WO2023106477A1 - Active material-conductive material-binder composite material for lithium secondary battery - Google Patents

Abstract

An embodiment of the present invention provides an active material-conductive material-binder composite material for a lithium secondary battery, the composite material being characterized by comprising: an active material; a conductive material which is coated on the surface of the active material and comprises carbon nanotubes; and a thermosetting binder which is coated on the surface of the active material. According to the present invention, it is possible to provide a lithium secondary battery electrode that has long-term stability with respect to performance and lifespan, whilst having a high ratio of Ni, and to provide a thick film electrode having uniform and excellent electrical conductivity, thus making it possible to achieve a lithium secondary battery having a high energy density, for the expansion of electric vehicles.

Description

Active material-conductive material-binder composite material for lithium secondary battery

The present invention relates to an electrode material for a lithium secondary battery, and more particularly, to a technique for solving the volume change problem of an active material containing a large amount of nickel in order to achieve high energy density and for solving the non-uniform problem that occurs during thick film formation. will be.

As the supply of electric vehicles expands, it is necessary to develop technology to secure a mileage of more than 500 km. In addition, considering the development speed of rapid charging technology and charging infrastructure, it is essential to develop a lithium secondary battery with a high energy density of 350Wh/kg or more that can travel long distances on a single charge.

In particular, in order to balance the positive electrode with relatively small capacity compared to the negative electrode with high theoretical capacity (500 mAh/g or more), it is urgent to use a high-capacity active material or increase the electrode loading of the positive electrode.

In order to solve the above problems, many cathode active materials have been researched and developed, and among them, Ni has shown excellent characteristics in increasing the capacity of a battery. Accordingly, various active materials with high Ni combinations have been tried, such as lithium-nickel oxide, lithium-nickel-cobalt oxide, lithium-nickel-cobalt-aluminum oxide (NCA), lithium-nickel-cobalt-manganese oxide (NCM), etc. this was developed

In addition, there has been an attempt to further increase the Ni content itself rather than just a combination showing excellent efficiency, but the more Ni is included, the more side effects occur, and there is a limit to forming a stable electrode.

Specifically, the higher the Ni content, the more severe the volume change of the active material due to charge and discharge, and the higher the probability of occurrence of micro-crack from the inside of the active material. There is a problem in that side reactions occur between active materials, thereby deteriorating the performance of the battery.

Therefore, in order to achieve high energy density using Ni, it is required to preemptively suppress micro-crack occurring in the active material and improve unstable surface properties.

Next, thick film of the anode is another method to achieve the above object. However, the existing positive electrode manufacturing method had limitations in uniformly forming a thick film of the conductive material and the binder included in the positive electrode material, and accordingly, the positive electrode material loading was lowered to 20 mg/cm ² or less.

In order to overcome the limitation of anode thick film, conventional batteries have been solved by increasing the number of stacks. However, as the number of stacks increases, the ratio of the accompanying current collector and separator increases, and as a result, the energy density shows a value of 300Wh/kg or less, which is less than 300Wh/kg. It failed to meet the demands of the industry to expand automobile supply. Therefore, it can be said that the thick film of the anode is an essential task to expand the spread of electric vehicles.

Specifically, the thick film of the cathode does not simply form a thick cathode material, and the active material, the conductive material, and the binder must be uniformly distributed in the thickness direction along with the thick thickness to form an electrical network. However, in the conventional wet process used for electrode manufacturing, the solvent evaporates during the solvent drying process, and the conductive material and binder are concentrated in the upper layer, and the non-uniform distribution of the conductive material and binder results in deterioration of battery performance.

Therefore, in order to make the film thicker on the anode, it is necessary to introduce a dry process that requires very little solvent evaporation, less concentration of the conductive material and binder even with solvent evaporation, or a dry process that does not require a solvent.

In order to solve the above problem, Korean Patent Publication No. 10-2015-0047098 (Name: Method for producing a surface-coated cathode active material and cathode active material produced thereby) mixes a cathode active material and δ-Al ₂ O ₃ , Disclosed is a method for producing a surface-coated cathode active material, including the step of coating the surface of the cathode active material with Al ₂ O ₃ by heat treatment of the mixture, thereby minimizing the loss of the cathode active material and aiming at a cathode having a high capacity energy density, The bias of the conductive material and the binder that occurs in the wet process is still not resolved, which limits film thickness, and the particle-type Al ₂ O ₃ coating has limitations in suppressing cracking of the active material.

Accordingly, an object of the present invention is to solve the above problems and provide a cathode material capable of increasing the efficiency of the process and capable of forming a thick film while containing a large amount of Ni.

