WO2023249444A1

WO2023249444A1 - Negative electrode composition, negative electrode for lithium secondary battery comprising same, and lithium secondary battery comprising negative electrode

Info

Publication number: WO2023249444A1
Application number: PCT/KR2023/008714
Authority: WO
Inventors: 박수진; 이상민; 이재욱; 권요한
Original assignee: 주식회사 엘지에너지솔루션
Priority date: 2022-06-23
Filing date: 2023-06-22
Publication date: 2023-12-28

Abstract

The present application relates to: a negative electrode composition; a negative electrode for a lithium secondary battery, the negative electrode comprising the negative electrode composition; and a lithium secondary battery including the negative electrode. The negative electrode composition includes a silicon-based active material, a negative electrode conductive material, and a negative electrode binder including a first binder which has a Young's modulus of at least 10³ MPa, and a second binder which has a strain of at least 15%, and satisfying 1≤X/Y<4, where Y refers to the parts by weight of the first binder per 100 parts by weight of the negative electrode binder, and X refers to the parts by weight of the second binder per 100 parts by weight of the negative electrode binder.

Description

Negative electrode composition, negative electrode for lithium secondary battery including same, and lithium secondary battery including negative electrode

This application claims the benefit of the filing date of Korean Patent Application No. 10-2022-0076784 filed with the Korea Intellectual Property Office on June 23, 2022, the entire contents of which are included in this specification.

This application relates to a negative electrode composition, a negative electrode for a lithium secondary battery including the same, and a lithium secondary battery including the negative electrode.

Due to the rapid increase in the use of fossil fuels, the demand for the use of alternative or clean energy is increasing, and as part of this, the most actively researched fields are power generation and storage using electrochemical reactions.

Currently, secondary batteries are a representative example of electrochemical devices that use such electrochemical energy, and their use area is gradually expanding.

As technology development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing. Among these secondary batteries, lithium secondary batteries with high energy density and voltage, long cycle life, and low self-discharge rate have been commercialized and are widely used. In addition, as an electrode for such a high-capacity lithium secondary battery, research is being actively conducted on methods for manufacturing a high-density electrode with a higher energy density per unit volume.

Generally, a secondary battery consists of an anode, a cathode, an electrolyte, and a separator. The negative electrode includes a negative electrode active material that inserts and desorbs lithium ions from the positive electrode, and silicon-based particles with a large discharge capacity may be used as the negative electrode active material.

In particular, in response to the recent demand for high-density energy batteries, research is being actively conducted on ways to increase capacity by using silicon-based compounds such as Si/C or SiOx, which have a capacity more than 10 times greater than graphite-based materials, as anode active materials. there is. In the case of silicon-based compounds, which are high-capacity materials, the capacity is large compared to conventionally used graphite, but there is a problem in that the volume expands rapidly during the charging process and the conductive path is cut off, deteriorating battery characteristics.

Accordingly, in order to solve the problem of using a silicon-based compound as a negative electrode active material, the volume expansion itself is suppressed, such as a method of controlling the driving potential, a method of additionally coating a thin film on the active material layer, and a method of controlling the particle size of the silicon-based compound. Various methods are being discussed to prevent the conductive path from being disconnected or to prevent the conductive path from being disconnected, but these methods have limitations in application because they can reduce battery performance, so the negative electrode battery still has a high content of silicon-based compounds. There are limits to commercialization of manufacturing.

In particular, research has been conducted on the composition of binders according to volume expansion, and research is being conducted to use binder polymers with strong side stress to suppress volume expansion due to charging and discharging of negative electrode active materials with large volume changes. However, these binder polymers alone had limitations in suppressing the increase in electrode thickness due to contraction and expansion of the negative electrode active material and the resulting deterioration in performance of lithium secondary batteries.

In addition, in order to solve the problem caused by volume expansion of the negative electrode containing the silicon-based active material as described above, an aqueous binder that has both dispersibility and adhesive properties is used. In the case of the water-based binder, there is an advantage in improving dispersibility, but as the cycle progresses due to poor stretching properties, electrical contact between active materials is broken due to volume expansion of the active material, causing a problem of poor lifespan properties. .

In addition, a rubber-based binder can also be applied to improve lifespan characteristics, but in the case of silicon-based active materials, it is known that this also has limitations because the binder does not have sufficient rigidity when it contains only a rubber-based binder.

In addition, water-based binders have a disadvantage in the process due to the problem of intensified shrinkage due to heat when drying the electrode, but SBR rubber-based binders, which have excellent ductility, have a comparatively less tendency to shrink when dried.

Therefore, even when high-capacity materials are used to manufacture high-capacity batteries, research is needed on binders that do not disconnect the conductive network due to volume expansion of the active material and also have excellent adhesive properties.

(Patent Document 1) Japanese Patent Publication No. 2009-080971

This application relates to a binder that does not disconnect the conductive network due to volume expansion of the silicon-based active material in manufacturing high-capacity and high-density negative electrodes and has excellent adhesion to the negative electrode current collector. The binder's Young's modulus and strain value are It was confirmed through research that the above-mentioned problem can be solved by adjusting the content at the same time. Accordingly, the present application relates to a negative electrode composition, a negative electrode for a lithium secondary battery containing the same, and a lithium secondary battery containing the negative electrode.

An exemplary embodiment of the present specification includes a silicon-based active material; cathode conductive material; and a cathode binder; wherein the cathode binder includes a first binder having a Young's modulus of 10 ³ MPa or more and a second binder having a strain of 15% or more, and the cathode binder satisfies the following equation 1: A negative electrode composition is provided.

[Equation 1]

1 ≤ X/Y < 4

In equation 1 above,

Y refers to parts by weight of the first binder based on 100 parts by weight of the negative electrode binder,

X refers to parts by weight of the second binder based on 100 parts by weight of the anode binder.

In another embodiment, a negative electrode current collector layer; and a negative electrode active material layer including the negative electrode composition according to the present application formed on one or both sides of the negative electrode current collector layer.

Finally, the anode; A negative electrode for a lithium secondary battery according to the present application; A separator provided between the anode and the cathode; It provides a lithium secondary battery including; and an electrolyte.

The anode composition according to an embodiment of the present invention is characterized by solving the problem of volume expansion of the silicon-based active material by applying a specific anode binder when using a silicon-based active material, which is a high-capacity material, to manufacture a high-capacity battery. .

In particular, the negative electrode binder includes a first binder having a Young's modulus of 10 ³ MPa or more and a second binder having a strain of 15% or more, and the negative electrode binder satisfies the range of a specific equation 1.

Specifically, the anode composition according to the present application includes first and second binders of a specific composition to improve dispersibility for dispersing the active material and improve adhesion even when using a silicon-based active material, and to improve adhesion. It can solve the problem of conductive network disconnection due to initial and late adhesion and volume expansion of the battery used.

That is, the negative electrode composition according to the present application has a high content of silicon-based active material particles, so that a negative electrode with high capacity and high density can be obtained, and at the same time, in order to solve problems such as volume expansion due to the high content of silicon-based active material particles, it has a specific composition and The main purpose of the present invention is to solve the above problem by using a binder of similar content.

Figure 1 is a diagram showing a stacked structure of a negative electrode for a lithium secondary battery according to an exemplary embodiment of the present application.

Figure 2 is a diagram showing a stacked structure of a lithium secondary battery according to an exemplary embodiment of the present application.

Figure 3 is a diagram showing a curl evaluation method of examples and comparative examples according to the present application.

10: Negative current collector layer

20: Negative active material layer

30: Separator

40: positive electrode active material layer

50: Anode current collector layer

100: Negative electrode for lithium secondary battery

200: Anode for lithium secondary battery

Before explaining the present invention, some terms are first defined.

In this specification, when a part “includes” a certain element, this means that it may further include other elements rather than excluding other elements, unless specifically stated to the contrary.

In this specification, 'p to q' means a range of 'p to q or less.'

In this specification, “specific surface area” is measured by the BET method, and is specifically calculated from the amount of nitrogen gas adsorption under liquid nitrogen temperature (77K) using BELSORP-mino II from BEL Japan. That is, in the present application, the BET specific surface area may mean the specific surface area measured by the above measurement method.

