KR101495302B1 - Multi Layered Electrode and the Method of the Same - Google Patents

Abstract

The present invention provides an electrode for a secondary battery in which an electrode mixture is applied to one or both surfaces of an electrode current collector, wherein the electrode mixture has a structure of two or more layers and a method for manufacturing the same.

Description

TECHNICAL FIELD [0001] The present invention relates to a multi-layered electrode,

The present invention relates to an electrode for a secondary battery in which an electrode mixture is applied on one surface or both surfaces of an electrode current collector, wherein the electrode mixture has a structure of two or more layers and a method for manufacturing 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 lithium secondary battery has a structure in which a non-aqueous electrolyte containing a lithium salt is impregnated in an electrode assembly having a porous separator interposed between a positive electrode and a negative electrode coated with an active material on an electrode current collector.

In such an electrode structure, the electrode mixture portion in contact with the current collector is required to have high electron conductivity because electrons must be transmitted to the electrode active material remote from the current collector. On the other hand, the portion of the electrode mixture remote from the current collector is required to have excellent electrolyte wettability and ion conductivity with the electrolyte, and should be advantageous for discharge of gases that may occur during charging and discharging.

Therefore, there is a great need for a technology capable of fundamentally solving such a demand.

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

The inventors of the present application have conducted intensive research and various experiments and, as will be described later, in the case of an electrode including an electrode material mixture having two or more layers each containing different active materials having spheroidization degree, And the present invention has been accomplished.

Therefore, the present invention provides an electrode for a secondary battery in which an electrode mixture is applied to one or both surfaces of an electrode current collector, wherein the electrode mixture has a structure of two or more layers.

The two or more electrode material mixture layers have different configurations, and the more the number of layers, the lower the efficiency in the process.

In one specific example, the electrode mixture has a sphericity of the electrode active material layer in the electrode mixture layer (A) near the current collector and a sphericity of the electrode active material layer in the electrode mixture layer (B) far from the current collector Can be.

The sphericity may be defined as the ratio (L _b / L _a) of the shortened length (L _b) of the major axis length of the particles (L _a), the maximum value of sphericity because of the above formula is 1.0.

In general, when the sphericity is small, the electrode density can be increased after pressing, and thus the electrode mix layer (A) can provide an electrode having a higher electrode active material density than the electrode mixture layer (B).

Therefore, the electrode material mixture layer (A) has a high density of the electrode material mixture and can have excellent electron conductivity. The electrode material mixture layer (B) has a relatively low density and has a large surface area in contact with the electrolyte solution, The relatively coarse structure improves the electrolyte impregnability, and the gas generated inside the electrode can escape to the outside.

In one specific example, the electrode active material sphericity of the electrode mixture layer (A) may range from 0.3 to 0.9. If the sphericity is less than 0.3, the absorption / release of lithium may not be smooth due to the ubiquitous nature of the arrangement. If the sphericity is more than 0.9, the sphericity is high and it is not preferable because it is difficult to differentiate from the structure of the electrode mixture layer (B) .

The electrode active material sphericity of the electrode mixture layer (B) may be in the range of 0.5 to 1.0 in a range larger than that of the electrode active material sphericity of the electrode mixture layer (A). If the sphericity is less than 0.5, it may be difficult to differentiate from the composition of the mixed layer (A), which is not preferable.

FIGS. 1 and 2 are schematic diagrams showing sphering of an electrode active material existing in the electrode mixture layer (A) and an electrode active material present in the electrode mixture layer (B).

1 and 2, the sphericity (b / a) of the electrode active material existing in the electrode mixture layer (A) is about 0.87 and the sphericity b / a of the electrode active material present in the electrode mixture layer (B) a) is about 0.97, which is close to 1. That is, the sphericity of the electrode active material of the electrode mixture layer (A) is made smaller than the sphericity of the electrode active material of the electrode mixture layer (B).

