KR102672053B1 - Negative active material, negative electrode and lithium secondary battery comprising thereof - Google Patents

Abstract

The present invention provides a negative electrode active material that can improve the charge/discharge characteristics and high-rate cycle life characteristics of a lithium secondary battery by suppressing volume expansion that occurs during charging and discharging of a lithium secondary battery by coating the negative electrode active material with a high molecular weight water-based polymer, and a negative electrode containing the same. and a lithium secondary battery.

Description

Negative active material, negative electrode containing the same, and lithium secondary battery {NEGATIVE ACTIVE MATERIAL, NEGATIVE ELECTRODE AND LITHIUM SECONDARY BATTERY COMPRISING THEREOF}

The present invention relates to a negative electrode active material, a negative electrode containing the same, and a lithium secondary battery.

Lithium secondary batteries have a high voltage of 4 V, a wide operating temperature of -20 degrees to more than 50 degrees, a high power density of more than 1 kW/kg, and a high energy density of more than 100 Wh/kg, and research is being actively conducted around the world. The lithium secondary battery is used in various fields such as portable mobile power sources such as laptops and mobile phones, as well as HEV (Hybrid Electric Vehicle), PHEV (Plug in Hybrid Electric Vehicle), EV (Electric Vehicle), and energy storage system (ESS). The scope of application is expanding.

The anode material of a lithium secondary battery accounts for about 15% of the material cost of a lithium ion battery, ranking third after the anode material and separator. However, as a counter electrode material of the anode material, it is a key material that determines the performance such as the capacity of the battery. .

The types of anode materials currently in use are divided into natural graphite and artificial graphite, but various candidates for anode active materials are being developed and studied.

Natural graphite has the advantage of high capacity and has been widely applied to existing IT LiB, but there are issues such as swelling of the battery volume to meet the needs of high performance such as electric vehicles/ESS. Silicon-based anode active material, which is emerging as a new material for this, has the highest theoretical capacity (4,200 mAh/g) as a cathode material, which is three times higher than that of graphite, but it also has the problem of volume expansion during charging and discharging.

Volume expansion of a lithium secondary battery occurs during the process of insertion and desorption of lithium ions within the lithium secondary battery. There is a disadvantage in that the volume expands rapidly, causing decomposition of the anode active material particles and subsequent loss of storage space for lithium ions, resulting in a rapid decrease in capacity. This problem occurs more seriously in silicon-based active materials, which are high-capacity negative electrode active materials.

When the silicon-based active material absorbs and stores the maximum amount of lithium, it is converted to Li _4.4 Si, and volume expansion occurs by charging. In this case, the volume increase rate due to charging expands to about 4.12 times compared to the volume of silicon before volume expansion. Accordingly, during charging and discharging, metals such as Si, Sn, and Al are alloyed with lithium, causing volume expansion and contraction, which causes metal micronization and deteriorates cycle characteristics.

Various methods are being attempted to suppress the volume expansion of anode active materials, such as silicon-based anode active materials.

In Patent Document 1, a silicon metal alloy mixture obtained by mixing silicon with one or more metals selected from the group 2, 13, 14, and 15 elements, primary mechanical processing, and powdering, carbon material powder compound, and carbon When using _a mixture of nanofibers, carbon nanotubes, or a mixture thereof, or a compound represented _by , it is disclosed that it has the effect of significantly improving the problem of conductivity decrease, surface side reaction problem, etc. However, this method still has the problem that cycle deterioration occurs as the interface between each component is broken and the structure is destroyed due to the insertion and release of lithium, resulting in micronization.

To overcome these shortcomings of silicon, research on porous silicon and hollow silicon is in progress. For example, Patent Document 2 discloses an active material particle structure in which a hollow portion is formed inside and silicon (Si) exists in a plate shape as a shell surrounding the hollow portion.

As another method to suppress the volume expansion of the negative electrode active material, in Patent Document 3 and Non-Patent Document 1, a carbon coating layer is formed on the surface of the electrode active material, and in Patent Document 4, a conductive polymer coating layer is formed on the surface of the electrode active material to reduce the volume of the negative electrode active material. It is mentioned that volume expansion can be suppressed.

Patent Document 5 describes a technology for producing a negative electrode with no change in the thickness of the electrode by forming a fiber composite of polyolefin fibers and PE fibers on the negative electrode active material layer, which has excellent elasticity and elastic recovery even when the active material layer expands and decreases in volume. It is mentioned. As the fiber, non-patent document 2 reported a study on adding carbon nanofibers (CNF), and non-patent document 3 reported a study on adding carbon nanotubes (CNT).

These methods reveal the limitations of composite synthesis technology due to problems such as controlling the shape of complex structures and high process costs.

In addition, recent research has shown that binders have a significant impact on the lithiation reaction, helping to improve the capacity and cycle stability of negative electrode active materials.

Meanwhile, Non-Patent Document 4 reports that an aqueous binder, which is a suitable binder for silicon-based active materials, surrounds the active material and forms a stable solid-electrolyte-interphase (SEI layer), thereby reducing irreversible capacity.

For example, in Patent Document 6, the surface of the negative electrode active material is coated with polyacrylic acid crosslinked using polyacrylic acid with a weight average molecular weight (Mw) of 1 million and 3,5-diaminobenzoic acid as a crosslinking agent, thereby forming a current collector and negative electrode active material layer. It is disclosed that the volume expansion of the negative electrode active material can be suppressed by increasing the binding force.

As another example, Patent Document 7 mentions that by forming a metal-substituted polyacrylic acid polymer coating layer formed on silicon-based particles, volume expansion due to insertion of lithium ions is reduced, thereby demonstrating high lifespan characteristics.

In addition, various patents suggest coating the surface of the anode active material with a binder component.

Despite these various technological proposals, volume expansion of anode active materials still remains an unresolved problem. Because of this, it is particularly difficult to universally use silicon-based active materials.

KR 10-2009-0099922A (published on 2009.09.23) KR 10-2021-0028920A (published on 2021.03.15) KR 10-2018-0033485A (published on 2018.04.03) KR 10-2020-0013933A (published on 2020.02.10) KR 10-2020-0141318A (published on December 18, 2020) JP 2021-077487A (published on 2021.05.20) KR 10-2019-0060698A (published on 2019.06.03)

Park, J. Y. et al., “Electrochemical Characteristics of Silicon/Carbon Composites for Anode Material of Lithium Ion Battery,” Appl Chem Eng., 26, 80-85 (2015) Zhang, M. et al., “Interweaved Si@C/CNTs&CNFs Composites as Anode Materials for Li-ion Batteries,” J. Alloys Compd., 588, 206-211 (2014). Park, J. Y. et al., “Synthesis and Electrochemical Characteristics of Mesoporous Silicon/Carbon/CNF Composite Anode,” Appl. Chem. Eng., 26, 543-548 (2015). Yim, T. et al., “Effect of Binder Properties on Electrochemical Performance for Silicon-graphite Anode: Method and Application of Binder Screening,” Electrochimica Acta, 136, 112-120 (2014).

Lithium secondary batteries undergo volume expansion due to lithium insertion, pulverization, contact losses with conducting agents and current collector, and unstable solid-electrolyte-interphase (SEI). ) may exhibit a fading mechanism such as formation. The volume expansion occurs during the process of insertion and desorption of lithium ions in a lithium secondary battery, and this occurs more seriously when a silicon-based active material is used.

Under the concept that the volume expansion can be suppressed when coating the negative electrode active material using a binder, in the present invention, a specific binder was selected and the surface of the negative electrode active material was coated using this.

An aqueous binder was selected as a binder candidate. If the molecular weight of the aqueous binder is high, it has elastic properties that can withstand volume expansion of the negative electrode active material, so the molecular weight is limited to a high molecular weight, and the solvent is used when coating with a high molecular weight aqueous binder. In order to overcome coating difficulties due to low solubility in solvents, negative active material particles were manufactured by applying the mechano-fusion (MF) method, a solvent-free dry coating method.

According to the present invention, negative electrode active material particles were manufactured by coating the negative electrode active material with a dry coating method using a high molecular weight aqueous binder, and when these negative electrode active material particles are introduced into the negative electrode, the problems of lifespan characteristics and deterioration due to volume expansion are effectively solved. It was confirmed that this can be done, and that the advantages of high capacity and energy density of anode active materials, especially silicon-based active materials, can be more preferably implemented.

The present invention provides negative electrode active material particles for secondary batteries, including a negative electrode active material that expands and contracts while inserting and releasing lithium ions, and a coating layer obtained by dry coating the negative electrode active material with an aqueous binder.

The negative electrode active material is one or more selected from the group consisting of materials capable of reversibly intercalating/deintercalating lithium ions, lithium metal, alloys of lithium metal, materials capable of doping and dedoping lithium, and transition metal oxides. am.

