JP6042514B2 - Positive electrode active material for secondary battery and method for producing the same - Google Patents

Description

  The present invention relates to a positive electrode active material for a secondary battery in which a water-insoluble conductive carbon material and a metal fluoride are both supported on an oxide.

Secondary batteries used in portable electronic devices, hybrid cars, electric cars, and the like have been developed. In particular, lithium ion secondary batteries are widely known as the most excellent secondary batteries that operate near room temperature. Under these circumstances, lithium-containing olivine-type phosphate metal salts such as Li (Fe, Mn) PO ₄ and Li ₂ (Fe, Mn) SiO ₄ are more resource-constrained than lithium transition metal oxides such as LiCoO _2. Therefore, it is possible to exhibit high safety, and therefore, it is an optimum positive electrode material for obtaining a high-output and large-capacity lithium ion secondary battery. However, these compounds have the property that it is difficult to sufficiently increase the conductivity due to the crystal structure, and there is room for improvement in the diffusibility of lithium ions. Has been made.

Furthermore, in lithium ion secondary batteries, which are spreading, it is known that the internal resistance gradually increases when the battery is left for a long time after charging, and the battery performance is deteriorated. This is because the moisture contained in the battery material at the time of manufacture is desorbed from the material during repeated charging and discharging of the battery, and by the chemical reaction between the moisture and the nonaqueous electrolyte LiPF ₆ filling the battery, This is because hydrogen fluoride is generated. It is also known that reducing the water content of the positive electrode active material used in the secondary battery is effective for effectively suppressing such deterioration in battery performance (see Patent Document 1).

  Under these circumstances, for example, Patent Document 2 discloses that after the firing treatment of the raw material mixture containing the carbonaceous material precursor, the water content is reduced to a certain value or less by performing pulverization treatment and classification treatment in a dry atmosphere. Technology is disclosed. In Patent Document 3, a predetermined lithium phosphate compound, lithium silicate compound, and the like and a conductive carbon material are mixed by a wet ball mill, and then a mechanochemical treatment is performed so that the conductive carbon material is uniformly applied to the surface. A technique for obtaining a composite oxide deposited is disclosed.

On the other hand, since lithium is a rare valuable material, various studies have been made on sodium ion secondary batteries using sodium instead of lithium ion secondary batteries.
For example, Patent Document 4 discloses a sodium ion secondary battery active material using marisite-type NaMnPO ₄ , and Patent Document 5 discloses a positive electrode containing sodium phosphate transition metal having an olivine structure. An active material is disclosed, and any literature indicates that a high-performance sodium ion secondary battery can be obtained.

JP2013-152911A JP 2003-292309 A US Patent Application Publication No. 2004/0140458 JP 2008-260666 A JP 2011-34963 A

  However, in any of the techniques described in any of the above documents, the surface of the lithium phosphate compound or the like is not sufficiently covered with the carbon source, and a part of the surface is exposed. It has been found that it is difficult to obtain a positive electrode active material for a secondary battery in which the moisture content is increased and the battery properties such as cycle characteristics are sufficiently high.

  Accordingly, an object of the present invention is to provide a positive electrode active material for a secondary battery that can effectively suppress moisture adsorption and a method for manufacturing the same, in order to obtain a high-performance lithium ion secondary battery or a sodium ion secondary battery. It is to provide.

  Accordingly, the present inventors have made various studies. As long as the positive electrode active material for a secondary battery is formed by supporting a water-insoluble conductive carbon material and a specific amount of metal fluoride on a specific oxide, Because both insoluble conductive carbon material and metal fluoride can efficiently coat the oxide surface and effectively suppress moisture adsorption, lithium ions or sodium ions can effectively carry electrical conduction. As a positive electrode active material, it was found to be extremely useful, and the present invention has been completed.

That is, the present invention includes at least the following formula (A), (B) or (C) containing iron or manganese:
LiFe _a Mn _b M _c PO ₄ (A)
(In the formula (A), M represents Mg, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd, or Gd. A, b, and c are 0 ≦ a ≦ 1, 0 ≦ b ≦ 1, 0 ≦ c ≦ 0.2, and 2a + 2b + (M valence) × c = 2 and a number satisfying a + b ≠ 0 are shown.)
_{Li 2 Fe d Mn e N f} SiO 4 ··· (B)
(In the formula (B), N represents Ni, Co, Al, Zn, V, or Zr. D, e, and f are 0 ≦ d ≦ 1, 0 ≦ e ≦ 1, and 0 ≦ f <1, 2d + 2e +. (The valence of N) × f = 2 is satisfied, and d + e ≠ 0 is satisfied.)
NaFe _g Mn _h Q _i PO ₄ (C)
(In the formula (C), Q represents Mg, Ca, Co, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd, or Gd. G, h, and i are 0 ≦ g ≦. 1, 0 ≦ h ≦ 1, 0 ≦ i <1, and 2g + 2h + (valence of Q) × i = 2 and a number satisfying g + h ≠ 0 are shown.)
The positive electrode active material for secondary batteries by which a water-insoluble conductive carbon material and 0.1-5 mass% metal fluoride are carry | supported by the oxide represented by these is provided.

The present invention also provides a process for obtaining an oxide X by subjecting slurry water containing a lithium compound or sodium compound, a phosphoric acid compound or a silicic acid compound, and a metal salt containing at least an iron compound or a manganese compound to a hydrothermal reaction. (I),
A step (II) of obtaining a composite X by adding a water-insoluble conductive carbon material to the obtained oxide X and dry-mixing, and the obtained composite X in an amount of 0. Step (III) of adding 1 to 40 parts by mass of a metal fluoride precursor, wet mixing and firing
The manufacturing method of the said positive electrode active material for secondary batteries provided with these is provided.

  According to the present invention, a water-insoluble conductive carbon material and a specific amount of metal fluoride are effectively supported on a predetermined oxide while complementing each other, so that the water-insoluble conductive property is partially formed on the surface of the oxide. Since the oxide is effectively suppressed from being exposed without the presence of both the carbon material and the metal fluoride, a positive electrode active material for a secondary battery in which the exposed portion on the oxide surface is effectively reduced is obtained. be able to. Therefore, since such a positive electrode active material can effectively suppress the adsorption of moisture, in a lithium ion secondary battery or a sodium ion secondary battery using the positive electrode active material, lithium ions or sodium ions effectively carry electric conduction, and various Excellent battery characteristics such as cycle characteristics can be stably exhibited even in a different use environment.

Hereinafter, the present invention will be described in detail.
The oxide used in the present invention contains at least iron or manganese and has the following formula (A), (B) or (C):
LiFe _a Mn _b M _c PO ₄ (A)
(In the formula (A), M represents Mg, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd, or Gd. A, b, and c are 0 ≦ a ≦ 1, 0 ≦ b ≦ 1, 0 ≦ c ≦ 0.2, and 2a + 2b + (M valence) × c = 2 and a number satisfying a + b ≠ 0 are shown.)
_{Li 2 Fe d Mn e N f} SiO 4 ··· (B)
(In the formula (B), N represents Ni, Co, Al, Zn, V, or Zr. D, e, and f are 0 ≦ d ≦ 1, 0 ≦ e ≦ 1, 0 ≦ f <1, and 2d + 2e +. (The valence of N) × f = 2 is satisfied, and d + e ≠ 0 is satisfied.)
NaFe _g Mn _h Q _i PO ₄ (C)
(In the formula (C), Q represents Mg, Ca, Co, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd, or Gd. G, h, and i are 0 ≦ g ≦. 1, 0 ≦ h ≦ 1, 0 ≦ i <1, and 2g + 2h + (valence of Q) × i = 2 and a number satisfying g + h ≠ 0 are shown.)
It is expressed by one of the following formulas.
These oxides all have an olivine structure and contain at least iron or manganese. When the oxide represented by the above formula (A) or (B) is used, a positive electrode active material for a lithium ion battery is obtained, and when the oxide represented by the above formula (C) is used. Provides a positive electrode active material for a sodium ion battery.

The oxide represented by the above formula (A) is an olivine-type transition metal lithium compound containing at least iron (Fe) and manganese (Mn) as so-called transition metals. In the formula (A), M represents Mg, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd, or Gd, and is preferably Mg, Zr, Mo, or Co. a is 0 ≦ a ≦ 1, preferably 0.01 ≦ a ≦ 0.99, and more preferably 0.1 ≦ a ≦ 0.9. b is 0 ≦ b ≦ 1, preferably 0.01 ≦ b ≦ 0.99, and more preferably 0.1 ≦ b ≦ 0.9. c satisfies 0 ≦ c ≦ 0.2, and preferably 0 ≦ c ≦ 0.1. These a, b and c are numbers satisfying 2a + 2b + (valence of M) × c = 2 and satisfying a + b ≠ 0. Specific examples of the olivine-type transition metal lithium compound represented by the above formula (A) include LiFe _0.2 Mn _0.8 PO ₄ , LiFe _0.9 Mn _0.1 PO ₄ , LiFe _0.15 Mn _0.75 Mg _0.1 PO ₄ , and LiFe. _Examples include _0.19 Mn _0.75 Zr _0.03 PO ₄ , and LiFe _0.2 Mn _0.8 PO ₄ is particularly preferable.

