KR20140039755A - Mixed oxide catalyst, cathode for lithium air battery and lithium air battery including the same - Google Patents

Abstract

The present invention relates to; a composite oxide catalyst for a cathode of a lithium air battery, which serves the function of a buffer for oxygen in the cathode in order for stable maintenance of the battery′s charged level; a cathode of a lithium air battery including the same; and a lithium air battery. The composite oxide catalyst for a cathode for a lithium air battery comprises a supporter and a catalyst material dipped in the supporter. The supporter is one selected or a mixture consiting of at least two selected from Ce-Al oxide, Ce-Zr oxide and Al-Zr oxide. The catalyst materials is at least one or a mixture consisting of at least two selected from silver (Ag) oxide, copper (Cu) oxide, platinum (Pt) oxide, palladium (Pd) oxide, rhodium (Rh) oxide, manganese (Mn) oxide, iron (Fe) oxide and perovoskite. The composite oxide catalyst for a cathode of a lithium air battery is characterized by comprising at least one among the perovoskite and ceria. [Reference numerals] (AA) Supporter; (BB) Catalyst; (CC) Composite oxide catalyst using the supporter; (DD) Composite oxide catalyst by mechanical mixture

Description

Mixed oxide catalyst, cathode for lithium air battery and lithium air battery including the same}

The present invention relates to a composite oxide catalyst for a lithium air battery positive electrode, and more particularly, to a composite oxide catalyst for a lithium air battery positive electrode for maintaining a stable discharge state of a battery by performing a buffer function of oxygen in the positive electrode, including the same. A positive electrode for lithium air batteries and a lithium air battery.

In general, a lithium air battery is a battery having a cathode using oxygen in air as an active material, and the battery is charged and discharged by performing a redox reaction of oxygen at the cathode.

Conventional lithium ion batteries can meet the energy storage requirements of plug-in hybrid electric vehicles (PHEVs) used for short-distance travel, but electric vehicles (EVs) used for long- There is a demand for a system capable of storing more energy, which is difficult to satisfy the storage requirement.

Among the known energy storage systems, lithium air battery systems have a relatively high theoretical capacity.

In the lithium air battery, during discharge, lithium cations emitted from lithium metal at the anode move to the anode through the electrolyte and are reacted with lithium oxide (Li ₂ O or Li ₂ O ₂ through an oxidation reaction with oxygen supplied from the atmosphere at the cathode). ) Electrons move through the electrical circuit from cathode to anode.

[Reaction Scheme 1]

As can be seen in the reaction scheme 1, when the lithium air battery is applied as an energy storage means of a vehicle, a constant oxygen supply acts as an important factor.

However, it is very difficult to maintain a constant amount of oxygen supplied to a lithium air battery while driving a vehicle. In particular, there is a problem in that the discharge of the battery also becomes incapable when a momentary oxygen supply failure occurs.

The present invention was devised to improve the above-mentioned point, and when oxygen used as the positive electrode active material is supplied in excess, oxygen is absorbed and stored, and when oxygen is insufficient, oxygen supply in the positive electrode is kept constant. An object of the present invention is to provide a composite oxide catalyst for a lithium air battery and a cathode for a lithium air battery including the same.

In addition, the present invention adopts a positive electrode including the composite oxide catalyst to reduce the vibration of the oxygen supply in the positive electrode and to maintain a constant discharge state of the lithium battery by maintaining a constant oxygen supply used for the oxidation reaction The purpose is to provide.

In order to achieve the above object, the present invention is composed of a support material and a catalyst material supported on the support, wherein the support is selected from Ce-Al oxide, Ce-Zr oxide, Al-Zr oxide is used or 2 A mixture of two or more species is used, and the catalyst material is silver (Ag) oxide, copper (Cu) oxide, platinum (Pt) oxide, palladium (Pd) oxide, rhodium (Rh) oxide, manganese (Mn) oxide, iron (Fe) oxide, and a mixture of one or two or more selected from perovskite is used, and the composite oxide for lithium air battery positive electrode, characterized in that it contains at least one of the perovskite and ceria. To provide a catalyst.

In addition, the present invention comprises a first oxide and a second oxide which are physically mixed with each other, wherein the first oxide is selected from CeO ₂ , Ce-Al oxide, Ce-Zr oxide, Al-Zr oxide A mixture of two or more species is used, and the second oxide may be silver (Ag) oxide, copper (Cu) oxide, platinum (Pt) oxide, palladium (Pd) oxide, rhodium (Rh) oxide, manganese (Mn) oxide, Iron (Fe) oxide, and a mixture of one or two or more selected from the perovskite is used, a composite for lithium air battery positive electrode comprising at least one of the perovskite and ceria It provides an oxide catalyst.

