KR20200122901A - Electrode using porous polymer composite scaffold and Li battery comprising the same - Google Patents

Abstract

In the present invention, provided are an electrode improved to facilitate the movement of lithium ions to an active material, a lithium secondary battery including the same, and a method for rapidly manufacturing the electrode. The electrode according to the present invention comprises: a current collector; and a porous polymer structure formed on the current collector, wherein the porous polymer structure includes a porous polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) film, and an active material and a conductive material included in the porous PVDF-HFP film. According to the present invention, by minimizing physical adhesion between the active material and a binder, the area in which lithium ions can react with the active material is maximized. Accordingly, the lithium secondary battery including such an electrode can be quickly charged/discharged and performance such as capacity preservation can be improved.

Description

Electrode using porous polymer composite scaffold and Li battery comprising the same

The present invention relates to a lithium secondary battery and a method of manufacturing the same, and more particularly, to a lithium secondary battery having an improved electrode and a method of manufacturing the same.

As the technology development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing. Among these secondary batteries, lithium secondary batteries having a high energy density and voltage, a long cycle life, and a low self-discharge rate have been commercialized and widely used.

A typical lithium secondary battery is manufactured by having a positive electrode, a negative electrode, and a separator interposed therebetween and sealed in a battery case together with an electrolyte. The positive and negative electrodes include an active material layer applied on the current collector. In the discharging process of a lithium secondary battery, lithium ions (Li ⁺ ) are formed by ionizing lithium stored in the negative active material. The lithium ions thus formed travel through the electrolyte, enter the positive electrode active material, and are reduced to lithium again. In this process, as the surface area of the active material and the electrolyte increases, more reactions can be performed at once, which realizes a fast charging/discharging speed and a high capacity.

Conventionally, an electrode of a lithium secondary battery is manufactured by coating a slurry obtained by mixing an active material, a conductive material, and a binder in a 1-Methyl-2-pyrrolidinone (NMP) solution on a current collector, followed by drying. The binder is necessary to mechanically stabilize the electrode by binding the active material and the conductive material on the current collector, and a polymer such as PVDF is usually used. The conductive material is added for the purpose of improving the electronic conductivity between the particles of the active material or with the current collector. In particular, it is necessary to prevent the binder region from acting as an electronic insulator and to compensate for insufficient electronic conductivity of the active material.

1 shows a conventional binding model of an active material and a binder.

Referring to FIG. 1, the binder 10 is attached to the surface of the active material 20 like a rubber band to bind the active material 20, and the adhesive bonding as shown in (a) and the surface bonding as shown in (b) may be performed. When the amount of the binder 10 is too large, conduction inhibition occurs when a binder region is formed between the current collector 30 as shown in (c).

However, in the case of an electrode manufactured by a conventional slurry method, there is a problem in that smooth movement of lithium ions to the active material is prevented through physical attachment between the binder and the active material. In addition, the NMP solution used has a high boiling point, which has the disadvantage of a long drying time.

The present invention has been invented by recognizing the problems of the prior art, and an object to be solved by the present invention is to provide an improved electrode and a lithium secondary battery including the same so that lithium ions move smoothly to an active material.

Another problem to be solved by the present invention is to provide a method for rapidly manufacturing such an electrode.

The electrode according to the present invention for solving the above technical problem, a current collector; And a porous polymer structure formed on the current collector, wherein the porous polymer structure includes a porous PVDF-HFP (Poly (vinylidene fluoride-co-hexafluoropropylene) film) formed on the current collector; And in the porous PVDF-HFP film Includes an active material and a conductive material to be included.

The active material may be Co ₃ O ₄ and the conductive material may be graphite.

In the present invention, a lithium secondary battery including an electrode and a separator or a polymer electrolyte according to the present invention is also provided.

The electrode manufacturing method according to the present invention comprises the steps of preparing a mixed solution by mixing a solvent that dissolves PVDF-HFP and a non-solvent that does not dissolve; Dissolving PVDF-HFP in the mixed solution and further mixing a conductive material and an active material to form an electrode solution; And coating and drying the electrode solution on a current collector.

It is preferable that the solvent is acetone and the non-solvent is methanol.

It is preferable to mix less methanol than the acetone.

The conductive material is graphite and the active material is Co ₃ O ₄ , and the weight ratio of the PVDF-HFP: active material: conductive material may be 2.0:6.4:1.6.

