JP2007214114A - Method of manufacturing air cell and air electrode for air cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air cell in which a three-phase interface of an air electrode catalyst layer is stably maintained and has an excellent heavy-load discharging property and preservation property. <P>SOLUTION: The catalyst layer is formed by mixing an oxygen reducing catalyst, a co-catalyst having a disintegration property of a product by an oxygen reduction and a conductive carbon and binder, and the catalyst layer is press-bonded with a collector and a water-repellant membrane to compose the air electrode to be used in the air cell. The above catalyst layer contains a non-polymer fluorine compound. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an air battery equipped with an air electrode that allows oxygen to act as an active material, and particularly to an improvement of the air electrode.

  An air electrode used in an air battery is composed of a catalyst layer, a current collector, and a water repellent film. The oxygen reduction reaction proceeds inside the catalyst layer. The catalyst layer is generally composed of an oxygen reduction catalyst, a cocatalyst having an action of decomposing a product by oxygen reduction, a conductive material, and a binder. As the oxygen reduction catalyst, a carbon material is often used, and examples thereof include activated carbon, graphite, and carbon black. As the promoter, manganese oxide is generally used. The oxygen reduction catalyst and the cocatalyst are mixed with conductive carbon and bound by a fluororesin binder such as polytetrafluoroethylene (PTFE). The fluororesin binder also has a function as a water repellent. The current collector holds the catalyst layer and plays a role of electron transfer. As the water repellent film, a porous polymer film having water repellency such as PTFE is used and plays a role of preventing the electrolyte solution from leaking out of the air electrode through the catalyst layer. The water repellent film has pores for supplying air to the catalyst layer.

  The oxygen reduction reaction inside the catalyst layer is thought to proceed at the interface (three-phase interface) where the three-phase surfaces of the solid-phase catalyst, the liquid-phase electrolyte, and the gas-phase air contact each other. Yes. Therefore, the output characteristics of the air electrode can be improved as the area of the three-phase interface is increased or the efficiency of supplying air to the three-phase interface per unit time is improved.

As an attempt to improve the output characteristics of the air electrode, for example, as shown in Patent Document 1, a conductive water repellent layer is provided on the water repellent film side of the catalyst layer, and the blending ratio of the fluororesin binder in the catalyst layer is optimized. The method of increasing the area of a three-phase interface by enlarging is mentioned. Moreover, as shown in Patent Document 2, there is a method of improving the efficiency of supplying air to the three-phase interface per unit time by setting the porosity of the catalyst layer to 30 to 60%. Further, as shown in Patent Document 3, the catalyst layer is formed of two layers having different porosity, the porosity of the catalyst layer adjacent to the water repellent film side is reduced, and the porosity of the catalyst layer adjacent to the negative electrode side is reduced. A method of increasing the efficiency of supplying air to the three-phase interface per unit time by enlarging the value.
JP-A-6-267594 JP 2000-164262 A JP-A-2005-19145

  However, in the method disclosed in Patent Document 1 in which a conductive water repellent layer is provided on the water repellent film side of the catalyst layer and the blending ratio of the fluororesin binder in the catalyst layer is optimized, the area of the three-phase interface is increased. In addition, it is necessary to reduce the blending ratio of the fluororesin binder. When the blending ratio of the fluororesin binder is decreased, the catalyst layer is easily wetted with the electrolytic solution, and the rate at which the electrolytic solution penetrates into the catalyst layer is increased. Therefore, if it preserve | saves for a long time at normal temperature, or preserve | saves at high temperature, electrolyte solution will osmose | permeate inside a catalyst layer. For this reason, the battery after storage has a problem of deterioration in storage characteristics in which the discharge voltage decreases.

  Further, as shown in Patent Document 2, in the method of improving the air supply efficiency by setting the porosity of the catalyst layer to 30 to 60%, the amount of oxygen supplied into the catalyst layer per unit time is increased. At the same time, water vapor and carbon dioxide are easily introduced into the catalyst layer. Therefore, in the long-term discharge such as light load discharge, the influence of water vapor or carbon dioxide appears more conspicuously, resulting in a problem that the discharge capacity or the discharge duration is reduced.

