JP5829570B2 - Method for producing separator for metal ion secondary battery - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a secondary battery separator having a high initial charge / discharge efficiency and an excellent discharge capacity retention rate, which is formed by supporting a pigment on a nonwoven fabric substrate, and a method for producing the secondary battery separator capable of stable production. Is.

  2. Description of the Related Art In recent years, various information terminal devices typified by notebook personal computers and mobile phones are rapidly becoming smaller, lighter, and thinner, and widely used. In addition, hybrid vehicles, electric vehicles, household storage batteries, and the like are becoming widespread. Due to such a background, the demand for high energy density secondary batteries (storage batteries) as these power supplies or power storage units is increasing, among them, lithium ion secondary batteries as batteries having high operating voltage and high energy density, Those using metal ions such as sodium ion secondary batteries have attracted attention.

  The secondary battery generally contains an electrode group having a separator having electrical insulation and liquid retention between a positive electrode and a negative electrode together with a nonaqueous electrolyte such as an organic electrolyte in a container, It is formed by sealing. Conventionally, a polyolefin microporous membrane has been generally used as a secondary battery separator. Polyolefin microporous membrane has a function (shutdown function) that melts and closes the microporous membrane when the temperature inside the battery reaches around 130 ° C, thus improving battery safety in the event of a short circuit. Can do. However, it has been suggested that if the temperature of the polyolefin microporous membrane further increases due to some circumstances, the polyolefin itself may melt and short-circuit, causing thermal runaway. Therefore, a heat-resistant separator that does not melt and shrink even at around 200 ° C. has been developed at present.

  As a heat-resistant separator, a nonwoven fabric composed of polyester fibers and a nonwoven fabric obtained by blending polyester fibers with aramid fibers that are heat-resistant fibers are disclosed (for example, see Patent Documents 1 to 3). However, these have a large hole diameter and an internal short circuit occurs, and this internal short circuit deteriorates the initial charge / discharge efficiency of the battery. In the present invention, the initial charge / discharge efficiency refers to the value obtained by dividing the discharge capacity by the charge capacity. When an internal short circuit occurs in the separator, the charge capacity mainly increases and the initial charge / discharge efficiency deteriorates. . The deterioration of the initial charge / discharge efficiency induces excessive decomposition of the electrolyte on the negative electrode, leading to depletion of the electrolyte and deposition of decomposition products on the negative electrode surface and separator pores. This causes problems in efficiency and capacity reduction.

  Moreover, the example which laminates | stacks the nonwoven fabric comprised with the polyester-type fiber on the polyolefin microporous film, and is compounded is described (for example, refer patent document 4). Furthermore, examples in which a nonwoven fabric or a woven fabric is supported by applying a pigment or a resin to impart heat resistance are disclosed (for example, Patent Documents 5 to 7). However, since the nonwoven fabric used as the base material has large pores and low surface smoothness, the coating has a large surface variation and the coating layer becomes non-uniform. When the coating layer becomes non-uniform, the current density in the separator As a result, unevenness is generated and a load is locally applied, so that the discharge capacity maintenance rate of the battery tends to deteriorate. In the present invention, the discharge capacity retention rate refers to a value obtained by dividing the charge capacity by the discharge capacity. When a load is locally applied to the separator, the charge capacity mainly decreases and the discharge capacity maintenance rate decreases. The discharge capacity maintenance rate suggests the life of the battery, and a low one is problematic because the life of the battery is short.

  Moreover, as a method for applying a pigment or the like to a nonwoven fabric substrate, Patent Document 5 describes printing, compression, press-fitting, roller coating, blade coating, brush coating, dip coating, spray coating, and casting coating. . Patent Document 6 describes a method of coating by applying or impregnating such as pulling application, applicator application, die coater application and the like. Patent Document 7 describes a coating method using a coating machine such as a die coater, a gravure coater, a reverse roll coater, a squeeze roll coater, a curtain coater, a blade coater, or a knife coater. Coating on non-woven fabric base material has large holes in the non-woven fabric, so coating defects called pinholes are likely to occur after coating / drying. This coating defect deteriorates the initial charge / discharge efficiency of the battery as well as internal short circuit. In addition, there is a problem that pigments, resins, and the like are easily dropped during coating / drying.

