Hard carbon composite for anode material of sodium secondary battery, and manufacturing method therefor

Abstract

The present invention relates to a hard carbon composite for an anode material of a sodium secondary battery, and a manufacturing method therefor. The hard carbon composite for an anode material of a sodium secondary battery, according to the present invention, can provide excellent electrochemical performance, structural stability and battery capacity in an anode material of a sodium secondary battery and minimize problems of metal volume expansion and dendrite formation. In addition, the method for manufacturing the hard carbon composite for an anode material of a sodium secondary battery, according to the present invention, can manufacture the hard carbon composite for an anode material, is environmentally friendly and is cost-effective. Additionally, a uniform composite is manufactured to enable material waste to be reduced and quality to be improved, and is suitable for large-scale manufacturing.

Description

Hard carbon composite for sodium secondary battery negative electrode material and method for manufacturing the same

[0001] The present invention relates to a hard carbon composite for a sodium secondary battery negative electrode material and a method for manufacturing the same, and more specifically, to a hard carbon composite for a sodium secondary battery negative electrode material having excellent electrochemical performance, structural stability and battery capacity; and a method for manufacturing a hard carbon composite for a sodium secondary battery negative electrode material having advantages in environment and cost and of excellent quality.

[0002]

[0003] Sodium-ion battery technology is garnering global attention as an alternative to overcome the limitations of lithium-ion batteries. The depletion of lithium resources and rising costs are acting as major obstacles to the development of energy storage technology worldwide; consequently, battery technology utilizing sodium, a relatively abundant and inexpensive resource, is gaining prominence. While lithium-ion batteries are widely used in electric vehicles and energy storage systems, their drawbacks include safety issues in high-temperature environments and performance degradation at low temperatures. In contrast, sodium-ion batteries are promising in terms of safety due to their low risk of explosion and fire, and they are highly likely to maintain performance even in both high and low-temperature environments. For this reason, sodium-ion batteries are evaluated as a technology with significant potential in various fields, including electric vehicles and energy storage systems.

[0004] However, for the commercialization of sodium-ion batteries, there are still challenges to overcome in various aspects, such as electrochemical performance, energy density, lifespan, and stability. Solving these challenges is a key to enhancing the market competitiveness of sodium-ion batteries and enabling a wider range of applications.

[0005]

[0006] Since the performance of the cathode material directly affects important indicators such as battery energy density, lifespan, charge / discharge efficiency, and safety, improving the cathode material is essential for enhancing overall battery performance.

[0007] Hard carbon is widely used as a negative electrode material in conventional sodium-ion batteries, and is suitable as a negative electrode material for sodium-ion batteries due to its excellent electrical properties and structural stability. However, when using negative electrode materials made of conventional hard carbon in sodium-ion batteries, the theoretical capacity was limited and the output performance was lower compared to lithium-ion batteries, so the development of high-capacity negative electrode materials remained an urgent task.

[0008] Meanwhile, cathode materials using only metals have faced limitations in the commercialization of sodium-ion batteries due to volume expansion problems and dendrite formation occurring during the alloying process of sodium and metal, which can shorten battery life and cause safety issues. Specifically, volume expansion causes physical deformation of the electrode, thereby shortening its lifespan, and dendrites can cause short circuits within the battery, posing a significant risk. Therefore, there was a need to develop a new cathode material that could compensate for these disadvantages while maintaining the advantages of metals.

[0009]

[0010] The present invention was devised to overcome the aforementioned problems, and the first problem to be solved in the present invention is to provide a hard carbon composite for a sodium secondary battery negative electrode that has excellent electrochemical performance, structural stability, and battery capacity, and can minimize metal volume expansion and dendrite formation problems.

[0011] The second problem to be solved in the present invention is to provide a method for manufacturing a hard carbon composite for a sodium secondary battery negative electrode material that can manufacture the hard carbon composite, is environmentally friendly and cost-effective, reduces material waste and improves quality through the manufacture of a uniform composite, and is suitable for large-scale manufacturing.

[0012]

[0013] To solve the first problem described above, a hard carbon composite for a sodium secondary battery negative electrode material comprising metal and hard carbon is provided.

[0014] According to one embodiment of the present invention, the metal may be a transition metal.

[0015] In addition, the above transition metal may be alloyed with Na ions.

[0016] In addition, the weight ratio of the metal and the hard carbon may be 1:9 to 9:1, and preferably 3:7 to 7:3.

[0017] In addition, the hard carbon composite may further include a binder.

