Dispersion lquid containing particles of manganese-containing metal oxide, aggregate, battery, method for producing dispersion lquid, method for producing aggregate, and dispersant

Abstract

The present disclosure provides a technology that uses powdery manganese oxide or the like as a raw material or the like, enables easy mixing with another powdery raw material or the like, and makes it possible to obtain a uniform mixture. The present disclosure is directed to a method for producing a dispersion liquid, the method being characterized by involving a step for re-dispersing a manganese-containing metal oxide in an aqueous dispersion medium by mixing a dispersant that is free of carbon atoms or contains 10 or less carbon atoms, the aqueous dispersion medium, and powder of the manganese-containing metal oxide.

Description

Dispersion containing manganese-containing metal oxide particles, aggregate, battery, method for producing the dispersion, method for producing the aggregate, and dispersant

[0001] The present invention relates to a dispersion liquid obtained by dispersing manganese-containing metal oxide particles, such as manganese oxide, in an aqueous dispersion medium, as well as aggregates obtained by removing the dispersion medium from the dispersion liquid, a battery, a method for producing the dispersion liquid, a method for producing the aggregates, and a dispersant.

[0002] Manganese oxide can exist in various divalent, trivalent, and tetravalent states, and exhibits diverse properties, such as the polymorphism of tetravalent manganese dioxide. Taking advantage of these properties, manganese oxide and manganese-containing oxides have traditionally been used in a wide range of applications, including as raw materials for electronic materials such as ferrites and thermistors, black pigments for toners, catalytic materials, adsorbents for gas molecules, and ion conductive materials.

[0003] Furthermore, particularly in the field of batteries, manganese oxide is indispensable as an electrode material for primary batteries such as manganese dry cells and alkaline dry cells, and is also widely used in the form of lithium manganese oxide as a cathode material for lithium-ion batteries, which are rechargeable secondary batteries. In addition, various developments are underway for its use as an electrode material for next-generation secondary batteries.

[0004] Manganese oxide is produced, for example, by methods described in Patent Documents 1 and 2, and generally, manganese oxide powder is supplied as an aggregate of secondary particles formed by the aggregation of primary manganese oxide particles with a particle size of about 1 μm or less. On the other hand, lithium manganate used as the positive electrode material for the lithium-ion battery is usually produced by mechanically dry-mixing a lithium compound powder, such as lithium hydroxide, with the manganese oxide powder obtained as described above using a mixer, and then firing it at a high temperature to diffuse atoms (ions) between the lithium compound and the manganese oxide (see, for example, Patent Document 3).

[0005] Furthermore, because manganese oxide is an electrically insulating material, when using manganese oxide as an electrode material, for example, it is necessary to mix the active material, manganese oxide particles, with conductive particles such as carbon (microcarbon particles), and then supply electricity to the manganese oxide particles through the carbon to induce an electrochemical reaction in the manganese oxide. In addition, in the mixing of particulate manganese oxide and carbon, a binder (adhesive agent) made of a polymer compound is generally added to adhere the two particles to each other, thereby forming a solid electrode material overall.

[0006] In the process of mixing particulate manganese oxide, which is the active material, with conductive materials such as carbon and binders, it is common to mix manganese oxide powder and conductive materials such as carbon powder with a solvent in which the binder is dissolved, mechanically knead the active material and conductive materials using various mixers, and then remove the solvent to obtain a solid electrode material in which the particulate active material and conductive materials are bound together by the binder (see, for example, Patent Documents 4 and 5).

[0007] JP 2-296732 JP 60-161340 JP 8-37006 JP 2023-13104 JP 2022-163278 JP 10-130024 JP 50-36239 Patent No. 7355215

[0008] Powdered manganese oxide produced by various methods generally has the form of aggregates of secondary particles formed by the aggregation of primary particles. Therefore, when using the manganese oxide in various applications, such as as a composite oxide obtained by chemically reacting it with other substances, or as a composite formed by mixing it with other substances and solidifying it, it is desirable to finely crush the powdered manganese oxide before carrying out the desired processing in subsequent steps.

[0009] For example, in the production of lithium manganate used as the positive electrode material for the lithium-ion battery described above, lithium manganate is produced by a solid-phase reaction between a lithium compound such as lithium hydroxide and manganese oxide. Therefore, by making the particle size of the manganese oxide finer, the diffusion distance is shortened and the diffusion area is increased, which is effective in obtaining lithium manganate with a uniform composition.

[0010] Furthermore, in electrode materials formed by solidifying a mixture of manganese oxide particles and carbon particles, it is believed that by making the particle size of the active material, the manganese oxide particles, finer, the path of the current flowing through the manganese oxide particles within the electrode material can be shortened, and the specific surface area of ​​the active material can be increased, thereby making it possible to form an electrode material that is highly efficient in the insertion and removal of electrolyte ions.

[0011] However, in general, in powdered manganese oxide produced by methods described in Patent Documents 1 and 2, the primary particles are strongly aggregated, and as described in Patent Documents 3 to 5, mechanical mixing with powders of other substances using a mixer or the like presents certain difficulties in sufficiently refining powders such as manganese oxide.

[0012] As a means of obtaining a homogeneous product while avoiding the difficulties of dry mixing using such mixers, for example, Patent Document 6 describes a technique for producing lithium manganate using manganese dioxide, in which lithium hydroxide, one of the raw materials, is mixed with an aliphatic lower alcohol having 1 to 3 carbon atoms and dissolved in the form of an alkoxide to form a liquid phase, which is then diffused into the pores of porous manganese dioxide powder to produce a homogeneous gel-like substance, and a composite oxide of lithium and manganese is obtained by drying and calcining the gel-like substance.

[0013] On the other hand, in manganese oxide powder, which is produced by various methods and consists of aggregated primary manganese oxide particles, means of breaking down the aggregate and finely dispersing it are not necessarily common. As a result, the only practical method is to pulverize the manganese oxide powder by mechanical action as described above, and mix it with other substances while preventing re-aggregation by the action of a binder or the like. This is an obstacle when uniformly mixing powdered manganese oxide with other substances to produce various materials.

[0014] In contrast to the conventional technologies described above, the present invention aims to provide a technology that uses the above-mentioned powdered manganese oxide or the like as a raw material, which can be easily mixed with other raw material powders, etc., and that makes it possible to obtain a uniform mixture.

[0015] To solve the above problems, the present invention provides the following means: (1) A method for producing a dispersion, characterized by comprising the step of mixing a dispersant that does not contain carbon atoms or contains 10 or fewer carbon atoms with an aqueous dispersion medium and a powder of a manganese-containing metal oxide to redisperse the manganese-containing metal oxide in the aqueous dispersion medium. (2) A method for producing the above dispersion, wherein the dispersant is a salt that exhibits basicity when dissolved in the aqueous dispersion medium and generates an ion shown in the following formula 1: where, in the following formula 1, R is an OH group, NH ２ This is an organic group containing a heteroatom with 9 or fewer carbon atoms, which may include a COOH group or a hydrogen ion that is dissociated. (3) A method for producing the above dispersion, wherein the dispersant comprises a molecule having the structure shown in the following formula 2 and a strong base: where R' is an OH group, NH ２ It is an organic group containing a heteroatom with 9 or fewer carbon atoms, including a COOH group. (4) A method for producing the above-mentioned dispersion, wherein the dispersant is a salt or molecule that generates hydroxide ions when dissolved in the aqueous dispersion medium. (5) A method for producing the above-mentioned dispersion, wherein the dispersant is a water-soluble alkylamine. (6) A method for producing the above-mentioned dispersion, wherein the dispersant is a complex salt containing ferrocyanic acid, ferricyanic acid, or permanganate ions. (7) A method for producing the above-mentioned dispersion, further comprising the step of dispersing fine carbon bodies in the aqueous dispersion medium. (8) A method for producing the above-mentioned dispersion, wherein the fine carbon bodies are carbon nanotubes. (9) A method for producing aggregates, comprising the step of removing the aqueous dispersion medium from the dispersion produced by any of the above methods to produce aggregates containing manganese-containing metal oxide particles. (10) A dispersion in which manganese-containing metal oxide particles with an average particle diameter of 1000 nm or less are dispersed in an aqueous dispersion medium. (11) The above-mentioned dispersion, wherein fine carbon bodies are further dispersed in the aqueous dispersion medium. (12) The above-mentioned dispersion, wherein the fine carbon bodies are carbon nanotubes. (13) An aggregate containing particles of a metal oxide containing manganese, wherein the aggregate is formed by removing at least a portion of the aqueous dispersion medium from the dispersion liquid described in any of the above. (14) A battery containing the above aggregate as an electrode material. (15) A dispersant for dispersing powder of a metal oxide containing manganese in an aqueous dispersion medium, wherein the dispersant does not contain carbon atoms, or contains 10 or fewer carbon atoms. (16) The above dispersant exhibits basicity when dissolved in the aqueous dispersion medium, and is subject to the following formula 1: (In the formula, R is an organic group having 9 or fewer carbon atoms, and the organic group is an OH group, NH ２ The above dispersant is a salt that generates an ion represented by the following formula 2: (In the formula, R' is an organic group having 9 or fewer carbon atoms, and the organic group is an OH group, NH ２The above dispersant containing a molecule having a structure represented by a group (including a group having a COOH group) and a strong base. (18) The above dispersant is a salt or molecule that generates hydroxide ions by dissolving in the above aqueous dispersion medium. (19) The above dispersant is the above dispersant that is a water-soluble alkylamine. (20) The above dispersant is the above dispersant that is a complex salt containing ferrocyanic acid, ferricyanic acid, or permanganate ion.

[0016] According to the present invention, a dispersion liquid in which primary particles such as metal oxides containing manganese, such as manganese oxide, are dispersed is provided using a powder containing secondary particles formed by aggregation of the primary particles as a raw material. By mixing the dispersion liquid with a dispersion liquid of another substance or the like, it is possible to easily produce a uniform mixture containing particles of a metal oxide containing manganese.

