JP2014186880A - Nickel-cadmium storage battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nickel-cadmium storage battery which allows a charge characteristic under a high temperature environment to be improved largely, but never suffers from the worsening of the easiness of filling an electrolytic solution.SOLUTION: A nickel-cadmium storage battery comprises: a positive electrode including nickel hydroxide as a positive electrode active material; an unbaked negative electrode including cadmium; and an electrolytic solution. In the nickel-cadmium storage battery, the positive electrode has an element of Y added thereto; the electrolytic solution contains an element of W and an element of Na. The addition amount of the element of W is preferably 0.4-2.8 mass% to the positive electrode active material.

Description

  The present invention relates to a nickel-cadmium storage battery.

  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.

  Among the alkaline storage batteries, the nickel-cadmium storage battery, when the environment at the time of charging is normal temperature, the overvoltage during the charge reaction of the nickel hydroxide of the positive electrode is smaller than the overvoltage required for the oxygen generation reaction from the alkaline electrolyte, The potential difference is large.

For this reason, the charge reaction of nickel hydroxide first proceeds, and after this charge reaction is almost completed, the reaction proceeds to the oxygen generation reaction from the alkaline electrolyte.
Therefore, the positive electrode can be charged reliably and sufficiently in a room temperature environment.

However, in the case of charging in a high temperature environment, since the overvoltage of the oxygen generation reaction from the alkaline electrolyte is reduced, the difference from the overvoltage during the nickel hydroxide charging reaction is reduced.
Therefore, a competitive relationship between the charging reaction and the oxygen generation reaction occurs from a relatively early stage of charging, and the nickel hydroxide charging reaction does not proceed sufficiently, and the positive electrode cannot be fully charged.

  That is, in a high temperature environment, there arises a problem that the charging efficiency is lowered, thereby reducing the discharge capacity of the battery.

  As means for solving such a problem, Patent Document 1 discloses a method in which a cobalt component is co-precipitated during the synthesis of nickel hydroxide as an active material to lower the equilibrium potential of the positive electrode.

  Patent Document 2 discloses a method of increasing the overvoltage required for the oxygen generation reaction of the positive electrode by using nickel hydroxide coprecipitated with cadmium or the like.

  Patent Document 3 discloses a method for improving high temperature characteristics by adding W element to an electrolyte in a nickel-hydrogen battery.

Japanese Patent Laid-Open No. 50-132441 JP-A-62-108458 JP-A-8-88020

However, in any of the above methods, the charging characteristics in a high temperature environment are not at a satisfactory level.

  The present invention solves the above-described problems, and provides a nickel-cadmium storage battery that can greatly improve the charging characteristics in a high-temperature environment and that does not deteriorate the pouring property of the electrolytic solution.

  In order to solve the above problems, a nickel-cadmium storage battery of the present invention has a positive electrode containing nickel hydroxide as a positive electrode active material, a non-sintered negative electrode containing cadmium, and an electrolyte solution, and the positive electrode contains Y element. The electrolyte solution contains W element and Na element.

  In such a configuration, since the Y element is added to the positive electrode containing nickel hydroxide, the present invention has a structure in which the Y element enters between the nickel hydroxide crystal layers and the crystal layers greatly expand.

  Further, since the Na element is contained in the electrolytic solution, Na ions having a small ionic radius are likely to enter between nickel hydroxide crystal layers on the surface of the secondary aggregate of the positive electrode active material. Due to the synergistic effect of both, the W element contained in the electrolyte can easily move to the deep part of the nickel hydroxide crystal.

  That is, the fact that the W element can easily penetrate to the deep part of the crystal makes it possible to exhibit the effect of the W element faster and more reliably.

INDUSTRIAL APPLICABILITY The present invention can provide a nickel-cadmium storage battery that can greatly improve the charging characteristics in a high temperature environment and that does not deteriorate the pouring property of the electrolytic solution.

  One embodiment of the nickel-cadmium storage battery of the present invention will be described in detail below, but the present invention is not limited to the following embodiment in any way, and may be appropriately modified and implemented without departing from the scope of the present invention. Is possible.

