JPS60100366A - Production method of negative electrode for zinc- alkaline cell - Google Patents

Abstract

PURPOSE:To improve the heavy-load discharge characteristic by mixing negative- electrode particles formed with a sizing material coating layer on the surface and negative-electrode particles having no sizing material coating layer and injecting an alkali electrolyte to the mixture to form a gel-like negative electrode. CONSTITUTION:Negative electrode particles made of zinc or zinc alloy powder and sizing material powder such as a carboxyvinyl polymer are mixed to form a sizing material coating layer on the surface of negative-electrode particles, which are mixed with 10-60wt% of negative-electrode particles having no sizing material coating layer to form a mixed negative-electrode particle group. A fixed amount of it is stored in a negative-electrode container, an alkali electrolyte is injected and absorbed to form a gel-like negative electrode, thus a negative electrode for a zinc-alkaline cell is formed. Accordingly, the heavy-load discharge characteristic of a cell can be improved by bringing zinc powder in contact with the low-viscosity portion in the gel structure of the gel-like negative electrode formed via the CZ method.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a negative electrode for use in a 11:1 lead-alkaline battery.

In general, zinc-alkaline batteries use alkali hydroxide as the main electrolyte and zinc as the negative electrode active material. This battery has the disadvantage that the reaction surface of the negative electrode becomes inactive during rapid discharge or low-temperature discharge because diffusion disturbance occurs on the negative electrode surface due to reaction products. For this reason, a granular zinc negative electrode granulated by an atomization method or the like is used to increase the effective area of the negative electrode, thereby preventing the above-mentioned drawbacks.

Early zinc-alkaline batteries used granular zinc molded into pellets as the negative electrode.

This product has excellent workability in the manufacturing process because the negative electrode can be handled as a molded body when assembling the battery. However, because it is made into pellets, the amount of alkaline electrolyte present on the surface of the granular zinc is small, resulting in poor rapid discharge characteristics and low-temperature discharge characteristics.

An improved negative electrode is a gel negative electrode in which granular zinc is dispersed in a viscous gel alkaline electrolyte in which a sizing agent is dissolved. This negative electrode manufacturing method is called a gel method, and because granular zinc is dispersed, the rapid discharge characteristics and low-temperature discharge characteristics are greatly improved. However, it is extremely difficult to manage the filling amount of this negative electrode. That is, in a zinc-alkaline battery, the discharge capacity is usually dominated by a small number of active materials, and the precision with which the gelled negative electrode is incorporated into the cell has a large effect on the discharge characteristics of the battery. On the other hand, when filling a gelled negative electrode into the negative electrode container constituting the cell, the valve electrode is gelled -C, so there is a large error in the filling amount, and adjustment is difficult. In the case of micro-button cells, the filling amount is small, so the error is relatively large, making it extremely difficult to manage the filling amount.

For this reason, instead of the above-mentioned gel method, a new and different method for producing negative electrodes has come to be used, particularly in the center of micro button cells. This method is
This is called the CZ method, in which a thin coating layer containing glue as the main component is formed in advance on the surface of zinc 1'+'r r-.
This is a method in which a certain amount of these particles are filled into a negative electrode container, and then an alkaline electrolyte is injected and absorbed to form a gel. According to this method, 1.1,1. Charge child IT Jl'1%
Therefore, the variation in the negative electrode-filled bone can be reduced compared to the gel method in which gelled material is filled. However, this method has a problem in that the heavy load discharge characteristics of the battery are poor.

As a result of intensive research into the cause of this problem, the present inventors found that the gel structure of the negative electrode gel itself has a characteristic inhibiting factor. In other words, the glue layer covering the surface of the zinc particles spontaneously absorbs most of the injected alkaline electrolyte and swells incompletely, and the incompletely swollen glue layers on the surfaces of adjacent zinc particles disappear after a considerable period of time. are also incompatible. The border was observed microscopically. The gaps between each swollen particle are filled with a low-viscosity alkaline electrolyte in which a portion of the sizing agent is dissolved. In other words, the gel structure of the CZ type gel negative electrode is
As shown in Figure 1 (micrograph) and Figure 2 (schematic diagram), the adhesive surrounding the surface of the zinc particle a statically absorbs the alkaline electrolyte, resulting in incomplete swelling and relatively high temperature. The viscous part is the low viscosity part C where the electrolyte dissolves a part of the glue.
It has a heterogeneous gel structure consisting of. In this case, a kind of distribution ratio relationship is established between the electrolyte and the adhesive. The present inventor recognized that the highly viscous, incompletely swollen layer on the surface of the zinc particles constituting such a heterogeneous pseudo-gel serves as a diffusion inhibiting layer during rapid discharge. Note that e in the figure is a negative electrode current collector.

