JP6236956B2 - Positive electrode active material, positive electrode, lithium ion secondary battery and sodium ion secondary battery - Google Patents

Description

  The present invention relates to a positive electrode active material, a positive electrode, a lithium ion secondary battery, and a sodium ion secondary battery.

Conventionally, a layered compound such as LiCoO ₂ or LiNi _1/3 Mn _1/3 Co _1/3 O ₂ or a spinel compound such as LiMn ₂ O ₄ has been used as a positive electrode material (positive electrode active material) of a lithium ion secondary battery. It was. In recent years, compounds of phosphoric acid positive electrode materials such as LiFePO ₄ , LiMnPO ₄ , LiCoPO ₄ , LiNiPO ₄ , LiVOPO ₄ , Li ₃ V ₂ (PO ₄ ) ₃ , and Li ₄ VO (PO ₄ ) ₂ have attracted attention. . These positive electrode materials are known to have high thermal stability at high temperatures and high safety. Among these positive electrode materials, in particular, Li ₄ VO (PO ₄ ) ₂ has a very high theoretical capacity of 377 mAh / g, but in a lithium ion secondary battery using this positive electrode material, the actual capacity is 70 mAh / g. It is as follows and sufficient reversible capacity is not obtained (nonpatent literature 1).

M.M. Satya Kisore et al. Electrochemistry Communications 8 (2006) 1558-1562

  The present invention has been made in view of the above-mentioned problems of the prior art, and is capable of obtaining a sufficient charge / discharge capacity of a lithium ion secondary battery, a positive electrode and a lithium ion secondary battery, or sodium. An object is to provide an ion secondary battery.

In order to achieve the above object, a positive electrode active material according to the present invention is a compound represented by Li _5-x VO (PO ₄ ) ₂ (0 ≦ x <5), and X using Cu Kα rays. in ray diffraction measurement, when a peak intensity appearing in the range diffraction angle 2θ of 12 to 16 ° and _{a 1,} and a peak intensity appearing in the range of diffraction angle 2θ is 19 to 23 ° and _{B 1, B 1} / _{a 1} Is 0.6 to 8.0.

  According to such a positive electrode active material, a sufficient charge / discharge capacity can be obtained. Since such a positive electrode active material has a structure in which lithium is easily inserted and extracted, the charge / discharge capacity is increased.

The positive electrode active material according to the present invention is M _5-y H _z VO (PO ₄ ) ₂ (0 ≦ y <5, 0 ≦ z <4, 0 ≦ y−z <5, M = Li, Na). In the X-ray diffraction measurement using Cu Kα ray, the peak intensity appearing in the range of 12 to 16 ° is A ₂ and the diffraction angle 2θ is in the range of 19 to 23 °. B ₂ / A ₂ is 0.6 to 8.0, where B ₂ is the peak intensity appearing in FIG.

  According to such a positive electrode active material, a sufficient charge / discharge capacity can be obtained. Since such a positive electrode active material has a structure in which lithium and sodium can be easily inserted and extracted, the charge / discharge capacity is increased.

  ADVANTAGE OF THE INVENTION According to this invention, the positive electrode active material which can obtain sufficient charging / discharging capacity | capacitance, the positive electrode using the same, a lithium ion secondary battery, and a sodium ion secondary battery can be provided.

It is a schematic cross section of the lithium ion secondary battery according to the present embodiment.

<First Embodiment>
(Positive electrode active material)
The positive electrode active material of the first embodiment (hereinafter also referred to as “active material”) is a compound represented by Li _5-x VO (PO ₄ ) ₂ (0 ≦ x <5), and is made of Cu. in X-ray diffraction measurement using a Kα line, the measurement conditions _{CuKα 1 = 1.540562Å, CuKα 2 =} 1.544398Å, CuKα 2 without removal, tube voltage 40 kV, tube current 40 mA, divergence slit 1/2 °, diverging vertical limiting slit 10 mm, scanning speed 5.0 ° / min, when the sampling width 0.01 °, the maximum value of the peak intensity diffraction angle 2θ appears in the range of 12 to 16 ° and _{a 1,} the diffraction angle 2θ is When the maximum value of the peak intensity appearing in the range of 19 to 23 ° is B ₁ , B ₁ / A ₁ is 0.6 to 8.0. In X-ray diffraction measurement using a concentrated optical system, the sample to be measured is mixed with an amorphous material in order to suppress the influence of selective orientation derived from the particle shape such as a plate shape or a needle shape. Further, it is necessary to fabricate the film by spray coating an amorphous organic material.

In the positive electrode active material, when the theoretical capacity is as high as 377 mAh / g and B ₁ / A ₁ is 0.6 to 8.0, when it is used for the positive electrode of a lithium ion secondary battery, the insertion and desorption of lithium is not It becomes the structure which is easy to do, and charging / discharging capacity improves.

B ₁ / A ₁ is more preferably 1.2 to 4.1, and still more preferably 1.6 to 3.1. Thereby, when it uses for the positive electrode of a lithium ion secondary battery, insertion / extraction of lithium ion becomes easier, and charge / discharge capacity improves.

  In the positive electrode active material, the value of x is preferably 1 to 4, and more preferably 1.6 to 3.5. Thereby, when it uses for the positive electrode of a lithium ion secondary battery, insertion / extraction of lithium ion becomes easier, and charge / discharge capacity improves.

  When used as a lithium ion secondary battery, the valence of V is further changed and the charge / discharge capacity is increased by using Li metal for the negative electrode or a commonly used negative electrode containing Li.

  In the positive electrode active material, by substituting Li, V, and P in the crystal structure with other elements, the charge / discharge capacity can be controlled and the crystal structure can be stabilized.

  In this case, specific examples of the element substituting for Li include one or more selected from the group consisting of H, Na, K, Mg, Ca, Ti, Zr, and Nb. Specific examples of elements that substitute V are Na, K, Rb, Cs, Ca, Sr, Sc, Y, Ta, Al, Fe, Co, Ga, Bi, Sn, Cr, Cu, Zn, Mg , Ti, Ge, Ta, Mo, W, Nb, Ni, Mn, and one or more selected from the group consisting of B and B. Specific examples of the element that substitutes P include one or more selected from the group consisting of V, Si, N, S, and Ge.

  If the amount of substitution of these elements is too large, the battery capacity will be too low. Therefore, it is usually 0.5 or less, preferably 0.2 or less, more preferably 0.1 or less with respect to Li, V and P before substitution. Substitution can be made within the following molar ratio range.

(Method for producing positive electrode active material)
Below, the manufacturing method of the active material which concerns on 1st Embodiment is demonstrated. According to the method for producing an active material according to the present embodiment, the active material according to the present embodiment described above can be formed.

