JP2002151044A - Separator for nonaqueous electrolytic solution secondary battery and nonaqueous electrolytic solution secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a separator for a nonaqueous electrolytic solution secondary battery having a shutdown function, a heat resistance, and a superior anti-electrochemical oxidation property, and provide the nonaqueous electrolytic solution secondary battery including the separator. SOLUTION: The separator for the nonaqueous electrolytic solution secondary battery is equipped with a shutdown layer and a heat-resistant porous layer, and on the surface of the heat-resistant porous layer but on the surface of the side where the shutdown layer is not arranged, it has a spacer of point-like, line-like, mesh-like, or porous film-like. The spacer is the separator which is an electrochemically stable organic polymer compound or a polymer compound containing an electrochemically stable inorganic compound. Further, this is a nonaqueous electrolytic solution secondary battery wherein the separator for the nonaqueous electrolytic solution secondary battery is contained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a separator used for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery including the same.

[0002]

2. Description of the Related Art In recent years, portable information devices including personal computers, portable telephones, personal digital assistants and the like have been remarkably popularized, and secondary batteries used as power supplies are small in size, light in weight and large in capacity. Energy density is required. In this regard, conventional aqueous secondary batteries such as lead storage batteries and nickel cadmium storage batteries are not satisfactory, and lithium secondary batteries capable of realizing higher energy densities, especially lithium cobalt oxide, lithium nickel oxide, and lithium manganese spinel Research and development of lithium secondary batteries using a composite oxide of lithium as a positive electrode active material and a carbon material capable of doping / dedoping lithium ions as a negative electrode active material have been actively conducted.

[0003] Non-aqueous electrolyte secondary batteries typified by these lithium secondary batteries have a large amount of energy, and therefore generate a large amount of heat when an internal short-circuit or an external short-circuit occurs due to an accident. There is a demand for ensuring high safety by preventing the above-mentioned heat generation.
As a method of preventing heat generation beyond a certain level in the event of an accident, a separator placed between the positive electrode and the negative electrode that separates the positive electrode and the negative electrode so that they do not come into direct contact with each other, cuts off the current when heat is generated, and generates more heat. In general, a method of providing a shutdown function for preventing the failure is provided. In other words, when the separator is made of a porous material that is melted by heat generation, ions can pass through the porous pores and conduct electricity before heat generation. By shutting off electricity, a shutdown function can be provided. For example, in a separator composed of a polyolefin-based porous layer, when heat is generated, the polyolefin layer becomes nonporous at about 80 ° C. to 180 ° C. and changes to a structure in which electricity does not flow, thereby generating heat or ignition at a certain level or more. Prevention and safety can be further improved. However, there has been a problem that the separator is deformed due to heat generation, a part of the positive electrode and the negative electrode are in contact with each other, electricity is passed, and a sufficient shutdown function is not exhibited.

[0004] In order to improve the heat resistance of the separator and prevent deformation due to heat generation, it has been studied to combine a heat-resistant porous layer with a shutdown layer mainly composed of polyolefin to form a separator. For example,
Japanese Patent Application Laid-Open No. H11-144697 describes a separator comprising a polyolefin porous film and a polyimide porous film using a polyimide porous film as a heat-resistant porous layer.

[0005]

However, the present inventors have found that when a separator comprising a heat-resistant porous layer and a shutdown layer is used, the heat-resistant porous layer is electrochemically oxidized with charge and discharge. I found that there was a problem that sometimes happened. Accordingly, an object of the present invention is to provide a non-aqueous electrolyte secondary battery separator having a shutdown function and heat resistance, and having excellent electrochemical oxidation resistance, and a non-aqueous electrolyte secondary battery including the same. It is in.

[0006]

Means for Solving the Problems As a result of intensive studies, the inventors of the present invention have a shutdown layer and a heat-resistant porous layer, and are arranged on the surface of the heat-resistant porous layer, where the shutdown layer is disposed. Dots, lines, meshes,
Alternatively, the inventors have found that the above problem can be solved by using a separator for a non-aqueous electrolyte secondary battery having a porous film-shaped spacer, and have completed the present invention.

That is, the present invention has [1] a shutdown layer and a heat-resistant porous layer, and a dot-like or line-shaped surface is formed on the surface of the heat-resistant porous layer on which the shutdown layer is not disposed. Provided is a separator for a non-aqueous electrolyte secondary battery having a spacer in the shape of a mesh, a mesh, or a porous film. The present invention also provides [2] a non-aqueous electrolyte secondary battery including the non-aqueous electrolyte battery separator of [1].

