WO2008093551A1

WO2008093551A1 - Compound having olivine structure, method for producing the same, positive electrode active material using compound having olivine structure, and nonaqueous electrolyte battery

Info

Publication number: WO2008093551A1
Application number: PCT/JP2008/050650
Authority: WO
Inventors: Kumiko Sueto; Shinji Iizuka; Takeshi Shimada; Yuan Gao
Original assignee: Kanto Denka Kogyo Co., Ltd.
Priority date: 2007-01-29
Filing date: 2008-01-11
Publication date: 2008-08-07
Also published as: JPWO2008093551A1; JP5385616B2

Abstract

Disclosed is a compound having an olivine structure, which makes a low-cost positive electrode active material having high safety and excellent battery characteristics such as energy density. Also disclosed are a method for producing such a compound, and a nonaqueous electrolyte battery having a positive electrode containing such a compound. Specifically disclosed is a method for producing a compound having an olivine structure, which is characterized in that an iron source containing iron oxide particles, a lithium source and a phosphorus source are mixed and fired.

Description

Specification

Compound having olivine structure and method for producing the same, and positive electrode active material and non-aqueous electrolyte battery using compound having olipine structure

Technical field

The present invention relates to an olivine-type positive electrode active material that is a low-cost, high-safety, battery property having excellent energy density, and a method for producing the same, and a nonaqueous electrolyte battery having a positive electrode including the same About.

Background art

At present, lithium secondary batteries are widely used as power sources for electronic devices such as mobile phones, video cameras, and laptop computers. In addition, because of environmental conservation issues and energy issues, the development of large-sized lithium secondary batteries that are inexpensive and highly safe for electric vehicles and nighttime power is also underway.

Conventionally, a layered rock salt type LiCoO ₂ has been mainly used as a positive electrode active material of a lithium secondary battery. Although L i C O_〇 ₂ is superior in charge-discharge cycle characteristics, abundance of raw Der Ru cobalt is small, cost is expensive. Therefore, as a positive electrode active material of an alternative, although L i N i 0 ₂ Ya spinel L i M n ₂ 0 ₄ of layered rock-salt type have been studied, L i N I_〇 ₂ safety problems of the state of charge Li M n ₂ 0 ₄ has a problem in chemical stability at high temperatures. New cathode materials combining these elements have been proposed for small batteries, but new alternative materials have been proposed as positive electrode active materials for large batteries, which are more demanding in terms of cost and safety. It has been desired.

L i F e P 0 ₄ a positive electrode active material of olivine type, cost, safety 'j raw, in recent years developed a superior material in reliability have become active. The olivine-type L i F e P 0 ₄ has a very high safety and stability, and because it is inexpensive, but that have been noted, electron conductivity low as a problem to practical use There is. As methods for improving this, mainly fine particles for increasing the reaction surface area, carbon coating for imparting conductivity, etc. are well known (for example, Non-Patent Document 1). It has been reported that battery characteristics can be improved by using fine particles, especially when the particles are uniform (Non-patent Documents 2 and 3). In addition, regarding the addition of Kibon There are numerous reports (for example, Patent Document 3 and Non-Patent Document 4).

Conventionally, a solid phase method (Patent Document 1, Non-Patent Document 5) using iron oxalate or iron acetate as a starting material has been generally used as a method for producing olipine-type lithium iron phosphate. In recent years, solid-phase methods using iron phosphate as a raw material (Patent Document 2), sol-gel methods for obtaining finer particles, hydrothermal methods (Non-Patent Documents 6 and 7) have been reported. . However, in either method, the raw materials are expensive, equipment for preventing the oxidation of divalent iron is necessary, and it is difficult to obtain a target product with uniform and good crystallinity. Therefore, by either method, it is difficult to industrially produce uniform fine particles with inexpensive raw materials and simple manufacturing equipment, and low lithium olivine phosphate with practical battery characteristics is reduced. Manufacturing methods that can be realized at low cost are needed.

Patent Document 1: Japanese Patent No. 3484003

Patent Document 2: Japanese Patent No. 3319258

Patent Document 3: Japanese Patent Application Laid-Open No. 2001-1511

Non-patent document 1: A. Yamada; Electrochemistry 71, o.3, 717-722 (2003) Non-patent document 2: A. Singhal, G. Skandan, G. Amatucci, F. Badway, N. Ye,

A. Man t hi ram, H. Ye, J. J. Xu, Journal of Power Sources 129, 38-44 (2004) Non-Patent Document 3: K. Striebel, J. Shim, V. Srinivasan, and J. Newman

J. Electrochem. Soc, 152, No. 4, A554-A670 (2005)

Non-Patent Document 4: N. Ravet, Y. Chouinard,]. F. Magnan, S. Besner, M. Gauthier, M. Armand

Journal of Power Sources 97-98, 503-507 (2001)

Non-Patent Document 5: A. K. Padhi, Κ. S. Nanjundaswamy, and J.B. Goodenough,

J. Electrochem. Soc, 144, No. 4, 1188-1194 (1997)

Non-Patent Document 6: S. Yang, P.Y. Zavalji, M. S. Whit tinghain

Electrochemistry Communicai ion 3, 505-508 (2001)

Non Patent Literature 7: J. Yang and J. J. Xu

Electrochemical and Solid-State Letters, 7 (12) A515-A518 (2004) Disclosure of the Invention Problems to be solved by the invention

The present invention provides a positive electrode active material that is excellent in cost, safety, and reliability, enables inexpensive industrial production of a high-capacity non-electrolyte battery, a method for producing the same, and a non-aqueous electrolyte battery using the same. For the purpose.

