Conductive composite binder for lithium secondary battery negative electrode, and lithium secondary battery negative electrode comprising same

Abstract

The present invention relates to a conductive composite binder for a lithium secondary battery negative electrode, the conductive composite binder comprising: a first compound having at least one carboxyl group (-COOH) or at least one hydroxyl group (-OH); a second compound physically connected to the first compound and having at least one hydroxyl group (-OH) and at least one benzene ring; and a carbon material physically connected to the first or second compound.

Description

Conductive composite binder for lithium secondary battery negative electrode and lithium secondary battery negative electrode comprising the same

[0001] The present invention relates to a conductive composite binder for a lithium secondary battery negative electrode and a lithium secondary battery negative electrode including the same.

[0002] Lithium-ion secondary batteries (LIBs) are seeing increasing demand for energy storage devices such as portable electronic devices, electric vehicles, and energy storage systems, and their market is expanding significantly. Consequently, the need to improve the power density and energy density of LIBs is growing.

[0003] To improve the energy density of lithium-ion secondary batteries, various materials with higher theoretical capacities than graphite, which is commonly used as an anode material, are being studied, and among them, silicon materials are being studied as a substitute for graphite.

[0004] Silicon (Silicon) is attracting attention as a high-capacity anode material due to its high theoretical capacity (4200 mAh / g). However, it has problems such as large expansion (approximately 400%) when reacting with lithium ions, material crushing during repeated charge / discharge, and unstable solid-electrolyte interface, which cause reduced cell lifespan, and therefore, improvement is necessary for practical use. In addition, low electrical conductivity and initial coulombic efficiency of silicon are factors that hinder the realization of high energy density in secondary batteries, and therefore, these must also be improved. Among silicon-based materials, silicon oxide (SiO x ) is attracting attention due to its improved volume expansion and lifespan compared to pure silicon materials, but has the disadvantages of reduced electrical conductivity and low initial Coulombic efficiency.

[0005] Accordingly, various studies are being conducted to improve electrochemical properties, mechanical properties, and cycle characteristics in order to apply silicon materials as cathodes.

[0006] Prior patent: KR 10-1142534 (April 26, 2012)

[0007] The purpose of the present invention is to provide a conductive composite binder for a lithium secondary battery negative electrode that improves cycle characteristics by reducing volume expansion of a silicon-based negative electrode active material during a charge / discharge process, and a lithium secondary battery negative electrode comprising the same.

[0008] The purpose of the present invention is to provide a novel conductive composite binder for a lithium secondary battery negative electrode, thereby reducing the use of a conductive material and a binder and effectively controlling the volume expansion of a silicon-based negative electrode active material, and to provide a conductive composite binder for a lithium secondary battery negative electrode and a lithium secondary battery negative electrode including the same.

[0009] One embodiment of the present invention provides a binder for a lithium secondary battery negative electrode, a method for manufacturing the same, and a lithium secondary battery negative electrode including the same.

[0010] In one embodiment, the conductive composite binder for a lithium secondary battery negative electrode may include a first compound having at least one carboxyl group (-COOH) or at least one hydroxyl group (-OH); a second compound physically connected to the first compound and having at least one hydroxyl group (-OH) and at least one benzene ring; and a carbon material physically connected to the first or second compound.

[0011] In one embodiment, the first compound comprises a polyphenol molecule, the second compound comprises a catechol structure and a pyrogallol structure, and the carbon material may comprise a 1D (Dimension) or 2D structure.

[0012] In one embodiment, the first compound comprises at least one of carboxymethyl cellulose (CMC), cellulose, sodium salt of carboxymethyl cellulose, hydroxyethyl cellulose, potassium salt of carboxymethyl cellulose, lithium salt of carboxymethyl cellulose, polyacrylic acid, sodium alginate, polyacrylamide, and polyvinyl alcohol, the second compound comprises at least one of tannic acid (TA), catechol, dopamine, dopamine hydrochloride, norepinephrine, L-dihydroxyphenylalanine, hydroxyphenolic acid, adrenaline, lignin monomer, ellagitannin, and pyrogallol, and the carbon material comprises at least one of graphene, carbon nanofiber, carbon nanotube (CNT), It may contain one or more of carbyne and MXene.

[0013] In one embodiment, the first compound and the second compound may be connected by a hydrogen bond, and the carbon material may be connected to the first compound by a hydrogen bond, or the carbon material may be connected to the second compound by a π-π interaction.

[0014] In one embodiment, the weight ratio of the first compound: the second compound is 1:0.1 to 1, and the first compound and the second compound are added to a base solvent to prepare a compound solution, after which the carbon material can be added.

[0015] In one embodiment, the content of the first compound in the conductive composite binder for the lithium secondary battery negative electrode may be 0.5 wt% to 5 wt%, and the content of the carbon material may be 0.1 wt% to 10 wt%.

[0016] In one embodiment, the base solvent includes at least one of water, N-methyl-2-pyrrolidone (NMP), methanol, ethanol, polypyrrolidone, isopropanol, acetone, petroleum ether, tetrahydrofuran, ethyl acetate, N,N-dimethylacetamide, N,N-dimethylformamide, n-hexane, and a halogenated hydrocarbon, and the viscosity of the compound solution may be 30 cP to 400 cP.

[0017] In one embodiment, the conductive composite binder for a lithium secondary battery negative electrode further includes a base solvent, and the first compound, the second compound, and the carbon material are chemically or physically connected in a network form in the base solvent, and the viscosity of the conductive composite binder for a lithium secondary battery negative electrode may be 300 cP to 1800 cP.

[0018] In one embodiment, the first compound may be carboxymethyl cellulose, the second compound may be tannic acid, and the carbon material may be graphene or carbon nanotubes (CNTs).

[0019] In one embodiment, the carbon material includes a carbon nanotube, and the carbon nanotube is formed in a bundle shape by partially converging 1 to 10 single-walled carbon nanotubes or multi-walled carbon nanotubes, and the diameter of the bundle shape is 2 nm to 35 nm, and the length is 4 ㎛ to 10 mm, and the carbon nanotube may have a content of oxygen atoms with respect to carbon atoms as a component of the carbon nanotube of 0.01 mol% to 10 mol%.

[0020] In one embodiment, the UV-Vis spectrum may exhibit a maximum peak intensity at 220 nm to 230 nm.

[0021] In one embodiment, the Fourier-transform infrared (FTIR) spectrum is characterized by a peak at 1620 cm -1 1700 cm inland -1 The first peak formed broadly at 3000 cm -1 3900 cm inland -1 A first peak formed in the second peak may have an intensity ratio of 1.3 to 3.

[0022] In one embodiment, the conductive composite binder for a lithium secondary battery negative electrode further includes a base solvent, and the conductive composite binder for a lithium secondary battery negative electrode is provided in a form in which a solid material is dispersed in the base solvent, and the solid material may be provided in a network form in which the first compound, the second compound, and the carbon compound are physically connected through hydrogen bonds or π-π interactions.

[0023] In one embodiment, the content of the solid material in the base solvent may be 1 wt% to 7 wt%.

[0024] In one embodiment, the method for manufacturing the conductive composite binder for the lithium secondary battery negative electrode includes the steps of: preparing a compound solution having a first viscosity by adding a first compound and a second compound to a base solvent; and adding a carbon material to the compound solution and stirring the solution; and the viscosity may be 300 cP to 1800 cP.

[0025] In one embodiment, the first compound has at least one carboxyl group (-COOH) or at least one hydroxyl group (-OH), the second compound is physically connected to the first compound and has at least one hydroxyl group (-OH) and at least one benzene ring, the carbon material is physically connected to the first or second compound, and the viscosity of the compound solution may be 30 cP to 400 cP.

[0026] In one embodiment, the negative electrode for a lithium secondary battery includes a negative electrode current collector; and a negative electrode mixture coated on the negative electrode current collector; the negative electrode mixture includes a negative electrode active material and the conductive composite binder for a lithium secondary battery negative electrode described above, and the negative electrode active material may be a silicon compound or a mixture of a silicon compound and graphite.

[0027] In one embodiment, the silicon compound is SiO x (0≤x<2), SiO containing lithium compound x (0≤x<2), SiO containing magnesium compounds x (0≤x<2), silicon alloy (Si-alloy), and silicon-carbon composite (Si-C composite).

[0028] In one embodiment, the negative electrode mixture further includes an auxiliary binder, and the auxiliary binder may include at least one of styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), nitrile butadiene rubber (NBR), polyacrylamide (PAM), polyacrylonitrile (PAN), polyimide (PI), and polyamideimide (PAI).

[0029] In one embodiment, for 100 parts by weight of the negative electrode material, the amount of the conductive composite binder for a lithium secondary battery negative electrode may be 80 to 500 parts by weight.

[0030] In one embodiment, the bulk resistance may be 0.02 Ω·cm to 0.06 Ω·cm, and the interface resistance may be 0.002 Ω / cm2 to 0.005 Ω / cm2.

[0031] In one embodiment, the bonding force of the negative electrode mixture obtained by peeling off the negative electrode mixture from the negative electrode current collector at a speed of 20 mm / min and an angle of 90° using a peel test device may be 2 N or more.

[0032] In one embodiment, the negative electrode mixture is prepared by adding the negative electrode active material to the conductive composite binder for a lithium secondary battery negative electrode to prepare a negative electrode slurry, coating the negative electrode slurry on the negative electrode current collector, and then drying the same. The conductive composite binder for a lithium secondary battery negative electrode includes a base solvent, a first compound, a second compound, and a carbon material, and the base solvent may include water.

