JP2014075561A - Composite of manganese compound and carbon raw material, electrode material using the composite, and method for manufacturing them - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a composite of a manganese compound and carbon, with which an electrode and electrochemical element achieving output characteristics and high energy density can be obtained; and a method for producing the composite.SOLUTION: In a method for producing an electrode material, a manganese compound and a carbon raw material are compounded. The method includes: a pH adjustment step of adjusting a pH of a solution containing one material source of the manganese compound; and a compounding step of performing compounding treatment in which the carbon raw material and the material source of the manganese compound containing the material source of the manganese compound subjected to the pH adjustment are mixed to produce a composite of carbon and the manganese compound. In an electrode using the composite, heightened input/output and increased capacity can be achieved. Such the electrode has characteristics causing no reduction in capacity even after discharge cycles.

Description

  The present invention relates to a composite of a manganese compound and a carbon material, an electrode using the composite, and a method for producing them.

  At present, carbon materials that store and release lithium are used as electrodes of lithium batteries, but there is a risk of decomposition of the electrolyte because the negative potential is smaller than the reductive decomposition potential of hydrogen. Thus, as described in Patent Document 1 and Patent Document 2, the use of lithium titanate having a negative potential larger than the reductive decomposition potential of hydrogen has been studied. However, lithium titanate has a problem that output characteristics are low. . Therefore, there is an attempt to improve output characteristics by using an electrode in which lithium titanate is made into nanoparticles and supported on carbon.

JP 2007-160151 A JP 2008-270795 A

  The inventions described in these patent documents are dispersed and supported on carbon by a method (generally called mechanochemical reaction) that promotes a chemical reaction by applying shear stress and centrifugal force to a reactant in a rotating reactor. Lithium titanate is obtained. In this case, for example, titanium alkoxide and lithium acetate, which are starting materials for lithium titanate, and carbon such as carbon nanotubes and ketjen black are used as reactants.

  Electrodes using carbon carrying lithium titanate nanoparticles described in these patent documents exhibit excellent output characteristics, but recently, in this type of electrode, the output characteristics have been further improved and the electric conductivity has been improved. There is a demand to improve. Moreover, it is also desired to use a manganese compound capable of occluding lithium, which is easier to obtain, instead of lithium titanate.

  As a manganese compound capable of occluding lithium, it is necessary to produce a highly pure manganese compound when a manganese compound and a carbon material are combined. Currently, various methods have been proposed as a method for combining a manganese compound and a carbon material. However, it is difficult to produce a complex of a high-purity, high-purity manganese compound and a carbon material. Manganese compounds with different valences are easily produced during the production, and a high-purity manganese compound is produced. That was difficult.

  The present invention has been proposed in order to solve the above-mentioned problems of the prior art, and the object thereof is to use a complex of a high purity manganese compound and a carbon material, or using this complex. An object of the present invention is to provide a method for producing an electrode material that achieves output characteristics and high energy density. Another object of the present invention is to provide the composite and electrode material.

In order to achieve the above object, the present invention is a method for producing an electrode material in which a manganese compound and a carbon material are combined, and includes the following steps.
(1) A pH adjustment step for adjusting the pH of a solution in which one of the material sources of the manganese compound is dissolved.
(2) A compounding step of mixing a carbon material and a manganese compound material source including a manganese compound material source whose pH has been adjusted, and performing a compounding process for generating a complex of the manganese compound and the carbon material. .

  In the compounding step, it is possible to further include a heating step of heating the complex.

  In the pH adjustment step, a solution containing one of the material sources of the manganese compound may be adjusted to pH 3-5.

  In the pH adjustment step, a solution containing one of the material sources of the manganese compound may be adjusted to pH 11.5-14.

  The process of compounding the manganese compound and the carbon material is a process in which a mechanochemical reaction is performed by applying shear stress and centrifugal force to a solution containing the carbon material and the metal compound material in a rotating reaction vessel. A so-called UC process may be used.

The step method for producing a composite body and having the above-described, the method for their preparation, in a complex and electrode material complexed manganese compound and carbon material, the manganese compound is alpha-MnO ₂ or birnessite Is also an embodiment of the present invention.

