KR20160039985A - Method for manufacturing electrode and electrode manufactured by the same - Google Patents

Abstract

The present invention relates to a method for manufacturing an electrode, capable of increasing adhesion between an electrode current collector and an electrode active material while increasing a rate of an electrode active material layer formation process, and to an electrode manufactured thereby and a lithium secondary battery including the same. According to the present invention, the method for manufacturing an electrode can increase a rate of a coating process, thereby improving productivity. In addition, the method for manufacturing an electrode can allow a binder to be appropriately distributed on an electrode active material layer and an electrode current collector interface. Therefore, in the electrode manufactured by the manufacturing method, the binder included in the electrode active material layer can be appropriately distributed on the electrode active material layer and the electrode current collector interface, so an electrode elimination phenomenon can be suppressed.

Description

METHOD FOR MANUFACTURING ELECTRODE AND METHOD FOR MANUFACTURING THE SAME

The present invention relates to a method of manufacturing an electrode capable of increasing the adhesion between an electrode current collector and an electrode active material layer while increasing the speed of forming an electrode active material layer, an electrode manufactured from the electrode, and a lithium secondary battery comprising the electrode.

Recently, in response to the rapid development of the communication industry such as electronic industry and various information communication including mobile communication, in order to meet the demand of light and short life of electronic devices, a variety of products such as notebooks, netbooks, tablet PCs, mobile phones, smart phones, PDAs, Portable electronic products, and communication terminals have been widely popularized, and development of a battery that is a driving power source for these devices is also increasing.

In addition, with the development of electric vehicles such as hydrogen electric vehicles, hybrid electric vehicles and fuel cell vehicles, great attention has been paid to the development of batteries having high performance, large capacity, high density, high output and high stability, The development of batteries is also a big issue.

Batteries that convert chemical energy into electrical energy are divided into primary cells, secondary cells, fuel cells, and solar cells depending on the type and characteristics of basic materials.

The dual primary cells produce energy through irreversible reactions such as manganese batteries, alkaline batteries, and mercury batteries. However, they have a disadvantage in that they are large in capacity but can not be recycled, and thus have various problems such as energy inefficiency and environmental pollution.

The secondary battery includes a lead-acid battery, a nickel-metal hydride battery, a nickel-cadmium battery, a lithium ion battery, a lithium polymer battery, and a lithium metal battery and repeats charge and discharge using reversible mutual conversion of chemical energy and electric energy. As a chemical cell that can be operated by reversible reaction, it has advantages of recycling and environment-friendly.

The secondary cell has four basic components: a positive electrode and a negative electrode, a separator and an electrolyte.

The positive and negative electrodes have positive and negative potentials, respectively, as electrodes for conversion and storage of energy such as oxidation / reduction. The separator is positioned between the anode and the cathode to maintain electrical insulation and provide a path for charge transport. In addition, the electrolyte acts as an intermediary for charge transfer.

Each of the electrodes includes each of the electrode active materials. Each of the active materials used in a lithium secondary battery, which is currently the most popular among the secondary batteries, is as follows.

Lithium cobalt oxide (Li _x CoO ₂ ), lithium nickel oxide (Li _x NiO ₂ ), lithium nickel cobalt oxide (Li _x (NiCo) O ₂ ), and the like are used as the cathode active material. Oxides such as lithium nickel cobalt manganese oxide (Li _x (NiCoMn) O ₂ ), spinel type lithium manganese oxide (Li _x Mn ₂ O ₄ ), manganese dioxide (MnO ₂ ), or lithium iron phosphate (Li _x FePO ₄ ) Olivine type or NASICON type phosphates, silicates, sulfates or polymer materials such as manganese phosphate (Li _x MnPO ₄ ) and the like can be used.

As the negative electrode active material, a compound capable of intercalating lithium metal, its alloy or lithium ion can be used. A polymer material or a carbon material can be used, and a graphite system such as artificial or natural graphite, Carbon nanotubes (CNTs), carbon nanofibers (CNFs), carbon nanotubes (CNTs), carbon nanotubes (CNTs), graphite- Carbon based materials such as carbon nonawall (CNW), etc. may be used.

