Electrode protective layer of carboxylated microporous polymer substrate and method for manufacturing the same

Abstract

The present invention relates to a carboxylated intrinsically microporous polymer-based electrode protection layer and a manufacturing method thereof, and more particularly to an intrinsically microporous polymer-based electrode protection layer manufactured by mixing a carboxylated intrinsically microporous polymer with a crosslinking agent and a solvent to prepare a film-forming composition, forming the composition into a film, and then crosslinking the film, and a manufacturing method thereof.

Description

[Technical Field]

[0001] The present invention relates to an electrode protective layer based on carboxylated polymers of intrinsic microporosity, and to a method for producing the same.

[0002] More specifically, the present invention relates to a crosslinked polymerized electrode protective layer of a microporous polymer substrate, in which a crosslinking reaction is ultimately carried out by mixing a carboxylated microporous polymer with a crosslinking agent and a solvent to produce a film-forming composition, applying the film-forming composition to the surface of an electrode, drying the solvent at room temperature, and finally a crosslinking reaction.

[0003] This application claims priority based on Korean Patent Application No. 10-2022-0053793 filed on April 29, 2022, and Korean Patent Application No. 10-2023-0054353 filed on April 25, 2023, and all content disclosed in the specifications and drawings of said applications is incorporated into this application. [Background technology]

[0004] As demand for high-capacity energy storage devices usable in electric vehicles, smart electronics, and drones increases, technologies using lithium metal (Li) metal as an anode material are being actively developed. When using lithium metal as an anode, currently commercially available carbon-based anodes (372mAh g) -1 ) Compared to 3860mAhg -1 It exhibits a high theoretical capacity, a low standard reduction potential (-3.04V vs. standard hydrogen electrode (SHE)), and 0.534g cm³. -3 This is because it has a low density.

[0005] Due to these advantages, batteries using lithium metal as an anode were commercialized in the 1980s. However, due to the instability of lithium metal anodes during battery use, accidents occurred where batteries exploded, and measures were taken to recall all batteries. Therefore, in order to commercialize secondary batteries that take advantage of the benefits of lithium metal anodes, ensuring the stability of the lithium metal anode is of paramount importance.

[0006] The instability of lithium metal anodes is caused by the formation of lithium dendrites, which are sharp, resinous structures generated during charging and discharging. Specifically, the non-uniformity of the solid electrolyte interface (SEI) layer, a passive film naturally formed on the surface of the lithium metal anode by the reaction with the electrolyte during charging and discharging, leads to localized differences in current density. Such variations in current distribution cause the lithium metal to grow into sharp, resinous structures during charging. These grown resinous lithium structures become dead lithium, which not only reduces the battery's Coulombic efficiency but, in the worst case, can cause explosions due to internal short circuits. Therefore, this is an issue that must be resolved to ensure the long lifespan and stability of batteries.

[0007] To ensure the stability and long lifespan of the lithium resin described above, research is actively being conducted on the introduction of artificial anode protective layers (Artificial SEI), the introduction of new electrolytes and additives, the structural design of metal current collectors, and the regulation of crystal nucleation growth. In particular, the introduction of artificial anode protective layers is a method of introducing an SEI layer, which is a passive film advantageous for lithium migration and interfacial properties, on the surface of lithium metal, and mainly utilizes polymers that are advantageous for lithium ion conduction and interfacial properties.

[0008] Such anode protective layers mainly contain various ion-conducting polymers, such as poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO), which are typical lithium-ion conductive polymers. Poly(ethylene oxide) (PEO) polymers are polymers containing ether groups that can interact with lithium ions and have a structure in which crystalline and amorphous regions coexist at room temperature. In this polymer, above the glass transition temperature, the flexibility of the amorphous region facilitates the dissolution of lithium salts and the movement of lithium ions, while the movement of lithium ions is restricted in the crystalline phase. As a result, PEO has a glass transition temperature of 10⁻¹⁰ -8 ~10 -9 Due to their low lithium-ion conductivity (S / cm insulator level), PEO polymers are difficult to apply to commercial batteries. Therefore, in order to develop PEO-based materials that exhibit high ionic conductivity, research is actively being conducted to reduce the degree of crystallinity through approaches such as the introduction of organic and inorganic particles and plasticizers, increasing the lithium salt content, and the production of copolymers. However, such efforts to reduce crystallinity can sometimes lead to a decrease in mechanical properties. Therefore, for PEO-based battery materials to be practical, it is necessary to satisfy both ionic conductivity and mechanical properties simultaneously.

