JP2005071844A - Current collection material for electrochemical element and battery using this as well as electric double layer capacitor using this - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make it a first purpose to provide a current collector in which an active material can be filled in a great deal because it is of a high void percentage and hard to be crushed in filling the active material, and with which an electrochemical element of a high capacity can be manufactured as a result, and make it a second purpose to provide the current collector with which the electrochemical element of high-rate charge and discharge characteristics can be manufactured in addition to the high capacity. <P>SOLUTION: As for the current collector for the electrochemical element, plating is applied to a non-woven fabric containing a high Young-modulus fiber of which the Young modulus is not less than 20 cN/dtex. If a fine fiber of the filament fineness 0.8 dtex or less is contained as a constituent in the non-woven fabric, the electrochemical element of high-rate charge and discharge characteristics can be manufactured. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a current collector for an electrochemical element, a battery using the same, and an electric double layer capacitor using the same.

  For example, alkaline secondary batteries are highly reliable and can be reduced in size and weight, and are therefore widely used as power sources for various devices ranging from portable devices to industrial large facilities. In most of the alkaline secondary batteries, a nickel electrode is used as a positive electrode. The nickel electrode has a structure in which a positive electrode active material for causing a battery reaction is supported on a current collector that shares a current collecting function. As a current collector in that case, a sintered nickel plate or a punched nickel plate obtained by sintering nickel powder has been widely used. The capacity of the battery is determined by the amount of the active material filled in the voids such as the nickel plate, and the filling amount of the active material is determined by the porosity of the nickel plate or the like. Is preferably as large as possible.

  For this reason, the applicant of the present application states that “an alkali 2 comprising a non-woven fabric hydrophilized by sulfonation, fluorine gas treatment, or vinyl monomer grafting, and a nickel plating film formed on the surface of the non-woven fabric”. Next, a current collector for electrochemical devices "was proposed (Patent Document 1). This current collector had a higher porosity than conventional nickel plates, etc., but the porosity was not sufficiently high, and this current collector was easily deformed by external force, and the current collector was not filled when filled with an active material. Since it is easy to be crushed, the filling amount of the active material tends to decrease. Thus, even when a battery is manufactured using a current collector with a small amount of active material, only a battery having a low capacity can be manufactured.

  In addition, if thin fibers are used as the fibers constituting the current collector, the surface area of the current collector can be increased, so that a battery excellent in high rate charge / discharge can be manufactured. However, if such thin fibers are used, the porosity is further increased. As a result, only a battery having a low capacity could be manufactured.

  Similarly, when the current collector as described above is used as a current collector for other electrochemical elements (for example, an electric double layer capacitor), the porosity is not sufficiently high (especially when thin fibers are used), And the active material (activated carbon in the case of an electric double layer capacitor) is easily crushed, the active material filling amount is reduced, and as a result, only a low-capacity electrochemical device (for example, an electric double layer capacitor) is produced. I couldn't.

JP 2001-313038 A (Claims etc.)

  The present invention has been made in order to solve the above-described problems, and has a high porosity and can be filled with a large amount of an active material by being hard to be crushed when filled with an active material. It is a first object to provide a current collector that can manufacture the above. A second object is to provide a current collector that can produce an electrochemical element that is excellent in high rate charge / discharge characteristics in addition to high capacity.

  The invention according to claim 1 of the present invention is “a current collector for an electrochemical element, characterized in that a non-woven fabric containing a high Young's modulus fiber having a Young's modulus of 20 cN / dtex or more is plated”. Since the high Young's modulus fiber has high rigidity to bending, it is difficult to be crushed by an external force during the production of the nonwoven fabric, and a desired thickness can be secured, so that it can be a current collector with a high porosity. Also, when plating on the nonwoven fabric, external force such as winding pressure that rolls up and the flow of plating solution may be applied, but the current collector has a high porosity because it is not easily crushed by external force. Can do. Furthermore, since it is difficult to be crushed by the pressure at the time of filling the active material, it can be filled with a large amount of active material, and as a result, an electrochemical device having a large capacity can be manufactured.

