Manufacturing method of PP / CA separation membrane and battery using the same

Abstract

The present invention is a technology relating to a double-layer separation membrane of PP and CA. In the present invention, CA is coated on a PP film containing a plasticizer, and then pores are formed in the CA film by water pressure treatment. When the separator of the present invention is used as a separator for a battery, it is possible to realize a battery that is thermally stable and can be used for a long period of time due to its thermal and mechanical stability.

Description

[Technical field]

[0001] The present invention relates to a PP-based separator membrane, which is a double-structure porous separator membrane in which two porous films, a PP film and a CA film, are bonded together, and relates to a technology that uses a plasticizer and water pressure treatment to form pores in the CA. [Background technology]

[0002] As one way to solve various energy problems related to energy storage / supply / demand, including environmental pollution and energy depletion, lithium-ion batteries (LIBs) are being applied in various technological fields such as energy storage technology, portable electronic products, and electric vehicles, and show superior electrical properties compared to conventional secondary batteries.

[0003] Due to the recent tightening of environmental regulatory standards in many countries, the market for lithium-ion secondary batteries is expected to further increase.

[0004] However, despite the high value of lithium-ion secondary batteries, the fire problem has emerged as their biggest drawback.

[0005] In particular, in a lithium ion secondary battery, the separator must maintain high porosity and ionic conductivity while also maintaining thermal and mechanical stability. The separator disposed between the electrodes plays a very important role in preventing short circuits between the electrodes and fires caused by external impact.

[0006] Looking at recent trends related to separators for lithium-ion secondary batteries, highly stable polyimide-based materials have been attracting attention as materials for polymer separators and are widely sold commercially.

[0007] However, polyimide-based materials are relatively expensive, and research into cheaper and more efficient materials is ongoing.

[0008] Zhao et al. published research showing that organic / inorganic hybrid cross-linking can enhance the thermal stability of commercially available olefin separation membranes.

[0009] The above studies have shown that cross-linking of silicon with oxygen enhances thermal stability and provides adhesion between films.

[0010] In addition, Zhang et al. 2 O 3 / PVDF coated separator was used to complement the performance of Li-S battery, but Al 2 O 3 The structure of the PVDF-coated separator promotes the mobility of lithium ions, and the reversible capacity was found to be extremely high even after 50 cycles.

[0011] In addition, Liu et al. 2 / Research results were presented showing that PAM-grafted PP separators have excellent thermal stability and electrochemical performance due to surface chemical modification.

[0012] Compared to the high temperature shrinkage rate of typical PP separators, the separators in the above study showed lower high temperature shrinkage rates.

[0013] The separator is reported to improve the stability and cycling performance of the battery.

[0014] In addition, Liu et al. used active silicon nanoparticles to uniformly support graphene.

[0015] The study reports that this method allows for the production of highly stable batteries because a three-dimensional network is formed and the interactions between the molecules are strong.

[0016] The study reported that the initial efficiency increased to 93.2% and the capacity retention rate was excellent even after 100 cycles at high current density. Summary of the Invention [Problem to be solved by the invention]

[0017] The present invention aims to provide a manufacturing technique for a novel PP-based separator having improved mechanical, thermal and electrical properties compared to conventional PP-based separators, and a technique relating to a battery using the same.

[0018] In particular, the present invention aims to provide a separator having excellent thermal and mechanical stability by using a double-layer separator of a PP film and a CA film.

[0019] In particular, the present invention aims to provide a technique for forming pore channels penetrating the PP film and the CA film. [Means for solving the problem]

[0020] The present invention relates to a method for producing a PP / CA separator having a double-layer structure of a PP film and a CA film, the method comprising the steps of preparing a porous PP film, and applying a CA film on the porous PP film. 、 Plasticizer and solution and applying water pressure to the PP / CA separation membrane to form pore channels penetrating the PP film and the CA film.

[0021] In particular, the plasticizer may be, for example, glycerin, lactic acid, CaO, glycolic acid, NaCl, NaNO 3 and propylene glycol.

[0022] In particular, in the mixed solution of CA and plasticizer, the molar ratio of CA:plasticizer is, for example, 1:0.001 to 0.3.

[0023] In particular, the solvent is, for example, a mixed solvent of two or more kinds.

[0024] In particular, the water pressure treatment direction is, for example, from the PP film to the CA film.

[0025] In particular, the water pressure is, for example, between 2 and 20 bar.

[0026] In addition, the present invention can further produce a battery using the PP / CA separator.

