JP2008305698A - Nonwoven-fabric board for battery, electrode of battery using the same, and battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode board for a battery having a high air gap ratio and greater tensile strength, and a battery having large battery capacity and high battery voltage. <P>SOLUTION: In the electrode board for a battery wherein metal including nickel is coated on the fiber surface of a nonwoven fabric made of resin, an air gap ratio is 90% or more and 98% or less, and a tensile strength of the board is 20 N/cm or more in a longitudinal direction and 10 N/cm or more in a width direction. A basis weight of the amount of metal including the coated nickel is preferable to be 150 to 350 g/m<SP>2</SP>. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a battery electrode substrate used for an alkaline secondary battery or the like.

Examples of current collectors produced by coating nickel on a nonwoven fabric used for alkaline secondary batteries that have been developed so far include the following.
Patent Document 1 proposes a method of manufacturing a nickel-plated nonwoven fabric electrode characterized in that electroless nickel plating is performed after hydroentanglement treatment is performed on the web, thereby pulling without using an organic solvent-based adhesive. It is said that the strength characteristics can be improved and the loss of fibers can be suppressed.
In Patent Document 2, a non-woven material subjected to surface treatment such as sulfonation treatment and nickel plating is applied to a current collector for an alkaline secondary battery. It is said that flexibility and strength can be secured by leaving the resin nonwoven fabric as a core material.

Patent Document 3 discloses a current collector capable of high capacity and high rate charge / discharge by defining the amount of plating on the surface of the nonwoven fabric by a cross-sectional area.
In Patent Document 4, nickel plated on the surface of the non-woven fabric, the specific surface area per unit volume is viscosity is power collector at ^{0.13m 2 / cm 3 ~0.35m 2 /} cm 3 0.3Pa. It is characterized by being obtained by filling an active material paste of s or less and drying. As a result, an alkaline battery capable of high output is obtained.

However, these conventional current collectors all have a nickel-plated non-woven fabric made of polyolefin fibers to improve the tensile strength, but the porosity of the base material could not be sufficiently increased. The battery has not been provided.
Moreover, in the case of the base material plated on the surface of the nonwoven fabric, since the heat treatment cannot be performed, the plated nickel is hard. Therefore, when the tensile elongation of nickel is small and the tensile strength of the substrate is small, nickel on the surface is easily damaged (cracked / peeled) during the rolling process during electrode production, and as a result of nickel damage, the electrical resistance increases, There has been a problem that the battery voltage is lowered and the battery capacity is also reduced.

JP-A-5-290838 JP 2001-313038 A JP 2003-109600 A JP 2005-347177 A

  An object of the present invention is to provide a battery electrode substrate having a high porosity and a high tensile strength, thereby providing a battery having a large battery capacity and a high battery voltage.

As a result of intensive studies to solve the above problems, the present inventors may adopt the following configurations (1) to (5) for a battery electrode substrate, a battery electrode using the same, and a battery. I found it effective.
(1) A battery electrode substrate formed by coating a metal surface containing nickel on the surface of a woven or non-woven fiber made of a resin, the porosity of which is 90% or more and 98% or less, and the substrate A tensile strength of the battery is 20 N / cm or more in the longitudinal direction and 10 N / cm or more in the width direction.
(2) The woven or non-woven fiber made of the resin has a core-sheath structure, the core is made of polypropylene and the sheath is made of polyethylene, and the weight ratio of PE to the total weight of the fiber is 30% or more 90 % Or less of the battery electrode substrate according to (1) above.
(3) The battery electrode substrate according to (1) or (2) above, wherein the weight per unit area of the metal containing the coated nickel is 150 to 350 g / m ² .
(4) The battery electrode substrate according to any one of (1) to (3) above, wherein an active material mixture mainly composed of nickel hydroxide is supported and roll-rolled in the longitudinal direction of the nonwoven fabric. A battery electrode.
(5) A battery using the battery electrode according to (4) above.