[0018]

[0019] To solve the second problem described above, a method for manufacturing a hard carbon composite for a sodium secondary battery negative electrode is provided, comprising: (1) a step of mixing a metal and hard carbon to form a mixture; and (2) a step of compounding the mixture to manufacture a hard carbon composite.

[0020] In addition, the metal and hard carbon can be mixed in a weight ratio of 1:9 to 9:1.

[0021] In addition, the above mixture can be compounded using a dry process.

[0022] According to one embodiment of the present invention, the dry process may be an air jet process.

[0023] In addition, the above air jet process may include a high-speed rotation process of 1000 to 4000 RPM.

[0024]

[0025] The hard carbon composite for a sodium secondary battery negative electrode according to the present invention has excellent electrochemical performance, structural stability, and battery capacity in a sodium secondary battery negative electrode, and can minimize metal volume expansion and dendrite formation problems.

[0026] In addition, the method for manufacturing a hard carbon composite for a sodium secondary battery negative electrode according to the present invention can manufacture the hard carbon composite for the negative electrode, is environmentally friendly, and cost-effective. Furthermore, by manufacturing a uniform composite, material waste can be reduced and quality improved, and it is suitable for large-scale manufacturing.

[0027]

[0028] The effects of the present invention are not limited to the effects described above, and should be understood to include all effects that can be inferred from the composition of the invention described in the description or claims of the present invention.

[0029]

[0030] FIG. 1 is a schematic diagram showing the manufacturing process of a hard carbon composite for a sodium secondary battery negative electrode material according to a preferred embodiment of the present invention.

[0031]

[0032] Hereinafter, the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement it. The present invention may be embodied in various different forms and is not limited to the embodiments described herein. In the drawings, parts unrelated to the explanation have been omitted to clearly explain the present invention.

[0033] The terms used in this specification are used merely to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, terms such as "comprising" or "having" are intended to indicate the presence of the features, numbers, steps, actions, components, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, or combinations thereof.

[0034] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this specification.

[0035]

[0036] As described above, when conventional hard carbon anode materials were used in sodium-ion batteries, their theoretical capacity was limited and their output performance was lower compared to lithium-ion batteries. Meanwhile, anode materials using only metals resulted in a shortened battery life and safety issues due to volume expansion problems and dendrite formation that occurred during the alloying process of sodium and metal.

[0037]

[0038] Accordingly, the present invention sought to solve the aforementioned problem by providing a hard carbon composite for a sodium secondary battery negative electrode material comprising metal and hard carbon.

[0039] A sodium secondary battery anode material containing this has excellent electrochemical performance, structural stability, and battery capacity, and can minimize metal volume expansion and dendrite formation problems.

[0040] FIG. 1 is a schematic diagram showing the manufacturing process of a hard carbon composite for a sodium secondary battery negative electrode material according to a preferred embodiment of the present invention. Hereinafter, the hard carbon composite of the present invention will be described with reference to FIG. 1.

[0041]

[0042] First, the metal included in the hard carbon composite of the present invention will be described.

[0043] When the above metal is included in a hard carbon composite and used as a negative electrode material, the electrical conductivity and battery capacity of the sodium secondary battery can be improved.

[0044] The above metal may be a transition metal, and preferably, the metal may be a transition metal capable of alloying with Na ions. For example, the above transition metal may be one or more selected from the group consisting of Sb, Bi, Sn, In, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu.

[0045] The above metal may be included in the hard carbon composite in the form of particles, and the average diameter of the metal particles may be 70 nm to 20 μm.

[0046]

[0047] The above hard carbon refers to amorphous carbon, which has an irregular atomic arrangement and includes nanocrystalline regions, and generally refers to a material produced by carbonizing organic matter.

[0048] When the above-mentioned hard carbon is included in a hard carbon composite and used as a negative electrode material, it can impart excellent electrical characteristics and structural stability to a sodium secondary battery. Specifically, the hard carbon provides a low-energy barrier suitable for interaction with Na ions, possesses an amorphous and micropore structure, and offers flexibility for Na ion insertion due to a wider interlayer distance than graphite, and can provide excellent electrical characteristics such as high battery capacity as it contains nanocrystalline regions and exhibits relatively high electronic conductivity. Furthermore, the hard carbon can have high durability and provide long-term lifespan characteristics due to its amorphous-crystalline mixed structure.

[0049] Since the above-mentioned hard carbon can be used without limitation as long as it is of a type commonly available in the industry, the present invention is not limited thereto.

[0050] The hard carbon may be included in the hard carbon composite in the form of particles, and the average diameter of the hard carbon particles may be 1 to 10 μm.

