KR101587854B1 - The Method of Preparing Electrodes for Secondary Battery and the Electrodes Prepared by Using the Same - Google Patents

Abstract

The present invention relates to a method of manufacturing an electrode for a secondary battery in which an electrode mixture containing an electrode active material, a binder and a conductive material is applied to a current collector, characterized in that the aluminum current collector is subjected to surface treatment to remove the aluminum oxide (Al ₂ O ₃ ) And then applying the electrode mixture to the electrode to reduce the electrode resistance. The present invention also provides a method of manufacturing an electrode for a secondary battery and an electrode for a secondary battery manufactured using the same.

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,

The present invention relates to a method for producing an electrode for a secondary battery in which an electrode mixture containing an electrode active material, a binder and a conductive material is applied to a current collector, and an electrode manufactured using the electrode. The aluminum current collector is surface- ₂ O ₃ ) layer is removed, and an electrode mixture is applied to reduce the electrode resistance. The present invention relates to an electrode manufactured using 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. Although a nickel metal hydride (Ni-MH) secondary battery is mainly used as a power source for such an electric vehicle (EV) and a hybrid electric vehicle (HEV), a lithium secondary battery having a high energy density, a high discharge voltage, Research is being actively carried out, and some are commercialized.

Conventionally, lithium-cobalt composite oxide is used for the positive electrode and graphite-based material is used for the negative electrode. In recent years, however, a lithium nickel metal oxide having a spinel structure has been used for the positive electrode , Lithium titanium oxide, and the like as a negative electrode active material.

In such a lithium secondary battery, charging and discharging proceed while repeating the process in which lithium ions in the positive electrode are inserted into the negative electrode and desorbed. The theoretical capacity of the battery varies depending on the kind of the electrode active material, but the charging and discharging capacities decrease with the progress of the cycle.

Therefore, there is a great need for a technique capable of improving the performance of the battery by improving the capacity of the battery and exhibiting excellent electrical 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 found that when the electrode mixture is applied after a predetermined surface treatment is performed on the Al current collector as described later, And the present invention has been accomplished.

Accordingly, the present invention provides a method of manufacturing a secondary cell electrode with an electrode material mixture containing an electrode active material, binder and conductive material is applied to the entire Al house, the aluminum oxide surface-treated throughout the Al house (Al ₂ O ₃₎ Layer is removed, and then an electrode mixture is applied to reduce the electrode resistance. The present invention also provides a method of manufacturing an electrode for a secondary battery.

Generally, aluminum reacts with oxygen in the air to form aluminum oxide (Al ₂ O ₃ ), so that in the case of an aluminum current collector, a natural aluminum oxide (Al ₂ O ₃ ) layer of 1 to 5 nm in air is formed.

Such an aluminum oxide layer may act as a resistor in the charging / discharging process of the battery, which may cause a deterioration of the charging / discharging performance of the secondary battery.

Accordingly, the present invention provides a secondary battery electrode by removing the aluminum oxide (Al ₂ O ₃ ) layer by surface treatment on the Al current collector, thereby facilitating the electron movement between the Al current collector and the electrode active material, Not only the internal resistance of the battery can be improved, but also the output and rate characteristics can be improved.

Such a surface treatment method is not limited as long as it is known in the art as to be able to remove the aluminum oxide layer formed on the Al current collector, but in detail, it can be achieved through mechanical treatment using a roller or chemical treatment through etching .

The mechanical treatment may be performed by grinding a roller having fine irregularities on the surface thereof to the Al current collector. The size, spacing, etc. of the fine irregularities can be appropriately adjusted to remove the aluminum oxide layer formed on the Al current collector.

The chemical treatment may be performed by reacting a strong acid or strong base or an Al current collector formed with an aluminum oxide layer. Specifically, a strong acid such as HNO ₃ , H ₂ SO ₄ , or HCl, or a strong base such as LiOH, NaOH or KOH have.

As one example, HCl or NaOH can remove the aluminum oxide layer formed on the Al current collector through the following reaction.

