阅读说明：本技术 电极涂覆液用分散剂、含有该电极涂覆液用分散剂的电极涂覆液组合物、使用该电极涂覆液组合物制成的蓄电装置用电极以及具有该电极的蓄电装置 (Dispersant for electrode coating liquid, electrode coating liquid composition containing the dispersant for electrode coating liquid, electrode for electricity storage device using the electrode coati) 是由 祖父江绫乃 齐藤恭辉 后居洋介 伊藤圭树 东崎哲也 星原悠司 松本真昌 于 2018-01-24 设计创作，主要内容包括：提供一种含有蓄电装置的电极涂覆液用分散稳定剂的组合物,该分散稳定剂的电极活性物质和导电材料的分散稳定性优异,即使使用弱剪切力的分散装置也能够制作均匀的电极。蓄电装置的电极涂覆液用分散剂的特征在于含有满足下述(a)至(c)的纤维素纤维。(a)宽度短者的数均宽度为2～200nm；(b)长宽比为7.5以上且250以下；(c)具有纤维素I型结晶,并且其结晶度为70％以上且95％以下。(Provided is a composition containing a dispersion stabilizer for an electrode coating liquid of an electricity storage device, which has excellent dispersion stability of an electrode active material and a conductive material and can produce a uniform electrode even when a dispersion device with a weak shear force is used. A dispersant for an electrode coating liquid for an electricity storage device is characterized by containing cellulose fibers satisfying the following (a) to (c). (a) The number average width of the shorter one is 2-200 nm; (b) an aspect ratio of 7.5 or more and 250 or less; (c) has a cellulose I-type crystal and has a crystallinity of 70% or more and 95% or less.)

1. A dispersant for an electrode coating liquid, characterized in that,

contains cellulose fibers satisfying the following (a) to (c),

(a) the number average width of the shorter one is 2nm to 200 nm;

(b) an aspect ratio of 7.5 or more and 250 or less;

(c) has a cellulose I-type crystal and has a crystallinity of 70% or more and 95% or less.

2. The dispersant for electrode coating liquids according to claim 1,

the cellulose fiber further satisfies the following (d),

(d) having an anionic functional group.

3. The dispersant for electrode coating liquids according to claim 2,

the cellulose fiber further satisfies the following (e),

(e) the anionic functional group is a carboxyl group, and the content of the carboxyl group is 1.2mmol/g to 2.5 mmol/g.

4. An electrode coating liquid composition characterized in that,

the electrode coating liquid composition contains the dispersant for electrode coating liquids according to any one of claims 1 to 3.

5. The electrode coating liquid composition according to claim 4,

the content of the cellulose fiber is 0.05 mass% or more and 5.00 mass% or less with respect to 100 mass% of the solid content of the electrode coating liquid composition.

6. An electrode for an electricity storage device, characterized in that,

the electrode for an electricity storage device comprises a dried product of the electrode coating liquid composition according to claim 4 or 5.

7. An electric storage device is characterized in that,

the electricity storage device has the electrode for an electricity storage device according to claim 6.

Technical Field

The present invention relates to a dispersant for an electrode coating liquid, an electrode coating liquid composition containing the dispersant for an electrode coating liquid, an electrode for an electric storage device made using the electrode coating liquid composition, and an electric storage device having the electrode for an electric storage device.

Background

In recent years, a power storage device having a high voltage and a high energy density has been required as a driving power source for electronic equipment. In particular, lithium ion secondary batteries, lithium ion capacitors, and the like are expected as high-voltage and high-energy-density power storage devices. The electrode used in the power storage device is generally manufactured by applying a mixture of electrode active material particles, conductive material particles, and a binder to the surface of a current collector and drying the applied mixture. Examples of the power storage device include: lithium ion secondary batteries, electric double layer capacitors, lithium ion capacitors, and the like. These power storage devices are mainly composed of components such as electrodes, nonaqueous electrolyte, and separators.

Among these, an electrode for an electric storage device is formed by, for example, applying an electrode mixture liquid for an electric storage device, which is obtained by dispersing an electrode active material and a conductive material together with a binder in an organic solvent or water, onto a metal foil as a surface of a current collector, and drying the applied liquid. The characteristics of the power storage device are largely influenced by the main constituent materials used, such as the electrode particle material, the electrolyte, and the current collector, but are largely influenced by the binder, the thickening stabilizer, and the dispersant used as additives. Binders for power storage devices are mainly classified into organic solvent-based binders in which a polymer is dissolved in an organic solvent, and aqueous binders in which a polymer is dissolved or dispersed in water. In particular, recently, an electrode mixture for an aqueous power storage device using an aqueous binder has been attracting attention because it is possible to reduce environmental load and manufacturing cost and improve working environment. Under the present circumstances, the electrode materials such as electrode active materials and conductive materials are being made into nanomaterials as the capacity and energy of batteries are increased.