[0017] Photographs showing the appearances of a dispersion liquid (Example 1-1) using trisodium citrate as a dispersant and a dispersion liquid (Example 2-2) using isopropylamine as a dispersant. Measurement results of dynamic light scattering particle size distribution (DLS) when particles of manganese oxide with different oxidation states are dispersed in an aqueous solvent using various dispersants. Measurement results of dynamic light scattering particle size distribution (DLS) when particles of a metal oxide containing manganese are dispersed in an aqueous solvent using various dispersants. SEM image of an aggregate of manganese oxide particles obtained by removing the dispersion medium from a dispersion liquid of manganese oxide. Photograph showing the appearance of a mixture of a dispersion liquid of manganese oxide and a dispersion liquid of single-walled carbon nanotubes (SWNT). SEM image of the surface of a composite of manganese oxide and single-walled carbon nanotubes (SWNT). Schematic diagram showing the structure of a zinc ion secondary battery used for evaluation. (a) Manganese oxide (Mn ３ O ４ ) dispersion liquid, (b) Charge-discharge characteristics graph of a zinc ion secondary battery using a positive electrode material prepared using a manganese oxide (Mn ３ O ４ ) dispersion liquid according to Example 2-1. (a) Manganese oxide (MnO ２ ) dispersion liquid according to Example 7-1, (b) Manganese oxide (Mn ２ O ３This graph shows the charge-discharge characteristics of a zinc-ion secondary battery using a cathode material prepared using a dispersion. The LiNi battery in Example 8-1... ０．５ Mn １．５ O ４ This graph shows the charge-discharge characteristics of a zinc-ion secondary battery using a cathode material prepared with a dispersion of [the specified material].

[0018] When attempting to obtain a mixture in which manganese oxide and other substances are finely and uniformly mixed by mixing powder of manganese oxide and other manganese metal oxides (hereinafter sometimes referred to as "manganese oxide, etc.") with powder of other substances, instead of using the method of mechanically mixing each powder inside a mixer as described above, the inventors have found that by redispersing the powder of manganese oxide, etc. in a dispersion medium in the form of primary particles (i.e., breaking down agglomeration and creating a dispersed state), a dispersion is produced, and the other substances are dispersed in the dispersion containing manganese oxide, etc., thereby easily and uniformly mixing the two in the liquid phase. Furthermore, the inventors believe that a mixture in which manganese oxide, etc. and other substances are finely and uniformly mixed can be easily obtained by removing the dispersion medium from the dispersion containing manganese oxide, etc. by filtration or evaporation, and have completed the present invention based on this finding.

[0019] Examples of dispersions containing particles of metal oxides such as manganese oxide, which have been known conventionally, include those described in Patent Documents 7 and 8. The dispersions described in Patent Documents 7 and 8 both form manganese oxide particles by oxidizing a manganese-containing salt in a solvent, and are produced by a so-called bottom-up method that grows particles at the molecular level. It is considered that particles produced in a solvent by the bottom-up method can be easily grown while maintaining a surface that has affinity for the solvent, and furthermore, it is relatively easy to maintain the dispersion state in the solvent due to the presence of a thickening component composed of a polymer compound such as gelatin.

[0020] On the other hand, there is no known technique for producing dispersions of manganese oxide, etc., by a so-called top-down method using manganese oxide powder, which can be manufactured relatively inexpensively and in large quantities by the methods described in Patent Documents 1 and 2 above. As a result, it is presumed that when mixing manganese oxide with other substances, it was unavoidable to perform mechanical mixing with the powders of other substances while preventing the re-aggregation of manganese oxide in the presence of binder components, etc., as described in Patent Documents 3 to 5 above.

[0021] On the other hand, the present inventors conducted various studies on means of obtaining a dispersion liquid in which manganese oxide powder, etc., produced by methods described in Patent Documents 1, 2, etc., is redispersed. They found that by interposing a predetermined substance in the dispersion medium while the manganese oxide powder, etc., is mixed with an aqueous dispersion medium and rotated with a stirrer or stirring blade, or during the process of grinding the powder with a ball mill, etc., the substance functions as a dispersant and can be redispersed into primary particles of the manganese oxide powder, etc., or into fine particles of about 1000 nm or less formed by the aggregation of multiple such primary particles, and that it is possible to produce a dispersion liquid in which the redispersed particles remain stably dispersed for a long time, leading to the present invention.

[0022] Furthermore, it is believed that powdered manganese oxide, etc., produced by the methods described in Patent Documents 1 and 2 above, etc., is composed of aggregates of numerous primary particles of manganese oxide, etc. In this specification, when distinguishing between powdered manganese oxide, etc., in which the primary particles are aggregates, and manganese oxide, etc., in which at least a portion of the aggregates has been dissolved by the method according to the present invention, etc., resulting in a particle size of approximately 1000 nm or less or approximately 500 nm or less, the latter may be specifically referred to as "particles" of manganese oxide, etc.

[0023] As described below, the present invention has discovered that various substances function as dispersants that enable the redispersion of powdered manganese oxide and the like in an aqueous solvent. Examples of substances that function as such dispersants include salts containing molecules or ions that exhibit basicity through ionization or dissociation equilibrium with water molecules in an aqueous dispersion medium, and in which the anions produced by such ionization (dissociation) can form bonds with oxidized manganese atoms present on the surface of particles such as manganese oxide. Such bonds may include electrostatic or coordination interactions. This is thought to result in the conferring of a negative charge to the particle surface and the generation of electrostatic repulsion between particles, thereby stabilizing the dispersion in the aqueous dispersion medium.

[0024] Manganese atoms contained in particles such as manganese oxide become positively charged when oxidized by oxygen atoms. When these molecules or salts are mixed with powdered manganese oxide in an aqueous solvent, the anions generated by the ionization or dissociation of the dispersant interact electrostatically or coordinatively with the sites of the positively charged manganese atoms. As a result, an electric double layer is formed on the surface of the manganese oxide particles (a zeta potential is generated), and a repulsive force is created between the particles, preventing re-aggregation and enabling the formation of a stable colloidal state.

[0025] As a dispersant as described above, if the molecule (salt) is a compound containing carbon atoms, it is possible to use compounds with 10 or fewer, 8 or fewer, or 6 or fewer carbon atoms. Furthermore, it has been found that inorganic compounds that do not contain carbon atoms can also be used as dispersants for manganese oxide, etc. Since these substances (molecules) are relatively low molecular weight, it is easy to remove the molecules used as a dispersant as needed, and it is possible to reduce the amount of impurity components in the target mixture containing manganese oxide, etc., compared to when conventionally using surfactants with large molecular weights or various hydrophilic polymers used as dispersants.

[0026] Another example of a substance (molecule) that functions as a dispersant is a molecule that is water-soluble and has a functional group that generates hydroxide ions in dissociation equilibrium with water. This functional group can be adsorbed by coordination bonds to manganese atoms present on the surface of particles such as manganese oxide. By using this molecule in an aqueous solvent, the surface of the particles such as manganese oxide is modified by the functional group, thereby imparting hydrophilicity to the surface of the particles such as manganese oxide. As a result, it is thought that re-aggregation between the particles such as manganese oxide is prevented, and a stable colloid can be formed.

[0027] Examples of substances (molecules) of this type include alkylamines that have at least one amino group and an alkyl group containing six or fewer carbon atoms, or four or fewer carbon atoms. By using such alkylamines as a dispersant, manganese oxide particles can be well dispersed in an aqueous solvent while minimizing impurity components to manganese oxide.

[0028] The following molecules can be cited as organic compounds with 10 or fewer carbon atoms that function as the above-mentioned dispersant. (1) Carboxylate ion systems As an example of a compound that functions as a dispersant for manganese oxide, etc. in the present invention, a salt that exhibits basicity in the solvent through dissociation equilibrium with water and generates the structure (ion) shown in the following formula 1 can be cited. However, in formula 1, R is a hydroxyl group (OH group), an amino group (NH ２ It is an organic group containing a heteroatom with 9 or fewer carbon atoms, which may include a carboxyl group (COOH group) in which the hydrogen ion may be dissociated. That is, R is an organic group with 9 or fewer carbon atoms, and the organic group is a group containing carbon atoms, such as a hydroxyl group (OH group) or an amino group (NH group). ２ It contains a carboxyl group (COOH group) in which the hydrogen ion may be dissociated. The heteroatom may contain O or N. COO shown in formula (1) － The group refers to a carboxylate group in which the terminal carboxyl group bonded to R is deprotonated. In this specification, unless otherwise specified, the expression "or" is used to mean both a single case and a combination of multiple cases.

[0029]

[0030] In the solvent, the hydrogen ions of the COOH group shown in formula 1 dissociate into COO － Typical examples of compounds that generate a group (a terminal functional group that bonds to R) include salts of carboxylic acids. Although not bound by theory, the mechanism by which these carboxylic acid salts function as dispersants for manganese oxide and the like is thought to be that the carboxylic acid salt ionizes in an aqueous dispersion medium, and the cation dissociates to form the structure shown in Equation 1, and this structure is electrically adsorbed onto manganese atoms exposed on the crystal surface of manganese oxide and the like. As a result, the anion shown in Equation 1 binds to the crystal surface constituting the particles of manganese oxide and the like, and is given a negative charge, which generates an electrostatic repulsion between the particles of manganese oxide and the like, breaking up aggregates constituting the powder of manganese oxide and the like, and resulting in a stable dispersion state. In this invention, "salt" refers to a structure in which a hydrogen that can dissociate as a hydrogen ion, such as a COOH group, is replaced with another cation. Furthermore, in this specification, "salt" refers to compounds derived from a group having dissociable hydrogen (e.g., a carboxyl group) or a basic moiety, and which have a structure capable of ionizing into cations and anions in an aqueous dispersion medium. This may include carboxylate salts, inorganic salts capable of generating hydroxide ions, complex salts having cations or anions, and organic amine salts containing protonated amines.

[0031] Among the molecules that form the structure shown in Formula 1 in the above solvent, polyvalent carboxylic acid salts having other carboxyl groups in the R portion that have dissociated hydrogen ions and become negatively charged are particularly preferred as dispersants when redispersing powders such as manganese oxide in a solvent. This is presumed to be because the carboxylic acid ions produced by the ionization of polyvalent carboxylic acid salts have a large amount of charge, which in turn makes it possible to impart a larger amount of surface charge to the surface of particles such as manganese oxide, thereby increasing the electrostatic repulsion acting between manganese oxide particles.

