JP2007048737A - Alkaline battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an alkaline battery which has an excellent high load discharge property and no reduction of a low load discharge property. <P>SOLUTION: In an alkaline battery provided with a cathode mixture containing gamma manganese dioxide and lambda manganese dioxide, an anode, and alkaline electrolyte, a mass ratio of lambda manganese dioxide and gamma manganese dioxide shall be 0.5/100 or more and 4.5/100 or less and an average particle diameter of lambda manganese dioxide shall be 3μm or more and 10μm or less. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an alkaline battery including a positive electrode mixture containing gamma-type manganese dioxide and lambda-type manganese dioxide, a negative electrode, and an alkaline electrolyte.

In recent years, the use of primary batteries such as alkaline manganese batteries has been expanded, and in addition to conventional low-load discharge applications, use in devices that require high-load discharge characteristics such as digital still cameras has increased. Yes.
Therefore, the present inventors have studied the use of lambda type manganese dioxide in order to improve the high load discharge characteristics without degrading the low load discharge characteristics. For example, as in Patent Document 1 and Patent Document 2, a method is proposed in which lambda type manganese dioxide is used for the positive electrode, or gamma type manganese dioxide (represented by electrolytic manganese dioxide) and lambda type manganese dioxide are used in combination. However, in the study by the present inventors, no clear effect was observed in both low load discharge and high load discharge. Non-Patent Document 1 describes a method in which lambda type manganese dioxide is used by adding it to electrolytic manganese dioxide. However, there is no history of studying the particle size of lambda type manganese dioxide. No significant improvement in properties is shown.
US Pat. No. 6,783,893 US Patent Application Publication No. 2004/0058242 New Technologies & Medicine, Vol. 2, p. 341-348 (2001)

When a conventional lambda type manganese dioxide or a mixture of lambda type manganese dioxide and gamma type manganese dioxide is used, the high load discharge characteristics are improved. However, the lambda-type manganese dioxide particles expand at the end of discharge during low-load discharge, and the positive electrode mixture also expands accordingly, which inhibits the movement of ions in the positive electrode mixture and increases the discharge polarization. There is a problem that the low-load discharge characteristic is remarkably deteriorated. Alkaline batteries are not always used for specific applications (high load discharge devices). Therefore, when used in a conventional low load discharge device, it is very inconvenient to reduce the discharge time.
The present invention solves the above problems.

  The alkaline battery of the present invention comprises a positive electrode mixture, a negative electrode, and an alkaline electrolyte, and the positive electrode mixture contains gamma type manganese dioxide and lambda type manganese dioxide, and the weight of lambda type manganese dioxide and gamma type manganese dioxide. The ratio is 0.5 / 100 or more and 4.5 / 100 or less, and the average particle diameter of the lambda type manganese dioxide is 3 μm or more and 10 μm or less.

  According to the present invention, it is possible to obtain an alkaline battery in which a high load discharge characteristic is improved as compared with a conventional alkaline battery without reducing the low load discharge characteristic.

  The inventors have mixed lambda type manganese dioxide with gamma type manganese dioxide and used it for the positive electrode of an alkaline manganese battery, thereby reducing the electrical resistance in the positive electrode in a region where the discharge depth is relatively shallow, and high load discharge characteristics. It was found that can be improved. At this time, it was found that if the weight ratio of lambda type manganese dioxide and gamma type manganese dioxide and the average particle size of lambda type manganese dioxide are not appropriate, the discharge capacity during low-load discharge decreases.

  Therefore, the present inventors have increased the discharge capacity at the time of high-load discharge, and to suppress the decrease in discharge capacity at the time of low-load discharge, the weight ratio of lambda type manganese dioxide and gamma type manganese dioxide used for the positive electrode, Various investigations were made on the average particle size of lambda type manganese dioxide.