  The battery electrode substrate according to the present invention is characterized in that a metal including nickel is coated on a fiber surface of a woven or nonwoven fabric made of a resin. The resin is not particularly limited, but when the battery electrode substrate according to the present invention is used for an alkaline battery, it is necessary to be a material that does not dissolve or decompose in a strong alkali, and is preferably a polyolefin. .

The battery electrode substrate according to the present invention is characterized in that the porosity is 90% or more and 98% or less, and the tensile strength of the substrate is 20 N / cm or more in the longitudinal direction and 10 N / cm or more in the width direction.
If the porosity is less than 90%, the active material filling amount is reduced and the battery capacity is reduced, which is not preferable. Further, when the porosity is more than 98%, the strength characteristics of the substrate are deteriorated, and nickel on the surface is easily damaged (cracked / peeled) in a rolling process at the time of electrode fabrication described later. If nickel is damaged, the electric resistance increases, the battery voltage decreases, and the battery capacity also decreases, which is not preferable. For this reason, it is preferable that the porosity of the battery electrode substrate is 90 to 98%. More preferably, it is 93% or more and 97% or less. In addition, a porosity means the percentage of the void | hole with respect to the volume of the whole nonwoven fabric.
The porosity of the battery electrode substrate can be adjusted by the basis weight of the woven or non-woven fiber. For example, the porosity can be set to 90% or more and 98% or less by setting the fiber basis weight of the woven or non-woven fabric to 10 g / m ² or more and 130 g / m ² or less. If the fiber areal weight is large, the tensile strength is increased, but the porosity is decreased, so that the battery capacity is also decreased, which is not preferable. For this reason, a more preferable value of the fiber basis weight is 60 g / m ² or less.

When the tensile strength of the substrate is 20 N / cm or more in the longitudinal direction and 10 N / cm in the width direction, damage to the metal film on the nonwoven fabric surface can be minimized by placing it in the rolling process during electrode production, and the electrical resistance can be increased. Since it can suppress, it is preferable.
Such an electrode substrate for a battery having good tensile strength can be obtained by adjusting the amount of the fiber fusion component and the fiber basis weight. For example, heat treatment is performed under the condition that only PE is melted by using a core-sheath fiber having a low melting point polyethylene (hereinafter also referred to as PE) as a sheath and a polypropylene having a higher melting point than polyethylene (hereinafter also referred to as PP) as a core. Thus, it becomes possible to adjust the tensile strength of the base material. From the viewpoint of securing the tensile strength, a more preferable value of the fiber basis weight is 30 g / m ² or more. The PE weight ratio is preferably 30% or more. If the PE weight ratio is less than 30%, the tensile strength decreases. Conversely, if the PE weight ratio exceeds 90%, the nonwoven fabric becomes thin, the porosity decreases, and the battery capacity decreases. For this reason, it is preferable that PE weight ratio is 30 to 90%. More preferably, it is 50-90%, More preferably, it is 70-90%. The tensile strength of the substrate can be adjusted by a method other than heat treatment as will be described later.
The tensile strength in the longitudinal direction and the width direction can be adjusted, for example, by changing the degree of fiber alignment when producing a nonwoven fabric. The degree of fiber alignment can be adjusted, for example, by changing the line speed when producing a nonwoven fabric.

The electrode substrate for a battery according to the present invention is characterized in that the amount of metal containing coated nickel is 150 to 350 g / m ² . If it is less than 150 g / m ² , the electric resistance of the electrode substrate increases and the battery voltage decreases, which is not preferable. On the other hand, if it exceeds 350 g / m ² , the porosity is decreased and the battery capacity is decreased, which is not preferable. For this reason, it is preferable that the metal amount containing the covered nickel is 150-350 g / m < ² >. More preferably 200 to 250 g
/ M ² .

