Method for preparing conductive material comprising halide-based solid electrolyte, conductive material prepared using same, and all-solid-state battery comprising same

Abstract

The present invention relates to a method for preparing a conductive material comprising a halide-based solid electrolyte, a conductive material prepared using same, and an all-solid-state battery comprising same. With respect to the conductive material comprising a halide-based solid electrolyte, a linear carbon material is island-coated or conformal-coated with a halide-based solid electrolyte so as to prevent direct contact with the solid electrolyte, thereby enabling oxidation and side reactions of the solid electrolyte in a battery to be suppressed, and improve the interfacial properties with a binder, thereby enabling battery performance to be improved.

Description

Method for manufacturing a conductive material equipped with a halide-based solid electrolyte, a conductive material manufactured thereby, and an all-solid-state battery including the same

[0001] The present invention relates to a conductive material for a battery, and more specifically, to a method for manufacturing a conductive material equipped with a halide-based solid electrolyte, a conductive material manufactured thereby, and an all-solid-state battery comprising the same.

[0002] With the advancement of industry, the development of batteries with high energy density and safety is actively underway. In particular, lithium-ion batteries are being actively commercialized in various information and communication devices and automotive fields. However, lithium-ion batteries have the potential for overheating and fire due to the electrolyte containing flammable organic solvents, so all-solid-state batteries containing a solid electrolyte instead of a liquid electrolyte are being proposed.

[0003] All-solid-state batteries utilize a solid electrolyte, eliminating the risk of leakage from external impacts and possessing high thermal stability, thereby minimizing the possibility of fire or explosion. Representative solid electrolytes for these batteries include sulfide-based, oxide-based, and polymer-based electrolytes. Sulfide-based solid electrolytes can form a wide interface between the electrode and the electrolyte, resulting in high ionic conductivity at room temperature; furthermore, thanks to their excellent ductility, interface formation is facilitated even through cold-pressing processes. While oxide-based solid electrolytes tend to have lower lithium ion conductivity than sulfide-based electrolytes, they offer superior mechanical and electrochemical stability. Additionally, polymer-based solid electrolytes are similar to conventional liquid electrolytes, providing good contact with the electrode and offering cost competitiveness due to their high versatility in manufacturing processes. Among these, sulfide-based solid electrolytes are being actively researched because their high ionic conductivity allows for a significant increase in energy density.

[0004] However, all-solid-state batteries containing sulfide-based solid electrolytes have a problem in which the conductive material added to improve electrode electrical conductivity causes oxidation reactions with the surrounding sulfide-based solid electrolyte due to its inherently high electrical conductivity, generating by-products and seriously affecting electrode stability. To solve this, coating the conductive material with zinc oxide (ZnO) or aluminum oxide (Al2O3) can suppress by-product reactions with the sulfide-based solid electrolyte, but it may result in lower electrical conductivity.

[0005] Therefore, it is necessary to develop conductive materials that can improve the stability and performance of all-solid-state batteries.

[0006] To solve the aforementioned problems, the present invention aims to provide a method for manufacturing a conductive material equipped with a halide-based solid electrolyte capable of increasing electrochemical stability, a conductive material manufactured thereby, and an all-solid-state battery comprising the same.

[0007] In addition, the present invention aims to provide a method for manufacturing a conductive material equipped with a halide-based solid electrolyte that can improve the performance of a battery containing the same by maintaining the intrinsic electrical conductivity of the conductive material, a conductive material manufactured thereby, and an all-solid-state battery containing the same.

[0008] The technical problems of the present invention are not limited to those mentioned above, and other unmentioned technical problems will be clearly understood by those skilled in the art from the description below.

[0009] To achieve the above objective, one aspect of the present invention provides a method for manufacturing a conductive material having a halide-based solid electrolyte, comprising the steps of coating a linear carbon material with a halide-based solid electrolyte precursor solution and heat-treating the linear carbon material coated with the halide-based solid electrolyte precursor solution.

[0010] The above halide-based solid electrolyte precursor solution may include a lithium (Li) halide and at least one metal halide in a solvent and react to form a halide-based solid electrolyte of the following chemical formula 1.

[0011] [Chemical Formula 1]

[0012] Li a M b X6

[0013] In the above chemical formula 1, 1≤a≤3, 0 <b≤1, a+3b=6일 수 있고, 상기 M은 In, Yb, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm 및 Lu 중에서 선택되는 어느 하나의 금속 원소일 수 있고, 상기 X는 F, Cl, Br 및 I 중에서 선택되는 어느 하나 이상의 할로겐 원소일 수 있다.

[0014] The above halide-based solid electrolyte precursor solution may include one or more selected from Li3InCl6, Li3YCl6, Li3YBr6, Li3HoCl6, and Li3ScCl6.

[0015] In the step of coating the halide-based solid electrolyte precursor solution, the process can be carried out by mixing 0.3 to 0.7 parts by weight of the halide-based solid electrolyte precursor solution with respect to 100 parts by weight of the linear carbon material.

[0016] The above heat treatment can be performed at 250 to 290°C for 2 to 4 hours.

[0017] In the above heat treatment step, a halide-based solid electrolyte can be synthesized in the form of islands on the surface of the linear carbon material.

[0018] Prior to the step of coating the above-mentioned halide-based solid electrolyte precursor solution, the method further includes the step of surface-treating the linear carbon material with acid to form oxygen-containing functional groups on the surface, and in the heat treatment step, the halide-based solid electrolyte can be synthesized in a conformal form on the surface of the linear carbon material.

[0019] Another aspect of the present invention provides a conductive material comprising a linear carbon material and a halide-based solid electrolyte provided on the surface of the linear carbon material.

[0020] The above halide-based solid electrolyte can be represented by the following chemical formula 1.

[0021] [Chemical Formula 1]

[0022] Li a M b X6

[0023] In the above chemical formula 1, 1≤a≤3, 0 <b≤1, a+3b=6이고, 상기 M은 In, Yb, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm 및 Lu 중에서 선택되는 어느 하나의 금속 원소이고, 상기 X는 F, Cl, Br 및 I 중에서 선택되는 어느 하나 이상의 할로겐 원소이다.

[0024] The above halide-based solid electrolyte can be coated on the surface of the above linear carbon material in the form of islands.

[0025] The above halide-based solid electrolyte can be coated in a conformal form on the surface of the above linear carbon material.

[0026] The above conductive material can be used in electrodes for all-solid-state batteries.

[0027] Another aspect of the present invention provides an all-solid-state battery comprising an anode, a cathode, and a solid electrolyte layer provided between the anode and the cathode, wherein at least one of the anode and the cathode is provided with a conductive material, and the conductive material comprises a linear carbon material and a halide-based solid electrolyte provided on the surface of the linear carbon material.

[0028] The method for manufacturing a conductive material equipped with a halide-based solid electrolyte according to the present invention and the conductive material manufactured thereby can suppress oxidation and side reactions of the solid electrolyte by providing a halide-based solid electrolyte having high electrochemical stability on a linear carbon material.

[0029] In addition, in one embodiment, the present invention can improve the interfacial characteristics with the binder by island coating a halide-based solid electrolyte on a linear carbon material, thereby improving mechanical properties.

[0030] In addition, in another embodiment, the present invention can prevent direct contact with the solid electrolyte by conformally coating a halide-based solid electrolyte on a linear carbon material.