In this specification, “Dn” refers to particle size distribution and refers to the particle size at the n% point of the cumulative distribution of particle numbers according to particle size. In other words, D50 is the particle size (average particle diameter) at 50% of the cumulative distribution of particle numbers according to particle size, D90 is the particle size at 90% of the cumulative distribution of particle numbers according to particle size, and D10 is the cumulative particle number according to particle size. This is the particle size at 10% of the distribution. Meanwhile, particle size distribution can be measured using a laser diffraction method. Specifically, after dispersing the powder to be measured in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (for example, Microtrac S3500), and when the particles pass through the laser beam, the difference in diffraction patterns according to particle size is measured to determine particle size distribution. Calculate .

In this specification, the fact that a polymer contains a certain monomer as a monomer unit means that the monomer participates in a polymerization reaction and is included as a repeating unit in the polymer. In this specification, when it is said that a polymer contains a monomer, this is interpreted the same as saying that the polymer contains a monomer as a monomer unit.

In this specification, the term 'polymer' is understood to be used in a broad sense including copolymers, unless specified as 'homopolymer'.

In this specification, the weight average molecular weight (Mw) and number average molecular weight (Mn) are determined by using monodisperse polystyrene polymers (standard samples) of various degrees of polymerization commercially available for molecular weight measurement as standard materials, and using gel permeation chromatography (Gel Permeation). This is the polystyrene equivalent molecular weight measured by chromatography (GPC). In this specification, molecular weight means weight average molecular weight unless otherwise specified.

In an exemplary embodiment of the present application, the method for measuring the Young's modulus involves putting the binder solution in a coated bowl and drying it at room temperature for a long time to remove moisture. The film that has lost moisture is vacuum dried at 130°C for 10 hours according to the electrode drying temperature to obtain a dried film. Afterwards, the dried film can be cut or punched into a sample size of 6mm x 100mm to collect a sample, and the tensile strength (Young's modulus) can be measured using UTM equipment.

The Young's modulus varies depending on the measurement method, speed, and measurement state of the binder, but the Young's modulus of the binder has a dew point of -5°C to 10°C, and may refer to a value measured in a dry room with a temperature of about 20°C to 22°C. there is.

In this application, the dew point refers to the temperature at which condensation begins when moist air is cooled, because the partial pressure of water vapor in the air becomes equal to the saturated vapor pressure of water at that temperature. In other words, when the temperature of the gas containing water vapor is lowered, the relative humidity becomes 100% and dew begins to form.

The dew point is -5°C to 10°C and the temperature is approximately 20°C to 22°C, which can generally be defined as a dry room, where the humidity is at a very low level.

In an exemplary embodiment of the present application, the strain measurement method involves putting the binder solution in a coated bowl and drying it at room temperature for a long time to remove moisture. The film that has lost moisture is vacuum dried at 130°C for 10 hours according to the electrode drying temperature to obtain a dried film. Afterwards, the dried film can be cut or punched into a sample size of 6mm x 100mm to collect a sample, and the tensile strain can be measured using UTM equipment.

The tensile strain of the binder varies depending on the measurement method, speed, and measurement state of the binder, but the strain of the binder is the same as the Young's modulus measurement conditions.

Hereinafter, the present invention will be described in detail with reference to the drawings so that those skilled in the art can easily practice the present invention. However, the present invention may be implemented in various different forms and is not limited to the following description.

[Equation 1]

1 ≤ X/Y < 4

In equation 1 above,

In an exemplary embodiment of the present application, the silicon-based active material may include one or more selected from the group consisting of SiOx (x=0), SiOx (0<x<2), SiC, and Si alloy.

The active material of the present invention includes a silicon-based active material. The silicon-based active material may be SiOx, Si/C, or Si. SiOx may include a compound represented by SiOx (0≤x<2). In the case of SiO ₂ , lithium cannot be stored because it does not react with lithium ions, so x is preferably within the above range. The silicon-based active material may be Si/C or Si, which is composed of a composite of Si and C. Additionally, two or more types of the above silicon-based active materials can be mixed and used. The negative electrode active material may further include a carbon-based active material along with the silicon-based active material described above. The carbon-based active material can contribute to excellent cycle characteristics or improved battery life performance of the anode or secondary battery of the present invention.

In general, silicon-based active materials are known to have a capacity that is more than 10 times higher than carbon-based active materials. Accordingly, when silicon-based active materials are applied to a negative electrode, it is expected that it will be possible to implement an electrode with a high level of energy density even with a thin thickness. .

In an exemplary embodiment of the present application, the silicon-based active material includes one or more selected from the group consisting of SiOx (x=0) and SiOx (0<x<2), and the SiOx (based on 100 parts by weight of the silicon-based active material) Provided is a negative electrode composition containing 70 parts by weight or more of x=0).

In another embodiment, the silicon-based active material may contain at least 70 parts by weight, preferably at least 80 parts by weight, and more preferably at least 90 parts by weight of SiOx (x=0) based on 100 parts by weight of the silicon-based active material. It may contain 100 parts by weight or less, preferably 99 parts by weight or less, and more preferably 95 parts by weight or less.

The silicon-based active material according to the present application contains more than 70 parts by weight of SiOx (x=0) based on 100 parts by weight of the silicon-based active material, and when compared to the silicon-based active material that uses SiOx (0<x<2) series as the main material. , the theoretical capacity is much higher than that of the silicon-based active material of the present application. That is, when using a SiOx (0<x<2) series active material, no matter what treatment is performed on the active material itself, equivalent charging and discharging capacity conditions cannot be achieved compared to the case with the silicon-based active material of the present invention.

In an exemplary embodiment of the present application, pure silicon (Si) may be used as the silicon-based active material. Using pure silicon (Si) as a silicon-based active material means that pure Si particles (SiOx (x=0)) that are not combined with other particles or elements are within the above range, based on 100 parts by weight of the total silicon-based active material as described above. It may mean including.

Compared to existing graphite-based active materials, silicon-based active materials have a significantly higher capacity, so attempts to apply them are increasing. However, due to the high volume expansion rate during the charging and discharging process, they are limited to cases where trace amounts are mixed with graphite-based active materials.

Therefore, the present invention uses a high content of silicon-based active material as a negative electrode active material to improve capacity performance, and in order to solve the problems of maintaining the conductive path and maintaining the combination of the conductive material, binder, and active material due to volume expansion as described above, It is characterized by the use of a conditional binder.

Meanwhile, the average particle diameter (D50) of the silicon-based active material of the present invention may be 5㎛ to 10㎛, specifically 5.5㎛ to 8㎛, and more specifically 6㎛ to 7㎛. When the average particle diameter is within the above range, the specific surface area of the particles is within an appropriate range, and the viscosity of the anode slurry is within an appropriate range. Accordingly, dispersion of the particles constituting the cathode slurry becomes smooth. In addition, since the size of the silicon-based active material is greater than the above lower limit, the contact area between the silicon particles and the conductive material is excellent due to the composite of the conductive material and the binder in the negative electrode slurry, and the possibility of the conductive network being maintained increases, increasing the capacity. Retention rate increases. Meanwhile, when the average particle diameter satisfies the above range, excessively large silicon particles are excluded to form a smooth surface of the cathode, thereby preventing current density unevenness during charging and discharging.

In one embodiment of the present application, the silicon-based active material generally has a characteristic BET surface area. The BET surface area of the silicon-based active material is preferably 0.01 to 150.0 m ² /g, more preferably 0.1 to 100.0 m ² /g, particularly preferably 0.2 to 80.0 m ² /g, most preferably 0.2 to 18.0 m ² It is /g. BET surface area is measured according to DIN 66131 (using nitrogen). The DIN 66131 measurement method corresponds to a method of measuring pores based on the amount of adsorption/desorption of nitrogen molecules.

In one embodiment of the present application, the silicon-based active material may exist, for example, in a crystalline or amorphous form, and is preferably not porous. The silicon particles are preferably spherical or fragment-shaped particles. Alternatively but less preferably, the silicon particles may also have a fibrous structure or be present in the form of a silicon-comprising film or coating.

In an exemplary embodiment of the present application, a negative electrode composition is provided in which the silicon-based active material is contained in an amount of 60 parts by weight or more based on 100 parts by weight of the negative electrode composition.

