WO2020066954A1

WO2020066954A1 - Binder composition for nonaqueous secondary cell, slurry composition for nonaqueous secondary cell functional layer, functional layer for nonaqueous secondary cell, cell member for nonaqueous secondary cell, and nonaqueous secondary cell

Info

Publication number: WO2020066954A1
Application number: PCT/JP2019/037132
Authority: WO
Inventors: 雄輝大久保; 徳一山本
Original assignee: 日本ゼオン株式会社
Priority date: 2018-09-28
Filing date: 2019-09-20
Publication date: 2020-04-02
Also published as: JPWO2020066954A1; JP2024100812A

Abstract

The purpose of the present invention is to provide a binder composition for a nonaqueous secondary cell, said binder composition allowing preparation of a slurry composition for a nonaqueous secondary cell functional layer, said slurry composition having excellent viscosity stability. A binder composition according to the present invention contains a polymer and water and does not substantially contain bacteria belonging to Burkholderia, Achromobacter, Alcaligenes, Stenotrophomonas, and Pseudomonas. The number of bacteria is 1.0×10³ /ml or less.

Description

Binder composition for non-aqueous secondary battery, slurry composition for non-aqueous secondary battery functional layer, functional layer for non-aqueous secondary battery, battery member for non-aqueous secondary battery, and non-aqueous secondary battery

The present invention relates to a binder composition for a non-aqueous secondary battery, a slurry composition for a non-aqueous secondary battery functional layer, a functional layer for a non-aqueous secondary battery, a battery member for a non-aqueous secondary battery, and a non-aqueous secondary battery. Things.

Non-aqueous secondary batteries such as lithium ion secondary batteries (hereinafter sometimes simply referred to as “secondary batteries”) have the characteristics of being small, lightweight, high in energy density, and capable of being repeatedly charged and discharged. Yes, used for a wide range of applications. A non-aqueous secondary battery generally includes a battery member for a non-aqueous secondary battery (such as an electrode (a positive electrode and a negative electrode) and a separator that separates the positive electrode and the negative electrode to prevent a short circuit between the positive electrode and the negative electrode). Hereinafter, it may be simply referred to as “battery member”.)

Here, the battery member includes a polymer as a binder, and optionally includes particles (hereinafter, referred to as “functional particles”) that are blended to exert a desired function on the battery member. A member provided with a functional layer consisting of
Specifically, as a separator for a secondary battery, a separator having an adhesive layer containing a binder and a porous membrane layer containing a binder and non-conductive particles as functional particles on a separator substrate. Is used. In addition, as an electrode of a secondary battery, an electrode provided with an electrode mixture layer containing a binder and electrode active material particles as functional particles on a current collector, or an electrode mixture layer on a current collector An electrode further comprising an adhesive layer and a porous membrane layer described above is used on an electrode substrate having a layer.

The functional layer described above includes, for example, a slurry composition for a non-aqueous secondary battery functional layer in which a polymer as a binder and optional functional particles are dispersed and / or dissolved in a solvent. It can be formed by drying. And, in order to further improve the performance of the secondary battery, improvement of the slurry composition has been conventionally attempted. For example, a technique for controlling the number of bacteria in a solvent used for preparing a slurry composition and improving the performance of a secondary battery has been studied (see Patent Documents 1 and 2).

In Patent Literature 1, a lithium ion-containing battery containing a positive electrode active material, a conductive material, a thickener, a binder, and a solvent is used by using a solvent to which sulfate-reducing bacteria are added so that the number of bacteria is within a predetermined range. By preparing a positive electrode paste for a secondary battery, sulfate (SO ₄ ²⁻ ) that causes deterioration in characteristics of a lithium ion secondary battery is reduced.
In Patent Literature 2, a lithium ion battery containing a negative electrode active material and a solvent is irradiated with ultraviolet rays or the like so that the number of bacteria is within a predetermined range, and the pH and the temperature are each within a predetermined range. By preparing the slurry for the secondary battery negative electrode, hydrolysis of the carboxymethylcellulose salt as a thickener by bacterial cellulase is suppressed, and a decrease in the viscosity of the negative electrode slurry is suppressed.

JP 2013-134924 A JP 2013-114959 A

However, in the above-mentioned conventional technique, it is difficult to sufficiently secure the viscosity stability of the slurry composition, for example, when the slurry composition is prepared, the obtained slurry composition may be excessively thickened. Met. In addition, the secondary battery could not exhibit excellent cycle characteristics while ensuring the adhesion of the functional layer obtained using the slurry composition. Therefore, there is room for improvement in the above-described conventional techniques in terms of improving the viscosity stability of the slurry composition, and improving the adhesiveness of the functional layer and the cycle characteristics of the secondary battery.

Therefore, an object of the present invention is to provide a binder composition for a non-aqueous secondary battery capable of preparing a slurry composition for a non-aqueous secondary battery functional layer having excellent viscosity stability.
Another object of the present invention is to provide a slurry composition for a non-aqueous secondary battery functional layer having excellent viscosity stability.
Further, an object of the present invention is to provide a functional layer for a non-aqueous secondary battery having excellent adhesiveness.
Further, another object of the present invention is to provide a battery member for a non-aqueous secondary battery which exhibits excellent cycle characteristics to the non-aqueous secondary battery.
In addition, an object of the present invention is to provide a non-aqueous secondary battery having excellent cycle characteristics.

(4) The present inventors have conducted intensive studies with the aim of solving the above problems. First, the present inventor, when preparing the binder composition, paying attention to the fact that there is a bacterium that can be unintentionally mixed in the manufacturing process, and among these bacterium, a specific bacterium type is particularly included in the binder composition. Has been found to significantly reduce the stability of the polymer. According to the present invention, a binder composition which does not substantially contain any of these specific bacteria and has a number of arbitrary bacteria that can be contained is equal to or less than a predetermined value is excellent in viscosity stability. Was found to be able to be prepared, and it was possible to improve the adhesiveness of the functional layer and the cycle characteristics of the secondary battery, thereby completing the present invention.

That is, an object of the present invention is to advantageously solve the above problems, the binder composition for a non-aqueous secondary battery of the present invention contains a polymer and water, genus Burkholderia, Achromobacter, Alcaligenes It is characterized by being substantially free of bacteria belonging to the genera, Stenotrophomonas, and Pseudomonas, and having a bacterial count of 1.0 × 10 ³ cells / ml or less. As described above, in the binder composition in which the polymer is dissolved and / or dispersed in water, bacteria belonging to the above genus are substantially eliminated, and if the number of bacteria is controlled to be equal to or less than the above value, The viscosity stability of the slurry composition prepared using the binder composition can be improved, and the adhesion of the functional layer obtained using the slurry composition can be improved while providing the functional layer. Excellent cycle characteristics can be exhibited in the secondary battery.
In the present invention, the "number of bacteria" contained in the binder composition can be measured according to JIS K 0350-10-10 (2002).
Further, in the present invention, the binder composition, `` substantially does not contain '' a bacterium belonging to a predetermined genus, when performing the specific operation of the bacterial species described in the examples of the present specification, It means that bacteria belonging to the genus are not detected.

Here, the binder composition for a non-aqueous secondary battery of the present invention preferably has a surface tension of 22 mN / m or more and 55 mN / m or less. By using a binder composition having a surface tension within the above range, the viscosity stability of the slurry composition, the adhesiveness of the functional layer, and the cycle characteristics of the secondary battery can be sufficiently improved.
In the present invention, the “surface tension” of the binder composition can be measured using the method described in the examples of the present specification.

In the binder composition for a non-aqueous secondary battery of the present invention, the amount of the tetrahydrofuran-insoluble content of the polymer is preferably 10% by mass or more and 95% by mass or less. A polymer having a tetrahydrofuran-insoluble content (hereinafter, sometimes referred to as “THF-insoluble content”) within the above-described range can be easily prepared. The cycle characteristics of the secondary battery can be further improved.
In the present invention, the “tetrahydrofuran-insoluble content” of the polymer can be measured using the method described in the examples of the present specification.

Another object of the present invention is to advantageously solve the above-mentioned problems, and the slurry composition for a non-aqueous secondary battery functional layer of the present invention includes any one of the binders for a non-aqueous secondary battery described above. It is characterized by being prepared using the composition. The slurry composition containing any of the binder compositions described above has excellent viscosity stability. When a functional layer is formed from the slurry composition, the adhesion of the functional layer can be enhanced, and the battery member including the functional layer can exhibit excellent cycle characteristics in a secondary battery.

