JP2006261060A - Manufacturing method of electrode material, electrode material, electrode and lithium battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of an electrode material in which a high discharge capacity, a stable charge and discharge cycle performance, a high filling property, and a high output can be realized by using elements of low cost and abundant in resource-wise, also to provide an electrode material, an electrode, and a lithium battery. <P>SOLUTION: This is a manufacturing method of an electrode material having a compound composed of Li<SB>x</SB>Al<SB>y</SB>A<SB>z</SB>PO<SB>4</SB>(where, A is one kind or two kinds or more selected from a group of Co, Mn, Ni, Fe, Cu, Cr, x+3y+z=3, x, y, z are positive numbers), asa main component. Li source, A source (where, A is one kind or two kinds or more selected from a group of Co, Mn, Ni, Fe, Cu, Cr), Al source, PO<SB>4</SB>source, and an organic acid are added to a solvent having water as a main component, and are made a solution, and then, this solution is made to react at high temperatures and high pressure. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention relates to a method for producing an electrode material, an electrode material and an electrode, and a lithium battery, and in particular, a method for producing an electrode material suitable for use in a positive electrode material for a battery, particularly a positive electrode material for a lithium battery, and an electrode material and electrode. The present invention relates to a lithium battery.

In recent years, lithium batteries, for example, non-aqueous electrolyte secondary batteries such as lithium ion batteries have been proposed and put into practical use as batteries expected to be reduced in size, weight, and capacity.
As a positive electrode material for this lithium battery, lithium (Li) compounds such as lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), and lithium manganate (LiMnO ₂ ) have been proposed, and some of them have already been put into practical use. ing.

On the other hand, iron (Fe) is a promising element to be used for a positive electrode material for a lithium battery because it is abundant and inexpensive in terms of resources and has no problems such as toxicity to the human body or the environment.
For example, an Fe-containing phosphoric acid compound represented by LiFePO ₄ has a potential of about 3.3 V with respect to metal Li, and thus can be used as a chargeable / dischargeable positive electrode material (for example, non-patent literature). 1).
A. K. Paddy et al., J. Electrochem. Soc. Vol. 144, p. 1609 (1997)

However, in the above-described LiCoO ₂ , since the amount of Co reserve is small, the price is easily affected by market conditions, and therefore, the problem that the positive electrode material becomes expensive and the Co itself is toxic, etc. There was a point.
Moreover, although LiNiO ₂ shows excellent charge / discharge characteristics, there is a problem that the cathode material becomes expensive because Ni itself is not cheap. In addition, there is a problem that stability at high temperature is not sufficient, and there is a possibility that sudden characteristic deterioration may occur when a composition deviation from a constant ratio occurs.

In addition, LiMnO ₂ has a problem that Mn is eluted at a high temperature and a cycle deterioration due to a Mn ³⁺ yarn-teller strain.
Moreover, when the Fe-containing phosphoric acid compound represented by LiFePO ₄ is used as a positive electrode material for a lithium battery, there is a problem that the current density at the time of charging and discharging is low, and therefore, it is difficult to increase the output, and practical use It is one of the factors that are preventing it.

  The present invention has been made in order to solve the above-described problems, and uses an inexpensive and resource-rich element to realize high discharge capacity, stable charge / discharge cycle performance, high fillability, and high output. It is an object of the present invention to provide an electrode material manufacturing method, an electrode material, an electrode, and a lithium battery.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that fine particles of the positive electrode material are effective for increasing the output of the lithium battery, and by hydrothermal synthesis. In order to complete the present invention, it is found that if Al is added when a material represented by LiFePO ₄ is added, the material represented by LiFePO ₄ is finely divided, and further, rate characteristics and low-temperature characteristics are improved. It came.

Further, a solvent containing water as a main component includes Li source, A source (where A is one or more selected from the group of Co, Mn, Ni, Fe, Cu, Cr), Al source, PO ₄ source and adding an organic acid to form a solution, by reacting the solution at a high temperature under high _{pressure, Li x Al y a z PO} 4 ( where, a is Co, Mn, Ni, Fe, Cu, the group of Cr It was also found that an electrode material containing as a main component a compound consisting of one or more selected from the group consisting of x + 3y + 2z = 3, x, y, and z being positive numbers) was easily obtained.

