JPH05174813A - Zinc negative plate and its manufacture and zinc-dioxide lead-acid battery - Google Patents

Abstract

PURPOSE:To provide a zinc negative plate having an amalgam layer in a high fixity without using a large quantity of mercury. CONSTITUTION:By soaking a zinc plate in sulphate solution prepared from In2SO4 aqueous solution, Zn-In alloy layer is formed on the surface of the zinc plate by substitution and deposition of In which is a metal having its melting point lower than that of zinc. Thereafter the zinc plate on which Zn-In alloy layer is formed is soaked in mercuric chloride (HgCl2) aqueous solution. Then the Zn-In alloy layer is amalgamated thereafter an amalgam layer composed of the alloy layer of Zn, In and Hg is formed on the surface of the zinc plate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zinc cathode plate, a method for manufacturing the same, and a zinc-lead dioxide storage battery.

[0002]

2. Description of the Related Art Zinc cathode plates used for batteries have large weight energy density, are inexpensive, and are non-polluting substances. Therefore, research and development have been carried out for practical use as cathode plates for portable type batteries. It is being appreciated. However, zinc is easily dissolved in an acidic solution or an alkaline solution which is an electrolytic solution, and since the alternating current density is low and the crystal formation is larger than the crystal nucleus formation, dendritic precipitation (dentrite formation) is likely to occur. Therefore, the zinc plate has not been put to practical use as a battery cathode plate. For example, in a battery using an acidic solution as an electrolytic solution, zinc in the zinc cathode plate is dissolved as zinc ions (Zn ²⁺ ) in the electrolytic solution when the battery is discharged, and is deposited on the surface of the zinc cathode plate when the battery is filled. However, when the battery is repeatedly charged and discharged, the zinc electrodeposition reaction becomes non-uniform, and the deposited zinc is likely to be dendritic to form dendrites. Therefore, when the battery is repeatedly charged and discharged, the active material undergoes shape deformation, and the reaction area of the zinc cathode plate decreases. Moreover, the capacity of the battery is reduced because a short circuit occurs due to the generation of dendrite. Further, when a zinc cathode plate is used in a battery, the hydrogen overvoltage of the battery tends to decrease.
For example, in a zinc-lead dioxide storage battery in which an acidic solution such as sulfuric acid having a pH of 1 or less is used as an electrolytic solution and lead dioxide is used as an anode plate, impurities or additives contained in the electrode plate and the electrolytic solution [arsenic (As)] , Antimony (Sb), copper (Cu), iron (Fe), vanadium (V), manganese (Mn), etc.] form a local battery, so that the hydrogen overvoltage of the battery is significantly lowered and hydrogen is easily generated. .. Therefore, in order to solve such a problem of generation of dendrite and reduction of hydrogen overvoltage, mercury (eg, amalgamation) is performed by rubbing mercury on the surface of the zinc cathode plate,
It was considered to form an amalgam layer on the surface portion.
When an amalgam layer is formed on the surface of the zinc cathode plate, zinc reduced on the surface of the amalgam layer diffuses in the amalgam layer, so that zinc does not form crystals and the generation of dentrite is suppressed. Also, since the amalgam layer has a smooth surface,
The area of the amalgam layer surface becomes smaller and the current density becomes higher. Therefore, it becomes difficult to discharge hydrogen.
Moreover, since mercury itself has a property of being less likely to generate a discharge with respect to hydrogen, hydrogen overvoltage increases when an amalgam layer is formed on the surface of the zinc cathode plate.

[0003]

However, since zinc has a relatively high melting point, it is difficult to form a solid solution with mercury. Therefore, if the surface of the zinc cathode plate is directly subjected to mercury in this way, the mercury diffuses toward the inside of the zinc cathode plate, so a large amount of mercury must be used. Further, even if the surface of the zinc cathode plate is directly agglomerated with mercury, since the fixability of the amalgam layer to the zinc cathode plate is low, there is a problem that the amalgam layer tends to come off when the battery is repeatedly charged and discharged at a high rate. there were.

The present invention solves the above problems and provides a zinc cathode plate having a high fixing property of the amalgam layer on the zinc cathode plate, a method for producing the same, and a zinc-lead dioxide storage battery having a high hydrogen overvoltage and a long life. ..

