JPH11185765A - Base material used for electrode of nonaqueous electrolyte secondary battery, electrode for nonaqueous electrolyte secondary battery using the base material, and nonaqueous electrolyte secondary battery provided with the electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To heighten mechanical strength of base materials holding an electrode plate active material, to heighten strength of electrodes and a rate of utilization of the active material, and to improve a battery characteristic of a nonaqueous electrolyte secondary battery. SOLUTION: The bases are formed out of a metal sheet having a great number of holes, and mechanical strength of the base material is heightened by equally setting intervals between an arbitrary hole H among the holes and six adjacent holes L1, L2, L3, L4, L5, L6, then a rate of utilization of an active material of electrodes holding the active material on both surfaces and in the holes of the base materials is improved, thus a battery characteristic of the nonaqueous electrolyte secondary battery provided with the electrodes is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a base material used for an electrode of a non-aqueous electrolyte secondary battery, and a non-aqueous electrolyte solution in which a mixture containing an active material as a main material is applied to both surfaces of the base material. The present invention relates to an electrode plate for a secondary battery and a non-aqueous electrolyte secondary battery provided with the electrode plate.

[0002]

2. Description of the Related Art In recent years, with the development of electronic equipment, there has been a demand for the development of a secondary battery that is small, lightweight, has a high energy density, and can be repeatedly charged and discharged. As such a secondary battery, a lithium secondary battery using a lithium-containing composite oxide such as lithium cobalt oxide as a positive electrode active material and a carbon material as a negative electrode active material has been actively researched and developed. .

[0003] In particular, since this type of battery uses a non-aqueous electrolyte, from the viewpoint of current characteristics, the positive electrode plate and the negative electrode plate are made into sheet-shaped electrodes, and these sheet-shaped electrodes are used as separators. Many proposals have been made for a non-aqueous solution secondary battery provided with a group of electrode plates spirally wound through the electrode.

Generally, such a sheet-shaped electrode plate is formed by applying a mixture containing an active material to both surfaces of a base material as a current collector. In order to increase, it is necessary to apply this mixture thinly and uniformly, and to increase the number of windings of the electrode group, so that a thickener is added as a binder to the solvent, the active material and the conductive agent, A method of applying a mixture mixed in a paste form to a base material as a current collector is often used. When creating an electrode in this way,
It is not easy to apply the mixture paste containing the active material uniformly on the front and back surfaces of the base material at the same thickness, and the battery was assembled using electrodes in which the thickness of the mixture was not uniform. In this case, in a portion where the thickness of the mixture is large, there is an active material that does not contribute to the battery reaction, and there is a problem that the utilization rate of the active material is reduced.

In order to solve this problem, a plurality of holes are provided in a base material, a layer of a mixture containing an active material as a main material is provided on the surface of the base material, and sintering is performed in an inert gas. By doing
An electrode in which a mixture containing an active material is fixed to a base material (for example, see JP-A-8-250109), and an electrode in which a porous sheet of metal titanium fibers is used as a base material for a positive electrode (for example, JP-A-8-250109) JP-A-138681), an electrode using a metal porous sheet having a large number of small holes as a base material (for example, see JP-A-9-45334), and a three-dimensional mesh-like porous structure. An electrode plate using a porous metal body as a base material (for example, see JP-A-8-170126) has been proposed.

[0006]

In the sheet-shaped electrode of the conventional non-aqueous electrolyte secondary battery described above, a mixture containing an active material as a main material is held on a porous base material. Although it is effective to improve the utilization rate of the active material, when such a porous base material is used as a current collector, it depends on the pore diameter, pore ratio, arrangement state, and the like. The strength may be insufficient. Then, when an electrode plate is formed by applying a mixture mainly composed of an active material to such a porous base material, in a processing step thereof, or a step of winding the electrode plate to form an electrode plate group, Due to insufficient strength of the base material, there has been a problem that the electrode plate is broken and cannot be moved to the next step during electrode plate processing, or the electrode plate group cannot be formed. In addition, when the electrode is manufactured, there is a problem that the mechanical strength is weak, the utilization rate of the active material is reduced, and when assembled into a nonaqueous electrolyte secondary battery, the battery characteristics are poor.

[0007] Therefore, the present invention is to improve the utilization rate of the active material held on the base material as a current collector, and at the same time to improve the mechanical strength of the base material.

