JP3695864B2 - Nickel-cadmium storage battery and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wound-type contact current collecting type nickel-cadmium storage battery using a paste type cadmium negative electrode.
[0002]
[Prior art]
As a negative electrode used for a nickel-cadmium storage battery, a sintered negative electrode plate has been conventionally used. However, a paste type negative electrode plate that has a simpler manufacturing process than that of a sintered type and has a high energy density is now available. It has become mainstream. However, since the paste-type negative electrode plate is inferior in the electron conductivity of the electrode as compared with the sintered type, the oxygen gas absorption performance is poor. In addition, since the paste type negative electrode plate has a weaker support force for the active material than the sintered type, the cadmium intermediate eluted in the electrolyte during charge / discharge tends to move to the separator, and this migration phenomenon is likely to occur. It has the problem of causing internal short circuits.
[0003]
For this reason, as a means for solving the above problem, Japanese Patent Application Laid-Open No. 64-12461 proposes a technique of forming a conductive layer made of carbon powder, fluororesin powder and paste on the surface of the negative electrode active material layer. Yes. According to this technique, the conductivity of the negative electrode surface and the oxygen gas permeability are improved, so that the oxygen gas absorption capacity of the negative electrode is enhanced. On the other hand, Japanese Patent Application Laid-Open No. 6-223823 proposes a technique of forming an alloy plating layer made of cadmium and indium on the surface of the negative electrode active material layer. According to this technique, migration of cadmium can be suppressed and migration can be prevented. It is said that the internal short circuit caused can be prevented.
[0004]
By the way, a wound type nickel-cadmium storage battery is formed by winding a cadmium negative electrode plate and a nickel positive electrode plate through a separator to form a spiral electrode body, and inserting the spiral electrode body and the electrolyte into a battery outer can. Although a battery is configured, there are the following two methods for collecting current of this type of battery.
(1) Current collecting tab method Positive and negative current collecting tabs are attached to the positive and negative electrode plates, and these positive and negative electrode plates are wound with separators on the outermost periphery so that the separator is positioned on the outermost periphery and completely covers the electrode plates. A separator is taped or thermally welded to the winding body in the vicinity of the turn end to form a spiral electrode body. A method in which the spiral electrode body is housed in a battery outer can with the positive and negative current collecting tabs welded to respective external electrode terminals.
(2) An outer peripheral contact current collecting system cadmium negative electrode plate and a nickel positive electrode plate provided with a positive electrode current collecting tab are wound through a separator so that the cadmium negative electrode plate is positioned at the outermost periphery, The positive electrode current collecting tab is welded to the positive electrode external terminal, and the spiral electrode body is connected to the negative electrode with the outermost outer peripheral surface of the cadmium negative electrode being in contact with the inner peripheral surface of the battery outer can also serving as the negative electrode external terminal. A method of storing in a battery outer can that also serves as an external terminal.
[0005]
When the outer peripheral contact current collecting method is adopted, it is not necessary to cover the outermost peripheral electrode surface of the spiral electrode body with a separator, and the current collecting tab is attached to the battery outer can that also serves as a negative electrode external terminal or a step of attaching the current collecting tab to the negative electrode plate The process of welding is unnecessary. Therefore, the outer peripheral contact current collection method has advantages in that the battery manufacturing process can be simplified and the effective power generation area (area of the electrode plate) can be increased as compared with the current collection tab method, but electrical connection is not good. It has an essential problem of being stable and causing a decrease in current collection efficiency due to contact resistance or the like.
[0006]
In particular, when the outer peripheral contact current collecting system is applied to the technique of the above-mentioned Japanese Patent Application Laid-Open No. 64-12461 in which a conductive layer containing a water repellent component and a paste is disposed on the negative electrode surface, these components increase the contact resistance. In addition, there is a problem that the current collection efficiency is significantly reduced due to swelling of the paste as the charge / discharge cycle progresses. In addition, when the outer peripheral contact current collection method is applied to the technique of Japanese Patent Laid-Open No. Hei 6-223823 in which an alloy plating layer is provided on the negative electrode surface, although the reduction in current collection efficiency is small, this technique still suppresses migration. And the improvement degree of oxygen gas absorption performance is not enough.
Therefore, further improvement is desired.
