KR100814329B1 - Negative active material, manufacturing method thereof and lithium secondary battery comprising the same - Google Patents

Abstract

An anode active material is provided to improve electrochemical properties including conductivity and charge/discharge characteristics, and to inhibit a swelling phenomenon during repeated charge/discharge cycles. An anode active material for a lithium secondary battery comprises a composite of FexMnySi (wherein each of x and y is greater than 0 and equal to or less than 2) doped with a dopant, wherein the composite of FexMnySi is coated with a carbon precursor and then heat treated. The carbon precursor is at least one material selected from the group consisting of pitch and conductive polymers. The carbon precursor is coated on the composite in an amount of 2-20 parts by weight based on 100 parts by weight of the composite.

Description

Negative electrode active material. The manufacturing method and a lithium secondary battery having the same {Negative Active Material, Manufacturing Method and And Lithium Secondary Battery Comprising The Same}

1 is a diagram measuring the electrical conductivity according to the amount of dopant,

2 is an XRD diffraction analysis result with or without pitch coating according to an embodiment of the present invention;

3 and 4 are FE-SEM picture with or without pitch coating according to an embodiment of the present invention,

5 is a thermal behavior analysis results using TGA of the FeMnSi composite according to an embodiment of the present invention,

6 and 7 are the results of the constant current charge and discharge test of the lithium secondary battery using the FeMnSi composite according to an embodiment of the present invention,

8 is a schematic cross-sectional view of a negative electrode active material according to an embodiment of the present invention.

** Description of the main symbols in the drawings *

1: lithium secondary battery 2: negative electrode

3: anode 4: separator

5: battery container 6: sealing member

The present invention relates to a negative electrode active material, a method for manufacturing the same, and a lithium secondary battery having the same, and more particularly, to an anode active material including a Fe _x Mn _y Si composite doped with a dopant, a method for manufacturing the same, and a lithium secondary battery having the same It is about.

With the rapid development of technology in the portable information and communication industry, these power sources are also being used as high-performance lithium secondary batteries, and demand is increasing rapidly. In addition, countries around the world are competing for technology to develop high performance lithium batteries. The performance improvement of the lithium secondary battery is possible by the performance improvement of the three core components of the positive electrode, the negative electrode, and the electrolyte.

Lithium secondary battery is a broad concept that includes not only secondary battery using lithium metal but also lithium ion secondary battery, and has high voltage and high energy density. It is also divided into a gel polymer battery using a mixture of polymers and a solid polymer battery using pure polymers.

The core components of a lithium secondary battery are the positive electrode, the negative electrode, and the electrolyte.

The lithium secondary battery is mainly composed of a positive electrode, a negative electrode, an electrolyte, a separator, a packaging material, and the like. The positive electrode is formed by binding a mixture of a positive electrode active material, a conductive agent, and a binder to a current collector. Lithium transition metal compounds such as LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , and LiMnO ₂ are mainly used as positive electrode active materials, and these materials have an electrochemical potential as lithium ions are intercalated / deintercalated into the crystal structure. high.

Lithium metal, carbon or graphite is mainly used as the negative electrode active material and has a low electrochemical reaction potential as opposed to the positive electrode active material.

The electrolyte is mainly composed of LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ , LiPF ₆ , LiBF ₄ , LiClO ₄ , LiN ( A salt containing lithium ions such as SO ₂ C ₂ F ₅ ) ₂ is dissolved and used.

In addition, the separator, which electrically insulates the positive electrode and the negative electrode and provides a passage of ions, mainly uses a polyoletin-based polymer such as porous polyethylene. As an exterior material that protects the contents of the battery and provides an electrical passage to the outside of the battery, a metal can or a packaging material composed of aluminum and several layers of polymer layers is mainly used.

Although lithium secondary batteries are the highest performance secondary batteries in existence, they require higher performance batteries in terms of electronic devices. High performance of lithium secondary batteries plays an important role in improving the characteristics of the positive electrode and the negative electrode, and the development of high performance negative electrode material is an important problem.

Significant improvements in the specific amount of the anode material have been made. The current graphite material has a theoretical specific capacity of 372 mAh / g and a density of 2.2 g / ml, but the silicon currently under development has a significantly higher value of 4200 mAh / g of theoretical capacity and a density of 2.33 g / ml. Lithium intercalation potential also shows similar characteristics as graphite. However, in the case of silicon materials, the electrical conductivity is low as ˜10-4 S / cm, which is a semiconductor region, and has a problem that volume expansion occurs up to 297% (Li ₂₁ Si ₅ ) due to lithium insertion.

