CN1254200A

CN1254200A - Cylindrical metal-air battery

Info

Publication number: CN1254200A
Application number: CN 98122215
Authority: CN
Inventors: 孙法炯; 王昉; 夏黎萱; 孙德全
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-11-15
Filing date: 1998-11-15
Publication date: 2000-05-24
Anticipated expiration: 2018-11-15
Also published as: CN1150651C; WO2000030204A1

Abstract

A cylindrical metal-air battery is prepared as setting diaphragm, metal anode and electrolyte in cylindrical metal-air electrode, forming air electrode by catalytic active layer, hydrophobic air-permeable layer, current collector conductive net and leakage-proof sealing layer, compacting said layers into one body, not contacting current collector with catalytic active layer, forming air electrode by column, sealing electrode port at two ends, having large electrode reaction area, strong leakage, large internal volume and flat discharge platform.

Description

Cylindrical metal-air battery

The invention relates to a cylindrical (such as AA type, AAA type, C type and D type) battery adopting an air electrode, the shape of the battery can also extend to be a hexahedron or an irregular polygon body, in particular to a cylindrical metal-air battery.

A metal-air battery is an electrochemical cell that is configured with a metal as an anode active material and oxygen in the air as a cathode active material. The anode material is generally zinc or aluminum, and zinc is usually used. During the discharge process, oxygen is reduced and the metal is oxidized. Since the air electrode consumes oxygen in the air, the positive electrode of the cell is only a gas-permeable, liquid-impermeable, electrically conductive, catalytically active sheet. For a cell, the proportion of the positive electrode therein is small and the remaining space is available for the negative electrode material. The structural characteristics of the metal-air battery determine that the metal-air battery has higher volumetric specific energy. Taking zinc-air battery as an example, the volumetric specific energy is 600-700 WH/L. While other types of cells have much lower volumetric energy than zinc-air cells.

In a traditional metal-air battery, an air electrode is generally formed by compounding a catalytic active layer, a current collector conductive net and a hydrophobic breathable layer. The hydrophobic and breathable layer is made of polytetrafluoroethylene as a main body, and the current collector conductive layer is pressed on the catalytic active layer more or pressed between the hydrophobic and breathable layer and the catalytic active layer. Such air electrodes are present in a planar state before they are used to manufacture a battery. When used for manufacturing a battery, the battery is formed into a desired size and shape by punching, pressing, or the like, in a planar state. Its advantages are high electrochemical performance, and wide application in button cell of hearing aid and square cell of large-size flashlight, road signal lamp and navigation lamp system. The hydrophobic and breathable layer mainly made of polytetrafluoroethylene is difficult to seal, and particularly, the hydrophobic and breathable layer is difficult to seal when the hydrophobic and breathable layer is used for manufacturing a cylindrical battery.

With the development of portable electrical appliances, small cylindrical series metal-air batteries can find wider and wider application. Wherein, the service condition of the pager is most suitable for the zinc-air battery to exert the advantages: continuous use, power medium, etc. The service time of the alkaline zinc-manganese dioxide battery can reach 3 to 4 months, which is 2 times of that of the common alkaline zinc-manganese dioxide battery. While in the mobile phone sector, the power of CDMA handsets has been less than 0.5 watts, such discharge power is affordable by zinc-air batteries. Therefore, the development of the small cylindrical series zinc-air battery is extremely significant.

Ordinary electric appliances (such as beepers, toys and mobile phones) need to work normally, and batteries need to output current with certain intensity. Regardless of the catalyst used, there is a limit to the current density per unit area of the metal-air battery. When the limit value is fixed, the effective reaction area of the electrode can only be increased to improve the output current of the battery. For cylindrical AA and AAA batteries, which are characterized by being thin and long, to increase the effective reaction area of the electrode, it is preferable to place a cylindrical electrode along the length of the battery rather than a planar circular electrode as in button cells. Some cylindrical air batteries have been explored at home and abroad, but the cylindrical air batteries are not successfully commercialized.

In patents U.S.3881959, U.S.4303743 and Chinese patent ZL96239541, there are mentioned methods of winding the electrode in the center of the cell, forming a gas chamber at the center, and enclosing the anode material on the outside. The defect is that the battery is easy to leak; 2. because the battery air chamber is arranged in the center of the battery and occupies more space, the advantage of high specific energy of the air battery cannot be fully embodied.

