JP2770396B2 - Zinc alkaline battery - Google Patents

Description

The present invention relates to zinc using zinc as a negative electrode active material, an aqueous alkaline solution as an electrolytic solution, and manganese dioxide, silver oxide, mercury oxide, oxygen, nickel hydroxide and the like as a positive electrode active material. An object of the present invention is to provide an effective means for reducing the amount of mercury used for converting a zinc negative electrode of an alkaline battery into a mercury.

2. Description of the Related Art Conventionally, in order to suppress corrosion of an electrolytic solution of a zinc anode,
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 by using a small amount of mercury. . For example, a corrosion-resistant zinc alloy powder in which indium, lead, gallium, aluminum, etc. is added to zinc is considered to be effective, and a zinc alloy in which indium and lead are added has already been put into practical use, and indium, which has further improved corrosion resistance, Zinc alloys to which aluminum and, if necessary, gallium are added in addition to lead have also been put to practical use. When these corrosion-resistant zinc alloys are used, corrosion resistance can be ensured even when the rate of calorification (the percentage by weight of mercury in the negative electrode zinc) is reduced. In the case of a zinc alloy to which indium and lead are added, the rate of calorification is 3%, In addition, a zinc alloy containing aluminum and, if necessary, gallium in addition to the above-mentioned indium and lead, which has improved corrosion resistance, has a corrosion resistance equivalent to that of pure zinc, which is equivalent to 7 to 10% even in the case of pure zinc. can get.
Although it is effective to use a corrosion-resistant zinc alloy as a method of reducing the rate of calcining, as seen in the above example,
Another effective method is to add an anticorrosive, and it is considered that the use of a corrosion-resistant zinc alloy and an anticorrosive is indispensable as a technique for reducing the mercury content in the battery to the utmost.

Conventionally, in order to prevent corrosion of a zinc negative electrode in an alkaline aqueous solution, glycols such as ethylene glycol, mercaptocarboxylic acid, aminonaphthalenesulfonic acid, azonaphthalenes, carbazole cyanohydrin, 2-mercaptobenzothiazole, etc. Various anticorrosive agents, such as thiazole derivatives, have been proposed.
It is a general application method to add a small amount of these anticorrosives to the electrolyte. However, at present, none of the anticorrosive agents has a remarkable anticorrosive effect, and is not an effective means for reducing the rate of calcining.

Problems to be Solved by the Invention If the corrosion prevention of the zinc negative electrode is insufficient, hydrogen gas is generated with the consumption of zinc during storage of the battery, the internal pressure of the battery increases, the electrolyte leaks, and the battery is deformed, If it is significant, the battery may burst. In addition, the corrosion of zinc causes deterioration of battery performance after storage, such as a decrease in battery capacity. An object of the present invention is to ensure the corrosion resistance of a zinc negative electrode sufficient to prevent the above-mentioned problems from occurring, while keeping the rate of calcining as low as possible. As a method, the anticorrosion effect is greater than the above-mentioned various anticorrosion agents conventionally proposed,
A new anticorrosion agent that is alkali-resistant and has no adverse effect on discharge performance has been newly searched for and applied to batteries equipped with a zinc anode with a low rate of mercury, and contains mercury without impairing the characteristics of practical batteries. The present invention provides a low-pollution, low-pollution zinc-alkali battery.

Means for Solving the Problems The present invention provides an alkaline solution containing potassium hydroxide, sodium hydroxide or the like as a main component in an electrolytic solution, zinc or a zinc alloy in a negative electrode active material, manganese dioxide, silver oxide, oxygen in a positive electrode active material. Perfluorophosphate ester as an anticorrosive that suppresses the corrosion of the negative electrode of so-called zinc-alkaline batteries using nickel, nickel oxyhydroxide, mercury oxide, etc. Is used.

These anticorrosives can be applied by adding them to the electrolyte, impregnating one or both of the separator and the liquid retaining material, adhering to the surface of the negative electrode active material, and mixing them with the alkaline electrolyte. it can. The anticorrosive preferably has a fluorocarbon group having 2 to 18 carbon atoms. In addition, although pure zinc or a zinc alloy is used as the negative electrode active material, it is effective to use a corrosion-resistant zinc alloy in combination with the above-mentioned anticorrosive agent in order to achieve a particularly large reduction in the rate of calcining. For example, when used in combination with a zinc alloy to which indium and lead are added, or a zinc alloy to which gallium is added, a battery having sufficient corrosion resistance of the negative electrode can be obtained even with a 0.2% mercurization ratio. In addition, when a zinc alloy containing at least one of aluminum, strontium, calcium, magnesium, barium, and nickel is used in combination, the corrosion resistance of the negative electrode can be ensured even at a 0.05% mercurization ratio.

