JPWO2013099967A1 - Oxide and method for producing the same - Google Patents

Abstract

The oxide of the present invention has a corundum structure and is represented by a chemical formula (Fe1-xMx) 2O3 (where M is at least one typical metal element, and 0 <x <1). When used as an active material for non-aqueous secondary batteries, it has excellent charge / discharge cycle characteristics.

Description

  The present invention relates to an oxide and a method for producing the same, and more particularly to an oxide comprising a solid solution of iron oxide and an oxide of at least one typical metal element and a method for producing the same.

  As a non-aqueous secondary battery, a lithium secondary battery has been put into practical use and widely used. Further, in recent years, lithium secondary batteries are attracting attention not only as small-sized batteries for portable electronic devices but also as large-capacity devices for on-vehicle use and power storage. Therefore, demands for safety, cost, life, etc. are higher.

  The lithium secondary battery has a positive electrode, a negative electrode, an electrolytic solution, a separator, and an exterior material as main components. The positive electrode includes a positive electrode active material, a conductive material, a current collector, and a binder (binder).

In general, a layered transition metal oxide typified by LiCoO ₂ is used as the positive electrode active material. However, the layered transition metal oxide easily causes oxygen desorption at a relatively low temperature of about 150 ° C. in a fully charged state, and the thermal desorption reaction of the battery can occur due to the oxygen desorption. Therefore, when a battery having such a positive electrode active material is used for a portable electronic device, there is a risk that an accident such as heat generation or ignition of the battery may occur. Further, since LiCoO ₂ contains Co, which is a rare metal, a lower cost positive electrode active material is required.

On the other hand, the use of iron oxide (Fe ₂ O ₃ ) as an active material for lithium secondary batteries has been studied. Iron oxide is not only inexpensive, but a high capacity can be expected because 6 moles of lithium ions per mole are involved in the charge / discharge reaction. However, iron oxide has a problem that its irreversible capacity is large and charge / discharge cycle characteristics are insufficient.

Therefore, in order to improve the charge / discharge cycle characteristics, a method using ultrafine particles of α-Fe ₂ O ₃ (Patent Document 1), an average particle size in the range of 1 to 10 nm, and a particle size distribution width of 1 to A method using iron oxide ultrafine particles in the range of 10 nm (Patent Document 2), a method using a composite material produced by heat-treating a mixed material of γ-FeO (OH) and a conductive additive (Patent Document 3), A method using a mixture of α-Fe ₂ O ₃ and Al ₂ O ₃ produced by a coprecipitation method (Non-patent Document 1) has been proposed.

JP 2003-257426 A JP 2008-204777 A JP 2008-243414 A

47th Battery Symposium Abstracts 3F-19

    However, in any of the above-mentioned patent documents, the charge / discharge cycle characteristics are insufficient, and further improvement of the charge / discharge cycle characteristics is required from a practical viewpoint.

  Accordingly, an object of the present invention is to provide an oxide that provides excellent charge / discharge cycle characteristics and a method for producing the same.

It is known that Fe ₂ O ₃ performs charge and discharge based on an oxidation-reduction reaction represented by the following formula. For example, when used for the positive electrode, Fe ₂ O ₃ is reduced to Fe during the first discharge. However, at the time of charging, the generated Fe cannot return to Fe ₂ O ₃ and the crystal growth is different, that is, irreversible crystals are deposited, causing irreversible capacity. As charge / discharge is repeated, Fe that cannot be returned to the original position increases, resulting in an increase in irreversible capacity and deterioration in charge / discharge cycle characteristics.

On the other hand, in the process of studying to improve the charge / discharge cycle characteristics of Fe ₂ O ₃ , the present inventors have made the active material an electrochemically active metal oxide and an electrochemically inactive oxide. It was found that the charge / discharge cycle characteristics are improved when a solid solution is used.
The present invention has been completed based on the above findings of the present inventors, and the oxide of the present invention has the chemical formula (Fe _1-x M _x ) ₂ O ₃ (where M is at least one typical species). It is a metal element and has a corundum type structure represented by 0 <x <1).

In addition, the production method of the present invention synthesizes a mixture of γ-Fe ₂ O ₃ and at least one metal oxide by a mechanochemical synthesis method, and has a chemical formula (Fe _1-x M _x ) ₂ O ₃ (provided that M is at least one metal element, and 0 <x <1)), and is characterized by producing an oxide having a corundum structure represented by:

The active material for a non-aqueous secondary battery of the present invention has a chemical formula (Fe _1-x M _x ) ₂ O ₃ (where M is at least one typical metal element, and 0 <x <1). It is characterized by comprising an oxide having a corundum type structure represented by

The nonaqueous secondary battery of the present invention is represented by the chemical formula (Fe _1-x M _x ) ₂ O ₃ (where M is at least one typical metal element, and 0 <x <1). It includes a positive electrode, a negative electrode, and a non-aqueous electrolyte that include an oxide having a corundum structure as a positive electrode active material.

Another non-aqueous secondary battery of the present invention has a chemical formula (Fe _1-x M _x ) ₂ O ₃ (where M is at least one typical metal element, and 0 <x <1). It includes a negative electrode, a positive electrode, and a non-aqueous electrolyte that include the oxide having a corundum type structure as a negative electrode active material.

  The present invention provides a novel oxide comprising a solid solution of iron oxide and at least one typical metal oxide. By using the oxide as an active material, a non-aqueous secondary battery having a high capacity and excellent charge / discharge characteristics can be provided.

It shows the XRD pattern of the synthesized _γ-Fe 2 _{O 3.} 6 is a diagram showing an XRD pattern of a composite material of Synthesis Example 1. FIG. 6 is a diagram showing an XRD pattern of a composite material of Synthesis Example 2. FIG. It is a figure which shows the XRD pattern of the composite material of the synthesis example 3. FIG. It is a figure which shows the XRD pattern of the composite material of the synthesis example 4. 10 is a diagram showing an XRD pattern of a composite material of Synthesis Example 5. FIG. 10 is a diagram showing an XRD pattern of a composite material of Synthesis Example 6. FIG. It is a figure which shows the XRD pattern of the composite material of the synthesis example 7. 10 is a diagram showing an XRD pattern of a composite material of Synthesis Example 8. FIG. 10 is a diagram showing an XRD pattern of a composite material of Synthesis Example 9. FIG. 14 is a diagram showing an XRD pattern of a composite material of Synthesis Example 10. FIG. 14 is a diagram showing an XRD pattern of a composite material of Synthesis Example 11. FIG. 14 is a diagram showing an XRD pattern of a composite material of Synthesis Example 12. FIG. It is a figure which shows the XRD pattern of the composite material of the synthesis example 13. It is a figure which shows the XRD pattern of the composite material of the synthesis example 14. 4 is a diagram showing an XRD pattern of γ-Fe ₂ O ₃ of Comparative Example 1. FIG. 6 is a diagram showing an XRD pattern of α-Fe ₂ O ₃ of Comparative Example 2. FIG. It is a figure which shows the charging / discharging curve of Example 1. FIG. It is a figure which shows the charging / discharging cycle characteristic of Example 1. FIG. It is a figure which shows the charging / discharging cycle characteristic of Example 2. FIG. It is a figure which shows the charging / discharging cycle characteristic of Example 3. FIG. It is a figure which shows the charging / discharging cycle characteristic of Example 4. FIG. It is a figure which shows the charging / discharging cycle characteristic of Example 5. FIG. It is a figure which shows the charging / discharging cycle characteristic of Example 6. It is a figure which shows the charging / discharging cycle characteristic of Example 7. It is a figure which shows the charging / discharging cycle characteristic of Example 8. It is a figure which shows the charging / discharging cycle characteristic of Example 9. FIG. It is a figure which shows the charging / discharging cycling characteristics of Example 10. FIG. It is a figure which shows the charging / discharging cycle characteristic of Example 11. FIG. It is a figure which shows the charging / discharging cycle characteristic of Example 12. It is a figure which shows the charging / discharging cycle characteristic of Example 13. It is a figure which shows the charging / discharging cycle characteristic of Example 14. It is a figure which shows the charging / discharging curve of the comparative example 1. 5 is a diagram showing charge / discharge cycle characteristics of Comparative Example 1. FIG. It is a figure which shows the charging / discharging curve of the comparative example 2. It is a figure which shows the charging / discharging cycle characteristic of the comparative example 2.

