KR20170031439A - Method of Manufacturing Negative Electrode for Secondary Battery Comprising Active Material Layers Having Different Particle Shape of Negative Active Material - Google Patents

Abstract

The present invention relates to a method for producing a negative electrode for secondary batteries. According to the present invention, the method for producing the negative electrode for secondary batteries comprises the following steps: (a) applying first slurry, consisting of a first negative electrode active material, a binder, and a solvent, to at least one side of a collector; and (b) applying, onto the undried first slurry, second slurry consisting of a second negative electrode active material having a particle shape different from the first negative electrode active material, the binder, and the solvent.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of manufacturing a negative electrode for a secondary battery, the negative electrode active material layer including active material layers having different shapes,

The present invention relates to a method of manufacturing an anode for a secondary battery, the anode active material particles including active material layers having different shapes.

Due to the rapid increase in the use of fossil fuels, the demand for the use of alternative energy or clean energy is increasing. As a part of this, the most active field of research is electric power generation and storage.

At present, a typical example of an electrochemical device utilizing such electrochemical energy is a secondary battery, and the use area thereof is gradually increasing.

The secondary battery is classified into a cylindrical battery and a prismatic battery in which the electrode assembly is housed in a cylindrical or rectangular metal can according to the shape of the battery case, and a pouch-shaped battery in which the electrode assembly is housed in a pouch-shaped case of an aluminum laminate sheet .

The electrode assembly incorporated in the battery case is a charge / dischargeable power generating element formed of a laminate structure of a positive electrode / separator / negative electrode. The electrode assembly is composed of a jelly-roll type in which a separator is interposed between a positive electrode and a negative electrode coated with an active material, Sized positive and negative electrodes are stacked in a stacked state in a state in which a separator is interposed therebetween.

A full cell or anode / separator / cathode / separator / separator / separator / cathode assembly having a positive electrode / separator / negative electrode structure with a constant unit size, which is a progressive structure of a jelly- A stack / folding type electrode assembly having a structure in which a bicell having a positive (negative) electrode structure is folded by using a continuous long separating film has been developed.

Further, in order to improve the processability of the conventional stacked electrode assembly and meet the demands of various types of secondary batteries, a lamination / stacked electrode structure in which unit cells alternately laminated and laminated are laminated Assemblies have also been developed.

On the other hand, the electrode of the secondary battery has a structure in which an electrode coating layer including an electrode active material and a binder is formed on the current collector. During the charging and discharging process of the secondary battery, the electrode coating layer is repeatedly shrunk and expanded, and a part of the electrode coating layer is separated from the current collector.

The portion of the electrode coating layer desorbed from the current collector reduces the capacity and the internal resistance of the secondary battery, thereby deteriorating the overall performance of the secondary battery.

Therefore, in order to prevent the electrode coating layer from separating from the current collector, it is necessary to improve the adhesion between them. As one example, there has been attempted to form a primer coating layer including a conductive material and a binder on the surface of an electrode and to form an electrode coating layer on the primer coating layer.

When such a primer coating layer is included, the adhesion of the electrode coating layer can be ensured, but problems such as reduction of energy density due to the volume occupied by the primer coating layer have occurred.

Therefore, there is a high need for a technique capable of preventing a reduction in the capacity of the secondary battery and ensuring adhesion between the current collector and the electrode coating layer.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art and the technical problems required from the past.

The inventors of the present application have conducted intensive research and various experiments and, as will be described later, a method of manufacturing a negative electrode for a secondary battery includes: forming a first coating layer containing a first negative electrode active material, It is possible to improve the energy density of the secondary battery and secure the adhesion between the current collector and the electrode coating layer. In addition, in the present invention, .

Accordingly, a method of manufacturing a negative electrode for a secondary battery according to the present invention includes:

(a) applying a first slurry including a first negative electrode active material, a binder, and a solvent on at least one surface of a current collector; And

(b) applying a second slurry containing a second negative active material, a binder and a solvent having different particle shapes to the first negative active material on the first slurry in an undried state, do.

The method may further comprise the following steps (c) and (d) after step (b):

(c) drying the first slurry and the second slurry applied to the current collector to form a first coating layer and a second coating layer; And

(d) rolling the first coating layer and the second coating layer.

The primer coating layer includes a conductive material that does not contribute to capacity improvement, while the first coating layer includes a negative electrode active material that improves capacity. That is, in the case of manufacturing the negative electrode according to the present invention, the energy density of the secondary battery can be improved by replacing the primer coating layer, which does not contribute to capacity improvement, with the first coating layer.

