JP3146439B2 - Manufacturing method of battery electrode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a battery electrode in which a conductive core having a portion carrying an active material and a belt-like portion substantially not carrying an active material is pressed by a roll. It is about the method.

[0002]

2. Description of the Related Art There are various types of battery electrodes. Among them, a battery electrode formed by pressing a conductive core having a portion supporting an active material and a belt-shaped portion substantially not supporting an active material by a roll is a long electrode. Can be manufactured continuously and then cut into a desired size and assembled into a battery, which is excellent in mass productivity. Therefore, many kinds of battery electrodes are manufactured industrially by this means.

[0003] The belt-like portion which does not substantially carry the active material is
Since the conductive core is exposed, the conductive core is used for current collection when charging and discharging the electrode to form a chemical, and for attaching the current collector to the electrode when assembling a battery.

[0004] Specific examples of this electrode include the following. That is, for example, in a cadmium electrode of an alkaline storage battery, a paste is prepared by dispersing an active material powder such as cadmium hydroxide in a highly viscous aqueous solution of polyvinyl alcohol, and this paste is plated with a nickel-plated perforated steel sheet.
There is a method in which the conductive core is coated on a long conductive core made of nickel mesh, nickel expanded metal, etc., dried, and then the conductive core is run in the long direction and pressed with a roll. . In this method, when the paste is applied, an uncoated portion of the paste is formed in a strip shape along the longitudinal direction of the long conductive core.

[0005] In this manner, after pressing, the electrode plate is cut along the uncoated portion of the paste, and the electrode plate having the conductive core substantially not carrying the active material exposed at the end is obtained. can get. When the active material-uncoated portion is originally the end of the long electrode plate, the conductive core is exposed at the end without cutting.

[0006] If such a band-shaped uncoated portion of the active material is not provided in advance, not only a complicated operation of removing the active material layer from the pressed electrode plate but also a complicated operation is required. There is also a disadvantage that the removed active material is wasted.

As described above, the active material powder is made into a paste and applied to a long conductive core, a strip-shaped active material-uncoated portion is provided in the long direction, and the substrate is caused to travel in that direction. In addition to the above, a means for pressing is also employed for a zinc electrode for applying a paste containing zinc oxide to a perforated plate made of, for example, copper or silver, an expanded metal, or a net.

In addition, instead of the paste, a dispersion of a fluororesin powder that becomes fine fibers by kneading is used, and the active material powder is held in a matrix made of fluororesin fibers to form a sheet. Alternatively, there is a method in which a metal perforated plate, expanded metal, or a long substrate made of a net is adhered and supported. Also in this case, a strip-shaped unsupported portion of the active material is provided in the long direction of the long substrate, and the substrate is run in the long direction and pressed by a roll.

The above method comprises the steps of: storing a hydrogen absorbing alloy, zinc oxide,
Cadmium hydroxide, cadmium oxide, manganese oxide,
It is widely used when manufacturing a battery electrode using a powdered active material such as nickel hydroxide.

[0010]

As described above, a conductive core having a portion supporting an active material and a band-shaped portion substantially not supporting an active material is pressed by a pressing roll. In a conventional battery electrode manufacturing method, in which the longitudinal direction of the band-shaped portion that does not substantially carry the active material is arranged in a direction perpendicular to the rotation axis of the pressing roll, It has been found that the following inconvenience occurs when is set to a large value of several t / cm ² or more.

That is, when pressed with a roll, the amount of elongation of the electrode plate becomes uneven and the electrode plate bends, and the flatness of the electrode plate is impaired. It became difficult to remove, and the active material fell off easily.

Therefore, means for solving such inconvenience has been required.

[0013]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a conductive core having a portion for supporting an active material and a band-shaped portion which does not substantially support the active material. To
In the method for manufacturing a battery electrode in which pressure is applied by a pressing roll, the longitudinal direction of the band-shaped portion that does not substantially carry an active material is added without being arranged in a direction perpendicular to the rotation axis of the pressing roll. Provided is a method for manufacturing a battery electrode arranged in a direction parallel to a rotation axis of a pressure roll.

