KR20130116038A - Multi layered electrode and the method of the same - Google Patents

Abstract

PURPOSE: An electrode for a secondary battery is provided to offer improved electrolyte impregnation property, ion conductivity, and electronic conductivity for improving the electrochemical performance of the secondary battery. CONSTITUTION: An electrode for a secondary battery has an electrode combining agent coated on one or both sides of an electrode current collector, and the electrode combining agent is formed of more than two layers. The electrode combining agent has an electrode active material strobilus rate of an electrode combining agent layer close to the electrode current collector is smaller than an electrode active material strobilus rate far from the electrode current collector. A production method of an electrode comprises the following steps: firstly coating the electrode combining agent which contains an active material having relatively low strobilus rate on the electrode; and secondly coating the electrode combining agent which contains an active material having relatively high strobilus rate on the electrode.

Description

Multilayered Electrode and Method for Manufacturing the Same

The present invention relates to a secondary battery electrode having an electrode mixture applied to one or both surfaces of an electrode current collector, wherein the electrode mixture relates to a secondary battery electrode and a method of 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 must transfer electrons to the electrode active material far from the current collector, so that the electron conductivity is high. On the other hand, the electrode mixture portion far from the current collector is required to have excellent electrolyte wettability and ionic conductivity with the electrolyte, and to be advantageous in discharging gas that may occur during charge and discharge.

Therefore, there is a very high need for a technology that can fundamentally solve this 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, after repeated in-depth research and various experiments, as described later, in the case of an electrode including an electrode mixture consisting of two or more layers each containing an active material having a different degree of sphericity, the desired effect It was confirmed that can be achieved, and came to complete the present invention.

Accordingly, the present invention provides an electrode for secondary batteries in which an electrode mixture is coated on one or both surfaces of an electrode current collector, and the electrode mixture provides a secondary battery electrode having a structure of two or more layers.

The two or more electrode mixture layers contain different structures from each other, and as the number of layers increases, the process efficiency decreases, and thus, the two-layer electrode mixture layer may be formed in detail.

In one specific example, the electrode mixture is configured such that the electrode active material spheroidization degree of the electrode mixture layer (A) in the portion close to the current collector is smaller than the electrode active material sphereization degree of the electrode mixture layer (B) in the portion farther from the current collector. There may be.

The degree of sphericity may be defined as the ratio L _b / L _a of the short axis length L _b to the major axis length L _a of the particles, and the maximum value of the degree of sphericity is 1.0.

In general, when the degree of sphericity is small, the electrode density after pressing can be increased. Therefore, in the above-described configuration, the electrode mixture layer (A) can provide an electrode having a higher electrode active material density than the electrode mixture layer (B).

Accordingly, the electrode mixture layer (A) may have excellent electron conductivity due to the high density of the electrode mixture, and the electrode mixture layer (B) may have a relatively low density to have a large surface area in contact with the electrolyte solution, thereby improving ion conductivity. Due to the relatively coarse structure, the electrolyte impregnation property may be improved, and the gas generated inside the electrode may well escape to the outside.

In one specific example, the electrode active material sphericity of the electrode mixture layer (A) may be in the range of 0.3 to 0.9. If the degree of sphericity is less than 0.3, the suction / release of lithium may not be smooth due to the ubiquitous arrangement, and if it is 0.9 or more, the degree of sphericity is high, and thus it is difficult to have differentiation and configuration of the electrode mixture layer (B). .

In addition, the electrode active material spheroidization degree of the electrode mixture layer (B) may be in the range of 0.5 to 1.0 in a larger range than the electrode active material spheroidization degree of the electrode mixture layer (A). If the degree of sphericity is less than 0.5, it is not preferable because it may be difficult to have a differentiation and configuration of the mixture layer (A).

1 and 2 are schematic diagrams showing spherical degrees of the electrode active material present in the electrode mixture layer (A) and the electrode active material present in the electrode mixture layer (B).

1 and 2, the degree of sphericity (b / a) of the electrode active material present in the electrode mixture layer (A) is about 0.87, and the degree of sphericity of the electrode active material present in the electrode mixture layer (B) (b / a) is about 0.97, close to 1. That is, the sphericity degree of the electrode active material of an electrode mixture layer (A) is comprised less than the sphericity degree of the electrode active material of an electrode mixture layer (B).

In the structure, the thickness ratio of the electrode mixture layer (A) and the electrode mixture layer (B) may be 30:70 to 70:30, in detail, may be 45:55 to 55:45. If the thickness of the electrode mixture layer (A) is out of the above range, the density of the electrode mixture layer (A) is too small, and the density of the electrode mixture layer (B) is too low to exert an effect of improving the electron conductivity, and the thickness of the electrode mixture layer (B) is too small. In this case, since the density increases even in a part far from the current collector and the surface area contacting the electrolyte is small, the electrolyte impregnation is lowered, which is not preferable because it is difficult to exert an effect of improving the ionic conductivity.