Means for solving the problem

In order to produce a positive electrode active material having excellent characteristics as described above, the present inventors have intensively studied, and as a result, completed the present invention.

That is, the present invention provides the following.

[I] A method for producing a compound having an olivine structure, comprising mixing an iron source containing iron oxide particles having an average particle size of 500 nm or less, a lithium source, and a phosphorus source, followed by firing.

[2] The method according to [1], wherein the iron oxide particles are obtained by reacting an iron salt with an alkali and oxidizing the reaction product.

[3] The method according to [1], wherein the iron oxide particles are magnetite.

[4] The method according to [3], wherein the iron oxide particles are magnetite having an average particle size of 500 nm or less and a coefficient of variation of the particle size of 0.5 or less.

[5] The method of [2], wherein the alkali is alkali hydroxide and Z or alkali carbonate.

[6] The method according to [2] or [5], wherein the oxidation is performed at a temperature of 30 to 90 ° C.

[7] A compound having an olipine structure characterized by mixing an iron source containing iron oxide particles having an average particle size of 500 nm or less, a lithium source and a phosphorus source and carbon or / and a carbon precursor, followed by firing. Production method.

[8] The method according to any one of [1] to [7], wherein the firing is performed in an inert gas atmosphere or a reducing atmosphere.

[9] The method according to [8], wherein the firing is performed in an N ₂ atmosphere.

[10] A compound having an olivine structure having an average particle size of 1000 nm or less obtained by any one of the methods [1 :) to [9].

[II] The average particle size obtained by any of the methods [1] to [9] is 1000. A compound having an olivine structure that is not more than nm and has a coefficient of variation of particle diameter of not more than 0.6.

[12] A positive electrode active material comprising a compound having an olivine structure obtained by any method of [1] to [9] or a compound having an olivine structure of [10] or [11].

[13] A nonaqueous electrolyte battery having a positive electrode comprising the positive electrode active material according to [12].

Brief Description of Drawings

FIG. 1 is a TEM photograph of the iron oxide particles produced in Example 1.

FIG. 2 is an X-ray diffraction pattern of the iron oxide particles produced in Example 1.

FIG. 3 is a SEM photograph of the lithium iron phosphate produced in Example 1.

FIG. 4 is an X-ray diffraction pattern of the lithium iron phosphate produced in Example 1.

FIG. 5 is a schematic diagram of the lithium secondary battery (coin cell) used in the examples. FIG. 6 is a graph showing the results of a charge / discharge test for the coin cell produced in Example 1. ,

FIG. 7 is a S EM photograph of the lithium iron phosphate produced in Example 2.

FIG. 8 is an X-ray diffraction pattern of lithium iron phosphate produced in Example 2;

FIG. 9 is a TEM photograph of the iron oxide particles produced in Example 3.

FIG. 10 is a SEM photograph of the lithium iron phosphate produced in Example 3.

FIG. 11 is an SEM photograph of lithium iron phosphate produced in Example 4.

FIG. 12 is a TEM photograph of the hematite particles used in Comparative Example 1.

FIG. 13 is an SEM photograph of the lithium iron phosphate produced in Comparative Example 1.

FIG. 14 is a TEM photograph of the lithium iron phosphate produced in Comparative Example 1.

FIG. 15 is a SEM photograph of the lithium iron phosphate produced in Comparative Example 2.

FIG. 16 is a schematic diagram of a coin cell.

FIG. 17 is a TEM photograph of the iron oxide particles produced in Example 5.

FIG. 18 is a SEM photograph of lithium iron phosphate produced in Example 5.

FIG. 19 is an X-ray diffraction pattern of the lithium iron phosphate produced in Example 5.

BEST MODE FOR CARRYING OUT THE INVENTION

[Method for producing compound having olivine structure] According to the present invention, there is provided a method for producing a compound having an olipine structure, particularly an olipine-type lithium iron phosphate, characterized in that an iron source, a lithium source and a phosphorus source are mixed and calcined. In this method, it is important that the iron source contains iron oxide particles. The iron oxide particles are fine and can be prepared with precisely controlled particle size distribution. The present inventors pay attention to this point, and by including iron oxide particles as an iron source, a compound having an olipine structure, particularly an olipine-type iron phosphate, having extremely fine particles and a controlled particle size distribution. By obtaining lithium and using a positive electrode active material containing a compound having a fine olivine structure with a fine particle size distribution, a non-aqueous electrolyte battery having excellent performance was successfully manufactured.

(Iron source)

The iron source used in the present invention includes iron oxide particles. The iron oxide particles preferably have an average particle size of not more than 500 nm, more preferably not more than 300 nm, especially 5 to 300 nm. From an iron oxide particle having an average particle diameter of about 5 nm, a compound having an olivine structure of about 5 to 50 nm is obtained, and from an iron oxide particle having an average particle diameter of about 300 nm is formed from 100 to 50 A compound having an olivine structure of about 0 nm is obtained. The iron oxide particles preferably also have a particle size distribution with a standard deviation σ of 50 or less, particularly 30 or less, and a coefficient of variation [-(standard deviation Ζaverage particle diameter)] of particle diameter of 0.5 or less. Preferably, it has a BET specific surface area value of .10 to 150 m ² / g.

