JP6879898B2 - Method for manufacturing separator film for non-aqueous electrolyte secondary battery and separator film cleaning device for non-aqueous electrolyte secondary battery - Google Patents

Description

The present invention relates to a manufacturing method and a cleaning device for a separator film for a non-aqueous electrolyte secondary battery used in a battery such as a lithium ion secondary battery.

Inside the lithium ion secondary battery, the positive electrode and the negative electrode are separated by a film-like and porous separator. The manufacturing process of this separator includes a cleaning step for later removing unnecessary substances from the film once formed.

Patent Document 1 discloses a cleaning device for performing the above cleaning step. The cleaning device according to Patent Document 1 cleans the film by passing the film through two cleaning tanks.

Japanese Unexamined Patent Publication No. 2001-228594 (published on August 24, 2001)

In the cleaning apparatus according to Patent Document 1, after being carried out from the cleaning tank on the upstream side (referred to as cleaning tank A here) in the film transport path, the cleaning tank on the downstream side (referred to as cleaning tank B here). Almost no liquid, especially on the top surface of the film, is removed before entering. Therefore, in the cleaning apparatus according to Patent Document 1, there is a risk that the liquid filled in the cleaning tank A may enter the cleaning tank B.

The cleaning tank A and the cleaning tank B are filled with a liquid for film cleaning, but usually, the liquid filled in the cleaning tank A on the upstream side of the transport path is more dirty than the liquid filled in the cleaning tank B. There is. Therefore, if the liquid filled in the cleaning tank A enters the cleaning tank B, there arises a problem that the liquid filled in the cleaning tank B is contaminated.

The present invention has been made in view of the above problems, and an object of the present invention is to suppress contamination of the cleaning liquid in the cleaning tank on the downstream side in the transport path of the separator film for a non-aqueous electrolyte secondary battery. It is an object of the present invention to provide a method for producing a separator film for a non-aqueous electrolyte secondary battery and a separator film cleaning device for a non-aqueous electrolyte secondary battery.

The method for producing a separator film for a non-aqueous electrolyte secondary battery according to one aspect of the present invention includes a cleaning step of cleaning the separator film for a non-aqueous electrolyte secondary battery in a first cleaning tank and carrying it out from the first cleaning tank. The first roller, the second roller, and the third roller are brought into contact with the separated film for the non-aqueous electrolyte secondary battery, and the separator film for the non-aqueous electrolyte secondary battery is conveyed to the second cleaning tank. In the transport step, the first roller and the third roller are in contact with one surface of the separator film for a non-aqueous electrolyte secondary battery, and the first roller and the third roller are in contact with each other. By contacting the second roller with the roller on the other surface of the non-aqueous electrolyte secondary battery separator film, the cleaning liquid is removed from the non-aqueous electrolyte secondary battery separator film, and then the cleaning liquid is removed. The non-aqueous electrolytic solution secondary battery separator film is conveyed to a second cleaning tank, and the cleaning liquid filled in the first cleaning tank and the cleaning liquid filled in the second cleaning tank are of the same type.

The separator film cleaning device for a non-aqueous electrolyte secondary battery according to one aspect of the present invention includes a first cleaning tank and a second cleaning tank for cleaning the separator film for a non-aqueous electrolyte secondary battery, and the first cleaning. The first roller, the second roller, which come into contact with the separator film for the non-aqueous electrolyte secondary battery carried out from the tank and convey the separator film for the non-aqueous electrolyte secondary battery to the second cleaning tank. The first roller and the third roller are in contact with one surface of the separator film for a non-aqueous electrolyte secondary battery, and the first roller and the third roller are in contact with each other. When the second roller comes into contact with the other surface of the non-aqueous electrolyte secondary battery separator film, the second roller removes the cleaning liquid from the non-aqueous electrolyte secondary battery separator film. Then, the separator film for the non-aqueous electrolyte secondary battery is conveyed to the second cleaning tank, and the cleaning liquid filled in the first cleaning tank and the cleaning liquid filled in the second cleaning tank are of the same type. Is.

Further, the speed of the surface of the second roller is preferably different from the transport speed of the separator film for the non-aqueous electrolytic solution secondary battery.

Further, it is preferable that the second roller is rotationally driven, and the second roller is a drive roller that is rotationally driven by power. Further, it is preferable that the second roller is rotationally driven and the second roller is a drive roller that is rotationally driven by power.

Further, it is preferable that the surface of the second roller is provided with an uneven shape.

Further, it is preferable that the surface of the second roller is provided with a spiral, curved or linear groove.

Further, it is preferable that the groove of the second roller extends beyond the end portion of the separator film for the non-aqueous electrolyte secondary battery in the width direction of the separator film for the non-aqueous electrolyte secondary battery. ..

Further, it is preferable that the surface of the second roller that slides on the separator film for the non-aqueous electrolytic solution secondary battery is formed of a resin.

Further, in the transfer step, the first roller and the third roller are in contact with one surface of the separator film for the non-aqueous electrolyte secondary battery, and between the first roller and the third roller. When the second roller comes into contact with the other surface of the separator film for the non-aqueous electrolyte secondary battery, the cleaning liquid adhering to the separator film for the non-aqueous electrolyte secondary battery is removed in the first cleaning tank. It is preferable to remove it from the separator film for the non-aqueous electrolyte secondary battery. Further, the first roller and the third roller are in contact with one surface of the separator film for the non-aqueous electrolyte secondary battery, and the second roller is between the first roller and the third roller. Is in contact with the other surface of the separator film for the non-aqueous electrolyte secondary battery, so that the second roller removes the cleaning liquid adhering to the separator film for the non-aqueous electrolyte secondary battery in the first cleaning tank. It is preferable to remove it from the separator film for the non-aqueous electrolyte secondary battery.

