JP2002117831A - Manufacturing method of positive electrode active material and manufacturing method of nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simple synthetic method of LiFePO4 wherein a manufacturing cost is inexpensive. SOLUTION: This has a coprecipitation process wherein a mixed aqueous solution is prepared by mixing a water-soluble organic reducer with a phosphoric acid aqueous solution containing lithium salts and iron salts, and wherein an alkaline solution is mixed with the mixed aqueous solution to form a coprecipitate of complex phosphate with lithium and iron, and has a calcination process to calcine the coprecipitate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive electrode active material using a positive electrode active material capable of reversibly doping and undoping lithium, and a method for manufacturing a non-aqueous electrolyte secondary battery using the same.

[0002]

2. Description of the Related Art In recent years, with the remarkable progress of various electronic devices, research on a rechargeable secondary battery has been advanced as a power source that can be used conveniently and economically for a long time. Typical secondary batteries include lead storage batteries, alkaline storage batteries,
Non-aqueous electrolyte secondary batteries and the like are known.

[0003] Among the above secondary batteries, a lithium ion secondary battery, which is a nonaqueous electrolyte secondary battery, has advantages such as high output and high energy density. A lithium ion secondary battery is composed of a positive electrode having an active material capable of reversibly inserting and removing lithium ions, a negative electrode, and a non-aqueous electrolyte.

Here, as the negative electrode active material, generally, lithium metal, a lithium alloy such as a Li-Al alloy, a conductive polymer doped with lithium such as polyacetylene or polypyrrole, an interlayer compound in which lithium ions are incorporated in a crystal, A carbon material or the like is used. As the electrolyte, a solution in which a lithium salt is dissolved in an aprotic organic solvent is used.

On the other hand, a metal oxide, a metal sulfide, or a polymer is used as the positive electrode active material.
S ₂ , MoS ₂ , NbSe ₂ , V ₂ O _{5 and the} like are known.
In the discharge reaction of a non-aqueous electrolyte secondary battery using these materials, lithium ions are eluted into the electrolyte at the negative electrode,
In the positive electrode, the process proceeds by intercalation of lithium ions between layers of the positive electrode active material. Conversely, when charging, the above reverse reaction proceeds, and in the positive electrode,
Lithium intercalates. That is, charge and discharge can be repeated by repeating a reaction in which lithium ions from the negative electrode enter and exit the positive electrode active material.

At present, LiCoO ₂ , LiNiO ₂ , LiMn ₂ O _{4 and the} like are used as a positive electrode active material of a lithium ion secondary battery because of its high energy density and high voltage. However, since these positive electrode active materials have a metal element having a low Clark number in their composition, they have a problem that the cost is high and a stable supply is difficult. In addition, these positive electrode active materials have relatively high toxicity,
Because of its great impact on the environment, there is a need for new positive electrode active materials to replace them.

On the other hand, it has been proposed to use a compound having an olivine structure as a positive electrode active material of a lithium ion secondary battery. For example, LiFePO ₄ , which is a compound having an olivine structure, has a volume density of 3.6 g / c.
large as m ^3, and generates a high potential of 3.4 V, with the theoretical capacity being as high as 170 mAh / g. LiFePO ₄ is
Initially, Li that can be electrochemically undoped is converted to Fe
Since one atom is contained per atom, it is a promising material as a positive electrode active material of a lithium ion battery. Moreover, Li
Since FePO ₄ has iron in its composition, which is a resource-rich and inexpensive material, the above-mentioned LiCoO ₂ , Li
Low cost compared to NiO ₂ , LiMn ₂ O _4, etc.
In addition, the effect on the environment is small due to low toxicity.

[0008]

By the way, LiFeP
As a method for synthesizing O ₄ , there is a synthesis method by a solid phase reaction.
As a method for synthesizing LiFePO ₄ by a solid-phase reaction, for example, lithium carbonate LiCo
₃ , a diammonium phosphate NH ₄ H ₂ PO ₄ and iron (II) acetate Fe (CH ₃ COO) ₂ using a synthesis method by a reaction represented by the following formula 1, lithium phosphate Li ₃ PO ₄ , Ferrous phosphate n-hydrate Fe ₃ (PO ₄ ) ₂ .nH ₂ O (provided that
n is the hydration number. )) And a synthesis method by the reaction shown in the following chemical formula 2.

[0009]

Embedded image

[0010]

Embedded image

However, the synthesis method as described above is
Since the reaction is carried out by a solid-phase reaction, a step of pulverizing and mixing the synthetic raw materials is required, and large-scale equipment such as a ball mill is required as equipment for this, and the process becomes complicated. Therefore, the presence of the step of pulverizing and mixing the synthetic raw material powder leads to an increase in production cost and a decrease in productivity, and an alternative step is desired.

Therefore, the present invention has been proposed in view of such a conventional situation, and has a low manufacturing cost.
It is another object of the present invention to provide a simple method for synthesizing a positive electrode active material and a method for manufacturing a nonaqueous electrolyte secondary battery.

[0013]

In order to achieve the above object, a method for producing a positive electrode active material according to the present invention comprises mixing a water-soluble organic reducing agent with a phosphoric acid aqueous solution containing a lithium salt and an iron salt. And preparing a mixed aqueous solution by mixing the mixed aqueous solution with an alkaline solution to form a coprecipitate of a composite phosphorous oxide of lithium and iron, and a firing step of firing the coprecipitate. It is characterized by the following.

The method for producing a positive electrode active material as described above involves forming a coprecipitate of a composite phosphorous oxide of lithium and iron and firing the coprecipitate, and is not a synthesis method by a solid phase reaction. Therefore, the step of pulverizing and mixing the raw material powder of the positive electrode active material is not required. That is, an apparatus for pulverizing and mixing the synthetic raw material powder of the positive electrode active material, for example, an apparatus such as a ball mill is not required, so that there is no increase in cost due to the introduction of equipment.

Further, pulverization of a raw material powder for synthesis of a positive electrode active material;
Since there is no mixing step, it is possible to easily produce the positive electrode active material without problems such as complication of the production process of the positive electrode active material and reduction in productivity caused by this step.

Further, in the case of the synthesis method by the solid phase reaction, since a rare and expensive material is used as a raw material for synthesizing the positive electrode active material, the raw material cost is increased. On the other hand,
In the case of this method for producing a positive electrode active material, since a general material is used as a raw material for synthesizing the positive electrode active material to be used, the raw material cost can be kept low.

Further, in order to achieve the above-mentioned object, a method for manufacturing a non-aqueous electrolyte secondary battery according to the present invention comprises a method of forming a positive electrode having a positive electrode active material, a negative electrode having a negative electrode active material, and a non-aqueous electrolyte. The method for producing a positive electrode active material comprises the steps of mixing a water-soluble organic reducing agent with a phosphoric acid aqueous solution containing a lithium salt and an iron salt, and further mixing an alkaline solution to form a lithium-iron complex phosphorous oxide. It is characterized by having a coprecipitation step of generating a precipitate and a firing step of firing the coprecipitate.

