JP2019091669A - Nonwoven fabric current collector for secondary battery - Google Patents

Abstract

A current collector for a secondary battery, which can be made thin and light, has little unevenness in electric conductivity, is excellent in strength and handleability during manufacturing, has a low risk of short circuit, etc., and has a low manufacturing cost. To provide. SOLUTION: At least one continuous long fiber layer (S) having an average fiber diameter of 10 to 30 μm and at least one fine fiber layer (M) having an average fiber diameter of 0.3 to 3 μm are provided and integrated by thermocompression bonding. There is provided a current collector for a secondary battery having the laminated non-woven fabric and a conductive material attached to the laminated non-woven fabric. [Selection diagram] None

Description

  The present invention relates to a current collector used in a secondary battery.

  In recent years, portable devices such as mobile phones, smartphones, personal computers, digital cameras and the like are widely used, and there is a strong demand for reduction in size and weight. Along with that, batteries (secondary batteries) used for those devices are also miniaturized and energy density is increased. In addition, development of EVs and HEVs is also in progress in the automobile industry, and reductions in size and weight, high voltages and outputs are desired for power supplies and capacitors for storing electric power mounted on these. Examples of secondary batteries include alkaline batteries, nickel cadmium batteries, lead batteries, nickel hydrogen batteries, proton batteries, lithium ion batteries, all solid lithium ion batteries, lithium ion capacitors, and electric double layer capacitors. Lithium-ion batteries and all-solid-state lithium-ion batteries are widely used from the viewpoint of downsizing and increasing the voltage.

  A lithium secondary battery is mainly composed of a positive electrode and a negative electrode capable of occluding and releasing lithium (these have a positive electrode active material, a negative electrode active material and a current collector), a separator, and an electrolyte. An aluminum foil is used as a positive electrode and a copper foil is used as a negative electrode, and a porous thin film separator is sandwiched between positive and negative electrode collectors carrying an active material.

On the other hand, electronic devices equipped with lithium secondary batteries are becoming smaller, lighter, and more multifunctional, and as a result, higher capacity and higher energy density of lithium secondary batteries are desired.
As a result, in the battery, the packing density of the active material and other members is high, and a short circuit is likely to occur. In order to solve these problems, the improvement of each material is being promoted. New development is in progress.

  The following are examples of current collectors for secondary batteries that have been developed. In Patent Documents 1 and 2, a metal porous body having a three-dimensional metal fiber structure is described. Patent Document 3 describes a metal non-woven fabric in which the surface of a resin non-woven fabric is subjected to sulfonation treatment or the like to form nickel plating. Patent Document 4 describes a current collector capable of high-rate charge and discharge by specifying the thickness and manufacturing method of a metal-coated resin non-woven fabric.

  In the metal porous body of Patent Document 1, the strength and flexibility of the current collector are not sufficient, and there is a problem of safety such as a short circuit due to a structural failure. Further, in order to increase the strength, in Patent Document 2, a helical nickel wire is used as a core material of a metal fiber, but using a nickel wire complicates the process and further makes the product thicker It becomes. In Patent Documents 2 and 3, although the fiber diameter is large and the strength is high, on the other hand, the open pore diameter and the electrical conductivity are uneven and there is a risk of short circuit. In addition, since the amount of metal adhesion such as nickel is also large, the cost is high.

  In order to solve these problems, Patent Document 5 describes a current collector in which non-woven fabrics having different bulk densities are coated with a nickel film. Moreover, in patent document 6, the current collector foil which formed the electrically conductive film in the microfiber nonwoven fabric produced by the electrospinning method is described.

JP-A-2-216766 JP 2001-313038 A Unexamined-Japanese-Patent No. 2003-228066 Unexamined-Japanese-Patent No. 2010-212244 JP 2012-109224 A

  However, the current collector using non-woven fabrics having different bulk densities in Patent Document 5 has a thickness as large as 0.8 mm or more in order to combine two non-woven fabrics. In addition, since the amount of nickel to be attached also increases, there is a problem of high cost. The current collector produced by the electrospinning method of Patent Document 6 is extremely expensive because the production efficiency of the electrospinning method is not good in the first place, and it is not suitable for mass production, and it is formed of ultrafine fibers. As a result, there is a problem that the strength is weak and there is a danger of a short circuit or the like due to the structural destruction.

