JP2023149190A - Manufacturing method of anode for non-aqueous secondary battery, anode for non-aqueous secondary battery, and non-aqueous secondary battery - Google Patents

Abstract

To provide an anode which is excellent in impact resistance and enables a non-aqueous secondary battery to exhibit the satisfactory rate characteristics, a manufacturing method of the anode, and the non-aqueous secondary battery excellent in rate characteristics.SOLUTION: A manufacturing method of an anode for non-aqueous secondary battery is provided, including: a primary sheet molding step of pressurizing a composition including resin and particulate carbon material and molding the pressurized composition into a sheet shape thereby obtaining a primary sheet: a laminate forming step of laminating the plurality of primary sheets in a thickness direction or folding or winding the primary sheet thereby obtaining a laminate; a slice step of obtaining a secondary sheet by slicing the laminate at an angle equal to or smaller than 45° with respect to the lamination direction; a calcination step of calcining the secondary sheet thereby obtaining an anode material sheet for non-aqueous secondary battery; a coated film forming step of forming a coated film by applying a slurry composition for undercoat layer formation including carbon material and a binder onto a current collector; and an adhesion step of adhering the anode material sheet for non-aqueous secondary battery to the coated film before the coated film is dried.SELECTED DRAWING: None

Description

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

Non-aqueous secondary batteries (hereinafter sometimes simply referred to as "secondary batteries") such as lithium-ion secondary batteries have the characteristics of being small, lightweight, and high in energy density, as well as being able to be repeatedly charged and discharged. Yes, and used for a wide range of purposes. Therefore, in recent years, improvements in battery components such as electrodes (positive electrode, negative electrode) have been studied with the aim of further improving the performance of secondary batteries.

Here, a negative electrode used in a secondary battery such as a lithium ion secondary battery usually includes a current collector and an electrode mixture layer (negative electrode mixture layer) formed on the current collector. This negative electrode composite material layer (sometimes referred to as a "negative electrode active material layer") includes, for example, a negative electrode active material and a resin component such as a binder used as necessary.

Therefore, in recent years, attempts have been made to further improve the performance of secondary batteries by improving this negative electrode composite material layer. For example, in Patent Document 1, for the purpose of improving the input/output characteristics (rate characteristics) of a secondary battery, at least 50% of the total amount of the negative electrode active material in the negative electrode active material layer is used to absorb and release charge carriers. The orientation is such that the direction in which the current is applied is 45° or more and 90° or less with respect to the surface of the current collector.

International Publication No. 2013/088540

However, when a negative electrode is manufactured using a resin binder as in Patent Document 1, this binder component inhibits the charge carrier absorption/release reaction of the negative electrode active material, resulting in the battery characteristics such as the rate characteristics of the secondary battery being affected. It is expected that the situation will worsen. Therefore, it is expected that battery characteristics can be improved by reducing the binder component in the negative electrode as much as possible. On the other hand, a binder is required to form a negative electrode composite material layer well.

Therefore, in hopes of obtaining a secondary battery with good rate characteristics, the present inventor considered removing the binder component by firing a negative electrode prepared using a binder at a high temperature. However, although it is possible to improve the rate characteristics of secondary batteries by removing the binder component by high-temperature firing, the strength of the negative electrode (resistance It was found that the negative electrode may not be able to withstand the bonding process with the separator.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a negative electrode that has excellent impact resistance and can exhibit excellent rate characteristics in a non-aqueous secondary battery, and a method for manufacturing the same.
Another object of the present invention is to provide a non-aqueous secondary battery with excellent rate characteristics.

The present inventor conducted extensive studies with the aim of solving the above problems. Then, the present inventor produced a negative electrode using a negative electrode material sheet for nonaqueous secondary batteries (hereinafter also simply referred to as "negative electrode material sheet") obtained by firing a predetermined sheet containing a resin and a particulate carbon material. In this case, a predetermined undercoat layer is provided on the current collector, and a negative electrode material sheet is attached to the undercoat layer before the coating film of this undercoat layer dries (that is, in a wet state). It has been found that a negative electrode can be obtained that has excellent impact resistance and can exhibit excellent rate characteristics in a non-aqueous secondary battery.

That is, the present invention aims to advantageously solve the above problems, and the method for producing a negative electrode for a non-aqueous secondary battery of the present invention involves adding a composition containing a resin and a particulate carbon material. A primary sheet forming step in which a primary sheet is obtained by pressing and forming into a sheet shape, and a laminate is formed by laminating a plurality of the primary sheets in the thickness direction, or by folding or winding the primary sheets. a laminate forming step to obtain a laminate, a slicing step to obtain a secondary sheet by slicing the laminate at an angle of 45° or less with respect to the stacking direction, and a slicing step to obtain a secondary sheet by firing the secondary sheet A firing step to obtain a negative electrode material sheet, a coating film forming step of applying a slurry composition for forming an undercoat layer containing a carbon material and a binder onto a current collector to form a coating film, and drying the coating film. The present invention is characterized in that it includes a pasting step of pasting the negative electrode material sheet for a non-aqueous secondary battery on the coating film. In this way, if an undercoat layer is provided on the current collector and a prescribed negative electrode material sheet is attached to the coating film before the coating film that becomes the undercoat layer dries, excellent impact resistance can be obtained. In addition, it is possible to produce a negative electrode that can exhibit excellent rate characteristics in a non-aqueous secondary battery.
In the present invention, "the coating film is dried and solidified" means that 70% by volume or more of the solvent component contained in the coating film made of the slurry composition for forming an undercoat layer is removed.

In the method for producing a negative electrode for a non-aqueous secondary battery according to the present invention, the secondary sheet is preferably fired at a temperature of 300°C or more and 2000°C or less. As described above, by firing the secondary sheet within the above-described predetermined temperature range, it is possible to further improve the rate characteristics of the non-aqueous secondary battery while ensuring a sufficiently high strength of the produced negative electrode material sheet. .

In the method for producing a negative electrode for a nonaqueous secondary battery according to the present invention, it is preferable that the particulate carbon material contains flaky graphite. In this way, if the particulate carbon material contains flaky graphite, the non-aqueous secondary battery can exhibit even more excellent rate characteristics.

Further, the present invention aims to advantageously solve the above-mentioned problems, and the negative electrode for a non-aqueous secondary battery of the present invention includes a current collector and an underlayer formed on the current collector. a coat layer; and a negative electrode composite layer formed on the undercoat layer and adhered to the undercoat layer, the undercoat layer containing a carbon material and a binder, and the negative electrode composite layer containing particles. the particulate carbon material is oriented perpendicularly to the surface of the negative electrode composite material layer, the resin content in the negative electrode composite layer is 8% by mass or less, and the The negative electrode composite material layer is characterized in that it exists as a self-supporting film. In this way, if a negative electrode composite layer with predetermined properties is adhered to a predetermined undercoat layer on the current collector, it will have excellent impact resistance and provide excellent rate characteristics for non-aqueous secondary batteries. It can be demonstrated.
In the present invention, the orientation of the particulate carbon material, the content of the resin in the negative electrode composite layer, and the self-supporting film properties of the negative electrode composite layer can be measured by the methods described in Examples.

In the negative electrode for a non-aqueous secondary battery of the present invention, the undercoat layer preferably has a thickness of 1 μm or more and 15 μm or less. As described above, when the thickness of the undercoat layer is within the above-mentioned predetermined range, not only is the impact resistance excellent, but also the non-aqueous secondary battery can exhibit even more excellent rate characteristics.
In the present invention, the thickness of the undercoat layer can be measured by the method described in Examples.

The negative electrode for a non-aqueous secondary battery of the present invention has a ratio of the diffraction intensity of the (110) plane to the diffraction intensity of the (004) plane in X-ray diffraction of the surface of the negative electrode composite layer, I(110)/I(004). is preferably 1.1 or more. In this way, if the ratio I(110)/I(004) of the diffraction intensity of the (110) plane to the diffraction intensity of the (004) plane in X-ray diffraction of the surface of the negative electrode composite layer is 1.1 or more, Non-aqueous secondary batteries can exhibit even more excellent rate characteristics.
In the present invention, the ratio I(110)/I(004) of the diffraction intensity of the (110) plane to the diffraction intensity of the (004) plane in the X-ray diffraction of the surface of the negative electrode composite layer is determined by It can be measured by a method.

In the negative electrode for a non-aqueous secondary battery of the present invention, it is preferable that the density of the negative electrode composite layer is 1.3 g/cm ³ or less. As described above, when the density of the negative electrode composite material layer is equal to or less than the above upper limit value, the non-aqueous secondary battery can exhibit even more excellent rate characteristics.
In the present invention, the density of the negative electrode composite layer can be measured by the method described in Examples.

