TWI381571B - Nonaqueous battery separator and manufacturing method thereof - Google Patents

Description

Separator for non-aqueous battery and manufacturing method thereof

The present invention relates to a separator for a nonaqueous battery and a method of manufacturing the same. Specifically, it relates to a separator which particularly improves the safety of a nonaqueous battery and a method of manufacturing the same.

A non-aqueous battery (lithium ion battery) that obtains an electromotive force by doping and dedoping lithium is widely used as a main power source for portable electronic devices such as mobile phones and notebook computers because of its high energy density. Due to the high performance and long-term driving requirements of these portable electronic devices, research and development on high energy density and high output power are being actively carried out. In addition, it is used for review of large-scale power supply as a power source for automobiles. Such a problem of high energy density, high output power, and large size can be exemplified by safety.

In the separator of the lithium ion battery, a polyolefin microporous film mainly composed of polyethylene is used, and a shut-down function is provided in order to function as a battery to ensure safety. This closing function is described in Japanese Patent No. 2642206. This shutdown function utilizes the melting of the polyolefin constituting the separator to occlude the holes, thereby making the resistance of the separator particularly improved. Even if the temperature rise caused by the battery abnormality occurs, the internal resistance of the battery is increased by this function, and the current does not flow substantially to ensure safety.

Since the closing function is the principle of clogging the hole by melting the constituent materials, when the battery is exposed to a higher temperature, the separator may break the film (melt down), and the positive electrode and the negative electrode may be internally short-circuited to make the battery Become a very dangerous state. Lithium-ion batteries have high energy density, high output power, and large size. The heating rate is gradually accelerated due to abnormality, and the hole clogging speed is not fast enough to show the shutdown function, and the risk of melting is also improved. In the case of a high energy density, a high output, and an increase in size, a separator having a shutdown function has been difficult in terms of safety, and thus a separator that does not melt and has high heat resistance is required.

In order to combine the shutdown function with the heat resistance for suppressing melting, a combination of a polyethylene microporous membrane and a polytetrafluoroethylene microporous membrane for use in a separator is described in Electrochem. Soc. L51 (1993). The shutdown performance was good, and melting was not confirmed at temperatures up to 250 °C. An example in which such a polyolefin microporous film is laminated with a porous film made of a heat-resistant resin is disclosed in Japanese Laid-Open Patent Publication No. Hei 10-3898, JP-A-2002-25526, and JP-A-2003-123724.

In addition, a composite porous film in which a porous layer formed of a heat-resistant resin is applied to a polyolefin microporous membrane and integrated as a separator having both shutdown characteristics and heat resistance is disclosed in Japanese Laid-Open Patent Publication No. 2001-23600. JP-A-2002-355938 and the like.

As described above, it is technically difficult to laminate a film having a shutdown function of a polyolefin microporous film having a shutdown function and a heat resistant porous film, which is technically difficult. Further, from the viewpoint of the high energy density of the battery, the separator is also required to be thinned. In order to align the two films to the thickness level of the current separator, it is necessary to make each film a very thin thickness. It is difficult to produce such a film, and its handling is difficult, and it is difficult to be practical from the viewpoint of the productivity of the separator.

On the other hand, the heat-resistant porous layer is applied to a polyolefin microporous film and integrated to obtain a similar problem of the above laminate. However, the conventionally disclosed matter is substantially obtained by coating only one side of the polyolefin microporous film, and it is difficult to handle due to the problem of curling. Actually, when it is used in the manufacturing steps of a battery, the yield is a problem due to a short circuit caused by a positional deviation. Although the description of the patent document is not necessarily limited to the single-sided coating, the technical method of coating on both sides is not specifically disclosed. Moreover, in the past, the integrated person is likely to be clogged at the interface between the polyolefin microporous membrane and the heat-resistant porous layer by coating, which causes a problem that the shutdown function is lowered and the battery performance is lowered.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a separator which is excellent in operability, has both a shutdown function and a heat resistance which sufficiently suppresses melting, and further performs an appropriate interface design to suppress clogging as much as possible, and has no deterioration in battery performance. problem.