  The present invention solves the above-mentioned problems and can make it thin and light, has less unevenness in electrical conductivity, is excellent in strength and handleability at the time of production, has a low risk of short circuit, etc. An object is to provide a low current collector for a secondary battery.

  As a result of intensive studies to solve the above problems, the present inventors laminate a continuous long fiber layer with an average fiber diameter of 10 to 30 μm and a fine fiber layer with an average fiber diameter of 0.3 to 3 μm, The inventors have found that the above-mentioned problems can be solved by electrically conducting a laminated non-woven fabric obtained by integrating by thermocompression bonding and completed the present invention.

That is, the present invention includes the following (1) to (10).
(1) A continuous long fiber layer (S) having an average fiber diameter of 10 to 30 μm and at least one fine fiber layer (M) having an average fiber diameter of 0.3 to 3 μm are integrated by thermocompression bonding A current collector for a secondary battery, comprising: a laminated non-woven fabric; and a conductive material attached to the laminated non-woven fabric.
(2) The collector for secondary batteries according to the above aspect 1, wherein the laminated non-woven fabric has an SMS structure or an MSM structure.
(3) The current collector for a secondary battery according to the above aspect 1 or 2, wherein the continuous long fiber layer is a spunbonded nonwoven fabric composed of synthetic long fibers.
(4) The collector for secondary batteries in any one of the said aspect 1-3 which is a melt-blown nonwoven fabric in which the said fine fiber layer was comprised with the synthetic long fiber.
(5) The collector for secondary batteries in any one of the said aspect 1-4 in which the said lamination | stacking nonwoven fabric is comprised with polyester-type fiber.
(6) The collector for secondary batteries in any one of the said aspect 1-5 whose thickness of the said lamination | stacking nonwoven fabric is 10-70 micrometers.
(7) The collector for secondary batteries in any one of the said aspect 1-6 whose said electrically conductive material is coating of carbon or a carbon-type compound.
(8) The collector for secondary batteries in any one of the said aspect 1-6 whose said electrically conductive material is a metal coating.
(9) The collector for secondary batteries in any one of the said aspect 1-6 whose said electroconductive material is a coating of an electroconductive polymer.
(10) A method of manufacturing a current collector for a secondary battery according to any one of the above embodiments 1 to 9,
Obtaining a laminated web by laminating a continuous long fiber layer (S) having an average fiber diameter of at least one layer of 10 to 30 μm and a fine fiber layer (M) having an average fiber diameter of 0.3 to 3 μm of at least one layer;
Integrating the laminated web by thermocompression bonding to obtain a laminated nonwoven fabric, and attaching the conductive material to the laminated nonwoven fabric,
Including
The method wherein the thermocompression bonding is performed by calendering.

  According to the present invention, it is possible to make it thin and light, to have less unevenness in electrical conductivity, to be excellent in strength and handleability at the time of production, low in risk of short circuit and the like, and low in production cost A current collector can be provided.

  Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments. Note that various characteristic values of the present disclosure mean values determined by a method understood by one skilled in the art to be equivalent to or the method described in the [Example] section unless otherwise specified.

(Form of non-woven fabric substrate)
The current collector for a secondary battery according to one aspect of the present invention has at least one continuous long fiber layer with an average fiber diameter of 10 to 30 μm and at least one fine fiber layer with an average fiber diameter of 0.3 to 3 μm, And it has the laminated nonwoven fabric integrated by thermocompression bonding, and the electrically-conductive material adhering to this laminated nonwoven fabric.

