JPH0745283A - Battery use electrode and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide an electrode for a battery by forming a layer containing impurities in a surface of a collector base material, and holding an active material on this layer, so as to prevent the active material from easily separating and a battery characteristic from easily deteriorating. CONSTITUTION:As a base material 2, nickel foil is immersed in a hydrochloric acid aqueous solution, to clean a main surface 2a of this base material 2. This main surface is immersed in nitric acid aqueous solution, and a layer 3 containing nickel oxide is formed in the main surface 2a. Here, surface roughness of the main surface is set to 0.4 to 3.0mum in center line mean roughness Ra and to 4mum or more in maximum height Rmax, and composition ratio of the layer 3 is set to 0.1 <= nickel oxide/nickel <= 2.5. A positive pole active material, formed into a paste shape by mixing nickel hydroxide, graphite powder, aqueous ammonia, etc., is applied to a surface 3a of the layer 3. In a secondary battery using this material in an electrode, the active material is prevented from easily separating from a collector surface, to prevent a characteristic from easily deteriorating even when repeated charge/discharge.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery electrode and a manufacturing method thereof, and more particularly to a battery electrode which can be suitably used as an electrode of a secondary battery such as a nickel-cadmium secondary battery and a manufacturing method thereof.

[0002]

2. Description of the Related Art Secondary batteries such as nickel-cadmium secondary batteries and nickel-hydrogen secondary batteries are among the secondary batteries.
It is highly reliable, has a relatively simple battery structure, is easy to maintain and handle, and has the advantages of low operating cost and economic efficiency. It is suitable for disaster prevention, home appliances, office equipment, etc. Widely used as various power sources.

Next, the battery structure will be described below by taking a nickel-cadmium alkaline secondary battery as an example.

FIG. 7 shows nickel-cadmium alkali 2
It is sectional drawing which shows the battery structure of a secondary battery schematically.

Referring to FIG. 7, this nickel-cadmium alkaline secondary battery 101 shows an example of a nickel-cadmium alkaline secondary battery as a cylindrical sealed storage battery, which comprises a positive electrode 102, a negative electrode 103, and Two separators 104 and 10 for separating the positive electrode 102 and the negative electrode 103
5 and an electrolytic solution (not shown).

The positive electrode 102 is composed of, for example, a positive electrode current collector 107 made of, for example, a nickel sintered body, and a positive electrode active material 108 held on both sides 107a and 107b of the positive electrode current collector 107.
a and 108b are included.

The negative electrode 103 is composed of, for example, a negative electrode current collector 109 made of, for example, a nickel sintered body, and a negative electrode active material 110 held on both surfaces 109a and 109b of the negative electrode current collector 109.
a, 110b.

Examples of the positive electrode active material include nickel hydroxide (Ni (OH) ₂ ) / nickel oxyhydroxide (N
iOOH) is used, and as the negative electrode active material, for example, cadmium hydroxide (Cd (OH) ₂ ) / cadmium (Cd) is used.

As the separators 104 and 105, for example, microporous polyethylene or the like is used.

As the electrolytic solution (not shown), for example, an alkaline aqueous solution of potassium hydroxide (KOH), sodium hydroxide (NaOH), lithium hydroxide (LiOH) or the like is used.

As a positive electrode active material, nickel hydroxide (Ni
(OH)₂) / Nickel oxyhydroxide (NiOOH)
Cadmium hydroxide (Cd (O
H) ₂) / Nicke with cadmium (Cd)
The charging / discharging reaction of a ru-cadmium alkaline secondary battery is as follows.
Indicated by.

[0012]

[Chemical 1]

An electromotive force of about 1.30 V is obtained by the above charge / discharge reaction. Next, a process of assembling the nickel-cadmium alkaline secondary battery 101 will be described below.

First, both sides 107a of the positive electrode current collector 107,
The positive electrode active material 108a and 108b are held by 107b, and the positive electrode 102 is produced.

In addition, both surfaces 109a of the negative electrode current collector 109,
The negative electrode active material 110a and 110b are held by 109b, and the negative electrode 103 is produced.

Next, the negative electrode 103, the separator 105, the positive electrode 102, and the separator 104 are laminated in this order to produce a laminated body (not shown).

Next, the spirally wound electrode body 111 is manufactured by winding a large number of spirals around this laminated body (not shown).

Next, the spirally wound electrode body 111 is housed in, for example, a nickel-plated iron battery can 112.

Next, the upper surface 111u of the spirally wound electrode body 111,
Insulating plates 113 and 114 are arranged on the lower surface 111d.

Next, the negative electrode lead 115 made of, for example, nickel and led out from the negative electrode current collector 109 is attached to the battery can 112.
Weld to the bottom of the. Further, the positive electrode lead 116 made of, for example, nickel, which is led out from the positive electrode current collector 107, is welded to the protruding portion 117 a of the metal safety valve 117.

Next, in the battery can 112, as an electrolytic solution,
For example, a small amount of lithium hydroxide (LiOH) is added and a potassium hydroxide (KOH) aqueous solution having a specific gravity of about 1.20 to 1.25 (20 ° C.) is filled.

Next, the battery can 112, the safety valve 117 and the metal battery lid 118 whose outer circumferences are in close contact with each other are caulked through the insulating sealing gasket 119 whose surface is coated with asphalt, etc. Can 1
A nickel-cadmium alkaline secondary battery 101 is manufactured by sealing 12.

Next, the electrode structures of the positive electrode and the negative electrode will be described in more detail. FIG. 8 is an enlarged schematic sectional view of the electrode structure of the positive electrode 102.

Referring to FIG. 8, the positive electrode 102 includes a strip-shaped positive electrode current collector 107 and positive electrode active materials 108a and 108b.
including.

As described above, the positive electrode current collector 107 is made of a porous base material such as a nickel sintered body. The positive electrode active materials 108a and 108b are formed on the pair of main surfaces 107a and 107b of the positive electrode current collector 107,
And the pores 107 existing inside the positive electrode current collector 107.
It is held on the surface 107ha of h.

To manufacture such a positive electrode 102, in order to fill the pores 107h of the nickel sintered body with the positive electrode active material, for example, an impregnation step such as a chemical impregnation method, an alkali treatment step, a water washing step, Many steps such as a drying step are required, and these steps are repeated several times for the purpose of improving the packing density of the positive electrode active material on the current collector.

The negative electrode 103 is the positive electrode active material 108.
negative electrode active material 109a, 109b instead of a, 108b
Since the electrode structure is the same as that of the positive electrode 102 except that is provided, the description thereof will be omitted. The process of manufacturing the negative electrode 102 is the same as the process of manufacturing the positive electrode 102, and thus the description thereof is omitted.

The term "surface" used in the present specification means
When the current collector is a porous member, it means both the surface that defines the outer shape (hereinafter referred to as the main surface) and the surface of the pores existing inside the current collector. When the current collector is a dense member manufactured by rolling or the like,
"Surface" means the major surface.

By the way, the above-mentioned electrode (positive electrode or negative electrode) is required to satisfy the following conditions.

(1) When the current collector constituting the electrode is a porous member, it is required to increase porosity (porosity).

This is because good battery characteristics can be obtained by increasing the porosity of the current collector and improving the packing density of the current collector.

(2) The electrode is required to have appropriate mechanical strength and flexibility. This is because if cracks or the like occur in the electrode in the process of manufacturing the electrode and / or the battery, the productivity will decrease.

(3) The active material is required to be hardly peeled from the surface of the current collector. This is because if the active material is peeled off from the surface of the current collector, the battery characteristics deteriorate.

(4) The active material and the current collector are required to have strong adhesion at the interface.

This is because the adhesion at the interface between the active material and the current collector has a great influence on the quality of the electrical contact between the active material and the current collector.

When the conventional nickel sintered body as described above is used as the current collector, the porosity of the current collector is at most
It is about 70% to 80%.

Therefore, a nickel-cadmium alkaline secondary battery using a battery electrode in which an active material is held on the surface of a nickel sintered body cannot obtain a good energy density.

If the porosity of the nickel sintered body is increased to 80% or more for the purpose of increasing the energy density of the nickel-cadmium alkaline secondary battery or the like, the mechanical strength of the current collector is significantly reduced. In addition, there are problems such that the electrode is easily cracked due to bending and the active material is easily separated from the surface of the current collector.

As a technique for solving such a problem, a battery electrode using a foam nickel substrate instead of a nickel sintered body as a current collector is known (Japanese Patent Publication No. 4-301).
45).

The foamed nickel substrate is a sponge-like foamed nickel substrate, which is a porous member having a fine pore structure inside the nickel substrate.

The foamed nickel substrate has an advantage that it has mechanical strength required for a battery electrode against bending and compression even when the porosity is increased to 90% or more.
For this reason, recently, a foamed nickel substrate is used as a current collector, and a positive electrode having a positive electrode active material such as nickel hydroxide held on the surface of the foamed nickel substrate or a surface of the foamed nickel substrate such as cadmium hydroxide. An electrode for a thin battery such as a negative electrode that holds a negative electrode active material has been prototyped and proposed.