  Since the electrode substrate for a battery according to the present invention has a porosity of 90% or more, the active material can be sufficiently filled and the battery capacity can be increased. In addition, because the substrate that uses nonwoven fabric cannot be heated, the problem is that the metal that coats the nonwoven fabric is hard and weak to processing. There is an effect that cracking and peeling of the metal film can be suppressed.

  Although the fiber which comprises a woven fabric or a nonwoven fabric will not be specifically limited if it is an alkali-resistant fiber, A polyolefin-type fiber and a polyamide resin-type fiber are mentioned as a preferable example. These fibers have already been used as battery separators, and the fibers do not dissolve even when contacted with 20-35 wt% KOH aqueous solution, so there is no change in physical properties, excellent alkali resistance, low cost, and general use It is highly probable.

  Examples of the resin constituting the polyolefin fiber include polyethylene, polypropylene, polymethylpentene, ethylene-propylene copolymer, ethylene-butene-propylene copolymer, and ethylene-vinyl alcohol copolymer. Examples of polyolefin fibers include those composed of one of these resins or composite fibers composed of two or more. Examples of the resin constituting the polyamide resin-based fiber include nylon 6, nylon 66, nylon 12, a copolymer of nylon 6 and nylon 12, and the like. Examples of the polyamide resin-based fibers include those composed of one of these resins or composite fibers composed of two or more.

  When the woven or non-woven fabric is made of polyolefin fibers, among the above examples, fibers made of polyethylene or polypropylene excellent in alkali resistance and acid resistance, or composite fibers combining polyethylene and polypropylene are preferable. In particular, a core-sheath type composite fiber in which a core made of polypropylene is covered with a sheath made of polyethylene is preferable because it can satisfy both alkali resistance and strength characteristics at the same time.

  A nonwoven fabric can be manufactured, for example, by forming a web of fibers constituting the nonwoven fabric and then bonding the fibers together. The fiber web can be obtained by a card method, an air lay method, a dry method such as a melt blow method or a spun bond method in which a sheet is continuously formed from a spun state, or a wet method in which fibers are dispersed in water and drawn. Can be manufactured.

  The fiber-to-fiber bonding method includes hydroentanglement treatment that impacts a very fine high-pressure water jet, entanglement treatment with a needle punch, heating the fiber to above its softening point and below the thermal decomposition temperature, Examples thereof include a heat treatment method for locally fusing at the contact point. Although only one of the entanglement treatment and the heat treatment may be performed, it is preferable to perform the heat treatment after the entanglement treatment because the strength characteristics of the resulting nonwoven fabric are improved. Further, the porosity can be adjusted to an appropriate value by the entanglement treatment and the heat treatment. In addition, when the said core-sheath-type composite fiber with which the circumference | surroundings of polypropylene are covered with polyethylene as a fiber is used, it is preferable that the temperature of heat processing is 110-140 degreeC.

In order to improve the adhesion between the woven or non-woven fabric and the nickel coating layer, the fiber surface may be subjected to a hydrophilic treatment. Examples of the hydrophilization treatment include fluorine treatment, corona discharge treatment, sulfonation treatment, vinyl monomer graft polymerization, treatment with a hydrophilic resin, or surfactant treatment.
The battery electrode substrate of the present invention can be obtained by coating the surface of fibers constituting the woven fabric or nonwoven fabric with a metal containing nickel. Examples of the coating method include a method in which a nickel layer is formed on the surface of a woven or non-woven fiber by electroless plating or sputtering, and the surface is made conductive, followed by electrolytic plating.

  Sputtering and electroless plating can be performed under the same conditions as general sputtering and electroless plating. For example, the electroless plating can be performed by a method in which a woven fabric or a non-woven fabric is immersed in a catalyst applying tank to apply a catalyst, and then immersed in a plating tank and plated (electroless plating step). The catalyst can be applied by, for example, a method of treating a woven or non-woven fabric with an aqueous solution of stannous chloride in hydrochloric acid and then catalyzing with an aqueous solution of palladium chloride in hydrochloric acid. The electroless plating step can be performed, for example, by a method in which a woven or non-woven fabric is immersed in an aqueous solution containing a nickel salt such as nickel nitrate, nickel chloride, or nickel sulfate, and nickel is reduced with a reducing agent such as a hydrazine derivative. .