In the negative electrode for a non-aqueous secondary battery of the present invention, the thickness of the negative electrode composite layer is preferably 80 μm or more. In this way, when the thickness of the negative electrode composite material layer is equal to or greater than the above lower limit, the capacity of the non-aqueous secondary battery can be increased.
In the present invention, the thickness of the negative electrode composite layer can be measured by the method described in Examples.

In the negative electrode for a non-aqueous secondary battery of the present invention, it is preferable that the particulate carbon material contains flaky graphite. In this way, if the particulate carbon material contains flaky graphite, the non-aqueous secondary battery can exhibit even more excellent rate characteristics.

Further, the present invention aims to advantageously solve the above-mentioned problems, and the non-aqueous secondary battery of the present invention is characterized by comprising any of the above-mentioned negative electrodes for non-aqueous secondary batteries. do. As described above, since the non-aqueous secondary battery of the present invention includes the above-described negative electrode for non-aqueous secondary batteries, it can exhibit excellent rate characteristics.

According to the present invention, it is possible to provide a negative electrode that has excellent impact resistance and allows a non-aqueous secondary battery to exhibit excellent rate characteristics, and a method for manufacturing the same.
Further, according to the present invention, a non-aqueous secondary battery with excellent rate characteristics can be provided.

Embodiments of the present invention will be described in detail below.
The method for producing a negative electrode for a non-aqueous secondary battery (hereinafter also simply referred to as "negative electrode") of the present invention can be used, for example, to produce the negative electrode of the present invention. The non-aqueous secondary battery (hereinafter also simply referred to as "secondary battery") of the present invention includes the negative electrode of the present invention.

(Method for manufacturing negative electrode for non-aqueous secondary battery)
The method for producing a negative electrode for a non-aqueous secondary battery of the present invention includes (A) a primary sheet forming step in which a composition containing a resin and a particulate carbon material is pressurized and formed into a sheet shape to obtain a primary sheet; (B) A laminate forming step in which a laminate is obtained by laminating a plurality of primary sheets in the thickness direction, or by folding or winding the primary sheets; (C) A laminate forming step in which a laminate is obtained by laminating a plurality of primary sheets in the thickness direction; slicing at an angle of 45° or less to obtain a secondary sheet; (D) a firing step of firing the secondary sheet to obtain a negative electrode material sheet for a non-aqueous secondary battery; (E) a binder and A coating film forming step of applying a slurry composition for forming an undercoat layer containing a carbon material onto a current collector to form a coating film; (F) Before the coating film dries, and a pasting step of pasting a negative electrode material sheet onto the coating film. Note that the method for producing a negative electrode for a non-aqueous secondary battery of the present invention may optionally include steps other than the above (A) to (F).

According to the method for producing a negative electrode for a non-aqueous secondary battery of the present invention, it is possible to produce a negative electrode for a secondary battery that has excellent impact resistance and can cause a secondary battery to exhibit an excellent rate. According to the method for producing a negative electrode for a non-aqueous secondary battery of the present invention, the negative electrode for a secondary battery of the present invention can be efficiently produced.

<(A) Primary sheet forming process>
In the primary sheet forming step, a composition containing a resin and a particulate carbon material is pressurized and formed into a sheet shape to obtain a primary sheet.

<<Composition>>
The composition includes a resin and a particulate carbon material. In addition, the said composition may further contain a fibrous carbon material. Further, the composition may further contain components (other components) other than the resin, particulate carbon material, and fibrous carbon material.

[resin]
The resin is not particularly limited, and any resin can be used. For example, as the resin, both liquid resin and solid resin can be used. In addition, one type of resin may be used alone, or two or more types may be used in combination. For example, both liquid resin and solid resin can be used as the resin. In addition, when a liquid resin and a solid resin are used together as resins, the mass ratio of the liquid resin and the solid resin can be adjusted within a range in which the desired effects of the present invention can be obtained. Note that the higher the content ratio of the liquid resin to the entire resin, the easier it is to increase the filling rate of the particulate carbon material in the primary sheet. On the other hand, the higher the solid resin content in the entire resin, the higher the strength of the primary sheet.

-Liquid resin-
The liquid resin is not particularly limited as long as it is liquid at room temperature and pressure, and for example, a thermoplastic resin that is liquid at room temperature and pressure can be used.
In the present invention, "normal temperature" refers to 23° C., and "normal pressure" refers to 1 atm (absolute pressure).

Examples of the liquid resin include fluororesin, silicone resin, acrylic resin, epoxy resin, acrylonitrile-butadiene copolymer (nitrile rubber), and polybutene. These may be used alone or in combination of two or more.

-Solid resin-
The solid resin is not particularly limited as long as it is not liquid at room temperature and pressure, and for example, thermoplastic resins that are solid at room temperature and pressure, thermosetting resins that are solid at room temperature and pressure, etc. can be used.

Examples of thermoplastic resins that are solid at room temperature and normal pressure include poly(2-ethylhexyl acrylate), a copolymer of acrylic acid and 2-ethylhexyl acrylate, polymethacrylic acid or its ester, and polyacrylic acid or its ester. Acrylic resins; silicone resins; fluororesins; polyethylene; polypropylene; ethylene-propylene copolymers; polymethylpentene; polyvinyl chloride; polyvinylidene chloride; polyvinyl acetate; ethylene-vinyl acetate copolymers; polyvinyl alcohol; polyacetals ; polyethylene terephthalate; polybutylene terephthalate; polyethylene naphthalate; polystyrene; polyacrylonitrile; styrene-acrylonitrile copolymer; acrylonitrile-butadiene copolymer (nitrile rubber); acrylonitrile-butadiene-styrene copolymer (ABS resin); styrene- Butadiene block copolymer or its hydrogenated product; Styrene-isoprene block copolymer or its hydrogenated product; Butyl rubber, butadiene rubber, polyphenylene ether; Modified polyphenylene ether; Aliphatic polyamides; Aromatic polyamides; Polyamideimide; Polycarbonate ; polyphenylene sulfide; polysulfone; polyether sulfone; polyether nitrile; polyether ketone; polyketone; polyurethane; liquid crystal polymer; ionomer; and the like. These may be used alone or in combination of two or more.
Note that in the present invention, rubber is included in the "resin".

Examples of thermosetting resins that are solid at normal temperature and normal pressure include natural rubber; butadiene rubber; isoprene rubber; nitrile rubber; hydrogenated nitrile rubber; chloroprene rubber; ethylene propylene rubber; chlorinated polyethylene; chlorosulfonated polyethylene; butyl rubber; Halogenated butyl rubber; polyisobutylene rubber; epoxy resin; polyimide resin; bismaleimide resin; benzocyclobutene resin; phenolic resin; unsaturated polyester; diallyl phthalate resin; polyimide silicone resin; polyurethane; thermosetting polyphenylene ether; thermosetting modification Examples include polyphenylene ether; etc. These may be used alone or in combination of two or more.

[Particulate carbon material]
A particulate carbon material is a particulate material formed from a carbon atom-containing substance that can insert and release a charge carrier such as lithium as a negative electrode active material of a non-aqueous secondary battery. The particulate carbon material is not particularly limited, and examples thereof include graphite, carbon black, and the like. Graphite includes natural graphite and artificial graphite depending on the origin. Furthermore, depending on the morphological characteristics, examples of graphite include flaky graphite, lumpy graphite (scaly graphite), earthy graphite, exfoliated graphite, and spheroidal graphite (ellipsoidal graphite). Furthermore, graphite may or may not be treated. Examples of the treated graphite include acid-treated graphite (eg, expandable graphite, expanded graphite), and the like. Carbon black is an aggregate of several layers of graphitic carbon microcrystals that form a turbostratic structure, and examples include acetylene black, Ketjen black, furnace black, channel black, and thermal lamp black. . Further, carbon black may contain a hetero element (eg, silicon, nitrogen, boron, etc.) different from the carbon element that is the main component. These particulate carbon materials may be used alone or in combination of two or more.
The particulate carbon material preferably contains flaky graphite, and more preferably consists of flaky graphite. This is because by using flaky graphite, it is possible to obtain excellent orientation in the vertical direction in the obtained negative electrode material sheet, and as a result, the rate characteristics of the secondary battery can be further improved. In addition, if flaky graphite is used, the filling properties and adhesion are improved, and as a result, the bonding strength between the negative electrode active materials is further improved, and the strength of the obtained negative electrode material sheet can be further improved. . In addition, examples of the flaky graphite include "UP20α" manufactured by Nippon Graphite Industries, Ltd.