The inventors of the present invention have focused on the above-mentioned problems, and have found that a polyolefin microporous film of an appropriate type is selected as a substrate of a composite porous film, and a polymer which is easy to form a porous structure is selected as a polymerization constituting the heat resistant porous layer. In the case where the heat-resistant porous layer is formed on the both sides of the polyolefin microporous film in an appropriate form and integrated, it is possible to provide a separator having operability, shutdown function, heat resistance, and no ion permeability. That is, the present invention provides a separator for a non-aqueous battery, which has a gas permeability (JIS P8117) per unit thickness of 15 sec/100 cc. μm or more, 50 sec/100 cc. μm or less, and a film thickness of 5 μm or more and 25 μm. The double-sided polyolefin microporous film is coated on both sides of a porous microporous film made of polymetaphenylene isophthalamiee and integrated into a composite porous film, and the film thickness of the composite porous film is coated. It is 6 μm or more and 35 μm or less, and the air permeability (JIS P8117) is 1.01 times or more and 2.00 times or less of the polyolefin microporous film, and the amount of poly-m-phenylene m-xylyleneamine is 1.0 g/m ² or more and 4.0. Below g/m ² . Further, the present invention also provides the following invention.

1. The separator for a nonaqueous battery according to the above aspect of the invention, wherein the polyolefin microporous film is characterized by having a pore diameter of 0.01 μm or more and 0.2 μm or less.

2. The separator for a non-aqueous battery according to the above aspect, wherein the amount of the poly-m-phenylene m-xylylenediamine is: the amount of the coating on the surface - the amount of the coating on the inner surface | / (the surface The coating amount + the coating amount of the inner surface is 0 or more and 0.2 or less.

3. The separator for a non-aqueous battery according to the invention, wherein the polyolefin microporous film is a polyolefin microporous film mainly composed of polyethylene.

Further, the present invention also provides a specific manufacturing method of the above separator. That is, a method for producing a separator for a nonaqueous battery according to the present invention is sequentially produced by the following steps: (1) dissolving poly(m-phenylene isophthalamide) in a solvent mainly composed of a guanamine solvent; a step of preparing a polymer solution, (2) a step of applying the polymer solution to both sides of the polyolefin microporous film, (3) a step of transporting the polyolefin microporous film coated with the polymer solution, and (4) a step of The polymer solution-coated polyolefin microporous membrane is immersed in a coagulating liquid made of the solvent and water to bring the both sides of the front and the back into contact with the coagulating liquid, and the step of solidifying the poly-m-phenylene m-xylamine (5) a water washing step of the solidified composite film, and (6) a drying step of the water-washed composite film. And a method for producing the separator for a non-aqueous battery according to the above, wherein the polymer solution contains a phase separating agent, and the concentration thereof is 5 to 50% by weight, and the ratio of water in the coagulating liquid is 30 to 80. A method for producing a separator for a non-aqueous battery of % by weight.

[Best Practice for Carrying Out the Invention]

The separator for a nonaqueous battery according to the present invention is a composite porous film in which a porous layer made of poly(m-phenylene isophthalamide) is coated on both surfaces of a polyolefin microporous membrane.

The polyolefin microporous membrane used in the separator for a non-aqueous battery of the present invention has a gas permeability per unit thickness (JIS P8117) of 15 seconds/100 cc. More than μm, 50 seconds / 100cc. Those below μm are preferred. The air permeability reflects the type of the polyolefin microporous film, and the smaller the value, the smaller the polyolefin microporous film is formed by the pores having a large pore diameter and the curved rate is small. On the contrary, the larger the value is, the smaller the hole diameter is, and the higher the curve rate. The separator for a non-aqueous battery of the present invention is a polyolefin layer formed of a porous layer made of poly-m-phenylene m-xylyleneamine, and has a gas permeability of less than 15 sec/100 cc. At μm, poly(m-phenylene isophthalamide) enters the pores of the polyolefin microporous membrane and exhibits significant clogging. As a result, the discharge characteristics are significantly degraded and the shutdown function cannot be sufficiently expressed. From this point of view, the polyolefin microporous membrane used in the separator for a nonaqueous battery of the present invention has a gas permeability (JIS P8117) of 15 seconds/100 cc. More than μm is better, with 20 seconds / 100cc. More preferably μm or more. The air permeability is greater than 50 seconds / 100cc. In the case of μm, the performance of the polyolefin microporous film itself becomes insufficient due to the decrease in performance due to clogging from the coating, and it is difficult to obtain sufficient battery performance. The gas permeability is 50 seconds / 100 cc from the viewpoint of obtaining good battery performance. Below μm is appropriate, with 40 seconds / 100cc. More preferably below μm. That is, the polyolefin microporous membrane has a gas permeability of 15 sec / 100 cc. More than μm, 50 seconds / 100cc. Below μm is better, 20 seconds / 100cc. More than μm, 50 seconds / 100cc. More preferably below μm, 20 seconds / 100cc. More than μm, 40 seconds / 100cc. Below μm is even better.

