KR20170092122A - Anode Coated with Primer Layer Comprising Graphene and CNT and Method of Manufacturing the Same - Google Patents

Abstract

The present invention relates to a negative electrode for secondary batteries, and a production method thereof. To this end, the negative electrode for secondary batteries comprises: a negative electrode collector; a primer layer formed on at least one side of the negative electrode collector, including a conductive carbon consisting of graphene and carbon nano tube (CNT) and a first binder for bonding the conductive carbon, collectors, and constituents of a negative electrode mixture layer together, and having the thickness of 0.3-2 m; and the negative electrode mixture layer positioned on the primer layer and containing a second binder for bonding gaps between the negative electrode active material and negative electrode active material particles. According to the present invention, it is possible to enhance overall performance of secondary batteries.

Description

[0001] The present invention relates to an anode coated with a primer layer containing graphene and CNTs,

The present invention relates to a negative electrode coated with a primer layer containing graphene and CNT and a method for producing the same.

As technology development and demand for mobile devices have increased, there has been a rapid increase in demand for secondary batteries as energy sources. Among such secondary batteries, lithium secondary batteries, which exhibit high energy density and operational potential, long cycle life, Batteries have been commercialized and widely used.

In recent years, there has been a growing interest in environmental issues, and as a result, electric vehicles (EVs) and hybrid electric vehicles (HEVs), which can replace fossil-fueled vehicles such as gasoline vehicles and diesel vehicles, And the like. Lithium secondary batteries having high energy density, high discharge voltage and output stability are mainly used as power sources for electric vehicles (EV) and hybrid electric vehicles (HEV).

The secondary battery has a structure in which an electrode assembly capable of charging / discharging with a positive electrode / separator / negative electrode structure is mounted on a battery case. The electrodes of the positive electrode and the negative electrode are made of an electrode active material and an organic compound on one surface or both surfaces of the metal current collector And then drying and rolling the electrode coating layer.

However, during the charging and discharging of the secondary battery, the electrode coating layer repeatedly shrinks and expands, thereby causing a phenomenon that part of the electrode coating layer is separated from the current collector. The portion of the electrode coating layer which has been separated from the collector as described above causes a problem in the safety of the secondary battery or increases the internal resistance, thereby deteriorating the overall performance of the secondary battery. Particularly, in the case of an anode using artificial graphite as an active material, this phenomenon is more serious due to the shape problem and the volume expansion.

Therefore, a method of improving the adhesive strength of the electrode coating layer has been actively studied in the art, and a method of containing a large amount of a binder in the electrode is widely used.

The electrode active material, the conductive material, and the current collector constituting the electrode are solid at room temperature, have different surface characteristics and are difficult to easily bond at room temperature. However, when the polymeric binder is used, , It is possible to suppress the desorption of the electrode during the electrode coating, drying and rolling processes.

However, if the content of the binder is increased in order to improve the adhesion of the electrode coating layer, the content of the conductive material and the active material is relatively decreased, thereby increasing the internal resistance of the electrode, decreasing the electron conductivity, and decreasing the capacity have.

As an approach to solve such a problem, an excess amount of conductive material can be used together with the binder. However, the use of such an excessive amount of conductive material may further lower the content of the electrode active material, thereby adversely affecting the capacity of the electrode.

On the other hand, for this purpose, a primer coating layer using a conductive material is adopted. However, since a conductive material such as carbon black has a porous structure, it is difficult to coat the primer coating layer, There is a problem that the consumed amount of the binder is increased and the primer coating layer is thickened.

Therefore, there is a high need for an electrode technology that solves the above problems and has excellent electron conductivity.

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 have succeeded in various experiments and have found that a method of manufacturing an anode current collector and a cathode current collector composed of a graphene and a carbon nano tube (CNT) In the case of including the conductive carbon and the primer layer including the first binder for binding the components, excellent adhesion and electron conductivity of the current collector and the electrode coating layer can be ensured even with a thin thickness, And thus the present invention has been accomplished.

