JP6042515B2 - 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 carbon derived from a water-soluble 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.

  Therefore, the present inventors have made various studies, as long as it is a positive electrode active material for a secondary battery in which carbon derived from a water-soluble carbon material and a specific amount of metal fluoride are supported on a specific oxide, Since carbon and metal fluoride derived from water-soluble carbon materials can effectively coat the oxide surface and effectively suppress moisture adsorption, lithium ions or sodium ions can effectively carry electrical conduction. It has been found that it is extremely useful as a positive electrode active material for batteries, 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 carbon derived from water-soluble carbon material and 0.1-5 mass% metal fluoride are carry | supported by the oxide represented by these are provided.

Further, the present invention provides a hydrothermal reaction to 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 and containing a water-soluble carbon material. Step (I) to obtain complex Y by attaching, and
Step (II) in which 0.1 to 40 parts by mass of a metal fluoride precursor is added to 100 parts by mass of the complex Y and the resulting composite Y is wet-mixed and fired.
The manufacturing method of the said positive electrode active material for secondary batteries provided with these is provided.

  According to the present invention, carbon and metal fluoride are partially supported on a part of the oxide surface by effectively supporting a predetermined oxide with carbon derived from a water-soluble carbon material and a specific amount of metal fluoride. Since it is possible to effectively prevent the oxide from being exposed without the presence of any compound, a positive electrode active material for a secondary battery in which the exposed portion on the oxide surface is effectively reduced can be obtained. 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 transition metal sodium phosphate compound represented by the 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 preferred.

  The positive electrode active material for a secondary battery of the present invention includes a carbon derived from a water-soluble carbon material and 0.1 to 5% by mass of a metal in the oxide represented by the above formula (A), (B) or (C). It is formed by supporting fluoride. That is, the oxide is formed by supporting both carbon and a specific amount of metal fluoride, and either one of carbon or metal fluoride is coated on the oxide surface, but one of them exists. The other of carbon or metal fluoride is effectively supported on the portion where the oxide surface is exposed. Therefore, since the carbon derived from the water-soluble carbon material and a specific amount of metal fluoride are combined and effectively suppressed the exposure of the oxide surface, it is firmly supported over the entire surface of the oxide. Thus, moisture adsorption in the positive electrode active material for secondary batteries can be effectively prevented.

  The water-soluble carbon material supported as carbon carbonized by the oxide represented by the above formula (A), (B) or (C) is equivalent to carbon atom of the water-soluble carbon material in 100 g of water at 25 ° C. This means a carbon material that dissolves in an amount of 0.4 g or more, preferably 1.0 g or more, and functions as a carbon source for coating the oxide surface represented by the above formulas (A) to (C). Examples of the water-soluble carbon material 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.

  The carbon atom equivalent of the water-soluble carbon material is present in the positive electrode active material for a secondary battery of the present invention as carbon supported by the oxide by carbonization of the water-soluble carbon material. The carbon atom equivalent amount of the water-soluble carbon material is preferably 0.1 to 4% by mass, more preferably 0.2 to 3.5% by mass in the positive electrode active material for a secondary battery of the present invention. Yes, and more preferably 0.3 to 3% by mass. The amount in terms of carbon atoms of the water-soluble carbon material present in the positive electrode active material for secondary battery can be confirmed by the amount of carbon measured using a carbon / sulfur analyzer.

  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). Among these, from the viewpoint of improving the hydrophobicity of the metal fluoride and improving the ionic conductivity, a metal selected from lithium, sodium, magnesium, calcium, and zirconium is preferable, and selected from lithium and magnesium. More preferably, it is a metal.

  From the viewpoint of effectively supporting the metal fluoride on the surface of the oxide containing no carbon formed by carbonizing the water-soluble carbon material, the amount of the metal fluoride supported is in the positive electrode active material for the secondary battery of the present invention. 0.1 to 5% by mass, preferably 0.2 to 4.5% by mass, and more preferably 0.3 to 4% by 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 required from the viewpoint of efficiently supporting carbon and metal fluoride on the oxide represented by the above (A), (B) or (C) while complementing each other. It is preferable that 0.1 to 5% by mass of a metal fluoride is supported on the oxide after supporting the carbon derived from the water-soluble carbon material, specifically, the oxide and the water-soluble carbon. It is preferable that 0.1 to 5% by mass of a metal fluoride is supported on a composite containing carbon derived from the material.
Further, from the viewpoint of effectively supporting the metal fluoride in a portion where the surface of the oxide is exposed without the presence of the water-soluble carbon material in the composite, the metal fluoride is 0% with respect to 100 parts by mass of the composite. It is preferable that 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 includes a composite containing an oxide and carbon derived from a water-soluble 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 of 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.