 The present invention is to solve the above problems, to provide a negative electrode active material based on a silicon material doped with a small amount of boron (Boron), arsenic (As), phosphorus (P), etc. improved electrical conductivity For the purpose of

In addition, by forming a composite of the iron (Fe) and manganese (Mn) with the silicon in a silicon material doped with a dopant improved electrical conductivity to provide a negative electrode active material that can suppress the volume expansion according to the cycle of the silicon The purpose.

In addition, it is an object to pitch coating the composite to further improve the electrical conductivity, improve the performance, to provide a high capacity negative electrode active material of improved properties.

In addition, an object of the present invention is to provide a method for producing a negative electrode active material having the above characteristics and a lithium secondary battery using the same.

The present invention for achieving the above object,

In the negative electrode active material of a lithium secondary battery, it provides a negative electrode active material comprising a Fe _x Mn _y Si (0 <x ≤ 2, 0 < _y ≤ 2) composite doped with a dopant. In addition, x and y values of the Fe _x Mn _y Si composite is preferably in the range of 0.9 to 1.1, respectively. The x value of the FexMnySi composite may be in the range of 0.4 to 0.6, the y value is in the range of 0.0 to 0.2, or the x value is in the range of 0.0 to 0.2, and the y value is in the range of 0.4 to 1.2, respectively.

In addition, the Fe _x Mn _y Si composite provides a negative electrode active material, characterized in that the heat treatment after coating with a carbon precursor.

In addition, the carbon precursor provides a negative electrode active material, characterized in that at least one selected from the pitch (Pitch), and the conductive polymer.

In addition, the carbon precursor provides a negative electrode active material, characterized in that the coating of 2 to 20 parts by weight based on 100 parts by weight of the Fe _x Mn _y Si composite.

In addition, the Fe _x Mn _y Si composite provides a negative electrode active material further comprises a conductive metal to improve conductivity.

In addition, the Fe _x Mn _y Si composite doped with the dopant provides a negative electrode active material, characterized in that it is prepared using a silicon doped with a dopant.

In addition, the dopant provides a negative electrode active material, characterized in that at least one selected from boron (Boron), arsenic (As) and phosphorus (Phosphorus).

The present invention also provides a process for preparing a Fe _x Mn _y Si (0 <x≤2, 0 <y≤2) composite by mixing iron (Fe), silicon (Si) and manganese (Mn); Putting a carbon precursor in a solvent to form a coating solution and coating the Fe _x Mn _y Si composite by mixing and stirring the coating solution; And heat-treating a Fe _x Mn _y Si composite coated with the carbon precursor.

In addition, the method for producing the Fe _x Mn _y Si composite are mixed mechanically using a ball miller (ball miller) it provides a method for preparing a negative active material, characterized in that for preparing the Fe _x Mn _y Si composite.

In addition, at least one of the above steps provides a method for producing a negative electrode active material, characterized in that performed in an inert gas atmosphere.

In addition, the inert gas provides a method for producing a negative electrode active material, characterized in that the argon (Ar) gas.

In addition, the heat treatment step provides a method for producing a negative electrode active material, characterized in that performed in the range of 800 ~ 1400 ℃.

The present invention also provides a lithium secondary battery including a negative electrode including a negative electrode active material and a positive electrode and an ion conductor including a positive electrode active material, wherein the negative electrode active material is doped with a dopant Fe _x Mn _y Si (0 <x≤2, Provided is a lithium secondary battery comprising 0 <y ≤ 2).

In addition, the negative electrode active material provides a lithium secondary battery, characterized in that the above-described negative electrode active material.

In addition, the negative electrode active material provides a lithium secondary battery, characterized in that further comprises germanium (Gr).

In addition, the negative electrode provides a lithium secondary battery, characterized in that further comprises a carbon black (Super P Black) as a conductive material.

Hereinafter, the present invention will be described in more detail.

First, the negative electrode active material according to the present invention will be described.

The negative electrode active material according to the present invention is characterized in that it comprises a Fe _x Mn _y Si (0 <x ≤ 2, 0 < _y ≤ 2) composite doped with a dopant. The Fe _x Mn _y Si composite may be heat-treated after coating with a carbon precursor. In addition, a negative electrode active material used in the technical field of the present invention may be mixed and used in the present invention.

