JP6313578B2 - Zinc alloy powder for alkaline battery, method for producing the same, and alkaline battery using the same - Google Patents

Description

The present invention provides a zinc alloy powder for an alkaline battery such as an alkaline manganese battery, which has a high discharge performance, a low gel viscosity and an excellent filling property by optimizing the surface state of the zinc alloy powder, and a method for producing the same. And an alkaline battery using the same.

There are various uses for alkaline manganese batteries, and there is a demand for improved characteristics. Accordingly, it has been desired to improve the properties of zinc alloy powder used as a negative electrode material for batteries.

In Patent Document 1, zinc atom powder for alkaline batteries is obtained by heat treating the zinc alloy powder after atomization in an inert atmosphere to obtain a bulk density ≧ 3.01 g / cm 3 and reducing the amount of hydrogen gas generated before and after discharge. Is disclosed.

JP 2006-40883 A

In addition to the conventional improvement in discharge performance, it was necessary to reduce the viscosity of the negative electrode gel in order to improve the productivity in the process of assembling the battery. Accordingly, an object of the present invention is to provide a zinc alloy powder for an alkaline battery and an alkaline battery using the same, which have improved discharge performance and a gel viscosity excellent in filling properties.

As a result of intensive studies aimed at solving the above problems, the present inventors have reached the following invention. Conventionally, the idea was to increase the surface area by introducing small particles into the voids of large particles. On the other hand, the idea of improving the bulk density by improving the sliding of the large particles and thereby improving the discharge characteristics was obtained. In addition, it was found that the gel viscosity decreases by oxidizing the surface, and a method for obtaining these simultaneously was found. That is, the zinc alloy powder is a method for producing zinc alloy powder that is subjected to a mixing process using a mixer in a gas containing oxygen, and has a bulk density of 3.0 g / cm 3 or more and an oxygen concentration of 0.04% or more. The zinc alloy powder is less than 0.10%, and is an alkaline battery using the zinc alloy powder.

In this manufacturing method, fine powder may increase and the amount of gas generation may increase significantly. Therefore, the fine powder having a particle size of 75 μm or less may be reduced to 5% or less.

The zinc alloy powder according to the present invention can improve the discharge characteristics and provide a zinc alloy powder having a low gel viscosity.

FIG. 1 is an SEM photograph of zinc alloy powder in Example 1 of the present invention. FIG. 2 is an SEM photograph of the zinc alloy powder in Comparative Example 1.

Zinc alloy powder is prepared by adding various elements such as aluminum (Al), bismuth (Bi), indium (In), lead (Pb), cadmium (Cd) to zinc (Zn) in order to improve battery characteristics. Yes. The composition of the zinc alloy powder represents the content for each element as the composition of the whole powder. In the analysis of the composition, about 50 g is taken from the whole powder to obtain an analysis sample, and the composition value (mass%, ppm) is obtained by ICP or chemical analysis. In addition, in this invention, the unit of the analysis value when there is no description in particular is mass ppm and mass%.

The zinc alloy composition in the present invention is particularly preferably a zinc alloy containing Al, Bi and In. Furthermore, it contains 50 to 150 ppm of Al, 50 to 150 ppm of Bi, and 150 to 250 ppm of In, and contains 10 ppm or less of at least one of magnesium, iron, copper, lead, nickel, cobalt, and manganese. A zinc alloy powder containing inevitable impurities and the balance being zinc. These compositions are not exact, and even if the lead content is increased instead of Bi, the same effects as the present invention may be obtained. Otherwise, the impurities may contain 0.1 to 1 ppm of at least one element selected from the group consisting of gallium, thallium, magnesium, calcium, strontium, cadmium, tin and lead. This is because there is almost no influence of an element contained in a trace amount.

The bulk density of the zinc alloy powder in the present invention is 3.0 g / cm ³ or more, more preferably 3.1 g / cm ³ or more. By increasing the bulk density as compared with the prior art, the discharge characteristics are improved.