In the method of manufacturing a non-aqueous electrolyte secondary battery as described above, a co-precipitate of a composite phosphorous oxide of lithium and iron is formed when a positive electrode active material is manufactured, and the co-precipitate is fired. Since the synthesis by the solid phase reaction is not performed, the step of pulverizing and mixing the raw material powder for the synthesis of the positive electrode active material is unnecessary. That is, an apparatus for pulverizing and mixing the synthetic raw material powder of the positive electrode active material, for example, an apparatus such as a ball mill is not required, so that there is no increase in cost due to the introduction of equipment.

Further, pulverization of raw material powder for synthesis of the positive electrode active material,
Since there is no mixing step, it is possible to easily produce the positive electrode active material without causing problems such as complication of the production process of the positive electrode active material and a decrease in productivity due to this step. Manufacture of the electrolyte secondary battery is simplified.

When a positive electrode active material is synthesized by a solid-phase reaction, a rare and expensive material is used as a raw material for synthesizing the positive electrode active material, so that the raw material cost increases. On the other hand, in this method of manufacturing a nonaqueous electrolyte secondary battery,
Since a general material is used as a raw material for synthesizing the positive electrode active material, the raw material cost can be kept low.

[0021]

Embodiments of the present invention will be described below. It should be noted that the present invention is not limited to the following description, and can be appropriately modified without departing from the present invention.

As shown in FIG. 1, a non-aqueous electrolyte battery 1 manufactured by applying the present invention contains a negative electrode 2, a negative electrode can 3 containing the negative electrode 2, a positive electrode 4, and a positive electrode 4. Positive electrode can 5
And a separator 6 disposed between the positive electrode 4 and the negative electrode 2,
An insulating gasket 7 is provided, and the negative electrode can 3 and the positive electrode can 5 are filled with a non-aqueous electrolyte.

The negative electrode 2 is made of, for example, a metal lithium foil serving as a negative electrode active material. When a material that can be doped and dedoped with lithium is used as the negative electrode active material, the negative electrode 2 is formed by forming a negative electrode active material layer containing the negative electrode active material on a negative electrode current collector. As the negative electrode current collector, for example, a nickel foil or the like is used.

As the negative electrode active material which can be doped with and dedoped with lithium, metal lithium, a lithium alloy, a conductive polymer doped with lithium, a layered compound such as a carbon material and a metal oxide can be used.

As the binder contained in the negative electrode active material layer, a known resin material or the like which is usually used as a binder for the negative electrode active material layer in this type of nonaqueous electrolyte battery can be used. .

The negative electrode can 3 houses the negative electrode 2 and serves as an external negative electrode of the nonaqueous electrolyte battery 1.

The positive electrode 4 contains a positive electrode active material capable of electrochemically releasing lithium and reversibly occluding lithium on a positive electrode current collector made of, for example, an aluminum foil. The positive electrode active material layer is formed. Here, the positive electrode active material layer is mainly composed of the positive electrode active material,
It contains a binder, a conductive material and the like as necessary.

The positive electrode active material has an olivine structure and a general formula Li _x FePO ₄ , which will be described in detail later.
(Wherein, 0 <x ≦ 1.0),
Alternatively, a composite of these compounds and a carbon material, that is, a Li _x FePO ₄ carbon composite is used.

Hereinafter, Li _x FePO _{4 will be referred to} as LiFePO _4.
4 , the case where a composite comprising this and a carbon material, that is, a LiFePO ₄ carbon composite is used as the positive electrode active material will be described.

LiFePO_FourThe carbon composite is LiFeP
O_FourThe surface of the particles has the LiFePO _FourCompared to particle size
Particles of carbon material with a very small particle size
Individually attached. Carbon material has conductivity
Therefore, carbon material and LiFePO_FourL composed of
iFePO_FourThe carbon composite is, for example, LiFePO_FourCompare with
Then, the electron conductivity is excellent. That is, LiFeP
O_FourThe carbon composite is LiFePO_FourAdhere to the surface of particles
Since the electron conductivity is improved by the carbon particles, LiFeP
O_FourThe original capacity is fully drawn out. Therefore, positive
LiFePO as pole active material_FourUsing carbon composite
Thereby, the non-aqueous electrolyte battery 1 having a high capacity can be realized.
You.

As the binder contained in the positive electrode active material layer, a known resin material or the like usually used as a binder for the positive electrode active material layer in this type of nonaqueous electrolyte battery can be used. .

The positive electrode can 5 accommodates the positive electrode 4 and serves as an external positive electrode of the nonaqueous electrolyte battery 1.

The separator 6 separates the positive electrode 4 and the negative electrode 2 from each other, and can be made of a known material usually used as a separator of this kind of non-aqueous electrolyte battery. A polymer film is used. Also, from the relationship between lithium ion conductivity and energy density, it is necessary that the thickness of the separator be as small as possible. Specifically, the thickness of the separator is suitably, for example, 50 μm or less.

The insulating gasket 7 is integrated into the negative electrode can 3. The insulating gasket 7 is for preventing the leakage of the nonaqueous electrolyte filled in the negative electrode can 3 and the positive electrode can 5.

As the non-aqueous electrolyte, a solution in which an electrolyte is dissolved in an aprotic non-aqueous solvent is used.

Examples of the non-aqueous solvent include propylene carbonate, ethylene carbonate, butylene carbonate, vinylene carbonate, γ-butyl lactone, sulfolane, 1,2-dimethoxyethane, 1,2-diethoxyethane, 2-methyltetrahydrofuran, -Methyl-1,3-dioxolane, methyl propionate, methyl butyrate, dimethyl carbonate, diethyl carbonate,
Dipropyl carbonate and the like can be used. In particular, from the viewpoint of voltage stability, propylene carbonate,
It is preferable to use cyclic carbonates such as ethylene carbonate, butylene carbonate, and vinylene carbonate, and chain carbonates such as dimethyl carbonate, diethyl carbonate, and dipropyl carbonate. Further, one kind of such a non-aqueous solvent may be used alone, or two or more kinds may be mixed and used.

As an electrolyte dissolved in a non-aqueous solvent,
Is, for example, LiPF₆, LiClO_Four, LiAsF₆,
LiBF_Four, LiCF_ThreeSO_Three, LiN (CF_ThreeSO_Two)_Twoetc
Can be used. These lithu
LiPF ₆, LiBF_FourUse
Is preferred.