[0033] In one embodiment, the conductive composite binder for a lithium secondary battery negative electrode is provided in a form in which a solid material is dispersed in a base solvent, and the solid material is provided in a network form in which the first compound, the second compound, and the carbon compound are physically connected by hydrogen bonds or π-π interactions, the base solvent includes water, the content of the solid material in the base solvent is 3 wt% to 7 wt%, and the negative electrode mixture can be manufactured by mixing the conductive composite binder for a lithium secondary battery negative electrode and the negative electrode active material without adding a solvent.

[0034] According to the present invention as described above, a conductive composite binder for a lithium secondary battery negative electrode can be provided, which can reduce the content of a conductive material and a binder, and reduce the volume expansion of a silicon-based negative electrode active material that occurs during a charge / discharge process, and a negative electrode for a lithium secondary battery including the same.

[0035] In addition, the negative electrode for lithium secondary batteries can be manufactured more simply than before, and is environmentally friendly as it can utilize an aqueous process.

[0036] FIG. 1 is a schematic drawing of a conductive composite binder for a lithium secondary battery negative electrode according to one embodiment of the present invention.

[0037] Figure 2 is a flow chart showing a method for manufacturing a conductive composite binder for a lithium secondary battery negative electrode according to one embodiment of the present invention.

[0038] Figure 3 shows the FT-IR analysis results of the composite binder used in Examples 1 and 2.

[0039] Figure 4 shows the results of the dispersion evaluation and UV-Vis spectrum of the composite binder of Example 1.

[0040] Figure 5 shows the results of confirming the bonding strength and viscosity through a vial turning test for the composite binder used in the examples and manufacturing examples and the carbon black and CNT aqueous solution.

[0041] Figure 6 shows the results of confirming the bonding strength of the cathodes of Example 1 and Comparative Examples 1 and 2.

[0042] Figure 7 shows the results of evaluating the electrochemical characteristics of half-cells using Example 1 and Comparative Examples 1 and 2.

[0043] Fig. 8 shows the results of confirming the distribution and volume expansion of carbon materials for the negative electrodes of Example 1 and Comparative Example 1, which were evaluated using the half-cell of Fig. 7.

[0044] Figure 9 shows the results of evaluating the electrochemical characteristics of the half-cell using Example 2 and Comparative Example 3.

[0045] Figure 10 shows the results of confirming the cycle characteristics and coulombic efficiency of a full cell using Example 2 and Comparative Example 3.

[0046] Specific details of other embodiments are included in the detailed description and drawings.

[0047] The advantages and features of the present invention, and the methods for achieving them, will become clear with reference to the embodiments described in detail below together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various different forms, and unless otherwise specified in the following description, all numbers, values, and / or expressions expressing components, reaction conditions, and contents of components in the present invention are to be understood as being modified in all cases by the term "about" because such numbers are approximations that reflect, among other things, various uncertainties in the measurement that occur in obtaining such values. In addition, when a numerical range is disclosed herein, such range is continuous and includes every value from the minimum value to the maximum value inclusive, unless otherwise indicated. Furthermore, when such a range refers to an integer, every integer from the minimum value to the maximum value inclusive, unless otherwise indicated, is included.

[0048] Additionally, when a range is described for a variable in the present invention, it will be understood that the variable includes all values ​​within the described range including the described endpoints of the range. For example, the range "5 to 10" will be understood to include the values ​​5, 6, 7, 8, 9, and 10, as well as any subranges such as 6 to 10, 7 to 10, 6 to 9, 7 to 9, etc., and also any value between integers that fall within the described range, such as 5.5, 6.5, 7.5, 5.5 to 8.5, and 6.5 to 9. For example, a range of "10% to 30%" would be understood to include all integers up to and including 30%, as well as any subranges such as 10% to 15%, 12% to 18%, 20% to 30%, etc., and any value between reasonable integers within the stated range, such as 10.5%, 15.5%, 25.5%, etc.

[0049] FIG. 1 is a schematic drawing of a conductive composite binder for a lithium secondary battery negative electrode according to one embodiment of the present invention.

[0050] A conductive composite binder for a lithium secondary battery negative electrode according to an embodiment of the present invention may include: a first compound having at least one carboxyl group (-COOH) or at least one hydroxyl group (-OH); a second compound physically connected to the first compound and having at least one hydroxyl group (-OH) and at least one benzene ring; and a carbon material physically connected to the first or second compound.

[0051] Recently, various studies have been conducted to apply materials with higher energy density than the commonly used graphite material to the anode active material used as the anode of lithium secondary batteries in order to improve the energy density. In order to increase the energy density of the anode, various silicon materials (SiO) have been used as the anode active material. x , SCN, Si-alloy, pure Si, micro-Si, etc.) are being used alone or blended with graphite materials, but when the silicon material content exceeds 10%, it is difficult to maintain the life characteristics of the lithium secondary battery due to excessive volume change of the silicon material that occurs during repeated charge and discharge. Specifically, when applying a silicon material as an anode active material, pulverization (cracks and destruction of particles) of the anode active material occurs during multiple charge and discharge processes, which causes the electron movement path to be lost and the electrochemical characteristics to deteriorate. In addition, there is a problem that the bonding strength between the anode active material, conductive material, and binder included in the anode deteriorates due to repeated volume changes of the anode active material, and electrode deterioration is accelerated due to uneven distribution of the conductive material.

[0052] The conductive composite binder for a lithium secondary battery anode according to the present invention can effectively control the volume expansion of a silicon material, thereby improving the capacity of a lithium secondary battery by applying a silicon material as an anode active material. In addition, the conductive composite binder for a lithium secondary battery anode can reduce the thickness of the anode more than that of graphite for the same energy capacity, thereby providing a high-capacity lithium secondary battery.

[0053] Typically, carbon black (Denka Black, Ketjen Black, etc.), a 0D (Dimension) conductive material used in the negative electrode, is available in powder form, and frequently causes problems such as clumping within the negative electrode active material, and is difficult to disperse evenly. In addition, when carbon black is used with silicon-based negative electrode active materials, there is a disadvantage in that it is not uniformly distributed within the silicon material, and is vulnerable to structural changes within the silicon material, which has a problem with volume expansion.

[0054] In this embodiment, the carbon material may include a 1D (Dimension) or 2D structure. By applying a carbon material having the function of a 1D conductive material, such as CNT, or a 2D conductive material, such as graphene, to the cathode, the volume expansion problem of the silicon material can be controlled, thereby maintaining the electron conduction path of the cathode.

[0055] The carbon material used in the embodiments of the present invention is provided in a 1D or 2D structure, so that it can be stably fixed to the silicon material and provide active sites to the negative electrode active material including the silicon material with low electronic conductivity, thereby increasing the energy capacity of the lithium secondary battery and improving the electrical conductivity. In addition, compared to carbon black, which is a 0D conductive material, it is uniformly dispersed with high binding force with the silicon material even when the same content is used or the content is reduced, so that the electron conduction path is maintained even when the volume of the silicon material expands and contracts during charge and discharge, thereby improving the electrochemical performance of the lithium secondary battery.

[0056] The carbon material may include at least one of graphene, carbon nanofibers, carbon nanotubes (CNTs), carbyne, and MXene. The carbon material may be provided in a 1D or 2D structure, and may be easily connected to the first compound or the second compound, thereby being closely fixed to the silicon material, thereby exhibiting high conductive performance.

[0057] The first compound and the second compound are connected by a hydrogen bond, and the carbon material may be connected to the first compound by a hydrogen bond, or the carbon material may be connected to the second compound by a π-π interaction. The hydrogen bond and the π-π interaction are physical bonds rather than chemical bonds, and thus can maintain the inherent properties of the first compound, the second compound, and the carbon material within the negative electrode active material without changing their properties. In addition, the hydrogen bond and the π-π interaction can maintain a high bonding strength among physical bonds, and thus can stably fix the carbon material and the silicon material even against volume expansion of the silicon material.

[0058] The hydrogen bond may be provided between the carboxyl group or hydroxyl group of the first compound and the silicon compound, or between the carboxyl group or hydroxyl group of the first compound and the hydroxyl group of the second compound. In addition, the hydrogen bond may be provided between the carbon material and the first or second compound when the carbon material has a functional group such as a hydroxyl group. In addition, the π-π interaction may be provided between the second compound and the carbon material.

[0059] Additionally, gelation may occur in at least a portion of the first compound and the second compound. The gelation may occur due to hydrogen bonding formed when the first compound and the second compound are present at a certain concentration or higher. Additionally, the carbon material may bind to the first and second compounds, thereby increasing the viscosity and decreasing the fluidity of the conductive composite binder for a lithium secondary battery negative electrode.

[0060] The first compound and the second compound can be combined with a silicon material to bind the silicon material and stably fix the negative electrode mixture including the silicon material to the negative electrode current collector. In addition, the first compound and the second compound can stably fix the particle positions of each silicon material even due to volume expansion of the silicon material, and improve the adhesive strength between the silicon material and the conductive material, thereby improving the cycle characteristics of the lithium secondary battery. Therefore, the conductive composite binder for a lithium secondary battery negative electrode according to an embodiment of the present invention can simultaneously perform the function of a conductive material in the negative electrode, bind the silicon material, and stably fix the negative electrode mixture including the silicon material to the negative electrode current collector. The conductive composite binder for a lithium secondary battery negative electrode according to an embodiment of the present invention can be uniformly distributed in the negative electrode, and maintain an electron conduction path even during repeated charge and discharge, thereby suppressing an increase in the resistance of the negative electrode and improving the life characteristics of the lithium secondary battery.