In the above structure, the thickness ratio of the electrode material mixture layer (A) and the electrode material mixture layer (B) may be 30:70 to 70:30, and more specifically, 45:55 to 55:45. If the thickness of the electrode mixture layer (A) is too small, the density of the portion close to the current collector is low and it is difficult to exhibit the effect of improving the electron conductivity. When the thickness of the electrode mixture layer (B) The density is increased even at a portion far from the current collector, and the surface area contacting the electrolyte is small, so that the electrolyte impregnability is lowered and it is difficult to exert the effect of improving the ion conductivity.

Specifically, the electrode resistance of the electrode satisfying the above conditions may be 0.07? / Cm or less, more specifically, 0.05? / Cm or less.

The electrode for the secondary battery may be a cathode including a cathode active material or 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. Examples of the positive electrode current collector include stainless steel, aluminum, nickel, titanium, sintered carbon, aluminum or stainless steel A surface treated with carbon, nickel, titanium, silver or the like may be used. The current collector may have 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 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. However, the present invention is not limited to these.

In one specific example, the cathode active material may be a lithium manganese composite oxide having a spinel structure which is a high-potential oxide represented by the general formula (1).

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.

Specifically, the lithium manganese composite oxide may be a lithium nickel manganese composite oxide represented by the following formula (2), more specifically, LiNi _0.5 Mn _1.5 O ₄ or LiNi _0.4 Mn _1.6 O ₄ .

Li _x Ni _y Mn _2-y O ₄ (2)

In the above formula, 0.9? X? 1.2 and 0.4? Y? 0.5.

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

The negative electrode active material may include, for example, carbon such as non-graphitized carbon or 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 &lt; x &lt; 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 can be used.

In one specific example, the negative electrode active material may be a lithium metal oxide represented by the following formula (3).

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.

Specifically, the lithium metal oxide represented by Formula 3 may be a lithium titanium oxide (LTO) represented by the following Formula 4, and specifically, Li _0.8 Ti _2.2 O ₄ , Li _2.67 Ti _1.33 O ₄ , LiTi ₂ O ₄ , Li _1.33 Ti _1.67 O ₄ , Li _1.14 Ti _1.71 O _4, etc. However, there is no particular limitation on the composition and kind of lithium ions capable of intercalating / deintercalating lithium ions, and more specifically, It may be a spinel structure of Li _1.33 Ti _1.67 O ₄ or LiTi ₂ O ₄ having a small change and excellent reversibility.

Li _a Ti _b O ₄ (4)

In the above formula, 0.5? A? 3, 1? B? 2.5.

In one example, when lithium-titanium oxide (LTO) is used as the negative electrode active material, the electrode structure as described above is preferable because LTO itself has low electronic conductivity. In this case, it is preferable to use the spinel lithium nickel manganese composite oxide of Li _x Ni _y Mn _2-y O ₄ represented by the above formula (2) having a relatively high potential due to the high potential of LTO as the cathode active material.

The present invention provides a secondary battery comprising the electrode, wherein the secondary battery is a lithium secondary battery having a structure in which an electrolyte solution containing a lithium salt is impregnated in an electrode assembly having a separator interposed between the positive electrode and the negative electrode have.

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 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 non-aqueous electrolyte.

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 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 (E-scooter); An electric golf cart; And a power storage system, but the present invention is not limited thereto.

The present invention relates to a method of manufacturing an electrode for a secondary battery in which an electrode mixture is applied on one surface or both surfaces of a current collector,

(i) first coating an electrode mixture containing an active material having a relatively low sphericity on the current collector; And

(ii) secondarily coating an electrode mixture containing the active material having a relatively high degree of sphericity on the first coated electrode;

The present invention also provides a method of manufacturing an electrode for a secondary battery.

The reason why the sphericity is relatively high and low is that the sphericity of the electrode active material of the primary coating electrode and the sphericity of the electrode active material of the secondary coating electrode are compared.

In the method of manufacturing the electrode, a first coating step and a drying step may further be included. It is possible to apply the mixture layer having a high degree of sphericity to the mixture layer having a low sphericity without drying, but it is effective to prevent the mixture from being mixed with each other when the drying process is carried out.

The method of manufacturing the electrode may further include a step of drying and pressing the electrode after the secondary coating.

