick positive electrode active material layer on both surfaces of an electrical power collector, respectively (Hereinafter, it may call a "double-sided positive electrode" suitably hereafter) was obtained.

(1-10. Preparation of lithium ion secondary battery)

The single-sided positive electrode and the double-sided positive electrode were cut into 5 cm x 15 cm. Moreover, the single-sided negative electrode and the double-sided negative electrode were cut into 5.5 cm x 15.5 cm. The single-sided positive electrode, the double-sided negative electrode, the double-sided positive electrode, and the single-sided negative electrode were arrange|positioned in this order, and the electrode laminated body was obtained. At this time, the direction of a single-sided positive electrode was set as the direction arrange|positioned in order of a positive electrode active material layer and a collector from the side close|similar to a double-sided negative electrode. In addition, the direction of a single-sided negative electrode was set as the direction arrange|positioned in this order of a porous layer, a negative electrode active material layer, and a collector from the side close|similar to a double-sided positive electrode.

This electrode laminate was wrapped in an aluminum wrapping material exterior. An electrolyte solution (solvent: EC/DEC/VC = 68.5/30/1.5 volume ratio, electrolyte: LiPF _{6 with a} concentration of 1 M) was injected into the exterior so that no air remained. Moreover, in order to seal the opening of the aluminum packaging material exterior, the aluminum packaging material exterior was closed by performing 150 degreeC heat sealing, and the battery exterior body was obtained. Then, the flat plate press process was performed to this battery exterior body at 100 Kgf for 100 degreeC, 2 minute(s), and the lithium ion secondary battery of 1000 mAh laminated|stacked type was manufactured.

The lithium ion secondary battery obtained in this way was evaluated by the method mentioned above.

[Example 2]

In the monomer composition used for manufacture of the core part which concerns on the said process (1-2), the quantity of methyl methacrylate was changed to 75.85 parts, and the quantity of ethylene dimethacrylate was changed to 0.15 parts.

Except the above matter, it carried out similarly to Example 1, and performed manufacture and evaluation of the lithium ion secondary battery.

[Example 3]

In the monomer composition used for manufacture of the core part which concerns on the said process (1-2), the quantity of methyl methacrylate was changed to 71.5 parts, and the quantity of ethylene dimethacrylate was changed to 4.5 parts.

Except the above matter, it carried out similarly to Example 1, and performed manufacture and evaluation of the lithium ion secondary battery.

[Example 4]

In the monomer composition used for manufacture of the core part which concerns on the said process (1-2), the quantity of methyl methacrylate was changed to 76.85 parts, and the quantity of ethylene dimethacrylate was changed to 0.05 parts.

Except the above matter, it carried out similarly to Example 1, and performed manufacture and evaluation of the lithium ion secondary battery.

[Example 5]

In the monomer composition used for manufacture of the core part which concerns on the said process (1-2), instead of 75 parts of methyl methacrylate, 55 parts of methyl methacrylate and 20 parts of 2-ethylhexyl acrylate were used in combination.

Except the above matter, it carried out similarly to Example 1, and performed manufacture and evaluation of the lithium ion secondary battery.

[Example 6]

In the monomer composition used for manufacture of the core part which concerns on the said process (1-2), acrylonitrile was used instead of methyl methacrylate.

Except the above matter, it carried out similarly to Example 1, and performed manufacture and evaluation of the lithium ion secondary battery.

[Example 7]

In the monomer composition used for manufacture of the core part which concerns on the said process (1-2), instead of 75 parts of methyl methacrylate, 65 parts of acrylonitrile and 10 parts of 2-ethylhexyl acrylate were used in combination.

Except the above matter, it carried out similarly to Example 1, and performed manufacture and evaluation of the lithium ion secondary battery.

[Example 8]

In the monomer composition used for manufacture of the shell part which concerns on the said process (1-2) WHEREIN: Instead of 19 parts of styrene, 9 parts of styrene and 10 parts of acrylonitrile were used in combination.

Except the above matter, it carried out similarly to Example 1, and performed manufacture and evaluation of the lithium ion secondary battery.

[Example 9]

In the monomer composition used for manufacture of the shell part concerning said process (1-2), instead of 19 parts of styrene, 4 parts of styrene and 15 parts of acrylonitrile were used in combination.