Although the nonaqueous electrolyte battery 1 using a nonaqueous electrolyte has been described as an example of the nonaqueous electrolyte battery to which the present invention is applied, the present invention is not limited to this. The present invention is also applicable when a solid electrolyte is used as the non-aqueous electrolyte. Here, as the solid electrolyte, any of a solid polymer electrolyte such as an inorganic solid electrolyte and a gel electrolyte can be used as long as the material has lithium ion conductivity. Here, examples of the inorganic solid electrolyte include lithium nitride and lithium iodide. The polymer solid electrolyte is composed of an electrolyte salt and a polymer compound that dissolves the electrolyte salt, and the polymer compound includes poly (ethylene oxide), an ether polymer such as a crosslinked product thereof, and a poly (methacrylate) ester. -Based polymers, acrylate-based polymers and the like can be used alone, or copolymerized or mixed in the molecule. In this case, as the matrix of the gel electrolyte, for example, various polymer materials can be used as long as they absorb the non-aqueous electrolyte and gel. Examples of such a polymer material include poly (vinylidene fluoride) and poly (vinylidene fluoride).
Fluorine-based polymers such as CO-hexafluoropropylene), poly (ethylene oxide), ether-based polymers such as crosslinked products thereof, and poly (acrylonitrile) can be used. In particular, among these, it is preferable to use a fluoropolymer from the viewpoint of oxidation-reduction stability.

Non-aqueous electrolyte battery 1 constructed as described above
The manufacturing method of the will be described below.

First, a composite of LiFePO ₄ and a carbon material as a positive electrode active material, that is, a LiFePO ₄ carbon composite is synthesized according to the following production method.

In the present invention, this positive electrode active material is produced by passing through a coprecipitation step of forming a coprecipitate of a composite phosphorous oxide of lithium and iron and a firing step of firing the coprecipitate. .

In the co-precipitation step, a co-precipitate of a composite phosphate of lithium and iron is formed using an aqueous phosphoric acid solution containing a lithium salt and an iron salt.

First, a water-soluble organic reducing agent is mixed with an aqueous phosphoric acid solution containing a lithium salt and an iron salt to prepare a mixed aqueous solution. Here, the water-soluble organic reducing agent is mixed to reduce Fe ³⁺ ions generated by oxidizing Fe present in the phosphoric acid aqueous solution in a mixed aqueous solution of the phosphoric acid aqueous solution and the water-soluble organic reducing agent. Is what you do. As such a water-soluble organic reducing agent, a water-soluble organic compound having a reducing property such as ascorbic acid or a phenol derivative such as phenol or pyroganol can be used. And among them, ascorbic acid can be suitably used.

Next, acetone is added to the mixed aqueous solution by a predetermined amount, for example, about 0.5% by volume of the mixed aqueous solution. This is added to improve the hydrophilicity of acetylene black to be subsequently added.

Next, a predetermined amount of the carbon material is added to the mixed aqueous solution to which acetone is added, for example, about 10% by weight of the weight of the coprecipitate expected to be produced. Here, the carbon material is a raw material of the LiFePO ₄ carbon composite. Further, by adding the carbon material and firing the coprecipitate, the carbon material enters the coprecipitate to reduce the reaction area. LiFeP in the firing step
The growth of O ₄ particles can be suppressed, and a LiFePO ₄ carbon composite having a small particle size can be synthesized.
Thereby, the specific surface area per weight of the LiFePO ₄ carbon composite can be increased, so that a LiFePO ₄ carbon composite having excellent electron conductivity can be synthesized.

Next, an alkaline solution is mixed with the mixed aqueous solution to which the carbon material has been added. Here, the alkaline solution increases the hydrogen ion concentration (pH) of a mixture of a phosphoric acid aqueous solution containing a lithium salt and an iron salt and a water-soluble organic reducing agent, and forms a composite phosphorous oxide of lithium and iron. It mixes to form a coprecipitate. Such an alkaline solution is not particularly limited, and for example, potassium hydroxide, sodium hydroxide and the like can be suitably used.

By performing the above-described operations, a coprecipitate of a composite phosphorous oxide of lithium and iron can be generated. .

Next, the coprecipitate obtained in the coprecipitation step is filtered, washed with water, and dried to collect the coprecipitate.

Subsequently, in the firing step, the recovered coprecipitate is fired. By firing the coprecipitate, a reaction occurs in the coprecipitate to synthesize a LiFePO ₄ carbon composite.

Here, the firing temperature for firing the coprecipitate
Is preferably set to 350 ° C. to 900 ° C. Firing
By setting the temperature to 350 ° C to 900 ° C, LiFe
PO _FourSingle phase synthesis of carbon composites
You. If the firing temperature is lower than 350 ° C, chemical reaction and
Crystallization does not proceed sufficiently, and the raw material Li_ThreePO_FourSuch as
Pure phase exists and uniform LiFePO_FourGet carbon composite
It may not be possible. On the other hand, firing temperature exceeds 900 ° C
When crystallization proceeds excessively, LiFePO_FourCarbon composite
LiFePO_FourThe particles become larger and LiFeP
O_FourThe contact area between carbon and carbon material is reduced, and electron conductivity is reduced.
Therefore, a sufficient discharge capacity may not be obtained. Further
In consideration of battery performance, the firing temperature is 400 ° C.
More preferably, the temperature is set to 800 ° C. Firing temperature 400
Excellent battery characteristics when the temperature is between 800C and 800C
LiFePO_FourReliable single-phase synthesis of carbon composites
Becomes possible.

By the way, at the time of firing, the synthesized L
iFePO_FourFe in the carbon composite is in a divalent state.
For this reason, LiFePO_FourFe in the carbon composite is calcined
With the oxygen in the atmosphere, F
e³⁺Is quickly oxidized. Due to this, 3
Impurities such as trivalent Fe compounds are produced, and LiFePO _Four
Single-phase synthesis of the carbon composite is hindered.

[0052]

Embedded image

Therefore, the firing atmosphere is nitrogen or argon.
Etc. or a reducing gas such as hydrogen or carbon monoxide.
And the oxygen concentration in the firing atmosphere was adjusted to LiFe
PO _FourThe range where Fe in the carbon composite is not oxidized, that is,
More preferably, it is 1012 ppm (volume) or less.
Reduce the oxygen concentration in the firing atmosphere to less than 1012 ppm (by volume)
By preventing the oxidation of Fe, LiFeP
O_FourSingle phase synthesis of carbon composites can be reliably performed.
You.

The oxygen concentration in the firing atmosphere is 1012 ppm
If the volume is higher than (volume), the amount of oxygen in the firing atmosphere is too large, so that Fe in the LiFePO ₄ carbon composite becomes F
Since it is oxidized to e ³⁺ and an impurity is generated due to the oxidation, there is a possibility that the single-phase synthesis of the LiFePO ₄ carbon composite is hindered.

[0055] For removal of the sintered LiFePO ₄ carbon composite material is taken out temperature of the sintered LiFePO ₄ carbon composite material, that is, the temperature of the LiFePO ₄ carbon composite material when exposed to atmosphere, the LiFePO ₄ carbon composite material is The temperature is preferably 305 ° C. or lower. In addition, L after firing
More preferably, the temperature for taking out the iFePO ₄ carbon composite is 204 ° C. or lower. By setting the temperature at which the LiFePO ₄ carbon composite is taken out to 305 ° C. or lower, it is possible to prevent the Fe in the fired LiFePO ₄ carbon composite from being oxidized by oxygen in the atmosphere and generating impurities.

[0056] When taken out in an insufficiently cooled state of the LiFePO ₄ carbon composite material after sintering, LiFePO ₄ Fe of carbon composite material is oxidized by oxygen in the atmosphere, there is a fear that impurities are generated. However, if the LiFePO ₄ carbon composite is cooled to a temperature that is too low, there is a possibility that the working efficiency will be reduced.

