Method for producing binder composition for non-aqueous secondary battery, method for producing slurry composition for functional layer of non-aqueous secondary battery, method for producing functional layer for non-aqueous secondary battery, method for producing battery member for non-aqueous secondary battery, and method for producing non-aqueous secondary battery

Abstract

To provide a production method of nonaqueous secondary battery binder composition that can prepare a slurry composition for nonaqueous secondary battery functional layers with excellent viscosity stability.SOLUTION: A production method of nonaqueous secondary battery binder composition that includes the process of polymerizing a monomer composition containing monomer and water at 70°C or higher to obtain a mixture containing polymer and water. The nonaqueous secondary battery binder composition includes the polymer and water, and does not substantially contain a microorganism belonging to genus Burkholderia, genus Achromobacter, genus Alcaligenes, genus Stenotrophomonas, and genus Pseudomonas. The number of microorganisms is 1.0×103 / ml or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a binder composition for a non-aqueous secondary battery, a slurry composition for a functional layer of a non-aqueous secondary battery, a functional layer for a non-aqueous secondary battery, a battery member for a non-aqueous secondary battery, and a non-aqueous secondary battery. [Background technology]

[0002] Non-aqueous secondary batteries such as lithium ion secondary batteries (hereinafter sometimes simply referred to as "secondary batteries") are small, lightweight, have high energy density, and are capable of repeated charging and discharging, and are therefore used in a wide range of applications. Non-aqueous secondary batteries generally include electrodes (positive and negative electrodes) and battery components for non-aqueous secondary batteries (hereinafter sometimes simply referred to as "battery components"), such as a separator that separates the positive and negative electrodes to prevent short circuits between them.

[0003] Here, the battery component used is a component that includes a polymer as a binder and, optionally, a functional layer that includes particles (hereinafter referred to as "functional particles") that are blended to enable the battery component to exhibit a desired function. Specifically, the separator for the secondary battery includes a separator substrate having an adhesive layer containing a binder or a porous membrane layer containing a binder and non-conductive particles as functional particles, while the electrode for the secondary battery includes an electrode substrate having a current collector and an electrode mixture layer containing a binder and electrode active material particles as functional particles, and an electrode substrate having a current collector and an electrode mixture layer on top of the electrode substrate, further including the adhesive layer or porous membrane layer.

[0004] The functional layer can be formed, for example, by drying a non-aqueous slurry composition for a secondary battery functional layer, which is obtained by dispersing and / or dissolving a polymer as a binder and optionally containing functional particles in a solvent. To further improve the performance of secondary batteries, attempts have been made to improve the slurry composition. For example, methods for improving the performance of secondary batteries by controlling the number of bacteria in the solvent used to prepare the slurry composition have been investigated (see Patent Documents 1 and 2).

[0005] In Patent Document 1, a positive electrode paste for lithium ion secondary batteries containing a positive electrode active material, a conductive material, a thickener, a binder, and a solvent is prepared using a solvent to which sulfate-reducing bacteria have been added so that the number of bacteria is within a predetermined range. This reduces sulfate radicals (SO4 2- ) has been reduced. In Patent Document 2, a slurry for a lithium-ion secondary battery negative electrode containing a negative electrode active material and a solvent is prepared using a solvent that has been irradiated with ultraviolet light or the like so that the number of bacteria falls within a predetermined range, and whose pH and temperature are each within a predetermined range. This prevents the thickener carboxymethyl cellulose salt from being hydrolyzed by bacterial cellulase, thereby preventing a decrease in the viscosity of the negative electrode slurry. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-134924 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-114959 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the conventional techniques, it is difficult to ensure sufficient viscosity stability of the slurry composition, for example, the resulting slurry composition may become excessively viscous when prepared. Furthermore, it is not possible to ensure the adhesiveness of the functional layer obtained using the slurry composition while also enabling the secondary battery to exhibit excellent cycle characteristics. Therefore, the conventional techniques have room for improvement in terms of improving the viscosity stability of the slurry composition, as well as the adhesiveness of the functional layer and the cycle characteristics of the secondary battery.

[0008] Therefore, an object of the present invention is to provide a binder composition for a non-aqueous secondary battery that can be used to prepare a slurry composition for a non-aqueous secondary battery functional layer that has excellent viscosity stability. Another object of the present invention is to provide a non-aqueous slurry composition for a secondary battery functional layer that has excellent viscosity stability. Another object of the present invention is to provide a functional layer for a non-aqueous secondary battery that has excellent adhesiveness. Another object of the present invention is to provide a battery member for a non-aqueous secondary battery that allows the non-aqueous secondary battery to exhibit excellent cycle characteristics. Another object of the present invention is to provide a non-aqueous secondary battery with excellent cycle characteristics. [Means for solving the problem]

[0009] The present inventors conducted extensive research to solve the above-mentioned problems. First, the present inventors focused on the fact that bacteria may be unintentionally mixed into binder compositions during the manufacturing process, and discovered that certain species of bacteria among these bacteria significantly reduce the stability of the polymer in the binder composition. The present inventors then discovered that a binder composition that is substantially free of these specific species of bacteria and in which the number of any bacteria that may be contained is below a predetermined value can prepare a slurry composition with excellent viscosity stability, and can improve the adhesion of a functional layer and the cycle characteristics of a secondary battery, thereby completing the present invention.

[0010] That is, an object of the present invention is to advantageously solve the above-mentioned problems, and the non-aqueous binder composition for a secondary battery of the present invention contains a polymer and water, is substantially free of bacteria belonging to the genera Burkholderia, Achromobacter, Alcaligenes, Stenotrophomonas, and Pseudomonas, and has a bacterial count of 1.0 × 10 3 In this way, in a binder composition in which a polymer is dissolved and / or dispersed in water, if bacteria belonging to the above-mentioned genera are substantially eliminated and the number of bacteria is controlled to be the above-mentioned value or less, the viscosity stability of a slurry composition prepared using the binder composition can be improved, and the adhesiveness of a functional layer obtained using the slurry composition can be increased, while a secondary battery including the functional layer can exhibit excellent cycle characteristics. In the present invention, the "number of bacteria" contained in the binder composition can be measured in accordance with JIS K 0350-10-10 (2002). In addition, in the present invention, the binder composition being "substantially free" of bacteria belonging to a specific genus means that when the procedure for identifying the bacterial species described in the examples of this specification is carried out, bacteria belonging to the genus are not detected.

[0011] The binder composition for a nonaqueous secondary battery of the present invention preferably has a surface tension of 22 mN / m or more and 55 mN / m or less. Use of a binder composition having a surface tension within the above range can sufficiently improve the viscosity stability of the slurry composition, the adhesion of the functional layer, and the cycle characteristics of the secondary battery. In the present invention, the "surface tension" of the binder composition can be measured by the method described in the examples of this specification.

[0012] In the binder composition for a non-aqueous secondary battery of the present invention, the polymer preferably has a tetrahydrofuran-insoluble content of 10% by mass to 95% by mass. A polymer having a tetrahydrofuran-insoluble content (hereinafter sometimes referred to as "THF-insoluble content") within the above range can be easily prepared, and the use of a binder composition containing such a polymer can further improve the cycle characteristics of a secondary battery. In the present invention, the "tetrahydrofuran insoluble content" of the polymer can be measured by the method described in the examples of this specification.

[0013] The present invention also aims to advantageously solve the above-mentioned problems. The present invention provides a slurry composition for a non-aqueous secondary battery functional layer, which is prepared using any of the binder compositions for non-aqueous secondary batteries described above. A slurry composition containing any of the binder compositions described above has excellent viscosity stability. Forming a functional layer from the slurry composition can improve the adhesion of the functional layer, and a battery component including the functional layer can provide a secondary battery with excellent cycle characteristics.

[0014] Here, the slurry composition for a non-aqueous secondary battery functional layer of the present invention can further contain functional particles. When the above-mentioned slurry composition contains functional particles, i.e., electrode active material particles or non-conductive particles, the slurry composition can be used to form an electrode mixture layer or a porous membrane layer that has excellent adhesiveness and can provide the secondary battery with excellent cycle characteristics.