The negative electrode for a secondary battery according to the present invention,

Cathode collector;

A conductive carbon formed on at least one surface of the anode current collector and composed of graphene and a carbon nanotube (CNT); and a conductive carbon layer formed by binding the constituent elements of the conductive carbon, A primer layer having a thickness of 0.3 占 퐉 to 2 占 퐉; And

A negative electrode mixture layer disposed on the primer layer and including a negative electrode active material and a second binder for binding between the negative electrode active material particles;

And a control unit.

That is, the negative electrode according to the present invention includes a primer layer using graphene and carbon nanotubes as the conductive carbon, instead of the conductive material generally used between the current collector and the negative electrode material mixture layer. The graphene and carbon nano- Compared to the conductive material such as carbon black, the tube is advantageous in forming a network structure of the web type and is easy to improve the electron conductivity. The tube has an anisotropy larger than that of the conventional conductive material and can be flatly coated on the current collector. The present invention is advantageous not only in terms of processability but also in adhesion even with a thinner thickness. As a result, it is possible to improve the overall performance of the secondary battery by securing excellent adhesion and conductivity even after charging / discharging of the secondary battery.

Here, the carbon nanotubes are more advantageous in forming a network structure in the form of a web in the thickness direction of the bar electrode having a tube shape in a three-dimensional structure, so that it is good for securing the electron transfer path between the negative electrode mixture layer and the current collector. It is most preferable that the fin is included in the primer layer in consideration of both the processability and the conductivity of the primer layer, and thus the primer layer is most preferably included in the primer layer. The graphene and carbon nanotubes can be contained in a weight ratio of 1: 9 to 9: 1, and the carbon nanotubes are advantageous for improving conductivity, which is a fundamental object of the present invention, ≪ / RTI >

However, unlike the present invention, when only graphene is included or carbon nanotubes are contained in too small amounts, it is difficult to ensure conductivity in the thickness direction of the electrode due to the planar structure of graphene. Similarly, when only carbon nanotubes are included or graphenes are contained too small, the coating properties are not advantageous, and the fairness of such coatings may affect secondary battery performance due to the difference in the local loading amount of the active material , Which is undesirable.

In addition, the carbon nanotubes may have an aligned type or an entangle type structure, and the carbon nanotubes according to the present invention may include any shape, .

Specifically, the bundle-shaped carbon nanotubes and the entangled carbon nanotubes are classified into particle size and shape, and in the chemical vapor deposition method, the carbon nanotubes having a bundle- can do. At this time, since the net structure of the entangled carbon nanotubes is similar to the intermediate form of the point conductive material and the bundled carbon nanotubes as a lumpy structure, the formation of the network structure is disadvantageous, Since carbon atoms are spaced apart from each other by a predetermined distance and are present in strands, it is easier to transfer electrons. Therefore, it is more preferable that the carbon nanotubes included in the primer layer of the present invention have a bundled structure.

The diameter and length of the carbon nanotubes having the most preferable electron transport path for improving the conductivity are specifically in the range of 0.1 to 20 nm in diameter and 100 nm to 5 탆 in length, 100 nm to 2 탆.

Here, the diameter and the length can be measured by AFM. When the thickness is within the above range, the thickness of the primer layer is not too thick, and it is more advantageous in forming a three-dimensional web-type network structure. .

If the diameter is too large, there is a problem that the thickness of the primer layer becomes thicker than necessary, the crystallinity is deteriorated and the conductivity is deteriorated. If the length is too short, there is a problem in forming a network structure, If it is longer than 5 탆, there is a problem in forming a thin and uniform primer layer, which is not preferable.

In addition, the primer layer is required to have a first binder for binding the conductive carbon with the components of the current collector and the negative electrode mixture layer in addition to the conductive carbon, and the total content of the conductive carbon, that is, graphene and carbon nanotubes And the first binder may be 1: 3 to 3: 1 by weight.

If the amount of the conductive carbon is too small, a desired degree of electron conductivity can not be ensured. When the amount of the first binder is too small, the adhesive strength can not be secured at a predetermined level. Rather, it is disadvantageous not only in terms of life characteristics but also in terms of cell resistance, which is undesirable because it deteriorates overall battery performance including electron conductivity.

As described above, the thickness of the primer layer having such a structure may be 0.3 탆 to 2 탆, more specifically 0.3 탆 to 1 탆, and more specifically, 0.3 탆 to 0.5 탆 .

