JP4225859B2 - Method for producing lithium iron phosphorus composite oxide carbon composite containing Mn atom - Google Patents

Description

  The present invention relates to a method for producing a lithium iron phosphorus-based composite oxide carbon composite containing Mn atoms, and more specifically, a lithium iron phosphorus composite oxide carbon containing Mn atoms particularly useful as a positive electrode active material for a lithium secondary battery. The present invention relates to a method for producing a composite.

  In recent years, as home appliances have become portable and cordless, lithium ion secondary batteries have been put to practical use as power sources for small electronic devices such as laptop computers, mobile phones, and video cameras. Regarding this lithium ion secondary battery, in 1980, Mizushima et al. Reported that lithium cobalt oxide was useful as a positive electrode active material for lithium ion secondary batteries ("Material Research Bulletin" vol15, P783-789 (1980)). Since then, research and development on lithium cobaltate has been actively promoted, and many proposals have been made so far.

However, Co is unevenly distributed on the earth and is a scarce resource. Therefore, for example, LiNiO ₂ , LiMn ₂ O ₄ , LiFeO ₂ , LiFePO _4, etc. are being developed as new positive electrode active materials to replace lithium cobalt oxide. ing.

Among these, regarding the lithium iron phosphorus composite oxide, a lithium iron phosphorus composite oxide carbon composite containing a Mn atom obtained by substituting Fe of LiFePO ₄ with Mn has been proposed (see Patent Documents 1 to 3). It has been reported that a lithium secondary battery using a lithium iron phosphorus-based composite oxide-carbon composite containing Mn atoms as a positive electrode active material has a high discharge capacity (see, for example, Patent Documents 1 to 4). .

に従って進行するため、製造時の有毒ガスの発生の問題や、原料系が複雑であるためＬｉ、Ｆｅ、Ｍｎ、Ｐの各元素の組成調整が難しく、また、リチウム二次電池の正極活物質として用いる場合に要望される物性として、平均粒径が０．５μｍ以下の微粒でＸ線回折的に単相のものが得られ難いと言う問題がある。 Conventionally, as a method for producing a lithium iron phosphorus-based composite oxide-carbon composite containing Mn atoms, for example, in which solid-phase reaction is performed, for example, lithium carbonate, iron oxalate, ammonium dihydrogen phosphate, manganese carbonate, and conductivity A method of reacting a carbon material with a reaction material (see, for example, Patent Documents 1 to 3) has been proposed. This reaction of lithium carbonate, iron oxalate, ammonium dihydrogen phosphate and manganese carbonate is represented by the following reaction formula (1)

Therefore, it is difficult to adjust the composition of each element of Li, Fe, Mn, and P because the raw material system is complicated and the composition of the raw material system is complicated. Also, as a positive electrode active material of a lithium secondary battery As a physical property desired for use, there is a problem that it is difficult to obtain a single particle having an average particle diameter of 0.5 μm or less in X-ray diffraction.

  In addition, Patent Document 1 (Japanese Patent Laid-Open No. 2002-117908) describes that various phosphates can be used as an example of a raw material that can be used. However, the Li source and the Fe source according to the patented invention are disclosed. There is no specific description or suggestion regarding making all the raw materials of the Mn source phosphate. Further, Patent Document 1 is at least intended for those having an average particle diameter of about several μm, but the present patent invention is also different in that it is intended for those having an average particle diameter of 0.5 μm or less.

JP 2002-117908 A, page 3. JP 2001-307732 A, page 5. WO 00/60679, page 17. JP 2003-157845 A, page 1.

  In view of such circumstances, the present inventors have no generation of toxic gas produced as a by-product during production, easy composition adjustment of each element of Li, Fe, Mn, and P, and a positive electrode active material for a lithium secondary battery As a result of extensive research on a method for obtaining a lithium iron-phosphorus-based composite oxide-carbon composite containing Mn atoms that can be used as a raw material, ferrous phosphate, lithium phosphate, manganese phosphate, and conductivity as raw materials When carbonaceous materials are used, no toxic gas is generated during production, the composition of each element of Li, Fe, Mn, and P can be easily adjusted, and the mixture containing the raw materials is pulverized to a specific volume. As a result of firing the reaction precursor in a specific temperature range, fine particles with an average particle size of 0.5 μm or less, which are necessary as a positive electrode active material for lithium secondary batteries, are single-phase lithium as seen from X-ray diffraction analysis. iron It found that the emission compound oxide carbon complex, and have completed the present invention.

  That is, the object of the present invention is that no toxic gas is generated during production, the composition of each element of Li, Fe, Mn, and P can be easily adjusted, and the average particle size is 0.5 μm or less from the viewpoint of X-ray diffraction analysis. An object of the present invention is to provide a method for producing a lithium iron phosphorus-based composite oxide carbon composite containing a single-phase Mn atom by an industrially advantageous method.