When the zinc alloy powder for batteries is manufactured by a gas atomizing method or the like, each particle forming the powder becomes a polymorphic species. The particle shape is spherical, needle-like, flat, rod-like, or other irregular shape. Spherical shape has a long axis length / short axis length of 2 or less in the axial ratio between the major axis length and minor axis length of the particle, and has a rod ratio with an axial ratio of 2 or more, and any part of the particle If there is a protrusion on the needle, make it needle-shaped. The flat shape is a rod-like shape and has an axial ratio of 2 or more in the cross section of the particle. A shape obtained by combining these spherical, needle-like, flat, and rod-like shapes is an indeterminate shape. The axial ratio is measured by an image obtained by enlarging the zinc alloy powder with an electron microscope (SEM) at a magnification of 100 times or more. Each particle in the image is sandwiched between two parallel lines and the outer edge of the particle is sandwiched. The vertical distance (shortest distance) between the two parallel lines at the longest distance is defined as the long axis length (μm). Similarly, the length obtained from the two intersecting lines with the longest distance between the outer edges of the particles is defined as the short axis length (μm). The zinc alloy powder incorporated in the alkaline battery is in a state of being mixed with an alkaline solution, a dispersion liquid or the like. In order to obtain the potential of the alkaline battery, a chemical reaction occurs.

The mixer in the present invention refers to a device that is usually used for mixing by the convolution action due to its own weight and centrifugal force without using the shearing force due to the rotation of a blade or the like. In the present invention, it is not intended to be used for mixing but avoids a large change in the particle size distribution due to a strong shearing force, and by rubbing the powders, the surface irregularities are gradually removed and smooth, and the bulk density or TAP density Improves the surface and oxidizes the surface.

The mixer is most preferably a V-type mixer in which two cylindrical containers are connected in a V-shape, but a mixer using the same principle may be used.

The inner wall of the container of the mixer into which the zinc alloy powder is charged is preferably made of a material in which an impurity element is not easily mixed into the zinc alloy powder. For example, glass or the like can be used.

The mixing time using the mixer, the number of rotations, and the filling rate depend on the volume of the container, but can be set to, for example, 1 to 20 hours, 5 to 100 rpm, and 5 to 60%. However, it is preferable that the conditions are such that no heat is generated by mixing. It is preferable that the temperature of the mixer is measured and controlled so as to be, for example, room temperature or 30 ° C. or lower. This is because if the heat generation is large, the oxidation proceeds excessively to the inside of the zinc alloy powder, which may deteriorate the discharge characteristics.

The atmosphere at the time of mixing may be a gas containing oxygen, that is, air or a mixed gas of oxygen and a gas such as nitrogen or argon. Even if oxygen is included from the start of mixing, oxygen is included in the middle of mixing. Also good. In order to control oxidation, it is more preferable to control the amount of water.

The oxidation concentration in the present invention is a value measured by a non-diffusion infrared absorption method, and is preferably 0.04 wt% or more and less than 0.10 wt%. This is because if it is less than 0.04 wt%, it is difficult to obtain the effect of reducing the gel viscosity, and if it is 0.10 wt% or more, there is a high possibility that the discharge characteristics will deteriorate.

Since the zinc alloy powder is oxidized by the discharge of the battery, the zinc oxide concentration (ZnO concentration) of the zinc alloy powder used in the battery is useful when designing the battery. In the present invention, the oxygen concentration measured by the above non-diffusive infrared absorption method is all converted to ZnO and used as the ZnO concentration. Strictly speaking, it is necessary to consider the oxidation of In and Al present in large amounts on the surface of the zinc alloy powder, but since the absolute amount thereof is small, it is considered as the ZnO concentration.

In the treatment using the mixer of the present invention, fine powder is generated by rubbing the powders, and the particle size distribution of the fine powder is increased. If the amount of fine powder increases excessively, the gas generation rate increases. Therefore, it is preferable to reduce the amount of fine powder that has increased. In the step of reducing the amount of fine particles having a particle size of 75 μm or less, it is preferable to reduce the amount of fine particles after the reduction to 5% or less. Setting it to 0% is difficult in the particle size distribution measurement using a sieve, and it is more preferably between 1% and 5%.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the technical scope of the present invention is not limited to these descriptions.

An evaluation method for zinc alloy powder will be described first. The particle size distribution of the zinc alloy powder was measured by the mass of the powder that did not pass through each sieve using a sieve. In addition, the thing of the particle size which passes through the 200 mesh sieves, ie, the thing of the particle size of 0.075 mm or less, is described as -75 micrometers here. A particle having a particle diameter (200 to 150 mesh) that passes through a 150 mesh sieve but not through a 200 mesh sieve is denoted as 75 μm. 150 to 100 mesh is represented as 106 μm, 100 to 65 mesh is represented as 150 μm, 65 to 48 mesh is represented as 212 μm, and 48 to 35 mesh is represented as 300 μm. A particle size that does not pass through a 35 mesh sieve is denoted as 425 μm.