  Further, in the method as shown in Patent Document 3, in order to reduce the influence of water vapor and carbon dioxide, the effect of reducing the porosity of the catalyst layer adjacent to the water-repellent film side causes a three-phase interface per unit time. The efficiency with which the air is supplied depends on the porosity of the catalyst layer adjacent to the water-repellent film side, which causes a problem that the output cannot be significantly improved.

  Furthermore, as a problem common to Patent Document 1 and Patent Document 3, forming the catalyst layer with two layers having different porosity may complicate the air electrode manufacturing process and reduce the production efficiency of the air battery. Can be mentioned.

  In view of the above, an object of the present invention is to provide an air battery excellent in heavy load discharge characteristics and storage characteristics by stably holding the three-phase interface of the catalyst layer of the air electrode.

  In order to solve the above problems, the air battery of the present invention includes an air electrode composed of a catalyst layer, a current collector, and a water repellent film, and the catalyst layer contains a non-polymeric fluorine compound. It is characterized by that.

  In the air electrode of the present invention, when the catalyst layer contains a non-polymeric fluorine compound, the water repellency of the catalyst layer increases and the wettability of the catalyst layer with respect to the electrolyte solution decreases. For this reason, the speed | rate in which an electrolyte solution osmose | permeates the inside of a catalyst layer reduces, and the preservation | save characteristic of an air battery can be improved. Furthermore, since it is possible to form a catalyst layer having high water repellency and a large porosity, it is possible to improve heavy load discharge characteristics without deteriorating storage characteristics.

  According to the present invention, an air electrode having a catalyst layer having high water repellency and a large porosity can be obtained, and an air battery excellent in storage characteristics and heavy load discharge characteristics can be provided.

  As described above, the air battery of the present invention is an air battery including an air electrode composed of a catalyst layer, a current collector, and a water repellent film, and the catalyst layer contains a non-polymeric fluorine compound. To do. By containing the non-polymeric fluorine compound in the catalyst layer, the wettability of the catalyst layer with respect to the electrolyte solution is reduced, and the effect of reducing the rate of penetration of the electrolyte solution into the catalyst layer is obtained. Therefore, the area of the three-phase interface in the catalyst layer is reduced during storage by controlling the amount of the non-polymeric fluorine compound contained in the catalyst layer and reducing the rate at which the electrolyte penetrates into the catalyst layer. Can be suppressed. Therefore, it is possible to suppress a decrease in discharge voltage after long-term storage or after high-temperature storage.

  The catalyst layer of the present invention further contains a non-polymeric fluorine compound in an ordinary catalyst layer containing an oxygen reduction catalyst, a cocatalyst having an action of decomposing a product of oxygen reduction, a conductive material, and a binder. The preferable composition of this catalyst layer is 15-50 wt% of oxygen reduction catalyst, 15-35 wt% of cocatalyst, 5-15 wt% of conductive material, 1-45% of binder, and 0.5-50 wt% of non-polymeric fluorine compound.

The non-polymeric fluorine compound has high water repellency, has a scaly shape, a spherical shape, or a needle shape, and may have any shape and composition as long as it is obtained as a powder.
Preferred non-polymeric fluorine compounds are fluorinated graphite or fluorinated pitch. When these non-polymeric fluorine compounds are mixed and kneaded with other catalyst layer constituent materials, even when the particles of the non-polymeric fluorine compound are deformed by applying a shearing force, the water repellency is unlikely to decrease. .

Fluorinated graphite can be obtained by directly fluorinating graphite . The composition formula is represented by (CF) _n or (C ₂ F) _n . The optimum composition is CF _x (0.5 ≦ x ≦ 1.0), and the lower the fluorine content ratio, that is, the higher the carbon content ratio, the higher the conductivity. Further, the fluorinated pitch can be obtained by directly fluorinating the pitch. The composition formula is represented by CF _x (x <1.6). The lower the reaction temperature for fluorinating the pitch, the smaller the fluorine content ratio of the resulting fluorinated pitch. The fluorinated pitch, like the fluorinated graphite, has higher conductivity as the fluorine content is lower, that is, as the carbon content is higher. These compounds have very high water repellency, and exhibit super water repellency with a water contact angle of 145 ° or more in the state of powder or thin film. Therefore, by adding a small amount of the non-polymeric fluorine compound to the catalyst layer and uniformly dispersing it, the water repellency of the catalyst layer is increased, and the rate of penetration of the electrolyte into the catalyst layer is reduced.

