阅读说明：本技术 蓄电装置的电极材料、电极、蓄电装置、电气设备以及蓄电装置的电极材料的制造方法 (Electrode material for electricity storage device, electrode, electricity storage device, electric apparatus, and method for producing electrode material for electricity storage device ) 是由 向井孝志 池内勇太 齐藤恭辉 祖父江绫乃 东崎哲也 柳田昌宏 于 2019-09-30 设计创作，主要内容包括：提供一种蓄电装置的电极材料,其在不会使电极特性下降的前提下,弥补疏水性的活性物质的缺点,对疏水性的活性物质赋予亲水性,并能够发挥优异的分散性。一种使用了非水电解质的蓄电装置的电极材料,所述电极材料包含复合粉末,在构成所述复合粉末的1个颗粒中包含A成分和B成分两者,所述颗粒是在所述A成分的表面担载、覆盖或露出有B成分的结构,所述A成分包含能够以电化学方式吸收和释放碱金属离子的材料,所述B成分是至少具有SO-3基作为官能团的硫改性纤维素,相对于所述A成分和所述B成分的合计量100质量％,所述B成分为0.01质量％以上。(Provided is an electrode material for an electricity storage device, which can compensate for the disadvantage of a hydrophobic active material, impart hydrophilicity to the hydrophobic active material, and can exhibit excellent dispersibility without deteriorating the electrode characteristics. An electrode material for an electricity storage device using a nonaqueous electrolyte, the electrode material comprising a composite powder, wherein 1 particle constituting the composite powder contains both a component A and a component B, the particle having a structure in which the component B is supported on, covered with, or exposed to the surface of the component A, the component A containing a material capable of electrochemically absorbing and releasing alkali metal ions, and the component B having at least SO 3 And a sulfur-modified cellulose having a functional group, wherein the amount of the component B is 0.01% by mass or more based on 100% by mass of the total amount of the components A and B.)

1. An electrode material for an electricity storage device using a nonaqueous electrolyte, wherein,

the electrode materialThe composite powder comprises a composite powder, and both of component A and component B are contained in 1 particle constituting the composite powder, the particle has a structure in which component B is supported on, covered with, or exposed to the surface of component A, component A comprises a material capable of electrochemically absorbing and releasing alkali metal ions, and component B comprises at least SO₃And a sulfur-modified cellulose having a functional group, wherein the amount of the component B is 0.01% by mass or more based on 100% by mass of the total amount of the components A and B.

2. The electrode material for a power storage device according to claim 1,

the sulfur-modified cellulose is a sulfur-modified cellulose nanofiber having a maximum fiber diameter of 1 μm or less.

3. The electrode material for a power storage device according to claim 1 or 2, wherein,

the particles are particles in a state where the component a is a matrix and the component B is dispersed in the matrix.

4. The electrode material for a power storage device according to any one of claims 1 to 3,

the electrode material also contains a conductive material,

the conductive material is 0.1 mass% or more and 30 mass% or less with respect to 100 mass% of the total amount of the component A, the component B and the conductive material.

5. The electrode material for a power storage device according to any one of claims 1 to 4, wherein,

the component A is a sulfur-based organic material.

6. The electrode material for a power storage device according to any one of claims 1 to 5,

the component A is sulfur modified polyacrylonitrile.

7. The electrode material for a power storage device according to any one of claims 1 to 6, wherein,

the composite powder has a median diameter (D50) of 0.1 to 50 [ mu ] m.

8. An electrode for an electric storage device, wherein,

the electrode comprises at least the electrode material according to any one of claims 1 to 7, a binder and a current collector.

9. The electrode of the power storage device according to claim 8,

the adhesive is an aqueous adhesive.

10. An electric storage device, wherein,

the power storage device includes a positive electrode, a negative electrode, and an electrolyte provided between the positive electrode and the negative electrode,

any one of the positive electrode and the negative electrode is the electrode according to claim 9.

11. An electric device using the power storage device according to claim 10.

12. A method for producing an electrode material for an electricity storage device,

the method for producing an electrode material for an electricity storage device according to any one of claims 1 to 7, comprising a step of heating the component A or a precursor of the component A, the precursor of the component B, and sulfur to 200 ℃ or higher and 800 ℃ or lower in a state in which the component A and the precursor of the component B are in contact with each other, wherein the component A is a material capable of electrochemically absorbing or releasing alkali metal ions, the precursor of the component A is an organic material, the precursor of the component B is a cellulose material, and the cellulose material has an anionic group constituting an alkali metal salt or an alkaline earth metal salt.

13. The method for manufacturing an electrode material of a power storage device according to claim 12, wherein,

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 contain a conductive material.

14. The method for manufacturing an electrode material of a power storage device according to claim 12 or 13, wherein,

the precursor of the component A is polyacrylonitrile.

15. The method for manufacturing an electrode material for a power storage device according to any one of claims 12 to 14, wherein,

the heating step is followed by a step of heating to 250 ℃ or higher under reduced pressure or in an inert gas atmosphere.

16. The method for manufacturing an electrode material for a power storage device according to any one of claims 12 to 15, wherein,

the precursor of the B component is a cellulose material dispersed or dissolved in a solvent.

17. The method for manufacturing an electrode material for a power storage device according to any one of claims 12 to 16, wherein,

the cellulose material has an alkali metal carboxylate as a functional group.

18. The method for manufacturing an electrode material for a power storage device according to any one of claims 12 to 17, wherein,

the cellulose material is a cellulose nanofiber having a maximum fiber diameter of 1 μm or less.

Technical Field

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

Background

In recent years, with the spread of portable electronic devices such as notebook personal computers, smart phones, portable game devices, and PDAs, electric vehicles, home solar power generation, and the like, there has been an increasing demand for the performance of power storage devices that can be repeatedly charged and discharged and are used in these devices. In order to make portable electronic devices lighter and usable for a long time or to make electric vehicles travel over long distances, power storage devices are required to be smaller and have higher energy density. Examples of the power storage device include a secondary battery and a capacitor. At present, secondary batteries are used as power sources for portable electronic devices, power sources for electric vehicles, power sources for homes, and the like.

Conventionally, alkaline secondary batteries using an aqueous electrolyte, such as nickel-chromium (Ni-Cd) batteries and nickel-hydrogen (Ni-MH) batteries, have been mainly used as secondary batteries, but the use of lithium ion batteries using a nonaqueous electrolyte has been increasing in view of the above-described demand for miniaturization and high energy density. Among capacitors having excellent output density, lithium ion capacitors have high energy density, and thus are expected to be increasingly used for output applications. Further, recently, a battery in which ions having a conductive function are replaced with lithium ions by sodium ions or potassium ions is also being researched and developed.

For example, a lithium ion battery and a sodium ion battery are generally composed of a positive electrode, a negative electrode, an electrolytic solution or electrolyte, a separator, and the like. The electrode (positive electrode or negative electrode) is fabricated, for example, by coating an electrode material (mainly, an active material), a slurry including a binder and a conductive assistant onto a current collector and drying.

Lithium cobaltate (LiCoO) is generally used as a commercially available positive electrode material (mainly, a positive electrode active material) for a lithium ion battery₂) Ternary material (Li (Ni, Co, Mn) O)₂) And the like. The practical discharge capacity of the material is about 150-160 mAh/g. Since cobalt and nickel are rare metals, a positive electrode material capable of replacing these rare metals is desired. As a negative electrode material (mainly, a negative electrode active material), graphite (black lead), hard carbon, and titanic acid are generally usedLithium (Li)₄Ti₅O₁₂) And the like. The practical available discharge capacity of the material is about 150-350 mAh/g, and the material is required to be further high-capacity.

Among various electrode materials, sulfur is considered to be an attractive electrode material because of its large number of reaction electrons per unit mass, its theoretical capacity of 1672mAh/g, and its low material cost. And sulfur is at 2V (vs. Li/Li)⁺) The vicinity of the positive electrode shows a charge/discharge plateau, and the charge/discharge plateau can be used as both the positive electrode and the negative electrode.

However, when an electrode formed of elemental sulfur is lithiated (discharged when used as a positive electrode and charged when used as a negative electrode), lithium polysulfide (Li) is generated₂S_x: x is 2 to 8) and a low molecular weight sulfide, and is easily eluted in an electrolyte (particularly a carbonate-based solvent), and it is difficult to maintain a reversible and stable capacity. Therefore, in order to suppress the elution of sulfur into the electrolyte, in addition to a sulfur-based organic material having a — CS-bond or S-bond, a sulfur-based electrode material such as a material obtained by compounding a material other than sulfur with sulfur has been proposed.

In addition, recently, sulfur-containing organic compounds have been proposed as electrode materials (patent documents 1 to 7 and non-patent documents 1 to 5). Among them, it is found that the vulcanized polyacrylonitrile (sulfur-modified polyacrylonitrile) can obtain a reversible capacity of 500-700 mAh/g and a stable life characteristic.

Furthermore, it is known that a sulfur-based material can also electrochemically react with an alkali metal ion other than lithium. Among alkali metals other than lithium, sodium is an element that is rich in seawater and is present in the 6 th position in the earth crust, and the production site is not as uniform as lithium, and therefore cost reduction of the power storage device can be expected.

For example, non-patent document 6 shows that sulfur-modified acrylonitrile exhibits excellent characteristics even when sodium is used as a charge carrier.

