JP5317507B2 - Cylindrical alkaline storage battery - Google Patents

Description

  The present invention relates to a cylindrical alkaline storage battery.

Nickel metal hydride secondary batteries, which are a type of alkaline storage battery, are used as power sources for electric tools, assist bicycles, electric vehicles, etc., and further increase in capacity, output, or improvement in high rate discharge characteristics are desired. ing.
For example, Patent Document 1 discloses a cylindrical nickel-hydrogen secondary battery excellent in high rate discharge characteristics. This battery includes an electrode group formed by spirally winding a positive electrode and a negative electrode with a separator interposed therebetween.
JP 2005-285638 A

As an effective means for increasing the output of the alkaline storage battery, it is conceivable to increase the reaction area by increasing the area or length of the electrode. However, in the case of a cylindrical alkaline storage battery, when the area or length of the electrode is increased, the life is reduced. This is due to the following reason.
During the charge / discharge reaction, heat is accumulated inside the battery, and therefore, non-uniform reaction occurs between the radial center side and the outside of the electrode group. For example, during charging of the cylindrical battery, the amount of heat stored on the radial center side exceeds the amount of heat stored on the radially outer side, and the temperature rises toward the radial center side.

The increase in temperature causes a decrease in oxygen overvoltage, and at the center side in the radial direction, the charging efficiency decreases and oxygen is generated. The generated oxygen corrodes the negative electrode which is the counter electrode, and the corrosion proceeds relatively faster on the radial center side than on the radial outer side.
Here, the non-uniformity of the reaction due to heat storage becomes particularly significant in a cylindrical alkaline storage battery in which the area or length of the electrode is increased for higher output. For this reason, in a cylindrical alkaline storage battery in which the area or length of the electrode is increased for higher output, the negative electrode is locally corroded at an early stage, and the internal pressure of the battery is likely to increase, resulting in a decrease in life. End up.

  The present invention has been made on the basis of the above-described circumstances, and its object is to suppress a decrease in charging efficiency on the center side in the radial direction of the electrode group, and to provide a high output and long life cylindrical alkaline storage battery. Is to provide.

In order to achieve the above object, according to the present invention, a cylindrical alkaline storage battery having an electrode group in which a positive electrode and a negative electrode are spirally wound via a separator, the positive electrode is in the radial direction of the electrode group. The winding water having a winding start end portion disposed on the center side and a winding end end portion disposed on the radially outer side, and nickel hydroxide as an active material and the water for suppressing a decrease in charging efficiency due to a temperature rise Cobalt dissolved in nickel oxide is included, and when looking at the concentration of cobalt dissolved in nickel hydroxide , a portion higher than the portion on the winding end portion side is formed on the winding start end portion side. A cylindrical alkaline storage battery is provided (claim 1).

Good Mashiku, the positive electrode is composed of the first positive electrode plate having the winding start portion by the second positive electrode plate having the winding end portion is wound after said first positive electrode plate The cobalt concentration dissolved in nickel hydroxide in the first positive electrode plate is higher than the cobalt concentration dissolved in nickel hydroxide in the second positive electrode plate (claim 2 ).

Preferably, the positive electrode is constituted by one positive electrode plate, and the concentration of cobalt dissolved in the nickel hydroxide in the positive electrode plate is gradually increased from the winding start end side toward the winding end end side. (Claim 3 )

In the cylindrical alkaline storage battery according to claim 1 of the present invention, a portion having a higher concentration of cobalt dissolved in nickel hydroxide than the winding end portion side is provided on the winding start end portion side of the positive electrode. Even if the electrode area or length is increased for higher output, the charging reaction proceeds uniformly. That is, on the radial center side, a decrease in charging efficiency due to a temperature rise is suppressed and oxygen generation is suppressed.

Thus, by suppressing the non-uniform progress of the oxygen generation reaction, the corrosion of the negative electrode proceeds uniformly on the radial center side and the outer side. As a result, even if this cylindrical alkaline storage battery has a higher output, local corrosion of the negative electrode is prevented and it has a long life. That is, according to this cylindrical alkaline storage battery, it is possible to achieve both high output and long life .