Hereinafter, embodiments of the present invention will be described in detail.
As the oxide of the present invention, an oxide comprising a solid solution of iron oxide and an oxide of at least one typical metal element is used. Here, iron oxide corresponds to an electrochemically active metal oxide, and an oxide of a typical metal element corresponds to an electrochemically inactive oxide.

  The electrochemically active metal oxide is a metal oxide that is oxidized and reduced during charging and discharging of the lithium secondary battery. The electrochemically inactive oxide is an oxide that does not intercalate lithium, does not form an alloy with lithium, and is not oxidized or reduced during charging and discharging of a lithium secondary battery.

In the present invention, the oxide of the typical metal element forming the solid solution is an oxide of a metal element of Group 1, Group 2, Group 13, Group 14, or a combination thereof, more preferably a Group 2 metal. It is an oxide of an element and / or a Group 13 metal element. Specific examples include Al ₂ O ₃ , SiO ₂ , MgO, CaO, Ga ₂ O ₃ , BaO, SrO, or combinations thereof, more preferably Al ₂ O ₃ , Ga ₂ O ₃ or combinations thereof, Al ₂ O ₃ is preferable.

  The oxide of the present invention contains a fine crystalline phase. The fine crystal phase includes crystal particles having an average crystal grain size of 500 nm or less, preferably 100 nm or less, and the crystal structure thereof is a corundum type structure. The average crystal grain size can be determined from the half-value width of the peak of X-ray diffraction by the Scherrer equation. It can also be calculated from an electron micrograph.

The oxide of the present invention is an oxide having a corundum structure, and is represented by the chemical formula (Fe _1-x M _x ) ₂ O ₃ . Here, the element M is at least one typical metal element and is an oxide of a metal element belonging to Group 1, Group 2, Group 13, Group 14, or a combination thereof. Specific examples of the element M include Al, Si, Mg, Ca, Ga, Ba, Sr, and combinations thereof, more preferably Al, Ga, and combinations thereof, and more preferably Al. Specific examples of M of one type include (Fe _1-x Al _x ) ₂ O ₃ and (Fe _1-x Ga _x ) ₂ O ₃ . X is 0 <x <1, preferably 0.25 <x <1, more preferably 0.25 <x <0.75, and still more preferably 0.4 <x <0.67. More preferably, 0.4 <x ≦ 0.6, and further preferably 0.43 ≦ x ≦ 0.6. When x is x = 0, the irreversible capacity increases when used as an active material for a non-aqueous secondary battery. When x is x = 1, it is used as an active material for a non-aqueous secondary battery. This is because the capacity becomes almost zero. When 0.25 <x <0.75, it is more preferable to use as an active material for a non-aqueous secondary battery because the cycle characteristics are further improved. When 0.4 <x <0.67, it is more preferable to use it as an active material for a non-aqueous secondary battery since cycle characteristics are further improved and irreversible capacity is further suppressed. When 0.43 ≦ x ≦ 0.6, it is more preferable to use it as an active material for a non-aqueous secondary battery because the cycle characteristics are further improved and the irreversible capacity is further suppressed.

  When Al is used for the typical metal element M, the lattice constant of the a axis is 4.75 to 5.04 and the lattice constant of the c axis is 12.99 to 13.75. Preferably, the a-axis lattice constant is 4.75 to 4.97 Å, and the c-axis lattice constant is 12.99 to 13.56 Å. More preferably, the lattice constant of the a axis is 4.82 to 4.97Å and the lattice constant of the c axis is 13.18 to 13.56Å. More preferably, the lattice constant of the a axis is 4.85 to 4.93 and the lattice constant of the c axis is 13.24 to 13.45. More preferably, the lattice constant of the a axis is 4.86 to 4.93 and the lattice constant of the c axis is 13.29 to 13.45. More preferably, the lattice constant of the a axis is 4.86 to 4.92 Å, and the lattice constant of the c axis is 13.29 to 13.43 Å.

  When Ga is used for the typical metal element M, the a-axis lattice constant is 4.97 to 5.04 Å, and the c-axis lattice constant is 13.42 to 13.75 Å. Preferably, the a-axis lattice constant is 4.97 to 5.03 Å, and the c-axis lattice constant is 13.42 to 13.68 Å. More preferably, the lattice constant of the a axis is 4.99 to 5.03 and the lattice constant of the c axis is 13.50 to 13.68. More preferably, the lattice constant of the a axis is 4.99 to 5.02 and the lattice constant of the c axis is 13.53 to 13.63. More preferably, the lattice constant of the a axis is 5.00 to 5.02 and the lattice constant of the c axis is 13.55 to 13.63. More preferably, the lattice constant of the a axis is 5.00 to 5.015 and the lattice constant of the c axis is 13.61 to 13.63.

The chemical formula _{(Fe 1-x M x)} 2 O 3 can be derived in the following manner.
First, the reaction with the case of producing a solid solution of _Fe 2 _{O 3} and _Al 2 _{O 3} according to the embodiment described below, _Fe 2 _{O 3} and _Al 2 _{O 3} can be expressed by the following equation.

In the production of the solid solution of _Fe 2 _{O 3} and _Ga 2 _{O 3,} the reaction of _Fe 2 _{O 3} and _Ga 2 _{O 3} can be expressed by the following equation.

Further, when the oxide is generalized as M ¹ ₂ O ₃ , the reaction can be represented by the following formula.

In addition, assuming that there are two types of oxides, M ¹ ₂ O ₃ and M ² ₂ O _3, and the ratio thereof is x ₁ and x ₂ as a whole, the reaction can be expressed by the following formula.

If this formula is generalized to the case of M ⁿ , the reaction can be expressed by the following formula.

Here, when x and M are defined as follows, the oxide of the present invention is
Generally, it can be represented by the chemical formula (Fe _1-x M _x ) ₂ O ₃ .

  The average particle size of the oxide of the present invention is 1 μm or less, preferably 0.001 to 0.5 μm, more preferably 0.001 to 0.1 μm. This is because if the average particle size is larger than 1 μm, the charge / discharge characteristics are deteriorated. The average particle size used in the present invention is a volume-based average particle size, and for example, a value obtained by a wet laser method can be used.

(Production method)
A mechanochemical synthesis method can be used to produce the oxide of the present invention. The mechanochemical synthesis method is a method of promoting a chemical reaction between reaction mixtures by mechanical energy by stirring and mixing and grinding the reaction mixture in the presence of a milling medium. This chemical reaction includes solid phase reaction, compound synthesis reaction, redox reaction, ion exchange reaction, crystal structure conversion, formation of microcrystalline phase, formation of amorphous phase, and the like.

The mechanochemical synthesis method uses a ball mill such as a rolling ball mill, a planetary ball mill, a vibration ball mill, or an attritor mill for the mill, and various shapes made of stainless steel or ceramic, for example, spherical or elliptical, for the milling medium. Or a rod-shaped medium can be used. Examples of the ceramic milling medium include aluminum oxide, zirconium oxide, yttria stabilized zirconia, silicon nitride (Si ₃ N ₄ ), tungsten carbide (WC), and the like. As the milling medium, it is preferable to select and use one that is chemically inert to the reaction mixture.

  The conditions for the mechanochemical synthesis vary depending on the type of mill, and are not particularly limited in the present invention. However, when a planetary ball mill is used, the rotation speed is 200 rpm or more and the time is in the range of 10 minutes to 500 hours. Can do. Moreover, the atmosphere at the time of mixing and grinding can use an air atmosphere or an inert gas atmosphere.

In the production method of the present invention, γ-Fe ₂ O ₃ is reacted with an oxide of at least one typical metal element by a mechanochemical synthesis method. As described above, the oxide of the typical metal element is an oxide of a metal element of Group 1, Group 2, Group 13, Group 14, or a combination thereof, more preferably a Group 2 metal element and / or Group 13 metal oxide. It is an oxide of a group metal element. Specific examples include Al ₂ O ₃ , SiO ₂ , MgO, CaO, Ga ₂ O ₃ , BaO, SrO, or combinations thereof, more preferably Al ₂ O ₃ , Ga ₂ O ₃ or combinations thereof, Al ₂ O ₃ is preferable.

In the production method of the present invention, γ-Fe ₂ O ₃ may be reacted with an oxide of at least one transition metal element by a mechanochemical synthesis method. Transition metal element oxides are Group 3, Group 4, Group 5, Group 6, Group 7, Group 8, Group 9, Group 10, Group 11, Group 12 metal elements Or an oxide of a metal element belonging to Group 4, Group 5, Group 6, or Group 9 or a combination thereof. Specific examples are Ti ₂ O ₃ , V ₂ O ₃ , Cr ₂ O ₃ , Rh ₂ O ₃ or combinations thereof. Further, γ-Fe ₂ O ₃ may be reacted with an oxide of at least one typical metal element and an oxide of at least one transition metal element.