[0008]

Next, the present invention will be described in detail.
The non-aqueous electrolyte secondary battery separator of the present invention has a shutdown layer and a heat-resistant porous layer, and a dot is formed on the surface of the heat-resistant porous layer on the side where the shutdown layer is not disposed. , Linear, mesh, or porous film spacers. The separator of the present invention can have a layer such as an adhesive layer or a stress buffer layer between the heat-resistant porous layer and the shutdown layer as long as the ions can pass, but the shutdown layer and the heat-resistant porous layer may be adjacent to each other. preferable. In the separator for a non-aqueous electrolyte secondary battery of the present invention, the surface of the heat-resistant porous layer on the side where the shutdown layer is not disposed (hereinafter referred to as the “outer surface of the heat-resistant porous layer” Has a spacer.

The spacer in the present invention has a function of preventing electrochemical oxidation of the heat-resistant porous layer. Since the spacer itself preferably does not cause electrochemical oxidation,
The spacer is preferably made of an electrochemically stable substance.

Since the spacer is inexpensive and lightweight, the spacer is preferably an organic polymer compound which is electrochemically stable. Further, the organic polymer compound may contain an electrochemically stable inorganic compound. Further, a thermoplastic resin which softens at a temperature of 80 ° C. to 180 ° C. can be used for the spacer to provide a shutdown function. If the shutdown temperature is equal to or higher than the practical temperature of the battery, it is preferable that the shutdown temperature be as low as possible from the viewpoint of ensuring the safety of the battery. Therefore, it is preferable to use a thermoplastic resin that softens at 80 to 140 ° C.

As the electrochemically stable substance used for the spacer in the present invention, a porous film is formed and used as a separator for a lithium ion battery.
There is one that does not deteriorate when held at a voltage of 4.5 V for a long time. Among them, polyolefins exemplified by polyethylene and polypropylene, polytetrafluoroethylene, fluoropolymers exemplified by copolymers of tetrafluoroethylene-hexafluoropropylene, celluloses exemplified by carboxymethylcellulose, polyolefin-based copolymers Coalescence, polycarbonate, an organic polymer compound selected from the group consisting of aromatic polyesters and polyethylene terephthalate, or an organic polymer compound containing an electrochemically stable inorganic compound is preferable, including an electrochemically stable inorganic compound Since the organic polymer compound, fluorine-containing polymer, cellulose such as carboxymethylcellulose increases the load characteristics of the battery,
More preferred.

In order to increase the electric capacity of the battery and suppress the inhibition of ion migration by the spacer, the thickness of the spacer is preferably as small as possible, and specifically, the thickness of the spacer is preferably from 0.02 to 5 μm. ,
More preferably, it is 0.02 to 3 μm. When the thickness of the spacer is less than 0.02 μm, the oxidation resistance of the heat-resistant layer may not be sufficiently improved. Here, the thickness of the spacer is the difference between the film thickness before and after the spacer is arranged on the outer surface of the heat-resistant porous layer. The thickness of the film is measured according to JIS K7130.

The spacer is in the form of a dot, a line, a mesh or a porous film. It is also possible to form linear spacers by arranging fibers made of organic polymers on the surface of the heat-resistant porous layer, and to form a mesh by bonding the organic polymer formed into a mesh shape to the surface of the heat-resistant porous layer. A spacer can be formed, and a spacer can be formed in a porous film shape by bonding a porous film made of an organic polymer such as a nonwoven fabric or a microporous film to the surface of the heat-resistant porous layer. It is industrially preferable that the spacer is dot-shaped because a spacer having a small thickness can be easily produced.

In particular, when produced by applying a suspension of organic fine particles, the fine particles are in a state of being arranged at least one layer on the surface of the heat-resistant porous layer. For example, if the fine particles are arranged in a single layer with a particle diameter of 3 μm, the thickness of the spacer is 3 μm. The fine particles do not necessarily need to completely cover the surface of the heat-resistant porous layer, and the fine particles need not be closely adjacent to each other. The particle size of the fine particles is preferably 3 μm or less, more preferably 1 μm or less. When the particle size of the fine particles is larger than 3 μm, the movement of ions is inhibited, and the load characteristics of the battery may be reduced. Further, two or more kinds of fine particles having different particle diameters may be used. In order to prevent aggregation of the particles when the suspension is applied and dried, it is preferable to mix particles of two or more different substances.

The shutdown layer according to the present invention will be described. The shutdown layer in the present invention is not particularly limited as long as it has a shutdown function, but is usually a porous layer made of a thermoplastic resin.

The size of the void in the shutdown layer, or the diameter of the sphere if the void can be approximated to a sphere (hereinafter, referred to as the sphere)
(May be referred to as a pore size) is preferably 3 μm or less.
μm or less is more preferable. If the average size or pore size of the voids exceeds 3 μm, there is a possibility that a problem such as a short circuit is likely to occur when carbon powder or a small piece of the main component of the positive electrode or the negative electrode falls off. If the average size or pore size of either of the heat-resistant porous layer and the shutdown layer is 3 μm or less, the other is more than 3 μm, which is a preferable range.

