JP4414165B2 - Electronic component separator and electronic component - Google Patents

Description

  The present invention relates to a separator provided in an electronic component such as a lithium ion secondary battery. Furthermore, it is related with the electronic component provided with this separator for electronic components.

2. Description of the Related Art In recent years, various information terminal devices such as notebook computers, mobile phones, and video cameras have become widespread as they have rapidly become smaller, lighter, and thinner. Some hybrid vehicles and fuel cell vehicles have been put into practical use.
Due to such a background, there is an increasing demand for high energy density secondary batteries as these power sources. In particular, lithium ion secondary batteries using non-aqueous electrolytes have high operating voltage and high energy density. Has already been put to practical use.
A lithium ion secondary battery generally has a predetermined organic electrolyte solution in a battery can that also serves as a negative electrode terminal, with an electrode group formed by interposing a separator having electrical insulation and liquid retention between a positive electrode and a negative electrode. The opening of the battery can is sealed with an insulating gasket with a sealing plate provided with a positive electrode terminal.

As a method of manufacturing such a lithium ion secondary battery, as shown in FIG. 3A, an adhesive paint 32 is applied on the electrode 31, and as shown in FIG. For example, a method of injecting an electrolytic solution after bonding a polyolefin separator 33 to the substrate and drying and making it porous and bonded as shown in FIG. 3C is exemplified (see, for example, Patent Document 1).
In addition, a separator in which a layer swelled with an electrolyte solution having a communicating hole having a thickness of 5 μm or less and a pore diameter of less than 0.1 μm is laminated on one side or both sides of a polyolefin-based porous membrane is sandwiched between electrodes and a lithium ion secondary A method of manufacturing a battery has been proposed (see, for example, Patent Document 2).
Japanese Patent No. 3225864 Japanese Patent No. 2981238

However, in the invention described in Patent Document 1, when an electrolyte is injected into the separator, the adhesiveness may be lowered in a high temperature region of about 50 ° C. or higher, and the adhesiveness is high in a wide temperature environment. It was difficult to express. Therefore, in a temperature range (about -20 to 100 ° C.) in which the electronic component is used, ion conductivity may be lowered, and performance such as cycle characteristics may be insufficient. In addition, the shutdown characteristics may be insufficient.
In the invention described in Patent Document 2, since the pore diameter is less than 0.1 μm, the liquid permeability is low, and when the electrolyte swells, the layer provided on one side or both sides of the porous membrane Since the pore diameter of the film becomes even narrower, ion conductivity may be hindered. As a result, the battery characteristics were not sufficient.
Also, electronic parts having a separator such as a polymer lithium battery, an aluminum electrolytic capacitor, and an electric double layer capacitor have the same problems as described above.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a separator for an electronic component that has high adhesion to an electrode under a wide temperature environment even when an electrolyte is injected into the separator. To do. Furthermore, it aims at providing the electronic component excellent in performance.

The separator for electronic components of the present invention is a separator for electronic components in which a porous layer made of an electrically insulating resin composition is formed on at least one surface of a porous substrate,
The electrically insulating resin composition has a gelation rate of 10 to 50% by mass of the first resin compound of 20% by mass or less and a second resin compound of 50 to 90% by mass of the gelation rate of 50% by mass or more. It is characterized by containing.
In the separator for electronic parts of the present invention, at least one of the first resin compound and the second resin compound is a resin containing a polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polystyrene, polyethylene oxide in the skeleton, or these A derivative of resin is preferable.
Alternatively, in the separator for electronic parts of the present invention, the first resin compound is a copolymer comprising at least one of ethylene tetrafluoride, propylene hexafluoride, and ethylene and vinylidene fluoride, or , A homopolymer composed of vinylidene fluoride,
The second resin compound is preferably a copolymer composed of propylene hexafluoride and vinylidene fluoride.
Furthermore, in the separator for electronic components of the present invention, the porous substrate is preferably a nonwoven fabric or a stretched porous film made of polyethylene and / or polypropylene.
In the separator for electronic components of the present invention, it is preferable that the air permeability measured by a Gurley air permeability measuring device is 1000 seconds / 100 ml or less.
The separator for electronic parts of the present invention is suitably provided for an electronic part selected from a lithium ion secondary battery, a polymer lithium battery, an aluminum electrolytic capacitor, and an electric double layer capacitor.
An electronic component of the present invention has a positive electrode and a negative electrode, the electronic component separator described above is disposed between them, and the electronic component separator is impregnated with an electrolyte. .

According to the separator for electronic components of the present invention, it is possible to prevent a decrease in adhesiveness in a high temperature region and maintain adhesiveness. Therefore, this separator has high ion conductivity and excellent battery performance such as cycle characteristics under a wide temperature environment.
In addition, the electronic component of the present invention has excellent performance such as cycle characteristics over a wide temperature range, and excellent shutdown characteristics.

