JP2023176321A - Method for manufacturing nonaqueous secondary battery electrode slurry and method for manufacturing nonaqueous secondary battery electrode - Google Patents

Abstract

To provide a method for manufacturing a nonaqueous secondary battery electrode slurry capable of greatly improving a discharge capacity retention rate after a charge and discharge cycle while improving peel strength of an electrode active material layer formed on a current collector.SOLUTION: A method for producing an electrode slurry for a nonaqueous secondary battery includes a first step of kneading a first mixture containing an electrode active material, a first binder, and dispersion media to prepare a first electrode slurry, and a second step of kneading a second mixture containing at least the first electrode slurry prepared in the first step and a second binder to prepare a second electrode slurry. In a total solid content of the electrode slurry for the nonaqueous secondary battery, content X of the first binder is 0.5 mass % or more, and content Y of the second binder is 0.2 mass % or more. The content X and the content Y satisfy a condition (1) represented by the following formula (I): 0.067≤X/Y≤4.0 (I).SELECTED DRAWING: None

Description

The present invention relates to a method for manufacturing an electrode slurry for a non-aqueous secondary battery, and a method for manufacturing an electrode for a non-aqueous secondary battery.

Secondary batteries using non-aqueous electrolytes (non-aqueous secondary batteries) are superior to secondary batteries using aqueous electrolytes in terms of higher voltage, smaller size, and lighter weight. Therefore, non-aqueous secondary batteries are widely used as power sources for notebook computers, mobile phones, power tools, and electronic and communication equipment. Furthermore, recently, non-aqueous batteries have been used for electric vehicles and hybrid vehicles from the viewpoint of application to environmentally friendly vehicles, but there is a strong demand for higher output, higher capacity, longer life, etc. A typical example of a non-aqueous secondary battery is a lithium ion secondary battery.

Non-aqueous secondary batteries have a positive electrode made of a metal oxide or other active material, a negative electrode made of a carbon material such as graphite, and a non-aqueous electrolyte solvent mainly made of carbonates or flame-retardant ionic liquids. Equipped with A non-aqueous secondary battery is a secondary battery in which ions move between a positive electrode and a negative electrode to charge and discharge the battery. Specifically, the positive electrode is obtained by applying a slurry consisting of a metal oxide and a binder to the surface of a positive electrode current collector such as an aluminum foil, drying it, and then cutting the slurry into an appropriate size. The negative electrode is obtained by applying a slurry made of a carbon material and a binder to the surface of a negative electrode current collector such as copper foil, drying the slurry, and cutting the slurry into an appropriate size. The binder serves to bind the active materials to each other and to the current collector in the positive electrode and the negative electrode, and to prevent the active material from peeling off from the current collector.

As a binder, a polyvinylidene fluoride (PVDF) binder using an organic solvent N-methyl-2-pyrrolidone (NMP) as a solvent is well known. However, this binder has low binding properties between the active materials and between the active materials and the current collector, and requires a large amount of binder for actual use. Therefore, there is a drawback that the capacity of the non-aqueous secondary battery is reduced. Furthermore, since NMP, which is an expensive organic solvent, is used as a binder, it has been difficult to reduce manufacturing costs.

As a method to solve these problems, development of water-dispersed binders is underway. As a water-dispersed binder, it is known to use, for example, carboxymethyl cellulose (CMC) as a thickener and a (meth)acrylic acid ester-based or styrene-butadiene rubber (SBR)-based water dispersion.

For example, in Patent Document 1, when a first binder is added, mixed and kneaded when preparing an electrode slurry, and then a second binder is added to prepare and manufacture the slurry, the physical properties of the electrode slurry are improved and the electrode slurry is mixed and kneaded. It is disclosed that the occurrence of drag lines can be suppressed.

Patent No. 6645705

However, Patent Document 1 does not disclose the peel strength of the active material layer produced using the slurry obtained by the described electrode slurry production method and the discharge capacity retention rate of the finally produced non-aqueous secondary battery. . In the present invention, based on a technical idea different from Patent Document 1, the peel strength of the active material layer produced using the slurry obtained by the electrode slurry production method and the discharge capacity of the finally produced non-aqueous secondary battery are maintained. The purpose of the present invention is to provide a manufacturing method that improves peel strength and discharge capacity retention rate over a wider range.

Therefore, the present invention provides a non-aqueous secondary battery that can greatly improve the discharge capacity retention rate after charge/discharge cycles of the non-aqueous secondary battery while improving the peel strength of the electrode active material layer formed on the current collector. The present invention aims to provide a method for producing electrode slurry.
Another object of the present invention is to provide a non-aqueous secondary battery electrode in which an electrode active material layer formed on a current collector has high peel strength and a high discharge capacity retention rate after charge/discharge cycles.
Furthermore, it is an object of the present invention to provide a non-aqueous secondary battery equipped with an electrode having a high peel strength of an electrode active material layer formed on a current collector and a high discharge capacity retention rate after charge/discharge cycles. shall be.

（一般式（１）において、Ｒ^１、Ｒ^２はそれぞれ独立に水素原子または炭素数１以上５以下のアルキル基を表す。）

（一般式（２）において、Ｒ^３は水素原子またはメチル基を表し、Ｚは水素原子、アルカリ金属及びＮＨ_４からなる群から選ばれる少なくとも１種を表す。）
〔５〕 前記共重合体（Ｐ）における、前記単量体（Ａ）に由来する構造単位の含有率は、０．５ｍｏｌ％以上２０ｍｏｌ％以下である、〔４〕に記載の非水系二次電池用電極スラリーの製造方法。
〔６〕 前記共重合体（Ｐ）における、前記単量体（Ｂ）に由来する構造単位の含有率は、５０ｍｏｌ％以上９８ｍｏｌ％以下である、〔４〕又は〔５〕に記載の非水系二次電池用電極スラリーの製造方法。
〔７〕 前記第１バインダー及び前記第２バインダーの両方が、前記共重合体（Ｐ）を含む、〔４〕～〔６〕の何れかに記載の非水系二次電池用電極スラリーの製造方法。
〔８〕 前記電極活物質が、炭素材料と、シリコン化合物と、を含む〔１〕～〔７〕の何れかに記載の非水系二次電池用電極スラリーの製造方法。
〔９〕 前記シリコン化合物の含有量は、前記電極活物質１００質量％に対して、５質量％以上６０質量％以下である、〔８〕に記載の非水系二次電池用電極スラリーの製造方法。
〔１０〕 前記第１混合物は、更に導電助剤を含む、〔１〕～〔９〕の何れかに記載の非水系二次電池用電極スラリーの製造方法。
〔１１〕 集電体と、前記集電体の少なくとも一方面に設けられた電極活物質層、とを備える非水系二次電池電極を製造する方法であって、
〔１〕～〔１０〕の何れかに記載の製造方法により得られた非水系二次電池用電極スラリーを、前記集電体に塗布し、乾燥して前記電極活物質層を得る工程を含む、非水系二次電池電極の製造方法。 The present invention includes the following aspects.
[1] A method for producing an electrode slurry for a non-aqueous secondary battery comprising an electrode active material, a first binder, a second binder, and a dispersion medium, comprising:
A first step of preparing a first electrode slurry by kneading a first mixture containing the electrode active material, the first binder, and the dispersion medium;
a second step of preparing a second electrode slurry by kneading a second mixture containing at least the first electrode slurry prepared in the first step and the second binder;
Equipped with
In the total solid content of the electrode slurry for non-aqueous secondary batteries, the content X of the first binder is 0.5% by mass or more,
In the total solid content of the electrode slurry for non-aqueous secondary batteries, the content Y of the second binder is 0.2% by mass or more,
A method for producing an electrode slurry for a non-aqueous secondary battery, wherein the content X of the first binder and the content Y of the second binder satisfy the conditions shown in the following formula (I).
0.067≦X/Y≦4.0 (I)
[2] The method for producing an electrode slurry for a non-aqueous secondary battery according to [1], wherein the content X of the first binder and the content Y of the second binder satisfy the conditions shown in the following formula (II). .
1.0 mass%≦X+Y (II)
[3] The non-aqueous secondary according to claim 1 or 2, wherein the ratio X/Y of the content X of the first binder and the content Y of the second binder satisfies the condition shown in the following formula (III). A method for producing electrode slurry for batteries.
X/Y≦1.5 (III)
[4] At least one of the first binder and the second binder contains a copolymer (P),
The copolymer (P) has a structural unit derived from a monomer (A) represented by the following general formula (1), and a monomer (B) represented by the following general formula (2). The method for producing an electrode slurry for a non-aqueous secondary battery according to any one of [1] to [3], which contains a structural unit derived from.