[0009] In addition, materials such as covalent organic frameworks (COFs) and polymers of intrinsic microposity (PIMs), which utilize micropores favorable for lithium ion movement, are also being actively researched. In particular, PIM materials possess a large number of micropores with a pore size of about 1 nm, which is favorable for lithium ion movement, and are materials that can be easily introduced as a polymer thin film layer on the surface of lithium metal through a solution process. Research on anode protective films using such intrinsic microposity polymers is being actively conducted, but there is a problem in that a gap is created between the electrode and the electrode protective layer of the polymer substrate because the interfacial properties between the intrinsic microposity polymer and the lithium metal anode are not good. (See Korean Patent No. 10-0542213, Korean Patent Publication No. 10-2017-0117649, Korean Patent Publication No. 10-2019-0033922, Korean Patent No. 10-0655674, and Putintseva, MN, Yushkin, AA, Bondarenko, GNet al. Crosslinking of Polybenzodioxane PIM-1 for Improving Its Stability in Aromatic Hydrocarbons. Polym. Sci. Ser. B 61, 795-805 (2019).) When using liquid electrolytes, the electrolyte can be consumed by the formation of an additional SEI layer and side reactions in such empty spaces; therefore, a polymer electrode protective film is needed that can minimize and remove these empty spaces.

[0010] Therefore, the inventors developed a lithium metal anode protective film that induces uniform lithium ion movement by introducing an epoxy resin into the carboxylated intrinsically porous polymer according to the present invention to produce a crosslinked film. Furthermore, by introducing an epoxy resin that is compatible with lithium metal anodes, the anode protective film according to the present invention not only ensures stable interfacial properties between the metal surface and the electrode protective layer, unlike when only the intrinsically porous polymer is used independently, but also provides high mechanical strength, which has been confirmed to suppress the formation of resinous lithium dendrites during charging and discharging, thus completing the present invention. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] Korean Patent Publication No. 10-0542213 [Patent Document 2] Korean Patent Publication No. 10-2017-0117649 [Patent Document 3] Korean Patent Publication No. 10-2019-0033922 [Patent Document 4] Korean Patent Publication No. 10-0655674 [Non-patent literature]

[0012] [Non-Patent Document 1] Polym.Sci.Ser.B 61, 795-805(2019) [Overview of the project] [Problems that the invention aims to solve]

[0013] The present invention was developed to solve the above-mentioned problems and aims to provide an electrode protective layer made of a carboxylated, intrinsically microporous polymer substrate that exhibits uniform lithium-ion conductivity, excellent interfacial properties with lithium metal, and suppression of lithium dendrite formation and growth.

[0014] The present invention provides a novel manufacturing method that is classified in terms of composition, manufacturing method, and its application, different from the crosslinked film in the form of an IPN (Interpenetrating Polymer Network) of a conventional PIM-1 polymer base and the ion crosslinked film of a固有 microporous polymer base.

Means for Solving the Problems

[0015] In order to solve the above problems, the present invention provides an electrode protection layer formed by the reaction and crosslinking of a homopolymer, copolymer, or a mixture containing one or more of the compounds represented by the following Chemical Formula 1 with a crosslinking agent.

Chemical Formula

Chemical Formula

[0016] In an embodiment of the present invention, the crosslinking agent may have the chemical structure of the following Chemical Formula 2.

Chemical Formula

[0017] Furthermore, the present invention provides an electrode protection layer of a carboxylated固有 microporous polymer base, which is in a form crosslinked during the drying process after manufacturing a composition by mixing a carboxylated固有 microporous polymer and an epoxy resin and applying the manufactured composition onto the surface of an electrode.

