KR20170071336A - Cathode for lithium air battery, preparation method thereof, and lithium air battery comprising the same - Google Patents

Abstract

The present invention relates to an electrode substrate; And a composite conductive material layer including a particulate first conductive material and a fibrous second conductive material on the electrode substrate, wherein the composite conductive material layer includes a plurality of pores, A method for manufacturing the same, and a lithium air battery including the same.
The anode according to an embodiment of the present invention can further improve the output characteristic. Particularly, due to a large number of pores included in the composite conductive material layer, ions and oxygen in the electrolyte can be easily transferred during charging and discharging, and the specific surface area of the discharge product can be widened. Thus, overvoltage and battery life deterioration can be remarkably improved have.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive electrode for a lithium-ion battery, a method for manufacturing the same, and a lithium-air battery including the same. BACKGROUND ART [0002]

The present invention relates to a positive electrode for a lithium air battery, a method of manufacturing the same, and a lithium air battery including the same.

A secondary battery, unlike a primary battery, is a rechargeable, rechargeable battery. Lithium-air batteries have the highest energy density among metal-air batteries, which typically consist of a combination of metal and air. Lithium air batteries are known to have an energy reserve of more than 10 times that of lithium ion batteries.

In addition, lithium-ion batteries have excellent properties in terms of price competitiveness and environment friendliness by using carbon such as nickel, manganese, and cobalt which were used in conventional lithium ion batteries. Such a lithium-air battery basically has a structure in which a lithium metal is used as a cathode and a carbon material is used as an anode (air electrode), and an electrolyte separation membrane is disposed therebetween. As shown in FIG. 1, oxygen is supplied to the anode of the porous carbon material As a result, electrons move between the cathode and the anode through the electrolyte to produce energy.

In the lithium-ion battery, the reaction of the following formula (1) proceeds at the cathode when discharging.

The electrons generated in Eq. (1) pass through an external circuit, work in an external load, and then reach the anode. The lithium ion (Li ⁺ ) generated in the formula (1) moves from the negative electrode side to the positive electrode side in the electrolyte existing between the negative electrode and the positive electrode, and reaches the positive electrode.

On the other hand, in a lithium ion battery, the reactions of the following formulas (2) to (3) can proceed at the anode during discharging.

Lithium oxide generated by the above formulas (2) to (3) is accumulated in the anode. At the time of charging, the opposite reaction of the above-mentioned formula (1) in the negative electrode and the opposite reaction of the above-mentioned formulas (2) to (3) are carried out on the positive electrode, and lithium metal is regenerated in the negative electrode so that repeated charging and discharging are possible.

However, the improvement of current lithium-ion battery is to improve the problem of very short charging / discharging life and low power. Porosity of the anode catalyst and conductive material is the main factor that shortens the lifetime. In addition, the output of a lithium-ion battery is affected by the following four factors: 1) transfer of lithium ions to the surface of carbon through the electrolyte 2) electron transfer between the substrate and the conductive material and conductive materials 3) supply of oxygen from the outside 4) reaction rate at the surface of the conductive material.

However, the lithium-ion battery studied to date has a high energy density compared to the lithium ion battery, but has a low output characteristic.

Therefore, development of an electrode capable of improving the output characteristics of a lithium-ion battery is urgently required.

J. Phys. Chem. Lett., 2010, 1 (14), pp 2193-2203

The present invention is intended to solve the above-mentioned problems.

A first technical object of the present invention is to provide a positive electrode capable of improving the output characteristics of a lithium-ion battery.

A second object of the present invention is to provide a method of manufacturing a positive electrode in which the pore size and internal porosity of the positive electrode can be controlled.

A third object of the present invention is to provide a lithium-ion battery including the positive electrode.

In order to solve the above-described problems, the present invention provides an electrode substrate, And a composite conductive material layer including a particulate first conductive material and a fibrous second conductive material on the electrode substrate, wherein the composite conductive material layer includes a plurality of pores, to provide.

