Slurry for forming lithium-ion battery positive electrode mixture layer, positive electrode for lithium-ion battery, and lithium-ion battery

Abstract

A slurry for forming a lithium-ion battery positive electrode mixture layer, the slurry comprising: a positive electrode active material; an alginic acid-based polymer compound including an aminocarboxylic acid-based chelate group; a polyol having 2-4 hydroxyl groups per molecule and having a molecular weight of 60-180; and an aqueous solvent.

Description

Slurry for forming a lithium-ion battery cathode composite layer, cathode for lithium-ion batteries, and lithium-ion battery

[0001] This disclosure relates to a slurry for forming a lithium-ion battery cathode composite layer, a lithium-ion battery cathode, and a lithium-ion battery.

[0002] Lithium-ion batteries have long been widely used as power sources for electrical equipment, and in recent years, their applications have been expanding to include electric vehicles. To meet these applications, lithium batteries require not only improved characteristics such as higher capacity, higher output, and longer cycle life, but also high safety. The positive electrode of such lithium-ion batteries basically has a structure in which a porous body containing powdered positive electrode active material and a binder is laminated and bonded onto a current collector. Therefore, it is known that the performance of the positive electrode of a lithium-ion battery is greatly influenced not only by the characteristics of the positive electrode active material, but also by the type and characteristics of the binder used for the positive electrode (positive electrode binder).

[0003] Conventionally, polyvinylidene fluoride (PVDF) has been the dominant binder for such cathodes, based on the assumption that organic solvents such as N-methylpyrrolidone would be used. However, the use of organic solvents presents problems in terms of environmental impact and work efficiency.

[0004] Therefore, in recent years, research has been progressing on water-based binders that can be used without organic solvents (Non-Patent Literature 1). However, many conventional water-based binders have low mechanical flexibility (flexibility), and in response to the need for higher battery capacity, the coating amount (basis weight) of the composite material layer on the positive electrode has been reduced to a practical 20 mg / cm². ２In summary, increasing the thickness of the composite layer to a practical thickness of 100 μm or more makes it impossible to impart excellent flexibility to the resulting positive electrode composite layer. This leads to problems such as cracks occurring in the composite layer during the drying process immediately after coating, or the composite layer peeling off from the current collector foil. Furthermore, the increased mechanical strain applied to the composite layer when the positive electrode is bent makes it difficult to perform winding and recovery using rolls (a winding process) after the positive electrode is manufactured, posing a problem in terms of efficiently manufacturing the positive electrode.

[0005] To solve these problems, for example, it has been proposed to insert an undercoat layer between the current collector foil and the composite layer (Patent Document 1).

[0006] Furthermore, as a measure to impart mechanical flexibility to the electrodes of lithium-ion batteries, although it pertains to the negative electrode, a solution has been proposed in which a plasticizer is added to the negative electrode composite layer. For example, a technology in which glycerin is added as a plasticizer to the negative electrode composite layer has been disclosed (Non-Patent Literature 2).

[0007] International Publication No. 2014 / 030208

[0008] Industrial Chemistry & Materials, 2024, 2, 191-225Electrochemical Society, 2022, 196, 040558

[0009] However, the method using the undercoat layer disclosed in Patent Document 1 has drawbacks compared to conventional processes, such as the increased number of steps required for forming the undercoat layer, resulting in the introduction of equipment for forming the undercoat layer (equipment for coating, drying, etc.) and increased running costs. Furthermore, since the undercoat layer described in Patent Document 1 is water-soluble, applying a slurry for forming a cathode composite layer (water-based slurry) containing an aqueous solvent onto it would dissolve the layer, making it unsuitable for coating with aqueous slurries.

[0010] Furthermore, the above-mentioned Non-Patent Document 2 does not evaluate flexibility. This is because the practical basis weight of the negative electrode is 10 mg / cm². ２As follows (in other words, the negative electrode composite layer thickness is 50 μm or less (more than twice as thin as the positive electrode film thickness)), it is clear that this is because, unlike the positive electrode, no problems such as cracks or delamination occur after forming the electrode using an aqueous slurry, and flexibility like that of the positive electrode is not required. On the other hand, there are no examples of studies on adding plasticizers to the positive electrode composite layer, and it is not specifically mentioned in Non-Patent Literature 2, etc.

[0011] This disclosure has been made in view of the problems of the prior art described above, and aims to provide at least one of the following: a slurry for forming a lithium-ion battery cathode composite layer, which is an aqueous slurry used to manufacture a cathode composite layer, but which can impart excellent flexibility to the cathode composite layer even when the cathode composite layer has a practical basis weight and thickness, thereby enabling the efficient manufacture of a cathode with excellent flexibility; a cathode for a lithium-ion battery obtained using the slurry; and a lithium-ion battery having the cathode for a lithium-ion battery.

[0012] The inventors have discovered that, even when using an aqueous slurry to manufacture a positive electrode composite layer, it is possible to impart excellent flexibility to the layer, even when the positive electrode composite layer has a practical basis weight and thickness. This makes it possible to efficiently manufacture a positive electrode with excellent flexibility.

[0013] In other words, the present invention is as described in the claims, and the gist of this disclosure is as follows.

[0014] [1] A slurry for forming a lithium-ion battery cathode composite layer, comprising: a positive electrode active material; an alginic acid polymer compound containing an aminocarboxylic acid chelating group; a polyol having 2 to 4 hydroxyl groups per molecule and a molecular weight of 60 to 180; and an aqueous solvent.

[0015] [2] The slurry for forming a lithium-ion battery cathode composite layer according to [1], wherein the ratio of the mass of the polyol to the mass of the alginate polymer compound containing the aminocarboxylic acid chelating group ([mass of polyol] / [mass of alginate polymer compound containing the aminocarboxylic acid chelating group]) is 1 to 5.

[0016] [3] A slurry for forming a lithium-ion battery positive electrode composite layer according to [1] or [2], further comprising a conductive additive.

[0017] [4] The slurry for forming a lithium-ion battery cathode composite layer according to any one of [1] to [3], wherein the content of the polyol is 1.5% by mass or more with respect to the total mass of all components other than the aqueous solvent contained in the slurry.

[0018] [5] The slurry for forming a lithium-ion battery cathode composite layer according to any one of [1] to [4], wherein the cathode active material is a cathode active material containing manganese.

[0019] A positive electrode for a lithium-ion battery, comprising a positive electrode composite layer consisting of a dried coating film of a slurry for forming a lithium-ion battery positive electrode composite layer described in any one of items [6], [1], to [5].

[0020] A lithium-ion battery having the positive electrode for lithium-ion batteries described in [7] and [6].

[0021] According to this disclosure, it is possible to provide at least one of the following: a slurry for forming a lithium-ion battery cathode composite layer, which is an aqueous slurry used to manufacture a cathode composite layer, and which can impart excellent flexibility to the cathode composite layer even when the cathode composite layer has a practical basis weight and thickness, thereby enabling the efficient manufacture of a cathode with excellent flexibility; a cathode for a lithium-ion battery obtained using the slurry; and a lithium-ion battery having the cathode for a lithium-ion battery.

[0022] The present disclosure will be described in detail below with reference to its preferred embodiments. The embodiments described below are examples of the present disclosure, and the present disclosure is not limited to these. The present disclosure includes any combination of each configuration and parameter disclosed herein, and also includes any combination of upper and lower limits of the values ​​disclosed herein. In this specification, numerical ranges indicated using "~" indicate a range that includes the numbers before and after "~" as the minimum and maximum values, respectively. Also, unless otherwise explicitly stated, the units of the numbers before and after "~" are the same. Furthermore, the present disclosure includes any combination of each configuration and parameter disclosed herein, and also includes any combination of upper and lower limits of the values ​​disclosed herein.

[0023] [Slurry for forming a lithium-ion battery cathode composite layer] A slurry for forming a lithium-ion battery cathode composite layer according to one aspect of the present disclosure comprises a cathode active material, an alginic acid-based polymer compound containing an aminocarboxylic acid-based chelating group, a polyol having 2 to 4 hydroxyl groups in the molecule and a molecular weight of 60 to 180, and an aqueous solvent.

[0024] <Regarding the components used in the slurry> Below, we will first explain each component separately: the positive electrode active material; the alginic acid polymer compound containing an aminocarboxylic acid chelating group; the polyol having 2 to 4 hydroxyl groups in the molecule and a molecular weight of 60 to 180; and the aqueous solvent. Then, we will explain the components that can be suitably used.

[0025] <Positive Electrode Active Material> In this disclosure, the positive electrode active material is not particularly limited as long as lithium ions can be inserted into and removed from it, and examples include transition metal oxides and lithium composite oxides. Thus, as the positive electrode active material, for example, at least one of the transition metal oxides and lithium composite oxides can be cited. Here, as the transition metal oxide, CuO, Cu ２ O, MnO ２ MoO ３ , V ２ O ５ ,CrO ３ Fe２ O ３ , Ni ２ O ３ , and CoO ３ is preferably at least one selected from the group consisting of, and the lithium composite oxide is Li Ｘ CoO ２ , Li Ｘ NiO ２ , Li Ｘ MnO ２ , Li Ｘ Mn ２ O ４ , LiNi Ｘ Co （１－Ｘ） O ２ , LiNi Ｘ Mn （２－Ｘ） O ４ , LiMn ａ Ni ｂ Co ｃ O ２ (a+b+c=1), and LiFePO ４ is preferably at least one selected from the group consisting of. Among these, as the positive electrode active material, a composite oxide of lithium and at least one transition metal selected from the transition metals Co, Ni and Mn is more preferable. Specific examples of preferable positive electrode active materials include LiCoO ２ , LiNiO ２ , LiMnO ２ , LiMn ２ O ４ , LiNi Ｘ Co （１－Ｘ） O ２ , LiNi Ｘ Mn （２－Ｘ） O ４ and LiMn ａ Ni ｂ Co ｃ O ２ (a+b+c=1), and one or more selected from the group consisting of the above are mentioned. These lithium composite oxides may be doped with a small amount of at least one element selected from the group consisting of fluorine, boron, Al, Cr, Zr, Mo, and Fe, or the particle surface of the lithium composite oxide may be coated with carbon, MgO, Al ２ O ３ , and SiO ２The positive electrode active material may be surface-treated with at least one element selected from the group consisting of the following. Thus, as the lithium composite oxide, a lithium composite oxide doped with at least one element selected from the group consisting of fluorine, boron, Al, Cr, Zr, Mo, and Fe may be used, and furthermore, the particle surface of the lithium composite oxide may be carbon, MgO, Al ２ O ３ and SiO ２ A surface-treated material may be used that has been surface-treated with at least one selected from the group consisting of the following:

[0026] Furthermore, examples of such lithium composite oxides include at least one selected from the group consisting of lithium cobalt oxide (LCO), lithium nickel cobalt manganese oxide (NCM), lithium nickel oxide (LNO), lithium nickel cobalt aluminum (NCA), lithium iron phosphate (LFP), lithium manganese iron phosphate (LMFP), lithium manganese oxide (LMO), and lithium nickel manganese oxide (LNMO).

[0027] Furthermore, from the viewpoint of increasing the operating voltage of the lithium-ion battery, a manganese-containing positive electrode active material is preferred. Examples of such manganese-containing positive electrode active materials include lithium manganese oxide (LiMnO). ２ ya LiMn ２ O ４ (etc.), lithium nickel manganese oxide (LiNi Ｘ Mn （２－Ｘ） O ４ ) and lithium nickel cobalt manganese oxide (LiMn ａ Ni ｂ Co ｃ O ２ At least one selected from the group consisting of (a + b + c = 1) can be listed as a preferred option.

[0028] Furthermore, when the positive electrode active material is in particulate form, its average particle diameter is not particularly limited, but it can be 1 μm or more, 2 μm or more, or 3 μm or more, and can be 50 μm or less, 40 μm or less, or 30 μm or less. The average particle diameter is preferably 1 μm or more and 50 μm or less, more preferably 2 μm or more and 40 μm or less, and even more preferably 3 μm or more and 30 μm or less.