However, various problems are involved in the production of electrodes for aqueous power storage devices, and particularly, solvent-based coatings are still the mainstream of positive electrode materials. Since the electrode active material and the conductive material have high hydrophobicity, it is difficult to uniformly disperse the electrode active material and the conductive material in an aqueous medium, and if an electrode mixture having insufficient dispersion is used, the coating property to the current collector is deteriorated, and there are problems that the electrode is not uniform, aggregates remain on the surface of the electrode, and short-circuiting occurs when the battery is manufactured.

In order to solve the above-described problems, it is necessary to provide a dispersion stabilizer capable of improving dispersion stability in an aqueous electrode coating liquid. The dispersion stabilizer is added to disperse and stabilize the electrode active material and the conductive material and to impart a viscosity suitable for coating with the electrode coating liquid. Conventionally, water-soluble polymers have been used as dispersion stabilizers, and among them, carboxymethyl cellulose salts have been used in many cases because of their excellent dispersion stabilizing ability (patent documents 1 and 2). However, carboxymethyl cellulose salts have problems such as insufficient dispersion stability, long time required for stable dispersion, and poor coating of the electrode coating solution, depending on the type of the electrode nanomaterial.

In particular, the dispersion of the electrode active material is carried out by mixing the electrode active material, the thickening/stabilizing agent, the dispersion medium, and other components to prepare an electrode coating solution. In this case, in order to improve the dispersibility of the electrode active material, a mixing/dispersing machine having a strong dispersing ability is preferably used (patent documents 3 and 4). However, when such a mixing/dispersing machine is used, if an excessively strong shearing force is applied to the electrode material, the surface of the electrode active material may be damaged or disintegrated, which may also result in deterioration of battery characteristics. Therefore, a technique and a dispersion stabilizer capable of dispersion even with a weak shear force are required.

Disclosure of Invention

Technical problem to be solved by the invention

The purpose of the present invention is to provide a dispersant for an electrode coating solution, which has excellent dispersion stability of an electrode active material and a conductive material and can produce a uniform electrode coating solution composition even when a dispersion device with a weak shear force is used, an electrode coating solution composition containing the dispersant, an electrode for an electricity storage device using the composition, and an electricity storage device having the electrode for an electricity storage device.

Means for solving the problems

The present inventors have conducted intensive studies to obtain a dispersant for an electrode coating liquid which is excellent in dispersion stability of an electrode active material and a conductive agent which is difficult to disperse and enables the production of a uniform electrode even with a dispersing device having a weak shear force. During the course of the study, attention was paid to cellulose fibers satisfying predetermined conditions. The present inventors have also found that a dispersant for an electrode coating liquid containing the cellulose fibers can solve the intended problems, and have completed the present invention. Namely, the present invention provides the following [1] to [7 ].

[1] A dispersant for an electrode coating solution, characterized by containing cellulose fibers satisfying the following (a) to (c),

(a) the number average width of the shorter one is 2nm to 200 nm;

(b) an aspect ratio of 7.5 or more and 250 or less;

(c) has a cellulose I-type crystal and has a crystallinity of 70% or more and 95% or less.

[2] The dispersant for an electrode coating solution according to [1], wherein the cellulose fiber further satisfies the following (d),

(d) having an anionic functional group.

[3] The dispersant for electrode coating liquids according to [2], wherein the cellulose fiber further satisfies the following (e),

(e) the anionic functional group is a carboxyl group, and the content of the carboxyl group is 1.2mmol/g to 2.5 mmol/g.

[4] An electrode coating liquid composition characterized by containing the dispersant for electrode coating liquid described in any one of [1] to [3 ].

[5] The electrode coating liquid composition according to item [4], wherein the content of the cellulose fiber is 0.05% by mass or more and 5.00% by mass or less with respect to 100% by mass of the solid content of the coating liquid composition for an electricity storage device.

[6] An electrode for an electric storage device, characterized in that the electrode for an electric storage device comprises a dried product of the composition for an electrode coating liquid according to [4] or [5 ].

[7] An electricity storage device, characterized in that the electricity storage device has the electrode for an electricity storage device of [6 ].

Effects of the invention

The dispersant for an electrode coating solution of the present invention has an effect of improving battery performance because it has a high dispersion stability effect and uniformly disperses an electrode material, and thus it is possible to obtain an electrode coating solution composition free from bias and an electrode produced therefrom.

Further, the dispersant for an electrode coating liquid of the present invention has the excellent dispersing effect described above, and therefore, does not require a strong mechanical dispersing operation required for uniform dispersion of an electrode coating liquid composition in the prior art, and can achieve uniform dispersion of an electrode coating liquid composition by a simple mechanical dispersing device having a weak shearing force.

Detailed Description

Next, embodiments of the present invention will be described in detail. The dispersant for an electrode coating solution of the present invention contains predetermined cellulose fibers.

(a) Number average width of shorter width

The number average width of the shorter of the cellulose fibers is 2nm to 200 nm. If the number-average width of the shorter one is less than 2nm, dispersion stability may be deteriorated, and if it exceeds 200nm, dispersibility may be deteriorated.