The present invention also relates to a method for producing a particulate first conductive material, Adding a fibrous second conductive material and a binder to the first mixture and then secondary mixing; And applying the secondary mixture on an electrode substrate. The present invention also provides a method for manufacturing a positive electrode for a lithium-air battery.

The present invention also provides a lithium air battery including the positive electrode.

The anode according to an embodiment of the present invention includes a composite conductive material layer including a particulate first conductive material and a fibrous second conductive material on an electrode substrate to improve the output characteristics efficiently while generating a reversible discharge product . Particularly, due to a large number of pores included in the composite conductive material layer, ions and oxygen in the electrolyte can be easily transferred during charging and discharging, and the specific surface area of the discharge product can be widened. Therefore, overvoltage and deterioration in life of the battery can be remarkably improved have.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description of the invention, It should not be construed as limited.
FIG. 1 is a schematic view showing a reaction process in an electrode during discharge.
FIG. 2 is a SEM photograph of a positive electrode containing only a ketjen black as a conventional conductive material layer and a schematic view of an anode structure.
3 is a schematic diagram of an anode structure including a composite conductive material layer according to an embodiment of the present invention.
4 is a schematic view of a cathode structure including a composite conductive material layer according to another embodiment of the present invention.
5 is a scanning electron microscope (SEM) photograph of a cathode according to Example 1 of the present invention.
6 is a scanning electron microscope (SEM) photograph of the anode of Comparative Example 1. Fig.
7 is a scanning electron microscope (SEM) photograph of the anode of Comparative Example 2. Fig.

Hereinafter, the present invention will be described in detail in order to facilitate understanding of the present invention.

The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention.

An anode for a lithium air battery according to an embodiment of the present invention includes: an electrode substrate; And a composite conductive material layer including a particulate first conductive material and a fibrous second conductive material on the electrode substrate, wherein the composite conductive material layer includes a plurality of pores.

The anode according to an embodiment of the present invention can improve the transfer of oxygen through the formation of the pore-forming first conductive material and the particle-type conductive material that affects the improvement of lithium ion transfer on the electrode substrate, By including the composite conductive material layer containing the fibrous second material, the dispersibility and the reaction area are improved as compared with the conventional lithium air battery, so that the output characteristics can be improved efficiently while producing the reversible discharge product. In particular, a large number of pores included in the composite conductive material layer not only facilitates ion movement in oxygen and electrolyte during charging and discharging, but also widens the specific surface area of the discharge product, thereby remarkably improving overvoltage and battery life deterioration have.

Specifically, in the composite conductive material layer included in the anode according to an embodiment of the present invention, the particle-shaped first conductive material may function as a reaction site for lithium ion transfer and surface discharge products through electrolyte hermit.

The particulate first conductive material according to an exemplary embodiment of the present invention may be any one selected from the group consisting of Super C, Super P, Ketjen Black, and acetylene black, or a mixture of two or more thereof. It is possible.

The first conductive type particle material may be a particulate conductive material having a specific surface area (BET) of 300 to 1,500 m 2 / g and an average particle diameter (D ₅₀ ) of 30 to 70 nm in consideration of conductivity. For example, the particulate first conductive material may be Ketjenblack having a specific surface area (BET) of 1000 to 1400 m 2 / g and an average particle diameter (D ₅₀ ) of 40 to 50 nm.

When the BET specific surface area of the particulate first conductive material is out of the above range and the specific surface area is large, the density of the electrode is low and the energy density is decreased. When the BET specific surface area is smaller than the above range, the output characteristic of the lithium-

In the present invention, the specific surface area of the conductive material can be measured by a BET (Brunauer-Emmett-Teller; BET) method. For example, it can be measured by a BET 6-point method by a nitrogen gas adsorption / distribution method using a porosimetry analyzer (Bell Japan Inc, Belsorp-II mini).

In the present invention, the average particle diameter of the conductive material particles can be defined as the particle diameter based on 50% of the particle diameter distribution of the particles. The average particle diameter (D ₅₀ ) of the particles according to an embodiment of the present invention can be measured using, for example, a laser diffraction method. The laser diffraction method generally enables measurement of a particle diameter of several millimeters from a submicron region, resulting in high reproducibility and high degradability.