Except the above matter, it carried out similarly to Example 1, and performed manufacture and evaluation of the lithium ion secondary battery.

[Example 10]

In the monomer composition used for production of the shell part according to the step (1-2), 20 parts of sodium salt of styrenesulfonic acid was used instead of using 19 parts of styrene and 1 part of methacrylic acid in combination.

Except the above matter, it carried out similarly to Example 1, and performed manufacture and evaluation of the lithium ion secondary battery.

[Example 11]

In the monomer composition used for production of the shell part according to the above step (1-2), instead of using 19 parts of styrene and 1 part of methacrylic acid in combination, 15 parts of sodium salt of styrenesulfonic acid and 5 parts of acrylonitrile are combined it was used

Except the above matter, it carried out similarly to Example 1, and performed manufacture and evaluation of the lithium ion secondary battery.

[Example 12]

The single-sided positive electrode and the double-sided positive electrode having no porous layer prepared in Example 1 were used as the electrode plate, and on each positive electrode active material layer of these electrode plates, the slurry for the porous layer was applied with a comma coater so that the dry thickness became 12 μm, dried. Drying was performed by conveying the inside of 60 degreeC oven over 1 minute for an electrode plate at a speed|rate of 0.5 m/min. Thereby, the positive electrode which has a positive electrode active material layer and a porous layer on one side of an electrical power collector, and the positive electrode which has a positive electrode active material layer and a porous layer on both surfaces of an electrical power collector were obtained.

In the said process (1-10), instead of the single-sided positive electrode and double-sided positive electrode which do not have a porous layer, the single-sided positive electrode and double-sided positive electrode which have the porous layer manufactured as mentioned above were used.

Further, in the step (1-10), instead of the single-sided negative electrode having a porous layer, an electrode plate for a negative electrode having a negative electrode active material layer on one side of the current collector but not having a porous layer is used, and instead of a double-sided negative electrode having a porous layer An electrode plate for a negative electrode having a negative electrode active material layer on both surfaces of the current collector but not having a porous layer was used.

Except the above matter, it carried out similarly to Example 1, and performed manufacture and evaluation of the lithium ion secondary battery.

[Example 13]

In the said process (1-10), instead of the single-sided positive electrode and double-sided positive electrode which do not have a porous layer, the single-sided positive electrode and double-sided positive electrode with a porous layer manufactured in Example 12 were used.

Except the above matter, it carried out similarly to Example 1, and performed manufacture and evaluation of the lithium ion secondary battery.

[Example 14]

In the step (1-10), between the single-sided positive electrode and the double-sided negative electrode, between the double-sided negative electrode and the double-sided positive electrode, and between the double-sided positive electrode and the single-sided negative electrode, respectively, between the double-sided positive electrode and the single-sided negative electrode, Celgard 2500 (thickness: 25 µm, Material: polypropylene (made by Celgard) was formed.

Except the above matter, it carried out similarly to Example 1, and performed manufacture and evaluation of the lithium ion secondary battery.

[Comparative Example 1]

In the said process (1-3), 100 parts of alumina particles (volume average particle diameter of 0.5 micrometer) were used instead of organic particle|grains.

Except the above matter, it carried out similarly to Example 1, and performed manufacture and evaluation of the lithium ion secondary battery.

[Comparative Example 2]

In the monomer composition used for production of the core part related to the step (1-2), 80 parts of styrene is used instead of using 75 parts of methyl methacrylate, 4 parts of methacrylic acid, and 1 part of ethylene dimethacrylate in combination. did.

Moreover, in the monomer composition used for manufacture of the shell part which concerns on the said process (1-2), 20 parts of styrene was used instead of using 19 parts of styrene and 1 part of methacrylic acid in combination.

Except the above matter, it carried out similarly to Example 1, and performed manufacture and evaluation of the lithium ion secondary battery.

This comparative example 2 is an example in which the organic particle|grains which have a core-shell structure which both a core part and a shell part consist of polystyrene are used.

[Comparative Example 3]

In the monomer composition used for production of the core part according to the step (1-2), the amount of methyl methacrylate is changed to 50 parts, the amount of methacrylic acid is changed to 5 parts, and ethylene dimethacrylate 1 part Instead, 25 parts of acrylonitrile were used.

Except the above matter, it carried out similarly to Example 1, and performed manufacture and evaluation of the lithium ion secondary battery.

