METHOD FOR MANUFACTURING BINARY Li-COMPOUND / CARBON COMPOSITE, ELECTRODE MATERIALS FOR SECONDARY BATTERY INCLUDING THE COMPOSITE MANUFACTURED THEREBY AND SECONDARY BATTERY INCLUDING THE SAME

Abstract

The present invention relates to a method for manufacturing a binary lithium compound / carbon composite, comprising: (a) synthesizing a binary lithium compound (LixA) represented by the following chemical formula; (b) preparing a mixed powder of the binary lithium compound (LixA) and carbon (C); and (c) applying mechanical energy to the mixed powder of the binary lithium compound (LixA) and carbon (C) to prepare a composite of the binary lithium compound (LixA) and carbon (C); an electrode material for a secondary battery comprising the binary lithium compound / carbon composite prepared thereby; and a secondary battery comprising the same. [Chemical Formula] LixA (In the above chemical formula, X ≤ 4.4, and A is one element selected from Sn, Bi, Sb, Si, Ge, P, B, Al, Ga, In, Zn, Ag, As, S, Se, and Te).

Description

Technology Field

[0001] The present invention relates to a method for manufacturing a composite that can be used as an electrode active material for a secondary battery, an electrode material for a secondary battery comprising a binary lithium compound / carbon composite manufactured thereby, and a secondary battery comprising the same. Background Technology

[0002] Lithium-ion rechargeable batteries, the most widely used representative energy storage devices worldwide, are widely utilized in various fields, including portable electronic devices, medium and large electric vehicles, and energy storage systems (ESS). Although graphite is currently used as the anode material in commercially available lithium-ion rechargeable batteries, there are limitations in realizing battery systems with higher energy density due to graphite's limited theoretical capacity (372 mAh / g).

[0003] Currently, lithium secondary battery anode materials are known to be classified into lithium metal, carbon-based, alloy-based, and oxide-based types. Lithium metal anodes have the highest theoretical capacity (3860 mAh / g) and the lowest potential (-3.04 V vs. standard hydrogen electrode), but they present serious safety issues due to dendrites formed on the electrode surface during charging and discharging. In the case of carbon-based anodes, hard and soft carbons have been commercialized in addition to graphite, but they have the problem of low initial efficiency due to a small discharge capacity compared to the initial charge capacity. Alloy-based anode materials are electrode materials utilizing metals that can be electrochemically alloyed with lithium, and among them, research is actively underway to apply Group IV elements, namely silicon (Si, theoretical capacity: 4200 mAh / g), tin (Sn, theoretical capacity: 993 mAh / g), and germanium (Ge, theoretical capacity: 1383 mAh / g), as anode active materials. However, alloy-based cathode materials exhibit significant volume changes during charging and discharging, and the resulting stress causes the breakdown of the electrode active material, leading to a major problem of capacity reduction with each cycle. Finally, while oxide-based cathode materials show more stable lifespan characteristics than alloy-based materials, they suffer from low initial efficiency due to the irreversible Li2O phase formed during initial charging and discharging, and also have a higher reaction potential compared to other cathode materials. Prior art literature

[0004] Republic of Korea Published Patent No. 10-2001-0076586 (Publication Date: Aug. 16, 2001) Republic of Korea Published Patent No. 10-2016-0025547 (Publication Date: March 8, 2016) Republic of Korea Published Patent No. 10-2016-0002281 (Publication Date: January 7, 2016) The problem to be solved

[0005] The objective of the present invention is to provide a method for manufacturing a new composite electrode active material for a lithium-ion secondary battery that exhibits excellent charge / discharge characteristics and high initial efficiency by combining a binary lithium compound obtained by a simple solid-state synthesis method with carbon.

[0006] In addition, the present invention aims to provide a novel electrode active material for a lithium secondary battery comprising a composite prepared by the above method, and a secondary battery comprising the same. means of solving the problem

[0007] The present invention for solving the above problem comprises: (a) a binary lithium compound (Li represented by the following chemical formula) x A) a step of synthesizing, (b) the binary lithium compound (Li x A) a step of preparing a mixed powder of carbon (C), and (c) the binary lithium compound (Li x Mechanical energy is applied to a mixed powder of A) and carbon (C) to form a binary lithium compound (Li x A method for manufacturing a binary lithium compound / carbon composite is provided, comprising the step of manufacturing a composite of A) and carbon (C).