The volume average particle diameter of the particulate carbon material is preferably 3 μm or more, more preferably 5 μm or more, even more preferably 8 μm or more, even more preferably 12 μm or more, and even more preferably 16 μm or more. is even more preferable, preferably 200 μm or less, more preferably 150 μm or less, even more preferably 100 μm or less, and even more preferably 50 μm or less. If the volume average particle diameter of the particulate carbon material is equal to or larger than the above lower limit, the density of the negative electrode material sheet will be moderately reduced, which will facilitate the movement of charge carriers such as lithium, and therefore the rate of the resulting secondary battery will increase. The characteristics can be further improved. On the other hand, if the volume average particle diameter of the particulate carbon material is below the above-mentioned upper limit, the density of the negative electrode material sheet can be appropriately increased, thereby making it possible to increase the capacity of the obtained secondary battery.
In addition, in the present invention, the "volume average particle diameter" can be measured in accordance with JIS Z8825, and in the particle size distribution (volume basis) measured by laser diffraction method, the cumulative volume calculated from the small diameter side is 50%. represents the particle size.

Further, the aspect ratio (major axis/breadth axis) of the particulate carbon material is preferably more than 1.2, more preferably more than 1.5, preferably 3 or less, and 2.1 It is more preferable that it is below. If the aspect ratio of the particulate carbon material is within the above-mentioned predetermined range, the orientation angle of the particulate carbon material with respect to the surface of the negative electrode material sheet can easily fall within the desired range, making it easy for charge carriers such as lithium to move. Therefore, the rate characteristics of the obtained secondary battery can be further improved.
In the present invention, the aspect ratio of a particulate carbon material refers to the ratio of the major axis length to the minor axis length (ie, maximum major axis length/maximum minor axis length) in a plane where the cross-sectional area of the particle is maximum. From the viewpoint of easy measurement and reduction of measurement errors, the aspect ratio of the particulate carbon material is preferably determined using the maximum major axis length and maximum minor axis length of flaky graphite. The device for measuring particle size is not particularly limited, and, for example, a scanning electron microscope (SEM) can suitably be used.

The content of the particulate carbon material in the composition is preferably 50 parts by mass or more, more preferably 80 parts by mass or more, and 120 parts by mass or more based on 100 parts by mass of the resin. It is more preferably 180 parts by mass or more, even more preferably 250 parts by mass or more, preferably 500 parts by mass or less, more preferably 450 parts by mass or less, and 400 parts by mass or less. It is more preferably less than parts by mass. If the content of the particulate carbon material in the composition is equal to or higher than the above lower limit, the density of the produced negative electrode material sheet can be appropriately increased, the strength of the negative electrode material sheet can be improved, and the negative electrode equipped with the negative electrode material sheet can be It is possible to increase the capacity of a secondary battery manufactured using this method. On the other hand, if the content of the particulate carbon material in the composition is below the above upper limit, the density of the produced negative electrode material sheet is appropriately reduced, and a secondary battery manufactured using a negative electrode equipped with the negative electrode material sheet is In addition to further improving the rate characteristics of the secondary battery, it is possible to improve the electrolyte injection performance of the secondary battery.

Further, the volume of the particulate carbon material in the composition is preferably 25% by volume or more, preferably 37% by volume or more, and 45% by volume with respect to the total volume of the resin and particulate carbon material. It is more preferably at least 53 vol%, even more preferably at least 75 vol%, more preferably at most 70 vol%, even more preferably at most 65 vol%. . If the volume ratio of the particulate carbon material to the total volume of the resin and particulate carbon material in the composition is equal to or higher than the above lower limit, the density of the produced negative electrode material sheet can be appropriately increased to improve the strength of the negative electrode material sheet. In addition, it is possible to increase the capacity of a secondary battery manufactured using a negative electrode including a negative electrode material sheet. On the other hand, if the volume ratio of the particulate carbon material to the total volume of the resin and particulate carbon material in the composition is below the above upper limit, the density of the negative electrode material sheet to be manufactured is appropriately reduced, and the negative electrode material is The rate characteristics of a secondary battery manufactured using a negative electrode including a sheet can be further improved, and the electrolyte injection performance of the secondary battery can be improved.

[Fibrous carbon material]
The fibrous carbon material that the composition may optionally contain is a material that can improve the strength of the resulting negative electrode material sheet.
The fibrous carbon material is not particularly limited, and for example, carbon nanotubes, vapor-grown carbon fibers, carbon fibers obtained by carbonizing organic fibers, and cut products thereof can be used. These may be used alone or in combination of two or more.

Here, among the fibrous carbon materials mentioned above, it is preferable to use fibrous carbon nanostructures such as carbon nanotubes, and it is more preferable to use fibrous carbon nanostructures containing carbon nanotubes. If fibrous carbon nanostructures such as carbon nanotubes are used, the strength of the resulting negative electrode material sheet can be further improved.

The content of the fibrous carbon material in the composition is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and 1 part by mass or more based on 100 parts by mass of the resin. It is more preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 2 parts by mass or less. If the content of the fibrous carbon material in the composition is at least the above lower limit, the strength of the produced negative electrode material sheet can be increased. On the other hand, if the content of the fibrous carbon material in the composition is below the above upper limit, a sufficiently high content ratio of the particulate carbon material in the produced negative electrode material sheet can be ensured, so that the negative electrode equipped with the negative electrode material sheet can be The capacity of a secondary battery manufactured using this method can be increased to a sufficiently high capacity.

Further, the content of the fibrous carbon material in the composition is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, based on 100 parts by mass of the particulate carbon material. , more preferably 0.4 parts by mass or more, preferably 5 parts by mass or less, more preferably 2 parts by mass or less, and even more preferably 1 part by mass or less. If the content of the fibrous carbon material in the composition is at least the above lower limit, the strength of the produced negative electrode material sheet can be increased. On the other hand, if the content of the fibrous carbon material in the composition is below the above upper limit, a sufficiently high content ratio of the particulate carbon material in the produced negative electrode material sheet can be ensured, so that the negative electrode equipped with the negative electrode material sheet can be The capacity of a secondary battery manufactured using this method can be increased to a sufficiently high capacity.

[Other ingredients]
Other components that the composition may optionally include include, for example, silicon active materials and dispersants. The silicon active material and dispersant are not particularly limited, and known ones can be used. Note that the contents of the silicon active material and the dispersant in the composition can be adjusted within a range that provides the desired effects of the present invention.

Also, in the composition that becomes the primary sheet, the amount of particulate carbon material relative to the total volume of solid components (i.e., the total volume of resin, particulate carbon material, optionally added fibrous carbon material, and other components) The volume ratio (volume fraction) is preferably 25 volume% or more, more preferably 37 volume% or more, even more preferably 45 volume% or more, and even more preferably 53 volume% or more. More preferably, the content is 75% by volume or less, more preferably 70% by volume or less, even more preferably 65% by volume or less. If the volume ratio of the particulate carbon material to the total volume of the resin and the solid components of the particulate carbon material in the composition is equal to or higher than the above lower limit, the density of the negative electrode material sheet to be produced is appropriately increased, and the negative electrode material In addition to improving the strength of the sheet, it is possible to increase the capacity of a secondary battery manufactured using a negative electrode including the negative electrode material sheet. On the other hand, if the volume ratio of the particulate carbon material to the total volume of the resin and the individual components of the particulate carbon material in the composition is below the above upper limit, the density of the produced negative electrode material sheet can be appropriately reduced. , the rate characteristics of a secondary battery manufactured using a negative electrode including a negative electrode material sheet can be further improved, and the electrolyte injection performance of the secondary battery can be improved.

[Preparation of composition]
The composition is not particularly limited and can be prepared by mixing the above-mentioned components.
The above-mentioned components can be mixed using known mixing devices such as a kneader; a mixer such as a Henschel mixer, a Hobart mixer, or a high-speed mixer; a twin-screw kneader; and a roll, without any particular limitation. can. Further, the mixing may be performed in the presence of a solvent such as ethyl acetate. The resin may be dissolved or dispersed in a solvent in advance to form a resin solution and mixed with the particulate carbon material, the optionally added fibrous carbon material, and other components. In addition, when using a fibrous carbon nanostructure containing CNT as the fibrous carbon material, a dispersion liquid obtained by dispersing the fibrous carbon nanostructure containing CNT and a dispersant in a solvent such as methyl ethyl ketone is used. After preparation, a small amount of resin may be added to the dispersion, the solvent may be distilled off, and the resulting masterbatch may be mixed with the resin and particulate carbon material. The mixing time can be, for example, 5 minutes or more and 60 minutes or less. Further, the mixing temperature can be, for example, 5° C. or higher and 150° C. or lower.

<<Formation of composition>>
The composition prepared as described above can be optionally defoamed and crushed, and then pressurized and molded into a sheet. A sheet-like product obtained by pressure-molding the composition in this manner can be used as a primary sheet. In addition, if a solvent is used during mixing, it is preferable to remove the solvent before forming into a sheet. For example, if defoaming is performed using vacuum defoaming, the solvent can be removed at the same time as defoaming. It can be carried out.

