JP2002367607A - Non-sintered electrode for alkali storage battery, and alkali storage battery using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an non-sintered electrode for an alkali storage battery from which, activator does not fall off, with excellent productivity and low production cost, with long life, suitable for large current charging, and to provide an alkali storage battery using the above electrode. SOLUTION: A boundary part 4 between an activator painted part 2 and an exposed part 3 to which, activator is not painted, is coated by a coating material 5 made by resin and the like. By the above, the generation of short circuit, caused by the fall-off of activator adjacent to the exposed part, is prevented, and the alkali storage battery with long life and low cost, suitable for large current discharging, can be provided with a good yield.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-sintered electrode for an alkaline storage battery formed by filling a porous metal substrate with an active material, and an alkaline storage battery using the same.

[0002]

2. Description of the Related Art As shown in FIG. 2 according to the present invention, an alkaline storage battery generally used for a portable power supply or the like has a sheet-like positive electrode 10 and a negative electrode 11 in a spiral shape with a separator 12 interposed therebetween. In which a wound body electrode group formed by winding the above is used as an electrode body. In this type of alkaline storage battery, a part of the upper and lower ends of the wound body electrode group is connected to the current collecting terminals 23 and 24 to extract current. For example, in an alkaline storage battery used for a power tool, 10
A or more, and sometimes a large current of about 50 A is used, so that its internal resistance needs to be reduced.

Therefore, in Ni-Cd batteries and the like, in order to reduce the internal resistance, the current collecting terminals 23 and 23 are provided at predetermined ends of the positive electrode 10 and the negative electrode 11 constituting the wound electrode group.
24 is welded at five or more points. This is because the resistance of each part of the electrode becomes relatively uniform by providing a large number of current extraction sites in the winding direction of the electrodes 10 and 11. The negative electrode of this Ni-Cd battery or nickel-metal hydride storage battery is produced by applying a paste containing an active material and a binder resin to a metal plate or a metal foil such as a punching metal as a base material.

[0004] Fig. 3 shows a joint of a negative electrode of a conventional Ni-Cd battery or nickel-metal hydride battery with a current collecting terminal. There, a negative electrode mixture-containing paste containing a negative electrode active material and a binder resin is applied on both surfaces of a base material 1 such as a metal plate or a metal foil, except for at least the lower end thereof, to form a negative electrode mixture layer 2. Has formed. The reason why the base material 1 is exposed at the lower end portion without forming the negative electrode mixture layer 2 to form the exposed portion 3 is to prevent generation of a spark when the current collecting terminal 24 is welded. The formation of the exposed portion 3 is performed by first applying a negative electrode mixture-containing paste to the entire surface of the substrate 1 to form the negative electrode mixture layer 2, and then removing the negative electrode mixture layer 2 at the lower end of the substrate 1. Done by The removal of the negative electrode mixture layer 2 is performed by a method such as rubbing off the negative electrode mixture-containing paste with a brush or scraping off the negative electrode mixture-containing paste with a metal blade.

[0005]

When the negative electrode mixture layer 2 is removed by the above-described method, a large force is physically applied to the negative electrode mixture layer 2 adjacent to the exposed portion 3. The adhesive strength between the negative electrode mixture layer 2 and the substrate 1 is reduced, and a part of the negative electrode mixture layer 2 is likely to fall off. When the negative electrode mixture layer 2, that is, the active material falls off, the dropped active material penetrates through the separator (see FIG. 2) in the battery and causes a short circuit of the battery.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has no loss of active material, is excellent in manufacturing cost and productivity, has a long life, and is suitable for non-sintering of alkaline storage batteries suitable for large current charging and discharging. An object of the present invention is to provide a combined electrode and an alkaline storage battery using the electrode.

[0007]

Means for Solving the Problems The present inventors have found that the above problems can be solved by coating the negative electrode mixture layer portion adjacent to the exposed portion with a resin, and have accomplished the present invention.

That is, according to the present invention, as shown in FIG. 1, an active material application section 2 on which an active material is applied is provided on at least one surface of a metal plate or a metal foil serving as a base material 1. The non-sintered electrode 11 for an alkaline storage battery in which the exposed portion 3 not formed is formed. The boundary portion 4 between the active material application portion 2 and the exposed portion 3 has a melting point of 5
It is characterized by being coated with a resin at 0 to 160 ° C.