Documents of the prior art

Patent document

Patent document 1: WO2010/044437 publication

Patent document 2: japanese patent laid-open No. 2014-179179

Patent document 3: japanese patent laid-open No. 2014-96327

Patent document 4: japanese patent laid-open No. 2014-96326

Patent document 5: japanese laid-open patent publication No. 2012-150933

Patent document 6: japanese laid-open patent publication No. 2012 and 99342

Patent document 7: japanese patent laid-open publication No. 2010-153296

Non-patent document

Non-patent document 1: fortunately, wide, et al, development of active materials and electrode materials for lithium ion batteries, Science & Technology, pp.194-222(2014)

Non-patent document 2: island senso et al, 53 th battery discussion lecture summary, 3C27, p.202(2012)

Non-patent document 3: fortunately cut wide, 53 th battery discussion lecture summary, 3C28, p.203(2012)

Non-patent document 4: island senso et al, 54 th battery discussion lecture summary, 1A08, p.7(2013)

Non-patent document 5: island senso et al, 54 th battery discussion lecture summary, 3E08, p.344(2013)

Non-patent document 6: fortunately cut wide, etc. "recent technological movement of secondary batteries without rare metals", CMC publication, pp.81-101(2013)

Disclosure of Invention

Technical problem to be solved by the invention

Polyvinylidene fluoride (PVDF) is widely used and widely used as a binder for binding an active material in an electrode of an electric storage device using a nonaqueous electrolyte. PVDF is a binder exhibiting 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 a slurry thereof. However, the production cost and the burden on the environment of these organic solvents are relatively high. Therefore, a de-organic solvent is required. Further, when a sulfur-based electrode material is used, NMP dissolves sulfur in the electrode material, and decreases the capacity of the electrode. PVDF is likely to swell in a high-temperature electrolyte, and swelling of PVDF causes a decrease in electron conductivity of an electrode material layer, and this causes 1 factor of deterioration in output characteristics and cycle life characteristics of an electrode. Therefore, it is preferable to use a binder which does not require an organic solvent such as NMP and is less likely to swell in an electrolytic solution.

In recent years, as binders which are less likely to swell in high-temperature electrolytes, aqueous binders such as carboxymethyl cellulose (CMC), acrylic resins, and alginic acid have been attracting attention. By using an aqueous binder for the electrode, water can be selected as a solvent for the slurry prepared in the electrode production process. Therefore, it is promising in terms of manufacturing cost and environment. Further, since water is insoluble in sulfur, when water is used as a solvent for the slurry, it is possible to prevent a decrease in capacity due to elution of sulfur into the solvent for the slurry.

However, various sulfur-based materials reported to date as electrode materials are hydrophobic and have low wettability with water. Therefore, when a binder (in other words, an aqueous binder) in which water is used as a solvent or a dispersion medium is used, it is difficult to disperse the hydrophobic sulfur-based material in the kneading step for preparing the slurry. In order to improve the dispersibility of the hydrophobic sulfur-based material and impart hydrophilicity, it is conceivable to use a surfactant or the like. However, many surfactants are decomposed by overcharge, high-temperature storage, and the like when used in a battery, and generate gas, thereby deteriorating battery characteristics.

The present invention has been made in view of the current state of the art, and a main object thereof is to provide an electrode material for an electricity storage device, which can compensate for the disadvantage of a hydrophobic active material without deteriorating the electrode characteristics, can impart hydrophilicity to the hydrophobic active material, and can exhibit excellent dispersibility.

Means for solving the problems

The first aspect of the present invention relates to an electrode material for an electricity storage device using a nonaqueous electrolyte, the electrode material comprising a composite powder, wherein 1 particle constituting the composite powder contains both a component a and a component B, the particle having a structure in which the component B is supported on, covered with, or exposed from the surface of the component a, and the component a contains a component that can be supported on, covered with, or exposed from the surface of the component aA material electrochemically absorbing and releasing alkali metal ions, and the component B is a material having at least SO₃And a sulfur-modified cellulose having a functional group, wherein the amount of the component B is 0.01% by mass or more based on 100% by mass of the total amount of the components A and B.

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

In the electrode material for the electricity storage device, the particles may be particles in a state in which the component a is a matrix and the component B is dispersed in the matrix.

In the electrode material for a power storage device, the electrode material may further contain a conductive material, and the conductive material may be 0.1 mass% or more and 30 mass% or less with respect to 100 mass% of the total amount of the component a, the component B, and the conductive material.

In the electrode material for the power storage device, the component a may be a sulfur-based organic material.

In the electrode material for an electricity storage device, the component a may be sulfur-modified polyacrylonitrile.

In the electrode material for an 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 invention relates to an electrode of an electric storage device that has at least the electrode material, a binder, and a current collector.

In the electrode of the power storage device, the binder may be an aqueous binder.

A third aspect of the present invention relates to an electric storage device including a positive electrode, a negative electrode, and an electrolyte provided between the positive electrode and the negative electrode, wherein one of the positive electrode and the negative electrode is the electrode.

A fourth aspect of the invention relates to an electric apparatus using the power storage device.

A fifth aspect of the present invention relates to a method for producing an electrode material for an electricity storage device, the method including a step of heating the component a or a precursor of the component a, a precursor of the component B, and sulfur to 200 ℃ or higher and 800 ℃ or lower in a state where the component a and the precursor of the component B are in contact with each other, the component a being a material capable of electrochemically absorbing or releasing alkali metal ions, the precursor of the component a being an organic material, the precursor of the component B being a cellulose material, and the cellulose material having an anionic group constituting an alkali metal salt or an alkaline earth metal salt.

In the method for producing an electrode material for a power 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 producing an electrode material for an electricity storage device, the precursor of the component a may be polyacrylonitrile.

In the method for producing an electrode material for a power storage device, the step of heating may be followed by a step of heating to 250 ℃ or higher under reduced pressure or in an inert gas atmosphere.

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

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

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

Effects of the invention

The present invention can provide an electrode material for an electricity storage device, which can compensate for the disadvantage of a hydrophobic active material without deteriorating the electrode characteristics, impart hydrophilicity to the hydrophobic active material, and can exhibit excellent dispersibility.

Drawings

Fig. 1 is a conceptual diagram of a cross section of a particle of the composite powder and a cross section of a particle of the mixed powder alone. (a) Is a conceptual sectional view of only the particles of the mixed powder, and (b), (c) and (d) are conceptual sectional views of the particles of the composite powder.

Fig. 2 is a diagram showing the water dispersibility of the trial powder. (a) The water dispersibility of the powder of the sulfur-modified compound of comparative example 1 is shown, and (b) the evaluation results of the water dispersibility of the composite powder of example 1 are shown.

Fig. 3 is a graph showing the volume-based particle size distribution of the powders obtained according to example 1 and comparative example 1, respectively.

Fig. 4 is a graph showing charge and discharge curves of the battery fabricated according to comparative example 1.

Fig. 5 is a graph showing charge and discharge curves of the battery fabricated according to example 1.

Fig. 6 is an IR spectrum showing the sulfur-modified cellulose powder B' 1.

Fig. 7 is an IR spectrum showing the sulfur-modified cellulose powder B' 2.

Fig. 8 is an IR spectrum showing the sulfur-modified cellulose powder B' 4.

Fig. 9 is an IR spectrum showing the sulfur-modified cellulose powder B' 5.

Detailed Description

[ electrode Material for Electrical storage device ]

An electrode material for an electricity storage device of the present invention is an electrode material for an electricity storage device using a nonaqueous electrolyte, the electrode material including a composite powder, wherein 1 particle constituting the composite powder includes both a component A and a component B, the particle having a structure in which the component B is supported on, covered with, or exposed from a surface of the component A, the component A is made of a material capable of electrochemically absorbing and releasing alkali metal ions, and the component B has at least SO₃And a sulfur-modified cellulose having a functional group, wherein the amount of the component B is 0.01% by mass or more based on 100% by mass of the total amount of the components A and B.

As described above, the particles constituting the composite powder have a structure in which the component B is supported on, covered with, or exposed from the surface of the component a, and even if the component a is a hydrophobic material, the component B is hydrophilic, and therefore the composite powder is excellent in hydrophilicity. Therefore, according to the electrode material for an electricity storage device of the present invention, even if water and a binder (aqueous binder) using water as a solvent or a dispersion medium are used, dispersibility is excellent, a slurry having excellent uniformity can be easily obtained, and the time for producing an electrode can be shortened. Therefore, according to the electrode material for a power storage device of the present invention, the yield of the electrode is significantly improved as compared with the conventional electrode material, and the capacity and output of the power storage device can be increased at the same time, thereby expanding the use range.

In the present invention, the electric storage device refers to a device, an element, or the like that has at least a positive electrode and a negative electrode and is capable of extracting energy stored chemically, physically, or physicochemically as electric power. Examples of the power storage device include a rechargeable secondary battery and a capacitor device such as a capacitor (capacitor) and a capacitor (capacitor). More specifically, examples thereof include a lithium ion battery, a lithium ion capacitor, a sodium ion battery, a sodium ion capacitor, a potassium ion battery, a potassium ion capacitor, and the like.

The electrode material is a material constituting an electrode. Examples of the material constituting the electrode include an active material, a conductive aid, a binder, a current collector, and other materials.

< composite powder >

In the composite powder of the present invention, 1 particle constituting the composite powder contains both the component a and the component B, and the particle has a structure in which the component B is supported on, covered with, or exposed from the surface of the component a. The particles may have any structure of being supported, covered or exposed.

For example, the component A may be used as a core, and the component B may be carried or coated on the periphery (surface) thereof. Supporting or covering means that the surface of the component A is partially or completely covered with the component B. The term "exposed" means a state in which the component a is used as a matrix, the component B is present in a dispersed state in the matrix, and the component B is present on the surface of the component a. The component B may be partially exposed on the surface of the component A.

Preferably, the particles are particles in a state in which the component a is a matrix and the component B is dispersed in the matrix. The dispersion in the matrix may also refer to a state in which the component B is contained as a filler in the component A.