A method for producing a lithium iron phosphorus-based composite oxide-carbon composite containing Mn atoms to be provided by the present invention includes mixing ferrous phosphate, lithium phosphate, manganese phosphate, and a conductive carbonaceous material. One step, then the second step of obtaining a reaction precursor having a specific volume of 1.5 mL / g or less by pulverizing the resulting mixture in a dry process, and then the third step of calcining the reaction precursor at 500 to 700 ° C. step only containing, Mn atoms lithium phosphate of the first step, the half-width of the average particle diameter of 10μm or less and the lattice plane (010) plane is characterized in that it is a more than 0.2 ° lithium phosphate It is a manufacturing method of the lithium iron phosphorus type complex oxide carbon composite containing this.
In the method for producing a lithium iron phosphorus composite oxide-carbon composite containing Mn atoms, it is preferable to provide a step of pressure-molding the obtained reaction precursor after the second step.
Further, the ferrous phosphate in the first step has an average particle diameter of 5 μm or less and a ferrous phosphate hydrate (Fe ₃ (PO ₃ )) having a lattice plane (020) plane with a half-value width of 0.20 ° or more. ₄ ) It is preferable to use ₂ · 8H ₂ O) .
Also, the manganese phosphate in the first step, the average particle size is preferably of a 10μm or less.

  According to the method for producing a lithium iron phosphorus-based composite oxide-carbon composite containing Mn atoms of the present invention, no toxic gas is generated during production, and composition adjustment of each element of Li, Fe, Mn, and P is possible. Lithium iron-phosphorus composite oxide that is easy and has an average particle size of 0.5 μm or less that can be expected for use as a positive electrode active material of a lithium secondary battery, and that contains single-phase Mn atoms as seen from X-ray diffraction analysis A carbon composite can be produced industrially advantageously.

Hereinafter, the present invention will be described in detail based on preferred embodiments thereof.
The first step of the present invention is a step of preparing a raw material mixture by mixing ferrous phosphate, lithium phosphate, manganese phosphate and a conductive carbon material.

The first raw material ferrous phosphate is not particularly limited as long as it is industrially available, but the phosphoric acid compound represented by the general formula Fe ₃ (PO ₄ ) ₂ · 8H ₂ O is used. A ferrous hydrate salt having an average particle size of 5 μm or less, preferably 1 to 5 μm determined by a laser diffraction method, and using the CuKα ray as a radiation source, the ferrous phosphate hydrate (Fe ₃ (PO ₄ ) ₂ · 8H ₂ O) is a crystal having a diffraction peak (020) plane near 2θ = 13.1 of 0.20 ° or more, preferably 0.20 to 0.40 ° when X-ray diffraction analysis is performed. When using ferrous phosphate hydrate (Fe ₃ (PO ₄ ) ₂ .8H ₂ O), which has low processability and excellent processability and reactivity such as pulverization, the specific volume of the reaction precursor described later can be easily increased. It is particularly preferable because it can be 5 mL / g or less.

Ferrous phosphate hydrate (Fe ₃ (PO ₄ ) ₂ · 8H ₂ O) having such physical properties is reacted by adding an alkali to an aqueous solution containing a divalent iron salt and phosphoric acid. Can be manufactured more easily.

Examples of the divalent iron salt that can be used in such a method for producing ferrous phosphate hydrate include ferrous sulfate, iron acetate, iron oxalate, and the like. It may be an anhydride. Among these, ferrous sulfate heptahydrate (FeSO ₄ .7H ₂ O) is particularly preferable because it is inexpensive and highly pure because it is easily available industrially.
The phosphoric acid that can be used is not particularly limited as long as it is industrially available.
As the alkali which can be used is not particularly limited, for example, ammonia gas, aqueous ammonia, sodium hydroxide, potassium _{hydroxide, NaHCO 3, Na 2 CO 3} , LiOH, K 2 CO 3, KHCO 3, Ca An inorganic alkali such as (OH) ₂ or an organic alkali such as ethanolamine can be used. These alkalis can be used alone or in combination of two or more. Among them, sodium hydroxide is particularly preferable because it is inexpensive and easily available industrially.
The divalent iron salt, phosphoric acid, and alkali of these raw materials are particularly preferably those having a low impurity content in order to obtain a lithium iron phosphorus-based composite oxide-carbon composite containing high-purity Mn atoms. .