[0007]
[Problems to be solved by the invention]
The present invention has been made in view of the above, and in a nickel-cadmium storage battery of an outer peripheral contact current collection system, migration of cadmium can be more effectively suppressed, and current collection efficiency and the like are not reduced by repeated charge and discharge. An object is to provide a battery having a high capacity and a long life.
[0008]
[Means for Solving the Problems]
As a result of earnest research to solve the above problems, the present inventor suitably combined the above-mentioned technologies (the technologies of JP-A-6-223823 and JP-A-64-12461), and a new one was added to this. It has been found that by adding elements, battery productivity can be improved, capacity can be increased, current collection efficiency can be improved, and the present invention having the following configuration has been completed.
[0009]
The invention according to claim 1 is a battery in which a spiral electrode body formed by winding a cadmium negative electrode and a nickel positive electrode with a separator interposed therebetween so that the cadmium negative electrode is positioned on the outermost periphery, the outermost surface of the outermost periphery also serving as a negative electrode external terminal nickel housed periphery contacted collector system comprising a collector Ikegaiso the can in contact with the inner peripheral surface of the outer can - in cadmium storage batteries, as the cadmium negative electrode was coated on both surfaces of the conductive core Ryomakekyoku An alloy plating layer containing cadmium and indium is formed on the surface of the active material layer, and the surface of the alloy plating layer is a conductive powder except for the outermost outer peripheral surface that contacts the inner peripheral surface of the battery outer can. and using a cadmium negative electrode of the structure where the conductive layer is formed containing a water repellent powder and paste, the battery outer alloy plating layer of the outermost outer side the conductive layer is not formed as a collector portion Characterized in that direct contact with the inner peripheral surface of the.
[0010]
With this configuration, the alloy plating layer formed on the surface of the active material layer suppresses diffusion of the soluble intermediate that causes migration into the electrolytic solution. The conductive layer formed on the alloy plating layer functions to improve the oxygen gas absorption performance of the negative electrode. More specifically, the conductive powder contained in the conductive layer contributes to preferential charging of the cadmium active material on the negative electrode surface, and the water-repellent powder is preferentially charged with the cadmium active material and oxygen gas (generated at the positive electrode). Acts to facilitate contact. Therefore, the oxygen gas absorption performance of the negative electrode is improved. In addition, since the conductive layer is strongly fixed to the alloy plating layer by the paste, there is also an effect of suppressing diffusion of the soluble intermediate of cadmium, which is the active material, into the electrolytic solution. Thus, as a result of the action of the alloy plating layer and the conductive layer, the effect of suppressing migration and the ability to absorb oxygen gas are further enhanced.
[0011]
Here, from the above-described actions of the alloy plating layer and the conductive layer, the conductive layer needs to be positioned on the outermost surface of the negative electrode. However, when the conductive layer is positioned on the outermost surface of the negative electrode, A certain water-repellent powder acts to increase the contact resistance, and further increases the contact resistance when the paste as a component of the conductive layer has a property of swelling by an electrolyte solution such as a hydrophilic paste. Acts as follows. Therefore, the contact resistance gradually increases due to repeated charging and discharging.
[0012]
For this reason, in this invention, it is set as the structure which exposes an alloy plating layer on the negative electrode surface so that a conductive layer may not be formed in the outer surface of the cadmium negative electrode located in the outermost periphery of a spiral electrode body. The exposed surface of the alloy plating layer is used as a current collector, and the current collector is configured to be in contact with the inner peripheral surface of the battery outer can. On the other hand, a conductive layer is formed on the negative electrode facing the positive electrode. It has a structure. With such a configuration, the disadvantages of the outer peripheral contact current collecting system can be improved, so that a low-cost, high capacity, long-life nickel-cadmium storage battery that can utilize the advantages of the outer peripheral contact current collecting system can be obtained.
[0013]
According to a second aspect of the present invention, in the configuration of the first aspect of the invention, the winding direction length of the outermost outer peripheral surface of the cadmium negative electrode is substantially equal to the peripheral length of the inner side surface of the outer can. And With this configuration, there is no conductive layer on the negative electrode surface in contact with the inner surface of the outer can, and the alloy plating layer comes into contact with the battery outer can, so that the contact resistance can be further reduced.
