JP2014026946A - Separator for nonaqueous electrolyte battery, and nonaqueous electrolyte battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a separator for a nonaqueous electrolyte battery which is excellent in the adhesiveness with an electrode, and allows the improvement of the battery cycle characteristics.SOLUTION: The separator comprises: a porous base material; and an adhesive porous layer provided on one or each side of the porous base material, and including a polyvinylidene fluoride-based resin. In the separator, the moisture content is 1000 ppm or less.

Description

  The present invention relates to a separator for a nonaqueous electrolyte battery and a nonaqueous electrolyte battery.

  Non-aqueous secondary batteries represented by lithium ion secondary batteries are widely used as power sources for portable electronic devices such as notebook computers, mobile phones, digital cameras, and camcorders. Furthermore, in recent years, these batteries have been studied for application to automobiles and the like because of their high energy density.

  With the miniaturization and weight reduction of portable electronic devices, the exterior of non-aqueous secondary batteries has been simplified. Instead of the stainless steel battery can originally used as the exterior, a battery can made of aluminum can In addition, a soft pack exterior made of an aluminum laminate pack has been developed.

  In the case of an aluminum laminate soft pack exterior, since the exterior is soft, a gap may be formed between the electrode and the separator along with charge and discharge. This is one factor that deteriorates the cycle life, and it is one of the important technical problems to maintain the adhesiveness of the adhesive portions such as electrodes and separators.

  Various techniques for improving the adhesion between the electrode and the separator have been proposed as techniques related to the adhesion. As one of such techniques, a technique using a separator in which a porous layer made of a polyvinylidene fluoride resin (hereinafter also referred to as “adhesive porous layer”) is formed on a polyolefin microporous film, which is a conventional separator, is used. Has been proposed (see, for example, Patent Document 1). The adhesive porous layer has a function as an adhesive that satisfactorily bonds the electrode and the separator when the electrode is hot-pressed on the electrode. Therefore, the adhesive porous layer contributes to the improvement of the cycle life of the soft pack battery.

  In the separator in which an adhesive porous layer is laminated on the above-mentioned polyolefin microporous membrane, attention should be paid to the porous structure and thickness of the polyvinylidene fluoride resin layer from the viewpoint of ensuring sufficient adhesion and ion permeability. New technical proposals have been made.

Japanese Patent No. 4127989

  However, when the adhesive porous layer is formed by a coating method on a porous substrate such as a polyolefin microporous film (hereinafter also simply referred to as a substrate), the coating method is a wet method, and thus formed. The adhesive porous layer can easily retain a large amount of moisture, and the moisture may adversely affect the battery.

  Specifically, moisture contained in a separator, particularly an adhesive porous layer, installed in the battery may react with the electrolytic solution to generate gas. In addition, the presence of moisture consumes lithium ions, and the cycle life of the entire battery may be significantly reduced.

  The present invention has been made in view of the above, and is excellent in adhesiveness with an electrode, improves the cycle characteristics of the battery, and improves the cycle characteristics of the battery, and non-aqueous stably expresses the excellent cycle characteristics. It aims at providing an electrolyte battery, and makes it a subject to achieve this objective.

Specific means for achieving the above object are as follows.
<1> A nonaqueous electrolyte battery having a porous base material and an adhesive porous layer including a polyvinylidene fluoride-based resin provided on one or both surfaces of the porous base material and having a moisture content of 1000 ppm or less Separator.

  <2> A non-aqueous battery comprising a positive electrode, a negative electrode, and the separator for a non-aqueous electrolyte battery according to <1> disposed between the positive electrode and the negative electrode, and obtaining electromotive force by doping or dedoping lithium. It is an electrolyte battery.

ADVANTAGE OF THE INVENTION According to this invention, the separator for nonaqueous electrolyte batteries which is excellent in the adhesiveness with an electrode and the cycling characteristics of a battery improve is provided. Also,
According to the present invention, a non-aqueous electrolyte battery that stably exhibits excellent cycle characteristics is provided.

  Hereinafter, the separator for nonaqueous electrolyte batteries of the present invention and the nonaqueous electrolyte battery using the same will be described in detail.

<Separator for non-aqueous electrolyte battery>
The separator for a non-aqueous electrolyte battery of the present invention is provided with a porous base material and an adhesive porous layer that is provided on one or both sides of the porous base material and contains a polyvinylidene fluoride resin, and has a moisture content of 1000 ppm or less. It is configured as.
The moisture content in the present invention refers to the moisture content [ppm] contained in the entire separator.