In the cylindrical alkaline storage battery according to claim 2 , by using two positive electrode plates, cobalt is dissolved in nickel hydroxide in a simple configuration on the winding start end side of the positive electrode rather than on the winding end end side. A site with a high concentration of is provided.
In the cylindrical alkaline storage battery according to claim 3 , the concentration of cobalt dissolved in nickel hydroxide gradually decreases from the radial center to the outside, so that the nickel hydroxide conforms to the temperature gradient of the electrode group. Dissolved cobalt is distributed. As a result, the non-uniform progress of the oxygen generation reaction is suppressed at a cobalt concentration dissolved in a smaller amount of nickel hydroxide .

FIG. 1 shows a cylindrical nickel-metal hydride secondary battery according to an embodiment of the present invention.
The nickel metal hydride secondary battery includes a metal cylindrical container (exterior can) 2 having one end opened, and the external can 2 has conductivity. In the outer can 2, a substantially cylindrical electrode group 4 is accommodated together with an alkaline electrolyte (not shown).
The electrode group 4 is formed by spirally winding a belt-like first positive electrode plate 6, second positive electrode plate 8, negative electrode plate 10, first separator 12, and second separator 14.

  More specifically, as shown in FIG. 2, the second positive electrode plate 8 is wound continuously after the first positive electrode plate 6, and the first positive electrode plate 6 is viewed along the spiral. Is positioned on the winding start side (radial direction center side), and the second positive electrode plate 8 is positioned on the winding end side (radial direction outer side). In other words, the first positive electrode plate 6 and the second positive electrode plate 8 are arranged in series when viewed in the direction along the spiral.

Therefore, when the first positive electrode plate 6 and the second positive electrode plate 8 are regarded as constituting one electrode (positive electrode), the first positive electrode plate 6 has a positive electrode winding start end, The second positive electrode plate 8 has a positive electrode winding end.
The first positive electrode plate 6 and the second positive electrode plate 8 are overlapped with the radially inner portion and the radially outer portion of the negative electrode plate 10 via the first separator 12 and the second separator 14, respectively. Yes.

In FIGS. 1 and 2, hatching of the negative electrode 10, the first separator 12, and the second separator 14 is omitted in order to avoid complex lines.
The open end of the outer can 2 is closed by a lid 16. The lid body 16 includes a circular lid plate 18, and the lid plate 18 has a valve hole 20 in the center. The outer peripheral portion of the cover plate 18 is fixed by caulking the opening edge of the outer can 2 via an insulating gasket 22, and a valve body made of rubber is provided on the outer surface of the cover plate 18 so as to close the valve hole 20. 24 is arranged. A cylindrical positive terminal 26 with a flange is fixed on the outer surface of the cover plate 18 so as to cover the valve body 24, and the valve body 24 is pressed against the cover plate 18 in the positive terminal 26.

One end of the bent positive electrode lead 28 is welded to the inner surface of the lid plate 18, and the other end of the positive electrode lead 28 is integrally connected to a circular current collector plate 30. On one end side of the electrode group 4, the current collector plate 30 and the positive electrode plate 6 are electrically connected, whereby the positive electrode plate 6 and the positive electrode terminal 26 are electrically connected.
More specifically, each of the first positive electrode plate 6 and the second positive electrode plate 8 is a non-sintered nickel electrode, and has a conductive positive electrode substrate having a strip shape. The positive electrode substrate is a porous metal body having a porous structure, and has a three-dimensional network structure skeleton including numerous pores. A positive electrode mixture is filled and held in the pores of the positive electrode substrate. The positive electrode active material is filled with nickel hydroxide particles.

  As shown in FIG. 3, connecting portions 32 and 34 protrude in the axial direction from the ends of the first positive electrode plate 6 and the second positive electrode plate 8 on the current collector plate 30 side. Reference numerals 34 respectively extend along the first positive electrode plate 6 and the second positive electrode plate 8. The connecting portions 32 and 34 are made of a metal porous body, and are integrated with the metal bodies in the first positive electrode plate 6 and the second positive electrode plate 8, respectively. However, the connecting portions 32 and 34 are not filled with the positive electrode mixture, and the connecting portions 32 and 34 are formed thinner than the first positive electrode plate 6 and the second positive electrode plate 8 by being compressed. Yes.