<Reflux process>
The manufacturing method of the active material according to the present embodiment includes the following reflux process. First, a phosphoric acid source, a vanadium source, a lithium source, and an alcohol described later are added to prepare a mixture (aqueous solution) in which these are dispersed.

As the phosphoric acid source, for example, at least one selected from the group consisting of H ₃ PO ₄ , NH ₄ H ₂ PO ₄ , (NH ₄ ) 2 HPO ₄ and Li ₃ PO ₄ can be used.

As the vanadium source, for example, at least one selected from the group consisting of V ₂ O ₅ and NH ₄ VO ₃ can be used.

As the lithium source, for example, at least one selected from the group consisting of LiBr, LiF, LiNO ₃ , Li ₂ CO ₃ , LiOH, LiCl, Li ₂ SO ₄ and CH ₃ COOLi can be used.

  Two or more phosphate sources, two or more vanadium sources, or two or more lithium sources may be used in combination.

  Examples of the alcohol source include ethanol, methanol, propanol, butanol, 1-hexanol, 2-hexanol, 3-hexanol, 1-octanol, 2-octanol, 3-octanol, 2-methyl-1-pentanol, 3- Methyl-1 pentanol, 4-methyl-1 pentanol, 2-methyl-2 pentanol, 3-methyl-2-pentanol, 4-methyl-2-pentanol, 2-methyl-3-pentanol 3- Methyl-3-pentanol, 2,2-dimethyl-1-butanol, 2,3-dimethyl-1-butanol, 3,3-dimethyl-1-butanol, 2,3-dimethyl-2-butanol, 3,3 At least one selected from the group consisting of -dimethyl-2-butanol can be used.

  In the refluxing step, a reducing agent may be added. As the reducing agent, for example, hydrazine, ascorbic acid, citric acid, tartaric acid, or hydrogen peroxide can be used.

  What is necessary is just to adjust suitably the time heated in a recirculation | reflux process according to the quantity of a mixture.

In the refluxing step, the mixture is preferably heated to 100 to 250 ° C, more preferably 120 to 200 ° C. The higher the heating temperature of the mixture, the more the crystal growth is promoted, and it becomes easier to obtain a Li _5-x VO (PO ₄ ) ₂ type crystal having a large particle size.

<Heat treatment process>
The method for producing an active material according to the present embodiment may include a heat treatment step for further heating the mixture after the reflux step. By the heat treatment step, the reaction of the lithium source, the phosphate source and the vanadium source that did not react in the reflux step proceeds, or the crystal growth of Li _5-x VO (PO ₄ ) ₂ generated in the reflux step is promoted. be able to. As a result, the capacity density of Li _5-x VO (PO ₄ ) ₂ is improved, and the discharge capacity and rate characteristics of a battery using the same tend to be improved.

In the heat treatment step, the mixture is preferably heated at a heat treatment temperature of 250 to 600 ° C. When the heat treatment temperature is too low, the crystal growth degree of Li _5-x VO (PO ₄ ) ₂ tends to be small and the capacity density improvement tends to be small. If the heat treatment temperature is too _{high, Li 5-x VO (PO 4} ) 2 growth proceeds _excessively, the particle size of the _{Li 5-x VO (PO 4} ) 2 tends to increase. As a result, the diffusion of lithium in the active material is slow, and the improvement in the capacity density of the active material tends to be small. By setting the heat treatment temperature within the above range, these tendencies can be suppressed.

  The heat treatment time of the mixture is preferably 3 to 20 hours. The heat treatment atmosphere of the mixture is preferably a nitrogen atmosphere, an argon atmosphere, or an air atmosphere.

In addition, you may preheat the mixture obtained at a recirculation | reflux process at about 60-150 degreeC for about 1 to 30 hours before heating at a heat treatment process. By preheating, the mixture becomes powder, and excess water and organic solvent are removed from the mixture. As a result, it is possible to prevent impurities from being taken into Li _5-x VO (PO ₄ ) ₂ in the heat treatment step and to make the particle shape uniform.

B ₁ / A ₁ of the diffraction angle 2θ can be adjusted by controlling the raw material composition, the heat treatment temperature, the heat treatment time, and the heat treatment atmosphere in the reflux process or the heat treatment process.

  As mentioned above, although suitable one Embodiment of the manufacturing method of the active material which concerns on this invention was described in detail, this invention is not limited to the said embodiment.

(Lithium ion secondary battery)
Next, the electrode and the lithium ion secondary battery according to this embodiment will be briefly described with reference to FIG.

  The lithium ion secondary battery 100 mainly includes a power generation element 30, a case 50 that houses the power generation element 30 in a sealed state, and a pair of leads 60 and 62 connected to the power generation element 30.

  The power generation element 30 is configured such that a pair of electrodes 10 and 20 are disposed to face each other with the separator 18 interposed therebetween. The positive electrode 10 is a product in which a positive electrode active material layer 14 is provided on a positive electrode current collector 12. The negative electrode 20 is a product in which a negative electrode active material layer 24 is provided on a negative electrode current collector 22. The positive electrode active material layer 14 and the negative electrode active material layer 24 are in contact with both sides of the separator 18. An electrolyte solution is contained inside the positive electrode active material layer 14, the negative electrode active material layer 24, and the separator 18. Leads 60 and 62 are connected to the end portions of the positive electrode current collector 12 and the negative electrode current collector 22, respectively, and the end portions of the leads 60 and 62 extend to the outside of the case 50.

(Positive electrode)
As the positive electrode current collector 12 of the positive electrode 10, for example, an aluminum foil or the like can be used. The positive electrode active material layer 14 is a layer containing a positive electrode active material, a binder, and a conductive material added as necessary. Examples of the conductive material added as necessary include carbon blacks, carbon materials, and conductive oxides such as ITO.

  The binder is not particularly limited as long as the positive electrode active material and the conductive material can be bound to the current collector, and a known binder can be used. Examples thereof include fluororesins such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and vinylidene fluoride-hexafluoropropylene copolymer.

  Such a positive electrode 10 is obtained by a known method, for example, an electrode active material including a positive electrode active material, a binder, and a conductive material, a solvent corresponding to the type thereof, for example, N-methyl-2-pyrrolidone in the case of PVDF, It can be produced by applying a slurry added to a solvent such as N, N-dimethylformamide on the surface of the positive electrode current collector 12 and drying it.

  As the negative electrode current collector 22, a copper foil or the like can be used. Moreover, as the negative electrode active material layer 24, the thing containing a negative electrode active material, a electrically conductive material, and a binder can be used. It does not specifically limit as a electrically conductive material, A well-known electrically conductive material can be used. Examples thereof include carbon blacks, carbon materials, metal powders such as copper, nickel, stainless steel, and iron, mixtures of carbon materials and metal powders, and conductive oxides such as ITO. As the binder used for the negative electrode, known binders can be used without any particular limitation. For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), ethylene-tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), ethylene-chlorotrifluoroethylene copolymer ( Fluorine resins such as ECTFE and polyvinyl fluoride (PVF).