  According to the present invention, when a manganese compound and a carbon material are combined, a high-purity manganese compound composite can be formed, and an electrode using the composite realizes a large capacity and high input / output. be able to.

It is a flowchart which shows the manufacturing process of the composite_body | complex of the manganese compound and carbon material which concern on this embodiment. It is a block diagram which shows the apparatus for UC processing. It is a schematic view illustrating the structure of the α-MnO _2. It is a schematic diagram showing the structure of a benesite. It is a flowchart which shows the manufacturing process of the composite_body | complex of the manganese compound which concerns on a 1st implementation characteristic, and a carbon raw material. It is the figure showing the thermal characteristic and carbon ratio by TG-DTA (differential heat-thermogravimetric simultaneous measurement) with respect to the composite_body | complex of a 1st implementation characteristic. It is a TEM image of the crystal structure of the composite of the 1st implementation characteristic. It is a TEM image of the crystal structure of the composite of the 1st implementation characteristic. It is the graph showing the result of the crystal structure analysis by XRD (X-ray powder diffraction method) performed with respect to the composite_body | complex of the Example of 1st implementation characteristic. It is the figure showing the discharge cycle characteristic performed with respect to the composite_body | complex of the Example of a 1st implementation characteristic. It is a flowchart which shows the manufacturing process of the composite_body | complex of the manganese compound which concerns on 2nd implementation characteristic, and a carbon raw material. It is a TEM image of the crystal structure of the composite of a 2nd implementation characteristic. It is a TEM image of the crystal structure of the composite of a 2nd implementation characteristic. It is a graph showing the result of the crystal structure analysis by XRD (X-ray powder diffraction method) performed with respect to the composite_body | complex of a 2nd implementation characteristic. It is a figure showing the discharge cycle characteristic performed with respect to the composite_body | complex of the Example of a 2nd implementation characteristic.

  Hereinafter, embodiments for carrying out the present invention will be described. In addition, this invention is not limited to embodiment described below.

(1) Composite and electrode material using the composite The electrode material according to the present invention is a composite in which a manganese compound is supported on a carbon material as a conductive additive, both of which are nanoparticles consistently in the manufacturing process. Is maintained. A nanoparticle refers to a secondary particle and is an aggregate of primary particles. Nanoparticles mean that the aggregate has a maximum diameter of 10 nm or less in a lump such as a circle, ellipse or polygon, and a fiber diameter of 10 nm or less in a fiber.

  This composite is obtained as a powder, and becomes an electrode for storing electrical energy by kneading the composite powder with a binder and molding it. This electrode can be used for an electrochemical capacitor or a battery using an electrolytic solution containing lithium. That is, the electrode made of this secondary battery electrode material can occlude and desorb lithium ions, and operates as a positive electrode.

  Carbon materials are carbon nanotubes with fiber structure, carbon black with hollow shell structure such as Ketjen black, acetylene black, etc., amorphous carbon, carbon fiber, natural graphite, artificial graphite, activated carbon, mesoporous carbon Alternatively, a plurality of types can be mixed and used. The carbon nanotube may be either a single wall carbon nanotube (SWCNT) or a multi-wall carbon nanotube (MWCNT).

(Manganese compounds)
The manganese compound according to the present invention is a manganese compound capable of generating a polymer capable of inserting and extracting lithium (Li) around it. As this manganese compound, a highly pure tetravalent manganese compound is preferable. As an example of the tetravalent manganese compound, α-MnO ₂ , banesite, and the like can be given. The tetravalent manganese compound used in this example is obtained by reacting a manganese compound having a valence of manganese of 2 ≦ x <4 and a manganese compound having 4 <x ≦ 7.