In another embodiment, the silicon-based active material may contain at least 60 parts by weight, preferably at least 65 parts by weight, more preferably at least 70 parts by weight, based on 100 parts by weight of the negative electrode composition, and not more than 95 parts by weight. , preferably 90 parts by weight or less, more preferably 85 parts by weight or less.

The anode composition according to the present application uses a specific conductive material and binder that can control the volume expansion rate during the charging and discharging process even when a silicon-based active material with a significantly high capacity is used within the above range, so that the performance of the anode is maintained even within the above range. It does not deteriorate and has excellent output characteristics during charging and discharging.

In an exemplary embodiment of the present application, the silicon-based active material may have a non-spherical shape and its sphericity is, for example, 0.9 or less, for example, 0.7 to 0.9, for example, 0.8 to 0.9, for example, 0.85 to 0.9. am.

In the present application, the circularity is determined by the following equation 1-1, where A is the area and P is the boundary line.

[Equation 1-1]

4πA/P ²

In the past, it was common to use only graphite-based compounds as negative electrode active materials, but recently, as demand for high-capacity batteries increases, attempts to use silicon-based compounds mixed to increase capacity are increasing. However, in the case of silicon-based compounds, even if the characteristics of the silicon-based active material itself are adjusted according to the present application as described above, the volume expands rapidly during the charging/discharging process, causing some problems in damaging the conductive path formed in the negative electrode active material layer. It can be.

Therefore, in an exemplary embodiment of the present application, the negative conductive material may include one or more selected from the group consisting of a point-shaped conductive material, a planar conductive material, and a linear conductive material.

In an exemplary embodiment of the present application, the point-shaped conductive material refers to a point-shaped or spherical conductive material that can be used to improve conductivity in the cathode and has conductivity without causing chemical change. Specifically, the dot-shaped conductive material is natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, channel black, Parness black, lamp black, thermal black, conductive fiber, fluorocarbon, aluminum powder, nickel powder, zinc oxide, It may be at least one selected from the group consisting of potassium titanate, titanium oxide, and polyphenylene derivatives, and preferably may include carbon black in terms of realizing high conductivity and excellent dispersibility.

In an exemplary embodiment of the present application, the point-shaped conductive material may have a BET specific surface area of 40 m ² /g or more and 70 m ² /g or less, preferably 45 m ² /g or more and 65 m ² /g or less, more preferably 50 m ^{2 /g.} It may be more than /g and less than 60m ² /g.

In an exemplary embodiment of the present application, the point-shaped conductive material may satisfy a functional group content (Volatile matter) of 0.01% or more and 1% or less, preferably 0.01% or more and 0.3% or less, and more preferably 0.01% or more and 0.1% or less. there is.

In particular, when the functional group content of the dot-shaped conductive material satisfies the above range, functional groups exist on the surface of the dot-shaped conductive material, so that when water is used as a solvent, the dot-shaped conductive material can be smoothly dispersed in the solvent. In particular, in the present invention, the functional group content of the point-shaped conductive material can be lowered by using silicon particles and a specific binder, which has an excellent effect in improving dispersibility.

In an exemplary embodiment of the present application, it is characterized in that it includes a point-shaped conductive material having a functional group content in the above range along with a silicon-based active material. The content of the functional group can be adjusted according to the degree of heat treatment of the point-type conductive material. there is.

In an exemplary embodiment of the present application, the particle diameter of the point-shaped conductive material may be 10 nm to 100 nm, preferably 20 nm to 90 nm, and more preferably 20 nm to 60 nm.

In an exemplary embodiment of the present application, the conductive material may include a planar conductive material.

The planar conductive material may serve to improve conductivity by increasing surface contact between silicon particles within the cathode and at the same time suppress disconnection of the conductive path due to volume expansion. The planar conductive material may be expressed as a plate-shaped conductive material or a bulk-type conductive material.

In an exemplary embodiment of the present application, the planar conductive material may include at least one selected from the group consisting of plate-shaped graphite, graphene, graphene oxide, and graphite flakes, and may preferably be plate-shaped graphite.

In an exemplary embodiment of the present application, the average particle diameter (D50) of the planar conductive material may be 2㎛ to 7㎛, specifically 3㎛ to 6㎛, and more specifically 3.5㎛ to 5㎛. . When the above range is satisfied, dispersion is easy without causing an excessive increase in viscosity of the anode slurry due to the sufficient particle size. Therefore, the dispersion effect is excellent when dispersed using the same equipment and time.

In an exemplary embodiment of the present application, the planar conductive material has a D10 of 0.5 μm or more and 2.0 μm or less, a D50 of 2.5 μm or more and 3.5 μm or less, and a D90 of 6.5 μm or more and 15.0 μm or less. It provides a negative electrode composition.

In an exemplary embodiment of the present application, the planar conductive material is a high specific surface area planar conductive material having a high BET specific surface area; Alternatively, a low specific surface area planar conductive material can be used.

In an exemplary embodiment of the present application, the planar conductive material includes a high specific surface area planar conductive material; Alternatively, a planar conductive material with a low specific surface area can be used without limitation, but in particular, the planar conductive material according to the present application can be affected to some extent by dispersion on electrode performance, so it is possible to use a planar conductive material with a low specific surface area that does not cause problems with dispersion. This may be particularly desirable.

In an exemplary embodiment of the present application, the planar conductive material may have a BET specific surface area of 1 m ² /g or more.

In another embodiment, the planar conductive material may have a BET specific surface area of 1 m ² /g or more and 500 m ² /g or less, preferably 5 m ² /g or more and 300 m ² /g or less, more preferably 5 m ² /g. It may be more than g and less than 250m ² /g.

The planar conductive material according to the present application includes a high specific surface area planar conductive material; Alternatively, a low specific surface area planar conductive material can be used.

In another embodiment, the planar conductive material is a high specific surface area planar conductive material, and has a BET specific surface area of 50 m ² /g or more and 500 m ² /g or less, preferably 80 m ² /g or more and 300 m ² /g or less, more preferably In other words, it can satisfy the range of 100m ² /g or more and 300m ² /g or less.

In another embodiment, the planar conductive material is a low specific surface area planar conductive material, and the BET specific surface area is 1 m ² /g or more and 40 m ² /g or less, preferably 5 m ² /g or more and 30 m ² /g or less, more preferably In other words, it can satisfy the range of 5m ² /g or more and 25m ² /g or less.

Other conductive materials may include linear conductive materials such as carbon nanotubes. The carbon nanotubes may be bundled carbon nanotubes. The bundled carbon nanotubes may include a plurality of carbon nanotube units. Specifically, the 'bundle type' herein refers to a bundle in which a plurality of carbon nanotube units are arranged side by side or entangled in substantially the same orientation along the longitudinal axis of the carbon nanotube units, unless otherwise specified. It refers to a secondary shape in the form of a bundle or rope. The carbon nanotube unit has a graphite sheet in the shape of a cylinder with a nano-sized diameter and an sp2 bond structure. At this time, the characteristics of a conductor or semiconductor can be displayed depending on the angle and structure at which the graphite surface is rolled. Compared to entangled type carbon nanotubes, the bundled carbon nanotubes can be uniformly dispersed when manufacturing a cathode, and can smoothly form a conductive network within the cathode, improving the conductivity of the cathode.

In an exemplary embodiment of the present application, an anode conductive material is provided in an amount of 0.1 part by weight or more and 40 parts by weight or less based on 100 parts by weight of the anode composition. Also, for example, it may include 10 parts by weight or more and 40 parts by weight or less.

In another embodiment, the anode conductive material is present in an amount of 0.1 to 40 parts by weight, preferably 0.2 to 30 parts by weight, more preferably 0.4 to 25 parts by weight, based on 100 parts by weight of the anode composition. parts or less, most preferably 0.4 parts by weight or more and 10 parts by weight or less.

In an exemplary embodiment of the present application, the negative electrode conductive material is a planar conductive material; and a linear conductive material.

In an exemplary embodiment of the present application, the negative electrode conductive material is 80 parts by weight or more and 99.9 parts by weight or less of the planar conductive material based on 100 parts by weight of the negative electrode conductive material; and 0.1 to 20 parts by weight of the linear conductive material.