An embodiment of an electronic component separator (hereinafter referred to as a separator) of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of this separator, and this separator 10 has a porous layer 12 formed on both surfaces of a porous substrate 11, and is provided in a lithium ion secondary battery. Hereinafter, each component of the separator 10 will be described in detail.

As the porous substrate 11, any polymer that is electrochemically stable can be used. Particularly, polyethylene, polypropylene, a copolymer thereof, a copolymer obtained by copolymerizing butene and hexene, Or it is preferable that it is a mixture which combined these. Moreover, the porous base material 11 can use the nonwoven fabric which made the fibrous material of the said material, the extending | stretching porous membrane which extended | stretched the said material, etc. There are no particular restrictions on these production methods, for example, as a method for producing a stretched porous membrane, organic particles or inorganic particles are added to and mixed with the polymer, and after forming into a film shape, the particles are extracted, dried, Furthermore, it can manufacture by extending | stretching. Moreover, when shape | molding in a film | membrane form, you may contain additives, such as a plasticizer, as needed.
The porous substrate 11 is preferably a non-woven fabric or a stretched porous membrane made of polyethylene and / or polypropylene because of better battery characteristics.

  Although there is no restriction | limiting in particular in the thickness of the porous base material 11, It is preferable that it is 200 micrometers or less. When the thickness exceeds 200 μm, the thickness of the separator 10 to be manufactured increases. As a result, when the separator 10 is provided in a battery, the distance between the electrodes tends to increase and the internal resistance tends to increase. A more preferable thickness is 5 to 50 μm. When the thickness is 50 μm or less, the thickness of the separator 10 can be reduced, and the battery can be thinned. If the thickness is less than 5 μm, the strength tends to decrease, making the separator 10 difficult to manufacture, and the productivity of the separator 10 and the battery tends to decrease. From such a viewpoint, the most preferable range is 10 to 25 μm. If the thickness is within this range, when the inside of the battery is heated due to an overcharge or abnormal short circuit condition, the porous structure changes to a nonporous structure due to thermal melting, so-called shutdown is stopped. More excellent characteristics.

The porous substrate 11 preferably has an air permeability measured by a Gurley air permeability measuring device of 1000 seconds / 100 ml or less. The lower the measured air permeability, the better the liquid permeability, the easier the electrolyte moves, and the better the ionic conductivity. Moreover, when the porous substrate 11 having such an air permeability is used, the air permeability of the separator can be easily set to a range of 1000 seconds / 100 ml or less, and as a result, a separator having good ion conductivity and can do. Moreover, when the porous base material 11 has such an air permeability, the porosity is in the range of 20 to 80% by volume.
Here, the air permeability measured by the Gurley air permeability measuring device is a value measured according to JIS P8117.

The porous layer 12 is a porous layer made of an electrically insulating resin composition. Furthermore, the electrically insulating resin composition has a gelation rate of 10 to 50% by mass and a second resin compound of 50 to 90% and a gelation rate of 50% by mass or more. It has an electric insulation property. As described above, in the electrically insulating resin composition, the content of the first resin compound having a low gelation rate and difficult to dissolve in the electrolytic solution, and the second resin having a high gelation rate and easy to dissolve in the electrolytic solution. Since the content of the compound is specified, the adhesive strength with the electrode can be increased in a wide temperature range. In particular, since it becomes a swollen gel in the high temperature region and does not completely dissolve, high adhesiveness can be maintained even in the high temperature region.
Even when the content of the first resin compound is less than 10% by mass or the content of the second resin compound is less than 50% by mass, the adhesiveness is low when the electrolyte is injected. It has a temperature range.

Here, the gelation rate is the gelation rate with respect to the electrolytic solution, and is determined as follows. First, 0.5 g (± 0.1 g) of a resin compound is weighed and immersed in 5.0 g of an electrolyte solvent composed of propylene carbonate (PC): diethyl carbonate (DEC) = 1: 2, sealed, and 90 ° C. And put it in a constant temperature bath for 1 hour. Next, after filtering this standing, the resin compound filtrate remaining on the filter paper is washed with methanol to remove the electrolyte. Then, the filtrate is dried, the mass after drying is measured, and the gelation rate is calculated by substituting the mass before and after the test into the following formula.
Gelation rate (mass%) = {mass before test (g) −mass after test (g)} / mass before test (g) × 100
This gelation rate is determined by the molecular weight and the degree of crosslinking of each resin compound.

  At least one of the first resin compound and the second resin compound contained in the electrically insulating resin composition is a resin or a resin containing polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polystyrene, polyethylene oxide in the skeleton It is preferable to be a derivative of If at least one of the first resin compound and the second resin compound contained in the electrical insulating resin composition is as described above, the affinity with the electrolytic solution is higher, and thus the battery characteristics are higher. . Moreover, the adhesiveness expressed by swelling of electrolyte solution becomes higher.