  As a result, in a range where the ratio of lambda type manganese dioxide to gamma type manganese dioxide is less than that in the past, and in the range where the average particle size of lambda type manganese dioxide is smaller than that in the past, the discharge capacity during low load discharge is reduced. It was suppressed, and the discharge capacity during high load discharge increased. It has been found that good results can be obtained when both the weight ratio of lambda type manganese dioxide and gamma type manganese dioxide and the average particle size of lambda type manganese dioxide satisfy the above conditions.

  When changes caused by the discharge of lambda-type manganese dioxide were examined in detail, it was found that when the discharge depth was increased, the particles of lambda-type manganese dioxide were finely cracked or cracked to cause the particles to expand. As the particles expand, the entire positive electrode mixture also expands. For this reason, the gap in the positive electrode mixture increases, so that the lack of electrolyte occurs, so-called concentration polarization increases, and it is considered that the discharge capacity is reduced. If the ratio of lambda manganese dioxide is small, the degree of capacity reduction is also small. Further, if the particle diameter of the lambda type manganese dioxide particles is small, the expansion can be absorbed in the gaps between relatively large gamma type manganese dioxide particles. Therefore, the expansion of the mixture as described above is small, and it is considered that the shortage of the electrolytic solution is unlikely to occur. In addition, since the crystal grains are small, it is also considered that the cracks of the grains due to lattice distortion due to discharge hardly occur.

  For the above reasons, good results can be obtained only when both the weight ratio of lambda type manganese dioxide and gamma type manganese dioxide and the average particle size of lambda type manganese dioxide satisfy the conditions of the present invention. . That is, the weight ratio of lambda type manganese dioxide and gamma type manganese dioxide contained in the positive electrode mixture is 0.5 / 100 or more and 4.5 / 100 or less, and the average particle size of lambda type manganese dioxide is 3 μm or more. When it is 10 μm or less, it is possible to obtain an excellent alkaline battery with improved high load discharge characteristics and no deterioration in discharge characteristics during low load discharge.

  If the weight ratio of lambda-type manganese dioxide and gamma-type manganese dioxide is less than 5/100, the characteristics of high-load discharge cannot be obtained sufficiently, and if it is more than 4.5 / 100, the discharge characteristics during low-load discharge are degraded. To do. The weight ratio of lambda type manganese dioxide to gamma type manganese dioxide is most preferably 2.0 / 100 or more and 3.5 / 100 or less because the electrical resistance of the positive electrode during discharge can be kept low.

  When the average particle diameter of the lambda type manganese dioxide is less than 3 μm, the packing density of the positive electrode mixture is remarkably lowered, and the discharge characteristics at a low load are lowered. When the average particle diameter of lambda type manganese dioxide exceeds 10 μm, discharge polarization is considered to occur due to expansion of the positive electrode mixture near the end of discharge during low-load discharge, and the discharge capacity during low-load discharge decreases. The average particle diameter of the lambda type manganese dioxide is most preferably 7 μm or more and 9 μm or less because the density of the positive electrode mixture is high and the deterioration of the low load discharge characteristics is almost eliminated.

The average particle size of manganese dioxide was measured by a laser diffraction / scattering particle size distribution measuring device (LA-920) manufactured by Horiba, Ltd.
The average particle size of gamma-type manganese dioxide is preferably 25 μm or more and 50 μm or less. This is because there is a balance from the viewpoint of the packing density of the positive electrode and the reaction area of gamma-type manganese dioxide.

The molar ratio Li / Mn between Li and Mn contained in the lambda type manganese dioxide is preferably 0.03 or more and 0.20 or less. If it is within this range, lambda type manganese dioxide is considered to discharge with higher efficiency.
For the alkaline electrolyte used in the alkaline battery of the present invention, an aqueous solution containing KOH as a main component and containing ZnO is used. In particular, the KOH concentration is preferably 34 wt% to 40 wt%, and the ZnO concentration is preferably 2 wt% to 10 wt%. Moreover, sodium hydroxide, lithium hydroxide, or calcium hydroxide may be included.