Accordingly, by setting the temperature at which the calcined LiFePO ₄ carbon composite is taken out to 305 ° C. or lower, Fe in the calcined LiFePO ₄ carbon composite is oxidized by atmospheric oxygen to generate impurities. LiFePO 4 having favorable characteristics as battery characteristics, while maintaining the work efficiency.
_{A four-} carbon composite can be efficiently synthesized.

The LiFePO ₄ carbon composite after firing is cooled in a firing furnace. The cooling method at this time may be natural cooling or forced cooling. However, in consideration of shortening the cooling time, that is, considering the working efficiency, it is preferable to perform forced cooling. Then, in the case of forced cooling, the inside of the firing furnace has the above-described oxygen concentration, that is, 1%.
What is necessary is just to supply a mixed gas of oxygen and an inert gas or only an inert gas into the firing furnace so as to be 012 ppm (volume) or less.

Since the above-described method for producing a positive electrode active material is not a synthesis method based on a solid phase reaction, a step of pulverizing and mixing the raw material powder for synthesis of the positive electrode active material is not required. That is, an apparatus for pulverizing and mixing the synthetic raw material powder of the positive electrode active material, for example, an apparatus such as a ball mill, is not required, so that cost increase due to the introduction of equipment does not occur.

In addition, since there is no problem such as complication of the production process of the positive electrode active material and reduction in productivity due to this step, the positive electrode active material can be easily produced.

Further, in the case of the synthesis method by the solid phase reaction, since a rare and expensive material is used as a raw material for synthesizing the positive electrode active material, the raw material cost is increased. On the other hand,
In the case of the above-described method for producing a positive electrode active material, a general material is used as a raw material for synthesizing the positive electrode active material, so that the raw material cost can be kept low. Therefore, according to the above-described method for producing a positive electrode active material, it is possible to surely synthesize a single-phase LiFePO ₄ carbon composite by an inexpensive and simple method.

The LiFePO ₄ obtained as described above
Non-aqueous electrolyte battery 1 using carbon composite as positive electrode active material 1
Is manufactured, for example, as follows.

For the negative electrode 2, first, a negative electrode mixture is prepared by dispersing a negative electrode active material and a binder in a solvent. Next, the obtained negative electrode mixture is uniformly applied on the current collector,
The negative electrode 2 is produced by drying to form a negative electrode active material layer. Known binders can be used as the binder of the negative electrode mixture, and known additives and the like can be added to the negative electrode mixture. Further, metallic lithium serving as a negative electrode active material can be used as the negative electrode 2 as it is.

As the positive electrode 4, first, a LiFePO ₄ carbon composite serving as a positive electrode active material and a binder are mixed to prepare a positive electrode mixture, and the mixture is dispersed in a solvent to form a slurry.

Next, the positive electrode 4 is produced by uniformly applying the obtained slurry-like positive electrode mixture on a current collector and drying to form a positive electrode active material layer. As the binder of the positive electrode mixture, a known binder can be used, and a known additive or the like can be added to the positive electrode mixture.

The non-aqueous electrolyte is prepared by dissolving an electrolyte salt in a non-aqueous solvent.

Then, the negative electrode 2 is accommodated in the negative electrode can 3, the positive electrode 4 is accommodated in the positive electrode can 5, and a separator 6 made of a porous polypropylene film or the like is disposed between the negative electrode 2 and the positive electrode 4. The coin-type nonaqueous electrolyte battery 1 is completed by injecting the nonaqueous electrolyte into the negative electrode can 3 and the positive electrode can 5 and caulking and fixing the negative electrode can 3 and the positive electrode can 5 via the insulating gasket 7. I do.

In the method for manufacturing a non-aqueous electrolyte secondary battery as described above, a co-precipitate of a composite phosphorous oxide of lithium and iron is produced when the positive electrode active material is produced, and the co-precipitate is fired. Since the synthesis by the solid phase reaction is not performed, the step of pulverizing and mixing the raw material powder for the synthesis of the positive electrode active material is unnecessary. That is, an apparatus for pulverizing and mixing the synthetic raw material powder of the positive electrode active material, for example, an apparatus such as a ball mill is not required, so that there is no increase in cost due to the introduction of equipment.

Further, pulverization of the raw material powder for the synthesis of the positive electrode active material,
Since there is no mixing step, it is possible to easily produce the positive electrode active material without problems such as complication of the production process of the positive electrode active material and a decrease in productivity caused by this step, so that A non-aqueous electrolyte secondary battery can be manufactured.

In the case of synthesizing a positive electrode active material by a solid-phase reaction, since a rare and expensive material is used as a raw material for synthesizing the positive electrode active material, the raw material cost is increased. On the other hand, in the method for manufacturing a nonaqueous electrolyte secondary battery, since a general material is used as a raw material for synthesizing the positive electrode active material, the raw material cost can be reduced.

[0071] In the above, the description has been given of the case using the LiFePO ₄ carbon composite material as the cathode active material, as the cathode active material is not limited to this, for example, carbon on the surface of the LiFePO ₄ particles LiFePO ₄ to which no material is attached may be used.

Here, LiFePO ₄ can be manufactured in the same manner as the above-described method for manufacturing a LiFePO ₄ carbon composite except that acetone is not added and a carbon material is not added. And LiFe in this case
Since the method for producing PO ₄ is not a synthesis method by a solid-phase reaction,
The step of pulverizing and mixing the raw material powder of the positive electrode active material is not required. That is, since a device for pulverizing and mixing the raw material powder of the positive electrode active material, for example, a device such as a ball mill, is not required, problems such as an increase in cost due to the introduction of equipment and a decrease in productivity due to this process occur. Absent. In addition, in the case of a synthesis method by a solid-phase reaction, since a rare and expensive material is used as a raw material for synthesizing a positive electrode active material,
Raw material costs increase. On the other hand, in the case of the above-described method for producing a positive electrode active material, a general material is used as a raw material for synthesizing the positive electrode active material to be used, so that the raw material cost can be reduced. Therefore, according to this method for producing a positive electrode active material, it is possible to surely synthesize LiFePO ₄ in a single phase at low cost and with a simple method.

The shape of the nonaqueous electrolyte battery 1 according to the present embodiment as described above is not particularly limited, such as a cylindrical type, a square type, a coin type, and a button type.
In addition, various sizes such as a thin type and a large size can be used.

[0074]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on specific experimental results. Here, in order to examine the effects of the present invention, LiFePO ₄ and LiFePO ₄ carbon composite were synthesized as a positive electrode active material, and a non-aqueous electrolyte battery was fabricated using these.
Its properties were evaluated.

Example 1 LiFePO ₄ was synthesized as a cathode active material by applying the method for producing a cathode active material according to the present invention. The method for producing this positive electrode active material is described below.

