KR20230173825A - Manufacturing method of carbon-based material and current collector for lithium secondary battery coated with the same - Google Patents

Abstract

The present invention relates to a method for producing a carbon-based material and a current collector coated with the carbon-based material produced by the production method. More specifically, the carbon-based material produced by the production method of the present invention is applied to a current collector for a lithium secondary battery. It relates to an invention that can be applied to improve battery performance and suppress lithium dendrite growth.

Description

Manufacturing method of carbon-based material and current collector for lithium secondary battery coated with carbon-based material {MANUFACTURING METHOD OF CARBON-BASED MATERIAL AND CURRENT COLLECTOR FOR LITHIUM SECONDARY BATTERY COATED WITH THE SAME}

The present invention relates to a method for producing a carbon-based material and a current collector coated with the carbon-based material produced by the production method. More specifically, the carbon-based material produced by the production method of the present invention is applied to a current collector for a lithium secondary battery. It relates to an invention that can improve overall battery performance and inhibit lithium dendrite growth by coating on .

Lithium secondary batteries have much better energy storage capacity and lifespan compared to existing secondary batteries (lead acid batteries, nickel hydride batteries).

The application field of the lithium secondary battery is expanding not only to portable devices but also to electric vehicles. Specifically, internal combustion engine vehicles using fossil fuels are gradually being replaced by electric vehicles using lithium-ion batteries, and if electric vehicles are fully commercialized, air pollution and global warming caused by fossil fuels can be reduced, and in the long run, human It will be of great significance in preserving the environment in which we live. In addition, lithium-ion batteries are also being applied to energy storage systems (ESS), which are essential for new and renewable systems such as wind power and solar power.

In this way, lithium metal batteries have been developed as next-generation lithium secondary batteries to improve the energy density of lithium secondary batteries used in various applications.

The lithium metal battery uses lithium metal as a negative electrode material. When the battery is discharged, the lithium metal in the negative electrode loses electrons and moves to the positive electrode through the electrolyte, and when the battery is charged, lithium ions move to the negative electrode through the electrolyte and become the negative electrode active material. It is a battery that uses electrochemical reactions stored in . This has the advantage of theoretically having a very high energy capacity compared to commercial lithium ion batteries that use graphite or the like as a negative electrode material.

However, as the lithium metal battery uses a lithium metal negative electrode material, there is a problem in that dendrites are generated on the surface of the lithium metal negative electrode material during charging and discharging. Dendrites are crystals that accumulate in the shape of tree branches on the surface of lithium metal and interfere with the movement of lithium ions, resulting in problems such as reduced charging and discharging efficiency, short circuits, and shortened lifespan.

Therefore, in order to commercialize lithium metal batteries using lithium metal as a negative electrode material, there remains a task of solving the problem of dendrite generation.

The first problem of the present invention is to provide a novel method for producing a carbon-based material capable of controlling the particle shape and particle size of the carbon-based material.

The second problem of the present invention is to provide a method for producing a carbon-based material and a current collector for a lithium secondary battery coated with the carbon material produced by the method.

The third problem of the present invention is to provide a current collector for a lithium secondary battery that can improve the performance of a lithium metal battery using lithium metal as a negative electrode and improve the overall performance of the battery by suppressing dendrite growth.

The objects of the present invention are not limited to the objects mentioned above, and other objects and advantages of the present invention that are not mentioned can be understood by the following description and will be more clearly understood by the examples of the present invention. Additionally, it will be readily apparent that the objects and advantages of the present invention can be realized by means and combinations thereof as set forth in the claims.

In order to achieve the above object, the present invention

(A) preparing a basic carbon nitride precursor composition and an acidic carbon nitride precursor composition; and

(B) providing a method for producing a carbon-based material, including the step of adding the acidic carbon nitride precursor composition to the basic carbon nitride precursor composition in a dropwise manner and reacting the acidic carbon nitride precursor composition.

According to one embodiment of the present invention, the acidic carbon nitride precursor composition and the basic carbon nitride precursor composition may react at 0°C to 20°C, or 5°C to 18°C.

According to one embodiment of the present invention, the basic carbon nitride precursor composition includes a carbon nitride precursor having a basic functional group, and the basic functional group is a group consisting of an amine group, an imine group, an amide group, an azide group, a nitrate group, or an ammonium group. One or more types may be selected from .

According to one embodiment of the present invention, the acidic carbon nitride precursor composition includes a carbon nitride precursor having an acidic functional group, wherein the acidic functional group is a hydroxyl group, a carboxyl group, an ester group, a phosphine group, a phosphoric acid group, a phosphonic acid group, or a sulfonic acid group. One or more types may be selected from the group consisting of groups.

According to one embodiment of the present invention, the particle size (diameter) of the prepared carbon-based material is 500 nm to 50 ㎛, the BET surface area is 50 m ² /g to 120 m ² /g, and the pore size is 10 to 120 m 2 /g. It is 30 nm, and the pore volume may be 0.2 to 0.6 cm ³ /g.

Meanwhile, in order to achieve the above object, the present invention

(A) preparing a basic carbon nitride precursor composition and an acidic carbon nitride precursor composition; and

(B) A current collector for a lithium secondary battery including a coating layer coated with a carbon-based material prepared by reacting the acidic carbon nitride precursor composition to the basic carbon nitride precursor composition in a dropwise manner.

