WO2013086753A1

WO2013086753A1 - Cathode used for metal-air cell, and preparation method therefor

Info

Publication number: WO2013086753A1
Application number: PCT/CN2011/084484
Authority: WO
Inventors: 孙公权; 王二东; 舒朝著; 王素力; 谷顺学
Original assignee: 中国科学院大连化学物理研究所
Priority date: 2011-12-15
Filing date: 2011-12-22
Publication date: 2013-06-20
Also published as: CN103165902B; CN103165902A

Abstract

The present invention relates to a cathode used for a metal-air cell, comprising a catalyst layer, a hydrophobic diffusion layer, and a flow collection layer. The catalyst layer uses a carbon contained manganese oxide as a catalyst and PTFE as a hydrophobic agent. The hydrophobic diffusion layer is a graphitized carbon fiber mat that is hydrophobized by using PTFE emulsion. The flow collection layer is nickel foam. Compared with the prior art, in the present invention, the carbon fiber mat hydrophobized by using PTFE is used as a substrate of the catalyst layer, thereby reducing the leakage of an electrolyte solution and alleviating corrosion of the electrolyte solution to a nickel foam flow collection net; the catalyst layer size is coated on the surface of the hydrophobic diffusion layer, thereby facilitating the improvement of the efficiency of the catalyst and the great improvement of the battery performance and stability; and meanwhile, the method makes preparation easy and is applicable to mass production.

Description

Cathode for metal air battery and preparation method thereof

The invention relates to a cathode for a metal air battery, in particular to a cathode for a metal air battery such as magnesium, aluminum or zinc;

The invention also relates to a process for the preparation of the above cathode. Background technique

The metal air battery is an electrochemical reaction device using a metal (such as magnesium, aluminum, zinc, etc.) as an anode fuel, oxygen in the air as an oxidant, and alkali or neutral brine as an electrolyte solution. China's magnesium, aluminum, zinc and other metals are abundant in reserves and low in price. Therefore, metal-air batteries have broad application prospects in many fields of mobile power, such as China's communication power supply, field emergency power supply, lighting power supply and reserve power supply. As a mobile power source, performance and stability are two important indicators. For metal air cells, the cathode is one of the important components that affect battery performance and stability. Cathode preparation technology is also the core technology of metal air batteries. Many countries in the world also keep related technologies confidential and not public. Therefore, the development of high performance, good stability cathodes is of great significance for the development and application of metal air batteries.

The conventional metal air battery cathode preparation method is a mechanical method for pressing a multi-layer composite structure (generally, a catalyst-carrying carbon paper-nickel mesh-catalyst-contained carbon paper-polytetrafluoroethylene microporous membrane pressure composite) The electrode structure prepared by this method is difficult to optimize, and the catalyst utilization efficiency is low and the polarization is large, resulting in poor performance.

A carbon dioxide and a hydrophobic material (e.g., PTFE) are filled in the foamed nickel as a diffusion layer to prepare a cathode of an air battery used under alkaline conditions. Since the cathode structure needs to balance gas diffusion and electron transport, the content of the hydrophobic material in the diffusion layer is not excessively high. However, when the above cathode is used in a metal/air battery using a neutral salt (such as aqueous NaCl solution) as an electrolyte, the electrode with foam nickel as a supporting material and a current collector is severely corroded due to the presence of cr, and the life is remarkably shortened. . At present, most of the cathodes used at home and abroad follow the cathodes used in alkaline metal air batteries, and no research has been reported on the corrosion of nickel in cathode current collectors. The conductivity and corrosion resistance of the metal air battery cathode material also become a key issue that restricts the performance of the electrode and the growth of the service life. Summary of the invention

The invention aims at the deficiencies of the existing metal air battery cathode technology, and proposes a novel carbon fiber felt base cathode structure and a preparation method thereof.

In order to achieve the above object, the present invention is achieved by the following specific scheme - a cathode for a metal air battery, comprising a catalytic layer, a hydrophobic diffusion layer and a current collecting layer which are sequentially stacked; the catalytic layer is a mixture of a catalyst and a water repellent The carbon-supported manganese oxide is used as a catalyst, and the PTFE is a water-repellent agent; the hydrophobic diffusion layer is a carbon fiber felt treated by hydration of a PTFE emulsion; the current collecting layer is foamed nickel.