The above-mentioned current collector for a secondary battery is, for example,
Obtaining a laminated web by laminating a continuous long fiber layer (S) having an average fiber diameter of at least one layer of 10 to 30 μm and a fine fiber layer (M) having an average fiber diameter of 0.3 to 3 μm of at least one layer;
Integration of the laminated web by thermocompression bonding (for example, thermocompression bonding by calendering) to obtain a laminated nonwoven fabric, and adhering the conductive material to the laminated nonwoven fabric,
Can be manufactured by a method including:

  One of the features of the current collector according to one embodiment of the present invention is that the electrical conductivity is reduced in spots. This is because the current collector has the above-mentioned fine fiber layer, so that the basis weight uniformity in the surface direction is high, and furthermore, the specific surface area as compared with a normal long-fiber non-woven fabric having a fiber diameter of 10 μm or more This is because a uniform and highly conductive conductive portion (typically a conductive film) is formed even if the amount of the conductive material attached is small.

  Another feature of the current collector according to one aspect of the present invention is that it is excellent in strength and can be made thin and light by appropriately selecting the layer configuration. This is because the current collector has at least one layer of a continuous long fiber layer (S) having an average fiber diameter of 10 to 30 μm and a fine fiber layer (M) having an average fiber diameter of 0.3 to 3 μm. It is because it is integrated and formed. The current collector has high base strength by having a continuous long fiber layer with an average fiber diameter of 10 to 30 μm, which is advantageous in terms of handleability, production efficiency, production cost, and yield improvement. In particular, when manufacturing a secondary battery, a positive electrode active material or a negative electrode active material is coated on a current collector and then subjected to a pressing process. At that time, since process tension is applied to the current collector, in the case of a short fiber substrate, a substrate of only fine fibers, etc., the substrate strength is low and the production speed can not be increased. Production is inefficient and tends to be expensive.

  That is, according to the laminated non-woven fabric having the combination of the continuous long fiber layer and the fine fiber layer, the current collector having few spots in electric conductivity and good strength can be obtained with excellent manufacturing efficiency and cost. Can be obtained.

  The average fiber diameter of the continuous long fiber layer is 10 to 30 μm, preferably 10 to 20 μm, and more preferably 10 to 15 μm. When the average fiber diameter is less than 10 μm, it becomes close to the average fiber diameter of the fibers constituting the fine fiber layer (M) having an average fiber diameter of 0.3 to 3 μm, and securing of strength, manufacturing efficiency and manufacturing cost of laminated nonwoven fabric It becomes difficult. On the other hand, when the average fiber diameter exceeds 30 μm, the specific surface area of the laminated non-woven fabric becomes low and the spots of electric conductivity become large.

  The average fiber diameter of the fine fiber layer is 0.3 to 3 μm, preferably 0.4 to 2.5 μm, and more preferably 0.6 to 2 μm. In order to spin to an average fiber diameter of less than 0.3 μm by the meltblowing method, severe conditions are required, and stable fibers can not be obtained. On the other hand, when the average fiber diameter exceeds 3 μm, it becomes close to the average fiber diameter of the fibers constituting the continuous long fiber layer (S) having an average fiber diameter of 10 to 30 μm, and the laminated non-woven fabric becomes a dense structure as a whole. The hole diameter can not be obtained, and the risk of short circuit and the like increases.

  Examples of methods for producing the continuous long fiber layer and the fine fiber layer include a spunbond method, a meltblown method, a flash spinning method and the like, but from the viewpoint of production efficiency and cost reduction, spunbond The method and the meltblown method are more preferred. The fine fiber layer may be a short fiber non-woven fabric obtained by a paper making method, a dry method or the like using short fibers, but in view of maintaining the strength of the non-woven fabric and easy processing. Preferably, a synthetic long-fiber non-woven fabric is more preferable in that it is easy to process (especially easy to be thermocompression-bonded).

  From the viewpoint of strength, processability, production efficiency, and cost, the continuous long fiber layer is particularly preferably a spunbonded non-woven fabric composed of synthetic long fibers, and the fine fiber layer is a meltblown composed of synthetic long fibers. Particularly preferred is a non-woven fabric.