In addition, the negative electrode active material affects the energy density and adhesion of the electrode depending on the shape of the particles. The overall performance of the secondary battery can be further increased by including the negative electrode active material having a particle shape suitable for the position of the active material coating layer in the negative electrode.

As one example, the first coating layer adjacent to the current collector may include a first anode active material having a particle shape capable of improving adhesion with a current collector so as to replace the primer coating layer, By including the second anode active material having a particle shape capable of improving the energy density of the secondary battery, both the adhesive force and the energy density of the cathode coating layer with the current collector in the cathode can be improved.

Since the first slurry and the second slurry do not have to be respectively dried through the process of applying the second slurry on the first slurry in an undried state as in the process (b), only one drying step is required, Can be simplified.

Further, the second slurry coated on the first slurry in an undried state may be partially mixed at the interface, and the bonding force between the first coating layer and the second coating layer may be further increased after drying.

In one specific example, another method for manufacturing a negative electrode for a secondary battery according to the present invention comprises:

(A) applying a first slurry containing a first negative electrode active material, a binder, and a solvent on at least one surface of a current collector, and drying the first slurry to form a first coating layer; And

(B) applying a second slurry containing a second negative electrode active material, a binder, and a solvent different in particle shape from the first negative active material on the first coating layer.

The method may further comprise the following step (C) after step (B):

(C) rolling the first coating layer and the second coating layer.

When the second slurry is applied after the first coating layer is formed as in the above processes (A) and (B), uniform application of the second slurry is possible.

In one specific example, the first active material may have a spherical or pseudo spherical shape of the particles. When the active material particle has a spherical or pseudo spherical shape, the adhesive force when mixed with the binder can be kept high, and thus the adhesion between the current collector and the first coating layer can be further improved.

The spherical or pseudo spherical particles can be produced through a sphering process.

In one specific example, the shape of the particles of the second active material may be planar. When the shape of the active material particle is a plan type, lithium can be occluded more in the particle, which can increase the capacity of the negative electrode and further improve the energy density of the secondary battery.

In one specific example, the first negative electrode active material and the second negative electrode active material may be natural graphite or artificial graphite, respectively.

In the case of natural graphite, the decrease in adhesive strength is relatively small when mixed with the binder, but the capacity is relatively small. In the case of artificial graphite, when the binder is blended with the binder, the adhesion is relatively large, but the capacity may be relatively large. Accordingly, the first negative electrode active material and the second negative electrode active material may be appropriately selected in consideration of such a characteristic difference between natural graphite and artificial graphite.

Specifically, the first negative electrode active material may be natural graphite for further improving the adhesion with the current collector, and the second negative electrode active material may be artificial graphite for further improving the energy density.

In one specific example, the first negative electrode active material and the second negative electrode active material may be coated or uncoated particles of a core-shell structure, respectively.

In detail, the first negative electrode active material may be uncoated particles. In the case of uncoated particles, the first negative electrode active material may be mixed with a binder and coated on the current collector, thereby further increasing the adhesion with the current collector.

The second negative electrode active material may be a core-shell structure coated particle. Through the core-shell structure, the mobility of lithium ions can be improved and the rate characteristic of the secondary battery can be improved.

The core-shell structure may be a structure in which amorphous carbon is coated on the surface of a graphite graphite-based core, and the amorphous carbon may be at least one selected from the group consisting of soft carbon and hard carbon.

Wherein the amorphous carbon is prepared by coating a precursor of amorphous carbon to a crystalline graphite core and carbonizing the precursor, wherein the precursor is selected from the group consisting of coal-based pitch, petroleum pitch, polyvinyl chloride, mesophase pitch, And tar. ≪ / RTI >

Meanwhile, the thickness of the second coating layer may be relatively thick compared to the thickness of the first coating layer.

It is advantageous that the first coating layer includes a negative electrode active material having a relatively high adhesion strength in order to secure adhesion with the current collector, and the second coating layer includes a negative active material having a relatively high capacity. Since the capacity of the negative electrode active material having relatively high adhesion is generally low, the first coating layer may have a smaller capacity per unit volume than the second coating layer. Therefore, when the second coating layer is relatively thicker than the first coating layer, the energy density can be further improved.

