KR102050832B1 - Positive electrode for lithium air battery, and lithium air battery employing thereof - Google Patents

Abstract

The present invention relates to a positive electrode for a lithium air battery and a lithium air battery including the same, and specifically includes a composite of two kinds of carbon nanotubes different in form as the positive electrode material for the lithium air battery.
According to the present invention, it is possible to provide a lithium air battery having a long life and improved charging and discharging capacity without a cracking phenomenon on the surface of the electrode.

Description

Positive electrode for lithium air battery and lithium air battery comprising same {Positive electrode for lithium air battery, and lithium air battery employing

The present invention relates to a positive electrode for a lithium air battery having a reduced electrode split phenomenon, and a lithium air battery including the same. The present invention also relates to a lithium-air battery having a long cycle life and improved charge and discharge capacity.

Batteries are widely used as a means for supplying power to electric devices. Such batteries include primary batteries that are disposable batteries, rechargeable secondary batteries, and fuel cells that receive an active material from the outside.

Among them, secondary batteries are widely used in various electronic products due to their chargeable characteristics, and examples thereof include nickel cadmium (Ni-Cd) batteries, nickel (Ni-MH) hydrogen batteries, and lithium ion batteries.

In particular, lithium secondary batteries have been widely applied to electric vehicles and power storage devices in addition to home appliances such as mobile phones and laptops due to their high energy density characteristics. However, in order to increase the use time of mobile phones, the mileage of electric vehicles, and the capacity of electric power storage devices, it is necessary to develop a next-generation secondary battery having a higher energy density, and as a solution, a lithium air battery, a lithium-air battery (Lithium) -air battery) has been proposed.

Lithium-air batteries are theoretically nearly 10 times more energy dense than conventional lithium-ion batteries, so they have an efficiency equivalent to gasoline, dramatically reduce the volume and weight of batteries, and are environmentally friendly. There is an advantage that the stability is higher than the ion battery.

In particular, the weight energy density of lithium air batteries is about 500 Wh / kg or more, which is much higher than that of current lithium ion batteries (200 Wh / kg) or the next generation of lithium ion batteries (300 Wh / kg). Many researches are being conducted to utilize the battery as a vehicle, and various attempts have been made to improve the performance of lithium air batteries.

In one aspect of such an attempt, there have been several proposals for the construction and material of positive electrodes (also called positive electrodes, cathodes, or 'air electrodes') in lithium air cells.

As a positive electrode material of a conventional lithium air battery, carbon black is mainly used. Specifically, the carbon black includes ketjen black, super P, and Denka black. Among them, Ketjen black has been studied as a high energy density anode material. However, prior art 'Bull. Korean Chem. Soc. 2010, Vol. 31, No. According to 11 3221 ', ketjen black has a large specific surface area and pore volume, so that the capacity per mass (mAh / g carbon) is large. However, when preparing an electrode slurry from the ketjen black, a large amount of solvent is required. Electrode cracking (mud crack) phenomenon easily occurs after electrode coating and drying. In addition, although ketjen black is a material having a large charge and discharge capacity, there is a disadvantage in that the cycle life is short even when continuous charging and discharging using only a part of the capacity.

In order to solve this problem and provide a material having more improved properties, a number of research results of applying carbon nanotubes as a cathode material of lithium air batteries have been reported recently. However, the preceding document 'Adv. Mater. According to 2013, 25, 1348-1352 ', when the carbon nanotube is applied, the cycle life is better than that of Ketjen black as the cathode material, but the charge and discharge capacity is small.

Such a problem of reducing the charge and discharge capacity narrows the application range of the battery and decreases the usability, which is a major obstacle to practical use.

Therefore, it is necessary to solve the problems of the conventional materials and to further develop a lithium air battery having better performance.

