JP5495646B2 - Current collector for electrochemical element and electrochemical element using the same - Google Patents

Description

  The present invention relates to a current collector for an electrochemical element and an electrochemical element using the same.

  Alkaline batteries are widely used as power sources for devices ranging from portable devices to large industrial facilities because they can be highly reliable and lightweight. The alkaline battery contains an electrode and a separator in a stacked state. In many cases, an electrode is formed by coating or filling a current collector made of a flat metal or a metal porous body with an active material responsible for a battery reaction. Since the power generation capacity of the alkaline battery depends on the amount of the active material filled in the current collector, the current collector may have a high porosity so that the active material can be filled in a larger amount. It has been demanded.

  As a current collector having such a high porosity, Japanese Patent Laid-Open No. 2007-305345 (hereinafter referred to as Patent Document 1) is manufactured by applying nickel plating to a nonwoven fabric oriented in a predetermined direction made of synthetic fibers. In JP 2009-26562 A (hereinafter referred to as Patent Document 2), a positive electrode substrate having a resin skeleton (current collector) is prepared by adjusting the thickness of a nonwoven fabric made of resin fibers by heat treatment, A battery electrode base material (current collector) having a metal film layer on a fiber surface of a nonwoven fabric made of resin fibers produced by forming a film layer is disclosed.

  However, since the resin skeleton is present in the current collector manufactured as described above, the bonding force when bonded to the terminal is weak. Therefore, it is necessary to perform the joining after processing the current collector to be tabless in the terminal attaching process, or it is necessary to perform the joining after the expanded metal is interposed between the current collector and the terminal. It was.

A porous metal is known as a current collector that does not require such tabless processing or expanded metal. For example, in Japanese Patent Application Laid-Open No. 08-69801 (hereinafter referred to as Patent Document 3), a non-woven fabric made of polypropylene short fibers is electroplated, and then the non-woven fabric is decomposed and removed by heat. A metal porous body of m ² is disclosed. In Reference 3, it is pointed out that when the alkaline storage battery is manufactured, the metal fiber on the surface of the porous metal body manufactured as described above causes a short circuit through the separator when the alkaline storage battery is manufactured. In addition, it discloses that the occurrence of a short circuit is prevented by smoothing the surface of the nonwoven fabric before electroplating by thermal welding using a roll.

As in the case of the cited document 3, as a porous metal body manufactured by decomposing and removing a nonwoven fabric by heat, Japanese Patent Application Laid-Open No. 08-69814 (hereinafter referred to as Patent Document 4) describes a method for electrically treating a nonwoven fabric made of an organic polymer such as polypropylene. Disclosed is a porous metal body produced by plating and removing a nonwoven fabric by heat. Although cited reference 4 does not disclose the winding method or the definition of short circuit, it is disclosed that the short circuit of the nickel-hydrogen battery formed by laminating the porous metal body and the separator was 0 out of 100. Has been. However, although the basis weight of the manufactured metal porous body is not disclosed in the cited document 4, the basis weight of the metal porous body that does not have the nonwoven fabric that becomes the resin skeleton is 300 to 500 g / m as in the cited reference 3. ^Since it is technical common sense that it is about ^2, it is considered that the porous body disclosed in the cited document 4 is also likely to cause a short circuit due to the fluff of the metal fiber, as in the cited document 3.

In fact, as a result of examining whether or not a short circuit occurs in a nickel-hydrogen battery manufactured in accordance with the manufacturing method disclosed in the cited document 4, the basis weight of conventional technical common sense (300 g / m ² and 450 g / m ² ) A large number of fluffing was observed on the surface of the current collector, and in the nickel-hydrogen battery manufactured using this current collector, the occurrence of a short circuit due to the fuzz of the current collector penetrating the separator was observed. It was.

Although the above is a problem in alkaline batteries, even in electrochemical elements such as capacitors, since the occurrence of a short circuit causes the stop of power generation capacity, development of a current collector that is unlikely to cause a short circuit is required. . However, since the current collector made of a porous metal body has many fiber fluffs on the surface thereof, a short circuit caused by penetrating the laminated separator can be prevented, such as a capacitor using the current collector. In some electrochemical devices, it may occur.

