JP7449527B2 - Electrode material for power storage device, electrode, power storage device, electrical equipment, and method for manufacturing electrode material for power storage device - Google Patents

Description

The present invention relates to an electrode material for a power storage device, an electrode, a power storage device, an electric device, and a method for manufacturing an electrode material for a power storage device.

In recent years, with the spread of notebook computers, smartphones, mobile game devices, portable electronic devices such as PDAs; electric vehicles; and home solar power generation, there has been a demand for the performance of energy storage devices that can be repeatedly charged and discharged. It's increasing. In order to make portable electronic devices lighter and allow them to be used for longer periods of time, and to enable electric vehicles to travel longer distances, there is a need for smaller power storage devices and higher energy density. Examples of power storage devices include secondary batteries and capacitors. Currently, secondary batteries in particular are used as power sources for portable electronic devices, electric vehicles, household power sources, and the like.

Conventionally, alkaline secondary batteries using water-based electrolytes, such as nickel-cadmium (Ni-Cd) batteries and nickel-hydrogen (Ni-MH) batteries, were the mainstream as secondary batteries, but the miniaturization described above Due to the demand for higher energy density, the use of lithium ion batteries using non-aqueous electrolytes is increasing. Furthermore, among capacitors with excellent output density, lithium ion capacitors have high energy density, and therefore are expected to be increasingly used in output applications. Recently, research and development has been progressing on batteries in which ions responsible for electrical conduction are replaced with sodium or potassium instead of lithium.

For example, a lithium ion battery or a sodium ion battery is generally composed of a positive electrode; a negative electrode; an electrolytic solution or electrolyte; and a separator. The electrode (positive electrode or negative electrode) is produced, for example, by applying a slurry consisting of an electrode material (mainly an active material), a binder, and a conductive additive onto a current collector and drying the slurry.

Lithium cobalt oxide (LiCoO ₂ ) and ternary materials (Li (Ni, Co, Mn) O ₂ ) are used as positive electrode materials (mainly positive electrode active materials) for commercially available lithium ion batteries. . The practical discharge capacity of these is about 150 to 160 mAh/g. Since cobalt and nickel are rare metals, there is a need for positive electrode materials that can replace these rare metals. Further, as negative electrode materials (mainly negative electrode active materials), graphite, hard carbon, lithium titanate (Li ₄ Ti ₅ O ₁₂ ), etc. are used. Although the practical discharge capacity of these is about 150 to 350 mAh/g, there is a demand for an even higher capacity.

Among a wide variety of electrode materials, sulfur is known as an attractive electrode material because it has a large number of reactive electrons per unit mass, has a theoretical capacity of 1672 mAh/g, and has a low material cost. Further, sulfur exhibits a charge/discharge plateau around 2V (vs. Li/Li ⁺ ), and can be used as both a positive electrode and a negative electrode.

However, when electrodes made of simple sulfur are lithiated (discharged when used as a positive electrode, charged when used as a negative electrode), lithium polysulfide (Li ₂ S _x : x = 2 to 8) or low molecular weight Sulfides are generated and are easily eluted into electrolytes (especially carbonate solvents), making it difficult to maintain a stable reversible capacity. Therefore, in order to suppress sulfur elution into the electrolyte, in addition to sulfur-based organic materials with -CS-CS- bonds or SS- bonds, sulfur-based materials such as composite materials with sulfur and materials other than sulfur are used. Electrode materials have been proposed.

Furthermore, recently, organic compounds containing sulfur have been proposed as electrode materials (Patent Documents 1 to 7 and Non-Patent Documents 1 to 5). Among them, sulfurized polyacrylonitrile (sulfur-modified polyacrylonitrile) has been found to have a reversible capacity of 500 to 700 mAh/g and stable life characteristics.

It is also known that sulfur-based materials can electrochemically react with alkali metal ions other than lithium. Among alkali metals other than lithium, sodium is abundant in seawater and is the 6th most abundant element in the earth's crust. Unlike lithium, sodium is not distributed as unevenly as lithium, making it a low-cost energy storage device. It is expected that

For example, Non-Patent Document 6 shows that sulfur-modified acrylonitrile exhibits excellent properties even when sodium is used as a charge carrier.

WO2010/044437 publication Japanese Patent Application Publication No. 2014-179179 JP2014-96327A JP2014-96326A Japanese Patent Application Publication No. 2012-150933 JP2012-99342A Japanese Patent Application Publication No. 2010-153296

Yukihiro et al., “Development of lithium ion battery active materials and electrode material technology,” Science & Technology Publishing, pp. 194-222 (2014) Toshikatsu Kojima et al., 53rd Battery Symposium Abstracts, 3C27, p. 202 (2012) Yukitakuhiro et al., 53rd Battery Symposium Abstracts, 3C28, p. 203 (2012) Toshikatsu Kojima et al., 54th Battery Symposium Abstracts, 1A08, p. 7 (2013) Toshikatsu Kojima et al., 54th Battery Symposium Abstracts, 3E08, p. 344 (2013) Yukihiro et al., “Latest technological trends in rare metal-free secondary batteries”, CMC Publishing, pp. 81-101 (2013)

Polyvinylidene fluoride (PVDF) has been widely put into practical use as a binder for binding active materials in electrodes of power storage devices using non-aqueous electrolytes. PVDF is a binder that exhibits high flexibility and excellent oxidation resistance and reduction resistance, and an organic solvent such as N-methyl-2-pyrrolidone (NMP) is preferably used as a solvent when making it into a slurry. However, these organic solvents have relatively high manufacturing costs and environmental burdens. Therefore, organic solvent removal is required. Furthermore, when a sulfur-based electrode material is used, NMP dissolves sulfur in the electrode material, resulting in a decrease in electrode capacity. In addition, PVDF easily swells in a high-temperature electrolyte, and the swelling of PVDF reduces the electronic conductivity of the electrode material layer, which is one factor that deteriorates the output characteristics and cycle life characteristics of the electrode. Therefore, it is desirable to use a binder that does not use an organic solvent such as NMP and does not easily swell in the electrolytic solution.

In recent years, water-based binders such as carboxymethyl cellulose (CMC), acrylic resins, and alginic acid have attracted attention as binders that do not easily expand even in high-temperature electrolytes. By using a water-based binder for the electrode, water can be selected as the solvent for the slurry prepared in the electrode manufacturing process. Therefore, it is promising in terms of manufacturing cost and environment. Furthermore, since sulfur is not soluble in water, if water is used as a solvent for the slurry, a decrease in capacity due to sulfur elution into the slurry solvent can be prevented.

However, various sulfur-based materials used as electrode materials that have been reported so far are hydrophobic and have low wettability with water. Therefore, when using a binder using water as a solvent or dispersion medium (in other words, a water-based binder), it is difficult to disperse the hydrophobic sulfur-based material in the kneading step of slurry preparation. In an attempt to improve the dispersibility of a hydrophobic sulfur-based material and impart hydrophilicity to it, it is easy to think of using a surfactant or the like. However, when many surfactants are used in batteries, they decompose due to overcharging or being left at high temperatures, generating gas and deteriorating battery characteristics.

The present invention has been made in view of the current state of the prior art as described above, and its main purpose is to compensate for the drawbacks of hydrophobic active materials and to make hydrophobic active materials hydrophilic without deteriorating electrode characteristics. An object of the present invention is to provide an electrode material for a power storage device that can exhibit excellent dispersibility.

A first aspect of the present invention is an electrode material for an electricity storage device using a non-aqueous electrolyte, wherein the electrode material includes a composite powder, and both A component and B component are contained in one particle constituting the composite powder. The particles have a structure in which component B is supported, coated, or exposed on the surface of component A, and component A is a material capable of electrochemically occluding and releasing alkali metal ions. Component B is sulfur-modified cellulose having at least ₃ SO groups as a functional group, and Component B is 0.01% by mass or more with respect to 100% by mass of the total amount of Component A and Component B. The present invention relates to an electrode material for a power storage device using a non-aqueous electrolyte.

In the electrode material of the electricity storage device, the sulfur-modified cellulose may be sulfur-modified cellulose nanofibers with a maximum fiber diameter of 1 μm or less.

In the electrode material of the electricity storage device, the particles may be particles in which the A component is used as a matrix and the B component is dispersed in the matrix.

In the electrode material of the electricity storage device, the electrode material further contains a conductive material, and the conductive material is 0.1% by mass or more with respect to 100% by mass of the total amount of the A component, the B component, and the conductive material. It may be 30% by mass or less.

In the electrode material of the electricity storage device, the A component may be a sulfur-based organic material.

In the electrode material of the electricity storage device, the component A may be sulfur-modified polyacrylonitrile.

In the electrode material of the electricity storage device, the composite powder may have a median diameter (D50) of 0.1 μm or more and 50 μm or less.

A second aspect of the present invention relates to an electrode for an electricity storage device, which includes at least the electrode material, the binder, and the current collector.

In the electrode of the electricity storage device, the binder may be a water-based binder.

A third aspect of the present invention is an electricity storage device comprising a positive electrode, a negative electrode, and an electrolyte interposed between the positive electrode and the negative electrode, wherein either the positive electrode or the negative electrode is the electrode. Regarding devices.

A fourth aspect of the present invention relates to an electrical device using the electricity storage device.

A fifth aspect of the present invention is a method for producing an electrode material for the electricity storage device, wherein the A component or the precursor of the A component, the B component precursor, and sulfur are brought into contact with each other at 200°C. Component A is a material capable of electrochemically occluding and releasing alkali metal ions, the precursor of component A is an organic material, and the precursor of component A is an organic material, The present invention relates to a method for producing an electrode material for an electricity storage device, in which the precursor of component B is a cellulose material, and the cellulose material has an anionic group forming an alkali metal salt or an alkaline earth metal salt.

In the method for manufacturing an electrode material for an electricity storage device, the precursor of the component A, the precursor of the component B, or the precursor of the component A and the precursor of the component B may contain a conductive material.

In the method for manufacturing an electrode material for an electricity storage device, the precursor of component A may be polyacrylonitrile.

The method for manufacturing an electrode material for an electricity storage device may further include, after the heating step, a step of heating to 250° C. or higher in a reduced pressure or inert gas atmosphere.

In the method for manufacturing an electrode material for an electricity storage device, the precursor of component B may be a cellulose material dispersed or dissolved in a solvent.