For example, when Al ₂ O ₃ is used as an oxide of at least one metal element, the mixing ratio of γ-Fe ₂ O ₃ and Al ₂ O ₃ is not particularly limited. The formula of the whole starting material can be described as (1-z) Fe ₂ O ₃ + zAl ₂ O ₃ using the molar mixing ratio z of the raw materials. z is 0 <z <1, preferably 0.25 <z <1, more preferably 0.25 <z <0.75, still more preferably 0.4 <z <0.67, and still more preferably. Is 0.4 <z ≦ 0.6, more preferably 0.45 ≦ z ≦ 0.6. When z is z = 0, the irreversible capacity increases when used as an active material for a non-aqueous secondary battery. When z is z = 1, it is used as an active material for a non-aqueous secondary battery. This is because the capacity becomes almost zero.

The primary particle size of γ-Fe ₂ O ₃ is 500 nm or less, preferably 100 nm or less. This is because the smaller the primary particle size, the better the reactivity. This is because if it is larger than 500 nm, the mechanochemical reactivity decreases.

In the mechanochemical synthesis method, when γ-Fe ₂ O ₃ is used as a starting material, the crystal structure changes to α-Fe ₂ O ₃ with the time of the synthesis reaction. The reason why γ-Fe ₂ O ₃ is used as a starting material is to increase the reactivity of forming a solid solution with a typical metal oxide in the course of the change. When α-Fe ₂ O ₃ is used as a starting material, a process in which the atomic arrangement is once disturbed such that γ-Fe ₂ O ₃ changes to α-Fe ₂ O ₃ hardly occurs. Therefore, the reactivity for forming a solid solution is low, and it is difficult to form a solid solution as compared with γ-Fe ₂ O ₃ . Thereby, compared with the case of using the α-Fe ₂ O ₃ in the starting material can be prepared a solid solution in a short time.
Similarly, γ-Al ₂ O ₃ may be used as a starting material. When γ-Al ₂ O ₃ is used, the crystal structure changes to α-Al ₂ O ₃ with the time of the synthesis reaction. The reason why γ-Al ₂ O ₃ is used as a starting material is to increase the reactivity of forming a solid solution with α-Fe ₂ O _{3 in} the course of the change. When α-Al ₂ O ₃ is used as a starting material, a process in which the atomic arrangement is once disturbed such that γ-Al ₂ O ₃ changes to α-Al ₂ O ₃ hardly occurs. Therefore, the reactivity for forming a solid solution is low, and it is difficult to form a solid solution as compared with γ-Al ₂ O ₃ . Thereby, compared with the case of using the α-Al ₂ O ₃ in the starting material can be prepared a solid solution in a short time.

(Application example)
The oxide of the present invention can be expected to be used in various ways as an oxide comprising an iron oxide solid solution. Particularly preferred applications are positive electrode active materials or negative electrode active materials for non-aqueous secondary batteries. For example, a lithium secondary battery in which the oxide of the present invention is used as a positive electrode active material and metal lithium or graphite is used as a negative electrode can be manufactured. As one embodiment thereof, an oxide having a corundum structure represented by a chemical formula (Fe _1-x M _x ) ₂ O ₃ (where M is at least one typical metal element, and 0 <x <1). And a non-aqueous secondary battery including a positive electrode, a negative electrode, and a non-aqueous electrolyte.

Further, the lithium oxide containing the oxide of the present invention as a negative electrode active material and a lithium-containing composite oxide such as LiCoO ₂ , LiMn ₂ O ₄ , LiMn _1.5 Ni _0.5 O ₄ , LiFePO ₄ , LiMnPO ₄ as a positive electrode is used. A secondary battery can also be produced. As one embodiment thereof, an oxide having a corundum structure represented by a chemical formula (Fe _1-x M _x ) ₂ O ₃ (where M is at least one typical metal element, and 0 <x <1). And a non-aqueous secondary battery including a negative electrode, a positive electrode, and a non-aqueous electrolyte.

The non-aqueous electrolyte secondary battery of the present invention has a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator. Hereinafter, each constituent material will be described.
(A) Positive electrode A positive electrode is producible using a well-known method. For example, the active material of the present invention, a conductive material and a binder can be kneaded and dispersed using an organic solvent to obtain a paste, and the paste can be applied to a current collector. Note that when the positive electrode active material has sufficiently high conductivity, the conductive material is not necessarily added.

  As binders, polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl chloride, ethylene propylene diene polymer, styrene-butadiene rubber, acrylonitrile-butadiene rubber, fluororubber, polyvinyl acetate, polymethyl methacrylate, polyethylene, nitrocellulose, styrene Butadiene rubber or the like can be used. If necessary, a thickener such as carboxymethylcellulose can also be used.

  As the conductive material, acetylene black, ketjen black, natural graphite, artificial graphite, needle coke, or the like can be used.

  As the current collector, foamed (porous) metal having continuous pores, metal formed in a honeycomb shape, sintered metal, expanded metal, non-woven fabric, plate, perforated plate, foil, and the like can be used.

  As the organic solvent, N-methyl-2-pyrrolidone, toluene, cyclohexane, dimethylformamide, dimethylacetamide, methyl ethyl ketone, methyl acetate, methyl acrylate, diethyltriamine, N, N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran, etc. are used. be able to. When a water-soluble binder is used, water can be used as a solvent.

  The thickness of the positive electrode is preferably about 0.01 to 20 mm. If it is too thick, the conductivity is lowered, and if it is too thin, the capacity per unit area is lowered. The positive electrode obtained by coating and drying may be compacted by a roller press or the like in order to increase the packing density of the active material.

(B) Negative electrode A negative electrode can be produced by a known method. For example, the active material of the present invention, a binder and a conductive material are mixed, the obtained mixed powder is formed into a sheet shape, and the obtained molded body is converted into a current collector, for example, a mesh-shaped current collector made of stainless steel or copper. Can be made by pressure bonding. Moreover, it can be produced using the method using the paste as described in the above (a) positive electrode. In that case, the negative electrode active material, the conductive material, and the binder are kneaded and dispersed using an organic solvent to obtain a paste. The paste can be produced by applying it to a current collector.

(C) Nonaqueous electrolyte As the nonaqueous electrolyte, for example, an organic electrolyte, a gel electrolyte, a polymer solid electrolyte, an inorganic solid electrolyte, a molten salt, or the like can be used.

  Examples of the organic solvent constituting the organic electrolyte include cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), and butylene carbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate, and dipropyl carbonate. Chain carbonates such as γ-butyrolactone (GBL), lactones such as γ-valerolactone, furans such as tetrahydrofuran and 2-methyltetrahydrofuran, diethyl ether, 1,2-dimethoxyethane, 1,2-diethoxy Examples include ethers such as ethane, ethoxymethoxyethane, dioxane, dimethyl sulfoxide, sulfolane, methyl sulfolane, acetonitrile, methyl formate, methyl acetate, and the like. Can.

  Moreover, since cyclic carbonates such as PC, EC and butylene carbonate are high-boiling solvents, they are suitable as solvents to be mixed with GBL.

The electrolyte salt constituting the organic electrolyte includes lithium perchlorate (LiClO ₄ ), lithium borofluoride (LiBF ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ). , Lithium salts such as lithium trifluoroacetate (LiCF ₃ COO), lithium bis (trifluoromethanesulfone) imide (LiN (CF ₃ SO ₂ ) ₂ ), and a mixture of one or more of these Can do. The salt concentration of the electrolytic solution is preferably 0.5 to 3 mol / L.

(D) Separator As the separator, a known material such as a porous material or a nonwoven fabric can be used. As a material for the separator, a material that does not dissolve or swell in the organic solvent in the electrolytic solution is preferable. Specific examples include polyester polymers, polyolefin polymers (for example, polyethylene and polypropylene), ether polymers, and glass fibers.

(E) Other members Various other known materials can be used for other members such as battery containers, and there is no particular limitation.

(F) Manufacturing method of secondary battery The secondary battery includes a laminate including, for example, a positive electrode, a negative electrode, and a separator sandwiched therebetween. The laminate may have, for example, a strip-like planar shape. In the case of producing a cylindrical or flat battery, the laminate may be wound to form a wound body.