[0031] In addition, the all-solid-state battery equipped with a conductive material having a halide-based solid electrolyte of the present invention can effectively utilize a halide-based solid electrolyte, which increases costs due to the inclusion of rare metals, by replacing only a portion of the sulfide-based solid electrolyte in the electrode with a halide-based solid electrolyte, thereby increasing competitiveness in manufacturing costs.

[0032] The technical effects of the present invention are not limited to those mentioned above, and other unmentioned technical effects will be clearly understood by those skilled in the art from the description below.

[0033] FIG. 1 is a flowchart for explaining a method for manufacturing a conductive material equipped with a halide-based solid electrolyte according to one embodiment of the present invention.

[0034] FIG. 2 is a schematic diagram showing a conductive material equipped with a halide-based solid electrolyte according to one embodiment of the present invention.

[0035] FIG. 3 is a schematic diagram showing a conductive material equipped with a halide-based solid electrolyte according to another embodiment of the present invention.

[0036] FIG. 4 is a schematic diagram showing the structure of an all-solid-state battery including a halide-based solid electrolyte according to one embodiment of the present invention.

[0037] FIG. 5 is a schematic diagram showing an enlarged view of the interface between the conductive material and the solid electrolyte in an all-solid-state battery manufactured with the structure of FIG. 4 in one embodiment of the present invention.

[0038] FIG. 6 is a schematic diagram showing an enlarged view of the interface between the conductive material and the solid electrolyte in an all-solid-state battery manufactured with the structure of FIG. 4 in another embodiment of the present invention.

[0039] FIG. 7 is a schematic diagram showing the process of coating vapor-grown carbon nanofibers (VGCF) according to one embodiment of the present invention with a halide-based solid electrolyte and then heat-treating them.

[0040] FIG. 8 is a schematic diagram showing the process of forming a functionalized linear carbon material (Functionalized VGCF) by acid treatment of vapor-grown carbon nanofibers (VGCF) according to another embodiment of the present invention.

[0041] FIG. 9 is a schematic diagram showing the process of coating a functionalized linear carbon material (Functionalized VGCF) according to another embodiment of the present invention with a halide-based solid electrolyte and then heat-treating it.

[0042] Figure 10 is an image of the bare vapor-grown carbon nanofiber (VGCF) of Comparative Example 1-1 of the present invention analyzed by a scanning electron microscope (SEM).

[0043] Figure 11 is a scanning electron microscope (SEM) image of vapor-grown carbon nanofibers (VGCF) coated with the halide-based solid electrolyte of Preparation Example 1-1 of the present invention in an island shape.

[0044] Figures 12a and 12b are scanning electron microscope (SEM) images of vapor-grown carbon nanofibers (VGCF) coated with the halide-based solid electrolyte of Preparation Examples 1-2 and 1-3 of the present invention in an island shape.

[0045] Figure 13 is a scanning electron microscope (SEM) image of vapor-grown carbon nanofibers (VGCF) coated in a conformal form with the halide-based solid electrolyte of Preparation Example 1-4 of the present invention.

[0046] Figure 14 is an image of vapor-grown carbon nanofibers (VGCF) coated with the halide-based solid electrolyte of Preparation Example 1-4 of the present invention in a conformal form, analyzed by transmission electron microscope-energy-dispersive X-ray spectroscopy (TEM-EDX).

[0047] FIGS. 15a and 15b are graphs comparing the X-ray diffraction (XRD) analysis and X-ray photoelectron spectroscopy (XPS) results of the bare VGCF of Comparative Example 1-1 of the present invention and the Conformal VGCF@Li3InCl6 of Preparation Example 1-4.

[0048] Figure 16 is a graph showing the results measured using cyclic voltammetry (CV) of the bare VGCF of Comparative Example 1-1 of the present invention and the conformal VGCF@Li3InCl6 of Preparation Example 1-4.

[0049] Figure 17 is a graph analyzing the ionic conductivity and tensile strength of an all-solid-state battery comprising the Bare VGCF of Comparative Example 2-1 of the present invention and the Conformal VGCF@Li3InCl6 of Preparation Example 2-4.

[0050] FIG. 18 is a graph showing the microstructure analysis results of an all-solid-state battery containing Bare VGCF of Comparative Example 2-1 of the present invention.

[0051] FIG. 19 is a graph showing the microstructure analysis results of an all-solid-state battery containing Conformal VGCF@Li3InCl6 of Preparation Example 2-4 of the present invention.

[0052] FIG. 20 is a voltage-capacity graph of the initial charge-discharge cycle of an all-solid-state battery comprising the Bare VGCF of Comparative Example 2-1 of the present invention and the Conformal VGCF@Li3InCl6 of Preparation Example 2-4.

[0053] FIG. 21 is a graph showing the rate performance of an all-solid-state battery comprising the Bare VGCF of Comparative Example 2-1 of the present invention and the Conformal VGCF@Li3InCl6 of Preparation Example 2-4.

[0054] FIG. 22 is a graph showing the lifespan characteristics of an all-solid-state battery including the Bare VGCF of Comparative Example 2-1 of the present invention and the Conformal VGCF@Li3InCl6 of Preparation Example 2-4.

[0055] FIGS. 23a and FIGS. 23b are graphs showing the XPS analysis results at S 2p and P 2p after evaluating the life characteristics of an all-solid-state battery containing the Bare VGCF of Comparative Example 2-1 of the present invention and the Conformal VGCF@Li3InCl6 of Preparation Example 2-4.

[0056] FIGS. 24a and FIGS. 24b are schematic diagrams of the interfacial reaction of an all-solid-state battery comprising the Bare VGCF of Comparative Example 2-1 of the present invention and the Conformal VGCF@Li3InCl6 of Preparation Example 2-4.

[0057] FIG. 25 is a voltage-capacity graph of the initial charge-discharge cycle of an all-solid-state battery comprising the Bare VGCF of Comparative Example 2-1 of the present invention, the Island VGCF@Li3InCl6 of Preparation Example 2-2, and the Conformal VGCF@Li3InCl6 of Preparation Example 2-4.

[0058] FIG. 26 is a graph showing the rate performance of an all-solid-state battery including the Bare VGCF of Comparative Example 2-1 of the present invention, the Island VGCF@Li3InCl6 of Preparation Example 2-2, and the Conformal VGCF@Li3InCl6 of Preparation Example 2-4.

[0059] FIG. 27 is a graph analyzing the ionic conductivity and tensile strength of an all-solid-state battery comprising the Bare VGCF of Comparative Example 2-1 of the present invention, the Island VGCF@Li3InCl6 of Preparation Example 2-2, and the Conformal VGCF@Li3InCl6 of Preparation Example 2-4.

[0060] Hereinafter, embodiments according to the present invention will be described in detail with reference to the attached drawings.

[0061] While the present invention allows for various modifications and variations, specific embodiments are illustrated in the drawings and will be described in detail below. However, it is not intended to limit the invention to the particular forms disclosed, but rather the invention includes all modifications, equivalents, and substitutions consistent with the spirit of the invention as defined by the claims.

[0062] When an element such as a layer, region, or substrate is referred to as existing "on" another component, it can be understood that this exists directly on the other element, or that an intermediate element may exist between them.

[0063] Although terms such as first, second, etc., may be used to describe various elements, components, regions, layers, and / or regions, it will be understood that these elements, components, regions, layers, and / or regions should not be limited by these terms.