  The invention according to claim 2 of the present invention is "the current collector for an electrochemical element according to claim 1, characterized in that high Young's modulus fibers are fused." If the high Young's modulus fiber itself acts as an adhesive fiber and the high Young's modulus fiber is fused, there is no need to use an adhesive fiber with a low Young's modulus, or a small amount can be used. The content of Young's modulus fiber can be increased. As a result, since it can be a current collector with a higher porosity and less crushing, it can be filled with a large amount of active material, and an electrochemical element with a large capacity can be manufactured.

  The invention according to claim 3 of the present invention is as follows: "The current collector for electrochemical device according to claim 1 or 2, characterized in that the nonwoven fabric comprises fine fibers having a fineness of 0.8 dtex or less. Is. By containing fine fibers, the current collector has a large surface area and a large contact area with the active material. Therefore, it is possible to manufacture an electrochemical device that has high current collection efficiency and is excellent in high rate charge / discharge characteristics that can be charged / discharged at a higher current.

  The invention according to claim 4 of the present invention is "the current collector for an electrochemical element according to claim 3, wherein the fine fibers are high Young's modulus fibers". Normal fine fibers have low bending stiffness and are likely to be thin nonwoven fabrics, but because the fine fibers are high Young's modulus fibers, the thickness can be secured, and the nonwoven fabric can have a high porosity, Since the contact area with the active material is wide, it is easy to produce an electrochemical device having a high capacity and a high rate charge / discharge characteristic.

  The invention according to claim 5 of the present invention is as described in any one of claims 1 to 4, characterized in that it includes high Young modulus thick fibers having a fineness of 3.3 dtex or more as high Young modulus fibers. Current collector for electrochemical device ". By including a high Young's modulus thick fiber, it can be a bulky and high porosity current collector, and it is less likely to be crushed by the pressure when filling the active material, and more active material can be filled. Therefore, it is easy to manufacture a high-capacity electrochemical element. In addition, since the pore diameter of the current collector becomes large, the current collector is excellent in fillability of the active material and is easy to fill the active material into the current collector.

  The invention according to claim 6 of the present invention is “the current collector for an electrochemical element according to any one of claims 1 to 5, wherein the porosity of the current collector is 85 to 95%”. It is. Thus, when the porosity is high, the amount of the active material filled can be increased, so that an electrochemical element having a high capacity can be manufactured.

  The invention according to claim 7 of the present invention is “the current collector for an electrochemical element according to any one of claims 1 to 6, wherein the compressive elastic modulus of the current collector is 85% or more”. It is. With such a compression elastic modulus, it is difficult to be crushed even by the pressure at the time of filling the active material, so that the filling amount of the active material can be increased.

  The invention according to an eighth aspect of the present invention is a “battery provided with the current collector for an electrochemical element according to any one of the first to seventh aspects”. Therefore, the battery has a large capacity. In particular, a battery using a current collector containing a high Young's modulus fiber as a fine fiber is a battery having a high capacity and excellent high rate charge / discharge characteristics, and is a battery suitable for power applications.

  The invention according to claim 9 of the present invention is “an electric double layer capacitor including the current collector for an electrochemical element according to any one of claims 1 to 7”. Therefore, the electric double layer capacitor has a large capacity. In particular, an electric double layer capacitor using a current collector containing a high Young's modulus fiber as a fine fiber is an electric double layer capacitor having high capacity and excellent high rate charge / discharge characteristics, and is an electric double layer capacitor suitable for power applications.

  The current collector of the present invention has a high porosity, is not easily crushed even when pressure is applied, and can increase the filling amount of the active material, so that a high-capacity electrochemical device can be manufactured. In addition, even if fine fibers are used, the porosity is high, and even if pressure is applied, they are not easily crushed. Therefore, an electrochemical element having a high capacity and excellent high rate charge / discharge characteristics can be produced.

  Since the battery or electric double layer capacitor of the present invention uses the current collector, it can be a high capacity battery or electric double layer capacitor. In particular, a battery or an electric double layer capacitor using a current collector containing a high Young's modulus fiber as a fine fiber is excellent in high capacity and high rate charge / discharge characteristics.