Furthermore, the first resin compound is a copolymer composed of one or more of ethylene tetrafluoride, hexafluoropropylene, and ethylene and a homopolymer composed of vinylidene fluoride. The second resin compound is preferably a copolymer composed of hexafluoropropylene and vinylidene fluoride.
Since these vinylidene fluoride resins containing vinylidene fluoride as an essential component are electrochemically stable and have a sufficient potential window between the electrode potentials of the battery, the first resin compound and the second resin compound When is a polymer, the battery characteristics are further improved.

  When the first resin compound and the second resin compound are the above-mentioned vinylidene fluoride resins, the vinylidene fluoride resin is, for example, a heterogeneous polymerization by a known polymerization method such as an emulsion polymerization method or a suspension polymerization method. In the system, the polymerization conditions may be set as appropriate. Specifically, water-soluble inorganic peroxides such as ammonium persulfate, and redox systems combined with reducing agents as catalysts, ammonium perfluorooctanoate, ammonium perfluoroheptanoate, ammonium perfluorononanoate, etc. as emulsifiers. Use under conditions of pressure and heating.

  This porous layer 12 has an outer surface average pore diameter in the range of 0.1 to 5 μm, an inner average pore diameter in the range of 0.5 to 10 μm, and an outer surface average pore diameter from the inner average pore diameter. It is preferable to be controlled to be small. The average pore diameter of the outer surface is calculated by observing the outer surface of the porous layer with an SEM or the like, measuring the pore diameters of at least 20 arbitrarily selected pores, and averaging these. The average internal pore diameter is determined by observing the longitudinal section of the porous layer with an SEM or the like, arbitrarily selecting at least 20 holes not exposed on the outer surface, measuring the pore diameters, and averaging these. Is calculated by In addition, the hole diameter herein refers to the long diameter when the hole is not substantially circular but substantially oval.

  The outer surface of the porous layer 12 is a portion that is in close contact with the electrode when the separator is used in a battery. Therefore, when the average pore diameter is too large, as a result, the contact area of the electrically insulating resin composition that comes into contact with the electrode tends to be small, and the adhesion and adhesion to the electrode tend to be reduced. On the other hand, when the average pore diameter is too small, it is difficult to pass the electrolytic solution, and the ionic conductivity tends to decrease. Therefore, by making the average pore diameter of the outer surface in the range of 0.1 to 5 μm, the adhesion with the electrode can be ensured and the electrolyte can be sufficiently passed. Moreover, although the particle diameter of the electrode active material used for a positive electrode or a negative electrode is various, generally it is often 5 micrometers or more. Also from this point, when the pore diameter of the outer surface is 5 μm or less, it is possible to further prevent the electrode active material from being mixed into the porous layer and causing a local short circuit when the separator and the electrode are joined. In addition, when the average pore diameter of the outer surface is in such a range, when the electrode and the outer surface are bonded, the outer surface hole absorbs irregularities on the electrode surface, and the positive electrode / separator / It is also possible to adhere the electrode and the separator without any gaps while reducing unevenness in the thickness of the composite of the negative electrode.

  On the other hand, the average pore diameter inside the porous layer 12 prevents the leakage of the electrolysis solution, and can maintain the strength of the porous layer 12 while ensuring the amount of the electrolytic solution to be retained and the freedom of movement of the electrolytic solution. It is important that the thickness is in a range of 0.5 to 10 μm. That is, when the average pore diameter is less than 0.5 μm, the amount of the electrolytic solution that can be held decreases, the degree of freedom of movement of the electrolytic solution also decreases, and the ionic conductivity deteriorates. On the other hand, when the average pore diameter exceeds 10 μm, the strength of the porous layer 12 is lowered, it is difficult to maintain the porous structure, and the affinity with the electrolytic solution originally possessed by the electrically insulating resin composition is not sufficiently expressed, Electrolyte tends to leak from the porous layer. A more preferable range is 0.5 to 5 μm.

Moreover, it is preferable that the outer surface and the inside average pore diameter of the porous layer 12 are in the above ranges, respectively, and that the outside surface average pore diameter is controlled to be smaller than the inside average pore diameter. Thus, when the hole diameter on the outer surface is smaller than the inner hole diameter, the electrolyte solution held in the hole by the weak interaction with the hole wall made of the electrically insulating resin composition is stabilized inside the hole. The electrolyte is not easily leaked.
Thus, if the pore diameters of the outer surface and the inner surface of the porous layer 12 are made different as described above and controlled to a specific relationship, the electrolyte solution has good liquid permeability and the electrolyte solution leakage is suppressed. Thus, it is possible to obtain a separator capable of maintaining strong adhesion with the electrode.