JP 2003-123728 A JP 2007-317675 A JP 2006-19191 A JP 2005-293891 A JP 2005-536857 A JP 2007-157723 A Republished WO2009 / 096451

  An object of the present invention is to provide a separator for a secondary battery using metal ions, which has a high initial charge / discharge efficiency and an excellent discharge capacity maintenance rate, and is particularly stable by supporting a pigment on a nonwoven fabric substrate. It is providing the manufacturing method of the separator for possible metal ion secondary batteries.

The present inventors have made intensive studies, as a result, have led to the invention of manufacturing how metal ion secondary battery separator that can solve the problem. That is,
(1) In the manufacturing method of the separator for metal ion secondary batteries including the process of applying the coating liquid containing a pigment to a nonwoven fabric base material, and drying, the strip | belt-shaped support body is used in this process, and this pigment is potassium titanate. , Barium titanate, aluminum borate, magnesium sulfate, silicon nitride, silicon carbide, calcium silicate, wollastonite, fiber gypsum, alumina, boehmite, calcium carbonate, zinc oxide, melamine resin, urea-formalin resin, polyethylene, Niro selected down or al least one, at least a step of coating a coating solution containing a pigment on one side of the surface, the step of bonding a support nonwoven substrate after coating the nonwoven substrate, the coating containing a pigment A metal comprising a step of drying a structure comprising a liquid / nonwoven fabric substrate / support, and a step of peeling the support from the structure Process for producing a separator for ion secondary batteries,
(2) The separator for a metal ion secondary battery according to the above (1), which comprises coating a coating liquid containing a pigment on a surface of at least one side of the nonwoven fabric substrate by 30 g / m ² or more by mass before drying. Manufacturing method ,
It is.

  According to the present invention, it is possible to provide a separator for a secondary battery using a metal ion having a high initial charge / discharge efficiency and an excellent discharge capacity maintenance rate, which is achieved by supporting a pigment on a nonwoven fabric base material, and stable production. The manufacturing method of this possible separator for secondary batteries can be provided.

It is a schematic block diagram of the coating machine concerning one Embodiment in the manufacturing method of the separator for metal ion secondary batteries.

  Hereinafter, the content of the present invention will be described more specifically.

  In the present invention, a separator for a metal ion secondary battery (hereinafter sometimes abbreviated as “separator”) is obtained by supporting a pigment on a nonwoven fabric substrate, and the production of a separator for a metal ion secondary battery in the present invention. The method (hereinafter sometimes abbreviated as “manufacturing method”) is characterized in that a support is used in the step of coating and drying a coating liquid containing a pigment on a nonwoven fabric substrate. More specifically, a step of applying a coating liquid containing a pigment to a nonwoven fabric substrate, a step of bonding a support to the nonwoven fabric substrate after coating, a coating solution containing a pigment / nonwoven fabric substrate / support It is obtained by a production method including a step of drying a structure comprising: and a step of peeling the support from the structure.

  FIG. 1 is a diagram showing a schematic configuration of a coating machine according to an embodiment for carrying out the manufacturing method of the present invention, but the present invention is not limited by this drawing.

  In FIG. 1, the raw fabric of the strip-shaped nonwoven fabric substrate 1 is mounted as a wound body 2 wound in a roll shape. The nonwoven fabric base material 1 unwound from the wound body 2 is sequentially conveyed by the conveyance rolls 11 to 22 constituting the conveyance system. An arrow 25 represents the traveling direction of the nonwoven fabric substrate 1.

