JP6724311B2 - Method for manufacturing non-aqueous secondary battery - Google Patents

Description

The present invention relates to a method for manufacturing a non-aqueous secondary battery.

Non-aqueous secondary batteries (non-aqueous electrolyte secondary batteries) such as lithium-ion secondary batteries are small and lightweight, have high energy density, and can be repeatedly charged and discharged, and are used in a wide range of applications. ing. Therefore, in recent years, various studies have been made for the purpose of further improving the performance of non-aqueous secondary batteries.

Specifically, for example, an electrode mixture layer (positive electrode mixture layer or negative electrode mixture layer) containing an electrode active material (positive electrode active material or negative electrode active material) and a binder is formed on a current collector. A non-aqueous secondary battery using a different electrode (positive electrode or negative electrode) by improving the life characteristics of the non-aqueous secondary battery by forming a SEI (Solid Electrolyte Interphase) film on the surface of the negative electrode mixture layer Is being attempted.

Then, conventionally, when manufacturing a non-aqueous secondary battery, the SEI film is charged with an electrolytic solution by charging the assembled secondary battery to a predetermined charge depth (SOC; State of Charge) (initial charging process). The electrolytic solution is reduced and decomposed at the interface with the negative electrode mixture layer to form it on the negative electrode mixture layer (see, for example, Patent Documents 1 and 2). In the conventional non-aqueous secondary battery manufacturing method, after the initial charge treatment, the non-aqueous secondary battery is stored in a heated state for a predetermined time (aging treatment), so that the formed SEI film becomes a good quality film. Has been modified.

JP, 2014-238961, A JP, 2005-95334, A

By the way, in recent years, from the viewpoint of further increasing the energy density of the non-aqueous secondary battery to provide a higher-performance non-aqueous secondary battery, increasing the density of the electrode mixture layer has been studied.

However, when the density of the electrode mixture layer is increased, it becomes difficult for the electrolytic solution to permeate into the electrode mixture layer during assembly of the non-aqueous secondary battery. Therefore, when an SEI film is formed by performing the above-described conventional initial charging treatment and aging treatment in a non-aqueous secondary battery in which the electrode composite material layer, particularly the negative electrode composite material layer is densified, when the SEI film is formed in the negative electrode composite material layer, Due to insufficient permeation of the electrolyte solution, the SEI film could be poorly formed and metal might be deposited on the negative electrode, resulting in a decrease in battery performance. On the other hand, when the assembled non-aqueous secondary battery is allowed to stand for a long time to allow the electrolyte solution to fully permeate the electrolyte solution and then perform the initial charge treatment, the SEI film is not formed properly. Further, although the occurrence of metal precipitation can be suppressed, the production efficiency of the non-aqueous secondary battery is reduced.

To solve such a problem, for example, a method such as heating may be used before the initial charge treatment to promote the permeation of the electrolytic solution into the electrode mixture layer, thereby preventing the formation of the SEI film and the occurrence of metal precipitation. It is also conceivable to efficiently manufacture the non-aqueous secondary battery while suppressing it.

However, when the non-aqueous secondary battery was heated before the initial charge treatment, that is, before the formation of the SEI film, the negative electrode composite material layer was peeled or cracked, and the battery performance was sometimes deteriorated.

Therefore, in the present invention, even when the electrode composite material layer (particularly, the negative electrode composite material layer) is densified, the SEI film is formed on the negative electrode composite material layer while suppressing the deterioration of the battery performance. It is an object of the present invention to provide a technique that enables efficient production of a water-based secondary battery.

The present inventors have earnestly studied to achieve the above object. And the present inventors, if a non-water-soluble polymer having a predetermined property and a water-soluble polymer are used together as a binder of the negative electrode mixture layer, the non-aqueous secondary battery is heated before initial charging. Even in such a case, it was found that peeling or cracking of the negative electrode mixture layer can be suppressed, and the present invention was completed.

That is, the present invention is intended to advantageously solve the above problems, a method for producing a non-aqueous secondary battery of the present invention, a positive electrode, a negative electrode, and an electrolytic solution is housed in a battery container. The assembly process of assembling the uncharged non-aqueous secondary battery, the heating process of heating the uncharged non-aqueous secondary battery to 40° C. or higher, and the initial charging process of charging the uncharged non-aqueous secondary battery after the heating process. The negative electrode includes a negative electrode mixture layer containing a negative electrode active material, a water-insoluble polymer, and a water-soluble polymer, and the water-insoluble polymer has an electrolytic solution swelling degree of more than 1.0 times 4. The water-soluble polymer has a gel content of not more than 0.0 times and not less than 80% by mass and not more than 95% by mass, and the water-soluble polymer has an electrolytic solution swelling degree of more than 1.0 times and not more than 2.0 times.
As described above, if the uncharged non-aqueous secondary battery is heated to 40° C. or higher before the initial charging, the electrolytic solution can be mixed with the negative electrode without leaving the uncharged non-aqueous secondary battery for a long time. The material layer can be satisfactorily penetrated. Therefore, the SEI film can be satisfactorily formed on the surface of the negative electrode when the initial charge is performed later. Further, if the negative electrode mixture layer contains a water-insoluble polymer having a predetermined electrolytic solution swelling degree and a gel amount and a water-soluble polymer having a predetermined electrolytic solution swelling degree, the uncharged non-aqueous secondary Even when the battery is heated before the initial charge, peeling or cracking of the negative electrode mixture layer can be suppressed. Therefore, a non-aqueous secondary battery having excellent battery performance can be manufactured.
In the present invention, the “temperature” for heating the uncharged non-aqueous secondary battery is not particularly limited as long as it can be measured as the ambient temperature around the battery assembly, but for example, the temperature can be adjusted and the actual temperature. It can be measured using a thermostat capable of measurement.
In addition, in the present invention, the “electrolyte swelling degree” and the “gel amount” can be measured using the measuring methods described in Examples of the present specification.
Furthermore, in the present invention, the “water-soluble polymer” refers to a polymer having an insoluble content of less than 1.0% by mass when 0.5 g of the polymer is dissolved in 100 g of water at a temperature of 25° C. Further, in the present invention, the “water-insoluble polymer” refers to a polymer having an insoluble content of 90% by mass or more when 0.5 g of the polymer is dissolved in 100 g of water at 25° C.

Here, in the method for producing a non-aqueous secondary battery of the present invention, the negative electrode active material preferably has a tap density of 0.8 g/cm ³ or more and 1.2 g/cm ³ or less. When the negative electrode active material having a tap density within the above range is used, a negative electrode mixture layer having a high density and strength and being easily penetrated by the electrolytic solution can be obtained.
In the present invention, the “tap density” of the negative electrode active material can be measured by using the measuring method described in the examples of this specification.

Further, in the method for producing a non-aqueous secondary battery of the present invention, the density of the negative electrode mixture layer is preferably 1.60 g/cm ³ or more. By using the manufacturing method of the present invention, even when the density of the negative electrode mixture layer is high, a non-aqueous secondary battery having a SEI film formed on the negative electrode mixture layer is suppressed while suppressing deterioration of battery performance. It can be manufactured efficiently.
In the present invention, the “density” of the negative electrode mixture layer can be calculated using the mass and thickness of the negative electrode mixture layer per unit area.

Further, in the method for producing a non-aqueous secondary battery of the present invention, the negative electrode mixture layer contains a water-insoluble polymer in a proportion of 0.5 parts by mass or more and 4 parts by mass or less per 100 parts by mass of the negative electrode active material, and It is preferable to contain a water-soluble polymer in a ratio of 0.5 parts by mass or more and 3 parts by mass or less.
By controlling the content of the water-insoluble polymer and the water-soluble polymer in the above range, it is possible to produce a non-aqueous secondary battery having excellent battery performance while suppressing the increase in internal resistance while increasing the strength of the negative electrode mixture layer. can do.