[0032] Typical compounds that produce such polyvalent carboxylate ions include salts of hydroxy acids and dicarboxylic acids. For example, as sodium salts, we can list trisodium citrate (5 carbon atoms), disodium hydrogen citrate (5 carbon atoms), sodium malate (3 carbon atoms), sodium tartrate (3 carbon atoms), sodium adipate (5 carbon atoms), sodium succinate (3 carbon atoms), sodium oxalate (1 carbon atom), sodium iminodiacetate (3 carbon atoms), sodium nitrilotriacetate (5 carbon atoms), tetrasodium ethylenediaminetetraacetate (9 carbon atoms), etc. The carbon atoms in parentheses above are the carbon atoms included in R in formula 1. The salts may also be hydrates. The sodium ion, which is the countercation of the above carboxylate ion, can be replaced by at least a portion of other alkali metal ions, hydrogen ions, or ammonium ions. It is also possible to use salts with water-soluble alkaline earth metal ions.

[0033] Furthermore, a salt that forms the structure shown in Formula 1 in the above solvent, and in which R contains an OH group and / or a COOH group, can also be preferably used as a dispersant when redispersing powders such as manganese oxide in a solvent. － When the group bonds to the manganese atom, the COO － It is thought that the interaction with the manganese atom is strengthened by the promotion of hydrogen ion dissociation from OH groups and COOH groups present in the vicinity of the group, resulting in the conferring of a larger amount of negative charge to the particle surface of manganese oxide, etc. Furthermore, in this salt, COO － It is believed that the group is electrostatically or coordinatively adsorbed to manganese ion sites on the particle surface, and that the negative charge attached to the particle surface can be stabilized through interactions such as the formation of a hydration layer by the hydroxyl or carboxyl group in R. Examples of molecules having this structure include sodium lactate, potassium lactate, lithium lactate, ammonium lactate, sodium glycolate, potassium glycolate, lithium glycolate, and ammonium glycolate.

[0034] Another example of a dispersant in the present invention is the use of a molecule having the structure shown in the following formula 2 in combination with a base. In formula 2, R' is an organic group having 9 or fewer carbon atoms, and the organic group is an OH group, NH ２ It contains a group or a COOH group. For example, carboxylic acids such as citric acid and tartaric acid, which have the structure shown in formula 2, are H in an aqueous solvent. ＋ Because the degree of dissociation is small, compared to carboxylate salts, the ionized COO shown in Equation 1 is formed. － The density of the group tends to decrease. On the other hand, when the carboxylic acid shown in formula 2 is neutralized with a base such as sodium hydroxide, COO － By increasing the density of the group, the structure shown in Equation 1 can be generated, making it possible to function as a suitable dispersant. ２ Amino acids such as glycine and alanine, which have a single COOH group, can also act as dispersions for powders such as manganese oxide by promoting the dissociation of the hydrogen ion of their COOH group in the presence of a strong base. At the same time, the amino group can strongly interact with the manganese atom on the surface of the manganese oxide particles, such as by coordinating with it, thus functioning as a good dispersant.

[0035]

[0036] (2) A molecule that functions as a dispersant by modifying the surface of particles such as alkylamine manganese oxide to make them hydrophilic, with NH at the end. ２ Examples include various water-soluble alkylamines containing amino groups. By using these alkylamines, powders such as manganese oxide can be well redispersed in an aqueous solvent as a dispersion medium. When various alkylamines containing amino groups are mixed with manganese oxide in an aqueous phase, the alkylamine molecules undergo an equilibrium reaction with water molecules, and some of them are converted into alkylammonium ions and hydroxide ions. The generated hydroxide ions are thought to contribute to dispersion stabilization by supplying a negative charge to the surface of the manganese oxide particles. Furthermore, NH in alkylamines ２It is presumed that particles such as manganese oxide can become dispersible in the aqueous phase through mechanisms such as the group coordinating with manganese atoms exposed on the crystal surface of manganese oxide, thereby chemically modifying the surface.

[0037] The alkylamine used as a dispersant for powders such as manganese oxide in this invention can be any alkylamine having an appropriate structure within the range of water solubility. For example, methylamine, ethylamine, propylamine, isopropylamine, butylamine, ethylenediamine, diethylenetriamine, 1,2-propanediamine, 2-aminoethanol, 3-amino-1-propanol, N-methyl-1,3-propanediamine, N,N-dimethyl-1,3-propanediamine, N,N-diethyl-1,3-propanediamine, 3-methoxypropylamine, 3-ethoxypropylamine, and 3-ethoxyethylamine all exhibit high affinity for the aqueous phase, thereby improving the dispersibility of manganese oxide and other powders in aqueous solvents. Furthermore, when using alkylamines as dispersants in this invention, other dispersants listed herein can be mixed and used in combination. In addition, when using alkylamines as dispersants in this invention, since the alkyl group of the alkylamine exhibits affinity for organic solvents, various organic solvents that are miscible with aqueous solvents such as various alcohols can be added to the dispersion medium.

[0038] (3) Inorganic salts that dissolve in aqueous dispersion media such as phosphates, borates, and carbonates to generate polyvalent anions, thereby imparting a negative charge to the particle surface of manganese oxide and other substances, and also generating hydroxide ions, can be used as dispersants. By using salts that generate polyvalent anions and hydroxide ions when dissolved in an aqueous solvent as dispersants, it is also possible to disperse powdered manganese oxide and other substances in an aqueous solvent. For example, monosodium phosphate (NaH), which is a general term for sodium phosphate, can be used. ２ PO ４ ), disodium phosphate (Na ２ HPO ４ ), trisodium phosphate (Na ３ PO ４Examples include phosphates such as sodium phosphate, borates such as sodium borate, and carbonates such as sodium carbonate and sodium bicarbonate. These salts produce polyvalent anions (PO) upon dissolution. ４ ３－ , B ４ O ７ ２ CO ３ ２－ These substances (etc.) are electrostatically or coordinatively adsorbed onto the positively charged regions on the surface of particles such as manganese oxide, thereby increasing the negative charge on the particle surface, imparting repulsion between particles, and changing the charge state of the particle surface by generating hydroxide ions, thereby suppressing re-aggregation in aqueous dispersion media and providing dispersion stability. Phosphates, borates, and carbonates are all salts containing polyvalent anions that can generate hydroxide ions by hydrolysis in aqueous solutions, and when dissolved in an aqueous dispersion media, hydroxide ions (OH) are generated by hydrolysis equilibrium with water as shown in the following equation. － It is a weakly basic salt that produces ) . Example of a carbonate: CO ３ ２－ +H ２ O⇔HCO ３ － +OH － Examples of phosphates: PO ４ ３－ +H ２ O⇔HPO ４ ２－ +OH － Example of borate: B ４ O ７ ２－ +7H ２ O ⇔ 4B (OH) ３ +2OH － The polyvalent anions (PO) produced by these salts ４ ３－ , B ４ O ７ ２－ CO ３ ２－These substances (etc.) can be adsorbed electrostatically or coordinatively onto the surface of particles such as manganese oxide, and it is believed that the deprotonation of the particle surface by the hydroxide ions generated simultaneously imparts a negative charge, thereby improving dispersion stability. Furthermore, salts in which at least a portion of the countercations of the above anions, such as sodium ions, are replaced with other alkali metal ions or ammonium ions can also be used as dispersants for manganese oxide and the like.

[0039] Furthermore, examples of salts that produce the structure shown in formula 1 above include carbamate salts such as sodium carbamate. Carbamate ion (RNHCOO － ) has an organic group containing a carbon atom in R and can raise the solution pH due to its basicity, so it can be used alone or in combination with other salts as a dispersant for manganese oxide, etc. Furthermore, when phosphates, borates, or carbonates are used in combination with amines, the amine reacts with carbon dioxide in an aqueous solvent to produce carbamate ions, and the dispersion stability can be further improved by electrostatic or coordination interactions with the particle surface by the carbamate ions and by the imparting of a negative charge by promoting deprotonation of the particle surface by hydroxide ions.

[0040] It is thought that the above-mentioned salts generate polyvalent anions, such as divalent or trivalent, in the solvent. These anions bond to manganese atoms on the surface of manganese oxide particles, thereby imparting a negative charge. As a result, electrostatic repulsion occurs between the manganese oxide particles, suppressing aggregation of the manganese oxide particles and maintaining their dispersed state. Furthermore, since these polyvalent anions generally originate from weak acids, they undergo hydrolysis equilibrium with water to form hydroxide ions (OH) － This can generate hydroxide ions. These hydroxide ions are also thought to be one of the factors that contribute to dispersion stability by stabilizing the charge state on the surface of particles such as manganese oxide.

[0041] On the other hand, in solvents containing sodium sulfate, which similarly generates divalent anions, redispersion of manganese oxide powder is difficult. Although not bound by theory, the reason for this difference is that phosphoric acid, boric acid, carbonic acid, etc., are all salts of weak acids and can form hydroxide ions in dissociation equilibrium with water. It is presumed that the generated hydroxide ions work in cooperation with polyvalent anions such as phosphate ions, borate ions, and carbonate ions to effectively impart a negative charge to the particle surface of manganese oxide, etc., resulting in good dispersibility. On the other hand, sulfates such as sodium sulfate contain polyvalent anions (SO4). ４ ２－ Although it generates a compound anion, because it is a salt derived from a strong acid, it has little effect on the pH of the aqueous dispersion medium and cannot sufficiently change the charge state of the particle surface of manganese oxide, etc. Therefore, even with the same polyvalent anion, it is difficult to redisperse powders such as manganese oxide when sulfates are used.

[0042] (4) In addition to alkali metal hydroxides such as sodium hydroxide, powders such as manganese oxide can also be redispersed in a solvent by using ammonia (ammonia water) as a dispersant, as an example of a salt or molecule that generates hydroxide ions when dissolved in the above aqueous solvent, such as a base. When such a molecule is used as a dispersant, it is presumed that the hydroxide ions generated when the molecule dissolves in the aqueous solvent react with the surface of the manganese oxide particles, thereby supplying a negative charge, and as a result, the manganese oxide particles can be dispersed in the aqueous dispersion medium. In addition, alkoxides such as sodium ethoxide, sodium methoxide, and potassium methoxide, which exhibit basicity in aqueous solvents, as well as compounds such as quaternary alkylammonium hydroxide, can also be used as dispersants. The basic compounds used in the present invention generate hydroxide ions (OH) in the aqueous dispersion medium. －It is thought that this improves dispersion stability by generating ammonium ions (NH₄) and adjusting the charge state of the particle surface, such as manganese oxide, thereby imparting electrostatic repulsion. For example, by adding alkali metal hydroxides such as sodium hydroxide, the pH increases, deprotonation of the particle surface progresses, increasing the surface negative charge and improving dispersibility. In addition, ammonia (ammonia water) generates ammonium ions (NH₄) in an aqueous dispersion medium. ４ ＋ Since it generates hydroxide ions, a similar effect can be obtained. Furthermore, alkoxides such as sodium ethoxide, sodium methoxide, and potassium methoxide can be hydrolyzed in water to generate hydroxide ions, which can control the charge state of the particle surface and impart dispersion stability.