JP 2007-305345 A (Claims 0010, 0029, 0040, 0050-0052) JP 2009-26562 (Claims, 0016, 0019-0023, 0043, 0052) JP 08-69801 A (claims, 0005-0010, 0017, 0019, 0022) JP 08-69814 A (Claims 0005-0008, 0012-0019)

  The present invention has been made to exceed the above-mentioned limitations of the prior art, and an object thereof is to provide a current collector for an electrochemical element in which an internal short circuit of the electrochemical element is difficult to occur, and an electrochemical element using the same. Is.

The current collector for an electrochemical element according to claim 1 is “a current collector for an electrochemical element, characterized by being an aggregate of hollow fibers made of nickel metal having a basis weight of 215 g / m ² or less”.

  The electrochemical element according to claim 2 is an “electrochemical element using the current collector for an electrochemical element according to claim 1”.

According to claim 1 of the present invention, since the current collector for an electrochemical element is an “aggregate of hollow fibers made of nickel metal having a basis weight of 215 g / m ² or less”, the current collector for an electrochemical element Even if there is fluff of the fiber on the surface, the fluff of the fiber is a hollow fiber made of a fragile metal that is easy to bend and thus does not penetrate the separator. Therefore, it is a current collector for an electrochemical element that does not easily cause an internal short circuit of the electrochemical element.

According to a second aspect of the present invention, there is provided an electrochemical element in which the occurrence of an internal short circuit is prevented by using the electrochemical element current collector according to the first aspect.

It is sectional drawing in the direction which makes perpendicular | vertical to the surface of the electrical power collector for electrochemical elements which showed the measuring method of the static friction force of the electrical power collector for electrochemical elements which concerns on this invention.

The current collector for an electrochemical element of the present invention (hereinafter referred to as a current collector) is an aggregate of hollow fibers made of metal, and its basis weight is 250 g / m ² or less.

The metal referred to here is not limited to various metal compounds such as nickel, copper, platinum, gold, silver, zinc, cadmium, tin, chromium, various alloys, metal oxides, and the like, for example. Further, the current collector may be composed of only one type of metal, or may be composed of a plurality of types of metals.

  The hollow fiber here refers to a fiber in which a metal non-existence region exists in the fiber cross section. It is preferable that the shape of the nonexistent region is a perfect circle because the strength of the entire hollow fiber is uniform. However, as long as the hollow fiber can suitably constitute the current collector, the shape of the nonexistent region may be any shape such as an ellipse, a polygonal shape, a star shape, a rice shape, or an alphabet shape such as a Y shape.

  It is preferable that the metal-free region exists in the center of the fiber cross section because the strength of the entire hollow fiber becomes uniform. However, as long as it is a hollow fiber that can suitably constitute the current collector, the location where the metal-free region is present may be eccentric. A hollow fiber having a part of the surface of the hollow fiber that is cleaved or opened and the surface of the hollow fiber is continuous with the metal-free region is also regarded as a hollow fiber.

When the ratio of the non-existing region in the cross-section of the hollow fiber is less than 10%, when the hollow fiber fluffs on the surface of the current collector, the hollow fiber is strong and penetrates the separator to produce an electrochemical element. There is a tendency to cause a short circuit. On the other hand, when the ratio exceeds 90%, the strength of the hollow fiber is lowered, and the current collector tends to be broken. Therefore, this ratio is preferably in the range of 10% to 90%, and more preferably in the range of 15% to 80%.

The term “aggregate” as used herein refers to a state in which the surfaces of hollow fibers made of metal are partially integrated by sintering.

Since the weight of the current collector is 250 g / m ² or less and is constituted by a hollow fiber made of metal, the fluff generated on the surface of the current collector becomes fragile and easily bent. Therefore, the possibility that the fluff generated when the electrochemical element is manufactured using the current collector penetrates the separator is low.

The lower the basis weight, the lower the possibility of penetrating the separator because the hollow fibers made of metal tend to become brittle fluff. Basis weight of the order current collector is more preferably at 215 g / m ² or less, more preferably at 200 g / m ² or less, most preferably 170 g / m ² or less.