[0027] In particular, said battery is, for example, an MFC. Effect of the Invention

[0028] The present invention relates to a technology for a double-layer separator of PP / CA. The separator of the present invention is a composite separator that has both the physical strength of PP and the thermal stability of CA. When the separator of the present invention is applied to a battery, it not only reduces the possibility of fire compared to batteries using conventional separators due to its high thermal stability, but also has the advantage that the electrical properties do not change even after long-term use.

[0029] In addition, in the present invention, by coating a CA film on a PP film to impart hydrophilicity to the surface of the PP film, fouling occurring on the surface of the PP film is reduced, and as a result, there is an advantage in that the durability of an MFC battery to which the separator of the present invention is applied can be improved. [Brief description of the drawings]

[0030] [Figure 1] FIG. 1 is a schematic diagram showing a method for producing a PP / CA-CaO separation membrane of the present invention when CaO is used as a plasticizer. [Figure 2a]FIG. 2a is a SEM photograph of the PP side surface of the PP / CA-lactic acid separation membrane. [Figure 2b] FIG. 2b is an enlarged view of the circle in FIG. 2a. [Figure 2c] Figure 2c is a SEM photograph of the CA side surface of the PP / CA-lactic acid film. [Figure 2d] FIG. 2d is an enlarged view of the circle in FIG. 2c. [Figure 2e] FIG. 2e is a SEM photograph of the cross section of the PP / CA-lactic acid separation membrane. [Figure 3a] FIG. 3a shows the results of an FT-IR experiment on the separation membrane of the present invention and the separation membrane of the comparative example. [Figure 3b] FIG. 3b shows the results of an FT-IR experiment on the separation membrane of the present invention and the separation membrane of the comparative example. [Figure 3c] FIG. 3c shows the results of an FT-IR experiment on the separation membrane of the present invention and the separation membrane of the comparative example. [Figure 4a] Figure 4a is a neat PP film. [Figure 4b] FIG. 4b is a SEM photograph of the PP side of the PP / CA-glycerin separation membrane. [Figure 5a] Figure 5b shows the surface SEM images of the CA-glycerin film before and after water treatment, respectively. [Figure 5b] Figure 5b shows the surface SEM images of the CA-glycerin film before and after water treatment, respectively. [Figure 5c] Figure 5c is a SEM photograph of the CA side of the PP / CA-glycerin separation membrane. [Figure 6a] Figure 6a shows the TGA data of neat PP, neat CA, CA-glycerin (before water pressure treatment), CA-glycerin (water pressure treatment at 8 bar), and PP / CA-glycerin separation membranes. [Figure 6b] FIG. 6b is an enlarged view of FIG. 6a. [Figure 7a] Figure 7a shows the FT-IR experimental results of the COC ether groups (960–1100 cm−1) of neat PP, CA-glycerin film, and PP / CA-glycerin separation membrane. [Figure 7b] Figure 7b shows the FT-IR experimental results of the COC ether groups (960–1100 cm−1) of neat PP, CA-glycerin film, and PP / CA-glycerin separation membrane. [Figure 8a] Figure 8a shows the deconvoluted data of the FT-IR measurement results for the ether groups (960-1100 cm-1) of the CA-glycerin (treated at 8 bar water pressure) and PP / CA-glycerin separation membranes (treated at 8 bar water pressure), respectively. [Figure 8b] Figure 8b shows the deconvoluted data of the FT-IR measurement results for the ether groups (960-1100 cm-1) of the CA-glycerin (treated at 8 bar water pressure) and PP / CA-glycerin separation membranes (treated at 8 bar water pressure), respectively. [Figure 9a] Figure 9a shows the FT-IR spectra of the carbonyl group (1690–1780 cm−1) of neat PP, CA-glycerin, and PP / CA-glycerin separation membranes. [Figure 9b] Figure 9b shows the FT-IR spectra of the carbonyl group (1690–1780 cm−1) of neat PP, CA-glycerin, and PP / CA-glycerin separation membranes. [Figure 10a] Figure 10a shows the deconvolution data of the FT-IR spectra of the carbonyl group (1690–1780 cm−1) of neat PP, CA-glycerin, and PP / CA-glycerin separation membranes, respectively. [Figure 10b] Figure 10b shows the deconvolution data of the FT-IR spectra of the carbonyl group (1690–1780 cm−1) for neat PP, CA-glycerin, and PP / CA-glycerin separation membranes, respectively. [Figure 11a] FIG. 11a shows the SEM measurement results of CA-CaO (all samples were after water treatment). [Figure 11b] FIG. 11b shows the SEM measurement results of the CA side of PP / CA-CaO (all samples were after water treatment). [Figure 11c] FIG. 11c shows the SEM measurement results of neat PP (all samples were after water treatment). [Figure 11d] FIG. 11d shows the SEM measurement results of the PP side of PP / CA-CaO (all samples were after water treatment). [Figure 12] Figure 12 shows the TGA experimental results for various samples (neat CA, CA-CaO, CA-CaO after water pressure, PP / CA-CaO after water pressure, and neat PP). [Figure 13a] Figure 13a shows the FT-IR data of carbonyl groups for the neat CA, CA-CaO (before hydraulic treatment), and CA-CaO (after hydraulic treatment) samples, respectively. [Figure 13b] Figure 13b shows the FT-IR data of carbonyl groups for the neat CA, CA-CaO (before hydraulic treatment), and CA-CaO (after hydraulic treatment) samples, respectively. [Figure 13c] Figure 13c shows the FT-IR data of carbonyl groups for the neat CA, CA-CaO (before hydraulic treatment), and CA-CaO (after hydraulic treatment) samples, respectively. [Figure 14a] FIG. 14a shows the FT-IR measurement results of various samples containing the PP / CA-CaO of the present invention. [Figure 14b] FIG. 14b is an enlarged view of the ether group (960 to 1100 cm-1) portion. [Figure 14c] FIG. 14c is an enlarged view of the carbonyl group (1700-1800 cm-1). [Figure 15a] FIG. 15 is deconvolution data of the ether group of CA-CaO. [Figure 15b] Figure 15b shows the deconvolution data of the ether groups on the CA side of P / CA-CaO. [Figure 15c] Figure 15c shows the deconvolution data of the ether groups on the PP side of PP / CA-CaO. [Figure 16a]FIG. 16a shows the deconvolution data of the carbonyl groups of CA-CaO. [Figure 16b] Figure 16b shows the deconvolution data of the carbonyl groups on the CA side of PP / CA-CaO. [Figure 16c] Figure 16c shows the deconvolution data of the carbonyl group on the PP side of PP / CA-CaO. [Figure 17] Figure 17 shows the voltage measurement results of the MFC. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] The present invention provides a method for manufacturing a PP / CA separator having a double-layer structure of a PP film and a CA film, the method including the steps of preparing a porous PP film, coating a mixed solution containing CA and a plasticizer on the porous PP film at least once and drying the film to manufacture a PP / CA separator, and applying water pressure to the PP / CA separator to form pore channels penetrating the PP film and the CA film.