The electrode can be generally manufactured by applying an electrode active material slurry on an electrode current collector and drying the electrode active material layer to form an electrode active material layer. The electrode active material slurry is generally prepared by adding an electrode active material, a conductive material, a binder, . Specifically, the electrode may be manufactured by wheating and mixing each material constituting the electrode active material slurry, coating and drying the electrode active material, and then pressing the electrode active material slurry. .

The coating and drying is a step of applying the electrode active material slurry to an electrode current collector and drying to obtain an electrode composed solely of the solid content, and the dispersion medium contained in the electrode active material slurry is evaporated.

At this time, when the application and drying, particularly the drying, is rapidly proceeded, the dispersion medium contained in the electrode active material slurry evaporates and the binder is attached so that the binder is concentrated on the upper part of the electrode active material layer distant from the electrode current collector, The binder is reduced at the portion contacting the electrode active material layer, and as a result, the adhesion between the electrode current collector and the electrode active material layer may be deteriorated. Therefore, in order to increase the adhesion between the electrode current collector and the electrode active material layer, it is important to control the application and drying speed in order to prevent the electrode from desorbing.

Under the above background, the present inventors have found that the process of forming the electrode active material layer by applying and drying the slurry of the electrode active material improves the productivity and improves the productivity while increasing the adhesion between the electrode current collector and the electrode active material layer, The electrode active material slurry is coated on one surface of the electrode current collector and dried, and at least one of the application and the drying is performed while electric charges are applied to the electrode active material, It is possible to improve the adhesion between the electrode and the electrode active material layer, thereby completing the present invention.

JP 2014-007037 A

It is an object of the present invention to provide a method of manufacturing an electrode capable of increasing the adhesion between the electrode and the electrode active material layer while increasing the speed of the electrode active material layer forming process.

Another object of the present invention is to provide an electrode manufactured by the above manufacturing method.

It is still another object of the present invention to provide a lithium secondary battery comprising the electrode.

According to an aspect of the present invention, there is provided a method of manufacturing an electrode active material slurry, comprising the steps of: (1) preparing an electrode current collector coated with an electrode active material slurry by applying an electrode active material slurry on one surface of an electrode current collector; And drying the electrode current collector coated with the electrode active material slurry (step 2), wherein the electrode active material slurry includes a binder having a first charge, and at least one of the application and drying is performed using the electrode active material Wherein the first and second electric charges are performed while applying a second electric charge to one surface of the electrode current collector opposite to the one surface of the electrode current collector coated with the slurry, wherein the first electric charge and the second electric charge are opposite to each other.

The present invention also provides an electrode manufactured from the above-mentioned production method.

In addition, the present invention provides a lithium secondary battery including the electrode.

The method of manufacturing an electrode according to the present invention can increase the speed of the coating process by performing the opposite process of charging the binder during at least one of the application and drying in the coating process including coating and drying, And at the same time, the binder can be appropriately distributed at the interface between the electrode active material layer and the electrode current collector.

In addition, since the electrode according to the present invention is manufactured by the above-described method, the binder contained in the electrode active material layer may be appropriately distributed at the interface between the electrode active material layer and the electrode current collector, so that the electrode desorption phenomenon can be suppressed.

Therefore, the method of manufacturing an electrode according to the present invention and the electrode manufactured therefrom can be easily applied to an industry requiring it, particularly, an electrode and a lithium secondary battery industry using the same.

Hereinafter, the present invention will be described in detail in order to facilitate understanding of the present invention.

The terms and words used in the present specification and claims should not be construed in an ordinary or dictionary sense and the inventor can properly define the concept of the term to describe its invention in the best possible way It should be construed as meaning and concept consistent with the technical idea of the present invention.