Further, in the method for producing a non-aqueous secondary battery of the present invention, the uncharged non-aqueous secondary battery further includes a separator between the negative electrode and the positive electrode, and the uncharged non-aqueous secondary battery is heated at a temperature of 60° C. for 15 hours. The adhesive strength between the negative electrode and the separator when left standing is preferably 1.0 N/m or less.
In this way, by lowering the adhesive force between the negative electrode and the separator, it is possible to prevent the negative electrode mixture layer from peeling due to expansion and contraction of the negative electrode active material due to charging and discharging, and a non-aqueous system excellent in battery performance. A secondary battery can be manufactured.
The "adhesive force" between the negative electrode and the separator can be measured using the measuring method described in the examples of this specification.

ADVANTAGE OF THE INVENTION According to this invention, the non-aqueous secondary battery which formed the SEI film|membrane on the negative electrode mixture layer can be manufactured efficiently, suppressing a fall of battery performance.

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

(Method for manufacturing non-aqueous secondary battery)
In the manufacturing method of the present invention, a non-aqueous secondary battery is manufactured in which a battery member including a positive electrode and a negative electrode and an electrolytic solution are housed in a battery container. Note that the battery member housed in the battery container may include, in addition to the positive electrode and the negative electrode, known battery members such as a separator that separates the positive electrode and the negative electrode to prevent a short circuit between the positive electrode and the negative electrode. Good.
In addition, the manufacturing method of the present invention includes an assembly step of assembling an uncharged non-aqueous secondary battery by housing a battery member and an electrolytic solution in a battery container, and heating the uncharged non-aqueous secondary battery to a predetermined temperature or higher. It includes a heating step and an initial charging step of charging the uncharged non-aqueous secondary battery after the heating step. Furthermore, in the production method of the present invention, as a negative electrode, a negative electrode comprising a negative electrode active material, a water-insoluble polymer having a predetermined property, and a negative electrode mixture layer containing a water-soluble polymer having a predetermined property. use.
Then, according to the method for producing a non-aqueous secondary battery of the present invention, since the heating step is performed before the initial charging of the uncharged non-aqueous secondary battery, the electrolytic solution in the negative electrode mixture layer before the initial charging is performed. It is possible to efficiently manufacture a non-aqueous secondary battery in which the SEI film is formed on the negative electrode mixture layer while promoting the permeation of the SEI film and suppressing the formation failure of the SEI film and the metal deposition on the negative electrode. Further, according to the method for producing a non-aqueous secondary battery of the present invention, since a non-water-soluble polymer having a predetermined property and a water-soluble polymer are used, when the heating step is performed before initial charging Even with this, peeling or cracking of the negative electrode mixture layer can be suppressed. Therefore, according to the method for producing a non-aqueous secondary battery of the present invention, a non-aqueous secondary battery having a negative electrode mixture layer on which a good SEI film is formed and having excellent battery characteristics such as life characteristics can be efficiently produced. Can be manufactured in a simple manner.

<Negative electrode>
The negative electrode of the non-aqueous secondary battery manufactured using the manufacturing method of the present invention is not particularly limited as long as it has a predetermined negative electrode mixture layer, and for example, a predetermined negative electrode mixture layer is collected. A negative electrode formed on an electric body can be used.

[Current collector]
Here, a known current collector can be used as the current collector. And as the material of the current collector, a metal is preferable because it has electrical conductivity, electrochemical durability, and heat resistance, for example, iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, Platinum or the like can be used.

[Negative electrode mixture layer]
The negative electrode mixture layer of the negative electrode used in the production method of the present invention contains a negative electrode active material, a water-insoluble polymer, and a water-soluble polymer.
Here, the density of the negative electrode material layer is preferably 1.60 g / cm ³ or more, more preferably 1.65 g / cm ³ or more, still be at 1.70 g / cm ³ or more It is preferably 2.0 g/cm ³ or less. When the density of the negative electrode mixture layer is 1.60 g/cm ³ or more, the energy density of the non-aqueous secondary battery can be sufficiently increased. In general, when the density of the negative electrode mixture layer is increased, it becomes difficult for the electrolytic solution to permeate the negative electrode mixture layer. However, according to the manufacturing method of the present invention, since the heating step is performed before the initial charging step, even if the density of the negative electrode mixture layer is 1.60 g/cm ³ or more, the negative electrode can be formed in a short time. It is possible to satisfactorily permeate the electrolytic solution into the composite material layer, and to suppress the formation failure of the SEI film and the occurrence of metal deposition due to the insufficient permeation of the electrolytic solution.

[[Water-insoluble polymer]]
The water-insoluble polymer contained in the negative electrode mixture layer holds the components contained in the negative electrode mixture layer so as not to be separated from the negative electrode mixture layer, and the negative electrode mixture layer formed on the current collector is It is a component that can be held so as to bind well with the current collector.

-Properties of water-insoluble polymer-
Then, the water-insoluble polymer contained in the negative electrode mixture layer needs to have an electrolytic solution swelling degree of more than 1.0 times and 4.0 times or less. Is preferably 1.1 times or more, more preferably 1.3 times or more, preferably 3.0 times or less, and more preferably 2.0 times or less. When the electrolyte swelling degree of the water-insoluble polymer is more than 1.0 times, the ionic conductivity of the negative electrode mixture layer can be sufficiently secured and the internal resistance of the secondary battery can be sufficiently lowered. If the electrolyte swelling degree of the water-insoluble polymer is 4.0 times or less, the strength of the negative electrode mixture layer is sufficiently increased, and even when the heating step is performed before the initial charging step, It is possible to suppress peeling or cracking of the negative electrode mixture layer.
The electrolytic solution swelling degree can be controlled by, for example, adjusting the composition of the water-insoluble polymer.

Further, the water-insoluble polymer needs to have a gel amount of 80% by mass or more and 95% by mass or less, and the gel amount of the water-insoluble polymer is preferably 82% by mass or more, 94 It is preferably not more than mass %. When the gel amount of the water-insoluble polymer is 80% by mass or more and 95% by mass or less, the strength and flexibility of the negative electrode mixture layer are sufficiently increased, and the heating step is performed before the initial charging step. Also, peeling or cracking of the negative electrode mixture layer can be suppressed.
The gel amount can be controlled by, for example, adjusting the composition of the water-insoluble polymer, the polymerization temperature, and the addition amount and type of the chain transfer agent used for the polymerization.

-Composition of water-insoluble polymer-
The water-insoluble polymer is not particularly limited as long as it has the electrolytic solution swelling degree and gel amount described above, and any polymer such as a conjugated diene polymer or an acrylic polymer is used. be able to. Among them, the water-insoluble polymer is preferably a conjugated diene polymer, and more preferably a copolymer having an aromatic vinyl monomer unit and a conjugated diene monomer unit as main constituent units. Here, "the aromatic vinyl monomer unit and the conjugated diene monomer unit are the main constituent units" means that in the copolymer, the aromatic vinyl monomer unit and the conjugated diene monomer unit It means that the total content exceeds 50 mass% of all the monomer units of the copolymer.

-Aromatic vinyl monomer unit-
Here, examples of the aromatic vinyl monomer capable of forming the aromatic vinyl monomer unit include styrene, α-methylstyrene, pt-butylstyrene, butoxystyrene, vinylnaphthalene, vinyltoluene, and chlorostyrene. And so on. Of these, styrene is preferable. These may be used alone or in combination of two or more.
The proportion of the aromatic vinyl monomer unit in the copolymer is preferably 10% by mass or more, more preferably 30% by mass or more, further preferably 50% by mass or more, It is preferably 80% by mass or less, more preferably 75% by mass or less, and further preferably 70% by mass or less. When the proportion of the aromatic vinyl monomer unit is 10% by mass or more, it is possible to suppress the electrolyte solution swelling degree of the water-insoluble polymer from becoming excessively large and to further enhance the strength of the negative electrode mixture layer. Because. Further, when the proportion of the aromatic vinyl monomer unit is 80% by mass or less, the toughness of the water-insoluble polymer can be increased and the occurrence of cracking or peeling of the negative electrode mixture layer can be sufficiently suppressed. Because.