Fe _x Mn _y Si composite of the present invention is characterized in that it is doped with a dopant to increase the electrical conductivity. As the dopant, any material that serves to increase the electrical conductivity is included in the present invention. Preferred examples include boron, arsenic, phosphorus, and the like, and may be used alone or in combination.

The amount of the dopant may be added in a general addition amount, but is not limited but is preferably included 0.01 to 10 parts by weight based on 100 weight of silicon.

In the case of silicon, there is a problem that the electrical conductivity is very low because it is close to the insulator. When forming the composite, when the composite is formed using silicon doped with a dopant, the electrical conductivity of the Fe _x Mn _y Si composite may be more effectively increased. Can be. Silicon doped with the dopant is not particularly limited, and includes all of single crystal, polycrystalline and amorphous silicon, and the type of dopant is not particularly limited.

The mixing ratio of the iron, manganese and silicon, that is, x, y indicating the atomic ratio is not limited, respectively, but is preferably 0 <x ≤ 2, and particularly, x, y is preferably in the range of 0.9 to 1.1. The x value of the FexMnySi composite may be in the range of 0.4 to 0.6, the y value is in the range of 0.0 to 0.2, or the x value is in the range of 0.0 to 0.2, and the y value is in the range of 0.4 to 1.2, respectively. The values of x, y and the like also include mixed weight ratios within an error range and an equivalent range.

In addition, the Fe _x Mn _y Si composite may be coated with a carbon precursor. By coating with the carbon precursor can further increase the electrical conductivity, it is possible to more efficiently suppress the expansion of the composite. The coating amount of the carbon precursor is not limited. Preferably it is preferably coated with 2 to 20 parts by weight based on 100 parts by weight of the Fe _x Mn _y Si composite. If the coating amount is out of the range of the coating amount is a small amount and the effect may be slightly lower the crystallinity of the composite.

Further, after coating with the carbon precursor, heat treatment is more preferable. Carbonization through heat treatment can result in carbon coating to further improve properties. The condition of the heat treatment is not limited, but the temperature is gradually increased to heat treatment for 30 minutes to 2 hours in the 800 ~ 1400 ℃ range.

Examples of the carbon precursor are not limited, but at least one selected from a pitch and a conductive polymer. The conductive polymer may be conductive in itself. Examples of the conductive polymer may include polyaniline (PAn), polyacetylene, polypyrrole, polythiophene, and the like. The conductive polymer may be a conductive polymer doped with hydrochloric acid or the like.

In addition, the Fe _x Mn _y Si composite may further include a conductive metal to improve conductivity. Examples of the conductive metal include metals that are used or expected as active materials in the art, and are well known and will not be described.

The negative electrode active material according to the present invention is not limited as long as it is a battery using an intercalation / deintercalation phenomenon of ions, and may be applied as a negative electrode active material.

Hereinafter will be described a method of manufacturing a negative electrode active material according to the present invention. Description of the following manufacturing method also includes a description of the negative electrode active material.

Method for producing a negative electrode active material according to the present invention,

Iron (Fe), silicon (Si) and manganese (Mn) is mixed to prepare a Fe _x Mn _y Si (0 <x ≤ 2, 0 < _y ≤ 2) composite, putting a carbon precursor in a solvent to form a coating solution And mixing and stirring the Fe _x Mn _y Si composite with the coating solution, and heat treating the Fe _x Mn _y Si composite coated with the carbon precursor.

At least one of each of the steps is preferably carried out in an inert gas atmosphere, the inert gas is preferably argon (Ar) gas.

In addition, at least one of the above steps is preferably to control the particle size by grinding the obtained result. Grinding method is well known in the art and accordingly.

A step of producing the Fe _x Mn _y Si composite is a mixture of iron (Fe), manganese (Mn) and silicon (Si) is a step for preparing a Fe _x Mn _y Si composite. Compositions x and y of the composite are omitted because they have been described above.

The method of preparing the Fe _x Mn _y Si composite by mixing the above components is not limited, but an alloying method may be used, and in particular, the alloy may be mechanically rotated while rotating the planetary ball miller. The rotation speed is not limited but rotates at 50 to 200 rpm, and the time is appropriate for 20 to 100 hours, but may be modified as necessary. The ball used in the ball miller may use a kind, but various kinds of balls having different diameters may be used. The alloy container preferably uses a sealed container to prevent oxidation of the material due to the incorporation of oxygen and moisture and is carried out under an inert gas, in particular argon gas atmosphere.

