Anode slurry, method for producing anode slurry, anode for lithium secondary battery including anode slurry, and method for producing anode for lithium secondary battery

Abstract

The present application relates to a negative electrode slurry, a method for producing the negative electrode slurry, a negative electrode for a lithium secondary battery including the negative electrode slurry, and a method for producing a negative electrode for a lithium secondary battery.

Description

[Technical Field]

[0001] This application claims the benefit of the filing date of Korean Patent Application No. 10-2022-0037218, filed with the Korean Intellectual Property Office on March 25, 2022, the entire contents of which are incorporated herein by reference.

[0002] The present application relates to a negative electrode slurry, a method for producing the negative electrode slurry, a negative electrode for a lithium secondary battery including the negative electrode slurry, and a method for producing a negative electrode for a lithium secondary battery. [Background technology]

[0003] The rapid increase in fossil fuel use has led to an increasing demand for alternative and clean energy, and one of the most actively researched fields in this area is the field of power generation and storage using electrochemical reactions.

[0004] Currently, a typical example of an electrochemical element that uses such electrochemical energy is a secondary battery, and the range of its use is tending to expand more and more.

[0005] As technological development and demand for mobile devices increase, the demand for secondary batteries as energy sources is rapidly increasing. Among these secondary batteries, lithium secondary batteries, which have high energy density and voltage, long cycle life, and low self-discharge rate, have been commercialized and widely used. In addition, active research is being conducted on methods for manufacturing high-density electrodes with higher energy density per unit volume as electrodes for such high-capacity lithium secondary batteries.

[0006] Generally, a secondary battery is composed of a positive electrode, a negative electrode, an electrolyte, and a separator. The negative electrode contains a negative electrode active material that inserts and extracts lithium ions from the positive electrode. Silicon-based particles with a large discharge capacity can be used as the negative electrode active material.

[0007] In particular, with the recent demand for high-density energy batteries, Si / C and SiO, which have capacities 10 times larger than graphite-based materials, are being used as negative electrode active materials. x However, silicon-based compounds, which are high-capacity materials, have a higher capacity than conventionally used graphite, but they suffer from a problem that their volume expands rapidly during charging, cutting off the conductive path and degrading battery performance.

[0008] Furthermore, in the case of a silicon-based negative electrode having a large capacity to satisfy the requirement for fast charging, the coating thickness of the negative electrode active material layer may be formed to be very thin compared to a carbon-based negative electrode. In this case, since silicon-based materials have hard properties compared to soft carbon-based materials, when a negative electrode including a silicon-based active material is manufactured, there is a problem that coating is not performed during the electrode manufacturing process, or even if coating is performed, a defective negative electrode is manufactured.

[0009] Therefore, attempts have been made to manufacture a negative electrode using a silicon-based negative electrode to enhance capacity characteristics, while also manufacturing a negative electrode with a thin negative electrode active material layer to satisfy the requirements for rapid charging. However, due to the problems described above, it is still not easy at present to manufacture a negative electrode that is capable of both capacity characteristics and rapid charging.

[0010] In other words, when soft carbon-based materials are used, the thickness of the negative electrode active material layer can be made thin for rapid charging, but the electrode becomes thinner, and the carbon-based material has a capacity 10 times less than that of silicon-based materials, so the capacity characteristics are not demonstrated.In the case of silicon-based negative electrodes, although the capacity characteristics can be ensured, it is difficult to form a thin electrode due to the process, which causes problems with rapid charging.

[0011] Therefore, when fabricating a silicon-based anode to maximize capacity characteristics, research is needed on a method that minimizes changes in the composition and content of the anode while minimizing the thickness of the silicon-based anode to achieve fast charging effects. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-080971 Summary of the Invention [Problem to be solved by the invention]

[0013] In silicon-based anodes, it is difficult to significantly change the composition and content of the anode active material layer composition in order to suppress volume expansion during charge and discharge and maximize capacity characteristics. Silicon-based anodes are characterized by the use of high-capacity materials, but when the electrode is formed thin due to material characteristics, defects occur during the battery fabrication process. As a result of research into forming a silicon-based anode thin for fast charging, we found that the above-mentioned problems can be solved by controlling the particle size distribution of the anode slurry used in the anode fabrication process, without significantly changing the composition of the anode active material layer.

[0014] Therefore, the present application relates to a negative electrode slurry, a method for producing the negative electrode slurry, a negative electrode for a lithium secondary battery including the negative electrode slurry, and a method for producing a negative electrode for a lithium secondary battery. [Means for solving the problem]

[0015] One embodiment of the present specification provides a negative electrode slurry comprising: a negative electrode active material layer composition; and a solvent; wherein the negative electrode active material layer composition comprises a silicon-based active material; a negative electrode conductive material; and a negative electrode binder; and the negative electrode slurry has a negative electrode slurry particle size (grinding gauge) Dmin of 8 μm or less and Dmax of 7 μm or more and 30 μm or less.

[0016] In another embodiment, there is provided a method for producing an anode slurry, the method including: mixing an anode conductive material and an anode binder to form a mixture; adding a solvent to the mixture to perform a first mixing; and adding a silicon-based active material to the mixed mixture to perform a second mixing; wherein the first and second mixing steps include mixing at 2,000 rpm to 3,000 rpm for 10 to 60 minutes, and the anode slurry has a Dmin of 8 μm or less and a Dmax of 7 μm or more and 30 μm or less.

[0017] In yet another embodiment, there is provided a negative electrode for a lithium secondary battery, comprising: a negative electrode current collector layer; and a negative electrode active material layer provided on one or both surfaces of the negative electrode current collector layer; wherein the negative electrode active material layer comprises the negative electrode slurry according to the present application or a dried product thereof.

[0018] Finally, there is provided a method for manufacturing a negative electrode for a lithium secondary battery, the method including the steps of: preparing a negative electrode current collector layer; coating one or both surfaces of the negative electrode current collector layer with the negative electrode slurry according to the present application to form a negative electrode coating layer; drying the negative electrode coating layer; and rolling the negative electrode coating layer to form a negative electrode active material layer. [Effects of the Invention]

[0019] In the case of the negative electrode slurry according to the present application, the particle size (grind gauge) of the negative electrode slurry satisfies the requirement that the Dmin of the negative electrode slurry is 8 μm or less and the Dmax is 7 μm or more and 30 μm or less. In the case of silicon-based negative electrodes, although the capacity characteristics are excellent, it is important to form the electrode thin for rapid charging. When the particle size value of the negative electrode slurry according to the present application satisfies the above range, the coating thickness of the negative electrode slurry is formed thin, thereby achieving the characteristic of being able to secure a negative electrode for a lithium secondary battery that has excellent capacity characteristics and is also capable of rapid charging.