[0008] [Chemical Formula]

[0009] Li x A

[0010] (In the above chemical formula,

[0011] X ≤ 4.4 and,

[0012] A is one element selected from Sn, Bi, Sb, Si, Ge, P, B, Al, Ga, In, Zn, Ag, As, S, Se, and Te)

[0013] In addition, the above binary lithium compound (Li xA) The step (a) of synthesizing A) comprises: (a-1) a step of preparing a mixed powder of lithium (Li) and element A powder; and (a-2) a step of applying mechanical energy or thermal energy to the mixed powder of lithium (Li) and element A powder to produce a binary lithium compound (Li x A) provides a method for manufacturing a binary lithium compound / carbon composite characterized by including a step of synthesizing A).

[0014] In addition, a method for manufacturing a binary lithium compound / carbon composite is provided, characterized by applying mechanical energy to a high-energy spex mill, a vibrotary mill, a Z-mill, a planetary ball mill, or an attrition mill in step (a-2).

[0015] In addition, a method for manufacturing a binary lithium compound / carbon composite is provided, characterized by applying thermal energy to a tube furnace, electric furnace, box furnace, or vacuum furnace in step (a-2).

[0016] In addition, a method for manufacturing a binary lithium compound / carbon composite is provided, characterized by manufacturing a binary lithium compound powder having an average diameter of 1 nm or more and 500 μm or less in step (a).

[0017] In addition, a method for manufacturing a binary lithium compound / carbon composite is provided, characterized by applying mechanical energy to a high-energy spex mill, a vibrotary mill, a Z-mill, a planetary ball mill, or an attrition mill in step (c) to composite the binary lithium compound with carbon.

[0018] In addition, a method for manufacturing a binary lithium compound / carbon composite is provided, characterized by manufacturing a composite powder containing binary lithium compound crystal grains having an average diameter of 1 nm or more and 100 nm or less in step (c).

[0019] In addition, a method for manufacturing a binary lithium compound / carbon composite is provided, characterized by manufacturing a composite comprising 50 to 90 wt% of a binary lithium compound and 10 to 50 wt% of carbon in step (c).

[0020] In addition, in another aspect of the invention, the present invention provides an electrode active material for a lithium secondary battery comprising a binary lithium compound / carbon composite manufactured by the above manufacturing method, and a lithium secondary battery comprising the same. Effects of the invention

[0021] According to the method for manufacturing a binary lithium compound / carbon composite of the present invention, a binary lithium compound / carbon composite can be manufactured simply and efficiently by compounding a binary lithium compound synthesized through a simple solid-state synthesis method, such as ball milling or heat treatment, with carbon, without undergoing complex and inefficient processes such as chemical methods.

[0022] In addition, when the binary lithium compound / carbon composite prepared by the above method is used as an electrode active material for a lithium secondary battery, a secondary battery system having excellent cycle life while maintaining high initial efficiency and capacity can be realized. Brief explanation of the drawing