  The composite containing the oxide and the carbon derived from the water-soluble carbon material specifically includes a lithium compound or a sodium compound, a phosphoric acid compound or a silicic acid compound, and at least an iron compound or a manganese compound, and is water-soluble. It is preferable that it is obtained by subjecting slurry water containing a carbon material to a hydrothermal reaction. That is, the composite containing the oxide and the carbon derived from the water-soluble carbon material includes a lithium compound or a sodium compound, a phosphoric acid compound or a silicic acid compound, and at least an iron compound or a manganese compound, and includes a water-soluble carbon material. The slurry water is preferably a hydrothermal reactant.

More specifically, the positive electrode active material for a secondary battery according to the present invention contains 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, and is water-soluble. The step (I) of obtaining slurry Y by subjecting slurry water containing a carbon material to a hydrothermal reaction, and the resulting complex Y are 0.1 to 40 parts by mass with respect to 100 parts by mass of the complex. Step of adding metal fluoride precursor, wet mixing and firing (II)
It is preferable that it is obtained by a manufacturing method provided with.

Step (I) is a hydrothermal reaction of 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 and containing a water-soluble carbon material. It is the process of attaching | subjecting and obtaining the composite Y.
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.

  The content of the water-soluble carbon material in the slurry water may be an amount such that the supported amount of the water-soluble carbon material as carbon obtained by carbonization falls within the above range in terms of carbon atoms, as described above. From the viewpoint of effectively carrying carbon derived from a water-soluble carbon material in an amount of 0.1 to 4% by mass on the surface of the oxide, preferably 0.03 to 3.5 with respect to 100 parts by mass of water in the slurry water. It is a mass part, More preferably, it is 0.03-2.5 mass part.

Step (I) is a mixture X containing a lithium compound or a sodium compound, from the viewpoint of improving the physical properties of the battery by increasing the dispersibility of each component contained in the slurry water and making the resulting positive electrode active material particles finer. Step (Ia) of mixing the phosphoric acid compound or silicic acid compound to obtain the complex X, and adding to the obtained complex X a metal salt containing at least an iron compound or a manganese compound and a water-soluble carbon material. It is preferable to include the step (Ib) of obtaining the composite Y by subjecting the obtained slurry water Y to a hydrothermal reaction.
At this time, the water-soluble carbon material only needs to be contained in the slurry water Y that is finally subjected to a hydrothermal reaction, and before mixing the phosphoric acid compound or the silicate compound in the step (Ia) or mixing. The slurry water Y may be added by adding together with a metal salt containing at least an iron compound or a manganese compound in the step (Ib). Among these, from the viewpoint of efficiently supporting carbon obtained by carbonizing a water-soluble carbon material on the oxide, the water-soluble carbon material is added together with a metal salt containing an iron compound or a manganese compound in the step (Ib). preferable.

  In the step (I) or (Ia), it is preferable to stir the mixture X in advance before mixing the phosphoric acid compound or the silicic acid compound with the mixture X. The stirring time of the mixture X is preferably 1 to 15 minutes, more preferably 3 to 10 minutes. Moreover, the temperature of the mixture X becomes like this. Preferably it is 20-90 degreeC, More preferably, it is 20-70 degreeC.

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 the step (I) or (Ia), when mixing the phosphoric acid into the mixture X, it is preferable to add the phosphoric acid dropwise while stirring the mixture. By adding phosphoric acid dropwise to the mixture X and adding it little by little, the reaction proceeds well in the mixture X, and the precursors of the oxides represented by the above (A) to (C) are uniformly in the slurry. It is possible to effectively suppress the generation of the oxide precursor while being dispersed, and the unnecessary aggregation of the oxide precursor.

The dropping rate of phosphoric acid into the mixture X 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 X 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 X while dropping phosphoric acid is preferably 200 to 700 rpm, more preferably 250 to 600 rpm, and further preferably 300 to 500 rpm.
In addition, when stirring the mixture X, it is preferable to further cool below the boiling point temperature of the mixture X. 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.