  One thin metal plate 36 made of, for example, a nickel ribbon or the like is fixed to the outer surfaces in the radial direction of the connecting portions 32 and 34 by welding or a conductive adhesive, and the end of the thin metal plate 36 is welded to the current collector plate 30. . Therefore, the first positive electrode plate 6 and the second positive electrode plate 8 are electrically connected to the positive electrode terminal 26 via the connecting portions 32 and 34, the metal thin plate 36, the current collector plate 30, the positive electrode lead 28, and the lid plate 18. Has been.

As shown in FIG. 4, the thin metal plate 36 extends over substantially the entire area of the connecting portions 32, 34, and the first positive plate 6 and the second positive plate 8 are mutually connected by the thin metal plate 36. It is connected.
On the other hand, referring to FIG. 3 again, the negative electrode plate 10 includes a negative electrode substrate 38 and a negative electrode mixture 40 held on both surfaces of the negative electrode substrate 38. As the negative substrate 38, for example, a punching metal can be used. The negative electrode mixture 40 includes hydrogen storage alloy particles capable of occluding and releasing hydrogen as a negative electrode active material, a conductive agent as necessary, and a binder for binding the hydrogen storage alloy particles to the negative electrode substrate 38. including.

The negative electrode substrate 38 of the negative electrode plate 10 protrudes from the electrode group 4 on the side opposite to the current collector plate 30, and the protruding portion of the negative electrode substrate 38 is welded to the negative electrode current collector plate 42 (FIG. 1). reference). That is, the negative electrode plate 10 is electrically connected to the outer can 2 as a negative electrode terminal via the negative electrode current collector plate 42.
Here, the positive electrode mixture held on the positive electrode substrate in the first positive electrode plate 6 and the second positive electrode plate 8 includes positive electrode active material particles containing a positive electrode active material as a main component, an oxygen generation suppression component, and a necessity. Correspondingly, it consists of additive particles and a binder for binding the mixed particles of the positive electrode active material particles and the additive particles to the positive electrode substrate.

Although the positive electrode active material is nickel hydroxide, in this specification, nickel hydroxide includes nickel hydroxide (high-order nickel hydroxide) in which the average valence of nickel exceeds divalent. . Preferably, the surfaces of the positive electrode active material particles are coated with a cobalt compound that has been subjected to an alkali heat treatment .

As the binder, a hydrophilic or hydrophobic polymer or the like can be used.
The oxygen generation suppression component is a component for suppressing a decrease in oxygen overvoltage accompanying a temperature rise, and is cobalt (hereinafter also referred to as solid solution Co) dissolved in nickel hydroxide of the positive electrode active material particles. That is, the positive electrode active material particles include nickel hydroxide and cobalt.
The positive electrode active material particles may contain zinc, cadmium and the like in addition to cobalt.

  Here, the first positive electrode plate 6 and the second positive electrode plate 8 have different oxygen generation suppression component concentrations, and the concentration of the oxygen generation suppression component in the first positive electrode plate 6 is the second positive electrode plate 8. It is higher than the concentration of the oxygen generation inhibiting component. For example, the first positive electrode plate 6 contains 2.0 parts by mass or more and 4.0 parts by mass or less of solid solution Co per 100 parts by mass of nickel, and the second positive electrode plate 8 per 100 parts by mass of nickel. 0.5 to 2.0 parts by mass of solute Co.

  In the nickel hydride secondary battery described above, the concentration of the oxygen generation suppression component in the first positive electrode plate 6 on the winding start end side is higher than the concentration of the oxygen generation suppression component in the second positive electrode plate 8 on the winding end end side. Is also expensive. Thus, by providing the portion where the concentration of the oxygen generation suppression component is higher on the winding start end side of the positive electrode than on the winding end end side, in this nickel metal hydride secondary battery, even for the sake of higher output, Even if the areas or lengths of the first positive electrode plate 6, the second negative electrode plate 8, and the negative electrode plate 10 are increased, the charging reaction proceeds uniformly. That is, on the radial center side, a decrease in charging efficiency due to a temperature rise is suppressed, and nonuniform oxygen generation is suppressed.

  Thus, by suppressing the non-uniform progress of the oxygen generation reaction, the corrosion of the hydrogen storage alloy of the negative electrode plate 10 proceeds uniformly on the central side and the outer side in the radial direction. As a result, even if the nickel hydride secondary battery has a high output, local corrosion of the negative electrode plate 10 is prevented and the battery has a long life. That is, according to the nickel metal hydride secondary battery, it is possible to achieve both high output and long life.