Examples of the negative electrode active material include graphite, non-graphitizable carbon, graphitizable carbon, and low-temperature calcined carbon that can occlude / release (intercalate / deintercalate, or dope / dedope) lithium ions. Carbon materials, metals that can be combined with lithium such as Al, Si, and Sn, amorphous compounds mainly composed of oxides such as SiO ₂ and SnO ₂ , lithium titanate (Li ₄ Ti ₅ O ₁₂ ), etc. The particle | grains containing are mentioned.

  The manufacturing method of the negative electrode 20 should just adjust slurry and apply | coat to a collector like the manufacturing method of the positive electrode 10. FIG.

The electrolyte solution is contained in the positive electrode active material layer 14, the negative electrode active material layer 24, and the separator 18. The electrolyte solution is not particularly limited. For example, in the present embodiment, an electrolyte solution containing a lithium salt (electrolyte aqueous solution, electrolyte solution using an organic solvent) can be used. However, the electrolyte aqueous solution is preferably an electrolyte solution (non-aqueous electrolyte solution) using an organic solvent because the electrochemical decomposition voltage is low, and the withstand voltage during charging is limited to a low level. As the electrolyte solution, a lithium salt dissolved in a non-aqueous solvent (organic solvent) is preferably used. Examples of the lithium salt include LiPF ₆ , LiClO ₄ , LiBF ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiCF ₃ , CF ₂ SO ₃ , LiC (CF ₃ SO ₂ ) ₃ , LiN (CF ₃ SO ₂ ) ₂ , A salt such as LiN (CF ₃ CF ₂ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), LiN (CF ₃ CF ₂ CO) ₂ , or LiBOB can be used. In addition, these salts may be used individually by 1 type, and may use 2 or more types together.

  Moreover, as an organic solvent, propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate etc. are mentioned preferably, for example. These may be used alone or in combination of two or more at any ratio.

  In the present embodiment, the electrolyte solution may be a gel electrolyte obtained by adding a gelling agent in addition to liquid. Further, instead of the electrolyte solution, a solid electrolyte (a solid polymer electrolyte or an electrolyte made of an ion conductive inorganic material) may be contained.

  The separator 18 may also be formed of an electrically insulating porous structure, for example, a single layer of a film made of polyethylene, polypropylene or polyolefin, a stretched film of a laminate or a mixture of the above resins, or cellulose. And a fiber nonwoven fabric made of at least one constituent material selected from the group consisting of polyester and polypropylene.

  The case 50 seals the power generation element 30 and the electrolyte solution therein. The case 50 is not particularly limited as long as it can suppress leakage of the electrolyte solution to the outside and entry of moisture or the like into the lithium ion secondary battery 100 from the outside. For example, as the case 50, as shown in FIG. 1, a metal laminate film in which a metal foil 52 is coated with a polymer film 54 from both sides can be used. For example, an aluminum foil can be used as the metal foil 52, and a film such as polypropylene can be used as the synthetic resin film 54. For example, the material of the outer polymer film 54 is preferably a polymer having a high melting point such as polyethylene terephthalate (PET) or polyamide, and the material of the inner polymer film 54 is preferably polyethylene or polypropylene.

  The leads 60 and 62 are made of a conductive material such as aluminum.

  As described above, the preferred embodiment of the positive electrode active material, the electrode including the positive electrode active material, and the method of manufacturing the lithium ion secondary battery including the electrode has been described in detail, but the present invention is limited to the above embodiment. It is not a thing.

Second Embodiment
Hereinafter, the second embodiment of the present invention will be described focusing on differences from the first embodiment.

The positive electrode active material of the second embodiment (hereinafter also referred to as “active material”) is M _5-y H _z VO (PO ₄ ) ₂ (0 ≦ y <5, 0 ≦ z <4, 0 ≦ yz <5, M = Li, Na). As described in the first embodiment, the X-ray diffraction measurement using the Kα line of Cu, the measurement conditions _{CuKα 1 = 1.540562Å, CuKα 2 =} 1.544398Å, CuKα 2 without removal, tube voltage 40 kV, tube current The peak intensity appears when the diffraction angle 2θ is in the range of 12 to 16 ° when 40 mA, the divergence slit is 1/2 °, the divergence length restriction slit is 10 mm, the scan speed is 5.0 ° / min, and the sampling width is 0.01 °. the maximum value and _{a 2,} when the maximum value of the peak intensity diffraction angle 2θ appears in the range of 19 to 23 ° was _{B 2, B 2} / _{a 2} is from 0.6 to 8.0. Here, Li _5-x VO (PO ₄ ) ₂ (0 ≦ x <5) shown in the first embodiment and M _5-y H _z VO (PO ₄ ) ₂ (0 ≦ 0) shown in the second embodiment. The crystal system of y <5, 0 ≦ z <4, 0 ≦ yz <5, M = Li, Na) is the same tetragonal crystal. Further, when the H content increases, the diffraction angle 2θ of the peak taking the value of B ₂ shifts to the wide angle side. In X-ray diffraction measurement using a concentrated optical system, the sample to be measured is mixed with an amorphous material in order to suppress the influence of selective orientation derived from the particle shape such as a plate shape or a needle shape. It is necessary to produce it by spray coating an amorphous organic material.

When the positive electrode active material has a theoretical capacity as high as 377 mAh / g and B ₂ / A ₂ is 0.6 to 8.0, when used for the positive electrode of a lithium ion secondary battery or a sodium ion secondary battery, The structure facilitates insertion / extraction of lithium or sodium, and the charge / discharge capacity is improved.

B ₂ / A ₂ is more preferably 1.2 to 4.1, and still more preferably 1.6 to 3.1. Thereby, when it uses for the positive electrode of a lithium ion secondary battery or a sodium ion secondary battery, insertion / extraction of lithium ion or sodium ion becomes easier, and charge / discharge capacity improves.

  In the positive electrode active material, the value of y is preferably 1 to 4, and more preferably 1.6 to 3.5. Further, the value of z is preferably less than 3, and more preferably less than 2.5. Thereby, when it uses for the positive electrode of a lithium ion secondary battery or a sodium ion secondary battery, insertion / extraction of lithium ion or sodium ion becomes easier, and charge / discharge capacity improves.

  When used as a lithium ion secondary battery, the valence of V is further changed and the charge / discharge capacity is increased by using Li metal for the negative electrode or a commonly used negative electrode containing Li. In addition, when used as a sodium ion secondary battery, the valence of V is changed and the charge / discharge capacity is increased by using Na metal or a negative electrode containing Na in a normally used negative electrode. .

