JPH09161785A - Electrode for storage battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the chemical efficiency and the discharged current utilization factor of an active material and the compatibility of the discharging capacity and life by using a current collector made of a solid bored body, and forming irregular sections on the surface of an active material layer in response to the undulations of the current collector. SOLUTION: A metal thin plate is inserted between rolls provided with projections and recesses in turn, tips of the projections of the rolls are protruded, and bored sections 3 are provided at the tip sections of the projections 2 of a current collector 1. Active material layers 5 are formed on both faces of the current collector 1, and active materials on both faces are connected through the bored sections 3. The recesses of the active material layer 5 corresponding to the recesses of the current collector 1 are formed, an electrolyte is diffused to the deepest recesses of the current collector 1, the active material near the recesses can be activated, and the active material at the surface portion left undercharged during discharging can be reduced. A large-capacity electrode is obtained while the quantity of the active material is decreased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode plate structure for a storage battery, and more particularly to providing an electrode plate structure for enhancing the conversion efficiency of lead acid batteries and the utilization rate of active materials in a large current discharge region.

[0002]

2. Description of the Related Art Increasing the utilization rate of active materials in the production of storage batteries regardless of whether they are lead storage batteries or alkaline storage batteries is an eternal task. In particular, the lead-acid battery has a low utilization factor, and its utilization factor in the large current discharge region is much lower than that of other battery systems.

Many efforts have been made for the purpose of improving the utilization rate. As a specific means therefor, an electrode plate using a three-dimensionally perforated current collector provided with minute perforations in a thin metal plate and processed three-dimensionally. The structure of is proposed.

In this structure, for example, a convex portion and a concave portion are formed on the surfaces of two rollers, and a corrugated apex formed by inserting a thin metal plate between them is pierced by the tip of the convex portion of the roller. 3D perforated body with fine holes formed by cutting or opening in a fixed shape, or by providing notches with a part left on a thin metal plate, and the notches are three-dimensionally formed in arbitrary shapes on both sides of the plate surface. A developed three-dimensional perforated body has been proposed. Since these have a large current-collecting area and the average distance from the current collector to the active material layer is shortened, a flat current collector surrounded by a thick grid, which has been generally used conventionally, is used. In this case, the utilization rate of the active material is improved to some extent as compared with the case of filling the large space with the active material. However, on the other hand, the diffusion path of the electrolytic solution from the current collector to the active material becomes substantially nonuniform in the thickness direction of the electrode plate,
Two problems arise with it.

The first problem is that after formation, a large amount of lead sulfate is likely to remain in the recessed portion corresponding to the undulations of the three-dimensional current collector, and the formation efficiency decreases. The second problem was that a large amount of unreacted active material was present in the portion where the thickness of the active material increased corresponding to the recesses in the undulating shape of the three-dimensional perforated body after the large current discharge. All of these were caused by the extremely insufficient diffusion of the electrolyte solution in relation to the shape of the three-dimensional structure, and the electrochemical reaction rate of this portion slowed down. It was a major obstacle to increasing the utilization rate of active materials.

Further, in an electrode plate using a strong binder such as fluororesin or carboxymethylcellulose for improving the life, the tendency of diffusion and alienation of the electrolytic solution is further promoted, and the utilization rate of the active material is increased. It has been an important issue to achieve both improvement and long life.

[0007]

The unevenness of the thickness of the active material layer caused by the uneven shape of the current collector of the three-dimensional perforated body results in non-uniform diffusion of the electrolytic solution, which causes the chemical conversion efficiency. Along with improving the problem that the discharge utilization rate of the active material is further reduced, it is possible to provide a means that is compatible with the improvement of the utilization rate even when applying a strong binder to improve the life characteristics. It is an object of the present invention.

[0008]

In order to solve the above-mentioned problems, the present invention uses a three-dimensional perforated body as a current collector of an electrode plate for a storage battery, and corresponds to the undulations of the current collector so that the surface of the active material layer is uneven. It is characterized in that it has an electrode plate structure in which parts are formed.