(Experimental example 1)
1. Production of Positive Electrode A sintered nickel substrate having a porosity of about 80% obtained by sintering in a reducing atmosphere was mixed with an aqueous solution of nickel nitrate and cobalt nitrate having a specific gravity of 1.75 (atomic ratio of nickel and cobalt is 10: 1), and then immersed in an aqueous sodium hydroxide solution.

  In this manner, immersion in a mixed aqueous solution of nickel nitrate and cobalt nitrate and an aqueous sodium hydroxide solution was alternately repeated, and a predetermined active material was filled into the substrate to obtain a sintered electrode plate.

  Next, after immersing the sintered electrode plate in an aqueous solution prepared by mixing nickel nitrate with a 2N yttrium nitrate aqueous solution so that the weight ratio of nitrate is 1: 1, Was immersed in the substrate to form various hydroxide layers, washed with water and dried at 120 ° C. for 30 minutes to obtain a nickel positive electrode containing Y element.

2. Production of Negative Electrode 20 parts by mass of cadmium as a precharge active material, 1 part by mass of organic polymer paste, 1 part by mass of nylon fiber, 30 parts by mass of water, and 80 parts by mass of cadmium oxide as an active material Were kneaded to prepare a negative electrode active material paste.

  Next, the obtained negative electrode active material paste was applied to both surfaces of the conductive substrate, and then dried to form an active material layer, which was cut into a predetermined size to produce a non-sintered cadmium negative electrode.

3. Production of Separator A nylon nonwoven fabric was cut to a predetermined size to produce a separator.

4). Preparation of Alkaline Electrolyte NaOH 2 having a specific gravity of 1.30 is used as the electrolyte of the alkaline electrolyte, and Na _{2 is used} so that the amount of W element is 0.4% by mass with respect to the positive electrode active material with respect to this alkaline electrolyte WO ₄ was added to prepare an alkaline electrolyte.

5. Production of Sealed Nickel-Cadmium Storage Battery A separator was interposed between the positive electrode and the negative electrode produced as described above and wound in a spiral shape to produce a spiral electrode body. The spiral electrode body was inserted into a bottomed cylindrical metal outer can made of nickel-plated iron, and the negative electrode and the metal outer can bottom were welded with a negative electrode lead to be electrically connected.

Thereafter, an insulating ring was inserted into the upper end portion of the spiral electrode body, and grooving processing was performed on the outer peripheral surface of the upper portion of the outer can to form an annular groove portion.
Next, a sealing body including a positive electrode cap and a lid was prepared, and the positive electrode and the bottom of the lid were welded with a positive electrode lead and electrically connected.

  Further, the electrolytic solution is poured into a metal outer can, and the sealing body is placed on the annular groove of the outer can via an insulating gasket, and the opening end of the outer can is crimped to the sealing body side and sealed. A nickel-cadmium storage battery was prepared. This nickel-cadmium storage battery is designated as A1.

(Experimental example 2)
NaOH having a specific gravity of 1.30 is used as the electrolyte of the alkaline electrolyte, and Na ₂ WO ₄ is added to the alkaline electrolyte so that the amount of W element is 0.8% by mass with respect to the positive electrode active material. A nickel-cadmium storage battery was prepared in the same manner as in Experimental Example 1 except that the alkaline electrolyte was prepared. This nickel-cadmium storage battery is designated as A2.

(Experimental example 3)
NaOH having a specific gravity of 1.30 is used as the electrolyte of the alkaline electrolyte, and Na ₂ WO ₄ is added to the alkaline electrolyte so that the amount of W element is 2.5% by mass with respect to the positive electrode active material. A nickel-cadmium storage battery was prepared in the same manner as in Experimental Example 1 except that the alkaline electrolyte was prepared. This nickel-cadmium storage battery is designated as A3.

(Experimental example 4)
NaOH having a specific gravity of 1.30 is used as the electrolyte of the alkaline electrolyte, and Na ₂ WO ₄ is added to the alkaline electrolyte so that the amount of W element is 2.8% by mass with respect to the positive electrode active material. A nickel-cadmium storage battery was prepared in the same manner as in Experimental Example 1 except that the alkaline electrolyte was prepared. This nickel-cadmium storage battery is designated as A4.