[0064] Throughout the specification, when a part is described as "including" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0065]

[0066] Method for manufacturing a conductive material equipped with a halide-based solid electrolyte

[0067] One aspect of the present invention may provide a method for manufacturing a conductive material equipped with a halide-based solid electrolyte. The conductive material may refer to a material having electronic conductivity, and the electrolyte may refer to an ion-conducting material. The present invention may provide a method for providing a halide-based solid electrolyte on the entire surface or a part of the surface of the conductive material.

[0068] FIG. 1 is a flowchart for explaining a method for manufacturing a conductive material equipped with a halide-based solid electrolyte according to one embodiment of the present invention.

[0069] Referring to FIG. 1, a halide-based solid electrolyte precursor solution can be coated onto a linear carbon material (S100). S100 can be performed using a sol-gel method.

[0070] First, the above-mentioned linear carbon material can be prepared. The above-mentioned linear carbon material may include various carbon materials such as linear carbon nanofibers, vapor-grown carbon nanofibers, or carbon nanotubes.

[0071] Specifically, the linear carbon material may be a vapor-grown carbon nanofiber. A vapor-grown carbon nanofiber refers to a carbon nanofiber that has been graphitized after being synthesized using a chemical vapor deposition method. The vapor-grown carbon nanofiber may be synthesized by condensing only carbon when a hydrocarbon gas comes into contact with a catalyst surface. The vapor-grown carbon nanofiber may have a structure in which the graphite planes are arranged in a tree-ring pattern with the carbon nanofiber as the axis. Accordingly, the vapor-grown carbon nanofiber is chemically stable and may have a high aspect ratio. Specifically, for example, the average diameter of the vapor-grown carbon nanofiber may be 80 to 220 nm, and the length may be 5 to 25 μm, but is not limited thereto.

[0072] A halide-based solid electrolyte precursor solution can be prepared to perform coating on S100. The halide-based solid electrolyte precursor solution can be formed by dispersing or dissolving a halide-based solid electrolyte precursor in a solvent and by a liquid-phase mixing method. Specifically, the halide-based solid electrolyte precursor solution may be formed by reacting a lithium (Li) halide with at least one metal halide in a solvent. The halide-based solid electrolyte precursor solution may include a halide-based solid electrolyte of the following chemical formula 1.

[0073] [Chemical Formula 1]

[0074] Li a M b X6

[0075] In the above chemical formula 1, 1≤a≤3, 0 <b≤1, a+3b=6이고, 상기 M은 In, Yb, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm 및 Lu 중에서 선택되는 어느 하나 이상의 금속 원소이고, 상기 X는 F, Cl, Br 및 I 중에서 선택되는 어느 하나 이상을 할로겐 원소이다. 구체적으로, 상기 M은 +3의 산화수를 갖는 전이금속 원소일 수 있다.

[0076] The forms of the lithium halide and the metal halide may be solids such as powders or aqueous solutions, but are not particularly limited.

[0077] Specifically, the lithium (Li) halide may include one or more of LiCl, LiBr, LiI, and LiF, and preferably may be lithium chloride (LiCl). The metal halide may include one or more of InCl, YCl, YBr, HoCl, and ScCl, and preferably may be indium chloride (InCl).

[0078] The above solvent may be water (H2O), but any solvent or dispersion medium used in liquid-phase mixing methods may be used, and is not specifically limited.

[0079] More specifically, the halide-based solid electrolyte precursor solution may include one or more selected from Li3InCl6, Li3YCl6, Li3YBr6, Li3HoCl6, and Li3ScCl6, and preferably may include Li3InCl6(LIC).

[0080] After adding the lithium halide and at least one metal halide to the solvent, stirring, for example, mechanical milling, can be performed within the solvent to form a halide-based solid electrolyte precursor solution. The mechanical milling can be performed for 20 to 30 hours at a rotational speed of 200 to 400 RPM, more specifically for 22 to 26 hours at a rotational speed of 250 to 350 RPM, preferably for 24 hours at 300 RPM.

[0081] The prepared linear carbon material can be mixed with the halide-based solid electrolyte precursor solution to coat the linear carbon material with the halide-based solid electrolyte precursor solution.

[0082] The above process can be performed by mixing the halide-based solid electrolyte precursor solution in an amount of less than 1 part by weight with respect to 100 parts by weight of the linear carbon material. For example, the above process can be performed by mixing the halide-based solid electrolyte precursor solution in an amount of 0.1 to 0.9 parts by weight. Specifically, the above process can be performed by mixing the halide-based solid electrolyte precursor solution in an amount of 0.2 to 0.8 parts by weight, more specifically 0.3 to 0.7 parts by weight, and preferably 0.5 parts by weight with respect to 100 parts by weight of the linear carbon material. By mixing the linear carbon material and the halide-based solid electrolyte precursor solution within the above-described range and performing the coating, the halide-based solid electrolyte can be provided relatively uniformly in an appropriate amount on the linear carbon material.

[0083] Referring to FIG. 1, next, the linear carbon material coated with the halide-based solid electrolyte precursor solution can be heat-treated (S200). By the heat treatment, the halide-based solid electrolyte precursor in the halide-based solid electrolyte precursor solution coated on the linear carbon material can be synthesized into a halide-based solid electrolyte.

[0084] The above heat treatment can be performed at 200 to 340°C for 2 to 6 hours. Specifically, the heat treatment can be performed at 230 to 310°C for 2 to 5 hours, more specifically at 250 to 290°C for 2 to 4 hours, and preferably at 270°C for 3 hours. By performing the heat treatment within the above range, the halide-based solid electrolyte precursor solution can be appropriately synthesized into a halide-based solid electrolyte and stably provided on the linear carbon material.

[0085] In the heat treatment step described above, a halide-based solid electrolyte can be synthesized in the form of islands on the surface of the linear carbon material. Specifically, as the halide-based solid electrolyte is formed in the form of particles in multiple regions on the surface of the linear carbon material, the halide-based solid electrolyte can be provided in the form of multiple islands.

[0086] In another embodiment, prior to performing the step of coating the halide-based solid electrolyte precursor solution, the method may further include the step of surface-treating the linear carbon material with an acid to form oxygen-containing functional groups on the surface. That is, after surface-treating the linear carbon material with an acid, the halide-based solid electrolyte precursor solution may be coated.

[0087] Specifically, the linear carbon material can be surface treated by immersing it in an acid solution. The acid solution may be one or more acidic solutions selected from nitric acid, sulfuric acid, phosphoric acid, and hydrochloric acid; more specifically, the acid solution may contain nitric acid and sulfuric acid in a volume ratio of 1:3 to 3:1, and preferably, nitric acid and sulfuric acid may be contained in a volume ratio of 1:3.

[0088] As oxygen-containing functional groups are formed on the surface of the linear carbon material, a coating layer of the halide-based solid electrolyte with a uniform thickness can be formed over the entire surface of the linear carbon material during the subsequent process of coating with the halide-based solid electrolyte precursor solution. Specifically, the surface of the linear carbon material may have a smooth or glossy surface due to characteristics of the fiber production process, making it difficult to coat (attach) other molecules to the surface. Accordingly, by forming oxygen-containing functional groups, specifically polar groups such as hydroxyl groups (OH) and / or other oxygen-containing compounds, on the surface of the linear carbon material through the acid treatment described above, the coating of the halide-based solid electrolyte precursor solution can be performed stably.