The porous layer 12 is preferably formed with a mass of 0.5 to 10 g per 1 m ² . When the porous layer 12 is formed with a mass of less than 0.5 g per 1 m ^2, the amount of the first resin compound and the second resin compound that contribute to the adhesion with the electrode is extremely reduced, which is sufficient. Adhesion may not be exhibited, but if the porous layer 12 is formed with a mass of 0.5 g or more per m ² , the adhesion is sufficient. On the other hand, even if the porous layer 12 is formed to exceed 10 g per 1 m ² , the adhesion is hardly improved further. Therefore, if the porous layer is formed in excess of 10 g per 1 m ^2, the thickness of the porous layer increases, which is disadvantageous for battery thinning, and also reduces the volume energy density. Therefore, when the porous layer 12 is formed at 0.5 to 10 g per 1 m ² , a separator that can provide a battery having the best balance of various performances can be obtained.

  Moreover, there is no restriction | limiting in particular in the thickness of the porous layer 12, However, 0.5-8 micrometers is preferable from a viewpoint of ion conductivity, adhesiveness with an electrode, and thickness reduction of a battery. When the thickness is less than 0.5 μm, particularly the adhesion with the electrode tends to decrease. Furthermore, when the thickness is preferably in the range of 0.5 to 5 μm, more preferably in the range of 0.5 to 1.5 μm, the ion conductivity is further improved.

  In addition, as long as the first resin compound and the second resin compound are the main components, the porous layer 12 contains electrochemically stable particles or fibrous materials as necessary. The mechanical strength and dimensional stability of the porous layer 12 may be improved. Examples of such particles include inorganic particles such as silicon oxide, aluminum oxide, titanium oxide, and magnesium oxide, organic particles such as phenol resin particles, polyimide resin particles, benzoguanamine resin particles, melamine resin, polyolefin resin, and fluorine resin particles. Examples of the fibrous material include inorganic fibrous materials such as apatite fibers, titanium oxide fibers and metal oxide whiskers, and organic fibrous materials such as aramid fibers and polybenzoxazole fibers. There is no restriction | limiting in particular in the shape of this particle | grain and a fibrous material, and a particle size, It can select suitably and can be used. In addition, when these particles and fibrous materials are contained, as described above, these are added to a solution or slurry to be coated when forming a porous layer by, for example, a drying method or an extraction method. Just keep it.

Examples of the method for forming the porous layer 12 from the electrically insulating resin composition include a phase separation method, a drying method, an extraction method, and a foaming method.
For example, when the porous layer 12 is formed by a drying method, first, a solution or slurry in which the electrically insulating resin composition is dissolved in a solvent is prepared, and this is released from a release-treated polymer film or the like. Coat the surface of the film and dry. At this time, in particular, a good solvent and a poor solvent of the electrically insulating resin composition to be used are used in combination as the solvent, and a poor solvent having a boiling point higher than that of the good solvent is selected. In this way, the solvent is selected and used in combination, and the solution or slurry in which the electrically insulating resin composition is dissolved is coated and dried, so that the good solvent evaporates before the poor solvent, and then the solubility. The electrical insulating resin composition having decreased is started to precipitate and takes a porous structure having a porosity corresponding to the volume of the poor solvent. At this time, the pore size in the porous layer 12 can be controlled by appropriately adjusting the combination of the good solvent and the poor solvent, the ratio thereof, the concentration of the electrically insulating resin composition in the solvent, the drying conditions, and the like.

As a method for producing the separator 10, for example, after forming a porous layer on the release film by the above-described method, the porous substrate 11 is disposed on the porous layer 12, and a flat plate press, a laminator roll, etc. The porous layer 12 can be formed on the porous substrate 11 by pasting them together and then peeling off the release film.
Instead of forming the porous layer 12 using the release film in this way, the surface of the porous substrate 11 is directly coated with a solution or slurry in which the electrically insulating resin composition is dissolved in a solvent. The porous layer 12 may be formed. Also in this case, the pore size in the porous layer 12 can be controlled by appropriately adjusting the combination of the good solvent and the poor solvent, the ratio thereof, the concentration of the electrically insulating resin composition in the solvent, the drying conditions, and the like.

  In the case where the porous layer 12 is formed by the extraction method, a solution obtained by dissolving the electrical insulating resin composition in a good solvent is coated on the release film, and then this is coated with the poor electrical insulating resin composition. A porous structure can be obtained by immersing in a solvent, extracting a good solvent in the coated electrically insulating resin composition, and substituting it with a poor solvent. And the porous layer 12 can be formed on the porous base material 11 by sticking this to the porous base material 11 and peeling the release film as in the case of the drying method. Also in the case of the extraction method, a solution obtained by dissolving the electrically insulating resin composition in a good solvent is directly coated on the porous substrate 11 without using a release film, and then this is applied. May be immersed in a poor solvent of the electrically insulating resin composition.

