Method for manufacturing a PP / CA separation membrane and a battery using the separation membrane.

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, specifically a double-layered porous separator membrane in which two porous films, a PP film and a CA film, are bonded together, and to a technique for using a plasticizer and hydrostatic treatment to form pores in the CA. [Background technology]

[0002] Lithium-ion batteries (LIBs) are being applied to various technological fields such as energy storage, portable electronic products, and electric vehicles as one way to solve various energy problems related to energy storage, supply, and demand, including environmental pollution and energy depletion, and they exhibit significantly superior electrical characteristics compared to conventional rechargeable batteries.

[0003] In recent years, with many countries raising environmental regulations, the market for lithium-ion rechargeable batteries is expected to grow even further.

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

[0005] In particular, in lithium-ion secondary batteries, the separator membrane must maintain thermal and mechanical stability while maintaining high porosity and ionic conductivity. The separator membrane, which is placed between the electrodes, plays a very important role in preventing short circuits between the two electrodes and fires caused by external shocks.

[0006] Recent trends related to separation membranes for lithium-ion secondary batteries show that highly stable polyimide-based materials are attracting attention as materials for polymer separation membranes and are widely sold commercially.

[0007] However, because polyimide-based materials are relatively expensive, research continues on finding cheaper and more efficient materials.

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

[0009] The above research demonstrated that crosslinking between silicon and oxygen enhances thermal stability and imparts adhesive strength between films.

[0010] Furthermore, Zhang et al. used a porous Al2O3 / PVDF-coated separation membrane to complement the performance of Li-S batteries, and reported that the structure of the Al2O3 / PVDF-coated separation membrane promoted lithium ion mobility, resulting in a very high reversible capacity even after 50 cycles.

[0011] Furthermore, Liu et al. published research results showing that SiO2 / PAM-grafted PP separation membranes possess excellent thermal stability and electrochemical properties through surface chemical modification.

[0012] Compared to the high-temperature shrinkage rate of a typical PP separation membrane, the separation membrane in the above study showed a lower high-temperature shrinkage rate.

[0013] The aforementioned separation membrane has been reported to improve the stability and cycle performance of the battery.

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

[0015] This study reports that because a three-dimensional network is formed and intermolecular interactions are strong, this method enables the production of highly stable batteries.

[0016] In this study, the initial efficiency increased up to 93.2%, and the capacity retention rate was reported to be excellent even after 100 cycles at high current density.

Summary of the Invention

Problems to be Solved by the Invention

[0017] An object of the present invention is to provide a manufacturing technique for a novel PP-based separator membrane having improved mechanical, thermal, and electrical properties compared to conventional PP-based separator membranes, and a technique for a battery using the same.

[0018] In particular, an object of the present invention is to provide a separator membrane excellent in thermal stability and mechanical stability by a double-layer separator membrane of a PP film and a CA film.

[0019] In particular, an object of the present invention is to provide a technique for forming pore channels penetrating through a PP film and a CA film.

Means for Solving the Problems

[0020] The present invention provides a method for manufacturing a PP / CA separator membrane including a PP film and a CA film having a double-layer structure, the method including the steps of preparing a porous PP film, coating and drying a mixed solution containing CA 、 plasticizer and solution one or more times to manufacture a PP / CA separator membrane, and applying a water pressure to the PP / CA separator membrane to form pore channels penetrating through the PP film and the CA film.

[0021] In particular, the plasticizer is any one selected from the group consisting of, for example, glycerin, lactic acid, CaO, glycolic acid, NaCl, NaNO3, and propylene glycol.

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

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

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

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

[0026] Furthermore, the present invention can be used to manufacture a battery using the PP / CA separation membrane.

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

[0028] This invention relates to a PP / CA bilayer separation membrane, and the separation membrane of this invention is a composite separation membrane that simultaneously possesses the physical strength of PP and the thermal stability of CA. When the separation membrane of this invention is applied to a battery, its high thermal stability not only reduces the possibility of fire compared to batteries using conventional separation membranes, but also has the advantage that its electrical characteristics do not change even after long-term use.