In another embodiment, the negative electrode conductive material is present in an amount of 80 parts by weight or more and 99.9 parts by weight or less, preferably 85 parts by weight or more and 99.9 parts by weight or less, more preferably, based on 100 parts by weight of the negative electrode conductive material. It may contain 95 parts by weight or more and 98 parts by weight or less.

In another embodiment, the anode conductive material is 0.1 part by weight or more and 20 parts by weight or less, preferably 0.1 part by weight or more and 15 parts by weight or less, more preferably 0.2 parts by weight, based on 100 parts by weight of the anode conductive material. It may contain more than 5 parts by weight and less than 5 parts by weight.

In an exemplary embodiment of the present application, since the negative conductive material includes a planar conductive material and a linear conductive material and satisfies the above composition and ratio, it does not significantly affect the lifespan characteristics of the existing lithium secondary battery, especially the planar conductive material. When ash and linear conductive materials are included, the number of charging and discharging points increases, resulting in excellent output characteristics at high C-rates and reduced high-temperature gas generation.

In an exemplary embodiment of the present application, the negative electrode conductive material may be made of a linear conductive material.

In particular, when a linear conductive material is used alone, the electrode tortuosity, which is a problem of silicon-based anodes, can be simplified, the electrode structure can be improved, and the movement resistance of lithium ions in the electrode can be reduced accordingly. do.

In an exemplary embodiment of the present application, when the negative electrode conductive material includes a linear conductive material alone, the negative electrode conductive material is 0.1 part by weight or more and 5 parts by weight or less, preferably 0.2 parts by weight or more, based on 100 parts by weight of the negative electrode composition. It may contain less than or equal to 0.4 parts by weight and less than or equal to 1 part by weight.

The cathode conductive material according to the present application has a completely separate configuration from the anode conductive material applied to the anode. In other words, in the case of the anode conductive material according to the present application, it serves to hold the contact point between silicon-based active materials whose volume expansion of the electrode is very large due to charging and discharging. The anode conductive material acts as a buffer when rolled and retains some conductivity. It has a role in providing , and its composition and role are completely different from the cathode conductive material of the present invention.

In addition, the negative electrode conductive material according to the present application is applied to a silicon-based active material and has a completely different structure from the conductive material applied to the graphite-based active material. In other words, the conductive material used in the electrode having a graphite-based active material has the property of improving output characteristics and providing some conductivity simply because it has smaller particles compared to the active material, and is different from the anode conductive material applied together with the silicon-based active material as in the present invention. The composition and roles are completely different.

In an exemplary embodiment of the present application, the planar conductive material used as the above-described negative electrode conductive material has a different structure and role from the carbon-based active material generally used as the negative electrode active material. Specifically, the carbon-based active material used as a negative electrode active material may be artificial graphite or natural graphite, and refers to a material that is processed into a spherical or dot-shaped shape to facilitate storage and release of lithium ions.

On the other hand, the planar conductive material used as a negative electrode conductive material is a material that has a plane or plate shape and can be expressed as plate-shaped graphite. In other words, it is a material included to maintain a conductive path within the negative electrode active material layer, and refers to a material that does not play a role in storing and releasing lithium, but rather secures a conductive path in a planar shape inside the negative electrode active material layer.

That is, in the present application, the use of plate-shaped graphite as a conductive material means that it is processed into a planar or plate-shaped shape and used as a material that secures a conductive path rather than storing or releasing lithium. At this time, the negative electrode active material included has high capacity characteristics for storing and releasing lithium, and plays a role in storing and releasing all lithium ions transferred from the positive electrode.

On the other hand, in the present application, the use of a carbon-based active material as an active material means that it is processed into a point-shaped or spherical shape and used as a material that plays a role in storing or releasing lithium.

In an exemplary embodiment of the present application, the cathode binder includes a first binder having a Young's modulus of 10 ³ MPa or more and a second binder having a strain of 15% or more.

In an exemplary embodiment of the present application, a negative electrode composition is provided wherein the first binder includes at least one selected from the group consisting of PAA, PAN, and PAM, and the second binder is a rubber-based binder.

In an exemplary embodiment of the present application, the negative electrode binder includes a first binder having a Young's modulus of 10 ³ MPa or more.

In another embodiment, the cathode binder may have a Young's modulus of 1x10 ³ MPa or more, preferably 2x10 ³ MPa, more preferably 5x10 ³ MPa or more, and most preferably 9x10 ³ MPa or more, It can satisfy 20x10 ³ MPa or less, preferably 18x10 ³ MPa or less, and more preferably 15x10 ³ MPa or less.

In another embodiment, the Young's modulus of the cathode binder is 3x10 ³ MPa or more, 4x10 ³ MPa or more, 6x10 ³ MPa or more, 7x10 ³ MPa or more, 8x10 ³ MPa or more, 10x10 ³ MPa or more, 19x10 ³ MPa or less, 17x10 It may be ³ MPa or less, 16x10 ³ MPa or less, 14x10 ³ MPa or less, 13x10 ³ MPa or less, 12x10 ³ MPa or less, and includes various combinations of the above ranges.

The first binder has both dispersibility for dispersing the negative electrode active material in the negative electrode slurry containing the negative electrode composition and adhesive power for binding to the negative electrode current collector layer and the negative electrode active material layer after drying. The adhesive strength is not high compared to the binder. It applies. That is, the first binder according to the present application includes an aqueous binder that satisfies the Young's modulus, and may mean a binder having a surface bonding form.

The first binder is a binder suitable for a lithium secondary battery in which a silicon active material with large volume expansion during the charging and discharging process is applied to the negative electrode. When the condition is below the lower limit of the above range, it is difficult to effectively control the volume expansion of silicon, and when the condition is above the upper limit of the above range, the first binder is a binder suitable for a lithium secondary battery. In this case, the rigidity is too hard, so there is a high possibility that the bond will be broken during the charging and discharging process.

In an exemplary embodiment of the present application, the aqueous binder is soluble in aqueous solvents such as water and includes polyvinyl alcohol (PVA), polyacrylic acid (PAA), and polyethylene glycol (PEG). , polyacrylonitrile (PAN), and polyacryl amide (PAM). Preferably, at least one selected from the group consisting of polyacrylic acid (PAA) and polyacryl amide (PAM), more preferably, in terms of excellent resistance to volume expansion/contraction of the silicone-based active material. It may include polyacrylic acid (PAA) and polyacryl amide (PAM).

More specifically, the first binder may be a PAM-based binder. In this case, the PAM-based binder is a binder whose main component is PAM, and can be used by adjusting the ratio of PAM, PAA, and PAN, and can be used as described above by appropriately changing the composition. Young's modulus can be satisfied.

In order to better disperse the first binder in an aqueous solvent such as water when producing a negative electrode slurry for forming a negative electrode active material layer and to improve binding force by covering the active material more smoothly, hydrogen in the first binder is used as Li , may include those substituted with Na or Ca, etc.

The first binder has hydrophilic properties and is generally insoluble in electrolytes or electrolyte solutions used in secondary batteries. These characteristics can provide strong stress or tensile strength to the first binder when applied to a negative electrode or lithium secondary battery, and thus can effectively suppress volume expansion/contraction problems due to charging and discharging of the silicon-based active material.

In an exemplary embodiment of the present application, a negative electrode composition is provided wherein the weight average molecular weight of the first binder is 100,000 g/mol or more and 2,000,000 g/mol or less.

Also, more preferably, it may be 500,000 g/mol or more and 1,500,000 g/mol or less.

In an exemplary embodiment of the present application, the second binder may have a strain of 15% or more, preferably a strain of 20% or more, more preferably a strain of 30% or more, and most preferably a strain of 40% or more. The strain may be 300% or less, preferably 200% or less, and more preferably 150% or less.

In another embodiment, the strain may be 25% or more, the strain may be 35% or more, the strain may be 45% or more, the strain may be 75% or less, the strain may be 65% or more, and the strain may be 55% or less, and the corresponding range Various combinations of may be included.

As described above, if the strain value of the second binder is less than the above range, the stress is high, making it difficult to effectively control the volume expansion of silicon, and if it exceeds the above range, it is difficult to effectively control the adhesion between electrodes.