As a result, the diffusion distance of the electrolytic solution from the surface of the active material layer in the concave portion of the three-dimensional perforated body to the surface of the current collector is shortened, the efficiency of the chemical conversion reaction of the active material subject to diffusion is increased, and the diffusion rate is increased. In the current discharge, the active material that cannot contribute to the reaction can be reduced, and the discharge utilization rate of the active material can be increased.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION By adopting the above configuration,
It seems that the theoretical filling amount of the concave portion formed in the active material layer is lost at first glance, but the portion that cannot be formed is excluded,
Further, since it is possible to effectively discharge and effectively utilize the portion that has been difficult to discharge, the utilization rate is improved and the actual discharge capacity can be increased.

Further, when the active material material is kneaded and filled with a binder, these binders dissipate the diffusion of the electrolytic solution, so that the chemical conversion efficiency and the effective discharge amount are likely to decrease. However, by adopting the configuration of the present invention, the distance that requires diffusion of the electrolytic solution can be shortened, so that it is possible to reduce factors that hinder the electrolytic solution from being diffused by the binder. as a result,
Dispersion and emulsion of polytetrafluoroethylene (PTFE), polyxafluoropropylene (PHFP), or copolymers thereof, and a water repellent binder such as polyvinylidene fluoride dissolved in a solvent such as n-methylpyrididenone. Can be applied, the formation efficiency of the active material, the discharge utilization rate can be improved, and the active material can be prevented from falling off from the electrode plate.Therefore, by using this electrode plate, the discharge characteristics are excellent and the charge-discharge cycle life is improved. A long high performance battery can be obtained.

FIG. 1 is an example of an embodiment of the electrode plate of the present invention and is a diagram for explaining structural features. FIG. 2 shows the structure of a conventional electrode plate as compared with the present invention. In FIG.
Reference numeral 1 denotes a current collector of a three-dimensional perforated body. In (A), a thin metal plate is inserted between rolls provided with convex portions and concave portions alternately and the tip of the convex portion of the roll is projected to project the convex portion of the current collector. A perforated portion 3 is provided at the tip of the portion 2. Further, in (B), a large number of cutouts are provided in the thin plate, leaving a part thereof, and the cutouts are three-dimensionally raised on both sides of the thin plate to form a three-dimensional processed portion 4 and a perforated portion extending across both sides. It was done. In FIGS. 1A and 1B, 5 is an active material layer, which is formed on both sides of the current collector, and the active materials on both sides are connected through the perforations. Reference numeral 6 denotes a recess formed on the surface of the active material layer corresponding to the recess of the current collector. 7
Is a concave portion of the active material layer provided corresponding to the convex side of the perforated portion.

In the conventional structure shown in FIG. 2, reference numeral 8 denotes an inactive active material layer which is likely to be generated in the vicinity of the concave portion of the current collector and is a portion where the chemical conversion reaction is difficult to occur. Further, 9 is a surface layer of the active material layer corresponding to the concave portion of the current collector, which is a portion where the discharge reaction is difficult to proceed.

As is apparent from the comparison between FIG. 1 and FIG. 2, in the present invention, the electrolytic solution is diffused to the deepest current collector recess by forming the recess of the active material layer corresponding to the current collector recess. It is possible to activate even the active material in the vicinity thereof, and at the same time, it is possible to reduce the active material on the surface portion that remains undischarged during discharge. As a result, the active material filling amount is reduced, but as a result, a high capacity electrode plate is obtained.

[0015]