The carbon-supported manganese oxide is one or a mixture of two or more of MnOZC, Mn ₃ 0 ₄ /C, M 0 ₃ /C, and Mn0 ₂ /C The catalyst has a catalyst loading of 2-10 mg cm- ² and a PTFE content of 10-40%.

The carbon fiber mat has a thickness of 2-10 mm _; the PTFE accounts for 40-85% of the total mass of the hydrophobic diffusion layer.

The preparation method of the cathode includes the following three steps,

(1) Preparation of hydrophobic diffusion layer:

a. PTFE emulsion with a concentration of 10-50% in water;

b. Select a carbon fiber felt with a thickness of 2-10mm and weigh it;

c immersing the carbon fiber felt in the above step (1) b in the PTFE emulsion prepared in the above step (1) a, taking it out, drying at 30 ° C - 200 ° C, weighing and calculating the PTFE content;

d. repeat the above steps (1) c to a PTFE content of 40-85%, that is, a hydrophobic diffusion layer;

(2) Preparation of catalytic layer - a. Adding carbon-supported manganese oxide catalyst to ethanol, stirring and mixing it uniformly, adding PTFE emulsion with concentration of 40-60% dropwise, stirring and mixing to form catalyst slurry;

b. Applying the catalyst slurry obtained in the above step (2) a to the hydrophobic diffusion layer obtained in the step (1) by brushing, or knife coating, or spraying, or rolling, to a catalyst loading of 1-10 mg. After cm- ² , sintering at a high temperature of 340 ° C -360 ° C for 30-60 minutes to obtain a catalytic layer based on a hydrophobic diffusion layer;

(3) Preparation of the cathode:

a. Cutting the foamed nickel of the same shape and size as the carbon fiber felt, and placing it on the surface of the hydrophobic diffusion layer of the catalytic layer obtained in the step (2);

b. Under the pressure of 5-20 MPa, press the nickel and catalytic layer placed in the above step (3) a at 80 ° C - 200 ° C for l-10 min, and take out the cathode for the metal air battery.

The carbon-supporting manganese oxide in the step (2) a is one or a mixture of two or more of MnO/C, Mn ₃ 0 ₄ /C, Mn ₂ 0 ₃ /C, and Mn0 ₂ /C.

The mass of the carbon-supported manganese oxide per 100 ml of ethanol in the step (2) a is 20-50 mg.

In the catalyst slurry of the step (2) a, the mass ratio of the PTFE to the carbon-supported manganese oxide catalyst is 1:9-2:3. The electrodes of the present invention will help to greatly improve the performance of the metal-air battery and reduce leakage of the electrolyte, while at the same time significantly simplifying the electrode preparation process.

Compared with the prior art, the cathode for a metal air battery of the present invention has the following advantages -

1. The preparation method is simple, and can be used for industrial production and large-scale preparation;

2. The PTFE hydration treated carbon fiber felt is used as the catalyst layer substrate to help reduce the leakage of the electrolyte solution and further reduce the corrosion of the electrolyte solution on the foamed nickel current collecting net;

3. Coating the catalyst layer slurry on the surface of the hydrophobic diffusion layer is beneficial to the improvement of catalyst efficiency and further promotes the substantial improvement of battery performance and stability. DRAWINGS

1 is a schematic view showing the structure of a cathode for a metal air battery. In the figure, 1 is a catalytic layer, 2 is a hydrophobic diffusion layer, and 3 is PTFE. 4 is foam nickel, A is the electrolyte solution side, and B is the air side.

Fig. 2 is a graph showing the performance of a single cell when the cathode of the present invention is used as a cathode of a magnesium air battery.

