JP2005196999A - Separator for battery, and manufacturing method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a separator hardly short-circuited even if charged for long period, and a manufacturing method of the same. <P>SOLUTION: The separator for a battery comprises a porous first film 10 made of organic material, and a second film 20 having vapor deposition particles 21 of inorganic material, formed on the first film. The manufacturing method of the separator comprises a process of supplying the film made of porous organic material into an airtight container, a process of reducing the pressure in the airtight container to 0.667 to 0.00133 Pa, a process of maintaining the inorganic material at a temperature higher than the melting point thereof by 200 to 1200°C in the airtight container, and a process of making the porous film made of organic material run on the inorganic material kept in the above temperature while cooling the upper side of the organic material. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a battery separator and a method for manufacturing the battery separator, and more particularly to a battery separator and a method for manufacturing the same that are less likely to be short-circuited even if charged for a long time.

  With the recent spread of small portable electronic devices, there is an increasing demand for secondary batteries that are small and light, have high energy density, and can be repeatedly charged. The demand for lithium ion batteries, which are secondary batteries that meet this requirement, is high. Lithium ion batteries use lithium with high energy density, lithium cobaltate as the positive electrode material, carbonaceous material that can be doped / undoped with lithium as the negative electrode material, and the positive electrode material and the negative electrode material are separated by a separator. .

  As a separator used in a lithium ion battery, a porous polyethylene film is widely used. The porous polyethylene membrane is resistant to the electrolyte solution, can hold a sufficient amount of the electrolyte solution, prevents conduction due to contact between the positive electrode material and the negative electrode material, and does not hinder lithium ion conduction. So it is excellent as a separator. Furthermore, in lithium ion batteries, there is a risk of overheating causing a rise in temperature due to decomposition of the electrolyte solution and an increase in internal pressure, that is, a fire or explosion due to a runaway reaction. Since the conduction is stopped, it has a so-called shutdown effect that prevents ignition or explosion due to a runaway reaction.

  However, when this lithium ion battery is charged for a long time, there is a problem that the polyethylene film in contact with the lithium cobalt oxide as the positive electrode material is carbonized and the positive electrode material and the negative electrode material are short-circuited. Then, an object of this invention is to provide the separator which cannot be short-circuited even if it charges for a long time, and its manufacturing method.

  In order to achieve the above object, a battery separator according to a first aspect of the present invention includes a porous first film 10 formed of an organic material and vapor deposition of an inorganic material, for example, as shown in FIG. And a second film 20 formed of particles 21 on the surface of the first film.

  When comprised in this way, there exists a 2nd film | membrane formed with the vapor deposition particle | grains of an inorganic material between the 1st film | membrane formed with an organic material, and a positive electrode material, and a 1st film | membrane and a positive electrode material are directly There is no contact, and carbonization of the first film is prevented. In addition, since the second film is formed of inorganic material vapor-deposited particles, ion conduction is not hindered, and the presence of the second film does not reduce the power generation efficiency.

  Moreover, the battery separator according to the invention described in claim 2 is, for example, as shown in FIG. 1, in the battery separator 1 according to claim 1, vapor deposition of an inorganic material on the surface of the second film 20. The average particle diameter d of the particles 21 is 0.05 to 1 μm.

  If comprised in this way, since the average particle diameter of the vapor deposition particle | grains of the inorganic material on the surface perpendicular | vertical to the direction which ion conducts is 0.05-1 micrometer, the porous 1st film | membrane formed with an organic material Therefore, contact between the positive electrode material and the first film of the organic material is prevented, and ion conduction is not hindered.

  Moreover, the battery separator according to the invention of claim 3 is the battery separator 1 of claim 1 or claim 2, for example, as shown in FIG. 0.1 to 1.5 μm.

  If comprised in this way, since the thickness of a 2nd film | membrane is appropriate, a contact with a positive electrode material and the 1st film | membrane of an organic material is prevented, and ion conduction is not prevented.

  The battery separator according to the invention of claim 4 is the battery separator 1 according to any one of claims 1 to 3, for example, as shown in FIG. Is one or more inorganic materials selected from the group consisting of aluminum Al, magnesium Mg, boron B, beryllium Be, gallium Ga, silicon Si, oxides, nitrides, and carbides thereof.