[0029] Furthermore, the present invention has the advantage that by imparting hydrophilicity to the surface of the PP film by coating it with a CA film, the fouling phenomenon that occurs on the surface of the PP film is reduced, and as a result, the durability of the MFC battery to which the separation film of the present invention is applied can be improved. [Brief explanation of the drawing]

[0030] [Figure 1] Figure 1 is a schematic diagram illustrating the method for producing a PP / CA-CaO separation membrane according to the present invention when CaO is used as a plasticizer. [Figure 2a]Figure 2a is an SEM image of the PP side surface of the PP / CA-lactic acid separation membrane. [Figure 2b] Figure 2b is an enlarged view of the circle in Figure 2a. [Figure 2c] Figure 2c is an SEM image of the CA-side surface of the PP / CA-lactic acid film. [Figure 2d] Figure 2d is an enlarged view of the circle in Figure 2c. [Figure 2e] Figure 2e is an SEM image of a cross-section of the PP / CA-lactic acid separation membrane. [Figure 3a] Figure 3a shows the FT-IR experimental results for the separation membrane of the present invention and the separation membrane of a comparative example. [Figure 3b] Figure 3b shows the FT-IR experimental results for the separation membrane of the present invention and the separation membrane of a comparative example. [Figure 3c] Figure 3c shows the FT-IR experimental results for the separation membrane of the present invention and the separation membrane of a comparative example. [Figure 4a] Figure 4a shows a neat PP film. [Figure 4b] Figure 4b is an SEM image of the PP side of the PP / CA-glycerin separation membrane. [Figure 5a] Figure 5b shows SEM images of the CA-glycerin film before and after water treatment. [Figure 5b] Figure 5b shows SEM images of the CA-glycerin film before and after water treatment. [Figure 5c] Figure 5c is an SEM image of the CA side of the PP / CA-glycerin separation membrane. [Figure 6a] Figure 6a shows the TGA data for neat PP, neat CA, CA-glycerin (before hydrostatic treatment), CA-glycerin (after 8 bar hydrostatic treatment), and PP / CA-glycerin separation membranes. [Figure 6b] Figure 6b is an enlarged view of Figure 6a. [Figure 7a] Figure 7a shows the FT-IR experimental results for COC ether groups (960-1100 cm-1) in neat PP, CA-glycerin film, and PP / CA-glycerin separation membrane. [Figure 7b] Figure 7b shows the FT-IR experimental results for COC ether groups (960-1100 cm-1) in neat PP, CA-glycerin film, and PP / CA-glycerin separation membrane. [Figure 8a] Figure 8a shows the deconvolution data of FT-IR measurements for ether groups (960-1100 cm-1) in the CA-glycerin (8 bar hydrostatic treatment) and PP / CA-glycerin separation membranes (8 bar hydrostatic treatment), respectively. [Figure 8b] Figure 8b shows the deconvolution data of FT-IR measurements for ether groups (960-1100 cm-1) in the CA-glycerin (8 bar hydrostatic treatment) and PP / CA-glycerin separation membranes (8 bar hydrostatic treatment), respectively. [Figure 9a] Figure 9a shows the FT-IR spectra of the carbonyl groups (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 groups (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 groups (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 groups (1690-1780 cm-1) of neat PP, CA-glycerin, and PP / CA-glycerin separation membranes, respectively. [Figure 11a] Figure 11a shows the SEM measurement results for CA-CaO (all samples are after water treatment). [Figure 11b] Figure 11b shows the SEM measurement results for the CA side of PP / CA-CaO (all samples are after water treatment). [Figure 11c] Figure 11c shows the SEM measurement results for neat PP (all samples are after water treatment). [Figure 11d] Figure 11d shows the SEM measurement results for the PP side of PP / CA-CaO (all samples are after water treatment). [Figure 12] Figure 12 shows the TGA experiment results for various samples (Neat CA, CA-CaO, CA-CaO after water pressure, PP / CA-CaO after water pressure, Neat PP). [Figure 13a] Figure 13a shows the FT-IR data of carbonyl groups for the samples neat CA, CA-CaO (before hydrostatic treatment), and CA-CaO (after hydrostatic treatment), respectively. [Figure 13b] Figure 13b shows the FT-IR data of carbonyl groups for the samples neat CA, CA-CaO (before hydrostatic treatment), and CA-CaO (after hydrostatic treatment), respectively. [Figure 13c] Figure 13c shows the FT-IR data of carbonyl groups for the samples neat CA, CA-CaO (before hydrostatic treatment), and CA-CaO (after hydrostatic treatment), respectively. [Figure 14a] Figure 14a shows the FT-IR measurement results of various samples containing the PP / CA-CaO of the present invention. [Figure 14b] Figure 14b is a magnified view of the ether group (960-1100 cm-1). [Figure 14c] Figure 14c is a magnified view of a carbonyl group (1700-1800 cm-1). [Figure 15a] Figure 15 shows the deconvolution data of the ether group in CA-CaO. [Figure 15b] Figure 15b shows the deconvolution data of the ether group on the CA side of P / CA-CaO. [Figure 15c] Figure 15c shows the deconvolution data of the ether group on the PP side of PP / CA-CaO. [Figure 16a]Figure 16a shows the deconvolution data of the carbonyl group of CA-CaO. [Figure 16b] Figure 16b shows the deconvolution data of the carbonyl group 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. [Modes for carrying out the invention]