[0029] <Alginate-based polymer compounds containing aminocarboxylic acid chelating groups> In this disclosure, the alginate-based polymer compounds containing aminocarboxylic acid chelating groups are compounds (polymer compounds) in which an aminocarboxylic acid chelating group is bonded to a portion (skeleton portion) of a polymer compound made of alginic acid via covalent bonds and / or ionic bonds. In other words, the "alginate-based polymer compounds containing aminocarboxylic acid chelating groups" in this disclosure are those in which an aminocarboxylic acid chelating group is bonded to a portion (skeleton portion) of a polymer compound made of alginic acid via at least one type of bond selected from the group consisting of covalent bonds and ionic bonds. Here, "chelating group" refers to a ligand having multiple coordination sites, and any functional group capable of forming a chelate with a polyvalent metal ion may be used, and may also form salts such as metal salts or ammonium salts. Furthermore, "aminocarboxylic acid chelating group" refers to a group containing a carboxyl group that forms a chelating group with respect to one nitrogen atom (N) (for example, formula: -CH ２ A group having a structure in which at least two groups (represented by COOH) are bonded (for example, formula; HOOC-H ２ C-N-CH ２ This refers to iminodiacetic acid groups, nitrilotriacetic acid groups, and ethylenediaminetetraacetic acid groups, which have a structure represented by -COOH.

[0030] In this disclosure, the alginate polymer compound containing the aminocarboxylic acid chelating group is a component used as a so-called binder in the positive electrode. By using such an alginate polymer compound as a binder, it becomes possible to capture heavy metal ions (manganese ions and nickel ions) eluting from the positive electrode active material near the positive electrode with the aminocarboxylic acid chelating group, thereby highly suppressing the precipitation and accumulation of these heavy metal ions on the negative electrode active material.

[0031] The aminocarboxylic acid chelating groups contained in such alginic acid polymer compounds are not particularly limited, but examples include functional groups such as iminodiacetic acid group, nitrilotriacetic acid group, hydroxyethyliminodiacetic acid group, ethylenediaminetriacetic acid group, ethylenediaminetetraacetic acid group, 1,2-bis(2-aminophenoxy)ethanetetraacetic acid group, 1,2-diaminocyclohexanetetraacetic acid group, diethylenetriaminepentaacetic acid group, (2-hydroxyethyl)ethylenediaminetriacetic acid group, bis(2-aminoethyl)ethyleneglycoltetraacetic acid group, and triethylenetriaminehexaacetic acid group; alkali metal salts of these functional groups; and ammonium salts of these functional groups. Furthermore, from the viewpoint of enabling ion exchange and capture of heavy metal ions (e.g., metal ions eluted from the positive electrode active material), the type of aminocarboxylic acid chelating group that forms a monovalent salt with at least one selected from the group consisting of alkali metal salts and ammonium salts (monovalent salt form) is more preferable than the type where the carboxylic acid portion is a proton (proton form).

[0032] Furthermore, among such aminocarboxylic acid-based chelating functional groups, at least one selected from the group consisting of iminodiacetic acid group, nitrilotriacetic acid group, ethylenediaminetriacetic acid group, ethylenediaminetetraacetic acid group, and alkali metal salts thereof is preferred, as it allows for the more efficient introduction of a larger number of aminocarboxylic acid-based chelating groups into alginic acid.

[0033] Furthermore, in the alginic acid polymer compound containing the aminocarboxylic acid chelating group, it is sufficient that the structure constituting the portion of the polymer compound excluding the chelating group (the compound constituting the backbone portion of the polymer compound) has a structure derived from alginic acid. Thus, in the alginic acid polymer compound, it is sufficient that the portion of the polymer compound excluding the chelating group has a structure derived from alginic acid. Therefore, the alginic acid polymer compound containing the aminocarboxylic acid chelating group may be manufactured using alginic acid itself, or it may be manufactured using alginic acid into which a sulfate group has been introduced (sulfated alginic acid), or it may be manufactured using a salt of alginic acid and / or a salt of sulfated alginic acid.

[0034] Furthermore, the sulfate group in sulfated alginic acid may be in the form of a basic salt or a neutral salt. This is because both basic and neutral salts are ion-exchangeable strongly acidic cation exchange groups. Also, the position where the sulfate group is introduced in alginic acid is at the site of the hydroxyl group contained in the structure of alginic acid, and the hydrogen of the hydroxyl group is -SO ３ It is introduced by substitution with H. The amount of sulfate group introduced into the polysaccharide can be 0.1 mmol / g or more, 0.3 mmol / g or more, or 0.5 mmol / g or more, and can be 10.0 mmol / g or less, 7.5 mmol / g or less, or 5.0 mmol / g or less. Since oxidation resistance is improved while maintaining the amount of chelating group introduced, the amount of sulfate group introduced into the polysaccharide is preferably 0.1 to 10.0 mmol / g, more preferably 0.3 to 7.5 mmol / g, and even more preferably 0.5 to 5.0 mmol / g.

[0035] Such alginic acid polymer compounds containing aminocarboxylic acid chelates can suitably utilize, for example, the reaction product of an aminocarboxylic acid chelate compound as a raw material and an alginic acid compound (at least one compound selected from the group consisting of alginic acid, sulfated alginic acid, and their salts). In particular, from the viewpoint of improving molecular weight controllability, the reaction product of an aminocarboxylic acid chelate compound (raw material) and alginic acid can be more suitably utilized. The reaction product of such an aminocarboxylic acid chelate compound (raw material) and an alginic acid compound is basically a compound in which the aminocarboxylic acid chelate group is bonded to the backbone of a polymer compound made of alginic acid via ionic bonds. That is, in the reaction system, the alginic acid compound has an anionic functional group, while the aminocarboxylic acid chelate compound has a cationic functional group such as an amino group. Ionic bonds are formed by these functional groups, and the reaction product can be a compound in which the aminocarboxylic acid chelate group is bonded to the backbone of a polymer compound made of alginic acid via ionic bonds.

[0036] Examples of aminocarboxylic acid-based chelating group-containing compounds used as raw materials in the production of such reaction products include iminodiacetic acid, nitrilotriacetic acid, hydroxyethyliminodiacetic acid, ethylenediaminetriacetic acid, ethylenediaminetetraacetic acid, 1,2-bis(2-aminophenoxy)ethanetetraacetic acid, 1,2-diaminocyclohexanetetraacetic acid, diethylenetriaminepentaacetic acid, N-(2-hydroxyethyl)ethylenediaminetriacetic acid, bis(2-aminoethyl)ethyleneglycoltetraacetic acid, bis(2-aminophenyl)ethyleneglycoltetraacetic acid, N-(2-hydroxyethyl)iminodiacetic acid, triethylenetetraminehexaacetic acid, and salts thereof. Such salts are preferably alkali metal salts or alkaline earth metal salts. The aminocarboxylic acid-based chelating group-containing compounds exemplified here all have basic functional groups such as amino groups or imino groups. Therefore, when combined with hydrogen ion-form alginic acid, they are components that can efficiently introduce the aminocarboxylic acid-based chelating group-containing compounds into alginic acid via ionic bonding in water, and thus can be suitably used when obtaining the aforementioned reaction products.

[0037] Furthermore, it is preferable that the aminocarboxylic acid-based chelating group-containing compound (raw material) is a compound whose aqueous solution has a pH of 3 to 11 when dissolved in water. Using a chelating group-containing compound with an aqueous solution pH of 3 to 11 as one component of the binder is preferable because, for example, when using an aqueous slurry for forming a lithium-ion battery cathode composite layer containing a positive electrode active material with a high nickel content, the pH of the slurry can be suppressed from becoming strongly alkaline when creating electrodes for lithium-ion batteries, thereby preventing corrosion of the current collector. Here, the pH value used is the pH value measured when the aqueous solution concentration of the aminocarboxylic acid-based chelating group-containing compound (raw material) is 1.0 mol / . Furthermore, examples of aminocarboxylic acid-based chelate group-containing compounds (raw materials) that exhibit an aqueous solution pH of 3 to 11 when dissolved in water include at least one selected from the group consisting of disodium nitrilotriacetate, disodium ethylenediaminetetraacetate, trisodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate, dipotassium ethylenediaminetetraacetate, tripotassium ethylenediaminetetraacetate, diammonium ethylenediaminetetraacetate, monocalcium ethylenediaminetetraacetate, monomagnesium ethylenediaminetetraacetate, O,O'-bis(2-aminophenyl)ethylene glycol-N,N,N',N'-tetrapotassium tetraacetate, N,N-bis(2-hydroxyethyl)glycine, trisodium diethylenetriaminepentaacetate, trisodium nitrilotrismethylphosphonate, and disodium hydroxyethylidene diphosphonate.

[0038] Furthermore, the alginate compound used in the production of the prereactant may be at least one compound selected from the group consisting of alginic acid, sulfated alginic acid, and salts thereof, and is not particularly limited. However, from the viewpoint of improving affinity with the active material (making it possible to more efficiently coat the surface of the active material), it is preferable to use alginic acid or sulfated alginic acid, and more preferably alginic acid. In addition, it is preferable that such alginic acid be hydrogen ion alginic acid. Note that "alginic acid" as used herein may be composed of two types of uronic acid (mannuronic acid and guluronic acid). In addition, the ratio of mannuronic acid and guluronic acid, which are constituent components of such alginic acid, is not particularly limited and can be any ratio. Note that such alginic acid may be alginic acid with a high mannuronic acid ratio that produces a flexible gel, or alginic acid with a high guluronic acid ratio that produces a rigid gel. Furthermore, "hydrogen ion alginic acid" as used herein refers to alginic acid in which the counterion of the carboxyl group in the constituent uronic acid is in the hydrogen ion form. Furthermore, it is preferable that such hydrogen ionized alginic acid is a linear polysaccharide composed of two types of uronic acid (mannuronic acid and guluronic acid).

[0039] Such hydrogen ion-based alginates can be obtained by known methods and used as appropriate. For example, they can be obtained by employing the method described in Japanese Patent Application Publication No. 2024-88569 (a method of dispersing alkali metal alginates and / or alkaline earth metal alginates in their poor solvents, and then adding an acid to exchange at least one of the alkali metal alginates or alkaline earth metal alginates in a dispersed state to a hydrogen ion form). Alternatively, commercially available hydrogen ion-based alginates can be used.

[0040] Such hydrogen ionized alginates may have a weight-average molecular weight of, for example, 10,000 or more, 50,000 or more, or 500,000 or more, and may also have a weight-average molecular weight of 1,500,000 or less, or 1,000,000 or less. Such hydrogen ionized alginates with a weight-average molecular weight of 10,000 to 1,500,000 (more preferably 50,000 to 1,500,000, and even more preferably 500,000 to 1,000,000) can be suitably used. The upper limit of such a weight-average molecular weight is more preferably 1,000,000. By setting the weight-average molecular weight within the above range, the alginate polymer compound containing the aminocarboxylic acid chelate group exhibits excellent binding properties and toughness, resulting in more favorable properties when used as a positive electrode binder. Such a weight-average molecular weight can be measured, for example, by the following conditions (method described below). Specifically, 10 mg of hydrogen ionized alginate and 10 ml of 0.1 M phosphate buffer (pH 6.8) eluent are added and allowed to stand overnight to dissolve. A sample (measurement sample) is then prepared by filtering through a cellulose acetate cartridge filter (0.45 μm). Using this measurement sample, an analysis is performed using a Tosoh HLC-8320GPC, an RI detector, and two Tosoh Tskgelα-M separation columns (7.8 mm inner diameter x 30 cm) connected in series. 0.1 M phosphate buffer (pH 6.8) is used as the developing solvent, and the analysis is performed at a flow rate of 1.0 ml / min on the separation column side and a column temperature of 40°C. The weight-average molecular weight (Mw) can then be determined by analyzing a cubic approximation curve using 10 standard PEO / PEG meter readings from Agilent with known molecular weights as the calibration curve. The molecular weights of standard PEO / PEG should be 1,511,000, 1,039,000, 538,000, 117,900, 68,900, 28,230, 15,190, 3,860, 194, and 106.