  Electrolytic plating is performed using, for example, a plating bath such as a watt bath, a chloride bath, or a sulfamic acid bath. A woven or non-woven fabric whose surface is made conductive by electroless plating or sputtering is immersed in a plating bath, and the DC or pulse intermittent current is applied by connecting the woven or non-woven fabric to the cathode and the nickel counter electrode to the anode. By doing so, it is possible to form a metal coating further containing nickel on the metal layer containing nickel formed by electroless plating or sputtering. The metal containing nickel may be nickel alone, or an alloy or mixed state of one or more kinds of metals selected from chromium, copper, iron, cobalt, titanium, zinc, and aluminum.

The basis weight of the metal containing nickel, preferably in the range of ^{150g / m 2 ~350g / m 2} . Here, the basis weight of the metal containing nickel is obtained by dividing the weight (g) of the metal containing nickel coated by electroless plating, sputtering, electrolytic plating, etc. by the area of the battery electrode substrate, It means the amount of metal coating containing nickel per unit area of the electrode substrate. When the basis weight of the metal containing nickel is less than 150 g, the electric conductivity of the battery electrode substrate is lowered, and the current collecting characteristics of an electrode manufactured using the battery electrode substrate tend to be lowered. When the current collection characteristic is lowered, the utilization rate is liable to be lowered, and this problem is particularly remarkable when the current rate during battery discharge is high (high rate discharge). Moreover, since the metal amount containing nickel with respect to the fiber amount increases by setting the basis weight of the metal amount containing nickel to 150 g / m ² or more, the obtained battery electrode substrate is excellent in weldability and preferable in this respect. .
The electrical conductivity of the battery electrode substrate tends to improve as the amount of metal containing nickel increases, but even if the amount of metal containing nickel exceeds 350 g / m ² , the electric conductivity is increased. The degree is not so much improved, and the porosity of the base material is lowered to lower the battery capacity. Therefore, 350 g / m ² or less is preferable.

The present invention provides a battery electrode characterized in that, in addition to the battery electrode substrate, the battery electrode substrate is filled with an active material. As the active material, a material mainly composed of nickel hydroxide can be used. In addition to the main component of nickel hydroxide, this active material is cobalt hydroxide, cobalt oxyhydroxide, cobalt monoxide, zinc hydroxide. And other components may be included. The active material is filled by immersing the battery electrode substrate having a thickness adjusted as described above in a paste containing a component mainly composed of nickel hydroxide, and applying pressure from the surface of the battery electrode substrate. It can be performed by a method, a method of spraying the paste on the surface of the battery electrode substrate, or the like. Thus, after filling the space | gap of a battery electrode substrate with the paste containing an active material, normally, drying and roll rolling can be performed and the battery electrode (positive electrode) can be obtained. The battery electrode (positive electrode) is further provided with a current collecting external terminal as necessary.

In the production of the battery electrode, the battery electrode substrate is formed into the shape of the battery electrode by trimming or the like, but this step may be performed before press-fitting of the paste, or after drying and roll rolling. , May be done in both.
Roll rolling is performed using a roller press or the like. The battery electrode can be obtained by roll rolling so that the battery electrode has an electrode plane that is further compressed and smoothed to a predetermined thickness.

The present invention further provides an alkaline secondary battery using the battery electrode. The alkaline secondary battery of the present invention can be formed by sealing a positive electrode composed of the above-mentioned battery electrode, a negative electrode and a separator, and an electrolyte in a battery container.
As the negative electrode, the electrolyte, and the battery container, those similar to those used in conventional alkaline secondary batteries can be used. For example, an electrode using a hydrogen storage alloy containing hydrogen is exemplified as the negative electrode, and a potassium hydroxide aqueous solution can be exemplified as the electrolyte. The separator is to prevent a short circuit between the negative electrode and the positive electrode and retain the electrolyte. This separator is also the same as that used in the conventional alkaline secondary battery, for example, a hydrophilic treatment. A nonwoven fabric made of polyolefin fibers can be used.

