JP2008181825A - Nickel electrode for alkaline batteries - Google Patents

Abstract

A 320~100g the amount of nickel active material is thereby collector holds the electrolytic plating conducted with resultant porous nickel current collector of nickel after imparting conductivity to the nonwoven surface / m ² preferably 250 The terminal removal by welding of the current collector reduced to ˜150 g / m ² is facilitated to ensure excellent discharge characteristics.
After imparting conductivity to the surface of the nonwoven fabric, the peripheral portion of the porous nickel current collector obtained by performing electrolytic nickel plating is left, and that portion is used as a terminal mounting portion. In the tabless method, the terminal is directly attached to the cross section of the nickel electrode. In this case, the nickel amount is plated so as to be 320 to 200 g / m ² .
[Selection figure] None

Description

  The present invention particularly relates to a nickel electrode for an alkaline battery using a current collector (electrode base material) obtained by nickel plating on a nonwoven fabric. Typical batteries using this are nickel-cadmium batteries and nickel-hydrogen batteries.

  Conventionally, alkaline secondary batteries have been widely used as secondary batteries used for portable, mobile, industrial and the like. The reason for this is that it is highly reliable, has a long service life, is inexpensive, and can be reduced in size and weight.

  Applications include power-assisted bicycles, vacuum cleaners, and power tools, and hybrid vehicles are attracting attention. Others include digital cameras, video cameras, compact audio, shavers, electric toothbrushes, notebook computers, various toys, and memory backups.

  In most of the alkaline secondary batteries, a nickel electrode is used as the positive electrode. The nickel electrode has a structure in which a positive electrode active material for causing a battery-like redox reaction is supported on a current collector that requires a current collecting function. In such a case, a sintered body obtained by sintering nickel powder or a foamed nickel porous body is used as a current collector.

  As a manufacturing method using foamed nickel, a portion to be attached by welding a terminal (referred to as a tab) of a current collector is pressurized in advance, then filled with an active material paste, and then pressurized. Since the pre-pressurized portion is not filled with an active material, a nickel electrode is manufactured by welding a nickel plate to the pressurizing portion. The porosity of the foamed nickel is very large at 92 to 96%. Therefore, a high capacity can be achieved by filling a large amount of active material per unit.

The remaining problem is cost reduction, simplification of the manufacturing process and reduction of the amount of nickel to be plated. In other words, since foamed nickel maintains high porosity only with nickel, a decrease in strength is inevitable when the amount of nickel is reduced. Therefore, it is about 450 to 360 g / m ² .

  Many proposals have been made on current collectors having a three-dimensional structure in which a non-foamed nickel is mainly subjected to nickel plating on a nonwoven fabric made of polyolefin fibers and the nonwoven fabric is left as it is, and the nonwoven fabric is retained. A three-dimensional current collector having a nonwoven fabric as a skeleton has been attracting attention before foamed nickel is put into practical use. However, there was no practical example because there was no nonwoven fabric suitable for this, and current collectors processed into a nonwoven fabric with metal fibers were not widely used due to cost and short circuit problems. .

  Japanese Patent Application Laid-Open No. 55-30180 (Patent Document 1) and Japanese Patent Application Laid-Open No. 3-17957 (Patent Document 2) are subjected to nickel plating on a urethane resin foam sheet or polyolefin fiber nonwoven fabric, and the skeleton of these organic substances. There has been disclosed a three-dimensional network structure in which only the surface of the skeleton portion can exhibit conductivity without thermally removing the portion. However, when a nickel electrode is manufactured using this current collector, a sufficient current collecting function cannot be obtained, and when the terminal is attached to the electrode, the nickel layer on the surface is broken and supported when the mounting part is pressurized. It is stated that the skeleton part of the body is exposed, a sufficient welding strength cannot be obtained when the nickel lead plate is welded, the electrical resistance of this part increases, and problems such as a decrease in the active material utilization rate occur.

Therefore, in JP-A-8-329956 (Patent Document 3), the strength characteristics are excellent, the flexibility is good, high-density filling of the active material mixture paste is possible, and the current collecting property of the manufactured electrode is improved. Thus, an electrode current collector has been proposed in which the utilization factor of the active material can be increased, and at the same time, the terminal can be easily attached. The improvement point is that attention is paid to the amount of nickel, and a value of 350 g / m ² or more is proposed. Since this current collector does not thermally remove the skeleton portion, the manufacturing process is relatively simple, and it is flexible and has a relatively high strength as compared with a conventional foamed nickel current collector that is thermally decomposed. As a result, it is possible to prevent the occurrence of protrusions such as cracks and fuzz even if the electrode using this current collector is wound together with the separator to be put into a cylindrical body or a rectangular electrode, and the charge and discharge characteristics are improved and light weight in recent years has been improved. It is said that it can fully meet the demands for downsizing and downsizing.

A current collector obtained by nickel plating on a non-woven fabric is a manufacturing method rather than incineration and removal of the skeletal resin after plating as disclosed in, for example, the above-mentioned JP-A-8-329956 (Patent Document 3). This contributes to the simplification of the strength and the improvement of the strength, but the basis weight of the nickel amount is required to be 350 g / m ² or more, which is a feature. In terms of the nickel amount, from the point of view that the foamed nickel currently in practical use has been reduced to about 360 g / m ² , an approximately equivalent nickel amount is required. Further, in this application, even if plating is performed when the amount of nickel is further reduced, when the current collector is used for the nickel electrode of a nickel metal hydride battery, when the terminal is attached to the electrode, the mounting portion is pressurized. The nickel layer on the surface is broken and the skeletal part of the support is exposed, so that sufficient welding strength cannot be obtained during welding of the nickel lead plate, and the electrical resistance of this part increases and the active material utilization rate decreases. Is supposed to occur.