The oxide represented by the above formula (B) is a so-called olivine-type transition metal lithium compound containing at least iron (Fe) and manganese (Mn) as transition metals. In the formula (B), N represents Ni, Co, Al, Zn, V, or Zr, and is preferably Co, Al, Zn, V, or Zr. d is 0 ≦ d ≦ 1, preferably 0 ≦ d <1, and more preferably 0.1 ≦ d ≦ 0.6. e is 0 ≦ d ≦ 1, preferably 0 ≦ e <1, and more preferably 0.1 ≦ e ≦ 0.6. f is 0 ≦ f <1, preferably 0 <f <1, and more preferably 0.05 ≦ f ≦ 0.4. These d, e, and f are numbers satisfying 2d + 2e + (N valence) × f = 2 and d + e ≠ 0. Specific examples of the olivine-type transition metal lithium compound represented by the above formula (B) include Li ₂ Fe _0.45 Mn _0.45 Co _0.1 SiO ₄ , Li ₂ Fe _0.36 Mn _0.54 Al _0.066 SiO ₄ , Li ₂ Fe _0.45 Mn _0.45 Zn _0.1 SiO ₄ , Li ₂ Fe _0.36 Mn _0.54 V _0.066 SiO ₄ , Li ₂ Fe _0.282 Mn _0.658 Zr _0.02 SiO _{4 and the} like can be mentioned, among which Li ₂ Fe _0.282 Mn _0.658 Zr _0.02 SiO ₄ is preferable.

The oxide represented by the formula (C) is an olivine-type transition metal sodium phosphate compound containing iron (Fe) and manganese (Mn) as at least transition metals. In the formula (C), Q represents Mg, Ca, Co, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd, or Gd, and is preferably Mg, Zr, Mo, or Co. g is 0 ≦ g ≦ 1, and preferably 0 <g ≦ 1. h is 0 ≦ h ≦ 1, and preferably 0.5 ≦ h <1. i is 0 ≦ i <1, preferably 0 ≦ i ≦ 0.5, and more preferably 0 ≦ i ≦ 0.3. These g, h, and i are numbers satisfying 0 ≦ g ≦ 1, 0 ≦ h ≦ 1, and 0 ≦ i <1, 2 + g + 2h + (Q valence) × i = 2 and satisfying g + h ≠ 0. It is. Specific examples of the olivine-type phosphate transition metal sodium compound represented by the above formula (C) include, for example, NaFe _0.2 Mn _0.8 PO ₄ , NaFe _0.9 Mn _0.1 PO ₄ , NaFe _0.15 Mn _0.7 Mg _0.15 PO ₄ , NaFe Examples include _0.19 Mn _0.75 Zr _0.03 PO ₄ , NaFe _0.19 Mn _0.75 Mo _0.03 PO ₄ , NaFe _0.15 Mn _0.7 Co _0.15 PO ₄ , and NaFe _0.2 Mn _0.8 PO ₄ is particularly preferable.

  The positive electrode active material for a secondary battery of the present invention includes a water-insoluble conductive carbon material and 0.1 to 5% by mass of a metal fluoride in the oxide represented by the above formula (A), (B) or (C). It is formed by supporting a compound. That is, the oxide is formed by supporting both a water-insoluble conductive carbon material and a specific amount of metal fluoride, and the surface of the oxide is covered with either the water-insoluble conductive carbon material or the metal fluoride. However, the other of the water-insoluble conductive carbon material or the metal fluoride is effectively supported on the portion where the oxide surface is exposed without the presence of one of them. Therefore, these water-insoluble conductive carbon materials and a specific amount of metal fluoride are combined and firmly supported on the entire surface of the oxide while effectively suppressing exposure of the oxide surface. It is possible to effectively prevent moisture adsorption in the positive electrode active material for secondary batteries.

  Moreover, the said oxide may contain the water-soluble carbon material mentioned later as needed. The composite obtained at this time contains a water-soluble carbon material together with an oxide and a water-insoluble conductive carbon material. The water-soluble carbon material to be supported as carbonized carbon on the composite containing the oxide and the water-insoluble conductive carbon material is such that the water-insoluble conductive carbon material exists in the composite. From the standpoint of effectively supporting the carbon on the part where the oxide surface is exposed, it is preferable that the oxide is supported on the oxide as carbon carbonized by firing. By firing for carbonizing the water-soluble carbon material, the crystallinity of both the oxide and the water-insoluble conductive carbon material, which have been reduced by dry mixing, can be more effectively recovered. Sexually can be enhanced effectively.

  The water-insoluble conductive carbon material supported on the oxide represented by the above formula (A), (B) or (C) means that the amount dissolved in 100 g of water at 25 ° C. is carbon of the water-insoluble conductive carbon material. A water-insoluble carbon material having an atomic conversion amount of less than 0.4 g, which itself is a conductive carbon source without firing. Examples of the water-insoluble conductive carbon material include one or more selected from graphite, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black. Among these, ketjen black or graphite is preferable from the viewpoint of reducing the amount of adsorbed moisture. The graphite may be any of artificial graphite (scale-like, lump-like, earthy, graphene) or natural graphite.

The BET specific surface area of the water-insoluble conductive carbon material that can be used is preferably 1 to 750 m ² / g, more preferably 3 to 500 m ² / g, from the viewpoint of effectively reducing the amount of adsorbed water. Moreover, from the same viewpoint, the average particle size of the water-insoluble conductive carbon material is preferably 0.5 to 20 μm, more preferably 1.0 to 15 μm.

  The water-insoluble conductive carbon material is present in the positive electrode active material for a secondary battery of the present invention as carbon supported by the oxide. The carbon atom equivalent amount of the water-insoluble conductive carbon material is preferably 0.5 to 7% by mass, more preferably 0.7 to 6% by mass in the positive electrode active material for a secondary battery of the present invention. More preferably, it is 0.85-5.5 mass%. The amount in terms of carbon atoms of the water-insoluble conductive carbon material present in the positive electrode active material for secondary batteries can be confirmed by the amount of carbon measured using a carbon / sulfur analyzer. In addition, when a water-soluble carbon material is used in combination, the carbon atom equivalent amount of the water-insoluble conductive carbon material present in the positive electrode active material for the secondary battery is determined from the carbon amount measured using a carbon / sulfur analyzer. This can be confirmed by subtracting the amount of water-soluble carbon material added in terms of carbon atoms.

  Examples of the metal fluoride metal supported on the oxide include lithium (Li), sodium (Na), magnesium (Mg), calcium (Ca), aluminum (Al), titanium (Ti), vanadium (V), Chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), zirconium (Zr), niobium (Nb), molybdenum (Mo) Examples include tantalum (Ta), tin (Sn), tungsten (W), potassium (K), barium (Ba), and strontium (Sr). Especially, it is preferable that it is a metal chosen from lithium, sodium, magnesium, calcium, and aluminum from a viewpoint of improving the hydrophobicity of metal fluoride, and improving ion conductivity, and is chosen from lithium and magnesium. More preferably, it is a metal.

  The amount of the metal fluoride supported is 0.1% in the positive electrode active material for the secondary battery of the present invention, from the viewpoint of effectively supporting the metal fluoride on the surface of the oxide where no water-insoluble conductive carbon material is present. It is -5 mass%, Preferably it is 0.2-4.5 mass%, More preferably, it is 0.3-4 mass%. If the supported amount of the metal fluoride is less than 0.1% by mass, the amount of adsorbed water cannot be sufficiently suppressed, and if the supported amount of the metal fluoride exceeds 5% by mass, details are unknown, Even if the amount of adsorbed moisture is suppressed, the cycle characteristics of the secondary battery may be deteriorated. The amount of fluorine present in the positive electrode active material for secondary batteries can be confirmed by an ion analyzer using a solution obtained by acid-dissolving the positive electrode active material for secondary batteries.