The present invention provides a method of manufacturing an electrode having an economical advantage in that an electrode active material coating process can be performed at a high speed while increasing adhesion between an electrode active material and an electrode current collector. At this time, the coating step may include coating the electrode active material slurry on one surface of the electrode current collector, and drying the electrode current collector coated on one surface of the electrode active material slurry.

The method of manufacturing an electrode according to an embodiment of the present invention includes the steps of: (1) preparing an electrode current collector coated with an electrode active material slurry by applying an electrode active material slurry on one surface of an electrode current collector; And drying the electrode current collector coated with the electrode active material slurry (step 2), wherein the electrode active material slurry includes a binder having a first charge, and at least one of the application and drying is performed using the electrode active material Wherein the first charge and the second charge are opposite to each other while the second charge is applied to one surface of the current collector coated with the slurry, the first charge and the second charge being opposite to each other.

The electrode according to the present invention may be a cathode or a cathode. When the electrode is an anode, the electrode active material may be a cathode active material. When the electrode is a cathode, the electrode active material may be an anode active material. That is, the method of manufacturing the electrode according to the present invention is not particularly limited to the positive electrode and the negative electrode, but can be easily applied to any electrode manufacturing process. Depending on the material (for example, the positive electrode active material or the negative electrode active material) Different electrodes can be produced. Preferably, the above production method may be easier to manufacture the positive electrode. Therefore, the term " electrode " used in an electrode, an electrode active material, an electrode current collector, and the like, which will be described later, may mean both a positive electrode and a negative electrode, unless otherwise defined.

The step 1 is a step of placing the electrode active material slurry on the electrode current collector and applying the slurry of the electrode active material onto one surface of the electrode current collector.

The electrode active material slurry may include an additive such as a binder, a conductive material, and a filler that has a first charge on the electrode active material, and may further include a dispersion medium in organic-based mixing.

The binder is a component that assists in bonding between the electrode active material and the conductive material and bonding to the electrode current collector. In order to ensure excellent adhesion between the electrode active material layer and the electrode current collector in the finally produced electrode, the distribution position of the binder is an important factor . That is, as the binder is distributed at a position adjacent to the interface between the electrode active material layer and the electrode collector, the adhesion of the electrode can be improved.

However, as described above, the electrode is manufactured through a coating process in which an electrode active material slurry is coated on one surface of an electrode current collector and dried, and when the speed of the coating and drying process, particularly the drying process, is high, The electrode active material layer moves away from the interface between the electrode active material layer and the electrode current collector and is concentrated on the upper portion of the electrode active material layer, resulting in desorption of the electrode. Therefore, it may be important to distribute an appropriate amount of binder to the interface between the electrode active material layer and the electrode current collector in order to improve the productivity by increasing the speed of the coating process without causing the desorption of the electrode. The above-described problems can be solved.

The first charge according to the present invention may be a positive charge or a negative charge, and the second charge described below may be controlled according to the first charge.

The binder having the first charge may be at least one binder such as a binder having a positive charge or a negative charge. Specifically, the binder may be at least one selected from the group consisting of polyvinylidene fluoride, polyvinyl biarolide, and tetrafluoroethylene. At this time, the binder having the first charge may be contained in the electrode active material slurry in an amount of 1% by weight to 30% by weight based on the total amount of the electrode active material (cathode active material or anode active material), but is not limited thereto.

The electrode active material may be a cathode active material or an anode active material as described above.

The cathode active material may be a lithium iron phosphate-based cathode active material represented by the following general formula (1).

[Chemical Formula 1]

Li _{1 + a} Fe _{1 - x} M _x (PO _{4 -b} ) X _b

In Formula 1,

M is at least one element selected from the group consisting of Al, Mg, Ni, Co, Mn, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, Y,

X is F, S, N or a combination thereof,

a is -0.5? a? 0.5,

x is 0? x? 0.5,

b is 0? b? 0.1.

Preferably, the lithium iron phosphate-based cathode active material may be LiFePO ₄ , LiFeMnPO ₄ , LiFeMgPO ₄ , LiFeNiPO ₄ , LiFeAlPO ₄ or LiFeCoNiMnPO ₄ , and most preferably LiFePO ₄ .

