JP2008004356A - Zinc alkaline battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a zinc alkaline battery which has solved a problem that discharge reaction of a negative electrode is hindered when a conventional organic anticorrosive is used, and excellent discharge characteristics and leakage resistance performance are realized at the same time. <P>SOLUTION: The zinc alkaline battery which contains an anionic compound having one kind or more of trifluoro-methyl group selected from a group of CF<SB>3</SB>-SO<SB>3</SB>X, CF<SB>3</SB>-O-SO<SB>3</SB>X, CF<SB>3</SB>-COOX, CF<SB>3</SB>-O-PO<SB>3</SB>X<SB>2</SB>(X is H or Na, K) in a negative electrode is manufactured. It is preferable that adding amount of the anticorrosive is 0.02-0.4 wt.% to the zinc or zinc alloy of the negative electrode active material. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a zinc-alkaline battery using zinc as a negative electrode active material, an alkaline aqueous solution as an electrolytic solution, manganese dioxide, nickel oxyhydroxide or the like as a positive electrode active material.

  Zinc alkaline batteries represented by alkaline manganese batteries are widely used as a power source for various devices because they are versatile and inexpensive. In such a zinc alkaline battery, an amorphous zinc powder produced by a gas atomizing method or the like is used as a negative electrode active material.

Zinc is an amphoteric metal and is easily corroded in an alkaline electrolyte to generate hydrogen gas, which causes an increase in battery internal pressure and leakage. Therefore, it can be said that the anticorrosion technology of zinc is a key for improving the reliability of the zinc alkaline battery. In the old days, anticorrosion techniques were adopted to amalgamate the surface of zinc powder by adding mercury into the negative electrode to increase the hydrogen overvoltage, but in order to increase environmental awareness, alkaline manganese dry batteries were installed around 1980-1990. At the center, anhydrous silver has progressed. And as a corrosion protection technique which replaces this, many contents such as the following (1) to (3) have been proposed, and currently, batteries are produced using zinc negative electrodes obtained by variously combining them. (1) When producing zinc powder, a small amount of aluminum, bismuth, indium or the like is contained in zinc to obtain a zinc alloy powder having excellent corrosion resistance (see, for example, Patent Document 1).
(2) An inorganic anticorrosive agent such as indium hydroxide or bismuth hydroxide is added to the electrolyte solution of the negative electrode (see, for example, Patent Documents 2 and 3).
(3) Various surfactants (organic anticorrosives) are added to the negative electrode electrolyte (see, for example, Patent Documents 4 to 7).
JP-A-5-166507 JP-A 48-77332 Japanese Patent No. 2606480 Japanese Patent No. 2737230 Japanese Patent No. 2737232 Japanese Patent No. 2737233 Japanese Patent No. 2770396

  Among the anticorrosion techniques (1) to (3) described above, the mechanism when a surfactant (organic anticorrosive) is added to the negative electrode electrolyte is that the hydrophilic groups of the surfactant molecules are adsorbed on the zinc surface. And it is thought that it is an effect which forms a protective film layer because a hydrophobic group orientates to the electrolyte solution side. The water repellent action of the protective coating layer prevents water or hydroxide ions from approaching the zinc surface, and the reactions of the following formulas (1) and (2) are suppressed.

Zn + 4OH ⁻ → Zn (OH) ₄ ²⁻ + 2e ⁻ (1)
2H ₂ O + 2e ⁻ → 2OH ⁻ + H ₂ (2)
On the other hand, the adsorbed surfactant molecules are dispersed from the surface of the zinc particles and diffused into the electrolytic solution when the negative electrode is discharged.

However, since the surfactants known in Patent Documents 4 to 7 and the like have a large number of carbon atoms in the hydrophobic group and have high water repellency, they have a strong tendency to be expelled from the electrolyte side and are strongly adsorbed on the zinc surface. Furthermore, since the molecular size of the surfactant is large, the diffusion rate into the electrolytic solution is also slow. For this reason, in a zinc alkaline battery in which a conventional surfactant is added to the negative electrode,
There was a problem that the discrete / diffusion of the surfactant molecules from the zinc surface could not follow, and the electrode reaction shown in the formula (1) was hindered, and the closed circuit voltage (CCV) of the battery was greatly reduced.