  The current collector of the present invention is not easily crushed by the pressure applied when the nonwoven fabric is manufactured, rolled up for plating, or when the plating solution flows, ensuring a desired thickness and high porosity. In addition, high Young's modulus fibers having a Young's modulus of 20 cN / dtex or more are included so that they are not easily crushed by the pressure at the time of filling the active material and can be filled with a large amount of the active material. The higher the Young's modulus of this high Young's modulus fiber, the better the performance, so it is preferably 30 cN / dtex or more. The upper limit of the Young's modulus of the high Young's modulus fiber is not particularly limited, but if it exceeds 100 cN / dtex, the bending stiffness is too high, and the fibers are difficult to get entangled, making it difficult to form a fiber web. Therefore, it is preferably 100 cN / dtex or less. The “Young's modulus” in this specification refers to the value of the apparent Young's modulus calculated from the initial tensile resistance measured by the method defined in JIS L 1015: 1999, paragraph 8.11.

  The resin constituting the high Young's modulus fiber of the present invention is a resin that does not deteriorate due to an electrolyte used in an electrochemical element such as a battery or an electric double layer capacitor, and that does not deteriorate due to an electrochemical reaction inside the electrochemical element. Although it does not specifically limit and it is preferable to comprise from polyolefin resin. More specifically, for example, propylene homopolymer, copolymer of propylene and α-olefin (for example, ethylene, butene-1, etc.), high density, medium density, low density polyethylene, linear low density polyethylene, etc. And ethylene-based polymer, poly-4-methylpentene-1, and the like.

  The high Young's modulus fiber of the present invention can be composed of one type of resin or two or more types. In particular, if the high Young's modulus fiber consists of two or more types of resins that differ in melting point, and there is a resin other than the resin having the highest melting point on the fiber surface, it can be fused with the resin and bend the high Young's modulus fiber. This is preferable because a reduction in rigidity can be suppressed. The difference in melting point between the resin having the highest melting point and the resin existing on the fiber surface is preferably 10 ° C. or more, and more preferably 20 ° C. or more. Examples of the arrangement state of the resin in the cross section of the high Young's modulus fiber composed of two or more kinds of resins include a core-sheath type, a side-by-side type, an orange type, a sea-island type, and a multilayer laminated type. It is preferably a core-sheath or sea-island type with a large amount of resin that can be involved in wearing. In particular, the high Young's modulus fibers constituting the current collector for nickel metal hydride batteries preferably include core-sheathed high Young's modulus fibers whose core is made of polypropylene and whose sheath is made of polyethylene.

  The fineness of the high Young's modulus fiber of the present invention is not particularly limited, but it is preferable to include a high Young's modulus fine fiber having a fineness of 0.8 dtex or less. The inclusion of high Young's modulus fine fibers ensures the thickness of the current collector, allows it to be a current collector with a high porosity, and has a wide contact area with the active material, resulting in excellent current collection performance and high capacity. This is because it is easy to produce an electrochemical element excellent in high rate charge / discharge characteristics. The high Young's modulus fine fibers are preferably contained in the nonwoven fabric in an amount of 5 mass% or more so as to be excellent in the performance.

  Moreover, it is preferable that the high Young's modulus fiber of the present invention includes a high Young's modulus thick fiber having a fineness of 3.3 dtex or more. When containing high Young's modulus thick fibers, it can be a bulky and high porosity current collector, and it is less likely to be crushed by the pressure when filling the active material, and more active material can be filled. This is because it is easy to produce a high-capacity electrochemical device. In addition, since the pore diameter of the current collector becomes large, the current collector is excellent in filling of the active material and is easy to fill the active material into the current collector. The higher the fineness of the high Young's modulus thick fiber, the better the performance. Therefore, the fineness of the high Young's modulus thick fiber is preferably 4.4 dtex or more, more preferably 5.5 dtex or more. More preferably, it is 6.6 dtex or more. In addition, it is preferable that 5 mass% or more of such a high Young's modulus thick fiber is contained in a nonwoven fabric so that the said performance is excellent.

  The high Young's modulus fiber may include both a high Young's modulus thick fiber and a high Young's modulus fine fiber, or may include a high Young's modulus fiber having a fineness of more than 0.8 dtex and less than 3.3 dtex. good.

The fineness in the present invention means a value calculated by the following formula based on the diameter of the fiber.
Fineness (dtex) = 1.1 × SGf × (R ÷ 11.89) ²
Here, SGf (g / cm ³ ) means the specific gravity of the fiber, and when the fiber is made of two or more kinds of resins, it means the mass average value of each resin. R (μm) means the fiber diameter. When the cross-sectional shape of the fiber is non-circular, the diameter of a circle having the same cross-sectional area is regarded as the fiber diameter.

