JPH04169058A - Alkali storage battery - Google Patents

Abstract

PURPOSE:To improve the oxygen gas absorbing performance of a cathode plate and suppress generation of hydrogen gas by preventing existence of active material at the portion of the cathode plate touching a battery can. CONSTITUTION:Active material 2 is kept out from the portion 3 of a cathode plate touching the battery can. In such a case as the active material layer 2 is kept out from the portion 3 of the cathode plate touching the battery can, the active material at the portion touching the battery can is not charged when the battery is charged, so that charging of the active material existing on the side opposite to an anode plate is expedited to that extent. Accordingly, for instance, in the case of a cadmium cathode plate, the active material of the cathode plate existing on the side opposite to the anode plate becomes cadmium more quickly. Thereby, the oxygen gas absorbing performance of the cathode plate is improved and the generation of hydrogen gas is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an alkaline storage battery, and more particularly to an improvement in an alkaline storage battery using paste-type electrode plates.

[Prior Art] Alkaline storage batteries can be roughly divided into types using sintered electrode plates and types using paste electrode plates.

To explain both types of electrode plates used in cadmium batteries in terms of cadmium cathode plates, the sintered type electrode plate is made by sintering nickel powder and then chemically injects cadmium hydroxide or metallic cadmium into the pores of the sintered plate. It is filled using a conventional method or an electrochemical method. Paste-type electrode plates, as shown in Figure 2, are made of nickel-plated punched steel plates made of a paste obtained by kneading powder mainly composed of cadmium oxide or cadmium hydroxide with an organic binder. The active material layer 2 is formed by coating both sides of the material support 1 and drying, and then chemical conversion treatment is performed in an alkaline solution in order to activate the active material layer 2. In a paste-type electrode plate that performs battery cell formation, a paste obtained by kneading a powder containing cadmium oxide or cadmium hydroxide and metal cadmium as a discharge reserve with an organic binder is applied to the active material holder 1. Some are made by drying.

The filling capacity density of the active material of the paste-type electrode plate is 1400~
1500 mAh/cj, and the filling capacity density of the active material of the sintered electrode plate is 900 to 1000 mAh/a/.

Paste-type plates have been attracting attention recently because they can hold more active material than sintered plates.

In alkaline storage batteries using general paste-type electrode plates,
An electrode plate group made by sandwiching a separator between a cathode plate and an anode plate as shown in Fig. 2 is wound in a spiral shape with the cathode plate positioned on the outside, and this spiral electrode plate group is assembled into a battery. The battery is housed in the can with a portion of the cathode plate touching the inside wall of the can. For boat fishing, the battery can constitutes a cathode terminal, and the end of the active material holder of the cathode plate is resistance welded to the bottom wall of the battery can. Note that the contact portion of the cathode plate that contacts the side wall portion of the battery can also contributes to electrical conduction.

[Problems to be Solved by the Invention] Conventionally, the advantage of paste-type electrode plates is that they hold a large amount of active material, so it was not thought that having a large amount of active material would adversely affect battery performance.

However, as a result of the inventor's research, especially regarding paste-type cathode plates, the active material held in the active material holder 1 in the portion that contacts the inner wall of the battery can has the following effects on battery performance. It was found that it had a negative impact.

(1) Decreases oxygen gas absorption performance during overcharging.

This is because when charging the battery, the active material at the contact portion that contacts the battery can, which is not directly involved in charging and discharging, is also charged (the active material becomes cadmium).

If such unnecessary charging is performed, charging of the back side of the portion of the negative plate that contacts the battery case (the side facing the positive plate with the separator in between) is delayed. Therefore, the ability of the cathode plate to absorb oxygen gas generated from the anode plate during overcharging is poor, and hydrogen gas is more likely to be generated. Particularly when continuous charging is performed for a long period of time, the amount of hydrogen gas generated increases and the internal pressure of the battery tends to rise. Due to such poor oxygen gas absorption performance, it was thought that rapid charging was difficult with conventional alkaline storage batteries using paste-type electrode plates.

(2) Charge acceptability deteriorates, it takes time to form a battery case, and high charging voltage is required.

Taking a cadmium cathode plate as an example, the active material is mainly cadmium oxide or cadmium hydroxide, which is a chemical change of cadmium oxide, which lowers the conductivity of the active material and reduces the charging and discharging efficiency of the cathode plate. It is caused by doing. When manufacturing an alkaline storage battery using the method of battery cell formation (a method in which the battery is assembled using unformed electrode plates and then the electrode plates are activated by charging the battery in the battery case), the contact parts As the conductivity of the active material decreases, the charging time becomes longer and the charging voltage must be increased.

(3) Although not directly related to battery manufacturing, there is also the problem that the cost of the battery itself increases because the active material in the contact portion does not participate in charging and discharging the battery.