  If comprised in this way, the vapor deposition particle | grains of an inorganic material can be formed appropriately, there is little deterioration, a contact with a 1st film | membrane and a positive electrode material is prevented, and ion conduction is not prevented.

  In addition, the battery separator according to the invention described in claim 5 is the battery separator 1 according to any one of claims 1 to 4, for example, as shown in FIG. The organic material that forms is polyethylene.

  With this configuration, since the first film of the organic material is polyethylene, it is resistant to the electrolyte solution, can hold a sufficient amount of the electrolyte solution, and when the temperature becomes high, the pores are blocked. In addition, the ion conduction is stopped, and a fire or explosion due to a runaway reaction can be prevented, which has a so-called shutdown effect.

In addition, the battery separator according to the invention described in claim 6 is the battery separator 1 according to any one of claims 1 to 5, for example, as shown in FIG. ˜500 seconds / 100 cm ³ .

If comprised in this way, since the hole whose air permeability will be 30-500 second / 100cm < ³ > is formed, it is suitable for conducting ion.

  In order to achieve the above-mentioned object, the battery separator manufacturing method according to the invention described in claim 7 has airtightness on the porous film 12 of the organic material as shown in FIGS. 1 and 2, for example. In the step of supplying into the container 33, the step of reducing the pressure in the airtight container 33 to 0.667 to 0.00133 Pa, and the airtight container 33, the inorganic material 22 is 200 to 1200 ° C. higher than the melting point. A step of maintaining the temperature, and the organic material porous film 10 is allowed to travel while being cooled above the temperature-maintained inorganic material 22 to deposit the inorganic material 22 on the organic material porous film 10. 21 to form a film 22.

  With this configuration, a film in which vapor-deposited particles of an inorganic material are formed on the surface of a porous film of an organic material is manufactured, and the organic material film and the positive electrode material are not in direct contact with each other. This is a battery separator manufacturing method in which carbonization of the membrane is prevented, ion conduction is not hindered, and power generation efficiency is not reduced. Moreover, since the porous film of the organic material is produced by running over the inorganic material, it is an industrial production method suitable for mass production.

  The battery separator manufacturing method according to claim 8 is the battery separator manufacturing method according to claim 7, wherein the inorganic material is aluminum Al, magnesium Mg, boron B, beryllium Be, gallium. One or more inorganic materials selected from the group consisting of Ga, silicon Si, oxides thereof, nitrides and carbides.

  If comprised in this way, the vapor deposition particle | grains of an inorganic material can be formed appropriately, and the manufacture of the battery separator by which contact with an organic material film | membrane and a positive electrode material is prevented, and ion conduction is not prevented. Become a method.

  The battery separator manufacturing method according to claim 9 is the battery separator manufacturing method according to claim 7 or 8, wherein the organic material porous film is a polyethylene film. is there.

  With this configuration, since the organic material film is polyethylene, the battery separator is resistant to the electrolyte solution, can hold a sufficient amount of the electrolyte solution, and has a shutdown effect when the temperature becomes high. The manufacturing method becomes.

  The battery separator according to the present invention provides a separator that is not easily short-circuited even when charged for a long time. Moreover, according to the manufacturing method of the battery separator which concerns on this invention, the method of manufacturing industrially suitable for mass production of the separator which is hard to short-circuit even if it charges for a long time is provided.