  The structure of the alkaline secondary battery of the present invention can also be the same as that of a conventional alkaline secondary battery. For example, the positive electrode, the negative electrode, and the separator are formed in a band shape, and after superposing them, they are wound into a roll to form a roll-shaped power generator, and this roll-shaped power generator is formed into a cylindrical battery container. A housed structure can be mentioned. A prismatic battery container is used, which is composed of a power generator in which a band in which a positive electrode, a negative electrode, and a separator are stacked is wound so as to conform to the cross-sectional shape of the battery container, and a prismatic battery container is used. And what consists of the electric power generation body which piled up the belt | belt which overlap | superposed the separator on the bellows form can also be illustrated. Since the battery electrode substrate of the present invention is excellent in mechanical strength and flexibility, it does not easily cause a problem of being damaged during winding or bellows-like superposition and deteriorating battery characteristics.

As in Examples 1 to 5 shown in Table 1, the non-woven fabrics having different tensile strengths were prepared by changing the fineness of the fibers, the PE ratio, the fiber basis weight, and the fiber alignment. The nonwoven fabric was coated with nickel by sputtering, and further electroplated to produce a battery current collector so that the total nickel basis weight was 200 g / m ² . The thickness of the nonwoven fabric was 1.6 mm.
The current collector was filled with an active material paste mainly composed of nickel hydroxide, dried at 80 ° C., and pressed with a roll press to form an electrode.
The results of measuring the fiber basis weight, fineness, PE ratio, porosity, tensile strength, electrode capacity density, and electrode electric resistance of the electrode base material produced by the above method are summarized in Table 1.
The porosity was determined as the ratio of the volume of the void to the apparent volume of the substrate by determining the material volume of the substrate from the fiber basis weight and metal basis weight of the electrode substrate and the fiber density and metal density.
The tensile strength was measured by pulling a substrate having a width of 10 mm and a length of 150 mm in both the width direction and the longitudinal direction of the substrate with a chuck span of 100 mm and breaking the substrate.
The electrode capacity density was obtained by calculating the capacity from the active material filling weight and dividing the value by the area of the electrode.
The electrical resistance was measured by the 4-terminal method in both the longitudinal direction and the width direction of the electrode.

In Comparative Examples 1, 2 and 3, the tensile strength of the substrate is low, and the electrical resistance when used as an electrode is high. Comparative Example 4 has high tensile strength and low electrical resistance, but has a low porosity and a small battery capacity. In Comparative Example 5, the porosity is high, but the tensile strength is weak and the electric resistance is large.
As described above, according to the present invention, it is possible to provide a battery substrate and electrode having a high capacity and a small electric resistance.

Claims (5)

  A battery electrode substrate formed by coating a metal containing nickel on the surface of a woven or non-woven fiber made of a resin, the porosity of which is 90% or more and 98% or less, and the tensile strength of the substrate Is an electrode substrate for a battery, characterized by having a longitudinal direction of 20 N / cm or more and a width direction of 10 N / cm or more.   The fiber of the woven fabric or nonwoven fabric made of the resin has a core-sheath structure, the core is polypropylene and the sheath is made of polyethylene, and the weight ratio of PE to the total weight of the fiber is 30% or more and 90% or less. The battery electrode substrate according to claim 1, wherein the battery electrode substrate is provided. 3. The battery electrode substrate according to claim 1, wherein the basis weight of the metal amount containing the coated nickel is 150 to 350 g / m ² .   The battery electrode substrate according to any one of claims 1 to 3, wherein an active material mixture mainly composed of nickel hydroxide is supported and rolled in the longitudinal direction of the nonwoven fabric. . A battery comprising the battery electrode according to claim 4.