  In FIG. 1, a die coater 24 is installed toward the nonwoven fabric substrate 1 traveling between the conveyance roll 13 and the conveyance roll 14, and a coating containing a pigment on the nonwoven fabric substrate 1 by the die coater 24. Liquid is applied.

  In FIG. 1, the raw material of the belt-shaped support body 4 is mounted as a wound body 5 wound in a roll shape. The support 4 unwound from the wound body 5 is pressure-bonded between the transport roll 14 and the die coater 24 to the nonwoven fabric substrate 1 coated with a coating liquid containing a pigment by the touch roll 9. After the support 4 is pressed, the structure 6 composed of the coating liquid containing the pigment / nonwoven fabric substrate 1 / support 4 is formed, and is then sequentially conveyed by the conveying rolls 14-21. By passing through the dryer 10 in this process, the coating liquid is heated and dried to form a coating film, and then the support 4 is peeled off from the structure 6 by the transport roll 22, thereby forming the separator 7. The wound body 3 is wound up. The support 4 is wound up as a wound body 8 via the transport roll 23. An arrow 26 represents the traveling direction of the support 4.

  By using the production method of the present invention, the coated surface of the nonwoven fabric substrate or the surface opposite to the coated surface, or both surfaces can be uniformly coated with the pigment, so that the positive electrode and the negative electrode can be satisfactorily separated, and A separator excellent in metal ion conductivity can be obtained. In the present invention, the metal ion is not limited as long as it is used as a secondary battery. For example, Co, Mn, Ni, Al, Li, Ti, Fe, Nb, Na, V, Examples include ions of Mo, Mg, Ca, K, etc. Among them, Li is preferable in terms of performance and cost when a secondary battery is used.

In the present invention, the method of coating the pigment-containing coating liquid on the nonwoven fabric substrate is not limited in any way, but is a blade coater, bar coater, roll coater, air knife coater, die coater, curtain coater, gravure coater. Various systems represented by a micro gravure coater, a lip coater, a comma coater, an impregnation coater and the like can be freely selected. If the support is not used, there are limitations on the coating methods and coating amounts that can be selected due to dropout of the coating liquid during transportation and drying due to the large holes present in the nonwoven fabric substrate, and insufficient strength of the nonwoven fabric substrate. This is not preferable because it occurs. On the other hand, in this invention, even if it is a coating amount impossible by the coating to the nonwoven fabric base material which does not use a support body, it can apply | coat / dry and can also improve the freedom degree of a compounding design. . Although the absolute dry coating amount in this invention is not specifically limited, 3-30 g / m < ² > is preferable, More preferably, it is 10-20 g / m < ² >. If it is less than 3 g / m ² , the surface of the nonwoven fabric cannot be covered and pinholes are likely to occur, and if it exceeds 30 g / m ² , the internal resistance value of the separator may become too high.

In the present invention, the coating amount when the coating liquid containing the pigment is applied to the nonwoven fabric substrate is preferably 30 g / m ² or more, more preferably 30 g / m ² or more, and 100 g / m by mass before drying. ^Is less than ² . When it is less than 30 g / m ² , it is difficult to form a uniform coating film, and unevenness and coating defects are likely to occur when the support is bonded. Moreover, since it will become thick too much when it becomes 100 g / m < ² > or more, the flow of a coating liquid will occur easily at the time of conveyance and drying, and when a support body is bonded together, it will become easy to produce a nonuniformity.

  The type of the support used in the present invention is not limited in any way, but a polyester resin film, a polyolefin resin film such as a polyethylene resin film, a synthetic resin film such as a polyvinyl chloride resin film, a metal foil, Paper such as high-quality paper, neutral paper, art paper, coated paper, synthetic paper, non-woven fabric and the like can be freely selected, and the thickness is not particularly limited. Among them, a synthetic resin film is preferable, and a polyethylene terephthalate (PET) film that has heat resistance and is inexpensive is more preferable. Moreover, not only a single layer film but a laminated film can also be used. Further, the mold release treatment is not particularly limited, and a general treatment method using a fluorine type mold release agent or a silicone type mold release agent can be employed. Two or more of these supports may be used in combination.