Here, the composition can be molded into a sheet using any known molding method such as press molding, rolling molding, or extrusion molding, as long as it is a molding method that applies pressure. . Among these, the composition is preferably formed into a sheet by rolling (primary pressing), and more preferably by being sandwiched between protective films and passed between rolls. Note that the protective film is not particularly limited, and a sandblasted polyethylene terephthalate (PET) film or the like can be used. In addition, the roll temperature should be 5°C or more and 150°C or less, the roll gap should be 50 μm or more and 2500 μm or less, the roll linear pressure should be 1 kg/cm or more and 3000 kg/cm or less, and the roll speed should be 0.1 m/min or more and 20 m/min or less. can.

<(B) Laminate formation process>
In the laminate forming step, a plurality of primary sheets obtained in the primary sheet forming step are laminated in the thickness direction, or the primary sheets are folded or rolled to form a laminate containing resin and particulate carbon material. Next, a laminate having a plurality of sheets formed in the thickness direction is obtained. Here, the formation of the laminate by folding the primary sheets is not particularly limited, and can be performed by folding the primary sheets to a constant width using a folding machine. In addition, the formation of a laminate by winding the primary sheet is not particularly limited, and can be performed by winding the primary sheet around an axis parallel to the transverse direction or longitudinal direction of the primary sheet. can. Furthermore, the formation of a laminate by laminating primary sheets can be performed using a laminating apparatus without any particular restriction. For example, if a sheet stacking device (manufactured by Nikkiso Co., Ltd., product name "High Stacker") is used, it is possible to suppress air from entering between the layers, so that a good laminate can be efficiently obtained.

In addition, in the lamination step, it is preferable to press the obtained laminate in the lamination direction (secondary pressurization) while heating it. By applying secondary pressure in the lamination direction while heating the laminate, it is possible to promote fusion between the laminated primary sheets.

Here, the pressure when pressurizing the laminate in the stacking direction can be 0.05 MPa or more and 0.50 MPa or less.
Further, the heating temperature of the laminate is not particularly limited, but is preferably 50°C or more and 170°C or less.
Furthermore, the heating time of the laminate can be, for example, 10 seconds or more and 30 minutes or less.

In addition, in a laminate obtained by laminating, folding, or winding primary sheets, it is presumed that the particulate carbon material is oriented in a direction substantially perpendicular to the lamination direction. For example, when the particulate carbon material has a scale shape, it is presumed that the direction of the long axis of the main surface of the scale shape is approximately perpendicular to the stacking direction.

<(C) Slice process>
In the slicing step, the laminate is sliced at an angle of 45° or less with respect to the lamination direction to obtain a secondary sheet made of sliced pieces of the laminate. Here, the method for slicing the laminate is not particularly limited, and examples thereof include a multi-blade method, a laser processing method, a water jet method, a knife processing method, and the like. Among these, the knife processing method is preferred because it facilitates making the thickness of the secondary sheet uniform. The cutting tool for slicing the laminate is not particularly limited, and a slicing member having a smooth board surface with a slit and a blade protruding from the slit (for example, a cutting tool with a sharp blade) may be used. A plane or slicer) can be used.

The angle at which the laminate is sliced is preferably 30° or less with respect to the laminating direction, more preferably 15° or less with respect to the laminating direction, and approximately 0° with respect to the laminating direction ( In other words, it is preferable that the direction be along the stacking direction.
In the secondary sheet thus obtained, the particulate carbon material is well oriented in the thickness direction. For example, when the particulate carbon material has a scale shape, the direction of the long axis of the main surface of the scale shape substantially coincides with the thickness direction of the secondary sheet.

<(D) Firing process>
In the firing step, the secondary sheet is fired to burn and remove the resin contained in the secondary sheet, thereby obtaining a negative electrode material sheet.

The heating temperature when firing the secondary sheet is preferably 300°C or higher, more preferably 500°C or higher, even more preferably 700°C or higher, and preferably 2000°C or lower, The temperature is more preferably 1500°C or lower, and even more preferably 1200°C or lower. If the heating temperature when firing the secondary sheet is equal to or higher than the above lower limit, the content ratio of resin in the produced negative electrode material sheet is reduced, and the secondary battery produced using the negative electrode equipped with the negative electrode material sheet is Rate characteristics can be further improved. On the other hand, if the heating temperature when firing the secondary sheet is below the above upper limit, damage to the structure of the negative electrode material sheet produced due to excessive heating can be suppressed, and the strength of the negative electrode material sheet can be sufficiently maintained. can be secured at a high rate.

Note that the heating time when firing the secondary sheet can be adjusted depending on the heating temperature, and can be, for example, 30 minutes or more and 72 hours or less.

<<Negative electrode material sheet>>
The negative electrode material sheet obtained as described above contains a particulate carbon material, and may optionally further contain a resin, a fibrous carbon material, and/or other components. Examples of other components include the silicon active material described in the above section <(A) Primary sheet forming step>.

[Particulate carbon material]
The particulate carbon material is oriented perpendicularly to the surface of the negative electrode material sheet. Here, "orientated in the vertical direction" means that the long axis of the particulate carbon material is oriented at an angle of a predetermined value or more with respect to the surface of the negative electrode material sheet. If the particulate carbon material is oriented perpendicularly to the surface of the negative electrode material sheet, charge carriers such as lithium can move easily, so the rate characteristics of the resulting secondary battery can be further improved. . The orientation of such a particulate carbon material can be evaluated using, for example, a measured value of the orientation angle of the particulate carbon material as an index. The orientation of the particulate carbon material is determined by, for example, the manufacturing process of the negative electrode material sheet mentioned above, the properties of the particulate carbon material used (e.g. aspect ratio), and the forming process including the film thickness of the primary sheet described below. It can be adjusted by adjusting the conditions, the cutting angle of the laminate, the firing conditions (for example, temperature and time), and the like.

When the orientation angle of the particulate carbon material is used as an index, the orientation angle of the particulate carbon material in the negative electrode material sheet is considered to be oriented perpendicular to the surface of the negative electrode material sheet. The angle is preferably 60° or more, more preferably 65° or more, even more preferably 70° or more, and preferably 90° or less with respect to the surface of the negative electrode material sheet. If the orientation angle of the particulate carbon material is within the above-mentioned predetermined range with respect to the surface of the negative electrode material sheet, charge carriers such as lithium can easily move, thereby further improving the rate characteristics of the resulting secondary battery. be able to. In the present invention, the orientation angle of the particulate carbon material with respect to the surface of the negative electrode material sheet can be measured by the method described in the Examples of this specification.

The content ratio of the particulate carbon material in the negative electrode material sheet is preferably 92% by mass or more, more preferably 95% by mass or more, even more preferably 97% by mass or more, and 100% by mass or less. It can be done. If the content rate of the particulate carbon material in the negative electrode material sheet is equal to or higher than the above lower limit, the rate characteristics of the obtained secondary battery can be further improved and the capacity of the secondary battery can be increased.

[resin]
The resin optionally included in the negative electrode material sheet is, for example, a part of the above-mentioned resin used to form the primary sheet and secondary sheet, which are precursors of the negative electrode material sheet, is burned during the firing process. It is what remained without doing so.

The resin content of the negative electrode material sheet is usually 8% by mass or less, preferably 3% by mass or less, and more preferably 1% by mass or less. If the content ratio of the resin in the negative electrode material sheet is below the above-mentioned predetermined value, the amount of resin that can hinder the movement of charge carriers such as lithium will be reduced, and the movement of charge carriers will be facilitated. can exhibit excellent rate characteristics.
Further, the content ratio of the resin in the negative electrode material sheet is not particularly limited, and can be 0% by mass or more. From the viewpoint of further improving the rate characteristics of the obtained secondary battery, it is particularly preferable that the content of the resin in the negative electrode material sheet is 0% by mass.
The content ratio of the resin in the negative electrode material sheet can be adjusted by, for example, the manufacturing process of the negative electrode material sheet described above, the type and amount of the resin used, the firing conditions (e.g., temperature and time), etc.

[Fibrous carbon material]
When the negative electrode material sheet contains a fibrous carbon material, the content of the fibrous carbon material in the negative electrode material sheet is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, It is more preferably 0.4% by mass or more, preferably 5% by mass or less, more preferably 2.5% by mass or less, and even more preferably 1% by mass or less. If the content rate of the fibrous carbon material in the negative electrode material sheet is at least the above-mentioned lower limit, the strength of the negative electrode material sheet can be further increased. On the other hand, if the content rate of the fibrous carbon material in the negative electrode material sheet is below the above upper limit, the content rate of the particulate carbon material in the negative electrode material sheet can be ensured sufficiently high, so that the resulting secondary battery can be Capacity can be increased.