Here, the background to which the present inventors have completed the present invention will be described in detail.
The present inventors have found that a phosphate-based material such as LiFePO ₄ has a lower electronic conductivity than a conventionally used electrode material such as LiCoO _2, which increases the current density that can flow during charging and discharging. I thought it was one of the reasons why I couldn't do it, that is, I couldn't increase the output.
Therefore, in order to flow more current, it is considered effective to increase the specific surface area of the material, that is, to make fine particles, and it is also effective to improve the electron conductivity of the material itself. Thought. Moreover, if the particle size of the material is reduced, the difference between the reaction area on the particle surface and the reaction area inside the particle after the reaction has progressed will not enable charging / discharging to a state closer to the theoretical capacity. I thought.
Further, it was considered that when the surface area of the particles is increased, the current density flowing through the reaction interface can be lowered, and charging / discharging with a larger current becomes possible.
Furthermore, if the electron conductivity of the material itself is improved, the electrons that have reached the surface of the material can easily move through the material, so that it is possible to cope with faster charge and discharge at a low temperature.

Moreover, when synthesizing a phosphoric acid compound represented by LiFePO ₄ , conventionally, in order to reduce the particle diameter, any method of (a) synthesis at a lower temperature and in a shorter time than (a) and (b) pulverization after production It was common to adopt. However, in the method (a), the LiFePO ₄ crystal phase is not sufficiently generated / developed, and sufficient effects cannot be obtained due to low crystallinity. Further, in the method (b), the particle size is likely to be coarsened and cannot be reduced to a sufficiently small particle size, and excessive force is applied to the particles themselves, so that distortion and cracking are likely to occur, and the crystallinity. However, a sufficient effect cannot be obtained due to the possibility of a decrease.

On the other hand, as a synthesis method capable of synthesizing a material having high crystallinity at a relatively low temperature, a raw material for each element constituting the target product is added to a solvent containing water as a main component, and the obtained solution is used. A so-called hydrothermal method in which a reaction is carried out in a closed reactor at high temperature and high pressure is known.
When synthesizing LiFePO ₄ by the hydrothermal method, the present inventors chelate a transition metal such as citric acid and add a water-soluble organic acid that decomposes at high temperature to completely react the raw materials. In addition, the present inventors have found that particles having a uniform particle diameter can be easily obtained without the possibility that the generated particles are coarsened.
When the present inventors synthesize LiFePO ₄ by the hydrothermal method, if Al is further added, the obtained particles are in a finer state. If these fine particles are used as a positive electrode material, the particle diameter is sufficiently large. It has been found that small fine particles can be easily obtained, and therefore the charge / discharge rate can be increased and sufficient performance can be obtained even when used at low temperatures.

When LiFePO ₄ is synthesized by this hydrothermal method, Li ⁺ , Fe ²⁺ , and PO ₄ ³⁻ existing in the reaction solution react to generate and grow LiFePO ₄ crystal nuclei.
Here, Al ³⁺ having a valence different from ions such as Li ⁺ and Fe ²⁺ , which are the main components of LiFePO ₄ , and having a small ion radius exists in the reaction system, and the Li site in the generated LiFePO ₄ crystal or When the Fe site is doped, the crystal is distorted and has an effect of hindering crystal growth. Accordingly, fine particles are generated.
Furthermore, since the particles once generated are difficult to grow any more, the ion concentration in the solution is higher than when no Al is added, and as a result, it becomes easy to generate crystal nuclei, and fine particles can be obtained more effectively. it can.
Further, by introducing Al, holes are easily generated in the LiFePO ₄ crystal, and improvement in electron conductivity and diffusibility due to Li ions can be expected.
Further, when the element of the B source is added simultaneously with Al, the crystal structure is further changed to improve the electron conductivity and Li ion diffusibility.
The present invention has been made based on the above idea.