If the boundary portion 4 between the active material application portion 2 and the exposed portion 3 is coated with the resin coating material 5 as described above, the adhesiveness between the active material application portion 2 and the base material 1 is improved. It is possible to prevent a short circuit due to the fall of the active material adjacent to the portion 3. The reason why the melting point of the resin as the coating material 5 is set to 50 ° C. or higher and 160 ° C. or lower is that if the temperature is lower than 50 ° C., the resin may be eluted during use of the battery. It depends on the fear.

The resin is a thermoplastic resin having alkali resistance, such as a polyolefin resin or a polyamide resin. The point is alkali resistance,
Any resin having a melting point in the range of 50 to 160 ° C may be used.

In addition, as shown in FIG. 2, the present invention provides a spirally wound electrode body in which positive and negative electrodes 10 and 11 are spirally wound via a separator 12 together with an electrolyte 13 and a battery case 14.
It is intended for alkaline storage batteries housed inside. There, the upper end of the positive electrode 10 of the spiral electrode body is welded to a positive current collecting terminal 23, and the lower end of the negative electrode 11 of the spiral electrode body is welded to a negative current collecting terminal 24. ing. Then, at least one of the positive electrode 10 and the negative electrode 11 is a non-sintered electrode for an alkaline storage battery according to any one of the above claims.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION When an active material is applied over the entire width (vertical direction) of a base material (ie, when a mixture layer is formed), a current collecting terminal and an electrode are welded. There is a possibility that a spark will be generated when performing the operation. Therefore, FIG.
As shown in (1), it is necessary to form an exposed portion 3 in which the active material is not applied and the substrate 1 itself is exposed at the widthwise end of the electrode 11. In the present invention, the boundary 4 between the active material application portion 2 formed by applying the active material and the exposed portion 3 from which the active material has been removed,
It is characterized by being coated with a coating material 5 made of a resin having a melting point of 50 to 160 ° C.

If the melting point is less than 50 ° C., the battery may be eluted during use of the battery, and the effects of the present invention cannot be expected. 1
If the temperature exceeds 60 ° C., the active material may be decomposed or oxidized when coated. Further, the ambient temperature may be set to 70 ° C. depending on the formation conditions of the battery, so that the melting point of the coating material is preferably 70 ° C. or higher. In order to completely prevent denaturation such as oxidation of the battery active material, the temperature is preferably 120 ° C. or lower.

When a resin is used as the coating material, for example, a polyolefin resin, a polyamide resin or the like can be used.

As shown in FIG. 1, the coating material 5 covers the active material coated portion 2 adjacent to the exposed portion 3 by 1 mm or more.
It is desirable to apply so as to cover with a width of not more than mm. This is because when the width is less than 1 mm, the entire active material that is easily dropped cannot be coated. When the width exceeds 2 mm, the area covering the active material increases, and the applied coating material 5 inhibits the battery reaction. This leads to a reduction in battery capacity and life. Also, the coating material 5 was not applied within 0.5 mm of the end in the electrode width direction (vertical direction in FIG. 1). This is because, when the coating material 5 is applied to the end in the electrode width direction, when the wound electrode group is formed and the current collecting terminal 24 (see FIG. 2) is welded, the contact resistance is increased by the applied coating material. Is increased, sparks are generated, the separator is dissolved, and a short circuit is likely to occur.

<< Structure of Alkaline Storage Battery >> The present invention is applied to, for example, a secondary battery as shown in FIG. The secondary battery includes a cylindrical battery case 14 having an open upper surface, positive and negative electrodes 10 and 11 loaded in the battery case 14, and a sealing structure for sealing the opening of the battery case 1. . The positive electrode 10 and the negative electrode 11 are housed in a battery case 14 together with an electrolyte 13 as an electrode body having a spirally wound structure wound spirally via a separator 12. In this battery, a nickel hydroxide positive electrode is used as the positive electrode 10,
As the negative electrode 11, a non-sintered electrode for an alkaline storage battery according to the present invention as shown in FIG. 1 which is spirally wound is used. In addition, it is of course possible to apply the non-sintered electrode for an alkaline storage battery according to the present invention to both the positive and negative electrodes 10 and 11.

The sealing structure includes a terminal plate 19 exposed on the outer surface.
And a sealing plate 16 below the terminal plate 19 and having a gas passage 25 in the center, and an annular gasket 21 covering the peripheral edges of the sealing plate 16 and the terminal plate 19. At the end of the battery case, a groove 20 is formed, which is recessed one step. The annular gasket 21 is narrowed by tightening the portion ahead of the groove 20 inward. The terminal plate 19 is made of rolled steel, nickel-plated on the surface, has a hat-shaped cross section with a peripheral edge formed in a flange shape, and has slits 19a formed at two locations on the peripheral surface. The sealing plate 16 is made of rolled steel whose surface is plated with nickel, and the annular gasket 21 is made of nylon. Reference numeral 26 denotes an insulator provided between the sealing plate 16 and the spiral electrode body.