  One or more of the laminates are inserted into the battery container. Usually, the positive electrode and the negative electrode are connected to the external conductive terminal of the battery. Thereafter, the battery container is sealed to block the positive electrode, the negative electrode, and the separator from the outside air.

  In the case of a cylindrical battery, the sealing method is generally a method in which a lid having a resin packing is fitted into the opening of the battery container and the battery container and the lid are caulked. In the case of a square battery, a method of attaching a lid called a metallic sealing plate to the opening and performing welding can be used. In addition to these methods, a method of sealing with a binder and a method of fixing with a bolt via a gasket can also be used. Furthermore, a method of sealing with a laminate film in which a thermoplastic resin is attached to a metal foil can also be used. An opening for electrolyte injection may be provided at the time of sealing. When using an organic electrolyte, the organic electrolyte is injected from the opening, and then the opening is sealed. Gas generated by energization before sealing may be removed.

The reason why the oxide of the present invention has an excellent effect as an active material for a non-aqueous secondary battery can be considered as follows.
In general, an electrochemically active metal oxide is reduced to a single metal during discharge and is oxidized back to a metal oxide during charging. According to the present invention, by using a solid solution of an electrochemically active metal oxide and an electrochemically inactive oxide as the active material, the electrochemically inactive oxide is electrochemically converted. The active metal oxide crystal skeleton can be retained. Therefore, even if it is reduced to metal once and the crystal skeleton of the metal oxide changes, when it is oxidized and returns to the metal oxide, it can return to the original crystal skeleton, so the reversibility of the reaction is improved, Irreversible capacity is reduced. Furthermore, since the average particle size of the active material is 1 μm or less, the reversibility of the reaction is further improved. Thereby, it becomes possible to perform charging / discharging repeatedly, suppressing the fall of capacity | capacitance, and charging / discharging cycling characteristics improve.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail using an Example, this invention is not limited to a following example.

Iron oxide synthesis (synthesis of aqueous solution of γ-Fe ₂ O ₃ )
A buffer solution was prepared by mixing 198 mL of 0.1 M potassium acetate and 6 mL of 0.1 M acetic acid, and ferric chloride tetrahydrate (FeCl ₂ .4H ₂ O) was added to the beaker containing the buffer solution. 7994 g was added and stirred for 36 minutes while blowing oxygen at room temperature. Next, the solution was filtered using a filter made of polytetrafluoroethylene having a pore size of 0.1 μm, and the precipitate separated by filtration was dried at 70 ° C. for 24 hours to obtain γ-Fe ₂ O ₃ powder. This γ-Fe ₂ O ₃ was pulverized in an agate mortar and heat-treated at 200 ° C. for 72 hours in a vacuum. Here, potassium acetate, acetic acid, and ferric chloride tetrahydrate used were those manufactured by Sigma-Aldrich Japan.

(X-ray diffraction (XRD) measurement)
The measurement was performed under the following conditions using an X-ray diffractometer Ultima IV manufactured by Rigaku Corporation.
Measurement condition:
Angular range 10-80 degrees Scan speed 2 degrees / minute Sampling width 0.04 degrees Voltage 40 kV
Current 40mA

It shows the XRD pattern of _γ-Fe 2 _{O 3} prepared in FIG. Only the peak of γ-Fe ₂ O ₃ was observed.

Synthesis Example 1 (Oxide Preparation by Mechanochemical Synthesis Method of γ-Fe ₂ O ₃ and γ-Al ₂ O ₃ )
As γ-Fe ₂ O ₃ , the one prepared in Synthesis Example 1 was used. As the γ-Al ₂ O ₃ , a product (purity 97%) manufactured by Strem Chemical Co. was used.

Using the molar mixing ratio z of the raw materials, γ-Fe ₂ O ₃ and γ-Fe ₂ O ₃ so that the formula of the entire starting raw material becomes z = 0.64 in the formula represented by (1-z) Fe ₂ O ₃ + zAl ₂ O ₃ γ-Al ₂ O ₃ was mixed and mechanochemically synthesized at room temperature using a planetary ball mill P-6 manufactured by Fritsch. The synthesis conditions are as follows.
Synthesis conditions:
Containers and balls Yttrium-stabilized zirconia (YSZ)
Rotation speed 600rpm
Ball diameter 5φ
Number of balls 90 pieces Mixing time 3 hours

(XRD measurement)
Except for the angle range of 20 to 80 degrees, the same conditions as in the iron oxide synthesis were performed.

FIG. 2 shows an XRD pattern of the manufactured oxide. No peak attributed to γ-Fe ₂ O ₃ was observed. On the other hand, many peaks that can be indexed by the corundum structure appeared. All the peaks were observed between the X-ray diffraction peak position of the corundum structure α-Al ₂ O _{3 and} the X-ray diffraction peak position of the corundum structure α-Fe ₂ O ₃ . This is presumably because this oxide is a solid solution of α-Fe ₂ O ₃ and α-Al ₂ O ₃ . The peak near 32 degrees is due to ZrO ₂ mixed from a container and a ball as a milling medium.

From the above XRD pattern, the a-axis and c-axis gratings from the peak position of the reflection index 024 (2θ = 51.04 degrees) and the reflection index 116 (2θ = 56.00 degrees) in the corundum structure (hexagonal lattice). Constants were calculated. Table 1 shows the lattice constants of the a-axis and c-axis and the unit cell volume obtained from the lattice constant. Furthermore, the calculated values of the lattice constants of the a-axis and c-axis of the solid solution represented by the chemical formula (Fe _1-x Al _x ) ₂ O ₃ (0 <x <1) are expressed as α-Fe ₂ O given to JCPDS. Using the lattice constants of ₃ and α-Al ₂ O ₃ , it is given as a function of x based on Vegard's law, and this can be used to give the calculated unit cell volume as a function of x. The value of x can be determined when this is equal to the measured value of the unit cell volume of the solid solution prepared by the mechanochemical synthesis method. When the value of x of the prepared solid solution (Fe _1-x Al _x ) ₂ O ₃ (0 <x <1) was calculated, x = 0.538 was obtained. This value is sufficiently close to the molar mixing ratio of the raw materials of γ-Fe ₂ O ₃ and γ-Al ₂ O ₃ , indicating that the solid solution synthesis reaction was performed smoothly.

Synthesis Example 2 (Oxide Preparation by Mechanochemical Synthesis Method of γ-Fe ₂ O ₃ and γ-Al ₂ O ₃ )
_γ-Fe 2 _{O 3} and _γ-Al 2 _{O 3} were the same as those used in Synthesis Example 1.

Γ-Fe ₂ O ₃ and γ-Fe ₂ O ₃ so that the formula of the whole starting material is z = 0.5 in the formula (1-z) Fe ₂ O ₃ + zAl ₂ O ₃ using the molar mixing ratio z of the raw materials γ-Al ₂ O ₃ was mixed and mechanochemically synthesized at room temperature using a planetary ball mill premium line P-7 manufactured by Fritsch. The synthesis conditions are as follows.
Synthesis conditions:
Container and ball Si ₃ N ₄
800 rpm
Ball diameter 0.5φ
Number of balls 80 Mixing time 40 minutes

(XRD measurement)
Except for the angle range of 20 to 80 degrees, the same conditions as in the iron oxide synthesis were performed.

FIG. 3 shows an XRD pattern of the manufactured oxide. No peak attributed to γ-Fe ₂ O ₃ was observed. On the other hand, many peaks that can be indexed by the corundum structure appeared. All the peaks were observed between the X-ray diffraction peak position of the corundum structure α-Al ₂ O _{3 and} the X-ray diffraction peak position of the corundum structure α-Fe ₂ O ₃ . This is presumably because this oxide is a solid solution of α-Fe ₂ O ₃ and α-Al ₂ O ₃ .

From the above XRD pattern, the a-axis and c-axis lattices from the peak position of the reflection index 024 (2θ = 50.61 degrees) and the reflection index 116 (2θ = 55.44 degrees) in the corundum structure (hexagonal lattice). Constants were calculated. Table 1 shows the lattice constants of the a-axis and c-axis and the unit cell volume obtained from the lattice constant. Furthermore, when the value of x of the produced solid solution (Fe _1-x Al _x ) ₂ O ₃ (0 <x <1) was calculated in the same manner as in Synthesis Example 1, x = 0.392 was obtained. This value is sufficiently close to the molar mixing ratio of the raw materials of γ-Fe ₂ O ₃ and γ-Al ₂ O ₃ , indicating that the solid solution synthesis reaction was performed smoothly.