An object of the present invention is to provide an alkaline storage battery that can solve the above problems.

[Means for Solving the Problems] The present invention provides an electrode plate group configured using a paste-type electrode plate in which an active material is held in an active material holder, so that a part of the cathode plate is attached to the inner wall of a battery can. The invention of claim 1 is directed to an alkaline storage battery arranged in a battery can so as to be in contact with the
The active material was not present in the part of the cathode plate that comes into contact with the battery can.

In the second aspect of the invention, when the active material holder is made of a porous metal plate, the surface of the contact portion of the cathode plate is covered with a conductive layer containing carbon.

In the third aspect of the invention, the part constituting the contact part of the active material holder has a flat surface.

In the fourth aspect of the invention, the contact portion of the cathode plate is coated with an insulating resin layer having water impermeability and alkali resistance.

An insulating tape can be used as this insulating resin layer.

In the invention of claim 5, the other surface portions of the cathode plate are covered with a conductive coating layer containing carbon.

[Function J] If the active material is not present in the part of the cathode plate that contacts the battery can as in the invention of claim 1, when charging the battery, the active material in the part that contacts the battery can as in the conventional case. Since the active material on the side facing the anode plate is not charged, charging of the active material on the side facing the anode plate proceeds faster. As a result, taking a cadmium cathode plate as an example, the active material on the side of the cathode plate facing the anode plate quickly turns into cadmium, which improves the oxygen gas absorption performance of the cathode plate.
Hydrogen gas is less likely to be generated.

In addition, when the active material holder is brought into direct contact with the battery can without the presence of active material in the contact area of the cathode plate with the battery can, the electrical conductivity between the battery can and the cathode plate is improved, and as a result, Not only does charging acceptability improve, but charging at a low charging voltage becomes possible. Note that the present invention does not only include batteries in which the contact portion of the cathode plate is always brought into conductive contact with the battery can (as in the invention of claim 4, there is no contact between the contact portion of the cathode plate and the battery can). This includes the case where an insulating layer is interposed between the two.

As in the invention of claim 2, when the active material holder is made of a porous metal plate, if the surface of the contact portion of the cathode plate is covered with a conductive layer containing carbon, the gap between the battery can and the active material holder is Conductivity can be improved.

If the part constituting the contact part of the active material holder has a flat surface as in the invention of claim 3, the contact area between the cathode plate and the battery can increases. , sufficient conductivity can be obtained between the battery can and the active material holder without providing a conductive layer containing carbon.

If the part of the active material holder that contacts the battery can is covered with a water-impermeable, alkali-resistant, and insulating resin layer as in the invention of claim 4, generation of hydrogen from the active material holder can be prevented. . Usually, the active material holder is made of iron plated with nickel, but nickel has a low hydrogen overvoltage.

Therefore, if the active material holder is brought into direct contact with the electrolyte without providing the active material in the part that contacts the battery can, hydrogen is likely to be generated from the contact part during charging. For example, in a nickel-cadmium battery, oxygen gas is absorbed by the cathode plate. However, since hydrogen gas is not absorbed or decomposed within the battery, the generated hydrogen gas accumulates within the battery and has the adverse effect of increasing internal pressure and decreasing the amount of electrolyte.

If the surface of the cathode plate other than the contact portion is covered with a conductive coating layer containing carbon as in the fifth aspect of the invention, the following effects can be obtained. For example, in the case of a cadmium cathode plate, the conductivity of carbon is higher than that of cadmium oxide or cadmium hydroxide, which constitutes the active material, so when a battery is charged, charging proceeds from the surface of the cathode plate. For this reason, a large amount of cadmium is generated on the surface of the electrode plate, improving oxygen gas absorption performance and making it difficult to generate hydrogen gas.

[Examples] Examples of the present invention will be described in detail with reference to the drawings. The battery of the present invention is characterized by the configuration of the cathode plate, and the configuration of other parts is the same as conventional batteries.

Therefore, FIG. 1 schematically shows an embodiment of a cathode plate that can be used when the present invention is applied to a nickel-cadmium battery. Note that FIGS. 1(a) to 1(d) are diagrams schematically showing cross-sectional views of various cathode plates cut along the longitudinal direction.

In Figure 1(a), 1 has a width of 4Qaun and a length of 85+
The active material holder is made by punching holes in a KR-AA steel plate with a thickness of 0.080 mm and then plating with nickel to a thickness of 4 to 6 μm, and 2 is an active material layer.