According to the present invention, an electrode including a porous polymer structure in which an active material is included in a porous PVDF-HFP film is provided. The porous PVDF-HFP film can maximize the contact area between the active material and the electrolyte. In addition, the porous PVDF-HFP film minimizes physical adhesion between the active material and the binder, so that even after the electrode is manufactured, lithium ions are directly transferred to the surface of the active material of the electrode through the electrolyte, thereby maximizing the area in which lithium ions can react with the active material. Accordingly, a lithium secondary battery including such an electrode can be quickly charged/discharged and performance such as capacity preservation is improved.

According to the present invention, a porous film is formed using PVDF-HFP, and the porous PVDF-HFP film can form a support serving as a conventional binder. Such a porous film can be formed using a mixed solution of acetone and methanol instead of using a high boiling point NMP solution used in conventional slurries. This makes it possible to quickly and easily manufacture an electrode. Therefore, it is possible to reduce the manufacturing time of the electrode of the lithium secondary battery, thereby reducing the process cost.

The following drawings attached to the present specification illustrate preferred embodiments of the present invention, and serve to further understand the technical idea of the present invention together with the detailed description of the present invention. It is limited to and should not be interpreted.
1 shows a conventional binding model of an active material and a binder.
2 is a schematic diagram of an electrode according to the present invention.
3 is a schematic diagram of a rechargeable lithium battery according to the present invention.
4 is a schematic diagram for comparing an electrode formed by a conventional slurry method and an electrode formed by the method according to the present invention.
5 is an image of a film in which an electrode solution formed in an experimental example of the present invention is deposited on a copper foil using a spin coating method.
6 shows capacities measured at a charge/discharge rate of 0.1 C-rate for electrodes formed at different ratios.
7 shows the capacitance measured at a charge/discharge rate of 0.1 C-rate for the electrode according to the present invention and the electrode deposited by the conventional slurry method.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. The drawings introduced below are provided as examples in order to sufficiently convey the spirit of the present invention. Accordingly, the present invention is not limited to the drawings presented below and may be embodied in other forms. Unless there are other definitions in the technical and scientific terms used in the present specification, it is obvious that they have the meanings commonly understood by one of ordinary skill in the art to which this invention belongs. In addition, in the following description and accompanying drawings, a description of known functions and configurations that may unnecessarily obscure the subject matter of the present invention will be omitted.

In particular, the present invention relates to an electrode manufacturing process in which an active material is attached to an electrode in a lithium secondary battery. Through this, it is possible to increase the amount of lithium ions occurring on the surface of the active material and the electrolyte by minimizing a decrease in the surface of the active material formed by physical attachment of the active material and the binder in the electrode. In addition, by replacing the previously used NMP solution with a mixed solution of acetone and methanol, the drying time required for electrode manufacturing can be drastically reduced.

2 is a schematic diagram of an electrode according to the present invention.

2, in the electrode 100 according to the present invention, a porous PVDF-HFP (Poly (vinylidene fluoride-co-hexafluoropropylene)) film 110 is formed on a current collector 130. And, a porous PVDF- The HFP film 110 includes an active material 120 and a conductive material 140. Al ₂ O ₃ , SiO ₂ , TiO _2, etc., which can improve the transfer characteristics of lithium ions or improve the mechanical strength of the electrode. Nanoparticles (not shown) may be further included.

The porous PVDF-HFP film 110, the active material 120, the conductive material, and nanoparticles that may be further included therein constitute a porous polymer structure. The porous polymer structure may be understood as a concept similar to a bulk heterojunction known in a solar cell or a light receiving device, which will be described in detail below.

When manufacturing a negative electrode, the current collector 130 may be copper. Alternatively, the current collector of the negative electrode may be stainless steel, aluminum, nickel, titanium, copper or stainless steel surface treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used. have.

The active material 120 may vary according to the type of secondary battery. For example, the negative active material is a carbon-based active material, and a carbon material such as crystalline carbon, amorphous carbon, carbon composite material, carbon fiber, lithium metal, lithium alloy, or the like may be used. For example, carbon; Li _x Fe ₂ O ₃ (0≤x≤1), Li _x WO ₂ (0≤x≤1), Au _x Me _{1 - x} Me' _y O _z (Me: Mn, Fe, Pb, Ge; Me' : Al, B, P, Si, elements of groups 1, 2 and 3 of the periodic table, halogen, metal complex oxides such as 0<x≦1;1≦y≦3;1≦z≦8); Lithium metal; Lithium alloy; Silicon-based alloys; Tin-based alloys; AuO, 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 metal oxides such as Bi ₂ O ₅ ; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials; Titanium oxide; Lithium titanium oxide or the like can be used. However, it should be understood that the specific examples listed above are only examples.