  Embodiments of the present invention will be described below with reference to the drawings. In each figure, the same or equivalent devices are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 shows a top view (a) and a cross-sectional view (b) of a battery separator 1 according to an embodiment of the present invention. The vapor deposition particles 21 are laminated on the porous organic material film 10 to form an inorganic material film 20. As the organic material film 10, it is preferable to use a polyethylene film because it has corrosion resistance to the electrolyte solution, can hold a sufficient amount of the electrolyte solution, and has a shutdown effect. As polyethylene, known resins can be used. For example, low density polyethylene, medium density polyethylene, high density polyethylene, ultrahigh molecular weight polyethylene, or these resin components are 50% by weight or more, and other resin components are 50% by weight or less. It is possible to use a mixture or a copolymer. The organic material film 10 may be another polyolefin resin film. As the polyolefin resin, a known resin can be used. For example, polypropylene, poly (4-methylpentene-1), poly (3-methylbutene-1) can be used. Etc.), or a mixture or copolymer in which these resin components are 50% by weight or more and other resin components are 50% by weight or less. In addition, the organic material film 10 is not limited thereto, but is a polyamide having corrosion resistance to an electrolyte solution, or a tetrafluoroethylene resin, a tetrafluoroethylene + perfluoroalkoxyne copolymer resin, or a tetrafluoroethylene-6. Fluoropropylene copolymer resin, ethylene-4 fluoroethylene resin, trifluoroethylene chloride resin, vinylidene fluoride resin, fluorine film such as vinyl fluoride resin, or these resin components are 50% by weight Various kinds of films such as a mixture and a copolymer having the above-mentioned and other resin components of 50% by weight or less can be used.

The organic material film 10 is porous. In FIG. 1, the display of holes is omitted. “Porosity” as used herein refers to the fact that the positive electrode and the negative electrode are prevented from coming into contact with each other, but there are a large number of pores through which the electrolyte permeates and maintains ionic conductivity. The method for making the organic material film 10 porous is not limited. For example, the film is extremely stretched to form pores in the fibrillated portion, or a component that is solidified and dispersed in a molten resin. An extraction method or the like in which pores are formed by extracting the dispersed components with an organic solvent or the like after dispersing the film into a film is preferably used. The organic material film 10 may be porous so long as the air permeability according to JIS P8117 is about 10 to 300 seconds / 100 cm ³ . If the air permeability is less than 10 seconds / 100 cm ³ , the pores are too large and the positive electrode material and the negative electrode material may be short-circuited. Conversely, if the air permeability is too high, ion conduction may be hindered. As will be described later, in order to obtain 500 sec / 100 cm ³ as the separator, about 300 sec / 100 cm ³ is suitable as the organic material film 10, but the air permeability as the separator is 300 sec / 100 cm ³ or more. Is 500 seconds / 100 cm ³ or less. In this document, unless otherwise specified, “air permeability” refers to the air permeability according to JIS P8117 (test method name: paper and paperboard—air permeability test method—Gurley test machine method). The organic material film 10 is preferably 10 to 50 μm thick. If it is thinner than 10 μm, the strength is insufficient and the organic material film 10 may be damaged. On the other hand, if the thickness is larger than 50 μm, ion conduction is hindered and the efficiency of the battery may be lowered. Further, in order to accommodate as much of the positive electrode material as possible in a battery having a predetermined capacity and to increase the battery capacity, it is preferable that the separator has a small film thickness, and is preferably 50 μm or less.

  The inorganic material vapor-deposited particles 21 are obtained by depositing an inorganic material on the organic material film 10 by vapor deposition. Deposition will be described in detail later. The shape of the vapor deposition particles 21 is random, but is roughly spherical or spherically crushed up and down like a meteorite. Here, “upper and lower” refers to the thickness direction of the organic material film 10. The size of the vapor deposition particles 21 is not uniform, but the variation is small. The average particle diameter d of the vapor deposition particles 21 is preferably 0.05 μm or more and 1 μm or less when measured on the surface of the inorganic material film 20, that is, the surface parallel to the organic material film 10. If the average particle diameter d is larger than 1 μm, the vapor deposition particles 21 block the pores of the organic material film 10, impeding ion conduction, which may reduce battery efficiency. On the other hand, if the average particle diameter d is smaller than 0.05 μm, the vapor deposition particles 21 enter the holes of the organic material film 10 to close the holes, impeding ion conduction, which may reduce the efficiency of the battery. The average particle size d is preferably 0.07 μm or more, more preferably 0.1 μm or more, and preferably 0.8 μm or less. The average particle diameter d is an average of a plurality of particle diameters obtained by observing the surface of the inorganic material film with an electron microscope, obtaining the particle diameter of one vapor deposition particle by the average of the major axis and minor axis of each particle. It can ask for.