The iron oxide, monoxide iron (F e O), triiron tetroxide (F e ₃ 0 _4), such as magnetite, ferric oxide, such as to hematite (F e ₂ 〇 _3), and the like. Of these, triiron tetroxide (F e ₃₀ ₄ ) is particularly preferable. Since triiron tetroxide (F e ₃ 0 ₄ ) can be prepared as a fine particle and with a precisely controlled particle size distribution by a wet process, using relatively inexpensive materials and equipment, the olivine of the present invention It is useful for producing type iron phosphate. In addition, since the oxygen content is lower than that of ferric trioxide (F e ₂₀ ₃ ) or the like, it is possible to obtain particles that are easy to reduce and that prevent sintering during firing. In addition, from such a fine F e ₂ 0 _3, since fine particles are obtained, it can be used to produce the onset bright olivine type lithium iron phosphate. For example, iron oxide is produced by reacting an iron salt with an alkali and mixing, for example, an iron salt and an alkaline water solution, in particular, alkali hydroxide and / or alkali carbonate, to produce iron hydroxide. Fe ₃ 0 ₄ obtained by heating (oxidation synthesis) a reaction product containing iron hydroxide to a temperature of 30 to 90 ° C in an oxygen-containing atmosphere (for example, under atmospheric pressure) is preferable.

Examples of iron salts include iron sulfate, iron acetate, and iron chloride.

Examples of the alkali hydroxide include sodium hydroxide, potassium hydroxide, and aqueous ammonia. Examples of the alkali carbonate include sodium carbonate, potassium carbonate, and ammonium carbonate. Even if an alkali metal is used as the alkali, most of the alkali metal generated as a by-product of the neutralization reaction can be removed by washing with water. However, in order to extremely reduce the alkali metal contamination, an ammonium salt is used. It is appropriate. In addition, fine particles can be obtained with only alkali hydroxide, but in order to obtain finer particles, it is effective to use a mixture with alkali carbonate. In order to obtain fine single-phase iron oxide particles, the neutralization rate is 0.8 to 3.0 (where the neutralization rate is the alkali source used for neutralization with respect to the molar equivalent of the acid source before neutralization. The molar equivalent ratio of, for example,

When using the 2 0 moles of F e S_〇 ₄ 1 0 mol N a OH, neutralization rate 2 0 Roh (1 0 X 2) = 1. 0 and becomes. ), It is appropriate to carry out the above oxidation synthesis within a temperature range of 30 to 90 ° C.

(Lithium source and phosphorus source)

Li source and P source are mixed with the above iron source and calcined to obtain olivine type iron phosphate lithium.

Li sources include lithium carbonate, lithium hydroxide, lithium phosphate, etc.P sources include phosphoric acid, ammonium dihydrogen phosphate, ammonium dihydrogen phosphate, lithium dihydrogen phosphate, lithium phosphate, etc. Can be mentioned.

(Mixing process)

The mixing method is not particularly limited, and wet mixing or dry mixing may be used. As a device, it is appropriate to use a planetary pole mill, a jet mill, a magnetic stirrer or the like. (Baking process)

In the firing step, by supplying thermal energy to the mixture of raw materials, the mixture is converted to a thermodynamically stable olivine-type lithium iron phosphate compound, and impurities are vaporized and removed. This is a step of generating fine particles of an active material.

Firing is performed in an inert gas atmosphere or a reducing atmosphere. Examples of the inert gas include nitrogen, helium, neon, and argon. Examples of the reducing atmosphere include hydrogen, lower alcohols, for example, reducing compounds such as methanol and ethanol, mixtures of reducing compounds and inert gases, and the like. When a mixture of a reducing compound and an inert gas is used, the mixing ratio (volume ratio) of the reducing compound and the inert gas is not particularly limited.

The firing temperature is preferably 400 to 800 ° C. Sufficient crystallinity can be obtained even by one-step firing, but crystallinity can be further improved by performing a two-step firing step including a temporary firing step and a main firing step. The pre-baking is usually performed at a temperature of 200 to 500 ° C, and the main baking is usually performed at a temperature of 400 to 80 ° C, preferably 5 ° 0 to 80 ° C. C, more preferably at a temperature of 500 to 75 ° C. It is also possible to change the gas atmosphere for pre-baking and main baking.

Further, before firing, various conductive materials (for example, carbon) or precursors thereof are mixed and fired in an inert gas atmosphere or a reducing atmosphere, so that the surface of the olivine type lithium iron phosphate particles is treated as such. It is possible to obtain a very fine positive electrode active material in which a conductive material is present. In particular, when a carbon source is mixed, a single-phase olivine-type lithium iron phosphate can be obtained using only N ₂ , for example, without using a reducing gas. Examples of the conductive substance include carbon. In particular, carbon is advantageous in terms of easy availability and handling.

The amount of carbon source added is not limited, but it goes without saying that the carbon content remaining after firing does not become excessive as the positive electrode, preferably 20% by weight or less based on the weight of the positive electrode active material, particularly 3 to It is desirable to add in the range of 20% by weight, and more preferably 5 to 15% by weight.

The carbon source is made up of at least carbon particles and carbon precursors that turn into conductive carbon upon firing. Including one. When a carbon precursor is used as a carbon source, the particle surface can be covered flat with carbon, and a positive electrode active material having a relatively low surface area can be produced.