The mechanism of action of the anticorrosive used in the present invention is unclear,
It is inferred as follows.

The anticorrosive agent of the present invention has a substantially linear molecular structure, having a phosphate group as a polar group at one end and a hydrophobic group at the other end. It is considered that the group is adsorbed on the zinc or zinc alloy surface of the negative electrode. When the corrosion reaction in the alkaline electrolyte of zinc is represented by the following formula, anticorrosive agent forms adsorbed film on the surface of the negative electrode, the anode reaction ^{Zn + 40H - → ▲ Zn (} OH) 2- 4 ▼ + 2e - cathodic reaction 2H _{^{2 O + 2e - → 20H -}} + H 2 causes the anode reaction proximity to hydroxyl ions of zinc negative electrode is disturbed, also corrosion of zinc can no longer exist in the water molecules near zinc anode surface required in the cathode reaction Is suppressed. Even when the amount of the anticorrosive is small and does not completely cover the surface of the zinc negative electrode, the corrosion reaction of zinc at the adsorbed portion of the surface of the zinc negative electrode by the added anticorrosive is suppressed, and the total amount of corrosion of the zinc negative electrode is reduced. Even when the anticorrosive is added by impregnating the separator and / or the liquid retaining material, attaching to the negative electrode active material surface, or mixing with the gel alkaline electrolyte, the anticorrosive dissolves in the electrolyte after the battery is formed. Alternatively, they are dispersed and adsorbed on the surface of the zinc negative electrode in the same manner as described above, whereby the corrosion of zinc is suppressed. As described above, it is considered that the anticorrosive used in the present invention covered the surface related to the corrosion reaction of zinc, and thus had an anticorrosive effect. Further, a zinc alloy containing indium and lead disclosed in JP-A-58-18266, or JP-A-60-175368, JP-A-61-772
67, JP-A-61-181068, JP-A-61-203563, Japanese Patent Application No. 61-150307
Zinc alloys containing indium and lead disclosed by the present inventors and containing at least one selected from the group consisting of gallium, aluminum, strontium, calcium, magnesium, barium and nickel bismuth all have excellent corrosion resistance. However, if the rate of calcining is reduced to about 0.2%, sufficient corrosion resistance cannot be secured. However, when the above anticorrosives are used in combination, the anticorrosive actions of both are combined, and in some cases, the corrosion resistance of the negative electrode is ensured even with a 0.05% calcining rate.

As described above, the present invention has experimentally studied the use of an anticorrosive agent effective for improving the corrosion resistance of a zinc negative electrode and a corrosion-resistant zinc alloy, and has completed a highly alkaline zinc-alkaline battery with a reduced rate of mercury.

 Hereinafter, the present invention will be described in detail with reference to examples.

EXAMPLES Example 1 First, the effect of the corrosion inhibitor of the present invention on corrosion of zinc in an alkaline solution was examined. The experiment was conducted by dissolving the anticorrosive agent of the present invention or the conventional anticorrosive agent to an almost saturated amount in an electrolyte solution obtained by dissolving zinc oxide in a 40% by weight aqueous solution of potassium hydroxide, and taking 5 ml of the solution. 10g of zinc powder, 45
The amount of hydrogen gas generated over 20 days at a temperature of ° C was measured.
The mercurization ratio of the mercurized zinc powder was 10%, and the particle size was 35 to 150 mesh. Table 1 shows the obtained measurement results.

As is clear from Table 1, N using the anticorrosive of the present invention
The O.1 to 8 groups produced less hydrogen gas than the NO.9 to 11 groups using the conventionally proposed anticorrosive and the NO.12 without the anticorrosive added. It can be seen that the effect of the anticorrosive is great. Further, the anticorrosive of the present invention has a large anticorrosive effect in any case where the carbon number of the fluorocarbon group is in the range of 2 to 18.

