KR101812268B1 - Preparation method of porous electrode active material, porous electrode active material prepared by the method, porous electrode active material, electrode comprising the same and secondary battery - Google Patents

Abstract

Dispersing the water dispersible polymer particles and the electrode active material primary particles in a solvent to prepare an electrode active material mixture composition; spray drying the electrode active material mixture composition to form an electrode active material mixture; and heat treating the electrode active material mixture The porous electrode active material is produced.

Description

TECHNICAL FIELD [0001] The present invention relates to a porous electrode active material, a porous electrode active material, a porous electrode active material produced by the method, and an electrode and a secondary battery comprising the same. BACKGROUND ART [0002] THE SAME AND SECONDARY BATTERY}

The present invention relates to a method for producing a porous electrode active material, a porous electrode active material produced therefrom, a porous electrode active material, an electrode including the same, and a secondary battery, and more particularly to a porous electrode active material having a porous structure and an excellent electrical conductivity The present invention also relates to a porous electrode active material, a porous electrode active material, an electrode including the electrode active material, and a secondary battery.

Recently, interest in energy storage technology is increasing. As the application fields of cell phones, camcorders, notebook PCs and even electric vehicles are expanding, efforts for research and development of electrochemical devices are becoming more and more specified. Electrochemical devices are the most popular field in this respect. Among them, the development of a rechargeable battery capable of charging and discharging has been the focus of attention. In recent years, in developing such a battery, improvement of capacity density and specific energy And research and development on the design of new electrodes and batteries are underway.

Such an electrochemical device generally includes a cathode, an anode, and a separator interposed between the cathode and the anode. At this time, the cathode and the anode are coated with an electrode active material slurry including an electrode active material, a polymer binder, and a dispersion medium on the surface of each current collector, and dried to form an electrode active material layer.

A large amount of lithium metal was used as the cathode material of the initial lithium secondary battery. Lithium metal has a merit that high capacity can be realized. However, as charging and discharging are repeated, there is a problem in cycle maintenance due to the formation of dendrite and increase of surface resistivity of dendrite in resin, and dendrites formed in the resin penetrate the separator There is a problem of safety that causes a short circuit with the anode, which causes the ignition of the battery.

In order to solve such a problem of the lithium metal electrode, the lithium ion battery which has been commercialized since the beginning can intercalate / deintercalate lithium ions, which are not metal lithium ions, from the interlayer, or adsorb / Based materials are used. In recent years, alloy type materials such as silicon (Si) and tin (Sn), which make alloying with lithium on the cathode, are also used to increase the capacity of the battery. In the case of the positive electrode, lithium-containing transition metal oxides typified by lithium cobalt oxide (LiCoO ₂ ) have been mainly used since the product launch.

A graphite material or a lithium metal used as a cathode has sufficient electrical conductivity, but an alloy type material such as silicon (Si), tin (Sn), and a lithium-containing transition metal oxide cathode material has a low electrical conductivity. In addition, in order to satisfy the characteristics of a large number of products (power tools and automobile batteries) which require a high output battery, it is required to improve the output of the electrode material. These properties can be improved through changes in the way the existing materials are synthesized or by additional post-processing.

Disclosure of Invention Technical Problem [8] Accordingly, the present invention has been made to solve the above problems, and it is an object of the present invention to provide a water- A method for manufacturing a porous electrode active material having improved characteristics is provided.

Other objects and advantages of the present invention will become apparent from the following description. It is also to be easily understood that the objects and advantages of the present invention can be realized by the means or method described in the claims, and the combination thereof.

According to an aspect of the present invention, there is provided a method for preparing an electrode active material mixture composition, comprising: preparing an electrode active material mixture composition by dispersing water dispersible polymer particles and an electrode active material primary particle in a solvent; spray drying the electrode active material mixture composition, Forming a mixture, and heat treating the electrode active material mixture.

The water-dispersible polymer particles may be spherical and the average diameter of the water-dispersible polymer particles may be smaller than the average diameter of the electrode active material primary particles.

The average diameter of the water-dispersible polymer particles may be 50 nm to 20 탆.