  The average particle diameter d of the vapor deposition particles 21 of the inorganic material is greatly affected by the temperature of the vapor deposition material and the degree of vacuum at the time of vapor deposition. The temperature of the vapor deposition material should be higher than the melting point of the material by 200 ° C. or more, preferably 300 ° C. or more, more preferably 400 ° C. or more. The temperature higher than the melting point of the material is 1200 ° C. or lower, preferably 1150 ° C. or lower, more preferably 1100 ° C. or lower. If the temperature of the vapor deposition material is lower than this range, the particle diameter of the vapor deposition particles 21 becomes too large, and if it is higher than this range, the particle diameter of the vapor deposition particles 21 becomes too small. The pressure at the time of vapor deposition is 0.667 Pa or less, preferably 0.6 Pa or less, more preferably 0.5 Pa or less. The pressure is 0.00133 Pa or more, preferably 0.0015 Pa or more, more preferably 0.002 Pa or more. When the degree of vacuum at the time of vapor deposition is lower than this range (pressure is low), the particle size of the vapor-deposited particles 21 becomes too small, and when higher than this range (high pressure), the particle size of the vapor-deposited particles 21 becomes too large. . Note that the degree of vacuum is preferably in the above range even when vapor deposition is performed while oxygen gas or nitrogen gas is supplied as a reaction gas.

As the material of the vapor deposition particles 21 of the inorganic material, it is preferable to use an inorganic material such as aluminum Al, magnesium Mg, boron B, beryllium Be, gallium Ga, silicon Si, oxides, nitrides or carbides thereof. When the vapor deposition particles 21 are formed of these materials, the vapor deposition particles can be formed in an appropriate shape and an appropriate size, and are resistant to an electrolyte solution used in a battery, particularly an electrolyte solution of a lithium ion battery. It is suitable because it is difficult to deteriorate. Note that a non-aqueous electrolyte solution in which a lithium salt is dissolved in an organic solvent is used as the electrolyte solution used in the lithium battery. Lithium salts include LiClO ₄ , LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiC (SO ₂ CF ₃ ) ₃ , Li ₂ B ₁₀ Cl ₁₀ , One or a mixture of two or more of lower aliphatic carboxylic acid lithium salts, LiAlCl _{4 and the} like are used. Examples of the organic solvent include cyclic carbonate solvents such as propylene carbonate, ethylene carbonate and butylene carbonate, cyclic carboxylic acid ester solvents such as γ-butyrolactone and γ-valerolactone, dimethoxymethane, 1,2-dimethoxyethane, 1, Chain ether solvents such as 3-dimethoxypropane, cyclic ether solvents such as tetrahydrofuran, 1,3-dioxolane, 2-methyltetrahydrofuran, 4-methyl-1,3-dioxolane, methyl formate, methyl acetate, methyl propionate, etc. Chain carboxylate solvents, chain carbonate solvents such as dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, acetonitrile, sulfolane, 3-methyl sulfolane, dimethyl sulfoxide, N, N-dimethyl phosphate One kind or a combination of two or more kinds of other organic solvents such as lumamide and N-methyloxazolidinone is used.

  The vapor deposition particles 21 of the inorganic material form a film having a thickness T as shown in FIG. Since the vapor deposition particles 21 have gaps between the particles, ions can be conducted through the gaps. Therefore, the conduction of ions is not hindered, and the efficiency of the battery is not reduced. The thickness T is preferably 0.1 μm to 1.5 μm. When the thickness T is less than 0.1 μm, it becomes difficult to obtain the effect of the vapor deposition particles 21 as a separator. If the thickness T is thicker than 1.5 μm, ions are difficult to conduct and the battery efficiency may be reduced. The thickness T is preferably 0.15 μm or more, preferably 1.0 μm or less, and more preferably 0.7 μm or less.

Further, even when the film 20 is formed by the vapor deposition particles 21 of the inorganic material on the surface of the organic material film 10 having the above-mentioned air permeability of about 10 to 300 seconds / 100 cm ³ , the air permeability as the battery separator 1 is 30 to 500 seconds / 100 cm ³ . The reason why the air permeability does not increase so much (the air permeability does not deteriorate) is because there is a gap between the particles as described above. The air permeability as the battery separator is 30 seconds / 100 cm ³ or more, preferably 80 seconds / 100 cm ³ or more, and more preferably 100 seconds / 100 cm ³ or more. Further, it is 500 seconds / 100 cm ³ or less, preferably 450 seconds / 100 cm ³ or less, more preferably 400 seconds / 100 cm ³ or less.