It is preferable that the mixture X after mixing a phosphoric acid compound or a silicic acid compound contains 2.0-4.0 mol of lithium or sodium with respect to 1 mol of phosphoric acid or silicic acid, and is 2.0-3. 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 the case where a phosphoric acid compound is used in the step (I) or (Ia) is used, the mixture X after mixing the phosphoric acid compound contains lithium or sodium with respect to 1 mol of phosphoric acid. It is preferable to contain 2.7 to 3.3 mol, more preferably 2.8 to 3.1 mol, and when the silicate compound is used in step (I) or (Ia), the silicate compound is added. It is preferable that the mixture X after mixing contains 2.0-4.0 mol of lithium with respect to 1 mol of silicic acid, and it is more preferable to contain 2.0-3.0.
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.

By purging the mixture X after mixing the phosphoric acid compound or the silicic acid compound with nitrogen, the reaction in the mixture X is completed, and the oxides represented by the above (A) to (C) A complex X which is a precursor of is formed in the mixture. When nitrogen is purged, the reaction can proceed in a state where the dissolved oxygen concentration in the mixture X is reduced, and the dissolved oxygen concentration in the mixture X containing the resulting complex X is also effectively reduced. Therefore, oxidation of the iron compound or manganese compound added in the next step can be suppressed. In the mixture X, the oxide precursors represented by the above (A) to (C) are present as fine dispersed particles. For example, in the case of the oxide represented by the above formula (A), the precursor of the composite 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. Moreover, the temperature of the mixture X after mixing a phosphoric acid compound or a silicic acid compound becomes like this. Preferably it is 20-80 degreeC, More preferably, it is 20-60 degreeC. 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.
Moreover, when purging nitrogen, it is preferable to stir the mixture X after mixing a phosphoric acid compound or a silicic acid compound from a viewpoint of making reaction progress favorable. 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 on the surface of the dispersed particles of the complex X and miniaturizing the dispersed particles, the dissolved oxygen concentration in the mixture X after mixing the phosphoric acid compound or the silicate compound is reduced to 0. 0.5 mg / L or less is preferable, and 0.2 mg / L or less is more preferable.

  In the step (I) or (Ib), the obtained complex X and a slurry water Y containing at least an iron compound or a manganese compound and containing a water-soluble carbon material are subjected to a hydrothermal reaction. Thus, the complex Y is obtained. The obtained complex X is used as a precursor of the oxide represented by the above (A) to (C) as a mixture, and a metal salt containing at least an iron compound or a manganese compound, and a water-soluble carbon material Is preferably used as slurry water Y. As a result, while simplifying the process, the oxides represented by the above (A) to (C) can efficiently carry carbon formed by carbonizing the water-soluble carbon material, and extremely fine particles. And a very useful positive electrode active material for a secondary battery 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 moles, more preferably 0.995, with respect to 1 mole of Li ₃ PO ₄ contained in the slurry water Y. ~ 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 water-soluble carbon material in the slurry Y is preferably 0.03 to 3.4% by mass, and more preferably 0.03 to 2.4% by mass.

  The amount of water used for the hydrothermal reaction is phosphoric acid or silicate ions contained in the slurry water Y 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 Y 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 slurry water Y 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 addition of the iron compound, the manganese compound and the metal (M, N or Q) salt, and the water-soluble carbon material 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 oxides represented by the above formulas (A) to (C) from being added in excess, the addition amount of the antioxidant is an iron compound, a manganese compound, and Preferably it is 0.01-1 mol with respect to the total of 1 mol of metal (M, N, or Q) salt used as needed, More preferably, it is 0.03-0.5 mol.

  The content of the complex Y in the slurry Y obtained by adding an iron compound, a manganese compound and a metal (M, N or Q) salt used as necessary, and a water-soluble carbon material or an antioxidant is preferable. Is 10-50 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 composite Y is a composite containing the oxides represented by the above formulas (A) to (C) and a water-soluble carbon material. After filtration, the composite Y is washed with water and dried. It can be isolated as body particles. As the drying means, freeze drying or vacuum drying is used.

The BET specific surface area of the obtained composite Y is preferably 5 to 40 m ² / g from the viewpoint of efficiently carrying the carbon and metal fluoride derived from the water-soluble carbon material and effectively reducing the amount of adsorbed water. More preferably, it is 5-20 m < ² > / g. If the BET specific surface area of the composite Y 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.

  In step (II), 0.1 to 40 parts by weight of a metal fluoride precursor is added to 100 parts by weight of the composite Y obtained in step (I), wet-mixed, and fired. It is a process to do. Thereby, while effectively suppressing the exposure of the oxide surface represented by the above (A) to (C), both the carbon derived from the water-soluble carbon material and the metal fluoride are firmly attached to the oxide. It can be supported.