[Comparative Example 4]

In the monomer composition used for manufacture of the shell part which concerns on the said process (1-2), instead of 19 parts of styrene, 10 parts of methyl methacrylate and 9 parts of acrylonitrile were used in combination.

Except the above matter, it carried out similarly to Example 1, and performed manufacture and evaluation of the lithium ion secondary battery.

"result"

The results of Examples and Comparative Examples are shown in the following table. In the table below, the meaning of the abbreviation is as follows. In addition, in the following table|surface, the numerical value described next to the abbreviation of a monomer in the term of a monomer shows the weight part of the monomer. In addition, in the following table|surface, in the term of an active material, the numerical value written next to the name of an active material shows the weight part of the active material.

LCO: LiCoO ₂

MAC350HC: Carboxymethylcellulose sodium salt

ST: Styrene

BD: 1,3-butadiene

IA: itaconic acid

PVDF: polyvinylidene fluoride

MMA: Methyl methacrylate

MAA: methacrylic acid

EDMA: Ethylene dimethacrylate

2-EHA: 2-ethylhexyl acrylate

AN: acrylonitrile

NaSS: sodium salt of styrenesulfonic acid

Tg: glass transition temperature

Core-Shell Ratio: Core-Shell Ratio

Coverage: Average ratio of the outer surface of the core part covered by the shell part

D50: Volume average particle diameter

BA: Butyl acrylate

AMA: allyl methacrylate

AAm: acrylamide

SN366: Polyethylene glycol type surfactant

[Review]

It was confirmed from the result of an Example and a comparative example that the lithium ion secondary battery excellent in high temperature cycling characteristics could be implement|achieved by this invention. From the comparison between Comparative Examples 2 and 3 and Examples, it can be seen that accommodating the degree of swelling of the polymer of the core portion within a predetermined range has technical significance in improving the high-temperature cycle characteristics. Further, from the comparison between Comparative Example 4 and Examples, it is understood that there is a technical significance in improving the high-temperature cycle characteristics to accommodate the swelling degree of the polymer in the shell portion within a predetermined range.

Further, since Examples 1 to 13 have superior low-temperature output characteristics than Example 14, by omitting the separator using the shutdown function of the porous layer, a lithium ion secondary battery excellent not only in high-temperature cycle characteristics but also in low-temperature output characteristics can be realized. It has been confirmed that there is

100: organic particles
110: core part
110S: outer surface of the core part
120: shell part

Claims (5)

An electrode for a lithium ion secondary battery comprising an electrode active material layer and a porous layer containing organic particles formed directly on the electrode active material layer,
The organic particles have a core-shell structure including a core portion and a shell portion partially covering the outer surface of the core portion,
The core part is made of a polymer having a swelling degree of 5 times or more and 30 times or less with respect to the electrolyte,
The shell part is made of a polymer having a swelling degree of more than 1 time and not more than 4 times with respect to the electrolyte,
_{In the electrolyte solution, LiPF 6} was dissolved in a mixed solvent of ethylene carbonate, diethyl carbonate, and vinylene carbonate (volume mixing ratio ethylene carbonate/diethyl carbonate/vinylene carbonate = 68.5/30/1.5) at a concentration of 1 mol/liter is a solution,
The degree of swelling of the polymer of the core part and the polymer of the shell part is determined by drying the polymer of the core part and the polymer of the shell part at 25° C. for 48 hours to obtain a test piece, and measuring the weight W0 of the test piece, The electrode for a lithium ion secondary battery is immersed in an electrolyte solution at 60° C. for 72 hours, the weight W1 of the test piece after immersion is measured, and swelling degree = W1/W0 is calculated using the weights W0 and W1. The method of claim 1,
The glass transition temperature of the polymer of the core part is 0 ° C. or more and 150 ° C. or less,
The glass transition temperature of the polymer of the said shell part is 50 degreeC or more and 200 degrees C or less, The electrode for lithium ion secondary batteries. The lithium ion secondary battery provided with the electrode for lithium ion secondary batteries of Claim 1 or 2, and electrolyte solution. 4. The method of claim 3,
The lithium ion secondary battery which equips the said porous layer side of the said lithium ion secondary battery electrode with a counter electrode through the member which does not have a direct or shutdown function. 4. The method of claim 3,
The electrode has a flat shape, a lithium ion secondary battery.

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