Conventionally, a separator is produced by forming an adhesive porous layer on a porous substrate by a wet method. When a polyvinylidene fluoride resin is used as the adhesive resin in the coating liquid used in this wet method, the adhesiveness of the adhesive porous layer becomes excellent.
In the separator for nonaqueous electrolyte batteries of the present invention, a porous layer using a polyvinylidene fluoride-based resin is provided as an adhesive layer, so that it has excellent adhesion between an electrode and a porous substrate, Deterioration of the film due to adhesion variation, and thus adverse effects on cycle characteristics are suppressed.

In the case of the above wet method, since the coating liquid is used for forming the porous layer, a large amount of moisture tends to remain in the formed porous layer, and there may be a lot of moisture in the separator. However, if the amount of moisture in the separator becomes too large, the moisture may act on the electrolyte solution and lithium ions in the battery to generate unnecessary gas and deteriorate battery characteristics (cycle life). On the other hand, it is difficult to say that the amount of water in the separator is desirably small. If the amount of water is too small, the influence of static electricity cannot be ignored and handling becomes difficult. Therefore, it is desirable that the moisture content in the separator is adjusted to an appropriate moisture content range.
In view of such a point, in the separator for nonaqueous electrolyte batteries of the present invention, the moisture content is set to a range of 1000 ppm or less.

If the water content exceeds 1000 ppm, the water reacts with the electrolyte, generating gas or consuming lithium ions, resulting in a significant decrease in battery cycle characteristics. In other words, when the moisture content of the separator is 1000 ppm or less, the cycle characteristics when the battery is configured are improved while ensuring excellent adhesiveness.
The moisture content in the present invention is preferably 100 ppm or less from the viewpoint of keeping the cycle characteristics of the battery good for a long period of time. The lower limit of the moisture content is preferably adjusted to a range of 10 ppm or more. When the moisture content is 10 ppm or more, the generation of static electricity is suppressed, and the handleability can be maintained satisfactorily.

  The moisture content in the separator can be adjusted by a method capable of evaporating and removing moisture such as heat drying, hot air drying, and vacuum heat drying. As a specific method, for example, the produced separator is blown and dried under predetermined heating and drying conditions (for example, temperature: 10 to 50 ° C., humidity: 10 to 60% RH environment), or a predetermined temperature and humidity environment ( For example, the method of storing for a predetermined period under temperature: 10-30 degreeC, humidity: 0-20% RH environment) etc. are mentioned.

  The moisture content of the separator can be measured by a moisture determination method using the Karl Fischer reaction. Specifically, the moisture content of the separator for a nonaqueous electrolyte battery of the present invention is a value measured by a trace moisture measuring device AQ-2200 (manufactured by Hiranuma Sangyo Co., Ltd.).

  Next, the porous base material and the adhesive porous layer constituting the separator for a nonaqueous electrolyte battery of the present invention will be described in detail.

-Porous substrate-
The porous substrate in the present invention means a substrate having pores or voids therein. Examples of such a substrate include a microporous film, a porous sheet made of a fibrous material such as a nonwoven fabric and a paper sheet, or one or more other porous layers laminated on the microporous film or the porous sheet. Composite porous sheet and the like.

  A microporous membrane means a membrane that has a large number of micropores inside and has a structure in which these micropores are connected, allowing gas or liquid to pass from one surface to the other. To do.

  As long as the material which comprises a porous base material is an electrically insulating material, any of an organic material and an inorganic material may be sufficient. The material constituting the porous substrate is preferably a thermoplastic resin from the viewpoint of imparting a shutdown function to the porous substrate.

In addition, the shutdown function refers to a function of preventing the thermal runaway of the battery by blocking the movement of ions by dissolving the constituent materials and closing the pores of the porous base material when the battery temperature increases.
As the thermoplastic resin, a thermoplastic resin having a melting point of less than 200 ° C. is suitable, and polyolefin is particularly preferable.

As the porous substrate using polyolefin, a polyolefin microporous membrane is suitable.
As the polyolefin microporous membrane, those having sufficient mechanical properties and ion permeability can be suitably used from among polyolefin microporous membranes applied to conventional separators for nonaqueous electrolyte batteries.
The polyolefin microporous membrane preferably contains polyethylene from the viewpoint of exhibiting a shutdown function, and the polyethylene content is preferably 95% by mass or more.