Between the terminal plate 19 and the sealing plate 16, a rubber valve body 18 that seals the gas passage 25 is arranged. The rubber valve element 18 is arranged between the terminal plate 19 and the sealing plate 16 in a compressed and deformed state, and the lower surface thereof is normally in close contact with the sealing plate 16. When the internal pressure of the battery case 14 exceeds a predetermined value, the battery case 14 is pushed up from the sealing plate 16 to open the gas passage 25 and discharge gas from the slit 19 a of the terminal plate 19.

The lead body 22 is made of nickel or rolled steel having a surface plated with nickel, and connects the sealing plate 16 and the positive electrode 10 via a current collecting terminal (positive current collecting terminal) 23. The negative electrode 11 and the bottom of the battery case 14 are connected by a nickel current collecting terminal (negative current collecting terminal) 24.

[0020]

EXAMPLES Examples of the present invention will be described below in more detail. However, it is needless to say that the present invention is not limited to only these examples, and can be appropriately changed without departing from the spirit of the present invention. In the following examples, “parts” means “parts by weight”, and “%” indicating the concentration or the amount of solid solution is “% by weight” unless otherwise specified.

Example 1 <Preparation of Negative Electrode> A negative electrode was prepared as follows. Commercially available Mm (containing La, Ce, Nd, Pr), Ni,
Each sample of Co, Mn, and Al (all with a purity of 99% by weight or more) was heated and melted by a high-frequency melting furnace so as to have a composition of MmNi _3.9 Co _0.6 Mn _0.35 Al _0.25 to obtain a hydrogen storage alloy. The hydrogen storage alloy was mechanically pulverized to obtain a hydrogen storage alloy powder having an average particle diameter of 35 μm. To 100 parts of this hydrogen storage alloy powder, 1 part of carbonyl nickel powder, 10 parts of a 5% poly-N-vinylacetamide aqueous solution and 1.7 parts of 40% styrene-2-ethylhexyl acrylate copolymer were added and mixed. A mixture-containing paste was prepared. This negative electrode mixture-containing paste is applied to a punched metal substrate, filled and dried to form a negative electrode mixture layer, and then pressure-molded to a thickness of 0.35 mm, and cut into a sheet of 355 mm × 52 mm. Was produced.

The exposed portion was formed by scraping off a 2 mm wide portion of the negative electrode mixture layer to one of the ends in the electrode width direction with a metal blade. Thereafter, the polyolefin resin of the present invention is heated and melted at 100 ° C. in a vat so as not to cover the end portion 0.5 mm in the electrode width direction of the exposed portion, and to cover the negative electrode mixture layer with a width of 1 mm. Applied. This electrode was cooled to room temperature to obtain a non-sintered negative electrode for an alkaline storage battery.

<Preparation of Positive Electrode> The positive electrode was prepared as follows. To 100 parts of nickel hydroxide powder, 1 part of cobalt hydroxide powder, 0.2 part of carboxymethylcellulose powder and 1 part of 60% polytetrafluoroethylene were added and mixed to prepare a positive electrode paste.

The porous metal substrate has a thickness of 1.30 mm,
Prepare a three-dimensional porous nickel foam material having a width of 120 mm and a length of 300 mm.
m, and a 1.5 mm wide, 150 μm thick F
The e-Ni plated ribbon was resistance welded.

The above-mentioned paste for a positive electrode was applied on this substrate, dried at 85 ° C., pressed to a total thickness of 0.62 mm to form a sheet, and then 52 mm in width. Cut into pieces. Excess active material in the ribbon weld was removed with compressed air, and this electrode was used as a non-sintered positive electrode for alkaline storage batteries.

<Preparation of Alkaline Storage Battery> The positive electrode and the negative electrode were wound through a separator made of a non-woven fabric of nylon, and a current-collecting terminal nickel plate (current collector) was placed on the positive and negative electrode end faces of the obtained wound electrode group. The terminal was subjected to resistance welding to obtain a wound body. The wound body was placed in an electrode can, and an alkaline electrolyte (1 liter of a 30% by weight aqueous potassium hydroxide solution) was added thereto.
An aqueous solution in which 17 g of iOH and 33 g of zinc oxide are dissolved)
, Sealed and stored at 40 ° C. for 6 hours.
After charging at mA for 6 hours, charging at 720 mA for 6 hours,
Discharged at 720 mA. Next, the battery was charged at 720 mA for 6 hours and discharged at 720 mA. This charge / discharge cycle was repeated until the discharge capacity became constant, thereby producing a nickel-metal hydride storage battery.