Since the present invention includes graphene and carbon nanotubes having large anisotropy rather than a conductive material having a porous structure as a constituent element of the primer layer, it is possible to form a coating layer in a more flat form, And it is advantageous to form a network structure of the web form. Therefore, it is not necessary to include a large amount in comparison with the conventional conductive material. Therefore, even if the thickness of the primer layer is made very thin without forming the thickness of the primer layer, It is possible to secure the desired electronic conductivity and adhesion.

Therefore, since a smaller amount of conductive carbon and a binder are required to exhibit the same electronic conductivity and adhesive force as in the case of applying a primer layer using a conventional conductive material, the thickness of the primer layer can be reduced, In the case of forming the primer layer with the same thickness as the conventional primer layer, more excellent adhesive force and electron conductivity can be exhibited.

However, in the case of considering all of the capacity, etc., the above range is the most preferable. When the thickness is less than 0.3 탆, the coating uniformity is poor and the primer layer is not formed well, It is impossible to ensure the electron conductivity. When the thickness exceeds 2 탆, a large amount of the binder and conductive carbon is required as in the case of the structure having the conventional primer layer, so that the manufacturing cost is increased and the content of the electrode mixture layer is relatively reduced It is not effective in terms of volume-to-volume and is not preferable.

The method of coating the primer layer is not limited to wet or dry, and any method related to conventional electrode coating can be used, but the wet coating method can be used in detail.

For example, the method is not limited, but can be prepared by gravure-roll coating.

May be carried out by a wet coating method in which a dispersion in which other conductive carbon and a first binder are dispersed in a solvent is applied by a coating method such as bar coating, doctor blade coating, spray coating, flow coating, roll coating, spin coating and gravure coating Of course. The primer layer may be coated and then dried to coat the negative electrode mixture layer, or may be coated with the negative electrode mixture layer before drying, but is not limited thereto.

On the other hand, the thickness of the negative electrode material mixture layer includes a negative electrode active material exhibiting a substantial capacity, and may be relatively much thicker, more specifically, 20 to 200 mu m, .

If the thickness exceeds 200 탆, the thickness of the electrode becomes too thick and the manufacturing cost is greatly increased. If the thickness exceeds 200 탆, the electrode mixture layer surface It is difficult to secure the electronic conductivity in the mixed layer, and the separating effect in the compounded layer can not be exerted against the manufacturing cost in terms of battery performance.

The negative electrode active material contained in the negative electrode material mixture layer is not limited and may include, for example, crystalline graphite, crystalline natural graphite, amorphous hard carbon, low crystalline soft carbon, carbon black, acetylene black, Ketjenblack, Super P, graphene, and fibrous carbon, Si-based materials, Li _x Fe ₂ O ₃ (0? _x? 1), Li _x WO ₂ (0? _x? 1), Sn _{x Me 1-x Me 'y O} z (Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, Group 1 of the Periodic Table, Group 2, Group 3 element, a halogen; 0 <x≤1 ; 1? Y? 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 materials; Titanium oxide; Lithium titanium oxide and the like. In detail, it may be a graphite based material which is most advantageous in application of the primer layer of the present invention, and in view of capacity, and more specifically artificial graphite.

The content of the second binder contained in the negative electrode material mixture layer can be reduced by at least 30% or more as compared with the case where the primer layer is not applied by application of the primer layer. In particular, according to the present invention, And the carbon nanotubes are used as the conductive carbon to form the primer layer, the adhesion strength is further improved by the shape of the conductive carbon, and the adhesion can be reduced by up to 40%.

Therefore, the content of the second binder in the negative electrode material mixture layer may be 0.5 to 2.5% by weight, and more specifically 0.8 to 1.5% by weight based on the total weight of the negative electrode material mixture layer, and the content of the negative electrode active material It is possible to increase the capacity of the battery.

The first binder contained in the primer layer and the second binder contained in the negative electrode mixture layer are not limited as long as they are components that assist in coupling of the active material and the conductive material and bonding to the current collector. For example, polyvinyl fluoride Polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene But may be selected from the group consisting of terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluorine rubber, various copolymers and the like. More specifically, ) Is more preferable.