  In the positive electrode active material, by replacing Li, Na, V, and P in the crystal structure with other elements, the charge / discharge capacity can be controlled and the crystal structure can be stabilized.

  In this case, specific examples of the element that substitutes Li or Na include one or more selected from the group consisting of K, Mg, Ca, Ti, Zr, and Nb. Specific examples of elements that substitute V are Na, K, Rb, Cs, Ca, Sr, Sc, Y, Ta, Al, Fe, Co, Ga, Bi, Sn, Cr, Cu, Zn, Mg , Ti, Ge, Ta, Mo, W, Nb, Ni, Mn, and one or more selected from the group consisting of B and B. Specific examples of the element that substitutes P include one or more selected from the group consisting of V, Si, N, S, and Ge.

  If the amount of substitution of these elements is too large, the battery capacity will be too low. Therefore, it is usually 0.5 or less, preferably 0.2 or less, more preferably 0.1 or less with respect to Li, V and P before substitution. Substitution can be made within the following molar ratio range.

(Method for producing positive electrode active material)
Below, the manufacturing method of the active material which concerns on 2nd Embodiment of this invention is demonstrated centering on a different point from 1st Embodiment. According to the method for producing an active material according to the present embodiment, the active material according to the present embodiment described above can be formed.

<Reflux process>
The manufacturing method of the active material according to the present embodiment includes the following reflux process. First, a phosphoric acid source, a vanadium source, a lithium source or a sodium source, and an alcohol described later are added to prepare a mixture (aqueous solution) in which these are dispersed.

  As the phosphate source, vanadium source, lithium source, and alcohol source, at least one selected from the group consisting of the examples described in the first embodiment can be used.

As the sodium source, for example, at least one selected from the group consisting of Na ₂ CO ₃ , NaHCO ₃ , Na ₂ O, NaF, NaCl, and NaOH can be used.

  Two or more phosphate sources, two or more vanadium sources, two or more lithium sources, or two or more sodium sources may be used in combination.

  In the refluxing step, a reducing agent may be added. As the reducing agent, for example, hydrazine, ascorbic acid, citric acid, tartaric acid, or hydrogen peroxide can be used.

  What is necessary is just to adjust suitably the time heated in a recirculation | reflux process according to the quantity of a mixture.

In the refluxing step, the mixture is preferably heated to 100 to 250 ° C, more preferably 120 to 200 ° C. The higher the heating temperature of the mixture, the more the crystal growth is promoted and the particle size is increased. M _5-y H _z VO (PO ₄ ) ₂ (0 ≦ y <5, 0 ≦ z <4, 0 ≦ y−z <5) , M = Li, Na) type crystal.

<H amount preparation process>
The manufacturing method of the active material according to the present embodiment may include the following H amount preparation step. H can be added by immersing the active material obtained in the reflux step in an acidic solution described later.

  In the H amount adjusting step, it is preferable to use a solution having a pH of less than 4, and the immersion time may be adjusted as appropriate according to the pH.

  As the acidic solution, for example, at least one selected from the group consisting of hydrochloric acid, phosphoric acid, nitric acid, hydrofluoric acid, sulfuric acid, acetic acid, citric acid, formic acid, and oxalic acid can be used.

<Heat treatment process>
The method for producing an active material according to the present embodiment may include a heat treatment step for further heating the mixture after the reflux step. By the heat treatment step, the reaction of the lithium source, phosphate source and vanadium source that did not react in the reflux step proceeds, or M _5-y H _z VO (PO ₄ ) ₂ (0 ≦ y <5) generated in the reflux step. , 0 ≦ z <4, 0 ≦ yz <5, M = Li, Na). As a result, the capacity density of M _5−y H _z VO (PO ₄ ) ₂ (0 ≦ y <5, 0 ≦ z <4, 0 ≦ y−z <5, M = Li, Na) is improved, There is a tendency that the discharge capacity and rate characteristics of the battery using the battery improve.

In the heat treatment step, the mixture is preferably heated at a heat treatment temperature of 250 to 600 ° C. When the heat treatment temperature is too low, the crystal growth degree of M _5-y H _z VO (PO ₄ ) ₂ (0 ≦ y <5, 0 ≦ z <4, 0 ≦ y−z <5, M = Li, Na) There is a tendency that the improvement of the capacity density is small. If the heat treatment temperature is too high, the growth of M _5-y H _z VO (PO ₄ ) ₂ (0 ≦ y <5, 0 ≦ z <4, 0 ≦ y−z <5, M = Li, Na) is excessive. , The particle size of M _5-y H _z VO (PO ₄ ) ₂ (0 ≦ y <5, 0 ≦ z <4, 0 ≦ y−z <5, M = Li, Na) tends to increase. is there. As a result, the diffusion of lithium in the active material is slow, and the improvement in the capacity density of the active material tends to be small. By setting the heat treatment temperature within the above range, these tendencies can be suppressed.

  The heat treatment time of the mixture is preferably 3 to 20 hours. The heat treatment atmosphere of the mixture is preferably a nitrogen atmosphere, an argon atmosphere, or an air atmosphere.

In addition, you may preheat the mixture obtained at a recirculation | reflux process at about 60-150 degreeC for about 1 to 30 hours before heating at a heat treatment process. By preheating, the mixture becomes powder, and excess water and organic solvent are removed from the mixture. As a result, impurities are incorporated in the heat treatment step _{M 5-y H z VO (} PO 4) 2 (0 ≦ y <5,0 ≦ z <4,0 ≦ y-z <5, M = Li, Na) This makes it possible to make the particle shape uniform.

  As mentioned above, although suitable one Embodiment of the manufacturing method of the active material which concerns on this invention was described in detail, this invention is not limited to the said embodiment.

(Lithium ion secondary battery and sodium ion secondary battery)
Next, an electrode, a lithium ion secondary battery, and a sodium ion secondary battery according to this embodiment will be briefly described with reference to FIG.

  The lithium ion secondary battery or the sodium ion secondary battery 100 mainly includes a power generation element 30, a case 50 that accommodates the power generation element 30 in a sealed state, and a pair of leads 60 and 62 connected to the power generation element 30. Yes.

As the negative electrode active material, for example, lithium ions can be occluded / released (intercalation / deintercalation or doping / dedoping) in the case of lithium ion secondary batteries and sodium ions in the case of sodium ion secondary batteries. Mainly composed of carbon materials such as non-graphite, non-graphitizable carbon, graphitizable carbon, low-temperature calcined carbon, metals that can be combined with lithium such as Al, Si and Sn, and oxides such as SiO ₂ and SnO ₂ In the case of an amorphous compound or a lithium ion secondary battery, particles containing lithium titanate (Li ₄ Ti ₅ O ₁₂ ) or the like can be given.