[0041] Furthermore, for such hydrogen ion-form alginic acid, a hydrogen ion substitution rate of 80-99% is preferred. The "hydrogen ion substitution rate" referred to here is the proportion in which the counterions of the carboxyl groups in uronic acid, a component of alginic acid, are hydrogen ions. The above hydrogen ion substitution rate is calculated by quantitatively determining the amount of inorganic ions such as alkali metal ions and alkaline earth metal ions, and organic ions such as tetramethylammonium ions, in the high molecular weight hydrogen ion-form alginic acid. When the hydrogen ion substitution rate is within the above range, it means that the alginic acid is mostly in hydrogen ion form, and when the above alginic acid is used as a binder raw material, it interacts more easily with chelating group-containing compounds, giving a favorable result.

[0042] Furthermore, when including an alginic acid polymer compound containing an aminocarboxylic acid chelating group in a slurry for forming a lithium-ion battery cathode composite layer according to one aspect of this disclosure, for example, by including hydrogen ionized alginic acid as alginic acid and the aminocarboxylic acid chelating group-containing compound (raw material), the alginic acid polymer compound containing the aminocarboxylic acid chelating group may be included. That is, when a slurry is produced by mixing hydrogen ionized alginic acid and the aminocarboxylic acid chelating group-containing compound in an aqueous solvent, an ionic bond is basically formed between the hydrogen ionized alginic acid and the aminocarboxylic acid chelating group-containing compound during mixing, resulting in the formation of an alginic acid polymer compound containing the aminocarboxylic acid chelating group in the slurry. Therefore, by including hydrogen ionized alginic acid as alginic acid and the aminocarboxylic acid chelating group-containing compound (raw material) in the slurry, the alginic acid polymer compound containing the aminocarboxylic acid chelating group can be included in the slurry.

[0043] Furthermore, the fact that the aminocarboxylic acid chelating group is bonded to alginic acid via ionic bonding can be confirmed, for example, by FT-IR measurement. When confirming the presence or absence of chelating group bonding by FT-IR measurement, for example, if the alginic acid polymer compound is a compound obtained by reacting hydrogen ionized alginic acid with iminodiacetate disodium salt, the raw material hydrogen ionized alginic acid is 1740 cm⁻¹. －１ While absorption originating from the stretching vibration of the carbonyl group of the carboxylic acid is observed, in the compound (reactant) into which the post-reaction iminodiacetate disodium salt has been introduced, absorption is observed at 1740 cm⁻¹. －１ The absorption of the previous amount disappeared, and a new amount of 1600 cm³ derived from iminodiacetate disodium salt was absorbed. －１ Since absorption originating from the stretching vibration of the carbonyl group of the carboxylate salt can be confirmed, the presence or absence of bonding (ionic bonding) of the chelate group introduced into the chelate group-containing polymer compound can be confirmed by measuring such changes in absorption wavelength. As for the FT-IR measurement method, a method may be adopted in which the FT-IR spectrum is measured using the ATR method with a Fourier transform infrared spectrophotometer (FT-IR) (SPECTRUM ONE, manufactured by Perkin Elmer) as the measuring device.

[0044] Furthermore, when the alginic acid-based polymer compound containing the aminocarboxylic acid-based chelating group is a compound in which the aminocarboxylic acid-based chelating group is bonded to alginic acid via a covalent bond, its structure is not particularly limited. For example, a structure similar to that described in International Publication No. 2025 / 028649, where the chelating group is bonded to the polymer compound via a covalent bond, can be appropriately adopted, except that the acidic polysaccharide or basic polysaccharide is alginic acid and the chelating group is an aminocarboxylic acid-based chelating group.

[0045] Furthermore, the method for obtaining the reaction product of the alginic acid compound and the aminocarboxylic acid chelate group-containing compound (raw material) is not particularly limited, and known methods (for example, methods described in International Publication No. 2025 / 028649, Japanese Patent Publication No. 2024-88569, Japanese Patent Publication No. 2024-88436, etc.) can be used as appropriate. For example, one method is to contact the alginic acid compound with an acid to convert the carboxyl groups and / or sulfate groups of the compound into hydrogen ions, and then contact it with the aminocarboxylic acid chelate group-containing compound to ionize and obtain the reaction product. In this case, when the reaction product is the reaction product of the hydrogen ionized alginic acid and the aminocarboxylic acid chelate group-containing compound, it is preferable that the amount of the aminocarboxylic acid chelate group-containing compound is 0.1 to 1.1 moles per mole of carboxyl groups in the hydrogen ionized alginic acid.

[0046] Furthermore, the alginic acid polymer compound containing the aminocarboxylic acid chelating group is preferably one with a weight-average molecular weight of 10,000 to 1,500,000 (more preferably 50,000 to 1,000,000, and even more preferably 500,000 to 1,500,000). A weight-average molecular weight within this range ensures sufficient mechanical strength, and the viscosity during electrode coating can be adjusted to a range that does not affect workability. The "weight-average molecular weight" can be determined using a Tosoh HLC-8320GPC measuring device, a TSKgel GMPXL column, a 0.1 mol / L phosphate-buffered aqueous solution with a pH of 8.0 as the eluent, polyethylene glycol as the standard sample, and a flow rate of 1 mL / min.

[0047] The amount of the aminocarboxylic acid-based chelating group contained in the alginate-based polymer compound is 0.2 mmol / g or more and 6 mmol / g or less, preferably 0.5 mmol / g or more and 5 mmol / g or less. A chelating group content within this range is preferable because it allows for rapid capture of heavy metal ions and provides sufficient heavy metal ion capture. The chelating group content is not particularly limited and can be appropriately determined depending on the type of chelating group. However, for example, if the chelating group contains nitrogen elements, such as aminocarboxylic acid-based or aminophosphonic acid-based chelating groups, and the polymer compound portion (the polymer portion into which the chelating group is introduced) does not contain nitrogen elements, a method may be employed in which elemental analysis is performed on the chelating group-containing polymer compound to determine the nitrogen atom content, and the molar amount of chelating group content is calculated from that content. The method of elemental analysis is not particularly limited, but for example, a MICRO CORDER JM10 manufactured by J-Science Co., Ltd. may be used as the measuring device, and the sample is completely combusted in an oxygen atmosphere to produce CO ２ , H ２ O, N ２ A method can be employed in which the amount of each element is determined by measuring the thermal conductivity with a thermal conductivity detector.

[0048] <Polyol having 2 to 4 hydroxyl groups per molecule and a molecular weight of 60 to 180> In this disclosure, the polyol is a compound that satisfies the conditions of having 2 to 4 hydroxyl groups per molecule and a molecular weight of 60 to 180. Such polyols are components used as plasticizers.

[0049] In such polyols, the number of hydroxyl groups in one molecule is 2 to 4. That is, the polyol must be a compound having 2 to 4 hydroxyl groups (-OH) in one molecule. Setting the number of hydroxyl groups in one molecule to be above the lower limit provides a greater effect in terms of improved miscibility with the alginic acid polymer compound containing the aminocarboxylic acid chelating group, while setting it to be below the upper limit provides a greater effect in terms of optimizing the viscosity of the slurry (improving workability). From a similar viewpoint, it is more preferable that the number of hydroxyl groups in one molecule of such polyol is 3 to 4.

[0050] Furthermore, the molecular weight of such polyols must be between 60 and 180. Setting the molecular weight above the lower limit provides a greater effect in suppressing the volatilization of the polyol during the process, while setting it below the upper limit provides a greater effect in terms of miscibility with the alginic acid-based polymer compound containing the aminocarboxylic acid-based chelating group. From a similar viewpoint, it is more preferable that the molecular weight of such polyols be between 90 and 170. Note that if the polyol is made of a polymer, this molecular weight refers to the weight-average molecular weight of the polymer. The weight-average molecular weight can be measured using a Tosoh HLC-8320GPC as the measuring device, a TSKgel GMPXL column, a 0.1 mol / L phosphate-buffered aqueous solution with a pH of 8.0 as the eluent, polyethylene glycol as the standard sample, and a flow rate of 1 mL / min.

[0051] Furthermore, examples of the polyols include ethylene glycol (molecular weight: 62), diethylene glycol (molecular weight: 106), triethylene glycol (molecular weight: 150), pentylene glycol (molecular weight: 104), butylene glycol (molecular weight: 90), propylene glycol (molecular weight: 76), dipropylene glycol (molecular weight: 134), glycerin (molecular weight: 92, also known as glycerol), diglycerin (molecular weight: 166), and glyceric acid (molecular weight: 106, also known as glycerate). At least one selected from the group consisting of glycolic acid (molecular weight: 76), dihydroxyacetone (molecular weight: 90), trimethylolpropane (molecular weight: 134), erythritol (molecular weight: 122), pentaerythritol (molecular weight: 136), xylose (molecular weight: 150), arabinose (molecular weight: 150), ribose (molecular weight: 150), deoxyribose (molecular weight: 134), glucosamine (molecular weight: 179), and ascorbic acid (molecular weight: 176) can be suitably used.

[0052] Among such polyols, at least one of diethylene glycol, triethylene glycol, glycerin, diglycerin, trimethylolpropane, erythritol, and pentaerythritol is preferred, and at least one of glycerin, diglycerin, trimethylolpropane, erythritol, and pentaerythritol is more preferred, from the viewpoint of more effectively suppressing the volatilization of the polyol during the process and improving miscibility with the alginic acid polymer compound containing the aminocarboxylic acid chelating group. Such polyols may be used individually or in combination of two or more.

[0053] In this disclosure, the slurry contains the polyol in combination with an alginate polymer compound containing the aminocarboxylic acid chelating group. By using these components in combination, it becomes easier to achieve high-level control over the volatilization of volatile components including the polyol during the process, control the miscibility with the alginate polymer compound containing the aminocarboxylic acid chelating group, and optimize the viscosity of the slurry (improving workability). This makes it possible to obtain a higher effect by uniformly dispersing the polyol in the composite layer.

[0054] <Aqueous Solvents> In this disclosure, aqueous solvents are components that function as solvents or dispersion media for a slurry. Such aqueous solvents may consist solely of water, or they may be mixed solvents of water and organic solvents. For example, pure water and deionized water can be suitably used as such water.

[0055] Furthermore, if the aqueous solvent contains an organic solvent, it is preferable that the organic solvent is miscible with water. Examples of such organic solvents include at least one alcohol selected from the group consisting of methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol (IPA), n-butyl alcohol, s-butyl alcohol, isobutyl alcohol, and t-butyl alcohol; at least one ester selected from the group consisting of methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, methoxybutyl acetate, cellosolve acetate, amyl acetate, methyl lactate, ethyl lactate, and butyl lactate; at least one ketone selected from the group consisting of acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, and cyclohexanone; at least one amide selected from the group consisting of N-methyl-2-pyrrolidone, N,N-dimethylacetamide, and N,N-dimethylformamide; and sulfoxides such as dimethyl sulfoxide. Organic solvents may be used individually or in combination of two or more. Furthermore, when the aqueous solvent is a mixed solvent of water and an organic solvent, the proportion of the organic solvent contained in the mixed solvent is preferably 1 to 50% by mass, and more preferably 1 to 20% by mass.

[0056] Furthermore, such an aqueous solvent is particularly preferably water, from the viewpoint of improving miscibility with the alginic acid-based polymer compound containing the aminocarboxylic acid-based chelating group.

[0057] <Regarding other usable components> Furthermore, the slurry for forming a lithium-ion battery cathode composite layer according to one aspect of the present disclosure may contain the cathode active material; an alginic acid polymer compound containing an aminocarboxylic acid chelating group; a polyol having 2 to 4 hydroxyl groups in its molecule and a molecular weight of 60 to 180; and the aqueous solvent; and other components may be used as appropriate, as long as their effect is not impaired.

[0058] Such other components are not particularly limited, but for example, known components used when forming the positive electrode composite layer of lithium-ion batteries can be used as appropriate, such as conductive additives, components that can be used as binders other than the alginic acid polymer compounds containing the aminocarboxylic acid chelating group (hereinafter, for convenience, sometimes simply referred to as "other binder components"), dispersants, plasticizer components other than the polyol, etc. Below, components that can be suitably used as such other components will be described separately.