In addition, the present invention includes a catalyst supported on a conductive material as a redox catalyst of oxygen as a cathode active material, and the catalyst provides a cathode for a lithium air battery, wherein the composite oxide catalyst is employed.

In addition, the present invention includes a negative electrode capable of occluding and releasing lithium ions, a positive electrode having oxygen as a positive electrode active material, and an electrolyte interposed between the positive electrode and the negative electrode, wherein the positive electrode for a lithium air battery is employed as the positive electrode. Provided is a lithium air battery.

The lithium air battery containing the composite oxide catalyst according to the present invention positively absorbs and stores oxygen when the oxygen is supplied in the positive electrode and releases the stored oxygen when the oxygen is insufficient. It is possible to maintain a constant supply of oxygen used in the oxidation reaction by including in the inside, thereby reducing the fluctuation of the oxygen supply and a constant supply of oxygen to maintain a stable discharge state of the battery, thereby high charge and discharge capacity By implementing this it is possible to obtain the effect of improving the performance of the battery.

1 is a schematic diagram showing a composite oxide catalyst for a lithium air battery according to the present invention,
2 is a view showing a unit grid of the Perovskite structure (Perovskite structure),
3 is a view showing a coin cell evaluation condition of Evaluation Example 1 for illustrating the effect of the present invention,
4 is a graph showing a comparison of output voltage over time of a lithium air battery coin cell according to Comparative Example 1 manufactured using a lithium air battery coin cell and a conventional oxygen redox catalyst according to Example 1 of the present invention;
5 is a graph showing a comparison between the output voltage over time of the lithium air battery coin cell according to Example 2 of the present invention and the lithium air battery coin cell according to Comparative Example 1.

Hereinafter, the present invention will be described so that the present invention can be easily implemented by those skilled in the art.

The present invention relates to a composite oxide catalyst of a cathode for a lithium air battery, to maintain a constant supply of oxygen supplied as an active material of the cathode (cathode) to maintain a stable discharge state of the battery and to improve battery performance.

Accordingly, the present invention provides a cathode for a lithium air battery using a composite oxide catalyst containing an oxide such as perovskite or ceria (cerium oxide) as a catalyst contained in the cathode, and a lithium air battery employing the same.

The composite oxide catalyst includes at least one of perovskite and ceria to absorb and store oxygen when oxygen is excessively supplied to a lithium air battery and to buffer oxygen to release stored oxygen when oxygen is insufficient. It is possible to maintain a constant oxygen supply used for the oxidation reaction in the anode.

As shown in FIG. 1, the composite oxide catalyst for lithium air battery according to the present invention may be prepared using a support or may be prepared through physical mixing.

First, when prepared using a support, the composite oxide catalyst is composed of a support and a catalyst material supported on the support, the mass ratio of the catalyst material and the support may be 1: 1 ~ 200 (support: catalyst material = 1 to 200: 1).

As the support, one or more oxides selected from Ce-Al oxide, Ce-Zr oxide, and Al-Zr oxide may be used, and the catalyst material may be silver (Ag) oxide, copper (Cu) oxide, or platinum (Pt) oxide. At least one oxide selected from among palladium (Pd) oxide, rhodium (Rh) oxide, manganese (Mn) oxide, iron (Fe) oxide, and perovskite may be used.

When manufactured through physical mixing, the composite oxide catalyst is composed of a first oxide and a second oxide that are physically mixed with each other without a support, and the mass ratio of the first oxide and the second oxide is 1: 0.1 to 200 days (First oxide: second oxide = 1: 0.1 to 200).

As the first oxide, one or more oxides selected from CeO ₂ , Ce-Al oxide, Ce-Zr oxide, and Al-Zr oxide may be used, and the second oxide may be silver (Ag) oxide or copper (Cu) oxide. At least one oxide selected from among platinum (Pt) oxide, palladium (Pd) oxide, rhodium (Rh) oxide, manganese (Mn) oxide, iron (Fe) oxide, and perovskite may be used.

The composite oxide catalyst contains at least one of ceria and perovskite so as to reduce the supply vibration of oxygen supplied to the cathode when applied to a lithium air battery and to maintain a constant supply of oxygen used for the oxidation reaction. In addition, it is possible to improve the performance of the battery through the various mixing of the components.

2 shows a unit grid of a Perovskite structure.

Perovskite is a metal oxide having an ABO ₃ crystal structure as shown in FIG. 2, and a component element (hereinafter, referred to as a "substituted component") partially substituted with lanthanum (La) and lanthanum may be applied to the A position of FIG. 2. 2, manganese, iron, chromium, or the like may be applied to the B position of FIG. 2, and potassium (K), strontium (Sr), or the like may be used as the substitution component. At this time, the ratio of the lanthanum and the substituted component may be 1: 0.01 to 1.5 (lanthanum: substituted component = 1: 0.01 ~ 1.5).