Here, the slurry composition for a non-aqueous secondary battery functional layer of the present invention may further contain functional particles. When the above-mentioned slurry composition contains functional particles, that is, electrode active material particles or non-conductive particles, using the slurry composition, an electrode that is excellent in adhesiveness and can exhibit excellent cycle characteristics in a secondary battery. A mixture layer or a porous membrane layer can be formed.

Another object of the present invention is to advantageously solve the above-mentioned problems, and the functional layer for a non-aqueous secondary battery of the present invention includes any one of the above-described slurry compositions for a non-aqueous secondary battery functional layer. It is characterized by being formed using an object. The functional layer formed from any of the above slurry compositions has excellent adhesiveness. Then, by using a battery member having the functional layer, a secondary battery can exhibit excellent cycle characteristics.

Another object of the present invention is to advantageously solve the above problem, and a battery member for a non-aqueous secondary battery of the present invention includes the above-described functional layer for a non-aqueous secondary battery. And According to the battery member including the above-described functional layer, the secondary battery can exhibit excellent cycle characteristics.

Another object of the present invention is to advantageously solve the above-described problem, and a non-aqueous secondary battery of the present invention includes the above-described battery member for a non-aqueous secondary battery. A secondary battery including the above-described battery member has excellent cycle characteristics.

In this specification, a functional layer containing a binder and electrode active material particles is referred to as an “electrode mixture layer”, and a functional layer containing a binder and non-conductive particles is referred to as a “porous membrane layer”. The functional layer including the material and not including any of the electrode active material particles and the non-conductive particles is referred to as an “adhesive layer”.

ADVANTAGE OF THE INVENTION According to this invention, the binder composition for non-aqueous secondary batteries which can prepare the slurry composition for non-aqueous secondary battery functional layers excellent in viscosity stability can be provided.
Further, according to the present invention, a slurry composition for a non-aqueous secondary battery functional layer having excellent viscosity stability can be provided.
And according to this invention, the functional layer for non-aqueous secondary batteries which is excellent in adhesiveness can be provided.
Further, according to the present invention, it is possible to provide a battery member for a non-aqueous secondary battery that exhibits excellent cycle characteristics to the non-aqueous secondary battery.
In addition, according to the present invention, a non-aqueous secondary battery having excellent cycle characteristics can be provided.

Hereinafter, embodiments of the present invention will be described in detail.
Here, the binder composition for a non-aqueous secondary battery of the present invention is used for production of a non-aqueous secondary battery, for example, the preparation of a slurry composition for a non-aqueous secondary battery functional layer of the present invention. Can be used. Then, the slurry composition for a non-aqueous secondary battery functional layer of the present invention may be any functional layer (for example, an electrode mixture layer) that performs functions such as transfer of electrons or reinforcement or adhesion in the non-aqueous secondary battery. , A porous membrane layer, an adhesive layer). Furthermore, the functional layer for a non-aqueous secondary battery of the present invention is formed from the slurry composition for a non-aqueous secondary battery functional layer of the present invention. Further, the battery member for a non-aqueous secondary battery of the present invention includes the functional layer for a non-aqueous secondary battery of the present invention. And the non-aqueous secondary battery of the present invention includes the battery member for a non-aqueous secondary battery of the present invention.

(Binder composition for non-aqueous secondary battery)
The binder composition of the present invention contains a polymer and water. Here, the binder composition of the present invention substantially includes bacteria belonging to the genus Burkholderia, the genus Achromobacter, the genus Alcaligenes, the genus Stenotrophomonas, and the genus Pseudomonas (hereinafter sometimes collectively referred to as “specific genus”). Not contained. Furthermore, the number of bacteria in the binder composition of the present invention is 1.0 × 10 ³ cells / ml or less.
The binder composition of the present invention may contain bacteria belonging to a genus other than the specific genus as long as the number of bacteria is equal to or less than the above-mentioned value. Further, the binder composition of the present invention may contain components other than the polymer, the bacterium, and water (hereinafter, referred to as “other components”).

And, the binder composition of the present invention does not substantially contain bacteria belonging to a specific genus, and since the number of bacteria is equal to or less than the above-described value, it is possible to favorably suppress decay of the polymer by the bacteria, A slurry composition having excellent viscosity stability can be prepared using the binder composition. Furthermore, according to the slurry composition having excellent viscosity stability, it is possible to obtain a functional layer having a uniform structure in which uneven distribution of components such as a polymer and functional particles is suppressed, while improving the adhesiveness of the functional layer. In addition, the functional layer allows the secondary battery to exhibit excellent cycle characteristics.

<Polymer>
The polymer in the binder composition is a component that can function as a binder, and in a functional layer formed using the slurry composition containing the binder composition, components such as functional particles are detached from the functional layer. In addition to holding the battery members together, the battery members can be bonded to each other via the functional layer.

<< kind of polymer >>
Here, as the polymer, any polymer can be used as long as it can be used as a binder in a secondary battery.
For example, the polymer may be a water-soluble polymer which may be present in a dissolved form in a binder composition containing water, or may be water-insoluble and may be present in a dispersed state in a binder composition containing water. It may be a particulate polymer. Further, the binder composition of the present invention may contain one kind of polymer or two or more kinds of polymers.
In the present invention, the term “water-soluble” means that when 0.5 g of the polymer is dissolved in 100 g of water at 25 ° C., the insoluble content is less than 0.5% by mass. Further, in the present invention, the term “water-insoluble” means that when 0.5 g of the polymer is dissolved in 100 g of water at 25 ° C., the insoluble content is 90% by mass or more.
Hereinafter, the case where the polymer is a particulate polymer will be described as an example, but the present invention is not limited to this.

The particulate polymer is not particularly limited, but an acrylic polymer or a conjugated diene polymer can be preferably used from the viewpoint of sufficiently securing the adhesiveness of the functional layer and the cycle characteristics of the secondary battery.

[Acrylic polymer]
The acrylic polymer is a polymer containing (meth) acrylate monomer units. Here, the acrylic polymer may include a repeating unit (other repeating unit) other than the (meth) acrylate monomer unit.
In the present invention, “(meth) acryl” means acryl and / or methacryl. Further, in the present invention, "including a monomer unit" means "a polymer obtained by using the monomer contains a repeating unit derived from the monomer".

-(Meth) acrylic acid ester monomer unit-
Examples of the (meth) acrylate monomer capable of forming the (meth) acrylate monomer unit include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, Acrylic alkyl esters such as pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, n-tetradecyl acrylate and stearyl acrylate; methyl methacrylate, ethyl methacrylate, n-propyl Methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, pentyl methacrylate Over DOO, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, lauryl methacrylate, n- tetradecyl methacrylate, and methacrylic acid alkyl esters such as stearyl methacrylate. These may be used alone or in combination of two or more.

The content ratio of the (meth) acrylate monomer unit in the acrylic polymer is preferably more than 50% by mass when the amount of all the repeating units contained in the acrylic polymer is 100% by mass. , 65% by mass or more, more preferably 80% by mass or more, particularly preferably 90% by mass or more, preferably 99% by mass or less, and more preferably 98% by mass or less. Is more preferable. When the content of the (meth) acrylate monomer unit in the acrylic polymer is within the above range, the flexibility of the acrylic polymer is sufficiently ensured, and the adhesiveness of the functional layer and the secondary The cycle characteristics of the battery can be further improved.

-Other repeating units-
The other repeating unit that the acrylic polymer may optionally include is not particularly limited as long as it is a repeating unit derived from a monomer copolymerizable with the (meth) acrylate monomer described above. Monomer units having a hydrophilic group (monomer units having a carboxylic acid group, monomer units having a phosphate group, monomer units having a sulfonic acid group, monomer units having a hydroxyl group, etc.), nitriles Examples include a group-containing monomer unit and a crosslinkable monomer unit. In addition, a hydrophilic group-containing monomer capable of forming a hydrophilic group-containing monomer unit (a monomer having a carboxylic acid group, a monomer having a phosphoric acid group, a monomer having a sulfonic acid group, a hydroxyl group Etc.), a nitrile group-containing monomer capable of forming a nitrile group-containing monomer unit, and a crosslinkable monomer capable of forming a crosslinkable monomer unit are not particularly limited, and include, for example, The thing described in International Publication WO2015 / 064099 can be used.

Here, the acrylic polymer may include an “aliphatic conjugated diene monomer unit” or an “aromatic vinyl monomer unit” which will be described later in the section “Conjugated diene polymer”. In the acrylic polymer, the content of the (meth) acrylate monomer unit is at least higher than the content of the aliphatic conjugated diene monomer unit.
Further, the acrylic polymer may include only one type of other repeating unit, or may include two or more types of repeating units.