The film thickness of the polyolefin microporous film is preferably 5 μm or more and 25 μm or less. The film thickness of the polyolefin microporous film is preferably thin when considering the energy density of the battery. However, it is necessary to consider sufficient mechanical properties at the time of productivity, and there is a limit to thinning. In the case where the separator is a polyolefin microporous film, the above-mentioned energy density and mechanical properties are designed in consideration of shutdown characteristics, melt resistance, and ion permeability, and the film thickness is preferably in the range of 15 μm to 25 μm. And practical. In the case of the separator for a nonaqueous battery according to the present invention, since the polyolefin is coated with poly(m-phenylene isophthalamide), the polyolefin microporous film can also be used in a relatively thin manner. That is, the film thickness of the polyolefin microporous film is preferably 5 μm or more, more preferably 10 μm or more. The film thickness of the polyolefin microporous film is preferably 25 μm or less, more preferably 20 μm or less, and still more preferably 15 μm or less. Specifically, the film thickness of the polyolefin microporous film is preferably 5 μm or more and 25 μm or less, and further preferably 5 μm or more and 20 μm or less, 10 μm or more and 20 μm or less, 5 μm or more and 15 μm or less, and 10 μm or more and 15 μm or less. .

The polyolefin microporous membrane preferably has a pore diameter of 0.01 μm or more and 0.2 μm or less. Here, the pore size can be obtained by observation with a scanning electron microscope (SEM). In the present invention, the surface of the polyolefin microporous membrane was observed by SEM, and pores of any 10 points were selected, and the respective pore diameters were determined, and the values obtained by the average value were used as the pore diameters. In the case of the separator of the present invention, since both sides of the polyolefin microporous membrane are coated with poly-m-phenylene m-xylyleneamine, the pore diameter of the polyolefin microporous membrane is large enough, and poly-m-phenylene-based benzene Dimethylamine enters and causes blockage. Also, when the pore diameter is very small, it is difficult to obtain good battery performance. From this point of view, the pore diameter of the polyolefin microporous membrane is preferably in the range of 0.01 μm or more and 0.2 μm or less.

The material constituting the polyolefin microporous film is preferably a polyethylene as a host. The best performance of the closing function is the use of polyethylene as the main body. Specifically, the polyethylene content is preferably 70% by weight or more, more preferably 90% by weight or more.

In the separator for a nonaqueous battery according to the present invention, a porous layer made of poly(m-phenylene isophthalamide) is coated on both sides of the polyolefin microporous membrane and integrated. Here, the coated porous layer has sufficient heat resistance and can suppress melting of the polyolefin microporous film.

Here, when the polyphenylene isophthalamide used in the present invention is dissolved in N-methyl-pyrrolidone, the logarithmic viscosity of the following formula (1) is preferably 0.8 to 2.5 dL/g, 1.0. The range of ~2.2dL/g is better. When the logarithmic viscosity is less than 0.8 dL/g, sufficient physical properties cannot be obtained. When the logarithmic viscosity exceeds 2.5 dL/g, it is difficult to obtain a stable polymer solution, and a uniform porous layer cannot be formed.