The positive electrode active material for a secondary battery of the present invention is efficiently supported on the oxide represented by (A), (B), or (C) while complementing each other with a water-insoluble conductive carbon material and a metal fluoride. In view of the above, it is preferable that 0.1 to 5% by mass of a metal fluoride is supported on the oxide after supporting the water-insoluble conductive carbon material. It is preferable that 0.1 to 5% by mass of a metal fluoride is supported on a composite containing a water-insoluble conductive carbon material.
In addition, the metal fluoride is added to the composite with respect to 100 parts by mass of the composite from the viewpoint of effectively supporting the composite in the part where the oxide surface is exposed without the presence of the water-insoluble conductive carbon material. It is preferable that 0.1 to 40 parts by mass of a metal fluoride precursor is added and wet mixed to be supported on the composite. That is, the positive electrode active material for a secondary battery of the present invention comprises a composite containing an oxide and a water-insoluble conductive carbon material, and 0.1 to 40 parts by mass of a metal fluoride with respect to 100 parts by mass of the composite. A fired product of a wet mixture with a precursor is preferred. Specifically, the precursor of the metal fluoride is then fired and supported as a metal fluoride, and is present in the positive electrode active material for a secondary battery of the present invention.

  Specifically, the water-insoluble conductive carbon material is preferably one obtained by dry-mixing with an oxide obtained by a hydrothermal reaction and then supporting it on the oxide, pre-mixed with the oxide. After that, it is more preferable that they are mixed while applying a compressive force and a shearing force and supported on an oxide. That is, the composite containing the oxide and the water-insoluble conductive carbon material is a hydrothermal reaction product of slurry water containing a lithium compound or a sodium compound, a phosphate compound or a silicate compound, and at least an iron compound or a manganese compound. A dry mixture of an oxide and a water-insoluble conductive carbon material is preferred. In addition, what was carry | supported by the oxide by baking a water-insoluble conductive carbon material is obtained as a composite_body | complex containing an oxide and a water-insoluble conductive carbon material. This firing makes it possible to recover the crystallinity of both the oxide and the water-insoluble conductive carbon material that have been lowered by dry mixing or the like, so that the conductivity of the obtained positive electrode active material can be effectively increased.

  In addition, a water-soluble carbon material may be added as necessary during the dry mixing. The composite obtained at this time contains a water-soluble carbon material together with an oxide and a water-insoluble conductive carbon material. The water-soluble carbon material to be supported as carbonized carbon on the composite containing the oxide and the water-insoluble conductive carbon material is such that the water-insoluble conductive carbon material exists in the composite. From the viewpoint of more effectively supporting carbon on the exposed oxide surface, the oxide is supported on the oxide as carbonized by being mixed with the above composite and wet-fired. Is preferred. By firing for carbonizing the water-soluble carbon material, the crystallinity of both the oxide and the water-insoluble conductive carbon material, which have been reduced by dry mixing, can be more effectively recovered. Sexually can be enhanced effectively.

  If necessary, the water-soluble carbon material contained in the oxide or added during dry mixing is 100 g of water at 25 ° C., 0.4 g or more in terms of carbon atoms of the water-soluble carbon material, Preferably, it means a carbon material that dissolves 1.0 g or more, and examples thereof include one or more selected from saccharides, polyols, polyethers, and organic acids. More specifically, for example, monosaccharides such as glucose, fructose, galactose and mannose; disaccharides such as maltose, sucrose and cellobiose; polysaccharides such as starch and dextrin; ethylene glycol, propylene glycol, diethylene glycol, polyethylene glycol and butane Examples include polyols and polyethers such as diol, propanediol, polyvinyl alcohol, and glycerin; and organic acids such as citric acid, tartaric acid, and ascorbic acid. Among these, glucose, fructose, sucrose, and dextrin are preferable, and glucose is more preferable from the viewpoint of improving the solubility and dispersibility in a solvent and effectively functioning as a carbon material.

More specifically, the positive electrode active material for a secondary battery of the present invention is a slurry water containing a lithium compound or a sodium compound, a phosphoric acid compound or a silicic acid compound, and a metal salt containing at least an iron compound or a manganese compound. A step (I) of obtaining an oxide X by subjecting to a thermal reaction;
A step (II) of obtaining a composite X by adding a water-insoluble conductive carbon material to the obtained oxide X and dry-mixing, and the obtained composite X in an amount of 0. Step (III) of adding 1 to 40 parts by mass of a metal fluoride precursor, wet mixing and firing
It is preferable that it is obtained by a manufacturing method provided with.

Step (I) is a step of obtaining an oxide X by subjecting a slurry water containing a lithium compound or sodium compound, a phosphoric acid compound or a silicic acid compound, and a metal salt containing at least an iron compound or a manganese compound to a hydrothermal reaction. It is.
Examples of the lithium compound or sodium compound that can be used include hydroxides (for example, LiOH.H ₂ O, NaOH), carbonates, sulfates, and acetates. Of these, hydroxide is preferable.
The content of the lithium compound or silicate compound in the slurry water is preferably 5 to 50 parts by mass and more preferably 7 to 45 parts by mass with respect to 100 parts by mass of water. More specifically, when a phosphoric acid compound is used in step (I), the content of the lithium compound or sodium compound in the slurry water is preferably 5 to 50 parts by mass with respect to 100 parts by mass of water, and more Preferably it is 10-45 mass parts. Moreover, when using a silicate compound, content of the silicate compound in slurry water becomes like this. Preferably it is 5-40 mass parts with respect to 100 mass parts of water, More preferably, it is 7-35 mass parts.

Step (I) is a mixture A containing a lithium compound or a sodium compound from the viewpoint of improving the dispersibility of each component contained in the slurry water and making the obtained positive electrode active material particles finer to improve battery physical properties. ^1, to obtain a mixture a ² was mixed phosphoric acid compound or a silicic acid compound (Ia), to the mixture a ² obtained as well, by adding a metal salt containing at least an iron compound or a manganese compound, and mixed It is preferable to include a step (Ib) of obtaining the oxide X by subjecting the obtained slurry water X to a hydrothermal reaction.

In step (I) or (Ia), prior to mixing the mixture A phosphoric acid compound to ^one or silicic acid compound, preferably it is allowed to stir in advance mixture A ^1. The stirring time of the mixture A ¹ is preferably 1 to 15 minutes, more preferably 3 to 10 minutes. The temperature of the mixture A ¹ is preferably 20 to 90 ° C., more preferably from 20 to 70 ° C..

Examples of the phosphoric acid compound used in the step (I) or (Ia) include orthophosphoric acid (H ₃ PO ₄ , phosphoric acid), metaphosphoric acid, pyrophosphoric acid, triphosphoric acid, tetraphosphoric acid, ammonium phosphate, and ammonium hydrogen phosphate. Etc. Of these, phosphoric acid is preferably used, and is preferably used as an aqueous solution having a concentration of 70 to 90% by mass. In this step (I) or (Ia), Upon mixing phosphoric acid to the mixture A ^1, preferably dropwise addition of phosphoric acid while stirring the mixture A ^1. By portionwise addition to the mixture A ¹ was added dropwise to phosphoric acid, the mixture reacted well in A in ¹ progresses, the (A) ~ oxide X of the precursor slurry which is represented by (C) It is also possible to effectively prevent the oxide X precursors from being aggregated unnecessarily while being uniformly dispersed.

The dropping rate of phosphoric acid into the mixture A ¹ is preferably 15 to 50 mL / min, more preferably 20 to 45 mL / min, and further preferably 28 to 40 mL / min. Moreover, the stirring time of the mixture A ¹ while dropping phosphoric acid is preferably 0.5 to 24 hours, and more preferably 3 to 12 hours. Furthermore, the stirring speed of the mixture A ¹ while dropping phosphoric acid is preferably 200 to 700 rpm, more preferably 250 to 600 rpm, and further preferably 300 to 500 rpm.
Note that when the mixture is stirred for A ^1, preferred to further cool the mixture A in the following ¹ the boiling point temperature. Specifically, cooling to 80 ° C. or lower is preferable, and cooling to 20 to 60 ° C. is more preferable.

The silicic acid compound used in the step (I) or (Ia) is not particularly limited as long as it is a reactive silica compound. Amorphous silica, Na ₄ SiO ₄ (for example, Na ₄ SiO ₄ .H ₂ O) Etc.

The mixture A ² after mixing the phosphoric acid compound or the silicic acid compound preferably contains 2.0 to 4.0 mol of lithium or sodium with respect to 1 mol of phosphoric acid or silicic acid, and 2.0 to 3 It is more preferable to contain 1 mol, and the lithium compound or sodium compound and the phosphoric acid compound or silicic acid compound may be used so as to obtain such an amount. More specifically, when a phosphoric acid compound is used in the step (I) or (Ia), the mixture A ² after mixing the phosphoric acid compound has 2.7 lithium or sodium per mol of phosphoric acid. ~ 3.3 mol is preferably contained, more preferably 2.8 to 3.1 mol, and when the silicate compound is used in step (I) or (Ia), the silicate compound is mixed. The mixture A ² preferably contains 2.0 to 4.0 moles of lithium, more preferably 2.0 to 3.0 moles per mole of silicic acid.
What is necessary is just to use the said lithium compound or sodium compound, and a phosphoric acid compound or a silicic acid compound so that it may become such quantity.

