KR20170131404A - Composition for functional layer of non-aqueous secondary battery and production method thereof, functional layer for non-aqueous secondary battery and non-aqueous secondary battery - Google Patents

Abstract

An object of the present invention is to provide a composition for a functional layer of a nonaqueous secondary battery capable of forming a functional layer for a nonaqueous secondary battery capable of exhibiting excellent peel strength and protective function and exhibiting excellent low temperature output characteristics in the secondary battery . The non-aqueous secondary battery functional layer composition of the present invention comprises non-conductive particles and a binder, wherein the non-conductive particles have a density of 4 to 7 g / cm 3 and a volume average particle diameter of 0.5 to 1.0 탆, And non-conductive inorganic particles B having a density of 4 to 7 g / cm < 3 >, wherein the ratio of the non-conductive inorganic particles A in the mixture is 50 to 90 mass%, and the volume average particle diameter of the non- The ratio of the volume average particle diameter of the non-conductive inorganic particles B to the non-conductive inorganic particles B is 0.05 to 0.6 times.

Description

Composition for functional layer of non-aqueous secondary battery and production method thereof, functional layer for non-aqueous secondary battery and non-aqueous secondary battery

The present invention relates to a composition for a non-aqueous secondary battery functional layer, a functional layer for a non-aqueous secondary battery, and a method for preparing a composition for a non-aqueous secondary battery and a non-aqueous secondary battery functional layer.

(Hereinafter sometimes simply referred to as " secondary battery "), such as a lithium ion secondary battery, is small and light in weight, has high energy density and is capable of repeated charge / discharge, It is widely used. The non-aqueous secondary battery generally includes a positive electrode, a negative electrode, and a battery member such as a separator that isolates the positive electrode from the negative electrode to prevent a short circuit between the positive electrode and the negative electrode.

Here, in the secondary battery, a battery member having a functional layer for imparting a desired performance (for example, heat resistance, strength, etc.) to the battery member is used. Specifically, for example, an electrode formed by forming a functional layer on a separator formed by forming a functional layer on a separator substrate and an electrode substrate formed by forming an electrode composite layer on the current collector is used as a battery member. As a functional layer capable of improving the heat resistance and strength of the battery member, a functional layer made of a porous film layer formed by binding non-conductive particles with a binder (binder) is used.

In recent years, a functional layer has been actively developed for the purpose of improving the performance of a single layer of a secondary battery (see, for example, Patent Document 1).

Specifically, for example, Patent Document 1 discloses a functional layer capable of providing a separator superior in thermal stability, thermal dimensional stability, stiffness and the like in addition to heat resistance, and has a particle diameter in the range of 0.01 to 0.05 탆 and a range of 0.1 to 1.0 탆 Heat-resistant porous layer formed by using an inorganic filler (non-conductive particle) having at least one maximum value of the particle size distribution and a slurry composition containing a heat-resistant resin (binder).

Patent Document 1: JP-A-2010-123383

However, in the functional layer formed of the heat-resistant porous layer formed using the conventional slurry composition, the fill strength is not sufficient and the gelling value (durability) is high (that is, the ion conductivity is low) There is a problem that the output characteristic is lowered.

Further, in recent years, it has been required to thin the functional layer from the viewpoint of higher capacity of a single layer of the secondary battery. Therefore, there has been room for improvement in that the functional layer made of the heat-resistant porous layer formed using the above-described conventional slurry composition has a protective function such as heat resistance and strength imparted to the battery member while further thinning the functional layer .

It is therefore an object of the present invention to provide a composition for a non-aqueous secondary battery functional layer capable of forming a functional layer for a non-aqueous secondary battery capable of exhibiting excellent peel strength and protective function and exhibiting excellent low- .

Another object of the present invention is to provide a functional layer for a non-aqueous secondary battery, which has excellent peel strength and protective function, and is capable of exhibiting excellent low temperature output characteristics in a secondary battery.

It is another object of the present invention to provide a non-aqueous secondary battery having excellent battery characteristics such as low-temperature output characteristics.

The present inventors have conducted intensive studies for the purpose of solving the above problems. The inventors of the present invention have found that when a non-conductive inorganic particle A having a predetermined density and volume average particle diameter as a non-conductive particle used for forming a functional layer and a non-conductive inorganic particle B having a predetermined density are used in combination at a predetermined ratio, Also, by setting the ratio of the volume average particle diameter of the non-conductive inorganic particles B to the volume average particle diameter of the non-conductive inorganic particles A within a predetermined range, the polymer particles having excellent peel strength and protective function and exhibiting excellent low- Based secondary battery capable of forming a functional layer for a non-aqueous secondary battery.

That is, the object of the present invention is to solve the above problems advantageously, and the composition for a nonaqueous secondary battery functional layer of the present invention is a composition for a nonaqueous secondary battery functional layer comprising nonconductive particles and a binder, Wherein the particles have a density of not less than 4 g / cm 3 and not more than 7 g / cm 3 and a volume average particle diameter of not less than 0.5 탆 and not more than 1.0 탆 and a non-conductive inorganic particle A having a density of not less than 4 g / cm 3 and not more than 7 g / cm 3, Conductive inorganic particles B smaller than the non-conductive inorganic particles A, wherein the ratio of the non-conductive inorganic particles A in the mixture is 50% by mass or more and 90% by mass or less, and the non-conductive inorganic particles A Wherein the ratio of the volume average particle diameter of the non-conductive inorganic particles B to the volume average particle diameter of the non-conductive inorganic particles B is 0.05 times or more and 0.6 times or less. When the non-conductive inorganic particle A having a predetermined density and volume average particle diameter and the non-conductive inorganic particle B having a predetermined density are used in combination at a predetermined ratio and the non-conductive inorganic particles A having the predetermined density and the volume- When the ratio of the volume average particle size of the inorganic particles B is within a predetermined range, a functional layer for a non-aqueous secondary battery capable of exhibiting excellent peel strength and protective function and exhibiting excellent low temperature output characteristics can be formed A composition for a non-aqueous secondary battery functional layer is obtained.

In the present invention, the " density of non-conductive inorganic particles " refers to the true density measured at 25 캜 using a gas phase substitution method. In the present invention, the "volume average particle diameter of the non-conductive inorganic particles" means a volume average particle diameter of the non-conductive inorganic particles of 50% or more calculated from the small diameter side in the particle diameter distribution (volume basis) measured by dynamic light scattering method, according to JIS Z8828. (D50). ≪ / RTI >

The non-aqueous secondary battery functional layer composition of the present invention preferably contains the binder in an amount of 1 part by mass or more and 20 parts by mass or less per 100 parts by mass of the non-conductive particles. When the content of the binder per 100 parts by mass of the non-conductive particles is 1 part by mass or more and 20 parts by mass or less, the peel strength of the functional layer for a non-aqueous secondary battery can be further increased, and the non-aqueous secondary battery using the functional layer for non- The low temperature output characteristic can be further improved.

In the composition for a non-aqueous secondary battery functional layer of the present invention, the volume average particle diameter of the non-conductive inorganic particles B is preferably 0.05 탆 or more and less than 0.3 탆. When the volume average particle diameter of the non-conductive inorganic particles B is 0.05 탆 or more and less than 0.3 탆, the fill strength and the protective function of the functional layer for a non-aqueous secondary battery can be further enhanced.

Further, the composition for a nonaqueous secondary battery functional layer of the present invention preferably further contains a polyacrylamide. When polyacrylamide is contained, the coating property of the composition for a non-aqueous secondary battery functional layer can be improved, and an excellent high temperature cycle characteristic can be exhibited in a secondary battery having a functional layer for a non-aqueous secondary battery.

It is another object of the present invention to solve the above problems advantageously, and the functional layer for a nonaqueous secondary battery of the present invention is formed using any one of the above-mentioned compositions for a nonaqueous secondary battery functional layer. As described above, by using the composition for a non-aqueous secondary battery functional layer of the present invention, it is possible to form a functional layer for a non-aqueous secondary battery capable of exhibiting excellent peel strength and protective function and exhibiting excellent low-temperature output characteristics in a secondary battery .

Here, the functional layer for a non-aqueous secondary battery of the present invention preferably has a thickness of 0.5 탆 or more and 2 탆 or less. When the thickness of the functional layer for a non-aqueous secondary battery is 0.5 m or more and 2 m or less, the functional layer for a non-aqueous secondary battery can be sufficiently thinned to further enhance the protection function and exhibit excellent low temperature output characteristics for the secondary battery.