Conversely, in the specification of Japanese Patent Application No. 2005-347177, it is described in claim 4 that the nickel plating amount is 80 to 150 g / m ² . The main purpose of this application is to increase the output, and the foamed nickel electrode has a limitation in increasing the output. By controlling the surface area, paste viscosity, and nickel amount of the nickel film, the active material filling amount is increased to enable high output. For high output, it is preferable that the amount of nickel is large. However, in this application, if the amount is 150 g / m ² or less, the pore diameter of the current collector does not become too small, the filling capacity of the active material does not deteriorate, and high output is achieved. It is possible. In addition, about extraction of a terminal, it describes that the external terminal for current collection is welded (for example, seam welding, spot welding, etc.). However, there is no mention of the terminal extraction process by reducing the amount of nickel or the strength on welding.
Japanese Patent Laid-Open No. 55-30180 Japanese Patent Laid-Open No. 3-17957 JP-A-8-329956

  An object of the present invention is to use a nickel nickel current collector that is currently widely used by reducing the amount of nickel in the active material holding layer of the nickel current collector having a nonwoven fabric skeleton, thereby facilitating the removal of the terminal. An object is to enable industrialization of a battery using a nickel electrode that exhibits lower or higher charge / discharge characteristics and lifetime than a nickel electrode.

  In general, a terminal (tab) is taken out when a battery is configured by welding one or two terminal plates to a nickel electrode and welding them to a battery case lid. This method is mainly used for batteries intended for general use and high capacity.

  On the other hand, for applications that require high output, a so-called tabless method is adopted in which the upper peripheral part of the nickel electrode is welded together with a single current collector terminal plate, and the terminal plate is taken out and welded to the battery case lid. Has been. A similar terminal extraction method may be employed for the negative electrode.

  As described above, the two methods of taking out the terminal, that is, the method of welding the lead terminal plate of the electrode to the battery case lid and the tabless method are widely known.

  In any case, the current collector of the nickel electrode and the nickel plate must be spot welded or ultrasonically welded, and it has been found that the amount of nickel in the terminal lead-out portion is extremely important for welding. In other words, if the amount of nickel in the lead terminal lead-out portion is small, welding becomes difficult, and even if the terminal portion can be welded, the welding strength is small and easily removed, or the current collector is partially damaged during welding. There arises a problem that the electric resistance of the welded portion is large. In other words, if the amount of nickel is reduced, the welding strength cannot be maintained. Therefore, even if the amount of nickel in the current collector holding the active material can be reduced, there is a problem in reducing the amount of nickel in the terminal extraction portion.

Normally, in the case of an electrode that uses a sintered metal plate, a punched metal, an expanded metal, a screen or other machined metal plate in the electrode, the terminal plate can be either spot or ultrasonic if the metal plate is exposed. The method can be easily installed. However, even a general-purpose foamed nickel current collector that does not have a metal plate can be welded to the lead plate because the amount of nickel in the welded portion is about 450 to 360 g / m ² . However, in order to maintain sufficient strength, metal foil, such as a nickel thin plate, is pre-welded to the welding site, and the density of the metal layer is increased by overlapping and pressing the foamed nickel current collector in this part. May be taken.

  However, in the case of the present invention, for the purpose of reducing the cost, the amount of nickel is reduced compared to general-purpose foamed nickel, so that it is more difficult to maintain the strength of the welded portion of the lead terminal. The terminal plays an important role in connecting the electrode to the positive electrode terminal and the negative electrode terminal as a power source. If the contact strength at this portion is not sufficient, the resulting electric resistance increases. Therefore, the discharge characteristics and life are greatly affected.

In other words, in the case of a current collector obtained by nickel plating on a nonwoven fabric using resin fibers, even if the weight of nickel is reduced to 320 to 150 g / m ² , the strength as a current collector remains the nonwoven fabric. It is clear that there are few problems. However, when the amount of nickel is reduced, it becomes difficult to attach the terminal regardless of the welding method, and the problem remains that the welding strength between the terminal and the electrode is small because the amount of nickel is small even if it is welded. .

  The inventor of the present invention has completed the present invention as a result of intensive studies to solve the above problems.

The present invention relates to the following nickel electrode for alkaline batteries.
1. After imparting conductivity to the surface of the nonwoven fabric, the peripheral portion of the porous nickel current collector obtained by performing electrolytic nickel plating is left, and the active material is applied to the current collector using the portion (peripheral portion) as a terminal mounting portion. Nickel electrode for alkaline batteries obtained by filling
2. The nickel electrode for an alkaline battery according to Item 1, wherein the peripheral portion is a region from the end of the current collector to 6 mm.
3. Item 2. The nickel electrode for alkaline battery according to Item 1, wherein the nonwoven fabric is made of a polyolefin-based resin.
4). After imparting conductivity to the nonwoven fabric surface, the nickel amount in the portion (portion other than the peripheral portion) filled with the active material of the porous nickel current collector obtained by performing electrolytic nickel plating is 320 to 100 g / m ² . The nickel electrode for alkaline batteries according to item 1, which is plated so as to be.
5. Item 5. The alkaline battery according to item 4, wherein the average amount of nickel in the peripheral portion of the porous nickel current collector obtained by applying electrolytic nickel plating after imparting conductivity to the nonwoven fabric surface is 700 to 250 g / m ² . Nickel pole.
6). Item ^{2. The} nickel electrode for an alkaline battery according to Item 1, wherein the total amount of nickel (peripheral portion and other portions) of the porous nickel current collector is 320 g to 160 / m ^{2 on} average.
7). Item 1. The peripheral portion of the porous nickel current collector obtained by applying electrolytic nickel plating after imparting conductivity to the nonwoven fabric surface is pressurized before filling the active material other than the peripheral portion. Alkaline battery nickel electrode.
8). The nickel electrode for an alkaline battery according to Item 1, wherein a three-dimensional porous nickel body is pressure-bonded to the terminal mounting portion.
9. Item 9. The nickel electrode for an alkaline battery according to Item 8, wherein the three-dimensional porous nickel body is foamed nickel or nickel-plated nonwoven fabric.
10. The above item wherein a current collector is used in which a terminal is attached by spot welding or ultrasonic welding to the periphery of a porous nickel current collector obtained by applying electrolytic nickel plating after imparting conductivity to the nonwoven fabric surface. 1. The alkaline battery nickel electrode according to 1.
11. A tabless structure in which a terminal is directly attached to the cross-section (peripheral edge) of a nickel electrode using a porous nickel current collector obtained by imparting conductivity to the nonwoven fabric surface and then performing electrolytic nickel plating Item 2. The alkaline battery nickel electrode according to item 1 above.
12 A tabless structure in which a terminal is directly attached to the cross-section (peripheral edge) of a nickel electrode using a porous nickel current collector obtained by imparting conductivity to the nonwoven fabric surface and then performing electrolytic nickel plating 12. The alkaline battery nickel electrode according to item 11, wherein the terminal is welded after the cross section is polished.
13. After imparting electrical conductivity to the nonwoven fabric surface, the nickel amount in the portion (portion other than the peripheral portion) filled with the active material of the porous nickel current collector obtained by performing electrolytic nickel plating is 320 to 200 g / m ² . Item 12. The nickel electrode for alkaline battery according to Item 11, which is plated so as to be.