[0089] Afterward, by performing the heat treatment of S200 described above, a halide-based solid electrolyte can be synthesized in a conformal form on the surface of the linear carbon material. A conformal coating may mean that the surface of the linear carbon material is coated with a uniform thickness to achieve full coverage in accordance with the cylindrical or irregular curvature of the linear carbon material. That is, the halide-based solid electrolyte can form a layer of uniform thickness that surrounds the entire surface area of ​​the linear carbon material.

[0090] As described above, the method for manufacturing a conductive material equipped with a halide-based solid electrolyte according to the present invention allows for the easy formation of a halide-based solid electrolyte having high electrochemical stability on a linear carbon material by coating a halide-based solid electrolyte precursor solution onto the linear carbon material using a sol-gel method and then heat-treating the material. Furthermore, by varying the surface pretreatment of the linear carbon material, the halide-based solid electrolyte can be provided in an island form or a conformal form, thereby enabling the realization of effects suitable for the purpose to which such a conductive material is applied.

[0091]

[0092] Conductive material equipped with a halide-based solid electrolyte

[0093] Another aspect of the present invention may provide a conductive material equipped with a halide-based solid electrolyte. The conductive material may be manufactured through the method for manufacturing a conductive material equipped with a halide-based solid electrolyte described above. Specifically, the conductive material equipped with a halide-based solid electrolyte may comprise a linear carbon material and a halide-based solid electrolyte provided on the surface of the linear carbon material. That is, the conductive material of the present invention may be a linear carbon material, which is a conductive material, equipped with a halide-based solid electrolyte having high electrochemical stability.

[0094] The above halide-based solid electrolyte can be represented by the following chemical formula 1.

[0095] [Chemical Formula 1]

[0096] Li a M b X6

[0097] In the above chemical formula 1, 1≤a≤3, 0 <b≤1, a+3b=6일 수 있고, 상기 M은 In, Yb, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm 및 Lu 중에서 선택되는 어느 하나 이상의 금속 원소일 수 있고, 상기 X는 F, Cl, Br 및 I 중에서 선택되는 어느 하나 이상을 할로겐 원소일 수 있다. 구체적으로, 상기 a는 3, b는 1일 수 있으며, 상기 M은 In, Sc, Y, 및 Ho 중에서 선택되는 어느 하나일 수 있고, 더욱 구체적으로, 상기 M은 In일 수 있다. 또한, 상기 X는 Cl 또는 Br일 수 있고, 더욱 구체적으로 상기 X는 Cl일 수 있다.

[0098] The halide-based solid electrolyte provided on the above linear carbon material can be coated in an island form or in a conformal form depending on the manufacturing method.

[0099] FIG. 2 is a schematic diagram showing a conductive material equipped with a halide-based solid electrolyte according to one embodiment of the present invention.

[0100] Referring to FIG. 2, a conductive material according to one embodiment of the present invention may be provided with a linear carbon material (101) and a halide-based solid electrolyte (201) coated in an island shape on the surface of the linear carbon material (101). As the halide-based solid electrolyte (201) is provided in the form of particles in a plurality of regions on the surface of the linear carbon material (101), the carbon layer of the linear carbon material (101) may be exposed between these halide-based solid electrolyte (201) particles. When applied to an electrode, the interfacial characteristics between the carbon layer of the linear carbon material (101) and a binder applied together with the active material, such as PTFE, may be improved. Accordingly, the occurrence of cracks between the linear carbon material (101) and the binder may be suppressed, and physical properties such as tensile strength may be improved.

[0101] FIG. 3 is a schematic diagram showing a conductive material equipped with a halide-based solid electrolyte according to another embodiment of the present invention.

[0102] Referring to FIG. 3, a conductive material according to another embodiment of the present invention may be provided with a linear carbon material (102) and a halide-based solid electrolyte (202) coated in a conformal form on the surface of the linear carbon material (102). The halide-based solid electrolyte (202) may be formed as a uniform coating layer having a thickness of several tens of nanometers, which is provided to achieve complete coverage by surrounding the entire surface area of ​​the linear carbon material (102). When applied to an electrode, direct contact between the solid electrolyte within the electrode, such as a sulfide-based solid electrolyte like Li6PS5Cl, can be prevented, thereby suppressing oxidation of the solid electrolyte and the formation of side reactions within the battery.

[0103] In addition, the conductive material equipped with the halide-based solid electrolyte of the present invention can reduce manufacturing costs compared to conventional methods by replacing only a very small portion of the sulfide-based solid electrolyte in the electrode with a halide-based solid electrolyte having high electrochemical stability.

[0104] The conductive material equipped with the halide-based solid electrolyte of the present invention can be applied to various fields where conductive materials are provided. Specifically, for example, the conductive material can be used in electrochemical energy storage systems, power supply and demand management systems, all-solid-state batteries for electric vehicles, and more specifically, electrodes for all-solid-state batteries.

[0105]

[0106] All-solid-state battery comprising a conductive material equipped with a halide-based solid electrolyte

[0107] Another aspect of the present invention can provide a lithium secondary battery comprising a conductive material manufactured by the method for manufacturing a conductive material equipped with the halide-based solid electrolyte described above, specifically, a solid electrolyte-based all-solid-state lithium secondary battery, i.e., an all-solid-state battery.

[0108] FIG. 4 is a schematic diagram showing the structure of an all-solid-state battery according to one embodiment of the present invention.

[0109] Referring to FIG. 4, the all-solid-state battery may include a positive electrode (10), a negative electrode (20), and a solid electrolyte layer (30) provided between the positive electrode (10) and the negative electrode (20). At this time, a conductive material is provided on at least one of the positive electrode (10) and the negative electrode (20), and the conductive material (C) may be provided with the halide-based solid electrolyte described above. Specifically, the conductive material provided with the halide-based solid electrolyte may include a linear carbon material and a halide-based solid electrolyte provided on the surface of the linear carbon material.

[0110] To avoid redundant descriptions regarding the conductive material equipped with the above-mentioned halide-based solid electrolyte, one may refer to the above-described method for manufacturing the conductive material and the contents of the conductive material manufactured thereby.

[0111] The anode (10) may include an anode active material layer (not shown). The anode (10) may further include an anode current collector layer (not shown) below the anode active material layer. The anode active material layer may contain a solid electrolyte (SE), an anode active material (CM), a conductive material (C), and a binder (not shown). The solid electrolyte (SE) and the anode active material (CM) may be contained in the form of particles. At this time, the anode (10) may include a linear carbon material equipped with the halide-based solid electrolyte of the present invention as the conductive material. The anode current collector layer may be any one selected from, for example, SUS, aluminum, nickel, iron, titanium, and carbon, and SUS may be preferred, but is not particularly limited.

[0112] The solid electrolyte within the positive electrode active material layer is a lithium-ion conductor and, for example, may be a sulfide-based solid electrolyte. The sulfide-based solid electrolyte may be a crystal system, glass system, or glass-ceramic system having a thio-lisicon, LGPS, or argyrodite structure. Specifically, for example, the solid electrolyte having a thio-lisicon crystal structure may be Li3PS4, and the solid electrolyte having an LGPS crystal structure may be Li 10 GeP2S 12 It may be, and the solid electrolyte having the azirodite crystal structure may be Li6PS5X (where X is Cl, Br, or I), and the glass-ceramic-based solid electrolyte may be xLi2S·(100- x )P2S5(x can be 60 to 90).

