KR100287122B1 - Alkali-zinc secondary battery - Google Patents

Abstract

PURPOSE: Provided is an alkali-zinc secondary battery having an alkali electrolyte containing barium fluoride, which can improve the lifetime of the battery and the charging and discharging efficiency. CONSTITUTION: The alkali-zinc secondary battery comprises a nickel cathode(1), a zinc anode(2), polyamide nonwoven fabric(3) formed on the nickel cathode(1), a polypropylene microcellular membrane(4) covering the polyamide nonwoven fabric(3), a cotton nonwoven fabric(6) formed on the zinc anode(2), a silver-coated polypropylene membrane(5) covering the cotton nonwoven fabric(6), and the alkali electrolyte containing the barium fluoride, wherein the concentration of the barium fluoride is 10¬-4 to 10¬-2M.

Description

[Name of invention]

Alkaline Zinc Secondary Battery

Detailed description of the invention

The present invention relates to an alkaline zinc secondary battery using zinc as an anode and using an alkaline solution as an electrolyte, and more particularly, using zinc as a negative electrode such as a nickel-zinc secondary battery or a silver-zinc secondary battery. In order to prevent the growth of zinc dendrite, which is one of the main causes of battery capacity reduction in alkaline zinc secondary batteries, a metal compound more susceptible to oxidation than zinc is added to the electrolyte to prevent battery capacity reduction and the growth of zinc dendrite. The present invention relates to an alkaline zinc secondary battery, which effectively suppresses the battery life and greatly improves the charge and discharge efficiency.

Alkaline zinc secondary casting using zinc as the negative electrode active material has the advantage of high energy density and low cost, and thus is widely used as a secondary battery for stationary power storage as well as for electric vehicles. However, in the alkaline zinc secondary battery, since the zinc negative electrode is dissolved in the alkaline solution and zinc is repeatedly eluted and precipitated by the charge and discharge reaction, the shape of the electrode plate changes with charge and discharge, and zinc is not uniformly deposited during charging. However, there is a disadvantage in that the cycle life is short because the dendritic zinc penetrates into the separator and causes a short circuit.

In order to improve the shortcomings of the cycle life, SANYO Corp. adds oxides and hydrates of In and T1 to zinc electrodes in Japanese Patent Laid-Open Nos. 60-185372 and 62-108467, respectively. A method of adding ions and GeO about 10 ^-4 M was proposed to suppress the densification of the surface of the zinc electrode.

However, the former method has a limitation in suppressing the densification of zinc electrodes because In and Tl oxides and hydrates are dissolved in small amounts in the electrolyte during charge and discharge. Accordingly, a small amount of In ions and GeO were added to the electrolyte in order to overcome the limitations of the former, but also satisfactory results were not obtained.

On the other hand, at FURUKAWA, Japanese Patent Application Laid-Open Nos. 6-208053 and 61-61366, and Japanese Patent Laid-Open No. Hei 1-239763 show TiO ₂ , ZrO ₂ , BaO, Ca (OH) ₂ , MgO, A method of adding Ba (OH) ₂ and the like was proposed to attempt to suppress self-discharge and growth of dendritic zinc.

However, this method has an undesirable problem because the additives are also dissolved in the zinc active material prepared by the dry compaction method because the additive is added to the zinc anode.

Accordingly, an object of the present invention is to provide an alkaline zinc secondary battery that not only solves the above problems but also greatly improves the cycle life and charge and discharge efficiency of the battery.

The alkaline zinc secondary battery of the present invention for achieving the above object is an alkali zinc secondary battery using zinc as the negative electrode and an alkaline solution as the electrolyte, it is composed of the barium fluoride in the electrolyte.

Hereinafter, the configuration of the present invention will be described in more detail with reference to the accompanying drawings.

Zinc dendrite, one of the factors that determine the cycle life of alkaline zinc secondary batteries, is caused by uneven current density at the surface of the zinc anode during charging, leading to the development of zinc into dendritic or acicular crystals, which cause a short circuit through the separator. Reduces the dose.

In the present invention, to improve this, barium fluoride was added to the alkaline electrolyte instead of the zinc negative electrode so that the conductivity of the electrolyte was not significantly lowered, but barium ions effectively prevented the growth of zinc dendrite, which is a dendritic crystal.