That is, the manufacturing method of the electrode material of the present invention is Li _x Al _y A _z PO ₄ (where A is one or more selected from the group of Co, Mn, Ni, Fe, Cu, Cr, x + 3y + 2z). = 3, x, y, z is a method for producing an electrode material mainly composed of a compound consisting of a compound consisting of Li, A source (where A is Co , Mn, Ni, Fe, Cu, Cr selected from the group consisting of one or two or more), an Al source, a PO ₄ source and an organic acid to form a solution, and this solution is then reacted under high temperature and pressure It is characterized by making it.

Another method for manufacturing an electrode material of the present _{invention, Li x Al y A z B} w PO 4 ( where, A is Co, Mn, Ni, Fe, Cu, 1 or more kinds selected from the group of Cr , B are Mg, Ca, Sr, Sc, Y, Ti, Zr, V, Nb, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Ag, Zn, In, Sn, Sb, rare earth elements A compound composed of one or more selected from the group and different from A, x + 3y + 2z + n · w = 3, x, y, z, w are positive numbers, and n is a valence of B) A method for producing an electrode material comprising: a Li source, an A source (where A is one or two selected from the group of Co, Mn, Ni, Fe, Cu, Cr) Seeds or more), B source (B is Mg, Ca, Sr, Sc, Y, Ti, Zr, V, Nb, Cr, M o, W, Mn, Fe, Co, Ni, Cu, Ag, Zn, In, Sn, Sb, one or more selected from the group of rare earth elements and different from A), Al source, PO _Four sources and an organic acid are added to form a solution, and then this solution is reacted under high temperature and high pressure.

In each of the above electrode material manufacturing methods, the organic acid is selected from the group of citric acid, malic acid, malonic acid, acrylic acid, polyacrylic acid, methacrylic acid, formic acid, lactic acid, tartaric acid, maleic acid, and succinic acid. It is preferable that they are 1 type, or 2 or more types.
The range of y is preferably 0.001 or more and 0.1 or less.

The electrode material of the present invention is obtained by each of the methods for producing an electrode material of the present invention.
The electrode of the present invention is characterized by using the electrode material of the present invention.
The lithium battery of the present invention comprises the electrode of the present invention as a positive electrode.

According to the method for producing an electrode material of the present invention, a solvent containing water as a main component, a Li source, and an A source (where A is one selected from the group consisting of Co, Mn, Ni, Fe, Cu, and Cr). Or two or more), Al source, PO ₄ source and organic acid are added to form a solution, and then this solution is reacted under high temperature and high pressure, so that the discharge capacity of the electrode material can be increased, and the charge / discharge cycle performance Can be stabilized, the filling property can be improved, and the output can be increased.

Also, Li source, Al source, because use of the PO ₄ source and an organic acid, by using in abundance as a resource element at a low _{cost, Li x Al y A z PO} 4 ( where, A is Co, Mn, Ni, To easily and inexpensively produce an electrode material mainly composed of a compound consisting of one or more selected from the group of Fe, Cu, and Cr, and x + 3y + 2z = 3, x, y, and z are positive numbers) Can do.

According to the method for producing another electrode material of the present invention, the solvent containing water as a main component, the Li source and the A source (where A is selected from the group of Co, Mn, Ni, Fe, Cu, Cr) 1 type or 2 types or more), B source (where B is Mg, Ca, Sr, Sc, Y, Ti, Zr, V, Nb, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Ag) , Zn, In, Sn, Sb, one or more selected from the group of rare earth elements and different from A), an Al source, a PO ₄ source and an organic acid are added to form a solution, and then this solution Therefore, the discharge capacity of the electrode material can be increased, the charge / discharge cycle performance can be stabilized, the filling property can be increased, and the output can be increased.

Also, Li source, Al source, because use of the PO ₄ source and an organic acid, by using in abundance as a resource element at a low _{cost, Li x Al y A z B} w PO 4 ( where, A is Co, Mn, One or more selected from the group of Ni, Fe, Cu, Cr, B is Mg, Ca, Sr, Sc, Y, Ti, Zr, V, Nb, Cr, Mo, W, Mn, Fe, One or more selected from the group consisting of Co, Ni, Cu, Ag, Zn, In, Sn, Sb, and rare earth elements, and different from A, x + 3y + 2z + n · w = 3, x, y, z, w It is possible to easily and inexpensively manufacture an electrode material mainly composed of a compound composed of a positive number and n is a valence of B.