The content of the water dispersible polymer particles may be 0.1 to 50 parts by weight based on 100 parts by weight of the primary active material particles.

The water dispersible polymer particles may be selected from the group consisting of polyacrylonitrile, polyethylene, polystyrene, polyvinyl chloride, poly (meth) acrylic acid, polymethyl (meth) acrylate, polyethyl (meth) acrylate, polybutyl (Meth) acrylate, polydodecyl (meth) acrylate, polystylyl (meth) acrylate, polybenzyl (meth) acrylate, polycyclohexyl (meth) acrylate and polyvinyl acetate Or at least one of them.

The solvent may be at least one of water and alcohol.

The electrode active material mixture may be formed by aggregating the water dispersible polymer particles and the electrode active material primary particles.

The heat treatment of the electrode active material mixture may be performed at a temperature of 500 to 1,000 DEG C for 2 to 10 hours.

The step of heat-treating the electrode active material mixture may include aggregating the electrode active material primary particles among the electrode active material mixture, carbonizing the water dispersible polymer particles to form voids, and carbonizing the water dispersible polymer particles to the aggregated electrode active material primary particles To form a carbon coating layer on the surface of the substrate.

The porosity of the porous electrode active material may be 0.1 to 50%.

According to another aspect of the present invention, there is provided a porous electrode active material produced by the above-described production method.

According to another aspect of the present invention, there is provided an electrode active material composition comprising primary particles of an electrode active material formed by agglomeration, having a plurality of pores formed between primary particles of the agglomerated electrode active material, There is provided a porous electrode active material formed.

Further, an electrode including the above-mentioned porous electrode active material is provided.

The electrode may be an anode or a cathode.

In addition, a secondary battery including the above-described electrode is provided.

The present invention is advantageous in that the surface of the electrode active material is coated with carbon and the pores are formed between the electrode active materials by using the water dispersible polymer particles serving as a carbon source and a porogen inducer without dissolving in a solvent.

Further, by forming the pores as described above, there is an advantage that the electrode active material has high capacity and excellent rate characteristics by improving mechanical properties and electrical conductivity.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate preferred embodiments of the invention and, together with the description of the invention, It is not interpreted.
1 is a flowchart illustrating a method of manufacturing a porous electrode active material according to an embodiment of the present invention.
2 is a schematic view showing a conventional method of manufacturing an electrode active material.
3 is a schematic view illustrating a method for manufacturing a porous electrode active material according to an embodiment of the present invention.
4 is a SEM photograph of the negative active material of Comparative Example 1. FIG.
5 is an SEM photograph of the negative electrode active material of Example 1. Fig.
6 is a graph showing the capacity of Example 2 and Comparative Example 2;

Hereinafter, the present invention will be described in detail. The terms or words used in the present specification and claims should not be construed in a conventional or dictionary sense and the inventor shall appropriately define the concept of the term in order to explain its invention in the best way The present invention should be construed in accordance with the meaning and concept consistent with the technical idea of the present invention. Therefore, the embodiments described in the present specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention, and not all of the technical ideas of the present invention are described. Therefore, It should be understood that various equivalents and modifications are possible.

1 is a flowchart illustrating a method of manufacturing a porous electrode active material according to an embodiment of the present invention.

Referring to FIG. 1, the method for preparing a porous electrode active material of the present invention includes preparing an electrode active material mixture composition (S10), forming an electrode active material mixture (S20), and performing a heat treatment (S30).

The electrode active material mixture composition preparation step (S10) is a step of dispersing the water dispersible polymer particles and the electrode active material primary particles in a solvent.

In this specification, the electrode active material primary particles mean aggregated electrode active material particles, wherein the electrode active material particles are particles of a cathode active material or particles of an anode active material, and may be preferably anode active material particles.