  The support used in the present invention may be cylindrical. By using a rotatable cylindrical support, it is possible to uniformly support the non-woven fabric substrate after coating. The cylindrical support used in the present invention is not limited in any way, but preferably has a diameter of 200 mm to 1500 mm. Two or more of the cylindrical supports having the same or different diameters may be used in combination, and the surface may be subjected to the mold release treatment or the mirror finish treatment.

  When the cylindrical support is heatable, it is more preferable because the nonwoven fabric substrate can be supported / conveyed / dried simultaneously. As the heating method, a method in which the surface temperature can be increased or decreased by passing steam or the like through the cylindrical support is preferable because the conveyance speed and the drying conditions can be easily adjusted.

  Although the coating liquid containing the pigment used for this invention is not restrict | limited at all, It is preferable that it is a liquid mixture of a pigment, a binder, a thickener, etc. from the point of coating property. Further, since it is necessary to uniformly coat the surface of the nonwoven fabric substrate, it is preferable that 70% by mass or more of the coating liquid is the pigment, and the increase in the binder component in the coating liquid is generally a separator. In order to increase the internal resistance of the coating liquid, the binder is preferably 30% by mass or less of the coating liquid, more preferably 90% by mass or more of the coating liquid and 10% by mass or less of the binder of the coating liquid. It is.

  Pigments used in the present invention are potassium titanate, barium titanate, aluminum borate, magnesium sulfate, silicon nitride, silicon carbide, calcium silicate, wollastonite, fiber gypsum, alumina, boehmite, calcium carbonate, zinc oxide, etc. One or more kinds can be freely selected from inorganic pigments and organic pigments such as melamine resin, urea-formalin resin, polyethylene, nylon, styrene plastic pigment, acrylic plastic pigment, and hydrocarbon plastic pigment.

  The binder used in the present invention is an ethylene-acrylic acid copolymer such as an ethylene-vinyl acetate copolymer or an ethylene-ethylene acrylate copolymer, a fluorine-based rubber, a styrene-butadiene rubber, a polyvinyl alcohol, a polyvinyl butyral, a polyvinyl pyrrolidone, One or more kinds can be freely selected from poly-N-vinylacetamide, crosslinked acrylic resin, polyurethane, epoxy resin and the like.

  The thickener used in the present invention includes synthetic polymers such as polyethylene glycol, polyacrylic acid, polyvinyl alcohol, vinyl methyl ether-maleic anhydride copolymer, xanthan gum, welan gum, gellan gum, guar gum, carrageenan, cellulose derivative, dextrin. , Natural polysaccharides such as starches such as pregelatinized starch, viscosity minerals such as montmorillonite and hectorite, inorganic oxides such as fumed silica, fumed alumina, and fumed titania . Furthermore, a wetting agent, an antifoaming agent, etc. can be freely added as needed.

  In the present invention, at the time of manufacturing the separator, the initial charge / discharge efficiency and the discharge capacity maintenance of the separator are performed through a process of bonding the coated surface of the nonwoven fabric substrate, the surface opposite to the coated surface, or both surfaces to the support. The rate can be improved. By laminating to the support after application to the nonwoven fabric substrate, the coating solution is uniformly attached to the nonwoven fabric substrate with low smoothness on the front and back surfaces, and the nonwoven fabric substrate surface or both surfaces are coated well. Thus, it is possible to manufacture a separator with little coating unevenness and very few pinholes. When coating unevenness occurs, the uniformity of the separator is lowered, and unevenness in ion conductivity in the separator occurs in the metal ion secondary battery, resulting in local defects such as metal deposition when charging and discharging are repeated. When the deposited metal becomes a dendrite-like crystal, an internal short circuit occurs, and the battery capacity decreases, so that the discharge capacity maintenance rate of the battery deteriorates. In addition, if there is a pinhole in the separator, the positive electrode and the negative electrode cannot be separated inside the metal ion secondary battery, and the initial charge / discharge efficiency is remarkably lowered, which causes a problem. In addition, the distance until pasting to the support after coating on the nonwoven fabric substrate is not limited at all, but it is possible to suppress the flow of the coating liquid on the nonwoven fabric substrate and the dropping of the coating liquid, It is preferable that it is within 5 m.