In addition, composite and mixing are different concepts, and a mixed powder is only a collection of particles composed of the a component and particles composed of the B component, whereas a composite powder contains both the a component and the B component in 1 particle constituting the powder. As an example, fig. 1(a) shows a conceptual sectional view of only the particles of the mixed powder, and fig. 1(b), (c), and (d) show conceptual sectional views of the particles of the composite powder. Fig. 1(B) is a conceptual view of the case where the surface of the component a is completely covered with the component B, fig. 1(c) is a conceptual view of the case where the surface of the component a is partially covered (in other words, supported) with the component B, and fig. 1(d) is a conceptual view of the case where the component B is dispersed in the matrix of the component a and the component B is partially exposed at the surface of the component a.

When the mixed powder of the components a and B is to be dispersed in water, the component B is excellent in hydrophilicity even with a monomer, and therefore, only the component B is dispersed as a monomer, and the component a and the component B are easily separated. However, since the particles constituting the composite powder of the present invention have a structure in which the component B is supported on, covered with, or exposed to the surface of the component a, the particles exhibit excellent dispersibility in water, and can be in a state in which both the component a and the component B are dispersed.

The median diameter (D50) of the composite powder of the present invention is preferably 0.1 to 50 μm, more preferably 0.1 to 30 μm, still more preferably 0.5 to 15 μm, and most preferably 0.55 to 14.5 μm. When the median diameter (D50) of the composite powder is in the above range, an electrode material capable of providing an electrode having excellent output characteristics and cycle life characteristics can be obtained. By setting the thickness to 0.1 μm or more, the specific surface area is not excessively high, and the amount of binder required for electrode formation is not increased. As a result, the output characteristics and energy density of the electrode are excellent. Further, by setting the particle diameter to 50 μm or less, the particle surface area becomes large, and practical input/output characteristics can be obtained.

Here, the median diameter (D50) is a particle diameter that has reached a frequency accumulation of 50% in volume conversion based on a volume by using a laser refraction/diffraction particle size distribution measurement method, and the same applies below. As the measurement apparatus, LA-960 manufactured by HORIBA, etc. can be used.

The proportion of the component a to the component B in the entire composite powder is 0.01 mass% or more, preferably 0.1 mass% or more, and more preferably 0.5 mass% or more, assuming that the total amount of both components is 100 mass%. When the content of the component B is 0.01% by mass or more, the component a has an excellent effect of imparting hydrophilicity thereto, and has sufficient dispersibility when a slurry using an aqueous binder is prepared. If the purpose is to impart hydrophilicity to the component A only, the component B does not need to be provided in an amount exceeding 10 mass%, and may be 10 mass% or less.

(A component)

The component a contains a material capable of electrochemically absorbing and releasing alkali metal ions. The component a is not particularly limited as long as it is an electrode material capable of electrochemically absorbing and releasing alkali metal ions. Examples of the case where the alkali metal ion is electrochemically absorbed include: reversibly forming an alloy (including solid solutions, intermetallic compounds, and the like) with an alkali metal, reversibly chemically bonding with an alkali metal, absorbing alkali metal ions, or reversibly incorporating an alkali metal, and the like. In addition, electrochemically releasing the alkali metal ions means that the absorbed alkali metal ions leave.

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

Among these, sulfur-based organic materials such as S (sulfur), sulfides of the above elements, and sulfur-modified compounds of organic compounds are preferable from the viewpoint of exhibiting a charge-discharge plateau range close to that of the component B (sulfur-modified cellulose). Examples of the sulfur-based organic material such as a sulfide of the element or a sulfur-modified compound of an organic compound include: sulfur-modified natural rubber, sulfur-modified asphalt, sulfur-modified anthracene, sulfur-modified polyacrylic acid, 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 N-vinyl formaldehyde copolymer, sulfur-modified diol, sulfur-modified polyacrylonitrile, and the like. The component A may be composed of 1 kind alone or 2 or more kinds.

Among these, sulfur-based organic materials are preferable because a stable capacity retention rate can be obtained. In addition, in any case of using lithium, sodium or potassium as a charge carrier, since reversible electric capacity of 500 to 700mAh/g can be stably expressed, sulfur-modified polyacrylonitrile is particularly preferable.

The component A is in the form of particles, and the median diameter (D50) is preferably 0.1 to 30 μm, more preferably 0.5 to 15 μm, and still more preferably 0.55 to 14.5 μm. When the median diameter (D50) is within the above range, the surface smoothness of the resulting electrode is not deteriorated. Further, it is easy to obtain particles in a state where the component B is supported or coated on the surface of the component a and/or in a state where the component B is dispersed in the matrix of the component a and the component B is partially exposed on the surface of the component a.

(component B)

Component B is at least SO₃A sulfur-modified cellulose having a functional group. The sulfur-modified cellulose refers to a material obtained by subjecting cellulose to dehydrogenation reaction and then to vulcanization, and includes a carbon skeleton derived from cellulose and sulfur bonded to the carbon skeleton. The sulfur-modified cellulose changed in appearance from white to black in the precursor (cellulose), and showed excellent hydrophilicity and was insoluble in water. In addition, with SO₃The group included as a functional group is a group in which SO is bonded to a carbon skeleton derived from cellulose in sulfur-modified cellulose₃The case of radicals. SO (SO)₃The radicals may be selected from the group consisting of SO₃H、SO₃Na、SO₃Li and SO₃K is at least one of the group consisting of K.

Illustrating the difference between cellulose and sulfur modified cellulose. Cellulose has not only the property of being dispersed in water or swelling by absorbing water but also the carbonization reaction starts by mass reduction at 180 ℃ or more. However, sulfur-modified cellulose is hydrophilic but insoluble in water, and therefore does not swell with water, and exhibits excellent heat resistance because the mass loss is 30 mass% or less even at 400 ℃. The sulfur-modified cellulose may be constituted by 10 to 60% by mass of sulfur, or 20 to 60% by mass of sulfur, as calculated by elemental analysis, depending on the production conditions such as the amount of raw materials added and the heat treatment temperature.

The component B is preferably sulfur-modified cellulose nanofibers (sometimes referred to as S-CeNF). S-CeNF is not dissolved and swelled by water, and shows excellent hydrophilicity. In addition, the reversible electric capacity of 300 to 400mAh/g can be stably expressed. Therefore, by compounding the component a and the component B, not only hydrophilicity can be imparted, but also a high capacity of the electrode can be expected.

Further, since S-CeNF is fibrous, a three-dimensional mesh structure having conductivity can be formed on the surface, inside, or both of the component a. When the three-dimensional mesh structure is formed by S — CeNF, the component a can contact the electrolyte solution, and sufficient output characteristics can be obtained for the electrode material. In addition, a sufficient current collecting effect as an active material of the electrode can be obtained.

The maximum fiber diameter of S-CeNF is preferably 1 μm or less, more preferably 1nm or more and 500nm or less, and still more preferably 2nm or more and 200nm or less. In particular, when the component a is used as a matrix, particles of sulfur-modified cellulose nanofibers having a three-dimensional network structure dispersed in the matrix can be easily obtained, and hydrophilicity can be imparted to the component a without degrading the electrode characteristics originally expected for the component a, specifically, the output characteristics and cycle life characteristics, and excellent dispersibility can be exhibited.

At least 10 fibers are randomly selected from a fiber image obtained by using an electron microscope or the like, the maximum value of the length of each fiber in the short axis direction is obtained, and the maximum fiber diameter is obtained by averaging the maximum values. From a fiber image obtained using an electron microscope or the like, at least 10 or more fibers are randomly selected, and the average value of the lengths of the respective fibers in the short axis direction is obtained to obtain the average fiber diameter.

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

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

The aspect ratio (length of S-CeNF fiber/diameter of S-CeNF fiber) is more preferably 10 or more and 100000 or less. This is because a three-dimensional mesh structure is easily formed on the surface and inside of the component a.

The aspect ratio is more preferably 8 or more and 50000 or less, and still more preferably 25 or more and 10000 or less. The battery or the capacitor has excellent output characteristics.

The aspect ratio is determined by the length of the fiber/the diameter of the fiber (average fiber diameter). The diameter of the fiber can be measured by the same apparatus as that for measuring the length of the fiber.

< conductive Material >

The electrode material of the power storage device of the present invention contains an arbitrary component such as a conductive material in addition to the component a or the component B.

The electrode material of the power storage device preferably contains a conductive material. This is because the electrode material can be expected to have a further higher output. In particular, when the component B contains a conductive material or the like so as to be carried on, cover or be exposed on the surface of the component a, both hydrophilicity and conductivity can be preferably imparted to the surface of the component a. Of course, a conductive material may be contained in the a component.

The conductive material refers to a material having electron conductivity (electron conductivity). For example, it may be: a metal selected from C (carbon), Al (aluminum), Ti (titanium), V (vanadium), Cr (chromium), Fe (iron), Co (cobalt), Ni (nickel), Cu (copper), Ta (tantalum), Pt (platinum), Au (gold); alloys containing these metals; and ceramics, polymers, and the like having conductivity. Among these, carbon is preferable from the viewpoint of low conductivity, material cost, and 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 them, carbon black is particularly preferable. Carbon black has different properties depending on the production 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 any problem. The conductive material can be used alone in 1 kind, can also be combined with more than 2 kinds.

The content of the conductive material is preferably 0.1 mass% or more and 30 mass% or less with respect to 100 mass% of the total amount of the composite powder containing the a component and the B component and the conductive material. The amount of 0.1 mass% or more is preferable because the effect of imparting conductivity is sufficient, and the amount of 30 mass% or less is preferable because the active material capacity is not too low.

[ production of electrode Material for Electrical storage device ]

The method for producing the electrode material of the power storage device of the present invention is not particularly limited. The method for obtaining the composite powder contained in the electrode material of the power storage device of the present invention is also not particularly limited.