-Conjugated diene monomer unit-
Examples of the conjugated diene monomer capable of forming the conjugated diene monomer unit include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3- Examples thereof include butadiene, 1,3-pentadiene, 2-chloro-1,3-butadiene and piperylene. Among these, 1,3-butadiene is preferable. These may be used alone or in combination of two or more.
The proportion of the conjugated diene monomer unit in the copolymer is preferably 20% by mass or more, more preferably 25% by mass or more, further preferably 30% by mass or more, 50 It is preferably not more than 40% by mass, more preferably not more than 45% by mass, further preferably not more than 40% by mass. When the proportion of the conjugated diene monomer unit is 20% by mass or more, the gel amount of the copolymer can be increased and the electrolytic solution swelling degree can be suppressed from becoming excessively large. As a result, a negative electrode mixture layer having excellent flexibility and strength can be obtained. Further, if the ratio of the conjugated diene monomer unit is 50% by mass or less, the negative electrode composite material layer can have an appropriate hardness and the strength of the negative electrode composite material layer can be sufficiently secured.

-Other monomer units-
Incidentally, the copolymer having an aromatic vinyl monomer unit and a conjugated diene monomer unit as a main constituent unit is a monomer unit other than the aromatic vinyl monomer unit and the conjugated diene monomer unit. May be included. Other monomer units are not particularly limited and include, for example, acidic group-containing monomer units such as unsaturated carboxylic acid monomer units, (meth)acrylic acid ester monomer units, and nitrile group-containing units. A monomer unit etc. are mentioned. These may be used alone or in combination of two or more. In addition, in this application, "(meth)acryl" means acryl and/or methacryl.

= Monomer unit containing acidic group =
Examples of the unsaturated carboxylic acid monomer capable of forming an unsaturated carboxylic acid monomer unit which is an acidic group-containing monomer unit include, for example, unsaturated monocarboxylic acid and its derivative, unsaturated dicarboxylic acid and its acid anhydride. The thing, and those derivatives are mentioned. Examples of unsaturated monocarboxylic acids include acrylic acid, methacrylic acid, and crotonic acid. Examples of unsaturated monocarboxylic acid derivatives include 2-ethylacrylic acid, isocrotonic acid, α-acetoxyacrylic acid, β-trans-aryloxyacrylic acid, α-chloro-β-E-methoxyacrylic acid, and β. -Diaminoacrylic acid. Examples of unsaturated dicarboxylic acids include maleic acid, fumaric acid, and itaconic acid. Examples of unsaturated dicarboxylic acid anhydrides include maleic anhydride, acrylic anhydride, methyl maleic anhydride, and dimethyl maleic anhydride. Examples of unsaturated dicarboxylic acid derivatives include methyl maleic acid, dimethyl maleic acid, phenyl maleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid, diphenyl maleate, nonyl maleate, decyl maleate, dodecyl maleate. , Octadecyl maleate, fluoroalkyl maleate, and the like. These can be used alone or in combination of two or more.

Among these, as the unsaturated carboxylic acid monomer, unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid, and maleic acid, fumaric acid, unsaturated dicarboxylic acids such as itaconic acid are preferable, and acrylic acid and itaconic acid. Is more preferable, and itaconic acid is further preferable.
And the ratio of the acidic group-containing monomer unit in the copolymer is preferably 0.5% by mass or more, more preferably 1% by mass or more, further preferably 2% by mass or more. It is preferably 10% by mass or less, more preferably 8% by mass or less, still more preferably 6% by mass or less. This is because if the proportion of the acidic group-containing monomer unit is 0.5% by mass or more, the adhesion between the negative electrode active materials and between the current collector and the negative electrode mixture layer can be improved. On the other hand, if the proportion of the acidic group-containing monomer unit is 10% by mass or less, it is possible to sufficiently suppress the occurrence of cracking or peeling of the negative electrode mixture layer.

=(meth)acrylic acid ester monomer unit=
Examples of the (meth)acrylic acid ester monomer capable of forming the (meth)acrylic acid ester monomer unit include, for example, methyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. , 2-hydroxyethyl acrylate. These can be used alone or in combination of two or more.

= Nitrile group-containing monomer unit =
Examples of the nitrile group-containing monomer capable of forming the nitrile group-containing monomer unit include α,β-ethylenically unsaturated nitrile monomers. Specifically, the α,β-ethylenically unsaturated nitrile monomer is not particularly limited as long as it is an α,β-ethylenically unsaturated compound having a nitrile group, for example, acrylonitrile; α-chloroacrylonitrile, and α-halogenoacrylonitrile such as α-bromoacrylonitrile; α-alkylacrylonitrile such as methacrylonitrile and α-ethylacrylonitrile; and the like. Among these, (meth)acrylonitrile is preferable from the viewpoint of appropriately increasing the electrolytic solution swelling degree of the water-insoluble polymer to increase the ionic conductivity of the negative electrode mixture layer and reduce the internal resistance of the secondary battery. These can be used alone or in combination of two or more.

-Method for preparing water-insoluble polymer-
Then, the method for preparing a water-insoluble polymer using the above-mentioned monomer is not particularly limited, and for example, any method such as a solution polymerization method, a suspension polymerization method, a bulk polymerization method, or an emulsion polymerization method may be used. You can As the polymerization method, addition polymerization such as ionic polymerization, radical polymerization, living radical polymerization can be used.

-Content-
The amount of the water-insoluble polymer contained in the negative electrode mixture layer is preferably 0.5 part by mass or more, and more preferably 1.0 part by mass or more, per 100 parts by mass of the negative electrode active material. It is more preferably 1.5 parts by mass or more, further preferably 4 parts by mass or less, more preferably 3 parts by mass or less, and further preferably 2.5 parts by mass or less. When the content of the water-insoluble polymer having a predetermined electrolytic solution swelling degree and gel amount is at least the above lower limit, flexibility is imparted to the negative electrode mixture layer, and the strength of the negative electrode mixture layer is sufficiently secured. Because you can. Further, when the content of the water-insoluble polymer having a predetermined electrolytic solution swelling degree and gel amount is not more than the above upper limit, the internal resistance is small, and a high-capacity non-aqueous secondary battery can be obtained. is there.

[[Water-soluble polymer]]
The water-soluble polymer contained in the negative electrode mixture layer, together with the water-insoluble polymer described above, holds the components contained in the negative electrode mixture layer so as not to be separated from the negative electrode mixture layer, and on the current collector. It is a component capable of favorably binding the negative electrode composite material layer formed on the current collector.

-Properties of water-soluble polymer-
The water-soluble polymer needs to have an electrolytic solution swelling degree of more than 1.0 times and 2.0 times or less, and the electrolytic solution swelling degree of the water-soluble polymer is 1.3 times or less. It is preferably 1.2 times or less, more preferably 1.1 times or less. When the electrolytic solution swelling degree of the water-soluble polymer is more than 1.0 times, the ionic conductivity of the negative electrode mixture layer can be sufficiently secured and the internal resistance of the secondary battery can be sufficiently lowered. If the degree of swelling of the electrolyte of the water-soluble polymer is 2.0 times or less, the strength of the negative electrode mixture layer is sufficiently increased, and even if the heating step is performed before the initial charging step, the negative electrode It is possible to prevent the composite material layer from peeling or cracking.
The electrolyte solution swelling degree of the water-soluble polymer can be controlled by, for example, adjusting the composition of the water-soluble polymer.

-Composition of water-soluble polymer-
The water-soluble polymer is not particularly limited as long as it has the electrolytic solution swelling degree described above, and includes, for example, carboxymethyl cellulose (CMC), carboxyethyl cellulose, ethyl cellulose, hydroxymethyl cellulose, hydroxypropyl cellulose, carboxyethyl methyl cellulose. Cellulose compounds such as cellulose compounds and salts thereof such as ammonium salts and alkali metal salts; oxidized starch and phosphate starch; casein; various modified starches; polyethylene oxide, polyethylene glycol, polyvinyl alcohol, polyvinylpyrrolidone, polysulfonic acid , Polycarboxylic acids; (meth)acrylic acid copolymers, acrylamide polymers, and salts thereof such as ammonium salts and alkali metal salts. These may be used alone or in combination of two or more.

Among them, the water-soluble polymer is preferably a cellulose-based polymer, a (meth)acrylamide-based polymer, or a combination thereof.