As the carbon particles, known particles can be used without limitation, and examples thereof include carbon black such as acetylene black; fullerene; carbon nanotubes and the like. Examples of carbon precursors include polyvinyl alcohol, polyolefins, polyacrylonitrile, saccharides such as cellulose, starch, glucose, and granulated sugar, and natural organic polymer compounds (especially water-soluble compounds); acrylonitrile, divinylbenzene And polymerizable monomers such as vinyl acetate (particularly, unsaturated organic compounds having a carbon-carbon double bond).

The carbon source may be added to the raw material at any stage of the firing process. For example, the carbon source may be added before the pre-firing, or may be added after the pre-firing and before the main firing. It may be added before and at both levels. Moreover, by adding a carbon source, it is possible to obtain an olivine single phase by firing only with an inert gas.

As described above, the feature of this method is to synthesize uniform iron oxide fine particles and perform solid phase synthesis using this as a raw material, thereby reducing the fine and uniform olivine type material with excellent battery characteristics. It is easy to manufacture industrially at a low cost.

[Positive electrode active material]

The positive electrode active material of the present invention needs to contain olivine-type lithium iron phosphate as a main component. However, as a component other than olivine-type lithium iron phosphate, a conductive material such as carbon is included. be able to. The blending ratio of the other components must be 30% or less of the positive electrode active material.

The average particle size of the positive electrode active material is preferably 5 to 500 nm, more preferably 30 to 300 nm. In the case of an olivine-type positive electrode active material with low conductivity, if the average particle diameter is too large, sufficient capacity cannot be obtained. The positive electrode active material or the standard deviation σ preferably has a particle size distribution of 50 or less, particularly 30 or less, and the variation coefficient of the particle diameter is preferably 0.6 or less, particularly preferably 0.5 or less, It preferably has a BET specific surface area value of 5 to 50 m ² Z g.

[Nonaqueous electrolyte battery] ' (Battery structure)

An example of a non-aqueous electrolyte battery using the positive electrode active material of the present invention will be described with reference to the attached drawings.

FIG. 16 is a cross-sectional view schematically showing the battery. In this figure, the nonaqueous electrolyte battery 1 is roughly composed of a negative electrode member 2 that functions as an external negative electrode of the battery, a positive electrode member 3 that functions as an external positive electrode of the battery, a negative electrode current collector 4, a negative electrode between the two members The active material layer 5, the separator 8, the positive electrode active material layer 7, and the positive electrode current collector 6 are provided in this order. The negative electrode member 2 has a substantially cylindrical shape, and is configured to accommodate the negative electrode current collector 4 and the negative electrode active material 5 therein. On the other hand, the positive electrode member 3 also has a substantially cylindrical shape, and is configured to accommodate the positive electrode current collector 6 and the positive electrode active material layer 7 therein. The radial dimension of the positive electrode member 3 and the separator plate 8 is set to be slightly larger than that of the negative electrode member 2, and the peripheral edge portion of the negative electrode member 2 and the peripheral edge portion of the separator member 8 and positive electrode member 3 are Are overlapping. The space inside the battery is filled with a non-aqueous electrolyte 9, and a sealing material 10 is applied to the overlapping portions of the negative electrode member 2, the separator 8 and the peripheral edge of the positive electrode member 3, so that the inside of the battery is airtight. It is kept.

The negative electrode comprises a negative electrode member 2 as an external negative electrode, a negative electrode current collector 4 in contact therewith, and a negative electrode active material layer 5 on the negative electrode current collector. As the negative electrode current collector, for example, nickel foil, copper foil or the like is used. As the negative electrode active material layer, a layer that can be doped with lithium is used. Specifically, metallic lithium, a lithium alloy, a conductive polymer doped with lithium, a layered compound (a carbon material or a metal oxide) Etc.) As the binder contained in the negative electrode active material layer, a known resin material or the like that is usually used as a binder for the negative electrode active material layer of this type of nonaqueous electrolyte battery can be used. In particular, since the metal lithium foil can be used not only as the negative electrode active material but also as the negative electrode current collector, the battery structure can be simplified by using the metal lithium foil for the negative electrode.

The positive electrode comprises a positive electrode member 3 as an external positive electrode, a positive electrode current collector 6 in contact therewith, and a positive electrode active material layer 7 on the positive electrode current collector. The positive electrode active material of the present invention described above is used as the positive electrode active material. As the positive electrode current collector, for example, an aluminum foil or the like is used. The As a binder contained in the positive electrode active material layer, as a binder for a positive electrode active material layer of this type of non-aqueous electrolyte battery such as polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE). Commonly used known resin materials can be used. A conductive material can be blended in the positive electrode active material layer in order to improve conductivity. Examples of the conductive material include graphite and acetylene black. The separator 8 is for separating the positive electrode and the negative electrode, and a known material that is usually used as a separator for this type of non-aqueous electrolyte battery can be used, for example, a polymer such as polypropylene. A film, a polyethylene-strength porous membrane, etc. are used. Also, from the relationship between lithium ion conductivity and energy density, it is desirable that the thickness of the separation evening be as thin as possible.

50 m or less is preferable.

As the sealing material 10, a known resin material or the like that is normally used as a sealing material for the positive electrode active material layer of this type of nonaqueous electrolyte battery can be used.