[0005]

The invention according to claim 1 is directed to a method for producing a zinc cathode plate having an amalgam layer on the surface thereof. Then, in the present invention, after a metal having a melting point lower than that of zinc is substituted and deposited on the surface of the zinc plate, the zinc plate is subjected to the aging treatment to form an amalgam layer. The zinc plate may have any shape as long as it functions as an electrode plate,
The shape is not limited to the plate shape. Further, the “agglomeration treatment” specifically means to amalgamate an alloy layer of zinc and a metal having a melting point lower than that of zinc deposited by substitution.

According to a second aspect of the invention, in the manufacturing method of the first aspect, at least one metal selected from indium, thallium, lead and cadmium is used as the metal having a melting point lower than that of zinc.

The invention of claim 3 is directed to a zinc cathode plate having an amalgam layer on the surface thereof. And in the present invention,
The amalgam layer is composed of an alloy layer of a metal having a melting point lower than that of zinc deposited on the surface of the zinc plate by substitution and an alloy of zinc and mercury.

The invention of claim 4 is directed to a zinc-lead dioxide storage battery having an electrode group formed by combining a lead dioxide anode plate and a zinc cathode plate. And in the present invention, as a zinc cathode plate, using a thing having an amalgam layer formed of an alloy layer of a metal having a melting point lower than zinc and zinc and mercury substituted and deposited on the surface of the zinc plate, antimony and a lead dioxide anode plate. An arsenic-free one is used, a zinc plate having a purity of 99.99% or more is used as the zinc cathode plate, and an aqueous sulfuric acid solution which does not substantially contain a substance that reduces hydrogen overvoltage is used as the electrolytic solution.

According to a fifth aspect of the invention, in the zinc-lead dioxide storage battery according to the fourth aspect of the invention, the electrode group is composed of a spiral electrode group.

[0010]

When the metal having a melting point lower than that of zinc is substituted and deposited on the surface of the zinc plate, an alloy layer of the metal having a melting point lower than that of zinc and zinc is formed on the surface of the zinc plate. To be done. Since a metal having a melting point lower than that of zinc is more likely to form a solid solution with mercury than zinc, this alloy layer also has a property of forming a solid solution with mercury. Therefore, as in the present invention, when the aging treatment is performed after the substitution precipitation, the aging can be performed without using a large amount of mercury as in the conventional case. Moreover, the amalgam layer thus formed has a high fixing property on the zinc cathode plate, and the amalgam layer is unlikely to fall off even if the battery is repeatedly charged and discharged. In particular, since metals such as indium, thallium, lead, and cadmium are likely to form a solid solution with mercury, at least one selected from indium, thallium, lead, and cadmium as a metal having a melting point lower than that of zinc, as in the invention of claim 2. This can be easily done by using one metal. By the way, when indium is used for substitutional deposition, indium (2In) is deposited on the surface of the zinc plate according to the following reaction formula.

3Zn + 2In ³⁺ → 2In + 3Zn ^{2+ As in} the invention of claim 3, when the amalgam layer is composed of an alloy layer of metal and zinc / mercury deposited by substitution on the surface of the zinc plate, the amalgam layer is used for the zinc cathode plate. The fixability is high, and the amalgam layer does not easily fall off even when the battery is repeatedly charged and discharged.

When the zinc-lead dioxide storage battery is constructed as in the invention of claim 4, it is possible to suppress the generation of a local battery due to impurities in the battery, so that the hydrogen overvoltage of the battery becomes high. In particular, since the lead dioxide anode plate does not contain antimony and arsenic, it is possible to prevent self-discharge and generation of gas which are caused by dissolution and precipitation of antimony and arsenic and a decrease in hydrogen overvoltage.

When the electrode group is formed in a spiral shape as in the fifth aspect of the invention, the electrode group is pressed in the thickness direction at a predetermined pressure, so that the amalgam layer can be prevented from falling off. Therefore, the life of the battery can be extended. Further, the electrode plate area per unit weight of the active material can be increased, and since the pressure can be applied almost uniformly, the potential gradient can be made uniform, and the discharge capacity at the time of high rate discharge can be improved.