Current collectors tend to have a low basis weight and poor rigidity, and when a current collector with a too low basis weight is used, it tends to be difficult to produce an electrochemical element. Therefore, the basis weight of the current collector is preferably 150 g / m ² or more.

The basis weight of the current collector in the present invention is obtained by measuring the area and mass of the current collector, calculating the mass per 1 m ² of the current collector, and using the calculated mass as the basis weight.

  When a cylindrical electrochemical device is manufactured by winding with a separator interposed between the electrodes, a force is applied to the electrode during winding to prevent the electrode from being broken. The electrode filled with the substance preferably has a high tensile strength in the winding direction.

  Since many electrodes used when manufacturing a cylindrical electrochemical element are rectangular, the winding direction and the long side direction of the electrode indicate the same direction. Therefore, the tensile strength in the long side direction of the current collector constituting the electrode is preferably strong so that a force can be applied to the electrode during winding to prevent the electrode from breaking. More specifically, the tensile strength in the long side direction of the current collector is preferably 11 N / 2 cm width or more, more preferably 20 N / 2 cm width or more, and most preferably 25 N / 2 cm width or more. preferable.

  The current collector having such a tensile strength in the long side direction is, for example, a hollow fiber oriented in the long side direction. Thus, when the hollow fibers are oriented in the long side direction, the tensile strength in the long side direction is stronger than the tensile strength in the short side direction.

  The tensile strength in the long side direction and the short side direction of the rectangular current collector is a value obtained by the following measurement method.

  The tensile strength in the long side direction was measured by cutting a test piece having a length of 4 cm in the long side direction and a length of 2 cm in the short side direction from a rectangular current collector, and then JIS L1096: 1999, 8.12. 1 (A method, strip method) is a value measured using a constant speed tension type tensile tester (ORIENTEC TENSILON UCT-100, 2 cm between chucks, pulling speed 100 mm / min.).

  The tensile strength in the short side direction is a value measured by the same method as described above after cutting out a test piece having a length of 2 cm in the long side direction and a length of 4 cm in the short side direction from a rectangular current collector. It is.

In addition, when the electrode is wound so that the direction in which the hollow fibers are oriented and the winding direction coincide with each other, there is a tendency that fluffing of the electrode is less likely to occur during winding, and an internal short circuit of the electrochemical element occurs. This is preferable because it becomes difficult.

Below, the manufacturing method of the electrical power collector which concerns on this invention is demonstrated.

The hollow fiber made of the metal constituting the current collector of the present invention is obtained, for example, by forming a metal film on a known organic fiber aggregate and then burning the organic fiber aggregate by firing, The current collecting material is formed by sintering the hollow fibers to be bonded together at the intersection.

  First, the organic fiber constituting the organic fiber assembly is not particularly limited, but the organic fiber assembly is easily burned out so that a metal film is suitably formed on the organic fiber assembly, which will be described later. For example, polyolefin fiber, polyimide fiber, polyamideimide fiber, polyamide fiber (aromatic polyamide fiber, aromatic polyetheramide fiber, nylon fiber), polyester fiber (fully aromatic polyester fiber, polyethylene terephthalate) Fiber), cellulosic fiber, and polybenzimidazole fiber can be suitably used.

  Further, the resin forming these organic fibers may be either a linear polymer or a branched polymer, and the polymer may be a block copolymer, a random copolymer, or a resin mixed with a multi-component polymer. It does not matter whether the polymer has any three-dimensional structure or crystallinity.

  The organic fiber assembly is not limited to one composed of one type of fiber, and may be composed of a plurality of types of fibers. Moreover, what was comprised using the organic fiber which consists of multiple types of resin may be used. As an example of an organic fiber composed of a plurality of types of resins, a composite-type fused fiber (particularly in the fiber cross section) in which the organic fiber includes a low melting point resin and a high melting point resin, and the low melting point resin is exposed on the surface of the organic fiber. The arrangement is preferably a core-sheath type or a sea-island type). It is preferable to use the above-described composite fusion fiber because the organic fiber aggregate can be obtained by integrating the organic fibers by heat fusion treatment.