The air electrode is coiled outside, and the anode material is arranged inside, so that the electrode has an effective large reaction area, the air chamber does not occupy the internal space of the battery basically, and the internal volume is large, thereby being an ideal design scheme. To achieve this design, first, the electrodes are thin. If the electrode is too thick, the space occupied by the externally wound electrode in the proportion of the battery is relatively large, which is not favorable for improving the specific energy of the battery. Second, reliable sealing. It includes sealing the side of the air electrode which is rolled up; two ports (defined as the mouth and bottom of the air electrode) were sealed. In addition, in the metal anode (zinc electrode is taken as an example), zinc is oxidized into zinc oxide during the reaction process, and the volume is expanded, so that the sealed part needs to have certain strength. Otherwise, the air electrode is cracked and liquid leakage occurs during the discharge process of the battery due to the expansion of zinc. U.S.4450211 mentions that the electrode is pressed into a bell shape, and the electrode is directly extruded and molded without a method of a multi-layer composite electrode in the manufacturing process, so that the problems of poor electrode performance, low reliability and inconvenience for mass production exist.

In the Chinese patent ZL94206870, an external oxygen type air electrode is mentioned, which has the defects of complex process, poor sealing performance of an adhesive electrode cylinder and unsuitability for industrial production and failure of commercialization.

The object of the invention is to produce a cylindrical air cell with a new multi-layer composite air electrode, whose hydrophobic and gas-permeable layer is mainly made of other polymers than polytetrafluoroethylene, but mainly with good welding properties, which is welded with an additional leak-proof sealing layer with a tight liquid-tight connection. The connection is maintained without a mechanical force that is always pressed, and has high reliability. The plane high-performance multilayer air electrode is rolled into a cylinder, a hexahedron or an irregular polyhedron to be made into air batteries of various non-plane electrodes;

another object of the present invention is to provide a novel method for sealing the butt joint of the side surfaces of a rolled composite air electrode to form at least one sealing line, so that the side edges of the electrode are tightly connected together to form a reliable, liquid-tight seal;

it is another object of the present invention to seal both ends of the air electrode to provide a tight, reliable, liquid-tight seal of the electrode port;

the purpose of the invention is realized by the following modes: the utility model provides a cylindrical metal-air battery, mainly comprises air electrode, diaphragm, metal anode and electrolyte, and wherein diaphragm, metal anode and electrolyte are located cylindrical metal air electrode's inside, its main characterized in that: a. the air electrode is composed of a catalytic active layer, a hydrophobic air-permeable layer, a current collector conductive net and a leakage-proof sealing layer, wherein at least 50% of single polymer in the hydrophobic air-permeable layer does not contain polytetrafluoroethylene and is conductive, the catalytic active layer and the hydrophobic air-permeable layer are compressed into a whole, the current collector is not in contact with the catalytic active layer, but an additional leakage-proof sealing layer composed of polymer is arranged on the other side of the hydrophobic air-permeable layer opposite to the catalytic active layer, the leakage-proof sealing layer and the hydrophobic air-permeable layer clamp and compress the current collector and are tightly connected with the hydrophobic air-permeable layer by using a method of thermal welding, ultrasonic welding or bonding;

b. the air electrode is cylindrical, and at least one sealing line which is formed by curling the planar air electrode and sealing the butt joint is arranged on the side surface of the air electrode, so that the side edges of the electrode are tightly connected together to form liquid-tight sealing;

c. having structure at both ends thereof for sealing the electrode ports;

d. the current collector conductive net is not immersed in the electrolyte and is directly led out through the leakage-proof sealing layer.

The metal-air battery adopting the structure has the advantages of larger electrode reaction area, strong leakage discharge performance, larger internal volume and flat discharge platform. The characteristic of high volumetric specific energy of the metal-air battery can be fully exerted. Taking zinc air AA type and AAA type batteries as examples, the volumetric specific energy is 700WH/L.