According to one embodiment of the present invention, coating the carbon-based material includes preparing a coating composition including the carbon-based material and a binder; And it may include coating the coating composition on at least one surface of the metal thin film layer.

According to one embodiment of the present invention, the metal may be one or two or more alloys selected from the group consisting of copper, aluminum, nickel, titanium, and stainless steel.

According to one embodiment of the present invention, the viscosity of the coating composition may be controlled to 0.05 to 0.2 g/ml.

According to one embodiment of the present invention, the thickness of the coating layer may be 1 to 10 ㎛.

The present invention is a cathode;

anode and

It includes a separator formed between the cathode and the anode,

The current collector of the negative electrode is the current collector for a lithium secondary battery described above, and in this case, a lithium secondary battery in which the negative electrode is lithium metal can be provided.

The means for solving the above problems do not enumerate all the features of the present invention. The various features of the present invention and its advantages and effects can be understood in more detail by referring to the specific examples below.

According to the present invention, it is possible to provide a current collector in which at least one surface of a metal thin film layer is coated with a carbon-based material manufactured by the manufacturing method of the present invention.

In particular, the carbon-based material produced by the manufacturing method of the present invention has porous spherical physical properties, and thus can effectively suppress the volume expansion of lithium and the growth of lithium dendrites, thereby improving the overall performance of the lithium metal battery.

In addition to the above-described effects, specific effects of the present invention are described below while explaining specific details for carrying out the invention.

Figure 1 shows a flow chart of a method for manufacturing a carbon-based material according to an embodiment of the present invention.
Figure 2 is a schematic diagram of a current collector coated with gC ₃ N ₄ according to an embodiment of the present invention.
Figure 3 shows a FE-SEM photograph of gC ₃ N ₄ synthesized according to an example of the present invention.
Figure 4 shows a FE-SEM photograph of gC ₃ N ₄ synthesized according to a comparative example of the present invention.
Figure 5 is a schematic diagram showing the structure of a half cell manufactured in one embodiment of the present invention.
Figure 6 shows the results of electrochemical testing of a battery manufactured in one embodiment of the present invention.

Hereinafter, the principles of preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings and description. However, the drawings shown below and the description below are for preferred implementation methods among various methods for effectively explaining the characteristics of the present invention, and the present invention is not limited to the drawings and description below.

Meanwhile, terms such as first or second may be used to describe various components, but these terms should be interpreted only for the purpose of distinguishing one component from other components. For example, a first component may be named a second component, and similarly, the second component may also be named a first component.

Singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as “comprise” or “have” are intended to designate the presence of the described features, numbers, steps, operations, components, parts, or combinations thereof, and are intended to indicate the presence of one or more other features or numbers, It should be understood that this does not exclude in advance the possibility of the presence or addition of steps, operations, components, parts, or combinations thereof.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the art. Terms as defined in commonly used dictionaries should be interpreted as having meanings consistent with the meanings they have in the context of the related technology, and unless clearly defined in this specification, should not be interpreted in an idealized or overly formal sense. No.

1 is a flowchart showing a method for producing a carbon-based material according to the present invention. Referring to Figure 1, the present invention,

(A) preparing a basic carbon nitride precursor composition and an acidic carbon nitride precursor composition; and

(B) providing a method for producing a carbon-based material including the step of adding the acidic carbon nitride precursor composition to the basic carbon nitride precursor composition in a dropwise manner and reacting the acidic carbon nitride precursor composition.

In addition, the present invention

(A) preparing a basic carbon nitride precursor composition and an acidic carbon nitride precursor composition; and

(B) A current collector for a lithium secondary battery is provided in which one surface of a metal thin film layer is coated with a carbon-based material prepared by reacting the basic carbon nitride precursor composition with the acidic carbon nitride precursor composition in a dropwise manner. .

Hereinafter, the present invention will be described in detail with reference to the drawings and examples of the present invention.

1. Steps for producing basic carbon nitride precursor composition and acidic carbon nitride precursor composition

According to one embodiment of the present invention, the basic carbon nitride precursor and the acidic carbon nitride precursor may each be a compound having a cyclic aromatic structure composed of carbon and nitrogen.

At this time, the basic carbon nitride precursor composition may include a carbon nitride precursor having a basic functional group, and the acidic carbon nitride precursor composition may include a carbon nitride precursor having an acidic functional group.

Here, the basic functional group may include, for example, an amine group, an imine group, an amide group, an azide group, a nitrate group, or an ammonium group. As a specific example, it may be an amine group, and the acidic functional group may include a hydroxy group, a carboxyl group, an ester group, It may include a phosphine group, a phosphoric acid group, a phosphonic acid group, or a sulfonic acid group, and a specific example may be a hydroxy group.

According to one embodiment of the present invention, the basic carbon nitride precursor composition may be a mixture of a basic carbon nitride precursor having a basic functional group and a solvent, and the basic carbon nitride precursor may include, for example, an aromatic ring of carbon and nitrogen. It may be melamine, which has an amine group as a functional group in its structure.