The reaction in the mixture A ² is completed by purging the mixture A ² after mixing the phosphoric acid compound or the silicate compound, and is represented by the above (A) to (C). to produce a precursor of the oxides in the mixture a ^2. When nitrogen is purged, the reaction can proceed in a state where the dissolved oxygen concentration in the mixture A ² is reduced, and the dissolved oxygen concentration in the mixture A ² containing the resulting oxide precursor is also effective. Therefore, oxidation of the iron compound or manganese compound added in the next step can be suppressed. In such mixtures A ^2, a precursor of the oxide X represented by the above (A) ~ (C) is present as fine dispersed particles. For example, in the case of the oxide represented by the above formula (A), the precursor of the oxide X is obtained as trilithium phosphate (Li ₃ PO ₄ ).

The pressure for purging nitrogen is preferably 0.1 to 0.2 MPa, more preferably 0.1 to 0.15 MPa. The temperature of the mixture A ² after mixing the phosphoric acid compound or a silicic acid compound is preferably 20 to 80 ° C., more preferably from 20 to 60 ° C.. For example, in the case of the oxide represented by the above formula (A), the reaction time is preferably 5 to 60 minutes, more preferably 15 to 45 minutes.
Further, when the purging nitrogen from the viewpoint of advancing satisfactorily reaction, it is preferred to stir the mixture A ² after mixing the phosphoric acid compound or a silicic acid compound. The stirring speed at this time is preferably 200 to 700 rpm, more preferably 250 to 600 rpm.

Further, from the viewpoint of more effectively suppressing the oxidation of the precursor of the oxide X on the surface of the dispersed particles and reducing the size of the dispersed particles, the dissolved in the mixture A ² after mixing the phosphoric acid compound or the silicic acid compound. The oxygen concentration is preferably 0.5 mg / L or less, more preferably 0.2 mg / L or less.

  In the step (I) or (Ib), the precursor of the obtained oxide X and slurry water containing a metal salt containing at least an iron compound or a manganese compound are subjected to a hydrothermal reaction to obtain the oxide X. . Using the obtained precursor of the oxide X as a mixture, a metal salt containing at least an iron compound or a manganese compound is added thereto, and a water-soluble carbon material is added if necessary, and the slurry water X and It is preferable to do this. Thereby, while simplifying the process, the oxide X represented by the above (A) to (C) can be obtained, and it is possible to obtain extremely fine particles, which is a very useful secondary battery. A positive electrode active material can be obtained.

  Examples of iron compounds that can be used include iron acetate, iron nitrate, and iron sulfate. These may be used alone or in combination of two or more. Among these, iron sulfate is preferable from the viewpoint of improving battery characteristics.

  Examples of manganese compounds that can be used include manganese acetate, manganese nitrate, and manganese sulfate. These may be used alone or in combination of two or more. Among these, manganese sulfate is preferable from the viewpoint of improving battery characteristics.

When both an iron compound and a manganese compound are used as the metal salt, the use molar ratio of these manganese compound and iron compound (manganese compound: iron compound) is preferably 99: 1 to 1:99, more preferably 90. : 10 to 10:90. The total amount of these iron compounds and manganese compounds is preferably 0.99 to 1.01 mol, more preferably 0.995, relative to 1 mol of Li ₃ PO ₄ contained in the slurry water X. ~ 1.005 mol.

Furthermore, you may use metal (M, N, or Q) salts other than an iron compound and a manganese compound as a metal salt as needed. M, N, and Q in the metal (M, N, or Q) salt have the same meanings as M, N, and Q in the above formulas (A) to (C), and as the metal salt, sulfate, halogen compound, organic Acid salts and hydrates thereof can be used. These may be used alone or in combination of two or more. Among them, it is more preferable to use a sulfate from the viewpoint of improving battery physical properties.
When these metal (M, N, or Q) salts are used, the total amount of iron compound, manganese compound, and metal (M, N, or Q) salt added is phosphoric acid in the mixture obtained in the above step (I). Or it is preferably 0.99 to 1.01 mole, and more preferably 0.995 to 1.005 mole relative to 1 mole of silicic acid.

  The amount of water used for the hydrothermal reaction is phosphoric acid or silicate ions contained in the slurry water X from the viewpoint of the solubility of the metal salt used, the ease of stirring, the efficiency of synthesis, etc. Preferably it is 10-50 mol with respect to 1 mol, More preferably, it is 12.5-45 mol. More specifically, when the ions contained in the slurry water X are phosphate ions, the amount of water used for the hydrothermal reaction is preferably 10 to 30 mol, more preferably 12 .5 to 25 moles. Moreover, when the ion contained in the slurry water X is a silicate ion, the usage-amount of the water used when attaching | subjecting to a hydrothermal reaction becomes like this. Preferably it is 10-50 mol, More preferably, it is 12.5-45. Is a mole.

In the step (I) or (Ib), the order of adding the iron compound, manganese compound and metal (M, N or Q) salt is not particularly limited. Moreover, while adding these metal salts, you may add antioxidant as needed. As such an antioxidant, sodium sulfite (Na ₂ SO ₃ ), hydrosulfite sodium (Na ₂ S ₂ O ₄ ), aqueous ammonia and the like can be used. From the viewpoint of preventing the generation of oxide X represented by the above formulas (A) to (C) from being suppressed by adding an excessive amount of the antioxidant, an iron compound and a manganese compound. And it is preferably 0.01 to 1 mol, more preferably 0.03 to 0.5 mol, relative to a total of 1 mol of the metal (M, N or Q) salt used as necessary.

  The content of the precursor of the oxide X in the slurry water X obtained by adding an iron compound, a manganese compound, and a metal (M, N or Q) salt or an antioxidant used as necessary is preferably 10. It is -50 mass%, More preferably, it is 15-45 mass%, More preferably, it is 20-40 mass%.

The hydrothermal reaction in process (I) or (Ib) should just be 100 degreeC or more, and 130-180 degreeC is preferable. The hydrothermal reaction is preferably carried out in a pressure vessel, and when the reaction is carried out at 130 to 180 ° C, the pressure at this time is preferably 0.3 to 0.9 MPa, and the reaction is carried out at 140 to 160 ° C. The pressure is preferably 0.3 to 0.6 MPa. The hydrothermal reaction time is preferably 0.1 to 48 hours, more preferably 0.2 to 24 hours.
The obtained oxide X is an oxide represented by the above formulas (A) to (C), which can be isolated by filtration, washing with water, and drying. As the drying means, freeze drying or vacuum drying is used.

The BET specific surface area of the obtained oxide X is preferably 5 to 40 m ² / g from the viewpoint of efficiently supporting the water-insoluble conductive carbon material and the metal fluoride and effectively reducing the amount of adsorbed moisture. More preferably, it is 5-20 m < ² > / g. When the BET specific surface area of the oxide X is less than 5 m ² / g, the primary particles of the positive electrode active material for the secondary battery become too large, and the battery characteristics may be deteriorated. On the other hand, if the BET specific surface area exceeds 40 m ² / g, the amount of adsorbed moisture of the positive electrode active material for secondary batteries may increase and affect battery characteristics.

  Step (II) is a step of obtaining a composite X by adding a water-insoluble conductive carbon material to the oxide X obtained in the step (I) and dry-mixing the oxide X. When two or more types of water-insoluble conductive carbon materials are used, or when a water-soluble carbon material is further added as necessary, the order of addition is not particularly limited. The addition amount of the water-insoluble conductive carbon material may be set to the carbon atom equivalent amount of the water-insoluble conductive carbon material in the positive electrode active material for the secondary battery of the present invention. For example, with respect to 100 parts by mass of the oxide X , Preferably it is 0.3-6.5 mass part, More preferably, it is 0.5-5.5 mass part, More preferably, it is 0.6-5 mass part. Further, here, if necessary, a water-soluble carbon material may be added and dry-mixed.