The material capable of doping and dedoping lithium is at least one selected from the group consisting of carbon-based active materials, silicon-based active materials, and Sn-based active materials.

The silicon-based active material is Si, SiOx (0<x<2), Si-C composite, Si-Q alloy (where Q is an alkali metal, alkaline earth metal, Group 13 element, Group 14 element, Group 15 element, Group 16 element, It is an element selected from the group consisting of transition metals, rare earth elements, and combinations thereof, but not Si.

The aqueous binder is polyacrylic acid, polyvinyl alcohol, polyethylene glycol, polyacrylonitrile, polyacryl amide, carboxymethyl cellulose, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyvinylpyridine, and chlorosulfonated Polyethylene, polyester resin, acrylic resin, phenol resin, epoxy resin, gum arabic, styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluorine rubber, ethylene propylene. At least one selected from the group consisting of diene copolymers and combinations thereof.

The water-based binder has a weight average molecular weight (Mw) of 2 million g/mol to 7.5 million g/mol.

The dry coating is performed in a solvent-free process.

The coating layer exists in a layer-type that continuously covers the surface of the negative electrode active material or an island-type that is discontinuously located.

It contains 0.1 to 50 parts by weight of aqueous binder based on 100 parts by weight of the negative electrode active material particles.

Negative active material particles for a secondary battery including a negative electrode active material that expands and contracts while inserting and releasing lithium ions, and a coating layer obtained by dry coating the negative electrode active material with an aqueous binder; conductive material; and a binder.

The negative electrode active material is one or more selected from the group consisting of materials capable of reversibly intercalating/deintercalating lithium ions, lithium metal, alloys of lithium metal, materials capable of doping and dedoping lithium, and transition metal oxides. am.

The material capable of doping and dedoping lithium is at least one selected from the group consisting of carbon-based active materials, silicon-based active materials, and Sn-based active materials.

The silicon-based active material is Si, SiOx (0<x<2), Si-C composite, Si-Q alloy (where Q is an alkali metal, alkaline earth metal, Group 13 element, Group 14 element, Group 15 element, Group 16 element, It is an element selected from the group consisting of transition metals, rare earth elements, and combinations thereof, but not Si.

The aqueous binder is polyacrylic acid, polyvinyl alcohol, polyethylene glycol, polyacrylonitrile, polyacryl amide, carboxymethyl cellulose, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyvinylpyridine, and chlorosulfonated Polyethylene, polyester resin, acrylic resin, phenol resin, epoxy resin, gum arabic, styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluorine rubber, ethylene propylene. At least one selected from the group consisting of diene copolymers and combinations thereof.

The water-based binder has a weight average molecular weight (Mw) of 2 million g/mol to 7.5 million g/mol.

The coating layer exists in a layer-type that continuously covers the surface of the negative electrode active material or an island-type that is discontinuously located.

Based on the total weight of solids in the negative electrode slurry, it contains 80% to 99% by weight of negative electrode active material particles, 0.1% to 20.0% by weight of conductive material, and 0.5% to 5.0% by weight of binder.

The binder is a water-based binder.

The aqueous binder is polyacrylic acid, polyvinyl alcohol, polyethylene glycol, polyacrylonitrile, polyacryl amide, carboxymethyl cellulose, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyvinylpyridine, and chlorosulfonated Polyethylene, polyester resin, acrylic resin, phenol resin, epoxy resin, gum arabic, styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluorine rubber, ethylene propylene. At least one selected from the group consisting of diene copolymers and combinations thereof.

The binder has a weight average molecular weight (Mw) of 150,000 g/mol to 750,000 g/mol.

In addition, the present invention is a current collector; and a negative electrode for a secondary battery including a negative electrode active material layer laminated on an upper surface of a current collector, wherein the negative electrode active material layer includes the above-mentioned negative electrode active material particles.

Additionally, the present invention provides a secondary battery including a negative electrode, a positive electrode, a separator, and an electrolyte, wherein the negative electrode includes the above-mentioned negative electrode active material particles.

The negative electrode active material particles according to the present invention coat the negative electrode active material with a high molecular weight water-based polymer, thereby effectively suppressing the volume expansion/contraction problem caused by charging and discharging of the high-capacity negative electrode active material, thereby preventing fine differentiation of the negative electrode active material and thickening of the SEI layer. (thickening) can be prevented.

As a result, it is possible to manufacture a lithium secondary battery with excellent charge/discharge characteristics and cycle life characteristics using the negative electrode active material particles.

In addition, as Mechano-fusion (MF), a solvent-free dry coating method, is applied to high molecular weight aqueous polymers, conventional high molecular weight aqueous binders have low solubility in solvents. This can solve the problem of forming an uneven cathode surface when wet coating.

1 is a schematic diagram of anode active material particles for secondary batteries according to the present invention.
Figure 2 is a cross-sectional view showing a negative electrode for a lithium secondary battery according to the present invention.

The terminology used herein is only intended to refer to specific embodiments and is not intended to limit the invention. As used herein, singular forms include plural forms unless phrases clearly indicate the contrary. As used in the specification, the meaning of "comprising" refers to specifying a particular characteristic, area, integer, step, operation, element and/or ingredient, and the presence or presence of another characteristic, area, integer, step, operation, element and/or ingredient. This does not exclude addition.

When a part is referred to as being “on” or “on” another part, it may be directly on or on the other part or may be accompanied by another part in between. In contrast, when a part is said to be "directly on top" of another part, there is no intervening part between them.

Additionally, unless specifically stated, % means weight%, and 1ppm is 0.0001% by weight.

Although not defined differently, all terms including technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art in the technical field to which the present invention pertains. Terms defined in commonly used dictionaries are further interpreted as having meanings consistent with related technical literature and currently disclosed content, and are not interpreted in ideal or very formal meanings unless defined.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein.

negative active material particles

Figure 1 is a schematic diagram of anode active material particles 10 for secondary batteries according to the present invention.

Referring to Figure 1, the negative electrode active material particles 10 include a negative electrode active material 11 whose volume expands and contracts while inserting and releasing lithium ions; and a coating layer 13 obtained by dry coating the negative electrode active material 11 with an aqueous binder.

The negative electrode active material 11 includes, for example, a material capable of reversibly intercalating/deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide. do.

The lithium metal alloy includes lithium and Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al and Sn. Any alloy of metals of choice may be used. The lithium metal alloy includes lithium and Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al and Sn. Any alloy of metals of choice may be used.

A material capable of doping and dedoping lithium may be, for example, a carbon-based active material.

Representative examples of carbon-based active materials include crystalline carbon, amorphous carbon, or a combination of these. Examples of the crystalline carbon include graphite such as amorphous, plate-shaped, flake, spherical or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon or hard carbon ( hard carbon), mesophase pitch carbide, calcined coke, etc.

Materials capable of doping and dedoping lithium include, for example, Si, SiOx (0<x<2), Si-C composite, Si-Q alloy (where Q is an alkali metal, an alkaline earth metal, a group 13 element, a group 14 element, 15 Silicon-based active materials such as elements selected from the group consisting of group elements, group 16 elements, transition metals, rare earth elements, and combinations thereof, but not Si, may be used, and at least one of these may be mixed with SiO ₂ . It may be possible. The element Q includes Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P, As, Sb, Bi, S, One selected from the group consisting of Se, Te, Po, and combinations thereof can be used. In particular, silicon-based active materials containing Si have the advantage of high initial capacity and maintaining capacity even after repeated cycles.

Materials capable of doping and dedoping lithium include, for example, Sn, SnO2, Sn-R (where R is an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a Group 15 element, a Group 16 element, a transition metal, a rare earth element, and Sn-based active materials such as an element selected from the group consisting of a combination of these, but not Sn, may be included, and at least one of these and SiO ₂ may be mixed and used. The elements R include Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P, As, Sb, Bi, S, One selected from the group consisting of Se, Te, Po, and combinations thereof can be used.

The Si-C composite, or Si-Q alloy, is a form in which Si nanoparticles are coated on the surface of a carbon-based material or metal (Q), such as graphite or metal (Q), or pores of graphite or metal (Q). It may be in a form impregnated within.

Si-C composite, Si-Q alloy, etc. may have a core-shell type structure. For example, the core is one of Si particles, Si, SiOx, Si-C composite, Si-Q alloy, Sn, SnO ₂ , or Sn-R, and the shell is a core and other Si particles, Si, SiOx, Si- It may be any one of C composite, Si-Q alloy, Sn, SnO2, or Sn-R. Additionally, a metal of the same material as the current collector of the negative electrode may be used as the shell.