Logarithmic viscosity (unit: dL/g) = ln(T/TO) / C (1) T: 0.5 g of m-phenylene isophthalamide dissolved in 100 mL of N-methyl-pyrrolidone solution at 30 ° C Flow time of capillary viscometer TO: Flow time of N-methyl-pyrrolidone at 30 ° C on capillary viscometer C: concentration of polyphenylene isophthalamide in solution (g/dL)

Since the polyolefin microporous film has been coated with a porous layer made of an expensive heat-resistant material, the concept of melting is suppressed. Here, the present invention is characterized in that it is coated on both sides with respect to the single-sided coating of the conventional one. Single-sided coating is generally a simple coating step, but there is a problem of curling after coating and the handling is very poor. Especially in the battery manufacturing step, the positional deviation is remarkable because of curling. Therefore, there is a serious adverse effect on the short-circuit yield of the battery, and the productivity of the battery is significantly degraded. However, the two-sided cover does not have the curling problem as described above and is excellent in operability. Specifically, the coating amount of the poly-m-phenylene m-xylyleneamine is such that the coating amount of the surface - the coating amount of the inner surface | / (the coating amount of the surface + the coating amount of the inner surface) satisfies 0 or more and 0.2 or less. The curl can be intentionally suppressed, and it is particularly preferably 0 or more and 0.1 or less, 0 or more and 0.05 or less, and 0 or more and 0.01 or less. Here, the surface and the inner surface are determined by the expedient, and there is no particular direction. When one side is used as the surface, the other side becomes the inner surface. Further, the coating amount may be defined by either weight or film thickness. When the weight is defined, the coating amount of one side can be obtained by peeling off the side of one side. Further, when the film thickness is defined, the cross section can be obtained by observing a cross section by a scanning electron microscope (SEM).

Another feature of the present invention is the use of poly-m-phenylene isophthalamide as the material of the coating. Poly-m-phenylene m-xylyleneamine is a meta-type of wholly aromatic polyamine. In the past, para-type wholly aromatic polyamines and polyamines have been proposed. Compared with the conventional proponents, poly(m-phenylene isophthalamide) has a feature of easily forming a porous structure having a large pore diameter. In order to prevent clogging and form a good interface, the coated porous layer must have a sufficiently large pore size than the polyolefin microporous membrane. From this point of view, it is possible to form a good interface with the polyolefin microporous membrane more easily than the series previously proposed, and it is easy to obtain a substance which hardly hinders ion permeability and shutdown function. Due to such characteristics, a double-sided coating of the two interfaces can also be formed.

Further, other characteristics of poly-m-phenylene m-xylyleneamine can also be exemplified in a solvent which can be easily dissolved in a sulfonium-based solvent. The series of conventional proposals in the step of integration also includes the step of applying a polymer solution obtained by dissolving a polymer in a solvent to a polyolefin microporous membrane. In the conventional series, since the solubility of the polymer is insufficient, when the polymer solution is produced, a method of adding a third component such as a salt and a solution of a catalyst precursor is added and coated, and after coating. The method of making the reaction into a polymer. Also, there are cases where a copolymer is used. The addition of such other ingredients is not ideal for adversely affecting the chemical stability of the electrical appliance. In the case of using poly-m-phenylene m-xylyleneamine, since the solubility of the polymer is high, it can be simply dissolved. Moreover, since the polymer itself has high electrical and chemical stability, it is less likely to adversely affect the durability of the battery as compared with the conventional series. Moreover, the production of the coating liquid is easy, and this point is also an ideal feature from the viewpoint of productivity.

The separator for a nonaqueous battery according to the present invention is a polyolefin microporous membrane and a porous layer formed of polyphenylene metaxylamine. The method of integration is as follows, and specifically, integration means that the layers are not easily separated in normal operation. When it is produced in the following ways, integration is fully satisfied by this concept.

The separator for a nonaqueous battery according to the present invention is the integrated composite porous film. The separator for a nonaqueous battery according to the present invention is characterized in that the gas permeability (JIS P8117) of the composite porous film is 1.01 times or more and 2.00 times or less of the polyolefin microporous film. The value of 1.01 times or more and 2.00 times or less is based on the interface between the polyolefin microporous film formed by the combination and the porous layer of poly-m-phenylene m-xylyleneamine, thereby suppressing the unfavorable situation such as clogging, and indicating that Form a good interface. This value can be easily obtained by selecting the above-mentioned materials and combining them in a later-described manner. Although the value was less than 1.01 times, the melt-inhibiting effect by coating was not observed, and the properties of the polyolefin microporous film itself were obtained. Further, when the value is more than 2.00 times, the unfavorable phenomenon due to clogging is not suitable, and the deterioration of the discharge performance and the hindrance of the shutdown function are exhibited, which is not preferable.