According to the electrode material of the present invention, since it is an electrode material obtained by the method for producing an electrode material of the present invention, it uses inexpensive and resource-rich elements, has a high discharge capacity, stable charge / discharge cycle performance, and high An electrode material with high fillability and high output can be realized, and it has extremely high utility value as an industrial material.
According to the electrode of the present invention, since the electrode material of the present invention is used, a high discharge capacity, stable charge / discharge cycle performance, high fillability, and a high output electrode can be realized. It will be expensive.

  According to the lithium battery of the present invention, since the electrode of the present invention is provided as a positive electrode, the charge / discharge capacity (particularly, discharge capacity) of the positive electrode using this electrode can be improved, and the charge / discharge cycle is stabilized. Output and output can be increased. Therefore, it is possible to provide a lithium battery excellent in various electric characteristics.

  An embodiment of a method for producing an electrode material, an electrode material, an electrode, and a lithium battery according to the present invention will be described.

The manufacturing method of the electrode material of the present invention is either of the following methods (1) and (2).
(1) In a solvent containing water as a main component, an Li source, an A source (where A is one or more selected from the group of Co, Mn, Ni, Fe, Cu, Cr), an Al source, and the solution added to PO ₄ source and organic acids, followed by reacting the solution at a high temperature under high _{pressure, Li x Al y a z PO} 4 ( where, a is Co, Mn, Ni, Fe, Cu, A method for producing an electrode material comprising as a main component a compound consisting of one or more selected from the group of Cr, x + 3y + 2z = 3, x, y, and z are positive numbers).

(2) Lithium source, A source (where A is one or more selected from the group consisting of Co, Mn, Ni, Fe, Cu, Cr), B source ( However, B is Mg, Ca, Sr, Sc, Y, Ti, Zr, V, Nb, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Ag, Zn, In, Sn, Sb, rare earth elements 1 or 2 or more selected from the group of the above and different from A), an Al source, a PO ₄ source and an organic acid are added to form a solution, and then this solution is reacted under high temperature and high pressure, _{li x Al y a z B w} PO 4 ( where, a is Co, Mn, Ni, Fe, Cu, Cr 1 , two or more selected from the group of, B is Mg, Ca, Sr, Sc, Y Ti, Zr, V, Nb, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Ag, Zn One or more selected from the group of In, Sn, Sb, and rare earth elements and different from A, x + 3y + 2z + n · w = 3, x, y, z, w are positive numbers, and n is a valence of B The electrode material which has as a main component the compound which consists of several).

The raw material to be used is not particularly limited, and may be any combination as long as the target substance can be obtained usually by a hydrothermal method. However, in consideration of reacting in a solvent containing water as a main component, it is soluble in water. Acetate, sulfate, chloride and the like are preferred.
Examples of the Li source include lithium chloride (LiCl), lithium bromide (LiBr), lithium carbonate (Li ₂ CO ₃ ), lithium nitrate (LiNO ₃ ), lithium sulfate (Li ₂ SO ₄ ), and lithium phosphate (Li ₃ PO ₄ ), lithium inorganic acid salts such as lithium hydroxide (LiOH), lithium organic acid salts such as lithium acetate (LiCH ₃ COO) and lithium oxalate ((COOLi) ₂ ), or lithium ethoxide (LiC ₂ H Li-containing organometallic compounds such as lithium alkoxides such as ₅ O), organic lithium compounds such as (Li ₄ (CH ₃ ) ₄ ), and the like can be used.

The A source is preferably a compound containing one or more elements selected from the group consisting of Co, Mn, Ni, Fe, Cu, and Cr, and in particular, any one of Fe, Co, Mn, and Ni Or a compound containing two or more of these elements is preferred from the viewpoint of high discharge potential, abundant resource amount, safety, and the like.
Examples of these compounds include iron sulfate (II) (FeSO ₄ ), iron acetate (II) (Fe (CH ₃ COO) ₂ ), iron chloride (II) (FeCl ₂ ) and the like. be able to.