[0015] The present invention also aims to advantageously solve the above-mentioned problems, and provides a functional layer for a nonaqueous secondary battery, characterized in that it is formed using any of the above-described slurry compositions for a nonaqueous secondary battery functional layer. The functional layer formed from any of the above-described slurry compositions has excellent adhesiveness. Furthermore, the use of a battery component including the functional layer allows the secondary battery to exhibit excellent cycle characteristics.

[0016] The present invention also aims to advantageously solve the above-mentioned problems, and provides a battery component for a non-aqueous secondary battery, characterized by including the functional layer for a non-aqueous secondary battery described above. The battery component including the functional layer described above allows the secondary battery to exhibit excellent cycle characteristics.

[0017] The present invention also aims to advantageously solve the above-mentioned problems, and provides a non-aqueous secondary battery comprising the above-mentioned battery component for a non-aqueous secondary battery. A secondary battery comprising the above-mentioned battery component has excellent cycle characteristics.

[0018] In this specification, a functional layer containing a binder and electrode active material particles is referred to as an "electrode mixture layer," a functional layer containing a binder and non-conductive particles is referred to as a "porous membrane layer," and a functional layer containing a binder but containing neither electrode active material particles nor non-conductive particles is referred to as an "adhesive layer." [Effects of the Invention]

[0019] According to the present invention, it is possible to provide a binder composition for a non-aqueous secondary battery that can prepare a slurry composition for a non-aqueous secondary battery functional layer having excellent viscosity stability. Furthermore, according to the present invention, it is possible to provide a non-aqueous slurry composition for a secondary battery functional layer that has excellent viscosity stability. According to the present invention, a functional layer for a non-aqueous secondary battery having excellent adhesiveness can be provided. Furthermore, according to the present invention, it is possible to provide a battery member for a non-aqueous secondary battery that allows the non-aqueous secondary battery to exhibit excellent cycle characteristics. Additionally, the present invention can provide a non-aqueous secondary battery with excellent cycle characteristics. DETAILED DESCRIPTION OF THE INVENTION

[0020] 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 in the manufacture of a non-aqueous secondary battery, and can be used, for example, to prepare a slurry composition for a non-aqueous secondary battery functional layer of the present invention. The slurry composition for a non-aqueous secondary battery functional layer of the present invention can be used to form any functional layer (e.g., an electrode mixture layer, a porous membrane layer, an adhesive layer) that performs functions such as electron transfer, reinforcement, or adhesion within a non-aqueous secondary battery. 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. Furthermore, the battery member for a non-aqueous secondary battery of the present invention comprises the functional layer for a non-aqueous secondary battery of the present invention. And the non-aqueous secondary battery of the present invention comprises the battery member for a non-aqueous secondary battery of the present invention.

[0021] (Binder composition for non-aqueous secondary batteries) The binder composition of the present invention contains a polymer and water. The binder composition of the present invention is substantially free of bacteria belonging to the genera Burkholderia, Achromobacter, Alcaligenes, Stenotrophomonas, and Pseudomonas (hereinafter, these may be collectively referred to as "specific genera"). Furthermore, the number of bacteria in the binder composition of the present invention is 1.0 × 10 3 It is less than 1 / ml. The binder composition of the present invention may contain bacteria belonging to a genus other than the specific genus described above, as long as the number of bacteria is not more than the above-mentioned value. The binder composition of the present invention may also contain components other than the polymer, bacteria, and water (hereinafter referred to as "other components").

[0022] Furthermore, since the binder composition of the present invention is substantially free of bacteria belonging to a specific genus and has a bacterial count below the above-mentioned value, it is possible to effectively suppress bacterial spoilage of the polymer, and a slurry composition having excellent viscosity stability can be prepared using the binder composition. Furthermore, the slurry composition having excellent viscosity stability can provide a functional layer having a uniform structure in which uneven distribution of components such as the polymer and functional particles is suppressed, and the functional layer can enhance the adhesiveness of the functional layer while allowing the secondary battery to exhibit excellent cycle characteristics.

[0023] <Polymer> The polymer in the binder composition is a component that can function as a binding material, and in a functional layer formed using a slurry composition containing the binder composition, it prevents components such as functional particles from detaching from the functional layer, and also enables adhesion of battery components to each other via the functional layer.

[0024] <<Type of polymer>> Here, 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 that can be dissolved in a binder composition containing water, or a water-insoluble particulate polymer that can be dispersed in a binder composition containing water. The binder composition of the present invention may contain one type of polymer or two or more types of polymers. In the present invention, the term "water-soluble" refers to the fact 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 mass %. In addition, in the present invention, the term "water-insoluble" refers to the fact that when 0.5 g of the polymer is dissolved in 100 g of water at 25° C., the insoluble content is 90 mass % or more. Hereinafter, an example will be described in which the polymer is a particulate polymer, but the present invention is not limited to this.

[0025] The particulate polymer is not particularly limited, but from the viewpoint of ensuring sufficient adhesion of the functional layer and cycle characteristics of the secondary battery, acrylic polymers and conjugated diene polymers can be preferably used.

[0026] [Acrylic polymer] The acrylic polymer is a polymer containing (meth)acrylic acid ester monomer units. Here, the acrylic polymer may contain repeating units other than (meth)acrylic acid ester monomer units (other repeating units). In the present invention, "(meth)acrylic" means acrylic and / or methacrylic. In addition, in the present invention, "containing a monomer unit" means that "a polymer obtained using the monomer contains a repeating unit derived from the monomer."

[0027] -(Meth)acrylic acid ester monomer unit- Examples of (meth)acrylic acid ester monomers that can form (meth)acrylic acid ester monomer units include alkyl acrylates such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, n-tetradecyl acrylate, and stearyl acrylate; and alkyl acrylates such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, pentyl methacrylate, hexyl methacrylate, and heptyl methacrylate. methacrylic acid alkyl esters such as octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, lauryl methacrylate, n-tetradecyl methacrylate, and stearyl methacrylate. These may be used alone or in combination of two or more.

[0028] The content of (meth)acrylic acid ester monomer units in the acrylic polymer is preferably more than 50% by mass, more preferably 65% ​​by mass or more, even more preferably 80% by mass or more, particularly preferably 90% by mass or more, and preferably 99% by mass or less, and more preferably 98% by mass or less, when the amount of all repeating units contained in the acrylic polymer is taken as 100% by mass. If the content of (meth)acrylic acid ester monomer units in the acrylic polymer is within the above-mentioned range, the flexibility of the acrylic polymer can be sufficiently ensured, and the adhesion of the functional layer and the cycle characteristics of the secondary battery can be further improved.

[0029] -Other repeating units- Other repeating units that the acrylic polymer may optionally contain are not particularly limited as long as they are derived from a monomer copolymerizable with the above-mentioned (meth)acrylic acid ester monomer, but examples thereof include hydrophilic group-containing monomer units (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.), nitrile group-containing monomer units, and crosslinkable monomer units. Hydrophilic group-containing monomers that can form hydrophilic group-containing monomer units (monomers having a carboxylic acid group, monomers having a phosphate group, monomers having a sulfonic acid group, monomers having a hydroxyl group, etc.), nitrile group-containing monomers that can form nitrile group-containing monomer units, and crosslinkable monomers that can form crosslinkable monomer units are not particularly limited, and those described in International Publication No. 2015 / 064099 can be used, for example.

[0030] Here, the acrylic polymer may contain "aliphatic conjugated diene monomer units" or "aromatic vinyl monomer units" which will be described later in the section "conjugated diene polymer", but usually, in the acrylic polymer, the content of (meth)acrylic acid ester monomer units is at least higher than the content of aliphatic conjugated diene monomer units. The acrylic polymer may contain only one type of other repeating unit, or may contain two or more types.