Such perovskite can show various physical properties by applying various component elements in A and B positions. The partial permutation of the component A positions facilitates the absorption and release of lattice oxygen, making it highly reactive and Oxidation and reducing properties can be improved.

가 생성되는데, 이때 불안정한 Co^{4 +}는 격자산소가 이탈하면서 안정한 Co^{3 +}로 바뀌게 되고, 그 결과 산소의 결합이 발생되며, 그 결합에 의해 산소의 확산이 용이해지므로 산소 확산계수가 증가하게 되고, 결국 촉매의 산화력 및 환원력이 상승되어진다.For example, if the perovskite La partially substituted by Sr ^{2 + 3 + 4 +} Co in the tree while the animation

In this case, unstable Co ^{4 +} is transformed into stable Co ^{3 +} as the lattice oxygen is released, and as a result, oxygen bonds are generated, and the diffusion of oxygen is facilitated by the bonds, thereby increasing the oxygen diffusion coefficient. As a result, the oxidizing and reducing power of the catalyst are increased.

On the other hand, a lithium air battery is generally known as a structure having a negative electrode capable of storing and releasing lithium ions, a positive electrode using oxygen in the air as a positive electrode active material, and an electrolyte interposed between the positive electrode and the negative electrode.

The positive electrode and the negative electrode of the lithium air battery each include a current collector, a conductive material, and a binder. In the case of the positive electrode, a catalyst having a conductive material as a carrier may be added.

In the positive electrode for a lithium air battery according to the present invention, oxygen is used as a positive electrode active material in air, and a complex oxide catalyst as described above is contained as a redox catalyst of oxygen supported on a conductive material (for example, a carbon-based material), The mass ratio of the conductive material and the composite oxide catalyst may be 1: 0 to 2 (conductive material: composite oxide catalyst = 1: 0 to 2).

As the conductive material, carbon-based materials such as graphite-based, carbon nanotube (CNT) -based, and carbon black-based materials such as Ketjen Black, Denka Black, Super C, and Super S may be used.

Hereinafter, examples and comparative examples are provided to help the understanding of the present invention, but the following examples are only for illustrating the present invention, and the present invention is not limited thereto.

Example  One

Support Ce _{0 .6} Zr _{0 .4} O ₂ after producing the composite oxide catalyst by supporting a catalytic substance on the MnO _2, the conductive material carrying the mixed oxide catalyst KB (Ketjen Black) 90wt% to 10wt% binder Kynar2801 mixed with Then, the mixture was coated on nickel foam, which is a positive electrode current collector, and a lithium air battery positive electrode was manufactured by a wet manufacturing method which was dried at 120 ° C. for 12 hours. The mass ratio of the KB and the complex oxide catalyst _{KB: MnO 2 / Ce 0 .6} Zr 0 .4 O 2 = 40: was set to 8/32.

A lithium air battery coin cell was manufactured by using a lithium metal thin film as a negative electrode and using 150 μl of a PC (polycarbonate) electrolyte as an electrolyte disposed between the prepared positive and negative electrodes.

Example  2

First oxide Ce _{0 .5} Zr _{0 .5} O ₂ and the second a mixture of oxide compound oxide MnO ₂ after preparing the catalyst, a mixed oxide catalyst supported by the conductive material, 90wt% of a binder KB Kynar2801 10wt% with a mixed Next, the mixture was coated on nickel foam, which is a positive electrode current collector, and a lithium air battery positive electrode was manufactured by a wet manufacturing method of drying at 120 ° C. for 12 hours. The mass ratio of the KB and the complex oxide catalyst KB: was set to _{1: MnO 2: Ce 0 .5} Zr 0 .5 O 2 = 2: 1.

A lithium air battery coin cell was manufactured using a lithium metal thin film as a negative electrode and 150 μl of a PC electrolyte as an electrolyte disposed between the prepared positive and negative electrodes.

Comparative Example  One

90 wt% of a cathode conductive material KB carrying MnO ₂ , a redox catalyst of oxygen, was mixed with 10 wt% of a binder Kynar2801, and then the mixture was coated on a nickel foam, which is a cathode current collector, and dried at 120 ° C. for 12 hours. A positive electrode for a lithium air battery was prepared. At this time, the mass ratio of KB and MnO ₂ was 1: 1.

A lithium air battery coin cell was manufactured using a lithium metal thin film as a negative electrode and 150 μl of a PC electrolyte as an electrolyte disposed between the prepared positive and negative electrodes.