[Ratio of diffraction intensity on the surface of negative electrode material sheet I(110)/I(004)]
The ratio I(110)/I(004) of the diffraction intensity of the (110) plane to the diffraction intensity of the (004) plane in X-ray diffraction of the surface of the negative electrode material sheet is preferably 1.1 or more, and 3 or more. The number is more preferably 5 or more, even more preferably 10 or more, and particularly preferably 20 or more.
Here, in the X-ray diffraction pattern of the particulate carbon material as the negative electrode active material, a peak belonging to the (004) plane and a peak belonging to the (110) plane are detected. The (110) plane in the crystal structure of particulate carbon material is a plane perpendicular to the plane consisting of a six-membered carbon ring (that is, the plane equivalent to the (004) plane), so the (110) plane in X-ray diffraction The ratio of the peak intensity of the plane to the peak intensity of the (004) plane indicates the crystal orientation of the particulate carbon material. A high value of I(110)/I(004) in the X-ray diffraction of the surface of the negative electrode material sheet means that the direction perpendicular to the surface of the negative electrode material sheet (typically, This shows that the (004) plane has a high degree of orientation (coincident with the direction perpendicular to the surface).
Therefore, if the ratio of diffraction intensity I(110)/I(004) is equal to or greater than the predetermined value, the orientation of the (004) plane in the direction perpendicular to the surface of the negative electrode material sheet increases, so that lithium, etc. Since charge carriers can easily move, the obtained secondary battery can exhibit excellent rate characteristics.
Further, the ratio of diffraction intensities I(110)/I(004) is not particularly limited, but is preferably 90 or less.
The diffraction intensity I(110)/I(004) depends on, for example, the manufacturing process of the negative electrode material sheet described above, the properties of the particulate carbon material used (e.g. aspect ratio), and the film thickness of the primary sheet described later. It can be adjusted by the molding conditions including, the firing conditions (for example, temperature and time), and the like.

[Density of negative electrode material sheet]
The density of the negative electrode material sheet is preferably 1.3 g/cm ³ or less, more preferably 1.26 g/cm ³ or less, and even more preferably 1.23 g/cm ³ or less. If the density of the negative electrode material sheet is below the predetermined value above, the number of voids in the negative electrode material sheet increases, making it easier for charge carriers such as lithium to move, so the resulting secondary battery exhibits excellent rate characteristics. can do. Furthermore, if the density of the negative electrode material sheet is equal to or less than the above-mentioned predetermined value, the number of voids in the negative electrode material sheet increases, so that the electrolyte injectability of the obtained secondary battery can be improved.
Further, the density of the negative electrode material sheet is not particularly limited, but is preferably 0.7 g/cm ³ or more, more preferably 0.85 g/cm ³ or more, and 1.05 g/cm ³ or more. More preferably. If the density of the negative electrode material sheet is at least the above-mentioned lower limit, the strength of the negative electrode material sheet can be ensured to be sufficiently high. Moreover, if the density of the negative electrode material sheet is at least the above-mentioned lower limit, the capacity of the obtained secondary battery can be increased.
Note that the density of the negative electrode material sheet is adjusted by, for example, the manufacturing process of the negative electrode material sheet described above, the types, properties and quantitative ratios of the resin and particulate carbon material used, the firing conditions (for example, temperature and time), etc. be able to.

[Thickness of negative electrode material sheet]
The thickness of the negative electrode material sheet is preferably 80 μm or more, more preferably 90 μm or more, even more preferably 100 μm or more, and preferably 500 μm or less, more preferably 300 μm or less. The thickness is preferably 200 μm or less, and more preferably 200 μm or less. If the thickness of the negative electrode material sheet is at least the above lower limit, the resulting secondary battery can have a high capacity. On the other hand, if the thickness of the negative electrode material sheet is below the above upper limit, the resulting secondary battery can be made thinner.

[Basic weight of negative electrode material sheet]
The basis weight of the negative electrode material sheet is preferably 7.5 g/cm ² or more, more preferably 9 g/cm ² or more, even more preferably 11 g/cm ² or more, and 12 g/cm ² or more. It is more preferable that If the basis weight of the negative electrode material sheet is equal to or greater than the above-mentioned predetermined value, the resulting secondary battery can have a high capacity.
Furthermore, the basis weight of the negative electrode material sheet is not particularly limited, but is preferably 30 g/cm ² or less, more preferably 15 g/cm ² or less. If the basis weight of the negative electrode material sheet is equal to or less than the above-mentioned predetermined value, charge carriers such as lithium can easily move, so that the rate characteristics of the resulting secondary battery can be ensured to be sufficiently high.
In the present invention, the basis weight of the negative electrode material sheet can be measured by the method described in the Examples of this specification.

<(E) Paint film formation process>
In the coating film forming step, a slurry composition for forming an undercoat layer (hereinafter also simply referred to as "slurry composition") is applied onto a current collector to form a coating film made of the slurry composition. The slurry composition is not particularly limited and can be applied using a known method. Among these, it is preferable to apply the slurry composition by a bar coating method. The amount of the slurry composition applied may be adjusted as appropriate depending on the desired thickness of the undercoat layer (thickness after drying).

<<Slurry composition>>
The slurry composition can be prepared by mixing the carbon material and the binder, and optionally, components other than the carbon material and the binder (other components) in a solvent. Mixing of these components can be performed using known mixing devices such as a kneader; a mixer such as a Henschel mixer, a Hobart mixer, or a high-speed mixer; a twin-screw kneader; and a roll.

[binder]
As the binder, the resins listed in the above-mentioned section of "(A) Primary sheet forming step" can be used. Among these, it is preferable to use styrene-butadiene rubber (SBR) as the binder.

[Carbon material]
Carbon materials include, but are not particularly limited to, particulate carbon materials and fibrous carbon materials. Among these, as the carbon material, it is preferable to use at least one of a particulate carbon material and a fibrous carbon material, and it is more preferable to use a particulate carbon material.

-Particulate carbon material-
Particulate carbon materials include, but are not particularly limited to, spheroidal graphites (such as flaky graphite, lumpy graphite (scaly graphite), earthy graphite, and exfoliated graphite) listed in the section of "(A) Primary sheet forming process". elliptical graphite), acid-treated products thereof (expandable graphite, expanded graphite), etc. can be used. These can be used alone or in combination of two or more. Among these, it is preferable to use expanded graphite as the particulate carbon material from the viewpoint of further increasing the impact resistance of the obtained negative electrode and further improving the rate characteristics of the obtained secondary battery.
In addition, from the viewpoint of further increasing the impact resistance of the obtained negative electrode and further improving the rate characteristics of the obtained secondary battery, the volume average particle diameter of the particulate carbon material is preferably 1 μm or more, and 2 μm or more. It is more preferably 20 μm or less, and more preferably 10 μm or less.

-Fibrous carbon material-
The fibrous carbon material is not particularly limited, but fibrous carbon nanostructures such as carbon nanotubes mentioned in the section "(A) Primary sheet forming step" can be used. Among these, it is preferable to use a fibrous carbon nanostructure containing carbon nanotubes, and it is more preferable to use carbon nanotubes.

[Other ingredients]
Other components include a thickener for improving the coating properties of the slurry composition and a dispersing agent for favorably dispersing fibrous carbon nanostructures that may be optionally included.
The thickener is not particularly limited, and includes cellulose polymers such as carboxymethyl cellulose, methyl cellulose, and hydroxypropyl cellulose, and ammonium salts thereof. These thickeners can be used alone or in combination of two or more. Among them, it is preferable to use carboxymethylcellulose.
Further, the dispersant is not particularly limited, and known ones can be used.

[solvent]
The solvent that can be used in the slurry composition is not particularly limited, and both water and organic solvents can be used. Examples of organic solvents include acetonitrile, N-methyl-2-pyrrolidone, tetrahydrofuran, acetone, acetylpyridine, cyclopentanone, dimethylformamide, dimethylsulfoxide, methylformamide, methyl ethyl ketone, furfural, ethylenediamine, dimethylbenzene (xylene), methyl Benzene (toluene), cyclopentyl methyl ether, isopropyl alcohol, and the like can be used. Among these, it is preferable to use water.
Further, these solvents can be used alone or in a mixture of two or more at any mixing ratio.

[Solid content concentration]
The solid content concentration of the slurry composition is not particularly limited, but from the viewpoint of improving the coating properties of the slurry composition, it is preferably 35% by mass or more and 58% by mass or less.