[0051]

[0052] The weight ratio of the metal and the hard carbon may be 1:9 to 9:1, and preferably 3:7 to 7:3. More preferably 4:6 to 6:4. For example, the metal and the hard carbon may be included in a hard carbon composite in a 5:5 ratio, and the metal and the hard carbon may offset each other's disadvantages to produce a synergistic effect in the cathode material.

[0053] If the weight ratio of the metal is less than 1 in the above weight ratio of 1:9, the metal content is excessively low, so the electrical conductivity of the battery may not increase, the battery capacity may be very insufficient, and a problem may occur where the hard carbon and the metal do not become composite. If the weight ratio of the metal exceeds 9 in the above weight ratio of 9:1, the hard carbon content is excessively low, so volume expansion and dendrite formation problems occur in the metallized negative electrode, which may reduce the durability of the negative electrode and decrease the battery life, and the capacity may decrease rapidly after the initial cycle.

[0054] Meanwhile, when the above weight ratio is in the range of 3:7 to 7:3, the electrical conductivity and battery capacity increase compared to when the weight ratio is 1:9 to 9:1, and the battery life may be increased.

[0055]

[0056] The metal and the hard carbon may be randomly arranged within the hard carbon composite, but may also be uniformly arranged. As the metal and the hard carbon are uniformly arranged, the electrochemical performance of the cathode material or sodium secondary battery containing the hard carbon composite can be excellent and consistent.

[0057]

[0058] The above hard carbon composite may further include a binder.

[0059] The above binder can bond metal, hard carbon, or negative current collectors together, thereby maintaining the mechanical stability and electrochemical performance of the electrode. Without the binder, there is a possibility that the active material will peel off or the electrode structure will collapse.

[0060] The above binder is not limited to any that can combine metal and hard carbon in the industry, but preferably the binder may be a polymer, and more preferably the binder may be one or more selected from the group consisting of CMC (Carboxymethyl Cellulose), PAA (Polyacrylic Acid), Sodium alginate, SBR (Styrene-Butadiene Rubber), PVDF (Polyvinylidene Fluoride), PEO (Polyethylene Oxide), PAN (Polyacrylonitrile), PVAm (Polyvinylamine), HEC (hydroxyethyl Cellulose), Xanthan Gum, PEG (Polyethylene Glycol), PEDOT:PSS (Poly(3,4-ethylenedioxythiophene) Polystyrene Sulfonate), PI (Polyimaide), and PTFE (Polytetrafluoroethylene).

[0061] The binder may be included in an amount of 0.1 to 50 weight percent relative to the total weight of the composite. Preferably, it may be included in an amount of 1 to 10 weight percent.

[0062]

[0063] Meanwhile, the hard carbon composite of the present invention can be included in a negative electrode active material and used as a negative electrode material. If the hard carbon composite is included in a negative electrode active material, the negative electrode active material can be combined with a negative electrode current collector.

[0064] At this time, since the above-mentioned cathode current collector can be used without limitation as long as it is a current collector commonly used in the industry, the present invention does not specifically limit it thereto.

[0065]

[0066] To solve the above-mentioned problem, a method for manufacturing a hard carbon composite for a sodium secondary battery negative electrode material is provided, comprising: (1) a step of mixing a metal and a hard carbon to form a mixture; and (2) a step of compounding the mixture to manufacture a hard carbon composite.

[0067] This manufacturing method can produce the aforementioned hard carbon composite for sodium secondary battery anode materials, and is environmentally friendly and cost-effective. Furthermore, the production of a uniform composite can reduce material waste and improve quality, and is suitable for large-scale manufacturing.

[0068] Hereinafter, a method for manufacturing a hard carbon composite of the present invention will be described in detail with reference to FIG. 1.

[0069]

[0070] First, as step (1), a mixture is formed by mixing the metal and the hard carbon. Since the metal and the hard carbon are as described above, their specific details are omitted.

[0071] The above metal and hard carbon may be mixed in powder form, but are not limited thereto. If mixed in powder form, the metal and hard carbon may be obtained in powder form by mechanical milling.

[0072] The metal and hard carbon may be mixed in a weight ratio of 1:9 to 9:1. If the weight ratio of the metal in the 1:9 ratio is less than 1, the metal content is excessively low, which may result in the electrical conductivity of the battery not increasing, the battery capacity being very insufficient, and a problem of failure to composite the hard carbon and the metal. If the weight ratio of the metal in the 9:1 ratio exceeds 9, the hard carbon content is excessively low, which may result in volume expansion and dendrite formation problems in the methylated cathode, leading to reduced durability of the cathode and a decrease in battery life, and a rapid decrease in capacity after the initial cycle.