In the method for manufacturing an electrode material for an electricity storage device, the cellulose material may have an alkali metal carboxylate salt as a functional group.

In the method for manufacturing an electrode material for an electricity storage device, the cellulose material may be cellulose nanofibers having a maximum fiber diameter of 1 μm or less.

According to the present invention, there is provided an electrode material for a power storage device that can compensate for the drawbacks of a hydrophobic active material, impart hydrophilicity to the hydrophobic active material, and exhibit excellent dispersibility without deteriorating electrode characteristics. can do.

It is a conceptual diagram of the cross section of the particle of composite powder, and the cross section of the particle of simple mixed powder. (a) shows a conceptual cross-sectional view of particles of a simple mixed powder, and (b), (c), and (d) show conceptual cross-sectional views of particles of a composite powder. It is a figure which shows the water dispersibility of the powder produced experimentally. (a) shows the water dispersibility of the sulfur-modified compound powder of Comparative Example 1, and (b) shows the evaluation results of the water dispersibility of the composite powder of Example 1. FIG. 2 is a diagram showing volume-based particle size distributions of powders obtained in Example 1 and Comparative Example 1, respectively. FIG. 3 is a diagram showing a charge-discharge curve of a battery produced in Comparative Example 1. 1 is a diagram showing a charge/discharge curve of a battery produced in Example 1. FIG. It is an IR spectrum of sulfur-modified cellulose powder B'1. It is an IR spectrum of sulfur-modified cellulose powder B'2. It is an IR spectrum of sulfur-modified cellulose powder B'4. This is an IR spectrum of sulfur-modified cellulose powder B'5.

[Electrode materials for power storage devices]
An electrode material for an electricity storage device according to the present disclosure is an electrode material for an electricity storage device using a non-aqueous electrolyte, and the electrode material includes a composite powder, and a component A and a component B are contained in one particle constituting the composite powder. The particles have a structure in which component B is supported, coated, or exposed on the surface of component A, and component A is capable of electrochemically occluding and releasing alkali metal ions. The B component is sulfur-modified cellulose having at least ₃ SO groups as a functional group, and the B component is 0.01 mass % with respect to 100 mass % of the total amount of the A component and the B component. % or more.

In this way, the particles constituting the composite powder have a structure in which component B is supported, coated, or exposed on the surface of component A, and even if component A is a hydrophobic material, component B is hydrophilic. Composite powder has excellent hydrophilicity. Therefore, according to the electrode material of the electricity storage device of the present disclosure, even if water and a binder using water as a solvent or dispersion medium (aqueous binder) are used, a slurry with excellent dispersibility and excellent uniformity can be easily produced. Therefore, the manufacturing time of the electrode can be shortened. Therefore, according to the electrode material of the electricity storage device of the present disclosure, the productivity of the electrode is significantly improved compared to conventional electrode materials, and it is possible to achieve both high capacity and high output of the electricity storage device, and use It becomes possible to expand the usage.

In the present disclosure, an electricity storage device refers to a device or element that has at least a positive electrode and a negative electrode and can extract chemically, physically, or physicochemically stored energy in the form of electric power. Examples of power storage devices include rechargeable and dischargeable secondary batteries, and capacitance devices such as capacitors and capacitors. More specifically, examples include lithium ion batteries, lithium ion capacitors, sodium ion batteries, sodium ion capacitors, potassium ion batteries, and potassium ion capacitors.

Further, the term "electrode material" refers to a material that constitutes an electrode. Examples of materials constituting the electrode include active materials, conductive aids, binders, current collectors, and other materials.

<Composite powder>
The composite powder of the present disclosure includes both component A and component B in one particle constituting the composite powder, and the particle has a structure in which component B is supported, coated, or exposed on the surface of component A. be. The particles may have at least one of supported, coated, and exposed structures.

For example, it may be one in which component A is the core and component B is supported or coated around the core (on the surface). Supporting or covering means that the surface of component A is partially or completely covered with component B. Moreover, exposure means a state in which the A component is used as a matrix, the B component exists in a dispersed state in the matrix, and the B component appears on the surface of the A component. Part of the B component may be exposed on the surface of the A component.

It is preferable that the particles have the component A as a matrix, and the component B exists in a dispersed state in the matrix. Dispersion in the matrix may be a state in which component A contains component B as a filler.

Composite is a different concept from mixing; mixed powder is simply an aggregation of particles composed of component A and particles composed of component B, whereas composite powder is a collection of particles composed of component A and component B, while composite powder is a combination of particles composed of component A and component B. Both A component and B component are contained in one particle. As an example, FIG. 1(a) shows a cross-sectional conceptual diagram of particles of a simple mixed powder, and FIGS. 1(b), (c), and (d) show cross-sectional conceptual diagrams of composite powder particles for comparison. FIG. 1(b) is a conceptual diagram when the surface of component A is completely covered with component B, and FIG. 1(c) is a conceptual diagram when the surface of component A is partially covered (in other words, supported) by component B. FIG. 1(d) is a conceptual diagram when the B component is dispersed in the matrix of the A component and a portion of the B component is exposed on the surface of the A component.

When dispersing a mixed powder of components A and B in water, component B alone has excellent hydrophilicity, so only component B is easily dispersed and the components A and B are easily separated. However, since the particles constituting the composite powder of the present disclosure have a structure in which component B is supported, coated, or exposed on the surface of component A, they exhibit excellent dispersibility in water, and both component A and component B are dispersed. It can be a state.

The median diameter (D50) of the composite powder of the present disclosure is preferably 0.1 μm or more and 50 μm or less, more preferably 0.1 μm or more and 30 μm or less, even more preferably 0.5 μm or more and 15 μm or less, and 0.55 μm or more and 14.5 μm or less. Most preferred. By setting the median diameter (D50) of the composite powder within the above range, the electrode material can provide an electrode with excellent output characteristics and cycle life characteristics. By being 0.1 μm or more, the specific surface area does not become too high and the amount of binder required for electrode formation does not increase. As a result, the electrode has excellent output characteristics and energy density. In addition, when the particle size is 50 μm or less, the particle surface area becomes large, and practical input/output characteristics can be obtained.

Here, the median diameter (D50) means the particle diameter at which the cumulative frequency is 50% in terms of volume based on volume using a laser diffraction/scattering particle size distribution measurement method, and the same applies hereafter. . As the measuring device, "LA-960" manufactured by HORIBA or the like can be used.

As for the ratio of component A and component B in the entire composite powder, when the total amount of both is 100% by mass, component B is 0.01% by mass or more, preferably 0.1% by mass or more, and 0. More preferably, the content is .5% by mass or more. When component B is 0.01% by mass or more, it has an excellent effect of imparting hydrophilicity to component A, and has sufficient dispersibility when producing a slurry using an aqueous binder. Note that if the purpose is only to impart hydrophilicity to component A, it is not necessary to provide component B in an amount exceeding 10% by mass, and the amount may be 10% by mass or less.

(A component)
Component A is made of a material capable of electrochemically occluding and releasing alkali metal ions. Component A is not particularly limited as long as it is an electrode material that can electrochemically occlude and release alkali metal ions. Electrochemical storage of alkali metal ions includes reversibly forming alloys (including solid solutions, intermetallic compounds, etc.) with alkali metals, reversibly chemically bonding with alkali metals, and alkali metal ions. Examples include adsorption of alkali metals and reversible encapsulation of alkali metals. Furthermore, electrochemically releasing alkali metal ions means that occluded alkali metal ions are separated.

The A component is, for example, Li, Na, K, C, Mg, Al, Si, P, S, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, It may contain at least one element selected from the group consisting of Ge, Y, Zr, Nb, Mo, Pd, Ag, Cd, In, Sn, Sb, W, Pb, and Bi. In addition, the A component may be an alloy containing these elements; oxides, sulfides, and halides of these elements; and sulfur-based organic materials such as sulfur-modified organic compounds.

Among these, sulfur-based organic materials such as S (sulfur), sulfides of the above elements, and sulfur-modified organic compounds are preferred from the viewpoint of exhibiting a charge-discharge plateau region similar to that of component B (sulfur-modified cellulose). Sulfur-based organic materials such as sulfides of the above elements or sulfur-modified organic compounds include, for example, metal sulfide, sulfur composite carbon, sulfur-modified natural rubber, sulfur-modified pitch, sulfur-modified anthracene, sulfur-modified polyacrylic, sulfur Modified phenol, sulfur-modified polyolefin, sulfur-modified polyvinyl alcohol, sulfur-modified nylon, sulfur-modified vinyl acetate copolymer, sulfur-modified terephthalic acid, sulfur-modified diaminobenzoic acid, sulfur-modified methacrylic resin, sulfur-modified polycarbonate, sulfur-modified polystyrene, sulfur-modified Examples include N-vinyl formaldehyde copolymer, sulfur-modified glycol, and sulfur-modified polyacrylonitrile. Component A may consist of one type alone, or may consist of two or more types.

Among these, sulfur-based organic materials are preferred because they provide stable capacity retention. In addition, sulfur-modified polyacrylonitrile is particularly suitable because it can stably exhibit a reversible electric capacity of 500 to 700 mAh/g regardless of whether lithium, sodium, or potassium is used as a charge carrier. be.

Component A is in the form of particles, and its median diameter (D50) is preferably 0.1 μm or more and 30 μm or less, more preferably 0.5 μm or more and 15 μm or less, and even more preferably 0.55 μm or more and 14.5 μm or less. If the median diameter (D50) is within the above range, the surface smoothness of the resulting electrode will not be deteriorated. In addition, a state in which the B component is supported or coated on the surface of the A component; and/or a state in which the B component is dispersed in the matrix of the A component and a part of the B component is exposed on the surface of the A component can be obtained. It's easy to get caught.

(B component)
Component B is a sulfur-modified cellulose having at least SO ₃ groups as functional groups. Sulfur-modified cellulose refers to a material in which cellulose is sulfurized through a dehydrogenation reaction, and is composed of a carbon skeleton derived from cellulose and sulfur bonded to the carbon skeleton. Sulfur-modified cellulose has changed in appearance from the white color of its precursor (cellulose) to black, exhibits excellent hydrophilicity, and is insoluble in water. Moreover, having an SO ₃ group as a functional group includes a case where the SO ₃ group is bonded to a carbon skeleton derived from cellulose in sulfur-modified cellulose. The SO ₃ group may be at least one selected from the group consisting of SO ₃ H, SO ₃ Na, SO ₃ Li, and SO ₃ K.

