WO2013099409A1 - Procédé de fabrication de phosphate de fer, phosphate de lithium et de fer, matière d'électrode active et batterie secondaire - Google Patents

Procédé de fabrication de phosphate de fer, phosphate de lithium et de fer, matière d'électrode active et batterie secondaire Download PDF

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WO2013099409A1
WO2013099409A1 PCT/JP2012/076793 JP2012076793W WO2013099409A1 WO 2013099409 A1 WO2013099409 A1 WO 2013099409A1 JP 2012076793 W JP2012076793 W JP 2012076793W WO 2013099409 A1 WO2013099409 A1 WO 2013099409A1
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iron phosphate
active material
fepo
electrode active
secondary battery
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PCT/JP2012/076793
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English (en)
Japanese (ja)
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金高　祐仁
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株式会社村田製作所
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B25/00—Phosphorus; Compounds thereof
    • C01B25/16—Oxyacids of phosphorus; Salts thereof
    • C01B25/26—Phosphates
    • C01B25/37—Phosphates of heavy metals
    • C01B25/375—Phosphates of heavy metals of iron
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B25/00—Phosphorus; Compounds thereof
    • C01B25/16—Oxyacids of phosphorus; Salts thereof
    • C01B25/26—Phosphates
    • C01B25/45—Phosphates containing plural metal, or metal and ammonium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a method for producing iron phosphate, lithium iron phosphate, an electrode active material, and a secondary battery, and more specifically, a method for producing iron phosphate as a raw material for lithium iron phosphate, and the production method.
  • the present invention relates to lithium iron phosphate using iron phosphate, an electrode active material mainly composed of this lithium iron phosphate, and a secondary battery including the electrode active material in a positive electrode.
  • lithium ion secondary batteries using an alkali metal ion such as lithium ion as a charge carrier and utilizing an electrochemical reaction accompanying the charge transfer have been developed.
  • lithium ion secondary batteries having a high energy density are now widely used.
  • the electrode active material is a substance that directly contributes to the battery electrode reaction such as the charge reaction and the discharge reaction, and has the central role of the secondary battery. That is, the battery electrode reaction is a reaction that occurs with the transfer of electrons by applying a voltage to an electrode active material that is electrically connected to an electrode disposed in the electrolyte, and proceeds during charging and discharging of the battery. To do. Therefore, as described above, the electrode active material has a central role of the secondary battery in terms of system.
  • a lithium-containing transition metal oxide is used as a positive electrode active material
  • a carbon material is used as a negative electrode active material
  • lithium ion insertion reaction and desorption reaction with respect to these electrode active materials.
  • lithium-containing transition metal oxides include lithium cobaltate (LiCoO 2 ), lithium nickelate (LiNiO 2 ), lithium manganate (LiMn 2 O 4 ), and the like.
  • LiCoO 2 is widely adopted because it has better charge / discharge characteristics and energy density than LiMn 2 O 4 and the like.
  • LiCoO 2 has a problem that it has high resource constraints and is expensive and contains highly toxic Co. Moreover, since LiCoO 2 releases a large amount of oxygen at a temperature of about 180 ° C., a lithium ion battery using a flammable organic electrolyte has a problem in terms of safety. For this reason, when LiCoO 2 is used as the electrode active material, it is suitable for a small capacity secondary battery, but there are many problems to be solved when it is used for a high output and large capacity secondary battery.
  • LiFePO 4 lithium iron phosphate having an olivine crystal structure
  • This LiFePO 4 contains phosphorus (P) as a constituent element, and all oxygen is strongly covalently bonded to phosphorus. For this reason, it does not release oxygen even at high temperatures, has excellent thermal stability, and is suitable for application to an electrode active material for secondary batteries with high output and large capacity.
  • Non-Patent Document 1 reports the effect of morphological characteristics on the electrochemical behavior of a LiFePO 4 -carbon composite having a high tap density produced by a coprecipitation method.
  • H 3 PO 4 containing the Fe (NO) 3 ⁇ 9H 2 O and pentavalent P is a trivalent Fe salt was used as a starting material, and using a co-precipitation method FePO 4 • nH 2 O is synthesized.
  • the reaction temperature is controlled to 50 ° C.
