JP2002100396A - Cylindrical alkaline secondary cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alkaline secondary cell which allows for controlling both an insulation failure and an internal short circuit in inserting a separator between a positive and negative electrode and winding them in a spiral. SOLUTION: The alkaline secondary cell is provided with electrodes group formed in a spiral by winding the positive electrode containing an electroconductive substrate of a three dimensional porous structure, and the negative electrode of a two dimensional porous structure through the separator, concerning to each electrodes of the positive electrode 2 and the negative electrode 4 respectively, the initial winding edges and the two surfaces with maximum area are covered by turnover of a double separator 3 so that the coverage of the doubled separator 3 at the surfaces with maximum area are no more than 20%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cylindrical alkaline secondary battery having an improved separator.

[0002]

2. Description of the Related Art As alkaline secondary batteries, nickel cadmium secondary batteries and nickel hydrogen secondary batteries are known. Due to the increasing demand for high-capacity batteries due to the recent spread of PCs (personal computers) and mobile phones, and environmental issues, nickel-metal hydride secondary batteries have become mainstream as alkaline secondary batteries. Nickel-metal hydride secondary batteries are generally known as batteries having a cylindrical structure and batteries having a rectangular structure.

[0003] Cylindrical nickel-metal hydride secondary batteries include, for example,
A positive electrode with a structure in which a paste containing nickel hydroxide is filled in a conductive substrate having a three-dimensional porous structure such as foam metal, and a two-dimensional porous structure such as punched metal in which a paste containing a hydrogen storage alloy is used An electrode group is formed by spirally winding a negative electrode having a structure filled in a conductive substrate with a separator (for example, composed mainly of a nonwoven fabric made of polyolefin) via a separator. It is manufactured by storing a group and an alkaline electrolyte in a metal can and closing the opening of the metal can.

[0004]

However, with the recent increase in capacity, the volume ratio of the electrode group in the metal can has increased, that is, the degree of tightness of the electrode group has increased, and as a result, the distance between the positive electrode and the negative electrode has decreased. As a result, insulation failure during manufacturing and internal short-circuiting during charging and discharging frequently occur.

That is, a conductive substrate having a three-dimensional porous structure is used as the conductive substrate of the positive electrode, and the active material filling density of the positive electrode is increased with the increase in the capacity of the secondary battery. When the flexibility of the positive electrode is greatly reduced and a spiral is wound with a separator between the positive electrode and the negative electrode,
The conductive substrate at the beginning of the winding of the positive electrode that is wound with a small radius of curvature is easily broken, and the occurrence rate of defective insulation in which the broken conductive substrate projects on the positive electrode surface and penetrates through the separator increases.

On the other hand, a negative electrode conductive substrate having a two-dimensional porous structure is used. For this reason, needle-like projections (burrs) formed by dividing the holes of the conductive substrate are present on the end face of the negative electrode. In cylindrical alkaline rechargeable batteries,
Since the positive electrode swells with the progress of the charge / discharge cycle, the distance between the positive electrode and the negative electrode, which is originally short, is further reduced in order to increase the capacity. Since the degree of swelling is greatest at the start of winding, the distance between the electrodes near the center of the electrode group is the smallest. As a result, many internal short-circuits in which the needle-like projections present on the end face of the start of winding of the negative electrode penetrate the separator and come into contact with the positive electrode occur during the charge / discharge cycle.

[0007] The present invention provides a cylindrical alkaline secondary battery in which both poor insulation and internal short circuit during a charge / discharge cycle are suppressed when spirally wound with a separator interposed between a positive electrode and a negative electrode. Is what you do.

[0008]

The cylindrical alkaline secondary battery according to the present invention comprises a separator including a positive electrode including a conductive substrate having a three-dimensional porous structure and a negative electrode including a conductive substrate having a two-dimensional porous structure. In a cylindrical alkaline secondary battery including an electrode group spirally wound through, for each of the positive electrode and the negative electrode, a double end is formed so that the end face at the beginning of winding straddles the two faces having the maximum area. It is characterized by being covered with a separator and having a double separator having a coverage of 20% or less on the surface having the maximum area.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of a cylindrical alkaline secondary battery according to the present invention will be described below with reference to FIGS.