[0059] <Conductive additive> The slurry for forming the lithium-ion battery positive electrode composite layer is preferably further to contain a conductive additive. Therefore, one preferred embodiment of the slurry for forming the lithium-ion battery positive electrode composite layer is a slurry comprising: the positive electrode active material; an alginic acid polymer compound containing an aminocarboxylic acid chelating group; a polyol having 2 to 4 hydroxyl groups in the molecule and a molecular weight of 60 to 180; an aqueous solvent; and a conductive additive.

[0060] Such conductive additives are not particularly limited, and known electronically conductive materials used in the field of lithium batteries can be used as appropriate. Examples of such conductive additives include at least one carbon selected from the group consisting of carbon black (CB), acetylene black (AB), graphene, graphite, fullerene, single-walled carbon nanotubes (SWCNT), multi-walled carbon nanotubes (MWCNT), branched carbon nanotubes (b-CNT), carbon nanofibers (CNF), and carbon nanobelts (CNB); poly(styrene sulfonate)-doped poly(3,4-ethylenedioxythiophene) (PEDOT:PSS), poly(styrene sulfonate)-doped polyaniline (PANI:PSS), poly(styrene sulfonate)-doped polypyrrole, poly(styrene sulfonate)-doped polythiophene, polycarboxylic acid-doped poly(3,4-ethylenedioxythiophene), polycarboxylic acid-doped polyaniline, and polycarboxylic acid-doped poly(styrene sulfonate) Examples include lipyrrole, polycarboxylic acid-doped polythiophene, poly(3,4-ethylenedioxythiophene) (SELFTRON®), polyaniline with sulfonate groups in its side chains, polypyrrole with sulfonate groups in its side chains, polythiophene with sulfonate groups in its side chains, poly(3,4-ethylenedioxythiophene) with carboxyl groups in its side chains, polyaniline with carboxyl groups in its side chains, polypyrrole with carboxyl groups in its side chains, polythiophene with carboxyl groups in its side chains, polyacetylene, polyaniline, polypyrrole, and polythiophene; at least one metal powder or metal fiber selected from the group consisting of Cu, Fe, Ag, Ni, Pd, Au, Pt, In, and W; and at least one conductive metal oxide selected from the group consisting of indium oxide and tin oxide.

[0061] As such a conductive additive, carbon is preferred because it provides a higher effect in terms of conductive path formation, and in particular, carbon nanotubes (CNTs) are preferred. Such conductive additives may be used individually or in combination of two or more.

[0062] <Other Binder Components> The slurry for forming the lithium-ion battery positive electrode composite layer may also contain other binder components.

[0063] Such other components are not particularly limited, and known components usable as binders in the field of lithium-ion batteries (known binders, etc.) may be used as appropriate. For example, other polymers usable as binders (preferably added to the slurry in the form of an aqueous polymer emulsion), silane coupling agents, and inorganic components (e.g., colloidal silica, biphosphates, alumina sols) are suitable. Among these, it is preferable to use other polymers usable as binders from the viewpoint of further improving the adhesion between the composite layer and the current collector, and from the viewpoint of imparting flexibility to the positive electrode. Such other polymers are preferably highly flexible polymers (flexible polymers).

[0064] Suitable flexible polymers for this purpose (polymers usable as binders other than the alginic acid-based polymer compounds containing the aminocarboxylic acid-based chelating group) include, for example, at least one fluororesin selected from the group consisting of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, perfluoromethyl vinyl ether-tetrafluoroethylene copolymer, polytetrafluoroethylene, and fluororubber; and at least one hydrocarbon elastomer selected from the group consisting of styrene-butadiene copolymer (styrene-butadiene rubber (SBR)) and ethylene-propylene copolymer. Furthermore, suitable flexible polymers for this purpose include polymers containing at least one aromatic vinyl monomer selected from the group consisting of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, and styrene-butadiene copolymer, and an aliphatic conjugated diene monomer. Additionally, metal salts of polyacrylic acid can be cited as a suitable example of such flexible polymers. Furthermore, suitable flexible polymers as other polymers are preferably at least one of the following: metal salts of polyacrylic acid, polyvinylidene fluoride and its copolymers, and polymers containing aromatic vinyl monomers and aliphatic conjugated diene monomers; more preferably at least one of the following: polyvinylidene fluoride and its copolymers, and polymers containing aromatic vinyl monomers and aliphatic conjugated diene monomers; and even more preferably at least one of the following: polyvinylidene fluoride and its copolymers, and copolymers containing at least styrene monomer and butadiene monomer. Such flexible polymers may also be used as mixtures of two or more types; for example, a mixture of styrene-butadiene rubber and acrylic copolymer (acrylic resin), or a mixture of polyvinylidene fluoride and acrylic copolymer can be suitably used.

[0065] Furthermore, other polymers that can be used as such binders are not limited to those mentioned above, and for example, vinyl acetate, ethylene vinyl acetate (EVA) copolymers, acrylic acid esters, vinyl versatate esters, styrene acrylic acid copolymers, rosin esters, chloroprene, polyurethane, polyvinyl alcohol (PVA), and cellulose can also be suitably used.

[0066] Furthermore, the molecular weight of such other polymers is preferably 50,000 to 2,000,000, and more preferably 100,000 to 1,000,000, in weight-average molecular weight. When the weight-average molecular weight is within this range, flexibility and sufficient mechanical strength can be imparted to the cathode composite layer more efficiently. The "weight-average molecular weight" of the flexible polymer can be determined by using a GPC as the measuring device, selecting a solvent that dissolves the polymer as the eluent, and using polyethylene glycol as the standard sample.

[0067] Furthermore, it is preferable that such other polymers are added to the slurry in the form of an emulsion in which the polymer is dispersed in an aqueous medium (aqueous polymer emulsion). Here, "aqueous" in aqueous polymer emulsion refers to a solvent mainly composed of water, and it is preferable that it be the same as the aqueous solvent mentioned above. Also, the emulsion in aqueous polymer emulsion refers to a dispersion medium in which fine particles are dispersed, and the size of the fine particles is approximately tens to hundreds of nanometers. The dispersion state of the polymer in the emulsion may be confirmed by whether or not sedimentation occurs from the static state.

[0068] Furthermore, specific examples of such water-based polymer emulsions include emulsions of styrene-butadiene rubber and acrylic copolymers, emulsions of polyvinylidene fluoride and acrylic copolymers, acrylic acid ester emulsions, vinyl versatate ester emulsions, vinyl acetate emulsions, ethylene-vinyl acetate (EVA) copolymer emulsions, styrene-acrylic acid copolymer emulsions, rosin ester emulsions, chloroprene emulsions, polyurethane emulsions, polyvinyl alcohol (PVA) emulsions, cellulose emulsions, and styrene-butadiene rubber emulsions. As such water-based polymer emulsions, emulsions of the aforementioned flexible polymers are preferred, and among them, styrene-butadiene rubber-acrylic copolymer emulsions and polyvinylidene fluoride-acrylic copolymer emulsions are preferred from the viewpoint of having a low glass transition temperature and easily becoming rubbery even at room temperature.

[0069] Furthermore, the proportion (content) of polymer in such an aqueous polymer emulsion is preferably 20% to 60% by mass, and more preferably 30% to 50% by mass. The method for preparing such an aqueous emulsion is not particularly limited, and known methods can be used as appropriate. Commercially available products may also be used as such aqueous polymer emulsions.

[0070] Furthermore, when such an aqueous polymer emulsion is included in a slurry, the water-based solvent in the emulsion becomes part of the aqueous solvent in the slurry.

[0071] A suitable example of a slurry for forming a lithium-ion ionization material layer in a form containing such other binder components is a slurry comprising, for example, the positive electrode active material; an alginate polymer compound containing an aminocarboxylic acid chelating group; the other polymer (a polymer derived from the aqueous polymer emulsion); a polyol having 2 to 4 hydroxyl groups in the molecule and a molecular weight of 60 to 180; the aqueous solvent; and a conductive additive.

[0072] <Dispersant> The slurry for forming the lithium-ion battery cathode composite layer may further contain a dispersant from the viewpoint of achieving a more uniform dispersion state of each component in the slurry. As such a dispersant, at least one polysaccharide selected from the group consisting of polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyacrylic acid (PAA), and carboxymethylcellulose (CMC) can be suitably used.

[0073] <Regarding other additive components such as plasticizer components other than the polyol> In addition, the slurry for forming the lithium-ion battery positive electrode composite layer may further contain other plasticizer components along with the polyol. Examples of such other plasticizer components include at least one selected from the group consisting of maltol, methyl glucopyranoside, glutamic acid, aspartic acid, hydroxyproline, galacturone, succinic acid, malic acid, and lactic acid.

[0074] Furthermore, the slurry for forming the lithium-ion battery cathode composite layer may optionally contain a pH adjusting agent such as an acid or alkali.

[0075] <Regarding the content of each component in the slurry> In the slurry for forming a lithium-ion battery cathode composite layer according to this disclosure, the solid content concentration of the slurry is not particularly limited, but from the viewpoint of optimizing the viscosity of the slurry (improving workability), improving the dispersibility of the solid content, and reducing the load on the drying process, it is preferably 20 to 80% by mass, and more preferably 40 to 75% by mass. By setting the solid content concentration within the above range, a greater effect can be obtained in terms of improving the coatability of the slurry (allowing the coating of a composite layer with a uniform film thickness).

[0076] In the lithium-ion battery cathode composite layer forming slurry according to this disclosure, the content of the cathode active material is preferably 85% by mass, more preferably 90% by mass or more, and even more preferably 94% by mass or more, based on the total mass of all components other than the aqueous solvent contained in the slurry (mass of solids in the slurry). By setting the content of the cathode active material to above the lower limit, a greater effect can be obtained in terms of increasing the capacity of the battery and improving the charge and discharge characteristics. The upper limit of the content of the cathode active material is less than 100% by mass or 99% by mass or less. In this specification, "total mass of all components other than the aqueous solvent contained in the slurry" refers to the total mass of all components other than the aqueous solvent present in the slurry (mass of solids in the slurry). For example, if the slurry for forming the positive electrode composite layer of a lithium-ion battery contains essential components such as the positive electrode active material, the alginic acid polymer compound containing the aminocarboxylic acid chelating group, the polyol having 2 to 4 hydroxyl groups in its molecule and a molecular weight of 60 to 180, and the aqueous solvent, along with other components (for example, the aforementioned conductive additive), then "total mass of all components, including the essential components other than the aqueous solvent and the other components" refers to the total mass of all components. When an aqueous polymer emulsion is added to the slurry, the water-based solvent in the aqueous polymer emulsion becomes indistinguishable from the aqueous solvent in the slurry. Therefore, the total mass of all components can be determined by using the mass of the component (solids) obtained by removing the solvent from such an aqueous polymer emulsion.

[0077] Furthermore, in the lithium-ion battery cathode composite layer forming slurry of the present disclosure, the content of the alginate polymer compound containing the aminocarboxylic acid chelating group is preferably 2 to 5% by mass, and more preferably 2 to 3% by mass, relative to the total mass of all components other than the aqueous solvent contained in the slurry. By setting the content of such alginate polymer compound to above the lower limit, a greater effect can be obtained in terms of improving the binding properties between the particles of the cathode active material, while by setting the content to below the upper limit, a greater effect can be obtained in terms of increasing the battery capacity and improving the charge-discharge characteristics.

[0078] Furthermore, in the slurry for forming a lithium-ion battery cathode composite layer according to this disclosure, the mass ratio of the cathode active material to the alginate polymer compound containing the aminocarboxylic acid chelate group ([cathode active material]:[alginate polymer compound]) is preferably 90:10 to 98:2, more preferably 93:7 to 98:2, and even more preferably 95:5 to 98:2. In such a mass ratio, setting the ratio of the alginate polymer compound above the lower limit provides a greater effect in terms of increasing the battery's capacity and improving its charge-discharge characteristics, while setting it below the upper limit provides a greater effect in terms of improving the bonding between the particles of the cathode active material.