[0014]
The invention according to claim 3 is to form an electrode plate by forming a negative electrode active material layer on both surfaces of the conductive core, and then forming an alloy plating layer containing cadmium and indium on the surface of both negative electrode active material layers, the longitudinal end portions near the one surface of the formed plates of the alloy plating layer and current collecting portion for contacting the inner circumferential surface of the battery outer can, except for the current collecting portion, on the front surface of the alloy plating layer A cadmium negative electrode preparation step for forming a conductive layer containing conductive powder, water-repellent powder and paste, and the cadmium negative electrode and nickel positive electrode through a separator so that the current collector is located outside the outermost periphery. The spirally wound electrode body is housed in the battery outer can in a state in which the spirally wound electrode is wound into an spirally wound electrode body and the current collector is in direct contact with the inner peripheral surface of the battery outer can. a spiral electrode body accommodating step, characterized in that it comprises a.
[0015]
According to this manufacturing method, the nickel-cadmium storage battery according to claim 1 can be manufactured reliably.
[0016]
According to a fourth aspect of the present invention, in the configuration of the third aspect of the present invention, the length in the winding direction of the current collector is substantially equal to the circumferential length of the inner surface of the battery outer can. It is characterized by being.
According to this manufacturing method, the nickel-cadmium storage battery according to claim 2 can be reliably manufactured.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to FIGS.
FIG. 1 is a front view of one surface (surface located outside after winding) of the cadmium negative electrode before being wound in a spiral shape, FIG. 2 is a cross-sectional view taken along line AA in FIG. FIG. 4 is a front view of the other surface of the cadmium negative electrode before winding in a spiral shape (the surface located on the inner side after winding), and FIG. 4 shows a spiral electrode body in which the cadmium negative electrode is spirally wound together with the nickel positive electrode and the separator. It is a perspective view. FIG. 2 is drawn with the thickness direction enlarged for convenience of drawing.
[0018]
As shown in FIG. 2, the cadmium negative electrode 10 has cadmium active material layers 2a and 2b formed on both surfaces of the conductive core 1, and an alloy plating layer 3a made of cadmium and indium on both surfaces of the cadmium active material layer. 3b is formed. Further, a conductive layer 4b made of conductive powder, water-repellent powder and paste is formed on the entire surface of the alloy plating layer 3b (see FIG. 3). On the other hand, the surface of the alloy plating layer 3a, as shown in FIGS. 1 and 2, a conductive layer is formed only on the portion of the length t ₁ from the winding start end portion 5 of the negative electrode, the remainder of the alloy plating The layer 3 a is exposed, and the exposed portion of the alloy plating layer 3 a is used as a current collector 6.
[0019]
The cadmium negative electrode 10 having such a structure is wound with the separator 12 and the nickel positive electrode 11 superimposed on the surface of the conductive layer 4b, with the start end 5 as a winding start end and the nickel positive electrode 11 inside. A spiral electrode body 13 as shown in FIG.
The spiral electrode body 13 has an exposed surface of the alloy plating layer (current collector 6) located on the outermost outer side (outer surface 14) of the electrode body, and on the surface of the cadmium negative electrode facing the nickel positive electrode 11. All have a structure in which the conductive layer 4a is formed. Therefore, when this spiral electrode body 13 is housed in a battery outer can (not shown) that also serves as a negative electrode external terminal, the spiral electrode body 13 tends to spread outward, so that the current collector 6 is disposed on the outer surface. The cadmium negative electrode and the battery outer can that also serves as the negative electrode external terminal are electrically connected to the inner peripheral surface of the can.
[0020]
The nickel-cadmium storage battery having the above structure is manufactured as follows. An active material paste is prepared by kneading a cadmium active material and a paste solution containing an organic fiber, an antihydration agent, etc., and this active material paste is applied to both sides of the conductive core 1 and dried. After the cadmium active material layers 2a and 2b are formed on both surfaces of the core, an alloy film containing cadmium and indium is applied to the conductive core on which the active material layer is formed to form alloy plating layers 3a and 3b.