As the non-aqueous electrolyte, not only a liquid electrolyte but also various forms such as a solid electrolyte and a gel electrolyte containing a solvent can be used. As the liquid electrolyte, a solution in which the electrolyte is dissolved in an aprotic non-aqueous solvent is used. Non-aqueous solvents include, for example, cyclic carbonates such as ethylene carbonate, propylene strength, butylene strength, vinylene carbonate, and chain carbonates such as dimethyl carbonate, jetyl carbonate, and dipropyl carbonate. , Aptyl lactone, sulfolane, 1,2-dimethoxyethane, 1,2-diethoxyethane, 2-methyltetrahydrofuran, 3-methyl 1,3-dioxolan, methyl propionate, methyl butyrate and the like. In particular, from the viewpoint of voltage stability, cyclic force monoponates such as ethylene carbonate, propylene force monoponate, and vinylene force monoponate, and chain force monoponates such as dimethyl carbonate, jetyl carbonate, and dipropyl carbonate are used. It is preferable to use it. Such non-aqueous solvents may be used alone or in combination of two or more. As the electrolyte, for example, the _{L i PF 6, L i C} 10 4, L i As F 6, L i BF 4, L i CF 3 S0 3, L i N (CF 3 S0 2) 2 and lithium salt of Can be used. Among these lithium salts However, it is preferable to use Li PF ₆ or Li BF ₄ . Examples of solid electrolytes include inorganic solid electrolytes such as lithium nitride and lithium iodide; organic polymer electrolytes such as poly (ethylene oxide), poly (methacrylate), and poly (acrylate). Furthermore, as a material for forming the gel electrolyte, any material that can be gelled by absorbing the liquid electrolyte can be used without particular limitation. For example, poly (vinylidene fluoride), vinylidene fluoride can be used. And fluorine-containing polymers such as / hexafluoropropylene copolymer.

(Battery manufacturing method)

A nonaqueous electrolyte battery using the positive electrode active material of the present invention is produced, for example, as follows.

First, the negative electrode manufacturing method will be described. A negative electrode active material and a binder are dispersed in a solvent to prepare a slurry. The obtained slurry is uniformly applied on a current collector and dried to form a negative electrode active material layer. The obtained laminate including the negative electrode current collector and the negative electrode active material layer is accommodated in the negative electrode member so that the negative electrode current collector and the inner surface of the negative electrode member are in contact with each other to form a negative electrode. Further, as described above, the metal lithium foil can be used as it is as the negative electrode current collector and the negative electrode active material.

Next, the manufacturing method of a positive electrode is demonstrated. The positive electrode active material, conductive material and binder of the present invention are dispersed in a solvent to prepare a slurry. The slurry is uniformly applied on the current collector and dried to form a positive electrode active material layer. The obtained laminate including the positive electrode current collector and the positive electrode active material layer is accommodated in the positive electrode member so that the positive electrode current collector and the inner surface of the positive electrode member are in contact with each other, thereby forming a positive electrode.

When a nonaqueous electrolyte is used, it is prepared by dissolving an electrolyte salt in a nonaqueous solvent.

The negative electrode and the positive electrode manufactured as described above are superposed so that a separate layer is interposed between the negative electrode active material layer and the positive electrode active material layer, filled with a nonaqueous electrolyte, and sealed with a sealing material. By sealing, a non-aqueous electrolyte battery is completed.

The shape of the nonaqueous electrolyte battery of the present invention is not particularly limited, and may be a cylindrical shape, a square shape, a coin shape, a button shape, or the like. Can be of various sizes. Further, the present invention can be applied to both a primary battery and a secondary battery.

Example

EXAMPLES Hereinafter, the present invention will be described in detail based on examples, but the present invention is not limited to these examples.

In the following examples, iron oxide, positive electrode active material, and nonaqueous electrolyte battery were analyzed by the following method.

(X-ray diffraction)

X-ray diffraction measurement was performed using CoKo! Rigaku R INT 2200V (manufactured by Rigaku Corporation).

(Specific surface area)

The specific surface area was measured using a fully automatic surface area measuring device Multisoap 12 (manufactured by Yuasa Ionics Co., Ltd.) according to the BET method.

(Metal composition analysis)

The metal composition analysis was measured by ICP emission spectroscopic analysis (ICP emission spectrophotometer SPS 1500 VR Seiko Instr umen ts Inc.) and calculated by the mo 1 ratio to Fe.

(Particle size)

For the particle size, we randomly selected 200 particles observed with TEM (Transmission Electron Microscope H-7600 manufactured by Hitachi) or SEM (Scanning Electron Microscope DS 130, manufactured by Topcon Electron Beam Service Co., Ltd.) The particle diameter of the particles was measured, the average value and standard deviation of the measured values were calculated, and this average value was taken as the particle diameter. The variation coefficient of the particle diameter is a value obtained by dividing the standard deviation thus obtained by the average particle diameter. Example 1

(1) Manufacture of iron oxide

A 60 L reaction vessel was charged with 40 L of an aqueous solution containing 23 mol of NaOH and 11 mol of Na ₂ C0 ₃ , and was replaced by aeration of nitrogen gas and kept at 60 ° C. Where nitrogen aeration, stirring, 1 81110 1? 630 ^ ₁ and 0. 9] 10 1? 6 ₂ 20 L of an aqueous solution containing (S0 ₄ ) ₃ was added to form a suspension containing iron hydroxide particles, and mixed at 60 ° C. for 60 minutes. Next, the air was passed through 1 OLZmin at 60 ° C, and the oxidation reaction was performed for 2 hours. The obtained suspension was filtered, washed and dried to obtain fine-particle magnetite (Fe ₃ 0 ₄ ). The specific surface area of the sample was measured by the BET method. The BET value of the obtained sample was 27.4 m ² / g. Figure 1 shows a TEM photograph of the sample obtained. The particle size was calculated as an average value by randomly measuring 200 particles from a TEM photograph. The obtained sample had an average particle size of 65 nm and a coefficient of variation of 0.32. X-ray diffraction measurement was performed on the obtained particles. Figure 2 shows the X-ray diffraction pattern of the particles obtained. From the X-ray diffraction pattern, it was confirmed to be Fe ₃ 0 ₄ single phase.