As a specific reaction operation, first, phosphoric acid is divalent so that the molar ratio to the iron atom in the divalent iron salt is 0.60 to 0.75, preferably 0.65 to 0.70. An aqueous solution in which an iron salt and phosphoric acid are dissolved is prepared. In this case, the concentration of the aqueous solution is not particularly limited as long as it can dissolve the divalent iron salt and phosphoric acid, but usually 0.1 mol / L or more, preferably 0.5 to 1 as the divalent iron salt. It is preferable to set it to 0.0 mol / L.
Next, an alkali is added to the aqueous solution to precipitate ferrous phosphate. The precipitation reaction of ferrous phosphate proceeds rapidly by the addition of this alkali. The addition amount of the alkali is 1.8 to 2.0, preferably 1.95 to 2.0 in terms of a molar ratio to the divalent iron salt.
There is no restriction | limiting in particular in the addition temperature of this alkali, Usually, 5-80 degreeC, Preferably it is 15-35 degreeC. The alkali dropping rate is not particularly limited, but it is preferable to gradually introduce it into the reaction system at a constant dropping rate in order to obtain a stable quality.
After completion of the reaction, solid-liquid separation is performed by a conventional method, and the precipitate is collected, washed and dried to obtain a product.
In the cleaning, particularly when sodium hydroxide is used as the alkali, the Na content of the precipitated ferrous phosphate hydrate (Fe ₃ (PO ₄ ) ₂ · 8H ₂ O) is 1% by weight or less. It is preferable to thoroughly wash with water until it becomes 0.8% by weight or less.
In addition, drying is preferably performed at 35 to 50 ° C. since drying takes time when the temperature is lower than 35 ° C., and oxidation of divalent iron and elimination of crystal water occur when the temperature exceeds 50 ° C.

The ferrous phosphate hydrate (Fe ₃ (PO ₄ ) ₂ · 8H ₂ O) thus obtained has an average particle size determined by a laser diffraction method of 5 μm or less, preferably 1 to 5 μm. The half-value width of the required diffraction peak of the lattice plane (020) plane is 0.20 ° or more, preferably 0.20 to 0.40 °, and more preferable physical properties include an Na content as an impurity of 1% by weight. Hereinafter, it is particularly preferably 0.8% by weight or less.

  The lithium phosphate as the second raw material is not particularly limited as long as it is industrially available, but the average particle size obtained from a scanning electron micrograph is 10 μm or less, preferably 1 to 5 μm, and further a radiation source. When the lithium phosphate is subjected to X-ray diffraction analysis using CuKα rays, the half value width of the diffraction peak (010) plane near 2θ = 16.8 ° is 0.2 ° or more, preferably 0.2-0. When lithium phosphate having a low 3 ° crystallinity and excellent processability and reactivity such as pulverization is used, the specific volume of the reaction precursor described later can be easily reduced to 1.5 mL / g or less, and is particularly preferable. Further, in addition to the above characteristics, the lithium phosphate is composed of fine primary particles having an angle of repose of 50 degrees or less, preferably 30 to 50 degrees, forming an aggregate of primary particles. The average particle size is 10 μm or more in the range The use of the lower lithium phosphate aggregate is particularly preferable because the uniform dispersibility of each raw material is improved.

  Such lithium phosphate is used in a method for producing lithium phosphate by a reaction between an aqueous solution containing lithium hydroxide and an aqueous solution containing phosphoric acid. It can be produced by carrying out the reaction at a reaction temperature of 70 ° C. or lower, preferably 5 to 40 ° C. under the conditions.

  The lithium hydroxide that can be used is not particularly limited as long as it is industrially available, and may be a hydrate or an anhydride, but it contains impurities to obtain a high purity lithium phosphate. It is preferable to use a small amount of lithium hydroxide, and industrially available lithium hydroxide contains Na of 20 ppm or more, Ca of 60 ppm or more, Al of 100 ppm or more, and Si of 100 ppm or more. It is particularly preferable to use purified lithium hydroxide from which impurities have been removed, in order to obtain a lithium iron-phosphorus composite oxide carbon composite containing high-purity Mn atoms. The purified lithium hydroxide is preferably purified lithium hydroxide in which impurities such as Na, Ca, Al, Si, etc. are reduced by microfiltration of an aqueous solution containing lithium hydroxide and crystallization. 2003-131032).

The third raw material manganese phosphate is not particularly limited as long as it is industrially available, but has an excellent fine reactivity with an average particle size of 10 μm or less, preferably 5 μm or less, determined by a laser diffraction method. The use of manganese phosphate is particularly preferable because the specific volume of the reaction precursor described later can be easily reduced to 1.5 mL / g or less. Such fine and excellent manganese phosphate contains, for example, manganese sulfate as MnSO _{4 in an amount} of 0.1 mol / L or more, preferably 0.1 to 1.0 mol / L, and phosphoric acid is manganese sulfate. After preparing an aqueous solution in which manganese sulfate and phosphoric acid are dissolved so that the molar ratio with respect to the Mn atom is 0.60 to 0.75, preferably 0.65 to 0.70, an alkali is added to the aqueous solution. It can manufacture easily by adding and reacting at 5-80 degreeC.

  Examples of the conductive carbon material as the fourth raw material include graphite such as natural graphite such as scaly graphite, scaly graphite and earthy graphite, and artificial graphite, carbon black, acetylene black, ketjen black, channel black, and furnace black. , Carbon blacks such as lamp black and thermal black, carbon fibers, and the like, and these may be used alone or in combination of two or more. Among these, those having fine ketjen black are particularly preferable because they can be easily obtained industrially.