[0061] The conductive composite binder for a lithium secondary battery negative electrode of the present invention can be applied not only to a silicon compound but also to a negative electrode in the form of a mixture of the silicon compound and graphite.

[0062] The first compound may include a polyphenol molecule, and the second compound may include a catechol structure and a pyrogallol structure.

[0063] Specifically, the first compound may include at least one of carboxymethyl cellulose (CMC), cellulose, a sodium salt of carboxymethyl cellulose, hydroxyethyl cellulose, a potassium salt of carboxymethyl cellulose, a lithium salt of carboxymethyl cellulose, polyacrylic acid, sodium alginate, polyacrylamide, and polyvinyl alcohol. In addition, the second compound may include at least one of tannic acid (TA), catechol, dopamine, dopamine hydrochloride, norepinephrine, L-dihydroxyphenylalanine, hydroxyphenolic acid, adrenaline, a lignin monomer, ellagitannin, and pyrogall (1,2,3-benzenetriol).

[0064] The weight ratio of the first compound to the second compound may be 1:0.1 to 1. The first compound may have a relatively long hydrocarbon chain, thereby fixing the silicon compound. In addition, the second compound has a benzene ring as a molecule smaller in size than the first compound, thereby fixing the carbon material and binding to the first compound to fix the carbon material to the silicon compound. If the weight ratio of the second compound to the first compound is less than 0.1, the carbon material may not be stably fixed in a sufficient amount, which may be problematic, and if it exceeds 0.8, the specific capacity of the negative electrode may be reduced and areas in which the carbon materials clump together may occur. Specifically, the weight ratio of the first compound to the second compound may be 1:0.1 to 0.7, or 1:0.2 to 0.7.

[0065] In the conductive composite binder for the lithium secondary battery negative electrode, the first compound and the second compound may be added to a base solvent to prepare a compound solution, and then the carbon material may be added. The first compound and the second compound may be first mixed in the base solvent to form a physical bond between the first and second compounds, and then the carbon material may be added to combine the carbon material with the second compound, thereby enabling the carbon material to be more uniformly distributed.

[0066] The viscosity of the compound solution may be 30 cP to 400 cP. If the viscosity of the compound solution is less than 30 cP, the binding force of the negative electrode active material may be reduced, and an additional process for removing the base solvent may be required, which may reduce process efficiency. In addition, if the viscosity of the compound solution exceeds 400 cP, it is difficult to uniformly disperse the carbon material, which is problematic. As the content of the second compound in the compound solution increases, the viscosity may decrease. Specifically, the viscosity of the compound may be 30 cP to 300 cP, or 30 cP to 200 cP, or 50 cP to 300 cP, or 50 cP to 200 cP, or 100 cP to 300 cP, or 100 cP to 200 cP.

[0067] The conductive composite binder for a lithium secondary battery negative electrode may be provided in such a manner that the first compound, the second compound, and the carbon material are chemically or physically connected in a network form in the base solvent. Specifically, the first compound, the second compound, and the carbon material may be connected in a network form and may exist as a solid material dispersed in the base solvent, and the conductive composite binder for a lithium secondary battery negative electrode may be used to manufacture the negative electrode in the form in which the solid material is dispersed in the base solvent without performing a process of removing the base solvent. The solid material may be provided in a network form in which the first compound, the second compound, and the carbon compound are physically connected through hydrogen bonds or π-π interactions.

[0068] The content of the solid material in the base solvent may be 1 wt% to 7 wt%. If the content of the solid material is less than 1 wt%, it is difficult for the solid material to efficiently attach to the negative electrode active material during the mixing process by adding the negative electrode active material, and if it exceeds 7 wt%, the negative electrode active material may clump together and not be uniformly mixed, which is problematic.

[0069] The viscosity of the conductive composite binder for a lithium secondary battery negative electrode may be 300 cP to 1800 cP. If the viscosity of the conductive composite binder for a lithium secondary battery negative electrode is less than 300 cP, it is difficult for the solid material composed of the first compound, the second compound, and the carbon material to be uniformly attached to the silicon compound, and if it is more than 1800 cP, it is difficult to mix the silicon compound and the conductive composite binder for a lithium secondary battery negative electrode, which may lower process efficiency, such as requiring the addition of more solvent. Specifically, the viscosity of the conductive composite binder for a lithium secondary battery negative electrode may be 300 cP to 1500 cP, or 300 cP to 1400 cP, or 400 cP to 1500 cP, or 400 cP to 1400 cP, or 400 cP to 1300 cP.

[0070] The content of the first compound in the conductive composite binder for the lithium secondary battery negative electrode may be 0.5 wt% to 5 wt%. If the content of the first compound is less than 0.5 wt%, the silicon compound may not be stably bound, which may be problematic, and if it exceeds 5 wt%, the silicon compound may act as an external force when the silicon compound expands in volume, which may be problematic. Specifically, the content of the first compound may be 0.5 wt% to 4 wt%, or 0.5 wt% to 3 wt%, or 0.5 wt% to 2 wt%.

[0071] The content of the carbon material may be 0.1 wt% to 10 wt%. If the content of the carbon material is less than 0.1 wt%, the carbon material may not sufficiently function as a conductive material, which may result in a decrease in the electrical conductivity of the lithium secondary battery. If the content exceeds 10 wt%, the specific capacity of the negative electrode may decrease, and areas such as the carbon material clumping may occur, which may result in a decrease in electron transfer efficiency. Specifically, the content of the carbon material may be 0.1 wt% to 9 wt%, or 0.1 wt% to 8 wt%, or 0.1 wt% to 7 wt%, or 0.1 wt% to 6 wt%, or 0.1 wt% to 5 wt%, or 0.5 wt% to 9 wt%, or 1 wt% to 9, or 1 wt% to 8 wt%, or 1 wt% to 7 wt%, or 1 wt% to 6 wt%, or 1 wt% to 5 wt%.

[0072] The base solvent may include at least one of water, N-methyl-2-pyrrolidone (NMP), methanol, ethanol, polypyrrolidone, isopropanol, acetone, petroleum ether, tetrahydrofuran, ethyl acetate, N,N-dimethylacetamide, N,N-dimethylformamide, n-hexane, and a halogenated hydrocarbon. Specifically, the base solvent may include water. By using water as the base solvent, in the process of manufacturing an anode using the conductive composite binder for a lithium secondary battery anode, an aqueous process can be easily applied using water without using an organic solvent.

[0073] More specifically, the first compound may be carboxymethyl cellulose (CMC), the second compound may be tannic acid, and the carbon material may include graphene or carbon nanotubes (CNT).

[0074] The above carboxymethyl cellulose may have a molecular weight (Mn) of 300,000 to 1,000,000, for example, 350,000 to 900,000, and specifically, 500,000 to 900,000. The above carboxymethyl cellulose may be prepared by substituting 40% or more of the hydroxyl group (cellulose-OH) on C6 of a glucose residue with a carboxymethyl group (-CH2COOH).

[0075] The dual functionality of the above tannic acid (TA) is used to induce a hydrogen bond between the terminal hydroxyl group and carboxymethyl cellulose, and the benzene ring contained in the above tannic acid is bonded to a carbon substance through π-π interaction, and can induce additional bonding between the carboxymethyl cellulose and the carbon substance.

[0076] The second compound acts as an intermediate between the first compound and the carbon material, thereby forming a bond between the first compound, which functions as a binder, and the carbon material, which functions as a conductive material, thereby producing a conductive composite binder for a lithium secondary battery negative electrode having a rigidity higher than a certain level, and by using this, the bonding strength between silicon compounds and between the negative electrode composite including the silicon compound and the negative electrode current collector can be increased. In addition, by uniformly distributing the conductive composite binder for a lithium secondary battery negative electrode within the negative electrode through a simple process, the electronic conductivity can be improved by flexibly responding to volume changes in the silicon compound during charge and discharge, and a mechanically robust three-dimensional negative electrode structure can be provided.

[0077] The above carbon material may include carbon nanotubes. The carbon nanotubes may be formed in a bundle shape by partially converging 1 to 10 single-walled carbon nanotubes or multi-walled carbon nanotubes, and the bundle shape may have a diameter of 2 nm to 35 nm and a length of 4 μm to 10 mm. The carbon nanotubes may have a content of oxygen atoms relative to carbon atoms of 0.01 mol% to 10 mol% as a constituent of the carbon nanotubes.

[0078] The above-mentioned bundle-shaped carbon nanotubes have a problem in that they are difficult to attach to the surface of the silicon compound when the diameter is less than 2 nm, and when the diameter is more than 35 nm, the coating thickness of the conductive composite binder for the lithium secondary battery negative electrode on the surface of the silicon compound increases and electron mobility decreases, which is a problem. Specifically, the diameter of the bundle-shaped carbon nanotubes may be 2 nm to 30 nm, or 3 nm to 25 nm, or 4 nm to 20 nm.

[0079] In addition, if the length of the bundle shape is less than 4 ㎛, it is difficult to maintain a network shape together with the first compound and the second compound, so that sufficient electrical connection is not provided, and if it exceeds 10 mm, the viscosity of the conductive composite binder for a lithium secondary battery negative electrode including carbon nanotubes may be high, which may reduce process efficiency. Specifically, the length of the bundle shape may be 5 ㎛ to 10 mm, 10 ㎛ to 10 mm, or 20 ㎛ to 10 mm, or 20 ㎛ to 5 mm, or 50 ㎛ to 10 mm, or 50 ㎛ to 5 mm. Specifically, the carbon nanotube may include at least one of MWCNT, TWCNT, and SWCNT.

