KR102094483B1 - Positive Electrode Mix for Secondary Battery Comprising Conductive Materials of Different Shapes - Google Patents

Abstract

The present invention is a positive electrode active material capable of storing and releasing lithium ions; A first conductive material having a spherical shape or a similar spherical shape positioned in the gap between the positive electrode active material particles and improving conductivity between the positive electrode active material particles; A second conductive material that is located on the surface of the positive electrode active material particle and improves the conductivity of the positive electrode active material particle surface; And a binder; relates to a positive electrode mixture for a secondary battery containing.

Description

{Positive Electrode Mix for Secondary Battery Comprising Conductive Materials of Different Shapes}

The present invention relates to a positive electrode mixture for a secondary battery comprising a conductive material of a different shape.

Due to the rapid increase in the use of fossil fuels, the demand for the use of alternative energy or clean energy is increasing, and as a part, the most actively researched field is the field of electricity generation and electricity storage using electrochemistry.

Currently, a representative example of an electrochemical device using such electrochemical energy is a secondary battery, and its use area is gradually expanding.

The positive electrode active material is a core material of the secondary battery that influences the capacity, voltage, and output performance of the secondary battery. However, even when a positive electrode active material having excellent overall performance has low conductivity, it may be difficult to use industrially due to low rate and cycle characteristics of the secondary battery.

Moreover, since secondary batteries used in electric vehicles and hybrid electric vehicles, which have received much attention recently, require high rate characteristics, cycle characteristics, and output characteristics, improving the conductivity of the secondary battery, particularly, the conductivity of the positive electrode need.

Conventionally, a spherical carbon black-based conductive material was mainly used, but there was a limit in improving the conductivity of the positive electrode active material.

Therefore, there is a high need for a technology that can further improve the conductivity of the secondary battery.

The present invention aims to solve the problems of the prior art as described above and the technical problems requested from the past.

The inventors of the present application have undergone in-depth studies and various experiments, and as described later, the first challenge of a spherical or similar sphere located in the gap between the positive electrode active material particles and improving the conductivity between the positive electrode active material particles When a second conductive material of a linear or tubular shape, which is located on the surface of the ash and positive electrode active material particles and improves the conductivity of the surface of the positive electrode active material particle, is confirmed, the overall performance of the secondary battery is improved and the present invention is completed. I came to Hagi.

Therefore, the positive electrode mixture according to the present invention includes a positive electrode active material capable of storing and releasing lithium ions; A first conductive material having a spherical shape or a similar spherical shape positioned in the gap between the positive electrode active material particles and improving conductivity between the positive electrode active material particles; A second conductive material that is located on the surface of the positive electrode active material particle and improves the conductivity of the positive electrode active material particle surface; And a binder.

The pseudo-spherical shape means a shape generally close to a spherical shape, such as a shape in which the cross-section of the cross section passing through the center of gravity of the conductive material particles is elliptical, or a partially protruding surface of the conductive material particles.

When the first conductive material and the second conductive material are included, the conductivity between the positive electrode active material particles is improved due to the first conductive material, and the conductivity of the positive electrode active material particle surface is improved due to the second conductive material, so that the positive electrode mixture as a whole is conductive. This can be significantly improved.

The first conductive material is mainly located between the positive electrode active material particles, for example, 60% to 99% of the first conductive material may be located between the positive electrode active material particles.

In addition, the second conductive material is mainly located on the surface of the positive electrode active material particles, for example, 60% to 99% of the second conductive material may be located on the surface of the positive electrode active material particles.

In one specific example, the positive electrode active material particles may be spherical or pseudo-spherical.

In addition, the average particle diameter of the positive electrode active material particles may be 7 μm to 30 μm.

On the other hand, the average particle diameter of the first conductive material compared to the average particle diameter of the positive electrode active material particles may be 0.01 to 0.1 times, and if it is less than 0.01 times, it is difficult to control the position of the first conductive material, and the effect of improving conductivity is not large, exceeding 0.1 times In the case, the size of the first conductive material is too large to be completely inserted into the pores between the positive electrode active material particles, and the distance between the positive electrode active material particles is increased, so that energy density and conductivity may be reduced.