A manganese compound having a valence of manganese of 2 ≦ x <4 is used as a starting material. Specifically, the following divalent manganese compounds can be used as manganese compounds having a valence of manganese of 2 ≦ x <4.
Manganese acetate: Mn (CH ₃ CO ₂ ) ₂
Manganese acetate tetrahydrate Mn (OAc) ₂・ 4H ₂ O
Manganese formate: Mn (COO) ₂
Manganese oxalate: MnC ₂ O ₄
Manganese tartrate: MnC ₄ H ₄ O ₆
Manganese oleate: Mn (C ₁₇ H ₃₃ COO) ₂
Manganese chloride: MnCl ₂
Manganese bromide: MnBr ₂
Manganese fluoride: MnF ₂
Manganese iodide: MnI ₂
Manganese hydroxide: Mn (OH) ₂
Manganese sulfide: MnS
Manganese carbonate: MnCO ₃
Manganese perchlorate: Mn (ClO ₄ ) ₂
Manganese sulfate: MnSO ₄
Manganese nitrate: Mn (NO ₃ ) ₂
Manganese phosphate: Mn ₃ (PO ₄ ) ₂ , MnHPO ₄ , Mn (H ₂ PO ₄ ) ₂
Manganese diphosphate: Mn ₂ P ₂ O ₇
Manganese hypophosphite: H ₄ MnO ₄ P ₂
Manganese metaphosphate: Mn (PO ₃ ) ₂
Manganese arsenate: Mannese arsenate: Mn ₃ (AsO ₄ ) ₂
Manganese borate Manganese borate: MnB ₄ O ₇

Moreover, the following trivalent manganese compounds can be used as the manganese compound having a valence of manganese of 2 ≦ x <4.
Manganese acetate: Mn (CH ₃ CO ₂ ) ₃
Manganese formate: Mn (COO) ₃
Manganese fluoride: MnF ₃
Manganese hydroxide: MnO (OH)
Manganese sulfate: Mn ₂ (SO ₄ ) ₃
Manganese phosphate: MnPO ₄
Manganese diphosphate: Mn ₄ (P ₂ O ₇ ) ₃
Manganese arsenate: MnAsO ₄
Manganese acetylacetonate: Mn (CH ₃ COCHCOCH ₃ ) ₃

On the other hand, the following 7-valent manganese compounds can be used as manganese compounds having a valence of manganese of 4 <x ≦ 7.
Potassium permanganate: KMnO ₄
Sodium permanganate: NaMnO ₄
Lithium permanganate: LiMnO ₄
Magnesium permanganate: Mg (MnO ₄ ) ₂
Calcium permanganate: Ca (MnO ₄ ) ₂

(2) Manufacturing method An example of the manufacturing process of the composite of a manganese compound and a carbon raw material is shown in FIG. As shown in FIG. 1, the following steps are provided.
(1) A pH adjusting step for adjusting the pH of a solution in which the material source of the manganese compound and the carbon material are dissolved.
(2) A compounding process in which a manganese compound and a carbon material are compounded to produce a complex of the manganese compound and the carbon material.
(3) A heating process in which heat treatment is performed on the composite obtained by the composite process.

  The complex of the manganese compound and the carbon material according to the present invention adjusts the pH of the solution in which the material source of the manganese compound and the carbon material are dissolved before the complex is formed. Thereafter, a composite treatment of the material source of the manganese compound and the carbon material is performed. Furthermore, in order to prevent aggregation of the composite and improve the performance of the electrode using the composite, the composite may be subjected to heat treatment.

(1) pH adjustment step In the pH adjustment step, the pH of the solution in which the material source of the manganese compound and the carbon material are dissolved is adjusted. The pH is adjusted by the following method.
(a) The amount of the material source of the manganese compound dissolved in the solution is adjusted.
(b) NaOH, KOH, and LiOH are added to the solution in which the material source of the manganese compound is dissolved.

In the case of (a), the amount of the material source of the manganese compound dissolved in the solution is adjusted so that impurities of the manganese compound are not generated during the composite treatment. When the produced manganese compound is α-MnO ₂ , the pH of the solution is adjusted to pH 3-5. When the range of pH adjusting is outside this range, α-MnO ₂ except manganese compound becomes to be produced, α-MnO ₂ of high purity can not be generated.

In order to adjust the pH of the solution to pH 3 to 5, the ratio of the manganese compound having a valence of 2 ≦ x <4 dissolved in the solution and the manganese compound having a valence of manganese of 4 <x ≦ 7 is adjusted. Can be done. As an example, Mn (OOCCH ₃ ) ₂ · 4H ₂ O is used as a manganese compound with a valence of manganese of 2 ≦ x <4, and KMnO ₄ is used as a manganese compound with a valence of manganese of 4 <x ≦ 7. The ratio is 3: 2 at the mol rate.