The porosity of the shutdown layer is 30 to 80.
% By volume, more preferably 40 to 70% by volume
It is. If the porosity is less than 30% by volume, the retained amount of the electrolyte may decrease. If the porosity exceeds 80%, the strength of the shutdown layer may be insufficient and the shutdown function may decrease. The thickness of the shutdown layer is
It is preferably 3 to 30 μm, more preferably 5 to 20 μm.
m. If the thickness is less than 3 μm, the shutdown function may be insufficient. If the thickness exceeds 30 μm, the thickness of the separator for a non-aqueous electrolyte secondary battery including a heat-resistant porous layer is too large to achieve high electric capacity. It may not be possible.

Since the shutdown layer is preferably a substantially non-porous layer at a temperature of 80 ° C. to 180 ° C., the thermoplastic resin forming the shutdown layer is softened at 80 ° C. to 180 ° C. Preferably, the porous resin is a thermoplastic resin in which the porous voids are closed and which does not dissolve in the electrolytic solution.
Specific examples include polyolefin and thermoplastic polyurethane. As the polyolefin, at least one type of thermoplastic resin selected from polyethylene such as low-density polyethylene, high-density polyethylene, and ultrahigh-molecular-weight polyethylene, and polypropylene is more preferable.

The heat-resistant porous layer according to the present invention will be described. In the separator of the present invention, the heat-resistant porous layer is made of a substance having heat resistance, but is preferably made of a heat-resistant resin. The heat-resistant resin forming the heat-resistant porous layer in the present invention is 18.6 based on JIS K 7207.
The deflection temperature under load in the measurement under a load of kg / cm ² is 1
At least one heat-resistant resin selected from resins having a temperature of 00 ° C. or higher is preferable. In order to be safer even at a high temperature due to severe use, the heat-resistant resin in the present invention is more preferably at least one heat-resistant resin selected from resins having a deflection temperature under load of 200 ° C. or higher.

The resin having a deflection temperature under load of 100 ° C. or more includes polyimide, polyamideimide, aramid, polycarbonate, polyacetal, polysulfone, polyphenylsulfide, polyetheretherketone,
Aromatic polyester, polyethersulfone, polyetherimide and the like can be mentioned. The deflection temperature under load is 20
Examples of the resin at 0 ° C. or higher include polyimide, polyamideimide, aramid, polyethersulfone, and polyetherimide. Further, it is particularly preferable that the heat-resistant resin is selected from the group consisting of polyimide, polyamideimide and aramid.

Further, the heat-resistant resin preferably has a limiting oxygen index of 20 or more. The limiting oxygen index is the minimum oxygen concentration at which a specimen placed in a glass tube can keep burning. This is because the heat-resistant porous layer is preferably flame-retardant in consideration of oxygen generated from the positive electrode material at a high temperature, in addition to heat resistance. Specific examples of such a resin include the above-described heat-resistant resin.

In the present invention, the pore size or pore size of the heat-resistant porous layer is preferably 3 μm or less, more preferably 1 μm or less. If the average size or pore size of the voids exceeds 3 μm, there is a possibility that a problem such as a short circuit is likely to occur when carbon powder or a small piece of the main component of the positive electrode or the negative electrode falls off. The porosity of the heat-resistant porous layer is preferably 30 to 80% by volume, more preferably 4% by volume.
0 to 70% by volume. If the porosity is less than 30% by volume, the retained amount of the electrolytic solution is small, and if it exceeds 80% by volume, the strength of the heat-resistant porous layer becomes insufficient. The thickness of the heat-resistant porous layer is preferably 2 to 30 μm, more preferably 2 to 30 μm.
0 μm. If the thickness is less than 2 μm, the effect on safety as a heat-resistant porous layer may be insufficient, and
When the thickness exceeds 0 μm, the thickness of the separator for a non-aqueous electrolyte secondary battery including a shutdown layer is too large, and it may be difficult to achieve high electric capacity.

In general, a nonaqueous electrolyte secondary battery is manufactured by laminating a positive electrode sheet and a negative electrode sheet with a separator interposed therebetween and spirally winding them to form an electrode group. At the time of winding, first, a part of the separator is wound around the winding core, and then the positive electrode sheet and the negative electrode sheet are supplied and wound through the separator. It is necessary to pull out the electrode group produced in this way from the core,
If the surface sliding property of the separator in contact with the winding core is not sufficient, force is applied to the electrode group, which may cause a winding deviation in the electrode group, resulting in unevenness or damage to the electrode group. Stainless steel is often used for the core, and it is preferable that the friction coefficient between the stainless steel and the separator be low. In a test in accordance with JIS K7125, the coefficient of static friction between the surface of the stainless steel polished flat with No. 1000 abrasive paper and the surface of the separator on the side where the spacers are arranged is preferably 0.5 or less. .3 or less.