[0023] FIG. 1a is a process flow diagram describing each step of the method for manufacturing a binary lithium compound / carbon composite according to the present invention in sequence. FIG. 1b is a process flow diagram describing each step in order constituting step (a), which is a process for synthesizing a binary lithium compound in a method for manufacturing a binary lithium compound / carbon composite according to the present invention. FIG. 2 is a conceptual diagram illustrating the synthesis steps of a binary lithium compound according to one embodiment of the present invention. FIG. 3 is a schematic diagram of a lithium secondary battery comprising a binary lithium compound / carbon composite according to the present invention as an electrode active material. FIG. 4 is a schematic diagram of a lithium secondary battery negative electrode comprising a binary lithium compound / carbon composite according to the present invention as an electrode active material. Figure 5a is a binary phase diagram of lithium (Li) and tin (Sn). Figure 5b is a binary phase diagram of lithium (Li) and antimony (Sb). Figure 5c is a binary phase diagram of lithium (Li) and bismuth (Bi). Figure 6a is a graph of the X-ray diffraction analysis results of a binary lithium compound (LiSn) according to one embodiment of the present invention. FIG. 6b is a graph of the X-ray diffraction analysis results of a binary lithium compound (Li2Sb) according to one embodiment of the present invention. FIG. 6c is a graph of the X-ray diffraction analysis results of a binary lithium compound (LiBi) according to one embodiment of the present invention. Figure 7a is the result of high-resolution transmission electron microscopy (HRTEM) analysis of a binary lithium compound (LiSn) / carbon composite according to one embodiment of the present invention. FIG. 7b is the result of high-resolution transmission electron microscopy (HRTEM) analysis of a binary lithium compound (Li2Sb) / carbon composite according to one embodiment of the present invention. FIG. 7c is the result of high-resolution transmission electron microscopy (HRTEM) analysis of a binary lithium compound (LiBi) / carbon composite according to one embodiment of the present invention. FIG. 8a is a graph of the results of a lithium secondary battery charge / discharge experiment of a binary lithium compound (LiSn) / carbon composite electrode according to one embodiment of the present invention. FIG. 8b is a graph of the results of a lithium secondary battery charge / discharge experiment of a binary lithium compound (Li2Sb) / carbon composite electrode according to one embodiment of the present invention. FIG. 8c is a graph of the results of a lithium secondary battery charge / discharge experiment of a binary lithium compound (LiBi) / carbon composite electrode according to one embodiment of the present invention. Figure 9 is a graph of the results of a lithium secondary battery cycle life experiment of a binary lithium compound (LiSn) / carbon composite electrode. Specific details for implementing the invention

[0024] In describing the present invention, if it is determined that a detailed description of related known functions or configurations could unnecessarily obscure the essence of the invention, such detailed description will be omitted.

[0025] Since embodiments according to the concept of the present invention may be subject to various modifications and may take various forms, specific embodiments are illustrated in the drawings and described in detail in this specification or application. However, this is not intended to limit embodiments according to the concept of the present invention to specific disclosed forms, and it should be understood that they include all modifications, equivalents, and substitutions that fall within the spirit and scope of the present invention.

[0026] The terms used herein are merely for describing specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as “comprising” or “having” are intended to specify the existence of the described features, numbers, steps, actions, components, parts, or combinations thereof, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0027] The present invention will be described in detail below.

[0028] A method for preparing a binary lithium compound / carbon composite according to the present invention comprises, as illustrated in FIG. 1a, (a) a binary lithium compound (Li) represented by the following chemical formula x A) a step of synthesizing, (b) the binary lithium compound (Li x A) a step of preparing a mixed powder of carbon (C), and (c) the binary lithium compound (Li x Mechanical energy is applied to a mixed powder of A) and carbon (C) to form a binary lithium compound (Li x A) and the step of manufacturing a composite of carbon (C).

[0029] [Chemical Formula]

[0030] Li x A

[0031] (In the above chemical formula, X ≤ 4.4, and A is one element selected from Sn, Bi, Sb, Si, Ge, P, B, Al, Ga, In, Zn, Ag, As, S, Se, and Te)

[0032] A binary lithium compound (Li represented by the above chemical formula) x A) includes various binary compounds depending on the type of element A and the stoichiometric ratio with lithium, for example, as a Li-Sn binary compound, Li 22 Sn5, Li 17 Sn4, Li 13 Li as a Li-Si binary compound, such as Sn5, Li7Sn2, Li7Sn3, Li5Sn2, LiSn, Li2Sn5, etc. 22 Si5, Li 21 Si5, Li 21 Si8, Li 17 Si4, Li 13 Si4, Li7Si3, Li 12 Li as a Li-Ge binary compound, such as Si7, Li7Si2, Li2Si, LiSi, etc. 22 Ge5, Li 17 Ge4, Li 11Ge6, Li9Ge4, Li7Ge2, Li3Ge, LiGe, etc., as Li-Sb binary compounds such as Li2Sb, Li3Sb, etc., as Li-Bi binary compounds such as LiBi, Li3Bi, etc., as Li-P binary compounds such as Li3P7, LiP7, LiP5, LiP, Li3P, etc., and as Li-B binary compounds such as Li7B6, Li5B4, Li3B 14 , Li 1.8 B 14 , LiB 12.93 etc., as Li-Al binary compounds such as LiAl, Li3Al2, Li9Al4, etc., as Li-Ga binary compounds such as Li3Ga, Li3Ga2, Li5Ga4, Li3Ga2, LiGa, etc., and as Li-In binary compounds Li 13 In3, Li3In2, Li2In, LiIn, etc., as Li-Zn binary compounds such as LiZn, Li2Zn3, LiZn2, Li2Zn5, LiZn4, etc., and as Li-Ag binary compounds such as LiAg, Li 10 There are Ag3, Li9Ag4, etc., Li-As binary compounds such as Li3As, LiAs, etc., Li-S binary compounds such as Li2S, Li2S2, Li2S4, etc., Li-Se binary compounds such as Li2Se, Li3Se, LiSe3, etc., and Li-Te binary compounds such as Li2Te, Li3Te, LiTe3, etc.