[0021]
Next, a conductive powder and a water-repellent powder are added to an aqueous solution containing a paste, mixed to form a conductive slurry, and this slurry is coated on the surface of the alloy plating layers 3a and 3b. At this time, the surface of the alloy plating layer 3a of these alloy plating layers 3a and 3b is coated with slurry only on the portion of the length t ₁ from the winding start end portion 5 of the negative electrode, while the alloy plating layer 3b is coated with the slurry. Coats the slurry on its entire surface. Then, the cadmium negative electrode plate 10 concerning this invention can be produced by drying the coated electrically conductive slurry.
[0022]
Winding the cadmium negative electrode plate 10 and the known nickel positive electrode 11 through the separator 12 so that the exposed portion of the alloy plating layer (current collector 6) of the cadmium negative electrode plate 10 is located on the outermost outer peripheral surface of the spiral electrode body. The spiral electrode body 13 is produced by turning. The spiral electrode body 13 is inserted from an opening (not shown) of the outer can, and after the electrolyte is injected, the opening of the outer can is sealed with a sealing lid. Thereby, the nickel-cadmium storage battery (sealed type) concerning this invention is producible.
[0023]
Here, as the conductive powder in the above, for example, carbon powder, graphite powder, acetylene black, ketjen black and the like can be used. Further, as the water repellent powder, fluororesin, polyethylene, silicon resin and the like can be used, and it is preferable to use a fluororesin from the viewpoint of water repellency and dispersibility. Furthermore, as the paste, for example , a hydrophilic paste such as polyvinyl pyrrolidone, polyvinyl alcohol, carboxymethyl cellulose, methyl cellulose, and hydroxypropyl cellulose can be suitably used, but a hydrophobic resin such as polyvinyl acetate and polyester resin is used. May be. Moreover, as a method of applying the alloy film, an electroplating method, an electroless plating method, or the like can be used. For example, a suitable alloy film can be easily formed by an electroplating method.
[0024]
【Example】
The contents of the present invention will be described more specifically based on the present invention examples and comparative examples. Note that the structure of the battery is the same as that shown in the above embodiment.
(Example of the present invention)
A negative electrode active material composed of cadmium oxide and metal cadmium, and a paste material solution containing nylon fiber and sodium phosphate (an antihydration agent) are kneaded to form an active material paste. t ₂ = 95 mm) and dried. An electroplating bath containing Cd ²⁺ 1.0 gdm ^-3 , In ²⁺ 20 gdm ^-3 , H ₂ NSO ₃ H50 gdm ^-3 , and glue 0.2 gdm ^-3 with the core having the active material layer formed thereon as a cathode. It was immersed and subjected to negative electroplating with a current of 300 mAdm ⁻² . By this operation, an alloy plating layer (thickness: about 2 μm) made of cadmium and indium is formed on the surface of the core active material layer.
[0025]
Next, 10 parts by weight of carbon powder as a conductive powder, 10 parts by weight of polyvinylpyrrolidone as a hydrophilic paste, and Teflon dispersion 30-J as a water-repellent powder (manufactured by Mitsui DuPont Fluorochemical Co., Ltd.) 100 parts by weight of an aqueous solution containing 10% by weight is mixed to form a conductive slurry. The conductive slurry is coated on the entire surface of one side of the alloy plating layer, and the winding start end 5 is formed on the other side. It was coated (thickness of about 10 [mu] m) to the position of the length (see FIG. ₁₎ 65mm (t 1). Thereafter, this electrode plate was dried to form a cadmium negative electrode plate according to the present invention. Of the entire surface of the cadmium negative electrode plate, a portion where the conductive layer is not formed (a portion where the alloy plating layer is exposed) is defined as a current collecting portion.
[0026]
Separator (full length approximately 65 mm) between the cadmium negative electrode plate (total length approximately 95 mm) and a known nickel positive electrode plate (total length approximately 65 mm) with a positive electrode current collecting tab so that the current collector is located on the outermost outermost surface. About 160 mm) was inserted and the winding start ends of the positive and negative electrode plates were aligned and wound to form a spiral electrode body. The positive electrode current collecting tab is electrically connected to a battery cap (not shown) that also serves as a positive electrode external terminal, and the current collector is in contact with the inner surface of the battery outer can so that the spiral electrode body is attached to the battery outer case. Inserted into the can. Thereafter, an electrolytic solution was injected to seal the opening of the battery outer can. In this manner, a nickel-cadmium storage battery according to an example of the present invention having a nominal capacity of 900 mAH was produced.