  In addition to the above, a polyolefin microporous film containing polyethylene and polypropylene is suitable from the viewpoint of imparting heat resistance to such an extent that it does not easily break when exposed to high temperatures. Examples of such a polyolefin microporous membrane include a microporous membrane in which polyethylene and polypropylene are mixed in one layer. Such a microporous membrane preferably contains 95% by mass or more of polyethylene and 5% by mass or less of polypropylene from the viewpoint of achieving both a shutdown function and heat resistance. Also, from the viewpoint of achieving both a shutdown function and heat resistance, the polyolefin microporous membrane has a laminated structure of two or more layers, and at least one layer contains polyethylene and at least one layer contains a polyolefin microporous membrane having a structure containing polypropylene. .

  The polyolefin contained in the polyolefin microporous membrane preferably has a weight average molecular weight of 100,000 to 5,000,000. When the weight average molecular weight is 100,000 or more, sufficient mechanical properties can be secured. On the other hand, when the weight average molecular weight is 5 million or less, the shutdown characteristics are good and the film can be easily formed.

  The polyolefin microporous membrane can be produced, for example, by the following method. That is, (i) the melted polyolefin resin is extruded from a T-die to form a sheet, (ii) the sheet is subjected to crystallization treatment, (iii) stretched, and (iv) the stretched sheet is heat-treated. Thus, a method of forming a microporous film can be mentioned. Alternatively, (i) a polyolefin resin is melted together with a plasticizer such as liquid paraffin, extruded from a T-die, cooled to form a sheet, and (ii) the sheet is stretched ( iii) A method of forming a microporous film by extracting a plasticizer from the stretched sheet and further (iv) heat-treating it may be mentioned.

  Examples of the porous sheet made of a fibrous material include polyesters such as polyethylene terephthalate; polyolefins such as polyethylene and polypropylene; heat-resistant polymers such as aromatic polyamide, polyimide, polyethersulfone, polysulfone, polyetherketone, and polyetherimide; And the like, or a porous sheet made of a mixture of the fibrous materials.

As a composite porous sheet, the structure which laminated | stacked the functional layer on the porous sheet which consists of a microporous film or a fibrous material is employable. Such a composite porous sheet is preferable in that a further function can be added by the functional layer. As the functional layer, for example, from the viewpoint of imparting heat resistance, a porous layer made of a heat resistant resin or a porous layer made of a heat resistant resin and an inorganic filler can be adopted. Examples of the heat resistant resin include one or more heat resistant polymers selected from aromatic polyamide, polyimide, polyethersulfone, polysulfone, polyetherketone and polyetherimide. As the inorganic filler, a metal oxide such as alumina or a metal hydroxide such as magnesium hydroxide can be suitably used.
In addition, as a composite method, a method of applying a functional layer to a microporous membrane or a porous sheet, a method of bonding the microporous membrane or porous sheet and the functional layer with an adhesive, a microporous membrane or a porous layer Examples thereof include a method of thermocompression bonding the sheet and the functional layer.

In addition to the above, preferred embodiments of various physical properties of the porous substrate are shown below.
The film thickness of the porous substrate is preferably in the range of 5 μm to 25 μm from the viewpoint of obtaining good mechanical properties and internal resistance.
The Gurley value (JIS P8117) of the porous substrate is preferably in the range of 50 seconds / 100 cc to 800 seconds / 100 cc from the viewpoint of preventing short circuit of the battery and obtaining sufficient ion permeability.

-Adhesive porous layer-
The adhesive porous layer in the present invention has a large number of micropores inside and has a porous structure in which these micropores are connected to each other, allowing gas or liquid to pass from one surface to the other. It is the layer that became. The porous structure of the adhesive porous layer is an important technical element.

  The adhesive porous layer is provided as the outermost layer of the separator on one side or both sides of the porous substrate, and can be adhered to the electrode by this adhesive porous layer. That is, the adhesive porous layer is a layer that can adhere the separator to the electrode when hot-pressed with the separator and the electrode overlapped. When the separator for nonaqueous electrolyte batteries of the present invention has an adhesive porous layer only on one side of the porous substrate, the adhesive porous layer is bonded to either the positive electrode or the negative electrode. Moreover, when the separator for nonaqueous electrolyte batteries of this invention has an adhesive porous layer on both sides of the said porous base material, an adhesive porous layer is adhere | attached on both a positive electrode and a negative electrode. The adhesive porous layer is preferable not only on one side of the porous base material but also on both sides in terms of excellent battery cycle characteristics. This is because the adhesive porous layer is on both surfaces of the porous substrate, so that both surfaces of the separator are well bonded to both electrodes via the adhesive porous layer.