[0043] (5) Complex anionic substances In addition, as other examples of inorganic compounds that function as dispersants for manganese oxide, etc., complex salts such as alkali metal salts of ferrocyanate ions, such as sodium ferrocyanate, or ferricyanate ions, can also be preferably used as dispersants for particles of manganese oxide, etc. Although not bound by theory, ferrocyanates are [Fe(CN) ６ ] ４－ , ferricyanate is [Fe(CN) ６ ] ３－ It generates a polyvalent anion (complex anion) represented by and a cyanide ligand (CN) that is not coordinated to the Fe atom. － Since the N atom of the manganese oxide can coordinate and bond with the manganese atoms on the surface of the manganese oxide, etc., it is presumed that this imparts a negative charge, making the manganese oxide particles dispersible in an aqueous dispersion medium.

[0044] Another example of an inorganic compound that functions as a dispersant for manganese oxide, etc., is potassium permanganate (KMnO ４ Permanganates such as ) can also be preferably used as dispersants for particles such as manganese oxide. Permanganates are polyvalent anions (MnO) in aqueous dispersion media. ４ －)(is generated, and the anion is electrostatically adsorbed on the particle surface to impart a negative charge, thereby increasing the electrostatic repulsion between particles and improving the dispersion stability. Although not bound by theory, permanganate generates MnO ４ － (complex anion) in an aqueous solvent, and its oxo ligand can coordinate and bond to the manganese atoms on the surface of the manganese oxide or the like. As a result of imparting a negative charge, it is also speculated that particles such as manganese oxide can be dispersed in an aqueous dispersion medium. The permanganate used as a dispersant for particles such as manganese oxide is not particularly limited as long as it is a water-soluble permanganate. In addition to potassium permanganate, sodium permanganate, ammonium permanganate, zinc permanganate, magnesium permanganate, calcium permanganate, barium permanganate, etc. can be used as dispersants.

[0045] In addition, an inorganic compound that generates a polyvalent complex anion can also be used as a dispersant. For example, ferrocyanide ion [Fe(CN) － containing (cyanide) is a complex anion that can electrostatically adsorb on the surface of particles such as manganese oxide as a polyvalent anion and contribute to improving the dispersion stability by imparting a negative charge. Also, as a complex anion having an oxo ligand (=O), permanganate ion [MnO ６ ４－ and the like can also impart dispersion stability by electrostatic adsorption. Furthermore, as a complex ion containing an oxalato ligand (C ６ ３－ which is a bidentate ligand, tris(oxalato)manganate(III) ion ([Mn(C ４ O － ) ２ O ４ ２－ ) or tris(oxalato)ferrate(III) ion ([Fe(C ２ O ４ ) ３ ３－ ) or tris(oxalato)ferrate(III) ion ([Fe(C ２ O ４ ) ３ ３－ ​​​​Similarly, it can be suitably used as a dispersant.

[0046] The molecules that function as dispersants for powders such as manganese oxide, as described above, all have smaller molecular weights compared to polymer compounds used as binders, etc. Therefore, when electrodes or the like containing manganese oxide particles are formed using a dispersion of manganese oxide particles prepared with these dispersants, it is possible to reduce the amount of material that coats the manganese oxide particles, and thus reduce the barrier when supplying power to the surface of the manganese oxide particles.

[0047] Furthermore, molecules that function as dispersants for powders such as manganese oxide, as described above, are thought to mainly generate anions that bind to manganese atoms exposed on the surface of the manganese oxide particles. In addition, hydroxide ions generated in the dissociation equilibrium between the dispersant and water are thought to interact with hydroxyl groups (Mn-OH) bound to manganese atoms with high oxidation states that are exposed on the surface. Furthermore, the anions (RCOO) generated by the dispersant used in this invention － It is presumed that the dispersant, by electrostatically or coordinatively adsorbing onto the surface of particles such as manganese oxide, imparts a negative charge, resulting in electrostatic repulsion between particles and the formation of a stable dispersion state. Furthermore, the hydroxide ions generated by the dispersant can contribute to the dispersion stabilization effect by assisting in the adjustment of the charge state on the particle surface. Since this interaction is reversible, after separating the manganese oxide particles from the dispersion by filtration or other means, the components of the dispersant can be easily removed from the surface of the manganese oxide particles by washing with appropriate water or acid, and if necessary, the manganese oxide particles can be re-aggregated by removing these components.

[0048] Furthermore, when using molecules such as alkylamines or ammonia as dispersants, drying the manganese oxide particles dispersed in the dispersion allows alkylammonium ions and ammonium ions attached to the surface of the manganese oxide particles to revert to molecules and be removed by evaporation. In addition, when using permanganates as dispersants, permanganate ions (MnO) can be removed. ４ － It is thought that the polyvalent anions electrostatically adsorb onto the surface of particles such as manganese oxide, imparting a negative charge and providing dispersion stability. Also, MnO ４ － The oxygen atom of the oxo ligand (=O) inside may coordinate bond with the manganese atom exposed on the surface of the particles such as manganese oxide, thereby conferring a negative charge. ４ － Since it is the permanganate ion of manganese (VII), which has the highest oxidation state, it is possible to reduce the amount of foreign elements introduced into the system.

[0049] The substance that functions as a dispersant for the above-mentioned manganese oxide powder is Mn ３ O ４ , Mn ２ O ３ , MnO ２ By mixing a suitable amount of manganese oxide powder with an aqueous dispersion medium, and, preferably, by stirring with a stirrer, stirring blade, or by crushing and / or grinding the manganese oxide powder for a predetermined time, the manganese oxide powder, which initially settles, can be dispersed in the aqueous dispersion medium. Furthermore, by applying ultrasound to the dispersion liquid as needed during the dispersion process, or to the dispersion after dispersion, the dispersibility of the manganese oxide particles can be further improved by increasing the contact opportunity between the surface of the manganese oxide particles and the dispersant.

[0050] The amount of substance added to powders such as manganese oxide as a dispersant can be appropriately determined depending on the type of substance, the amount of aqueous solvent, and the particle size of the manganese oxide particles contained in the powder. Generally, however, by using an amount of aqueous solvent such that the weight percentage of manganese oxide is about 1% or more, and mixing the dispersant with the manganese oxide in a ratio of, for example, 0.5 to 40 mol%, 1 to 35 mol%, or 5 to 30 mol%, for example, about 30 mol%, the manganese atoms on the surface of the manganese oxide particles interact well with the dispersant, modifying the surface of the manganese oxide particles and imparting dispersibility to the manganese oxide particles.

[0051] In this invention, "dispersion" means that after dispersing particles such as manganese oxide by stirring, a stable dispersion state is observed while evaluating the particle size of the dispersed particles by a conventional method such as dynamic light scattering particle size distribution (DLS). For example, the dispersion in this invention also includes cases where some coarse particles contained in the powder used are not dispersed, or where partial sedimentation occurs after standing for a long period of time after the stirring is completed.

[0052] As shown in the following examples, in dispersions obtained by adding a dispersant to powders such as manganese oxide and performing stirring or ball milling, the particle size was evaluated by dynamic light scattering particle size distribution (DLS). The results showed that dispersed particles with a particle size in the range of 1 to 10 times, particularly in the range of 2 to 5 times, the primary particle size contained in the manganese oxide powder used, were observed as the main distribution peaks. This confirmed that at least some of the manganese oxide particles that were aggregated in the powder were broken down by the dispersant, and that they could maintain their dispersed state in an aqueous dispersion medium.

[0053] The solvent (dispersion medium) used to disperse particles such as manganese oxide can be appropriately determined according to the intended use of the dispersion and the dispersant used. For example, as an aqueous dispersion medium, water or a mixed solvent of water and a water-soluble organic solvent such as ethanol can be used, and by using it in combination with the aforementioned dispersant or carboxylate salt that can generate hydroxide ions, high dispersion stability can be imparted to particles such as manganese oxide. Furthermore, for example, when using the dispersion according to the present invention in the preparation of electrodes for lithium-ion batteries that use an organic solvent as the electrolyte, an appropriate organic solvent such as NMP (N-methyl-2-pyrrolidone) or DMF (dimethylformamide) can be used as the dispersion medium, and an alkylamine or the like that has affinity for the organic solvent can be used as the dispersant.

[0054] When manufacturing electrodes for batteries that use aqueous solutions as electrolytes, such as manganese batteries and alkaline batteries, an aqueous solvent can be used along with a water-soluble dispersant. When preparing a dispersion of manganese oxide or the like using an aqueous dispersion medium, an organic solvent that is compatible with the aqueous solvent, such as a lower alcohol, can be added to promote the modification of the particle surface of manganese oxide or the like by the dispersant, and to improve the dispersibility of the dispersant-modified manganese oxide or the like. This can assist the solubility of the dispersant and its interaction with the particle surface of manganese oxide or the like, thereby contributing to the stabilization of the dispersion. Furthermore, by adding an acid or basic substance to adjust the pH of the aqueous solvent, it is possible to control the charge state of the particle surface of manganese oxide or the like and adjust the dispersion stability. In addition, by adding an appropriate surfactant along with the above dispersant, the hydrophilization of the particle surface of manganese oxide or the like is promoted, improving the wettability and stability of the entire system, and making it possible to maintain the dispersion stably for a longer period of time.

[0055] The dispersion according to the present invention can be preferably used to mix particles such as manganese oxide with other substances in a liquid phase. In this mixing, the substances to be mixed with the manganese oxide particles can be uniformly mixed with the other substances in a liquid phase by adding the substance to be mixed with the dispersion according to the present invention in a form that can be dispersed in a solvent and dispersing it, or by mixing the liquid phase in which the substance is dispersed with the dispersion according to the present invention and stirring. Furthermore, since the dispersed manganese oxide particles can be uniformly mixed, when used as a slurry for battery electrodes, a composite material, or a support for a carrier material, particle aggregation can be suppressed and uniform particle arrangement can be achieved, allowing the desired performance to be stably expressed.