EXAMPLES In order to further clarify the effects of the present invention, various lead-acid battery electrode plates according to the present invention were produced, and the characteristics of lead-acid batteries constructed using these were investigated and compared with the conventional example. The current collector metal is a thin plate of lead-calcium-tin alloy having a thickness of 80 μm, and the positive electrode has a total thickness of 130.
The three-dimensional perforated body was processed to have a total thickness of 0 micron and 1000 micron for the negative electrode. Similar results were obtained when the structure of the electrode plate used either (A) or (B) of FIG. 1, but here, an example in which the structure of FIG. 1 (A) is used will be shown.
As an electrode plate of an example of the present invention, a positive electrode and a negative electrode were filled with lead powder, water, and a paste material, and a sulfuric acid-free slurry-like kneaded material containing carboxymethyl cellulose as a main component was filled and dried (sample P).
1), an electrode plate (sample Q1) filled with a slurry-like kneaded product obtained by kneading lead powder with an emulsion of polytetrafluoroethylene as a main component and drying, and lead powder and polyfluoride as a binder. Three types of electrode plates (Sample R1) were prepared by filling and drying a slurry-like kneaded product using an N-methylpyrididenone solution of vinylidene chloride. Theoretical filling amount is positive electrode 2500mAh
The negative electrode was 1500 mAh, and the electrode plate area was 50 cm 2. Note that the negative electrode material was added with negative electrode additives such as lignin and barium sulfate. Due to the shrinkage of the kneaded product filled in these both electrodes during drying, irregularities on the surface of the active material layer corresponding to the undulations of the current collector were formed.

For comparison with this, the kneaded product was applied and dried several times to prepare an electrode plate having a smooth active material surface and a structure shown in FIG. These electrode plates were produced using the above-mentioned three kinds of kneaded products, and were designated as (Sample P2), (Sample Q2), and (Sample R2), respectively. The theoretical filling amount of these plates is 3OOmA positive electrode
h, and the negative electrode was 1800 mAh.

These electrode plates were combined with one positive electrode and two negative electrodes via a glass mat to form a battery, which was formed in 37% by weight of dilute sulfuric acid and then discharged at a high current of 3 C and a maximum current of 1 C. A voltage of 2.45 V and charging for 1 hour were repeated to perform a charge / discharge cycle test. FIG. 3 shows the relationship between the initial capacity and the number of cycles until the discharge capacity decreases to ½ of the initial capacity in that case. As is clear from this figure, the initial capacity of each formulation is as shown in FIG.
2, sample Q2, sample R2), the battery using the electrode plate of the configuration of the present invention (sample P1, sample Q1, sample R1) of FIG. On the contrary, the discharge capacity was increased, and the effect of the present invention was remarkably confirmed especially in the battery using the electrode plates (Sample Q1 and Sample R1) filled with the kneaded material using the binder. When the cross sections of these electrode plates were confirmed by an X-ray profile after formation, a large amount of lead sulfate and lead oxide were confirmed at the portion 8 in FIG. 2 in the conventional example, and the progress of formation was alienated. After the initial discharge, a large amount of unreacted lead dioxide was confirmed in the area 9 in FIG.

From the above, it is understood that by using the electrode plate having the structure of the present invention, a storage battery having both discharge capacity and long life can be constructed.

[0019]

INDUSTRIAL APPLICABILITY As described above, the present invention uses a current collector having a three-dimensional perforated body, and by forming irregularities on the surface of the active material layer corresponding to the undulations of the current collector, the chemical conversion efficiency and the active material The discharge utilization factor is improved, the utilization factor is prevented from lowering when a strong binder is applied, and both discharge capacity and life can be achieved, and its industrial value is great.

[Brief description of the drawings]

FIG. 1A is a sectional view of an electrode plate showing an example of an embodiment of the present invention. FIG. 1B is a sectional view of an electrode plate showing an example of another embodiment of the present invention.

FIG. 2 is a sectional view of a conventional electrode plate.

FIG. 3 is a diagram showing a relationship between cycle life and initial capacity of various electrode plates.

[Explanation of symbols]

 1 Current collector of three-dimensional perforated body 2 Convex portion of three-dimensional perforated body 3 Perforated portion of three-dimensional perforated body 4 Three-dimensional processed portion 5 Active material layer 6 Recess formed on surface of active material layer 7 At tip of convex portion of perforated portion Concavity of formed active material 8 Inactive active material layer 9 Hard discharge active material layer

Claims (3)

[Claims] 1. An electrode plate for a storage battery, wherein the three-dimensional perforated body is used as a current collector, and the active material layer surface is provided with irregularities corresponding to the undulations of the three-dimensional perforated body. 2. The electrode plate for a storage battery according to claim 1, wherein the current collector is lead or a lead alloy, and the active material is lead or lead dioxide. 3. A binder is added to the active material.
Alternatively, the storage battery electrode plate according to claim 2.