In any case, it is preferable to form an organic fiber aggregate using organic fibers having a fineness of 0.01 to 30 dtex so that the active material can be filled well when the current collector is manufactured. The fiber length of the organic fiber varies depending on the method of forming the organic fiber aggregate, and is preferably 30 mm or more when the organic fiber aggregate is formed by a dry method, and when the organic fiber aggregate is formed by a wet method. It is preferable that it is 10 mm or less.

An organic fiber web is then formed. For example, a dry method such as a card method, an air lay method, a melt blow method, or a spun bond method, which is known as a means for forming an organic fiber assembly from the above organic fiber or a resin capable of producing the above organic fiber. Or can be formed using wet methods. When forming the organic fiber web, if the organic fibers are easily oriented in one direction, the tensile strength in the orientation direction is stronger than the tensile strength in the direction perpendicular to the direction. As a result, it is possible to produce a current collector in which the hollow fibers are oriented in one direction and the tensile strength in the orientation direction is strong. Such an organic fiber web oriented in one direction can be formed, for example, by increasing the conveying speed of a support such as a conveyor for receiving organic fibers.

  Next, one organic fiber web or a plurality of organic fiber webs laminated by performing entanglement treatment (water entanglement treatment, needle punching treatment), heat fusion treatment, or adhesion treatment alone or in combination. Can be integrated to produce an organic fiber assembly. In particular, it is preferable that the organic fibers are fused and integrated by heat fusion treatment because an organic fiber aggregate having excellent strength is obtained.

The thickness of the organic fiber aggregate varies depending on the current collector manufactured according to the type of electrochemical element (for example, whether it is cylindrical or flat), and is not particularly limited. However, for example, when manufacturing a current collector for a cylindrical battery, the thickness of the organic fiber assembly is 0.3 to 1.8 mm so that winding can be easily performed at the time of preparing the electrode plate group. Is preferred.

  Subsequently, a plating aggregate can be obtained by forming a metal film on the organic fiber aggregate.

  In order to improve the adhesion and adhesion between the organic fiber aggregate and the metal, it is preferable to hydrophilize the organic fiber aggregate. Examples of the hydrophilization treatment include a sulfonation treatment, a treatment with a fluorine gas containing oxygen gas, carbon dioxide gas and / or sulfur dioxide gas, a graft treatment with a hydrophilic vinyl monomer, or a corona discharge treatment. The hydrophilic treatment to be applied is selected according to the type of organic fiber constituting the organic fiber aggregate, and the degree of the hydrophilic treatment is appropriately adjusted.

Examples of a method for forming a metal film on an organic fiber assembly include, for example, a method using only a known electroless plating method, a method of performing electroplating after electroless plating, a method using metal vapor deposition, a method using sputtering, and ion plating. And a method by metal spraying. The formation treatment of the metal film can be selected as appropriate, and the weight of the metal film is adjusted so that the basis weight of the aggregate of hollow fibers made of metal obtained after firing the plating aggregate is 250 g / m ² or less. The amount of formation and the thickness of the film are adjusted as appropriate.

In addition, the type of the metal film may be any metal that does not deteriorate due to the reaction of the electrolytic solution or the electrochemical element, for example, nickel for an alkaline secondary battery, copper, nickel or titanium for a negative electrode for a lithium ion secondary battery, Nickel or titanium can be used for the positive electrode, and nickel or titanium can be used for the electric double layer capacitor.

  By heating and firing the thus produced plating aggregate, the organic fiber aggregate is burned off from the plating aggregate. A current collector can be produced by leaving only the metal film by firing.

  The temperature at the time of firing is not limited because it varies depending on the type of organic fiber to be burned off, and the heating temperature and the apparatus for heating are appropriately adjusted so that the organic fiber can be burned off suitably. Further, it is preferable to fire the plating assembly under vacuum conditions or in an atmosphere of nitrogen or a rare gas so that the metal is not oxidized or modified during firing.

Such a current collector can be used after being cut into a size and shape depending on the type of electrochemical element (for example, whether the shape is cylindrical or flat).