In the case of (b), the pH is adjusted by adding NaOH, KOH, and LiOH to the solution in which the material source of the manganese compound is dissolved. When the produced manganese compound is birnessite, the pH of the solution is adjusted to pH 11.5-14. When the pH range to be adjusted is outside this range, manganese compounds other than banesite are produced, and α-MnO ₂ with high purity is not produced.

  In order to adjust the pH of the solution for generating banesite to pH 11.5 to 14, adjustment of pH of a solution in which a manganese compound having a valence of manganese of 2 ≦ x <4 is dissolved or a solution in which carbon is mixed with the solution By doing so, the pH of the solution for performing the complexing treatment may be set to the target pH. Further, by adjusting the pH of a solution in which a manganese compound having a valence of manganese of 4 <x ≦ 7 or a solution obtained by mixing carbon in the solution is adjusted, the pH of the solution for performing the complexing treatment is adjusted to the target pH. Anyway.

(2) Compounding step In the compounding step, the manganese compound material source and the carbon material are mixed, and the manganese compound is generated on the carbon material while making the carbon material into nanoparticles.

  A mixed solution is prepared by mixing a material source of a manganese compound and a carbon material in a solvent. As the solvent, alcohol such as IPA (isopropyl alcohol) or water is used. This mixed solution is subjected to ultracentrifugal force processing (hereinafter referred to as UC treatment).

  By the UC treatment, the carbon material is converted into nanoparticles. In addition, by performing UC treatment on a manganese compound material source having a manganese valence of 2 ≦ x <4 and a manganese compound material source having a manganese valence of 4 <x ≦ 7. Then, a manganese compound having a valence of manganese of 4 is formed on the nanoparticulated carbon.

  Here, the UC treatment applies shear stress and centrifugal force to the material source of the manganese compound generated on the carbon material. For example, it can be carried out using the reaction vessel shown in FIG.

  As shown in FIG. 2, the reaction vessel includes an outer cylinder 1 having a cough plate 1-2 at an opening, and an inner cylinder 2 having a through hole 2-1 and turning. By putting the reactant into the inner cylinder 2 of this reactor and turning the inner cylinder 2, the reactant inside the inner cylinder 2 passes through the through-hole 2-1 of the inner cylinder by the centrifugal force, and the inner wall of the outer cylinder Move to the 1-3 side. At this time, the reaction product collides with the inner wall 1-3 of the outer cylinder by the centrifugal force of the inner cylinder 2, and forms a thin film and slides up to the upper part of the inner wall 1-3. In this state, both the shear stress between the inner wall 1-3 and the centrifugal force from the inner cylinder are simultaneously applied to the reactant, and a large mechanical energy is applied to the thin-film reactant. This mechanical energy seems to be converted into chemical energy required for the reaction, so-called activation energy, but the reaction proceeds in a short time.

In this reaction, if the reactant is a thin film, the mechanical energy applied to the reactant is large, so the thickness of the thin film is 5 mm or less, preferably 2.5 mm or less, more preferably 1.0 mm or less. . The thickness of the thin film can be set according to the width of the dam plate and the amount of the reaction solution. For example, the centrifugal force required to produce this thin film is 1500 n (kgms ⁻² ) or more, preferably 60000 n (kgms ⁻² ) or more, more preferably 270000 n (kgms ⁻² ) or more.

(3) Heating step In the heating step, the composite obtained in the compounding step is heated. In the present embodiment, aggregation of the manganese compound can be prevented by heating the composite that has undergone the composite process. That is, in the heating process of the composite obtained by the UC treatment, heating is performed in a temperature range of 100 ° C. to 200 ° C. in a vacuum. By heating within this range, aggregation of the manganese compound can be prevented. When the temperature during the heat treatment is 100 ° C. or less, amorphous manganese oxide is formed and aggregation easily occurs. When the temperature during the heat treatment exceeds 200 ° C., the particles are aggregated. proceed.

