JP2008071541A - Alkaline battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an alkaline battery excelling in a load characteristic while keeping excellent electrolyte leakage resistance. <P>SOLUTION: A positive electrode part 2 is formed into a hollow cylindrical shape, and is structured such that a positive electrode pellet formed by molding a positive electrode mix into a hollow cylindrical shape is arranged inside a positive electrode can 1. Positive electrode mix density after molding the positive electrode mix before battery assemblage is 2.90-3.20 g/cm<SP>3</SP>; a moisture amount containing the positive electrode mix after the battery assemblage is 6.0-8.0 wt.% with respect to the weight of the positive electrode mix containing an electrolyte after the battery assembly; the average particle diameter of graphite is 10-50 μm; and apparent density of graphite is 0.01-0.05 g/cm<SP>3</SP>. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an alkaline battery, and more particularly to an alkaline battery having excellent load resistance while having good liquid leakage resistance.

  In recent years, alkaline batteries are increasingly used in electronic devices such as digital cameras that require large currents, and there is a need for improved load characteristics. In many electronic devices, there is a lower limit on the operable voltage, and the device is designed to turn off when the discharge voltage of the battery falls below that voltage.

  In a device that requires a large current, a voltage drop (hereinafter referred to as iR drop as appropriate) due to internal resistance is large during discharge, so that there is still enough active material that can be discharged. In most cases, the discharge voltage of the battery falls below the minimum operating voltage of the device and the device stops.

  One of the methods for reducing the above-mentioned iR drop in a large current discharge is to allow the reaction at the positive electrode to proceed smoothly. For example, the following method has been proposed. . In either method, the battery system or the positive electrode contains a large amount of moisture consumed by the positive electrode reaction during discharge in advance, so that the reaction at the positive electrode proceeds smoothly.

  For example, as a method of simply increasing the water content of the entire battery system, an increase in the amount of electrolyte in the negative electrode zinc gel or the positive electrode mixture, or an increase in the amount of electrolyte impregnated in the separator can be considered. As described, it has been proposed that the water content of the entire battery system be 0.947 g to 1.146 g per 1 AH of theoretical discharge capacity of manganese dioxide. When converted to the amount per 1 g of the positive electrode active material, 0.292 g to 0.353 g of water is added to this amount of water, which is compared with the amount of water required for the discharge reaction of 1 g of manganese dioxide (0.207 g). It is quite a large value.

JP 2001-68121 A

  Further, for example, as described in Patent Document 2, as a method of adding more water to the positive electrode without increasing the water content of the battery system, A method has been proposed in which a concentration difference is made between the solution concentration, the concentration of the electrolyte in the negative electrode gel, and the concentration of the electrolyte impregnated in the separator.

JP 2005-203380 A

  However, in the method proposed in Patent Document 1, since the moisture inside the battery is large, the volume of the gap is small, and liquid leakage due to gas generation is likely to occur.

  In addition, in the method proposed in Patent Document 2, although the moisture in the electrolyte injected into the gel and the separator after the battery production once moves to the positive electrode due to the concentration gradient, the electrolyte distribution in the battery with the passage of time. Since it becomes uniform, there remains a question as to whether a large amount of moisture can be retained in the positive electrode in the long term.

Furthermore, Patent Document 1 and Patent Document 2 have been described in terms of the positive electrode mixture density, its value, Patent Document 1 ^{3.1g / cm 3 ~3.4g / cm 3} , Patent Document 2 3. and ^{2g / cm 3 ~3.35g / cm 3} , merely set forth the scope of the positive electrode mixture density have been used in general conventionally, nor particularly plus twist with respect positive electrode mixture density.

  Accordingly, an object of the present invention is to provide an alkaline battery containing, as a main component, at least one of manganese dioxide and nickel oxyhydroxide as a positive electrode active material, while maintaining good liquid leakage resistance and improving load characteristics. The object is to provide an excellent alkaline battery.

  In order to solve the above-mentioned problems, the inventors of the present application have conducted earnest studies focusing on the fact that the positive electrode reaction has a great influence on the battery characteristics during large current discharge. By making the density of the battery lower than before and including more electrolyte in the voids in the positive electrode mixture, substantially without reducing the void volume in the battery, that is, without risk of leakage It was found that the load characteristics can be improved. In addition, in order to prevent an increase in contact resistance and a decrease in the form stability of the positive electrode mixture due to a decrease in the positive electrode density, the particle size is larger than that of conventional graphite used in the positive electrode mixture. It has been found that graphite having a small apparent density may be used.

That is, in order to solve the above-described problem, the present invention
A positive electrode mixture comprising at least one of manganese dioxide and nickel oxyhydroxide and graphite;
The positive electrode mixture density after forming the positive electrode mixture before battery assembly is in the range of 2.90 g / cm ^{3 to} 3.20 g / cm ³ ,
The amount of water contained in the positive electrode mixture after battery assembly is in the range of 6.0 wt% to 8.0 wt% with respect to the weight of the positive electrode mixture containing the electrolyte solution after battery assembly,
The average particle size of the graphite is in the range of 10 μm to 50 μm,
Apparent density of the graphite is an alkali battery, which is a range of ^{0.01g / cm 3 ~0.05g / cm 3} .