Description of the drawings:

FIG. 1: the front section view of the air electrode after sealing the bottom and sealing the edge;

FIG. 2 is a schematic diagram: a top sectional view of the electrode in a cylindrical shape;

FIG. 3: a hexahedral sectional view of the electrode;

FIG. 4: a cross-sectional view of the cell;

FIG. 5 is a schematic view of: comparative discharge curves for AA cylindrical cells and alkaline zinc-manganese cells;

FIG. 6: comparative discharge curves for AAA cylindrical cells versus alkaline zinc manganese cells.

The invention is further described with reference to the following figures and examples.

The invention relates to a metal air battery, wherein an air electrode of the metal air battery consists of a catalytic active layer 1, a hydrophobic breathable layer 2, a current-collecting conductive net 3 and a leakage-proof sealing layer 4. Referring to the enlarged portion of fig. 1 in detail, the catalytically active layer 1 is made of a catalyst, a conductive material, activated carbon, teflon or the like. There are many specific formulations, which are described in many electrochemical articles and patents. The catalyst may be any of various conventional noble metal catalysts such as silver and platinum, or a general catalyst such as manganese dioxide may be used. One method is to mix 70% of activated carbon, 20% of manganese dioxide and 10% of polytetrafluoroethylene uniformly, and roll the mixture into a sheet with the thickness of 0.05-2mm for later use.

The hydrophobic and breathable layer 2 is formed by uniformly mixing carbon black with a certain proportion into one or more of polyethylene, polyvinyl chloride, nylon and polypropylene plastics and pressing. One method is to mix 85% polypropylene and 15% acetylene black in acetone uniformly, and roll the mixture to 0.1-2mm after half drying. Laminating the catalytic active layer 1 and the hydrophobic and air-permeable layer 2 into a sheet with a thickness of 0.2-2mm, and drying. Because polytetrafluoroethylene is not used as the main material of the layer, the welding and bonding performance is good. The polypropylene in the above process can also be replaced by other polymers and correspondingly suitable solvents.

The hydrophobic and air permeable layer is hydrophobic due to the fact that the main constituent material, namely the polymer, is hydrophobic, and meanwhile, the inside of the hydrophobic and air permeable layer is provided with enough micropores. The micropores can not be pressed due to the existence of the solvent in the semi-drying manufacturing process, and the solvent is separated out and left after the drying. It can make oxygen permeate to active layer to take part in reaction, and at the same time can prevent electrolyte from leaking out from catalytic active layer. The hydrophobic air permeable layer of the invention contains carbon black, so the layer has conductivity and plays a role of positive current collection after being compressed with the catalytic active layer. The current generated by the electrochemical reaction at the three-phase interface of the catalytically active layer can flow through the hydrophobic gas-permeable layer to the current collector mesh 3.

The current collector conductive mesh 3 is generally made of stainless steel, low carbon steel with silver, gold, or nickel, or corrosion-resistant metal such as silver, gold, nickel, or copper, and is formed in the forms of woven mesh, stretched mesh, punched tape, and the like. The current collector is pressed together with the hydrophobic and gas-permeable layer, part of the metal being embedded in the hydrophobic and gas-permeable layer, but not penetrating the layer to reach the catalytically active layer, which could lead to leakage. The degree of intercalation determines the impedance of the air electrode and thus the cell output current.

And the leakproof sealing layer 4 is made of plastic with the similar property to that of the hydrophobic and breathable layer 2. It may be one or several of polypropylene, polyethylene, polyvinyl chloride, nylon, etc. Commercially available polypropylene sheets can be used, having a thickness of between 0.1 and 1 mm. The plastic sheet must have good mutual welding or bonding properties with the hydrophobic and gas-permeable layer 2. The material of the leakage-proof seal layer 4 may be a plastic having micropores which are gas-permeable and liquid-impermeable. Oxygen in the air can penetrate through the film to reach the hydrophobic and air-permeable layer 2 to participate in the reaction, and the electrolyte cannot penetrate through the film. The material of the leak-proof sealing layer 4 may also be gas-tight or liquid-tight, so that at least one or more holes 7 are made in the layer 4 to allow gas to penetrate into the hydrophobic gas-permeable layer 2 through the gas diffusion zone.