The spacer need not completely cover the surface of the heat-resistant porous layer even when it is applied in the form of a line, a mesh or a porous film. Further, it is preferable that the linear, mesh or porous film-shaped spacer has a large opening degree so as not to hinder the movement of ions.

As a method of disposing a linear, mesh-like or porous film-shaped spacer on the outer surface of the heat-resistant porous layer, a nonwoven fabric, a woven fabric, or a porous film is laminated on the outer surface of the heat-resistant porous layer. A method of directly forming a nonwoven fabric on the outer surface of the heat-resistant porous layer by a method such as melt blowing; and a method of applying a polymer solution capable of forming a porous film on the outer surface of the heat-resistant porous layer.

The porosity of the shutdown layer or the heat-resistant porous layer is determined by measuring the weight (Wg) and thickness (Dcm) by cutting the heat-resistant porous layer into a square having a side length of 10 cm and measuring the weight of the material in the sample. Is calculated, the weight (Wi) of each material is divided by the true specific gravity, the volume of each material is obtained, and the porosity (volume%) is obtained from the following equation. Porosity (%) = [1-｛(W1 / true specific gravity 1) + (W2 /
True specific gravity 2) + ·· + (Wn / true specific gravity n)｝ / (100 ×
D)] × 100

In the separator for a non-aqueous electrolyte secondary battery of the present invention, a coating solution containing an electrochemically stable substance is applied to the outer surface of the heat-resistant porous layer to form a spacer on the outer surface. It is preferable from the industrial point of view that the spacer is easily manufactured by forming the spacer. In particular,
In order to arrange the dot-like spacer on the outer surface of the heat-resistant porous layer, it is preferable that the application liquid is a suspension because the thickness of the spacer can be reduced. Here, examples of the suspension include a suspension made of fine particles of an organic polymer.

In the present invention, any of the heat-resistant porous layer, the shutdown layer, and the spacer may contain an inorganic compound. The inorganic compound contained in the heat-resistant porous layer, the shutdown layer, and the spacer may be a high-order metal oxide having electrochemical oxidation resistance and being inert to the electrolyte. Specific examples include aluminum oxide, calcium carbonate, silica, and the like, but the present invention is not limited to these.

In the separator for a non-aqueous electrolyte secondary battery of the present invention, the respective layers may be simply superposed, but are preferably joined from the viewpoint of handleability. Examples of the method of joining the respective layers, for example, the method of joining the shutdown layer and the heat-resistant porous layer, and the method of joining the heat-resistant porous layer and the spacer include a method using an adhesive and a method using heat fusion.

The following is an example of a method of producing the spacer of the separator of the present invention by applying a coating solution containing an electrochemically stable substance to the outer surface of the heat-resistant porous layer to form a spacer. It is not limited to.

For example, a spacer can be formed on the outer surface of the heat-resistant porous layer by a method including the following steps (a) to (c). (A) A suspension liquid comprising an electrochemically stable substance is prepared. When an inorganic compound is used, a slurry liquid composed of a finely powdered inorganic compound is prepared and mixed with the suspension liquid. (B) applying the suspension liquid to the surface of the heat-resistant porous layer to form a coating layer. (C) drying the coating layer;

As a preferred method of laminating the shutdown layer and the heat-resistant porous layer, a porous layer such as a porous film for forming either the heat-resistant porous layer or the shutdown layer is used as a base and the other is in a solution state. This is a production method in which a solution layer is formed on the substrate by applying the solution to the substrate, and then a desolvation treatment is performed on the solution layer. Hereinafter, examples of a manufacturing method using a method of forming a heat-resistant porous layer by applying a heat-resistant resin solution on a shutdown layer will be described below, but the present invention is not limited thereto.

For example, a heat-resistant porous layer can be formed on the shutdown layer by a method including the following steps (A) to (E). (A) A solution comprising a heat-resistant resin and an organic solvent is prepared. When using inorganic fine powder, a slurry solution is prepared by dispersing 1 to 200 parts by weight of inorganic fine powder with respect to 100 parts by weight of heat-resistant resin. (B) Apply the solution or slurry solution to the shutdown layer to form a coating film. (C) depositing the heat-resistant resin in the coating film. (D) removing the organic solvent from the coating film; (E) drying the coating film;

Here, a polar organic solvent is usually used as the organic solvent. As the polar organic solvent, for example, N,
Examples include N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone (hereinafter abbreviated as “NMP”), tetramethylurea, and the like.

The non-aqueous electrolyte secondary battery of the present invention is characterized by including the above-described separator for a non-aqueous electrolyte secondary battery of the present invention. In the nonaqueous electrolyte secondary battery of the present invention, the separator of the present invention in which the spacer is adjacent to the positive electrode is preferable because the heat-resistant porous layer adjacent to the spacer is hardly electrochemically oxidized.