  The amount of the metal fluoride precursor added is 100 parts by mass of the composite Y from the viewpoint of effectively supporting the metal fluoride in an amount of 0.1 to 5% by mass on the surface of the oxide in which no water-soluble carbon material is present. On the other hand, it is 0.1-40 mass parts, Preferably it is 0.2-36 mass parts, More preferably, it is 0.3-32 mass parts. 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 composite Y.

  The metal fluoride precursor may be any compound that can be fired later to form a metal fluoride to be supported on an oxide. Specifically, as a metal fluoride precursor, 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 the step (II) is not particularly limited and can be performed by a conventional method. The temperature at the time of mixing after adding the metal fluoride precursor to the composite Y in the above amount 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 the step (II), 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, and further preferably 650 to 750 ° C, from the viewpoint of effectively carbonizing the water-soluble carbon material. 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 of the present invention is such that the carbon derived from the water-soluble carbon material and the metal fluoride are both supported on the oxide and act synergistically to adsorb on the positive electrode active material for the secondary battery. The amount of moisture can be effectively reduced. Specifically, the amount of adsorbed moisture of the positive electrode active material for secondary battery of the present invention is the same for the secondary battery in the case of the positive electrode active material for secondary battery in which the oxide is represented by the above formula (A) or (C). In the positive electrode active material, preferably it is 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 is represented by the above formula (B), preferably 2500 ppm or less, and 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]
12.72 g of LiOH.H ₂ O and 90 mL of water were mixed to obtain slurry water. Next, 11.53 g of 85% aqueous phosphoric acid solution was added dropwise at 35 mL / min while stirring the resulting slurry water at a temperature of 25 ° C. for 5 minutes, followed by 12 hours under a nitrogen gas purge at 400 rpm. By stirring at a speed, a mixture X ¹ (slurry water X ¹ , dissolved oxygen concentration 0.5 mg / L) containing the complex X ¹ was obtained. The slurry water X ¹ contained 2.97 mol of lithium with respect to 1 mol of phosphorus.

Next, 5.56 g of FeSO ₄ .7H ₂ O, 19.29 g of MnSO ₄ .5H ₂ O and 1.18 g of glucose (positive electrode active material for a lithium ion secondary battery) with respect to 114.2 g of the obtained slurry water X ¹ And equivalent to 3.0% by mass in terms of carbon atoms) was added and stirred at a speed of 400 rpm for 30 minutes while maintaining the temperature at 25 ° C. to obtain slurry water Y ¹ . 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.
Next, the obtained slurry water Y ¹ was put into a synthesis container installed in a steam heating 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 crystal was freeze-dried at −50 ° C. for 12 hours to give a composite Y ¹ (powder, chemical composition of oxide represented by formula (A): LiFe _0.2 Mn _0.8 PO ₄ , BET specific surface area 21 m ² / g, An average particle size of 60 nm) was obtained.

4.0 g of the obtained composite Y ¹ , 0.033 g of LiOH and 0.029 g of ammonium fluoride (corresponding to 0.5% by mass in terms of the amount of LiF supported in the positive electrode active material for a lithium ion secondary battery) ) Was mixed with 5 ml of water, and LiF-coated composite Y ¹ was obtained by stirring for 1 hour. Next, it was calcined at 700 ° C. for 1 hour in a reducing atmosphere, and a positive electrode active material for a lithium ion secondary battery (LiFe _0.2 Mn _0.8 PO ₄ , amount of carbon = 3.0 mass%, amount of LiF = 0.5 mass) %).

[Example 1-2]
Except for 0.066 g of LiOH added to the composite Y ¹ 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), A positive electrode active material for lithium ion secondary batteries (LiFe _0.2 Mn _0.8 PO ₄ , amount of carbon = 3.0 mass%, amount of LiF = 1.0 mass%) was obtained in the same manner as in Example 1-1. .

[Example 1-3]
Except for 0.132 g of LiOH added to the composite Y ¹ 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 lithium ion secondary battery), A positive electrode active material for lithium ion secondary batteries (LiFe _0.2 Mn _0.8 PO ₄ , amount of carbon = 3.0 mass%, amount of LiF = 2.0 mass%) was obtained in the same manner as in Example 1-1. .