Further, it is preferable that the cleaning liquid removed from the separator film for the non-aqueous electrolytic solution secondary battery by the second roller is returned to the first cleaning tank. Further, it is preferable that the second roller returns the cleaning liquid removed from the separator film for the non-aqueous electrolytic solution secondary battery to the first cleaning tank.

The temperature of the cleaning liquid is preferably 20 ° C. or higher and 100 ° C. or lower.

According to the present invention, it is possible to suppress contamination of the cleaning liquid in the cleaning tank on the downstream side in the transport path of the separator film for the non-aqueous electrolyte secondary battery.

It is a schematic diagram which shows the cross-sectional structure of a lithium ion secondary battery. It is a schematic diagram which shows the detailed structure of the lithium ion secondary battery shown in FIG. It is a schematic diagram which shows the other structure of the lithium ion secondary battery shown in FIG. It is sectional drawing which shows the structure of the cleaning apparatus which concerns on one Embodiment of this invention. It is sectional drawing of the 1st roller and 2nd roller in the cleaning apparatus shown in FIG. It is sectional drawing which shows the arrangement example of the gutter when the gutter is provided in the cleaning apparatus.

Hereinafter, embodiments for carrying out the present invention will be described with reference to FIGS. 1 to 5.

(Lithium-ion secondary battery)
Non-aqueous electrolyte secondary batteries represented by lithium ion secondary batteries have a high energy density and are therefore currently used for devices such as personal computers, mobile phones and mobile information terminals, and mobile bodies such as automobiles and aircraft. It is widely used as a battery and as a stationary battery that contributes to the stable supply of electric power.

FIG. 1 is a schematic view showing a cross-sectional configuration of the lithium ion secondary battery 1. As shown in FIG. 1, the lithium ion secondary battery 1 includes a cathode 11, a separator (film) 12, and an anode 13. Outside the lithium ion secondary battery 1, an external device 2 is connected between the cathode 11 and the anode 13. Then, the electrons move in the direction A when the lithium ion secondary battery 1 is charged and in the direction B when the lithium ion secondary battery 1 is discharged.

(Separator)
The separator 12 is arranged so as to be sandwiched between the cathode 11 which is the positive electrode of the lithium ion secondary battery 1 and the anode 13 which is the negative electrode thereof. The separator 12 is a porous film that allows the movement of lithium ions between the cathode 11 and the anode 13 while separating them. The separator 12 contains, for example, polyolefins such as polyethylene and polypropylene as its material.

2A and 2B are schematic views showing a detailed configuration of the lithium ion secondary battery 1 shown in FIG. 1, in which FIG. 2A shows a normal configuration and FIG. 2B shows a temperature rise of the lithium ion secondary battery 1. The state at the time is shown, and (c) shows the state at the time when the temperature of the lithium ion secondary battery 1 suddenly rises.

As shown in FIG. 2A, the separator 12 is provided with a large number of holes P. Normally, the lithium ions 3 of the lithium ion secondary battery 1 can come and go through the holes P.

Here, for example, the temperature of the lithium ion secondary battery 1 may rise due to overcharging of the lithium ion secondary battery 1, a large current caused by a short circuit of an external device, or the like. In this case, as shown in FIG. 2B, the separator 12 is melted or softened, and the hole P is closed. Then, the separator 12 shrinks. As a result, the movement of the lithium ion 3 is stopped, so that the above-mentioned temperature rise is also stopped.

However, when the temperature of the lithium ion secondary battery 1 rises sharply, the separator 12 shrinks sharply. In this case, as shown in FIG. 2 (c), the separator 12 may be destroyed. Then, since the lithium ion 3 leaks from the destroyed separator 12, the movement of the lithium ion 3 does not stop. Therefore, the temperature rise continues.

3A and 3B are schematic views showing another configuration of the lithium ion secondary battery 1 shown in FIG. 1, in which FIG. 3A shows a normal configuration and FIG. 3B shows the lithium ion secondary battery 1 suddenly. The state when the temperature is raised is shown.

As shown in FIG. 3A, the separator 12 may be a heat-resistant separator (film) including the porous film 5 and the heat-resistant layer 4. The heat-resistant layer 4 is laminated on one side of the porous film 5 on the cathode 11 side. The heat-resistant layer 4 may be laminated on one side of the porous film 5 on the anode 13 side, or may be laminated on both sides of the porous film 5. The heat-resistant layer 4 is also provided with a hole similar to the hole P. Usually, the lithium ions 3 come and go through the pores P and the pores of the heat-resistant layer 4. The heat-resistant layer 4 contains, for example, a total aromatic polyamide (aramid resin) as a material thereof.

As shown in FIG. 3B, the heat-resistant layer 4 assists the porous film 5 even if the lithium ion secondary battery 1 rapidly heats up and the porous film 5 melts or becomes flexible. Therefore, the shape of the porous film 5 is maintained. Therefore, the porous film 5 is melted or softened, and the pores P are only closed. As a result, the movement of the lithium ion 3 is stopped, so that the above-mentioned over-discharge or over-charge is also stopped. In this way, the destruction of the separator 12 is suppressed.