The present invention was made based on such knowledge, and is a zinc-alkaline battery that can improve the heavy load discharge characteristics of the battery even in the CZ system by bringing the zinc powder into contact with the low viscosity part. This is an advantageous method for producing a negative electrode.

That is, the present invention mixes negative electrode particles made of zinc or zinc alloy with glue powder to form a glue coating layer on the surface of the negative electrode particles, and then coats the negative electrode particles with no glue coating layer on the negative electrode particles. The method is characterized in that a mixed negative electrode particle group is formed by mixing, and then a certain amount of the same particle group is stored in a negative electrode container, and then an alkaline electrolyte is injected to form a liquid-absorbing and collapsing gel-like negative electrode.

Again/J? The content of negative electrode particles without a glue coating layer in the composite negative electrode particle group is 10 to 60% by weight, and the negative electrode will be explained.

First, negative electrode particles made of zinc or zinc alloy powder, a sizing agent, and, if necessary, a filler are mixed by stirring on their side. As negative electrode particles, zinc hydrate particles, group 1b, group 1b
Zinc alloy grains containing a small amount of one to several elements arbitrarily selected from the group of metallic elements belonging to Group 111b, Group 1b, Group Vb, such as Pb-Cd, Pb-G
Examples include zinc alloy grains containing a small amount of a, Pb-In or Pl)-○a-In, or low-icing products thereof, and those having a grain size of usually 0.05 to 0.25 mmφ (average grain size) are used. . In addition, as a sizing agent, synthetic polymers such as carboxyvinyl polymer, acrylic acid or its copolymer, fiber derivatives such as carboxymethyl cellulose,
Various glues having carboxyl groups or alkali metal salts thereof in their low-molecular side chains and having affinity with alkaline electrolytes can be used. Further, examples of the filler include magnesia, titanium white, aluminum silicate, and the like. In this case, no filler may be added.

These mixing ratios are the same as in the normal CZ method,
For example, for 1.00 parts by weight of negative electrode particles J'', 05 to 2 parts of glue
0 parts by weight and 03 to 15 parts by weight of filler.

By this stirring and mixing, a glue coating layer is formed on the surface of the negative electrode particles. After this, humidify and adjust the humidity. This humidification and humidity control step may be unnecessary depending on the type of adhesive.

The glue-coated negative electrode particles thus obtained and the negative electrode particles made of zinc or zinc alloy that are not coated with the glue are each weighed and mixed by stirring to obtain a mixed negative electrode particle group. The mixing ratio is 10 parts by weight per 100 parts by weight of the mixed negative electrode particles.
~60 parts by weight is preferred. This is because the heavy load discharge characteristics in this range are particularly excellent.

1-, 2'-゛-2-+shima〒Next, this mixed negative electrode particle group is weighed to a certain degree and stored in a negative electrode container. In this case, the mixed negative electrode particles can be measured by volumetric measurement or gravimetric measurement. Furthermore, if the entire negative electrode container containing the mixed negative electrode powder is weight-sorted again, it is possible to more strictly control the amount of negative electrode active material that is mixed into the battery.

A caustic electrolyte is injected and absorbed to form a gel-like negative electrode. In this case, if the liquid injection operation is performed under reduced pressure, liquid absorption gelation can proceed in a shorter time. As shown in FIG. 4 (schematic diagram), the gelled negative electrode obtained in this way is made up of an incompletely swollen material by the glue surrounding the surface of the negative electrode particles aI statically absorbing the alkaline electrolyte. It has a heterogeneous gel structure consisting of a high viscosity part and a low viscosity part C in which the electrolyte surrounding the surface of the negative electrode particle a2 partially dissolves the paste. Since the negative electrode particles a2 are in contact with the low-viscosity portion C in this way, this gel-like negative electrode has excellent heavy load characteristics.

