JPH043403Y2 - - Google Patents

Description

[Detailed explanation of the invention] (a) Industrial application field The present invention is applied to alkaline storage batteries such as nickel-cadmium batteries, in particular, a separator is inserted between the anode plate and the cathode plate, and these plates are wound in a spiral shape. The present invention relates to a sealed alkaline storage battery including an electrode body configured by rotating.

(b) Conventional technology In recent years, portable electronic devices have become extremely popular.
The demand for secondary batteries as a driving power source is rapidly increasing, and alkaline storage batteries such as nickel-cadmium batteries are often used as the driving power source. This alkaline storage battery is mainly composed of a spiral electrode body, and generally has a tertiary electrode body.
As shown in the figure, the anode plate 9 and the cathode plate 10 are wound into a spiral shape with a separator 11 interposed between them to form an electrode body. The spiral electrode body thus constructed is temporarily fixed with adhesive tape 12 so that the winding pressure is maintained, and the spiral electrode body thus constructed is stored in a battery exterior can that also serves as a cathode terminal, and then an insulating packing is inserted into the opening of the battery exterior can. A sealing body that also serves as an anode terminal is fixed through the anode terminal to seal the inside.

However, as the portable devices become lighter and smaller, there are various demands for alkaline storage batteries to be lighter and have higher capacities, and there is a need for batteries that satisfy these demands.

As a method of reducing the weight of the battery, it is advantageous to use a paste type cathode plate. This is because a paste-type electrode plate has an active material fixed to the surface of a conductive thin plate with a binder, so like a sintered-type electrode plate, the active material is fixed to the surface of a conductive thin plate in a porous metal sintered body formed on the surface of a conductive thin plate. This is because a polarization plate without the metal sintered body can be made lighter than one in which the metal sintered body is impregnated with an active material.

However, increasing the capacity of batteries is technically quite difficult. For example, alkaline storage batteries are generally constructed with a cathode plate that has a larger capacity than an anode plate, but when increasing the volume of the anode plate, which controls the capacity of the battery, to achieve a high capacity, the volume inside the battery remains constant. Therefore, the volume of the cathode plate decreases,
The ratio of the capacity of the cathode plate to the capacity of the anode plate becomes small, and the rapid charging performance deteriorates.

Therefore, one idea is to increase the occupation rate of the electrode plates in the internal space of the battery. In the alkaline storage battery equipped with the spiral electrode body described above, when inserting the electrode body into the battery outer can, if there is not a certain amount of space between the outer circumferential surface of the electrode body and the battery outer can, the electrode body cannot be inserted into the battery outer can. Because it is difficult to insert the battery into the battery case and the active material tends to fall off when the electrode body is stored, there is an extra space between the battery outer can and the electrode body. In addition, when using a paste type electrode plate for the cathode plate located at the outermost periphery of the electrode body, the mechanical strength of the cathode plate is weak and the active material easily falls off, so it is necessary to make the separator long in advance. The electrode body is wound so that the outer peripheral surface of the cathode plate located on the outer periphery is further covered with a separator, and the separator on the outermost periphery of the electrode body protects the cathode plate and allows the cathode plate to be directly wound when the electrode body is wound. This prevents the electrode plates from deforming due to contact with the rollers.

As a method for eliminating the gap between the outer peripheral surface of the electrode body and the battery outer can, there is a method of reducing the diameter of the battery outer can of the completed battery, as proposed in Tokukai No. 57-130368. There is, and this results in the above 〓
It is possible to obtain a battery with high energy density. However, when reducing the diameter of this battery outer can, if the cathode plate is present on the outermost periphery of the electrode body, the cathode plate on the outer periphery will collapse, and the active material that falls off due to the collapse may cause a short circuit inside the battery. Therefore, it is necessary to place a separator or the like on the outermost periphery of the electrode body to prevent the cathode plate from collapsing. However, the thickness of separators is usually 0.18 to 0.22.
mm, and if this separator covers the outermost periphery of the electrode body, there is a drawback that the volume occupied by the electrode plate in the internal space of the battery cannot be sufficiently increased.