Figure 3 is a comparison of the performance of the battery open circuit for one month before using the cathode of the present invention as the cathode of the magnesium air battery. Fig. 4 is a graph showing the constant current discharge performance of the battery when the cathode of the present invention is used as a cathode of a magnesium air battery. detailed description

The invention will now be described in detail in connection with the embodiments. Of course, the invention is not limited to these specific embodiments. Example 1

The cathode for a metal air battery was prepared by the following method:

(1) Preparation of hydrophobic diffusion layer

a. PTFE emulsion with a mass concentration of 20% in water as a solvent;

b. Select a carbon fiber felt with a thickness of 8 mm, cut it into 6 cm x 6 cm pieces and weigh it; c Immerse the carbon fiber felt weighed in step b in the PTFE emulsion prepared in step a, and remove it at 80°. Drying under C, weighing and calculating the PTFE content;

d. Repeat step c to a PTFE mass content of 50% to obtain a hydrophobic diffusion layer;

(2) Preparation of catalytic layer:

a. 260mg of Mn ₃ 0 ₄ /C catalyst was added to 1300ml of ethanol, wherein Mn ₃ 0 ₄ accounted for 35% of the total mass of the catalyst, stirred and uniformly mixed, and 160mg of PTFE emulsion with a mass concentration of 40% was added dropwise, and stirred. Mixing uniformly to form a catalyst slurry;

b. Brushing method The catalyst slurry is applied onto the hydrophobic diffusion layer obtained in the step (1) until the catalyst loading is 5 mg cm- ² , and then sintered at 340 ° C for 60 minutes at a high temperature to obtain a hydrophobic diffusion layer. Catalytic layer;

(3) Preparation of the cathode:

. a cut area 6 _C mx6cm Foaming of the nickel, and placed in the step (2) surface of the hydrophobic catalyst layer of the resulting diffusion layer;. b lOMPa under pressure will be placed in a good Foam layer 180 of nickel and a catalytic The pressure was pressed for 5 min, and it was taken out as a cathode of a magnesium air battery after being taken out.

The anode of the magnesium air battery is made of AZ61 magnesium alloy with a thickness of 5 mm and a pole spacing of 3 mm. When the battery is discharged, the mass concentration of 10% NaCl is used as the electrolyte, and the working temperature is room temperature. Single cell performance curve shown in Figure 2, can be seen from Figure 2, the battery discharge project, when the air discharge current of magnesium 100 mAcm- ^2, the cell voltage of 1. IV; when the discharge current of 200 mAcm_ ² The battery voltage reaches 1.4V. During the whole performance test, the peak power density of the magnesium air battery unit is 125mWcm- ² .

Example 2:

The cathode for a metal air battery was prepared by the following method:

(1) Preparation of hydrophobic diffusion layer

a. PTFE emulsion with a concentration of 10% in water:

. b choice of thickness of 2mm graphitized carbon fiber mat, which was cut into small pieces 4cmx4 _C m and weighing it; c. The carbon fiber felt weighed in step b is immersed in the PTFE emulsion prepared in step a, taken out, dried at 30 ° C, weighed and calculated PTFE content;

e. Repeat step c to a PTFE content of 40% to obtain a hydrophobic diffusion layer;

(2) Preparation of catalytic layer:

a. Add 100 mg of Mn0 ₂ /C catalyst in 200 ml of ethanol, wherein Mn0 ₂ accounts for 25% of the total mass of the catalyst, stir and mix uniformly, add 134 mg of PTFE emulsion with a concentration of 50% dropwise, stir and mix to form a catalyst. Slurry:

b. Brushing method The catalyst slurry is applied onto the hydrophobic diffusion layer obtained in the step (1) until the catalyst loading is 4 mg cm- ² , and then sintered at 360 ° C for 30 minutes at high temperature to obtain a hydrophobic diffusion layer. Catalytic layer;

(3) Preparation of the cathode:

a. Cutting the area of 4 _C mx4 cm of foamed nickel and placing it on the surface of the hydrophobic diffusion layer of the catalytic layer obtained in the step (2); b. placing the nickel and catalytic layer at 80 MPa under pressure °C is pressed for 10 minutes, and it is taken out as a cathode of a magnesium air battery after being taken out.