On the other hand, the negative electrode material mixture layer may further include an electron conductive conductive material. Specifically, the negative electrode material mixture layer may contain 0.1 to 5% by weight, specifically 0.3 to 2% by weight, based on the total weight of the negative electrode material mixture layer Such a conductive material is not particularly limited as long as it is a conventionally known conductive material and has electrical conductivity without causing a chemical change in the battery. For example, carbon black, acetylene black, ketjen black, channel black, , Lamp black, and summer 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.

Further, the negative electrode material mixture layer may further include a filler or 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.

The present invention also provides a method of manufacturing the negative electrode for a secondary battery,

Forming a primer layer comprising a conductive carbon composed of carbon nanotubes and graphene and a first binder on at least one surface of the negative electrode current collector; And

Forming a negative electrode mixture layer including the negative active material and the second binder on the primer layer;

. &Lt; / RTI &gt;

Here, the negative electrode current collector is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, and examples thereof include copper, stainless steel, aluminum, nickel, titanium, sintered carbon, copper or stainless steel A surface treated with carbon, nickel, titanium, silver or the like, an aluminum-cadmium alloy, or the like may 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.

A primer layer and a negative electrode mixture layer are formed on the negative electrode current collector as described above.

In this case, the primer layer and the negative electrode material mixture layer may be formed by a wet method, for example, a gravure-roll coating method, although the primer layer and the negative electrode material mixture layer may be formed by conventional electrode coating methods. Layer can be formed by a wet method in which an electrode slurry in which a negative electrode active material and a second binder are mixed in a solvent is coated on the primer layer and then dried.

The present invention also provides a lithium secondary battery including the negative electrode for a secondary battery.

The lithium secondary battery may have a structure in which the electrode assembly including the negative electrode, the positive electrode, and the separator is embedded in the battery case together with the electrolyte solution.

The positive electrode may be prepared by, for example, applying a positive electrode mixture mixed with a positive electrode active material and a binder to a positive electrode collector, and if necessary, further adding a conductive material and a filler as described in the negative electrode .

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.

Examples of the binder, conductive material, and filler are as described for the negative electrode.

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 provides a battery module including the lithium secondary battery as a unit cell, and a device including the battery module as a power source. Of course, the battery pack including the battery module can be used as the power source of the device.

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.

Such a battery module, a battery pack, and a structure and a manufacturing method of the device are well known in the art, so a detailed description thereof will be omitted herein.

As described above, the negative electrode for a secondary battery according to the present invention is characterized in that a conductive carbon composed of graphene and carbon nano tube (CNT) is formed between the negative electrode current collector and the negative electrode mixture layer, A network structure in the form of a web in the primer layer ensures the electron transfer path between the current collector and the negative electrode mixture layer so that the conductivity can be further improved , The conductive carbon of the present invention has a greater anisotropy than conventional conductive materials and can be flatly coated on the current collector. As a result, the conductive carbon is advantageous in terms of coating processability and can exhibit excellent adhesion even with a thinner thickness. As a result, It is possible to secure excellent adhesive force and conductivity even after discharging, so that the overall performance of the secondary battery can be improved.

Hereinafter, the present invention will be described in detail with reference to the following examples. However, the following examples are intended to illustrate the present invention, and the scope of the present invention is not limited thereto.

&Lt; Example 1 >

The mixture of CMC, SBR, and conductive carbon as a binder was mixed with a mixture of bundled CNT (diameter: 5 nm, length: 1 탆): graphene = 5: 5 as a binder in a weight ratio of 1:10:10 To prepare a precursor for producing a primer layer.

The negative electrode slurry was prepared by mixing artificial graphite as a negative electrode active material, CMC, SBR as a binder, and carbon black as a conductive material in a weight ratio of 96: 1: 2: 1 and adding water as a solvent.

The primer layer was applied to a copper foil having a thickness of 40 占 퐉 in a thickness of 0.3 占 퐉 by a gravure-roll coating method, and then an anode slurry was coated to a thickness of 150 占 퐉. Pressed to have a porosity of 25% and dried at 130 DEG C under vacuum for about 12 hours to prepare a negative electrode.