Synthesis Example 3 (Oxide Preparation by Mechanochemical Synthesis Method of γ-Fe ₂ O ₃ and γ-Al ₂ O ₃ )
As γ-Fe ₂ O ₃ , Sigma-Aldrich (purity 98.7%) was used. _γ-Al 2 _{O 3} were the same as those used in Synthesis Example 1.

Γ-Fe ₂ O ₃ and γ-Fe ₂ O ₃ so that the formula of the whole starting material is z = 0.5 in the formula (1-z) Fe ₂ O ₃ + zAl ₂ O ₃ using the molar mixing ratio z of the raw materials γ-Al ₂ O ₃ was mixed and mechanochemically synthesized at room temperature using a planetary ball mill premium line P-7 manufactured by Fritsch. The synthesis conditions are as follows.
Synthesis conditions:
Container and ball Si ₃ N ₄
800 rpm
Processing time 15 minutes Rest time 2 minutes Number of cycles 2 cycles Ball diameter 5φ
Number of balls: 80 The above conditions were mixed twice for a total of 60 minutes.

FIG. 4 shows an XRD pattern of the manufactured oxide. No peak attributed to γ-Fe ₂ O ₃ was observed. On the other hand, many peaks that can be indexed by the corundum structure appeared. All peaks were observed between the X-ray diffraction peak position of the corundum structure α-Al ₂ O ₃ and the same X-ray diffraction peak position of the corundum structure α-Fe ₂ O ₃ . All the peaks were observed between the X-ray diffraction peak position of the corundum structure α-Al ₂ O _{3 and} the X-ray diffraction peak position of the corundum structure α-Fe ₂ O ₃ . This is presumably because this oxide is a solid solution of α-Fe ₂ O ₃ and α-Al ₂ O ₃ .

From the XRD pattern, the lattice constants of the a-axis and c-axis from the peak position of the reflection index 024 (2θ = 50.82) and the peak position of the reflection index 116 (2θ = 55.60 degrees) in the corundum structure (hexagonal lattice). Was calculated. Table 1 shows the lattice constants of the a-axis and c-axis and the unit cell volume obtained from the lattice constant. Furthermore, when the value of x of the produced solid solution (Fe _1-x Al _x ) ₂ O ₃ (0 <x <1) was calculated in the same manner as in Synthesis Example 1, x = 0.552 was obtained. This value is sufficiently close to the molar mixing ratio of the raw materials of γ-Fe ₂ O ₃ and γ-Al ₂ O ₃ , indicating that the solid solution synthesis reaction was performed smoothly.

Synthesis Example 4 (Preparation of oxide by mechanochemical synthesis of γ-Fe ₂ O ₃ and γ-Al ₂ O ₃ )
_gamma-Fe 2 _{O 3} and _γ-Al 2 _{O 3} were the same as those used in Synthesis Example 3.

Γ-Fe ₂ O ₃ and γ-Fe ₂ O ₃ so that the formula of the whole starting material is z = 0.5 in the formula (1-z) Fe ₂ O ₃ + zAl ₂ O ₃ using the molar mixing ratio z of the raw materials γ-Al ₂ O ₃ was mixed and mechanochemically synthesized at room temperature using a planetary ball mill premium line P-7 manufactured by Fritsch. Under the same mixing conditions as in Synthesis Example 3, the mixture was mixed 8 times for a total of 240 minutes.

FIG. 5 shows an XRD pattern of the manufactured oxide. No peak attributed to γ-Fe ₂ O ₃ was observed. On the other hand, many peaks that can be indexed by the corundum structure appeared. All the peaks were observed between the X-ray diffraction peak position of the corundum structure α-Al ₂ O _{3 and} the X-ray diffraction peak position of the corundum structure α-Fe ₂ O ₃ . This is presumably because this oxide is a solid solution of α-Fe ₂ O ₃ and α-Al ₂ O ₃ .

From the XRD pattern, the a-axis and c-axis lattice constants from the peak position of the reflection index 024 (2θ = 50.86) and the reflection index 116 (2θ = 55.64 degrees) in the corundum structure (hexagonal lattice). Was calculated. Table 1 shows the lattice constants of the a-axis and c-axis and the unit cell volume obtained from the lattice constant. Further, in the same manner as in Synthesis Example 1, the x value of the produced solid solution (Fe _1-x Al _x ) ₂ O ₃ (0 <x <1) was calculated, and x = 0.470 was obtained. This value is sufficiently close to the molar mixing ratio of the raw materials of γ-Fe ₂ O ₃ and γ-Al ₂ O ₃ , indicating that the solid solution synthesis reaction was performed smoothly.

Synthesis Example 5 (Oxide Preparation by Mechanochemical Synthesis Method of γ-Fe ₂ O ₃ and γ-Al ₂ O ₃ )
_gamma-Fe 2 _{O 3} and _γ-Al 2 _{O 3} were the same as those used in Synthesis Example 3.

As will be z = 0.333 in using the molar mixing ratio z of raw material expression of the entire starting material _{(1-z) Fe 2 O} 3 + zAl represented by expressions 2 _{O 3,} and _γ-Fe 2 _{O 3} γ-Al ₂ O ₃ was mixed and mechanochemically synthesized at room temperature using a planetary ball mill premium line P-7 manufactured by Fritsch. Under the same synthesis conditions as in Synthesis Example 3, the mixture was mixed 8 times for a total of 240 minutes.

FIG. 6 shows an XRD pattern of the manufactured oxide. No peak attributed to γ-Fe ₂ O ₃ was observed. On the other hand, many peaks that can be indexed by the corundum structure appeared. All the peaks were observed between the X-ray diffraction peak position of the corundum structure α-Al ₂ O _{3 and} the X-ray diffraction peak position of the corundum structure α-Fe ₂ O ₃ . This is presumably because this oxide is a solid solution of α-Fe ₂ O ₃ and α-Al ₂ O ₃ .

From the XRD pattern, the a-axis and c-axis lattice constants from the peak position of the reflection index 024 (2θ = 50.36) and the peak position of the reflection index 116 (2θ = 55.08 degrees) in the corundum structure (hexagonal lattice). Was calculated. Table 1 shows the lattice constants of the a-axis and c-axis and the unit cell volume obtained from the lattice constant. Furthermore, when the value of x of the prepared solid solution (Fe _1-x Al _x ) ₂ O ₃ (0 <x <1) was calculated in the same manner as in Synthesis Example 1, x = 0.305 was obtained. This value is sufficiently close to the molar mixing ratio of the raw materials of γ-Fe ₂ O ₃ and γ-Al ₂ O ₃ , indicating that the solid solution synthesis reaction was performed smoothly.

Synthesis Example 6 (Oxide Preparation by Mechanochemical Synthesis Method of γ-Fe ₂ O ₃ and γ-Al ₂ O ₃ )
_gamma-Fe 2 _{O 3} and _γ-Al 2 _{O 3} were the same as those used in Synthesis Example 3.

As will be z = 0.667 in using the molar mixing ratio z of raw material expression of the entire starting material _{(1-z) Fe 2 O} 3 + zAl represented by expressions 2 _{O 3,} and _γ-Fe 2 _{O 3} γ-Al ₂ O ₃ was mixed and mechanochemically synthesized at room temperature using a planetary ball mill premium line P-7 manufactured by Fritsch. Under the same synthesis conditions as in Synthesis Example 3, the mixture was mixed 8 times for a total of 240 minutes.

FIG. 7 shows an XRD pattern of the manufactured oxide. No peak attributed to γ-Fe ₂ O ₃ was observed. On the other hand, many peaks that can be indexed by the corundum structure appeared. All the peaks were observed between the X-ray diffraction peak position of the corundum structure α-Al ₂ O _{3 and} the X-ray diffraction peak position of the corundum structure α-Fe ₂ O ₃ . This is presumably because this oxide is a solid solution of α-Fe ₂ O ₃ and α-Al ₂ O ₃ .

From the XRD pattern, the a-axis and c-axis lattice constants from the peak position of the reflection index 024 (2θ = 51.43) and the reflection index 116 (2θ = 56.24 degrees) in the corundum type structure (hexagonal lattice). Was calculated. Table 1 shows the lattice constants of the a-axis and c-axis and the unit cell volume obtained from the lattice constant. Further, in the same manner as in Synthesis Example 1, the x value of the produced solid solution (Fe _1-x Al _x ) ₂ O ₃ (0 <x <1) was calculated, and x = 0.655 was obtained. This value is sufficiently close to the molar mixing ratio of the raw materials of γ-Fe ₂ O ₃ and γ-Al ₂ O ₃ , indicating that the solid solution synthesis reaction was performed smoothly.