In the present invention, the "thickness of the functional layer for a non-aqueous secondary battery" refers to an average value of the thicknesses of the layers measured at arbitrary 10 points in the functional layer for a non-aqueous secondary battery.

The functional layer for a nonaqueous secondary battery of the present invention preferably has a density of 2.0 g / cm3 or more and 3.0 g / cm3 or less. When the density of the functional layer for a non-aqueous secondary battery is 2.0 g / cm3 or more and 3.0 g / cm3 or less, the protective function can be further enhanced and the secondary battery can exhibit excellent low temperature output characteristics.

In the present invention, the " density of functional layer for non-aqueous secondary battery " can be obtained by dividing the mass of the functional layer for non-aqueous secondary battery per unit area by the thickness of the functional layer for non-aqueous secondary battery.

In addition, the present invention aims to solve the above problems advantageously, and the non-aqueous secondary battery of the present invention is characterized by comprising any one of the above-described functional layers for a non-aqueous secondary battery. Thus, when the functional layer for a non-aqueous secondary battery of the present invention is used, a non-aqueous secondary battery having excellent battery characteristics such as low temperature output characteristics can be obtained.

The present invention also aims at solving the above problems in an advantageous manner, and a method for producing a composition for a non-aqueous secondary battery functional layer of the present invention is a method for producing a composition for a non-aqueous secondary battery functional layer comprising non-conductive particles and a binder A non-conductive inorganic particle A having a density of not less than 4 g / cm 3 and not more than 7 g / cm 3 and having a volume average particle diameter of not less than 0.5 탆 and not more than 1.0 탆 and a non-conductive inorganic particle A having a density of not less than 4 g / cm 3 and not more than 7 g / Conductive inorganic particle B smaller than the non-conductive inorganic particle A and a non-conductive inorganic particle B in which the ratio of the non-conductive inorganic particle A to the total of the non-conductive inorganic particle A and the non-conductive inorganic particle B is 50 mass% %, Wherein the ratio of the volume average particle diameter of the non-conductive inorganic particle B to the volume average particle diameter of the non-conductive inorganic particle A is 0.05 times Phase is characterized in that not more than 0.6 times. Thus, when the predetermined non-conductive inorganic particles A, the predetermined non-conductive inorganic particles B, and the binder are mixed at a predetermined ratio, they have excellent peel strength and protection function, and exhibit excellent low-temperature output characteristics for the secondary battery A composition for a non-aqueous secondary battery functional layer capable of forming a functional layer for a non-aqueous secondary battery is obtained.

According to the present invention, it is possible to provide a non-aqueous secondary battery functional layer composition capable of forming a functional layer for a non-aqueous secondary battery capable of exhibiting excellent peel strength and protective function and exhibiting excellent low-temperature output characteristics in a secondary battery .

Further, according to the present invention, it is possible to provide a functional layer for a non-aqueous secondary battery capable of exhibiting excellent peel strength and protective function and exhibiting excellent low-temperature output characteristics in a secondary battery.

Further, according to the present invention, it is possible to provide a non-aqueous secondary battery having excellent battery characteristics such as low-temperature output characteristics.

Hereinafter, embodiments of the present invention will be described in detail.

Here, the composition for a non-aqueous secondary battery functional layer of the present invention can be produced, for example, by the method for producing a composition for a non-aqueous secondary battery functional layer of the present invention, Is used as the material of the time. The functional layer for a nonaqueous secondary battery of the present invention is formed using the composition for a nonaqueous secondary battery functional layer of the present invention. In addition, the non-aqueous secondary battery of the present invention includes at least the functional layer for a non-aqueous secondary battery of the present invention.

(Composition for non-aqueous secondary battery functional layer)

The composition for a nonaqueous secondary battery functional layer of the present invention contains non-conductive particles and a binder, and optionally further contains an additive and the like. The non-aqueous secondary battery functional layer composition of the present invention may be a slurry composition comprising water or the like as a dispersion medium. The non-aqueous secondary battery functional layer composition of the present invention is characterized in that the non-conductive particles A have a density of not less than 4 g / cm 3 and not more than 7 g / cm 3 and a volume average particle diameter of not less than 0.5 탆 and not more than 1.0 탆, / Cm < 3 > to 7 g / cm < 3 >, and non-conductive inorganic particles B having a volume average particle diameter smaller than that of the non-conductive inorganic particles A are mixed. The non-aqueous secondary battery functional layer composition of the present invention is characterized in that the ratio of the non-conductive inorganic particles A in the mixture is 50% by mass or more and 90% by mass or less. The nonaqueous secondary battery functional layer composition of the present invention is characterized in that the ratio of the volume average particle diameter of the non-conductive inorganic particles B to the volume average particle diameter of the non-conductive inorganic particles A is 0.05 times or more and 0.6 times or less.

The non-aqueous secondary battery functional layer composition of the present invention is a non-aqueous secondary battery functional layer composition comprising a non-conductive inorganic particle A having a predetermined density and a volume average particle diameter and a non-conductive inorganic particle B having a predetermined density at a predetermined ratio, Since the ratio of the volume average particle diameter of the non-conductive inorganic particles B to the volume average particle diameter of the inorganic particles A is within a predetermined range, the functional layer formed using the composition for the functional layer exhibits excellent peel strength and protective function And at the same time, excellent secondary battery characteristics can be exhibited.

<Non-conductive particle>

Here, the non-conductive particles contained in the composition for a non-aqueous secondary battery functional layer of the present invention include a mixture of a non-conductive inorganic particle A and a non-conductive inorganic particle B having a volume average particle diameter smaller than that of the non-conductive inorganic particle A . Since the composition for the functional layer contains the non-conductive inorganic particle A and the non-conductive inorganic particle B having a volume-average particle diameter smaller than that of the non-conductive inorganic particle A as non-conductive particles, the non-conductive inorganic particle A and non- The density of the functional layer to be formed can be increased by arranging the charged inorganic particles B in high density. Therefore, even when the functional layer is thinned to 2 탆 or less, for example, it is possible to secure the function of protecting the functional layer (a function of imparting heat resistance and strength to the battery member in which the functional layer is formed).

The composition for a non-aqueous secondary battery functional layer of the present invention may contain known non-conductive inorganic particles other than known non-conductive organic particles, non-conductive inorganic particles A and non-conductive inorganic particles B, as long as the effects of the present invention are not impaired significantly. Conductive particles, it is preferable that the non-conductive particles consist of only a mixture of the non-conductive inorganic particles A and the non-conductive inorganic particles B. [ The mixing of the non-conductive inorganic particle A and the non-conductive inorganic particle B may be performed before mixing the non-conductive inorganic particle A and the non-conductive inorganic particle B with the binder or optional additives to prepare the functional layer composition, May be mixed with an additive to prepare a composition for a functional layer.

[Non-conductive inorganic particle A]

Here, the non-conductive inorganic particle A is preferably a particle made of an inorganic material that stably exists under the use environment of the non-aqueous secondary battery and is electrochemically stable. In this respect, preferred examples of the non-conductive inorganic particle A include aluminum oxide (alumina), hydrate of aluminum oxide (boehmite (AlOOH), gibbsite (Al (OH) ₃ ), silicon oxide, magnesium oxide (magnesia) hydroxide, magnesium, calcium, titanium oxide (titania), barium titanate (BaTiO _3), ZrO, alumina oxide-silica composite oxide, such as oxide particles; aluminum nitride, nitride particles such as boron nitride; covalent bond of silicon and diamonds, and sex Fine particles of clay such as talc, montmorillonite, etc. Among them, the non-conductive inorganic particles A are preferably barium sulfate particles and barium titanate particles. , And barium sulfate particles are more preferable. These particles may be subjected to element substitution, surface treatment, solidification or the like as necessary.

-density-

The density of the non-conductive inorganic particles A is required to be 4 g / cm 3 or more and 7 g / cm 3 or less, preferably 4.05 g / cm 3 or more, more preferably 4.10 g / cm 3 or more, More preferably 6.0 g / cm 3 or less, and still more preferably 5.0 g / cm 3 or less. When the density of the non-conductive inorganic particle A is 4 g / cm3 or more, the density of the functional layer can be increased and the protective function of the functional layer can be sufficiently improved. When the density of the non-conductive inorganic particle A is 7 g / cm 3 or less, the protective layer of the functional layer can be sufficiently improved by increasing the dispersibility and the coatability of the composition for the functional layer, and the functional layer formed using the composition for the functional layer The lowering of the low-temperature output characteristics of the secondary battery can be suppressed.