[0008]

In order to solve the above-mentioned problems, the present invention provides a method in which a base material that holds an electrode active material and functions as a current collector is formed of a porous metal sheet, Of the hole, the interval between the adjacent hole and the same interval,
Moreover, the holes are arranged in a staggered manner in the width direction.

When a tensile stress in the longitudinal direction is applied to the base material, the stress is applied in the staggered direction, so that the cutting force of the base material is reduced, and the mechanical strength of the base material is improved. When it is used for an electrode plate, it is not damaged when forming an electrode group, and when a non-aqueous electrolyte secondary battery is formed, it has excellent discharge characteristics and charge / discharge characteristics. It will be.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, the constructions described in the claims can be adopted as the embodiments. Hereinafter, the embodiments will be described in addition to the constructions and the operational effects. That is, the base material used for the electrode of the non-aqueous electrolyte secondary battery of the present invention is formed of a porous metal sheet having a large number of holes as described in claim 1, and any of the holes is adjacent to the porous metal sheet. The distance between all the holes is equal, and the holes can be arranged in a staggered manner in the width direction and can be implemented.

[0011] By arranging the holes in this manner, the tensile strength can be improved.

Further, the electrode for a non-aqueous electrolyte secondary battery of the present invention has a large number of holes as described in claim 4, and the distance between any one of the holes and all the holes adjacent thereto is set to be large. The present invention can be realized by holding the active material on both sides of the porous substrate in which the holes are arranged in a staggered manner in the width direction and inside the holes.

[0013] Since a predetermined amount of the active material is held on both surfaces of the base material at a predetermined thickness, and the inside of the hole is sufficiently filled and held, the mechanical strength is improved and the active material is improved. Material utilization can be improved.

Further, the non-aqueous electrolyte secondary battery of the present invention
8. A porosity in which at least one of the positive electrode plate and the negative electrode plate has an equal interval between an arbitrary hole and all adjacent holes and the holes are arranged in a staggered manner in the width direction. It can be realized by forming an electrode plate having an active material held on both sides of the base material and inside the holes.

By improving the utilization rate of the active material while maintaining the mechanical strength of the electrode plate, battery characteristics such as battery capacity and charge / discharge cycle life can be improved.

In any of the above-described embodiments, to improve the mechanical strength of the base material itself and the movement of active material ions through the pores, etc.
As described in 6, 8, or 9, it is preferable that the diameter of the hole is φ1.0 mm or less and the opening ratio is 35% or less.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a schematic diagram illustrating the arrangement of holes in a substrate used for an electrode of a non-aqueous electrolyte secondary battery of the present invention.
FIG. 2 is a schematic view showing an arrangement state of the holes of the base material (A) and an arrangement state of the holes of the base material of the comparative example (B). FIG. 3 is a diagram of the present invention provided with an electrode using the base material. FIG. 4 is a vertical sectional view of the non-aqueous electrolyte secondary battery, FIG. 4 is a discharge characteristic diagram of the non-aqueous electrolyte secondary battery at a low temperature, and FIG. 5 is a charge / discharge cycle characteristic diagram of the non-aqueous electrolyte secondary battery. .

In FIG. 1, an arbitrary hole provided in the base material is H
In this case, holes H1, H2, H3, H
4, H5, H6, and six holes H1, H2, H3, H4, H
L1, L2, L3, L4, L5, L6
Are arranged at equal intervals, and at the same time, the arrangement of the holes in the width direction of the base material is arranged in a staggered manner in the width direction as shown by a broken line a. In addition, from the viewpoint of mechanical strength, six holes H1, H2, H3, H4, H5, H
6 are also equal to the intervals between the holes H, are arranged so as to form an equilateral triangle with the holes H, and have six holes H1, H
2, H3, H4, H5, and H6 are preferably located at the vertices of a regular hexagon.

The shape of the hole H provided on the substrate is described as being circular, but is not limited to this. The hole H can be formed in any shape. A circle is preferred from the viewpoint of strength.

A base material having the above-described arrangement of holes is used as a current collector, and a base material whose pore size and porosity are changed as shown in Table 1 is used. Table 1 also shows the results of investigating the situation where the positive electrode plates were cut by applying a paste-like mixture containing the same and applying heat treatment to these positive electrode plates and then rolling them.