[Conjugated diene polymer]
The conjugated diene-based polymer is a polymer containing an aliphatic conjugated diene monomer unit. Here, specific examples of the conjugated diene-based polymer include an aliphatic conjugated diene polymer such as polybutadiene and polyisoprene; an aromatic vinyl-aliphatic conjugated diene copolymer such as styrene-butadiene-based polymer (SBR); Vinyl cyanide-conjugated diene copolymers such as acrylonitrile-butadiene polymer (NBR); hydrogenated SBR, hydrogenated NBR, and the like. Among these, an aromatic vinyl / aliphatic conjugated diene copolymer such as a styrene-butadiene polymer (SBR) is preferable.
Here, the aromatic vinyl / aliphatic conjugated diene copolymer includes an aromatic vinyl monomer unit and an aliphatic conjugated diene monomer unit, and optionally includes an aromatic vinyl monomer unit and an aliphatic vinyl monomer unit. A repeating unit (other repeating unit) other than the conjugated diene monomer unit may be included.

-Aromatic vinyl monomer unit-
Examples of the aromatic vinyl monomer capable of forming an aromatic vinyl monomer unit include styrene, α-methylstyrene, vinyltoluene, divinylbenzene, and the like. These can be used alone or in combination of two or more. And among these, styrene is preferable.

The content ratio of the aromatic vinyl monomer unit in the aromatic vinyl / aliphatic conjugated diene copolymer was set to 100 mass% with respect to the amount of all the repeating units contained in the aromatic vinyl / aliphatic conjugated diene copolymer. In this case, the content is preferably 35% by mass or more, more preferably 45% by mass or more, still more preferably 55% by mass or more, preferably 80% by mass or less, and more preferably 70% by mass or less. It is more preferable that the content be 65% by mass or less. When the content of the aromatic vinyl monomer unit in the aromatic vinyl / aliphatic conjugated diene copolymer is within the above range, the strength and the adhesiveness of the functional layer are sufficiently ensured, and the Cycle characteristics can be further improved.

―Aliphatic conjugated diene monomer unit―
Examples of the aliphatic conjugated diene monomer capable of forming an aliphatic conjugated diene monomer unit include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, substituted linear conjugated pentadienes, substituted and side chain conjugated hexadienes, and the like. These can be used alone or in combination of two or more. Among these, 1,3-butadiene is preferred.

The content ratio of the aliphatic conjugated diene monomer unit in the aromatic vinyl / aliphatic conjugated diene copolymer is such that the amount of all the repeating units contained in the aromatic vinyl / aliphatic conjugated diene copolymer is 100% by mass. In this case, the content is preferably 20% by mass or more, more preferably 30% by mass or more, preferably 70% by mass or less, more preferably 60% by mass or less, and more preferably 50% by mass or less. More preferably, it is particularly preferably 35% by mass or less. If the content of the aliphatic conjugated diene monomer unit in the aromatic vinyl / aliphatic conjugated diene copolymer is within the above range, the flexibility and adhesion of the functional layer are sufficiently ensured, and the secondary The cycle characteristics of the battery can be further improved.

-Other repeating units-
Other repeating units that the aromatic vinyl / aliphatic conjugated diene copolymer may optionally include are derived from monomers copolymerizable with the aromatic vinyl monomer and the aliphatic conjugated diene monomer described above. Although it is not particularly limited as long as it is a repeating unit, for example, a hydrophilic group-containing monomer unit (a monomer unit having a carboxylic acid group, a monomer unit having a phosphate group, a monomer unit having a sulfonic acid group) , A monomer unit having a hydroxyl group), a nitrile group-containing monomer unit, and a crosslinkable monomer unit. In addition, a hydrophilic group-containing monomer capable of forming a hydrophilic group-containing monomer unit (a monomer having a carboxylic acid group, a monomer having a phosphoric acid group, a monomer having a sulfonic acid group, a hydroxyl group Etc.), a nitrile group-containing monomer capable of forming a nitrile group-containing monomer unit, and a crosslinkable monomer capable of forming a crosslinkable monomer unit are not particularly limited, and include, for example, The thing described in International Publication WO2015 / 064099 can be used.

Note that a conjugated diene-based polymer such as an aromatic vinyl / aliphatic conjugated diene copolymer may contain the “(meth) acrylate monomer unit” described above in the section “Acrylic polymer”. Although good, usually, in the conjugated diene-based polymer, the content ratio of the aliphatic conjugated diene monomer unit is larger than the content ratio of the (meth) acrylate monomer unit.

<<< Amount of tetrahydrofuran insoluble content of polymer >>>
Here, the THF-insoluble content of the polymer is preferably 10% by mass or more, more preferably 50% by mass or more, further preferably 80% by mass or more, and more preferably 85% by mass or more. Is particularly preferred, and is preferably 95% by mass or less. When the THF-insoluble content of the polymer is 10% by mass or more, the polymer in the functional layer is prevented from being eluted into the electrolytic solution inside the secondary battery, and the cycle characteristics of the secondary battery can be further improved. it can. Further, a polymer having a THF-insoluble content of 95% by mass or less can be easily prepared, so that a binder composition containing the polymer can be efficiently produced.
The THF-insoluble content of the polymer is determined by the monomer composition of the polymer (the type and ratio of the monomers used) and the polymerization conditions of the polymer (such as the amount of the molecular weight modifier used, the reaction temperature and the reaction time). ) Can be adjusted.

<Fungus>
<< Bacteria belonging to specific genera >>
Here, the binder composition of the present invention is a bacterium belonging to the specific genus described above (a bacterium belonging to the genus Burkholderia, a bacterium belonging to the genus Achromobacter, a bacterium belonging to the genus Alcaligenes, a bacterium belonging to the genus Stenotrophomonas, and a bacterium belonging to the genus Pseudomonas). Must not be contained.

菌 These bacteria are bacteria that can be easily mixed in the production process of the binder composition. According to the study of the present inventors, it has been clarified that these bacteria particularly promote decay of a polymer contained as a binder in a binder composition for a non-aqueous secondary battery. Therefore, by intentionally removing bacteria belonging to these specific genera from the binder composition, the decay of the polymer is suppressed, and the viscosity stability of the slurry composition, the adhesiveness of the functional layer, and the cycle of the secondary battery are reduced. Characteristics can be enhanced.

<< Bacteria belonging to genera other than specific genera >>
On the other hand, the binder composition of the present invention may contain bacteria belonging to a genus other than the specific genus. Here, the genus other than the specific genus includes the genus Bacillus and the genus Serratia. In addition, the binder composition of the present invention may contain one kind of bacteria or two or more kinds of bacteria as bacteria belonging to a genus other than the specific genus. And when the binder composition of the present invention contains two or more bacteria belonging to a genus other than the specific genus, these bacteria may belong to one genus or may belong to different genus. .

<< Bacteria count >>
The binder composition of the present invention needs to have a bacterial count of 1.0 × 10 ³ cells / ml or less, and preferably 10 cells / ml or less. When the number of bacteria of the binder composition (generally, the number of bacteria belonging to a genus other than the specific genus) exceeds 1.0 × 10 ³ / ml, even when the bacterium belonging to the specific genus is not substantially contained. The decay of the polymer cannot be suppressed, and the viscosity stability of the slurry composition decreases. And even if it uses the said slurry composition, it cannot form a functional layer excellent in adhesiveness, and cannot exhibit the outstanding cycle characteristics to a secondary battery. The lower limit of the number of bacteria is not particularly limited, but the production efficiency is reduced due to excessive sterilization operations such as washing, and the performance of the polymer in the binder composition due to excessive sterilization operations (such as binding ability). ) From the viewpoint of suppressing the decrease, it is preferable that the number is 1 / ml or more.

<Other ingredients>
The binder composition of the present invention may optionally include, as other components, a conductive material, a wetting agent, an electrolyte solution additive, and the like, which may be added to a functional layer such as an electrode mixture layer, a porous membrane layer, and an adhesive layer. An additive or a pH adjuster may be contained. Further, various preparations (emulsifiers and the like) used for preparing the polymer may be brought into the binder composition.
And the binder composition of the present invention may contain a known preservative and / or bactericide capable of suppressing corrosion of the polymer. However, from the viewpoint of preventing deterioration in battery characteristics (such as cycle characteristics) due to carry-in to these secondary batteries, the blending amounts of the preservative and the bactericide in the binder composition are each 1 to 100 parts by mass of the polymer. It is preferably not more than 0.1 part by mass, more preferably not more than 0.1 part by mass, still more preferably not more than 0.01 part by mass, and 0 part by mass (that is, not including a preservative and a disinfectant). Is particularly preferred.