  The non-polymeric fluorine compound can be pulverized using a ball mill or the like, and may be pulverized by a ball mill or the like when used with a small particle diameter. The average particle size of the non-polymeric fluorine compound is preferably in the range of 0.5 μm or more and 30 μm or less. When the average particle size is less than 0.5 μm, the non-polymeric fluorine compound tends to aggregate between the powders, and it becomes difficult to uniformly disperse the non-polymeric fluorine compound in the catalyst layer. If it exceeds 30 μm, the particle size becomes larger than that of the catalyst component, so that the reaction of the catalyst component is hindered and the discharge characteristics may be deteriorated.

  The weight ratio (b / a) of the non-polymeric fluorine compound content b to the binder content a in the catalyst layer is preferably in the range of 0.1 to 11.5. When the ratio is smaller than 0.1, most of the surface of the non-polymeric fluorine compound is covered with the binder, and the water repellency of the catalyst layer is lowered. For this reason, the effect which reduces the wettability with respect to the electrolyte solution of a catalyst layer decreases. On the other hand, when the ratio is larger than 11.5, the water repellency of the catalyst layer becomes too large, and the electrolyte solution hardly penetrates into the catalyst layer. Therefore, the three-phase interface is not sufficiently formed, and the discharge characteristics are deteriorated. A more optimal range of b / a that can appropriately maintain the water repellency of the catalyst layer is in the range of 0.25 to 3.0.

  The total content of the binder and the non-polymeric fluorine compound in the total weight of the catalyst layer is preferably in the range of 5 to 50% by weight. When the amount is less than 5% by weight, the water repellency of the catalyst layer is lowered, and the catalyst layer is easily wetted with the electrolytic solution. When the amount is more than 50% by weight, the blending ratio of the oxygen reduction catalyst and the co-catalyst in the catalyst layer is reduced, and the oxygen reduction ability is lowered, so that the output characteristics are lowered. A more preferable range of the total content of the binder and the non-polymeric fluorine compound that appropriately maintains the water repellency of the catalyst layer and does not cause a decrease in output characteristics is 20 to 45 with respect to the total weight of the catalyst layer. % By weight.

  The porosity of the catalyst layer is preferably 50 to 80%. Here, increasing the porosity of the catalyst layer has the effect of improving the efficiency of supplying air to the three-phase interface and improving the heavy load discharge characteristics. However, an increase in the porosity of the catalyst layer increases the rate at which the electrolyte permeates into the catalyst layer, and thus has a contradictory effect of reducing storage characteristics.

  However, when the non-polymeric fluorine compound is contained in the catalyst layer, the water repellency of the catalyst layer is increased, and the catalyst layer is difficult to wet with the electrolyte. Therefore, even when the porosity of the catalyst layer is increased, the rate at which the electrolytic solution penetrates into the catalyst layer can be reduced, and a decrease in storage characteristics can be suppressed.

  As described above, the addition of the non-polymeric fluorine compound to the catalyst layer has an advantage that it is possible to improve both of the contradictory characteristics such as the heavy load discharge characteristic and the storage characteristic of the air battery. When the porosity of the catalyst layer is less than 50%, the efficiency with which air is supplied to the three-phase interface of the catalyst layer is reduced, and the output characteristics are degraded. When the porosity is greater than 80%, a significant increase in the porosity counteracts the delay effect of the electrolyte penetration rate due to the improvement in water repellency of the catalyst layer by the non-polymeric fluorine compound, thereby degrading the storage characteristics. A more preferable range of the porosity of the catalyst layer is 60 to 75%.

The catalyst layer preferably contains activated carbon and manganese oxide. Activated carbon functions as a catalyst for two-electron reduction of oxygen and generates O ₂ H ⁻ and OH ⁻ as two-electron reduction products. Manganese oxide functions as a cocatalyst for decomposing generated O ₂ H ⁻ .
The catalyst for reducing oxygen is not limited to activated carbon, and may be a carbon material that functions as an oxygen reduction catalyst, platinum, or the like. As the oxygen reduction catalyst, activated carbon is optimal in terms of the specific surface area and material cost.

