KR101100029B1 - Manufacturing method of positive electrode active material for lithium secondary battery and lithium secondary battery - Google Patents

Abstract

Lithium phosphate (LiH ₂ PO ₄ ) and an iron precursor compound are mixed, a conductive carbon material is added to the mixture to prepare a mixed product, and the process of firing the mixed product is a lithium secondary represented by the following formula (1) Provided is a method for producing a positive electrode active material for a battery.

[Formula 1]

LiFePO ₄

Cathode active material, lithium iron phosphate, lithium raw material, lithium hydride phosphate, additional lithium raw material

Description

Manufacturing method of positive electrode active material for lithium secondary battery and lithium secondary battery {METHOD OF PREPARING POSITIVE ACTIVE MATERIAL FOR LITHIUM SECONDARY BATTERY AND RECHARGEABLE LITHIUM BATTERY}

The present disclosure relates to a method of manufacturing a cathode active material for a lithium secondary battery and a lithium secondary battery including the same.

With the recent trend toward miniaturization and light weight of portable electronic devices, the necessity for high performance and high capacity of batteries used as power sources of these devices is increasing.

Cells generate electricity by using materials that can electrochemically react to the positive and negative electrodes. A typical example of such a battery is a lithium secondary battery that generates electric energy by a change in chemical potential when lithium ions are intercalated / deintercalated at a positive electrode and a negative electrode.

The lithium secondary battery is manufactured by using a material capable of reversible intercalation / deintercalation of lithium ions as a positive electrode and a negative electrode active material, and filling an organic electrolyte or a polymer electrolyte between the positive electrode and the negative electrode.

A lithium composite metal compound is used as a positive electrode active material of a lithium secondary battery, and examples thereof include LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiNi _1-x Co _x O ₂ (0 <x <1), and LiMnO ₂ . Composite metal oxides are being studied.

In addition, LiFePO ₄ , which has recently been spotlighted as a cathode active material of a large-capacity battery, has excellent thermal stability, rich reserves, and raw material prices.

Methods of synthesizing the positive electrode active material LiFePO ₄ include a coprecipitation method, a solid phase reaction method, a hydrothermal synthesis method and the like. In Japanese Patent Laid-Open No. 2000-294238, iron oxalate (FeC ₂ O ₄ .2H ₂ O) is used as an iron raw material, and ammonium hydrogen phosphate (NH ₄ H ₂ PO ₄ ) and lithium carbonate (Li ₂ CO ₃ ) are synthesized. A method for synthesizing LiFePO ₄ as a raw material is described. US Patent Publication No. 20020004169 discloses the synthesis of LiFePO ₄ using iron acetate 2Fe (CH ₃ COO) ₂ , lithium carbonate (Li ₂ CO ₃ ) and ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ ) as a raw material. The method is presented.

Many other patents use LiFePO ₄ as a raw material using phosphate and iron acetate (2Fe (CH ₃ COO) ₂ ) as NH ₄ H ₂ PO ₄ , (NH ₄ ) ₂ HPO ₄ , (NH ₄ ) ₃ PO _4, etc. A method of synthesis is shown.

However, when the raw material is used, harmful reaction gases such as ammonia or acetic acid are generated during firing, and a manufacturing cost is inevitably increased because a facility for collecting such harmful reaction gases is required. Therefore, there is a problem that is not suitable for producing LiFePO ₄ on an industrial scale.

In addition, Korean Patent Publication No. 2008-0006928 discloses a method of using iron raw materials such as lithium phosphate (Li ₃ PO ₄ ) and ferrous phosphate (Fe ₃ (PO ₄ ) ₂ nH ₂ O). However, this method does not produce harmful by-products because the by-products are non-toxic water. However, as the lithium phosphate used is manufactured by a method of adding sodium phosphate to an aqueous lithium hydroxide solution, there is a tendency that the sodium content necessarily increases as an impurity, which causes problems such as deterioration of battery characteristics.

One embodiment of the present invention is to provide a method for producing a cathode active material for a lithium secondary battery that is eco-friendly, easy to mass-produce, economical because no harmful reaction gas is generated.

Another embodiment of the present invention is to provide a lithium secondary battery including the positive electrode active material prepared by the manufacturing method.