[Prior art literature]

[Patent Literature]

(Patent Document) Republic of Korea Patent Publication No. 10-2015-0047098

An object of the present invention to solve the above problems is to provide a stable active material-conductive material-binder composite material for a lithium secondary battery, a method for manufacturing the same, and an electrode for a lithium secondary battery including the same even when a high proportion of Ni is contained. .

Another object of the present invention is an active material-conductive material-binder composite material for lithium secondary batteries capable of removing or minimizing the drifting of the conductive material and binder that occurs during solvent evaporation in a wet process for thick film formation of the cathode, and manufacturing thereof is to provide a way

Another object of the present invention is to provide an electrode for a lithium secondary battery having a high energy density, including the composite material.

The technical problem to be achieved by the present invention is not limited to the above-mentioned technical problem, and other technical problems not mentioned can be clearly understood by those skilled in the art from the description below. There will be.

In one embodiment of the present invention for achieving the above technical problem, an active material-conductive material-binder composite material for a lithium secondary battery includes an active material; a conductive material coated on the surface of the active material and containing carbon nanotubes; and a thermosetting binder coated on the surface of the active material.

In an embodiment of the present invention, the composite material may further include a dispersant coated on the surface of the active material.

In an embodiment of the present invention, the thermosetting binder may include polysiloxane.

In an embodiment of the present invention, the polysiloxane may include an epoxy group and a hydroxyl group.

In an embodiment of the present invention, the thermosetting binder may be included in an amount of 0.01 wt% or more and 10 wt% or less based on the total weight of the composite material.

In an embodiment of the present invention, the conductive material is selected from the group consisting of single wall carbon nanotubes (SWCNTs), multi wall carbon nanotubes (MWCNTs), and combinations thereof. Any one or more may be included.

In an embodiment of the present invention, the conductive material may be included in an amount of 0.01 wt% or more and 10 wt% or less based on the total weight of the composite material.

In an embodiment of the present invention, the coverage of the active material by the conductive material may be 0.1% or more and 90% or less.

In an embodiment of the present invention, the carbon nanotubes may have an average diameter of 1 nm or more and 10 nm or less, and an aspect ratio of 1:1000 or more.

In an embodiment of the present invention, the dispersant is any one selected from the group consisting of hydrogenated acrylonitrile butadiene rubber (HNBR), polyvinylidene fluoride (PVDF), and combinations thereof may be ideal

As another embodiment of the present invention for achieving the above technical problem, a method for manufacturing an active material-conductive material-binder composite material for a lithium secondary battery comprises the steps of (i) preparing a conductive material dispersion by mixing carbon nanotubes and a dispersant; and (ii) coating the surface of the active material with a coating solution obtained by mixing the conductive material dispersion, the active material, and the thermosetting binder solution.

In an embodiment of the present invention, the carbon nanotubes are a group consisting of single wall carbon nanotubes (SWCNTs), multi wall carbon nanotubes (MWCNTs), and combinations thereof. It may include any one or more selected from.

In an embodiment of the present invention, the dispersant is any one selected from the group consisting of hydrogenated acrylonitrile butadiene rubber (HNBR), polyvinylidene fluoride (PVDF), and combinations thereof may contain more than

In an embodiment of the present invention, the thermosetting binder may include polysiloxane.

In an embodiment of the present invention, the polysiloxane may include an epoxy group and a hydroxyl group.

As another embodiment of the present invention for achieving the above technical problem, the electrode for a lithium secondary battery is an electrode for a lithium secondary battery including the active material-conductive material-binder composite material for a lithium secondary battery.

In an embodiment of the present invention, the electrode may have an energy density of 350 Wh/kg or more.

The effect of the present invention according to the above configuration is,

Even if the electrode is manufactured by containing Ni at a high rate, the probability of occurrence of cracks inside the active material during charging and discharging is suppressed, thereby providing an electrode material with long-term stability and an electrode including the same.

In addition, it is possible to make the anode thicker by resolving the biasing of the conductive material and the binder that occurs when a wet process is used in manufacturing the anode.

In addition, by including the active material-conductive material-binder composite material presented in the present invention, the solid content is increased when preparing the slurry, so that problems caused by solvent vaporization during the wet process can be eliminated or minimized, thereby enabling thick film formation of the anode.

In addition, the active material-conductive material-binder composite material proposed in the present invention has high utilization in that it can be used in a dry process.

In addition, the electrode manufactured by including the active material-conductive material-binder composite material proposed in the present invention has a high energy density of 350 Wh/kg or more.

In addition, the active material-conductive material-binder composite material and the electrode including the active material-conductive material-binder composite material proposed by the present invention have greatly improved electrical conductivity.