- Volume average particle size -

The volume average particle diameter of the non-conductive inorganic particles A is larger than the volume average particle diameter of the non-conductive inorganic particles B. The volume average particle diameter of the non-conductive inorganic particle A is required to be 0.5 mu m or more and 1.0 mu m or less, preferably 0.55 mu m or more, more preferably 0.6 mu m or more, and preferably 0.9 mu m or less, Do. When the volume average particle diameter of the non-conductive inorganic particles A is 0.5 탆 or more, it is possible to suppress the increase in the gully value of the functional layer (i.e., decrease in ion conductivity), thereby exhibiting excellent low- . When the volume average particle diameter of the non-conductive inorganic particle A is 1.0 탆 or less, the functional layer can be thinned and the density of the functional layer is increased by arranging the non-conductive inorganic particles A in the functional layer at a high density , The protective function of the functional layer can be ensured even when the functional layer is thinned.

- Particle size distribution -

The non-conductive inorganic particle A is not particularly limited, and it is preferable that the particle size distribution on the volume basis measured by the dynamic light scattering method has only one peak or shoulder, more preferably a normal distribution. The peak or shoulder is preferably in the range of 0.5 占 퐉 or more, more preferably in the range of 0.55 占 퐉 or more, more preferably in the range of 0.6 占 퐉 or more, and 1.0 占 퐉 or less More preferably in the range of 0.9 탆 or less, and more preferably in the range of 0.8 탆 or less.

-content-

The ratio of the non-conductive inorganic particles A in the mixture (100 mass%) obtained by mixing the non-conductive inorganic particles A and the non-conductive inorganic particles B is required to be 50 mass% or more and 90 mass% or less, preferably 55 mass% or more , More preferably 60 mass% or more, and most preferably 85 mass% or less, and more preferably 80 mass% or less. When the ratio of the non-conductive inorganic particles A in the mixture is 50% by mass or more, the ratio of the non-conductive inorganic particles B having a small volume average particle diameter becomes too large, and the gelled value of the functional layer increases (that is, the ion conductivity decreases) The secondary battery including the functional layer can exhibit excellent low-temperature output characteristics. When the ratio of the non-conductive inorganic particles A in the mixture is 50% by mass or more, the viscosity of the functional layer composition can be prevented from increasing, so that the density of the functional layer can be increased and the protective function of the functional layer can be sufficiently enhanced have. Further, since the aggregation of the non-conductive inorganic particles B can be suppressed, the functional layer becomes uniform and the peel strength of the functional layer becomes high. When the ratio of the non-conductive inorganic particles A in the mixture is 90% by mass or less, the proportion of the non-conductive inorganic particles A having a large volume average particle diameter becomes too large to prevent the function layer from becoming difficult to break, The non-conductive inorganic particles A and the non-conductive inorganic particles B are arranged in a high density, and the protective function of the functional layer can be sufficiently enhanced.

[Non-conductive inorganic particle B]

As the non-conductive inorganic particles B, particles made of the same inorganic material as the conductive inorganic particles A described above can be used. Among them, as the non-conductive inorganic particles B, barium sulfate particles and barium titanate particles are preferable, and barium sulfate particles are more preferable.

-density-

The density of the non-conductive inorganic particles B is required to be not less than 4 g / cm 3 and not more than 7 g / cm 3, preferably not less than 4.05 g / cm 3, more preferably not less than 4.10 g / cm 3 and not more than 6.5 g / More preferably 6.0 g / cm 3 or less, and still more preferably 5.0 g / cm 3 or less. When the density of the non-conductive inorganic particles B is 4 g / cm 3 or more, the density of the functional layer can be increased and the protective function of the functional layer can be sufficiently improved. When the density of the non-conductive inorganic particle B is 7 g / cm 3 or less, the protective layer of the functional layer can be sufficiently improved by increasing the dispersibility and the coatability of the composition for the functional layer, and the functional layer formed using the composition for the functional layer It is possible to suppress deterioration of the low-temperature output characteristics of the secondary battery.

- Volume average particle size -

The volume average particle diameter of the non-conductive inorganic particles B is smaller than the volume average particle diameter of the non-conductive inorganic particles A. The volume average particle diameter of the non-conductive inorganic particles B is required to be not less than 0.05 times and not more than 0.6 times the volume average particle diameter of the non-conductive inorganic particles A, preferably 0.1 times or more, more preferably 0.2 times or more, More preferably 0.45 times or less. When the ratio of the volume average particle diameter of the non-conductive inorganic particles B to the volume average particle diameter of the non-conductive inorganic particles A is 0.05 or more when the above-described non-conductive inorganic particles A and non-conductive inorganic particles B are used together, It is possible to suppress an increase in the gully value of the layer (that is, decrease in the ion conductivity) and to exert excellent low-temperature output characteristics in the secondary battery having the functional layer. When the ratio of the volume average particle diameter of the non-conductive inorganic particles B to the volume average particle diameter of the non-conductive inorganic particles A is 0.05 or more, the decrease in the dispersibility of the composition for the functional layer can be suppressed, It is possible to suppress the decrease in the peel strength of the functional layer formed by using the composition. When the ratio of the volume average particle diameter of the non-conductive inorganic particles B to the volume average particle diameter of the non-conductive inorganic particles A is 0.6 or less, it is possible to make the functional layer thinner and, at the same time, A and the non-conductive inorganic particles B are arranged in a high density, the protective function of the functional layer can be sufficiently enhanced. Accordingly, when the ratio of the volume average particle diameter of the non-conductive inorganic particles B to the volume average particle diameter of the non-conductive inorganic particles A falls within the above-mentioned range, the functional layer can be densely moderately densified, , The decrease in the fill strength of the functional layer and the deterioration in the low-temperature output characteristics of the secondary battery can be suppressed.

The non-conductive inorganic particles B preferably have a volume-average particle diameter of 0.05 mu m or more, more preferably 0.05 mu m or more, more preferably 0.08 mu m or more, particularly preferably 0.1 mu m or more, , And more preferably 0.28 탆 or less. When the volume average particle diameter of the non-conductive inorganic particles B is 0.05 m or more, the decrease in the dispersibility of the composition for the functional layer can be suppressed, and the peel strength of the functional layer formed using the composition for the functional layer can be sufficiently increased. In addition, it is possible to suppress an increase in the gully value of the functional layer (i.e., decrease in ion conductivity), and to exert an excellent low-temperature output characteristic in the secondary battery having the functional layer. When the volume average particle diameter of the non-conductive inorganic particles B is less than 0.3 mu m, the functional layer can be thinned, and the non-conductive inorganic particles A and non-conductive inorganic particles B in the functional layer are arranged in a high density The function of the functional layer can be secured even when the density of the functional layer is increased and the functional layer is thinned.

- Particle size distribution -

The non-conductive inorganic particle B is not particularly limited, and it is preferable that the particle size distribution based on volume measured by the dynamic light scattering method has only one peak or shoulder, more preferably a normal distribution. The peak or shoulder is preferably in the range of 0.05 탆 or more, more preferably in the range of more than 0.05 탆, more preferably in the range of 0.08 탆 or more, and more preferably in the range of 0.1 탆 or more Particularly preferably in a range of less than 0.3 mu m, more preferably in a range of 0.28 mu m or less.

[Properties of the mixture]

The mixture of the non-conductive inorganic particles A and the non-conductive inorganic particles B described above is not particularly limited, and the density is usually 4 g / cm3 or more and 7 g / cm3 or less, preferably 4.05 g / Cm 2 or less, preferably 6.5 g / cm 3 or less, more preferably 6.0 g / cm 3 or less, and still more preferably 5.0 g / cm 3 or less.

The mixture is not particularly limited, and it is preferable that the particle size distribution on the volume basis measured by the dynamic light scattering method has two peaks or shoulders. When the particle size distribution of the mixture has two peaks or shoulders, the peak or shoulder on the small particle size side is mainly a peak or shoulder originating from the non-conductive inorganic particle B, and the peak or shoulder on the large- Is a peak or shoulder originating from the volatile inorganic particle A.