Synthesis Example 7 (Oxide Preparation by Mechanochemical Synthesis Method of γ-Fe ₂ O ₃ and γ-Al ₂ O ₃ )
As the γ-Fe ₂ O ₃ , those having a purity of 99% or more manufactured by Alpha Co., Ltd. were used. _γ-Al 2 _{O 3} were the same as those used in Synthesis Example 1.

Using the molar mixing ratio z of the raw materials, γ-Fe ₂ O ₃ and γ-Fe ₂ O ₃ so that the formula of the whole starting raw material becomes z = 0.4 in the formula represented by (1-z) Fe ₂ O ₃ + zAl ₂ O ₃ γ-Al ₂ O ₃ was mixed and mechanochemically synthesized at room temperature using a planetary ball mill premium line P-7 manufactured by Fritsch. Under the same synthesis conditions as in Synthesis Example 3, the mixture was mixed twice for a total of 60 minutes.

FIG. 8 shows an XRD pattern of the manufactured oxide. No peak attributed to γ-Fe ₂ O ₃ was observed. On the other hand, many peaks that can be indexed by the corundum structure appeared. All the peaks were observed between the X-ray diffraction peak position of the corundum structure α-Al ₂ O _{3 and} the X-ray diffraction peak position of the corundum structure α-Fe ₂ O ₃ . This is presumably because this oxide is a solid solution of α-Fe ₂ O ₃ and α-Al ₂ O ₃ .

From the above XRD pattern, the a-axis and c-axis lattice constants from the peak position of the reflection index 024 (2θ = 50.56) and the peak position of the reflection index 116 (2θ = 55.31 degrees) in the corundum structure (hexagonal lattice). Was calculated. Table 1 shows the lattice constants of the a-axis and c-axis and the unit cell volume obtained from the lattice constant. Furthermore, when the value of x of the prepared solid solution (Fe _1-x Al _x ) ₂ O ₃ (0 <x <1) was calculated in the same manner as in Synthesis Example 1, x = 0.371 was obtained. This value is sufficiently close to the molar mixing ratio of the raw materials of γ-Fe ₂ O ₃ and γ-Al ₂ O ₃ , indicating that the solid solution synthesis reaction was performed smoothly.

Synthesis Example 8 (Oxide Preparation by Mechanochemical Synthesis Method of γ-Fe ₂ O ₃ and γ-Al ₂ O ₃ )
_γ-Fe 2 _{O 3} and _γ-Al 2 _{O 3} were the same as those used in Synthesis Example 7.

As will be z = 0.6 in using the molar mixing ratio z of raw material expression of the entire starting material _{(1-z) Fe 2 O} 3 + zAl represented by expressions 2 _{O 3,} and _γ-Fe 2 _{O 3} γ-Al ₂ O ₃ was mixed and mechanochemically synthesized at room temperature using a planetary ball mill premium line P-7 manufactured by Fritsch. Under the same synthesis conditions as in Synthesis Example 3, the mixture was mixed twice for a total of 60 minutes.

FIG. 9 shows an XRD pattern of the manufactured oxide. No peak attributed to γ-Fe ₂ O ₃ was observed. On the other hand, many peaks that can be indexed by the corundum structure appeared. All the peaks were observed between the X-ray diffraction peak position of the corundum structure α-Al ₂ O _{3 and} the X-ray diffraction peak position of the corundum structure α-Fe ₂ O ₃ . This is presumably because this oxide is a solid solution of α-Fe ₂ O ₃ and α-Al ₂ O ₃ .

From the XRD pattern, the lattice constants of the a-axis and c-axis from the peak position of the reflection index 024 (2θ = 51.21) and the peak position of the reflection index 116 (2θ = 56.01 degrees) in the corundum structure (hexagonal lattice). Was calculated. Table 1 shows the lattice constants of the a-axis and c-axis and the unit cell volume obtained from the lattice constant. Furthermore, when the value of x of the prepared solid solution (Fe _1-x Al _x ) ₂ O ₃ (0 <x <1) was calculated in the same manner as in Synthesis Example 1, x = 0.583 was obtained. This value is sufficiently close to the molar mixing ratio of the raw materials of γ-Fe ₂ O ₃ and γ-Al ₂ O ₃ , indicating that the solid solution synthesis reaction was performed smoothly.

Synthesis Example 9 (Oxide Preparation by Mechanochemical Synthesis Method of γ-Fe ₂ O ₃ and γ-Al ₂ O ₃ )
_γ-Fe 2 _{O 3} and _γ-Al 2 _{O 3} were the same as those used in Synthesis Example 7.

Γ-Fe ₂ O ₃ and γ-Fe ₂ O ₃ so that the formula of the whole starting material is z = 0.5 in the formula (1-z) Fe ₂ O ₃ + zAl ₂ O ₃ using the molar mixing ratio z of the raw materials γ-Al ₂ O ₃ was mixed and mechanochemically synthesized at room temperature using a planetary ball mill premium line P-7 manufactured by Fritsch. Under the same synthesis conditions as in Synthesis Example 3, the mixture was mixed twice for a total of 60 minutes.

FIG. 10 shows an XRD pattern of the manufactured oxide. No peak attributed to γ-Fe ₂ O ₃ was observed. On the other hand, many peaks that can be indexed by the corundum structure appeared. All the peaks were observed between the X-ray diffraction peak position of the corundum structure α-Al ₂ O _{3 and} the X-ray diffraction peak position of the corundum structure α-Fe ₂ O ₃ . This is presumably because this oxide is a solid solution of α-Fe ₂ O ₃ and α-Al ₂ O ₃ .

From the XRD pattern, the lattice constants of the a-axis and c-axis from the peak position of the reflection index 024 (2θ = 50.88) and the peak position of the reflection index 116 (2θ = 55.67 degrees) in the corundum structure (hexagonal lattice). Was calculated. Table 1 shows the lattice constants of the a-axis and c-axis and the unit cell volume obtained from the lattice constant. Further, in the same manner as in Synthesis Example 1, the x value of the produced solid solution (Fe _1-x Al _x ) ₂ O ₃ (0 <x <1) was calculated, and x = 0.479 was obtained. This value is sufficiently close to the molar mixing ratio of the raw materials of γ-Fe ₂ O ₃ and γ-Al ₂ O ₃ , indicating that the solid solution synthesis reaction was performed smoothly.

Synthesis Example 10 (Oxide Preparation by Mechanochemical Synthesis Method of γ-Fe ₂ O ₃ and β-Ga ₂ O ₃ )
_γ-Fe 2 _{O 3} were the same as those used in Synthesis Example 7. As Ga ₂ O ₃ , Wako Pure Chemical's 99.99% pure (β-Ga ₂ O ₃ ) was used.

Using the molar mixing ratio z of the raw materials, γ-Fe ₂ O ₃ and γ-Fe ₂ O ₃ so that the formula of the entire starting material is z = 0.5 in the formula represented by (1-z) Fe ₂ O ₃ + zGa ₂ O ₃ β-Ga ₂ O ₃ was mixed and mechanochemically synthesized at room temperature using a planetary ball mill premium line P-7 manufactured by Fritsch. Under the same synthesis conditions as in Synthesis Example 3, the mixture was mixed twice for a total of 60 minutes.

FIG. 11 shows an XRD pattern of the manufactured oxide. No peak attributed to γ-Fe ₂ O ₃ was observed. On the other hand, many peaks that can be indexed by the corundum structure appeared. All peaks were observed between the X-ray diffraction peak position of the corundum structure α-Fe ₂ O ₃ and the same X-ray diffraction peak position of the corundum structure α-Ga ₂ O ₃ . This is presumably because this oxide is a solid solution of α-Fe ₂ O ₃ and α-Ga ₂ O ₃ .