The number average width can be measured by the following method. That is, an aqueous dispersion of fine cellulose fibers is prepared in an amount of 0.05 to 0.1 mass% in terms of solid fraction, and the dispersion is cast on a hydrophilized carbon film-coated grid to be used as a sample for observation by a Transmission Electron Microscope (TEM). Then, observation based on an electron microscope image was performed at any magnification of 5000 times, 10000 times, or 50000 times, depending on the size of the constituting fibers. At this time, the sample and observation conditions (magnification, etc.) are adjusted so that 20 or more fibers intersect the axis of an arbitrary vertical and horizontal image width in the obtained image. Then, after obtaining an observation image satisfying this condition, 2 random axes are drawn vertically and horizontally for each image, and the width of the fiber intersecting the axes is visually read. In this way, at least three non-overlapping surface portions were imaged by an electron microscope, and the width values of the fibers intersecting 2 axes were read (thus, width information of 120 fibers, i.e., at least 20 fibers × 2 × 3 fibers, was obtained). The number average width of the short and long fibers is calculated from the data of the number average width of the fibers obtained in this way.

(b) Aspect ratio

The aspect ratio of the cellulose fibers is 7.5 or more and 250 or less, and more preferably 25 or more and 75 or less. When the aspect ratio is less than 7.5, dispersibility of the electrode material may be insufficient, and when it exceeds 250, a strong shearing force is required for dispersing the electrode material, which may damage the electrode material.

The aspect ratio of the cellulose fibers can be measured, for example, by the following method: after casting cellulose on a carbon film-coated grid on which hydrophilization treatment has been completed, the number-average width of the cellulose fiber with the shorter width and the number-average width of the cellulose fiber with the longer width were observed from a TEM image (magnification: 10000 times) after negative dyeing with 2% uranyl acetate. That is, the number-average width of the short width and the number-average width of the long width are calculated according to the method described above, and the aspect ratio is calculated according to the following formula (1) using these values.

Length-width ratio (nm) of longer width/width of shorter width (1)

(c) Crystallinity of cellulose type I

The cellulose fiber has a cellulose I-type crystal and has a crystallinity of 70% or more. When the crystallinity is less than 70%, the properties derived from the cellulose crystal structure may not be exhibited, and the dispersibility of the electrode material may be insufficient. The crystallinity may be more preferably 80% or more. The upper limit of the crystallinity is not particularly limited, but is preferably 95% or less, and more preferably 92% or less, from the viewpoint of the shearing force required for dispersion of the electrode material.

In the present invention, the crystallinity of cellulose is the crystallinity of cellulose type I calculated by Segal method from the diffraction intensity value by X-ray diffraction method, and is defined by the following formula (2).

Cellulose type I crystallinity (%) ═ I (I)_22.6-I_18.5)/I_22.6〕×100…(2)

In the formula I_22.6The diffraction intensity of the crystal plane (002 plane) (diffraction angle 2 θ of 22.6 °) in X-ray diffraction is represented as I_18.5The diffraction intensity of an amorphous portion (diffraction angle 2 θ is 18.5 °) is shown. The cellulose type I refers to a crystal form of natural cellulose, and the cellulose type I crystallinity refers to a ratio of a crystal domain amount in the entire cellulose.

The cellulose fibers can be produced by a known method. Although not particularly limited, the natural cellulose fibers are specifically obtained by suspending natural cellulose fibers in water and treating the same with a high-pressure homogenizer, a grinder, or the like to be micronized, for example.

The natural cellulose fiber is not particularly limited as long as it is derived from a plant, an animal, or a microorganism, and includes: kraft pulp derived from coniferous trees or broad-leaved trees, dissolving pulp, cotton linters, lignocellulose with low cellulose purity, wood flour, plant cellulose, bacterial cellulose, and the like.

In addition, bacterial cellulose fibers produced by bacteria can be used as the cellulose fibers. Examples of the bacterium include those belonging to the genus Acetobacter (Acetobacter), and more specifically, those belonging to the genus Acetobacter: acetobacter (Acetobacter aceti), Acetobacter subsp (Acetobacter subsp.), Acetobacter xylinum, and the like. By culturing these bacteria, cellulose is produced by the bacteria. Since the obtained product includes bacteria and cellulose fibers (bacterial cellulose) produced by the bacteria and bonded to the bacteria, the product is taken out from the culture medium and subjected to water washing, alkali treatment, or the like to remove the bacteria, whereby water-containing bacterial cellulose containing no bacteria can be obtained.

(d) Anionic functional group

The cellulose fiber is preferably a cellulose fiber having an anionic group, from the viewpoint that the I-type crystal structure can be maintained and the cellulose fiber can be efficiently defibered to a predetermined fiber diameter.

The anionic group is not particularly limited, and examples thereof include: the carboxylic acid group, phosphoric acid group, sulfonic acid group, sulfuric acid group, or salt-forming group may have one of these groups, or may have two or more of these groups. Further, a linking group may be provided between the glucose unit constituting the cellulose and the anionic group.

The salt of an anionic group is not particularly limited, and examples thereof include: alkali metal salts such as sodium salt, potassium salt and lithium salt; alkaline earth metal salts such as magnesium salt, calcium salt and barium salt; onium salts such as ammonium salts and phosphonium salts; amine salts of primary amines, secondary amines, tertiary amines, and the like.