The positive electrode active material particles may be used in the art materials are available without restrictions, non-limiting examples _{LixCoO 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) O 2 (0.5 <x <1.3, 0 <a <1, 0 < 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), Lix (Ni a Co b Mn c) 0 < b < 2, 0 <c <2, a + b + c = 2), Li _x Mn _{2 -z} Ni _z O ₄ (0.5 <x <1.3, 1.3, 0 <z <2) , Li x Mn 2- 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), or a mixture of two or more thereof. The lithium-containing transition metal oxide may be coated with a metal such as aluminum (Al) or a metal oxide. In addition to the lithium-containing transition metal oxide, sulfide, selenide and halide may also be used.

The negative electrode active material particles may also be used without limitation. Examples of the negative electrode active material particles include carbonaceous materials such as natural graphite and artificial graphite, lithium-containing titanium composite oxide (LTO), Si, Sn , Metals (Me) which are Li, Zn, Mg, Cd, Ce, Ni or Fe; An alloy composed of the metal (Me); An oxide of the metal (Me) (MeOx); And a composite of the metal (Me) and carbon, and the like.

The solvent may be any material that can disperse the electrode active material primary particles uniformly without reacting with the electrode active material primary particles, and may be used without limitation, and examples thereof include water and at least one of alcohol And preferably water.

In the present invention, the water-dispersible polymer particle is a polymer capable of carbon coating the surface of the primary active material of the electrode active material without being dissolved in a solvent. Examples of the polymer include polyacrylonitrile, polyethylene, polystyrene, polyvinyl chloride, (Meth) acrylic acid, polymethyl (meth) acrylate, polyethyl (meth) acrylate, polybutyl (meth) acrylate, polyhexyl (Meth) acrylate, polybenzyl (meth) acrylate, polycyclohexyl (meth) acrylate, and polyvinyl acetate, preferably polyacrylonitrile.

In addition, the shape of the water-dispersible polymer particle may be in the form of the particle itself without physical strain, and preferably it may be spherical. This is because the place of the water-dispersible polymer particle becomes a void through the heat treatment, This is because not only the pores can be uniformly distributed, but also an excellent porosity can be obtained.

The electrode active material mixture composition is prepared by mixing 100 parts by weight of the primary active material particles and 0.1 part by weight of the water dispersible polymer particles with 0.1 To 50 parts by weight, preferably 1 to 30 parts by weight, more preferably 5 to 20 parts by weight. When the weight of the water-dispersible polymer is more than 50 parts by weight, energy density decreases. When the weight of the water-dispersible polymer is less than 0.1 parts by weight, there is a problem that structural control and conductivity improvement are insufficient.

The average diameter of the water-dispersible polymer particles may be smaller than the average diameter of the electrode active material primary particles, and more specifically, the average diameter of the water-dispersible polymer particles is preferably 50 nm to 20 탆, 10 μm, more preferably 300 nm to 5 μm. When the average diameter of the water-dispersible polymer particles is less than 50 nm, the effect of controlling the structure is insufficient. When the average diameter of the water-dispersible polymer particles is more than 20 μm, There is a problem that can collapse.

Next, the step S20 of forming the electrode active material mixture is a step of spray drying the electrode active material mixture composition to form a mixture of the water dispersible polymer particles and the electrode active material aggregated primary active material particles.

Through spray drying, the liquid-like electrode active material mixture composition including the solvent is dried with a powdery electrode active material mixture, and the electrode active material mixture composition is sprayed into the hot air steam inside the spray dryer to remove the solvent .

More specifically, the aqueous dispersion polymer particles and the electrode active material primary particles are agglomerated while the solution of the electrode active material mixture composition is sprayed into an inner chamber through which hot air steam flows at the top of the spray dryer. The agglomerated particles contact the hot air to evaporate the solvent and fall under the inner chamber while being uniformly exposed to heat. In this case, the length of the inner chamber can be adjusted to a length sufficient for the solvent to evaporate completely.

The step (S30) of heat-treating the electrode active material mixture is a step of heating the spray-dried electrode active material mixture at a high temperature. The water dispersible polymer particles are carbonized to coat the surface of the primary active material of the electrode active material, The seat is a step to become a pore.