[0113] More specifically, the sulfide-based solid electrolyte may have a cubic argyrodite-type crystal structure. Specifically, it may be Li6PS5X, where X can be Cl, Br, or I. As an example, the sulfide-based glass-ceramic-based solid electrolyte may contain lithium sulfide and phosphorus sulfide. The lithium sulfide may be Li2S, and the phosphorus sulfide may be P2S5. Additionally, the sulfide-based glass-ceramic may have a salt added to a sulfide (Li2S-P2S5) composed of lithium sulfide and phosphorus sulfide. The salt may include a lithium salt. As an example, the lithium salt may be lithium sulfate (Li2SO4), lithium chloride (LiCl), lithium iodide (LiI), trilithium borate (Li3BO3), or lithium phosphate (Li3PO4). Sulfide-based glass-ceramic solid electrolytes may be obtained by adding salt to sulfide (Li2S-P2S5).

[0114] The above-mentioned positive electrode active material (CM) may be a lithium-transition metal oxide or a lithium-transition metal phosphate. The above-mentioned lithium-transition metal oxide may be a composite oxide of lithium and at least one transition metal selected from the group consisting of cobalt, manganese, nickel, and aluminum. The above-mentioned positive electrode active material (CM) may utilize a lithium-cobalt-based composite oxide such as LiCoO2, a lithium-nickel-based composite oxide such as LiNiO2, a lithium-manganese-based composite oxide such as LiMn2O4, a lithium-vanadium-based composite oxide such as LiV2O5, or a lithium-iron-based composite oxide such as LiFeO2. Additionally, an NCM material may be used as the above-mentioned positive electrode active material (CM). As an example, the above-mentioned lithium-transition metal oxide is Li(Ni 1-x-y Co x Mn y )O2(0≤x≤1, 0≤y≤1, 0≤x+y≤1), Li(Ni 1-x-y Co x Al y )O2(0≤x≤1, 0 <y≤1, 0<x+y≤1), 또는 Li(Ni 1-x-y Co x Mn yIt may be )2O4(0≤x≤1, 0≤y≤1, 0≤x+y≤1). Alternatively, the lithium-transition metal oxide may be a complex phosphate of lithium with at least one transition metal selected from the group consisting of iron, cobalt, and nickel. As an example, the lithium-transition metal phosphate is Li(Ni 1-x-y Co x Fe y )PO4(0≤x≤1, 0≤y≤ 1, 0≤x+y≤1) may be.

[0115] The binder mentioned above may be provided within the electrode along with the materials described above, although it is not illustrated in FIG. 4. For example, the binder may be a polymer compound of a fluorine-based, diene-based, acrylic-based, or silicone-based polymer, and more specifically, it may be nitrile butadiene rubber (NBR), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), carboxymethylcellulose (CMC), styrene butadiene rubber (SBR), or polyimide (PI), but is not limited thereto.

[0116] The anode (10) above may be manufactured by applying a slurry formed by mixing at least one of an anode active material (CM), a solid electrolyte (SE), a conductive material (C), and a binder. Specifically, for example, the anode (10) may have a thickness in the range of 0.1 μm to 1,000 μm, but may vary depending on the embodiment.

[0117] The above-mentioned cathode (20) may include a cathode active material layer (not shown), and the cathode active material layer may include at least one of a cathode active material (AM), a solid electrolyte (SE), a conductive material (C), and a binder. In this case, if a conductive material (C) is provided in the cathode active material layer, a conductive material equipped with the halide-based solid electrolyte of the present invention may be used. The above-mentioned cathode (20) may further include a cathode current collector layer (not shown) below the cathode active material layer. The cathode current collector layer may be, for example, any one selected from SUS, copper, nickel, and carbon, and SUS may be preferred, but is not particularly limited.

[0118] The above-mentioned negative electrode active material (AM) is a material capable of electrochemically inserting or extracting lithium through a redox reaction, and specifically, for example, may be metallic lithium or a LiAl-based, LiAg-based, LiPb-based, LiSi-based, or LiIn-based alloy that alloys with lithium. Alternatively, the above-mentioned negative electrode active material (AM) may be a carbon material such as graphite, non-graphitized carbon obtained by calcining resin, digraphitized carbon obtained by heat-treating coke, or fullerene. Alternatively, the above-mentioned negative electrode active material (AM) may be a metal oxide such as TiO2 or SnO2 having a potential with respect to lithium of less than 2V, but is not limited thereto.

[0119] The solid electrolyte (SE) in the above-mentioned negative electrode active material layer is a lithium-ion conductor and, for example, may be a sulfide-based solid electrolyte. The description of the above-mentioned sulfide-based solid electrolyte may be the same composition as the solid electrolyte included in the above-mentioned positive electrode (10), and the above-mentioned description may be referenced.

[0120] The above-mentioned cathode (20) can be manufactured by applying a slurry formed by mixing at least one of a cathode active material (AM), a solid electrolyte (SE), a conductive material (C), and a binder. Specifically, for example, the above-mentioned cathode (20) may have a thickness in the range of 0.1 μm to 1,000 μm, but may vary depending on the embodiment.

[0121] The electrolyte layer (30) is a layer provided between the anode (10) and the cathode (20), and the electrolyte layer (30) may include solid electrolyte particles as an example of a solid electrolyte (SE). The solid electrolyte (SE) in the electrolyte layer (30) may be a sulfide-based solid electrolyte as a lithium-ion conductor. The description of the sulfide-based solid electrolyte may have the same composition as the solid electrolyte of the anode (10) and cathode (20) described above, or it may have a different composition depending on the embodiment. In this embodiment, a solid electrolyte with the same composition was used, and the description described above may be referenced. Specifically, for example, the electrolyte layer (30) may have a thickness in the range of 0.1 μm to 1,000 μm, more specifically in the range of 0.1 μm to 300 μm, but may vary depending on the embodiment.

[0122] The above electrolyte layer (30) can be manufactured by compression molding the solid electrolyte (SE) or by applying a slurry formed by mixing the solid electrolyte (SE) with a binder and a solvent.

[0123] FIG. 5 is a schematic diagram showing an enlarged view of the interface between the conductive material and the solid electrolyte in an all-solid-state battery manufactured with the structure of FIG. 4 in one embodiment of the present invention.

[0124] Referring to FIG. 5, a halide-based solid electrolyte (201) is provided in an island shape on a linear carbon material (101) used as a conductive material (c), so that the carbon layer of the linear carbon material (101) can be exposed between the particles of the halide-based solid electrolyte (201). Accordingly, since direct contact between the linear carbon material (101) and the solid electrolyte (SE) is prevented, oxidation of the solid electrolyte (SE) and degradation due to oxidation can be suppressed. In addition, although not shown in the drawing, a binder included in the electrode can come into contact with the exposed carbon layer of the linear carbon material (101), thereby improving the interfacial characteristics with the binder. Accordingly, since the occurrence of cracks between the carbon layer and the binder is suppressed, physical properties such as tensile strength can be improved.

[0125] FIG. 6 is a schematic diagram showing an enlarged view of the interface between the conductive material and the solid electrolyte in an all-solid-state battery manufactured with the structure of FIG. 4 in another embodiment of the present invention.

[0126] Referring to FIG. 6, a halide-based solid electrolyte (202) is provided in a conformal form on a linear carbon material (102) used as a conductive material (C), so that direct contact between the linear carbon material (102) and the solid electrolyte (SE) can be prevented as the surface of the linear carbon material (102) is completely coated.