  In addition, when a composite of a manganese compound having a tunnel structure and a carbon material is obtained by the composite process, the composite is promoted to form a tunnel structure of the manganese compound by heating the composite in vacuum. Improve the capacity and output characteristics of electrodes and electrochemical devices using The heating in this case is also performed in a vacuum, and a temperature range of 100 ° C. to 200 ° C. is suitable. When the temperature during the heat treatment is 100 ° C. or lower, amorphous manganese oxide is formed, and tunnel structure manganese oxide is not generated. Moreover, when the temperature at the time of heat treatment exceeds 200 ° C., the aggregation of particles proceeds, the diameter of the tunnel structure increases, the tunnel structure collapses, and the charge / discharge capacity decreases.

(3) Features of the product The manganese compound produced by this production method is a tetravalent manganese compound. Examples of the tetravalent manganese compound include α-MnO ₂ , RyMnO ₂ .xH ₂ O (Burnesite), and the like.

FIG. 3 is a schematic diagram showing the structure of α-MnO ₂ . α-MnO ₂ is a tetravalent manganese compound, and is a manganese compound having a 2 × 2 tunnel structure as shown in FIG. The theoretical capacity of α-MnO ₂ is 1333 mAhg ⁻¹ . Since it is also a structure having a 2 × 2 tunnel structure, it can be used as an ion sieve. Α-MnO ₂ produced in the present embodiment is a needle-like crystal having a few hundred nm.

  FIG. 4 is a schematic diagram showing the structure of banesite. Banesite is a tetravalent manganese compound, and as shown in FIG. 4, it is a manganese compound having a 2 × ∞ structure. The birnessite produced in this embodiment is a needle-like crystal of several hundred nm.

  In the electrode using the composite of the tetravalent manganese compound and the carbon material, the electrolyte solution around the electrode becomes a polymer and is stabilized by the discharge in the first cycle to form a polymer layer. In the second and subsequent cycles of charge and discharge, the polymer layer causes a redox reaction while maintaining the polymer layer stabilized in the first cycle. A part of this polymer layer undergoes a reversible reaction during charge / discharge, but is generally stabilized. That is, after the polymer layer is stabilized through a charge / discharge cycle, the growth is suppressed and a certain shape is maintained.

(4) Action The phenomenon mainly contributing to the invention of the present application generated by this manufacturing method is considered as follows.
In the present invention, by adjusting the pH of one of the material sources of the manganese compound, a highly pure manganese compound can be produced on the nanonized carbon. Conventionally, since the pH of the material source of the manganese compound was not adjusted, MnOx having various compositions was generated. It is unclear whether MnOx contributes to capacity development for each composition.

  Therefore, by adjusting the pH of one of the material sources of the manganese compound, MnOx having a composition that can achieve high input / output and high capacity can be generated with high purity. By compounding a manganese compound of this composition and a carbon material, a battery or a capacitor using the composite as an electrode material for a secondary battery can achieve higher input / output and higher capacity. .

  Hereinafter, the present invention will be described more specifically with reference to examples.

[1. First characteristic comparison]
In Example 1, manganese acetate tetrahydrate (Mn (OOCCH ₃ ) ₂ · 4H ₂ O) was used as a manganese compound having a valence of manganese of 2 ≦ x <4 as shown in FIG. The pH of the solution in which the compound was dissolved was adjusted. Further, potassium permanganate (KMnO ₄ ) was used as a manganese compound having a valence of manganese of 4 <x ≦ 7.

The composites of Example 1 and Comparative Example 1 were synthesized as follows.
(1) Mn (OOCCH ₃₎ with respect to ₂ · 4H _{2 O1.268g,} distilled water 30mL added Mn (OOCCH ₃₎ to create a ₂ · 4H ₂ O solution.
(2) Add KB to the Mn (OOCCH ₃ ) ₂ · 4H ₂ O aqueous solution whose pH has been adjusted and mix.
(3) On the other hand, with respect to KMnO ₄ 0.5453g, distilled water 30mL was added, creating a KMnO ₄ solution.
(4) The KMnO ₄ solution is added to the Mn (OOCCH ₃ ) ₂ · 4H ₂ O aqueous solution that has been subjected to the above treatment, and the UC treatment is performed for 5 minutes.
(5) Further, after washing and filtration, vacuum drying was performed at 130 ° C. for 16 hours to synthesize a complex of manganese compound and KB as the final product.