[0042]

However, the battery electrode including the conventional nickel sintered body or the current collector made of the foamed nickel substrate and the active material held on the surface of the current collector is used. The nickel-cadmium alkaline secondary battery or the like has a problem that the battery characteristics such as charge / discharge cycle characteristics deteriorate as the charging / discharging operation is repeated.

The present inventors have used a battery electrode including a conventional nickel sintered body or a current collector made of a foamed nickel substrate, and an active material held on the surface of the current collector.
When a cause of deterioration of battery characteristics such as charge / discharge cycle characteristics of a nickel-cadmium alkaline secondary battery and the like was repeated as charging / discharging operations were repeated, the following causes were found.

In an electrode in which the active material is directly held on the surface of a current collector made of a nickel sintered body or a foamed nickel substrate, the electrolytic solution of the battery is the surface of the current collector and the surface of the active material. And the nickel sintered body or the foamed nickel substrate and the electrolytic solution directly cause a chemical reaction,
A substance (a by-product) having a high electrical insulation property such as nickel oxide is generated on the surface of the current collector, and hydrogen (H ₂ ), oxygen (O ₂ ) and the like are generated on the surface of the current collector. Gas is generated.

When a substance (a by-product) having a high electrical insulation property is formed on the surface of the current collector, the internal resistance of the battery increases,
As a result, the electromotive force of the battery decreases.

Further, when gas is generated on the surface of the current collector, the gas causes the active material to peel off from the surface of the current collector, resulting in a decrease in battery capacity and deterioration of charge / discharge cycle characteristics. To do

Further, when a substance (by-product) having a high electrical insulation property is generated on the surface of the current collector or a gas is generated on the surface of the current collector, the current collector and the active material are separated from each other. The adhesiveness of the battery is lowered, and as a result, smooth electron transfer between the current collector and the active material is hindered, and the battery characteristics are gradually deteriorated.

In addition, during use of the battery, the active material and / or the current collector expands or contracts with repeated charging / discharging operations, whereby the current collector and the active material come into close contact with each other. As a result, the smooth movement of electrons between the current collector and the active material is hindered, and the battery characteristics are gradually deteriorated.

The present invention has been made to solve the above problems, and reduces the chemical reaction (side reaction) between the current collector and the electrolytic solution on the surface of the current collector. Prevents the active material from peeling off from the surface of the current collector by suppressing an increase in the electrical resistance of the current collector, or the adhesion between the active material and the current collector decreases even after repeated charge and discharge operations. It is an object of the present invention to provide a battery electrode and a method for manufacturing the same, which is difficult to do so that battery characteristics such as charge / discharge cycle characteristics are less likely to deteriorate.

[0050]

In order to solve the above problems, the present inventors consider that it is indispensable to modify the surface of the current collector, and are eager to modify the surface of the current collector. As a result of research, a nickel-based material in which the surface of the nickel-based material is oxidized, a dissimilar metal is added to the surface of the nickel-based material, and / or the surface of the nickel-based material is roughened to a predetermined condition It was found that when the material is used as an electrode of a secondary battery such as a nickel-cadmium alkaline secondary battery, a battery having excellent battery characteristics such as charge / discharge cycle characteristics can be provided, and the present invention has been completed. It was

The battery electrode according to the first invention comprises a substrate,
A current collector including an impurity-containing layer formed on the surface of the base material, and an active material held on the surface of the impurity-containing layer of the current collector.

The main surface of the current collector preferably has a center line average roughness (Ra) of 0.4 μm or more and 3.0 or less.
It is characterized by being less than or equal to μm.

The surface roughness of the main surface of the current collector is more preferably characterized in that the maximum height (Rmax) is 4 μm or more.

Next, the definition of surface roughness will be described below. Regarding the surface roughness, the center line average roughness (Ra) and the maximum height (Rma) are defined in JIS B0601.
x) and ten-point average roughness (Rz) are respectively defined.

FIG. 9 is for explaining the definition of the center line roughness (Ra), and is a cross-sectional view of the uneven surface. As shown in FIG. 9, the center line is drawn so that the areas surrounded by the surface irregularities (cross-sectional curves) and the straight line are equal on both sides of this straight line. The cross section curve is represented by y = f (x) with the center line as the x-axis and the vertical direction as the y-axis. At this time, the value obtained from the following equation in units of micrometers (μm) is defined as the center line roughness (Ra).

[0056]

[Equation 1]

Further, FIG. 10 is a cross-sectional view of the uneven surface for explaining the definition of the maximum height (Rmax).

As shown in FIG. 10, when a section curve is sandwiched by two straight lines parallel to the center line, the distance between the two straight lines is measured in the y direction of the section curve, and this value is measured in micrometers (μ).
The maximum height (Rmax) is defined in m).

By appropriately roughening the surface of the current collector, the adhesion between the surface of the current collector and the active material is improved.

Further, the battery electrode according to the first invention is preferably characterized in that the base material is a nickel base material and the impurities are nickel oxides.

The surface of the layer containing the impurities of the current collector is
Preferably, the composition ratio of nickel and nickel oxide is
It is characterized in that 0.1 ≦ nickel oxide / nickel ≦ 2.5.

The composition ratio of nickel and nickel oxide can be calculated, for example, from the XPS spectrum intensity ratio.

The XPS spectrum intensity ratio is, for example,
It is a value quantitatively calculated by surface analysis by photoelectron spectroscopy using an X-ray photoelectron spectrometer (ESCA or XPS).

The base material of the battery electrode according to the first invention is preferably a nickel base material, and the impurities are titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron. It is characterized by containing at least one selected from the group consisting of (Fe) and cobalt (Co).

At least one selected from the group consisting of titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe) and cobalt (Co) (hereinafter referred to as "heteroatom"). The surface of the layer containing impurities preferably has a composition ratio of nickel and the heteroatom of 1
It is characterized in that 0/100 ≦ heteroatom / nickel ≦ 100/100. The composition ratio of nickel and the heteroatom is
For example, it can be calculated from the XPS spectrum intensity ratio.

A method of manufacturing a battery electrode according to a second aspect of the present invention is a method of manufacturing a battery electrode including a current collector made of a nickel base material, wherein the main surface of the nickel base material has a Baume degree of 48 °. The method includes a step of roughening using a ferric chloride aqueous solution of Be 'or less and a step of holding an active material on the surface of a nickel base material having a roughened main surface.

The concentration of the ferric chloride aqueous solution is 4 in terms of Baume degree.
It is preferably 8 ° Be ′ or less, and more preferably 20 ° Be ′ or more and 45 ° Be ′ or less.

The term "Baume degree" used in the present specification
Is a scale obtained with a Baume hydrometer, and the Baume degree (in the present specification, is represented by ° Be 'for convenience of notation).
Is 0 ° Be 'for pure water and 66 ° Be' for concentrated sulfuric acid with d ¹⁵ = 1.8249.
The unit used in the range of e'to 72 ° Be '(see RIKEN).

D = 1443.3 / (1443.3-B) In the formula, d is the density, and B is the Baume degree.

[0070]

The battery electrode according to the first invention has the following structure.

(1) The current collector comprises a base material and an impurity-containing layer formed on the surface of the base material.

(2) The active material is retained on the surface of the layer containing the impurities of the current collector. In the battery electrode according to the first aspect of the invention, the layer containing impurities formed on the surface of the base material prevents deterioration of the battery characteristics of the secondary battery using the battery electrode according to the first aspect of the invention. It is not clear about the mechanism of action itself.

However, in the secondary battery using the battery electrode according to the first invention, the deterioration of the charge / discharge cycle characteristics of the secondary battery is suppressed even when the charge / discharge operation is repeated. The following mechanism of action is presumed as the mechanism of action of the layer containing impurities formed on the surface of the base material.

(1) Action Mechanism for Deterioration of Charge / Discharge Cycle Characteristics of Battery when Impurity is Oxide Below, a nickel base material is used as a base material, and impurities oxidize the surface of the nickel base material. The operation mechanism of the first invention will be described below by taking as an example a battery electrode which is a nickel oxide formed by the above process.

Growing an oxide film of nickel oxide or the like on the surface of the nickel base material increases the electric resistance of the surface of the nickel base material and hinders electron transfer between the nickel base material and the battery active material. While causing the cause, at the same time, it is possible to reduce the chemical reaction (side reaction) between the nickel base material and the electrolytic solution of the battery. That is, on the surface of the current collector, charge transfer to a substance that does not participate in the charge / discharge reaction is hindered.

Therefore, if a layer containing nickel oxide is grown as an electrode with an appropriate film thickness that does not cause a fatal increase in electrical resistance, the chemical reaction between the nickel base material and the electrolytic solution of the battery is performed. The reaction (side reaction) is reduced, and it is possible to suppress the generation and accumulation of a substance (by-product) having a high electrical insulation property such as nickel oxide on the surface of the current collector.

As a result, it is considered that the deterioration of the charge / discharge cycle characteristics due to the accumulation of the substance (by-product) having a high electrical insulation property can be suppressed.

(2) Action mechanism for suppressing deterioration of charge / discharge cycle characteristics of battery when impurities are heteroatoms: A nickel base material is used as the base material, and the impurities are titanium (Ti) and vanadium. (V), Chromium (Cr), Manganese (Mn), Iron (Fe) and Cobalt (Co) At least one selected from the group consisting of at least one battery electrode will be taken as an example to describe the mechanism of action of the first invention. This will be described below.