After the Fe _{1 - x} Mn _x Si ₂ composite is not limited, it is preferable to adjust the particle size by grinding and sieving the particles.

Next, the step of coating the composite with a carbon precursor will be described. First, a carbon precursor is added to a solvent to form a coating solution, and then, the Fe _x Mn _y Si composite is added to the coating solution, mixed with the coating solution, and stirred to coat. The solvent is not limited, but an organic solvent, particularly tetrahydrofuran (THF) is preferable. The carbon precursor is omitted because it has been described above.

Next, after the coating is finished, it is more preferable to heat treatment. The heat treatment can further stabilize the composite coated with pitch. The heat treatment is not limited, but is gradually heated to a heat treatment for 30 minutes to 2 hours in the 800 ~ 1400 ℃ range.

Physical properties of the material prepared according to the embodiment of the present invention manufactured by the above process was measured and the measurement results will be described in more detail in Examples and Experimental Examples to be described below.

Hereinafter, a lithium secondary battery having a negative electrode active material according to an embodiment of the present invention will be described in detail.

In a lithium secondary battery having a negative electrode active material according to the present invention, a lithium secondary battery having a negative electrode including a negative electrode active material and a positive electrode and an ion conductor including a positive electrode active material, the negative electrode active material is doped with a dopant Fe _x Mn _It is characterized by comprising a _y Si (0 <x ≤ 2, 0 < _y ≤ 2) composite. As for the said negative electrode active material, it is more preferable that it is the above-mentioned negative electrode active material.

In addition, germanium (Gr) may be further added to the anode active material. The addition amount is not limited but may be mixed with the Fe _x Mn _y Si composite at a weight ratio of 1: 1.

Except the Fe _x Mn _y Si (0 <x ≤ 2, 0 < _y ≤ 2) composite doped with a dopant can be applied to select the configuration known in the art without limitation. Preferably, the negative electrode may further include carbon black (Super P Black) as a conductive material, and the negative electrode may further include a polyvinylidene fluoride (PVDF) as a binder and a current collector. In addition, the ion conductor may be an electrolyte solution or a polymer electrolyte.

The lithium secondary battery according to an embodiment of the present invention may further include a negative electrode active material known in the art, in addition to the above-described negative electrode active material. That is, although not limited, it may further include lithium metal, non-graphitizable carbon, digraphitizable carbon, natural graphite, artificial graphite, and the like. It is also possible to use more activated carbon.

8 shows a lithium secondary battery 1 according to an embodiment of the present invention. The lithium secondary battery 1 includes a negative electrode 2, an electrode 3, a separator 4 disposed between the negative electrode 2 and the positive electrode 3, the negative electrode 2, the positive electrode 3, and the separator 4. ), The ion conductor impregnated in the ()), the battery container (5), and the sealing member (6) for sealing the battery container (5) as a main portion. The shape of the lithium secondary battery illustrated in FIG. 2 may be in the form of a cylinder, in addition to a cylindrical shape, a square shape, a coin shape, a sheet shape, or the like.

The positive electrode 3 is provided with a positive electrode mixture composed of a positive electrode active material, a conductive material and a binder. The positive electrode active material is a compound capable of reversibly intercalating / deintercalating lithium, including LiMn ₂ O ₄ , LiCoO ₂ , LiNiO ₂ , LiFeO ₂ , V ₂ O ₅ , TiS, MoS, and the like.

As the separator, an olefin porous film such as polyethylene or polypropylene can be used.

The ion conductor may be propylene carbonate (hereinafter referred to as PC), ethylene carbonate (hereinafter referred to as EC), butylene carbonate, benzonitrile, acetonitrile, tetrahydrofuran, 2-methyl tetrahydrofuran, γ-butyrolactone, dioxane, and the like. Solan, 4-methyldioxolane, N, N-dimethylformamide, dimethylacetoamide, dimethyl sulfoxide, dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, dimethyl carbonate ( Hereinafter, DMC), ethyl methyl carbonate (hereinafter EMC), diethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, ethyl butyl carbonate, dipropyl carbonate, diisopropyl carbonate, dibutyl carbonate, diethylene glycol, dimethyl ether LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ , LiPF ₆ , LiBF ₄ , LiClO ₄ , LiN (S) in an aprotic solvent such as or a mixed solvent of two or more of these solvents mixed. O ₂ C ₂ F ₅₎ may be used that prepared by dissolving a mixture of the electrolyte alone or in combination of two or more made of a lithium salt of _2, and so on.