In the separator for a non-aqueous battery of the present invention, the film thickness is preferably 6 μm or more and 35 μm or less. The total thickness of the coating on both sides is preferably in the range of 1 μm or more and 10 μm or less, and in the range of 6 μm or more and 35 μm or less in consideration of the film thickness of the polyolefin microporous film, the separator is suitable. When the film thickness of the separator is considered in consideration of the energy density of the battery, it is preferably a relatively thin one, and particularly preferably 30 μm or less, further 25 μm or less, and further preferably 20 μm or less. The coating thickness of the total of both sides is also preferably 5 μm or less.

Further, the coating amount of m-phenylene m-xylylenediamine is preferably in the range of 1.0 g/m ² or more and 4.0 g/m ² or less, and the coating amount is the total of both surfaces. When the coating amount is less than 1.0 g/m ² , a sufficient effect of coating the poly(m-phenylene isophthalamide) is not obtained. Moreover, when the coating amount is more than 4.0 g/m ² , the coating thickness becomes too thick, and the portion of the poly(m-phenylene isophthalamide) porous layer may impair ion permeability and may be unsuitable.

The separator for a nonaqueous battery according to the present invention is produced in the following steps: (1) dissolving poly(m-phenylene isophthalamide) in a solvent mainly composed of a guanamine solvent to prepare a polymer solution. a step of (2) applying the polymer solution to both sides of the polyolefin microporous membrane, (3) carrying the polymer microporous membrane coated with the polymer solution, and (4) coating the polymer solution The olefin microporous membrane is immersed in a coagulating liquid formed by the solvent and water, so that both sides of the front and back are in contact with the coagulating liquid, and the poly(m-phenylene isophthalamide) is solidified, and (5) is solidified. a water washing step of the composite film, and (6) a drying step of the water-washed composite film.

The most characteristic feature of the present manufacturing method is that a poly-m-phenylene meta-xylyleneamine solution is coated on both sides of a polyolefin microporous membrane, which is immersed in a coagulating liquid to bring the two sides of the surface into contact with the coagulating liquid, and the polyphenylene is made. The phthalocyanine is solidified. By this method, the porous layer of poly-m-phenylene isophthalamide is coated on both sides of the polyolefin microporous film, and the integration can be easily achieved. Since the coating is applied simultaneously on both sides, the productivity is very good. Further, in the formation of a good interface between the polyolefin microporous membrane and the polyphenylene meta-xylyleneamine porous layer, the polymer solution penetrates into the polyolefin microporous membrane from the coating operation of the polymer solution to the solidification thereof. The main factors are the unsuitable conditions such as blockage in the middle. This is determined by the viscosity of the polymer solution and the time from application to solidification. In the present manufacturing method, the distance between the transfer speed and the coagulation bath of the coating device can be easily adjusted.

The amide-based solvent may, for example, be dimethylacetamide, N-methylpyrrolidone or dimethylformamide. In the present production method, it is preferred that the solvent of the polymer solution is used in the case of using such a guanamine-based solvent, and it is preferred to use a mixed solvent containing a phase-separating agent as the case may be. When the total solvent amount is 100, the concentration of the phase separating agent is preferably in the range of 5 to 50% by weight. The phase separating agent may, for example, be polypropylene glycol, tripropylene glycol, ethylene glycol, methanol, ethanol, butylene glycol or polyvinylpyrrolidone.

The concentration of the polyphenylene isophthalamide in the polymer solution is preferably in the range of 5 to 15% by weight.

When the polymer solution is simultaneously applied to both sides of the polyolefin microporous film, the polyolefin microporous film is supplied between the two coating devices by applying the polymer solution from both sides to achieve simultaneous coating on both sides. Specifically, it is conceivable to pass the polyolefin microporous film through two Meyer bars or two dies to simultaneously coat both sides. With this method, it is easy to apply the same amount on both sides of the watch. Thus, the separator of the present invention which is not crimped can be easily produced.

After the polymer solution is applied, it is necessary to transport the polyolefin microporous membrane to the coagulation liquid. The coagulating liquid is disposed downstream of the coating device to preferably employ a method of continuous impregnation after coating. Regarding the form of the polyolefin microporous film and the viscosity of the polymer solution, the distance between the conveying speed and the coagulating liquid of the coating device is very important, and this is appropriately adjusted to obtain the separator of the present invention.