Briefly, the alkaline zinc secondary battery of the present invention is characterized in that the alkaline zinc secondary battery using zinc as the negative electrode and the alkaline solution as the electrolyte solution includes barium fluoride in the electrolyte solution.

1 is a cross-sectional view of a nickel-zinc secondary battery as an embodiment of the battery of the present invention, in which 1 is a nickel anode, 2 is a zinc anode, 3 is a polyamide nonwoven fabric, 4 is a polypropylene microporous film, and 5 is Ag. Polypropylene film, 6, is a cotton nonwoven fabric.

According to FIG. 1, the nickel-zinc secondary battery according to the present invention is hydrophilic with a moisture content of 300% and high permeability of oxygen gas so that the nickel anode 1 can have a sufficient capacity in the nickel anode 1 and retain an electrolyte solution. The polyamide nonwoven fabric 3 is formed and the polyamide nonwoven fabric 3 is surrounded by two layers of hydrophilic polypropylene microporous membranes 4 for the production and suppression of zinc dendrites, and the zinc cathode 2 is generated during charging. In order to suppress penetration of zinc dendrites and to quickly absorb oxygen generated from the nickel anode, a cotton nonwoven fabric 6 is formed, and the cotton nonwoven fabric 6 is coated with Ag to minimize the humidity of the electrolyte and accelerate the absorption of oxygen gas. It is a structure enclosed by the dough polypropylene film 5.

The present invention is to add a barium fluoride to the alkaline electrolyte when the battery configuration of the above structure to solve the problems of the conventional battery described above.

That is, since barium fluoride is added to the alkaline electrolyte, the growth of zinc dendrites generated by the nonuniform distribution of the zinc cathode during charge and discharge is effectively prevented, and fluorine ions are introduced into the electrolyte, thereby improving charge and discharge efficiency. In other words, if barium fluoride, which is poorly soluble in alkali, is dissolved to the limit of dissolution and then filtered and added to the electrolyte containing KOH, KF and LiOH as the main component, barium ions are more easily electrochemically oxidized than zinc ions in the electrolyte. Therefore, due to the non-uniform distribution, oxidized before the zinc dendrites grown, the growth of the dendrites is suppressed. In addition, fluorine ions compensate for the decrease in conductivity due to barium ions because of their high electrical conductivity and mobility.

Meanwhile, the concentration of barium fluoride is 10 ^-4 M- ^10-10 M are preferable. The reason for limiting the concentration of barium fluoride is that barium fluoride is very poorly soluble in alkaline solution, so when it exceeds 10 ^-2 M, a supersaturated precipitate causes a rather adverse effect. In addition, 10 ^-4 When added below M, the additive effect does not appear.

The present invention will be described in more detail with reference to the following Examples and Comparative Examples, but this does not limit the scope of the present invention.

Example 1

In this embodiment, a positive electrode was used as a nickel sintered electrode, and a negative electrode was used as an electrode manufactured by a dry compaction method.

First, 80 wt.% Zinc oxide, 10 wt.% Zinc powder, and 5 wt% PTFE (polytetrafluoroethylene) resin and ethylene oxide resin as binders were added in a total of 10 wt.% With 5 wt% lead oxide, 3 wt% lead oxide, and 2 wt% cadmium oxide. After kneading well, a negative electrode active material was prepared using a roller.

The nickel sintered anode used a current collector in which a nickel plate was expanded as a sintered substrate having a porosity of 75%.

Since the zinc negative electrode manufactured by the dry compaction method is weak in stiffness and the active material is likely to drop off, the cellulose-based nonwoven fabric is used to suppress the electrode capacity reduction as much as possible.

As an electrolyte solution, as shown in Table 1, a solution of potassium hydroxide 6M and LiOH 0.6M was used so as to have a concentration of barium fluoride.

In this example, two experimental batteries were made for experiments, where the experimental values are their average values. On the other hand, the electrode of the experimental battery used in this Example was 6 cm x 4 cm in size, two nickel anodes were used as one sheet, and two sheets were used and the capacity was 3.4 Ah. In addition, three zinc electrodes were used in the same size as the nickel anode, and the electrode capacity was 11.7 Ah, and the capacity ratio of the anode and the cathode was 3.45: 1.