[0127] As described above, the all-solid-state battery of the present invention can suppress direct contact between the linear carbon material, which is a conductive material, and the solid electrolyte layer (30) by providing a conductive material having a halide-based solid electrolyte on at least one of the positive electrode (10) and the negative electrode (20). Accordingly, oxidation of the solid electrolyte layer (30), specifically, for example, a sulfide-based solid electrolyte such as Li6PS5Cl, due to the electron transfer characteristics of the conductive material can be minimized. Furthermore, the conductive material having a halide-based solid electrolyte with a thickness of several tens of nanometers on the linear carbon material can lower manufacturing costs by replacing only a very small portion of the sulfide-based solid electrolyte in the electrode with the halide-based solid electrolyte.

[0128] Hereinafter, preferred manufacturing examples and experimental examples are presented to aid in understanding the present invention. However, the following manufacturing examples and experimental examples are intended only to aid in understanding the present invention, and the present invention is not limited by the following manufacturing examples and experimental examples.

[0129] <Preparation Examples 1-1 to 1-3: Preparation of a conductive material equipped with a halide-based solid electrolyte (Island type)>

[0130] FIG. 7 is a schematic diagram showing the process of coating vapor-grown carbon nanofibers (VGCF) according to one embodiment of the present invention with a halide-based solid electrolyte and then heat-treating them.

[0131] Referring to Fig. 7, lithium chloride and indium chloride were added to a solvent and stirred at 300 RPM for 1 hour using a stirrer to prepare a Li3InCl6 precursor solution (Li3InCl6 solution), which was then placed on a magnetic stirrer.

[0132] Then, vapor-grown carbon nanofibers (VGCF) were added to the above Li3InCl6 precursor solution, and the Li3InCl6 precursor was coated onto the linear carbon material using the sol-gel method at different addition ratios for each preparation example, at 0.5 wt% (Preparation Example 1-1), 1.0 wt% (Preparation Example 1-2), and 3.0 wt% (Preparation Example 1-3) relative to 100 wt% of the linear carbon material.

[0133] Afterwards, the Li3InCl6 precursor was synthesized into Li3InCl6(LIC) by performing annealing at 270°C for 3 hours. This was vacuum dried to produce a conductive material (hereinafter referred to as "Island VGCF@Li3InCl6") in which the halide-based solid electrolyte Li3InCl6 was coated in an island shape on a linear carbon material.

[0134] <Preparation Example 1-4: Preparation of a conductive material equipped with a halide-based solid electrolyte (Conformal type)>

[0135] FIG. 8 is a schematic diagram showing the process of forming a functionalized linear carbon material (Functionalized VGCF) by acid treatment of vapor-grown carbon nanofibers (VGCF) according to another embodiment of the present invention, and FIG. 9 is a schematic diagram showing the process of coating a functionalized linear carbon material (Functionalized VGCF) with a halide-based solid electrolyte and then heat-treating it according to another embodiment of the present invention.

[0136] Referring to Fig. 8, the vapor-grown carbon nanofibers (VGCF) were immersed in an acid solution in which nitric acid (HNO3) and sulfuric acid (H2SO4) were mixed in a volume ratio of 1:3 to perform acid treatment. Through acid treatment, functionalized vapor-grown carbon nanofibers (Fuctionalized VGCF) were prepared in which oxygen functional groups were formed on the surface of the linear carbon material.

[0137] Referring to Fig. 9, lithium chloride and indium chloride were added to a solvent and stirred at 300 RPM for 1 hour using a stirrer to prepare a Li3InCl6 precursor solution (Li3InCl6 solution), which was then placed on a magnetic stirrer.

[0138] Then, the functionalized vapor-grown carbon nanofiber (Fuctionalized VGCF) was added to the Li3InCl6 precursor solution, and the Li3InCl6 precursor was coated onto the functionalized linear carbon material using the sol-gel method at 0.5 wt% relative to 100 wt% of the linear carbon material.

[0139] Afterwards, the Li3InCl6 precursor was synthesized into Li3InCl6(LIC) by performing annealing at 270°C for 3 hours. This was vacuum dried to produce a conductive material (hereinafter referred to as "Conformal VGCF@Li3InCl6") in which the halide-based solid electrolyte Li3InCl6 was coated in a conformal form on a linear carbon material.

[0140] <Comparative Example 1-1: Bare Vapor-Growthed Carbon Nanofibers (VGCF)>

[0141] As a control group, bare vapor-grown carbon nanofibers (VGCF) were prepared (hereinafter referred to as "Bare VGCF").

[0142] FIG. 10 is a scanning electron microscope (SEM) image of the bare vapor-grown carbon nanofiber (VGCF) of Comparative Example 1-1 of the present invention, and FIG. 11 is a scanning electron microscope (SEM) image of the vapor-grown carbon nanofiber (VGCF) coated with a halide-based solid electrolyte in an island form of Preparation Example 1-1 of the present invention.

[0143] Referring to Fig. 10, it can be seen that the bare vapor-grown carbon nanofiber (VGCF) of Comparative Example 1-1 has a relatively smooth surface.

[0144] In contrast, it can be seen that a halide-based solid electrolyte is coated in the form of islands, where particles are clustered in multiple regions of the surface of the linear carbon material of Preparation Example 1-1 of FIG. 11.

[0145] Figures 12a and 12b are scanning electron microscope (SEM) images of vapor-grown carbon nanofibers (VGCF) coated with the halide-based solid electrolyte of Preparation Examples 1-2 and 1-3 of the present invention in an island shape.

[0146] Referring to FIGS. 12a and 12b, it can be seen that in the case of the conductive material coated by adding 1.0 wt% of a halide-based solid electrolyte precursor solution relative to 100 wt% of a linear carbon material in Preparation Example 1-2, and the conductive material coated by adding 3.0 wt% of a halide-based solid electrolyte precursor solution relative to 100 wt% of a linear carbon material in Preparation Example 1-3, the aggregation phenomenon between halide-based solid electrolyte particles provided on the linear carbon material is intensified. When a conductive material having this form is applied to an electrode, microfibrillation behavior does not occur during the manufacturing process, and the electrolyte distribution may become non-uniform. Consequently, the mechanical properties of the electrode may be degraded.

[0147] FIG. 13 is an image of vapor-grown carbon nanofibers (VGCF) coated with the halide-based solid electrolyte of Preparation Example 1-4 of the present invention in a conformal form, analyzed by scanning electron microscope (SEM), and FIG. 14 is an image of vapor-grown carbon nanofibers (VGCF) coated with the halide-based solid electrolyte of Preparation Example 1-4 of the present invention in a conformal form, analyzed by transmission electron microscope-energy-dispersive X-ray spectroscopy (TEM-EDX).

[0148] Referring to FIGS. 13 and 14, it can be seen that the Conformal VGCF@Li3InCl6 of Preparation Example 1-4 has a Li3InCl6 coating layer formed to have a relatively uniform thickness while surrounding the surface of the linear carbon material.

[0149] FIGS. 15a and 15b are graphs comparing the X-ray diffraction (XRD) analysis and X-ray photoelectron spectroscopy (XPS) results of the bare VGCF of Comparative Example 1-1 of the present invention and the Conformal VGCF@Li3InCl6 of Preparation Example 1-4.

[0150] Referring to Fig. 15a, in contrast to the bare VGCF without the halide-based solid electrolyte of Comparative Example 1-1, the spectrum of Conformal VGCF@Li3InCl6 of Preparation Example 1-4 showed a peak of Li3InCl6, and in Fig. 15b, Preparation Example 1-4 also showed new peaks at Cl 2p and In 3d. Through this, it can be seen that the Li3InCl6 precursors coated on the linear carbon material of the conductive material of Preparation Example 1-4 were successfully synthesized into a Li3InCl6 alloy through a heat treatment process.