Describe the difference between cellulose and sulfur-modified cellulose. Cellulose has the property of dispersing in water or absorbing water and swelling, and at temperatures above 180° C., the mass decreases and a carbonization reaction begins. However, since sulfur-modified cellulose is hydrophilic but insoluble in water, it does not swell with water and exhibits excellent heat resistance, with a mass loss of 30% by mass or less even at 400°C. Sulfur-modified cellulose may be composed of 10 to 60% by mass of sulfur according to elemental analysis, and may be composed of 20 to 60% by mass of sulfur, although this varies depending on manufacturing conditions such as the amount of raw materials charged and the heat treatment temperature. .

Component B is preferably sulfur-modified cellulose nanofibers (sometimes referred to as S-CeNF). S-CeNF exhibits excellent hydrophilicity without dissolving or swelling in water. Further, it can stably exhibit a reversible electric capacity of 300 to 400 mAh/g. Therefore, by combining component A with component B, it is expected that not only hydrophilicity will be imparted, but also higher capacity of the electrode will be achieved.

Furthermore, since S-CeNF is fibrous, it is possible to form a conductive three-dimensional network structure on the surface, inside, or on the surface and inside of component A. If a three-dimensional network structure is formed by S-CeNF, the A component can come into contact with the electrolyte, and sufficient output characteristics can be obtained as an electrode material. Further, a sufficient current collecting effect can be obtained as an active material of an electrode.

The maximum fiber diameter of S-CeNF is preferably 1 μm or less, more preferably 1 nm or more and 500 nm or less, and even more preferably 2 nm or more and 200 nm or less. A structure in which sulfur-modified cellulose nanofibers with a three-dimensional network structure are supported, coated, or exposed on the surface of component A, in particular, component A is used as a matrix, and sulfur-modified cellulose nanofibers with a three-dimensional network structure are included in the matrix. It is easy to obtain particles in which component A is dispersed, and it is possible to impart hydrophilicity to component A and achieve excellent dispersibility without deteriorating the electrode properties originally expected of component A, specifically, the output characteristics and cycle life characteristics. I can demonstrate it.

The maximum fiber diameter is determined by randomly selecting at least 10 fibers from a fiber image obtained using an electron microscope, finding the maximum length of each fiber in the short axis direction, and calculating the maximum fiber diameter. Obtained by averaging the maximum values. The average fiber diameter is determined by randomly selecting at least 10 fibers from a fiber image obtained using an electron microscope, etc., and calculating the average length of each fiber in the short axis direction. can get.

Further, the fiber length of S-CeNF is preferably 0.2 μm or more, more preferably 0.5 μm or more, and even more preferably 0.8 μm or more.

The length of the fiber can be measured using a fiber length measuring machine (model FS-200) manufactured by KAJAANI AUTOMATION.

The aspect ratio (S-CeNF fiber length/S-CeNF fiber diameter) is more preferably 10 or more and 100,000 or less. This is because it is easy to form a three-dimensional network structure on the surface or inside of component A.

Further, the aspect ratio is more preferably 8 or more and 50,000 or less, and even more preferably 25 or more and 10,000 or less. Excellent battery or capacitor output characteristics.

The aspect ratio is determined by fiber length/fiber diameter (average fiber diameter). Fiber diameter can also be measured by the same device that measures fiber length.

<Conductive material>
The electrode material of the electricity storage device of the present disclosure may include an arbitrary component such as a conductive material in the A component or the B component.

The electrode material of the electricity storage device preferably contains a conductive material. This is because the electrode material can be expected to have even higher output power. In particular, it is preferable that component B contains a conductive material such that it is supported, coated, or exposed on the surface of component A, since both hydrophilicity and conductivity can be imparted to the surface of component A. Of course, the A component may contain a conductive material.

A conductive material refers to a material having electronic conductivity (electronic conductivity). For example, C (carbon), Al (aluminum), Ti (titanium), V (vanadium), Cr (chromium), Fe (iron), Co (cobalt), Ni (nickel), Cu (copper), Ta (tantalum). ), Pt (platinum), and Au (gold); alloys made of these metals; and conductive ceramics and polymers. Among these, carbon is preferred from the viewpoint of conductivity, material cost, and low irreversible capacity. Examples of carbon include graphite, carbon black, carbon fiber, carbon nanotube, carbon nanohorn, graphene, hard carbon, soft carbon, glassy carbon, and vapor grown carbon fiber (VGCF; registered trademark). Among these, carbon black is particularly preferred. Carbon black has different properties depending on the manufacturing method, but furnace black (FB), channel black, acetylene black (AB), thermal black, lamp black, Ketjen black (KB; registered trademark), and the like can be used without problems. The conductive materials may be used alone or in combination of two or more.

The content of the conductive material is preferably 0.1% by mass or more and 30% by mass or less with respect to 100% by mass of the composite powder consisting of component A and component B and the conductive material. When the content is 0.1% by mass or more, the effect of imparting conductivity is sufficient, and when it is 30% by mass or less, the active material capacity does not become too low, which is preferable.

[Manufacture of electrode materials for power storage devices]
The method for manufacturing the electrode material of the electricity storage device of the present disclosure is not particularly limited. The method for obtaining the composite powder contained in the electrode material of the electricity storage device of the present disclosure is also not particularly limited.

First, the preparation of component B will be described. Component B can be obtained by using a precursor of component B (cellulose material) and sulfur as raw materials and heat-treating the precursor of component B in a state where the precursor is brought into contact with sulfur. The state in which the precursor of component B is in contact with sulfur only requires that the precursor of component B and sulfur are in physical contact with each other. For example, solid powder of a mixture of the precursor of component B and sulfur, Examples include those in which component precursors and sulfur are dispersed in a solvent and dried. By bringing the precursor of component B into contact with sulfur and heat-treating it in this way, sulfur diffuses into the cellulose in a solid phase, so component B (sulfur-modified cellulose) can be obtained with a high yield.

The heat treatment may be performed at any temperature at which the precursor of component B is modified with sulfur, and is preferably 200°C or more and 800°C or less. Thereby, component B (sulfur-modified cellulose) consisting of a carbon skeleton derived from the precursor of component B (cellulose material) and sulfur bonded to the carbon skeleton can be synthesized. When the temperature is 200°C or higher, the precursor of component B is sufficiently sulfur-modified, and the conductivity of the resulting component B (sulfur-modified cellulose) is higher than that at lower than 200°C. In addition, when the temperature is 800° C. or lower, sulfur is difficult to desorb from component B and the sulfur content is difficult to decrease, so that it is possible to prevent the formation of carbide and a decrease in the electric capacity of the electrode material. From the viewpoint of high yield and electric capacity of component B, the temperature is more preferably 220°C or more and 600°C or less. Further, from the viewpoint of excellent conductivity of component B, the temperature is more preferably 250°C or more and 500°C or less.

The atmosphere during the heat treatment is not particularly limited, but since oxidation due to oxygen may occur in the air, it is preferably a non-oxygen atmosphere such as an inert gas atmosphere or a reducing atmosphere. Specifically, examples thereof include a reduced pressure atmosphere, a helium atmosphere, a neon atmosphere, an argon atmosphere, a nitrogen atmosphere, a hydrogen atmosphere, and a sulfur gas atmosphere.

The heat treatment time may be any time as long as component B is produced, and may be 1 hour or more and 50 hours or less, or 1 hour or more and 40 hours or less. This range is preferable because the cellulose is sufficiently sulfur-modified and the resulting composite powder has excellent electric capacity. Furthermore, since the heating time is not too long, the sulfur modification reaction proceeds sufficiently and unnecessary heating energy is not consumed, which is economically preferable.

The mass of sulfur used as a raw material may be equal to or greater than the mass of the precursor of component B (cellulose material). Specifically, the mass of sulfur is preferably, for example, 1 to 10 times the mass of the precursor of component B, and more preferably 2 to 6 times. When the mass of sulfur is one or more times the mass of the precursor of component B, sulfur modification occurs sufficiently, resulting in an electrode material with excellent electric capacity. When the amount is 10 times or less, raw material sulfur is unlikely to remain in the obtained electrode material, and it does not take much time to perform desulfurization treatment in a subsequent step. If elemental sulfur remains in the electrode material, the initial capacitance increases, but cycle life characteristics may deteriorate. In such a case, it is preferable to perform a desulfurization treatment.

The cellulose material that is the precursor of component B is a carbohydrate represented by the molecular formula (C ₆ H ₁₀ O ₅ ) _n or a derivative thereof, and has an anionic group forming an alkali metal salt or an alkaline earth metal salt. That's fine. In addition, derivatives of carbohydrates represented by the molecular formula (C ₆ H ₁₀ O ₅ ) _n refer to derivatives of carbohydrates represented by the molecular formula (C ₆ H ₁₀ O ₅ ) _n , including introduction of functional groups, oxidation, reduction, and atom replacement. Refers to compounds that have been modified to the extent that the structure and properties of carbohydrates are not significantly changed.

The cellulose material that is the precursor of component B is a carbohydrate derivative represented by the following molecular formula (C ₆ H ₁₀ O ₅ ) _n substituted with an anionic group forming an alkali metal salt or an alkaline earth metal salt. There are many things that can be mentioned. For example, methylcellulose, ethylcellulose, ethylmethylcellulose, carboxymethylcellulose (CMC), hydroxyethylcellulose, hydroxybutylmethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, hydroxyethylmethylcellulose, hydroxypropylmethylcellulose stearoxy ether, carboxymethylhydroxyethylcellulose, alkylhydroxyethylcellulose, Nonoxynyl hydroxyethylcellulose, cellulose sulfate, cellulose acetate, methylcellulose ether, methylethylcellulose ether, ethylcellulose ether, low nitrogen hydroxyethylcellulose dimethyldiallylammonium chloride (polyquaternium-4), -[2-hydroxy-3-(trimethylammonium) chloride ) propyl] hydroxyethylcellulose (polyquaternium-10), chloride-[2-hydroxy-3-(lauryldimethylammonio)propyl]hydroxyethylcellulose (polyquaternium-24), hemicellulose, microcrystalline cellulose, cellulose nanocrystals, and cellulose nanofibers (CeNF), etc. Among these, CeNF is preferred.