Since the first binder satisfies the above-mentioned modulus range and has strong stress, if the first binder is used alone, there is a risk of warping of the cathode, occurrence of cracks due to bending, and deterioration of life characteristics. The second binder can be well dissolved in an electrolyte or electrolyte solution generally used in secondary batteries, and can relieve the stress of the first binder to a certain level when used together with the first binder.

Therefore, the negative electrode composition of the present invention can improve lifespan characteristics by effectively solving the volume expansion/contraction problem of the silicon-based active material by using a negative electrode binder containing the first binder and the second binder in a specific weight ratio, and can improve the lifespan characteristics of the thin film negative electrode. It can solve the problem of bending during manufacturing and also has the feature of improving adhesion.

At this time, the strain value of the second binder can be implemented in a range that satisfies the above-mentioned range by specifically adjusting the ST/BD ratio of the SBR binder to an appropriate range.

In an exemplary embodiment of the present application, the second binder is a material different from the first binder, and may be defined as being insoluble in aqueous solvents such as water, but capable of smooth dispersion in aqueous solvents. Specifically, the second binder with a strain of 15% or more includes styrene butadiene rubber (SBR), hydrogenated nitrile butadiene rubber (HNBR), acrylonitrile butadiene rubber, and acrylic rubber ( It may include at least one selected from the group consisting of acrylic rubber, butyl rubber, and fluoro rubber, and is preferably styrene-butadiene rubber and It may include at least one selected from the group consisting of hydrogenated nitrile butadiene rubber, more preferably styrene butadiene rubber.

In general, the second binder is a material that has very high electrolyte wettability compared to the first binder. When the aforementioned second binder is located near the silicon-based cathode surface, the cathode resistance is lowered because the FEC solvent or LiPF ₆ salt that can create an SEI layer can be quickly supplied.

In an exemplary embodiment of the present application, Equation 1 may satisfy 1≤X/Y<4, preferably 1.1≤X/Y<3.9, and more preferably 1.2≤X/Y<3.8.

More specifically, 1.3 ≤ X/Y < 3.7, 1.4 ≤ X/Y < 3.6, 1.5 ≤ X/Y < 3.5, 1.6 ≤ It may be 3.2, 1.9 ≤ X/Y < 3.1, 2.0 ≤ X/Y < 3.0, 1.2 ≤ X/Y < 2.0.

In an exemplary embodiment of the present application,

In another embodiment, the amount of It may be below. Additionally, it may be 50 parts by weight or more and 70 parts by weight or less, 55 parts by weight or more and 67 parts by weight or less, and 60 parts by weight or more and 67 parts by weight or less.

In another embodiment, Y is 5 parts by weight or more and 50 parts by weight or less, preferably 10 parts by weight or more and 45 parts by weight or less, more preferably 20 parts by weight or more and 45 parts by weight, based on 100 parts by weight of the negative binder. It may be below. Additionally, it may be 33 parts by weight or more and 45 parts by weight or less, 35 parts by weight or more and 45 parts by weight or less, and 40 parts by weight or more and 45 parts by weight or less.

As described above, the negative electrode binder according to the present application has the first binder and the second binder satisfying the above contents, and has the feature of improving dispersibility even when using a silicon-based active material and also solving the problem of adhesion. .

Furthermore, the above-mentioned negative electrode binder and negative electrode conductive material include a planar conductive material; And when a linear conductive material is included, the adhesion problem can be improved and the cathode internal resistance can also be improved.

In an exemplary embodiment of the present application, the negative electrode binder is polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidenefluoride, polyacrylonitrile, Polymethylmethacrylate, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene. -Selected from the group consisting of propylene-diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluororubber, poly acrylic acid, and materials whose hydrogen is replaced with Li, Na, or Ca, etc. It may include at least one of the following, and may also include various copolymers thereof.

In an exemplary embodiment of the present application, the anode binder is provided in an amount of 1 part by weight or more and 20 parts by weight or less based on 100 parts by weight of the anode composition.

In an exemplary embodiment of the present application, the negative electrode binder may include 20 parts by weight or less, preferably 15 parts by weight or less, based on 100 parts by weight of the negative electrode composition, and 1 or more parts by weight, 5 or more parts by weight, or 10 parts by weight. It can be more than wealth.

In an exemplary embodiment of the present application, a negative electrode current collector layer; and a negative electrode active material layer including the negative electrode composition according to the present application formed on one or both sides of the negative electrode current collector layer.

Figure 1 is a diagram showing a stacked structure of a negative electrode for a lithium secondary battery according to an exemplary embodiment of the present application. Specifically, it can be seen that the negative electrode 100 for a lithium secondary battery includes a negative electrode active material layer 20 on one side of the negative electrode current collector layer 10, and Figure 1 shows that the negative electrode active material layer is formed on one side, but the negative electrode collector layer 10 has a negative electrode active material layer 20 on one side. It can be included on both sides of the entire floor.

In an exemplary embodiment of the present application, the negative electrode may be formed by coating a negative electrode slurry containing the negative electrode composition on one or both sides of a current collector to form a negative electrode for a lithium secondary battery.

In an exemplary embodiment of the present application, the negative electrode slurry includes a negative electrode composition; and a slurry solvent.

In an exemplary embodiment of the present application, the solid content of the anode slurry may satisfy 5% or more and 40% or less.

In another embodiment, the solid content of the anode slurry may be within the range of 5% to 40%, preferably 7% to 35%, and more preferably 10% to 30%.

The solid content of the negative electrode slurry may mean the content of the negative electrode composition contained in the negative electrode slurry, and may mean the content of the negative electrode composition based on 100 parts by weight of the negative electrode slurry.

When the solid content of the negative electrode slurry satisfies the above range, the viscosity is appropriate when forming the negative electrode active material layer, thereby minimizing particle agglomeration of the negative electrode composition, thereby enabling efficient formation of the negative electrode active material layer.

In an exemplary embodiment of the present application, the negative electrode current collector layer generally has a thickness of 1 μm to 100 μm. This negative electrode current collector layer is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, for example, copper, stainless steel, aluminum, nickel, titanium, fired carbon, copper or stainless steel. Surface treatment of carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, the bonding power of the negative electrode active material can be strengthened by forming fine irregularities on the surface, and it can be used in various forms such as films, sheets, foils, nets, porous materials, foams, and non-woven fabrics.

In an exemplary embodiment of the present application, a negative electrode for a lithium secondary battery is provided, wherein the negative electrode current collector layer has a thickness of 1 μm or more and 100 μm or less, and the negative electrode active material layer has a thickness of 20 μm or more and 500 μm or less.

However, the thickness may vary depending on the type and purpose of the cathode used and is not limited to this.

In an exemplary embodiment of the present application, the porosity of the negative electrode active material layer may satisfy a range of 10% to 60%.

In another embodiment, the porosity of the negative electrode active material layer may be within the range of 10% to 60%, preferably 20% to 50%, and more preferably 30% to 45%.

The porosity includes the silicon-based active material included in the negative electrode active material layer; conductive material; and varies depending on the composition and content of the binder, especially the silicon-based active material according to the present application; and a conductive material of a specific composition and content satisfies the above range, and thus the electrode is characterized by having an appropriate range of electrical conductivity and resistance.

In an exemplary embodiment of the present application, the adhesive strength of the surface of the negative electrode active material layer in contact with the negative electrode current collector layer satisfies 100 gf / 5mm or more and 500 gf / 5mm or less under normal pressure conditions at 25 ° C. A negative electrode for a lithium secondary battery is provided. do.

In another embodiment, the adhesive strength of the surface of the negative electrode active material layer in contact with the negative electrode current collector layer is 100gf/5mm or more and 500gf/5mm or less, preferably 300gf/5mm or more and 450gf/5mm or less under normal pressure conditions at 25°C. , more preferably 350gf/5mm or more and 430gf/5mm or less.