[0014]

In the conventional method for manufacturing a battery electrode, the following has been clarified as a result of examining the cause of the above-mentioned inconvenience particularly when the pressing force is increased.

That is, when a conductive core having a portion supporting an active material and a band-shaped portion substantially not supporting an active material is pressurized, most of the pressure is such that the active material is supported. Applied to the part. Then, as the pressing force is larger, the object to be pressed is deformed to extend in a direction parallel to the pressing surface.
Therefore, in the portion where the active material is supported, the amount of elongation of the electrode plate caused by pressurization is larger than in the portion where the active material is not substantially supported.

Further, when pressure is applied by a pressure roll,
The amount of elongation of the plate carrying the active material is large in the direction perpendicular to the rotation axis of the roll and small in the direction parallel to the rotation axis of the roll. It was found that the amount of elongation was anisotropic.

Incidentally, it was also found that such anisotropy in the amount of elongation of the electrode plate was not remarkable when pressed with a flat plate, but became remarkable when pressed with a roll. The cause of the influence of the pressing method on the anisotropy of elongation of the electrode plate is not clear, but the following may be considered.

That is, when pressing with a roll, the pressing surface is long in the direction parallel to the rotation axis of the roll and short in the direction perpendicular to the rotation axis of the roll. Then, when the electrode plate is deformed in a direction parallel to the pressing surface, a frictional force acts between the pressing surface of the roll and the electrode plate. As the length of the pressing surface increases, the total amount of deformation increases. Since it becomes large, the frictional force becomes large in the direction in which the length of the pressing surface is large, and the deformation of the electrode plate per unit length is suppressed. As a result, in the case of a flat plate press in which the anisotropy of the dimension of the pressing surface is small, the elongation of the electrode plate is suppressed and the anisotropy of the elongation is also suppressed. On the other hand, when pressing with a roll, the length of the pressing surface is extremely anisotropic, and in the direction perpendicular to the rotation axis of the roll, the length of the pressing surface is extremely short. This is difficult, and since the pressing surface is long in a direction parallel to the rotation axis of the roll, the elongation of the electrode plate is suppressed, and as a result, the anisotropy of the elongation of the electrode plate becomes remarkable.

Therefore, in the conventional method for manufacturing a battery electrode, the longitudinal direction of the belt-like portion that does not substantially carry the active material is arranged in a direction perpendicular to the rotation axis of the roll. Despite the fact that the part carrying the active material extends in the direction perpendicular to the axis of rotation of the roll, the elongation of the belt-like part that is substantially not carrying the active material and that is integral with this part carrying the active material Amount remains small. Such non-uniform elongation of the plates results in bending of the plates.

In the present invention, the anisotropy of the elongation of the active material application portion of the electrode plate in the roll press as described above,
By skillfully utilizing the relationship between the direction of the strip-shaped part with a small amount of elongation during pressing, when the conductive core having the strip-shaped part that does not substantially carry the active material is pressed with a roll In addition, the occurrence of bending of the electrode plate is suppressed.

That is, in the method of the present invention, the longitudinal direction of the strip-shaped portion that does not substantially carry the active material is not arranged in the direction perpendicular to the rotation axis of the roll. And there is substantially no portion. Therefore, even if the amount of elongation of the portion supporting the active material increases, the amount of elongation of the electrode plate in the direction perpendicular to the rotation axis of the roll does not become uneven.

Furthermore, according to the means of the present invention, the length of the band-like portion substantially not supporting the active material is set in the direction parallel to the rotation axis of the roll, where the amount of extension of the portion supporting the active material is reduced. Since the direction is arranged, the non-uniformity of the amount of extension of the electrode plate in this direction is also reduced.

After all, according to the means of the present invention, the non-uniformity of the amount of elongation of the electrode plate is small both in the direction parallel to the rotation axis of the roll and in the direction perpendicular to the rotation axis of the roll. Is suppressed.

[0024]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.

In this embodiment, a method of manufacturing a battery electrode in which a paste in which a hydrogen storage alloy powder is dispersed is applied to a punching metal, dried, and then pressed is described. [Battery Electrode (A) According to the Manufacturing Method of the Present Invention] The battery electrode (A) according to the manufacturing method of the present invention was manufactured as follows.