Hereinafter, the present invention will be described in detail.

  In the present invention, the peripheral portion of the porous nickel current collector obtained by electroplating nickel after imparting conductivity to the surface of the nonwoven fabric mainly composed of polyolefin is left, and the portion (peripheral portion) is attached to the terminal. And filling this with an active material (the active material is filled in a portion other than the peripheral portion) to obtain a nickel electrode for an alkaline battery. Here, the peripheral portion refers to a width of about 4 to 6 mm in the case of the lead plate extraction method, and a width of about 2 to 4 mm in the tabless method.

  In the present invention, a polyolefin-based material that is excellent in oxidation resistance and alkali resistance and inexpensive is adopted as the material for the nonwoven fabric. For the conductivity imparted to the surface of the nonwoven fabric before the nickel electroplating, a known method such as nickel electroless plating or nickel sputtering can be employed.

Here, the amount of nickel in the active material holding layer (other than the peripheral part, also referred to as the central part) formed on the nonwoven fabric is 360 g / m ² or more of the foamed nickel mainly for the purpose of cost reduction. 320 g / m ² or less (including the amount of nickel for imparting conductivity).

When plating was performed by a normal method of electrolytic plating while moving the band-shaped object to be plated in a nickel plating bath, for example, the nickel plating amount of the active material holding layer (portion other than the peripheral portion) was close to the upper limit of 300 g / m ^2. If the average nickel content of the peripheral portion, 540 g / ^{m 2} by 5mm width about required terminal lead type, ² about 900 g / ^m a necessary 2mm width tabless method, when the 1mm width 1350 g / ^{m 2} or more Become. Therefore, it is estimated that the cross-sectional portion (end portion of the peripheral portion) corresponds to about 1800 g / m ² .

Further, it was found that even if the nickel weight per unit area of the active material holding layer was reduced to 150 g / m ² , the peripheral part was about 350 g / m ² with a width of about 6 mm required for the terminal extraction method.

  In this way, when electrolytic plating is performed continuously in a sheet-like form to be plated which is a nonwoven fabric, the peripheral portion has a larger plating amount than the central portion. That is, the peripheral part can easily diffuse the plating solution and the plating efficiency is high. Naturally, even in the case of foamed nickel that has been put to practical use, plating is performed by this method, so the amount of plating in the peripheral portion is large. However, in order to reduce the variation between the electrodes, the peripheral portion is cut and removed, and the remainder is used as a current collector. Therefore, in order to reduce the peripheral portion, it is effective to use a wide object to be plated (foamed urethane resin imparted with conductivity).

The present invention is made by paying attention to the fact that the amount of nickel in the active material holding layer has little influence on the charge / discharge characteristics of the nickel electrode in a current collector obtained by nickel plating on a nonwoven fabric. For example, the nickel electrode using 420 g / m ² of foamed nickel and the nickel electrode using 200 g / m ² non-woven nickel plating current collector at the 73rd Annual Meeting of the Electrochemical Society p293 (2006) have the same high discharge characteristics. It is made clear to show.

  In the present invention, a peripheral portion of a porous nickel current collector obtained by imparting conductivity to a nonwoven fabric surface and then performing nickel electroplating is used as a terminal extraction portion. It is more effective to pressurize the peripheral part or weld nickel foil to the peripheral part before filling the central part with the active material. The welding may be spot welding or ultrasonic welding, but the latter is desirable for mass productivity.

  Normally, the terminal board is welded after filling with the active material paste, so if the active material adheres to this part, welding becomes difficult. A known method may be employed such as peeling after filling the active material, or removing the active material filled in the portion by washing or polishing.

In the present invention, the preferred amount of nickel in the current collector (portion other than the peripheral portion) filled with the active material is in the range of 320 to 100 g / m ² (more preferably 320 to 150 g / m ² ). As the active material, a spherical nickel hydroxide in which a cobalt compound is included in nickel hydroxide having excellent conductivity and a cobalt oxide is coated on a known surface is excellent in conductivity and is optimal.

The active material-filled portion of the present invention is manufactured in the range of 320 to 100 g / m ² for reducing the amount of nickel in the current collector, and the resulting peripheral portion (nickel amount is 700 to 250 g / m ² ). The method using the terminal mounting portion provides excellent results regardless of whether the electrode group in the battery is a tab type or a tabless type.

  As the material of the nonwoven fabric used, polyethylene, polypropylene, copolymers thereof, a mixture thereof, and a nonwoven fabric composed of alkali- and oxidation-resistant fibers such as polypropylene at the center and polyethylene fibers at the periphery are preferable.