  The nonwoven fabric substrate used in the present invention has an average diameter of 0.5 to 10 μm, vinylon; polyamide such as nylon and aramid; cellulose such as rayon, lyocell and pulp; polyethylene terephthalate, polybutylene terephthalate, aromatic polyester, etc. Polyester such as polyethylene, polypropylene, etc .; Acrylic; One or two or more ultrafine yarns formed using glass or the like are used in combination or in combination, and the major diameter of the pore is 0.1 to 70 μm. It is desirable that the pores contain 50% or more based on the total number of pores, and the thickness of the nonwoven fabric substrate is desirably 9 to 30 μm, but is not limited by these.

  In the present invention, pressure may be applied when the coated surface of the nonwoven fabric substrate, the surface opposite to the coated surface, or both surfaces are bonded to the support. By adjusting the pressure at the time of bonding, the amount of the coating liquid penetrating into the nonwoven fabric when bonded can be adjusted, and the internal resistance and strength of the separator can be adjusted. When the pressure is increased, the penetration of the coating liquid into the nonwoven fabric can be increased, and the strength of the separator can be improved. When the pressure is weakened, the penetration can be reduced and the internal resistance of the separator can be reduced. Therefore, by controlling the pressure, a separator can be designed according to the purpose.

  In the present invention, in the drying process, by drying the structure comprising the coating liquid containing the pigment / nonwoven fabric substrate / support, the discharge capacity retention rate and initial charge / discharge efficiency of the separator can be improved, and The degree of freedom in selecting a drying method can be improved. By drying in the state of the structure, hot air applied from the support side is prevented, so that the flow of the coating liquid hardly occurs, and the coating liquid existing between the nonwoven fabric substrate and the support is Since the flow due to mechanical vibration can be suppressed, the occurrence of coating unevenness can be suppressed. The flow of the coating liquid at the time of drying causes repelling, and repelling induces the generation of pinholes, thus significantly reducing the initial charge / discharge efficiency. In addition, when uneven coating occurs, uneven ion conductivity in the separator occurs in the metal ion secondary battery, which deteriorates the discharge capacity retention rate.

  The drying method of the structure is not particularly limited, but drying methods represented by convective heat transfer drying such as fluidized bed drying, airflow drying, superheated steam drying, conduction heat transfer drying, radiant heat transfer drying, etc. Can be freely selected, and two or more dryers of different drying methods may be used in combination. In addition, when a cylindrical support that is a support and a dryer is used, unevenness in the heat transferred to the nonwoven fabric substrate during drying is less likely to occur than in the case of using a support that does not have a drying function. Can be further suppressed. Furthermore, by using two or more cylindrical supports together, the coated surface of the nonwoven fabric substrate and the surface opposite to the coated surface can be freely supported and dried. Uniform coating can be facilitated and the occurrence of pinholes can be further suppressed, so that the initial charge / discharge efficiency of the separator can be further improved.

  Examples of the cylindrical support include a cylinder dryer. After the coating liquid containing the pigment is applied to the nonwoven fabric substrate, it may be preheated using a non-hot air dryer such as an infrared (IR) dryer before or after bonding to the support or both. . Preheating is preferable because the flow of the coating liquid on the nonwoven fabric substrate can be further suppressed and the occurrence of coating unevenness can be further suppressed. The temperature of the dryer can be freely selected between 50 ° C. and 180 ° C. as required. Only a coating liquid / nonwoven fabric substrate containing a pigment is not preferable because it easily induces the flow of the coating liquid in the drying process and easily causes coating unevenness.