First, the preparation of the component B will be described. The component B can be obtained by a step of heating a precursor of the component B (cellulose material) and sulfur as raw materials in a state where the sulfur is in contact with the precursor of the component B. The state in which sulfur is brought into contact with the precursor of the component B may be achieved by bringing the precursor of the component B into physical contact with sulfur, and examples thereof include: a solid powder obtained by mixing a precursor of component B with sulfur; and a product obtained by dispersing the precursor of the component B and sulfur in a solvent and drying the dispersion. By bringing sulfur into contact with the precursor of the component B and performing the heat treatment in this manner, sulfur is diffused in a solid phase into the cellulose, and therefore the component B (sulfur-modified cellulose) can be obtained in a high yield.

The heat treatment may be carried out at a temperature at which the precursor of the component B undergoes sulfur modification, and is preferably 200 ℃ to 800 ℃. This enables synthesis of a component B (sulfur-modified cellulose) composed of a carbon skeleton derived from a precursor of the component B (cellulose material) and sulfur bonded to the carbon skeleton. When the temperature is 200 ℃ or higher, the precursor of the component B is sufficiently modified with sulfur, and the conductivity of the obtained component B (sulfur-modified cellulose) is higher than that when the temperature is less than 200 ℃. Further, by setting the temperature to 800 ℃ or lower, sulfur is less likely to be desorbed from the B component, and the sulfur content is less likely to decrease, so that it is possible to prevent the electric capacity of the electrode material from decreasing due to the formation of carbide. From the viewpoint of high yield of the component B and high electric capacity, it is more preferably 220 ℃ to 600 ℃. Further, from the viewpoint of excellent conductivity of the component B, it is more preferably 250 ℃ to 500 ℃.

The atmosphere during the heat treatment is not particularly limited, but is preferably a non-oxygen atmosphere such as an inert gas atmosphere or a reducing atmosphere because oxidation may occur in the atmosphere due to oxygen. Specific 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 atmosphere.

The time of the heat treatment may be 1 hour to 50 hours, or 1 hour to 40 hours, as long as the component B is produced. When the amount is within this range, the cellulose is sufficiently modified with sulfur, and the resulting composite powder has excellent electrical capacity. Further, since the heating time is not excessively long, the reaction of sulfur modification proceeds sufficiently, and excessive heating energy is not consumed, which is economically preferable.

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

The cellulose material as the precursor of the component B is represented by the formula (C)₆H₁₀O₅)_nThe carbohydrate represented by the formula (I) or a derivative thereof may have an anionic group which forms an alkali metal salt or an alkaline earth metal salt. In addition, the formula (C)₆H₁₀O₅)_nThe carbohydrate derivative represented by the formula (C) represents an unpaired molecular formula such as introduction, oxidation, reduction, and replacement of an atom of a functional group₆H₁₀O₅)_nThe structure and properties of the represented carbohydrates are responsible for the greatly changed degree of the compounds.

The cellulose material as the precursor of the component B includes the following formula (C)₆H₁₀O₅)_nThe carbohydrate derivative is a derivative obtained by substituting an anionic group constituting an alkali metal salt or an alkaline earth metal salt. Examples thereof include: methyl cellulose, ethyl methyl cellulose, carboxymethyl cellulose (CMC), hydroxyethyl cellulose, hydroxybutyl methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose stearyl ether, carboxymethyl hydroxyethyl cellulose, alkyl hydroxyethyl cellulose, nonyloxy hydroxyethyl cellulose, cellulose sulfate, cellulose acetate, methyl cellulose ether, methyl ethyl cellulose ether, low nitrogen hydroxyethyl cellulose dimethyldiallyl ammonium chloride (polyquaternium-4), chloro- [ 2-hydroxy-3- (trimethylamino) propyl ] chloride]Hydroxyethyl cellulose (polyquaternium-10), chloro- [ 2-hydroxy-3- (lauryl dimethylamino) propyl ] chloride]Hydroxyethyl cellulose (polyquaternium-24), hemicellulose, microcrystalline protein cellulose, cellulose nanocrystals, cellulose nanofibers (CeNF), and the like. Among these, CeNF is preferable.

CeNF is a cellulose fiber obtained by physically or chemically refining cellulose, which is a structural material of wood or the like, or cellulose obtained from animals, algae, or fungi, to a maximum fiber diameter of 1 μm or less. More specifically, the cellulose fiber preferably has a length of 0.2 μm or more, an aspect ratio (length of cellulose fiber/diameter of cellulose fiber (fiber diameter)) of 10 or more and 100000 or less, and an average degree of polymerization of 100 to 100000, and more preferably the cellulose fiber has a length of 0.5 μm or more, an aspect ratio (length of cellulose fiber/diameter of cellulose fiber (fiber diameter)) of 10 or more and 250 or less, and an average degree of polymerization of 100 to 10000. Here, the average polymerization degree is a value calculated by a viscosity method described in TAPPI T230 standard method.

The CeNF having an anionic group forming an alkali metal salt or an alkaline earth metal salt can efficiently disintegrate the cellulose fiber to a predetermined fiber diameter.

The alkali metal salt or alkaline earth metal salt formed of an anionic group contained in the cellulose material, which is a precursor of component B, is not particularly limited, and examples thereof include: alkali metal salts or alkaline earth metal salts of carboxylic acids; alkali metal salts or alkaline earth metal salts of phosphoric acid; alkali metal salts or alkaline earth metal salts of sulfonic acids; and alkali metal salts or alkaline earth metal salts of sulfuric acid, and the like. There may be 1 or more of them. Among these, cellulose materials having an alkali metal carboxylate as a functional group are preferable in terms of high discharge capacity and water dispersibility of the obtained active material.

The kind of the alkali metal salt or the alkaline earth metal salt is not particularly limited, and examples thereof include: alkali metal salts such as sodium salt, potassium salt and lithium salt; and alkaline earth metal salts such as magnesium salt, potassium salt, and barium salt.

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

When cellulose nanofibers (CeNF) are used as a precursor of component B, the obtained sulfur-modified cellulose forms sulfur-modified cellulose nanofibers (S-CeNF). When the component B is a fibrous sulfur-modified cellulose nanofiber (S-CeNF), a conductive three-dimensional mesh structure can be formed on the surface and inside of the component a, and a sufficient current collecting effect as an active material of an electrode can be obtained, which is preferable.

The precursor of the component B desirably contains at least SO after the treatment (after the heat treatment in a state where sulfur is brought into contact with the precursor of the component B)₃Cellulose material with the group as a functional group. Examples thereof include: TEMPO oxidizes alkali or alkaline earth metal salts of 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 or alkaline earth metal salts of carboxymethyl cellulose. There may be 1 or more of them. Among these, alkali metal salts of TEMPO-oxidized cellulose are preferable, and alkali metal salts of TEMPO-oxidized cellulose nanofibers are more preferable because high discharge capacity can be obtained.

Next, the preparation of the composite powder is described. The method for obtaining the composite powder containing the component a and the component B is not particularly limited, and examples thereof include a mechanical milling method, a spray drying method, a fluidized bed granulation method, a sintering pulverization method, and the like.

The mechanical milling method is a method of applying an external force such as impact, tension, friction, compression, shear, etc. to the raw material powder (at least component a and component B), and can use a rotary mill, a vibration mill, a planetary mill, a shaking mill, a horizontal mill, a ball mill, an attritor, a jet mill, a stirring mill, a homogenizer, a fluidized bed, a paint mixer, a mixer, etc. According to this method, a composite powder containing the component A and the component B can be obtained. In particular, a composite in which the component B is supported or coated on the surface of the component A is easily formed. In this method, the mechanical strength of the component B is preferably lower than that of the component A. That is, the component B is preferably more easily pulverized than the component A. The component B to be fine particles is preferably mechanically pressed against the surface of the component A, and the component B can be carried, covered, or exposed on the component A.

In the spray drying method, a liquid in which the component a and the component B are dispersed in water or an organic solvent is spray dried, whereby a composite in which the component B is supported on, covers, or exposes the surface of the component a can be formed. When the component a is a hydrophobic material, it is preferable to use an organic solvent for dispersing the component a, and particularly when the component a is a sulfur or sulfur-based organic material, it is preferable to use a solvent obtained by adding a surfactant, alcohol, or the like to water. The surfactant, alcohol, and the like are decomposed or gasified by the heat treatment, and therefore do not adversely affect the electrode material.

In the fluidized bed granulation method, a composite in which the component B is supported or coated on the surface of the component a can be formed by blowing hot air from the lower part of a granulation chamber to which the component a is added, and spraying a solvent in which the component B is dispersed, while the component a is blown up into the air and fluidized. When the component a is sulfur or a sulfur-based organic material, a composite in which the component B is supported on, covered with, or exposed to the surface of the component a can also be formed by blowing hot air from the lower part of the granulation chamber to which the component a or the precursor of the component a is added, spraying the precursor of the component a with a solvent in which the precursor of the component B is dispersed while the component a or the precursor of the component a is blown up into the air and flows, thereby preparing a composite powder in which the precursor of the component B is supported on or covered with the surface of the precursor of the component a, and then performing a heating treatment at 200 ℃.

In the sintering pulverization method, the component a, the precursor of the component B, and sulfur are dispersed in a solvent, and then the dispersion is subjected to a heat treatment at 200 ℃ or higher and then pulverized, whereby a composite powder in which the component B is supported or coated on the surface of the component a can be formed. When the component a is sulfur or a sulfur-based organic material, a composite can be formed in which the component B is supported on, covered with, or exposed to the surface of the component a by dispersing the component a or a precursor of the component a, a precursor of the component B, and sulfur in a solvent, then subjecting the dispersion to a heat treatment, and thereafter pulverizing the dispersion. In the sintering pulverization method, a solvent obtained by adding a surfactant, alcohol, or the like to water is preferably used as the solvent. The surfactant, alcohol, and the like are decomposed or gasified by the heat treatment, and therefore do not adversely affect the electrode material.