[0151] FIG. 16 is a graph showing the results measured using cyclic voltammetry (CV) of the bare VGCF of Comparative Example 1-1 of the present invention and the conformal VGCF@Li3InCl6 of Preparation Example 1-4.

[0152] Referring to FIG. 16, unlike the Bare VGCF of Comparative Example 1-1, which is not equipped with a halide-based solid electrolyte, the Conformal VGCF@Li3InCl6 of Preparation Example 1-4 is equipped with Li3InCl6, and thus the electrochemical stability is improved.

[0153] <Preparation Examples 2-1 to 2-3: Preparation of All-Solid State Batteries Containing Island-Type VGCF@Li3InCl6>

[0154] Island-type VGCF@Li3InCl6 2wt% of Preparation Examples 1-1 to 1-3, NCM active material (LiNi 0.8 Co 0.1 Mn 0.1 75 wt% of O2 and 22 wt% of the sulfide-based solid electrolyte Li6PS5Cl were placed in a mortar and hand-mixed. 1 wt% of polytetrafluoroethylene (PTFE) was added as a binder to the well-mixed cathode composite and hand-mixed to fabricate an all-solid-state battery. Subsequently, the fabricated electrode was die-cut to a diameter of 13 mm (capacity 5 mAh / cm²). 2 ) did.

[0155] The anode was placed inside the cell and pressurized to 400 MPa to maximize electrode density (maximum solid-solid contact). Then, 150 mg of Li6PS5Cl powder, a sulfide-based solid electrolyte, was added to the top of the anode, and pressurized to 400 MPa to pelletize the solid electrolyte and maximize the anode-solid electrolyte contact.

[0156] Subsequently, lithium (Li) metal was introduced as the cathode onto the top of a solid electrolyte pellet, and an all-solid-state battery was fabricated by applying pressure of 50 MPa to maximize the solid electrolyte-lithium contact. After establishing an external pressure environment of 25 MPa, an electrochemical evaluation was conducted.

[0157] <Preparation Example 2-4: Preparation of an all-solid-state battery containing a conformal type VGCF@Li3InCl6>

[0158] An all-solid-state battery containing a conformal type VGCF@Li3InCl6 was prepared by performing the same procedure as in Preparation Example 2-1, except that 2 wt% of the conformal type VGCF@Li3InCl6 of Preparation Example 1-4 was used as the conductive material.

[0159] <Comparative Example 2-1: Preparation of an all-solid-state battery containing bare VGCF>

[0160] An all-solid-state battery containing Bare VGCF was prepared by performing the same procedure as in Preparation Example 2-1, except that 2 wt% of Bare VGCF of Comparative Example 1-1 was used as the conductive material.

[0161] Figure 17 is a graph analyzing the ionic conductivity and tensile strength of an all-solid-state battery comprising the Bare VGCF of Comparative Example 2-1 of the present invention and the Conformal VGCF@Li3InCl6 of Preparation Example 2-4.

[0162] Referring to FIG. 17, it can be seen that the ionic conductivity and tensile strength of the all-solid-state battery containing Conformal VGCF@Li3InCl6 of Preparation Example 2-4 are both higher than those of the all-solid-state battery containing Bare VGCF of Comparative Example 2-1. This can be seen as a result of the provision of Li3InCl6 having high ionic conductivity.

[0163] FIG. 18 is a graph showing the microstructural analysis results of an all-solid-state battery containing Bare VGCF of Comparative Example 2-1 of the present invention, and FIG. 19 is a graph showing the microstructural analysis results of an all-solid-state battery containing Conformal VGCF@Li3InCl6 of Manufacturing Example 2-4 of the present invention.

[0164] Referring to FIGS. 18 and 19, the NCM active material included in the all-solid-state battery containing the bare VGCF of Comparative Example 2-1 of FIG. 18 exhibits an agglomeration pattern, and uneven lithium ion percolation can be observed. On the other hand, in the all-solid-state battery containing the Conformal VGCF@Li3InCl6 of FIG. 19, no agglomeration of the NCM active material is observed, and smooth lithium ion percolation can be observed. Through this, it can be seen that the conductive material of the present invention, when equipped with a halide-based solid electrolyte, can secure solid electrolyte agglomeration inhibition and stability, and enables uniform ion transfer within the electrode.

[0165] FIG. 20 is a voltage-capacity graph of the initial charge-discharge cycle of an all-solid-state battery comprising the Bare VGCF of Comparative Example 2-1 of the present invention and the Conformal VGCF@Li3InCl6 of Preparation Example 2-4.

[0166] Referring to FIG. 20, it can be seen that the initial discharge capacity of the electrode containing the conductive material equipped with the halide-based solid electrolyte of Preparation Example 2-4 is higher than that of Comparative Example 2-1.

[0167] FIG. 21 is a graph showing the rate performance of an all-solid-state battery comprising the Bare VGCF of Comparative Example 2-1 of the present invention and the Conformal VGCF@Li3InCl6 of Preparation Example 2-4.

[0168] Referring to FIG. 21, it can be seen that the electrode containing the conductive material equipped with the halide-based solid electrolyte of Preparation Example 2-4, compared to Comparative Example 2-1, exhibits excellent rate capability characteristics that maintain a higher capacity even as the number of charge-discharge cycles increases.

[0169] FIG. 22 is a graph showing the lifespan characteristics of an all-solid-state battery including the Bare VGCF of Comparative Example 2-1 of the present invention and the Conformal VGCF@Li3InCl6 of Preparation Example 2-4.

[0170] Referring to FIG. 22, it can be seen that the electrode containing the conductive material equipped with the halide-based solid electrolyte of Preparation Example 2-4 maintains a higher capacity than Comparative Example 2-1 up to about 150 charge-discharge cycles. Through this, it can be seen that the lifespan characteristics are improved when the conductive material equipped with the halide-based solid electrolyte of the present invention is applied to an electrode.

[0171] FIGS. 23a and FIGS. 23b are graphs showing the XPS analysis results at S 2p and P 2p after evaluating the life characteristics of an all-solid-state battery containing the Bare VGCF of Comparative Example 2-1 of the present invention and the Conformal VGCF@Li3InCl6 of Preparation Example 2-4.

[0172] Referring to FIG. 23a and FIG. 23b, it can be seen that in the case of the electrode containing the bare VGCF of Comparative Example 2-1, peaks related to lithium sulfide, phosphorus sulfide, and sulfate appear after 100 cycles. This can be seen as a result of the linear carbon material reacting with the sulfide-based solid electrolyte in the electrode after charge-discharge cycles, causing the solid electrolyte to oxidize or side reactions to occur.

[0173] On the other hand, in the case of the electrode containing Conformal VGCF@Li3InCl6 of Preparation Example 2-4, it can be confirmed that lithium sulfide, phosphorus sulfide, and sulfate peaks, such as those of Comparative Example 2-1, do not appear even after 100 cycles. Through this, it can be seen that the conductive material of the present invention effectively suppresses side reactions with the solid electrolyte (Li6PS5Cl) in the electrode by providing a halide-based solid electrolyte to a linear carbon material.

[0174] FIGS. 24a and FIGS. 24b are schematic diagrams of the interfacial reaction of an all-solid-state battery comprising Bare VGCF of Comparative Example 2-1 of the present invention and Conformal VGCF@Li3InCl6 of Preparation Example 2-4, respectively.