[0031] The present invention provides a method for producing a PP / CA separator comprising a double-layer structure of a PP film and a CA film, comprising the steps of: preparing a porous PP film; producing a PP / CA separator by coating the porous PP film with a mixed solution containing CA and a plasticizer one or more times and drying it; and applying water pressure to the PP / CA separator to form pore channels that penetrate the PP film and the CA film.

[0032] In this invention, PP refers to polypropylene, CA refers to cellulose acetate, neat PP refers to a porous separation membrane made solely of PP, and neat CA refers to a film (or separation membrane) made solely of CA. "PP / CA-lactic acid" refers to a bilayer separation membrane of PP and CA manufactured by coating a PP layer with a mixed solution of CA and lactic acid as a plasticizer and drying it. "PP / CA-glycerin" refers to a bilayer separation membrane of PP and CA using glycerin as a plasticizer, and "PP / CA-CaO" refers to a bilayer separation membrane of PP and CA manufactured using CaO as a plasticizer. "PP / CA" is used in the claims and other documents as a general term for bilayer separation membranes of PP and CA manufactured using the various plasticizers mentioned above.

[0033] In this invention, the terms "film" and "layer" are used interchangeably to mean thin films. For example, the terms "PP film" and "PP layer" are used interchangeably depending on the explanation.

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

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

[0036] For example, some CaO remains in the CA film layer even after hydraulic treatment, while lactic acid is removed.

[0037] In this invention, the role of the plasticizer is to weaken the bonding force of the CA chains, allowing pores to form between the CA chains during hydraulic treatment. The plasticizer's components have a strong interaction force with CA and are removed during pore formation by hydraulic treatment, although some may remain within the CA film.

[0038] The plasticizer of the present invention can be any of the various chemical substances that can impart a plasticizing effect to the CA layer.

[0039] Examples include glycerin, lactic acid, CaO, glycolic acid, NaCl, NaNO3, and propylene glycol, but the present invention is not limited to specific types of plasticizers.

[0040] The present invention is not limited to specific plasticizer components, as it only requires weakening the bonding force of the CA chain and forming pores in the weakened CA chain through hydraulic treatment.

[0041] In the present invention, the water pressure during the hydraulic 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, etc.

[0042] In the aforementioned mixed solution, the plasticizer can be mixed in a range of 0.001 to 0.3 moles per mole of CA.

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

[0044] Figure 1 is a schematic diagram illustrating the method for producing a PP / CA-CaO separation membrane according to the present invention when CaO is used as a plasticizer.