In the present invention, the density of the positive electrode mixture in the battery is selected in the range of 2.90 g / cm ^{3 to} 3.20 g / cm ³ . The amount of water contained in the positive electrode mixture after battery assembly is selected within the range of 6.0 wt% to 8.0 wt% with respect to the weight of the positive electrode mixture including the electrolyte solution after battery assembly. As a result, it is possible to realize a battery that is excellent in both leakage resistance and load characteristics while the amount of the positive electrode mixture is substantially reduced. If the positive electrode mixture density and the moisture content contained in the positive electrode mixture deviate from the above upper limit and lower limit ranges, both the leakage resistance characteristics and the load characteristics are impaired.

Further, in this invention, in a range the average particle size is 10 m to 50 m, and an apparent density containing graphite in the range of 0.01g / cm ³ ~0.05g / cm ³ in the positive electrode mixture . Thereby, when the positive electrode mixture density is in the range of 2.90 g / cm ^{3 to} 3.20 g / cm ^3, an increase in resistance due to a decrease in the contact area between the positive electrode mixture and the positive electrode can, Strength reduction can be prevented. If the average density of the graphite deviates from the above upper limit and lower limit ranges, an increase in resistance due to a decrease in the contact area between the positive electrode mixture and the positive electrode can and a decrease in the strength of the positive electrode mixture are caused.

  According to the present invention, excellent load characteristics can be obtained while maintaining good leakage resistance.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a configuration example of an alkaline battery according to an embodiment of the present invention. This alkaline battery is, for example, an AA cylindrical alkaline battery.

  This battery includes a positive electrode can 1, a positive electrode portion 2, a separator 3, a negative electrode mixture 4, a sealing member 5, a washer 6, a negative electrode terminal plate 7, and a current collector 8.

  The positive electrode can 1 has, for example, iron plated with nickel and serves as an external positive electrode terminal of the battery. The positive electrode portion 2 has a hollow cylindrical shape, and is configured such that a positive electrode pellet obtained by forming a positive electrode mixture into a hollow cylindrical shape is disposed inside the positive electrode can 1.

The positive electrode mixture contains at least one of manganese dioxide and nickel oxyhydroxide as an active material, potassium hydroxide as an electrolytic solution, an average particle diameter of 10 μm to 50 μm, and an apparent density of 0.01 g / cm. ^It contains graphite selected in the range of ^{3 to} 0.05 g / cm ³ . In addition, the positive electrode mixture was selected so that the positive electrode mixture density after forming the positive electrode mixture before battery assembly was in the range of 2.90 g / cm ^{3 to} 3.20 g / cm ³ . Further, the positive electrode mixture is one in which the amount of water contained in the positive electrode mixture after battery assembly is selected within the range of 6.0 wt% to 8.0 wt%.

The positive electrode mixture retains the electrolyte in the voids present in the mixture and discharges while consuming H ₂ O in the electrolyte. In the conventional alkaline battery, during a large current discharge, there is a tendency that the diffusion resistance in the positive electrode increases and the discharge voltage decreases due to the lack of H ₂ O around the positive electrode active material.

Therefore, in one embodiment, the density of the positive electrode mixture after forming the positive electrode mixture before assembling the battery is selected in the range of 2.90 g / cm ^{3 to} 3.20 g / cm ³ . The range of the density of the positive electrode mixture is selected to be a range relatively smaller than the conventional one (for example, 3.1 g / cm ^{3 to} 3.4 g / cm ³ ). More electrolyte solution can be retained even with an apparent volume similar to that of a conventional positive electrode. Therefore, even if H ₂ O in the positive electrode mixture is rapidly consumed during heavy load discharge, the positive electrode reaction proceeds smoothly because H ₂ O necessary for the positive electrode reaction is sufficiently present around the positive electrode active material, and the internal resistance As a result, there is little increase in the discharge voltage, and the decrease in the discharge voltage is small.

  However, when the density of the positive electrode mixture is selected in a range that is relatively smaller than the conventional one, the contact resistance between the positive electrode can 1 and the positive electrode mixture increases due to the decrease in the contact area between the positive electrode can and the positive electrode mixture, IR drop in large current discharge increases and discharge characteristics tend to deteriorate. In addition, since the density of the positive electrode mixture is weak because the density is low and the shape of the positive electrode mixture in the battery tends to collapse during storage of the battery, the proportion of the positive electrode mixture that can be conductive is reduced and the discharge characteristics are reduced. Tend to.

  Therefore, in one embodiment of the present invention, graphite is included in the positive electrode mixture. Thereby, the fall of a discharge characteristic can be prevented.

The effect of containing graphite is effective when the density of the positive electrode mixture before battery assembly is selected within the above range (2.90 g / cm ^{3 to} 3.20 g / cm ³ ). This is because if the density of the positive electrode mixture is smaller than 2.9 g / cm ^3, it is difficult to prevent a decrease in discharge characteristics due to a decrease in the density of the positive electrode mixture even if graphite is used. If the density of the positive electrode mixture is larger than 3.2 g / cm ³ , since there are few voids in the positive electrode mixture, the amount of electrolyte that can be held is small, and there is a large amount of electrolyte that is not absorbed by the positive electrode and the separator 3. This is because, in the negative electrode gel injection step, problems such as the electrolyte jumping out of the positive electrode can occur.