Evaluation example  One

To evaluate the electrochemical characteristics of the lithium air battery coin cell by performing an evaluation in the air, an argon (Ar) atmosphere, and the evaluation in the air for 6 hours each for 18 hours as shown in FIG. 3, the current amount is 100 mA / As the g-carbon, voltages of the lithium air battery coin cells according to Examples 1 and 2 and Comparative Example 1 were measured and evaluated, respectively, and the results are shown in FIGS. 4 and 5.

4 is a graph showing a comparison of output voltage over time of a lithium air battery coin cell according to Comparative Example 1 manufactured using a lithium air battery coin cell and a conventional oxygen redox catalyst according to Example 1 of the present invention. 5 is a graph illustrating output voltages of a lithium air battery coin cell according to Example 2 and a lithium air battery coin cell according to Comparative Example 1 in comparison with time.

Lithium-air battery of Fig. 4, Example 1, as shown in coin cell was evaluated, but this evaluation after the oxygen supply in an atmosphere of argon in the air support including ceria _{(Ce 0 .6 Zr 0 .4 O} 2) is evaluated in the air When the oxygen was absorbed and stored, the discharge state was maintained for a longer time compared to the coin cell of Comparative Example 1, and when oxygen was supplied again in the atmospheric evaluation after the evaluation in argon atmosphere (after 12 hours). It was confirmed that the voltage recovery ability is also relatively superior to the coin cell of Comparative Example 1.

And, Figure 5 As shown in Example 2, the lithium air battery is also of a coin cell (after 6 hours) after the evaluation of the atmosphere Ce _{0 .5} Although there is no evaluation of the oxygen supply in an argon atmosphere containing ceria Zr _{0 .5} O containing ₂ and that the coin cell was discharged state compared to the Comparative example 1 by the use of the oxygen stored by absorption at the time of the evaluation in the atmosphere to determine the retained for a longer time, and the first oxide (Ce _{0 .5} Zr _{0. By using} a mixture of ₅ O ₂ ) and the second oxide (MnO ₂ ) it was confirmed that the more effective in the recovery and maintenance of voltage compared to the coin cell of Comparative Example 1 using only a single catalyst (MnO ₂ ).

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the scope of the present invention is not limited to the disclosed exemplary embodiments. Modified forms are also included within the scope of the present invention.

Claims (8)

It is composed of a support material and a catalyst material supported on the support, and the support material is one selected from Ce-Al oxide, Ce-Zr oxide, Al-Zr oxide, or a mixture of two or more thereof is used, the catalyst material Furnaces include silver (Ag) oxide, copper (Cu) oxide, platinum (Pt) oxide, palladium (Pd) oxide, rhodium (Rh) oxide, manganese (Mn) oxide, iron (Fe) oxide, and perovskite. A mixture of one or more selected ones is used, and the composite oxide catalyst for a cathode of a lithium air battery, characterized in that it contains at least one of the perovskite and ceria.
The method according to claim 1,
The mass ratio of the catalyst material and the support is a composite oxide catalyst for a cathode of a lithium air battery, characterized in that 1: 1 to 200.
It consists of a first oxide and a second oxide that are physically mixed with each other, the first oxide is CeO ₂ , Ce-Al oxide, Ce-Zr oxide, Al-Zr oxide selected from the group consisting of one or two or more As the second oxide, silver (Ag) oxide, copper (Cu) oxide, platinum (Pt) oxide, palladium (Pd) oxide, rhodium (Rh) oxide, manganese (Mn) oxide, iron (Fe) oxide And a mixture of one or two or more selected from perovskite is used, and the composite oxide catalyst for a cathode of a lithium air battery, characterized in that it contains at least one of the perovskite and ceria.
The method of claim 3,
The mass ratio of the first oxide and the second oxide is 1: 0.1 ~ 200 composite oxide catalyst for a cathode of a lithium air battery, characterized in that.
A catalyst for carrying a conductive material as a redox catalyst of oxygen, which is a positive electrode active material, wherein the composite oxide catalyst according to any one of claims 1 to 4 is adopted.
The method of claim 5,
A mass ratio of the conductive material and the composite oxide catalyst is 1: 0 to 2, characterized in that the lithium air battery positive electrode.
The method of claim 5,
The cathode material for a lithium air battery, characterized in that a mixture of one or two or more selected from graphite-based, carbon nanotube-based, and carbon black-based carbon-based materials is used.
A negative electrode capable of occluding and releasing lithium ions, a positive electrode having oxygen as a positive electrode active material, and an electrolyte interposed between the positive electrode and the negative electrode,
Lithium air battery, characterized in that the positive electrode for the lithium air battery of any one of claims 5 to 7 adopted as the positive electrode.

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