The source B is an element different from the source A, and Mg, Ca, Sr, Sc, Y, Ti, Zr, V, Nb, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, A compound containing one or more elements selected from the group consisting of Ag, Zn, In, Sn, Sb and rare earth elements is preferred.
Here, the rare earth elements are 15 elements of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu which are lanthanum series.

As such a compound, one or more metal salts of elements different from the A source among the above elements are used. For example, sulfates such as MgSO ₄ and Ti (SO ₄ ) ₂ , Mg Acetates such as (CH ₃ COO) ₂ and chlorides such as CaCl ₂ and TiCl ₄ are preferably used.

Examples of the Al source include aluminum sulfate (Al ₂ (SO ₄ ) ₃ ), aluminum chloride (AlCl ₃ ), aluminum acetate (Al (CH ₃ COO) ₃ ), and the like.
The addition amount (y) of the Al source is not limited as long as no impurities are generated. However, in the present invention, 0.001 ≦ y ≦ 0.100 is preferable, and 0.01 ≦ y ≦ 0.05 is more preferable. .
This is because, when y is less than 0.001, fine particles of _Li x _Al y _A z PO ₄ or _{Li x Al y A z B w} PO 4 does not proceed by Al addition, also electronic conductivity, Li-ion This is because a sufficient effect cannot be expected for the improvement of diffusion, and if y is more than 0.100, impurities including Al are easily generated, so that many Li defects are generated in the crystal. As a result, problems such as a decrease in capacity occur.

Examples of the PO ₄ source include phosphoric acid such as orthophosphoric acid (H ₃ PO ₄ ) and metaphosphoric acid (HPO ₃ ), diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ), and ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ ) ammonium hydrogenphosphate salts.
Of these, orthophosphoric acid, diammonium hydrogen phosphate, and ammonium dihydrogen phosphate are preferred because of their relatively high purity and ease of composition control.

The organic acid is preferably a water-soluble organic acid, for example, hydroxycarboxylic acids such as citric acid, malic acid, lactic acid, and tartaric acid, malonic acid, acrylic acid, polyacrylic acid, methacrylic acid, formic acid, maleic acid, and succinic acid. Carboxylic acid such as
Among them, citric acid is
(A) Low toxicity and high safety.
(B) high chelate effect against metal ions, the resulting _Li x _Al y _A z PO ₄ or _{Li x Al y A z B w} PO 4 for suppressing the growth of crystal nuclei.
(C) Since it exhibits reducibility during decomposition, oxidation of the A element can be prevented.
It is particularly preferable for the reasons described above.

As a solvent containing water as a main component, pure water, water-alcohol solution, water-ketone solution, or water-ether solution can be used. However, pure water is preferable from the viewpoint of ease of use and safety. preferable.
The reason is that pure water is cheaper than other solvents and shows a large change in dielectric constant near the critical point. Therefore, by changing the temperature and pressure, the physical properties as a solvent such as solubility in each substance This is because it can be easily controlled.

In the present invention, a Li source, an A source, an Al source, a PO ₄ source and an organic acid are added to a solvent containing water as a main component, and a B source is also added as necessary to form a solution.
The solution is then reacted under high temperature and pressure. For example, it is housed in a pressure-resistant airtight container such as an autoclave and then heated to a predetermined maximum holding temperature.

Since the pressure in the pressure-resistant airtight container is in a high pressure state when reaching the maximum holding temperature, a predetermined high temperature and high pressure state can be ensured for a predetermined time by holding this maximum holding temperature for a predetermined time. Thereby, said solution can be made to react under high temperature and high pressure.
The reaction conditions vary depending on the intended composition, but are generally maintained at 120 to 350 ° C. and 0.1 MPa to 30 MPa for 100 hours or less, preferably 0.5 hours to 100 hours. of composition _"Li x _Al y compounds consisting _a z PO _4" or "consisting of _{Li x Al y a z B w} PO 4 compound" is synthesized.
Filtered solution the reaction is complete, drying, or by centrifugation and drying, the _"Li x _Al y compounds consisting _A z PO _4" or "consisting of _{Li x Al y A z B w} PO 4 compound" Fine particles containing the main component can be obtained.