One embodiment of the present invention is to mix lithium phosphate (LiH ₂ PO ₄ , lithium dihydrogen phosphate) and iron precursor compound; Adding a conductive carbon material to the mixture to prepare a mixed product; It is to provide a method for producing a cathode active material for a lithium secondary battery represented by the following formula (1) comprising the step of firing the mixed product.

[Formula 1]

LiFePO ₄

Another embodiment of the present invention to provide a lithium secondary battery comprising a positive electrode including a positive electrode active material prepared by the above method, a negative electrode including a negative electrode active material, and an electrolyte.

Other specific details of embodiments of the present invention are included in the following detailed description.

In the manufacturing method of the present invention, since no harmful reaction gas is generated during the firing process, it is possible to manufacture a cathode active material for an LiFePO ₄ lithium secondary battery, which is environmentally friendly, easy to mass produce, and economically.

Hereinafter, embodiments of the present invention will be described in detail. However, this is presented as an example, by which the present invention is not limited and the present invention is only defined by the scope of the claims to be described later.

A first embodiment of the present invention comprises the steps of mixing the lithium phosphate (LiH ₂ PO ₄ ) and iron precursor compound, adding a carbon-based material to the mixture to prepare a mixed product, and calcining the mixed product It provides a method for producing a cathode active material for a lithium secondary battery represented by the formula (1).

[Formula 1]

LiFePO ₄

Next, the manufacturing method according to the first embodiment of the present invention will be described in detail for each process.

First, lithium hydride phosphate (LiH ₂ PO ₄ ) and the iron precursor compound are mixed.

As the iron precursor compound, a compound containing Fe ²⁺ may be used, and representative examples thereof may be iron oxalate (FeC ₂ O ₄ .2H ₂ O), iron acetate (Fe (CH ₃ COO) ₂ ), or a combination thereof. Mixtures can be used. Among these, iron oxalate (FeC ₂ O ₄ .2H ₂ O) can be most suitably used.

The lithium hydride phosphate (LiH ₂ PO ₄ ) is a compound capable of providing both lithium and phosphorus, and may be used in a solid or liquid state in powder form. When used in the above liquid state, lithium phosphate lithium (LiH ₂ PO ₄ ) may be dissolved in water and used as an aqueous solution, or may be used as a slurry dissolved in an alcohol solvent such as ethanol or isopropyl alcohol.

When using lithium phosphate (LiH ₂ PO ₄ ) in the production of LiFePO ₄ , it is environmentally friendly because no harmful by-products such as toxic ammonia or acetic acid are produced during firing, and it is environmentally friendly, and a process for removing such harmful by-products and It is economical because the process is simple because no device is required and manufacturing cost can be reduced.

In preparing LiFePO ₄ , the use of lithium phosphate (LiH ₂ PO ₄ ) does not produce harmful by-products. For example, when iron oxalate (FeC ₂ O ₄ · 2H ₂ O) is used as an iron precursor, It is represented by Scheme 1 below.

Scheme 1

_{LiH 2 PO 4 + FeC 2 O} 4 · 2H 2 O → LiFePO 4 + 3H 2 O + CO 2 + CO

As shown in Scheme 1, when LiH ₂ PO ₄ is used as a starting material for synthesis, it can be seen that no harmful substances are produced, and harmless water is produced as a by-product.

On the other hand, in one conventional method, Li ₂ CO ₃ , FeC ₂ O ₄ · 2H ₂ O, and (NH ₄ ) ₂ HPO ₄ are mixed at a predetermined ratio and calcined, that is, LiFePO ₄ is synthesized by a reaction as in Scheme 2 below. It was.

Scheme 2

_{Li 2 CO 3 + 2FeC 2 O} 4 · 2H 2 O + 2 (NH 4) 2 HPO 4 → 2LiFePO 4 + 4NH 3 + 5CO 2 + 5H 2 O + 2H 2

As can be seen from the reaction formula shown in Chemical Formula 2, in the conventional method for synthesizing LiFePO ₄ , harmful by-products such as ammonia, which are toxic upon firing, are produced.

Further, in another conventional method, Li ₂ CO ₃ , 2Fe (CH ₃ COO) ₂ , and 2NH ₄ H ₂ PO ₄ were mixed at a predetermined ratio and calcined, that is, LiFePO ₄ was synthesized by a reaction as in Scheme 3 below. .