[0018] Furthermore, the present invention provides an electrochemical cell including an anode, an electrolyte, and a cathode including the electrode protection layer. [Effects of the Invention]

[0019] According to the present invention, a crosslinked film can be produced in a simple manner by combining a carboxylated microporous polymer and an epoxy compound, and by introducing this film onto the surface of a lithium metal anode through a solution process, the stability and long lifespan of a lithium metal battery can be ensured.

[0020] Furthermore, according to the present invention, the microporous structure of the intrinsically microporous polymer and the ionic conductivity of the ion-conducting polymer facilitate the uniform movement of lithium ions, and excellent interfacial properties between the lithium metal battery and the polymer film can be achieved through an appropriate combination of the intrinsically microporous polymer and the epoxy resin.

[0021] Furthermore, according to the present invention, the growth of resinous lithium dendrites can be suppressed due to the excellent mechanical properties of the manufactured crosslinked film. Based on the characteristics of the crosslinked film of the carboxylated intrinsically porous polymer and epoxy resin substrate described above, not only have the lifespan characteristics and stability of batteries in actual lithium symmetric cells or lithium full cells been confirmed, but their effects are also expected to be beneficial in commercial applications. [Brief explanation of the drawing]

[0022] [Figure 1] This is the result of confirming the excellent interfacial properties of a crosslinked film for lithium metal anode protection layer made of a carboxylated, intrinsically microporous polymer substrate, manufactured according to the embodiment of the present invention. [Figure 2] This graph shows experimental results of lithium symmetric cells using lithium metal anodes with or without a carboxylated, intrinsically microporous polymer substrate crosslinked film, manufactured according to the examples of the present invention. [Figure 3]These are the results of electrochemical impedance spectroscopy experiments (measurement of ionic conductivity and lithium ion migration number) on a lithium symmetric cell fabricated using a lithium metal anode into which a carboxylated, intrinsically microporous polymer substrate crosslinked film was introduced, as produced in an example according to one embodiment of the present invention. [Figure 4] These are the results of electrochemical impedance spectroscopy experiments (measurement of ionic conductivity and lithium ion migration number) on a lithium symmetric cell fabricated using a lithium metal anode into which a carboxylated, intrinsically microporous polymer substrate crosslinked film was introduced, as produced in an example according to one embodiment of the present invention. [Figure 5] This report presents the results of testing the capacity change according to the charge / discharge rate and long-term performance of a lithium metal secondary battery full cell fabricated using a lithium metal anode with a carboxylated, intrinsically microporous polymer substrate crosslinked film introduced, and a Ni83 cathode, as manufactured according to an embodiment of the present invention. [Figure 6] This report presents the results of testing the capacity change according to the charge / discharge rate and long-term performance of a lithium metal secondary battery full cell fabricated using a lithium metal anode with a carboxylated, intrinsically microporous polymer substrate crosslinked film introduced, and a Ni83 cathode, as manufactured according to an embodiment of the present invention. [Figure 7] This report presents the results of testing the capacity change according to the charge / discharge rate and long-term performance of a lithium metal secondary battery full cell fabricated using a lithium metal anode with a carboxylated, intrinsically microporous polymer substrate crosslinked film introduced, and a Ni83 cathode, as manufactured according to an embodiment of the present invention. [Figure 8] This is the result of casting PIM-COOH (without PEO) onto copper foil, which can be used as a current collector in a battery according to one embodiment of the present invention, and then confirming the interface properties using a scanning electron microscope (SEM). [Figure 9] This is the result of casting an epoxy resin composition of PIM-COOH and PEO substrate onto copper foil that can be used as a current collector for batteries (PIM-COOH:PEO (1:1)), and then confirming the interfacial properties using SEM. [Figure 10]This is the result of a comparative test to clarify the differences between the conventional PIM-1 polymer substrate interpenetrating polymer network and the present invention. [Figure 11] This is the result of a comparative test to clarify the differences between the conventional PIM-1 polymer substrate interpenetrating polymer network and the present invention. [Figure 12] This is an XRD result for an epoxy resin composition with a PIM-COOH and PEO substrate, according to one embodiment of the present invention. [Figure 13] This is a DSC result for a PIM-COOH and PEO-based epoxy resin composition according to one embodiment of the present invention. [Figure 14] This is the result of confirming the reaction between methanol, used as the solvent in the crosslinking agent solution, and lithium metal, which corresponds to the anode of a battery, in the interpenetrating polymer network of the conventional PIM-1 polymer substrate. [Modes for carrying out the invention]

[0023] The present invention will be described in detail below with reference to examples. Terms and words used in this specification and in the claims should not be interpreted in a manner limited to their ordinary and dictionary meanings, but rather in a manner corresponding to the technical idea of ​​the present invention, in accordance with the principle that the inventor himself can appropriately define the concepts of terms in order to best describe the invention.