In the present invention, when the adhesive porous layer is formed on both sides of the porous substrate, the coating amount of the adhesive porous layer is 0.5 g / m as the amount of one side of the porous substrate. ^{2 to} 1.5 g / m ² is preferable, and 0.7 g / m ^{2 to} 1.3 g / m ² is more preferable. When the coating amount is 0.5 g / m ² or more, it is easy to suppress variation in the coating amount of the adhesive porous layer within the above-described range, and the adhesion to the electrode is improved. Thus, the cycle characteristics of the battery are excellent. On the other hand, when the coating amount is 1.5 g / m ² or less, it is easy to suppress variation in the coating amount of the adhesive porous layer within the aforementioned range, and good ion permeability is ensured, and the load on the battery is reduced. Good characteristics.

  When the adhesive porous layer is provided on both sides of the porous substrate, the difference between the coating amount on one side and the coating amount on the other side is 20% with respect to the total coating amount on both sides. The following is preferable. If it is 20% or less, the separator is difficult to curl. As a result, the handling property is good and the problem that the cycle characteristics are deteriorated hardly occurs.

  The thickness of the adhesive porous layer is preferably 0.3 μm to 5 μm on one side of the porous substrate. When the thickness is 0.3 μm or more, the coating amount variation of the adhesive porous layer can be easily suppressed within the above-described range, and the adhesiveness to the electrode is improved. Thus, the cycle characteristics of the battery are good. When the thickness is 5 μm or less, good ion permeability is secured and the load characteristics of the battery are excellent. For the same reason as described above, the thickness of the adhesive porous layer is more preferably 0.5 μm to 5 μm and still more preferably 1 μm to 2 μm on one side of the porous substrate.

  In the present invention, the adhesive porous layer preferably has a sufficiently porous structure from the viewpoint of ion permeability. Specifically, the porosity is preferably 30% to 60%. When the porosity is 30% or more, the ion permeability is good and the battery characteristics are excellent. Further, when the porosity is 60% or less, sufficient mechanical properties are obtained such that the porous structure is not crushed when bonded to the electrode by hot pressing. Further, when the porosity is 60% or less, the surface porosity becomes low, and the area occupied by the adhesive resin (preferably polyvinylidene fluoride resin) increases, so that a better adhesive force can be secured. it can. In addition, the porosity of the adhesive porous layer is more preferably in the range of 30 to 50%.

The adhesive porous layer preferably has an average pore size of 1 nm to 100 nm. When the average pore size of the adhesive porous layer is 100 nm or less, a porous structure in which uniform pores are uniformly dispersed can be easily obtained, and the adhesion points with the electrode can be evenly dispersed. Sex is obtained. In that case, the movement of ions is also uniform, better cycle characteristics can be obtained, and better load characteristics can be obtained. On the other hand, the average pore diameter is desirably as small as possible from the viewpoint of uniformity, but it is practically difficult to form a porous structure smaller than 1 nm. In addition, when the adhesive porous layer is impregnated with an electrolytic solution, the resin (for example, polyvinylidene fluoride resin) may swell. If the average pore diameter is too small, the pores are blocked by swelling and the ion permeability is impaired. It is. From this point of view. The average pore diameter is preferably 1 nm or more.
The average pore size of the adhesive porous layer is more preferably 20 nm to 100 nm.

  The adhesive porous layer in the present invention contains at least a polyvinylidene fluoride resin (PVdF) as an adhesive resin. In addition, the adhesive porous layer can be constituted by using other components such as an adhesive resin other than the filler, PVdF, and various additives as necessary.

[Polyvinylidene fluoride resin]
The adhesive porous layer in the present invention contains at least one kind of polyvinylidene fluoride resin (PVdF). By including PVdF, the adhesiveness with the electrode is excellent.
As the polyvinylidene fluoride resin, a homopolymer of vinylidene fluoride (that is, polyvinylidene fluoride); a copolymer of vinylidene fluoride and another copolymerizable monomer (polyvinylidene fluoride copolymer); a mixture thereof ;
Examples of the monomer copolymerizable with vinylidene fluoride include tetrafluoroethylene, hexafluoropropylene (HFP), trifluoroethylene, trichloroethylene, vinyl fluoride, and the like, and one kind or two or more kinds can be used. .
The polyvinylidene fluoride resin is obtained by emulsion polymerization or suspension polymerization.