<Method for producing binder composition>
The method for producing the binder composition of the present invention described above, wherein the binder composition does not substantially contain bacteria belonging to a specific genus, and the number of bacteria in the binder composition is 1.0 × 10 ³ cells / ml. There is no particular limitation as long as control is possible below. However, the binder composition of the present invention described above,
A step (washing step) of washing the inner surface of a pipe for transferring a mixed solution containing a polymer and water with water at 70 ° C. or higher;
A step of polymerizing the monomer and the monomer composition containing water in the reactor to obtain a mixed solution containing the polymer and water (polymerization step);
Transferring the mixed liquid containing the polymer and water through the pipe after performing the above-described washing, and collecting the mixed liquid (recovery step);
It is preferable to manufacture via. Bacteria easily grow and adhere to the inner surface of the pipe for transferring the polymer. However, if the binder composition is manufactured through the above-described washing step, polymerization step, and recovery step, the bacteria (particularly, bacteria belonging to a specific genus) on the inner surface of the pipe are removed by the washing step, and the number of bacteria in the binder composition is reduced. And it is not necessary to perform an excessive sterilization treatment (such as irradiation with ultraviolet light) after the polymerization step, so that a sufficiently good performance (such as binding ability) of the obtained polymer can be ensured. Therefore, by using the binder composition obtained through the above-described steps, it is possible to provide a slurry composition having excellent viscosity stability, a functional layer having excellent adhesion, and a secondary battery having excellent cycle characteristics. Become.

<< Cleaning process >>
In the washing step, the inner surface of the pipe is washed with water at 70 ° C. or higher. Specifically, the cleaning of the inner surface of the pipe can be performed by passing water of 70 ° C. or higher into the pipe. In addition, the temperature of the water used for washing needs to be 70 ° C. or more, and is preferably 80 ° C. or more, from the viewpoint of effectively removing bacteria from the inner surface of the pipe.
In the washing step, facilities other than the piping may be performed with water at 70 ° C. or higher. For example, prior to the polymerization step described below, the reactor used for the polymerization in the polymerization step may be washed together with the pipe.

<< polymerization step >>
In the polymerization step, for example, a monomer composition containing the monomer described above in the section “Polymer” and water is polymerized. The content ratio of each monomer in the monomer composition can be determined according to the content ratio of a desired monomer unit (repeating unit) in the polymer.
Here, the polymerization method is not particularly limited, and any method such as a solution polymerization method, a suspension polymerization method, a bulk polymerization method, and an emulsion polymerization method can be used. As the polymerization reaction, any reaction such as ionic polymerization, radical polymerization, living radical polymerization, various kinds of condensation polymerization, and addition polymerization can be used. In the polymerization, known emulsifiers and polymerization initiators can be used as necessary.
The polymerization temperature is not particularly limited, but is preferably 60 ° C. or more, and more preferably 70 ° C. or more, from the viewpoint of reducing the number of bacteria of the obtained binder composition while favorably promoting the polymerization reaction. The temperature is more preferably 80 ° C. or higher, further preferably 90 ° C. or lower.

<< Recovery process >>
Then, a mixed solution (aqueous solution or aqueous dispersion of the polymer) containing the polymer and water obtained in the above-mentioned polymerization step is transferred and collected through the pipe that has been washed in the above-mentioned washing step.

<< Other steps >>
The method for producing a binder composition described above may include steps (other steps) other than the washing step, the polymerization step, and the recovery step.
For example, the above-mentioned method for producing a binder composition includes a step of adding additional water and optionally other components described above to a mixed solution containing the obtained polymer and water after the polymerization step (optional). (Component addition step). The water used in the optional component addition step is subjected to a sterilization treatment such as an ultraviolet treatment from the viewpoint of reducing the number of bacteria contained in the binder composition and preventing bacteria belonging to a specific genus from being introduced into the binder composition. Preferably, water is used.
Further, for example, the above-described method for producing a binder composition may include a step (sterilization treatment step) of performing a sterilization treatment such as ultraviolet irradiation on the mixed solution obtained in the polymerization step. However, the sterilization treatment with ultraviolet rays or the like may lower the performance of the polymer, and may impair the adhesiveness of the functional layer and the cycle characteristics of the secondary battery. Therefore, the method for producing a binder composition of the present invention preferably does not include a sterilization treatment step.

<Surface tension of binder composition>
Here, the surface tension of the binder composition is preferably from 22 mN / m to 55 mN / m, more preferably from 25 mN / m to 55 mN / m. If a binder composition having a surface tension within the above range is used, the polymer sufficiently exerts the performance as a binder, etc., so that the viscosity stability of the slurry composition, the adhesiveness of the functional layer, and the secondary The cycle characteristics of the battery can be sufficiently improved.
Further, the surface tension of the binder composition can be adjusted by changing the type and / or property (for example, the type and / or property of the polymer) of the components contained in the binder composition.

(Slurry composition for non-aqueous secondary battery functional layer)
The slurry composition of the present invention is a composition used for forming a functional layer, and is prepared using the above-described binder composition. Further, the slurry composition of the present invention is excellent in viscosity stability because it is prepared using the binder composition of the present invention that does not substantially contain specific bacteria and has a bacterial count of not more than a predetermined value. Further, by using the slurry composition of the present invention, a functional layer having excellent adhesiveness can be obtained. When a battery member having the functional layer is used, a secondary battery can exhibit excellent cycle characteristics.

<Binder composition>
As the binder composition, the above-described binder composition of the present invention is used. The amount of the binder composition in the slurry composition is not particularly limited. For example, when the slurry composition is a slurry composition for an electrode, the compounding amount of the binder composition is, per 100 parts by mass of the electrode active material particles, in terms of solid content, the amount of the polymer derived from the binder composition is 0.5% by mass. To 15 parts by mass or less. Further, for example, when the slurry composition is a slurry composition for a porous membrane layer, the blending amount of the binder composition is such that the amount of the polymer derived from the binder composition is 0 in terms of solid content per 100 parts by mass of the non-conductive particles. The amount can be from 0.5 parts by mass to 30 parts by mass.

<Functional particles>
Here, examples of the functional particles for causing the functional layer to exhibit an intended function include, for example, electrode active material particles when the functional layer is an electrode mixture layer, and the functional layer is a porous film layer. In some cases, non-conductive particles are mentioned.

<< electrode active material particles >>
The electrode active material particles are not particularly limited, and include particles made of a known electrode active material used in a secondary battery. Specifically, for example, the electrode active material particles that can be used in the electrode mixture layer of a lithium ion secondary battery as an example of a secondary battery are not particularly limited, and particles made of the following electrode active material Can be used.

[Positive electrode active material]
As the positive electrode active material to be mixed in the positive electrode mixture layer of the positive electrode of the lithium ion secondary battery, for example, a compound containing a transition metal, for example, a transition metal oxide, a transition metal sulfide, a composite of lithium and a transition metal Metal oxide or the like can be used. In addition, as a transition metal, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, etc. are mentioned, for example.
Specifically, the positive electrode active material is not particularly limited, and lithium-containing cobalt oxide (LiCoO ₂ ), lithium manganate (LiMn ₂ O ₄ ), lithium-containing nickel oxide (LiNiO ₂ ), Co- Ni-Mn lithium-containing composite oxide, Ni-Mn-Al lithium-containing composite oxide, Ni-Co-Al lithium-containing composite oxide, olivine-type lithium iron phosphate (LiFePO ₄ ), olivine-type manganese phosphate Lithium (LiMnPO ₄ ), lithium-rich spinel compound represented by Li _{1 + x} Mn _2-x O ₄ (0 <X <2), Li [Ni _0.17 Li _0.2 Co _0.07 Mn _0.56 ] O ₂ , LiNi _0.5 Mn _1.5 O _{4 and the} like.
The above-described positive electrode active materials may be used alone or in a combination of two or more.

[Negative electrode active material]
Examples of the negative electrode active material mixed in the negative electrode mixture layer of the negative electrode of the lithium ion secondary battery include a carbon-based negative electrode active material, a metal-based negative electrode active material, and a negative electrode active material obtained by combining these.
Here, the carbon-based negative electrode active material refers to an active material having a main skeleton of carbon into which lithium can be inserted (also referred to as “doping”). As the carbon-based negative electrode active material, specifically, coke, mesocarbon microbeads (MCMB), mesophase pitch-based carbon fiber, pyrolysis vapor-grown carbon fiber, phenol resin fired body, polyacrylonitrile-based carbon fiber, Examples include carbonaceous materials such as quasi-isotropic carbon, fired furfuryl alcohol resin (PFA) and hard carbon, and graphite materials such as natural graphite and artificial graphite.
The metal-based negative electrode active material is an active material containing a metal, and usually includes a lithium-insertable element in its structure, and has a theoretical electric capacity per unit mass of 500 mAh / in which lithium is inserted. The active material is g or more. As the metal-based active material, for example, a lithium metal, a simple metal capable of forming a lithium alloy (eg, Ag, Al, Ba, Bi, Cu, Ga, Ge, In, Ni, P, Pb, Sb, Si) , Sn, Sr, Zn, Ti, etc.) and their oxides, sulfides, nitrides, silicides, carbides, phosphides and the like. Further, an oxide such as lithium titanate can be used.
The above-mentioned negative electrode active materials may be used alone or in combination of two or more.