One of the factors that determines the electrochemical process can be the exchange current density between the electrode surface material and the chemical species in the electrolyte. "Exchange current density" is a measure of the ease with which a current can flow between a redox couple and a material when a certain material is immersed in an electrolyte containing the redox couple. . The value of the exchange current density depends on both the material and the redox couple in the electrolyte and is not determined by either one alone. In addition, the fact that the exchange current density is high means that the oxidation or reduction reaction of the redox couple is likely to occur on the surface of the material.

Therefore, in order to suppress side reactions other than the charge / discharge reaction, a material having a low exchange current density with the redox couple which may cause the side reaction may be used as the electrode.

The present inventors have found that titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (F).
It was found that the deterioration of charge / discharge cycle characteristics due to the repeated charge / discharge operation of the secondary battery can be suppressed by using the current collector having e) and cobalt (Co) supported on the surface of the nickel base material. The reason is that the above-mentioned carrying of the heteroatom (metal) changes the physical properties of the surface of the current collector and reduces the exchange current density between the surface of the current collector and the redox couple that may cause a side reaction. It is thought that there is.

(3) Working Mechanism of Suppressing Deterioration of Charge / Discharge Cycle Characteristics of Battery When Roughening Main Surface of Current Collector Main surface of current collector is appropriately roughened by roughening It is considered that the substantial surface area of the current collector is increased. It is considered that the active material coated on the surface of the current collector repeats expansion and contraction as the charging / discharging operation is repeated. It is considered that there is an active material that is peeled (desorbed) from the surface of the current collector as the active material expands and contracts.

In the battery electrode according to the first aspect of the present invention, by appropriately roughening the main surface of the current collector, the adhesion between the active material and the main surface of the current collector is improved, and charge / discharge operation is improved. It is considered that peeling (desorption) of the active material that expands and contracts with the repetition from the main surface of the current collector was suppressed, and deterioration of charge-discharge cycle characteristics was suppressed.

A method of manufacturing a battery electrode according to the second aspect of the present invention is a method of manufacturing a battery electrode including a current collector made of a nickel base material, and includes the following steps.

(1) A step of roughening the main surface of the nickel base material with an aqueous solution of ferric chloride having a Baume degree of 48 ° Be 'or less is provided.

(2) Providing a step of holding the active material on the surface of the nickel base material whose main surface is roughened.

The step of roughening the main surface of the nickel base material with an aqueous solution of ferric chloride is considered to proceed by the following mechanism.

First step: Fe ³⁺ ions are adsorbed on the surface of the nickel base material.

Second step: Fe ³⁺ ions adsorbed on the surface of the nickel base material exchange electrons with nickel constituting the nickel base material.

[0090]

[Chemical 2]

Third step: From the surface of the nickel base material,
Fe ²⁺ is ^dissociated , metallic nickel (Ni ⁰ ) atoms are ^dissociated as Ni ²⁺ from the surface of the nickel base material, or Ni ²⁺ is deposited as Ni ⁰ on the surface of the nickel base material. To do.

In the second aspect of the present invention, the main surface of the nickel base material is simultaneously etched in the depth direction and the Ni ⁰ is deposited on the main surface of the nickel base material at the same time.

Further, in the second invention, the concentration of the second aqueous chloride solution is appropriately selected. Therefore, according to the second aspect of the present invention, the main surface of the nickel base material has a Baume degree of 48 ° B.
In the step of roughening with an aqueous solution of ferric chloride having an e ′ or less, a nickel base material having a desired surface roughness,
It can be manufactured efficiently.

Then, a nickel base material having a desired surface roughness produced in the step of roughening the main surface of the nickel base material with an aqueous ferric chloride solution having a Baume degree of 48 ° Be 'or less. Can be used as it is as a current collector, and an active material is held on the surface of the current collector, whereby a battery electrode can be manufactured. In the battery electrode manufactured according to the second invention, the surface of the current collector is roughened to a desired surface roughness, so that the adhesion between the surface of the current collector and the active material is improved. ing.

[0095]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to the following examples.

Example 1 and Comparative Example 1 FIG. 1 is a sectional view schematically showing an example of a battery electrode according to the present invention.

Referring to FIG. 1, this battery electrode 1 includes a current collector 4 and an active material 5. The current collector 4 includes the base material 2,
A layer 3 containing impurities formed on the main surface 2a of the base material 2. The active material 5 is held on the surface 3a of the layer 3 containing impurities.

Next, description will be made using concrete data.
Example 1 shows an example in which a dense member having almost no pores inside is used as the base material 2, and a current collector having an oxide-containing layer is used as the impurity-containing layer 3.

(1) Adjustment of Current Collector As the substrate 2, a commercially available nickel foil manufactured by rolling or the like (manufactured by Niraco, purity 99.5%, thickness 20 μm)
Prepared.

Next, 1 mol of this nickel foil was used.
The main surface 2a of the nickel foil was cleaned by immersing it in a hydrochloric acid aqueous solution of 1 / liter.

Next, by immersing the nickel foil whose main surface 2a is cleaned in an aqueous nitric acid solution, the main surface 2a of the nickel foil, more specifically, the main surface 2a and / or the main surface 2a, is covered with the nickel foil. A layer containing nickel oxide was formed to spread toward the inside of the.

The layer containing nickel oxide is formed of nickel (N
i) and nickel oxide (for example, NiO) coexist. Nickel (N
The composition ratio between i) and nickel oxide varies depending on the degree of oxidation of the main surface 2a of the nickel foil.

The composition ratio of nickel and nickel oxide is different on the main surface 2a of the nickel foil by adjusting the time for immersing the nickel foil in the nitric acid aqueous solution and / or adjusting the concentration, temperature and the like of the nitric acid aqueous solution. , Layers with various nickel oxides were formed and labeled Samples 1-7.

For each of Samples 1 to 7, at least two samples, a sample used as a positive electrode current collector and a sample used as a negative electrode current collector, were prepared.

Next, for each of Samples 1 to 7, a photoelectron spectrometer (Perkin Elmer ESCA5400M) was used.
C), the composition ratio of nickel and nickel oxide present on the surface 3a of the layer containing nickel oxide formed in each of Samples 1 to 7 by photoelectron spectroscopy (ESCA), nickel oxide / Nickel was analyzed quantitatively.

In the case of nickel, the position of the peak of the photoemission spectrum due to 2p _3/2 electrons is 852.3 eV in the case of pure nickel, and in the case of nickel, the peak position of the photoemission spectrum as nickel is oxidized. The position of the peak shifts to the high energy side. In this example, a pure nickel peak at a position of 852.3 eV and 8
The intensity ratio with respect to the peak of nickel oxide at the position of 53.3 eV was determined by assuming a Gaussian distribution, and defined as the nickel oxide / nickel composition ratio (R _Ni ).

The results are shown in Table 1. For comparison, a nickel foil similar to the nickel foil used in Samples 1 to 7 was prepared, and this nickel foil was used at 1 mol / mol (l).
The main surface 2a of the nickel foil was cleaned by immersing the nickel foil in the iter) aqueous hydrochloric acid solution, and the nickel foil having the cleaned main surface 2a was labeled as Sample 8.

As for the sample 8, at least two samples, that is, a sample used as a positive electrode current collector and a sample used as a negative electrode current collector were prepared.

Next, with respect to Sample 8, the composition ratio (R _Ni ) of nickel and nickel oxide present on the main surface 2a of the nickel foil was quantified by the same photoelectron spectroscopy (ESCA) as in Samples 1 to 7. analyzed.

The results are shown in Table 1. (2) Preparation of Electrodes Next, using Samples 1 to 7, positive electrodes A _{1 to} A ₇ and negative electrodes B _{1 to} B ₇ were prepared.

That is, for each of the samples used as the positive electrode current collector of each of samples 1 to 7, by coating the surface 3a of the layer containing nickel oxide with the positive electrode active material, the positive electrodes A _{1 to} A _{1 7} was produced. Note that nickel hydroxide (Ni (OH) ₂ ) was used as the positive electrode active material. More specifically, each of Samples 1 to 7 used as the positive electrode current collector was coated on its surface with a mixture of nickel hydroxide, graphite powder, aqueous ammonia and the like in the form of a paste.

For each of the samples used as the negative electrode current collectors of samples 1 to 7, by supporting the negative electrode active material on the surface 3a of the layer containing nickel oxide, the negative electrodes B _{1 to} B _{7 were formed.} Was produced. Cadmium hydroxide (Cd (OH) ₂ ) was used as the negative electrode active material. More specifically, the surface of each sample used as the negative electrode current collector of each of Samples 1 to 7 was coated with a paste that was prepared by mixing cadmium hydroxide, graphite powder, aqueous ammonia, and the like.

(3) Preparation of Battery FIG. 2 is a sectional view schematically showing the nickel-cadmium alkaline secondary battery prepared in this example.