On the other hand, the solvent mixed with the basic carbon nitride precursor may include, for example, one or more selected from the group consisting of alcohols having 1 to 3 carbon atoms, acetonitrile, dialkylovamide, and dialkyl sulfoxide, and specific As an example, the solvent may be dimethyl sulfoxide (DMSO).

According to one embodiment of the present invention, the acidic carbon nitride precursor composition may be a mixture of an acidic carbon nitride precursor having an acidic functional group and a solvent, and the acidic carbon nitride precursor may include, for example, an aromatic ring of carbon and nitrogen. It may be cyanuric acid, which has a hydroxy group as a functional group in its structure.

Meanwhile, the solvent mixed with the acidic carbon nitride precursor may include, for example, one or more selected from the group consisting of alcohols having 1 to 3 carbon atoms, acetonitrile, dialkylovamide, and dialkyl sulfoxide, and specific As an example, the solvent may be dimethyl sulfoxide (DMSO).

2. Dropwise adding the acidic carbon nitride precursor composition to the basic carbon nitride precursor composition.

The method for producing a carbon-based material of the present invention includes reacting the basic carbon nitride precursor composition and the acidic carbon nitride precursor composition to produce a final carbon-based material.

Specifically, in the method for producing a carbon-based material of the present invention, the reaction can be carried out by dropping the acidic carbon nitride precursor composition into the basic carbon nitride precursor composition.

In the past, carbon-based materials were synthesized by simply pouring an acidic carbon nitride precursor composition into a basic carbon nitride precursor composition. However, in the present invention, when pouring dropwise at a specific rate, the final The present invention was developed after discovering that the particle size, shape, and specific surface area of the product could be controlled.

In particular, when the precursor composition added in a dropwise manner was limited to an acidic carbon nitride precursor composition, porous particles (carbon-based material) having a three-dimensional spherical shape could be secured as the final product (FIGS. 3 and 3 4 comparison).

Additionally, in the present invention, the reaction between the basic carbon nitride precursor composition and the acidic carbon nitride precursor composition is characterized in that it is carried out at 0°C to 20°C, or 5°C to 18°C.

If the basic carbon nitride precursor composition and the acidic carbon nitride precursor composition react within the above-described temperature range, that is, a relatively low temperature range below room temperature, and the precursor composition added dropwise is limited to the acidic carbon nitride precursor composition, the final The resulting carbon-based material can be manufactured into three-dimensional spherical particles, making it possible to manufacture a carbon-based material with a controlled structure to maximize the desired effects of inhibiting lithium dendrite growth and improving battery performance.

Meanwhile, the method for producing a carbon-based material of the present invention includes the steps of (C) drying the reaction product generated through the reaction to produce a powder; and (D) heat treating the powder under a nitrogen atmosphere.

In the step of drying the reaction product produced through the reaction to produce a powder, the reaction product prepared by adding an acidic carbon nitride precursor composition to the basic carbon nitride precursor composition and reacting at an appropriate temperature is statically stored for 1 to 4 hours. It can be performed after remaining in a (static) state, centrifuging, and washing 1 to 5 times with deionized water and alcohol solution.

In this way, when retention, centrifugation, and washing steps are performed, a precipitate containing the desired carbon-based material can be effectively obtained as a reaction product.

The reaction product obtained through the above process can be manufactured into powder through drying. The drying step may be performed at 40°C to 100°C or 50°C to 70°C for 12 hours to 48 hours or 12 hours to 36 hours.

According to one embodiment of the present invention, the step of heat treating the powder in a nitrogen atmosphere includes raising the temperature to 1.8 ℃/min to 2.6 ℃/min for 2 to 6 hours at 450 ℃ to 600 ℃ in an inert gas atmosphere. It can be performed as:

As a specific example, the step of heat treating the powder under a nitrogen atmosphere may be performed by raising the temperature to 2°C/min to 2.5°C/min for 3 to 5 hours at 500°C to 600°C under a nitrogen atmosphere. In this case, a carbon-based material of the desired size and structure can be manufactured.

3. Physical properties of carbon-based materials

In one embodiment of the present invention, the carbon-based material is carbon nitride, graphene, carbon nanotube, fullerene, carbon nanoparticle, carbon nanowire ( carbon nanowire), natural graphite, artificial graphite, expanded graphite, activated carbon, and carbon fiber. As a specific example, the carbon-based material may be carbon nitride.

As a specific example, the carbon nitride may include graphitic carbon nitride (g-C3N4). The graphite-type carbon nitride is a carbon material containing nitrogen, and is a binary compound having a two-dimensional layered structure in which carbon and nitrogen are arranged alternately and hexagonal rings similar to graphene are spread out in two dimensions.

The graphite-type carbon nitride has stable allotropes of various CN structures, and has a higher nitrogen content than other nitrogen-carbon materials, so it can create effective reaction sites, thereby increasing electron donors/acceptors. Additionally, the concentration of nitrogen enhances wetting with the electrolyte, improving the efficiency of mass transfer and providing much additional pseudo-capacitance. Furthermore, graphite-type carbon nitride can be well crystallized due to its lamellar structure characteristics to promote charge transfer, and compared to graphene, it has the advantage of being easily synthesized by direct poly-condensation without complicated post-processing. there is.