When the concentration of O ₂ H ⁻ , which is a two-electron reduction product of oxygen, increases in the catalyst layer, the potential of the air electrode is lowered. Therefore, a promoter for decomposing O ₂ H ⁻ is used in the catalyst layer. Is the best. The cocatalyst for decomposing O ₂ H ⁻ is preferably manganese oxide or a mixture of manganese oxide and metal powder such as nickel, but is not limited thereto. Other than these, for example, nickel-cobalt composite oxide, phthalocyanine compounds, silver, platinum, and the like can be given. As the cocatalyst for decomposing O ₂ H ⁻ , manganese oxide is optimal in view of high catalytic activity and material cost.

  As described above, by providing an air electrode with high water repellency and a large porosity, an air battery excellent in storage characteristics and heavy load discharge characteristics can be obtained.

The present invention also provides a method for producing an air electrode for an air battery comprising a catalyst layer, a current collector, and a water repellent film.
This production method includes (1) a step of dry mixing a powdery catalyst layer constituting material and a non-polymeric fluorine compound, and (2) a mixture of a binder, a surfactant, and a dispersion medium water in the dry mixture. (3) a step of drying the wet mixture at 100 ° C. or lower and then pulverizing it; (4) a step of compression-molding the pulverized product to form a catalyst layer; A step of bonding a current collector to one surface of the catalyst layer under pressure, (6) a step of applying a water repellent material to the other surface of the catalyst layer, and heat-treating the catalyst layer at 200 ° C. or more and 300 ° C. or less. And (7) a step of bonding a water repellent film to the application surface of the catalyst layer on the water repellent material under pressure.
The dispersion medium preferably further contains an alcohol such as methanol, ethanol or isopropyl alcohol.

In this manufacturing method, first, all materials except the binder are dry-mixed in advance, thereby improving the uniform dispersibility of the materials. Non-polymeric fluorine compounds have very high water repellency and good slipperiness, so that they can be dispersed well by dry mixing, so that they are non-polymeric among the catalyst components when wet mixed with binders. Aggregation of the fluorine compound can be prevented. Furthermore, by mixing alcohol in the binders, the effect of preventing the non-polymeric fluorine compound from aggregating in the catalyst component when wet mixing is further enhanced. The mixing of the alcohol further reduces the surface tension of the dispersion medium containing the binders and improves the wettability of the dispersion medium with respect to the catalyst component and the non-polymeric fluorine compound, so that aggregation of the non-polymeric fluorine compound is less likely to occur. . After the formation of the catalyst layer, a heat treatment is performed at 200 ° C. or more and 300 ° C. or less, whereby the surfactant in the catalyst layer is removed and the porosity of the catalyst layer is improved.
Thus, according to the production method of the present invention, a catalyst layer having high water repellency and a large porosity can be formed by a simple method. Therefore, the production efficiency of the air battery can be improved without complicating the air electrode manufacturing process.

Examples of the present invention will be described below.
Example 1
(Air electrode manufacturing method)
FIG. 1 is a perspective view of a main part of an air electrode in the present embodiment. 1 is a catalyst layer, and 2 is a current collector bonded to one side thereof. A water repellent film is joined to the assembly 14 of the catalyst layer 1 and the current collector 2 to form an air electrode. The water repellent film is bonded to the side surface of the catalyst layer 1 opposite to the current collector.

The materials used for the catalyst layer 1 of the air electrode are as follows. Coconut charcoal activated carbon powder was used as the oxygen reduction catalyst. As the coconut shell activated carbon powder, a powder having a specific surface area of 1500 to 1900 m ² / g and a median diameter of 2 to 7 μm by laser diffraction / scattering particle size distribution measurement was used. The cocatalyst having an action of decomposing the oxygen reduction product was manganese oxide, and Brownox (Mn ₃ O ₄ ) manufactured by Tosoh Corporation was used. As the conductive carbon, Ketjen Black ECP manufactured by Ketjen Black International Co., Ltd. was used. As the non-polymeric fluorine compound, two types of graphite fluoride and fluoride pitch were used. As the fluorinated graphite, an off-white powder obtained by directly fluorinating natural graphite under the conditions of a reaction temperature of 600 ° C., a reaction time of 0.5 to 1 hour, and a fluorine pressure of 2.6 × 10 ⁴ Pa was used. In these fluorinated graphites, the molar composition ratio of fluorine to carbon, that is, F / C, was about 1.0, and the median diameter measured by laser diffraction / scattering type particle size distribution was 8 to 12 μm. As the fluorinated pitch, white powder obtained by directly fluorinating a coal-based pitch under the conditions of a reaction temperature of 90 ° C., a reaction time of 6 to 12 hours, and a fluorine gas flow rate of 10 μm ³ / min was used. The molar composition ratio of fluorine to carbon in these fluorinated pitches, that is, F / C, was about 1.5, and the median diameter measured by laser diffraction / scattering type particle size distribution was 10 to 20 μm.
The binder used was Polyflon D1, which is a dispersion of PTFE manufactured by Daikin Industries, Ltd. in which PTFE is dispersed in water with a surfactant.