In addition, one layer of a nylon nonwoven fabric having a thickness of 100 µm was encapsulated on a nickel anode side, and two layers of 25 µm hydrophilic polypropylene membranes were used to inhibit penetration of zinc dendrites. On the other hand, one layer of cellulose-based nonwoven fabric treated with PTFE was bonded to the zinc anode side by using an adhesive to minimize moisture in the electrolyte, and by using a hydrophobic polypropylene membrane to facilitate the permeation of oxygen gas and absorption of hydrogen gas. The increase in pressure inside the battery was minimized.

On the other hand, the charge and discharge test of the battery at 80% DOD at 90% charge. In other words, the battery was charged in three stages and discharged at a discharge rate of 3 hours, until the battery contact voltage was 1.2V, and the battery capacity was calculated, and the cycle was calculated until 60% of the rated capacity. In addition, the amount of the electrolyte was regulated to 1.4ml / Zn, Ah, and after the injection of the electrolyte was left at atmospheric pressure for 24 hours to allow the electrode to fully aging with the electrolyte (aging). Thereafter, a pressure measuring transmitter was attached to the electrolyte inlet and completely sealed, and the internal pressure during charging was measured according to the cycle life according to the charge and discharge conditions.

Example 2

In the present embodiment, the battery was manufactured in the same manner as in Example 1, except that the concentration of barium fluoride was as shown in Table 1, unlike in Example 1, and the battery was charged using the same measuring method. The discharge characteristic was measured.

Example 3

In the present Example, a battery was manufactured in the same manner as in Example 1 except that the concentration of barium fluoride was different from that in Example 1, as shown in Table 1 below. Charge and discharge characteristics were measured.

Comparative Example 1

This Comparative Example was introduced for comparison with the present invention, and unlike the above-described Example 1, except that the barium fluoride was not added to the electrolyte as shown in Table 1, the battery in the same manner as in Example 1 Was prepared, and the charge and discharge characteristics of the battery were measured using the same measurement method.

TABLE 1

Turning to the second illustrating the cycle life of the battery is changed when the concentration of barium fluoride, and barium fluoride at 10 ^-2 M 10 ^-4 It was found that the battery life according to the present invention (Examples 1 to 3) contained in the electrolyte in the concentration range of M was superior to the battery (Comparative Example 1) containing no barium fluoride at all.

Figure 3 shows the change in the ionic conductivity of the electrolyte according to the change in the concentration of barium fluoride, it can be seen that the ionic conductivity is slightly smaller than the pure KOH, but almost similar to the other.

The fourth turn shows an internal pressure variation of the battery of the cycle when charging, barium fluoride eseo 10 ^-2 M 10 ^-4 The internal pressure of the battery according to the charging cycle is lower than that of the battery according to the present invention (Examples 1 to 3) contained in the electrolyte in the concentration range of M (Comparative Example 1) containing no barium fluoride at all. It is considered that the gas generation was effectively absorbed by the separator.

Therefore, the alkaline zinc secondary battery of the present invention can effectively suppress zinc dendrites and greatly improve the life of the battery, and since the conductivity of the electrolyte is not significantly reduced since fluorine ions are added, the charge and discharge efficiency can be improved. There is an advantage.

[Brief Description of Drawings]

1 is a cross-sectional view of one embodiment of a battery of the present invention,

2 is a graph showing the cycle life of the battery according to the amount of BaF ₂ added,

3 is a graph showing the change in electrical conductivity of the electrolyte according to the amount of BaF ₂ added,

4 is a graph showing a change in the internal pressure of the battery according to the charging cycle.

* Explanation of symbols for main parts of the drawings

1: nickel anode 2: zinc cathode

3: polyamide nonwoven fabric 4: polypropylene microporous membrane

5: polypropylene film coated with Ag 6: cotton nonwoven fabric

Claims (2)

An alkaline zinc secondary battery using zinc as an anode and using an alkaline solution as an electrolyte, wherein the alkaline zinc secondary battery comprises barium fluoride in the electrolyte. The method of claim 1, wherein the concentration of barium fluoride is 10 ^-4 Alkaline zinc secondary battery, characterized in that M ~ 10 ^-2 M.