CeNF is a cellulose fiber obtained by physically or chemically loosening cellulose, which is a constituent material of wood or the like, or cellulose obtained from animals, algae, or bacteria, to a maximum fiber diameter of 1 μm or less. More specifically, the cellulose fiber length is 0.2 μm or more, the aspect ratio (cellulose fiber length/cellulose fiber diameter (fiber diameter)) is 10 to 100,000, and the average degree of polymerization is 100 to 100,000. Cellulose fibers are preferable, and the cellulose fibers have a length of 0.5 μm or more, an aspect ratio (cellulose fiber length/cellulose fiber diameter (fiber diameter)) of 10 to 250, and an average degree of polymerization of 100 to 250. 10,000 cellulose fibers are more preferred. Note that the average degree of polymerization herein refers to a value calculated by the viscosity method described in the TAPPI T230 standard method.

Note that CeNF having an anionic group forming an alkali metal salt or an alkaline earth metal salt can efficiently defibrate cellulose fibers to a predetermined fiber diameter.

The alkali metal salt or alkaline earth metal salt formed by the anionic group of the cellulose material that is the precursor of component B is not particularly limited, but includes, for example, alkali metal salt or alkaline earth metal salt of carboxylic acid; alkali phosphate; Examples include metal salts or alkaline earth metal salts; sulfonic acid alkali metal salts or alkaline earth metal salts; and sulfuric acid alkali metal salts or alkaline earth metal salts. It may contain any one type of these, or it may contain two or more types. Moreover, among these, it is preferable that the cellulose material has an alkali metal carboxylic acid salt as a functional group from the viewpoint of high discharge capacity and water dispersibility of the obtained active material.

The types of the alkali metal salts or alkaline earth metal salts are not particularly limited, but include alkali metal salts such as sodium salts, potassium salts, and lithium salts; and alkaline earth metal salts such as magnesium salts, calcium salts, and barium salts. etc.

The cellulose material that is the precursor of component B contains not only an anionic group forming an alkali metal salt or alkaline earth metal salt, but also an anionic group forming an alkali metal salt or alkaline earth metal salt, and a carboxylic acid group. It may have both acid type anionic groups such as phosphoric acid groups, sulfonic acid groups, and sulfuric acid groups.

When cellulose nanofibers (CeNF) are used as the precursor of component B, the resulting sulfur-modified cellulose becomes sulfur-modified cellulose nanofibers (S-CeNF). If component B is a fibrous sulfur-modified cellulose nanofiber (S-CeNF), a three-dimensional network structure with conductivity can be formed on the surface or inside of component A, and it can be used as an active material for an electrode. This is preferable because an electric effect can be obtained.

The precursor of component B is preferably a cellulose material having at least SO ₃ groups as a functional group after treatment (after heat treatment in a state where the precursor of component B is brought into contact with sulfur). For example, alkali metal salts or alkaline earth metal salts of TEMPO-oxidized cellulose; alkali metal salts or alkaline earth metal salts of sulfonic acid-modified cellulose; alkali metal salts or alkaline earth metal salts of sulfuric acid-modified cellulose; and alkali metal salts of carboxymethyl cellulose. Examples include metal salts and alkaline earth metal salts. It may contain any one type of these, or it may contain two or more types. Moreover, among these, an alkali metal salt of TEMPO-oxidized cellulose is preferable, and an alkali metal salt of TEMPO-oxidized cellulose nanofiber is more preferable because a high discharge capacity can be obtained.

Next, the preparation of the composite powder will be described. Methods for obtaining the composite powder consisting of component A and component B are not particularly limited, and examples include methods such as mechanical milling, spray drying, fluidized bed granulation, and sintering and pulverization.

Mechanical milling is a method of applying external forces such as impact, tension, friction, compression, and shear to the raw material powder (at least A component and B component), and uses a rolling mill, a vibration mill, a planetary mill, an oscillating mill, a horizontal mill, etc. A ball mill, an attritor mill, a jet mill, an agitator and a crusher, a homogenizer, a fluidizer, a paint shaker, a mixer, and the like can be used. By this method, a composite powder consisting of component A and component B is obtained. In particular, it is easy to form a composite in which the surface of component A is supported or coated with component B. However, in this method, it is preferable that the B component has a lower mechanical strength than the A component. That is, it is preferable that component B is more easily crushed than component A. Component B, which has become fine particles, is preferentially mechanically pressed onto the surface of component A, making it possible for component A to support, cover, or expose component B to component A.

In the spray drying method, by spray drying a liquid in which component A and component B are dispersed in water or an organic solvent, it is possible to form a composite in which the surface of component A is supported, covered, or exposed with component B. When the A component is a hydrophobic material, it is preferable to use an organic solvent to disperse the A component. In particular, when the A component is sulfur or a sulfur-based organic material, a surfactant or a surfactant is added to the water. It is preferable to use a solvent to which alcohol or the like is added. Surfactants, alcohols, and the like are decomposed or vaporized by heat treatment, so they do not adversely affect the electrode material.

In the fluidized bed granulation method, hot air is sent from the bottom of the granulation chamber containing component A, and while component A is rolled up into the air and fluidized, a solvent in which component B is dispersed is sprayed onto component A. A complex can be formed in which component B is supported or coated on the surface of component A. In addition, when the A component is sulfur or a sulfur-based organic material, hot air is sent from the bottom of the granulation chamber containing the A component or the precursor of the A component to blow up the A component or the precursor of the A component into the air. After spraying a solvent in which the B component precursor is dispersed onto the A component precursor in a fluidized state to produce a composite powder in which the B component precursor is supported or coated on the surface of the A component precursor, By heating the composite powder at 200° C. or higher while bringing it into contact with sulfur, it is possible to form a composite in which component B is supported, coated, or exposed on the surface of component A.

In the sintering and pulverization method, component A, a precursor of component B, and sulfur are dispersed in a solvent, and then this dispersion is heat-treated at 200°C or higher, and then crushed, so that component B is on the surface of component A. Supported or coated composite powders can be formed. In addition, when component A is sulfur or a sulfur-based organic material, after dispersing component A or a precursor of component A, a precursor of component B, and sulfur in a solvent, this dispersion is heat-treated, and then pulverized. By doing so, it is possible to form a complex in which component B is supported, coated, or exposed on the surface of component A. In the sintering and pulverizing method, it is preferable that the solvent used be water with a surfactant, alcohol, or the like added thereto. Surfactants, alcohols, and the like are decomposed or vaporized by heat treatment, so they do not adversely affect the electrode material.

In a method such as a mechanical milling method, a spray drying method, a fluidized bed granulation method, or a pyrolysis method, when the A component is prepared first and then manufactured, the A component is sulfur, a sulfide of the above element, or sulfur. In the case of organic materials, component A can be obtained by sulfurizing the above elements or modifying the organic compound with sulfur by heat treatment. Moreover, as this organic compound, polyacrylonitrile (PAN) is preferable from the viewpoint of large electric capacity and excellent life characteristics.

Further, when the A component is a sulfide of the above element exemplified as the A component or a sulfur-based organic material, the electrode material of the electricity storage device of the present disclosure includes the A component or a precursor of the A component, and the B component. The precursor and sulfur are brought into contact with each other and heated to 200°C or more and 800°C or less, and the A component is a material capable of electrochemically occluding and releasing alkali metal ions, An electrode for an electricity storage device, wherein the precursor of component A is an organic material, the precursor of component B is a cellulose material, and the cellulose material has an anionic group forming an alkali metal salt or an alkaline earth metal salt. It may be manufactured by the manufacturing method of the material. Thereby, a composite powder in which component B is supported, coated, or exposed on the surface of component A can be obtained.

In particular, a method using a precursor of component A as a raw material is suitable for obtaining a composite powder in which component B is exposed on the surface of component A. Furthermore, when obtaining a composite powder in which component B is exposed on the surface of component A, it is preferable that the precursor of component A is in a liquefied state. The state in which the precursor of the A component is liquefied includes, for example, a state in which the A component is softened by heat or chemical reaction, a state in which the A component is dissolved in a solvent, a state in which the A component can be deformed by pressure, etc. Can be mentioned.

Below, we will mainly explain in detail the method of using the precursor of component A as a raw material, but when using component A as a raw material, the method is the same as the method detailed below, except that the precursor of component A is replaced with component A. It can be manufactured by

The state in which the precursor of component A, the precursor of component B, and sulfur are in contact with each other may be as long as the precursor of component A, the precursor of component B, and sulfur are in physical contact with each other. For example, a solid powder obtained by mixing a precursor of component A, a precursor of component B, and sulfur; and a precursor of component A, a precursor of component B, and sulfur are dispersed in a solvent and dried. Examples include things. By bringing the precursor of component A, the precursor of component B, and sulfur into contact with each other and heat-treating them in this way, sulfur is solid-phase diffused into the precursor of component A and the precursor of component B. , a composite powder can be obtained with good yield.

In particular, when a precursor of component A and a precursor of component B are dissolved in a solvent, sulfur is dispersed therein, and then dried, the resulting composite particles have the component B exposed on the surface of the component A. structure (a state in which component B is dispersed in a matrix of component A).

The heating temperature may be 200°C or more and 800°C or less. Further, the temperature may be any temperature as long as the precursor of component A and the precursor of component B are modified with sulfur. Thereby, a sulfur-modified cellulose consisting of a carbon skeleton derived from a cellulose material and sulfur bonded to the carbon skeleton can be synthesized as the A component and the B component. When the temperature is 200°C or higher, the precursor of component A and the precursor of component B are sufficiently sulfur-modified, and the conductivity of the resulting composite powder is higher than that of the composite powder that is heated below 200°C. In addition, when the temperature is 800° C. or lower, sulfur is difficult to desorb from component A and component B, and the sulfur content is difficult to decrease, so that it is possible to prevent the formation of carbide and a decrease in the electric capacity of the electrode material. From the viewpoint of high yield and capacitance of component A and component B, the temperature is more preferably 220° C. or higher and 600° C. or lower. Moreover, from the viewpoint of excellent conductivity of the A component and the B component, the temperature is more preferably 250° C. or more and 500° C. or less.