[0032] In the present invention, PP means polypropylene, CA means cellulose acetate, neat PP means a porous separation membrane made of PP only, neat CA means a film (or separation membrane) made of CA only, "PP / CA-lactic acid" means a double-layer separation membrane of PP and CA prepared by coating a mixed solution of CA and lactic acid as a plasticizer on a PP layer and drying it, "PP / CA-glycerin" means a double-layer separation membrane of PP and CA using glycerin as a plasticizer, and "PP / CA-CaO" means a double-layer separation membrane of PP and CA prepared using CaO as a plasticizer. "PP / CA" is used in the claims to generically refer to the double-layer separation membrane of PP and CA prepared using the various plasticizers.

[0033] In the present invention, the terms "film" and "layer" are used interchangeably as terms meaning a thin film. For example, the terms "PP film" and "PP layer" are used interchangeably depending on the description.

[0034] The plasticizer of the present invention may be completely removed in the CA after the hydraulic treatment, or a portion may remain.

[0035] Whether or not this remains after hydraulic treatment is determined by the presence or absence of a chemical bond between the plasticizer and CaO.

[0036] For example, some of the CaO remains in the CA film layer even after the water pressure treatment, and the lactic acid is removed.

[0037] In the present invention, the role of the plasticizer is to weaken the binding strength of CA chains and to allow pores to form between the CA chains during water pressure treatment. The components of the plasticizer have a strong interaction with CA and are removed when pores are formed by water pressure treatment, but some may remain in the CA film.

[0038] The plasticizer of the present invention can be a variety of chemicals that can impart a plasticizing effect to the CA layer.

[0039] For example, glycerin, lactic acid, CaO, glycolic acid, NaCl, NaNO 3 , propylene glycol, but the present invention is not limited to a specific type of plasticizer.

[0040] The present invention is not limited to a specific plasticizer component as long as it is sufficient to weaken the binding force of the CA chain and form pores in the CA chain weakened by the water pressure treatment.

[0041] In the present invention, the water pressure during the water pressure treatment is, for example, 2 to 20 bar, but the pressure can be adjusted within the above range depending on the type of plasticizer, the desired pore size, and the like.

[0042] In the mixed solution, the plasticizer can be mixed in the range of 0.001 to 0.3 mol per 1 mol of CA.

