JPS58186161A - Negative electrode for alkaline battery - Google Patents

Abstract

PURPOSE:To improve the gas absorbing capacity of a negative pole gas absorbing enclosed alkaline battery, by providing a resin layer composed of polytetra phloroethylene only on the electrode face or electrode face layer of a paste negative pole. CONSTITUTION:Fine powder of active substance and carbonickel powder or carbon powder as required is dissolved in solution where thickener or binder such as polybinyl alcohol is dissolved in ethylene glycol to produce paste, which is applied uniformly on both sides of porous metallic supporter such as punching metal and dried, then electrolyzed in alkali solution and activated to produce a paste negative pole for alkaline battery and a resin layer of polytetra phloroethylene is provided only on the face or the face layer of the electrode in such a manner that fine powder of resin is applied uniformly on the surface of the electrode then pressure molded. In an enclosed alkaline battery of negative pole gas absorbing type employing the negative pole in accordance to the invention will cause no increase of inner pressure even when charging with 1hr rate or 30min rate or the lowering of capacity when discharging large current.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a paste type negative electrode used in a negative electrode gas absorption type sealed alkaline storage battery.

The paste type negative electrode used in negative electrode gas absorption type sealed alkaline storage batteries has a manufacturing method that is ni'j compared to the sintered type negative electrode.
Although it has characteristics such as high energy density -1, it also has problems such as many restrictions in terms of characteristics. One of these functions is as a gas absorption electrode. Conventionally, paste-type negative electrodes were obtained by kneading active material powder with binders, thickeners, and solvents to form a paste7, coating it on both sides of a porous support, and drying it. The gas absorption capacity of the negative electrode obtained by this method was not so high, and it was particularly unsuitable for short-time charging with a large current.

Inclusion of polytetrafluoroethylene resin in an electrode is widely used not only in paste-type negative electrodes for alkaline storage batteries. Paste-type negative electrodes for alkaline storage batteries are also used by mixing polytetrafluoroethylene resin powder into the active material powder, or by immersing the material in an aqueous dispersion of polytetrafluoroethylene resin and drying it. This is especially aimed at ensuring strength, and it cannot be said to be sufficient for the same gas absorption capacity.
.

Ta. When polytetrafluoroethylene resin powder is mixed into the active material powder, the strength is significantly improved, but hardly any improvement in gas absorption capacity can be expected. In addition, when electrodes are immersed in an aqueous dispersion of polytetrafluoroethylene resin and then dried, the strength is not significantly improved, but the gas absorption capacity (1 - 1 time per time) is increased.However, on the other hand, the water repellency of the electrodes increases. Therefore, there is a problem in that the discharge characteristics deteriorate and the internal resistance increases significantly.

The present invention is directed to an electrode of a paste-type negative electrode for alkaline storage batteries.
+ (In 6-4, by providing a resin layer made of polytetrafluoroethylene only on the electrode surface layer, the gas absorption capacity of the negative electrode gas absorption type sealed alkaline storage battery is reduced, such as the discharge characteristics. (The aim is to improve the width to 6 people.

The present invention (cl, fine powder of active material and carb.
・A solution prepared by dissolving conductive materials such as Lenokel powder and carbon powder, thickeners and binders such as polyvinyl alcohol in a solvent such as ethylene glycol (this solution is made into a paste and applied to all areas such as punched metal). After coating both sides of the L-type support uniformly and drying it, electrolysis etc. are performed in an alkaline solution to obtain an active 11'-treated F11 (-IL) for alkaline storage battery paste type 1'↓. A resin layer of polybutran[]roethylene is applied only to the electrode surface layer or the electrode surface layer, for example, by applying it uniformly with a resin layer and then press-molding it [2]. The 1'↓ group obtained according to the present invention, the positive electrode using a negative metal or the like as an active material, and the separator interposed between the positive and negative electrodes constitute an electrode group, and after being stored in a metal container. ,
A negative electrode gas absorption type sealed alkaline storage battery, in which a concentrated alkaline aqueous solution is injected in a controlled quantity so that no free liquid is produced, and then sealed with a lid, has a high rate of 1 hour to 0.130 minutes. Even during current charging, there is little increase in the internal pressure of the L battery, and there is also little capacity drop during high current charging.

Hereinafter, an embodiment of the present invention G' will be described as a sealed cylindrical nickel, cadmium alkaline storage battery (C size).

Compare the nominal capacity (1650 mAh) with the conventional example.