  As the graphite, a material having a small apparent density and a small particle size is used although the apparent density is small. Examples of such graphite include highly exfoliated graphite. Since such graphite has a small apparent density, it can be dispersed extremely uniformly in the positive electrode mixture. Moreover, since the particle size is not so small, the contact between the adjacent graphite particles in the positive electrode mixture is good and the electrical conductivity is high. Therefore, even if the density of the positive electrode mixture is made smaller than before and the contact area with the positive electrode can slightly decreases, the contact resistance between the positive electrode mixture and the positive electrode can does not increase compared to the conventional alkaline battery. .

  Further, this graphite has a function as a binder between the positive electrode active materials in addition to a function as a conductive agent. Since this graphite can be dispersed very uniformly in the positive electrode mixture, the density of the positive electrode mixture after molding is high, and the strength can be supplemented even if the density of the positive electrode mixture is made smaller than before.

Specifically, the average particle diameter of 10 m to 50 m, and an apparent density used graphite chosen in the range of ^{0.01g / cm 3 ~0.05g / cm 3} .

This is because if the average particle size of the graphite is smaller than 10 μm, the contact between the graphite and the positive electrode active material is deteriorated, and the discharge characteristics are deteriorated. This is because if the average particle diameter of graphite is larger than 50 μm, the contact between the graphite and the positive electrode active material is similarly deteriorated and the discharge characteristics are deteriorated. If the apparent density of the graphite is less than 0.01 g / cm ³ , the handling property at the time of mixing the positive electrode material is difficult, and if it exceeds 0.05 g / cm ³ , the dispersibility in the positive electrode mixture is not so good. is there.

  From the point which can acquire the more outstanding characteristic, a graphite is 5 wt%-10 wt% with respect to the total weight of the positive mix containing manganese dioxide and nickel oxyhydroxide, a graphite, and the potassium hydroxide solution which is electrolyte solution. % Is preferably blended within the range of%. If the amount is less than 5 wt%, sufficient conductivity cannot be obtained. If the amount is more than 10 wt%, the amount of manganese dioxide or nickel oxyhydroxide, which is a positive electrode active material, is relatively reduced. Because it ends up.

  Further, according to one embodiment of the present invention, the amount of water contained in the positive electrode mixture after battery assembly is selected to be 6.0 wt% to 8.0 wt%. In a conventional alkaline battery, the amount of water contained in the positive electrode mixture after battery assembly is about 5 with respect to the weight of the positive electrode mixture including the amount of electrolyte contained in the positive electrode mixture, assuming that no leakage occurs. It was necessary to be 7 wt% or less.

On the other hand, in one embodiment of the present invention, the density of the positive electrode mixture is selected within the range (2.90 g / cm ^{3 to} 3.20 g / cm ³ ) that is relatively lower than the conventional density. Since there are more voids inside, even with the same apparent volume as the positive electrode mixture used in the conventional alkaline battery, more electrolytic solution can be retained and more than 5.7 wt% water can be contained.

  For example, if the moisture content after battery assembly is less than 6.0 wt%, the voids in the positive electrode mixture cannot be completely filled with the electrolytic solution, so the discharge reaction at the positive electrode does not proceed smoothly and the discharge characteristics deteriorate. . Also, if the water content after battery assembly is more than 8.0 wt%, the shape of the positive electrode mixture will be lost during storage, and the proportion of the positive electrode mixture in contact will be reduced, resulting in reduced discharge characteristics. It tends to end up.

  The separator 3 has a hollow cylindrical shape with a bottom, and is disposed inside the positive electrode part 2. The negative electrode mixture 4 is composed of granular zinc (Zn) serving as a negative electrode active material, an electrolytic solution using potassium hydroxide (KOH), and the negative electrode mixture 4 is gelled to uniformly disperse the granular zinc and the electrolytic solution. And a gelling agent for storing.

  A sealing member 5 for sealing the opening is fitted into the opening of the positive electrode can 1 in which the positive electrode 2 and the separator 3 filled with the negative electrode mixture 4 are housed. The sealing member 5 is made of plastic, and a washer 6 and a negative electrode terminal plate 7 are attached so as to cover the sealing member 5.

  In the through hole of the sealing member 5 to which the washer 6 is attached, for example, a current collector 8 in which tin is plated on brass is press-fitted from above. Current collection for the negative electrode is ensured by reaching the negative electrode mixture 4 by pressing a nail-like current collector 8 bonded to the negative electrode terminal plate 7 into a through-hole formed in the central portion of the sealing member 5. Yes. Moreover, the current collection of the positive electrode is ensured by connecting the positive electrode part 2 and the positive electrode can 1. The outer peripheral surface of the positive electrode can 1 is covered with an exterior label (not shown), and the positive electrode terminal is located below the positive electrode can 1.

An example of a method for manufacturing an alkaline battery according to an embodiment of the present invention will be described. First, the inside of the positive electrode can 1, a positive electrode active material, the average particle size of 10 m to 50 m, and apparent density was chosen in the range of 0.01g / cm ³ ~0.05g / cm ³ of graphite, electrolytic The positive electrode pellet which shape | molded the positive mix containing the potassium hydroxide aqueous solution which is a liquid in the shape of a hollow cylinder is arrange | positioned.

  Next, after providing the bottomed cylindrical separator 3 in the hollow part of the positive electrode pellet, an alkaline electrolyte is injected into the positive electrode can 1 to wet the positive electrode pellet and the separator 3. Next, the gelled negative electrode mixture 4 is filled inside the separator 3.