  • NH 4 OH is dropped into a mixed aqueous solution in which Fe (NO) 3 .9H 2 O and H 3 PO 4 are dissolved for 24 hours.
  • the reaction vessel was stirred at a stirring speed of 1000 rpm while adjusting the pH to 2.0 M and the pH to 5.0, thereby obtaining FePO 4 ⁇ nH 2 O precipitated powder (hereinafter referred to as “FePO 4 precipitated powder”). Yes.
  • LiFePO 4 is a material suitable as a positive electrode material of a lithium ion battery as described above. Further, the rate characteristics of the lithium ion battery greatly depend on the particle size of LiFePO 4 , and the better the fineness and uniformity of the particle size, the larger the charge / discharge capacity, and the higher the capacity maintenance rate during high rate charge / discharge. It is possible.
  • the particle size and particle size distribution of the LiFePO 4 since it largely depends on the particle size and particle size distribution of the FePO 4 precipitate powder as a precursor, the control of particle size and particle size distribution of the FePO 4 precipitate powder, very It becomes important.
  • the particle size and particle size distribution of the FePO 4 precipitated powder are easily influenced by synthesis conditions such as the dropping rate of the pH adjusting agent, the stirring method and stirring rate of the mixed aqueous solution, and the reaction temperature. Therefore, in order to synthesize the desired FePO 4 precipitated powder described above, it is necessary to optimize these synthesis conditions and strictly manage the synthesis conditions.
  • Non-Patent Document 1 when NH 4 OH is dropped into a mixed aqueous solution in which Fe 3+ and P 5+ are dissolved, the pH around the dropping temporarily increases. Fe (OH) 3 is preferentially generated over FePO 4 . And once produced Fe (OH) 3 is not easily changed to FePO 4, and thus the obtained precipitated powder becomes a mixture of FePO 4 and Fe (OH) 3, and Fe and P are not uniformly dispersed. Dispersion unevenness occurs, the particle size distribution varies widely, and the shape is uneven.
  • the present invention has been made in view of such circumstances, a method of manufacturing a iron phosphate which can be obtained fine and iron phosphate having a uniform particle size distribution (FePO 4) easily, using this production method
  • An object of the present invention is to provide lithium iron phosphate (LiFePO 4 ) obtained in this manner, an electrode active material mainly composed of this lithium iron phosphate, and a secondary battery including the electrode active material in a positive electrode.
  • the present inventor put a pH adjuster into a mixed aqueous solution in which an iron compound containing phosphorus (P) source and iron (hereinafter referred to as “Fe compound”) was dissolved, and conducted earnest research.
  • an iron compound containing phosphorus (P) source and iron hereinafter referred to as “Fe compound”
  • the pH is less than a certain threshold, the precipitation yield is low, and the precipitated iron phosphate is chemically unstable, and the precipitated powder tends to grow and become coarse, but when the pH exceeds the above threshold,
  • the present inventors have found that the precipitation yield of iron phosphate can be improved rapidly, and a fine powdered iron phosphate powder having good uniformity in particle size can be obtained.
  • the present invention has been made on the basis of such knowledge, and the method for producing iron phosphate according to the present invention comprises introducing a pH adjuster into a mixed aqueous solution in which a phosphorus source and an Fe compound are dissolved. It is characterized in that iron phosphate is produced by reaching a predetermined pH over time.
  • the pH adjuster preferably has a pH of 6 to 9, and more preferably a pH of 6.5 to 7.5.
  • the predetermined pH is preferably 1.5 or more.
  • the short time is preferably within 60 seconds.
  • the pH adjuster is selected from ammonium acetate, sodium lactate, sodium hydrogen tartrate, ammonium hydrogen tartrate, disodium maleate, ammonium chloride, and ammonium formate. It is preferable to include at least one kind.
  • the pH adjuster is in a liquid state.
  • the pH adjusting agent can be poured into the mixed aqueous solution at once, and the mixed aqueous solution can be efficiently reached the predetermined pH in a short time.
  • the Fe compound is preferably produced by oxidizing at least one of iron (II) sulfate and iron (II) chloride in the mixed aqueous solution.