The anode of the magnesium air battery is made of AZ61 magnesium alloy with a thickness of 5mm and a pole spacing of 3mm. When the battery is discharged, 10% NaCl is used as the electrolyte, and the working temperature is room temperature. Figure 3 shows the comparison between the initial constant current discharge performance and the constant current discharge performance after the battery is placed for one month. It can be seen that the performance and initial performance of the battery after one month of placement are not significantly changed.

Example 3:

The cathode for a metal air battery was prepared by the following method:

(1) Preparation of hydrophobic diffusion layer

a. 5% emulsion with a concentration of 50% in water:

b. Select a graphitized carbon fiber felt with a thickness of 10 mm, cut it into small pieces of 8 cm×8 cm and weigh it; c immerse the carbon fiber felt weighed in step b in the PTFE emulsion prepared in step a, and take it out after removal. Dry at 200 ° C, weigh and calculate the PTFE content;

d. Repeat step c to a PTFE content of 85% to obtain a hydrophobic diffusion layer;

(2) Preparation of catalytic layer - a. Add 960 mg of MnO/C, Mn ₃ 0 ₄ /C, Mn ₂ O ₃ /C mixture in a mass ratio of 1:1:1 to 3.2 L of ethanol as a cathode catalyst, of which MnO 20% of the total mass of the MnO/C catalyst, Mn ₃ 0 ₄ accounts for 20% of the total mass of the Mn ₃ 0 ₄ ZC catalyst, and Mn ₂ 0 ₃ accounts for 20% of the total mass of the Mn ₂ 0 ₃ /C catalyst, which is mixed by stirring. Uniformly, 107 mg of PTFE emulsion with a concentration of 60% was added dropwise, and stirred to homogenize to form a catalyst slurry;

b. Brushing method The catalyst slurry is applied onto the hydrophobic diffusion layer obtained in the step (1) until the catalyst loading is 10 mg cm- ² , and then sintered at 340 ° C for 60 minutes at a high temperature to obtain a hydrophobic diffusion layer. Catalytic layer;

(3) Preparation of the cathode:

. a cut area of the Foam 8 _C mx8cm nickel, and placed in the step (2) surface of the hydrophobic catalyst layer of the resulting diffusion layer;. b under a pressure of 20MPa in a placed in a nickel layer and a catalytic 200 ° C was pressed for 1 min and taken out as a cathode for a magnesium air battery. The anode of the magnesium air battery is made of AZ61 magnesium alloy with a thickness of 5 mm and a pole spacing of 3 mm. When the battery is discharged, 10% NaCl is used as the electrolyte, and the working temperature is room temperature. Figure 4 shows the constant current discharge curve of the battery at 30 mAcm- ² constant current discharge. It can be seen that the battery performance is not significantly attenuated during the 200-hour discharge time. Currently, the battery is still in operation and is expected to work stably. The time can be as long as several months.

Example 4:

The cathode for a metal air battery was prepared by the following method:

(1) Preparation of hydrophobic diffusion layer

a. concentrating 30% PTFE emulsion with water as solvent;

b. Select a graphitized carbon fiber felt with a thickness of 4 mm, cut it into small pieces of 2 cm x 2 cm and weigh it; c immerse the carbon fiber felt weighed in step b in the PTFE emulsion prepared in step a, and take it out after removing Dry at 120 ° C, weigh and calculate the PTFE content;

d. Repeat step c to a PTFE content of 60% to obtain a hydrophobic diffusion layer;

. (2) Preparation of the catalytic layer - a added 6mg mass in 15ml of ethanol ratio of 2: 1 Mn ₃ 0 ₄ / C and Mn ₂ 0 ₃ / C the mixture was homogeneous as cathode catalyst I ", wherein Mn ₃ 0 ₄ occupy 18% of the total mass of the Mn ₃ 0 ₄ /C catalyst, Mn ₂ 0 ₃ accounted for 25% of the total mass of the Mn ₂ 0 ₃ /C catalyst, stirred and uniformly mixed, and 6.7 mg of a PTFE emulsion having a concentration of 45% was added dropwise, and stirred. Mixing them uniformly to form a catalyst slurry;

b. Using a brushing method, the catalyst slurry is applied onto the hydrophobic diffusion layer obtained in the step (1) until the catalyst loading is 1 mg cm- ² , and then sintered at a high temperature for 40 minutes at 340 ° C to obtain a hydrophobic diffusion layer. Catalytic layer;

(3) Preparation of the cathode:

a. Cutting the nickel of 2 _C mx2 cm and placing it on the surface of the hydrophobic diffusion layer of the catalytic layer obtained in the step (2); b. placing the nickel and catalytic layer of the buffer at a pressure of 6 MPa at 160 The pressure was pressed for 3 min, and it was taken out as a cathode of a magnesium air battery after being taken out.