The hydrogen storage alloy is composed of an atomic ratio of LmNi
The constituent elements were melted in a vacuum in a high-frequency induction furnace in a metal state so as to obtain _3.8 Co _0.7 Al _0.5 , cast, and then pulverized. Here, Lm is a lanthanum-rich misch metal which is a mixture of rare earth metals containing about 90% by weight of La. 100 parts by weight of this alloy powder and 3 parts by weight of acetylene black as a conductive additive were dispersed in about 40 parts by weight of a 3 wt% aqueous solution of polyvinyl alcohol which functions as a thickener and a binder to form a paste.

This paste is applied to both sides of an iron punched metal hoop having a thickness of about 0.08 mm and a width of 140 mm, which is plated with nickel having a thickness of about 50 μm, and dried to form a plate. Made. In the paste application step, at both ends and the center of the punched metal, a band-shaped unpasted portion having a width of 10 mm and having a longitudinal direction corresponding to the longitudinal direction of the hoop, that is, an active material-unsupported portion (C) ) Was formed, and two strips of the paste-applied portion having a width of 55 mm, that is, the active material-supporting portion (B) were left. The amount of the hydrogen storage alloy carried per unit area of the paste applied portion is about 0.2 g / cm ² .

Next, the plate was pressed by a roll press. The pressure applied per 1 cm ² of the paste-coated portion of the electrode plate was about 5 t.

FIG. 1 is a schematic diagram showing a perspective view of a main part around the roll at the time of pressurization.

In FIG. 1, (A) shows two rolls used for pressing the electrode plate passed between them. (E) indicates the direction of roll rotation in this test. (D)
Is the direction of the axis of rotation of these two rolls. (B)
Are two strip-shaped active material carrying portions. (C) is a band-shaped active material-unsupported portion, the longitudinal direction of which corresponds to the longitudinal direction of the hoop of the punched metal. And the electrode plate was arrange | positioned so that the longitudinal direction of (B) might become parallel to the direction (D) of the rotation axis of a roll.

When the pressure roll (A) rotates and presses in this configuration, the electrode plate moves in the direction of arrow (F) with respect to the roll.

In order to press the long electrode plate in this configuration, the movement of the electrode plate in the longitudinal direction is stopped, and the pressing by the roll is performed from one end of the electrode plate to the other end. After that, the distance between the rolls is increased, the electrode plate is moved in the direction of the arrow (D) and the direction opposite to the arrow (F) to stop, and then pressurization by the rolls is performed again. It is good to repeat various operations. In addition, stop the movement of the electrode plate in the longitudinal direction, and after pressing by the roll from one end of the electrode plate to the other end, increase the distance between the rolls or The plate is allowed to escape from the gap between the rolls, and thereafter, the electrode plate is moved in the direction of arrow (D) and then stopped. Then, the roll is reversed, and the direction of movement of the electrode plate relative to the roll is opposite to that of arrow (F). By repeating such an intermittent operation, the long electrode plate can be pressed.

In these methods of pressing a long electrode plate with a roller, it goes without saying that the method can be realized by moving the pressing roller in the opposite direction instead of moving the electrode plate. [Battery electrode (a) according to the manufacturing method of the present invention] The battery electrode (a) according to the manufacturing method of the present invention was manufactured as follows.

A paste of the same composition as that used for the battery electrode (A) was coated with nickel plating having a thickness of about 50 μm and having a thickness of 0.08 mm and a width of 600 mm. This paste was applied to the plate and dried to produce a plate. In the paste application process,
A strip-shaped paste-uncoated portion, in which the length of the punched metal hoop is aligned with the direction perpendicular to the length of the punched metal hoop so that the width is 10 mm and the period is 65 mm, that is, the portion not carrying the active material (C '). Was formed. As a result, a strip-shaped paste-applied portion having a width of 55 mm and a period of 65 mm, that is, an active material-carrying portion (B ′) was formed. The amount of the hydrogen storage alloy carried in the paste-applied portion is about 0.2 g / cm ² as in the battery electrode (A).