Porous carbon-based composite material, a positive electrode and lithium air battery comprising the same, and a method for manufacturing the same (Korea Patent Publication No. 2013-0084903)

In order to solve the above-mentioned problems, the inventors of the present invention have conducted various studies. As a result, an electrode layer is formed by mixing two kinds of carbon nanotubes having different shapes while using carbon nanotubes as they are. In this case, it was confirmed that the splitting of the positive electrode was reduced and the charge / discharge capacity of the battery was improved, thereby completing the present invention.

Accordingly, it is an object of the present invention to provide a positive electrode for a lithium air battery with reduced electrode splitting.

In addition, another object of the present invention is to provide a lithium air battery having the positive electrode for a lithium air battery, thereby improving the charge, discharge capacity and battery efficiency.

In order to achieve the above object, the present invention

Consisting of a porous current collector and an electrode layer,

The electrode layer provides a cathode for a lithium air battery including a composite of two types of carbon nanotubes having different shapes.

Specifically, the two types of carbon nanotubes may be bundle type and spherical entangled carbon nanotubes.

In addition, the present invention

A positive electrode, a negative electrode, and an electrolyte charged therebetween or impregnated with at least one of them,

The positive electrode provides a lithium air battery which is the positive electrode as described above.

In the lithium air battery positive electrode according to the present invention, the splitting of the electrode is significantly reduced as compared with the case of using carbon black as a conventional positive electrode material.

In addition, the lithium air battery of the present invention having the positive electrode has an effect of increasing the charge and discharge capacity by up to 51% and the battery efficiency by up to 8% compared to the lithium air battery having the positive electrode composed of a single carbon nanotube.

1 is the result of observing the positive electrode surface of the lithium air battery of Example 1, Example 2, and the comparative example 3 of this invention with the optical microscope.
2 is a graph showing the results of measuring charge and discharge capacities and battery efficiency of lithium air batteries of Examples 1, 2, Comparative Examples 1 and 2 of the present invention.

The present invention

Consisting of a porous current collector and an electrode layer,

The electrode layer provides a cathode for a lithium air battery including a composite of two types of carbon nanotubes having different shapes.

In another aspect, the present invention provides a lithium air battery having the positive electrode.

Hereinafter, the configuration of the present invention in more detail. However, the following contents are described only for the most representative embodiments in order to help the understanding of the present invention, and the scope of the present invention is not limited thereto, and the present invention should be understood to cover all ranges equivalent to the following contents.

<Anode for lithium air battery>

1. Porous House

The porous current collector of the present invention can be used without limitation as long as it can be used as a current collector for a conventional lithium air battery. It is common to use a porous current collector through which oxygen easily passes, due to the characteristics of the air cell, and preferably, a porous metal plate or a porous membrane made of a carbon material. However, in the case of using a porous membrane made of carbon material such as carbon paper, it may be easily torn, but may have a higher strength than that of the porous metal.

Porous metal not only plays a role of transporting electrons and diffuses oxygen from inside the cell, but also directly participates in the electrochemical reaction depending on the type of metal, thereby improving the electrochemical performance of the battery and thus manufacturing a high capacity battery. And life cycle of a battery can be improved. In addition, since the process of coating the electrode material on the porous metal is easy, there is also a process advantage in manufacturing the electrode.

As the porous metal, an alloy containing at least one element selected from the group consisting of elements of Groups IA to VA and Groups IB to VIIIB of the periodic table can be used. In particular, the stainless steel in the group may be STS or SUS.

In addition, the porous metal may be used in the form of a metal foil, a metal mesh, or a metal foam. Most preferably, it may be a metal foil, because the metal foil is easy to process pores or holes at regular intervals, and the electrode coating is convenient.

In the case of the metal mesh, the shape of the unit structure constituting the mesh structure is not limited, and shapes of triangles, squares, pentagons, polygons, or trapezoids may be regularly or irregularly repeated.

As the porous current collector of the present invention, the porous metal plate preferably has a pore diameter of 20 nm to 1 mm. If the pore diameter is 20 nm or less, the pores are too small to diffuse oxygen sufficiently, and if the diameter is 1 mm or more, the material may escape into the pores when the material of the positive electrode is coated on the surface of the current collector, resulting in uneven thickness of the electrode.