The atmosphere during the heat treatment is not particularly limited. The same atmosphere as for the heat treatment in the preparation of component B can be used.

The heat treatment time may be any time as long as component B is produced, and may be 1 hour or more and 50 hours or less, or 1 hour or more and 40 hours or less. This range is preferable because the cellulose is sufficiently sulfur-modified and the resulting composite powder has excellent electric capacity. Furthermore, since the heating time is not too long, the sulfur modification reaction proceeds sufficiently and unnecessary heating energy is not consumed, which is economically preferable. In addition, when producing|generating A component, the heating time is the same as the said B component.

When the total amount of the precursor of component A and the precursor of component B is 100% by mass, the precursor of component B is preferably 0.01% by mass or more, and preferably 0.1% by mass or more. is more preferable, and even more preferably 0.5% by mass or more. When the amount of the precursor of component B is 0.01% by mass or more, it has an excellent effect of imparting hydrophilicity to component A, and has sufficient dispersibility when producing a slurry using an aqueous binder. Note that if the purpose is only to impart hydrophilicity to component A, it is not necessary to provide component B in an amount exceeding 10% by mass, and the amount may be 10% by mass or less.

The mass of sulfur used as a raw material may be equal to or greater than the respective mass of the precursor of component A and the precursor of component B. Specifically, the amount of sulfur is preferably 1 to 10 times the mass of the precursor of component A and the precursor of component B, and more preferably 2 times to 6 times the mass of each of the precursors of component B. When the mass of sulfur as a raw material is one or more times the mass of each of the precursors of component A and component B, sulfur modification occurs sufficiently, resulting in an electrode material with excellent electric capacity. When the amount is 10 times or less, raw material sulfur is less likely to remain in the obtained electrode material, and it does not take much time to perform desulfurization treatment in a subsequent step. If elemental sulfur remains in the electrode material, the initial capacitance increases, but cycle life characteristics may deteriorate. In such a case, it is preferable to perform a desulfurization treatment.

Desulfurization treatment is a treatment for removing elemental sulfur contained in the manufactured composite powder, and is not limited as long as residual sulfur can be removed by heat treatment, reduced pressure treatment, etc. For example, after obtaining the composite powder, it may be further heated to 250° C. or higher under reduced pressure or in an inert gas atmosphere. Residual sulfur can be effectively removed by performing this heating for about 1 to 20 hours. The upper limit of the heating temperature is not particularly limited, but may be 800° C. or lower from the viewpoint of increasing the capacitance of the electrode material. Alternatively, residual sulfur may be dissolved in carbon disulfide after obtaining the composite powder, but since carbon disulfide is highly toxic, desulfurization treatment by heat treatment as described above is preferred.

When component A is a sulfur-based organic material, the precursor of component A is an organic material. Examples of the organic materials include carbon, natural rubber, pitch, anthracene, polyacrylic, phenol, polyolefin, polyvinyl alcohol, nylon, vinyl acetate copolymer, acrylic acid, terephthalic acid, diaminobenzoic acid, methacrylic resin, polycarbonate, Examples include polystyrene, N-vinyl formaldehyde copolymer, glycol, and polyacrylonitrile (PAN). Among these, polyacrylonitrile is preferred.

When the precursor of component A is polyacrylonitrile (PAN), PAN, the precursor of component B (cellulose material), and sulfur are used as raw materials, and the PAN, the precursor of component B, and sulfur are brought into contact with each other. , PAN becomes sulfur-modified polyacrylonitrile (S-PAN; equivalent to component A), and the precursor of component B becomes sulfur-modified cellulose (corresponds to component B) by the step of heating at 200 ° C. or more and 800 ° C. or less, At the same time, it is possible to obtain a composite powder in which component B is supported, coated, or exposed on the surface of component A.

The precursor of component B is a cellulose material, and the cellulose material may be a simple substance or may be a cellulose material dispersed or dissolved in a solvent.

In addition, when the electrode material contains a conductive material, the method for manufacturing the electrode material includes, for example, dispersing the precursor of component A, the precursor of component B, the conductive material, and sulfur in a solvent such as water, and One example is heat treatment. When dispersing the precursor of component A in a solvent such as water, if it becomes powder (clumps or aggregates), use a surfactant or alcohol together to improve its dispersibility in a solvent such as water. can be improved. The surfactant, alcohol, etc. used in combination are decomposed or vaporized by heat treatment, so they do not have a negative effect on the electrode material.

At this time, the precursor of the A component, the B component precursor, or the A component precursor and the B component precursor may contain a conductive material. Moreover, after performing the above desulfurization treatment, a conductive material may be added.

In addition, a composite powder composed of particles in which component A is used as a matrix and component B is dispersed in the matrix, for example, a liquefied precursor of component A is mixed with component B (or component B precursor) and sulfur. It can also be obtained by dispersing and then heat-treating this dispersion at a temperature of 200° C. or more and 800° C. or less. By dispersing the B component in the matrix of the A component, the surface of the A component has a structure in which the B component is partially exposed.

The liquefied precursor of component A is, for example, a liquid obtained by dissolving the precursor of component A in a solvent, or a component A that is liquefied by raising the temperature to around the melting point by heat treatment or the like. For example, by dissolving polyacrylonitrile in an organic solvent, dispersing cellulose nanofibers and sulfur powder in this liquid, and heat-treating this dispersion at 200°C or higher, sulfur-modified cellulose nanofibers are dissolved in sulfur-modified polyacrylonitrile. A composite powder is obtained in which the components are dispersed. The solvent is not particularly limited as long as it is a liquid that can dissolve the precursor of component A, but when the precursor of component A is polyacrylonitrile, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, aqueous zinc chloride solution, and thiocyanic acid can be used. A preferred example is a sodium aqueous solution.

[Electrode of electricity storage device]
The electrode of the power storage device of the present disclosure includes at least the electrode material of the power storage device of the present disclosure, a binder, and a current collector. Further, the electrode of the electricity storage device of the present disclosure may contain an optional component such as a conductive aid.

In the electrode of the electricity storage device of the present disclosure, a composite powder consisting of component A and component B in the electrode material of the present disclosure is mainly used as an active material. Note that the active material refers to a substance that can electrochemically occlude and release alkali metal ions.

Specifically, the electrode is prepared by adding an appropriate solvent such as N-methyl-pyrrolidone (NMP), water, alcohol, xylene, and toluene to the electrode material, binder, and conductive agent of the electricity storage device of the present disclosure. The electrode slurry obtained by adding and sufficiently kneading is applied to the surface of the current collector, dried, and further press-pressured to form an active material-containing layer on the surface of the current collector, and use it as a battery electrode. Can be done.

The current collector is not particularly limited as long as it has electron conductivity and can conduct electricity to the negative electrode material held therein. For example, conductive substances such as C, Ti, Cr, Fe, Mo, Ru, Rh, Ta, W, Os, Ir, Pt, Au, Cu, Ni, Al; containing two or more of these conductive substances Alloys (eg, stainless steel), etc. may be used. From the viewpoint of high electron conductivity, stability in electrolyte, good oxidation resistance, and good reduction resistance, C, Al, Cu, Ni, stainless steel, etc. are preferable as the current collector, and C, Al, and stainless steel are preferable. Steel is more preferred.

There are no particular restrictions on the shape of the current collector. For example, a foil-like base material, a three-dimensional base material, etc. can be used. Examples of the three-dimensional base material include foamed metal, mesh, woven fabric, nonwoven fabric, expanded fabric, and the like. When a three-dimensional base material is used, an electrode with high capacitance density can be obtained even with a binder that lacks adhesiveness with the current collector. In addition, high rate charge/discharge characteristics are also improved.

Further, even with a foil-shaped current collector, high output can be achieved by forming a primer layer on the surface of the current collector in advance. The primer layer may be of any material as long as it has good adhesion to the electrode material layer and the current collector, and has electrical conductivity. For example, the primer layer can be formed by applying a binding material that is a mixture of a carbon-based conductive additive and a primer binder onto the current collector. The thickness of the primer layer is, for example, 0.1 μm to 20 μm. Note that, as the binder for the primer, a known binder used for electrodes can be used.

(binder)
There are no restrictions on the binder contained in the electrode of the power storage device as long as it is conventionally used as a binder for the electrode of the power storage device. For example, carboxymethyl cellulose salt (CMC), acrylic resin, alginate, polyvinylidene fluoride (PVDF), polyimide (PI), polytetrafluoroethylene (PTFE), polyamide, polyamideimide, styrene-butadiene rubber (SBR), polyurethane, Styrene-ethylene-butylene-styrene copolymer (SEBS), styrene-butadiene-styrene copolymer (SBS), styrene-isoprene-styrene copolymer (SIS), styrene-ethylene-propylene-styrene copolymer (SEPS) ), polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyethylene (PE), polypropylene (PP), polyester resin, polyvinyl chloride, and ethylene acetic acid copolymer (EVA). These may be used alone or in combination of two or more.

Among the above binders, CMC, acrylic resin, alginate, PVA, SBR, etc. are preferably used because they are water-based binders that can use water as a solvent or dispersion medium. It is preferable to use a water-based binder because it suppresses sulfur elution into the slurry solvent and improves the high-temperature durability of the electrode.

Generally, when an electrode is made of a water-based binder and a hydrophobic electrode material (especially an active material, etc.), the hydrophobic material repels water and becomes particles (such as lumps and aggregates) and disperses. However, in the composite powder of the present disclosure, component B, which has excellent hydrophilicity, is supported, coated, or exposed on the surface of component A, so even if a water-based binder is used, the problem of difficulty in dispersion does not occur.

The binder content is preferably 0.1% by mass or more and 30% by mass or less, and 0.5% by mass or more and 15% by mass or less, based on 100% by mass of the composite powder consisting of component A and component B and the binder. is more preferable. If it is outside the above range, the electrode will be difficult to obtain stable life characteristics and output characteristics. That is, if the amount of binder is too small, the binding force with the current collector is insufficient, making it difficult to obtain stable life characteristics.On the other hand, if the amount is too large, electrode resistance increases and output characteristics deteriorate.

(Conductivity aid)
A conductive aid is a substance that helps conductivity between active materials, and is a material that is filled or bridged between separate active materials to establish conduction between the active materials or between the active materials and a current collector. .