[Example 1-4]
Instead of LiOH added to the composite Y ¹ , 0.078 g of Al (OH) ₃ and 0.353 g of ammonium fluoride (2.0 in terms of the amount of AlF ₃ supported in the positive electrode active material for a lithium ion secondary battery) The positive electrode active material for a lithium ion secondary battery (LiFe _0.2 Mn _0.8 PO ₄ , amount of carbon = 3.0 mass%, amount of AlF ₃ ) = 2.0% by mass).

[Example 1-5]
Instead of LiOH added to the composite Y ¹ , 0.277 g of Mg (CH ₃ COO) ₂ .4H ₂ O and 0.236 g of ammonium fluoride (support of MgF ₂ in the positive electrode active material for a lithium ion secondary battery) Except that the amount was equivalent to 2.0% by mass), a positive electrode active material for a lithium ion secondary battery (LiFe _0.2 Mn _0.8 PO ₄ , amount of carbon = 3.0% by mass) in the same manner as in Example 1-1. %, The amount of MgF ₂ = 2.0 mass%).

[Comparative Example 1-1]
Except for 0.396 g of LiOH added to the composite Y ¹ and 0.353 g of ammonium fluoride (corresponding to 5.7 mass% in terms of the amount of LiF supported in the positive electrode active material for a lithium ion secondary battery), A positive electrode active material for a lithium ion secondary battery (LiFe _0.2 Mn _0.8 PO ₄ , the amount of carbon = 3.0 mass%, the amount of LiF = 5.7 mass%) was obtained in the same manner as in Example 1-1. .

[Comparative Example 1-2]
A positive electrode active material for a lithium ion secondary battery (LiFe _0.2 Mn _0.8 PO ₄ , amount of carbon = 3.0 mass%, metal fluoride, in the same manner as in Example 1-1, except that no metal fluoride was added. Not supported).

[Example 2-1]
LiOH · H ₂ O 4.28g, was obtained slurry water ^{X 2} were mixed ultrapure water 37.5mL to _{Na 4 SiO 4 · nH 2 O} 13.97g. To this slurry water ^{_{X 2, FeSO 4 · 7H 2}} O 3.92g, MnSO 4 · 5H 2 O 7.93g, and Zr (SO ₄₎ was added to ₂ · 4H ₂ O 0.53g, at a temperature of 25 ° C. It was stirred for 30 minutes at speed 400rpm while maintaining, to obtain a slurry water ^{Y 2.} 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.
Then, the resulting slurry water Y ² was charged into the synthesis vessel installed in a steam-heated 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 a composite Y ² (powder, chemical composition of an oxide represented by the formula (B): Li ₂ Fe _0.28 Mn _0.66 Zr _0.03 SiO ₄ , BET specific surface area of 35 m. ² / g, average particle size 50 nm).

4.0 g of the obtained complex Y ² was fractionated, and 1.0 g of glucose (corresponding to 10.0% by mass in terms of carbon atom in the positive electrode active material for a lithium ion secondary battery) was obtained. , And 0.029 g of ammonium fluoride (corresponding to 0.5% by mass in terms of the amount of LiF supported in the positive electrode active material for lithium ion secondary batteries) and 5 mL of water are mixed, and glucose and LiF are stirred by stirring for 1 hour. After being coated, it was baked at 650 ° C. for 1 hour in a reducing atmosphere to obtain 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 = 10.0 mass%, LiF Of 0.5% by mass).

[Example 2-2]
Except for 0.066 g of LiOH added to the composite Y ² 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 = 10.0% by mass, amount of LiF = 1.0% by mass in the same manner as in Example 2-1. )

[Example 2-3]
Except for 0.132 g of LiOH added to the composite Y ² and 0.118 g of ammonium fluoride (corresponding to 2.0% 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 = 10.0% by mass, amount of LiF = 2.0% by mass in the same manner as in Example 2-1. )

[Example 2-4]
2.0 Al _{(OH) 3} in place of LiOH added to the complex ^{Y 2} 0.078 g, in a loading amount in terms of AlF ₂ in the positive electrode active material in a 0.353 g (lithium ion secondary battery of ammonium fluoride Except for the equivalent to mass%), a positive electrode active material for a lithium ion secondary battery (Li ₂ Fe _0.28 Mn _0.66 Zr _0.03 SiO ₄ , the amount of carbon = 10.0 mass%) in the same manner as in Example 2-1. Amount of AlF ₂ = 2.0% by mass) was obtained.