In the case where the component a is prepared and then produced in the methods such as the mechanical milling method, the spray drying method, the fluidized bed granulation method, the sintering pulverization method, and the like, particularly in the case where the component a is sulfur, a sulfide of the above-mentioned element, or a sulfur-based organic material, the component a is obtained by vulcanizing the above-mentioned element by heat treatment or modifying an organic compound with sulfur. Further, Polyacrylonitrile (PAN) is preferable as the organic compound in terms of large electric capacity and excellent life characteristics.

In the case where the component a is a sulfide or a sulfur-based organic material of the above-described elements exemplified as the component a, the electrode material of the power storage device of the present invention is produced by a method for producing an electrode material of a power storage device, the method comprising a step of heating the component a or a precursor of the component a, which is a material capable of electrochemically absorbing or releasing alkali metal ions, a precursor of the component B, which is a cellulose material having an anionic group constituting an alkali metal salt or an alkaline earth metal salt, and sulfur to 200 ℃ or higher and 800 ℃ or lower in a state where the components a and B are in contact with each other. This can provide a composite powder in which the component B is carried on, covered with, or exposed to the surface of the component a.

In particular, the method using a precursor of the component a as a raw material is suitable for a composite powder in which the component B is exposed on the surface of the component a. In the case of obtaining a composite powder in which the component B is exposed on the surface of the component a, it is preferable to use a material in which a precursor of the component a is in a liquefied state as a raw material. The precursor of the component A in a liquefied state means that: for example, the component A is softened by heat or chemical reaction, the component A is dissolved in a solvent, and the component A can be deformed by pressure.

Hereinafter, the details will be described mainly on the method of using the precursor of the component a as a raw material, but when the component a is used as a raw material, the production can be performed by the same method as the method described in detail below, except that the precursor of the component a is replaced with the component a.

The state in which the precursor of component a, the precursor of component B, and sulfur are brought into contact may be any state as long as the precursor of component a, the precursor of component B, and sulfur are brought into physical contact, and examples thereof include: a solid powder obtained by mixing a precursor of component A, a precursor of component B and sulfur; and solid powders obtained by dispersing the precursor of component a, the precursor of component B, and sulfur in a solvent and drying the dispersion. By bringing the precursor of the component a, the precursor of the component B, and sulfur into contact and heating them in this manner, sulfur is diffused in a solid phase in the precursor of the component a and the precursor of the component B, and thus a composite powder can be obtained with high yield.

In particular, if a mixture is obtained by dissolving a precursor of the component a and a precursor of the component B in a solvent and dispersing sulfur therein, the obtained composite particles have a structure in which the component B is exposed on the surface of the component a (a state in which the component B is dispersed in a matrix of the component a).

The heating temperature may be 200 ℃ to 800 ℃. The temperature at which the precursor of the component A and the precursor of the component B are sulfur-modified may be any temperature. Thus, the component a and the sulfur-modified cellulose containing a carbon skeleton derived from the cellulose material and sulfur bonded to the carbon skeleton as the component B can be synthesized. When the temperature is 200 ℃ or higher, the precursor of the component a and the precursor of the component B are sufficiently modified with sulfur, and the electrical conductivity of the obtained composite powder is higher than that when the temperature is less than 200 ℃. Further, by setting the temperature to 800 ℃ or lower, sulfur is less likely to be desorbed from the components a and B, and the sulfur content is less likely to decrease, so that it is possible to prevent the electric capacity of the electrode material from decreasing due to the formation of carbide. From the viewpoint of high yield of the component A and the component B and high electric capacity, the temperature is more preferably 220 ℃ to 600 ℃. Further, from the viewpoint of excellent conductivity of the components a and B, it is more preferably 250 ℃ or higher and 500 ℃ or lower.

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

The time of the heat treatment may be 1 hour to 50 hours, or 1 hour to 40 hours, as long as the component B is produced. When the amount is within this range, the cellulose is sufficiently modified with sulfur, and the resulting composite powder has excellent electrical capacity. Further, since the heating time is not excessively long, the reaction of sulfur modification proceeds sufficiently, and excessive heating energy is not consumed, which is economically preferable. The heating time for producing the component A is also the same as that for the component B.

When the total amount of the precursor of the component a and the precursor of the component B is 100% by mass, the precursor of the component B is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and still more preferably 0.5% by mass or more. By setting the precursor of the component B to 0.01 mass% or more, the component a has an excellent effect of imparting hydrophilicity thereto, and has sufficient dispersibility when producing a slurry using an aqueous binder. If the purpose is to impart hydrophilicity to the component A, the component B does not need to be provided in an amount exceeding 10 mass%, and may be 10 mass% or less.

The mass of sulfur to be a raw material may be the same as or more than the mass of each of the precursor of the component a and the precursor of the component B. Specifically, the amount of sulfur is preferably 1 to 10 times, more preferably 2 to 6 times the mass of each of the precursor of the component a and the precursor of the component B. The amount of sulfur as a raw material is 1 time or more the amount of the precursor of the component a and the precursor of the component B, so that sulfur modification is sufficiently caused, and an electrode material having excellent electrical capacity is obtained. By making the amount of sulfur to be 10 times or less, it becomes difficult to leave sulfur as a raw material in the obtained electrode material, and it does not take much time to perform desulfurization treatment in a subsequent step. When elemental sulfur remains in the electrode material, the initial electric capacity increases, but the cycle life characteristics may deteriorate. In such a case, the desulfurization treatment is preferably performed.

The desulfurization treatment is a treatment for removing elemental sulfur contained in the produced composite powder, and is not limited as long as residual sulfur can be removed by heating treatment, pressure reduction treatment, or the like. Examples thereof include: and heating the resultant composite powder to 250 ℃ or higher under reduced pressure or in an inert gas atmosphere. Then, the heating is performed for about 1 to 20 hours, whereby the residual sulfur can be removed satisfactorily. The upper limit of the heating temperature is not particularly limited, and may be 800 ℃ or lower from the viewpoint of a large electrical capacity of the electrode material. After the composite powder is obtained, residual sulfur can be dissolved in carbon disulfide, but since carbon disulfide is highly toxic, it is preferable to perform desulfurization treatment by the above-described heat treatment.

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

When the precursor of the component a is Polyacrylonitrile (PAN), PAN and the precursor of the component B (cellulose material) and sulfur are used as raw materials, and PAN is sulfur-modified polyacrylonitrile (S-PAN; corresponding to the component a) and the precursor of the component B is sulfur-modified cellulose (corresponding to the component B) by heating the precursors of PAN and the component B and sulfur in a state of contact with each other to 200 ℃ to 800 ℃ inclusive, and at the same time, a composite powder in which the component B is supported on, covered with, or exposed to the surface of the component a can be obtained.

The precursor of component B is cellulose material, which may be monomer or dispersed or dissolved in solvent.

In addition, when the electrode material contains a conductive material, examples of the method for producing the electrode material include: the precursor of the component a, the precursor of the component B, the conductive material, and sulfur are dispersed in a solvent such as water, and heat treatment is similarly performed. When the precursor of component a is dispersed in a solvent such as water, when the precursor becomes lumps (lumps or aggregates), the dispersibility in the solvent such as water can be improved by using a surfactant, alcohol, or the like in combination. The surfactant and alcohol used in combination are decomposed or gasified by the heat treatment, and therefore do not adversely affect the electrode material.

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

In addition, a composite powder composed of particles in which the component a is used as a matrix and the component B is dispersed in the matrix can be obtained, for example, as follows: the liquefied A component precursor is prepared by dispersing the B component (or B component precursor) and sulfur, and then subjecting the dispersion to a heat treatment at 200 ℃ to 800 ℃. By dispersing the component B in the matrix of the component a, the surface of the component a has a structure in which the component B is partially exposed.

The precursor of the liquefied a component includes, for example: a liquid in which a precursor of the component a is dissolved in a solvent, a component a liquefied by raising the temperature to the vicinity of the melting point by heat treatment or the like. For example, polyacrylonitrile is dissolved in an organic solvent, cellulose nanofibers and sulfur powder are dispersed in the liquid, and the dispersion is subjected to a heat treatment at 200 ℃ or higher to obtain a composite powder in which sulfur-modified cellulose nanofibers are dispersed in sulfur-modified polyacrylonitrile. The solvent is not particularly limited as long as it is a liquid capable of dissolving the precursor of component a, and when the precursor of component a is polyacrylonitrile, preferable examples thereof include: dimethylformamide, dimethylacetamide, dimethylsulfoxide, an aqueous solution of zinc chloride, an aqueous solution of sodium thiocyanate, and the like.

[ electrode of electric storage device ]

An electrode of the power storage device of the present invention includes at least an electrode material, a binder, and a current collector of the power storage device of the present invention. The electrode of the power storage device of the present invention may contain any component such as a conductive assistant.

In the electrode for a power storage device of the present invention, the composite powder containing the component a and the component B in the electrode material of the present invention is mainly used as an active material. The active material is a material capable of electrochemically absorbing and releasing alkali metal ions.

Specifically, the electrode can be used as an electrode of a battery by adding an appropriate solvent such as N-methyl-pyrrolidone (NMP), water, alcohol, xylene, and toluene to the electrode material, binder, and conductive assistant of the power storage device of the present invention, sufficiently kneading the mixture to obtain an electrode slurry, applying the electrode slurry to the surface of a current collector, drying the electrode slurry, and further performing pressure regulation to form an active material-containing layer on the surface of the current collector.