As the conductive aid contained as an optional component in the electrode of the power storage device, those conventionally used as conductive aids for the electrode of the power storage device can be used. Examples include carbon materials such as acetylene black (AB), Ketjen black (KB), graphite, carbon fiber, carbon nanotubes, graphene, amorphous carbon, and vapor grown carbon fiber (VGCF). The conductive aids may be used alone or in combination of two or more.

Among these, those that can form a conductive three-dimensional network structure are preferred. Examples of materials that can form a conductive three-dimensional network structure include flaky conductive materials such as flake aluminum powder and flake stainless steel powder; carbon fiber; carbon tube; and amorphous carbon. If a conductive three-dimensional network structure is formed, a sufficient current collection effect can be obtained, and volumetric expansion of the electrode during charging and discharging can be effectively suppressed.

The content of the conductive aid is 0% by mass based on 100% by mass of the composite powder in which component B is supported, coated, or exposed on the surface of component A (in other words, component A and component B), and the total amount of the conductive aid. It is preferably at least 1% by mass and at most 20% by mass, and more preferably at least 1% by mass and at most 10% by mass. By being within the above range, the battery has excellent output characteristics and a decrease in capacity is small. That is, the conductive aid is contained as necessary.

[Electricity storage device]
An electricity storage device can be made using the electrode of the electricity storage device of the present disclosure. The electricity storage device includes a positive electrode, a negative electrode, and an electrolyte interposed between the positive electrode and the negative electrode. The electrode of the present disclosure can be used as either a positive electrode or a negative electrode of an electricity storage device. That is, the electrode of the present disclosure can be used as either the positive electrode or the negative electrode of an electricity storage device, but it is excluded that the positive electrode and the negative electrode use exactly the same electrode among the electrodes of the present disclosure at the same time. When the electrode of the electricity storage device of the present disclosure is used as a positive electrode of the electricity storage device, the electricity storage device can be manufactured by combining it with an electrode that is more base in charge/discharge potential than the charge/discharge potential of the electrode of the electricity storage device of the present disclosure. On the other hand, when the electrode of the electricity storage device of the present disclosure is used as a negative electrode of the electricity storage device, the electricity storage device can be manufactured by combining with an electrode whose charging/discharging potential is higher than the charging/discharging potential of the electrode of the electricity storage device of the present disclosure.

It is preferable that the electrodes of the electricity storage device are doped with alkali metal ions in advance before the electricity storage device is assembled. Alternatively, it is preferable that the counter electrode of the electricity storage device be doped with an alkali metal ion.

The method of doping with alkali metal ions is not particularly limited as long as the electrode can be doped with alkali metals, but for example, non-patent literature (Taiji Sakamoto et al., "Measurement and analysis data collection of lithium secondary battery parts" published by Technical Information Association, (1) electrochemical doping, (2) adhesion doping of lithium metal foil, (3) mechanical lithium doping using a high-speed planetary mill, as described in Section 30, pp. 200-205); Examples include.

When using the electrode of the electricity storage device of the present disclosure as a positive electrode, the counter electrode (negative electrode) is not particularly limited as long as it is an electrode used as a negative electrode used in the electricity storage device. For example, Li, Na, K, C, Mg, Al, Si, P, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Y, Zr, At least one element selected from the group consisting of Nb, Mo, Pd, Ag, Cd, In, Sn, Sb, W, Pb, and Bi; alloys containing these elements; oxides of these elements; Examples include electrodes containing materials (in other words, negative electrode materials) such as sulfides and halides; sulfur-based organic materials such as sulfur-modified organic compounds; Note that these materials may be used alone or in combination of two or more.

When using the electrode of the electricity storage device of the present disclosure as a negative electrode, the counter electrode (positive electrode) is not particularly limited as long as it is an electrode used as a positive electrode used in the electricity storage device. For example, ACoO ₂ , ANiO ₂ , AMnO ₂ , ANi _0.33 Mn _0.33 Co _0.33 O ₂ , ANi _0.5 Mn _0.3 Co _0.2 O ₂ , ANi _0.6 Mn _0.2 Co _0.2 O ₂ , ANi _0.8 Mn _0.1 Co _0.1 O ₂ , AMn ₂ O ₄ , ANi _0.5 Mn _1.5 O ₄ , AFePO ₄ , AFe _0.5 Mn _0.5 PO ₄ , _AMnPO4 , _{ACoPO4 ,} ANiPO4, _{A3V2 ( PO4 ) 3} , _AV2O5 , _AVO2 , _ANb2O5 , _ANbO2 , _AFeO2 , _AMgO2 , _ACaO2 , _{ATiO2 , ACrO2} , ARuO ₂ , ACuO ₂ , AZnO ₂ , AMoO ₂ , ATaO ₂ or AWO ₂ , and other known electrodes containing an alkali metal element-transition metal oxide are used. These alkali metal element-transition metal oxides may be used alone or in combination of two or more. Here, A represents an alkali metal element, and examples of A include Li, Na, or K. The same applies below.

Further, the electrolyte used in this battery may be any liquid or solid that can move alkali metal ions from the positive electrode to the negative electrode or from the negative electrode to the positive electrode. That is, the same electrolyte as used in power storage devices using known non-aqueous electrolytes can be used. Examples include electrolytes, gel electrolytes, solid electrolytes, ionic liquids, and molten salts. Here, the electrolytic solution refers to a state in which an electrolyte is dissolved in a solvent.

The electrolytic solution is obtained by dissolving a supporting salt in a solvent. The solvent for the electrolytic solution is not particularly limited, but includes cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate; ethers such as tetrahydrofuran; hydrocarbons such as hexane; and γ-butyl. Lactones such as lactones can be used. Among these, a cyclic carbonate electrolyte such as EC or PC is preferred from the viewpoint of discharge rate characteristics. The discharge rate is an index based on the "1C rate", which is the current value at which a cell with a nominal capacity is discharged at a constant current and is completely discharged in one hour. The current value at which a complete discharge occurs is expressed as a "0.2C rate," and the current value at which a complete discharge occurs in 10 hours is expressed as a "0.1C rate." On the other hand, the charging rate is an index based on the current value at which a cell having a nominal capacity is charged at a constant current and is fully charged in one hour as the "1C rate". The current value for full charge in minutes is "60C rate", the current value for full charge in 6 minutes is "10C rate", the current value for full charge in 5 hours is "0.2C rate", and the current value for full charge in 10 hours is "0.2C rate". The current value for charging is expressed as "0.1C rate".

Since EC is usually solid at room temperature, EC alone does not function as an electrolyte. However, by creating a mixed solvent obtained by mixing PC, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), etc., it functions as an electrolytic solution that can be used even at room temperature.

As such a mixed solvent, EC (ethylene carbonate)-DEC (diethylene carbonate), EC-DMC (dimethyl carbonate), and EC-PC are preferably used, and EC-DEC and EC-PC are particularly preferably used. .

The supporting salt for the electrolytic solution is not particularly limited, but salts commonly used in power storage devices can be used. For example, APF ₆ , ABF ₄ , AClO 4 , ATiF ₄ , AVF ₅ , AAsF ₆ , ASbF ₆ , ACF ₃ SO ₃ , A(C _{2 F 5} SO ₂ ) ₂ N, AB(C ₂ O ₄ ) ₂ , AB ₁₀ Cl ₁₀ , AB ₁₂ Cl ₁₂ , ACF ₃ COO, A ₂ S ₂ O ₄ , ANO ₃ , A ₂ SO ₄ , APF ₃ (C ₂ F ₅ ) ₃ , AB(C ₆ F ₅ ) ₄ , and A( Salts such as CF ₃ SO ₂ ) ₃ C can be used. Note that one type of the above salts may be used alone, or two or more types may be used in combination.

Among these, an alkali metal element-hexafluorophosphate compound (APF ₆ ) is preferably used. By using APF ₆ as a salt, the effect of improving the discharge capacity and cycle life of the positive electrode and the cycle life of the negative electrode is enhanced. Further, the concentration of the electrolytic solution (concentration of the salt in the solvent) is not particularly limited, but is preferably 0.1 to 3 mol/L, more preferably 0.8 to 2 mol/L.

The structure of the power storage device is not particularly limited, but existing forms and structures such as a stacked type and a wound type can be adopted. That is, an electrode group in which a positive electrode and a negative electrode are stacked or wound facing each other with a separator interposed therebetween is immersed in an electrolytic solution and hermetically sealed to form a power storage device. Alternatively, an electrode group in which a positive electrode and a negative electrode are stacked or wound facing each other with a solid electrolyte interposed therebetween is hermetically sealed to form a power storage device.

[Electrical equipment]
Since the power storage device (especially lithium ion battery or lithium ion capacitor) using the electrode material of the power storage device of the present disclosure has high capacity and high output, it can be used, for example, in air conditioners, washing machines, televisions, refrigerators, freezers, and air conditioners. Equipment, notebook computers, tablets, smartphones, computer keyboards, computer displays, desktop computers, CRT monitors, computer racks, printers, all-in-one computers, mice, hard disks, computer peripherals, irons, clothes dryers, window fans, transceivers , blowers, ventilation fans, televisions, music recorders, music players, ovens, microwaves, toilet seats with cleaning functions, hot air heaters, car components, car navigation systems, flashlights, humidifiers, portable karaoke machines, ventilation fans, dryers, air purifiers, mobile phones Telephones, emergency lights, game consoles, blood pressure monitors, coffee mills, coffee makers, kotatsu, copy machines, disc changers, radios, shavers, juicers, shredders, water purifiers, lighting equipment, dehumidifiers, dish dryers, rice cookers, Stereos, stoves, speakers, trouser presses, vacuum cleaners, body fat scales, weight scales, health meters, movie players, electric carpets, electric kettles, rice cookers, electric razors, desk lamps, electric kettles, electronic game consoles, portable game consoles , electronic dictionaries, electronic notebooks, microwave ovens, induction cookers, calculators, electric carts, electric wheelchairs, power tools, electric toothbrushes, foot massagers, haircuts, telephones, watches, intercoms, air circulators, electric insect killers, photocopiers, Hot plate, toaster, hair dryer, electric drill, water heater, panel heater, crusher, soldering iron, video camera, VCR, facsimile, fan heater, food processor, futon dryer, headphones, electric kettle, hot carpet, microphone , massage machines, mini light bulbs, mixers, sewing machines, mochi making machines, floor heating panels, lanterns, remote controls, refrigerators, water coolers, frozen stockers, air coolers, word processors, whisks, GPS, electronic musical instruments, motorcycles, toys. , lawn mowers, floats, bicycles, motorcycles, automobiles, hybrid vehicles, plug-in hybrid vehicles, electric vehicles, trains, ships, airplanes, submarines, aircraft, satellites, and emergency power systems. It can be used as a power source.