As the transition metal oxide, lithium titanium oxide such as Li ₄ Ti ₅ O ₁₂ can be used.

The negative electrode active material 11 described above has a large degree of volume expansion during the charging and discharging process of the battery, and microdifferentiation of the active material particles occurs due to mechanical stress generated when reacting with lithium ions. Due to the micronization, electrical contact between particles is lost and a new surface of the micronized particles is revealed, resulting in a significant lithium loss reaction due to the continuous formation of an SEI layer. As a result, it causes problems with deterioration of lifespan characteristics due to volume expansion of the anode active material, making commercialization difficult. This occurs more seriously in high-capacity silicon-based anode active materials.

In the present invention, the coating layer 13 is formed on the surface of the negative electrode active material 11 with an aqueous binder using a dry coating method, thereby effectively solving the problem of deterioration of life characteristics caused by volume expansion of the negative electrode active material 11, especially the high-capacity silicon-based active material. This can be done, and the advantages of high capacity and energy density of silicon-based active materials can be more preferably implemented.

Water-based binders have hydrophilic properties and are generally insoluble in electrolytes or electrolyte solutions used in lithium secondary batteries. These characteristics can provide strong stress or tensile strength to the water-based 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 negative electrode active material 11. .

Focusing on the characteristics of the aqueous binder, the present invention forms a coating layer 13 on the surface of the anode active material 11 with an aqueous binder, and uses an aqueous binder as the binder used in the slurry composition for producing the anode.

Water-based binders have the advantage of high elasticity and stress, but when used alone, they cause bending of the cathode, cracks due to bending, and deterioration of lifespan characteristics.

In the present invention, the volume expansion/contraction problem of the negative electrode active material 11 is effectively solved by varying the molecular weight of the water-based binder formed in the coating layer 13 of the negative electrode active material 11 and the water-based binder used in the slurry composition for producing the negative electrode. It is possible to improve the lifespan characteristics and solve the problem of bending when manufacturing a thin film cathode, making it possible to implement a cathode with a thin thickness and high energy density.

Aqueous binders that can be used include polyacrylic acid, polyvinyl alcohol, polyethylene glycol, polyacrylonitrile, polyacryl amide, carboxymethyl cellulose, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyvinylpyridine, and chlorine. Sulfonated polyethylene, polyester resin, acrylic resin, phenol resin, epoxy resin, gum arabic, styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluorine rubber, One or more types selected from the group consisting of ethylene propylene diene copolymer and combinations thereof are possible. According to one embodiment, polyacrylic acid, polyvinyl alcohol, polyethylene glycol, etc. may be used, and polyacrylic acid may be preferably used. In particular, the water-based binder used in the coating layer 13 of the negative electrode active material 11 has a high molecular weight with a weight average molecular weight (Mw) of 2 million g/mol or more. The high molecular weight aqueous binder has excellent binding properties for the negative electrode active material 11 and elasticity and stiffness that can withstand volume expansion. For example, in the case of polyacrylic acid, a strong interaction occurs between the carboxy group of acrylic acid and the hydroxy group of silicone, thereby ensuring the above-mentioned effect.

Specifically, the water-based binder used in the coating layer 13 has a weight average molecular weight of 2 million g/mol or more, 2.5 million g/mol or more, 3 million g/mol or more, 3.5 million g/mol or more, or 4 million g/mol. or more, 4.5 million g/mol or more, 5 million g/mol or more, 5.5 million g/mol or more, 6 million g/mol or more, 6.5 million g/mol or more, 7.5 million g/mol or less, 7 million g/mol or less , 6.5 million g/mol or less, 6 million g/mol or less, 5.5 million g/mol or less, 5 million g/mol or less, 4.5 million g/mol or less, 4 million g/mol or less, 3.5 million g/mol or less, It has a range of less than 3 million g/mol and less than 2.5 million g/mol. Preferably, 2 million g/mol or more, 2.5 million g/mol or more, 3 million g/mol or more, 3.5 million g/mol or more, 7.5 million g/mol or less, 7 million g/mol or less, 6.5 million g/mol Hereinafter, the range is 6 million g/mol or less, 5.5 million g/mol or less, 5 million g/mol or less, 4.5 million g/mol or less, and 4 million g/mol or less. More preferably, 2.5 million g/mol or more, 3 million g/mol or more, 3.5 million g/mol or more, 5.5 million g/mol or less, 5 million g/mol or less, 4.5 million g/mol or less, 4 million g It has a range of /mol or less. Even more preferably, it has a range of 3 million g/mol or more, 3.5 million g/mol or more, 5 million g/mol or less, 4.5 million g/mol or less, and 4 million g/mol or less. In the present invention, the weight average molecular weight (Mw) is the weight average molecular weight (Mw) converted to polystyrene measured by gel permeation chromatography (GPC).

The coating method of the negative electrode active material 11 using a high molecular weight aqueous binder may be a dry method different from wet coating methods such as conventional sol-gel process, dip coating, and spray coating.

When applying a high molecular weight aqueous binder using a wet coating method, it is difficult to manufacture a coating solution due to the high molecular weight of the aqueous binder. Even if a coating solution is manufactured, processes such as excessive solvent use, mechanical mixing, or heating are required, and the negative electrode active material (11 ), an uneven coating layer 13 is formed.

In the present invention, the mechano-fusion (MF) method, which is a solvent-free dry coating method, can be used.

The mechanofusion method is a method of diffusion and immobilization by applying mechanical energy to the child particles on the surface of the parent particle and adding heat energy. The negative electrode active material 11 is mixed with the particle-state negative electrode active material 11 and the particle-state aqueous binder. A water-based binder coating layer 13 is formed on the surface.

Devices for performing the mechano fusion method include, for example, a high energy ball mill device, a planetary mill device, a stirred ball mill device, and a vibrating mill device. etc., of which coating may be performed in a high-energy ball mill device, but is not limited thereto.

The water-based binder coating layer 13 formed through the mechanofusion method covers the particles of the negative electrode active material 11. At this time, the water-based binder coating layer 13 is about 0.1% to about 10% of the particle surface of the negative electrode active material 11, for example, the ratio of the coating layer 13 to the negative electrode active material 11 is about 0.5% to about 99.5%, about 2. The binder coating layer may cover the negative electrode active material from % to about 98%, from about 5% to about 95%, or from about 10% to about 90%. Additionally, the coating layer 13 may be a capsule or shell that partially covers, surrounds, or encapsulates the particles of the negative electrode active material 11. In addition, the coating layer 13 may exist in a layer-type that continuously covers the surface of the negative electrode active material 11, or may exist in an island-type discontinuously located on the surface of the negative electrode active material. It may be possible.

The negative electrode active material particles 10 obtained through the mechanofusion method may have spaced portions, that is, pores, formed by the negative electrode active material 11 and the water-based binder particles. The volume expansion of the negative electrode active material 11 is sucked in by the pores, thereby minimizing the volume expansion that occurs when the negative electrode active material is used, preventing micronization of the negative electrode active material 11, and preventing thickening of the SEI layer. It can be suppressed. In particular, the high elasticity and strength of the high molecular weight aqueous binder allows it to sufficiently withstand volume expansion of the negative electrode active material 11.

According to one embodiment, the negative electrode active material particles 10 using the mechanofusion method are made by rotating the negative electrode active material 11 on the particles and a high molecular weight aqueous binder on the particles with a rotational force of 500 rpm to 5000 rpm in a mechanofusion device. can do. If the rotational force is outside the above range, dry coating may not work well. In addition, the mechanofusion process may be performed by rotating the machine at a low rotation speed of 500 rpm to 1,500 rpm for 5 to 30 minutes and then rotating it at a high speed of 2,000 to 4,000 rpm for 5 to 30 minutes.

When rotation is performed using the rotational force, shear stress is formed within the mechanofusion device, and high molecular weight water-based binder particles are physically bound to the surface of the negative electrode active material 11 on the particles to form the coating layer 13. .

When performed using a wet coating method, the coating on the negative electrode active material 11 is not uniform due to the low dispersibility of the water-based binder, resulting in the problem of producing a non-uniform negative electrode with an uneven surface when manufacturing the negative electrode through slurry composition production. . In addition, the use of a low molecular weight aqueous binder has relatively low elasticity and cannot sufficiently withstand the volume expansion of the negative electrode active material 11. Additionally, in the case of crosslinking after coating with a water-based binder, the elasticity is low, and the effect according to the present invention cannot be secured due to the absence of the spaced portion.

In order to ensure a better effect, the particles of the negative electrode active material 11, the water-based binder particles, their content ratio, and the thickness of the coating layer 13 may be limited.