(Experimental example 5)
A sintered nickel substrate having a porosity of about 80% obtained by sintering in a reducing atmosphere is mixed into a mixed aqueous solution of nickel nitrate and cobalt nitrate having a specific gravity of 1.75 (atomic ratio of nickel to cobalt is 10: 1). Immersion and then immersion in an aqueous solution of sodium hydroxide. In this way, immersion in a mixed aqueous solution of nickel nitrate and cobalt nitrate and an aqueous solution of sodium hydroxide is alternately repeated, and a predetermined active material is filled in the substrate. A nickel-cadmium storage battery was produced in the same manner as in Experimental Example 1 except that a sintered electrode plate was obtained and NaOH having a specific gravity of 1.30 was used as the electrolyte of the alkaline electrolyte. This nickel-cadmium storage battery is designated as A5. The positive electrode of battery A5 does not contain Y element.

(Experimental example 6)
A nickel-cadmium storage battery was produced in the same manner as in Experimental Example 1 except that NaOH having a specific gravity of 1.30 was used as the electrolyte of the alkaline electrolyte. This nickel-cadmium storage battery is designated as A6.

(Experimental example 7)
NaOH having a specific gravity of 1.30 is used as the electrolyte of the alkaline electrolyte, and Na ₂ WO ₄ is added to the alkaline electrolyte so that the amount of W element is 0.8% by mass with respect to the positive electrode active material. A nickel-cadmium storage battery was prepared in the same manner as in Experimental Example 5 except that the alkaline electrolyte was prepared. This nickel-cadmium storage battery is designated as A7.

(Experimental example 8)
A nickel-cadmium storage battery was produced in the same manner as in Experimental Example 5 except that KOH having a specific gravity of 1.30 was used as the electrolyte of the alkaline electrolyte. This nickel-cadmium storage battery is designated as A8.

(Experimental example 9)
KOH having a specific gravity of 1.30 is used as the electrolyte of the alkaline electrolyte, and WO ₃ is added to the alkaline electrolyte so that the amount of W element is 0.8% by mass with respect to the positive electrode active material. A nickel-cadmium storage battery was produced in the same manner as in Experimental Example 1 except that the electrolytic solution was produced. This nickel-cadmium storage battery is designated as A9.

6). Battery evaluation <Measurement of high-temperature charging characteristics>
The high-temperature charge characteristics were measured using 4 cells each of the nickel-cadmium storage batteries A1 to A9.

The conditions for the high temperature charge characteristics were as follows. First, each measurement battery was kept in an atmosphere of 70 ° C. for 24 hours to set the temperature inside the battery to 70 ° C. Thereafter, this battery was charged with a charging current of 0.1 It (160 mA) in an atmosphere of 70 ° C. for 16 hours.
Next, after the charged battery is rested for 3 hours in an atmosphere at 25 ° C., the battery is discharged at a discharge current of 1 It (1600 mA) in an atmosphere at 25 ° C. until the battery voltage reaches 1.0 V, and the discharge capacity is obtained. It was.

In addition, the discharge capacity of each battery is an average value of 4 cells, and is shown as a ratio when the discharge capacity of the battery A5 is 100.
Table 1 shows the results of the high temperature charge characteristics of each battery.

  From the results shown in Table 1, when the high temperature charge characteristic of the battery A5 containing no Y element in the positive electrode and containing Na element but not containing W element is 100, the positive electrode contains Y element and the electrolyte contains Na element. The high-temperature charge characteristic of the battery A6 containing no element but not containing the W element is 110, which is a slight improvement. From this, it can be seen that when the electrolyte solution does not contain the W element, the positive electrode simply does not contain the Y element, and sufficient effects on the high-temperature charge characteristics cannot be obtained.

  Moreover, the high temperature charge characteristic of battery A7 which does not contain Y element in a positive electrode, and contains Na element and W element in an electrolyte solution (0.8 mass%) is 102. From the results of the batteries A5 and A7, it can be seen that when the Y element is not included in the positive electrode, it is not possible to obtain a sufficient effect on the high temperature charge characteristics only by adding the W element to the electrolytic solution.