<< non-conductive particles >>
The non-conductive particles to be incorporated in the porous membrane layer are not particularly limited, and include known non-conductive particles used for a secondary battery.
Specifically, as the non-conductive particles, both inorganic fine particles and organic fine particles can be used, but usually, inorganic fine particles are used. Above all, as the material of the non-conductive particles, a material which is stably present in an environment in which the secondary battery is used and is electrochemically stable is preferable. Preferred examples of the material of the non-conductive particles from this viewpoint include aluminum oxide (alumina), hydrated aluminum oxide (boehmite), silicon oxide, magnesium oxide (magnesia), calcium oxide, and titanium oxide (titania). Oxide particles such as BaTiO ₃ , ZrO, alumina-silica composite oxide; nitride particles such as aluminum nitride and boron nitride; covalent crystal particles such as silicon and diamond; barium sulfate, calcium fluoride, barium fluoride And the like, and fine clay particles such as talc and montmorillonite. These particles may be subjected to element substitution, surface treatment, solid solution formation, and the like, as necessary.
The above-mentioned non-conductive particles may be used alone or in combination of two or more.

<Other ingredients>
In preparing the slurry composition, components (other components) other than the binder composition and the functional particles described above can also be used. Other components that can be added to the slurry composition are not particularly limited, and include the same components as the other components that can be added to the binder composition of the present invention. As the other components, one type may be used alone, or two or more types may be used in combination at an arbitrary ratio.

<Preparation of slurry composition>
The method for preparing the slurry composition is not particularly limited.
For example, when the slurry composition is a slurry composition for an electrode, the binder composition, the electrode active material particles, and other components used as necessary are mixed in the presence of a solvent containing water. A slurry composition can be prepared.
When the slurry composition is a slurry composition for a porous membrane layer, the binder composition, the non-conductive particles, and other components used as necessary are mixed in the presence of a solvent containing water. Thus, a slurry composition can be prepared.
When the slurry composition is a slurry composition for an adhesive layer, the binder composition can be used as it is or diluted with a solvent such as water to be used as a slurry composition. A slurry composition can also be prepared by mixing other components used accordingly in the presence of a solvent containing water.
The mixing method used for preparing the slurry composition is not particularly limited, but mixing is performed using a commonly used stirrer or disperser.

(Functional layer for non-aqueous secondary battery)
The functional layer of the present invention is a layer having a function of transferring or reinforcing or bonding electrons in a non-aqueous secondary battery. As the functional layer, for example, an electrode assembly that transfers electrons through an electrochemical reaction is used. Examples include a material layer, a porous film layer for improving heat resistance and strength, and an adhesive layer for improving adhesion. And the functional layer of the present invention is formed from the above-described slurry composition of the present invention.For example, after applying the above-mentioned slurry composition to the surface of an appropriate substrate to form a coating film, It can be formed by drying the formed coating film.

Since the functional layer of the present invention is formed from the slurry composition of the present invention prepared using the binder composition of the present invention, it has excellent adhesiveness, and a battery member having the functional layer of the present invention. Excellent secondary battery characteristics can be exhibited.

<< Substrate >>
Here, the substrate on which the slurry composition is applied is not limited. For example, a coating film of the slurry composition is formed on the surface of the release substrate, and the coating film is dried to form a functional layer. The release substrate may be peeled from the substrate. As described above, the functional layer peeled from the release substrate can be used as a self-supporting film for forming a battery member of a secondary battery.
However, from the viewpoint of increasing the production efficiency of the battery member by omitting the step of peeling the functional layer, it is preferable to use a current collector, a separator substrate, or an electrode substrate as the substrate. Specifically, when preparing the electrode mixture layer, it is preferable to apply the slurry composition onto a current collector as a substrate. When preparing the porous membrane layer and the adhesive layer, it is preferable to apply the slurry composition on a separator substrate or an electrode substrate.

[Current collector]
As the current collector, a material having electrical conductivity and being electrochemically durable is used. Specifically, for example, a current collector made of iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, platinum, or the like can be used as the current collector. Among them, a copper foil is particularly preferable as the current collector used for the negative electrode. As the current collector used for the positive electrode, an aluminum foil is particularly preferable. One of the above materials may be used alone, or two or more thereof may be used in combination at an arbitrary ratio.

[Separator substrate]
Although it does not specifically limit as a separator base material, A well-known separator base material, such as an organic separator base material, is mentioned. The organic separator substrate is a porous member made of an organic material, and examples of the organic separator substrate include a microporous film or a nonwoven fabric including a polyolefin resin such as polyethylene and polypropylene, and an aromatic polyamide resin. From the viewpoint of excellent strength, a microporous film or nonwoven fabric made of polyethylene is preferred.

[Electrode substrate]
The electrode base material (the positive electrode base material and the negative electrode base material) is not particularly limited, but the electrode base material in which the electrode mixture layer including the electrode active material particles and the binder is formed on the current collector described above is used. No.
The electrode active material particles and the binder contained in the electrode mixture layer in the electrode base material are not particularly limited, and the electrode active material particles described above in the section “Slurry composition for non-aqueous secondary battery functional layer”. And the polymer described in the section of “Binder composition for non-aqueous secondary battery” can be used.

<< Functional Layer Forming Method >>
Examples of a method for forming a functional layer on a substrate such as the above-described current collector, separator substrate, and electrode substrate include the following methods.
1) A method in which the slurry composition of the present invention is applied to the surface of a substrate (in the case of an electrode substrate, the surface of the electrode mixture layer side, the same applies hereinafter), and then dried;
2) a method of immersing a substrate in the slurry composition of the present invention and then drying it; and 3) applying the slurry composition of the present invention on a release substrate and drying to produce a functional layer. Transferring the obtained functional layer to the surface of the substrate.
Among them, the method 1) is particularly preferable because the thickness of the functional layer can be easily controlled. The method (1) specifically includes a step of applying a slurry composition on a substrate (application step) and a step of drying the slurry composition applied on the substrate to form a functional layer (drying). Step).

[Coating process]
In the coating step, the method for coating the slurry composition on the substrate is not particularly limited, and includes, for example, a doctor blade method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, a brush coating method, and the like. Method.

[Drying process]
In the drying step, the method for drying the slurry composition on the substrate is not particularly limited, and a known method can be used. Examples of the drying method include drying with warm air, hot air, low-humidity air, vacuum drying, and drying by irradiation with infrared rays, electron beams, or the like.

(Battery components for non-aqueous secondary batteries)
The battery member (separator, electrode, etc.) of the present invention has the above-mentioned functional layer of the present invention. For example, the above-mentioned functional layer and the above-mentioned base material (current collector, separator base material, electrode base material) ). The battery member of the present invention may include the above-described functional layer of the present invention and components other than the base material, as long as the effects of the present invention are not significantly impaired. Such components are not particularly limited, and include an electrode mixture layer, a porous membrane layer, an adhesive layer, and the like, which do not fall under the functional layer of the present invention.
Further, the battery member of the present invention may include a plurality of types of the functional layer of the present invention. For example, the electrode is provided with an electrode mixture layer formed from the slurry composition for an electrode of the present invention on a current collector, and on the electrode mixture layer for a porous membrane layer and / or an adhesive layer of the present invention. May be provided with a porous membrane layer and / or an adhesive layer formed from the slurry composition for use. Further, for example, the separator includes a porous film layer formed from the slurry composition for a porous film layer of the present invention on a separator substrate, and formed from the slurry composition for an adhesive layer of the present invention on the porous film layer. May be provided.
ADVANTAGE OF THE INVENTION The battery member of this invention can adhere | attach well with an adjacent battery member, and can exhibit the outstanding cycle characteristic to a secondary battery.

(Non-aqueous secondary battery)
A secondary battery of the present invention includes the above-described battery member of the present invention. More specifically, the nonaqueous secondary battery of the present invention includes a positive electrode, a negative electrode, a separator, and an electrolytic solution, and includes the battery member of the present invention as at least one of the positive electrode, the negative electrode, and the separator. And the secondary battery of the present invention can exhibit excellent cycle 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 is a battery member of the present invention including the above-described functional layer of the present invention. In addition, as a positive electrode, a negative electrode, and a separator which are not provided with the functional layer of this invention, a well-known positive electrode, a negative electrode, and a separator can be used without particular limitation.