  The fiber length of the high Young's modulus fiber of the present invention varies depending on the method for producing the nonwoven fabric and is not particularly limited. For example, when manufacturing a nonwoven fabric by a dry method, it is preferable that it is 40 mm or more so that fibers may be sufficiently entangled. When a nonwoven fabric is manufactured by a wet method, the fibers are likely to be dispersed in the slurry. Further, it is preferably 10 mm or less. In addition, the fiber length in this specification means the length obtained by JISL1015 (chemical fiber staple test method) B method (correction staple diagram method).

  Such high Young's modulus fibers can be used as a current collector with a high porosity, and are preferably contained in an amount of 5 mass% or more in the nonwoven fabric so that they are not easily crushed by an external force. More preferably, 20% by mass or more is further included, 30% by mass or more is further preferable, 40% by mass or more is further preferable, and 50% by mass or more is further included. preferable.

  In addition, the high Young's modulus fiber of this invention can be manufactured by the method as described in Unexamined-Japanese-Patent No. 2002-180330 or Unexamined-Japanese-Patent No. 11-350283, for example.

  The non-woven fabric that is the basis of the current collector of the present invention can contain fine fibers having a fineness of 0.8 dtex or less in addition to the above-described high Young's modulus fibers. By including such fine fibers, the surface area of the current collector is large and the contact area with the active material is widened. As a result, it is easy to manufacture an electrochemical device having high current collection efficiency and excellent high-rate charge / discharge characteristics. Because. The resin constituting this fine fiber may be a resin that is not deteriorated by an electrolytic solution used in an electrochemical element such as a battery or an electric double layer capacitor, and that is not deteriorated by an electrochemical reaction inside the electrochemical element. Although it does not limit, it is preferable to be comprised from the polyolefin resin similar to resin which comprises a high Young's modulus fiber. When the high Young's modulus fiber as described above is made of a single resin, the fine fiber has a high Young's modulus so that the nonwoven fabric can be maintained and the decrease in bending rigidity of the high Young's modulus fiber can be suppressed. It is preferable that a resin having a lower melting point (preferably lower by 10 ° C. or more) than the resin constituting the fiber is included on the fiber surface and can act as an adhesive fiber. The fine fibers can also be composed of one kind of resin, or two or more kinds, but when acting as an adhesive fiber, two or more kinds having a melting point difference (preferably 10 ° C. or more) so that the fiber form can be maintained. It is preferable that it is comprised from this resin. In the case of acting as an adhesive fiber, it is preferable that the resin is arranged in a cross-section in a core-sheath or sea-island type with a wide adhesive area. Furthermore, the fiber length of the fine fibers varies depending on the production method of the nonwoven fabric. When the nonwoven fabric is produced by a dry method, it is preferably 40 mm or more, and when the nonwoven fabric is produced by a wet method, it is 10 mm or less. preferable. Such fine fibers can be produced by melt spinning, and by extracting and removing the sea component of the sea-island type composite fiber, fine fibers comprising the island component can be produced and divided by external force. Fine fibers can also be produced by splitting by applying an external force to possible composite fibers. The content of such fine fibers is not particularly limited, but when the fine fibers act as adhesive fibers, it is preferable that the content is 5 mass% or more in the nonwoven fabric.