[0024] The "Polymers of Intrinsic Microposity (PIM)" according to the present invention is a polymer having a twisted structural backbone, which induces a large amount of microporosity (microporousness) because the polymer structure does not densely stack. Also, according to the definition of the International Union of Pure and Applied Chemistry (IUPAC), porous materials are classified into micropores (pore size < 2 nm), mesopores (2 nm < pore size < 50 nm), and macropores (pore size > 50 nm) according to the pore size. In the porous material containing the intrinsic porous polymer according to the present invention, micropores and mesopores can coexist, but mainly contain micropores less than 2 nm.

[0025] The crosslinked film of the carboxylated intrinsic microporous polymer base according to the present invention is produced by mixing the carboxylated intrinsic microporous polymer and an epoxy resin as a crosslinking agent in a solution state and using the solution casting method, and is different from the crosslinked film in the form of an Interpenetrating Polymer Network (IPN) of the conventional PIM-1 polymer base and the ion crosslinked film produced by the reaction of the carboxylated intrinsic microporous polymer with aluminum ions (Polym. Sci. Ser. B 61, 795-805 (2019)) in terms of the production method and its application. The crosslinked films produced by the above two methods have been applied as examples of utilization for the separation of aromatic hydrocarbons.

[0026] First, in the case of the conventional PIM-1 polymer substrate interpenetrating polymer network, unlike the reaction between PIM-COOH and epoxy resin as a crosslinking agent according to the present invention, it is not possible to induce a direct reaction between PIM-1 and the crosslinking agent. Furthermore, in order to manufacture the PIM-1 substrate interpenetrating polymer network, poly(ethyleneimine) is first impregnated into the interior of PIM-1, and then the crosslinking reaction between poly(ethyleneimine) and epoxy resin is induced. In other words, the present invention is distinguished from the conventional technology because it can realize a crosslinked film using only two types of combinations: a uniquely microporous polymer and an epoxy resin as a crosslinking agent, and it is also a method that allows for easy adjustment of the ratio of PIM to the crosslinking agent.

[0027] Furthermore, the present invention differs from the prior art in terms of its composition. The composition according to the present invention is a one-component type in which the resin and crosslinking agent coexist in a solution state, whereas the prior art is a two-component type in which the solution containing the resin and crosslinking agent is separated and stored, and then mixed in a subsequent step for reaction. In most industrial fields, there is a need for the development of one-component compositions instead of two-component compositions in order to make epoxy resins easier to use under a variety of conditions. Similarly, since the composition according to the present invention is a one-component type composition that contains both a resin and a crosslinking agent simultaneously, it is a technology that enables uniform coating and optimization of the coating layer, and it is easier to manufacture in the form of a one-component composition in which crosslinking does not occur in solution.

[0028] In particular, with two-component systems where the resin and crosslinking agent are stored separately, there is a very high possibility that the chemical composition of the composition will vary when the solutions are mixed on-site, resulting in non-uniform physical properties of the final crosslinked product. However, since the film produced by the present invention is a one-component system, the composition is uniform, and the thickness can be easily adjusted, making it easier to realize a film with uniform physical properties. In this respect, it exhibits superior performance compared to conventional technologies in terms of storage, application, and final physical properties.

[0029] Next, in the case of the conventional PIM-1 polymer-based interpenetrating polymer network, when manufacturing a membrane through ionic crosslinking between PIM-COOH and divalent or trivalent ions (e.g., aluminum ions), the PIM-COOH polymer membrane is manufactured by first manufacturing the PIM-1 polymer membrane and then hydrolyzing the manufactured polymer membrane until it can maintain its membrane morphology. For reference, hydrolysis until it can maintain its morphology provides only carboxylated intrinsically microporous polymers with a low conversion rate of 50% or less, whereas in the present invention, the membrane manufacturing method can be distinguished in that it first manufactures PIM-COOH with a high conversion rate of 90% or more, and then manufactures the membrane through a solution process.