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

1 is a schematic image of an active material-conductive material-binder composite material for a lithium secondary battery according to an embodiment of the present invention.

Figure 2 is an image showing the polymer structure of polysiloxane having an epoxy group.

Figure 3 is data showing the relationship between the Ni content of the battery containing Ni and the battery life.

4 is an image showing a cross section of an active material to compare the degree of micro-crack generated according to the Ni content ratio.

5 is an image showing a phenomenon in which a conductive material and a binder are concentrated due to vaporization of a solvent when an electrode is manufactured by a wet process method.

6 is a flowchart of a method for manufacturing an active material-conductive material-binder composite material for a lithium secondary battery according to an embodiment of the present invention.

7 is a SEM image of a surface confirmed by implementing an active material-conductive material-binder composite material for a lithium secondary battery, which is an embodiment of the present invention.

8 is a table summarizing experimental groups with different contents of binders in order to confirm the characteristics of an electrode for a lithium secondary battery including an active material-conductive material-binder composite material for a lithium secondary battery and a battery.

9 is an experimental result obtained by measuring the initial capacity and charge/discharge behavior of the experimental group summarized in FIG. 8 as batteries.

10 is an experimental result obtained by measuring the output characteristics of the experimental group summarized in FIG. 8 as a battery.

FIG. 11 is an experimental result obtained by measuring the lifespan characteristics of the experimental group summarized in FIG. 8 as batteries.

12 is a table summarizing the experimental results of FIGS. 9 to 11.

13 is an SEM image of a cross section confirmed to compare the degree of micro-crack occurrence after charging and discharging for the electrode including Comparative Example 1 and the electrode including Example 1 summarized in FIG. 8.

FIG. 14 is data obtained by analyzing the elution amount of the transition metal included in the active material after charging and discharging for the electrode including Comparative Example 1 and the electrode including Example 1 summarized in FIG. 8 .

Hereinafter, the present invention will be described with reference to the accompanying drawings. However, the present invention may be embodied in many different forms and, therefore, is not limited to the embodiments described herein. And in order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and similar reference numerals are attached to similar parts throughout the specification.

Throughout the specification, when a part is said to be "connected (connected, contacted, combined)" with another part, this is not only "directly connected", but also "indirectly connected" with another member in between. "Including cases where In addition, when a part "includes" a certain component, it means that it may further include other components without excluding other components unless otherwise stated.

Terms used in this specification are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as "include" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It should be understood that the presence or addition of numbers, steps, operations, components, parts, or combinations thereof is not precluded.

Hereinafter, an active material-conductive material-binder composite material for a lithium secondary battery according to an embodiment of the present invention will be described in detail with reference to FIGS. 1 to 4 attached thereto.

1 is a schematic image of an active material-conductive material-binder composite material for a lithium secondary battery according to an embodiment of the present invention.

According to FIG. 1, the active material-conductive material-binder composite material for a lithium secondary battery according to the present invention includes an active material 100; a conductive material 200 coated on the surface of the active material 100 and containing carbon nanotubes; and a thermosetting binder 300 coated on the surface of the active material 100.

In addition, the composite material may be coated by mixing the dispersant 400 with the conductive material 200 on the surface of the active material 100 .

Prior to a detailed description of each configuration, looking at the reason why the present invention has the above configuration, the present invention is intended to solve the problem of micro-crack caused by containing a high ratio of Ni in the active material as a first purpose.

Referring to Figure 3 it can be confirmed the life of the electrode made of the active material containing Ni. According to Figure 3 (a), as the Ni ratio increases, the energy capacity increases, but the capacity retention due to self-discharge tends to decrease. According to Figure 3 (b), as the Ni ratio increases, the continuous charge , it can be confirmed that the life characteristics due to discharge rapidly deteriorate.

The cause of this trend is shown in FIG. 4 . The higher the Ni ratio, the larger the change in the volume of the active material due to charging and discharging, thereby increasing the probability and degree of micro-crack occurrence in the active material.

Cracks generated inside propagate throughout the active material and cause particle destruction, and the increase in the specific surface area caused by the destruction and the inflow of the electrolyte through the crack accelerate the side reaction between the active material and the electrolyte and cause the isolation of the primary particles of the active material, resulting in the performance of the electrode. and rapidly deteriorate life expectancy.

Therefore, in the present invention, carbon nanotubes having a high aspect ratio are coated on the surface of the active material 100 to suppress the occurrence of micro-crack by suppressing the increase in volume change due to the high Ni content.

The carbon nanotubes coated on the surface of the active material 100 cover the active material 100 as a whole and play a role in partially resolving the physical volume expansion, and also cover the active material 100 as a whole to form an electrical network so that the active material 100 is primary. It serves to block the isolation of particles.