  The above materials were mixed and kneaded according to the following procedure, and catalyst layer 1 was produced. Coconut shell activated carbon powder, manganese oxide, conductive carbon, and non-polymeric fluorine compound powder were weighed in predetermined amounts and dry mixed using a high speed mixer so that all powders were uniformly dispersed. A binder, water and, if necessary, ethanol were added to the mixed powder to obtain a wet state, and the mixed powder was stirred and kneaded while applying a shearing force. Thereafter, the kneaded product was dried at 100 ° C. for several hours to remove moisture, and pulverized using a high speed mixer to obtain a powdery catalyst mixture.

  The powdery catalyst mixture was formed into a sheet-like catalyst layer by the following procedure. The powdered catalyst mixture was supplied at a constant speed between two rolling rolls having a constant pressure to form a sheet, and then pressure-bonded to a net-like 30 mesh stainless steel current collector 2 plated with nickel. Thus, a catalyst layer-current collector assembly 14 including the sheet-like catalyst layer 1 and the current collector 2 bonded to one surface thereof was produced. The surface of the catalyst layer 1 opposite to the surface where the current collector 2 is bonded is the surface where the water repellent film is bonded. On the surface of the catalyst layer to which the water repellent film is to be bonded, a 5-fold diluted aqueous solution of Polyflon D1 was thinly applied and dried at 250 ° C. for 5 hours. The surfactant contained in the binder was decomposed and removed by high-temperature drying to leave only PTFE as a binder component.

  Through the above steps, a catalyst layer having a predetermined porosity and thickness was obtained. A water repellent film 15 made of a PTFE microporous film was bonded to the surface of the catalyst layer on which the water repellent film was to be bonded by pressing with a urethane roll so that the porosity did not change. Then, it punched and cut | disconnected to the predetermined dimension, and was set as the air electrode.

(Production method of air zinc battery)
FIG. 2 is a longitudinal sectional view of the button type zinc-air battery 10 in the present embodiment. The battery was R44 size, that is, a button shape (JIS standard) having a diameter of 11.6 mm and a height of 5.4 mm. This battery was produced as follows.

  The positive electrode case 11 is formed by press working from a 0.2 mm plate whose main material is an iron material SPCD (JIS standard) and the surface is plated with nickel. In the recess at the center of the bottom of the case 11, four through holes having a diameter of 0.5 mm are formed as the air holes 12, and the upper end has an open shape. A polyamide resin was applied to the inner peripheral surface of the side wall portion of the positive electrode case 11 for the purpose of preventing leakage of the electrolyte.

  On the inner surface of the bottom of the positive electrode case 11, an air diffusion paper 16, a catalyst layer-current collector assembly 14 bonded with a water repellent film 15, and a separator 13 are sequentially stacked. The air diffusion paper 16 is for uniformly diffusing the air taken in from the air holes 12 into the inside of the battery, and is made of a vinylon nonwoven fabric having a thickness of 0.13 mm. The water repellent film 15 has a role of supplying oxygen to the air electrode and preventing leakage of the electrolyte to the outside of the battery, and is made of a PTFE microporous film having a thickness of 0.1 mm and a porosity of 20%. The catalyst layer-current collector assembly 14 is stamped so that the end face of the current collector 2 is sharp. Therefore, the end face of the current collector 2 bites into the polyamide resin applied to the inner peripheral surface of the side wall portion of the positive electrode case 11, and the electrical connection between the current collector 2 and the positive electrode case 11 is ensured. As the separator 13, a membrane having a thickness of 0.1 mm in which a polypropylene microporous membrane subjected to hydrophilic treatment and a polypropylene nonwoven fabric were integrated by pressure bonding. A seal tape (not shown) is attached to the bottom outer surface of the positive electrode case 11 so as to close the air holes 12 when the battery is not used. By removing the seal tape from the positive electrode case 11, Oxygen enters and electromotive reaction is started.

