JP5116076B2 - Battery electrode substrate, battery electrode using the same, and battery - Google Patents

Description

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

Examples of current collectors used in alkaline secondary batteries that have been developed so far include the following.
Patent Document 1 proposes a method for producing a nickel-plated non-woven electrode characterized by electroless nickel plating after hydroentanglement treatment of a 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, the surface of the nonwoven fabric is nickel-plated, and the current collector with a specific surface area per unit volume of 0.13 m ² / cm ^{3 to} 0.35 m ² / cm ³ has a viscosity of 0.3 Pa · s or less. It is characterized by being obtained by filling an active material paste and drying it. As a result, an alkaline battery capable of high output is obtained.

  In any of the inventions described in the above-mentioned patent documents, a non-woven fabric made of polyolefin-based fibers is subjected to nickel plating as an electrode substrate. However, these inventions have yet to provide batteries with high capacity and high voltage (high output).

JP 5-2903838 A JP 2001-313038 A JP 2003-109600 A JP-A-2005-347177

  The object of the present invention is to solve the above-mentioned problems, that is, to provide a battery electrode substrate capable of producing a battery having a high capacity and a high voltage.

As a result of intensive studies to solve the above problems, the present inventors have found that the fineness of the fibers of the nonwoven fabric used for the battery electrode substrate is 2 dTex or more and 4 dTex or less, and the thickness of the nonwoven fabric is 0.9 mm or more . The inventors have found that it is effective that the amount of coated nickel is 150 to 250 g / m ² , thereby completing the present invention. That is, the present invention employs the following configuration.

(1) A battery electrode substrate in which a fiber surface of a woven or nonwoven fabric made of resin is coated with nickel, the fineness of fibers constituting the nonwoven fabric is 2 dTex or more and 4 dTex or less, and the thickness of the original nonwoven fabric is 0. and a 9mm or more, the amount coated nickel, battery electrode substrate, which is a 150 to 250 g / ^{m 2.}
(2) The battery electrode substrate according to (1) above, wherein the woven or non-woven fiber made of the resin is a fiber made of polypropylene (PP) and polyethylene (PE).
(3) The above-mentioned (1), wherein the PP / PE weight ratio of the fiber is 0.25 or more.
Or the electrode substrate for batteries as described in (2).
(4) The battery electrode substrate as described in any one of (1) to (3) above, wherein the thickness of the battery electrode substrate after nickel plating is 0.9 mm or more.

( 5 ) The battery electrode substrate according to any one of (1) to ( 4 ), wherein the battery electrode substrate has a porosity of 95 to 98%.
( 6 ) A battery electrode, wherein the battery electrode substrate according to any one of (1) to ( 5 ) above carries an active material mixture mainly composed of nickel hydroxide.
( 7 ) A battery using the battery electrode substrate according to any one of (1) to ( 5 ) above.

  According to the present invention, it is possible to provide a battery electrode substrate capable of producing a high-capacity and high-voltage battery.

  The battery electrode substrate according to the present invention is a battery electrode in which a fiber surface of a woven or nonwoven fabric made of resin is coated with nickel, and the fineness of the fibers constituting the nonwoven fabric is 2 dTex or more and 4 dTex or less, and the battery electrode substrate The original nonwoven fabric has a thickness of 0.9 mm or more. In order to increase the voltage of the battery, the fineness of the fibers constituting the nonwoven fabric is preferably 2 dTex or more and 4 dTex or less. Thereby, since the number of conductive paths can be increased, the voltage of the battery can be improved. Furthermore, in order to ensure the capacity of the battery, the thickness of the original nonwoven fabric is preferably 0.9 mm or more, more preferably 1.1 mm or more, and further preferably 1.2 mm or more. By setting the thickness of the nonwoven fabric made of resin fibers having a fineness of 2 dTex or more and 4 dTex to 0.9 mm or more, it is possible to achieve both battery capacity and voltage. If the fiber fineness of the nonwoven fabric is less than 2 dTex, the stiffness of the fiber will be weakened, and the thickness of the nonwoven fabric will decrease. Conversely, if it exceeds 4 dTex, the number of conductive paths will decrease and the battery voltage cannot be increased. . Moreover, since the battery capacity falls that the thickness of the original nonwoven fabric is less than 0.9 mm, it is not preferable. If the original nonwoven fabric is too thick, the battery electrode substrate after plating with nickel will also be thick, and it will be necessary to adjust the thickness of the substrate as will be described later, so the original nonwoven fabric thickness is 5 mm or less. It is preferable.