(c) Problems to be solved by the invention The invention effectively increases the proportion of the volume occupied by the electrode plates in the internal space of the battery without deteriorating the battery performance, thereby creating a high-capacity sealed alkaline storage battery. It is an attempt to obtain.

(d) Means for solving the problem The present invention constructs a sealed alkaline storage battery with an electrode body formed by inserting a separator between an anode plate and a cathode plate, and winding these plates in a spiral shape. In doing so, a cathode plate is positioned at the outermost circumferential portion of the electrode body, and an adhesive tape having a large number of openings is placed in close contact with the entire outermost circumferential surface of the electrode body.

(E) Effect The above method creates a thickness of 0.18 to 0.22 on the outermost periphery of the electrode body.
Since it is possible to remove the 0.06 mm thick adhesive tape by removing the 0.06 mm thick separator, the electrode body can be constructed using an electrode plate that is as large as the outermost separator. This protects the cathode plate located at the outermost part of the electrode body, and when configuring the electrode body by winding,
It is possible to prevent the cathode plate from collapsing when reducing the diameter of the battery case.

In addition, since the adhesive tape has many openings, the cathode plate located at the outermost periphery of the electrode body comes into contact with oxygen gas generated inside the battery at the openings of the adhesive tape and consumes oxygen gas. For this reason, when the entire outermost surface of the electrode body is covered with adhesive tape without openings, the cathode plate located at the outermost circumference of the electrode body is prevented from coming into contact with oxygen gas and may not be absorbed into the battery. It is possible to prevent the oxygen gas consumption capacity of the plant from decreasing. Furthermore, since the adhesive tape has a large number of openings,
By using only one piece of this adhesive tape, the entire outermost circumferential surface of the electrode body can be covered with the part exposed to the cathode plate, and the workability when attaching the adhesive tape to the electrode body is also good.

(E) Embodiment FIG. 1 is a partial sectional view of a spiral electrode body used in a sealed alkaline storage battery of the present invention. 1 in the figure shows a non-woven fabric in which a paste mainly composed of cadmium oxide is applied to both sides of a metal porous thin plate, and a carbon powder layer is further formed on the surface of the paste as shown in JP-A-60-63875. A chemical paste type cadmium cathode plate, 2 a sintered nickel anode plate produced by a known method, and 3 a separator inserted so as to be always present between the cathode plate 1 and the anode plate 2;
By spirally winding these three members, an electrode plate is constructed with the cathode plate 1 located at the outermost periphery.
In addition, 4 is an adhesive tape with a width of 32 mm and has a large number of circular openings 5 with a diameter of 2.0 mm, an opening pitch (horizontal) of 5.0 mm, and an opening pitch (vertical) of 2.5 mm, and an adhesive is attached to one side of the polypropylene tape. are doing. By attaching this adhesive tape 4 to the end of the winding of the cathode plate 1 in advance, when forming the spiral electrode body by winding, it is simultaneously wrapped and attached in a single layer around the outermost circumference of the electrode body. The attached adhesive tape 4 covers the entire outermost peripheral surface of the electrode body and maintains the winding pressure of the electrode body.

After welding a current collector to the anode plate edge 6 and cathode plate edge 7 that protrude from the upper and lower end surfaces of this electrode body, the electrode body is inserted into a metal battery case with an inner diameter of 23.0 mm, and the electrolyte is poured into the case and the seal is sealed. The battery was assembled by performing the above steps, and the battery diameter was reduced to 22.5 mm by narrowing the inner diameter of the battery outer can to produce an SC-sized battery of the present invention with a nominal capacity of 1700 mAH.