In the present invention, it is necessary to increase the volume of the non-woven fabric to increase the void volume, which becomes a factor that brings about a high capacity as in the case of conventional foamed nickel. The weight per unit area occupied by the nonwoven fabric is about ²⁰ to 100 g / m ² , and the porosity is preferably 87 to 98%. The average pore size is preferably smaller than general-purpose foamed nickel. Although it is difficult to reduce the range of the pore diameter due to the structure of the nonwoven fabric, the range is 20 to 200 μm, preferably 30 to 150 μm. On the other hand, if the pore diameter is smaller than 20 μm, the nickel hydroxide particles as the active material are usually used at 15 to 25 μm.

  Moreover, since the thickness of the nickel electrode is usually about 350 to 550 μm for high output and about 550 to 800 μm for high capacity after pressurization, the thickness of the nickel electrode is 30 to more than the thickness of the current collector after nickel plating. It is preferable to use a nonwoven fabric that is about 80% thick. This is plated and pressurized after filling with the active material paste to obtain a nickel electrode having a desired thickness.

  The manufacturing method of a nonwoven fabric is not limited in this invention. The dry method and the wet method are known, and the non-woven fabric obtained by the wet method has less variation in the weight and thickness of the non-woven fabric obtained by the dry method, so that a uniform current collector can be obtained. It is said that it can be done. However, it is not limited to a manufacturing method. Moreover, although a nonwoven fabric may be used as it is, it is preferable to use it after performing an entanglement process and improving a strength characteristic.

  The next step imparts conductivity to the nonwoven as is known in the art for electroplating nickel. For this purpose, there are methods by electroless plating and sputtering.

  Subsequent electrolytic plating of nickel may be performed by a known method. That is, as the plating bath, a Watt bath is well known, and a chloride bath and a sulfamic acid bath are also known. In some cases, additives such as a pH buffer and an interface buffer may be used. A non-woven fabric imparted with conductivity to this bath is used as a cathode, and a nickel plate is used as a counter electrode to form a porous nickel body.

  By the way, when nickel plating is carried out industrially continuously in a plating bath on the nonwoven fabric imparted with conductivity in this way, the nickel ions in the plating bath are easily supplied to the peripheral portion, and the nickel is more than the central portion. The amount of adhesion increases. Conventionally, the same phenomenon occurs naturally in the case of foamed nickel obtained by nickel-plating a polyurethane foam porous body, but usually, this end portion is cut off and used.

  The present invention pays attention to a phenomenon in which a large amount of nickel is plated on the peripheral portion of such an object to be plated, and a terminal plate is welded to that portion while leaving this end portion. The welding method includes spot and ultrasonic methods. In addition, when unevenness is generated in the short part, even if it is cut and removed by about 1 to 2 mm, the amount of nickel is much larger than that of the active material holding layer.

  The active material paste is filled, but since it is normal to attach the terminal plate after filling the active material, means to attach an adhesive tape to prevent the paste from adhering to this terminal part, and to peel off after applying the paste Or, after filling the paste, a means such as removing the paste from the terminal take-out part is adopted. That is, the active material paste is filled not in the peripheral part but in the central part.

  An example of a specific electrode structure is shown. First, a nickel electrode with a terminal attached to a current collector used for a normal application such as a portable device is shown. FIG. 1 shows a one-terminal structure with one terminal attached. Reference numeral 1 denotes an active material layer filled in a current collector, and reference numeral 2 denotes a terminal. FIG. 2 shows a structure in which two terminals having terminals 4 and 5 attached to both ends of an electrode layer 3 containing an active material so that an output can be taken out larger than in FIG.

  For example, in order to manufacture FIG. 1, a non-woven hoop having a width twice that of the current collector is used, and the current collector obtained by plating the active material is filled with an active material and cut at the center. A terminal may be attached to the opposite side. In order to manufacture FIG. 2, a non-woven fabric hoop having this width may be used, and terminals may be attached to both ends after plating and filling with an active material. In any case, it is preferable to pressurize the terminal mounting portion before filling the active material paste. Moreover, it is preferable that the terminal attachment part includes a step of cleaning and removing the active material adhering after filling the active material and a polishing step.

  Industrially, it is efficient to use a wide nonwoven fabric having a width of 600 to 1000 mm. In such a case, the end of the current collector is limited. Therefore, as one solution, the steps up to electrolytic nickel plating are performed on a wide range of nonwoven fabrics as they are, the nonwoven fabric is cut into a predetermined width, and electrolytic nickel plating is performed, thereby holding the active material. The amount of nickel in the part can be reduced and the amount of nickel in the end can be increased automatically.

  Further, if a wide non-woven fabric is cut in a portion corresponding to the terminal mounting portion, more nickel than other portions is plated around the periphery, so that the terminal may be attached to this portion. FIG. 4 shows an example in which 8 is a current collector for holding an active material, and 9 is a notch (slit). Therefore, the portion indicated by the oblique lines becomes the peripheral portion of the object to be plated, and if it is cut as indicated by the dotted line after filling the active material, an electrode for tabless described in detail later is obtained. In the example of FIG. 4, 24 (3 × 8) tabless electrodes are obtained.

  In the nickel-hydrogen secondary battery, the nickel electrode obtained in this way is, as is well known, for example, a polyolefin non-woven separator that has been subjected to hydrophilic treatment and a hydrogen storage alloy negative electrode integrated into an electrode group. Insert into the battery case. The terminal of the nickel electrode is welded to the lid after the electrolyte is injected, and sealed to form a battery. In the case of a rectangular shape, a nickel electrode is usually manufactured in a one-terminal shape, and is inserted into a battery case over a negative electrode via a separator.

  Next, a so-called tabless nickel electrode is shown in FIG. 6 is an active material holding layer, and a terminal is welded to the cross section above 7.