By forming a coating layer on the current collector according to the present invention using this graphite-type carbon nitride, the overvoltage can be reduced by acting as an active site when lithium is electrodeposited due to the high affinity of nitrogen in carbon nitride for lithium. , the increased provision of active sites due to the high specific surface area of carbon nitride can stabilize the flux distribution of lithium ions, leading to uniform lithium electrodeposition, and in particular, the high porosity of spherical carbon nitride creates a space for storing lithium. By providing this, the volume expansion of lithium can be suppressed and dendrite growth can be suppressed, thereby improving the performance of lithium secondary batteries manufactured using it, especially lithium metal batteries.

The BET specific surface area of the final carbon-based material prepared according to the production method of the present invention is 30 m ² /g to 120 m ² /g, preferably 50 m ² /g to 120 m ² /g, more preferably 85 m 2 /g. It may be ² /g to 120 m ² /g. In particular, if the basic carbon nitride precursor composition and the acidic carbon nitride precursor composition react within a temperature range below room temperature, and the precursor composition introduced dropwise is limited to the acidic carbon nitride precursor composition, the BET specific surface area can be increased ( (see Table 1).

In one embodiment of the present invention, the average particle size of the carbon-based material may be 500 nm to 50 ㎛, preferably 1 ㎛ to 20 ㎛, more preferably 1 ㎛ to 10 ㎛. As the average particle size of the carbon-based material becomes smaller, the dispersibility of the carbon-based material improves when coated on a metal thin film layer, thereby improving the processability of battery manufacturing.

In one embodiment of the invention, the carbon-based material includes pores having a size of 20 nm to 30 nm, and the volume of the pores is 0.2 cm ³ /g to 0.6 cm ³ /g, preferably 0.2 cm ^{3 /} g. g to 0.5 cm ³ /g, more preferably 0.2 cm ³ /g to 0.4 cm ³ /g. Specifically, the size of the pores of the carbon-based material can be adjusted due to the bonding structure of the precursor, and the volume of pores having a size within the above range will be formed from 0.2 cm ³ /g to 0.4 cm ³ /g. In this case, it has the effect of effectively storing lithium and suppressing dendrite formation, but if it is formed smaller than 0.2 cm ³ /g, problems with dendrite formation may occur due to limited space.

In one embodiment of the present invention, the current collector coated with the carbon-based material may be a negative electrode current collector. Specifically, a current collector including a coating layer coated with a carbon-based material on at least one surface of the metal thin film layer can be used as a negative electrode current collector when applied to a full cell.

By using a current collector coated with the carbon-based material as a negative electrode current collector, dendrite growth caused by lithium metal can be suppressed, thereby improving battery performance and safety.

4. Current collector for lithium secondary battery and lithium secondary battery

Meanwhile, according to one embodiment of the present invention, the present invention

(A) preparing a basic carbon nitride precursor composition and an acidic carbon nitride precursor composition; and

(B) A current collector for a lithium secondary battery is provided in which at least one side of a metal thin film layer is coated with a carbon-based material prepared by reacting the basic carbon nitride precursor composition with the acidic carbon nitride precursor composition in a dropwise manner.

Here, the step of coating a carbon-based material on at least one surface of the metal thin film layer includes (E) preparing a coating composition including the carbon-based material and a binder; and (F) coating the coating composition on at least one surface of the metal thin film layer. The coating composition can be formed by mixing the above-described carbon-based material with a binder.

The binder is polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene, polyvinylpyrrolidone, polyacrylonitrile, polyvinylidene fluoride-trichloroethylene, polyvinylidene fluoride- Chlorotrifluoroethylene (PVdF-CTFE), polymethyl methacrylate, polyvinyl acetate, ethylene-co-vinyl acetate copolymer, polyethylene oxide, cellulose acetate, cellulose acetate butylate, cellulose acetate propionate, cyanoethyl An aqueous solution containing at least one selected from the group consisting of pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, acrylonitrile styrene butadiene copolymer, and polyimide. Alternatively, it may include non-aqueous (organic) polymers.

The binder may be mixed in an amount of 1 to 50 parts by weight or 10 to 30 parts by weight based on 100 parts by weight of the coating composition. When the binder within the above range is included, the adhesion between the coating layer formed from the slurry and the metal thin film layer on which the coating layer is formed can be improved to prevent the coating layer from peeling.

According to one embodiment of the present invention, the coating composition may include the carbon-based material and the binder in a weight ratio of 9:1 to 6:4 or 9:1 to 7:3. Through this, when forming a coating layer on at least one side of the metal thin film layer, it is possible to bind the carbon-based material to the current collector and facilitate the bonding of the carbon-based materials to each other, and to uniformly disperse the carbon-based material to improve battery performance. can be improved.

According to one embodiment of the present invention, the coating composition may further include a solvent. The solvent is not particularly limited as long as it can dissolve the carbon-based material, binder, etc. that constitute the coating composition to a certain level or more. For example, acetone, tetrahydrofuran, acetonitrile, dimethylformamide, dimethyl sulfoxide, Examples include dimethylacetamide, N-methyl-2-pyrrolidone (NMP), or water, and two or more of these may be used in combination.