[0056] The mixture obtained above, containing particles such as manganese oxide and other substances in the liquid phase, can then be processed to remove the solvent by means of filtration, evaporation, or centrifugation, resulting in a mixture of manganese oxide particles and the other substances. Furthermore, if necessary, dispersants adhering to the surface of the manganese oxide particles can be removed by means of washing, vacuum drying, or heating. Removal of the dispersant can induce re-aggregation between the manganese oxide particles, and this cohesive force can impart stability to the mixture of manganese oxide and the other substances even without the use of binders.

[0057] Furthermore, the dispersion according to the present invention can be used to form layers containing manganese oxide or the like on the surface of various substrates by means of spraying, coating, spin coating, etc. For example, it can be used to form a laminate of a layer containing manganese oxide or the like and a layer composed of other substances. By using the dispersion according to the present invention, aggregation of manganese oxide or the like particles in the layer is suppressed, and a uniform particle distribution and good adhesion to the substrate can be obtained. By this method, for example, by forming a laminate of a thin layer containing manganese oxide or the like particles and a conductive layer, it becomes possible to apply an electric field more uniformly to the manganese oxide or the like particles in the thin layer. As a result, when applied to electrodes, etc., improved conductivity due to the uniformity of the electron supply path and improved reliability due to the suppression of localized electric field concentration can be expected.

[0058] When forming electrodes using manganese oxide or the like as the active material, fine carbon particles acting as conductive additives can be mixed within a dispersion containing the manganese oxide particles, and then the solvent can be removed to form a mixture of manganese oxide particles and carbon. Compared to conventional methods of mechanically mixing manganese oxide powder and carbon material in the presence of a binder, this method allows for uniform mixing of the two materials via the solvent, reduces the amount of binder component required, or even allows for the formation of a mixture without using a binder component. This increases interfacial contact between the active material particles and the conductive additive, ensuring electron supply pathways and enabling the construction of a good conductive network during electrode formation, thus improving electrochemical properties.

[0059] Furthermore, when using carbon nanotubes as the fine carbon material for the conductive additive, the difference in morphology between the carbon nanotube powder and powders such as manganese oxide makes it difficult to uniformly mix them in an extended state by conventional mechanical mixing methods, as the tubular fibers of the carbon nanotube powder are intricately intertwined with each other. On the other hand, by using a dispersion of particles such as manganese oxide and mixing it with carbon nanotubes that have been pre-dispersed in a solvent, for example, within the dispersion, it becomes possible to easily form a composite in which the extended carbon nanotubes and particles such as manganese oxide are intertwined and distributed. This ensures a continuous conductive path and increases interfacial contact between manganese oxide and the conductive additive, thus improving the electronic conductivity of the electrode.

[0060] In the battery electrodes manufactured as described above using the dispersion according to the present invention, since particles such as manganese oxide, which are the active material, can be uniformly mixed with minute carbon bodies such as carbon nanotubes, which are the conductive additive, electron transport pathways formed by the conductive additive are uniformly constructed within the electrode, and the electric field applied via the conductive additive is uniformly applied to the particles such as manganese oxide. Furthermore, a space is created around the active material particles, and the electrolyte solution enters this space, thereby shortening the diffusion distance of ions and making it possible to construct a three-dimensional structure suitable for high-speed charging and discharging. In addition, since the amount of binder component added can be reduced, or a mixture with the conductive additive can be formed without using a binder component, the degree to which the electrochemical reaction on the surface of the particles such as manganese oxide is inhibited by the binder component is low, and the surface area of ​​the particles such as manganese oxide that generate the electrochemical reaction is increased, improving the electrochemical reaction activity and making it possible to form electrodes suitable for high-speed charging and discharging.

[0061] The particle size of manganese oxide and the like used in the present invention is preferably about 50 to 1000 nm, more preferably about 50 to 500 nm, and even more preferably about 50 to 350 nm. The particle size of manganese oxide and the like can be measured by dynamic light scattering (DLS). When forming electrodes for batteries using the dispersion according to the present invention, it is preferable that the particles of manganese oxide and the like dispersed in the dispersion are within the above particle size range. By using manganese oxide and the like having the dispersed particle size, the specific surface area of ​​the manganese oxide and the like particles is secured, the electrochemical reaction at the interface with the electrolyte solution proceeds efficiently, and the diffusion distance of ions is shortened, making it possible to produce an electrode material with excellent charge-discharge characteristics.

[0062] As described above, a mixture formed by mixing particles such as manganese oxide as an active material with carbon materials such as carbon nanotubes as a conductive additive can be used as the positive electrode material (or negative electrode material) of a battery. By combining this mixture with a negative electrode material (or positive electrode material) and an electrolyte, which are appropriately selected according to the electromotive force, a battery can be constructed. Such batteries can be primary batteries such as manganese batteries and alkaline batteries, as well as secondary batteries that can be repeatedly charged and discharged by selecting the counter electrode material and electrolyte. The following describes in detail, using examples, the method for producing a dispersion of manganese oxide, etc., according to the present invention, and batteries that can be obtained by using said dispersion, but the present invention should not be interpreted as being limited to these examples.

[0063] 1. Dispersion of manganese oxide and other particles As shown below, commercially available manganese oxide and other powders were redispersed in an aqueous phase using various salts and molecules as dispersants to prepare a dispersion of manganese oxide and other particles.

[0064] (1) Evaluation of dispersants: Carboxylate ion type [Example 1-1] In a polypropylene container, Mn ３ O ４2.0 g of powder (high-purity chemical, 99.9% purity) was added, and an amount of trisodium citrate dihydrate equivalent to 1 mol% of the powder was added as a dispersant, followed by 2.5 mL of pure water. A 1 cm diameter zirconia ball was added to the resulting mixture, and ball milling was performed for 2 days using a dual-axis driven poly bottle rotating stand (Tanaka Tech, RPB-2). Then, a small amount of pure water was added to the container, and Mn ３ O ４ The dispersion was recovered as a particle dispersion. When this dispersion was filtered with a cotton plug, there was almost no residue of coarse particles on the cotton plug, and Mn ３ O ４ Almost the entire amount could be recovered as a dispersion. The obtained dispersion maintained its dispersion state even when diluted with pure water, and contained 5-10% by weight of Mn ３ O ４ We were able to prepare an ochre-colored aqueous dispersion containing particles.

[0065] [Comparative Example 1] Mn was used in the same manner as in Example 1-1, except that no dispersant was added and no cotton plug filtration was performed. ３ O ４ We attempted to prepare a dispersion by ball milling the powder in pure water. Figure 1 shows the state of the dispersion prepared in Example 1-1 in comparison with the dispersion prepared in Comparative Example 1. The dispersion of Example 1-1 showed the same dispersion state as immediately after the dispersion treatment, even after standing for 24 hours. On the other hand, in Comparative Example 1, where the dispersion treatment was attempted without adding a dispersant such as trisodium citrate dihydrate, immediately after stirring, Mn ３ O ４ Although the particles were suspended, sedimentation of manganese oxide particles began immediately after standing, and after 24 hours of standing, a clear supernatant liquid formed, indicating that the dispersion state was not maintained.

[0066] The results shown in Figure 1 demonstrate that, without a dispersant, while it is possible to temporarily disperse manganese oxide powder by ball milling, maintaining that dispersion state is difficult. In contrast, using a specific dispersant allows the dispersion state to be easily maintained. It is presumed that the effect of this dispersant is that the dispersant imparts a negative charge to the surface of the manganese oxide particles, forming an electric double layer (zeta potential) on the surface and generating electrostatic repulsion between the particles.

[0067] [Examples 1-2] Mn is produced under milder conditions compared to ball mills, etc., by the following means. ３ O ４ The powder was dispersed. Mn ３ O ４ For every 1.00 g (4.37 mmol) of powder (high-purity chemical, 99.9% purity), add 0.129 g (4.39 x 10) of trisodium citrate dihydrate (Kanto Chemical, special grade), which is equivalent to 10 mol% of the powder. －１ A dispersant (mmol) was added, and then 10 mL of pure water was added and the mixture was stirred for 24 hours. The stirring was performed by rotating a magnetic stirring bar in a glass container for centrifugation. This stirring resulted in Mn ３ O ４ Most of the powder disappeared, and it turned into a yellowish-brown dispersion.

[0068] The resulting dispersion was centrifuged (4000 rpm, 5 minutes) to precipitate the dispersed phase. The supernatant containing excess trisodium citrate was removed, and pure water was added to the precipitate to redisperse it in the pure water. The dispersion was then filtered using a cotton plug, and only a few coarse brown particles remained on the cotton, indicating the presence of Mn ３ O ４ Almost the entire amount could be recovered as a dispersion. Similar to Example 1-1, in which dispersion was performed using a ball mill, the dispersion maintained a good dispersion state even after standing for 24 hours, demonstrating that a good dispersion can be obtained even when dispersion is performed under mild conditions. Furthermore, the dispersion state was maintained even when diluted with pure water, with a content of about 5-10% by weight of Mn ３ O ４ It was possible to prepare an ochre-colored aqueous dispersion containing particles.

[0069] [Examples 1 and 3] The amount of trisodium citrate dihydrate mixed as a dispersant is Mn ３ O ４ Mn was prepared in the same manner as in Example 1-2, except that it was equivalent to 1.0 mol% of the powder. ３ O ４ When the powder was dispersed in pure water, almost all of the Mn ３ O ４ The powder is dispersed in pure water, and the resulting color is yellowish-brown Mn ３ O ４An aqueous dispersion was obtained.

[0070] [Examples 1-4 to 1-13], [Comparative Examples 1, 2] Various carboxylic acids or their salts are used as dispersants, and the mixing amounts are changed as appropriate, and Mn is prepared in the same manner as in Examples 1 and 2. ３ O ４ The effectiveness of the dispersant for dispersing particles in pure water was evaluated. Table 1 shows the type and amount of the dispersant, the stirring time, and the dispersibility when using the dispersant, along with the results from Examples 1-1 to 1-3 described above. The reagents used as dispersants were all commercially available and used as is.

[0071] In the table below, a dispersion rating of "A" indicates that a good dispersion can be produced, and no significant separation occurs even after standing for several days after stirring. Ratings "B" to "D" indicate that a good yellowish-brown dispersion can be produced, similar to those rated "A," but tend to gradually separate after standing after stirring. The degree of this tendency is evaluated in three stages from "B" to "D." Even in the case of "D," which shows the greatest tendency towards separation, good dispersion is observed for several hours after stirring, and a uniform dispersion can be easily obtained by shaking the container. For example, it can be suitably used when mixing particles such as manganese oxide with dispersions containing other substances.