Moreover, in the nickel hydride secondary battery mentioned above, the fall of the charge efficiency accompanying a temperature rise is reliably suppressed by the cobalt dissolved in nickel hydroxide. Since solute cobalt shifts the charge potential of nickel hydroxide to the base, even when the oxygen overvoltage is lowered as the temperature rises, the charge reaction can sufficiently proceed.
Further, in the above-described nickel-metal hydride secondary battery, by using the two positive plates 6 and 8 as the positive electrodes, the generation of oxygen is more suppressed at the winding start end side than the winding end end side with a simple configuration. Sites with high component concentrations are provided.

1. Battery production example 1
(1) Production of first positive electrode plate A mixed aqueous solution of nickel sulfate, zinc sulfate and cobalt sulfate was prepared so that the mass ratio of Ni: Zn: Co was 94: 3: 3 in terms of conversion amount. To this mixed aqueous solution, a sodium hydroxide aqueous solution was gradually added and reacted with stirring. At this time, the pH of the mixed aqueous solution during the reaction was maintained at 13 to 14, and substantially spherical nickel hydroxide particles containing zinc and cobalt were precipitated in the mixed aqueous solution.

  Next, an aqueous cobalt sulfate solution was added to the mixed aqueous solution in which nickel hydroxide particles were precipitated, and reacted. At this time, the pH of the mixed aqueous solution during the reaction was maintained at 9 to 10, and cobalt hydroxide was deposited on the surface of the substantially spherical nickel hydroxide particles deposited earlier. The substantially spherical nickel hydroxide particles whose surface is coated with cobalt hydroxide are washed three times with 10 times the amount of pure water, then dehydrated and dried, and water whose surface is coated with cobalt hydroxide. Nickel oxide particles were obtained.

  Thereafter, the obtained particles were subjected to alkali heat treatment. That is, an aqueous solution of sodium hydroxide having a concentration of 25% by mass was sprayed over 0.5 hours while stirring in a heated atmosphere at a temperature of 100 ° C. on nickel hydroxide particles whose surfaces were coated with cobalt hydroxide. Thereby, the cobalt hydroxide covering the nickel hydroxide particles was oxidized to be a higher cobalt compound.

Then, the alkali-heat-treated particles are washed three times with 10 times the amount of pure water, dehydrated and dried, and the surface of the nickel hydroxide particles containing zinc and cobalt disturbs the crystal structure and alkali cations. Composite particles covered with a coating layer made of a higher cobalt compound containing
Then, 100 parts by mass of composite particles and 0.3 part by mass of HPC (hydroxypropylcellulose) dispersion (dispersion medium: 40 parts by mass of water, solid content of 60 parts by mass) are mixed to obtain a slurry for positive electrode. It was. After filling this positive electrode slurry into a metal porous body made of Ni, the filled metal porous body was pressed and cut after drying the positive electrode slurry.

Thereafter, in the cut metal porous body, the positive electrode material mixture was removed by applying ultrasonic waves from the portion to be the connecting portion. Then, the portion from which the positive electrode mixture is removed is further rolled to produce a non-sintered first positive electrode plate having a length of 150 mm and an active material amount adjusted to have a capacity of 1500 mAh. did.
(2) Production of second positive plate Except that a mixed aqueous solution of nickel sulfate, zinc sulfate and cobalt sulfate was prepared, it was 150 mm in length and 1500 mAh in the same manner as in the case of the first positive plate. A non-sintered second positive electrode plate having an active material amount adjusted so as to have a capacity was produced.
(3) Production of Negative Electrode Hydrogen storage alloy particles having an average particle size of 30 μm and a maximum particle size of 45 μm were prepared. 0.4 parts by mass of sodium polyacrylate, 0.1 part of carboxymethylcellulose with respect to 100 parts by mass of the alloy particles. After adding 1 part by mass and 2.5 parts by mass of a polytetrafluoroethylene dispersion (dispersion medium: water, solid content 60 parts by mass), kneading was performed to obtain a slurry for negative electrode.