  These conductive carbon materials have an average particle size determined from a scanning electron micrograph (SEM) of 0.5 μm or less, preferably 0.1 μm or less, and particularly preferably 0.01 to 0.1 μm. It is preferable because it can be attached in a highly dispersed state to the particle surface of the lithium iron phosphorus-based composite oxide containing atoms.

  In the operation of the first step, first, a predetermined amount of ferrous phosphate, lithium phosphate, manganese phosphate and conductive carbon material as the first to fourth raw materials are mixed.

  The blending ratio of ferrous phosphate, lithium phosphate and manganese phosphate is expressed as a molar ratio of Fe atom in ferrous phosphate, Li atom in lithium phosphate and Mn atom in manganese phosphate. When (Fe + Mn) is 0.9 to 1.1, preferably 1.00 to 1.05, it is particularly preferable in that a single phase of a lithium iron phosphorus composite oxide containing Mn atoms is obtained. In the present invention, the molar ratio of Fe atoms to Mn atoms can be arbitrarily set.

  In addition, the conductive carbon material has a tendency that the amount of C atoms contained in the conductive carbon material is slightly decreased after firing compared to before firing. When the amount of the conductive carbon material is 0.08 to 15.5% by weight, preferably 3.8 to 9.5% by weight, based on the total amount of iron, lithium phosphate and manganese phosphate, The content of C atoms with respect to the lithium iron-phosphorus composite oxide containing 0.1 to 20% by weight, preferably 5 to 12% by weight. When the blending amount of the conductive carbon material is less than 0.08% by weight, for example, it is sufficient when the lithium iron phosphorus composite oxide carbon composite containing the Mn atom is used as a positive electrode active material of a lithium secondary battery. In the lithium secondary battery using the obtained lithium iron phosphorus-based composite oxide carbon composite containing Mn atoms as the positive electrode active material, the internal resistance tends to increase. On the other hand, if it exceeds 5% by weight, the discharge capacity per unit weight or volume tends to decrease.

  In the first step, it is preferable that the raw material is sufficiently mixed in a dry manner using a blender or the like so that the raw materials are uniformly mixed in advance in performing the second step described later.

  The second step is a step of obtaining a reaction precursor by sufficiently mixing and pulverizing these first to fourth raw material mixtures in a dry manner using a pulverizer in order to further improve the reactivity.

  In this second step, it is an important requirement that the raw material mixture is sufficiently dry-mixed and pulverized until it reaches the specific volume range described below.

  Here, the reaction precursor improves the reactivity of the mixture containing the first to fourth raw materials of ferrous phosphate, lithium phosphate, manganese phosphate and a conductive carbon material prior to subsequent firing. Therefore, each raw material is highly dispersed and the interparticle distance between the raw materials is made as close as possible to increase the contact area of each raw material.

  In the present invention, the mixture after the pulverization treatment has a specific volume of 1.5 ml / g or less, preferably 1.0 to 1.4 ml / g. In addition, the average particle size obtained from a scanning electron micrograph is 0.5 μm or less, and the surface of lithium iron phosphorus composite oxide particles containing a single-phase Mn atom in X-ray diffraction analysis is uniformly made of a conductive carbon material. Since a lithium iron phosphorus-based composite oxide carbon composite containing Mn atoms coated on is obtained, a raw material mixture having a specific volume within this range is used as a reaction precursor.

（式中、Ｆ；受器内の処理した試料の質量（ｇ）、Ｖ；タップ後の試料の容量（ｍｌ）を示す。） The specific volume in the present invention is based on the method of apparent density or apparent specific volume described in JIS-K-5101, 10 g of sample is put into a 50 ml graduated cylinder by the tap method, and after tapping 500 times, left standing. The volume is read and obtained by the following formula.

(Wherein, F represents the mass (g) of the processed sample in the receiver, and V represents the volume (ml) of the sample after tapping.)

  Furthermore, in the method for producing a lithium iron phosphorus-based composite oxide-carbon composite containing Mn atoms of the present invention, the reaction precursor is included in the reaction precursor in addition to the specific volume being in the range. When the raw material ferrous phosphate crystals are in an almost amorphous state, the reaction proceeds completely even when baked at a low temperature of 500 to 700 ° C. for the purpose of suppressing the growth of the particle diameter, and Mn atoms are It is particularly preferable because a single phase of the lithium iron phosphorus composite oxide is obtained.

  As the dry pulverizer that can be used, a pulverizer having a strong shearing force is preferable. Examples of the pulverizer having such a strong shearing force include a rolling ball mill, a vibration mill, a planetary mill, and a medium agitating mill. It is preferable to use it. This type of pulverizer is a pulverizer in which a pulverization medium such as balls and beads is contained in a container and pulverization is performed mainly by the shearing and frictional action of the medium. A commercially available apparatus can be used as such an apparatus.