As described above, there are acid groups such as a carboxylic acid group, a phosphoric acid group, a sulfonic acid group, and a sulfuric acid group, and salt types such as a carboxylate group, a phosphate group, a sulfonate group, and a sulfate group, but in a preferred embodiment, cellulose fibers having only a salt type anionic group may be used, or cellulose fibers in which a salt type anionic group and an acid type anionic group are mixed may be used.

Here, as an example of the cellulose fiber having an anionic functional group according to one embodiment, an oxidized cellulose obtained by oxidizing a hydroxyl group of a glucose unit constituting cellulose is exemplified, and more specifically, an example of a production method is also described.

The oxidized cellulose is not particularly limited, and is preferably cellulose in which a hydroxyl group at the 6-position of a glucose unit is selectively oxidized. Oxidized cellulose is cellulose in which the hydroxyl group at the 6-position of the glucose unit is selectively oxidized, for example, by¹³And C-NMR spectrum.

The oxidized cellulose may have an aldehyde group or a ketone group in addition to a carboxylic acid group (COOH) and/or a carboxylic acid salt group (COOX, where X represents a cation forming a salt with a carboxylic acid), but it is preferable that the oxidized cellulose does not substantially have an aldehyde group or a ketone group.

(e) Carboxyl group content

The content of the carboxylic acid group (hereinafter referred to as the amount of the carboxylic acid group) in the cellulose fiber is preferably 1.2mmol/g or more, and more preferably 1.5mmol/g or more. Further, it is preferably not more than 2.5mmol/g, more preferably not more than 2.0 mmol/g. When the amount of the carboxyl group is within the above range, the dispersibility of the electrode material is good. The amount of carboxyl groups in the cellulose fibers can be measured, for example, as follows: 60mL of 0.5 to 1 mass% slurry was prepared from a cellulose sample of which dry mass was accurately weighed, the pH was adjusted to about 2.5 with a 0.1M hydrochloric acid aqueous solution, and then a 0.05M sodium hydroxide aqueous solution was added dropwise to measure the conductivity. The measurement was continued until the pH was about 11. The amount of carboxyl groups can be determined from the amount (V) of sodium hydroxide consumed in the neutralization step of a weak acid having a slowly changing conductivity according to the following formula (3).

Amount of carboxyl group (mmol/g) ═ V (mL) × [ 0.05/mass of cellulose ] … (3)

The amount of the carboxyl group can be adjusted by controlling the amount of the co-oxidant to be added and the reaction time in the oxidation step of the cellulose fiber, as will be described later.

The oxidized cellulose fiber can be obtained by a production method comprising: an oxidation reaction step (1) in which a natural cellulose fiber is oxidized to obtain a reactant by using the natural cellulose fiber as a raw material, and an N-oxyl compound as an oxidation catalyst in water and by allowing a co-oxidant to act thereon; a purification step (2) for removing impurities to obtain a reaction product containing water; and a dispersion step (3) for dispersing the water-impregnated reactant in a solvent.

(1) Procedure of Oxidation reaction

After dispersing the natural cellulose fibers and the N-oxyl compound in water (dispersion medium), a co-oxidant is added to start the reaction. During the reaction, a 0.5M aqueous sodium hydroxide solution was added dropwise to maintain the pH at 10 to 11, and the reaction was considered to be completed at a point of time when no change in pH was observed. Here, the co-oxidant refers not to a substance that directly oxidizes a cellulose hydroxyl group but to a substance that oxidizes an N-oxyl compound used as an oxidation catalyst.

The natural cellulose fiber refers to a purified cellulose fiber isolated from a biosynthetic system of cellulose such as plant, animal, and bacteria producing gel. More specifically, there may be mentioned: conifer pulp, hardwood pulp, cotton pulp such as cotton linter and cotton lint, nonwood pulp such as wheat straw pulp and bagasse pulp, bacterial cellulose fibers (BC), cellulose fibers isolated from ascidians, cellulose fibers isolated from seaweeds, and the like. These may be used alone or in combination of two or more. Among these, preferred are cotton-based pulps such as coniferous pulp, broadleaf pulp, linters, and lint; non-wood pulp such as straw pulp and bagasse pulp. The natural cellulose fibers are preferably subjected to a treatment for increasing the surface area, such as beating, because the reaction efficiency can be increased and the productivity can be improved. Further, it is preferable to use, as the natural cellulose fibers, fibers which are not dried (never dried) after separation and purification and are stored, because the bundles of microfibrils are easily swollen, and therefore, the reaction efficiency can be improved and the number average fiber diameter after the refining treatment can be reduced.

The dispersion medium of the natural cellulose fibers in the reaction is water, and the concentration of the natural cellulose fibers in the reaction aqueous solution may be any concentration as long as the reagent (natural cellulose fibers) can sufficiently diffuse. Usually, the reaction concentration is about 5% or less based on the mass of the reaction aqueous solution, but the reaction concentration can be increased by using a device having a strong mechanical stirring force.