The electrolyte solution is contained in the positive electrode active material layer 14, the negative electrode active material layer 24, and the separator 18. The electrolyte solution is not particularly limited. For example, in the present embodiment, an electrolyte solution containing a lithium salt in the case of a lithium ion secondary battery and a sodium salt in the case of a sodium ion secondary battery (using an aqueous electrolyte solution or an organic solvent) Electrolyte solution) can be used. However, the electrolyte aqueous solution is preferably an electrolyte solution (non-aqueous electrolyte solution) using an organic solvent because the electrochemical decomposition voltage is low, and the withstand voltage during charging is limited to a low level. As the electrolyte solution, a lithium salt in the case of a lithium ion secondary battery and a sodium salt dissolved in a nonaqueous solvent (organic solvent) in the case of a sodium ion secondary battery are preferably used. Examples of the lithium salt include LiPF ₆ , LiClO ₄ , LiBF ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiCF ₃ , CF ₂ SO ₃ , LiC (CF ₃ SO ₂ ) ₃ , LiN (CF ₃ SO ₂ ) ₂ , A salt such as LiN (CF ₃ CF ₂ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), LiN (CF ₃ CF ₂ CO) ₂ , or LiBOB can be used. Examples of the sodium salt include NaPF ₆ , NaTFSA, NaClO ₄ , NaAsF ₆ , NaSbF ₆ , NaBF ₄ , NaCF ₃ SO ₃ , NaN (SO ₂ CF ₃ ) ₂ , lower aliphatic carboxylic acid sodium salt, NaAlCl _{4 and the} like. Can be used. In addition, these lithium salts and sodium salts may be used individually by 1 type, and may use 2 or more types together.

  Moreover, as an organic solvent, propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate etc. are mentioned preferably, for example. These may be used alone or in combination of two or more at any ratio.

  The preferred embodiments of the positive electrode active material, the electrode including the positive electrode active material, the lithium ion secondary battery including the electrode, and the method for producing the sodium ion secondary battery have been described in detail above. The present invention is not limited to the above embodiment.

  The active material of the present invention can also be used as an electrode material for electrochemical devices other than lithium ion secondary batteries or sodium ion secondary batteries. As such an electrochemical element, a secondary battery other than a lithium ion secondary battery, such as a metal lithium secondary battery (the electrode containing the active material according to the present invention is used as a positive electrode and metal lithium is used as a negative electrode). Examples include batteries and electrochemical capacitors such as lithium capacitors. These electrochemical elements can be used for power sources such as self-propelled micromachines and IC cards, and distributed power sources arranged on or in a printed circuit board.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.

Example 1
<Reflux process>
In a 500 ml flask, 150 g octanol (Aldrich), 3.75 g V ₂ O ₅ (Nacalai Tesque, purity 99%), and 9.42 g H ₃ PO ₄ (Nacalai Tesque, purity 85) %) And stirred with a magnetic stirrer. Subsequently, the heater was turned on and held at 170 ° C. for 16 hours.

Next, after the heater was turned off and the temperature in the container was lowered to room temperature, 17.30 g of LiBr · H ₂ O (manufactured by Nacalai Tesque, purity 98%) was added and stirred with a magnetic stirrer. Subsequently, it was kept at 120 ° C. for 24 hours after the heater was turned on.

  Further, the heater was turned off, the temperature in the container was lowered to room temperature, a small amount of methanol was added, and a light blue solid was removed by suction filtration. Next, the filtrate was washed with acetone and suction filtered again. The filtrate was heat-treated at 60 ° C. for about 2 hours using an oven to obtain 8.29 g of a light-colored solid cathode active material.

<Baking process>
3.00 g of the solid obtained in the above step was placed in an alumina crucible, heated from room temperature to 350 ° C. over 3 hours in an air atmosphere, and heat-treated at 350 ° C. for 5 hours to obtain 2.748 g of a light blue powder. Got.

<X-ray diffraction measurement>
The positive electrode active material obtained in Example 1 was subjected to X-ray diffraction measurement by the following method and conditions.

(Sample preparation method for X-ray diffraction measurement)
0.1 g of the positive electrode active material obtained in Example 1 and 0.4 g of amorphous silicon dioxide (manufactured by Kanto Chemical Co., Ltd.) were each pulverized in an agate mortar for 3 minutes, and then mixed. A sample for X-ray diffraction measurement was obtained.

(Measurement condition)
Measuring device: Rigaku Corporation X-ray diffractometer Ultima IV
X-ray source: CuKa ray _{(CuKα 1 = 1.540562Å, CuKα 2} = 1.544398Å, CuKα 2 without removal)
Tube voltage: 40 kV
Tube current: 40 mA
Divergent slit: 1/2 °
Divergence length restriction slit: 10 mm
Scan speed: 5.0 ° / min
Sampling width: 0.01 °

The results obtained measurement, the diffraction angle 2θ is the maximum value of the peak intensity appearing in the range of 12 to 16 ° and A _1, also the maximum value of the peak intensity diffraction angle 2θ appears in the range of 19 to 23 ° B ₁ And B ₁ / A ₁ was calculated. The results are shown in Table 1.

[Production of evaluation cell]
A mixture of the active material of Example 1, polyvinylidene fluoride (PVDF) as a binder, and acetylene black was dispersed in N-methyl-2-pyrrolidone (NMP) as a solvent to prepare a slurry. The slurry was prepared so that the weight ratio of the active material, acetylene black, and PVDF was 84: 8: 8 in the slurry. This slurry was applied onto an aluminum foil as a current collector, dried, and then rolled to obtain an electrode (positive electrode) on which an active material layer containing the active material of Example 1 was formed.

<H amount measurement>
About the positive electrode active material obtained in Example 1, the amount of H was measured by the following method.

The total amount of H was measured at a heating temperature of 1500 ° C. by an inert gas melting method. Further, in order to measure the amount of H ₂ O contained in the positive electrode active material, measurement was performed by the Karl Fischer method. From the total amount of H obtained by the inert gas melting method, the amount of H contained in H ₂ O was removed to obtain the amount of H contained in the positive electrode active material. The results are shown in Table 1.

Next, the obtained electrode and the Li foil as the counter electrode were laminated with a separator made of a polyethylene microporous film interposed therebetween to obtain a laminate (power generation element). This laminated body was put in an aluminum laminate pack, and a 1M LiPF ₆ solution was injected into the aluminum laminate pack as an electrolyte solution, followed by vacuum sealing to produce an evaluation cell of Example 1.

(Example 2)
A positive electrode active material of Example 2 was obtained in the same manner as in Example 1 except that LiBr · H ₂ O was dispersed in 30 g of 1 hexanol (manufactured by Nacalai Tesque) in the second refluxing step. It was.