The thickness of the second coating layer may be in the range of 1.5 to 40 times the thickness of the first coating layer. If the thickness of the second coating layer is less than 1.5 times, the effect of increasing the energy density is not significant. 1 coating layer is relatively thin, it may be difficult to provide a sufficient adhesion force with the current collector.

More specifically, the thickness of the first coating layer may be in the range of from 10 탆 or more to less than 200 탆 within a range satisfying the thickness relative to the second coating layer, and the thickness of the second coating layer may be a relative thickness The thickness may be in the range of 80 占 퐉 or more to 400 占 퐉 or less.

On the other hand, in one specific example, the binder may be an aqueous binder which is eco-friendly and has less emission of harmful components.

When such an aqueous binder is used, it may be difficult to ensure sufficient adhesion to artificial graphite having a relatively small hydrophilic group on the surface of the negative electrode active material.

The aqueous binder is not particularly limited, and examples thereof include an acrylic binder, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone , Ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM styrene-butadiene rubber, fluorine rubber, and the like.

In order to improve the dispersibility of the negative electrode active material in the negative electrode, the first slurry and the second slurry may each further include a dispersing agent.

Such a dispersant is not particularly limited as long as it is a substance that improves the dispersibility of the negative electrode active material and does not significantly deteriorate the adhesive force. Examples of the dispersant include an oil soluble polyamine, an oil soluble amine compound, fatty acids, fatty alcohols, Sorbitan fatty acid esters, and the like.

The dispersant may be contained in an amount of 0.5 to 5 parts by weight based on the total weight of the negative electrode active material and the binder. When the dispersant is less than 0.5 parts by weight, it is difficult to ensure dispersibility of the negative electrode active material. When the dispersant is more than 5 parts by weight, The energy density can be lowered.

The present invention also provides a negative electrode for a secondary battery manufactured by such a method.

The negative electrode comprising: a first coating layer formed on at least one surface of the current collector; And a second coating layer formed on the first coating layer, wherein the first coating layer includes a first negative electrode active material having a shape in which spherical or spherical particles are rolled, and the two coating layers are planar And the second negative electrode active material in a shape in which the particles are rolled.

The present invention also provides an electrode assembly including the negative electrode, wherein the electrode assembly is embedded in a battery case together with an electrolyte solution.

Hereinafter, other components of the secondary battery will be described.

The secondary battery includes a positive electrode, a negative electrode, and a separator. The positive electrode may be manufactured by, for example, applying a positive electrode mixture mixed with a positive electrode active material, a conductive material, and a binder to a positive electrode collector, A filler may further be added to the positive electrode mixture.

The cathode current collector is generally formed to a thickness of 3 to 201 탆 and is not particularly limited as long as it has high conductivity without causing chemical change in the battery. For example, stainless steel, aluminum, nickel, titanium , And a surface treated with carbon, nickel, titanium or silver on the surface of aluminum or stainless steel can be used. Specifically, aluminum can be used. The current collector may form fine irregularities on the surface thereof to increase the adhesive force of the cathode active material, and various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric are possible.

The cathode active material may be, for example, a layered compound such as lithium cobalt oxide (LiCoO ₂ ) or lithium nickel oxide (LiNiO ₂ ) or a compound substituted with one or more transition metals; Lithium manganese oxides such as Li _{1 + x} Mn _{2 -x} O ₄ (where x is 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ , LiMnO ₂ and the like; Lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxides such as LiV ₃ O ₈ , LiV ₃ O ₄ , V ₂ O ₅ and Cu ₂ V ₂ O ₇ ; A Ni-site type lithium nickel oxide expressed by the formula LiNi _1-x M _x O ₂ (where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga and x = 0.01 to 0.3); Formula _{LiMn 2-x M x O 2} ( where, M = Co, Ni, Fe , Cr, and Zn, or Ta, x = 0.01 ~ 0.1 Im) or Li ₂ Mn ₃ MO ₈ (where, M = Fe, Co, Ni, Cu, or Zn); LiMn ₂ O _{4 in} which a part of Li in the formula is substituted with an alkaline earth metal ion; Disulfide compounds; Fe ₂ (MoO ₄ ) ₃ , and the like. However, the present invention is not limited to these.

The conductive material is usually added in an amount of 1 to 30% by weight based on the total weight of the positive electrode material mixture containing the positive electrode active material. Such a conductive material is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, and examples thereof include carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, Carbon black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskey such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.