The polyolefin microporous membrane enters the coagulating liquid in such a manner that both sides of the watch are in contact with the coagulating liquid. Thereby, both sides can be simultaneously solidified, and the surface can be integrated at the same time. By using this method, a porous layer made of poly(m-phenylene isophthalamide) having the same form as the surface is formed, and thus the product has no anisotropy. Therefore, it is not easy to cause an unsuitable phenomenon of curling, and it is a thing with good workability. In addition, the management of the products is easy, and it is not necessary to consider the table when using it.

The coagulating liquid is preferably a mixture of a solvent and water used in the polymer solution, and the ratio of water is particularly preferably in the range of 30 to 80% by weight. The method of washing with water is not particularly limited, and it is preferred to use a condition in which the solvent can be sufficiently washed.

The drying step is also not particularly limited, and the former method can be suitably used. For example, a method of drying a contact hot roll, a method of drying by hot air, or the like can be mentioned.

[Examples]

Hereinafter, the present invention will be described in detail by way of examples.

[test methods]

[Method for Measuring Pore Size of Polyolefin Microporous Membrane] The surface of the polyolefin microporous membrane was observed by a scanning electron microscope (SEM), and holes of ten points were arbitrarily selected, and the pore diameters of the pores were averaged to calculate the pore diameter.

[Method for Measuring Film Thickness] A contact thickness meter (LITEMATIC manufactured by Mitutoyo Co., Ltd.) was used for the measurement. For the measurement terminal, a diameter of 5 mm was used, and the load to be adjusted was 7 g during the measurement.

[Method for Measuring Unit Weight] The weight per unit area was measured by cutting a measurement sample into 10 cm × 10 cm. The weight per unit area is obtained by dividing the weight by the area.

[Method for Measuring Coating Amount] The coating amount by weight is calculated from the weight per unit area of the composite porous film minus the weight per unit area of the polyolefin microporous film. The coating amount per one side was obtained by peeling off the other side to obtain the weight per unit area of the surface, and the weight per unit area of the polyolefin microporous film was subtracted.

The coating amount of the thickness was calculated by subtracting the film thickness of the polyolefin microporous film from the film thickness of the composite porous film. The coating amount per one side was obtained by peeling off the other side, and the thickness of this surface was calculated, and the film thickness of the polyolefin microporous film was subtracted and calculated.

[Method for Measuring Air Permeability] The air permeability was measured in accordance with JIS P8117.

[Evaluation of Air Permeability per Unit Thickness] The air permeability per unit thickness was calculated by dividing the air permeability by the film thickness.

[Change in Air Permeability of Composite Porous Film] The change in gas permeability was calculated by dividing the gas permeability of the composite porous film by the gas permeability of the polyolefin microporous film.

[Measurement method of shutdown characteristics] The evaluation of the shutdown characteristics was such that the electrolyte (1M LiBF ₄ PC/EC (1/1 by weight)) was impregnated in the separator, sandwiched between stainless steel (SUS) plates having a diameter of 15.5 mm, and sealed. In the battery can for the button battery, try to evaluate the battery. The battery was placed in a thermostatic bath capable of controlling the temperature, and the temperature was raised to 250 ° C at a rate of 1.5 ° C / min, and the resistance value of the battery was measured. The resistance value of the battery was measured by an alternating current method. The measurement conditions of the alternating current method were such that an alternating current having an amplitude of 10 mV and a number of cycles of 1 kHz was applied, and a real axis component was used as the battery resistance. The temperature is plotted against the battery resistance, and the shutdown temperature and the melting temperature are measured, and the temperature resistance value is turned on during the rising process to a temperature of 1000 ohm or more, and the melting temperature resistance value is reduced to 1000 ohms or less.

[Method for Measuring Battery Performance] Using a lithium cobalt oxide (LiCoO ₂ ; manufactured by Nippon Chemical Industry Co., Ltd.) powder of the positive electrode active material, 89.5 parts by weight, and 4.5 parts by weight of acetylene black (denka black; manufactured by Electrochemical Industries, Ltd.) powder A positive electrode paste was prepared by a dry weight of 6 parts by weight of a polyvinylidene fluoride N-methylpyrrolidone solution of polyvinylidene fluoride (Kureha Chemical Industry Co., Ltd.). The obtained paste was applied to the surface of an aluminum foil having a thickness of 20 μm, dried, and extruded to prepare a positive electrode.