The current collector is not particularly limited as long as it is a material having electron conductivity and capable of conducting electricity to the negative electrode material held. For example, the following may be used: C. conductive materials such as Ti, Cr, Fe, Mo, Ru, Rh, Ta, W, Os, Ir, Pt, Au, Cu, Ni, Al, etc.; an alloy (for example, stainless steel) containing 2 or more of these conductive substances. From the viewpoint of high electron conductivity, good stability in an electrolytic solution, good oxidation resistance, and good reduction resistance, the current collector is preferably C, Al, Cu, Ni, stainless steel, or the like, and more preferably C, Al and stainless steel.

The shape of the current collector is not particularly limited. For example, a foil-like substrate, a three-dimensional substrate, or the like can be used. Examples of the three-dimensional substrate include metal foams, nets, woven fabrics, non-woven fabrics, and expanded steel sheets. When the three-dimensional base material is used, an electrode having a high capacity density can be obtained even with a binder having insufficient adhesion to the current collector. In addition, the high-rate charge-discharge characteristics were also good.

Even in the case of a foil-shaped current collector, a primer layer is formed on the surface of the current collector in advance, thereby achieving high output. The primer layer may have good adhesion to each of the electrode material layer and the current collector and conductivity. For example, the primer layer can be formed by applying a binder, which is a mixture of a carbon-based conductive aid and a primer binder, to the current collector. The thickness of the primer layer is, for example, 0.1 to 20 μm. As the primer binder, a known binder that can be used for the electrode can be used.

(Binder)

The binder contained in the electrode of the power storage device is not particularly limited as long as it is a binder conventionally used as a binder for an electrode of a power storage device. Examples thereof include: 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, ethylene-vinyl acetate copolymer (EVA), and the like. These may be used alone in 1 kind, or may be used in combination of 2 or more kinds.

Among the above binders, CMC, acrylic resins, alginates, PVA, SBR and the like are preferably used because they are aqueous binders that can use water as a solvent or a dispersion medium. The use of an aqueous binder is preferable because elution of sulfur into the slurry solvent can be suppressed and the high-temperature durability of the electrode can be improved.

In general, when an electrode is composed of an aqueous binder and a hydrophobic electrode material (particularly, an active material or the like), the hydrophobic material is repelled by water to form lumps (for example, lumps, aggregates or the like) and is difficult to disperse, but the composite powder of the present invention has the B component having excellent hydrophilicity supported on, covered with, or exposed to the surface of the a component, and therefore, does not cause a problem of difficult dispersion even when an aqueous binder is used.

The content of the binder is preferably 0.1 mass% or more and 30 mass% or less, and more preferably 0.5 mass% or more and 15 mass% or less, with respect to 100 mass% of the total amount of the composite powder including the component a and the component B and the binder. Outside the above range, it is difficult to obtain stable life characteristics and output characteristics. That is, if the binder amount is small, the adhesion to the current collector is insufficient, and thus it is difficult to obtain stable life characteristics, whereas if it is too large, the electrode resistance becomes high, and the output characteristics are degraded.

(conductive auxiliary agent)

The conductive aid refers to a substance that contributes to conductivity between active materials, and refers to a material that fills or crosslinks between separated active materials to achieve conduction between the active materials or between the active materials and a current collector.

As the conductive aid contained as an arbitrary component in the electrode of the power storage device, a conductive aid conventionally used as a conductive aid for the electrode of the power storage device can be used. For example, carbon materials such as Acetylene Black (AB), Ketjen Black (KB), graphite, carbon fiber, carbon nanotube, graphite, amorphous carbon, and Vapor Grown Carbon Fiber (VGCF) may be mentioned. The conductive assistant may be used alone in 1 kind, or may be used in combination in 2 or more kinds.

Among these, a conductive aid capable of forming a conductive three-dimensional network structure is preferable. Examples of the conductive aid capable of forming a conductive three-dimensional network structure include: flake conductive materials such as flake aluminum powder and flake stainless steel powder; carbon fibers; a carbon nanotube; amorphous carbon, and the like. When a conductive three-dimensional network structure is formed, a sufficient current collecting effect can be obtained, and volume expansion of the electrode during charge and discharge can be effectively suppressed.

The content of the conductive additive is preferably 0 mass% to 20 mass%, more preferably 1 mass% to 10 mass%, relative to 100 mass% of the total amount of the composite powder in which the component B is supported on, covered with, or exposed to the surface of the component a (in other words, the components a and B) and the conductive additive. By setting the above range, not only the output characteristics of the battery are excellent, but also the capacity drop is small. That is, a conductive assistant is contained as necessary.

[ Electrical storage device ]

An electric storage device can be produced using the electrode of the electric storage device of the present invention. The power storage device includes a positive electrode, a negative electrode, and an electrolyte provided between the positive electrode and the negative electrode. The electrode of the present invention can be used as either a positive electrode or a negative electrode of an electric storage device. That is, the electrode of the present invention may be used for either a positive electrode or a negative electrode of an electric storage device, except for the case where the same electrode as the electrode of the present invention is used for both the positive electrode and the negative electrode. When the electrode of the power storage device of the present invention is used as a positive electrode of the power storage device, the power storage device can be manufactured by combining the electrode with an electrode having a lower charge/discharge potential than the electrode of the power storage device of the present invention. On the other hand, when the electrode of the power storage device of the present invention is used as the negative electrode of the power storage device, the power storage device can be manufactured by combining the electrode with an electrode having a higher charge/discharge potential than the electrode of the power storage device of the present invention.

The electrode of the power storage device is preferably doped with alkali metal ions in advance before the power storage device is assembled. Alternatively, it is preferable that the counter electrode of the electricity storage device is doped with alkali metal ions.

The method for doping the alkali metal ion is not particularly limited as long as the alkali metal ion can be doped into the electrode, and examples thereof include: examples of the doping method include (1) electrochemical doping, (2) sticking doping of lithium metal foil, (3) mechanical lithium doping using a high-speed planetary mill, and the like, as described in non-patent documents (published by the institute of technical information, "measurement and analysis data set for lithium secondary battery members", section 30, pp.200 to 205, by sakutayashi et al).

When the electrode of the power storage device of the present invention is used as a positive electrode, the electrode (negative electrode) is not particularly limited as long as it can be used as a negative electrode for the power storage device. Examples thereof include: an electrode comprising: at least one or more elements selected from the group consisting of Li, Na, K, C, Mg, Al, Si, P, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Y, Zr, Nb, Mo, Pd, Ag, Cd, In, Sn, Sb, W, Pb, and Bi; alloys containing these elements; oxides, sulfides and halides of these elements; sulfur-based organic materials such as sulfur-modified compounds of organic compounds; etc. (in other words, a negative electrode material). These materials may be used alone in 1 kind, or 2 or more kinds may be used in combination.

When the electrode of the power storage device of the present invention is used as a negative electrode, the counter electrode (positive electrode) is not particularly limited as long as it can be used as a positive electrode for the power storage device. For example, a composition comprising ACoO may be used₂、ANiO₂、AMnO₂、ANi_0.33Mn_0.33Co_0.33O₂、ANi_0.5Mn_0.3Co_0.2O₂、ANi_0.6Mn_0.2Co_0.2O₂、ANi_0.8Mn_0.1Co_0.1O₂、AMn₂O₄、ANi_0.5Mn_1.5O₄、AFePO₄、AFe_0.5Mn_0.5PO₄、AMnPO₄、ACoPO₄、ANiPO₄、A₃V₂(PO₄)₃、AV₂O₅、AVO₂、ANb₂O₅、ANbO₂、AFeO₂、AMgO₂、ACaO₂、ATiO₂、ACrO₂、ARuO₂、ACuO₂、AZnO₂、AMoO₂、ATaO₂Or AWO₂And the like, alkali metal element-transition metal oxide. These alkali metal element-transition metal oxides may be used alone in 1 kind, or may be used in combination in 2 or more kinds. Here, a represents an alkali metal element, and examples of a include Li, Na, and K. The same applies hereinafter.

The electrolyte used in the battery may be a liquid or a 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 that used in a known power storage device using a nonaqueous electrolyte can be used. Examples thereof include an electrolytic solution, a colloidal electrolyte, a solid electrolyte, an ionic liquid, and a molten salt. Here, the electrolyte solution refers to an electrolyte solution in which an electrolyte is dissolved in a solvent.

The electrolyte is obtained by dissolving a supporting salt in a solvent. The solvent of the electrolyte solution is not particularly limited, and a cyclic carbonate such as Ethylene Carbonate (EC), Propylene Carbonate (PC), and butylene carbonate; ether systems such as tetrahydrofuran; hydrocarbon series such as hexane; and lactone systems such as γ -butyrolactone. Among them, cyclic carbonate-based electrolytes such as EC and PC are preferable from the viewpoint of discharge rate characteristics. As for the discharge rate, a battery cell having a capacity of a nominal capacity value is subjected to constant current discharge, and a current value at which complete discharge is achieved in 1 hour is referred to as "1C rate", and the discharge rate is an index based on this, and for example, a current value at which complete discharge is achieved in 5 hours is referred to as "0.2C rate", and a current value at which complete discharge is achieved in 10 hours is referred to as "0.1C rate". On the other hand, as for the charge rate, a battery cell having a capacity of a nominal capacity value is subjected to constant current discharge, and a current value to be fully charged in 1 hour is referred to as "1C rate", and the charge rate is an index based on this, and for example, a current value to be fully charged in 1 minute is referred to as "60C rate", a current value to be fully charged in 6 minutes is referred to as "10C rate", a current value to be fully charged in 5 hours is referred to as "0.2C rate", and a current value to be fully charged in 10 hours is referred to as "0.1C rate".

Generally, EC is solid at room temperature, and thus cannot function as an electrolyte solution with EC alone. However, a mixed solvent obtained by mixing PC, dimethyl carbonate (DMC), diethyl carbonate (DEC), Ethyl Methyl Carbonate (EMC), or the like can function as an electrolyte solution that can be used at normal temperature.