Specifically, the average particle diameter of the first conductive material may be 50 nm to 1 μm.

In one specific example, the length of the second conductive material compared to the average particle diameter of the positive electrode active material particles may be 0.05 to 2.0 times, and if less than 0.05 times, it is difficult to control the position of the second conductive material, and the effect of improving conductivity is not large. In the case of more than 2.0 times, the length of the second conductive material is too long, which makes it difficult to be located on the surface of the positive electrode active material particle, and the conductivity may be reduced by forming a secondary structure by interaction between the particles of the second conductive material.

Specifically, the average length of the second conductive material may be 0.5 μm to 50 μm.

Meanwhile, a ratio of the content of the first conductive material to the content of the second conductive material may be greater than 0 to 10.0 based on weight, and may be 0.1 to 6.0 in detail. When the content of the first conductive material is 0, the conductivity between the positive electrode active material particles decreases, so that the conductivity of the positive electrode mixture as a whole may decrease, and when it exceeds 10.0, the conductivity decreases at the surface of the positive electrode active material particles, thereby reducing the overall conductivity of the positive electrode mixture. Can be.

In one specific example, the ratio of the content of the first conductive material to the content of the second conductive material may depend on the porosity of the positive electrode. That is, when the porosity of the positive electrode is large, the content of the first conductive material is relatively increased to improve the conductivity between the particles of the positive electrode active material, and when the porosity of the positive electrode is small, the content of the first conductive material is relatively reduced, By increasing the content relatively, it is possible to maximize the conductivity of the positive electrode mixture. The porosity of the anode can be calculated through the relationship between the density of the anode slurry and the loading amount.

In detail, the content of the second conductive material, the content of the first conductive material, and the porosity of the positive electrode may satisfy the relationship of Equation 1 below.

a / b = k * [exp (10p-1.5) -1] (1)

In the above formula, a is the content of the first conductive material, b is the content of the second conductive material, p is the porosity of the positive electrode, p> 0.15, and k is 0 <k <2.0 as a proportionality constant.

The proportionality constant k may vary depending on the type and size of the positive electrode active material and the conductive material, and the desired conductive performance, but may maximize the conductive performance when in the above range.

Meanwhile, the first conductive material may be a carbon black-based conductive material, for example, one or more selected from the group consisting of carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black. However, it is not limited thereto.

The second conductive material may be a carbon fiber-based conductive material, for example, carbon nano tube (CNT), graphite nano fiber (GNF), carbon nano fiber (CNF) , And one or more selected from the group consisting of activated carbon fibers (ACF), but is not limited thereto.

The present invention also provides a positive electrode for a secondary battery comprising the positive electrode mixture, an electrode assembly comprising the positive electrode, and a secondary battery in which the electrode assembly is embedded in a battery case together with an electrolyte.

Hereinafter, other components of the secondary battery will be described.

The electrode assembly includes a positive electrode, a negative electrode, and a separator, and the positive electrode may be manufactured, for example, by applying a positive electrode mixture in which a positive electrode active material, a conductive material, and a binder are mixed to a positive electrode current collector, if necessary A filler may be further added to the positive electrode mixture.

The positive electrode current collector is generally manufactured to a thickness of 3 to 201 μm, and is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, for example, stainless steel, aluminum, nickel, titanium , And may be used one selected from carbon, nickel, titanium or silver surface treatment on the surface of aluminum or stainless steel, specifically aluminum may be used. The current collector may also increase the adhesion of the positive electrode active material by forming fine irregularities on its surface, and various forms such as a film, sheet, foil, net, porous body, foam, and nonwoven fabric are possible.