Examples of the N-oxyl compound include: generally, a compound having a nitroxide radical is used as an oxidation catalyst. The above N-oxyl compound is preferably a water-soluble compound, and among them, Piperidine nitroxide (PIPERIDINE NITROXYOXY RADICAL) is preferable, and 2,2,6, 6-tetramethylpiperidine nitroxide (TEMPO) or 4-acetamide-TEMPO is particularly preferable. The amount of the N-oxyl compound added is sufficient as a catalyst, and is preferably 0.1 to 4mmol/L, more preferably 0.2 to 2mmol/L, to the reaction aqueous solution.

Examples of the co-oxidant include: hypohalous acids or salts thereof, perhalogenic acids or salts thereof, hydrogen peroxide, perorganic acids, and the like. These may be used alone or in combination of two or more. Among them, alkali metal hypohalites such as sodium hypochlorite and sodium hypobromite are preferable. In addition, when the sodium hypochlorite is used, it is preferable to carry out the reaction in the presence of an alkali metal bromide such as sodium bromide from the viewpoint of the reaction rate. The amount of the alkali metal bromide to be added is about 1 to 40 times by mol, preferably about 10 to 20 times by mol, based on the N-oxyl compound.

The pH of the aqueous reaction solution is preferably maintained in the range of about 8 to 11. The temperature of the aqueous solution is arbitrary from about 4 to 40 ℃, but the reaction can be carried out at room temperature (25 ℃) without particularly controlling the temperature. The degree of oxidation is controlled by the amount of co-oxidant added and the reaction time in order to obtain a desired amount of carboxyl groups, etc. Generally, the reaction time is about 5 to 120 minutes, and the reaction is completed within 240 minutes at the maximum. Further, the degree of hydrolysis of cellulose molecules can be controlled by controlling the amount of the co-oxidant to be added and the pH of the reaction aqueous solution, and the aspect ratio of the cellulose fiber can be arbitrarily set.

(2) Refining step

Subsequently, purification is performed to remove unreacted co-oxidant (hypochlorous acid, etc.), various by-products, and the like. Since the reactant fibers are not dispersed in the nanofiber unit in general at this stage, a dispersion of the reactant fibers and water having a high purity (99 mass% or more) is produced by repeating washing with water and filtration, which are common refining methods.

The purification method in the purification step may be any method as long as the above object can be achieved by a centrifugal dewatering method (for example, a continuous decanter). The aqueous dispersion of the reactant fibers thus obtained has a solid content (cellulose fiber) concentration in the range of about 10 to 50% by mass in a squeezed state. In view of the subsequent dispersing step, if the solid content concentration is set to be higher than 50 mass%, extremely high energy is required for dispersion, which is not preferable.

(3) Dispersing step (micronization treatment step)

The reaction product (aqueous dispersion) impregnated with water obtained in the purification step is dispersed in a dispersion medium to carry out a dispersion treatment. The viscosity increases with the treatment, and a dispersion of the cellulose fibers after the micronization treatment can be obtained. Since the cellulose fibers are simultaneously cut in the longitudinal direction with the miniaturization of the cellulose fibers, the aspect ratio of the cellulose fibers can be arbitrarily set by controlling the degree of the miniaturization treatment (for example, the treatment shearing force, the treatment pressure, the number of treatments, the treatment time, and the like of the dispersing machine). The cellulose fibers may be dried as needed, and as a drying method of the dispersion of the cellulose fibers, for example, in the case where the dispersion medium is water, a spray drying method, a freeze drying method, a vacuum drying method, or the like may be used, and in the case where the dispersion medium is a mixed solution of water and an organic solvent, a drying method by a drum dryer, a spray drying method by a spray dryer, or the like may be used. The cellulose fiber dispersion may be used in the form of a dispersion without drying the cellulose fiber dispersion.

The disperser used in the dispersing step is preferably an apparatus having a capability of beating with a strong force, such as a homomixer, a high-pressure homogenizer, an ultrahigh-pressure homogenizer, an ultrasonic dispersion treatment machine, a beater, a disc refiner, a conical refiner, a double disc refiner, or a grinder, which operates at a high speed, and is capable of reducing the size of the lubricant composition more efficiently and highly, and is economically advantageous in obtaining the aqueous lubricant composition. The dispersing machine may be, for example, a screw mixer, a paddle mixer, a dispersive mixer, a turbine mixer, a disperser, a propeller mixer, a kneader, a mixer, a homogenizer, an ultrasonic homogenizer, a colloid mill, a pebble mill, a bead mill, or the like. Further, two or more dispersing machines may be used in combination.

(4) Reduction step

The cellulose fiber is preferably subjected to a reduction reaction after the oxidation reaction. Specifically, the oxidized microfibrillated cellulose fiber after the oxidation reaction is dispersed in purified water, the pH of the aqueous dispersion is adjusted to about 10, and reduction is performed with various reducing agentsAnd (4) reacting. As the reducing agent used in the present invention, a general reducing agent can be used, but preferably, there can be mentioned: LiBH₄、NaBH₃CN、NaBH₄And the like. Among these, NaBH is preferred from the viewpoint of cost and availability₄。

The amount of the reducing agent is preferably in the range of 0.1 to 4% by mass, and particularly preferably in the range of 1 to 3% by mass, based on the finely oxidized cellulose fibers. The reaction is carried out at room temperature or a temperature slightly higher than room temperature, usually for 10 minutes to 10 hours, preferably for 30 minutes to 2 hours.

