JP6561915B2 - Nickel metal hydride battery - Google Patents

Description

  The present disclosure relates to nickel metal hydride batteries.

  Japanese Patent Laying-Open No. 2013-012428 (Patent Document 1) discloses a battery structure in which a resin sealing material is disposed between a housing and an electrode terminal. According to this battery structure, it is said that leakage of the electrolyte can be suppressed.

JP 2013-012428 A

  The electrolyte of the nickel metal hydride battery is strongly alkaline. The nickel metal hydride battery needs to have a structure that does not allow the electrolytic solution to leak. This is because when the electrolyte leaks, the leaked electrolyte may corrode the members around the battery.

  Nickel metal hydride batteries are also used for in-vehicle applications. In vehicle applications, severe environments such as high temperature, high humidity, and vibration are assumed. There is a demand for the development of a sealed structure that can suppress leakage of the electrolyte even in such a harsh environment.

  A “creep phenomenon” is known as a phenomenon that promotes leakage of electrolyte in a harsh environment. The creep phenomenon is a phenomenon in which the electrolyte crawls up on the surface of the electrode terminal. The electrode terminal penetrates the housing. Due to the creep phenomenon, the electrolytic solution leaks outside through the electrode terminal.

The nickel-metal hydride battery of the present disclosure includes: a housing; an electrolytic solution housed in the housing; an electrode group housed in the housing; an electrode terminal penetrating the housing; and an electrode terminal and the housing A sealing material interposed therebetween.
A nonconductive layer is formed on the surface of the electrode terminal. A metal layer is laminated on the non-conductive layer. The metal layer contains at least one of nickel and nickel iron alloy.

  The sealing material interposed between the electrode terminal and the housing is a member for suppressing leakage of the electrolyte from the inside of the housing. The sealing material is a material that is difficult for the electrolyte to pass therethrough. Further, the sealing material needs to be insulative. Therefore, the sealing material is usually a resin material. Conventionally, attention is not paid to the gas barrier property of the sealing material.

However, according to the new knowledge of the present disclosure, the penetration of oxygen and water vapor from the outside of the housing promotes the creep phenomenon. FIG. 1 is a diagram for explaining the creep phenomenon. The surface of the electrode terminal 4 is negatively charged. That is, electrons (e ⁻ ) are collected near the surface of the electrode terminal 4. The electrolytic solution 1 is, for example, a concentrated aqueous potassium hydroxide solution [Conc. KOH (aq)]. The electrolytic solution 1 forms a liquid surface (meniscus) that rises along the surface of the electrode terminal 4.

Oxygen [O ₂ (g)] and water vapor [H ₂ O (g)] in the atmosphere slightly permeate the sealing material (resin material). Oxygen and water vapor that have passed through the sealing material reach the electrode terminal 4. Oxygen becomes dissolved oxygen [O ₂ (aq)] by dissolving in the electrolytic solution 1. The water vapor is mixed with the electrolytic solution 1. The electrode terminal 4 supplies electrons to the electrolytic solution 1. As a result, an oxidation-reduction reaction [2H ₂ O + O ₂ + 4e ⁻ → 4OH ⁻ ] occurs. By this reaction, the concentration of OH ⁻ ions locally increases around the meniscus. This OH ^- ion concentration gradient becomes a driving force that pushes up the liquid surface. That is, mass transfer occurs in the electrolyte 1 in order to alleviate the concentration gradient of OH ⁻ ions. As a result, the electrolytic solution 1 scoops up the surface of the electrode terminal 4.

  In the nickel hydride battery of the present disclosure, the creep phenomenon is suppressed. That is, in the nickel metal hydride battery, a nonconductive layer is formed on the surface of the electrode terminal. Furthermore, a metal layer is laminated on the nonconductive layer.

  The nonconductive layer suppresses the wettability of the electrode terminal, that is, the contact between the electrode terminal and the electrolytic solution. Further, the non-conductive layer suppresses the electrode terminal from providing electrons to the electrolytic solution.

  The metal layer suppresses atmospheric oxygen and water vapor from reaching the electrode terminals. The metal layer contains at least one of nickel (Ni) and nickel iron alloy (Ni-Fe). Ni and Ni-Fe exhibit excellent gas barrier properties against oxygen and water vapor. Furthermore, since Ni and Ni-Fe have alkali resistance, they are unlikely to corrode even when in contact with the electrolytic solution.

  According to the above, the creep phenomenon is suppressed.