The conductive material 140 is used to impart conductivity to the electrode 100, and in the configured battery, any material may be used as long as it is an electronically conductive material without causing chemical changes. For example, natural graphite or artificial graphite Graphite such as; Carbon blacks such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; Conductive fibers such as carbon fibers and metal fibers; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskers such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Polyphenylene derivatives; Alternatively, a conductive material including a mixture of two or more thereof may be used. It should be understood that the examples listed here are only examples.

In the case of a lithium secondary battery formed by a conventional slurry method, there is a problem in that smooth movement of lithium ions to the active material 20 through physical attachment between the binder 10 and the active material 20 as shown in FIG. 1 is hindered. In the electrode 100 according to the present invention, the porous PVDF-HFP film 110 serves as a binder to hold the active material 120 when manufacturing the electrode, while minimizing physical adhesion between the active material 120 and the binder. It can serve as a matrix or porous support. Since physical adhesion between the active material 120 and the binder is minimized, lithium ions can be directly transferred to the surface of the active material 120 of the electrode 100 through the porous PVDF-HFP film 110 and the electrolyte even after the electrode 100 is formed. I can.

When driving a lithium secondary battery including the electrode 100 according to the present invention, the porous PVDF-HFP film 110 including the active material 120 and the conductive material 140, that is, the porous polymer structure, is a bulk heterojunction. It becomes similar to forming. Usually, bulk heterojunction is a state in which high molecular compounds that act as electron acceptors and donors are mixed in a bulk state, and since the electron acceptor and electron donor form an interpenetrating network structure at intervals of about 10 to 20 nm, excitons are separated from numerous interfaces. Since it is located within a short distance suitable for, it can effectively separate electrons and holes, and has numerous reaction sites. In the porous polymer structure included in the electrode 100 of the present invention, since the active material 120, the conductive material 140, and PVDF-HFP are mixed in a bulk state, a lithium secondary battery is formed by forming a large reaction surface area as in the concept of bulk heterojunction. Can increase the performance of

A method of manufacturing such an electrode 100 is as follows.

A mixed solution is prepared by mixing a solvent that can dissolve PVDF-HFP and a non-solvent that cannot dissolve PVDF-HFP. Preferably, a mixed solution of acetone and methanol is prepared. Acetone is a solvent and methanol is a non-solvent. The non-solvent is mixed in a small amount compared to the solvent only to the extent that it can form a porous membrane upon vaporization. For example, less methanol is mixed than acetone in the mixed solution. For example, acetone:methanol in the mixed solution may be in a ratio of 5:1 Vol%. Since the ratio of acetone and methanol and the ambient temperature during film formation can determine the microstructure of the porous PVDF-HFP film 110, it is carefully controlled.

Next, PVDF-HPF is added and dissolved in this mixed solution. It is not necessary to use a specific molecular weight range for the PVDF-HFP used.

Thereafter, the conductive material and the active material are further mixed to form an electrode solution. The concentration of the electrode solution may be determined in consideration of a degree suitable for subsequent coating, a degree of easy handling, an amount of loading of an active material after electrode formation, and the like, depending on the selected coating method, and may be, for example, 0.25 mg/ml. Al ₂ O ₃ , SiO ₂ , TiO ₂ It may be prepared by further including nanoparticles capable of improving the transfer characteristics of lithium ions or improving the mechanical strength of the electrode in the electrode solution.

A negative electrode can be manufactured by using graphite as a conductive material and Co ₃ O ₄ as an active material. The weight ratio of PVDF-HFP: active material: conductive material may be selected for appropriate capacity characteristics. For example, it can be 2.0: 6.4: 1.6. Increasing the amount of PVDF-HFP decreases the electrical conductivity. Reducing the amount of PVDF-HFP can make it difficult to expect binder properties. Increasing the amount of the active material is preferable in terms of capacity. However, physical limitations exist to increase the amount of active material such as loading density without limitation. When the amount of the conductive material is increased, the electrical conductivity increases. However, increasing the amount of the conductive material is not preferable because the amount of the active material must be reduced by that much. The 2.0:6.4:1.6 weight ratio cited above is a preferable weight ratio selected in consideration of these points.