  In addition, since conventional surfactants are easy to foam, when added to the negative electrode, the density decreases and the amount of negative electrode active material decreases, so the discharge performance is inevitably reduced. There was also.

In view of the above problems, the present invention provides the negative electrode with CF ₃ —SO ₃ X, CF ₃ —O—SO ₃ X, CF ₃ —COOX, CF ₃ —O—PO ₃ X ₂ (where X is H or A zinc-alkaline battery containing an anionic compound having one or more trifluoromethyl groups selected from the group of Na, K).

  As a result of intensive studies by the present inventors on the above-mentioned problems, when an anionic compound (surfactant) having a trifluoromethyl group is used as the anticorrosive for the negative electrode, a trifluoromethyl having a hydrophobic group is used. The size and water repellency of the base are suitable for maintaining the balance between the formation of the protective coating layer on the zinc surface and the absorption / desorption for the discrete during discharge, and since the molecular size of the surfactant is small, It has been found that the diffusion rate is high, and a high anti-corrosion effect can be obtained while maintaining sufficient high-current discharge performance.

  Furthermore, an anionic compound having a trifluoromethyl group has an effect of suppressing a decrease in density of the negative electrode because the foaming property is weaker than that of a surfactant used in a conventional alkaline battery.

  According to the present invention, even when a negative electrode containing an organic anticorrosive (surfactant) is used, gas generation can be effectively suppressed without hindering the discharge reaction. A zinc-alkaline battery having both liquid performance can be obtained.

In the present invention, the negative electrode is selected from the group consisting of CF ₃ —SO ₃ X, CF ₃ —O—SO ₃ X, CF ₃ —COOX, and CF ₃ —O—PO ₃ X ₂ (where X is H or Na, K). A zinc-alkaline battery containing an anionic compound having one or more trifluoromethyl groups selected from:

  By using an anionic compound (surfactant) having a trifluoromethyl group as the anticorrosive for the negative electrode, the balance between the formation of the protective coating layer on the zinc surface and the absorption / desorption for the discrete during discharge is suitably maintained. In addition, since the surfactant size is small, the diffusion rate at the time of discharging is also high, so that a battery having excellent leakage resistance can be obtained without impairing the large current discharging performance. In that case, it is preferable that the addition amount of an anticorrosive agent is 0.02 to 0.5 weight% with respect to the zinc or zinc alloy in a negative electrode. When the addition amount of the anticorrosive agent is less than 0.02% by weight with respect to zinc or zinc alloy as the negative electrode active material, it becomes difficult to obtain a sufficient anticorrosive effect, while it exceeds 0.5% by weight. If it becomes, it will cause the fall of discharge performance. From these points, the addition amount of the anticorrosive is most preferably in the range of 0.02 to 0.5% by weight with respect to zinc or zinc alloy.

Examples of the present invention will be described in detail below.
(Zinc negative electrode adjustment)
A zinc alloy powder containing Al: 0.003% by weight, Bi: 0.02% by weight, and In: 0.01% by weight is prepared by a gas atomization method, and the particle size range is 35-30 by classification with a sieve.
The ratio of fine powder of 0 mesh and 200 mesh (75 μm) or less was adjusted to be 30%, and this was used as a zinc alloy powder for evaluation.

  Next, as preparation of the gelled negative electrode for constituting an alkaline battery, first, 2.3 parts by weight of polyacrylic acid was added to 100 parts by weight of 36% by weight aqueous potassium hydroxide solution (containing 2% by weight of ZnO in the aqueous solution). Sodium acid was added and mixed to gel. The obtained gel electrolyte was then allowed to stand for 24 hours and aged sufficiently. And the zinc alloy powder for evaluation 1.8 times in weight ratio with respect to the predetermined amount of this gel electrolyte solution, and the surfactant (Tokyo Chemical Industry Co., Ltd.) shown in (1) to (16) in Table 1 And the mixture was sufficiently mixed to prepare gelled negative electrodes (1) to (16) corresponding to the respective surfactants. Here, the addition amount of the surfactant was adjusted to 0.05% by weight with respect to the zinc alloy powder for evaluation.