[0033] In particular, among the various binary lithium compounds mentioned above, it is preferable to use a compound composed of a phase that is stable under the atmosphere for the manufacture of a composite with carbon.

[0034] The above binary lithium compound (Li x The above step (a), in which the process of synthesizing A) is carried out, comprises, as illustrated in FIG. 1b, (a-1) a step of preparing a mixed powder of lithium (Li) and element A powder, and (a-2) a step of applying mechanical energy or thermal energy to the mixed powder of lithium (Li) and element A powder to produce a binary lithium compound (Li x It is performed by including a step of synthesizing A).

[0035] First, step (a-1) above is a step of preparing a mixed powder by mixing lithium (Li) metal, which is a starting material for the preparation of a compound, and element A powder. The method used to prepare the mixed powder in this step is not particularly limited as long as it is a method that can uniformly mix the lithium (Li) metal and element A powder.

[0036] The lithium (Li) used in the preparation of the mixed powder in this step may be metallic lithium in powder form, as well as lithium obtained by finely grinding metallic lithium in the form of foil, aggregates, etc. For example, if lithium in the form of metal fragments is used, its size is 1 cm 2 It is desirable that it be less than.

[0037] In this step (a-1), the element A powder is not affected by product purity, and it is desirable to consider the effect of moisture when manufacturing a binary lithium compound.

[0038] Next, step (a-2) is a step of synthesizing a binary lithium compound containing lithium and element A from lithium (Li) metal and element A powder by applying mechanical energy or thermal energy to the mixed powder obtained in the previous step, and preferably preparing the most stable binary lithium compound among various binary lithium compounds.

[0039] Figure 2 is a conceptual diagram illustrating the method for preparing a binary lithium compound in step (a-2).

[0040] That is, in step (a-2), mechanical energy is applied to a mixed powder containing lithium (Li) metal and element A powder through ball milling or thermal energy is applied through heat treatment to cause a reaction between the lithium (Li) metal and element A powder to produce a binary lithium compound, and the series of processes for synthesizing, for example, LiSn, Li2Sb, and LiBi as binary lithium compounds can be expressed by the following reaction schemes 1, 2, and 3, respectively.

[0041] <Reaction Equation 1>

[0042] Li + Sn → LiSn

[0043] <Reaction Equation 2>

[0044] 2Li + Sb → Li2Sb

[0045] <Reaction Equation 3>

[0046] Li + Bi → LiBi

[0047] In step (a-2), by using ball milling or heat treatment, which are simple solid-state synthesis methods, to induce a chemical reaction between lithium (Li) metal and element A, the compound can be prepared simply and efficiently without performing conventional chemical synthesis methods.

[0048] In step (a-2), the method of applying mechanical energy to a mixed powder containing lithium (Li) and element A powder to synthesize a binary lithium compound is not particularly limited, but it is preferable to use high-energy ball milling to pulverize the powder.

[0049] For reference, high-energy ball milling can not only atomize powders by applying high energy to reactants through high rotational force, but also induce chemical reactions in the reactants through maximized diffusion forces between powder particles.

[0050] The above high-energy ball milling can be performed by any known ball milling device used for high-energy ball milling, such as a vibrotary-mill, Z-mill, planetary ball-mill, or attrition-mill. For reference, in a typical high-energy ball milling process, the temperature can rise to 200°C during ball milling, and the pressure can also be on the order of 6 GPa.

[0051] Meanwhile, a more specific method for preparing the compound according to the present invention through a solid-state synthesis method using high-energy ball milling is as follows.