In addition, a polymer solid electrolyte may be used instead of the electrolyte solution. In this case, it is preferable to use a polymer having high ion conductivity with respect to lithium ions, and polyethylene oxide, polypropylene oxide, polyethyleneimine and the like can be used. The solvent and the solute may be added to the polymer of to form a gel.

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>

(a) Preparation of FeMnSi Composite Doped with Dopant

Synthesis of FeMnSi doped with dopant was performed by mechanical ball milling. Silicon (Si) was used by crushing a small amount of boron-doped single crystal silicon wafer, and iron (Fe) had a particle size of less than 53㎛ of High Purity Chemicals, and a purity of 99.9% or more, and manganese (Mn) was used. Silver having a purity of 99% or more of 325 mesh (Aldrich) company or less was used.

The molar ratio of each material was calculated in a milling pot, and a FeMnSi composite doped with a dopant was synthesized through a ball milling method at 300 rpm for 100 hours in an argon (Ar) atmosphere. Ball used was zirconia (zirconia) material and 5, 10㎜ size was used by mixing 1: 2 by weight ratio.

(b) Preparation of pitch coated FeMnSi composite

Pitch coating of the FeMnSi composite doped with the dopant prepared above to increase the conductivity. First, 10 parts by weight of the pitch of FeMnSi was added to tetrahydrofuran (THF) and stirred for 30 minutes to prepare a coating solution, and the prepared FeSiMn composite was prepared, and then stirred for about 30 minutes. After the coating was finished and dried. The heat treatment was performed in an argon (Ar) atmosphere, and the temperature was raised to 1200 ° C. at a rate of 5 ° C./min, and maintained for 1 hour to prepare a pitch coated FeMnSi composite.

(c) Preparation of Lithium Secondary Battery

A lithium secondary battery having an active material including the prepared FeMnSi composite was prepared. In order to investigate the charge and discharge behavior of the synthesized material, a coin cell using Li foil as a counter electrode was fabricated. When manufacturing the electrode, a material in which a FeMnSi composite material and germanium (Gr) were mixed 1: 1 was used, and germanium was made of DAG-68 manufactured by Sodiff Advanced Materials. Super-P Black was used as the conductive material and PVDF was used as the binder, and each composition was set to active material / conductive material / binder = 80/10/10 wt.%. As the electrolyte, 1M LiPF6 + EC / EMC (1/1 vol.%) + VC2% of Techno Semichem Co., Ltd. was used.

Experimental Example

The synthesized FeMnSi confirmed the morphology (morphology) through FE-SEM. FE-SEM analysis was performed using Hitachi S-4800. The thermal behavior of FeSiMn was investigated by TA Q600 series.

In addition, charging and discharging of the manufactured coin cell was performed using Toyo's Toscat-3000 series. Charging was cut off at 1.5V with a constant current of 0.1C rate, and discharge was performed in two ways. The first was a constant current of 0.1C rate and a constant voltage of 0.01C rate up to 0.01V, and the other method was a cut-off condition of a capacity of 700mAh / g.

The experimental results are as follows.

As described above, the reason why it is not commercialized despite the high theoretical capacity of silicon is that the volume expansion is very large and the electrical conductivity is very low when lithium ions are inserted and detached as they are charged and discharged. Pure silicon is close to insulators. To solve this problem, silicon materials with a small amount of dopant are used.

Figure 1 shows the change in resistance according to the concentration of the dopant affects the electron conductivity. As the figure shows, the conductivity increases steadily as the amount of dopant increases. In this experiment, the experiment was performed using a silicon material of 5 × 10 ^-3 cm level.

Figure 2 shows the XRD pattern according to the presence or absence of the pitch coating of the prepared FeMnSi. JCPDS analysis showed that the peaks of FeSi and Si appeared together and the crystallinity was slightly decreased depending on the pitch coating. This result is expected to show a problem in cycle life characteristics, although better in charge and discharge efficiency characteristics due to the improvement of electronic conductivity. Therefore, it is judged that the amount of pitch coating and heat treatment condition are in the above-mentioned ranges.