Further, a comparative gelled negative electrode (17) in which only the zinc alloy powder for evaluation 1.8 times by weight with respect to a predetermined amount of the gelled electrolyte solution was added and no surfactant was added was also produced.
(Production of alkaline manganese batteries)
Subsequently, an alkaline manganese dry battery was produced. FIG. 1 is a front view, partly in section, of an alkaline manganese battery used in the present invention. The positive electrode case 1 is made of a nickel-plated steel plate. A graphite coating film 2 is formed inside the positive electrode case 1. A plurality of short cylindrical positive electrode mixture pellets 3 containing manganese dioxide as a main component are inserted into the positive electrode case 1 and are re-pressurized in the case to be brought into close contact with the inner surface of the case 1. Then, after the separator 4 and the bottom paper 5 for insulation are inserted inside the positive electrode mixture pellet 3, an electrolytic solution is injected for the purpose of wetting the separator 4 and the positive electrode mixture pellet 3. As the electrolytic solution, a potassium hydroxide aqueous solution of about 30 to 40% by weight is used. After the injection, the gelled negative electrode 6 is filled inside the separator 4. Next, the negative electrode current collector 10 integrated with the resin sealing plate 7, the bottom plate 8 also serving as the negative electrode terminal, and the insulating washer 9 is inserted into the gelled negative electrode 6. Then, the opening end portion of the positive electrode case 1 is caulked to the peripheral edge portion of the bottom plate 8 via the end portion of the sealing plate 7, thereby closely contacting the opening portion of the positive electrode case 1. Next, the outer label 11 is coated on the outer surface of the positive electrode case 1. Thus, an alkaline manganese battery is completed.

  In this embodiment, electrolytic manganese dioxide and graphite are blended at a weight ratio of 94: 6, and after mixing 1 part by weight of the electrolyte with 100 parts by weight of the mixed powder, the mixture is stirred and mixed uniformly with a mixer. And sized to a certain particle size. The obtained granular material is pressure-molded into a hollow cylindrical shape to form a positive electrode mixture, and after inserting a separator and bottom paper, an electrolyte solution (36 wt% potassium hydroxide aqueous solution containing 2 wt% ZnO) is injected. Then, the gelled negative electrode (1) was filled to assemble an AA size alkaline manganese dry battery (1) shown in FIG.

In addition, the same as described above except that the gelled negative electrodes (2) to (17) are used instead of the gelled negative electrode (1), the AA alkaline manganese batteries (AA size) corresponding to the respective gelled negative electrodes ( 2) to (17) were prepared.
(Evaluation of alkaline manganese batteries)
The following (1) to (3) were evaluated for the 17 types of alkaline manganese dry batteries produced above.
(1) CCV measurement at 1Ω connection: 1 cell produced above was connected to a resistance of 1Ω for 100 milliseconds in an atmosphere of 20 ° C., and the closed circuit voltage (CCV) was measured with an oscilloscope. As a representative example, the measurement results of the batteries (1), (5), and (17) are shown in FIG. Compared with the battery (17) to which no surfactant was added, the battery (1) shows almost the same CCV behavior, but in the battery (5), a rapid CCV decrease is observed in the initial stage. Such a difference is presumed to be determined by whether or not the surfactant molecules in the gelled negative electrode can be smoothly dispersed and diffused from the zinc surface during discharge. The lowest voltage that each battery reached during the 1Ω connection (100 milliseconds) was read and listed in Table 2. The number of tests was n = 3 and the average value was shown.
(2) DSC pulse discharge characteristics: A cycle in which 1 cell produced above was discharged at 20 ° C. with a constant power of 650 mW for 28 seconds and then pulsed with a constant power of 1500 mW for 2 seconds. The number of cycles was measured repeatedly until the lower limit voltage of the discharge reached 1.05V. The results were obtained with the number of tests n = 3, and the average values are shown in Table 2. This discharge pattern is intended for use with a digital still camera (DSC). The state in which a 650 mW discharge is turned on to drive a liquid crystal monitor or the like, and the state in which a 1500 mW discharge is taken with a camera flash. Each is simulated.
(3) Leakage resistance test: 50 cells (undischarged state) of each of the batteries prepared above were stored for 2 weeks in an environment of 80 ° C., and the occurrence index (%) of the leakage was obtained from the number of leaked batteries. It was. The results are shown in Table 1.