[0043] The content of the plasticizer can be adjusted within the above range depending on the components of the plasticizer.

[0044] FIG. 1 is a schematic diagram showing a method for producing a PP / CA-CaO separation membrane of the present invention when CaO is used as a plasticizer.

[0045] In the present invention, a PP film with pores formed therein is fixed on a glass substrate, and then a mixed solution of CA and CaO is coated on the PP film and dried to prepare a double-layer separator of PP / CA-CaO.

[0046] In addition, in the present invention, the mixed solution of CA and CaO can be coated again on the PP / CA-CaO double layer separator and dried, and a third or fourth coating can be performed as necessary.

[0047] In the present invention, water pressure is applied to the PP / CA-CaO double-layer separation membrane from the PP side toward the CA-CaO.

[0048] By the water pressure treatment, the water pressure is transmitted to the CA-CaO film through the pores in the PP film where pores have already been formed, and as a result, pores are also formed in the CA-CaO film by the water pressure.

[0049] In particular, since the water pressure is transmitted to the CA-CaO film through the pores of the PP film, pores connected to the pores of the PP film are naturally formed in the CA-CaO film.

[0050] As mentioned above, CaO acts as a plasticizer that loosens the chain connections between CA chains to form pores in the CA film. The CA chains weakened by CaO become pores that are connected to the pores in the PP film by water pressure, forming almost straight pore channels that penetrate the PP film and the CA film.

[0051] In the following, the present invention will be explained in more detail with experimental results of various plasticizers.

[0052] Experimental example 1: PP / CA-lactic acid separation membrane In this experiment, we propose a method to combine an environmentally friendly and low-cost CA film with a PP film to manufacture a single separation membrane.

[0053] 1-1) Manufacturing of "PP / CA-lactic acid" separation membrane In this experiment, CA (Mw=30000, Sigma-Aldrich, USA), lactic acid (Daejung Chemical, Korea), and acetone (Daejung Chemical) were used. In this experiment, PP film (pore size 20 nm, GVS) was used as a polymer support. In this experiment, all materials were used without additional treatment after purchase. In this experiment, H 2 CA was dissolved in a mixed solvent with a weight ratio of O:acetone = 2:8 to prepare a 10 wt% CA mixed solution. Lactic acid was added to the CA solution so that the molar ratio of CA:lactic acid was 1:0.07 to prepare a CA-lactic acid mixed solution, which was then stirred at room temperature for 4 hours.

[0054] A PP film with pores already formed (pore size: 200 nm) was fixed on a glass plate. The CA-lactic acid mixed solution was coated on the PP film to a thickness of 300 μm using a doctor blade and dried. The CA-lactic acid solution was coated again on the first coated PP film and dried, so that the CA-lactic acid solution was coated on the PP film a total of two times. The PP / CA-lactic acid film was subjected to water pressure in a water treatment equipment, with the water pressure being applied in the direction from the PP film to the CA-lactic acid film. The water pressure was applied starting from 2 bar and increasing to 8 bar. The water flux during the water pressure treatment was also measured.

[0055] 1-2) SEM Figure 2a is a SEM photograph of the PP side of the PP / CA-lactic acid separation membrane, and it was confirmed that sponge-like pores were formed. Figure 2b is an enlarged view of the circle in Figure 2a, and the white part is the PP part affected by CA.

[0056] Figure 2c is a SEM photograph of the CA side surface of the PP / CA-lactic acid film, and Figure 2d is an enlarged view of the circle in Figure 2c. The white parts are the parts where the CA was plasticized by lactic acid, and many pores were observed in the plasticized areas. In other words, the CA parts weakened by lactic acid were formed as pores by water pressure treatment. The average pore size was less than 1 μm.

[0057] Figure 2e is an SEM photograph of the cross section of the PP / CA-lactic acid separation membrane. The top is the cross section of the CA film, and the bottom is the cross section of the PP film. No separation phenomenon was observed at the interface between CA and PP, confirming that the PP film and CA-lactic acid film were well bonded. Because the two films were well bonded, it was found that the physical strength of the PP / CA-lactic acid separation membrane was strengthened compared to each film alone.

[0058] 1-3) FT-IR 3a to 3c show FT-IR experimental results for the separation membrane of the present invention and a comparative example.

[0059] FT-IR experiments on the PP / CA-lactic acid separation membrane were conducted to verify the interaction between CA and PP. FT-IR experiments were conducted on the CA-lactic acid film, PP / CA-lactic acid composite membrane, and neat PP. Except for the neat PP film, the other two films were treated with 8 bar water pressure and then dried in a vacuum oven for 2 days.