The coating liquid for an electrode of an electric storage device of the present invention contains the cellulose fiber as a dispersion stabilizer.

The content of the cellulose fiber is preferably 0.05% by mass or more and 5.00% by mass or less, and more preferably 0.1% by mass or more and 2.0% by mass or less, based on 100% by mass of the solid content of the coating liquid composition for an electricity storage device. When the content of the cellulose fiber is less than 0.05% by mass, a problem occurs in that dispersion stability is deteriorated, and when it exceeds 5.00% by mass, internal resistance of the battery is increased and thixotropy of the coating material is increased, so that it is difficult to produce the coating material.

In the coating liquid composition for an electrode of an electric storage device of the present invention, other thickener and dispersion stabilizer may be added within a range not to impair the effects of the present invention. The mixing ratio of the cellulose fibers to the other thickener and dispersion stabilizer is preferably 99: 1-50: a range of 50. In particular, in view of viscosity at the time of paint preparation, storage stability of the paint after preparation, thixotropy during coating, and the like, it is preferably 95: 5-80: 20. in this case, the content of the cellulose fibers and the other thickening/stabilizing agent is preferably 0.2 mass% or more and 10.00 mass% or less with respect to 100 mass% of the solid content of the coating liquid composition for an electric storage device.

The thickener and dispersion stabilizer may be any known thickener and dispersion stabilizer, and are not particularly limited, and specifically, cellulose such as hydroxymethyl cellulose, carboxymethyl cellulose and alkali metal salts thereof, methyl cellulose, ethyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose, and the like; polycarboxylic acid compounds such as Polyacrylic acid and Polyacrylic acid sodium salt (Polyacrylic acid soda); compounds having a vinylpyrrolidone structure such as polyvinylpyrrolidone; one or more selected from polyacrylamide, polyethylene oxide, polyvinyl alcohol, sodium alginate, xanthan gum, carrageenan, guar gum, agar, and starch. Among them, carboxymethyl cellulose salt can be preferably used.

Examples of the binder for an electrode used in the coating liquid composition for an electrode of an electric storage device of the present invention include water-soluble and/or water-dispersible polymer compounds, for example, polyvinylidene fluoride copolymer resins such as polyvinylidene fluoride and copolymers of polyvinylidene fluoride with hexafluoropropylene or perfluoromethyl vinyl ether and tetrafluoroethylene, fluorine-based resins such as polytetrafluoroethylene and fluororubber, polymers such as styrene-butadiene rubber, ethylene-propylene rubber and styrene-acrylonitrile copolymer, and water dispersions such as polyurethane resins, acrylic resins, polyester resins, polyimide resins, polyamide resins and epoxy resins, but are not limited thereto. These binders may be used alone, or two or more kinds may be used in combination, or two or more kinds of resin composite binders may be used.

The power storage device of the present invention includes known power storage devices, and is not particularly limited, and specifically includes: lithium secondary batteries, lithium ion capacitors, and the like.

The positive electrode active material used for the positive electrode of the lithium secondary battery of the present invention is not particularly limited as long as it can intercalate and deintercalate lithium ions. By way of example, mention may be made of: CuO, Cu₂O、MnO₂、MoO₃、V₂O₅、CrO₃、MoO₃、Fe₂O₃、Ni₂O₃、CoO₃And the like metal oxides; li_xCoO₂、Li_xNiO₂、Li_xMn₂O₄、LiFePO₄Complex oxides of lithium and transition metals; TiS₂、MoS₂、NbSe₃And the like metal chalcogenides; and conductive high molecular compounds such as polyacene, polyparaphenylene, polypyrrole, polyaniline, and the like.

Among the above, a composite oxide of lithium and at least one kind selected from transition metals such as cobalt, nickel, and manganese, which are generally called high voltage type, is preferable in terms of lithium ion releasability and easiness of obtaining a high voltage. Specific examples of the composite oxide of cobalt, nickel, manganese and lithium include LiCoO₂、LiMnO₂、LiMn₂O₄、LiNiO₂、LiNi_xCo_(1-x)O₂、LiMn_aNi_bCo_cAnd (a + b + c ═ 1).

In addition, among these lithium composite oxides, composite oxides doped with a small amount of fluorine, boron, aluminum, chromium, zirconium, molybdenum, iron, or the like, and a method of using carbon, MgO, Al for the particle surface of the lithium composite oxide may be used₂O₃、SiO₂And the like after the surface treatment. Two or more kinds of the positive electrode active materials may be used in combination.