According to one embodiment of the present invention, the viscosity of the coating composition may be controlled to 0.01 g/mL to 1 g/mL, 0.01 g/mL to 0.5 g/mL, or 0.05 g/mL to 0.2 g/mL. . Specifically, the viscosity of the coating composition can be adjusted within the above range by controlling the content of the components constituting the coating composition, and by controlling the viscosity of the coating composition within the above range, a coating layer is formed on at least one surface of the metal thin film layer. When forming, the carbon-based material can be uniformly dispersed by preventing the thickness from becoming too thin, and at the same time, the resistance can be prevented from becoming too high by preventing the thickness from becoming too thick. According to one embodiment of the present invention, the coating layer may be formed through a typical slurry coating method.

Meanwhile, according to one embodiment of the present invention, the metal forming the metal thin film layer may be one or two or more alloys selected from the group consisting of copper, aluminum, nickel, titanium, and stainless steel. As a specific example, The metal thin film layer may be copper foil (Cu foil).

According to one embodiment of the present invention, the thickness of the metal thin film layer may be 5 ㎛ to 500 ㎛, 5 ㎛ to 300 ㎛, or 5 ㎛ to 30 ㎛. When the thickness of the metal thin film layer is within the above range, deposition of carbon-based materials is easy and is effective in lowering the sheet resistance of the electrode.

According to one embodiment of the present invention, the coating layer is formed by dispersing and applying a carbon-based material, and may be formed on one or both sides of the metal thin film layer. As a specific example, the coating layer may be formed on one side of the metal thin film layer. The thickness of the coating layer may be 1 ㎛ to 100 ㎛, 1 ㎛ to 50 ㎛, or 1 ㎛ to 10 ㎛. If the thickness of the coating layer is too thin, an area where the metal thin film layer is exposed occurs and the coating layer is formed non-uniformly, and if the thickness of the coating layer is too thick, resistance due to the coating layer increases, which may reduce battery performance.

5. Lithium secondary battery including a current collector coated with a carbon-based material

According to one embodiment of the present invention, a cathode; A lithium secondary battery is provided, including a positive electrode and a separator formed between the negative electrode and the positive electrode, and the current collector of the negative electrode or the positive electrode includes a current collector according to the present invention. As a specific example, the current collector according to the present invention may be a current collector of a negative electrode.

According to one embodiment of the present invention, the negative electrode may use lithium metal (Li metal) alone.

In addition, the negative electrode current collector is not particularly limited as long as it is conductive without causing chemical changes in the battery, for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, carbon on the surface of copper or stainless steel. , surface treated with nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used.

In addition, the negative electrode current collector may be used in various forms such as films, sheets, foils, nets, porous materials, foams, and non-woven fabrics with fine irregularities formed on the surface, depending on the case.

According to one embodiment of the present invention, lithium metal can be used alone as the negative electrode active material. In this case, lithium ions can be released on a large scale, thereby dramatically improving battery performance. However, in the past, there were difficulties in application due to problems caused by the generation of lithium dendrites.

However, even if lithium metal is used alone as a negative electrode material, when a current collector coated with a carbon-based material according to the present invention is used, battery performance is improved due to lithium metal and safety is improved by suppressing lithium dendrite growth. It can be implemented.

According to one embodiment of the present invention, the negative electrode may include a current collector according to the present invention in which a coating layer containing a carbon-based material is formed on at least one surface of a copper foil as a current collector. Specifically, the negative electrode can be manufactured by forming the lithium metal layer on one surface of the current collector where the coating layer is formed.

In this way, by using copper foil coated with a carbon-based material with a controlled structure and size as a cathode, the overvoltage during lithium electrodeposition is lowered through the carbon-based material and the flux of lithium ions is uniformly controlled through an increase in active sites, resulting in uniform By providing space for lithium electrodeposition, volume expansion of lithium can be suppressed and lithium dendrite growth on the cathode can be suppressed.

In one embodiment of the present invention, the anode located opposite the cathode is not particularly limited and may be a material used in known all-solid-state batteries.

In one embodiment of the present invention, the positive electrode may have a structure in which a positive active material layer is formed on one surface of a positive electrode current collector, but is not limited thereto.

The positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or carbon on the surface of aluminum or stainless steel, Surface treatment with nickel, titanium, silver, etc. can be used. As a specific example, the positive electrode current collector may be aluminum foil.

The positive electrode active material layer includes a positive active material and a binder, and may further include additives such as a conductive material, if necessary.

The positive electrode active material may vary depending on the use of the lithium secondary battery, LiNi _0.8-x Co _0.2 Al _x O ₂ , LiCo _x Mn _y O ₂ , LiNi _x Co _y O ₂ , LiNi _x Mn _y O ₂ , LiNi _x Co lithium transition metal oxides such as _y Mn _z O ₂ , LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiFePO ₄ , LiCoPO ₄ , LiMnPO ₄ and Li ₄ Ti ₅ O ₁₂ ; Chalcogenides such as Cu ₂ Mo ₆ S ₈ , FeS, CoS and MiS, and oxides, sulfides or halides such as scandium, ruthenium, titanium, vanadium, molybdenum, chromium, manganese, iron, cobalt, nickel, copper and zinc. It may be used, and more specifically, TiS ₂ , ZrS ₂ , RuO ₂ , Co ₃ O ₄ , Mo ₆ S ₈ , V ₂ O ₅ , etc. may be used, but it is not limited thereto. As a specific example, the positive electrode active material may include lithium transition metal oxide containing nickel, cobalt, and manganese.