(2) Manufacturing method of Li FeP0 ₄

Li FeP0 ₄ was synthesized from the magnetite cake (Fe ₃ ₄ ) obtained in (1) above. Iron oxide obtained in (1) 0.05 mol 1, Li ₂ C 0 ₃ 0.083 mol, (NH ₄ ) ₂ HP0 ₄ 0.15 mol 1 and dalcose 5 g 8 OmL planetary pole mill container In addition, 2 OmL of pure water was added and mixed at 25 Or. Pm for 12 hours. After drying, powdered in an agate mortar and mixed with hydrogen (H ₂ ) and nitrogen (N ₂ ) in a volume ratio of 2: 5 at 450 ° C for 2 hours and N ₂ atmosphere at 600 ° C for 15 hours. firing to obtain a positive electrode active material L i F e P0 _4. The BET value of the obtained sample was 33.8 m ² /. Figure 3 shows an SEM photograph of the sample obtained. The particle size was calculated as an average value by randomly measuring 200 particles from a TEM photograph. The obtained sample had an average particle size of 52 nm and a coefficient of variation of 0.39.

X-ray diffraction measurement was performed on the obtained particles. Figure 4 shows the X-ray diffraction pattern of the particles obtained. From the X-ray diffraction pattern, it was confirmed to be an olivine type lithium iron phosphate single phase.

Table 1 shows the results of composition analysis by ICP analysis.

(3) (Production of coin cell)

Using the positive electrode active material obtained in (2), a lithium secondary battery was produced. Using the obtained sample and polytetrafluoroethylene as the binder and acetylene black as the conductive material, positive electrode active material: conductive material: binder = 70:25 (total amount of C, ie, pre-treated The amount of acetylene black added to the amount of bonbon (derived from glucose) ): After mixing at a weight ratio of 5 and kneading in an agate mortar, it was punched out into a disk with a diameter of 1.0 cm and a thickness of 0.2 mm using a cork poller, and this was taken as the positive electrode pellet. Used.

A coin cell was produced using the positive electrode pellet. As the counter electrode of the positive pellet, a lithium foil having a diameter of 1.5 cm and a thickness of 0.15 mm was used. As a separator, a porous polyethylene sheet having a diameter of 22 mm and a thickness of 02 mm was used. The non-aqueous electrolyte solution is Li PF ₆ dissolved in a mixed solvent of ethylene carbonate (EC) and dimethyl carbonate (DMC) at a volume ratio of 1: 1 at a concentration of about 1 mol Z liter. It was used. These components are assembled into a stainless steel positive electrode container and negative electrode lid, sealed with a gasket, and a coin-type measuring cell shown in Fig. 5 with a thickness of 3.2 mm and a diameter of 20 mm (2032 type) is produced. did. A series of battery assembly operations were performed in a dry box with a dew point of 90 ° C or less equipped with an Argon purification device.

A charge / discharge test was conducted on the simple lithium secondary battery thus obtained. The charge / discharge test was performed at 25 ° C, with a potential range of 2000 to 4500 mV, a rate of 1 C, and C. C. — C. V. The initial charge / discharge characteristics are shown in Fig. 6 ("Chg." Represents charge and "Dis." Represents discharge). Table 2 shows the initial charge / discharge capacity.

Example 2

Magnetite obtained in Example 1 (Fe ₃ 0 ₄₎ was synthesized L i FeP0 ₄ as a raw material. Put the iron oxide obtained in Example 1 0.05 mol, Li ₂ C 0 ₃ 0 083 mol 1, (NH ₄ ) ₂ HP0 ₄ 0.15 mol, 3 g glucose into an 80 mL planetary pole mill container. Further, 2 OmL of pure water was added and mixed at 25 Or.pm for 5 hours. After drying, was ground in an agate mortar, N ₂ atmosphere, 65 O: 3 hours, and calcined, to obtain a positive electrode active material L i F e Ρ0 _4. The BET value of the obtained sample was 13.8 m ² // g. Figure 7 shows a SEM photograph of the sample obtained. The particle size was calculated from an average value of 200 particles randomly measured from a TEM photograph. The average particle size of the obtained sample is 6

The variation coefficient was 0 nm and 0 nm.

X-ray diffraction measurement was performed on the obtained particles. Figure 8 shows the X-ray diffraction pattern of the particles obtained. From the X-ray diffraction pattern, it was confirmed to be an olipine-type lithium iron phosphate single phase. Table 1 shows the composition analysis results by ICP analysis.

In the same manner as in Example 1, a coin cell was assembled and a charge / discharge test was performed. Table 2 shows the initial charge / discharge capacity.