  • the oxidation treatment is preferably performed using an oxidizing agent containing hydrogen peroxide.
  • the lithium iron phosphate according to the present invention is characterized in that iron phosphate and lithium compound produced by any one of the production methods described above are synthesized.
  • the electrode active material according to the present invention is an electrode active material used as an active material of a secondary battery that repeats charging and discharging by a battery electrode reaction, and is characterized by being mainly composed of the above-described lithium iron phosphate. Yes.
  • the secondary battery according to the present invention has a positive electrode, a negative electrode, and an electrolyte, and the positive electrode is formed of the electrode active material described above.
  • a pH adjuster having a pH of preferably 6 to 9, more preferably 6.5 to 7.3 is preferably added to a mixed aqueous solution in which a phosphorus source and an Fe compound are dissolved. Since iron phosphate is produced by reaching a predetermined pH (preferably 1.5 or more) in a time (preferably within 60 seconds), iron phosphate having fine particles and good uniformity in particle size can be obtained.
  • the mixed aqueous solution exhibits a low pH of 1 or less before the pH adjusting agent is added.
  • the precipitation yield is low, and the produced FePO 4 is chemically unstable and the nucleation rate is slow. Therefore, grain growth is likely to occur, and large grains are formed in the FePO 4 precipitated powder. Easy to mix particles of diameter.
  • a pH adjusting agent is added to the mixed aqueous solution and allowed to reach a predetermined pH in a short time, so that the precipitation yield is low and the chemically unstable state is short.
  • a pH adjusting agent is added to the mixed aqueous solution and allowed to reach a predetermined pH in a short time, so that the precipitation yield is low and the chemically unstable state is short.
  • the highly purified lithium phosphate suitable for the electrode active material for secondary batteries is obtained. be able to.
  • the electrode active material used as the active material of the secondary battery that repeats charging and discharging by the battery electrode reaction is mainly composed of the lithium iron phosphate, so that it is safe and high energy.
  • An electrode active material having a density can be obtained.
  • the secondary battery has a positive electrode, a negative electrode, and an electrolyte, and the positive electrode is formed of the electrode active material.
  • a battery can be obtained.
  • FIG. 2 is a SEM image of FePO 4 in an example sample of Example 1.
  • FIG. 2 is a SEM image of FePO 4 in a comparative example sample of Example 1.
  • 2 is a SEM image of LiFePO 4 in an example sample of Example 1.
  • FIG. 2 is a SEM image of LiFePO 4 in a comparative example sample of Example 1.
  • FIG. 1 is a SEM image of LiFePO 4 in a comparative example sample of Example 1.
  • a pH adjuster is introduced into a mixed aqueous solution in which a phosphorus (P) source and an Fe compound are dissolved, and a predetermined pH is reached in a short time to produce FePO 4 .
  • P phosphorus
  • FePO 4 high-purity FePO 4 having fine particles and good uniformity in particle size can be produced with high efficiency.
  • the mixed aqueous solution in which the P source such as H 3 PO 4 and the Fe compound are dissolved has a pH of 1 or less.
  • the pH of the mixed aqueous solution is 1.3.
  • the temperature rises to the extent production of FePO 4 is started.
  • FePO 4 is chemically unstable, and the nucleation rate of the precipitate is slow.
  • the resulting precipitated powder tends to increase in particle size.
  • the precipitated powder generated in the pH region where the precipitation yield is low as described above is easy to grow and coarsen, if the time in the low pH region becomes long, the coarsened particles in the synthesized FePO 4 precipitated powder. Are present, the particle size distribution is widened, and the variation in particle size is increased.
  • the precipitation yield of FePO 4 is dramatically improved as the pH is increased.
  • the pH is 1.5
  • the precipitation yield is about 90%
  • the pH is increased to 1.8
  • the precipitation yield is decreased. About 98%.
  • the low pH region with a low precipitation yield is removed early to reach a predetermined pH in a short time, thereby obtaining FePO 4 having fine particles and good uniformity in particle size.
  • the predetermined pH is not particularly limited as long as FePO 4 having fine particles and good uniformity in particle size can be obtained with a high precipitation yield, but the pH reaches 1.5 as described above. Then, since a precipitation yield improves dramatically to 90%, 1.5 or more are preferable, More preferably, it is 2.0.