[0020] The main purpose of the negative electrode slurry according to the present application is to solve the above problems by adjusting the particle size of the negative electrode slurry itself, rather than adjusting the viscosity of the slurry to prevent particle aggregation, etc. That is, rather than adjusting the types and contents of the negative electrode active material, negative electrode binder, and negative electrode conductive material contained in the negative electrode slurry, the particle size contained in the negative electrode slurry is adjusted to improve capacity characteristics and fast charging characteristics.

[0021] In other words, in the case of the negative electrode for a lithium secondary battery according to the present application, the volume expansion and contraction due to charging and discharging, which is a problem associated with using a silicon-based active material, can be suppressed by the use of a highly rigid aqueous binder, and further, the particle size of the negative electrode slurry satisfies the above range, allowing the thickness of the electrode to be controlled to be thin. As a result, the negative electrode has the advantages of high capacity and high output, which are the advantages of a silicon-based negative electrode, as well as the ability to be rapidly charged. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a diagram showing a laminated structure of a negative electrode for a lithium secondary battery according to an embodiment of the present application. [Figure 2] FIG. 1 is a diagram showing a stack structure of a lithium secondary battery according to an embodiment of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0023] Before describing the present invention, some terms will first be defined.

[0024] In this specification, when a part is said to "comprise" a certain component, this means that it may further include other components, rather than excluding other components, unless otherwise specified.

[0025] In this specification, "p to q" means a range of "not less than p and not more than q."

[0026] In this specification, the "specific surface area" is measured by the BET method, and specifically, is calculated from the amount of nitrogen gas adsorption at liquid nitrogen temperature (77 K) using a BELSORP-mini II manufactured by BEL Japan Co., Ltd. That is, in the present application, the BET specific surface area may mean the specific surface area measured by the above-mentioned measurement method.

[0027] In this specification, "Dn" refers to particle size distribution, and refers to the particle size at the n% point of the cumulative particle number distribution corresponding to the particle size. That is, D50 is the particle size (median particle size) at the 50% point of the cumulative particle number distribution corresponding to the particle size, D90 is the particle size at the 90% point of the cumulative particle number distribution corresponding to the particle size, and D10 is the particle size at the 10% point of the cumulative particle number distribution corresponding to the particle size. Meanwhile, the median particle size can be measured using the laser diffraction method. Specifically, the powder to be measured is dispersed in a dispersion medium and then introduced into a commercially available laser diffraction particle size analyzer (e.g., Microtrac S3500). The particle size distribution is calculated by measuring the difference in diffraction patterns corresponding to the particle size when the particles pass through a laser beam.

[0028] In one embodiment of the present application, the particle size or particle size may refer to the average diameter or typical diameter of individual grains that make up the particle.

[0029] In this specification, when a polymer contains a certain monomer as a monomer unit, it means that the monomer participates in a polymerization reaction and is contained as a repeating unit in the polymer. In this specification, when a polymer contains a monomer, this is interpreted as the same as when a polymer contains the monomer as a monomer unit.

[0030] In this specification, the term "polymer" is understood to be used in a broad sense, including copolymers, unless otherwise specified as a "homopolymer."

[0031] In this specification, the weight average molecular weight (Mw) and number average molecular weight (Mn) are polystyrene-equivalent molecular weights measured by gel permeation chromatography (GPC) using commercially available monodisperse polystyrene polymers (standard samples) with various degrees of polymerization as standard substances for molecular weight measurement. In this specification, molecular weight means weight average molecular weight unless otherwise specified.

[0032] The present invention will now be described in detail with reference to the accompanying drawings so that those skilled in the art can easily practice the present invention, although the present invention may be embodied in various different forms and is not limited to the following description.

[0033] One embodiment of the present specification provides a negative electrode slurry comprising: a negative electrode active material layer composition; and a solvent; wherein the negative electrode active material layer composition comprises a silicon-based active material; a negative electrode conductive material; and a negative electrode binder; and the negative electrode slurry has a negative electrode slurry particle size (grind gauge) of Dmin of 8 μm or less and Dmax of 7 μm or more and 30 μm or less.

[0034] In the case of the negative electrode slurry according to the present application, the particle size (grind gauge) of the negative electrode slurry satisfies the requirement that the Dmin of the negative electrode slurry is 8 μm or less and the Dmax is 7 μm or more and 30 μm or less. In the case of silicon-based negative electrodes, although the capacity characteristics are excellent, it is important to form the electrode thin for rapid charging. When the particle size value of the negative electrode slurry according to the present application satisfies the above range, the coating thickness of the negative electrode slurry is formed thin, thereby achieving the characteristic of being able to secure a negative electrode for a lithium secondary battery that has excellent capacity characteristics and is also capable of rapid charging.

[0035] In one embodiment of the present application, the negative electrode slurry particle size (grind gauge) refers to the particle size of secondary particles formed by aggregation of primary particles contained in the negative electrode slurry, and specifically may refer to the particle size of secondary particles formed by aggregation of one or more particles selected from the group consisting of a negative electrode active material, a negative electrode conductive material, and a negative electrode binder contained in the negative electrode slurry.

[0036] In this case, the particle size of the negative electrode slurry is indicated by a value that allows particle size measurement and can be measured using a measuring device with fine grooves according to size. Specifically, 5 mL of the prepared negative electrode slurry is poured at the 0 μm reference point, and then a steel bar, which is a secondary measuring device, is slid along the grooves. Depending on the size of the slurry particles, measurements are taken starting from the smallest value (Dmin) and ending with the largest value (Dmax), and these values ​​are set as the Dmin and Dmax values ​​to measure the particle size of the slurry.

[0037] In this regard, in one embodiment of the present application, the Dmin of the particle size (grind gauge) of the negative electrode slurry means the particle size of the smallest particle in the negative electrode slurry, and the Dmax of the particle size (grind gauge) of the negative electrode slurry may mean the particle size of the largest particle in the negative electrode slurry, but may include some error.

[0038] In one embodiment of the present application, the negative electrode slurry particle size (grind gauge) may have a Dmin of 8 μm or less and a Dmax of 7 μm or more and 30 μm or less.

[0039] In another embodiment, the Dmin of the negative electrode slurry particle size (grind gauge) may be in the range of 8 μm or less, preferably 7.5 μm or less, more preferably 7 μm or less, and most preferably 6 μm or less. The lower limit of the range is not particularly limited, but may be in the range of 0.1 μm or more, preferably 1 μm or more.