  Among the polyvinylidene fluoride-based resins, a copolymer obtained by copolymerizing at least vinylidene fluoride and hexafluoropropylene is preferable from the viewpoint of adhesiveness with an electrode, and further, a structural unit derived from vinylidene fluoride and a molar basis. And more preferably 0.1 to 5 mol% of a copolymer containing hexafluoropropylene-derived structural units.

  The polyvinylidene fluoride-based resin preferably includes a resin containing 98 mol% or more of vinylidene fluoride as a structural unit. When 98 mol% or more of vinylidene fluoride is contained, sufficient mechanical properties and heat resistance can be ensured even under severe hot press conditions.

  The fibril diameter of the polyvinylidene fluoride resin is preferably in the range of 10 nm to 1000 nm from the viewpoint of cycle characteristics.

  The polyvinylidene fluoride resin preferably has a weight average molecular weight (Mw) in the range of 300,000 to 3,000,000. When the weight average molecular weight is 300,000 or more, mechanical properties that the adhesive porous layer can withstand the adhesion treatment with the electrode can be secured, and sufficient adhesion can be obtained. On the other hand, when the weight average molecular weight is 3 million or less, the viscosity at the time of molding does not become too high, the moldability and crystal formation are good, and the porosity is good. The weight average molecular weight is more preferably in the range of 300,000 to 2,000,000, still more preferably in the range of 500,000 to 1,500,000, and particularly preferably in the range of 600,000 to 1,000,000.

When the adhesive porous layer is impregnated with the electrolytic solution, the degree of swelling of the resin contained in the adhesive porous layer varies depending on the type of resin and the composition of the electrolytic solution. In order to suppress problems associated with resin swelling, it is preferable to select a polyvinylidene fluoride resin that does not easily swell. For example, a polyvinylidene fluoride-based resin containing a large amount of a copolymer component tends to swell, whereas a polyvinylidene fluoride-based resin containing 98 mol% or more of vinylidene fluoride is less likely to swell.
Polyvinylidene fluoride-based resins have a high cyclic carbonate content such as ethylene carbonate and propylene carbonate, and are likely to swell in electrolytes having a high dielectric constant. Polyvinylidene fluoride-based resins containing 98 mol% or more of vinylidene fluoride are It is suitable because it is relatively difficult to swell.

[Filler]
The adhesive porous layer may contain a filler made of an inorganic material or an organic material. When the adhesive porous layer contains a filler, the slipperiness and heat resistance of the separator are improved.
Examples of the inorganic filler include metal oxides such as alumina and metal hydroxides such as magnesium hydroxide. Moreover, as an organic filler, an acrylic resin etc. are mentioned, for example.

~ Various characteristics of separator ~
The separator for a nonaqueous electrolyte battery of the present invention preferably has a total film thickness of 5 μm to 35 μm from the viewpoint of mechanical strength and energy density when used as a battery.

  The porosity of the separator for a nonaqueous electrolyte battery of the present invention is preferably 30% to 60% from the viewpoints of mechanical strength, handling properties, and ion permeability.

The Gurley value (JIS P8117) of the separator for a nonaqueous electrolyte battery of the present invention is preferably 50 seconds / 100 cc to 800 seconds / 100 cc from the viewpoint of a good balance between mechanical strength and membrane resistance.
The separator for a nonaqueous electrolyte battery of the present invention has a difference between the Gurley value of the porous substrate and the Gurley value of the separator provided with the adhesive porous layer on the porous substrate from the viewpoint of ion permeability. 300 seconds / 100 cc or less, more preferably 150 seconds / 100 cc or less, and even more preferably 100 seconds / 100 cc or less.

Membrane resistance of the separator for a nonaqueous electrolyte battery of the present invention, from the viewpoint of the load characteristics of the ^battery, it is preferable that ^{1ohm · cm 2 ~10ohm · cm 2} . Here, the membrane resistance is a resistance value when the separator is impregnated with an electrolytic solution, and is measured by an alternating current method. Of course, the type of the electrolyte varies depending on the temperature, the above figures are 1M LiBF 4 as an electrolytic solution _- using a propylene carbonate / ethylene carbonate (mass ratio 1/1), is a value measured at 20 ° C..