Next, a thermosetting binder 300 was coated on the surface of the active material 100 coated with carbon nanotubes. 100) from side reactions with the electrolyte.

According to the above configuration, the active material-conductive material-binder composite material for a lithium secondary battery proposed by the present invention reduces volume expansion due to charge and discharge, reduces the possibility and degree of micro-crack, and reduces electrolyte and active material The side reaction of (100) is suppressed, and deterioration of the performance and lifetime of the electrode is remarkably improved even when a high proportion of Ni is contained.

Next, the reason for the above configuration in terms of the thick film of the lithium secondary battery electrode will be examined.

A second object of the present invention is to make electrodes thicker in order to achieve high energy density. Referring to FIG. 5, in order to make the film thicker, (1) not only the thick thickness of the electrode, but also the active material, conductive material and binder constituting the electrode must be uniformly distributed, so the bias phenomenon that occurs during the wet process must be solved, (2) Since the thick electrode increases the moving distance of lithium ions and electrons passing through the electrode, electrical conductivity capable of compensating for this is required.

The above problem (1) can be solved by reducing the amount of vaporized solvent by increasing the specific gravity of the solid content in the wet process or by increasing the bonding force between the active material, the conductive material and the binder to prevent separation between components. In particular, it is important to prevent separation between the conductive material and the active material, which lack adhesive strength.

In view of this point, the present invention combines the active material 100, the conductive material 200, and the binder 300 to prepare a composite material prior to preparing the slurry for the wet process, and mixes the slurry using the manufactured composite material Suggest how to do it as a solution.

Specifically, when a composite material is separately manufactured and added to prepare a slurry, the solid content of the slurry is increased to reduce the amount of vaporized solvent, and the conductive material 200 coated on the surface of the active material 100 is also in the solvent vaporization process. Since it is not separated, the bias phenomenon during electrode manufacturing is reduced, and for the same reason, it is possible to form an electrode in which components are uniformly distributed.

The above problem (2) can also be solved through the composite material of the present invention. The conductive material 200 coated on the surface of the active material 100 is uniformly positioned between the active materials 100 during electrode manufacturing and forms an electrical network to increase the electrical conductivity of the electrode.

In particular, in the present invention, carbon nanotubes are used as the material of the conductive material 200 . Carbon nanotubes are materials with very excellent electrical properties, such as electrical conductivity, and especially in the case of single-walled carbon nanotubes, since the aspect ratio is very high, electrical connection between the active material 100 and the conductive material 200 can be effectively made during electrode manufacturing.

In addition, in the present invention, single-walled carbon nanotubes and multi-walled carbon nanotubes can be used together as the conductive material 200, and in this case, electrical properties and physical properties are further improved compared to the case of using only single-walled carbon nanotubes. It can be.

Additionally, the active material-conductive material-binder composite material for a lithium secondary battery presented in the present invention is prepared prior to slurry preparation and can be used in a dry process as well as a wet process.

Therefore, when the electrode is manufactured by a dry process using the composite material, the problem caused by the vaporization of the solvent is completely eliminated, and the electrical and physical properties due to the conductive material 200 uniformly distributed on the surface of the active material 100 This improved electrode for a lithium secondary battery can be provided.

Hereinafter, each configuration of an active material-conductive material-binder composite material for a lithium secondary battery according to an embodiment of the present invention will be described in detail.

In the first configuration, in the active material-conductive material-binder composite material for a lithium secondary battery according to an embodiment of the present invention, the active material 100 is an active material that can be used in a lithium secondary battery and can reversibly occlude and release lithium ions. Not particularly limited.

For example, lithium-cobalt oxide (LCO), lithium-nickel oxide, lithium-nickel-cobalt oxide, lithium-nickel-cobalt-aluminum oxide (NCA), lithium-nickel-cobalt-manganese oxide (NCM), lithium- manganese oxide (LMO), lithium iron phosphate (LFP), and the like. These positive electrode active materials may be used alone or in combination of two or more.

In an embodiment of the present invention, high-nickel NCM811 containing 80% or more of Ni among the cathode active materials was used to achieve high energy density.

In the composite material, the content of the active material 100 may be 90 wt% or more and 99.99 wt% or less.

The conductive material 200 in one embodiment of the present invention will be described with the following configuration.

The conductive material 200 is coated on the surface of the active material 100 and includes carbon nanotubes.

Referring to FIG. 1 , it can be seen that the conductive material 200 is located on the surface of the active material 100 . As will be described in the manufacturing method below, since the coating is performed by injecting and attaching the active material 100 to the dispersion of the conductive material 200, the conductive material 200 including the conductive material 200 and the dispersant 400 The dispersion covers the surface of the active material 100 . Also, the particles of the active material 100 are connected.