  The laminated non-woven fabric may be an SM structure of one continuous long fiber layer (S) and one fine fiber layer (M), or two or more layers such as SMM type, SMMM type, SMMS type, but strength In terms of thickness and thickness, the SMS type or the MSM type is more preferable.

  When the outermost surface of the laminated nonwoven fabric is the continuous long fiber layer (S), the strength of the fibers of the outermost layer is high and it is difficult to break, so scratch strength is high and fluff is less likely to occur, and product shape stability is It has the advantage of being high and easy to handle, while in the case of the fine fiber layer (M), the contact area with the electrode is large, so that efficient electrical conduction can be achieved when applied to an actual battery Has the advantage of being able to

  As a method of mixing and laminating the continuous long fiber layer and the fine fiber layer and thermocompression bonding, the method of integrating by heat embossing maintains the tensile strength and bending flexibility of the fabric and maintains the heat stability. It is preferable because it can be More preferable in this sense is a method of sequentially performing the spun bonding method, the melt-blowing method, and the spun bonding method, laminating the non-woven fabrics obtained by each of these methods and pressing them with an embossing roll or a hot press roll. That is, a continuous long-fiber non-woven fabric layer is spun on a conveyor using one or more spunbonds using a thermoplastic synthetic resin, and a fiber diameter of 0.01 by a meltblow method using a thermoplastic synthetic resin thereon. Spray one or more fine fiber non-woven fabric layers of ~ 3.0 μm. Then, the method of unifying by crimping using an embossing roll or a flat roll is preferable. Furthermore, prior to thermocompression bonding, one or more continuous long fiber layers using a thermoplastic synthetic resin are laminated on the meltblown layer, and then the method is integrated by pressure bonding using an embossing roll or flat roll. preferable. The fine fiber non-woven fabric layer is combined with the continuous long fiber non-woven fabric layer and thermocompression-bonded, so that the physical properties derived from the continuous long fiber non-woven fabric layer which can not be expressed by the fine fiber non-woven fabric layer alone, such as tensile strength and thermal dimensional stability Product shape stability becomes high because of having. Moreover, since the movement by the external force of an ultrafine fiber nonwoven fabric layer becomes difficult to occur, it becomes difficult to delaminate. Methods for obtaining these laminated non-woven fabrics are disclosed in, for example, WO 2004/94136 and WO 2010/126109, and therefore they are used as a reference to obtain an optimal laminated non-woven fabric for the present invention. be able to. A preferred example of thermocompression bonding is calendering with a flat roll.

  As thickness of a lamination | stacking nonwoven fabric, in consideration of size reduction of the secondary battery which is a product by which the collector for secondary batteries is mounted, 10-70 micrometers is preferable and 10-50 micrometers is more preferable. When the thickness is 10 μm or more, the number of long fibers is not too small to obtain good substrate strength. When the thickness is 70 μm or less, the secondary battery is advantageously miniaturized.

The basis weight of the laminated non-woven fabric may preferably be 10 to 150 g / m ² , more preferably 10 to 70 g / m ² .

  The laminated nonwoven fabric preferably has an average opening diameter of 0.5 μm to 10.0 μm, and more preferably an average opening diameter of 0.5 μm to 3.0 μm. The average opening diameter of the non-woven fabric suitable for the current collector of the secondary battery depends on the positive electrode or the negative electrode active material used when producing the secondary battery, but the average opening diameter of the positive electrode or the negative electrode active material coated on the current collector Since the particle size is large in the range of about 1 to 10 μm, the active material does not easily fall off if the average opening diameter of the laminated non-woven fabric is 0.5 μm or more. On the other hand, if the average open pore diameter of the laminated nonwoven fabric is 10.0 μm or less, the pore diameter does not become too large, and there is little risk of the active material falling off.

  Specific examples of the fibers constituting the laminated non-woven fabric include polyolefins such as polypropylene and polyethylene, polyalkylene terephthalate resins (PET, PBT, PTT etc.) and their derivatives, polyamide resins such as N6, N66, N612 and their derivatives, poly Examples thereof include oxymethylene ether resins (POM etc.), PEN, PPS, PPO, polyketone resins, polyketone resins such as PEEK, thermoplastic polyimide resins such as TPI, etc., and fibers formed from a combination thereof.

