KR101775189B1 - The method of preparing electrodes for secondary battery and the electrodes prepared by using the same - Google Patents

Abstract

According to an embodiment of the present invention, there is provided a method of manufacturing an electrode slurry, comprising: preparing an electrode slurry by mixing an electrode mixture composed of an electrode active material, a binder, and a conductive material in a solvent; Applying the electrode slurry to an electrode current collector; And drying the electrode current collector coated with the electrode slurry, wherein the drying is air drying.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of manufacturing an electrode for a secondary battery and an electrode for the secondary battery,

One embodiment of the present invention relates to a method of manufacturing an electrode for a secondary battery and an electrode for a secondary battery produced thereby.

Recent trends in electronic industry development can be summarized as device's wireless, mobile trend and analog to digital conversion. Rapid dissemination of wireless phones (aka mobile phones) and notebook computers, and the transition from analog cameras to digital cameras are examples of this.

Along with this tendency, research and development of a secondary battery as an operation power source of a device is actively proceeding.

The lithium secondary battery has a structure in which a positive electrode / separator / negative electrode assembly is embedded in a sealed container together with an electrolyte. Generally, a manufacturing process of a battery electrode includes a step of applying a slurry obtained by mixing a binder, water, an organic solvent or the like to a common electrode active material onto a metal foil of a thin plate in an appropriate amount and thickness and drying the same. In the case of an electrode material having a porous or hydrophilic surface such as a hard carbon, the slurry has high moisture adsorption ability even in a relatively dry environment in which an electrochemical device is assembled, .

As described above, the moisture contained in the electrode during the manufacturing process or in the material properties reacts with the fluorine component in the electrolyte dissolved in the electrolyte to form hydrofluoric acid, and the formed hydrofluoric acid dissolves the cathode active material, thereby causing unnecessary electrode surface reaction, .

In addition, in the case of a lithium ion battery, water present in the electrode reacts with lithium to generate hydrogen gas, thereby deteriorating the performance of the battery, raising the pressure in the battery and causing a risk of explosion.

An object of the present invention is to provide a method for manufacturing an electrode for a secondary battery capable of minimizing the residual moisture content of the electrode by an air drying method and an electrode for a secondary battery manufactured by the method, We will do it.

According to an aspect of the present invention, there is provided a method of manufacturing an electrode slurry, comprising: preparing an electrode slurry by mixing an electrode mixture comprising an electrode active material, a binder, and a conductive material in a solvent; Applying the electrode slurry to an electrode current collector; And drying the current collector coated with the electrode slurry, wherein the drying is performed by air drying.

In another embodiment of the present invention, there is provided an electrode for a secondary battery manufactured by the above manufacturing method.

In still another embodiment of the present invention, there is provided a secondary battery including the electrode for the secondary battery.

The method for manufacturing an electrode for a secondary battery according to an embodiment of the present invention can minimize moisture content by removing moisture from an electrode by an air drying method.

If the residual water content is minimized, the performance of the secondary battery can be improved by minimizing the performance deterioration such as generation of a side reaction and a large amount of gas during the charging / discharging process after manufacturing the secondary battery due to the residual moisture.

FIG. 1 is a graph showing residual water contents in Examples and Comparative Examples according to an embodiment of the present invention. FIG.

Hereinafter, the present invention will be described in more detail.

An embodiment of the present invention provides a method of manufacturing an electrode slurry, comprising: preparing an electrode slurry by adding an electrode mixture composed of an electrode active material, a binder, and a conductive material to a solvent; Applying the electrode slurry to an electrode current collector; And drying the electrode current collector coated with the electrode slurry, wherein the drying is performed by air drying.

In the method for manufacturing an electrode for a secondary battery, the moisture content of the electrode is removed by the air drying method, thereby minimizing the residual water content. In addition, if the residual water content is minimized, performance degradation such as generation of a side reaction and a large amount of gas during charging / discharging after the manufacture of the secondary battery due to residual moisture is minimized, and the performance of the secondary battery can be improved

The electrode may be a positive electrode or a negative electrode, and the electrode mixture may include an electrode active material, a binder, and a conductive material.

The electrode active material may be a positive electrode active material or a negative electrode active material.

When the cathode active material is not a lithium nickel manganese composite oxide (LNMO), 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 metal ; 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 and LiMnO ₂ ; Lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ and Cu ₂ V ₂ O ₇ ; Formula LiNi _{1- x} M _x O ₂ (where, the M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, x = 0.01 ~ 0.3 Im) Ni site type lithium nickel oxide which is represented by; Formula LiMn ₂ -xMxO 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.

Typical examples of the negative electrode active material include graphite carbon, non-graphitized carbon, amorphous carbon such as non-graphitized carbon, and regular carbon. Other examples include LixFe ₂ O ₃ (0 = x = 1), LixWO 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, Group 2 and Group 3 elements of the periodic table, < 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, Bi ₂ O ₅ and the like; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials, and the like. However, the present invention is not limited thereto.