  The zinc alloy used for the negative electrode gel 18 was produced by an atomizing method. The zinc alloy may be amalgamated with mercury, but the zinc alloy used in this example contained 60 ppm aluminum, 150 ppm bismuth, and 500 ppm indium, and was not used. In addition to these, trace amounts of inevitable impurities are also included. The particle size of the obtained powder was adjusted by classification, and a powder of 45 to 150 mesh was used. The negative electrode gel 18 is prepared by blending sodium acrylate, which is a gelling agent, and zinc alloy particles with an electrolytic solution composed of an aqueous solution containing 40 wt% potassium hydroxide and 3.5 wt% zinc oxide. . These compounding ratios were 50 parts by weight of zinc alloy and 3 parts by weight of sodium polyacrylate with respect to 100 parts by weight of the alkaline electrolyte.

  A negative electrode gel 18 is filled in a negative electrode case 17 that also serves as a negative electrode current collector. The negative electrode case 17 is combined with the positive electrode case 11 to form a battery container. The inner wall surface of the negative electrode case 17 is in electrical contact with the negative electrode gel 18 made of zinc alloy particles, while the positive electrode case 11 opening is sealed. Yes. The negative electrode case 17 is formed by press working using a three-layer clad material having a thickness of 0.2 mm made of nickel, stainless steel, and copper so that the surface in contact with the electrolyte is copper. An insulating gasket 19 made of 66 nylon is disposed between the negative electrode case 17 and the positive electrode case 11. The insulating gasket 19 is preliminarily coated with polyamide resin on the contact surface with the negative electrode case 17. Finally, the sealed button-type zinc-air battery is completed by caulking the opening of the positive electrode case 11 to the peripheral edge on the bottom side of the negative electrode case 17 via a gasket.

  In accordance with the above procedure, the mixing ratio of the catalyst layer constituting material was 35% by weight of activated carbon, 35% by weight of manganese oxide, 10% by weight of conductive carbon, 19.1% by weight of PTFE, and 0.9% by weight of fluorinated graphite. A button-type zinc-air battery was produced using an air electrode in which the weight ratio b / a of the fluorinated graphite content b to the PTFE content a was 0.05 and the porosity was 70%.

Examples 2 to 21
The batteries of Examples 2 to 21 were assembled in the same manner as in Example 1 except that the air electrode was prepared by variously changing the blending ratio of the catalyst layer constituting material and the weight ratio b / a as shown in Table 1.

In Examples 1 to 7, the ratio of the total amount of the binder and the fluorinated graphite to the catalyst layer and the porosity of the catalyst layer are constant, and the weight of the content b of the fluorinated graphite with respect to the binder content a in the catalyst layer The ratio b / a is changed.
In Examples 8 to 14, the weight ratio b / a and the porosity of the catalyst layer were made constant, and the ratio of the total amount of the binder and fluorinated graphite to the catalyst layer was changed.
In Examples 15 to 21, the weight ratio b / a and the ratio of the total amount of the binder and fluorinated graphite in the catalyst layer are constant, and the porosity of the catalyst layer is changed.

Comparative Examples 1-4
A button type air battery was produced in the same manner as in the example except that fluorinated graphite was not added to the catalyst layer.
In Comparative Examples 1 to 4, graphite fluoride is not added to the catalyst layer, the porosity of the catalyst layer is kept constant, and the PTFE content in the catalyst layer is changed.

  Composition of air electrode catalyst layer used in the battery, ratio b / a of fluorinated graphite content b to binder content a in the catalyst layer, ratio of total amount of binder and fluorinated graphite in the catalyst layer Table 1 shows the porosity of the catalyst layer.

  The batteries of Examples 1 to 21 and Comparative Examples 1 to 4 were evaluated for discharge characteristics and storage characteristics. As for the discharge characteristics, the assembled battery was continuously discharged at a constant current, and the discharge duration was measured. The discharge was performed continuously at a constant current of 2 mA and 15 mA in an environment of 20 ° C. to a final voltage of 0.9 V. The storage characteristic is that the battery with the air holes sealed is stored for 10 days in a constant temperature environment of 60 ° C., and then continuously discharged to a final voltage of 0.9 V at a constant current of 15 mA in an environment of 20 ° C. The discharge duration was measured. Table 2 shows the average values of the discharge durations of the three batteries.