[0060] Figure 3a and 3b (1650-1850 cm -1 ) is 1750 cm -1 It is possible to confirm the interaction between the C=O group (carbonyl group) of CA and PP at 8 bar. There is no difference in the C=O band in the FT-IR results for the CA-lactic acid film (CA+latic acid at 8 bar) and the CA side of the PP / CA-lactic acid separation membrane. On the other hand, there is a large difference in the C=O band between the PP side of the PP / CA-CaO and neat PP. Naturally, no C=O band was observed in the neat PP film, but in the measurement of the PP side of the PP / CA-lactic acid separation membrane, the C=O band was observed at a wavenumber of 1750 cm -1 The C=O band was confirmed at 1000 Hz. Also, the C=O band on the PP side of the PP / CA-lactic acid separation membrane was observed at a higher wavenumber than the C=O band on the CA side of the PP / CA-CaO membrane. The above results can be interpreted as the CA-lactic acid bond being weakened and the bond on the PP side being strengthened, which is why the C=O peak was observed at a higher wavenumber on the PP side. The above FT-IR experimental results showed that the CA-CaO film was successfully bonded to the PP film.

[0061] According to Figure 3c, the wave number is 1250 cm -1 It was possible to confirm whether the C-0-C group of CA interacted with PP. In the case of a single PP film, the wave number of 1250 cm, which indicates a CO bond, was observed. -1No peak was observed at 100 nm, and a CO bond similar in shape to that of the CA side was observed on the PP side of the PP / CA-lactic acid film. However, the measurement results of the CO bond on the PP side of the PP / CA-lactic acid film shifted to a higher wavenumber than the measurement results of the CO bond on the CA side. The above FT-IR experimental results indicate that the bond between the PP / CA-lactic acid film and the PP film has become stronger.

[0062] 1-4) TGA The thermal stability of the separator was confirmed by measuring the decomposition temperature of each film through a TGA experiment. As with the FT-IR experiment above, the TGA experiment was also conducted after drying the other films for 2 days after water treatment, except for the neat PP film.

[0063] The TGA experiment showed that the decomposition of neat PP started at 410°C and was completely decomposed at 450°C. The decomposition of CA-lactic acid film started at about 275°C and was almost complete at about 380°C.

[0064] In the PP / CA-lactic acid separation membrane of the present invention, decomposition began in a range similar to that of the CA-lactic acid film. In the PP / CA-lactic acid separation membrane, a small amount of lactic acid remained in the CA film layer and acted to flexibly (=plasticize) the CA chain. In the PP / CA-lactic acid separation membrane, PP began to decompose at 350-400°C, and decomposition was almost completed at 450°C.

[0065] The thermal decomposition temperature of CA film is lower than that of PP film, but the melting temperature of CA is higher than that of PP. The melting temperature of CA is 230 to 300°C, and that of PP is 160°C. Even if PP melts at a relatively low temperature, the CA film does not melt, so the separator remains at a relatively high temperature compared to PP alone, and it can prevent short circuits of battery electrodes up to high temperatures.

[0066] Experimental example 2: PP / CA-glycerin separation membrane

[0067] 2-1) Manufacturing of PP / CA-glycerin separation membrane CA (Mw, 30000) was purchased from Sigma-Aldrich, acetone (99.8%) and glycerin (99%) from Daejung Chemical, and PP film (pore size: 100 nm, diameter: 90 mm, thickness: 110 μm) was purchased from GVS.

[0068] A mixed solvent with a mass ratio of acetone:distilled water = 8:2 was used as the solvent. CA:glycerin was mixed with the mixed solvent at a molar ratio of 1:0.05 to prepare a 10 wt% CA-glycerin mixed solution. The mixed solution was mixed at 25°C and 50% humidity for 15 hours.

[0069] A PP film was placed on a glass plate, and after 30 seconds, the CA-glycerin solution was coated on the PP film to a thickness of 300 μm using a doctor blade, and the PP / CA-glycerin film was dried in a thermo-hygrostat for 20 minutes. The PP / CA-glycerin separation membrane was subjected to water pressure treatment at 8 bar for 1.5 hours. After the total water pressure treatment, pores were formed through the PP film and the CA-glycerin film, and the adhesion between the PP and CA films was also strengthened by the water pressure treatment.