[0052] First, uniformly mixed lithium (Li) metal powder and element A (Sn, Sb, Bi, etc.) powder are loaded into a cylindrical vial along with balls and mounted on a high-energy ball milling machine, and then mechanical synthesis is performed at a rotational speed of 500 to 2000 revolutions per minute to produce binary lithium compounds (LiSn, Li2Sb, LiBi, etc.). The ball milling can be performed for 1 to 24 hours. Here, the weight ratio of balls to the mixture is maintained, for example, at 10:1 to 30:1, and the mechanical synthesis is prepared in a glove box under an argon gas atmosphere to minimize the influence of oxygen and moisture.

[0053] In addition, in step (a-2), the method of applying thermal energy to a mixed powder containing lithium (Li) and element A powder to synthesize a binary lithium compound is not particularly limited, and, for example, 100 to the mixed powder in a furnace such as a tube furnace, electric furnace, box furnace, or vacuum furnace o C~1000 o The reaction between lithium and element A can be induced by applying thermal energy of C.

[0054] Next, in step (b) above, the binary lithium compound (Li synthesized in step (a) x A) A step of preparing a mixed powder by mixing powder and carbon (C) powder, wherein the method used to prepare the mixed powder in this step is a binary lithium compound (Li x A) As long as it is a method that can uniformly mix the powder and carbon (C) powder, it is not particularly limited.

[0055] The carbon-based material constituting the carbon powder introduced in step (b) is not particularly limited in type, but may be one or more combinations selected from graphite-based carbon such as natural graphite, artificial graphite, expanded graphite and graphene; carbon black-based carbon such as Super P, Super C, Acetylene black, Denka black, Ketjen black, Channel black, Furnace black, Thermal black, Contact black, Lamp black; active carbon-based carbon; carbon nanostructures such as carbon fiber, carbon nanotube (CNT), fullerene, and graphene; hard carbon; and soft carbon.

[0056] Meanwhile, it is preferable that the above mixed powder contains 50 to 90 wt% of a binary lithium compound and 10 to 50 wt% of carbon.

[0057] Subsequently, in step (c) above, the binary lithium compound (Li xA) A binary lithium compound / carbon complex is produced by applying mechanical energy to a mixture of powder and carbon (C) powder to complex the binary lithium compound with carbon.

[0058] When the binary lithium compound / carbon composite produced by the above-described manufacturing method is applied to a secondary battery as a phase containing some lithium prior to application to the secondary battery, particularly when used in a lithium secondary battery, it has high initial efficiency during the initial charging and discharging process, which can resolve the problem of initial efficiency required for secondary battery anode materials. Furthermore, because the volume of the binary lithium compound is partially expanded due to the phase containing some lithium prior to application to the secondary battery, it can resolve the volume expansion problem, which is the biggest problem of alloy-based anode materials. Moreover, it can solve the capacity and initial efficiency limitations of lithium secondary battery anodes with a higher reversible capacity and higher initial efficiency than currently commercialized graphite.

[0059] In addition, in another aspect of the invention, the present invention provides a secondary battery comprising an electrode active material for a secondary battery comprising a binary lithium compound / carbon composite prepared by the above-described manufacturing method.

[0060] FIG. 3 is a schematic diagram of a lithium secondary battery comprising a binary lithium compound / carbon composite according to the present invention as an electrode active material.

[0061] The secondary battery (1) may include a positive electrode (12), a negative electrode (11), and a separator (13) disposed between the positive electrode (12) and the negative electrode (11). The secondary battery (1) may further include an electrolyte (not shown), a battery container (14), and a sealing member (15) that encloses the battery container (14). Such a secondary battery (1) may be manufactured by stacking the positive electrode (12), the negative electrode (11), and the separator (13) in sequence, and then storing them in the battery container (14) in a wound state.

[0062] FIG. 4 is a schematic diagram of a secondary battery negative electrode comprising a binary lithium compound / carbon composite according to the present invention as an electrode active material.

[0063] The above-mentioned cathode (11) may include a current collector (111) and an active material layer (112) formed on the current collector (111). The active material layer (112) includes a binary lithium compound / carbon composite according to the present invention. The above-mentioned cathode (11) may further include a water-insoluble binder such as polyvinylidene fluoride (PVdF) or a water-soluble binder such as polyethyleneimine, polyaniline, polythiophene, polyacrylic acid (PAA), carboxymethylcellulose (CMC), or styrene-butadiene lever (SBR).

