KR102498353B1 - Electrode for lithium secondary battery and lithium secondary battery indluding the same - Google Patents

Abstract

The present invention is to reduce the resistance of the battery by preventing the binder from moving to the interface of the active material layer, the current collector; and an electrode active material layer formed on one surface of the current collector and containing an electrode active material, a conductive material, and a binder, wherein the conductive material includes a magnetic conductive material, and the conductive material is formed on a surface thereof. An electrode for a lithium secondary battery further comprising attached organic particles and a lithium secondary battery including the same are provided.

Description

Electrode for lithium secondary battery and lithium secondary battery including the same {Electrode for lithium secondary battery and lithium secondary battery indluding the same}

The present invention relates to a lithium secondary battery electrode and a lithium secondary battery including the same, and more particularly, to a lithium secondary battery having high capacity characteristics and a lithium secondary battery including the same.

Recently, interest in energy storage technology is increasing. Cell phones, camcorders, notebook PCs, and furthermore, as the application fields are expanded to the energy of electric vehicles, efforts for research and development of batteries are becoming more concrete. The electrochemical device is the field that is attracting the most attention in this respect, and in particular, according to the recent trend of miniaturization and weight reduction of electronic devices, the development of a secondary battery as a battery that can be charged and discharged with a small size and light weight and high capacity has become a focus of interest.

Electrochemical devices have been developed as electrode active materials through continuous research, and in particular, those with significantly improved output. Among the secondary batteries currently applied, the lithium secondary battery developed in the early 1990s is in the limelight due to its high operating voltage and high energy density compared to conventional batteries such as Ni-MH.

Such a lithium secondary battery is composed of a positive electrode, a negative electrode, and an electrolyte, and energy is transferred while reciprocating between both electrodes, such as lithium ions from the positive electrode active material by the first charge being inserted into the negative electrode active material, for example, carbon particles, and desorbed again during discharge. Because it plays a role, charging and discharging are possible.

As technology development and demand for mobile devices increase, demand for secondary batteries as an energy source is rapidly increasing. Among these secondary batteries, lithium secondary batteries having high energy density and voltage, long cycle life, and low branch discharge rate have been commercialized and widely used. In addition, as interest in environmental issues grows, the market for devices employing high-capacity batteries such as electric vehicles and hybrid electric vehicles that can replace vehicles that use fossil fuels such as gasoline vehicles and diesel vehicles, which are one of the main causes of air pollution, is growing. As the demand base for high-capacity batteries expands, high-capacity design of electrodes for manufacturing lithium secondary batteries having high energy density, high output, and high discharge voltage as a power source for these devices is required.

A high loading electrode with a thick electrode is attempted by increasing the amount of active material to design a high capacity electrode, but in this electrode, the binder moves to the interface of the active material layer during the drying process after application of the active material, and the interface of the active material layer There is a problem in that the resistance of the battery increases as the binder distributed therein increases.

The problem to be solved by the present invention is to provide a lithium secondary battery electrode and a lithium secondary battery including the same that can reduce the resistance of the battery by preventing the binder from moving to the interface of the active material layer in the high loading electrode will be.

In order to solve the above problems, according to an aspect of the present invention, the current collector; and an electrode active material layer formed on one surface of the current collector and containing an electrode active material, a conductive material, and an organic binder, wherein the conductive material includes a magnetic conductive material, and the conductive material has a surface thereof. There is provided an electrode for a lithium secondary battery, characterized in that it further comprises organic particles attached to.

Preferably, the magnetic conductive material may be at least one selected from the group consisting of iron, nickel, and cobalt, or an alloy thereof.

Preferably, the organic particles may have a functional group.

Preferably, the organic binder may have a functional group.

Preferably, the functional group is a carboxyl group (-COOH), a hydroxyl group (-OH), an ester group (-COOR, where R is an alkyl, phenyl, or benzyl group having 1 to 10 carbon atoms), an amine group (- NH ₂ ) and at least one selected from the group consisting of a thiol group (-SH).

Preferably, the magnetic conductive material may be included in an amount of 0.1 to 20% by weight.

Preferably, the magnetic conductive material may have a particle size of 0.01 to 10 μm.

Preferably, the organic binder is carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, Polybutadiene, butyl rubber, fluororubber, polyethylene oxide, polyvinyl alcohol, poly(meth)acrylic acid and its salts, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, poly Vinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenolic resin, epoxy resin, polymer of propylene and olefin having 2 to 8 carbon atoms, copolymers of (meth)acrylic acid and (meth)acrylic acid alkyl ester, and these It may include one selected from a combination of.

Preferably, the electrode active material layer may have a thickness of 70 μm or more.

Preferably, the loading amount of the electrode active material layer may be 500 mg/25 cm ² or more.