  The non-woven fabric that is the basis of the current collector of the present invention can contain thick fibers having a fineness of 3.3 dtex or more in addition to the high Young's modulus fibers and fine fibers as described above. By including such a thick fiber, the current collector is bulky to a certain extent and has a high porosity, and is less likely to be crushed by the pressure when filling the active material, and more active material can be filled. . Moreover, the pore diameter of the current collector can be increased, the active material can be easily filled, and the active material can be easily filled into the current collector. The resin constituting this thick fiber may be a resin that is not deteriorated by an electrolyte used in an electrochemical element such as a battery or an electric double layer capacitor, and that is not deteriorated by an electrochemical reaction inside the electrochemical element. Although it does not limit, it is preferable to be comprised from the polyolefin resin similar to resin which comprises a high Young's modulus fiber. When the high Young's modulus fiber as described above is made of a single resin, the thick fiber has a high Young's modulus so that the nonwoven fabric can be maintained and the decrease in bending rigidity of the high Young's modulus fiber can be suppressed. It is preferable that a resin having a lower melting point (preferably lower by 10 ° C. or more) than the resin constituting the fiber is included on the fiber surface and can act as an adhesive fiber. Thick fibers can also be composed of one type of resin, or two or more types, but when acting as an adhesive fiber, two or more types having a melting point difference (preferably 10 ° C. or higher) so that the fiber form can be maintained. It is preferable that it is comprised from this resin. In the case of acting as an adhesive fiber, it is preferable that the resin is arranged in a cross-section in a core-sheath or sea-island type with a wide adhesive area. Furthermore, the fiber length of the thick fiber varies depending on the method for producing the nonwoven fabric, and when the nonwoven fabric is produced by a dry method, it is preferably 40 mm or more, and when the nonwoven fabric is produced by a wet method, it is 10 mm or less. preferable. The content of such a thick fiber is not particularly limited, but when the thick fiber acts as an adhesive fiber, it is preferably contained in 5 mass% or more in the nonwoven fabric.

The basis weight and thickness of the nonwoven fabric that is the basis of the current collector of the present invention are not particularly limited because it varies depending on the type of electrochemical element, for example, whether the form is cylindrical or flat. For example, in the case of a cylindrical battery, it is preferable that the basis weight is 200 g / m ² or less and the thickness is 2 mm or less so that the winding property at the time of preparing the electrode plate group is excellent.

  Although the nonwoven fabric used as the base of the current collection material of this invention contains the above high Young's modulus fibers, this nonwoven fabric can be manufactured by a conventional method. That is, after a fiber web is formed by a dry method or a wet method, the fibers can be manufactured by being entangled, fused, or bonded by an adhesive. In general, it is preferable to use thick fibers (including high Young's modulus thick fibers) to produce a nonwoven fabric with a higher porosity, and therefore, by a dry method suitable for forming a fiber web using thick fibers. It is preferred to form a fiber web. Moreover, since it is preferable to use fine fibers (including high Young's modulus fine fibers) to produce a nonwoven fabric with a larger surface area and uniform basis weight, it is suitable for forming a fiber web using fine fibers. The fiber web is preferably formed by the method.

  As a method of bonding the fiber web, if the high Young's modulus fiber is fused, it is not necessary to use an adhesive fiber having a low Young's modulus, or a small amount can be used. It is possible to increase the content, to fix the intersection of the high Young's modulus fibers, to produce a current collector with a high degree of compression modulus and a low degree of freedom of the high Young's modulus fibers. Therefore, it is preferable because it is possible to manufacture a current collector that has a higher porosity and is less likely to be crushed by pressure when filling the active material, can be filled with a large amount of active material, and can produce an electrochemical element with a large capacity. .

  The current collector of the present invention is obtained by plating the above-described nonwoven fabric. The type of plating metal differs depending on the type of electrochemical element, and it is sufficient to select a metal that is resistant to the electrolytic solution and electrochemical reaction, and is not particularly limited. For example, a current collector for nickel-metal hydride batteries or nickel cadmium Nickel plating is suitable for battery current collectors, copper or aluminum plating for lithium ion secondary battery current collectors, and nickel plating or aluminum plating is suitable for current collectors for electric double layer capacitors.

  Also, the amount of plating is not particularly limited, but if the plating mass is 30% or more of the current collector mass, the electrical resistance is preferably low. Since the pore diameter of the electric material is reduced and the filling property of the active material is deteriorated, it is preferably 70% or less.

  In addition, the plating method to a nonwoven fabric is not specifically limited, For example, it can carry out by using together the electroless plating method and the electroplating method as needed. For example, nickel plating can be performed as follows.

  First, a catalyst provision process is implemented. This catalyst imparting step includes a method of treating with a hydrochloric acid aqueous solution of stannous chloride and then catalyzing with an aqueous hydrochloric acid solution of palladium chloride, a method of fixing only with a hydrochloric acid solution of palladium chloride containing an amino group of a curing agent, and the like. However, the former method is preferable because of excellent uniformity of the plating film thickness.