  Also in this case, the nickel electrode is integrated with the separator and the negative electrode to form an electrode group, and in the case of a cylindrical battery, it is wound and inserted into the battery case. A nickel plate processed into a circle is put on the wound nickel electrode and welded. This circular nickel plate is welded at right angles to the cross section of the nickel electrode. Therefore, a large amount of nickel in the cross section facilitates welding. Also, polishing this cross section before welding results in improved weld strength.

  The battery case lid becomes a positive electrode terminal by welding this terminal plate to the lid. The battery is completed by electrolyte injection and sealing through an insulating ring.

  In the case of a square shape, a nickel electrode is produced in the same manner, and is superimposed on the negative electrode via a separator and inserted into a battery case. The entire upper part of the electrode is welded with a single terminal plate, which is used as a positive electrode terminal. As described above, in the known tabless method, the terminal is taken out from the entire electrode with a single terminal plate, so that the electric resistance is reduced and high output is possible.

  As described above, both the cylindrical type and the square type terminal plate are welded at right angles to the nickel electrode, that is, welded to the cross section, and therefore, it is necessary that the amount of nickel existing in the cross section is large.

When a metal plate such as a punching metal is present in the electrode, welding with the nickel plate is easy if the punching metal of the cross section is exposed. However, in the case of general-purpose foamed nickel, if the nickel amount of the current collector is set to, for example, 400 g / m ² , the cross section is the same amount. With this amount of nickel, welding with a nickel plate is not easy. Even if it is possible, the welding strength is small, the contact resistance is large, and the voltage drop is large during discharge. Therefore, welding strength is increased by increasing the amount of nickel in the cross section by welding nickel foil or nickel porous body. Also for the non-woven nickel current collector, when the entire current collector is, for example, 300 g / m ² as in the prior art, it is preferable to employ means for increasing the amount of surrounding nickel for welding.

  In this way, as used in the case of foamed nickel current collectors, such as welding the nickel foil to the terminal mounting part, or stacking the porous body and pressing and integrating, It is preferable to increase the amount of nickel in order to increase the welding strength.

However, when a portion with a large amount of nickel at the end portion is left as in the present invention, the nickel amount in the cross-sectional portion is larger than that in the peripheral portion. For example, when the current collector portion is 200 g / m ² , the width Since the average of the portion of 2 mm is 700 g / m ² or more, the cross section is 900 g / m ² or more, and it has become clear that the terminal plate can be easily welded as it is in the tabless method. In this case, there is no means for increasing the amount of nickel in the terminal mounting portion, so the current collector that holds the active material also needs to be plated so that the amount of nickel is about 320 to 200 g / m ^2. It is. Thus, it has been found that the present invention is more effective particularly in the tabless type terminal extraction.

In the present invention, when the amount of nickel in the active material holding layer is further reduced to, for example, about 150 g / m ² , it is preferable to increase the amount of nickel as in the prior art. However, even in that case, since the amount of nickel at the end is large, there is an advantage that welding of a nickel plate or a nickel porous body is easy.

Preferably 320~100g / m ² nickel amount of the central portion for holding the active material of the porous nickel current collector obtained by performing the electrolytic plating of nickel after imparting conductivity to the nonwoven surface 250~150g / m ^The terminal can be easily taken out by welding the current collector so that excellent discharge characteristics are ensured.

  That is, conductive treatment is performed on a hoop-shaped nonwoven fabric, and the peripheral portion of the nonwoven fabric porous nickel current collector obtained by continuously performing electrolytic nickel plating in an electrolytic nickel plating bath is left, and the portion is a terminal mounting portion. And By this means, excellent discharge characteristics can be obtained even if the amount of nickel in the current collector portion is reduced.

In particular, in the tabless method, when the amount of nickel in the active material holding layer (central portion) of the current collector is 320 to 200 g / m ² , the terminal can be welded without taking measures to increase the amount of nickel in the cross section. The process can be simplified.

  The present invention will be specifically described below with reference to examples and comparative examples. However, the present invention is not limited to the examples.

Example 1
An embodiment based on a general terminal mounting method (two-terminal method shown in FIG. 2) will be described.

  As a non-woven fabric material, a fiber in which polypropylene is coated around the center of polypropylene is used. The fiber diameter was about 15 μm and the weight ratio of polypropylene to polyethylene was 6: 4. The nonwoven fabric was manufactured using the wet method, and the entanglement process which fuses the cross | intersection part of a well-known fiber was performed.

The obtained nonwoven fabric was manufactured so that the fabric weight was 50 g / m ² , the average thickness was 1.3 mm, the porosity was 95%, and the pore diameter was 20 to ²⁰⁰ μm. This was cut into a width of 600 mm. This was used as a skeleton for the current collector.

Next, conductivity was imparted to the nonwoven fabric. A conductive layer was formed by electroless nickel plating. That is, it was immersed in a cleaning solution manufactured by Nippon Kanisen, immersed in an activation solution, and then immersed in a plating bath. As is well known, it is utilized that the plating proceeds continuously by the autocatalytic action of nickel produced by reduction, and 8 g / m ^{2 of} nickel was added. A sputtering method may be employed instead of electroless plating.

  Thereafter, the non-woven fabric provided with conductivity was divided into three parts having a width of 200 mm, and immersed in a nickel electrolytic plating bath in a state separated by 10 mm.

Electrolytic nickel plating was performed using a known Watt bath as a plating bath. Nickel sulfate was 240 g / liter, nickel chloride was 45 g / liter, boric acid was 30 g / liter, pH was adjusted to 4-5, and temperature was adjusted to 45-55 ° C. The cathode current density was set to 2A / dm ^2. As the counter electrode, nickel pieces were injected into a nickel basket.

Here, the amount of electricity was adjusted so that the average amount of nickel in the current collector was 210 g / m ² . Under these conditions, the nickel amount at the end was 550 g / m ² at the endmost 1 mm width at both ends. The average up to the inside of 5 mm was 300 g / m ² .