-Content-
The amount of the water-soluble polymer contained in the negative electrode mixture layer is preferably 0.5 parts by mass or more, and more preferably 0.7 parts by mass or more, per 100 parts by mass of the negative electrode active material. , 0.8 parts by mass or more, preferably 3 parts by mass or less, more preferably 2 parts by mass or less, and further preferably 1.5 parts by mass or less. If the content of the water-soluble polymer having a predetermined electrolyte swelling degree is equal to or more than the above lower limit, the negative electrode composite material layer has an appropriate hardness, and the strength of the negative electrode composite material layer can be sufficiently secured. is there. Further, if the content of the water-soluble polymer having a predetermined electrolytic solution swelling degree is equal to or less than the upper limit value, the internal resistance of the secondary battery is reduced, and a high-capacity non-aqueous secondary battery can be obtained. ..

[[Negative electrode active material]]
The negative electrode active material contained in the negative electrode mixture layer is not particularly limited, and a known negative electrode active material can be used. Examples of the known negative electrode active material include a carbon-based active material, a silicone-based active material, and a single metal or an alloy forming a lithium alloy when the non-aqueous secondary battery is a lithium-ion secondary battery. .. Among them, as the negative electrode active material, a carbon-based active material is preferable, a carbon-based active material using natural graphite is more preferable, and natural graphite is coated with a low crystalline carbon material (hereinafter, referred to as “amorphous coat”). Is more preferable. Examples of the amorphous coating method include the method disclosed in Japanese Patent Application Laid-Open No. 2013-45714.

− Properties of negative electrode active material −
The negative electrode active material preferably has a tap density of 0.8 g/cm ³ or more, more preferably 0.85 g/cm ³ or more, still more preferably 0.9 g/cm ³ or more. preferably .2g / cm ³ or less, more preferably 1.1 g / cm ³ or less, further preferably 1.05 g / cm ³ or less. This is because when a negative electrode active material having a tap density of 0.8 g/cm ³ or more is used, a negative electrode including a negative electrode mixture layer having high density and strength can be easily obtained. Also, if a negative electrode active material having a tap density of 1.2 g/cm ³ or less is used, the electrolytic solution will more easily penetrate into the negative electrode mixture layer.

The volume average particle diameter of the negative electrode active material is preferably 5 μm or more, more preferably 7 μm or more, further preferably 10 μm or more, preferably 30 μm or less, and 25 μm or less. It is more preferable that it is present, and it is further preferable that it is 20 μm or less. In the present invention, the “volume average particle size” of the negative electrode active material is, for example, 50% using a laser diffraction/scattering particle size distribution measuring device (Microtrack Bell, model number: Microtrack MT3000II). The diameter can be measured by a wet method.

Here, the volume average particle diameter and tap density of the negative electrode active material can be controlled by, for example, spheroidizing the amorphous or non-spherical negative electrode active material particles. A preferable method of the spheroidizing treatment is not particularly limited, and examples thereof include the method disclosed in JP 2010-34036A. Specifically, the spheroidizing treatment is performed by, for example, using a hybridization system (manufactured by Nara Machinery Co., Ltd., model number: NHS-3) to give impact force or the like to the negative electrode active material particles dispersed in a high-speed air stream. It can be carried out.

[Preparation of negative electrode]
The negative electrode including the above-mentioned negative electrode mixture layer is not particularly limited, and can be manufactured by a known method. Specifically, the negative electrode collects a negative electrode slurry composition containing, for example, a negative electrode active material, a water-insoluble polymer, a water-soluble polymer, an optional additive, and a dispersion medium such as water. It can be prepared by applying it on the body and drying the applied negative electrode slurry composition to form a negative electrode mixture layer. The density of the negative electrode mixture layer formed on the current collector may be adjusted by applying a pressure treatment such as pressing.
Further, the water-insoluble polymer is usually present in the form of particles in the negative electrode slurry composition, but may be in the form of particles in the formed negative electrode mixture layer, or in any other form. It may be.

<Positive electrode>
A known positive electrode can be used as the positive electrode of the non-aqueous secondary battery manufactured using the manufacturing method of the present invention. Specifically, the positive electrode is not particularly limited, and a positive electrode having a current collector and a positive electrode mixture layer formed on the current collector can be used. The positive electrode mixture layer usually contains a positive electrode active material, a conductive material, and a binder.
Here, as the current collector, the positive electrode active material in the positive electrode mixture layer, the conductive material, the binder, and the method for forming the positive electrode mixture layer on the current collector, known methods may be used. For example, those described in JP-A-2013-145763 can be used.

<Electrolyte>
As the electrolytic solution of the non-aqueous secondary battery manufactured using the manufacturing method of the present invention, a known electrolytic solution can be used. Specifically, when the non-aqueous secondary battery is a lithium ion secondary battery, it is not particularly limited, and for example, a non-aqueous solvent in which a lithium salt is dissolved as a supporting electrolyte can be used. 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, and (CF ₃ CO) ₂ NLi. Lithium salts such as (CF ₃ SO ₂ ) ₂ NLi and (C ₂ F ₅ SO ₂ )NLi. Particularly, LiPF ₆ , LiClO ₄ , and CF ₃ SO ₃ Li which are easily dissolved in a solvent and have a high dissociation degree are preferably used. The electrolyte may be used alone or in combination of two or more at an arbitrary ratio. Usually, 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 solvent used in the electrolytic solution is not particularly limited as long as it can dissolve the supporting electrolyte, but is usually dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene. Alkyl carbonates such as carbonate (BC) and ethylmethyl carbonate (EMC); γ-butyrolactone, esters such as methyl formate, ethers such as 1,2-dimethoxyethane, and tetrahydrofuran; sulfolane, dimethyl sulfoxide, etc. Sulfur-containing compounds; It is also possible to use the electrolytic solution containing an additive. As the additive, a carbonate-based compound such as vinylene carbonate (VC) is preferable.

<Separator>
The separator optionally included in the non-aqueous secondary battery manufactured using the manufacturing method of the present invention is not particularly limited, and a known separator can be used. As the known separator, for example, a microporous membrane using a polyolefin-based (polyethylene, polypropylene, polybutene, polyvinyl chloride) resin, polyethylene terephthalate, polycycloolefin, polyether sulfone, polyamide, polyimide, polyimide amide, polyaramid, Examples thereof include a microporous film made of a resin such as polycycloolefin, nylon, polytetrafluoroethylene, a woven or non-woven fabric made of a polyolefin fiber, and an aggregate of particles made of an insulating material. Among these, it is possible to reduce the thickness of the entire separator, thereby increasing the ratio of the electrode mixture layer in the non-aqueous secondary battery and increasing the capacity per volume, A microporous membrane using a polyolefin-based (polyethylene, polypropylene, polybutene, polyvinyl chloride) resin is preferable.

[Adhesive layer]
Here, when a separator is provided between the positive electrode and the negative electrode, a known adhesive layer may be provided between the electrode and the separator in order to integrate the electrode (positive electrode, negative electrode) and the separator well. it can.
However, the negative electrode active material in the negative electrode mixture layer included in the non-aqueous secondary battery expands and contracts as the battery is charged and discharged. Therefore, for example, when the negative electrode mixture layer and the separator are firmly bonded via the adhesive layer, the stress due to the expansion and contraction of the negative electrode active material cannot be sufficiently relaxed, and the negative electrode mixture layer It can cause cracks and cracks. Therefore, it is preferable not to provide an adhesive layer between the negative electrode mixture layer and the separator. Further, even if an adhesive layer is provided between the negative electrode mixture layer and the separator, it is preferable to use an adhesive layer having low adhesive strength.
Specifically, the adhesive force between the negative electrode and the separator when the uncharged non-aqueous secondary battery is left for 15 hours at a temperature of 60° C. is preferably 1.0 N/m or less, and 0.5 N/m or less. Is more preferable, 0.3 N/m or less is more preferable, and 0.15 N/m or more can be set. This is because if the adhesive force is 1.0 N/m or less, it is possible to prevent the peeling of the negative electrode mixture layer due to the expansion and contraction of the negative electrode active material during charge/discharge from being promoted.

<Battery container>
The battery container of the non-aqueous secondary battery manufactured using the manufacturing method of the present invention is not particularly limited, and any container body can be used. Specifically, for the battery container, for example, a packaging material or a case formed by using a lightweight metal such as aluminum or steel can be adopted.