The particle size of the granular medium is preferably 1 to 25 mm because pulverization can be sufficiently performed. As the material of the granular medium, zirconia and alumina ceramic beads are particularly preferable since they have high hardness and resistance to wear and can prevent metal contamination of the material.
In addition, the granular medium is stored in a container with a space volume of 50 to 90%, and the shearing force and frictional force due to the fluid medium are appropriately managed. preferable.

  Further, in the method for producing a lithium iron phosphorus-based composite oxide carbon composite containing Mn atoms of the present invention, if necessary, the reaction precursor is subjected to pressure molding treatment in addition to the above pulverization treatment, Increasing the contact area of the raw material allows the reaction to proceed more completely. In this case, the molding pressure varies depending on the press, the amount charged, etc., and is not particularly limited, but is usually 5 to 200 MPa. The press molding machine can be suitably used such as a tableting machine, a briquette machine, a roller compactor, etc., but may be any press as long as it can be pressed, and is not particularly limited.

Next, in the third step, the reaction precursor obtained in the second step is baked.
The firing temperature is 500 to 700 ° C, preferably 550 to 650 ° C. In the present invention, the reason for setting the firing temperature in this range is that when the firing temperature is less than 500 ° C., the reaction does not proceed sufficiently, so that the unreacted raw material remains. Since it progresses and particle growth occurs, it is not preferable because it has characteristics that are not suitable for the use of the positive electrode active material of the lithium secondary battery.
The firing time is 2 to 20 hours, preferably 5 to 10 hours.
Firing is preferably performed in an inert gas atmosphere such as nitrogen or argon or in a reducing atmosphere such as hydrogen or carbon monoxide in order to prevent oxidation of Fe and Mn elements. Moreover, these baking can be performed as many times as necessary.

After firing, it is cooled appropriately, and pulverized or classified as necessary, and the lithium iron phosphorus-based composite oxide containing Mn atoms in which the particle surface of the lithium iron-phosphorus composite oxide containing Mn atoms is uniformly coated with a conductive carbon material. A composite oxide carbon composite is obtained. In order to prevent oxidation of Fe and Mn elements, it is preferable to perform the reaction system in an inert gas atmosphere such as nitrogen or argon or a reducing atmosphere such as hydrogen or carbon monoxide during cooling. In addition, the pulverization performed as necessary is appropriately performed when the lithium iron phosphorus-based composite oxide-carbon composite containing Mn atoms obtained by firing is in a brittlely bonded block form. According to the production method of a preferred embodiment of the lithium iron phosphorus-based composite oxide carbon composite containing Mn atoms, the particles of the lithium iron phosphorus composite oxide-carbon composite containing Mn atoms are specified as follows. Having an average particle size of BET and a BET specific surface area. That is, the obtained lithium iron phosphorus composite oxide-carbon composite containing Mn atoms has an average particle size of 0.5 μm or less, preferably 0.05 to 0.5 μm, as determined from a scanning electron micrograph (SEM). The BET specific surface area is 10 to 100 m ² / g, preferably 30 to 70 m ² / g.

に示すが如く、製造時に副生するのは水のみで、また、本発明は基本的に３つの原料系で固溶反応を行うため従来の４つの原料系の反応と比べて容易に所望のＬｉ、Ｆｅ、Ｍｎ、Ｐの組成調整を行うことができる。更に、本発明のＭｎ原子を含有するリチウム鉄リン系複合酸化物炭素複合体の製造方法において、第一工程で前記第１〜第４の原料混合物を得、第二工程で得られた原料混合物を乾式粉砕処理して当該範囲内の比容積の反応前駆体を調製することで、第三工程の焼成温度を粒子成長が起こらないような低温での焼成を行ってもＸ線回折分析からみて単相のＭｎ原子を含有するリチウム鉄リン系複合酸化物炭素複合体を得ることができる。 According to the method for producing a lithium iron phosphorus-based composite oxide-carbon composite containing Mn atoms according to the present invention, ferrous phosphate, lithium phosphate, manganese phosphate and a conductive carbon material are used as reaction raw materials, phosphorus Reaction of ferrous acid, lithium phosphate and manganese phosphate is represented by the following reaction formula (2)

As shown in FIG. 5, only water is produced as a by-product during production, and the present invention basically performs a solid solution reaction with three raw material systems, so that it can be easily obtained as compared with the conventional four raw material system reactions. The composition of Li, Fe, Mn, and P can be adjusted. Furthermore, in the method for producing a lithium iron phosphorus-based composite oxide-carbon composite containing Mn atoms of the present invention, the first to fourth raw material mixtures are obtained in the first step, and the raw material mixture obtained in the second step As a result of X-ray diffraction analysis, even if the firing temperature in the third step is low-temperature so that particle growth does not occur, the reaction precursor having a specific volume within the above range is prepared by dry pulverization. A lithium iron phosphorus composite oxide-carbon composite containing a single-phase Mn atom can be obtained.