&Lt; Example 2 >

A negative electrode was prepared in the same manner as in Example 1, except that a mixture of a conductive carbon-type CNT (diameter: 10 nm, length: 1.3 μm): graphene = 5: 5 was used.

&Lt; Example 3 >

A negative electrode was prepared in the same manner as in Example 1, except that a mixture of bundled CNT (diameter: 5 nm, length: 1 탆): graphene = 9: 1 was used as the conductive carbon.

<Example 4>

A negative electrode was prepared in the same manner as in Example 1 except that a mixture of bundled CNT (diameter: 5 nm, length: 1 탆): graphene = 1: 9 was used as the conductive carbon.

&Lt; Example 5 >

Except that artificial graphite as a negative electrode active material, a mixture of CMC, SBR as a binder, and carbon black as a conductive material in a weight ratio of 97: 1: 1: 1 and water was added as a solvent to prepare a negative electrode slurry A negative electrode was prepared in the same manner as in Example 1.

&Lt; Comparative Example 1 &

A negative electrode was prepared in the same manner as in Example 1, except that graphene alone was used as the conductive carbon.

&Lt; Comparative Example 2 &

A negative electrode was prepared in the same manner as in Example 1 except that acetylene black was used as the conductive carbon.

&Lt; Comparative Example 3 &

A negative electrode was prepared in the same manner as in Example 1, except that only bundled CNT (diameter: 5 nm, length: 1 mu m) was used as the conductive carbon.

&Lt; Comparative Example 4 &

A negative electrode was prepared in the same manner as in Example 1, except that the negative electrode was prepared by applying only the negative electrode slurry without forming the primer layer.

&Lt; Comparative Example 5 &

A negative electrode was prepared in the same manner as in Example 1, except that the primer layer was formed to a thickness of 0.1 탆.

<Experimental Example 1>

A positive electrode mixture of 90 wt% of a positive electrode active material (LiCoO ₂ ), 5 wt% of Super-P (conductive material) and 5 wt% of PVDF (binder) was added to NMP (N-methyl-2-pyrrolidone) A positive electrode slurry was prepared and then coated on an aluminum current collector to prepare a positive electrode.

A polyethylene film (Celgard, thickness: 20 占 퐉) and a mixture of ethylene carbonate, dimethyl carbonate, and diethyl carbonate in a ratio of 1: 2: 1 were mixed with the positive and negative electrodes prepared in the above Examples and Comparative Examples, And a liquid electrolyte in which LiPF ₆ was dissolved at 1 M in a solvent was used to prepare secondary batteries.

These secondary cells were subjected to a rate test in the voltage range of 2.5 V to 4.4 V, and the results are shown in Table 1 below.

0.1C / 0.1C
etc.
0.1C / 0.1C 0.5C / 0.5C
etc.
0.1C / 0.1C 1C / 1C
etc.
0.1C / 0.1C 2C / 2C
etc.
0.1C / 0.1C Example 1 100% 98.7% 97.7% 93.4% Example 2 100% 98.6 96.2 88.3 Example 3 100% 98.8 98.3 94.1 Example 4 100% 98.4 97.1 93.1 Example 5 100% 99.3 98.1 95.6 Comparative Example 1 100% 97.4 92.4 81.1 Comparative Example 2 100% 98.1 95.2 83.4 Comparative Example 3 100% 98.8 96.8 92.2 Comparative Example 4 100% 96.2 88.3 74.1 Comparative Example 5 100% 96.8 90.4 75.5

Referring to Table 1, the rate characteristics of the secondary battery (Example 1) using the electrode including the primer layer according to the present invention were evaluated in the case of using either CNT (based on all types) or graphene (Comparative Examples 1 and 3), the use of a primer layer containing other materials (Comparative Example 2), and the use of a primer layer (Comparative Example 4).

In addition, the use of a CNT having a bundle structure (Example 1) is better than that of CNT having a tantalum type structure (Example 2), and the content of CNT and graphene is higher than that of CNT The better the effect is.

Furthermore, referring to Embodiment 5, it can be confirmed that even if the content of the binder in the negative electrode slurry is reduced, it has excellent rate characteristics.

Finally, referring to Example 1 and Comparative Example 5, it can be confirmed that an excellent effect is exerted only when the thickness of the primer layer is thicker than a predetermined value.