The leak-proof sealing layer 4 and the hydrophobic and breathable layer 2 are tightly connected in a liquid-tight way at 15 by ultrasonic welding, thermal welding, bonding and other methods, and the connection simultaneously compresses the current collector net 3 between the

layers

2 and 4 to fix the position of the current collector net. Since the current collector is porous or reticulated, the 2 and 4 electrodes can be securely joined together by close welding or bonding through the interperforated portions of the 3 electrode. Such tight connection lines 15 consist of the material of the hydrophobic and gas permeable layer and the leakproof sealing layer only, or have some adhesive, and are thus impermeable to the electrolyte. The connecting line 15 may be gas permeable, but more likely is gas impermeable because the micro-pores inside the leakproof sealing layer 4 and the hydrophobic gas permeable layer 2 are likely to be blocked during welding or bonding.

The feature that electrolyte on either side of the connecting line 15 cannot penetrate through it to the other side is used to achieve an integral seal of the cell. The connecting lines 15 can be adjusted in base width, length and shape as desired, whose essential requirement is that the connecting lines 15 themselves form a closed geometric figure. Due to the tightness of the connection line 15 itself against the electrolyte, the electrolyte outside the closed geometry does not penetrate through the connection line 15 and reach the gas diffusion area 16, which is perforated with holes 7 (or not perforated, if the material of the leak-proof sealing layer 4 is permeable to gas and impermeable to liquid), inside the geometry.

The air electrode described above was formed into the shape shown in fig. 1. Specifically, the electrode is rolled up to form a desired shape according to the shape and size of the battery to be manufactured. They may be cylindrical, hexahedral, elliptic cylindrical, polyhedral, etc., of which fig. 2 gives a cross-section by way of example of a cylinder, fig. 3 gives a cross-section by way of example of a hexahedral, and so on. Here, the manufacturing process is described by taking a cylindrical shape as an example. Firstly, taking the electrode processed according to the requirement, considering the requirement of the next processing, the leakage-proof sealing layer is preferably wider than the hydrophobic and air-permeable layer at least at one end edge. The electrode is coiled with the catalytic active layer inside, and the coiled electrode sequentially comprises the catalytic active layer, the hydrophobic breathable layer, the current collector conductive net and the leakage-proof sealing layer from inside to outside. At least one butt or lap seam to be sealed is present on the side of the electrode, and in order to ensure a large reaction area of the electrode, the seam is preferably one and as thin as possible.

The sealing line 5 can be formed by filling the joint of the air electrode by directly utilizing the materials on the hydrophobic and air-permeable layer and the leakproof sealing layer or supplementing the materials similar to or the same with the hydrophobic and air-permeable layer and the leakproof sealing layer by adopting a method of thermal welding, ultrasonic welding, bonding or injection molding. The thickness of the seal line is basically the same as that of the air electrode, the length of the seal line is the same as that of the air electrode, and the seal line and the materials of the leak-proof seal layer and the hydrophobic breathable layer are mutually fused together. The electrodes after connection have at least one sealing line 5 on the side to keep the electrodes in the shape they have. Since this connection is achieved by force between molecules, it has high strength. Meanwhile, the electrode is liquid-tight, so that liquid can be prevented from permeating through the electrode and can be prevented from permeating between the leakage-proof sealing layer and the hydrophobic breathable layer. Under this condition, the shape of the electrode is fixed, and both ends are open. The length of the leak-proof sealing layer at the port part is not less than that of the other three layers.

The following is the sealing of its ports. The methods that can be used are: as in the method of fig. 1, bottom 6, a certain amount of high molecular polymer similar or identical to the materials of the electrode leakproof seal layer and the hydrophobic gas permeable layer is added or a rubber ring prepared in advance (the material can be polyethylene, polyvinyl chloride, polystyrene, polypropylene, polyamide, etc.) is used, and the added material is connected with the leakproof seal layer and the hydrophobic gas permeable layer at the port part by using a thermal welding, ultrasonic welding or bonding method. Or injecting a certain amount of molten high molecular polymer (material properties are the same as those described above) into the mold by using an injection molding method to connect with the electrode port, cooling, and then manufacturing the bottom 6. The essence of the method is that the added materials are mutually fused with the materials of the hydrophobic and breathable electrode layer and the port of the leakproof sealing layer, so as to achieve the purpose of sealing.

