JPH0750612B2 - Zinc alkaline battery - Google Patents

Description

TECHNICAL FIELD The present invention relates to zinc as a negative electrode active material, an alkaline aqueous solution as an electrolyte, and manganese dioxide, silver oxide as a positive electrode active material.
It is an object of the present invention to provide an effective means for reducing the amount of mercury used to screen a zinc negative electrode of a zinc-alkaline battery using mercury oxide, oxygen, nickel hydroxide or the like.

Conventional technology Conventionally, in order to suppress corrosion of the electrolytic solution of this type of zinc negative electrode,
A method of adding about 7 to 10% by weight of mercury to zinc has been industrially adopted. However, in recent years, social needs for reduction of mercury content have increased due to low pollution, and various corrosion resistant zinc alloys have been developed or proposed in order to secure sufficient corrosion resistance with the use of a small amount of mercury. . For example, a corrosion-resistant zinc alloy powder in which indium, lead, gallium, aluminum, etc. are added to zinc is considered to be a promising one, and a zinc alloy in which indium and lead are added has already been put into practical use. In addition to lead, a zinc alloy in which aluminum and, if necessary, gallium are further added is being considered as a typical one. When these corrosion resistant zinc alloys are used, the corrosion resistance can be ensured even if the conversion rate (the weight percentage of mercury in the negative electrode zinc) is reduced, and in the case of a zinc alloy to which indium and lead are added, the conversion rate is 3%, Furthermore, in the above-mentioned zinc alloy in which aluminum and, if necessary, gallium are added in addition to the above indium and lead, the corrosion resistance equivalent to 7 to 10% in the case of pure zinc is obtained even if the conversion rate is about 1.5%. can get. Although it is seen in the above example that it is effective to use a corrosion resistant zinc alloy as a method of reducing the conversion rate, as another effective method, the addition of an anticorrosive agent is considered, and the mercury content in the battery is considered. It is considered that the combined use of corrosion resistant zinc alloy and anticorrosive is indispensable as a technology to reduce the amount to the limit.

Conventionally, in order to prevent corrosion of zinc negative electrode in an alkaline aqueous electrolyte, glycols such as ethylene glycol, mercaptocarboxylic acid, aminonaphthalenesulfonic acid, azonaphthalene, carbazole, cyanohydrin, and thiazole such as 2-meltcaptobenzothiazole are used. The application of various anticorrosive agents such as the derivative benzotriazole or its derivative has been proposed. It is a general application method to add a small amount of these anticorrosive agents to the electrolytic solution. However, none of the anticorrosive agents has a remarkable anticorrosive effect, and the present situation is that they are not effective means for reducing the rate of conversion.

Problems to be Solved by the Invention In such a conventional configuration, when the corrosion protection of the zinc negative electrode is insufficient, hydrogen gas is generated along with zinc consumption during storage of the battery, the internal pressure of the battery rises, and the electrolyte solution This may cause leakage, deformation of the battery, or, in extreme cases, rupture of the battery. Moreover, there is a problem that corrosion of zinc causes deterioration of battery performance after storage such as battery capacity reduction.

An object of the present invention is to ensure sufficient corrosion resistance of a zinc negative electrode to prevent the above-mentioned problems from occurring in a state where the degree of conversion is reduced as much as possible. As a method, a new anticorrosion agent having a larger anticorrosion effect than the previously proposed various anticorrosion agents, alkali resistance, and not adversely affecting the discharge performance is newly found and a zinc negative electrode with a low degree of reduction is selected. The present invention provides a low-pollution zinc-alkaline battery having a small mercury content, which is applied to a battery equipped with the battery, without impairing various practical battery characteristics.

Means for Solving the Problems In order to solve this problem, the present invention uses an alkaline aqueous solution as an electrolytic solution, zinc or zinc alloy as a negative electrode active material, and manganese dioxide, silver oxide, oxygen, oxyhydroxide as a positive electrode active material. The terminal functional group of polyoxyethylene alkyl ether (RO (CH ₂ CH ₂ O) _n H) is used as an anticorrosive agent that suppresses the corrosion of the negative electrode of so-called zinc alkaline batteries using nickel, mercury oxide, etc. Or a methylenecarboxylic acid group substituted derivative [RO (CH ₂ CH ₂ O) _n PO ₃ H ₂ , RO (CH ₂ C
H ₂ O) _n SO ₃ H, RO (CH ₂ CH ₂ O) _n CH ₂ COOH], or salts obtained by neutralizing an alkali metal derivative such as RO (CH ₂ CH ₂ O) PO.
₃ K ₂ , RO (CH ₂ CH ₂ O) _n SO ₃ Ha, RO (CH ₂ CH ₂ O) _n CH ₂ COOLi, etc. are used.