  Although the said fiber can be suitably selected according to the environment where a secondary battery is used, it can select as follows, for example.

  Since polyamide-based resins such as N6, N66, and N612 and their derivatives are resins with high water absorption rates, it is desirable to avoid applying them to electronic parts that are extremely averse to moisture as compared to other resins. When heat resistance is required, it is preferable to use a fiber formed of a PET-based resin, a PPS-based resin, and / or a PEEK-based resin. On the other hand, polyolefin resins, PET resins, PPS resins, PPO resins, PEEK resins, and fluorine resins are preferable in view of electric properties such as dielectric constant and tan δ. From the viewpoint of spinning production stability and production cost, the laminated nonwoven fabric is preferably made of polyester fibers.

  The melting point of the fibers constituting the continuous long fiber layer and the fibers constituting the fine fiber layer is preferably 200 ° C. or more, more preferably 250 ° C. or more, from the viewpoint of the good heat resistance of the current collector. From the viewpoint of favorably performing thermocompression bonding, the temperature is preferably 300 ° C. or less, more preferably 270 ° C. or less.

  The secondary battery current collector further includes a conductive material. The conductive material is preferably one excellent in adhesion to the laminated nonwoven fabric as the base material, and further to the electrode layer of the secondary battery. Examples of the conductive material include carbon and carbon-based compounds, and a conductive material containing a conductive polymer and optionally a binder material.

  As carbon, carbon black, graphite and the like can be mentioned. In particular, ketjen black, which is a type of carbon black, and acetylene black are preferable because they are excellent in conductivity and can impart desired conductivity even in small amounts. Examples of carbon-based compounds include carbon nanotubes and carbon nanofibers. The conductive material is preferably a coating of carbon or a carbon-based compound.

  The conductive polymer may be used as a conductive material in combination with a binder material, or may be used alone as a conductive material if it has both functions as a conductive material and a binder. Examples of the conductive polymer include polyaniline, polythiophene, polypyrrole, poly (p-phenylenevinylene), poly (p-phenylene sulfide), and derivatives thereof. Polyaniline, polythiophene, polypyrrole or a derivative thereof is more preferable because the conductivity is easily controlled by coating processing because it has high conductivity. As a preferred example, the conductive material is a coating of a conductive polymer.

  As the binder material, a material capable of dispersing a conductive polymer and having adhesiveness to the material for forming the laminated nonwoven fabric and the electrode layer is preferable. Such materials include polyvinylidene fluoride, fluoroolefin copolymer, carboxymethyl cellulose, polyvinyl pyrrolidone, polyvinyl alcohol, polyacrylic acid or salts thereof, polyimide and the like.

  The conductive material containing the conductive polymer may be formed by coating the coating liquid containing the conductive polymer, optionally the binder material, and the solvent, followed by removal of the solvent. The solvent is not particularly limited as long as it can dissolve or disperse the conductive material and the binder material and does not dissolve the laminated nonwoven fabric as the substrate. As the solvent, for example, aliphatic hydrocarbons such as hexane, heptane and octane, halogenated hydrocarbons such as dichloroethane, chloroform, 1,2-dichloroethane, chlorobenzene and dichlorobenzene, diethyl ether, di-n-propyl ether , Ethers such as diisopropyl ether, di-n-butyl ether, tert-butyl methyl ether etc., esters such as ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate etc. ketones such as methyl ethyl ketone, N-methyl pyrrolidone And nitrogen-containing solvents such as and organic solvents such as. These solvents may be used as a mixture of two or more.