A non-aqueous electrolyte solution, a positive electrode sheet, and other components other than the separator of the non-aqueous electrolyte secondary battery are described below.
The negative electrode sheet and the negative electrode current collector will be described, but the present invention is not limited thereto.

As the non-aqueous electrolyte solution used in the non-aqueous electrolyte secondary battery of the present invention, for example, a non-aqueous electrolyte solution obtained by dissolving a lithium salt in an organic solvent can be used. As the lithium salt, LiClO ₄ , LiPF ₆ , LiAs
F ₆ , LiSbF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , Li
N (SO ₂ CF ₃ ) ₂ , LiC (SO ₂ CF ₃ ) ₃ , Li ₂ B
₁₀ Cl ₁₀ , lithium lower carboxylic acid lithium salt, LiAl
One or a mixture of two or more of Cl _{4 and the} like can be mentioned. As the lithium salt, LiPF ₆ containing fluorine Among _{these, LiAsF 6, LiSbF 6, LiBF} 4, L
iCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , and LiC
At least one selected from the group consisting of (CF ₃ SO ₂ ) ₃
It is preferable to use those containing seeds.

Examples of the organic solvent for the non-aqueous electrolyte solution used in the non-aqueous electrolyte secondary battery of the present invention include propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and 4-trifluoromethyl-1. , 3-dioxolane-
Carbonates such as 2-one and 1,2-di (methoxycarbonyloxy) ethane; 1,2-dimethoxyethane, 1,3-dimethoxypropane, pentafluoropropylmethyl ether, 2,2,3,3-tetrafluoro Ethers such as propyldifluoromethyl ether, tetrahydrofuran and 2-methyltetrahydrofuran;
Esters such as methyl formate, methyl acetate and γ-butyrolactone; nitriles such as acetonitrile and butyronitrile; amides such as N, N-dimethylformamide and N, N-dimethylacetamide; carbamates such as 3-methyl-2-oxazolidone , Sulfur-containing compounds such as sulfolane, dimethyl sulfoxide, and 1,3-propane sultone; or those obtained by introducing a fluorine substituent into the above-mentioned organic solvent, and usually two or more of these are mixed. Used.

Among these, a mixed solvent containing a carbonate is preferable, and a mixed solvent of a cyclic carbonate and an acyclic carbonate, or a mixed solvent of a cyclic carbonate and an ether is more preferable. The mixed solvent of cyclic carbonate and acyclic carbonate has a wide operating temperature range, excellent load characteristics, and is hardly decomposable when a graphite material such as natural graphite or artificial graphite is used as a negative electrode active material. so,
A mixed solvent containing ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate is preferred.

As the positive electrode sheet used in the non-aqueous electrolyte secondary battery of the present invention, a sheet in which a positive electrode active material, a conductive material, a binder, and the like are supported on a current collector is used. Specifically, a material containing a material capable of doping and undoping lithium ions, a carbonaceous material as a conductive material, and a thermoplastic resin as a binder can be used as the positive electrode active material. Examples of the material capable of doping / dedoping lithium ions include lithium composite oxides containing at least one transition metal such as V, Mn, Fe, Co, and Ni.
Among them, α-Na such as lithium nickelate and lithium cobaltate are preferable in that the average discharge potential is high.
Examples include a layered lithium composite oxide which is a compound having an FeO ₂ type structure and a lithium composite oxide which is a compound having a spinel type structure such as lithium manganese spinel.

The lithium composite oxide may contain various elements, in particular, Ti, V, Cr, Mn, Fe, Co,
With respect to the sum of the number of moles of at least one metal selected from the group consisting of Cu, Ag, Mg, Al, Ga, In and Sn and the number of moles of Ni in lithium nickelate, at least one of When the composite lithium nickelate containing the metal is used such that the metal is 0.1 to 20 mol%,
This is preferable because the capacity may be reduced due to high capacity and repeated charge / discharge.

As the binder used for the positive electrode sheet, a thermoplastic resin is usually used. Examples of the thermoplastic resin include polyvinylidene fluoride, a vinylidene fluoride copolymer, polytetrafluoroethylene, and tetrafluoroethylene. -A copolymer of hexafluoropropylene, a copolymer of tetrafluoroethylene-perfluoroalkylvinyl ether, a copolymer of ethylene-tetrafluoroethylene, a copolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene,
Examples thereof include thermoplastic polyimide, carboxymethyl cellulose, polyethylene, and polypropylene.

As the conductive agent used for the positive electrode sheet, a carbonaceous material is usually used, and examples of the carbonaceous material include natural graphite, artificial graphite, cokes, and carbon black. As the conductive material, each may be used alone, or for example, a mixture of artificial graphite and carbon black may be used.