  Then, with reference to FIG. 2, the manufacturing method of the separator 1 for batteries is demonstrated. The inorganic material 22 is vapor-deposited on the organic material film 10 in the vacuum chamber 33 to form the film 20 of the vapor-deposited particles 21 (see FIG. 1). The vacuum chamber 33 is a highly airtight container for keeping the inside in a vacuum, and is, for example, a rectangular parallelepiped container of 3 m long × 5 m wide × 3 m high. An intake pipe 34 is connected to the vacuum chamber 33, and the other end is connected to a vacuum pump 35. A piping for introducing a reaction gas (not shown) may be connected to the vacuum chamber 33.

  In the vacuum chamber 33, an original fabric 12 in which the organic material film 10 is wound in a roll shape is installed. The organic material film 10 is guided from the raw fabric 12 to the guide roller 32 and reaches the lower portion of the roller 31. The roller 31 has a cylindrical shape, and rotates at the same speed in the same direction as the direction in which the organic material film 10 is fed (arrow in FIG. 2). Refrigerant pipes 36 and 37 are connected to the roller 31. The pipes 36 and 37 are connected to a refrigerant cooling device (not shown) outside the vacuum chamber 33, from which the refrigerant r is supplied into the roller 31 and returned. The roller 31 is cooled by the refrigerant r and kept at a low temperature.

  The organic material film 10 in contact with the lower surface of the roller 31 is guided to the guide roller 32 ′ and wound around the product roller 2.

  Under the roller 31, a container 23 in which the vapor deposition material 22 is stored is installed. The container 23 is configured to be heated by electricity (not shown). The heating by electricity may be an electric resistance heating, dielectric heating, high-frequency induction heating, or any other heating method as long as it is a method capable of heating to a temperature sufficiently higher than the melting point of the vapor deposition material and maintaining the temperature. . The vapor deposition material 22 is selected from inorganic materials, and aluminum Al, magnesium Mg, boron B, beryllium Be, gallium Ga, silicon Si, and oxides, nitrides or carbides thereof are preferably used. The gap between the lower portion of the roller 31 and the upper surface of the container 23 varies depending on the type of inorganic material, temperature conditions, and the like, and is in the range of 1 to several 100 mm, but is not limited to the above range.

  In order to manufacture a battery separator using the above-described apparatus, first, the raw fabric 12 is placed in the vacuum chamber 31, and the organic material film 10 is guided to the product roller 2 as described above. Subsequently, after the inside of the vacuum chamber 33 is airtight, the pressure is reduced by the vacuum pump 35 until the degree of vacuum is 0.667 to 0.00133 Pa. At that time, a reaction gas such as oxygen, nitrogen, ammonia, or acetylene may be supplied in a minute amount as a reaction gas. When oxygen is supplied, the evaporated particles become oxides, when nitrogen or ammonia is supplied, the evaporated particles become nitrides, and when acetylene is supplied, the evaporated particles become carbides.

  Therefore, the container 23 storing the vapor deposition material 22 is heated, and the vapor deposition material 22 is heated to a temperature 200 to 1200 ° C. higher than its melting point to maintain the temperature. In the above degree of vacuum, the vapor of the vapor deposition material is generated by setting the vapor deposition material to a temperature 200 to 1200 ° C. higher than the melting point.

  The generated vapor adheres to the organic material film 10 above the container 23. This is vapor deposition. Since vapor is also at a high temperature when adhering to the organic material film 10, the organic material film 10 may be damaged by heat. Therefore, the roller 31 is cooled by the refrigerant r. The organic material film 10 in contact with the roller 31 is cooled from the contact surface with the roller 31 and does not become high temperature even when vapor of the vapor deposition material adheres to it, so that damage due to heat can be prevented.