The cathode structure in the above Examples 1-4 is a catalytic layer on the side close to the electrolyte solution, a hydrophobic treated carbon fiber felt in the middle, and a foamed nickel current collector on the air side. Different from the spherical electrode material such as acetylene black, the carbon fiber felt in the electrode can directly connect the catalytic layer and the current collector by using its rich fibrous network structure, so the electron transport performance is better, and the battery test shows better. Battery performance and stability. At the same time, the hydrophobically treated carbon fiber felt in the electrode structure separates the catalytic layer from the current collector. During the test, no electrolyte solution was found to penetrate from the catalytic layer to the catalytic layer side, and at the same time, the current collector was not corroded after the stability test. .

Claims

& ^ U 3⁄4 l . A cathode for a metal air battery, comprising: a catalytic layer, a hydrophobic diffusion layer and a current collecting layer arranged in sequence;

The catalytic layer is composed of a catalyst and a water repellent, and the carbon-supported manganese oxide is used as a catalyst, and the PTFE is a water-repellent agent; the hydrophobic diffusion layer is a carbon fiber felt treated by hydration of a PTFE emulsion; and the current collecting layer is foamed nickel.

2. The cathode according to claim 1, wherein: the carbon-supported manganese oxide is one or two of MnO/C, Mn ₃ 0 ₄ /C, Mn ₂ 0 ₃ /C, and Mn0 ₂ /C. For the above mixture, the catalyst has a catalyst loading of 2-10 mg cm ² and a PTFE content of 10-40%.

3. The cathode according to claim 1, wherein: the carbon fiber felt has a thickness of 2 to 10 mm _{; and the} PTFE accounts for 40 to 85% of the total mass of the hydrophobic diffusion layer.

A method of preparing a cathode according to claim 1, 2 or 3, characterized in that it comprises the following three steps,

(1) Preparation of a hydrophobic diffusion layer - a. Configuring a PTFE emulsion having a concentration of 10-50% with water as a solvent;

b. Select a carbon fiber felt with a thickness of 2-10mm and weigh it;

(2) Preparation of catalytic layer - a. Adding carbon-supported manganese oxide catalyst to ethanol, stirring and mixing uniformly, adding PTFE emulsion with concentration of 40-60% dropwise, stirring and mixing to form catalyst slurry;

b. Applying the catalyst slurry obtained in the above step (2) a to the hydrophobic diffusion layer obtained in the step (1) by brushing, or knife coating, or spraying, or rolling, to a catalyst loading of l-10 m. _{After g} cm_ ² , sintering at a high temperature of 340 ° C -360 ° C for 30-60 minutes to obtain a catalytic layer based on a hydrophobic diffusion layer;

(3) Preparation of the cathode - a. Cutting the foamed nickel of the same shape and size as the carbon fiber felt, and placing it on the surface of the hydrophobic diffusion layer of the catalytic layer obtained in the step (2);

The method for preparing a cathode according to claim 4, wherein: the carbon-supporting manganese oxide in the step (2) a is MnO/C, Mn ₃ 0 ₄ /C, Mn ₂ 0 ₃ /C, Mn0. One or a mixture of two or more of ₂ / C.

The method for preparing a cathode according to claim 4, wherein the mass of the carbon-supported manganese oxide per 100 liters of ethanol in the step (2) a is 20-50 mg.

The method for preparing a cathode according to claim 4, wherein: in the catalyst slurry, the mass ratio of the PTFE to the carbon-supported manganese oxide catalyst is 1:9-2:3.