Next, carbon nanotube is an allotrope of carbon having a cylindrical nanostructure, and sp ² formed between carbon atoms. Due to the covalent bond, it has very excellent physical properties such as tensile strength and elastic modulus, and especially excellent electrical conductivity and low density, so when used in a battery, it is a material that very effectively reduces battery deterioration due to charging and discharging.

At this time, the conductive material 200 is at least one selected from the group consisting of single wall carbon nano tubes (SWCNTs), multi wall carbon nano tubes (MWCNTs), and combinations thereof. can include

Specifically, carbon nanotubes can be classified into single-walled carbon nanotubes and multi-walled carbon nanotubes. Single-walled carbon nanotubes are relatively flexible and have the advantage of being formed very long, but are relatively expensive and difficult to synthesize. On the other hand, multi-walled carbon nanotubes are relatively hard and short, but can be synthesized relatively inexpensively and easily.

The present invention is characterized in that the carbon nanotubes have an average diameter of 1 nm or more and 10 nm or less, and an aspect ratio of 1:1000 or more to take advantage of the advantages of carbon nanotubes that are relatively flexible and very long compared to other carbon-based materials.

Preferably, the single-walled carbon nanotubes may have an average diameter of 1.5 nm or more and 10 nm or less and an aspect ratio of 1:1000. , There is an advantage in effectively suppressing isolation due to cracking of the active material 100 during the charging and discharging process.

In addition, the present invention is characterized in that the conductive material 200 including the carbon nanotubes is included in an amount of 0.01 wt% or more and 10 wt% or less based on the total weight of the composite material, and accordingly, the active material by the conductive material 200 (100) is characterized in that the coverage is 0.1% or more and 50% or less.

Specifically, when the conductive material 200 is included in less than 0.01wt% of the total weight of the composite material, conductivity is not secured, and when it is included in more than 10wt%, the energy density is lowered, so the conductive material 200 is the composite material. It is preferably 0.01wt% or more and 10wt% or less based on the total weight.

The thermosetting binder 300 in one embodiment of the present invention will be described with the following configuration.

The thermosetting binder 300 may be coated on the surface of the active material 100 including the conductive material 200 . In this case, the coating may cover the entire surface of the active material 100 or may be partially attached to the surface of the active material 100 .

In the present invention, since the thermosetting binder 300 should have a high affinity with the active material 100 to suppress side reactions between the electrolyte and the active material 100, it is characterized in that it contains polysiloxane capable of performing this role. do.

Referring to FIG. 2, specifically, the polysiloxane may be functionalized to include an epoxy group and a hydroxyl group. The epoxy group and the hydroxyl group have very good affinity with lithium-based active materials including nickel.

In addition, the polysiloxane having an epoxy group forms a cross-linking structure through cross-linking during the thermal curing process (drying), and accordingly, the volume expansion of the active material 100 is effectively suppressed.

In addition, polysiloxane containing a hydroxyl group forms a covalent bond through condensation between the hydroxyl group and the active material 100, thereby forming a very strong bond between the binder 300 and the active material 100.

Therefore, the thermosetting binder 300 preferably includes at least one selected from the group consisting of polysiloxane, polysiloxane functionalized to include an epoxy group and a hydroxyl group, and combinations thereof.

At this time, since the content of the binder 300 should be limited in order to increase the specific gravity of the active material 100 in the active material-conductive material-binder composite material for a lithium secondary battery, the thermosetting binder 300 is, compared to the total weight of the composite material It is characterized in that it is contained in 0.01wt% or more and 10wt% or less.

Specifically, when the thermosetting binder 300 is included in less than 0.01wt% of the total weight of the composite material, the surface coverage of the active material 100 decreases, and when it is included in more than 10wt%, diffusion of lithium ions due to excessive binder 300 And in that the energy density can be reduced, the thermosetting binder 300 is preferably included in an amount of 0.01 wt% or more and 10 wt% or less based on the total weight of the composite material in order to implement a battery having a high energy density.

The dispersant 400 in one embodiment of the present invention will be described with the following configuration.

The dispersant 400 is coated with the conductive material 200 on the surface of the active material 100 . Specifically, since the coating is performed by injecting the active material 100 into a dispersion of the conductive material 200 including the conductive material 200 and the dispersant 400, the conductive material 200 and the dispersant 400 are included. The dispersion of the conductive material 200 covers the surface of the active material 100.