[0040] In another embodiment, the negative electrode slurry particle size (grind gauge) Dmax may be in the range of 7 μm or more and 30 μm or less, preferably 7 μm or more and 25 μm or less, more preferably 7 μm or more and 20 μm or less, and most preferably 7 μm or more and 15 μm or less.

[0041] In one embodiment of the present application, there is provided a negative electrode slurry, wherein the negative electrode slurry has an average particle size (D50) value of 5 μm or more and 20 μm or less.

[0042] As described above, by adjusting the particle size range of the negative electrode slurry, even if a silicon-based active material having high rigidity is included, a thin negative electrode active material layer can be formed by adjusting the particle size range of the negative electrode slurry, thereby achieving a fast charging effect. As a result, a high-quality electrode can be obtained, and a negative electrode without problems such as the generation of electrode lines can be obtained.

[0043] In one embodiment of the present application, the negative electrode slurry may include a negative electrode active material layer composition; and a solvent.

[0044] In one embodiment of the present application, the solid content of the negative electrode slurry may be 5% or more and 40% or less.

[0045] In another embodiment, the solid content of the negative electrode slurry may be in the range of 5% to 40%, preferably 7% to 35%, more preferably 10% to 30%.

[0046] The solid content of the negative electrode slurry refers to the content of the negative electrode active material layer composition contained in the negative electrode slurry, and may refer to the content of the negative electrode active material layer composition based on 100 parts by weight of the negative electrode slurry.

[0047] When the solid content of the negative electrode slurry satisfies the above range, the viscosity is suitable during the formation of the negative electrode active material layer, and particle aggregation of the negative electrode active material layer composition is minimized, thereby enabling the negative electrode active material layer to be efficiently formed.

[0048] In one embodiment of the present application, the solvent may be any solvent that can dissolve the negative electrode active material layer composition, and specifically, water, acetone, or NMP may be used.

[0049] In one embodiment of the present application, the weight loading of the negative electrode slurry is 80 mg / 25 cm 2 More than 160mg / 25cm 2 The following negative electrode for a lithium secondary battery is provided:

[0050] In another embodiment, the weight loading (B1) of the negative electrode slurry is 80 mg / 25 cm 2 More than 160mg / 25cm 2 Less than 85 mg / 25 cm 2 More than 140mg / 25cm 2 Less than 85mg / 25cm, more preferably 2 Over 130mg / 25cm 2 The following ranges may be satisfied:

[0051] The weight loading of the negative electrode slurry may refer to the amount of negative electrode slurry applied to the negative electrode current collector layer. When the weight loading of the negative electrode slurry satisfies the above range, the performance characteristics (capacity, output) of the negative electrode can be maximized. In addition, when the particle size range of the negative electrode slurry is satisfied, the capacity characteristics are maintained and the electrode can be formed thin, thereby achieving the advantage of fast charging.

[0052] In one embodiment of the present application, the viscosity of the negative electrode slurry may be in the range of 1,000 cP to 10,000 cP.

[0053] In another embodiment, the viscosity of the negative electrode slurry may be 3,000 cP or more and 10,000 cP or less, preferably 3,000 cP or more and 7,000 cP or less.

[0054] As described above, the particle size distribution of the negative electrode slurry satisfies the above range, and the viscosity is adjusted by the dispersion process described below to satisfy the above viscosity range, which improves subsequent mixing and thereby improves the output of the secondary battery.

[0055] The silicon-based active material, negative electrode conductive material, and binder contained in the negative electrode active material layer composition contained in the negative electrode slurry will be described below.

[0056] In one embodiment of the present application, the negative electrode slurry includes a negative electrode active material layer composition; and a solvent; and the negative electrode active material layer composition may include a silicon-based active material; a negative electrode conductive material; and a negative electrode binder.

[0057] In one embodiment of the present application, the silicon-based active material is SiO x (x = 0), SiO x (0 < x < 2), SiC, and at least one selected from the group consisting of Si alloys, to provide a negative electrode slurry.

[0058] In one embodiment of the present application, the silicon-based active material is SiO x (x = 0), SiO x (0 < x < 2), and based on 100 parts by weight of the silicon-based active material, the SiO x (x = 0) may be included in an amount of 70 parts by weight or more.

[0059] In another embodiment, based on 100 parts by weight of the silicon-based active material, the SiO x (x = 0) may be included in an amount of 70 parts by weight or more, preferably 80 parts by weight or more, more preferably more than 90 parts by weight, and may be included in an amount of 100 parts by weight or less, preferably 99 parts by weight or less, more preferably 95 parts by weight or less.

[0060] In one embodiment of the present application, particularly pure silicon (Si) may be used as the silicon-based active material. Using particularly pure silicon (Si) as the silicon-based active material means that, as described above, when based on a total of 100 parts by weight of the silicon-based active material, pure Si (SiO x (x = 0)) not bonded to other particles or elements is included within the above range.

[0061] Meanwhile, the average particle size (D50) of the silicon-based active material of the present invention may be 5 μm to 10 μm, specifically 5.5 μm to 8 μm, and more specifically 6 μm to 7 μm. When the average particle size is within the above range, the specific surface area of ​​the particles is within an appropriate range, and the viscosity of the negative electrode slurry is formed within an appropriate range. This allows for smooth dispersion of the particles constituting the negative electrode slurry. Furthermore, when the size of the silicon-based active material is equal to or greater than the above lower limit range, the contact area between the silicon particles and the conductive material is improved by the composite of the conductive material and the binder in the negative electrode slurry, increasing the likelihood of maintaining the conductive network and improving the capacity retention rate. Meanwhile, when the average particle size is within the above range, excessively large silicon particles are excluded, resulting in a smooth negative electrode surface, thereby preventing non-uniform current density during charge and discharge.

[0062] In one embodiment of the present application, the silicon-based active material generally has a characteristic BET specific surface area. The BET specific surface area of ​​the silicon-based active material is preferably 0.01 m 2 / g~150.0m 2 / g, more preferably 0.1m 2 / g~100.0m 2 / g, particularly preferably 0.2m 2 / g~80.0m 2 / g, most preferably 0.2m 2 / g~18.0m 2 / g. The BET specific surface area is determined in accordance with DIN 66131 (using nitrogen).

[0063] In one embodiment of the present application, silicon-based active material can be, for example, in crystalline or amorphous form, and is preferably non-porous.Silicon particles are preferably spherical or shard particles.Alternatively, but less advantageously, silicon particles can have a fibrous structure or be in the form of silicon-containing film or coating.