I will explain in detail. 15 parts carbonyl nickel powder per 100 parts cadmium oxide powder, 1 part 1 synthetic resin single fiber 0.5 parts by weight, 30 parts ethylene glycol;
part (ζ polyvinyl alcohol 0.75% (iHi part υ
This Jl is 100t+ thick iron plated with nickel.
Schiff 1 - Both 1tflll + of perforated iron plate [E liner thickness is 0
．． So that there are 6 pieces (ζ painting surface:, adjust 1- and paint 1]
After cooling, it is dried at about 110°C. Next, this negative electrode 'f
3 to 38>, 260 rtan ・J"
11 Terama negative electrolysis with i-stream, remove alkali^ by washing with water, and dry. The negative electrode thus obtained is designated as B(f, 'C Example 1). Next, a fine powder of polytetrafluoroethylene is coated uniformly and thinly on the surface of the negative electrode B, and then pressure molded at a constant pressure. This VT resistance is designated as A (negative electrode in the present invention). comparison fr-V) to B's i''
J electrode was immersed in an aqueous dispersion of 6% by weight polytetrafluoroethylene for 3 minutes/1- then dried to form negative electrode C.
(Conventional Example 2) is obtained. In addition, in the process of obtaining negative electrode B in the previous step 1, when making it into a paste, 5 parts by weight of polytetrafluoroethylene fine powder was mixed in with the negative electrode D.
(Conventional example 3).

Like this! For the negative electrodes A, B, C, and D, the sintered nickel electrode was used as the positive electrode, and the nylon nonwoven fabric was used as the separator.
A sealed cylindrical Niracle with a nominal capacity of 1660mAh. A cadmium alkaline storage battery is constructed with the following γ; f'l,
-tt sheet electrical test was conducted.

The battery was rapidly charged at a charging current of 3.3 A at an ambient temperature of 2 parts Celsius, and the behavior of the battery's internal pressure was determined.

(2) Discharge test A discharge curve was obtained when a fully charged battery was discharged with a discharge current of 6 A at an ambient temperature of o'c.

The above results are summarized in figures, and the behavior of the battery internal pressure during rapid charging is shown in Fig. 1, and the discharge curve is shown in Fig. 2.

As is clear from this result, in the battery using the negative electrode A of the present invention, the internal pressure of the battery is approximately 2 to 9/- even during charging.
It shows stable rapid charging characteristics, with a high discharge voltage and long duration during discharging. On the other hand, negative electrodes B, C, and D in the conventional examples were not able to obtain good results in both charging and discharging characteristics like the negative electrodes in the present invention.

The reason why the negative electrode A according to the present invention has excellent charging and discharging characteristics is believed to be mainly due to the following reasons.

In other words, in order to increase the gas absorption capacity of a negative electrode gas absorption type alkaline storage battery during charging, it is necessary to quickly diffuse oxygen generated from the positive electrode during charging into the negative electrode. If it is less than the conventional example, in a configuration like negative electrode B, the amount of electrolyte retained at the boundary between the electrode and the separator increases, and the diffusion of oxygen gas is inhibited, resulting in a limit to the gas absorption capacity. On the other hand, if one of the present inventions is to provide a polytetrafluoroethylene resin layer on the electrode surface or electrode surface layer, the polytetrafluoroethylene resin itself has water repellency and gas permeability. It is thought that the amount of electrolyte retained at the boundary between the electrode and separator will be reduced, and the diffusion of oxygen gas will no longer be inhibited, improving the gas absorption ability. For example, negative electrode C has the same effect, but since a polytetrafluoroethylene resin layer is formed over the entire electrode, the amount of electrolyte retained within the electrode is reduced, and the discharge characteristics have a negative impact on

It is thought that the negative electrode of soil D has poor gas absorption ability because the polytetrafluoroethylene fine powder is uniformly dispersed in the paste and does not improve the water repellency and gas permeability of the negative electrode surface. In the negative electrode of the present invention, a polytetrafluoroethylene resin layer is formed only at the electrode edges or the electrode surface layer, so the amount of electrolyte retained inside the electrode is appropriate, and it has no negative effect on discharge characteristics. It seems that it does not give any.

As described above, the negative electrode for alkaline storage batteries according to the present invention has significantly improved rapid charging characteristics without deteriorating discharge characteristics.

[Brief explanation of the drawing]

Fig. 1 1i A diagram showing the behavior of the battery internal pressure during rapid charging of a cylindrical sealed alkaline storage battery constructed using the negative electrode of the present invention. Fig. 2 1 is a diagram showing the discharge curve during large current discharge at low temperature. It is. A...Negative electrode in the present invention, B...Negative electrode in Conventional Example 1, C...Negative electrode in Conventional Example 2, D...Negative electrode in Conventional Example 3 .

Claims (1)

[Claims] A negative electrode for an alkaline storage battery, characterized in that a resin layer made of polytetrafluoroethylene is provided on the electrode surface of a paste-type negative electrode in which a paste-like active material is applied on both sides of a porous support or on the electrode surface layer O. .