<Assembly process>
In the assembly process included in the method for manufacturing a non-aqueous secondary battery of the present invention, a positive electrode, a negative electrode, and an electrolytic solution are housed in a battery container to prepare an uncharged non-aqueous secondary battery. The positive electrode and the negative electrode may be housed in the battery container with a separator disposed between the positive electrode and the negative electrode.

Specifically, in the assembly step, for example, typically in a normal temperature range, the positive electrode and the negative electrode are laminated via a separator to obtain a laminate, and then the obtained laminate is required. Depending on the shape of the battery, wrap or fold it into the battery container. Then, an uncharged non-aqueous secondary battery is assembled by injecting an electrolytic solution into the battery container containing the laminated body and sealing the battery container. Here, in the present specification, the “normal temperature range” refers to 20° C.±10° C.

In addition, in order to prevent an increase in internal pressure of the non-aqueous secondary battery and the occurrence of overcharging/discharging, the uncharged non-aqueous secondary battery may include an overcurrent prevention element such as a fuse or a PTC element as necessary. , Expanded metal, lead plate, etc. may be provided. The shape of the uncharged non-aqueous secondary battery to be assembled may be any of coin type, button type, sheet type, cylindrical type, prismatic type, flat type and the like.

<Heating process>
In the heating step included in the method for producing a non-aqueous secondary battery of the present invention, the uncharged non-aqueous secondary battery obtained by the above-described assembly step is heated to a high temperature range of 40° C. or higher to obtain an electrode mixture. The layer (particularly the negative electrode mixture layer) is allowed to penetrate the electrolytic solution well. In the heating step, the uncharged non-aqueous secondary battery, which has been heated to a predetermined temperature, is kept at the temperature for a predetermined time to further promote the permeation of the electrolytic solution into the electrode mixture layer.

Here, the heating temperature of the uncharged non-aqueous secondary battery needs to be 40° C. or higher, preferably 50° C. or higher, more preferably 55° C. or higher, preferably 85° C. or lower, and 70° C. or lower. preferable. When the uncharged non-aqueous secondary battery is heated at 40° C. or higher, the viscosity of the electrolytic solution in the battery is lowered, so that the electrolytic solution easily enters the electrode mixture layer and is sufficiently contained in the electrode mixture layer. It becomes easy to spread. As a result, even when a high-density negative electrode mixture layer is used, it is possible to suppress the formation failure of the SEI film and the occurrence of metal deposition at the time of initial charging described later, and to obtain good life characteristics and rate characteristics. A non-aqueous secondary battery having is obtained. Further, if the uncharged non-aqueous secondary battery is heated at 85° C. or lower, ignition of the electrolytic solution at the time of heating can be prevented and the non-aqueous secondary battery can be manufactured safely.

Furthermore, the heating and holding (temperature holding) time of the heated uncharged non-aqueous secondary battery is preferably 1 hour or longer, more preferably 5 hours or longer, further preferably 10 hours or longer, and preferably 50 hours or shorter. This is because if the uncharged non-aqueous secondary battery is heated for 1 hour or more, the electrolytic solution can be sufficiently permeated into the electrode mixture layer. Further, if the uncharged non-aqueous secondary battery is heated for 50 hours or less, deterioration of the electrode mixture layer due to long-time heating can be prevented, and reduction in production efficiency of the non-aqueous secondary battery can be suppressed. Because.

Incidentally, in the method for producing a non-aqueous secondary battery of the present invention, since the negative electrode mixture layer containing a non-water-soluble polymer and a water-soluble polymer having predetermined properties is used, the above heat treatment is performed. Also, the occurrence of peeling or cracking of the negative electrode mixture layer can be suppressed.

<Initial charging process>
In the initial charging step included in the method for producing a non-aqueous secondary battery of the present invention, by charging the uncharged non-aqueous secondary battery heated by the heating step to a predetermined charging depth, on the negative electrode mixture layer Efficiently forms a good SEI film. Here, from the viewpoint of efficiently forming a sufficient SEI film on the negative electrode mixture layer, the charging depth is preferably 5% or more and 80% or less.
In addition, in the method for manufacturing a non-aqueous secondary battery of the present invention, since the heating step described above is performed before the initial charging step, it is possible to suppress the formation failure of the SEI film and the occurrence of metal precipitation, which is good. A non-aqueous secondary battery having excellent battery characteristics can be obtained.

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, heating temperature of uncharged non-aqueous secondary battery, electrolyte swelling degree of water-insoluble polymer and water-soluble polymer, gel amount of water-insoluble polymer, tap density of negative electrode active material, The adhesive strength between the negative electrode and the separator, the state of the negative electrode mixture layer after the initial full charge, and the rate characteristic of the non-aqueous secondary battery were measured, evaluated, or observed using the following methods.

<Heating temperature>
The heating temperature was set to an arbitrary temperature using a thermostat (manufactured by ESPEC Corp., model number: PU-2KT), and then measured as an actual ambient temperature around the uncharged non-aqueous secondary battery. The measurement results are shown in Table 1.

<Electrolyte swelling degree>
The degree of swelling of the electrolytic solution is the weight of the water-insoluble polymer or the dry film piece containing the water-soluble polymer and the water-insoluble polymer or the water-soluble polymer for the water-insoluble polymer and the water-soluble polymer, respectively. It can be determined by using the weight of the swollen film piece obtained by immersing the containing dry film piece in the electrolytic solution. Specifically, an aqueous dispersion or aqueous solution in which a water-insoluble polymer or a water-soluble polymer is dispersed or dissolved in water is prepared, and the prepared aqueous dispersion or aqueous solution is used at a humidity of 50% and a temperature of 23°C or higher 25 It was dried in an environment of ℃ or below to obtain a dry dispersion. Then, the obtained dried dispersion was formed into a film having a thickness of 3±0.3 mm and cut into a diameter of 12 mm to prepare a dried film piece.
The prepared dry film piece was precisely weighed, and the weight of the obtained dry film piece was defined as W0.
Next, a precisely weighed dry film piece was used as a mixed solvent of LiPF ₆ electrolyte solution (solvent: ethylene carbonate/ethyl methyl carbonate=3/7 (volume ratio)) having a concentration of 1.0 M, and 2 mass% of vinylene carbonate as an additive. % (Including solvent ratio) was immersed for 72 hours at 60° C. to allow the electrolytic solution to permeate the dried film piece. Then, a film piece swollen by permeation of the electrolytic solution, that is, a swollen film piece was obtained.
After that, the swelling film piece lifted up from the electrolytic solution was lightly wiped and then precisely weighed, and the weight of the swelling film piece was set to W1.
Then, using the obtained precise measured value, the following formula (I):
Electrolyte swelling degree=(W1/W0) (I)
According to the above, the degree of swelling (fold) of the electrolytic solution was calculated. The measurement results are shown in Table 1.

<Amount of gel>
The gel amount can be determined as a ratio (mass%) of the weight of the solid content of the water-insoluble polymer, which is insoluble in tetrahydrofuran, to the total weight of the solid content of the water-insoluble polymer. Specifically, an aqueous dispersion in which a water-insoluble polymer is dispersed in water is dried for 3 days in an environment of a humidity of 50% and a temperature of 23° C. or higher and 25° C. or lower, and then using a hot air oven, A dried dispersion was obtained by drying in an environment of 120° C. for 1 hour. The obtained dried dispersion was formed into a film having a thickness of 3±0.3 mm, and a dry film piece was prepared by cutting into a substantially square shape with one side of 3 mm or more and 5 mm or less.
The prepared dry film piece was precisely weighed, and the weight of the obtained dry film piece was defined as V0.
Next, the dried film piece was immersed and dissolved in 100 g of tetrahydrofuran at 23° C. or higher and 25° C. or lower for 24 hours. The residual film piece lifted up from tetrahydrofuran was vacuum dried in an environment of 105° C. for 3 hours, and the dried residual film piece was precisely weighed, and the weight of the obtained residual film piece was defined as V1.
Then, using the obtained precise measured value, the following formula (II):
Gel amount=(V1/V0)×100 (II)
The gel amount (mass %) was calculated in accordance with. The measurement results are shown in Table 1.