(In general formula (1), R ¹ and R ² each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms.)

(In general formula (2), R ³ represents a hydrogen atom or a methyl group, and Z represents at least one selected from the group consisting of a hydrogen atom, an alkali metal, and NH _4. )
[5] The non-aqueous secondary according to [4], wherein the content of structural units derived from the monomer (A) in the copolymer (P) is 0.5 mol% or more and 20 mol% or less. A method for producing electrode slurry for batteries.
[6] The non-aqueous system according to [4] or [5], wherein the content of structural units derived from the monomer (B) in the copolymer (P) is 50 mol% or more and 98 mol% or less. A method for producing electrode slurry for secondary batteries.
[7] The method for producing an electrode slurry for a non-aqueous secondary battery according to any one of [4] to [6], wherein both the first binder and the second binder contain the copolymer (P). .
[8] The method for producing an electrode slurry for a non-aqueous secondary battery according to any one of [1] to [7], wherein the electrode active material contains a carbon material and a silicon compound.
[9] The method for producing an electrode slurry for a non-aqueous secondary battery according to [8], wherein the content of the silicon compound is 5% by mass or more and 60% by mass or less with respect to 100% by mass of the electrode active material. .
[10] The method for producing an electrode slurry for a non-aqueous secondary battery according to any one of [1] to [9], wherein the first mixture further contains a conductive additive.
[11] A method for manufacturing a non-aqueous secondary battery electrode comprising a current collector and an electrode active material layer provided on at least one surface of the current collector,
A step of applying an electrode slurry for a non-aqueous secondary battery obtained by the manufacturing method according to any one of [1] to [10] to the current collector and drying it to obtain the electrode active material layer. , a method for manufacturing a non-aqueous secondary battery electrode.

According to the present invention, there is provided a method for producing a nonaqueous secondary battery electrode slurry that can greatly improve the discharge capacity retention rate after charge/discharge cycles while improving the peel strength of the electrode active material layer formed on the current collector. can be provided.
Further, the present invention can provide a nonaqueous secondary battery electrode in which the electrode active material layer formed on the current collector has high peel strength and a high discharge capacity retention rate after charge/discharge cycles.
Further, the present invention can provide a non-aqueous secondary battery including an electrode having a high peel strength of an electrode active material layer formed on a current collector and a high discharge capacity retention rate after charge/discharge cycles. .

(Method for producing electrode slurry for non-aqueous secondary batteries)
A method for manufacturing an electrode slurry for a non-aqueous secondary battery according to an embodiment of the present invention (“a method for manufacturing an electrode slurry for a non-aqueous secondary battery according to the present embodiment”) or “a method for manufacturing an electrode slurry according to the present embodiment” ) is a method for producing an electrode slurry for a non-aqueous secondary battery containing an electrode active material, a first binder, a second binder, and a dispersion medium. The method for manufacturing an electrode slurry of this embodiment includes the following first step and second step.
First step: A step of preparing a first electrode slurry by kneading a first mixture containing the electrode active material, the first binder, and the dispersion medium.
Second step: A step of preparing a second electrode slurry by kneading a second mixture containing at least the first electrode slurry prepared in the first step and the second binder.
In the total solid content of the electrode slurry for non-aqueous secondary batteries, the content X of the first binder is 0.5% by mass or more. In the total solid content of the electrode slurry for nonaqueous secondary batteries, the content Y of the second binder is 0.2% by mass or more. The content X of the first binder and the content Y of the second binder satisfy the conditions shown in the following formula (I).

0.067≦X/Y≦4.0 (I)

By manufacturing an electrode using the electrode slurry obtained by the above manufacturing method, the peel strength of the electrode active material layer is improved, and the discharge capacity retention rate after charge/discharge cycles of a non-aqueous secondary battery using the electrode is improved. will improve.
Although the reason for such an effect is not clear, the present inventors speculate as follows. That is, it is presumed that by using the manufacturing method of this embodiment, the first binder is disposed near the active material, and the second binder is omnipresent in the slurry. Due to this effect, when the binder is added all at once, a large amount of the binder is placed near the active material in the electrode active material layer, whereas when it is added in portions, the binder is not only near the active material but also inside the electrode active material layer. It is thought that they are evenly distributed. Therefore, it is believed that the above effects are achieved by increasing the strength of the electrode active material layer.

It is preferable that the content X of the first binder and the content Y of the second binder satisfy the conditions shown in the following formula (II).
1.0 mass%≦X+Y (II)

The content X of the first binder and the content Y of the second binder satisfy the conditions shown in the following formula (III) to improve the peel strength of the prepared electrode active material layer and to improve the peel strength after charge/discharge cycles. This is more preferable from the viewpoint of improving the discharge capacity retention rate.
X/Y≦1.5 (III)

[First step]
The first step according to the present embodiment may be a step of first mixing each component of the first mixture and then kneading the first mixture, or adding and mixing each component of the first mixture. However, it may also be a kneading process.
The first step according to this embodiment preferably includes a step of preparing a first mixture and a step of preparing a first electrode slurry.

<Step of preparing the first mixture>
In the step of preparing the first mixture according to the present embodiment, the first mixture is prepared by appropriately mixing the above-mentioned components contained in the first mixture. A conductive additive may be added if necessary.
The mixing method is not limited, but examples include methods using a mixing device such as a stirring type, a rotating type, or a shaking type. As the mixing device in the step of preparing the first mixture, the device used for kneading in the step of preparing the first electrode slurry described below may be used.

The solid content concentration of the first mixture can be adjusted as appropriate. From the viewpoint of effectively dispersing powders such as electrode active materials and conductive additives during kneading, the solid content concentration in the first mixture is preferably 50% by mass or more and 95% by mass or less, and 55% by mass or more and 90% by mass or less. It is more preferable to make the content less than or equal to 60% by mass and less than 88% by mass.

<Step of preparing first electrode slurry>
In the step of preparing the first electrode slurry according to the present embodiment, the first mixture obtained above is kneaded using a device such as a rotation-revolution type stirrer or a planetary mixer.
When kneading, it is preferable to use a rotation-revolution type stirrer from the viewpoint of being able to apply sufficient external force during kneading.
From the viewpoint of ensuring the dispersibility of the electrode active material, the kneading conditions are preferably kneading at 2000 revolutions/min for 2 minutes, more preferably kneading at 2000 revolutions/min for 3 minutes, and even more preferably kneading at 2000 revolutions/min for 4 minutes. .

When kneading, the first mixture may be kneaded once and then the solid content concentration may be changed to obtain the first electrode slurry. In this case, the compositions of the first mixture and the first electrode slurry will be different.
For example, when using a rotation-revolution type stirrer, the first mixture prepared to have a solid content concentration of 65% by mass or more and 95% by mass or less is kneaded at 1000 to 3000 rpm for 2 to 10 minutes. Preferably, a dispersion medium is added to adjust the solid content concentration to 55% by mass or more and 90% by mass or less, and the mixture is kneaded at 1000 to 3000 rpm for 2 to 10 minutes to obtain the first electrode slurry.

As a specific example, when using a rotation-revolution type stirrer, the first mixture prepared to have a solid content concentration of 80% by mass or more and 95% by mass or less is kneaded at 2000 rpm for 4 minutes, and then Preferably, a dispersion medium is added to adjust the solid content concentration to 65% by mass or more and 80% by mass or less, and the mixture is kneaded at 2000 revolutions/minute for 2 minutes.
As another specific example, when using a planetary mixer, the first mixture adjusted to a solid content concentration of 70% by mass or more and 80% by mass or less is kneaded at 20 revolutions/minute for 4 minutes, and then Preferably, a dispersion medium is added to adjust the solid content concentration to 60% by mass or more and 70% by mass or less, and the mixture is kneaded at 60 revolutions/minute for 2 hours.