Comparative Example 1 A nickel-metal hydride battery was produced in the same manner as in Example 1 except that no resin was applied.

Comparative Example 2 A nickel-metal hydride storage battery was produced in the same manner as in Example 1 except that the resin was applied so as to cover the end in the electrode width direction.

(Comparative Example 3) The active material adjacent to the exposed portion was
A nickel-metal hydride storage battery was produced in the same manner as in Example 1, except that the resin was covered by 0.5 mm.

(Evaluation) Example 1 and Comparative Examples 1 and 2
Table 1 shows the percentage defective in each step when 1,000 nickel hydrogen storage batteries were manufactured.

[0031]

[Table 1]

In Example 1, no failure occurred. In Comparative Example 1, no short circuit occurred during winding and current collector terminal welding, but a short circuit occurred during chemical formation.
This seems to be due to the fact that the active material was dropped because the coating process was not performed, and when the distance between the electrodes was reduced due to swelling of the electrodes, the dropped active material was pushed by the electrodes and penetrated the separator. It is. In Comparative Example 2, since the coating material was applied, the fall of the active material at the time of winding was reduced and the short circuit was eliminated. However, since the coating material was applied to the end in the electrode width direction, the spark generated at the time of welding of the current collecting terminal was applied. As a result, the separator was dissolved, and a short circuit occurred. Also during the formation, a short circuit occurred in the dissolving portion of the separator. In Comparative Example 3, since the width of the coating material applied to the active material portion was too small, a short circuit occurred during winding, current collecting terminal welding, and formation.

From the above, it can be seen that if the boundary between the exposed portion and the coated portion is coated with the resin, the active material can be prevented from falling off. Further, it can be seen that, unless the resin is applied within 0.5 mm of the uncoated end, no failure occurs due to sparks during welding of the current collecting terminal.

[0034]

As described above, according to the present invention, if the boundary between the exposed portion and the active material application portion adjacent to the exposed portion is coated with the resin, the short-circuit caused by the fall of the active material adjacent to the exposed portion is prevented. It is possible to provide a high-yield alkaline storage battery that prevents generation and is suitable for large-current charging and discharging with a long life and low cost.

[Brief description of the drawings]

FIG. 1 is a partially enlarged view of a non-sintered electrode for an alkaline storage battery according to the present invention.

FIG. 2 is a sectional view schematically showing an example of the alkaline storage battery according to the present invention.

FIG. 3 is a partially enlarged view of a conventional non-sintered electrode for an alkaline storage battery.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base material 2 Active material application part 3 Exposed part 4 Boundary part 5 Coating material 10 Positive electrode 11 Negative electrode 12 Separator 13 Electrolyte 14 Battery case 23 Positive current collecting terminal (current collecting terminal) 24 Negative current collecting terminal (current collecting terminal)

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Fukunaga 1-1-88 Ushitora, Ibaraki-shi, Osaka F-term within Hitachi Maxell, Ltd. (Reference) 5H028 AA01 BB03 BB05 BB07 CC05 CC12 HH08 5H050 AA02 AA07 AA12 AA14 AA19 BA11 CA03 CB11 DA20 FA05 GA02 GA07 GA09 GA22 HA14

Claims (2)

[Claims] At least one surface of a metal plate or a metal foil as a base material is provided with an active material applied portion on which the active material is applied and an exposed portion on which the active material is not applied. A non-sintered electrode for an alkaline storage battery, wherein a boundary portion between the active material application portion and the exposed portion has a melting point of 50 to
A non-sintered electrode for an alkaline storage battery, which is coated with a resin at 160 ° C. 2. An alkaline storage battery in which a positive electrode and a negative electrode are spirally wound with a separator interposed therebetween in a battery case together with an electrolytic solution, wherein a positive electrode of the spiral electrode body is An upper end portion is welded to a positive electrode current collecting terminal, a lower end portion of the negative electrode of the spiral electrode body is welded to a negative electrode current collecting terminal, and at least one of the positive electrode and the negative electrode is formed. An alkaline storage battery, characterized by being a non-sintered electrode for an alkaline storage battery according to (1).