Scheme 3

Li ₂ CO ₃ + 2Fe (CH ₃ COO) ₂ + 2NH ₄ H ₂ PO ₄ → 2LiFePO ₄ + CO ₂ + H ₂ O + 2NH ₃ + 4CH ₃ COOH

As shown in Scheme 3, in the conventional method for synthesizing LiFePO ₄ , harmful by-products such as ammonia or acetic acid, which are toxic upon firing, are produced. Therefore, since a large-scale dust collector and the like for treating such harmful by-products are required, manufacturing cost increases.

That is, according to the present invention, lithium Fe phosphate (LiH ₂ PO ₄ ) can be used to obtain the resulting LiFePO ₄ without producing toxic by-products. Therefore, compared with the conventional manufacturing method, the safety by a harmful by-product at the time of baking improves remarkably. In addition, in the past, a large-scale treatment facility for treating toxic by-products was required, but in the above-described manufacturing method, since the by-products are non-toxic water, the process can be simplified and the treatment equipment can be reduced. Therefore, manufacturing cost can be reduced compared with the case of processing ammonia etc. which are conventional by-products.

In the process of mixing lithium phosphate (LiH ₂ PO ₄ ) and the iron precursor compound, their mixing ratio may be 1: 1 to 1.05: 1 mol (mol) ratio. When the equivalent ratio of lithium phosphate hydride and iron precursor compound is included in the above range, P of lithium phosphate hydride is appropriate since it does not exist as an unreacted substance.

In addition, Li ₂ CO ₃ , LiOH or a mixture thereof may be further added after the process or pre-sintering of mixing the lithium phosphate (LiH ₂ PO ₄ ) and the iron precursor compound. When further adding Li ₂ CO ₃ , LiOH or a mixture thereof, there is an advantage to replenish lithium volatilized during the firing process. In this case, the amount of Li ₂ CO ₃ , LiOH or a mixture thereof may be added in an amount of 0.05 to 0.1 moles based on 1 mole of lithium hydride lithium phosphate (LiH ₂ PO ₄ ), and when Li ₂ CO ₃ and LiOH are mixed and mixed, Can be adjusted appropriately.

Subsequently, a conductive carbon material is added to the mixture of the lithium hydride phosphate and the iron precursor to prepare a mixed product. This addition step can be carried out by a mixing step using a ball mill or the like such as a planetary ball mill. In this case, the mixing process may be performed for 30 minutes to 1 hour.

The conductive carbon material may be added before firing the mixture or after pre-sintering. The conductive carbon material maintains the internal atmosphere of the reactor in a reducing atmosphere during firing, thereby reducing iron ions, and serves as a conductive component in the final product.

Examples of the conductive carbon material that can be used include materials capable of generating conductive carbon by thermal decomposition such as ketjen black, Super-P, acetylene black, and petroleum pitch.

The mixing ratio of the mixture and the conductive carbon material may be 1 to 10 parts by weight based on 100 parts by weight of the mixture. When using a conductive carbon material in this range, the conductivity improvement effect by using a conductive carbon material can be suitably acquired, without the problem of the density fall of an active material.

In the plasticizing process, a mixture of lithium phosphate hydride and an iron precursor may be plasticized at 600 to 850 ° C. The plastic maintenance interval may be 4 to 6 hours.

The mixed product is then calcined. At this time, the firing step can be carried out at 600 to 850 ℃.

The firing time may be performed for 4 to 6 hours when plasticizing is performed, and may be performed for 8 to 10 hours when plasticizing is not performed.

In addition, when plasticizing is performed, the process of crushing after cooling a plastic product can also be performed.

In the case where the firing step is carried out in the above temperature range and time range, the active material particles having an appropriate size can be formed without decreasing the crystallinity of the active material, and the formation of the impurity phase can be suppressed.

In addition, the firing step may be carried out in an inert atmosphere or a reducing atmosphere. The inert atmosphere may be an N ₂ gas atmosphere, and the reducing atmosphere may be a mixed gas atmosphere of Ar / H ₂ . The content of H ₂ in the mixed gas atmosphere of the Ar / H ₂ may be 2 to 7% by volume. The content of H ₂ gas in the mixed atmosphere of Ar / H ₂ has the advantage of maintaining the reducing atmosphere when included in the range.

After cooling the calcined product, it is ground again to prepare a positive electrode active material.