[0064] In one embodiment of the present application, there is provided a negative electrode slurry, in which the silicon-based active material is 60 parts by weight or more based on 100 parts by weight of the negative electrode active material layer composition.

[0065] In another embodiment, the silicon-based active material may be included in an amount of 60 parts by weight or more, preferably 65 parts by weight or more, more preferably 70 parts by weight or more, based on 100 parts by weight of the negative electrode active material layer composition, and may be included in an amount of 95 parts by weight or less, preferably 90 parts by weight or less, more preferably 85 parts by weight or less.

[0066] In one embodiment of the present application, the silicon-based active material may have a non-spherical shape, and the 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.

[0067] In this application, the circularity is determined by the following formula 1, where A is the area and P is the perimeter. [Formula 1] 4πA / P 2

[0068] While graphite-based compounds have traditionally been used exclusively as negative electrode active materials, attempts to incorporate silicon-based active materials into batteries to increase capacity have been increasing in recent years as demand for high-capacity batteries has grown. However, even if the properties of silicon-based active materials are partially adjusted as described above, their volume can rapidly expand during charge / discharge processes, potentially damaging the conductive paths formed in the negative electrode active material layer.

[0069] Therefore, in one embodiment of the present application, the negative electrode conductive material may include one or more selected from the group consisting of dot-shaped conductive materials, sheet-shaped conductive materials, and linear conductive materials.

[0070] In one embodiment of the present application, the dot-like conductive material refers to a spherical or dot-like conductive material that can be used to improve the conductivity of a negative electrode, does not induce chemical changes, and is conductive. Specifically, the dot-like conductive material may be at least one selected from the group consisting of natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, conductive fiber, fluorocarbon, aluminum powder, nickel powder, zinc oxide, potassium titanate, titanium oxide, and polyphenylene derivatives, and preferably includes carbon black in order to achieve high conductivity and excellent dispersibility.

[0071] In one embodiment of the present application, the point-like conductive material has a BET specific surface area of ​​40 m 2 / g or more 70m 2 / g or less, preferably 45m 2 / g or more 65m 2 / g or less, more preferably 50m 2 / g or more 60m 2 / g or less.

[0072] In one embodiment of the present application, the dot-like conductive material may have 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.

[0073] In particular, when the content of functional groups in the dot-like conductive material satisfies the above range, functional groups are present on the surface of the dot-like conductive material, and when water is used as a solvent, the dot-like conductive material can be smoothly dispersed in the solvent.

[0074] In one embodiment of the present application, the silicon-based active material is characterized by including a dot-like conductive material having a functional group content within the above range, and the content of the functional group can be adjusted depending on the degree of heat treatment of the dot-like conductive material.

[0075] In one embodiment of the present application, the particle size of the dotted conductive material may be 10 nm to 100 nm, preferably 20 nm to 90 nm, and more preferably 20 nm to 60 nm.

[0076] In one embodiment of the present application, the conductive material may include a sheet-shaped conductive material.

[0077] The sheet-like conductive material can improve conductivity by increasing surface contact between silicon particles in the negative electrode and can also serve to prevent the conductive path from being disconnected due to volume expansion, and can be referred to as a plate-like conductive material or a bulk-like conductive material.

[0078] In one embodiment of the present application, the sheet-like conductive material may include at least one selected from the group consisting of platelet graphite, graphene, graphene oxide, and graphite flakes, and may preferably be platelet graphite.

[0079] In one embodiment of the present application, the average particle size (D50) of the sheet-shaped conductive material may be 2 μm to 7 μm, specifically 3 μm to 6 μm, and more specifically 4 μm to 5 μm. When the above range is satisfied, the sufficient particle size does not cause an excessive increase in viscosity of the negative electrode slurry, and dispersion is easy. Therefore, excellent dispersion effect is achieved when dispersing using the same device and for the same time.

[0080] In one embodiment of the present application, there is provided a negative electrode active material layer composition, wherein the sheet-shaped conductive material has a D10 of 0.5 μm or more and 1.5 μm or less, a D50 of 2.5 μm or more and 3.5 μm or less, and a D90 of 7.0 μm or more and 15.0 μm or less.

[0081] In one embodiment of the present application, the sheet-shaped conductive material may be a sheet-shaped conductive material having a high BET specific surface area; or a sheet-shaped conductive material having a low specific surface area.

[0082] In one embodiment of the present application, the sheet-like conductive material may be a sheet-like conductive material with a high specific surface area or a sheet-like conductive material with a low specific surface area, without any restrictions. However, since dispersion may have some effect on electrode performance, it is particularly preferable to use a sheet-like conductive material with a low specific surface area in which dispersion does not cause problems.

[0083] In one embodiment of the present application, the sheet-shaped conductive material has a BET specific surface area of ​​5 m 2 / g or more.

[0084] In another embodiment, the sheet-shaped conductive material has a BET specific surface area of ​​5 m 2 / g or more 500m 2 / g or less, preferably 5m 2 / g or more 300m 2 / g or less, more preferably 5m 2 / g or more 250m 2 / g or less.

[0085] In another embodiment, the sheet-shaped conductive material is a sheet-shaped conductive material having a high specific surface area, and a BET specific surface area of ​​50 m 2 / g or more 500m 2 / g or less, preferably 80m 2 / g or more 300m 2 / g or less, more preferably 100m 2 / g or more 300m 2 / g or less.

[0086] In yet another embodiment, the sheet-shaped conductive material is a sheet-shaped conductive material having a low specific surface area, and a BET specific surface area of ​​5 m 2 / g or more 40m 2 / g or less, preferably 5m 2 / g or more 30m 2 / g or less, more preferably 5m 2 / g or more 25m 2 / g or less.

[0087] Other conductive materials include linear conductive materials such as carbon nanotubes. The carbon nanotubes may be bundled carbon nanotubes. The bundled carbon nanotubes may include multiple carbon nanotube units. Specifically, unless otherwise specified, the term "bundle type" refers to a secondary shape in which multiple carbon nanotube units are arranged side by side or entangled with each other, in a bundle or rope-like configuration. The carbon nanotube units each have a cylindrical graphite sheet with a nanometer-sized diameter and an sp2 bonding structure. Depending on the angle and structure of the graphite sheet, the bundled carbon nanotubes can exhibit conductive or semiconductive properties. Compared to entangled carbon nanotubes, the bundled carbon nanotubes can be more uniformly dispersed during negative electrode fabrication, smoothly forming a conductive network within the negative electrode and improving the conductivity of the negative electrode.