After pressurizing 5 mm at both ends with 100 kg / cm ² , an adhesive tape was applied to this part to prevent the active material paste from entering when filling the active material described later. The amount of nickel in the active material holding layer of this current collector was 195 g / m ² on average.

  Nickel hydroxide powder whose surface is coated with cobalt oxyhydroxide equivalent to 4% by weight as cobalt as a positive electrode active material as an active material paste, 94 parts by weight of this active material, 2 parts by weight of cobalt hydroxide powder, and 0% aqueous carboxymethylcellulose solution. An active material paste was prepared by adding 19 parts by weight of a 25% polypropylene emulsion to 0.8 parts by weight of polypropylene and 0.1 parts by weight of a surfactant (polyoxyethylene alkyl ether).

  This active material paste was filled by a known press-fitting method in which the paste was filled into a current collector while being pressurized from one side with a pump employed for foamed nickel. Thereafter, the film was dried at 100 ° C. for 30 minutes, and after removing the tape, it was pressed with a roller press to have an average thickness of 0.65 mm.

  The nickel electrode thus obtained was cut into 32 mm to produce a nickel electrode having a length of 200 mm. This is a. The calculated capacity calculated from the nickel hydroxide filling amount based on the size of the nickel electrode was 3.2 Ah.

On the other hand, for comparison, a non-woven fabric having a width of 660 mm was subjected to electrolytic nickel plating in the same manner as a, and both ends were cut and removed by 15 mm to obtain a current collector. That is, the current collector was manufactured by performing nickel plating so that the average amount of nickel in the active material holding layer was 200 g / m ² . This was cut to 32 mm to produce a nickel electrode having a length of 200 mm. Similarly, after pressurizing the peripheral part with a width of 5 mm at 100 kg / cm ² , this part was protected with a tape and then filled with the active material paste. This is a nickel electrode b.

For further comparison, the same nonwoven fabric as described above was used so that the nickel content of the active material holding layer after cutting and removing both ends in the same manner as b was 400 g / m ² on average, which was the same as that of foamed nickel. Nickel plating was performed to produce a current collector. Similarly, the periphery was pressurized and protected with tape, and then filled with the active material paste. This is a nickel electrode c. Note that the calculated capacity of the nickel electrode is 3.2 Ah for both comparative b and c.

  The present invention is intended to enable the lead terminal to be easily and firmly welded to the nickel electrode even if the amount of nickel in the current collector portion is reduced. First, the nickel electrodes a, b, and c The welding state will be described.

  In this embodiment, nickel plates having a width of 5 mm and a thickness of 120 μm are attached to both ends by spot welding. As a result, the nickel electrodes a and c could be welded, but with the nickel electrode b, spot welding was difficult, and the welded part was damaged due to heat generation. Although it was possible with ultrasonic welding, the welding strength was low and it was difficult to construct a battery.

Since it is difficult to measure the welding strength quantitatively and accurately, a battery is constructed, and the voltage at the discharge is compared, and a battery using a nickel electrode having a current collector made of general-purpose foamed nickel Judgment was made by showing the same discharge voltage. Here, as a comparative example, a nickel electrode in which an active material similar to that of the example was filled in foamed nickel having a basis weight of nickel of 400 g / m ² , a porosity of 96% and a thickness of 1.3 mm, and pressurized to the same 650 μm Was used. The lead plate was attached in the same manner as a battery.

Nickel electrodes a and c and foamed nickel were used, and a hydrogen storage alloy was used for the negative electrode. As the alloy, an AB _5- based alloy, that is, an MmNiAlMnCo alloy, which is a known ternary hydrogen storage alloy obtained by adding Al, Mn, and Co to an MmNi-based alloy (Mm is a misch metal) was used. Punching metal was used as the current collector, and the alloy powder was pasted into a paste and applied to the current collector. Then, it was used as a known paste-type negative electrode by drying and pressing.

  A known polypropylene nonwoven fabric with a thickness of 125 μm was used as the separator, and a 28 wt% aqueous potassium hydroxide solution in which 20 g / liter of lithium hydroxide was dissolved was used as the electrolyte. The battery type is a cylindrical SubC. The batteries using nickel electrodes a and c and foamed nickel were designated as batteries A, C and D, respectively.

  For a battery configured using each nickel electrode, charge at 130% of the capacity at 0.1C, discharge to a final voltage of 0.9V at 0.2C, 120% charge at 0.2C, zero final voltage at 0.2C Discharging up to .9V, charging at 115% at 0.5C, and discharging up to 0.9V at 0.5C were repeated once for chemical conversion.

  Thereafter, each battery was charged at 0.5 C with a current of −ΔV (3 mV), and discharging at 0.5 C to 0.9 V was repeated 20 cycles at room temperature (25 ° C.). Then, 1C and 2C continuous discharge was performed with a final voltage of 0.8V. Table 1 shows the value of the intermediate voltage of each battery.

  As shown in Table 1, the discharge voltage of each battery is almost the same, leaving the end after nickel plating as in the present invention, and welding the terminal there, the nickel content of the active material holding layer is halved. However, the discharge voltage did not decrease.

Since the comparative nickel electrode b was difficult to weld the nickel plate, the same non-woven nickel material as the current collector was cut into a length of 32 mm and a width of 5 mm in advance and applied to this nickel plate welded portion. The pressure was integrated. By this means, the amount of nickel in the welded part was 400 g / m ² , and spot welding of the nickel plate became possible.

  In this case, a two-dimensional structure such as a nickel plate cannot be integrated with the current collector even if pressure is applied. By pressurizing a three-dimensional porous body such as foamed nickel or non-woven nickel, entanglement between the porous bodies occurs simultaneously with compression, and integration is possible.

  Regarding the nickel electrodes a and c of the present invention, a non-woven nickel piece was applied by the same means to produce a pressure-integrated nickel electrode. Nickel plate welding has become even easier. Let each battery be A ′, B ′, and C ′.