  Next, after the sealing member 5, the washer 6, and the negative electrode terminal plate 7 are attached in advance to the current collector 8, the current collector 8 is inserted into the center of the negative electrode mixture 4. Next, the opening end of the positive electrode can 1 is sealed by caulking the opening end portion of the positive electrode can 1 to the peripheral edge portion of the negative electrode terminal plate 7 via the peripheral edge portion of the sealing member 5. Next, the outer surface of the positive electrode can 1 is covered with an exterior label (not shown). As described above, an alkaline battery according to an embodiment of the present invention can be manufactured.

  A specific embodiment of the present invention will be described with reference to FIG. However, the present invention is not limited to these examples.

<Example 1>
A positive electrode mixture obtained by mixing manganese dioxide, graphite having an average particle diameter of 10 μm, an apparent density of 0.01 g / cm ³ , and a potassium hydroxide aqueous solution so that the blending ratio of graphite is 5 wt% is hollow. Molded into a cylindrical shape to obtain a positive electrode pellet. Here, when the density of the positive electrode mixture after molding was measured, it was 2.90 g / cm ³ . The positive electrode mixture density was measured by dividing the weight of the obtained positive electrode mixture by the volume of the positive electrode mixture calculated from the inner diameter, the outer shape, and the height dimension. The average particle diameter of graphite was measured by a laser scattering method. The apparent density of graphite was measured by a stationary method.

  Next, a plurality of the obtained positive electrode pellets were arranged inside the positive electrode can 1. Next, after the bottomed cylindrical separator 3 was provided in the hollow portion of the pellet, an alkaline electrolyte was injected into the positive electrode can 1 to wet the positive electrode pellet and the separator 3.

  Next, the gelled negative electrode mixture 4 was filled inside the separator 3. The negative electrode mixture 4 was obtained by mixing granular zinc, a gelling agent, and an aqueous potassium hydroxide solution.

  Next, after the sealing member 5, the washer 6, and the negative electrode terminal plate 7 are attached to the current collector 8 in advance, the current collector 8 is inserted into the center of the negative electrode mixture 4, and then the positive electrode can 1 is opened. The opening of the positive electrode can 1 was sealed by caulking the end portion to the peripheral edge portion of the negative electrode terminal plate 7 via the peripheral edge portion of the sealing member 5. Thus, the alkaline battery of Example 1 was produced.

  In addition, the alkaline battery of Example 1 was disassembled, the positive electrode mixture containing the electrolytic solution was taken out, dried at 107 ° C. for 2 hours, and the reduced weight was used as the amount of water contained in the positive electrode mixture after battery assembly. The weight percent concentration was calculated based on the positive electrode mixture containing the liquid. For the three alkaline batteries, the concentration was calculated as the weight percent concentration with respect to the positive electrode mixture containing the electrolytic solution, and the average value was taken as the amount of water contained in the positive electrode mixture after the battery assembly of Example 1; Was 6.0 wt%.

<Example 2>
Graphite having an average particle size of 10 μm and an apparent density of 0.03 g / cm ³ is used at a blending ratio of 6 wt%, the positive electrode mixture density is 3.05 g / cm ³ , and the moisture content contained in the positive electrode mixture after battery assembly is 7.0 wt. The alkaline battery of Example 2 was produced in the same manner as in Example 1 except that the positive electrode mixture was prepared so as to be%.

<Example 3>
The average particle size of 10 [mu] m, using a graphite apparent density 0.05 g / cm ³ at the mixing ratio 7 wt%, 8.0 wt moisture content comprising a positive electrode mixture density 3.20 g / cm ^3, the positive electrode mixture after battery assembly The alkaline battery of Example 3 was made in the same manner as Example 1 except that the positive electrode mixture was prepared so as to be%.

<Example 4>
Graphite having an average particle size of 30 μm and an apparent density of 0.01 g / cm ³ is used at a blending rate of 5 wt%, the positive electrode mixture density is 3.05 g / cm ³ , and the moisture content contained in the positive electrode mixture after battery assembly is 8.0 wt. An alkaline battery of Example 4 was produced in the same manner as in Example 1 except that the positive electrode mixture was prepared so as to be%.

<Example 5>
Graphite having an average particle size of 30 μm and an apparent density of 0.03 g / cm ³ is used at a blending ratio of 6 wt%, the positive electrode mixture density is 3.20 g / cm ³ , and the moisture content contained in the positive electrode mixture after battery assembly is 6.0 wt. The alkaline battery of Example 5 was produced in the same manner as Example 1 except that the positive electrode mixture was prepared so that the content of the positive electrode mixture was 5%.

<Example 6>
Graphite having an average particle size of 30 μm and an apparent density of 0.05 g / cm ³ is used at a blending rate of 7 wt%, the positive electrode mixture density is 2.90 g / cm ³ , and the moisture content contained in the positive electrode mixture after battery assembly is 7.0 wt. The alkaline battery of Example 6 was made in the same manner as Example 1 except that the positive electrode mixture was prepared so as to be%.