Example 3

(1) Manufacture of iron oxide

60 L 20 mo l the Na_〇_H reaction vessel, Na ₂ C_〇 ₃ g of aqueous 35 L containing 10 mo 1, was replaced by a stream of nitrogen gas was maintained at 60 ° C. Here, nitrogen aeration, stirring, and adding an aqueous solution 25L containing FeC 1 ₂ of 18Mo 1, a suspension containing the iron hydroxide particles were mixed for 60 minutes at 60 ° C. Next, the air was passed through lLZmin while maintaining the temperature at 60 ° C., and the oxidation reaction was performed for 12 hours. Resulting et suspension is filtered, washed and dried to obtain fine magnetite (Fe ₃ 〇 ₄₎ .. The specific surface area of the sample was measured by the BET method. The BET value of the obtained sample was 13.5 m ² Zg. Figure 9 shows a TEM photograph of the obtained sample. The particle size was calculated as an average value by randomly measuring 200 particles from a TEM photograph. The obtained sample had an average particle size of 107 nm and a coefficient of variation of 0.28.

It from X-ray diffraction pattern of the resulting particles is F e ₃ 〇 ₄ single phase was observed.

(2) A method of manufacturing L i F e P0 ₄

Magunetai Bok obtained above in (1) to (Fe ₃ 0 ₄₎ was form if the L i F e P_〇 ₄ as a raw material. Put iron oxide obtained in (1) 0.05 mol, Li ₂ C0 ₃ 0. 083 mol 1, (NH ₄ ) ₂ HP 0 ₄ 0.15 mo 1 into an 8 OmL planetary ball mill container, and add pure water 20 mL was added and mixed at 250 rpm for 12 hours. After drying, the mixture is pulverized in an agate mortar and calcined at 450 ° C for 5 hours in a mixed atmosphere of hydrogen (H ₂ ) and nitrogen (N ₂ ) at a volume ratio of 2: 5. Positive electrode active material Li F e P0 Got ₄ . The BET value of the obtained sample was 5.3 m ² Zg. Figure 10 shows a SEM photograph of the obtained sample. The particle size was calculated from an average value of 200 particles randomly measured from a TEM photograph. The obtained sample had an average particle size of 11 nm and a coefficient of variation of 0.39.

From the X-ray diffraction pattern of the obtained particles, it was confirmed to be a olivine-type lithium iron phosphate single phase. Table 1 shows the composition analysis results by ICP analysis.

Example 4

Magne evening Ito obtained in Example 3 (Fe ₃ 〇 ₄₎ was synthesized L i F e P0 ₄ in the raw material. Put the iron oxide obtained in Example 3 0.05 mol, Li ₂ C0 ₃ 0.086 mol 1, (NH ₄ ) ₂ HP0 ₄ 0.15 mol, 5 g glucose into an 80 mL planetary pole mill container, Further, 2 OmL of pure water was added and mixed for 12 hours at 25 Or.pm. After drying, Kona碎in an agate mortar, N ₂ atmosphere, for 3 hours at 650 ° C, and fired to obtain a positive electrode active material L i Fe P_〇 _4. The BET value of the obtained sample was 27.7m ² Zg. Figure 11 shows an SEM photograph of the sample obtained. The particle size was calculated from an average value of randomly measured 200 particles from a TEM photograph. The obtained sample had an average particle size of 66 nm and a coefficient of variation of 0.36.

From the X-ray diffraction pattern of the obtained particles, it was confirmed to be a olivine-type lithium iron phosphate single phase.

Table 1 shows the results of composition analysis by ICP analysis.

Comparative Example 1

Was synthesized L i F e P0 ₄ Matthew Bok a (Co. Kojundo Chemical Laboratory Ltd. purity 99% BET value 10. 3m ² / g) in the raw material into the amorphous as shown in FIG. 12. Hematite 0.075mo 1, Li ₂ C0 ₃ 0.0883mo 1, (NH ₄ ) ₂ HP0 ₄ 0.15 mol, 5 g of glucose are placed in an 8 OmL planetary polymill container, and pure water 2 OmL was added and mixed for 12 hours at 25 Or.pm. After drying, was ground in an agate mortar, N ₂ atmosphere, 12 hours at 600 ° C, and fired to obtain a positive electrode active material L i FeP_〇 _4. The BET value of the obtained sample was 32. θπι ² // ^. Fig. 13 shows an S-photograph of the obtained sample, and Fig. 14 shows a photo. The obtained particles were also amorphous. From the X-ray diffraction pattern of the obtained particles, it was confirmed that it was a single phase olivine type lithium iron phosphate. confirmed.

Table 1 shows the results of composition analysis by ICP analysis.

Comparative Example 2

Synthesized magnetic evening site (BET value 2. 6 m ² Zg, average particle size 520 nm, coefficient of variation 0.53) was synthesized L i F e P0 ₄ in the raw material. Put the above magnetite 0.05 mol, Li ₂ C0 ₃ 0.083 mol 1, (NH ₄ ) ₂ HP 0 ₄ 0.15 mol, glucose 5 g into an 8 OmL planetary pole mill container, and then add 2 OmL of pure water. Add and mix at 25 Or. Pm for 5 hours. After drying, was ground in an agate mortar, under N ₂ Kiri囲air, 4 hours at 650 ° C, and fired to obtain a positive electrode active material L i FeP_〇 _4. The BET value of the obtained sample was 25. Yn ^ Zg. Figure 15 shows an SEM photograph of the sample obtained. The particle size was calculated as an average value by randomly measuring 200 particles from a TEM photograph. The obtained sample had an average particle size of 109 nm and a coefficient of variation of 0.62. From the obtained particle X-ray diffraction pattern, it was confirmed to be an olivine-type lithium iron phosphate single phase.