[0080] The conductive composite binder for a lithium secondary battery negative electrode can exhibit a maximum peak intensity at 220 nm to 230 nm in a UV-Vis spectrum. Based on the UV-Vis spectrum, it can be confirmed that in the conductive composite binder for a lithium secondary battery negative electrode, the second compound and the carbon material are not present independently but are combined.

[0081] In addition, the conductive composite binder for the lithium secondary battery negative electrode has a Fourier-transform infrared (FTIR) spectrum at 1620 cm -1 1700 cm inland -1 The first peak formed broadly at 3000 cm -1 3900 cm inland -1 Including a first peak formed in, the ratio of the intensity of the second peak to the first peak may be 1.3 to 3. In the conductive composite binder for a lithium secondary battery negative electrode, the first compound, the second compound, and the carbon material are not individually present, but are provided in the form of a single macromolecule through interaction, so that the FTIR spectrum can be provided within the aforementioned range.

[0082] The conductive composite binder for a lithium secondary battery anode according to an embodiment of the present invention forms a 3D network structure together with an anode active material inside the anode, thereby maintaining uniform ionic and electronic conductivity within the anode. In addition, since an aqueous process is possible and a separate conductive agent is not added, process defects that occurred due to difficulties in uniform mixing of conductive agents in the past can be reduced. In addition, by using the conductive composite binder for a lithium secondary battery anode according to an embodiment of the present invention, the problem of silicon compounds having an issue of volume expansion can be improved, thereby improving life characteristics.

[0083] Figure 2 is a flow chart showing a method for manufacturing a conductive composite binder for a lithium secondary battery negative electrode according to one embodiment of the present invention.

[0084] Referring to FIG. 2, a method for manufacturing a conductive composite binder for a lithium secondary battery negative electrode according to one embodiment of the present invention may include a step of manufacturing a compound solution having a first viscosity by adding a first compound and a second compound to a base solvent; and a step of adding a carbon material to the compound solution and stirring the solution. In addition, the conductive composite binder for a lithium secondary battery negative electrode may have a viscosity of 300 cP to 1800 cP.

[0085] The step of preparing the compound solution may be performed at room temperature. The first compound and the second compound may be combined and provided within the base solvent. Specifically, the first compound may include one or more carboxyl groups (-COOH) or one or more hydroxyl groups (-OH), and the second compound may include one or more hydroxyl groups (-OH), thereby being physically connected to the first compound by a hydrogen bond. The viscosity of the compound solution may be 30 cP to 400 cP. If the viscosity of the compound solution is less than 30 cP, the bonding force with the carbon material may be reduced, which may be problematic, and if it is more than 400 cP, the carbon material may not be uniformly dispersed, which may be problematic. In addition, as the content of the second compound in the compound solution increases, the viscosity of the compound solution may decrease.

[0086] In the step of adding and stirring the carbon material, the carbon material may be physically connected to the second compound. Specifically, the second compound may include a benzene ring, and the benzene ring may be connected to the carbon material through a π-π interaction. In addition, when the carbon material includes a functional group such as a carboxyl group (-COOH) or a hydroxyl group (-OH), the carbon material may be connected to the first compound or the second compound through a hydrogen bond.

[0087] According to another aspect of the present invention, the present invention can manufacture a negative electrode for a lithium secondary battery using the conductive composite binder for a negative electrode for a lithium secondary battery described above.

[0088] The above lithium secondary battery negative electrode includes a negative electrode current collector; and a negative electrode mixture coated on the negative electrode current collector; and the negative electrode mixture can be manufactured using a negative electrode active material and the conductive composite binder for a lithium secondary battery negative electrode described above.

[0089] The above negative electrode active material may include a silicon compound or a mixture of a silicon compound and graphite.

[0090] The above negative electrode current collector may be made of a material that does not react with lithium and is electrically conductive. The negative electrode current collector may be made of a metal material such as copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni), but is not limited thereto, and any material that can be used as an electrode current collector in the relevant technical field may be used. The negative electrode current collector may be made of one type of the above-mentioned metal material, or may be made of an alloy or a coating material of two or more types of metals. The negative electrode current collector may be provided in the form of a plate or foil having a thickness of 5 ㎛ to 30 ㎛ and having flexible characteristics that can support the negative electrode composite.

[0091] The above silicon compound is SiO x (0≤x<2), SiO containing lithium compound x (0≤x<2), SiO containing magnesium compounds x (0≤x<2), silicon alloy (Si-alloy), and silicon-carbon composite (Si-C composite).

[0092] For example, the silicon compound (110) is SiO containing the lithium compound. x (0≤x<2) Si or silicon oxide can contain lithium by a prelithiation method. Specifically, the prelithiation method includes a method of manufacturing a negative electrode after lithiating a silicon compound (110) by a physicochemical method or an electrochemical charging method.

[0093] SiO containing the above magnesium compound x (0≤x<2) may include MgSiO3 crystals and Mg2SiO4 crystals in silicon oxide.

[0094] The above silicon alloy may be represented as Si-M, where M may be Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P, As, Sb, Bi, S, Se, Te, Po, or a combination thereof. Specifically, the silicon alloy may be one selected from SiTiNi, SiAlMn, SiAlFe, SiFeCu, SiCuMn, SiMgAl, SiMgCu, and a combination thereof.

[0095] The above silicon-carbon composite may be a material formed of silicon and carbon through heat treatment or the like, wherein the carbon may be at least one of carbon, carbon nanotubes, and graphene.

[0096] The above graphite may be artificial graphite, natural graphite, or a mixture of artificial graphite and natural graphite. The form of the artificial graphite or natural graphite may be amorphous, plate-like, flake-like, spherical, fibrous, or a combination thereof. In addition, when the artificial graphite and natural graphite are mixed and used, the mixing ratio may be 70:30 to 95:5 by weight.

[0097] The above-described negative electrode composite may further include an auxiliary binder. The auxiliary binder may be added to the conductive composite binder for a lithium secondary battery negative electrode, and then the negative electrode active material may be added thereto. The content of the auxiliary binder may be such that the weight ratio of the first compound included in the conductive composite binder for a lithium secondary battery negative electrode to the auxiliary binder is 1:0.01 to 5. By including the auxiliary binder within the above-described range, the binding force of the silicon compound may be further improved. Specifically, the weight ratio of the first compound included in the conductive composite binder for a lithium secondary battery negative electrode to the auxiliary binder may be 1:0.1 to 5, or 1:0.1 to 4, or 1:0.1 to 3.5, or 1:0.2 to 5, or 1:0.3 to 5.

[0098] The above auxiliary binder includes at least one of styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), nitrile butadiene rubber (NBR), polyacrylamide (PAM), polyacrylonitrile (PAN), polyimide (PI), and polyamideimide (PAI).

[0099] With respect to 100 parts by weight of the negative electrode mixture, the amount of the conductive composite binder for a lithium secondary battery negative electrode may be 80 parts by weight to 500 parts by weight. If the amount of the conductive composite binder for a lithium secondary battery negative electrode is less than 80 parts by weight, there may be difficulty in preparing a slurry due to insufficient solvent, and the negative electrode active material may not be sufficiently bound, which may be problematic. If the amount exceeds 500 parts by weight, the amount of solvent may be too large, which may reduce the binding force. Specifically, with respect to 100 parts by weight of the negative electrode mixture, the amount of the conductive composite binder for a lithium secondary battery negative electrode may be 80 parts by weight to 450 parts by weight, or 80 parts by weight to 400 parts by weight, or 90 parts by weight to 500 parts by weight, or 90 parts by weight to 400 parts by weight, or 100 parts by weight to 400 parts by weight.

[0100] The above negative electrode mixture may be prepared by adding the negative electrode active material to the conductive composite binder for the lithium secondary battery negative electrode to prepare a negative electrode slurry, coating the negative electrode slurry on the negative electrode current collector, and then drying the same. In addition, if necessary, a process of coating the negative electrode slurry on the negative electrode current collector and then applying pressure may be further included.

[0101] The conductive composite binder for the lithium secondary battery negative electrode includes a base solvent, a first compound, a second compound, and a carbon material, and the base solvent may include water. The lithium secondary battery negative electrode according to an embodiment of the present invention uses water as the base solvent, can be manufactured without adding a solvent, and can be manufactured in an environmentally friendly manner by using an aqueous process.

[0102] The above-described conductive composite binder for a lithium secondary battery negative electrode may be provided in the form of a solid material dispersed in a base solvent. The solid material may be provided in the form of a network in which the first compound, the second compound, and the carbon compound are physically connected through hydrogen bonds or π-π interactions.

[0103] In the conductive composite binder for the lithium secondary battery negative electrode, the content of the solid material in the base solvent may be 3 wt% to 7 wt%. If the content of the solid material in the base solvent is less than 3 wt%, it may be difficult to sufficiently bind the negative electrode active material, which may be problematic, and if it exceeds 7 wt%, it may be difficult to uniformly mix the negative electrode active material, and the process efficiency may be reduced, such as requiring the addition of a solvent.

[0104] The above-described negative electrode mixture can be manufactured by mixing the above-described conductive composite binder for a lithium secondary battery negative electrode with the above-described negative electrode active material without adding a solvent, using the above-described conductive composite binder for a lithium secondary battery negative electrode. The content of the solid material in the above-described negative electrode mixture can be 20 wt% to 50 wt%. By maintaining the solid material of the above-described negative electrode mixture within the above-described range, the process efficiency during the manufacture of the negative electrode can be improved, and the electrochemical and mechanical properties of the secondary battery can be effectively improved.