FIG. 1 is a partially cutaway perspective view showing an example of a cylindrical alkaline secondary battery according to the present invention, FIG. 2 is a sectional view showing the vicinity of the center of the electrode group in FIG. 1, and FIG. 3 shows the positive electrode in FIG. FIG. 4 is a perspective view showing the negative electrode of FIG.

That is, an electrode group 5 produced by laminating the positive electrode 2, the separator 3, and the negative electrode 4 and spirally winding them is accommodated in the bottomed cylindrical metal container 1. . As shown in FIG. 3, the positive electrode 2 includes a conductive substrate having a three-dimensional porous structure, a current collector 6 formed of a band-shaped metal plate fixed to the conductive substrate, and a positive electrode 2 held by the conductive substrate. Active material-containing layer 7. The positive electrode 2
Has two surfaces 2b having the maximum area. The surface 2b having the maximum area is defined by the area of the length L ₁ of the short side of the positive electrode 2.
It means a surface obtained by the product of the length L ₂ of the long side and. On the other hand, the negative electrode 4 has a conductive substrate 8 having a two-dimensional porous structure and an active material-containing layer 9 held on the conductive substrate 8 as shown in FIG. The negative electrode 4 has two surfaces 4b having a maximum area. Surface 4 with largest area
b and has its area is meant a surface determined by the product of the length L ₄ of the length L ₃ and the long side of the short sides of the negative electrode 4.

The separator 3 has an end face 2a at the beginning of winding of the positive electrode 2 and two faces 2b having a maximum area.
A strip-shaped main separator 10 is provided to cover four portions of an end surface 4a at the beginning of winding of the negative electrode 4 and two surfaces 4b having a maximum area. However, the region constituting the outermost periphery of the electrode group in the surface 4 b of the negative electrode 4 having the maximum area is not covered with the main separator 10 because it needs to be electrically connected to the container 1. Band-shaped sub-separator 11
The main separator 10 has a winding end surface 2 a of the positive electrode 2, a winding start portion of the surface 2 b having the largest area, a winding end surface 4 a of the negative electrode 4 and a winding start surface 4 b having the largest area. The four parts are arranged in areas facing each other. The sub-separator 11 can be fixed to either the surface of the main separator 10 facing the positive electrode or the surface facing the negative electrode. In this case, the sub-separator 11 is fixed to the surface facing the negative electrode. By forming the separator 3 from the main separator 10 and the sub-separator 11, for each of the electrodes of the positive electrode 2 and the negative electrode 4, the end face at the beginning of winding straddles two surfaces having the maximum area with a double separator. Coated.

Two surfaces 2 having the maximum area of the positive electrode 2
b, It is preferable that the coverage of each surface with the double separator be 20% or less. However, the area covered by the double separator is the maximum width X of the facing region between the surface 2b having the maximum area and the double separator, and the length L of the short side of the positive electrode 2.
Calculated by multiplying by ₁ .

On the other hand, it is preferable that the coverage of the two surfaces 4b having the maximum area of the negative electrode 4 with the double separator on each surface be 20% or less. However, coverage of a double separator is calculated by the product of the surface 4b and the maximum width Y and the length L ₃ of the short sides of the negative electrode 4 in a region opposed to the double separator having a maximum area.

If the coverage of the positive electrode 2 with the double separator exceeds 20%, or if the coverage of the negative electrode 4 with the double separator exceeds 20%, the rate of decrease in discharge capacity when discharging at a high rate is obtained. May increase. The rate characteristics are improved as the coverage of the positive electrode 2 with the double separator and the coverage of the negative electrode 4 with the double separator are reduced, but the rate of occurrence of insulation failure during production and the rate of internal short circuit during use are improved. Therefore, it is more preferable that the coverage be 5 to 20%. A more preferred range is 7 to 12%. The coverage of the double separator in the positive electrode and the coverage of the double separator in the negative electrode may be the same or different from each other. The coverage of the double separator on one surface of the positive electrode may be the same as the coverage of the double separator on the other surface, or may be different from each other. The same applies to the negative electrode. In particular, for both the positive electrode and the negative electrode, the coverage of the double separator on one surface and the coverage of the double separator on the other surface are equal, and the coverage of the positive separator on the double separator and The sum of the coverage with the double separator of the negative electrode is 2
Most preferably, it is 0%. By adopting such a configuration, it is possible to realize an alkaline secondary battery having excellent rate characteristics and suppressing occurrence of insulation failure during manufacturing and internal short circuit during use.