<Electrolyte>
As the electrolyte, an organic electrolyte obtained by dissolving a supporting electrolyte 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 , (CF ₃ SO ₂ ) ₂ NLi, (C ₂ F ₅ SO ₂ ) NLi and the like. Among them, LiPF ₆ , LiClO ₄ , and CF ₃ SO ₃ Li are preferable because they are easily soluble in a solvent and show a high degree of dissociation. In addition, an electrolyte may be used individually by 1 type, and may be used in combination of 2 or more types. In general, the higher the dissociation degree of the supporting electrolyte, the higher the lithium ion conductivity tends to be. Therefore, the lithium ion conductivity can be adjusted depending on the type of the supporting electrolyte.

The organic solvent used for the electrolytic solution is not particularly limited as long as it can dissolve the supporting electrolyte. For example, in a lithium ion secondary battery, dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC) , Carbonates such as propylene carbonate (PC), butylene carbonate (BC), ethyl methyl carbonate (EMC), and vinylene carbonate (VC); esters such as γ-butyrolactone and methyl formate; 1,2-dimethoxyethane, tetrahydrofuran and the like Ethers; sulfur-containing compounds such as sulfolane and dimethyl sulfoxide; and the like are preferably used. Further, a mixture of these solvents may be used. Among them, carbonates are preferable because they have a high dielectric constant and a wide stable potential region. Usually, the lower the viscosity of the solvent used, the higher the lithium ion conductivity tends to be. Therefore, the lithium ion conductivity can be adjusted depending on the type of the solvent.
Note that the concentration of the electrolyte in the electrolytic solution can be appropriately adjusted. Further, a known additive may be added to the electrolytic solution.

<Production method of non-aqueous secondary battery>
In the above-described secondary battery of the present invention, for example, the positive electrode and the negative electrode are overlapped with a separator interposed therebetween, and if necessary, this is wound, folded, or the like, placed in a battery container, and the electrolytic solution is injected into the battery container. And can be manufactured by sealing. In addition, at least one member among the positive electrode, the negative electrode, and the separator is a battery member of the present invention. The battery container may be provided with an expanded metal, a fuse, an overcurrent prevention element such as a PTC element, a lead plate, or the like, if necessary, to prevent the pressure inside the battery from rising and preventing overcharging and discharging. The shape of the battery may be, for example, any of a coin shape, a button shape, a sheet shape, a cylindrical shape, a square shape, a flat shape, and the like.

Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. In the following description, “%” and “parts” representing amounts are based on mass unless otherwise specified.
In Examples and Comparative Examples, the THF-insoluble content of the polymer, the number of bacteria and the type of bacteria contained in the binder composition, the surface tension of the binder composition, the viscosity stability of the slurry composition, and the adhesion of the porous membrane layer The cycle characteristics of the secondary battery were measured and evaluated by the following methods.

<THF insoluble content>
The obtained aqueous dispersion of the polymer (binder composition) was dried under an environment of 50% humidity and 23 ° C. to 25 ° C. to prepare a film having a thickness of 3 ± 0.3 mm. The produced film was cut into 5 mm square to prepare a plurality of film pieces, and about 1 g of these film pieces was precisely weighed. The weight of the precisely weighed film piece was designated as W0. Next, the precisely weighed film piece was immersed in 100 g of tetrahydrofuran (THF) at 25 ° C. for 24 hours. Thereafter, the film piece was lifted from THF, and the lifted film piece was vacuum-dried at 105 ° C. for 3 hours, and its weight (weight of insoluble matter) W1 was measured. Then, the THF insoluble content (%) was calculated according to the following equation.
THF-insoluble content (%) = W1 / W0 × 100
<Bacteria count>
According to JIS K 0350-10-10 (2002), the number of bacteria (cells / ml) per 1 ml of the binder composition was measured.
<Specification of bacterial species>
Bacteria were isolated from the binder composition by an agar plate method, and the bacteria grown on a medium having an optimum concentration were pure-cultured. From the purely cultured bacteria, different bacterial strains are selected from the colony morphology and Gram-stained images, and the bacterial species contained in the binder composition are further analyzed by matrix-assisted laser desorption / ionization time-of-flight mass spectrometry (MALDI / TOFMS). Identified.
Here, the bacterial separation and pure culture by the agar plate method were specifically performed as follows.
Using an SCD medium (manufactured by Nippon Pharmaceutical Co., Ltd., product name “Digo (registered trademark)”), a 10-fold serial dilution of the sample was prepared. Next, 100 μL of each of the binder composition and the diluent of each concentration was spread on an SCD agar medium (manufactured by Nippon Pharmaceutical Co., Ltd., product name “Digo”). After aerobically culturing at 35 ° C. for 3 days, strains having different colony shapes, sizes, colors, etc. were picked from the strains grown on the SCD agar medium, and a new SCD agar medium (manufactured by Nippon Pharmaceutical Co., Ltd., product ("Digo").
When the number of bacteria contained in the binder composition is low, 10 mL of the binder composition is inoculated into 90 mL of an SCD medium (manufactured by Nippon Pharmaceutical Co., Ltd., product name "Digo") and aerobically grown at 35 ° C. After culturing for one day, the bacteria were isolated and purely cultured according to the above procedure.
<Surface tension>
The binder composition was poured on a glass Petri dish, and the surface tension was measured by a plate method using a platinum plate. Note that "CBVP-Z" manufactured by Kyowa Interface Science Co., Ltd. was used as a surface tensiometer. The measurement was performed twice in total, and the average value of the two measured values was defined as the surface tension of the binder composition.
<Viscosity stability>
The viscosity η0 of the obtained slurry composition was measured using a B-type viscometer (manufactured by Toki Sangyo Co., Ltd., product name “TVB-10”, rotation speed: 60 rpm). Next, the slurry composition whose viscosity was measured was stirred for 24 hours using a planetary mixer (rotation speed: 60 rpm), and the viscosity η1 of the slurry composition after stirring was measured using the same B-type viscometer (rotation speed) as described above. (Number: 60 rpm). Then, the viscosity maintenance ratio Δη = η1 / η0 × 100 (%) of the slurry composition before and after stirring was calculated, and the viscosity stability of the slurry composition was evaluated based on the following criteria. The temperature at the time of measuring the viscosity was 25 ° C. The closer the value of the viscosity retention ratio Δη is to 100%, the more excellent the viscosity stability of the slurry composition is.
A: viscosity maintenance ratio Δη is 90% or more and 110% or less B: viscosity maintenance ratio Δη is 80% or more and less than 90% C: viscosity maintenance ratio Δη is 70% or more and less than 80% D: viscosity maintenance ratio Δη is less than 70% <Adhesiveness>
The prepared separator having the porous membrane layer is cut into a rectangle having a length of 100 mm and a width of 10 mm to form a test piece, and the surface of the test piece having the porous membrane layer facing down is made of cellophane tape (specified in JIS Z1522). SUS substrate). Thereafter, the stress (N / m) when one end of the separator substrate was pulled in a vertical direction at a pulling speed of 50 mm / min and peeled off was measured (the cellophane tape was fixed to a test table). The same measurement as described above was performed three times, the average value was determined, and this was defined as the peel strength, which was evaluated according to the following criteria. The larger the peel strength, the stronger the porous membrane layer and the separator substrate are in close contact with each other, indicating that the porous membrane layer is more excellent in adhesion.
A: Peel strength of 3.0 N / m or more B: Peel strength of 2.5 N / m or more and less than 3.0 N / m C: Peel strength of 1.5 N / m or more and less than 2.5 N / m D: Peel strength Less than 1.5 N / m <cycle characteristics>
The manufactured lithium ion secondary battery was allowed to stand for 24 hours in an environment of 25 ° C., and then charged to 4.4 V at a charge rate of 0.1 C and discharged at a rate of 0.1 C in an environment of 25 ° C. , A charge / discharge operation of discharging to 2.75 V was performed, and the initial capacity C0 was measured. Thereafter, the same charge / discharge operation was further repeated in an environment of 60 ° C., and the capacity C1 after 1000 cycles was measured.
Then, a capacity retention ratio ΔC (= (C1 / C0) × 100%) before and after the cycle was calculated and evaluated based on the following criteria. A larger value of the capacity retention ratio ΔC indicates that the secondary battery has more excellent cycle characteristics and a longer life.
A: Capacity maintenance rate ΔC is 85% or more B: Capacity maintenance rate ΔC is 80% or more and less than 85% C: Capacity maintenance rate ΔC is 75% or more and less than 80% D: Capacity maintenance rate ΔC is less than 75%