The porosity of the porous metal plate is characterized in that 20 to 50%.

On the other hand, the thickness of the porous current collector of the present invention is preferably 10 ~ 50um. This is because when the thickness is more than 10um, the pores can be effectively utilized, and the mechanical strength is excellent, and when the thickness is less than 50um, the weight or volume of the current collector can be prevented from becoming too large. The thickness of the porous current collector may be more preferably 15 ~ 30um.

2. Electrode layer

Carbon Nano Tube  Complex

Carbon nanotubes (CNTs) are a type of carbon allotrope that combines carbon atoms in the form of hexagonal honeycomb to form a tube. Carbon nanotubes are excellent electrical and thermal conductors and have a high specific surface area due to nanostructures.

Carbon nanotubes have a graphite sheet rounded to a nanometer diameter, and the graphite sheet has various structures having different characteristics according to the angle and shape of the graphite sheet. It is characterized by consisting of a bundle of carbon nanotubes and spherical entangled carbon nanotubes.

In addition, depending on the number of walls made of graphite, it can be classified into single-walled carbon nanotubes (SWCNT) or multi-walled carbon nanotubes (MWCNT). It also exists as a bundle of carbon nanotube ropes.

The positive electrode for a lithium air battery of the present invention is characterized by including two types of carbon nanotubes of different forms. Specifically, the two types of carbon nanotubes may be bundle type and spherical entangled carbon nanotubes, which are referred to herein as 'carbon nanotube composites'.

In the case of manufacturing the electrode only with the bundled carbon nanotubes, the bundled carbon nanotubes are closely stacked, so that it is difficult to sufficiently increase the electrode porosity, and thus there is a limitation in manufacturing a high capacity lithium air battery. On the other hand, when the electrode is manufactured only with the spherical aggregated carbon nanotubes, there are large pores between the aggregated carbon nanotubes, which are not effective for realizing the capacity of a lithium-air battery.

In particular, the meaning of 'composite' in the 'carbon nanotube composite' should be interpreted to include all forms in which two carbon nanotubes can be mixed, for example, a simple mixed form in a regular or irregular arrangement. It may include an inter-composite form and / or chemically-combined mutual compound form in which one carbon nanotube forms a kind of unit structure such as a form surrounding the carbon nanotube as a core. .

On the other hand, the two kinds of carbon nanotubes may be in the form of any one of single-wall, double-walled or multi-walled carbon nanotubes, respectively. In particular, in the form of multi-walled carbon nanotubes, there is an advantage that mass production is possible at a lower price than single-walled carbon nanotubes.

Two types of carbon nanotubes constituting the carbon nanotube composite are preferably included in a weight ratio of 1:10 to 10: 1, more preferably 1: 3 to 3: 1.

In addition, the carbon nanotube composite may be composed of 60 to 95% by weight relative to the total weight of the electrode layer.

As described above, the positive electrode for a lithium air battery composed of a carbon nanotube composite has no or significantly reduced electrode splitting as compared to a positive electrode composed of a conventional carbon black material, and also has a charge, discharge capacity, and battery of a lithium air battery including the same. The efficiency can be improved effectively.

bookbinder

The binder is a material that is commonly added in the manufacture of the electrode layer in order to aggregate electrode materials such as carbon nanotubes and form the electrode layer in a sheet form.