At this time, the heat treatment is carried out at a temperature of 500 to 1,000 DEG C, preferably 600 to 800 DEG C for 2 to 10 hours, more preferably 5 to 8 hours. When the heating temperature is less than 500 ° C. and the heating time is less than 2 hours, the water dispersible polymer is not completely carbonized, the porosity of the porous electrode active material is low and the conductivity is poor. On the other hand, , The reaction is required to be maintained at a high temperature for a long time, resulting in an increase in manufacturing cost and a decrease in process stability.

As described above, the electrode active material mixture solidifies the electrode active material primary particles through heat treatment, carbonizes the water dispersible polymer particles to form pores, and the carbonized water dispersible polymer particles are coated on the surface of each primary active material A carbon coating layer may be formed, or a carbon coating layer may be formed on the surface of the aggregated primary active material particles.

The porosity of the electrode active material thus formed is 0.1 to 50%, preferably 1 to 20%, and more preferably 5 to 10%. When the porosity is less than 0.1%, there is a problem that the resistance reduction effect is insufficient. When the porosity is more than 50%, there is a problem that it is difficult to maintain the structure of the secondary particles.

Hereinafter, a difference between the method for manufacturing a porous electrode active material according to an embodiment of the present invention and the conventional method will be described with reference to the schematic diagrams of FIGS. 2 and 3. FIG.

2 - (a) is a mixture of a carbon source, a solvent, and an electrode active material primary particle 10 dissolved in a solvent, and the solution is sprayed And dried to form a mixture in which the electrode active material primary particles aggregate as shown in FIG. 2- (b). When the mixture is heat-treated, the electrode active material primary particles 20 coated with the carbon source are densely packed closely to each other, The electrode active material is coated with carbon with almost no voids.

On the other hand, FIG. 3 is a schematic view showing a method of manufacturing a porous electrode active material according to an embodiment of the present invention. Unlike the conventional method, the polymer particles 20, which are not dissolved in a solvent, , The electrode active material primary particles 10 and the polymer particles 20 are aggregated without discrimination as shown in FIG. 3- (b), and the polymer particles are coated with the primary particles of the electrode active material through heating, A coated electrode active material 12 is produced.

According to another embodiment of the present invention, there is provided a porous electrode active material produced by the above-described production method, and specifically, an electrode active material primary particle is formed by agglomeration, and a plurality of electrode active material primary particles formed between the agglomerated electrode active material primary particles There is provided a porous electrode active material having pores and a carbon coating layer formed on the surface of the agglomerated electrode active material primary particles.

Another embodiment of the present invention may be an electrode including the above-mentioned porous electrode active material, wherein the electrode may be an anode or a cathode.

In addition, the electrode may include an electrode current collector and the porous electrode active material according to an embodiment of the present invention. Non-limiting examples of the anode current collector include copper, gold, nickel, copper alloy, And examples of the cathode current collector include, but are not limited to, foil produced by aluminum, nickel, or a combination thereof.

According to another aspect of the present invention, there is provided a secondary battery including the above-described electrode.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to examples. However, the embodiments according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. Embodiments of the present invention are provided to more fully describe the present invention to those skilled in the art.

Porous electrode active material manufacturing

[Example 1]

50: 1 parts by weight of acrylonitrile and [(methacryloyloxy) ethyl] trimethylammonium chlorite (MTC) were used, and water was used as a medium to prepare a polymerization initiator (2,2'-azobis Emulsion polymerization was carried out at 60 DEG C for 18 hours with 0.4 g of 2-methylpropionamidine) dihydrochloride (AIBA), and the resultant was centrifuged to remove the residue to obtain PAN as a water-dispersible polymer. The PAN and Li ₄ Ti ₅ O ₁₂ (LTO) were dispersed in water at 60 ° C to prepare an electrode active material mixture composition. The electrode active material mixture was spray dried and then heat treated in an inert gas atmosphere at 600 ° C to form a porous To prepare an electrode active material.

[Comparative Example 1]

Li ₄ Ti ₅ O ₁₂ (LTO) was mixed with water dissolved in sucrose, spray dried, and then heat treated in an inert gas atmosphere at 600 ° C. to prepare a porous electrode active material.