Next, the plate was pressed by a roll press. The pressure applied to the active material-coated portion 1 cm ² of the electrode plate was about 5 t.

FIG. 2 is a schematic view showing a perspective view of a main part around the roll at the time of pressurization.

In FIG. 2, (A ') shows two rolls used for pressing the electrode plate passed between them. (E ') represents the direction of roll rotation in this test.
(D ') is the direction of the rotation axis of these two rolls. (B ′) is a belt-like active material-carrying portion.
(C ′) is a band-shaped active material non-supporting portion, and its longitudinal direction coincides with the direction perpendicular to the longitudinal direction of the hoop of the punched metal. The electrode plates were arranged such that the longitudinal direction of (C ′) was parallel to the direction (D ′) of the rotation axis of the roll.

When the pressure roll (A ') rotates and presses in this configuration, the electrode plate moves in the direction of the arrow (F') with respect to the roll.

In this configuration, the direction of travel of the electrode plate during pressurization coincides with the longitudinal direction of the punched metal hoop. Therefore, it is possible to manufacture a long electrode plate by continuously moving it while applying pressure. it can. [Battery electrode (c) by conventional manufacturing method] A battery electrode (c) by a conventional manufacturing method was manufactured as follows.

A paste having the same composition as that used for the battery electrode (A) is applied to the same punching metal as the battery electrode (A) in the same pattern and the same amount as the battery electrode (A). Then, after drying, the plate was pressed by a roll press. The pressure applied to 1 cm ² of the electrode plate is
It was about 5t.

FIG. 3 is a schematic view showing a perspective view of a main part around the roll at the time of pressurization.

In FIG. 3, (A ") shows two rolls used for pressing the electrode plate passed therebetween. (E") shows the direction of roll rotation in this test.
(D ″) is the direction of the rotation axis of these two rolls. (B ″) is the belt-like active material carrying portion.
(C ″) is a belt-shaped active material unsupported portion, the longitudinal direction of which coincides with the longitudinal direction of the hoop of the punched metal. The longitudinal direction of (C ″) is the rotation axis of the roll. The electrode plates were arranged to be perpendicular to the direction (D ").

When the pressure roll (A ") rotates and presses in this configuration, the electrode plate moves in the direction of the arrow (F") with respect to the roll.

In this configuration, the direction of travel of the electrode plate during pressurization coincides with the longitudinal direction of the punched metal hoop, so that the long electrode plate can be manufactured by continuously moving it while applying pressure. it can.

After the above-mentioned three electrode plates are pressed by a pressure roll, they are composed of three rows of active material-unsupported portions in a strip shape and two rows of active material-supported portions alternately arranged therewith,
The strip was cut so that the length of the unsupported portion of the active material became 60 cm. FIG. 4 is a perspective view of the external appearance of the cut battery electrodes (A) and (A). FIG. 5 is a perspective view of the appearance of the battery electrode (c).

In FIG. 4, (B ″ ′) is an active material-supporting portion of the battery electrodes (A) and (A) of the present invention,
(C ″ ′) is an active material-unsupported portion of these electrodes. In FIG. 5, (B ″ ″) is an active-material-supported portion of a conventional battery electrode (c). C "") is the active material-unsupported portion of these electrodes.The hydrogen-absorbing alloy carried amount of the active material-supported portion per volume of these three types of electrode plates is about 4.6 g / cm3. There was no significant difference due to the method of pressurization.

However, when these electrode plates were wound up on a bobbin, a remarkable difference occurred.

That is, as shown in FIG. 4, the battery electrodes (a) and (b) of the present invention hardly bend even after pressurization, and these electrode plates are wound around a bobbin having a diameter of 20 cm. At that time, it could be wound tightly and no active material was dropped.

On the other hand, in the conventional battery electrode (c), as can be seen from FIG. 5, the amount of elongation of the active material-carrying portion (B "") is smaller than that of the active material-carrying portion (C ""). Since it is significantly larger than the amount of elongation, the electrode plate is bent into a shape like a belly of a drum. With such a shape, the electrode plate has a state similar to a curl, so that the following inconvenience occurs when this long electrode plate is wound on a bobbin.