[0088] In one embodiment of the present application, the linear conductive material may include SWCNT; or MWCNT.

[0089] In one embodiment of the present application, the negative electrode conductive material may be 5 parts by weight or more and 40 parts by weight or less based on 100 parts by weight of the negative electrode active material layer composition.

[0090] In another embodiment, the negative electrode conductive material may be contained in an amount of 5 parts by weight or more and 40 parts by weight or less, preferably 10 parts by weight or more and 30 parts by weight or less, and more preferably 10 parts by weight or more and 25 parts by weight or less, based on 100 parts by weight of the negative electrode active material layer composition.

[0091] In one embodiment of the present application, a negative electrode slurry is provided, wherein the negative electrode conductive material includes a sheet-shaped conductive material and a linear conductive material.

[0092] In one embodiment of the present application, the negative electrode conductive material includes a sheet-like conductive material and a linear conductive material, and may include 0.01 parts by weight or more and 10 parts by weight or less of the linear conductive material and 90 parts by weight or more and 99.99 parts by weight or less of the sheet-like conductive material, based on 100 parts by weight of the negative electrode conductive material.

[0093] In another embodiment, the linear conductive material may be 0.01 parts by weight or more and 10 parts by weight or less, preferably 0.05 parts by weight or more and 5 parts by weight or less, and more preferably 0.1 parts by weight or more and 3 parts by weight or less, based on 100 parts by weight of the negative electrode conductive material.

[0094] In another embodiment, the sheet-shaped conductive material may be 90 parts by weight or more and 99.99 parts by weight or less, preferably 95 parts by weight or more and 99.95 parts by weight or less, and more preferably 97 parts by weight or more and 99.9 parts by weight or less, based on 100 parts by weight of the negative electrode conductive material.

[0095] In particular, in one embodiment of the present application, the negative electrode conductive material includes a sheet-like conductive material and a linear conductive material, and by satisfying the above-mentioned compositions and proportions, the battery does not have a significant effect on the life characteristics of conventional lithium secondary batteries, and the number of points at which charging and discharging are possible increases, resulting in excellent output characteristics at high C-rates.

[0096] The negative electrode conductive material according to the present application has a completely different structure from the positive electrode conductive material used in the positive electrode. That is, the negative electrode conductive material according to the present application serves to form a contact between silicon-based active materials, which undergo a very large volume expansion of the electrode upon charging and discharging, while the positive electrode conductive material serves as a buffer that has a shock-absorbing function during rolling and also serves to impart some conductivity, and therefore has a completely different structure and role from the negative electrode conductive material of the present invention.

[0097] Furthermore, 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 conductive materials applied to graphite-based active materials. That is, conductive materials used in electrodes having graphite-based active materials simply have smaller particles than the active material, and therefore have the properties of improving output characteristics and imparting some conductivity, and are completely different in structure and role from negative electrode conductive materials applied together with silicon-based active materials as in the present invention.

[0098] In one embodiment of the present application, the dot-like conductive material used as the negative electrode conductive material has a structure and function different from that of a carbon-based active material generally used as a conventional negative electrode active material. Specifically, the carbon-based active material used as the negative electrode active material may be artificial graphite or natural graphite, and refers to a material that is processed into a spherical or dot-like shape to facilitate the storage and release of lithium ions.

[0099] In contrast, the sheet-like conductive material used as the negative electrode conductive material is a material having a sheet or plate shape and can be expressed as plate-like graphite. That is, it is a material contained in the negative electrode active material layer to maintain a conductive path, and does not play a role in storing and releasing lithium, but refers to a material that ensures a conductive path in a sheet shape inside the negative electrode active material layer.

[0100] That is, in this application, the term "plate-shaped graphite is used as a conductive material" means that the graphite is processed into a sheet or plate shape and used as a material to ensure a conductive path rather than to store or release lithium. In this case, the negative electrode active material contained therein has high capacity characteristics for storing and releasing lithium, and serves to store and release all lithium ions transferred from the positive electrode.

[0101] In contrast, in the present application, the term "carbon-based active material is used as an active material" means that the carbon-based active material is processed into a dotted or spherical shape and used as a material that stores or releases lithium.

[0102] That is, in one embodiment of the present application, the carbon-based active material, artificial graphite or natural graphite, is in a dot-like shape and has a BET specific surface area of ​​0.1 m 2 / g or more 4.5m 2 The sheet-shaped conductive material, plate-shaped graphite, may have a sheet shape and a BET specific surface area of ​​5 m 2 / g or more.

[0103] In one embodiment of the present application, the negative electrode binder may include at least one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, polyacrylic acid, and substances in which hydrogen is substituted with Li, Na, Ca, or the like, or may include various copolymers thereof.

[0104] The negative electrode binder according to one embodiment of the present application plays a role in holding the active material and the conductive material together to prevent distortion and structural deformation of the negative electrode structure when the volume of the silicon-based active material expands and relaxes. As long as the binder fulfills the above role, any common binder can be used. Specifically, a water-based binder may be used, and more specifically, a PAM-based binder may be used.

[0105] In one embodiment of the present application, there is provided a negative electrode slurry, wherein the negative electrode binder includes a water-based binder, and the negative electrode binder is in an amount of 5 parts by weight to 15 parts by weight based on 100 parts by weight of the negative electrode active material layer composition.

[0106] In another embodiment, the amount of the negative electrode binder may be 5 parts by weight or more and 15 parts by weight or less, preferably 7 parts by weight or more and 13 parts by weight or less, and more preferably 10 parts by weight or more and 12 parts by weight or less, based on 100 parts by weight of the negative electrode active material layer composition.

[0107] The negative electrode slurry according to the present application uses a silicon-based active material to maximize capacity characteristics, and exhibits greater volume expansion during charge and discharge than conventional carbon-based active materials. Conventional carbon-based active materials have low volume expansion, so rubber-based binders with low rigidity have been used, and the binder content has been low, making the binder in silicon-based negative electrodes unimportant.

[0108] However, in order to suppress the expansion of the volume of the silicon-based active material, the aqueous binder as described above, which has high rigidity, is used. As a result, by having the above range, the expansion of the volume of the silicon-based active material due to charging and discharging can be effectively prevented, and the conductive material can be easily dispersed.