A second embodiment of the present invention is to provide a lithium secondary battery comprising a positive electrode active material prepared according to the first embodiment. That is, the positive electrode active material prepared according to the first embodiment of the present invention may be usefully used for the positive electrode of a lithium secondary battery. The lithium secondary battery includes a negative electrode including a negative electrode active material together with a positive electrode, and an electrolyte.

The positive electrode is prepared by mixing a positive electrode active material according to the present invention, a conductive material, a binder and a solvent to prepare a positive electrode active material composition, and then coating and drying the aluminum active material directly. Alternatively, the cathode active material composition may be cast on a separate support, and then the film obtained by peeling from the support may be manufactured by laminating on an aluminum current collector.

The conductive material is carbon black, graphite, metal powder, the binder is vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene And mixtures thereof. In addition, N-methylpyrrolidone, acetone, tetrahydrofuran, decane, etc. are used as a solvent. In this case, the contents of the positive electrode active material, the conductive material, the binder, and the solvent are used at levels commonly used in lithium secondary batteries.

Like the positive electrode, the negative electrode is mixed with a negative electrode active material, a binder, and a solvent to prepare a negative electrode active material composition, which is directly coated on a copper current collector or cast on a separate support and peeled from the support to a copper current collector It is prepared by lamination. At this time, the negative electrode active material composition may further contain a conductive material if necessary.

As the negative electrode active material, a material capable of intercalating / deintercalating lithium is used, and for example, lithium metal, lithium alloy, coke, artificial graphite, natural graphite, organic polymer compound combustor, carbon fiber, or the like is used. . In addition, a conductive material, a binder, and a solvent are used similarly to the case of the positive electrode mentioned above.

The separator may be used as long as it is commonly used in lithium secondary batteries. For example, polyethylene, polypropylene, polyvinylidene fluoride or two or more multilayer films thereof may be used, and a polyethylene / polypropylene two-layer separator, It goes without saying that a mixed multilayer film such as polyethylene / polypropylene / polyethylene three-layer separator, polypropylene / polyethylene / polypropylene three-layer separator and the like can be used.

As the electrolyte to be charged in the lithium secondary battery, a non-aqueous electrolyte or a known solid electrolyte may be used, and a lithium salt is used.

Although the solvent of the said non-aqueous electrolyte is not specifically limited, Chain carbonate methyl acetate, ethyl acetate, such as cyclic carbonate dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, such as ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, Esters such as propyl acetate, methyl propionate, ethyl propionate and γ-butyrolactone 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 1,2-dioxane, 2-methyltetrahydro Amides, such as nitriles, such as ether acetonitrile, such as furan, and dimethylformamide, etc. can be used. These can be used individually or in combination of multiple. In particular, a mixed solvent of a cyclic carbonate and a linear carbonate can be preferably used.

As the electrolyte, a gel polymer electrolyte in which an electrolyte solution is impregnated with a polymer electrolyte such as polyethylene oxide or polyacrylonitrile, or an inorganic solid electrolyte such as LiI or Li 3 N can be used.

At this time, the lithium salt is LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , LiSbF ₆ , LiAlO ₄ , LiAlCl ₄ , LiCl , And one selected from the group consisting of LiI is possible.

Hereinafter, preferred examples and comparative examples of the present invention are described. However, the following examples are only preferred embodiments of the present invention, and the present invention is not limited to the following examples.

Example 1

The Fe ²⁺ containing compound FeC ₂ O ₄ · 2H ₂ O and LiH ₂ PO ₄ as a lithium salt includes a P starting material in a ratio 1 mole (mol): was mixed to 1.

3 parts by weight of Ketjen Black was added to 100 parts by weight of the mixture, followed by mixing and grinding for about 3 to 4 hours using a planetary ball mill to prepare a mixed product.

The resulting mixed product was obtained with Ar / H ₂ (content of H ₂ 5% by volume). The mixture was calcined by holding at 750 ° C. for 10 hours under a reducing atmosphere of the mixed gas. After cooling it slowly, it was ground again to prepare a carbon-containing LiFePO ₄ positive electrode active material.

Example 2

FeC ₂ O 4 .2H ₂ O as a Fe ²⁺ -containing compound and LiH ₂ PO ₄ containing P raw material as a lithium salt were mixed at a molar ratio of 1: 1.

The mixture was mixed and ground for about 2 to 3 hours using a planetary ball mill.