[0031] [Conjugated diene polymer] Conjugated diene polymers are polymers containing aliphatic conjugated diene monomer units. Specific examples of conjugated diene polymers include aliphatic conjugated diene polymers such as polybutadiene and polyisoprene; aromatic vinyl-aliphatic conjugated diene copolymers such as styrene-butadiene polymers (SBR); vinyl cyanide-conjugated diene copolymers such as acrylonitrile-butadiene polymers (NBR); hydrogenated SBR, hydrogenated NBR, etc. Among these, aromatic vinyl-aliphatic conjugated diene copolymers such as styrene-butadiene polymers (SBR) are preferred. Here, the aromatic vinyl-aliphatic conjugated diene copolymer contains aromatic vinyl monomer units and aliphatic conjugated diene monomer units, and may optionally contain repeating units other than the aromatic vinyl monomer units and the aliphatic conjugated diene monomer units (other repeating units).

[0032] -Aromatic vinyl monomer unit- Examples of aromatic vinyl monomers that can form aromatic vinyl monomer units include styrene, α-methylstyrene, vinyltoluene, and divinylbenzene. These can be used alone or in combination of two or more. Among these, styrene is preferred.

[0033] The content of aromatic vinyl monomer units in the aromatic vinyl-aliphatic conjugated diene copolymer is preferably 35% by mass or more, more preferably 45% by mass or more, and even more preferably 55% by mass or more, and preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 65% ​​by mass or less, when the amount of all repeating units contained in the aromatic vinyl-aliphatic conjugated diene copolymer is taken as 100% by mass. If the content of aromatic vinyl monomer units in the aromatic vinyl-aliphatic conjugated diene copolymer is within the above-mentioned range, the strength and adhesiveness of the functional layer can be sufficiently ensured, and the cycle characteristics of the secondary battery can be further improved.

[0034] - Aliphatic conjugated diene monomer unit - Examples of aliphatic conjugated diene monomers that can form aliphatic conjugated diene monomer units include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, substituted linear conjugated pentadiene, and substituted and side-chain conjugated hexadienes. These can be used alone or in combination of two or more. Among these, 1,3-butadiene is preferred.

[0035] The content of the aliphatic conjugated diene monomer units in the aromatic vinyl-aliphatic conjugated diene copolymer is preferably 20% by mass or more, more preferably 30% by mass or more, and preferably 70% by mass or less, more preferably 60% by mass or less, even more preferably 50% by mass or less, and particularly preferably 35% by mass or less, when the amount of all repeating units contained in the aromatic vinyl-aliphatic conjugated diene copolymer is taken as 100% by mass. If the content of the aliphatic conjugated diene monomer units in the aromatic vinyl-aliphatic conjugated diene copolymer is within the above-mentioned range, the flexibility and adhesiveness of the functional layer can be sufficiently ensured, and the cycle characteristics of the secondary battery can be further improved.

[0036] -Other repeating units- Other repeating units that may be optionally contained in the aromatic vinyl-aliphatic conjugated diene copolymer include, but are not limited to, repeating units derived from monomers copolymerizable with the aromatic vinyl monomer and aliphatic conjugated diene monomer described above. Examples include hydrophilic group-containing monomer units (e.g., monomer units having a carboxylic acid group, monomer units having a phosphate group, monomer units having a sulfonic acid group, and monomer units having a hydroxyl group), nitrile group-containing monomer units, and crosslinkable monomer units. The hydrophilic group-containing monomers that can form the hydrophilic group-containing monomer units (e.g., monomers having a carboxylic acid group, monomers having a phosphate group, monomers having a sulfonic acid group, and monomers having a hydroxyl group), the nitrile group-containing monomers that can form the nitrile group-containing monomer units, and the crosslinkable monomers that can form the crosslinkable monomer units are not particularly limited, and examples thereof include those described in International Publication No. WO 2015 / 064099.

[0037] Conjugated diene polymers such as aromatic vinyl-aliphatic conjugated diene copolymers may contain the (meth)acrylic acid ester monomer units described above in the "acrylic polymers" section, but typically, the content of aliphatic conjugated diene monomer units in conjugated diene polymers is greater than the content of (meth)acrylic acid ester monomer units.

[0038] <<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, even more preferably 80% by mass or more, particularly preferably 85% by mass or more, and preferably 95% by mass or less. If the THF-insoluble content of the polymer is 10% by mass or more, the polymer in the functional layer inside the secondary battery can be prevented from eluting into the electrolyte, thereby further improving the cycle characteristics of the secondary battery. Furthermore, since a polymer having a THF-insoluble content of 95% by mass or less can be easily prepared, it becomes possible to efficiently produce a binder composition containing the polymer. The THF-insoluble content of the polymer can be adjusted by changing the monomer composition of the polymer (types and ratios of monomers used) and polymerization conditions of the polymer (amount of molecular weight modifier used, reaction temperature, reaction time, etc.).

[0039] <Bacteria> <<Bacteria belonging to a specific genus>> Here, it is necessary that the binder composition of the present invention does not contain bacteria belonging to the above-mentioned specific genera (bacteria belonging to the genus Burkholderia, bacteria belonging to the genus Achromobacter, bacteria belonging to the genus Alcaligenes, bacteria belonging to the genus Stenotrophomonas, and bacteria belonging to the genus Pseudomonas).

[0040] These bacteria can easily be mixed into the binder composition during its production process. Studies by the present inventors have revealed that these bacteria particularly promote the decay of the polymer contained as a binder in the binder composition for a non-aqueous secondary battery. Therefore, intentionally removing bacteria belonging to these specific genera from the binder composition can suppress the decay of the polymer, thereby improving the viscosity stability of the slurry composition, the adhesiveness of the functional layer, and the cycle characteristics of the secondary battery.

[0041] <<Bacteria belonging to a genus other than a specific genus>> On the other hand, the binder composition of the present invention may contain bacteria belonging to a genus other than the specific genus. Examples of genera other than the specific genus include the genus Bacillus and the genus Serratia. The binder composition of the present invention may contain one type of bacteria as the bacteria belonging to a genus other than the specific genus, or may contain two or more types of bacteria. When the binder composition of the present invention contains two or more types of bacteria belonging to a genus other than the specific genus, these bacteria may belong to one genus or different genera.

[0042] <<Number of bacteria>> The binder composition of the present invention has a bacterial count of 1.0 × 10 3The number of bacteria in the binder composition (usually the number of bacteria belonging to a genus other than the specific genus) must be 1.0 × 10 or less, and preferably 10 or less. 3 If the bacterial count exceeds 1 / ml, even if the slurry composition is substantially free of bacteria belonging to a specific genus, the polymer cannot be inhibited from decaying, and the viscosity stability of the slurry composition decreases. Furthermore, even if the slurry composition is used, a functional layer with excellent adhesiveness cannot be formed, and the secondary battery cannot exhibit excellent cycle characteristics. While there is no particular lower limit for the bacterial count, a bacterial count of 1 / ml or more is preferred from the viewpoint of preventing a decrease in production efficiency due to excessive sterilization operations such as washing, and a decrease in the performance (e.g., binding ability) of the polymer in the binder composition due to excessive sterilization operations.

[0043] <Other ingredients> The binder composition of the present invention may optionally contain, as other components, known additives that can be added to functional layers such as an electrode mixture layer, a porous membrane layer, and an adhesive layer, such as a conductive material, a wetting agent, and an electrolyte additive, as well as a pH adjuster. Furthermore, the binder composition may contain various preparations (such as an emulsifier) ​​used in preparing a polymer. The binder composition of the present invention may contain a known antiseptic and / or bactericide capable of inhibiting corrosion of the polymer. However, from the viewpoint of preventing deterioration of battery characteristics (such as cycle characteristics) due to their incorporation into the secondary battery, the amount of the antiseptic and bactericide in the binder composition is preferably 1 part by mass or less, more preferably 0.1 part by mass or less, even more preferably 0.01 part by mass or less, and particularly preferably 0 part by mass (i.e., no antiseptic or bactericide is included) per 100 parts by mass of the polymer.