[0109] In one embodiment of the present application, there is provided a method for producing a negative electrode slurry, the method including the steps of: mixing a negative electrode conductive material and a negative electrode binder to form a mixture; adding a solvent to the mixture to perform a first mixing; and adding a silicon-based active material to the mixed mixture to perform a second mixing; wherein the first mixing and second mixing steps include mixing at 2,000 rpm to 3,000 rpm for 10 minutes to 60 minutes, and the negative electrode slurry has a negative electrode slurry particle size (grind gauge e) of Dmin of 8 μm or less and Dmax of 7 μm or more and 30 μm or less.

[0110] The above description of the negative electrode slurry may be applied to each description of the method for producing the negative electrode slurry.

[0111] In one embodiment of the present application, there is provided a method for producing a negative electrode slurry, in which the mixing temperature in the first mixing and second mixing steps is 50°C or less. Here, the temperature in the mixing step refers to the temperature of the negative electrode slurry itself, and the mixing temperature may be 50°C or less, preferably 40°C or less, and more preferably 30°C or less, or 20°C or more.

[0112] In one embodiment of the present application, the viscosity of the negative electrode slurry in the production process is not limited as long as it is at a level that allows the process, and specifically may be in the range of 1000 cP to 15000 cP, more specifically may be in the range of 4000 cP to 8000 cP. In this case, the viscosity may refer to the viscosity of the negative electrode slurry itself in the production process of the negative electrode slurry.

[0113] That is, in the manufacturing process of the negative electrode slurry as described above, by adjusting the conditions of the mixing process, the temperature conditions of the negative electrode slurry, and the viscosity conditions of the negative electrode slurry to specific ranges, it is possible to adjust the range of the negative electrode slurry particle size (grind gauge) of the negative electrode slurry according to the present application to a specific range.

[0114] As a result, the particle size (grind gauge) range of the anode slurry according to the present invention is not changed by adjusting only one factor, but rather the present application has identified an optimal particle size (grind gauge) range based on multiple factors, such as the composition and content (material properties) of the anode composition contained in the anode slurry and the processing conditions of the anode slurry (temperature, mixing conditions, viscosity), which corresponds to the main object of the present invention.

[0115] In one embodiment of the present application, there is provided a negative electrode for a lithium secondary battery, comprising: a negative electrode current collector layer; and a negative electrode active material layer provided on one or both surfaces of the negative electrode current collector layer; wherein the negative electrode active material layer comprises the negative electrode slurry of the present application or a dried product thereof.

[0116] In one embodiment of the present application, the negative electrode active material layer includes the negative electrode slurry of the present application or a dried product thereof. Including the dried product of the negative electrode slurry may mean that the solvent is evaporated and the content of the solvent is 0.1 parts by weight or less based on 100 parts by weight of the negative electrode slurry.

[0117] In one embodiment of the present application, the negative electrode current collector generally has a thickness of 1 μm to 100 μm. Such a negative electrode current collector is not particularly limited as long as it does not induce chemical changes in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like, aluminum-cadmium alloy, etc. may be used. Furthermore, the surface may be formed with fine irregularities to strengthen the binding force of the negative electrode active material, and the negative electrode current collector may be used in various forms such as a film, sheet, foil, mesh, porous material, foam, nonwoven fabric, etc.

[0118] In one embodiment of the present application, there is provided a negative electrode for a lithium secondary battery, wherein the thickness of the negative electrode current collector layer is 1 μm or more and 100 μm or less, the thickness of the negative electrode active material layer is 1 μm or more and 50 μm or less, and the thickness of the negative electrode for a lithium secondary battery is 2 μm or more and 100 μm or less.

[0119] That is, in the case of the negative electrode for a lithium secondary battery according to the present application, a silicon-based active material is included in the negative electrode active material layer, and the negative electrode active material layer is formed by coating the negative electrode slurry having the above-mentioned specific conditions, thereby achieving excellent capacity characteristics like conventional silicon-based negative electrodes, and also achieving a fast charging effect by being formed thinly within the above-mentioned thickness range.

[0120] However, the thickness of the negative electrode current collector layer may vary depending on the type and application of the negative electrode, and is not limited thereto.

[0121] 1 is a diagram showing a laminated structure of a negative electrode for a lithium secondary battery according to one embodiment of the present application. Specifically, a negative electrode for a lithium secondary battery 100 can be seen, including a negative electrode active material layer 20 on one side of a negative electrode current collector layer 10. While FIG. 1 shows a negative electrode active material layer formed on one side, it may be formed on both sides of the negative electrode current collector layer.

[0122] In one embodiment of the present application, the porosity of the negative electrode active material layer may be in the range of 10% or more and 60% or less.

[0123] In another embodiment, the porosity of the negative electrode active material layer may be in the range of 10% or more and 60% or less, preferably 20% or more and 50% or less, and more preferably 30% or more and 45% or less.

[0124] The porosity varies depending on the composition and content of the silicon-based active material, conductive material, and binder contained in the negative electrode active material layer. In particular, the silicon-based active material and negative electrode conductive material according to the present application are contained in a specific composition and content, thereby satisfying the above range, and the electrode is characterized by having an appropriate range of electrical conductivity and resistance.

[0125] In one embodiment of the present application, there is provided a method for manufacturing a negative electrode for a lithium secondary battery, the method including the steps of: preparing a negative electrode current collector layer; coating one or both surfaces of the negative electrode current collector layer with the negative electrode slurry according to the present application to form a negative electrode coating layer; drying the negative electrode coating layer; and rolling the negative electrode coating layer to form a negative electrode active material layer.

[0126] In this case, the thickness of the negative electrode coating layer is 20 μm or more and 50 μm or less.

[0127] That is, in the manufacture of the negative electrode for a lithium secondary battery according to the present application, the thickness range can be achieved by forming a coating layer by applying the negative electrode slurry, the particle size of which is controlled under specific conditions according to the present application, to a portion of the active material layer of a silicon-based negative electrode, which is a conventional problem and which is difficult to control the thickness of, thereby solving the problem.

[0128] In one embodiment of the present application, there is provided a lithium secondary battery comprising: a positive electrode; a negative electrode for a lithium secondary battery according to the present application; a separator provided between the positive electrode and the negative electrode; and an electrolyte.

[0129] 2 is a diagram showing a laminated structure of a lithium secondary battery according to one embodiment of the present application. Specifically, a negative electrode 100 for a lithium secondary battery including a negative electrode active material layer 20 on one side of a negative electrode current collector layer 10 can be seen, and a positive electrode 200 for a lithium secondary battery including a positive electrode active material layer 40 on one side of a positive electrode current collector layer 50 can be seen, and the negative electrode 100 for a lithium secondary battery and the positive electrode 200 for a lithium secondary battery are stacked with a separator 30 interposed therebetween.