[0079] In the slurry for forming a lithium-ion battery cathode composite layer according to this disclosure, the ratio of the mass of the polyol to the mass of the alginate polymer compound containing the aminocarboxylic acid chelating group ([mass of polyol] / [mass of alginate polymer compound]) is preferably 1 to 5, and more preferably 1 to 3. Setting such a ratio (mass ratio of the alginate polymer compound to the polyol) above the lower limit provides a greater effect in improving the flexibility of the composite layer, while setting such a mass ratio below the upper limit provides a greater effect in reducing the penetration resistance of the composite layer.

[0080] Furthermore, in the lithium-ion battery cathode composite layer forming slurry according to this disclosure, the polyol content is preferably 1.5% by mass or more, more preferably 1.7% by mass or more, and even more preferably 2% by mass or more, based on the total mass of all components other than the aqueous solvent contained in the slurry. By setting the polyol content above the lower limit, a greater effect in terms of improving the flexibility of the composite layer can be obtained. In addition, the polyol content may be 5.0% by mass or less, 4.0% by mass or less, or 3.0% by mass or less, based on the total mass of all components other than the aqueous solvent contained in the slurry. When the polyol content is below the upper limit, a greater effect in terms of reducing the penetration resistance of the composite layer can be obtained compared to when it exceeds the upper limit.

[0081] Furthermore, in the slurry for forming a lithium-ion battery cathode composite layer according to this disclosure, as described above, an alginate polymer compound containing the aminocarboxylic acid chelating group is used as the binder for the cathode. The ratio of the mass of the solid content of such an alginate polymer compound binder (the binder described herein may contain other binder components as described above, or may contain only the alginate polymer compound) to the mass of the polyol ([the binder]:[the polyol]) is preferably 1:5 to 1:1, more preferably 1:4 to 1:1, and even more preferably 1:3 to 1:1. In such a mass ratio, setting the ratio of the binder above the lower limit provides a greater effect in reducing the penetration resistance of the composite layer, while setting the ratio of the binder below the upper limit provides a greater effect in improving the flexibility of the composite layer.

[0082] Furthermore, in the slurry for forming a lithium-ion battery positive electrode composite layer according to this disclosure, when the aforementioned other polymer (more preferably a flexible polymer) is added as another binder component, the binder of the positive electrode can consist of an alginate polymer compound containing the aminocarboxylic acid chelating group and the other polymer (or, if an aqueous polymer emulsion is used for the addition of such polymer, the dried product thereof). In this case, the mass ratio of the alginate polymer compound to the other polymer (for example, the dried product of an aqueous polymer emulsion) ([the alginate polymer compound]:[the other polymer]) is preferably 50 to 90:10 to 50, and more preferably 60 to 80:20 to 40. In such a mass ratio, setting the ratio of the alginate polymer compound above the lower limit provides a greater effect in improving the bonding between the particles of the positive electrode active material, while setting the ratio of the alginate polymer compound below the upper limit provides a greater effect in improving the bonding between the composite layer and the current collector foil.

[0083] Furthermore, in the lithium-ion battery cathode composite layer forming slurry of the present disclosure, the binder content is preferably 1 to 10% by mass, and more preferably 1 to 5% by mass, based on the total mass of all components other than the aqueous solvent contained in the slurry.

[0084] Furthermore, in the slurry for forming the positive electrode composite layer of a lithium-ion battery according to this disclosure, when the conductive additive is included, the content of the conductive additive is preferably 0.1 to 10% by mass relative to the positive electrode active material contained in the slurry. Setting the content of the conductive additive above the lower limit provides a greater effect in reducing the penetration resistance of the composite layer, while setting it below the upper limit provides a greater effect in increasing the battery capacity and improving the charge-discharge characteristics. In addition, when a conductive additive is included in this way, the mass ratio of the positive electrode active material, conductive additive, and binder in terms of solid content (positive electrode active material: conductive additive: binder) is preferably 70 to 98: 0.1 to 10: 1 to 20, and more preferably 90 to 98: 0.1 to 5: 1 to 5.

[0085] Furthermore, in the slurry for forming a lithium-ion battery cathode composite layer according to this disclosure, when the dispersant is included, the content of the dispersant is preferably 0.01 to 2% by mass, and more preferably 0.01 to 1% by mass, based on the total mass of all components other than the aqueous solvent contained in the slurry. By setting the content of the dispersant to above the lower limit, all components other than the aqueous solvent contained in the slurry can be dispersed more uniformly, while setting it to below the upper limit yields greater benefits in terms of increasing the battery capacity and improving charge-discharge characteristics.

[0086] Furthermore, the method for producing the slurry for forming the lithium-ion battery cathode composite layer according to this disclosure is not particularly limited, but examples include: a method of adding the alginate polymer compound containing the aminocarboxylic acid chelating group and the cathode active material (and, if necessary, other binder components and / or conductive additives together) to an aqueous solvent (preferably water) and mixing them to disperse and / or dissolve each component in the aqueous solvent to produce a slurry; a method of first dissolving and / or dispersing the alginate polymer compound containing the aminocarboxylic acid chelating group (or, if other binder components are used, the alginate polymer compound and other binder components) in water to obtain an aqueous solution or dispersion, and then adding the cathode active material (or, if conductive additives are used, the cathode active material and conductive additives) to the aqueous solution or dispersion and mixing them to produce a slurry; and a method of mixing the cathode active material (or, if conductive additives are used, the cathode active material and conductive additives) with an aqueous solution or dispersion of the binder components.

[0087] Furthermore, when manufacturing the slurry for forming the cathode composite layer of lithium-ion batteries according to this disclosure, a mixer can be used as appropriate. There are no particular restrictions on such mixers, and mortars, roll mills, ball mills, screw mills, vibratory mills, homogenizers, planetary mixers, etc., can be used as appropriate.

[0088] Furthermore, in the method for producing the lithium-ion battery cathode composite layer slurry described above, when adding the other polymer (more preferably a flexible polymer) to the slurry, it is preferable to add an aqueous polymer emulsion to the slurry. By preparing the slurry using an aqueous polymer emulsion in this way, it becomes possible to produce a cathode with higher flexibility more efficiently.

[0089] According to the lithium-ion battery positive electrode composite layer forming slurry of this disclosure, for example, by applying it to a current collector and drying it, it is possible to efficiently produce an electrode composite layer (positive electrode composite layer) consisting of a dried coating film on the current collector, and it is also possible to efficiently produce a positive electrode for a lithium-ion battery in a form consisting of a positive electrode composite layer and a current collector. Furthermore, according to the lithium-ion battery positive electrode composite layer forming slurry of this disclosure, when producing a positive electrode composite layer using it, the composite layer can be prepared in a practical basis weight (preferably 20 mg / cm³). ２ For a comfortable level, use 25 mg / cm³. ２ While having a practical film thickness (preferably 100 μm or more, more preferably 120 μm or more), the composite layer can be given excellent flexibility at any stage, both during the manufacturing process and after manufacturing. Therefore, with the lithium-ion battery cathode composite layer forming slurry of this disclosure, a cathode with excellent flexibility can be efficiently manufactured without performing an undercoat layer formation process (without increasing the number of steps). Furthermore, with the lithium-ion battery cathode composite layer forming slurry of this disclosure, cracks and peeling of the cathode composite layer can be suppressed to a high degree during the cathode manufacturing process and the process of winding the cathode after manufacturing, thereby improving the manufacturing yield of the cathode. The upper limit of the basis weight (coating amount) of the cathode composite layer is 50 mg / cm². ２ The following or 40 mg / cm³ ２ The following are some examples:

[0090] [Positive electrode for lithium-ion battery] A positive electrode for a lithium-ion battery according to one aspect of the present disclosure comprises a positive electrode composite layer consisting of a dried coating film of the lithium-ion battery positive electrode composite layer forming slurry described above.

[0091] In one aspect of the present disclosure, it is preferable that the positive electrode for a lithium-ion battery comprises a positive electrode composite layer consisting of a dried coating obtained by applying the above-mentioned slurry for forming a lithium-ion battery positive electrode composite layer of the present disclosure onto a current collector and drying it, and the current collector. Thus, in the positive electrode for a lithium-ion battery of the present disclosure, a current collector and a positive electrode composite layer consisting of a dried coating of the slurry for forming a lithium-ion battery positive electrode composite layer of the present disclosure, laminated on the current collector, can be cited as a preferred example (preferred embodiment).

[0092] Furthermore, from a practical standpoint, the thickness of such a positive electrode composite layer is preferably 100 μm or more, and more preferably 120 μm or more. The upper limit of the thickness of the positive electrode composite layer is 300 μm or less, or 250 μm or less. Also, from a practical standpoint, the basis weight (coating amount) of the positive electrode composite layer is 20 mg / cm². ２ Preferably, the amount is 25 mg / cm² or more. ２ It is more preferable to have the above. In the lithium-ion battery cathode of the present disclosure, since the cathode composite layer consists of a dried coating of the slurry for forming the lithium-ion battery cathode composite layer of the present disclosure, even if the thickness (film thickness) and basis weight of the cathode composite layer are within the above range, the cathode composite layer will have excellent flexibility.

[0093] Furthermore, the current collector can be any conductor whose surface in contact with the electrode composite layer (positive electrode composite layer) exhibits conductivity, and is not particularly limited otherwise. For example, a conductor made of at least one metal selected from the group consisting of copper, gold, aluminum, titanium, nickel, stainless steel and their alloys, at least one conductive metal oxide selected from the group consisting of indium oxide and tin oxide, or conductive carbon can be used as appropriate. There are also no particular restrictions on the shape of the current collector, and shapes such as foil, film, sheet, net, expanded metal, perforated metal, and foam can be used. There are also no particular restrictions on the thickness of the current collector, for example, it can be 1 to 100 μm.

[0094] The method for manufacturing the positive electrode for lithium-ion batteries according to the present disclosure is not particularly limited, but it is preferable to employ the method of applying the slurry of the present disclosure onto a current collector and drying it, as this allows for efficient manufacturing of the positive electrode.

[0095] Furthermore, the method of applying the slurry onto the current collector is not particularly limited, and known methods such as slit coating, die coating, roll coating, dip coating, blade coating, knife coating, and wire bar coating can be used as appropriate.

[0096] Furthermore, there are no particular restrictions on the method or conditions for drying the slurry when manufacturing the positive electrode. For example, known drying methods (including drying conditions) using conventional hot air circulation dryers, vacuum dryers, infrared dryers, microwave heating dryers, etc., can be used as appropriate. Also, when heating is used during drying, there are no restrictions on the heating temperature. For example, the slurry may be heated to 50 to 150°C for drying. Moreover, when manufacturing the positive electrode, it is preferable to press and roll the electrode under pressure during or after drying to make the porous structure uniform. By carrying out the drying and, if necessary, press-rolling processes as described above, a positive electrode composite layer consisting of the dried slurry coating can be efficiently manufactured on the current collector.

[0097] Thus, when manufacturing a cathode composite layer consisting of a dried coating film using the lithium-ion battery cathode composite layer forming slurry of this disclosure described above, excellent flexibility can be imparted to the cathode composite layer at both the manufacturing process and the post-manufacturing stage. For example, the occurrence of cracks and delamination can be highly prevented both before and after rolling by pressing as described above. Therefore, it becomes possible to manufacture cathodes with a high manufacturing yield.

[0098] [Lithium-ion battery] A lithium-ion battery according to one aspect of the present disclosure has the positive electrode for the lithium-ion battery described above.

[0099] The lithium-ion battery of this disclosure requires the use of the lithium-ion battery positive electrode described above as the positive electrode, but the other components are not particularly limited and may be the same as those used in known lithium-ion batteries. A preferred example of such a lithium-ion battery of this disclosure is one composed of a positive electrode (the lithium-ion battery positive electrode described above as the positive electrode), a negative electrode, a separator, a non-aqueous electrolyte, etc. (such as one in a laminate cell shape).

[0100] In such a lithium-ion battery, the positive electrode must be the lithium-ion battery positive electrode described above. The negative electrode can be any known material, and is not particularly limited; however, a negative electrode having a configuration in which a negative electrode active material and the above-mentioned conductive additive are bound to a negative electrode current collector with a binder is preferably used. Such negative electrode active material and negative electrode binder are not particularly limited, and known materials can be used as appropriate.