<(F) Pasting process>
In the pasting step, before the paint film formed in step (E) above dries, the negative electrode material sheet obtained through steps (A) to (D) above is pasted onto this paint film. In other words, in the attaching step, the negative electrode material sheet is attached to the wet undercoat layer. Even if an attempt is made to attach a negative electrode material sheet after the coating film has dried, the negative electrode material sheet and the undercoat layer cannot be bonded to each other, and the impact resistance of the resulting negative electrode deteriorates.
The reduction rate of the solvent component contained in the coating film when pasting the negative electrode material sheet is preferably 65% by volume or less, more preferably 30% by volume or less, and 0% by volume, i.e. It is particularly preferable that the solvent component is not reduced. The smaller the reduction rate of the solvent component, the higher the adhesiveness (adhesion) between the negative electrode material sheet and the undercoat layer.
The method of pasting the negative electrode material sheet is not particularly limited, and for example, the negative electrode material sheet is placed on a coating film before drying (i.e., a wet coating film) and pressed against the coating film. This can be done by

<Other processes>
Other steps include a drying step of further drying the laminated electrode (negative electrode) composed of the current collector, the undercoat layer, and the negative electrode material sheet obtained through the step (F) above. The temperature for drying the laminate can be, for example, 10° C. or more and 100° C. or less, and the drying time can be, for example, 1 minute or more and 24 hours or less. Further, the drying may be performed while applying pressure to the laminated electrode.

(Negative electrode for non-aqueous secondary batteries)
The negative electrode for a non-aqueous secondary battery of the present invention comprises a current collector, an undercoat layer formed on the current collector, and an undercoat layer formed on the undercoat layer and adhered to the undercoat layer. It is characterized by comprising a negative electrode composite material layer. Further, the negative electrode for a non-aqueous secondary battery of the present invention is characterized in that the undercoat layer contains a carbon material and a binder. Furthermore, in the negative electrode for a non-aqueous secondary battery of the present invention, the negative electrode composite material layer contains a particulate carbon material, the particulate carbon material is oriented perpendicularly to the surface of the negative electrode composite material layer, and the negative electrode composite material layer contains a particulate carbon material. It is characterized in that the resin content in the layer is 8% by mass or less, and the negative electrode composite layer exists as a self-supporting film. The negative electrode for a non-aqueous secondary battery of the present invention has excellent impact resistance and can exhibit excellent rate characteristics in a non-aqueous secondary battery.

<Negative electrode composite material layer>
The negative electrode composite material layer contains a particulate carbon material, and may optionally further contain other components such as a resin and a fibrous carbon material. The negative electrode composite material layer can be the negative electrode material sheet described in the above-mentioned section of "Method for manufacturing negative electrode for non-aqueous secondary battery." The properties and preferred attributes of the negative electrode composite material layer and the properties and preferred attributes of each component contained in the negative electrode composite material layer are the same as those of the negative electrode material sheet described above.

Specifically, the particulate carbon material contained in the negative electrode composite material layer is oriented perpendicularly to the surface of the negative electrode composite material layer. If the particulate carbon material is not oriented perpendicularly to the surface of the negative electrode composite layer, the rate characteristics of the resulting secondary battery will deteriorate. Further, the content rate of the resin in the negative electrode composite material layer is 8% by mass or less. If the content of the resin in the negative electrode composite layer exceeds 8% by mass, the rate characteristics of the resulting secondary battery will deteriorate. Furthermore, it is preferable that the particulate carbon material in the negative electrode composite material layer contains scaly graphite.

Here, the negative electrode composite material layer needs to be adhered to the undercoat layer. Specifically, the negative electrode composite material layer needs to be bonded to the current collector via an undercoat layer. If the negative electrode composite material layer is not adhered to the undercoat layer, the negative electrode composite material layer will not be integrated with the current collector, and the impact resistance of the negative electrode cannot be ensured. Adhesion can be achieved, for example, as described above, by pasting the negative electrode material sheet before the coating film of the slurry composition for forming an undercoat layer is dried.

Note that whether or not the negative electrode composite material layer is adhered to the undercoat layer can be confirmed by the method described in Examples.

The negative electrode composite material layer exists as a self-supporting film. If a negative electrode material sheet is used as the negative electrode composite material layer, the negative electrode composite material layer can be satisfactorily present as a self-supporting film.
If the negative electrode composite material layer is a self-supporting film, the negative electrode can be manufactured by individually manufacturing the members that constitute the negative electrode and bonding them together, so that productivity can be improved.

<Undercoat layer>
The undercoat layer contains a carbon material and a binder, and optionally further contains components other than the carbon material and the binder (other components). As the carbon material, binder, and other components, those explained in the above-mentioned "Method for manufacturing a negative electrode for a non-aqueous secondary battery" can be used. Further, the properties and preferable attributes of these components are also the same as those explained in the section of "Method for manufacturing a negative electrode for a non-aqueous secondary battery."

<<Carbon material>>
The carbon material contained in the undercoat layer is not particularly limited, but preferably includes at least one of a particulate carbon material and a fibrous carbon material, and more preferably a particulate carbon material.
The content of the carbon material in the undercoat layer is preferably 90% by mass or more, more preferably 95% by mass or more, and preferably 99% by mass or less, and 98% by mass or less. It is more preferable. If the content of the carbon material in the undercoat layer is within the above range, the rate characteristics of the resulting secondary battery can be further improved.

＜＜Binder＞＞
The binder included in the undercoat layer is not particularly limited, but preferably includes styrene-butadiene rubber (SBR).
The content ratio of the binder in the undercoat layer is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and preferably 0.5% by mass or less, and More preferably, the content is .4% by mass or less. If the content of the binder in the undercoat layer is within the above range, the rate characteristics of the resulting secondary battery can be further improved while improving the impact resistance of the negative electrode.

<<Other ingredients>>
The content of other components in the undercoat layer can be adjusted within a range that does not impair the desired effects of the present invention.

＜＜Thickness＞＞
The thickness of the undercoat layer is preferably 1 μm or more, more preferably 2 μm or more, even more preferably 4 μm or more, and preferably 15 μm or less, more preferably 10 μm or less. preferable. If the thickness of the undercoat layer is within the above-mentioned predetermined range, it is possible to further improve the rate characteristics of the non-aqueous secondary battery while improving the impact resistance of the negative electrode.

<Current collector>
As the current collector, for example, a current collector made of a material such as iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, or platinum can be used. Among these, copper foil is particularly preferred as the current collector used for the negative electrode. Note that the above-mentioned materials may be used alone or in combination of two or more in any ratio.

(Non-aqueous secondary battery)
The non-aqueous secondary battery of the present invention is characterized by comprising the above-described negative electrode for a non-aqueous secondary battery of the present invention.
For example, the non-aqueous secondary battery of the present invention includes a positive electrode, a negative electrode, an electrolyte, and a separator, and uses the negative electrode for non-aqueous secondary batteries of the present invention as the negative electrode. Since the non-aqueous secondary battery of the present invention uses the negative electrode for non-aqueous secondary batteries of the present invention, it can exhibit excellent rate characteristics. Hereinafter, the case where the non-aqueous secondary battery is a lithium ion secondary battery will be taken as an example, and the positive electrode, electrolyte, and separator will be described, but the present invention is not limited to these examples.

<Positive electrode>
As the positive electrode, a known positive electrode used as a positive electrode for lithium ion secondary batteries can be used. Specifically, as the positive electrode, for example, a positive electrode formed by forming a positive electrode composite material layer on a current collector can be used.
Note that as the current collector, one made of a metal material such as aluminum can be used. Further, as the positive electrode composite material layer, a layer containing a known positive electrode active material, a conductive material, and a binder can be used.

<Electrolyte>
As the electrolytic solution, an electrolytic solution in which an electrolyte is dissolved in a solvent can be used.
Here, as the solvent, an organic solvent that can dissolve the electrolyte can be used. Specifically, the solvent includes alkyl carbonate solvents such as ethylene carbonate, propylene carbonate, and γ-butyrolactone, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, diethyl carbonate, ethylmethyl carbonate, dimethyl carbonate, methyl acetate, and dimethoxyethane. , dioxolane, methyl propionate, methyl formate, etc. can be used.
A lithium salt can be used as the electrolyte. As the lithium salt, for example, those described in JP-A-2012-204303 can be used. Among these lithium salts, LiPF ₆ , LiClO ₄ , and CF ₃ SO ₃ Li are preferred as electrolytes because they are easily soluble in organic solvents and exhibit a high degree of dissociation.

<Separator>
The separator is not particularly limited, and any known separator can be used. For example, the separator described in JP-A No. 2012-204303 can be used. Among these, polyolefins are preferred because they can reduce the overall film thickness of the separator, thereby increasing the ratio of the electrode active material in the lithium ion secondary battery and increasing the capacity per volume. Microporous membranes made of resins (polyethylene, polypropylene, polybutene, polyvinyl chloride) are preferred.

<Method for manufacturing non-aqueous secondary battery>
The non-aqueous secondary battery of the present invention can be produced by, for example, stacking a positive electrode and a negative electrode with a separator interposed therebetween, and rolling or folding this according to the shape of the battery as necessary and placing it in a battery container. It can be manufactured by injecting an electrolyte into the container and sealing it. In order to prevent an increase in pressure inside the secondary battery, overcharging and discharging, etc., a fuse, an overcurrent prevention element such as a PTC element, an expanded metal, a lead plate, etc. may be provided as necessary. The shape of the secondary battery may be, for example, a coin shape, a button shape, a sheet shape, a cylindrical shape, a square shape, a flat shape, or the like.