The electrode material of the present invention thus obtained has an average particle size of preferably 0.01 μm or more and 0.5 μm or less, more preferably 0.02 μm or more and 0.2 μm or less.
If the average particle size is smaller than 0.01 μm, the particles may be destroyed due to structural changes accompanying Li insertion / extraction, and the surface area is too large, so that a large amount of binder is required. This is because there is a problem that the conductivity of the positive electrode becomes low and the packing density of the positive electrode is remarkably lowered. This is because of problems such as delay and reduced efficiency.
In order to further increase the output, particles having a size of 0.2 μm or less are preferable because the influence of the internal resistance of the active material is small.

Here, the "compound composed of _Li x _Al y _A z PO _4" is a compound identified as _"Li x _Al y _A z PO _4" by X-ray diffraction method, _"Li x _Al y _A z PO ₄ "The main component is a compound consisting of" means that this compound is contained at least 90% by weight or more, and the remaining less than 10% by weight may be other compounds.
As for the _{"Li x Al y A z B w} PO compounds consisting of ₄ ', similar to the" compound consisting _Li x _Al y _A z PO ₄ "above," _Li x by X-ray diffractometry _Al y _{A z} a B _w PO ₄ compound identified as "a" mainly composed of _Li x _Al y _a z consisting _B w PO ₄ compound "is meant that the compound comprises at least 90 wt% or more, Other compounds may be less than 10% by weight of the balance.

In the electrode of the present invention, the electrode material of the present invention and the binder resin are kneaded, and then the kneaded product is rolled to form an electrode material mixture film. It is crimped onto an electric body, and this crimped body is punched out into a disk shape having a predetermined area using a molding machine.
Examples of the binder resin include polytetrafluoroethylene (PTFE) resin and polyvinylidene fluoride (PVdF) resin.
The mixing ratio of the electrode material and the binder resin is not particularly limited. For example, the binder resin is about 3 to 20 parts by weight with respect to 100 parts by weight of the electrode material.

  The lithium battery of the present invention uses the electrode of the present invention as a positive electrode, and the negative electrode, electrolyte, separator, battery shape and the like are not particularly limited. This lithium battery is formed by the electrode material of the present invention, which is a fine spherical powder having a high purity and a uniform particle size, and thus has a high charge / discharge capacity and a stable charge / discharge cycle. High performance is achieved with high performance.

EXAMPLES Hereinafter, although this invention is demonstrated concretely by Examples 1-4 and Comparative Examples 1 and 2, this invention is not limited by these Examples.
For example, in this embodiment, metal Li is used for the negative electrode in order to reflect the behavior of the electrode material itself in the data. However, a negative electrode material such as a carbon material, a Li alloy, or Li ₄ Ti ₅ O ₁₂ may be used. . A solid electrolyte may be used instead of the electrolytic solution and the separator.

"Example 1"
In 100 ml of pure water, 0.3 mol of lithium hydroxide (LiOH), 0.1 mol of iron (II) sulfate (FeSO ₄ ), 0.0002 mol of aluminum sulfate (Al ₂ (SO ₄ ) ₃ ), 0.1 mol of Phosphoric acid (H ₃ PO ₄ ), 0.1 mol of citric acid and pure water were mixed so that the total amount was 0.2 liter (L), and a uniform transparent solution A was prepared.
Subsequently, this solution A was accommodated in a pressure-resistant airtight container and kept at a maximum attained temperature: 170 ° C. for 6 hours to be reacted.
The obtained powder was washed with water and dried to obtain a sample of Example 1.

"Example 2"
A sample of Example 2 was obtained in the same manner as Example 1 except that the addition amount of aluminum sulfate (Al ₂ (SO ₄ ) ₃ ) was 0.005 mol.

"Example 3"
A sample of Example 3 was obtained in the same manner as Example 1 except that the addition amount of aluminum sulfate (Al ₂ (SO ₄ ) ₃ ) was 0.010 mol.

Example 4
Further, a sample of Example 4 was obtained in the same manner as Example 2 except that 0.002 mol of magnesium sulfate (MgSO ₄ ) was added.

