JP2019153550A - Alkaline battery electrode - Google Patents

Abstract

To reduce internal resistance of an alkaline storage battery.SOLUTION: An alkaline storage battery electrode includes at least a substrate 1, first particles 11, and second particles 12. The substrate 1 supports the first particles 11 and the second particles 12. The first particles 11 include electrode active material. The second particles 12 include at least one selected from a group consisting of an organic compound having an acidic functional group and an amphoteric metal.SELECTED DRAWING: Figure 3

Description

  The present disclosure relates to an electrode for an alkaline storage battery.

  Japanese Patent Laying-Open No. 2003-229131 (Patent Document 1) discloses that a niobium compound or the like is added to an electrode for an alkaline storage battery (hereinafter, abbreviated as “electrode”).

JP 2003-229131 A

  For example, in high output applications such as in-vehicle applications, thin electrodes are used to obtain high output. Generally, a thin electrode is manufactured by applying a paste containing an electrode active material to a substrate and drying it. The thin electrode manufactured by applying the paste is considered to have a smooth surface and a small surface area. Therefore, it is considered that the contact area between the electrode active material and the alkaline electrolyte is small. That is, it is considered that the effective reaction area is small.

  The purpose of this disclosure is to reduce the internal resistance of alkaline storage batteries.

  The technical configuration and operational effects of the present disclosure will be described below. However, the mechanism of action of the present disclosure includes estimation. The scope of the claims should not be limited by the correctness of the action mechanism.

  The alkaline storage battery electrode of the present disclosure includes at least a base material, first particles, and second particles. The base material carries the first particles and the second particles. The first particles include an electrode active material. The second particles include at least one selected from the group consisting of an organic compound having an acidic functional group and an amphoteric metal.

  The second particles of the present disclosure are so-called pore formers. The second particles include at least one selected from the group consisting of an organic compound having an acidic functional group and an amphoteric metal. Any of these substances can be dissolved in an alkaline electrolyte.

  During the production of the alkaline storage battery, an alkaline electrolyte is injected into the alkaline storage battery. It is considered that at least a part of the second particles is dissolved in the alkaline electrolyte by contacting the second particles with the alkaline electrolyte. It is considered that open pores are formed in the electrode by dissolving at least part of the second particles. This is thought to increase the contact area between the electrode active material contained in the first particles and the alkaline electrolyte. That is, the effective reaction area is considered to increase. An increase in the effective reaction area is expected to reduce the internal resistance of the alkaline storage battery.

FIG. 1 is a first conceptual diagram showing the configuration of the alkaline storage battery electrode of the present embodiment. FIG. 2 is a second conceptual diagram showing the configuration of the alkaline storage battery electrode of the present embodiment. FIG. 3 is a third conceptual diagram showing the configuration of the alkaline storage battery electrode of the present embodiment. FIG. 4 is a graph showing an example of the relationship between the volume ratio of the second particles and the internal resistance.

  Hereinafter, an embodiment of the present disclosure (also referred to as “this embodiment” in the present specification) will be described. However, the following description does not limit the scope of the claims. For example, a nickel metal hydride storage battery will be described below. However, the nickel metal hydride storage battery is only an example of the alkaline storage battery of this embodiment. The alkaline storage battery of this embodiment may be, for example, a nickel zinc storage battery. Moreover, a positive electrode is demonstrated below. However, the positive electrode is only an example of the electrode of this embodiment. The electrode of this embodiment may be a negative electrode.

<Alkaline battery electrode>
FIG. 1 is a first conceptual diagram showing the configuration of the alkaline storage battery electrode of the present embodiment.
The electrode 10 has a sheet shape. The electrode 10 may have an arbitrary planar shape depending on battery specifications. The planar shape of the electrode 10 may be, for example, a belt shape. The electrode 10 can be a thin electrode. The electrode 10 may have a thickness of 5 μm to 100 μm, for example.

FIG. 2 is a second conceptual diagram showing the configuration of the alkaline storage battery electrode of the present embodiment.
FIG. 2 conceptually shows a part of the electrode 10. The electrode 10 includes at least a substrate 1, first particles 11, and second particles 12.

  The electrode 10 may further include, for example, a binder. The binder should not be particularly limited. The binder may be, for example, carboxymethyl cellulose (CMC), polytetrafluoroethylene (PTFE), styrene butadiene rubber (SBR), or the like. The binder content may be, for example, 0.1 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the electrode active material.

"Base material"
The external shape of the base material 1 is a sheet form, for example. The substrate 1 carries the first particles 11 and the second particles 12. The substrate 1 in FIG. 2 is a porous metal material. The porous metal material may be sponge-like. The porous metal material may have a three-dimensional network structure. The substrate 1 can also function as a current collector. The substrate 1 may be made of, for example, nickel (Ni). However, the base material 1 should not be limited to a porous metal material. The substrate 1 may be, for example, a metal foil (for example, Ni foil, Ni-plated steel foil, etc.), a perforated metal plate, or the like.

<First particle>
The first particles 11 include an electrode active material. The electrode active material of this embodiment is at least one selected from the group consisting of nickel hydroxide [Ni (OH) ₂ ] and nickel oxyhydroxide [NiO (OH)]. The first particles 11 may be particles that are substantially composed only of an electrode active material. The first particles 11 may further include, for example, a conductive material. The conductive material may cover the surface of the electrode active material. The conductive material may be, for example, cobalt oxide.