When only the particulate first conductive material is included in the conductive material layer, an increase in the capacity per unit carbon weight may contribute to a large specific surface area, but the output performance may be significantly lowered. Further, as shown in a scanning electron microscope (SEM) photograph of the anode shown in FIG. 2 and a structural schematic diagram of the anode, it is considered that due to the accumulation of conductive material particles, a shortage of pores in the electrode causes generation of discharge products such as Li ₂ O ₂ Oxygen and ion transport in the electrolyte can be difficult. In addition, there is a risk of causing overvoltage and deterioration in life due to discharge products intensively formed only on the surface.

Accordingly, in order to solve the above-described problems, the present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a fiber- macro) pores can be easily formed and the output characteristics can be further increased.

The fibrous second conductive material according to an embodiment of the present invention may serve to improve oxygen transfer, electrolyte migration, and electrical conductivity from the electrode substrate through pore formation in an electrode reaction.

The fibrous second conductive material may be, for example, a carbon fiber having a diameter of 100 to 200 nm and a length of 5 to 25 占 퐉. For example, the fibrous second conductive material may be a carbon fiber having a diameter of 130 to 170 nm and a length of 10 to 20 탆.

Specific examples of the fibrous second conductive material include polyacrylonitrile-based carbon fibers, rayon-based carbon fibers, pitch-based carbon fibers, vapor grown carbon fibers (VGCF-based carbon nanotubes), and carbon nanotubes nano tube), or a mixture of two or more thereof. For example, the fibrous second conductive material may be vapor-grown carbon fiber. The aspect ratio of the fibrous second conductive material may be from 50 to 200, for example, from 80 to 120. [

The composite conductive material layer according to an embodiment of the present invention is partially or wholly surrounded by the particulate first conductive material on the fibrous second conductive material as shown in the schematic view of the anode structure of Figs. 3 and 4, The conductive material acts as the reaction site of the discharge product to efficiently generate the specific surface area of the discharge product wider and thinner, thereby further improving the overvoltage induction and the service life deterioration. Further, The output characteristic can be improved while maintaining a high discharge capacity.

In the present invention, when the distribution of the pores is analyzed according to the pore size, the interval of 0.1 to 1 占 퐉 is due to the pores between the inside of the first conductive material and the first conductive material attached to the surface pores, This affects the output related to the accumulation capacity and reaction rate. The interval of 1 to 10 [micro] m represents pores between the first conductive material, pores between the first conductive material and the second conductive material, and the second conductive material, and is a region due to the capacity of accumulating the discharge products. It is also a part of the electrolyte passage. The section between 10 and 50 ㎛ is the main moving path of the electrolyte, and the section over 50 ㎛ is the moving path of oxygen.

If the average diameter of the pores exceeds the above range, the volume energy density of the battery can be reduced due to a too large empty space. If the pore diameter is less than the above range, problems such as oxygen transfer through the pore and electrolyte migration occur, .

Further, the internal porosity of the composite conductive material layer may be 40 to 80%, for example, 50 to 60%.

According to an embodiment of the present invention, the inner porosity of the composite conductive material layer may be defined as a ratio of voids of 50 m or less to the total volume of the composite conductive layer.

The measurement of the internal porosity is not particularly limited, and may be measured by a mercury porosimetry method using, for example, a Quantumrome's Poarmaster apparatus according to an embodiment of the present invention. The mercury porosimetry method is an analysis method of measuring pores based on the sensed pressure by penetrating mercury into the electrode, and it is easier to analyze pores having a diameter of 500 nm or more than the BET measurement method.

The weight ratio of the particulate first conductive material: fibrous second conductive material according to an embodiment of the present invention may affect the pore structure formed in the composite conductive material layer, and the pore size and the internal porosity of the conductive material layer are satisfied For example, from 1: 0.5 to 4: 1, for example, from 1: 0.6 to 2: 1. For example, it may be 1: 1 to 1.5 weight ratio.