As the base material, an aluminum foil having a thickness of 20 μm was used. The criteria were as follows: ○: when the positive electrode plate was rolled, no cut of the electrode plate was visually observed; The case where cutting occurred was evaluated as x. In addition, as a mixture for producing a positive electrode plate, a carbon powder as a conductive agent and a dispersion of polytetrafluoroethylene resin as a binder are mixed as an active material, and carboxy as a thickener is further mixed. A mixture prepared by mixing a methylcellulose aqueous solution into a paste is used, and the mixture is also filled in the pores of the base material.

[0023]

[Table 1]

As is clear from Table 1, the hole diameter is φ1.0.
mm or less, and a base material having a porosity of 35% or less also has a tensile strength of 147 gf / mm or more from the viewpoint of mechanical strength, which indicates that it is preferable as a base material used as a current collector in an electrode plate.

Next, for comparison, a base material having a judgment result of "o" in Table 1, that is, a base material in which holes are arranged in a staggered manner in the width direction (see FIG. 2A), for comparison. In the same manner as in Table 1, these substrates were used in the same manner as in Table 1 by using a substrate having the same hole diameter and opening ratio, and using a substrate in which holes were arranged in a line in the width direction (see FIG. 2B). The substance was applied to both sides of the base material and filled into the holes to prepare a positive electrode plate. After heat treatment of the positive electrode plate, the positive electrode plate was rolled and cut into a positive electrode plate having a predetermined size. The positive electrode plate and the normal negative electrode plate were spirally wound with a separator interposed therebetween to form an electrode plate group.
As shown in FIG.

[0026]

[Table 2]

As is evident from Table 2, by arranging the holes in a zigzag manner in the width direction, it becomes difficult to cut the electrode plates when forming the electrode plate group.
This is because when the holes are arranged in a zigzag pattern in the width direction (see FIG. 2A), when a tensile stress is applied in the longitudinal direction of the base material when forming the electrode plate group, the broken line a When a zigzag-shaped force is applied in the direction indicated by, the holes are arranged in a line in the width direction (see FIG. 2 (B)), and a linear force is applied in the direction indicated by the broken line b. It is considered that the electrode plate is easily cut.

Next, as described above, a base material in which holes are arranged in a staggered manner in the width direction (see FIGS. 1 and 2A).
A cylindrical non-aqueous electrolyte secondary battery provided with an electrode plate manufactured using the method will be described with reference to FIG. The mixture used for the positive electrode plate 1 is obtained by mixing a carbon powder as a conductive agent and a dispersion of polytetrafluoroethylene resin as a binder into an active material, and further adding an aqueous solution of carboxymethyl cellulose as a thickener. It is kneaded and adjusted to a paste.
This mixture is applied to the surface of a substrate having holes made of a metal foil, for example, an aluminum foil, and the inside of the holes is filled with the mixture and dried, then heat-treated at 300 ° C. for 3 minutes, and then rolled. Then, the sheet is cut into a predetermined size, and a positive electrode lead 2 is spot-welded to a base material as a current collector to form a positive electrode plate 1.

In the case of the negative electrode plate 3, similarly to the case of the positive electrode plate 1, an active material, a water-soluble dispersion of synthetic rubber (SBR) as a binder, and an aqueous solution of carboxymethyl cellulose as a thickener are used. And kneading the mixture to prepare a paste-like mixture, apply the paste-like mixture to the surface of a substrate having holes made of metal foil, for example, copper foil, and apply the mixture also inside the holes. After filling and drying, it is rolled into a sheet, cut, and spot-welded with the negative electrode lead 4 to a base material as a current collector.

A separator 5 made of polyethylene is disposed between the positive electrode plate 1 and the negative electrode plate 3, and a group of electrode plates formed by spirally winding is inserted into the battery case 6, and an appropriate amount of electrolyte After that, the open end of the battery case 6 was sealed with a sealing plate 8 via a gasket 7 made of polypropylene to obtain a completed battery.

As the base material used for the positive electrode plate 1 and the negative electrode plate 3, the base material of base material No. 3 in Table 1, that is, holes having a diameter of 0.3 mm and an opening ratio of 17.0% were staggered in the width direction. Substrates arranged in a hanging pattern are used. As the electrolyte, a solution prepared by dissolving 1.5 mol of lithium hexafluorophosphate in a mixed solvent of ethylene carbonate, diethyl carbonate, and methyl propionate is used.

Since the completed battery is in a discharged state immediately after trial production, the battery is charged and a characteristic test is started.