  The curvature of the separator for a nonaqueous electrolyte battery of the present invention is preferably 1.5 to 2.5 from the viewpoint of ion permeability.

~ Manufacturing method of separator ~
The separator for a non-aqueous electrolyte battery of the present invention is formed by, for example, applying a coating liquid containing a polyvinylidene fluoride resin (PVdF) onto a porous substrate to form a coating layer, and forming the coating layer By solidifying the PVdF, it is suitably produced by a method of integrally forming an adhesive porous layer on a porous substrate.

The adhesive porous layer using the polyvinylidene fluoride resin as the adhesive resin can be suitably formed by, for example, the following wet coating method.
In the wet coating method, a polyvinylidene fluoride resin is dissolved in an appropriate solvent to prepare a coating solution, and this coating solution is applied to a porous substrate and then immersed in an appropriate coagulation solution. This is a film-forming method in which a polyvinylidene fluoride resin is solidified while inducing phase separation, washed with water and dried to form a porous layer on a porous substrate. The details of the wet coating method suitable for the present invention are as follows.

Solvents (hereinafter also referred to as “good solvents”) for dissolving the polyvinylidene fluoride resin used for preparing the coating liquid include polar amide solvents such as N-methylpyrrolidone, dimethylacetamide, dimethylformamide, and dimethylformamide. Preferably used.
From the viewpoint of forming a good porous structure, it is preferable to mix a phase separation agent that induces phase separation in addition to a good solvent. Examples of the phase separation agent include water, methanol, ethanol, propyl alcohol, butyl alcohol, butanediol, ethylene glycol, propylene glycol, and tripropylene glycol. The phase separation agent is preferably added in a range that can ensure a viscosity suitable for coating.
The solvent is preferably a mixed solvent containing 60% by mass or more of a good solvent and 40% by mass or less of a phase separation agent from the viewpoint of forming a good porous structure.

The coating liquid preferably contains a polyvinylidene fluoride resin at a concentration of 3% by mass to 10% by mass from the viewpoint of forming a good porous structure.
What is necessary is just to mix or dissolve in a coating liquid, when making an adhesive porous layer contain a filler and another component.

  The coagulating liquid is generally composed of a good solvent used for preparing the coating liquid, a phase separation agent, and water. It is preferable in production that the mixing ratio of the good solvent and the phase separation agent is adjusted to the mixing ratio of the mixed solvent used for dissolving the polyvinylidene fluoride resin. It is appropriate that the water concentration is 40% by mass to 90% by mass from the viewpoint of formation of a porous structure and productivity.

  The coating liquid may be applied to the porous substrate by a conventional coating method such as a Meyer bar, a die coater, a reverse roll coater, or a gravure coater. In the case where the adhesive porous layer is formed on both surfaces of the porous substrate, it is preferable from the viewpoint of productivity to apply the coating liquid to both surfaces simultaneously on both surfaces.

The adhesive porous layer may be manufactured by a dry coating method in addition to the wet coating method described above.
The dry coating method refers to, for example, coating a porous substrate with a coating solution containing a polyvinylidene fluoride resin and a solvent, drying the coating layer, and removing the solvent by volatilization to obtain a porous layer. Is the method. However, in the dry coating method, the coating layer tends to be denser and the moisture content tends to be remarkably reduced as compared with the wet coating method. Therefore, a wet coating method is preferable because a good porous structure can be obtained and the moisture content can be easily adjusted within a predetermined range.

  After coating, in order to adjust the moisture content of the separator to a range of preferably 1000 ppm or less (preferably 10 ppm or more), it is preferable to provide a drying step capable of evaporating and removing moisture as described above.

  The separator for a non-aqueous electrolyte battery of the present invention is produced by a method in which an adhesive porous layer is produced as an independent sheet, and this adhesive porous layer is laminated on a porous substrate and combined by thermocompression bonding or an adhesive. Can also be manufactured. As a method for producing the adhesive porous layer as an independent sheet, a coating liquid containing a resin is applied onto a release sheet, and the above-mentioned wet coating method or dry coating method is applied to form the adhesive porous layer. The method of forming and peeling an adhesive porous layer from a peeling sheet is mentioned.