<Tap density>
The tap density of the negative electrode active material was measured using Powder Tester (registered trademark) (PT-D manufactured by Hosokawa Micron Corp.). Specifically, first, the powder of the negative electrode active material filled in the measurement container was scraped off on the upper surface of the container. Then, a cap attached to the measuring instrument was attached to the measurement container, powder of the negative electrode active material was additionally filled up to the upper edge of the attached cap, and tapping was performed by repeatedly dropping from a height of 1.8 cm 180 times. After the tapping was completed, the cap was removed, and the powder of the negative electrode active material was scraped again on the upper surface of the container. The sample scraped off after tapping was weighed, and the bulk density in this state was solidified and measured as the bulk density, that is, the tap density (g/cm ³ ). It is shown that the higher the tap density, the higher the density of the negative electrode active material, and that a non-aqueous secondary battery suitable for high-density charge/discharge can be obtained. The measurement results are shown in Table 1.

<Adhesive force between negative electrode and separator>
The adhesive force between the negative electrode and the separator was measured as a tensile stress on the negative electrode surface. Specifically, the uncharged non-aqueous secondary battery obtained in the assembly process was subjected to heat treatment at the heating temperature and the heating holding time in each Example and each Comparative Example described in Table 1. Then, a laminate including the negative electrode and the separator that had been immersed in the electrolytic solution was taken out from the heat-treated uncharged non-aqueous secondary battery and cut into a size of length 10 mm×width 10 mm to obtain a test piece. It was Then, the electrolyte solution adhering to the surface of the obtained test piece was wiped off, and an adhesive tape was attached to the surface of the wiped test piece on the negative electrode surface side. At this time, the adhesive tape specified in JIS Z1522 was used. Then, the stress when peeling one end of the test piece vertically upward at a pulling speed of 50 mm/min was measured as an adhesive force (the adhesive tape was fixed to a horizontal test stand).
The measurement results are shown in Table 1. Even when the adhesive layer is not provided between the negative electrode and the separator, the stress due to the liquid film of the electrolytic solution acts at the negative electrode mixture layer interface, so that the adhesive force is usually 0 regardless of the presence or absence of the adhesive layer. A measured value of 1 N/m or more is shown.

<State of negative electrode mixture layer after initial full charge>
Five non-aqueous secondary batteries manufactured by the methods described in each example and each comparative example were disassembled in a dry room, and the negative electrode mixture layer was visually observed for cracks and peeling. Here, in Comparative Example 4, a non-aqueous secondary battery after completion of heating was used. The evaluation criteria are as follows. The measurement results are shown in Table 1.
A: The number of batteries with a defect (cracking or peeling) in the negative electrode mixture layer was 1 or less. B: The number of batteries with a defect (cracking or peeling) in the negative electrode mixture layer was 2 C: Negative electrode mixture. The number of batteries with layer loss (cracking or peeling) is 3 D: The number of batteries with negative electrode mixture layer loss (cracking or peeling) is 4 or more

<Rate characteristics of non-aqueous secondary battery>
After confirming the initial capacity of the non-aqueous secondary battery manufactured by the method described in each of the examples and each of the comparative examples, the non-aqueous secondary battery was subjected to a constant current constant voltage up to 4.2 V at 0.2 C under a 25° C. environment. Method (cut-off condition: 0.02C). After that, the non-aqueous secondary battery was discharged at a constant current of 0.2 C to 3.0 V under a 25° C. environment, and the discharge capacity C1 at that time was measured. Then, after fully recharging the non-aqueous secondary battery by the constant current constant voltage method of 4.2V (cutoff condition: 0.02C) under the environment of 25°C, under the environment of 25°C, up to 3.0V at 1C. A constant current discharge was performed and the discharge capacity C2 at that time was measured. The rate characteristic C ₂ /C ₁ of the non-aqueous secondary battery is expressed by the following formula (III):
_{C 2 / C 1 = (C2} / C1) × 100 ··· (III)
According to the above, the ratio (%) of C2 to C1 was calculated. The evaluation criteria are as follows. The larger the C ₂ / C ₁ value shows that the superior rate characteristics of a nonaqueous secondary battery produced. The measurement results are shown in Table 1.
A: C ₂ / C ₁ is 85% or more B: C ₂ / C ₁ is 75% or more than _{85% C: C 2 / C} 1 is 65% or more than _{75% D: C 2 / C} 1 is less than 65%

(Example 1)
<Preparation of water-insoluble polymer>
63 parts of styrene as an aromatic vinyl monomer, 33 parts of 1,3-butadiene as an aliphatic conjugated diene monomer, 4 parts of itaconic acid as an acidic group-containing monomer, t-dodecyl as a chain transfer agent. 0.3 part of mercaptan and 0.35 part of sodium lauryl sulfate as an emulsifier were put in a container A to obtain a mixture. Polymerization was started by adding 1 part of potassium persulfate as a polymerization initiator to the pressure resistant container B at the same time as adding the obtained mixture from the container A to the pressure resistant container B. The polymerization reaction temperature was maintained at 75°C.
When the polymerization conversion rate reached 97%, the mixture was cooled and the reaction was stopped to obtain a mixture containing a water-insoluble polymer. A pH of 8 was adjusted by adding a 5% aqueous sodium hydroxide solution to the obtained mixture containing the water-insoluble polymer. Then, the unreacted monomer was removed by heating under reduced pressure. Then, it was cooled to obtain an aqueous dispersion containing a water-insoluble polymer (solid content concentration: 40%).

<Preparation of negative electrode active material>
Spheroidal graphite particles with an average particle diameter of 100 μm are made spherical by using a hybridization system (manufactured by Nara Machinery Co., Ltd., model number: NHS-3, rotational speed (rotor peripheral speed): 65 m/sec, rotational residence time: 15 minutes). By the treatment, spherical graphite particles having a volume average particle diameter (50% diameter) of 15 μm and a tap density of 1.02 g/cm ³ were obtained.
Then, 30 parts of tar pitch as a low crystalline film-forming carbon material was added to 100 parts of the obtained spherical graphite particles and mixed for 30 minutes in a 200° C. environment using a Henschel mixer. The obtained mixture was pre-fired at 1000° C. under a nitrogen atmosphere, further fired at 1500° C. under a nitrogen atmosphere, and pulverized to obtain a carbon-based carbonaceous material in which the core of spherical graphite particles was amorphous-coated with tar pitch. A negative electrode active material was obtained. The obtained negative electrode active material had a volume average particle size (50% size) of 15 μm and a tap density of 1.04 g/cm ³ .

<Preparation of negative electrode slurry composition>
In a planetary mixer equipped with a disper, 100 parts of the carbon-based negative electrode active material obtained as described above and an acrylamide-based polymer (acrylic acid unit/acrylamide unit=50%/50%) as a water-soluble polymer were added. A mixture was obtained by adding 1 part in terms of solid content. Ion-exchanged water was added to the obtained mixture to adjust the solid content concentration to 60%, and then the mixture was mixed in an environment of 25° C. for 60 minutes. Next, the solid content concentration was adjusted to 48% with ion-exchanged water, and the mixture was further mixed for 15 minutes in an environment of 25° C. to obtain a mixed liquid of the negative electrode active material and the water-soluble polymer.
To the obtained mixed liquid of the negative electrode active material and the water-soluble polymer, an aqueous dispersion containing the water-insoluble polymer prepared by the above method (2 parts in terms of solid content of the water-insoluble polymer) was added, A negative electrode slurry composition was obtained by adjusting the final solid content concentration to 50% with ion-exchanged water, mixing for 10 minutes, and then performing defoaming treatment under reduced pressure.