The mechanical edge-buckling method commonly used in the production of alkaline zinc-manganese batteries can also be utilized: the rubber ring with the core is inserted into the port part, and the outside of the rubber ring is sleeved with a steel shell. In the mould, the outer steel shell is bent inwards by means of pressure. The air electrode and the rubber ring at the port area are tightly pressed to achieve sealing. This method, in order to prevent the leakage of liquid from between the hydrophobic gas-permeable layer and the leak-proof sealing layer, requires that the connecting line 15 between the

electrodes

2 and 4 used is located close to the port and intersects the sealing line and the connecting line on the side.

For the current collector conductive net, the current collector conductive net can be directly led out through holes in the leakage-proof sealing layer; the leak-proof sealing layer is provided with no hole and directly penetrates through the leak-proof sealing layer to be led out. And finally, detecting the electrodes (called positive electrode cylinders) with sealed bottom and side edges, and standing by after no leakage.

The following was a battery. FIG. 4 shows 14 a septum. The separator can be made of non-woven fabric made of polyamide; a hydrophilic treated polypropylene membrane; polyethylene grafted acrylic acid membranes, and the like. The thickness is 0.025-0.4 mm. The shape of the electrode is similar to that of the anode, and the outer side of the electrode is attached to the inner part of the air electrode. Take polyamide non-woven fabric diaphragm manufactured by Zhejiang paper making research as an example. Taking this separator with a thickness of 0.13 mm, the rolled three layers were inserted into the electrode from the open end. The metal anode of the battery can be made of zinc or aluminum and the like. Here, zinc powder is taken as an example. The electrolyte may be a neutral or alkaline electrolyte, and the power of a neutral electrolyte battery is generally much lower than that of an alkaline electrolyte battery. Here, an AA battery using an alkaline electrolyte is taken as an example. The formula can be as follows: taking 35 g of potassium hydroxide solution, adding 3 g of the potassium hydroxide solution into 7 g of zinc powder, fully stirring and homogenizing to obtain zinc paste 12, and completely filling the zinc paste into the positive electrode inserted with the diaphragm.

A copper needle 11 is arranged at the center of the pre-prepared rubber ring 9 and is used as a negative current collector. One end of the negative current collector is inserted into the zinc paste, and the other end of the negative current collector is connected with a negative cover of the battery. The material of the rubber ring can be polyethylene, polyvinyl chloride, polystyrene, polypropylene, polyamide and the like. And inserting the rubber ring with the negative current collector into the opening end of the air electrode added with the zinc paste. The rubber ring and the electrode can be tightly combined together by using methods of injection molding, thermal welding, ultrasonic welding and bonding. The essence of the connection is that the added material is mutually fused with the hydrophobic and breathable layer of the electrode and the material of the other port of the leakage-proof sealing layer, so as to achieve the purpose of sealing. Or by means of mechanical crimping. The metal-air battery sealed by the method can prevent the leakage of the internal electrolyte and ensure the smooth implementation of electrochemical reaction in the storage and use processes.

Finally, the sealed battery is covered with an outer shell 8 (the shell can be made of nickel-plated steel, tinplate, engineering plastics and the like) which plays a role in protecting and packaging the battery inside. The upper cover 10 is connected with a negative current collector, and the lower cover 13 is connected with a positive current collector through a lead 17. At least one air permeable portion 7 is present in the housing and the upper and lower covers to allow air to enter the interior of the battery. According to the method, cylindrical (AA type, AAA type, C type and D type), hexahedral and other metal-air batteries with different heights, diameters and shapes can be manufactured according to the requirements.

Cylindrical AA and cylindrical AAA type zinc-air batteries are exemplified.

And taking five qualified positive pole cylinders to respectively manufacture the AA type zinc-air battery and the AAA type zinc-air battery. Wherein, 10 g of zinc paste is added into the AA type battery, and 40 holes with the diameter of 1mm are uniformly distributed on the package and the steel shell; 4.3 g of zinc paste is added into the AAA type battery, and 25 holes with the diameter of 1mm are uniformly distributed on a package and a steel shell. Resistance-fixed discharge (temperature 21 ℃, humidity 60%) results are shown in the following table:

table 1: AA type battery sample discharging resistance (omega) platform voltage (volt) end voltage (volt) time (hour)