  • the time until the pH is reached after the pH adjusting agent is added as the time in the low pH region becomes longer as described above, the time during which the precipitated FePO 4 is chemically unstable becomes longer. Therefore, a time as short as possible is desirable, and it is preferably within 60 seconds.
  • the pH adjusting agent may be either liquid or powdery, but from the viewpoint of quickly reaching the predetermined pH in a short time, a liquid in which a predetermined amount of the pH adjusting agent can be poured into the mixed aqueous solution at a stretch is preferable.
  • the pH value of the pH adjuster is not particularly limited, but a pH adjuster having a pH of 6 to 9 is preferably used, and more preferably 6.5 to 7.5.
  • the precipitated powder of FePO 4 is an amorphous hydrate (FePO 4 .nH 2 O)
  • chemical decomposition is likely to occur when it comes into contact with a strong alkaline substance having a pH of 9 or more in the mixed aqueous solution.
  • a strong alkaline substance such as NH 4 OH (pH: about 11) having a pH exceeding 9 is used as a pH adjuster as in Non-Patent Document 1
  • Fe (OH) 3 is mixed in the precipitated powder, There is a risk of segregation of Fe and P in FePO 4 .
  • the pH of the pH adjuster is preferably 6 to 9, and more preferably 6.5 to 7.5.
  • ammonium acetate, sodium lactate, sodium hydrogen tartrate, ammonium hydrogen tartrate, disodium maleate, ammonium chloride, ammonium formate and the like can be preferably used.
  • the FePO 4 can be produced by the following method.
  • an Fe compound containing divalent Fe such as FeSO 4 .7H 2 O and FeCl 2 .4H 2 O (hereinafter referred to as “divalent Fe compound”), H 3 PO 4 , (NH 4 ) H
  • a P source such as 2 PO 4 , (NH 4 ) 2 HPO 4 , and an oxidizing agent such as H 2 O 2 , and mix them so that they are in a predetermined ratio to prepare a mixed aqueous solution having a pH of 1 or less.
  • the divalent Fe compound and the P source are mixed so that the molar ratio is equal to or substantially equal, and the oxidizing agent is such that the divalent Fe is completely oxidized to Fe in the trivalent state. It is preferable to contain an excess of the divalent Fe compound (for example, about 1.5 times in molar ratio).
  • a pH adjuster having a pH of preferably 6 to 9, more preferably 6.5 to 7.5 is prepared.
  • the powdery pH adjusting agent may be dissolved in an aqueous solution and then charged into the mixed aqueous solution, or the powdered pH adjusting agent may be directly charged into the mixed aqueous solution. Then, the pH of the mixed aqueous solution suddenly increases in a short time (for example, within 60 seconds) after the pH adjusting agent is added, reaches a predetermined pH (for example, 1.5), and may cause grain growth. Thus, the coarsening of the particles can be suppressed, and a brown FePO 4 precipitated powder having fine particles and good uniformity in particle size can be obtained.
  • this FePO 4 precipitated powder is filtered, washed, and dried, thereby obtaining FePO 4 .
  • LiFePO 4 lithium iron phosphate
  • these FePO 4 and lithium compound are weighed so that the molar ratio of FePO 4 and lithium compound is 1: 1, and this weighed product is ball milled together with pure water and a polymer dispersant such as polycarboxylic acid. And mixed and pulverized to obtain a slurry-like mixed powder.
  • the lithium compound is not particularly limited, and for example, CH 3 COOLi ⁇ 2H 2 O, LiOH ⁇ H 2 O, or the like can be used.
  • a carbon source such as sucrose to the mixed powder and coat the surface of the mixed powder with carbon.
  • the mixed powder is dried and granulated, and then heat-treated at a predetermined temperature (for example, 500 to 700 ° C.) for about 5 hours in a predetermined reducing atmosphere.
  • a predetermined temperature for example, 500 to 700 ° C.
  • trivalent Fe is reduced to divalent, and LiFePO 4 is obtained.
  • the LiFePO 4 thus obtained has high purity, fine particles and good particle size uniformity, and can be suitably used as an electrode active material for a secondary battery.