Example 2 Next, based on the results obtained in Example 1, a representative anticorrosive was selected, and the effect of reducing zinc oxide or zinc alloy as a negative electrode active material on the rate of calorification was shown in FIG. A silver battery was prototyped and compared. In FIG. 1, reference numeral 1 denotes a stainless steel sealing plate, whose inner surface is plated with copper. No. 2 shows that a 40 wt% aqueous solution of potassium hydroxide saturated with zinc oxide and an electrolytic solution in which a corrosion inhibitor shown in Table 2 is dissolved in a saturated amount when an anticorrosive is added is gelled with carboxymethyl cellulose. This is a zinc negative electrode in which powder of 50 to 150 mesh of calcined zinc or a calcined zinc alloy is dispersed in the gel. 3 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 pressurized, 6 is a positive electrode ring made of nickel plated iron, 7 is nickel plated. This is a stainless steel positive electrode can that has been subjected to the above. Reference numeral 8 denotes a polypropylene gasket, which is compressed between the positive electrode can 7 and the sealing plate 1 by bending the positive electrode can 7. The prototype battery has a diameter of 11.6.
mm, total height 5.4mm. Table 2 shows the change in the discharge performance and the total battery height of the prototype batteries after storage at 60 ° C. for one month, and the number of batteries in which liquid leakage was observed by visual judgment. The discharge performance was represented by a discharge duration time when the battery was discharged at 510 Ω at 20 ° C. with a final voltage of 0.9 V.

In addition, all of the anticorrosives of the present invention used in Example 2 were used. Was used.

In normal button batteries, the total battery height usually decreases slightly with time after the battery is sealed until the stress relationship between the battery components stabilizes, but the generation of hydrogen gas due to the corrosion of the negative electrode zinc occurs. In many batteries, the tendency of the total battery height to increase due to an increase in the battery internal pressure increases. Therefore, the corrosion resistance of the negative electrode zinc can be evaluated based on the change in the total battery height during the storage period. Batteries with insufficient corrosion resistance increase the total battery height, easily leak due to an increase in the internal pressure of the battery, and also deteriorate the discharge performance due to consumption of the negative electrode zinc due to corrosion and oxidation of the surface. From such a viewpoint, the results of the trial production experiment in Table 2 are evaluated as follows. First, NO.1 to 3 are extremely excellent in corrosion resistance as a negative electrode active material. Normally, a zinc alloy (Pb Alloy containing 0.05%, In, Al)
This is a comparison of the effect of the anticorrosive agent by forming a battery with an extremely low calomelization rate.

No. 1 to which the anticorrosive of the present invention was added showed that the addition of the anticorrosive of the conventional example of No. 2 or the case of no addition of NO. This shows that the use of the anticorrosive agent in combination can sufficiently secure the corrosion resistance of the negative electrode with a calorification ratio of 0.05% or more, and can constitute a zinc-alkali battery with an extremely low calorification ratio. In addition, NO.4 to No.6 show the melting rate of zinc alloy (zinc alloy containing Pb and In), which is already in practical use at a 3% melting rate as a popular material.
The effect of the anticorrosive agent of the present invention was examined by reducing it to 0.2%. Also in this case, the embodiment of NO.4 clearly shows a difference in battery performance between the conventional example of NO.5 or the case of no addition, and 0.2% when the zinc alloy and the anticorrosive of the present invention are used in combination.
The results show that a zinc-alkali battery having a low rate of calorization with sufficient corrosion resistance of the negative electrode and excellent practical performance can be formed at a rate of calorification of not less than 10%. Further, in the case of NOs. 7 to 9, the present invention is applied to a case where pure zinc powder requiring a calorification rate of about 7 to 10% is used as a negative electrode active material, and the calorification rate is reduced to 3%. This shows that a battery having sufficient practicality can be constructed. Also, N
O.10 to 12 were confirmed to make sure the effect of the present invention when a zinc alloy having a calorification rate of 1.5 to 3%, in which the corrosion resistance of the negative electrode can be substantially secured without the use of an anticorrosive agent, was used for the negative electrode. , N
In the case of the embodiment of O.10 and NO.13, NO.11-12 and NO.1
The characteristics are further improved as compared with the conventional examples of Nos. 4 to 15 or the case of no addition, indicating that the quality was stabilized by securing a high degree of corrosion resistance.