  In view of such fine X-ray diffraction analysis, the lithium iron-phosphorus-based composite oxide-carbon composite containing a single-phase Mn atom can be expected particularly for use as a positive electrode active material of a lithium secondary battery. In this case, the form may be a primary particle aggregate having an average particle diameter of 1 μm or more and 75 μm formed by aggregating primary particles having an average particle diameter of 0.05 μm or more and 0.5 μm or less. Furthermore, it is preferable that 70% or more, preferably 80% or more of the total volume in the primary aggregate is a particle size of 1 μm or more and 20 μm or less, and the lithium iron phosphorus composite oxide carbon composite containing the Mn atom. Since the lithium iron phosphorus-based composite oxide carbon composite obtained by pulverizing in the atmosphere contains 3000 ppm or more of water, an operation such as vacuum drying is performed before using as a positive electrode active material. Thus, it is preferable to use the lithium iron phosphorus composite oxide-carbon composite at a moisture content of 2000 ppm or less, preferably 1500 ppm or less.

注）表１中の「Ｎ．Ｄ．」は検出限界１ｐｐｍ以下を示す。 EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these.
[Synthesis Example 1]: Synthesis of ferrous phosphate Ferrous sulfate heptahydrate (FeSO ₄ .7H ₂ O) 907 g (3 mol) and 75% phosphoric acid (H ₃ PO ₄ ) 261 g (2 mol) Was dissolved in 3 L of water to prepare a mixed solution (temperature 17 ° C., pH 1.6). To this mixed solution, 1500 mL (6 mol) of a 16% sodium hydroxide (NaOH) aqueous solution was added dropwise at a dropping rate of 83 mL / min over 18 minutes to precipitate ferrous phosphate (temperature 31 ° C., pH 6. 7).
Next, the ferrous phosphate was recovered by filtration, and the recovered ferrous phosphate was carefully washed with 4.5 L of water.
Next, the washed ferrous phosphate was dried at a temperature of 50 ° C. for 23 hours to obtain 490 g of a dried product. When the obtained dried product was analyzed by X-ray diffraction, it was confirmed that this dried product was Fe ₃ (PO ₄ ) ₂ · 8H ₂ O because the diffraction pattern was in agreement with JCPDS card number 30-662. (Yield 98%).
Table 1 shows various physical properties of the obtained Fe ₃ (PO ₄ ) ₂ · 8H ₂ O.
In addition, X-ray diffraction analysis was performed using the obtained Fe ₃ (PO ₄ ) ₂ · 8H ₂ O as a radiation source using CuKα rays, and the half width of the peak (020) plane near 2θ = 13.1 ° was measured. .
The contents of Na, Si, Al, Ca, Ti, Mn, Zn, Cr, Ni, Cu, and Co were obtained by ICP spectroscopy. The SO ₄ content was obtained by converting the S atom concentration measurement result by ICP spectroscopy, and the P content of the dried product was obtained by absorptiometry. The average particle size was determined by a laser diffraction method.

Note) “ND” in Table 1 indicates a detection limit of 1 ppm or less.

注）表２中の「Ｎ．Ｄ．」は検出限界１ｐｐｍ以下を示す。 [Synthesis Example 2]: Synthesis of manganese phosphate Manganese sulfate monohydrate (MnSO ₄ · H ₂ O) 1352 g (8 mol) and 75% phosphoric acid (H ₃ PO ₄ ) 697 g (5.3 mol) Was dissolved in 25 L of water to prepare a mixed solution (pH 1.3). To this mixed solution, 16 L (16 mol) of a 4 wt% sodium hydroxide (NaOH) aqueous solution was dropped at a dropping rate of 161 mL / min in about 100 minutes to precipitate manganese phosphate (pH 6.5).
Next, filtration was performed to recover manganese phosphate, and the recovered manganese phosphate was carefully washed with 40 L of water.
Next, the washed manganese phosphate was dried at a temperature of 50 ° C. for 23 hours to obtain 1241 g of a dried product. When the obtained dried product was analyzed by X-ray diffraction, the data described in the literature (RUSS. J. Inorg. Chem. 23, 341, 1978) was in agreement with the surface spacing and diffraction intensity, and the Mn content Was 34.8% by weight and the PO ₄ content was 40.2% by weight, it was confirmed that this dried product was Mn ₃ (PO ₄ ) ₂ · 6H ₂ O (yield 98%).
Various physical properties of the obtained Mn ₃ (PO ₄ ) ₂ · 6H ₂ O were determined in the same manner as in Synthesis Example 1 and are shown in Table 2.

Note) “ND” in Table 2 indicates a detection limit of 1 ppm or less.