[0105] The above lithium secondary battery negative electrode may have a bulk resistance of 0.02 Ω·cm to 0.06 Ω·cm and an interface resistance of 0.002 Ω / cm2 to 0.005 Ω / cm2.

[0106] The above bulk resistance can be measured using Hioki's XF057 electrode resistance measuring device under the conditions of a measurement current of 2 mA and a measurement voltage of 1 V. In addition, the above interfacial resistance can be measured using Hioki's XF057 electrode resistance measuring device under the conditions of a measurement current of 100 μA or 10 mA and a measurement voltage of 1 V or 10 V. The above interfacial resistance may be the resistance at the interface between the negative electrode mixture and the negative electrode current collector.

[0107] The lithium secondary battery negative electrode according to the present embodiment is provided in a form in which the conductive composite binder for the lithium secondary battery negative electrode is uniformly coated with a powder-type negative electrode active material, thereby exhibiting a bulk resistance within the aforementioned range. In addition, in the lithium secondary battery negative electrode, the conductive composite binder for the lithium secondary battery negative electrode is provided between the negative electrode mixture and the negative electrode current collector, thereby exhibiting the numerical range of the interfacial resistance, and thereby improving the bonding strength between the negative electrode mixture and the negative electrode current collector.

[0108] The negative electrode according to an embodiment of the present invention may exhibit high bonding strength between the negative electrode mixture and the negative electrode current collector by uniformly providing the conductive composite binder for a lithium secondary battery negative electrode as described above. With respect to the bonding strength, the bonding strength of the negative electrode mixture obtained by peeling off the negative electrode mixture from the negative electrode current collector at a speed of 20 mm / min and an angle of 90° using peel test equipment may be 2 N or more.

[0109] Hereinafter, examples and comparative examples of the present invention are described. However, the following examples are only preferred embodiments of the present invention and the scope of the present invention is not limited by the following examples.

[0110] 1. Cathode manufacturing

[0111] Example 1 (SiO x single)

[0112] 0.5 g of carboxymethyl cellulose (CMC, Sigma-Aldrich) was dissolved in 50 mL of deionized water at room temperature, and 0.3 g of tannic acid (TA, Sigma-Aldrich) was added to prepare a compound solution. 1 g of multi-walled carbon nanotube powder (CNTs, BT1003M, LG Chem Co., Ltd.) was mixed with the prepared compound solution, and the mixture was treated using tip sonication at an operating frequency of 20 kHz for 30 min. The prepared composite binder contained 1 wt% of CMC and 2 wt% of CNT.

[0113] SiO in the manufactured composite binder solution x Powder (Osaka Titanium Technologies Co., Ltd, Japan) (negative active material) and styrene-butadiene rubber (SBR, Sigma-Aldrich) were mixed in a weight ratio of 85:3.75:3.75:7.5 (SiO x Active material: CMC: SBR: CNT) was mixed to prepare a negative electrode slurry. The prepared negative electrode slurry was applied onto a copper current collector, dried to remove the solvent, and then prepared into a negative electrode. The prepared negative electrode is shown in Table 1 below.

[0114] Comparative Example 1 (SiO x single)

[0115] SiO in 50 mL deionized water at room temperature x Powder (Osaka Titanium Technologies Co., Ltd, Japan), CMC (Sigma-Aldrich), SBR (Sigma-Aldrich) and carbon black (Super P) as a conductive agent were mixed in a weight ratio of 85:3.75:3.75:7.5 (SiO x: CMC : SBR : CB) was mixed to prepare a negative electrode slurry. The prepared negative electrode slurry was applied onto a copper current collector, dried to remove the solvent, and then prepared into a negative electrode. The prepared negative electrode is shown in Table 1 below.

[0116] Comparative Example 2 (SiO x single)

[0117] SiO in 50 mL deionized water at room temperature x Powder (Osaka Titanium Technologies Co., Ltd, Japan), CMC (Sigma-Aldrich), SBR (Sigma-Aldrich) and multi-walled carbon nanotube powder (CM-280, Hanwha Co. Ltd.) as a conductive agent were mixed in a weight ratio of 85:3.75:3.75:7.5 (SiO x : CMC : SBR : CNT) was mixed to prepare a negative electrode slurry. The prepared negative electrode slurry was applied onto a copper current collector, and then dried to remove the solvent, thereby preparing a negative electrode. The prepared negative electrode is shown in Table 1 below.

[0118] Example 2 (SiO x and Graphite Mix)

[0119] The same composite binder (deionized water, CMC, tannic acid and CNT mixture) as in Example 1 was used, and SiO was added to the prepared binder solution. x A mixture of powder (Osaka Titanium Technologies Co., Ltd, Japan) and graphite (mixed negative electrode active material), and SBR (Sigma-Aldrich) were mixed in a weight ratio of 85:3.75:3.75:7.5 to prepare a negative electrode slurry. The prepared negative electrode slurry was applied onto a copper current collector, and then dried to remove the solvent, thereby preparing a negative electrode. The prepared negative electrode is shown in Table 1 below. In Example 2, the mixed negative electrode active material was prepared by mixing SiO to have a specific capacity of 550 mAh / cm2. x Powder and graphite were mixed.

[0120] Comparative Example 3

[0121] SiO in 50 mL deionized water at room temperature x A negative electrode slurry was prepared by mixing a mixture of powder (Osaka Titanium Technologies Co., Ltd, Japan) and graphite (mixed negative electrode active material), SBR (Sigma-Aldrich), and carbon black (Super P) as a conductive agent in a weight ratio of 85:3.75:3.75:7.5. The prepared negative electrode slurry was applied onto a copper current collector and then dried to remove the solvent, thereby preparing a negative electrode. The prepared negative electrode is shown in Table 1 below.

[0122] Cathode slurry weight ratio (wt%) Cathode SiO x GraphiteCMCSBRCNTCB Mixture Density Example 185 wt% 0.3.75 wt% 3.75 wt% 7.5 wt% 0.1.3 g / cc Comparative Example 185 wt% 0.3.75 wt% 3.75 wt% 0.75 wt% 1.3 g / cc Comparative Example 285 wt% 0.3.75 wt% 3.75 wt% 7.5 wt% 0.1.3 g / cc Example 219.74 wt% 74.26 wt% 1.5 wt% 1.5 wt% 3 wt% 0.1.3 g / cc Comparative Example 319.74 wt% 74.26 wt% 1.5 wt% 1.5 wt% 0.3 wt% 1.3 g / cc

[0123] 2. Secondary battery manufacturing

[0124] Manufacturing of anodes

[0125] The cathodes manufactured according to Examples 1 and 2 and Comparative Examples 1 and 2 were used, and the anodes manufactured as follows were used in the same manner in Examples 1 and 2 and Comparative Examples 1 and 2.

[0126] The cathode active material is LiNi 0.8 Co 0.15 Al 0.05Lithium transition metal oxide (SC-NCA) represented by O2 was used, and poly(vinylidene fluoride) (PVdF, Solef 6020, Solvay) as a binder and carbon black (Super P, CB) as a conductive material were mixed at a weight ratio of 96:2:2 (SC-NCA: PVDF: CB) to prepare a cathode slurry. The prepared cathode slurry was applied to an aluminum current collector at a weight of 20 mg / cm2, dried at 120°C, and roll-pressed to produce an electrode density of ~3.5 g / cm3. The electrode was manufactured so that the N / P ratio (cathode / anode ratio) was 1.1.

[0127] Manufacturing of half cells

[0128] CR2032 coin-type batteries (half-cells) were manufactured using a mixed solvent (ethylene carbonate:diethyl carbonate:dimethyl carbonate = 25:45:30 v%), 1% vinylene carbonate, and 1 wt% LiPO2F2 as an electrolyte, and a polyethylene separator (W-SCOPE KOREA Co., Ltd., Korea). The CR2032 coin cells were subjected to three cycles at 0.1 C (silicon compound 1 C = 1700 mA / g, pre-lithiated silicon compound 1 C = 1500 mA / g, mixed cathode active material 1 C = 550 mA / g) before performing charge / discharge cycling.

[0129] The cycle performance of the coin cells was performed using CC-CV charge / discharge at 0.2 C charge (cutoff 0.05 C) and 0.5 C discharge. The C-rate performance was determined at current rates of 0.2, 0.5, 1, and 2 C in the voltage range of 0.005–1.5 V vs. Li / Li+ using a battery cycler (WBCS3000L, WonATech). Cyclic voltammetry was performed at scan rates of 0.03, 0.05, 0.07, and 0.1 mV / s. Electrochemical impedance spectroscopy (EIS) was performed using a potentiostat (VSP-100, Biologic) at a voltage of 5 mV and a frequency range of 1 MHz to 1 mHz.

[0130] Manufacturing of full cells

[0131] For full cell battery testing, a pouch-type battery was used, and the negative electrode (5.4 cm Х 4.4 cm) and positive electrode (5 cm Х 4 cm) manufactured by the above-described method were assembled as a pair at an N / P ratio of ~ 1.1. A mixed solvent (ethylene carbonate: diethyl carbonate: dimethyl carbonate = 25:45:30 v%), 1% vinylene carbonate, and 1 wt% LiPO2F2 was used as the electrolyte, and a polyethylene separator (W-SCOPE KOREA Co. Ltd., Korea) was used for manufacturing. The cycle characteristics and electrochemical characteristics of the full cell manufactured in this way were all evaluated in the same manner as those of the coin cell.