&Lt; Adhesive material &

The binder to be contained in the composition for a non-aqueous secondary battery functional layer of the present invention is not particularly limited, and a known binder, for example, a thermoplastic elastomer can be mentioned. As the thermoplastic elastomer, a conjugated diene-based polymer and an acrylic polymer are preferable, and an acrylic polymer is more preferable.

Here, the conjugated diene polymer refers to a polymer comprising a conjugated diene monomer unit. Specific examples of the conjugated diene polymer include, but are not limited to, copolymers containing aromatic vinyl monomer units such as styrene-butadiene copolymer (SBR) and aliphatic conjugated diene monomer units, butadiene rubber (BR), acrylic rubber (NBR ) (Copolymers containing acrylonitrile units and butadiene units), and hydrides thereof.

The acrylic polymer refers to a polymer containing a (meth) acrylic acid ester monomer unit. Examples of the (meth) acrylic acid ester monomer capable of forming the (meth) acrylic acid ester monomer unit include (meth) acrylate monomers such as methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, ) Acrylic acid alkyl ester can be used. In the present invention, (meth) acryl means acryl and / or methacryl.

These binder materials may be used alone or in combination of two or more.

The acrylic polymer preferably used as the binder is more preferably a (meth) acrylonitrile monomer unit. As a result, the strength of the functional layer can be increased. In the present invention, (meth) acrylonitrile means acrylonitrile and / or methacrylonitrile.

[Glass transition temperature]

The glass transition temperature of the polymer used as the binder is preferably 50 占 폚 or lower, more preferably 0 占 폚 or lower, and still more preferably -10 占 폚 or lower. When the glass transition temperature of the polymer is 50 DEG C or lower, sufficiently high adhesiveness is exerted, the component contained in the functional layer is sufficiently prevented from falling off from the functional layer, and the peel strength of the functional layer can be sufficiently increased. The glass transition temperature of the polymer used as the binder is usually -50 ° C or higher. The glass transition temperature of the polymer can be measured according to JIS K7121.

[Volume average particle diameter]

When the polymer used as the binder is a particulate polymer, the volume average particle diameter of the polymer is preferably 50 nm or more, more preferably 100 nm or more, more preferably 150 nm or more, and preferably 500 nm or less More preferably 450 nm or less, and further preferably 400 nm or less. When the volume average particle diameter of the binder is 50 nm or more, the dispersibility of the binder can be enhanced, and the binder material in the functional layer can be tightly packed to increase the gluing value of the functional layer, have. Further, by setting the volume average particle size of the binder to 500 nm or less, the fill strength of the functional layer can be increased.

[content]

The content of the binder in the composition for non-aqueous secondary battery functional layer is preferably 1 part by mass or more, more preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and 20 parts by mass or less per 100 parts by mass of non- More preferably 18 parts by mass or less, and even more preferably 10 parts by mass or less. By setting the content of the binder to be not less than 1 part by mass per 100 parts by mass of the non-conductive particles, it is possible to sufficiently prevent the non-conductive particles from falling off from the functional layer and to increase the peel strength of the functional layer. In addition, when the content of the binder is 20 parts by mass or less per 100 parts by mass of the non-conductive particles, deterioration of the ion conductivity of the functional layer is suppressed and deterioration of low temperature output characteristics of the secondary battery can be suppressed.

Examples of the method for producing the above-mentioned polymer which can be used as a binder include a solution polymerization method, a suspension polymerization method and an emulsion polymerization method. Among them, an emulsion polymerization method and a suspension polymerization method are preferable because an aqueous dispersion containing a particulate polymer can be used as it is as a material for a composition for a nonaqueous secondary battery functional layer as it is, which can be polymerized in water.

<Additives>

The composition for a non-aqueous secondary battery functional layer may contain any other components in addition to the above components. The other components are not particularly limited as long as they do not affect the cell reaction, and known ones can be used. These other components may be used singly or in combination of two or more.

Examples of the other components include known additives such as a dispersant, a viscosity adjuster, and a wetting agent.

[Dispersant]

The dispersing agent is not particularly limited, and sodium polycarboxylate or ammonium polycarboxylate can be used.

The amount of the dispersing agent used is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, more preferably 1.0 part by mass or more, and more preferably 4 parts by mass or less, per 100 parts by mass of the non- More preferably 3.5 parts by mass or less, and still more preferably 3.3 parts by mass or less. When the amount of the dispersing agent used is within the above range, the dispersibility and coatability of the composition for a functional layer can be sufficiently improved.

[Viscosity adjuster]

The viscosity adjuster is not particularly limited, and water-soluble polymers such as carboxymethyl cellulose and its salts, polyacrylic acid, and polyacrylamide can be used. Among them, polyacrylamide is preferable as the viscosity adjusting agent. When polyacrylamide is used as the viscosity adjusting agent, the coating property of the functional layer composition can be improved. In addition, when polyacrylamide is used as the viscosity adjusting agent, it is possible to reduce the residual moisture content of the functional layer and to improve the heat shrinkage resistance, and at the same time, it is possible to impart the ability to capture impurities such as halogen to the functional layer. It is possible to exhibit an excellent high temperature cycle characteristic in the secondary battery.

The amount of the viscosity adjusting agent to be used is preferably 0.1 part by mass or more per 100 parts by mass of non-conductive particles, more preferably 1 part by mass or more, more preferably 3 parts by mass or less, and more preferably 2.5 parts by mass or less Is more preferable. When the amount of the viscosity modifier is within the above range, the dispersibility and the coating property of the composition for a functional layer can be sufficiently improved, and the peel strength of the functional layer can be increased.

[Milking agent]

The wetting agent is not particularly limited, and a nonionic surfactant or an anionic surfactant can be used. Among them, it is preferable to use a nonionic surfactant such as an ethylene oxide-propylene oxide copolymer.

The amount of the wetting agent to be used is preferably 0.05 part by mass or more, more preferably 0.1 part by mass or more, more preferably 0.15 part by mass or more, and 2 parts by mass or less More preferably 1.5 parts by mass or less, and further preferably 1 part by mass or less. When the amount of the wetting agent is within the above range, the coating property of the functional layer composition can be sufficiently improved, and the low temperature output characteristics of the secondary battery having the functional layer formed using the functional layer composition can be sufficiently improved.

&Lt; Properties of non-aqueous secondary battery functional layer composition >

The composition for a nonaqueous secondary battery functional layer of the present invention preferably has a solid content concentration of 35 mass% or more, more preferably 40 mass% or more, more preferably 60 mass% or less, still more preferably 55 mass% And more preferably 50 mass% or less. When the solid content concentration of the composition for the functional layer is within the above range, the solid content concentration can be increased while securing the dispersibility of the non-conductive particles.

The composition for a nonaqueous secondary battery functional layer of the present invention preferably has a viscosity at a rotation number of 60 rpm of 10 mPa · s or more and 110 mPa · s or less and a viscosity at a rotation number of 6 rpm of 30 mPa · s or more and 120 mPa · s or less . When the viscosity of the composition for the functional layer is within the above range, the coating property of the composition for the functional layer can be sufficiently improved and the peel strength of the functional layer can be increased. In the present invention, the &quot; viscosity of the composition for a non-aqueous secondary battery functional layer &quot; can be measured by a B-type viscometer at a temperature of 25 캜.

(Method for producing composition for non-aqueous secondary battery functional layer)

The above-mentioned composition for a non-aqueous secondary battery functional layer of the present invention is not particularly limited and can be obtained by mixing the above-mentioned non-conductive particles, a binder and optional additives used in the presence of a dispersion medium such as water . Specifically, the composition for a non-aqueous secondary battery functional layer of the present invention comprises a non-conductive inorganic particle A having the above-described property, the non-conductive inorganic particle B having the above-described property, the above-mentioned binder, Wherein the ratio of the non-conductive inorganic particles A to the total of the total inorganic particles A and the non-conductive inorganic particles B is 50% by mass or more and 90% by mass or less. Can be obtained by the method.

Here, the mixing method of the above-mentioned components is not particularly limited, but in order to efficiently disperse the respective components, it is preferable to perform mixing using a dispersing machine as a mixing device. The dispersing device is preferably an apparatus capable of uniformly dispersing and mixing the components. Examples of the dispersing machine include a ball mill, a sand mill, a pigment dispersing machine, a brain ball, an ultrasonic dispersing machine, a homogenizer, and a planetary mixer.