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

The filler is optionally used as a component for suppressing the expansion of the anode, and is not particularly limited as long as it is a fibrous material without causing a chemical change in the battery. Examples of the filler include olefin polymers such as polyethylene and polypropylene; Fibrous materials such as glass fibers and carbon fibers are used.

On the other hand, as described above, the negative electrode may be manufactured by applying a negative electrode mixture containing a negative electrode active material and a binder to the negative electrode collector, and may further include a dispersant, a filler, and the like selectively.

The negative electrode current collector is not particularly limited as long as it has electrical conductivity without causing a chemical change in the battery. For example, the negative electrode current collector may be formed on the surface of copper, stainless steel, aluminum, nickel, titanium, sintered carbon, Carbon, nickel, titanium, silver or the like, an aluminum-cadmium alloy, or the like can be used. In addition, like the positive electrode collector, fine unevenness can be formed on the surface to enhance the bonding force of the negative electrode active material, and it can be used in various forms such as films, sheets, foils, nets, porous bodies, foams and nonwoven fabrics.

In the present invention, the thickness of the anode current collector may be the same within the range of 3 to 201 [mu] m, but may have different values depending on the case.

In addition to the natural graphite and artificial graphite, the negative electrode active material may include Li _x Fe ₂ O ₃ (0? _X? 1), Li _x WO ₂ (0? _X? 1), Sn _x Me _1-x Me _{y, z, and z in the} periodic table, Me, Mn, Fe, Pb, and Ge; Me ': Al, B, P, Si, 3; 1? Z? 8); Lithium metal; Lithium alloy; Silicon-based alloys; Tin alloy; _{SnO, SnO 2, PbO, PbO} 2, Pb 2 O 3, Pb 3 O 4, Sb 2 O 3, Sb 2 O 4, Sb 2 O 5, GeO, GeO 2, Bi 2 O 3, Bi 2 O 4, and Bi ₂ O ₅ ; Conductive polymers such as polyacetylene; Li-Co-Ni-based material, or the like may be used.

In one specific example, the separation membrane may be a polyolefin-based film commonly used in the art, and may be, for example, high density polyethylene, low density polyethylene, linear low density polyethylene, ultra high molecular weight polyethylene, polypropylene, polyethylene terephthalate polyethyleneterephthalate, polybutyleneterephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyetheretherketone, A sheet made of at least one selected from the group consisting of polyethersulfone, polyphenylene oxide, polyphenylenesulfrode, polyethylene naphthalene, and mixtures thereof.

The separation membrane may be made of the same material but is not limited thereto and may be made of materials different from each other depending on safety, energy density, and overall performance of the battery cell.

The pore size and porosity of the separation membrane are not particularly limited, but the porosity may be in the range of 10 to 95% and the pore size (diameter) may be 0.1 to 50 탆. When the pore size and porosity are 0.1 μm or less and 10% or less, respectively, it acts as a resistive layer. If the pore size and porosity are more than 50 μm and 95%, it is difficult to maintain the mechanical properties.

The electrolyte solution may be a non-aqueous electrolyte containing a lithium salt, and the non-aqueous electrolyte containing a lithium salt is composed of a non-aqueous electrolyte and a lithium salt. Non-aqueous organic solvents, organic solid electrolytes, inorganic solid electrolytes, The present invention is not limited thereto.

Examples of the non-aqueous organic solvent include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma -Butyrolactone, 1,2-dimethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile , Nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, Tetrahydrofuran derivatives, ether, methyl pyrophosphate, ethyl propionate and the like can be used.

Examples of the organic solid electrolyte include a polymer electrolyte such as a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphate ester polymer, an agitation lysine, a polyester sulfide, a polyvinyl alcohol, a polyvinylidene fluoride A polymer containing an acid dissociation group and the like may be used.

Examples of the inorganic solid electrolyte include Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, LiSiO ₄ , LiSiO ₄ -LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Nitrides, halides and sulfates of Li such as Li ₄ SiO ₄ -LiI-LiOH and Li ₃ PO ₄ -Li ₂ S-SiS ₂ can be used.

The lithium salt is a substance that is soluble in the nonaqueous electrolyte and includes, for example, LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB ₁₀ Cl ₁₀ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiAlCl ₄ , CH ₃ SO ₃ Li, (CF ₃ SO ₂ ) ₂ NLi, chloroborane lithium, lower aliphatic carboxylate lithium, lithium tetraphenylborate, and imide.