Examples will be described below, but the present invention is not limited to these examples. The electrode of the present disclosure is an electrode of a power storage device, but in this example, a lithium ion battery was manufactured and tested as described below. Lithium ion capacitors can be manufactured in the same manner as lithium ion batteries, except that the operation of the counter electrode is different. Specifically, for example, it can be produced in the same manner as the battery described below, except that the conventional positive electrode for lithium ion capacitors is used as the positive electrode and the electrode of the present disclosure is used as the negative electrode. Alkali metal ion batteries other than lithium ion batteries can be produced in the same manner as lithium ion batteries, except that Li, which is a charge carrier in lithium ion batteries, is replaced with Na or K. Specifically, for example, in a sodium ion battery, a conventional positive electrode for sodium ion batteries is used as the positive electrode, the electrode of the present disclosure is used as the negative electrode, and a sodium supporting salt is used as the electrolyte. It can be made by The same applies to other alkali metal ions.

When the electrode of the present disclosure is used as an electrode of a lithium ion capacitor, an electrode manufactured by, for example, applying a slurry consisting of activated carbon, a binder, and a conductive additive to aluminum foil and heat-treating the same can be used as the counter electrode. Can be done.

The activated carbon for such a lithium ion capacitor is preferably a carbon material in which countless fine pores are formed and a large specific surface area. A typical method for manufacturing activated carbon is to heat a carbon material such as petroleum coke and an alkali metal compound such as potassium hydroxide at 600 to 1,500°C in a non-oxygen atmosphere to allow the alkali metal to penetrate between graphite crystal layers. It can be obtained by activating the reaction. The median diameter (D50) of the activated carbon particles is preferably 0.5 to 30 μm.

[Comparative example 1]
(1) Synthesis of electrode material Sulfur and polyacrylonitrile were mixed at a mass ratio of sulfur: polyacrylonitrile = 1:5, and the resulting mixture was heated at 350° C. for 5 hours. After heating, the mixture was pulverized using a stirring grinder and classified using a 325-mesh (opening 45 μm) sieve. After classification, the mixture was heated at 300° C. for 5 hours in a nitrogen gas atmosphere to perform a desulfurization treatment to obtain a sulfur-modified compound powder (S-PAN). Note that the median diameter (D50) of the obtained powder was 36.3 μm. This value was obtained based on data shown in FIG. 3, which will be described later.

(Evaluation of dispersibility in water)
The obtained powder was placed in a glass bottle containing water 100 times the weight of the powder, the lid was closed, and the bottle was shaken well for about 1 minute. A photograph immediately after shaking is shown in FIG. 2, and the results are shown in Table 1.

(Volume-based particle size distribution)
The volume-based particle size distribution of the obtained powder was measured using a laser diffraction/scattering method using water as a dispersion medium. The measuring device used was "LA-960" manufactured by HORIBA. Measurement was performed using laser beams with wavelengths of 650 nm and 405 nm. The results are shown in Figure 3.

(2) Preparation of test electrode The obtained sulfur-modified compound powder, acetylene black (AB), vapor grown carbon fiber (VGCF), and acrylic resin binder were mixed into sulfur-modified compound powder: acetylene black (AB): Vapor grown carbon fiber (VGCF): acrylic resin binder = 82:3:8:7 mass% ratio was kneaded in a private mixer (2000 rpm, 40 minutes) until fully dispersed in water, and slurried ( Solid ratio: 35%). The obtained slurry was applied as a current collector onto an aluminum foil having a thickness of 20 μm, and a test electrode was obtained by drying under reduced pressure at 160° C. for 12 hours. Powder of sulfur-modified compound was used as the active material. As described below, the obtained test electrode was used as a positive electrode, and the amount of slurry applied was adjusted so that the positive electrode capacity per unit area of one side of the positive electrode was 1 mAh/cm ² .

(3) Production of battery A battery was produced using the obtained test electrode as a positive electrode, and a charge/discharge test A was conducted. Details are as follows. For the charge/discharge test, a test electrode obtained as a positive electrode; a glass filter (manufactured by ADVANTEC, GA-100 GLASS FIBER FILTER) as a separator; metallic lithium as a negative electrode; 1M LiPF ₆ (ethylene carbonate (EC): diethyl) as an electrolyte A CR2032 coin cell containing carbonate (DEC) (50:50 vol% solution) was prepared.

(Charge/discharge test A)
A charge/discharge test was conducted on the obtained battery. The conditions for charge/discharge test A were an environmental temperature of 30° C., a cutoff potential of 1.0 to 3.0 V (vs. Li/Li ⁺ ), and a charge/discharge current rate of 0.2C. The charge-discharge curve is shown in Figure 4. This gives an idea of the cycle life characteristics of the electrode. Further, the results of discharge capacity are shown in Table 1.

(Charge/discharge test B)
A charge/discharge test was conducted on the obtained battery. The conditions for charge/discharge test B were an environmental temperature of 30° C., a cutoff potential of 1.0 to 3.0 V (vs. Li/Li ⁺ ), and a charge/discharge current rate of 0.2C. The ratio of the discharge capacity (mAh/g) after 100 cycles of charging and discharging to the "initial discharge capacity (mAh/g)" is calculated as the "capacity retention rate (%)", and this is used to determine the cycle life characteristics of the electrode. was evaluated. The results are shown in Table 2. The evaluation criteria for cycle life characteristics are as follows. Discharge capacity retention rate 90% or more: ○, 90% or less: ×

(High temperature storage test)
A laminate cell was produced using the obtained test electrode, and a high temperature storage test was conducted on the laminate cell. Details are as follows. Test electrode obtained as a positive electrode; polypropylene microporous membrane (thickness 20 μm) as a separator; SiO whose irreversible capacity was electrochemically canceled as a negative electrode; 1M LiPF ₆ (ethylene carbonate (EC): diethyl carbonate (DEC)) as an electrolyte. = 50:50vol%) was produced. After charging the produced laminate cell to 3.0V at a rate of 0.1C, it was left for one week in a 60°C environment. The results are shown in Table 1.

[Reference example 1]
A battery was produced in the same manner as in Comparative Example 1, except that sulfur-modified cellulose nanofiber powder obtained by the following method was used as the sulfur-modified compound powder, and charge-discharge test A was conducted. The results are shown in Table 1.

Using a mixture of CeNF (product name: LeoCrysta I-2SX, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and sulfur at a mass ratio of CeNF:sulfur = 1:5, this was heated at 350 ° C. for 5 hours, After pulverization, it was classified using a 325 mesh (opening 45 μm) sieve to obtain sulfur-modified cellulose nanofiber powder.

[Example 1]
A battery was produced in the same manner as Comparative Example 1, except that a composite powder obtained by the following method was used as the sulfur-modified compound powder. Evaluation of the dispersibility of the composite powder in water obtained in the process up to battery production, battery charge/discharge test A, and high temperature storage test were conducted using the electrodes. The results are shown in Table 1, FIG. 2, FIG. 3, and FIG. 5.

The sulfur-modified polyacrylonitrile powder obtained in Comparative Example 1, cellulose nanofiber (CeNF (product name: LeoCrysta I-2SX, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)), and sulfur were added to the sulfur-modified polyacrylonitrile powder: cellulose nano The fibers (CeNF) and sulfur were mixed at a mass ratio of 94:1:5, and the resulting mixture was heated at 350° C. for 5 hours. After heating, it was crushed with a stirrer and crushed, and classified with a 325 mesh (opening 45 μm) sieve to obtain a composite powder (S-CeNF+S-PAN) in which sulfur-modified polyacrylonitrile powder was supported or coated with sulfur-modified cellulose on the surface. ) was obtained. The median diameter (D50) of the obtained powder was 14.2 μm. This value was obtained based on the data shown in FIG.

[Example 2]
A battery was produced in the same manner as Comparative Example 1, except that a composite powder obtained by the following method was used as the sulfur-modified compound powder. "Evaluation of dispersibility in water" was performed on the composite powder obtained in the process up to the production of the battery, "Charge/Discharge Test B" was conducted on the battery, and "High Temperature Storage Test" was conducted using the electrode. The results are shown in Table 2.

As polyacrylonitrile and cellulose material B1, carboxymethylcellulose sodium salt (CMC-Na (product name: Celogen 7A, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)) and sulfur were added in a ratio of polyacrylonitrile:B1:sulfur=99:1:20. They were mixed in mass ratio and the resulting mixture was heated at 350° C. for 5 hours. After heating, the powder was crushed using a stirrer and crushed, and then classified using a 325-mesh (opening 45 μm) sieve to obtain a composite powder (S-PAN+S) in which sulfur-modified cellulose was supported, coated, or exposed on the surface of sulfur-modified polyacrylonitrile powder. -Cel) was obtained.

[Example 3]
Instead of cellulose material B1, Na salt of TEMPO oxidized cellulose nanofiber (product name: RheoCrysta I-2SX, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was used as cellulose material B2, and B2 was mixed with polyacrylonitrile and then dried. The obtained powder and sulfur were mixed in the same manner as in Example 2, except that the powder: sulfur = 100 (including 99 polyacrylonitrile and 1 B2): 20 mass ratio. A composite powder was obtained in which sulfur-modified cellulose was supported, coated, or exposed on the surface of sulfur-modified polyacrylonitrile powder. "Evaluation of dispersibility in water" was performed on the composite powder obtained in the process up to the production of the battery, "Charge/Discharge Test B" was conducted on the battery, and "High Temperature Storage Test" was conducted using the electrode. The results are shown in Table 2.

[Example 4]
The surface of sulfur-modified polyacrylonitrile powder was sulfur-modified in the same manner as in Example 3, except that the following sulfonic acid-modified cellulose nanofiber Na salt of Synthesis Example 1 was used as cellulose material B3 instead of cellulose material B2. A composite powder in which cellulose was supported, coated, or exposed was obtained. "Evaluation of dispersibility in water" was performed on the composite powder obtained in the process up to the production of the battery, "Charge/Discharge Test B" was conducted on the battery, and "High Temperature Storage Test" was conducted using the electrode. The results are shown in Table 2.