[0064] Embodiments of the present invention are described below. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided to ensure that the disclosed content is thorough and complete and to sufficiently convey the concept of the present invention to those skilled in the art.

[0065] <Example>

[0066] (1) Binary lithium compounds (LiSn, Li) which are intermetallic compounds between lithium (Li) metal and metals (Sn, Sb, Bi, etc.) 2 Manufacture of (Sb, LiBi, etc.)

[0067] Figures 5a, 5b, and 5c show binary phase diagrams of lithium (Li) and metals (Sn, Sb, Bi, etc.), and lithium (Li) and metals (Sn, Sb, Bi, etc.) have various binary compound groups. In this embodiment, a phase (LiSn, Li2Sb, LiBi, etc.) having a specific molar ratio among these groups of lithium (Li) and metal (Sn, Sb, Bi, etc.) compounds was selected and synthesized.

[0068] First, size 1 cm 2Lithium metal fragments of less than 100 mesh and commercially available metal powders (Sn, Sb, Bi, etc.) with a particle size of less than 100 mesh were mixed in a molar ratio of 1:1 or 2:1, then loaded into a cylindrical vial made of SKD11 material with a diameter of 5.5 cm and a height of 9 cm along with 3 / 8-inch balls, mounted on a ball mill (vibrating mill, Spex 8000), and mechanical synthesis was performed at a rotational speed of 900 revolutions per minute.

[0069] At this time, the weight ratio of balls to powder was maintained at 20:1, and mechanical synthesis was prepared in a glove box under an argon gas atmosphere to minimize the influence of oxygen and moisture. The above mechanical synthesis was performed for 3 hours to produce a binary lithium compound.

[0070] Or, size 1 cm 2 A lithium metal piece of less than 100% and a commercially available metal powder (Sn, Sb, Bi, etc.) with a particle size of 100 mesh or less were mixed in a molar ratio of 1:1 or 2:1, and then heat treatment was performed at 400°C for 3 hours using an electric furnace containing a quartz-type tube under an argon atmosphere to prepare a binary lithium compound.

[0071] Figures 6a, 6b, and 6c are graphs showing the X-ray diffraction analysis characteristics of binary lithium compounds (LiSn, Li2Sb, LiBi). The prepared binary lithium compounds (LiSn, Li2Sb, LiBi) can be synthesized by a 1:1 or 2:1 molar ratio of lithium (Li) and metals (Sn, Sb, Bi), and when manufactured using a solid-state synthesis method, they can be easily synthesized in a form ranging from several micrometers to several nanometers. When metals (Sn, Sb, Bi), which are alloy-based anode materials, are used as electrode materials for lithium secondary batteries, a higher capacity can be achieved than that of carbon-based graphite currently commercialized. However, there are issues with poor lifespan characteristics due to volume expansion of alloy-based cathode materials during the charge-discharge process, as well as low initial efficiency caused by the formation of a solid-electrolyte interface (SEI) layer and electrochemical irreversible reactions during the initial charge-discharge process. These problems can be effectively resolved by using binary lithium compounds as electrode materials for lithium secondary batteries, which enable the realization of high reversible capacity and high initial efficiency. Furthermore, since the volume partially expanded prior to the charging process can accommodate volume changes during the subsequent charge-discharge process, lifespan characteristics can be effectively improved. For the preparation of binary lithium compounds (LiSn, Li2Sb, LiBi) used in the embodiments of this study, lithium metal pieces and metal powders are prepared together in a specific molar ratio of 1:1 or 2:1.

[0072] (2) Binary lithium compounds (LiSn, Li 2 Preparation of a composite containing Sb, LiBi) and carbon and evaluation of the initial efficiency characteristics, cycle characteristics, and high-rate characteristics of a secondary battery containing the same

[0073] After mixing the binary lithium compound powder and carbon powder obtained in (1) above in an appropriate ratio, mechanical energy was applied to composite the binary lithium compound and carbon.

[0074] Figures 7a, 7b, and 7c are high-resolution transmission electron microscope (HRTEM) images of the binary lithium compound / carbon composite prepared above. Referring to Figures 7a, 7b, and 7c, it can be confirmed that the binary lithium compound (LiSn, Li2Sb, LiBi) having crystal grains of 10 nm or less is well dispersed in the carbon matrix through the preparation method above, and it can be seen through diffraction pattern (DP), energy dispersive spectroscopy (EDS), and electron energy loss spectroscopy (EELS) analysis that the binary lithium compound (LiSn, Li2Sb, LiBi) is well formed.