In the production method described above, there is no particular limitation on the method for coating the release film or the porous substrate 11 with a solution or slurry. The dip coating method, the spray coating method, the roll coating method, the doctor blade method, and the gravure coating. Method, screen printing method and the like.
Examples of the good solvent for the electrically insulating resin composition include amides such as 1-methyl-2-pyrrolidone (NMP), N, N-dimethylacetamide, and N, N-dimethylformamide, and sulfones such as dimethyl sulfoxide. Examples thereof include ketones such as 2-butanone and cyclohexanone, ethers such as tetrahydrofuran, etc. Examples of the poor solvent include alcohols such as methanol, 1-hexanol, 1-heptanol and 1-octanol, ethylene glycol, propylene Glycols such as glycol, diethylene glycol and glycerin, ethers such as methyl cellosolve, ethyl cellosolve and butyl cellosolve, carbonates such as propylene carbonate, dimethyl carbonate, diethyl carbonate and methyl carbonate Ether-based, decane, hydrocarbon such as dodecane, diethyl phthalate, although such a phthalate such as dibutyl phthalate may be cited but are not limited thereto. Moreover, in a good solvent and a poor solvent, 2 or more types can also be mixed and used, respectively.

  When the porous layer 12 is formed on both sides of the porous substrate 11 as in this embodiment, the porous layer 12 may be formed on each side, or may be coated on both sides at the same time, or separately manufactured on both sides simultaneously. The quality layers may be stacked and bonded together using a flat plate press or the like.

In addition, such a separator 10 preferably has an air permeability measured by a Gurley air permeability measuring device of 1000 seconds / 100 ml or less. When the air permeability of the separator 10 exceeds 1000 seconds / 100 ml, the ion conductivity tends to decrease. By setting the air permeability to 500 sec / 100 ml or less, more preferably 1 to 200 sec / 100 ml, a separator having excellent ion conductivity can be obtained.
Here, the air permeability measured by the Gurley air permeability measuring device is a value measured according to JIS P8117.

In the separator 10 described above, the porous layer 12 is formed on both surfaces of the porous substrate 11, and the electrically insulating resin composition forming the porous layer 12 includes the first resin compound 10 to 10. Since it contains 50% by mass and the second resin compound 50 to 90% by mass, the porous layer 12 becomes a swollen gel when the electrolyte is injected, and it does not completely dissolve. Deterioration can be prevented, and adhesiveness can be maintained. As a result, it has high adhesiveness under a wide range of temperature environments. Specifically, the adhesive strength becomes 10 g / cm or more after being left in an environment of −20 to 100 ° C. for 1 hour or more while being adhered to the electrode of the electronic component and impregnated with the electrolytic solution. Therefore, this separator 10 has high ion conductivity and excellent battery performance such as cycle characteristics under a wide temperature environment.
Such a separator 10 is particularly suitable for electronic parts such as a lithium ion secondary battery, a polymer lithium battery, an aluminum electrolytic capacitor, and an electric double layer capacitor because the effect is particularly exerted.

Here, the adhesive strength is a strength measured as follows. That is, the separator 10 and the electrode are laminated, pressed on a hot plate at 100 ° C. under conditions of 1.5 MPa for 10 seconds, and the obtained test piece is peeled off at a peeling speed of 50 mm / min by a 180 ° peel test. . The peel strength measured at that time is defined as the adhesive strength.
The electrolytic solution impregnated in the measurement of the adhesive strength is a solution obtained by dissolving LiPF ₆ in a solvent in which ethylene carbonate and dimethyl carbonate are mixed at a mass ratio of 1: 1 so as to be 1 mol / l. is there.

Moreover, the electrode used in the measurement of adhesive strength is produced by the following manufacturing method. That is, 100 parts by mass of lithium cobaltate (LiCoO ₂ ) as an active material, 5 parts by mass of acetylene black as a conductive additive, 10 parts by mass of vinylidene fluoride-hexafluoropropylene copolymer as a binder, and N, N-dimethyl A coating solution in which 100 parts by mass of acetamide and 30 parts by mass of dibutyl phthalate are mixed and dispersed is applied on an aluminum foil having a thickness of 40 μm so that the thickness after drying becomes 200 μm and dried at 150 ° C. . Thereafter, pressing is performed with a hot roll to obtain an electrode (positive electrode) having a total thickness of about 150 μm. The electrode thus obtained is used for measuring the adhesive strength.
Alternatively, 100 parts by mass of mesophase carbon black as an active material, 5 parts by mass of acetylene black as a conductive additive, 20 parts by mass of vinylidene fluoride-hexafluoropropylene copolymer as a binder, and 150 parts by mass of N, N-dimethylacetamide Then, a coating liquid in which 40 parts by mass of dibutyl phthalate is mixed and dispersed is applied on a copper foil having a thickness of 40 μm so that the thickness after drying becomes 200 μm, and dried at 150 ° C. Thereafter, pressing is performed with a hot roll to obtain an electrode (negative electrode) having a total thickness of about 150 μm. The electrode thus obtained is used for measuring the adhesive strength.
In addition, these electrodes are used in the case of adhesive strength measurement, and the electrode adhere | attached on the separator for electronic components of this invention is not limited to the said electrode.