(Example 1)
<Preparation of binder composition>
<< Polymerization step (acrylic polymer) >>
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 part of ammonium peroxy acid were added. And the gas phase was replaced with nitrogen gas, and the temperature was raised to 60 ° C.
On the other hand, in a separate container, 50 parts of ion-exchanged water, 0.5 part of sodium dodecylbenzenesulfonate as a dispersant, 94 parts of n-butyl acrylate as a (meth) acrylate monomer, and a hydrophilic group-containing monomer Was mixed with 2 parts of methacrylic acid, 2 parts of acrylonitrile as a nitrile group-containing monomer, and 1 part of allyl methacrylate and 1 part of allyl glycidyl ether as crosslinkable monomers to obtain a monomer composition. This monomer composition was continuously added to the reactor over 4 hours to carry out polymerization. During the addition, the reaction was performed at 60 ° C. After completion of the addition, the mixture was further stirred at 70 ° C. for 3 hours to complete the reaction, and an aqueous dispersion of an acrylic polymer as a particulate polymer (a mixed solution containing an acrylic polymer and water) was obtained.
<< Recovery process >>
The aqueous dispersion of the acrylic polymer obtained in the above polymerization step was transferred through a pipe and collected in a collection container.
<<< arbitrary component addition process >>
Water and a pH adjuster were added to the aqueous dispersion collected in the collection container in order to adjust to a desired solid content concentration and pH to obtain a binder composition. The washing step was not performed prior to the recovery step, the polymerization step, and the optional component addition step. Water added in the optional component addition step was subjected to sterilization treatment (ultraviolet treatment). Using the obtained binder composition, measurement of the number of bacteria and identification of the bacterial species were carried out.The binder composition did not substantially contain bacteria belonging to the specific genus, but the specific genus such as the genus Bacillus was used. Bacteria belonging to genera other than the above were contained at a bacterial count of 10 / ml. In addition, the surface tension of the binder composition and the THF-insoluble content of the acrylic polymer were measured. The results are shown in Table 1.
<Preparation of slurry composition for porous membrane layer>
Alumina particles (manufactured by Sumitomo Chemical Co., Ltd., product name “AKP-3000”, volume average particle diameter D50: 0.45 μm, tetrapod-like particles) were prepared as non-conductive particles.
In addition, carboxymethyl cellulose (manufactured by Daicel Finechem, product name “D1200”, degree of etherification: 0.8 to 1.0, viscosity of 1% aqueous solution: 10 to 20 mPa · s) was prepared as a viscosity modifier.
100 parts of the non-conductive particles, 1.5 parts of the viscosity modifier, and ion-exchanged water were mixed and dispersed so that the solid content concentration became 40%. To the obtained dispersion, 4 parts (solid content equivalent) of the binder composition obtained above and 0.2 part of a polyethylene glycol type surfactant (Sannopco SN Wet 366) were further added and mixed. Thus, a slurry composition for a porous membrane layer was obtained. The viscosity stability of the slurry composition for a porous membrane layer was evaluated. Table 1 shows the results.
<Preparation of separator with porous membrane layer>
On a separator substrate (made of polypropylene, product name "Celgard 2500"), the slurry composition for a porous membrane layer obtained above was coated with an amount of the slurry composition for a porous membrane layer of 0.3 mg / cm ² . And dried at 50 ° C. for 3 minutes. By performing this operation on one surface of the separator substrate, a separator with a porous film layer having a porous film layer formed on one surface of the separator substrate was obtained. Using this separator with a porous membrane layer, the adhesiveness of the porous membrane layer was evaluated. Table 1 shows the results.
<Preparation of positive electrode>
100 parts of LiCoO ₂ (volume average particle diameter D50: 12 μm) as positive electrode active material particles, ₂ parts of acetylene black (manufactured by Denka Corporation, product name “HS-100”) as conductive material, binding for positive electrode mixture layer 2 parts of PVDF (polyvinylidene fluoride, manufactured by Kureha Corporation, product name “# 7208”) corresponding to the solid content is mixed in NMP (N-methylpyrrolidone) to give a total solid content concentration of 70%. These were further mixed by a planetary mixer to prepare a slurry composition for a positive electrode.
The obtained slurry composition for a positive electrode was applied on a 20 μm-thick aluminum foil as a current collector by a comma coater so that the film thickness after drying was about 150 μm, and dried. This drying was performed by transporting the aluminum foil at a speed of 0.5 m / min in an oven at 60 ° C. for 2 minutes. Thereafter, a heat treatment was performed at 120 ° C. for 2 minutes to obtain a positive electrode raw material before pressing. The positive electrode raw material before pressing was rolled by a roll press to obtain a positive electrode having a positive electrode mixture layer having a thickness of 80 μm.
<Preparation of negative electrode>
In a 5 MPa pressure vessel equipped with a stirrer, 33.5 parts of 1,3-butadiene, 3.5 parts of itaconic acid, 62 parts of styrene, 1 part of 2-hydroxyethyl acrylate, 0.4 parts of sodium dodecylbenzenesulfonate as an emulsifier, ions 150 parts of exchanged water and 0.5 part of potassium peroxodisulfate as a polymerization initiator were added, and after sufficiently stirring, the mixture was heated to 50 ° C. to start polymerization. When the polymerization conversion reached 96%, the mixture was cooled to stop the reaction, and a mixture containing a binder for a negative electrode mixture layer (SBR) was obtained. To the mixture containing the binder for the negative electrode mixture layer, a 5% aqueous sodium hydroxide solution was added to adjust the pH to 8, then unreacted monomers were removed by heating under reduced pressure, and then to 30 ° C or less. After cooling, an aqueous dispersion containing the desired binder for the negative electrode mixture layer was obtained.
A mixture of 100 parts of artificial graphite (having a volume average particle diameter D50 of 15.6 μm) and a 2% aqueous solution of a sodium salt of carboxymethylcellulose (MAC350HC, manufactured by Nippon Paper Industries Co., Ltd.) as a thickener was mixed with 1 part of a solid content equivalent. After adjusting the solid content to 68% with ion-exchanged water, the mixture was mixed at 25 ° C. for 60 minutes. Further, the solid content was adjusted to 62% with ion-exchanged water, and then mixed at 25 ° C. for 15 minutes. 1.5 parts of the above-mentioned binder for negative electrode mixture layer (SBR) in a solid content equivalent amount and ion-exchanged water were added, and the mixture was adjusted to a final solid concentration of 52% and mixed for 10 minutes. This was subjected to a defoaming treatment under reduced pressure to prepare a slurry composition for a negative electrode having good fluidity.
The obtained negative electrode slurry composition was applied on a 20 μm-thick copper foil as a current collector using a comma coater so that the film thickness after drying was about 150 μm, and dried. This drying was performed by transporting the copper foil at a rate of 0.5 m / min in an oven at 60 ° C. for 2 minutes. Thereafter, a heat treatment was performed at 120 ° C. for 2 minutes to obtain a negative electrode raw material before pressing. The negative electrode material before pressing was rolled by a roll press to obtain a negative electrode having a negative electrode mixture layer having a thickness of 80 μm.
<Manufacture of secondary batteries>
The positive electrode obtained above was cut out to 49 × 5 cm. Then, the separator with the porous membrane layer obtained above is cut into 55 × 5.5 cm, and the surface on which the porous membrane layer is not formed faces the mixture layer of the positive electrode on the cut out mixture layer of the positive electrode. It was arranged as follows. Further, the negative electrode obtained above was cut into 50 × 5.2 cm, and placed on a separator with a porous membrane layer so that the surface of the negative electrode mixture layer side faced the porous membrane formed on the separator to obtain a laminate. Was. This laminate was wound by a winding machine to obtain a wound body. The wound body was pressed at 60 ° C. and 0.5 MPa to obtain a flat body. This flat body is wrapped with an aluminum packaging material as a battery, and an electrolytic solution (solvent: ethylene carbonate (EC) / diethyl carbonate (DEC) / vinylene carbonate (VC) = 68.5 / 30 / 1.5 ( (Volume ratio), electrolyte: LiPF _{6 at a} concentration of 1 M) was injected so that no air remained. Further, in order to seal the opening of the aluminum packaging material, heat sealing at 150 ° C. was performed to close the aluminum exterior, and a wound lithium ion secondary battery was manufactured.
The cycle characteristics of the fabricated wound lithium ion secondary battery were evaluated. Table 1 shows the results.