Incidentally, the alkaline electrolyte is charged in the container 1
Housed within. A circular sealing plate 13 having a hole 12 in the center is arranged at the upper opening of the container 1.
The ring-shaped insulating gasket 14 is disposed between the peripheral edge of the sealing plate 13 and the inner surface of the upper opening of the container 1, and the sealing plate is attached to the container 1 by caulking to reduce the diameter of the upper opening inward. 13 is hermetically fixed via the gasket 14. One end of the positive electrode current collector 6 is
And the other end is connected to the lower surface of the sealing plate 13. A positive electrode terminal 15 having a hat shape is mounted on the sealing plate 13 so as to cover the hole 12. A rubber safety valve 16 is disposed in a space surrounded by the sealing plate 13 and the positive electrode terminal 15 so as to close the hole 12. Circular holding plate 1 made of insulating material with a hole in the center
Numeral 7 is arranged on the positive electrode terminal 15 so that the projection of the positive electrode terminal 15 projects from the hole of the holding plate 17. The outer tube 18 covers the periphery of the holding plate 17, the side surface of the container 1, and the periphery of the bottom of the container 1.

Next, the positive electrode, the negative electrode, the separator and the alkaline electrolyte will be described.

1) Positive Electrode This positive electrode has a structure in which a positive electrode material containing nickel hydroxide particles as an active material, a conductive material and a binder is carried on a conductive substrate having a three-dimensional porous structure.

As the nickel hydroxide particles, for example, a single nickel hydroxide particle or a nickel hydroxide particle in which a metal such as zinc, cobalt, bismuth, or copper is coprecipitated with metallic nickel can be used. In particular, the latter positive electrode containing nickel hydroxide particles can further improve the charging efficiency in a high-temperature state.

Examples of the conductive material include cobalt oxide such as metallic cobalt, cobalt trioxide (Co ₂ O ₃ ) and cobalt monoxide (CoO), and cobalt hydroxide (C
and cobalt hydroxide such as o (OH) ₂ ).

Examples of the binder include hydrophobic polymers such as polytetrafluoroethylene (PTFE), polyethylene, and styrene-butadiene rubber (SBR), carboxymethylcellulose (CMC), methylcellulose, and hydroxypropyl cymethylcellulose (HPM).
C), hydrophilic polymers such as sodium polyacrylate (SPA) and polyvinyl alcohol (PVA). As the binder, two or three or more selected from the above-mentioned polymers can be used. The polytetrafluoroethylene can be used in the form of a dispersion.

The conductive substrate having the three-dimensional porous structure includes, for example, a sponge formed of nickel, stainless steel, nickel-plated resin, or the like.
Examples thereof include those having a fibrous or felt-like porous structure.

The positive electrode is prepared, for example, by adding a conductive material to nickel hydroxide particles as an active material and kneading the paste with a binder and water to prepare a paste. This paste is used as a conductive substrate having a three-dimensional porous structure. , Dried, and then pressure molded.

2) Negative Electrode The negative electrode has a structure in which a negative electrode material containing a hydrogen storage alloy, a conductive material and a binder is filled in a conductive substrate having a two-dimensional porous structure.

As the hydrogen storage alloy, for example, La
Ni _5, MmNi ₅ (Mm is misch metal), LmN
i ₅ (Lm is a La-enriched misch metal), and a multi-element alloy in which a part of Ni of these alloys is substituted by at least Al and Mn. The above-described multi-element hydrogen storage alloy has Al and Mn as substitution elements for Ni.
In addition, at least one element selected from Co, Ti, Cu, Zn, Zr, Cr and B may be included.
Above all, the general formula _{LnNi w Co x Al y Mn z} ( However, Ln is a rare earth element, the atomic ratio w, x, y, z respectively 3.30 ≦ w ≦ 4.50,0.50 ≦ x ≦ 1.10 ,
0.20 ≦ y ≦ 0.50, 0.05 ≦ z ≦ 0.20,
And the total value is 4.90 ≦ w + x + y + z ≦ 5.50
Is preferably used.

