JP2011171220A - Alkaline storage battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an alkaline storage battery that can eliminate carbonate ions which increase as a cycle is passed by charge and discharge at a high rate, and can suppress deterioration of a discharge capacity caused by the carbonate ions. <P>SOLUTION: The alkaline storage battery includes an electrode group formed of a positive electrode 12, a negative electrode 11, and a separator 13, and an alkaline electrolyte. The electrolyte contains calcium hydroxide of 0.60-0.80 mol/l. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electrolyte for alkaline storage batteries such as nickel-cadmium storage batteries and nickel-hydrogen storage batteries.

  In recent years, the use of secondary batteries (storage batteries) has expanded, and storage batteries have come to be used in a wide range such as personal computers, mobile phones, electric vehicles, hybrid vehicles, electric bicycles, and electric tools. Among these, alkaline storage batteries such as nickel-hydrogen storage batteries and nickel-cadmium storage batteries are used as power sources for devices that require high output, such as electric vehicles, hybrid vehicles, electric bicycles, and electric tools.

  When the above alkaline storage battery is repeatedly charged and discharged at a high rate of current, heat is generated inside the alkaline storage battery and the temperature inside the battery becomes high. Thus, when the inside of a battery becomes high temperature, a separator will be decomposed | disassembled by the alkali contained in electrolyte solution, or a separator will be oxidized with the oxygen inside a battery, and it will be thought that a carbonate ion is generated. When carbonate ions are generated inside the battery, the carbonate ions themselves have poor conductivity, and the carbonate ions inhibit the reaction between cadmium and hydroxide ions at the negative electrode / electrolyte interface, so the battery characteristics, especially the discharge capacity This is presumed to be a cause of deterioration. Therefore, in order to improve the discharge capacity in a high rate cycle, it is necessary to suppress carbonate ions generated inside the battery.

Incidentally, for the purpose of improving the charge / discharge characteristics at high temperature, an alkaline storage battery containing calcium phosphate in an electrolytic solution has been proposed in Patent Document 1 (Japanese Patent Laid-Open No. 10-106619).
However, even when calcium phosphate is contained in the electrolytic solution proposed in Patent Document 1, the generation of carbonate ions cannot be suppressed, and the discharge capacity in a high rate cycle cannot be improved.

JP-A-10-106619

  An object of the present invention is to solve the above-mentioned problems, and in particular to provide an alkaline storage battery capable of improving the discharge capacity in a high rate cycle.

In order to achieve the above object, the alkaline storage battery of the present invention comprises:
In an alkaline storage battery comprising an electrode group consisting of a positive electrode, a negative electrode and a separator, and an alkaline electrolyte,
The electrolytic solution contains 0.60 mol / l or more and 0.80 mol / l or less calcium hydroxide.

The alkaline storage battery of the present invention contains 0.60 mol / l or more and 0.80 mol / l or less calcium hydroxide in the electrolytic solution.
Calcium hydroxide dissociates into calcium ions and hydroxide ions in the alkaline electrolyte.
Of these, calcium ions react and precipitate as calcium carbonate in the presence of the aforementioned carbonate ions. By this reaction, carbonate ions that are considered to be a cause of deterioration of discharge capacity in a high rate cycle can be removed.

However, the amount of calcium hydroxide contained in the electrolytic solution must be 0.60 mol / l or more and 0.80 mol / l or less. This is because when calcium hydroxide is less than 0.60 mol / l, there are few calcium ions generated by the dissociation of calcium hydroxide, the reaction with carbonate ions cannot be performed sufficiently, and carbonate ions cannot be sufficiently removed as calcium carbonate. Moreover, when calcium hydroxide exceeds 0.80 mol / l, the problem that an excess calcium ion will inhibit an electrode reaction will arise.
Therefore, the calcium hydroxide contained in the electrolytic solution must be 0.60 mol / l or more and 0.80 mol / l or less.

  Furthermore, the reason for containing calcium hydroxide is that hydroxide ions are generated in addition to calcium ions by the dissociation of calcium hydroxide, in addition to the fact that calcium ions easily react with carbonate ions. This hydroxide ion is the same as the hydroxide ion in the dissociation of potassium hydroxide used in the alkaline electrolyte of the alkaline storage battery, so even if the hydroxide ion is dissociated in the alkaline electrolyte, the battery characteristics are improved. This is because there is no adverse effect.