The mixing order of the above-mentioned components is not particularly limited. For example, a mixture of the non-conductive inorganic particle A and the non-conductive inorganic particle B mixed in advance, the above-mentioned binder, and optional additives are mixed, The composition for the functional layer may be prepared by mixing together the non-conductive inorganic particles A, the non-conductive inorganic particles B, the above-mentioned binder and any of the optional additives. The non-conductive inorganic particles A and non- The functional inorganic layer particles B and some optional additives may be mixed together and then the above-mentioned binder and other additives may be added and further mixed to prepare the functional layer composition.

(Functional layer for non-aqueous secondary battery)

The functional layer for a nonaqueous secondary battery of the present invention is formed from the composition for a nonaqueous secondary battery functional layer described above. For example, the above-described composition for a functional layer is applied to the surface of an appropriate base material to form a coating film, Followed by drying.

Since the functional layer for a nonaqueous secondary battery of the present invention is formed by using the composition for a nonaqueous secondary battery functional layer described above, it is possible to exhibit excellent peel strength and a protective function, and also to provide a secondary battery having the functional layer The low temperature output characteristic can be exhibited.

<Description>

Here, the substrate to which the composition for a functional layer is applied is not limited. For example, a coating film of the composition for a functional layer is formed on the surface of the releasable substrate, the coating film is dried to form a functional layer, You can. Thus, the functional layer peeled off from the release-type substrate can be used as a self-sustaining film for forming the battery member of the secondary battery. Specifically, a separator having a functional layer may be formed by laminating a functional layer peeled from the releasable substrate on a separator substrate, or an electrode having a functional layer may be formed by laminating a functional layer, which is peeled off from the mold- .

However, from the viewpoint of omitting the step of peeling the functional layer and increasing the production efficiency of the battery member, it is preferable to use the separator base material or the electrode base material as the base material. The separator base material and the functional layer formed on the electrode base material can be suitably used as a protective layer for improving the heat resistance and strength of the separator and the electrode.

[Separator substrate]

The separator substrate is not particularly limited, but may be a known separator substrate such as an organic separator substrate. The organic separator base material is a porous member made of an organic material, and examples of the organic separator base material include a microporous film or nonwoven fabric including a polyolefin resin such as polyethylene and polypropylene, an aromatic polyamide resin, etc., A microporous membrane made of polyethylene or a nonwoven fabric is preferable. The thickness of the separator base material may be any thickness, and is preferably 5 占 퐉 or more and 30 占 퐉 or less, more preferably 5 占 퐉 or more and 20 占 퐉 or less, and still more preferably 5 占 퐉 or more and 18 占 퐉 or less. When the thickness of the separator base is 5 占 퐉 or more, sufficient safety is obtained. When the thickness of the separator base material is 30 占 퐉 or less, deterioration of the ion conductivity can be suppressed and deterioration of the low-temperature output characteristics of the secondary battery can be suppressed, and heat shrinkage of the separator base material can be prevented from increasing, .

[Electrode substrate]

The electrode base material (positive electrode base material and negative electrode base material) is not particularly limited, but an electrode base material having an electrode composite layer formed on the current collector may be mentioned.

Here, the current collector, the electrode active material (positive electrode active material, negative electrode active material) and the binder for the electrode composite layer (binder for positive electrode composite layer, binder for negative electrode composite layer) in the electrode composite layer and method for forming the electrode composite layer on the current collector For example, those described in Japanese Laid-Open Patent Publication No. 2013-145763 can be used.

&Lt; Method of forming functional layer for non-aqueous secondary battery >

Examples of a method for forming a functional layer on a substrate such as the above-described separator substrate, electrode substrate and the like include the following methods.

1) a method of applying the non-aqueous secondary battery functional layer composition of the present invention to the surface of a separator base or an electrode substrate (in the case of an electrode substrate, the surface of the electrode composite layer side, hereinafter the same);

2) a method of immersing the separator base or the electrode substrate in the composition for a non-aqueous secondary battery functional layer of the present invention, followed by drying thereof;

3) a method of applying the composition for a non-aqueous secondary battery functional layer of the present invention onto a release substrate, drying the functional layer, and transferring the obtained functional layer to the surface of the separator base or the electrode base;

Among them, the method 1) is particularly preferable because it is easy to control the layer thickness of the functional layer. The method 1) above specifically includes a step of applying a composition for a functional layer on a substrate (coating step), a step of drying a composition for a functional layer applied on a substrate to form a functional layer (a functional layer forming step) .

[Application step]

There is no particular limitation on the method of applying the functional layer composition on the substrate in the coating step. For example, a method such as a doctor blade method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, .

[Functional layer forming step]

In the functional layer forming step, a method for drying the composition for a functional layer on a substrate is not particularly limited, and a known method can be used. For example, a method of drying by a hot air, hot air, Or a drying method by irradiation with an electron beam or the like. The drying conditions are not particularly limited, but the drying temperature is preferably 50 to 150 占 폚, and the drying time is preferably 5 to 30 minutes.

&Lt; Thickness of functional layer &

The thickness of the functional layer formed by using the composition for a non-aqueous secondary battery functional layer of the present invention is preferably 0.5 μm or more and 2 μm or less, more preferably 0.5 μm or more and less than 2 μm, more preferably 0.5 μm or more and 1.5 μm or less More preferably 0.5 m or more and 1.2 m or less. When the thickness of the functional layer is 0.5 탆 or more, the protective function can be further enhanced, so that the heat resistance and strength of the battery member in which the functional layer is formed can be further improved. Further, when the thickness of the functional layer is 2 m or less, excellent low-temperature output characteristics can be exhibited in the secondary battery. Further, the capacity of the secondary battery can be increased by thinning the battery member having the functional layer formed thereon. The functional layer for a non-aqueous secondary battery of the present invention is formed by using a composition for a non-aqueous secondary battery functional layer comprising a mixture of non-conductive inorganic particles A and non-conductive inorganic particles B having the above- Therefore, even when the battery is thinned, the secondary battery can exhibit excellent low-temperature output characteristics while sufficiently securing the protection function.

<Density of functional layer>

The density of the functional layer formed using the composition for a nonaqueous secondary battery functional layer of the present invention is preferably 2.0 g / cm3 or more and 3.0 g / cm3 or less, more preferably 2.05 g / cm3 or more and 3.0 g / cm3 or less, , More preferably from 2.1 g / cm3 to 3.0 g / cm3. If the density of the functional layer is 2.0 g / cm3 or more, the protective function of the functional layer can be further enhanced, and the heat resistance and strength of the battery member having the functional layer can be further improved. Particularly, when the density of the functional layer is 2.0 g / cm3 or more, the protection function can be sufficiently secured even when the functional layer is thinned. When the density of the functional layer is 3.0 g / cm 3 or less, deterioration of ion conductivity of the functional layer is suppressed, and excellent low-temperature output characteristics can be exhibited in the secondary battery.

(A battery member having a functional layer)

The battery member (separator and electrode) provided with the functional layer of the present invention may be provided with a separator substrate or an electrode substrate and, in addition to the functional layer of the present invention, other than the functional layer of the present invention described above Or may be provided with components.

Here, the constituent elements other than the functional layer of the present invention are not particularly limited as long as they do not correspond to the functional layer of the present invention, and examples thereof include an adhesive layer formed on the functional layer of the present invention and used for bonding between the battery elements .

(Non-aqueous secondary battery)

The non-aqueous secondary battery of the present invention comprises the above-described functional layer for a non-aqueous secondary battery of the present invention. More specifically, the non-aqueous secondary battery of the present invention includes a positive electrode, a negative electrode, a separator, and an electrolytic solution. The functional layer for a non-aqueous secondary battery is included in at least one of a positive electrode, a negative electrode and a separator. Since the nonaqueous secondary battery of the present invention includes the functional layer obtained from the composition for a nonaqueous secondary battery functional layer of the present invention, it exhibits excellent battery characteristics (for example, low temperature output characteristics).