87 parts by weight of a powder of a graphitized mesoporous carbon material (MCMB (mesophase carbon microbead) manufactured by Osaka Gas Chemical Co., Ltd.), 3 parts by weight of acetylene black, and a dry weight of polyvinylidene fluoride of 10 parts by weight. A solution of a weight percent of polyvinylidene fluoride in N-methylpyrrolidone was used to prepare a negative electrode paste. The obtained paste was applied to the surface of a copper foil having a thickness of 18 μm, dried, and extruded to prepare a negative electrode.

The above positive electrode was cut into a size of 30 mm × 50 mm and labeled. The above negative electrode was cut into a size of 32 mm × 52 mm and labeled. The separator is cut to a size of 36 mm x 56 mm. The positive electrode/separator/negative electrode was joined, and an electrolytic solution was injected and sealed in an aluminum laminate film to prepare an aluminum laminate film exterior battery. Here, the electrolytic solution was dissolved in a solution of ethylene carbonate/ethyl methyl carbonate (3/7 by weight) using 1 M of LiPF ₆ .

Regarding the battery, the discharge capacity at 0.2 C and 2 C was measured, and (the discharge amount at 2 C) / (the discharge amount at 0.2 C) × 100 was taken as the battery performance. Here, the charging condition was 0.2 C 4.2 V CC/CV for 8 hours, and the discharge condition was a CC discharge of 2.75 V cutoff.

[Production Example of Composite Porous Membrane] 6.0% by weight of poly(m-phenylene isophthalamide) (Conex (registered trademark) manufactured by Teijin Technology Co., Ltd.) and 65.8 wt% of dimethylacetamide (DMAc). A polymer solution for film formation was prepared by a composition of 28.2% by weight of tripropylene glycol (TPG). Here, using a poly(m-phenylene isophthalamide) having a logarithmic viscosity of 1.4 dL/g, a polyolefin microporous film was passed through a die and supplied from both sides of the polyolefin microporous film by a die. The polymer solution for film formation is applied. Next, the coated polyolefin microporous membrane was immersed in a coagulating liquid composed of a composition of DMAc of 35 wt%, TPG of 15 wt%, and water of 50 wt%, and the both surfaces thereof were brought into contact with the coagulating liquid. Then, it is washed with water and dried to obtain a composite porous film of a separator for a nonaqueous battery.

[Test example]

[Review of Polyolefin Microporous Membrane] Using the polyolefin microporous membrane of A, B, and C of Table 1, a composite porous membrane was produced in accordance with the production example of the composite porous membrane described above. Furthermore, this review is to adjust the die to supply an equal amount of the polymer solution for film formation on both sides of the polyolefin microporous film. The properties of the obtained samples are shown in Table 2.

As shown in Table 2, when a polyolefin microporous film having an appropriate gas permeability and pore diameter is selected, the melting inhibition effect can be exhibited without impairing the shutdown function of the polyolefin microporous film. On the other hand, if a suitable polyolefin microporous film is not selected, the shutdown function of the polyolefin microporous film is impaired.

[Review of Coating Amount] B of Table 1 was used as a polyolefin microporous film. A composite porous film was produced in accordance with the production example of the above composite porous film. This review is to adjust the die to supply an equal amount of the polymer solution for film formation to both sides of the polyolefin microporous film. The sample shown in Table 3 was prepared by adjusting the supply amount of the polymer solution for film formation supplied from the die and adjusting the gap between the dies to control the amount of coating.

As shown in Table 3, if the coating amount is not appropriate, the battery performance, the shutdown property, and the melt suppression effect cannot coexist.

[Review of the coating amount balance in the table] B of Table 1 was used as the polyolefin microporous film. A composite porous film was produced in accordance with the production example of the composite porous film described above. In this review, the test piece was adjusted so that the polymer solution for film formation of one side and the other side of the polyolefin microporous film was supplied, and the sample shown in Table 4 was produced.

As shown in Table 4, if the coating was not carried out in an appropriate balance, the composite porous film having sufficient workability could not be obtained due to the curling.