As the conductive material, for example, carbon black, graphite and the like can be used.

As the binder, at least one selected from the same types as those described for the positive electrode can be used.

Examples of the conductive substrate having a two-dimensional porous structure include punched metal, expanded metal, wire mesh, and the like.

The negative electrode may be, for example, the following (1):
It can be manufactured by the method described in (2).

(1) A conductive material is added to the powder of the hydrogen storage alloy and kneaded together with a binder and water to prepare a paste. The paste is filled in a conductive substrate and dried.
It is manufactured by press molding.

(2) A conductive material and a binder are added to the powder of the hydrogen storage alloy, kneaded to form a sheet, and the obtained sheet is laminated on a conductive substrate.

As the negative electrode, a sintered hydrogen storage alloy negative electrode can be used in place of the paste-type hydrogen storage alloy negative electrode or the dry hydrogen storage alloy negative electrode described above.

3) Separator The main separator and the sub-separator constituting the separator are, for example, non-woven fabrics made of polyamide fiber, non-woven fabrics made of polyolefin fiber such as polyethylene and polypropylene, or those obtained by adding a hydrophilic functional group to these non-woven fabrics. Can be formed. As a method for providing a hydrophilic functional group, for example, graft polymerization of a vinyl monomer, corona discharge treatment, and plasma treatment can be employed.

It is preferable that the main separator and the sub-separator are fixed by, for example, ultrasonic fusion or heat fusion. As a fixing method, ultrasonic fusion is desirable.

The sub-separator may be fixed on the surface of the main separator facing the positive electrode, or may be fixed on the surface of the main separator facing the negative electrode. In particular, it is preferable to fix to the negative electrode side. When fixed to the negative electrode surface side, it is possible to prevent the sub-separator from peeling off from the separator when producing the spiral electrode group.

The average diameter of the fibers constituting the main separator is preferably 5 to 30 μm. A more preferred range is from 10 to 20 μm.

The thickness of the main separator is 0.1 to 0.5.
Preferably, it is 2 mm. A more preferred range is 0.
14 to 0.16 mm.

The basis weight of the main separator is 45-60.
g / m ² is preferred. A more preferred range is 5
0 to 55 g / m ² .

On the other hand, the average diameter of the fibers constituting the sub-separator is preferably 5 to 30 μm. A more preferred range is from 10 to 20 μm.

The thickness of the sub-separator is 0.05 to
Preferably, it is 0.15 mm. A more preferred range is 0.1 to 0.12 mm.

The basis weight of the sub-separator is 30 to 60.
g / m ² is preferred. A more preferred range is 4
0 to 45 g / m ² .

4) Alkaline Electrolyte As the alkaline electrolyte, for example, a mixed solution of sodium hydroxide (NaOH) and lithium hydroxide (LiOH),
A mixture of potassium hydroxide (KOH) and LiOH, KOH
And a mixed solution of LiOH and NaOH.

In the cylindrical alkaline secondary battery according to the present invention described above, the positive electrode including the conductive substrate having the three-dimensional porous structure and the negative electrode including the conductive substrate having the two-dimensional porous structure are swirled through the separator. It has an electrode group wound in a shape. For each of the positive electrode and the negative electrode, the end face at the beginning of winding is covered with a double separator so as to straddle the two surfaces having the maximum area, and the surface having the maximum area is a double separator on each surface. The coating rate is set to 20% or less.

According to such an alkaline secondary battery, when a separator is interposed between the positive electrode and the negative electrode and spirally wound to form an electrode group, the winding of the positive electrode wound with a small radius of curvature is performed. Although the conductive substrate at the beginning is broken and the broken conductive substrate is exposed on the positive electrode surface, the separator facing this part is doubled, so the conductive substrate exposed on the positive electrode surface passes through the separator. Can be prevented. As a result, the rate of occurrence of insulation failure when the electrode group is manufactured can be reduced.