<Positive electrode, negative electrode and separator>

At least one of the positive electrode, the negative electrode and the separator used in the secondary battery of the present invention includes the functional layer of the present invention. Specifically, as the positive electrode and the negative electrode having a functional layer, an electrode formed by forming a functional layer of the present invention on an electrode substrate formed by forming an electrode composite layer on a current collector can be used. As the separator having a functional layer, a separator formed by forming the functional layer of the present invention on a separator substrate can be used. As the electrode base material and the separator base material, the same materials as those exemplified in the section "functional layer for non-aqueous secondary battery" can be used.

The positive electrode, negative electrode and separator not having a functional layer are not particularly limited, and an electrode made of the above-described electrode substrate and a separator made of the above-described separator base can be used.

<Electrolyte>

As the electrolytic solution, an organic electrolytic solution in which a supporting electrolyte is dissolved in an organic solvent is usually used. As the supporting electrolyte, for example, a lithium salt is used in a lithium ion secondary battery. 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 , and the like _{(CF 3 SO 2) 2 NLi} , (C 2 F 5 SO 2) NLi. Of these, LiPF ₆ , LiClO ₄ , and CF ₃ SO ₃ Li are preferred because they are easily soluble in solvents and exhibit a high degree of dissociation. The electrolyte may be used singly or in combination of two or more. Generally, the lithium ion conductivity tends to increase with the use of a supporting electrolyte having a high degree of dissociation, so that the lithium ion conductivity can be controlled depending on the type of the supporting electrolyte.

The organic solvent used in the electrolytic solution is not particularly limited as long as it can dissolve the supporting electrolyte. For example, in the lithium ion secondary battery, dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC) (PC), butylene carbonate (BC), and methyl ethyl carbonate (MEC); esters such as? -butyrolactone and methyl formate; Ethers such as 1,2-dimethoxyethane and tetrahydrofuran; Sulfur compounds such as sulfolane and dimethylsulfoxide, and the like are suitably used. A mixed solution of these solvents may also be used. Among them, carbonates are preferable because the dielectric constant is high and the stable potential region is wide. Generally, the lower the viscosity of the solvent used is, the higher the lithium ion conductivity tends to be, so that the lithium ion conductivity can be controlled depending on the type of the solvent.

Also, the concentration of the electrolyte in the electrolytic solution can be appropriately adjusted. A known additive may be added to the electrolytic solution.

(Production method of non-aqueous secondary battery)

The non-aqueous secondary battery of the present invention can be produced by, for example, stacking a positive electrode and a negative electrode with a separator interposed therebetween, inserting them into a battery container by winding or folding as necessary, can do. Also, at least one member of the positive electrode, the negative electrode, and the separator is used as the functional layer mounting member. In addition, an overcurrent prevention element such as expanded metal, a fuse, a PTC element, or the like, or a lead plate may be inserted into the battery container as necessary to prevent an increase in pressure inside the battery and overcharge discharge. The shape of the battery may be, for example, a coin shape, a button shape, a sheet shape, a cylindrical shape, a square shape, or a flat shape.

Example

Hereinafter, the present invention will be described concretely based on examples, but the present invention is not limited to these examples. In the following description, &quot;% &quot; and &quot; part &quot; representing amounts are on a mass basis unless otherwise specified.

Unless otherwise stated, the ratio of the structural units formed by polymerizing any of the monomers in the polymer produced by copolymerizing a plurality of monomers is not particularly limited as long as the total monomers used for the polymerization of the polymer (Input ratio) of the monomers occupied.

In Examples and Comparative Examples, the density and the volume average particle diameter of the non-conductive inorganic particles, the glass transition temperature and the volume average particle diameter of the binder, the viscosity of the composition for the functional layer, the thickness of the functional layer, the density and the peel strength, The low-temperature output characteristics of the secondary battery were measured and evaluated by the following method.

&Lt; Density of non-conductive inorganic particles &

The true density at 25 캜 was measured by a gas-phase substitution method using a dry density meter (product name "Akyppe 1330" manufactured by Shimadzu Seisakusho Co., Ltd.). In addition, helium gas was used as the gas.

&Lt; Volume average particle diameter of non-conductive inorganic particles and binder &

The aqueous dispersion was diluted 1000 times with an aqueous solution of hexametaphosphoric acid having a concentration of 2% by mass and irradiated with ultrasonic waves at an output of 300 W for 2 minutes. Thereafter, a dynamic light scattering particle size analyzer (product name "Zetasizer Nano" Was used to measure the particle size distribution (volume basis). Then, in the measured particle size distribution, the particle diameter at which the cumulative volume calculated from the small diameter side was 50% was taken as the volume average particle size (D50).

&Lt; Glass transition temperature of the binder &

The DSC curve was measured according to JIS K7121 using a differential thermal analysis analyzer (trade name: EXSTAR DSC6220, manufactured by SAI NANO TECHNOLOGY CO., LTD.). Specifically, 10 mg of the dried test sample was weighed in an aluminum pan, and a DSC curve was measured under normal temperature and normal humidity at a heating rate of 10 ° C / min between the measurement temperature range of -100 ° C and 500 ° C using an empty aluminum pan as a reference Respectively. From the intersection of the baseline immediately before the endothermic peak of the DSC curve with the derivative signal DDSC of 0.05 mW / min / mg or more and the tangent line of the DSC curve at the inflection point first appearing after the endothermic peak, The transition temperature was determined.

<Viscosity of Composition for Functional Layer>

The viscosity at a rotation number of 6 rpm and the viscosity at a rotation number of 60 rpm were measured at a temperature of 25 캜 using a B-type viscometer (product name: TVB-10M, manufactured by Toki Sangyo K.K.).

&Lt; Thickness of functional layer &

The layer thickness of the functional layer was measured at arbitrary 10 locations of the functional layer-mounted separator manufactured using a high precision digital side panel (product name: "Lightmatic VL-50-B" manufactured by Mitsutoyo Corporation) The average value of the measured layer thickness was calculated to be the thickness of the functional layer.

<Density of functional layer>

The sample for measurement of 12 cm x 12 cm was cut out from the prepared separator of the functional layer and the separator base before the functional layer was formed, and the mass of each sample was measured to determine the mass of the functional layer per unit area. Then, the density of the functional layer was calculated by dividing the mass of the functional layer per unit area by the thickness of the functional layer.

&Lt; Peel strength of functional layer >

A rectangular test piece having a length of 100 mm and a width of 10 mm was cut out from the prepared separator equipped with a functional layer. In addition, a cellophane tape was fixed in advance on the test stand. As the cellophane tape, those specified in JIS Z1522 were used.

Then, the test piece cut out from the separator was attached to the cellophane tape with the functional layer facing downward. Thereafter, one end of the separator was pulled in a vertical direction at a tensile speed of 100 mm / min and the stress at the time of peeling was measured. Measurement was carried out three times, and an average value of the measured stress was obtained, and this was regarded as the peak strength of the functional layer. Then, evaluation was made based on the following criteria.

A: Peel strength of 100 N / m or more

B: Peel strength of 80 N / m or more and less than 100 N / m

C: Peel strength of 60 N / m or more and less than 80 N / m

D: Peel strength less than 60 N / m

<Heat Resistance of Separator>

The prepared separator was cut into a square of 12 cm x 12 cm, and a square having one side of 10 cm was drawn inside the square to obtain a test piece. Then, the test piece was placed in a thermostatic chamber at 150 DEG C for 1 hour, and then the change in area of the green square inside (= (area of square before leaving) - area of square after leaving} Was determined as a heat shrinkage percentage, and evaluated according to the following criteria. The smaller the heat shrinkage ratio, the higher the protective function of the functional layer and the better the heat shrinkability of the separator having the functional layer.

A: Heat shrinkage less than 5%

B: Heat shrinkage is 5% or more and less than 10%

C: Heat shrinkage rate of 10% or more and less than 20%

D: Heat shrinkage rate is 20% or more and less than 30%

E: Heat shrinkage rate of 30% or more

&Lt; Low Temperature Output Characteristics of Secondary Battery >

The wound type lithium ion secondary battery having a discharge capacity of 1000 mAh thus prepared was allowed to stand in an environment of 25 캜 for 24 hours and then charged at a charging rate of 4.35 V and 0.1 C under an environment of 25 캜 for 5 hours. The voltage V0 was measured. Thereafter, the discharge operation was performed at a discharge rate of 1C under an environment of -10 DEG C, and a voltage V1 after 15 seconds from the start of discharge was measured. Then, the voltage change? V (= V0-V1) was determined and evaluated based on the following criteria. The smaller the voltage change? V, the better the secondary battery has low-temperature output characteristics.