The separator of the lithium ion secondary battery 1 and the heat-resistant separator can be manufactured by using the following methods. Hereinafter, the case where the porous film 5 mainly contains polyethylene as its material will be described. However, even when the porous film 5 contains other materials, the separator 12 (heat-resistant separator) can be manufactured by the same manufacturing process.

Examples thereof include a method in which an inorganic filler or a plasticizer is added to a thermoplastic resin to form a film, and then the inorganic filler and the plasticizer are washed and removed with an appropriate solvent. When the porous film 5 is a polyolefin separator formed of a polyethylene resin containing ultra-high molecular weight polyethylene, it can be produced by the method shown below.

In this method, (1) ultra-high molecular weight polyethylene is kneaded with an inorganic filler (for example, calcium carbonate, silica) or a plasticizer (for example, low molecular weight polyolefin, liquid paraffin) to obtain a polyethylene resin composition. Steps, (2) a rolling step of forming a film using a polyethylene resin composition, (3) a removing step of removing an inorganic filler or a plasticizer from the film obtained in step (2), and (4). The stretching step of stretching the film obtained in the step (3) to obtain a porous film 5 is included. The step (4) can also be performed between the steps (2) and (3).

The removal step provides a large number of micropores in the film. The fine pores of the film stretched by the stretching step become the above-mentioned pores P. As a result, a porous film 5 (separator 12 having no heat-resistant layer), which is a polyethylene microporous film having a predetermined thickness and air permeability, can be obtained.

In the kneading step, 100 parts by weight of ultra-high molecular weight polyethylene, 5 to 200 parts by weight of low molecular weight polyolefin having a weight average molecular weight of 10,000 or less, and 100 to 400 parts by weight of an inorganic filler may be kneaded.

Then, in the coating step, the heat-resistant layer 4 is formed on the surface of the porous film 5. For example, the heat-resistant layer 4 which is an aramid heat-resistant layer is formed by applying an aramid / NMP (N-methyl-pyrrolidone) solution (coating solution) (coating step) to the porous film 5 and coagulating it (coagulation step). To form. The heat-resistant layer 4 may be provided on only one side of the porous film 5 or may be provided on both sides.

Further, in the coating step, the surface of the porous film 5 is coated with a polyvinylidene / dimethylacetamide solution (coating liquid) (coating step), and the porous film 5 is coagulated (coagulated step) to form the porous film 5. An adhesive layer can also be formed on the surface. The adhesive layer may be provided on only one side of the porous film 5 or may be provided on both sides.

In the present specification, a layer having a function such as adhesiveness to an electrode or heat resistance equal to or higher than the melting point of polyolefin is referred to as a functional layer.

The method of applying the coating liquid to the porous film 5 is not particularly limited as long as it can be uniformly wet-coated, and a conventionally known method can be adopted. For example, a capillary coating method, a slit die coating method, a spray coating method, a dip coating method, a roll coating method, a screen printing method, a flexographic printing method, a bar coater method, a gravure coater method, a die coater method and the like can be adopted. The thickness of the heat-resistant layer 4 can be controlled by the thickness of the coating wet film and the solid content concentration in the coating liquid.

As the support for fixing or transporting the porous film 5 at the time of coating, a resin film, a metal belt, a drum, or the like can be used.

As described above, the separator 12 (heat-resistant separator) in which the heat-resistant layer 4 is laminated on the porous film 5 can be manufactured. The manufactured separator is wound around a cylindrical core. The target manufactured by the above manufacturing method is not limited to the heat-resistant separator. This manufacturing method does not have to include a coating step. In this case, the object to be manufactured is a separator having no heat-resistant layer.

(Washing process)
Hereinafter, the film manufacturing method and the cleaning apparatus 6 according to the present embodiment will be described with reference to FIGS. 4 and 5.

In the following embodiments, a method (film manufacturing method) for cleaning a heat-resistant separator, which is a long and porous battery separator, is described. The heat-resistant layer of the heat-resistant separator is formed by applying an aramid / NMP (N-methyl-pyrrolidone) solution (coating liquid) to a porous film. At this time, the solvent NMP (substance to be removed) also impregnates the pores of the porous film.

The air permeability of the heat-resistant separator in which NMP remains in the pores is lower than the air permeability of the heat-resistant separator in which NMP does not remain in the holes. The lower the air permeability, the more the movement of lithium ions in the lithium ion secondary battery using the heat-resistant separator is hindered, so that the output of the lithium ion secondary battery decreases. Therefore, it is preferable that NMP can be washed so as not to remain in the holes of the heat-resistant separator.

FIG. 4 is a cross-sectional view showing the configuration of the cleaning device 6 according to the present embodiment. As shown in FIG. 4, the cleaning device 6 (film cleaning device) includes cleaning tanks 15 to 19. The washing tanks 15 to 19 are each filled with washing water W (cleaning liquid). Further, the cleaning device 6 further includes a plurality of rotatable rollers for conveying the heat-resistant separator S. Of these rollers, rollers a to n are rollers that convey the heat-resistant separator S to be washed in the washing tank 15.