In the present invention, the average particle diameter of particles can be defined as the particle size based on 50% of the particle size distribution. The average particle diameter (D50) of the particles according to an embodiment of the present invention can be measured using, for example, a laser diffraction method. The laser diffraction method is generally capable of measuring particle diameters ranging from the submicron region to several millimeters, and can obtain results with high reproducibility and high resolution.

The average particle diameter (D50) of the negative electrode active material 11 used in the present invention is more than 0 μm and less than 20 μm, specifically 0.01 μm or more, 0.05 μm or more, 0.1 μm or more, 0.15 μm or more, 0.2 μm or more, 0.5 μm or more, 1 More than μm, more than 1.2 μm, more than 1.5 μm, more than 2.0 μm, more than 2.5 μm, more than 3.0 μm, more than 3.5 μm, more than 4.0 μm, more than 4.5 μm, more than 5.0 μm, more than 5.5 μm, more than 6.0 μm, more than 6.5 μm , 7.0 μm or more, 7.5 μm or more, 8.0 μm or more, 8.5 μm or more, 9.0 μm or more, 9.5 μm or more, 10.0 μm or more, 10.5 μm or more, 11.0 μm or more, 11.5 μm or more, 12.0 μm or more, 12.5 μm or more, 13.0 More than μm, more than 13.5 μm, more than 14.0 μm, more than 14.5 μm, more than 15.0 μm, more than 15.5 μm, more than 16.0 μm, more than 16.5 μm, more than 17.0 μm, more than 17.5 μm, more than 18.0 μm, more than 18.5 μm, more than 19.0 μm , is more than 19.5 μm. Also, less than 20μm, 19.5μm or less, 19.0μm or less, 18.5μm or less, 18.0μm or less, 17.5μm or less, 17.0μm or less, 16.5μm or less, 16.0μm or less, 15.5μm or less, 15.0μm or less, 14.5μm or less, 14.0μm or less μm or less, 13.5μm or less, 13.0μm or less, 12.5μm or less, 12.0μm or less, 11.5μm or less, 11.0μm or less, 10.5μm or less, 10.0μm or less, 9.5μm or less, 9.0μm or less, 8.5μm or less, 8.0μm or less , 7.5μm or less, 7.0μm or less, 6.5μm or less, 6.0μm or less, 5.5μm or less, 5.0μm or less, 4.5μm or less, 4.0μm or less, 3.5μm or less, 3.0μm or less, 2.5μm or less, 2.0μm or less, 1.5μm or less It ranges from μm or less, 1.2μm or less, 1.0μm or less, 0.5μm or less, 0.2μm or less, 0.15μm or less, 0.1μm or less, 0.05μm or less, and 0.02μm or less.

If the average particle diameter of the negative electrode active material 11 is too small, side reactions with the electrolyte may increase and lifespan performance may be reduced, and if the average particle diameter is too large, volume expansion may be large during charging and discharging, which may cause particle cracks, thus causing lifespan performance. This may deteriorate. When the negative electrode active material 11 satisfies the above range, excellent output and initial efficiency can be appropriately balanced, excellent tap density can be exhibited, and excellent loading amount can be exhibited during electrode coating.

If the average particle diameter of the water-based binder is less than the above range, agglomeration may occur during the manufacturing process, and conversely, if it exceeds the above range, uniform reaction with lithium is difficult, and the lifespan characteristics and thickness expansion inhibition characteristics may be greatly reduced.

According to an embodiment of the present invention, the thickness of the water-based binder coating layer 13 may be 0.01 μm or more and 20 μm or less. Specifically, 0.01 μm or more, 0.05 μm or more, 0.1 μm or more, 0.15 μm or more, 0.2 μm or more, 0.5 μm or more, 1 μm or more, 1.2 μm or more, 1.5 μm or more, 2.0 μm or more, 2.5 μm or more, 3.0 μm or more , 3.5 μm or more, 4.0 μm or more, 4.5 μm or more, 5.0 μm or more, 5.5 μm or more, 6.0 μm or more, 6.5 μm or more, 7.0 μm or more, 7.5 μm or more, 8.0 μm or more, 8.5 μm or more, 9.0 μm or more, 9.5 More than μm, more than 10.0 μm, more than 10.5 μm, more than 11.0 μm, more than 11.5 μm, more than 12.0 μm, more than 12.5 μm, more than 13.0 μm, more than 13.5 μm, more than 14.0 μm, more than 14.5 μm, more than 15.0 μm, more than 15.5 μm , 16.0 μm or more, 16.5 μm or more, 17.0 μm or more, 17.5 μm or more, 18.0 μm or more, 18.5 μm or more, 19.0 μm or more, 19.5 μm or more. Also, less than 20μm, 19.5μm or less, 19.0μm or less, 18.5μm or less, 18.0μm or less, 17.5μm or less, 17.0μm or less, 16.5μm or less, 16.0μm or less, 15.5μm or less, 15.0μm or less, 14.5μm or less, 14.0μm or less μm or less, 13.5μm or less, 13.0μm or less, 12.5μm or less, 12.0μm or less, 11.5μm or less, 11.0μm or less, 10.5μm or less, 10.0μm or less, 9.5μm or less, 9.0μm or less, 8.5μm or less, 8.0μm or less , 7.5μm or less, 7.0μm or less, 6.5μm or less, 6.0μm or less, 5.5μm or less, 5.0μm or less, 4.5μm or less, 4.0μm or less, 3.5μm or less, 3.0μm or less, 2.5μm or less, 2.0μm or less, 1.5μm or less It ranges from μm or less, 1.2μm or less, 1.0μm or less, 0.5μm or less, 0.2μm or less, 0.15μm or less, 0.1μm or less, 0.05μm or less, and 0.02μm or less.

If the thickness of the coating layer 13 of the water-based binder is less than the above range, the volume expansion of the negative electrode active material 11 cannot be sufficiently suppressed. Conversely, if the above range is exceeded, the mobility of lithium ions may be impaired and resistance may increase.

According to one embodiment, the negative electrode active material particles 10 including the negative electrode active material 11 and the water-based binder coating layer 13 of the present invention have an average particle diameter (D50) of 0.02 μm or more and less than 30 μm. Specifically, 0.02 μm or more, 0.05 μm or more, 0.1 μm or more, 0.15 μm or more, 0.2 μm or more, 0.5 μm or more, 1 μm or more, 1.2 μm or more, 1.5 μm or more, 2.0 μm or more, 2.5 μm or more, 3.0 μm or more , 3.5 μm or more, 4.0 μm or more, 4.5 μm or more, 5.0 μm or more, 5.5 μm or more, 6.0 μm or more, 6.5 μm or more, 7.0 μm or more, 7.5 μm or more, 8.0 μm or more, 8.5 μm or more, 9.0 μm or more, 9.5 More than μm, more than 10.0 μm, more than 10.5 μm, more than 11.0 μm, more than 11.5 μm, more than 12.0 μm, more than 12.5 μm, more than 13.0 μm, more than 13.5 μm, more than 14.0 μm, more than 14.5 μm, more than 15.0 μm, more than 15.5 μm , 16.0 μm or more, 16.5 μm or more, 17.0 μm or more, 17.5 μm or more, 18.0 μm or more, 18.5 μm or more, 19.0 μm or more, 19.5 μm or more, 20.0 μm or more, 20.5 μm or more, 21.0 μm or more, 21.5 μm or more, 22.0 More than μm, more than 22.5 μm, more than 23.0 μm, more than 23.5 μm, more than 24.0 μm, more than 24.5 μm, more than 25.0 μm, more than 25.5 μm, more than 26.0 μm, more than 26.5 μm, more than 27.0 μm, more than 27.5 μm, more than 28.0 μm , 28.5 μm or more, 29.0 μm or more, and 29.5 μm or more. In addition, 30 μm or less, 29.5 μm or less, 29.0 μm or less, 28.5 μm or less, 28.0 μm or less, 27.5 μm or less, 27.0 μm or less, 26.5 μm or less, 26.0 μm or less, 25.5 μm or less, 25.0 μm or less, 24.5 μm or less, 24.0 μm or less, 23.5 μm or less, 23.0 μm or less, 22.5 μm or less, 22.0 μm or less, 21.5 μm or less, 21.0 μm or less, 20.5 μm or less, 20 μm or less, 19.5 μm or less, 19.0 μm or less, 18.5 μm or less, 18.0 μm or less or less, 17.5 μm or less, 17.0 μm or less, 16.5 μm or less, 16.0 μm or less, 15.5 μm or less, 15.0 μm or less, 14.5 μm or less, 14.0 μm or less, 13.5 μm or less, 13.0 μm or less, 12.5 μm or less, 12.0 μm or less, 11.5 μm or less, 11.0 μm or less, 10.5 μm or less, 10.0 μm or less, 9.5 μm or less, 9.0 μm or less, 8.5 μm or less, 8.0 μm or less, 7.5 μm or less, 7.0 μm or less, 6.5 μm or less, 6.0 μm or less, 5.5 μm or less 5.0 μm or less, 4.5 μm or less, 4.0 μm or less, 3.5 μm or less, 3.0 μm or less, 2.5 μm or less, 2.0 μm or less, 1.5 μm or less, 1.2 μm or less, 1.0 μm or less, 0.5 μm or less, 0.2 μm or less, It has a range of 0.15 μm or less, 0.1 μm or less, 0.05 μm or less, and 0.02 μm or less.