<Example 7>
Graphite having an average particle size of 50 μm and an apparent density of 0.01 g / cm ³ is used at a blending rate of 5 wt%, the positive electrode mixture density is 3.20 g / cm ³ , and the moisture content contained in the positive electrode mixture after battery assembly is 7.0 wt. An alkaline battery of Example 7 was produced in the same manner as in Example 1 except that the positive electrode mixture was prepared so as to be%.

<Example 8>
Graphite having an average particle size of 50 μm and an apparent density of 0.03 g / cm ³ is used at a blending ratio of 6 wt%, the positive electrode mixture density is 2.90 g / cm ³ , and the moisture content contained in the positive electrode mixture after battery assembly is 8.0 wt. An alkaline battery of Example 8 was produced in the same manner as in Example 1 except that the positive electrode mixture was prepared so as to be%.

<Example 9>
Graphite having an average particle size of 50 μm and an apparent density of 0.05 g / cm ³ is used at a blending rate of 7 wt%, the positive electrode mixture density is 3.05 g / cm ³ , and the moisture content contained in the positive electrode mixture after battery assembly is 6.0 wt. The alkaline battery of Example 9 was made in the same manner as Example 1 except that the positive electrode mixture was prepared so as to be%.

<Example 10>
Graphite having an average particle size of 30 μm and an apparent density of 0.03 g / cm ³ is used at a blending rate of 4 wt%, the positive electrode mixture density is 3.05 g / cm ³ , and the moisture content contained in the positive electrode mixture after battery assembly is 7.0 wt. An alkaline battery of Example 10 was produced in the same manner as in Example 1 except that the positive electrode mixture was prepared so as to be%.

<Example 11>
Graphite having an average particle size of 30 μm and an apparent density of 0.03 g / cm ³ is used at a blending rate of 11 wt%, the positive electrode mixture density is 3.05 g / cm ³ , and the moisture content contained in the positive electrode mixture after battery assembly is 7.0 wt. An alkaline battery of Example 11 was produced in the same manner as in Example 1 except that the positive electrode mixture was prepared so as to be%.

<Comparative Example 1>
Graphite having an average particle size of 9 μm and an apparent density of 0.03 g / cm ³ is used at a compounding ratio of 6 wt%, the positive electrode mixture density is 2.85 g / cm ³ , and the moisture content contained in the positive electrode mixture after battery assembly is 5.0 wt. An alkaline battery of Comparative Example 1 was produced in the same manner as in Example 1 except that the positive electrode mixture was prepared so as to be%.

<Comparative example 2>
Graphite having an average particle size of 30 μm and an apparent density of 0.1 g / cm ³ is used at a blending rate of 8 wt%, the positive electrode mixture density is 2.85 g / cm ³ , and the moisture content contained in the positive electrode mixture after battery assembly is 7.0 wt. An alkaline battery of Comparative Example 2 was produced in the same manner as in Example 1 except that the positive electrode mixture was prepared so as to be%.

<Comparative Example 3>
Graphite having an average particle size of 55 μm and an apparent density of 0.06 g / cm ³ is used at a blending rate of 7 wt%, the positive electrode mixture density is 2.85 g / cm ³ , and the moisture content contained in the positive electrode mixture after battery assembly is 9.0 wt. An alkaline battery of Comparative Example 3 was produced in the same manner as in Example 1 except that the positive electrode mixture was prepared so as to be%.

<Comparative Example 4>
Graphite having an average particle size of 55 μm and an apparent density of 0.1 g / cm ³ is used at a compounding rate of 9 wt%, the positive electrode mixture density is 3.05 g / cm ³ , and the moisture content contained in the positive electrode mixture after battery assembly is 5.0 wt. An alkaline battery of Comparative Example 4 was produced in the same manner as in Example 1 except that the positive electrode mixture was prepared so as to be%.

<Comparative Example 5>
Graphite having an average particle size of 9 μm and an apparent density of 0.06 g / cm ³ is used at a blending rate of 7 wt%, the positive electrode mixture density is 3.05 g / cm ³ , and the moisture content contained in the positive electrode mixture after battery assembly is 7.0 wt. An alkaline battery of Comparative Example 5 was produced in the same manner as in Example 1 except that the positive electrode mixture was prepared so as to be%.

<Comparative Example 6>
Graphite having an average particle size of 30 μm and an apparent density of 0.03 g / cm ³ is used at a compounding ratio of 8 wt%, the positive electrode mixture density is 3.05 g / cm ³ , and the moisture content contained in the positive electrode mixture after battery assembly is 9.0 wt. An alkaline battery of Comparative Example 6 was produced in the same manner as in Example 1 except that the positive electrode mixture was prepared so as to be%.

<Comparative Example 7>
Graphite having an average particle size of 30 μm and an apparent density of 0.06 g / cm ³ is used at a blending ratio of 6 wt%, the positive electrode mixture density is 3.25 g / cm ³ , and the moisture content contained in the positive electrode mixture after battery assembly is 5.0 wt. An alkaline battery of Comparative Example 7 was produced in the same manner as in Example 1 except that the positive electrode mixture was prepared so as to be%.

<Comparative Example 8>
Graphite having an average particle size of 55 μm and an apparent density of 0.03 g / cm ³ is used at a compounding rate of 9 wt%, the positive electrode mixture density is 3.25 g / cm ³ , and the moisture content contained in the positive electrode mixture after battery assembly is 7.0 wt. An alkaline battery of Comparative Example 8 was produced in the same manner as in Example 1 except that the positive electrode mixture was prepared so as to be%.