  Next, an electroless plating process is performed. This step is generally a step of reducing nickel with a reducing agent in an aqueous solution containing nickel salts such as nickel nitrate, nickel chloride, nickel sulfate and the like, complexing agent, pH adjusting agent, buffering agent as required Add stabilizers. In order to obtain a nickel film having particularly high purity, it is preferable to use a hydrazine derivative such as hydrated hydrazine, hydrazine sulfate, or hydrazine oxide as a reducing agent. As this electroless plating step, a method of continuously feeding a long nonwoven fabric from a catalyst application tank to a plating tank and plating it, putting the nonwoven fabric in a roll shape into a cheese dyeing machine, forcing For example, a method of plating by circulating a plating solution may be used. When electroless plating is carried out with the nonwoven fabric wound up in a roll shape, only the catalyst application step or only the electroless plating step may be carried out in a roll shape, or both You may implement a process with the state wound up in roll shape. Thus, since the nonwoven fabric is not easily crushed by the pressure taken up in a roll shape or the liquid pressure when the plating solution is forcedly circulated, a current collector with a high porosity can be produced.

  An electrolytic plating film can be further formed as necessary. The electrolytic plating method can be performed using a plating bath. As the plating bath, a watt bath, a chloride bath, or a sulfamic acid bath can be used. To this, additives such as a pH buffer and an interface buffer can be added. An electroless plating film is further formed on the electroless plating film by connecting the non-electrolytically plated non-woven fabric to the cathode, connecting a nickel counter electrode to the anode, and applying a direct current or pulse intermittent current. be able to.

  Before plating, for example, sulphonation can be performed to increase the permeability of the plating solution, increase the adhesion between the fiber and the plating metal, prevent the plating metal from falling off, and prevent the surface resistance from increasing. The nonwoven fabric is preferably subjected to hydrophilic treatment such as treatment, fluorine gas treatment, vinyl monomer graft polymerization treatment, surfactant treatment, discharge treatment, or hydrophilic resin application treatment.

  The current collector of the present invention is obtained by plating the nonwoven fabric as described above, and the porosity is preferably 85 to 95% (more preferably 85 to 90%). The porosity is preferably 85% or more so that the amount of the active material that can be filled can be increased and the capacity of the electrochemical device can be increased. On the other hand, when the porosity is too large, the contact area between the current collector and the active material is narrowed and the current collection performance is reduced, or the number of intersections between fibers is reduced, the strength of the current collector is lowered, and the active material is reduced. Since it becomes easy to fracture | rupture at the time of filling or an electrochemical element manufacture, it is preferable that it is 95% or less. Thus, a current collector with a high porosity can be obtained by performing fiber bonding at the time of manufacturing a nonwoven fabric under a pressure that is weak enough to adjust the thickness even if no pressure is applied. More specifically, the porosity current collector can be easily manufactured by fusing the fibers with hot air. In addition, it is preferable not to make a pressure act by a nip roll, a calendar | calender, etc. after a melt | fusion.

The porosity is a value calculated from the following equation.
Porosity (%) = {1-W / (t × SGm)} × 100
Here, W means the weight of the current collector (g / m ² ), t means the thickness of the current collector (μm), and SGm means the density of the plated fibers (g / cm ³ ). Note that the basis weight is a value obtained by measuring the mass of a 20 cm square current collector and multiplying the mass by 25 times. The thickness is a compression elasticity tester (manufactured by Nakayama Electric Industry Co., Ltd.) and is loaded at 500 g / 5 cm ^2. SGm is a value calculated from the following equation.
SGm = (AW + BW) / (AV + BV)
Here, AW is the basis weight of the fiber before plating (g / m ² ), that is, the basis weight of the nonwoven fabric, and AV is the volume per square meter (cm ³ / m ² ) occupied by the fiber before plating. / ASG (Fiber density before plating (g / cm ³ )), BW is the weight of the plated metal (g / m ² ), BV is per square meter occupied by the plated metal in a volume ^(cm 3 / ^{m 2),} it means the value calculated from the equation of BW / BSG (density of plated metal (g / ^cm 3)), respectively.