上記した粗製水酸化リチウム１水塩１０６２ｇを純水５０００ｇに５０℃で溶解し水溶液を調製した。
次いで、上記で調製した粗製水酸化リチウムを溶解した水溶液を４０℃で孔径０．５μｍのＰＴＦＥ製メンブランフィルターを使用して濾過を行った。
次いで、９５℃に加温し、減圧下に水分を抑留しながら４時間晶析を行った。なお、回収した水分は３３００ｇであった。冷却後、常法により固液分離して析出した水酸化リチウムを回収し、次いで、減圧下に乾燥を行って精製水酸化リチウム試料とした。また、得られた精製水酸化リチウム（ＬｉＯＨ・Ｈ₂Ｏ）試料中の主な不純物含有量を表４に示した。

上記で調製した精製水酸化リチウム１水塩１２６ｇを純水に溶解し１５００ｇとし、４．８重量％水酸化リチウム水溶液を調製した（ｐＨ １１．６）。
次いでこの反応容器にリン酸を９．８重量％含むリン酸水溶液１０００ｇを８３ｍＬ／分の速度で反応系の温度を４０℃以下に維持しながら全量を約１２分間かけて滴下しリン酸リチウムを析出させた（ｐＨ １０．５）。
次に、ろ過してリン酸リチウムを回収した。
次いで、回収したリン酸リチウムを温度１１０℃で２０時間乾燥し、微細な一次粒子が集合した集合体の乾燥品を得た。得られた乾燥品をＸ線回折で分析したところＪＣＰＤＳカード番号（２５−１０３０）と回折パターンが一致していることから、この乾燥品はＬｉ₃ＰＯ₄であることを確認した。
得られたＬｉ₃ＰＯ₄の諸物性値を合成例１と同様に求め，合わせて安息角を測定し、その結果を表５に示す。
また、得られたＬｉ₃ＰＯ₄を線源としてＣｕＫα線を用いてＸ線回折分析を行い２θ＝１６．８近傍の回折ピーク（０１０）面の半値幅を測定した。また、一次粒子と一次粒子の集合体の粒径は走査型電子顕微鏡写真（ＳＥＭ）により求めた。

注）表５中の「Ｎ．Ｄ．」は検出限界１ｐｐｍ以下を示す。 [Synthesis Example 3]; Synthesis of Lithium Phosphate Lithium hydroxide was obtained by subjecting a commercially available lithium hydroxide monohydrate to the following purification operation and was used as a raw material for the synthesis of lithium phosphate.
Table 3 shows the main impurity contents in this commercially available lithium hydroxide sample.
The impurity content is a value obtained by ICP mass spectrometry and turbidimetry.

The above-mentioned crude lithium hydroxide monohydrate 1062 g was dissolved in pure water 5000 g at 50 ° C. to prepare an aqueous solution.
Next, the aqueous solution in which the crude lithium hydroxide prepared above was dissolved was filtered at 40 ° C. using a PTFE membrane filter having a pore size of 0.5 μm.
Next, the mixture was heated to 95 ° C. and crystallized for 4 hours while retaining moisture under reduced pressure. The recovered water was 3300 g. After cooling, the precipitated lithium hydroxide was recovered by solid-liquid separation by a conventional method, and then dried under reduced pressure to obtain a purified lithium hydroxide sample. Table 4 shows the main impurity contents in the obtained purified lithium hydroxide (LiOH.H ₂ O) sample.

126 g of the purified lithium hydroxide monohydrate prepared above was dissolved in pure water to 1500 g to prepare a 4.8 wt% lithium hydroxide aqueous solution (pH 11.6).
Next, 1000 g of an aqueous phosphoric acid solution containing 9.8% by weight of phosphoric acid was added dropwise to the reaction vessel at a rate of 83 mL / min over a period of about 12 minutes while maintaining the temperature of the reaction system at 40 ° C. or less. Precipitated (pH 10.5).
Next, it filtered and lithium phosphate was collect | recovered.
Next, the recovered lithium phosphate was dried at a temperature of 110 ° C. for 20 hours to obtain a dried product of aggregates in which fine primary particles were aggregated. When the obtained dried product was analyzed by X-ray diffraction, the diffraction pattern was in agreement with the JCPDS card number (25-1030), and it was confirmed that this dried product was Li ₃ PO ₄ .
Various physical properties of the obtained Li ₃ PO ₄ were determined in the same manner as in Synthesis Example 1, and the angle of repose was measured together. Table 5 shows the results.
Further, X-ray diffraction analysis was performed using the obtained Li ₃ PO ₄ as a radiation source using CuKα rays, and the half width of the diffraction peak (010) plane in the vicinity of 2θ = 16.8 was measured. Moreover, the particle diameter of the aggregate | assembly of a primary particle and a primary particle was calculated | required by the scanning electron micrograph (SEM).

Note) “ND” in Table 5 indicates a detection limit of 1 ppm or less.

（式中、Ｆ；受器内の処理した試料の質量（ｇ）、Ｖ；タップ後の試料の容量（ｍＬ）を示す。）
なお、振動ミルの運転条件は以下の通りである。
・振動数；１０００Ｈｚ
・処理時間；３分
・原料の仕込量；１２ｇ Examples 1-3 and Reference Examples 1-2
As shown in Table 6, ferrous phosphate, manganese phosphate, lithium phosphate and Ketjen Black (trade name ECP, manufactured by Ketjen Black International Co., Ltd.) having an average particle diameter of 0.05 μm were synthesized. A predetermined amount was weighed so that the molar ratio x (= Mn / (Fe + Mn)) of manganese to the total amount of iron and manganese was 0, 0.25, 0.5, 0.75, and 1.0, and mixed with a mixer. This mixture was pulverized using a vibration mill to obtain a reaction precursor. Further, the specific volume of the vibration mill pulverized product was obtained by putting 10 g of a sample in a 50 mL measuring cylinder, setting it on a Yuasa Ionics Co., Ltd., DUAL AUTOTAP device, tapping 500 times, reading the volume, and obtaining the following formula. .