According to an embodiment of the present invention, in the above range, the particulate first conductive material may be complexized to partially or wholly surround the surface of the fibrous second conductive material to include suitable pores, Can be very well represented.

If the content of the particulate first conductive material is less than the above range, it can not be uniformly formed on the surface of the fibrous second conductive material, and the capacity characteristics of the lithium air battery may be deteriorated. Also, when the content of the fibrous second conductive material is less than the above range, the life characteristics and output characteristics of the lithium air battery may be deteriorated.

According to an embodiment of the present invention, the composite conductive material layer may further include a dispersing agent to reduce aggregation of the conductive materials. As long as the effect of the present invention is not impaired, the dispersant may be one that is commonly used. Examples thereof include acrylonitrile-butadiene rubber, modified acrylonitrile rubber, acrylonitrile-butadiene-styrene Rubber or the like can be used. Specifically, as the dispersing agent, BM-720H, BM-730H and the like of ZEON can be used.

The weight ratio of the particulate first conductive material: dispersant may be from 1: 0.05 to 0.5, for example, from 1: 0.1 to 0.4. For example, it may be 1: 0.15 to 0.25.

When the content of the dispersing agent is less than the above-mentioned content ratio, sufficient dispersing performance can not be exhibited and output characteristics and capacity characteristics may be deteriorated. On the contrary, when the content of the dispersing agent exceeds the above range, the binder is present on the surface of the conductive material in an excessive amount, and the dispersing material covers the surface of the carbonaceous material, thereby reducing the output characteristics and the capacity characteristics.

In addition, the present invention can provide a method of manufacturing the positive electrode for a lithium air battery.

A method of manufacturing a positive electrode according to an embodiment of the present invention includes a method of forming a composite conductive material layer on a positive electrode substrate by a mixing method as shown in FIG. 3, and a method of forming a free- There may be a method of forming a layer.

Specifically, as a mixing method according to an embodiment of the present invention, a method of manufacturing a positive electrode is a method in which a mixture of a particulate first conductive material, a particulate second conductive material, a binder, and a dispersant are mixed and the mixture is applied onto a cathode substrate Step.

According to still another embodiment of the present invention, there is provided a method of manufacturing a positive electrode, comprising: mixing and mixing the particulate first conductive material and a dispersant; Adding a fibrous second conductive material and a binder to the first mixture and then secondary mixing; And applying the secondary mixture onto the cathode substrate. Further, after the application step, it may further include drying in an oven at 50 to 120 DEG C for 5 to 20 hours.

The method comprises mixing the particulate first conductive material with a dispersant to minimize the aggregation of the particulate first conductive material and then mixing the first conductive material with the fibrous second conductive material so that the desired pore size and / It is advantageous to realize the pore structure, so that the capacity characteristics, the output characteristics and the life characteristics per unit area of the lithium air battery can be further increased.

According to an embodiment of the present invention, the fibrous second conductive material may be manufactured by various methods. For example, fine fibrous materials such as carbon nanotubes and carbon nanofibers having a multi-structure structure produced by an arc discharge method and a laser method are produced, vapor grown carbon fibers manufactured by a vapor grown method , VGCF), and the like.

By using the mechanical milling method, the secondary mixing can be performed so as to partially or entirely surround the particulate first conductive material on the fibrous second conductive material as shown in the schematic view of the anode structure shown in Fig. 3, Size porosity and porosity can be achieved. At this time, the mechanical milling may be selected from a high energy ball mill, a planetary mill, a stirred ball mill, and a vibrating mill method.

According to another embodiment of the present invention, there is provided a method of forming an electrode-free free-standing composite conductive layer, comprising the steps of: (1) 2 conductive material are dispersed in deionized water (DI water); (2) mixing and stirring the dispersed particle type first conductive material and the fibrous second conductive material; (3) filtering and drying the agglomerated particulate first conductive material and the fibrous second conductive material dispersion to form a free-standing composite structure; And (4) applying the stand alone composite structure on the cathode substrate.