  In this state, the organic material film 10 is caused to travel from the raw fabric 12 toward the product roller 2. During traveling, the vapor deposition particles adhere to the organic material film 10 on the upper part of the vapor deposition material 22, that is, on the lower part of the roller 31. The film 1 in which the film of the vapor deposition particles 21 is formed on the organic material film 10 is wound around the product roller 2 as a battery separator (see FIG. 1). The speed of traveling the organic material film 10 is preferably about 10 to 100 m / min, but is not limited to the above range. When the traveling speed is increased, the film thickness T (see FIG. 1) of the vapor deposition particles 21 is decreased, and when the traveling speed is decreased, the film thickness T is increased.

  Since the separator film can be manufactured by the above method using the above apparatus, a large amount of the film can be industrially manufactured. In order to use as a separator, the film wound up by the product roller 2 may be taken out after making the inside of the vacuum chamber 33 normal pressure, and cut into an appropriate size while pulling out the film from the product roller 2. In addition, the film | membrane manufactured in this way is not restricted to a battery separator, It can also be used for various filters.

Hereinafter, the effect of the battery separator according to the present invention will be confirmed by Examples and Comparative Examples. In Example 1, vapor deposition using aluminum Al as a deposition material was performed on a polyethylene film having a thickness of 20 μm, a width of 500 mm, a winding length of 1000 m, and an air permeability of 53 seconds / 100 cm ³ . Vapor deposition was performed by setting the inside of the vacuum chamber to 0.0133 Pa and maintaining the temperature by heating aluminum Al (melting point: 660 ° C.) as a vapor deposition material to 1300 ° C. in a dielectric heating furnace. The running speed (winding speed) of the film was 60 m / min. The air permeability after vapor deposition was 160 seconds / 100 cm ³ . In addition, the air permeability was measured according to JIS P8117 as described above using “Gurley Densometer” manufactured by Tozai Seiki Co., Ltd. The vapor deposition particles formed on the surface had an average particle diameter of 0.18 μm and a film thickness of the vapor deposition particles of 0.2 μm as observed by a scanning electron micrograph.

A lithium ion battery was manufactured using the above membrane as a separator. In the lithium ion battery, lithium cobalt oxide LiCoO ₂ was used as the positive electrode material, and a carbonaceous material was used as the negative electrode material. The above film was sandwiched between the positive electrode material and the negative electrode material so that the surface of the vapor deposition particles faced the positive electrode material side. The membrane was impregnated with an electrolyte solution obtained by dissolving lithium fluorophosphate LiPF ₆ in a 1: 1 solvent of diethyl carbonate and ethylene carbonate as the electrolyte solution. The positive electrode material, the separator, and the negative electrode material were rounded and placed in a nickel-plated metal case with a diameter of 15 mm, and the electrode was attached and sealed to prepare a secondary battery. This battery was charged for a long time with a commercially available filling device and tested for durability. As shown in FIG. 3, the results showed durability up to 200 hours. The term “durability” as used herein refers to a charging time until the separator deteriorates due to long-term charging, a short circuit occurs between the positive electrode material and the negative electrode material, and the battery cannot be used.

Next, in Example 2, the same polyethylene film as in Example 1 was deposited using aluminum oxide Al ₂ O ₃ as a deposition material. Vapor deposition was performed at 0.0267 Pa in a vacuum chamber, and aluminum oxide Al ₂ O ₃ (melting point: 2020 ° C.) as a vapor deposition material was heated to 2600 ° C. with an electron beam while maintaining the temperature. The running speed of the film was 30 m / min. The air permeability after vapor deposition was 280 seconds / 100 cm ³ . The vapor deposition particles formed on the surface had an average particle size of 0.36 μm and a film thickness of the vapor deposition particles of 0.45 μm as observed by a scanning electron micrograph. A lithium ion battery was produced in the same manner as in Example 1 using the above membrane as a separator. This battery was charged for a long time with a commercially available filling device and tested for durability. As a result, as shown in FIG. 3, durability up to 260 hours was shown.