The binder included in the positive electrode is not particularly limited, and fluorine-containing binders such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE) may be used. The content of the binder is not particularly limited as long as it can fix the positive electrode active material, and may be in the range of 0 to 10% by weight based on the entire positive electrode.

The conductive material is not particularly limited as long as it can improve the conductivity of the anode, and may include nickel powder, cobalt oxide, titanium oxide, carbon, etc. The carbon may include one or more selected from the group consisting of Ketjen black, acetylene black, furnace black, graphite, carbon fiber, and fullerene.

In one embodiment of the present invention, the separator separates the cathode from the anode and provides a passage for lithium ions, and any separator commonly used in lithium secondary batteries can be used.

That is, one that has low resistance to ion movement in the electrolyte and has excellent electrolyte moisturizing ability can be used. For example, it is selected from glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or a combination thereof, and may be in the form of non-woven or woven fabric. As a specific example, as the separator, polyolefin-based polymers such as polyethylene and polypropylene may be used, and a separator coated with a ceramic component or polymer material may be used to ensure heat resistance or mechanical strength. Additionally, the separator may optionally be formed in a single-layer or multi-layer structure.

According to one embodiment of the present invention, the cathode, anode, and separator may be housed in separate cases, and a liquid electrolyte may be injected into the case.

The liquid electrolyte may be a material used as an electrolyte in conventional lithium ion batteries. For example, the liquid electrolyte may include a lithium salt and a solvent, and may include additives as needed.

The lithium salt may be a material that acts as a source of lithium ions in the battery, enables the basic operation of a lithium secondary battery, and promotes the movement of lithium ions between the anode and the cathode.

The solvent may be an organic liquid used to dissolve the lithium salt.

Additives may be substances added in small amounts for a specific purpose.

This liquid electrolyte moves only ions to the electrode and prevents electrons from passing through, and the movement and speed of lithium ions can be controlled depending on the type of component.

The lithium salt is an ionizable lithium salt and can be expressed ^as Li ⁺ The anion of the lithium salt is not limited thereto, but for example, F ^- , Cl ^- , Br ^- , I ^- , NO ₃ ^- , N(CN) ₂ ^- , BF ₄ ^- , ClO ₄ ^- , PF ₆ ^- , ( CF ₃ ) ₂ PF ₄ ^- , (CF ₃ ) ₃ PF ₃ ^- , (CF ₃ ) ₄ PF ₂ ^- , (CF ₃ ) ₅ PF ^- , (CF ₃ ) ₆ P ^- , CF ₃ SO ₃ ^- , CF ₃ CF ₂ SO ₃ ^- , (CF ₃ SO ₂ ) ₂ N ^- , (FSO ₂ ) ₂ N ^- , CF ₃ CF ₂ (CF ₃ ) ₂ CO ^- , (CF ₃ SO ₂ ) ₂ CH ^- , (SF ₅ ) ₃ C ^- , (CF ₃ SO ₂ ) ₃ C ^- , CF ₃ (CF ₂ ) ₇ SO ₃ ^- , CF ₃ CO ₂ ^- , CH ₃ CO ₂ ^- , SCN ^- and (CF ₃ CF ₂ SO ₂ ) ₂ N ^- It may include at least one selected from the group consisting of.

The solvent may be a non-aqueous solvent, and the non-aqueous solvent may be, for example, propylene carbonate (PC), ethylene carbonate (EC), vinylene carbonate (VC), diethyl carbonate ( DEC), dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), tetrahydrofuran (THF), 2-methyltetrahydrofuran (2MeTHF), dioxolane (DOX) ), dimethoxyethane (DME), diethoxyethane (DEE), γ-butyrolactone (GBL), acetonitrile (AN), and sulfolane.

Hereinafter, the present invention will be described in detail with reference to examples. However, the embodiments according to the present invention may be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described in detail below. Examples of the present invention are provided to more completely explain the present invention to those with average knowledge in the art.

Manufacturing example

Manufacturing Example 1

Add 1 g of melamine to 40 mL of dimethyl sulfoxide (DMSO) and stir to prepare a basic carbon nitride precursor composition, and add 1 g of cyanuric acid to 40 mL of dimethyl sulfoxide (DMSO). ) Added to 20 mL and stirred to prepare an acidic carbon nitride precursor composition. The acidic carbon nitride precursor composition was added dropwise to the basic carbon nitride precursor composition, and the heat generated in the experiment was removed through cooling. The reaction was performed to prepare a mixed solution. At this time, the reaction temperature was about 15°C.

The mixed solution was left in a static state for 2 hours, centrifuged, and washed three times using deionized water and ethanol.

Then, the white precipitate was dried at 60°C for 24 hours, and then heat-treated at 550°C for 4 hours under a nitrogen atmosphere while raising the temperature at 2.3°C/min to prepare gC ₃ N ₄ particles.