The heat-resistant separator S conveyed from the upstream process (for example, the coating process) of the cleaning process passes through the cleaning water W filled in the cleaning tank 15 (hereinafter, “underwater”) via the rollers a to n. The rollers a to n (conveying rollers) define a transport path for the heat-resistant separator S in the cleaning tank 15. Also in the washing tanks 17 and 18, the heat-resistant separator S is conveyed by the same rollers a to n as in the washing tank 15. In the washing tanks 16 and 19, the heat-resistant separator S is conveyed by the same rollers a to m as in the washing tank 15, except that the roller n is omitted.

The cleaning device 6 further includes a drive roller R and auxiliary rollers p and q. The drive roller R is a roller that is rotationally driven by the power of a motor or the like. The drive roller R is driven so that the speed on the surface of the drive roller R is the same as the transfer speed of the heat resistant separator S. The drive roller R applies a force in the transport direction (MD: Machine direction) to the heat-resistant separator S between the washing tanks. The auxiliary rollers p and q define the range of the surface (so-called “holding angle”) of the drive roller R that comes into contact with the heat-resistant separator S. The hugging angle means the angle of the arc in contact with the film on the outer circumference of the roller with respect to the axis of the roller. The drive roller R and the auxiliary rollers p and q may be arranged in the washing water W, but it is preferable to arrange them between the washing tanks as shown in FIG. 4 because it is not necessary to take waterproof measures. ..

As described above, the drive roller R applies a force for conveying to the heat-resistant separator S between the position of the roller a of the cleaning tank 15 and the position of the roller m of the cleaning tank 19. Here, the roller a of the cleaning tank 15 is a roller immediately before the heat-resistant separator S is carried into the cleaning tank 15. The roller m of the cleaning tank 19 is a roller immediately after the heat-resistant separator S is carried out from the cleaning tank 19.

Then, the force of the drive roller R described above is preferably applied to the heat-resistant separator S between the roller l of the cleaning tank 16 and the roller b of the cleaning tank 17. For example, in the transport path, the heat-resistant separator S is driven after being carried out from the washing tank 16 on the upstream side (from water) and before being carried into the washing tank 17 on the downstream side (in water). It is preferable to arrange the roller R and the auxiliary rollers p and q.

In the cleaning method according to the present embodiment, the step of transporting the heat-resistant separator S in the longitudinal direction thereof and the heat-resistant separator S being transported are sequentially passed through the cleaning water W filled in the cleaning tanks 15 to 19. Includes a step of cleaning by. In this way, the heat-resistant separator S is sequentially conveyed from the upstream cleaning tank to the downstream cleaning tank. Here, unless otherwise specified, "upstream" and "downstream" mean upstream and downstream in the transport direction of the separator.

After the washing in the washing tanks 15 to 19 is completed, the heat-resistant separator S is conveyed to a downstream step (for example, a drying step) of the washing step.

By passing the heat-resistant separator S through the washing water W, NMP diffuses into the water through the holes of the heat-resistant separator S. Here, the diffusion amount of NMP increases as the NMP concentration of the washing water W decreases.

Since the heat-resistant separator S is washed in order in the washing tanks 15 to 19, the NMP concentration of the washing water W in the downstream washing tank is lower than that in the upstream washing tank. That is, since the diffusion of NMP progresses step by step, the NMP stuck in the holes can be reliably removed.

As shown in FIG. 4, the cleaning water W may flow in the direction D from the downstream cleaning tank 19 to the upstream cleaning tank 15 in the separator transport direction. For this reason, for example, the barrier between the cleaning tanks 15 to 19 may be lowered from downstream to upstream in the separator transport direction. At this time, in the cleaning method according to the present embodiment, the cleaning water W is supplied to the downstream cleaning tank, and the cleaning water W in the downstream cleaning tank is supplied to the upstream cleaning tank. The step of renewing the cleaning liquid of the above will be further included. A part of the cleaning water W is discharged from the upstream cleaning tank 15. According to this, the NMP concentration of the washing water W in the downstream washing tank in the separator transport direction can be made lower than the NMP concentration of the washing water W in the upstream washing tank while effectively using the washing water W. it can.

By advancing the diffusion of NMP step by step, NMP can be removed more efficiently than cleaning with only one washing tank. Therefore, the transport distance of the heat-resistant separator S during cleaning can be shortened. Therefore, the heat-resistant separator S, which has lower mechanical strength than the non-porous film, can be washed while suppressing breakage and tearing.

The wider the heat-resistant separator S, the higher the productivity. Therefore, the width of the heat-resistant separator S (the length in the direction perpendicular to the MD) is often increased to near the width of the washing tanks 15 to 19. The width of the cleaning tanks 15 to 19 is designed according to the width of the heat-resistant separator S.

When the width of the heat-resistant separator S is widened and the gap between the end of the heat-resistant separator S and the cleaning tanks 15 to 19 is narrowed, the cleaning water W filled in the cleaning tanks 15 to 19 becomes one surface side of the heat-resistant separator S (cleaning tank). (Center side) and other side (both ends of the cleaning tank (left and right ends in FIG. 4)).

In cleaning by the cleaning tanks 15 to 19, the cleaning water W is often supplied and discharged due to overflow between the cleaning tanks. At this time, although the cleaning water W divided on one surface side of the heat resistant separator S is supplied and discharged, the cleaning water W divided on the other surface side of the heat resistant separator S may stay.