The battery electrode substrate according to the present invention is characterized in that the woven or non-woven fibers made of resin are fibers made of polypropylene (hereinafter also referred to as PP) and polyethylene (hereinafter also referred to as PE). In particular, a core-sheath composite fiber structure having PP as the core and PE as the sheath is preferable. In the case of a PP / PE core-sheath composite fiber structure, PE in the sheath part has a lower melting point than PP in the core part. Therefore, by heat-treating the woven or non-woven fabric, the PE in the sheath part is maintained while maintaining the porous structure. The layer can be melted. Thereby, since the adhesion between the resin fibers can be strengthened, the strength characteristics can be improved. Further, since the nickel film can be coated at a high rate, a sufficient conductive path between the fibers when coated can be secured, and the conductivity of the battery electrode substrate can be improved.
Further, the PP / PE weight ratio of the fibers at this time is preferably 0.25 or more because the thickness of the battery electrode substrate can be secured. More preferably, it is 0.4 or more, More preferably, it is 0.5 or more. In addition, if the sheath portion has too little PE, the fibers cannot be bonded to each other well, so the PP / PE weight ratio is preferably 0.8 or less. Furthermore, since the material which does not elute and decompose | disassemble in the strong alkali in a battery is required, it is preferable that the fiber which comprises a nonwoven fabric is an olefin type compound.

The battery electrode substrate according to the present invention is characterized in that the thickness after nickel plating is 0.9 mm or more. Thereby, the electrical resistance of the battery electrode substrate can be reduced, and at the same time, a sufficient amount of the active material mixture can be held, so that the battery capacity can be improved, which is preferable. The thickness of the battery electrode substrate is more preferably 1.1 mm or more, and still more preferably 1.2 mm or more. If the battery electrode substrate is too thick, it is difficult to uniformly fill the active material. For this reason, it is necessary to adjust the thickness of the thick substrate, but there is a risk that the skeleton is damaged in the adjustment process. Therefore, the thickness of the battery electrode substrate is preferably 1.6 mm or less.
The battery electrode substrate according to the present invention preferably has a coated nickel amount of 150 to 250 g / m ² . If the amount of nickel to be coated is less than 150 g / m ² , the battery voltage decreases, and if it exceeds 250 g / m ² , the cost for producing the battery electrode substrate increases, which is not preferable.

The battery electrode substrate of the present invention preferably has a substrate porosity of 95 to 98%. As a result, a sufficient amount of the active material mixture can be retained, so that the battery capacity can be improved. As the active material mixture to be supported on the battery electrode substrate, a material mainly composed of nickel hydroxide is preferable.
Such a battery electrode substrate according to the present invention can be preferably used for a battery such as an alkaline secondary battery.

The present invention will be described in more detail below based on examples.
A core-sheath structure in which the periphery of PP is covered with PE, and its weight per unit area is 45 g / m ² using PP / PE weight ratio of 5/5 and fineness of 2.2 dTex and 3.3 dTex, respectively. In addition, a nonwoven fabric is prepared by a thermal bond method. A battery electrode substrate was prepared by applying nickel of 8 g / m ² to the nonwoven fabric by sputtering or electroless plating, and then by electro nickel plating so that the total nickel basis weight was 200 g / m ² .
The substrate was adjusted to a thickness of 1.4 mm by a roller press, and then charged with a positive electrode active material mixture for a nickel metal hydride battery containing nickel hydroxide and cobalt hydroxide as main components. After filling, the electrode surface was smoothed and dried at 80 ° C. for 30 minutes, and then a positive electrode for a nickel metal hydride battery was prepared using a roller press. Details of this electrode are shown in Table 1.