It is a figure for demonstrating a creep phenomenon. It is a schematic diagram showing an example of composition of a nickel metal hydride battery concerning an embodiment of this indication. It is a schematic sectional drawing in the III-III line of FIG. It is a schematic sectional drawing which shows IV area | region of FIG.

  Hereinafter, an embodiment of the present disclosure (hereinafter referred to as “the present embodiment”) will be described. However, the following description does not limit the invention of the present disclosure. Hereinafter, the nickel metal hydride battery may be simply referred to as “battery”.

<Nickel metal hydride battery>
FIG. 2 is a schematic diagram illustrating an example of the configuration of a nickel metal hydride battery. The battery 10 includes a housing 2, an electrolytic solution (not shown in FIG. 2), an electrode group 3, an electrode terminal 4, and a sealing material (not shown in FIG. 2).

<Case>
In FIG. 2, a rectangular (rectangular) housing 2 is shown as an example. However, the shape of the housing 2 should not be limited to a square. The housing 2 may be cylindrical, for example. The housing 2 may be made of metal, for example. The housing | casing 2 may be comprised from the some member. The housing 2 may include, for example, a lid and a main body.

<Electrolyte>
The electrolytic solution is accommodated in the housing 2. The electrolytic solution is an alkaline aqueous solution. The electrolytic solution may contain, for example, KOH, sodium hydroxide (NaOH), lithium hydroxide (LiOH) and the like as solutes. The concentration of the electrolytic solution may be, for example, 1 to 10 mol / l.

<Electrode group>
The electrode group 3 is accommodated in the housing 2. In FIG. 2, a stacked electrode group 3 is shown as an example. However, the electrode group 3 should not be limited to a laminated type. The electrode group 3 may be, for example, a winding type. The electrode group 3 is configured by alternately stacking positive electrodes and negative electrodes. A separator is interposed between the positive electrode and the negative electrode.

The positive electrode includes a positive electrode current collector and a positive electrode active material. The positive electrode current collector may be, for example, a metal foam (foamed nickel or the like), a punching metal, or the like. The positive electrode active material is supported by the positive electrode current collector. The positive electrode active material contains at least one of nickel hydroxide (Ni (OH) ₂ ) and nickel oxyhydroxide (NiOOH). Nickel hydroxide is a positive electrode active material in a charged state. Nickel oxyhydroxide is a positive electrode active material in a discharged state. The positive electrode active material may further contain, for example, cobalt (Co).

  The negative electrode includes a negative electrode current collector and a negative electrode active material. The negative electrode current collector may be, for example, a nickel mesh. The negative electrode active material is a hydrogen storage alloy. The composition of the hydrogen storage alloy should not be limited as long as hydrogen can be stored and released. The hydrogen storage alloy may be, for example, an Mm—Ni—Mn—Al—Co alloy. “Mm” indicates a mixture of rare earth elements called misch metal.

  The separator may be, for example, a synthetic fiber nonwoven fabric. The synthetic fiber may be, for example, polypropylene (PP) fiber or nylon fiber. The separator may be subjected to a hydrophilic treatment or the like on its surface. Examples of the hydrophilic treatment include sulfonation treatment, plasma treatment, and acrylic acid graft polymerization treatment.

<Electrode terminal>
The electrode terminal 4 penetrates the housing 2. The electrode terminal 4 is connected to the electrode group 3 in the housing 2. The electrode terminal 4 may be connected to the positive electrode or may be connected to the negative electrode. That is, the electrode terminal 4 may be a positive electrode terminal or a negative electrode terminal. The surface of the negative electrode terminal tends to be negatively charged. Therefore, it is desirable that the configuration of the present disclosure be applied at least to the negative electrode terminal side.

  The electrode terminal 4 is made of metal. The metal which comprises the electrode terminal 4 should not be specifically limited. The metal constituting the electrode terminal 4 may be, for example, Ni, Fe, copper (Cu), or the like. However, it is convenient that the electrode terminal 4 has a volume expansion coefficient approximate to that of a metal layer 7 (at least one of Ni and Ni—Fe) described later. When these volume expansion coefficients are approximated, the formation of a gap between the electrode terminal 4 and the sealing material 5 can be suppressed. The electrode terminal 4 may be, for example, Fe plated with Ni.

  On the surface of the electrode terminal 4, a non-conductive layer 6 described later is formed. Therefore, the surface of the electrode terminal 4 is desired to be smooth. The surface of the electrode terminal 4 can be smoothed by, for example, predetermined polishing or etching.