負極にトリフルオロメチル基（ＣＦ₃）を有するアニオン性化合物を添加した電池（１）〜（４）は、界面活性剤を添加していない電池（１７）と比較して、１Ω接続時のＣＣＶ低下が殆ど無く、また、高レベルのＤＳＣパルス特性を維持し、なお且つ、耐漏液性能については格段に向上している。これに対して、ペンタフルオロエチル基（Ｃ₂Ｆ₅）を有するアニオン性化合物を添加した電池（５）〜（８）では、耐漏液性能は向上するが、１Ω接続時のＣＣＶ低下が大きく、ＤＳＣパルス特性も低下している。

Batteries (1) to (4) to which an anionic compound having a trifluoromethyl group (CF ₃ ) is added to the negative electrode have a CCV at the time of 1Ω connection as compared with the battery (17) to which no surfactant is added. There is almost no decrease, a high level of DSC pulse characteristics is maintained, and the leakage resistance performance is remarkably improved. On the other hand, in the batteries (5) to (8) to which an anionic compound having a pentafluoroethyl group (C ₂ F ₅ ) is added, the leakage resistance performance is improved, but the CCV drop when connecting 1Ω is large, DSC pulse characteristics are also degraded.

  A possible cause of such a difference is the difference in water repellency of the hydrophobic group. Since the pentafluoroethyl group has higher water repellency than the trifluoromethyl group, it tends to be expelled from the electrolyte side at the electrolyte / zinc interface. That is, the adsorption to the zinc surface becomes strong. Furthermore, since the size of the surfactant is larger for the pentafluoroethyl group-containing compound, the diffusion rate in the electrolytic solution is slower. For this reason, in the battery in which the pentafluoroethyl group-containing compounds (5) to (8) are added to the negative electrode, the discrete / diffusion of the surfactant molecules from the zinc surface can be sufficiently followed during the instantaneous high-current discharge. It is presumed that the surfactant molecules hindered the discharge reaction, resulting in a decrease in CCV and a decrease in DSC pulse characteristics.

  On the other hand, in the trifluoromethyl group-containing compounds (1) to (4), the size and water repellency of the trifluoromethyl group are such that the formation of the protective coating layer on the zinc surface and the absorption / dissipation for the discrete during discharge It is suitable for keeping the balance of desorption, and since the surfactant size is small and the discrete (diffusion) speed at the time of discharge is high, it seems that a high anticorrosive effect was obtained while maintaining a sufficiently high current discharge performance. .

On the other hand, in the systems (9) to (16) to which an anionic compound having a methyl group (CH ₃ ) or an ethyl group (C ₂ H ₅ ) is added, no CCV reduction or DSC pulse characteristics are observed. The leakage resistance cannot be improved. This is presumably because the hydrophobicity of methyl and ethyl groups, which are poor in water repellency, does not function as a sufficient protective coating layer against corrosion even if these surfactants adsorb on the zinc surface.

  As described above, in a zinc alkaline battery using an anionic compound having a trifluoromethyl group as an anticorrosive for the negative electrode, the anticorrosive effectively suppresses only gas generation without inhibiting the discharge reaction. Thus, a battery having both excellent discharge characteristics and leak-proof performance can be obtained.

  Here, the amount of the anionic compound (surfactant) having a trifluoromethyl group (manufactured by Tokyo Chemical Industry Co., Ltd.) was examined.