The nonaqueous electrolyte may contain, for the purpose of improving charge / discharge characteristics, flame retardancy, etc., for example, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, glyme, N, N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, aluminum trichloride and the like may be added have. In some cases, halogen-containing solvents such as carbon tetrachloride and ethylene trifluoride may be further added to impart nonflammability. In order to improve the high-temperature storage characteristics, carbon dioxide gas may be further added. FEC (Fluoro-Ethylene Carbonate, PRS (Propene sultone), and the like.

In one specific _{example, LiPF 6, LiClO 4, LiBF} 4, LiN (SO 2 CF 3) 2 , such as a lithium salt, a highly dielectric solvent of DEC, DMC or EMC Fig solvent cyclic carbonate and a low viscosity of the EC or PC of And then adding it to a mixed solvent of linear carbonate to prepare a lithium salt-containing nonaqueous electrolyte.

The present invention also provides a battery pack including such a secondary battery as a unit cell, and a device including such a battery pack as a power source.

The device may be, for example, a notebook computer, a netbook, a tablet PC, a mobile phone, MP3, a wearable electronic device, a power tool, an electric vehicle (EV), a hybrid electric vehicle (HEV) , A plug-in hybrid electric vehicle (PHEV), an electric bike (E-bike), an electric scooter (E-scooter), an electric golf cart, However, the present invention is not limited thereto.

The structure and manufacturing method of such a device are well known in the art, so a detailed description thereof will be omitted herein.

As described above, the method for manufacturing a negative electrode for a secondary battery according to the present invention is a method for manufacturing a negative electrode for a secondary battery, comprising the steps of: forming, on a first coating layer including a first negative electrode active material, a first negative electrode active material and a second negative electrode active material, 2 coating layer, it is possible to improve the energy density of the secondary battery and improve the adhesion of the current collector and the negative electrode coating layer.

1 is a schematic view showing a negative electrode for a secondary battery including a first coating layer and a second coating layer before rolling according to one embodiment of the present invention;
2 is a schematic view showing a negative electrode manufactured by rolling the negative electrode of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited by the scope of the present invention.

FIG. 1 schematically shows a negative electrode for a secondary battery including a first coating layer and a second coating layer before rolling according to an embodiment of the present invention.

Referring to FIG. 1, a cathode 100 includes a current collector 110, a first coating layer 120, and a second coating layer 130.

Specifically, a first coating layer 120 including a spherical first negative electrode active material is formed on an upper surface of the current collector 110, and a second negative electrode active material is formed on the upper surface of the first coating layer 120 A second coating layer 130 is formed.

FIG. 2 schematically shows a negative electrode manufactured by rolling the negative electrode of FIG.

2, the cathode 200 includes a first coating layer 220 on an upper surface of a current collector 210 and a second coating layer 230 on an upper surface of a first coating layer 220 And has a structure similar to the cathode 100 in general.

The first coating layer 220 of the cathode 200 includes a first anode active material in the form of spherical particles rolled and the second coating layer 230 is coated with a second cathode There is a difference in that the thickness of the first coating layer 220 and the second coating layer 230 is reduced as compared with the thicknesses of the first coating layer 120 and the second coating layer 130 due to the presence of the active material and rolling.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, but it should be understood that the scope of the present invention is not limited thereto.

≪ Example 1 >

The first slurry was prepared by mixing spherical natural graphite as a negative electrode active material, styrene-butadiene rubber (SBR) as a binder, and CMC-Na as a dispersant in a weight ratio of 96: 2.5: 1.5, .

SBR as a binder, and CMC-Na as a dispersant were mixed in a weight ratio of 96: 2.5: 1.5 as a negative electrode active material, and water was added as a solvent to prepare a second slurry.

A first slurry was coated on a copper foil having a thickness of 10 占 퐉 and dried to form a first coating layer having a thickness of 60 占 퐉. A second slurry was coated on the first coating layer and dried to form a second coating layer having a thickness of 100 占 퐉 Respectively.

≪ Comparative Example 1 &

SBR as a binder and CMC-Na as a dispersant were mixed at a ratio of 96: 2.5: 1.5 on the basis of weight, and water was added as a solvent to prepare a negative electrode slurry. A negative electrode slurry having a thickness of 10 占 퐉 The negative electrode slurry was coated on the copper foil and dried to form a negative electrode coating layer having a thickness of 160 탆.