The positive electrode active material may include, 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 metals; Lithium manganese oxides such as the formula Li _{1 + x} Mn _2-x O ₄ (where x is 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ , LiMnO ₂ ; Lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxides such as LiV ₃ O ₈ , LiV ₃ O ₄ , V ₂ O ₅ and Cu ₂ V ₂ O ₇ ; A Ni-site type lithium nickel oxide represented 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, Zn or Ta, x = 0.01 to 0.1) or Li ₂ Mn ₃ MO ₈ (where M = Fe, Co, Lithium manganese composite oxide represented by Ni, Cu or Zn); LiMn ₂ O _{4 in} which part of Li in the formula is substituted with alkaline earth metal ions; Disulfide compounds; Fe ₂ (MoO ₄ ) ₃ and the like, but are not limited to these.

The total content of the conductive material may be added in an amount of 0.1 to 3.0% by weight based on the total weight of the positive electrode material mixture.

The binder included in the positive electrode is a component that assists in bonding the active material and the conductive material and the like to the current collector, and is usually added in an amount of 0.1 to 3.0% by weight based on the total weight of the mixture containing the positive electrode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropyl cellulose, recycled cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene , Polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluorine rubber, and various copolymers.

The filler is optionally used as a component that inhibits the expansion of the positive electrode, and is not particularly limited as long as it is a fibrous material without causing chemical changes in the battery, and includes, for example, an olefinic polymer such as polyethylene and polypropylene; Fibrous materials such as glass fibers and carbon fibers are used.

On the other hand, the negative electrode may be prepared by applying a negative electrode mixture containing a negative electrode active material, a conductive material, and a binder to the negative electrode current collector, and thus a filler, etc. may be optionally further included.

The negative electrode current collector is not particularly limited as long as it has conductivity without causing a chemical change in the battery, for example, on the surface of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel. Carbon, nickel, titanium, silver, or the like, aluminum-cadmium alloy, or the like may be used. In addition, like the positive electrode current collector, it is also possible to form a fine unevenness on the surface to enhance the bonding force of the negative electrode active material, and may be used in various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics.

In the present invention, the thickness of the negative electrode current collector may be all within the range of 3 to 201 μm, but may have different values depending on the case.

The negative active material includes, for example, carbon such as non-graphitized carbon and graphite-based 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' : Al, B, P, Si, group 1, group 2, group 3 elements of the periodic table, halogen; metal composite oxides such as 0 <x≤1;1≤y≤3;1≤z≤8); Lithium metal; Lithium alloys; Silicon-based alloys; Tin-based alloys; 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 can be used.

In one specific example, the porous substrate may be a polyolefin-based separation film commonly used in the art, for example, high density polyethylene, low density polyethylene, linear low density polyethylene, ultra high molecular weight polyethylene, polypropylene, polyethylene terephthalate (polyethyleneterephthalate), polybutyleneterephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone , Polyethersulfone, polyphenyleneoxide, polyphenylenesulfidro, polyethylenenaphthalene, and a sheet of one or more selected from the group consisting of a mixture thereof.

The pore size and porosity of the porous substrate are not particularly limited, but the porosity may range from 10 to 95%, and the pore size (diameter) may be 0.1 to 50 μm. When the pore size and porosity are less than 0.1 μm and 10%, respectively, it acts as a resistive layer, and when the pore size and porosity exceeds 50 μm and 95%, it is difficult to maintain mechanical properties.

The electrolyte solution may be a lithium salt-containing non-aqueous electrolyte, and the lithium salt-containing non-aqueous electrolyte is composed of a non-aqueous electrolyte and a lithium salt, and the non-aqueous electrolyte includes a non-aqueous organic solvent, an organic solid electrolyte, and an inorganic solid electrolyte. It is not limited to.

Examples of the non-aqueous organic solvent include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and gamma. -Butyl lactone, 1,2-dimethoxy ethane, tetrahydroxyfuran, 2-methyl tetrahydrofuran, dimethylsulfoxide, 1,3-dioxorun, formamide, dimethylformamide, dioxorun, acetonitrile , Nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxy methane, dioxoren derivative, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivative, Aprotic organic solvents such as tetrahydrofuran derivatives, ethers, methyl pyropionate, and ethyl propionate can be used.