In addition, according to another aspect of the present invention, the current collector; and an electrode active material layer formed on one surface of the current collector and containing an electrode active material, a conductive material, and an organic binder, wherein the conductive material includes a magnetic conductive material, and the magnetic conductive material includes a magnetic conductive material. An electrode for a lithium secondary battery characterized by having a protrusion on the surface is provided.

In addition, according to another aspect of the present invention, in a lithium secondary battery including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, the positive electrode or the negative electrode is a lithium secondary battery, characterized in that the above-described electrode Provided.

In addition, according to another aspect of the present invention, preparing an electrode slurry containing an electrode active material, a magnetic conductive material and an organic binder; applying the electrode slurry to one surface of a current collector; drying the electrode slurry applied on the current collector; and drying the slurry while applying a magnetic field to one surface of the current collector on which the electrode slurry is not applied.

The electrode for a lithium secondary battery according to one aspect of the present invention can reduce the resistance of the battery by preventing the binder from moving to the interface of the active material layer.

The following drawings attached to this specification illustrate preferred embodiments of the present invention, and serve to further understand the technical idea of the present invention together with the contents of the above-described invention, so the present invention is limited to those described in the drawings. It should not be construed as limiting.
1 is a cross-sectional view schematically showing a conventional high loading electrode.
2 is a schematic cross-sectional view of an electrode according to an embodiment of the present invention.

The terms used in this specification and claims should not be construed as being limited to their usual or dictionary meanings, and the inventors can properly define the concept of terms in order to explain their invention in the best way. Based on the principle, it should be interpreted as a meaning and concept consistent with the technical idea of the present invention. Therefore, since the configurations shown in the embodiments described herein are only one of the most preferred embodiments of the present invention and do not represent all of the technical spirit of the present invention, various equivalents that can replace them at the time of this application It should be understood that there may be waters and variations.

1 is a cross-sectional view schematically showing a conventional high loading electrode. Referring to FIG. 1, the conventional electrode 100 for a lithium secondary battery has a thickness of an active material layer 20 including a conductive material 21 and a binder 22 on one surface of a current collector 10 in order to improve capacity. However, in this case, the resistance of the battery increases as the binder 22 moves to the interface of the active material layer in the manufacturing process of the electrode.

2 is a schematic cross-sectional view of an electrode according to an embodiment of the present invention. Referring to FIG. 2, in the present invention, a magnetic device 200 applies a magnetic field to one surface of a current collector 10 on which electrode slurry is not applied using a magnetic conductive material 21 having affinity with a binder 22 By doing so, the magnetic conductive material 21 having affinity with the binder 22 moves together with the binder 22, and the binder 22 distributed on the interface of the active material layer 20 moves toward the surface of the current collector 10. can make it

An electrode for a lithium secondary battery according to an aspect of the present invention includes a current collector; and an electrode active material layer formed on one surface of the current collector and containing an electrode active material, a conductive material, and an organic binder, wherein the conductive material includes a magnetic conductive material, and the conductive material has a surface thereof. It further includes organic particles attached to.

By including organic particles attached to the surface of the conductive material, the conductive material has affinity with the organic binder, and when a magnetic field is applied, the organic binder distributed on the interface of the active material layer can be moved toward the surface of the current collector.

The conductive material may include carbon black, graphite, carbon fiber, carbon nanotube, metal powder, conductive metal oxide, organic conductive material, and the like, and the magnetic conductive material may be one selected from the group consisting of iron, nickel, and cobalt. It may be one or more species or alloys thereof.

The organic particles or organic binder may have a functional group. By having a functional group, it is possible to further improve the affinity between the conductive material to which the organic particles are attached and the organic binder, and more organic binders distributed on the interface of the active material layer can be moved toward the surface of the current collector.

The functional group can provide affinity between organic binders or organic particles, for example, a carboxyl group (-COOH), a hydroxyl group (-OH), an ester group (-COOR, where R is an alkyl having 1 to 10 carbon atoms) , phenyl, or a benzyl group), an amine group (-NH2), and a thiol group (-SH).

The magnetic conductive material may be included in an amount of 0.1 to 20% by weight, and a particle size of 0.01 to 10 μm may be used.

The binder is carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, polybutadiene, butyl rubber , fluororubber, polyethylene oxide, polyvinyl alcohol, poly(meth)acrylic acid and its salts, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, polyvinylpyridine, chlorosul Phoned polyethylene, latex, polyester resins, acrylic resins, phenol resins, epoxy resins, polymers of propylene and olefins having 2 to 8 carbon atoms, copolymers of (meth)acrylic acid and (meth)acrylic acid alkyl esters, and combinations thereof may contain one.

The binder may be included in an amount of 0.5 to 10% by weight.