At this time, the particulate first conductive material and the fibrous second conductive material treated in the step (1) are mixed with sulfuric acid and nitric acid at a ratio of 1:10 to 100 (v / v), for example, 1: 1 to 10 / v) is added to the acid mixture and the particulate first conductive material and the fibrous second conductive material are added to the mixture at 20 to 150 ° C, for example, at 40 to 80 ° C for 30 minutes to 24 hours, for example, 2 To < RTI ID = 0.0 > 8 hours. ≪ / RTI >

Further, the binder used in the production method of the present invention may be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, polyvinylchloride, Polyvinyl chloride, a polymer containing ethylene oxide, styrene-butadiene rubber, or a combination thereof.

The anode substrate is not particularly limited as long as it has conductivity, but a metal foam having porosity is preferable from the viewpoint of high oxygen supply performance and excellent current collection efficiency. For example, nickel foam or aluminum foam can be used .

Furthermore, the present invention can provide a lithium air battery including the positive electrode.

The lithium ion battery according to an embodiment of the present invention is manufactured by a manufacturing method commonly used in the art, and may include the anode (cathode), the cathode, the separator, and the electrolyte.

The negative electrode included in the lithium ion battery according to an embodiment of the present invention includes a negative electrode layer containing a negative active material capable of discharging lithium ions. And a negative electrode substrate (current collector) which is usually added to the negative electrode layer and which collects the negative electrode layer. And a negative electrode lead connected to the negative electrode substrate as required.

The negative electrode layer contains a negative electrode active material capable of discharging lithium ions. Examples of the anode active material include lithium aluminum alloys, lithium tin alloys, lithium lead alloys, lithium silicon alloys, and the like. Examples of the lithium compound include oxides such as lithium titanium oxide, nitrides such as lithium cobalt nitride, lithium iron nitride and lithium manganese nitride. The use of lithium metal is intended to increase the absolute amount of lithium, so it is preferable to use lithium metal itself in view of battery capacity. However, since lithium metal is highly reactive, lithium alloys may be used in terms of safety.

The material for the negative electrode substrate is not particularly limited as long as it has conductivity, and examples thereof include copper, stainless steel, nickel, carbon and the like. For example, the negative electrode substrate uses a metal having a suitable oxidation potential so as not to oxidize at the negative electrode during battery reaction, and copper, nickel, aluminum and the like are suitable. Examples of the shape of the negative electrode substrate include a thin film, a plate shape, and a loop (grid) shape. In the present invention, the battery case described later may also have the function of the negative electrode substrate.

The separation membrane may be made of a polyethylene-polypropylene (PE-PP) material or a glass fiber material, which is capable of permeating a liquid electrolyte, but is not limited thereto.

The lithium ion battery device according to the present invention can be applied not only to automobiles but also to other devices such as IT devices, ships, airplanes, and energy storage devices.

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. The embodiments of the present invention are provided to enable those skilled in the art to more fully understand the present invention.

Examples and Comparative Examples

EXAMPLES The present invention will be further illustrated by the following examples and experimental examples, but the present invention is not limited by these examples and experimental examples.

Example 1

≪ Preparation of positive electrode &

Ketjen Black KB (600 J, LION Corp.) was used as the particulate first conductive material, BM-720H (ZEON) was used as the dispersant, and N-methyl-2-pyrrolidone NMP; N-methyl-2-pyrrolidone). Vapor grown carbon fibers (VGC) and polytetrafluoroethylene (PTFE) as a binder were mixed in the mixture as N-methyl-2-pyrrolidone (NMP) 2-pyrrolidone) was added to the mixed solution to prepare a cathode slurry.

The positive electrode slurry was coated on a nickel foam and dried in an oven at 120 ° C for 12 hours to obtain a positive electrode (air electrode) for a lithium air battery.

<Lithium air battery coin cell manufacturing>

A lithium-metal battery coin cell was manufactured using a lithium metal thin film as a cathode and using 150 L of a 1M LITFSI in TEGDME electrolyte as an electrolyte disposed between the prepared positive and negative electrodes.