The bulk density of the zinc alloy powder was measured according to JIS Z2504.

The BET (specific surface area, unit m ² / g) of the zinc alloy powder is based on the BET 1-point method by the nitrogen gas replacement method.

The oxygen concentration (unit mass%) of the zinc alloy powder was measured by a non-diffusion infrared absorption method using an oxygen / nitrogen / hydrogen analyzer (ONH836 manufactured by LECO Japan). Further, assuming that all the oxygen concentration values measured as described above were zinc oxide (ZnO), the value converted to the zinc oxide weight was defined as the ZnO concentration (unit mass%) of the zinc alloy powder.

Take 5 g of each zinc alloy powder, immerse it in a solution of 3% by weight zinc oxide in 40% KOH aqueous solution, and generate gas from the amount of gas generated by holding at 60 ° C. for 3 days using the apparatus shown in FIG. The rate (μl / g · day) was determined.

For evaluation of gel viscosity and discharge characteristics of a gelled negative electrode active material containing zinc alloy powder, each zinc alloy powder, 1% by mass of polyacrylic acid, and 40% KOH aqueous solution in which 3% by mass of zinc oxide were dissolved were mixed. A gelled negative electrode active material was used.

Gel viscosity is measured using a viscometer (TVB-10U) manufactured by Toki Sangyo Co., Ltd. The above gel-like negative electrode active material (negative electrode gel) is prepared in a container with a diameter of about 7 cm and a height of about 6 cm. Place on the stage (T-BAR STAGE TS-20), insert the T-bar for measurement (bar length 5cm) into the negative electrode gel to a depth of about 7mm, and then measure the stage while rotating the T-bar at 5rpm. Was increased at a constant speed, and the viscosity when the T bar reached a depth of 15 mm of the negative electrode gel was measured. The measurement temperature was room temperature.

The discharge characteristics were evaluated by preparing an LR6-type prototype battery using the positive electrode as manganese dioxide for the above gelled negative electrode active material. The heavy load discharge (high rate pulse discharge) performance of this prototype battery was measured with 1.2 A for 3 seconds of discharge and 7 seconds of rest. When this battery was initially 1.6 V, it was continuously discharged repeatedly as described above, the discharge time up to 1.0 V was measured, and the relative value when the discharge time of Comparative Example 1 described later was taken as 100. Expressed in

(Example 1) A zinc alloy having a composition consisting of 100 ppm of aluminum, 100 ppm of bismuth and 200 ppm of indium and the balance of zinc and the balance of zinc was melted at a temperature of 500 ° C., and then trickled to 2 to 4 mm using a ceramic nozzle and dropped. Spraying was performed by injecting compressed air with air gas to obtain zinc alloy powder. Thereafter, 2 kg of this zinc alloy powder was placed in a V-type mixer having an internal volume of 2 L and a container inner wall made of glass, and subjected to a mixing process of rotating at 50 rpm for 8 hours to obtain the zinc alloy powder of Example 1. Note that the inside of the container for the mixing treatment was at room temperature and in the atmosphere. There was no temperature rise in the mixer vessel during the mixing process. (Example 2) A zinc alloy powder of Example 2 was obtained in the same manner as in Example 1 except that the mixing treatment time was 16 hours. (Example 3) After the mixing process of Example 1, a 200-mesh sieve was used to add a process of reducing fine particles having a particle size of 75 µm or less to obtain a zinc alloy powder of Example 3. (Example 4) After the mixing process of Example 2, a 200-mesh sieve was used to add a process of reducing fine particles having a particle size of 75 µm or less to obtain a zinc alloy powder of Example 4. (Comparative Example 1) A zinc alloy powder of Comparative Example 1 was obtained in the same manner as in Example 1 except that no mixing treatment was performed. (Comparative example 2) About the comparative example 1 which does not perform a mixing process, the process which sifts using a 200 mesh sieve and reduces the microparticles | fine-particles with a particle size of 75 micrometers or less was added, and the zinc alloy powder of the comparative example 2 was obtained. (Comparative Example 3) A zinc alloy having a composition consisting of 100 ppm of aluminum, 100 ppm of bismuth and 200 ppm of indium and the balance of zinc and the balance of zinc was melted at a temperature of 500 ° C., and then trickled to 2 to 4 mm using a ceramic nozzle and dropped. Spraying was performed by injecting compressed air with air gas to obtain zinc alloy powder. Thereafter, 0.5 kg of this zinc alloy powder was put in a polyethylene bag and subjected to surface oxidation treatment for 312 hours in a constant temperature and humidity chamber at 40 ° C. and 80% humidity to obtain the zinc alloy powder of Comparative Example 3. .