As a method of applying these anticorrosive agents, methods such as addition to the electrolytic solution, impregnation of both or one of the separator and the liquid retaining material, and adhesion to the surface of the negative electrode active material can be adopted.

In addition, the above-mentioned anticorrosive has 1 to 10 carbon atoms in the alkali group (R).
40, the degree of polymerization (n) of oxyethylene (CH ₂ CH ₂ O ⁻ ) is 1 to 50,
RO (CH ₂ CH ₂ O) _n ^-having a chemical formula amount of 187 to 2231 is preferable.

Further, pure zinc or a zinc alloy is used as the negative electrode active material, and it is effective to use the corrosion-resistant zinc alloy in combination with the above-mentioned anticorrosive agent in order to realize a particularly large reduction in the conversion rate. For example, when used in combination with a zinc alloy containing indium or lead, or a zinc alloy containing gallium added thereto, a battery with sufficient corrosion resistance of the negative electrode can be obtained even at a 0.2% conversion rate. In addition, if a zinc alloy containing at least one of aluminum, strontium, calcium, magnesium, barium, and nickel is used together, the corrosion resistance of the negative electrode can be secured even with a conversion rate of 0.05%.

Action The action mechanism of the anticorrosive agent used in the present invention is unclear, but it is presumed as follows.

The anticorrosive agent of the present invention has a substantially linear molecular structure, and has a phosphonic acid group, a sulfonic acid group, or a methylenecarboxylic acid group as a polar group at one end and a hydrophobic alkyl group at the opposite end. It is considered that when added to the electrolytic solution, the polar group is dissolved or dispersed and the polar group is adsorbed on the surface of the zinc or zinc alloy of the negative electrode. The corrosion reaction of zinc in an alkaline electrolyte is represented by the following equation.

Anode reaction ^{Zn + 4OH - → Zn (OH} ) 2- 4 + 2e - cathodic reaction ^{_{2H 2 O + 2e - → 2OH}} - + When H ₂ anticorrosive agent forms adsorbed film on the surface of the negative electrode, causing the anode reaction Access of hydroxide ions to the zinc negative electrode is hindered, and water molecules necessary for the cathode reaction cannot exist near the surface of the zinc negative electrode, and corrosion of zinc is suppressed. Even in a state where the amount of the anticorrosive agent is small and does not completely cover the surface of the zinc negative electrode, the corrosion reaction of zinc at the adsorption portion of the added anticorrosive agent on the surface of the zinc negative electrode is suppressed, and the total corrosion amount of the zinc negative electrode is reduced. Further, even if the anticorrosive agent is added by a method such as impregnation into the separator and / or the liquid-retaining material or adhesion to the surface of the negative electrode active material, the anticorrosive agent dissolves or disperses in the electrolytic solution after the battery construction, and Adsorbs on the surface of the zinc negative electrode and suppresses corrosion of zinc. As described above, it is considered that the anticorrosive agent used in the present invention has the anticorrosive effect because it covers the surface involved in the corrosion reaction of zinc. Further, a zinc alloy containing indium and lead disclosed in JP-A-58-18266, or JP-A-58-18266.
-175368, JP 61-77267, JP 61-181068, JP 61
-203563, Japanese Patent Application No. 61-150307, etc., containing indium and lead, and zinc containing at least one selected from the group consisting of gallium, aluminum, strontium, calcium, magnesium, barium, and nickel. All of the alloys have excellent corrosion resistance, but the conversion rate is 0.2
If it is reduced to about 10%, sufficient corrosion resistance cannot be secured.
However, when the above anticorrosive agent is used in combination, both anticorrosive effects are combined, and in some cases, the corrosion resistance of the negative electrode is secured even at a conversion rate of 0.05%.