[0045] In this invention, a PP film with pre-formed pores is fixed onto a glass substrate, a mixed solution of CA and CaO is coated onto the PP film, and then dried to produce a PP / CA-CaO bilayer separation membrane.

[0046] Furthermore, in this invention, a mixed solution of CA and CaO can be coated and dried again on the PP / CA-CaO bilayer separation membrane, and if necessary, a third or fourth coating can also be performed.

[0047] In this invention, water pressure is applied to the PP / CA-CaO bilayer separation membrane from the PP side towards the CA-CaO side.

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

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

[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, then connect with the pores in the PP film under water pressure, forming nearly straight pore channels that penetrate both the PP film and the CA film.

[0051] The present invention will be explained in more detail below based on experimental results with various plasticizers.

[0052] Experimental Example 1: PP / CA-Lactate Separation Membrane This experiment proposes a method for manufacturing an environmentally friendly and low-cost CA film by bonding it with a PP film to create a single separation membrane.

[0053] 1-1) Manufacturing of "PP / CA-lactic acid" separation membranes In this experiment, CA (Mw=30000, manufactured by Sigma-Aldrich, USA), lactic acid (manufactured by Daejung Chemical, South Korea), and acetone (manufactured by Daejung Chemical) were used. In this experiment, PP film (pore size 20 nm, GVS) was used as the polymer support. In this experiment, all materials were used without any additional treatment after purchase. In this experiment, CA was dissolved in a mixed solvent of H2O:acetone = 2:8 by weight ratio to prepare a 10 wt% CA mixed solution. Lactic acid was added to the CA solution to prepare a CA-lactic acid mixed solution with a molar ratio of CA:lactic acid = 1:0.07, and the mixture was stirred at room temperature for 4 hours.

[0054] A PP film with pre-formed pores (pore size 200 nm) was fixed onto a glass plate. A CA-lactic acid mixed solution was coated onto the PP film to a thickness of 300 μm using a doctor blade and then dried. The CA-lactic acid solution was then coated onto the first coated PP film again and dried, resulting in a total of two coatings of CA-lactic acid solution on the PP film. The PP / CA-lactic acid film was subjected to water pressure using water treatment equipment, with the water pressure applied from the PP film towards the CA-lactic acid film. The water pressure was increased from 2 bar to 8 bar. The water flux during the water pressure treatment was also measured.

[0055] 1-2) SEM Figure 2a is an SEM image of the PP side surface of the PP / CA-lactic acid separation membrane, confirming the formation of sponge-like pores. Figure 2b is a magnified view of the circle in Figure 2a, where the white area represents the PP portion affected by CA.

[0056] Figure 2c is an SEM image of the CA side surface of the PP / CA-lactic acid film, and Figure 2d is a magnified view of the circle in Figure 2c. The white area represents the region where CA was plasticized by lactic acid, and many pores were observed in the plasticized region. In other words, the CA portion weakened by lactic acid was formed as pores by hydrostatic treatment. The average pore size was less than 1 μm.

[0057] Figure 2e is an SEM image of a cross-section of the PP / CA-lactic acid separation membrane. The upper part is the CA film cross-section, and the lower part is the PP film cross-section. No separation phenomenon was observed at the interface between CA and PP, confirming that the PP film and the CA-lactic acid film adhered well. Because the two films adhered well, the physical strength of the PP / CA-lactic acid separation membrane was found to be enhanced compared to each film alone.

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

[0059] FT-IR experiments were conducted on PP / CA-lactic acid separation membranes to verify the interaction between CA and PP. FT-IR experiments were performed on 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 of water pressure and then dried in a vacuum oven for two days.