[0030] Furthermore, conventional technology uses a method in which, after manufacturing a film, the film is immersed in an aluminum chloride (AlCl3) solution to induce ion exchange and produce an ion-crosslinked film based on PIM-COOH. In other words, this manufacturing method first manufactures a polymer film and then ultimately produces an ion-crosslinked film through ion exchange, which is fundamentally different from the method presented in the present invention, which directly introduces an electrode protection layer to the lithium surface through solution casting. More specifically, in the case of a polymer film manufactured through ion crosslinking, its solubility in organic solvents is limited, making it difficult to directly introduce an electrode protection layer in the solution process. Therefore, a conventionally manufactured film must be introduced to the electrode surface, and it is unavoidable that a gap will be formed at the interface between the electrode and the electrode protection layer. In contrast, the solution composition manufactured in the present invention can be introduced directly to the electrode surface, thereby improving the interfacial properties.

[0031] Furthermore, when applying films manufactured using conventional technology to the battery field, there is a disadvantage that aluminum ions randomly introduced into the anode protective layer for ion crosslinking and residual aluminum chloride solution may cause side reactions such as lithium aluminum alloy reactions within the battery during electrode operation.

[0032] Therefore, in the present invention, in order to solve the above problems, there is provided an electrode protective layer formed by the reaction and crosslinking of a homopolymer, copolymer, or a mixture containing one or more of the compounds represented by the following Chemical Formula 1 with a crosslinking agent. [Chemical Formula] In Chemical Formula 1, X is any one selected from the group consisting of the following X1 to X17. [Chemical Formula]

[0033] In one embodiment of the present invention, the crosslinking agent may have the chemical structure of the following Chemical Formula 2. [Chemical Formula] In Chemical Formula 2, R is any one of a linear or branched alkylene group, a linear or branched alkylene group containing an oxygen atom, or an arylene group.

[0034] In one embodiment of the present invention, in Chemical Formula 2, R may be any one of the following chemical formulas. -(CH2) m - -(CH2) m -O-(CH2) l - -(CH2) m -O-(CH2) l - -CH2-O-(CH2)4-O-CH2- [Chemical Formula] Here, m and l are each an integer of 1 to 6 that are the same or different, and n is an integer of 1 to 10000.

[0035] In one embodiment of the present invention, the electrode protective layer may have a thickness of 10 nm to 300 μm.

[0036] Furthermore, the present invention provides an electrode comprising an anode and an electrode protective layer according to any one of claims 1 to 13, which is coated on the anode.

[0037] In one embodiment of the present invention, the anode may be capable of storing and releasing lithium ions and may be one or more selected from the group including Li, Na, K, Mg, Ca, Zn, Al, Si, Ge, Sn, or alloys thereof.

[0038] Furthermore, the present invention provides an electrochemical battery comprising the anode, electrolyte, and cathode.

[0039] In one embodiment of the present invention, a separation membrane may be further included between the anode and the cathode.

[0040] Furthermore, the present invention provides a method for forming an electrode protective layer, comprising the steps of: preparing an anode; providing a polymer-providing step of providing a homopolymer, copolymer, or mixture containing one or more of the compounds represented by the following chemical formula 1; manufacturing a film-forming composition by mixing the polymer, a crosslinking agent, and a solvent; forming a film on the anode using the film-forming composition; and manufacturing a crosslinked polymer film by crosslinking the film. [ka] In chemical formula 1, X is one selected from the group consisting of X1 to X17 below, and n is a repeating unit, an integer from 10 to 500. [ka]

[0041] In one embodiment of the present invention, the crosslinking agent may have the chemical structure of the following chemical formula 2. [ka] In chemical formula 2, R is one of the following: a linear or branched alkylene group, a linear or branched alkylene group containing an oxygen atom, or an arylene group.