  An alloy powder containing zinc as a main component is preferably used for the negative electrode. Usually, a gelled negative electrode formed by mixing the alloy solution with a gelling agent such as sodium polyacrylate is used. The negative electrode active material may be any metal that exhibits a base potential in an alkaline aqueous solution, can be discharged and is stable, and is added with other metals or organic or inorganic additives for corrosion resistance and stability. It may be what you did.

  The gamma-type manganese dioxide used as the positive electrode active material in the present invention is defined as a mixed crystal of a ramsdellite phase and a pyrolsite phase (rutile structure). Electrolytic manganese dioxide synthesized by electrolysis corresponds to this. Some natural manganese dioxide and chemically synthesized chemical manganese dioxide belong to gamma-type manganese dioxide. Of these, electrolytic manganese dioxide is preferred.

  The average particle diameter of gamma-type manganese dioxide is preferably 25 μm to 50 μm from the viewpoint of increasing the packing density of the positive electrode. The positive electrode mixture may contain other metal peroxides such as nickel oxyhydroxide, metal oxides, and metal hydroxides. In addition, it is preferable to use artificial graphite powder in the range of 4 to 8% by weight in the positive electrode mixture as the conductive agent of the positive electrode mixture, but natural graphite, expanded graphite, and other carbon-based conductive agents may also be included. Good.

For the separator, a non-woven fabric containing alkali-resistant rayon, pulp, or the like is used, but a non-woven fabric or porous film made of resin may be used.
As the form of the battery, an AA (LR6 type) cylindrical shape is most effective. For the exterior, a nickel-plated steel cylindrical case is used. The size and shape of the battery are not limited to this, and the case material may be resin.

Lambda-type manganese dioxide is obtained by treating lithium manganese spinel approximately represented by the general formula LiMn ₂ O ₄ with an acid as described in US Pat. No. 4,246,253, Li _{x It} is preferable to use an oxide approximated by Mn ₂ O ₄ . A spinel-like compound in which a spinel structure and another manganese oxide structure are mixed may be used.

More specific embodiments of the present invention will be described in detail below.
(1) Preparation of Lambda-type Manganese Dioxide Electrolytic manganese dioxide (HTHF manufactured by Tosoh Corp.) and lithium carbonate (Deer Special Grade manufactured by Kanto Chemical Co., Ltd.) pulverized and sized so as to have an average particle size of 8 μm. Lithium manganese spinel as a precursor of lambda type manganese dioxide was obtained by mixing at a molar ratio of Li / Mn of 0.55 and firing in air at 950 ° C. for 20 hours. This was lightly pulverized using a mortar to break up the agglomeration, and then classified with a sieve to adjust the particle size to 15 μm or less.

  100 g of the lithium manganese spinel powder thus obtained was put into 200 ml of distilled water, and 500 ml of 2N sulfuric acid was slowly poured while stirring with a screw at room temperature. After stirring for 1 hour, the powder was collected from the sulfuric acid reaction solution using a Buchner funnel and filter paper, and the powder was washed with distilled water. The obtained powder was dried at 100 ° C., pulverized with a porcelain mortar to break up the agglomeration, and classified with a sieve to obtain lambda type manganese dioxide having an average particle size of 8.2 μm. The molar ratio Li / Mn in this lambda type manganese dioxide was 0.12.

(2) Preparation of positive electrode mixture Electrolytic manganese dioxide (NTA manufactured by Delta) having an average particle diameter of 36 μm was used as gamma-type manganese dioxide. This manganese dioxide and the lambda type manganese dioxide obtained in (1) were mixed in the ratio shown in Table 1, and artificial graphite (SP20 manufactured by Nippon Graphite Co., Ltd.) 6.5 was added to 100 parts by weight of the mixture. A part by weight was added and mixed with a mixer to obtain a positive electrode mixture.