Next, a lithium ion secondary battery that is one type of electronic component including the separator described above will be described. This lithium ion secondary battery has a positive electrode and a negative electrode, in which the separator described above is disposed, and this separator is impregnated with an electrolytic solution.
An electrode active material is used for the positive electrode and the negative electrode. The positive electrode active material of the lithium ion secondary battery is represented by a composition formula Li _x M ₂ O ₂ or Li _y M ₂ O ₂ (where M is a transition metal, 0 ≦ x ≦ 1, 0 ≦ y ≦ 2). Composite oxide, oxide having tunnel-like holes, metal chalcogen compound having a layer structure, and the like. Specific examples thereof include LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , and Li ₂ Mn ₂ O _4. , MnO ₂ , FeO ₂ , V ₂ O ₅ , V ₆ O ₁₃ , TiO ₂ , TiS _{2 and the} like. Examples of the organic compound include conductive polymers such as polyaniline, polyacene, and polypyrrole. Furthermore, these various active materials may be mixed and used regardless of an inorganic compound or an organic compound.

Examples of the negative electrode active material of the lithium ion secondary battery include carbon materials, graphite, coke, etc., which are materials capable of occluding and releasing lithium and / or lithium ions, Al, Si, Pb, Sn, Zn, Cd, etc. Alloys with lithium, transition metal composite oxides such as LiFe ₂ O ₃ , transition metal oxides such as WO ₂ and MoO ₂ , carbonaceous materials such as graphite and carbon, lithium nitrides such as Li ₅ (Li ₃ N), Further, lithium metal such as metal lithium foil, or a mixture thereof may be used.

Particularly preferred negative electrode active materials include carbon materials, lithium metals, lithium alloys or oxide materials, and positive electrode active materials include oxides or carbon materials capable of intercalating and deintercalating lithium ions. Can be mentioned. By using an electrode in which such an active material is used, a battery having good characteristics can be obtained.
Here, specific examples of the carbon material may be appropriately selected from mesophase carbon black, mesocarbon microbeads, natural or artificial graphite, resin-fired carbon material, carbon black, carbon fiber, and the like. These are used as powders. Among these, graphite and mesophase carbon black are preferable, and the average particle diameter is preferably 1 to 30 μm, particularly preferably 5 to 25 μm. When the average particle size is too smaller than the above range, the charge / discharge cycle life is shortened and the variation in capacity tends to be large. On the other hand, if it is larger than the above range, the variation in capacity becomes remarkably large and the average capacity becomes small. It is considered that the variation in capacity when the average particle size is large is due to uneven and uneven contact between the graphite and the current collector or between the graphites.
The oxide capable of intercalating and deintercalating lithium ions is preferably a composite oxide containing lithium, and examples thereof include LiCoO ₂ , LiNiO ₂ , LiMnO ₄ , and LiV ₂ O ₄ . These oxides are used as a powder, but the average particle diameter of the powder is preferably 1 to 40 μm.

  Moreover, a conductive support agent is added to an electrode as needed. Preferred examples of the conductive assistant include metals such as graphite, carbon black, acetylene black, carbon fiber, nickel, aluminum, copper, and silver. Among these, graphite and carbon are particularly preferable. Examples of the binder used for forming the electrode include fluororesin and fluororubber, and the amount of the binder is suitably in the range of about 3 to 30% by mass of the electrode.

In order to produce a lithium ion secondary battery, first, an electrode coating material is prepared by dispersing an electrode active material and a conductive additive added as necessary in a gel electrolyte solution or a binder solution. Apply the coating solution to the current collector. The current collector may be used by appropriately selecting from known current collectors according to the shape of the device including the battery and the arrangement method in the case. Usually, aluminum or the like is used for the positive electrode, and copper or nickel is used for the negative electrode.
After the electrode coating liquid is applied to the current collector, the solvent is evaporated to obtain a positive electrode and a negative electrode each having an active material layer formed on the current collector. The coating thickness of the electrode coating solution is preferably about 50 to 400 μm.

  As shown in FIG. 2A, the positive electrode and negative electrode thus obtained and the separator described above are combined into a positive electrode 15 comprising a positive electrode active material layer 13 and a current collector 14, a separator 10, and a negative electrode active material. The negative electrode 18 composed of the layer 16 and the current collector 17 is laminated in this order, and is crimped to produce an electronic element body, which is filled in an exterior material. Note that, when stacking, the electrode is disposed so that the active material layer side of the electrode is in contact with the separator. Here, as shown in FIG. 2 (b), the separator 10 may be preliminarily impregnated with an electrolyte when pressure bonding, or the electrolyte is injected after the electronic element body is filled in the exterior material. Also good. Then, after connecting an electrode terminal, a safety device, etc. suitably, an exterior material is sealed.