  • FIG. 1 is a cross-sectional view showing a coin-type secondary battery as an embodiment of a secondary battery according to the present invention.
  • an electrode active material mainly composed of LiFePO 4 is used as a positive electrode active material. Used for substances.
  • the battery can 1 has a positive electrode case 2 and a negative electrode case 3, and both the positive electrode case 2 and the negative electrode case 3 are formed in a disk-like thin plate shape.
  • the positive electrode 4 which formed the electrode active material in the sheet form is distribute
  • a separator 5 formed of a porous film such as polypropylene is laminated on the positive electrode 4, and a negative electrode 6 is further laminated on the separator 5.
  • a negative electrode current collector 7 made of Cu or the like is laminated on the negative electrode 6, and a metal spring 8 is placed on the negative electrode current collector 7. Further, the electrolyte 9 is filled in the internal space, and the negative electrode case 3 is fixed to the positive electrode case 2 against the urging force of the metal spring 8 and is sealed through the gasket 10.
  • LiFePO 4 as a main component of the electrode active material is formed into an electrode shape.
  • LiFePO 4 is mixed with a conductive additive and a binder, a solvent is added to form a slurry, the slurry is applied on the positive electrode current collector by an arbitrary coating method, and dried to form the positive electrode 4.
  • the conductive auxiliary agent is not particularly limited, for example, carbonaceous fine particles such as graphite, carbon black, and acetylene black, vapor grown carbon fibers, carbon nanotubes, carbon fibers such as carbon nanohorns, polyaniline, Conductive polymers such as polypyrrole, polythiophene, polyacetylene, and polyacene can be used. Further, two or more kinds of conductive assistants can be mixed and used.
  • the content of the conductive auxiliary agent in the positive electrode 4 is preferably 10 to 80% by weight.
  • the binder is not particularly limited, and various resins such as polyethylene, polyvinylidene fluoride, polyhexafluoropropylene, polytetrafluoroethylene, polyethylene oxide, carboxymethylcellulose, and the like can be used.
  • the solvent is not particularly limited, and examples thereof include basic solvents such as dimethyl sulfoxide, dimethylformamide, N-methyl-2-pyrrolidone, propylene carbonate, diethyl carbonate, dimethyl carbonate, and ⁇ -butyrolactone, acetonitrile, Nonaqueous solvents such as tetrahydrofuran, nitrobenzene, and acetone, and protic solvents such as methanol and ethanol can be used.
  • basic solvents such as dimethyl sulfoxide, dimethylformamide, N-methyl-2-pyrrolidone, propylene carbonate, diethyl carbonate, dimethyl carbonate, and ⁇ -butyrolactone, acetonitrile
  • Nonaqueous solvents such as tetrahydrofuran, nitrobenzene, and acetone
  • protic solvents such as methanol and ethanol can be used.
  • the type of solvent, the compounding ratio between the organic compound and the solvent, the type of additive and the amount of the additive, etc. can be arbitrarily set in consideration of the required characteristics and productivity of the secondary battery.
  • the positive electrode 4 is impregnated in the electrolyte 9 so that the positive electrode 4 is impregnated with the electrolyte 9, and then the positive electrode 4 is placed on the positive electrode current collector at the bottom center of the positive electrode case 2.
  • the separator 5 impregnated with the electrolyte 9 is laminated on the positive electrode 4, the negative electrode 6 and the negative electrode current collector 7 are sequentially laminated, and then the electrolyte 9 is injected into the internal space.
  • a metal spring 8 is placed on the negative electrode current collector 9 and a gasket 10 is arranged on the periphery, and the negative electrode case 3 is fixed to the positive electrode case 2 by a caulking machine or the like, and the outer casing is sealed.
  • a type secondary battery is produced.
  • the electrolyte 9, performs the charge carrier transport between being interposed both electrodes between the anode 6 which is a counter electrode of the positive electrode 4 and the positive electrode 4, as such a electrolyte 9, 10 at room temperature -
  • Those having an electric conductivity of 5 to 10 ⁇ 1 S / cm can be used.
  • an electrolytic solution in which an electrolyte salt is dissolved in an organic solvent can be used.