As described above, the electrode for a secondary battery according to the present invention is improved in electrolyte impregnation property, ion conductivity, electron conductivity, and the like by producing a multi-layered electrode using an active material having a different sphericity, Thereby improving the electrochemical performance.

1 is a schematic diagram showing a sphericity of an electrode active material present in an electrode mixture layer (A);
2 is a schematic diagram showing the sphericity of the electrode active material present in the electrode mixture layer (B).

Hereinafter, the present invention will be described in further detail with reference to the following examples. However, the following examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

&Lt; Example 1 >

Cathode manufacturing

As a result of observation with a scanning microscope (SEM: Hitachi, S-4800), Li _1.33 Ti _1.67 O ₄ having an average sphericity of 0.87 was used as a first negative electrode active material and a conductive material (Super-C) and a binder (PVdF) Were mixed in NMP (N-methyl-2-pyrrolidone) at a weight ratio of 90: 5: 5 and mixed to prepare a first negative electrode mixture. Li _1.33 Ti _1.67 O ₄ having an average sphericity of 0.97 was used as a second negative electrode active material , A conductive material (Super-C) and a binder (PVdF) were put into NMP at a weight ratio of 90: 5: 5 respectively and mixed to prepare a second negative electrode material mixture. At this time, the ratio (b / a) of the short axis length to the long axis length is defined as a spheroidization degree.

The prepared first negative electrode material mixture was coated on a copper foil having a thickness of 20 탆 to a thickness of 40 탆 and then dried. A second negative electrode material mixture was coated on the first negative electrode material mixture coating layer to a thickness of 40 탆, rolled and dried, . The porosity and the negative electrode resistance of the negative electrode were measured. As a result, the porosity was 40% and the resistance was 0.05 Ω / cm.

Manufacture of Secondary Battery

LiNi _0.5 Mn _1.5 O ₄ was used as a positive electrode active material, a conductive material (Super-C) and a binder (PVdF) were mixed in NMP at a weight ratio of 90: 6.5: 3.5, Coated on a foil, rolled and dried to prepare a positive electrode.

After the electrode assembly was manufactured through a separator (Celgard ^TM , thickness: 20 탆) between the cathode and the anode, the electrode assembly was housed in a pouch-shaped battery case, and a carbonate-based one containing 1 M of LiPF ₆ Was injected into the electrolyte and then sealed to prepare a lithium secondary battery.

&Lt; Comparative Example 1 &

A negative electrode active material (Li _1.33 Ti _1.67 O ₄ ), an electroconductive material (Super-C) and a binder (PVdF) having an average spherical degree of 0.97 were mixed in NMP at a weight ratio of 90: 5: 5, A lithium secondary battery was prepared in the same manner as in Example 1, except that a negative electrode was prepared by coating a 20 탆 thick copper foil with a thickness of 80 탆 and rolling and drying the negative electrode. At this time, the porosity and the negative electrode resistance of the negative electrode were measured. As a result, the porosity was 40% and the resistance was 0.08? / Cm.

<Experimental Example 1>

The capacity of the lithium secondary batteries prepared in Example 1 and Comparative Example 1 was measured at 3 C rate to confirm rate characteristics. The results are shown in Table 1 below.

3C-rate, capacity ratio (%) Example 1 92.0% Comparative Example 1 89.0%

As shown in Table 1, the battery of Example 1 according to the present invention has improved rate characteristics as compared with the battery of Comparative Example 1.

This is because only the electrode active material having an average degree of spheroidization of 0.97 is used by coating the electrode mixture containing the active material having relatively low sphericity and the electrode mixture containing the active material with relatively high sphericity This is because an electrode having a higher density at a portion close to the electrode current collector can be manufactured as compared with the case where the electrode is used, thereby improving the electronic conductivity.

Although the electrolyte impregnating property of the secondary battery having the two-layer structure according to the present invention may be somewhat lowered as the density of the portion near the electrode current collector is higher than the case of using only the electrode active material having a high average sphericity, It was confirmed that the electrolytic solution impregnability of the desired degree can be maintained while exhibiting the effect of improving the rate characteristics as well. Further, when the manufacturing method according to the present invention is applied to both the positive electrode and the negative electrode, the rate characteristic is further improved.