<Comparative Example 9>
Graphite having an average particle size of 12 μm and an apparent density of 0.08 g / cm ³ is used at a blending rate of 7 wt%, the positive electrode mixture density is 3.25 g / cm ³ , and the moisture content contained in the positive electrode mixture after battery assembly is 6.0 wt. An alkaline battery of Comparative Example 9 was produced in the same manner as in Example 1 except that the positive electrode mixture was prepared so as to be%.

<Comparative Example 10>
Graphite having an average particle diameter of 5 μm and an apparent density of 0.03 g / cm ³ is used at a blending rate of 7 wt%, the positive electrode mixture density is 3.05 g / cm ³ , and the moisture content contained in the positive electrode mixture after battery assembly is 7.0 wt. The alkaline battery of Comparative Example 10 was produced in the same manner as in Example 1 except that the positive electrode mixture was prepared so as to be%.

<Comparative Example 11>
Graphite having an average particle size of 55 μm and an apparent density of 0.03 g / cm ³ is used at a compounding ratio of 8 wt%, the positive electrode mixture density is 3.05 g / cm ³ , and the moisture content contained in the positive electrode mixture after battery assembly is 7.0 wt. An alkaline battery of Comparative Example 11 was produced in the same manner as in Example 1 except that the positive electrode mixture was prepared so as to be%.

<Comparative Example 12>
Graphite having an average particle size of 30 μm and an apparent density of 0.005 g / cm ³ is used at a blending ratio of 6 wt%, the positive electrode mixture density is 3.05 g / cm ³ , and the moisture content contained in the positive electrode mixture after battery assembly is 7.0 wt. An alkaline battery of Comparative Example 12 was produced in the same manner as in Example 1 except that the positive electrode mixture was prepared so as to be%.

<Comparative Example 13>
Graphite having an average particle size of 30 μm and an apparent density of 0.1 g / cm ³ is used at a blending rate of 8 wt%, the positive electrode mixture density is 3.05 g / cm ³ , and the moisture content contained in the positive electrode mixture after battery assembly is 7.0 wt. An alkaline battery of Comparative Example 13 was produced in the same manner as in Example 1 except that the positive electrode mixture was prepared so as to be%.

<Comparative example 14>
Graphite having an average particle size of 30 μm and an apparent density of 0.03 g / cm ³ is used at a blending rate of 7 wt%, the positive electrode mixture density is 2.85 g / cm ³ , and the moisture content contained in the positive electrode mixture after battery assembly is 7.0 wt. An alkaline battery of Comparative Example 14 was produced in the same manner as in Example 1 except that the positive electrode mixture was prepared so as to be%.

<Comparative Example 15>
Graphite having an average particle size of 30 μm and an apparent density of 0.03 g / cm ³ is used at a blending rate of 7 wt%, the positive electrode mixture density is 3.25 g / cm ³ , and the moisture content contained in the positive electrode mixture after battery assembly is 7.0 wt. An alkaline battery of Comparative Example 15 was produced in the same manner as in Example 1 except that the positive electrode mixture was prepared so as to be%.

<Comparative Example 16>
Graphite having an average particle size of 30 μm and an apparent density of 0.03 g / cm ³ is used at a blending rate of 7 wt%, the positive electrode mixture density is 3.05 g / cm ³ , and the moisture content contained in the positive electrode mixture after battery assembly is 5.0 wt. An alkaline battery of Comparative Example 16 was produced in the same manner as in Example 1 except that the positive electrode mixture was prepared so as to be%.

<Comparative Example 17>
Graphite having an average particle size of 30 μm and an apparent density of 0.03 g / cm ³ is used at a blending rate of 7 wt%, the positive electrode mixture density is 3.05 g / cm ³ , and the moisture content contained in the positive electrode mixture after battery assembly is 9.0 wt. An alkaline battery of Comparative Example 17 was produced in the same manner as in Example 1 except that the positive electrode mixture was prepared so as to be%.

Evaluation of discharge characteristics The discharge characteristics in large current discharge were evaluated based on the number of shots when an alkaline battery was mounted on a digital still camera S-40 manufactured by SONY and shot under an ambient temperature of 25 ° C. and CIPA conditions. The CIPA condition is that zoom (one direction) → one shot (alternately with or without flash) is repeated a total of 10 times at 30-second intervals, with an appropriate pause (power OFF) time for each 10 shots. Repeated test conditions. The number of photographs taken when the digital still camera was turned off was counted. For each of the examples and comparative examples, the test was repeated three times under the same conditions, and the discharge characteristics were evaluated by the average value of the counted number of shots.

Evaluation of Storage Stability The alkaline battery was left under the condition of 60 ° C. dry and evaluated by the number of photographs taken with a digital still camera after 20 days. When the number of shots after storage was 90% or more of the number of shots before storage, the evaluation was ○, and when it was less than 90%, the evaluation was ×.