[0060] Figures 3a and 3b (1650~1850cm) -1 According to the source, 1750cm -1The interaction between the C=O group (carbonyl group) of CA and PP can be confirmed. FT-IR results on the CA side of the CA-lactic acid film (CA + lactic acid at 8 bar) and the PP / CA-lactic acid separation membrane showed no difference in the C=O band. On the other hand, there was a significant difference in the C=O band between the PP side of PP / CA-CaO and neat PP. Naturally, the C=O band was not observed in the neat PP film, but in the measurement of the PP side of the PP / CA-lactic acid separation membrane, at wavenumber 1750 cm⁻¹, -1 A C=O band was confirmed. Furthermore, 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 bond between CA and lactic acid weakening and the bond between PP and lactic acid strengthening, and for this reason, the C=O peak was observed at a higher wavenumber on the PP side. From the above FT-IR experiment results, it was found that the CA-CaO film bonded well with the PP film.

[0061] According to Figure 3c, wavenumber 1250 cm -1 This allowed us to confirm whether or not the C-O-C group of CA interacted with PP. In the PP-only film, the CO bond was observed at a wavenumber of 1250 cm⁻¹. -1 No peak was observed, and on the PP side of PP / CA-lactic acid, a CO bond similar in shape to that on the CA side was observed. However, the measurement results of the CO bond on the PP side of PP / CA-lactic acid 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 became stronger.

[0062] 1-4) TGA The thermal stability of the separation membranes was confirmed by measuring the decomposition temperature of each film using TGA experiments. Similar to the FT-IR experiments described above, the TGA experiments were conducted on all films except the neat PP film after water treatment and drying for two days.

[0063] TGA experiment results showed that neat PP began to decompose at 410°C and was completely decomposed by 450°C. CA-lactic acid film began to decompose at approximately 275°C and was almost completely decomposed by approximately 380°C.

[0064] The PP / CA-lactic acid separation membrane of the present invention began to decompose within 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, which had the effect of making the CA chain flexible (=plasticizing). In the PP / CA-lactic acid separation membrane, PP began to decompose at 350-400°C and was almost completely decomposed at 450°C.

[0065] Although the thermal decomposition temperature of CA film is lower than that of PP film, the melting temperature of CA is higher than that of PP. The melting temperature of CA is 230-300°C, while that of PP is 160°C. Even though PP melts at a relatively lower temperature, the CA film remains unmelted, so the separation film remains at a relatively higher temperature compared to PP alone, and can block short circuits in battery electrodes up to high temperatures.

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

[0067] 2-1) Production of PP / CA-glycerol separation membrane CA (Mw, 30000) was purchased from Sigma-Aldrich, and acetone (99.8%) and glycerin (99%) were purchased from Daejung Chemical for the experiment. 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 to distilled water of 8:2 was used as the solvent. A 10 wt% CA-glycerin mixed solution was prepared by mixing CA to glycerin in a molar ratio of 1:0.05. The mixed solution was stirred 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 onto the PP film to a thickness of 300 μm using a doctor blade. The PP / CA-glycerin film was then dried in a constant temperature and humidity chamber for 20 minutes. The PP / CA-glycerin separation membrane was subjected to hydrostatic treatment at 8 bar for 1.5 hours. After the total hydrostatic treatment, pores were formed penetrating the PP film and the CA-glycerin film, and the adhesion between the PP and CA film was also strengthened by the hydrostatic treatment.

[0070] 2-2) SEM Figure 4a shows an SEM measurement image of a neat PP film, and Figure 4b shows an SEM measurement image of the PP side of a PP / CA-glycerin separation membrane. Referring to Figure 4a, the neat PP film has both small pores of 100-200 nm and large pores of 2 μm. As shown in the results of Figure 4b, there was no change in the SEM measurement results of the PP side of PP / CA-glycerin, and there was no change in the shape of the pores. Figures 5a and 5b are SEM images of the surface of the CA-glycerin film before and after water treatment, respectively, and Figure 5c is an SEM measurement image of the CA side of the PP / CA-glycerin separation membrane. As shown in Figure 5a, in the case of a sample dried after adding glycerin to CA (before hydrostatic treatment), it was found that the cosolvents, acetone and distilled water, vaporized, leaving behind porous material. Figure 5b shows a CA-glycerin film subjected to hydrostatic treatment up to 8 bar (after hydrostatic treatment) without the water treatment shown in Figure 5a, and it was confirmed that the top surface of the chains cracked little by little and pores were formed inside. Also, as shown in Figure 5c, in the case of a PP / CA-glycerin separation membrane, channels with connected pores were formed inside after hydrostatic treatment at 8 bar.