The electrode active material layer may have a thickness of 70 μm or more, or a loading amount of the electrode active material layer may be 500 mg/25 cm ² or more. In the lithium secondary battery, in order to increase the energy density, a high loading electrode may be used, and the active material layer may be thick or the loading amount may be increased to manufacture the high loading electrode. The electrode according to one aspect of the present invention can further reduce the resistance of the electrode in the high loading electrode.

The current collector may be a positive current collector or a negative current collector.

The cathode current collector may generally have a thickness of 10 to 500 μm. The positive electrode current collector is not particularly limited as long as it does not cause chemical change in the battery and has high conductivity. For example, stainless steel, aluminum, nickel, titanium, fired carbon, or aluminum or stainless steel. A surface treated with carbon, nickel, titanium, silver, etc. may be used. The current collector may form fine irregularities on its surface to increase the adhesion of the positive electrode active material, and various forms such as films, sheets, foils, nets, porous materials, foams, and non-woven fabrics are possible.

The anode current collector may generally have a thickness of 10 to 500 μm. The negative electrode current collector is not particularly limited as long as it has conductivity without causing chemical change in the battery, and for example, the surface of copper, stainless steel, aluminum, nickel, titanium, fired carbon, copper or stainless steel. For the surface treatment with carbon, nickel, titanium, silver, etc., an aluminum-cadmium alloy or the like may be used. In addition, like the positive electrode current collector, fine irregularities may be formed on the surface to enhance the bonding strength 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.

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

The cathode active material may be a lithium-containing oxide, and a lithium-containing transition metal oxide may be preferably used. For example, the lithium-containing transition metal oxide is Li _x CoO ₂ (0.5<x<1.3), Li _x NiO ₂ (0.5<x<1.3), Li _x MnO ₂ (0.5<x<1.3), Li _x Mn ₂ O ₄ (0.5<x<1.3), Li _x (Ni _a Co _b Mn _c )O2(0.5<x<1.3, 0<a<1, 0<b<1, 0<c<1, a+ b+c=1), Li _x Ni _1-y Co _y O ₂ (0.5<x<1.3, 0<y<1), Li _x Co _{1 - y} Mn _y O ₂ (0.5<x<1.3, 0≤ y<1), Li _x Ni _{1 -y} Mn _y O ₂ (0.5<x<1.3, O≤y<1), Li _x (Ni _a Co _b Mn _c )O4(0.5<x<1.3, 0<a <2, 0<b<2, 0<c<2, a+b+c=2), Li _x Mn _{2 - z} Ni _z O4 (0.5<x<1.3, 0<z<2), Li _x Mn _{2 -} selected from the group consisting of _z Co _z O ₄ (0.5<x<1.3, 0<z<2), Li _x CoPO ₄ (0.5<x<1.3) and Li _x FePO ₄ (0.5<x<1.3) It may be any one or a mixture of two or more of them, and the lithium-containing transition metal oxide may be coated with a metal or metal oxide such as aluminum (Al). In addition, sulfide, selenide, and halide may also be used in addition to the lithium-containing transition metal oxide.

The negative electrode active material may generally use a lithium metal, a carbon material, a metal compound, or a mixture thereof capable of intercalating and releasing lithium ions.

Specifically, both low crystalline carbon and high crystalline carbon may be used as the carbon material. Soft carbon and hard carbon are typical examples of low crystalline carbon, and examples of high crystalline carbon include natural graphite, kishgraphite, pyrolytic carbon, liquid crystal pitch-based carbon fiber ( High-temperature calcined carbon such as mesophase pitch based carbon fiber, meso-carbon microbeads, mesophase pitches, and petroleum or coal tar pitch derived cokes are typical examples.

Examples of the metal compound include metal elements such as Si, Ge, Sn, Pb, P, Sb, Bi, Al, Ga, In, Ti, Mn, Fe, Co, Ni, Cu, Zn, Ag, Mg, Sr, and Ba. A compound containing one or more types of is exemplified. These metal compounds can be used in any form, such as simple elements, alloys, oxides (TiO ₂ , SnO ₂ , etc.), nitrides, sulfides, borides, alloys with lithium, etc. It can be high-capacity. Among them, one or more types of elements selected from Si, Ge, and Sn can be contained, and one or more types of elements selected from Si and Sn can further increase the capacity of the battery.

In addition, an electrode for a lithium secondary battery according to another aspect of the present invention includes a current collector; and an electrode active material layer formed on one surface of the current collector and containing an electrode active material, a conductive material, and a binder, wherein the conductive material includes a magnetic conductive material, and the magnetic conductive material has a surface thereof. It has a protrusion on it. Since the magnetic conductive material has protrusions on the surface, affinity with the binder is improved by the protrusions, and magnetic force can be applied to move the binder distributed at the interface of the active material layer toward the surface of the current collector during manufacturing of the electrode.