When the negative electrode active material particles 10 have an average particle diameter within the above range, excellent electrode manufacturing process efficiency and electrode density can be obtained.

According to one embodiment, the negative electrode active material particles 10 of the present invention contain an aqueous binder of 0.1 parts by weight to 50 parts by weight based on 100 parts by weight of the negative electrode active material 11. Specifically, 0.1 parts by weight or more, 0.2 parts by weight or more, 0.5 parts by weight or more, 1.0 parts by weight or more, 5.0 parts by weight or more, 10.0 parts by weight or more, 15.0 parts by weight or more, 20.0 parts by weight or more, 25.0 parts by weight or more, 30.0 parts by weight or more. parts or more, 35.0 parts by weight or more, 40.0 parts by weight or more, 45.0 parts by weight or more, and 47.0 parts by weight or more. Also, 50 parts by weight or less, 49 parts by weight or less, 45 parts by weight or less, 40 parts by weight or less, 35 parts by weight or less, 30 parts by weight or less, 25 parts by weight or less, 20 parts by weight or less, 15 parts by weight or less, 10 parts by weight or less. Hereinafter, it is 5.0 parts by weight or less, 1.0 parts by weight or less, 0.5 parts by weight or less, and 0.3 parts by weight or less. If the content of the water-based binder is less than the above range, the thickness of the coating layer 13 is too thin to effectively prevent the expansion of the negative electrode active material 11. Conversely, when used beyond the above range, the thickness of the coating layer 13 may increase, which may impede the movement of lithium ions and increase battery resistance.

Slurry composition for cathode

The negative electrode for a lithium secondary battery of the present invention includes a negative electrode active material 11 whose volume expands and contracts while inserting and releasing lithium ions, and a coating layer 13 obtained by dry coating the negative electrode active material 11 with an aqueous binder. Active material particles (10); conductive material; and a binder.

The negative electrode active material particles 10 described above may be used as the negative electrode active material particles 10.

Conductive materials are used to further improve the conductivity of the negative electrode active material. These conductive materials are not particularly limited as long as they have conductivity without causing chemical changes in the battery, and examples include graphite such as natural graphite or artificial graphite; Carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskeys such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used. Specific examples of commercially available conductive materials include acetylene black (Chevron Chemical Company, Denka Black (Denka Singapore Private Limited), Gulf Oil Company products, etc.), Ketjenblack, and EC series. (from Armak Company), Vulcan XC-72 (from Cabot Company), and Super P (from Timcal).

The binder may be a water-based binder, but is not limited thereto. The water-based binder is used in the water-based binder mentioned in the negative electrode active material particles 10, and the same or different water-based binders may be used. Preferably, the same water-based binder used in the negative electrode active material may be used to increase bonding strength.

The binder has a lower molecular weight than the water-based binder used in the negative electrode active material particles 10 to enable wet coating.

The binder has a weight average molecular weight of 150,000 g/mol or more, 170,000 g/mol or more, 200,000 g/mol or more, 250,000 g/mol or more, 300,000 g/mol or more, 350,000 g/mol or more, or 400,000 g/mol or more. g/mol or more, 450,000 g/mol or more, 500,000 g/mol or more, 550,000 g/mol or more, 600,000 g/mol or more, 650,000 g/mol or more, and 700,000 g/mol or more. Also, less than 750,000 g/mol, less than 700,000 g/mol, less than 650,000 g/mol, less than 600,000 g/mol, less than 550,000 g/mol, less than 500,000 g/mol, less than 450,000 g/mol , 400,000 g/mol or less, 350,000 g/mol or less, 300,000 g/mol or less, 250,000 g/mol or less, 200,000 g/mol or less. Preferably, 150,000 g/mol or more, 170,000 g/mol or more, 200,000 g/mol or more, 250,000 g/mol or more, 300,000 g/mol or more, 350,000 g/mol or more, 400,000 g/mol or more. mol or more, 450,000 g/mol or more, 500,000 g/mol or less, 750,000 g/mol or less, 700,000 g/mol or less, 650,000 g/mol or less, and 600,000 g/mol or less. More preferably, it has a range of 300,000 g/mol or more, 350,000 g/mol or more, 400,000 g/mol or more, 700,000 g/mol or less, 650,000 g/mol or less, and 600,000 g/mol or less. . A binder within this range exhibits high dispersing power and can uniformly disperse the negative electrode active material particles 10 and the conductive material. In addition, the negative electrode active material particles 10 have excellent compatibility with the water-based polymer of the coating layer 13, thereby increasing adhesion, thereby increasing the adhesion between the negative electrode active material particles 10 and the current collector to prevent interfacial peeling.

An anode slurry composition for a lithium secondary battery can be prepared by a known method. The slurry composition according to one embodiment may be prepared by adding the negative electrode active material particles 10, a conductive material, and a binder to an aqueous solvent and then uniformly mixing them.

The negative electrode active material particles 10 in the negative electrode slurry composition are 80% to 99% by weight based on the total weight of the solid content of the negative electrode slurry, and specifically, 80% by weight or more, 85% by weight or more, 90% by weight or more, and 95% by weight. 97% by weight or more, 98% by weight or more, 99% by weight or less, 98% by weight or less, 97% by weight or less, 95% by weight or less, 90% by weight or less, 85% by weight or less, 82% by weight or less. have At this time, if the content of the negative electrode active material particles 10 is less than the above range, the capacity and lifespan characteristics of the lithium secondary battery may be significantly reduced. Conversely, if the above range is exceeded, the content of the conductive material and binder may be relatively reduced, thereby reducing the conductivity of the negative electrode containing the negative electrode active material particles 10 and the adhesion between the negative electrode active material particles 10 and the negative electrode current collector.

The conductive material in the anode slurry composition is 0.1% to 20.0% by weight based on the total weight of the solid content of the anode slurry, specifically 0.1% by weight or more, 0.5% by weight or more, 1.0% by weight or more, 3.0% by weight or more, 5.0% by weight or more. or more, 10.0% by weight or more, 15.0% by weight or more, 17.0% by weight or more, 19.0% by weight or more, and 19.5% by weight or more. In addition, 20% by weight or less, 19.5% by weight or less, 19.0% by weight or less, 17.0% by weight or less, 15.0% by weight or less, 10.0% by weight or less, 5.0% by weight or less, 3.0% by weight or less, 1.0% by weight or less, 0.5% by weight or less. Hereinafter, the range is 0.2% by weight or less. At this time, if the content of the conductive material is less than the above range, there may be difficulty in providing conductivity between the negative electrode active material particles 10 and the negative electrode current collector due to the insufficient amount of the conductive material. Conversely, if the above range is exceeded, the content of the negative electrode active material particles 10 may be relatively reduced, thereby deteriorating the capacity and lifespan characteristics of the lithium secondary battery.

The binder in the negative electrode slurry composition is 0.5% to 5.0% by weight based on the total weight of solids of the negative electrode slurry, specifically 0.5% by weight or more, 0.7% by weight or more, 1.0% by weight or more, 1.5% by weight or more, 2.0% by weight or more. or more, 2.5% by weight or more, 3.0% by weight or more, 3.5% by weight or more, 4.0% by weight or more, and 4.5% by weight or more. In addition, 5.0% by weight or less, 4.5% by weight or less, 4.0% by weight or less, 3.5% by weight or less, 3.0% by weight or less, 2.5% by weight or less, 2.0% by weight or less, 1.5% by weight or less, 1.0% by weight or less, 0.7% by weight. It has the following range. At this time, if the content of the binder is less than the above range, the bonding strength between the negative electrode active material particles 10 and the conductive material and the bonding force to the current collector may be reduced. Conversely, if the above range is exceeded, the content of the negative electrode active material particles 10 may be relatively reduced, thereby deteriorating the capacity and lifespan characteristics of the lithium secondary battery.

The solvent may be an aqueous solvent, but is not limited thereto. The aqueous solvent includes not only water but also alcohols such as isopropyl alcohol, methyl alcohol, ethyl alcohol, and t-butyl alcohol, and N-methyl alcohol. A solvent mixed with 40% by weight or less of additives such as cyclic amides such as N-Methyl pyrrolidone based on water may be used.