[0175] As shown in FIG. 24a, in the electrode containing the bare VGCF of Comparative Example 2-1, the solid electrolyte (SE) and the bare VGCF react during the charge-discharge cycle, and a degradation reaction may occur in region A where the solid electrolyte (SE) and the bare VGCF come into contact.

[0176] On the other hand, as shown in FIG. 24b, in the case of the electrode containing the Conformal VGCF@Li3InCl6 of Preparation Example 2-4, as the halide-based solid electrolyte is coated in a conformal form on the surface of the linear carbon material, the conductive material and the solid electrolyte can form a stable interface as in region B during the charge-discharge cycle. This is consistent with the results of FIG. 23a and FIG. 23b described above.

[0177] FIG. 25 is a voltage-capacity graph of the initial charge-discharge cycle of an all-solid-state battery comprising the Bare VGCF of Comparative Example 2-1 of the present invention, the Island VGCF@Li3InCl6 of Preparation Example 2-2, and the Conformal VGCF@Li3InCl6 of Preparation Example 2-4. The specific charge-discharge capacities and Coulomb efficiencies are as shown in Table 1 below.

[0178] Classification Charge Capacity (mAh g) -1)Discharge Capacity (mAh g -1 )First Coulomb Efficiency (%) Comparison Example 2-1 207.1 154.6 75.4 Manufacturing Example 2-2 212.8 161.3 75.8 Manufacturing Example 2-4 209.1 159.0 75.8

[0179] Referring to Figure 25 and Table 1, it can be seen that the initial charge / discharge capacity of the electrode containing the conductive material of the Island VGCF@Li3InCl6 of Preparation Example 2-2 is the highest.

[0180] FIG. 26 is a graph showing the rate performance of an all-solid-state battery comprising the Bare VGCF of Comparative Example 2-1 of the present invention, the Island VGCF@Li3InCl6 of Preparation Example 2-2, and the Conformal VGCF@Li3InCl6 of Preparation Example 2-4. The specific capacity retention rate and average Coulomb efficiency are as shown in Table 2 below.

[0181] Separation capacity retention rate @ 40 th (%) Average Coulomb efficiency (~40 th cycle, %) Comparative Example 2-180.299.7 Manufacturing Example 2-285.899.8 Manufacturing Example 2-484.499.8

[0182] Referring to Figure 26 and Table 2, it can be seen that the highest capacity retention rate was observed after 40 cycles of the electrode containing Island VGCF@Li3InCl6 of Preparation Example 2-2.

[0183] FIG. 27 is a graph analyzing the ionic conductivity and tensile strength of an all-solid-state battery comprising the Bare VGCF of Comparative Example 2-1 of the present invention, the Island VGCF@Li3InCl6 of Preparation Example 2-2, and the Conformal VGCF@Li3InCl6 of Preparation Example 2-4. The specific ionic conductivity and tensile strength values ​​are as shown in Table 3 below.

[0184] Classification Ionic Conductivity (S / cm) Tensile Strength (MPa) Comparative Example 2-11.09 E-40.23 Manufacturing Example 2-21.26 E-40.39 Manufacturing Example 2-41.34 E-40.33

[0185] Referring to Figure 27 and Table 3, it can be confirmed that the ionic conductivity and tensile strength of the electrode containing Island VGCF@Li3InCl6 of Preparation Example 2-2 are the highest. This can be attributed to the fact that the Island VGCF@Li3InCl6 of Preparation Example 2-2 has excellent interfacial characteristics with PTFE, the binder, as the carbon layer of the linear carbon material is exposed between the Li3InCl6 particles, thereby minimizing cracks between the carbon layer and PTFE. As described above, the conductive material equipped with the halide-based solid electrolyte of the present invention can be provided on a linear carbon material by island coating or conformal coating of the halide-based solid electrolyte, which has high electrochemical stability and ionic conductivity. This allows for increased stability by suppressing reactions with sulfide-based solid electrolytes, and since it exhibits improved mechanical properties such as tensile strength, capacity, and excellent charge / discharge characteristics, it can be usefully utilized as a conductive material for all-solid-state batteries.

[0186] The present invention is not limited to the above embodiments and can be manufactured in various different forms, and those skilled in the art will understand that the invention can be implemented in other specific forms without changing the technical concept or essential features of the invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

1. A step of coating a linear carbon material with a halide-based solid electrolyte precursor solution; and A method for manufacturing a conductive material comprising the step of heat-treating a linear carbon material coated with the above-mentioned halide-based solid electrolyte precursor solution.

2. In Paragraph 1, A method for manufacturing a conductive material comprising a halide-based solid electrolyte of the following chemical formula 1, wherein the above-mentioned halide-based solid electrolyte precursor solution is prepared by reacting a lithium (Li) halide with at least one metal halide in a solvent: [Chemical Formula 1] Li a M b X6 In the above chemical formula 1, 1≤a≤3, 0 <b≤1, a+3b=6이고, The above M is one or more metallic elements selected from In, Yb, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Lu, and The above X is one or more halogen elements selected from F, Cl, Br, and I.

3. In Paragraph 1, A method for manufacturing a conductive material, wherein the above-mentioned halide-based solid electrolyte precursor solution comprises one or more selected from Li3InCl6, Li3YCl6, Li3YBr6, Li3HoCl6, and Li3ScCl6.

4. In Paragraph 1, In the step of coating the above halide-based solid electrolyte precursor solution, A method for manufacturing a conductive material, comprising mixing 0.3 to 0.7 parts by weight of the halide-based solid electrolyte precursor solution with 100 parts by weight of the linear carbon material.

5. In Paragraph 1, A method for manufacturing a conductive material, wherein the above heat treatment is performed at 250 to 290°C for 2 to 4 hours.

6. In the step of heat treatment according to claim 1, A method for manufacturing a conductive material, comprising synthesizing a halide-based solid electrolyte in the form of an island on the surface of the above linear carbon material.

7. In Paragraph 1, Prior to the step of coating the above halide-based solid electrolyte precursor solution, The method further includes the step of surface-treating the linear carbon material with acid to form oxygen-containing functional groups on the surface, In the above heat treatment step, A method for manufacturing a conductive material, comprising synthesizing a halide-based solid electrolyte in a conformal form on the surface of the above linear carbon material.

8. Linear carbon materials; and A conductive material comprising a halide-based solid electrolyte provided on the surface of the above linear carbon material.

9. In Paragraph 8, The above halide-based solid electrolyte is a conductive material represented by the following chemical formula 1: [Chemical Formula 1] Li a M b X6 In the above chemical formula 1, 1≤a≤3, 0 <b≤1, a+3b=6이고, The above M is one or more metallic elements selected from In, Yb, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Lu, and The above X is one or more halogen elements selected from F, Cl, Br, and I.

10. In Paragraph 8, The above halide-based solid electrolyte is a conductive material coated in an island shape on the surface of the above linear carbon material.

11. In Paragraph 8, The above halide-based solid electrolyte is a conductive material coated in a conformal form on the surface of the above linear carbon material.

12. In Paragraph 8, The above conductive material is a conductive material used in electrodes for all-solid-state batteries.

13. A solid electrolyte layer provided between the anode and the cathode, and A conductive material is provided on at least one of the above anode and cathode, and The above conductive material comprises a linear carbon material and a halide-based solid electrolyte provided on the surface of the linear carbon material, in an all-solid-state battery.

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