INDUSTRIAL APPLICABILITY As described above, the present invention experimentally examines a combination of an anticorrosive agent effective for improving the corrosion resistance of a zinc negative electrode, a difference in its molecular structure, and a corrosion-resistant zinc alloy, and a zinc alkaline battery having a high reduction rate and high practicality. Is completed.

This will be described in detail below with reference to examples.

Example (Example 1) First, the corrosion inhibitory effect of the anticorrosive agent of the present invention on zinc in an alkaline solution was examined. The experimental method was to dissolve the anticorrosive agent of the present invention or the conventional example anticorrosive agent to an almost saturated amount in an electrolytic solution prepared by dissolving zinc oxide in a 40 wt% potassium hydroxide aqueous solution, and take 5 ml of the solution. Add 10 g of zinc powder, 45
The amount of hydrogen gas generated in 20 days at a temperature of ℃ was measured. The conversion rate of zinc fluorinated powder was 1.0%, and the particle size was 35 to 150 mesh. The measurement results obtained are shown in Table 1.

In Table 1, the groups of Nos. 1 to 26 using the anticorrosive agent of the present invention are Nos. 27 to 29 using the anticorrosion agents conventionally proposed.
It can be seen that the amount of hydrogen gas generated is smaller than that of the group No. 30 and No. 30 to which the anticorrosive is not added, and the anticorrosive effect of the anticorrosive of the present invention is large. Of the groups No. 1 to 26, No. 1 to 8 have a carbon number of the alkyl group of the anticorrosive agent of 9 and a polymerization degree of oxyethylene of 5
The difference in the anticorrosion effect due to the type of terminal functional group and neutralization with alkali metal was examined. Both of them have a large anticorrosion effect, and among them, No. 1 whose end group is -PO ₃ H _2.
Was judged to be the best.

Nos. 9 to 16 are those in which -PO ₃ H ₂ was used as the terminal group, and the anticorrosion effect was examined when the carbon number of the alkyl group and the degree of polymerization of oxyethylene were changed. No.1 and No.7
As you can see by comparing ~ 16, the carbon number of the alkali group is 1-40
Among those whose degree of polymerization of oxyethylene is 1 to 50, RO (C
H ₂ CH ₂ O) _n ^- molecular formula weight those 187 to 2231 (No.2 and No.1
1 to 16) show a hydrogen gas generation amount that is 1/3 or less of that of No. 33 without addition, which is particularly good.

The carbon number, the degree of polymerization, the
It is clear from the comparison between the examples of Nos. 17 to 26, the conventional examples of Nos. 27 to 30 and the case of no addition, that the anticorrosion effect is obtained in the range of molecular weight.

(Example 2) Next, based on the results obtained in Example 1, a representative anticorrosive agent was selected, and the effect of reducing the conversion rate of zinc or zinc alloy, which is the negative electrode active material, is shown in FIG. A prototype silver oxide battery was manufactured and compared.

In FIG. 1, 1 is a stainless steel sealing plate, the inner surface of which is copper-plated. 2 is potassium hydroxide
A 40 wt% aqueous solution saturated with zinc oxide (when adding an anticorrosive agent, an electrolytic solution containing a saturated amount of the anticorrosive agent shown in Table 2) was gelled with carboxymethylcellulose. 50% of zinc hydride or zinc hydride alloy
It is a zinc negative electrode in which powder of ˜150 mesh is dispersed. Three
Is a cellulosic liquid retaining material, 4 is a separator made of porous polypropylene, 5 is a positive electrode formed by mixing graphite with silver oxide and pressure-molded, 6 is a positive electrode ring formed by plating nickel on iron,
7 is a nickel-plated positive electrode can made of stainless steel. 8 is a gasket made of polypropylene, and the positive electrode can 7
It is compressed between the positive electrode can and the sealing plate 1 by bending. The prototype battery has a diameter of 11.6 mm and a total height of 5.4 mm.

Table 2 shows the changes in discharge performance and total battery height of the prototype batteries after storage at 60 ° C for one month, and the number of batteries in which leakage was observed by visual inspection. Discharge performance is 510 at 20 ℃
It was expressed as the discharge duration when the discharge was performed with a final voltage of 0.9 V in Ω.