  • electrolyte salt for example, LiPF 6 , LiClO 4 , LiBF 4 , LiCF 3 SO 3 , Li (CF 3 SO 2 ) 2 , Li (C 2 F 5 SO 2 ) 2 N, Li (CF 3 SO 2 ) 3 C, Li (C 2 F 5 SO 2 ) 3 C, or the like can be used.
  • organic solvent ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ⁇ -butyrolactone, tetrahydrofuran, dioxolane, sulfolane, dimethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone, etc. are used. be able to.
  • this invention is not limited to the said embodiment, A various deformation
  • a divalent Fe compound and an oxidizing agent are mixed to oxidize divalent Fe to trivalent Fe to obtain a trivalent Fe compound.
  • the oxidation treatment method is not particularly limited.
  • the divalent Fe compound to obtain a trivalent Fe compound may be used trivalent Fe compounds from the beginning, as a Fe compound in this case, for example, FeCl 3 ⁇ 6H 2 O or the like can be used.
  • the coin-type secondary battery has been described.
  • the battery shape is not particularly limited, and can be applied to a cylindrical type, a square type, a sheet type, and the like.
  • the exterior method is not particularly limited, and a metal case, mold resin, aluminum laminate film, or the like may be used.
  • Example Sample (Production of FePO 4 ) FeSO 4 ⁇ 7H 2 O was dissolved in water, and a mixed aqueous solution was prepared by adding H 3 PO 4 (85% aqueous solution) and H 2 O 2 (30% aqueous solution) as a P source.
  • H 3 PO 4 85% aqueous solution
  • H 2 O 2 (30% aqueous solution)
  • FeSO 4 ⁇ 7H 2 O, H 3 PO 4 , and H 2 O 2 were mixed so as to have a molar ratio of 1: 1: 1.5.
  • powdered ammonium acetate was prepared as a pH adjuster.
  • a predetermined amount of ammonium acetate was weighed so that the pH was 2.0 when all of the weighed ammonium acetate was put into the mixed aqueous solution. And this ammonium acetate was dissolved in water, and ammonium acetate aqueous solution was produced.
  • FePO 4 precipitated powder was filtered and washed, and then dried and powdered to obtain FePO 4 .
  • this mixed powder was dried with a spray dryer, granulated, adjusted to a reducing atmosphere having an oxygen partial pressure of 10 ⁇ 20 MPa using a mixed gas of H 2 —N 2 , and maintained at a temperature of 700 ° C. for 5 hours. Then, heat treatment was performed to obtain LiFePO 4 .
  • LiFePO 4 produced as described above, acetylene black as a conductive auxiliary agent, and polyvinylidene fluoride as a binder were prepared. Then, these LiFePO 4 , acetylene black, and polyvinylidene fluoride are weighed and mixed so that the weight ratio is 88: 6: 6, and this is dispersed in N-methyl-2-pyrrolidone as a solvent. A slurry was prepared.
  • this slurry was applied on an aluminum foil having a thickness of 20 ⁇ m so as to be 6 mg / cm 2 , dried at a temperature of 140 ° C., and then pressed at a pressure of 98 MPa, whereby an electrode sheet was produced, and the diameter was further increased.
  • the positive electrode was punched to 12 mm.
  • this positive electrode was impregnated with an electrolytic solution, and the electrolytic solution was infiltrated into voids in the positive electrode.
  • an ethylene carbonate / diethyl carbonate mixed solution which is an organic solvent containing LiPF 6 (electrolyte salt) having a molar concentration of 1.0 mol / L, was used.
  • this positive electrode was placed on a positive electrode current collector, and a separator having a thickness of 20 ⁇ m made of a polypropylene porous film impregnated with the electrolytic solution was laminated on the positive electrode.
  • the negative electrode to which was attached was laminated on the separator.
  • Example sample except that the ammonium acetate aqueous solution charging speed was slowed and the time for reaching the pH of 2.0 at all measurement locations after the start of the ammonium acetate aqueous solution solution was 300 seconds (5 minutes) FePO 4 , LiFePO 4 , and a secondary battery were produced by the same method and procedure as in Example 1.
  • Example evaluation Using a scanning electron microscope (hereinafter referred to as “SEM”), FePO 4 produced from the example sample and the comparative example sample was observed.