Manufacture of half-cell

[Example 2]

As the active material, the active material prepared in Example 1, polyvinylidene fluoride (PVdF) as a binder and carbon black as a conductive material were respectively 96% by weight, 3% by weight and 1% by weight, -Methyl-2-pyrrolidone (NMP) to prepare an electrode mixture slurry. The electrode mixture slurry was applied to a copper (Cu) thin film as a current collector having a thickness of 10 mu m and dried to produce a half-cell, followed by roll pressing.

[Comparative Example 2]

The active material prepared in Comparative Example 1, polyvinylidene fluoride (PVdF) as a binder, and carbon black (carbon blzz) as a conductive material were respectively adjusted to 96 wt%, 3 wt%, and 1 wt% -Methyl-2-pyrrolidone (NMP) to prepare an electrode mixture slurry. The electrode mixture slurry was applied to a copper (Cu) thin film as a current collector having a thickness of 10 mu m and dried to produce a half-cell, followed by roll pressing.

Character rating

(1) Surface properties

The surface of the electrode active material prepared in Example 1 and Comparative Example 1 was observed with an SEM photograph.

4 (a) and 4 (b) are SEM photographs of the electrode active material of Comparative Example 1, and almost no pores are observed. FIGS. 5 (a) and 5 (b) SEM photographs clearly show that the pores can be observed more clearly than the comparative example 1.

(2) Capacity evaluation

The capacity of the half-cell produced in Example 2 and Comparative Example 2 was evaluated and shown in Fig.

Specifically, FIG. 6 is a graph showing the capacities of the secondary batteries of Example 2 (Carbon in Particle) and Comparative Example 2 (Carbon in Solution) measured at 0.1 C and 2 C, respectively. .

While the present invention has been described with reference to the particular embodiments and drawings, it is to be understood that the invention is not limited thereto but that the invention may be practiced other than those of ordinary skill in the art, And various modifications and variations are possible within the scope of the appended claims.

10: electrode active material primary particles
11: electrode active material before carbonization primary particles
12: Carbon-coated electrode active material primary particles
20: Water-dispersible polymer particles

Claims (15)

Dispersing the water dispersible polymer particles and the electrode active material primary particles in a solvent to prepare an electrode active material mixture composition;
Spray drying the electrode active material mixture composition to form an electrode active material mixture; And
And thermally treating the electrode active material mixture at a temperature of 500 ° C to 1,000 ° C to carbonize the water dispersible polymer particles in the electrode active material mixture,
The water dispersible polymer particles may be selected from the group consisting of polyacrylonitrile, polyethylene, polystyrene, polyvinyl chloride, poly (meth) acrylic acid, polymethyl (meth) acrylate, polyethyl (meth) acrylate, polybutyl (Meth) acrylate, polydodecyl (meth) acrylate, polystylyl (meth) acrylate, polybenzyl (meth) acrylate, polycyclohexyl (meth) acrylate and polyvinyl acetate Wherein the porous electrode active material is at least one of the following. The method according to claim 1,
The water dispersible polymer particles are spherical,
Wherein the average diameter of the water dispersible polymer particles is smaller than the average diameter of the electrode active material primary particles. The method according to claim 1,
Wherein the water-dispersible polymer particles have an average diameter of 50 nm to 20 탆. The method according to claim 1,
Wherein the content of the water dispersible polymer particles is 0.1 to 50 parts by weight based on 100 parts by weight of the primary active material particles. delete The method according to claim 1,
Wherein the solvent is at least one of water and alcohol. The method according to claim 1,
Wherein the electrode active material mixture is formed by aggregating the water dispersible polymer particles and the electrode active material primary particles. delete The method according to claim 1,
The step of heat-treating the electrode active material mixture may include aggregating the electrode active material primary particles in the electrode active material mixture, carbonizing the water dispersible polymer particles to form voids, and carbonizing the water dispersible polymer particles into the aggregated electrode active material And forming a carbon coating layer on the surface of the primary particles. The method according to claim 1,
Wherein the porosity of the porous electrode active material is 0.1 to 50%. delete delete delete delete delete

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