(3) Preparation of positive electrode pellet The positive electrode mixture obtained above was pressure-formed into a hollow cylindrical shape using a mold.
(4) Preparation of gelled negative electrode The electrolytic solution and sodium polyacrylate as a gelling agent were mixed at a weight ratio of 100: 3 to obtain a gelled electrolytic solution. This gel electrolyte and zinc alloy powder were mixed at a weight ratio of 1: 2 to obtain a gelled negative electrode. As the electrolytic solution, an aqueous solution containing 37% by weight of potassium hydroxide and 3% by weight of zinc oxide was used.

(5) Assembly of alkaline battery An AA alkaline battery having the structure shown in FIG. 1 was prepared according to the following procedure. Two pieces of the positive electrode pellets obtained above were inserted into the battery case 1, and the positive electrode mixture 2 was remolded with a pressure jig and adhered to the inner wall of the battery case 1. Next, a bottomed cylindrical separator 4 was placed in the center of the positive electrode mixture 2 placed in the battery case 1, and a predetermined amount of the same electrolyte solution was injected into the separator 4. After a predetermined time had elapsed, the gelled negative electrode 3 obtained above was filled inside the separator 4. For the separator 4, a non-woven fabric mainly composed of polyvinyl alcohol fiber and rayon fiber was used.

  Subsequently, a negative electrode current collector 6 was inserted into the center of the gelled negative electrode 3. The negative electrode current collector 6 is previously integrated with a gasket 5 and a bottom plate 7 that also serves as a negative electrode terminal. Next, the opening end portion of the battery case 1 was caulked to the peripheral edge portion of the bottom plate 7 via the end portion of the gasket 5 to seal the opening portion of the battery case 1. Finally, the outer surface of the battery case 1 was covered with the exterior label 8 to obtain an alkaline battery (battery 1).

  Furthermore, the weight ratio of lambda type manganese dioxide and gamma type manganese dioxide, the average particle size of lambda type manganese dioxide, the average particle size of gamma type manganese dioxide, and the molar ratio Li / Mn in lambda type manganese dioxide are shown in Table 1 Batteries 2 to 19 were produced in the same manner as the battery 1 except that the values shown in Table 4 were used.

  Adjustment of the molar ratio Li / Mn in the lambda type manganese dioxide was performed by changing the input amount of sulfuric acid described in (1) in the battery 1 described above. Increasing the amount of sulfuric acid decreases the molar ratio Li / Mn, and decreasing the amount of sulfuric acid increases the molar ratio Li / Mn.

  On the other hand, as a comparative example, Comparative Battery 1 was produced in the same manner as Battery 1 except that the positive electrode mixture was a mixture of gamma-type manganese dioxide and artificial graphite and did not contain lambda-type manganese dioxide.

Further, Table 1 to Table 1 show the weight ratio of lambda type manganese dioxide to gamma type manganese dioxide, the average particle size of lambda type manganese dioxide, the average particle size of gamma type manganese dioxide, and the Li / Mn ratio in lambda type manganese dioxide. Comparative battery 2 to comparative battery 8 were produced in the same manner as battery 1 except that the values shown in FIG. The total amount of lambda type manganese dioxide (λ-MnO ₂ ) and gamma type manganese dioxide (γ-MnO ₂ ) in batteries 1 to 19 and comparative batteries 1 to 8 is the same.

(Battery evaluation)
Each of the above batteries was allowed to stand at room temperature for 10 days after fabrication, and then evaluated as follows.
(1) High-load discharge characteristics Battery discharge was repeated for 10 cycles (5 minutes in total) with an operation of discharging at 1500 mW for 2 seconds and then at 500 mW for 28 seconds (total 5 minutes), and then repeated for 55 minutes (total 1 hour). The discharge time until the voltage reached 1.05 V was measured.

(2) Low-load discharge characteristics The discharge time until the battery voltage reached 0.9 V at a current of 100 mA was measured.
All the above evaluations were performed in an environment of 20 ° C. The discharge time of each battery was expressed as an index with respect to 100 as the discharge time of the comparative battery 1.