<Seal material>
FIG. 3 is a schematic cross-sectional view taken along line III-III in FIG. The arrows in FIG. 3 indicate the electrolyte leakage path in the creep phenomenon. A seal material 5 is interposed between the electrode terminal 4 and the housing 2. When the sealing material 5 receives pressure from the electrode terminal 4 and the housing 2, the housing 2 is sealed. The sealing material 5 may be made of PP, polyethylene (PE), or the like, for example.

《Nonconductive layer》
4 is a schematic cross-sectional view showing a region IV in FIG. The nonconductor layer 6 is formed on the surface of the electrode terminal 4. The nonconductor layer 6 is a layer composed of a nonconductor. The “non-conductor” in the present specification indicates an object having a resistivity of 1 × 10 ⁴ Ω · m or more and 1 × 10 ²⁰ Ω · m or less at 20 ° C. The nonconductor layer 6 suppresses contact between the electrode terminal 4 and the electrolytic solution. The nonconductor layer 6 suppresses the electrode terminal 4 from supplying electrons to the electrolytic solution. The nonconductive layer 6 has a thickness of 5 to 30 μm, for example.

  The nonconductive layer 6 may have alkali resistance. From the viewpoint of alkali resistance, the nonconductive layer 6 may contain, for example, PP, polytetrafluoroethylene (PTFE), or the like. The nonconductive layer 6 may have gas barrier properties. From the viewpoint of gas barrier properties, the nonconductive layer 6 may contain, for example, polyvinyl alcohol (PVOH). Further, from the viewpoint of gas barrier properties, the nonconductive layer 6 may contain an oxygen scavenger (for example, Fe particles, polyhydric phenol, etc.) and the like.

  The formation method of the nonconductor layer 6 should not be specifically limited. The nonconductive layer 6 can be formed on the surface of the electrode terminal 4 by, for example, injection molding, hot melt spray coating, solution coating, or the like.

《Metallic layer》
The metal layer 7 is laminated on the nonconductive layer 6. For example, the metal layer 7 may be formed directly on the surface of the nonconductive layer 6. Alternatively, for example, an adhesive (epoxy resin) or the like may be interposed between the metal layer 7 and the nonconductive layer 6. The metal layer 7 has a thickness of 5 to 50 μm, for example.

  The metal layer 7 suppresses oxygen and water vapor in the atmosphere from reaching the electrode terminal 4. That is, the metal layer 7 has oxygen gas barrier properties and water vapor barrier properties. The metal layer 7 contains at least one of Ni and Ni—Fe. Ni and Ni-Fe exhibit excellent gas barrier properties against oxygen and water vapor. Furthermore, since Ni and Ni-Fe have alkali resistance, they are unlikely to corrode even when in contact with the electrolytic solution. In Ni—Fe, the element ratio of Ni and Fe is not particularly limited. Ni-Fe can have any conventionally known element ratio.

  The metal layer 7 may be a single layer, for example. The metal layer 7 may include a plurality of layers, for example. The metal layer 7 may be a metal foil (Ni foil or the like), for example. The metal layer 7 may be configured, for example, by stacking a Ni foil and a Ni—Fe foil.

  The metal layer 7 may contain other metals as long as it contains at least one of Ni and Ni-Fe. The metal layer 7 may contain, for example, at least one selected from the group consisting of silicon (Si), zirconium (Zr), tungsten (W), tantalum (Ta), and Cu. These metals also have oxygen gas barrier properties and water vapor barrier properties, and also have alkali resistance.

  The method for laminating the metal layer 7 on the nonconductive layer 6 should not be particularly limited. However, it is desired that the method hardly causes a gap between the metal layer 7 and the nonconductive layer 6. The metal layer 7 can be laminated on the nonconductive layer 6 by, for example, solution coating, plating, or the like.

  It should be thought that embodiment disclosed this time is an illustration and restrictive at no points. The scope of the present disclosure is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Electrolyte solution, 2 housing | casing, 3 electrode group, 4 electrode terminal, 5 sealing material, 6 nonconductor layer, 7 metal layer, 10 battery.

Claims (1)

Housing,
An electrolyte contained in the housing,
An electrode group housed in the housing;
An electrode terminal penetrating the housing; and
A sealing material interposed between the electrode terminal and the housing;
With
A nonconductive layer is formed on the surface of the electrode terminal,
A metal layer is laminated on the non-conductive layer,
The metal layer contains at least one of nickel and nickel iron alloy,
Nickel metal hydride battery.

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