Production example 2

When preparing a mixed solution by dropping the acidic carbon nitride precursor composition into the basic carbon nitride precursor composition, the reaction temperature was controlled to 25°C instead of 15°C, as in Preparation Example 1. This was performed to prepare gC ₃ N ₄ particles.

Production example 3

When preparing a mixed solution by dropping the acidic carbon nitride precursor composition into the basic carbon nitride precursor composition, as in Preparation Example 1, except that the reaction temperature was controlled to 60 ° C. instead of 15 ° C. This was performed to prepare gC ₃ N ₄ particles.

Comparative manufacturing example

Comparative Manufacturing Example 1

Add 1 g of melamine to 40 mL of dimethyl sulfoxide (DMSO) and stir to prepare a basic carbon nitride precursor composition, and add 1 g of cyanuric acid to 40 mL of dimethyl sulfoxide (DMSO). ) Added to 20 mL and stirred to prepare an acidic carbon nitride precursor composition, the basic carbon nitride precursor composition was added dropwise to the acidic carbon nitride precursor composition, and the heat generated in the experiment was removed through cooling. The reaction was performed to prepare a mixed solution. At this time, the reaction temperature was about 15°C.

The mixed solution was left in a static state for 2 hours, centrifuged, and washed three times using deionized water and ethanol.

Then, the white precipitate was dried at 60°C for 24 hours, and then heat-treated at 550°C for 4 hours under a nitrogen atmosphere while raising the temperature at 2.3°C/min to prepare gC ₃ N ₄ particles.

Comparative Manufacturing Example 2

gC ₃ N ₄ particles were prepared in the same manner as Comparative Preparation Example 1, except that the reaction temperature was controlled to 25°C instead of 15°C.

Comparative Manufacturing Example 3

gC ₃ N ₄ particles were prepared in the same manner as Comparative Preparation Example 1, except that the reaction temperature was controlled to 60°C instead of 15°C.

Examples and Comparative Examples

Example 1

The gC ₃ N ₄ particles prepared in Preparation Example 1 were mixed with a solution of NMP and PVdF to prepare a coating composition having a viscosity of 0.1 g/ml. At this time, the mass ratio of gC ₃ N ₄ and PVdF is 8:2.

Then, the coating composition is applied to one side of the copper foil (Cu foil) and dried at a temperature of 120°C to remove solvent components other than the carbon-based material, thereby binding the carbon-based material to the current collector and carbon-based material. A current collector was manufactured by binding the materials together to form a coating layer with a thickness of 5㎛.

Example 2

A current collector was manufactured in the same manner as Example 1, except that the gC ₃ N ₄ particles prepared in Preparation Example 2 were used.

Example 3

A current collector was manufactured in the same manner as Example 1, except that the gC ₃ N ₄ particles prepared in Preparation Example 3 were used.

Comparative Example 1

A current collector was manufactured in the same manner as Example 1, except that the g-C3N4 particles prepared in Comparative Preparation Example 1 were used.

Comparative Example 2

A current collector was manufactured in the same manner as Example 1, except that the gC ₃ N ₄ particles prepared in Comparative Preparation Example 2 were used.

Comparative Example 3

A current collector was manufactured in the same manner as in Example 1, except that the gC ₃ N ₄ particles prepared in Comparative Preparation Example 1 were used.

Experiment example

Experimental Example 1

The FE-SEM images of the gC ₃ N ₄ particles prepared in Preparation Examples 1 to 3 are shown in Figure 3. The FE-SEM images of the gC ₃ N ₄ particles prepared in Comparative Preparation Examples 1 to 3 are shown in Figure 3. Each is shown in 4.

Looking at Figures 3 and 4, it can be seen that there are differences in the growth, shape, size, etc. of carbon-based material particles depending on the reaction temperature and the order of dropwise materials.

Specifically, the gC ₃ N ₄ particles prepared in Preparation Example 1 where the reaction temperature was controlled at 15°C had a size of about 2 to 3 ㎛, and in the case of Preparation Example 2 where the reaction temperature was controlled at 25°C, the particles had a size of about 4 to 5 ㎛. In the case of Preparation Example 3, which was controlled at 60°C, it had a size of 8 to 9 ㎛, and it can be seen that as the reaction temperature increases, the particle size of gC ₃ N ₄ produced increases. On the other hand, in the case of the comparative preparation example, the gC ₃ N ₄ particles were not formed in a spherical shape, and the particle size was also confirmed to be larger than that of the carbon-based material prepared in Preparation Examples 1 to 3.

Experimental Example 2

The BET specific surface area and pore distribution of the gC ₃ N ₄ particles prepared in Preparation Examples 1 to 3 and Comparative Preparation Examples 1 to 3 were measured by the method below and are shown in Table 1 below.

BET and pore distribution were measured using ASAP 2420 (Micromeritics, U.S.A.) equipment to determine the specific surface ?О? by physical adsorption of N2. Pore volume and pore size were measured. After degassing at 90°C for 30 minutes and pretreatment at 200°C for 4 hours, measurements were performed at room temperature.