Table 1 shows the results of composition analysis by ICP analysis.

IGP analysis result c Analysis value

Fe U P%

Mol ratio to Fe Example 1 1 1.0 1.0 5.8 Example 2 1 1.0 1.0 2.7 Example 3 1 1.0 1.0 0 Example 4 1 1.0 1.0 5.7 Comparative Example 1 1 1.0 1.0 5.3 Comparative Example 2 1 1.0 1.0 5.7

Coin battery evaluation result Charging capacity Discharging capacity mAh / g

Example 1 131 138 Example 2 138 134 Example 3 117 110 Example 4 132 126 Comparative Example 1 87 66 Comparative Example 2 113 87 Example 5

(1) Manufacture of iron oxide

A 60 L reaction vessel was charged with 40 L of an aqueous solution containing 52.8 mo 1 of NaOH, purged with nitrogen gas, and kept at 80 ° C. To this, 20 L of an aqueous solution containing 6 mol of Fe S0 ₄ and 6 mol of Fe ₂ (S 0 ₄ ) ₃ was added with nitrogen aeration and stirring, and mixed at 80 ° C. for 3 hours. The obtained suspension was filtered, washed and dried to obtain fine-particle magnetite (Fe ₃ 0 ₄ ). The specific surface area of the sample was measured by the BET method. The BET value of the obtained sample was 74.2 m ² / g. Figure 17 shows a TEM photograph of the sample obtained. The particle size was calculated from an average value of 200 particles randomly measured from a TEM photograph. The obtained sample had an average particle size of 11 nm and a coefficient of variation of 0.34.

From the X-ray diffraction pattern of the obtained particles, it was confirmed to be Fe ₃ 0 ₄ single phase.

(2) The method of producing L i FeP_〇 ₄

The olivine-type iron phosphate was synthesized from the iron oxide (Fe ₃ ₄ ) obtained in (1) above. Put the iron oxide obtained in (1) 0.05 mol, Li ₂ C0 ₃ 0.0 0.0 mol, (NH ₄ ) ₂ HP0 ₄ 0.15 mo 1 and 4 g glucose into an 80 mL planetary pole mill container, Further, 2 OmL of pure water was added and mixed at 25 Or.pm for 12 hours. After drying at 120 ° C., the mixture was pulverized in an agate mortar and fired at 650 ° C. for 6 hours in an N ₂ atmosphere to obtain a positive electrode active material L 1 Fe P0 ₄ . The obtained sample had a BET value of 12.501 ² and a carbon content of 3.3% by weight. Figure 18 shows a SEM photograph of the obtained sample. The particle size was calculated as an average value by randomly measuring 200 particles from a TEM photograph. The obtained sample had an average particle size of 80 nm and a coefficient of variation of 0.32.

X-ray diffraction measurement was performed on the obtained particles. Figure 19 shows the X-ray diffraction pattern of the obtained particles. From the X-ray diffraction pattern, it was confirmed to be an olivine type lithium iron phosphate single phase. In the same manner as in Example 1, a coin cell was assembled and a charge / discharge test was performed. The initial charge / discharge capacity was a charge capacity of 14 OmAh / g and a discharge capacity of 138 mAh / g.

Industrial applicability Examples of the non-aqueous electrolyte battery using the positive electrode active material of the present invention include lithium secondary batteries such as a metal lithium battery, a lithium ion battery, and a lithium polymer battery.

Claims

The scope of the claims

[I] A method for producing a compound having an olivine structure, comprising mixing an iron source containing an iron oxide particle having an average particle size of 500 nm or less, a lithium source, and a phosphorus source, followed by firing.

[2] The method according to claim 1, wherein the iron oxide particles are obtained by reacting an iron salt and an alkali and oxidizing the reaction product.

[3] The method of claim 1, wherein the iron oxide particles are magnetite.

[4] The method according to claim 3, wherein the iron oxide particles are magnetite having an average particle size of 500 nm or less and a particle size variation coefficient of 0.5 or less. '

[5] The method according to claim 2, wherein the strength is Al hydroxide and Z or Al carbonate.

[6] The method according to claim 2 or 5, wherein the oxidation is carried out at a temperature of 30 to 90 ° C.

'

[7] A compound having an olivine structure characterized by mixing an iron source including an iron oxide particle having an average particle diameter of 500 nm or less, a lithium source and a phosphorus source, and carbon or Z and a carbon precursor, followed by firing. Manufacturing method. '

[8] The method according to any one of claims 1 to 7, wherein the firing is performed in an inert gas atmosphere or a reducing atmosphere.

[9] The method according to claim 8, wherein the firing is performed in an N ₂ atmosphere.

[10] A compound having an olivine structure, obtained by the method according to any one of claims 1 to 9, and having an average particle size of 100 nm or less.

[II] An olivine structure having an average particle size of 10 O nm or less obtained by the method of any one of claims 1 to 9 and a coefficient of variation of the particle size of 0.6 or less. Compound.

[12] A positive electrode active material comprising the compound having an olipine structure obtained by the method according to any one of claims 1 to 9 or the compound having an olivine structure according to claim 10 or 11.

13. A nonaqueous electrolyte battery having a positive electrode comprising the positive electrode active material according to claim 12.