  In the second refluxing step, the positive electrode active material of Example 3 was obtained in the same manner as in Example 1 except that the heating and holding time was 144 hours.

  In the second refluxing step, the positive electrode active material of Example 4 was obtained in the same manner as in Example 1 except that the heating and holding time was 160 hours.

(Example 5)
In the second refluxing step, a positive electrode active material of Example 5 was obtained in the same manner as Example 1 except that 2.42 g of LiF (manufactured by Nacalai Tesque) was added.

(Example 6)
In the first refluxing step, 0.5 g of (CH ₃ COO) ₂ Co · 4H ₂ O was added to the place where H ₃ PO ₄ and octanol were added, and then V ₂ O ₅ was further added, followed by the second reflux. In the process, the positive electrode active material of Example 6 was obtained in the same manner as in Example 1 except that the heating and holding time was 60 hours.

(Example 7)
In the second reflux step, the positive electrode active material of Example 7 was obtained in the same manner as in Example 1 except that the heating and holding time was 1 hour.

(Example 8)
In the second refluxing step, the positive electrode active material of Example 8 was obtained in the same manner as in Example 1 except that the heating and holding time was 12 hours.

Example 9
In the second refluxing step, the positive electrode active material of Example 9 was obtained in the same manner as in Example 1 except that the heating and holding time was 80 hours.

(Example 10)
In the second reflux step, the positive electrode active material of Example 10 was obtained in the same manner as in Example 1 except that the heating and holding time was 100 hours.

(Example 11)
After the first reflux, the temperature inside the container was lowered to room temperature after the heater was turned off, a small amount of methanol was added, and a light blue solid was removed by suction filtration. Next, the filtrate was washed with acetone and suction filtered again. The filtrate was heat-treated in an oven at 60 ° C. for about 2 hours, and in the second reflux step, all the obtained solids after the heat treatment and 18.03 g of LiBr (manufactured by Tokyo Chemical Industry Co., Ltd.), 5.6 g of ascorbine The acid and 500 g of 1-hexanol were added and stirred with a magnetic stirrer. A positive electrode active material of Example 11 was obtained in the same manner as in Example 1 except that the temperature was kept at 120 ° C. for 120 hours after the heater was turned on.

(Example 12)
Li ₅ VOPO ₄ was prepared, and the positive electrode active material of Example 12 was obtained in the same manner as in Example 1 after the firing step.

(Example 13)
In the second refluxing step, the heating and holding time was set to 30 hours, and before the firing step, the obtained light blue solid and 200 ml of pH 1.3 HCl solution were placed in a 500 ml beaker and stirred with a magnetic stirrer. After maintaining for 5 hours, the temperature in the container was lowered to room temperature after the heater was turned off, and the light blue solid was removed by suction filtration. Next, the filtered material was washed with acetone and suction filtered again. The positive electrode of Example 13 was obtained in the same manner as in Example 1 except that the filtered material was heat-treated at 60 ° C. for about 2 hours using an oven. An active material was obtained.

(Example 14)
In the second refluxing step, LiBr · H ₂ O was dispersed and added to 50 g of 1 hexanol (manufactured by Nacalai Tesque), the heating and holding time was 60 hours, and the HCl solution immersion time was 0.5 hours. Obtained a positive electrode active material of Example 14 in the same manner as Example 13.

(Example 15)
In the second refluxing step, the same procedure as in Example 13 was conducted except that the amount of LiBr · H ₂ O added was 8.65 g, the heating and holding time was 90 hours, and the HCl solution immersion time was 10 hours. A positive electrode active material of Example 15 was obtained.

(Example 16)
In the second refluxing step, the positive electrode active material of Example 16 was obtained in the same manner as in Example 13 except that the amount of LiBr · H ₂ O added was 8.65 g and the heating and holding time was 120 hours. It was.

(Example 17)
In the second refluxing step, the amount of LiBr · H ₂ O input was 9.53 g, LiBr and 2.42 g LiF (manufactured by Nacalai Tesque) were added, and the HCl solution immersion time was 24 hours. Obtained a positive electrode active material of Example 17 in the same manner as Example 13.

(Example 18)
In the first refluxing step, 0.5 g of (CH ₃ COO) ₂ Co · 4H ₂ O was added to the place where H ₃ PO ₄ and octanol were added, and then V ₂ O ₅ was further added, followed by the second reflux. In the process, the positive electrode active material of Example 18 was obtained in the same manner as in Example 13 except that the heating and holding time was 50 hours and the HCl solution immersion time was 0.2 hours.

(Example 19)
In the second refluxing step, the positive electrode active material of Example 19 was obtained in the same manner as in Example 1 except that the heating and holding time was 2 hours and the HCl solution immersion time was 0.5 hours.

(Example 20)
In the second reflux step, the positive electrode active material of Example 20 was obtained in the same manner as Example 13 except that the heating and holding time was 6 hours and the HCl solution immersion time was 3 hours.

(Example 21)
In the second refluxing step, the same procedure as in Example 13 was performed except that the amount of LiBr · H ₂ O added was 8.65 g, the heating and holding time was 140 hours, and the HCl solution immersion time was 3 hours. The positive electrode active material of Example 21 was obtained.

(Example 22)
In the second refluxing step, the same procedure as in Example 13 was performed except that the amount of LiBr · H ₂ O added was 8.65 g, the heating and holding time was 160 hours, and the HCl solution immersion time was 4.5 hours. Thus, a positive electrode active material of Example 22 was obtained.

(Example 23)
In the second reflux step, 10.60 g of Na ₂ CO ₃ was added without adding LiBr · H ₂ O, and the resulting electrode and its counter electrode carbon were not immersed in the HCl solution. The materials were laminated with a separator made of a polyethylene microporous film interposed therebetween to obtain a laminate (power generation element). This laminate was put in an aluminum laminate pack, and a 1M NaPF ₆ solution was injected as an electrolyte solution into the aluminum laminate pack, followed by vacuum sealing to produce an evaluation cell. Other than that was carried out similarly to Example 13, and obtained the positive electrode active material of Example 23.

(Example 24)
In the second reflux step, the positive electrode active material of Example 24 was obtained in the same manner as Example 23, except that the heating and holding time was 60 hours.

(Example 25)
In the second refluxing step, the positive electrode active material of Example 25 was obtained in the same manner as in Example 23 except that the heating and holding time was 120 hours.

(Example 26)
In the second refluxing step, a positive electrode active material of Example 26 was obtained in the same manner as Example 23 except that 17.30 g of LiBr · H ₂ O was added.