[0101] Furthermore, the separator can be any type suitable for lithium batteries, and any separator known in the field of lithium-ion batteries can be used as appropriate; it is not particularly limited. Examples of such separators include porous films such as polyolefins, and more specifically, polyethylene microporous membranes; polypropylene microporous membranes; laminated films of polyethylene microporous membranes and polypropylene microporous membranes; and nonwoven fabrics made of at least one selected from the group consisting of polyester fibers, aramid fibers, and glass fibers. Since such a separator performs a shutdown function when the battery experiences thermal runaway, it is preferable to position it so as to be sandwiched between the positive and negative electrodes.

[0102] Furthermore, the non-aqueous electrolyte is not particularly limited, but LiPF ４ These electrolyte salts can be suitably used in solutions of cyclic carbonates or other organic solvents.

[0103] Furthermore, for a lithium-ion battery composed of a positive electrode, a negative electrode, a separator, a non-aqueous electrolyte, and other components, it is preferable that the interior of the battery is filled with the non-aqueous electrolyte. This allows efficient movement of lithium ions from the positive electrode to the negative electrode during battery charging, and from the negative electrode to the positive electrode during battery discharging.

[0104] There are no particular limitations on such a non-aqueous electrolyte, and publicly known materials can be used. The non-aqueous electrolyte is obtained by dissolving an electrolyte salt in an organic solvent. As the electrolyte salt, CF ３ SO ３ Li, (CF ３ SO ２ ) ２ NLi, (CF ３ SO ２ ) ２ CLi, LiBF ４ , LiB(C ６ H ８ ) ４ , LiPF ４ , LiClO ４ , LiAsF ６ , LiCl, and LiBr. Examples of the organic solvent for dissolving the electrolyte salt include at least one selected from the group consisting of ethylene carbonate, vinylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 1,4-dioxane, anisole, diethyl ether, sulfolane, methylsulfolane, acetonitrile, propionitrile, butyronitrile, valeronitrile, benzonitrile, dimethylformamide, dimethyl sulfoxide, trimethyl phosphate, and triethyl phosphate. The concentration of the electrolyte salt in the non-aqueous electrolyte is preferably selected in the range of 0.1 to 5 mol / L (more preferably 0.5 to 3 mol / L).

[0105] The method for manufacturing such a lithium-ion battery is not particularly limited, and it can be manufactured using known methods, except that the positive electrode for the lithium-ion battery described above is used as the positive electrode.

[0106] The embodiments of this disclosure will be described in more detail below based on examples, but the embodiments of this disclosure are not limited to these examples.

[0107] Here, we will first explain the method for evaluating the characteristics of the positive electrodes and other components manufactured in the examples described below.

[0108] [Method for Evaluating the Characteristics of the Positive Electrode, etc.] <Confirmation of the Appearance of the Positive Electrode Precursor> In each example, the appearance (electrode appearance) of the dried coating film (dried coating film of slurry: immediately after drying) in the positive electrode precursor obtained during the manufacture of the positive electrode was visually inspected to check for the presence or absence of cracks on the surface of the dried coating film. The results obtained are shown in Table 1. In the table, "A" is written for those in which no cracks were observed in the appearance, and "B" is written for those in which cracks were observed in the appearance.

[0109] <Evaluation of Flexibility (Bendability) of Positive Electrode Precursor by Winding Test> In each example, the positive electrode precursor obtained during the manufacturing of the positive electrode was wound around a metal rod with a diameter of 3.2 cm, and the presence or absence of cracks and peeling of the dried coating on the surface of the dried coating was checked. The results obtained (results of the winding test) are shown in Table 1. In the table, "A" indicates that neither cracks nor peeling occurred, and "B" indicates that both cracks and peeling occurred.

[0110] <Confirmation of the appearance of the positive electrode> The positive electrodes obtained in each example were visually inspected for their appearance (electrode appearance) to check for the presence or absence of cracks on the surface of the asphalt layer after press rolling. The results are shown in Table 1. In the table, electrodes in which no cracks were observed on the appearance are marked "A", and electrodes in which cracks were observed on the appearance are marked "B".

[0111] <Evaluation of Flexibility (Bendability) of Positive Electrode by Winding Test> The positive electrodes manufactured in each example were wound around a metal rod with a diameter of 3.2 cm, and the presence or absence of cracks in the asphalt layer after press rolling and the presence or absence of delamination of the asphalt layer were checked. The results obtained (results of the winding test) are shown in Table 1. In the table, "A" indicates that neither cracks nor delamination occurred, and "B" indicates that both cracks and delamination occurred.

[0112] <Measurement of Peel Strength> A polyester tape (7.3 N / 19 mm, manufactured by Nitto Denko Corporation) was laminated onto the surface of the composite material layer of the positive electrode manufactured in each example, and the peel strength was measured when the composite material layer was peeled off the current collector using a tensile testing machine (MCT-2150W, A&D Corporation) at a peeling speed of 100 mm / min. The results obtained are shown in Table 1. If the peel strength measured in this way is 10 mN / mm or higher (>10), it can be said that the peeling of the composite material layer was suppressed to a high degree.

[0113] <Measurement of Electrical Resistance> Two positive electrodes, punched to a diameter of 13.8 cm, were stacked in a jig with the composite material layers facing each other. In this state, a force of 100 kg was applied to the jig using a press machine (J2-D, AS ONE Corporation) in the direction from the current collector to the composite material layer. The electrical resistance (through resistance) in the direction from the current collector to the composite material layer was measured using a resistance meter (BT3562, HIOKI E.E. CORPORATION) at room temperature (25°C) using the two-probe method, applying a current of 100 mA to 10 μA (auto-ranging). The results obtained are shown in Table 1. If the through resistance measured in this way is 10 Ω or less, it can be said that the electrode is suitable for use as a battery electrode.

[0114] [Regarding the manufacture of slurry and cathode for cathode composite layer production] First, in Reference Example 1, the method for producing the component used in the production of the slurry (alginic acid into which tetrasodium ethylenediaminetetraacetate groups have been introduced by ionic bonding) will be explained, and then the method for producing the slurry and cathode will be explained in each example.

[0115] (Reference Example 1) <Production of alginic acid having ethylenediaminetetraacetic acid tetrasodium groups introduced therein via ionic bonding (ionic conjugate of hydrogen-form alginic acid and ethylenediaminetetraacetic acid tetrasodium)> 1.0 g (5.7 mmol as monosaccharide units) of hydrogen-form alginic acid (manufactured by Kimica Corporation, trade name: Kimica Acid G) was added little by little to 100 ml of pure water under stirring to prepare a white paste-like homogeneous dispersion (alginic acid dispersion). Next, a solution obtained by dissolving 2.37 g (5.7 mmol) of ethylenediaminetetraacetic acid tetrasodium (manufactured by Tokyo Chemical Industry Co., Ltd.) in 20 ml of pure water was added dropwise to the above alginic acid dispersion. Along with the dropwise addition of this solution, the dispersion gradually became transparent, and turned into a transparent viscous aqueous solution after the completion of the dropwise addition. After this aqueous solution was stirred at room temperature (25°C) for 1 hour, it was added dropwise to 4 L of acetone to form a precipitate. The obtained precipitate was collected by filtration, further washed with acetone, and then isolated by drying under reduced pressure. The isolated yield was 2.4 g, the nitrogen content determined by elemental analysis was 3.9% by mass, and the chelate functional group content calculated from the nitrogen content was 1.4 mmol / g. As described above, based on the detection of nitrogen element by elemental analysis, the types of raw materials used, and the like, it can be confirmed that the isolated component is alginic acid having ethylenediaminetetraacetic acid tetrasodium groups introduced therein via ionic bonding. Hereinafter, for convenience, the component isolated in this manner is sometimes referred to as "chelate group-containing alginic acid".

[0116] In addition, in order to confirm that ethylenediaminetetraacetic acid tetrasodium groups have been introduced into alginic acid, FT-IR spectra before and after the reaction were compared. Hydrogen-form alginic acid before the reaction has a peak at 1740 cm －１ where absorption derived from the stretching vibration of the carbonyl of carboxylic acid was observed, whereas after the reaction, the peak at 1740 cm －１ disappeared, and the peak at 1600 cm －１A new absorption was observed, originating from the stretching vibration of the carbonyl group of the carboxylate salt. This indicates that alginic acid and the tetrasodium ethylenediaminetetraacetate group are bonded via ionic bonding, and the isolated component is alginic acid into which the tetrasodium ethylenediaminetetraacetate group has been introduced via ionic bonding. Next, the molecular weight of the obtained compound was measured using aqueous GPC. The weight-average molecular weight was 350,000.

[0117] (Example 1) <Slurry Preparation> 29.03 g of lithium manganate compound (LMO, manufactured by Toyoshima Seisakusho, used as cathode active material), 0.15 g of chelate-containing alginic acid (used as binder) prepared in Reference Example 1, 0.75 g of glycerin (manufactured by Wako Pure Chemical Industries, a polyol used as a plasticizer, molecular weight: 92), and 8.0 g of pure water were placed in a 150 mL polyethylene ointment container and kneaded at 2000 rpm for 3 minutes using a rotary-orbit mixer (ARE-310, manufactured by THINKY). Next, 7.5 g of an aqueous dispersion (WPB-030, manufactured by Kusumoto Chemical Co., Ltd., solvent: water) containing 0.40% by mass of single-walled carbon nanotubes (SWCNTs) as a conductive additive and 0.6% by mass of carboxymethylcellulose (CMC) as a dispersant was added, and the mixture was stirred and degassed for 1 minute at 2000 rpm using a rotary-orbit mixer (ARE-310, manufactured by THINKY Co., Ltd.) to produce a slurry. The composition of the total components (solids) of the slurry obtained in this way, excluding the aqueous solvent (water), was 96.75% by mass of lithium manganate compound (LMO: positive electrode active material), 0.50% by mass of chelate group-containing alginic acid (binder), 2.5% by mass of glycerin (polyol, plasticizer), 0.10% by mass of SWCNT (conductive additive), and 0.15% by mass of CMC (dispersant). The solids concentration of the slurry was 65% by mass.

[0118] <Manufacturing of positive electrode for lithium-ion battery> The slurry obtained as described above is applied to an aluminum foil (20 μm thick), which is the current collector, using a coater at a speed of 20 mm per second, so that the basis weight of the composite layer is 25 ± 2 mg / cm². ２The material was coated in such a manner, and dried by heating at 100°C for 10 minutes to evaporate the aqueous solvent, thereby producing a positive electrode precursor for lithium-ion batteries (in this embodiment, press rolling is performed after drying, so for convenience it is referred to as a "positive electrode precursor") consisting of the current collector foil and the dried coating film of the slurry.

[0119] Subsequently, the obtained positive electrode precursor was rolled (press-rolled) in a roll press machine to achieve a volume density of 2.5 ± 0.2 g / cc in the composite layer, thereby producing a press-rolled positive electrode for lithium-ion batteries (for convenience, hereafter referred to as simply "positive electrode" or "press-rolled positive electrode" as needed). The resulting positive electrode had a film thickness of approximately 120 μm.

[0120] (Example 2) A slurry and cathode were prepared in the same manner as in Example 1, except that the amount of chelate-containing alginic acid (binder) used was changed to 0.30 g and the amount of glycerin used was changed to 0.6 g. The composition of the total components of the slurry obtained in this manner, excluding the aqueous solvent (water), was 96.75% by mass of lithium manganate compound (LMO: cathode active material), 1.0% by mass of chelate-containing alginic acid (binder), 2.0% by mass of glycerin (polyol, plasticizer), 0.10% by mass of SWCNT (conductive additive), and 0.15% by mass of CMC (dispersant). The solid content concentration of the slurry was 65% by mass.

[0121] (Example 3) A slurry and cathode were prepared in the same manner as in Example 1, except that the amount of chelate-containing alginic acid (binder) used was changed to 0.45 g and the amount of glycerin used was changed to 0.45 g. The composition of the total components of the slurry obtained in this manner, excluding the aqueous solvent (water), was 96.75% by mass of lithium manganate compound (LMO: cathode active material), 1.5% by mass of chelate-containing alginic acid (binder), 1.5% by mass of glycerin (polyol, plasticizer), 0.10% by mass of SWCNT (conductive additive), and 0.15% by mass of CMC (dispersant). The solid content concentration of the slurry was 65% by mass.