[0014]

Embodiments of the present invention will now be described in detail with reference to the drawings. The zinc cathode plate and the zinc-lead dioxide storage battery of the examples of the present invention were manufactured as follows. 1 (a)-
(D) is a schematic diagram showing a process in the case of producing a zinc cathode plate by performing displacement precipitation using indium (In).
First, the size of the effective surface of the electrode plate is 34 mm x 65 mm x 0.5
A zinc plate having a purity of 99.99% or more, preferably 99.999% or more, which was cut to have a size of mm, was sufficiently polished with emery paper or the like, and immersed in a 1% sulfuric acid solution for 5 minutes for activation. Next, as shown in FIGS. 1 (a) and 1 (b),
The zinc plate was immersed for 5 seconds in a sulfate solution composed of an In ₂ SO ₄ aqueous solution adjusted to 50 mg / dm ³ to partially zinc (Zn) on the surface of the zinc plate and In ^{3 +} in the In ₂ SO ₄ solution.
In, which is a metal having a melting point lower than that of zinc by substituting ions
Was deposited on the surface of the zinc plate by substitution to form a Zn-In alloy layer. As the sulfate aqueous solution, other than the In ₂ SO ₄ aqueous solution, Me _n (SO ₄ ) _m [Me; thallium (Tl),
It is preferable to use an aqueous solution of lead (Pb) and cadmium (Cd). By using these aqueous solutions, Tl, Pb, and Cd can be substituted and deposited on the surface of the zinc plate. Further, various sulfate aqueous solutions may be mixed and used. Next, Zn-I
The zinc plate on which the n-alloy layer is formed is dipped in a mercury salt aqueous solution composed of a mercuric chloride (HgCl ₂ ) aqueous solution adjusted to 50 g / dm ³ for 60 seconds to subject the Zn-In alloy layer to iodization (amalgamation). Then, an amalgam layer made of an alloy layer of Zn, In and Hg was formed on the surface of the zinc plate to manufacture a zinc cathode plate [see FIGS. 1 (c) and 1 (d)]. In addition, as shown in FIG. 1 (c), a case where two layers of an amalgam layer (Zn-In-Hg alloy layer) and a Zn-In alloy layer are formed depending on the immersion conditions in the mercury salt aqueous solution, and As shown in 1 (d), there is a case where only the amalgam layer (Zn-In-Hg alloy layer) is formed. By the way, in the conventional method in which the surface of the zinc cathode plate is directly amalgamated with mercury, the amount of mercury with respect to zinc is 50 to 1000 μg / g, whereas in the present embodiment, a very small amount of mercury of 1 to 10 μg / g is used. The amalgam layer could be formed in a quantity. With this amount, environmental pollution due to mercury can be reduced to the level of a manganese battery. Further, in the present embodiment, the aging was carried out with the mercury salt aqueous solution, but the aging may be carried out using metallic mercury. In that case, metallic mercury may be applied to the surface of the Zn—In alloy layer.

Next, a zinc cathode plate manufactured as described above,
An unformed anode plate made of pure lead that does not contain antimony (Sb) and arsenic (As) with the same dimensions as the zinc cathode plate (lead dioxide anode plate after chemical conversion) and has a thickness of 1.2 mm The spirally wound electrode group was formed by spirally winding it through a retainer consisting of. Then, after inserting the spirally wound electrode group into a battery case, a sulfuric acid aqueous solution (specific gravity: 1.320) 7c.c consisting of sulfuric acid that does not substantially contain substances that reduce hydrogen overvoltage such as iron (Fe) and vanadium (V). Was injected into a battery case as an electrolytic solution to manufacture a zinc-lead dioxide storage battery of an example of the present invention.