Referring to FIG. 2, this nickel-cadmium alkaline secondary battery 6 has a positive electrode 11, a negative electrode 21, a separator 7 for separating the positive electrode 11 and the negative electrode 21, a container 8, and an electrolytic solution 9. Including and

The positive electrode 11 includes a positive electrode current collector 14 and a positive electrode active material 15. The positive electrode current collector 14 includes a nickel foil 12 and
And a layer 13 containing nickel oxide formed on the main surface 12a of the nickel foil 12. The positive electrode active material 15 is held on the surface 13a of the layer 13 containing nickel oxide.

On the other hand, the negative electrode 21 has the same structure as the positive electrode 11. That is, the negative electrode 21 includes the negative electrode current collector 24 and the negative electrode active material 25. The negative electrode current collector 24 is the nickel foil 2
2 and a layer 23 containing nickel oxide formed on the main surface 22a of the nickel foil 22. Negative electrode active material 25
Are retained on the surface 23a of the layer 23 containing nickel oxide.

The storage tank 8 is partitioned by the separator 7, and the storage tank 8 stores the electrolytic solution 9.

As the separator 7, a microporous polyethylene film was used. Further, as the electrolytic solution 9, a potassium hydroxide (KOH) aqueous solution was used.

Next, the positive electrodes A _{1 to} A ₇ and the negative electrodes B _{1 to} B
₇ using nickel cadmium secondary battery C ₁ shown in Table _1.
The ~C ₇ were prepared.

For comparison, positive electrode A ₈ and negative electrode B
₈ and nickel-cadmium alkali 2 shown in Table 1
Next battery C ₈ was produced.

Next, using the nickel-cadmium alkaline secondary batteries C _{1 to} C ₈ produced as described above, at a current density of 10 mA / cm ² at 25 ° C. in a conventional manner,
A charging / discharging cycle in which one cycle consists of charging for 10 hours and discharging at 10 mA / cm ² for 8 hours was repeated.

Nickel-Cadmium Alkaline Secondary Battery C
Each of the charge and discharge voltage drop of the battery at the first charge-discharge cycle of ₁ -C ₈ and (V), charge-discharge voltage drop value of the battery at the 50th charge-discharge cycles and (V) was measured.

The charging / discharging voltage drop value (V) indicates the magnitude of the voltage drop of the battery when switching from charging to discharging. The larger the charging / discharging voltage drop value (V), the more It shows that the internal resistance is large and the energy efficiency of the battery is poor.

The results are shown in Table 1.

[0125]

[Table 1]

As is clear from the results of Table 1, the nickel oxide / nickel composition ratio (R _Ni ) is 0.1 or more.2.
It can be seen that when it is 5 or less, deterioration of the charge / discharge cycle characteristics is suppressed as compared with Comparative Example 1.

Example 2 and Comparative Example 2 Example 2 shows an example in which a porous member was used as the base material and a current collector having an oxide-containing layer was used as the impurity-containing layer.

FIG. 3 is a sectional view schematically showing an embodiment of the battery electrode according to the present invention. With reference to FIG. 3, this battery electrode 31 includes a current collector 34 and an active material 35. The current collector 34 includes a porous base material 32 and pores 32 existing inside the main surface 32 a of the base material 32 and the base material 32.
and a layer 33 containing impurities formed on the surface 32ha of h. The active material 35 is the surface 33 of the layer 33 containing impurities.
a, held at 33 ha.

Next, description will be made using concrete data. (1) Adjustment of Current Collector As the base material 32, a nickel mesh porous body (trade name Celmet, manufactured by Sumitomo Electric Industries, Ltd., porosity 95%, average pore diameter 150 μm, thickness 1 mm) was prepared.

FIG. 11 is a schematic view showing this nickel mesh porous body. In FIG. 11, 32 indicates a nickel mesh porous body, and 32h indicates pores.

Then, in the same manner as in Example 1, 1 mol (mol) / liter (liter) of this nickel reticulated porous body was used.
By dipping in the aqueous hydrochloric acid solution of r), the main surface 32a of the nickel reticulated porous body and the surface 32ha of the pores 32h existing inside the nickel reticulated porous body were cleaned.

Then, in the same manner as in Example 1, the nickel reticulated porous body having the cleaned surface was dipped in an aqueous nitric acid solution so that the main surface 32a of the nickel reticulated porous body and the inside of the nickel reticulated porous body were exposed. A layer containing nickel oxide was formed on the surface 32ha of the existing pores 32h.

The composition ratio of nickel to nickel oxide in the layer containing nickel oxide depends on the degree of oxidation of the main surface 32a of the nickel mesh porous body and the surface 32ha of the pores 32h existing inside the nickel mesh porous body. Will be different.

By immersing the nickel reticulated porous body in an aqueous nitric acid solution and / or adjusting the concentration, temperature and the like of the nitric acid aqueous solution, the main surface 3 of the nickel reticulated porous body is adjusted.
2a and pores 3 present inside the nickel reticulated porous body
Layers containing various nickel oxides having different composition ratios of nickel and nickel oxides were formed on the surface 32ha of 2h, and the samples 9 to 15 were labeled.

For each of Samples 9 to 15,
At least two samples, a sample used as a positive electrode current collector and a sample used as a negative electrode current collector, were prepared.

Next, for each of the samples 9 to 15,
By the same photoelectron spectroscopy (ESCA) as in Example 1, the composition ratio of nickel and nickel oxide existing on the surface of the layer containing nickel oxide formed in each of Samples 9 to 15 was quantitatively analyzed.

That is, each of Samples 9 to 15 was cut into a rod shape having a length of 5 mm, and this was used as a sample for photoelectron spectroscopy, and a photoelectron spectrometer (ESCA5 manufactured by Perkin Elmer Co., Ltd.) was used.
400MC) of the surface of the nickel reticulated porous body,
The composition ratio of nickel and nickel oxide was determined.

The results are shown in Table 2. Also, for comparison, a nickel reticulated porous body similar to the nickel reticulated porous body used in Samples 9 to 15 was prepared, and this nickel reticulated porous body was immersed in a 1 mol (mol) / liter (liter) hydrochloric acid aqueous solution. The main surface 3 of the nickel reticulated porous body is
2a and pores 3 present inside the nickel reticulated porous body
The surface of the surface 32ha of 2h was cleaned, and the nickel reticulated porous body in which the main surface 32a and the surface 32ha of the pores 32h were cleaned was labeled as Sample 16.

As for the sample 16, at least two samples, that is, a sample used as a positive electrode current collector and a sample used as a negative electrode current collector were prepared.

Next, with respect to Sample 16, the composition ratio of nickel and nickel oxide present on the surface 32a of the layer containing nickel oxide was quantitatively analyzed by the same photoelectron spectroscopy (ESCA) as in Samples 9 to 15. .

The results are shown in Table 2. (2) Preparation of Electrodes Next, using Samples 9 to 15, positive electrodes A _{9 to} A ₁₅ and negative electrodes B _{9 to} B ₁₅ were prepared.

That is, for each of the samples used as the positive electrode current collector of each of the samples 9 to 15, the surface 33a of the layer containing nickel oxide was impregnated with the positive electrode active material and coated to form the positive electrodes A _{9 to} A _{9. 15} were produced. Note that nickel hydroxide (Ni (OH) ₂ ) was used as the positive electrode active material. More specifically, nickel hydroxide is added to the surface of the sample used as the positive electrode current collector of each of Samples 9 to 15,
A paste obtained by mixing graphite powder and aqueous ammonia was applied to form a positive electrode.

For each of the samples used as the negative electrode current collector of each of samples 9 to 15, negative electrodes B _{9 to} B ₁₅ were obtained by impregnating and supporting the negative electrode active material on the surface 33a of the layer containing nickel oxide. It was made. Cadmium hydroxide (Cd (OH) ₂ ) was used as the negative electrode active material. More specifically, on the surface of the sample used as the negative electrode current collector of each of Samples 9 to 15, cadmium hydroxide and
A graphite powder and ammonia water were mixed to form a paste, which was applied to form a negative electrode.

In the step of producing the electrode, if the pore diameter of the nickel reticulated porous body is small, it may be difficult for the battery active material to enter the inside of the nickel reticulated porous body. By appropriately adjusting the concentration, it is possible to uniformly support the battery active material inside the nickel mesh porous body.

For comparison, Sample 16 was used to prepare positive electrode A ₁₆ and negative electrode B ₁₆ . That is, with respect to the sample used as the positive electrode current collector of the sample 16, the positive electrode 16 was manufactured by impregnating and coating the cleaned main surface 32a and the cleaned surfaces of the pores 32h with the positive electrode active material.
As the positive electrode active material, nickel hydroxide (Ni (O
H) ₂ ) was used.

Regarding the sample used as the negative electrode current collector of sample 16, the cleaned main surface 32a and pores 32 were prepared.
A negative electrode B ₁₆ was prepared by impregnating and supporting a negative electrode active material on the cleaned surface of h.

Cadmium hydroxide (Cd (OH) ₂ ) was used as the negative electrode active material. (3) Preparation of Battery Example 1 using positive electrodes A _{9 to} A ₁₅ and negative electrodes B _{9 to} B ₁₅
Nickel-Cadmium Alkali 2 shown in Table 2, similar to
The following cell C ₉ -C ₁₅ were prepared.

For comparison, positive electrode A ₁₆ and negative electrode B
₁₆ using nickel-cadmium alkali 2 shown in Table 2.
Next battery C ₁₆ was produced.