From the XRD pattern, the lattice constants of the a-axis and c-axis from the peak position of the reflection index 024 (2θ = 49.82) and the peak position of the reflection index 116 (2θ = 54.56 degrees) in the corundum structure (hexagonal lattice). Was calculated. Table 1 shows the lattice constants of the a-axis and c-axis and the unit cell volume obtained from the lattice constant. Furthermore, the calculated values of the lattice constants of the a-axis and c-axis of the solid solution represented by the chemical formula (Fe _1-x Ga _x ) ₂ O ₃ (0 <x <1) are expressed as α-Fe ₂ O given to JCPDS. Using the lattice constants of ₃ and α-Ga ₂ O ₃ , based on Vegard's law, it is given as a function of x, and this can be used to give a calculated unit cell volume as a function of x. The value of x can be determined when this is equal to the measured value of the unit cell volume of the solid solution prepared by the mechanochemical synthesis method. When the value of x of the produced solid solution (Fe _1-x Ga _x ) ₂ O ₃ (0 <x <1) was calculated, x = 0.532 was obtained. This value is sufficiently close to the molar mixing ratio of the raw materials of γ-Fe ₂ O ₃ and β-Ga ₂ O ₃ , indicating that the solid solution synthesis reaction was performed smoothly.

Synthesis Example 11 (Preparation of oxide by mechanochemical synthesis of γ-Fe ₂ O ₃ and γ-Al ₂ O ₃ )
_γ-Fe 2 _{O 3} and _γ-Al 2 _{O 3} were the same as those used in Synthesis Example 7.
Using the molar mixing ratio z of the raw materials, γ-Fe ₂ O ₃ and γ-Fe ₂ O ₃ so that the formula of the whole starting raw material becomes z = 0.45 in the formula represented by (1-z) Fe ₂ O ₃ + zAl ₂ O ₃ γ-Al ₂ O ₃ was mixed and mechanochemically synthesized at room temperature using a planetary ball mill premium line P-7 manufactured by Fritsch. Under the same synthesis conditions as in Synthesis Example 3, the mixture was mixed twice for a total of 60 minutes.

FIG. 12 shows an XRD pattern of the manufactured oxide. No peak attributed to γ-Fe ₂ O ₃ was observed. On the other hand, many peaks that can be indexed by the corundum structure appeared. All the peaks were observed between the X-ray diffraction peak position of the corundum structure α-Al ₂ O _{3 and} the X-ray diffraction peak position of the corundum structure α-Fe ₂ O ₃ . This is presumably because this oxide is a solid solution of α-Fe ₂ O ₃ and α-Al ₂ O ₃ .

From the XRD pattern, the lattice constants of the a-axis and c-axis from the peak position of the reflection index 024 (2θ = 50.76) and the reflection index 116 (2θ = 55.51 degrees) in the corundum structure (hexagonal lattice). Was calculated. Table 1 shows the lattice constants of the a-axis and c-axis and the unit cell volume obtained from the lattice constant. Further, in the same manner as in Synthesis Example 1, the value of x of the produced solid solution (Fe _1-x Al _x ) ₂ O ₃ (0 <x <1) was calculated, and x = 0.437 was obtained. This value is sufficiently close to the molar mixing ratio of the raw materials of γ-Fe ₂ O ₃ and γ-Al ₂ O ₃ , indicating that the solid solution synthesis reaction was performed smoothly.

Synthesis Example 12 (Oxide Preparation by Mechanochemical Synthesis Method of γ-Fe ₂ O ₃ and γ-Al ₂ O ₃ )
_γ-Fe 2 _{O 3} and _γ-Al 2 _{O 3} were the same as those used in Synthesis Example 7.
Using the molar mixing ratio z of the raw materials, γ-Fe ₂ O ₃ and γ-Fe ₂ O ₃ so that the formula of the whole starting raw material becomes z = 0.65 in the formula represented by (1-z) Fe ₂ O ₃ + zAl ₂ O ₃ γ-Al ₂ O ₃ was mixed and mechanochemically synthesized at room temperature using a planetary ball mill premium line P-7 manufactured by Fritsch. Under the same synthesis conditions as in Synthesis Example 3, the mixture was mixed twice for a total of 60 minutes.

FIG. 13 shows an XRD pattern of the manufactured oxide. No peak attributed to γ-Fe ₂ O ₃ was observed. On the other hand, many peaks that can be indexed by the corundum structure appeared. All the peaks were observed between the X-ray diffraction peak position of the corundum structure α-Al ₂ O _{3 and} the X-ray diffraction peak position of the corundum structure α-Fe ₂ O ₃ . This is presumably because this oxide is a solid solution of α-Fe ₂ O ₃ and α-Al ₂ O ₃ .

From the above XRD pattern, the a-axis and c-axis lattice constants from the peak position of the reflection index 024 (2θ = 51.38) and the peak position of the reflection index 116 (2θ = 56.19 degrees) in the corundum structure (hexagonal lattice). Was calculated. Table 1 shows the lattice constants of the a-axis and c-axis and the unit cell volume obtained from the lattice constant. Further, in the same manner as in Synthesis Example 1, the value of x of the produced solid solution (Fe _1-x Al _x ) ₂ O ₃ (0 <x <1) was calculated, and x = 0.537 was obtained. This value is sufficiently close to the molar mixing ratio of the raw materials of γ-Fe ₂ O ₃ and γ-Al ₂ O ₃ , indicating that the solid solution synthesis reaction was performed smoothly.

Synthesis Example 13 (Oxide Preparation by Mechanochemical Synthesis Method of γ-Fe ₂ O ₃ and γ-Al ₂ O ₃ )
_γ-Fe 2 _{O 3} and _γ-Al 2 _{O 3} were the same as those used in Synthesis Example 7.
Using the molar mixing ratio z of the raw materials, γ-Fe ₂ O ₃ and γ-Fe ₂ O ₃ so that the formula of the entire starting material is z = 0.05 in the formula represented by (1-z) Fe ₂ O ₃ + zAl ₂ O ₃ γ-Al ₂ O ₃ was mixed and mechanochemically synthesized at room temperature using a planetary ball mill premium line P-7 manufactured by Fritsch. Under the same synthesis conditions as in Synthesis Example 3, the mixture was mixed twice for a total of 60 minutes.

FIG. 14 shows an XRD pattern of the manufactured oxide. No peak attributed to γ-Fe ₂ O ₃ was observed. On the other hand, many peaks that can be indexed by the corundum structure appeared. All the peaks were observed between the X-ray diffraction peak position of the corundum structure α-Al ₂ O _{3 and} the X-ray diffraction peak position of the corundum structure α-Fe ₂ O ₃ . This is presumably because this oxide is a solid solution of α-Fe ₂ O ₃ and α-Al ₂ O ₃ .

From the XRD pattern, the a-axis and c-axis lattice constants from the peak position of the reflection index 024 (2θ = 49.69) and the peak position of the reflection index 116 (2θ = 54.29 degrees) in the corundum structure (hexagonal lattice). Was calculated. Table 1 shows the lattice constants of the a-axis and c-axis and the unit cell volume obtained from the lattice constant. Further, in the same manner as in Synthesis Example 1, when the value of x of the produced solid solution (Fe _1-x Al _x ) ₂ O ₃ (0 <x <1) was calculated, x = 0.077 was obtained. This value is sufficiently close to the molar mixing ratio of the raw materials of γ-Fe ₂ O ₃ and γ-Al ₂ O ₃ , indicating that the solid solution synthesis reaction was performed smoothly.

Synthesis Example 14 (Oxide Preparation by Mechanochemical Synthesis Method of γ-Fe ₂ O ₃ and γ-Al ₂ O ₃ )
_γ-Fe 2 _{O 3} and _γ-Al 2 _{O 3} were the same as those used in Synthesis Example 7.
Using the molar mixing ratio z of the raw materials, γ-Fe ₂ O ₃ and γ-Fe ₂ O ₃ so that the formula of the entire starting raw material becomes z = 0.95 in the formula (1-z) Fe ₂ O ₃ + zAl ₂ O ₃ γ-Al ₂ O ₃ was mixed and mechanochemically synthesized at room temperature using a planetary ball mill premium line P-7 manufactured by Fritsch. Under the same synthesis conditions as in Synthesis Example 3, the mixture was mixed twice for a total of 60 minutes.

FIG. 15 shows an XRD pattern of the manufactured oxide. peak attributed to _γ-Fe 2 _{O 3} was observed. On the other hand, many peaks that can be indexed by the corundum structure appeared. All the peaks were observed between the X-ray diffraction peak position of the corundum structure α-Al ₂ O _{3 and} the X-ray diffraction peak position of the corundum structure α-Fe ₂ O ₃ . This is presumably because this oxide is a solid solution of α-Fe ₂ O ₃ and α-Al ₂ O ₃ . Incidentally, the peaks at around 27 degrees, around 34 degrees, around 36 degrees, and around 41 degrees, which cannot be indexed with the corundum structure, are due to β-Si ₃ N ₄ mixed from the milling medium and the container. .