The batteries A to D manufactured to investigate the characteristics of the zinc-lead dioxide storage battery of this example are as follows.
Battery A is the battery of this embodiment. Battery B is a battery of another example manufactured without winding the electrode group of battery A of this example. Battery B was manufactured as follows. First, the zinc negative electrode plate and the positive electrode plate of the present example, which are connected to the poles having the valve portion, are laminated via a retainer to form a flat electrode group, and the electrode group is left with the valve portion of the pole portion remaining. It was placed in a laminate film, and the laminate film was heat-welded except for the lower end portion. Next, after injecting sulfuric acid from the lower end, the entire laminated film was heat-welded to manufacture. Battery C is a conventional battery using a zinc cathode plate in which the amalgam layer is formed by directly amalgamating the surface of the zinc plate with mercury without displacement precipitation. The zinc cathode plate of Battery C was manufactured by rubbing mercury on a zinc plate. Battery D is a conventional battery using a zinc cathode plate in which an amalgam layer is not formed on the surface of the zinc plate. The batteries C and D were manufactured in the same manner as the battery B without winding the electrode group. Each of the batteries A to D was manufactured by using a zinc plate for a cathode plate, an anode plate and a retainer of the same size and the same material, and using the same amount of the same material of the electrolytic solution. Next, the batteries A to D were heated at a temperature of 25 ± 1 ° C. and a constant voltage limiting current of 3.00 V was set to 150.
After charging for 6 hours with mA, pause for 10 minutes, then 100mm
The charging / discharging cycle in which charging / discharging was performed until the terminal voltage reached 1.7 V at A was repeated as a cycle, and the time until the end-of-discharge voltage reached 1.7 V at each cycle was measured. The measurement results are as shown in FIG.
The battery reaches the end of its life when the discharge time is less than 2.5 hours. From FIG. 2, the batteries A and B of this embodiment are the conventional batteries C and D.
It can be seen that the charging / discharging characteristics are improved compared to. In particular, it can be seen that the charge / discharge characteristics of the battery A of the present example in which the zinc cathode plate was formed by displacement deposition and the electrode group was composed of the spiral electrode group were greatly improved.

[0017]

According to the first aspect of the present invention, the aging can be performed without using a large amount of mercury as in the conventional case. Moreover, since the fixing property of the amalgam layer to the zinc cathode plate is increased,
The amalgam layer does not easily fall off even when the battery is repeatedly charged and discharged. Therefore, according to the present invention, the zinc plate can be put to practical use as a battery cathode plate.

According to the second aspect of the invention, the zinc cathode plate can be manufactured by easily carrying out this aging.

According to the invention of claim 3, the fixing property of the amalgam layer on the zinc cathode plate is high, and the amalgam layer is unlikely to fall off even if the battery is repeatedly charged and discharged. Therefore, a long-life zinc cathode plate can be obtained.

According to the invention of claim 4, it is possible to suppress the generation of a local battery due to impurities in the battery, so that the hydrogen overvoltage of the battery becomes high.

According to the fifth aspect of the invention, since the amalgam layer can be prevented from falling off, the life of the battery can be extended and the discharge capacity at high rate discharge can be improved.

[Brief description of drawings]

1A to 1D are schematic diagrams showing a process of producing a zinc cathode plate by substitution deposition using indium.

FIG. 2 is a diagram showing life characteristics of a battery.

Claims (5)

[Claims] 1. A method for producing a zinc cathode plate having an amalgam layer on a surface thereof, wherein a metal having a melting point lower than that of zinc is substituted and deposited on the surface of the zinc plate, and then the zinc plate is subjected to an aging treatment. Forming said amalgam layer. 2. The method for producing a zinc cathode plate according to claim 1, wherein at least one metal selected from indium, thallium, lead and cadmium is used as the metal having a melting point lower than that of zinc. 3. A zinc cathode plate having an amalgam layer on the surface thereof, wherein the amalgam layer comprises an alloy layer of a metal having a melting point lower than that of zinc deposited by substitution and deposition on the surface of the zinc plate, and an alloy of zinc and mercury. A zinc cathode plate characterized in that 4. A zinc-lead dioxide storage battery having an electrode group formed by combining a lead dioxide anode plate and a zinc cathode plate, the zinc cathode plate being lower than zinc deposited by substitution on the surface of the zinc plate. The one having an amalgam layer composed of an alloy layer of a metal having a melting point, zinc and mercury is used, the lead dioxide anode plate not containing antimony and arsenic is used, and the zinc plate of the zinc cathode plate is 99.99%. What is claimed is: 1. A zinc-lead dioxide storage battery characterized by using an aqueous solution of sulfuric acid which does not substantially contain a substance for lowering hydrogen overvoltage, which has the above-mentioned purity. 5. The zinc-lead dioxide storage battery according to claim 4, wherein the electrode group is a spiral type electrode group.