The solid content concentration of the first electrode slurry can be adjusted as appropriate. From the viewpoint of effectively dispersing powders such as electrode active materials and conductive additives during kneading, the solid content concentration in the first mixture is preferably 50% by mass or more and 85% by mass or less, and 55% by mass or more and 80% by mass or less. It is more preferable that the content be 60% by mass or more and 75% by mass or less.

[Second process]
The second step according to the present embodiment may be a step of first mixing each component of the second mixture and then kneading the second mixture, and the first electrode slurry prepared in the first step The step may also be a step of kneading the mixture while adding at least the second binder.
The second step according to this embodiment preferably includes a step of preparing a second mixture and a step of preparing a second electrode slurry.

<Step of preparing the second mixture>
In the step of preparing the second mixture according to the present embodiment, a dispersion medium may be added in addition to the second binder as necessary. Further, in the step of preparing the second mixture, an electrode active material may be further added, but it is preferable that no electrode active material is added. That is, in the second step according to this embodiment, it is preferable that no electrode active material be added.
Although the mixing method is not limited, examples include a method using a mixing device such as a stirring type, a rotating type, or a shaking type. As the mixing device for preparing the second mixture, the device used for kneading in the step of preparing the second electrode slurry described below may be used.
The solid content concentration of the second mixture can be adjusted as appropriate. From the viewpoint of ensuring coating properties, the solid content concentration in the second mixture is preferably 30% by mass or more and 70% by mass or less, more preferably 35% by mass or more and 65% by mass or less, and 40% by mass or more and 60% by mass or less. It is more preferable to make it less than % by mass. When the solid content of the second mixture is within the above range, the viscosity of the slurry during coating becomes suitable, and sagging and repelling after coating can be suppressed. In addition, the heating time during drying can be suppressed, providing process advantages.

<Step of preparing second electrode slurry>
In the step of preparing the second electrode slurry according to the present embodiment, the second mixture obtained above is kneaded using a device such as a rotation-revolution type stirrer or a planetary mixer.
For example, when using a rotation-revolution type stirrer, it is preferable to adjust the solid content concentration to 30% by mass or more and 80% by mass or less using a dispersion medium, and knead for 7 to 15 minutes at 300 to 800 revolutions/minute. .
As a specific example, when using a rotation-revolution type stirrer, for example, it is possible to adjust the solid content concentration to 30% by mass or more and 70% by mass or less using a dispersion medium, and knead at 500 revolutions / minute for 10 minutes. preferable.
As another specific example, when a planetary mixer is used, it is preferable to adjust the solid content concentration to 30% by mass or more and 65% by mass or less using a dispersion medium, and knead at 30 revolutions/minute for 1 hour.

The solid content concentration of the manufactured second electrode slurry, that is, the electrode slurry in this embodiment, is not particularly limited, but is preferably 30% by mass or more and 70% by mass or less, and 35% by mass or more and 65% by mass or less. is more preferable, and even more preferably 40% by mass or more and 60% by mass or less. This is because it is suitable because it can suppress sagging and repellency after coating and can also suppress heating time during drying. Further, if the solid content concentration in the first step is higher than the solid content concentration in the second step, kneading can be performed more effectively.

(Electrode slurry for non-aqueous secondary batteries)
The electrode slurry for an aqueous secondary battery according to the method for producing an electrode slurry for an aqueous secondary battery according to the present embodiment (also referred to as "the electrode slurry according to the present embodiment") contains an electrode active material and a first binder. , a second binder, and a dispersion medium. The electrode slurry according to this embodiment may further contain a conductive additive or an additive.

[First binder and second binder]
The first binder and the second binder according to this embodiment are preferably binders for non-aqueous secondary battery electrodes, which will be described later.
The first binder and the second binder according to this embodiment may be the same type or different types. From the viewpoint of simplifying the process in slurry production, the first binder and the second binder according to this embodiment are preferably of the same type. "The same type" means that the types of resins contained in the binders are the same. For example, when the resins are polymers or copolymers of the same monomer, they are the same type of resin. From the viewpoint of simplifying the process in producing the slurry, it is more preferable that the first binder and the second binder according to this embodiment are the same binder.
In manufacturing the electrode slurry, the first binder and the second binder may be different.
At least one of the first binder and the second binder is preferably the above-mentioned copolymer (P), more preferably both the first binder and the second binder contain the copolymer (P), and the first binder It is more preferable that the second binder consists only of the copolymer (P).

<Content of first binder and second binder in electrode slurry>
Hereinafter, in the description regarding the content of the first binder and the second binder in the electrode slurry, the content in the total solid content of the electrode slurry for a non-aqueous secondary battery, that is, mass % will be used.
In the present embodiment, the total solid content of the electrode slurry for non-aqueous secondary batteries is defined as 1 g of the electrode slurry is weighed in an aluminum dish with a diameter of 5 cm, and while air is circulated in a dryer under atmospheric pressure. It refers to the components remaining after drying at 110°C for 5 hours.
The content X of the first binder based on the total solid content in the electrode slurry is 0.5% by mass or more, preferably 0.7% by mass or more, and more preferably 1.0% by mass or more. This is because the first binder disperses the electrode active material in the first step, making it possible to obtain a uniform slurry. The content X of the first binder relative to the total solid content in the electrode slurry is preferably 7.0% by mass or less, more preferably 6.0% by mass or less, and 5.0% by mass or less. is even more preferable.
The content Y of the second binder based on the total solid content in the electrode slurry is 0.2% by mass or more, preferably 0.5% by mass or more, and more preferably 1.0% by mass or more. This is because the presence of the second binder that is not placed near the electrode active material in the second step improves the strength of the electrode composite layer. The content Y of the second binder relative to the total solid content in the electrode slurry is preferably 7.0% by mass or less, more preferably 6.0% by mass or less, and 5.0% by mass or less. is even more preferable.

The ratio X/Y of the content X of the first binder and the content Y of the second binder is 0.067 or more, preferably 0.1 or more, more preferably 0.3 or more, and 0. More preferably, it is .5 or more. This is because the electrode active material is effectively kneaded in the first step, improving the performance of the electrode.
The ratio X/Y of the content X of the first binder and the content Y of the second binder is 4.0 or less, preferably 3.5 or less, more preferably 3.0 or less, and 2 It is more preferably .0 or less, particularly preferably 1.5 or less, and most preferably 1.2 or less. This is because the presence of a suitable amount of the second binder that is not disposed near the electrode active material improves the strength of the electrode composite material layer. That is, while improving the peel strength of the electrode active material layer, it is easy to improve the discharge capacity retention rate after charge/discharge cycles in a nonaqueous secondary battery using the electrode.

Further, the total binder content (X+Y) is 0.7% by mass or more, preferably 1.2% by mass or more, more preferably 1.5% by mass or more, and 2.0% by mass. It is more preferable that it is above. By setting the binder content in the electrode within the above range, it is possible to ensure binding between the electrode active materials and between the electrode active material and the current collector, and to maintain the charge/discharge capacity of the electrode active material layer. This is because it can be made larger and the internal resistance when used as a battery can be lowered.
The total binder content (X+Y) is preferably 14% by mass or less, more preferably 12% by mass or less, and even more preferably 10% by mass or less. Further, the total binder content may be 8.0% by mass or less, or 6.0% by mass or less. This is because when the binder content in the electrode is within the above range, inactive substances in the electrode can be suppressed, and an increase in electrical resistance and a decrease in capacity can be suppressed.

[Binder for non-aqueous secondary battery electrodes]
The nonaqueous secondary battery electrode binder (or nonaqueous secondary battery electrode binder, hereinafter sometimes referred to as "electrode binder") according to the present embodiment contains a copolymer (P) described below. It is preferable. The electrode binder may contain other components, such as a polymer other than the copolymer (P), a surfactant, and the like.