  The current collector of the present invention is not easily crushed by the pressure during filling with the active material, the amount of filling of the active material can be increased, and the capacity of the electrochemical device can be increased so that the compression elastic modulus is 85% or more. It is preferable that it is 90% or more. A current collector having such a compressive elastic modulus is easy to manufacture by using high Young's modulus fibers having a large fineness or increasing the amount of high Young's modulus fibers.

Compressive modulus in the present invention using a compressive elasticity tester (manufactured by Nakayama electrical industry (Ltd.)), 100g / 5cm and a thickness _T 100 (mm) at ² load, 500 g / 5 cm thickness during ² Load _{T 500} (Mm) is measured and the value calculated from the following equation.
Compression elastic modulus (%) = (T ₅₀₀ / T ₁₀₀ ) × 100

  The current collector of the present invention has a high porosity and can be filled with a large amount of active material by being hard to be crushed when filled with the active material. As a result, a large-capacity electrochemical device can be produced, and it has excellent high rate charge / discharge characteristics As a current collector for nickel-metal hydride batteries, nickel-cadmium batteries and other alkaline secondary batteries, lithium-ion secondary batteries and other non-aqueous batteries, electric double-layer capacitors and other power storage devices, and fuel cell current collectors It can be preferably used, and in particular, can be suitably used as a current collector for batteries such as alkaline secondary batteries or lithium secondary batteries, and electric double layer capacitors. These electrochemical elements are used in large current discharge applications such as electric (including hybrid) automobiles, electric assist bicycles, power tools, remote control toys, etc., low current discharge applications such as backup power supplies for PCs, emergency light power supplies, etc. It can be suitably used for long-time discharge applications such as batteries for digital cameras and digital video power supplies.

  The electrochemical element of the present invention can be composed of the same material as the conventional one except that the current collector is the current collector of the present invention. 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.

  Examples of the present invention will be described below, but the present invention is not limited to the following examples.

(Examples 1-5, Comparative Examples 1-2)
After forming a fiber web from the slurry in which fibers shown in Table 1 are dispersed by a wet papermaking method, the fiber web is heat-treated with a hot air drier set at a temperature of 135 ° C. to obtain a core-sheath type high Young's modulus composite The sheath component of the fiber and the sheath component of the core-sheath type regular composite fiber were fused to produce nonwoven fabrics each having a basis weight of 100 g / m ² .

  Subsequently, the non-woven fabric was immersed in a fuming sulfuric acid bath at a temperature of 80 ° C. to perform sulfonation treatment. Thereafter, the sulfonated non-woven fabric is wound around the carrier of the dyeing machine, the refining agent is circulated and washed with water, and then an aqueous solution containing 10 g / liter of stannous chloride and 20 ml / liter of hydrochloric acid is circulated and washed with water. Catalysis was carried out by circulating an aqueous solution containing 1 g / liter of palladium chloride and 20 ml / liter of hydrochloric acid. Thereafter, further washing with water is performed, and an electroless nickel plating solution of nickel sulfate 18 g / liter, sodium citrate 10 g / liter, hydrated hydrazine 50 ml / liter, 25% aqueous ammonia 100 ml / liter is circulated at a temperature of 80 ° C. and washed with water. And dried to produce a nickel-plated current collector (nickel plating accounts for 50 mass% of the total current collector). Table 1 shows the thickness, porosity, specific surface area, and compressive modulus of these current collectors. The specific surface area was measured by the BET method.

R1: A core-sheath type with a core component made of polypropylene (melting point: 160 ° C) and a sheath component made of high-density polyethylene (melting point: 130 ° C), a fineness of 6.6 dtex, a fiber length of 5 mm, and a Young's modulus of 11.1 cN / dtex Regular composite thick fiber R2: core component is made of polypropylene (melting point: 160 ° C.), sheath component is made of high-density polyethylene (melting point: 130 ° C.), fineness 0.8 dtex, fiber length 5 mm, Young's modulus 19.2 cN / dtex Core-sheath type regular composite fine fiber Y1: core component is made of polypropylene (melting point: 160 ° C.), sheath component is made of high-density polyethylene (melting point: 130 ° C.), fineness 6.6 dtex, fiber length 5 mm, Young's modulus 36 .9 cN / dtex core-sheath type high Young's modulus composite thick fiber Y2: core component is made of polypropylene (melting point: 160 ° C.) Is made of high-density polyethylene (melting point: 130 ° C.), core-sheath type high Young's modulus composite fine fiber Y3 having a fineness of 0.8 dtex, a fiber length of 5 mm, and a Young's modulus of 32.0 cN / dtex: the core component is polypropylene (melting point: 160 ° C. And a sheath component of high density polyethylene (melting point: 130 ° C.), a core-sheath type high Young's modulus composite fine fiber having a fineness of 0.8 dtex, a fiber length of 5 mm and a Young's modulus of 23.7 cN / dtex.