Next, the dispersant 400 may be a rubber-based dispersant 400 . For example, it may be at least one selected from the group consisting of hydrogenated acrylonitrile butadiene rubber (HNBR), polyvinylidene fluoride (PVDF), and combinations thereof. Preferably, it may be hydrogenated acrylonitrile butadiene rubber (HNBR).

In addition, the dispersant 400 is characterized in that it is included in 0.01wt% or more and 5wt% or less based on the total weight of the composite material.

Hereinafter, a method for manufacturing an active material-conductive material-binder composite material for a lithium secondary battery according to another embodiment of the present invention will be described in detail with reference to attached FIG. 6 . In the description, a configuration overlapping with the active material-conductive material-binder composite material for a lithium secondary battery should be interpreted in the same way, and overlapping descriptions will be omitted.

Referring to FIG. 6, the method for manufacturing an active material-conductive material-binder composite material for a lithium secondary battery according to the present invention includes (i) preparing a conductive material dispersion by mixing carbon nanotubes and a dispersant (S100); and (ii) coating the surface of the active material with a coating solution obtained by mixing the conductive material dispersion, the active material, and the thermosetting binder solution (S200).

Looking at the characteristics of the manufacturing method of the present invention, unlike the conventional slurry manufacturing process in which an active material, a conductive material and a binder are simultaneously added and mixed to prepare a slurry, the composite material is prepared separately.

Due to this step difference, the slurry prepared according to the existing process and the slurry including the composite material prepared according to the present invention clearly show differences in characteristics and performance even if the included materials are the same.

Specifically, when an electrode is manufactured using a slurry prepared according to an existing process, especially when an electrode is manufactured by a wet process, the conductive material and binder included in the slurry are separated from the active material according to the vaporization of the solvent, and There is a problem of being excessively focused on the upper part of the electrode.

This biasing phenomenon means an imbalance in electrode performance and also makes it difficult for lithium ions and electrons to move through the thick film electrode, thereby seriously degrading battery performance.

On the other hand, the slurry containing the composite material manufactured according to the present invention reduces separation between the active material 100, the conductive material 200, and the binder 300 included in the slurry even when a wet process is used, and in particular, the conductive material 200 excellently solves the problem of non-uniform distribution of

In addition, when the composite material is manufactured and introduced into the slurry, the solid content in the slurry can be increased in that the addition of the conductive material 200 dispersion and the binder 300 solution is minimized, and the increase in the solid content increases the solvent content decrease, so the effect of vaporization of the solvent is reduced. That is, it is possible to manufacture electrodes with a remarkably uniform distribution.

Accordingly, the conductive material 200 coated on the surface of the active material 100 and uniformly distributed in the electrode supplements electrical conductivity so that lithium ions and electrons can move smoothly even when the electrode becomes thick due to film thickness, and the surface of the active material 100 The thermosetting binder 300 uniformly coated on the inside effectively suppresses a side reaction between the active material 100 and the electrolyte solution having a micro-crack.

Looking at each step based on this, first, the step (i) (S100) is a step (S100) of preparing a conductive material dispersion by adding and mixing the carbon nanotubes and the dispersant 400 in a solvent.

In step (i) (S100), the solvent is methylpyrrolidone (N-Methyl-2-pyrrolidone, NMP), isopropanol (IPA), dimethylformamide (N,N-dimethylformamide, DMF) And it may be any one or more selected from the group consisting of combinations thereof.

Next, looking at the step (ii) (S200), the conductive material 200 and the binder 300 are uniformly applied on the surface of the active material 100 with a coating solution in which the conductive material dispersion, the active material 100, and the thermosetting binder solution are mixed. This is the step of coating with one distribution.

In the coating method, the coating solution containing the active material 100 is coated by performing filtering, or a solution in which a conductive material dispersion liquid and a thermosetting binder solution are mixed is applied through spraying equipment to the active material 100. ) can be coated by spraying on the surface.

The active material-conductive material-binder composite material for a lithium secondary battery manufactured according to the manufacturing method includes the conductive material 200 in an amount of 0.01 wt% or more and 10 wt% or less based on the total weight of the composite material, and thus the conductive material ( The coverage of the active material 100 by 200) is 0.1% or more and 90% or less.

In addition, the thermosetting binder 300 is included in an amount of 0.01 wt% or more and 10 wt% or less based on the total weight of the composite material, and accordingly, the coverage of the active material 100 by the thermosetting binder 300 is 0.1% or more and 90%. Since it is characterized by the following and shows an even and uniform distribution, it can be expected that an excellent electrical network will be formed when manufactured as an electrode later.

Hereinafter, an electrode for a lithium secondary battery including the active material-conductive material-binder composite material for a lithium secondary battery, which is another embodiment of the present invention, will be described.