The anode active material is not particularly limited and a carbonaceous material, lithium metal, silicon, or tin, which is commonly known in the art and capable of intercalating and deintercalating lithium ions, may be used. Preferably, the carbon material may be used. As the carbon material, both low-crystalline carbon and highly-crystalline carbon may be used. Examples of the low crystalline carbon include soft carbon and hard carbon. Examples of highly crystalline carbon include natural graphite, kish graphite, pyrolytic carbon, liquid crystal pitch carbon High temperature calcined carbon such as mesophase pitch based carbon fiber, meso-carbon microbeads, mesophase pitches and petroleum or coal tar pitch derived cokes.

The electrode current collector generally has a thickness of 3 to 500 탆. The electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. Examples of the current collector include copper, stainless steel, aluminum, nickel , Titanium, sintered carbon, or a surface treated with carbon, nickel, titanium or silver on the surface of aluminum or stainless steel, or the like can be used.

The conductive material is not particularly limited as long as it has electrical conductivity without causing side reactions with other elements of the battery. Examples of the conductive material include graphite such as natural graphite and artificial graphite; Carbon black such as carbon black (super-p), acetylene black, ketjen black, channel black, furnace 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 whiskers such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; And conductive materials such as polyphenylene derivatives can be used. The conductive material may be included in the electrode active material slurry in an amount of 0.05 wt% to 5 wt% based on the total amount of the electrode active material (cathode active material or anode active material), but is not limited thereto.

The filler is a component for inhibiting the expansion of the electrode. The filler may be used or not, depending on necessity. The filler is not particularly limited as long as it is a fibrous material without causing any chemical change in the battery. Examples of the filler include an olefin polymer such as polyethylene and polypropylene ; Glass fiber, carbon fiber, or the like.

The solvent is not particularly limited, but may be, for example, isopropyl alcohol, N-methylpyrrolidone (NMP), acetone or the like.

The electrode active material slurry may be sprayed or distributed on the electrode current collector and uniformly dispersed using a doctor blade or the like. can do. In addition, it can be performed by a method such as die casting, comma coating, screen printing and the like.

Step 2 is a step for forming an electrode active material layer having a solid content by applying heat or the like to the electrode current collector coated with the electrode active material slurry to evaporate water in the electrode active material slurry.

The drying may be performed by applying heat directly to the upper portion of the electrode current collector coated with the electrode active material slurry, or by applying hot air, preferably by applying hot air.

Specifically, the drying may be performed at a temperature ranging from 100 ° C to 130 ° C and at a rate of 50 l / min to 150 l / min.

The coating and drying may be performed while applying a second electric charge to one surface of the one surface of the electrode current collector coated with the slurry of the electrode active material in one or more steps as described above. And the second charge may be applied by a moving roll that moves the electrode current collector.

The second charge means the charge opposite to the first charge described above. For example, when the first charge is positive, the second charge can be adjusted to a negative charge, and when the first charge is negative, the second charge can be adjusted to positive charge. That is, the manufacturing method according to the present invention is carried out while applying a second electric charge to the lower portion of the electrode current collector (below the surface opposite to the surface on which the electrode active material slurry is coated) in at least one of the coating and drying, Can be distributed in a portion adjacent to the current collector, so that the desorption phenomenon of the produced electrode can be suppressed.

Specifically, as described above, the manufacturing method according to the present invention is performed while applying a second charge to one surface of a lower surface of the electrode current collector, to which the electrode active material slurry is applied, at one or more stages of coating and drying And if the second charge is applied in both the application and drying phases, the second charge may be applied by the same moving roll, or may be applied by different moving rolls.

The moving roll may be a corona wire or a Teflon roll.