(Example 2)
Except for using the binder composition prepared as follows, in the same manner as in Example 1, to produce a slurry composition for a porous membrane layer, a separator with a porous membrane layer, a negative electrode, a positive electrode, and a secondary battery, Various measurements and evaluations were made. Table 1 shows the results.
<Preparation of binder composition>
<< Polymerization step (styrene-butadiene polymer) >>
In a reactor, 150 parts of ion-exchanged water, 25 parts of an aqueous solution of sodium dodecylbenzenesulfonate (concentration: 10%) as an emulsifier, 63 parts of styrene as an aromatic vinyl monomer, and 3.5 of itaconic acid as a hydrophilic group-containing monomer And 1 part of 2-hydroxyethyl acrylate, and 0.5 part of t-dodecyl mercaptan as a molecular weight modifier were added in this order. Next, after the gas inside the reactor was replaced with nitrogen three times, 32.5 parts of 1,3-butadiene was charged as an aliphatic conjugated diene monomer. Into a reactor maintained at 60 ° C., 0.5 part of potassium persulfate was charged as a polymerization initiator to start the polymerization reaction, and the polymerization reaction was continued with stirring. When the polymerization conversion reached 96%, the mixture was cooled, and 0.1 part of an aqueous hydroquinone solution (concentration: 10%) was added as a polymerization terminator to terminate the polymerization reaction, and a styrene-butadiene polymer as a particulate polymer was obtained. (A mixed liquid containing a styrene-butadiene polymer and water) was obtained.
<< Recovery process >>
The aqueous dispersion of the styrene-butadiene polymer obtained in the above polymerization step was transferred through a pipe and collected in a collection container.
<<< arbitrary component addition process >>
Water and a pH adjuster were added to the aqueous dispersion collected in the collection container in order to adjust to a desired solid content concentration and pH to obtain a binder composition. Note that the washing step was not performed prior to the recovery step and the polymerization step. Water added in the optional component addition step was subjected to sterilization treatment (ultraviolet treatment).

(Example 3)
In preparing the binder composition, the binder composition and the slurry for the porous membrane layer were prepared in the same manner as in Example 1 except that the water added in the optional component addition step was retained for a long time in the pipe for supplying the water. A composition, a separator with a porous membrane layer, a negative electrode, a positive electrode, and a secondary battery were manufactured, and various measurements and evaluations were performed. Table 1 shows the results.

(Example 4)
In preparing the binder composition, prior to the polymerization step, the recovery step and the optional component addition step, except that a washing step of passing water at 80 ° C. through the pipe was performed, in the same manner as in Example 1, the binder composition, A slurry composition for a porous membrane layer, a separator with a porous membrane layer, a negative electrode, a positive electrode, and a secondary battery were manufactured, and various measurements and evaluations were performed. Table 1 shows the results. The water used in the washing step was subjected to a sterilization treatment (ultraviolet treatment).

(Comparative Example 1)
In preparing the binder composition, the binder composition and the slurry composition for the porous membrane layer were prepared in the same manner as in Example 1 except that the water added in the optional component addition step was not subjected to a sterilization treatment. , A separator with a porous membrane layer, a negative electrode, a positive electrode, and a secondary battery were manufactured, and various measurements and evaluations were performed. Table 1 shows the results.

(Comparative Example 2)
In preparing the binder composition, except that the aqueous dispersion of the acrylic polymer obtained in the polymerization step was allowed to stay in the piping for a long time in the recovery step, the binder composition was prepared in the same manner as in Example 1. A slurry composition for a membrane layer, a separator with a porous membrane layer, a negative electrode, a positive electrode, and a secondary battery were manufactured, and various measurements and evaluations were performed. Table 1 shows the results.

(Comparative Example 3)
Example 1 was repeated except that the aqueous dispersion of the acrylic polymer obtained in the polymer step was retained in the reactor for a long time during the preparation of the binder composition, and was further retained in the piping for a long time in the recovery step. In the same manner as described above, a binder composition, a slurry composition for a porous membrane layer, a separator with a porous membrane layer, a negative electrode, a positive electrode, and a secondary battery were manufactured, and various measurements and evaluations were performed. Table 1 shows the results.

(Comparative Example 4)
In preparing the binder composition, a binder composition and a porous membrane were prepared in the same manner as in Comparative Example 2 except that production equipment (reactor used in the polymerization step, piping used in the recovery step, and the like) different from Comparative Example 2 was used. A slurry composition for a layer, a separator with a porous membrane layer, a negative electrode, a positive electrode, and a secondary battery were manufactured, and various measurements and evaluations were performed. Table 1 shows the results.

(Comparative Example 5)
In preparing the binder composition, except that production equipment (reactors used in the polymerization step, piping used in the recovery step, etc.) different from those in Comparative Examples 2 and 4 were used, the binder composition was prepared in the same manner as in Comparative Example 2. A slurry composition for a porous membrane layer, a separator with a porous membrane layer, a negative electrode, a positive electrode, and a secondary battery were manufactured, and various measurements and evaluations were performed. Table 1 shows the results.

(Comparative Example 6)
In preparing the binder composition, the binder composition was changed in the same manner as in Comparative Example 2 except that production equipment (reactors used in the polymerization step, piping used in the recovery step, and the like) different from those in Comparative Examples 2, 4, and 5 were used. , A slurry composition for a porous membrane layer, a separator with a porous membrane layer, a negative electrode, a positive electrode, and a secondary battery were subjected to various measurements and evaluations. Table 1 shows the results.

(Comparative Example 7)
In preparing the binder composition, the binder composition was changed in the same manner as in Comparative Example 2 except that production equipment (reactors used in the polymerization step, piping used in the recovery step, etc.) different from those in Comparative Examples 2 and 4 to 6 were used. , A slurry composition for a porous membrane layer, a separator with a porous membrane layer, a negative electrode, a positive electrode, and a secondary battery were subjected to various measurements and evaluations. Table 1 shows the results.

In Table 1 shown below,
“ACL” indicates an acrylic polymer,
“SBR” indicates a styrene-butadiene-based polymer.

As shown in Table 1, in Examples 1 to 4 using a binder composition containing a polymer and water, containing substantially no bacteria belonging to a specific genus, and having a number of bacteria of a predetermined value or less, the viscosity stability It can be seen that a slurry composition for a porous membrane layer having excellent sinterability can be obtained, and the cycle characteristics of the secondary battery can be improved while exhibiting excellent adhesiveness to the porous membrane layer.
On the other hand, from Table 1, in Comparative Example 1 in which the binder composition containing the polymer and water and the number of bacteria exceeded a predetermined value, the viscosity stability of the slurry composition for a porous membrane layer and the adhesiveness of the porous membrane layer , And that the cycle characteristics of the secondary battery deteriorate.
Also, from Table 1, a binder containing a polymer and water, and containing a bacterium belonging to the genus Burkholderia, a bacterium belonging to the genus Achromobacter, a bacterium belonging to the genus Alcaligenes, a bacterium belonging to the genus Stenotrophomonas, or a bacterium belonging to the genus Pseudomonas, respectively. In Comparative Examples 2, 4 to 7 using the composition, it can be seen that the viscosity stability of the slurry composition for a porous membrane layer is reduced.
Furthermore, from Table 1, in Comparative Example 3 using a binder composition containing a polymer and water and containing a bacterium belonging to the genus Burkholderia and having a bacterium count exceeding a predetermined value, a slurry composition for a porous membrane layer was used. It can be seen that the viscosity stability, the adhesiveness of the porous membrane layer, and the cycle characteristics of the secondary battery deteriorate.

Claims

Containing polymer and water,
Burkholderia, Achromobacter, Alcaligenes, Stenotrophomonas, and substantially free of bacteria belonging to the genus Pseudomonas,
A binder composition for a non-aqueous secondary battery, wherein the number of bacteria is 1.0 × 10 3 cells / ml or less.
The binder composition for a non-aqueous secondary battery according to claim 1, wherein the surface tension is from 22 mN / m to 55 mN / m.
The binder composition for a non-aqueous secondary battery according to claim 1 or 2, wherein the tetrahydrofuran-insoluble content of the polymer is from 10% by mass to 95% by mass.
A slurry composition for a non-aqueous secondary battery functional layer prepared using the binder composition for a non-aqueous secondary battery according to any one of claims 1 to 3.
The slurry composition for a non-aqueous secondary battery functional layer according to claim 4, further comprising a functional particle.
A functional layer for a non-aqueous secondary battery formed using the slurry composition for a non-aqueous secondary battery functional layer according to claim 4 or 5.
A battery member for a non-aqueous secondary battery, comprising the functional layer for a non-aqueous secondary battery according to claim 6.
A non-aqueous secondary battery comprising the battery member for a non-aqueous secondary battery according to claim 7.