Since the electrode for a lithium secondary battery according to this embodiment is manufactured by including the active material-conductive material-binder composite material, the active material 100 and the conductive material 200 are uniformly distributed in the electrode, and thus lithium ions and electrons An electrical network that can move smoothly is formed, and the electrical conductivity is excellent.

Accordingly, since the film can be made thick, the specific gravity occupied by the electrode in the battery is greatly improved.

In addition, since the electrode for a lithium secondary battery according to this embodiment solves the problem caused by the volume expansion of the active material 100 in the conductive material 200 and the binder 300, the performance and lifespan of the electrode even when a large amount of Ni showing high capacity is added. It does not cause degradation problems and shows long-term stability.

Therefore, the electrode for a lithium secondary battery proposed by the present invention can achieve a high energy density of 350 Wh/kg or more.

Preparation Example 1

Preparation of a polysiloxane binder having an epoxy group and a hydroxyl group

In a flask, 100 parts by weight of 2-ethoxyethanol solvent and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (2-(3,4-Epoxycyclohexyl) based on 100 parts by weight of 2-ethoxyethanol solvent 30 parts by weight of ethyltrimethoxysilane and 20 parts by weight of tetramethoxysilane were mixed, and 5 parts by weight of ammonium hydroxide having a concentration of 0.1 N was added to 100 parts by weight of a 2-ethoxyethanol solvent, and the mixture was heated at 60° C. By stirring for a period of time, an alicyclic epoxy-siloxane binder containing 50 wt% of solid content was synthesized.

Preparation Example 2

Manufacture of active material-conductive material-binder composite material for lithium secondary battery

NCM811 active material, mixed conductive material (SWCNT) dispersion and binder solution are mixed in a certain ratio. (Example, active material: conductive material: binder = 97.74wt%: 0.1wt%: 0.8wt%)

When mixing, it is stirred for 30 minutes at 3000 rpm with a general homo-mixer.

The stirred solution is filtered to remove the solvent, and the powder obtained on the filter is vacuum-dried to prepare a composite material in powder form.

Experimental example 1

Battery performance measurement of active material-conductive material-binder composite material for lithium secondary battery

8 to 12 will be described.

In this experiment, in order to confirm the electrochemical characteristics of the active material-conductive material-binder composite material for lithium secondary batteries, which is an embodiment of the present invention, electrodes and batteries including the same were prepared, and battery capacity, output characteristics, and life characteristics were measured.

In the experiment, as summarized in FIG. 8, the initial capacity was measured at 0.1 C for the experimental group classified by varying the content of the thermosetting binder, and the output characteristics were confirmed while changing the C-Rate (0.1 to 2 C), and 0.33 Life characteristics were measured at C/0.5C charge/discharge rate.

9 to 12 are the results of this experiment, and according to this, the composite material to which the thermosetting binder is applied in a high content showed high capacity and excellent output and lifespan characteristics.

This result is due to the fact that the thermosetting binder uniformly and sufficiently covers the surface of the active material to effectively block direct contact between the surface of the active material and the surface of the electrolyte during charging and discharging, and to suppress metal elution.

Therefore, through this comparative experiment, it was confirmed that the active material-conductive material-binder composite material for lithium secondary batteries proposed in the present invention can significantly improve the lifespan characteristics of the high-capacity active material (NCM811).

Experimental Example 2

Experiment to confirm micro-crack state and side reaction suppression effect according to charging and discharging of active material-conductive material-binder composite material for lithium secondary battery

A description will be made with reference to FIGS. 13 and 14.

In this experiment, the active material-conductive material-binder composite material for lithium secondary battery, which is the present invention, effectively suppresses the generation of micro-crack due to volume expansion with the conductive material and binder coating, and effectively suppresses side reactions between the active material and the electrolyte. In order to confirm, the cross-sectional state of the active material was checked after charging and discharging by making it into an electrode, and the elution state of the transition metal according to the presence or absence of a thermosetting binder was analyzed.

Specifically, for the experimental group summarized in FIG. 8, the battery was disassembled after 50 cycles, and the cross section of the electrode was observed, and the amount of transition metal generated from the positive electrode was measured through ICP analysis of the surface of the negative electrode.

Figure 13 is a SEM image of the cross section of the active material after charging and discharging. According to Figure 13 (b), the active material-conductive material-binder composite material proposed in the present invention is well coated with the conductive material and the binder on the outside of the active material. It can be confirmed, and the appearance of internal cracks was confirmed to be less. On the other hand, according to FIG. 13 (a), it was confirmed that internal cracks were severely generated in Comparison 1 to which the composite material was not applied.