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 (25)

An electrode for a secondary battery, wherein an electrode mixture is applied to one or both surfaces of an electrode current collector, wherein the electrode mixture has a two-layer structure,
The spherical shape of the electrode active material in the electrode mixture layer (A) near the current collector is smaller than the spheroidization degree of the electrode mixture layer (B) far from the current collector,
The sphericity is a secondary cell electrode, characterized in that the ratio (L _b / L _a) of the shortened length (L _b) of the major axis length of the particles (L _a). delete delete The electrode for a secondary battery according to claim 1, wherein the electrode mixture layer (A) has an electrode active material sphericity ranging from 0.3 to 0.9. The electrode for a secondary battery according to claim 1, wherein the electrode active material sphericity of the electrode mixture layer (B) is in the range of 0.5 to 1.0 in a range larger than that of the electrode active material sphericity of the electrode mixture layer (A). The electrode for a secondary battery according to claim 1, wherein a thickness ratio of the electrode material mixture layer (A) to the electrode material mixture layer (B) is 30:70 to 70:30. The electrode for a secondary battery according to claim 6, wherein the thickness ratio of the electrode material mixture layer (A) to the electrode material mixture layer (B) is 45:55 to 55:45. The electrode for a secondary battery according to claim 1, wherein the electrode has an electrode resistance of 0.07? / Cm or less. The electrode for a secondary battery according to claim 1, wherein the electrode has an electrode resistance of 0.05? / Cm or less. The electrode for a secondary battery according to claim 1, wherein the electrode is an anode or a cathode. 11. The electrode for a secondary battery according to claim 10, wherein the anode is a high-voltage anode comprising a lithium manganese composite oxide having a spinel structure represented by the following Formula 1 as a cathode 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. 12. The electrode for a secondary battery according to claim 11, wherein the lithium manganese composite oxide represented by the formula (1) is a lithium nickel manganese complex oxide (LNMO) represented by the following formula (2)
Li _x Ni _y Mn _2-y O ₄ (2)
In the above formula, 0.9? X? 1.2 and 0.4? Y? 0.5. The secondary battery electrode according to claim 12, wherein the lithium nickel manganese composite oxide represented by Formula 2 is LiNi _0.5 Mn _1.5 O ₄ or LiNi _0.4 Mn _1.6 O ₄ . 11. The electrode for a secondary battery according to claim 10, wherein the negative electrode comprises a lithium metal oxide represented by the following formula (3)
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. 15. The electrode for a secondary battery according to claim 14, wherein the lithium metal oxide represented by Formula 3 is Lithium Titanium Oxide (LTO)
Li _a Ti _b O ₄ (4)
In the above formula, 0.5? A? 3, 1? B? 2.5. 16. The electrode for a secondary battery according to claim 15, wherein the lithium titanium oxide is Li _1.33 Ti _1.67 O ₄ or LiTi ₂ O ₄ . A secondary battery comprising an electrode according to any one of claims 1 to 16. The secondary battery according to claim 17, wherein the secondary battery is a lithium secondary battery. A battery module comprising a secondary battery according to claim 17 as a unit cell. A battery pack comprising the battery module according to claim 19. A device comprising a battery pack according to claim 20. 23. The device of claim 21, wherein the device is an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or a system for power storage. A method of manufacturing an electrode for a secondary battery in which an electrode mixture is applied on one surface or both surfaces of an electrode current collector,
(i) first coating an electrode mixture containing an active material having a relatively low sphericity on the current collector; And
(ii) secondarily coating an electrode mixture containing the active material having a relatively high degree of sphericity on the first coated electrode;
The method of manufacturing an electrode for a secondary battery according to claim 1, 24. The method of claim 23, wherein the first coating step is followed by a drying step. 24. The method of claim 23, wherein the secondary coating is followed by a drying step and a pressing step.

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