“Comparative Example 1”
A sample of Comparative Example 1 was obtained in the same manner as in Example 1 except that aluminum sulfate (Al ₂ (SO ₄ ) ₃ ) was not added.

“Comparative Example 2”
A sample of Comparative Example 2 was obtained in the same manner as in Example 1 except that the amount of aluminum sulfate (Al ₂ (SO ₄ ) ₃ ) was 0.015 mol.

`` Generation phase identification ''
The obtained samples of Examples 1 to 4 and Comparative Examples 1 and 2 were phase-identified.
Here, powder X-ray diffraction patterns (charts) of these samples were obtained using an X-ray diffractometer.
The X-ray, CuKa ₁ line (wavelength: lambda = 1.5418 Å) with the identification of these samples performed by Hanawaruto method (Hanawait method), it was examined phases of these samples. The powder X-ray diffraction patterns of Examples 1 to 4 and Comparative Examples 1 and 2 are shown in FIG. 1, and the enlarged powder X-ray diffraction pattern of Comparative Example 2 is shown in FIG. In FIG. 1 and FIG. 2, “●” marks indicate diffraction lines of LiFePO ₄ (triphyllite), and in FIG. 2, “×” marks indicate diffraction lines of impurity phases that are difficult to identify.

“Observation with a scanning electron microscope (SEM)”
From the obtained SEM images of Examples 1 to 4 and Comparative Examples 1 and 2, the particle diameter of each sample was measured, and the state of the particles was observed.
The SEM image of Example 1 is shown in FIG. 3, the SEM image of Example 2 is shown in FIG. 4, the SEM image of Example 3 is shown in FIG. 5, and the SEM image of Example 4 is shown in FIG. Further, the SEM image of Comparative Example 1 is shown in FIG. 7, and the SEM image of Comparative Example 2 is shown in FIG. Furthermore, Table 1 shows specific surface areas and particle sizes of Examples 1 to 4 and Comparative Examples 1 and 2, respectively.

"Production of lithium battery"
Kneading 85 parts by weight of the sample of Example 1 and 10 parts by weight of carbon black (CB) having an average primary particle diameter of 14 nm and a specific surface area of 290 m ² g ⁻¹ together with 5 parts by weight of polyvinylidene fluoride (PVdF), The obtained kneaded material was applied on an aluminum (Al) foil and vacuum-dried. Then, it crimped | bonded and it was set as the positive electrode (positive electrode).
Next, after the positive electrode was vacuum-dried, a lithium battery of Example 1 was produced using a 2016 coin type cell made of stainless steel (SUS) in a dry Ar atmosphere. Metal Li was used for the negative electrode, a porous polypropylene film was used for the separator, and a 1M LiPF ₆ solution was used for the electrolyte solution. As a solvent for this LiPF ₆ solution, a solvent having a ratio of ethylene carbonate to diethyl carbonate of 1: 1 was used.

  Moreover, using the samples of Examples 2 to 4 and Comparative Examples 1 and 2, lithium batteries of Examples 2 to 4 and Comparative Examples 1 and 2 were fabricated in exactly the same manner as the lithium battery of Example 1.

"Battery charge / discharge test"
The charge / discharge test of each of the lithium batteries of Examples 1 to 4 and Comparative Examples 1 and 2 was performed under a constant current (cut off for 1 hour after charging for 1 hour) at a cutoff voltage of 2-4.5V and a charge / discharge rate of 1C. Carried out. In addition, environmental temperature was made into two points, 0 degreeC and room temperature (25 degreeC).
Table 1 shows the discharge capacities of Examples 1 to 4 and Comparative Examples 1 and 2 at 0 ° C. and room temperature (25 ° C.).

According to the above results, it was found that in the samples of Examples 1 to 4, no impurity phase was generated even when Al or Mg was added, and single-phase LiFePO ₄ having a particle diameter of 400 nm or less was obtained. . In addition, in the lithium battery using these samples, the discharge capacity at 0 ° C. was improved as the amount of Al added increased. In particular, in Example 4, Mg was used together with Al at 0 ° C. It was found that the discharge capacity was further improved as compared with the case of adding only Al in Examples 1 to 3.