Based on the results in Table 2, the effect of the present invention will be described.
In Comparative Examples 1 to 4, the non-polymeric fluorine compound was not added and the blending ratio of PTFE as a binder was changed. In the order of Comparative Examples 1 to 4, the PTFE content ratio in the catalyst layer is increased, and the blending ratio of the catalyst components in the catalyst layer, that is, activated carbon, manganese oxide, and conductive carbon is decreased. A decrease in the blending ratio of the catalyst component will deteriorate the discharge characteristics. There was a tendency for the duration in the continuous discharge at 2 mA and 15 mA constant current after assembly to decrease as the PTFE content ratio increased. On the other hand, when the duration in 15 mA constant current continuous discharge after assembly and storage at 60 ° C. for 10 days was compared, the difference tended to decrease as the PTFE content ratio increased. This is presumably because the water repellency of the catalyst layer increased due to an increase in the PTFE content ratio, and the penetration of the electrolyte into the catalyst layer during storage was suppressed.

Then, the battery which performed 15 mA continuous discharge after 60 degreeC preservation | save for 10 days of Comparative Examples 1-4 was decomposed | disassembled, the air electrode was taken out, the longitudinal cross-section of the catalyst layer was observed, and the wetness degree of the catalyst layer was investigated. As a result, in all the air electrodes of Comparative Examples 1 to 4, the electrolyte solution penetrated into the catalyst layer. In Comparative Examples 1 and 2, the electrolyte solution penetrated to the interface between the catalyst layer and the water repellent film. As described above, it is considered that the discharge duration was lowered because the electrolyte solution penetrated into the voids in the catalyst layer and the three-phase interface in the catalyst layer was remarkably reduced.
From the above results, it was confirmed that the air electrode used in Comparative Examples 1 to 4 has a high rate of penetration of the electrolyte into the catalyst layer during storage.

  In Examples 1 to 7, the ratio of the total amount of the binder and the fluorinated graphite to the catalyst layer and the porosity of the catalyst layer are constant, and the weight of the content b of the fluorinated graphite with respect to the binder content a in the catalyst layer The ratio b / a is changed. By adding fluorinated graphite to the catalyst layer, the 15 mA constant current discharge duration after assembly is equivalent to Comparative Example 1 and Comparative Example 2, and is greater than Comparative Example 3 and Comparative Example 4. When the 15 mA discharge time after storage at 60 ° C. for 10 days is compared, Examples 1 to 7 are larger than Comparative Examples 1 to 4. In Examples 1 to 7, the difference between the 15 mA discharge time after assembly and storage is small, and it is considered that the deterioration of the catalyst layer due to storage is small. In particular, in the case of Examples 2 to 6 in which the value of b / a is in the range of 0.1 to 11.5, the increase in the 15 mA discharge time after storage is larger than in Examples 1 and 7.

  From the above results, the weight ratio b / a of the graphite fluoride content b to the binder content a in the catalyst layer is preferably in the range of 0.1 to 11.5. Furthermore, in the case of Examples 3 to 5 where the value of b / a is in the range of 0.25 to 3.0, the 15 mA discharge time after storage is further increased. Therefore, the weight ratio b / a of the fluorinated graphite content b to the binder content a in the catalyst layer is optimally in the range of 0.25 to 3.0.

In Examples 8 to 14, the weight ratio b / a of the fluorinated graphite content b to the binder content a in the catalyst layer and the porosity of the catalyst layer are constant, and the total amount of the binder and fluorinated graphite is the catalyst. The ratio in the layer is changed. The 15 mA discharge time after assembly was the same in Examples 8 to 13, but Example 14 was somewhat reduced. Further, comparing the difference between the 15 mA discharge time after assembly and after storage, Example 8 shows that the difference in discharge time is larger than that in Examples 9 to 14, and the deterioration of the catalyst layer due to storage is slightly larger. It is done.
From the above results, the proportion of the total amount of binder and fluorinated graphite in the catalyst layer is preferably in the range of 5 to 50% by weight. Furthermore, in Examples 10-12, the difference of 15 mA discharge time after an assembly and a preservation | save is lose | eliminated, and when it preserve | saves at 60 degreeC for 10 days, it is thought that there is almost no deterioration of a catalyst layer. Therefore, the ratio of the total amount of binder and fluorinated graphite in the catalyst layer is optimally in the range of 20 to 45% by weight.