EXAMPLES Hereinafter, the present invention will be specifically explained based on Examples, but the present invention is not limited to these Examples. In the following description, "%" and "part" representing amounts are based on mass unless otherwise specified. In addition, various measurements and evaluations in Examples were performed according to the following methods.
<X-ray diffraction>
X-ray diffraction of the surface of the negative electrode material sheet (or the negative electrode composite layer of the coated electrode) was performed using "X' Pert PRO MPD" manufactured by PANalytical. Among the obtained peaks, the peak height (diffraction intensity) at 2Θ = 77 degrees corresponding to the (110) plane, and the peak height (diffraction intensity) at 2Θ = 54.5 degrees corresponding to the (004) plane. ) was used to calculate the value of the ratio I(110)/I(004) of the diffraction intensity of the (110) plane to the diffraction intensity of the (004) plane.
<Resin content ratio>
The following numerical values were calculated from the formulations in each Example and Comparative Example and a comparison of the weights before and after firing.
Theoretical residue rate = (total value of particulate carbon material) ÷ (total value of each blend)
Actual residue rate = (weight after firing) ÷ (weight before firing)
Resin content ratio = 1 - (theoretical residue rate) ÷ (actually measured residue rate)
<Orientation angle of particulate carbon material>
The orientation angle of the particulate carbon material in the negative electrode material sheet (or the negative electrode composite layer of the coated electrode) was determined by scanning a cross section of the negative electrode material sheet into a regular octagon using a scanning electron microscope (SEM, Hitachi High-Technologies SU-3500). '') at a magnification that covered the sheet from the top to the bottom. Note that the magnification at this time was 700 times. Fifty lines were drawn along the long axis of the particulate carbon material in this cross section, and the average angle of the long axis with respect to the surface of the negative electrode material sheet was calculated. This was carried out for 8 surfaces, and the largest value among the 8 surfaces was taken as the orientation angle of the particulate carbon material in the negative electrode material sheet (negative electrode composite material layer).
<Thickness>
Using a film thickness meter (manufactured by Mitutoyo, product name "Digimatic Indicator ID-C112XBS"), measure the thickness at a total of five points, approximately the center point and the four corners (squares) of the negative electrode material sheet (or the negative electrode composite layer of the coated electrode). was measured, and the average value (μm) of the measured thickness was taken as the thickness of the negative electrode material sheet (negative electrode composite material layer). Similarly, the thickness of the undercoat layer (thickness of the dry film) was measured.
<Density>
Calculate the density of the negative electrode material sheet (negative electrode composite layer) by measuring the mass, area, and thickness of the negative electrode material sheet (or negative electrode composite layer of the coated electrode), and dividing the mass by the volume (=area x thickness). did.
<Basic weight>
The basis weight of the negative electrode material sheet (negative electrode composite material layer) was calculated by multiplying the density of the negative electrode material sheet (or the negative electrode composite material layer of the coated electrode) by the thickness.
<Whether there is adhesion between the negative electrode composite layer and the undercoat layer>
When the negative electrodes (laminated electrodes) prepared in Examples and Comparative Examples were tilted 90 degrees from a horizontal state so that the stacking direction was parallel to the horizontal direction, the negative electrode material sheet (or coated electrode) separated from the undercoat layer. If the negative electrode material sheet (or the coated electrode) was separated from the undercoat layer, it was determined that the two were not adhered.
<Impact resistance>
Each of the negative electrodes produced in Examples and Comparative Examples was punched out using a 13Φ hand punch (manufactured by Nogami Giken). The degree of collapse of the negative electrode when punched out was evaluated based on the following criteria. Note that if the negative electrode composite material layer is integrated with the current collector, the negative electrode will not collapse due to the impact of punching, but if the adhesion is insufficient, the negative electrode will collapse due to the impact during punching.
A: No chips are found in the negative electrode composite layer after punching B: Cracks appear in the negative electrode composite layer during punching C: Two or less chips appear in the negative electrode composite layer during punching D: Three or more negative electrodes It splits into pieces and cannot keep its shape.
<Self-supporting film>
By making each negative electrode produced in Examples and Comparative Examples spread over the surface of a cylinder with a diameter of 10 cm with the current collector in close contact with the current collector, the negative electrode material sheet (negative electrode composite layer) was separated from the current collector and undercoat layer. Peeled off. When only the negative electrode material sheet is peeled off, it is determined that the negative electrode material sheet (negative electrode composite layer) is a self-supporting film, and the negative electrode material sheet (negative electrode composite layer) is peeled off as one with the undercoat layer. It was determined that the negative electrode material sheet (negative electrode composite material layer) was not a self-supporting film.
Note that whether or not the peeling has occurred may be determined visually, but if visual inspection is difficult, analysis may be performed using a scanning electron microscope (SEM) or the like.
<Rate characteristics>
<<Manufacture of electrode evaluation cell>>
A half cell (half cell) of a lithium ion secondary battery for evaluation was produced with the configuration shown below. The half cells were produced by punching out each member to a size of 17 mm, vacuum drying (120° C. x 10 hours), and then placing it in a dry box with a dew point of −80° C. or lower.
[Half cell configuration]
Working electrode: negative electrode (negative electrode formed by pasting a negative electrode material sheet on an undercoat layer, or a negative electrode formed by pasting a coated electrode on an undercoat layer)
Counter electrode: Li metal Reference electrode: Li metal Separator: Glass nonwoven fabric, polyethylene (PE) microporous membrane Electrolyte: LiPF ₆ solution with a concentration of 1.0M (solvent: ethylene carbonate (EC)/methyl ethyl carbonate (MEC) = 3/ 7 (volume ratio) mixed solvent, containing 1 volume % (solvent ratio) of vinylene carbonate (VC) as an additive)
<<Charging/discharging test>>
A charge/discharge test was conducted on the obtained half cell for evaluation under Condition 1 below.
(Charge/discharge test conditions)
(Condition 1)
Charging conditions: 0.2C Charging voltage 0.01V-CCCV (0.05Ccut)
Discharge conditions: 0.2C Final voltage 2.5V-CC
Number of cycles: 10 cycles Next, a charge/discharge test was further conducted under Condition 2 below.
(Condition 2)
Test temperature: 25℃
Charging conditions: 0.2C Charging voltage 0.01V-CCCV (0.05Ccut)
Discharge conditions: 2.0C Final voltage 2.5V-CC
Number of cycles: 10 cycles Test temperature: 25℃
Then, the ratio of the discharge capacity at 2.0C (measured under condition 2) to the discharge capacity at 0.2C (measured under condition 1) is calculated as a percentage (=(discharge capacity at 2.0C/0.2C The charge/discharge rate characteristics were evaluated using the following criteria: The results are shown in Table 1. The larger the value of the charge/discharge rate characteristic, the smaller the internal resistance and the higher the rate of charge/discharge (ie, the better the rate characteristic).
A: The value of the charge/discharge rate characteristic is 65% or more B: The value of the charge/discharge rate characteristic is 47.5% or more and less than 65% C: The value of the charge/discharge rate characteristic is 30% or more and less than 47.5% D: Charge/discharge Rate characteristic value is less than 30%

(Example 1)
<Preparation of composition>
140 parts of nitrile rubber (NBR) that is liquid at room temperature and normal pressure (manufactured by Nippon Zeon Co., Ltd., product name "Nipol 1312", decomposition start temperature: 336°C) and nitrile rubber (NBR) that is solid at room temperature and normal pressure (Nippon Zeon Co., Ltd., product name "Nipol 3350", decomposition start temperature: 375 ° C.) 140 parts, and scaly graphite as particulate carbon material (Nippon Graphite Industries Co., Ltd., product name "UP20α", volume average particle diameter: 20 μm, aspect ratio = 2) 950 parts (equivalent to 60 parts by volume when the whole is 100 parts by volume) were stirred at a temperature of 150°C for 20 minutes using a pressure kneader (manufactured by Nippon Spindle). Mixed. Next, the obtained mixture was put into a crusher (manufactured by Osaka Chemical Co., Ltd., trade name "Wonder Crush Mill D3V-10") and crushed for 10 seconds to obtain a composition.

<Formation of primary sheet>
Next, 50 g of the obtained composition was sandwiched between sandblasted PET films (protective films) with a thickness of 50 μm, and the conditions were as follows: roll gap 1000 μm, roll temperature 50°C, roll linear pressure 50 kg/cm, and roll speed 1 m/min. The sheet was rolled and formed (primary pressing) to obtain a primary sheet having a thickness of 0.8 mm.