  In the present invention, by separating the support from the dried structure, it is possible to produce a separator with less coating unevenness, minimal pinholes, and high smoothness on the front surface, back surface, or both surfaces. . When this separator is used in a metal ion secondary battery, it has a high discharge capacity maintenance rate due to less coating unevenness, pinholes are minimized, and short-circuiting is suppressed, so that metal ions with high initial charge / discharge efficiency are obtained. A secondary battery can be obtained. In addition, the discharge capacity maintenance ratio can be further improved due to the high smoothness of the separator. Although the effect of the smoothness is not clear, since the smoothness is high, the separator adheres more uniformly to the electrode, and the ion conductivity becomes more uniform in the metal ion secondary battery. When repeated, defects such as metal deposition are less likely to occur, and as a result, the occurrence of a short circuit can be further suppressed, so the discharge capacity maintenance rate of the battery is considered to have further improved. Further, when the cylindrical support is used as the support, the smoothness of the separator can be further improved by mirror-treating the surface, and therefore the discharge capacity maintenance rate of the battery can be further improved.

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. In Examples,% and part are based on mass unless otherwise specified. The coating amount is an absolutely dry coating amount. Examples 4, 10 and 11 are reference examples.

Example 1
(1) Preparation of separator coating liquid 100 parts of granular boehmite (trade name: C-20, manufactured by Daimei Chemical Industry Co., Ltd.) was dispersed in 100 parts of a 2% aqueous solution of carboxymethyl cellulose to prepare a boehmite dispersion. To this dispersion, 15 parts of 45% styrene butadiene latex was added and stirred vigorously to prepare a separator coating solution.

(2) Production of separator On the PET nonwoven fabric substrate having a basis weight of 11 g / m ² and a thickness of 18 μm, the separator coating liquid is applied so that the absolute dry coating amount is 10 g / m ^2, and then the thickness is increased. A 25 μm PET film was bonded to the surface opposite to the coated surface and dried as it was, and after drying, the PET film was peeled off to prepare a separator having a nonwoven fabric substrate carrying a pigment.

Example 2
In preparation of the coating liquid for separator of Example 1 (1), instead of 100 parts of granular boehmite (trade name: C-20, manufactured by Daimei Chemical Co., Ltd.), 50% modified styrene butadiene particles (trade name: V1004). Non-woven fabric substrate in the same manner as in Example 1, except that 200 parts of latex (manufactured by Nippon Zeon Co., Ltd.) and 150 parts of carboxymethylcellulose 1.5% aqueous solution were used instead of 100 parts of carboxymethylcellulose 2% aqueous solution. A separator having a pigment supported thereon was prepared.

Example 3
In the production of the separator of Example 1 (2), a separator having a nonwoven fabric substrate carrying a pigment was produced in the same manner as in Example 1 except that a process paper having a thickness of 100 μm was used instead of a PET film having a thickness of 25 μm. did. As the process paper, glassine paper coated with a silicone release agent was used.

Example 4
In the production of the separator of Example 1 (2), a separator having a non-woven fabric substrate carrying a pigment was produced in the same manner as in Example 1 except that a cylindrical dryer was used instead of a PET film having a thickness of 25 μm. did. As the cylindrical dryer, a cylinder dryer having a diameter of 700 mm and a silicone release agent applied thereto was used.

Example 5
In the preparation of the coating liquid for separator of Example 1 (1), a non-woven fabric base was prepared in the same manner as in Example 1, except that 230 parts of carboxymethylcellulose 0.8% aqueous solution was used instead of 100 parts of carboxymethylcellulose 2% aqueous solution. A separator having a pigment supported on the material was produced.

Example 6
In the production of the separator coating liquid of Example 1 (1), a nonwoven fabric base was prepared in the same manner as in Example 1 except that 550 parts of a 0.3% aqueous solution of carboxymethylcellulose was used instead of 100 parts of a 2% aqueous solution of carboxymethylcellulose. A separator having a pigment supported on the material was produced.