The resulting mixture was calcined by holding at 750 ° C. for 4 hours in a reducing atmosphere of an Ar / H ₂ (content of 5% by volume of H ₂ ) mixed gas. To the powder obtained after plasticization, 3 parts by weight of Ketjen Black was added to 100 parts by weight of the powder, and the mixture was mixed and ground again for 30 minutes to 1 hour using a planetary ball mill to prepare the mixed product. Prepared.

The obtained mixed product was obtained with Ar / H ₂ (content of H ₂ by 5% by volume). The mixed gas was kept at 750 ° C. for 6 hours under a reducing atmosphere and calcined. After cooling it slowly, it was pulverized again to prepare LiFePO ₄ containing carbon.

Example 3

The Fe ²⁺ containing compound FeC ₂ O ₄ · 2H ₂ O and LiH ₂ PO ₄ as a lithium salt includes a P starting material in a ratio 1 mole (mol): was mixed to 1.

3 parts by weight of acetylene black, based on 100 parts by weight of the mixture, was added to the mixture and mixed and ground for about 3 to 4 hours using a planetary ball mill to prepare a mixed product.

The obtained mixed product was obtained with Ar / H ₂ (content of H ₂ by 5% by volume). The mixture was calcined by holding at 750 ° C. for 10 hours under a reducing atmosphere of the mixed gas. After cooling it slowly, it was pulverized again to prepare LiFePO ₄ containing carbon.

Example 4

The Fe ²⁺ containing compound FeC ₂ O ₄ · 2H ₂ O and LiH ₂ PO ₄ as a lithium salt includes a P starting material in a ratio 1 mole (mol): was mixed to 1. Li ₂ CO ₃ was added to this mixture, and the amount of Li ₂ CO ₃ added was 0.1 mol relative to 1 mol of LiH ₂ PO ₄ .

3 parts by weight of Ketjen Black was added to the resulting product, and mixed and ground for about 3 to 4 hours using a planetary ball mill to prepare a mixed product, based on 100 parts by weight of the obtained product.

The resulting mixed product was calcined by holding at 750 ° C. for 10 hours under a reducing atmosphere of an Ar / H ₂ (H ₂ content 5% by volume) mixed gas. After cooling it slowly, it was pulverized again to prepare LiFePO ₄ containing carbon.

Example 5

The Fe ²⁺ containing compound FeC ₂ O ₄ · 2H ₂ O and LiH ₂ PO ₄ as a lithium salt includes a P starting material in a ratio 1 mole (mol): was mixed to 1.

3 parts by weight of acetylene black, based on 100 parts by weight of the mixture, was added to the mixture and mixed and ground for about 2 to 3 hours using a planetary ball mill to prepare a mixed product.

The resulting mixture was calcined by holding at 750 ° C. for 4 hours in a reducing atmosphere of an Ar / H ₂ (content of 5% by volume of H ₂ ) mixed gas. Li ₂ CO ₃ was added to the powder obtained after plasticization, and the amount of Li ₂ CO ₃ added was 0.1 mol relative to 1 mol of LiH ₂ PO ₄ .

The mixture was mixed and ground again for 30 minutes to 1 hour using a planetary ball mill to prepare a mixed product.

The resulting mixed product was calcined by holding at 750 ° C. for 6 hours under an Ar / H ₂ (content of 5 vol.% H ₂ ) mixed gas reducing atmosphere. After cooling it slowly, it was pulverized again to prepare LiFePO ₄ containing carbon.

Comparative Example 1

The Fe ²⁺ -containing compound was mixed with FeC ₂ O ₄ .2H ₂ O, lithium salt with Li ₂ CO ₃ , phosphate (NH ₄ ) ₂ HPO ₄ in a molar ratio of 1: 0.5: 1.

3 parts by weight of acetylene black was added to the mixture with respect to 100 parts by weight of the mixture, and the mixture was mixed and ground for about 3 to 4 hours using a planetary ball mill to prepare a mixed product.

The resulting mixed product was calcined by holding at 750 ° C. for 10 hours under a reducing atmosphere of an Ar / H ₂ (H ₂ content 5% by volume) mixed gas. After cooling it slowly, it was pulverized again to prepare LiFePO ₄ containing carbon.