First, lithium hydroxide monohydrate and iron sulfate heptahydrate were added to a diluted phosphoric acid aqueous solution having a concentration of 10% by volume so that the molar ratio of Li: Fe became 1: 1. , And dissolved to prepare a mixed solution.

Next, ascorbic acid, which is a typical water-soluble organic reducing agent, is added to the mixture at 1% by weight of the mixture.

Next, an aqueous solution of sodium hydroxide having a concentration of 1 mol / l was added dropwise to the mixed solution to which ascorbic acid was added, thereby forming a precipitate (coprecipitate). Then, the precipitate was collected by filtration, washed with water and dried.

The collected precipitate was subjected to elemental analysis using inductively coupled high frequency plasma spectroscopy.
i, Fe, and P were confirmed to be contained, and
The molar ratio of these components is Li: Fe: P = 1: 1: 1.
Was confirmed.

Thereafter, the collected precipitate was placed in a ceramic crucible and calcined at a temperature of 350 ° C. for 5 hours in an electric furnace in a nitrogen atmosphere to obtain LiFePO ₄ .

Next, the LiFePO 4 obtained above is obtained.
_{Using 4} as a positive electrode active material, a non-aqueous electrolyte battery was fabricated.

First, as the positive electrode active material, the L obtained above was used.
After mixing 85 parts by weight of iFePO ₄ , 10 parts by weight of acetylene black as a conductive material, and 5 parts by weight of poly (vinylidene fluoride), which is a fluororesin powder, as a binder, the mixture was press-molded to have a diameter of 15.5 mm. And a pellet-shaped positive electrode having a thickness of 0.1 mm.

Next, a negative electrode was obtained by punching the lithium metal foil into substantially the same shape as the positive electrode.

Next, LiPF ₆ was added to a mixed solvent of propylene carbonate and dimethyl carbonate in equal volumes.
A non-aqueous electrolyte was prepared by dissolving at a concentration of mol / l.

The positive electrode obtained as described above was accommodated in a positive electrode can, the negative electrode was accommodated in a negative electrode can, and a separator was arranged between the positive electrode and the negative electrode. A non-aqueous electrolyte solution was injected into the positive and negative electrode cans, and the positive and negative electrode cans were caulked and fixed, whereby a 2016 coin-type test cell having a diameter of 20.0 mm and a thickness of 1.6 mm was produced.

<Example 2> A coin-type test cell was produced in the same manner as in Example 1 except that the sintering temperature at the time of synthesizing the positive electrode active material was set at 400 ° C.

Example 3 A coin-type test cell was manufactured in the same manner as in Example 1, except that the firing temperature at the time of synthesizing the positive electrode active material was set at 500 ° C.

Example 4 A coin-type test cell was produced in the same manner as in Example 1 except that the firing temperature at the time of synthesizing the positive electrode active material was set at 600 ° C.

Example 5 A coin-type test cell was produced in the same manner as in Example 1, except that the firing temperature at the time of synthesizing the positive electrode active material was 700 ° C.

Example 6 A coin-type test cell was manufactured in the same manner as in Example 1, except that the firing temperature at the time of synthesizing the positive electrode active material was 750 ° C.

Comparative Example 1 A coin-type test cell was produced in the same manner as in Example 1 except that the firing temperature at the time of synthesizing the positive electrode active material was 300 ° C.

Comparative Example 2 A coin-type test cell was prepared in the same manner as in Example 1, except that the firing temperature at the time of synthesizing the positive electrode active material was 800 ° C.

X-ray diffraction measurements were performed on the positive electrode active materials synthesized in Examples 1 to 6 and Comparative Examples 1 and 2 as described above. Table 1 shows the results. In Table 1, JCPDS-No. A sample which conforms to the powder X-ray diffraction line described in No. 401499 and for which no other diffraction line is confirmed was marked as having been subjected to single-phase synthesis of LiFePO ₄ . Then, JCPDS-No. 4014
Those which do not conform to the powder X-ray diffraction line described in No. 99, or which are confirmed to have another diffraction line even if conforming to the above, are LiFePO4.
The symbol x indicates that the single-phase synthesis of No. ₄ was not performed.

[0094]

[Table 1]

As shown in Table 1, in Examples 1 to 6 where the sintering temperature was 350 ° C. or higher and Comparative Example 2, the JCPDS
-No. LiFeP conforms to the powder X-ray diffraction line described in No. 401499, and no other diffraction lines have been confirmed.
It can be seen that a single-phase synthesis of O ₄ was performed.

Comparative Example 1 in which the firing temperature was 300 ° C.
In, such as _{Li 3 PO 4, JCPDS-No} . 40149
Since diffraction lines other than the powder X-ray diffraction line described in No. 9 were confirmed, it can be seen that single-phase synthesis of LiFePO ₄ was not performed. This is because the firing temperature is low and LiFePO
_This is probably because the synthesis reaction of No. ₄ did not proceed and impurities remained in the fired body.

[0097] From the above facts, in the synthesis of the above LiFePO _4, it can be said that the firing temperature can be reliably performed by the single-phase synthesis of the LiFePO ₄ by a 350 ° C. or higher.

The coin-type test cells manufactured in Examples 1 to 6 and Comparative Examples 1 and 2 were subjected to a charge / discharge test as described below to evaluate the initial discharge capacity density.

<Charge / Discharge Test> Each test cell was charged with a constant current, and when the battery voltage reached 4.2 V, the voltage was switched from the constant current charge to the constant voltage charge, and the voltage was changed to 4.2 V.
The battery was charged while keeping And the current is 0.01m
The charging was terminated when the charge / discharge rate reached A / cm ² or less. Thereafter, discharging was performed, and the discharging was terminated when the battery voltage dropped to 2.0 V. The charging and discharging were performed at room temperature (25 ° C.), and the current density at this time was 0.1 mA /
cm ² . The results are shown in Table 1 together.
The battery evaluation in Table 1 indicates that the initial discharge capacity density was 14%.
A mark of 0 mAh / g or more is marked as "O" as a practical recommended level, and the initial discharge capacity density is 110 mAh / g or more and 140 mA or more.
Those with a h / g of less than 110 mAh / g were marked as unusable when the initial discharge capacity density was less than 110 mAh / g.

As can be seen from Table 1, in Examples 1 to 6 in which the sintering temperature at the time of synthesizing LiFePO ₄ was 350 ° C. to 750 ° C., the initial discharge capacity density showed a good value in all cases. .

On the other hand, in Comparative Example 1 in which the firing temperature at the time of synthesizing LiFePO ₄ was 300 ° C., the initial discharge capacity density was as low as 98 mAh / g. It is considered that this is because the synthesis temperature of LiFEPO ₄ did not progress because the firing temperature was too low, LiFePO _{4 as the} positive electrode active material was not synthesized in a single phase, and the amount of the positive electrode active material contributing to the battery reaction was small.

Also, in Comparative Example 2 in which the sintering temperature for synthesizing LiFePO ₄ was 800 ° C., the initial discharge capacity density was as low as 86 mAh / g. This is because the firing temperature is too high, the particle growth of LiFePO ₄ particles during firing becomes remarkable, LiFePO ₄ having a huge particle size is synthesized, and the contact area with the conductive material is reduced, so that the electron conductivity is reduced. It is considered that the polarization at the closed circuit of the battery was increased, and as a result, the capacity was reduced.