As a comparative example, a positive electrode plate and a negative electrode plate were formed by using a substrate having no holes, and a completed battery was fabricated under the same conditions to obtain a comparative example battery II.

Here, Example Battery I and Comparative Example Battery I
FIG. 4 shows the results of testing the discharge characteristics of the battery I at an ambient temperature of −10 ° C. and a discharge condition of 1.0 C. As is clear from FIG. It can be seen that the initial voltage is high and the discharge capacity is excellent.

The battery of Example I and the battery of Comparative Example II
The results of testing the charge and discharge characteristics at room temperature
As shown in FIG. 5, as is clear from FIG. 5, in the case of the battery of Example I, the utilization rate of the active material is increased, and the capacity decrease due to the charge / discharge cycle is reduced.

In the above embodiment, the hole diameter φ0.
Although the battery characteristics in the case of an electrode plate formed using a substrate having a hole having a hole diameter of 3 mm and an opening ratio of 17.0% are shown, the hole diameter and the opening ratio of the substrate are not limited thereto. The same effect can be obtained if an electrode plate is formed using a base material in which an arbitrary hole and an adjacent hole have the same distance between all the holes and the holes are arranged in a staggered manner in the width direction. Further, it is effective that the hole diameter is φ1.0 mm or less and the hole opening ratio is 35% or less.

[0037]

According to the present invention, a metal sheet having a large number of holes is used as a base material as a current collector, and the distance between any of the holes and all holes adjacent to the holes is equal. ,And,
By arranging these holes in a zigzag manner in the width direction, it has a mechanical strength that does not cut even when processing the electrode plate, and can also improve the utilization rate of the active material,
Further, a non-aqueous electrolyte secondary battery excellent in battery characteristics such as battery capacity and charge / discharge cycle characteristics can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an arrangement state of holes in a base material used for an electrode of a nonaqueous electrolyte secondary battery in an example of the present invention.

FIG. 2A is a schematic diagram showing an arrangement state of holes in the base material, and FIG. 2B is a schematic diagram showing an arrangement state of holes in the base material of Comparative Example.

FIG. 3 is a longitudinal sectional view of a nonaqueous electrolyte secondary battery in an embodiment of the present invention provided with an electrode using the same substrate.

FIG. 4 is a discharge characteristic diagram of the nonaqueous electrolyte secondary battery at a low temperature.

FIG. 5 is a charge / discharge cycle characteristic diagram of the nonaqueous electrolyte secondary battery.

[Explanation of symbols]

 1 Positive electrode plate 3 Negative electrode plate H, H1, H2, H3, H4, H5, H6 holes L1, L2, L3, L4, L5, L6 Distance between holes

Claims (9)

[Claims] 1. A space formed by a porous metal sheet having a large number of holes, the distance between an arbitrary hole and all holes adjacent thereto is equal, and the holes are arranged in a staggered manner in the width direction. Substrate used for the electrode of the prepared non-aqueous electrolyte secondary battery. 2. The base material used for an electrode of a non-aqueous electrolyte secondary battery according to claim 1, wherein the diameter of the hole is φ1.0 mm or less. 3. The base material used for an electrode of a non-aqueous electrolyte secondary battery according to claim 1, wherein the porosity is 35% or less. 4. Both surfaces of a porous base material having a large number of holes, the distance between any of the holes and all the holes adjacent thereto is equal, and the holes are arranged in a staggered manner in the width direction. And an electrode for a non-aqueous electrolyte secondary battery in which an active material is held inside the hole. 5. The electrode for a non-aqueous electrolyte secondary battery according to claim 4, wherein a porous substrate having a hole diameter of 1.0 mm or less is used. 6. The electrode for a non-aqueous electrolyte secondary battery according to claim 4, wherein a porous substrate having a porosity of 35% or less is used. 7. A porous substrate in which at least one of a positive electrode plate and a negative electrode plate has an equal distance between an arbitrary hole and all adjacent holes, and the holes are arranged in a staggered manner in the width direction. A non-aqueous electrolyte secondary battery in which an active material is held on both sides of a material and inside the hole. 8. The non-aqueous electrolyte secondary battery according to claim 7, wherein the electrode plate is made of a porous substrate having a pore diameter of φ1.0 mm or less. 9. The non-aqueous electrolyte secondary battery according to claim 7, wherein the electrode plate is made of a porous substrate having a porosity of 35% or less.