[0070] 2-2) SEM Figure 4a is a SEM photograph of a neat PP film, and Figure 4b is a SEM photograph of the PP side of a PP / CA-glycerin separation membrane. Referring to Figure 4a, small pores of 100-200 nm and large pores of 2 μm coexist in the neat PP film. As shown in Figure 4b, there was no change in the SEM measurement results of the PP side of the PP / CA-glycerin, and there was no change in the shape of the pores. 5a and 5b are SEM photographs of the surface of the CA-glycerin film before and after water treatment, respectively, and FIG. 5c is an SEM photograph of the CA side of the PP / CA-glycerin separation membrane. As shown in Figure 5a, in the case of the sample (before water pressure treatment) that was dried after adding glycerin to CA, the co-solvents acetone and distilled water evaporated, leaving behind a porous material. Figure 5b shows the CA-glycerin film (after water pressure treatment) that was water-pressurized up to 8 bar without water treatment (Figure 5a), and it was confirmed that the top surface of the chains cracked little by little, and pores were formed inside as well. In addition, in the case of the PP / CA-glycerin separation membrane, channels with connected pores were formed inside by water pressure treatment at 8 bar (Figure 5c).

[0071] 2-3) TGA FIG. 6a shows the TGA data of neat PP, neat CA, CA-glycerin (before water pressure treatment), CA-glycerin (water pressure treatment at 8 bar), and PP / CA-glycerin separation membrane samples, and FIG. 6b is an enlarged view of FIG. 6a.

[0072] Analysis of the TGA data of each film showed that the thermal decomposition of neat CA and neat PP started at 265°C and 350°C, respectively. Due to the plasticizing effect of OH groups of glycerin, the CA-glycerin (0 bar) sample started decomposing at 140°C. However, the CA-glycerin (8 bar) sample, in which glycerin was removed by water pressure treatment, started decomposing at a temperature higher than 140°C. On the other hand, the PP / CA-glycerin separation membrane started decomposing at a higher temperature (325°C) than neat CA (265°C). These results indicate that the water pressure treatment strengthened the cross-linking between CA and PP chains and strengthened the bond (adhesion) between CA and PP layers.

[0073] 2-4) FT-IR Figures 7a and 7b show the COC ether groups (960–1100 cm) of neat PP, CA-glycerin film, and PP / CA-glycerin separation membrane. -1 ) FT-IR experimental results. Referring to FIG. 7a, the 960-1100 cm -1The FT-IR analysis results of the ether groups of the CA-glycerin film confirmed that the CA-glycerin film showed higher wavenumbers than the CA-glycerin film. These results can be interpreted as the CA-glycerin film was successfully coated on the PP and the ether groups had new interactions with each other.

[0074] Figures 8a and 8b show the ether groups (960–1100 cm) of CA-glycerin (treated at 8 bar water pressure) and PP / CA-glycerin separation membrane (treated at 8 bar water pressure), respectively. -1 ) The deconvoluted data of the FT-IR measurement results for CA. As a result of deconvolution on the CA side, the peak at 1034 cm was observed in the PP / CA-glycerin separation membrane compared to the CA-glycerin film. -1 This result can be interpreted as being due to the new interactions between the ether group of CA and PP.

[0075] 9a and 9b show the carbonyl groups (1690 to 1780 cm) of neat PP, CA-glycerin, and PP / CA-glycerin separation membranes. -1 FT-IR spectrum of the PP / CA-glycerin separation membrane. The FT-IR results showed that the carbonyl groups measured on the PP side of the PP / CA-glycerin separation membrane shifted to higher wavenumbers compared to the control sample (see Fig. 9a), which can be interpreted for the same reasons as the experimental results for ethers above.

[0076] 10a and 10b show the carbonyl groups (1690 to 1780 cm) of neat PP, CA-glycerin, and PP / CA-glycerin separation membranes, respectively. -1 ) deconvoluted data of the FT-IR spectrum. As a result of deconvolution of the CA side of the PP / CA-glycerin separation membrane, about 4.16% of the PP / CA-glycerin separation membrane shifted to a lower wavenumber than CA-glycerin. This means that a new interaction between PP and CA occurred.

[0077] Experimental example 3: PP / CA-CaO separation membrane 3-1) Manufacturing of PP / CA-CaO separation membrane CaO (99.9%), N,N-dimethylformamide (DMF, 99.8%), CA (Mw=30000), acetone (99.8%), and PP film (average pore size 100nm, thickness 110μm) were purchased and used. CA was stirred for 2 hours in a mixed solvent with a weight ratio of DMF:acetone = 8:2 as a co-solvent to produce a 15wt% CA solution. CaO was mixed into the solution so that the molar ratio of CA:CaO = 1:0.006. The mixed solution was stirred again for 48 hours.