Next, using the nickel-cadmium alkaline secondary batteries C _{9 to} C ₁₆ produced as described above, in the same manner as in Example 1, charge at 25 ° C. and a current density of 10 mA / cm ² for 8 hours. Then, the charging / discharging operation in which one cycle is the operation of discharging at a current density of 10 mA / cm ² for 8 hours was repeated for each of the batteries C _{9 to} C ₁₆ .

Nickel-Cadmium Alkaline Secondary Battery C
The charge / discharge voltage drop value (V) of the battery in the first charge / discharge cycle of each of _{9 to} C ₁₆ and the charge / discharge voltage drop value (V) of the battery in the 50th charge / discharge cycle were measured.

The results are shown in Table 2.

[0152]

[Table 2]

As is clear from the results of Table 2, when the nickel oxide / nickel composition ratio is 0.1 or more and 2.5 or less, deterioration of charge / discharge cycle characteristics is suppressed as compared with Comparative Example 2. You can see that An experiment similar to that of Example 2 was performed using a nickel sintered body (porosity 80%) or a foamed nickel base material (porosity 95%) instead of the nickel reticulated porous body. Was the result. In Examples 1 and 2, when forming a layer containing impurities on the surface of a substrate having a cleaned surface,
Although the example using the nitric acid aqueous solution is shown, various methods can be used as the step of forming the layer containing impurities on the surface of the substrate having the cleaned surface.

For example, as such a method, a substrate having a cleaned surface may be heated in air.

When a nickel base material is used as the base material, the heating temperature is preferably 250 ° C. or higher and 700 ° C. or lower, and more preferably 300 ° C. or higher and 500 ° C. or lower.

The composition ratio of nickel and nickel oxide in the layer containing nickel oxide varies depending on the degree of oxidation of the surface of the nickel base material.

Generally, the rate of metal oxidation depends on the heating temperature,
The higher the heating temperature and / or the higher the oxygen content in the atmosphere during heating, the faster the heating rate, although it depends on the oxygen content in the atmosphere during heating.

Example 3 and Comparative Example 2 In Example 3, a dense member having almost no pores inside was used as the base material, and as the layer containing impurities, a different kind of metal from the base material was used. An example using a current collector having a layer containing a metal is shown.

FIG. 4 is a sectional view schematically showing an embodiment of the battery electrode according to the present invention. With reference to FIG. 4, the battery electrode 41 includes a current collector 44 and an active material 45. The current collector 44 includes a porous base material 42 and an impurity-containing layer 43 formed on the main surface 42 a of the base material 42. The active material 45 is held on the surface 43a of the layer 43 containing impurities.

Next, description will be made using concrete data. (1) Adjustment of Current Collector As the base material 42, a commercially available nickel foil manufactured by rolling or the like (manufactured by Niraco, purity 99.5%, thickness 20 μ)
m) was prepared.

Next, 1 mol of this nickel foil was used.
The main surface 42a of the nickel foil was cleaned by immersing it in a 1 / liter (liter) aqueous solution of hydrochloric acid.

Next, by using an ion accelerator (manufactured by Nisshin Denki Co., Ltd.) by the ion beam method, the main surface 42a of the nickel foil is formed.
By implanting cobalt (Co ⁺ ) ions into
The main surface 42a of the nickel foil, more specifically, the main surface 4
A layer containing cobalt (Co) as an impurity that spreads from 2a toward the inside of the nickel foil was formed.

In the layer containing cobalt (Co) as an impurity, nickel (Ni) and cobalt (Co) coexist. The composition ratio of nickel (Ni) and cobalt (Co) in the layer containing cobalt (Co) as an impurity depends on the acceleration voltage, the amount of electricity such as current, and the injection time when implanting cobalt ions into the nickel foil. It can be controlled by adjusting.

The acceleration voltage when implanting cobalt (Co ⁺ ) ions into the main surface 42a of the nickel foil is 1 MeV.
And the irradiation amount was set to 1 × 10 ³ counts / sec, and by adjusting the injection time, various cobalts having different composition ratios of nickel (Ni) and cobalt (Co) were formed on the main surface 42a of the nickel foil. A layer containing (Co) as an impurity was formed and labeled with Samples 17 to 23.

Next, for each of Samples 17 to 23, the same apparatus as in Example 1 was used and photoelectron spectroscopy (ES
CA), the composition ratio of nickel (Ni) and cobalt (Co) existing on the surface 43a of the layer containing cobalt (Co) as an impurity, cobalt (Co) / nickel (N).
The composition ratio (R _{Co / Ni} ) of i) was quantitatively analyzed.

The results are shown in Table 3. For comparison, a nickel foil similar to the nickel foil used in Samples 17 to 23 was prepared, and this nickel foil was immersed in a 1 mol (mol) / liter (liter) hydrochloric acid aqueous solution,
The main surface 42a of the nickel foil was cleaned, and the nickel foil having the cleaned main surface 42a was labeled as Sample 24.

Next, for sample 24, samples 17 to 2
By the same photoelectron spectroscopy as in No. 3, the main surface of the nickel foil 4
The composition ratio of nickel (Ni) and cobalt (Co) present in 2a and the ratio of cobalt (Co) / nickel (Ni) (R _{Co / Ni} ) were quantitatively analyzed.

The results are shown in Table 3. (2) Production of Electrodes Next, in the same manner as in Example 1, Samples 17 to 23 were used to produce positive electrodes A _{17 to} A ₂₃ and negative electrodes B _{17 to} B ₂₃ .

For comparison, Sample 24 was used to prepare positive electrode A ₂₄ and negative electrode B ₂₄ . (3) Preparation of Battery Example 1 using positive electrodes A _{17 to} A ₂₃ and negative electrodes B _{17 to} B ₂₃
Nickel-cadmium alkaline secondary battery C ₁₇ ~
The C ₂₃ was prepared.

For comparison, positive electrode A ₂₄ and negative electrode B
₂₄ , nickel-cadmium alkali 2 shown in Table 3
Next battery C ₂₄ was produced.

Next, the same charging / discharging operation as in Example 1 was repeated for each of the batteries C _{17 to} C ₂₄ , and the charging / discharging voltage drop value (V) of the battery in the first charging / discharging cycle and the 50th charging / discharging were performed. Battery charge / discharge voltage drop (V) during discharge cycle
And were measured.

The results are shown in Table 3.

[0173]

[Table 3]

As is clear from the results of Table 3, the ratio of cobalt (Co) / nickel (Ni) (R _{Co / Ni} ) is 10
Batteries using current collectors in the range of 100/100 or more are Comparative Example 3
It can be seen that the deterioration of the charge / discharge cycle characteristics is suppressed as compared with the above.

Next, on the main surface 42a of the nickel foil, instead of cobalt (Co ⁺ ) ions, titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn),
Various collectors were prepared by ion implantation of iron (Fe).

Next, with respect to each of these current collectors, the composition ratio of nickel (Ni) present on the main surface 42a of the nickel foil and these dissimilar metals (Me) by photoelectron spectroscopy (ESCA), Quantitative analysis of the composition ratio (R _{Me / Ni} ) of dissimilar metal (Me) / nickel (Ni)
A nickel-cadmium alkaline secondary battery similar to that of Example 1 was produced by using only a current collector having a _{Me / Ni ratio of 10/100} or more.

Next, the same charging / discharging operation as in Example 1 was performed, and the charging / discharging voltage drop value (V) of the battery in the first charging / discharging cycle and the charging / discharging voltage drop of the battery in the 50th charging / discharging cycle. The value (V) was measured.

The results were almost the same as those of the battery using the current collector having the layer containing cobalt (Co) as an impurity on the main surface 42a of the nickel foil.

That is, the charging / discharging voltage drop value (V) of the battery in the first charging / discharging cycle is the main surface 42a of the nickel foil.
In addition, a battery using a current collector ion-implanted with a dissimilar metal,
A battery using a current collector in which the dissimilar metal is not ion-implanted on the main surface 42a of the nickel foil is 0.05 ±
Although no significant difference was observed within the range of 0.01 V, in the battery using the current collector in which the dissimilar metal was not ion-implanted into the main surface 42a of the nickel foil, the battery was charged at the 50th charge / discharge cycle. The discharge voltage drop value (V) exceeded 0.2 V, while the main surface 42a of the nickel foil was ion-implanted with one of different metals selected from the group consisting of iron, chromium, vanadium, titanium, and cobalt. In the battery using the (supported) current collector, the charge / discharge voltage drop value (V) of the battery in the 50th charge / discharge cycle was 0.1 V or less.

When the ion beam method is used to form a layer containing impurities of different metals such as cobalt (Co) on the main surface 42a of the nickel foil, the acceleration voltage is 0.1 MeV or more. It is preferably 0 MeV or less, and more preferably 1 MeV or more and 5.0 MeV or less.

The atmosphere for ion-implanting impurities composed of a different metal such as cobalt (Co) into the main surface 42a of the nickel foil is preferably a high vacuum of 10 ^-2 torr or less. At a pressure higher than 10 ^-2 torr, when ion implantation is performed, except for the main surface 42a of the nickel foil activated by the irradiation of the ion beam and the beam source existing inside the vacuum chamber (ion chamber). It is not preferable because it reacts with the gas etc.