The dry mixing in the step (II) is preferably mixing with a normal ball mill, and more preferably mixed with a planetary ball mill capable of revolving to obtain the complex X (herein referred to as complex X ¹ ). Further, a water-insoluble conductive carbon material and a water-soluble carbon material used in combination as necessary are densely and uniformly dispersed on the surface of the oxide X represented by the above formulas (A) to (C), From the viewpoint of effective loading, it is more preferable that the composite X ² is mixed by adding a compressive force and a shearing force. The process of mixing while applying a compressive force and a shearing force is preferably performed in a closed container equipped with an impeller. The peripheral speed of the impeller is preferably 25 to 40 m / s, more preferably 27 from the viewpoint of increasing the tap density of the obtained positive electrode active material and effectively reducing the amount of adsorbed moisture by reducing the BET specific surface area. ~ 40 m / s. The mixing time is preferably 5 to 90 minutes, more preferably 10 to 80 minutes.
The peripheral speed of the impeller means the speed of the outermost end of the rotary stirring blade (impeller), which can be expressed by the following formula (1), and is mixed while applying compressive force and shearing force. The processing time may vary depending on the peripheral speed of the impeller so that it becomes longer as the peripheral speed of the impeller is slower.
Impeller peripheral speed (m / s) =
Impeller radius (m) × 2 × π × rotational speed (rpm) ÷ 60 (1)

In the step (II), the processing time and / or the impeller peripheral speed when performing the mixing process while applying the compression force and the shearing force are appropriately adjusted according to the amount of the complex X ¹ charged into the container. There is a need. And by operating a container, it becomes possible to perform the process which mixes this, adding compression force and shear force to these mixtures between an impeller and a container inner wall, and said Formula (A)-(C ) The water-insoluble conductive carbon material and the water-soluble carbon material used together as necessary are finely and uniformly dispersed on the surface of the oxide X represented by A positive electrode active material for a secondary battery that can be reduced to a low level can be obtained.
For example, when the mixing process is performed for 6 to 90 minutes in an airtight container equipped with an impeller rotating at a peripheral speed of 25 to 40 m / s, the amount of the complex X ¹ charged into the container is an effective container (equipped with an impeller). Among sealed containers, a container corresponding to a part capable of accommodating the complex X ¹ ) per cm ³ is preferably 0.1 to 0.7 g, more preferably 0.15 to 0.4 g.

Examples of the apparatus equipped with a closed container that can easily perform mixing while applying compressive force and shear force include a high-speed shear mill, a blade-type kneader, and the like. Fine particle composite apparatus Nobilta (manufactured by Hosokawa Micron Corporation) can be suitably used.
As the processing conditions for the mixing, the processing temperature is preferably 5 to 80 ° C, more preferably 10 to 50 ° C. The treatment atmosphere is not particularly limited, but is preferably an inert gas atmosphere or a reducing gas atmosphere.

In step (III), (in the case to obtain a composite X ² or in step (II), X ² complex) process complex X obtained in (I), the relative complex 100 parts by 0 .1 to 40 parts by mass of a metal fluoride precursor, wet mixed and fired. Thereby, the water-soluble carbon material and the metal fluoride are both firmly supported on the oxide while effectively suppressing the exposure of the surface of the oxide X represented by (A) to (C). be able to.

The amount of the metal fluoride precursor added is from the viewpoint of effectively loading the metal fluoride in an amount of 0.1 to 5% by mass on the surface of the oxide X where no water-insoluble conductive carbon material is present. (or complex X ²⁾ with respect to 100 parts by mass of a 0.1 to 40 parts by weight in total, preferably 0.2 to 36 parts by weight, more preferably from 0.3 to 32 parts by weight. Further, from the viewpoint of effectively supporting the metal fluoride, it is preferable to add water together with the metal fluoride precursor. The amount of water added is preferably 30 to 300 parts by mass, more preferably 50 to 250 parts by mass, and even more preferably 75 to 200 parts by mass with respect to 100 parts by mass of the complex X (or complex X ² ). Part.

  The metal fluoride precursor may be any compound that can be subsequently fired to form a metal fluoride to be supported on an oxide. Specifically, the metal fluoride precursor is a metal fluoride precursor. As above, it is preferable to use a fluorine compound and a metal compound which are compounds other than the metal fluoride in combination. Examples of the fluorine compound that is a compound other than the metal fluoride include hydrofluoric acid, ammonium fluoride, and hypofluoric acid. Among them, ammonium fluoride is preferably used. Examples of the metal compound which is a compound other than the metal fluoride include metal acetate, metal nitrate, metal lactate, metal oxalate, metal hydroxide, metal ethoxide, metal isopropoxide, metal butoxide and the like. Of these, metal hydroxides are preferred. In addition, the metal of a metal compound is synonymous with the metal of the said metal fluoride.

The wet mixing means in step (III) is not particularly limited, and can be performed by a conventional method. After the metal fluoride precursor is added to the complex X (or complex X ² ) in the above amount, the temperature at the time of mixing is preferably 5 to 80 ° C., more preferably 10 to 60 ° C. . The resulting mixture is preferably dried before firing. Examples of the drying means include spray drying, vacuum drying, freeze drying and the like.

  In step (III), the mixture obtained by the wet mixing is fired. Firing is preferably performed in a reducing atmosphere or an inert atmosphere. The firing temperature is preferably 500 to 800 ° C., more preferably 600 to 770 ° C., from the viewpoint of improving the conductivity by increasing the crystallinity of the oxide X and the water-insoluble conductive carbon material that are lowered by dry mixing or the like. More preferably, it is 650-750 degreeC. The firing time is preferably 10 minutes to 3 hours, more preferably 30 minutes to 1.5 hours.

The positive electrode active material for a secondary battery according to the present invention is characterized in that the water-insoluble conductive carbon material and the metal fluoride are both supported on the oxide and act synergistically to adsorb moisture in the positive electrode active material for a secondary battery. Can be effectively reduced. Specifically, the amount of adsorbed moisture of the positive electrode active material for a secondary battery of the present invention is the secondary battery in the case of the positive electrode active material for a secondary battery in which the oxide X is represented by the above formula (A) or (C). In the positive electrode active material for a battery, it is preferably 1200 ppm or less, more preferably 1000 ppm or less, and in the positive electrode active material for a secondary battery in which the oxide X is represented by the above formula (B), preferably 2500 ppm or less. More preferably, it is 2000 ppm or less. The amount of adsorbed moisture is such that moisture is adsorbed until equilibrium is reached at a temperature of 20 ° C. and a relative humidity of 50%, the temperature is raised to 150 ° C. and held for 20 minutes, and further raised to a temperature of 250 ° C. Measured as the amount of water volatilized from the start point to the end point, starting from when the temperature rise is resumed from 150 ° C. when held for 20 minutes and ending at the constant temperature state at 250 ° C. It is assumed that the amount of adsorbed moisture of the positive electrode active material for a secondary battery and the amount of moisture volatilized from the start point to the end point are the same, and the measured value of the volatilized moisture amount is This is the amount of moisture adsorbed on the positive electrode active material for the secondary battery.
Thus, since the positive electrode active material for a secondary battery of the present invention hardly adsorbs moisture, the amount of adsorbed moisture can be effectively reduced without requiring strong drying conditions as a production environment, and the resulting lithium In both the ion secondary battery and the sodium ion secondary battery, it is possible to stably exhibit excellent battery characteristics even under various usage environments.
When water is adsorbed until equilibrium is reached at a temperature of 20 ° C. and a relative humidity of 50%, the temperature is raised to 150 ° C. and held for 20 minutes, and further raised to a temperature of 250 ° C. and held for 20 minutes. The amount of water volatilized between the start point and the end point, starting from when the temperature rise is resumed from 150 ° C. and the end point when the constant temperature state at 250 ° C. is completed, is measured using a Karl Fischer moisture meter, for example. Can be measured.

Moreover, the tap density of the positive electrode active material for a secondary battery of the present invention is preferably 0.5 to 1.6 g / cm ³ , more preferably 0.8, from the viewpoint of effectively reducing the amount of adsorbed moisture. ˜1.6 g / cm ³ .

Furthermore, the BET specific surface area of the positive electrode active material for secondary batteries of the present invention is preferably 5 to 21 m ² / g, more preferably 7 to ²⁰ m ² / g, from the viewpoint of effectively reducing the amount of adsorbed moisture. It is.

  The secondary battery to which the positive electrode for a secondary battery including the positive electrode active material for a secondary battery of the present invention can be applied is not particularly limited as long as it has a positive electrode, a negative electrode, an electrolytic solution, and a separator as essential components.

  Here, as for the negative electrode, as long as lithium ions or sodium ions can be occluded at the time of charging and can be released at the time of discharging, the material configuration is not particularly limited, and those having a known material configuration can be used. . For example, a carbon material such as lithium metal, sodium metal, graphite, or amorphous carbon. It is preferable to use an electrode formed of an intercalating material capable of electrochemically inserting and extracting lithium ions or sodium ions, particularly a carbon material.