Next, in Example 3, vapor deposition using magnesium Mg as a vapor deposition material was performed on the same polyethylene film as in Example 1. Vapor deposition was performed while maintaining the temperature by supplying oxygen O ₂ as a reaction gas to 0.0933 Pa in the vacuum chamber and heating magnesium Mg (melting point: 649 ° C.) as a vapor deposition material to 950 ° C. The vapor deposition particles formed in this case are oxides of magnesium Mg, but are not necessarily magnesium oxide MgO, and may be mixed with magnesium oxides of other components. The running speed of the film was 30 m / min. After vapor deposition on one side, a similar vapor deposition film was formed on an undeposited surface under the same conditions. That is, a film of vapor deposition particles was formed on both sides of a polyethylene film. The air permeability after vapor deposition was 340 seconds / 100 cm ³ . The vapor deposition particles formed on the surface had an average particle size of 0.27 μm and a film thickness of the vapor deposition particles of 0.38 μm, as observed by scanning electron micrographs on both sides. A lithium ion battery was produced in the same manner as in Example 1 using the above membrane as a separator. This battery was charged for a long time with a commercially available filling device and tested for durability. As shown in FIG. 3, the results showed durability up to 284 hours.

Next, in Example 4, vapor deposition using aluminum oxide Al ₂ O ₃ as a vapor deposition material was performed on the same polyethylene film as in Example 1. Vapor deposition was performed by setting the inside of the vacuum chamber to 0.267 Pa and maintaining the temperature by heating aluminum oxide Al ₂ O ₃ as a deposition material to 2520 ° C. with an electron beam. The running speed of the film was 30 m / min. The air permeability after vapor deposition was 252 seconds / 100 cm ³ . The vapor deposition particles formed on the surface had an average particle size of 0.65 μm and a film thickness of the vapor deposition particles of 0.5 μm, as observed by scanning electron micrographs on both sides. A lithium ion battery was produced in the same manner as in Example 1 using the above membrane as a separator. This battery was charged for a long time with a commercially available filling device and tested for durability. As a result, as shown in FIG. 3, durability up to 260 hours was shown.

Comparative Example 1

  Next, in Comparative Example 1, the same polyethylene film as in Example 1 was used as a separator without being deposited, and a lithium ion battery similar to that in Example 1 was produced. This battery was subjected to a long-term charge test using a commercially available filling device. As shown in FIG. 3, the results showed durability up to 100 hours.

Comparative Example 2

Next, in Comparative Example 2, vapor deposition using aluminum oxide Al ₂ O ₃ as a vapor deposition material was performed on the same polyethylene film as in Example 1. Vapor deposition was performed by setting the inside of the vacuum chamber to 0.213 Pa, and heating aluminum oxide Al ₂ O ₃ as a deposition material to 2600 ° C. with an electron beam and maintaining the temperature. The running speed of the film was 30 m / min. The air permeability after vapor deposition was 1050 seconds / 100 cm ³ . The vapor deposition particles formed on the surface had an average particle diameter of 1.2 μm and a film thickness of the vapor deposition particles of 0.7 μm as observed by a scanning electron micrograph. A lithium ion battery was produced in the same manner as in Example 1 using the above membrane as a separator. This battery was charged with a commercially available filling device and an endurance test was attempted, but the result could not be charged as shown in FIG.

Comparative Example 3

Next, in Comparative Example 3, vapor deposition using magnesium Mg as a vapor deposition material was performed on the same polyethylene film as in Example 1. Vapor deposition was performed by supplying oxygen O ₂ as a reaction gas, setting the inside of the vacuum chamber to 0.000933 Pa, and heating magnesium oxide Mg as a vapor deposition material to 950 ° C. in an induction heating furnace to maintain the temperature. The running speed of the film was 30 m / min. The air permeability after vapor deposition was 860 seconds / 100 cm ³ . The vapor deposition particles formed on the surface had an average particle size of 0.03 μm and a film thickness of the vapor deposition particles of 0.08 μm as observed by a scanning electron micrograph. A lithium ion battery was produced in the same manner as in Example 1 using the above membrane as a separator. This battery was charged with a commercially available filling device and an endurance test was attempted, but the result could not be charged as shown in FIG.