[0072] The difference in dispersibility due to the above dispersants is Mn ３ O ４ It is presumed that this is due to differences in the amount of charge imparted when each dispersant modifies the particle surface, resulting in differences in the magnitude of the repulsive force acting between particles. On the other hand, in the table, those marked with "×" for dispersibility show no substantial coloration in the liquid phase even after prolonged stirring, and Mn ３ O ４ This indicates that the particles could not be dispersed in pure water.

[0073] As shown in Table 1, in the salts of carboxylic acids (hydroxy acids) containing OH groups and COOH groups, such as citric acid, malic acid, and tartaric acid (Examples 1-1 to 1-8), the type of cation (Na ＋ , K＋ NH ４ ＋ Regardless of the method used, it was found that there is a strong tendency to promote the dispersion of particles such as manganese oxide. Furthermore, among the salts of the hydroxy acid, it was found that the salts of citrate that form trivalent anions (Examples 1-1 to 1-5) tend to promote the dispersion of particles such as manganese oxide more strongly than the salts of malic acid and tartaric acid (Examples 1-7, 1-8), in which all the hydrogen ions of the COOH groups dissociate to form divalent anions. In addition, when a portion of the trisodium citrate salt was replaced with citric acid (Example 1-11), the dispersibility decreased, and citric acid itself without forming a salt (Comparative Example 2) did not show any dispersibility of particles such as manganese oxide. From these results, it was found that improving the dispersibility of particles such as manganese oxide requires the dissociation of the ionized COOH in the dispersant. － The group contributes, and COO is contained within a single ion. － It was inferred that the greater the number of groups, the more effective the dispersant becomes.

[0074] Meanwhile, two COOs － It was confirmed that even in the case of anions containing a hydroxyl group, the effect as a dispersant differs depending on the presence or absence of the hydroxyl group. Specifically, the dispersing effect of salts of succinic acid and oxalic acid (Examples 1-9, 1-10) that do not contain a hydroxyl group was lower than that of salts of malic acid and tartaric acid (Examples 1-7, 1-8) that contain a hydroxyl group. From this, COO － It was hypothesized that the presence of an OH group along with the COOH group would impart higher dispersibility to particles such as manganese oxide. This is further supported by the fact that good dispersibility was observed in systems (Examples 1-6) where equimolar sodium hydroxide was added to lactic acid having one OH group to dissociate the hydrogen ion of the COOH group and form lactate ions.

[0075] In general, in hydroxy acids having both an OH group and a COOH group in a single molecule, it is known that the presence of an OH group near the COOH group facilitates the dissociation of the hydrogen ion of the OH group. The good dispersibility of the above-mentioned carboxylic acids with OH groups on particles such as manganese oxide is presumed to be due to at least some of the OH groups interacting with manganese atoms on the surface of the particles, releasing the hydrogen ions of the OH groups and resulting in a negative surface charge.

[0076] Furthermore, the OH group of the lactic acid mentioned above is NH ２ Alanine is an amino acid that has a structure equivalent to that of a substituted group, and CH is different from alanine. ２ In systems where sodium hydroxide, a strong base, was added to glycine with few groups to dissociate the hydrogen ions of the COOH group (Examples 1-12, 1-13), the effect of dispersing particles such as manganese oxide was also observed. From this, it was inferred that the presence of an amino group near the carboxyl group also enhances the effect of manganese oxide and other powders as a dispersant.

[0077]

[0078] (2) Evaluation of dispersants: alkylamine [Example 2-1] The above Mn ３ O ４ Mn was prepared in the same manner as in Example 1-2, except that 0.0780 g (1.32 mmol) of isopropylamine (Tokyo Chemical Industries, purity >99.0%), equivalent to 30 mol% of the powder (1.00 g), was added as a dispersant. ３ O ４ The powder was dispersed in pure water. As a result, almost all of the Mn used was dispersed. ３ O ４ The powder is dispersed in pure water and is yellowish-brown Mn ３ O ４ A dispersion of particles was obtained.

[0079] When the resulting dispersion was mixed with methanol in the same volume as pure water and stirred, a good dispersion state was maintained, and Mn dispersed in the pure water. ３ O ４It was demonstrated that the particles could be transferred into an organic solvent while maintaining their dispersion state. Generally, alkylamines such as isopropylamine have affinity for various organic solvents, so it was inferred that manganese oxide particles dispersed in the aqueous phase using isopropylamine could subsequently be dispersed in an organic solvent as well.

[0080] [Example 2-2] As a dispersant, Mn ３ O ４ Ball milling was performed in the same manner as in Example 1-1, except that an amount of isopropylamine equivalent to 3 mol% of the powder was used, and then a small amount of pure water was added, and Mn ３ O ４ The particles were recovered as a dispersion. When this dispersion was filtered with a cotton plug, there was almost no residue of coarse particles on the cotton plug, and the Mn used was recovered. ３ O ４ Almost the entire amount could be recovered as a dispersion. A photograph of the manganese oxide particle dispersion prepared in Example 2-2 is shown in Figure 1. It was shown that when isopropylamine was used as a dispersant, the resulting dispersion could maintain a stable dispersion state for at least one day, similar to when trisodium citrate was used as the dispersant.

[0081] [Examples 2-3 to 2-6], [Comparative Example 4] As a dispersant, a water-soluble substance with NH at the end. ２ Using various alkylamines having a group, and appropriately changing the mixing ratio, etc., Mn ３ O ４ We attempted to disperse the powder in pure water. The type and amount of dispersant used, the stirring time, and the dispersibility when using the dispersant are shown in Table 2, along with the results from Examples 2-1 and 2-2 above. The reagents used as dispersants were all commercially available reagents.

[0082] As shown in Table 2, it was found that powders such as manganese oxide could be well dispersed in the aqueous phase regardless of which alkylamine was used in Examples 2-1 to 2-6. On the other hand, NH has a cyclic structure. ２ When pyridine (Comparative Example 4), a water-soluble amine without a group, was used, no dispersion of manganese oxide in the aqueous phase was observed.

[0083] From these results, NH ２ By mixing various alkylamines having a group with manganese oxide or the like in an aqueous phase, the alkylamine molecules can partially generate alkylammonium ions and hydroxide ions through an equilibrium reaction with water molecules, and these hydroxide ions supply a negative charge to the particle surface of manganese oxide or the like, or the NH ２ It is presumed that the group becomes dispersible in the aqueous phase through a mechanism such as coordinating with manganese atoms exposed on the crystal surface of manganese oxide, thereby modifying the surface. The hydrophobic alkyl chain of the alkylamine can be used within a range that does not hinder the water solubility of the molecule. Furthermore, as shown in Examples 2-3 to 2-5, it is presumed that the hydrophilicity of heteroatom portions such as oxygen and nitrogen contained in the alkyl chain makes it possible to disperse particles such as manganese oxide in the aqueous phase.

[0084]

[0085] (3) Evaluation of dispersants: phosphates, borates, carbonates [Example 3-1] As a dispersant, sodium phosphate dodecahydrate (Na) was used instead of the above trisodium citrate dihydrate. ３ PO ４ 12H ２ O, Kanto Chemical, Special Grade) 0.166g (4.37 x 10) －１ Except for using mmol, Mn was prepared in the same manner as in Example 1-2. ３ O ４ When the powder was dispersed in pure water, almost all of the Mn ３ O ４ The powder is dispersed in pure water and is yellowish-brown Mn ３ O ４ An aqueous dispersion was obtained.

[0086] [Examples 3-2 to 3-5], [Comparative Examples 5 to 7] Various inorganic acid salts, etc., were used as dispersants, and the mixing amounts were changed as appropriate, in the same manner as in Examples 1 and 2. ３ O ４We attempted to disperse the powder in pure water. The type and amount of dispersant used, the stirring time, and the dispersibility when using the dispersant are shown in Table 3, along with the results from Example 3-1 above. The reagents used as dispersants were all commercially available reagents.

[0087] As shown in Table 3, when using sodium nitrate (Comparative Example 5) or sodium chloride (Comparative Example 6), which form monovalent ions, it was difficult to disperse the manganese oxide powder. However, when using salts of phosphoric acid, boric acid, or carbonate, which can form polyvalent anions, it was possible to disperse the manganese oxide powder in pure water and prepare an aqueous dispersion of manganese oxide particles.

[0088] From the above results, it was observed that when using salts of inorganic acids such as phosphoric acid, boric acid, and carbonic acid as dispersants, dispersants that form polyvalent anions in pure water tend to exhibit high dispersibility of particles such as manganese oxide. This suggests that the high valency of the ions increases their ability to interact with the surface of manganese oxide particles, and that the amount of negative charge attached to the surface of manganese oxide particles modified by these polyvalent ions increases, resulting in improved dispersibility of manganese oxide.

[0089] On the other hand, when sodium sulfate (Comparative Example 7), which similarly forms divalent ions, was used, no dispersion of manganese oxide powder was observed. Similar to polyvalent carboxylic acids, polyvalent salts such as phosphates, borates, and carbonates function as good dispersants, while sulfates do not provide dispersibility. Although not bound by theory, it is presumed that the salts that exhibit dispersion effects are all salts of weak acids, their aqueous solutions are weakly basic, and they can bond with manganese atoms on the surface of particles such as manganese oxide via multiple oxygen atoms contained in their polyvalent ions.

[0090]

[0091] (4) Evaluation of dispersants: bases etc. [Example 4-1] As a dispersant, Mn ３ O ４Except for using an amount of sodium hydroxide (Kanto Chemical, special grade) equivalent to 30 mol% relative to Mn, the method was the same as in Example 1-2. ３ O ４ When the powder was dispersed in pure water, almost all of the Mn ３ O ４ The powder is dispersed in pure water and is yellowish-brown Mn ３ O ４ An aqueous dispersion was obtained.

[0092] [Example 4-2] Mn ３ O ４ To the powder (1.00 g), 88 μL of aqueous ammonia (Kanto Chemical, special grade, 28-30%) was added using a micropipette, and then pure water was added to make a total volume of 10 mL. Otherwise, the process was the same as in Example 1-2. ３ O ４ When the powder was dispersed in pure water, almost all of the Mn ３ O ４ The powder is dispersed in pure water and is yellowish-brown Mn ３ O ４ Aqueous dispersions were obtained. The results of Examples 4-1 and 4-2 are shown in Table 4.