This negative electrode slurry was applied evenly and uniformly on both surfaces of a 60 μm thick Fe punching metal plated with Ni. After the slurry for the negative electrode was dried, the punching metal was pressed and cut to prepare a negative electrode plate for SC size.
(4) Assembly of nickel-hydrogen secondary battery The first positive electrode plate and the second positive electrode plate obtained as described above were arranged, and a nickel ribbon was fixed to the connecting portion by resistance electric welding. Then, the first positive electrode plate, the second positive electrode plate, and the negative electrode plate were spirally wound through a separator made of a polypropylene or nylon nonwoven fabric to form an electrode group.

After the positive electrode and negative electrode current collector plates were welded to both ends of the obtained electrode group, the electrode group was inserted into an outer can. Then, the negative electrode current collector plate was spot welded to the bottom wall of the outer can and the positive electrode positive electrode lead was welded to the lid plate.
Thereafter, an aqueous sodium hydroxide solution containing 30% by mass of lithium and potassium as an alkaline electrolyte was poured into the outer can. Then, the outer can was sealed with a sealing body, and an SC size nickel-hydrogen secondary battery having the configuration shown in FIG. 1 and having a nominal capacity of 3000 mAh was assembled.

Comparative Example 1
A nickel hydride secondary battery of Comparative Example 1 was assembled in the same manner as in Example 1 except that the second positive electrode plate used in Example 1 was used as the first positive electrode plate.
Comparative Example 2
A nickel-metal hydride secondary battery of Comparative Example 1 was assembled in the same manner as in Example 1 except that the first positive electrode plate used in Example 1 was used as the second positive electrode plate.

Comparative Example 3
The case of Example 1 except that the second positive electrode plate used in Example 1 was used as the first positive electrode plate, and the first positive electrode plate used in Example 1 was used as the second positive electrode plate. Similarly, the nickel metal hydride secondary battery of Comparative Example 3 was assembled.
2. Battery Evaluation Method (1) High-Temperature Charge Test For each battery of Example 1 and Comparative Examples 1 to 3 manufactured as described above, a charging current of 300 mA (0.1 It) at an ambient temperature of 25 ° C. And then discharged at an ambient temperature of 25 ° C. with a discharge current of 3000 mA (1 It) to a discharge end voltage of 1.0 V. At this time, the discharge capacity (initial discharge capacity) of each battery was measured.

After that, each battery whose initial discharge capacity was measured was charged at a charging current of 300 mA (0.1 It) at an ambient temperature of 60 ° C. for 16 hours, and then, at a ambient temperature of 25 ° C., 3000 mA ( 1 It) was discharged to a discharge end voltage of 1.0 V with a discharge current of 1 It). The discharge capacity (discharge capacity after being left at high temperature) of each battery at this time was measured.
For each battery, the ratio of the discharge capacity after standing at high temperature to the initial discharge capacity was determined, and the result is shown in Table 1 as a percentage as the high temperature charge efficiency.

(2) High rate discharge test About each battery of Example 1 and Comparative Examples 1 to 3 manufactured as described above, charging was performed at an ambient temperature of 25 ° C. with a charging current of 300 mA (0.1 It) for 16 hours. Then, it was discharged to a discharge end voltage of 0.6 V with a discharge current of 30 A (10 It) at an ambient temperature of 25 ° C. The operating voltage of each battery measured at the time of discharging is shown in Table 1 as a high rate discharge operating voltage.
(3) Cycle test Each battery of Example 1 and Comparative Examples 1 to 3 manufactured as described above was charged with dV control (ΔV = −10 mV) at a charging current of 3000 mA (1.0 It). A charge / discharge cycle in which a discharge was performed at a discharge current of 9000 mA (3.0 It) to a final voltage of 0.8 V after a 30-minute pause was repeated until the discharge capacity became 1800 mAh or less, and the number of cycles was measured. The results are shown in Table 1 as the cycle life (∞).

3. Battery Evaluation Results From Table 1, the following is clear.
(1) The high temperature charging efficiency of Example 1 is greater than the high temperature charging efficiency of Comparative Example 1. This is because, in Example 1, the concentration of solute Co is higher in the first positive electrode plate on the radial center side than the second positive electrode plate on the outer side in the radial direction, thereby increasing the temperature on the radial center side. This is considered to be because the accompanying decrease in charging efficiency was suppressed.
(2) The cycle life of Example 1 is greater than the cycle life of Comparative Example 1. This is because, in Example 1, since the decrease in charging efficiency due to the temperature increase at the radial center side is suppressed, oxygen is uniformly generated at the radial center side and outside, and the corrosion of the negative electrode plate is uniform. This is thought to be due to progress.