The active material layer 2 is made of cadmium oxide 7 with an average particle size of 1 to 3 μm.
A paste produced by kneading powder consisting of 0 parts by weight, 18 parts by weight of metal cadmium with an average particle size of 1 to 3 μm, 10 parts by weight of metal nickel with an average particle size of 10 to 15 μm, and 2 parts by weight of polyvinyl alcohol with ethylene glycol. After being coated on the active material holder 1, it was dried at 150° C. for 1 hour, and pressure was applied so that the thickness of the electrode plate became a predetermined thickness. In this example, the active material layer 2 was formed by applying the paste to the active material holder 1 except for the contact portion 3 that contacts the battery can. Then, an insulating tape 4 made of polypropylene was attached to the contact portion 3 to cover the contact portion 3 with an insulating resin layer. The wall thickness of the electrode plate is 0.156 mm in the part where paste 2 is applied on both sides, and 0.30 mm in the part where insulating tape 4 is pasted on one side. Further, the contact portion 3 occupies a position up to 40 mm from the longitudinal end of the active material holder 1a. The insulating resin layer may be formed by applying a thermosetting resin to the outside of the insulating tape.

In the following description, this cathode plate will be referred to as cathode plate A, and a battery using this cathode plate A will be referred to as battery A.

FIG. 1(b) is a sectional view of a cathode plate B used in a battery B according to an embodiment of the present invention. In FIG. 1(b), 5 is a carbon black layer and 6 is a carbon layer. This electrode plate is manufactured based on the electrode plate shown in FIG. 1(a). Therefore, in this example, the conditions for the active material holder 1, the active material layer 2, and the insulating tape 4 are the same as those for the cathode plate A in FIG. 1(a). In this embodiment, the carbon black layer 5 and the carbon layer 6 constitute a conductive coating layer containing carbon. In this cathode plate B, a paste in which carbon black with a particle size of 0.05 to 0.1 μm is dispersed in ethylene glycol is applied to the surface of the active material layer 2.
The carbon black layer 5 is formed by drying at 150° C. for 1 hour. Next, a carbon layer 6 was formed on the surface of the carbon black layer 5.

FIG. 1(C) is a sectional view of a cathode plate C used in a battery C according to another embodiment of the present invention. The cathode plate C of this example is characterized by the structure of the active material holder 10 and the fact that no insulating tape is attached. In the active material holder 10 used in this example, no punching is performed in a portion corresponding to the contact portion 30, and the contact portion 30 has a flat surface.

In this embodiment, the contact portion 30 is exposed, unlike the cathode plates shown in FIGS. 1(a) and 1(b). The other points are the same as the cathode plate B shown in FIG. A carbon layer 6 is formed on the surface of the carbon black layer 5, and the thickness of the part where the active material layer is formed on both sides is 0.56 mm, and the thickness of the part where the active material layer is formed on one side is 0. Cathode plate C is manufactured by applying pressure to a thickness of .30 mm.

FIG. 1(d) is a sectional view of a cathode plate used in a battery according to still another embodiment of the present invention. For the cathode plate, the active material layer 2 is formed in the same manner as for the cathode plate B in FIG. 1(b), except for the contact portion 3 of the active material holder 1 that contacts the battery can,
A carbon black layer 5 constituting a conductive coating layer containing carbon is formed on the surface of the active material layer 2. Furthermore, a carbon layer 16 constituting a conductive layer containing carbon is formed on the surface of the contact portion 3.

Each cathode plate prepared as above was inserted through a separator made of polyamide resin non-woven fabric to a wall thickness of 0°57mm x mm.
KR-700AA type batteries A-D were manufactured by combining and winding the paste-type anode plate with a width of 4 Q mm and a length of 67 mm so that the contact portions 3 and 30 were in contact with the battery can. Further, a battery E similar to that described above was manufactured using a conventional negative electrode plate having the structure shown in FIG. 2 and manufactured by pressurizing the electrode plate until the thickness of the electrode plate became 0.52 mm. Next, a charge/discharge test was conducted using these batteries A to E. The measurement results are shown in Tables 1 and 3.
As shown in the figure. Table 1 shows the discharge characteristics of the battery, 0.2
The discharge capacity (mAh) when discharging at a current of 0 capacity, that is, 1/5 of the nominal capacity, and the discharge capacity (mAh) when discharging at a current of 30 capacity, that is, 3 times the nominal capacity of each battery, are 0. 2
It represents the value of the capacity ratio divided by the C capacity (mA, h). Figure 3 shows the charging characteristics of each battery.
The horizontal axis represents the charging time when charging at CmA, and the vertical axis represents the voltage of each battery. In addition, in the figure, lines A to E
represents the characteristic curves of each battery A to E.

Table 1 It can be seen from Table 1 that batteries A to D of the present invention all have higher values in capacity and capacity ratio than conventional battery E. This is because the characteristics of conventional batteries are poor because the active material in the part that comes into contact with the battery case contains a substance with low conductivity such as cadmium oxide or cadmium hydroxide, which is a chemically modified form of cadmium oxide, which causes a discharge reaction. This is because it is inhibited. Furthermore, when an unformed electrode plate is charged, since the conductivity of the cathode plate itself is low, the charging reaction also proceeds in the portion of the cathode plate that comes into contact with the battery can. However, since the portion of the cathode plate that contacts the battery case does not face the anode plate, it is difficult for discharge to occur. In the battery of the present invention, the charging reaction does not proceed in the portion of the cathode plate that contacts the battery can, so it is thought that the discharge characteristics are improved.