[0073] Meanwhile, when the above weight ratio is in the range of 3:7 to 7:3, the electrical conductivity and battery capacity increase compared to when the weight ratio is 1:9 to 9:1, and the battery life may be increased.

[0074]

[0075] When forming the above mixture, a binder may be further mixed and may be mixed in an amount of 0.1 to 50 weight percent relative to the total weight of the mixture. Preferably, it may be mixed in an amount of 1 to 10 weight percent. Specific details regarding the binder are as described above.

[0076]

[0077] Next, as step (2), the mixture formed in step (1) is combined to produce a hard carbon composite.

[0078] The above mixture can be compounded through a dry process. For example, the dry process may be a thermal evaporation process, a vacuum deposition process, an atomic layer deposition (ALD) process, a chemical vapor deposition (CVD) process, a physical vapor deposition (PVD) process, or an air jet process, but is not limited thereto.

[0079] Since the present invention is compounded through a dry process, it is environmentally friendly as it does not use solvents, thus preventing the release of volatile organic compounds and eliminating the need for solvent treatment, and can reduce costs due to the absence of solvent treatment costs and the simplicity of the process.

[0080]

[0081] The above dry process is preferably an air jet process. By using an air jet process, uniform dispersion of metal and hard carbon is ensured, particle size can be finely controlled, and thermal deformation of metal or hard carbon can be minimized by not using high temperatures. In addition, since the air jet process can be performed with simple equipment, particle processing is possible without additional chemical treatment, and continuous processing is possible, which can be advantageous for automation and mass production.

[0082] If the composite is formed using an air jet process, the hard carbon composite can be manufactured on a substrate, and preferably on a negative current collector.

[0083] In addition, the air jet process may include a high-speed rotation process of 1,000 to 4,000 RPM, and preferably a high-speed rotation process of 2,000 to 3,000 RPM. Specifically, the high-speed rotation process may involve the rotation of a rotary impeller inside a classifier or grinder. Through this, efficient grinding of metals and hard carbons is possible, particle sizes can be precisely classified, and particle size uniformity can be ensured, thereby ensuring uniform quality of the manufactured hard carbon composite and maximizing electrochemical performance.

[0084]

[0085] Furthermore, the above dry process can be performed at 10 to 80 ℃ for 5 to 30 minutes. Preferably, the above dry process can be performed as an air jet process at 20 to 50 ℃ for 5 to 30 minutes.

[0086]

[0087] Meanwhile, a negative electrode material comprising a hard carbon composite according to the present invention or a sodium secondary battery comprising the negative electrode material may be provided.

[0088] The above sodium secondary battery may include a cathode material, an electrolyte, and a separator, and each of the cathode material, electrolyte, and separator is not limited as long as it is one that can be conventionally used in the industry.

Claims

1. A hard carbon composite for a sodium secondary battery negative electrode material comprising metal and hard carbon.

2. In Paragraph 1, A hard carbon composite for a sodium secondary battery negative electrode material, characterized in that the above metal is a transition metal.

3. In Paragraph 2, A hard carbon composite for a sodium secondary battery negative electrode material, characterized in that the above transition metal is capable of alloying with Na ions.

4. In Paragraph 1, A hard carbon composite for a sodium secondary battery negative electrode material, characterized in that the weight ratio of the metal and the hard carbon is 1:9 to 9:

1.

5. In Paragraph 4, A hard carbon composite for a sodium secondary battery negative electrode material, characterized in that the weight ratio of the metal and the hard carbon is 3:7 to 7:

3.

6. In Paragraph 1, A hard carbon composite for a sodium secondary battery negative electrode material, characterized by further including a binder.

7. (1) A step of mixing metal and hard carbon to form a mixture; and (2) A step of manufacturing a hard carbon composite by compounding the above mixture; a method for manufacturing a hard carbon composite for a sodium secondary battery negative electrode material.

8. In Paragraph 7, A method for manufacturing a hard carbon composite for a sodium secondary battery negative electrode material, characterized in that the metal and hard carbon are mixed in a weight ratio of 1:9 to 9:

1.

9. In Paragraph 7, A method for manufacturing a hard carbon composite for a sodium secondary battery negative electrode material, characterized by compounding the above mixture using a dry process.

10. In Paragraph 9, A method for manufacturing a hard carbon composite for a sodium secondary battery negative electrode material, characterized in that the above dry process is an air jet process.

11. In Paragraph 10, A method for manufacturing a hard carbon composite for a sodium secondary battery negative electrode material, characterized in that the above air jet process includes a high-speed rotation process of 1,000 to 4,000 RPM.

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