In Example 3, a dense member was used as the base material, but a porous member such as a nickel sintered body or a foamed nickel base material is used as the base material. However, the same effect is obtained.

In the third embodiment, the ion beam method is used as a method for forming a layer containing impurities of different metals such as cobalt (Co) on the main surface 42a of the nickel foil. The method of forming a layer containing impurities made of a different metal such as cobalt (Co) on the main surface 42a of the nickel foil is not limited to the ion beam method.

As a method of forming a layer containing impurities made of a different metal such as cobalt (Co) on the main surface 42a of the nickel foil, an ion beam method or an electrochemical method can be used. .

The process of forming (supporting) a layer containing impurities made of a dissimilar metal such as cobalt (Co) on the surface of a base material such as nickel foil will be described below by using an electrochemical method.

First, a dissimilar metal supported on the surface of the base material, more specifically, cobalt (Co) supported on the surface of the base material.
Dissimilar metals such as the above are dissolved in a solution in an ionic state.

Next, the base material is dipped in a solution containing a dissimilar metal such as cobalt (Co) in an ionic state. Next, by applying an appropriate voltage from the outside so that the base material has an appropriate potential, a dissimilar metal such as cobalt (Co) is deposited (carried) on the surface of the base material, A layer containing impurities of different metals is formed on the surface.

When the ion beam method is used, a layer containing impurities that spreads from the surface of the base material to the inside of the base material is formed with a desired impurity concentration distribution by controlling the acceleration voltage and the implantation amount. In addition, the electrochemical method is different in that a layer containing impurities can be formed on the surface of the base material.

Further, as a metal (element) that can be used as an impurity of the layer containing impurities formed on the surface of the base material, when nickel is used as the base material, titanium,
Vanadium, chromium, manganese, iron and cobalt can be mentioned, but the characteristics of the electrode according to the present invention are that the characteristics of the metal atoms constituting the impurities as well as the formation of a layer containing such impurities on the surface of the base material. A slight difference is observed depending on the method, the amount of the layer containing impurities formed on the surface of the base material, the form of the support, and / or the amount of the active material held on the surface of the layer containing the impurities, and the form of the support. .

Examples 4 to 6 Examples 4 to 6 show examples in which the main surface of the base material is roughened.

FIG. 5 is a sectional view schematically showing an embodiment of a battery electrode manufactured according to the present invention.

Referring to FIG. 5, the battery electrode 51 is
A current collector (base material) 52 and an active material 55 are included. Current collector 5
2 is composed of a dense member having almost no pores inside.

The active material 55 is held on the main surface 52a of the current collector 52. In addition, the main surface 52d of the current collector 52
The surface roughness of is adjusted within the following range.

The surface roughness of the main surface 52a of the current collector 52 is
Center line average roughness (Ra) is 0.4 μm or more and 3.0 μm
It is described below.

The main surface 52a of the current collector 52 preferably has a maximum surface roughness (Rmax) of 4 μm or more.

The surface roughness of the main surface 52a of the current collector 52 is
More preferably, in order to maintain the mechanical strength of the current collector 52, the maximum height (Rmax) is adjusted within the range of the following equation.

4 (μm) ≦ Rmax ≦ 3/4 · D (μm) (In the formula, D represents the film thickness of the current collector.) This battery electrode 51 has a main surface 52 a of the current collector 52. As a result of being appropriately roughened, in the battery electrode 51, a current collector 52,
Adhesion with the active material 55 is improved.

Therefore, in a secondary battery such as a nickel-cadmium alkaline secondary battery using this battery electrode 51, the adhesion between the current collector 52 and the active material 55 is improved, resulting in charge / discharge. Battery characteristics such as cycle characteristics are improved.

Regarding the electrode whose purpose is to improve the adhesion between the current collector and the active material by appropriately roughening the surface of the current collector, see, for example, JP-A-5-6.
There is an invention as described in Japanese Patent No. 766.

The invention described in JP-A-5-6766 uses a titanium foil or an aluminum foil as a current collector of an electrode of a non-aqueous solvent type secondary battery, and uses a titanium foil or an aluminum foil as a main surface. By appropriately roughening the surface, the adhesion between the current collector and the active material is improved.

By the way, when a nickel base material is used as the current collector 52, there is a problem that it is difficult to efficiently roughen the main surface 52a of the nickel base material within the above range.

The present inventors have completed the present invention as a result of earnest efforts for a method of efficiently roughening the main surface 52a of the nickel base material within the above range.

Example 4 Example 4 shows an example in which the main surface of the nickel foil is roughened according to the second invention.

(1) Adjustment of Current Collector As the base material 52, a commercially available nickel foil manufactured by rolling (manufactured by Niraco Co., purity 99.5%, thickness 20 μm)
Prepared.

Next, 1 mol (mol) of this nickel foil was used.
The main surface 52a of the nickel foil was cleaned by immersing it in a 1 / liter aqueous hydrochloric acid solution.

Next, the nickel foil whose main surface 52a was cleaned was treated with ferric chloride (FeC) with a Baume degree of 30 ° Be '.
l ₃ ) After immersing in an aqueous solution (temperature of 40 ° C.), the roughened main surface 52a is washed with water to efficiently produce a nickel foil having the roughened main surface 52a within the above range. I was able to.

The degree of roughening of the main surface 52a is adjusted by immersing the nickel foil in an aqueous solution of ferric chloride (FeCl ₃ ) and various nickel foils having different surface roughness on the main surface 52a are prepared. Prepared and labeled Samples 25-30.

Next, for each of the samples 25 to 30, a known stylus electric surface roughness meter (surfcoder model SE-3C, KOSAKA LABORATORY) was used.
Center line average roughness (Ra) and maximum height (R)
max) was measured.

The results are shown in Table 4. (2) Preparation of Electrodes Next, in the same manner as in Example 1, Samples 25 to 30 were used to prepare positive electrodes A _{25 to} A ₃₀ and negative electrodes B _{25 to} B ₃₀ .

(3) Preparation of Battery Using the positive electrodes A _{25 to} A ₃₀ and the negative electrodes B _{25 to} B ₃₀ , Example 1 was used.
Similar to nickel-cadmium alkaline secondary battery C ₂₅ ~
_C30 was produced.

Next, the same charging / discharging operation as in Example 1 was performed, and the charging / discharging voltage drop value (V) of the battery in the first charging / discharging cycle and the charging / discharging voltage drop of the battery in the 50th charging / discharging cycle. The value (V) was measured.

The results are shown in Table 4.

[0213]

[Table 4]

As is clear from the results shown in Table 4, Battery C ₂₅
In all of C to C ₃₀ , the charging / discharging voltage drop value (V) tends to increase as the charging / discharging operation is repeated. However, as the roughening of the main surface 52a of the nickel foil increases, charging / discharging increases. It can be seen that the increase in the voltage drop value (V) is suppressed.

In Example 4, ferric chloride (FeC
l ₃ ) An aqueous solution having a Baume degree of 30 ° Be 'was used, but an aqueous ferric chloride (FeCl ₃ ) solution having a Baume degree of 48 ° Be' or less is preferable, and more preferably, An aqueous solution having a temperature of 20 ° Be ′ or more and 45 ° Be ′ or less can be used. If it exceeds 48 ° Be ′, the viscosity of the ferric chloride (FeCl ₃ ) aqueous solution becomes high, and the etching rate of the substrate surface becomes slow, which is not preferable, while if it is less than 20 ° Be ′, the substrate surface becomes less than 20 ° Be ′. It is not preferable because the surface roughening is difficult to proceed.

The temperature of the ferric chloride (FeCl ₃ ) aqueous solution is not particularly limited, but is preferably 20 ° C. or higher and 60 ° C. or lower. If it exceeds 60 ° C., the etching rate cannot be controlled, which is not preferable. On the other hand, if it is less than 20 ° C., the roughening rate of the substrate surface becomes slow, which is not preferable.

Example 5 Example 5 shows another example for efficiently roughening the main surface of the nickel foil within the above range.

(1) Adjustment of Current Collector As the base material 52, a commercially available nickel foil manufactured by rolling or the like (manufactured by Niraco Co., purity 99.5%, thickness 20 μm)
m) was prepared.

Next, 1 mol of this nickel foil was used.
The main surface 52a of the nickel foil was cleaned by immersing it in a 1 / liter aqueous hydrochloric acid solution.

Next, the nickel foil whose main surface 52a was cleaned was electrolytically plated under the following conditions to roughen the main surface 52a of the nickel foil.

[0221]

[Table 5]

Under the above conditions, the main surface 52a of the nickel foil can be efficiently roughened within the above range.

In the present embodiment, under the above conditions, the surface roughness of the main surface 52a is a center line average roughness (Ra) of 0.
A 7.2 μm nickel foil having a thickness of 7 μm and a maximum height (Rmax) was prepared and labeled as Sample 31.

(2) Preparation of Electrode Next, as in Example 4, Sample 31 was used to prepare positive electrode A _31.
And a negative electrode was produced B _31.