[0122] (Example 4) A slurry and cathode were prepared in the same manner as in Example 1, except that the amount of chelate-group-containing alginic acid (binder) produced in Reference Example 1 was changed to 0.30 g, and 0.60 g of diglycerin (manufactured by Tokyo Chemical Industry Co., Ltd., molecular weight: 166) was used instead of glycerin. The composition of the total components of the slurry obtained in this manner, excluding the aqueous solvent (water), was 96.75% by mass of lithium manganate compound (LMO: cathode active material), 1.0% by mass of chelate-group-containing alginic acid (binder), 2.0% by mass of diglycerin (polyol, plasticizer), 0.10% by mass of SWCNT (conductive additive), and 0.15% by mass of CMC (dispersant). The solid content concentration of the slurry was 65% by mass.

[0123] (Example 5) A slurry and cathode were prepared in the same manner as in Example 1, except that the amount of chelate-containing alginic acid (binder) produced in Reference Example 1 was changed to 0.30 g, and 0.60 g of ethylene glycol (manufactured by Tokyo Chemical Industry Co., Ltd., molecular weight: 62) was used instead of glycerin. The composition of the total components of the slurry obtained in this manner, excluding the aqueous solvent (water), was 96.75% by mass of lithium manganate compound (LMO: cathode active material), 1.0% by mass of chelate-containing alginic acid (binder), 2.0% by mass of ethylene glycol (polyol, plasticizer), 0.10% by mass of SWCNT (conductive additive), and 0.15% by mass of CMC (dispersant). The solid content concentration of the slurry was 65% by mass.

[0124] (Example 6) A slurry and cathode were prepared in the same manner as in Example 1, except that the amount of chelate-containing alginic acid (binder) produced in Reference Example 1 was changed to 0.30 g, and 0.60 g of diethylene glycol (manufactured by Tokyo Chemical Industry Co., Ltd., molecular weight: 106) was used instead of glycerin. The composition of the total components of the slurry obtained in this manner, excluding the aqueous solvent (water), was 96.75% by mass of lithium manganate compound (LMO: cathode active material), 1.0% by mass of chelate-containing alginic acid (binder), 2.0% by mass of diethylene glycol (polyol, plasticizer), 0.10% by mass of SWCNT (conductive additive), and 0.15% by mass of CMC (dispersant). The solid content concentration of the slurry was 65% by mass.

[0125] (Example 7) A slurry and cathode were prepared in the same manner as in Example 1, except that the amount of chelate-group-containing alginic acid (binder) produced in Reference Example 1 was changed to 0.30 g, and 0.60 g of propylene glycol (manufactured by Tokyo Chemical Industry Co., Ltd., molecular weight: 76) was used instead of glycerin. The composition of the total components of the slurry obtained in this manner, excluding the aqueous solvent (water), was 96.75% by mass of lithium manganate compound (LMO: cathode active material), 1.0% by mass of chelate-group-containing alginic acid (binder), 2.0% by mass of propylene glycol (polyol, plasticizer), 0.10% by mass of SWCNT (conductive additive), and 0.15% by mass of CMC (dispersant). The solid content concentration of the slurry was 65% by mass.

[0126] (Example 8) A slurry and cathode were prepared in the same manner as in Example 1, except that the amount of chelate-containing alginic acid (binder) prepared in Reference Example 1 was changed to 0.30 g, and 0.60 g of pentaerythritol (manufactured by Tokyo Chemical Industry Co., Ltd., molecular weight: 136) was used instead of glycerin. The composition of the total components of the slurry obtained in this manner, excluding the aqueous solvent (water), was 96.75% by mass of lithium manganate compound (LMO: cathode active material), 1.0% by mass of chelate-containing alginic acid (binder), 2.0% by mass of pentaerythritol (polyol, plasticizer), 0.10% by mass of SWCNT (conductive additive), and 0.15% by mass of CMC (dispersant), and the solid content concentration of the slurry was 65% by mass.

[0127] (Example 9) A slurry and cathode were prepared in the same manner as in Example 1, except that the amount of chelate-group-containing alginic acid (binder) prepared in Reference Example 1 was changed to 0.30 g, and 0.60 g of trimethylolpropane (manufactured by Tokyo Chemical Industry Co., Ltd., molecular weight: 134) (manufactured by Tokyo Chemical Industry Co., Ltd.) was used instead of glycerin. The composition of the total components of the slurry obtained in this manner, excluding the aqueous solvent (water), was 96.75% by mass of lithium manganate compound (LMO: cathode active material), 1.0% by mass of chelate-group-containing alginic acid (binder), 2.0% by mass of trimethylolpropane (polyol, plasticizer), 0.10% by mass of SWCNT (conductive additive), and 0.15% by mass of CMC (dispersant), and the solid content concentration of the slurry was 65% by mass.

[0128] (Example 10) In order to use a combination of chelate-containing alginic acid produced in Reference Example 1 and styrene-butadiene rubber (SBR) as a binder, instead of putting 0.15 g of chelate-containing alginic acid produced in Reference Example 1 into a polyethylene ointment container, 0.30 g of chelate-containing alginic acid produced in Reference Example 1 together with 0.30 g of an aqueous emulsion of SBR (TRD2001, solid content concentration 48% by mass, manufactured by ENEOS Material Co., Ltd.) was put into the polyethylene ointment container, and the amount of glycerin used was changed to 0.45 g. The slurry and cathode were produced in the same manner as in Example 1. The composition of the slurry obtained in this way, excluding the aqueous solvent (water), was as follows: lithium manganate compound (LMO: positive electrode active material) 96.75% by mass, chelate group-containing alginic acid (binder) 1.0% by mass, SBR (binder) 0.50% by mass, glycerin (polyol, plasticizer) 1.5% by mass, SWCNT (conductive additive) 0.10% by mass, and CMC (dispersant) 0.15% by mass. The solid content concentration of the slurry was 65% by mass.

[0129] (Example 11) A slurry and cathode were prepared in the same manner as in Example 10, except that 0.30 g of an aqueous emulsion containing polyvinylidene fluoride (PVDF) and acrylic resin (PAA) as polymers (Kynar Aquatec® ARC, solids content 44% by mass, manufactured by Arkema) was used instead of 0.30 g of an aqueous emulsion of SBR. The composition of the slurry obtained in this way, excluding the aqueous solvent (water), was as follows: lithium manganate compound (LMO: positive electrode active material) 96.75% by mass, chelate group-containing alginic acid (binder) 1.0% by mass, mixture of PVDF and PAA (binder) 0.50% by mass, glycerin (polyol, plasticizer) 1.5% by mass, SWCNT (conductive additive) 0.10% by mass, and CMC (dispersant) 0.15% by mass. The solid content concentration of the slurry was 65% by mass.

[0130] (Example 12) A slurry and cathode were prepared in the same manner as in Example 10, except that the amount of chelate-containing alginic acid produced in Reference Example 1 was changed to 0.15 g, and the amount of glycerin (manufactured by Wako Pure Chemical Industries, Ltd.) was changed to 0.60 g. The composition of the total components of the slurry obtained in this manner, excluding the aqueous solvent (water), was 96.75% by mass of lithium manganate compound (LMO: cathode active material), 0.50% by mass of chelate-containing alginic acid (binder), 0.50% by mass of SBR (binder), 2.0% by mass of glycerin (polyol, plasticizer), 0.10% by mass of SWCNT (conductive additive), and 0.15% by mass of CMC (dispersant). The solid content concentration of the slurry was 65% by mass.

[0131] (Example 13) A slurry and cathode were prepared in the same manner as in Example 11, except that the amount of chelate-containing alginic acid produced in Reference Example 1 was changed to 0.15 g, and the amount of glycerin (manufactured by Wako Pure Chemical Industries, Ltd.) was changed to 0.60 g. The composition of the total components of the slurry obtained in this manner, excluding the aqueous solvent (water), was 96.75% by mass of lithium manganate compound (LMO: cathode active material), 0.50% by mass of chelate-containing alginic acid (binder), 0.50% by mass of a mixture of PVDF and PAA (binder), 2.0% by mass of glycerin (polyol, plasticizer), 0.10% by mass of SWCNT (conductive additive), and 0.15% by mass of CMC (dispersant). The solid content concentration of the slurry was 65% by mass.

[0132] (Comparative Example 1) A slurry was prepared in the same manner as in Example 1, except that the types of components added to the polyethylene ointment container before solid mixing at 2000 rpm for 3 minutes using a rotation-orbit mixer (ARE-310, manufactured by THINKY Co., Ltd.) were changed, and glycerin was not used, and 29.03 g of LMO, 0.90 g of chelate-containing alginic acid produced in Reference Example 1, and 8.0 g of pure water were added to the polyethylene ointment container. Subsequently, an attempt was made to manufacture a positive electrode using the slurry in the same manner as in Example 1. However, cracks occurred in the dried coating film in the positive electrode precursor used during the manufacture of the positive electrode, and due to the lack of flexibility of the dried coating film, the composite layer peeled off from the current collector foil during press rolling. As a result, it was difficult to perform press rolling to adjust the volume density of the composite layer to the desired range, and therefore the positive electrode could not be manufactured. The composition of the slurry obtained in this manner, excluding the aqueous solvent (water), was as follows: lithium manganate compound (LMO: positive electrode active material) 96.75% by mass, chelate group-containing alginic acid (binder) 3.0% by mass, SWCNT (conductive additive) 0.10% by mass, and CMC (dispersant) 0.15% by mass. The solid content concentration of the slurry was 65% by mass.

[0133] (Comparative Example 2) A slurry was prepared in the same manner as in Example 1, except that the amount of chelate-containing alginic acid produced in Reference Example 1 was changed to 0.30 g, and 0.60 g of ethylhexylglycerin (manufactured by Tokyo Chemical Industry Co., Ltd., molecular weight: 204) was used instead of glycerin. Subsequently, an attempt was made to produce a positive electrode using the slurry in the same manner as in Example 1. However, cracks occurred in the dried coating film in the positive electrode precursor used during the production of the positive electrode, and due to the lack of flexibility of the dried coating film, the composite layer peeled off from the current collector foil during press rolling. As a result, it was difficult to perform press rolling that would adjust the volume density of the composite layer to the desired range, and therefore the positive electrode could not be produced. The composition of the slurry obtained in this manner, excluding the aqueous solvent (water), was as follows: lithium manganate compound (LMO: positive electrode active material) 96.75% by mass, chelate group-containing alginic acid (binder) 1.0% by mass, ethylhexylglycerin (polyol for comparison, plasticizer) 2.0% by mass, SWCNT (conductive additive) 0.10% by mass, and CMC (dispersant) 0.15% by mass. The solid content concentration of the slurry was 65% by mass.

[0134] (Comparative Example 3) A slurry was prepared in the same manner as in Example 1, except that the amount of chelate-containing alginic acid produced in Reference Example 1 was changed to 0.30 g, and 0.60 g of polyethylene glycol (polyethylene glycol 200, manufactured by Wako Pure Chemical Industries, Ltd., weight-average molecular weight: 200) was used instead of glycerin. Then, an attempt was made to produce a positive electrode using the slurry in the same manner as in Example 1. However, cracks occurred in the dried coating film in the positive electrode precursor used during the production of the positive electrode, and the asphalt layer peeled off from the current collector foil during press rolling due to insufficient flexibility of the dried coating film. As a result, it was difficult to perform press rolling that would adjust the volume density of the asphalt layer to the desired range, and therefore, a positive electrode could not be produced. The composition of the slurry obtained in this manner, excluding the aqueous solvent (water), was as follows: lithium manganate compound (LMO: positive electrode active material) 96.75% by mass, chelate group-containing alginic acid (binder) 1.0% by mass, polyethylene glycol 200 (polyol for comparison, plasticizer) 2.0% by mass, SWCNT (conductive additive) 0.10% by mass, and CMC (dispersant) 0.15% by mass. The solid content concentration of the slurry was 65% by mass.