Binders that can be used in the present invention include all conventional binders known to be used in lithium air batteries, preferably polyvinyl alcohol, poly (vinylacetate), polyethylene oxide, polyvinyl pyrrolidone, alkyl Rated polyethylene oxide, crosslinked polyethylene oxide, polyethylene, polypropylene, styrene-butadiene rubber, polyvinyl ether, poly (methyl methacrylate), poly (ethyl acrylate), polyvinylidene fluoride (PVDF), polytetra Fluoro ethylene (PTFE), polychlorotrifluoroethylene, poly tetrafluoroethylenepolyvinylchloride, polyacrylonitrile, polyvinylpyridine, polystyrene, tetrafluoroethylene-perfluoroalkylvinylether copolymer, polyvinyl fluoride Liden-hexafluoropropylene copolymer (trade name: Kynar), vinylidene fluoride Chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer, propylene-tetrafluoroethylene copolymer, vinylidene fluoride-pentafluoro propylene copolymer, ethylene-chlorotrifluoroethylene copolymer, vinylidene fluoride Hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethylvinylether-tetrafluoroethylene copolymer, ethylene-acrylic acid copolymer, Nafion (Dupont, Nafion) One or more substances selected from the group or derivatives thereof can be used.

More preferably, at least one of polyvinylidene fluoride (PVDF), polytetrafluoro ethylene (PTFE), and Nafion may be used.

The binder is preferably included 5 to 40% by weight based on the total weight of the electrode layer. If the content of the binder is less than 5% by weight, the physical properties of the positive electrode may be degraded, so that the active material in the electrode may be dropped or the electrode material such as carbon nanotubes may be difficult to aggregate. As a result, the charging and discharging effects may also be reduced.

In addition to the structure of the binder and the carbon nanotube composite described above, the electrode layer of the present invention may optionally further include an oxygen reduction catalyst.

Specifically, the oxygen reduction catalyst may be added to promote the reaction of oxygen used as the active material in the positive electrode. The oxygen reduction catalyst is not limited to any particular kind, but may be selected from one or more selected from the group consisting of noble metals, nonmetals, metal oxides and organometallic complexes.

More specifically, the precious metal may be one or two or more selected from the group consisting of platinum (Pt), gold (Au) and silver (Ag), and the nonmetal may be boron (B), nitrogen (N) and sulfur (S). It may be one or more selected from the group consisting of. In addition, the metal oxide may be at least one oxide selected from the group consisting of manganese (Mn), nickel (Ni), cobalt (Co), and ruthenium (Ru), such as ruthenium oxide. The organometallic complex may be at least one selected from the group consisting of metal porphyrins and metal phthalocyanines.

The content of the oxygen reduction catalyst may be 0.1 to 10% by weight relative to the total weight of the electrode layer. If it is 0.1 wt% or more, it is preferable to play the role of a catalyst, and if it is 10 wt% or less, it is possible to prevent the phenomenon that the dispersibility is lowered and is preferable in terms of cost.

The total thickness of the electrode layer including the above-described configuration is preferably in the range of 10 ~ 300um, more preferably 20 ~ 200um. This is because it is possible to prevent the electrochemical reaction site from decreasing too much and the capacity of the electrode layer at a thickness of 10 μm or more, and to prevent the efficiency of the electrode reaction site from falling below 300 μm.

<Lithium air battery>

On the other hand, the present invention

Comprising a positive electrode, a negative electrode and an electrolyte charged therebetween or impregnated in any one or more, the positive electrode provides a lithium air battery which is the positive electrode as described above.

The lithium air battery of the present invention has the effect of improving the charge, discharge capacity and battery efficiency compared to the case of using the same type of carbon nanotubes of the same shape as the cathode material. Specifically, as can be seen in Test Example 2 described later, the discharge capacity is improved by up to 51% and the battery efficiency by up to 8%.

The lithium air battery of the present invention will be described in more detail.

The negative electrode is a site capable of occluding and releasing lithium (Li), which releases lithium ions at discharge and receives lithium ions at charge, and the positive electrode reduces oxygen at discharge and releases oxygen at charge. .

The negative electrode active material may include one selected from the group consisting of lithium metal and an alloy based on lithium metal.

Specifically, the lithium metal-based alloy is, for example, lithium and sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), beryllium (Be), magnesium (Mg), calcium It may be an alloy of one or more metals selected from the group consisting of (Ca), strontium (Sr), barium (Ba), radium (Ra), aluminum (Al), and tin (Sn).