In each example, the ratio of Mn (OOCCH ₃ ) ₂ .4H ₂ O and KMnO ₄ was adjusted as follows.
In Example 1, the ratio of Mn (OOCCH ₃ ) ₂ .4H ₂ O and KMnO ₄ dissolved in the solution to be subjected to UC treatment is adjusted to 3: 2 at a molar rate, and the pH of the aqueous solution is adjusted to 4.
In Comparative Example 1, the ratio of Mn (OOCCH ₃ ) ₂ .4H ₂ O and KMnO ₄ dissolved in the UC treatment solution is adjusted to a molar rate other than 3: 2, and the pH of the aqueous solution is adjusted to other than 3-5. .

  In Example 1 and Comparative Example 1, the weight ratio between the material source of the manganese compound and the carbon material is 60:40.

  The composite of Example 1 and Comparative Example 1 was analyzed by TG-DTA (differential thermo-thermogravimetric measurement), crystal structure analysis by XRD (X-ray powder diffraction method), and TEM (transmission electron microscope). The crystal system was identified and observed, and the discharge cycle characteristics of the composite were compared.

[Thermal analysis by TG-DTA, calculation of carbon ratio]
FIG. 6 is a diagram showing TG-DTA (thermal characteristics and carbon ratio by simultaneous differential thermal-thermogravimetric measurement) for the composite of Example 1 heated at 130 ° C. in vacuum.

According to the result of DTA (differential thermal analysis), the carbon ratio by TG (simultaneous thermogravimetric measurement) of the composite of Example 1 shows that manganese compound: KB is 59:41. Manganese compound: Since the manganese compound with KB of 3: 2 is α-MnO ₂ , manganese other than α-MnO ₂ can be obtained by setting the molar rate of the solution for the complexing treatment to 3: 2 and the pH to 4. It can be seen that no compound was formed. This result is the same as that obtained when the pH adjusted for the mol rate of the solution to be subjected to the complexing treatment is 3-5.

[Identification and morphology observation of crystal system by TEM]
7 and 8 are TEM images of the crystal structure of the composite of Example 1. FIG. The crystal structure of the composite was observed by using a TEM (transmission electron microscope). From FIG. 7, it can be seen that needle-like crystals not containing impurities of several hundred nm are generated. Moreover, it can be observed from FIG. 8 that the acicular crystal has a tunnel structure and is α-MnO ₂ . That is, it can be seen that a complex having a single α-MnO ₂ crystal structure is generated by setting the mol rate of the solution for the complexing treatment to 3: 2 and the pH to 4. This result is the same as that obtained when the pH adjusted for the mol rate of the solution to be subjected to the complexing treatment is 3-5.

[Crystal structure analysis by XRD]
FIG. 9 is a diagram showing the results of crystal structure analysis by XRD (X-ray powder diffraction method) performed on the composite of Example 1.

FIG. 9 shows that only α-MnO ₂ is produced as the manganese compound as the crystal structure of the composite of Example 1. It can be seen that by adjusting the pH of the solution containing one of the material sources of the manganese compound to a certain value, a composite having a single manganese compound crystal structure is formed. In particular, it can be seen that α-MnO ₂ is produced alone by setting the molar rate of the solution for the complexing treatment to 3: 2 and the pH to 4. This result is the same as that obtained when the pH adjusted for the mol rate of the solution to be subjected to the complexing treatment is 3-5. In the XRD analysis result of Comparative Example 1, it can be seen that impurities such as banesite are detected and α-MnO ₂ is not produced alone.

[Charging cycle characteristics]
FIG. 10 is a diagram showing the discharge cycle characteristics of the composite. In FIG. 10, the composite of Example 1 is put together with polyvinylidene fluoride PVDF as a binder (MnO2 / KB: PVDF = 80: 20) into a SUS mesh welded on a SUS plate, and the working electrode W.V. E. It was. A separator and a counter electrode on the electrode C.I. E. Lithium foil is placed as a reference electrode, and 1.0M lithium hexafluorophosphate (LiPF ₆ ) / ethylene carbonate (EC): dimethyl carbonate (DEC) (1: 1 w / w) is infiltrated as an electrolyte. And cell. In this state, the charge / discharge characteristics were examined with an operating current of 200 mAg ⁻¹ and an operating voltage of 0.0-2.5 V.