[0042] In one embodiment of the present invention, in chemical formula 2, R may be any one of the following chemical formulas. -(CH2) m -, -(CH2) m -O-(CH2) l -, -(CH2) m -O-(CH2) l -, -CH2-O-(CH2)4-O-CH2- [ka] Here, m and l are integers from 1 to 6, either identical or distinct, and n is an integer from 1 to 10000.

[0043] In one embodiment of the present invention, the solvent may be one or more selected from the group consisting of tetrahydrofuran (THF), N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), dimethylformamide (DMF), and dimethylacetamide (DMAc).

[0044] In one embodiment of the present invention, the step of producing a crosslinked polymerized film for crosslinking the film may be carried out through the reaction shown in the following reaction formula 1. [ka] In the above reaction equation 1, n is a repeating unit and is an integer between 10 and 500, and R is one of the following: a linear or branched alkylene group, a linear or branched alkylene group containing an oxygen atom, or an arylene group.

[0045] The following describes preferred embodiments and examples of the present invention in detail with reference to the attached drawings, so that those with general skill in the art to which this application pertains can easily implement it. However, this does not limit the technical idea of ​​the present invention, its core structure, and its operation. Furthermore, the content of the present invention can be realized in a variety of forms of devices and is not limited by the embodiments and examples described herein.

[0046] <Manufacturing Example 1> Manufacturing of Particle Inherent Porous Polymers (PIMs) After removing internal moisture from a two-necked round-bottom flask (250 ml), 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobindan (TTSBI) (10.21 g, 30 mmol), K2CO3 (8.29 g, 60 mmol), tetrafluorophthalonitrile (TFTPN) (6.00 g, 30 mmol), and dimethylformamide (DMF) (210 ml) were added to the flask under a nitrogen atmosphere, and polymerization was carried out at 55°C for 72 hours. After the reaction was completed, 350 ml of tetrahydrofuran (THF) was added to the reactor, which had been cooled to room temperature, to precipitate the high molecular weight PIM-1, and the supernatant containing the low molecular weight and oligomers was removed. The polymer was redissolved in tetrahydrofuran (THF), and reprecipitation was repeated twice using methanol. The final product was vacuum-dried to obtain a yellowish, intrinsically microporous polymer (PIM-1) (10.3g) represented by the following chemical formula 3. GPC (Gel Permeation Chromatography) measurements showed that M n The values ​​were 60,900 and PDI (Polydispersity index) of 1.58. [ka]

[0047] <Manufacturing Example 2> Production of Carboxylated Microporous Polymer (PIM-COOH) A 20% by weight NaOH solution was prepared by adding 480 ml of distilled water, 600 ml of ethanol, and 240 g of NaOH to a 2000 ml three-necked round-bottom flask. The intrinsically porous polymer (PIM-1) obtained in Preparation Example 1 was then added, and the mixture was modified at 125°C for 360 hours. After the reaction was complete, the aqueous and organic layers were separated using a liquid-liquid separator. The organic layer containing the modified intrinsically porous polymer was separated and slowly precipitated in approximately 5% by weight HCl solution, followed by filtration. After several washes with distilled water, the filtrate was dried in a vacuum dryer at 60°C for 24 hours. It was then dissolved in tetrahydrofuran (THF), and reprecipitation was repeated twice using water and methanol. The final product was vacuum-dried to obtain a yellowish carboxylated intrinsically porous polymer (PIM-1) (7.0 g) of the following chemical formula 4. GPC measurement results showed M n The values ​​were 25,700 and PDI 1.07. [ka]

[0048] <Example 1> Preparation of a polymer crosslinked film for lithium metal anode protective layer containing a carboxylated, intrinsically porous polymer To produce a polymer crosslinked film for the anode protective layer, the carboxylated intrinsically porous polymer (PIM-COOH) produced in Production Example 2 and poly(ethylene glycol) diglycidyl ether (Mn=500) were mixed in mass ratios of 1:2, 1:1, and 2:1. Tetrahydrofuran (THF) was added to the mixture to increase the solution concentration to 12.5 mg mL. -1 The polymer solution was fixed to the lithium metal. The prepared polymer solution was coated onto the lithium metal while filtering out impurities using a 5 μm syringe filter. The coated polymer solution was dried at room temperature for more than 12 hours to remove the solvent. All processes were carried out in a glove box filled with argon. Polymer crosslinked films for anode protective layers with a thickness of 10 μm to 100 μm containing carboxylated intrinsically porous polymers were produced by the above method.