The gelled negative electrode thus obtained is applied to batteries of various structures (button type, flat type, coin type, cylindrical type, etc.) using zinc as the negative electrode active material.

Next, examples of the present invention will be described.

Average particle size (1) I) ) 980 parts by weight of 160 μm 10-layered zinc grains,] 7 equal parts! After stirring and mixing 10 parts by weight of carboxyvinyl polymer of @3,000,000 and 1.0 parts by weight of fine powder magnesia, the mixture was heated at 60°C, R; IL
Humidify in a constant temperature and humidity chamber at 90% for 8 hours, then heat to 25°C.
, RoH.

Humidity was controlled for 16 hours in a constant humidity tank of 50 parts, and the glue-coated negative electrode particles were dried. The glue-coated negative electrode particles and the glue-coated layer; non-white negative electrode particles are shown in Table 1.
The mixtures were stirred and mixed at different ratios to obtain a negative electrode particle group (A) consisting only of mixers of five types of furnaces.

(10 margins) 1st Table Next, the amount of these negative electrode particle groups (A, -F) corresponding to the zinc content of 175 mA was weighed using an automatic weighing device and stored in the negative electrode container. Thereafter, 100 μl of a 35% potassium hydroxide solution saturated with zinc oxide was injected, and after 5 minutes, an SR44 type silver oxide button battery was assembled according to a conventional method.

The assembled battery was subjected to repeated pulse discharge of 22 μA for 3 seconds and a 27-second rest at 20°C. The average operation "Ogawa" at this time is shown in Figure 5, and the discharge utilization of the negative sand active material (fMJ lead) at that time is shown in Figure 6. Also, this battery cell is shown at 60'
Figure 7 shows the 1yt Kdl when 50 mA pulse discharge was performed after storage at /10FI at C.

As is clear from the results shown in Fig. 5, the average operating voltage during pulse discharge is 1'σ (1'σ) for the negative electrode without a glue coating layer.
It was found that the addition of Y improves the resistance of Al, and it becomes constant at an addition rate of 10 parts or more. Also, from Figure 6, the discharge utilization rate of the negative electrode active material is 1゛☆j
It was found that by adding 1rf, the temperature was improved and became constant at the addition rate of 50 or higher.

In addition, from FIG. 7, the capacity j, 1 (the holding weight is improved by adding negative electrodes 1 to 'rr7VY that do not have a glue coating layer, but it is recognized that the samurai is λ1 when the addition level is 70% or more I-).
is.

As mentioned above, according to the present invention, in the CZ, )) formula, a group of negative electrode particles that do not have a glue layer is added, so that the heavy load discharge characteristics of the curved lead-alkaline battery can be improved. Toward”
- It can produce remarkable effects.

4 Figure 1 is an enlarged micrograph of the gel negative electrode obtained by the conventional CZ method, Figure 2 is a schematic diagram of the same photograph, and Figures 3~
FIG. 7 shows an embodiment of the present invention, and FIG. The figure shows a characteristic diagram showing the relationship between the addition rate of MZ and the average operating voltage for the negative electrode without a glue coating layer. Figure 6 shows the relationship between the average operating voltage and the negative electrode without a glue coating layer. Figure 7 shows the relationship between the addition rate of (MZ) and the discharge utilization rate. It is a diagram showing the relationship between the addition rate of negative/elementary particle noi-Y (MZ) and the capacity layer (holding weight).

Patent applicant name Figure 1 (x56) Figure 2 Figure 3 r-”lZ isotropic σ cow 111.

Claims (2)

[Claims] (1) After mixing negative electrode particles made of zinc or zinc alloy with glue powder to form a glue coating layer on the surface of the negative electrode particles, negative electrode particles without a glue coating layer are mixed with the negative electrode particles. to form a mixed negative electrode particle group, and then the same particles F JrY
o) A method for producing a negative electrode for a zinc-alkaline battery, which comprises storing a certain amount in a negative electrode container, and then injecting and absorbing an alkaline electrolyte to form a gel-like negative electrode. (2) The method for producing a negative electrode for a zinc-alkaline battery according to claim 1, characterized in that the mixed negative electrode particles contain 10 to 60 negative electrode particles without a glue enveloping layer by weight. .