<< second particle >>
FIG. 3 is a third conceptual diagram showing the configuration of the alkaline storage battery electrode of the present embodiment.
FIG. 3 conceptually shows a state in the alkaline storage battery (that is, a state after the alkaline electrolyte has permeated the electrode 10). The second particles 12 include at least one selected from the group consisting of an organic compound having an acidic functional group and an amphoteric metal. Any of these substances can be dissolved in an alkaline electrolyte. The alkaline electrolyte may be, for example, an aqueous potassium hydroxide (KOH) solution.

  It is considered that the alkaline electrolyte and the second particles 12 come into contact with each other when the alkaline electrolyte penetrates into the electrode 10 in the alkaline storage battery. It is considered that at least a part of the second particles 12 is dissolved in the alkaline electrolyte by the contact between the alkaline electrolyte and the second particles 12. As a result, open pores are formed in the electrode 10 and the effective reaction area is considered to increase. A portion surrounded by a dotted line in FIG. 3 corresponds to a portion where the second particles 12 are dissolved. An increase in the effective reaction area is expected to reduce the internal resistance of the alkaline storage battery. In addition, the charge / discharge efficiency of the alkaline storage battery is also expected to improve.

  The second particles 12 that do not come into contact with the alkaline electrolyte remain in the electrode 10. It is expected that a decrease in electrode strength is suppressed when a part of the second particles 12 remains in the electrode 10.

  In addition, these substances are unlikely to dissolve in neutral water. Therefore, it is considered possible to form a paste containing the first particles and the second particles using water as a solvent. It is considered that the electrode 10 can be manufactured stably because the second particles 12 are difficult to dissolve when the paste is applied and dried.

  The acidic functional group may be, for example, a phenolic hydroxy group, a carboxy group, a sulfo group, or the like. The organic compound may have a plurality of acidic functional groups. The organic compound may have multiple types of acidic functional groups. The organic compound having an acidic functional group may be, for example, phenol or 2-naphthol. The amphoteric metal may be aluminum (Al), zinc (Zn), or the like. The second particles 12 may include at least one selected from the group consisting of phenol, 2-naphthol, Al, and Zn, for example.

  The size of the open pores formed in the electrode 10 can be adjusted according to the size of the second particles 12. The ratio of the size of the second particles 12 to the size of the first particles 11 (hereinafter also referred to as “size ratio”) may be, for example, 0.5 or more and 1.5 or less. When the size ratio is 0.5 or more, the effect of reducing internal resistance is expected to increase. This is probably because open pores of a suitable size are formed. When the size ratio is 1.5 or less, the effect of reducing internal resistance is expected to increase. It is considered that the electrical contact (that is, the conductive network) between the first particles 11 is maintained appropriately.

  For example, the ratio of D50 of the second particle 12 to D50 of the first particle 11 may be 0.5 or more and 1.5 or less. “D50” indicates the particle size at which the cumulative particle volume from the fine particle side is 50% of the total particle volume in the volume-based particle size distribution. D50 can be measured by, for example, a laser diffraction particle size distribution measuring apparatus.

  The porosity of the electrode 10 can be adjusted by the volume ratio of the second particles 12. Higher porosity is thought to mean an increase in effective reaction area. For example, the second particles 12 may have a volume ratio of 20% to 80% with respect to the total of the first particles 11 and the second particles 12. When the volume ratio of the second particles 12 is 20% or more, it is expected that the effect of reducing the internal resistance is increased. This is probably because open pores of a suitable size are formed. When the volume ratio of the second particles 12 is 80% or less, it is expected that the effect of reducing internal resistance is increased. It is considered that the electrical contact between the first particles 11 is kept moderate. The second particles 12 may have a volume ratio of 31% to 35%, for example.

  Examples of the present disclosure are described below. However, the following description does not limit the scope of the claims.

Electrodes 10 (six levels) having the following configurations were manufactured.
First particle: Nickel hydroxide Second particle: 2-naphthol Size ratio = 1.0
Volume ratio of second particles = 31 to 35% (6 levels)

  Nickel metal hydride storage batteries including the respective electrodes 10 were manufactured. The internal resistance (DC internal resistance, DC-IR) of each nickel metal hydride storage battery was measured.

FIG. 4 is a graph showing an example of the relationship between the volume ratio of the second particles and the internal resistance.
When the volume ratio of the second particles 12 is in the range of 31% to 35%, a linear correlation is observed between the volume ratio of the second particles 12 and the internal resistance. That is, it is recognized that the internal resistance tends to decrease as the volume ratio of the second particles 12 increases. It is considered that as the volume ratio of the second particles 12 is increased, the increase width of the effective reaction area accompanying the dissolution of the second particles 12 is increased.

  Embodiments and examples of the present disclosure are illustrative in all respects and not restrictive. The technical scope defined by the description of the claims includes all modifications within the meaning and scope equivalent to the description of the claims.

  1 base material, 10 electrode, 11 1st particle, 12 2nd particle.

Claims (1)

Comprising at least a substrate, first particles and second particles;
The base material carries the first particles and the second particles,
The first particles include an electrode active material,
The second particles include at least one selected from the group consisting of an organic compound having an acidic functional group and an amphoteric metal.
Alkaline battery electrode.

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