1 10 1.22 0.9 33.0

2 10 1.22 0.9 33.1

3 10 1.23 0.9 32.5

4 1000 1.37 0.9 3361

5 1000 1.37 0.9 3358

Table 2: AAA type battery sample discharge resistance (omega) platform voltage (volt) end voltage (volt) time (hour)

1 20 1.25 0.9 29.1

2 20 1.24 0.9 29.5

3 20 1.24 0.9 29.3

4 1000 1.35 0.9 1350

5 1000 1.35.9 1343 discharge curves are shown in FIGS. 5 and 6

Fig. 5 shows a discharge curve of AA type batteries continuously discharged under a constant resistance condition of 10 (Ω), and fig. 6 shows a discharge curve of AAA type batteries continuously discharged under a constant resistance condition of 20 (Ω). This is compared to the discharge curve of an alkaline zinc-manganese cell. It can be seen from the figure that the discharge curves of the AA type and AAA type zinc-air batteries of the invention are flatter, and the service life of the batteries is more than doubled. The volumetric specific energy reaches 700WH/L.

Claims

1. The utility model provides a cylindrical metal-air battery, mainly comprises air electrode, diaphragm, metal anode and electrolyte, and wherein diaphragm, metal anode and electrolyte are located cylindrical metal-air electrode's inside, its characterized in that:

a. the air electrode is composed of a catalytic active layer, a hydrophobic and breathable layer, a current collector conductive net and a leak-proof sealing layer, wherein at least 50% of single polymer in the hydrophobic and breathable layer does not contain polytetrafluoroethylene and is conductive, the catalytic active layer and the hydrophobic and breathable layer are compressed into a whole, the current collector is not in contact with the catalytic active layer, but an additional leak-proof sealing layer composed of polymer is arranged on the other side of the hydrophobic and breathable layer opposite to the catalytic active layer, the leak-proof sealing layer and the hydrophobic and breathable layer clamp and compress the current collector and are tightly connected with the hydrophobic and breathable layer by means of thermal welding, ultrasonic welding, bonding or the like;

b. the air electrode is cylindrical, and the side surface of the air electrode is provided with at least one sealing line which is formed by curling the planar air electrode and sealing the butt joint, so that the side edges of the electrode are tightly connected together to form liquid-tight sealing;

c. having a structure for sealing the electrode port at both ends thereof;

d. the current collector conductive net is not soaked in the electrolyte and is directly led out through the leakage-proof sealing layer.

2. Metal-air battery according to claim 1, characterized in that at least 50% of the material in its hydrophobic gas-permeable layer is one of the following polymers: polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyamide.

3. The metal-air cell of claim 1, wherein the air electrode is formed by rolling a planar air electrode into a cylindrical shape, a hexahedral shape, or an irregular polyhedral shape.

4. The metal-air cell according to claim 1, wherein the sealing line formed on the side surface is formed by directly sealing the hydrophobic and gas-permeable layer or the leak-proof sealing layer, or by adding one of the following materials: polyethylene, polypropylene, polyvinyl chloride, polystyrene and polyamide are subjected to sealing treatment.

5. The metal-air battery according to claim 1, wherein the sealing treatment of the rolled air electrode side is one or more of heat welding, ultrasonic welding, injection molding, and adhesion.

6. The metal-air cell of claim 1, wherein the electrolyte cannot leak through or around the seal wire.

7. The metal-air cell of claim 1, having structures at both ends that seal the electrode ports to prevent electrolyte from leaking through or around the structures that seal.

8. The metal-air cell of claim 1, wherein the material of the structure of the electrode port seal is one of the following: polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyamide.

9. The metal-air cell of claim 1, wherein the electrode port is sealed by one or more of heat welding, ultrasonic welding, injection molding, adhesive bonding, and mechanical crimping.

10. The metal-air battery of claim 1, wherein the current collector conductive mesh is not immersed in the electrolyte and is led out directly through the holes in the leak-proof sealing layer, and the holes in the leak-proof sealing layer are led out directly through the leak-proof sealing layer.

11. The metal-air cell of claim 1, wherein the metal anode is comprised of zinc or aluminum.

12. The metal-air cell of claim 1, wherein the electrolyte is comprised of a neutral electrolyte or an alkaline electrolyte.