Here, the electrode binder is a component that remains without being volatilized in a process involving heating in the battery manufacturing process described below. More specifically, it is the component that remains after weighing 1 g of the electrode binder into an aluminum dish with a diameter of 5 cm and drying it at 110° C. for 5 hours while circulating air in a dryer under atmospheric pressure. The nonvolatile content of the electrode binder includes, for example, a copolymer (P).

The content of the copolymer (P) in the electrode binder is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and 98% by mass. It is more preferable that it is above. This is to increase the contribution of the copolymer (P) to the desired effects of the present invention.

The copolymer (P) includes a structural unit derived from a monomer (A) represented by the formula (1) described below and a structural unit derived from the monomer (B) represented by the formula (2). Further, the copolymer (P) may include a structural unit derived from a monomer (C) and a structural unit derived from a monomer (D), which will be described later.

Monomers (A) to (D) are listed below as monomers suitably used in the production of copolymer (P), but the monomers are not limited to these, and other monomers may also be used. Monomers can also be used.

<Monomer (A)>
The monomer (A) according to this embodiment is a compound represented by the following formula (1). Monomer (A) may contain multiple types of compounds represented by formula (1).

（一般式（１）において、Ｒ^１、Ｒ^２はそれぞれ独立に水素原子または炭素数１以上５以下のアルキル基を表す。）

(In general formula (1), R ¹ and R ² each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms.)

In general formula (1), R ¹ and R ² are preferably each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and R ¹ and R ² are each independently a hydrogen atom or a methyl group. It is more preferable.

Specific examples of the monomer (A) include the compounds shown below (R ¹ and R ² in parentheses correspond to R ¹ and R ² in formula (1), respectively). It will be done. N-vinylformamide (R ¹ : hydrogen atom, R ² : hydrogen atom)), N-vinylacetamide (R ¹ : hydrogen atom, R ² : methyl group), and the like. Among these, the monomer (A) is used to improve the dispersibility of the solid content of the electrode active material, conductive agent, etc. in the slurry for non-aqueous secondary battery electrodes containing the electrode binder containing the copolymer (P). N-vinylacetamide is preferred because it provides good performance.

<Monomer (B)>
The monomer (B) according to this embodiment is a compound represented by the following general formula (2). Monomer (B) may contain multiple types of compounds represented by general formula (2).

(In general formula (2), R ³ represents a hydrogen atom or a methyl group, and Z represents at least one selected from the group consisting of a hydrogen atom, an alkali metal, and NH _4. )

In general formula (2), R ³ is preferably a hydrogen atom. Z is a hydrogen atom, an alkali metal or _NH4 , preferably an alkali metal or _NH4 . Examples of the alkali metal when Z is an alkali metal include lithium, sodium, potassium, and the like. Specific examples of preferable monovalent cations corresponding to Z include lithium ions, sodium ions, potassium ions, and ammonium ions.
Specifically, the monomer (B) according to the present embodiment is a compound shown below (R ³ and Z in parentheses correspond to R ³ and Z in formula (2), respectively.) can be mentioned.
Acrylic acid (R ³ : hydrogen atom, Z: hydrogen atom), methacrylic acid (R ³ : methyl group, Z: hydrogen atom), and salts thereof (Z in formula (2) is an alkali metal or NH ₄ compound).
Among these, it is more preferable that the monomer (B) contains at least one selected from sodium (meth)acrylate, lithium (meth)acrylate, potassium (meth)acrylate, and ammonium (meth)acrylate. . This is because it serves as a material for a non-aqueous secondary battery electrode that provides a non-aqueous secondary battery with a higher discharge capacity retention rate after charge/discharge cycles.
As the monomer (B), it is more preferable that sodium (meth)acrylate is included, and it is particularly preferable that sodium acrylate is included. This is because it serves as a material for a non-aqueous secondary battery electrode that can provide a non-aqueous secondary battery with an even higher discharge capacity retention rate after charge/discharge cycles.
(Meth)acrylates can be obtained, for example, by neutralizing (meth)acrylic acid with hydroxide, aqueous ammonia, etc., but from the viewpoint of easy availability, neutralization with sodium hydroxide is preferable. preferable.

For pH adjustment, monomer (B) preferably contains (meth)acrylate in an amount of 60% by mass or more, more preferably 80% by mass or more, and even more preferably 95% by mass or more.

Here, when (meth)acrylic acid is used as the monomer (B) and neutralized using a neutralizing agent after polymerization, the structural unit derived from (meth)acrylic acid is a cation contained in the neutralizing agent. It is assumed that the equivalent amount of salt (valence of cation x number of moles of cation, same hereinafter) is formed. When the equivalent weight of cations contained in the neutralizing agent is greater than the number of moles of (meth)acrylic acid used in polymerization, all (meth)acrylic acid is considered to form a salt. On the other hand, if the equivalent weight of cations contained in the neutralizing agent is less than the number of moles of (meth)acrylic acid used in the polymerization, it is considered that all the cations form a salt with (meth)acrylic acid. In addition, when the cation contained in the neutralizing agent has a valence of two or more, it is considered that one cation is bonded to the same number of (meth)acrylic acid-derived structural units as the valence.

<Monomer (C)>
Monomer (C) is a compound represented by the following general formula (3). Monomer (C) may include multiple types of compounds represented by general formula (3).

（一般式（３）において、Ｒ^７、Ｒ^４、Ｒ^６は各々独立に水素原子または炭素数１以上５以下のアルキル基である。Ｒ^５は、炭素数１以上６以下のアルキル基であり、Ｒ^４よりも炭素数が多い。ｎは１以上の整数、ｍは０以上の整数であり、ｎ＋ｍ≧２０である。）

(In general formula (3), R ⁷ , R ⁴ , and R ⁶ are each independently a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. R ⁵ is an alkyl group having 1 to 6 carbon atoms; , R has more carbon atoms than ^4. n is an integer of 1 or more, m is an integer of 0 or more, and n+m≧20.)

In general formula (3), R ⁷ , R ⁴ , and R ⁶ are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and R ⁷ , R ⁴ , and R ⁶ are each independently hydrogen. More preferably, it is an atom or a methyl group. More preferably, R ⁶ is a methyl group.

In general formula (3), n is an integer of 1 or more, m is an integer of 0 or more, and n+m≧20. This is because when an electrode is produced using the copolymer (P) as a binder for the electrode active material, the flexibility of the electrode is improved and the occurrence of cracks is suppressed. From this viewpoint, it is preferable that n+m≧30, and more preferably that n+m≧40. Moreover, it is preferable that n+m≦500, it is more preferable that n+m≦200, and it is even more preferable that n+m≦150. This is because the binding force of the binder becomes higher.

Although the general formula (3) is limited to n structural units containing R ⁴ and m structural units containing R ⁵ , there is no limitation on the arrangement of these structural units. . That is, in the case of m≧1, in general formula (3), each structural unit may have a continuous block structure in whole or in part, and a periodic structure such as a structure in which two structural units are arranged alternately. It may be a structure in which two structural units are arranged with regularity, or a structure in which two structural units are arranged randomly. A preferred form of the copolymer of general formula (3) is a structure arranged with periodic regularity or a structure arranged randomly. This is to suppress the bias in the distribution of each structural unit within the molecular chain forming the general formula (3). A more preferred form of the copolymer of general formula (3) is a randomly arranged structure. This is because polymerization can be performed using a radical polymerization initiator without using a special catalyst, and manufacturing costs can be reduced.

In general formula (3), preferred examples of combinations of R ⁷ , R ⁴ , R ⁵ , R ⁶ , n, and m include the examples shown in Table 1 below.

More preferably, m=0 in general formula (3). Examples of the monomer (D) with m=0 include mono(meth)acrylate of polyethylene glycol, more specifically, methoxypolyethylene glycol (meth)acrylate (for example, monomer d1 in Table 1, d2) etc. An example of methoxypolyethylene glycol methacrylate is VISIOMER® MPEG2005 MA W manufactured by EVONIK INDUSTRIES. In this product, R ⁷ =CH ₃ , R ⁴ =H, R ⁶ =CH ₃ , n=45, and m=0. Other examples of methoxypolyethylene glycol methacrylate include VISIOMER® MPEG5005 MA W from EVONIK INDUSTRIES. In this product, R ⁷ =CH ₃ , R ⁴ =H, R ⁶ =CH ₃ , n=113, m=0.