In this alkaline secondary battery, when the positive electrode swells with the progress of the charge / discharge cycle, needle-like projections (burrs) present on the end surface of the negative electrode at the beginning of winding are opposed to the secondary protrusion. A heavy separator cannot be penetrated, and as a result, an internal short circuit during use can be suppressed.

Further, in both the positive electrode and the negative electrode, the coverage of the surface having the largest area with the double separator is 20%.
Because of the following, the internal resistance of the secondary battery can be suppressed low, and a decrease in discharge capacity when discharging at a high rate can be suppressed.

Therefore, according to the present invention, even when the capacity is increased, the excellent rate characteristics are maintained, and the insulation failure and the internal short circuit during use are suppressed when the spiral electrode group is manufactured. Therefore, a cylindrical alkaline secondary battery having high capacity, excellent rate characteristics, and long life can be realized.

In the alkaline secondary battery according to the present invention,
By setting the total of the coverage of the double separator on the surface having the maximum area of the positive electrode and the coverage of the double separator on the surface having the maximum area of the negative electrode to 20%, poor insulation and an internal short circuit occur. It is possible to minimize the increase in the internal resistance due to the doubling of the separator while suppressing the increase.

[0049]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

Example 1 <Preparation of Paste Type Positive Electrode> A mixed powder consisting of 90 parts by mass of nickel hydroxide powder and 10 parts by mass of cobalt monoxide powder was mixed with 0.25 parts by mass of carboxymethyl cellulose.
A paste was prepared by adding 0.25 parts by mass of sodium polyacrylate and 3.0 parts by mass of a dispersion of polytetrafluoroethylene (specific gravity 1.5, solid content 60% by weight) in terms of solid content and kneading. . Subsequently, the paste is filled in a nickel-plated fiber substrate as a conductive substrate having a three-dimensional porous structure, dried, rolled by roller pressing, and cut into 37.7 mm × 37.0 mm. A positive electrode was prepared.

<Preparation of Paste Type Negative Electrode> A commercially available lanthanum-enriched misch metal Lm and Ni, Co, Mn,
Al, LmNi _4.0 Co
_A hydrogen storage alloy having a composition of _0.4 Mn _0.3 Al _0.3 was produced. The hydrogen storage alloy is mechanically pulverized and
It was passed through a mesh sieve. Obtained hydrogen storage alloy 10
0.5 parts by mass of sodium polyacrylate, 0.125 parts by mass of carboxymethyl cellulose with respect to 0 parts by mass,
A paste was prepared by mixing 2.5 parts by mass of a dispersion of polytetrafluoroethylene (specific gravity 1.5, solid content 0.6% by weight) and 1.0 part by mass of carbon powder as a conductive material together with 50 parts by mass of water. Prepared. The obtained paste is applied to a punched metal, which is a conductive substrate having a two-dimensional porous structure, dried, roll-formed, and then 37.7.
A paste-type negative electrode was manufactured by cutting to a size of 5 mm × 59.0 mm.

<Preparation of Main Separator> A long fiber having a fiber diameter of 9 μm was formed from a polypropylene resin by a spun bond method, the basis weight was 50 g / m ² , and the thickness was 0.16.
mm nonwoven fabric was produced. Then, the first with a smooth surface
A roll and a second roll having a plurality of pinpoint-shaped irregularities formed on the surface thereof are arranged to face each other, and the rolls are rotated in opposite directions and heated to 130 ° C. Passed through the nonwoven. Next, after irradiating the non-woven fabric with ultraviolet rays, it is immersed in an aqueous solution of acrylic acid to remove excess acrylic acid, dried, and dried.
The main separator was obtained by cutting to 0.0 mm × 96.0 mm.