In addition, the negative electrode may further include a current collector. The material of the negative electrode current collector may be any material that is capable of performing current collecting of the negative electrode and which is electrochemically stable under battery operating conditions. Specifically, one or more selected from the group consisting of copper, carbon, stainless, nickel, aluminum, iron, and titanium can be used, and more specifically, a copper current collector on which lithium is deposited can be used.

The negative electrode current collector may be in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, or a nonwoven fabric.

On the other hand, the electrolyte constituting the lithium-air battery of the present invention is generally provided between the negative electrode and the positive electrode, but due to the nature of the non-solid liquid, part or all of the electrolyte is present in the form impregnated in the positive electrode and / or negative electrode structure It is also possible. In addition, when the separator is present, it may be present in the form impregnated with the separator.

The electrolyte may comprise a lithium salt. The lithium salt may be dissolved in a solvent to act as a source of lithium ions in the battery and to promote the movement of lithium ions between the negative electrode, the lithium ions, and the conductive solid electrolyte membrane.

Examples of the lithium salt include LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiN (SO ₂ C ₂ F ₅ ) ₂ , Li (CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , LiClO ₄ , LiAlO ₂ , LiAlCl ₄ , LiF, LiBr, LiCl, LiI, LiB (C ₂ O ₄ ) ₂ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ (LiTFSI), LiN (SO ₂ C ₂ F ₅ ) ₂ and LiC One or more types selected from the group consisting of (SO ₂ CF ₃ ) ₃ can be used. The concentration of the lithium salt can be in the range of 0.1 ~ 1.5 M, within this range the electrolyte has an appropriate conductivity and viscosity can exhibit excellent electrolyte performance and lithium ions can move effectively.

Meanwhile, the electrolyte may be classified into an aqueous electrolyte or a non-aqueous electrolyte according to the type of solvent. Specifically, the aqueous electrolyte may be in the form containing the lithium salt in water, the non-aqueous electrolyte may be in the form containing the lithium salt in an organic solvent.

The organic solvent of the non-aqueous electrolyte is one selected from the group consisting of carbonates, esters, ethers, ketones, organosulfurs, organophosphorouss, aprotic solvents, and combinations thereof. More specifically, the non-aqueous organic solvent may include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and dipropyl carbonate. (DPC), dibutyl carbonate (DBC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), fluoroethylene carbonate (FEC), dibutyl ether, tetraglyme, diglyme , Dimethoxyethane, tetrahydrofuran, 2-methyl tetrahydrofuran, 1,3-dioxolane (1,3-dioxolane), 1,4-dioxane, 1,2-dimethoxyethane, 1,2-die Methoxyethane, 1,2-dibutoxyethane, Cetonitrile, dimethylformamide, methyl formate, ethyl formate, propyl formate, butyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, Butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, γ-butyrolactone, 2-methyl-γ-butyrolactone, 3-methyl-γ-butyrolactone, 4-methyl-γ-buty Rolactone, β-propiolactone, δ-valerolactone, trimethyl phosphate, triethyl phosphate, tris (2-chloroethyl) phosphate, tris (2,2,2-trifluoroethyl) phosphate, tripropyl phosphate, Triethylene glycol dimethyl ether (TEGDME), triisopropylphosphate, tributyl phosphate, trihexyl phosphate, triphenyl phosphate, tri Tolyl phosphate (tritolylphosphate), polyethylene glycol may be used dimethyl ether (PEGDME), and one or more selected from the group consisting of.

The non-aqueous organic solvent may further include other metal salts in addition to lithium salts. For example AlCl ₃ , MgCl ₂ , NaCl, KCl, NaBr, KBr or CaCl ₂ , LIi, NaI, KI and the like.