Examples of the organic solid electrolyte include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphoric acid ester polymers, poly agitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, and ions. A polymerization agent containing a sex dissociating group and the like can 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 , Li ₄ nitrides such as SiO ₄ -LiI-LiOH, Li ₃ PO ₄ -Li ₂ S-SiS ₂ , halides, sulfates, and the like can be used.

The lithium salt is a material that is soluble in the nonaqueous 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, lithium chloroborane, lower aliphatic lithium carboxylate, lithium 4-phenyl borate, imide, and the like.

In addition, non-aqueous electrolytes are used for the purpose of improving charge / discharge characteristics, flame retardancy, etc., for example, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphate triamide, Nitrobenzene derivatives, sulfur, quinone imine dye, N-substituted oxazolidinone, N, N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxy ethanol, aluminum trichloride, etc. may be added. have. In some cases, in order to impart non-flammability, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride may be further included, or carbon dioxide gas may be further included to improve high temperature storage characteristics, and FEC (Fluoro-Ethylene) Carbonate), PRS (Propene sultone), etc. may be further included.

In one specific example, lithium salts such as LiPF ₆ , LiClO ₄ , LiBF ₄ , and LiN (SO ₂ CF ₃ ) ₂ are formed of a cyclic carbonate of EC or PC as a highly dielectric solvent and DEC, DMC or EMC of a low viscosity solvent. A lithium salt-containing non-aqueous electrolyte may be prepared by adding it to a mixed solvent of linear carbonate.

The present invention also provides a battery pack including such a secondary battery as a unit cell, and a device including such a battery pack as a power source.

The device includes, for example, a notebook computer, a netbook, a tablet PC, a mobile phone, an MP3, wearable electronic devices, a power tool, an electric vehicle (EV), and a hybrid electric vehicle (HEV). It can be a plug-in hybrid electric vehicle (PHEV), electric bike (E-bike), electric scooter (E-scooter), electric golf cart, or power storage system. However, it goes without saying that these are not limited to these.

Since the structure and manufacturing method of such a device are known in the art, detailed description thereof is omitted in this specification.

As described above, the positive electrode material mixture according to the present invention is located in the voids between the positive electrode active material particles and is located on the surface of the first conductive material and the positive electrode active material particles having a spherical or similar shape that improves the conductivity between the positive electrode active material particles. In addition, by including the second conductive material of a linear or tubular (tubular) to improve the conductivity of the surface of the positive electrode active material particles, it is possible to significantly improve the conductivity of the secondary battery, to improve the rate characteristics and overall performance of the secondary battery.

1 is a schematic diagram showing a positive electrode mixture including a first conductive material and a second conductive material having different shapes and positions according to an embodiment of the present invention.

In the following, description will be made with reference to examples of the present invention, but this is for easier understanding of the present invention, and the scope of the present invention is not limited thereto.

<Example 1>

Preparation of anode

As the positive electrode active material, spherical LiCoO ₂ having an average particle diameter of 20 μm, spherical carbon black having an average particle diameter of 0.2 μm as the first conductive material, carbon nanotube having an average length of 10 μm as the second conductive material, and PVdF as a binder Used. At this time, based on the total weight of the positive electrode mixture, the positive electrode active material: first conductive material: second conductive material: binder = 98.5: 0.5: 0.1: 0.9.

In the first mixing process, the second conductive material was dispersed in the solvent NMP, the binder was dissolved, and then mixed with the positive electrode active material to adsorb the second conductive material to the positive electrode active material surface.

In the second mixing process, the first conductive material was introduced to prepare a positive electrode slurry in which the first conductive material is located in the void.

The positive electrode slurry thus prepared was coated on an aluminum foil having a thickness of 12 μm and dried to prepare a positive electrode having a loading amount of 23.9 mg / cm ² , and then rolled to prepare a positive electrode having a porosity of 28.0%.