In a normal button battery, after the battery is normally sealed, the total battery height slightly decreases with time until the stress relationship between the battery components stabilizes, but hydrogen gas is generated due to corrosion of the negative electrode zinc. In many batteries, the total battery height tends to increase as the battery internal pressure increases. Therefore, the corrosion resistance of the negative electrode zinc can be evaluated by changing the total height of the battery during the storage period. In the case of a battery with insufficient corrosion resistance, the total height of the battery increases, and the internal pressure of the battery rises to cause liquid leakage, and the corrosion of negative electrode zinc due to corrosion and surface oxidation deteriorates the discharge performance. From this point of view, the experimental test results in Table 2 are evaluated as follows. First, Nos. 1 to 9 have extremely excellent corrosion resistance as a negative electrode active material, and a zinc alloy (Pb) that is expected to be used as a negative electrode of a practical battery without the aid of an anticorrosive agent if the conversion rate is usually 1.5% or more. , Zinc alloy containing In, Al) was constructed at a very low conversion rate of 0.05% to compare the effect of the anticorrosive agent. These results show that the cases of Nos. 1 to 6 to which the anticorrosive agent of the present invention is added are significantly better than the cases of addition or no addition of the conventional anticorrosion agents of Nos. 9 to 10. It is shown that the corrosion resistance of the negative electrode can be sufficiently ensured at a conversion rate of 0.05% or more by using the corrosion-resistant zinc alloy and the anticorrosive agent of the present invention, and a zinc alkaline battery having an extremely low conversion rate can be constructed. In addition, Nos. 10 to 16 reduce the degree of conversion of zinc alloys (zinc alloys containing Pb, In) that have already been put into practical use as a popular material at a rate of 3% to 0.2%, The effect of the anticorrosive agent of the present invention was examined. Also in this case, the examples of No. 10 to 13 are clearly different in battery performance from the conventional examples of No. 14 to 16 or the case of no addition, and the zinc alloy and the anticorrosive agent of the present invention are If used together,
It is shown that a corrosion rate of the negative electrode is sufficient at a conversion rate of 0.2% or more and a zinc alkali battery with a low conversion rate having excellent practical performance can be constructed. Further, in Nos. 17 to 23, when the pure zinc powder, which normally requires a degree of conversion of about 7 to 10%, is used as the negative electrode active material, the present invention is applied to reduce the ratio of reduction to 3%. Also indicates that a battery with sufficient practicality can be constructed. In addition, Nos. 24 to 33 confirmed the effect of the present invention as a precaution, when a zinc alloy having a degree of conversion of 1.5 to 3%, which can ensure the corrosion resistance of the negative electrode, was used for the negative electrode without the aid of an anticorrosive agent. In the case of the examples of No. 24, 25 and No. 29, 30, No. 27,
The characteristics are further improved as compared with the conventional examples of Nos. 28 and No. 31 to 33 or the case of no addition, which shows that the quality is stabilized by ensuring a high degree of corrosion resistance.

Nos. 34 and 35 have corrosion resistance almost equal to that of a zinc alloy containing Pb and In, and a zinc alloy containing Pb, In, Ga has a conversion ratio of 0.2.
The effect of the present invention was investigated as%, and in the case of the No. 34 example, 0.2% of the conversion rate was achieved as in the case of the No. 10 to 13 Pb, In-containing zinc alloys. It shows that you can do it.

No. 36 to 45 are Pb, In, as a zinc alloy having corrosion resistance almost equal to the zinc alloy containing Al with improved corrosion resistance,
The expected effect was obtained by examining the effect of the present invention at a conversion rate of 0.05%, and any of the examples (No. 36, 38, 40, 42, 4
4) also shows excellent battery performance even with a low selection rate of 0.05%, as in the case of the No. 1 to No. 6 examples with the zinc alloy containing Pb, In, and Al.

In any of the above cases are results of examining the effect of the present invention by dissolving the anticorrosive agent in the electrolytic solution, No. 46, 47 of the present invention other than the method of adding the anticorrosive agent in the electrolytic solution As an example, all of Nos. 46 and 47 in which the separator or the liquid-retaining material was impregnated with the anticorrosive agent in advance showed substantially the same effect as when the anticorrosive agent was dissolved in the electrolytic solution. In all of these cases, the anticorrosive agent gradually dissolves in the electrolyte after the battery is constructed to exert the anticorrosive effect.In particular, when the anticorrosive agent is impregnated in the separator or the liquid retaining material, the penetration of the electrolyte solution Since it becomes faster, the structure of the battery becomes easier and the productivity is increased.