[0132] 3. Evaluation of physical and electrochemical properties

[0133] Table 2 below shows the results of confirming the viscosity of compound solutions prepared by varying the contents of carboxymethyl cellulose (CMC) and tannic acid (TA) in deionized water at room temperature before adding CNTs. 0.5 g of carboxymethyl cellulose (CMC, Sigma-Aldrich) was dissolved in 50 mL of deionized water at room temperature, and 0 g, 0.1 g, 0.3 g, 0.5 g, 0.7 g, and 1.0 g of tannic acid were added to a 1 wt% CMC solution, followed by stirring at 200 rpm. The concentrations of the prepared compound solutions were measured twice each, once for the first measurement and once for the second measurement, to eliminate errors, and the average value was confirmed.

[0134] Concentration (cP) by tannic acid content Tannic acid content 0g 0.1g 0.3g 0.5g 0.7g 1.0g 1st measurement 445.8163.8151.8134.497.265.4 2nd measurement 164.4149.2136.298.460.6 Average 445.8164.1150.5135.397.863

[0135] Referring to Table 2, the concentration of a 1 wt% CMC solution without added tannic acid was 445.8 cP (based on 200 rpm), and the viscosity tended to decrease as tannic acid was added. This is believed to be because CMC and tannic acid form hydrogen bonds in the compound solution, thereby reducing the interaction between the hydrophilic portion of CMC and the deionized water used as a solvent. That is, it was confirmed that as the hydrogen bond between CMC and deionized water decreased, the affinity for the deionized water decreased, and the viscosity in the compound solution decreased. In addition, as the content of the tannic acid increased, the interaction between CMC and deionized water was blocked, so the fluidity of the compound solution increased and the viscosity decreased.

[0136] Figure 3 shows the FT-IR analysis results of the composite binder used in Examples 1 and 2.

[0137] FT-IR measurements were performed using a Thermo Fisher Scientific Nicolet 6700 FTIR System and SMART Orbit ATR Accessory (ZnSe), and the mid-IR region was 500-4000 cm -1 4 cm in area -1 It was performed under the condition of resolution. The FT-IR spectrum includes a spectrum having the wavenumber of the irradiated infrared light as one axis and the transmittance according to the wavenumber of the light as the other axis, and the transmittance of the other axis includes % transmittance which has 100% transmittance when all of the light of a specific wavenumber irradiated is transmitted, and the peak on the FT-IR spectrum may include a peak in the direction of decreasing transmittance.

[0138] In Fig. 3, FT-IR analysis of the composite binder (CMC@TA) according to the embodiment of the present invention was performed along with FT-IR analysis of CMC and tannic acid (TA), thereby confirming the bonding form of CMC and tannic acid. CMC has a wavelength of 1589 cm -1 A peak appeared at 1703 cm, and tannic acid was detected at 1703 cm -1 , 1606 cm -1 , 1533 cm -1 and 2800 cm -1 3600 cm inland -1 A broad peak appeared at 1637 cm. The composite binder -1 and 2800 cm -1 3600 cm inland -1 In each case, a broad peak was confirmed, which confirmed that in the case of the complex binder, the peaks of CMC and tannic acid did not appear individually, but rather appeared in an overlapping form. In other words, within the complex binder, CMC and tannic acid showed behavior similar to a large macromolecule through mutual interaction, and it was confirmed that CMC and tannic acid existed by being combined and connected with each other within the complex binder.

[0139] Figure 4 shows the results of the dispersion evaluation and UV-Vis spectrum of the composite binder of Example 1.

[0140] In Fig. 4, tannic acid (TA), CNT, and tannic acid and CNT (TA@CNT) were added to deionized water, respectively, and the degree of bonding between tannic acid and CNT was confirmed along with the degree of dispersion. Tannic acid was a colorless liquid and well dispersed in deionized water, whereas CNT was not uniformly dispersed in deionized water and settled to the bottom. On the other hand, when CNT and tannic acid were added together, CNT was confirmed to be uniformly dispersed in deionized water. In other words, it was confirmed that CNT was dispersed by bonding with tannic acid in the deionized water when tannic acid was added together.

[0141] As a result of evaluating the UV-Vis spectra for each of these, the π-π* transition absorption of tannic acid appeared at 213 nm, and that of CNT was observed at 221 nm. On the other hand, when tannic acid and CNT were added together in deionized water, it was confirmed that there was a shift to a long wavelength of 225 nm, which confirmed that tannic acid and CNT existed combined rather than individually in deionized water.

[0142] Table 3 shows the active material resistance and interfacial resistance of the composite binder and carbon black, respectively.

[0143] Graphite CMCSBRCNTCBBulk resistance (Ω cm)Interface resistance (Ω cm) -2 ) Manufacturing example 195 wt% 1.25 wt% 1.25 wt% 2.5 wt% 0 4.51 x 10 -2 3.724 x 10 -3 Manufacturing Example 295 wt%1.25 wt%1.25 wt%02.5 wt%3.61 x 10 -2 1.037 x 10 -3

[0144] In Table 3, the bulk resistance is the resistance of the negative active material, and was measured using the XF057 electrode resistance measuring device from Hioki Co., Ltd. under the conditions of a measurement current of 2 mA and a measurement voltage of 1 V. The interfacial resistance refers to the interfacial resistance between the negative active material layer and the negative current collector, and was measured using the XF057 electrode resistance measuring device from Hioki Co., Ltd. under the conditions of a measurement current of 100 μA or 10 mA and a measurement voltage of 1 V or 10 V.

[0145] In the case of the composite binder used in Example 1 of the present invention, since it is manufactured in a dispersed state in deionized water, it is difficult to measure the electronic conductivity of the solution itself or the electronic conductivity of the solid powder itself after removing the deionized water. Therefore, the electronic conductivity of the composite binder was indirectly confirmed by measuring the resistance of the negative electrode. Here, when measuring the resistance using a silicon compound as the negative electrode active material, the electronic conductivity could not be measured. Therefore, in Manufacturing Examples 1 and 2, graphite was used as the negative electrode active material as shown in Table 3, and the composite binder (Manufacturing Example 1) and carbon black, CMC, and SBR (Manufacturing Example 2) were each added and mixed, and the negative electrode was manufactured using the composite binder. In Manufacturing Examples 1 and 2, the negative electrodes were manufactured in the same manner as in Example 1 and Comparative Example 1, respectively, except that the contents of each material and graphite were used as the negative electrode active material as shown in Table 3.

[0146] In the case of Manufacturing Example 1 using the composite binder of the present invention, it was confirmed that the bulk resistance and interface resistance were slightly higher than those of Manufacturing Example 2. This is believed to be because, in the case of Manufacturing Example 1, a composite binder was used, and the composite binder was provided so as to be uniformly distributed within the negative electrode mixture and to uniformly cover the negative electrode active material. Since the composite binder of the present invention includes CNTs and is provided so as to uniformly cover the negative electrode active material, it is expected to improve electrical conductivity by allowing the CNTs, which enable the conductive material, to come into close contact with the negative electrode active material.

[0147] Figure 5 shows the results of confirming the bonding strength and viscosity through a vial turning test for the composite binder used in the examples and manufacturing examples and the carbon black and CNT aqueous solution.

[0148] In Fig. 5, the composite binder, carbon black, and CNT, which function as the conductive agent in Examples 1 and 2 and Manufacturing Examples 1 and 2, were dispersed in deionized water at the same concentration to prepare a carbon black aqueous solution (CB), a CNT aqueous solution (CNT), and a composite binder aqueous solution (CNTB), and these were evaluated.

[0149] In the vial turning test, equal volumes of carbon black aqueous solution (CB), CNT aqueous solution (CNT), and composite binder aqueous solution (CNTB) were added to the vials at room temperature, and the vials were then turned over to confirm that the carbon black aqueous solution (CB), CNT aqueous solution (CNT), and composite binder aqueous solution (CNTB) moved downward due to gravity. The fluidity was in the order of CNT aqueous solution (CNT) > carbon black aqueous solution (CB) > composite binder aqueous solution (CNTB), and it was confirmed that the composite binder aqueous solution (CNTB) was attached to the lower side of the vial and did not flow even after the vial was turned over. That is, in the case of the composite binder aqueous solution (CNTB), gelation occurred at the lower side before the vial was turned over, and it was confirmed that this improved the viscosity and prevented it from flowing downward.

[0150] The above gelation is a type of combination of CMC and tannic acid (TA), and when the CMC and tannic acid reach a certain concentration or higher, hydrogen bonding is formed, resulting in gelation. In addition, the added CNT also combined with tannic acid, thereby increasing the viscosity and decreasing the fluidity of the solution containing CMC, tannic acid, and CNT. As a result, it was confirmed that the CNT contained in the composite binder solution (CNTB) does not exist separately from CMC and tannic acid, but rather exists in a form in which it is combined and connected with CMC and tannic acid.

[0151] The viscosity of CNT aqueous solution (CNT) and composite binder aqueous solution (CNTB) was measured at 25 ℃ and a shear rate of 12 rpm using a Type B viscometer (VISCOMETER, TOKIMEC). The CNT aqueous solution (CNT), which was a mixture of CNT and deionized water, showed a viscosity of approximately 50 cP, and the composite binder aqueous solution (CNTB), which was formed by combining CNT with CMC and tannic acid in deionized water, showed a very low viscosity level of approximately 560 cP. In other words, it was confirmed that the viscosity of the composite binder aqueous solution (CNTB) increased due to the combination of CMC and tannic acid.