Examples 2 to 6

A positive electrode and a lithium air battery coin cell were prepared in the same manner as in Example 1, except that the content of the particle-formable first conductive material, the fibrous second conductive material, the binder, and the dispersant was used in the content ratio shown in Table 1 below.

Example 7

Except that the content of the particulate first conductive material, the fibrous second conductive material, the binder and the dispersing agent was used in the content ratio shown in Table 1, except that Ketjenblack KB (300J, LION Co.) was used as the particulate first conductive material , A positive electrode and a lithium air battery coin cell were produced in the same manner as in Example 1. [

Comparative Example 1

Vapor grown carbon fibers (VGCF) were used solely as a conductive material in Table 1 below, and PTFE was mixed as a binder in an NMP (N-methyl-2-pyrrolidone) solvent to prepare a positive electrode slurry.

The positive electrode slurry was coated on a nickel foam and dried in an oven at 120 ° C for 12 hours to obtain a positive electrode (air electrode) for a lithium air battery.

Comparative Examples 2 and 3

A cathode slurry was prepared by using Ketjen Black KB (600 J, LION Corp.) alone as a conductive material and PTFE as a binder in an NMP (N-methyl-2-pyrrolidone) , A positive electrode and a lithium air battery coin cell were produced in the same manner as in Comparative Example 1. [

Comparative Example 4

Except that KETJEN BLACK KB (600 J, LION Corp.) was used solely as a conductive material in the content ratios shown in the following Table 1 and BM-720H (ZEON) was used as a dispersant thereof, a positive electrode slurry was prepared , A positive electrode and a lithium air battery coin cell were produced in the same manner as in Comparative Example 1. [

division Particle type
The first conductive material Fiber type
The second conductive material Weight ratio
(First conductive material / second conductive material) Composition (weight ratio)
(First conductive material / second conductive material / binder / dispersant) Dispersant Kinds BET / particle size (D ₅₀ ) Kinds Aspect ratio Example 1 KB (600J) 1300/50 VGCF-H 100 20/80 16/64 / 16.8 / 3.2 BM-720H Example 2 KB (600J) 1300/50 VGCF-H 100 40/60 32/48 / 13.6 / 6.4 BM-720H Example 3 KB (600J) 1300/50 VGCF-H 100 60/40 48/32 / 10.4 / 9.6 BM-720H Example 4 KB (600J) 1300/50 VGCF-H 100 20/80 12/48 / 37.6 / 2.4 BM-720H Example 5 KB (600J) 1300/50 VGCF-H 100 40/60 24/36 / 35.2 / 4.8 BM-720H Example 6 KB (600J) 1300/50 VGCF-H 100 60/40 36/24 / 32.8 / 7.2 BM-720H Example 7 KB (300 J) 800/50 VGCF-H 100 60/40 36/24 / 32.8 / 7.2 BM-720H Comparative Example 1 - - VGCF-H 100 0/100 0/90/10/0 - Comparative Example 2 KB (600J) 1300/50 - - 100/0 80/0/20/0 - Comparative Example 3 KB (600J) 1300/50 - - 100/0 60/0/40/0 - Comparative Example 4 KB (600J) 1300/50 - - 100/0 60/0/28/12 BM-720H 1) BM-720H: Modified acrylonitrile rubber (ZEON)
2) KB (600J) and KB (300J): Ketjenblack (LION)
3) VGCF: Vapor grown carbon fiber (Showa Denko)

Experimental Example 1: Evaluation of output characteristics and discharge capacity characteristics of a lithium-ion battery

The lithium-air batteries produced in Examples 1 to 7 and Comparative Examples 1 to 4 were discharged at a current of 0.5, 1, 2, 5 mA (0.05, 0.1, 0.2, 0.5 C) , 1, 2, and 5 mA, and the discharge characteristics were measured.