<Nonaqueous electrolyte battery>
The non-aqueous electrolyte battery of the present invention is a non-aqueous electrolyte battery that obtains an electromotive force by doping or dedoping lithium, and includes a positive electrode, a negative electrode, and the separator for a non-aqueous electrolyte battery of the present invention described above. Has been. The dope means occlusion, support, adsorption, or insertion, and means a phenomenon in which lithium ions enter the active material of an electrode such as a positive electrode.

  A non-aqueous electrolyte battery has a structure in which a battery element in which a negative electrode and a positive electrode face each other with a separator interposed therebetween is impregnated with an electrolytic solution. The nonaqueous electrolyte battery of the present invention is suitable for a nonaqueous electrolyte secondary battery, particularly a lithium ion secondary battery.

  The nonaqueous electrolyte battery of the present invention is provided with the above-described separator for nonaqueous electrolyte batteries of the present invention as a separator, so that the adhesiveness between the electrode and the separator is excellent, and the yield in the manufacturing process is high. It also has excellent retention. Therefore, the nonaqueous electrolyte battery of the present invention exhibits stable cycle characteristics.

The positive electrode can have a structure in which an active material layer containing a positive electrode active material and a binder resin is formed on a current collector. The active material layer may further contain a conductive additive.
Examples of the positive electrode active material include lithium-containing transition metal oxides. Specifically, LiCoO ₂ , LiNiO ₂ , LiMn _1/2 Ni _1/2 O ₂ , LiCo _1/3 Mn _1/3 Ni _{1 / 3 O 2, LiMn 2 O 4} , LiFePO 4, LiCo 1/2 Ni 1/2 O 2, LiAl 1/4 Ni 3/4 O 2 and the like.
Examples of the binder resin include a polyvinylidene fluoride resin and a styrene-butadiene copolymer.
Examples of the conductive aid include carbon materials such as acetylene black, ketjen black, and graphite powder.
Examples of the current collector include aluminum foil, titanium foil, and stainless steel foil having a thickness of 5 μm to 20 μm.

In the non-aqueous electrolyte battery of the present invention, when the separator includes an adhesive porous layer containing a polyvinylidene fluoride resin, and the adhesive porous layer is disposed on the positive electrode side, the polyvinylidene fluoride resin has oxidation resistance. Since it is excellent, it is easy to apply positive electrode active materials such as LiMn _1/2 Ni _1/2 O ₂ and LiCo _1/3 Mn _1/3 Ni _1/3 O ₂ that can be operated at a high voltage of 4.2 V or more. is there.

The negative electrode may have a structure in which an active material layer including a negative electrode active material and a binder resin is formed on a current collector. The active material layer may further contain a conductive additive.
Examples of the negative electrode active material include materials that can occlude lithium electrochemically, and specifically include carbon materials, silicon, tin, aluminum, wood alloys, and the like.
Examples of the binder resin include a polyvinylidene fluoride resin and a styrene-butadiene copolymer.
Examples of the conductive aid include carbon materials such as acetylene black, ketjen black, and graphite powder.
Examples of the current collector include copper foil, nickel foil, and stainless steel foil having a thickness of 5 to 20 μm.
Moreover, it may replace with said negative electrode and may use metal lithium foil as a negative electrode.

The electrolytic solution is a solution in which a lithium salt is dissolved in a non-aqueous solvent.
Examples of the lithium salt include LiPF ₆ , LiBF ₄ , LiClO _{4, and the} like.
Examples of the non-aqueous solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate, fluoroethylene carbonate, and difluoroethylene carbonate; chain carbonates such as dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and fluorine-substituted products thereof; γ-butyrolactone , Cyclic esters such as γ-valerolactone; and these may be used alone or in combination.
As the electrolytic solution, a solution in which a cyclic carbonate and a chain carbonate are mixed at a mass ratio (cyclic carbonate / chain carbonate) of 20/80 to 40/60 and a lithium salt is dissolved in an amount of 0.5 M to 1.5 M is preferable. is there.

Examples of the exterior material include a metal can and a pack made of an aluminum laminate film.
The shape of the battery includes a square shape, a cylindrical shape, a coin shape, and the like, but the nonaqueous electrolyte battery separator of the present invention is suitable for any shape.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist thereof. Unless otherwise specified, “part” is based on mass.