The electrochemical device according to the present invention can be manufactured from the same material as the conventional one except that the current collector as described above is used. For example, a cylindrical nickel-hydrogen battery includes an electrode plate group obtained by winding a positive electrode in which the current collector of the present invention is filled with nickel hydroxide and a hydrogen storage alloy negative electrode plate in a spiral shape with a separator interposed therebetween. And an electrolytic solution of potassium hydroxide / lithium hydroxide or potassium hydroxide / sodium hydroxide / lithium hydroxide is poured into a metal case. In addition, the electric double layer capacitor has a separator between a pair of electrode materials filled in the current collector of the present invention after kneading activated carbon, a conductive filler (carbon black, acetylene black, etc.) and a binder. These are all housed in a case or an aluminum laminate pack, and have an organic solvent or an electrolyte solution of a sulfuric acid solution.

  When the current collector for an electrochemical device of the present invention is laminated with a separator, the fluff of hollow fibers made of metal generated on the surface of the current collector for electrochemical device is easily bent and fragile. Since the fluff can be prevented from penetrating the separator, it is possible to prevent the occurrence of an internal short circuit that occurs when an electrochemical element is manufactured. Therefore, for example, it can be suitably used as an electric storage device such as an alkaline secondary battery such as a nickel metal hydride battery or a nickel cadmium battery, a non-aqueous battery such as a lithium ion secondary battery, or an electric double layer capacitor. It can be suitably used as a current collector for batteries such as lithium secondary batteries and electric double layer capacitors. In addition, since the current collector of the present invention has a small basis weight, it is lower in cost than the conventional current collector and reduces the weight of the electrochemical element.

Therefore, the electrochemical element using the current collector is an electric (including hybrid) automobile, an electric assist bicycle, an electric tool, a remote control toy, a backup power source for a personal computer, a power supply for an emergency light, a battery for a digital camera, and a digital video. It can be suitably used as an electrochemical element used for a power source or the like.

EXAMPLES Hereinafter, the present invention will be specifically described by way of examples, but these do not limit the scope of the present invention.

The thickness in the present invention is a dial gauge (load: 2.3 N / cm ² , measuring element: 5 cm ² cylindrical shape) at 30 measurement points on the surface having the widest area of the object whose thickness is to be measured. Thickness is measured using, and the arithmetic average value of 30 points obtained is said.

(Example 1)
(1) Selection of organic fibers As the organic fibers constituting the organic fiber aggregate, the following core-sheath type fibers showing a heat-sealing action were used.

[Core-sheath fiber]
Core component material: Polypropylene core component melting point: 160 ° C
Sheath component material: Polyethylene sheath component melting point: 135 ° C
Fineness: 6.6dtex, fiber length: 76mm

(2) Forming method of organic fiber aggregate The above-described core-sheath fiber is opened using a card machine, and the basis weight is 50 g / m ² cross lay web (overlap 3 times) and the basis weight is 35 g / m. ^Two unidirectional webs were produced. All these webs were manufactured so that the final line tempo was 15 m / min. Next, while laminating the obtained web, it is supplied to an air-through dryer having a temperature set at 140 ° C., and by expressing the heat-sealing action of the core-sheath fiber, the basis weight is 85 g / m ² , thickness A fused organic fiber aggregate having a thickness of 0.9 mm was obtained.

(3) Forming method of metal film The fused organic fiber assembly is then sandwiched between flat electrodes carrying silicone rubber (silicone rubber is in contact with the fused organic fiber assembly) and at atmospheric pressure. In the presence of air (humidity: 60 RH%), an AC voltage is applied between the electrodes (voltage: 24 kVp, output: 2.8 kW, output per unit area: 1.83 W / cm ² , frequency: 25 KHz, waveform : Sine wave), and a hydrophilization treatment was performed by generating electric discharge inside the fused organic fiber assembly.