[0075] Figures 8a, 8b, and 8c are graphs showing the results of charge-discharge experiments when binary lithium compound / carbon composites are used as electrodes for lithium secondary batteries. Figure 8a shows the charge-discharge results of a LiSn composite, which is an embodiment of the present invention; Figure 8b shows the charge-discharge results of a Li2Sb composite, which is an embodiment of the present invention; and Figure 8c shows the charge-discharge results of a LiBi composite, which is an embodiment of the present invention. The charge and discharge capacities of the LiSn composite in the first cycle were 412 mAh / g and 610 mAh / g, respectively, and the efficiency of the initial cycle was approximately 148%. The charge and discharge capacities of the Li2Sb composite in the first cycle were 415 mAh / g and 602 mAh / g, respectively, and the efficiency of the initial cycle was approximately 145%. The charge and discharge capacities of the first cycle of the LiBi composite were 283 mAh / g and 377 mAh / g, respectively, and the efficiency of the initial cycle was approximately 133%. The fabricated binary lithium compound / carbon composite showed significantly higher values ​​compared to the reversible capacity (approx. 300 mAh / g) and initial efficiency (approx. 90%) of the conventional carbon-based anode.

[0076] Figure 9 is a graph showing cycle characteristic data when a binary lithium compound / carbon composite is used as a negative electrode active material in a lithium secondary battery. In the case of a lithium secondary battery using a LiSn composite, which is the first embodiment of the present invention, as a negative electrode active material, it exhibits excellent lifespan characteristics without capacity change for several cycles at a reaction potential of 0V to 2V.

[0077] Accordingly, it is possible to secure the initial efficiency, which is considered most important in secondary batteries, particularly lithium secondary battery electrodes, and to improve capacity and cycle life. Furthermore, secondary batteries, especially lithium secondary batteries, using the above-mentioned binary lithium compound exhibit higher capacity, initial efficiency, and superior cycle characteristics compared to conventional carbon-based anode materials.

[0078] Although embodiments of the present invention have been described above with reference to the attached drawings, those skilled in the art will understand that the present invention may be implemented in other specific forms without changing its technical concept or essential features. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. Explanation of the symbols

[0079] 1: Lithium secondary battery 11: Negative electrode 12: Anode 13: Separator 14: Battery container 15: Encapsulating member 111: Entire house 112: Active material layer