[0044] <Method for producing binder composition> The method for producing the binder composition of the present invention described above is also advantageous in that the binder composition is substantially free of bacteria belonging to a specific genus and the number of bacteria in the binder composition is 1.0 × 10 3However, the binder composition of the present invention is not particularly limited as long as it can be controlled to be less than 1 / ml. a step of cleaning the inner surface of a pipe for transporting a mixed liquid containing a polymer and water with water at 70°C or higher (cleaning step); a step of polymerizing a monomer composition containing a monomer and water in a reactor to obtain a mixed solution containing a polymer and water (polymerization step); a step of transferring a mixed liquid containing a polymer and water through the piping after the above-mentioned cleaning and recovering the mixed liquid (recovery step); It is preferable to produce the binder composition through the steps described above. Bacteria tend to grow and adhere to the inner surface of the pipe through which the polymer is transported. However, if the binder composition is produced through the above-described washing, polymerization, and recovery steps, the washing step can remove bacteria (especially bacteria belonging to a specific genus) from the inner surface of the pipe, thereby reducing the number of bacteria in the binder composition. Furthermore, since excessive sterilization treatment (such as ultraviolet irradiation) after the polymerization step is not necessary, the resulting polymer can have sufficiently good performance (such as binding ability). Therefore, by using the binder composition obtained through the steps described above, it is possible to provide a slurry composition with excellent viscosity stability, a functional layer with excellent adhesion, and a secondary battery with excellent cycle characteristics.

[0045] <<Cleaning process>> In the cleaning process, the inner surface of the pipe is cleaned with water at 70°C or higher. Specifically, cleaning of the inner surface of the pipe can be performed by passing water at 70°C or higher through the inside of the pipe. Note that, from the viewpoint of effectively disinfecting the inner surface of the pipe, the temperature of the water used for cleaning must be 70°C or higher, and preferably 80°C or higher. In addition, in the washing step, equipment other than the piping may be washed with water at 70° C. or higher. For example, prior to the polymerization step described below, the reactor to be used in the polymerization step may be washed together with the washing of the piping.

[0046] <<Polymerization process>> In the polymerization step, a monomer composition containing, for example, the monomers described in the "Polymer" section and water is polymerized. The content ratio of each monomer in the monomer composition can be determined based on the content ratio of the desired monomer unit (repeating unit) in the polymer. The polymerization method is not particularly limited, and any of solution polymerization, suspension polymerization, bulk polymerization, emulsion polymerization, etc. can be used. The polymerization reaction can be any of ionic polymerization, radical polymerization, living radical polymerization, various condensation polymerizations, addition polymerization, etc. Known emulsifiers and polymerization initiators can be used in the polymerization, if necessary. The polymerization temperature is not particularly limited, but from the viewpoint of smoothly progressing the polymerization reaction while reducing the number of bacteria in the resulting binder composition, it is preferably 60°C or higher, more preferably 70°C or higher, even more preferably 80°C or higher, and preferably 90°C or lower.

[0047] <<Recovery process>> Then, the mixed liquid containing the polymer and water obtained in the above polymerization step (aqueous solution or aqueous dispersion of the polymer) is transferred and recovered through the piping that has been washed in the above washing step.

[0048] <<Other processes>> The above-described method for producing the binder composition may include steps (other steps) other than the washing step, the polymerization step, and the recovery step. For example, the above-described method for producing a binder composition may include a step (optional component addition step) of adding additional water or the above-described other optional components to a mixed liquid containing the obtained polymer and water after the polymerization step. Note that, as the water used in the optional component addition step, it is preferable to use water that has been subjected to a sterilization treatment such as 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. Furthermore, for example, the method for producing the binder composition described above may include a step of sterilizing the mixed solution obtained in the polymerization step by irradiating it with ultraviolet light or the like (sterilization step). However, sterilization by ultraviolet light or the like may reduce the performance of the polymer, and there is a risk that the adhesiveness of the functional layer and the cycle characteristics of the secondary battery may be impaired. Therefore, it is preferable that the method for producing the binder composition of the present invention does not include a sterilization step.

[0049] <Surface tension of binder composition> Here, the surface tension of the binder composition is preferably 22 mN / m or more and 55 mN / m or less, and more preferably 25 mN / m or more and 55 mN / m or less. If a binder composition having a surface tension within the above range is used, the polymer can fully exhibit its performance as a binding material, and 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. The surface tension of the binder composition can be adjusted by changing the type and / or properties of the components contained in the binder composition (for example, the type and / or properties of the polymer).

[0050] (Slurry composition for non-aqueous secondary battery functional layer) The slurry composition of the present invention is a composition used to form a functional layer and is prepared using the binder composition described above. The slurry composition of the present invention is prepared using the binder composition of the present invention, which is substantially free of specific bacteria and has a bacterial count below a predetermined value, and therefore has excellent viscosity stability. Furthermore, by using the slurry composition of the present invention, a functional layer with excellent adhesiveness can be obtained. Furthermore, by using a battery component including the functional layer, a secondary battery can exhibit excellent cycle characteristics.

[0051] <Binder composition> The binder composition used is the binder composition of the present invention described above. The amount of the binder composition in the slurry composition is not particularly limited. For example, when the slurry composition is an electrode slurry composition, the amount of the binder composition can be set to an amount such that the amount of the polymer derived from the binder composition is 0.5 parts by mass or more and 15 parts by mass or less, in terms of solid content, per 100 parts by mass of electrode active material particles. Furthermore, for example, when the slurry composition is a porous membrane layer slurry composition, the amount of the binder composition can be set to an amount such that the amount of the polymer derived from the binder composition is 0.5 parts by mass or more and 30 parts by mass or less, in terms of solid content, per 100 parts by mass of non-conductive particles.

[0052] <Functional particles> Here, examples of functional particles that allow the functional layer to exhibit the intended function include electrode active material particles when the functional layer is an electrode mixture layer, and non-conductive particles when the functional layer is a porous membrane layer.

[0053] <<Electrode active material particles>> The electrode active material particles are not particularly limited, and examples thereof include particles made of known electrode active materials used in secondary batteries. Specifically, for example, the electrode active material particles that can be used in the electrode mixture layer of a lithium ion secondary battery, which is an example of a secondary battery, are not particularly limited, and particles made of the following electrode active materials can be used.

[0054] [Cathode active material] The positive electrode active material to be blended in the positive electrode composite layer of the positive electrode of the lithium ion secondary battery can be, for example, a compound containing a transition metal, such as a transition metal oxide, a transition metal sulfide, or a composite metal oxide of lithium and a transition metal, etc. Examples of the transition metal include Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Mo. Specifically, the positive electrode active material is not particularly limited, and includes lithium-containing cobalt oxide (LiCoO2), lithium manganate (LiMn2O4), lithium-containing nickel oxide (LiNiO2), lithium-containing composite oxides of Co-Ni-Mn, lithium-containing composite oxides of Ni-Mn-Al, lithium-containing composite oxides of Ni-Co-Al, olivine-type lithium iron phosphate (LiFePO4), olivine-type lithium manganese phosphate (LiMnPO4), and lithium-excess spinel compounds represented by Li 1+x Mn 2-x O4 (0 < X < 2), Li[Ni 0.17 Li 0.2 Co 0.07 Mn 0.56 O2, LiNi 0.5 Mn 1.5 O4, etc. In addition, the above-mentioned positive electrode active material may be used alone or in combination of two or more kinds.

[0055] [Negative electrode active material] Examples of the negative electrode active material blended in the negative electrode composite material layer of the negative electrode of the lithium ion secondary battery include carbon-based negative electrode active materials, metal-based negative electrode active materials, and negative electrode active materials combining these. Here, the carbon-based negative electrode active material refers to an active material having carbon as a main skeleton into which lithium can be inserted (also referred to as "doped"). Specific examples of the carbon-based negative electrode active material include carbonaceous materials such as coke, mesocarbon microbeads (MCMB), mesophase pitch-based carbon fibers, pyrolytic vapor-grown carbon fibers, phenolic resin fired bodies, polyacrylonitrile-based carbon fibers, isotropic carbon, furfuryl alcohol resin fired bodies (PFA), and hard carbon, as well as graphite materials such as natural graphite and artificial graphite. Metal-based negative electrode active materials are active materials containing metals, typically active materials containing an element capable of intercalating lithium, and having a theoretical electrical capacity per unit mass of 500 mAh / g or more when lithium is intercalated. Examples of metal-based active materials include lithium metal, elemental metals capable of forming lithium alloys (e.g., Ag, Al, Ba, Bi, Cu, Ga, Ge, In, Ni, P, Pb, Sb, Si, Sn, Sr, Zn, Ti, etc.), and oxides, sulfides, nitrides, silicides, carbides, phosphides, etc. of these. Furthermore, oxides such as lithium titanate can be used. The above-mentioned negative electrode active materials may be used singly or in combination of two or more.