These electrode solutions are coated on the current collector by coating, spin coating, painting, doctor blade, die casting, comma coating, screen printing, etc., and then dried, including the active material 120 and the conductive material 140. A porous PVDF-HPF film 110 can be obtained. The method of evenly coating the electrode solution on the current collector may be selected from known methods or may be performed by a new suitable method in consideration of the properties of the material. Alternatively, it may be formed on a separate substrate and then bonded to the current collector by pressing or lamination.

PVDF-HFP is soluble in acetone and insoluble in methanol. That is, for PVDF-HFP, acetone is a solvent and methanol is a non-solvent. In the present invention, using this point, it is proposed to form a porous film by mixing a mixed solution of acetone and methanol with PVDF-HFP. When the mixed solution and the PVDF-HFP solution are coated and dried, acetone and methanol vaporize at different rates to form pores. In the case of acetone, PVDF-HFP is dissolved and vaporized, PVDF-HFP is formed in the form of a film, and methanol is vaporized because it does not contain PVDF-HFP and forms only empty spaces (porous pores).

The NMP solution used in the conventional slurry method has a high boiling point, and thus has a disadvantage of a long drying time. According to the present invention, since a mixed solution of acetone and methanol is used without using an NMP solution, there is an advantage in that the drying time is increased.

3 is a schematic diagram of a rechargeable lithium battery according to the present invention.

The electrode 100 as shown in FIG. 2 may be implemented as a negative electrode or a positive electrode depending on the type of active material. In this embodiment, an example implemented as a cathode is shown.

In Figure 3 (a), the lithium secondary battery 1000 includes a negative electrode, which is the electrode 100 according to the present invention, a separator 200 stacked on the negative electrode, and a positive electrode 300 stacked on the separator 200. Includes an electrode assembly. The electrode assembly is sealed in the battery case together with the liquid electrolyte.

The anode 300 may be manufactured by other known methods. According to a conventional method, a positive electrode active material slurry including a positive electrode active material, a conductive material, a binder, and a solvent may be coated, dried, and rolled on a positive electrode current collector to prepare and prepare. The method according to the present invention may be used, but only the active material may be prepared as a positive electrode active material. The positive electrode active material is, for example, a lithium-based active material, and representative examples are LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiFePO ₄ or Li _{1 + z} Ni _{1 -x- y} Co _x M _y O ₂ (0≤x ≦1, 0≦y≦1, 0≦x+y≦1, 0≦z≦1, M is a metal oxide such as Al, Sr, Mg, La, Mn, etc.). The positive electrode 300 may be a lithium metal without a positive electrode current collector.

The separator 200 is not particularly limited as long as it has a porous material. The separation membrane 200 is a porous polymer membrane, such as a porous polyolefin membrane, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-trichloroethylene, polymethylmethacrylate, polyacrylonitrile, Polyvinylpyrrolidone, polyvinyl acetate, ethylene vinyl acetate copolymer, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethylpolyvinyl alcohol, cyanoethylcellulose , Cyanoethyl sucrose, pullulan, carboxyl methyl cellulose, acrylonitrile styrene butadiene copolymer, polyimide, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polyetheretherketone, poly It may be made of ether sulfone, polyphenylene oxide, polyphenylene sulfide, polyethylene naphthalene, a nonwoven fabric film, a film having a porous web structure, or a mixture thereof. Inorganic particles may be bound to one side or both sides of the separation membrane 200.

The electrolyte may include an organic solvent and a lithium salt as a representative electrolyte solution. The organic solvent may minimize decomposition due to an oxidation reaction or the like in the charging and discharging process of the battery, and there is no limitation as long as it can exhibit desired properties, and may be, for example, a cyclic carbonate, a linear carbonate, an ester, an ether, or a ketone. These may be used alone, or two or more may be used in combination. Among the organic solvents, a carbonate-based organic solvent may be preferably used, and examples of the cyclic carbonate include ethylene carbonate (EC), propylene carbonate (PC) and butylene carbonate (BC), and the linear carbonate includes dimethyl carbonate (DMC ), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethylmethyl carbonate (EMC), methylpropyl carbonate (MPC), and ethylpropyl carbonate (EPC) are representative. Lithium salts are LiPF ₆ , LiAsF ₆ , LiCF ₃ SO ₃ , LiN(CF ₃ SO ₂ ) ₂ , LiBF ₄ , LiBF ₆ , LiSbF ₆ , LiN(C ₂ F5SO ₂ ) ₂ , LiAlO ₄ , LiAlCl ₄ , LiSO ₃ CF Lithium salts commonly used in electrolytes of lithium secondary batteries, such as ₃ and LiClO ₄ , may be used without limitation, and these may be used alone, or two or more may be used in combination. The step of preparing such an electrolyte is not particularly limited and may be performed according to a known method.