From the above test examples, it was confirmed that the separator for a nonaqueous battery of the present invention and the composite porous membrane to be formed have a suitable configuration. The following is an example of a separator designed based on the knowledge and insights of the test examples.

In the following, the present invention will be described in detail, and these embodiments and descriptions are illustrative of the present invention, and other forms are also within the scope of the present invention.

[Examples]

A polyethylene microporous film (manufactured by Toyo Chemical Co., Ltd.; E-16MMS) was used as a polyolefin microporous film having a film thickness of 17 μm and a gas permeability per unit thickness of 25 seconds/100 cc. Μm, pore size 0.1 μm. A composite porous film was produced in accordance with the production example of the composite porous film described above. Here, the die is adjusted so that the same amount of the polymer solution for film formation can be supplied from the die. The obtained composite porous film had a gas permeability of 1.4 times and a film thickness of 20 μm with respect to the polyolefin microporous film, and the coating amount was 1.6 g/m ² . Further, the coating amount of the surface was 0.8 g/m ² in terms of weight, 1.5 μm in terms of thickness, the coating amount in the inner surface was 0.8 g/m ² in terms of weight, 1.5 μm in thickness, and the weight and thickness were: | Coating amount of the surface - coating amount of the inner surface | / (coating amount of the surface + coating amount of the inner surface) = 0.

Evaluation of the shutdown characteristics and battery performance of this composite porous membrane was carried out. The shutdown temperature was 141 ° C and the melting temperature was 250 ° C. Further, the battery performance was 94%, which was the same as that of the polyolefin microporous film before coating.

[Industrial use possibility]

According to the present invention, it is possible to provide a high-energy-density, high-output, high-power, high-performance non-aqueous battery with a desired shutdown function and heat resistance which effectively suppresses the melting effect, and is excellent in workability and ion permeability. Separator for non-aqueous battery.

Claims (7)

A separator for a non-aqueous battery, which has a gas permeability per unit thickness (JIS P8117) of 15 seconds/100 cc. More than μm, 50 seconds / 100cc. a composite porous film in which a porous layer of poly(m-phenylene isophthalamide) is coated and integrated with both sides of a polyolefin microporous film having a thickness of 5 μm or more and 25 μm or less and having a thickness of 5 μm or more and 25 μm or less. The film thickness is 6 μm or more and 35 μm or less, and the air permeability (JIS P8117) is 1.01 times or more and 2.00 times or less of the polyolefin microporous film, and the amount of poly-m-phenylene m-xylyleneamine is 1.0 g/m ² or more. 4.0g/m ² or less. The separator for a nonaqueous battery according to the first aspect of the invention, wherein the polyolefin microporous membrane has a pore diameter of 0.01 μm or more and 0.2 μm or less. For the non-aqueous battery separator according to the first or second aspect of the patent application, the coating amount of the poly-m-phenylene m-xylyleneamine is: the coating amount of the surface - the coating amount of the inner surface | / ( The coating amount of the surface + the coating amount of the inner surface is 0 or more and 0.2 or less. The separator for a non-aqueous battery according to the first aspect of the invention, wherein the polyolefin microporous film is a polyolefin microporous film mainly composed of polyethylene. A method for producing a separator for a non-aqueous battery according to the first or second aspect of the patent application, which is produced by sequentially performing the following steps: (1) a step of dissolving poly(m-phenylene isophthalamide) in a solvent mainly composed of a guanamine solvent to prepare a polymer solution, and (2) applying the polymer solution to a polyolefin microporous film a step of both sides, (3) a step of transporting the polyolefin microporous film coated with the polymer solution, and (4) immersing the polyolefin microporous film coated with the polymer solution in the coagulating liquid formed by the solvent and water a step of causing both sides of the watch to be in contact with the coagulating liquid, and a step of solidifying the poly(m-phenylene isophthalamide), (5) a water washing step of the solidified composite film, and (6) a drying step of the water-washed composite film . The method for producing a separator for a nonaqueous battery according to the fifth aspect of the invention, wherein the polymer solution contains a phase separation agent, and the concentration of the separating agent is 5 to 50% by weight. The method for producing a separator for a nonaqueous battery according to the fifth or sixth aspect of the invention, wherein the ratio of water in the coagulating liquid is 30 to 80% by weight.