The negative electrode active material used for the negative electrode of the lithium secondary battery is not particularly limited as long as it is a negative electrode active material capable of intercalating and deintercalating metal lithium or lithium ions, and a known active material can be used. For example, carbon materials such as natural graphite, artificial graphite, non-graphitizable carbon, and the like can be used. In addition, metal materials such as metallic lithium, alloys, and tin compounds, lithium transition metal nitrides, crystalline metal oxides, amorphous metal oxides, silicon compounds, conductive polymers, and the like can also be used, and specific examples thereof include: li₄Ti₅O₁₂、NiSi₅C₆And the like.

In the electric storage device of the present invention, carbon allotropes are generally used as electrode active materials used for electrodes for electric double layer capacitors, for example. Specific examples of carbon allotropes include: activated carbon, polyacene, carbon whisker, graphite, and the like, and powder or fiber thereof can be used. The electrode active material is preferably activated carbon, and specifically, activated carbon using a phenol resin, rayon, an acrylonitrile resin, pitch, coconut shell, or the like as a raw material is exemplified.

Among the electrode active materials used in the electrode for a lithium ion capacitor of the present invention, the electrode active material used in the positive electrode of the electrode for a lithium ion capacitor may be one that can reversibly support lithium ions and anions such as tetrafluoroborate. Specifically, in general, electrode active materials used in electric double layer capacitors using carbon allotropes can be widely used.

An electrode active material used for a negative electrode of an electrode for a lithium ion capacitor is a material capable of reversibly supporting lithium ions. Specifically, an electrode active material used in a negative electrode of a lithium ion secondary battery can be widely used. Preferably, there may be enumerated: crystalline carbon materials such as graphite and non-graphitizable carbon, and polyacene-based materials (PAS) also described as the positive electrode active material. As the carbon material and PAS, those obtained by carbonizing a phenol resin or the like, activating the carbonized phenol resin or the like as necessary, and then pulverizing the activated phenol resin or the like can be used.

The electrode for an electric storage device of the present invention may be used with a conductive agent as needed. The conductive agent may be any electronically conductive material that does not adversely affect the battery performance. Carbon black such as acetylene black or ketjen black is generally used, but a conductive material such as natural graphite (scale graphite, flake graphite, earthy graphite, etc.), artificial graphite, carbon whiskers, carbon fibers, metal (copper, nickel, aluminum, silver, gold, etc.) powder, metal fibers, conductive ceramic material, etc. may be used. These may be used alone or in admixture of two or more. The amount of the surfactant added is preferably 0.1 to 30% by mass, particularly preferably 0.2 to 20% by mass, based on the mass of the active material.

As the current collector of the electrode active material used in the power storage device of the present invention, any current collector may be used as long as it is an electronic conductor that does not adversely affect the battery. For example, as the positive electrode current collector, in addition to aluminum, titanium, stainless steel, nickel, calcined carbon, conductive polymers, conductive glass, and the like, a surface of aluminum, copper, or the like, which is treated with carbon, nickel, titanium, silver, or the like, may be used in order to improve adhesiveness, conductivity, and oxidation resistance. In addition, as the current collector for the negative electrode, in addition to copper, stainless steel, nickel, aluminum, titanium, calcined carbon, conductive polymer, conductive glass, Al — Cd alloy, and the like, in order to improve adhesiveness, conductivity, and oxidation resistance, a surface of copper or the like may be treated with carbon, nickel, titanium, silver, or the like. These current collector materials may also be surface treated with oxidation. In addition to the foil shape, a film, sheet, net, pressed or stretched material, a molded body such as a lath, a porous body, or a foam may be used as the shape. The thickness is not particularly limited, but a thickness of 1 to 100 μm is usually used.

The electrode of the power storage device of the present invention can be manufactured, for example, by: an electrode material in the form of a slurry is prepared by mixing an electrode active material, a conductive agent, a current collector of the electrode active material, a binder for binding the electrode active material and the conductive agent to the current collector, and the like, and is applied to an aluminum foil, a copper foil, or the like which becomes the current collector, and the dispersion medium is volatilized.

The method and order of mixing the electrode materials are not particularly limited, and for example, the active material and the conductive agent may be mixed in advance and used, and in this case, a mortar, a milling mixer, a ball mill such as a planetary ball mill or a shaker ball mill, or mechanofusion may be used for the mixing. Further, since the dispersion stabilizer of the present invention does not cause a decrease in viscosity due to cutting during mixing, a high shear disperser such as a high pressure homogenizer, an ultrahigh pressure homogenizer, a high speed rotary mixer, a thin film rotary disperser, or the like can be used, and the dispersibility of the electrode active material is further improved. In the present invention, the nanomaterial dispersion can be used without mixing the active material and the conductive agent in advance, and in addition to the above-described methods, an aqueous nanomaterial dispersion having excellent storage stability can be produced by using an automatic rotary mixer or a high-speed homomixer. In the present invention, the excellent dispersion characteristics of the cellulose fibers are utilized to produce a nanomaterial water dispersion having good storage stability. The nanomaterial is not limited to the active material and the conductive agent, and a nanomaterial may be used.