Manufacturing Example 1 Production example 2 Production example 3 Comparative Manufacturing Example 1 Comparative Manufacturing Example 2 Comparative Manufacturing Example 3 BETspecific surface area
( ^m2 /g) 120 80 63 111 90 45 Pore volume (cm ³ /g) 0.4 0.37 0.24 0.42 0.43 0.35 Pore size (nm) 22 21 17.6 24 22.8 22

Referring to Table 1 above, it was confirmed that the BET specific surface area and pore distribution differed depending on the reaction temperature and the order of dropping the materials.

Experimental Example 3

In order to confirm the degree of lithium dendrite growth and battery performance, a half-cell (lithium metal battery) containing the current collector prepared in Examples 1 to 3 and Preparation Examples 1 to 3 was manufactured.

Specifically, as shown in FIG. 5, a gasket 40 formed of ring-structured PP in a main body 50 including a receiving portion therein, each current collector manufactured in Examples 1 to 3 and Comparative Production Examples 1 to 3. (10), a PP separator (20) and a negative electrode (30) with a lithium metal layer formed on the copper foil were placed and sealed with a cap (60) to prepare a half battery.

Using the half-cell manufactured as above, the cycle performance of the battery was measured in the following manner and is shown in Table 2 and Figure 6.

After charging the half-cell using a charger/discharger at a current density of 1.0 mA/cm ² for 1 hour (Li-deposition), discharging it at the same current density of 1.0 mA/cm ² under 0.5 V cut-off conditions (Li-deposition) -Stripping), the same process was repeated to evaluate cycle performance, and the number of cycles at which the coulombic efficiency of each battery fell below 80% was recorded and shown in Table 2 below.

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 number of cycles 200 153 139 99 76 64

Referring to Table 2 above, it was confirmed that the battery containing the current collectors of Examples 1 to 3 was the most effective when considering the degree of dendrite growth and cycle performance, and in the case of the comparative example, the electrochemical performance was very poor. I was able to confirm.

Although the embodiments have been described with limited drawings as described above, those skilled in the art can apply various technical modifications and variations based on the above. Therefore, other implementations, other embodiments, and equivalents of the claims also fall within the scope of the claims described below.

10: Current collector
11: Metal thin film layer
12: Coating layer
13: Carbon-based material
20: Separator
30: cathode
40: gasket
50: body
60: cap

Claims (13)

(A) preparing a basic carbon nitride precursor composition and an acidic carbon nitride precursor composition; and
(B) comprising adding the acidic carbon nitride precursor composition to the basic carbon nitride precursor composition in a dropwise manner to react,
Method for producing carbon-based materials.
According to paragraph 1,
A method of producing a carbon-based material, wherein the acidic carbon nitride all-solid composition and the basic carbon nitride precursor composition react at 0°C to 20°C, or 5°C to 18°C.
According to paragraph 1,
The basic carbon nitride precursor composition includes a carbon nitride precursor having a basic functional group,
A method of producing a carbon-based material, characterized in that the basic functional group is one or more selected from the group consisting of an amine group, an imine group, an amide group, an azide group, a nitrate group, or an ammonium group.
In paragraph 1
The acidic carbon nitride precursor composition includes a carbon nitride precursor having an acidic functional group,
A method of producing a carbon-based material, wherein the acidic functional group is one or more selected from the group consisting of a hydroxyl group, a carboxyl group, an ester group, a phosphine group, a phosphoric acid group, a phosphonic acid group, or a sulfonic acid group.
According to paragraph 1,
The particle size of the prepared carbon-based material is 1 to 10㎛,
The BET surface area is from 50 m ² /g to 120 m ² /g,
The pore size is 20 to 30 nm,
A method of producing a carbon-based material, wherein the pore volume is 0.2 to 0.6 cm ³ /g.
(A) preparing a basic carbon nitride precursor composition and an acidic carbon nitride precursor composition; and
(B) A current collector for a lithium secondary battery comprising a coating layer coated with a carbon-based material prepared by adding the acidic carbon nitride precursor composition to the basic carbon nitride precursor composition in a dropwise manner and reacting the acidic carbon nitride precursor composition.
According to clause 6,
A current collector for a lithium secondary battery, wherein the acidic carbon nitride all-solid composition and the basic carbon nitride precursor composition react at 0°C to 20°C, or 5°C to 18°C.
According to clause 6,
The step of coating the carbon-based material is
Preparing a coating composition containing the carbon-based material and a binder; and
A method of manufacturing a current collector coated with a carbon-based material, comprising the step of coating the coating composition on at least one surface of the metal thin film layer.
In paragraph 8
A current collector for a lithium secondary battery, wherein the metal is one or two or more alloys selected from the group consisting of copper, aluminum, nickel, titanium, and stainless steel.
According to clause 6,
A current collector for a lithium secondary battery, characterized in that the viscosity of the coating composition is controlled to 0.05 to 0.2 g/ml.
According to clause 6,
A current collector for a lithium secondary battery, characterized in that the thickness of the coating layer is 1 to 10 ㎛.
cathode;
anode and
It includes a separator formed between the cathode and the anode,
A lithium secondary battery, wherein the current collector of the negative electrode is a contact material for a lithium secondary battery according to claim 6.
The lithium secondary battery of claim 12, wherein the negative electrode is lithium metal.