The electrode resistance of the electrode satisfying the above conditions may be, in detail, 0.07 Ω / cm or less, and more specifically, 0.05 Ω / cm or less.

The secondary battery electrode may be a cathode including a cathode active material or an anode 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 Chemical 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.

In detail, the lithium manganese composite oxide may be a lithium nickel manganese composite oxide represented by the following Chemical Formula 2, and 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 whiskeys 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 Chemical 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 of Formula 3 may be lithium titanium oxide (LTO) represented by the following formula (4), 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., but if the lithium ions can be occluded / released there is no restriction in the composition and type, and more specifically, the crystal structure of the charge and discharge It may be Li _1.33 Ti _1.67 O ₄ or LiTi ₂ O ₄ of the spinel structure with little 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 the electron conductivity of LTO itself is low. In this case, it is preferable to use a spinel lithium nickel manganese composite oxide of Li _x Ni _y Mn _2-y O ₄ represented by Formula 2 having a relatively high potential due to the high potential of LTO as the positive electrode active material.

The present invention provides a secondary battery including the electrode, and the secondary battery may be a lithium secondary battery having a structure in which a lithium salt-containing electrolyte is impregnated in an electrode assembly having a structure in which a separator is 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, sulfates, and the like of Li, such as Li ₄ SiO ₄ -LiI-LiOH, Li ₃ PO ₄ -Li ₂ S-SiS ₂ , and the like, may 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, lithium salts such as LiPF ₆ , LiClO ₄ , LiBF ₄ , LiN (SO ₂ CF ₃ ) _2, and the like, may be prepared by cyclic carbonate of EC or PC, which is a highly dielectric solvent, and DEC, DMC, or EMC, which are low viscosity solvents. Lithium salt-containing non-aqueous electrolyte can be prepared by adding to a mixed solvent of linear carbonate.

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, high rate characteristics, and the like.

Specific examples of the device include a power tool moving by being driven by an electric motor; 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.

This invention is a method of manufacturing the electrode for secondary batteries in which the electrode mixture is apply | coated to one side or both sides of an electrical power collector,

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

(ii) second coating an electrode mixture including an active material having a relatively high sphericity on the primary coated electrode;

It provides a method for manufacturing a secondary battery electrode comprising a.

Relatively high and low sphericity is to compare the spheroidization degree of the electrode active material of the electrode mixture for primary coating and the electrode active material sphericity of the electrode mixture for secondary coating.

In the manufacturing method of the electrode, it may further comprise a drying process after the primary coating. It is possible to apply the high sphericity mixture layer on the low spherical mixture layer without drying, but when the drying process is to prevent the mixture between the mixture is effective.

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

As described above, the electrode for secondary batteries according to the present invention is manufactured by using a multi-layered electrode using an active material having a different degree of sphericity, thereby improving electrolyte solution impregnation, ion conductivity, and electron conductivity, and the like. There is an effect of improving the electrochemical performance.

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

When observed 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 the first anode active material, and a conductive material (Super-C) and a binder (PVdF) were used. Each was mixed with N-methyl-2-pyrrolidone (NMP) at a weight ratio of 90: 5: 5 to prepare a first negative electrode mixture, and Li _1.33 Ti _1.67 O ₄ having an average sphericity of 0.97 was used as a second negative electrode active material. Then, a conductive material (Super-C) and a binder (PVdF) were put into NMP at a weight ratio of 90: 5: 5 and mixed, respectively, to prepare a second negative electrode mixture. At this time, the ratio (b / a) of the short axis length to the long axis length is defined as a spherical degree.

The prepared first negative electrode mixture was coated with 20 μm thick copper foil at a thickness of 40 μm and dried, and the second negative electrode mixture was coated on the first negative electrode mixture coating layer with a thickness of 40 μm, and then rolled and dried to form a negative electrode. Prepared. At this time, the porosity and the negative electrode resistance of the negative electrode were measured, and the porosity was 40% and the resistance was 0.05 Ω / cm.

Manufacture of Secondary Battery

LiNi _0.5 Mn _1.5 O ₄ is used as a positive electrode active material, and a conductive material (Super-C) and a binder (PVdF) are added to NMP in a weight ratio of 90: 6.5: 3.5, respectively, and mixed to prepare a positive electrode mixture. The foil was coated, rolled and dried to prepare a positive electrode.

After preparing an electrode assembly through a separator (Celgard ^TM , thickness: 20 μm) between the cathode and the anode, the electrode assembly was housed in a pouch-type battery case, and a carbonate-based series containing 1 M LiPF ₆ was present. The composite solution of was injected into an 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 ), a conductive material (Super-C), and a binder (PVdF) each having an average sphericity of 0.97 in the preparation of the negative electrode were mixed in NMP at a weight ratio of 90: 5: 5 and mixed with the negative electrode. After the mixture was prepared, a lithium secondary battery was prepared in the same manner as in Example 1 except that the copper foil having a thickness of 20 μm was coated with a thickness of 80 μm, rolled, and dried to prepare a negative electrode. At this time, the porosity and the negative electrode resistance of the negative electrode were measured, and the porosity was 40%, and the resistance was 0.08 Ω / cm.