Furthermore, it can be seen from Table 1 that the capacity ratios of batteries C and D of the present invention are particularly high. This is because there is more conductivity between the cathode plate and the battery can than in Batteries A and B of the present invention in which a non-conductive tape is attached to the contact area.

In particular, since the battery cell has no punched holes in the contact area on one side, the conductivity is greatly improved.

Furthermore, from FIG. 3, it can be seen that all of the batteries A to D of the present invention can be charged at a low voltage and have improved charging characteristics. In particular, it can be seen that charging characteristics can be greatly improved when the surface of the electrode plate is covered with a conductive coating layer containing carbon as in batteries BD of the present invention.

Furthermore, it can be seen that when the conductivity between the cathode plate and the battery case is improved as in Batteries C and D of the present invention, the charge acceptance is also improved and the charging voltage can be lowered.

Therefore, in the battery of the present invention, rapid charging performance can be improved.

In addition, in batteries A-D of the present invention, in addition to improving the charge/discharge characteristics, the amount of active material can be reduced by 20%, and since there is no cathode active material, the space inside the battery can be utilized, so that the anode and cathode The active material filling capacity of the plate can be improved by 5%.

Furthermore, if an insulating tape is attached to the exposed part of the active material holder as in Batteries A and B of the present invention, it is possible to prevent contact between the nickel on the surface of the active material holder and the electrolyte, thereby preventing hydrogen gas from coming into contact with the electrolyte. can suppress the occurrence of

[Effects of the present invention] According to the invention of claim 1, since no active material is present in the portion of the cathode plate that contacts the battery can, charging of the active material on the side facing the anode plate can proceed quickly. As a result, the oxygen gas absorption performance of the cathode plate is improved, and hydrogen gas is less likely to be generated.

In addition, when the active material holder is brought into direct contact with the battery can without the presence of active material in the contact area of the cathode plate with the battery can, the electrical conductivity between the battery can and the cathode plate is improved, and as a result, This has the advantage of improving charging acceptability and enabling charging at a low charging voltage.

According to the invention of claim 2, when the active material holder is made of a porous metal plate, the surface of the contact portion of the cathode plate is covered with a conductive layer containing carbon, so that the connection between the battery can and the active material holder is It is possible to improve the conductivity between the two.

According to the third aspect of the invention, since the part constituting the contact part of the active material holder has a flat surface, the contact area between the cathode plate and the battery can can be increased. There is an advantage that sufficient conductivity can be obtained between the battery can and the active material holder without providing a layer.

According to the invention of claim 4, since the portion of the active material holder that comes into contact with the battery can is covered with a resin layer having water impermeability, alkali resistance, and insulation, generation of hydrogen from the active material holder can be prevented. There are advantages.

According to the invention of claim 5, since the surface of the cathode plate other than the contact portion is covered with a conductive coating layer containing carbon, charging proceeds from the surface of the cathode plate, improving oxygen gas absorption performance and hydrogen gas absorption. This has the advantage that gas is less likely to be generated.

[Brief explanation of the drawing]

1(a) to 1(d) are schematic cross-sectional views of cathode plates used in embodiments of the present invention, and FIG. 2 is a schematic cross-sectional view of cathode plates used in conventional batteries. Figure 3 is a diagram showing the charging characteristics of each test battery. 1, 10... Active material holder, 2... Active material layer, 3,
30... Contact portion, 4... Insulating tape, 5... Carbon black layer, 6... Carbon layer. Agent: Patent attorney Hidetoshi Matsumoto (1 other person) 2
- Figure 1 (b) (C) Figure 2

Claims (5)

[Claims] (1) Place an electrode plate group made up of paste-type electrode plates in which active material is held on an active material holder into the battery can so that a part of the cathode plate contacts the inner wall of the battery can. 1. An alkaline storage battery characterized in that an active material is not present in a contact portion of the cathode plate that contacts the battery can. (2) When the active material holder is made of a porous metal plate,
The alkaline storage battery according to claim 1, wherein the surface of the contact portion of the cathode plate is covered with a conductive layer containing carbon. (3) The alkaline storage battery according to claim 1, wherein a portion of the active material holder that constitutes the contact portion has a flat surface. (4) The alkaline storage battery according to claim 1, wherein the contact portion of the cathode plate is coated with an insulating resin layer having water impermeability and alkali resistance. (5) The alkaline storage battery according to claim 1, wherein the other surface portion of the cathode plate is covered with a conductive coating layer containing carbon.