This difference in the results indicates that the active material-conductive material-binder composite material proposed in the present invention blocks direct contact of the surface of the active material with the electrolyte through the conductive material-binder coating, thereby effectively suppressing the occurrence of internal cracks.

14 is data analyzing the amount of transition metal elution according to the presence or absence of a thermosetting binder after charging and discharging. According to this, as a result of applying the composite material, relatively little transition metal elution was confirmed on the cathode side.

This means that the thermosetting binder suppresses transition metal elution through active material surface passivation.

Therefore, it was confirmed that the composite material including the thermosetting binder proposed in the present invention is effective in improving the performance of a high energy density battery.

The above description of the present invention is for illustrative purposes, and those skilled in the art can understand that it can be easily modified into other specific forms without changing the technical spirit or essential features of the present invention. will be. Therefore, the embodiments described above should be understood as illustrative in all respects and not limiting. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined form.

The scope of the present invention is indicated by the following claims, and all changes or modifications derived from the meaning and scope of the claims and equivalent concepts should be interpreted as being included in the scope of the present invention.

[Description of code]

100: active material

200: conductive material

300: thermosetting binder

400: Dispersant

Claims (17)

1. active material;

   a conductive material coated on the surface of the active material and containing carbon nanotubes; and

   A thermosetting binder coated on the surface of the active material; characterized in that it comprises an active material-conductive material-binder composite material for a lithium secondary battery.
2. According to claim 1,

   The active material-conductive material-binder composite material for a lithium secondary battery, characterized in that the composite material further comprises a dispersant coated on the surface of the active material.
3. According to claim 1,

   The thermosetting binder is an active material-conductive material-binder composite material for a lithium secondary battery, characterized in that it comprises polysiloxane.
4. According to claim 3,

   The polysiloxane is an active material-conductive material-binder composite material for a lithium secondary battery, characterized in that it contains an epoxy group and a hydroxyl group.
5. According to claim 1,

   The thermosetting binder is an active material-conductive material-binder composite material for a lithium secondary battery, characterized in that contained in 0.01wt% or more and 10wt% or less relative to the total weight of the composite material.
6. According to claim 1,

   The conductive material includes at least one selected from the group consisting of single wall carbon nanotubes (SWCNTs), multi wall carbon nanotubes (MWCNTs), and combinations thereof. To, active material-conductive material-binder composite material for lithium secondary batteries.
7. According to claim 1,

   The conductive material is characterized in that it is included in 0.01wt% or more and 10wt% or less relative to the total weight of the composite material, active material for a lithium secondary battery-conductive material-binder composite material.
8. According to claim 1,

   An active material-conductive material-binder composite material for a lithium secondary battery, characterized in that the coverage of the active material by the conductive material is 0.1% or more and 90% or less.
9. According to claim 1,

   The carbon nanotubes have an average diameter of 1 nm or more and 10 nm or less, and an aspect ratio of 1:1000 or more, active material-conductive material-binder composite material for a lithium secondary battery.
10. According to claim 2,

    The dispersant is lithium secondary, characterized in that at least one selected from the group consisting of hydrogenated acrylonitrile butadiene rubber (HNBR), polyvinylidene fluoride (PVDF), and combinations thereof. Active material-conductive material composite material for batteries.
11. (i) preparing a conductive material dispersion by mixing carbon nanotubes and a dispersant; and

    (ii) coating the surface of the active material with a coating solution in which the conductive material dispersion, the active material and the thermosetting binder solution are mixed; characterized in that it comprises a lithium secondary battery active material-conductive material-binder composite manufacturing method.
12. According to claim 11,

    The carbon nanotubes include at least one selected from the group consisting of single wall carbon nanotubes (SWCNTs), multi-wall carbon nanotubes (MWCNTs), and combinations thereof Characterized in that, active material-conductive material-binder composite material manufacturing method for lithium secondary batteries.
13. According to claim 11,

    The dispersant is lithium secondary, characterized in that at least one selected from the group consisting of hydrogenated acrylonitrile butadiene rubber (HNBR), polyvinylidene fluoride (PVDF), and combinations thereof. Active material-conductive material composite material manufacturing method for batteries.
14. According to claim 11,

    The thermosetting binder is characterized in that it comprises a polysiloxane, active material-conductive material-binder composite material manufacturing method for a lithium secondary battery.
15. According to claim 14,

    The polysiloxane is an active material-conductive material-binder composite material manufacturing method for a lithium secondary battery, characterized in that it contains an epoxy group and a hydroxyl group.
16. An electrode for a lithium secondary battery comprising the active material-conductive material-binder composite material of claim 1.
17. According to claim 16,

    The electrode is an electrode for a lithium secondary battery, characterized in that it has an energy density of 350 Wh / kg or more.

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