Therefore, in the cleaning method according to the present embodiment, in at least one of the cleaning tanks 15 to 19, cleaning water is used to promote the replacement of the cleaning water W between one surface side and the other surface side of the heat-resistant separator S. It may include a step of circulating W. At this time, the cleaning device 6 may further include a circulation device having a supply / discharge port for the cleaning water W in at least one of the cleaning tanks 15 to 19. Thereby, the NMP concentration of the washing water W in one washing tank can be made more uniform, and the efficient removal of NMP can be promoted.

The cleaning water W is not limited to water, and may be any cleaning liquid that can remove NMP from the heat-resistant separator S. Further, the cleaning water W may contain a cleaning agent such as a surfactant, an acid (for example, hydrochloric acid) or a base. The temperature of the washing water W is preferably 120 ° C. or lower. At this temperature, the heat-resistant separator S is less likely to shrink. Further, the temperature of the washing water W is more preferably 20 ° C. or higher and 100 ° C. or lower.

The above method for cleaning the heat-resistant separator S can also be applied to a method for cleaning a separator having no heat-resistant layer (for example, a polyolefin separator).

The separator is formed by molding a polyolefin resin composition obtained by kneading a high molecular weight polyolefin such as ultra high molecular weight polyethylene with an inorganic filler or a plasticizer into a film shape and stretching the separator. Then, the inorganic filler or the plasticizer (substance to be removed) is washed away to form the pores of the separator.

The air permeability of the separator in which the substance to be removed remains in the pores without being washed away is lower than the air permeability of the separator in which the substance to be removed does not remain in the pores. The lower the air permeability, the more the movement of lithium ions in the lithium ion secondary battery using the separator is hindered, so that the output of the lithium ion secondary battery decreases. Therefore, it is preferable that the substance to be removed can be washed so as not to remain in the pores of the separator.

The cleaning liquid for cleaning the separator containing the inorganic filler may be any cleaning liquid capable of removing the inorganic filler from the separator. An aqueous solution containing an acid or a base is preferable.

The cleaning liquid for cleaning the separator containing the plasticizer may be any cleaning liquid capable of removing the plasticizer from the separator. An organic solvent such as dichloromethane is preferable.

Summarizing the above, the method for cleaning the polyolefin resin composition (film) formed into a film includes a step of transporting a long film, which is an intermediate product of a separator, in the longitudinal direction, and a step of transporting this film during transport. It includes a step of performing cleaning by sequentially passing through the cleaning liquid filled in the cleaning tanks 15 to 19 described above.

As described above, in FIG. 4, the heat-resistant separator S may be used as a film which is an intermediate product of the separator. Further, the washing water W may be an aqueous solution containing an acid or a base.

The method for producing a polyolefin separator is a molding step of molding a long film containing polyolefin as a main component, which is an intermediate product of a long and porous separator, and the above-mentioned molding step executed after the molding step. It can be interpreted as including each step included in the film cleaning method.

The present invention also includes a method for manufacturing a heat-resistant separator S using a method for cleaning the heat-resistant separator S, which is a laminated separator. Here, the heat-resistant separator S is a laminated separator including the porous film 5 (base material) shown in FIG. 3 and the heat-resistant layer 4 (functional layer) laminated on the porous film 5. Then, this manufacturing method can be interpreted to include a molding step of molding a long and porous heat-resistant separator S, and each step of the above-mentioned separator cleaning method executed after the molding step.

The "molding step" is a coating step of applying NMP (liquid substance) containing an aramid resin (substance) constituting the heat-resistant layer 4 to the porous film 5 in order to laminate the heat-resistant layer 4, and after this coating step. It includes a coagulation step of coagulating the aramid resin.

The "steps" are a step of transporting the heat-resistant separator S in the longitudinal direction thereof and a step of sequentially passing the heat-resistant separator S being transported through the cleaning water W filled in the cleaning tanks 15 to 19 to perform cleaning. It means the process to be performed.

As described above, it is possible to manufacture a laminated separator having a small amount of NMP and suppressed breakage and tearing. The heat-resistant layer may be the above-mentioned adhesive layer.

(M-shaped path)
From here, the roller m, the roller n, and the roller a included in the cleaning device 6 will be described in more detail. Here, the roller m, the roller n, and the roller a arranged between the cleaning tank 15 and the cleaning tank 16 will be described. However, the same can be said for the rollers m, the rollers n, and the rollers a arranged between the cleaning tank 17 and the cleaning tank 19.

FIG. 5 is a cross-sectional view of a set of rollers m, n, and a in the cleaning device 6 shown in FIG. The set of roller m (first roller), roller n (second roller), and roller a (third roller) is a cleaning tank 15 (first cleaning tank) on the upstream side and a cleaning tank 16 on the downstream side in the transport path. It is provided between (the second washing tank). The roller n is arranged between the roller m and the roller a. In top view, the roller m and the roller n are located within the range of the cleaning tank 15, and the roller a is located within the range of the cleaning tank 16. The rollers m, n, and a may be drive rollers that are rotationally driven by power, or may be driven rollers that rotate by frictional force with the heat-resistant separator S. Here, the speed of the surfaces of the rollers m, n, and a is the same as the transport speed of the heat-resistant separator S.

The heat-resistant separator S carried out from the washing tank 15 (from the water) comes into contact with the roller m, the roller n, and the roller a in this order, and is carried into the washing tank 16 (in the water). The roller m, the roller n, and the roller a transport the heat-resistant separator S between the washing tanks (conveying step).