The lithium ion batteries manufactured in Examples 1 to 7 were charged at a constant current-constant voltage up to 4.3 V and then discharged at a constant current of 2.0 V to measure discharge capacity. The results obtained are shown in Table 2 below.

Experimental Example  2: Measurement of pore distribution

The anodes produced in Examples 1 to 7 and Comparative Examples 1 to 4 were measured for distribution of sizes of the internal pores using a Poarmaster equipment manufactured by Quantachrome. The results obtained are shown in Table 3 below.

division Total amount of conductive material to be loaded Composition (weight ratio)
(First conductive material / second conductive material / binder / dispersant) The porosity inside the composite conductive material layer
(%) Discharge capacity
(mAh / cm ² , 0.05C) Output performance life span
(time) 0.05C 0.1 C 0.2C 0.5 C Example 1 3 mg / cm ² 16/64 / 16.8 / 3.2 63.0 2.98 100% 97.0% 92.0% 78.0% 48 Example 2 32/48 / 13.6 / 6.4 66.6 5.35 100% 96.5% 91.0% 75.0% 38 Example 3 48/32 / 10.4 / 9.6 69.9 7.25 100% 96.0% 89.0% 70.0% 27 Example 4 12/48 / 37.6 / 2.4 58.6 2.12 100% 96.5% 90.0% 73.0% 71 Example 5 24/36 / 35.2 / 4.8 60.1 3.80 100% 95.7% 88.7% 69.0% 64 Example 6 36/24 / 32.8 / 7.2 61.3 5.11 100% 95.0% 87.0% 63.0% 55 Example 7 36/24 / 32.8 / 7.2 32.0 2.20 100% 95.3% 88.0% 66.0% 61 Comparative Example 1 0/90/10/0 18.4 0.14 100% 98.5% 96.0% 91.0% 153 Comparative Example 2 80/0/20/0 55.5 7.91 100% 93.1% 82.2% 53.0% 5 Comparative Example 3 60/0/40/0 46.5 6.30 100% 93.0% 82.0% 51.0% 19 Comparative Example 4 60/0/28/12 52.0 7.20 100% 93.5% 83.0% 56.0% 22

division Pore distribution ratio 0.1 to 1 탆 1 to 10 μm 10 to 50 μm 50 ㎛ or more Example 1 0.0 4.1 17.6 81.6 Example 2 12.4 29.0 14.0 44.5 Example 3 8.8 21.4 16.3 53.5 Example 4 11.5 23.0 17.5 48.0 Example 5 8.9 8.9 45.2 37.0 Example 6 14.7 17.4 34.5 33.4 Example 7 18.1 25.4 26.4 30.1 Comparative Example 1 6.1 6.7 45.8 41.4 Comparative Example 2 9.9 12.9 37.3 39.9 Comparative Example 3 12.0 18.7 30.6 38.7 Comparative Example 4 2.2 11.0 18.8 68.0

As can be seen from the above Table 2, it was confirmed that the output performance and the lifetime characteristics were significantly improved as compared with Comparative Examples 2 to 4 in Examples 1 to 7.

Specifically, Examples 1 to 7 of the present invention showed improved output characteristics by about 10 to 20% or more as compared with Comparative Examples 2 to 4. Particularly, it can be seen that the output performance and lifetime characteristics of the Example 6 were higher than those of the Comparative Examples 2 to 4.

The results of Examples 6 and 7 in which ketene blacks having different specific surface areas were compared showed that the capacity was decreased in Example 7 using the Ketjen black having a smaller specific surface area than in Example 6, The output characteristics are improved.

On the other hand, when only the fibrous second conductive material is used without using the particulate first conductive material as in Comparative Example 1, the life characteristics and the output characteristics are excellent, but the discharge capacity is significantly reduced to about 7 times of the embodiment Able to know.

Comparing Comparative Examples 3 and 4 in which the results were compared according to the presence or absence of the dispersant under the same conditions, it can be confirmed that the capacity, output, and lifetime characteristics per unit area were improved by the application of the dispersant.