From the above, it can be said that the firing temperature for synthesizing LiFePO ₄ is preferably 350 ° C. to 750 ° C. However, from the viewpoint of battery characteristics, the initial discharge capacity density of the positive electrode active material is preferably 140 mAh / g or more. Therefore, the firing temperature when synthesizing LiFePO ₄ should be 400 ° C. to 700 ° C. Is more preferable.

Next, a polymer battery was manufactured and its characteristics were evaluated.

<Example 7> First, a gel electrolyte was prepared as follows. First, polyvinylidene fluoride in which hexafluoropropylene was copolymerized at a ratio of 6.9% by weight, a non-aqueous electrolyte, and dimethyl carbonate were mixed, stirred, and dissolved to prepare a sol electrolyte solution. Next, vinylene carbonate (VC) was added to the sol electrolyte solution at a ratio of 0.5% by weight to obtain a gel electrolyte solution. In addition, ethylene carbonate (EC) and propylene carbonate (P
C) and L at a ratio of 6: 4 by volume.
The iPF ₆ was used after dissolved in a proportion of 0.85 mol / kg.

Next, a positive electrode was prepared as described below. First, 85% of the LiFePO ₄ prepared in Example 4 was used.
After mixing 10 parts by weight of graphite as a conductive agent and 5 parts by weight of poly (vinylidene fluoride) which is a fluororesin powder as a binder, a positive electrode mixture was prepared, and then N-methylpyrrolidone was added. A slurry was prepared. Next, this slurry was applied to an aluminum foil having a thickness of 20 μm, heated and dried, and then subjected to a pressing step to produce a positive electrode coated foil. Next, a gel electrolyte solution was applied to one side of the positive electrode coating foil, dried, and the solvent was removed. Then, a 15 mm diameter circle was punched out according to the cell diameter to obtain a positive electrode.

Next, a negative electrode was manufactured as described below. First, a slurry was prepared by mixing 10% by weight of a fluororesin powder as a binder with graphite powder and adding N-methylpyrrolidone. Next, this slurry was applied to a copper foil, heated and dried, and then subjected to a pressing step to punch out a 16.5 mm diameter circle in accordance with the size of the cell to obtain a negative electrode.

The positive electrode obtained as described above was accommodated in a positive electrode can, the negative electrode was accommodated in a negative electrode can, and a separator was disposed between the positive electrode and the negative electrode. Then, by caulking and fixing the positive electrode can and the negative electrode can, the diameter is 20 mm and the thickness is 1.6 mm.
No. 2016 coin-type lithium polymer battery was produced.

<Example 8> A coin-type lithium polymer battery was manufactured in the same manner as in Example 7, except that the LiFePO ₄ manufactured in Example 5 was used when manufacturing the positive electrode.

The coin-type lithium polymer batteries of Examples 7 and 8 manufactured as described above were subjected to a charge / discharge cycle characteristic test as follows, and the initial discharge capacity density and the discharge capacity maintenance after 30 cycles were performed. The rate was determined.

<Charge / Discharge Cycle Characteristics Test> The charge / discharge cycle characteristics were evaluated based on the capacity retention ratio after repeated charge / discharge.

A constant current charge was performed on the coin-type lithium polymer battery, and when the battery voltage became 4.2 V,
Switching from constant-current charging to constant-voltage charging, and changing the voltage to 4.2
The battery was charged while being kept at V. And the current is 0.01
The charging was terminated when the current became mA / cm ² or less. Thereafter, discharging was performed, and the discharging was terminated when the battery voltage dropped to 2.0 V.

The above process is defined as one cycle, and
After 0 cycles, the discharge capacities at the first cycle and the 30th cycle were determined. Then, the discharge capacity at the 30th cycle (C1) with respect to the discharge capacity at the first cycle (C1)
The ratio (2) ((C2 / C1) × 100) was determined as the discharge capacity retention ratio. At the time of charging and discharging, the room temperature (2
5 ° C.), and the current density at this time is 0.1 mA / cm
^{And 2} . Table 2 shows the results.

[0114]

[Table 2]

As can be seen from Table 2, the initial discharge capacity density,
The capacity retention rate after 30 cycles shows a good value. From this, the positive electrode active material manufactured by the manufacturing method according to the present invention obtains good battery characteristics even when a polymer battery is configured using a gel electrolyte instead of a nonaqueous electrolyte as a nonaqueous electrolyte. You can say that

Example 9 A LiFePO ₄ carbon composite was synthesized as a positive electrode active material by applying the method for producing a positive electrode active material according to the present invention. The method for producing this positive electrode active material is described below.

First, lithium hydroxide monohydrate and iron sulfate heptahydrate were added to a diluted phosphoric acid aqueous solution having a concentration of 10% by volume so that the molar ratio of Li: Fe became 1: 1. And dissolved to prepare a mixed solution.

Next, ascorbic acid, which is a typical water-soluble organic reducing agent, was added to the mixture at 1% by weight of the mixture.

Next, 0.5% by volume of acetone of the mixed solution to which ascorbic acid was added was added, and acetylene black powder was added by 10% by weight of the weight of the precipitate (coprecipitate) estimated from the calculation. Was added.

Next, a concentration of 1 mol / l was added to this mixed solution.
Is added dropwise,
A precipitate (coprecipitate) was formed. Then, the precipitate was collected by filtration, washed with water and dried.

The collected precipitate was subjected to elemental analysis using inductively coupled high-frequency plasma spectroscopy.
i, Fe, and P were confirmed to be contained, and
The molar ratio of these components is Li: Fe: P = 1: 1: 1.
Was confirmed.

Thereafter, the collected precipitate was placed in a ceramic crucible and fired in an electric furnace in a nitrogen atmosphere at a temperature of 350 ° C. for 5 hours to obtain a LiFePO ₄ carbon composite.

Next, the LiFePO 4 obtained above is obtained.
_A non-aqueous electrolyte battery was fabricated using the _four- carbon composite as a positive electrode active material.

First, as the positive electrode active material, L obtained above was used.
After mixing 85 parts by weight of the iFePO ₄ carbon composite, 10 parts by weight of acetylene black as a conductive material, and 5 parts by weight of a poly (vinylidene fluoride) which is a fluororesin powder as a binder, the mixture was pressure-molded to obtain a diameter. 15.
A pellet-shaped positive electrode having a thickness of 5 mm and a thickness of 0.1 mm was obtained.

Next, a negative electrode was obtained by punching the lithium metal foil into substantially the same shape as the positive electrode.

Next, LiPF ₆ was added to a mixed solvent of propylene carbonate and dimethyl carbonate in equal volumes.
A non-aqueous electrolyte was prepared by dissolving at a concentration of mol / l.