(Wherein, F represents the mass (g) of the processed sample in the receiver, and V represents the volume (mL) of the sample after tapping.)
The operating conditions of the vibration mill are as follows.
・ Frequency: 1000Hz
・ Processing time: 3 minutes ・ Material charge: 12 g

Table 6 shows the main physical properties of the obtained reaction precursor.
Next, 10 g of the reaction precursor was press-molded at 44 MPa by hand press. Subsequently, the obtained pulverized product was fired at 600 ° C. for 5 hours in a nitrogen atmosphere, cooled and pulverized. Main physical properties were determined in the same manner as in Synthesis Example 1 except that the average particle size of the obtained powder was determined by scanning electron micrograph (SEM), and are shown in Table 6. The obtained powder was subjected to X-ray diffraction analysis using CuKα rays as a radiation source, and the obtained XRD pattern is shown in FIG.

1 that the XRD pattern is a single phase having an olivine structure. Looking at the peak position on the (200) plane of the XRD pattern in detail, as the value of x changes from 0 to 1, the peak position is 29.7 °, which is the peak position of lithium iron phosphate, and manganese phosphate. It was found that it continuously changed toward 29.2 ° which is the peak position of lithium (see FIG. 1). From these, the obtained powder shows a single phase of olivine structure in which iron and manganese are dissolved, and is a lithium iron phosphorus-based composite oxide represented by the composition formula LiFe _1-x Mn _x PO _4. I can say that.

注）表６中の^注1)ｘは原料仕込み量から求められるＭｎ／(Ｆｅ＋Ｍｎ)のモル比、^注2)ｘは焼成品をＩＣＰ質量分析法して求めたＭｎ／(Ｆｅ＋Ｍｎ)の実測値を示す。

Note) ^{Note 1} ) in Table 6 x ⁾ M is the molar ratio of Mn / (Fe + Mn) obtained from the raw material charge, and ^{Note 2)} x is the actual value of Mn / (Fe + Mn) obtained by ICP mass spectrometry of the fired product. Indicates.

  From the results of Table 6, the theoretical Mn / (Fe + Mn) molar ratio determined from the raw material charge and the calcined product according to the method for producing a lithium iron phosphorus composite oxide-carbon composite containing Mn atoms of the present invention Since the molar ratio of Mn / (Fe + Mn) obtained from the actual measurement value of (lithium iron phosphorus-based composite oxide-carbon composite containing Mn atoms) is almost the same, the composition adjustment of Li, Fe, Mn, and P Is easy to understand. From the results shown in FIG. 1 and Table 6, the lithium iron phosphorus composite oxide-carbon composite containing Mn atoms obtained by the production method of the present invention is a fine particle having an average particle size of 0.5 μm or less. From the X-ray diffraction analysis, it can be seen that the lithium iron phosphorus composite oxide-carbon composite contains a single-phase Mn atom.

The X-ray-diffraction figure of the lithium iron phosphorus type complex oxide carbon composite obtained in Examples 1-3 and Reference Examples 1-2.

Claims (4)

The first step of mixing ferrous phosphate, lithium phosphate, manganese phosphate and conductive carbonaceous material, and then the resulting mixture is dry pulverized to give a reaction precursor having a specific volume of 1.5 mL / g or less a second step of obtaining a body, then the reaction seen including a third step of the precursor is calcined at 500 to 700 ° C., lithium phosphate of the first step, an average particle diameter of 10μm or less and the lattice plane (010) A method for producing a lithium iron-phosphorus-based composite oxide-carbon composite containing Mn atoms, wherein the surface is a lithium phosphate having a half-width of 0.2 ° or more .   The method for producing a lithium iron-phosphorus-based composite oxide-carbon composite containing Mn atoms according to claim 1, wherein a step of pressure-molding the obtained reaction precursor is provided after the second step. The ferrous phosphate in the first step has an average particle size of 5 μm or less and a ferrous phosphate hydrate (Fe ₃ (PO ₄ )) having a lattice plane (020) plane half width of 0.20 ° or more. _The method for producing a lithium iron phosphorus-based composite oxide carbon composite containing Mn atoms according to claim 1 or 2, wherein ₂ · 8H ₂ O) is used. The manganese phosphate in the first step, the manufacturing method according to claim 1 or lithium-iron-phosphorus compound oxide carbon complex containing Mn atoms of 3, wherein an average particle diameter used as the 10μm or less.

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