[0135] (Comparative Example 4) A slurry was prepared in the same manner as in Example 1, except that the amount of chelate-containing alginic acid produced in Reference Example 1 was changed to 0.30 g, and 0.60 g of polyoxyethylene (20) sorbitan monooleate diethylene glycol (manufactured by Wako Pure Chemical Industries, Ltd., molecular weight: 1310) was used instead of glycerin. Subsequently, an attempt was made to produce a positive electrode using the slurry in the same manner as in Example 1. However, cracks occurred in the dried coating film in the positive electrode precursor used during the production of the positive electrode, and due to insufficient flexibility of the dried coating film, the composite layer peeled off from the current collector foil during press rolling. As a result, it was difficult to perform press rolling that would adjust the volume density of the composite layer to the desired range, and therefore the positive electrode could not be produced. The composition of the slurry obtained in this manner, excluding the aqueous solvent (water), was as follows: lithium manganate compound (LMO: positive electrode active material) 96.75% by mass, chelate group-containing alginic acid (binder) 1.0% by mass, polyoxyethylene (20) sorbitan monooleate diethylene glycol (a comparative polyol, plasticizer) 2.0% by mass, SWCNT (conductive additive) 0.10% by mass, and CMC (dispersant) 0.15% by mass. The solid content concentration of the slurry was 65% by mass.

[0136] (Comparative Example 5) A slurry was prepared in the same manner as in Example 1, except that the amount of chelate-containing alginic acid produced in Reference Example 1 was changed to 0.30 g, and 0.60 g of sorbitol (manufactured by Tokyo Chemical Industry Co., Ltd., molecular weight: 182) was used instead of glycerin. Subsequently, an attempt was made to produce a positive electrode using the slurry in the same manner as in Example 1. However, cracks occurred in the dried coating film in the positive electrode precursor used during the production of the positive electrode, and due to the lack of flexibility of the dried coating film, the composite layer peeled off from the current collector foil during press rolling. As a result, it was difficult to perform press rolling that would adjust the volume density of the composite layer to the desired range, and therefore the positive electrode could not be produced. The composition of the slurry obtained in this manner, excluding the aqueous solvent (water), was as follows: lithium manganate compound (LMO: positive electrode active material) 96.75% by mass, chelate group-containing alginic acid (binder) 1.0% by mass, sorbitol (polyol for comparison, plasticizer) 2.0% by mass, SWCNT (conductive additive) 0.1% by mass, and CMC (dispersant) 0.15% by mass. The solid content concentration of the slurry was 65% by mass.

[0137] (Comparative Example 6) A slurry was prepared in the same manner as in Example 1, except that the amount of chelate-containing alginic acid produced in Reference Example 1 was changed to 0.30 g, and 0.60 g of mannitol (manufactured by Tokyo Chemical Industry Co., Ltd., molecular weight: 182) was used instead of glycerin. Subsequently, an attempt was made to produce a positive electrode using the slurry in the same manner as in Example 1. However, cracks occurred in the dried coating film in the positive electrode precursor used during the production of the positive electrode, and due to the lack of flexibility of the dried coating film, the composite layer peeled off from the current collector foil during press rolling. As a result, it was difficult to perform press rolling that would adjust the volume density of the composite layer to the desired range, and therefore the positive electrode could not be produced. The composition of the slurry obtained in this manner, excluding the aqueous solvent (water), was as follows: lithium manganate compound (LMO: positive electrode active material) 96.75% by mass, chelate group-containing alginic acid (binder) 1.0% by mass, mannitol (polyol for comparison, plasticizer) 2.0% by mass, SWCNT (conductive additive) 0.1% by mass, and CMC (dispersant) 0.15% by mass. The solid content concentration of the slurry was 65% by mass.

[0138] (Comparative Example 7) A slurry was prepared in the same manner as in Example 1, except that the amount of chelate-containing alginic acid produced in Reference Example 1 was changed to 0.30 g, and 0.60 g of glucose (manufactured by Tokyo Chemical Industry Co., Ltd., molecular weight: 180, number of hydroxyl groups: 5) was used instead of glycerin. Subsequently, an attempt was made to produce a positive electrode using the slurry in the same manner as in Example 1. However, cracks occurred in the dried coating film in the positive electrode precursor used during the production of the positive electrode, and due to the lack of flexibility of the dried coating film, the composite layer peeled off from the current collector foil during press rolling. As a result, it was difficult to perform press rolling that would adjust the volume density of the composite layer to the desired range, and therefore the positive electrode could not be produced. The composition of the slurry obtained in this manner, excluding the aqueous solvent (water), was as follows: lithium manganate compound (LMO: positive electrode active material) 96.75% by mass, chelate group-containing alginic acid (binder) 1.0% by mass, glucose (polyol for comparison, plasticizer) 2.0% by mass, SWCNT (conductive additive) 0.1% by mass, and CMC (dispersant) 0.15% by mass. The solid content concentration of the slurry was 65% by mass.

[0139] (Comparative Example 8) A slurry was prepared in the same manner as in Example 1, except that the amount of chelate-containing alginic acid produced in Reference Example 1 was changed to 0.30 g, and 0.6 g of sucrose (manufactured by Tokyo Chemical Industry Co., Ltd., molecular weight: 342) was used instead of glycerin. Subsequently, an attempt was made to produce a positive electrode using the slurry in the same manner as in Example 1. However, cracks occurred in the dried coating film in the positive electrode precursor used during the production of the positive electrode, and due to the lack of flexibility of the dried coating film, the composite layer peeled off from the current collector foil during press rolling. As a result, it was difficult to perform press rolling that would adjust the volume density of the composite layer to the desired range, and therefore the positive electrode could not be produced. The composition of the slurry obtained in this manner, excluding the aqueous solvent (water), was as follows: lithium manganate compound (LMO: positive electrode active material) 96.75% by mass, chelate group-containing alginic acid (binder) 1.0% by mass, sucrose (polyol for comparison, plasticizer) 2.0% by mass, SWCNT (conductive additive) 0.10% by mass, and CMC (dispersant) 0.15% by mass. The solid content concentration of the slurry was 65% by mass.

[0140]

[0141] As is clear from the descriptions of each example and Table 1, when a cathode was manufactured using the slurry obtained in Examples 1 to 13, no cracks were observed on the surface appearance of either the cathode precursor (before press rolling) or the cathode (after press rolling), and no cracks or delamination occurred even when a 3.2 cm diameter bend was applied in the winding test. Thus, the slurry obtained in Examples 1 to 13 had a basis weight of 25 ± 2 mg / cm² during coating. ２ When a composite material layer with a thickness of approximately 120 μm was formed (to a practical basis weight required for the positive electrode composite material layer), no cracks or delamination were observed in winding tests, confirming that it possessed excellent flexibility. Furthermore, when a positive electrode was manufactured using the slurry obtained in Examples 1 to 13, not only was delamination of the composite material layer highly suppressed due to the high delamination strength, but the penetration resistance was also an excellent value for an electrode. From these results, it was found that the slurry of this disclosure makes it possible to impart excellent flexibility (mechanical flexibility) without affecting the characteristics of the battery electrode. In addition, from these results, it was found that the slurry of this disclosure makes it possible to efficiently manufacture a positive electrode using a winding process.

[0142] In contrast, when no polyol was used (Comparative Example 1), or when a comparative polyol that did not satisfy the conditions of having 2 to 4 hydroxyl groups in one molecule and a molecular weight of 60 to 180 was used (Comparative Examples 2 to 8), the basis weight at the time of coating using the obtained slurry was 25 ± 2 mg / cm². ２When attempting to form the asphalt mixture layer to a practical basis weight (required for the positive electrode asphalt mixture layer), cracks appeared in the dried coating (asphalt mixture layer) from the state immediately after drying (positive electrode precursor), and furthermore, peeling of the dried coating from the positive electrode precursor occurred during winding tests. From these results, it was found that the slurry obtained in Comparative Examples 1 to 8 had a basis weight of 25 ± 2 mg / cm² during coating. ２ When used in applications requiring a certain amount of coating, such as those described above, it was not always sufficient in terms of imparting excellent flexibility to the dried coating film.

[0143] <Battery Performance Evaluation> Batteries were manufactured using the same positive electrodes as those obtained in Examples 1-3 and 10-13, and their characteristics were evaluated as follows. First, positive electrodes were manufactured using the same methods as those used in Examples 1-3 and 10-13. Next, using the obtained positive electrodes, laminates were obtained by stacking the positive electrode, separator (polyethylene porous membrane, manufactured by Double Scope Co., Ltd., product name: SB-20D), and glass filter (manufactured by Advantec Co., Ltd., product name: GA-100) in that order. After that, an electrolyte (LiPFF to a concentration of 1.2 M) was added to the obtained laminate. ６ The laminate was impregnated with an electrolyte solution (an electrolyte solution in which ethylene carbonate (EC) and diethyl carbonate (DEC) were dissolved in a mixed solvent with a volume ratio (EC:DEC) of 1:1) by casting. Next, a CR2032 type coin half-cell was manufactured by laminating lithium metal foil (manufactured by Honjo Metal Co., Ltd.) and a SUS spacer (manufactured by Hosen Co., Ltd.) in that order onto a glass filter of the laminate impregnated with the electrolyte.

[0144] Each of the coin half-cells obtained in this way was repeatedly charged and discharged under the following conditions: temperature: room temperature (25°C), C rate: 1C, potential range: 3.0 to 4.25V, charging: constant current constant voltage (CCCV mode), and discharging: constant current (CC mode). For each cell, the initial capacity (discharge capacity after 1 cycle) and the discharge capacity after 10 cycles were measured, and the discharge capacity retention rate ([Retention rate (%)] = [Discharge capacity after 10 cycles] ÷ [Initial capacity] × 100) was calculated. As a result, a discharge capacity retention rate of 80% or more was confirmed for all cells. From these results, it was found that when lithium-ion batteries are manufactured using the positive electrodes obtained in Examples 1 to 3 and 10 to 13, batteries with excellent cycle characteristics can be obtained.

[0145] As described above, the present disclosure provides at least one of the following: a slurry for forming a lithium-ion battery cathode composite layer, which is an aqueous slurry used to manufacture a cathode composite layer, yet can impart excellent flexibility to the cathode composite layer even when the cathode composite layer has a practical basis weight and film thickness, thereby enabling the efficient manufacture of a cathode with excellent flexibility; a cathode for a lithium-ion battery obtained using the slurry; and a lithium-ion battery having the cathode for a lithium-ion battery. The slurry for forming a lithium-ion battery cathode composite layer according to the present disclosure is useful as a material for manufacturing the cathode of a lithium-ion battery because it can form a highly flexible composite layer even when forming a cathode composite layer with a practical basis weight and film thickness, and can enable the manufacture of a cathode with good workability using winding processes, etc.

Claims

1. A slurry for forming a lithium-ion battery cathode composite layer, comprising: a positive electrode active material; an alginate-based polymer compound containing an aminocarboxylic acid-based chelating group; a polyol having 2 to 4 hydroxyl groups per molecule and a molecular weight of 60 to 180; and an aqueous solvent.

2. The slurry for forming a lithium-ion battery cathode composite layer according to claim 1, wherein the ratio of the mass of the polyol to the mass of the alginate polymer compound containing the aminocarboxylic acid chelating group ([mass of polyol] / [mass of alginate polymer compound containing the aminocarboxylic acid chelating group]) is 1 to 5.

3. The slurry for forming a lithium-ion battery cathode composite layer according to claim 1, further comprising a conductive additive.

4. The slurry for forming a lithium-ion battery cathode composite layer according to claim 1, wherein the content of the polyol is 1.5% by mass or more relative to the total mass of all components other than the aqueous solvent contained in the slurry.

5. The slurry for forming a lithium-ion battery cathode composite layer according to claim 1, wherein the cathode active material is a cathode active material containing manganese.

6. A positive electrode for a lithium-ion battery, comprising a positive electrode composite layer consisting of a dried coating film of a slurry for forming a lithium-ion battery positive electrode composite layer according to any one of claims 1 to 5.

7. A lithium-ion battery having the positive electrode for a lithium-ion battery as described in claim 6.

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