The positive electrode obtained as described above was accommodated in a positive electrode can, the negative electrode was accommodated in a negative electrode can, and a separator was disposed between the positive electrode and the negative electrode. A non-aqueous electrolyte solution was injected into the positive and negative electrode cans, and the positive and negative electrode cans were caulked and fixed, whereby a 2016 coin-type test cell having a diameter of 20.0 mm and a thickness of 1.6 mm was produced.

Example 10 A coin-type test cell was manufactured in the same manner as in Example 9, except that the firing temperature at the time of synthesizing the positive electrode active material was 400 ° C.

<Example 11> A coin-type test cell was produced in the same manner as in Example 9 except that the sintering temperature at the time of synthesizing the positive electrode active material was set at 500 ° C.

Example 12 A coin-type test cell was produced in the same manner as in Example 9, except that the firing temperature at the time of synthesizing the positive electrode active material was set at 600 ° C.

Example 13 A coin-type test cell was produced in the same manner as in Example 9, except that the firing temperature at the time of synthesizing the positive electrode active material was 700 ° C.

Example 14 A coin-type test cell was produced in the same manner as in Example 9 except that the sintering temperature at the time of synthesizing the positive electrode active material was 800 ° C.

Example 15 A coin-type test cell was manufactured in the same manner as in Example 9, except that the firing temperature at the time of synthesizing the positive electrode active material was 900 ° C.

Comparative Example 3 A coin-type test cell was produced in the same manner as in Example 9, except that the firing temperature at the time of synthesizing the positive electrode active material was 300 ° C.

Comparative Example 4 A coin-type test cell was produced in the same manner as in Example 9 except that the sintering temperature at the time of synthesizing the positive electrode active material was 1000 ° C.

The positive electrode active materials synthesized in Examples 9 to 15 and Comparative Examples 3 and 4 were subjected to X-ray diffraction measurement. Table 3 shows the results. Table 3
In JCPDS-No. Compatible with the powder X-ray diffraction lines described in 401,499, and single-phase synthesis of what other diffraction line is not observed LiFePO ₄ carbon composite material describing the ○ as having been performed. And JCPDS-N
o. Those which are not compatible with the powder X-ray diffraction line described in No. 401499, or whose other diffraction lines have been confirmed even if matched,
The symbol x indicates that the single-phase synthesis of the LiFePO ₄ carbon composite was not performed.

[0137]

[Table 3]

As shown in Table 3, in Examples 9 to 15 and Comparative Example 4 in which the firing temperature was 350 ° C. or higher, JCPDS
-No. LiFeP conforms to the powder X-ray diffraction line described in No. 401499, and no other diffraction lines have been confirmed.
It can be seen that a single-phase synthesis of the O ₄ carbon composite was performed.

Comparative Example 3 in which the firing temperature was 300 ° C.
In, such as _{Li 3 PO 4, JCPDS-No} . 40149
Since diffraction lines other than the powder X-ray diffraction line described in No. 9 were confirmed, it can be seen that the single-phase synthesis of the LiFePO ₄ carbon composite was not performed. This is because the firing temperature is low,
This is probably because the synthesis reaction of the iFePO ₄ carbon composite did not proceed and impurities remained in the fired body.

[0140] From the above facts, when synthesizing the LiFePO ₄ carbon composite material described above, it can be said that the firing temperature can be reliably performed by the single-phase synthesis of the LiFePO ₄ carbon composite material by a 350 ° C. or higher.

Examples 9 to 15 and Comparative Example 3
And about the coin-type test cell produced in Comparative Example 4,
A charge / discharge test was performed in the same manner as above to evaluate the initial discharge capacity density. The results are shown together with the results in Table 3. The battery evaluation in Table 3 indicates that the initial discharge capacity density was 14%.
A mark of 0 mAh / g or more is marked as "O" as a practical recommended level, and the initial discharge capacity density is 110 mAh / g or more and 140 mA or more.
Those with a h / g of less than 110 mAh / g were marked as unusable when the initial discharge capacity density was less than 110 mAh / g.

As can be seen from Table 3, in Examples 9 to 15 in which the firing temperature at the time of synthesizing the LiFePO ₄ carbon composite was 350 ° C. to 900 ° C., the initial discharge capacity density was a good value in all cases. showed that.

On the other hand, in Comparative Example 3, in which the firing temperature at the time of synthesizing the LiFePO ₄ carbon composite was 300 ° C., the initial discharge capacity density was as low as 103 mAh / g. This is considered to be because the amount of the positive electrode active material contributing to the battery reaction is small because the LiFePO ₄ carbon composite as the positive electrode active material has not been synthesized in a single phase.

In Comparative Example 4 in which the sintering temperature for synthesizing the LiFePO ₄ carbon composite was 1000 ° C., the initial discharge capacity density was as low as 74 mAh / g. This is because the firing temperature is too high, and the LiFePO ₄
The particle growth of the particles becomes remarkable, and Li having a huge particle size
This is considered to be because the FePO ₄ carbon composite was synthesized and the contact area with the conductive material was reduced, so that the polarization at the time of the closed circuit of the battery was increased due to the decrease in the electronic conductivity, and as a result, the capacity was reduced.

From the above, it can be said that the sintering temperature when synthesizing the LiFePO ₄ carbon composite is preferably 350 ° C. to 900 ° C. However, from the viewpoint of battery characteristics, the initial discharge capacity density of the positive electrode active material is 140 mAh /
g or more, so that LiFeP
The firing temperature for synthesizing the O ₄ carbon composite is 400 ° C.
It can be said that 800 ° C. is more preferable.

Next, a polymer battery was fabricated and its characteristics were evaluated.

Example 16 First, a gel electrolyte was prepared as described below. First, polyvinylidene fluoride in which hexafluoropropylene was copolymerized at a ratio of 6.9% by weight, a non-aqueous electrolyte, and dimethyl carbonate were mixed, stirred, and dissolved to prepare a sol electrolyte solution. Next, vinylene carbonate (VC) was added to the sol electrolyte solution at a ratio of 0.5% by weight to obtain a gel electrolyte solution. In addition, ethylene carbonate (EC) and propylene carbonate (P
C) and L at a ratio of 6: 4 by volume.
The iPF ₆ was used after dissolved in a proportion of 0.85 mol / kg.

Next, a positive electrode was prepared as follows. First, 85 parts by weight of the LiFePO ₄ carbon composite prepared in Example 12 and 10 parts of graphite as a conductive agent were used.
A positive electrode mixture was prepared by mixing 5 parts by weight of poly (vinylidene fluoride), which is a fluororesin powder, as a binder, and then a slurry was prepared by adding N-methylpyrrolidone. Next, this slurry was applied to a thickness of 2
After coating and heating and drying on an aluminum foil of 0 μm, a positive electrode coated foil was produced through a pressing step. Next, after applying a gel electrolyte solution to one side of the positive electrode coating foil, drying and removing the solvent, the sheet was punched into a circle having a diameter of 15 mm according to the diameter of the cell,
A positive electrode was used.