Leakage occurrence rate when undischarged 20 alkaline batteries in a temperature environment of 60 ° C. and a relative humidity of 90% H. The liquid leakage occurrence rate was calculated by the following equation by determining the presence or absence of leakage after 10 days.
“Leakage occurrence rate” = (“number of batteries in which leakage occurred” / 20) × 100 (%)

Leakage occurrence rate during overdischarge 20 alkaline batteries were discharged to 40V to 0.1 V to be overdischarged and left in a temperature environment of 60 ° C. to determine the presence or absence of leakage after 10 days. . The leakage occurrence rate was calculated by the following formula.
“Leakage occurrence rate” = (“number of batteries in which leakage occurred” / 20) × 100 (%)

  The measurement results and evaluations of Examples 1 to 11 are shown in Table 1. The measurement results and evaluation of Comparative Examples 1 to 17 are shown in Table 2.

  Here, Comparative Example 9 in Table 2 is a conventional alkaline dry battery assuming the current specification. The liquid leakage resistance and storage characteristics were good, the electrolyte did not pop out in the gel filling process, and the number of photographs taken with a digital still camera was 123.

As shown in Table 1 and Table 2, in the alkaline batteries of Examples 1 to 11, the positive electrode mixture density after the positive electrode mixture molding before battery assembly was 2.90 g / cm ^{3 to} 3.20 g / cm ^3. In addition, the amount of water contained in the positive electrode mixture after battery assembly is selected within the range of 6.0 wt% to 8.0 wt% with respect to the weight of the positive electrode mixture including the electrolytic solution. The leak occurrence rate was 0%, and the leak-proof characteristics were good.

Further, the alkaline battery of Example 1 to Example 9, an average particle diameter of 10 m to 50 m, and an apparent density of graphite in the positive electrode mixture is in the range of 0.01g / cm ³ ~0.05g / cm ³ since comprising, if the positive electrode mixture density is in the conventional (e.g., ^{3.1g / cm 3 ~3.4g / cm 3} ) than the relatively low range ^{(2.90g / cm 3 ~3.20g / cm} 3 However, since the contact resistance between the positive electrode mixture and the positive electrode can 1 does not increase, the number of photographs taken with a digital still camera can be increased as compared with the alkaline battery of Comparative Example 9 assuming the current specification. In the alkaline battery of Example 11, the blending ratio of graphite is 4 wt%, and in the alkaline battery of Example 12, the blending ratio of graphite is 11 wt%. The number of shots decreased slightly.

Furthermore, in the alkaline battery of Example 1 to Example 11, the average particle diameter of 10 m to 50 m, the graphite and the apparent density is in the range of ^{0.01g / cm 3 ~0.05g / cm 3} , the positive electrode mixture The storage stability is also good, and even after storage for 20 days in a 60 ° C temperature environment, 90% of the number of shots taken with a digital still camera before storage. The above number of images could be taken and the storage stability was good.

Further, in Comparative Example 1 to Comparative Example 5, since the average particle diameter of the graphite is 10 m to 50 m, and an apparent density does not satisfy the range of ^{0.01g / cm 3 ~0.05g / cm 3} , storage stability It got worse. Further, in Comparative Example 1 to Comparative Example 6, the number of shots in the digital still cameras, within an average particle size of 10 m to 50 m, and an apparent density of 0.01g / cm ³ ~0.05g / cm ³ range There was a decrease from Examples 1 to 11 using graphite as the inner layer.

Furthermore, in Comparative Example 1 to Comparative Example 3 in which the positive electrode mixture density is smaller than 2.9 g / cm ³ , even if the moisture content in the positive electrode mixture is adjusted within the range of 5.0 wt% to 9.0 wt%, The number of photographs taken by the digital still camera was smaller than that of Comparative Example 9 assuming the current specification. Furthermore, in Comparative Example 3, since the amount of water in the positive electrode mixture was 9.0 wt%, which was higher than 8.0 wt%, liquid leakage occurred.

Furthermore, in Comparative Example 4 to Comparative Example 6 in which the positive electrode mixture density is 3.05 g / cm ³ , the moisture content included in the positive electrode mixture after battery assembly is compared with the positive electrode mixture including the electrolytic solution. Even in the case of 5.0 wt% in Example 4, 7.0 wt% in Comparative Example 5, and 9.0 wt% in Comparative Example 6, the number of shots of the digital still camera is the same as or greater than that in Comparative Example 9 assuming the current specifications. It was. Among them, in Comparative Example 6, the number of photographs taken with the digital still camera was the largest, but the amount of water in the positive electrode mixture was 9.0 wt%, which was more than 8.0 wt%, and thus liquid leakage occurred.

Furthermore, in Comparative Example 7, the positive electrode mixture after the battery assembly contains 5.0 wt%, which is less than 6.0 wt%. Therefore, no leakage occurs, but the number of photographs taken by the digital still camera is small. It was. Further, in Comparative Example 8, the amount of water was more than 6.0 wt%, and thus liquid leakage occurred. In Comparative Example 9, although the water content is 6.0 wt%, since it is 3.25 g / cm ³ which the positive electrode mixture density exceeding 3.2 g / cm ^3, leakage occurs.

In Comparative Example 10 and Comparative Example 11, the positive electrode mixture density is in the range of 2.90 g / cm ^{3 to} 3.20 g / cm ³ , and the water content in the positive electrode mixture is in the range of 6.0 wt% to 8.0 wt%. among them, although the apparent density of the graphite is in the range of ^{0.01g / cm 3 ~0.05g / cm 3} , an average particle diameter of the graphite Comparative example 10 in 5 [mu] m, a 55μm Comparative example 11, 10 m to Since it is outside the range of 50 μm, the contact between graphite in the positive electrode mixture or between graphite and the positive electrode active material is poor, and the number of shots of the digital still camera is almost the same as in Comparative Example 9 assuming the current specification. It was.