The separator used in the power storage device of the present invention may be any separator used in a general power storage device without particular limitation, and examples thereof include: porous resins including polyethylene, polypropylene, polyolefin, polytetrafluoroethylene, etc., ceramics, nonwoven fabrics, etc.

The electrolyte used in the power storage device of the present invention may be any electrolyte used in a normal power storage device, and a general electrolyte such as an organic electrolyte and an ionic liquid may be used. Examples of the electrolyte salt used in the power storage device of the present invention include: LiPF₆、LiBF₄、LiClO₄、LiAsF₆、LiCl、LiBr、LiCF₃SO₃、LiN(CF₃SO₂)₂、LiC(CF₃SO₂)₃、LiI、LiAlCl₄、NaClO₄、NaBF₄And NaI, and the like, and particularly, there may be mentioned: LiPF₆、LiBF₄、LiClO₄、LiAsF₆Inorganic lithium salt such as LiN (SO)₂C_xF_2x+1)(SO₂C_yF_2y+1) The organic lithium salt shown. Here, x and y represent 0 or an integer of 1 to 4, and x + y represents 2 to 8. Specific examples of the organic lithium salt include: LiN (SO)₂F)₂、LiN(SO₂CF₃)(SO₂C₂F₅)、LiN(SO₂CF₃)(SO₂C₃F₇)、LiN(SO₂CF₃)(SO₂C₄F₉)、LiN(SO₂C₂F₅)₂、LiN(SO₂C₂F₅)(SO₂C₃F₇)、LiN(SO₂C₂F₅)(SO₂C₄F₉) And the like. Wherein if LiPF is used in the electrolyte₆、LiBF₄、LiN(CF₃SO₂)₂、LiN(SO₂F)₂、LiN(SO₂C₂F₅)₂And the like, the electrical characteristics are excellent, and therefore, the method is preferable. One or two or more of the electrolyte salts may be used. Such a lithium salt is contained in the electrolyte at a concentration of usually 0.1 to 2.0moL/L, preferably 0.3 to 1.5 moL/L.

The organic solvent for dissolving the electrolyte salt used in the power storage device of the present invention is not particularly limited as long as it is an organic solvent used in the nonaqueous electrolytic solution of the power storage device, and examples thereof include: carbonate compounds, lactone compounds, ether compounds, sulfolane compounds, dioxolane compounds, ketone compounds, nitrile compounds, halogenated hydrocarbon compounds, and the like. In detail, there may be enumerated: carbonates such as dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, ethylene glycol dimethyl carbonate, propylene glycol dimethyl carbonate, ethylene glycol diethyl carbonate, and vinylene carbonate; lactones such as γ -butyrolactone; ethers such as dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, and 1, 4-dioxane; sulfolanes such as sulfolane and 3-methylsulfolane; dioxolanes such as 1, 3-dioxolane; ketones such as 4-methyl-2-pentanone; nitriles such as acetonitrile, propionitrile, valeronitrile, and benzonitrile; halogenated hydrocarbons such as 1, 2-dichloroethane; other plasma liquids such as methyl formate, dimethylformamide, diethylformamide, dimethylsulfoxide, imidazolium salts, and quaternary ammonium salts. Further, a mixture thereof may also be used. Among these organic solvents, in particular, a case where one or more nonaqueous solvents selected from the group consisting of carbonates are contained is preferable because it is excellent in solubility of an electrolyte, dielectric constant, and viscosity.

In the power storage device of the present invention, if used in a polymer electrolyte or a polymer gel electrolyte, there are included: the polymer compound may be a polymer of ether, ester, siloxane, acrylonitrile, vinylidene fluoride, hexafluoropropylene, acrylate, methacrylate, styrene, vinyl acetate, vinyl chloride, oxetane, or the like, or a polymer having a copolymer structure thereof or a crosslinked product thereof, and the polymer may be one kind or two or more kinds. The polymer structure is not particularly limited, but a polymer having an ether structure such as polyethylene oxide is particularly preferable.

In the electric storage device of the present invention, the liquid-based battery contains an electrolytic solution in a battery container, the gel-based battery contains a precursor solution in which a polymer is dissolved in the electrolytic solution in the battery container, and the solid-electrolyte battery contains a polymer in which an electrolyte salt is dissolved before crosslinking in the battery container.

The power storage device according to the present invention may be formed in any shape such as a cylindrical shape, a coin shape, a rectangular shape, a laminate shape, and others, and the basic structure of the battery is the same regardless of the shape, and various design changes may be made according to the purpose. For example, in the case of a cylindrical shape, a negative electrode obtained by applying a negative electrode active material to a negative electrode current collector and a positive electrode obtained by applying a positive electrode active material to a positive electrode current collector are wound with a separator interposed therebetween, the wound body is stored in a battery can, and a nonaqueous electrolytic solution is injected and an insulating plate is placed over and under the wound body, thereby sealing the wound body. In addition, if applied to a coin-type battery, the battery is stored in a coin-type battery can in a state in which a disk-shaped negative electrode, a separator, a disk-shaped positive electrode, and a stainless steel plate are stacked, and a nonaqueous electrolytic solution is injected and sealed.