<Preparation of Secondary Separator> A long fiber having a fiber diameter of 9 μm was formed from a polypropylene resin by a spun bond method, the basis weight was 40 g / m ² , and the thickness was 0.12.
mm nonwoven fabric was produced. Then, the first with a smooth surface
A roll and a second roll having a plurality of pinpoint-shaped irregularities formed on the surface thereof are arranged to face each other, and the rolls are rotated in opposite directions and heated to 130 ° C. Passed through the nonwoven. Next, after irradiating the non-woven fabric with ultraviolet rays, it is immersed in an aqueous solution of acrylic acid to remove excess acrylic acid, dried, and dried.
A sub-separator was obtained by cutting to 0.0 mm × 100 mm.

<Fusion of Sub-Separator> A sub-separator was fusion-bonded by ultrasonic waves to the surface of the obtained main separator facing the negative electrode to obtain a partially doubled separator.

Next, the above-described double separator was interposed between the negative electrode and the positive electrode, and was spirally wound to produce an electrode group having the structure shown in FIG. 2 described above. That is, in the obtained electrode group, each of the electrodes of the positive electrode 2 and the negative electrode 4 was covered so that the end face at the beginning of winding straddled the two surfaces having the maximum area by the double separator. The coverage ratio of the two surfaces 2b having the maximum area of the positive electrode 2 and the double separator on each surface was 5%. On the other hand, the coverage of the two surfaces 4b having the maximum area of the negative electrode 4 and the double separator on each surface was 5%.

[0056] After receiving such an electrode group into a bottomed cylindrical shape metal container, containing an alkaline electrolyte consisting of lithium hydroxide of 7 mol / potassium hydroxide m ³ and 1 mol / m ^3, a sealing or the like As a result, an AAA-size cylindrical nickel-metal hydride secondary battery having the structure shown in FIG. 1 and having a nominal capacity of 550 mAh was assembled.

(Examples 2 to 6) The coverage of the positive electrode 2 with the double separator on the surface 2b having the maximum area and the coverage of the negative electrode 4 with the double separator on the surface 4b having the maximum area are as follows. A cylindrical nickel-metal hydride secondary battery was assembled in the same manner as in Example 1 except for the change as shown in Table 1.

(Comparative Example 1) Only two places, the end face at the beginning of winding of the positive electrode and the beginning of winding of the two faces having the largest area, were covered with the double separator, and the face having the largest area was covered with the duplex separator. A cylindrical nickel-metal hydride secondary battery was assembled in the same manner as in Example 1 except that the coverage was set to 20%.

(Comparative Example 2) Only two places, the end face at the winding start of the negative electrode and the winding start part of the two faces having the largest area, were covered with the double separator, and the face having the largest area was covered with the duplex separator. A cylindrical nickel-metal hydride secondary battery was assembled in the same manner as in Example 1 except that the coverage was set to 20%.

Comparative Example 3 The coverage of the positive electrode 2 with the double separator on the surface 2b having the maximum area and the coverage of the negative electrode 4 with the double separator on the surface 4b having the maximum area are shown in Table 1 below. A cylindrical nickel-metal hydride secondary battery was assembled in the same manner as in Example 1 except for the change as shown in FIG.

(Comparative Example 4) Only two places, the end face at the beginning of winding of the negative electrode and the beginning of winding of the two faces having the largest area, were covered with the double separator, and the face having the largest area was covered with the duplex separator. A cylindrical nickel-metal hydride secondary battery was assembled in the same manner as in Example 1 except that the coverage was 25%.

(Comparative Example 5) Only two places, the end face at the beginning of winding of the positive electrode and the beginning of winding of the two faces having the largest area, were covered with the double separator, and the face having the largest area was covered with the duplex separator. A cylindrical nickel-metal hydride secondary battery was assembled in the same manner as in Example 1 except that the coverage was 25%.

For the obtained secondary batteries of Examples 1 to 6 and Comparative Examples 1 to 5, 10,000 electrode groups were prepared,
A voltage of 400 V is applied to one in which each electrode group is housed in a container.
A resistance value of 0 MΩ was added for 0.1 msec, and a current-carrying one was determined to be insulation failure. The results are shown in Table 1 below.

Further, 10,000 secondary batteries of Examples 1 to 6 and Comparative Examples 1 to 5 were prepared at 25 ° C.
After charging 150% at 1.0 CmA, a 30-minute rest period is set, and a charge / discharge cycle of discharging at 1.0 CmA until the battery voltage reaches 1.0 V is repeated 100 times, and an internal short circuit occurs during the charge / discharge cycle. The numbers were measured and the results are shown in Table 1 below.