  As for the discharge voltage of each battery, A ′ and C ′ are almost the same as those in Table 1, and B ′ can be discharged by taking means for increasing the amount of nickel in the terminal connection portion in this way.

Example 2
FIG. 3 shows an example of a tabless nickel electrode preferable for general-purpose high-power applications. The portion 7 in this figure is usually doubled with foamed nickel or welded with a nickel piece (nickel ribbon). A nickel plate (positive current collector plate) is attached to the cross section of the upper surface.

  As in Example 1, it is difficult to measure the welding strength quantitatively and accurately, so batteries were constructed and the voltages at the high rate discharge that was most practically required were compared.

  As a non-woven fabric material, a fiber in which polypropylene is coated around the center of polypropylene is used. The diameter of the fiber was about 15 μm, and the weight ratio of polypropylene to polyethylene was 7: 3. The nonwoven fabric was manufactured using the wet method, and the entanglement process which fuses the cross | intersection part of a well-known fiber was performed.

The obtained non-woven fabric was manufactured so as to have a basis weight of 45 g / m ² , an average thickness of 0.95 mm, a porosity of 95%, and a pore diameter of 15 to 200 μm. This was cut into a width of 600 mm. This was used as the skeleton of the current collector.

Next, conductivity was imparted to the nonwoven fabric. As in Example 1, a conductive layer was formed by electroless nickel plating. The amount of nickel was 9 g / m ² .

  Thereafter, slits were provided in the conductive nonwoven fabric and electrolytic nickel plating was performed. The slits had a width of 64 mm and a length of 270 mm, and the space between the slits was 10 mm.

  The portion facing the slit becomes the electrode periphery. Since the width is set to 64 mm, a current collector having a width of 32 mm and a length of 270 mm can be obtained by dividing into 2 minutes. A terminal is attached to the end on the slit side.

  In this embodiment, both the case where the disk-shaped nickel plate is directly welded and the case where the end portion is reinforced with a nickel plate or a nickel porous body to increase the amount of nickel in the cross section are shown. (Figure 3). In this case, the end portion was 3 mm wide.

The plating bath was the same as in Example 1, with nickel sulfate 240 g / L, nickel chloride 45 g / L, boric acid 30 g / L, pH 4-5, and temperature 45-55 ° C. Cathode current density was set to 2A / dm ^2. The counter electrode was also used by injecting nickel pieces into a nickel basket. Here, the amount of electricity was adjusted so that the average amount of nickel in the current collector was 270 g / m ² . Under these conditions, the nickel amount at the end was 750 g / m ² at the endmost 1 mm width at both ends. It is 550 g / m ^{2 on} average up to 3 mm. Presuming from these values, nickel corresponding to 900 g / m ² or more appears to exist in the cross section.

Adhesive tape was affixed to a width of 3 mm at both ends to prevent the active material paste from entering when filling the active material described later. The average amount of nickel in the active material holding layer of this current collector was 250 g / m ² .

  Nickel hydroxide powder whose surface is coated with cobalt oxyhydroxide equivalent to 3% by weight as cobalt as a positive electrode active material as an active material paste, and 94 parts by weight of this active material, 2.5 parts by weight of cobalt hydroxide powder, carboxymethylcellulose An active material paste was prepared by adding 0.19 parts by weight of an aqueous solution and 0.1 parts by weight of a surfactant (polyoxyethylene alkyl ether).

  The active material paste was filled by a known press-fitting method in which the paste was filled into a current collector while being pressurized from one side with a pump employed for foamed nickel. Thereafter, the film was dried at 100 ° C. for 20 minutes, and after removing the tape, it was pressed with a roller press to obtain an average thickness of 0.48 mm.

  The nickel electrode thus obtained was cut to 32 mm in the lateral direction. Therefore, the nickel electrode has a width of 32 mm and a length of 270 mm. This is i. The calculated capacity calculated from the nickel hydroxide filling amount based on the size of the nickel electrode was 3.2 Ah.

On the other hand, for comparison, a current collector was produced by performing nickel plating so that the average amount of nickel in the active material holding layer after cutting off both ends was 250 g / m ² on average. Similarly, after protecting the peripheral part with a tape having a width of 3 mm, the active material paste was filled. This is a nickel electrode ii.

Further, for comparison, a current collector was produced by applying nickel plating to the same non-woven fabric as described above so that the nickel content of the active material holding layer after cutting and removing both ends was 400 g / m ² on average. Similarly, the active material paste was filled after the peripheral portion was protected with a tape. This is referred to as a nickel electrode iii. Note that the calculation capacity of both comparative ii and iii is 2.3 Ah.

  An object of the present invention is to make it possible to easily and firmly weld a lead terminal to a nickel electrode even if the amount of nickel in the current collector portion is reduced. First, let the nickel electrode used as it is, without increasing the nickel amount at the end, be i. Next, let ii be the case where the amount of nickel is increased as in the comparative example. As comparative examples, four types of welding states iii and iv will be described.

In ii, iii, and iv, 400 g / m ² nickel-plated foamed nickel commercially available in the periphery is cut into a width of 3 mm and a length of 270 mm, and this is applied to the end of the current collector in advance. Pressurization was performed at a pressure of 100 kg / cm ² , and pressure integration was performed, followed by spot welding. This is the nickel electrode ii.

  On the other hand, in Comparative Examples iii and iv, with the same reinforcement as ii, the welding of the collective terminal plate was insufficient, so two sheets of foamed nickel were pressed from both sides of the end of the current collector, and then spot welded .

  As the negative electrode, a known paste electrode obtained by applying a hydrogen storage alloy as a paste on punching metal, drying, and applying pressure was used. As the alloy, an AB5 alloy, that is, an MmNiAlMnCo alloy, which is a known ternary hydrogen storage alloy obtained by adding Al, Mn, and Co to an MmNi alloy, was used.