<Example 2>

In Example 1, the positive electrode in the same manner as in Example 1, except that the positive electrode active material: first conductive material: second conductive material: binder = 98.5: 0.1: 0.5: 0.9 based on the total weight of the positive electrode material mixture Was prepared.

<Example 3>

In Example 1, the positive electrode in the same manner as in Example 1, except that the positive electrode active material: first conductive material: second conductive material: binder = 98.5: 0.3: 0.3: 0.9 based on the total weight of the positive electrode material mixture Was prepared.

<Example 4>

In Example 2, a positive electrode was prepared in the same manner as in Example 2, except that the porosity was rolled to be 18%.

<Example 5>

An anode was prepared in the same manner as in Example 1, except that the first conductive material having an average particle diameter of 1.1 μm was used instead of the first conductive material having an average particle diameter of 0.2 μm in Example 1.

<Example 6>

A positive electrode was prepared in the same manner as in Example 1, except that in Example 1, a second conductive material having an average length of 0.3 μm was used instead of a second conductive material having an average length of 10 μm.

<Example 7>

In Example 1, an anode was prepared in the same manner as in Example 1, except that the porosity was rolled to be 18%.

<Comparative Example 1>

In Example 1, only the first conductive material was used without using the second conductive material, and a positive electrode active material based on the total weight of the positive electrode mixture: first conductive material: binder = 98.5: 0.6: 0.9 An anode was prepared in the same manner as in Example 1.

<Comparative Example 2>

In Example 1, only the second conductive material was used without using the first conductive material, and it was carried out except that the positive electrode active material: second conductive material: binder = 98.5: 0.6: 0.9 was used based on the total weight of the positive electrode mixture. An anode was prepared in the same manner as in Example 1.

<Comparative Example 3>

In Example 1, a positive electrode was prepared in the same manner as in Example 1, except that the positive electrode slurry was prepared by injecting the first conductive material and the second conductive material together in the primary mixing process without a secondary mixing process. .

<Experimental Example 1>

Coin cells were prepared using the positive electrodes prepared in Examples 1 to 7 and Comparative Examples 1 to 3, respectively, and using lithium foil as a negative electrode. At this time, a 12 μm-thick porous polyethylene separator (porosity 47%) was used, and based on weight, an electrolyte solution in which LiPF ₆ electrolyte was dissolved at a concentration of 1 M in a mixed solvent of EC: PC: PP = 3: 1: 6 was used. Used.

The rate characteristics of each coin-type battery thus prepared were measured. The coin-type battery was charged and discharged twice from 3 V to 4 V at 0.1 C-rate to measure the initial charge / discharge capacity. Subsequently, the capacity change was measured while sequentially changing the C-rate to 0.5 C-rate, 1 C-rate, 2 C-rate, and 3 C-rate, and the results are shown in Table 1.

Initial charge / discharge capacity
(mAh / g) 0.5 C-rate
Volume
(mAh / g) 1.0 C-rate
Volume
(mAh / g) 2.0 C-rate
Volume
(mAh / g) 3.0 C-rate
Volume
(mAh / g) Example 1 181.1 177.5 165.6 144.8 108.8 Example 2 181.1 177.5 166.1 145.6 110.5 Example 3 181.2 177.6 165.8 145.2 109.6 Example 4 181.2 177.6 166.0 145.4 110.0 Example 5 181.1 177.2 160.0 138.6 100.6 Example 6 181.1 177.3 159.8 136.9 96.9 Example 7 181.0 177.1 160.5 136.5 97.7 Comparative Example 1 181.1 177.1 152.2 126.9 84.5 Comparative Example 2 181.0 177.0 153.9 128.1 86.6 Comparative Example 3 181.0 176.8 150.6 123.7 80.3

Referring to Table 1, Examples 1 to 7 can be confirmed that the capacity was increased when charging and discharging at a high rate of 2.0 C-rate or higher compared to Comparative Examples 1 to 3.

That is, Examples 1 to 7 can be seen that the spherical first conductive material is positioned in the gap between the positive electrode active material particles, and the tubular second conductive material is located on the surface of the positive electrode active material particle, so that the conductivity of the positive electrode is significantly improved. .