(Example 27)
In the second refluxing step, a positive electrode active material of Example 27 was obtained in the same manner as in Example 23 except that 17.30 g of LiBr · H ₂ O was added and the heat holding time was set to 60 hours. .

(Example 28)
In the second refluxing step, a positive electrode active material of Example 28 was obtained in the same manner as Example 23, except that 17.30 g of LiBr · H 2 O was added and the heating and holding time was 120 hours.

(Example 29)
Before performing the firing process, put the obtained solid and 200 ml of pH 1.3 HCl solution in a 500 ml beaker, stir with a magnetic stirrer and hold for 5 hours, lower the temperature in the container to room temperature from heater off Then, the light blue solid was removed by suction filtration. Next, the filtrate was washed with acetone and then suction filtered again. The positive electrode of Example 29 was obtained in the same manner as in Example 23 except that the filtrate was heat-treated at 60 ° C. for about 2 hours using an oven. An active material was obtained.

(Example 30)
In the second reflux step, the positive electrode active material of Example 30 was obtained in the same manner as in Example 23 except that the heating and holding time was 60 hours and the HCl solution immersion time was 15 hours.

(Example 31)
In the second reflux step, the positive electrode active material of Example 31 was obtained in the same manner as in Example 23 except that the heating and holding time was 120 hours and the HCl solution immersion time was 10 hours.

(Example 32)
In the second refluxing step, a positive electrode active material of Example 32 was obtained in the same manner as Example 29, except that 17.30 g of LiBr · H ₂ O was added and the HCl solution immersion time was 1 hour. It was.

(Example 33)
In the second reflux step, the positive electrode active material of Example 33 was obtained in the same manner as Example 32 except that the heating and holding time was 60 hours and the HCl solution immersion time was 0.5 hours.

(Example 34)
In the second reflux step, the positive electrode active material of Example 34 was obtained in the same manner as in Example 32 except that the heating and holding time was 120 hours and the HCl solution immersion time was 5 hours.

(Comparative Example 1)
A positive electrode active material of Comparative Example 1 was obtained in the same manner as in Example 1 except that the reflux time was 120 hours in the second reflux process and the heating temperature was 150 ° C. in the heat treatment process.

(Comparative Example 2)
A positive electrode active material of Comparative Example 2 was obtained in the same manner as in Example 1 except that the reflux time was 120 hours in the second reflux process and the heating temperature was 750 ° C. in the heat treatment process.

(Comparative Example 3)
A positive electrode active material of Comparative Example 3 was obtained in the same manner as in Example 1, except that the reflux time was 120 hours in the second reflux process and the heating temperature was 820 ° C. in the heat treatment process.

(Comparative Example 4)
A positive electrode active material of Comparative Example 4 was obtained in the same manner as in Example 1 except that the reflux time was 120 hours in the second reflux process and the heating temperature was 100 ° C. in the heat treatment process.

(Comparative Example 5)
A positive electrode active material of Comparative Example 5 was obtained in the same manner as in Example 1 except that the reflux time was 120 hours in the second reflux process and the heating temperature was 950 ° C. in the heat treatment process.

(Comparative Example 6)
A positive electrode active material of Comparative Example 6 was obtained in the same manner as in Example 1 except that the heating and holding time was 15 hours in the second refluxing step and the heating temperature was 150 ° C. in the heat treatment step.

(Comparative Example 7)
A positive electrode active material of Comparative Example 7 was obtained in the same manner as in Example 1 except that the heating and holding time was 15 hours in the second refluxing step and the heating temperature was 750 ° C. in the heat treatment step.

(Comparative Example 8)
A positive electrode active material of Comparative Example 8 was obtained in the same manner as in Example 13 except that the reflux time was 60 hours in the second reflux step and the heating temperature was 120 ° C. in the heat treatment step.

(Comparative Example 9)
In the second reflux step, the reflux time was 80 hours, in the heat treatment step, the heating temperature was 800 ° C., and the HCl solution immersion time was 0.5 hours. A positive electrode active material was obtained.

(Comparative Example 10)
In the second reflux step, the reflux time was 110 hours, in the heat treatment step, the heating temperature was 850 ° C., and the HCl solution immersion time was 0.2 hours. A positive electrode active material was obtained.

(Comparative Example 11)
In the second reflux step, the reflux time was 100 hours, in the heat treatment step, the heating temperature was 100 ° C., and the HCl solution immersion time was 0.5 hours. A positive electrode active material was obtained.

(Comparative Example 12)
The positive electrode activity of Comparative Example 12 was the same as in Example 13 except that the reflux time was 12 hours in the second reflux process, the heating temperature was 950 ° C., and the HCl solution immersion time was 24 hours in the heat treatment process. Obtained material.

(Comparative Example 13)
In the second reflux step, the heating and holding time was set to 60 hours, and in the heat treatment step, the heating temperature was set to 120 ° C., and the HCl solution immersion time was set to 4 hours. A positive electrode active material was obtained.

(Comparative Example 14)
In the heat treatment step, a positive electrode active material of Comparative Example 14 was obtained in the same manner as in Example 13 except that the heating temperature was 800 ° C. and the HCl solution immersion time was 10 hours.

(Comparative Example 15)
In the second refluxing step, 9.54 g of Na ₂ CO ₃ was added, and in the heat treatment step, the heating temperature was set to 750 ° C., and the H amount preparation step was not performed, and the obtained electrode and its counter electrode carbon material Were laminated with a separator made of a polyethylene microporous film interposed therebetween to obtain a laminate (power generation element). This laminate was put in an aluminum laminate pack, and a 1M NaPF ₆ solution was injected as an electrolyte solution into the aluminum laminate pack, followed by vacuum sealing to produce an evaluation cell. Other than that was carried out similarly to Example 13, and obtained the positive electrode active material of the comparative example 15.

(Comparative Example 16)
A positive electrode active material of Comparative Example 16 was obtained in the same manner as in Example 23 except that the reflux time was 50 hours in the second reflux step and the heating temperature was 110 ° C. in the heat treatment step.

(Comparative Example 17)
A positive electrode active material of Comparative Example 18 was obtained in the same manner as in Example 23 except that the reflux time was 20 hours in the second reflux step and the heating temperature was 800 ° C. in the heat treatment step.

(Comparative Example 18)
A positive electrode active material of Comparative Example 18 was obtained in the same manner as in Example 23 except that the reflux time was 100 hours in the second reflux process and the heating temperature was 900 ° C. in the heat treatment process.

(Comparative Example 18)
A positive electrode active material of Comparative Example 18 was obtained in the same manner as in Example 26 except that the reflux time was 50 hours in the second reflux process and the heating temperature was 800 ° C. in the heat treatment process.

(Comparative Example 19)
A positive electrode active material of Comparative Example 19 was obtained in the same manner as in Example 26 except that the reflux time was 20 hours in the second reflux process and the heating temperature was 850 ° C. in the heat treatment process.