[0056] <<Non-conductive particles>> The non-conductive particles to be blended in the porous membrane layer are not particularly limited, and examples thereof include known non-conductive particles used in secondary batteries. Specifically, both inorganic and organic particles can be used as non-conductive particles, but inorganic particles are typically used. Among these, materials that are stable and electrochemically stable in the environment in which a secondary battery is used are preferred. From this perspective, preferred examples of non-conductive particle materials include oxide particles such as aluminum oxide (alumina), hydrated aluminum oxide (boehmite), silicon oxide, magnesium oxide (magnesia), calcium oxide, titanium oxide (titania), BaTiO3, ZrO, and alumina-silica composite oxide; nitride particles such as aluminum nitride and boron nitride; covalently bonded crystalline particles such as silicon and diamond; sparingly soluble ionic crystalline particles such as barium sulfate, calcium fluoride, and barium fluoride; and clay particles such as talc and montmorillonite. Furthermore, these particles may be subjected to element substitution, surface treatment, solid solution formation, etc., as needed. The non-conductive particles may be used alone or in combination of two or more kinds.

[0057] <Other ingredients> In preparing the slurry composition, components other than the binder composition and functional particles (other components) can also be used. The other components that can be blended into the slurry composition are not particularly limited, and include the same components as those that can be blended into the binder composition of the present invention. The other components may be used alone or in combination of two or more in any ratio.

[0058] <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, electrode active material particles, and other components used as needed can be mixed in the presence of a solvent containing water to prepare the slurry composition. In addition, 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 needed can be mixed in the presence of a solvent containing water to prepare the slurry composition. When the slurry composition is a slurry composition for an adhesive layer, the binder composition can be used as is or diluted with a solvent such as water to form a slurry composition, or the binder composition and other components used as needed can be mixed in the presence of a solvent containing water to prepare a slurry composition. The mixing method used in preparing the slurry composition is not particularly limited, but mixing can be carried out using a commonly used stirrer or disperser.

[0059] (Functional layer for non-aqueous secondary batteries) The functional layer of the present invention is a layer that performs functions such as electron transfer, reinforcement, or adhesion in a non-aqueous secondary battery, and examples of the functional layer include an electrode mixture layer that transfers electrons via an electrochemical reaction, a porous membrane layer that improves heat resistance and strength, and an adhesive layer that improves adhesion. The functional layer of the present invention is formed from the above-mentioned slurry composition of the present invention, and can be formed, for example, by applying the above-mentioned slurry composition to the surface of a suitable substrate to form a coating film, and then drying the formed coating film.

[0060] 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, and therefore has excellent adhesive properties and can enable secondary batteries having battery components equipped with the functional layer of the present invention to exhibit excellent cycle characteristics.

[0061] <<Base material>> Here, there is no limitation on the substrate to which the slurry composition is applied, and for example, a coating film of the slurry composition may be formed on the surface of a release substrate, the coating film may be dried to form a functional layer, and the release substrate may be peeled off from the functional layer. In this way, the functional layer peeled off from the release substrate may be used as a free-standing film to form a battery component of a secondary battery. However, from the viewpoint of omitting the step of peeling off the functional layer and improving the manufacturing efficiency of the battery component, 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 the substrate. Furthermore, when preparing the porous membrane layer or the adhesive layer, it is preferable to apply the slurry composition onto a separator substrate or an electrode substrate.

[0062] [Current collector] The current collector is made of a material that is electrically conductive and electrochemically durable. Specifically, the current collector may be made of, for example, iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, platinum, or the like. Among these, copper foil is particularly preferred as the current collector for the negative electrode. The current collector to be used is particularly preferably an aluminum foil. The above materials may be used singly or in combination of two or more kinds in any ratio.

[0063] [Separator substrate] The separator substrate is not particularly limited, but examples thereof include known separator substrates such as organic separator substrates. The organic separator substrate is a porous member made of an organic material. Examples of the organic separator substrate include a microporous membrane or nonwoven fabric containing a polyolefin resin such as polyethylene or polypropylene, or an aromatic polyamide resin, and polyethylene microporous membranes and nonwoven fabrics are preferred because of their excellent strength.

[0064] [Electrode base material] The electrode substrate (positive electrode substrate and negative electrode substrate) is not particularly limited, but examples thereof include an electrode substrate in which an electrode mixture layer containing electrode active material particles and a binder is formed on the above-mentioned current collector. The electrode active material particles and 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 above in the section "Binder composition for non-aqueous secondary battery" can be used.

[0065] <<Method for forming functional layers>> Examples of methods for forming a functional layer on a substrate such as the current collector, separator substrate, or 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 on 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 the same; and 3) A method in which the slurry composition of the present invention is applied to a release substrate, dried to produce a functional layer, and the resulting functional layer is transferred to the surface of the substrate. Among these, the method 1) is particularly preferred because it allows for easy control of the thickness of the functional layer. Specifically, the method 1) includes a step of applying a slurry composition onto a substrate (application step) and a step of drying the slurry composition applied onto the substrate to form a functional layer (drying step).

[0066] [Coating process] In the coating step, the method for coating the slurry composition onto the substrate is not particularly limited, and examples thereof include a doctor blade method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, and a brush coating method.

[0067] [Drying process] In the drying step, the method for drying the slurry composition on the substrate is not particularly limited and any known method can be used. Examples of the drying method include drying with warm air, hot air, or low-humidity air, vacuum drying, and drying by irradiation with infrared rays or electron beams.

[0068] (Battery materials for non-aqueous secondary batteries) The battery components (separators, electrodes, etc.) of the present invention have the functional layer of the present invention described above, and for example, include the functional layer and the substrate (current collector, separator substrate, electrode substrate). The battery components of the present invention may also include components other than the functional layer of the present invention and the substrate, as long as the effects of the present invention are not significantly impaired. Examples of such components include, but are not limited to, an electrode mixture layer, a porous membrane layer, and an adhesive layer, which do not fall under the functional layer of the present invention. The battery component of the present invention may also include multiple types of functional layers of the present invention. For example, the electrode may include an electrode mixture layer formed on a current collector from the electrode slurry composition of the present invention, and a porous membrane layer and / or adhesive layer formed on the electrode mixture layer from the porous membrane layer and / or adhesive layer slurry composition of the present invention. For example, the separator may include a porous membrane layer formed on a separator substrate from the porous membrane layer slurry composition of the present invention, and an adhesive layer formed on the porous membrane layer from the adhesive layer slurry composition of the present invention. The battery component of the present invention can be well bonded to adjacent battery components and can also provide the secondary battery with excellent cycle characteristics.

[0069] (Non-aqueous secondary battery) The secondary battery of the present invention includes the above-described battery component 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 electrolyte solution, and includes the battery component of the present invention as at least one of the positive electrode, the negative electrode, and the separator. The secondary battery of the present invention can exhibit excellent cycle characteristics.

[0070] <Positive electrode, negative electrode, and separator> At least one of the positive electrode, negative electrode, and separator used in the secondary battery of the present invention is a battery component of the present invention having the functional layer of the present invention described above. Note that the positive electrode, negative electrode, and separator not having the functional layer of the present invention are not particularly limited, and known positive electrodes, negative electrodes, and separators can be used.

[0071] <Electrolyte> As the electrolyte, an organic electrolyte solution in which a supporting electrolyte is dissolved in an organic solvent is usually used. For example, in lithium-ion secondary batteries, a lithium salt is used as the supporting electrolyte. Examples of lithium salts include LiPF6, LiAsF6, LiBF4, LiSbF6, LiAlCl4, LiClO4, CF3SO3Li, CF4F9SO3Li, CF3COOLi, (CF3CO)2NLi, (CF3SO2)2NLi, and (C2F5SO2)NLi. Among these, LiPF6, LiClO4, and CF3SO3Li are preferred because they are easily soluble in solvents and exhibit a high degree of dissociation. One type of electrolyte may be used alone, or two or more types may be used in combination. Generally, the lithium ion conductivity tends to increase as the supporting electrolyte with a higher degree of dissociation is used, so the lithium ion conductivity can be adjusted by the type of supporting electrolyte.