[0130] A secondary battery according to an embodiment of the present specification may include the negative electrode for a lithium secondary battery described above. 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 negative electrode has been described above, detailed description thereof will be omitted.

[0131] The positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector and including the positive electrode active material.

[0132] The positive electrode current collector in the positive electrode is not particularly limited as long as it does not induce chemical changes in the battery and is conductive. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like may be used. The positive electrode current collector may typically have a thickness of 3 μm to 500 μm, and the surface of the current collector may be formed with fine irregularities to enhance the adhesive strength of the positive electrode active material. The positive electrode current collector may be used in various forms, such as a film, sheet, foil, mesh, porous material, foam, or nonwoven fabric.

[0133] The positive electrode active material may be a commonly used positive electrode active material. Specifically, the positive electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; a lithium iron oxide such as LiFe3O4; 1+c1 Mn 2-c1 O4 (0≦c1≦0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, and Cu2V2O7; chemical formula LiNi 1-c2 Ni-site type lithium nickel oxide represented by the chemical formula LiMn 2-c3 M c3 Examples of suitable lithium manganese composite oxides include, but are not limited to, lithium manganese composite oxides represented by Li2Mn3MO8 (where M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, and satisfying 0.01≦c3≦0.1) or Li2Mn3MO8 (where M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); and LiMn2O4, in which part of the Li in the chemical formula is substituted with an alkaline earth metal ion. The positive electrode may be Li metal.

[0134] The positive electrode active material layer may contain a positive electrode conductive material and a positive electrode binder in addition to the above-described positive electrode active material.

[0135] In this case, the positive electrode conductive material is used to impart conductivity to the electrode, and can be any material that has electronic conductivity without causing chemical changes in the battery that is 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, thermal black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives. These materials may be used alone or in combination.

[0136] The positive electrode binder improves adhesion between positive electrode active material particles and between the positive electrode active material and the positive electrode current collector. Specific examples of the positive electrode binder include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, and various copolymers thereof. One or more of these may be used alone or in combination.

[0137] The separator separates the negative electrode and the positive electrode and provides a path for lithium ions to move. Any separator typically used in secondary batteries can be used without particular limitation. It is particularly preferred that the separator exhibit low resistance to electrolyte ion migration and excellent electrolyte humidification. Specifically, porous polymer films, such as those made from polyolefin polymers such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers, or laminates of two or more layers thereof, may be used. Conventional porous nonwoven fabrics, such as nonwoven fabrics made from high-melting-point glass fibers or polyethylene terephthalate fibers, may also be used. To ensure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymeric material may be used, and it may be selectively used as a single-layer or multi-layer structure.

[0138] Examples of the electrolyte 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 manufacturing lithium secondary batteries.

[0139] Specifically, the electrolyte may include a non-aqueous organic solvent and a metal salt.

[0140] Examples of the non-aqueous organic solvent that can be used include aprotic organic solvents such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, and ethyl propionate.

[0141] In particular, among the carbonate organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, can be preferably used as high-viscosity organic solvents, because they have a high dielectric constant and dissociate lithium salts well. When such cyclic carbonates are mixed in an appropriate ratio with linear carbonates having low viscosity and low dielectric constants, such as dimethyl carbonate and diethyl carbonate, an electrolyte having high electrical conductivity can be prepared, and therefore such cyclic carbonates can be used more preferably.

[0142] The metal salt may be a lithium salt, which is a substance that is easily dissolved in the non-aqueous electrolyte. For example, the anion of the lithium salt may be F - , Cl - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3- , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - , and (CF3CF2SO2)2N - One or more selected from the group consisting of:

[0143] In addition to the constituent components of the electrolyte, the electrolyte may further include one or more additives, such as a haloalkylene carbonate compound such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinoneimine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing a decrease in battery capacity, and improving the discharge capacity of the battery.

[0144] According to one embodiment of the present invention, there is provided a battery module including the secondary battery as a unit cell, and a battery pack including the same. The battery module and the battery pack include the secondary battery having high capacity, high rate characteristics, and high cycle characteristics, and therefore can be used as a power source for medium- to large-sized devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems. [Example]

[0145] Below, preferred examples are presented to help understand the present invention. However, the following examples are merely for the purpose of illustrating the present description, and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope and technical spirit of the present description, and it is natural that such changes and modifications fall within the scope of the appended claims.

[0146] <Production example> <Production of negative electrodes> A negative electrode active material layer composition including Si (average particle size (D50): 3.5 μm) as a silicon-based active material, a first conductive material, a second conductive material, and polyacrylamide (PAM) as a binder was added to distilled water as a solvent for forming a negative electrode slurry in the weight ratios shown in Table 1 below to prepare a negative electrode slurry (solid concentration 25 wt %).

[0147] [Table 1]

[0148] The first conductive material is plate-shaped graphite (specific surface area: 17 m 2 / g, average particle size (D50): 3.5 μm), and the second conductive material was SWCNT. In Table 1, the weight parts of each material are shown based on 100 parts by weight of the total of the silicon-based active material, the first conductive material, the second conductive material, and the negative electrode active material layer composition consisting of polyacrylamide (PAM) as a binder.

[0149] As a specific mixing method, the first conductive material, the second conductive material, the binder, and water were first mixed and dispersed using a homomixer under the conditions shown in Table 2 below, and then the silicon-based active material was added and second mixed and dispersed under the conditions shown in Table 2 below to prepare a negative electrode slurry.

[0150] In this case, the Dmin and Dmax values ​​of the particle size of the negative electrode slurry each satisfied the ranges shown in Table 3 below.

[0151] The negative electrode slurry was coated on one side of a copper current collector having a thickness of 8 μm as a negative electrode current collector layer at the weight loading shown in Table 3 below, rolled, and dried in a vacuum oven at 130°C for 10 hours to form a negative electrode active material layer. The thickness of the rolled electrode and the thickness of the negative electrode active material layer were as shown in Table 3 below (negative electrode porosity: 40.0%).

[0152] [Table 2]

[0153] [Table 3]

[0154] In Table 3, the presence or absence of defects in the electrodes was indicated by "x" if the electrodes were produced without any problems in the electrode manufacturing process, by "0" if a problem occurred in the electrode manufacturing process itself and the electrodes could not be manufactured, and by "△" if the electrodes themselves were manufactured but problems such as particle generation occurred in the manufactured electrodes.