In addition, as a comparison, the electrode body shown in FIG. 2 obtained by replacing the adhesive tape used in the battery of the present invention with a non-opening adhesive tape 8 of the same size was used to fabricate a comparative battery that was otherwise completely the same. A cycle test was conducted on the battery of the present invention and the comparative battery.

Figure 4 shows this result.The cycle condition was to charge at 1.7A, stop charging when the voltage decreased by a certain value (-ΔV = 100mV) from the peak voltage shown at the end of charging, and then charge at 1.2A. It is something that discharges electricity. In addition, the initial capacity of each battery is shown as 100%.

As is clear from Figure 4, a wide adhesive tape is attached to the outermost periphery of the electrode body without a separator,
Similarly, in the battery of the present invention and the comparative battery, both of which have a high capacity, there is a large difference in performance depending on the presence or absence of openings in the attached adhesive tape. The superior performance of the battery of the present invention using an adhesive tape having a large number of openings is thought to be due to the difference in oxygen gas absorption ability. In other words, since the comparative battery uses adhesive tape without openings, the adhesive tape covers the surface of the cathode plate located at the outermost periphery of the electrode body, making it impossible to absorb oxygen gas at all in this area. However, since the battery of the present invention uses an adhesive tape with many openings, the cathode plate located at the outermost periphery comes into contact with oxygen gas through the openings and absorbs oxygen gas. This is thought to have prevented deterioration of cycle life.

In addition, in order to prevent the cathode plate located at the outermost periphery of the electrode body from being completely covered, we have also considered a method of using narrow adhesive tape and attaching it to the outermost periphery of the electrode body at a certain interval. However, the disadvantage is that the workability during attachment is poor and automation is difficult. In contrast, the battery of the present invention is superior in that it is only necessary to attach one piece of adhesive tape to the outermost circumferential surface of the electrode body, and workability is good, and the attachment work can be automated.

The adhesive tape used in the battery of the present invention is preferably made of polyolefin film, polyethylene film, or polypropylene film as an alkali-resistant material, and the shape of the opening of the adhesive tape is preferably circular in terms of the strength of the tape. desirable. In addition, the higher the aperture ratio of the adhesive tape, the better, but since there is a limit to its strength, it is preferably between 10 and 40%.If the apertures are formed after the adhesive has been coated on the base material, cracks may occur in the base material. can be prevented.

Furthermore, in the above embodiments, a carbon powder layer was formed on the surface of the cathode plate, and this is effective because it helps increase the strength of the surface of the cathode plate and improves the oxygen gas absorption ability.

(G) Effects of the invention The sealed alkaline storage battery of the invention has an electrode body in which a separator is inserted between an anode plate and a cathode plate, and these plates are wound in a spiral. Since the cathode plate is located at the outermost circumference of the electrode body, and an adhesive tape having a large number of openings is placed in close contact with the entire outermost circumferential surface of the electrode body,
The separator can be removed from the outermost periphery of the electrode body, thereby effectively increasing the proportion of the volume occupied by the electrode plate in the internal space of the battery, making it possible to increase the capacity of the battery.

[Brief explanation of the drawing]

Figure 1 is a partial cross-sectional view of the electrode body used in the battery of the present invention, Figure 2 is a partial cross-sectional view of the electrode body used in the comparative battery, Figure 3 is a partial cross-sectional view of the conventional electrode body, and Figure 4 is a partial cross-sectional view of the electrode body used in the battery of the present invention. It is a cycle characteristic diagram. 1... Cathode plate, 2... Anode plate, 3... Separator, 4... Adhesive tape, 5... Opening.

Claims (1)

[Scope of utility model registration request] A separator is inserted between the anode plate and the cathode plate,
In a battery equipped with an electrode body formed by spirally winding these electrode plates, the cathode plate is located on the outermost circumference of the electrode body, and an adhesive tape having a large number of openings covers the entire outermost circumferential surface of the electrode body. A sealed alkaline storage battery characterized by being arranged in close contact with each other.