The rollers m and a come into contact with one surface Sm of the heat resistant separator S. Between the roller m and the roller a, the roller n comes into contact with the other surface Sn of the heat resistant separator S. The rollers m and a support one side (lower side) of the heat-resistant separator S, and the roller n presses the heat-resistant separator S from the other side (upper side) of the heat-resistant separator S. With the roller n as a boundary, the transport direction of the heat-resistant separator S changes from descending to ascending. The heat-resistant separator S passes through an M-shaped transport path when viewed from the axial direction of the roller m. When the rollers m come into contact with each other, the cleaning water W adhering to the surface Sm side of the heat resistant separator S is removed from the heat resistant separator S. Further, when the rollers n come into contact with each other, the cleaning water W adhering to the surface Sn side of the heat resistant separator S is removed from the heat resistant separator S. The cleaning water W adhering to the heat-resistant separator S carried out from the cleaning tank 15 has the same degree of contamination (equivalent concentration of the object to be removed) as the cleaning water W filled in the cleaning tank 15.

The cleaning water W removed from the surface Sm by the roller m returns to the upstream cleaning tank 15. Similarly, the cleaning water W removed from the surface Sn by the roller n returns to the upstream cleaning tank 15. For example, the washing water W moves on the upper surface Sn of the heat-resistant separator S along the roller n in the width direction of the heat-resistant separator S and spills from the end of the heat-resistant separator S.

When the rollers m and n are within the range of the washing tank 15 in the top view, the washing water W dropped from the rollers m and n returns to the washing tank 15. Alternatively, if at least the lower ends of the rollers m and n are within the range of the washing tank 15, the washing water W dropped from the rollers m and n returns to the washing tank 15. Alternatively, a gutter may be provided under the rollers m and n, and the removed washing water W may be returned to the washing tank 15 through the gutter.

As a result, the moisture adhering to both sides of the heat-resistant separator S carried out from the cleaning tank 15 is removed from the heat-resistant separator S and dropped into the cleaning tank 15. As a result, the amount of the washing water W filled in the washing tank 15 (dirty than the washing water W filled in the washing tanks 16 to 19) is brought into the washing tanks 16 to 19 on the downstream side of the washing tank 15. Can be reduced. Therefore, it is possible to prevent contamination of the cleaning water W filled in the cleaning tanks 16 to 19 (increased concentration of the object to be removed). Further, by removing the liquid having a high concentration of the object to be removed adhering to the surface of the heat-resistant separator S from the surface of the heat-resistant separator S between the cleaning tanks, the object to be removed from the heat-resistant separator S more efficiently in the downstream cleaning tank. Things can be diffused.

FIG. 6 is a cross-sectional view showing an example of arrangement of gutters when a gutter is provided in the cleaning device. As shown in FIG. 6, a gutter 20 may be provided between the washing tank 15 and the washing tank 16. Here, in top view, the lowest points of the rollers n and a are included in the range of the gutter 20. When a gutter is provided under the roller m, the roller n, or the roller a, the roller need not be located within the range of the washing tank 15. Here, the roller n is located between the washing tank 15 and the washing tank 16. The washing water W that has fallen from the roller m returns to the washing tank 15 as it is. The washing water that has fallen from the rollers n and a is received by the gutter 20 and returns to the washing tank 15 through the gutter 20.

When viewed from the transverse direction (TD), the positions of the rotation axes of the three rollers m, n, and a are preferably arranged in a straight line. In other words, it is preferable that the rotation axes of the three rollers m, n, and a are located on one plane. Further, the holding angle of the roller n is preferably less than 180 degrees. The holding angle means the angle of the arc in contact with the heat-resistant separator S on the roller with respect to the axis of the roller. That is, the transport direction of the heat-resistant separator S before and after the roller changes by the amount of the holding angle of the roller.

(Rotation of rollers)
The speed of the surface np of the roller n may be different from the transport speed of the heat resistant separator S. That is, the surface np (curved surface) of the roller n and the heat-resistant separator S slide. In this case, the roller n may be a drive roller that is rotationally driven at a predetermined speed, or may be a driven roller. When the surface np of the roller n and the heat-resistant separator S slide, the surface np of the roller n (the portion in contact with the heat-resistant separator S) is preferably formed of resin. If the surface np of the roller n is a resin, the frictional force with the heat-resistant separator S can be reduced, and wear and breakage of the heat-resistant separator S can be suppressed.

When the roller n is a driven roller, the surface np of the roller n can be configured to be dragged by the heat-resistant separator S by increasing the frictional force between the roller n and its shaft to some extent.

When the roller n is a drive roller, the direction in which the surface np of the roller n rotates and moves may be the same as or different from the transport direction of the heat-resistant separator S. When the direction in which the surface np of the roller n rotates is different from the transport direction of the heat-resistant separator S, the cleaning water W is more efficiently removed from the surface Sn of the heat-resistant separator S by sliding between the roller n and the heat-resistant separator S. be able to.

Further, the roller n may be fixed so as not to rotate. Further, the surface of the roller n may be made of metal.

The rollers m and a may have the same configuration as the rollers n.