In particular, the negative electrode according to the present application includes a specific negative electrode binder in the negative electrode composition described above, and the adhesion is improved as described above. In addition, even if expansion and contraction of the silicon-based active material is repeated due to repeated charging and discharging of the negative electrode, the conductive network is maintained by applying a negative electrode binder and negative electrode conductive material of a specific composition, and the increase in resistance is suppressed by preventing disconnection. have it

The adhesive strength was measured at 90° and a speed of 5 mm/s using a peel strength meter using 3M 9070 tape. Specifically, one side of the negative electrode active material layer of the negative electrode for a lithium secondary battery is adhered to one side of a slide glass (3M 9070 tape) to which an adhesive film is attached. Afterwards, it was attached by reciprocating 5 to 10 times with a 2 kg rubber roller, and the adhesive force (peel force) was measured at a speed of 5 mm/s in an angular direction of 90°. At this time, adhesion can be measured at 25°C and normal pressure.

Specifically, the adhesion was measured at 25°C and normal pressure on a 5mm x 15cm electrode.

In an exemplary embodiment of the present application, atmospheric pressure may mean pressure without applying or lowering a specific pressure, and may be used in the same sense as atmospheric pressure. It can generally be expressed as 1 atmosphere.

In an exemplary embodiment of the present application, an anode; A negative electrode for a lithium secondary battery according to the present application; A separator provided between the anode and the cathode; It provides a lithium secondary battery including; and an electrolyte.

Figure 2 is a diagram showing a stacked structure of a lithium secondary battery according to an exemplary embodiment of the present application. Specifically, a negative electrode 100 for a lithium secondary battery including a negative electrode active material layer 20 can be confirmed on one side of the negative electrode current collector layer 10, and a positive electrode active material layer 40 on one side of the positive electrode current collector layer 50. A positive electrode 200 for a lithium secondary battery can be confirmed, indicating that the negative electrode 100 for a lithium secondary battery and the positive electrode 200 for a lithium secondary battery are formed in a stacked structure with a separator 30 in between.

The secondary battery according to an exemplary embodiment of the present specification may particularly include the above-described negative electrode for a lithium secondary battery. Specifically, the secondary battery may include a negative electrode, a positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, and the negative electrode is the same as the negative electrode described above. Since the cathode has been described above, detailed description will be omitted.

The positive electrode is formed on the positive electrode current collector and the positive electrode current collector, and may include a positive electrode active material layer containing the positive electrode active material.

In the positive electrode, the positive electrode current collector is not particularly limited as long as it is conductive without causing chemical changes in the battery, for example, stainless steel, aluminum, nickel, titanium, fired carbon, or carbon on the surface of aluminum or stainless steel. , surface treated with nickel, titanium, silver, etc. can be used. Additionally, the positive electrode current collector may typically have a thickness of 3㎛ to 500㎛, and fine irregularities may be formed on the surface of the current collector to increase the adhesion of the positive electrode active material. For example, it can be used in various forms such as films, sheets, foils, nets, porous materials, foams, and non-woven materials.

The positive electrode active material may be a commonly used positive electrode active material. Specifically, the positive electrode active material is a layered compound such as lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), or a compound substituted with one or more transition metals; Lithium iron oxide such as LiFe ₃ O ₄ ; Lithium manganese oxide with the formula Li _1+c1 Mn _2-c1 O ₄ (0≤c1≤0.33), LiMnO ₃ , LiMn ₂ O ₃ , LiMnO _{2 ,} etc.; lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxides such as LiV ₃ O ₈ , V ₂ O ₅ , and Cu ₂ V ₂ O ₇ ; Chemical formula LiNi _1-c2 M _c2 O ₂ (where M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B and Ga, and satisfies 0.01≤c2≤0.3). Ni site-type lithium nickel oxide; Chemical formula LiMn _2-c3 M _c3 O ₂ (where M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn and Ta, and satisfies 0.01≤c3≤0.1) or Li ₂ Mn ₃ MO lithium manganese composite oxide represented by ₈ (where M is at least one selected from the group consisting of Fe, Co, Ni, Cu and Zn); Examples include LiMn ₂ O ₄ in which part of Li in the chemical formula is replaced with an alkaline earth metal ion, but it is not limited to these. The anode may be Li-metal.

The positive electrode active material layer may include the positive electrode active material described above, a positive conductive material, and a positive electrode binder.

At this time, the anode conductive material is used to provide conductivity to the electrode, and can be used without particular limitation as long as it does not cause chemical change and has electronic conductivity in the battery being constructed. Specific examples include graphite such as natural graphite and artificial graphite; Carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, and carbon fiber; Metal powders or metal fibers such as copper, nickel, aluminum, and silver; Conductive whiskeys such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Or conductive polymers such as polyphenylene derivatives, etc., of which one type alone or a mixture of two or more types may be used.

Additionally, the positive electrode binder serves to improve adhesion between positive electrode active material particles and adhesion between the positive electrode active material and the positive electrode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, and carboxymethyl cellulose (CMC). ), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber. (SBR), fluorine rubber, or various copolymers thereof, and one type of these may be used alone or a mixture of two or more types may be used.

The separator separates the cathode from the anode and provides a passage for lithium ions. It can be used without particular restrictions as long as it is normally used as a separator in secondary batteries. In particular, it has low resistance to ion movement in the electrolyte and has an electrolyte moisture capacity. Excellent is desirable. Specifically, porous polymer films, for example, porous polymer films made of polyolefin polymers such as ethylene homopolymer, propylene homopolymer, ethylene/butene copolymer, ethylene/hexene copolymer, and ethylene/methacrylate copolymer, or these. A laminated structure of two or more layers may be used. In addition, conventional porous non-woven fabrics, for example, non-woven fabrics made of high melting point glass fibers, polyethylene terephthalate fibers, etc., may be used. In addition, a coated separator containing ceramic components or polymer materials may be used to ensure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

The electrolytes include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

Specifically, the electrolyte may include a non-aqueous organic solvent and a metal salt.

Examples of the non-aqueous organic solvent include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butylo lactone, and 1,2-dimethyl. Toxy ethane, tetrahydrofuran, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxoran, formamide, dimethylformamide, dioxoran, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid. Triesters, trimethoxy methane, dioxoran derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ether, methyl pyropionate, propionic acid. Aprotic organic solvents such as ethyl may be used.

In particular, among the carbonate-based organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, are high-viscosity organic solvents and have a high dielectric constant, so they can be preferably used because they easily dissociate lithium salts. These cyclic carbonates include dimethyl carbonate and diethyl carbonate. If linear carbonates of the same low viscosity and low dielectric constant are mixed and used in an appropriate ratio, an electrolyte with high electrical conductivity can be made and can be used more preferably.

The metal salt may be a lithium salt, and the lithium salt is a material that is easily soluble in the non-aqueous electrolyte. For example, anions of the lithium salt include F ^- , Cl ^- , I ^- , NO ₃ ^- , N(CN ) ₂ ^- , BF ₄ ^- , ClO ₄ ^- , PF ₆ ^- , (CF ₃ ) ₂ PF ₄ ^- , (CF ₃ ) ₃ PF ₃ ^- , (CF ₃ ) ₄ PF ₂ ^- , (CF ₃ ) ₅ PF ^- , (CF ₃ ) ₆ P ^- , CF ₃ SO ₃ ^- , CF ₃ CF ₂ SO ₃ ^- , (CF ₃ SO ₂ ) ₂ N ^- , (FSO ₂ ) ₂ N ^- , CF ₃ CF ₂ (CF ₃ ) ₂ CO ^- , (CF ₃ SO ₂ ) ₂ CH ^- , (SF ₅ ) ₃ C ^- , (CF ₃ SO ₂ ) ₃ C ^- , CF ₃ (CF ₂ ) ₇ SO ₃ ^- , CF ₃ CO ₂ ^- , CH ₃ CO ₂ ^- , SCN ^- and (CF ₃ CF ₂ SO ₂ ) ₂ N ^- At least one selected from the group consisting of can be used.

In addition to the electrolyte components, the electrolyte includes, for example, haloalkylene carbonate-based compounds such as difluoroethylene carbonate, pyridine, and trifluoroethylene for the purpose of improving battery life characteristics, suppressing battery capacity reduction, and improving battery discharge capacity. Ethyl phosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexanoic acid triamide, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N, N-substituted imida. One or more additives such as zolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxy ethanol, or aluminum trichloride may be further included.