Example 7
In the production of the separator coating liquid of Example 1 (1), a nonwoven fabric base was prepared in the same manner as in Example 1 except that 900 parts of carboxymethylcellulose 0.2% aqueous solution was used instead of 100 parts of carboxymethylcellulose 2% aqueous solution. A separator having a pigment supported on the material was produced.

Example 8
In the production of the separator coating liquid of Example 1 (1), a nonwoven fabric base was prepared in the same manner as in Example 1, except that 1000 parts of 0.2% aqueous solution of carboxymethylcellulose was used instead of 100 parts of 2% aqueous solution of carboxymethylcellulose. A separator having a pigment supported on the material was produced.

Example 9
In the production of the separator of Example 1 (2), the nonwoven fabric substrate was prepared in the same manner as in Example 1 except that the PET film was bonded to the coated surface of the nonwoven fabric substrate instead of being bonded to the surface opposite to the coated surface. A separator having a pigment supported thereon was prepared.

Example 10
In the production of the separator in Example 1 (2), two cylindrical dryers were used in succession instead of the PET film having a thickness of 25 μm, and the first surface was bonded to the surface opposite to the coating surface, followed by two A separator having a non-woven fabric substrate carrying a pigment was prepared in the same manner as in Example 1 except that the coated surface was bonded to the eyes and dried. Both cylindrical dryers used a cylinder dryer having a diameter of 700 mm and a silicone release agent applied thereto.

Example 11
In the production of the separator of Example 10, a separator having a nonwoven fabric substrate carrying a pigment was produced in the same manner as in Example 10 except that the separator coating liquid was produced by the method used in Example 7.

Comparative Example 1
In the production of the separator of Example 1 (2), without using a PET film having a thickness of 25 μm, an absolutely dry coating amount is 10 g / m ² on a PET nonwoven fabric having a basis weight of 10 g / m ² and a thickness of 18 μm. A separator having a non-woven fabric substrate carrying a pigment was prepared in the same manner as in Example 1 except that the separator coating liquid was directly applied and dried without using a cylindrical dryer.

Comparative Example 2
50% modified styrene butadiene particles (trade name: V1004 latex) instead of 100 parts of granular boehmite (trade name: C-20, manufactured by Daimei Chemical Co., Ltd.) (2) Zeolite Co., Ltd. (200 parts) was used. (2) In the production of the separator, a PET film having a thickness of 25 μm was not used, and a dry coating was applied on a PET nonwoven fabric having a basis weight of 10 g / m ² and a thickness of 18 μm. The non-woven fabric substrate was loaded with the pigment in the same manner as in Example 1 except that the separator coating liquid was directly applied so that the amount was 10 g / m ² and dried without using a cylindrical dryer. A separator was prepared.

<Preparation of positive electrode>
80 parts of lithium cobaltate as a positive electrode active material, 10 parts of acetylene black as a conductive additive, and 5 parts of polyvinylidene fluoride (PVDF) as a binder are uniformly mixed in N-methyl-2-pyrrolidone (NMP). A positive electrode paste was prepared. This paste was applied onto an aluminum foil having a thickness of 20 μm, dried and calendered to produce a positive electrode having a thickness of 100 μm. Further, the exposed portion of the aluminum foil of the positive electrode was tabbed.

<Production of negative electrode>
90 parts of graphite as a negative electrode active material and 5 parts of PVDF as a binder were uniformly mixed in NMP to prepare a negative electrode agent paste. This paste was applied onto a copper foil having a thickness of 20 μm, dried and calendered to prepare a negative electrode having a thickness of 90 μm. Further, a tab was attached to the exposed portion of the copper foil of the negative electrode.