Other examples of monomers (C) with m=0 include mono(meth)acrylates of polypropylene glycol, more specifically methoxypolypropylene glycol (meth)acrylates (e.g. monomers of Table 1). d3, d4), etc.

<Monomer (D)>
Monomer (D) is an ethylenically unsaturated carboxylic acid ester compound of aromatic alcohol. The monomer (D) may contain only one type of compound, or may contain two or more types of compounds. Monomer (D) preferably contains (meth)acrylate of aromatic alcohol ((meth)acrylate of aromatic alcohol), and (meth)acrylate of aromatic alcohol ((meth)acrylate of aromatic alcohol). meth)acrylate).

Examples of (meth)acrylic esters of aromatic alcohols ((meth)acrylates of aromatic alcohols) include benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxyethylene glycol (meth)acrylate, and phenoxydiethylene glycol. (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, ethoxylated-o-phenylphenol (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, and the like. Among these compounds, monomer (D) more preferably contains at least one of benzyl (meth)acrylate and phenoxyethyl (meth)acrylate, and further preferably contains benzyl (meth)acrylate. preferable.

The monomers (A) to (D) mentioned above are listed as monomers suitably used in the production of the copolymer (P), but the monomers are not limited to these, and other monomers may also be used. mer can also be used. Examples of other monomers include acrylamide, acrylonitrile, butyl acrylate, and the like.

<Content of structural units in copolymer (P)>
The content of each structural unit in the copolymer (P) will be explained below. Here, when (meth)acrylic acid is used as the monomer (B) and neutralized using a neutralizing agent after polymerization, the structural unit derived from (meth)acrylic acid is It is assumed that a salt is formed by the equivalent amount of cations contained in (valent number of cation x number of moles of cation, the same applies hereinafter). The details are as explained in the section <Monomer (B)>.

In this embodiment, the content of structural units derived from each monomer in the copolymer (P) can be determined by using the blending amount of each monomer added for producing the copolymer (P). , can be calculated. Below, the content of structural units derived from each monomer in the copolymer (P) is calculated as 100 mol% in total of the monomers from which the structural units in the copolymer are derived. The content will be explained using the value of mol%. In addition, when a compound other than a monomer, such as a chain transfer agent, is used in the polymerization of the copolymer (P), the structural unit derived from the compound is also considered to be the structure of the copolymer.

The content of the structural unit (a) derived from the monomer (A) according to the present embodiment is preferably 0.5 mol% or more, more preferably 1 mol% or more in the copolymer (P). It is preferably at least 3 mol%, more preferably at least 5 mol%, particularly preferably at least 5 mol%. This is because an electrode slurry having excellent dispersibility of an electrode active material, a conductive additive, etc. during the production of an electrode slurry, which will be described later, and good coating properties can be produced. The content of the structural unit (a) derived from the monomer (A) may be 7 mol% or more.
The content of structural units derived from the monomer (A) according to the present embodiment is preferably 20 mol% or less, more preferably 15 mol% or less, and 13 mol% or less in the copolymer (P). It is more preferable that This is because the occurrence of cracks in the electrode, which will be described later, is suppressed and the productivity of the electrode is improved. The content of structural units derived from monomer (A) may be 10 mol% or less.

The content of structural units derived from the monomer (B) according to this embodiment (total amount of (meth)acrylic acid and (meth)acrylate) is 50 mol% or more in the copolymer (P). It is preferably at least 70 mol%, more preferably at least 80 mol%. This is because an electrode active material layer having high peel strength against the current collector can be obtained.
The content of structural units derived from the monomer (B) according to the present embodiment (total amount of (meth)acrylic acid and (meth)acrylate) is 98 mol% or less in the copolymer (P). It is preferably at most 95 mol%, more preferably at most 92 mol%. This is because the dispersibility of solid contents such as an electrode active material and a conductive aid during preparation of an electrode slurry, which will be described later, is further improved.

The content of structural units derived from the monomer (C) according to this embodiment is preferably 0.05 mol% or more, more preferably 0.1 mol% or more in the copolymer (P). , more preferably 0.15 mol% or more. The content of the structural unit derived from the monomer (C) may be 0.25 mol% or more.
The content of structural units derived from the monomer (C) according to this embodiment is preferably 5 mol% or less, more preferably 3 mol% or less, and 1 mol% or less in the copolymer (P). It is more preferable that This is to suppress the generation of cracks in the electrode, which will be described later, to improve the peel strength of the electrode active material layer, and to suppress swelling of the electrode active material layer. This is also to improve cycle characteristics (discharge capacity retention rate) in non-aqueous secondary batteries to be described later.

The content of structural units derived from the monomer (D) according to this embodiment is preferably 1 mol% or more, more preferably 2 mol% or more, and 2.5 mol% or more in the copolymer (P). % or more is more preferable. This is because the occurrence of cracks in the electrode, which will be described later, is suppressed and the productivity of the electrode is improved.
The content of structural units derived from the monomer (D) according to the present embodiment is preferably 20 mol% or less, more preferably 15 mol% or less, and 10 mol% or less in the copolymer (P). It is more preferable that This is to improve the peel strength of the electrode active material layer and to suppress swelling of the electrode active material layer in the electrode described below. This is also to improve cycle characteristics (discharge capacity retention rate) in non-aqueous secondary batteries to be described later.

<Method for producing copolymer (P)>
The copolymer (P) is preferably synthesized by radical polymerization in an aqueous medium. As the polymerization method, for example, a method in which all the monomers used in the polymerization are charged at once and polymerized, a method in which the monomers used in the polymerization are continuously supplied and polymerized, etc. can be applied. The content of each monomer in all the monomers used in the synthesis of the copolymer (P) is the content of structural units corresponding to that monomer in the copolymer (P). For example, the content of monomer (A) in all monomers used in the synthesis of copolymer (P) is the content of structural unit (a) in copolymer (P) to be synthesized. be. However, when (meth)acrylic acid is used as the monomer (B) and neutralized using a neutralizing agent after polymerization, the structural unit derived from (meth)acrylic acid is the cation contained in the neutralizing agent. It is assumed that the equivalent amount (valence of cation x number of moles of cation, hereinafter the same) forms a salt. When the equivalent weight of cations contained in the neutralizing agent is greater than the number of moles of (meth)acrylic acid used in polymerization, all (meth)acrylic acid is considered to form a salt. On the other hand, if the equivalent weight of cations contained in the neutralizing agent is less than the number of moles of (meth)acrylic acid used in the polymerization, it is considered that all the cations form salts with (meth)acrylic acid (i.e., ( meth)acrylic acid forms a salt corresponding to the amount of cations contained in the neutralizing agent). Radical polymerization is preferably carried out at a temperature of 30 to 90°C. In addition, a specific example of the polymerization method of the copolymer (P) will be explained in detail in the Examples below.

Examples of the radical polymerization initiator include, but are not limited to, ammonium persulfate, potassium persulfate, hydrogen peroxide, t-butyl hydroperoxide, and an azo compound. Examples of the azo compound include 2,2'-azobis(2-methylpropionamidine) dihydrochloride. When polymerization is carried out in water, it is preferable to use a water-soluble polymerization initiator. Further, if necessary, a radical polymerization initiator and a reducing agent may be used together during the polymerization to carry out redox polymerization. Examples of the reducing agent include sodium bisulfite, Rongalit, ascorbic acid, and the like.

[Method for producing non-aqueous secondary battery electrode binder]
The method for producing the non-aqueous secondary battery electrode binder may be the same as the method for producing the copolymer (P), or may include additional steps. The method for producing the copolymer (P) is as described above. Examples of additional steps include a purification step, an additive mixing step, and the like.