The lithium air battery of the present invention may further include a separator provided between the positive electrode and the negative electrode. As the separator, any one may be used without limitation as long as it separates or insulates both electrodes from each other and blocks only other materials while passing only lithium ions. For example, it may be made of a porous, nonconductive or insulating material. More specifically, for example, a polymer nonwoven fabric such as a nonwoven fabric of polypropylene or a nonwoven fabric of polyphenylene sulfide, a porous film of an olefin resin such as polyethylene or polypropylene may be used. It is also possible to use these 2 or more types together.

The separation form of the separator may be an independent member such as a film, or may be a coating layer added to the anode and / or the cathode. In addition, the separator may serve as a support for the electrolyte by impregnating the electrolyte.

The shape of the lithium air battery of the present invention including the above configuration is not limited and may be variously manufactured according to the use, for example, may be coin type, flat plate type, cylindrical type, horn type, button type, sheet type, or stacked type.

In addition, the lithium air battery of the present invention can be used as a battery module including it as a unit cell. The battery module may be formed by stacking by inserting a bipolar plate between lithium air batteries.

Lithium-air battery of the present invention is a battery without the electrode split, the charging and discharging capacity and battery efficiency is improved, the battery module including the same specifically for electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles or power storage It can be used for power supply of the device.

Hereinafter, Comparative Examples 1 and 2, Examples 1 and 2, and test examples using the same will be described to help the understanding of the present invention. However, the following Comparative Examples, Examples and Test Examples are only one aspect of the configuration and effects of the present invention, so the scope of the present invention is not limited thereto.

< Example  And Comparative example >

The positive electrode of Examples 1 and 2 was prepared by varying the combination ratio of the two carbon nanotubes constituting the positive electrode of the lithium air battery according to the present invention.

Example  One

Carbon nanotube composites and PVDF binders having a combination ratio of 3: 1 to bundle carbon nanotubes and spherical agglomerated carbon nanotubes are mixed at a weight ratio of 80:20, and NMP is mixed with 1300 weight% of solids. Slurry was prepared. Carbon paper (Toray TGP-H-030) was used as the positive electrode current collector, and the electrode slurry was coated on a carbon paper with a doctor blade, followed by vacuum drying at 120 ° C. for 12 hours to prepare a positive electrode. Electrode loading was adjusted to about 0.5 mg / cm ² based on carbon nanotubes (CNT) carbon. The dried anode was processed into a 19 mm diameter circular electrode was used for cell assembly. The electrolyte was prepared using 1M LiTFS1 lithium salt and TEGDME solvent, and the negative electrode was used by processing a 150 mm thick lithium foil into a 15 mm diameter circular electrode. As the separator of the positive electrode and the negative electrode, a coin cell having a diameter of 20 mm and a thickness of 3.2 mm was assembled using a glass fiber (glass fiber: Whatman GF / C) having a diameter of 420 μm.

Example  2

A cell was assembled in the same manner as in Example 1, with a combination ratio of carbon nanotubes in the form of bundles and carbon nanotubes in the form of spherical agglomerations constituting the carbon nanotube composite as the cathode material.

For comparison with the above embodiment, a cell having a positive electrode composed of one kind of carbon nanotubes (Comparative Example 1 and Comparative Example 2) or carbon black (Comparative Example 3) of the same type as a conventional lithium air battery was manufactured. It was.

Comparative example  One

A cell was manufactured in the same manner as in Example 1, using carbon nanotubes in a bundle form as a cathode material.

Comparative example  2

Cells were prepared in the same manner as in Example 1 using spherical entangled carbon nanotubes as the cathode material.

Comparative example  3

A cell was prepared in the same manner as in Example 1 using Ketjen black EC600JD as a cathode material.

< Test Example  1>-Observe the splitting of the electrode

The surface of the positive electrode of the lithium air batteries of Examples 1 and 2 including the composite of two carbon nanotubes of the present invention as the positive electrode material was compared with the case of Comparative Example 3 using the conventional carbon black as the positive electrode material. Observed. The observations are shown in FIG. 1.

Referring to FIG. 1, while the cracks are large and distinctly observed on the anode surface of Comparative Example 3, the cracks are completely removed in Example 1, and in Example 2, the cracks are significantly reduced and hardly occur.