  • SEM scanning electron microscope
  • FIG. 2 is an SEM image of FePO 4 in the example sample
  • FIG. 3 is an SEM image of FePO 4 in the comparative example sample.
  • the FePO 4 of the example sample had a short arrival time of 15 seconds, and as shown in FIG. 2, the presence of coarse particles was not observed, and it was confirmed that the particle size uniformity was also good. . That is, the time until the pH at which the precipitation yield of FePO 4 is increased to reach 2.0 (arrival time) is as short as 15 seconds after addition of the aqueous ammonium acetate solution. It seems that the generation of enlarged particles could be suppressed. That is, it is considered that the nucleation rate of FePO 4 is high in the pH range where the precipitation yield is high, but most of the FePO 4 is synthesized in the pH range of 1.5 to 2.0. It seems that FePO 4 having a uniform particle size distribution was obtained.
  • FIG. 4 is an SEM image of LiFePO 4 in the example sample
  • FIG. 5 is an SEM image of LiFePO 4 in the comparative example sample.
  • the secondary battery manufactured as described above was charged in a constant temperature bath at 25 ° C. with a voltage range of 2.0 to 4.2 V and charge / discharge rates of 0.2 C and 5 C (1 C is charged in 1 hour). Or the amount of current until the discharge is completed). That is, the battery was charged until the voltage reached 4.2 V at each charging rate of 0.2 C and 5 C, and then discharged until the voltage reached 2.0 V at each discharging rate of 0.2 C and 5 C. .
  • the capacity retention rate was determined as a ratio of the charge / discharge capacity density when the charge / discharge rate was 5C, based on the charge / discharge capacity density of 0.2C.
  • Table 1 shows the arrival times and measurement results of the samples of Examples and Comparative Examples.
  • the charge capacity is as low as 145.6 mAh / g
  • the discharge capacity is as low as 144.8 mAh / g
  • the charge capacity maintenance rate is also 85.2%
  • the discharge capacity was as low as 79.8%. This is because the coarse particles are mixed in LiFePO 4 , and thus the diffusion rate of Li + in the particles is slow, and therefore, it is difficult to insert and desorb Li + at the center of the particles with large diameter particles. Therefore, it seems that the deterioration of battery characteristics was caused.
  • the example sample has a large specific surface area of 20.9 m 2 / g, fine LiFePO 4 particles, and good particle size uniformity, so that the charge capacity is 155.1 mAh / g and the discharge capacity is 154.4 mAh. / G, high charge capacity retention rate of 95.8%, and discharge capacity retention rate of 92.2%.
  • FePO 4 was fine and uniform in particle size, and thus LiFePO 4 was also fine and uniform in particle size, so that it was confirmed that good rate characteristics could be obtained.
  • FePO 4 , LiFePO 4 , and Sample Nos. 1 to 5 in the same manner and procedure as in Example 1 except that sodium lactate, ammonium hydrogen tartrate, disodium maleate, ammonium chloride, and ammonium formate were used as pH adjusters. And the secondary battery was produced sequentially.
  • Table 2 shows the types and pH of pH adjusting agents, and measurement results.
  • LiFePO 4 having a fine particle size and good particle size uniformity can be obtained with a pH of 6.8 to 7.3 and a specific surface area of 19.8 to 20.9 m 2 / g. It was. As a result, it was found that a high discharge capacity of 152 mAh / g or more and a good discharge capacity maintenance ratio of 90% or more can be obtained.
  • FePO 4 , LiFePO 4 , and secondary batteries of sample numbers 11 to 19 were sequentially prepared in the same manner and procedure as in Example 1 except that the concentration of the aqueous ammonium acetate solution was changed variously as a pH adjuster.
  • Table 3 shows the reached pH and the measurement results.
  • Sample No. 11 had a specific pH of as low as 16.2 m 2 / g, a discharge capacity of 147 mAh / g, and a discharge capacity retention rate of 82.8% because the ultimate pH was slightly low at 1.4. That is, although the capacity characteristics and rate characteristics were good compared to the comparative example sample of Example 1 (see Table 1), it was slightly lower than that of sample numbers 12-19.