Claims

Claim 1 (a) A binary lithium compound represented by the following chemical formula (Li x A) A step of synthesizing; (b) the binary lithium compound (Li x A) a step of preparing a mixed powder of carbon (C); and (c) the binary lithium compound (Li x Mechanical energy is applied to a mixed powder of A) and carbon (C) to form a binary lithium compound (Li x A) and a step of preparing a composite of carbon (C); wherein step (a) comprises: (a-1) a step of preparing a mixed powder of lithium (Li) and element A powder; and (a-2) applying thermal energy to the mixed powder of lithium (Li) and element A powder at a temperature of 100°C or higher and 1000°C or lower under an argon atmosphere in a tube furnace, electric furnace, box furnace, or vacuum furnace to prepare a binary lithium compound (Li x A) A method for preparing a binary lithium compound / carbon composite, characterized by including the step of synthesizing; [Chemical Formula]Li x A (in the above chemical formula, X ≤ 4.4, and A is one element selected from Sn, Bi, Sb, Ge, P, B, Al, Ga, In, Zn, Ag, As, S, Se, and Te). Claim 2 delete Claim 3 In claim 1, the binary lithium compound is Li 22 Sn5, Li 17 Sn4, Li 13 A method for preparing a binary lithium compound / carbon complex, characterized in that it is a Li-Sn binary compound that is Sn5, Li7Sn2, Li7Sn3, Li5Sn2, LiSn, or Li2Sn5. Claim 4 A method for manufacturing a binary lithium compound / carbon composite according to claim 1, wherein the binary lithium compound is a Li-Sb binary compound that is Li2Sb or Li3Sb. Claim 5 A method for manufacturing a binary lithium compound / carbon composite, wherein, in claim 1, the binary lithium compound is a Li-Bi binary compound that is LiBi or Li3Bi. Claim 6 delete Claim 7 In claim 1, the binary lithium compound is Li 22 Ge5, Li 17 Ge4, Li 11 A method for preparing a binary lithium compound / carbon complex, characterized in that it is a Li-Ge binary compound that is Ge6, Li9Ge4, Li7Ge2, Li3Ge, or LiGe. Claim 8 A method for manufacturing a binary lithium compound / carbon composite according to claim 1, wherein the binary lithium compound is a Li-P binary compound that is Li3P7, LiP7, LiP5, LiP, or Li3P. Claim 9 In claim 1, the binary lithium compound is Li7B6, Li5B4, Li3B 14 , Li 1.8 B 14 or LiB 12.93 A method for manufacturing a binary lithium compound / carbon composite characterized by being a Li-B binary compound. Claim 10 A method for manufacturing a binary lithium compound / carbon composite according to claim 1, wherein the binary lithium compound is a Li-Al binary compound such as LiAl, Li3Al2, or Li9Al4. Claim 11 A method for manufacturing a binary lithium compound / carbon composite according to claim 1, wherein the binary lithium compound is a Li-Ga binary compound such as Li3Ga, Li3Ga2, Li5Ga4, Li3Ga2, or LiGa. Claim 12 In claim 1, the binary lithium compound is Li 13 A method for preparing a binary lithium compound / carbon composite, characterized in that it is a Li-In binary compound in which In3, Li3In2, Li2In, or LiIn. Claim 13 A method for manufacturing a binary lithium compound / carbon composite according to claim 1, wherein the binary lithium compound is a Li-Zn binary compound such as LiZn, Li2Zn3, LiZn2, Li2Zn5, or LiZn4. Claim 14 In claim 1, the binary lithium compound is LiAg, Li 10 A method for preparing a binary lithium compound / carbon complex, characterized in that it is a Li-Ag binary compound, such as Ag3 or Li9Ag4. Claim 15 A method for manufacturing a binary lithium compound / carbon composite according to claim 1, wherein the binary lithium compound is a Li-As binary compound that is Li3As or LiAs. Claim 16 A method for manufacturing a binary lithium compound / carbon composite, wherein, in claim 1, the binary lithium compound is a Li-S binary compound that is Li2S, Li2S2, or Li2S4. Claim 17 A method for manufacturing a lithium compound / carbon composite according to claim 1, wherein the binary lithium compound is a Li-Se binary compound that is Li2Se, Li3Se, or LiSe3. Claim 18 A method for manufacturing a binary lithium compound / carbon composite comprising, wherein, in claim 1, the binary lithium compound is a Li-Te binary compound that is Li2Te, Li3Te, or LiTe3. Claim 19 delete Claim 20 delete Claim 21 A method for manufacturing a binary lithium compound / carbon composite according to claim 1, characterized in that, in step (a), a binary lithium compound powder having an average diameter of 1 nm or more and 500 μm or less is manufactured. Claim 22 A method for manufacturing a binary lithium compound / carbon composite, characterized in that, in step (c) of claim 1, mechanical energy is applied using a high-energy spex mill, a vibrotary mill, a Z-mill, a planetary ball mill, or an attrition mill. Claim 23 A method for manufacturing a binary lithium compound / carbon composite according to claim 1, characterized in that, in step (c), a composite comprising 50 to 90 wt% of a binary lithium compound and 10 to 50 wt% of carbon is manufactured. Claim 24 A method for manufacturing a binary lithium compound / carbon composite according to claim 1, characterized in that the carbon is one or more selected from the group consisting of graphite-based carbon, carbon black-based carbon, activated carbon-based carbon, hard carbon, soft carbon, and carbon nanostructures. Claim 25 A method for manufacturing a binary lithium compound / carbon composite according to claim 1, characterized in that, in step (c), a composite powder comprising binary lithium compound crystal grains having an average diameter of 1 nm or more and 100 nm or less is manufactured. Claim 26 An electrode active material for a secondary battery comprising a binary lithium compound / carbon composite manufactured by any one of the manufacturing methods of claims 1, 3 to 5, 7 to 18 and 21 to 25. Claim 27 A secondary battery comprising the electrode active material for a secondary battery according to claim 26. Claim 28 delete Claim 29 delete

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