On the other hand, it can be seen that Comparative Examples 1 and 2 use only one type of conductive material, so that the rate characteristics are not significantly improved.

Further, in the case of Comparative Example 3, although both the first conductive material and the second conductive material having different shapes are included, the positions of the first conductive material and the second conductive material are not specified and mixed with each other. As described above, even if both the first conductive material and the second conductive material having different shapes are located, the position of the first conductive material is a gap between the positive electrode active material particles, and the position of the second conductive material is the surface of the positive electrode active material particles, and is not specified. , It can be seen that rate characteristics and conductivity are not significantly improved.

On the other hand, when Example 1 and Example 5 are compared, it can be seen that when the average particle diameter of the first conductive material is 50 nm to 1 μm, rate characteristics and conductivity are further improved.

Further, comparing Example 1 and Example 6, it can be seen that when the average length of the second conductive material is 0.5 μm to 50 μm, rate characteristics and conductivity are further improved.

Moreover, when Example 1, Example 4 and Example 7 are compared, when the relationship between the content of the first conductive material, the content of the second conductive material, and the porosity, as in Examples 1 and 4, meets Equation 1 below , It can be seen that rate characteristics and conductivity are significantly improved.

a / b = k * [exp (10p-1.5) -1] (1)

(In the above formula, a is the content of the first conductive material, b is the content of the second conductive material, p is the porosity of the positive electrode, p> 0.15, and k is a proportionality constant 0 <k <2.0.)

Although described above with reference to the embodiments of the present invention, those skilled in the art to which the present invention pertains will be able to perform various applications and modifications within the scope of the present invention based on the above.

Claims (19)

A positive electrode active material capable of storing and releasing lithium ions;
A first conductive material having a spherical shape or a similar spherical shape positioned in the gap between the positive electrode active material particles and improving conductivity between the positive electrode active material particles;
A second conductive material that is located on the surface of the positive electrode active material particle and improves the conductivity of the positive electrode active material particle surface; And
bookbinder;
Including,
60% to 99% of the first conductive material is located between the positive electrode active material particles,
60% to 99% of the second conductive material is located on the surface of the positive electrode active material particles,
The ratio of the content of the first conductive material to the content of the second conductive material depends on the porosity of the positive electrode in the range of 0.1 to 6 based on weight,
The content of the second conductive material, the content of the first conductive material, and the porosity of the positive electrode satisfy the relationship of Equation 1 below,
The first conductive material has an average particle diameter of 50 nm and 1 μm,
The average length of the second conductive material is 0.5 μm to 50 μm,
The first conductive material is carbon black, and the second conductive material is a carbon nanotube (CNT), characterized in that the secondary battery positive electrode mixture:
a / b = k * [exp (10p-1.5) -1] (1)
(In the above formula, a is the content of the first conductive material, b is the content of the second conductive material, p is the porosity of the positive electrode, p> 0.15, and k is a proportionality constant 0 <k <2.0.) The positive electrode mixture according to claim 1, wherein the positive electrode active material particles are spherical or similar spherical. The positive electrode mixture according to claim 1, wherein the positive electrode active material particles have an average particle diameter of 7 μm to 30 μm. The positive electrode mixture according to claim 1, wherein an average particle diameter of the first conductive material is 0.01 to 0.1 times compared to an average particle diameter of the positive electrode active material particles. delete The positive electrode mixture according to claim 1, wherein the length of the second conductive material is 0.05 to 2.0 times the average particle diameter of the positive electrode active material particles. delete delete delete delete delete delete delete delete A positive electrode for a secondary battery comprising the positive electrode mixture according to claim 1. Electrode assembly comprising the anode according to claim 15. A secondary battery, characterized in that the electrode assembly according to claim 16 is embedded in a battery case together with an electrolyte. A battery pack comprising the secondary battery according to claim 17 as a unit cell. A device comprising the battery pack according to claim 18 as a power source.

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