[0152] Figure 6 shows the results of confirming the bonding strength of the cathodes of Example 1 and Comparative Examples 1 and 2.

[0153] In Fig. 6, Example 1, Comparative Examples 1 and 2 all use the same negative electrode active material, SiO. x was used, and a peel test was performed, which is shown in Table 4 below.

[0154] Classification SiOxCMCSBRCNTCBAverage bonding strengthExample 1CNTB / SiO x 853.753.757.502.26 N Comparative Example 1CB / SiO x 853.753.7507.51.75 N Comparative Example 2CNT / SiO x 853.753.757.500.11 N

[0155] In order to confirm the bonding strength between the negative electrode collector and the negative electrode mixture, the negative electrode mixture was peeled off from the negative electrode collector at a speed of 20 mm / min and an angle of 90° using a peel tester. The bonding strength was shown in the order of Example 1 > Comparative Example 1 > Comparative Example 2, which was a similar result to the vial turning test described above. In particular, when Example 1 and Comparative Example 2 containing the same CNTs were compared, a difference of approximately 20 times was shown, and it was confirmed that Example 1 exhibited very excellent bonding strength. That is, it was confirmed that the bonding strength between the negative electrode mixture and the negative electrode collector can be improved by including CNTs in the negative electrode active material in the same form as in Example 1. In addition, when a silicon compound having a problem of excessive volume expansion is used as a negative electrode active material, it is believed that the silicon compound can be stably fixed to the negative electrode collector by using the composite binder according to the embodiment of the present invention.

[0156] Figure 7 shows the results of evaluating the electrochemical characteristics of half-cells using Example 1 and Comparative Examples 1 and 2.

[0157] In Fig. 7, Example 1 (CNTB / SiO x ), Comparative Example 1 (CB / SiO x ) and Comparative Example 2 (CNT / SiO x ) were manufactured for the half-cell, and the capacity development and coulombic efficiency of the 1st, 2nd, and 3rd Mars processes, the cycle characteristics for 30 cycles, and the rate characteristics for 0.2 C, 0.5 C, 1 C, and 2 C were confirmed. Table 5 shows the specific capacities of the 1st and 3rd cycles of Example 1 and Comparative Examples 1 and 2, and the retention after 30 cycles.

[0158] 1st Cap.(mAh g) -1 )3th Cap.(mAh g -1 )30 cy. Cap.(mAh g -1)30 cy. Retention Example 1CNTB / SiO x 1878.91829.31560.191.0Comparative Example 1CB / SiO x 1854.61621.0400.830.8Comparative example 2CNT / SiO x 1846.31668.8647.745.4

[0159] Referring to the capacity development and coulombic efficiency of the 1st, 2nd, and 3rd Mars processes in Fig. 7, Example 1 and Comparative Examples 1 and 2 showed similar capacities in the 1st cycle, but as the charge and discharge cycles were performed, it was confirmed that the specific capacity of Comparative Examples 1 and 2 decreased significantly, while that of Example 1 was maintained. In addition, in the coulombic efficiency, Example 1 showed superior characteristics compared to Comparative Examples 1 and 2. That is, when a silicon compound is used as an anode active material, it was confirmed that the electrochemical characteristics were greatly improved when Example 1 was used as in the present invention.

[0160] In addition, even when performing 30 cycles of repetitive charging and discharging, it was confirmed that while Comparative Examples 1 and 2 gradually decreased in capacity, Example 1 maintained a constant capacity without decreasing in capacity during the cycle.

[0161] In the rate-dependent characteristics of 0.2 C, 0.5 C, 1 C, and 2 C, Example 1 showed superior capacity characteristics as the rate increased compared to Comparative Example 1, and even when charge / discharge was performed at 0.2 C, 0.5 C, 1 C, and 2 C, and then again at 0.2 C, Example 1 showed superior capacity recovery characteristics compared to Comparative Example 1. That is, Example 1 showed the best capacity retention rate even during repeated charge / discharge, and it was confirmed that it was reversible and had less overvoltage even at a high rate of 2 C in the rate-dependent characteristics. This is because, in the process of performing charge / discharge cycles while increasing the charge current, the volume expansion of the silicon compound in Example 1 was performed reversibly and the position of the silicon compound was also stably maintained, but in Comparative Example 1, the position of the silicon compound changed due to the volume expansion of the silicon compound and the contact with the conductive material was reduced.

[0162] Fig. 8 shows the results of confirming the distribution and volume expansion of carbon materials for the negative electrodes of Example 1 and Comparative Example 1, which were evaluated using the half-cell of Fig. 6.

[0163] In Fig. 8, EDS / FE-SEM measurements were taken for Example 1 (CNTB) and Comparative Example 1 (CB). Here, EDS measured the pristine electrode to see the carbon distribution after electrode fabrication without performing a cycle, and FE-SEM compared the thickness difference between the pristine electrode and the electrode after a 30-cycle life evaluation. In the case of Example 1, the carbon materials were CNT, CMC, and SBR, and in the case of Comparative Example 1, the carbon materials were carbon black (CB), CMC, and SBR. In Example 1, it was confirmed that CNT, CMC, and SBR, which function as binders, were uniformly distributed throughout the negative electrode mixture. On the other hand, in Comparative Example 1, it was confirmed that carbon black, CMC, and SBR, which function as binders, were not uniformly distributed and were aggregated in local areas.

[0164] That is, in Example 1 and Comparative Example 1, CNTs and carbon black each function as conductive materials, and the more uniformly they are distributed, the more the electron transfer efficiency can be improved. In addition, CMC and SBR function as binders that fix the position of the silicon compound, which is an anode active material, and the more uniformly they are distributed, the more the position of the silicon compound is maintained without significant change even due to reversible volume expansion of the silicon compound. That is, Example 1, in which the carbon material was uniformly distributed within the anode mixture, exhibited higher electron transfer efficiency than Comparative Example 1, and it was confirmed that the position of the silicon compound hardly changed even after performing multiple cycles.

[0165] In addition, Example 1 and Comparative Example 1 showed similar thicknesses of 31.2 ㎛ and 30.3 ㎛, respectively, immediately after manufacturing, but it was confirmed that there was a large difference in thicknesses of 38.3 ㎛ and 86.7 ㎛, respectively, after performing 30 cycles. In Example 1, the silicon compound, which is the negative electrode active material, was stably fixed by the composite binder including CMC and SBR, and the volume expansion of the silicon compound was effectively controlled, so that the volume change of the negative electrode mixture did not occur significantly. On the other hand, in Comparative Example 1, a thickness increase of approximately 56 ㎛ occurred after performing 30 charge and discharge cycles. This can be expected because it was difficult to control the volume expansion after charge and discharge in Comparative Example 1, which caused a fracture of the negative electrode and a break in the electron conduction path.

[0166] Figure 9 shows the results of evaluating the electrochemical characteristics of the half-cell using Example 2 and Comparative Example 3.

[0167] In Fig. 9, Example 2 (CNTB-AG / p-SiO x ), Comparative Example 3 (CB-AG / p- / SiO x) was used to confirm the effect of the composite binder when using a mixed negative electrode active material that mixed silicon compound and graphite. Specifically, the rate characteristics for 0.2 C, 0.5 C, 1 C, 2 C, and 3 C, the charge / discharge characteristics for 30 cycles, and the EIS resistance before and after performing 30 cycles were compared. Table 6 shows the retention after performing 30 cycles of Example 2 and Comparative Example 3.

[0168] 30 cy. Cap. (mAh g -1 )30 cy. Retention Example 2CNTB-AG / p-SiO x 519.194.1% Comparative Example 3CB-AG / p-SiO x 366.169.2%

[0169] Referring to Fig. 9, it was confirmed that Example 2 showed almost no capacity reduction during the cycle process. On the other hand, Comparative Example 3 showed a gradual capacity reduction during the cycle process.

[0170] Comparing the cell resistance measured by EIS after 1 cycle (after formation) and after 30 cycles (after cycling), there was no significant difference between Example 2 and Comparative Example 3 in the 1st cycle, but after 30 cycles, it was confirmed that Example 2 had a lower resistance than Comparative Example 3. In addition, it was confirmed that Example 2 had less overvoltage at high rates.

[0171] In addition, in the rate-dependent characteristics for 0.2 C, 0.5 C, 1 C, 2 C, and 3 C, it was confirmed that the discharge capacity of Comparative Example 3 decreased significantly as the charging current increased, but Example 1 exhibited better capacity characteristics than Comparative Example 1 even at high charging currents. In addition, when the capacity of 0.2 C was checked again after performing 0.2 C, 0.5 C, 1 C, 2 C, and 3 C, respectively, it was confirmed that the capacity decrease of Example 1 did not occur significantly for the initial 0.2 C capacity, but that of Comparative Example 3 decreased significantly. It is believed that this is because, in the process of performing charge and discharge while increasing the charging current, the volume expansion of the silicon compound occurred in the case of Comparative Example 3, which lowered the electrical conductivity and changed the position between the silicon compound and the graphite, thereby lowering the adhesion with the conductive material.

[0172] In the negative electrode active material mixed with a silicon compound and graphite designed to have a specific capacity of 550 mAh / g as in Example 2 and Comparative Example 3, the composite binder according to the present invention showed higher life stability than Comparative Example 3 using carbon black as in Example 2, and it was confirmed that the negative electrode using the mixed negative electrode active material had a similar tendency to the negative electrode using only a silicon compound.

[0173] Figure 10 shows the results of confirming the cycle characteristics and coulombic efficiency of a full cell using Example 1 and Comparative Example 2.