A: voltage change? V is 500 mV or less

B: voltage change? V is more than 500 mV and less than 700 mV

C: Voltage change ΔV is more than 700mV and less than 900mV

D: voltage change? V exceeds 900mV

(Example 1)

&Lt; Preparation of binder >

In a reactor equipped with a stirrer, 70 parts of ion-exchanged water, 0.15 part of sodium lauryl sulfate (manufactured by Kao Chemical Co., Ltd., "Emal (registered trademark) 2F") as an emulsifier and 0.5 parts of ammonium peroxodisulfate serving as a polymerization initiator were fed respectively, Exchanged with nitrogen gas, and heated to 60 캜.

On the other hand, 50 parts of ion-exchanged water, 0.5 part of sodium dodecylbenzenesulfonate as a dispersant and 93.8 parts of butyl acrylate, 2.0 parts of methacrylic acid, 1.2 parts of N-methylol acrylamide, 2.0 parts of acrylonitrile, And 1.0 part of acrylic glycidyl ether were mixed to obtain a monomer mixture. The monomer mixture was continuously added to the reactor over 4 hours to conduct polymerization. The reaction was carried out at 60 占 폚 during the addition. After completion of the addition, the mixture was further stirred at 70 DEG C for 3 hours to terminate the reaction, thereby preparing an aqueous dispersion containing the binder in the particulate polymer.

Then, the volume average particle diameter and the glass transition temperature of the obtained binder were measured. The results are shown in Table 1.

<Preparation of Composition for Functional Layer>

70 parts of barium sulfate particles (density: 4.4 g / cm 3, specific surface area: 3.0 m 2 / g, volume average particle diameter: 0.70 탆) as non-conductive inorganic particles A and 70 parts of barium sulfate particles (density: Water) was added to 30 parts of a polycarboxylic acid ammonium salt as a dispersing agent and 2.5 parts of a polycarboxylic acid ammonium salt as a dispersant so as to have a solid content concentration of 50 mass% LMZ-015 &quot;, manufactured by Ashizawa Finetech Co., Ltd.). The dispersion was carried out using 0.4 mm diameter beads at a circumferential speed of 6 m / sec and a flow rate of 0.3 L / min. Thereafter, 1.5 parts of an aqueous solution of polyacrylamide (solids concentration: 15% by mass) corresponding to the solid content was added to the obtained dispersion solution as a viscosity adjusting agent and mixed. Subsequently, 5 parts of the aqueous dispersion of the binder corresponding to the solid content and 0.2 part of the ethylene oxide-propylene oxide copolymer as the wetting agent were added, and water was added thereto so as to have a solid content concentration of 40% by mass, A composition was obtained.

Then, the viscosity of the obtained composition for a functional layer was measured. The results are shown in Table 1.

<Fabrication of Separator>

A separator base made of polyethylene having a width of 250 mm, a length of 1000 m, and a thickness of 12 占 퐉 manufactured by a wet method (gel value: 155 sec / 100 cc) was prepared. Then, the composition for the functional layer was applied on the separator base material at a rate of 20 m / min using a gravure coater so that the thickness after drying was 1.0 탆, and then dried in a drying furnace at 50 캜 to form a functional layer (porous film layer) A functional layer-mounted separator was produced and wound thereon.

Then, the thickness, density and fill strength of the functional layer were measured, and the heat resistance of the resulting separator was evaluated. The results are shown in Table 1.

<Fabrication of negative electrode>

33 parts of 1,3-butadiene, 3.5 parts of itaconic acid, 63.5 parts of styrene, 0.4 part of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of ion-exchanged water and 0.5 parts of potassium persulfate as a polymerization initiator were placed in a 5 MPa pressure vessel equipped with a stirrer, After stirring, the mixture was heated to 50 DEG C to initiate polymerization. When the polymerization conversion rate reached 96%, the reaction mixture was cooled and the reaction was stopped to obtain a mixture containing particulate binder (SBR). Then, a 5% aqueous solution of sodium hydroxide was added to the mixture containing the particulate binder, adjusted to pH 8, and then unreacted monomers were removed by distillation under reduced pressure by heating. Thereafter, the mixture was cooled to 30 DEG C or lower to obtain an aqueous dispersion containing particulate binder.

Subsequently, 100 parts of artificial graphite (volume average particle diameter: 15.6 mu m) serving as a negative electrode active material, 1 part of a 2% aqueous solution of carboxymethylcellulose sodium salt (product name "MAC350HC", product of Nippon Seisai Co., Exchanged water having a concentration of 68% was mixed at 25 DEG C for 60 minutes. Further, the solid content concentration was adjusted to 62% with ion-exchanged water, and the mixture was then mixed at 25 占 폚 for 15 minutes. To the resulting mixed solution, 1.5 parts of the particulate binder corresponding to the solid content and ion-exchanged water were added, and the final solid content concentration was adjusted to 52%, followed by further mixing for 10 minutes. The obtained mixture was subjected to defoaming treatment under reduced pressure to obtain a slurry composition for a secondary battery negative electrode having good flowability.

Then, the resulting negative electrode slurry composition was coated on a copper foil having a thickness of 20 mu m as a current collector by a comma coater so as to have a thickness of about 150 mu m after drying and dried. This drying was carried out by conveying the copper foil in an oven at 60 ° C for 2 minutes at a speed of 0.5 m / min. Thereafter, the resultant was heat-treated at 120 DEG C for 2 minutes to obtain a negative electrode cloth before pressing. The negative electrode raw material before this press was rolled by a roll press to obtain a pressed negative electrode having a thickness of the negative electrode composite material layer of 80 mu m.

&Lt; Preparation of positive electrode &

100 parts of LiCoO ₂ (volume average particle diameter: 12 탆) as a positive electrode active material, ₂ parts of acetylene black (product name: "HS-100" manufactured by Denki Kagaku K.K.) as a conductive material, polyvinylidene fluoride , Product name &quot;# 7208 &quot;) as solid content, and N-methylpyrrolidone were mixed to give a solid concentration of 70%. These were mixed by a planetary mixer to obtain a positive electrode slurry composition.

The resulting positive electrode slurry composition was coated on an aluminum foil having a thickness of 20 mu m as a current collector by a comma coater so as to have a thickness of about 150 mu m after drying and dried. This drying was carried out by conveying the aluminum foil in an oven at 60 캜 for 2 minutes at a speed of 0.5 m / min. Thereafter, it was heat-treated at 120 DEG C for 2 minutes to obtain a positive electrode cloth before pressing. The cathode raw material before this press was rolled by a roll press to obtain a pressed positive electrode having a thickness of the positive electrode composite material layer of 80 mu m.

&Lt; Preparation of Secondary Battery >

The obtained positive electrode was cut into 49 cm x 5 cm and the surface on the side of the positive electrode composite layer was placed on the upper side. A functional layer-mounted separator cut out thereon with a size of 120 cm x 5.5 cm was formed on the positive electrode composite material layer and the functional layer, So as to be located on the left side in the longitudinal direction. The negative electrode thus obtained was cut out to a size of 50 cm x 5.2 cm and placed on the separator such that the surface of the negative electrode composite material layer side was opposed to the separator and the negative electrode was located on the right side in the longitudinal direction of the separator. This was wound around the center in the longitudinal direction of the separator by a winding machine to obtain a winding body. This rolled body was pressed at 60 占 폚 and 0.5 MPa to form a flat body and wrapped in an aluminum casing as an exterior of the battery. The electrolytic solution (solvent: ethylene carbonate / diethyl carbonate / vinylene carbonate (volume ratio) = 68.5 / 30 / 1.5 , Electrolyte: LiPF _{6 with a} concentration of 1M) was poured in such a manner that air was not left. Further, to seal the opening of the casing of the aluminum casing, the casing of the aluminum casing was closed by heat sealing at 150 ° C. Thereafter, the wound body and the outer casing of the aluminum casing were pressed at 60 DEG C and 0.5 MPa to produce a wound lithium ion secondary battery having a discharge capacity of 1000 mAh as a non-aqueous secondary battery.

The low-temperature output characteristics of the obtained lithium ion secondary battery were evaluated. The results are shown in Table 1.