(High-rate test using batteries)
An active material paste is prepared by mixing nickel hydroxide 80%, carboxymethyl cellulose (CMC) 1% aqueous solution 16%, and water 4%, and each current collector cut into a predetermined size is immersed in this paste. The excess paste on the surface was removed between the slits having the same thickness as the active material and filled with the active material. Subsequently, it dried and adjusted the thickness with the roll press machine, and manufactured the positive electrode plate.

  An alloy paste was prepared by mixing 90% of a hydrogen storage alloy and 10% of a 1% CMC aqueous solution, and a current collector made of foamed nickel was filled with the alloy by the same method as that of the positive electrode plate to produce a negative electrode plate.

A separator was sandwiched between the positive electrode plate and the negative electrode plate and wound in a spiral shape to produce an electrode group corresponding to AA size. This electrode group was housed in an outer can, and 5N potassium hydroxide and 1N lithium hydroxide were poured into the outer can as electrolytes and sealed to produce a cylindrical AA size nickel metal hydride battery. The theoretical capacity (mAh) was calculated by the following formula based on the active material filling amount (g). This theoretical capacity was as shown in Table 2.
Theoretical capacity = active material filling amount × 289

Then, each nickel metal hydride battery was charged and discharged for 5 cycles at 0.1 C to activate the battery. After that, the battery is charged with a constant current of 0.3 C for 4 hours, and charging is paused for 15 minutes. Then, the battery is discharged to 0.8 V with a constant current of 6 C (current value 6 times the theoretical capacity), and the discharge is paused for 15 minutes. The process was defined as one cycle, and this cycle was repeated three times, and the average value of the three discharge currents was 6 C discharge capacity (mAh). Based on the 6C discharge capacity, the 6C utilization rate (%) was calculated by the following formula. This 6C utilization rate was as shown in Table 2.
6C utilization rate = (6C discharge capacity / theoretical capacity) × 100

From the comparison between the examples of Tables 1 and 2 and the comparative example, the inclusion of a high Young's modulus fiber having a Young's modulus of 20 cN / dtex or higher increases the compression modulus, and is less likely to be crushed when filled with the active material. It was found that the amount of filling was increased and a battery with a high theoretical capacity could be manufactured. Further, from comparison between Examples 1-2 and Examples 3-5, the specific surface area is increased by using the core-sheath type high Young's modulus composite fine fiber having a fineness of 0.8 dtex, and the 6C utilization rate is high. It was also found that a battery capable of high rate charge / discharge can be manufactured.

Claims (9)

A current collector for an electrochemical device, wherein a non-woven fabric containing a high Young's modulus fiber having a Young's modulus of 20 cN / dtex or more is plated. 2. The current collector for an electrochemical element according to claim 1, wherein high Young's modulus fibers are fused. The current collector for an electrochemical element according to claim 1 or 2, wherein the nonwoven fabric constituent fibers include fine fibers having a fineness of 0.8 dtex or less. 4. The current collector for an electrochemical device according to claim 3, wherein the fine fibers are high Young's modulus fibers. 5. The current collector for an electrochemical element according to claim 1, comprising high Young modulus thick fibers having a fineness of 3.3 dtex or more as the high Young modulus fibers. The current collector for an electrochemical element according to any one of claims 1 to 5, wherein the porosity of the current collector for an electrochemical element is 85 to 95%. The current collector for an electrochemical device according to any one of claims 1 to 6, wherein the current collector for an electrochemical device has a compressive elastic modulus of 85% or more. The battery provided with the electrical power collector for electrochemical elements in any one of Claims 1-7. The electrical double layer capacitor provided with the electrical power collector for electrochemical elements in any one of Claims 1-7.