  In addition, various metals can be used as the conductive material. Examples of the metal include metals such as aluminum, tantalum, niobium, titanium, molybdenum, iron, nickel, cobalt, chromium, copper, silver, gold, platinum, lead, tin, tungsten, SUS, etc., and mixtures or oxides thereof In the case where the conductive material which may be a mixture of two or more of these is a metal, as a conductive processing method of the laminated non-woven fabric, a physical metal vapor deposition method (evaporation as EB deposition, ion plating, etc.) A high frequency method, a magnetron method, a counter target type magnetron method etc. can be used as ion sputtering, and a plating method (electroless plating, electrolytic plating) etc. can be used as a chemical method. In a preferred example, the conductive material is a metal coating.

  For example, when the current collector is a current collector for a negative electrode, the conductive material may contain nanosilicon powder, lithium powder, polyacene or the like.

  The thickness of the current collector for a secondary battery is preferably 10 to 70 μm, more preferably 10 to 50 μm, in consideration of the miniaturization of the secondary battery as a product on which the current collector for a secondary battery is mounted. When the thickness is 10 μm or more, the number of long fibers in the laminated non-woven fabric is not too small to obtain good substrate strength. When the thickness is 70 μm or less, the secondary battery is advantageously miniaturized.

The basis weight of the current collector for a secondary battery may be preferably 13 to 200 g / m ² , more preferably 15 to 90 g / m ² .

  The secondary battery current collector can have a surface resistance value suitable for secondary battery applications. The surface resistance may be preferably 0.01 to 10 Ω / □, more preferably 0.01 to 1 Ω / □.

Hereinafter, the present invention will be further described by way of examples, but the present invention is not limited to these examples.
The measuring method and the evaluation method are as follows.

[(1) Average fiber diameter]
Average fiber diameter (μm): A magnified image was taken with an electron microscope, and the number average value of 10 was determined.

[(2) basis weight of non-woven fabric]
The basis weight of the non-woven fabric is measured according to the method prescribed in JIS L-1906, measuring 3 samples of 20 cm long x 25 cm wide per 1 m width of the sample and measuring the mass, and the number average value is the mass per unit area Converted to

[(3) Thickness of non-woven fabric]
According to the method prescribed in JIS L-1906, the thickness at 10 points per 1 m was measured, and the number average value was used as the thickness of the non-woven fabric. The load was 9.8 kPa.

[(4) average opening diameter (μm)]
A PMI palm porometer (model: CFP-1200AEX) was used. The sample was immersed in the immersion liquid, sufficiently degassed, and measured, using a Silwick manufactured by PMI as the immersion liquid.
This measuring device immerses the non-woven fabric in a liquid whose surface tension is known in advance, applies pressure to the non-woven fabric from the state in which all pores of the non-woven fabric are covered with a liquid film, and the pressure and liquid surface Measure the pore size of the pore calculated from the tension. The following equation (2) was used to calculate the average opening diameter.

d = C × r / P formula (2)
(Wherein d (unit: μm) is the open pore diameter of the non-woven fabric, r (unit: N / m) is the surface tension of the liquid, and P (unit: Pa) the liquid film of that pore diameter is broken) Pressure, and C is a constant.)

When the flow rate (wet flow rate) when the pressure P applied to the non-woven fabric soaked in liquid is continuously changed from low pressure to high pressure, even the liquid film of the largest pore is not broken at the initial pressure, the flow rate is It is 0. As the pressure is increased, the largest pore liquid film is broken and a flow rate is generated (bubble point). As the pressure is further increased, the flow rate is increased according to each pressure, and the liquid film of the smallest pore is broken, which corresponds to the dry flow rate (dry flow rate).
In this measurement device, the wet flow rate at a certain pressure divided by the dry flow rate at the same pressure is referred to as the cumulative flow rate (unit:%). Further, the pore diameter of the liquid film which is broken at a pressure at which the cumulative flow rate is 50% is referred to as an average flow pore diameter, which is defined as the average pore diameter of the nonwoven fabric of the present disclosure.
In the present disclosure, the maximum pore size is a pore size of the liquid film which is broken at a pressure in the range of −2σ where the cumulative flow rate is 50%, ie, the cumulative flow rate is 2.3%.