On the other hand, in the sample of Comparative Example 1, since Al was not added, single-phase LiFePO ₄ was obtained, but it was found that the discharge capacity at 0 ° C. was greatly reduced as compared with Examples 1-3. It was.
Further, it was found that the sample of Comparative Example 2 produced some diffraction lines that were difficult to identify because of excessive addition of Al. This diffraction line is considered an impurity phase. Moreover, although single-phase LiFePO _{4 with} a particle size of 200 nm or less was obtained, the particles became finer and the specific surface area increased with the excessive addition of Al.

Solvents mainly composed of water include Li source, A source (where A is one or more selected from the group of Co, Mn, Ni, Fe, Cu, Cr), Al source, PO4 source, and adding an organic acid to form a solution, by reacting the solution at a high temperature under high _{pressure, Li x Al y a z PO} 4 ( where, a is selected Co, Mn, Ni, Fe, Cu, from the group of Cr In addition, it is possible to easily obtain an electrode material mainly composed of a compound consisting of one or more kinds, x + 3y + 2z = 3, x, y, and z are positive numbers). For next-generation secondary batteries that are expected to be smaller, lighter and have higher capacity, as well as improved capacity (particularly discharge capacity), stable charge / discharge cycles, and higher output. Next generation secondary battery Case, the effect is very large.

It is a figure which shows the powder X-ray-diffraction figure of each sample of Examples 1-4 of this invention, and Comparative Examples 1 and 2. FIG. It is a figure which shows the powder X-ray-diffraction figure which the sample of the comparative example 2 expanded. It is a SEM image which shows the shape of the sample of Example 1 of this invention. It is a SEM image which shows the shape of the sample of Example 2 of this invention. It is a SEM image which shows the shape of the sample of Example 3 of this invention. It is a SEM image which shows the shape of the sample of Example 4 of this invention. 3 is an SEM image showing the shape of a sample of Comparative Example 1. 10 is a SEM image showing the shape of a sample of Comparative Example 2.

Claims (7)

_{Li x Al y A z PO 4} ( where, A is Co, Mn, Ni, Fe, Cu, Cr 1 , two or more selected from the group of, x + 3y + 2z = 3 , x, y, z is a positive number A method for producing an electrode material mainly comprising a compound comprising:
In a solvent mainly containing water, Li source, A source (where A is one or more selected from the group of Co, Mn, Ni, Fe, Cu, Cr), Al source, PO ₄ source And an organic acid to make a solution,
Next, a method for producing an electrode material, wherein the solution is reacted under high temperature and high pressure. _{Li x Al y A z B w} PO 4 ( where, A is Co, Mn, Ni, Fe, Cu, Cr 1 , two or more selected from the group of, B is Mg, Ca, Sr, Sc, Y , Ti, Zr, V, Nb, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Ag, Zn, In, Sn, Sb, one or more selected from the group of rare earth elements and A method for producing an electrode material comprising as a main component a compound consisting of x + 3y + 2z + n · w = 3, x, y, z, w being a positive number and n being a valence of B, different from A,
Solvents mainly composed of water include Li source, A source (where A is one or more selected from the group of Co, Mn, Ni, Fe, Cu, Cr), B source (provided that B Is Mg, Ca, Sr, Sc, Y, Ti, Zr, V, Nb, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Ag, Zn, In, Sn, Sb, from the group of rare earth elements 1 type or two or more selected and different from A), an Al source, a PO ₄ source and an organic acid are added to form a solution,
Next, a method for producing an electrode material, wherein the solution is reacted under high temperature and high pressure.   The organic acid is one or more selected from the group consisting of citric acid, malic acid, malonic acid, acrylic acid, polyacrylic acid, methacrylic acid, formic acid, lactic acid, tartaric acid, maleic acid, and succinic acid. The method for producing an electrode material according to claim 1 or 2.   The method for producing an electrode material according to claim 1, 2 or 3, wherein the range of y is 0.001 or more and 0.1 or less.   An electrode material obtained by the method for producing an electrode material according to any one of claims 1 to 4.   An electrode comprising the electrode material according to claim 5.   A lithium battery comprising the electrode according to claim 6 as a positive electrode.

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