_{Al 2 O 3 + 6HCl → 2AlCl} 3 + 3H 2 O

Al ₂ O ₃ + 6 NaOH + 3H ₂ O? 2Na ₃ Al (OH) ₆

The electrode may be an anode or a cathode, and the anode may include a cathode active material, and the cathode may be a cathode including a cathode active material.

The positive electrode for a secondary battery is prepared by applying a mixture of a positive electrode active material, a conductive material and a binder on a positive electrode current collector, followed by drying and pressing. If necessary, a filler may be further added to the mixture.

The cathode current collector generally has a thickness of 3 to 500 mu m. Such a positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, but may be aluminum as described above.

The cathode active material may be a layered compound such as lithium cobalt oxide (LiCoO ₂ ), 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 , LiFe 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); A lithium manganese composite oxide having a spinel structure represented by LiNi _x Mn _2-x O ₄ ; 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. In detail, it may include a lithium metal oxide having a spinel structure represented by the following formula (1).

Li _x M _y Mn _{2 - y} O _{4 - z z} (1)

Wherein M is at least one element selected from the group consisting of Al, Mg, Ni, Co, Fe, Cr, V, Ti, Cu, B, Ca, Zn, Zr, Nb, Mo, Sr, Sb, W, Ti and Bi; A is one or more of an anion of -1 or -2.

More specifically, the lithium metal oxide may be represented by the following formula (2).

Li _x Ni _y Mn _2-y O ₄ (2)

Wherein 0.9? X? 1.2, 0.4? Y? 0.5;

More specifically, the lithium metal oxide may be LiNi _0.5 Mn _1.5 O ₄ or LiNi _0.4 Mn _1.6 O ₄ .

The conductive material is usually added in an amount of 1 to 50% by weight based on the total weight of the mixture including the cathode active material. Such a conductive material is not particularly limited as long as it has electrical 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 binder is a component that assists in bonding of the active material and the conductive material and bonding to the current collector, and is usually added in an amount of 1 to 50 wt% based on the total weight of the mixture containing the cathode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene , Polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butylene rubber, fluorine rubber, various copolymers and the like.

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

On the other hand, the negative electrode is manufactured by applying, drying and pressing an anode active material on an anode current collector, and may optionally further include a conductive material, a binder, a filler, and the like as described above.

The negative electrode current collector is generally made to have a thickness of 3 to 500 mu m. The negative electrode current collector is not particularly limited as long as it has conductivity without causing chemical change in the battery, but may be aluminum as described above.

Examples of the negative electrode active material include carbon such as non-graphitized carbon and graphite carbon; _{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' : Metal complex oxides such as Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, Halogen, 0 < x < 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; And the like. In detail, a lithium metal oxide represented by the following general formula (3) can be used.

Li _a M ' _b O _{4-ca c} (3)

In the above formula, M 'is at least one element selected from the group consisting of Ti, Sn, Cu, Pb, Sb, Zn, Fe, In, Al and Zr; a and b are 0.1? a? 4; Is determined according to the oxidation number of M 'in the range of 0.2? B? 4; c is determined according to the oxidation number in the range of 0? c <0.2; A is one or more of an anion of -1 or -2.

The oxide of Formula 3 may be represented by Formula 4 below.

Li _a Ti _b O ₄ (4)

More specifically, the lithium metal oxide may be Li _1.33 Ti _1.67 O ₄ or LiTi ₂ O ₄ .

That is, when lithium-titanium oxide (LTO) is used as the negative electrode active material, LTO itself has low electronic conductivity, and thus may have the same electrode structure. In this case, a spinel lithium manganese composite oxide of LiNi _x Mn _2-x O ₄ (x = 0.01 to 0.6) having a relatively high potential due to the high potential of LTO can be used as the cathode active material.

The present invention also provides an electrode for a secondary battery, characterized in that an electrode mixture containing an electrode active material conductive material and a binder is applied to an Al current collector from which an aluminum oxide (Al ₂ O ₃ ) layer has been removed. Specifically, the electrode for the secondary battery may be manufactured by the manufacturing method according to the present invention.