[0071] 2-3) TGA Figure 6a shows the TGA data for samples of neat PP, neat CA, CA-glycerin (before hydrostatic treatment), CA-glycerin (after 8 bar hydrostatic treatment), and PP / CA-glycerin separation membrane, while Figure 6b is an enlarged view of Figure 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 the OH groups of glycerin, the sample of CA-glycerin (0 bar) started to decompose at 140 °C. However, in the sample of CA-glycerin (8 bar) from which glycerin was removed by hydrostatic pressure treatment, decomposition started at a temperature higher than 140 °C. On the other hand, the PP / CA-glycerin separation membrane started to decompose at a higher temperature (325 °C) compared to neat CA (265 °C). From the above results, it was found that the hydrostatic pressure treatment strengthened the crosslinking of the CA and PP chains and strengthened the bonding (adhesion) between the CA and PP layers.

[0073] 2-4) FT-IR Figures 7a and 7b show the experimental results of FT-IR of the C–O–C ether group (960–1100 cm -1 ) of neat PP, CA-glycerin film, and PP / CA-glycerin separation membrane. Referring to Fig. 7a, from the FT-IR analysis results of the ether group at 960–1100 cm -1 for the PP side of the PP / CA-glycerin separation membrane, it was confirmed that a higher wave number was shown compared to the CA-glycerin film. The above results can be interpreted as that the CA-glycerin film was well coated on PP and the new interaction in the ether group affected the ether group.

[0074] Figures 8a and 8b are the deconvoluted data of the FT-IR measurement results for the ether group (960–1100 cm -1 ) of CA-glycerin (8 bar hydrostatic pressure treatment) and PP / CA-glycerin separation membrane (8 bar hydrostatic pressure treatment), respectively. As a result of deconvolution on the CA side, in the PP / CA-glycerin separation membrane, the peak at 1034 cm -1 showed a tendency to be more symmetric compared to the CA-glycerin film. Such results can be interpreted as being due to the ether group of CA making a new interaction with PP.

[0075] Figures 9a and 9b show the carbonyl groups (1690-1780 cm) of neat PP, CA-glycerin, and PP / CA-glycerin separation membranes. -1 This is the FT-IR spectrum of ). The FT-IR results show that the carbonyl group measured on the PP side of the PP / CA-glycerol separation membrane shifted to a higher wavenumber compared to the comparison sample (see Figure 9a), which can be interpreted for the same reasons as the experimental results for ether described above.

[0076] Figures 10a and 10b show the carbonyl groups (1690-1780 cm²) of the neat PP, CA-glycerin, and PP / CA-glycerin separation membrane, respectively. -1 This is the deconvolution data of the FT-IR spectrum of the PP / CA-glycerin separation membrane. As a result of deconvolution on the CA side of the PP / CA-glycerin separation membrane, approximately 4.16% shifted to a lower wavenumber compared to CA-glycerin. This indicates that a new interaction occurred between PP and CA.

[0077] Experimental Example 3: PP / CA-CaO Separation Membrane 3-1) Manufacturing of PP / CA-CaO separation membranes CaO (99.9%), N,N-dimethylformamide (DMF, 99.8%), CA (Mw=30000), acetone (99.8%), and PP film (average pore size 100 nm, thickness 110 μm) were purchased and used. As a cosolvent, a mixed solvent with a weight ratio of DMF:acetone = 8:2 was used to prepare a 15 wt% CA solution by stirring CA in this mixture for 2 hours. CaO was then mixed into the solution to achieve a molar ratio of CA:CaO = 1:0.006. The mixed solution was stirred again for 48 hours.