Then, the hydrophilic organic fiber assembly subjected to the hydrophilic treatment is wound around a carrier of a dyeing machine, a refining agent is circulated and washed with water, and then an aqueous solution containing 10 g / L of stannous chloride and 20 ml / L of hydrochloric acid is obtained. The mixture was circulated, washed with water, and then catalyzed by circulating an aqueous solution containing 1 g / L of palladium chloride and 20 ml / L of hydrochloric acid. Thereafter, washing with water is further performed, and an electroless nickel plating solution of nickel sulfate 18 g / L, sodium citrate 10 g / L, hydrated hydrazine 50 ml / L, 25% aqueous ammonia 100 ml / L is heated to a temperature of 60 ° C. and circulated. I let you. After heating and circulating for 1 hour, the plating solution became almost transparent, and then the circulation was stopped to form a nickel coating, and the hydrophilized fused organic fiber assembly was taken out, washed with water, dried, and dried. Of 285 g / m ² was obtained.

(4) Plating assembly firing method The plating assembly is supplied to a firing furnace set at a temperature of 500 ° C. in an oxygen atmosphere, the fused organic fiber assembly is burned off, and then 900 ° C. in a hydrogen atmosphere. The current collector was obtained by sintering at a location where hollow fibers made of nickel metal having a basis weight of 200 g / m ² and a thickness of 0.8 mm intersect. Further, in the hollow fiber made of nickel metal, the shape of the metal-free region was a perfect circle and was present at the center of the fiber cross section, and the proportion of the metal-free region was 56%.

The tensile strength of the current collector in the longitudinal direction (coincident with the production direction of the fused organic fiber aggregate) is 30 N / 2 cm width, and the tensile strength in the short direction (corresponding to the width direction of the fused organic fiber aggregate). Was 17 N / 2 cm wide.

(5) Method for producing positive electrode of secondary battery The current collector was cut into a rectangle having a long side (matching the longitudinal direction) of 105 mm and a short side (matching the short direction) of 40 mm. The positive electrode paste was filled in the gaps of the collected current collector, dried, and roll-rolled at room temperature, and then a current collector external terminal was welded to the current collector to produce a positive electrode.

Here, as the positive electrode paste agent, nickel hydroxide powder is 90% by mass, cobalt monoxide powder is 10% by mass as a conductive additive, carboxymethyl cellulose is used as a thickener, and polytetrafluoroethylene is used as an adhesive. used.

(6) Production of negative electrode for secondary battery Nickel plating is applied to a urethane resin foam sheet, and further, the urethane resin is pyrolyzed and removed by firing in a reducing atmosphere. A current collector with a three-dimensional network structure (weight per unit: 420 g / m ² , thickness: 0.8 mm) was produced. Next, after filling the voids of the current collector with the negative electrode paste, drying and roll-rolling at room temperature, a current collector external terminal was welded to the current collector to produce a negative electrode.

Here, as the negative electrode paste agent, a material containing hydrogen storage alloy powder as a base, carboxymethyl cellulose as a thickener, and polytetrafluoroethylene as an adhesive was used.

3. Production of secondary battery AA battery size cylindrical battery case was prepared. Moreover, the separator which consists of a fusion | melting nonwoven fabric to which the core-sheath-type composite fiber (fineness: 2.2 dtex, fiber length: 5 mm) which a core component consists of a polypropylene and a sheath component consists of polyethylene was prepared.

Next, the separator, the positive electrode, the separator, and the negative electrode were stacked in this order, and the stacked laminate was wound in a spiral shape so that the positive electrode was inside, and inserted into the cylindrical battery case. And the negative electrode current collection external terminal was welded to the bottom of the can in the cylindrical battery case, then necking was performed, and a predetermined amount of alkaline electrolyte was injected. Thereafter, the upper part of the cylindrical battery case was sealed with an encapsulating plate to produce an alkaline secondary battery.

(Example 2)
A current collector and a secondary battery were produced in the same manner as in Example 1 except that the plating amount was adjusted so that the weight of the aggregate of hollow fibers made of nickel metal was 215 g / m ² .

( Reference example )
A current collector and a secondary battery were produced in the same manner as in Example 1 except that the plating amount was adjusted so that the weight of the aggregate of hollow fibers made of nickel metal was 250 g / m ² .

(Example 3 )
A current collector and a secondary battery were produced in the same manner as in Example 1 except that the plating amount was adjusted so that the basis weight of the hollow fiber aggregate made of nickel metal was 170 g / m ² .