  The present invention can provide an alkaline storage battery that can remove carbonate ions that increase with the passage of a high rate cycle, and that can suppress a decrease in discharge capacity due to carbonate ions.

It is sectional drawing which shows the alkaline storage battery of this invention typically.

  Next, one embodiment of the alkaline storage battery of the present invention will be described in detail below with reference to FIG. 1. However, the present invention is not limited to the following embodiment in any way, and the gist thereof is not changed. It is possible to implement with appropriate changes.

Example 1
1. Production of Negative Electrode A cadmium negative electrode 11 is formed by applying a negative electrode active material paste composed of an active material mainly composed of cadmium oxide, a conductive agent, and a binder on both surfaces of a negative electrode core 11a made of punching metal, After being rolled to a thickness, it is cut to a predetermined size. The negative electrode core 11a is exposed at the lower end of the cadmium negative electrode 11 after fabrication, and the negative electrode current collector 11b is welded to the exposed negative electrode core 11a later.

2. Preparation of Positive Electrode After forming a nickel sintered porous body on the surface of a positive electrode core body 12a made of punching metal, the nickel positive electrode 12 is filled with an active material mainly composed of nickel hydroxide by a chemical impregnation method. After being rolled to a predetermined thickness, it is cut to a predetermined size. The positive electrode core 12a is exposed at the upper end of the nickel positive electrode plate 12 after fabrication, and the positive electrode current collector 12b is welded to the exposed positive electrode core 12a later.

3. Production of Separator A non-woven fabric made of nylon was cut to a predetermined size to produce a separator 13.

4). Production of a spiral electrode group A separator 13 made of a nylon nonwoven fabric is interposed between the cadmium negative electrode 11 and the nickel positive electrode 12, and the spiral electrode group is formed by winding in a spiral shape. In this case, after the negative electrode core body 11a where the cadmium negative electrode 11 is exposed protrudes from the lower end portion of the separator 13 and the positive electrode core body 12a where the nickel positive electrode 12 is exposed protrudes from the upper end portion of the separator 13, It is designed to be spirally wound. In addition, a space part formed by removing the core axis is provided at the center of the spiral electrode group.

5. Preparation of Alkaline Electrolyte Using KOH having a specific gravity of 1.30 as the electrolyte of the alkaline electrolyte, adjusting the calcium hydroxide to 0.60 mol / l with respect to this alkaline electrolyte, producing an alkaline electrolyte did.
In this case, the amount of calcium hydroxide is 3.4% by mass with respect to the total amount of electrolyte.

6). Production of sealed nickel-cadmium storage battery Next, the negative electrode current collector 11b is resistance-welded to the negative electrode core 11a extending to the lower part of the spiral electrode group produced as described above, and extended to the upper part of the spiral electrode group. The positive electrode current collector 12b was resistance welded to the positive electrode core body 12a to be produced, and spiral electrode bodies were respectively produced.

  Next, after inserting a spiral electrode body into a bottomed cylindrical metal outer can 15 in which nickel was plated on iron, the negative electrode current collector 11b and the bottom of the metal outer can 15 were spot welded.

  Thereafter, the insulating ring 14 was inserted into the upper end surface of the spiral electrode body. Next, the upper outer peripheral surface of the outer can 15 was grooved to form an annular groove 15 a at the upper end of the insulating ring 14. Thereafter, a sealing body 17 composed of a positive electrode cap 17b and a lid body 17a is prepared, and the lead portion 12c provided on the positive electrode current collector 12b is brought into contact with the lid body bottom portion 17c, so that the lid body bottom portion 17c and the lead portion 12c are provided. Were welded, and 4.5 g of electrolyte was poured into the metal outer can 15. Further, the sealing body 17 is placed on the annular groove 15a of the outer can 15 through the insulating gasket 16, and the outer end of the outer can 15 is crimped to the sealing body side to seal the nickel-cadmium storage battery having a nominal capacity of 2000 mAh. 10 was produced. This nickel-cadmium storage battery is designated as A1.

(Example 2)
A nickel-cadmium storage battery was produced in the same manner as in Example 1 except that calcium hydroxide was adjusted to 0.70 mol / l as the alkaline electrolyte. This nickel-cadmium storage battery is designated as A2.
In this case, the amount of calcium hydroxide is 4.0% by mass with respect to the total amount of the electrolytic solution.