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

[0079] [Table 1]

[0080] The PP / CA-CaO separation membrane formed pores in the membrane due to the physical force of water pressure, but the water pressure treatment was applied from the PP film side to the CA film side. The average water permeability from numerous experiments was 208 L / m³. 2 The value was h(LMH). Furthermore, according to the porosity meter results, the porosity of the PP / CA-CaO separation membrane was 68.8%. From the experimental results of porosity and water permeability, 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 hydrostatic treatment. When used in lithium-ion batteries, the separation membrane of the present invention will be able to conduct lithium ions well due to its high porosity and water permeability. This is because, in the separation membrane of the present invention, pores are formed in a straight line penetrating the PP and CaO films by hydrostatic treatment. Separation membranes with high porosity have the advantage of increased wettability due to the increased surface area. In the case of MFCs, fouling can occur, where microorganisms adhere to the surface of the separation membrane and block the pores. However, the separation membrane of the present invention can prevent fouling due to its hydrophilicity, and when the separation membrane of the present invention is applied to an MFC, there is the advantage that the performance of the MFC is maintained for a long period of time.

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

[0082] When a CA and CaO solution is coated onto PP, the mixed solution of Ca and CaO permeates the PP layer along with the solvent, wrapping a portion of the PP chain. As shown in the SEM measurement results from the CA side of PP / CA-CaO in Figure 11b, pores were formed throughout the CA layer, with some of the pores blocked. When viewed from the PP side of the PP / CA-CaO separation membrane in Figure 11d, the pores were more clearly visible compared to Figure 11b. Some of the pores were still blocked by the 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] To confirm the thermal stability of the separation membrane, a TGA (Thermal Gain Analysis) was performed. Neat CA (solvent DMF / Acetone) began to decompose at approximately 250°C. The CA-CaO sample with added CaO (without hydrostatic treatment) showed a slight increase in thermal stability compared to the Neat CA. The CA-CaO (hydrostatic treatment) sample began to decompose at 310°C, which is more than 60°C higher than the decomposition temperature of the Neat CA. Generally, when additives are dispersed between CA chains, the CA chains become more flexible, and plasticization occurs due to the additives, resulting in weaker thermal stability. However, as in the present invention, when CaO is added, a crosslinking effect occurs in the CA chains, and a stronger crosslinking effect occurs after hydrostatic treatment. The PP / CA-CaO separation membrane of the present invention began to decompose at 310°C, indicating that the decomposition occurs slowly.

[0085] From the above results, when the separation membrane of the present invention is applied to a lithium-ion battery, even if the lithium-ion battery overheats, the PP film layer melts first, causing a shutdown phenomenon that blocks the pores. Because the CA layer has thermal stability up to a higher temperature, it has the positive effect of delaying the complete melting and collapse of the separation membrane compared to a neat PP film, and can delay battery fires up to high temperatures.

[0086] 3-4) FT-IR Figures 13a and 13c show FT-IR data of carbonyl groups for samples of neat CA, CA-CaO (before hydrostatic treatment), and CA-CaO (after hydrostatic treatment), respectively. When CaO was added to CA, the carbonyl groups moved to lower wavenumbers, and after hydrostatic treatment, they moved to even lower wavenumbers. This result is because CaO remains after hydrostatic treatment, strengthening the interaction between CaO and carbonyl groups. Compared to neat CA (Figure 13a), as shown in Figure 13c, when CaO is added and hydrostatic treatment is performed, the carbonyl groups of the CA-CaO film move to a lower wavenumber of 6.7%. This result is because hydrostatic treatment increases the mobility of the CA chain, inducing interaction with CaO.

[0087] Figure 14a shows the FT-IR measurement results of various samples containing the PP / CA-CaO of the present invention, and Figure 14b shows the ether group (960~1100 cm⁻¹). -1 Figure 14c is an enlarged view of the carbonyl group (1700-1800 cm²). -1 This is an enlarged view of ).