(Examples 2 to 3)

The composition for the functional layer, the separator, the negative electrode and the non-conductive inorganic particle B were prepared in the same manner as in Example 1 except that the amounts of the non-conductive inorganic particles A and the non-conductive inorganic particles B were changed as shown in Table 1, , A positive electrode and a secondary battery. Various evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

(Examples 4 to 5)

Barium sulfate particles (density: 4.4 g / cm 3, specific surface area: 2.1 m 2 / g, volume average particle diameter: 0.90 탆) were used as non-conductive inorganic particles A in Example 4, 5, a composition for a binder, a functional layer, a separator, and a negative electrode were prepared in the same manner as in Example 1 except that barium sulfate particles (density: 4.4 g / cm 3, specific surface area: 8.3 m 2 / g, volume average particle diameter: 0.50 μm) , A positive electrode and a secondary battery. Various evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

(Examples 6 to 7)

Barium sulfate particles (density: 4.1 g / cm 3, specific surface area: 15.0 m 2 / g, volume average particle diameter: 0.17 탆) were used as non-conductive inorganic particles B in Example 6, 7, a binder, a composition for a functional layer, a separator, and a negative electrode were prepared in the same manner as in Example 1 except that barium sulfate particles (density: 4.1 g / cm 3, specific surface area: 20.0 m 2 / g, volume average particle diameter: , A positive electrode and a secondary battery. Various evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

(Example 8)

Same as Example 1 except that barium titanate particles (density: 6.02 g / cm 3, specific surface area: 2.3 m 2 / g, volume average particle diameter: 0.50 μm) were used as non-conductive inorganic particles A at the time of preparing the composition for the functional layer. To prepare a binder, a composition for a functional layer, a separator, a negative electrode, a positive electrode and a secondary battery. Various evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

(Examples 9 to 10)

A composition for a binder, a functional layer, a separator, a negative electrode, a positive electrode and a secondary battery were produced in the same manner as in Example 1 except that the formulation amount of the binder was changed as shown in Table 1 at the preparation of the composition for the functional layer. Various evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Examples 1 and 2)

The composition for the functional layer, the separator, the negative electrode and the non-conductive inorganic particle B were prepared in the same manner as in Example 1 except that the amounts of the non-conductive inorganic particles A and the non-conductive inorganic particles B were changed as shown in Table 1, , A positive electrode and a secondary battery. Various evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 3)

(Density: 7.09 g / cm 3, specific surface area: 1.4 m 2 / g, volume average particle diameter: 0.5 탆) was used as non-conductive inorganic particles A, and as non-conductive inorganic particles B A composition for a functional layer, a separator, a negative electrode, and a positive electrode were prepared in the same manner as in Example 1 except that zirconium nitride particles (density: 7.09 g / cm 3, specific surface area: 50 m 2 / g, volume average particle diameter: And a secondary battery. However, the dispersibility and fluidity of the composition for the functional layer was poor, and it was impossible to evaluate the composition for the functional layer and to manufacture the separator and the secondary battery.

(Comparative Example 4)

Same as Example 1 except that barium sulfate particles (density: 4.0 g / cm 3, specific surface area: 74 m 2 / g, volume average particle diameter: 0.03 μm) were used as non-conductive inorganic particles B at the preparation of the composition for the functional layer To prepare a binder, a composition for a functional layer, a separator, a negative electrode, a positive electrode and a secondary battery. Various evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 5)

(Density: 3.94 g / m 2, specific surface area: 4.0 m 2 / g, volume average particle diameter: 0.6 탆) was used as the non-conductive inorganic particle A, and alumina The composition for a functional layer, the separator, the negative electrode, the positive electrode and the secondary (positive electrode) were prepared in the same manner as in Example 1, except that the particles (density: 3.94 g / m 3, specific surface area: 6.1 m 2 / g, volume average particle diameter: A battery was produced. Various evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

From Table 1, it can be seen that the non-conductive inorganic particle A having a predetermined density and volume average particle diameter and the non-conductive inorganic particle B having a predetermined density are used in combination at a predetermined ratio, In Examples 1 to 10 in which the ratio of the volume average particle diameter of the non-conductive inorganic particles B was within a predetermined range, the functional layer having excellent peel strength and protective function and capable of exhibiting excellent low- It can be seen that the thickness can be formed.

From Table 1, in Comparative Example 1 in which the ratio of the non-conductive inorganic particles A having a predetermined density and volume average particle diameter was too small, the low-temperature output characteristics of the secondary battery were lowered, and the density and the volume average particle diameter The protective function of the functional layer is lowered in Comparative Example 2 in which the ratio of the non-conductive inorganic particles A is too large. From Table 1, it can be seen that in Comparative Example 3 in which the density of the non-conductive inorganic particles A and B is too high, the dispersibility of the composition for the functional layer deteriorates and the functional layer can not be formed. In Comparative Example 4 in which the ratio of the volume average particle diameter of the non-conductive inorganic particles B to the volume average particle diameter of the non-conductive inorganic particles A was too small as shown in Table 1, the peel strength of the functional layer and the low- Able to know. In addition, it can be seen from Table 1 that the protective function of the functional layer is lowered in Comparative Example 5 using the non-conductive inorganic particle A and the non-conductive inorganic particle B having no predetermined density.

Industrial availability

According to the present invention, it is possible to provide a non-aqueous secondary battery functional layer composition capable of forming a functional layer for a non-aqueous secondary battery capable of exhibiting excellent peel strength and protective function and exhibiting excellent low-temperature output characteristics in a secondary battery .

Further, according to the present invention, it is possible to provide a functional layer for a non-aqueous secondary battery capable of exhibiting excellent peel strength and protective function and exhibiting excellent low-temperature output characteristics in a secondary battery.

Further, according to the present invention, it is possible to provide a non-aqueous secondary battery having excellent battery characteristics such as low-temperature output characteristics.

Claims (9)

A non-aqueous secondary battery functional layer composition comprising non-conductive particles and a binder,
Conductive particles having a density of not less than 4 g / cm 3 and not more than 7 g / cm 3 and having a volume average particle diameter of not less than 0.5 탆 and not more than 1.0 탆 and a non-conductive inorganic particle A having a density of not less than 4 g / cm 3 and not more than 7 g / cm 3, And a non-conductive inorganic particle B having a particle diameter smaller than that of the non-conductive inorganic particle A,
The ratio of the non-conductive inorganic particles A in the mixture is 50% by mass or more and 90% by mass or less,
Wherein the ratio of the volume average particle diameter of the non-conductive inorganic particles B to the volume average particle diameter of the non-conductive inorganic particles A is 0.05 times or more and 0.6 times or less.
The method according to claim 1,
Wherein the binder is contained in an amount of 1 part by mass or more and 20 parts by mass or less per 100 parts by mass of the non-conductive particles.
3. The method according to claim 1 or 2,
Wherein the non-conductive inorganic particles B have a volume-average particle diameter of at least 0.05 탆 and less than 0.3 탆.
4. The method according to any one of claims 1 to 3,
A composition for a nonaqueous secondary battery functional layer further comprising a polyacrylamide.
A functional layer for a nonaqueous secondary battery, formed by using the composition for a nonaqueous secondary battery functional layer according to any one of claims 1 to 4.
6. The method of claim 5,
A functional layer for a non-aqueous secondary battery, wherein the thickness is 0.5 占 퐉 or more and 2 占 퐉 or less.
The method according to claim 5 or 6,
Functional layer for a non-aqueous secondary battery, wherein the density is 2.0 g / cm3 or more and 3.0 g / cm3 or less.
A non-aqueous secondary battery comprising the functional layer for a non-aqueous secondary battery according to any one of claims 5 to 7.
A method for producing a composition for a non-aqueous secondary battery functional layer comprising non-conductive particles and a binder,
And a non-conductive inorganic particle A having a density of 4 g / cm 3 or more and 7 g / cm 3 or less and a volume average particle diameter of 0.5 to 1.0 m, and a non-conductive inorganic particle A having a density of 4 g / cm 3 to 7 g / Conductive inorganic particles B smaller than the inorganic particles A and the non-conductive inorganic particles A in a proportion of 50% by mass or more and 90% by mass or less with respect to the total of the non-conductive inorganic particles A and the non-conductive inorganic particles B So as to be mixed,
Wherein the ratio of the volume average particle diameter of the non-conductive inorganic particles B to the volume average particle diameter of the non-conductive inorganic particles A is 0.05 times or more and 0.6 times or less.