In Comparative Example 12 and Comparative Example 13, the positive electrode mixture density is in the range of 2.90 g / cm ^{3 to} 3.20 g / cm ³ , and the water content in the positive electrode mixture is in the range of 6.0 wt% to 8.0 wt%. among them, the average particle size of the graphite is in the range of 10 m to 50 m, apparent density of the graphite is a 0.005 g / cm ³ Comparative example 12, since less than 0.01 g / cm ^3, a positive electrode material mixture Because of its poor handling, it was not suitable for mass production. Further, a apparent density of the graphite Comparative Example 13 In 0.1 g / cm ^3, since larger 0.05 g / cm ^3, poor load characteristics dispersibility of graphite hardly changed as compared with the conventional.

In Comparative Example 14 and Comparative Example 15, the water content in the positive electrode mixture is in the range of 6.0 wt% to 8.0 wt%, the average particle diameter of graphite is 10 μm to 50 μm, and the apparent density of graphite is 0.01 g / cm. ³ is a range of ~0.05g / cm ^3, a 2.85 g / cm ³ in the positive electrode mixture density Comparative example 14, since less than 2.9 g / cm ^3, the positive electrode can 1 during storage As a result, the storage characteristics deteriorated. Moreover, since the positive electrode mixture density was 3.25 g / cm ³ in Comparative Example 15 and larger than 3.20 g / cm ³ , the positive electrode filling amount increased, the void amount decreased, and liquid leakage occurred. . Furthermore, in Comparative Example 15, the electrolyte solution injected into the separator 3 was not sufficiently absorbed by the positive electrode, so that the electrolyte solution jumped out of the battery during the gel filling process, resulting in large variations in product characteristics.

In Comparative Example 16 and Comparative Example 17, the density of the positive electrode mixture is 2.90 g / cm ^{3 to} 3.20 g / cm ³ , the average particle diameter of graphite is 10 μm to 50 μm, and the apparent density of graphite is 0.01 g / cm ³ to Although it is within the range of 0.05 g / cm ^3, the amount of water in the positive electrode mixture is 5.0 wt% in Comparative Example 16 and less than 6.0 wt%, so that the water necessary for the positive electrode reaction is not sufficient. The load characteristics were almost the same as the conventional products. In addition, in Comparative Example 17, the amount of water in the positive electrode mixture was 9.0 wt%, which is larger than 8.0 wt%. Therefore, the number of digital still cameras is larger than the conventional one, but liquid leakage is likely to occur. .

Although not shown in the table, in Comparative Examples 7 to 9 and Comparative Example 15 in which the positive electrode mixture density is 3.25 g / cm ³ , when a large amount of electrolytic solution is injected into the separator 3, In the process of injecting the negative electrode mixture 4, a phenomenon that the electrolyte solution jumped out occurred.

As described above, in an alkaline battery including a positive electrode mixture containing at least one of manganese dioxide and nickel oxyhydroxide as a positive electrode active material and containing graphite as a conductive agent, the density after forming the positive electrode mixture before battery assembly Is in the range of 2.90 g / cm ^{3 to} 3.20 g / cm ^{3, and} the amount of water contained in the positive electrode mixture after assembling the battery is 6.0 wt% to 8. wt% with respect to the weight of the positive electrode mixture including the electrolytic solution. in the range of 0 wt%, in the range the average particle size of the graphite is 10 m to 50 m, that the apparent density of the graphite is selected in the range of ^{0.01g / cm 3 ~0.05g / cm 3} , excellent leakage-resistance And heavy load characteristics can be obtained. Moreover, it turned out that the graphite mixture rate has the preferable within the range of 5 wt%-10 wt%.

  The present invention is not limited to the above-described embodiments of the present invention, and various modifications and applications are possible without departing from the spirit of the present invention. For example, in the embodiment, a cylindrical alkaline battery has been described. However, the present invention is not limited to this, and can be applied to other shapes such as a flat shape and a square shape.

It is sectional drawing which shows the structural example of the alkaline battery by one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Positive electrode can 2 ... Positive electrode part 3 ... Separator 4 ... Negative electrode mixture 5 ... Sealing member 6 ... Washer 7 ... Negative electrode terminal board 8 ... Current collector

Claims (3)

A positive electrode mixture comprising at least one of manganese dioxide and nickel oxyhydroxide and graphite;
The positive electrode mixture density after forming the positive electrode mixture before battery assembly is in the range of 2.90 g / cm ^{3 to} 3.20 g / cm ³ ,
The amount of water contained in the positive electrode mixture after battery assembly is in the range of 6.0 wt% to 8.0 wt% with respect to the weight of the positive electrode mixture containing the electrolyte solution after battery assembly,
The average particle size of the graphite is in the range of 10 μm to 50 μm,
The apparent density of the graphite, alkaline batteries, characterized in that it is in the range of ^{0.01g / cm 3 ~0.05g / cm 3} . 2. The alkaline battery according to claim 1, wherein the graphite is made into a thin piece. 2. The alkaline battery according to claim 1, wherein the graphite is blended in a range of 5 wt% to 10 wt% with respect to the positive electrode mixture.

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