(Roller surface shape)
Further, the surface np of the roller n may be provided with an uneven shape. For example, as an uneven shape, a spiral groove, a curved groove, or a linear groove may be formed on the surface np of the roller n. It is preferable that the groove on the surface np of the roller n extends beyond the end portion of the heat resistant separator S in the width direction of the heat resistant separator S. As a result, the washing water removed between the roller n and the heat-resistant separator S is discharged to the outside in the width direction from the heat-resistant separator S through the groove. It is preferable that the spiral groove is formed so that the portion facing the heat-resistant separator S shifts outward in the width direction of the heat-resistant separator S with time. Further, the linear groove may be formed so as to be parallel to the axis of the roller n.

Similarly, an uneven shape (groove) may be formed on the surfaces of the rollers m and a. A gutter may be provided under the roller a so that the washing water W removed by the roller a returns to the washing tank 15.

In the cleaning device 6, instead of the heat-resistant separator S, various films such as a separator having no functional layer or a plastic film having no holes may be cleaned.

[Another interpretation of this embodiment]
The present embodiment can also be interpreted as follows.

The film manufacturing method according to the present embodiment includes a cleaning step of cleaning the film in the first cleaning tank and contacting the first roller, the second roller, and the third roller with the film carried out from the first cleaning tank. In the transporting step, the first roller and the third roller are in contact with one surface of the film, and the first roller and the first roller are included. When the second roller comes into contact with the other surface of the film with the third roller, the cleaning liquid is removed from the film, and the cleaning liquid removed from the film by the second roller is used as the first cleaning liquid. Return to the washing tank.

According to the above configuration, the cleaning liquid adhering to both sides of the film is removed by the first roller and the second roller between the cleaning tanks. The cleaning liquid removed by the second roller is returned to the upstream first cleaning tank. Therefore, the amount of the cleaning liquid in the first cleaning tank brought into the second downstream cleaning tank can be reduced. Therefore, contamination of the cleaning liquid in the second cleaning tank can be suppressed.

Further, the speed of the surface of the second roller may be different from the transport speed of the film.

According to the above configuration, the second roller and the film slide. Therefore, the cleaning liquid adhering to the film can be removed more efficiently.

Further, the second roller may be rotationally driven.

According to the above configuration, the film can be pulled in the transport direction by setting the speed of the surface of the second roller to be equal to or higher than the transport speed of the film. The film that passes through the liquid is subject to resistance due to the viscosity of the liquid. By driving the second roller between the washing tanks, the tension of the film on the upstream side of the second roller can be reduced and the film can be prevented from breaking. Further, by setting the speed of the surface of the second roller to be lower than the transport speed of the film, the cleaning liquid adhering to the film can be removed more efficiently.

Further, the surface of the second roller may be provided with an uneven shape.

According to the above configuration, the cleaning liquid removed from the film due to the uneven shape can be efficiently discharged to the outside of the film.

Further, a spiral, curved, or linear groove may be provided on the surface of the second roller.

According to the above configuration, the cleaning liquid removed from the film can be discharged through the groove.

Further, the groove of the second roller may extend beyond the end portion of the film in the width direction of the film.

According to the above configuration, the cleaning liquid removed from the film can be discharged to the outside in the width direction of the film through the groove.

Further, the surface of the second roller that slides on the film may be formed of resin.

According to the above configuration, it is possible to prevent the film from being worn or broken.

The film cleaning apparatus according to the present embodiment is in contact with the first cleaning tank and the second cleaning tank for cleaning the film and the film carried out from the first cleaning tank, and the film is brought into contact with the second cleaning tank. The first roller, the second roller, and the third roller are provided, the first roller and the third roller come into contact with one surface of the film, and the first roller and the third roller are conveyed to the film. When the second roller comes into contact with the other surface of the film with the roller, the second roller removes the cleaning liquid from the film, and the cleaning liquid removed from the film by the second roller is the first. 1 The configuration returns to the washing tank.

Further, the speed of the surface of the second roller may be different from the transport speed of the film.

Further, the second roller may be configured to be rotationally driven.

Further, the surface of the second roller may be provided with an uneven shape.

Further, the surface of the second roller may be provided with a spiral or linear groove.

Further, the groove of the second roller may extend beyond the end portion of the film in the width direction of the film.

Further, the surface of the second roller that slides on the film may be formed of a resin.

The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and the embodiments obtained by appropriately combining the technical means disclosed in the different embodiments. Is also included in the technical scope of the present invention.

6 Cleaning equipment (film cleaning equipment)
12 Separator (film)
15 and 16 cleaning tanks (1st cleaning tank, 2nd cleaning tank)
S heat resistant separator (film)
W Washing water (cleaning liquid)
m roller (first roller)
n roller (second roller)
a Roller (3rd roller)

Claims (20)