[0174] In Fig. 10, a full cell was manufactured using Example 1 and Comparative Example 1, and the cycle characteristics were confirmed. The positive electrode was SC-NCA with a capacity of 5 mAh / cm 2 When applied with a base N / P ratio of 1.1, the current density of the cathode was 5.5 mAh / cm 2Example 1 and Comparative Example 1 were used to manufacture the battery. As a result of performing 300 cycles of charge and discharge, the capacity retention rate of Comparative Example 1 was 29%, whereas that of Example 1 was about 64%, indicating that Example 1 exhibited superior cycle characteristics. In terms of coulombic efficiency, when the initial coulombic efficiency and the average coulombic efficiency after 300 cycles were compared, Comparative Example 1 exhibited a value in which the coulombic efficiency continuously changed during the charge and discharge process, whereas Example 1 exhibited a stable value within a predetermined numerical range. That is, it was confirmed that the negative electrode according to Example 1 of the present invention exhibited high electrochemical stability even in a commercialized full cell.

[0175] Those skilled in the art will appreciate that the present invention can be implemented in other specific forms without altering its technical spirit or essential characteristics. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims below rather than the detailed description above, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

Claims

1. A first compound having at least one carboxyl group (-COOH) or at least one hydroxyl group (-OH); A second compound physically connected to the first compound and having at least one hydroxyl group (-OH) and at least one benzene ring; and A conductive composite binder for a lithium secondary battery negative electrode, comprising a carbon material physically connected to the first or second compound.

2. In paragraph 1, The first compound comprises a polyphenol molecule, The second compound comprises a catechol structure and a pyrogallol structure, The above carbon material is a conductive composite binder for a lithium secondary battery negative electrode having a 1D (Dimension) or 2D structure.

3. In paragraph 1, The first compound comprises at least one of carboxymethyl cellulose (CMC), cellulose, a sodium salt of carboxymethyl cellulose, hydroxyethyl cellulose, a potassium salt of carboxymethyl cellulose, a lithium salt of carboxymethyl cellulose, polyacrylic acid, sodium alginate, polyacrylamide, and polyvinyl alcohol. The second compound comprises at least one of tannic acid (TA), catechol, dopamine, dopamine hydrochloride, norepinephrine, L-dihydroxyphenylalanine, hydroxyphenolic acid, adrenaline, lignin monomer, ellagitannin, and pyrogall (1,2,3-benzenetriol). The above carbon material is a conductive composite binder for a lithium secondary battery negative electrode, comprising at least one of graphene, carbon nano fiber, carbon nanotube (CNT), carbyne, and MXene.

4. In paragraph 1, The first compound and the second compound are connected by hydrogen bonds, A conductive composite binder for a lithium secondary battery negative electrode, wherein the carbon material is connected to the first compound through a hydrogen bond, or the carbon material is connected to the second compound through a π-π interaction.

5. In paragraph 1, The weight ratio of the first compound: the second compound is 1:0.1 to 1, A conductive composite binder for a lithium secondary battery negative electrode, wherein the first compound and the second compound are added to a base solvent to prepare a compound solution, and then the carbon material is added.

6. In paragraph 5, A conductive composite binder for a lithium secondary battery negative electrode, wherein the content of the first compound in the conductive composite binder for a lithium secondary battery negative electrode is 0.5 wt% to 5 wt%, and the content of the carbon material is 0.1 wt% to 10 wt%.

7. In paragraph 5, The above base solvent comprises at least one of water, N-Methyl-2-pyrrolidone (NMP), methanol, ethanol, polypyrrolidone, isopropanol, acetone, petroleum ether, tetrahydrofuran, ethyl acetate, N,N-dimethylacetamide, N,N-dimethylformamide, n-hexane, and halogenated hydrocarbons. A conductive composite binder for a lithium secondary battery negative electrode, wherein the viscosity of the compound solution is 30 cP to 400 cP.

8. In paragraph 5, The above conductive composite binder for a lithium secondary battery negative electrode further contains a base solvent, Among the above base solvents, the first compound, the second compound and the carbon material are chemically or physically connected in a network form, A conductive composite binder for a lithium secondary battery negative electrode, wherein the viscosity of the conductive composite binder for a lithium secondary battery negative electrode is 300 cP to 1800 cP.

9. In paragraph 1, A conductive composite binder for a lithium secondary battery negative electrode, wherein the first compound is carboxymethyl cellulose, the second compound is tannic acid, and the carbon material is graphene or carbon nanotube (CNT).

10. In paragraph 1, The above carbon material includes carbon nanotubes, The above carbon nanotube is formed in a bundle shape by partially converging 1 to 10 single-walled carbon nanotubes or multi-walled carbon nanotubes, and the diameter of the bundle shape is 2 nm to 35 nm, and the length is 4 ㎛ to 10 mm. The above carbon nanotube is a conductive composite binder for a lithium secondary battery negative electrode having a content of oxygen atoms of 0.01 mol% to 10 mol% with respect to carbon atoms as a component of the carbon nanotube.

11. In paragraph 1, A conductive composite binder for a lithium secondary battery negative electrode exhibiting a maximum peak intensity at 220 nm to 230 nm in a UV-Vis spectrum.

12. In paragraph 1, 1620 cm on the Fourier-transform infrared (FTIR) spectrum -1 Within 1700 cm -1 The first peak formed broadly at 3000 cm -1 3900 cm inland -1 A conductive composite binder for a lithium secondary battery negative electrode, comprising a first peak formed in which an intensity ratio of a second peak to the first peak is 1.3 to 3.

13. In paragraph 1, The above conductive composite binder for a lithium secondary battery negative electrode further contains a base solvent, The above conductive composite binder for a lithium secondary battery negative electrode is provided in the form of a solid material dispersed in a base solvent, The above-mentioned solid material is a conductive composite binder for a lithium secondary battery negative electrode, wherein the first compound, the second compound, and the carbon compound are physically connected through hydrogen bonds or π-π interactions to form a network.

14. In paragraph 13, A conductive composite binder for a lithium secondary battery negative electrode, wherein the content of the solid material in the base solvent is 1 wt% to 7 wt%.

15. A step of preparing a compound solution having a first viscosity by adding a first compound and a second compound to a base solvent; and A step of adding a carbon material to the compound solution and stirring it; A method for manufacturing a conductive composite binder for a lithium secondary battery negative electrode according to any one of claims 1 to 14 having a viscosity of 300 cP to 1800 cP.

16. In paragraph 15, The first compound has at least one carboxyl group (-COOH) or at least one hydroxyl group (-OH), the second compound is physically connected to the first compound and has at least one hydroxyl group (-OH) and at least one benzene ring, and the carbon material is physically connected to the first or second compound, A method for producing a conductive composite binder for a lithium secondary battery negative electrode, wherein the viscosity of the compound solution is 30 cP to 400 cP.

17. Negative current collector; and Including a cathode composite coated on the above cathode collector; The above negative electrode composite comprises a negative electrode active material, a conductive composite binder for a lithium secondary battery negative electrode according to any one of claims 1 to 14, A negative electrode for a lithium secondary battery, wherein the negative electrode active material is a silicon compound or a mixture of a silicon compound and graphite.

18. In paragraph 17, The above silicon compound is SiO x (0≤x<2), SiO containing lithium compound x (0≤x<2), SiO containing magnesium compound x A negative electrode for a lithium secondary battery comprising at least one of (0≤x<2), a silicon alloy (Si-alloy), and a silicon-carbon composite (Si-C composite).

19. In Article 17, The above cathode compound further includes an auxiliary binder, A negative electrode for a lithium secondary battery, wherein the auxiliary binder comprises at least one of styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), nitrile butadiene rubber (NBR), polyacrylamide (PAM), polyacrylonitrile (PAN), polyimide (PI), and polyamideimide (PAI).

20. In paragraph 17, For 100 parts by weight of the above cathode compound, A lithium secondary battery negative electrode, wherein the conductive composite binder for the lithium secondary battery negative electrode is 80 to 500 parts by weight.

21. In paragraph 17, A negative electrode for a lithium secondary battery having a bulk resistance of 0.02 Ω cm to 0.06 Ω cm and an interfacial resistance of 0.002 Ω / cm2 to 0.005 Ω / cm2.

22. In paragraph 17, A negative electrode for a lithium secondary battery, wherein the bonding strength of the negative electrode mixture obtained by peeling off the negative electrode mixture from the negative electrode current collector at a speed of 20 mm / min and an angle of 90° using peel test equipment is 2 N or more.

23. In paragraph 17, The above cathode compound is, The negative electrode active material is added to the conductive composite binder for the above lithium secondary battery negative electrode to prepare a negative electrode slurry, The above negative electrode slurry is coated on the negative electrode collector and then dried to prepare the negative electrode slurry. The above conductive composite binder for a lithium secondary battery negative electrode comprises a base solvent, a first compound, a second compound, and a carbon material. A negative electrode for a lithium secondary battery, wherein the base solvent contains water.

24. In paragraph 17, The above conductive composite binder for a lithium secondary battery negative electrode is provided in the form of a solid material dispersed in a base solvent, The above solid material is formed in a network form in which the first compound, the second compound, and the carbon compound are physically connected through hydrogen bonds or π-π interactions, The above base solvent contains water, The content of the solid material in the above base solvent is 3 wt% to 7 wt%, The above negative electrode composite is a lithium secondary battery negative electrode manufactured by mixing the above conductive composite binder for a lithium secondary battery negative electrode and the above negative electrode active material without adding a solvent.

Images