[0049] <Comparative Example 1> Production of Carboxylated Microporous Polymer Films To produce a carboxylated, intrinsically microporous polymer crosslinked membrane, 12.5 mg mL of PIM-COOH and tetrahydrofuran (THF) prepared in Production Example 2 was used. -1 A polymer solution of a certain concentration was prepared. The prepared polymer solution was coated onto lithium metal while filtering out impurities using a 5 μm syringe filter. After slowly evaporating the solvent in an air atmosphere for two days, the dried film was separated from the glass petri dish. It was dried for 24 hours in a vacuum dryer adjusted to 100°C. Polymer films with carboxylated, intrinsic micropores and a thickness of 10 μm to 100 μm were prepared by the above method.

[0050] <Analysis Example 1> Lithium (Li-Li) Symmetric Cell Test Two lithium metal electrodes coated with a polymer crosslinked film containing a carboxylated, intrinsically microporous polymer, prepared in Example 1 of the present invention, were assembled in a 2032 coin cell type (performed in an argon glove box). Cellguard 2500 and an ethylene carbonate (EC):diethyl carbonate (DEC) (1:1, v / v%) electrolyte containing 1M LiPF6 with fluoroethylene carbonate (FEC, 10 w / w%) and vinylene carbonate (VC, 1 w / w%) were used.

[0051] <Analysis Example 2> Measurement of Ionic Conductivity and Lithium Ion Transfer Rate Electrochemical impedance spectroscopy (EIS) was performed in the range of 300 kHz to 1 Hz. Li-Li symmetric cells were fabricated using lithium electrodes containing or without a PIM-COOH / PEO crosslinked film, and experiments were conducted.

[0052] <Analysis Example 3> Electrochemical experiment of lithium full cell A lithium metal electrode coated with a polymer crosslinked film containing a carboxylated, uniquely microporous polymer, manufactured in Example 1 of the present invention, was used as the anode, and Ni83 was used as the cathode material to assemble a 2032 coin cell type (performed in an argon glove box). Charge and discharge experiments were performed using a charge / discharge device in the voltage range of 3.0 to 4.3V.

[0053] Figure 1 shows the results of confirming the interfacial properties of a crosslinked film for a lithium metal anode protective layer on a carboxylated microporous polymer substrate, manufactured in an example according to one embodiment of the present invention. The samples shown in Figure 1 are as follows: (a) PIM-1, (b) PIM-COOH, (c) PIM-1:PEO(1:2), (d) PIM-COOH:PEO(2:1), (e) PIM-COOH:PEO(1:1), (f) PIM-COOH:PEO(1:2). In the case of (a) PIM-1 and (b) PIM-COOH, the respective solutions were applied to the surface of the electrode and the solvent was dried at room temperature, but no crosslinking was induced in the film. The (c) PIM-1:PEO(1:2) film is a film introduced by the above method, but unlike samples (d) to (f), it is a mixed film of PIM-1 and PEO epoxy that was simply mixed without inducing crosslinking. In this case, unlike the crosslinked film, the anode protective layer film was observed to detach from the electrode. Samples (d) to (f) are films in which PIM-COOH and PEO-based epoxy compounds were mixed in weight ratios of 2:1, 1:1, and 1:2, respectively, coated onto the electrode surface, and the solvent was dried at room temperature to induce crosslinking.

[0054] Referring to Figure 1, it can be seen that delamination occurs in the case of PIM-1 material that has not undergone the modification process. On the other hand, in the case of crosslinked films manufactured from carboxylated intrinsically porous polymers or combinations thereof with epoxy resins, excellent interfacial properties are observed, and phenomena such as delamination are not seen. Therefore, it was possible to manufacture polymer crosslinked films with optimized interfacial properties with lithium metal anodes using carboxylated intrinsically porous polymers or combinations thereof with epoxy resins.