  The electrolytic solution is obtained by dissolving a supporting salt in an organic solvent. The organic solvent is not particularly limited as long as it is an organic solvent that is usually used for an electrolyte solution of a lithium ion secondary battery or a sodium ion secondary battery. For example, carbonates, halogenated hydrocarbons, ethers, ketones Nitriles, lactones, oxolane compounds and the like can be used.

The type of the supporting salt is not particularly limited, but in the case of a lithium ion secondary battery, an inorganic salt selected from LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , a derivative of the inorganic salt, LiSO ₃ CF ₃ , an organic material selected from LiC (SO ₃ CF ₃ ) ₂ , LiN (SO ₃ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ and LiN (SO ₂ CF ₃ ) (SO ₂ C ₄ F ₉ ) It is preferably at least one of a salt and a derivative of the organic salt. In the case of a sodium ion secondary battery, an inorganic salt selected from NaPF ₆ , NaBF ₄ , NaClO ₄ and NaAsF ₆ , a derivative of the inorganic salt, NaSO ₃ CF ₃ , NaC (SO ₃ CF ₃ ) ₂ and NaN (SO ₃ CF ₃ ) ₂ , NaN (SO ₂ C ₂ F ₅ ) ₂ and NaN (SO ₂ CF ₃ ) (SO ₂ C ₄ F ₉ ), and at least one of derivatives of the organic salt It is preferable.

  The separator plays a role of electrically insulating the positive electrode and the negative electrode and holding the electrolytic solution. For example, a porous synthetic resin film, particularly a polyolefin polymer (polyethylene, polypropylene) porous film may be used.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.

[Example 1-1]
4.9 kg of LiOH.H ₂ O and 11.7 L of ultrapure water were mixed to obtain slurry water. Then, with stirring for 30 minutes at speed 400rpm while maintaining the resulting slurry water temperature of 25 ° C., a 70% aqueous solution of phosphoric acid 5.09kg was added dropwise at 35 mL / min, to obtain a mixture A ¹¹ . The pH of the mixed slurry was 10.0 and contained 0.33 mol of phosphoric acid with respect to 1 mol of lithium.

Next, the obtained mixture A ¹¹ was purged with nitrogen while stirring at a speed of 400 pm for 30 minutes to complete the reaction with the mixture A ¹¹ (dissolved oxygen concentration 0.5 mg / L). Subsequently, 1.63 kg of FeSO ₄ .7H ₂ O and 5.60 kg of MnSO ₄ .H ₂ O were added to 21.7 kg of the mixture A ^{11, and} 46.8 g of Na ₂ SO _{3 was} further added to the mixture at a speed of 400 rpm. stirring and mixing to at obtain a mixture a ^12. In this case, the added FeSO ₄ · 7H ₂ O and MnSO ₄ · H ₂ O molar ratio of _{(FeSO 4 · 7H 2 O:} MnSO 4 · H 2 O) is 20: was 80.
The mixture A ¹² was placed in a synthesis vessel installed in a steam-heated autoclave. After the addition, the mixture was heated with stirring at 170 ° C. for 1 hour using saturated steam obtained by heating water (dissolved oxygen concentration less than 0.5 mg / L) with a membrane separator. The pressure in the autoclave was 0.8 MPa. The produced crystal was filtered, and then washed with 12 parts by mass of water with respect to 1 part by mass of the crystal. The washed crystals were vacuum-dried at 60 ° C. and 1 Torr, and oxide A ¹² (powder, chemical composition represented by the formula (A): LiFe _0.2 Mn _0.8 PO ₄ , BET specific surface area 21 m ² / g, average grain 60 nm in diameter) was obtained.

100 g of the obtained oxide A ¹² was fractionated, and 1.6 g of glucose (corresponding to 0.6% by mass in terms of carbon atom in the positive electrode active material for a lithium ion secondary battery) and Ketjen Black After 0 g (corresponding to 1.0 mass% in terms of carbon atom in the positive electrode active material for a lithium ion secondary battery) was dry-mixed by a ball mill, it was fired at 700 ° C. for 1 hour in a reducing atmosphere. The composite X ¹¹ obtained was mixed with Nobilta (manufactured by Hosokawa Micron Corporation, NOB130) at 40 m / s (6000 rpm) for 5 minutes to obtain a composite Y ¹¹ (powder).

40.00 g of the obtained composite Y ¹¹ was taken, and 0.29 g of ammonium fluoride (corresponding to 0.5% by mass in terms of LiF in the positive electrode active material for a lithium ion secondary battery) and 25 mL of water It was added and the slurry a ¹¹ was prepared by mixing. On the other hand, 0.33 g of LiOH.H ₂ O and 25 mL of water were mixed to prepare a solution B ¹¹ . Next, the solution B ¹¹ was added to the slurry A ¹¹ and mixed for 3 hours, followed by drying at 80 ° C. for 12 hours and baking at 700 ° C. for 11 hours in a reducing atmosphere to obtain a lithium ion secondary battery. A positive electrode active material (LiFe _0.2 Mn _0.8 PO ₄ , amount of carbon = 1.6 mass%, amount of LiF = 0.5 mass%) was obtained.

[Example 1-2]
0.59 g of ammonium fluoride to be added to the composite Y ¹¹ (corresponding to 1.0% by mass in terms of LiF in the positive electrode active material for a lithium ion secondary battery), and LiOH • for adjusting the solution B ¹² A positive electrode active material for a lithium ion secondary battery (LiFe _0.2 Mn _0.8 PO ₄ , amount of carbon = 1.6% by mass, LiF) in the same manner as in Example 1-1 except that H ₂ O was changed to 0.66 g. Amount = 1.0% by mass).

[Example 1-3]
1.47 g of ammonium fluoride to be added to the composite Y ¹¹ (corresponding to 2.5% by mass in terms of LiF in the positive electrode active material for a lithium ion secondary battery), and LiOH • for adjusting the solution B ¹³ A positive electrode active material for a lithium ion secondary battery (LiFe _0.2 Mn _0.8 PO ₄ , the amount of carbon = 1.6% by mass, LiF) in the same manner as in Example 1-1, except that H ₂ O was changed to 1.65 g. Amount = 2.5% by mass).

[Example 1-4]
0.59 g of ammonium fluoride to be added to the composite Y ¹¹ (corresponding to 0.5 mass% in terms of MgF ₂ in the positive electrode active material for a lithium ion secondary battery), and LiOH for adjusting the solution B ¹⁴ A positive electrode active material for a lithium ion secondary battery (LiFe _0.2 Mn _0.8 PO ₄ , carbon, in the same manner as in Example 1-1, except that 0.69 g of magnesium acetate tetrahydrate was used instead of H ₂ O. Amount = 1.6% by mass, and MgF ₂ amount = 0.5% by mass).

[Example 1-5]
1.18 g of ammonium fluoride to be added to the composite Y ¹¹ (corresponding to 1.0% by mass in terms of MgF ₂ in the positive electrode active material for a lithium ion secondary battery), and LiOH for adjusting the solution B ¹⁵ A positive electrode active material for a lithium ion secondary battery (LiFe _0.2 Mn _0.8 PO ₄ , carbon, in the same manner as in Example 1-1, except that 1.39 g of magnesium acetate tetrahydrate was used instead of H ₂ O. Amount = 1.6 mass%, MgF ₂ amount = 1.0 mass%).

[Comparative Example 1-1]
The resulting complex Y ¹¹ by adding water 50 mL, without the use of ammonium fluoride and LiOH · H ₂ O, except that the solution B ¹⁶ was prepared, in the same manner as in Example 1-1, a lithium ion secondary A positive electrode active material for a secondary battery (LiFe _0.2 Mn _0.8 PO ₄ , amount of carbon = 1.6% by mass, no metal fluoride supported) was obtained.

[Example 2-1]
3.75 L of ultrapure water was mixed with 0.428 kg of LiOH.H ₂ O and 1.40 kg of Na ₄ SiO ₄ .nH ₂ O to obtain slurry water. Next, 0.39 kg of FeSO ₄ .7H ₂ O, 0.79 kg of MnSO ₄ .5H ₂ O, and 53 g of Zr (SO ₄ ) ₂ .4H ₂ O were added to the obtained slurry water, and the temperature was adjusted to 25 ° C. It was stirred for 30 minutes at speed 400rpm while maintaining, to obtain a mixture a ^21. At this time, the molar ratio of FeSO ₄ · 7H ₂ O, MnSO ₄ · 5H ₂ O and Zr (SO ₄ ) ₂ · 4H ₂ O added (FeSO ₄ · 7H ₂ O: MnSO ₄ · 5H ₂ O: Zr (SO _{4) 2} · 4H ₂ O) is 28: 66: 3.
Subsequently, the obtained mixture A ²¹ was put into a synthesis container installed in a steam heating autoclave. After the addition, the mixture was heated with stirring at 150 ° C. for 12 hours using saturated steam obtained by heating water (dissolved oxygen concentration less than 0.5 mg / L) with a membrane separator. The pressure in the autoclave was 0.4 MPa. The produced crystal was filtered, and then washed with 12 parts by mass of water with respect to 1 part by mass of the crystal. The washed crystal was freeze-dried at −50 ° C. for 12 hours to obtain oxide A ²¹ (powder, chemical composition represented by the formula (B): Li ₂ Fe _0.28 Mn _0.66 Zr _0.03 SiO ₄ , BET specific surface area 35 m ² / g. The average particle size was 50 nm).