[Example 2-5]
0.277 g of Mg (CH ₃ COO) ₂ .4H ₂ O and 0.236 g of ammonium fluoride instead of LiOH added to the composite Y ² (support of MgF ₂ in the positive electrode active material for a lithium ion secondary battery) The amount of carbon = a positive electrode active material for lithium ion secondary battery (Li ₂ Fe _0.28 Mn _0.66 Zr _0.03 SiO ₄ , carbon = 10.0% 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 ² 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 = 10.0 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 = 10.0% 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 6.00 g of NaOH and 90 mL of water. The resulting solution is then stirred for 5 minutes while maintaining the temperature at 25 ° C., and 5.77 g of 85% aqueous phosphoric acid solution is added dropwise at 35 mL / min, followed by stirring at a speed of 400 rpm for 12 hours. gave a slurry ^{X 3} containing complex ^{X 3.} Such slurry ^{X 3,} compared per mole of phosphorus and contained sodium 3.00 mol. To slurry ^{X 3} obtained after the dissolved oxygen concentration with nitrogen gas was purged and adjusted to _{0.5mg / L, FeSO 4 · 7H} 2 O 1.39g, MnSO 4 · 5H 2 O 9.64g, MgSO ₄ · _7H 2 O 1.24g, and glucose 0.59 g (corresponding to 1.4 wt% in terms of carbon atoms content in the sodium ion secondary battery positive electrode active material in) was added to obtain a slurry solution ^{Y 3} . 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.
Then, the slurry water Y ³ obtained was placed in a steam-heated autoclave was charged in the synthesis vessel was purged with nitrogen gas. After the addition, the mixture was heated with stirring at 200 ° C. for 3 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 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 crystal was freeze-dried at −50 ° C. for 12 hours to give a composite Y ³ (chemical composition of an oxide represented by the formula (C): NaFe _0.1 Mn _0.8 Mg _0.1 PO ₄ , BET specific surface area 15 m ² / g, An average particle size of 100 nm) was obtained.

4.0 g of the obtained composite Y ³ was taken, and 0.033 g of LiOH and 0.029 g of ammonium fluoride (0 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, and LiF coating by stirring for 1 hour, followed by firing at 700 ° C. for 1 hour in a reducing atmosphere to obtain a positive electrode active material for sodium ion secondary battery (NaFe _0.1 Mn _0.8 Mg _0.1 PO ₄ , carbon amount = 1.4 mass%, LiF amount = 0.5 mass%).

[Example 3-2]
Except for 0.066 g of LiOH added to the composite Y ² 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 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 = 1.4 mass%, amount of LiF = 1.0 mass%) Obtained.

[Example 3-3]
Except for 0.132 g of LiOH added to the composite Y ² 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 = 1.4 mass%, amount of LiF = 2.0 mass%) Obtained.

[Example 3-4]
Instead of LiOH added to the composite Y ² , 0.078 g of Al (OH) ₃ and 0.353 g of ammonium fluoride (2.0 in terms of the amount of AlF ₃ supported in the positive electrode active material for a 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 , amount of carbon = 1.4 mass%, AlF ₃₎ Of 2.0% by mass).

[Example 3-5]
Instead of LiOH added to the composite Y ² , 0.277 g of Mg (CH ₃ COO) ₂ .4H ₂ O and 0.236 g of ammonium fluoride (support of MgF ₃ in the positive electrode active material for a sodium ion secondary battery) A positive electrode active material for sodium ion secondary battery (NaFe _0.1 Mn _0.8 Mg _0.1 PO ₄ , amount of carbon = 1. 4 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 ² 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 = 1.4% by mass, amount of LiF = 6.0% by 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 = 1.4 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 (6)

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 lithium ion secondary battery or a sodium ion secondary battery positive electrode 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 carbon derived from a water-soluble carbon material. Active 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-soluble carbon material is one or more selected from saccharides, polyols, polyethers, and organic acids.   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 composite Y obtained 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 and containing a water-soluble carbon material to a hydrothermal reaction. To the obtained composite Y, and 0.1 to 40 parts by weight of a metal fluoride precursor is added to 100 parts by weight of the composite, wet-mixed, and fired ( II)
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. Fluorine compound whose precursor of metal fluoride is selected from ammonium fluoride, hydrofluoric acid, and hypofluorite, and metal acetate, metal nitrate, metal lactate, metal oxalate, metal hydroxide 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 compound is selected from metal ethoxide, metal isopropoxide, and metal butoxide. 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 or 5 , wherein the metal of the metal fluoride is selected from lithium, sodium, magnesium, calcium, and aluminum.