(Example 3) Next, C ₉ H ₁₉ O (CH ₂ CH ₂ O) ₅ PO ₃ H ₂ was selected as a representative anticorrosive agent, and the dissolved concentration in the electrolytic solution and the corrosion amount of the zinc hydride alloy powder were selected. I investigated the relationship. Zinc fluoride alloy powder contains 0.05% Pb, In, and Al, respectively.
% Of zinc alloy powder containing 35% to 150 mesh, which has been blunted in an alkaline solution by a mercury dropping method at a blunting rate of 0.05%, 10 g of which is weighed and a 40% aqueous solution of potassium hydroxide is used. It was immersed in 5 cc of an electrolytic solution in which zinc oxide was saturated and an anticorrosive was dissolved, and the mixture was allowed to stand at 45 ° C for 10 days, and the amount of hydrogen gas generated during that period was measured.

The concentration of the anticorrosive agent in the electrolytic solution was adjusted by mixing the electrolytic solution saturated with the anticorrosive and the electrolytic solution containing no anticorrosive agent at an appropriate ratio. The results are shown in FIG. As shown in Fig. ₂ , when the concentration of C ₉ H ₁₉ O (CH ₂ CHO) ₅ PO ₃ H ₂ is about 500 ppm or more, a remarkable effect is observed, and when it is about 1000 ppm or more, the saturation concentration is about 4%.
An almost constant effect can be obtained up to 000 ppm. In addition to this anticorrosive agent, the anticorrosive agents used in Nos. 1 to 7 of Example 1 show almost the same effect, and the proper concentration of the anticorrosive agent of the present invention is from about 1000 ppm or more to the saturated concentration or less. It has been found that is preferable.

EFFECTS OF THE INVENTION As described above, according to the present discovery, it is possible to obtain an effect that the corrosion rate of the negative electrode of the zinc alkaline battery can be significantly reduced by the newly searched anticorrosive agent.

[Brief description of drawings]

FIG. 1 is a side view showing a cross section of a part of a button type silver oxide battery used in an embodiment of the present invention, and FIG. 2 is a diagram showing a relationship between an amount of a corrosion inhibitor dissolved in an electrolytic solution and an amount of hydrogen gas generated. Is. 2 ... Zinc negative electrode, 4 ... Separator, 5 ... Silver oxide positive electrode.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H01M 4/62 C

Claims (6)

[Claims] 1. An anticorrosive agent for a negative electrode active material, wherein the terminal functional group of polyoxyethylene alkyl ether (RO (CH ₂ CH ₂ O) _n H) is a phosphonic acid group, a sulfonic acid group, or a methylenecarboxylic acid group. Substituted derivative [RO (CH ₂ CH ₂ O) _n PO ₃ H ₂ , R
O (CH ₂ CH ₂ O) _n SO ₃ H, RO (CH ₂ CH ₂ O) _n CH ₂ COOH), and at least one selected from the group of salts of its derivatives neutralized with alkali metals Zinc alkaline battery. 2. The number of carbon atoms of the alkali group (R) of the anticorrosive agent is 1 to
40, the degree of polymerization of oxyethylene (n) is 1 to 50, and RO (CH ₂ CH ₂
O) _n ^- of Formula weight first the claims is 187-2231
The zinc alkaline battery according to the item. 3. The zinc alkaline battery according to claim 1 or 2, wherein an anticorrosive agent is dissolved in an electrolytic solution. 4. The zinc alkaline battery according to claim 1 or 2, wherein an anticorrosive agent is impregnated in advance in one or both of the separator and the electrolyte holding material. 5. A zinc alloy containing indium and lead as essential additive elements and gallium as an optional additive element is used as a negative electrode active material, and the degree of conversion of the negative electrode active material is 3 to 0.2% by weight. The zinc alkaline battery according to any one of claims 1 to 4. 6. A negative electrode active material is a zinc alloy containing indium and lead as essential additive elements and further containing at least one selected from the group consisting of aluminum, strontium, calcium, magnesium, barium, nickel and gallium. The zinc alkaline battery according to any one of claims 1 to 4, wherein the negative electrode active material has a conversion rate of 1.5 to 0.05% by weight.