  From FIG. 10, it can be seen that the cell using the composite of Example 1 stably developed the capacity even after exceeding 100 cycles. That is, in an electrode using a composite having a single manganese compound crystal structure produced by adjusting the pH of a solution containing one of the material sources of the manganese compound, the capacity decreases even after a discharge cycle. It has characteristics that never happen.

[effect]
As described above, in the electrode using the composite in which α-MnO ₂ is generated as the manganese compound as in the example, high input / output and high capacity can be achieved. Further, such an electrode has a characteristic that the capacity does not decrease even after the discharge cycle. That is, higher input / output and higher capacity are achieved.

[2. Second characteristic comparison]
In Examples 4 to 6, as shown in FIG. 11, manganese acetate tetrahydrate (Mn (OOCCH ₃ ) ₂ .4H ₂ O) was used as the manganese compound having a valence of manganese of 2 ≦ x <4. The pH of the solution in which the manganese compound was dissolved was adjusted. Further, potassium permanganate (KMnO ₄ ) was used as a manganese compound having a valence of manganese of 4 <x ≦ 7.

The composites of Example 2 and Comparative Example 2 were synthesized as follows.
(1) Mn (OOCCH ₃₎ with respect to ₂ · 4H _{2 O1.268g,} distilled water 30mL added Mn (OOCCH ₃₎ to create a ₂ · 4H ₂ O solution.
(2) Adjust the pH of the aqueous solution by adding KOH to the Mn (OOCCH ₃ ) ₂ · 4H ₂ O solution.
(3) Add KB to the Mn (OOCCH ₃ ) ₂ · 4H ₂ O aqueous solution whose pH has been adjusted and mix.
(4) On the other hand, with respect to KMnO ₄ 0.5453G, distilled water 30mL was added, creating a KMnO ₄ solution.
(5) The KMnO ₄ solution is added to the Mn (OOCCH ₃ ) ₂ · 4H ₂ O aqueous solution that has been subjected to the above treatment, and the UC treatment is performed for 5 minutes.
(6) Further, after washing and filtration, vacuum drying was performed at 130 ° C. for 16 hours to synthesize a complex of manganese compound and KB as the final product.

In each example, the following adjustment was made in (2).
In Example 2, 11 ml of 1M KOH is added to the Mn (OOCCH ₃ ) ₂ .4H ₂ O solution to adjust the pH of the aqueous solution to 12.
In Comparative Example 2, 4 ml of 1M KOH is added to the Mn (OOCCH ₃ ) ₂ .4H ₂ O solution to adjust the pH of the aqueous solution to 8.5.

In Example 2 and Comparative Example 2, the ratio of Mn (OOCCH ₃ ) ₂ .4H ₂ O and KMnO ₄ was set to 3: 2 at the mol rate. The weight ratio of the material source of the manganese compound and the carbon material is 60:40.

  For the composite of Example 2 and Comparative Example 2, identification of the crystal system by TEM (transmission electron microscope), analysis of the crystal structure by XRD (X-ray powder diffraction method), and comparison of discharge cycle characteristics of the composite I did it.

[Identification and morphology observation of crystal system by TEM]
12 and 13 are TEM images of the crystal structure of the composite of Example 2. FIG. The crystal structure of the composite was observed by using a TEM (transmission electron microscope). From FIG. 12, it can be seen that a rod-like crystal containing no impurities of several hundred nm is generated. Further, from FIG. 13, it is observed that the rod-like crystals are barnesites having a 2 × ∞ rod structure. That is, it can be seen that by adjusting the pH of the solution containing one of the material sources of the manganese compound to a certain value, a complex having a single manganese compound crystal structure is generated. That is, it turns out that the composite_body | complex which has the crystal structure of a single birnessite is produced | generated by setting the pH of the solution which performs a composite process to 12. This result can be obtained even when the pH of the solution for performing the complexing process is 11.5 to 14.

[Crystal structure analysis by XRD]
FIG. 14 is a diagram showing the results of crystal structure analysis by XRD (X-ray powder diffraction method) performed on the composites of Example 2 and Comparative Example 2.