As such a mixed solvent, EC (ethylene carbonate) -DEC (diethyl 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, and a salt generally used in an electric storage device can be used. For example, APF can be used₆、ABF₄、AClO₄、ATiF₄、AVF₅、AAsF₆、ASbF₆、ACF₃SO₃、A(C₂F₅SO₂)₂N、AB(C₂O₄)₂、AB₁₀Cl₁₀、AB₁₂Cl₁₂、ACF₃COO、A₂S₂O₄、ANO₃、A₂SO₄、APF₃(C₂F₅)₃、AB(C₆F₅)₄And A (CF)₃SO₂)₃C, and the like. In addition, the salt can be used alone, can also be combined with 2 or more.

Among them, alkali metal element-hexafluorophosphoric acid compound (APF) is preferably used₆). By using APF₆As a salt, thereby improving the discharge capacity and cycle life of the positive electrode, and improving the effect of improving the cycle life of the negative electrode. The concentration of the electrolyte (the concentration of the salt in the solvent) is not particularly limited, but is preferably 0.1 to 3mol/L, and more preferably 0.8 to 2 mol/L.

The structure of the power storage device is not particularly limited, and conventional 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 laminated or wound so as to face each other with a separator interposed therebetween is sealed in a state of being immersed in an electrolyte solution, and thus the electric storage device is obtained. Alternatively, an electrode group in which a positive electrode and a negative electrode are stacked or wound in a face-to-face manner with a solid electrolyte interposed therebetween is sealed to form a power storage device.

[ Electrical Equipment ]

An electric device (particularly, a lithium ion battery or a lithium ion capacitor) using the electrode material of the electric storage device of the present invention has a high capacity and a high output, and therefore, can be used as, for example: air conditioner, washing machine, television, refrigerator, freezer, air conditioner, notebook computer, tablet computer, smartphone, computer keyboard, computer monitor, desktop computer, CRT monitor, computer rack, printer, all-in-one computer, mouse, hard disk, computer peripheral, iron, clothes dryer, window sash, radio transceiver, blower, ventilator, television, music recorder, music player, oven, toilet seat with cleaning function, warm air heater, car audio equipment, car navigator, flashlight, humidifier, portable karaoke machine, ventilator, dryer, air purifier, mobile phone, emergency light, game machine, sphygmomanometer, coffee grinder, coffee maker, quilt maker, copier, disc changer, radio, razor, juice extractor, paper shredder, water purifier, lighting fixture, dehumidifier, air conditioner, dryer, air conditioner, humidifier, air conditioner, humidifier, air conditioner, Tableware dryer, cooker, stereo, stove, speaker, trousers ironing machine, dust collector, body fat meter, body weight meter, health scale, movie player, electric blanket, electric pot, tableware, electric shaver, table lamp, electric pan, electronic game machine, portable game machine, electronic dictionary, electronic notebook, microwave oven, electromagnetic oven, calculator, electric cart, electric chair, electric tool, electric toothbrush, anchor member, hair clipper, telephone, clock, interphone, air circulator, electric shock insect killer, photocopier, electric hot plate, bread roaster, dryer, electric drill, water heater, panel heater, crusher, soldering iron, video camera, video recorder, facsimile machine, warm air blower, food processor, bedding dryer, earphone, electric kettle, hot blanket, microphone, massager, small bulb, mixer, sewing machine, yam pounding machine, electric heating device, electric heater, microphone, massage machine, small bulb, electric heating device, electric, A power source for various electric devices such as a floor heating panel, a lantern, a remote controller, a refrigerator, a water cooler, a freezer, a fan cooler, a word processor, a bubbler, a GPS, an electronic musical instrument, a motorcycle, a toy, a lawn mower, a swim ring, a bicycle, a motorcycle, an automobile, a hybrid automobile, a plug-in hybrid automobile, an electric automobile, a rail, a ship, an airplane, a submarine, an aircraft, a satellite, and an emergency power supply system.

Examples

The following examples are given by way of illustration and not by way of limitation. Although the electrode of the present invention is an electrode of an electric storage device, in the present example, a lithium ion battery was produced and tested as described below. A lithium ion capacitor is manufactured in the same manner as a lithium ion battery except that the operation of the electrode is mainly different. Specifically, for example, the battery can be manufactured in the same manner as the battery described later, except that the conventional positive electrode for a lithium ion capacitor is used as the positive electrode and the electrode of the present invention is used as the negative electrode. An alkali metal ion battery other than a lithium ion battery can be produced in the same manner as the lithium ion battery except that Li, which is a charge carrier of the lithium ion battery, is mainly replaced with Na and K. Specifically, for example, a sodium ion battery can be manufactured in the same manner as a battery described later, except that a conventional positive electrode for a sodium ion battery is used as a positive electrode, an electrode of the present invention is used as a negative electrode, and a sodium supporting salt is used as an electrolytic solution. The same applies to other alkali metal ions.

In the case of using the electrode of the present invention as an electrode of a lithium ion capacitor, as a counter electrode thereof, for example, an electrode manufactured by coating a slurry containing activated carbon, a binder and a conductive assistant onto an aluminum foil and performing heat treatment can be used.

The activated carbon of the lithium ion capacitor is preferably a carbon material having numerous fine pores and a large specific surface area. A typical method for producing activated carbon is to heat a carbon material such as petroleum coke and an alkali metal compound such as potassium hydroxide at 600 to 1500 ℃ in a non-oxygen atmosphere, and to cause the alkali metal to enter between graphite crystal layers to react and activate the graphite crystal layers. The median diameter (D50) of the activated carbon particles is preferably 0.5 to 30 μm.

Comparative example 1

(1) Synthesis of electrode materials

Mixing sulfur and polyacrylonitrile in a ratio of sulfur: polyacrylonitrile 1: 5, and heating the resulting mixture at 350 ℃ for 5 hours. After the heating, the mixture was pulverized by a mill and classified by a 325 mesh (45 μm pore size) sieve. After the classification, the resultant was heated at 300 ℃ for 5 hours under a nitrogen atmosphere to conduct desulfurization treatment, thereby obtaining a powder of a sulfur-modified compound (S-PAN). The median diameter (D50) of the powder obtained was 36.3 μm. This value is obtained from the data shown in fig. 3 described later.

(evaluation of dispersibility in Water)

The obtained powder was put into a glass bottle to which water was added in an amount of 100 times the mass of the powder, and the bottle was closed with a cap and shaken for about 1 minute. Fig. 2 shows the photograph immediately after the vibration, and the results are shown in table 1.

(volume-based particle size distribution)

The obtained powder was measured for volume-based particle size distribution by laser diffraction scattering using water as a dispersion medium. The measurement apparatus used was LA-960 (manufactured by HORIBA). The measurement was carried out using lasers with wavelengths of 650nm and 405 nm. The results are shown in FIG. 3.

(2) Fabrication of test electrodes

The obtained powder of the sulfur-modified compound, Acetylene Black (AB), Vapor Grown Carbon Fiber (VGCF), and acrylic resin binder were modified with a powder of the sulfur-modified compound: acetylene Black (AB): vapor Grown Carbon Fiber (VGCF): acrylic resin binder 82: 3: 8: the resulting mixture was sufficiently dispersed in water at a ratio of 7% by mass, and kneaded by a rotation and revolution mixer (2000rpm, 40 minutes) to form a slurry (solid content ratio: 35%). The resulting slurry was coated on an aluminum foil having a thickness of 20 μm as a current collector, and subjected to a reduced-pressure drying treatment at 160 ℃ for 12 hours, thereby obtaining a test electrode. Using sulfur-modifying compoundsPowder as active substance. The obtained test electrode was used as a positive electrode as described below, and the positive electrode capacity per unit area of one surface of the positive electrode was 1mAh/cm²The amount of the slurry to be applied is adjusted.

(3) Manufacture of batteries

A battery using the obtained test electrode as a positive electrode was produced, and a charge/discharge test a was performed. The details are as follows. For the charge and discharge test, a CR2032 coin cell was produced, which had: the resulting test electrode as the positive electrode; a GLASS FILTER (GA-100 GLASS FIBER FILTER, manufactured by ADVANTEC); metallic lithium as a negative electrode; and 1M LiPF as an electrolyte₆(ethylene carbonate (EC): diethyl carbonate (DEC): 50 vol% solution).

(Charge and discharge test A)

The obtained battery was subjected to a charge-discharge test. The conditions for the charge/discharge test A are set to an ambient temperature of 30 ℃ and a cut-off potential of 1.0 to 3.0V (vs. Li/Li)⁺) And the charge-discharge current rate is 0.2C rate. The charge and discharge curves are shown in fig. 4. From this, the cycle life characteristics of the electrode were known. The results of the discharge capacity are shown in table 1.

(Charge and discharge test B)

The obtained battery was subjected to a charge-discharge test. The conditions for the charge/discharge test B were set to an ambient temperature of 30 ℃ and a cut-off potential of 1.0 to 3.0V (vs. Li/Li)⁺) And the charge-discharge current rate is 0.2C rate. The cycle life characteristics of the electrode were evaluated by obtaining the ratio of the discharge capacity (mAh/g) to the "first discharge capacity (mAh/g)" after 100 cycles of repeated charging and discharging as "capacity retention (%)". The results are shown in Table 2. Evaluation criteria for cycle life characteristics are as follows. The discharge capacity retention ratio was not less than 90%, and found to be good, and 90% or less was not more than x.