The battery case may be a pouch made of an aluminum laminate sheet or a metal can. The step of preparing such a battery case is not particularly limited and may be performed according to a known method.

In (b) of FIG. 3, the lithium secondary battery 1000 ′ is a negative electrode 100 according to the present invention, a polymer electrolyte 200 ′ stacked on the negative electrode, and a positive electrode stacked on the polymer electrolyte 200 ′ ( It includes an electrode assembly including 300). The lithium secondary battery 1000 ′ may be manufactured by a method such as additionally forming a porous PDVF-HFP film on the electrode 100 according to the present invention without using the separator 200 separately. In addition, the polymer electrolyte 200 ′ is, for example, a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphate ester polymer, a poly agitation lysine, a polyester sulfide, a polyvinyl alcohol, a polyvinylidene fluoride. , A polymerization agent containing an ionic dissociation group, or the like may be used. Of course it is not limited to these only.

4 is a schematic diagram of an active material portion of an electrode formed by a conventional slurry method and an electrode formed by the method according to the present invention. Arrows in FIG. 4 indicate the diffusion path of lithium.

4A is a conventional electrode 1, in which the active material 20' and the conductive material 40 are bound by a binder 10', and the liquid electrolyte 50 is between the active material 20'. It is included in the interface. Due to the physical bonding between the binder 10 ′ and the active material 20 ′, the surface area of the active material 20 ′ capable of participating in the reaction decreases, indicating that the movement of lithium ions is small.

4B is an electrode 100 according to the present invention, and an active material 120 and a conductive material 140 are included in the porous PDVF-HFP film 110. A relatively large amount of lithium ions may move due to movement of lithium ions on all surface areas of the active material 120.

In the case of a lithium secondary battery, especially a lithium ion secondary battery, the battery is driven through the movement of lithium ions dissolved in an electrolyte between the negative electrode and the positive electrode inside the battery. Electrons are generated and destroyed through reaction with lithium ions on the surface of the active material, and the reaction amount increases as the surface area of the active material increases.

Conventionally, electrodes are formed using a slurry. PVDF, which is used as a binder included in the slurry, adheres to the surface of the active material and inhibits the reaction, and has a disadvantage in that a long drying process is used because NMP with a high boiling point is used when manufacturing an electrode.

In contrast, the method of the present invention uses PVDF-HFP to form a porous polymer support. A direct reaction occurs with the electrolyte on the surface of the active material formed together with the porous polymer support, and even when PVDF-HFP is attached to the active material on the surface of the active material, there is an advantage that the electrolyte can directly react to the surface of the active material through pores. In addition, by using a mixed solution of acetone and methanol, the drying time required for electrode manufacturing is reduced, so that the electrode can be manufactured more easily.

Hereinafter, an experimental example including an example in which a negative electrode according to the present invention is prepared and a lithium secondary battery is manufactured using the negative electrode to test the performance will be described. Although the present invention may be described in more detail by experimental examples, the embodiments described herein are merely examples of the present invention, and the present invention is not limited thereto.

Experimental example

A mixed solution of acetone:methanol at a ratio of 5:1 Vol% was used as a solvent. Dissolve PVDF-HPF (Sigma Aldrich, average mW ~400,000, pellets) in 0.2 g and 4 ml of solvent. Melt it by rotating the magnetic at 400 rpm for 1 hour at 40°C. Thereafter, 0.16 g of carbon black (Graphene supermarket) was added as a conductive material and mixed at 400 rpm for 30 minutes. As an active material, 0.64 g of Cobalt(II,III) oxide (Sigma Aldrich, nanopowder, <50 nm particle size) was added and mixed at 400 rpm for one day to form an electrode solution. PVDF-HFP: Cobalt (II, III) oxide: Carbon black was prepared in Example 1 prepared in a ratio of 6.0: 3.6: 0.4 and Example 2 prepared in a ratio of 2.0: 6.4: 1.6. In all cases, the concentration of the electrode solution was made to be 0.25 mg/ml.

The preparation process of the electrode solution was the same, but a comparative example including only an active material without a conductive material was also tested. PVDF-HFP: Cobalt(II,III) oxide was prepared in Comparative Example 1 prepared in a ratio of 6.0: 4.0 and Comparative Example 2 prepared in a ratio of 2.0: 8.0. In all cases, the concentration of the electrode solution was made to be 0.25 mg/ml.