  In Examples 15 to 21, the weight ratio b / a of the fluorinated graphite content b to the binder content a in the catalyst layer, and the ratio of the total amount of the binder and fluorinated graphite in the catalyst layer were constant, This is a case where the porosity of the layer is changed. In Examples 16 to 21 in which the porosity of the catalyst layer is in the range of 50 to 85%, the 15 mA discharge time after assembly is longer than that in Example 15, and the greater the porosity of the catalyst layer, the more after assembly. It can be said that the discharge characteristics are improved. On the other hand, when the 15 mA discharge time after storage is compared, the degree of decrease in Example 21 is larger than that in Examples 16 to 20, and when the porosity of the catalyst layer becomes excessive, the deterioration of the catalyst layer due to storage increases. It is suggested.

From the above results, the porosity of the catalyst layer is preferably in the range of 50 to 80%. Further, in Examples 17 to 19 where the porosity of the catalyst layer is in the range of 60 to 75%, the difference between the 15 mA discharge time after assembly and storage is small, and the catalyst layer deteriorates due to storage. Is considered to be less. Therefore, the range of 60 to 75% is optimal for the porosity of the catalyst layer.
As a non-polymeric fluorine compound, it was confirmed that even when fluorinated pitch was added to the catalyst layer, the same effect as that obtained using fluorinated graphite was obtained.

  From the above results, an air battery excellent in heavy load discharge characteristics and storage characteristics can be obtained by adding a non-polymeric fluorine compound to the catalyst layer and controlling the blending amount and the porosity of the catalyst layer.

  In the air battery according to the present invention, the water repellency of the catalyst layer is improved so that the rate at which the electrolyte solution penetrates into the catalyst layer is reduced, so that the three-phase interface is stably maintained, and the heavy load discharge characteristics and the storage characteristics are excellent. . Therefore, it is useful as a power source for various electronic devices including portable devices.

It is a perspective view of the principal part of the air electrode in the Example of this invention. It is a longitudinal cross-sectional view of the button type air zinc battery in the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Catalyst layer 2 Current collector 11 Positive electrode case 12 Air hole 13 Separator 14 Catalyst layer-current collector assembly 15 Water repellent film 16 Air diffusion paper 17 Negative electrode case 18 Negative electrode gel 19 Insulating gasket

Claims (8)

  An air battery comprising an air electrode comprising a catalyst layer, a current collector, and a water repellent film, wherein the catalyst layer contains a non-polymeric fluorine compound.   The air battery according to claim 1, wherein the non-polymeric fluorine compound is graphite fluoride or fluoride pitch.   The catalyst layer includes an oxygen reduction catalyst, a cocatalyst having an action of decomposing a product by oxygen reduction, conductive carbon, and a binder, and the weight of the content b of the non-polymeric fluorine compound with respect to the content a of the binder The air battery according to claim 1, wherein the ratio (b / a) is 0.1 to 11.5.   The air battery according to claim 1, wherein the total amount of the binder and the non-polymeric fluorine compound is 5 to 50% by weight with respect to the total weight of the catalyst layer.   The air battery according to claim 1, wherein the porosity of the catalyst layer is 50 to 80%.   The air battery according to claim 3, wherein the oxygen reduction catalyst is activated carbon and the promoter manganese oxide. A method for producing an air electrode for an air battery comprising a catalyst layer, a current collector, and a water repellent film,
A step of dry-mixing an oxygen reduction catalyst, a cocatalyst having an action of decomposing a product by oxygen reduction, conductive carbon, and a non-polymeric fluorine compound;
Adding a mixture of a binder, a surfactant and water of a dispersion medium to the dry mixture and wet-mixing the mixture,
Drying the wet mixture at a temperature of 100 ° C. or lower and then crushing;
Forming the pulverized product to form a catalyst layer;
Bonding a current collector to one side of the catalyst layer under pressure;
A step of applying a water repellent material to the other surface of the catalyst layer and heat-treating at 200 ° C. to 300 ° C., and a step of bonding a water repellent film to the other surface of the catalyst layer under pressure. A method for producing an air electrode for an air battery.   The method for producing an air electrode for an air battery according to claim 7, wherein the dispersion medium further contains alcohol.

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