Test Example 1: XRD Structure Analysis

The olivine-based positive electrode active materials of Examples 1 to 2, Example 5 and Comparative Example 1 were subjected to an X-ray diffraction pattern using an X-ray diffraction analyzer (trade name: Rint-2200, company name: Rigaku, Japan) and CuKα rays. It measured and the result is shown in FIG. As shown in FIG. 1, the LiFePO 4 powders prepared in Examples 1 to 2 and 5 and Comparative Example 1 are single phase, and it can be confirmed that the peaks of the standard LiFePO ₄ compounds are consistent with all peaks.

Test Example 2 Evaluation of Electrochemical Properties

The initial discharge capacity and cycle life characteristics of the olivine-based positive active materials of Examples 1 to 2 and 5 and Comparative Example 1 were measured, and the results are shown in FIG. 2.

The cycle life characteristics shown in FIG. 2 show that the lithium half battery including the positive electrode active materials of Examples 1 to 2 and 5 and Comparative Example 1 was charged and discharged at 0.5 C for 30 times, and the discharge capacity thereof. The lithium half cell was manufactured by a conventional method using an electrolyte including a positive electrode including the positive electrode active material, a lithium metal counter electrode, and an ethylene carbonate and ethyl methyl carbonate (1: 2 volume ratio) non-aqueous organic solvent in which 1M LiPF ₆ was dissolved. .

As shown in FIG. 2, the battery including the cathode active materials of Examples 1 to 2 and 5 has an initial capacity similar to that of Comparative Example 1, but has a higher cycle characteristic than that of Comparative Example 1 as the charge and discharge cycle is repeated. You can see it.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings. Naturally, it belongs to the scope of the invention.

1 is a graph analyzing the XRD structure of Example 1, Example 2 and Example 5 of the present invention, and the positive electrode active material prepared according to Comparative Example 1.

2 is a graph showing battery characteristics including Example 1, Example 2 and Example 5 of the present invention, and the positive electrode active material prepared according to Comparative Example 1. FIG.

Claims (12)

Mixing lithium phosphate (LiH ₂ PO ₄ ) and an iron precursor compound; Adding a conductive carbon material to the mixture to prepare a mixed product; Firing the mixed product; Including the process, In the process of mixing the lithium phosphate (LiH ₂ PO ₄ ) and the iron precursor, Li ₂ CO ₃ , LiOH or a mixture thereof is further added The manufacturing method of the positive electrode active material for lithium secondary batteries represented by following General formula (1). [Formula 1] LiFePO ₄ The method of claim 1, The iron precursor compound is iron oxalate (FeC ₂ O ₄ · 2H ₂ O), iron acetate (Fe (CH ₃ COO) ₂ ) or a mixture thereof. The method of claim 1, A method for producing a positive electrode active material for a lithium secondary battery in which the mixing ratio of lithium phosphate lithium (LiH ₂ PO ₄ ) and the iron precursor compound is from 1: 1 to 1.05: 1 molar ratio. The method of claim 1, The addition amount of the said conductive carbon material is 1-10 weight part with respect to 100 weight part of said mixtures, The manufacturing method of the positive electrode active material for lithium secondary batteries. The method of claim 1, The firing step is a method for producing a positive electrode active material for a lithium secondary battery that is carried out at 600 to 850 ℃. The method of claim 1, The firing step is a method for producing a positive electrode active material for a lithium secondary battery that is carried out in an inert atmosphere or a reducing atmosphere. delete The method of claim 1, The amount of the Li ₂ CO ₃ , LiOH or a mixture thereof is 0.05 to 0.1 mole per 1 mole of lithium hydride phosphate (LiH ₂ PO ₄ ). The method of claim 1, Hydrogenated lithium phosphate (LiH ₂ PO ₄₎ and then subjected to a step of mixing an iron precursor, and a method for producing a cathode active material for a lithium secondary battery is to before the step of adding the conductive carbon material, further subjected to a plastic process. 10. The method of claim 9, Li ₂ CO ₃ , LiOH or a mixture thereof is further added after the plasticity step and before the step of adding the conductive carbon material. The method of claim 10, The amount of the Li ₂ CO ₃ , LiOH, or a mixture thereof is 0.05 to 0.1 mole with respect to 1 mole of lithium hydride phosphate (LiH ₂ PO 4). A positive electrode comprising a positive electrode active material prepared by the method of any one of claims 1 to 6 and 8 to 11; A negative electrode including a negative electrode active material; And Electrolyte Lithium secondary battery comprising a.

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