The binder provides a bonding force to the electrode active material, the conductive material, and the like and the electrode current collector. The binder may be added in an amount of 1 to 50 wt% based on the total weight of the mixture including the cathode active material. have.

The binder may use an aqueous binder to ensure the uniformity of the slurry. However, it is also possible to use a binder in the electrode mixture, such as an electrode active material, a conductive material, and the like, Anything that can provide a binding force can be used without limitation.

The aqueous binder may be selected from the group consisting of acrylonitrile butadiene rubber, styrene-butadiene rubber, acrylic rubber, hydroxyethyl celluloses, carboxymethyl celluloses, and polyvinylidene fluoride, Anything that is used can be used without restriction.

The conductive material may be added in an amount of 1 to 50% by weight based on the total weight of the mixture including the cathode active material. The conductive material is not particularly limited as long as it has conductivity without causing chemical changes in the battery, For example, graphite such as natural graphite or artificial graphite; Carbon black such as carbon black, 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 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 electrode may further include other components such as a filler, a separator, an electrolyte, a viscosity adjusting agent, a coupling agent, and an adhesion promoter, in addition to the electrode active material, the binder and the conductive material.

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 separation membrane is interposed between the anode and the cathode, and an insulating thin film having high ion permeability and mechanical strength is used. The pore diameter of the separator is generally 0.01 to 10 mu m and the thickness is generally 5 to 300 mu m.

Generally, conventional porous polymer films used as separators, for example, polyolefin-based polymers such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers and ethylene / methacrylate copolymers The porous polymer film may be used singly or in a laminated form. Non-woven fabrics made of conventional porous nonwoven fabrics, for example, glass fibers having a high melting point, polyethylene terephthalate fibers, and the like can be used, but the present invention is not limited thereto.

Further, when a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte may also serve as a separation membrane.

The electrolyte is composed of an electrolyte solution and a lithium salt. As the electrolyte solution, non-aqueous organic solvents, organic solid electrolytes, inorganic solid electrolytes, and the like are used.

Examples of the non-aqueous organic solvent include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl Methylene carbonate, gamma-butylolactone, 1,2-dimethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide , Dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone , Propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl 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 ionic 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 material that is readily soluble in the non-aqueous electrolyte, 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 carboxylic acid lithium, lithium tetraphenyl borate and imide.

For the purpose of improving the charge / discharge characteristics and the flame retardancy, the electrolytic solution is preferably mixed with an organic solvent such as pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, glyme, Benzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N, N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, . 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 a preferred _{embodiment, 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 non-aqueous electrolyte.

The electrode slurry comprising the electrode active material, the binder and the conductive material may be mixed with a solvent to prepare an electrode slurry.

The solvent may be mixed with the electrode mix to provide an appropriate level of viscosity so that an electrode slurry coating layer can be formed at a desired level on the electrode collector surface.

The solvent may be selected from the group consisting of water, isopropyl alcohol, methyl alcohol, ethyl alcohol, and t-butyl alcohol, but any solvent conventionally used for an aqueous electrode can be used without limitation.

The electrode slurry may be applied to the electrode collector by mixing the electrode mixture and the solvent to form an electrode slurry. The electrode slurry may be coated on the electrode collector, and then the electrode slurry may be coated with the electrode slurry Drying step can be carried out.

The drying is performed by an air drying method, and the air drying can be performed by supplying atmospheric air to the drying chamber.

The drying chamber may include a heating device, and the inside of the drying chamber may be heated by the heating device.

When the atmospheric air is supplied into the heated drying chamber, the gas contained in the atmospheric air can act as a medium in the drying chamber.

The gas may be a gas such as nitrogen, oxygen, carbon dioxide, and argon, but various gases may exist in the air.

When air in the atmospheric air is supplied into the heated drying chamber, the gases are activated so that heat in the drying chamber can be rapidly transferred to the electrode current collector and the drying speed can be improved.

 Therefore, the air drying can remove moisture using air in the atmosphere, thereby minimizing the amount of residual moisture and reducing the drying time.

If the residual moisture content is minimized by the air drying, the performance degradation such as generation of a side reaction and a large amount of gas during the charging / discharging process after the manufacture of the secondary battery due to the residual moisture is minimized, and the performance of the secondary battery can be improved.

The residual moisture content of the electrode current collector dried by the air drying method may be 10 to 200 ppm.

The drying may be performed at a temperature at which the binder in the electrode current collector is not denatured, and the temperature inside the drying chamber may be selected under the condition that water, alcohol and solvent are vaporized as reaction byproducts in the electrode current collector.

The temperature inside the drying chamber may be 20 to 300 ° C. If it is less than 20 ° C, the water in the electrode current collector may be insufficient to remove. If it is more than 300 ° C, the temperature may be too high, The efficiency can be reduced.