[0078] After fixing the PP film on a glass plate, the CA-CaO solution was coated on the PP film to a thickness of 300 μm using a doctor blade. The PP / CA-CaO separator was dried for 20 minutes at 25° C. and 50% humidity. In this experiment, the separator was subjected to water pressure treatment at 8 bar for 3 hours. The porosity data of the separator is shown in the table below (the diameter and porosity of neat PP were also measured after water pressure treatment).

[0079] [Table 1]

[0080] The PP / CA-CaO separation membrane had pores formed in the separation membrane due to the physical force of water pressure, and the water pressure treatment was applied from the PP film side to the CA film side. The average water permeability from multiple experiments was 208 L / m 2h (LMH). Also, the porosity of the PP / CA-CaO separator was 68.8% according to the results of the porosity test. From the results of the porosity and water permeability test, it was confirmed that the two film layers of PP and CA-CaO were physically well bonded, and that pores were formed in both the PP and CA-CaO films by the water pressure treatment. When used in a lithium ion battery, the separator of the present invention has high porosity and water permeability, and is capable of high ion conduction of lithium ions. This is because the separator of the present invention has pores formed in a straight line penetrating the PP and CaO films by the water pressure treatment. A separator with high porosity has the advantage of increasing wettability due to an increase in surface area. In the case of MFC, a fouling phenomenon may occur in which microorganisms adhere to the surface of the separation membrane and block the pores. However, the separation membrane of the present invention is hydrophilic and can prevent the fouling phenomenon. When the separation membrane of the present invention is applied to an MFC, the performance of the MFC can be advantageously maintained for a long period of time.

[0081] 3-2) SEM Fig. 11a shows the SEM measurement results of CA-CaO, Fig. 11b shows the CA side of PP / CA-CaO, Fig. 11c shows neat PP, and Fig. 11d shows the PP side of PP / CA-CaO (all samples were water-treated).

[0082] When CA and CaO solution is coated on PP, the mixed solution of Ca and CaO, together with the solvent, penetrates the PP layer and wraps some of the PP chains. As shown in the SEM measurement results from the CA side of PP / CA-CaO in Figure 11b, pores are formed throughout the CA layer, and some of the pores are blocked. When viewed from the PP side of the PP / CA-CaO separation membrane in Figure 11d, the pores are more visible than in Figure 11b. Some of the pores are blocked by the still remaining CA.

[0083] 3-3) TGA Figure 12 shows the TGA experimental results for neat PP, neat CA, CA-CaO (without hydraulic treatment), CA-CaO (hydraulic treatment), and PP / CA-CaO (hydraulic treatment).

[0084] TGA was performed to confirm the thermal stability of the membrane. Neat CA (solvent DMF / Acetone) started to decompose at about 250°C. It was confirmed that the CA-CaO sample with CaO added (without hydraulic treatment) had a slightly increased thermal stability compared to neat CA. The CA-CaO (hydraulic treatment) sample started to decompose at 310°C, which is a value where the decomposition temperature is increased by more than 60°C compared to neat CA. In general, when an additive is dispersed between CA chains, the CA chains become flexible and the additive causes a plasticizing effect, resulting in weak thermal stability. However, when CaO is added as in the present invention, a crosslinking effect occurs in the CA chains, and after hydraulic treatment, a stronger crosslinking effect occurs. It was found that the PP / CA-CaO membrane of the present invention started to decompose at 310°C, and the decomposition occurred slowly.

[0085] From the above results, when the separator of the present invention is applied to a lithium ion battery, even if the lithium ion battery overheats, the PP film layer melts first, blocking the pores and causing a shutdown phenomenon. Since the CA layer has thermal stability up to high temperatures, it has a positive effect of delaying complete melting and collapse of the separator compared to a neat PP film, and can delay a fire caused by the battery up to high temperatures.

[0086] 3-4) FT-IR Figures 13a-c show the FT-IR data of carbonyl groups for neat CA, CA-CaO (before water pressure treatment), and CA-CaO (after water pressure treatment), respectively. When CaO was added to CA, the carbonyl groups shifted to lower wavenumbers, and after water pressure treatment, they shifted to even lower wavenumbers. This result is because CaO remains after water pressure treatment, and the interaction between CaO and the carbonyl groups is strengthened. Compared to neat CA (Figure 13a), the addition of CaO and water pressure treatment shifted the carbonyl groups of the CA-CaO film to a wavenumber 6.7% lower, as shown in Figure 13c. This result is because the mobility of CA chains increases with water pressure treatment, inducing an interaction with CaO.

[0087] FIG. 14a shows the FT-IR measurement results of various samples containing the PP / CA-CaO of the present invention, and FIG. 14b shows the FT-IR measurement results of the ether group (960-1100 cm -1 ) part, and FIG. 14c shows the carbonyl group (1700-1800 cm -1 ) is an enlarged view.

