JPS5887759A - Alkaline battery - Google Patents

Abstract

PURPOSE:To obtain an alkaline battery having excellent storage performance and shock resistance, stabilized intermittent discharge performance, and no stringiness of a gelled anode by using together crosslinked graft sodium polyacrylate and carboxymethylcellulose as a gelling agent. CONSTITUTION:A various concentration (wt%) of mixtures of crosslinked graft sodium polyacrylate and CMC were added to an electrolyte comprising potassium hydroxide, zinc oxide, and water to form a gelled anode 4. AA sized alkaline manganese batteries manufactured by using these gelled anodes were tested. An alkaline battery having good shock resistance and storage performance and a stabilized, easily workable gelled anode is obtained in such a way that both crosslinked graft sodium acrylate and CMC are used as a gelling agent, and 0.5-2.5wt% sodium polyacrylate, 0.5-1.5wt% CMC, and moreover 2.0wt% or more the sum of these two agents are preferable as the concentration of the gelling agent adding to the electrolyte.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in alkaline batteries such as alkaline manganese batteries and mercury batteries, and aims to improve battery performance and stability.

Conventionally, carboxymethyl cellulose (hereinafter referred to as CMC), sodium polyacrylate, and the like have been widely used as gel fusing agents for gel cathodes used in alkaline (alkaline) 6 ponds. Kneading is a gel [Characteristics that an arsenic agent should have include: ■ It must be stable in an alkaline electrolyte ■ It exhibits a gel state in an alkaline electrolyte, and when, for example, zinc powder as a cathode active material is dispersed. This is due to the fact that the scales can be held sufficiently stably and the gel cathode (hereinafter referred to as gel cathode) has as little stringiness as possible.

Generally, when CMC is used alone with a powdered cathode active material in an alkaline electrolyte, it initially maintains a good gel state with almost no stringiness, but as time passes, CMC separates. A decrease in the reaction surface area due to the adhesion of powdered cathode active materials that can maintain a gel state, or an anode mixture of electrolyte released from CMC, Sebaret 2 fl! ! Discharge performance deteriorates due to insufficient supply of melted liquid required for cathode reaction due to transfer to the
The decrease in E is significant.

Furthermore, the decrease in the open circuit voltage of the battery due to the decomposition of CMC is particularly significant in alkaline manganese batteries that use r-himanganese diacid as the anode active material.

In order to eliminate these drawbacks, attempts have been made to use linear sodium polyacrylate. Cono-linear sodium polyacrylate can overcome many of the drawbacks of CMC, but cannot be used alone because it forms a sticky gel with high stringiness, making it extremely difficult to fill it into batteries. It is difficult to use, and has the disadvantage that it can only be added in small amounts as an adjuvant to CMC.

On the other hand, cross-linked branched sodium polyacrylate
It has alkali resistance, has a three-dimensional branched molecular structure due to crosslinking reaction, has almost no stringiness, and exhibits chikuntropic fluidity and a high drop value, making it a powder cathode with a large specific gravity. It is possible to prevent sedimentation of the active material and maintain a good dispersion state over a long period of time.

Therefore, the decrease in open circuit voltage after long-term storage at room temperature or high temperature storage is
9. On the other hand, due to its strong and stable liquid retention property, the gel cathode can be used at the end of discharge when the electrolyte in the separator tends to be insufficient, especially at the end of VCfftl missing discharge. It becomes difficult for the electrolyte to be smoothly supplied from the battery to the battery, and unstable fluctuations are likely to occur in the maintenance voltage. In addition, this cross-linked branched sodium polyacrylate has high thixotrobinox properties, so when a strong impact is applied to the battery, such as a drop or strong vibration, the gel cathode easily flows and is difficult to return to its original state. A misalignment occurs in the contact between the dispersed active material particles and the cathode current collector,
The current collection effect tends to be incomplete or unstable.

As a result, the short-circuit current of the battery and the terminal voltage at the initial stage of discharge may significantly decrease or fluctuate.

One way to prevent this drawback is to increase the ratio of the cathode active material in the gel cathode to increase the probability of contact with the current collector, but if the dispersed cathode active materials are fixed to each other and fluctuate. If the ratio is increased to an effective degree of dispersion, the electrolyte required for the cathode reaction will be insufficient, which will lead to a decrease in heavy load discharge performance, which is one of the important characteristics of alkaline batteries, and a decrease in reaction efficiency. Therefore, it is not a good idea.

On the other hand, as mentioned above, CMC has slightly poor alkali resistance and has problems with MIE during storage, but its thixotropic et is smaller than cross-linked branched sodium polyacrylate, so it has strong impact resistance and is sufficient for practical use. I can endure it. It's raining again (
Since the value is small and the gel cathode easily flows, it has the advantage of weakening the liquid holding power in the gel cathode, smoothing the supply of electrolyte to the separator at the end of intermittent discharge, and preventing unstable fluctuations in the terminal voltage. ing.

The present invention improves the conventional drawbacks mentioned above, and improves the following: ■ Reduction of poor battery performance during long-term room temperature storage and high temperature storage ■ Stability of battery performance against drops and vibrations ◎ General Preventing unstable fluctuations in terminal voltage that tend to occur at the end of intermittent discharge, which is a typical usage. ○ At the same time, it is possible to provide a gel cathode without stringiness, which facilitates the work of filling 1c inside the battery. Our goal is to provide superior alkaline batteries.