< Test Example  2>-Charge and discharge capacity and efficiency measurement of lithium air battery

Charge and discharge capacity and battery efficiency were measured using the lithium air battery of Examples 1-2 and Comparative Examples 1-2.

How to measure discharge capacity

Potentiostat (Potentiostat, bio-Logic, VMP3) was conducted using the discharge experiment of the battery. 100 mA / g current density was added to the electrode weight of Example 1, which is made of two kinds of carbon nanotube composites, and discharged by a voltage cut-off method. The lower limit voltage was set to 2.0 V. Examples 1 to 2 And electrochemical experiments of the coin cells prepared in Comparative Examples 1 and 2. Pure oxygen was charged to 1.5 atm in a sealed space in the prepared cell, and the measurement was started after sufficient wet time for 5 hours to sufficiently infiltrate the electrode and the separator.

How to measure charge capacity

The cell prepared for the measurement of the discharge capacity was 100 mA / with respect to the electrode weight after completing the discharge experiment of the battery using a potentiostat (Potentiostat, bio-Logic, VMP3) without changing the state as it was discharged. The current density of g was charged and charged by the voltage cut-off method, and the upper limit voltage was set to 4.6 V to conduct an electrochemical experiment of the coin cells prepared in Examples 1 and 2 and Comparative Examples 1 and 2.

Battery efficiency calculation

 Battery efficiency (%) = (charge capacity / discharge capacity) X 100

The measurement results are shown in FIG. 2 and Table 1 below.

Comparative example  One Comparative example  2 Example  One Example  2 Discharge Capacity (A) ( mAh / g) 2397 2072 2885 2901 Charge capacity (B) ( mAh / g) 2233 1875 2835 2847 Efficiency (B / A) ( % ) 93.1 90.5 98.3 98.1

As a result of the measurement, in contrast to the lithium air batteries of Comparative Examples 1 and 2 each having an electrode containing a single type of carbon nanotube as a positive electrode, an example having two types of composite carbon nanotube electrodes having different types as the positive electrode It can be seen that the charge and discharge capacities in the lithium air batteries of 1 and 2 were remarkably improved by 27 to 51%.

In addition, it can be seen that the lithium air batteries of Examples 1 and 2 exhibited 5 to 8% improved efficiency in comparison with the case of Comparative Examples 1 and 2 in battery efficiency.

The positive electrode for a lithium air battery of the present invention and a lithium air battery having the same have a long cycle life and have improved charging and discharging capacities, and thus can be conveniently used for various electric and electronic products.

Claims (9)

Consisting of a porous current collector and an electrode layer,
The electrode layer includes bundle carbon nanotubes and spherical entangled carbon nanotubes.
The bundled carbon nanotubes and spherical entangled carbon nanotubes are included in a weight ratio of 1: 3 to 3: 1.
delete The method of claim 1,
The bundle type carbon nanotubes and the spherical entangled carbon nanotubes are a simple mixed type positive electrode for a lithium air battery.
The method of claim 1,
The bundle type carbon nanotubes and the spherical entangled carbon nanotubes are a composite of a lithium air battery, characterized in that the composite form.
The method of claim 1,
The bundle carbon nanotubes and the spherical entangled carbon nanotubes are mutually combined form, the positive electrode for a lithium air battery.
The method of claim 1,
The bundle type carbon nanotubes and the spherical entangled carbon nanotubes are single-walled, double-walled, or multi-walled carbon nanotubes, respectively.
delete The method of claim 1,
The composite of the bundle carbon nanotubes and the spherical entangled carbon nanotubes is 60 to 95% by weight relative to the total weight of the electrode layer, characterized in that the lithium air battery positive electrode.
A positive electrode, a negative electrode, and an electrolyte charged therebetween or impregnated with one or more poles,
The positive electrode is a lithium air battery is a positive electrode for a lithium air battery of any one of claims 1, 3 to 6 and 8.

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