For the negative electrode sheet used in the non-aqueous electrolyte secondary battery of the present invention, for example, a material capable of doping / de-doping with lithium ions, lithium metal or lithium alloy can be used. Materials that can be doped or undoped with lithium ions include carbonaceous materials such as natural graphite, artificial graphite, cokes, carbon black, pyrolytic carbons, carbon fibers, and fired organic polymer compounds, and a lower potential than the positive electrode. And chalcogen compounds such as oxides and sulfides for doping / dedoping lithium ions. A carbonaceous material containing graphite material such as natural graphite or artificial graphite as a main component is preferable because it has a high potential flatness and a large average energy density when combined with a positive electrode because of a low average discharge potential.

As the negative electrode current collector used in the non-aqueous electrolyte secondary battery of the present invention, Cu, Ni, stainless steel, etc. can be used. In particular, in a lithium secondary battery, it is difficult to form an alloy with lithium, and Cu is preferred because it can be easily processed into a thin film. As a method of supporting the mixture containing the negative electrode active material on the negative electrode current collector, a method of pressure molding, or a method of pasting using a solvent or the like, applying a paste on the current collector, drying and pressing, or the like, is used. Is mentioned.

The shape of the nonaqueous electrolyte secondary battery of the present invention is not particularly limited, and may be any of a paper type, a coin type, a cylindrical type, a square type, and the like.

[0047]

The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the invention thereto. (1) Intrinsic Viscosity In the present invention, the intrinsic viscosity is defined by the following measuring method. A solution in which 0.5 g of a para-aramid polymer is dissolved in 100 ml of 96-98% by weight sulfuric acid;
The weight% sulfuric acid was 30
The flow time was measured at ° C., and the intrinsic viscosity was determined from the ratio of the determined flow time by the following equation. Intrinsic viscosity = ln (T / T ₀ ) / C [unit: dl / g] where T and T ₀ are the flow times of the para-aramid sulfate solution and sulfuric acid, respectively, and C is the concentration of para-aramid in the para-aramid sulfate solution ( g / dl).

(2) Air permeability Air permeability was measured according to JIS P8117. (3) Film thickness The film thickness was measured according to JIS K7130. (4) Coefficient of Static Friction The coefficient of static friction of the film was determined by using JIS K7125 as a mating material made of stainless steel polished flat with No. 1000 abrasive paper.
It measured according to.

(5) Load Characteristics of Battery In order to evaluate the performance when a battery was manufactured using the separator, a flat battery was prepared by the following method, and the load characteristics of the battery were measured. 3 parts by weight of polyvinylidene fluoride are dissolved in NMP, and 9 parts by weight of artificial graphite powder as a conductive material, 1 part by weight of acetylene black, and 87 parts by weight of lithium cobalt oxide powder as a positive electrode active material are dispersed and kneaded,
A positive electrode material paste was used. The paste was applied to a 20 μm-thick Al foil as a current collector, dried, and roll-pressed to obtain a positive electrode sheet.

The positive electrode sheet and lithium metal to be used as a negative electrode were laminated with the spacer interposed therebetween such that a spacer was adjacent to the positive electrode sheet and the shutdown layer was adjacent to the negative electrode made of metallic lithium. Volume% ethyl methyl carbonate, 35 volume%
A flat battery was manufactured using an electrolytic solution in which 1 M LiPF ₆ was dissolved in a mixed solvent of dimethyl carbonate.

The flat battery thus obtained was subjected to a charging / discharging test by constant current / constant voltage charging and constant current discharging under the following conditions, and the load characteristics were measured. Charge / discharge X
The maximum charge voltage is 4.3 V, the charge time is 8 hours, the charge current is 0.5 mA / cm 2, the minimum discharge voltage is 3.0 V, and the discharge current is 0.5 mA / cm ^2. , Charging time 8 hours, charging current 0.5 mA / cm
² , when the minimum discharge voltage is 3.0 V and the discharge current is 10 mA / cm ² , the load characteristics are (discharge capacity of charge / discharge Y) /
(Discharge capacity of charge / discharge X), and the higher the value, the better the performance.

(6) Evaluation of Electrochemical Oxidation Resistance A flat battery was prepared in the same manner as in the evaluation of the load characteristics of the battery, and was subjected to constant current and constant voltage charging under the following conditions. The battery after the maximum charging voltage of 4.5 V, the charging time of 24 hours, and the charging current of 0.5 mA / cm ² was disassembled, and the separator was taken out and observed.