[0088] Measurements of the CA and PP sides of CA-CaO, neat PP, and PP / CA-CaO showed differences between samples in ether groups (Figure 14b) and carbonyl groups (Figure 14c). Both ether and carbonyl groups shifted to higher wavenumbers in the membrane of the present invention compared to the hydraulically treated CA-CaO sample.

[0089] Figures 15a, 15b, and 15c show the deconvolution data of the ether groups on CA-CaO, the CA side of PP / CA-CaO, and the PP side of PP / CA-CaO, respectively. Figures 16a, 16b, and 16c show the deconvolution data of the carbonyl groups on CA-CaO, the CA side of PP / CA-CaO, and the PP side of PP / CA-CaO, respectively.

[0090] The ether group of the CA-CaO sample is at 1032 cm -1 is the main peak, and this main peak is 1044 cm in the measurement result on the CA side of the separation membrane of the present invention. -1(Fig. 15b), the measurement result on the PP side was 1046 cm -1 (Figure 15c). In the case of carbonyl groups, the main peak of CA-CaO shifted to 1732 cm -1 However, the measurement result on the CA side of the separation membrane of the present invention was 1741 cm -1 (Fig. 16b), the measurement result on the PP side was 1742 cm -1 (Fig. 16c). This is because the mixed solution of CA and CaO penetrates into the PP chains and deteriorates the binding force between the molecules of the PP chains. Because both PP and CA molecules have strong binding force between the molecules, each polymer chain is well packed. However, it was found that the CA-CaO solution penetrates into the PP chains, disturbs the polymer packing, weakens the bonds, and forms new bonds.

[0091] Experimental example 4: Application experiment of MFC (microbial fuel cell) 4-1) Experimental method In this experiment, an experiment was carried out on a microbial fuel cell (MFC) using the separation membrane of the present invention. 30cc of organic matter was supplied to the anode every three days to allow anaerobic microorganisms to decompose and oxidize, and the cathode was operated without replenishing the receptor during the experiment. The experimental device was composed of an acrylic cell fuel cell consisting of two chambers, a microbial anode and a polymer receptor cathode, each of which was 500cc, an electrode made of carbon sole, and an anion exchange pore-filling separation membrane, and the PP / CA-CaO separation membrane of Experimental Example 3 was used as the separation membrane.

[0092] 4-2) Voltage Figure 17 shows the voltage measurement results, with the microbial culture voltage being 0.05V. This is a lower level compared to the microbial voltage of 0.3V in previous experiments. This is due to changes in the microorganisms, and it is analyzed that there is a case where an open circuit voltage of 0.6V was recorded in another experiment using a similar type of microorganism used in the experiment, meaning that there is a lot of room for the voltage to increase depending on the addition of microorganisms.

[0093] After starting the discharge experiment, the measured voltage was 1.206V to 0.9V, close to 1V, and discharge was continued for three months. In particular, the discharge duration showed a large difference from previous experiments. In an experiment using a conventional commercial separator, the voltage started at 1.45V and continued to drop, dropping to less than 0.8V after 10 days, at which point the discharge experiment was discontinued, whereas the MFC of the present invention showed a relatively constant voltage for three months. The fact that discharge can be continued without electrolyte replacement is an indicator of the economic viability of a fuel cell, and it is expected that the application of the separator of the present invention will lead to progress in the commercialization of batteries in the future.

Claims

1. A method for producing a separator including a double-layered PP film and a CA film, Providing a porous PP film; a mixed solution including CA and a plasticizer is coated on the porous PP film at least once and dried to prepare a PP / CA separator; and applying water pressure to the PP / CA separation membrane to form pore channels penetrating the PP film layer and the CA film layer.

2. The plasticizer is glycerin, lactic acid, CaO, glycolic acid, NaCl, NaNO ３ and propylene glycol.

3. The method for manufacturing a PP / CA separator according to claim 1, wherein the mixed solution of CA and plasticizer is a solution in which CA:plasticizer is mixed in a molar ratio of 1:0.001 to 0.

3.

4. The method for producing a PP / CA separation membrane according to claim 1 , wherein the solvent is a mixed solvent of two or more kinds.

5. The method for producing a PP / CA separation membrane according to claim 1 , wherein the water pressure treatment is performed by applying water pressure in a direction from the PP layer to the CA layer.

6. The method for producing a PP / CA separation membrane according to claim 1, wherein the water pressure is 2 to 20 bar.

7. A battery to which the separator according to any one of claims 1 to 6 is applied.

8. The battery of claim 7 , wherein the battery is an MFC.

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