3 and 4 show FE-SEM photographs after heat treatment before and after pitch coating. The particles of FeMnSi synthesized in FIGS. 3 and 4 were formed in a size of about 10 μm in size from 2 to 3 μm, and a small amount of liquefied pitch was distributed in the case of pitch coated material.

5 is a result of analyzing the thermal behavior of the FeMnSi material synthesized by the ball milling (ballmilling) method synthesized by the above method using TGA, Figure 6 and 7 shows the charge and discharge characteristics of the manufactured lithium secondary battery It is also. As shown, it can be seen that the thermal behavior and the charge and discharge characteristics are excellent.

The negative electrode active material and the lithium secondary battery according to the present invention, as a result of analyzing physical and electrochemical properties, are excellent in electrical conductivity, and excellent in electrochemical properties such as charge and discharge characteristics, and are industrially useful.

Claims (20)

delete In the negative electrode active material of a lithium secondary battery, An anode active material comprising a Fe _x Mn _y Si (0 <x ≤ 2, 0 < _y ≤ 2) composite doped with a dopant, The Fe _x Mn _y Si composite is coated with a carbon precursor and then heat-treated negative electrode active material. The negative active material of claim 2, wherein the carbon precursor is selected from at least one of a pitch and a conductive polymer. The negative active material of claim 2, wherein the carbon precursor is coated with 2 to 20 parts by weight based on 100 parts by weight of the Fe _x Mn _y Si composite. In the negative electrode active material of a lithium secondary battery, An anode active material comprising a Fe _x Mn _y Si (0 <x ≤ 2, 0 < _y ≤ 2) composite doped with a dopant, The Fe _x Mn _y Si composite is a negative electrode active material, characterized in that it further comprises a conductive metal to improve conductivity. In the negative electrode active material of a lithium secondary battery, An anode active material comprising a Fe _x Mn _y Si (0 <x ≤ 2, 0 < _y ≤ 2) composite doped with a dopant, The Fe _x Mn _y Si composite doped with the dopant is manufactured using silicon doped with a dopant. In the negative electrode active material of a lithium secondary battery, An anode active material comprising a Fe _x Mn _y Si (0 <x ≤ 2, 0 < _y ≤ 2) composite doped with a dopant, The x, y value of the Fe _x Mn _y Si composite is each in the range of 0.9 to 1.1, the negative electrode active material. delete In the negative electrode active material of a lithium secondary battery, An anode active material comprising a Fe _x Mn _y Si (0 <x ≤ 2, 0 < _y ≤ 2) composite doped with a dopant, The dopant is at least one selected from boron (Boron), arsenic (As) and phosphorus (Phosphorus). Mixing Fe (Fe), silicon (Si) and manganese (Mn) to produce a Fe _x Mn _y Si (0 <x≤2, 0 <y≤2) composite; Putting a carbon precursor in a solvent to form a coating solution and coating the Fe _x Mn _y Si composite by mixing and stirring the coating solution; And And heat-treating the Fe _x Mn _y Si composite coated with the carbon precursor. The method of claim 10, wherein the manufacturing of the Fe _x Mn _y Si composite comprises using a ball miller to mechanically mix iron, manganese, and silicon to produce the Fe _x Mn _y Si composite. The manufacturing method of the negative electrode active material. The method of claim 10, wherein at least one of the steps is performed in an inert gas atmosphere. The method of claim 12, wherein the inert gas is argon (Ar) gas. The method of claim 10, wherein the heat treatment is performed at 800 to 1400 ° C. 12. delete In a lithium secondary battery provided with a negative electrode including a negative electrode active material, a positive electrode containing a positive electrode active material and an ion conductor, The negative electrode active material is a lithium secondary battery comprising Fe _x Mn _y Si (0 <x ≤ 2, 0 < _y ≤ 2) doped with a dopant, The said negative electrode active material is a negative electrode active material in any one of Claims 2-7, The lithium secondary battery characterized by the above-mentioned. The lithium secondary battery of claim 16, wherein the anode active material further comprises germanium (Gr). The lithium secondary battery of claim 16, wherein the negative electrode further comprises carbon black (Super P Black). The lithium secondary battery of claim 16, wherein the anode further comprises polyvinylidene fluoride (PVDF) as a binder. The lithium secondary battery of claim 16, wherein the ion conductor is an electrolyte or a polymer electrolyte.

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