(Comparative Example 20)
A positive electrode active material of Comparative Example 20 was obtained in the same manner as in Example 26 except that the reflux time was 100 hours in the second reflux process and the heating temperature was 130 ° C. in the heat treatment process.

(Comparative Example 21)
In the second reflux step, the reflux time was 50 hours, the HCl solution immersion time was 3 hours, and the heating temperature was 130 ° C. in the heat treatment step. Obtained material.

(Comparative Example 22)
The positive electrode activity of Comparative Example 22 was the same as in Example 29 except that the reflux time was 20 hours in the second reflux step, the HCl solution immersion time was 7 hours, and the heating temperature was 850 ° C. in the heat treatment step. Obtained material.

(Comparative Example 23)
In the second refluxing step, the positive electrode activity of Comparative Example 23 was set in the same manner as in Example 29 except that the refluxing time was 100 hours, the HCl solution immersion time was 10 hours, and the heating temperature was 950 ° C. in the heat treatment step. Obtained material.

(Comparative Example 24)
The positive electrode activity of Comparative Example 24 was the same as in Example 32 except that the reflux time was 50 hours in the second reflux step, the HCl solution immersion time was 3 hours, and the heating temperature was 120 ° C. in the heat treatment step. Obtained material.

(Comparative Example 25)
In the second reflux step, the positive electrode activity of Comparative Example 25 was changed in the same manner as in Example 32 except that the reflux time was 20 hours, the HCl solution immersion time was 7 hours, and the heating temperature was 850 ° C. in the heat treatment step. Obtained material.

(Comparative Example 26)
In the second reflux step, the positive electrode activity of Comparative Example 26 was changed in the same manner as in Example 32 except that the reflux time was 100 hours, the HCl solution immersion time was 10 hours, and the heating temperature was 750 ° C. in the heat treatment step. Obtained material.

Ｌｉ量にかかわらず、Ｂ_１／Ａ_１が０．６以上８．０以下となるとき、放電容量は１７０ｍＡｈ／ｇ以上となり、１．６以上、３．１以下では放電容量は２００ｍＡｈ／ｇ以上となる。また、Ｂ_１／Ａ_１が０．６未満、もしくは８．０以上となるとき、放電容量は１３７ｍＡｈ／ｇ以下という結果であった。 In the same manner as in Example 1, evaluation cells were produced using each of the active materials of Examples 2 to 12 and Comparative Examples 1 to 7 alone.
<Measurement of discharge capacity>
Using each of the cells for evaluation of Examples 1 to 12 and Comparative Examples 1 to 7, the discharge rate was set to 0.1 C (current value at which discharge was completed in 10 hours when constant current discharge was performed at 25 ° C.). The discharge capacity (unit: mAh / g) was measured. The results are shown in Table 1. The discharge capacity of a compound of a phosphoric acid positive electrode material such as LiFePO ₄ , LiMnPO ₄ , or LiCOPO ₄ has a theoretical capacity of about 170 mAh / g, so that the actual capacity is preferably 170 mAh / g or more. .

Regardless of the amount of Li, when B ₁ / A ₁ is 0.6 or more and 8.0 or less, the discharge capacity is 170 mAh / g or more, and when 1.6 or 3.1 or less, the discharge capacity is 200 mAh / g or more. It becomes. In addition, when B ₁ / A ₁ was less than 0.6 or 8.0 or more, the discharge capacity was 137 mAh / g or less.

Ｌｉ量、Ｈ量、Ｎａ量にかかわらず、Ｂ_２／Ａ_２が０．６以上８．０以下となるとき、放電容量は１７０ｍＡｈ／ｇ以上となり、１．６以上、３．１以下では放電容量は２００ｍＡｈ／ｇ以上となる。また、Ｂ_２／Ａ_２が０．６未満、もしくは８．０以上となるとき、放電容量は１２９ｍＡｈ／ｇ以下という結果であった。 Evaluation cells using each of the active materials of Examples 13 to 34 and Comparative Examples 8 to 26 were produced in the same manner as in Example 1.
<Measurement of discharge capacity>
Using each of the evaluation cells of Examples 13 to 34 and Comparative Examples 8 to 26, the discharge rate was set to 0.1 C (current value at which discharge was completed in 10 hours when constant current discharge was performed at 25 ° C.). The discharge capacity (unit: mAh / g) was measured. The results are shown in Table 2.

Regardless of the amount of Li, H, or Na, when B ₂ / A ₂ is 0.6 or more and 8.0 or less, the discharge capacity is 170 mAh / g or more, and when B ₂ / A ₂ is 1.6 or more and 3.1 or less, discharge is performed. The capacity is 200 mAh / g or more. When B ₂ / A ₂ was less than 0.6 or 8.0 or more, the discharge capacity was 129 mAh / g or less.

DESCRIPTION OF SYMBOLS 10 ... Positive electrode, 20 ... Negative electrode, 12 ... Positive electrode collector, 14 ... Positive electrode active material layer, 18 ... Separator, 22 ... Negative electrode collector, 24 ... Negative electrode Active material layer, 30 ... power generation element, 50 ... case, 60, 62 ... lead, 100 ... lithium ion secondary battery, or sodium ion secondary battery

Claims (6)

Li _5-x VO (PO ₄ ) ₂ ( 1.6 ≦ x ≦ 3.5 ) is a compound represented by a diffraction angle 2θ of 12 to 16 ° in X-ray diffraction measurement using Cu Kα ray. B ₁ / A ₁ is 0.6 to 8. When the maximum value of the peak intensity appearing in the range of A is ₁ and the maximum value of the peak intensity appearing in the range of the diffraction angle 2θ of 19 to 23 ° is B ₁ . A positive electrode active material characterized by being zero. _{M 5-y H z VO (} PO 4) 2 (1.6 ≦ y ≦ 3.5, 0 ≦ z <4,0 ≦ y-z ≦ 3.5, M = Li, Na) a compound represented by In the X-ray diffraction measurement using Cu Kα ray, the maximum value of the peak intensity appearing in the diffraction angle 2θ range of 12-16 ° is A ₂ and the diffraction angle 2θ appears in the range of 19-23 °. A positive electrode active material, wherein B ₂ / A ₂ is 0.6 to 8.0 when the maximum peak intensity is B ₂ . Wherein _B 1 / _{A 1} or _B 2 / _{A 2} is a 1.6 to 3.1, the positive electrode active material according to any one of claims 1 2.   A positive electrode comprising the positive electrode active material according to claim 1.   A lithium ion secondary battery comprising the positive electrode according to claim 4. A sodium ion secondary battery comprising a positive electrode containing the positive electrode active material according to claim 2.

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