[0072] The organic solvent used in the electrolyte is not particularly limited as long as it can dissolve the supporting electrolyte. For example, in lithium ion secondary batteries, carbonates such as dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene carbonate (BC), ethyl methyl carbonate (EMC), and vinylene carbonate (VC) are preferred; esters such as γ-butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; and sulfur-containing compounds such as sulfolane and dimethyl sulfoxide. Mixtures of these solvents may also be used. Among these, carbonates are preferred due to their high dielectric constant and wide stable potential range. Generally, the lower the viscosity of the solvent used, the higher the lithium ion conductivity, so the lithium ion conductivity can be adjusted by the type of solvent. The concentration of the electrolyte in the electrolytic solution can be adjusted as appropriate. Known additives may also be added to the electrolytic solution.

[0073] <Method of manufacturing non-aqueous secondary battery> The secondary battery of the present invention described above can be manufactured, for example, by overlapping a positive electrode and a negative electrode with a separator interposed therebetween, and if necessary, winding, folding, etc., putting it into a battery container, injecting an electrolyte into the battery container, and sealing it. Among the positive electrode, negative electrode, and separator, at least one member is used as the battery member of the present invention. In addition, the battery container may be provided with an expanded metal, a fuse, an overcurrent prevention element such as a PTC element, a lead plate, etc., if necessary, to prevent an increase in the pressure inside the battery and overcharge / discharge. The shape of the battery may be, for example, a coin type, button type, sheet type, cylindrical type, rectangular type, flat type, etc., any of which is acceptable.

Example

[0074] 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 the examples and comparative examples, the THF-insoluble content of the polymer, the identification of the number and species of bacteria contained in the binder composition, and the surface tension of the binder composition, the viscosity stability of the slurry composition, the adhesion of the porous film layer, and the cycle characteristics of the secondary battery were measured and evaluated by the following methods.

[0075] <THF-insoluble content> The obtained aqueous dispersion of the polymer (binder composition) was dried in an environment of 50% humidity and 23°C to 25°C to prepare a film with a thickness of 3 ± 0.3 mm. The prepared film was cut into 5 mm squares to prepare a plurality of film pieces, and these film pieces were precisely weighed to about 1 g. 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. Then, the film piece was lifted from the THF, and the lifted film piece was vacuum dried at 105°C for 3 hours to measure its weight (the weight of the insoluble matter) W1. And the THF-insoluble content (%) was calculated according to the following formula. THF-insoluble content (%) = W1 / W0 × 100 <Number of bacteria> The number of bacteria (cells / ml) per ml of the binder composition was measured according to JIS K 0350-10-10 (2002). <Identification of bacterial species> Bacteria were isolated from the binder composition using the agar plate method, and the bacteria grown in the optimal medium were cultured as pure cultures. Different bacterial strains were selected from the pure cultures based on colony morphology and Gram staining images, and the bacterial species contained in the binder composition were identified using matrix-assisted laser desorption / ionization time-of-flight mass spectrometry (MALDI / TOFMS). Here, the isolation of bacteria and the establishment of pure cultures by the agar plate method were specifically carried out as follows. Ten-fold serial dilutions of the specimen were prepared using SCD medium (manufactured by Nippon Pharmaceutical Co., Ltd., product name "Daigo (registered trademark)"). Next, 100 μL each of the binder composition and each dilution was smeared onto SCD agar medium (manufactured by Nippon Pharmaceutical Co., Ltd., product name "Daigo"). After aerobically culturing for 3 days at 35°C, strains that differed in colony shape, size, color, etc. were picked from those grown on the SCD agar medium and subcultured on new SCD agar medium (manufactured by Nippon Pharmaceutical Co., Ltd., product name "Daigo"). If the number of bacteria contained in the binder composition was small, 10 mL of the binder composition was inoculated into 90 mL of SCD medium (manufactured by Nippon Pharmaceutical Co., Ltd., product name "Daigo") and cultured aerobically at 35°C for 3 days, after which bacterial isolation and pure culture were carried out according to the procedure described above. <Surface tension> The binder composition was poured onto a glass petri dish, and the surface tension was measured by the plate method using a platinum plate. The surface tensiometer used was a "CBVP-Z" manufactured by Kyowa Interface Science Co., Ltd. The measurement was performed twice in total, and the average value of the two measurements was taken as the surface tension of the binder composition. <Viscosity stability> The viscosity η0 of the resulting slurry composition was measured using a Brookfield viscometer (manufactured by Toki Sangyo Co., Ltd., product name "TVB-10", rotation speed: 60 rpm). Next, the slurry composition whose viscosity had been 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 Brookfield viscometer (rotation speed: 60 rpm) as above. The viscosity retention rate Δη of the slurry composition before and after stirring was then calculated as Δη = η1 / η0 × 100 (%), and the viscosity stability of the slurry composition was evaluated according to the following criteria. The temperature during viscosity measurement was 25°C. The closer the value of the viscosity retention rate Δη is to 100%, the better the viscosity stability of the slurry composition. A: Viscosity maintenance rate Δη is 90% or more and 110% or less B: Viscosity retention rate Δη is 80% or more and less than 90% C: Viscosity retention rate Δη is 70% or more and less than 80% D: Viscosity retention rate Δη is less than 70% <Adhesiveness> The separator with the prepared porous membrane layer was cut into a rectangle 100 mm long and 10 mm wide to prepare a test piece. The porous membrane layer surface of the test piece was placed face down, and the porous membrane layer surface of the test piece was attached to a test stand (SUS substrate) via cellophane tape (specified in JIS Z1522). Then, one end of the separator substrate was pulled vertically at a pulling rate of 50 mm / min and peeled off, and the stress (N / m) was measured (note that the cellophane tape was fixed to the test stand). The same measurement as above was performed three times, and the average value was calculated as the peel strength, which was evaluated according to the following criteria. A higher peel strength value indicates stronger adhesion between the porous membrane layer and the separator substrate, and better adhesion of the porous membrane layer. A: Peel strength is 3.0N / m or more B: Peel strength is 2.5N / m or more and less than 3.0N / m C: Peel strength is 1.5N / m or more and less than 2.5N / m D: Peel strength is less than 1.5 N / m <Cycle characteristics> The manufactured lithium-ion secondary battery was left to stand in an environment of 25°C for 24 hours, and then subjected to a charge-discharge cycle in an environment of 25°C in which the battery was charged to 4.4 V at a charge rate of 0.1 C and discharged to 2.75 V at a discharge rate of 0.1 C, and the initial capacity C0 was measured. Thereafter, the same charge-discharge cycle was repeated in an environment of 60°C, and the capacity C1 after 1000 cycles was measured. The capacity retention rate ΔC (= (C1 / C0) × 100%) before and after the cycle was calculated and evaluated according to the following criteria. A larger value of the capacity retention rate ΔC indicates that the secondary battery has better cycle characteristics and a longer life. A: Capacity retention rate ΔC is 85% or more B: Capacity retention rate ΔC is 80% or more and less than 85% C: Capacity retention rate ΔC is 75% or more but less than 80% D: Capacity retention rate ΔC is less than 75%