[0093]

[0094] As shown in Table 4, it was demonstrated that powders such as manganese oxide can be well dispersed by dissolving strongly alkaline sodium hydroxide or weakly alkaline ammonia in a solvent (pure water). When sodium hydroxide or ammonia dissolves in pure water, hydroxide ions (OH) are released. － Since it generates ), it is presumed that the hydroxide ions interact with the surface of particles such as manganese oxide, and, similar to the case of ionic dispersants such as citrate, the surface of the particles such as manganese oxide becomes negatively charged, creating a repulsive force between the particles and making them dispersible in water.

[0095] Furthermore, especially when aqueous ammonia is used, it is presumed that the dispersibility of particles such as manganese oxide is improved by a mechanism similar to that when alkylamines are used as dispersants, such as ammonium ions coordinating with manganese atoms exposed on the crystal surface of manganese oxide and modifying that surface.

[0096] (5) Evaluation of dispersants: Complex anionic substances [Example 5-1] The above Mn ３ O ４ For every 1.00 g of powder, add 0.106 g of sodium ferrocyanate decahydrate (Kanto Chemical, special grade), which is equivalent to 5.01 mol% of the powder (2.19 x 10 －１ Mn was added in the same manner as in Example 1-2, except that mmol was added as a dispersant. ３ O ４ When the powder was dispersed in pure water, almost all of the Mn ３ O ４ The powder is dispersed in pure water and is yellowish-brown Mn ３ O ４ An aqueous dispersion was obtained. The supernatant liquid obtained by centrifugation of this dispersion was yellow, suggesting that some of the ferrocyanate ions were oxidized and converted to ferricyanate ions.

[0097] [Example 5-2] Mn was prepared in the same manner as in Example 1-2, except that sodium ferrocyanate was replaced with potassium ferricyanate (Kanto Chemical, special grade). ３ O ４ When the powder was dispersed in pure water, Mn ３ O ４ The powder is dispersed in pure water and is yellowish-brown Mn ３ O ４ An aqueous dispersion was obtained.

[0098] [Example 5-3] The above sodium ferrocyanate was mixed with 0.0345 g of potassium permanganate (Nacalai Tesque, special grade) (2.18 x 10 －１ Except for replacing it with mmol, the method is the same as in Example 1-2, but Mn ３ O ４When the powder was dispersed in pure water, a dark brown aqueous dispersion was obtained in which almost all of the powder was dispersed in the pure water. The dispersed particles were black in color, and Mn was found in potassium permanganate. ３ O ４ It was inferred that at least some of the manganese atoms contained in the solution had been oxidized. Furthermore, the supernatant liquid obtained by centrifugation of the dispersion was purple in color, suggesting the presence of unreacted potassium permanganate.

[0099] Table 5 shows the type and amount of dispersant added, the stirring time, and the dispersibility when using the dispersant for Examples 5-1 to 5-3 described above. As shown in Table 5, it was demonstrated that the presence of tetravalent anions such as ferrocyanate ions and trivalent anions such as ferricyanate ions in the aqueous phase resulted in good dispersion of particles such as manganese oxide.

[0100] Although not bound by theory, the reason why the above-mentioned ferrocyanate ions and ferricyanate ions exhibit dispersibility of powders such as manganese oxide is due to the cyanide ligands (CN) in these complex anions. － Of these, the N atom located at the end of the structure coordinated to the Fe atom via a carbon atom can form a coordinate bond with the manganese atom on the surface of the manganese oxide particle. It is presumed that this coordinate bond imparts a negative charge to the manganese oxide particle, resulting in its dispersion in the dispersion medium.

[0101] Furthermore, it has been shown that the presence of monovalent permanganate ions in the aqueous phase also allows for good dispersion of powders such as manganese oxide. Although not bound by theory, the reason for the resulting dispersibility is presumed to be that permanganate ions are composed of the same elements as manganese oxide, thus creating a certain affinity between them, and that the oxo ligands of permanganate ions can coordinate bond to manganese atoms on the surface of manganese oxide, etc. As a result of this coordination bonding, negative charges are imparted to the manganese oxide particles, etc., making them dispersible in the dispersion medium.

[0102]

[0103] (6) Manganese oxide (Mn３ O ４ Evaluation of the effect of differences in manganese oxide (Mn) on dispersibility [Example 6] Disperse manganese oxide (Mn ３ O ４ In order to verify the differences in dispersibility due to the manufacturing method and purity of the powder, the Mn used ３ O ４ The powder was changed from the above-mentioned high-purity chemical product to Mn from Tokyo Chemical Industry Co., Ltd. and Sigma-Aldrich Co., Ltd. (purity 97%). ３ O ４ The powder was changed, and in the same manner as in Examples 1-1, 1-2, 2-1, and 2-2, trisodium citrate or isopropylamine was used as a dispersant, and Mn was added to pure water by stirring with a stirrer or ball milling. ３ O ４ The powder was dispersed. As a result, Mn ３ O ４ Regardless of the source from which the powder was purchased, a good dispersion of manganese oxide particles was obtained in all cases.

[0104] (7) Evaluation of the effect of differences in oxidation state on dispersibility [Example 7] In order to verify the difference in dispersibility depending on the oxidation state of the manganese oxide powder to be dispersed, the manganese oxide powder used was MnO ２ (Fujifilm Wako, 99.5% purity, and Mn) ２ O ３ Dispersion treatment of manganese oxide powder in pure water was carried out in the same manner as in Example 1-2 (dispersant: trisodium citrate), Example 2-1 (dispersant: isopropylamine), Example 3-1 (dispersant: sodium phosphate), and Example 5-1 (dispersant: sodium ferrocyanate), except that the dispersant was changed to (Sigma-Aldrich, 99% purity, 325 mesh). Dispersion treatment of manganese oxide powder using ball milling was also carried out in the same manner as in Example 1-1 and Example 2-2.

[0105] Table 6 shows the conditions for the dispersion treatment and the dispersibility observed during the dispersion treatment. As shown in Table 6, manganese oxide (MnO) has different oxidation states of manganese atoms. ２ powder, Mn ２ O ３It has been shown that all of the powders can be dispersed in an aqueous dispersion medium by using the dispersant discovered by the present invention. The manganese atoms contained in the manganese oxide are Mn ３ O ４ Since it is thought to carry a positive charge, similar to the case mentioned above, it is presumed that it can be dispersed in an aqueous dispersion medium by the aforementioned dispersant.

[0106]

[0107] (8) Evaluation of the effect of other metal elements on dispersibility [Examples 8-1, 8-2] In order to verify the effect of the above dispersant on metal oxides containing other metal elements along with manganese, LiMn, which functions as an electrode active material similar to manganese oxide, was used. ２ O ４ (Sigma-Aldrich, battery grade), and LiNi ０．５ Mn １．５ O ４ (Tokyo Chemical Industries, purity > 99.9%) was dispersed in pure water using the same method as in Example 2-2 (dispersant: isopropylamine).

[0108] Table 7 shows the conditions for the dispersion treatment and the results of the dispersibility evaluation observed during the dispersion treatment. As shown in Table 7, it was demonstrated that even substances that are manganese-containing co-oxides due to the presence of metal elements other than manganese (Li, Ni) can be dispersed in an aqueous dispersion medium by using the dispersant discovered by the present invention. In the case of such manganese and other metal elements co-oxides, the manganese atoms contained in the substance are in a high oxidation state of trivalent or tetravalent, similar to the case of manganese oxide, and it is presumed that they can interact with the dispersant by a similar mechanism and be dispersed in an aqueous dispersion medium. Thus, it was confirmed that the dispersant of the present invention is applicable not only to single-component manganese oxide but also to multi-component oxide active materials for lithium-ion batteries, such as lithium manganese spinel and nickel-manganese composite oxides.

[0109]

[0110] The manganese oxide dispersions obtained in Examples 1-3, 2-1, 7-1, 7-2, 7-11, and 7-12 were diluted with pure water (12 μL) to a manganese oxide weight percentage of 5%, and then further diluted with pure water (3.0 mL). The particle size of these dilutions was measured using dynamic light scattering particle size distribution (DLS, Otsuka Electronics Co., Ltd., ELSZ-1000ZS). Figure 2 summarizes the measurement results. DLS measurements were also performed on the manganese-containing co-oxide dispersions obtained in Examples 8-1 and 8-2 in the same manner. Figure 3 shows the measurement results.

[0111] As shown in Figure 2, in the dispersions prepared in each of the above examples, regardless of the type of dispersant or the oxidation state of manganese oxide, the dispersed phase mainly had particle sizes of approximately 80 to 250 nm or 200 to 700 nm, confirming the formation of a stable dispersion structure. This indicates that each dispersant uniformly modifies the surface of the manganese oxide particles and suppresses aggregation between particles. Furthermore, as shown in Figure 3, LiMn containing manganese atoms in an oxidized state as a co-oxide ２ O ４ LiNi ０．５ Mn １．５ O ４ In this regard, it was confirmed that particles were dispersed within a particle size range of approximately 100 to 1000 nm by using a dispersant, and it became clear that a stable dispersion state could be maintained in the dispersion medium, similar to that of a single manganese oxide system. These results demonstrate that the dispersant of the present invention can stably disperse not only manganese oxide systems but also complex oxide systems in the dispersion medium.

[0112] Figure 4 shows scanning electron microscope (SEM) images (JEOL Ltd., JSM-IT800) of aggregates obtained by dropping the dispersions prepared in Examples 1-3 and 2-1 onto an observation base made of carbon and drying them. As shown in Figure 4, the dispersions prepared in the above examples re-aggregated in a porous manner while maintaining their particle shape even after the dispersion medium was removed, indicating that they were formed as aggregates with a high porosity. This suggests that in dispersions using the dispersant according to the present invention, the bonding between particles is not by strong sintering, but mainly by reversible aggregation via electrostatic or coordination interactions. Therefore, the particle surface remains active even after drying, making it suitable for re-dispersion and compounding with other components in subsequent processes.

[0113] 2. Secondary battery using a dispersion of manganese oxide, etc. obtained in the present invention [Example 9] A positive electrode made using a dispersion of manganese oxide, etc. particles obtained in the present invention by the method described below is used with metallic zinc foil as the negative electrode, and zinc sulfate (ZnSO4) is used. ４ ) and manganese sulfate (MnSO4) ４ A secondary battery was fabricated using a mixed aqueous solution of ) as the electrolyte.