The present invention firstly proposes that in the case of a single gelatin agent, the simultaneous VC/l+1
We decided to use three simultaneous vCM methods to solve the four problems mentioned above, which cannot be combined, by combining two types of gel-resistance, cross-linked and branched polyacrylic sodium monoxide and CMC, to take advantage of their respective strengths.

Second, the concentration of each gel specific gravity and the sum of the concentrations are set for the gel electrolyte.

The present invention will be explained below with reference to Examples. As shown in FIG. 1, an anode mixture 2 made of manganese diacid and graphite is pre-molded into a cylindrical shape and installed in the anode case 1, and a cup-shaped plate (7) (later 3) is inserted into the center of the anode mixture 2. The gel cathode 4 is injected into the cup of the separator. After that, the negative assembly body 6 with the gasket 5 is inserted into the center of the gel cathode 4 to form a cell. 7゛ is an anode terminal, and 8 is a cathode. terminal, 9 is an outer can, and 1Q is an insulating tube. Gel shade W with varying concentrations (wt%)
A drop resistance test and a storage test were conducted using the JLI type 3 alkaline manganese battery. Table 1 shows the presence or absence of abnormality (instability) that appears in the terminal voltage when the 1Ω closing loop pressure is measured for 10 seconds after the battery is dropped from a height of 1 m.

Table-1 In the table, ○ indicates an area where no abnormality occurs, △ indicates an area where an abnormality may occur, and × indicates an area where an abnormality has occurred.
vinegar.

As shown in Table 1, 0.6 to 2.5% by weight of cross-linked branched sodium polyacrylate and C
In the range of MC 0.5 to 2.5%, the drop resistance of the battery is generally stable.

Table 2 shows the open circuit voltage of the battery after it was stored at 600+:2°C for one month, and the difference between the open circuit voltage immediately after manufacture and the small mV unit.

Table 2 As shown above, it can be seen that CMC has a greater influence on open circuit voltage degradation than cross-linked branched sodium polyacrylate. Judging from the poor open circuit voltage, the concentration of CMC in the gel electrolyte is preferably .about.1.6% by weight.

On the other hand, if the total concentration of each gel agent is 2.0% by weight or less based on the gel electrolyte, the cathode active material particles can maintain a stable dispersion state in the gel electrolyte, and the gel does not flow into the battery. When filling the cathode, the gel electrolyte and cathode active material separate, and due to variations in the filling amount and natural underflow from the filling port,
Free-flowing ponds cause serious problems in manufacturing.

'Also, the concentration of gel 1 and 4 for gel electrolyte is
．． ○If it exceeds % by weight, the viscosity of the gel electrolyte will be too high.
When creating a gel cathode, air bubbles are significantly trapped.
This tends to adversely affect variations in the filling 111 and custom-made batteries, and the workability in the gel cathode filling process also deteriorates.

The preferable ranges for the gel cathode for each of the above-mentioned drop resistance +1 production test, storage test, gel cathode stability and workability are shown in FIG. 2.

Therefore, alkali bending resistance V means drop resistance.

The gelling agent in the gel electrolyte used for gel cathodes with good fp-o during storage, stable gel cathodes, and good working Pt is @1 cross-linked branched polyacrylic acid. Using sodium and CMC together, secondly, the concentration with respect to the gel electrolyte is 0.5 with cross-linked branched sodium polyacrylate.
-2.5% by weight, CMC''cO, 5-1.6% by weight, and the sum of each concentration is preferably about 2.0% by weight or more.

We also prototyped an AA alkaline manganese battery using a gel cathode prepared with a gel electrolyte within the above range, with a resistance of 1o.
Ω, discharge mode 30 minutes/day, and test temperature 20°±2°C. When intermittent discharge was performed, no abnormal terminal voltage curve was observed at the end of discharge, as shown in an example in Figure 3. In the figure, A is a custom-made prototype battery using a combination of 2.0% by weight of cross-linked branched sodium polyacrylate and 1% by weight of CMC as a gel agent, and B is a custom-made prototype battery using cross-linked and branched polyacrylic as a gel agent. A custom-made prototype battery using 4.0% by weight of sodium chloride alone is shown.

As mentioned above, the present invention makes it possible to obtain an alkaline battery that has excellent impact resistance and stable intermittent discharge during storage, and is easy to manufacture because the gel cathode does not have strong stringiness. can. It is something.

[Brief explanation of drawings]

Fig. 1 is a half-cut side view of an AA-size Alka-417 manganese battery in an example of the present invention, Fig. 2 is a diagram showing the preferred range of gel concentration, and Fig. 3 is a change in intermittent discharge characteristics of the same battery. It is a diagram. '1...Anode case, 2...Anode mixture, 3...Separator, 4.II+10.Gel cathode. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure ie3叡11畦〉胃hyong-gai (-'s plate stomach ε,

Claims (2)

[Claims] (1) A gelled cathode assembly in which a cathode active material is dispersed in a gelled electrolyte consisting of an alkaline electrolyte and a gelling agent,
An alkaline battery characterized in that cross-linked branched sodium polyacrylate and carboxymethyl cellulose are used together as the gel fusing agent. (2) Cross-linked branched polyacrylic acid for the gel electrolyte) The concentration of IJium added is 0.5 to 2.5% by weight, and the concentration of carboxymethylcellulose is 0.6 to 1% by weight.
．． 5. The alkaline battery according to claim 1, wherein the total concentration of the gelling agent is in the range of 2.6 to 4.0 weight percent relative to the gel electrolyte.