One embodiment of the present invention provides a battery module including the secondary battery as a unit cell and a battery pack including the same. Since the battery module and battery pack include the secondary battery with high capacity, high rate characteristics, and cycle characteristics, they are medium-to-large devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems. It can be used as a power source.

In an exemplary embodiment of the present application, a method for manufacturing a negative electrode using the negative electrode composition is provided. More specifically, a solvent is added to the negative electrode composition to obtain a negative electrode slurry. The negative electrode slurry is applied to at least one surface of the negative electrode current collector layer to form a negative electrode active material layer. Afterwards, the negative electrode is manufactured by drying and rolling the negative electrode active material layer coated on the negative electrode current collector layer.

In the present application, the solvent included in the cathode slurry may be, for example, distilled water.

In one embodiment of the present application, the anode slurry may have a solid content of 5% or more and 40% or less.

In another embodiment, the anode slurry may satisfy a solid content range of 5% to 40%, preferably 7% to 35%, and more preferably 10% to 30%.

The solid content of the negative electrode slurry may refer to the amount of the negative electrode composition contained in the negative electrode slurry, and may refer to the amount of the negative electrode composition based on 100 parts by weight of the negative electrode slurry.

When the negative electrode slurry satisfies the solid content range of 5% to 40%, the negative electrode active material layer has an appropriate viscosity when forming the negative electrode active material layer, so the particle agglomeration phenomenon of the negative electrode active material minimizes the electrode composition and efficiently forms the negative electrode active material layer. It has characteristics that can be formed.

Hereinafter, preferred embodiments are presented to aid understanding of the present invention. However, the above examples are merely illustrative of the present description, and it is clear to those skilled in the art that various changes and modifications are possible within the scope and technical spirit of the present description, It is natural that such variations and modifications fall within the scope of the attached patent claims.

<제조예><Manufacturing example>

<음극 조성물의 제조><Preparation of negative electrode composition>

Anode compositions satisfying the composition and content in Table 1 below were prepared.

	실리콘계 활물질Silicone-based active material		음극 도전재 cathode conductive material		음극 바인더cathode binder
	종류type	함량content	종류type	함량content	제1 바인더 (함량)1st binder (content)	제2 바인더 (함량)2nd binder (content)	식 1Equation 1
실시예 1Example 1	SiSi	8989	SWCNTSWCNTs	1One	PAM-1 (4.5)PAM-1 (4.5)	SBR-1 (5.5)SBR-1 (5.5)	1.21.2
실시예 2Example 2	SiSi	8989	SWCNTSWCNTs	1One	PAM-2 (4.5)PAM-2 (4.5)	SBR-1 (5.5)SBR-1 (5.5)	1.21.2
실시예 3Example 3	SiSi	8989	SWCNTSWCNTs	1One	PAM-1 (4.5)PAM-1 (4.5)	SBR-2 (5.5)SBR-2 (5.5)	1.21.2
실시예 4Example 4	SiSi	8989	SWCNTSWCNTs	1One	PAM-1 (3.3)PAM-1 (3.3)	SBR-1 (6.7)SBR-1 (6.7)	22
실시예 5Example 5	SiSi	8080	SWCNT/판상형도전재 ASWCNT/plate-type conductive material A	0.4/9.60.4/9.6	PAM-1 (4.5)PAM-1 (4.5)	SBR-1 (5.5)SBR-1 (5.5)	1.21.2
실시예 6Example 6	SiSi	8080	SWCNTSWCNTs	1One	PAM-2 (4.5)PAM-2 (4.5)	SBR-2 (5.5)SBR-2 (5.5)	1.21.2
비교예 1Comparative Example 1	SiSi	8989	SWCNTSWCNTs	1One	PAM-1 (10)PAM-1 (10)	--	--
비교예 2Comparative Example 2	SiSi	8989	SWCNTSWCNTs	1One	--	SBR-1 (10)SBR-1 (10)	--
비교예 3Comparative Example 3	SiSi	8989	SWCNTSWCNTs	1One	PAM-1 (1.6)PAM-1 (1.6)	SBR-1 (8.4)SBR-1 (8.4)	5.255.25
비교예 4Comparative Example 4	SiSi	8989	SWCNTSWCNTs	1One	PAM-1 (6)PAM-1 (6)	SBR-1 (4)SBR-1 (4)	0.660.66
비교예 5Comparative Example 5	SiSi	8989	SWCNTSWCNTs	1One	PAN(5.5)PAN(5.5)	SBR-1 (4.5)SBR-1 (4.5)	0.820.82
비교예 6Comparative Example 6	SiSi	8989	SWCNTSWCNTs	1One	PAM-1 (5.5)PAM-1 (5.5)	SBR-3 (4.5)SBR-3 (4.5)	0.820.82

In Table 1, the silicon-based active material is Si (average particle diameter (D50): 5 μm), and the plate-shaped conductive material A has a BET specific surface area of 17 m ² /g, D10: 1.7 μm, D50: 3.5 μm, D90: 6.8. μm, and for SWCNT, a material with a BET specific surface area of around 1000 to 1500 m ² /g and an aspect ratio of 10000 or more was used.

In addition, in Table 1, as the first binder, PAM-1 is a binder with a Young's modulus of 15x10 ³ MPa (=15GPa), and PAM-2 is a binder with a Young's modulus of 9x10 ³ MPa (9GPa). and PAN has a Young's modulus of 10 ² MPa.

Also, in Table 1, as the second binder, SBR-1 is a binder with a strain of 60%, SBR-2 is a binder with a strain of 40%, and SBR-3 is a binder with a strain of 10%.

At this time, the Young's modulus of the first binder satisfied the above range by adjusting the mixing ratio of PAA and PAN in the binder containing PAM as the main component, and the strain value of the second binder was adjusted by adjusting the ratio of ST/BD in the SBR binder. It was implemented to satisfy the above range.

The weight average molecular weight of the first binder satisfies the level ^of ^5.0 Weight average molecular weight cannot be measured.

In Table 1, the content may refer to the weight ratio (parts by weight) of each composition based on 100 parts by weight of the total negative electrode composition.

음극의 제조Preparation of cathode

A negative electrode slurry was prepared by adding distilled water as a solvent for forming the negative electrode slurry to the negative electrode composition having the composition shown in Table 1 (solids concentration: 25% by weight).

Afterwards, a negative electrode active material layer was coated on 8 μm thick Cu foil at a thickness of 38 μm with a negative electrode loading amount of 76.34 mg/25 cm ² , dried at 130°C for 12 hours, and rolled to a porosity of 40% to form the negative electrode. was manufactured.

<이차전지의 제조><Manufacture of secondary batteries>

LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (average particle diameter (D50): 15㎛) as the positive electrode active material, carbon black (product name: Super C65, manufacturer: Timcal) as the conductive material, and polyvinylidene fluoride (PVdF) as the binder. A positive electrode slurry was prepared by adding N-methyl-2-pyrrolidone (NMP) as a solvent for forming positive electrode slurry at a weight ratio of :1.5:1.5 (solid concentration: 78% by weight).

As a positive electrode current collector, the positive electrode slurry was coated at a loading amount of 537 mg/25 cm ² on both sides of an aluminum current collector (thickness: 12㎛), rolled, and dried in a vacuum oven at 130°C for 10 hours to form a positive electrode. An active material layer (thickness: 65㎛) was formed to prepare a positive electrode (anode thickness: 77㎛, porosity 26%).

A lithium secondary battery was manufactured by interposing a polyethylene separator between the positive electrode and the negative electrode of the examples and comparative examples and injecting electrolyte.

The electrolyte is made by adding 3% by weight of vinylene carbonate based on the total weight of the electrolyte to an organic solvent mixed with fluoroethylene carbonate (FEC) and diethyl carbonate (DMC) at a volume ratio of 10:90, and LiPF as a lithium salt. ₆ was added at a concentration of 1M.

Monocells were manufactured in the same manner as above except that the cathodes of the examples and comparative examples were used, and lifespan characteristics were evaluated in the range of 4.2-3.0V.