Embodiment 1 1. Application of heat-resistant porous layer and production of separator (1) Synthesis of para-aramid solution 5 with stirring blade, thermometer, nitrogen inlet pipe and powder addition port
Using a liter (l) separable flask, poly (paraphenylene terephthalamide) (hereinafter referred to as PPTA)
Abbreviation). Dry the flask thoroughly,
After adding 200 g of NMP, 272.65 g of calcium chloride dried at 200 ° C. for 2 hours was added, and the temperature was raised to 100 ° C. After the calcium chloride is completely dissolved, the temperature is returned to room temperature, and paraphenylenediamine (hereinafter abbreviated as PPD) 1
32.91 g was added and completely dissolved. This solution is
While maintaining the temperature at 0 ± 2 ° C., 243.32 g of terephthalic acid dichloride (hereinafter abbreviated as TPC) is divided into 10 portions to obtain approximately 5
Added every minute. Thereafter, the solution was aged for 1 hour while maintaining the solution at 20 ± 2 ° C., and stirred for 30 minutes under reduced pressure to remove bubbles. The obtained polymerization liquid showed optical anisotropy. A part is sampled, reprecipitated with water and taken out as a polymer,
When the intrinsic viscosity of the obtained PPTA was measured, it was 1.97.
dl / g. Next, 100 g of the polymerization liquid was added to a 50-liter flask having a stirring blade, a thermometer, a nitrogen inlet pipe, and a liquid addition port.
The mixture was weighed in a 0 ml separable flask, and the NMP solution was gradually added. Finally, the PPTA concentration is 2.0% by weight.
Was prepared, and this was designated as P solution.

(2) Application of Para-Aramid Solution and Preparation of Separator A porous film made of PE (polyethylene) (25 μm in film thickness, air permeability of 700 sec / 100 cc,
The average pore radius (mercury intrusion method: 0.04 μm) was used.
Tester Sangyo Co., Ltd. bar coater (gap 200μ)
m), the P solution, which is a heat-resistant resin solution, was applied on the PE porous membrane placed on a glass plate, and kept in a draft in a laboratory for about 20 minutes. A cloudy film was obtained on the porous membrane. The porous membrane made of PE to which the film was adhered was immersed in ion-exchanged water. After 5 minutes, the film was peeled from the glass plate, washed sufficiently with flowing ion-exchanged water, and then free water was wiped off. . This film was sandwiched between nylon cloths, and further sandwiched between aramid felts. With the PE porous membrane to which the film is attached sandwiched between nylon cloth and aramid felt, put an aluminum plate, cover the nylon film on it, seal the nylon film and aluminum plate with gum, A conduit for decompression was attached. The whole is put into a hot oven and dried under reduced pressure at 60 ° C. to dry the membrane, and a shutdown layer composed of a PE porous membrane and an aramid porous membrane (thickness: 5 μm)
A composite film in which a heat-resistant porous layer made of was laminated was obtained.

2. Evaluation of shutdown function The prepared composite film was cut into a 40 mm square,
between the stainless steel electrode of 90 mm square and 90 mm square, 3
Immersed in an electrolyte obtained by dissolving 1 M LiPF _{6 in} a mixed solvent of 0 vol% ethylene carbonate, 35 vol% ethyl methyl carbonate, and 35 vol% dimethyl carbonate,
A voltage of 1 volt was applied between the electrodes at 1 kHz, and the electrical resistance of the composite film was measured. Place the composite film in an electric oven and measure the electric resistance.
As a result of heating up to 200 ° C. at 2 ° C./min, the electrical resistance at 25 ° C. was 20 Ω.
In the vicinity, the electric resistance rapidly increased and showed 10 kΩ. This test confirmed that the shutdown function was activated.

3. Coating of Spacer The composite film prepared in item 1 of Example 1 was placed on a glass plate, and a bar coater manufactured by Tester Sangyo Co., Ltd. (gap 10
μm), a suspension of polypropylene (trade name: Chemipearl WP100, manufactured by Mitsui Chemicals, Inc., particle size: 1)
μm (measured by a Coulter counter method), adjusted to a solid content of 20% by weight by adding ion-exchanged water] to the surface of the aramid porous layer side, and then naturally dried. The thickness of the spacer was 1 μm. Table 1 shows the evaluation results of the obtained separator.

Example 2 The composite film prepared in item 1 of Example 1 was placed on a glass plate, and a bar coater (with a gap of 10) manufactured by Tester Sangyo Co., Ltd.
μm), a suspension of polyethylene [manufactured by Mitsui Chemicals, Inc., trade name: Chemipearl W950, particle size: 0.6]
μm (measured by Coulter counter method), adjusted to a solid content of 20% by weight by adding ion-exchanged water] to the surface of the aramid porous layer side, and then air-dried as it is. The thickness of the spacer was 1 μm. Table 1 shows the evaluation results of the obtained separator.