(Synthesis example 1)
10 g of microcrystalline cellulose ("KC Flock W-50" manufactured by Nippon Paper Industries Co., Ltd.) having an average particle size of 45 μm was suspended in 200 mL of distilled water in a separable glass flask. This separable flask was placed in an ice bath, and concentrated sulfuric acid was gradually added while stirring and maintaining the temperature in the system below 40° C. until the final concentration of sulfuric acid was 48% by mass. Next, this suspension was transferred to a 60° C. water bath and stirring was continued for 30 minutes, and then the crude product was taken out and centrifuged at 8000 rpm for 10 minutes. Excess sulfuric acid was removed by this centrifugation operation, the residue was resuspended in distilled water, and after centrifugation, the operation of adding distilled water again was repeated to repeat washing and resuspension five times. The residue obtained by this operation was suspended in distilled water, the pH was adjusted to 8 with sodium hydroxide, and the solid content concentration was adjusted to 5% by mass. Thereafter, the obtained cellulose suspension was treated once at a pressure of 140 MPa using a high-pressure homogenizer to obtain a sulfonic acid-modified cellulose nanofiber sodium salt.

[Comparative example 2]
A composite powder was obtained in the same manner as in Example 3, except that TEMPO-oxidized cellulose nanofiber tetrabutylammonium salt (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) was used as cellulose material B4 instead of cellulose material B2. Ta. "Evaluation of dispersibility in water" was performed on the composite powder obtained in the process up to the production of the battery, "Charge/Discharge Test B" was conducted on the battery, and "High Temperature Storage Test" was conducted using the electrode. The results are shown in Table 2.

[Comparative example 3]
A composite powder was obtained in the same manner as in Example 2, except that unmodified softwood bleached kraft pulp (NBKP) was used as cellulose material B5 instead of cellulose material B1. "Evaluation of dispersibility in water" was performed on the composite powder obtained in the process up to the production of the battery, "Charge/Discharge Test B" was performed on the battery, and "High Temperature Storage Test" was performed using the electrode. The results are shown in Table 2.

As is clear from FIGS. 2 and 3, it can be seen that Example 1 (FIG. 2(b)) exhibits superior water dispersibility to Comparative Example 1 (FIG. 2(a)). Compared to the powder of Example 1, the powder of Comparative Example 1 has a narrow peak at large particle size values, and the powder of Example 1 has a broad peak at small particle size values. It can be seen that the powder is well dispersed in the water. Furthermore, as is clear from Table 1, the discharge capacity of the electrode of Comparative Example 1 decreased by about 4.9% from 674 mAh/g for 1 cycle to 641 mAh/g for 100 cycles, whereas the electrode of Example 1 The electrode showed a decrease in discharge capacity of about 4.9% from 652 mAh/g for 1 cycle to 620 mAh/g for 100 cycles, and exhibited reversible capacity and cycle life characteristics comparable to those of the electrode of Comparative Example 1. The electrode of Reference Example 1 showed a decrease in discharge capacity of about 19% from 353 mAh/g at 1 cycle to 287 mAh/g at 100 cycles, and although it had somewhat excellent cycle life characteristics, it did not match those of Example 1 and Comparative Example 1. It was shown that the electrical capacity was particularly low compared to the capacity exceeding 600 mAh/g. No major changes were observed visually in the batteries using the electrodes of Example 1 and Comparative Example 1, and no battery swelling due to gas generation was observed.

All of the samples of the examples showed good dispersibility as shown in Figure 2(b), but in the sample of the comparative example, most of the powder aggregated and settled as shown in Figure 2(a), resulting in poor dispersibility. was not seen. As is clear from Table 1, Table 2, and FIG. 2, it can be seen that the Examples exhibit superior water dispersibility compared to the Comparative Examples.

Furthermore, as is clear from Table 2, the electrode of the example exhibited similar initial discharge capacity and cycle life characteristics as compared to Comparative Example 1, demonstrating that it has both water dispersibility and excellent discharge performance. show. On the other hand, Comparative Examples 2 and 3 showed good initial discharge capacity, but had poor water dispersibility, cycle and life characteristics. In the batteries using the electrodes of Examples and Comparative Examples, no major changes were observed visually, and no battery swelling due to gas generation was observed.

(Evaluation of surface functional groups)
Cellulose material B1 and sulfur were mixed at a mass ratio of B1:sulfur=1:5, and the resulting mixture was heated at 350° C. for 5 hours. After heating and flowing, it was pulverized and classified using a 325 mesh (opening 45 μm) sieve to obtain sulfur-modified cellulose powder B'1. IR measurement was performed on the sulfur-modified cellulose powder B'1 by the micro-tablet method using KBr. The results are shown in Figure 6.

In addition, cellulose material B1 was replaced with cellulose materials B2, B4, and B5, and sulfur-modified cellulose powders B'2, B'4, and B'5 were obtained respectively by the same procedure, and by the micro-tablet method using KBr. IR measurement was performed. The results are shown in FIGS. 7 to 9, respectively.

As is clear from FIGS. 6 to 9, the sulfur-modified cellulose powders B'1 and B'2 derived from cellulose materials used in the examples have a characteristic absorption in the vicinity of 600 to 700 cm ^-1 in the IR spectrum evaluation. , SO ₃ groups are present. On the other hand, the sulfur-modified cellulose powders B'4 and B'5 derived from cellulose materials used in the comparative examples do not have characteristic absorption in the region of 600 to 700 cm ⁻¹ and can be said to have no SO ₃ group.

Furthermore, as shown in Table 2, the examples using sulfur-modified cellulose having at least SO ₃ groups as functional groups have lower electrode properties compared to sulfur-modified cellulose that does not have SO ₃ groups as functional groups. It can be seen that it has excellent dispersibility. In addition, since there is a good correlation between the characteristic absorption in the vicinity of 600 to 700 cm ^-1 and hydrophilicity, it can be said that the presence of SO ₃ groups with characteristic absorption in this region is the reason for the excellent dispersibility. .

Claims (18)

An electrode material for a power storage device using a non-aqueous electrolyte,
The electrode material includes a composite powder,
Both A component and B component are contained in one particle constituting the composite powder, and the particle has a structure in which the B component is supported, coated, or exposed on the surface of the A component,
The particles are particles in which the A component is used as a matrix, and the B component is present in a dispersed state in the matrix,
The A component is made of a material capable of electrochemically occluding and releasing alkali metal ions,
The B component is a sulfur-modified cellulose having at least ₃ SO groups as a functional group,
An electrode material for an electricity storage device using a non-aqueous electrolyte, wherein the B component is 0.01% by mass or more with respect to 100% by mass of the total amount of the A component and the B component. The electrode material for an electricity storage device according to claim 1, wherein the sulfur-modified cellulose is a sulfur-modified cellulose nanofiber having a maximum fiber diameter of 1 μm or less. The electrode material further contains a conductive material,
The electrode material for an electricity storage device according to claim 1 or 2, wherein the amount of the conductive material is 0.1% by mass or more and 30% by mass or less with respect to 100% by mass of the total amount of the A component, the B component, and the conductive material. . The electrode material for an electricity storage device according to any one of claims 1 to 3 , wherein the component A is a sulfur-based organic material. The electrode material for an electricity storage device according to any one of claims 1 to 4 , wherein the component A is sulfur-modified polyacrylonitrile. The electrode material for an electricity storage device according to any one of claims 1 to 5 , wherein the composite powder has a median diameter (D50) of 0.1 μm or more and 50 μm or less. An electrode for an electricity storage device, comprising at least the electrode material according to any one of claims 1 to 6 , a binder, and a current collector. The electrode for a power storage device according to claim 7 , wherein the binder is a water-based binder. An electricity storage device comprising a positive electrode, a negative electrode, and an electrolyte interposed between the positive electrode and the negative electrode, wherein either the positive electrode or the negative electrode is the electrode according to claim 7 or 8 . device. An electrical device using the electricity storage device according to claim 9 . A method for manufacturing an electrode material for a power storage device, the method comprising:
The electrode material of the electricity storage device is
An electrode material for a power storage device using a non-aqueous electrolyte,
The electrode material includes a composite powder,
Both A component and B component are contained in one particle constituting the composite powder, and the particle has a structure in which the B component is supported, coated, or exposed on the surface of the A component,
The A component is made of a material capable of electrochemically occluding and releasing alkali metal ions,
The B component is a sulfur-modified cellulose having at least ₃ SO groups as a functional group,
The B component is 0.01% by mass or more with respect to 100% by mass of the total amount of the A component and the B component,
A step of heating the A component or a precursor of the A component, the B component precursor, and sulfur to a temperature of 200° C. or higher and 800° C. or lower while in contact with each other,
The A component is a material capable of electrochemically occluding and releasing alkali metal ions, and the precursor of the A component is an organic material,
A method for producing an electrode material for an electricity storage device, wherein the precursor of component B is a cellulose material, and the cellulose material has an anionic group forming an alkali metal salt or an alkaline earth metal salt. The method for manufacturing an electrode material for an electricity storage device according to claim 11, wherein the particles are particles in which the A component is used as a matrix and the B component is present in a dispersed state in the matrix. Production of an electrode material for an electricity storage device according to claim 11 or 12, wherein the precursor of component A, the precursor of component B, or the precursor of component A and the precursor of component B contain a conductive material. Method. The method for producing an electrode material for a power storage device according to any one of claims 11 to 13 , wherein the precursor of component A is polyacrylonitrile. After the heating step,
The method for producing an electrode material for a power storage device according to any one of claims 11 to 14, further comprising the step of heating to 250° C. or higher in a reduced pressure or inert gas atmosphere. The method for producing an electrode material for an electricity storage device according to any one of claims 11 to 15, wherein the precursor of component B is a cellulose material dispersed or dissolved in a solvent. The method for producing an electrode material for a power storage device according to any one of claims 11 to 16, wherein the cellulose material has an alkali metal carboxylic acid salt as a functional group. The method for producing an electrode material for a power storage device according to any one of claims 11 to 17, wherein the cellulose material is cellulose nanofibers having a maximum fiber diameter of 1 μm or less.

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