The corona wire is connected to a power supply unit, and the second charge can be drawn by a voltage transmitted from the power supply unit. In this case, the second charge can be controlled according to the first charge as described above, and the charge can be controlled by adjusting the charge amount, and the charge amount can be 1 C (coulomb) to 2 C. The corona wire may have a diameter of 300 nm to 1,000 nm, and the voltage may be adjusted to a range of 0.9 kV to 1.5 kV. At this time, when the voltage is lower than 0.9 kV, the voltage is weak and sufficient charge is not applied, so that the coating speed is lowered and the adhesion force between the electrode current collector and the electrode active material layer may be decreased. When the voltage is higher than 1.5 kV, The above effect is insignificant and the economic efficiency may be lowered.

In addition, the Teflon roll may have two to five Teflon rolls connected thereto, and the second charge may be drawn by rotational friction between the adjacent (adjacent) Tetron rolls. At this time, the second charge can be adjusted according to the first charge as described above, and the adjustment can be controlled by the size and number of rolls.

The present invention also provides an electrode manufactured from the above-mentioned production method.

The electrode according to an exemplary embodiment of the present invention may be a cathode or a cathode, and may be preferably a cathode.

In addition, the electrode may be such that the binder is distributed in the electrode active material layer close to the electrode current collector without being densely packed on the electrode active material layer, and the adhesion between the electrode current collector and the electrode active material layer may be excellent, Can be suppressed.

In addition, the present invention provides a lithium secondary battery including the electrode.

The lithium secondary battery according to an embodiment of the present invention includes an anode, a cathode, and a separator interposed between the anode and the cathode, and an electrolyte.

At this time, at least one of the positive electrode and the negative electrode may be one produced by the above-described manufacturing method.

The separator may be an insulating thin film having high ion permeability and mechanical strength, and may have a pore diameter of 0.01 to 10 m and a thickness of 5 to 300 m. As such a separation membrane, a porous polymer membrane such as a porous polymer membrane made of a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, Or a laminate thereof, or a nonwoven fabric made of a conventional porous nonwoven fabric such as a glass fiber having a high melting point, polyethylene terephthalate fiber or the like can be used, but the present invention is not limited thereto.

In addition, the electrolyte may include an organic solvent and a lithium salt commonly used in an electrolyte, and is not particularly limited.

With the lithium salt of the anion is ^{F -, Cl -, I -} , NO 3 -, N (CN) 2 -, BF 4 -, ClO 4 -, PF 6 -, (CF 3) 2 PF 4 -, (CF 3 ^{_{) 3 PF 3 -, (CF}} 3) 4 PF 2 -, (CF 3) 5 PF -, (CF 3) 6 P -, CF 3 SO 3 -, CF 3 CF 2 SO 3 -, (CF 3 SO 2 _{^{) 2 N -, (FSO 2}} ) 2 N -, CF 3 CF 2 (CF 3) 2 CO -, (CF 3 CO 2) 2 CH -, (SF 5) 3 C -, (CF 3 SO 2) 3 _{^{C -, CF 3 (CF 2}} ) 7 SO 3 -, CF 3 CO 2 -, CH 3 CO 2 -, SCN - , and _{(CF 3 CF 2 SO 2)} 2 N - may be at least one member selected from the group consisting of .

Examples of the organic solvent include propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate, methylpropyl carbonate, dipropyl carbonate, dimetal sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, vinylene And may be one or more selected from the group consisting of carbonates, sulfolane, gamma-butyrolactone, propylene sulfite and tetrahydrofuran.

In particular, ethylene carbonate and propylene carbonate, which are cyclic carbonates in the carbonate-based organic solvent, can be preferably used because they have a high dielectric constant as an organic solvent having a high viscosity and thus dissociate the lithium salt in the electrolyte well. These cyclic carbonates, When a low viscosity, low dielectric constant linear carbonate such as carbonate is mixed in an appropriate ratio, an electrolyte having a high electric conductivity can be prepared, and thus it can be more preferably used.