(3) Preparation of Battery A nickel-cadmium alkaline secondary battery C ₃₁ similar to that of Example 1 was prepared using the positive electrode A ₃₁ and the negative electrode B ₃₁ .

Next, the same charging / discharging operation as in Example 1 was performed, and the charging / discharging voltage drop value (V) of the battery in the first charging / discharging cycle and the charging / discharging voltage drop of the battery in the 50th charging / discharging cycle. The value (V) was measured.

The charging / discharging voltage drop value (V) in the first charging / discharging cycle of the battery C ₃₁ was 0.03V, and the charging / discharging voltage drop value (V) in the 50th charging / discharging cycle was 0.05V. Met.

By comparison with the data of Example 4, the use of nickel foil electrolytically plated on the main surface 52a as a current collector suppresses the deterioration of the charge / discharge cycle characteristics due to the repeated charging / discharging operation of the battery C _31. You can see that it is done.

The disclosure of Example 5 merely shows an example of a method for efficiently roughening the main surface 52a of the nickel foil to a predetermined range.

The method of roughening the main surface 52a of the nickel substrate by an electrochemical method is not particularly limited to the following cases, but the following two methods can be mentioned.

(1) The first method is a method of immersing a nickel substrate in an appropriate electrolytic solution and applying a noble potential higher than the melting potential of nickel.

(2) The second method is a method of immersing a nickel substrate in an appropriate electrolytic solution and applying a base potential lower than the dissolution potential of nickel.

The term “dissolution potential” used in the present specification
Is the total voltage required for electroplating, ie the decomposition voltage E
Corresponding to _dec. , the dissolution potential (E _dec. ) is a value based on the standard hydrogen electrode.

When an aqueous solution is used as the electrolytic solution, nickel is an extremely stable element. Therefore, in the first method, it is considered that the decomposition of water occurs preferentially over the dissolution of nickel. It is not the proper method.

On the other hand, in the second method, on a nickel substrate,
This is a method of depositing nickel non-uniformly, which corresponds to so-called electroplating. Generally, electroplating is aimed at uniform deposition on a substrate, whereas the second method is non-uniform. It is precipitation.

Generally, in nickel plating for the purpose of uniform deposition, plating is performed in an alkaline aqueous solution bath to aim for nickel deposition in an environment in which hydrogen generation is unlikely to occur. However, in the second method, on the contrary, at least , The pH value (pH) indicating the hydrogen ion concentration of the electrolytic solution in the bath is
The nickel base material is dipped in an electrolytic solution bath having a nickel content of 7 or less and containing nickel ions Ni ²⁺ , and a base potential lower than the dissolution potential is applied.

On the surface of the nickel base material in the plating bath, nickel deposition due to reduction of nickel ions in the plating bath and hydrogen generation due to reduction of hydrogen ions in the plating bath occur at the same time. The uniform deposition of nickel on the surface of the substrate is hindered, and uneven nickel deposits on the surface. The deposition shape depends largely on the amount of hydrogen generated, the concentration of nickel ions in the plating bath, the electrode potential, the diffusion rate of nickel ions in the plating bath, and the pH value of the solution. Has a hydrogen generation amount of at least 4.0 × 10 ⁴ cc /
hour · m ² or more, pH of the solution in the plating bath (pH) is desirably 4 or less.

Example 6 Example 6 shows another example in which the main surface of the nickel foil is efficiently roughened within the above range.

(1) Adjustment of Current Collector As the substrate 52, a commercially available nickel foil manufactured by rolling (manufactured by Niraco Co., purity 99.5%, thickness 20 μm)
Prepared.

Next, 1 mol (mol) of this nickel foil was added.
The main surface 52a of the nickel foil was cleaned by immersing it in a 1 / liter aqueous hydrochloric acid solution.

Next, the cleaned nickel foil main surface 52
An ion accelerator (manufactured by Nisshin Denki Co., Ltd.) is used for a, and nitrogen ions or argon ions are used at an accelerating voltage of 1 MeV to
× 10 ⁷ counts / sec or more 1 × 10 ³⁰ count
Irradiation was performed in the range of ts / sec or less.

The degree of vacuum in the vacuum chamber (ion chamber) when irradiating the main surface 52a of the nickel foil with nitrogen ions or argon ions is 2 × 10 ^-2 t.
It was set to orr or less.

In the present embodiment, under the above conditions, the surface roughness of the main surface 52a is a center line average roughness (Ra) of 0.
A plurality of 7.2 μm nickel foils having a size of 7 μm and a maximum height (Rmax) were produced and labeled with Sample 32.

Further, the sample 32 was examined for specific surface area by the BET single point method before and after irradiation with nitrogen ion or argon ion, and the sample 32 was irradiated with nitrogen ion or argon ion, so that the surface area was larger than that before irradiation. 3-
It had increased to 5 times.

Also, no significant difference was observed in the surface irregularities formed by the irradiation of nitrogen ions and argon ions.

(2) Preparation of Electrode Next, as in Example 4, Sample 32 was used to prepare positive electrode A _32.
And the negative electrode B ₃₂ was produced.

(3) Preparation of Battery Using the positive electrode A ₃₂ and the negative electrode B ₃₂ , a nickel-cadmium alkaline secondary battery C ₃₂ similar to that of Example 1 was prepared.

Next, the same charging / discharging operation as in Example 1 was performed, and the charging / discharging voltage drop value (V) of the battery in the first charging / discharging cycle and the charging / discharging voltage drop of the battery in the 50th charging / discharging cycle. The value (V) was measured.

Also, for comparison, the nickel shown in Example 1
Ru-cadmium alkaline secondary battery C ₈Battery C similar to₃₃
Was produced.

[0250] For cell C ₃₃ also performs a similar charge and discharge operation as in Example 6, the charge and discharge voltage drop of the battery at the first charge-discharge cycle and (V) charging and discharging of the battery at the 50th charge-discharge cycles The voltage drop value (V) was measured.

The charge / discharge voltage drop values (V) of the battery C ₃₂ and the battery C ₃₃ in the first charge / discharge cycle were both 0.0
5 significant difference in the range of ± 0.01 V has been observed, the charge-discharge voltage drop of the battery at the 50th charge-discharge cycles (V) is, in the battery C _33, though exceeded 0.2V On the other hand, in the battery C ₃₂ , the charge / discharge voltage drop value (V) of the battery in the 50th charge / discharge cycle was 0.07 V or less.

The disclosure shown in Example 6 merely shows one example of the method of roughening the main surface 52a of the nickel foil.

When the main surface 52a of the nickel foil is roughened by the ion beam method, the acceleration voltage is 0.1 MeV.
It is preferably 5.0 MeV or less and more preferably,
It is 1 MeV or more and 5.0 MeV or less.

The atmosphere for ion irradiation is preferably a high vacuum of 2 × 10 ^-2 torr or less. At a pressure higher than 2 × 10 ^-2 torr, when ion irradiation is performed, the main surface of the nickel foil activated by the irradiation of the ion beam and the beam source existing inside the vacuum chamber (ion chamber) Gases other than the above react, which is not preferable.

In Examples 4 to 6, a dense nickel base material was used as the base material, but as the base material,
By using a porous base material such as a nickel sintered body or a foamed nickel base material and roughening the main surfaces thereof, the same effects as in Examples 4 to 6 are achieved.

Example 7 FIG. 6 is a sectional view schematically showing an example of the battery electrode according to the present invention.

Referring to FIG. 6, the battery electrode 61 is
A current collector 64 and an active material 65 are included.

The collector 64 includes a base material 62 and a layer 63 containing impurities formed on the main surface 62a of the base material 62. The active material 65 is held on the surface 63a of the layer 63 containing impurities. The base material 62 is composed of a dense member having almost no pores inside.

The surface 63a of the layer 63 containing impurities of the current collector 64, that is, the surface roughness of the current collector 64a of the current collector 64 has a center line average roughness (Ra) of 0.4 μm or more. It is set to 3.0 μm or less.

The surface roughness of the main surface 64a of the current collector 64 is preferably such that the maximum height (Rmax) is 4 μm or more.

The surface roughness of the main surface 64a of the current collector 64 is
More preferably, in order to maintain the mechanical strength of the current collector 64, the maximum height (Rmax) is adjusted within the following range.

4 (μm) ≦ Rmax ≦ 3/4 · D (μm) (In the formula, D represents the film thickness of the current collector.) Next, description will be made based on specific data.

(1) Adjustment of Current Collector As the base material 62, a commercially available nickel foil manufactured by rolling or the like (manufactured by Niraco Co., purity 99.8%, thickness 20 μm)
m) was prepared.

Next, 1 mol (mo
The main surface 62a of the nickel foil was cleaned by immersing it in a l) / liter hydrochloric acid aqueous solution.

Then, in the same manner as in Example 4, the main surface 62 was prepared.
After immersing the nickel foil from which a was cleaned in a ferric chloride (FeCl ₃ ) aqueous solution (temperature 40 ° C.) having a Baume degree of 30 ° Be ′, the roughened main surface 62a was washed with water, and A nickel foil having a main surface 62a roughened within the range was manufactured.

In the present embodiment, under the above conditions, the surface roughness of the main surface 62a is a center line average roughness (Ra) of 0.
A nickel foil having a thickness of 7 μm and a maximum height (Rmax) of 7.2 μm was produced.