[0076] Example 1 <Preparation of Binder Composition> <<Polymerization process (acrylic polymer)>> To a reactor equipped with a stirrer, 70 parts of ion-exchanged water, 0.15 parts of sodium lauryl sulfate (manufactured by Kao Chemical Corporation, "EMAL (registered trademark) 2F") as an emulsifier, and 0.5 parts of ammonium persulfate were supplied, the gas phase was replaced with nitrogen gas, and the temperature was raised to 60°C. Meanwhile, in a separate vessel, 50 parts of ion-exchanged water, 0.5 parts of sodium dodecylbenzenesulfonate as a dispersant, 94 parts of n-butyl acrylate as a (meth)acrylic acid ester monomer, 2 parts of methacrylic acid as a hydrophilic group-containing monomer, 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 were mixed to obtain a monomer composition. This monomer composition was continuously added to the reactor over 4 hours to carry out polymerization. The reaction was carried out at 60°C during the addition. After the addition was completed, the mixture was stirred for an additional 3 hours at 70°C to terminate the reaction, yielding an aqueous dispersion of an acrylic polymer, which is a particulate polymer (a mixture containing an acrylic polymer and water). <<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. <<Optional component addition process>> Water and a pH adjuster were added to the aqueous dispersion collected in the collection container to adjust the solids concentration and pH to the desired level, thereby obtaining a binder composition. Note that no washing process was performed prior to the collection process, polymerization process, and optional component addition process. Furthermore, the water added in the optional component addition process had been sterilized (ultraviolet treatment). Using the obtained binder composition, the number of bacteria was measured and the bacterial species identified. It was found that the binder composition was substantially free of bacteria belonging to a specific genus, but contained bacteria belonging to genera other than the specific genus, such as Bacillus, at a bacterial count of 10 / ml. The surface tension of the binder composition and the THF-insoluble content of the acrylic polymer were also 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-shaped 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 to a solids concentration of 40%. 4 parts (solids equivalent) of the binder composition obtained above and 0.2 parts of a polyethylene glycol surfactant (San Nopco SN Wet 366) were further added to the resulting dispersion and mixed to obtain a slurry composition for a porous membrane layer. The viscosity stability of this slurry composition for a porous membrane layer was evaluated. The results are shown in Table 1. <Preparation of separator with porous membrane layer> The slurry composition for a porous membrane layer obtained above was applied to a separator substrate (made of polypropylene, product name "Celgard 2500") in an amount of 0.3 mg / cm. 2The coating was applied so that the thickness was 1 / 4 of the porous membrane layer, and the coating was dried at 50°C for 3 minutes. This procedure was carried out on one side of the separator substrate to obtain a separator with a porous membrane layer, in which a porous membrane layer was formed on one side of the separator substrate. The adhesiveness of the porous membrane layer was evaluated using this separator with a porous membrane layer. The results are shown in Table 1. <Preparation of positive electrode> 100 parts of LiCoO2 (volume average particle diameter D50: 12 μm) as positive electrode active material particles, 2 parts of acetylene black (manufactured by Denka Company, Ltd., product name "HS-100") as a conductive material, and 2 parts (solids equivalent) of PVDF (polyvinylidene fluoride, manufactured by Kureha Corporation, product name "#7208") as a binder for the positive electrode composite layer were mixed in N-methylpyrrolidone (NMP) to give a total solids concentration of 70%, and these were further mixed using a planetary mixer to prepare a positive electrode slurry composition. The obtained positive electrode slurry composition was applied to a 20 μm thick aluminum foil current collector using a comma coater so that the dried film thickness was approximately 150 μm, and then dried. This drying was performed by conveying the aluminum foil at a speed of 0.5 m / min through an oven at 60 ° C for 2 minutes. Then, a heat treatment was performed at 120 ° C for 2 minutes to obtain a pre-pressed positive electrode blank. This pre-pressed positive electrode blank was rolled using a roll press to obtain a positive electrode with a positive electrode composite layer thickness of 80 μm. <Preparation of negative electrode> A 5 MPa pressure vessel equipped with a stirrer was charged with 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, 150 parts of ion-exchanged water, and 0.5 parts of potassium peroxodisulfate as a polymerization initiator. After thorough stirring, the mixture was heated to 50 °C to initiate polymerization. When the polymerization conversion rate reached 96%, the reaction was stopped by cooling to obtain a mixture containing a binder (SBR) for the negative electrode composite layer. A 5% aqueous sodium hydroxide solution was added to the mixture containing the binder for the negative electrode composite layer, adjusting the pH to 8. Unreacted monomer was removed by heating and vacuum distillation, and the mixture was then cooled to below 30 °C to obtain an aqueous dispersion containing the desired binder for the negative electrode composite layer. A mixture of 100 parts of artificial graphite (volume average particle diameter D50 of 15.6 μm) and 1 part of a 2% aqueous solution of carboxymethylcellulose sodium salt (manufactured by Nippon Paper Industries Co., Ltd., MAC350HC) as a thickener, in terms of solids content, was adjusted with ion-exchanged water to a solids concentration of 68%, and then mixed at 25°C for 60 minutes. The mixture was further adjusted with ion-exchanged water to a solids concentration of 62%, and then mixed at 25°C for 15 minutes. 1.5 parts of the above-mentioned binder for the negative electrode composite layer (SBR), in terms of solids content, and ion-exchanged water were added to adjust the final solids concentration to 52%, and then mixed for an additional 10 minutes. This was degassed under reduced pressure to prepare a negative electrode slurry composition with good fluidity. The obtained negative electrode slurry composition was applied to a 20 μm thick copper foil current collector using a comma coater so that the dried film thickness was approximately 150 μm, and then dried. This drying was performed by conveying the copper foil at a speed of 0.5 m / min through an oven at 60 ° C for 2 minutes. Then, heat treatment was performed at 120 ° C for 2 minutes to obtain a pre-press negative electrode blank. This pre-press negative electrode blank was rolled using a roll press to obtain a negative electrode with a negative electrode composite layer thickness of 80 μm. <Secondary battery manufacturing> The positive electrode obtained above was cut to 49 x 5 cm. Then, the separator with porous membrane layer obtained above was cut to 55 x 5.5 cm, and the surface on which the porous membrane layer was not formed was placed on the composite layer of the cut positive electrode so that it faced the composite layer of the positive electrode. Furthermore, the negative electrode obtained above was cut to 50 x 5.2 cm, and the surface on the separator with porous membrane layer was placed so that the surface on the negative electrode composite layer faced the porous membrane formed on the separator to obtain a laminate. This laminate was wound using a winding machine to obtain a wound body. This wound body was pressed at 60 ° C and 0.5 MPa to form a flat body. This flat body was wrapped in an aluminum packaging exterior as the exterior of the battery, and an electrolyte solution (solvent: ethylene carbonate (EC) / diethyl carbonate (DEC) / vinylene carbonate (VC) = 68.5 / 30 / 1.5 (volume ratio), electrolyte: LiPF6 with a concentration of 1M) was injected so that no air remained. Furthermore, to seal the opening of the aluminum packaging, the aluminum packaging was closed by heat sealing at 150°C, and a wound-type lithium-ion secondary battery was produced. The cycle characteristics of the wound-type lithium-ion secondary battery were evaluated, and the results are shown in Table 1.

[0077] Example 2 Except for using the binder composition prepared as follows, 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 produced in the same manner as in Example 1, and various measurements and evaluations were carried out. The results are shown in Table 1. <Preparation of Binder Composition> <<Polymerization process (styrene-butadiene polymer)>> A reactor was charged with 150 parts of ion-exchanged water, 25 parts of an aqueous solution of sodium dodecylbenzenesulfonate (10% concentration) as an emulsifier, 63 parts of styrene as an aromatic vinyl monomer, 3.5 parts of itaconic acid and 1 part of 2-hydroxyethyl acrylate as hydrophilic group-containing monomers, and 0.5 parts of t-dodecyl mercaptan as a molecular weight modifier, in this order. The gas inside the reactor was then purged with nitrogen three times, and 32.5 parts of 1,3-butadiene as an aliphatic conjugated diene monomer was then charged. The reactor was maintained at 60°C, and 0.5 parts of potassium persulfate was added as a polymerization initiator to initiate the polymerization reaction, which was then continued with stirring. When the polymerization conversion reached 96%, the reactor was cooled, and 0.1 parts of an aqueous solution of hydroquinone (10% concentration) was added as a polymerization terminator to terminate the polymerization reaction, yielding an aqueous dispersion of a particulate styrene-butadiene polymer (a mixture containing a styrene-butadiene polymer and water). <<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. <<Optional component addition process>> Water and a pH adjuster were added to the aqueous dispersion collected in the collection container to adjust the solid content and pH to the desired values, thereby obtaining a binder composition. No washing step was performed prior to the collection step and polymerization step. Furthermore, the water added in the optional component addition step was sterilized (ultraviolet ray treatment).