[0027]
[Comparative Example 1]
A nickel-cadmium storage battery according to Comparative Example 1 was produced in the same manner as in the above-described invention except that the conductive slurry was directly coated on both sides of the cadmium active material layer without forming any alloy plating layer. The cadmium negative electrode plate of Comparative Example 1 differs from the inventive example in that it does not have any alloy plating layer and the outermost surface is completely covered with a conductive layer. In this comparative example 1 battery, the conductive layer serves as a current collector, and the conductive layer serves as an opposing surface of the nickel positive electrode.
[0028]
[Comparative Example 2]
A nickel-cadmium storage battery according to Comparative Example 2 was produced in the same manner as in the above invention example except that the conductive slurry was not coated at all. The cadmium negative electrode plate of Comparative Example 2 is different from the example of the present invention in that it does not have a conductive layer and the outermost layer surface (exposed surface) is an alloy plating layer. In the battery of Comparative Example 2, the alloy plating layer serves as a current collector, and the alloy plating layer serves as a surface facing the nickel positive electrode.
[0029]
[Comparative Example 3]
A nickel-cadmium storage battery according to Comparative Example 3 was fabricated in the same manner as in the above invention example, except that the conductive slurry was coated on the entire surface of both alloy plating layers. The cadmium negative electrode plate of Comparative Example 3 differs from the example of the present invention in that the entire surface of the outermost layer is a conductive layer and there is no portion where the alloy plating layer is exposed. In this comparative example 3 battery, the conductive layer serves as a current collector, and the conductive layer serves as an opposing surface of the nickel positive electrode.
[0030]
[Experiment]
Regarding the batteries of the present invention and the batteries of Comparative Examples 1 to 3, the transition of the battery capacity and the internal resistance when the charge / discharge cycle was repeated was examined. The results are shown in FIGS. 5 and 6, respectively. The charge / discharge cycle is a condition that repeats the cycle of charging to a fully charged state with a current of 1 C, resting for 1 hour, discharging to a final discharge voltage of 1.0 V with a current of 1 C, and then resting for another hour. I went there.
[0031]
As is clear from FIG. 5, in the present invention example and comparative example 2 in which the alloy plating layer is a surface (current collection part) that contacts the inner peripheral surface of the battery outer can, the comparative example 1 in which the conductive layer is the current collection part and Compared with Comparative Example 3, the increase in internal resistance accompanying the progress of the cycle was small. And the internal resistance of the comparative example 1 which does not have an alloy plating layer was especially large. From this, it can be seen that at least in terms of current collection efficiency, the surface in contact with the outer can can be an alloy plating layer.
[0032]
On the other hand, in FIG. 6, the present invention example> comparative example 3> comparative example 2> comparative example 1 in order of good cycle characteristics. More specifically, the present invention example in which both the conductive layer and the alloy plating layer were formed on the surface of the cadmium negative electrode and the current collecting portion was the alloy plating layer was particularly excellent in cycle characteristics. Moreover, although both the conductive layer and the alloy plating layer were formed, the comparative example 3 which used the current collection part as the conductive layer was a cycle characteristic a little inferior to the example of this invention. Further, Comparative Example 1 in which only the conductive layer was formed and Comparative Example 2 in which only the alloy plating layer was formed had inferior cycle characteristics as compared with the present invention example and Comparative Example 3.
[0033]
From the results of Comparative Example 2 having no conductive layer in FIGS. 5 and 6, it is possible to suppress an increase in contact resistance if the alloy plating layer is used as a current collector, but sufficient cycle characteristics cannot be obtained only with this configuration. Was supported. 5 and 6, a cadmium negative electrode structure in which an alloy plating layer and a conductive layer are sequentially formed on the surface of the cadmium active material layer and only the current collector is exposed on the surface of the alloy plating layer (the present invention). Example) proved to have the best cycle characteristics.
[0034]
【The invention's effect】
In the cadmium negative electrode according to the present invention, since the cadmium active material, the alloy plating layer, and the conductive layer are sequentially formed on the conductive core, the alloy plating layer and the conductive layer cooperate to suppress cadmium migration. In addition, since the conductive layer mainly increases the absorption of oxygen gas, the oxygen gas absorption performance of the negative electrode is significantly improved.