As a comparative example, a core-sheath structure in which the periphery of PP is covered with PE, the weight ratio of PP / PE is 5/5, the fineness is 1.1 dTex and 6.7 dTex, respectively, and the fiber basis weight is 45 g / m. Create a non-woven fabric by thermal bonding so that it becomes ² . Table 1 also shows the details of the electrodes produced using these in the same manner as in the example. The capacity density in Table 1 indicates the capacity density calculated from the weight of the active material mixture filled in the positive electrode. The thickness was measured at 3.0 g weight / cm ² (75 g load was applied to a 5 cm × 5 cm range).

  From Table 1, the electrodes of Examples 1 and 2 and Comparative Example 2 can produce a battery having a large capacity density. However, in Comparative Example 1, the active material mixture filling amount decreased due to insufficient thickness, and the electrode became thinner. This is because the thickness of the nonwoven fabric could not be increased because fibers having a small fineness were used. In addition, since the capacity density is slightly small, the battery capacity is small. Since the thickness of the electrode is small, the number of wrinkles increases. However, since the ratio of other than the positive electrode (separator and negative electrode) in the battery increases, the capacity of the battery also decreases. The reason why the thickness after plating is higher than the original thickness is that the strength of the nonwoven fabric in the thickness direction is increased because the fiber is coated with nickel, and the nonwoven fabric is compressed against the load for measuring the thickness. This is because the proportion of

  In order to investigate the battery characteristics of these electrodes, a sealed cylindrical battery was prepared using a known hydrogen storage alloy negative electrode and separator as the negative electrode. As an electrolytic solution, 30 g / liter of lithium hydroxide was dissolved in a 30 wt% potassium hydroxide aqueous solution. After charging and discharging several times at a low rate for chemical conversion treatment, charging / discharging was performed at the current rates shown in Table 2 to examine the utilization rate. The utilization rate was calculated by the ratio of the discharge capacity to the calculated capacity. Charging was performed up to 120% of the calculated capacity, and the final discharge voltage was 0.8V. The results are shown in Table 2.

From Table 2, the batteries using the electrodes of Examples 1 and 2 and Comparative Example 1 showed a utilization rate of 90% or more even in 2C discharge. However, in the battery using the electrode of Comparative Example 2, when the discharge rate increased, the discharge voltage decreased greatly, and a sufficient utilization rate was not obtained. This is presumably because the use of fibers with a high fineness resulted in a lack of a sufficient number of conductive paths and an increase in electrical resistance.
From the above results, the present invention can provide a battery substrate capable of achieving both high battery capacity and battery voltage.

Claims (7)

A battery electrode substrate in which a fiber surface of a woven or nonwoven fabric made of resin is coated with nickel, the fineness of the fibers constituting the nonwoven fabric is 2 dTex or more and 4 dTex or less, and the thickness of the original nonwoven fabric is 0.9 mm or more There, battery electrode substrate, wherein the amount coated nickel is 150 to 250 g / ^{m 2.}   The battery electrode substrate according to claim 1, wherein the woven or non-woven fiber made of resin is a fiber made of polypropylene (PP) and polyethylene (PE).   The battery electrode substrate according to claim 1 or 2, wherein a PP / PE weight ratio of the fibers is 0.25 or more.   The battery electrode substrate according to any one of claims 1 to 3, wherein a thickness of the battery electrode substrate after the nickel coating is 0.9 mm or more. Battery electrode substrate, wherein the porosity of the electrode substrate for a battery according to any one of claims 1-4 is a 95% to 98%. An electrode for a battery according to any one of claims 1 to 5 , wherein an active material mixture mainly composed of nickel hydroxide is supported. A battery using the battery electrode substrate according to any one of claims 1 to 5 .