The thickness of the aluminum oxide layer of the current collector of the electrode for the secondary battery may be formed within 0-1 nm by the surface treatment.

The present invention also provides a secondary battery having a structure in which an electrode assembly having a separator interposed between the positive electrode and the negative electrode is impregnated with a lithium salt-containing electrolyte.

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. Such separation membranes include, for example, olefinic polymers such as polypropylene, which are chemically resistant and hydrophobic; A sheet or nonwoven fabric made of glass fiber, polyethylene or the like is used. When a solid electrolyte such as a polymer is used as an electrolyte, the solid electrolyte may also serve as a separation membrane.

The electrolyte solution containing the lithium salt is composed of an electrolyte solution and a lithium salt. The electrolyte solution may be a non-aqueous organic solvent, an organic solid electrolyte, or an inorganic solid electrolyte, but 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 Nonionic organic solvents such as 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 one _{example, LiPF 6, LiClO 4, LiBF} 4, LiN (SO 2 CF 3) A lithium salt of _2, and so on, highly dielectric solvent of DEC, DMC or EMC linear in FIG solvent cyclic carbonate and a low viscosity of the EC or PC Carbonate in a mixed solvent to prepare a non-aqueous electrolyte containing a lithium salt.

The present invention also provides a battery module including the secondary battery as a unit cell, and a battery pack including the battery module.

The battery pack can be used as a power source for a medium and large-sized device requiring high temperature stability, long cycle characteristics, and high rate characteristics.

Examples of the above medium and large-sized devices include a power tool that 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 (E-scooter); An electric golf cart; And a power storage system, but the present invention is not limited thereto.

As described above, the electrode for a secondary battery according to the present invention includes a surface treatment on an Al current collector to remove an aluminum oxide (Al ₂ O ₃ ) layer, and then an electrode active material, a binder, and a conductive material are contained on the surface treatment layer So that the electrical conductivity is improved and the internal resistance of the battery is reduced. As a result, excellent output characteristics and rate characteristics can be exhibited.

FIG. 1 is a graph showing a resistance change rate according to the SOC (state of charge) of a secondary battery according to Experimental Example 1. FIG.

&Lt; Example 1 >

95 wt% of lithium titanate oxide (anode active material), 2.5 wt% of Super-P (conductive agent) and 2.5 wt% of PVdF (binder) were added to NMP to prepare an anode mix. Thereafter, the roller having fine irregularities was polished on the aluminum current collector to polish the front and back surfaces of the aluminum current collector having a thickness of 20 占 퐉 to a total of 5 占 퐉 to remove the aluminum oxide layer. Then, And applied to the whole of the collector to prepare a negative electrode for a secondary battery.

&Lt; Comparative Example 1 &

A negative electrode for a secondary battery was produced in the same manner as in Example 1 except that a 15 탆 aluminum current collector containing an aluminum oxide layer was used on the aluminum current collector.

<Experimental Example 1>

90 wt% of LiNi _0.5 Mn _1.5 O ₄ (cathode active material), 5 wt% of Super-P (conductive agent), and 5 wt% of PVdF (binder) were added to the negative electrode prepared in Example 1 and Comparative Example 1 to NMP The electrode assembly was fabricated using a porous separator made of a positive electrode coated with the prepared positive electrode mixture and polypropylene. Thereafter, the electrode assembly was put in a pouch, and lead wires were connected. After injecting ethylene carbonate (EC) and dimethyl carbonate (DMC) solutions having a volume ratio of 1: 1 in which 1 M of LiPF ₆ salt was dissolved into an electrolyte, And sealed to assemble the lithium secondary battery. The resistance change rate according to the SOC (state of charge) of the secondary battery was measured and is shown in FIG.