  The gelled negative electrodes (21) to (26) and (31) to (36) were the same as in Example 1 except that the surfactant added to the gelled negative electrode and the amount added were changed as shown in Table 2. , (41) to (46), (51) to (56), (61) to (66), and (71) to (76) were produced.

  As for the evaluation of the battery thus manufactured, as in Example 1, (1) CCV (minimum voltage reached) connection at 1Ω, (2) DSC pulse discharge characteristics, (3) Leakage resistance test (80 ° C.) Went. The results are summarized in Table 2.

これより、ＣＦ₃−ＳＯ₃Ｎａ、ＣＦ₃−Ｏ−ＳＯ₃Ｎａ、ＣＦ₃−ＣＯＯＮａ、ＣＦ₃−Ｏ−ＰＯ₃Ｎａ₂の何れを用いた場合についても、亜鉛合金に対する添加量が０．０１重量％では耐漏液性能（防食効果）が不完全であり、一方、添加量を０．６重量％まで増やすと、ＣＣＶ低下やＤＳＣパルス放電特性の低下が顕著になることがわかる。

Accordingly, the amount of addition to the zinc alloy is 0. 0 for any of CF ₃ —SO ₃ Na, CF ₃ —O—SO ₃ Na, CF ₃ —COONa, and CF ₃ —O—PO ₃ Na ₂ . It can be seen that at 01% by weight, the leak-proof performance (anticorrosion effect) is incomplete, and when the addition amount is increased to 0.6% by weight, the CCV drop and the DSC pulse discharge characteristic are markedly reduced.

From the above results, if the addition amount of the anionic compound having a trifluoromethyl group is in the range of 0.02 to 0.5% by weight with respect to the zinc alloy, both high discharge characteristics and liquid leakage resistance performance can be achieved. It can be seen that it is possible.

  Further, from the results of the batteries (21) to (26), (61) to (66), and (71) to (76), the same effect was obtained regardless of whether the residue is Na, K, or H. .

  Even if these anionic compounds having a trifluoromethyl group are used singly or in a mixed form, almost the same effect can be obtained.

  In Examples 1 and 2 described above, zinc alloy powder containing Al: 0.003% by weight, Bi: 0.02% by weight, and In: 0.01% by weight as the negative electrode active material (particle size range: 35-300 mesh) However, the present invention is not limited to this, and is also applicable to a system using zinc or zinc alloy powder having other composition or particle size as a negative electrode active material. Is possible.

  Further, in Examples 1 and 2 described above, the battery was manufactured and evaluated as an AA size alkaline manganese dry battery. However, the effect of the present invention itself is that other than the AA size alkaline manganese dry battery, the alkaline button type, and the corner. It is possible to adapt to a battery having a different structure such as a mold. In addition to manganese dioxide as a positive electrode active material, the same effect can be expected even in a zinc alkaline battery using nickel oxyhydroxide, silver oxide, air, or the like.

  Since the zinc alkaline battery according to the present invention has both excellent discharge characteristics and leak-proof performance, it is suitably used for a wide range of applications from various electronic devices to general-purpose devices such as toys and lights. .

1 is a cross-sectional front view of an alkaline battery according to an embodiment of the present invention. The figure which showed the voltage measurement result at the time of connecting with a resistance of 1 ohm regarding battery (1), (5), (17)

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Positive electrode case 2 Graphite coating film 3 Positive electrode mixture pellet 4 Separator 5 Bottom paper 6 Gel-like negative electrode 7 Resin sealing board 8 Bottom plate 9 Insulating washer 10 Negative electrode collector 11 Exterior label

Claims (2)

1 selected from the group consisting of CF ₃ —SO ₃ X, CF ₃ —O—SO ₃ X, CF ₃ —COOX, and CF ₃ —O—PO ₃ X ₂ (X is H or Na, K). A zinc alkaline battery containing an anionic compound having at least one kind of trifluoromethyl group. 2. The zinc alkaline battery according to claim 1, wherein the negative electrode includes an active material made of zinc or a zinc alloy, and the addition amount of the anionic compound is 0.02 to 0.5 wt% with respect to the negative electrode active material.

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