[0035]
Furthermore, the cadmium negative electrode according to the present invention has a structure in which a part of the alloy plating layer excellent in electronic conductivity is exposed and this exposed surface is used as a current collecting part to be in contact with the inner peripheral surface of the battery outer can serving as the negative electrode external terminal. did. As a result, the advantage of the outer peripheral contact current collecting system that simplifies the manufacturing process and increases the capacity can be utilized, and the decrease in the current collecting efficiency due to the progress of the cycle, which is the disadvantage of the outer peripheral contact current collecting system, can be suppressed.
[0036]
As described above, according to the present invention, a high-performance and long-life nickel-cadmium storage battery can be provided.
[Brief description of the drawings]
FIG. 1 is a front view of one surface (a surface located outside after winding) of a cadmium negative electrode plate before being wound in a spiral shape.
FIG. 2 is a cross-sectional view taken along line AA in FIG.
FIG. 3 is a front view of the other surface (the surface located on the inner side after winding) of the cadmium negative electrode before being spirally wound.
FIG. 4 is a perspective view of a spiral electrode body in which a negative electrode and a positive electrode are spirally wound via a separator.
FIG. 5 is a graph showing the relationship between the number of cycles and the internal resistance in the present invention example and the comparative example.
FIG. 6 is a graph showing cycle characteristics in an example of the present invention and a comparative example.
[Explanation of symbols]
1: Conductive core 2a: Cadmium active material layer 2b: Cadmium active material layer 3a: Alloy plating layer 3b: Alloy plating layer 4a: Conductive layer 4b: Conductive layer 5: Winding start end 6: Current collector 10: Cadmium Negative electrode 11: Nickel positive electrode 12: Separator 13: Spiral electrode body 14: Outermost outer surface of the spiral electrode body

Claims (4)

A spiral electrode body formed by winding a cadmium negative electrode and a nickel positive electrode through a separator so that the cadmium negative electrode is positioned on the outermost periphery is in contact with the inner peripheral surface of the battery outer can whose outermost outer surface also serves as a negative electrode external terminal in cadmium storage batteries, - nickel outer peripheral contact collector system is accommodated in a state in electrostatic Ikegaiso the can comprising
In the cadmium negative electrode, an alloy plating layer containing cadmium and indium is formed on the surfaces of both negative electrode active material layers applied to both surfaces of the conductive core,
On the surface of the alloy plating layer, a conductive layer containing a conductive powder, a water-repellent powder, and a paste is formed except for the outermost outer peripheral surface contacting the inner peripheral surface of the battery outer can.
The alloy plating layer on the outermost outer peripheral surface where the conductive layer is not formed is in direct contact with the inner peripheral surface of the battery outer can ,
A nickel-cadmium storage battery characterized by the above.  The nickel-cadmium storage battery according to claim 1, wherein a length in a winding direction of an outermost outer peripheral surface of the cadmium negative electrode is substantially equal to a peripheral length of an inner surface of the battery outer can. After forming the negative electrode active material layers on both surfaces of the conductive core, an electrode plate was formed by forming an alloy plating layer containing cadmium and indium on the surfaces of both negative electrode active material layers, and this alloy plating layer was formed. the longitudinal end portions near the one side of the plate and the inner peripheral surface contacted thereby collector portion of the battery outer can, except for the current collector, the conductive powder on the front surface of the alloy plating layer and the water repellent powder A cadmium negative electrode preparation step for forming a conductive layer containing a paste;
An electrode winding step in which the cadmium negative electrode and the nickel positive electrode are spirally wound through a separator so that the current collector is positioned outside the outermost periphery, and a spiral electrode body is formed;
A spiral electrode body housing step of housing the spiral electrode body in the battery outer can in a state where the current collector is in direct contact with the inner peripheral surface of the battery outer can;
A method for producing a nickel-cadmium storage battery.  The method for producing a nickel-cadmium storage battery according to claim 3, wherein a length of the current collecting part in a winding direction is configured to be substantially equal to a circumferential length of an inner surface of the battery outer can.

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