<Experimental Example 2>

In order to evaluate the adhesion of each of the negative electrode, embodiments and then laminating the membrane to the produced negative electrode in Comparative Example, and pressed for 5 minutes heating / pressurizing step to 5kg / cm ² thereof at 85 ℃, peel off the membrane from the cathode The results are shown in Table 2 below. &Lt; tb &gt;&lt; TABLE &gt;

Adhesion (gf / cm) Example 1 26.6 Example 2 25.8 Example 3 27.8 Example 4 19.3 Example 5 18.3 Comparative Example 1 18.2 Comparative Example 2 23.1 Comparative Example 3 23.6 Comparative Example 4 16.5 Comparative Example 5 17.1

Referring to Table 2, it can be confirmed that the negative electrode adhesive force of the examples according to the present invention is better or at least similar to the adhesive force.

However, this adhesive strength is not always good as it is a preliminary one for the purpose of exerting the effect of other battery characteristics, and thus the adhesive strength of the negative electrode according to the embodiments of the present invention is generally excellent. However, , And the rate characteristics of Examples 4 and 5, which are not so, can have characteristics superior to Comparative Examples 2 and 3 that have excellent adhesion.

Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims (19)

Cathode collector;
A conductive carbon formed on at least one surface of the anode current collector and composed of graphene and a carbon nanotube (CNT); and a conductive carbon layer formed by binding the constituent elements of the conductive carbon, A primer layer having a thickness of 0.3 占 퐉 to 2 占 퐉; And
A negative electrode mixture layer disposed on the primer layer and including a negative electrode active material and a second binder for binding between the negative electrode active material particles;
And a negative electrode for a secondary battery. The negative electrode for a secondary battery according to claim 1, wherein the graphene and the carbon nanotube are contained in a weight ratio of 1: 9 to 9: 1. The negative electrode for a secondary battery according to claim 1, wherein the carbon nanotubes have an aligned type or an entangle type structure. The negative electrode for a secondary battery according to claim 1, wherein the carbon nanotube has a diameter of 0.1 nm to 20 nm and a length of 100 nm to 5 탆. The negative electrode for a secondary battery according to claim 1, wherein the content ratio of the conductive carbon and the first binder in the primer layer is 1: 3 to 3: 1 based on weight. The negative electrode for a secondary battery according to claim 1, wherein the primer layer is formed by a wet coating method. The negative electrode for a secondary battery according to claim 1, wherein the thickness of the negative electrode material mixture layer is 20 占 퐉 to 200 占 퐉. The negative electrode for a secondary battery according to claim 1, wherein the negative active material is a graphite based material. The negative electrode for a secondary battery according to claim 8, wherein the graphite-based material is artificial graphite. The negative electrode for a secondary battery according to claim 1, wherein the content of the second binder in the negative electrode mixture layer is 0.5 to 2.5 wt% based on the total weight of the negative electrode mixture layer. The negative electrode for a secondary battery according to claim 1, wherein the first binder and the second binder are the same kind of compound. The negative electrode for a secondary battery according to claim 1, wherein the negative electrode material mixture layer further comprises an electrically conductive conductive material. The negative electrode for a secondary battery according to claim 12, wherein the content of the conductive material is 0.1 wt% to 5 wt% based on the total weight of the negative electrode material mixture layer. Forming a primer layer including a first binder and conductive carbon composed of carbon nanotubes and graphenes on at least one surface of the negative electrode current collector; And
Forming a negative electrode mixture layer including the negative active material and the second binder on the primer layer;
Wherein the negative electrode comprises a positive electrode and a negative electrode. 15. The method according to claim 14, wherein the primer layer is formed by a wet coating method. 15. The method of manufacturing a negative electrode for a secondary battery according to claim 14, wherein the negative electrode mixture layer is formed by applying an electrode slurry prepared by mixing and mixing a negative electrode active material and a second binder in a solvent, followed by drying. A lithium secondary battery comprising a negative electrode for a secondary battery according to any one of claims 1 to 13. A battery module comprising the lithium secondary battery according to claim 17 as a unit cell. The device as claimed in claim 18, comprising the battery module as a power source.