[0114] Mn produced in the example shown ３ O ４ Using a particle dispersion, Mn ３ O ４ A binder-free cathode was prepared as follows, using as the active material and single-walled carbon nanotubes (SWNTs) as a conductive additive. The dispersion of manganese oxide and other particles obtained above and the SWNT dispersion (0.4% by weight, KJ Special Paper Co., Ltd., TB004M) as a conductive additive were mixed with Mn ３ O ４ A mixture was prepared by mixing the particles and SWNT so that the mass percentage of SWNT relative to the total mixture was 3% by mass.

[0115] Figure 5 shows an example of the above mixture, Mn prepared in Example 2-2 (dispersant: isopropylamine). ３ O ４ The appearance of the mixture prepared using the particle dispersion and the SWNT dispersion is shown. At this time, the Mn in the mixture ３ O ４The mass percentage of the particles is 2.5% by mass, and the Mn ３ O ４ The mixture of particles and SWNTs was mixed so that the mass ratio of SWNTs to the total mixture was 3% by mass. As shown in Figure 5, the dispersion according to the present invention can be mixed with the SWNT dispersion while maintaining its dispersion state, and it was confirmed that it maintains a stable dispersion state without separation or precipitation of the dispersed phase even when left standing for at least one day after mixing.

[0116] Using a mixture of manganese oxide particles and SWNTs as described above, a PTFE membrane filter (pore size 0.1 μm, Sumitomo Electric Industries, Ltd., HPW-010-30) was loaded with manganese oxide particles at a concentration of 0.5 mg / cm³. ２ The above mixture, in an amount of approximately that size, is subjected to suction filtration, and Mn ３ O ４ After separating the dispersion medium from the mixture of particles and SWNTs, the mixture was heated and dried at 120°C to obtain a composite of SWNTs and manganese oxide particles in film form on a PTFE membrane filter. Despite not containing any binder components, the composite exhibited a certain degree of shape retention due to the SWNTs functioning as a structural retainer, and could be handled as a self-supporting film.

[0117] Figure 6 shows an example of the above-mentioned film body, Mn prepared in Example 1-2. ３ O ４ Using a dispersion of particles, Mn formed into a film by the above method ３ O ４ The image shows an SEM image of the composite of particles and SWNT. As shown in the low-magnification SEM image (a), a film of substantially uniform thickness was formed by the suction filtration described above. Furthermore, as shown in the high-magnification SEM image (b), the film contains stretched SWNT and Mn ３ O ４ The particles are uniformly intertwined with each other, and within the network formed by SWNTs, Mn ３ O ４ It was observed that the secondary particles composed of these elements were distributed in a form that retained them, and that the structure also possessed a high porosity.

[0118] Metallic zinc foil (0.1 mm thick, Takeuchi Metal Foil & Powder Industry Co., Ltd., 99.99%) was processed into a φ16 mm circular shape using an electrode punching machine (MTI Corp., MSK-T-10) and used as the negative electrode of the secondary battery. In addition, 2.0 mol / L of ZnSO4 was used. ４ (Kanto Chemical, special grade) and 0.6 mol / L MnSO ４ An aqueous solution containing (Kanto Chemical, special grade) was used as the electrolyte.

[0119] A zinc-ion secondary battery with the structure shown in Figure 7 was created using a PTFE membrane filter to which the composite of film-like manganese oxide particles and SWNTs was attached, and its characteristics as a battery were evaluated. In this zinc-ion secondary battery, a PTFE membrane filter 3 to which the composite of manganese oxide particles and SWNTs 2 was attached was used as a reference, and a 350 μm thick glass filter 4 (manufactured by ADVANTEC, GF-75) was laminated on the membrane filter side, forming a separator together with the PTFE membrane filter 3, and a metallic zinc foil 5 was further laminated as the negative electrode. ３ O ４ Carbon paper 6 (Mitsubishi Chemical Corporation, MFO) was laminated on the surface of the particle / SWNT composite as a current collector. The laminate was sandwiched between spacers 7 and 8 on both sides and placed in coin cell cases 9 and 9' (MTI Corp., CR2032 coin cell), and the electrolyte was permeated to fabricate a zinc-ion secondary battery.

[0120] Figure 8 shows (a) manganese oxide (Mn) related to Example 1-2. ３ O ４ ) dispersion, and (b) manganese oxide (Mn) according to Example 2-1 ３ O ４ The charge-discharge characteristics of zinc-ion secondary batteries using cathode materials prepared with each dispersion are shown. The charge-discharge characteristics were measured under constant current conditions using a charge-discharge evaluation device (Meiden Hokuto Co., Ltd., HJ1001SD8). In all cases, Mn ３ O ４ By using a particle / SWNT composite as the cathode material, excellent charge-discharge characteristics exhibiting high capacity were obtained, confirming that the composite effectively functions as a cathode material.

[0121] Figure 9 shows (a) manganese oxide (MnO) related to Example 7-1. ２ ) dispersion, and (b) manganese oxide (Mn) according to Example 7-8 ２ O ３ The charge-discharge characteristics of zinc-ion secondary batteries using cathode materials prepared with each dispersion are shown below, evaluated using a charge-discharge evaluation device under a constant current (2.5 A / g). In all cases, good charge-discharge characteristics showing high capacity were obtained. Manganese oxide (Mn ３ O ４ ) Similar to the case using particle / SWNT composites, MnO ２ Particle or Mn ２ O ３ By using a composite of particles and SWNTs as the cathode material, excellent charge-discharge characteristics exhibiting high capacity were observed, confirming that the composite functions as a cathode material.

[0122] Figure 10 shows the LiNi according to Example 8-1. ０．５ Mn １．５ O ４ Using the dispersion, the particle load is 1.5 mg / cm ２ The charge-discharge characteristics of a zinc-ion secondary battery using a cathode material fabricated to achieve the following characteristics were evaluated using a charge-discharge evaluation device under a constant current (2.5 A / g). The results are shown below. Mn ３ O ４ Similar to the case where manganese oxide dispersions such as the above are used, LiNi, a metal composite oxide containing manganese ０．５ Mn １．５ O ４ By using a composite of these particles and SWNTs as the cathode material, good charge-discharge characteristics exhibiting high capacity were obtained, confirming that the composite functions as a cathode material.

[0123] By using the dispersion of manganese oxide and other particles according to the present invention, it is possible to mix manganese oxide and other substances well, and it can be used in the manufacture of articles that use various manganese oxide powders, such as electrode materials containing manganese oxide.

[0124] 1. Zinc-ion secondary battery 2. Composite of manganese oxide particles and SWNT 3. PTFE membrane filter 4. Glass filter 5. Metallic zinc foil 6. Carbon paper 7,8. Spacer 9,9' Coin cell case

Claims

1. A method for producing a dispersion, characterized by comprising the step of mixing a dispersant that does not contain carbon atoms or contains 10 or fewer carbon atoms, an aqueous dispersion medium, and a powder of a manganese-containing metal oxide, thereby redispersing the manganese-containing metal oxide in the aqueous dispersion medium.

2. A method for producing the dispersion according to claim 1, characterized in that the dispersant is a salt that exhibits basicity when dissolved in the aqueous dispersion medium and generates ions represented by the following formula 1: However, in the following formula 1, R is an OH group, NH ２ This is an organic group containing a heteroatom with 9 or fewer carbon atoms, which may include a COOH group or a hydrogen ion that is dissociated.

3. The method for producing the dispersion liquid according to claim 1, characterized in that the dispersant contains a molecule having a structure represented by the following formula 2 and a strong base: However, in formula 2, R' is an organic group containing a heteroatom having 9 or less carbon atoms and containing an OH group, NH ２ group, or a COOH group.

4. The method for producing a dispersion according to claim 1, characterized in that the dispersant is a salt or molecule that generates hydroxide ions when dissolved in the aqueous dispersion medium.

5. The method for producing the dispersion according to claim 1, characterized in that the dispersant is a water-soluble alkylamine.

6. The method for producing the dispersion according to claim 1, characterized in that the dispersant is a complex salt containing ferrocyanic acid, ferricyanic acid, or permanganate ions.

7. A method for producing a dispersion according to claim 1, characterized by further comprising the step of dispersing fine carbon particles in the aqueous dispersion medium.

8. The method for producing the dispersion according to claim 7, characterized in that the above-mentioned minute carbon material is a carbon nanotube.

9. A method for producing aggregates, characterized by comprising the step of removing the aqueous dispersion medium from a dispersion produced by any one of claims 1 to 8 to produce aggregates containing particles of a metal oxide containing manganese.

10. A dispersion characterized in which particles of a metal oxide containing manganese with an average particle diameter of 1000 nm or less are dispersed in an aqueous dispersion medium.

11. The dispersion according to claim 10, characterized in that fine carbon particles are further dispersed in the aqueous dispersion medium.

12. The dispersion according to claim 11, characterized in that the above-mentioned minute carbon material is a carbon nanotube.

13. An aggregate comprising particles of a metal oxide containing manganese, characterized in that the aggregate is formed by removing at least a portion of the aqueous dispersion medium from the dispersion described in any one of claims 10 to 12.

14. A battery characterized by containing the aggregate described in claim 13 as an electrode material.

15. A dispersant for dispersing a powder of a metal oxide containing manganese in an aqueous dispersion medium, wherein the dispersant does not contain carbon atoms, or contains 10 or fewer carbon atoms.

16. The above dispersant exhibits basicity upon dissolution in the above aqueous dispersion medium, and the following formula 1: (In the formula, R is an organic group having 9 or fewer carbon atoms, and the organic group is an OH group, NH ２ The dispersant according to claim 15, characterized in that it is a salt that generates an ion represented by a group or a COOH group in which a hydrogen ion may be dissociated.

17. The above dispersant is given by the following formula 2: (In the formula, R' is an organic group having 9 or fewer carbon atoms, and the organic group is an OH group, NH ２ The dispersant according to claim 15, characterized by comprising a molecule having a structure represented by a group or a COOH group, and a strong base.

18. The dispersant according to claim 15, characterized in that the dispersant is a salt or molecule that generates hydroxide ions when dissolved in the aqueous dispersion medium.

19. The dispersant according to claim 15, characterized in that the above dispersant is a water-soluble alkylamine.

20. [Correction based on Rule 91 16.01.202] 6] The dispersant according to claim 15, characterized in that the dispersant is a complex salt containing ferrocyanic acid, ferricyanic acid, or permanganate ions.

Images