  A known polypropylene nonwoven fabric with a thickness of 125 μm treated as a separator was used. After insertion into the battery case, a disk-shaped nickel having a thickness of 150 μm was applied, and a disk-shaped nickel plate was spot-welded to the upper part of each of the nickel electrodes i to iv. Thereafter, a disk-shaped nickel plate and a battery case lid were welded with a terminal plate to obtain a tabless battery structure having a known structure.

  In addition, the punching metal was exposed for the negative electrode except for the negative electrode alloy on the bottom side, and a disk-shaped nickel plate was welded to the negative electrode in the same manner as the positive electrode, and this was spot welded to the bottom of the battery case to make it tabless. . The battery type is cylindrical SubC as in Example 1.

A 28% by weight potassium hydroxide aqueous solution in which 20 g / liter of lithium hydroxide was dissolved was used as an electrolytic solution, which was then sealed to complete the battery.
The batteries using the nickel electrodes i, ii, iii, and iv were designated as batteries i, ii, iii, and iv, respectively. Further, as a comparative example, the case where a foamed nickel plated with 400 g / m ² nickel was used as a current collector was also examined, but the nickel electrode iv, that is, the same discharge characteristics as the battery iv was shown, so it is not shown in the table. .

  About the battery comprised using each nickel electrode, 150% of capacity | capacitance charge at 0.1C, discharge to 0.9V of final voltage at 0.2C, 120% charge at 0.2C, and final voltage 0 at 0.2C Discharging up to .9V, charging at 115% at 0.5C, and discharging up to 0.9V at 0.5C were repeated once for chemical conversion.

  Thereafter, each battery was charged at 1 C with a current of -ΔV (5 mV), and discharging to 0.9 V at 1 C was repeated at room temperature (25 ° C.). After 20 cycles, 10C and 15C discharges were performed at a final voltage of 0.7V.

  Table 3 shows the discharge capacity and intermediate voltage of each battery.

  As is apparent from Table 3, the discharge voltages of the batteries were almost equal, and the tabless method was excellent even if the nickel amount at the end portion was not increased, noting that the nickel amount in the current collector cross section was very large. Characteristics were obtained. Also, by leaving the end after nickel plating, when welding the terminal, it is excellent even if the amount of nickel in the active material holding layer is greatly reduced compared to general-purpose foamed nickel with less nickel than the comparative example The discharge voltage was shown.

It is a schematic diagram which shows a one-terminal structure. It is a schematic diagram which shows a two-terminal structure. It is a schematic diagram which shows a tabless system. It is a schematic diagram at the time of putting a slit in a nonwoven fabric (the hatched portion is the peripheral portion of the current collector, and 24 tabless electrodes are obtained by cutting along the dotted line).

Explanation of symbols

1 Current collector (active material layer)
2 Terminals attached around the current collector 3 Current collector (active material layer)
4 Terminals attached to the periphery of the current collector 5 Terminals attached to the periphery of the current collector 6 Current collector (active material layer)
7 Terminal-less welded part (peripheral part)
8 Current collector (active material layer)
9 Slit (The shaded area around the slit is the periphery of the current collector)

Claims (13)

  After imparting conductivity to the nonwoven fabric surface, leave the peripheral part of the porous nickel current collector obtained by performing electrolytic nickel plating, and fill the current collector with that part as the terminal mounting part with the active material. Obtained nickel electrode for alkaline batteries.   The nickel electrode for an alkaline battery according to claim 1, wherein the peripheral portion is a region from the end of the current collector to 6 mm.   The nickel electrode for alkaline batteries according to claim 1, wherein the nonwoven fabric is made of a polyolefin-based resin. After imparting conductivity to the surface of the nonwoven fabric, plating is performed so that the nickel amount in the portion filled with the active material of the porous nickel current collector obtained by performing electrolytic nickel plating is 320 to 100 g / m ² . The nickel electrode for alkaline batteries according to claim 1. 5. The alkaline battery according to claim 4, wherein the average amount of nickel in the peripheral portion of the porous nickel current collector obtained by applying electrolytic nickel plating after imparting conductivity to the nonwoven fabric surface is 700 to 250 g / m ² . Nickel pole. The nickel electrode for an alkaline battery according to claim 1, wherein the total amount of nickel in the porous nickel current collector is 320 g to 160 / m ^{2 on} average.   The peripheral part of the porous nickel electrical power collector obtained by giving electroconductivity nickel electroplating after imparting electroconductivity to the nonwoven fabric surface is pressurized before filling an active material other than a peripheral part. Alkaline battery nickel electrode.   The nickel electrode for alkaline batteries according to claim 1, wherein a three-dimensional porous nickel body is pressure-bonded to the terminal mounting portion.   The nickel electrode for an alkaline battery according to claim 8, wherein the three-dimensional porous nickel body is foamed nickel or nickel-plated nonwoven fabric.   A current collector in which a terminal is attached by spot welding or ultrasonic welding to the periphery of a porous nickel current collector obtained by applying electrolytic nickel plating after imparting conductivity to the surface of the nonwoven fabric is used. 1. The alkaline battery nickel electrode according to 1.   2. The tabless method according to claim 1, wherein a terminal is directly attached to a cross-sectional portion of a nickel electrode using a porous nickel current collector obtained by applying electrolytic nickel plating after imparting conductivity to the nonwoven fabric surface. Alkaline battery nickel electrode.   In the tabless method, which has a structure in which a terminal is directly attached to the cross section of a nickel electrode using a porous nickel current collector obtained by applying electrolytic nickel plating after imparting conductivity to the nonwoven fabric surface, the cross section is polished. The alkaline battery nickel electrode according to claim 11, wherein the terminal is welded. After imparting conductivity to the surface of the nonwoven fabric, plating is carried out so that the nickel amount in the portion filled with the active material of the porous nickel current collector obtained by performing electrolytic nickel plating is 320 to 200 g / m ² . The nickel electrode for alkaline batteries according to claim 11.

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