[Electrode active material]
The non-aqueous secondary battery to which the non-aqueous secondary battery electrode binder of this embodiment is applied is not particularly limited. When the nonaqueous secondary battery is a lithium ion secondary battery, the negative electrode active material shown below can be used as the electrode active material, for example. Only one type of negative electrode active material may be used, or two or more types may be used.
Examples of negative electrode active materials include conductive polymers, carbon materials, lithium titanate, silicon compounds, and the like. Among these negative electrode active materials, it is preferable to use one or more selected from carbon materials, lithium titanate, and silicon compounds because a lithium ion secondary battery with a high energy density per volume can be obtained. .
Examples of the conductive polymer include polyacetylene and polypyrrole.
Examples of the carbon material include coke such as petroleum coke, pitch coke, and coal coke; graphite such as artificial graphite and natural graphite. Examples of the artificial graphite include SCMG (registered trademark)-XRs (manufactured by Showa Denko K.K.). Among these, graphite is preferred from the viewpoint of capacity.
Examples of silicon compounds include silicon (Si) and silicon oxide. Specific examples of the silicon oxide include SiO _x (0.1≦x≦2.0).
Among these, SiOx (0.1≦x≦2.0) is preferable from the viewpoint of achieving both capacity and cycle characteristics.

Moreover, it is preferable that the negative electrode active material contains a carbon material and a silicon compound. This is because the effect of improving peel strength becomes more remarkable in the non-aqueous secondary battery electrode formed using the non-aqueous secondary battery electrode slurry of this embodiment. In particular, since a lithium ion secondary battery with a high energy density per volume and a high discharge capacity retention rate after charge/discharge cycles can be obtained, the negative electrode active material preferably contains a silicon compound and graphite. More preferably, SiO _x (0.1≦x≦2.0) and graphite are included.

The content of the silicon compound is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more, based on 100% by mass of the electrode active material. This is because an electrode with high capacity can be obtained.
In addition, when the negative electrode active material contained in the electrode slurry contains 5% by mass or more of a silicon compound, by applying the electrode slurry on a current collector and drying it, the negative electrode active material containing 5% by mass or more of a silicon compound can be prepared. A negative electrode active material layer is obtained.
Further, the silicon compound in the negative electrode active material is preferably 60% by mass or less, more preferably 30% by mass or less, and 25% by mass or less based on 100% by mass of the negative electrode active material. It is even more preferable. If the silicon compound in the negative electrode active material is 60% by mass or less, a lithium ion secondary battery may be obtained that achieves high capacity and even higher discharge capacity retention rate after charge/discharge cycles. It is.
The content of the silicon compound is 5% by mass or more and 60% by mass or less based on 100% by mass of the electrode active material.The negative electrode active material layer is formed using the electrode slurry for non-aqueous secondary batteries of this embodiment. In this case, it is easy to obtain the effect of improving the peel strength of the electrode active material layer and improving the discharge capacity retention rate after charge/discharge cycles in a non-aqueous secondary battery using the electrode.

Examples of positive electrode active materials for lithium ion secondary batteries include lithium cobalt oxide (LiCoO2), lithium composite oxide containing nickel, spinel-type lithium manganate (LiMn2O4), olivine-type lithium iron phosphate, TiS2, MnO2, MoO3, V2O5. Examples include chalcogen compounds such as. The positive electrode active material may contain any one of these compounds alone or may contain a plurality of kinds. In addition, oxides of other alkali metals can also be used. Examples of nickel-containing lithium composite oxides include Ni-Co-Mn-based lithium composite oxides, Ni-Mn-Al-based lithium composite oxides, and Ni-Co-Al-based lithium composite oxides. Specific examples of the positive electrode active material include LiNi1/3Mn1/3Co1/3O2 and LiNi3/5Mn1/5Co1/5.

[Dispersion medium]
The dispersion medium in the electrode slurry is not particularly limited, but an aqueous medium is preferable from the viewpoint of environmental suitability and working environment. An example of an aqueous medium is water. The aqueous medium of the electrode slurry may include a hydrophilic solvent. Examples of hydrophilic solvents include methanol, ethanol, and N-methylpyrrolidone. In the case of a negative electrode slurry, it is preferable that water is included as a dispersion medium. In the case of a positive electrode slurry, it is preferable to include N-methylpyrrolidone as a dispersion medium.
The content of water in the aqueous medium is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. The composition of the aqueous medium of the electrode slurry may be the same as or different from the aqueous medium contained in the electrode binder composition.

[Conductivity aid]
The electrode slurry may contain carbon black, vapor grown carbon fiber, etc. as a conductive aid. A specific example of the vapor grown carbon fiber is VGCF (registered trademark)-H (Showa Denko KK).

[Additive]
In addition to the above components, additives may be used in the electrode slurry as long as the effects of the invention are achieved.

(Method for manufacturing non-aqueous secondary battery electrode)
The method for manufacturing a non-aqueous secondary battery electrode of the present embodiment includes manufacturing a non-aqueous secondary battery electrode including a current collector and an electrode active material layer provided on at least one surface of the current collector. It's a method. The electrode slurry for a non-aqueous secondary battery obtained by the method for producing an electrode slurry for a non-aqueous secondary battery of the present embodiment described above is applied to the current collector and dried to obtain the electrode active material layer. Including process.

<Nonaqueous secondary battery electrode>
The non-aqueous secondary battery electrode of this embodiment (also referred to as "the electrode of this embodiment") includes a current collector and an electrode active material layer formed on the surface of the current collector. The electrode active material layer contains an electrode active material and the electrode binder of this embodiment. The shape of the electrode includes, for example, a laminate or a wound body, but is not particularly limited. The current collector is preferably a metal sheet with a thickness of 0.001 to 0.5 mm. Examples of the metal include iron, copper, aluminum, nickel, and stainless steel. In the case of a secondary battery, aluminum is preferable for the positive electrode and copper is preferable for the negative electrode, but these are not particularly limited.

The electrode of this embodiment can be manufactured, for example, by applying an electrode slurry onto a current collector and drying it, but the method is not limited to this method.

Examples of methods for applying the electrode slurry onto the current collector include reverse roll method, direct roll method, doctor blade method, knife method, extrusion method, curtain method, gravure method, bar method, dip method, and squeeze method. can be mentioned. Among these, a doctor blade method, a knife method, or an extrusion method is preferred, and application using a doctor blade is more preferred. This is because it is suitable for various physical properties such as viscosity and drying properties of the electrode slurry, and it is possible to obtain a coating film with a good surface condition.

The electrode slurry may be applied only to one side of the current collector, or may be applied to both sides. When applying the electrode slurry to both sides of the current collector, it may be applied to one side at a time, or both sides may be applied at the same time. Further, the electrode slurry may be applied continuously to the surface of the current collector, or may be applied intermittently. The amount and range of application of the electrode slurry can be determined as appropriate depending on the size of the battery and the like. The basis weight of the electrode active material layer after drying is preferably 4 to 25 mg/cm ² , more preferably 6 to 16 mg/cm ² .

An electrode sheet is obtained by drying the electrode slurry applied to the current collector. The drying method is not particularly limited, and for example, hot air, vacuum, (far) infrared rays, electron beams, microwaves, and low-temperature air can be used alone or in combination. The drying temperature is preferably 40°C or more and 180°C or less, and the drying time is preferably 1 minute or more and 30 minutes or less.

The electrode sheet may be used as an electrode as it is, or may be cut into a size and shape suitable for use as an electrode. The method for cutting the electrode sheet is not particularly limited, and for example, a slit, a laser, a wire cut, a cutter, a Thomson, etc. can be used.

Before or after cutting the electrode sheet, it may be pressed if desired. This allows the electrode active material to be more firmly bound to the electrode, and by making the electrode thinner, it is possible to make the non-aqueous battery more compact. As the pressing method, a general method can be used, and it is particularly preferable to use a mold pressing method or a roll pressing method. The pressing pressure is not particularly limited, but it is preferably 0.5 to 5 t/cm ² , which is within a range that does not affect the doping/undoping of lithium ions, etc. into the electrode active material by pressing.