  • sample Nos. 12 to 19 have an ultimate pH of 1.5 or more, so that the specific surface area is as large as 18.5 to 21.4 m 2 / g, and the desired LiFePO 4 can be obtained.
  • 150 mAh It was found that a high discharge capacity of at least / g and a good discharge capacity maintenance rate of at least 88% can be obtained.
  • FePO 4 , LiFePO 4 , and secondary batteries of sample numbers 21 to 25 were sequentially prepared in the same manner and procedure as in Example 1 except that the charging rate of the aqueous ammonium acetate solution as the pH adjuster was changed.
  • Table 4 shows arrival times and measurement results.
  • Sample No. 25 had a specific surface area as small as 15.0 m 2 / g because the arrival time was slightly long as 75 seconds. Therefore, the discharge capacity was 145.3 mAh / g and the discharge capacity maintenance rate was 80.2%. Although the capacity characteristics and rate characteristics were good compared to the comparative example sample of Example 1 (see Table 1), it was slightly lower than that of sample numbers 21 to 24.
  • sample numbers 21 to 24 have an arrival time of 60 seconds or less, so that the specific surface area is as high as 18.20 m 2 / g or more, the discharge capacity is as high as 150 mAh / g or more, and the discharge capacity retention rate is high. Also, good results were obtained with 85% or more.
  • FePO 4 , LiFePO 4 , and secondary battery of sample number 31 were sequentially prepared in the same manner and procedure as in Example 1 except that ammonium acetate powder was used instead of the ammonium acetate aqueous solution as a pH adjuster.
  • Example 1 the pH of the sample No. 31 was measured with a pH meter, and the specific surface area, discharge capacity, and discharge capacity retention rate were measured by the same method and procedure as in Example 1.
  • Table 5 shows arrival times and measurement results.
  • High-purity FePO 4 having fine particles and good uniformity in particle size can be obtained with high efficiency from the P source and Fe compound.
  • LiFePO 4 obtained from FePO 4 as the positive electrode active material of the secondary battery, a secondary battery having a high charge / discharge capacity and excellent rate characteristics during charge / discharge can be obtained.

Abstract

Une solution aqueuse mixte, dans laquelle une source de phosphore telle que H3PO4, un composé Fe divalent tel que FeSO4·7H2O et un oxydant tel que H2O2 sont mélangés à un rapport prédéterminé, est préparée. Un agent de régulation de pH ayant un pH de 6-9 (de préférence un pH de 6,5-7,5) est introduit dans la solution aqueuse mixte, permettant ainsi d'augmenter le pH de la solution à 1,5 ou plus en l'espace de 60 secondes et de produire une poudre de sédimentation de FePO4. Cette poudre de sédimentation de FePO4 est filtrée, nettoyée et séchée de façon à être transformée en une poudre, puis synthétisée avec un composé de lithium tel que Li(CH3COO), permettant ainsi d'obtenir LiFePO4. Une matière active d'électrode, qui est principalement composée de ce LiFePO4 est utilisée pour une électrode positive (4) d'une batterie secondaire. En conséquence, l'invention propose : un procédé de fabrication de phosphate de fer, par lequel du phosphate du fer sous la forme de fines particules ayant une distribution uniforme de dimension des particules peut être facilement obtenu; un phosphate de lithium et de fer qui est obtenu à l'aide du procédé de fabrication; une matière active d'électrode qui est principalement composée de ce phosphate de lithium et de fer; et une batterie secondaire qui contient la matière active d'électrode dans l'électrode positive.
PCT/JP2012/076793 2011-12-26 2012-10-17 Procédé de fabrication de phosphate de fer, phosphate de lithium et de fer, matière d'électrode active et batterie secondaire WO2013099409A1 (fr)

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CN111591970A (zh) * 2020-05-30 2020-08-28 康桓铭 一种电池级磷酸铁及其制备方法
CN114014292A (zh) * 2021-11-04 2022-02-08 湖南安尔信新材料有限责任公司 一种磷酸锰铁锂的制备方法

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CN114014292A (zh) * 2021-11-04 2022-02-08 湖南安尔信新材料有限责任公司 一种磷酸锰铁锂的制备方法

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