<Preparation of negative electrode for non-aqueous secondary battery>
The slurry composition for a negative electrode obtained as described above was coated on one surface of a copper foil (thickness: 15 μm) as a current collector with a comma coater (manufactured by Sank Metal Co., Ltd.) at a coating amount of 9 mg/cm ^2. It was applied so as to be 10 mg/cm ² or less. The copper foil coated with the negative electrode slurry composition is dried by conveying it in an oven at 60° C. for 2 minutes (speed: 0.5 m/min), and further heat-treated in the oven at 120° C. for 2 minutes. Then, a negative electrode raw material was obtained.
A negative electrode mixture layer having a density of 1.75 g/cm ³ is provided on the current collector by pressing the obtained negative electrode raw material with a load of 11 tons to 14 tons using a roll press machine. A negative electrode for an aqueous secondary battery was obtained.

<Preparation of positive electrode for non-aqueous secondary battery>
In a planetary mixer, 100 parts of LiCoO ₂ as a positive electrode active material, ₂ parts of acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd., product number: HS-100) as a conductive material, polyvinylidene fluoride as a binder (Kreha Chemical (Manufactured by K.K., product number: KF-1100), and 2-methylpyrrilodon in an amount such that the total solid content concentration was 67% were added and mixed to prepare a positive electrode slurry composition.
The obtained positive electrode slurry composition was applied to one side of an aluminum foil (thickness 20 μm) as a current collector by the comma coater. The aluminum foil coated with the positive electrode slurry composition is dried by conveying it in an oven at 60° C. for 2 minutes (speed: 0.5 m/min), and further heat-treated in the oven at 120° C. for 2 minutes. Did. The same coating and drying operations were performed on the other surface of the current collector to obtain a positive electrode raw material.
The obtained positive electrode raw material is pressed using the roll press so that the positive electrode mixture layer has a density of 3.40 mg/cm ³ or more and 3.50 g/cm ³ or less, whereby a non-aqueous secondary material is obtained. A positive electrode for a battery was obtained.

<Manufacture of non-aqueous secondary battery>
On one surface of a single-layer polypropylene separator (length 500 mm×width 65 mm×thickness 25 μm, porosity 55%, produced by a dry method), an adhesive layer composition (manufactured by Zeon Corporation, product name: BM-2500M) was used. The adhesive layer having a thickness of 1 μm per layer was formed on the separator by applying by the gravure coating method (300 lines) and drying for 1 minute in an environment of 50° C. Next, the separator having the adhesive layer formed thereon was cut into a length of 50 mm and a width of 40 mm, the positive electrode prepared as described above was cut into a length of 45 mm and a width of 35 mm, and the negative electrode prepared as described above was formed into a length of 47 mm and a width of 37 mm. I cut it out. Then, the cut out positive electrode, separator, and negative electrode were stacked as follows to manufacture a non-aqueous secondary battery.
Specifically, separators were arranged on both sides of a positive electrode having positive electrode mixture layers on both sides, and the positive electrodes were sandwiched between the separators. The surface of the positive electrode mixture layer on the side on which the adhesive layer of the separator was applied was in contact. Then, the negative electrode was laminated on the surface of the separator not in contact with the positive electrode (the surface on the side where the adhesive layer was not provided) to obtain a laminate. Then, the obtained laminated body was put in an aluminum packaging material exterior as a battery container to obtain a laminated battery.
Then, in the laminated battery, a LiPF ₆ solution (solvent: ethylene carbonate (EC)/ethyl methyl carbonate (EMC)=3/7 (volume ratio)) as an electrolytic solution, which was a mixed solvent, was used as an additive. As a result, vinylene carbonate (containing 2% by mass) was charged. Furthermore, the laminated battery filled with the electrolytic solution was heat-sealed at a temperature of 150° C., the opening of the aluminum packaging material exterior was hermetically closed, and then pressed at a pressure of 10 MPa for 5 seconds in an environment of 25° C. to positive electrode and separator. And were pressure-bonded to obtain an uncharged non-aqueous secondary battery (assembly process). Then, the adhesive force between the negative electrode and the separator was evaluated using the obtained uncharged non-aqueous secondary battery.
Moreover, after heating the obtained uncharged non-aqueous secondary battery for 15 hours at a temperature of 60° C. (heating step), in a 25° C. environment, a constant current constant voltage method (cutoff at 0.2 C to 4.2 V) was performed. The battery was charged to a depth of charge of 20% under the condition: 0.02 C (initial charging step) to manufacture a lithium ion secondary battery as a non-aqueous secondary battery. Then, using the manufactured lithium ion secondary battery, the state of the negative electrode mixture layer after the initial full charge and the rate characteristic of the non-aqueous secondary battery were evaluated.

(Example 2)
At the time of manufacturing the non-aqueous secondary battery, a water-insoluble polymer, a negative electrode active material, a slurry composition, a negative electrode, a positive electrode and a non-aqueous system were prepared in the same manner as in Example 1 except that the heating temperature in the heating step was changed to 50°C. A secondary battery was manufactured. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

(Example 3)
When preparing the water-insoluble polymer, the amount of styrene was 29.5 parts, the amount of 1.3-butadiene was 47.5 parts, the amount of itaconic acid was 3 parts, and the amount of t-dodecyl mercaptan was 1 part. 0.3 parts, and 20 parts of acrylonitrile as another monomer was further added to the mixture. Further, at the time of preparing the slurry composition, the type of the water-soluble polymer was changed to sodium salt of carboxymethyl cellulose (manufactured by Daicel Finechem, product name: CMC Daicel 2200). Furthermore, in the assembly process during the production of the non-aqueous secondary battery, the negative electrode mixture layer is brought into contact with the adhesive layer of the separator, and the surface of the separator not in contact with the negative electrode (the side not provided with the adhesive layer). Surface), and after further sealing and closing the opening of the aluminum wrapping material exterior by heat sealing, press at a pressure of 10 MPa for 5 seconds in an environment of 25° C. to bond the negative electrode and the separator under pressure. Then, an uncharged non-aqueous secondary battery was obtained. A water-insoluble polymer, a negative electrode active material, a slurry composition, a negative electrode, a positive electrode and a non-aqueous secondary battery were manufactured in the same manner as in Example 1 except the above. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

(Example 4)
When the negative electrode active material was prepared, the tap density of the amorphous coated negative electrode active material was adjusted by adjusting the conditions of the hybridization system such that the rotation speed (rotor peripheral speed): 40 m/sec and the rotation residence time: 10 minutes. Was changed to 0.86 g/cm ^3, and the kind of the water-soluble polymer was changed to sodium salt of carboxymethyl cellulose (manufactured by Daicel Finechem, product name: CMC Daicel 2200) at the time of preparing the slurry composition. In the same manner as in Example 1, a water-insoluble polymer, a negative electrode active material, a slurry composition, a negative electrode, a positive electrode and a non-aqueous secondary battery were manufactured. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

(Example 5)
At the time of preparing the slurry composition, the type of the water-soluble polymer was changed to sodium salt of carboxymethyl cellulose (manufactured by Daicel FineChem, product name: CMC Daicel 2200), and the amount of the water-insoluble polymer was changed to 1 part by mass. A water-insoluble polymer, a negative electrode active material, a slurry composition, a negative electrode, a positive electrode and a non-aqueous secondary battery were manufactured in the same manner as in Example 1 except for the above. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

(Example 6)
At the time of preparing the slurry composition, the type of the water-soluble polymer was changed to sodium salt of carboxymethyl cellulose (manufactured by Daicel FineChem, product name: CMC Daicel 2200). Furthermore, in the assembly process during the production of the non-aqueous secondary battery, the negative electrode mixture layer is brought into contact with the adhesive layer of the separator, and the surface of the separator not in contact with the negative electrode (the side not provided with the adhesive layer). Surface), and after further sealing and closing the opening of the aluminum wrapping material exterior by heat sealing, press at 10 MPa pressure for 5 seconds in a 50° C. environment to bond the negative electrode and the separator under pressure. Then, an uncharged non-aqueous secondary battery was obtained. A water-insoluble polymer, a negative electrode active material, a slurry composition, a negative electrode, a positive electrode and a non-aqueous secondary battery were manufactured in the same manner as in Example 1 except the above. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 1)
At the time of preparing the water-insoluble polymer, the water-insoluble polymer, the negative electrode active material, the slurry composition, the negative electrode were prepared in the same manner as in Example 3 except that the amount of t-dodecyl mercaptan was changed to 3.0 parts. A positive electrode and a non-aqueous secondary battery were manufactured. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