<Experimental Example 1>

The negative electrode prepared in Example 1 and Comparative Example 1 was cut into a size of 10 mm x 200 mm to prepare a test piece. A tape stronger than the peeling force of the negative electrode was adhered on the specimen, and the sheet was closely contacted by reciprocating twice at a speed of 2 kg roller 300 mm / min. The peel force between the copper foil and the negative electrode coating layer was measured while peeling 90 degrees at a speed of 300 mm / min using a TA (Texture Analyzer). The results are shown in Table 1 below.

Peel force (gf / 10 mm) Example 1 35.2 Comparative Example 1 14.6

Referring to Table 1, in Example 1, the first coating layer contained a spherical negative active material and had a very large peeling force. On the other hand, Comparative Example 1 included a negative active material in a negative electrode coating layer facing the current collector, It can be confirmed that the power is very low.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims (24)

A method of manufacturing a negative electrode for a secondary battery,
(a) applying a first slurry including a first negative electrode active material, a binder, and a solvent on at least one surface of a current collector; And
(b) applying a second slurry containing a second negative active material, a binder, and a solvent different in particle shape from the first negative active material onto the first slurry in an undried state;
&Lt; / RTI &gt; The method of claim 1, further comprising the following steps (c) and (d):
(c) drying the first slurry and the second slurry applied to the current collector to form a first coating layer and a second coating layer; And
(d) rolling the first coating layer and the second coating layer. A method of manufacturing a negative electrode for a secondary battery,
(A) applying a first slurry containing a first negative electrode active material, a binder, and a solvent on at least one surface of a current collector, and drying the first slurry to form a first coating layer; And
(B) applying a second slurry on the first coating layer, the second slurry including a second negative electrode active material having a different particle shape from the first negative active material, a binder, and a solvent;
&Lt; / RTI &gt; 4. The method of claim 3, further comprising the following step (C):
(C) rolling the first coating layer and the second coating layer. The method according to claim 1 or 3, wherein the first active material has a spherical or pseudo spherical shape. The method according to any one of claims 1 to 3, wherein the shape of the particles of the second active material is a planar shape. The method according to any one of claims 1 to 3, wherein the first negative electrode active material and the second negative electrode active material are natural graphite or artificial graphite, respectively. The method according to claim 1 or 3, wherein the first negative electrode active material is natural graphite. The method according to claim 1 or 3, wherein the second negative electrode active material is artificial graphite. 4. The method of claim 1 or 3, wherein the thickness of the second coating layer is relatively thick compared to the thickness of the first coating layer. 11. The method of claim 10, wherein the thickness of the second coating layer is in the range of 1.5 to 40 times the thickness of the first coating layer. 11. The method according to claim 10, wherein the thickness of the first coating layer is in a range from 10 mu m or more to less than 200 mu m within a range satisfying a thickness relative to the second coating layer. 11. The method according to claim 10, wherein the thickness of the second coating layer is not less than 80 mu m and not more than 400 mu m within a range satisfying a thickness relative to the first coating layer. The method according to claim 1 or 3, wherein the binder is an aqueous binder. 15. The method of claim 14, wherein the aqueous binder is selected from the group consisting of an acrylic binder, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, A diene terpolymer (EPDM), a sulfonated EPDM styrene-butadiene rubber, and a fluororubber. The method of any one of claims 1 to 3, wherein the first slurry and the second slurry each further comprise a dispersing agent. 17. The method according to claim 16, wherein the dispersing agent is at least one selected from the group consisting of an oil soluble polyamine, an oil-soluble amine compound, fatty acids, fatty alcohols, cellulosic ion exchangers and sorbitan fatty acid esters. 17. The method of claim 16, wherein the dispersant is included in an amount of 0.5 to 5 parts by weight based on the total weight of the negative electrode active material and the binder. A negative electrode for a secondary battery, which is produced by the method according to claim 1 or 3. The method as claimed in claim 19, wherein the negative electrode comprises: a first coating layer formed on at least one surface of the current collector; And a second coating layer formed on the first coating layer,
Wherein the first coating layer comprises a first negative electrode active material having a shape in which spherical or pseudo spherical particles are rolled and the second coating layer includes a second negative electrode active material having a shape in which flake- cathode. An electrode assembly comprising a cathode according to claim 20. The secondary battery according to claim 21, wherein the electrode assembly is embedded in the battery case together with the electrolyte solution. A battery pack comprising the secondary battery according to claim 22 as a unit cell. A device comprising the battery pack according to claim 23 as a power source.

Images