Next, a negative electrode was manufactured as follows. First, a slurry was prepared by mixing 10% by weight of a fluororesin powder as a binder with graphite powder and adding N-methylpyrrolidone. Next, this slurry was applied to a copper foil, heated and dried, and then subjected to a pressing step to punch out a 16.5 mm diameter circle in accordance with the size of the cell to obtain a negative electrode.

The positive electrode obtained as described above was accommodated in a positive electrode can, the negative electrode was accommodated in a negative electrode can, and a separator was disposed between the positive electrode and the negative electrode. Then, by caulking and fixing the positive electrode can and the negative electrode can, the diameter is 20 mm and the thickness is 1.6 mm.
No. 2016 coin-type lithium polymer battery was produced.

Example 17 A coin-type lithium polymer battery was produced in the same manner as in Example 16, except that the LiFePO ₄ carbon composite produced in Example 13 was used when producing the positive electrode.

With respect to the coin-type lithium polymer batteries of Examples 16 and 17 manufactured as described above,
A charge / discharge cycle characteristic test was performed in the same manner as described above, and the initial discharge capacity density and the discharge capacity retention rate after 30 cycles were obtained. Table 4 shows the results.

[0153]

[Table 4]

As can be seen from Table 4, the initial discharge capacity density,
The capacity retention rate after 30 cycles shows a good value. From this, the positive electrode active material manufactured by the manufacturing method according to the present invention obtains good battery characteristics even when a polymer battery is configured using a gel electrolyte instead of a nonaqueous electrolyte as a nonaqueous electrolyte. You can say that

[0155]

The method for producing a positive electrode active material according to the present invention comprises:
A mixed aqueous solution is prepared by mixing a water-soluble organic reducing agent with a phosphoric acid aqueous solution containing a lithium salt and an iron salt, and an alkaline solution is mixed with the mixed aqueous solution to co-precipitate a composite phosphorous oxide of lithium and iron. It has a co-precipitation step for producing a body and a firing step for firing the co-precipitate.

Since the above-described method for producing a positive electrode active material is not a synthesis method based on a solid-phase reaction, the step of pulverizing and mixing the raw material powder for the synthesis of the positive electrode active material is not required, so that the cost increase due to the introduction of equipment is increased. In addition, it is possible to easily produce a positive electrode active material.

Further, since a general material is used as a raw material for synthesizing the positive electrode active material, the raw material cost can be kept low.

Therefore, according to the present invention, it is possible to provide a method for manufacturing a positive electrode active material which is inexpensive and easy to manufacture.

The method for manufacturing a nonaqueous electrolyte secondary battery according to the present invention is a method for manufacturing a nonaqueous electrolyte secondary battery including a positive electrode having a positive electrode active material, a negative electrode having a negative electrode active material, and a nonaqueous electrolyte. Then, a water-soluble organic reducing agent is mixed with a phosphoric acid aqueous solution containing a lithium salt and an iron salt, and an alkali solution is further mixed to form a coprecipitate of a composite phosphorous oxide of lithium and iron. The positive electrode active material is produced through a step and a firing step of firing the coprecipitate.

In the method for manufacturing a non-aqueous electrolyte secondary battery as described above, the cathode active material is produced not by a solid phase reaction but by a synthesis method using co-precipitation, so that the raw material of the cathode active material is synthesized. Since the step of pulverizing and mixing the powder is not required, there is no increase in cost due to the introduction of equipment, and the nonaqueous electrolyte secondary battery can be easily manufactured.

Further, since a general material is used as a raw material for synthesizing the positive electrode active material, the raw material cost can be kept low.

Therefore, according to the present invention, it is possible to provide a method for manufacturing a non-aqueous electrolyte secondary battery which is inexpensive and easy to manufacture.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a configuration example of a nonaqueous electrolyte secondary battery to which the present invention is applied.

[Description of Signs] 1 Non-aqueous electrolyte battery, 2 negative electrode, 3 negative electrode can, 4 positive electrode, 5 positive electrode can, 6 separator, 7 insulating gasket

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H029 AJ14 AK03 AL02 AL06 AL12 AL16 AM02 AM03 AM04 AM05 AM07 CJ02 CJ08 DJ09 HJ14 5H050 AA19 BA16 BA17 CA07 CB02 CB07 CB12 CB20 DA02 GA02 GA10 HA14

Claims (12)

[Claims] An aqueous phosphoric acid solution containing a lithium salt and an iron salt is mixed with a water-soluble organic reducing agent to prepare a mixed aqueous solution, and an alkaline solution is mixed with the mixed aqueous solution to form a complex phosphorous mixture of lithium and iron. A method for producing a positive electrode active material, comprising: a coprecipitation step of generating a coprecipitate of an oxide; and a firing step of firing the coprecipitate. 2. Between the co-precipitation step and the firing step,
The method for producing a positive electrode active material according to claim 1, further comprising a drying step of drying the coprecipitate. 3. The firing temperature in the firing step is 35.
The method for producing a positive electrode active material according to claim 1, wherein the temperature is 0C to 750C. 4. In the co-precipitation step, a water-soluble organic reducing agent is mixed with a phosphoric acid aqueous solution containing a lithium salt and an iron salt, a carbon material is added, and an alkali solution is mixed to form lithium and iron. The method for producing a positive electrode active material according to claim 1, wherein a coprecipitate of a composite phosphorous oxide is produced. 5. The firing temperature in the firing step is 35.
The method for producing a positive electrode active material according to claim 4, wherein the temperature is 0C to 900C. 6. A method for producing a non-aqueous electrolyte secondary battery comprising a positive electrode having a positive electrode active material, a negative electrode having a negative electrode active material, and a non-aqueous electrolyte, comprising: a phosphorus containing a lithium salt and an iron salt. A coprecipitation step of mixing a water-soluble organic reducing agent with an acid aqueous solution, further mixing an alkaline solution to form a coprecipitate of a composite phosphorous oxide of lithium and iron, and a firing step of firing the coprecipitate; A method for producing a non-aqueous electrolyte secondary battery, comprising producing the above-mentioned positive electrode active material through the following. 7. The method for producing a nonaqueous electrolyte secondary battery according to claim 6, further comprising a drying step of drying the coprecipitate after the coprecipitation step. 8. The firing temperature in the firing step is 35.
The method for producing a non-aqueous electrolyte secondary battery according to claim 6, wherein the temperature is 0C to 750C. 9. In the coprecipitation step, a water-soluble organic reducing agent is mixed with a phosphoric acid aqueous solution containing a lithium salt and an iron salt, a carbon material is further added, and an alkali solution is mixed to form lithium and iron. 7. The method for producing a non-aqueous electrolyte secondary battery according to claim 6, wherein a coprecipitate of a composite phosphorous oxide is formed. 10. The firing temperature in the firing step is 3
The method for producing a non-aqueous electrolyte secondary battery according to claim 9, wherein the temperature is 50C to 900C. 11. The method for producing a non-aqueous electrolyte secondary battery according to claim 6, wherein the non-aqueous electrolyte is a liquid electrolyte. 12. The method for producing a non-aqueous electrolyte secondary battery according to claim 6, wherein the non-aqueous electrolyte is a polymer electrolyte.