[0078] Example 3 In preparing the binder composition, except that the water added in the optional component addition step was allowed to remain in the piping for supplying the water for a long time, 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 produced in the same manner as in Example 1, and various measurements and evaluations were carried out. The results are shown in Table 1.

[0079] Example 4 In preparing the binder composition, 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 produced in the same manner as in Example 1, except that a washing step of passing water at 80°C through the piping was carried out prior to the polymerization step, recovery step, and optional component addition step, and various measurements and evaluations were carried out. The results are shown in Table 1. The water used in the washing step was sterilized (ultraviolet treatment).

[0080] (Comparative Example 1) In preparing the binder composition, except that the water added in the optional component addition step was not sterilized, the binder composition, the slurry composition for the porous membrane layer, the separator with the porous membrane layer, the negative electrode, the positive electrode, and the secondary battery were manufactured in the same manner as in Example 1, and various measurements and evaluations were carried out. The results are shown in Table 1.

[0081] (Comparative Example 2) In preparing the binder composition, except that the aqueous dispersion of the acrylic polymer obtained in the polymerization step was retained in the piping for a long time in the recovery step, the binder composition, the slurry composition for the porous membrane layer, the separator with the porous membrane layer, the negative electrode, the positive electrode, and the secondary battery were produced in the same manner as in Example 1, and various measurements and evaluations were carried out. The results are shown in Table 1.

[0082] (Comparative Example 3) In preparing the binder composition, the aqueous dispersion of the acrylic polymer obtained in the polymerization step was retained in the reactor for a long time, and furthermore, in the recovery step, it was retained in the piping for a long time, except that in the same manner as in Example 1, 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 produced, and various measurements and evaluations were carried out. The results are shown in Table 1.

[0083] Comparative Example 4 In preparing the binder composition, except that different production equipment (such as a reactor used in the polymerization process and a piping used in the recovery process) from that of Comparative Example 2 was used, 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 produced in the same manner as in Comparative Example 2, and various measurements and evaluations were carried out. The results are shown in Table 1.

[0084] (Comparative Example 5) In preparing the binder composition, except that different production equipment (such as a reactor used in the polymerization process and a piping used in the recovery process) from those in Comparative Examples 2 and 4 was used, 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 produced in the same manner as in Comparative Example 2, and various measurements and evaluations were carried out. The results are shown in Table 1.

[0085] (Comparative Example 6) In preparing the binder composition, except that different production equipment (such as a reactor used in the polymerization process and a piping used in the recovery process) from those in Comparative Examples 2, 4, and 5 was used, 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 produced in the same manner as in Comparative Example 2, and various measurements and evaluations were carried out. The results are shown in Table 1.

[0086] (Comparative Example 7) In preparing the binder composition, except that different production facilities (reactor used in the polymerization process, piping used in the recovery process, etc.) from those in Comparative Examples 2, 4 to 6 were used, the binder composition, the slurry composition for the porous membrane layer, the separator with the porous membrane layer, the negative electrode, the positive electrode, and the secondary battery were produced in the same manner as in Comparative Example 2, and various measurements and evaluations were carried out. The results are shown in Table 1.

[0087] In addition, in Table 1 shown below, "ACL" refers to an acrylic polymer; "SBR" refers to a styrene-butadiene polymer.

[0088] [Table 1]

[0089] From Table 1, it can be seen that in Examples 1 to 4, which use binder compositions containing a polymer and water, substantially not containing bacteria belonging to a specific genus, and having a bacterial count of a predetermined value or less, a slurry composition for a porous membrane layer having excellent viscosity stability can be obtained, and the cycle characteristics of the secondary battery can be improved while the porous membrane layer exhibits excellent adhesiveness. On the other hand, from Table 1, it can be seen that in Comparative Example 1, which used a binder composition containing a polymer and water and in which the number of bacteria exceeded a predetermined value, the viscosity stability of the slurry composition for the porous membrane layer, the adhesiveness of the porous membrane layer, and the cycle characteristics of the secondary battery were reduced. Furthermore, Table 1 shows that in Comparative Examples 2 and 4 to 7, which used binder compositions containing a polymer and water and bacteria belonging to the genus Burkholderia, bacteria belonging to the genus Achromobacter, bacteria belonging to the genus Alcaligenes, bacteria belonging to the genus Stenotrophomonas, or bacteria belonging to the genus Pseudomonas, the viscosity stability of the slurry composition for the porous membrane layer was reduced. Furthermore, from Table 1, it can be seen that in Comparative Example 3, which used a binder composition containing a polymer and water, and containing bacteria belonging to the genus Burkholderia, and in which the number of bacteria exceeded a predetermined value, the viscosity stability of the slurry composition for the porous membrane layer, the adhesiveness of the porous membrane layer, and the cycle characteristics of the secondary battery were reduced. [Industrial Applicability]

[0090] According to the present invention, it is possible to provide a binder composition for a non-aqueous secondary battery that can prepare a slurry composition for a non-aqueous secondary battery functional layer having excellent viscosity stability. Furthermore, according to the present invention, it is possible to provide a non-aqueous slurry composition for a secondary battery functional layer that has excellent viscosity stability. According to the present invention, a functional layer for a non-aqueous secondary battery having excellent adhesiveness can be provided. Furthermore, according to the present invention, it is possible to provide a battery member for a non-aqueous secondary battery that allows the non-aqueous secondary battery to exhibit excellent cycle characteristics. Additionally, the present invention can provide a non-aqueous secondary battery with excellent cycle characteristics.

Claims

1. a step of polymerizing a monomer composition containing a monomer and water at 70°C or higher to obtain a mixed solution containing a polymer and water; a step of washing the inner surface of the pipe with water at 70°C or higher; transferring the mixed liquid through the pipe that has been washed, and recovering the transferred mixed liquid; A method for producing a binder composition for a non-aqueous secondary battery, comprising: The non-aqueous secondary battery binder composition contains the polymer and water, is substantially free of bacteria belonging to the genera Burkholderia, Achromobacter, Alcaligenes, Stenotrophomonas, and Pseudomonas, and has a bacterial count of 1.0×10 ３ A method for producing a binder composition for a non-aqueous secondary battery, wherein the binder composition has a density of 1000 or less particles / ml.

2. 2. The method for producing a binder composition for a non-aqueous secondary battery according to claim 1, wherein the binder composition for a non-aqueous secondary battery has a surface tension of 22 mN / m or more and 55 mN / m or less.

3. The method for producing a binder composition for a non-aqueous secondary battery according to claim 1 or 2, wherein the polymer has a tetrahydrofuran insoluble content of 10% by mass or more and 95% by mass or less.

4. The method for producing the binder composition for a non-aqueous secondary battery according to claim 1, further comprising the step of adding sterilized water to the mixed solution.

5. a step of producing a binder composition for a non-aqueous secondary battery by the method for producing a binder composition for a non-aqueous secondary battery according to any one of claims 1 to 4; preparing a slurry composition for a non-aqueous secondary battery functional layer using the binder composition for a non-aqueous secondary battery; A method for producing a slurry composition for a non-aqueous secondary battery functional layer, comprising:

6. a step of producing a slurry composition for a non-aqueous secondary battery functional layer by the method for producing a slurry composition for a non-aqueous secondary battery functional layer according to claim 5; forming a non-aqueous secondary battery functional layer using the slurry composition for the non-aqueous secondary battery functional layer; A method for producing a functional layer for a non-aqueous secondary battery, comprising:

7. a step of producing the functional layer for a non-aqueous secondary battery by the method for producing the functional layer for a non-aqueous secondary battery according to claim 6; a step of producing a battery member for a non-aqueous secondary battery using the functional layer for a non-aqueous secondary battery; A method for producing a battery member for a non-aqueous secondary battery, comprising:

8. a step of producing a battery member for a non-aqueous secondary battery by the method of producing a battery member for a non-aqueous secondary battery according to claim 7; a step of fabricating a non-aqueous secondary battery using the battery member for a non-aqueous secondary battery; A method for producing a non-aqueous secondary battery, comprising:

Images