As the electrolytic solution, a mixed solution in which an electrolyte salt is dissolved in an organic solvent is used. Further, as the organic solvent, those which do not decompose even when a high voltage is applied are preferable, for example, ethylene carbonate, propylene carbonate, dimethyl carbonate, γ-butyrolactone, sulfolane, dimethyl sulfoxide, acetonitrile, dimethylformamide, dimethylacetamide, Examples include polar solvents such as 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrohydrafuran, 2-methyltetrahydrofuran, dioxolane, and methyl acetate, or a mixture of two or more of these solvents.
As the electrolyte salt dissolved in the electrolytic solution, in the case of a lithium ion secondary battery, LiClO ₄ , LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiCF ₆ , LiCF ₃ CO ₂ , LiPF ₆ SO ₃ , LiN (SO ₃ CF ₃ ) ₂ , lithium-containing salts such as Li (SO ₂ CF ₂ CF ₃ ) ₂ , LiN (COCF ₃ ) ₂ and LiN (COCF ₂ CF ₃ ) ₂ , or mixtures of two or more thereof.

  The lithium ion secondary battery described above includes the separator described above, and has high adhesive strength between the electrode and the separator over a wide range of temperatures even when the electrode liquid is injected. Therefore, ion conductivity is high in a wide range of temperatures, and battery performance is high. Moreover, it has excellent shutdown characteristics over a wide range of temperatures and is difficult to melt down.

The present invention is not limited to the above-described embodiment example. For example, in the embodiment described above, the porous layer is formed on both surfaces of the porous substrate, but may be formed only on one surface of the porous substrate. However, if the porous layer is formed on both surfaces of the porous base material, the adhesion and adhesion between the separator and the electrode are improved, so that the ion conductivity is further improved.
Also, the electronic component may be other than a lithium ion secondary battery, and is not particularly limited as long as it is an electronic component composed of a positive electrode, a negative electrode, and a separator, but other than a lithium ion secondary battery, a polymer lithium battery , Aluminum electrolytic capacitors, electric double layer capacitors and the like.

In the following examples and comparative examples, “%” means “mass%”.
<Preparation of separator>
(Examples 1-7, Comparative Examples 1-3)
Using the electrically insulating resin composition shown in Table 2 containing the resin compound shown in Table 1 below, a separator was prepared as follows.
That is, the electrically insulating resin composition shown in Table 2 was added to 1-methyl-2-pyrrolidone (NMP), dissolved in a nitrogen atmosphere at room temperature, cooled to room temperature, and the resulting mixture was used as a coating solution. Next, the obtained coating solution is cast by a doctor blade method on one side of a polyethylene stretched porous substrate having a thickness of about 12 μm and a measured value of air permeability of about 100 seconds / 100 ml, and then poured into methanol. And soaked for 10 minutes. Subsequently, after raising from methanol, it was dried in a dryer at 40 ° C. to form a porous layer on one side of a stretched porous substrate made of polyethylene. Furthermore, the same process was performed on the other side of the stretched porous substrate made of polyethylene to obtain a separator in which a porous layer was formed on both sides of the stretched porous substrate made of polyethylene.
In Comparative Example 1, a stretched porous substrate made of polyethylene in which no porous layer was formed was used as a separator. Moreover, in Comparative Example 2, a vinylidene fluoride polymer (gelation rate: about 4%) was filled into the polyethylene stretched porous base material to obtain a separator.

<Method for measuring gelation rate>
The gelation rate of each resin compound shown in Table 1 was measured as follows. First, 0.5 g (± 0.1 g) of a resin compound was weighed and immersed in 5.0 g of an electrolyte solvent composed of propylene carbonate (PC): diethyl carbonate (DEC) = 1: 2, sealed, and −20 It was put into a constant temperature bath at 25 ° C, 90 ° C and left for 1 hour. Next, after filtering this standing, the resin compound filtrate remaining on the filter paper was washed with methanol to remove the electrolyte. And the filtrate was dried, the mass after drying was measured, and the gelation rate was computed by substituting the mass before and behind a test into a following formula.
Gelation rate (mass%) = {mass before test (g) −mass after test (g)} / mass before test (g) × 100

<Physical properties of separator>
Moreover, about the obtained separator, the film thickness and the air permeability were measured as follows. The measurement results are shown in Table 2.
(Film thickness)
It measured using the micrometer (dot type thickness meter).
(Air permeability)
The Gurley air permeability was measured according to JIS P8117.

<Measurement of adhesive strength>
The obtained separator and positive electrode, and the separator and negative electrode were respectively laminated and pressed on a hot plate at 100 ° C. under conditions of 1.5 MPa and 10 seconds. A test piece (test piece width: 10 mm) obtained by this press was impregnated with an electrolytic solution of PC: DEC = 1: 2 containing 1 mol / L LiPF ₆ , and −20 ° C., 25 ° C., 50 ° C., It was left for 1 hour or more in a temperature environment of 100 ° C. After returning to room temperature, the separator and the electrode were peeled at 180 ° C. at a peeling speed of 50 mm / min by an ORIENTEC Tensilon universal testing machine, and the peeling strength was defined as the adhesive strength.