실험예 1: 모노셀 상온 수명 특성 평가(25℃, 4.2-3.OV)Experimental Example 1: Evaluation of monocell room temperature lifespan characteristics (25℃, 4.2-3.OV)

The secondary batteries containing the negative electrodes manufactured in the above Examples and Comparative Examples were evaluated for their lifespan using an electrochemical charger and discharger, and the capacity maintenance rate was evaluated. A cycle test was performed on the secondary battery at 4.2-3.0V 1C/0.5C, and the number of cycles was measured when the capacity retention rate reached 80%.

Capacity maintenance rate (%) = {(discharge capacity in Nth cycle)/(discharge capacity in first cycle)} Х 100

The results were as shown in Table 2 below.

실험예 2: 모노셀 저항 증가율 측정 평가(250cycle, @SOC50, 방전)Experimental Example 2: Monocell resistance increase rate measurement evaluation (250cycle, @SOC50, discharge)

In the test in Experimental Example 1, the capacity maintenance rate was measured by charging/discharging (4.2-3.0V) at 0.33C/0.33C every 50 cycles, and then the resistance was measured by discharging at 2.5C pulse at SOC50 to determine the resistance increase rate. A comparative analysis was conducted.

For the evaluation of the resistance increase rate measurement, data at 250 cycles were calculated, and the results are shown in Table 2 below.

실험예 3: 모노셀 고온 수명 특성 평가(45℃, 4.2-3.OV)Experimental Example 3: Evaluation of monocell high temperature lifespan characteristics (45℃, 4.2-3.OV)

The results were as shown in Table 2 below.

실험예 4: 전극 Curl 측정Experimental Example 4: Electrode Curl Measurement

As shown in Figure 3, the degree of bending was measured by placing the coated part of the coated electrode on top and measuring the height of the center. In other words, when the binder dries, the coating becomes concave due to tensile action and thus curl occurs. The degree of curl was measured, and the results are listed in Table 2 below.

	실시예 1Example 1	실시예 2Example 2	실시예 3Example 3	실시예 4Example 4	실시예 5Example 5	실시예 6Example 6	비교예 1Comparative Example 1	비교예 2Comparative Example 2	비교예 3Comparative Example 3	비교예 4Comparative Example 4	비교예 5Comparative Example 5	비교예 6Comparative Example 6
SOH80%(cycle)상온 수명 특성 평가 (4.2-3.0V)SOH80%(cycle) room temperature lifespan characteristics evaluation (4.2-3.0V)	248248	238238	241241	230230	223223	242242	203203	150150	163163	200200	170170	131131
저항 증가율 (%, @250cycle, 방전)resistance increase rate (%, @250cycle, discharge)	4343	4747	4545	5050	5353	6060	100100	200200	130130	105105	120120	300300
SOH80%(cycle)고온 수명 특성 평가 (4.2-3.0V)SOH80%(cycle) high temperature lifespan characteristics evaluation (4.2-3.0V)	230230	218218	--	--	--	--	189189	130130	--	--	--	--
컬 평가(mm)Curl rating (mm)	1313	--	99	77	--	--	2525	--	--	2020	55	--

As in Examples 1 to 6, it contains a first binder and a second binder and satisfies Specific Equation 1. In particular, SBR with a certain range of strain is blended to maintain the contact point between active materials even when the volume expands as the cycle progresses. It was confirmed that the rate of increase in resistance is low, and thus the lifespan performance at room temperature and high temperature is also excellent.

For reference, when comparing Examples 1, 3, and 4 with Comparative Examples 1, 4, and 5, it was confirmed that the higher the ratio of SBR, the less curling of the electrode occurs, which is advantageous for process stability. As in the case of Comparative Example 4, It was confirmed that the curl phenomenon became worse when the ratio of SBR was less than the ratio of this application.

For reference, Comparative Example 1 does not include the second binder, Comparative Example 2 does not include the first binder, and Comparative Example 3 includes the first and second binders, but the content range is Equation 1 exceeds the range of, Comparative Example 4 corresponds to a case where it is below the range of Equation 1, Comparative Example 5 corresponds to a case where the range of Equation 1 is satisfied but the Young's modulus of the first binder is below the range of the present application, and Comparative Example 6 is This applies to a case where the range of Equation 1 is satisfied but the strain of the second binder is less than the range of this application.

When each of the Comparative Examples 1 to 6 was confirmed, it was confirmed that the lifespan characteristics were lower and the resistance increase rate was higher compared to Examples 1 to 6 according to the present application, and it was also confirmed that the curl phenomenon occurred a lot. .

That is, the anode composition according to the present application includes first and second binders of a specific composition to improve dispersibility for dispersing the active material and improve adhesion even when using a silicon-based active material. It was confirmed that the problem of conductive network disconnection due to early and late adhesion and volume expansion of the battery can be solved.

In other words, it was confirmed that the negative electrode composition according to the present application has a high content of silicon-based active material particles to obtain a negative electrode with high capacity and high density, and at the same time solves problems such as volume expansion due to the high content of silicon-based active material particles.

Claims

Silicone-based active material; cathode conductive material; A negative electrode composition comprising: and a negative electrode binder,

The cathode binder includes a first binder having a Young's modulus of 10 3 MPa or more and a second binder having a strain of 15% or more,

A negative electrode composition in which the negative electrode binder satisfies the following formula 1:

[Equation 1]

1 ≤ X/Y < 4

In equation 1 above,

Y refers to parts by weight of the first binder based on 100 parts by weight of the negative electrode binder,

X refers to parts by weight of the second binder based on 100 parts by weight of the anode binder.
In claim 1,

The X is 50 parts by weight or more and 95 parts by weight or less based on 100 parts by weight of the negative electrode binder,

A negative electrode composition wherein Y is in an amount of 5 parts by weight or more and 50 parts by weight or less based on 100 parts by weight of the negative electrode binder.
In claim 1,

A negative electrode composition wherein the negative electrode binder is contained in an amount of 1 part by weight or more and 20 parts by weight or less based on 100 parts by weight of the negative electrode composition.
In claim 1,

The first binder includes at least one selected from the group consisting of PAA, PAN, and PAM,

The negative electrode composition wherein the second binder is a rubber-based binder.
In claim 1,

The silicon-based active material is an anode composition in an amount of 60 parts by weight or more based on 100 parts by weight of the anode composition.
In claim 1,

A negative electrode composition wherein the silicon-based active material includes one or more selected from the group consisting of SiOx (x=0), SiOx (0<x<2), SiC, and Si alloy.
The method of claim 1, wherein the silicon-based active material includes one or more selected from the group consisting of SiOx (x=0) and SiOx (0<x<2), and based on 100 parts by weight of the silicon-based active material, the SiOx (x=0) A negative electrode composition comprising 70 parts by weight or more.
In claim 1,

The anode conductive material is in an amount of 0.1 part by weight or more and 40 parts by weight or less based on 100 parts by weight of the anode composition.
In claim 1,

The cathode conductive material is a point-shaped conductive material; Planar conductive material; and a negative electrode composition comprising at least one selected from the group consisting of linear conductive materials.
In claim 9,

The negative electrode conductive material is 80 parts by weight or more and 99.9 parts by weight or less of the planar conductive material based on 100 parts by weight of the negative electrode conductive material; And a negative electrode composition comprising 0.1 part by weight or more and 20 parts by weight or less of the linear conductive material.
The anode composition according to claim 1, wherein the weight average molecular weight of the first binder is 100,000 g/mol or more and 2,000,000 g/mol or less.
Negative current collector layer; and

a negative electrode active material layer comprising the negative electrode composition according to any one of claims 1 to 11 formed on one or both sides of the negative electrode current collector layer;

A negative electrode for a lithium secondary battery containing.
In claim 12,

A negative electrode for a lithium secondary battery, wherein the adhesive strength of the surface of the negative electrode active material layer in contact with the negative electrode current collector layer satisfies 100 gf/5mm or more and 500 gf/5mm or less under normal pressure conditions at 25°C.
In claim 12,

The thickness of the negative electrode current collector layer is 1 μm or more and 100 μm or less,

A negative electrode for a lithium secondary battery, wherein the thickness of the negative electrode active material layer is 20 μm or more and 500 μm or less.
anode;

Negative electrode for lithium secondary battery according to claim 12;

A separator provided between the anode and the cathode; and

A lithium secondary battery containing an electrolyte.