The drying is carried out in a state in which the electrode of 500 to 1500 m is wound on a roll, and the time for drying the current collector in the drying chamber may be 3 to 9 hours,

It is possible to dry within tens of minutes if it is not rolled but rolled up one by one. Also, the drying time may be adjusted according to the amount of water remaining in the electrode current collector.

In another embodiment of the present invention, there is provided an electrode for a secondary battery manufactured by the method for manufacturing an electrode for a secondary battery.

As described above, the electrode composed of the anode, the cathode and the separator can be manufactured in various forms such as a jelly-roll type (wound type) and a stack type (laminate type).

In addition, the secondary battery according to the present invention can be preferably used for a middle- or large-sized battery pack including a plurality of unit cells, in particular, due to its high battery capacity, excellent discharge characteristics and uniform battery performance.

In still another embodiment of the present invention, there is provided a secondary battery including the electrode for the secondary battery.

The present invention provides a battery module including the secondary battery as a unit battery, and a battery pack including the battery module. The battery pack may be used as a power source for devices requiring high temperature stability, long cycle characteristics, and high rate characteristics.

Specific examples of the device include a power tool which is powered by an electric motor and moves; An electric vehicle including an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and the like; An electric motorcycle including an electric bike (E-bike) and an electric scooter (Escooter); An electric golf cart; And a power storage system, but the present invention is not limited thereto.

Hereinafter, the present invention will be described more specifically by way of examples. However, the following examples are intended to aid understanding of the present invention, and the scope of the present invention is not limited to these examples in any sense.

Example

1-1. Manufacture of anode

A positive electrode mixture slurry was prepared by adding 95 wt% of LiCoO ₂ , 3 wt% of Super-P (conductive agent) and 2 wt% of acrylonitrile butadiene rubber (aqueous binder) as a positive electrode active material to a mixed solvent of water and ethanol , Coated on an aluminum foil, air-dried at 100 ° C for 1 hour, and pressed to produce a positive electrode.

1-2. Cathode manufacturing

A negative electrode mixture slurry was prepared by adding 95.5% by weight of artificial graphite, 1.5% by weight of Super-P (conductive agent) and 3% by weight of acrylonitrile butadiene rubber (aqueous binder) as a negative electrode active material to a mixed solvent of water and ethanol, Coated on a copper foil, air-dried at 100 ° C for 1 hour, and pressed to produce a negative electrode.

1-3. Preparation of electrolytic solution

As the electrolyte solution, 1M LiPF ₆ -containing EC / EMC system solution was used.

1-4. Manufacture of Secondary Battery

Using the CELLGARD TM as the separator, the positive electrode of 1-1, the negative electrode of 1-2, and the separator were laminated in this order and wound up, and the electrolyte prepared in 1-3 was added to prepare a lithium secondary battery.

Comparative Example

A secondary battery was prepared in the same manner as in Example 1 except that vacuum drying was performed in a vacuum oven at 120 캜 for 2 hours in the production of the positive electrode.

Experimental Example

1. Measurement of the residual moisture content of the anode according to the Examples and Comparative Examples.

Example Comparative Example Residual moisture content (ppm) 200 350

The residual moisture content of the positive electrode according to the above Examples and Comparative Examples was measured and the results are shown in Table 1 and FIG.

As shown in Table 1 and FIG. 1, the residual moisture content of the anode dried by the air drying according to one embodiment of the present invention was significantly reduced compared to the comparative example in which the anode was dried by the vacuum drying method Can be confirmed.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, Those skilled in the art will readily appreciate that many suitable modifications and variations are possible in light of the above teachings. Accordingly, all such modifications and variations as fall within the scope of the present invention should be considered.

Claims (12)

Preparing an electrode slurry by mixing an electrode mixture composed of an electrode active material, a binder and a conductive material in a solvent;
Applying the electrode slurry to an electrode current collector; And
And drying the electrode current collector coated with the electrode slurry, the method comprising the steps of:
The drying is air drying in which atmospheric air is supplied to the drying chamber to dry it,
The temperature in the drying chamber is 20 to 300 캜,
The drying time is 3 to 9 hours,
Wherein the residual moisture content of the secondary battery electrode is 10 to 200 ppm.
The method according to claim 1,
Wherein the electrode is a cathode or an anode.
The method according to claim 1,
Wherein the binder is an aqueous binder.
The method of claim 3,
The aqueous binder is one or more selected from the group consisting of acrylonitrile butadiene rubber, styrene-butadiene rubber, acrylic rubber, hydroxyethyl celluloses, carboxymethyl celluloses, and polyvinylidene fluoride By weight based on the weight of the secondary battery.
The method according to claim 1,
Wherein the conductive material is at least one selected from the group consisting of natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, metal powder, metal fiber and polyphenylene derivative. Way.
The method according to claim 1,
Wherein the solvent is at least one selected from the group consisting of water, isopropyl alcohol, methyl alcohol, ethyl alcohol and t-butyl alcohol.
delete delete delete delete delete delete

Images