<Nonaqueous secondary battery>
A lithium ion secondary battery will be described as a preferable example of the non-aqueous secondary battery according to the present embodiment (sometimes referred to as "the battery according to the present embodiment"), but the configuration of the battery is limited to the configuration described below. I can't. In the lithium ion secondary battery according to the example described here, components such as a positive electrode, a negative electrode, an electrolytic solution, and, if necessary, a separator are housed in an exterior body.

"Electrolyte"
As the electrolyte, a non-aqueous liquid having ionic conductivity is used. Examples of the electrolytic solution include a solution in which an electrolyte is dissolved in an organic solvent, an ionic liquid, and the like, but the former is preferable because it has low manufacturing cost and can provide a battery with low internal resistance.

As the electrolyte, an alkali metal salt can be used, and can be appropriately selected depending on the type of electrode active material. Examples of the electrolyte include LiClO ₄ , LiBF ₆ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiB ₁₀ Cl ₁₀ , LiAlCl ₄ , LiCl, LiBr, LiB(C ₂ H ₅ ) ₄ , CF ₃ SO ₃ Li, CH ₃ SO ₃ Li, LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , Li(CF ₃ SO ₂ ) ₂ N, lithium aliphatic carboxylate, and the like. Moreover, other alkali metal salts can also be used as the electrolyte.

The organic solvent for dissolving the electrolyte is not particularly limited, but includes, for example, ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), dimethyl carbonate (DMC), and fluoroethylene carbonate. (FEC), carbonate ester compounds such as vinylene carbonate (VC), nitrile compounds such as acetonitrile, and carboxylic acid esters such as ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, and propyl propionate. These organic solvents may be used alone or in combination of two or more.

"Exterior body"
As the exterior body, metal, aluminum laminate, or the like can be used as appropriate. The shape of the battery may be any shape, such as a coin shape, a button shape, a sheet shape, a cylindrical shape, a square shape, or a flat shape.

EXAMPLES Below, the present invention will be explained in further detail by showing Examples and Comparative Examples of electrode binders, negative electrode slurries, negative electrodes, and lithium ion secondary batteries for lithium ion secondary batteries. Note that the present invention is not limited to these examples.

(Preparation examples 1 to 3)
<Preparation of electrode binder (copolymer (P))>
Table 2 shows the composition of the monomers used in Preparation Examples 1 to 3. The manufacturing method of the electrode binder in Preparation Examples 1 to 3 is the same except for the composition of the monomer. Details of monomers and reagents are as follows. When a monomer is used as a solution, the amount of monomer used in the table indicates the amount of the monomer itself without solvent.

Monomer (A): N-vinylacetamide (NVA) (manufactured by Showa Denko K.K.)
Monomer (B): Sodium acrylate (AaNa) (28.5% by mass aqueous solution)
Monomer (C): Methoxypolyethylene glycol methacrylate (manufactured by EVONIK INDUSTRIES; VISIOMER (registered trademark) MPEG2005 MA W) (R ⁷ = CH ₃ , R ⁴ = H, R ⁶ = CH ₃ , n in formula (2) = 45, m = 0, m + n = 45) Monomer (D): benzyl acrylate Polymerization initiator: 2,2'-azobis(2-methylpropionamidine) dihydrochloride (sum V-50) and ammonium persulfate (manufactured by Wako Pure Chemical Industries, Ltd.)

A total of 100 parts by mass of monomers having the composition shown in Table 2 and 2,2'-azobis(2-methylpropion) as a polymerization initiator were placed in a separable flask equipped with a cooling tube, a thermometer, and a stirrer. 0.2 parts by mass of (amidine) dihydrochloride, 0.05 parts by mass of ammonium persulfate, and 693 parts by mass of water were charged at 30°C. This was heated to 80° C. under a nitrogen stream and polymerized for 4 hours. Copolymers P1 to P3 were obtained as electrode binders for Preparation Examples 1 to 3, respectively. The copolymers were not isolated from the reaction solution, and the aqueous solutions of copolymers P1 to P3 were used as they were in the following examples.

(Examples 1 to 8, Comparative Examples 1 to 8)
<Preparation of negative electrode slurry>
"First step"
A negative electrode slurry, which is an example of the electrode slurry of this embodiment, will be described below. As a negative electrode active material, 76.8 parts by mass of carbon material, that is, SCMG (registered trademark)-XRs (manufactured by Showa Denko K.K.) as graphite, and 19 parts by mass of silicon monoxide (SiO) (manufactured by Sigma-Aldrich) as a silicon compound. .2 parts by mass, 1 part by mass of VGCF (registered trademark)-H (Showa Denko K.K.) as a conductive aid, and the binder of each example and comparative example shown in Table 3 (copolymer obtained in the preparation example). Combined materials P1 to P3) and 15 parts by mass of water were mixed to obtain a first mixture.
As shown in Table 3, the amount of binder added in the first step was adjusted to be X% by mass based on the total solid content of the electrode slurry for non-aqueous secondary batteries. Note that the aqueous solutions of copolymers P1 to P3 of Preparation Examples 1 to 3 were used as they were, and the solid content of copolymers P1 to P3 was added so that the amount of binder added was as shown in Table 3. The same applies to the second step below. The water contained in the aqueous solutions of copolymers P1 to P3 in Preparation Examples 1 to 3 is contained in the above 15 parts by mass of water.
Thereafter, the mixture was kneaded for 4 minutes at 2,000 revolutions/minute using a stirring type mixer (rotation/revolution mixer), 30 parts by mass of water was added, and the mixture was kneaded at 2,000 revolutions/minute using a stirring type mixer (rotation/revolution mixer). The mixture was kneaded for 2 minutes to obtain a first electrode slurry.

"Second process"
To the obtained first electrode slurry, the same binder as in the first step, the binder in the second step shown in Table 3, and 55 parts by mass of water were added and mixed to obtain a second mixture.
The amount of binder added in the second step was adjusted to be Y% by mass based on the total solid content of the electrode slurry for non-aqueous secondary batteries.
In the above mixing device, the obtained second mixture was kneaded for 10 minutes at 500 revolutions/minute using a stirring type mixing device (rotation/revolution stirring mixer), and the second electrode slurry was mixed as the electrode slurry of each example and comparative example. I got it.
In addition, in the comparative example, when the amount of binder added in the second step is 0 parts by mass, that is, when Y = 0% by mass, only 55 parts by mass of water was added to the first electrode slurry and the same conditions were used. Kneaded.
In each Example and Comparative Example, the total addition amount (X+Y, mass %) of binder addition amount X and binder addition amount Y in the electrode slurry solid content and the ratio of both (X/Y) are shown in Table 3.

<Preparation of negative electrode and battery>
<Preparation of negative electrode>
The electrode slurry prepared in each example and comparative example, that is, the negative electrode slurry, was applied to one side of a 10 μm thick copper foil (current collector) using a doctor blade so that the drying weight was 8 mg/ ^cm2 . It was applied. The copper foil coated with the negative electrode slurry was dried at 60° C. for 10 minutes and then further dried at 100° C. for 5 minutes to produce a negative electrode sheet on which a negative electrode active material layer was formed. This negative electrode sheet was pressed using a mold press at a pressing pressure of 1 t/cm ² . The pressed negative electrode sheet was cut out into a size of 22 mm x 22 mm, and a conductive tab was attached thereto to produce a negative electrode.

<Preparation of positive electrode>
90 parts by mass of LiNi _1/3 Mn _1/3 Co _1/3 O ₂ , 5 parts by mass of acetylene black, and 5 parts by mass of polyvinylidene fluoride were mixed, and then 100 parts by mass of N-methylpyrrolidone was mixed. A positive electrode slurry was prepared (the ratio of LiNi _1/3 Mn _1/3 Co _1/3 O ₂ in the solid content was 0.90).