(Example 3)
A nickel-cadmium storage battery was produced in the same manner as in Example 1 except that calcium hydroxide was adjusted to 0.80 mol / l as the alkaline electrolyte. This nickel-cadmium storage battery is designated as A3.
In this case, the amount of calcium hydroxide is 4.6% by mass with respect to the total amount of the electrolytic solution.

(Comparative Example 1)
A nickel-cadmium storage battery was produced in the same manner as in Example 1 except that calcium hydroxide was not contained as the alkaline electrolyte. This nickel-cadmium storage battery is designated X1.

(Comparative Example 2)
A nickel-cadmium storage battery was produced in the same manner as in Example 1 except that calcium hydroxide was adjusted to 0.53 mol / l as the alkaline electrolyte. This nickel-cadmium storage battery is designated X2.
In this case, the amount of calcium hydroxide is 3.0% by mass with respect to the total amount of the electrolytic solution.

(Comparative Example 3)
A nickel-cadmium storage battery was produced in the same manner as in Example 1 except that calcium hydroxide was adjusted to 0.90 mol / l as the alkaline electrolyte. This nickel-cadmium storage battery is designated X3.
In this case, the amount of calcium hydroxide is 5.1% by mass with respect to the total amount of the electrolytic solution.

7). High rate cycle characteristics Next, each of the nickel-cadmium storage batteries A1 to A3 and X1 to X3 was charged with a charging current of 2 A at room temperature (about 25 ° C.), and the peak voltage was exceeded. Later, when the battery voltage drops by 10 mV, charging is stopped (-ΔV method). Next, after stopping charging for 1 hour, the battery was discharged at a discharge current of 20 A until the battery voltage reached 0.8 V, and the discharge capacity of the first cycle was determined from the discharge time. Next, the charge capacity after 500 cycles is determined by repeating such charge and discharge cycles, and the ratio of the discharge capacity at the 500th cycle to the discharge capacity at the first cycle is determined as the discharge capacity ratio after 500 cycles (after 500 cycles). Discharge capacity ratio (%) = (discharge capacity after 500 cycles (mAh) / discharge capacity at the first cycle (mAh)) × 100).

Table 1 shows the average value of the results of experiments on three batteries.

As is clear from the results in Table 1 above, the batteries A1 to A3 having a calcium hydroxide amount of 0.60 mol / l or more and 0.80 mol / l or less have a discharge capacity ratio after 500 cycles of 84.2% to The result was as high as 84.5%.
In contrast, the batteries X2 and X3 having calcium hydroxide amounts of 0.53 mol / l and 0.90 mol / l have a discharge capacity ratio after 500 cycles as compared with the battery X1 not containing calcium hydroxide. 82.9% to 83.2%, which is the same or worse.

From this result, it can be seen that even if calcium hydroxide is contained in the electrolytic solution, the effect cannot be obtained unless the content is 0.60 mol / l or more and 0.80 mol / l or less.
This is considered to be because the effect of removing carbonate ions cannot be sufficiently obtained when the amount of calcium hydroxide is less than 0.60 mol / l. Further, if the amount of calcium hydroxide exceeds 0.80 mol / l, carbonate ions can be removed, but excessive calcium ions themselves inhibit the electrode reaction, so that the discharge capacity ratio is rather lowered.

  From the above, it can be seen that it is necessary to contain 0.60 mol / l or more and 0.80 mol / l or less calcium hydroxide in the alkaline electrolyte in order to improve the discharge capacity in the high rate cycle.

  In the embodiment described above, an example in which the present invention is applied to a nickel-cadmium storage battery has been described. However, the present invention is similarly applied to an alkaline storage battery other than a nickel-cadmium storage battery, for example, a nickel-hydrogen storage battery. It is clear that the effect of can be obtained.

10: Nickel-cadmium storage battery,
11 ... Cadmium negative electrode, 11a ... Negative electrode core, 11b ... Negative electrode current collector,
12 ... Nickel positive electrode, 12a ... Positive electrode core, 12b ... Positive electrode current collector, 12c ... Lead part,
13 ... Separator,
14: Insulating ring,
15 ... metal outer can, 15a ... annular groove,
16 ... Insulating gasket,
17 ... Sealing body, 17a ... Lid, 17b ... Positive electrode cap, 17c ... Bottom of lid,

Claims (1)

In an alkaline storage battery comprising an electrode group consisting of a positive electrode, a negative electrode and a separator, and an alkaline electrolyte,
The alkaline electrolyte battery, wherein the electrolytic solution contains 0.60 mol / l or more and 0.80 mol / l or less calcium hydroxide.

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