213.9 g of the obtained oxide A ²¹ was fractionated and dried with a ball mill together with 16.1 g of ketjen black (equivalent to 7.0% by mass in terms of carbon atom in the positive electrode active material for a lithium ion secondary battery). Mixed. The composite X ²¹ obtained was mixed with Nobilta (manufactured by Hosokawa Micron Corporation, NOB130) at 40 m / s (6000 rpm) for 5 minutes to obtain a composite Y ²¹ (powder).

4.0 g of the obtained composite Y ²¹ was collected, and 0.033 g of LiOH and 0.029 g of ammonium fluoride (0.5 mass in terms of the amount of LiF supported in the positive electrode active material for a lithium ion secondary battery) %) And 5 mL of water, and the mixture was stirred for 1 hour and then calcined at 650 ° C. for 1 hour in a reducing atmosphere to obtain a positive electrode active material for lithium ion secondary battery (Li ₂ Fe _0.28 Mn _0.66 Zr _0.03 SiO ₄ and carbon amount = 7.0% by mass, LiF amount = 0.5% by mass).

[Example 2-2]
Except for 0.066 g of LiOH added to the composite Y ²¹ and 0.059 g of ammonium fluoride (corresponding to 1.0 mass% in terms of the amount of LiF supported in the positive electrode active material for a lithium ion secondary battery), Positive electrode active material for lithium ion secondary battery (Li ₂ Fe _0.28 Mn _0.66 Zr _0.03 SiO ₄ , amount of carbon = 7.0% by mass, amount of LiF = 1.0% by mass in the same manner as in Example 2-1. )

[Example 2-3]
0.132 g of LiOH and 0.118 g of ammonium fluoride to be added to the composite Y ²¹ (corresponding to 2.0% by mass in terms of the amount of LiF supported in 100% by mass of the positive electrode active material for a lithium ion secondary battery) In the same manner as in Example 2-1, a positive electrode active material for a lithium ion secondary battery (Li ₂ Fe _0.28 Mn _0.66 Zr _0.03 SiO ₄ , amount of carbon = 7.0 mass%, amount of LiF = 2. 0% by mass) was obtained.

[Example 2-4]
In place of LiOH added to the composite Y ²¹ , 0.078 g of Al (OH) ₃ and 0.353 g of ammonium fluoride ( ₂ in terms of the amount of AlF ₂ supported in 100% by mass of the positive electrode active material for a lithium ion secondary battery) 0.02 mass%) in the same manner as in Example 2-1, the positive electrode active material for lithium ion secondary battery (Li ₂ Fe _0.28 Mn _0.66 Zr _0.03 SiO ₄ , amount of carbon = 7.0 mass) %, The amount of AlF ₃ = 2.0 mass%).

[Example 2-5]
Instead of LiOH added to the composite Y ²¹ , 0.277 g of Mg (CH ₃ COO) ₂ .4H ₂ O and 0.236 g of ammonium fluoride (in terms of the amount of MgF ₂ supported in the positive electrode active material for a lithium ion secondary battery) In the same manner as in Example 2-1, the positive electrode active material for a lithium ion secondary battery (Li ₂ Fe _0.28 Mn _0.66 Zr _0.03 SiO ₄ , amount of carbon = 7. 0% by mass, the amount of MgF ₂ = 2.0% by mass).

[Comparative Example 2-1]
Except for 0.396 g of LiOH added to the composite Y ²¹ and 0.353 g of ammonium fluoride (corresponding to 6.0% by mass in terms of the amount of LiF supported in the positive electrode active material for a lithium ion secondary battery), Positive electrode active material for lithium ion secondary battery (Li ₂ Fe _0.28 Mn _0.66 Zr _0.03 SiO ₄ , amount of carbon = 7.0 mass%, amount of LiF = 6.0 mass% in the same manner as in Example 2-1. )

[Comparative Example 2-2]
A positive electrode active material for a lithium ion secondary battery (Li ₂ Fe _0.28 Mn _0.66 Zr _0.03 SiO ₄ , amount of carbon = 7.0% by mass) in the same manner as in Example 2-1, except that no metal fluoride was added. No metal fluoride was supported).

[Example 3-1]
A solution was obtained by mixing 0.60 kg of NaOH and 9.0 L of water. Next, the obtained solution is stirred for 5 minutes while maintaining the temperature at 25 ° C., and 0.577 kg of 85% phosphoric acid aqueous solution is dropped at 35 mL / min, followed by stirring at a speed of 400 rpm for 12 hours. Thus, a slurry containing the mixture A ³¹ was obtained. Such a slurry contained 3.00 moles of sodium per mole of phosphorus. The obtained slurry was purged with nitrogen gas to adjust the dissolved oxygen concentration to 0.5 mg / L, then 0.139 kg of FeSO ₄ .7H ₂ O, 0.964 kg of MnSO ₄ .5H ₂ O, MgSO _4. 0.124 kg of 7H ₂ O was added. At this time, the molar ratio of FeSO ₄ · 7H ₂ O, MnSO ₄ · 5H ₂ O and MgSO ₄ · 7H ₂ O added (FeSO ₄ · 7H ₂ O: MnSO ₄ · 5H ₂ O: MgSO ₄ · 7H ₂ O is 10:80:10.
Subsequently, the obtained liquid mixture was thrown into the autoclave purged with nitrogen gas, and the hydrothermal reaction was performed at 200 degreeC for 3 hours. The pressure in the autoclave was 1.4 MPa. The produced crystal was filtered, and then washed with 12 parts by mass of water with respect to 1 part by mass of the crystal. The washed crystals were freeze-dried at −50 ° C. for 12 hours to obtain oxide A ³¹ (powder, chemical composition represented by the formula (C): NaFe _0.1 Mn _0.8 Mg _0.1 PO ₄ , BET specific surface area 15 m ² / g, average A particle size of 100 nm) was obtained.

153.6 g of the obtained oxide A ³¹ was fractionated, and dried with a ball mill together with 6.4 g of ketjen black (corresponding to 4.0% by mass in terms of carbon atom in the positive electrode active material for a sodium ion secondary battery). Mixed. The composite X ³¹ obtained was mixed with Nobilta (manufactured by Hosokawa Micron Corporation, NOB130) at 40 m / s (6000 rpm) for 5 minutes to obtain a composite Y ³¹ (powder). 4.0 g of the obtained composite Y ³¹ was collected, and 0.033 g of LiOH and 0.029 g of ammonium fluoride (0.5 mass in terms of the amount of LiF supported in the positive electrode active material for a sodium ion secondary battery) %) And 5 mL of water were mixed and stirred for 1 hour, and then calcined at 700 ° C. for 1 hour in a reducing atmosphere to obtain a positive electrode active material for sodium ion secondary batteries (NaFe _0.1 Mn _0.8 Mg _0.1 PO ₄ , Carbon amount = 4.0% by mass, LiF amount = 0.5% by mass).

[Example 3-2]
Except for 0.066 g of LiOH added to the composite Y ³¹ and 0.059 g of ammonium fluoride (corresponding to 1.0% by mass in terms of the amount of LiF supported in the positive electrode active material for a sodium ion secondary battery), In the same manner as in Example 3-1, a positive electrode active material for a sodium ion secondary battery (NaFe _0.1 Mn _0.8 Mg _0.1 PO ₄ , amount of carbon = 4.0% by mass, amount of LiF = 1.0% by mass) Obtained.

[Example 3-3]
Except for 0.132 g of LiOH added to the composite Y ³¹ and 0.118 g of ammonium fluoride (corresponding to 2.0 mass% in terms of the amount of LiF supported in the positive electrode active material for a sodium ion secondary battery), In the same manner as in Example 3-1, a positive electrode active material for a sodium ion secondary battery (NaFe _0.1 Mn _0.8 Mg _0.1 PO ₄ , amount of carbon = 4.0% by mass, amount of LiF = 2.0% by mass) Obtained.