The prepared positive electrode slurry was applied to one side of a 20 μm thick aluminum foil (current collector) using a doctor blade method so that the drying weight was 22.5 mg/cm ² (22.5×10 ⁻³ g/cm 2 ). It was applied using a doctor blade. The aluminum foil coated with the positive electrode slurry was dried at 120° C. for 5 minutes and then pressed using a roll press to produce a positive electrode sheet on which a positive electrode active material layer with a thickness of 100 μm was formed. The obtained positive electrode sheet was cut out to a size of 20 mm x 20 mm (2.0 cm x 2.0 cm), and a conductive tab was attached to produce a positive electrode.

The theoretical capacity of the prepared positive electrode is calculated as follows: drying weight of positive electrode slurry (22.5 x 10 ^-3 g/cm ² ) x coating area of positive electrode slurry (2.0 cm x 2.0 cm) x LiNi _1/3 Mn It is determined by the capacity of _1/3 Co _1/3 O ₂ as a positive electrode active material (160 mAh/g) x the ratio of LiNi _1/3 Mn _1/3 Co _1/3 O ₂ in solid content (0.90). , the calculated value is 13mAh.

<Preparation of electrolyte>
A mixed solvent was prepared by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and fluoroethylene carbonate (FEC) at a volume ratio of 30:60:10. In this mixed solvent, LiPF ₆ was dissolved at a concentration of 1.0 mol/L, and vinylene carbonate (VC) was dissolved at a concentration of 1.0% by mass to prepare an electrolytic solution.

<Battery assembly>
A positive electrode and a negative electrode were arranged with a separator made of a porous polyolefin film interposed therebetween so that their respective active material layers faced each other, and housed in an aluminum laminate exterior body (battery pack). An electrolytic solution was injected into this exterior body, and it was packed with a vacuum heat sealer to obtain a laminate type battery.

<Evaluation of negative electrode and battery>
The negative electrodes and batteries of each Example and Comparative Example were evaluated. The evaluation method was as follows, and the evaluation results are shown in Table 3.

<Peel strength of negative electrode active material layer>
At 23°C, the negative electrode active material layer formed on the negative electrode sheet and the SUS plate were bonded together using double-sided tape (NITTOTAPE (registered trademark) No. 5, manufactured by Nitto Denko Corporation) to prepare a sample for peel strength evaluation. Created. Using this sample, the negative electrode active material layer was peeled 180° from the negative electrode sheet at a peeling width of 25 mm and a peeling speed of 100 mm/min, and the value of the peeling force obtained was divided by the peeling width of 25 mm, and the peel strength was determined. .

<Battery discharge capacity maintenance rate (100 cycles)>
Measurement of the discharge capacity retention rate of the battery (charge/discharge cycle test of the battery) was performed under the condition of 25° C. according to the following procedure. First, it was charged with a current of 1C until the voltage reached 4.2V (CC charging), and then it was charged with a voltage of 4.2V until the current reached 0.05C (CV charging). After leaving it for 30 minutes, it was discharged with a current of 1C until the voltage reached 2.75V (CC discharge). A series of operations of CC charging, CV charging, and CC discharging is defined as one cycle. The sum of the time-integrated values of the current in the n-th cycle of CC charging and CV charging is the n-th cycle charge capacity (mAh), and the time-integrated value of the current in the n-th cycle of CC discharge is the n-th cycle discharge capacity (mAh). shall be. The n-th cycle discharge capacity retention rate of the battery is the ratio (%) of the n-th cycle discharge capacity to the first cycle discharge capacity. In the present example and comparative example, the discharge capacity retention rate at the 100th cycle was evaluated.

<Evaluation results>
As can be seen from Table 3, in Examples 1 to 8 using the method for producing an electrode slurry for a non-aqueous secondary battery according to the present embodiment, compared with Comparative Examples 1 to 8, the total amount of binder and binder copolymer The peel strength and discharge capacity retention rate were improved in the monomer composition used for this purpose.
In Comparative Example 1, Comparative Example 2, Comparative Example 5, Comparative Example 7, and Comparative Example 8, a formulation was used in which a binder was added only in the first step and no binder was added in the second step. In Comparative Example 3, a formulation that did not satisfy the conditions shown in formula (I) was used. In Comparative Example 4, X was too small and a prescription that did not satisfy the conditions was used. In Comparative Example 6, a prescription in which X was too small and did not satisfy the conditions shown in formula (I) was used.
In Examples 2 to 8, peel strength and discharge capacity retention rate were improved compared to Example 1. In Example 1, the amount X of binder added in the first step is greater than the amount Y of binder added in the second step. In Examples 2, 4, 6, 7, and 8, which were more effective than Example 1, the addition amount X and the addition amount Y were the same, and in Examples 3 and 5, the addition amount X was The amount added is less than Y.

Claims (12)

A method for producing an electrode slurry for a non-aqueous secondary battery comprising an electrode active material, a first binder, a second binder, and a dispersion medium, the method comprising:
A first step of preparing a first electrode slurry by kneading a first mixture containing the electrode active material, the first binder, and the dispersion medium;
a second step of preparing a second electrode slurry by kneading a second mixture containing at least the first electrode slurry prepared in the first step and the second binder;
Equipped with
In the total solid content of the electrode slurry for non-aqueous secondary batteries, the content X of the first binder is 0.5% by mass or more,
In the total solid content of the electrode slurry for non-aqueous secondary batteries, the content Y of the second binder is 0.2% by mass or more,
A method for producing an electrode slurry for a non-aqueous secondary battery, wherein the content X of the first binder and the content Y of the second binder satisfy the conditions shown in the following formula (I).
0.067≦X/Y≦4.0 (I) The method for producing an electrode slurry for a non-aqueous secondary battery according to claim 1, wherein the content X of the first binder and the content Y of the second binder satisfy the conditions shown in the following formula (II).
1.0 mass%≦X+Y (II) The electrode for a non-aqueous secondary battery according to claim 1 or 2, wherein the ratio X/Y of the content X of the first binder and the content Y of the second binder satisfies the condition shown in the following formula (III). Slurry manufacturing method.
X/Y≦1.5 (III) At least one of the first binder and the second binder contains a copolymer (P),
The copolymer (P) has a structural unit derived from a monomer (A) represented by the following general formula (1), and a monomer (B) represented by the following general formula (2). The method for producing an electrode slurry for a non-aqueous secondary battery according to claim 1 or 2, comprising a structural unit derived from.

(In general formula (1), R ¹ and R ² each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms.)

(In general formula (2), R ³ represents a hydrogen atom or a methyl group, and Z represents at least one selected from the group consisting of a hydrogen atom, an alkali metal, and NH _4. ) The electrode for a nonaqueous secondary battery according to claim 4, wherein the content of structural units derived from the monomer (A) in the copolymer (P) is 0.5 mol% or more and 20 mol% or less. Slurry manufacturing method. The electrode slurry for a non-aqueous secondary battery according to claim 4, wherein the content of structural units derived from the monomer (B) in the copolymer (P) is 50 mol% or more and 98 mol% or less. Production method. The content of structural units derived from the monomer (A) in the copolymer (P) is 0.5 mol% or more and 20 mol% or less,
The electrode slurry for a non-aqueous secondary battery according to claim 4, wherein the content of structural units derived from the monomer (B) in the copolymer (P) is 50 mol% or more and 98 mol% or less. Production method. The method for producing an electrode slurry for a non-aqueous secondary battery according to claim 4, wherein both the first binder and the second binder contain the copolymer (P). The method for producing an electrode slurry for a non-aqueous secondary battery according to claim 1 or 2, wherein the electrode active material contains a carbon material and a silicon compound. The method for producing an electrode slurry for a non-aqueous secondary battery according to claim 9, wherein the content of the silicon compound is 5% by mass or more and 60% by mass or less based on 100% by mass of the electrode active material. The method for producing an electrode slurry for a non-aqueous secondary battery according to claim 1 or 2, wherein the first mixture further contains a conductive additive. A method for manufacturing a non-aqueous secondary battery electrode comprising a current collector and an electrode active material layer provided on at least one surface of the current collector, the method comprising:
A non-aqueous secondary battery comprising the step of applying an electrode slurry for a non-aqueous secondary battery obtained by the manufacturing method according to claim 1 or 2 to the current collector and drying it to obtain the electrode active material layer. Method for manufacturing battery electrodes.