<Production of lithium ion secondary battery>
The obtained separator was laminated with a positive electrode and a negative electrode, and pressed on a hot plate at 100 ° C. under conditions of 1.5 MPa for 10 seconds to obtain an electrochemical device. In addition, what was laminated | stacked when measuring adhesive strength was used as a positive electrode and a negative electrode. Subsequently, after connecting an electrode extraction terminal or the like to this electrochemical element, it was loaded into a laminate pack for a battery. Next, an electrolyte solution containing PC: DEC = 1: 2 containing 1 mol / L LiPF ₆ was poured therein, the laminate pack was sealed, and a small lithium ion secondary battery was produced.
(Impedance measurement)
The impedance inside the obtained battery was measured. In the measurement, an AC impedance measuring device manufactured by Solartron was used.
(Cycle test)
The cycle characteristics were measured by repeating charge and discharge 500 times.
Cycle characteristics (%) = battery capacity after 500 cycles / initial battery capacity × 100
(Forced overcharge / discharge test)
The battery surface temperature and the presence or absence of battery rupture were confirmed by charging at 12 V and 2 C, and evaluated as follows.
◎: 50 ° C. or less, no rupture, ○: 100 ° C. or less, no rupture, Δ: 130 ° C. or less, no rupture, ×: ruptured

  In the separators of Examples 1 to 7, the electrically insulating resin composition forming the porous layer has a gelation rate of 10 to 50% by mass of the first resin compound having a gelation rate of 20% by mass or less, and a gelation rate of 50% by mass. Since it contained 50 to 90% by mass of the second resin compound as described above, as shown in Table 3, it was bonded to the electrode of the electronic component and was impregnated with the electrolytic solution at -20 to 100 ° C. The adhesive strength after standing for 1 hour or more below was 10 g / cm or more. Therefore, as shown in Table 4, the lithium ion secondary batteries of Examples 1 to 7 had high ion conductivity and excellent battery performance such as cycle characteristics under a wide temperature environment. Also, there was no problem with overcharging.

On the other hand, in Comparative Example 1, since only the porous substrate was used as a separator and no adhesive was used, the adhesive strength with the electrode was low, the cycle characteristics of the lithium ion secondary battery were insufficient, Burst after overcharging.
In the separator of Comparative Example 2, since the porous layer was not formed on the porous substrate, the adhesive strength with the electrode was low. Moreover, since the air permeability of the separator was low, the impedance was high even when the electrolyte was injected, and the cycle characteristics of the lithium ion secondary battery were low. Moreover, it burst after overcharging.
In Comparative Example 3, since only the resin compound having a low gelation rate formed the porous layer, the adhesive strength decreased at high temperatures. As a result, the cycle characteristics of the lithium ion secondary battery were low and burst after overcharging.

It is sectional drawing which shows one example of embodiment of the separator for electronic components of this invention. It is sectional drawing which shows the process at the time of manufacturing the electronic component of this invention. It is sectional drawing which shows the process at the time of manufacturing the conventional electronic component.

Explanation of symbols

10 Separator (Separator for electronic parts)
11 Porous substrate 12 Porous layer

Claims (7)

An electronic component separator in which a porous layer made of an electrically insulating resin composition is formed on at least one surface of a porous substrate,
The electrically insulating resin composition has a gelation rate of 10 to 50% by mass of the first resin compound of 20% by mass or less and a second resin compound of 50 to 90% by mass of the gelation rate of 50% by mass or more. A separator for electronic parts, comprising:   At least one of the first resin compound and the second resin compound is a resin containing a polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polystyrene, or polyethylene oxide in the skeleton, or a derivative of these resins. The separator for electronic components according to claim 1. The first resin compound is a copolymer composed of at least one of ethylene tetrafluoride, propylene hexafluoride, and ethylene and vinylidene fluoride, or a homopolymer composed of vinylidene fluoride,
The electronic component separator according to claim 1, wherein the second resin compound is a copolymer composed of propylene hexafluoride and vinylidene fluoride.   The separator for electronic parts according to any one of claims 1 to 3, wherein the porous substrate is a nonwoven fabric or a stretched porous film made of polyethylene and / or polypropylene.   The separator for electronic parts according to any one of claims 1 to 4, wherein an air permeability measured by a Gurley air permeability measuring device is 1000 seconds / 100 ml or less.   The separator for electronic parts according to any one of claims 1 to 5, which is provided in an electronic part selected from a lithium ion secondary battery, a polymer lithium battery, an aluminum electrolytic capacitor, and an electric double layer capacitor.   It has a positive electrode and a negative electrode, The electronic component separator in any one of Claims 1-6 is arrange | positioned among these, The electrolyte solution is impregnated in this electronic component separator, It is characterized by the above-mentioned. Electronic parts.

Images