(Comparative Example 1)
A current collector and a secondary battery were produced in the same manner as in Example 1 except that the plating amount was adjusted so that the weight of the aggregate of hollow fibers made of nickel metal was 300 g / m ² .

(Comparative Example 2)
A current collector and a secondary battery were produced in the same manner as in Example 1 except that the plating amount was adjusted so that the weight of the aggregate of hollow fibers made of nickel metal was 450 g / m ² .

Various physical properties of the current collector and the secondary battery obtained as described above were measured using the following methods. The measurement results are summarized in Table 1.

(Static friction force measurement)
A web of 100g / m ^{2 with} a fabric weight of 2.2dtex made of polyester and nylon and a fiber length of 51mm (orange-type 16 divisions) is applied once from the surface and 2 times from the back surface with a water flow of 10MPa pressure. An organic fiber assembly having a thickness of 0.5 mm was obtained by performing hydroentanglement once.

  Each current collector was cut into a rectangle having a long side (matching the longitudinal direction) of 200 mm and a short side (matching the short side direction) of 50 mm.

  Hereinafter, description will be made with reference to FIG.

  The aluminum plate (11) and the water-entangled organic fiber assembly (12) were adhered to produce a measurement plate (20). The measurement plate (20) was placed on a flat desk (not shown) so that the aluminum flat plate (11) side was in the direction of gravity. The size of the contact surface with the collected current collector (13) and then the current collector (13) on the side of the water-entangled organic fiber aggregate (12) of the measurement plate (20) is 3 cm in length × width Lamination was performed in the order of a load body (14) of 3 g and 200 g.

Using a constant speed tension type tensile testing machine (not shown, ORIENTEC TENSILON UCT-100, tensile speed 500 mm / min), the current collector (13) under the above conditions is pulled in the long side direction (a). The static friction force generated at that time was measured. The static friction force of the collected current collector (13) was calculated by calculating the arithmetic average value obtained by measuring the static friction force on the front and back surfaces of the current collector (13) twice.

(sensory evaluation)
When the surface of the current collector was touched with a fingertip, it was evaluated whether it felt resistance due to fluffing.
○: No resistance due to fluffing △: Feeling resistance due to fluffing ×: Very much resistance due to fluffing

(Internal resistance measurement)
Using an LCR meter (manufactured by HIOKI), the specific resistance of each alkaline secondary battery at an alternating current of 1 KHz was measured, and the internal resistance was calculated by calculating the arithmetic average value of each three.

(Battery failure rate measurement)
When the cylindrical nickel-metal hydride secondary battery was manufactured by the above-described method, the percentage that the short-circuit occurred and the secondary battery could not be manufactured appropriately was defined as the battery defect rate.

From the above results, the current collector of the electrochemical device according to the present invention has a lower basis weight, so that the static friction force decreases and resistance due to fuzz is not felt, and the battery failure rate decreases corresponding to the result. Turned out to be. In particular, when the current collector for an electrochemical element has a basis weight of 250 g / m ² or less, it becomes a current collector for an electrochemical element that does not feel resistance due to fluffing, and the effect of reducing the battery defect rate becomes remarkable. It was.

Since the current collector for an electrochemical element of the present invention is an “aggregate of hollow fibers made of metal having a basis weight of 250 g / m ² or less”, there is a fuzz of fibers on the surface of the current collector for an electrochemical element. Even so, since the fluff of the fiber is a hollow fiber made of a fragile metal that is easily bent, it can be prevented from penetrating the separator. Therefore, an electrochemical element using the current collector for an electrochemical element is a current collector for an electrochemical element that hardly causes an internal short circuit.

The current collector for an electrochemical device of the present invention can be used for electrochemical device applications.

11 ... Aluminum plate
12 ... Water-entangled organic fiber assembly
13 ... Collected current collector
14 ・ ・ ・ 200g load body with 3cm vertical x 3cm horizontal contact surface with current collector (13)
20 ... Measurement plate
a: Long side direction of hollow fiber made of metal of current collector

Claims (2)

A current collector for an electrochemical element, characterized by being an aggregate of hollow fibers made of nickel metal having a basis weight of 215 g / m ² or less. An electrochemical device using the current collector for an electrochemical device according to claim 1.

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