Additionally, the aqueous solvent may be a solvent to which a metal salt is added. When the metal salt is dissolved in the aqueous solvent to form a film appropriately surrounding the outer surface of the negative electrode active material, the film includes the above-mentioned substances such as Li ₂ CO ₃ , LiOCH ₃ , LiOC ₂ H ₅ , or Li ₂ O. Components that make up SEI may be included. Since the components constituting the SEI are water-soluble, they are uniformly included in the film located on the outer surface of the negative electrode active material particles 10 in the negative electrode slurry composition and exist together in the form of a film to perform the same or similar function as SEI, thereby forming the negative electrode. Initial irreversibility can be minimized.

Considering the viscosity, coating properties, and dispersibility of the anode slurry, the aqueous solvent has a solid concentration of 15% by weight or more, 20% by weight, 25% by weight, or 30% by weight, including the anode active material, binder, and optionally a conductive material. It is % by weight or more, 35% by weight or more, 40% by weight or more, and 42% by weight or more. In addition, it has a range of 45% by weight or less, 42% by weight or less, 40% by weight or less, 35% by weight or less, 30% by weight or less, 25% by weight or less, 20% by weight or less, and 17% by weight or less. Preferably, it has a range of 20% by weight or more, 23% by weight or more, 30% by weight or less, and 27% by weight or less.

Meanwhile, the negative electrode slurry composition may additionally include a thickener. The thickener may be a cellulose-based compound, for example, one or more selected from the group consisting of carboxymethylcellulose (CMC), hydroxymethylcellulose, hydroxyethylcellulose, and hydroxypropylcellulose, and specifically carboxymethylcellulose. (CMC) can be

The negative electrode slurry composition contains the thickener in an amount of 0.1% to 3% by weight based on the total weight of solids of the negative electrode slurry, specifically 0.1% by weight or more, 0.5% by weight or more, 1.0% by weight or more, 1.5% by weight or more, It is 2.0% by weight or more, 2.5% by weight or more. Additionally, it is 3.0% by weight or less, 2.5% by weight or less, 2.0% by weight or less, 1.5% by weight or less, 1.0% by weight or less, and 0.5% by weight or less. Preferably, it is 0.5% by weight or more, 1.0% by weight or more, and 2.5% by weight or less, and 2.0% by weight or less. When the negative electrode slurry composition contains the thickener in the above range, an appropriate thickening effect can be achieved to ensure storage stability of the negative electrode slurry composition, and the thickener is included in the negative electrode slurry in an amount that does not affect the performance of the battery. You can.

Additionally, the negative electrode slurry composition may further include a dispersant, and the dispersant may specifically be an aqueous dispersant.

The dispersing agent includes cellulose-based compounds, polyvinyl alcohol, polyvinylpyrrolidone, polyvinyl acetal, polyvinyl ether, polyvinyl sulfonic acid, polyvinyl chloride (PVC), polyvinylidene fluoride, chitosan, starch, and amyl. Rose (amylose), polyacrylamide, poly-N-isopropylacrylamide, poly-N,N-dimethylacrylamide, polyethyleneimine, polyoxyethylene, poly(2-methoxyethoxyethylene), poly(acrylamide) -co-diallyldimethylammonium chloride), acrylonitrile/butadiene/styrene (ABS) polymer, acrylonitrile/styrene/acrylic ester (ASA) polymer, acrylonitrile/styrene/acrylic ester (ASA) polymer and propylene carbonate. A mixture of styrene/acrylonitrile (SAN) copolymer, or methyl methacrylate/acrylonitrile/butadiene/styrene (MABS) polymer may be used, and any one or a mixture of two or more of these may be used.

The anode slurry contains the dispersant in an amount of 0.01% to 0.5% by weight based on the total weight of solids of the anode slurry, specifically 0.01% by weight or more, 0.05% by weight or more, 0.1% by weight or more, 0.2% by weight or more, 0.3% by weight. % or more, 0.4% by weight or more, or 0.45% by weight or more. Additionally, it is 0.5% by weight or less, 0.45% by weight or less, 0.4% by weight or less, 0.3% by weight or less, 0.2% by weight or less, 0.1% by weight or less, and 0.05% by weight or less. Preferably, it is 0.05% by weight or more, 0.1% by weight or more, and 0.5% by weight or less, or 0.3% by weight or less. When the negative electrode slurry contains the dispersant within the above range, the dispersant can appropriately improve the dispersibility of the negative electrode active material, and the dispersant is included in the negative electrode slurry within a certain amount and does not deteriorate battery performance.

In some cases, fillers, etc. may be additionally included in the water-based cathode slurry.

The filler can be used as a component to suppress expansion of the negative electrode, and is not particularly limited as long as it is a fibrous material that does not cause chemical changes in the secondary battery. For example, olipine polymers such as polyethylene and polypropylene; Fibrous materials such as glass fiber and carbon fiber may be used.

cathode

Figure 2 is a cross-sectional view showing the negative electrode 100 for a lithium secondary battery according to the present invention.

Referring to Figure 2, the negative electrode 100 for a lithium secondary battery includes a current collector 50; and a negative electrode active material layer 60 laminated on the upper surface of the current collector 50.

The negative electrode active material layer 60 is manufactured from the negative electrode slurry composition described above, and has negative electrode active material particles 10 dispersed in a substrate 20 containing a binder and a conductive material.

Specifically, the negative electrode 100 may be manufactured by coating the upper surface of the negative electrode current collector 50 with the negative electrode slurry composition described above, followed by drying and rolling.

The negative electrode current collector 50 is not particularly limited as long as it is conductive without causing chemical changes in the battery, and may be made of, for example, copper, gold, stainless steel, aluminum, nickel, titanium, fired carbon, copper, or stainless steel. Surface treatment with 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. At this time, the negative electrode current collector generally has a thickness of 3 μm to 500 μm.

The negative electrode active material layer 60 can suppress the volume expansion of the negative electrode active material described above, and it may be possible to implement a thin film negative electrode having excellent adhesion between the negative electrode active material particles 10 and high energy density. Specifically, the thickness of the negative active material layer 60 is 10 μm or more, 15 μm or more, 20 μm or more, 25 μm or more, 30 μm or more, 35 μm or more, 40 μm or less, 35 μm or less, 30 μm or less, 25 μm or less, 20 μm or less, 15 μm or less, Preferably, it is 20μm or more, 25μm or more, 35μm or less, and 30μm or less.

Lithium secondary battery

Additionally, the present invention provides a lithium secondary battery including a negative electrode, a positive electrode, a separator interposed between the negative electrode and the positive electrode, and an electrolyte.

At this time, the cathode described above may be used as the cathode.

The lithium secondary battery of the present invention can be manufactured by injecting the non-aqueous electrolyte solution of the present invention into an electrode structure consisting of a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode. At this time, the positive electrode, negative electrode, and separator that make up the electrode structure can all be used as those commonly used in manufacturing lithium secondary batteries.

At this time, the positive electrode can be manufactured by coating a positive electrode active material slurry containing a positive electrode active material and optionally a binder, a conductive material, and a solvent on a positive electrode current collector, followed by drying and rolling.

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, calcined carbon, or carbon on the surface of aluminum or stainless steel. , surface treated with nickel, titanium, silver, etc. can be used.

The positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and may specifically include a lithium composite metal oxide containing lithium and one or more metals such as cobalt, manganese, nickel, or aluminum. there is. More specifically, the lithium composite metal oxide is lithium-manganese-based oxide (for example, LiMnO ₂ , LiMn ₂ O ₄ , etc.), lithium-cobalt-based oxide (for example, LiCoO ₂ , etc.), lithium-nickel-based oxide. (e.g., LiNiO ₂ , etc.), lithium-nickel-manganese oxide (e.g., LiNi _1-Y Mn _Y O ₂ (here, 0<Y<1), LiMn _2-z Ni _z O4 (here , 0<Z<2), etc.), lithium-nickel-cobalt oxide (for example, LiNi _1-Y1 Co _Y1 O ₂ (where 0<Y1<1), etc.), lithium-manganese-cobalt oxide Oxide (for example, LiCo _1-Y2 Mn _Y2 O ₂ (where 0<Y2<1), LiMn _2-z 1Co _z1 O ₄ (where 0<Z1<2), etc.), lithium-nickel- Manganese-cobalt-based oxide (e.g., Li(Ni _p Co _q Mn _r1 )O2 (where 0<p<1, 0<q<1, 0<r1<1, p+q+r1=1) or Li(Ni _p1 Co _q1 Mn _r2 )O4 (where 0<p1<2, 0<q1<2, 0<r2<2, p1+q1+r2=2), etc.), or lithium-nickel-cobalt. -Transition metal (M) oxide (for example, Li(Ni _p2 Co _q2 Mn _r3 MS ₂ )O ₂ (where M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg and Mo) is selected, and p2, q2, r3 and s2 are each independent atomic fractions of elements, 0<p2<1, 0<q2<1, 0<r3<1, 0<s2<1, p2+q2+r3+ s2 = 1), etc., and any one or two or more of these compounds may be included. Among these, in that the capacity characteristics and stability of the battery can be improved, the lithium composite metal oxide is LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , lithium nickel manganese cobalt oxide (for example, Li(Ni _0.6 Mn _0.2 Co _0.2 )O ₂ , Li(Ni _0.5 Mn _0.3 Co _0.2 )O ₂ , or Li(Ni _0.8 Mn _0.1 Co _0.1 )O ₂ etc.), or lithium nickel cobalt aluminum oxide (for example, Li(Ni _0.8 Co _0.15 Al _0.05 )O ₂ etc.), etc., and considering the significant improvement effect due to control of the type and content ratio of the constituent elements forming the lithium composite metal oxide, the lithium composite metal oxide is Li(Ni _0.6 Mn _0.2 Co _0.2 )O ₂ , Li (Ni _0.5 Mn _0.3 Co _0.2 )O ₂ , Li(Ni _0.7 Mn _0.15 Co _0.15 )O ₂ or Li(Ni _0.8 Mn _0.1 Co _0.1 )O ₂ , etc., and any one or a mixture of two or more of these may be used. .

The positive electrode active material may be included in an amount of 80% to 99% by weight based on the total weight of each positive electrode mixture.

The binder is a component that assists in the bonding of the active material and the conductive material and the bonding to the current collector, and is usually added in an amount of 1% to 30% by weight based on the total weight of the positive electrode mixture. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, Examples include polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluorine rubber, and various copolymers.

The conductive material is typically added in an amount of 1% to 30% by weight based on the total weight of the positive electrode mixture.

These conductive materials are not particularly limited as long as they have conductivity without causing chemical changes in the battery. For example, graphite; Carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskeys such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used. Specific examples of commercially available conductive materials include acetylene black (Chevron Chemical Company, Denka Singapore Private Limited, Gulf Oil Company products, etc.), Ketjenblack, and EC series. (from Armak Company), Vulcan XC-72 (from Cabot Company), and Super P (from Timcal).

The solvent may include an organic solvent such as NMP (N-methyl-2-pyrrolidone), and may be used in an amount that provides a desirable viscosity when including the positive electrode active material, and optionally a binder and a conductive material. For example, the solid concentration including the positive electrode active material, and optionally the binder and the conductive material may be included such that the concentration is 50% by weight to 95% by weight, preferably 70% by weight to 90% by weight.

In the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. It can be used without particular restrictions as long as it is normally used as a separator in a lithium secondary battery, and in particular, it has low resistance to ion movement in the electrolyte. It is desirable to have excellent resistance and electrolyte moisturizing ability. 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. Additionally, a coated separator containing a ceramic component or polymer material may be used to ensure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

In addition, electrolytes used in the present invention include 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 production of lithium secondary batteries, and are limited to these. It doesn't work.

Specifically, the electrolyte may include an organic solvent and a lithium salt.

The organic solvent may be used without particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent includes ester solvents such as methyl acetate, ethyl acetate, gamma-butyrolactone, and ε-caprolactone; Ether-based solvents such as dibutyl ether or tetrahydrofuran; Ketone-based solvents such as cyclohexanone; Aromatic hydrocarbon-based solvents such as benzene and fluorobenzene; Carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); Alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (R is a C ₂ to C ₂₀ straight-chain, branched or ring-structured hydrocarbon group, and may include a double bond aromatic ring or ether bond); Amides such as dimethylformamide; Dioxolanes such as 1,3-dioxolane; Alternatively, sulfolane, etc. may be used. Among these, carbonate-based solvents are preferable, and cyclic carbonates (e.g., ethylene carbonate or propylene carbonate, etc.) with high ionic conductivity and high dielectric constant that can improve the charging and discharging performance of the battery, and low-viscosity linear carbonate-based compounds ( For example, ethylmethyl carbonate, dimethyl carbonate, diethyl carbonate, etc.) are more preferable. In this case, excellent electrolyte performance can be obtained by mixing cyclic carbonate and chain carbonate in a volume ratio of about 1:1 to about 1:9.

The lithium salt can be used without particular restrictions as long as it is a compound that can provide lithium ions used in lithium secondary batteries. Specifically, the lithium salt is LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAlO ₄ , LiAlCl ₄ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN(C ₂ F ₅ SO ₃ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ₂ , LiN(CF ₃ SO ₂ ) ₂ , LiCl, LiI, or LiB(C ₂ O ₄ ) ₂ , etc. may be used. The concentration of the lithium salt is preferably used within the range of 0.1 to 2.0M. When the concentration of lithium salt is within the above range, the electrolyte has appropriate conductivity and viscosity, so excellent electrolyte performance can be achieved and lithium ions can move effectively.

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. At this time, the additive may be included in an amount of 0.1% to 5% by weight based on the total weight of the electrolyte.

As described above, the lithium secondary battery according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity maintenance rate, and is therefore widely used in portable devices such as mobile phones, laptop computers, digital cameras, and hybrid electric vehicles (HEV). ), etc., and is useful in the field of electric vehicles, etc., and can be particularly preferably used as a component battery of medium to large-sized battery modules. Accordingly, the present invention also provides a medium to large-sized battery module including the above secondary battery as a unit cell.

These medium-to-large battery modules can be preferably applied to power sources that require high output and large capacity, such as electric vehicles, hybrid electric vehicles, and power storage devices.

[Example]

Hereinafter, examples and comparative examples of the present invention will be described. However, the following example describes a preferred embodiment of the present invention, and the present invention is not limited by the following example.

[Manufacture of negative electrode active material particles]

(Method 1) Preparation of negative electrode active material particles: MF dry coating

2 parts by weight of the water-based binder on the particles were added to the mechanofusion facility relative to 100 parts by weight of the negative electrode active material on the particles, and the mechanofusion process was performed by rotating at a low speed of 1000 rpm for 10 minutes and then rotating at 2000 rpm for 5 minutes. According to the mechanofusion process, negative electrode active material particles (average particle diameter (D50): 3.5 μm) coated with a water-based binder on the surface of the silicon-based negative electrode active material particles were manufactured.

(Method 2) Preparation of negative electrode active material particles: Solvent coating

After dissolving 2 parts by weight of the water-based binder in 500 parts by weight of water, 100 parts by weight of the negative electrode active material was added and stirred at 2000 rpm for 20 minutes. Then, after filtration, it was dried in a vacuum oven at 120°C for 10 hours to prepare negative electrode active material particles coated with an aqueous binder.

(Method 3) Manufacturing negative active material particles: Spray coating

A coating solution was prepared by adding 2 parts by weight of an aqueous binder to 500 parts by weight of water and stirring. The coating solution was sprayed onto 100 parts by weight of the negative electrode active material, and then dried in a vacuum oven at 120°C for 10 hours to prepare negative electrode active material particles coated with an aqueous binder.

At this time, PAA (MW 3.5 million g/mol, average particle size (D50) 0.5 μm) and PVA (MW 3 million g/mol, average particle size (D50) 0.4 μm) were used as water-based binders.

In addition, the average particle diameter (D50) of the negative electrode active material was 2.5 μm.

[Slurry composition for anode production and anode production]

A slurry composition was prepared by adding the negative electrode active material particles prepared above, carbon black (product name: Super C65, manufacturer: Timcal) as a conductive material, and a binder as a solvent for forming a negative electrode slurry at a weight ratio of 80:10:10 to distilled water.

The negative electrode slurry is coated on one side of a copper current collector (thickness: 8 μm) as a negative electrode current collector, rolled, and dried in a vacuum oven at 130°C for 10 hours to form a negative electrode active material layer, which is used as a negative electrode. did.

[Lithium secondary battery manufacturing: Half cell]

Li metal was used as a counter electrode, and a polyolefin separator was interposed between each cathode prepared above and Li metal, and then ethylene carbonate (EC) and diethyl carbonate (DEC) were added at a volume ratio of 30:70. Coin-type half-cells were manufactured by injecting an electrolyte containing 1% by weight of vinylene carbonate (VC), 12.5% by weight of fluoroethylene carbonate (FEC), and 1M LiPF ₆ dissolved in the mixed solvent.

[Test Methods]

(1) Dispersibility: More than half of the prepared negative electrode slurry was placed in a 40ml vial container and changes over time were measured. At this time, if the sedimentation rate is fast, the dispersibility is low, and if the sedimentation rate is high, the dispersibility is good.