From the above results, the following can be understood.
The batteries of the examples all have improved high-load discharge characteristics as compared to conventional alkaline batteries that do not use lambda type manganese dioxide as the positive electrode. The high-load discharge characteristic is an index of 110 or more, and it is considered that the effect is clearly shown. Moreover, the batteries of all the examples have a low load discharge characteristic of 99 or more, and it is considered that there is almost no capacity deterioration.

  Since the ratio of the lambda type manganese dioxide to the gamma type manganese dioxide is too small in the comparative battery 2, the high load discharge characteristics are not improved so much. Since the ratio of the lambda type manganese dioxide to the gamma type manganese dioxide is too large in the comparative battery 3, the low load discharge capacity is significantly reduced. Further, in the comparative battery 4, the ratio of lambda type manganese dioxide / gamma type manganese dioxide is as large as 10/100, and the deterioration of the low load discharge characteristics is remarkable. This is considered to be due to the fact that when the positive electrode mixture expands at the end of discharge, the amount of lambda-type manganese dioxide is excessive, thereby inhibiting the movement of the electrolyte. In addition, the relatively small improvement in the high-load discharge characteristics is considered to have already started to cause the above-mentioned adverse effects due to the expansion of the positive electrode mixture from the time of high-load discharge with a relatively low positive electrode utilization rate. Furthermore, since the comparative battery 5 uses lambda type manganese dioxide having a large average particle diameter and has a large ratio to gamma type manganese dioxide, the above tendency is more remarkable.

  On the other hand, in the comparative battery 6, since the average particle diameter of the lambda type manganese dioxide is too small, the filling property of the positive electrode mixture is lowered and the low load discharge characteristic is lowered. In Comparative Battery 7, since the average particle size of lambda type manganese dioxide is too large, it is considered that the positive electrode mixture expanded at the end of discharge, and the low-load discharge characteristics are deteriorated. Since the comparative battery 8 has a larger average particle diameter of lambda type manganese dioxide, the tendency is remarkable.

  As is clear from the above, according to the present invention, it is possible to suppress a decrease in discharge characteristics due to expansion of the positive electrode mixture at the end of discharge during low load discharge, and to obtain high discharge characteristics during high load discharge.

  As described above, since the alkaline battery of the present invention is excellent in high load discharge characteristics and does not deteriorate in low load discharge characteristics, a wide range of devices using alkaline batteries from the beginning, including electronic devices such as digital cameras. Is preferably used.

It is the front view which made a part of alkaline battery in one example of the present invention a section.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Battery case 2 Positive electrode mixture 3 Gel-like negative electrode 4 Separator 5 Gasket 6 Negative electrode current collector 7 Bottom plate 8 Exterior label

Claims (5)

  A positive electrode mixture containing gamma-type manganese dioxide and lambda-type manganese dioxide, a negative electrode, and an alkaline electrolyte, wherein the weight ratio of the lambda-type manganese dioxide to the gamma-type manganese dioxide is 0.5 / 100 or more and 4.5 / 100. An alkaline battery in which the average particle diameter of lambda-type manganese dioxide is 3 μm or more and 10 μm or less. The weight ratio of the lambda type manganese dioxide and gamma type manganese dioxide is:
2. The alkaline battery according to claim 1, wherein the alkaline battery is 2.0 / 100 or more and 3.5 / 100 or less.   The alkaline battery according to claim 1 or 2, wherein an average particle diameter of the lambda type manganese dioxide is 7 µm or more and 9 µm or less.   The alkaline battery according to claim 1, wherein the gamma-type manganese dioxide has an average particle size of 25 μm or more and 50 μm or less.   The alkaline battery according to claim 1, wherein a molar ratio Li / Mn contained in the lambda type manganese dioxide is 0.03 or more and 0.20 or less.

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