[(5) Amount of adhesion of conductive material (basis weight)]
The basis weight of the non-woven fabric after application and drying of the conductive material is measured according to the method prescribed in JIS L-1906 by measuring three 20 cm long × 25 cm wide test pieces per 1 m width of the sample and measuring the mass , The number average value was converted to the mass per unit area and determined. The adhesion amount of the conductive material was calculated by calculating the difference between this value and the basis weight of the non-woven fabric before the conductive material application.

[(6) Surface resistivity]
It measured by the 4-probe method using Mitsubishi Chemical's low resistance meter Loresta-GP and model MCP-T600. The measurement was performed with n = 3 and the number average value was used.

Example 1
Polyethylene terephthalate (1% using orthochlorophenol, solution viscosity sp sp / c 0.77 at 25 ° C method, melting point 263 ° C) is spun from a spinneret, and spun at a spinning temperature of 300 ° C to form a fiber web (S1) ) Was formed on the collection net. On the obtained continuous long fiber web (basis weight: 7.7 g / m ² , average fiber diameter: 13 μm), polyethylene terephthalate (also solution viscosity sp sp / c 0.50, melting point 260 ° C.) is melt-blown with a spinning temperature of 300 ° C., jetted directly heated air 320 ° C. 1000 Nm ³ / hr conditions to form a fine fiber web (M) (basis weight 4.6 g / m ^2, average fiber diameter 1.7 [mu] m). A continuous filament web (S2) of polyethylene terephthalate was formed on the obtained microfiber web in the same manner as the fiber web (S1). Subsequently, the obtained laminated web was thermocompression-bonded with a pair of flat rolls / flat rolls to obtain a laminated non-woven fabric. The average thickness of the obtained laminated nonwoven fabric was 30.5 μm, and the average open pore diameter was 8.1 μm.

The obtained laminated non-woven fabric was coated with carbon black and a polyester-based binder as a conductive material to prepare a current collector for a secondary battery. Specifically, a carbon black dispersion containing 20% by weight of carbon black and 15% by weight of a polyester-based binder is coated on the surface and the back of the laminated non-woven fabric twice by bar coating, and then the solvent is dried at 105 ° C. Was removed. The coating weight of the conductive material comprising carbon black and the polyester binder was 27 g / m ² , the thickness of the obtained current collector was 40.7 μm, and the surface resistance was 1.7 Ω / □.

(Example 2)
Polyethylene terephthalate (1% using orthochlorophenol, solution viscosity sp sp / c 0.77 at 25 ° C method, melting point 263 ° C) is spun from a spinneret, and spun at a spinning temperature of 300 ° C to form a fiber web (S1) ) Was formed on the collection net. On the obtained continuous long fiber web (basis weight: 7.7 g / m ² , average fiber diameter: 13 μm), polyethylene terephthalate (also solution viscosity sp sp / c 0.50, melting point 260 ° C.) is melt-blown with a spinning temperature of 300 ° C., jetted directly heated air 320 ° C. 1000 Nm ³ / hr conditions to form a fine fiber web (M) (basis weight 4.6 g / m ^2, average fiber diameter 1.7 [mu] m). Subsequently, the obtained laminated web was thermocompression-bonded with a pair of flat rolls / flat rolls to obtain a laminated non-woven fabric. The average thickness of the obtained laminated nonwoven fabric was 18.7 μm, and the average opening diameter was 8.7 μm.

A conductive polymer (polyaniline manufactured by Idemitsu Kosan Co., Ltd.) was applied to the obtained laminated nonwoven fabric as a conductive material to produce a current collector for a secondary battery. The coating method was a gravure printing method, and printing was performed once on the front and back of the laminated nonwoven fabric. The gravure plate had a coating amount of 100 g / m ² as a basic condition, and was dried by hot air drying at 100 ° C. for 5 minutes. The coating weight of the conductive polymer was 12 g / m ² , the thickness of the obtained current collector was 20.5 μm, and the surface resistance was 8.0 Ω / □.