A comparative example using a conventional slurry system using PVDF as a binder was also tested. In Comparative Example 3, a slurry prepared with PVDF: Cobalt(II, III) oxide: Carbon black in a ratio of 1.0:8.9:1.0 is used.

5 is an image of a film in which an electrode solution formed in an experimental example of the present invention is deposited on a copper foil using a spin coating method. Electrodes having different composition ratios were formed on the left and right sides of FIG. 5 to compare capacities according to films. In FIG. 5, a) is according to Example 1, b) is according to Comparative Example 1, c) is according to Example 2, and d) is according to Comparative Example 2.

6 shows capacities measured at a charge/discharge rate of 0.1 C-rate for electrodes formed at different ratios. In FIG. 6, a) is a charge and discharge curve of Example 1 and Comparative Example 1, and b) is a charge and discharge curve of Example 2 and Comparative Example 2.

As a result of charging and discharging, it was confirmed that in the case of Example 1 and Comparative Example 1, charging/discharging was not performed properly, and a low charging/discharging of 200 mAh/g or less was observed after the first discharge. It is understood that this occurred because electrons formed after the reaction of the active material occurred in the electrode was not well transferred to the outside of the electrode. Therefore, it is preferable that the content of PVDF-HFP, which is a non-conductor, decreases compared to Example 1.

In Example 2, compared to Example 1, the PVDF-HFP content was small and the active material content was large. Comparative Example 2 has no conductive material compared to Example 2. Comparing Example 2 and Comparative Example 2, the capacity of Example 2 is high, which is judged to be due to the increased capacity due to the easier movement of electrons depending on whether or not the conductive material is added.

In Example 2, when 64 wt% of the active material, 16 wt% of the conductive material, and 20 wt% of the binder were used, the capacity was found to be the highest. In particular, in Example 2, except for the first discharge capable of forming a solid electrolyte interface (SEI) layer, the second cycle exhibited a capacity of 920 mAh/g over the theoretical value of 890 mAh/g of Co ₃ O ₄ It was confirmed. Accordingly, it is supported that, according to the present invention, a capacity close to the theoretical value can be expressed through the concept of a bulk heterojunction, and performance of a lithium secondary battery can be improved.

7 shows the capacitance measured at a charge/discharge rate of 0.1 C-rate for the electrode according to the present invention and the electrode deposited by the conventional slurry method. PVDF-HFP: Co ₃ O ₄ : Carbon Black was shown in Example 2 and Comparative Example 3, which are electrodes in which the ratio of 2.0:6.4:1.6 was mixed.

Referring to FIG. 7, it can be seen that the capacity is better maintained even when the cycle increases according to the present invention.

As described above, according to the present invention, when PVDF-HFP is used as an electrode material and a porous PVDF-HFP film is used as a support for an electrode, it is possible to increase the lithium secondary battery performance by increasing the surface area between the electrolyte and the active material.

In the above, the present invention has been illustrated and described with reference to specific preferred embodiments, but the present invention is not limited to the above-described embodiment, and those skilled in the art to which the present invention pertains within the scope of the spirit of the present invention. Various changes and modifications may be made by the person.

100: electrode
110: Porous PVDF-HFP film
120: active material
130: current collector
140: conductive material
200: separator
200': polymer electrolyte
300: anode
1000, 1000': lithium secondary battery

Claims (7)

Current collector; And
Including a porous polymer structure formed on the current collector,
The porous polymer structure,
Porous PVDF-HFP (Poly (vinylidene fluoride-co-hexafluoropropylene) film; And
An electrode comprising an active material and a conductive material included in the porous PVDF-HFP film. The electrode of claim 1, wherein the active material is Co ₃ O ₄ and the conductive material is graphite. A lithium secondary battery comprising the electrode of claim 1 and a separator or a polymer electrolyte. Preparing a mixed solution by mixing a solvent that dissolves PVDF-HFP and a non-solvent that does not dissolve;
Dissolving PVDF-HFP in the mixed solution and further mixing a conductive material and an active material to form an electrode solution; And
And drying the electrode solution after coating the electrode solution on a current collector. The method of claim 4, wherein the solvent is acetone and the non-solvent is methanol. The method of claim 5, wherein the methanol is mixed less than that of the acetone. The method of claim 5, wherein the conductive material is graphite and the active material is Co ₃ O ₄ , and the weight ratio of the PVDF-HFP: active material: conductive material is 2.0:6.4:1.6.

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