Further, the secondary batteries of Examples 1 to 6 and Comparative Examples 1 to 5 were charged 150% at 25 ° C. and 1.0 CmA, after which a 30-minute rest period was set and each rate (0.2
CmA, 1.0 CmA, 2.0 CmA, 3.0 CmA)
, The discharge capacity at the time of discharging until the battery voltage reaches 1.0 V is measured, and the discharge capacity at 1.0 CmA, 2.0 CmA and 3.0 CmA when the discharge capacity at 0.2 CmA is 100% is calculated. As shown in FIG.

[0066]

[Table 1]

As is clear from Table 1, the separator is doubled from the end of the positive electrode to the area having the largest area from the end face at the beginning of the winding, and from the end of the negative electrode to the area having the largest area from the end face to the beginning of the winding. In addition, the secondary batteries of Examples 1 to 6, in which the coverage of the surface with the largest area with the duplex separator is 20% or less, can reduce the number of insulation failures at the time of electrode group production, and can reduce the number of defects during the charge / discharge cycle. No occurrence of internal short circuit and 1C, 2
It can be seen that a decrease in discharge capacity when the discharge rate is increased to C and 3C can be suppressed.

On the other hand, it can be seen that the secondary batteries of Comparative Examples 1 and 5, in which only the vicinity of the winding start end face of the positive electrode is covered with the double separator, cause an internal short circuit during the charge / discharge cycle. Also, it can be seen that the secondary batteries of Comparative Examples 2 and 4, in which only the vicinity of the end face at the beginning of winding of the negative electrode is covered with the double separator, have a greater number of insulation failures during electrode group production than Examples 1 to 6. . Furthermore, it can be seen that the secondary battery of Comparative Example 3 in which the coverage of the surface with the largest area with the duplex separator exceeds 20% has a larger capacity reduction rate when the discharge rate is increased than in Examples 1 to 6. .

[0069]

As described above in detail, according to the present invention, poor insulation and an internal short circuit during a charge / discharge cycle during the production of a spiral electrode group are suppressed, and a cylindrical alkaline electrode having excellent rate characteristics and high capacity is provided. A secondary battery can be provided.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view showing an example of a cylindrical alkaline secondary battery according to the present invention.

FIG. 2 is a sectional view showing the vicinity of the center of the electrode group in FIG. 1;

FIG. 3 is a perspective view showing a positive electrode of FIG. 1;

FIG. 4 is a perspective view showing the negative electrode of FIG. 1;

FIG. 5 is a characteristic diagram showing a relationship between a discharge rate and a discharge capacity in the cylindrical nickel-metal hydride secondary batteries of Examples 1 to 6 and Comparative Examples 1 to 5.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Container, 2 ... Positive electrode, 2a ... End face of the start of winding of a positive electrode, 2b ... Surface having the largest area of a positive electrode, 3 ... Separator, 4 ... Negative electrode, 4a ... End face of the beginning of winding of a negative electrode, 4b ... Maximum area of the negative electrode 5 ... electrode group, 10 ... main separator, 11 ... sub separator.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H021 AA06 BB12 BB17 CC17 HH01 HH10 5H028 AA05 BB07 CC08 CC10 CC13 HH01

Claims (2)

[Claims] 1. A cylindrical alkali having an electrode group in which a positive electrode including a conductive substrate having a three-dimensional porous structure and a negative electrode including a conductive substrate having a two-dimensional porous structure are spirally wound via a separator. In the secondary battery, for each of the positive electrode and the negative electrode, an end face at the beginning of winding is covered with a double separator so as to straddle two surfaces having the maximum area, and a double separator on the surface having the maximum area A cylindrical alkaline rechargeable battery characterized in that the coverage ratio is 20% or less. 2. The sum of the coverage ratio of the double separator on the surface having the maximum area of the positive electrode and the coverage ratio of the double separator on the surface having the maximum area of the negative electrode is 20.
%. The cylindrical alkaline secondary battery according to claim 1, wherein