[Example 3-4]
Instead of LiOH added to the composite Y ³¹ , 0.078 g of Al (OH) ₃ and 0.353 g of ammonium fluoride (2.0 mass in terms of the amount of AlF ₃ supported in the positive electrode active material for sodium ion secondary battery) The positive electrode active material for a sodium ion secondary battery (NaFe _0.1 Mn _0.8 Mg _0.1 PO ₄ , the amount of carbon = 4.0% by mass, AlF ₃ ) in the same manner as in Example 3-1. Amount = 2.0% by mass).

[Example 3-5]
Instead of LiOH added to the composite Y ³¹ , 0.277 g of Mg (CH ₃ COO) ₂ .4H ₂ O and 0.236 g of ammonium fluoride (conversion amount of MgF ₃ in the positive electrode active material for sodium ion secondary battery) In the same manner as in Example 3-1, the positive electrode active material for sodium ion secondary battery (NaFe _0.1 Mn _0.8 Mg _0.1 PO ₄ , amount of carbon = 4.0 mass) %, The amount of MgF ₃ = 2.0 mass%).

[Comparative Example 3-1]
Except for 0.396 g of LiOH added to the composite Y ³¹ and 0.353 g of ammonium fluoride (corresponding to 6.0% by mass in terms of the amount of LiF supported in the positive electrode active material for a sodium ion secondary battery), In the same manner as in Example 3-1, a positive electrode active material for a sodium ion secondary battery (NaFe _0.1 Mn _0.8 Mg _0.1 PO ₄ , amount of carbon = 4.0 mass%, amount of LiF = 6.0 mass%) Obtained.

[Comparative Example 3-2]
A positive electrode active material for a sodium ion secondary battery (NaFe _0.1 Mn _0.8 Mg _0.1 PO ₄ , amount of carbon = 4.0% by mass, metal) in the same manner as in Example 3-1, except that no metal fluoride was added. Without fluoride support).

<Measurement of adsorbed water content>
The adsorbed moisture content of each positive electrode active material obtained in Examples 1-1 to 3-5 and Comparative Examples 1-1 to 3-2 was measured according to the following method.
About the positive electrode active material (composite particle), after allowing it to stand for 1 day in an environment of a temperature of 20 ° C. and a relative humidity of 50% and adsorbing moisture until reaching equilibrium, raising the temperature to 150 ° C. and holding for 20 minutes, Furthermore, when the temperature is raised to 250 ° C. and held for 20 minutes, the start point is when the temperature rise is resumed from 150 ° C., and the end point is when the constant temperature state at 250 ° C. is finished. The amount of water that volatilized was measured with a Karl Fischer moisture meter (MKC-610, manufactured by Kyoto Electronics Industry Co., Ltd.) and determined as the amount of moisture adsorbed in the positive electrode active material.
The results are shown in Table 1.

<< Evaluation of charge / discharge characteristics using secondary battery >>
Using the positive electrode active materials obtained in Examples 1-1 to 3-5 and Comparative Examples 1-1 to 2-3, positive electrodes of lithium ion secondary batteries or sodium ion secondary batteries were produced. Specifically, the obtained positive electrode active material, ketjen black and polyvinylidene fluoride were mixed at a mass ratio of 75: 20: 5, and N-methyl-2-pyrrolidone was added thereto and kneaded sufficiently. A positive electrode slurry was prepared. The positive electrode slurry was applied to a current collector made of an aluminum foil having a thickness of 20 μm using a coating machine, and vacuum dried at 80 ° C. for 12 hours.
Thereafter, it was punched into a disk shape of φ14 mm and pressed at 16 MPa for 2 minutes using a hand press to obtain a positive electrode.
Next, a coin-type secondary battery was constructed using the positive electrode. A lithium foil punched to φ15 mm was used for the negative electrode. For the electrolyte, LiPF ₆ (in the case of a lithium ion secondary battery) or NaPF ₆ (in the case of a sodium ion secondary battery) is mixed in a mixed solvent in which ethylene carbonate and ethyl methyl carbonate are mixed at a volume ratio of 1: 1. Those dissolved at a concentration of 1 mol / L were used. As the separator, a known one such as a polymer porous film such as polypropylene was used. These battery components were assembled and housed in a conventional manner in an atmosphere with a dew point of −50 ° C. or lower to produce a coin-type secondary battery (CR-2032).

A charge / discharge test was performed using the manufactured coin-type secondary battery. In the case of a lithium ion battery, the charging condition is a constant current and constant voltage charge with a current of 1 CA (330 mA / g) and a voltage of 4.5 V, the discharge condition is 1 CA (330 mA / g), and a constant current discharge with a final voltage of 1.5 V. As a result, the discharge capacity at 1 CA was obtained. In the case of a sodium ion battery, the charging conditions are a constant current and constant voltage charging with a current of 1 CA (154 mA / g) and a voltage of 4.5 V, the discharging conditions are a constant current discharge of 1 CA (154 mA / g) and a final voltage of 2.0 V. As a result, the discharge capacity at 1 CA was obtained. Furthermore, 50 cycle repetition tests were performed under the same charge / discharge conditions, and the capacity retention rate (%) was determined by the following formula (2). All charge / discharge tests were performed at 30 ° C.
Capacity retention rate (%) = (discharge capacity after 50 cycles) / (discharge capacity after 1 cycle) × 100 (2)
The results are shown in Table 1.

  From the above results, it can be seen that the positive electrode active material of the example can surely reduce the amount of adsorbed moisture as compared with the positive electrode active material of the comparative example, and can also exhibit excellent performance in the obtained battery.

Claims (7)

The following formula (A), (B) or (C) containing at least iron or manganese:
LiFe _a Mn _b M _c PO ₄ (A)
(In the formula (A), M represents Mg, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd, or Gd. A, b, and c are 0 ≦ a ≦ 1, 0 ≦ b ≦ 1, 0 ≦ c ≦ 0.2, and 2a + 2b + (M valence) × c = 2 and a number satisfying a + b ≠ 0 are shown.)
Li ₂ Fe _d Mn _e N _f SiO ₄ (B)
(In the formula (B), N represents Ni, Co, Al, Zn, V, or Zr. D, e, and f are 0 ≦ d ≦ 1, 0 ≦ e ≦ 1, and 0 ≦ f <1, 2d + 2e +. (The valence of N) × f = 2 is satisfied, and d + e ≠ 0 is satisfied.)
NaFe _g Mn _h Q _i PO ₄ (C)
(In the formula (C), Q represents Mg, Ca, Co, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd, or Gd. G, h, and i are 0 ≦ g ≦. 1, 0 ≦ h ≦ 1, 0 ≦ i <1, and 2g + 2h + (valence of Q) × i = 2 and a number satisfying g + h ≠ 0 are shown.)
A positive electrode active for a lithium ion secondary battery or a sodium ion secondary battery in which 0.1 to 5% by mass of a metal fluoride is supported on a composite comprising an oxide represented by formula (I) and a water-insoluble conductive carbon material. material.   The positive electrode active material for a lithium ion secondary battery or a sodium ion secondary battery according to claim 1, wherein the water-insoluble conductive carbon material is ketjen black or graphite.   The positive electrode active material for a lithium ion secondary battery or a sodium ion secondary battery according to claim 1 or 2, wherein the metal of the metal fluoride is selected from lithium, sodium, magnesium, calcium, and aluminum. A step (I) of obtaining an oxide X by subjecting a slurry water containing a lithium compound or sodium compound, a phosphoric acid compound or a silicic acid compound, and a metal salt containing at least an iron compound or a manganese compound to a hydrothermal reaction;
A step (II) of obtaining a composite X by adding a water-insoluble conductive carbon material to the obtained oxide X and dry-mixing, and the obtained composite X with 0.1 parts by mass relative to 100 parts by mass of the composite. Step (III) of adding 1 to 40 parts by mass of a metal fluoride precursor, wet mixing and firing
The manufacturing method of the positive electrode active material for lithium ion secondary batteries or sodium ion secondary batteries of any one of Claims 1-3 provided with these. The method for producing a positive electrode active material for a lithium ion secondary battery or a sodium ion secondary battery according to claim 4 , wherein the metal of the metal fluoride is selected from lithium, sodium, magnesium, calcium, and aluminum. Step dry mixing in (II) is an oxide and the water-insoluble conductive carbon material are premixed, and then a lithium ion secondary of claim 4 or 5 is mixed to mix while adding a compressive force and shear force The manufacturing method of the positive electrode active material for a secondary battery or a sodium ion secondary battery. The method for producing a positive electrode active material for a lithium ion secondary battery or a sodium ion secondary battery according to claim 6 , wherein the mixing time while applying a compressive force and a shearing force is 5 to 90 minutes.