In addition, according to one aspect of the present invention, there is provided a lithium secondary battery including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, wherein the positive electrode or the negative electrode is the electrode described above.

The separator may be a porous polymer substrate, and examples of the porous polymer substrate include, but are not limited to, polyethylene, polypropylene, polyethyleneterephthalate, polybutyleneterephthalate, and polyester. , polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyaryletherketone, polyetherimide, polyamide polyamideimide, polybenzimidazole, polyethersulfone, polyphenyleneoxide, cyclic olefin copolymer, polyphenylenesulfide and polyethylene naphthalene ( polyethylenenaphthalene), but may be a polymer film formed of any one polymer selected from the group consisting of or a mixture of two or more of them, or a multilayer, woven fabric, or non-woven fabric thereof.

The thickness of the porous polymer substrate is not particularly limited, but may be about 5 to about 50 μm. The pore size and porosity present in the porous polymer substrate are also not particularly limited, but may be about 0.01 to about 50 μm and about 10 to about 95%, respectively.

In addition, according to an aspect of the present invention, a method for manufacturing an electrode for a lithium secondary battery includes preparing an electrode slurry including an electrode active material, a magnetic conductive material, and a binder; applying the electrode slurry to one surface of a current collector; drying the electrode slurry applied on the current collector; and drying the slurry while applying a magnetic field to one surface of the current collector on which the electrode slurry is not applied.

As the magnetic conductive material, the magnetic conductive material described above may be used.

The above description is merely an example of the technical idea of the present invention, and various modifications and variations can be made to those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention, but to explain, and the scope of the technical idea of the present invention is not limited by these embodiments. The protection scope of the present invention should be construed according to the following claims, and all technical ideas within the equivalent range should be construed as being included in the scope of the present invention.

10: entire collector
20: active material layer
21: conductive material
22: binder
100: electrode
200: magnetic device

Claims (13)

current collector; and an electrode active material layer formed on one surface of the current collector and containing an electrode active material, a conductive material, and an organic binder.
The conductive material includes a magnetic conductive material,
The electrode for a lithium secondary battery, characterized in that the conductive material further comprises organic particles attached to the surface thereof. According to claim 1,
The magnetic conductive material is an electrode for a lithium secondary battery, characterized in that at least one selected from the group consisting of iron, nickel and cobalt or an alloy thereof. According to claim 1,
The electrode for a lithium secondary battery, characterized in that the organic particles have a functional group. According to claim 1,
The organic binder is an electrode for a lithium secondary battery, characterized in that it has a functional group. According to any one of claims 3 or 4,
The functional group is a carboxyl group (-COOH), a hydroxyl group (-OH), an ester group (-COOR, where R is an alkyl, phenyl, or benzyl group having 1 to 10 carbon atoms), an amine group (-NH ₂ ), and An electrode for a lithium secondary battery, characterized in that at least one selected from the group consisting of a thiol group (-SH). According to claim 1,
The magnetic conductive material is an electrode for a lithium secondary battery, characterized in that contained in 0.1 to 20% by weight. According to claim 1,
The magnetic conductive material is an electrode for a lithium secondary battery, characterized in that it has a particle size of 0.01 to 10㎛. According to claim 1,
The organic binder is carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, polybutadiene, butyl Rubber, fluororubber, polyethylene oxide, polyvinyl alcohol, poly(meth)acrylic acid and its salts, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, polyvinylpyridine, chloro Selected from sulfonated polyethylene, latex, polyester resin, acrylic resin, phenolic resin, epoxy resin, polymer of propylene and olefin having 2 to 8 carbon atoms, copolymer of (meth)acrylic acid and (meth)acrylic acid alkyl ester, and combinations thereof An electrode for a lithium secondary battery, characterized in that it comprises one that is. According to claim 1,
The electrode for a lithium secondary battery, characterized in that the thickness of the electrode active material layer is 70㎛ or more. According to claim 1,
The electrode for a lithium secondary battery, characterized in that the loading amount of the electrode active material layer is 500 mg / 25 cm ² or more. current collector; and an electrode active material layer formed on one surface of the current collector and containing an electrode active material, a conductive material, and an organic binder.
The conductive material includes a magnetic conductive material,
The magnetic conductive material is an electrode for a lithium secondary battery, characterized in that it has a projection on its surface. In a lithium secondary battery comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode,
The positive electrode or the negative electrode is a lithium secondary battery, characterized in that the electrode according to any one of claims 1 or 11. Preparing an electrode slurry containing an electrode active material, a magnetic conductive material and an organic binder;
applying the electrode slurry to one surface of a current collector;
drying the electrode slurry applied on the current collector; and
Method for manufacturing an electrode for a lithium secondary battery comprising: applying a magnetic field to one surface of a current collector on which the electrode slurry is not applied and drying the slurry at the same time.

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