(3) The cycle life of Example 1 is much greater than the cycle life of Comparative Example 3. This is because, in Comparative Example 3, the concentration of solute Co is higher in the second positive electrode plate on the radially outer side than the first positive electrode plate on the radial center side, thereby increasing the temperature on the radial center side. The accompanying decrease in charging efficiency is large, and it is considered that a large amount of oxygen is generated on the center side in the radial direction and the negative electrode plate is locally corroded.
(4) The high rate discharge operating voltage of Example 1 is higher than the high rate discharge operating voltage of Comparative Example 2. This is presumably because the concentration of the solid solution Co in the second positive electrode plate was reduced in Example 1 as compared with Comparative Example 2. From this, it can be seen that the battery of Example 1 is excellent in cycle life and also in high current discharge characteristics.

The present invention is not limited to the above-described embodiment and examples, and various modifications can be made. For example, the type of battery is not limited to a nickel-hydrogen secondary battery, but a nickel-cadmium secondary battery. There may be .

In one embodiment noted above, but using the first positive electrode plate 6 and the second of the positive electrode plate 8, the number of the positive electrode plate constituting the positive electrode is not particularly limited. However, in order to prevent the manufacturing process from becoming complicated, the number of positive electrode plates is preferably two or less.

  In the above-described embodiment, the use of the first positive electrode plate 6 and the second positive electrode plate 8 changes the solid solution Co concentration discontinuously as shown in FIG. As shown in FIG. 6, the solute Co concentration may be gradually decreased from the radial center side toward the outside along the spiral direction using a plate. In this case, solid solution Co is distributed in accordance with the temperature gradient of the electrode group 4, and the non-uniform progress of the oxygen generation reaction is suppressed with a smaller amount of solid solution Co.

  In addition, as shown in FIG. 7, one or a plurality of positive electrode plates may be used to provide a portion where the concentration of solute Co gradually inclines between the radial center side and the outer side.

It is a figure which shows the outline of the nickel-hydrogen secondary battery which concerns on one Embodiment of this invention, the left side is a side view, and the right side is sectional drawing. It is sectional drawing which follows the II-II line of FIG. It is an enlarged view of the area | region III of FIG. It is a schematic perspective view which expands and shows the 1st positive electrode plate and the 2nd positive electrode plate with a metal thin plate. 2 is a graph showing a relationship between a position in a spiral direction and a solute Co concentration in the battery of FIG. It is a graph which shows the relationship between a spiral direction position and solid solution Co density | concentration in the battery of a modification. It is a graph which shows the relationship between a spiral direction position and solid solution Co density | concentration in another modification.

Explanation of symbols

4 Electrode group 6 First positive electrode plate (positive electrode)
8 Second positive electrode plate (positive electrode)
10 Negative electrode plate (negative electrode)
12 First separator (separator)
14 Second separator (separator)

Claims (3)

In a cylindrical alkaline storage battery having an electrode group formed by spirally winding a positive electrode and a negative electrode through a separator,
The positive electrode is
A winding start end disposed on the radial center side of the electrode group and a winding end end disposed on the radial outside;
Nickel hydroxide as an active material and cobalt dissolved in the nickel hydroxide for suppressing a decrease in charging efficiency due to temperature rise, and
A cylindrical alkaline storage battery characterized by having a higher portion on the winding start end side than on the winding end end side when the concentration of cobalt dissolved in nickel hydroxide is viewed. The positive electrode is composed of a first positive electrode plate having the winding start end portion and a second positive electrode plate wound after the first positive electrode plate and having the winding end end portion,
The cobalt concentration dissolved in nickel hydroxide in the first positive electrode plate is higher than the cobalt concentration dissolved in nickel hydroxide in the second positive electrode plate.
The cylindrical alkaline storage battery according to claim 1. The positive electrode is composed of one positive electrode plate,
The concentration of cobalt dissolved in the nickel hydroxide in the positive electrode plate gradually decreases from the winding start end side toward the winding end end side.
The cylindrical alkaline storage battery according to claim 1.

Images