<Experimental Example 1>

For lithium secondary batteries prepared in Example 1 and Comparative Example 1, the capacity at 3C rate was measured to confirm rate characteristics, and 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, in the case of the battery of Example 1 according to the present invention it can be seen that the rate characteristic is improved compared to the battery of Comparative Example 1.

This method uses a method of primary coating an electrode mixture containing an active material having a relatively low sphericity, and secondary coating of an electrode mixture containing an active material having a relatively high sphericity, thereby obtaining only an electrode active material having an average sphericity of 0.97. This is because an electrode having a higher density of a portion closer to the electrode current collector can be produced than in the case of use, thereby improving the electronic conductivity.

Although, the electrolyte impregnability of the secondary battery having the electrode having a two-layer structure according to the present invention may be slightly lowered since the density of the portion close to the electrode current collector is higher than that of using only the electrode active material having a high average sphericity. Similarly, it was confirmed that the electrolyte solution impregnation of the desired degree can be maintained while exhibiting the effect of improving the rate characteristic. In addition, if the manufacturing method according to the present invention is applied to both the positive electrode and the negative electrode, there is an effect that 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)

A secondary battery electrode having an electrode mixture applied to one surface or both surfaces of an electrode current collector, wherein the electrode mixture has a structure of two or more layers. 2. The secondary electrode according to claim 1, wherein the electrode mixture has a smaller degree of spheroidization of the electrode active material layer of the electrode mixture layer (A) near the current collector than that of the electrode mixture layer (B) of the portion farther from the current collector. Battery electrode. 3. The secondary battery electrode according to claim 2, wherein the degree of sphericity is a ratio L _b / L _a of the short axis length L _b to the major axis length L _a of the particles. The electrode for secondary batteries according to claim 2, wherein the electrode active material spheroidization degree of the electrode mixture layer (A) is in a range of 0.3 to 0.9. The electrode according to claim 2, wherein the electrode active material spheroidization degree of the electrode mixture layer (B) is in the range of 0.5 to 1.0 in a range larger than the electrode active material sphericity degree of the electrode mixture layer (A). The electrode for secondary batteries according to claim 2, wherein the thickness ratio of the electrode mixture layer (A) and the electrode mixture layer (B) is 30:70 to 70:30. The electrode for secondary batteries according to claim 6, wherein the thickness ratio of the electrode mixture layer (A) and the electrode mixture layer (B) is 45:55 to 55:45. The electrode of claim 1, wherein the electrode has an electrode resistance of 0.07 Ω / cm or less. The method of claim 1, wherein the electrode has a secondary battery electrode, characterized in that the electrode resistance is 0.05 Ω / cm or less. According to claim 1, wherein the electrode is a secondary battery electrode, characterized in that the positive electrode or the negative electrode. The electrode of claim 10, wherein the cathode is a high voltage cathode including a lithium manganese composite oxide having a spinel structure represented by Chemical 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. The method of claim 11, wherein the lithium manganese composite oxide of Formula 1 is a lithium nickel manganese complex oxide (Lithium Nickel Manganese complex oxide: LNMO) represented by the 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 method of claim 12, wherein the lithium nickel manganese composite oxide of Formula 2 is LiNi _0.5 Mn _1.5 O ₄ or LiNi _0.4 Mn _1.6 O _{4 The} electrode for secondary batteries, characterized in that. The method of claim 10, wherein the negative electrode is a negative electrode active material for a secondary battery comprising 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. The method of claim 14, wherein the lithium metal oxide of Formula 3 is a lithium titanium oxide (Lithium Titanium Oxide: LTO) represented by the formula (4):
Li _a Ti _b O ₄ (4)
In the above formula, 0.5? A? 3, 1? B? 2.5. The electrode of claim 15, wherein the lithium titanium oxide is Li _1.33 Ti _1.67 O ₄ or LiTi ₂ O ₄ . The secondary battery according to any one of claims 1 to 16, comprising the electrode. The secondary battery of claim 17, wherein the secondary battery is a lithium secondary battery. A battery module comprising the secondary battery according to claim 17 as a unit cell. A battery pack comprising the battery module according to claim 19. Device comprising a battery pack according to claim 20. 22. 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. As a method of manufacturing an electrode for secondary batteries, the electrode mixture is coated on one or both sides of the electrode current collector,
(i) first coating an electrode mixture including an active material having a relatively low sphericity on the electrode current collector; And
(ii) second coating an electrode mixture including an active material having a relatively high sphericity on the primary coated electrode;
Method for producing a secondary battery electrode comprising a. 24. The method of claim 23, wherein a drying process is added after the primary coating. 24. The method of claim 23, wherein the secondary coating includes a drying process and a pressing process after the secondary coating.

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