Next, the main surface 6 having the above-mentioned surface roughness.
The nickel foil having 2a was dipped in a nitric acid aqueous solution in the same manner as in Example 1 to form a layer containing nickel oxide on the main surface 62a of the nickel foil, and then the sample 33
Labeled.

Then, in the same manner as in Example 1, a sample 33 was obtained.
About the sample 33 by photoelectron spectroscopy (ESCA)
Present on the surface 63a of the formed layer containing nickel oxide
Composition ratio of nickel and nickel oxide, nickel acid
Compound / nickel composition ratio (R _Ni) Was quantitatively analyzed.

The composition ratio of nickel and nickel oxide existing on the surface 63a of the layer containing nickel oxide formed in Sample 33 and the composition ratio of nickel oxide / nickel (R _Ni ) were 0.5. It was

Also, the surface roughness of the surface 63a of the layer containing nickel oxide formed on the sample 33 was measured. Regarding the surface roughness of the surface 63a of the layer containing nickel oxide, the center line average roughness (Ra) is 0.7 μm and the maximum height (Rmax).
Was 7.2 μm.

(2) Production of Electrode Next, as in Example 1, Sample 33 was used to prepare positive electrode A _33.
And a negative electrode was produced B _33.

(3) Preparation of Battery Using the positive electrode A ₃₃ and the negative electrode B ₃₃ , a nickel-cadmium alkaline secondary battery C ₃₃ similar to that of Example 1 was prepared.

Next, the same charging / discharging operation as in Example 1 was performed, and the charging / discharging voltage drop value (V) of the battery in the first charging / discharging cycle and the charging / discharging voltage drop of the battery in the 50th charging / discharging cycle. The value (V) was measured.

The charge / discharge voltage drop value (V) in the first charge / discharge cycle of Battery C ₃₃ was 0.04 V, and the charge / discharge voltage drop value (V) in the 50th charge / discharge cycle was 0.05 V. Met.

By comparison with the data of Example 4, battery C
₃₃ deterioration in charge-discharge cycle characteristics due to the repetition of charging and discharging operations are seen to have been suppressed compared with the battery C ₁₇ -C ₂₃ used in Example 4.

In the present embodiment, an example in which a dense member having almost no pores inside is used as the base material 62 is shown. However, as the base material 62, a nickel sintered body, a nickel foam base material or the like is used. The same effect as in Example 7 can be obtained by using the porous base material.

In this embodiment, the current collector having the layer containing nickel oxide is used as the layer containing impurities, but the layer containing impurities is different from the metal constituting the base material. Metals such as titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (F
e) and Example 7 even when a layer containing at least one selected from the group consisting of cobalt (Co) is formed.
Has the same effect as.

In this example, in the step of adjusting the current collector, first, the main surface of the nickel base material was roughened,
After that, an example was shown in which a layer containing impurities was formed on the surface of the nickel base material having the appropriately roughened main surface, but the step of adjusting the current collector is limited to the above method. There is no such thing. In the step of adjusting the current collector, first, a layer containing impurities may be formed on the surface of the nickel base material, and then the main surface of the nickel base material having the layer containing impurities on the surface may be roughened.

The above-mentioned disclosures regarding Examples 1 to 7 are merely specific examples of the present invention, and do not limit the technical scope of the present invention.

In Examples 1 to 7, the surface modification was mainly performed on one surface of the current collector, and the active material was applied to one surface of the current collector. The surface may be modified and the active material may be coated on both sides of the current collector.

In Examples 1 to 7, nickel was used as the material of the base material. However, in the first invention, other than nickel, for example, titanium or aluminum is used as the material of the base material. Etc. can be used.

When the material of the base material is other than nickel, nickel can be mentioned as an impurity of the layer containing impurities formed on the surface of the base material.

That is, the impurities of the layer containing impurities formed on the surface of the base material are metals different from those of the base material, such as titanium (Ti), vanadium (V), chromium (Cr) and manganese. At least one selected from the group consisting of (Mn), iron (Fe), cobalt (Co) and nickel (Ni) can be used.

Further, when a dense member is used as the base material, it is particularly suitable for manufacturing a thin battery electrode.

Further, when a dense member is used as the base material, the step of applying the active material on the surface of the base material becomes simpler than when a porous member is used as the base material. As a result, the manufacturing cost of the battery electrode can be reduced.

[0286]

As described in detail above, the battery electrode according to the first aspect of the present invention is a nickel-cadmium alkali 2
It can be suitably used as an electrode of a secondary battery such as a secondary battery.

In the secondary battery using the battery electrode according to the first invention, the chemical reaction (side reaction) between the base material and the electrolytic solution of the battery is reduced, and the surface of the current collector is electrically insulated. As a result of being able to suppress the generation and accumulation of substances (by-products) with high electrical properties, it is possible to suppress deterioration of charge / discharge cycle characteristics due to the accumulation of substances (by-products) with high electrical insulation properties. can do.

The secondary battery using the battery electrode according to the first aspect of the present invention is such that the active material is less likely to be peeled off from the surface of the current collector, resulting in a battery having charge / discharge cycle characteristics even after repeated charge / discharge operations. The characteristics do not easily deteriorate.

Further, in the method of manufacturing a battery electrode according to the second invention, the surface roughness of the current collector can be efficiently formed within the above range.

Then, in the secondary battery using the battery electrode manufactured according to the second invention, the active material is peeled from the surface of the current collector as a result of the main surface of the current collector being appropriately roughened. Battery characteristics such as charge / discharge cycle characteristics are less likely to deteriorate even after repeated charge / discharge operations.

Further, in the method of manufacturing a battery electrode according to the second aspect of the present invention, the main surface of the current collector is appropriately roughened so that when the battery electrode is manufactured, it is removed from the surface of the current collector. The active material is less likely to be peeled off, and as a result, the productivity in manufacturing battery electrodes can be improved.

The battery electrode according to the present invention is not particularly limited to the following cases, but is preferably used as an electrode of an alkaline secondary battery such as a nickel-cadmium alkaline secondary battery or a nickel-hydrogen secondary battery. be able to.

[Brief description of drawings]

FIG. 1 is a cross-sectional view schematically showing an embodiment of a battery electrode according to the present invention.

FIG. 2 is a cross-sectional view schematically showing a nickel-cadmium alkaline secondary battery produced in this example.

FIG. 3 is a cross-sectional view schematically showing an embodiment of a battery electrode according to the present invention.

FIG. 4 is a cross-sectional view schematically showing an embodiment of the battery electrode according to the present invention.

FIG. 5 is a cross-sectional view schematically showing an embodiment of a battery electrode according to the present invention.

FIG. 6 is a cross-sectional view schematically showing an embodiment of the battery electrode according to the present invention.

FIG. 7 is a cross-sectional view schematically showing a battery structure of a nickel-cadmium alkaline secondary battery.

8 is an enlarged schematic cross-sectional view of an electrode structure of a positive electrode 102 of the nickel-cadmium alkaline secondary battery shown in FIG.

FIG. 9 is a cross-sectional view for explaining the definition of center line average roughness (Ra).

FIG. 10 is a cross-sectional view for explaining the definition of maximum height (Rmax).

FIG. 11 is a schematic view schematically showing a nickel mesh porous body.

[Explanation of symbols]

1, 31, 41, 51, 61 Battery electrode 2, 12, 22, 32, 42, 52, 62 Base material 2a, 12a, 22a, 32a, 42a, 62a Main surface of base material 3, 13, 23, 33 , 43, 63 layers containing impurities 3a, 13a, 23a, 33a, 43a, 63a Surfaces of layers containing impurities 4, 14, 24, 34, 54, 64 Current collectors 5, 15, 25, 35, 45, 55 , 65 Active material 6 Nickel-cadmium alkaline secondary battery 7 Separator 8 Storage tank 11 Positive electrode 21 Negative electrode 32h Pore 32ha Pore surface 52a Main surface of current collector

Claims (7)

[Claims] 1. A current collector comprising a base material and a layer containing impurities formed on the surface of the base material; and an active material held on the surface of the layer containing impurities of the current collector. , Battery electrodes. 2. The surface roughness of the main surface of the current collector has a center line average roughness (Ra) of 0.4 μm or more and 3.0 μm or less. Battery electrode. 3. The electrode for a battery according to claim 2, wherein the surface roughness of the main surface of the current collector has a maximum height (Rmax) of 4 μm or more. 4. The battery electrode according to claim 1, wherein the base material is a nickel base material, and the impurities are nickel oxides. 5. The surface of the impurity-containing layer has a composition ratio of nickel and nickel oxide of 0.1 ≦ nickel oxide / nickel ≦ 2.5. Battery electrode. 6. The substrate is a nickel substrate, and the impurities include at least one selected from the group consisting of titanium, vanadium, chromium, manganese, iron and cobalt. 1, 2 or 3
The electrode for battery according to. 7. A method for manufacturing a battery electrode including a current collector made of a nickel base material, wherein the main surface of the nickel base material is an aqueous ferric chloride solution having a Baume degree of 48 ° Be ′ or less. And a surface roughening step, and a step of holding an active material on the surface of the nickel base material whose main surface is roughened.