That is, when the concave surface of the electrode plate is on the inner side and the radius of curvature is smaller than the radius of curvature of the concave surface, the electrode plate can be easily wound. However, when the winding of the electrode plate is advanced and it is necessary to wind the electrode on a circumference having a large radius of curvature larger than the radius of curvature of such a bent electrode plate, it is necessary to move in the direction of the convex surface of the electrode plate. It becomes necessary to bend. As a result, the active material layer dropped off at the position of the bend. In addition, since the electrode plate is bent at the bent position, a gap is formed between the wound electrode plates. Therefore, the amount of the battery electrode (c) wound on one bobbin until the diameter becomes 2 m is determined by the amount of the battery. About 20% less than in the case of the electrodes (a) and (b).

In the above-described embodiment, the case where the hydrogen storage alloy powder is used as the active material, the punching metal is used as the conductive core, the active material paste is applied thereto, dried, and then pressed. However, the operation and effect of the present invention are not only achieved in the case of this embodiment. In addition to the hydrogen storage alloy powder, zinc oxide, cadmium hydroxide, cadmium oxide, manganese oxide, When using mainly nickel or the like, or when using an expanded metal, metal net, sintered metal fiber, etc. instead of punching metal as the conductive core, Instead of coating and drying the core, the same operation and effect as in the above embodiment can be obtained when the sheet-like material in which the active material powder is entangled and held by the fine fibrous fluororesin is pressure-bonded to the conductive core. To play. In addition, as the shape of the active material, not only the powder,
For example, even in the case of a non-porous continuous body such as a metal lithium sheet used for a negative electrode of a lithium battery, and a porous continuous body such as a sintered metal silver body used for a positive electrode of a silver oxide battery before formation, The same operation and effect as the embodiment can be obtained.

[0052]

According to the present invention, when a conductive core having a belt-like portion which does not substantially carry an active material is pressed by a roll, an effect is obtained that bending of an electrode plate is suppressed. .

[Brief description of the drawings]

FIG. 1 shows that a longitudinal direction of a belt-shaped portion that does not substantially carry an active material is arranged in a direction parallel to a rotation axis of a pressure roll without being arranged in a direction perpendicular to a rotation axis of the pressure roll. FIG. 4 is a schematic perspective view of the periphery of the pressure roll of the configuration of the present invention in which the direction of the axis of the pressure roll and the longitudinal direction of the long conductive core are matched.

FIG. 2 shows that a longitudinal direction of a belt-like portion that does not substantially carry an active material is arranged in a direction parallel to a rotation axis of a pressure roll without being arranged in a direction perpendicular to a rotation axis of the pressure roll. FIG. 3 is a schematic perspective view of the periphery of the pressure roll of the present invention in which the direction of the axis of the pressure roll is perpendicular to the longitudinal direction of the long conductive core.

FIG. 3 is a diagram illustrating a configuration in which a longitudinal direction of a belt-shaped portion that does not substantially support an active material is arranged in a direction perpendicular to a rotation axis of a pressing roll, and a direction of an axis of the pressing roll is elongated. FIG. 2 is a schematic perspective view of a conventional configuration around a pressure roll perpendicular to the longitudinal direction of a core.

FIG. 4 is a perspective external view of a battery electrode manufactured by the method of the present invention.

FIG. 5 is a perspective external view of a battery electrode manufactured by a conventional method.

[Explanation of symbols]

A, A ', A "Pressure rolls B, B', B", B "', B""Active material-carrying part C, C', C", C "', C"" D, D ', D "The direction of the axis of the pressure roll

Claims (1)

(57) [Claims] 1. A method for producing a battery electrode, comprising: pressing a conductive core having a portion supporting an active material and a belt-shaped portion substantially not supporting an active material by a pressing roll. The longitudinal direction of the strip-shaped portion that does not substantially support a substance is not disposed in a direction perpendicular to the rotation axis of the pressure roll, but is disposed in a direction parallel to the rotation axis of the pressure roll. A method for producing a battery electrode.