  Furthermore, the high-temperature charge characteristic of the battery A8 in which the positive electrode does not contain the Y element and the electrolyte solution contains neither the Na element nor the W element is 102. On the other hand, the high temperature charge characteristic of the battery A9 containing the positive electrode Y element, not containing the Na element in the electrolytic solution, and containing the W element is lowered to 86. From this, it can be seen that when the electrolytic solution does not contain Na element, the high-temperature charge characteristics are lowered even if the positive electrode contains Y element and the electrolytic solution contains W element.

  In contrast, the high-temperature charge characteristics of the batteries A1 to A4 containing the Y element in the positive electrode and the Na element and the W element in the electrolytic solution are 117 to 125, and it can be seen that they are greatly improved.

  The reason for this is that the Y element that can be dissolved in the acid is filled in the pores of the sintered substrate as a mixed aqueous solution of yttrium nitrate and nickel nitrate and hydrated, so that the Y element is previously introduced into the crystal of nickel hydroxide. This is because crystals with expanded layers can be formed.

  Then, the W element that can be dissolved in alkali is brought into contact with the positive electrode active material in the form of being dissolved in NaOH. Since it moves, it can penetrate to the deep part of the crystal.

  It is presumed that due to the synergistic effect of both, nickel hydroxide, which is a positive electrode active material, can be in a good state with respect to charge acceptability during high-temperature charging.

Further, in the case of a nickel-cadmium storage battery, when Na element is present in the electrolyte, the negative electrode active material forms γ-type cadmium hydroxide. Further, it is known that the negative electrode active material forms β-type cadmium hydroxide when K element is present in the electrolytic solution.
In addition, the crystalline form of γ-type cadmium hydroxide and β-type cadmium hydroxide may have a synergistic effect due to the compatibility with further contained elements in the electrolytic solution.
That is, in the nickel-cadmium storage battery containing the W element in the electrolytic solution, it can be seen from the results of the batteries A2 and A9 that the high-temperature charge characteristics are remarkably improved when the electrolytic solution further contains the Na element.

  In addition, as addition amount of W element of electrolyte solution, 0.4 mass% or more and 2.8 mass% or less are preferable with respect to a positive electrode active material.

<Measurement of liquid injection properties>
In Experimental Example 4, an assembly work in progress before injection of the alkaline electrolyte was prepared. This is designated as battery A10. From this state, the time from when the alkaline electrolyte used in Experimental Example 4 was injected to when the electrolyte completely penetrated into the spiral electrode body (visual observation) was measured.

Moreover, the assembly work-in-process before alkaline electrolyte injection was produced like the experiment example 4 except using the sintering type cadmium negative electrode generally used as a negative electrode. This is designated as battery A11. Similarly, from this state, the time from when the alkaline electrolyte used in Experimental Example 4 was poured to when the electrolyte completely penetrated into the spiral electrode body (visual observation) was measured.
The results are shown in Table 2.

  When the amount of W element added to the electrolytic solution is increased, the viscosity of the electrolytic solution increases and the pouring property of the electrolytic solution decreases. When a sintered cadmium negative electrode was used as the negative electrode as in the battery A11, a liquid pool was formed on the upper end surface of the spiral electrode body, and it took 25 seconds for the electrolyte to completely penetrate into the spiral electrode body.

  On the other hand, in the battery A10 using the non-sintered conducting cadmium negative electrode, the electrolyte completely penetrated into the spiral electrode body in 0.5 seconds.

  From the above results, in general, when battery assembly is produced on an automatic line, electrolyte permeability in 1 to 2 seconds or less is required. Therefore, when a sintered cadmium negative electrode is used, it is not suitable for automatic production. It can be seen that a battery using a non-sintered cadmium negative electrode is more appropriate.

The nickel-cadmium storage battery of the present invention has good charging characteristics in a high-temperature environment and is suitable for mass production by an automatic line because it does not deteriorate the pouring property of the electrolytic solution, and has great industrial applicability.

Claims (2)

A positive electrode containing nickel hydroxide as a positive electrode active material;
A non-sintered negative electrode containing cadmium;
An electrolyte,
In a nickel-cadmium storage battery having
Y element is added to the positive electrode,
The electrolyte contains W element and Na element;
A nickel-cadmium storage battery characterized by that. The nickel-cadmium storage battery according to claim 1, wherein the W element is 0.4 mass% or more and 2.8 mass% or less with respect to the positive electrode active material.