1, it can be seen that the battery of Example 1 has a 1 to 6% reduction in resistance in the SOC 10-70% region as compared with the battery of Comparative Example 1. [

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (19)

A method of manufacturing an electrode for a secondary battery, in which an electrode mixture including an electrode active material, a binder, and a conductive material is applied to a current collector,
The electrode is a positive electrode or a negative electrode,
The positive electrode includes a lithium metal oxide having a spinel structure represented by the following Formula 1 as a positive electrode active material,
The surface of the Al current collector is subjected to surface treatment to remove the aluminum oxide (Al ₂ O ₃ ) layer, and then the electrode mixture is applied to reduce the electrode resistance,
The surface treatment is performed by a mechanical treatment using a roller or a chemical treatment through etching,
Wherein the chemical treatment is performed by reacting a strong base of HNO ₃ , H ₂ SO ₄ , or HCl or a strong base of LiOH, NaOH or KOH with an Al current collector.
Li _x M _y Mn _{2 - y} O _{4 - z z} (1)
Wherein 0.9? X? 1.2, 0 <y <2, 0? Z <0.2;
M is at least one element selected from the group consisting of Al, Mg, Ni, Co, Fe, Cr, V, Ti, Cu, B, Ca, Zn, Zr, Nb, Mo, Sr, Sb, W, ;
A is one or more of an anion of -1 or -2. delete The method of manufacturing an electrode for a secondary battery according to claim 1, wherein the mechanical treatment is performed by polishing a roller having fine irregularities on a surface thereof to an Al current collector. delete delete delete The method for manufacturing an electrode for a secondary battery according to claim 1, wherein the lithium metal oxide is represented by the following formula (2)
Li _x Ni _y Mn _2-y O ₄ (2)
Wherein 0.9? X? 1.2, 0.4? Y? 0.5; The method according to claim 7, wherein the lithium metal oxide is LiNi _0.5 Mn _1.5 O ₄ or LiNi _0.4 Mn _1.6 O ₄ . The method of claim 1, wherein the negative electrode comprises a lithium metal oxide represented by the following formula (3) as a negative electrode active material:
Li _a M ' _b O _{4-ca c} (3)
In the above formula, M 'is at least one element selected from the group consisting of Ti, Sn, Cu, Pb, Sb, Zn, Fe, In, Al and Zr;
a and b are 0.1? a? 4; Is determined according to the oxidation number of M 'in the range of 0.2? B? 4;
c is determined according to the oxidation number in the range of 0? c <0.2;
A is one or more of an anion of -1 or -2. The method for manufacturing a secondary battery electrode according to claim 9, wherein the lithium metal oxide is represented by the following formula (4)
Li _a Ti _b O ₄ (4)
In the above formula, 0.5? A? 3, 1? B? 2.5. The method of claim 10, wherein the lithium metal oxide is Li _1.33 Ti _1.67 O ₄ or LiTi ₂ O ₄ . 1. An electrode for a secondary battery characterized in that an electrode mixture containing an active material , a conductive material and a binder is applied to an Al current collector from which an aluminum oxide (Al ₂ O ₃ ) layer has been removed,
The electrode is a positive electrode or a negative electrode,
Wherein the positive electrode comprises a lithium metal oxide having a spinel structure represented by the following Formula 1 as a positive electrode active material:
Li _x M _y Mn _{2 - y} O _{4 - z z} (1)
Wherein 0 < y < 2, 0 z < 0.2,
M is at least one element selected from the group consisting of Al, Mg, Ni, Co, Fe, Cr, V, Ti, Cu, B, Ca, Zn, Zr, Nb, Mo, Sr, Sb, W, ;
A is one or more of an anion of -1 or -2. The secondary battery electrode according to claim 12, wherein the thickness of the aluminum oxide layer of the collector of the secondary battery electrode is 0.1 nm or less. A secondary battery comprising an electrode according to claim 12. 15. The secondary battery according to claim 14, wherein the secondary battery is a lithium secondary battery. 15. A battery module comprising a secondary battery according to claim 14 as a unit cell. A battery pack comprising the battery module according to claim 16. A device comprising a battery pack according to claim 17. 19. The device of claim 18, wherein the device is an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or a system for power storage.

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