(high temperature standing test)

A laminated battery using the obtained test electrode was produced, and the laminated battery was subjected to a high-temperature standing test. The details are as follows. A laminate battery is produced, which is provided with: the resulting test electrode as the positive electrode; a polypropylene microporous membrane (thickness 20 μm) as a spacer; electrochemical elimination as negative electrodeSiO with irreversible capacity is obtained; and 1M LiPF as an electrolyte₆(ethylene carbonate (EC): diethyl carbonate (DEC) ═ 50: 50 vol%). The laminate battery thus produced was charged to 3.0V at a rate of 0.1C and then left to stand at 60 ℃ for 1 week. The results are shown in Table 1.

[ reference example 1]

A battery was produced and a charge and discharge test a was performed in the same manner as in comparative example 1, except that the sulfur-modified cellulose nanofiber powder obtained by the following method was used as the powder of the sulfur-modified compound. The results are shown in Table 1.

CeNF (product name: Rheorysta I-2SX, manufactured by first Industrial pharmaceutical Co., Ltd.) and sulfur were mixed to prepare a mixture of CeNF: 1 of sulfur: 5, heating the mixture at 350 ℃ for 5 hours, crushing the mixture, and classifying the crushed mixture by using a sieve with 325 meshes (the aperture is 45 mu m) to obtain sulfur modified cellulose nano fiber powder.

[ example 1]

A battery was produced in the same manner as in comparative example 1, except that the composite powder obtained by the following method was used as the powder of the sulfur-modified compound. The dispersibility of the composite powder obtained in the step before the production of the battery into water was evaluated, and a charge/discharge test a of the battery was performed, and a high-temperature standing test was performed using an electrode. 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 nanofibers (CeNF (product name: rheochrysta I-2SX, manufactured by first industrial pharmaceutical company)) and sulfur were mixed in the following ratio: cellulose nanofibers (CeNF): sulfur 94: 1: 5, and heating the resulting mixture at 350 ℃ for 5 hours. After the heating, the mixture was pulverized by a mill and classified by a 325 mesh (45 μm pore size) sieve to obtain a composite powder (S-CeNF + S-PAN) in which the surface of the sulfur-modified polyacrylonitrile powder is supported or coated with sulfur-modified cellulose. The median diameter (D50) of the powder obtained was 14.2. mu.m. This value was obtained from the data shown in fig. 3.

[ Table 1]

[ example 2]

A battery was produced in the same manner as in comparative example 1, except that the composite powder obtained by the following method was used as the powder of the sulfur-modified compound. The composite powder obtained in the step before the battery was manufactured was subjected to "dispersibility evaluation into water", a "charge and discharge test B" for the battery, and a "high temperature standing test" using an electrode. The results are shown in Table 2.

Polyacrylonitrile, sodium carboxymethyl cellulose (CMC-Na (product name: CELLOGEN 7A, manufactured by seiki industrial pharmaceutical corporation)) as cellulose material B1, and sulfur were mixed in the following ratio: b1: sulfur 99: 1: 20, and heating the resulting mixture at 350 ℃ for 5 hours. After the heating, the mixture was pulverized by a mill and classified by a 325 mesh (45 μm pore diameter) sieve, and a composite powder (S-PAN + S-Cel) in which the sulfur-modified cellulose was supported on, covered with, or exposed to the surface of the sulfur-modified polyacrylonitrile powder was obtained.

[ example 3]

In place of cellulose material B1, Na salt of TEMPO oxidized cellulose nanofibers (product name: Rheocrysta I-2SX, manufactured by first Industrial Co., Ltd.) was used as cellulose material B2, B2 was mixed with polyacrylonitrile, and the resulting powder was dried with sulfur as a powder: sulfur-100 (where polyacrylonitrile is 99, B2 is 1): a composite powder having sulfur-modified cellulose supported on, covered with, or exposed to the surface of the sulfur-modified polyacrylonitrile powder was obtained in the same manner as in example 2 except that the components were mixed at a mass ratio of 20. The composite powder obtained in the step before the battery was manufactured was subjected to "evaluation of dispersibility in water", a "charge and discharge test B" for the battery, and a "high temperature standing test" using an electrode. The results are shown in Table 2.

[ example 4]

A composite powder having sulfur-modified cellulose supported on, covered with, or exposed to the surface of sulfur-modified polyacrylonitrile powder was obtained in the same manner as in example 3, except that the sulfonic acid-modified cellulose nanofiber Na salt of synthesis example 1 below was used as the cellulose material B3 instead of the cellulose material B2. The composite powder obtained in the step before the battery was manufactured was subjected to "evaluation of dispersibility in water", a "charge and discharge test B" for the battery, and a "high temperature standing test" using an electrode. The results are shown in Table 2.

(Synthesis example 1)

In a separable flask made of glass, 10g of microcrystalline cellulose having an average particle diameter of 45 μm ("KC Flock W-50" manufactured by Nippon paper-making Co., Ltd.) was suspended in 200mL of distilled water. The separable flask was placed in an ice bath, and concentrated sulfuric acid was slowly added to the system while maintaining the temperature of the system at 40 ℃ or lower with stirring until the final concentration of sulfuric acid reached 48 mass%. Subsequently, the suspension was transferred to a water bath at 60 ℃ and stirred for 30 minutes, and then the crude product was taken out and centrifuged at 8000rpm for 10 minutes. The residual sulfuric acid was removed by this centrifugal separation operation, and the operation of resuspending the residue in distilled water and centrifuging and then adding distilled water again was repeated for 5 times of washing and resuspension. The residue obtained in this operation was suspended in distilled water, and after adjusting the pH to 8 with sodium hydroxide, the solid content concentration was adjusted to 5 mass%. Then, the obtained cellulose suspension is treated for 1 time by a high-pressure homogenizer under the pressure of 140MPa to obtain the sulfonic acid modified cellulose nano-fiber sodium salt.

Comparative example 2

A composite powder was obtained in the same manner as in example 3, except that a tetrabutylammonium salt of cellulose nanofibers (manufactured by first industrial pharmaceutical company) was oxidized by TEMPO as cellulose material B4 instead of cellulose material B2. The composite powder obtained in the step before the battery was manufactured was subjected to "evaluation of dispersibility in water", a "charge and discharge test B" for the battery, and a "high temperature standing test" using an 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 bleached softwood pulp (NBKP) was used as the cellulose material B5 in place of the cellulose material B1. The composite powder obtained in the step before the battery was manufactured was subjected to "evaluation of dispersibility in water", a "charge and discharge test B" for the battery, and a "high temperature standing test" using an electrode. The results are shown in Table 2.

[ Table 2]

As is apparent from fig. 2 and 3, example 1 (fig. 2(b)) exhibits superior water dispersibility to comparative example 1 (fig. 2 (a)). The powder of comparative example 1 had a narrow peak at a larger particle size value and the powder of example 1 had a broad peak at a smaller particle size value than the powder of example 1, and thus it was found that the powder of example 1 was sufficiently dispersed in water. As is apparent from table 1, the electrode of comparative example 1 reduced the discharge capacity by about 4.9% from 674mAh/g at 1 cycle to 641mAh/g at 100 cycle, while the electrode of example 1 reduced the discharge capacity by about 4.9% from 652mAh/g at 1 cycle to 620mAh/g at 100 cycle, and exhibited the reversible capacity and cycle life characteristics comparable to those of the electrode of comparative example 1. The electrode of reference example 1 exhibited a discharge capacity reduced by about 19% from 353mAh/g at 1 cycle to 287mAh/g at 100 cycles, and although having a certain degree of excellent cycle life characteristics, exhibited a particularly small electric capacity as compared with the capacity exceeding 600mAh/g of example 1 and comparative example 1. In the batteries using the electrodes of example 1 and comparative example 1, no significant change was observed visually, and swelling of the batteries due to gas generation was not observed.

The samples of the examples all showed good dispersibility as shown in fig. 2(b), but many of the powders of the samples of the comparative examples were aggregated and settled as shown in fig. 2(a), and no dispersibility was observed. As is apparent from tables 1 and 2 and fig. 2, the examples show excellent water dispersibility as compared with the comparative examples.

As is apparent from table 2, the electrodes of the examples exhibited the same degree of first discharge capacity and cycle life characteristics as those of comparative example 1, and demonstrated both water dispersibility and excellent discharge performance. On the other hand, in comparative examples 2 and 3, the results showed that the water dispersibility, cycle performance and life characteristics were poor although good first discharge capacity was exhibited. In the batteries using the electrodes of examples and comparative examples, no significant change was observed visually, and swelling of the batteries due to gas generation was not observed.

(evaluation of surface functional group)

Mixing cellulosic material B1 and sulfur in a ratio of B1: 1 of sulfur: 5, and heating the resulting mixture at 350 ℃ for 5 hours. After the flow rate was increased, the mixture was pulverized and classified by a 325-mesh sieve (having a pore size of 45 μm) to obtain a sulfur-modified cellulose powder B' 1. For the sulfur-modified cellulose powder B'1, IR measurement was performed by the mini-tablet method using KBr. The results are shown in FIG. 6.

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

As is apparent from FIGS. 6 to 9, the sulfur-modified cellulose powders B '1 and B'2 derived from cellulose materials used in the examples were 600 to 700cm in the IR spectrum evaluation^-1The vicinity has characteristic absorption, SO to speak, SO exists₃And (4) a base. On the other hand, the sulfur-modified cellulose powders B '4 and B'5 derived from cellulose material used in the comparative examples were 600 to 700cm^-1Has no characteristic absorption, namely no SO₃And (4) a base.

In addition, as shown in Table 2, it was found that SO was not contained₃The sulfur-modified cellulose having at least SO is used as the functional group₃Examples of the sulfur-modified cellulose having a functional group are excellent in dispersibility without deteriorating the electrode characteristics. In addition, the thickness is 600-700 cm^-1Since the characteristic absorption in the vicinity is well correlated with the hydrophilicity, it can be said that SO having the characteristic absorption in this range₃The presence of the radical is responsible for the excellent dispersibility.