In FIG. 14, it can be seen that, as the crystal structure of the complex of Example 2 having a pH of 12, only banesite is generated as the manganese compound. On the other hand, as for the crystal structure of the composite of Comparative Example 2 having a pH of 8.5, it can be seen that banesite is not generated and α-MnO ₂ and other manganese compounds are generated. That is, it turns out that the composite_body | complex which has the crystal structure of a single birnessite is produced | generated by setting the pH of the solution which performs a composite process to 12. This result can be obtained even when the pH of the solution for performing the complexing process is 11.5 to 14.

[Charging cycle characteristics]
FIG. 15 is a diagram showing the discharge cycle characteristics of the composite. In FIG. 15, the composite of Example 2 was put together with polyvinylidene fluoride PVDF as a binder (MnO ₂ / KB: PVDF = 80: 20) into a SUS mesh welded on a SUS plate, and the working electrode W.V. E. It was. A separator and a counter electrode on the electrode C.I. E. Lithium foil is placed as a reference electrode, and 1.0M lithium hexafluorophosphate (LiPF ₆ ) / ethylene carbonate (EC): dimethyl carbonate (DEC) (1: 1 w / w) is infiltrated as an electrolyte. And cell. In this state, the charge / discharge characteristics were examined with an operating current of 200 mAg ⁻¹ and an operating voltage of 0.0-2.5 V.

  From FIG. 15, it can be seen that the cell using the composite of Example 2 stably developed the capacity even after exceeding 100 cycles. That is, in an electrode using a composite having a single manganese compound crystal structure produced by adjusting the pH of a solution containing one of the material sources of the manganese compound, the capacity decreases even after a discharge cycle. It has characteristics that never happen.

[effect]
As described above, in an electrode using a composite in which banesite is generated as a manganese compound as in the examples, higher input / output and higher capacity can be achieved. Further, such an electrode has a characteristic that the capacity does not decrease even after the discharge cycle. That is, higher input / output and higher capacity are achieved.

DESCRIPTION OF SYMBOLS 1 ... Outer cylinder 1-2 ... Baffle 1-3 ... Inner wall 2 ... Inner cylinder 2-1 ... Through-hole

Claims (9)

A method for producing a composite comprising a manganese compound and a carbon material,
A pH adjusting step for adjusting the pH of the solution in which the material source of the manganese compound and the carbon material are mixed;
A compounding step of combining a material source of a manganese compound and a carbon material to generate a composite of carbon and a manganese compound;
The manufacturing method of the composite_body | complex characterized by having. A method for producing an electrode material comprising a composite of a manganese compound and a carbon material,
A pH adjusting step for adjusting the pH of the solution in which the material source of the manganese compound and the carbon material are mixed;
A compounding step of combining a material source of a manganese compound and a carbon material to generate a composite of carbon and a manganese compound;
A method for producing an electrode material comprising:   3. The electrode material according to claim 2, wherein the material source of the manganese compound is a manganese compound having a valence of manganese of 2 ≦ x <4 and a manganese compound having a valence of manganese of 4 <x ≦ 7. Production method. The manganese compound in which the valence of manganese is 2 ≦ x <4 is Mn (OOCCH ₃ ) ₂ · 4H ₂ O, and the manganese compound in which the valence of manganese is 4 <x ≦ 7 is KMnO ₄ The method for producing an electrode material according to claim 3.   5. The method for producing an electrode material according to claim 2, wherein, in the pH adjustment step, a solution containing one of the material sources of the manganese compound is adjusted to a pH of 3 to 5. 5.   The method for producing an electrode material according to any one of claims 2 to 4, wherein, in the pH adjustment step, a solution containing one of the material sources of the manganese compound is adjusted to a pH of 11.5 to 14. . The compounding process includes
7. A process of applying a shear stress and a centrifugal force to a solution containing a carbon material and a metal compound material source to cause a mechanochemical reaction, respectively, in a rotating reaction vessel. A method for producing the electrode material according to claim 1. A composite of a manganese compound and a carbon material,
The complex characterized in that the complexed manganese compound is α-MnO ₂ or birnessite. An electrode material that combines a manganese compound and a carbon material,
An electrode material, wherein the complexed manganese compound is α-MnO ₂ or birnessite.