[0155] As can be seen from the results in Tables 1 to 3, the negative electrode slurry according to the present application satisfies the requirement that the particle size (grind gauge) of the negative electrode slurry has a Dmin of 8 μm or less and a Dmax of 7 μm to 30 μm. Although silicon-based negative electrodes have excellent capacity characteristics, it is important to form the electrode thinly for fast charging. When the particle size value of the negative electrode slurry according to the present application satisfies the above range, it was confirmed that the coating thickness of the negative electrode slurry can be thinly formed, thereby providing a negative electrode for a lithium secondary battery that has excellent capacity characteristics and is capable of fast charging.

[0156] In Comparative Examples 1 and 2, the negative electrode slurry particle size (grind gauge e) Dmin was within the range of 8 μm or less, but Dmax exceeded the range specified in the present application. This was due to a combination of factors including the composition and content of the materials contained in the negative electrode composition and the process conditions. As can be seen from Table 2, the main cause was an increase in the temperature of the slurry due to the long mixing time, which caused the phase of the slurry containing a large amount of binder to become unstable. In this case, clogging occurred during the slurry transfer process, preventing the process from proceeding, and it was confirmed that the negative electrode active material layer could not be coated.

[0157] In Comparative Example 3, the Dmax of the anode slurry particle size (grind gauge) was within the range of the present application, but the Dmin exceeded the range of the present application. The above results were due to a combination of factors, including the composition, content, and process conditions of the materials contained in the anode composition, but the main factors were issues with the materials contained in the anode composition and differences in the mixing method. Unlike Comparative Examples 1 and 2, no clogging occurred during the transfer process. However, it was confirmed that particles were generated after the formation of the anode active material layer, causing problems after manufacturing.

[0158] Comparative Example 4 corresponds to a case where the Dmax and Dmin of the negative electrode slurry particle size (grind gauge) all exceeded the ranges set forth in the present application. As mentioned above, this was the result of a combination of multiple factors, and as can be seen from Table 2, this was primarily due to problems with the working time. In this case, as in Comparative Examples 1 and 2, clogging occurred during the slurry transfer process, preventing the process from progressing, and therefore preventing the coating of the negative electrode active material layer.

[0159] Finally, Comparative Example 5 corresponds to a case where the Dmax of the negative electrode slurry particle size (grind gauge) is below this range. This case also corresponds to the same factors as Comparative Example 3. In this case, no clogging occurred during the transfer process, but particles were generated after the formation of the negative electrode active material layer, which caused problems after manufacturing. [Explanation of symbols]

[0160] 10 Negative electrode current collector layer 20...Negative electrode active material layer 30 Separator 40...Cathode active material layer 50 Positive electrode current collector layer 100 ···Negative electrode for lithium secondary battery 200 ···Positive electrode for lithium secondary battery

Claims

1. A negative electrode slurry comprising: a negative electrode active material layer composition; and a solvent; the negative electrode active material layer composition includes a silicon-based active material; a negative electrode conductive material; and a negative electrode binder; the silicon-based active material is present in an amount of 60 parts by weight or more and 90 parts by weight or less based on 100 parts by weight of the negative electrode active material layer composition; the negative electrode conductive material is contained in an amount of 5 parts by weight or more and 35 parts by weight or less based on 100 parts by weight of the negative electrode active material layer composition, the negative electrode conductive material includes a sheet-shaped conductive material; and a linear conductive material, the negative electrode binder includes an aqueous binder, the negative electrode binder is present in an amount of 5 parts by weight to 15 parts by weight based on 100 parts by weight of the negative electrode active material layer composition; The negative electrode slurry has a particle size (grind gauge) of 8 μm or less in Dmin and 7 μm or more and 30 μm or less in Dmax.

2. The negative electrode slurry according to claim 1 , wherein the negative electrode slurry has an average particle size (D50) value of 5 μm or more and 20 μm or less.

3. 2. The negative electrode slurry according to claim 1, wherein the silicon-based active material comprises one or more selected from the group consisting of SiOx (x=0), SiOx (0<x<2), SiC, and a Si alloy.

4. 2. The negative electrode slurry according to claim 1, wherein the silicon-based active material comprises one or more selected from the group consisting of SiOx (x=0) and SiOx (0<x<2), and the silicon-based active material comprises 70 parts by weight or more of the SiOx (x=0) based on 100 parts by weight of the silicon-based active material.

5. The negative electrode slurry according to claim 1 , wherein the sheet-like conductive material is at least one selected from the group consisting of plate-like graphite, graphene, graphene oxide, and graphite flakes, and the linear conductive material is carbon nanotubes.

6. The negative electrode slurry of claim 1 , wherein the negative electrode binder is polyacrylamide.

7. A method for producing the negative electrode slurry according to any one of claims 1 to 6, comprising: mixing a negative electrode conductive material; and a negative electrode binder to form a mixture; adding a solvent to the mixture and performing a first mixing; and adding a silicon-based active material to the mixed mixture and performing a second mixing; the first mixing and second mixing steps include mixing at 2,000 rpm to 3,000 rpm for 10 minutes to 60 minutes; the negative electrode slurry has a particle size (grind gauge) Dmin of 8 μm or less and Dmax of 7 μm or more and 30 μm or less.

8. The method for producing a negative electrode slurry according to claim 7 , wherein a mixing temperature in the first mixing and the second mixing is 50° C. or less.

9. A negative electrode for a lithium secondary battery, comprising: a negative electrode current collector layer; and a negative electrode active material layer provided on one or both surfaces of the negative electrode current collector layer, 7. A negative electrode for a lithium secondary battery, wherein the negative electrode active material layer comprises the negative electrode slurry according to claim 1 or a dried product thereof.

10. the thickness of the negative electrode current collector layer is 1 μm or more and 100 μm or less, the thickness of the negative electrode active material layer is 1 μm or more and 50 μm or less, 10. The negative electrode for a lithium secondary battery according to claim 9, wherein the thickness of the negative electrode for a lithium secondary battery is 2 μm or more and 100 μm or less.

11. providing a negative electrode current collector layer; Coating one or both surfaces of the negative electrode current collector layer with the negative electrode slurry according to any one of claims 1 to 6 to form a negative electrode coating layer; drying the negative electrode coating layer; and rolling the negative electrode coating layer to form a negative electrode active material layer; A method for producing a negative electrode for a lithium secondary battery, comprising:

12. The method for producing a negative electrode for a lithium secondary battery according to claim 11, wherein the thickness of the negative electrode coating layer is 20 μm or more and 50 μm or less.

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