(Example 3)
Polyethylene terephthalate (1% using orthochlorophenol, solution viscosity sp sp / c 0.77 at 25 ° C method, melting point 263 ° C) is spun from a spinneret, and spun at a spinning temperature of 300 ° C to form a fiber web (S1) ) Was formed on the collection net. On the obtained continuous long fiber web (basis 20.8 g / m ² , average fiber diameter 13 μm), polyethylene terephthalate (also solution viscosity sp sp / c 0.50, melting point 260 ° C.) with a melt blow nozzle, spinning temperature 330 ° C. The mixture was directly jetted under heating air at 370 ° C. and 1500 Nm ³ / hr to form a fine fiber web (M) (20.0 g / m ² basis weight, 0.5 μm average fiber diameter). On the obtained ultrafine fiber web, a continuous continuous fiber web (S2) of polyethylene terephthalate was formed in the same manner as the fiber web (S1). The obtained laminated web was thermocompression-bonded with a pair of flat rolls / flat rolls to obtain a laminated non-woven fabric. The average thickness of the obtained laminated nonwoven fabric was 65.7 μm, and the average opening diameter was 1.6 μm.

Aluminum was attached as a conductive material to the obtained laminated non-woven fabric to prepare a current collector for a secondary battery. Vacuum deposition was used as a deposition method. The surface of the laminated nonwoven fabric and the pressure of 5 V, the deposition time of 180 seconds as the basic condition, using a Nirakco standard stand board (type: SF-106 tungsten) as the heat source, the degree of vacuum is 5 × 10 ^-5 torr, and the deposition time is 180 seconds. Each back side was vapor-deposited once. The thickness of the obtained current collector was 65.7 μm, and the surface resistance was 0.52 Ω / □.

  The present invention provides a secondary battery that can be made thin and light, has less unevenness in electrical conductivity, is excellent in strength and handleability at the time of manufacture, has a low risk of short circuit, and has a low cost of manufacture. The current collector is a lithium ion secondary battery, an all solid lithium ion secondary battery, a lead storage battery, a nickel cadmium battery, a nickel hydrogen battery, by appropriately selecting a conductive material suitable for the type of secondary battery. It can be suitably used for proton batteries, alkaline batteries, lithium ion capacitors, electric double layer capacitors and the like.

Claims (10)

  A laminate comprising at least one continuous continuous fiber layer (S) having an average fiber diameter of 10 to 30 μm and a fine fiber layer (M) having an average fiber diameter of 0.3 to 3 μm and integrated by thermocompression bonding A collector for a secondary battery, comprising a non-woven fabric and a conductive material attached to the laminated non-woven fabric.   The current collector for a secondary battery according to claim 1, wherein the laminated non-woven fabric has an SMS structure or an MSM structure.   The current collector for a secondary battery according to claim 1, wherein the continuous long fiber layer is a spunbonded nonwoven fabric made of synthetic long fibers.   The current collector for a secondary battery according to any one of claims 1 to 3, wherein the fine fiber layer is a meltblown nonwoven fabric composed of synthetic long fibers.   The current collector for a secondary battery according to any one of claims 1 to 4, wherein the laminated nonwoven fabric is made of polyester fibers.   The current collector for a secondary battery according to any one of claims 1 to 5, wherein a thickness of the laminated nonwoven fabric is 10 to 70 m.   The current collector for a secondary battery according to any one of claims 1 to 6, wherein the conductive material is a coating of carbon or a carbon-based compound.   The current collector for a secondary battery according to any one of claims 1 to 6, wherein the conductive material is a metal coating.   The current collector for a secondary battery according to any one of claims 1 to 6, wherein the conductive material is a coating of a conductive polymer. A method of manufacturing a current collector for a secondary battery according to any one of claims 1 to 9,
Obtaining a laminated web by laminating a continuous long fiber layer (S) having an average fiber diameter of at least one layer of 10 to 30 μm and a fine fiber layer (M) having an average fiber diameter of 0.3 to 3 μm of at least one layer;
Integrating the laminated web by thermocompression bonding to obtain a laminated nonwoven fabric, and attaching the conductive material to the laminated nonwoven fabric,
Including
The method wherein the thermocompression bonding is performed by calendering.