Table 1 shows the measurement results of the particle size distribution by sieving for Examples 1, 2, 4 and Comparative Examples 1, 3.

From the comparison between Comparative Example 1 and Example 1 and Example 2, it can be seen that when the V-type mixer is used, there is no significant difference in the particle size distribution except that the proportion of fine powder of 75 μm or less increases. Further, from the difference between Example 2 and Example 4, the ratio of fine particles having a particle size of 75 μm or less can be reduced to 5% or less by sieving using a 200 mesh sieve to reduce the fine particles having a particle size of 75 μm or less. I understand that.

Table 2 shows the results of each evaluation performed on the above Examples and Comparative Examples. In addition, about the gel viscosity and the discharge characteristic, it described with the relative value (%) on the basis of the comparative example 1. FIG.

From the results of Table 2, in Examples 1 to 4, the bulk density could be 3 or more, which was higher than that of Comparative Example 1 before the mixing treatment, and as a result, the discharge characteristics could be improved by 20%. From the results of Comparative Example 3, it can be seen that the oxidation of the surface reduces the gel viscosity. However, when the mixing treatment is used, the density of the ZnO and the oxygen concentration are increased at the same time as the bulk density is improved. done.

In addition, as described in the cited documents 1 to 3, the presence of the fine particles may improve the discharge characteristics, but when reducing the fine particles after the mixing treatment as in Example 2 and Example 4 of the present invention, It has been found that by reducing the amount of fine particles, the gas generation rate can be reduced and the gel viscosity can be reduced without reducing the discharge characteristics.

In order to investigate the surface state of the zinc alloy powder, the surface of Example 1 and Comparative Example 1 was observed using SEM. A zinc alloy powder having a particle size (75 μm of particle size distribution) that does not pass through a 150 mesh sieve sieve having a particle size distribution but passes through a 200 mesh sieve sieve was observed at 500 times. The SEM image of Example 1 is shown in FIG. 1, and the SEM image of Comparative Example 1 is shown in FIG. Since the surface of Example 1 seems to have a reduced surface pattern as compared with Comparative Example 1, it is considered that the surface became smooth.

Further, in order to investigate the depth of oxidation from the surface of the zinc alloy powder, an Auger measuring apparatus was used for Example 1 and Comparative Example 1 above, and an area having a surface diameter of 10 μm was used in the depth direction using Ar sputtering. When the analysis was performed while digging, in Comparative Example 1 where the oxygen concentration was not 0.015% by mass, oxygen was detected up to a depth of 34 nm from the surface, but the mixing treatment was performed. In Example 1 where the oxygen concentration was 0.051% by mass, oxygen was detected from the surface to a depth of 143 nm. In Comparative Example 1, Al and In peaks were observed from the surface to a depth of about 17 nm. However, in Example 1, since the peaks were not observed, Al and In on the surface diffused inside. It is thought that it was done.

Claims (7)

2. Bulk density is 3. 1 g / cm ³ or more and a zinc alloy powder for alkaline batteries, wherein the oxygen concentration is less than 0.10 wt% 0.0 6% by weight or more. The zinc alloy powder for alkaline batteries according to claim 1, wherein the ZnO concentration exceeds 0.3 mass%. 3. The zinc alloy powder for alkaline batteries according to claim 1, wherein a weight percentage of a particle size of 75 μm or less by particle size distribution measurement using a 200 mesh sieve is 5% or less. The zinc alloy powder for alkaline batteries according to any one of claims 1 to 3, comprising Al, Bi and In. An alkaline battery, wherein the zinc alloy powder for an alkaline battery according to any one of claims 1 to 4 is contained as a negative electrode active material. Alkaline battery zinc alloy powder produced by gas atomization have rows surface oxidation treatment using a mixer at a gas containing oxygen, and a bulk density of 3.1 g / cm ³ or more, the oxygen concentration is 0.06 A method for producing a zinc alloy powder for an alkaline battery, comprising obtaining a zinc alloy powder for an alkaline battery having a mass percentage of less than 0.10 mass% . The method for producing a zinc alloy powder for an alkaline battery according to claim 6 , wherein the mixer is a V-type mixer .