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

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

[0090] The ether group of the CA-CaO sample is 1032 cm². -1 This is the main peak, and this main peak is 1044 cm⁻¹ in the CA measurement results for the separation membrane of the present invention. -1 (Figure 15b) The measurement result on the PP side was 1046 cm -1 (Moved to Figure 15c). In the case of the carbonyl group, the main peak of CA-CaO is at 1732 cm⁻¹. -1 However, the measurement result for the CA side of the separation membrane of the present invention was 1741 cm⁻¹ -1 (Figure 16b) Measurement result on the PP side: 1742 cm -1 (See Figure 16c). This is because the mixed solution of CA and CaO penetrates the PP chain, degrading the intermolecular bonding forces of the PP chain. Since both PP and CA molecules have strong intermolecular bonding forces, each polymer chain is well packed. However, it was found that the CA-CaO solution penetrates the PP chain, hindering polymer packing and weakening bonds, thereby forming new bonds.

[0091] Experiment Example 4: Application Experiment of MFC (microbial fuel cell) 4-1) Experimental Method In this experiment, we conducted experiments using a microbial fuel cell (MFC) to which the separation membrane of the present invention was applied. 30cc of organic matter was supplied to the anode every three days to enable anaerobic microorganisms to decompose and oxidize it, while the cathode was left unreplenished with the receptor during the experiment. The experimental apparatus consisted of an acrylic cell fuel cell with two chambers, each containing 500cc of material (a microbial anode and a polymer receptor cathode), electrodes made of carbon sole, and an anion exchange pore-filling separation membrane. The PP / CA-CaO separation membrane described in Experimental Example 3 above was used as the separation membrane.

[0092] 4-2) Voltage Figure 17 shows the voltage measurement results, with the voltage of the microbial culture being 0.05V. This is lower than the 0.3V recorded in previous experiments. This is due to changes in the microorganisms, and in other experiments using similar types of microorganisms, an open-circuit voltage of 0.6V was recorded, suggesting that there is considerable room for the voltage to increase depending on the microbial composition.

[0093] The voltage measured after the discharge experiment began ranged from 1.206V to 0.9V, close to 1V, and the discharge was sustained for three months. In particular, the discharge persistence showed a significant difference from existing experiments. In experiments using existing commercial separator membranes, the voltage started at 1.45V, steadily decreased, and after 10 days dropped to below 0.8V, forcing the discharge experiment to be terminated. However, the MFC of the present invention showed a relatively uniform voltage for three months. The fact that the discharge was sustained without replacing the electrolyte is an indicator of the economic feasibility of fuel cells, and it is expected that applying the separator membrane of the present invention will lead to progress in the commercialization of batteries in the future.

Claims

1. A method for manufacturing a microfuel cell (MFC) to which a separator membrane (Separator) comprising a double-layer structure of laminated PP film and CA film is applied, The steps include preparing a porous PP film and The steps include: coating the porous PP film with a mixed solution containing CA and a plasticizer one or more times and drying it to produce a PP / CA separation membrane; A method for manufacturing a battery which is an MFC to which a PP / CA separation membrane is applied, comprising the step of applying water pressure to the PP / CA separation membrane to form pore channels penetrating the PP film layer and the CA film layer.

2. A method for producing an MFC to which the PP / CA separation membrane described in claim 1 is applied, wherein the plasticizer is one or more selected from the group consisting of glycerin, lactic acid, CaO, glycolic acid, NaCl, NaNO3, and propylene glycol.

3. A method for manufacturing an MFC using the PP / CA separation membrane described in claim 1, wherein the mixed solution of CA and plasticizer is a solution mixed in a ratio of CA:plasticizer = 1:0.001 to 0.3 molars.

4. A method for manufacturing an MFC to which the PP / CA separation membrane described in Claim 1 is applied, wherein the water pressure treatment involves applying water pressure from the PP layer to the CA layer.

5. A method for manufacturing a battery which is an MFC to which the PP / CA separation membrane described in claim 1 is applied, wherein the water pressure is 2 to 20 bar.

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