Example 1
-Production of separator-
As the polyvinylidene fluoride resin (PVdF), a vinylidene fluoride / hexafluoropropylene copolymer (= 98.9 / 1.1 [molar ratio]) and a weight average molecular weight: 1.8 million were prepared.
This polyvinylidene fluoride resin was dissolved in a mixed solvent of dimethylacetamide and tripropylene glycol (= 7/3 [mass ratio]) to a concentration of 5 mass% to prepare a coating solution. The obtained coating solution was applied on both sides of a polyethylene microporous film (thickness: 9 μm, Gurley value: 160 seconds / 100 cc, porosity: 43%) in an equal amount. Subsequently, this was immersed in a coagulation liquid at 40 ° C. (water / dimethylacetamide / tripropylene glycol = 57/30/13 [mass ratio]) and solidified.
Next, after washing with water, it was dried by allowing it to stand for 24 hours under environmental conditions of a temperature of 30 ° C. and a humidity of 10% RH. The PVdF weight at this time was 2 g / m ² .
As described above, a separator having an adhesive porous layer made of a polyvinylidene fluoride resin formed on both surfaces of a polyolefin microporous film was obtained.

  About the obtained separator, the moisture content was measured by trace moisture measuring device AQ-2200 (made by Hiranuma Sangyo Co., Ltd.). As a result, the moisture content of the separator was 100 ppm.

-Fabrication of non-aqueous electrolyte battery-
(1) Production of negative electrode 300 g of artificial graphite as a negative electrode active material, 7.5 g of a water-soluble dispersion containing 40% by mass of a modified styrene-butadiene copolymer as a binder, 3 g of carboxymethyl cellulose as a thickener, and An appropriate amount of water was stirred with a double-arm mixer to prepare a slurry for negative electrode. This negative electrode slurry was applied to a 10 μm thick copper foil as a negative electrode current collector, dried and pressed to obtain a negative electrode having a negative electrode active material layer.

(2) Production of positive electrode 89.5 g of lithium cobaltate powder as a positive electrode active material, 4.5 g of acetylene black as a conductive auxiliary agent, and 6 g of polyvinylidene fluoride as a binder, the concentration of polyvinylidene fluoride is 6% by mass. Thus, it melt | dissolved in N-methyl- pyrrolidone (NMP), and it stirred with the double arm type mixer, and produced the slurry for positive electrodes. This positive electrode slurry was applied to a 20 μm thick aluminum foil as a positive electrode current collector, dried and pressed to obtain a positive electrode having a positive electrode active material layer.

(3) Preparation of battery After welding a lead tab to the positive electrode and the negative electrode, the positive electrode, the separator, and the negative electrode were overlapped and joined in this order, soaked with an electrolyte solution, and sealed in an aluminum pack using a vacuum sealer. As the electrolytic solution, a 1M LiPF ₆ mixed solution in which ethylene carbonate (EC) and ethyl methyl carbonate (DMC) were mixed at a mass ratio of 3: 7 (= EC: DMC) was used.
A test battery (lithium ion secondary battery) is manufactured by applying a load of 20 kg per 1 cm ² of electrode to the aluminum pack in which the electrolytic solution is sealed, and performing hot pressing at 90 ° C. for 2 minutes. did.

-Evaluation-
A. Adhesiveness The test battery is disassembled, and the negative electrode and the positive electrode are separated from the separator in a direction of 90 degrees with respect to the surface direction of the separator at a speed of 20 mm / min using a tensile tester (manufactured by A & D, RTC-1225A). A peeling test was performed by a method of pulling and peeling.
As a result, the separator and the electrode active material were peeled at the interface between the electrode active material and the current collector while being in close contact with each other, and showed good adhesion.

B. Cycle characteristics The capacity retention rate when charging / discharging was repeated for the prepared test battery at a charge voltage of 4.2 V and a discharge voltage of 2.75 V, and the discharge capacity at the 100th cycle was divided by the initial capacity. Was used as an index for evaluating the cycle characteristics.
As a result, the capacity retention was 95%. The test batteries of the examples achieved a capacity retention of 85% or more and exhibited good cycle characteristics.

Claims (2)

  A separator for a nonaqueous electrolyte battery having a porous substrate and an adhesive porous layer provided on one or both surfaces of the porous substrate and containing a polyvinylidene fluoride resin, and having a moisture content of 1000 ppm or less. A nonaqueous electrolyte battery comprising a positive electrode, a negative electrode, and a separator for a nonaqueous electrolyte battery according to claim 1 disposed between the positive electrode and the negative electrode, and obtaining an electromotive force by doping or dedoping lithium.