<Battery assembly>
The positive electrode and the negative electrode obtained as described above were superposed through the separators produced in Examples 1 to 11 and Comparative Examples 1 and 2, to produce an electrode separator laminate. The electrode separator laminate was loaded into a laminate film exterior material, and an ethylene carbonate / diethyl carbonate (volume ratio 7/3) solution in which 1 mol / l LiPF ₆ was dissolved was injected as an electrolyte, and vacuum sealing was performed. A lithium ion secondary battery having a rated capacity of 30 mAh was produced.

[Initial charge / discharge efficiency]
The produced lithium ion secondary battery is subjected to constant current charging at 1 C up to 4.2 V and constant voltage charging at 4.2 V, and then constant current discharging at 1 C up to 2.8 V, and then discharge capacity / charge The volume ratio was calculated.

[Discharge capacity maintenance rate]
The produced lithium ion secondary battery was subjected to constant current charging at 1 C up to 4.2 V and constant voltage charging at 4.2 V, and then repeated constant current discharging at 1 C up to 2.8 V, with respect to the first time The ratio of charge capacity / discharge capacity at the 100th time was calculated.

As is clear from Table 1, the separators of Examples 1 to 11 manufactured using the support were excellent in the initial charge / discharge efficiency and excellent in the discharge capacity maintenance rate as compared with the separators of Comparative Examples 1 and 2. Further, when Examples 1 and 5 to 8 are compared, Examples 5 to 8 in which the coating amount before drying is 30 g / m ² or more are excellent in initial charge / discharge efficiency, and further, the coating amount before drying is 30 g / m. Examples 5-7 which are ² or more and less than 100 g / m < ² > are excellent also in the discharge capacity maintenance factor.

When Examples 1, 3 and 4 are compared, Example 4 manufactured using a cylindrical support is excellent in initial charge / discharge efficiency and discharge capacity retention rate. In addition, when Examples 4 and 10 are compared, Example 10 in which a separator is manufactured by bonding a cylindrical support on both sides is superior in initial charge / discharge efficiency. Furthermore, when Examples 4, 10 and 11 are compared, Example 11 in which the pre-drying coating amount is 30 g / m ² or more and a cylindrical support is bonded to both sides to produce a separator is initial. Excellent charge / discharge efficiency and discharge capacity retention rate.

1 Nonwoven fabric base material 2 Nonwoven fabric base material wound (unwinding side)
3 Winding body of separator (winding side)
4 Support body 5 Rolled body of support body (unwinding side)
6 Nonwoven fabric substrate / Structure comprising coating liquid / support containing pigment 7 Separator 8 Rolled body of support (winding side)
9 touch roll 10 dryer 11 transport roll 12 transport roll 13 transport roll 14 transport roll 15 transport roll 16 transport roll 17 transport roll 18 transport roll 19 transport roll 20 transport roll 21 transport roll 22 transport roll 23 transport roll 24 die coater 25 nonwoven fabric Arrow 26 representing the traveling direction of the substrate Arrow representing the traveling direction of the support

Claims (2)

In a method for producing a separator for a metal ion secondary battery including a step of applying a coating liquid containing a pigment to a nonwoven fabric substrate and drying, a belt-like support is used in the step, and the pigment is potassium titanate or titanic acid. barium, aluminum borate, magnesium sulfate, silicon nitride, silicon carbide, calcium silicate, wollastonite, fibrous gypsum, alumina, boehmite, calcium carbonate, zinc oxide, melamine resins, urea - formalin resin, polyethylene, nylon or al One or more kinds selected, a step of applying a coating liquid containing a pigment on at least one surface of the nonwoven fabric substrate, a step of bonding a support to the nonwoven fabric substrate after coating, a coating solution / nonwoven fabric containing a pigment A metal ion comprising a step of drying a structure comprising a substrate / support, and a step of peeling the support from the structure Method of manufacturing a separator for the next battery. The manufacturing method of the separator for metal ion secondary batteries of Claim 1 including apply | coating the coating liquid containing a pigment 30g / m < ² > or more by the mass before drying to the surface of at least one side of a nonwoven fabric base material.