From the XRD pattern, the lattice constants of the a-axis and c-axis from the peak position of the reflection index 024 (2θ = 52.38) and the peak position of the reflection index 116 (2θ = 57.34 degrees) in the corundum structure (hexagonal lattice). Was calculated. Table 1 shows the lattice constants of the a-axis and c-axis and the unit cell volume obtained from the lattice constant. Furthermore, when the value of x of the produced solid solution (Fe _1-x Al _x ) ₂ O ₃ (0 <x <1) was calculated in the same manner as in Synthesis Example 1, x = 0.957 was obtained. This value is sufficiently close to the molar mixing ratio of the raw materials of γ-Fe ₂ O ₃ and γ-Al ₂ O ₃ , indicating that the solid solution synthesis reaction was performed smoothly.

Example 1
(Beaker cell production)
AB and PTFE are mixed with the composite material prepared in Synthesis Example 1 so that the composite material: acetylene black (AB): polytetrafluoroethylene (PTFE) is 70: 30: 2 (weight ratio), and ground in a mortar. After that, it was pressure-bonded to a copper mesh and dried in a vacuum at 150 ° C. for 12 hours to produce a working electrode.

Next, a three-electrode beaker cell using metallic lithium as a counter electrode and a reference electrode was produced in a glove box under an argon atmosphere. As the electrolytic solution, 1M LiClO ₄ ethylene carbonate-dimethoxyethane (EC-DME = 1: 1 (volume ratio)) solvent was used.

(Charge / discharge measurement)
The charge / discharge measurement was performed at a current density of 0.1 A / g and in a potential range of 0.1 to 3.5 V (vs. Li ⁺ / Li).

Example 2
A beaker cell was produced and charge / discharge measurement was performed in the same manner as in Example 1 except that the working electrode was produced using the composite material prepared in Synthesis Example 2.

Example 3
A beaker cell was prepared and charge / discharge measurement was performed in the same manner as in Example 1 except that the working electrode was prepared using the composite material prepared in Synthesis Example 3.

Example 4
A beaker cell was prepared and charge / discharge measurement was performed in the same manner as in Example 1 except that the working electrode was prepared using the composite material prepared in Synthesis Example 4.

Example 5
A beaker cell was produced and charge / discharge measurement was performed in the same manner as in Example 1 except that the working electrode was produced using the composite material prepared in Synthesis Example 5.

Example 6
A beaker cell was prepared and charge / discharge measurement was performed in the same manner as in Example 1 except that the working electrode was prepared using the composite material prepared in Synthesis Example 6.

Example 7
A beaker cell was prepared and charge / discharge measurement was performed in the same manner as in Example 1 except that the working electrode was prepared using the composite material prepared in Synthesis Example 7.

Example 8
A beaker cell was produced and charge / discharge measurement was performed in the same manner as in Example 1 except that the working electrode was produced using the composite material prepared in Synthesis Example 8.

Example 9
A beaker cell was produced and charge / discharge measurement was performed in the same manner as in Example 1 except that the working electrode was produced using the composite material prepared in Synthesis Example 9.

Example 10
A beaker cell was produced and charge / discharge measurement was performed in the same manner as in Example 1 except that the working electrode was produced using the composite material prepared in Synthesis Example 10.

Example 11
A beaker cell was produced and charge / discharge measurement was performed in the same manner as in Example 1 except that the working electrode was produced using the composite material prepared in Synthesis Example 11.

Example 12
A beaker cell was produced and charge / discharge measurement was performed in the same manner as in Example 1 except that the working electrode was produced using the composite material prepared in Synthesis Example 12.

Example 13
A beaker cell was prepared and charge / discharge measurement was performed in the same manner as in Example 1 except that the working electrode was prepared using the composite material prepared in Synthesis Example 13.

Example 14
Production of beaker cells and charge / discharge measurement were performed in the same manner as in Example 1 except that the working electrode was produced using the composite material prepared in Synthesis Example 14.

Comparative Example 1
Only γ-Fe ₂ O ₃ was subjected to solid phase mixing at room temperature using a planetary ball mill premium line P-7 manufactured by Fritsch. Under the same mixing conditions as in Synthesis Example 3, mixing was performed 8 times for a total of 240 minutes. _gamma-Fe 2 _{O 3} were the same as those used in Synthesis Example 3.

FIG. 16 shows an XRD pattern of the manufactured oxide. A peak attributed to γ-Fe ₂ O ₃ and a peak attributed to α-Fe ₂ O ₃ were confirmed.

A beaker cell was prepared and charge / discharge measurement was performed in the same manner as in Example 1 except that a working electrode was prepared using γ-Fe ₂ O ₃ mixed in a solid phase.

Comparative Example 2
Only α-Fe ₂ O ₃ was subjected to solid phase mixing at room temperature using a planetary ball mill premium line P-7 manufactured by Fritsch. Under the same mixing conditions as in Synthesis Example 3, the mixture was mixed 8 times for a total of 240 minutes. The same α-Fe ₂ O ₃ as in Synthesis Example 3 was used.

FIG. 17 shows an XRD pattern of the manufactured oxide. A peak attributed to α-Fe ₂ O ₃ was confirmed.

A beaker cell was prepared and charge / discharge measurement was performed in the same manner as in Example 1 except that a working electrode was prepared using α-Fe ₂ O ₃ mixed in a solid phase.

(result)
FIG. 18 shows the charge / discharge curve of Example 1, FIG. 33 shows the charge / discharge curve of Comparative Example 1, and FIG. 35 shows the charge / discharge curve of Comparative Example 2. In either case, charging / discharging was possible in a potential range of 0.1 to 3.5 V (vs. Li ⁺ / Li).

  19 to 32 show the charge / discharge cycle characteristics of Examples 1 to 14, FIG. 34 shows the charge / discharge cycle characteristics of Comparative Example 1, and FIG. 36 shows the charge / discharge cycle characteristics of Comparative Example 2. Table 2 shows the specific capacity and specific capacity retention after a certain cycle (ratio of specific capacity after a predetermined cycle to the specific capacity of the first cycle (%)). When the specific capacity at the 100th cycle was compared, it was about 100 mAh / g in Example 1 and about 75 mAh / g in Example 2, whereas it was 3 mAh / g in Comparative Example 1. Considering that the amount of active material of Example 1 and Example 2 is approximately half that of Comparative Example 1, according to the present invention, the irreversible capacity can be reduced and the charge / discharge cycle characteristics can be improved. In particular, in Example 1, at least 500 cycles were possible, and even at the 500th cycle, it had a specific capacity of about 200 mAh / g and had excellent charge / discharge cycle characteristics.

  As described above, since the oxide of the present invention can greatly improve the charge / discharge characteristics when used in an active material, a non-aqueous secondary battery having excellent charge / discharge cycle characteristics at a lower cost and higher capacity can be obtained. It becomes possible to provide.

Claims (14)

An oxide having a corundum structure represented by a chemical formula (Fe _1-x M _x ) ₂ O ₃ (where M is at least one typical metal element, and 0 <x <1).   The oxide according to claim 1, wherein the element M is a Group 13 element.   The oxide according to claim 2, wherein the element M is Al and / or Ga.   The oxide according to claim 2, wherein the element M is Al.   The oxide according to claim 2, wherein the element M is Ga.   2. The oxide according to claim 1, wherein the range of x is 0.4 <x <0.67. A mixture of γ-Fe ₂ O ₃ and at least one metal oxide was synthesized by a mechanochemical synthesis method, and a chemical formula (Fe _1-x M _x ) ₂ O ₃ (where M is at least one metal element) , 0 <x <1). A method for producing an oxide, which produces an oxide having a corundum type structure represented by:   The manufacturing method according to claim 7, wherein the metal oxide is an oxide of a typical metal element.   The manufacturing method according to claim 7, wherein the metal oxide is an oxide of a Group 2 element and / or a Group 13 element. The method according to claim 8, wherein the metal oxide is γ-Al ₂ O ₃ . The manufacturing method according to claim 8, wherein the metal oxide is Ga ₂ O ₃ .   An active material for a non-aqueous secondary battery comprising the oxide according to claim 1.   A non-aqueous secondary battery comprising a positive electrode comprising the oxide according to claim 1 as a positive electrode active material, a negative electrode, and a non-aqueous electrolyte.   A nonaqueous secondary battery comprising a negative electrode comprising the oxide according to claim 1 as a negative electrode active material, a positive electrode, and a nonaqueous electrolyte.

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