<Formation of laminate>
Subsequently, the obtained primary sheet was cut into 150 mm long x 150 mm wide x 0.8 mm thick, 188 sheets were laminated in the thickness direction of the primary sheet, and further, the sheets were cut at a temperature of 120° C. and a pressure of 0.1 MPa for 3 minutes. A laminate with a height of about 150 mm was obtained by pressing (secondary pressing) in the stacking direction.

<Formation of secondary sheet>
After that, while pressing the stacked side surface of the secondary pressurized laminate with a pressure of 0.3 MPa, use a wood slicer (manufactured by Marunaka Iron Works Co., Ltd., product name "Super Finish Planer Super Mecha S"). Then, by slicing at an angle of 0 degrees to the stacking direction (in other words, in the normal direction of the main surface of the stacked primary sheets), a secondary sheet of 150 mm long x 150 mm wide x 0.10 mm thick is made. Got a sheet.

<Preparation of negative electrode material sheet>
Thereafter, the obtained secondary sheet was fired at 1000° C. for 8 hours in a nitrogen atmosphere to burn and remove the resin component, thereby obtaining a negative electrode material sheet. Regarding the obtained negative electrode material sheet, the ratio of the diffraction intensity of the (110) plane to the diffraction intensity of the (004) plane, I(110)/I(004), the orientation angle, thickness, density, and basis weight of the particulate carbon material. was measured. The results are shown in Table 1.

<Preparation of slurry composition for forming undercoat layer>
Small particle size graphite powder prepared by crushing expanded graphite with an average particle size of 7 μm (manufactured by Ito Graphite Co., Ltd., product name "EC-1500") and adjusting the average particle size to 1.5 μm, and styrene-butadiene rubber as a binder ( SBR) and carboxymethylcellulose (CMC) as a thickener were blended so that the mass ratio of these materials was 100:0.2:0.2. The obtained mixture was added to water as a solvent and mixed so that the solid content concentration was 27% to obtain a slurry composition for forming an undercoat layer.

<Preparation of laminated electrode (negative electrode)>
Bar coater No. 10 (manufactured by Tester Sangyo Co., Ltd., SA-203, No. 10), the obtained slurry composition for forming an undercoat layer was applied onto a copper foil as a current collector to obtain a coating film. Thereafter, before the coating film dried (solvent reduction rate: 10%), a negative electrode material sheet was placed on the coating film, and then the negative electrode material sheet was adhered to the coating film by pressing lightly with a finger. Note that the time from application to adhesion with fingers was 3 seconds.
Then, the obtained laminate was vacuum dried at 60° C. for 8 hours to obtain a negative electrode. Note that the dry film thickness of the undercoat layer was 4 μm. Various measurements and evaluations were performed using this negative electrode. The results are shown in Table 1.

(Example 2)
When applying the slurry composition for forming an undercoat layer, bar coater No. A negative electrode was manufactured in the same manner as in Example 1, except for using No. 22 (manufactured by Tester Sangyo Co., Ltd., SA-203, No. 22), and various measurements and evaluations were performed. The results are shown in Table 1.

(Example 3)
When applying the slurry composition for forming an undercoat layer, bar coater No. A negative electrode was manufactured in the same manner as in Example 1, except that 6 (manufactured by Tester Sangyo Co., Ltd., SA-203, No. 6) was used, and various measurements and evaluations were performed. The results are shown in Table 1.

(Example 4)
Same as Example 1 except that when producing the negative electrode material sheet, the blending amount of flaky graphite was changed from 950 parts to 700 parts (an amount equivalent to 50 parts by volume when the whole is 100 parts by volume). A negative electrode was manufactured using the same method, and various measurements and evaluations were performed. The results are shown in Table 1.

(Comparative example 1)
The procedure was the same as in Example 1, except that before pasting the negative electrode material sheet, the coating film of the slurry composition for forming an undercoat layer was vacuum dried at 60 ° C. for 8 hours to dryness (solvent reduction rate: 90%). A negative electrode was manufactured and various measurements and evaluations were performed. The results are shown in Table 1. Although the adhesion between the copper foil, which is the current collector, and the undercoat layer was good, there was no adhesion between the negative electrode material sheet and the undercoat layer, so the impact resistance of the negative electrode was poor. . Furthermore, since the negative electrode material sheet did not adhere to the undercoat layer, it was not possible to fabricate a half cell, and it was not possible to measure the rate characteristics of the secondary battery.

(Comparative example 2)
A negative electrode was produced in the same manner as in Example 1, except that the unfired secondary sheet was used as the negative electrode material sheet instead of the negative electrode material sheet produced in Example 1, and various measurements and evaluations were performed. . The results are shown in Table 1. Note that because the negative electrode material sheet was not fired and contained a large amount of resin component, the negative electrode did not function as an electrode and did not exhibit any battery performance.

(Comparative example 3)
Instead of the negative electrode material sheet prepared in Example 1, a slurry composition for a negative electrode composite layer prepared as below was applied onto the undercoat layer, and then the resulting coating film was dried to form a slurry composition on the undercoat layer. A negative electrode was manufactured in the same manner as in Example 1, except that a coated electrode on which a negative electrode composite layer (thickness: 108 μm) was formed was manufactured, and various measurements and evaluations were performed. The results are shown in Table 1.
<Preparation of slurry composition for negative electrode composite layer>
The flaky graphite used as the particulate carbon material in Example 1 (manufactured by Nippon Graphite Industries Co., Ltd., trade name "UP20α"), carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) were mixed into UP20α:CMC. :SBR=97.5:1.0:1.5 (mass ratio) to obtain a slurry composition for a negative electrode composite layer.

From Table 1, before the coating film made of the slurry composition for forming an undercoat layer was dried, a negative electrode produced by baking a prescribed secondary sheet and laminating the negative electrode material sheet to the coating film was used. It can be seen that in Examples 1 to 4, the impact resistance of the negative electrode is excellent, and the rate characteristics of the non-aqueous secondary battery are excellent.

According to the present invention, it is possible to provide a negative electrode that has excellent impact resistance and allows a non-aqueous secondary battery to exhibit excellent rate characteristics, and a method for manufacturing the same.
Further, according to the present invention, a non-aqueous secondary battery with excellent rate characteristics can be provided.

Claims (10)

A primary sheet forming step of pressurizing and forming a composition containing a resin and a particulate carbon material into a sheet to obtain a primary sheet;
a laminate forming step of laminating a plurality of the primary sheets in the thickness direction, or folding or winding the primary sheets to obtain a laminate;
A slicing step of slicing the laminate at an angle of 45° or less with respect to the lamination direction to obtain a secondary sheet;
a firing step of firing the secondary sheet to obtain a negative electrode material sheet for a non-aqueous secondary battery;
a coating film forming step of applying a slurry composition for forming an undercoat layer containing a carbon material and a binder onto a current collector to form a coating film;
A method for producing a negative electrode for a non-aqueous secondary battery, the method comprising: pasting the negative electrode material sheet for a non-aqueous secondary battery on the coating film before the coating film dries. The method for manufacturing a negative electrode for a non-aqueous secondary battery according to claim 1, wherein the secondary sheet is fired at a temperature of 300°C or higher and 2000°C or lower. The method for manufacturing a negative electrode for a non-aqueous secondary battery according to claim 1 or 2, wherein the particulate carbon material contains flaky graphite. comprising a current collector, an undercoat layer formed on the current collector, and a negative electrode composite layer formed on the undercoat layer and adhered to the undercoat layer,
The undercoat layer includes a carbon material and a binder,
The negative electrode composite material layer includes a particulate carbon material,
The particulate carbon material is oriented perpendicularly to the surface of the negative electrode composite layer,
The content of the resin in the negative electrode composite layer is 8% by mass or less,
The negative electrode for a non-aqueous secondary battery, in which the negative electrode composite material layer exists as a self-supporting film. The negative electrode for a nonaqueous secondary battery according to claim 4, wherein the undercoat layer has a thickness of 1 μm or more and 15 μm or less. 4. The ratio I(110)/I(004) of the diffraction intensity of the (110) plane to the diffraction intensity of the (004) plane in X-ray diffraction of the surface of the negative electrode composite layer is 1.1 or more. Or the negative electrode for non-aqueous secondary batteries according to 5. The negative electrode for a non-aqueous secondary battery according to any one of claims 4 to 6, wherein the negative electrode composite material layer has a density of 1.3 g/cm ³ or less. The negative electrode for a non-aqueous secondary battery according to any one of claims 4 to 7, wherein the negative electrode composite material layer has a thickness of 80 μm or more. The negative electrode for a non-aqueous secondary battery according to any one of claims 4 to 8, wherein the particulate carbon material contains scaly graphite. A non-aqueous secondary battery comprising the negative electrode for a non-aqueous secondary battery according to any one of claims 4 to 9.