Example 3 The composite film prepared in item 1 of Example 1 was placed on a glass plate, and a bar coater (with a gap of 10) manufactured by Tester Sangyo Co., Ltd.
μm), a suspension of polyethylene [manufactured by Mitsui Chemicals, Inc., trade name: Chemipearl W950] and a suspension of tetrafluoroethylene-hexafluoropropylene copolymer [manufactured by Daikin Industries, Ltd., trade name: ND
-1, particle size of 0.1 to 0.25 μm] at a weight ratio of solid content of 2: 1 and ion-exchanged water is added to obtain a solid content of 20%.
% Of the suspension was applied to the surface of the aramid porous layer, and then air-dried. The thickness of the spacer was 1 μm. Table 1 shows the evaluation results of the obtained separator.

Example 4 The composite film prepared in item 1 of Example 1 was placed on a glass plate, and a bar coater (gap 10) manufactured by Tester Sangyo Co., Ltd. was used.
μm), carboxymethyl cellulose [manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name: cellogen 4H] is dissolved in ion-exchanged water, and alumina fine particles [trade name, manufactured by Nippon Aerosil, trade name:
Alumina C, particle size 0.013 μm] was dispersed, and the mixture was applied to the surface of the aramid porous layer side adjusted to a solid content of 1.5% by adding ion-exchanged water, and then air-dried as it was.
The thickness of the spacer was 1 μm. Table 1 shows the evaluation results of the obtained separator.

Comparative Example 1 The composite film prepared in item 1 of Example 1 was evaluated as a separator without forming a spacer. Table 1 shows the evaluation results of the obtained separator.

[Table 1]

[0061]

The separator for a non-aqueous electrolyte secondary battery of the present invention has a shutdown function, heat resistance, and excellent electrochemical oxidation resistance. This suppresses the heat generation of the non-aqueous electrolyte secondary battery with high safety. Further, the non-aqueous electrolyte secondary battery using the separator of the present invention has excellent characteristics as a battery. In addition, since the surface has good slipperiness, it is suitable as a separator for a non-aqueous electrolyte secondary battery. Further, the separator for a non-aqueous electrolyte secondary battery of the present invention is extremely useful industrially by a coating method.

Continued on the front page (72) Inventor Tsutomu Takahashi 6 Kitahara, Tsukuba-shi, Ibaraki F-term (reference) 5H021 AA06 BB12 CC02 CC03 CC11 EE02 EE04 HH00 HH03 5H029 AJ12 AK03 AL02 AL04 AL06 AL07 AL08 AL12 AM03 AM04 AM05 AM07 DJ04 DJ13 DJ14 DJ16 EJ03 EJ12 HJ00 HJ05 HJ12

Claims (11)

[Claims] 1. A heat-resistant porous layer having a shutdown layer and a heat-resistant porous layer, on the surface of the heat-resistant porous layer on which the shutdown layer is not arranged, a dot-like, linear, mesh-like,
Alternatively, a separator for a non-aqueous electrolyte secondary battery comprising a porous film-shaped spacer. 2. The non-aqueous electrolyte secondary battery separator according to claim 1, wherein the heat-resistant porous layer is made of a heat-resistant resin. 3. The separator for a non-aqueous electrolyte secondary battery according to claim 1, wherein said spacer is made of an electrochemically stable substance. 4. The non-aqueous electrolyte secondary battery according to claim 1, wherein said spacer is an electrochemically stable organic polymer compound or an organic polymer compound containing an electrochemically stable inorganic compound. Separator. 5. The method according to claim 1, wherein said spacer is in the form of particles and has a particle size of 3 μm.
The separator for a non-aqueous electrolyte secondary battery according to claim 1, wherein m is not more than m. 6. The coefficient of static friction between the surface of the separator on which the spacers are disposed and the stainless steel surface polished flat with No. 1000 abrasive paper is 0.5 or less.
The separator for a non-aqueous electrolyte secondary battery according to the above. 7. The non-woven fabric according to claim 1, which is manufactured by applying a coating solution containing an electrochemically stable substance and forming a spacer on the surface of the heat-resistant porous layer. Water electrolyte secondary battery separator. 8. The separator for a non-aqueous electrolyte secondary battery according to claim 7, wherein the coating solution is a suspension. 9. An organic material selected from the group consisting of polyolefins, polyolefin-based copolymers, fluoropolymers, polycarbonates, aromatic polyesters, celluloses such as carboxymethylcellulose, and polyethylene terephthalate. Polymer compound,
9. The separator for a non-aqueous electrolyte secondary battery according to claim 1, wherein the organic polymer compound contains an electrochemically stable inorganic compound. 10. A non-aqueous electrolyte secondary battery comprising the non-aqueous electrolyte battery separator according to any one of claims 1 to 9. 11. The non-aqueous electrolyte secondary battery according to claim 10, wherein a spacer of the non-aqueous electrolyte battery separator is adjacent to the positive electrode.