A cleaning step of cleaning the separator film for the non-aqueous electrolyte secondary battery in the first cleaning tank, and
The first roller, the second roller, and the third roller are brought into contact with the separator film for the non-aqueous electrolyte secondary battery carried out from the first cleaning tank in order, and the separator film for the non-aqueous electrolyte secondary battery is brought into contact with each other in this order. Includes a transfer step of transporting the battery to the second cleaning tank.
In the above transfer process,
The first roller and the third roller are in contact with one surface of the separator film for a non-aqueous electrolyte secondary battery, and the second roller is between the first roller and the third roller. By contacting the other surface of the separator film for the non-aqueous electrolyte secondary battery, the cleaning liquid is removed from the separator film for the non-aqueous electrolyte secondary battery, and then the separator film for the non-aqueous electrolyte secondary battery is removed. To the second washing tank,
A method for producing a separator film for a non-aqueous electrolytic solution secondary battery, wherein the cleaning liquid filled in the first cleaning tank and the cleaning liquid filled in the second cleaning tank are of the same type. The method for producing a separator film for a non-aqueous electrolyte secondary battery according to claim 1, wherein the speed of the surface of the second roller is different from the transport speed of the separator film for the non-aqueous electrolyte secondary battery. Rotately drive the second roller to
The method for producing a separator film for a non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the second roller is a drive roller that is rotationally driven by power. The method for producing a separator film for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the surface of the second roller is provided with an uneven shape. The method for producing a separator film for a non-aqueous electrolyte secondary battery according to claim 4, wherein a spiral, curved, or linear groove is provided on the surface of the second roller. The groove according to claim 5, wherein the groove of the second roller extends beyond the end of the separator film for the non-aqueous electrolyte secondary battery in the width direction of the separator film for the non-aqueous electrolyte secondary battery. Non-aqueous electrolyte solution Separator film manufacturing method for secondary batteries. The method for producing a separator film for a non-aqueous electrolyte secondary battery according to claim 2, wherein the surface of the second roller that slides on the separator film for the non-aqueous electrolyte secondary battery is formed of a resin. .. In the above transfer process,
The first roller and the third roller are in contact with one surface of the separator film for a non-aqueous electrolyte secondary battery, and the second roller is between the first roller and the third roller. By contacting the other surface of the separator film for the non-aqueous electrolyte secondary battery, the cleaning liquid adhering to the separator film for the non-aqueous electrolyte secondary battery in the first cleaning tank is removed from the non-aqueous electrolyte secondary battery. The method for producing a separator film for a non-aqueous electrolytic solution secondary battery according to any one of claims 1 to 7, wherein the separator film is removed from the battery separator film. The non-aqueous electrolyte secondary battery according to any one of claims 1 to 8, wherein the cleaning liquid removed from the separator film for the non-aqueous electrolyte secondary battery by the second roller is returned to the first cleaning tank. Separator film manufacturing method. The method for producing a separator film for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 9, wherein the temperature of the cleaning liquid is 20 ° C. or higher and 100 ° C. or lower. The first cleaning tank and the second cleaning tank for cleaning the separator film for the non-aqueous electrolyte secondary battery, and
A first roller that sequentially contacts the separator film for the non-aqueous electrolyte secondary battery carried out from the first cleaning tank and conveys the separator film for the non-aqueous electrolyte secondary battery to the second cleaning tank. , A second roller, and a third roller,
The first roller and the third roller are in contact with one surface of the separator film for a non-aqueous electrolyte secondary battery, and the second roller is between the first roller and the third roller. By contacting the other surface of the non-aqueous electrolyte secondary battery separator film, the second roller removes the cleaning liquid from the non-aqueous electrolyte secondary battery separator film, and then the non-aqueous electrolyte solution. Transfer the separator film for the secondary battery to the second cleaning tank and
A separator film cleaning device for a non-aqueous electrolytic solution secondary battery in which the cleaning liquid filled in the first cleaning tank and the cleaning liquid filled in the second cleaning tank are of the same type. The separator film cleaning device for a non-aqueous electrolyte secondary battery according to claim 11, wherein the speed of the surface of the second roller is different from the transport speed of the separator film for the non-aqueous electrolyte secondary battery. The second roller is rotationally driven and driven.
The separator film cleaning device for a non-aqueous electrolyte secondary battery according to claim 11 or 12, wherein the second roller is a drive roller that is rotationally driven by power. The separator film cleaning device for a non-aqueous electrolyte secondary battery according to any one of claims 11 to 13, wherein the surface of the second roller is provided with an uneven shape. The separator film cleaning apparatus for a non-aqueous electrolyte secondary battery according to claim 14, wherein a spiral, curved, or linear groove is provided on the surface of the second roller. The groove according to claim 15, wherein the groove of the second roller extends beyond the end of the separator film for the non-aqueous electrolyte secondary battery in the width direction of the separator film for the non-aqueous electrolyte secondary battery. Separator film cleaning device for non-aqueous electrolyte secondary batteries. The separator film cleaning apparatus for a non-aqueous electrolyte secondary battery according to claim 12, wherein the surface of the second roller that slides on the separator film for the non-aqueous electrolyte secondary battery is formed of a resin. .. The first roller and the third roller are in contact with one surface of the separator film for a non-aqueous electrolyte secondary battery, and the second roller is between the first roller and the third roller. By contacting the other surface of the non-aqueous electrolyte secondary battery separator film, the second roller removes the cleaning liquid adhering to the non-aqueous electrolyte secondary battery separator film in the first cleaning tank. The separator film cleaning device for a non-aqueous electrolyte secondary battery according to any one of claims 11 to 17, which is removed from the separator film for a water electrolyte secondary battery. The non-aqueous electrolyte secondary battery according to any one of claims 11 to 18, wherein the second roller returns the cleaning liquid removed from the separator film for the non-aqueous electrolyte secondary battery to the first cleaning tank. Separator film cleaning device for. The separator film cleaning apparatus for a non-aqueous electrolytic solution secondary battery according to any one of claims 11 to 19, wherein the temperature of the cleaning liquid is 20 ° C. or higher and 100 ° C. or lower.

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