Also, it can be seen from Tables 2 and 3 that 1 to 10 탆 pores are required at a rate of 10 to 25% for capacity expression. In addition, a certain ratio of 10 to 50 탆 pores is required for the output performance, and the value is large in the electrode where the first and second conductive materials are mixed, and it can be confirmed that the ratio is 20 to 50%. In addition, pores of 50 ㎛ or more can be used as an electrolyte and an oxygen passage, but it can be confirmed that when the numerical value is large, it affects the reduction of the energy density.

Experimental Example 3: SEM micrograph

The positive electrodes obtained in Example 1 and Comparative Examples 1 and 2 were confirmed by scanning electron microscope (SEM) photographs. The results are shown in Figs.

Fig. 5 is a SEM photograph of Example 1, wherein the composite conductive material layer of the anode of Example 1 is partially or wholly surrounded by the particulate first conductive material on the fibrous second conductive material, have.

Fig. 6 is an SEM photograph of Comparative Example 1, showing the shape of the fibrous second conductive material. Fig. 7 is a SEM photograph of Comparative Example 2, showing that only the particle-shaped first conductive material is aggregated.

Claims (15)

An electrode substrate; And
And a composite conductive material layer comprising a particulate first conductive material and a fibrous second conductive material on the electrode substrate,
Wherein the composite conductive material layer comprises a plurality of pores. The method according to claim 1,
Wherein the composite conductive material layer partially or entirely surrounds the particulate first conductive material on the fibrous second conductive material, and the internal porosity of the composite conductive material layer is 40 to 80%. The method according to claim 1,
Wherein the fibrous second conductive material has an aspect ratio of 50 to 200. &lt; Desc / Clms Page number 19 &gt; The method according to claim 1,
Wherein the fibrous second conductive material is a carbon fiber having a diameter of 100 to 200 nm and a length of 5 to 25 占 퐉. The method according to claim 1,
The fibrous second conductive material may be at least one selected from the group consisting of polyacrylonitrile carbon fibers, rayon carbon fibers, pitch carbon fibers, vapor grown carbon fibers (VGCF carbon nanotubes), carbon nanotubes (CNT carbon nanotubes) Or a mixture of two or more thereof. The method according to claim 1,
The particulate material is first conductive surface area (BET) of 300 to 1500 ㎡ / g and an average particle diameter (D ₅₀₎ of 30 to 70 nm for the positive electrode of lithium-air battery, characterized in that the particulate conductive recognition. The method according to claim 1,
Wherein the particulate first conductive material is any one selected from the group consisting of Super C, Super P, Ketjen Black, and acetylene black, or a mixture of two or more thereof. The method according to claim 1,
Wherein the weight ratio of the particulate first conductive material to the fibrous second conductive material is 1: 0.5 to 4. Mixing the particulate first conductive material and the dispersing agent and mixing them first;
Adding a fibrous second conductive material and a binder to the first mixture and then secondary mixing; And
And applying the secondary mixture onto an electrode substrate. The method of claim 9,
Wherein the secondary mixing comprises mechanical milling and compounding the particulate first conductive material so as to partially or totally surround the particulate first conductive material on the fibrous second conductive material. The method of claim 10,
Wherein the mechanical milling is selected from a high energy ball mill, a planetary mill, a stirred ball mill, and a vibrating mill method. . The method of claim 9,
Wherein the ratio of the particulate first conductive material to the fibrous second conductive material is from 1: 0.5 to 4. &lt; Desc / Clms Page number 19 &gt; The method of claim 9,
Wherein the ratio of the particulate first conductive material: dispersant is 1: 0.05 to 0.5. Treating the acid-treated particulate first conductive material and the fibrous second conductive material, respectively, with ultrasonic waves to disperse them in deionized water (DI water);
Mixing and stirring the dispersed particulate first conductive material and the fibrous second conductive material;
Filtering the stirred particulate first conductive material and the fibrous second conductive material dispersion followed by drying to form a free-standing composite structure; And
And applying the composite structure onto an electrode substrate. A lithium air battery comprising the anode of claim 1.

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