(Comparative example 2)
At the time of preparing the slurry composition, the type of the water-soluble polymer was changed to sodium salt of carboxymethylcellulose (manufactured by Daicel FineChem, product name: CMC Daicel 2200), and further, heating in a heating step was performed at the time of manufacturing the non-aqueous secondary battery. A water-insoluble polymer, a negative electrode active material, a slurry composition, a negative electrode, a positive electrode and a non-aqueous secondary battery were manufactured in the same manner as in Example 1 except that the temperature was changed to 25°C. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

(Comparative example 3)
When preparing the slurry composition, the type of the water-soluble polymer is a copolymer of ethyl acrylate unit (EA)/butyl acrylate unit (BA)/methacrylamide unit (MAA)=40/30/30 (mass ratio) Changed to. Furthermore, in the assembly process during the production of the non-aqueous secondary battery, the negative electrode mixture layer is brought into contact with the adhesive layer of the separator, and the surface of the separator not in contact with the negative electrode (the side not provided with the adhesive layer). Surface), and after further sealing and closing the opening of the aluminum wrapping material exterior by heat sealing, press at 10 MPa pressure for 5 seconds in an environment of 30° C. to bond the negative electrode and the separator under pressure. Then, an uncharged non-aqueous secondary battery was obtained. A water-insoluble polymer, a negative electrode active material, a slurry composition, a negative electrode, a positive electrode and a non-aqueous secondary battery were manufactured in the same manner as in Example 1 except the above. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 4)
At the time of preparing the slurry composition, the type of the water-soluble polymer was changed to sodium salt of carboxymethyl cellulose (manufactured by Daicel FineChem, product name: CMC Daicel 2200). Further, at the time of manufacturing the non-aqueous secondary battery, the uncharged non-aqueous secondary battery obtained in the assembly process was charged to 0.1C at a charge depth of 20% without performing a heating process, and then under an environment of 60°C. It was heated for 15 hours at 0.2 C and further charged by a constant current constant voltage charging method (cut-off condition: 0.02 C) at 0.2 C to 4.2 V to manufacture a non-aqueous secondary battery. A water-insoluble polymer, a negative electrode active material, a slurry composition, a negative electrode, a positive electrode and a non-aqueous secondary battery were manufactured in the same manner as in Example 1 except the above. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

ＴＤＭ：ｔ−ドデシルメルカプタン
ＴＨＦ：テトラヒドロフラン
ＡＡ／Ａａｍ：アクリル酸／アクリルアミド共重合体
ＣＭＣ：カルボキシメチルセルロースのナトリウム塩
ＥＡ／ＢＡ／ＭＡＡ：アクリル酸エチル／アクリル酸ブチル／メタクリルアミド共重合体

TDM: t-dodecyl mercaptan THF: tetrahydrofuran AA/Aam: acrylic acid/acrylamide copolymer CMC: sodium salt of carboxymethyl cellulose EA/BA/MAA: ethyl acrylate/butyl acrylate/methacrylamide copolymer

From Table 1, in Examples 1 to 6 in which the heating step was performed before the initial charging step, as compared with Comparative Example 4 in which the heating treatment was performed after the initial charging, the non-aqueous secondary having excellent rate characteristics immediately after the initial charging and discharging was performed. It turns out that a battery is obtained.
However, even if the heating process is performed before the initial charging process, in Comparative Example 2 in which the heating temperature is 25° C., the rate immediately after the initial charge/discharge is compared with Examples 1 to 6 in which the heating temperature is 40° C. or higher. It can be seen that the characteristics are significantly deteriorated.
Further, in Comparative Example 1 using a water-insoluble polymer having an electrolytic solution swelling degree of more than 4.0 times and a gel amount of less than 80% by mass, the electrolytic solution swelling degree of more than 1.0 times 4.0. Double or less, and compared with Examples 1 to 6 using a water-insoluble polymer having a gel amount of 80% by mass or more and 95% by mass or less, the loss of the negative electrode mixture layer after initial charging is significantly advanced, and It can be seen that the rate characteristic immediately after the initial charge/discharge is remarkably deteriorated.
Further, in Comparative Example 3 using a water-soluble polymer having an electrolyte swelling degree of more than 2.0 times, an example using a water-soluble polymer having an electrolyte solution swelling degree of more than 1.0 times and 2.0 times or less. It can be seen that, as compared with Nos. 1 to 6, the loss of the negative electrode mixture layer after the initial charge is significantly advanced, and the rate characteristics immediately after the initial charge and discharge are significantly deteriorated.
In Examples 1 to 6 in which the negative electrode mixture layer having a density of 1.70 g/cm ³ or more was used, the negative electrode mixture layer after initial charging had a low degree of defects and a good rate immediately after initial charge/discharge. Therefore, it is understood that the manufacturing method of the present invention is suitable for manufacturing a non-aqueous secondary battery that maintains high battery performance even when a high-density electrode is used.

According to the present invention, it is possible to provide a method for efficiently producing a non-aqueous secondary battery in which an SEI film is formed on a negative electrode mixture layer while suppressing deterioration of battery performance.

Claims (2)

An assembling process of assembling the positive electrode, the negative electrode, and the electrolytic solution in a battery container to assemble an uncharged non-aqueous secondary battery,
A heating step of heating the uncharged non-aqueous secondary battery at 40° C. or higher and 85° C. or lower for 1 hour or more and 50 hours or less;
An initial charging step of charging the uncharged non-aqueous secondary battery after the heating step,
A method of manufacturing a non-aqueous secondary battery comprising:
The negative electrode includes a negative electrode active material, a water-insoluble polymer, a negative electrode mixture layer containing a water-soluble polymer,
The water-insoluble polymer has an electrolyte swelling degree of more than 1.0 times and 4.0 times or less, and a gel amount of 80% by mass or more and 95% by mass or less,
The water-soluble polymer has an electrolyte swelling degree of more than 1.0 times and 2.0 times or less,
The degree of swelling of the electrolytic solution is a thickness 3 produced by drying an aqueous dispersion of the water-insoluble polymer or an aqueous solution of the water-soluble polymer in an environment of a humidity of 50% and a temperature of 23° C. or higher and 25° C. or lower. Using a weight W0 of a dry film piece having a diameter of ±0.3 mm and a diameter of 12 mm and a weight W1 of a swollen film piece obtained by immersing the dry film piece in a measuring electrolyte solution at 60° C. for 72 hours, : Electrolyte swelling degree=(W1/W0)
The measurement electrolytic solution contains LiPF ₆ having a concentration of 1.0 M ,
The solvent of the measurement electrolytic solution is a mixed solvent of ethylene carbonate/ethyl methyl carbonate=3/7 (volume ratio), and contains 2 mass% of vinylene carbonate (solvent ratio) as an additive,
The density of the negative electrode mixture layer is 1.60 g/cm ³ or more,
The negative electrode mixture layer contains the water-insoluble polymer in a ratio of 0.5 parts by mass or more and 4 parts by mass or less, and 0.5 parts by mass of the water-soluble polymer, per 100 parts by mass of the negative electrode active material. Contains at a ratio of 3 parts by mass or less and
The uncharged non-aqueous secondary battery further comprises a separator between the negative electrode and the positive electrode,
The adhesive strength between the negative electrode and the separator when the uncharged non-aqueous secondary battery is left for 15 hours at a temperature of 60° C. is 1.0 N/m or less,
The water-insoluble polymer is a conjugated diene polymer, or an acrylic polymer,
The water-soluble polymer is a cellulose-based polymer; oxidized starch or starch phosphate; casein; modified starch; polyethylene oxide, polyethylene glycol, polyvinyl alcohol, polyvinylpyrrolidone, polysulfonic acid, polycarboxylic acid; (meth)acrylic acid copolymer At least one selected from coalesce, acrylamide polymer, and salts thereof,
The electrolytic solution is a method for manufacturing a non-aqueous secondary battery, in which a lithium salt is dissolved as a supporting electrolyte in a non-aqueous solvent. The method for producing a non-aqueous secondary battery according to claim 1, wherein the negative electrode active material has a tap density of 0.8 g/cm ³ or more and 1.2 g/cm ³ or less.