In order to improve the charge-discharge characteristics and the flame retardant characteristics, the electrolyte may further contain at least one selected from the group consisting of pyridine, triethylphosphate, triethanolamine, cyclic ether, ethylenediamine, glyme, hexaphosphoric triamide, , Sulfur, quinone imine dyes, N-substituted oxazolidinones, N, N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, aluminum trichloride, . In some cases, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride may be further added to impart nonflammability. In order to improve the high-temperature storage property, a carbon dioxide gas may be further added. FEC (fluoro-ethylene carbonate ), PRS (propene sulfone), FPC (fluoro-propylene carbonate), and the like.

The lithium secondary battery of the present invention can be manufactured by disposing a separator between an anode and a cathode to form an electrode assembly, inserting the electrode assembly into a cylindrical battery case or a prismatic battery case, and then injecting an electrolyte. Alternatively, the electrode assembly may be laminated, impregnated with the electrolyte, and the resultant may be sealed in a battery case.

The battery case used in the present invention may be of any type that is commonly used in the art, and is not limited in its external shape depending on the use of the battery. For example, a cylindrical case, a square type, a pouch type, (coin) type or the like.

The lithium secondary battery according to the present invention can be used not only in a battery cell used as a power source of a small device but also as a unit cell in a middle- or large-sized battery module including a plurality of battery cells. Preferable examples of the above medium and large-sized devices include, but are not limited to, electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric power storage systems, and the like.

Claims (16)

Preparing an electrode current collector to which an electrode active material slurry is applied by applying an electrode active material slurry on one surface of the electrode current collector; And
And drying the electrode current collector coated with the electrode active material slurry,
Wherein the electrode active material slurry includes a binder having a first charge,
Wherein at least one of the application and the drying is performed while applying a second charge to a lower surface of one surface of the electrode current collector to which the electrode active material slurry is applied,
Wherein the first charge and the second charge are charges opposite to each other.
The method according to claim 1,
And the second electric charge is applied by a moving roll for moving the electrode current collector.
The method of claim 2,
Wherein the moving roll is at least one selected from a corona wire and a Teflon roll.
The method of claim 3,
The corona wire is connected to a power supply,
Wherein the corona wire has a second electric charge due to a voltage transmitted from the power supply unit.
The method of claim 4,
Wherein the voltage is between 0.9 kV and 1.5 kV.
The method of claim 3,
Wherein the corona wire has a diameter of 300 nm to 1,000 nm.
The method of claim 3,
The Teflon roll has two to five Teflon rolls connected thereto,
Wherein the Teflon roll has a second electric charge due to rotational friction between the Teflon rolls connected thereto.
The method according to claim 1,
The application and drying are performed while applying a second charge to a lower surface of one surface of the electrode current collector to which the electrode active material slurry is applied,
And the second charge is applied by the same moving roll.
The method according to claim 1,
The application and drying are performed while applying a second charge to a lower surface of one surface of the electrode current collector to which the electrode active material slurry is applied,
Wherein the second charge is applied by a different moving roll.
The method according to claim 1,
The electrode is an anode,
Wherein the electrode active material is a cathode active material.
The method of claim 10,
Wherein the cathode active material is a lithium iron phosphate-based cathode active material represented by the following Formula 1:
[Chemical Formula 1]
Li _{1 + a} Fe _{1 - x} M _x (PO _{4 -b} ) X _b
In Formula 1,
M is at least one element selected from the group consisting of Al, Mg, Ni, Co, Mn, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, Y,
X is F, S, N or a combination thereof,
a is -0.5? a? 0.5,
x is 0? x? 0.5,
b is 0? b = 0.1.
The method of claim 11,
The lithium iron phosphate-based positive electrode active material is _{LiFePO 4, LiFeMnPO 4, LiFeMgPO 4} , LiFeNiPO 4, LiFeAlPO 4 or LiFeCoNiMnPO method for manufacturing an electrode according to claim _4.
The method according to claim 1,
Wherein the binder is at least one of polyvinylidene fluoride, polyvinyl birolidone, and tetrafluoroethylene.
An electrode fabricated from the method of claim 1.
15. The method of claim 14,
Wherein the electrode is an anode.
A lithium secondary battery comprising the electrode of claim 14.