(2) Capacity maintenance rate at 50 cycles (%): The capacity retention rate at 50 cycles is defined by the following equation (1).

<Equation 1>

Capacity maintenance rate (%) = Discharge capacity in 50 cycles / Discharge capacity in 1 cycle

(3) 50 charge/discharge efficiency (%):

The charge/discharge efficiency at 50 cycles is defined by Equation 2.

<Equation 2>

Charge/discharge efficiency (%) = Discharge capacity in 50 cycles / Charge capacity in 50 cycles

(4) Expansion rate (%): After charging the cathode, disassemble the coin half cell and measure the thickness of the cathode. At this time, the expansion rate is defined by Equation 3.

<Equation 3>

Expansion rate (%) = Thickness of anode mixture after charging / Thickness of anode mixture before charging

Test example 1

In order to measure the physical properties of the battery according to the coating method, the composition was performed using the composition shown in Table 1 below, and the results are shown.

division negative active material water-based binder Coating method dispersibility Remaining Life Capacity (C.P) 50 charge/discharge efficiency (C.E) Expansion rate (%) Example 1 Si PAA MF dry award 90 99.95 70 Example 2 Si PVA MF dry award 86 99.96 72 Example 3 SiO PAA MF dry award 95 99.98 61 Example 4 Si-C PAA MF dry award 94 99.98 63 Comparative Example 1 Si - - award 70 99.8 80 Comparative Example 2 Si PAA solution coating under 52 99.5 150 Comparative Example 3 Si PVA spray coating middle 60 99.6 130

Looking at the table above, the secondary battery using the negative active material particles manufactured by the MF dry coating method had superior dispersibility and showed excellent results in battery characteristics compared to Comparative Examples 2 and 3, which were wet coating methods. In particular, when comparing the expansion rates, it can be seen that when dry coating is performed, the volume expansion of the battery is effectively suppressed due to the use of water-based polymers, PAA and PVA.

Test example 2

In order to measure the physical properties of the battery according to the molecular weight of the water-based binder, the composition was performed using the composition shown in Table 2 below, and the results are shown. At this time, all coatings of the negative electrode active material particles were performed using the MF dry method.

division negative active material particles cathode slurry dispersibility Remaining Life Capacity (C.P) 50 charge/discharge efficiency (C.E) Expansion rate (%) negative active material PAA MW Binder (PAA MW) Example 6 Si 2 million 150,000 award 84 99.96 75 Example 7 Si 5 million 450,000 award 91 99.98 58 Example 8 Si 7.5 million 75KS middle 81 99.98 82 Reference example 1 Si 1 million 450,000 award 75 99.8 85 Reference example 2 Si 1 million 1 million under 69 99.6 120

Looking at the table above, the higher the molecular weight of the PAA of the negative electrode active material particle, the higher the charge/discharge capacity maintenance rate, and when the molecular weight was greater than 7.5 million, the coating uniformity tended to decrease and the capacity retention rate tended to decrease. However, it can be seen that the batteries of Examples 6 to 8 using high molecular weight have superior characteristics compared to the batteries of Reference Examples 1 and 2.

What has been described above is only one example for carrying out the negative electrode active material, its manufacturing method, and a secondary battery containing the negative electrode active material according to the present invention, and the present invention is not limited to the above-described embodiments, and the following patent claims As claimed in the scope, it is included in the technical idea of the present invention to the extent that anyone skilled in the art can make various changes without departing from the gist of the present invention.

10: Negative active material particles
11: Negative active material
13: Coating layer
20: Description
50: cathode current collector
60: Negative active material layer
100: cathode

Claims (22)

A negative electrode active material whose volume expands and contracts while inserting and releasing lithium ions; and
Negative active material particles for secondary batteries comprising a coating layer obtained by dry coating the negative active material with an aqueous binder,
The dry coating is performed by a solvent-free and mechanofusion process, and the surface of the particle-state anode active material is coated with a particle-state aqueous binder by thermal energy from shear stress. Negative active material particles for secondary batteries. According to paragraph 1,
The negative electrode active material is one or more selected from the group consisting of materials capable of reversibly intercalating/deintercalating lithium ions, lithium metal, alloys of lithium metal, materials capable of doping and dedoping lithium, and transition metal oxides. , negative active material particles for secondary batteries. According to paragraph 2,
The material capable of doping and dedoping lithium is at least one selected from the group consisting of a carbon-based active material, a silicon-based active material, and a Sn-based active material, an anode active material particle for a secondary battery. According to paragraph 3,
The silicon-based active material is Si, SiOx (0<x<2), Si-C composite, Si-Q alloy (where Q is an alkali metal, alkaline earth metal, Group 13 element, Group 14 element, Group 15 element, Group 16 element, Negative active material particles for secondary batteries, which are at least one element selected from the group consisting of transition metals, rare earth elements, and combinations thereof, but not Si. According to paragraph 1,
The aqueous binder is polyacrylic acid, polyvinyl alcohol, polyethylene glycol, polyacrylonitrile, polyacryl amide, carboxymethyl cellulose, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyvinylpyridine, and chlorosulfonated Polyethylene, polyester resin, acrylic resin, phenol resin, epoxy resin, gum arabic, styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluorine rubber, ethylene propylene. Negative active material particles for secondary batteries, which are at least one selected from the group consisting of diene copolymers and combinations thereof. According to paragraph 1,
The aqueous binder is a negative electrode active material particle for a secondary battery having a weight average molecular weight (Mw) of 2 million g/mol to 7.5 million g/mol. delete According to paragraph 1,
The coating layer is a negative electrode active material particle for a secondary battery that exists in a layer-type or discontinuously located island-type that continuously covers the surface of the negative electrode active material. According to paragraph 1,
Negative active material particles for a secondary battery, comprising 0.1 to 50 parts by weight of an aqueous binder based on 100 parts by weight of the negative electrode active material particles. Negative active material particles for a secondary battery including a negative electrode active material that expands and contracts while inserting and releasing lithium ions, and a coating layer obtained by dry coating the negative electrode active material with an aqueous binder;
conductive material; A negative electrode slurry composition for a secondary battery comprising a binder,
The dry coating is performed by a solvent-free and mechanofusion process, and the surface of the particle-state anode active material is coated with a particle-state aqueous binder using heat energy from shear stress. A negative electrode slurry composition for a secondary battery. According to clause 10,
The negative electrode active material is one or more selected from the group consisting of materials capable of reversibly intercalating/deintercalating lithium ions, lithium metal, alloys of lithium metal, materials capable of doping and dedoping lithium, and transition metal oxides. , Negative slurry composition for secondary batteries. According to clause 11,
The material capable of doping and dedoping lithium is a negative electrode slurry composition for a secondary battery, wherein the material is at least one selected from the group consisting of a carbon-based active material, a silicon-based active material, and a Sn-based active material. According to clause 12,
The silicon-based active material is Si, SiOx (0<x<2), Si-C composite, Si-Q alloy (where Q is an alkali metal, alkaline earth metal, Group 13 element, Group 14 element, Group 15 element, Group 16 element, A negative electrode slurry composition for a secondary battery, which is at least one element selected from the group consisting of transition metals, rare earth elements, and combinations thereof, but not Si. According to clause 10,
The aqueous binder is polyacrylic acid, polyvinyl alcohol, polyethylene glycol, polyacrylonitrile, polyacryl amide, carboxymethyl cellulose, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyvinylpyridine, and chlorosulfonated Polyethylene, polyester resin, acrylic resin, phenol resin, epoxy resin, gum arabic, styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluorine rubber, ethylene propylene. A negative electrode slurry composition for a secondary battery, which is at least one selected from the group consisting of diene copolymers and combinations thereof. According to clause 10,
The water-based binder has a weight average molecular weight (Mw) of 2 million g/mol to 7.5 million g/mol, a negative electrode slurry composition for a secondary battery. According to clause 10,
The coating layer is a negative electrode slurry composition for a secondary battery that exists in a layer-type or discontinuously located island-type that continuously covers the surface of the negative electrode active material. According to clause 10,
A negative electrode slurry composition for a secondary battery comprising 80% to 99% by weight of negative electrode active material particles, 0.1% to 20.0% by weight of a conductive material, and 0.5% to 5.0% by weight of a binder, based on the total weight of solids of the negative electrode slurry. delete delete delete house collector; and
A negative electrode for a secondary battery including a negative electrode active material layer laminated on the upper surface of the current collector,
The negative electrode active material layer is a negative electrode for a secondary battery including the negative electrode active material particles according to claim 1. A secondary battery containing a cathode, anode, separator, and electrolyte,
The negative electrode is a secondary battery comprising the negative electrode active material particles according to claim 1.