Comparative Example 4

Next, in Comparative Example 4, vapor deposition using aluminum oxide Al ₂ O ₃ as the vapor deposition material was performed on the same polyethylene film as in Example 1. Vapor deposition was performed at 0.0267 Pa in the vacuum chamber, and aluminum oxide Al ₂ O ₃ as a vapor deposition material was heated to 2600 ° C. with an electron beam and the temperature was maintained. The running speed of the film was 80 m / min. The air permeability after vapor deposition was 87 seconds / 100 cm ³ . The vapor deposition particles formed on the surface had an average particle diameter of 0.14 μm and a film thickness of the vapor deposition particles of 0.06 μm as observed by a scanning electron micrograph. A lithium ion battery was produced in the same manner as in Example 1 using the above membrane as a separator. This battery was charged for a long time with a commercially available filling device and tested for durability. As shown in FIG. 3, the results showed durability up to 120 hours.

The results of Examples 1 to 4 and Comparative Examples 1 to 4 are summarized in FIG. In Comparative Example 1 in which the polyethylene film was used as a separator as it was, the durability was only 100 hours, but in Examples 1 to 4, which are embodiments of the present invention, the durability was 200 hours or more, and the present invention. The effect of was shown. On the other hand, in Comparative Example 2 where the average particle diameter of the vapor deposition particles was as large as 1.2 μm, charging could not be performed. This is presumably because the air permeability was as high as 1050 seconds / 100 cm ³ , so that the pores of the polyethylene film were blocked by the large vapor deposition particles, preventing the ion conduction. Further, in Comparative Example 3 in which the average particle diameter of the vapor deposition particles was as small as 0.03 μm, charging could not be performed. This is presumably because the air permeability was as high as 860 seconds / 100 cm ^3, and thus small vapor deposition particles were clogged inside the pores of the polyethylene film, preventing ion conduction. Further, in Comparative Example 4 where the thickness of the deposited particle film was as thin as 0.06 μm, the durability was increased by 120% for 20 hours as compared with the case where the deposited particle film was not formed, and the deposited particle film was formed. The effect was not noticeable.

It is the top view (a) and sectional drawing (b) explaining the battery separator which is embodiment of this invention. It is a schematic diagram of the manufacturing apparatus for demonstrating the manufacturing method of the battery separator which is embodiment of this invention. It is a table | surface which shows the measurement result of durability of the Example of this invention and a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Battery separator 2 Product roller 10 Porous film | membrane 12 formed with organic material 20 Original fabric 20 Film | membrane formed with the vapor deposition particle of inorganic material 21 Vapor deposition particle 22 Vapor deposition material 23 (Vapor deposition material) container 31 Rollers 32 and 32 'Guide roller 33 Vacuum tank 34 Intake pipe 35 Vacuum pumps 36, 37 Refrigerant piping d Average particle diameter T of deposited particles T Film thickness r of deposited particles Refrigerant

Claims (9)

A porous first membrane formed of an organic material;
A second film formed on the surface of the first film with vapor deposition particles of inorganic material;
Battery separator. The average particle diameter of the vapor deposition particles of the inorganic material on the surface of the second film is 0.05 to 1 μm;
The battery separator according to claim 1. The thickness of the second film is 0.1-1.5 μm;
The battery separator according to claim 1 or 2. The inorganic material forming the second film is one or more selected from the group consisting of aluminum Al, magnesium Mg, boron B, beryllium Be, gallium Ga, silicon Si, oxides thereof, nitrides or carbides thereof. An inorganic material;
The battery separator according to any one of claims 1 to 3. The organic material forming the first film is polyethylene;
The battery separator according to any one of claims 1 to 4. The air permeability is 30-500 sec / 100 cm ³ ;
The battery separator according to any one of claims 1 to 5. Supplying a porous membrane of an organic material into an airtight container;
Reducing the pressure inside the airtight container to 0.667 to 0.00133 Pa;
Maintaining the inorganic material at a temperature 200 to 1200 ° C. higher than the melting point in the airtight container;
A step of forming a porous film of the organic material on the porous film of the organic material with a vapor deposition particle of the inorganic material by running the porous film of the organic material while cooling the inorganic material maintained at the temperature. Prepare;
Manufacturing method of battery separator. The inorganic material is one or more inorganic materials selected from the group consisting of aluminum Al, magnesium Mg, boron B, beryllium Be, gallium Ga, silicon Si, oxides, nitrides and carbides thereof;
The manufacturing method of the battery separator of Claim 7. The porous membrane of organic material is a polyethylene membrane;
The manufacturing method of the battery separator of Claim 7 or Claim 8.

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