NO.16 and 17 have almost the same corrosiveness as zinc alloys containing Pb and In.
The effect of the present invention was examined at 2%. In the case of the embodiment of No. 16, it was found that the same as the embodiment with the zinc alloy containing Pb and In of NO. Is shown.

NO.18 to 19 are Pb, In, Al-containing zinc alloys that have almost the same corrosion resistance as corrosion-resistant zinc alloys, and those containing expected Pb, In, Al, and Ni.
The effect of the present invention was examined at a mercurization rate of 0.05%. Even at a low calorification rate of 0.05%, the Nb content in a zinc alloy containing Pb, In, and Al was reduced.
As in the example of O.1, it shows excellent battery performance. All of the above cases are the results of examining the effects of the present invention by dissolving the anticorrosive in the electrolytic solution, but NO. 20 to 23 are implementations of the present invention other than the method of adding the anticorrosive to the electrolytic solution. In the example shown, the gel electrolyte solution was gelled with NO.20 in which an anticorrosive agent was previously attached to a zinc-alloyed zinc alloy, and NO.21 and 22CMC in which a corrosion inhibitor was previously impregnated in a separator or a liquid retaining material. No. 23 mixed with each other had almost the same effect as when the anticorrosive was dissolved in the electrolytic solution. In each of these cases, the anticorrosive is gradually dissolved in the electrolytic solution after the battery is formed to exhibit the anticorrosive effect.Especially, when the anticorrosive is impregnated in the separator or the liquid retaining material, the electrolytic solution is Since the permeation becomes faster, the battery configuration becomes easier, and there is also an effect of increasing productivity.

In addition, the anticorrosive of the present invention is effective for zinc and zinc alloys and powders thereof which are not subjected to the treatment of mercurization, and reduces mercury in open-type zinc-alkaline batteries such as zinc-alkaline batteries and air-zinc batteries which have a short usage period. Some that are not used at all are possible.

Also, although not shown in the examples, contains In, Pb,
Furthermore, it has been confirmed that a zinc alloy containing strontium, calcium, magnesium, and bismuth can achieve the same effect as described above. Furthermore, it has been confirmed that the anticorrosive agent of the present invention can obtain substantially the same effect even in a manganese dry battery using a neutral salt electrolyte.

Effects of the Invention As described above, the present invention has made it possible to significantly reduce the rate of calcining of the negative electrode of a zinc-alkaline battery by the effect of a newly found anticorrosive agent.

[Brief description of the drawings]

FIG. 1 is a cross-sectional side view of a part of a button-type silver oxide battery used in an embodiment of the present invention. 2 ... a zinc negative electrode, 4 ... a separator, 5 ... a silver oxide positive electrode.

Continuation of the front page (56) References JP-A-61-27063 (JP, A) US Patent 4,195,120 (US, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01M 4/62 H01M 4 / 42

Claims (8)

(57) [Claims] 1. A perfluorophosphate ester as an anticorrosive for a negative electrode active material. Zinc alkaline battery using. 2. The zinc alkaline battery according to claim 1, wherein the anticorrosive has a fluorocarbon group having 2 to 18 carbon atoms. 3. The zinc alkaline battery according to claim 1, wherein the anticorrosive is dissolved in the electrolytic solution. 4. The zinc alkaline battery according to claim 1, wherein both or one of the separator and the electrolyte holding material is impregnated with an anticorrosive in advance. 5. A zinc alkaline battery according to claim 1, wherein an anticorrosive is previously attached to the surface of the negative electrode active material. 6. The zinc alkaline battery according to claim 1, wherein the anticorrosive is mixed with a gel alkaline electrolyte gelled with a water-soluble polymer. 7. A negative electrode active material comprising a zinc alloy containing indium and lead as essential additive elements and gallium as an optional additive element, wherein the negative electrode active material has a rate of mercurization of 3 to 0.2%. Item 7. A zinc alkaline battery according to any one of items 1 to 6. 8. A negative electrode active material comprising a zinc alloy containing indium and lead as essential addition elements and further containing at least one selected from the group consisting of aluminum, strontium, calcium, magnesium, barium, nickel and bismuth. The zinc-alkali battery according to any one of claims 1 to 6, wherein the negative electrode active material has a calorization ratio of 1.5 to 0.05%.