[0055] Figure 2 is a graph showing experimental results of lithium symmetric cells using lithium metal anodes with or without a cross-linked film of a carboxylated microporous polymer substrate, manufactured according to an embodiment of the present invention. In Figure 2, COOH:PEO(1:2), (1:1), and (2:1) refer to cross-linked films manufactured by mixing carboxylated microporous polymer (PIM-COOH) and poly(ethylene glycol) diglycidyl ether (Mn=500) in mass ratios of 1:2, 1:1, and 2:1, respectively, and COOH refers to the carboxylated microporous polymer (PIM-COOH).

[0056] Figure 2 shows that the crosslinked film exhibits superior long-life characteristics compared to the uncrosslinked carboxylated, intrinsically porous polymer crosslinked film (-COOH) with epoxy resin (poly(ethylene glycol) diglycidyl ether; PEO), as confirmed by the results for lithium symmetric cells. This is thought to be because, as confirmed in Figure 1, the carboxyl groups and hydroxyls contained in the polymer film provide excellent interfacial properties with the lithium metal anode, preventing delamination or additional side reactions due to delamination during battery operation.

[0057] Figures 3 and 4 show the results of electrochemical impedance spectroscopy experiments performed on lithium symmetric cells, which were manufactured using a lithium metal anode into which a crosslinked film, prepared by mixing a carboxylated microporous polymer with poly(ethylene glycol) diglycidyl ether in a mass ratio of 2:1, was introduced as a protective layer, according to an embodiment of the present invention. The ionic conductivity and lithium ion migration rate were measured.

[0058] As can be seen from Figures 3 and 4, the carboxylated intrinsically porous polymer substrate crosslinked film is composed of a combination of micropores favorable for lithium ion movement and a polymer capable of ion movement. As a result, it exhibits a high lithium ion mobility of 0.67, which is superior to the lithium ion mobility of approximately 0.2 to 0.4 observed in commercial liquid electrolytes. Such a high lithium ion mobility in the carboxylated intrinsically porous polymer substrate crosslinked film enables uniform electrical application and lithium ion movement, rather than localized electrical application, even during high-speed charging and discharging, due to the rapid lithium ion movement.

[0059] Figures 5 to 7 show the results of tests on the capacity change according to charge / discharge speed and long-term performance of lithium metal secondary battery full cells fabricated using lithium metal anodes and Ni83 cathodes, respectively, which were manufactured using a crosslinked film produced by mixing a carboxylated microporous polymer with poly(ethylene glycol) diglycidyl ether in mass ratios of 2:1, 1:1, and 1:2 according to an embodiment of the present invention. As shown in Figure 5, it can be confirmed that the introduction of a crosslinked film of the carboxylated microporous polymer substrate does not result in a large capacity decrease even during high-speed charge / discharge. This is thought to be because lithium ions move smoothly through the introduced crosslinked film. Furthermore, as shown in Figure 6, it can be confirmed that the capacity has not decreased significantly even after more than 100 charge / discharge cycles. In the performance results of the full cell in Figure 7, the cell with the electrode protective film introduced shows superior capacity maintenance characteristics and Coulomb efficiency compared to the case of a lithium metal anode without the crosslinked film. This is thought to be because the introduced cross-linked film protects the lithium metal anode, suppressing side reactions with the electrolyte and capacity reduction due to dead lithium that occur during battery operation.

[0060] Figures 8 and 9 show the results of confirming the interfacial properties via SEM after casting PIM-COOH (without PEO) and an epoxy resin composition of PIM-COOH and PEO (PIM-COOH:PEO(1:1)) onto copper foil usable as a current collector in a battery according to one embodiment of the present invention. When a solution composition consisting only of PIM-COOH (PIM-COOH(without PEO)) is solution-cast without the introduction of epoxy resin, a large gap can be observed between the polymer film and the copper foil, as can be seen in Figure 8. On the other hand, in Figure 9, by additionally introducing epoxy resin (PIM-COOH:PEO(1:1)), no gap can be observed between the copper foil and the polymer electrode protective film. In other words, by introducing epoxy resin with a PEO base, it is possible to achieve excellent interfacial properties that could not be achieved with conventional microporous polymers alone.

[0061] Figures 10 and 11 show the results of a comparative test to clarify the differences between the conventional PIM-1 polymer substrate interpenetrating polymer network and the present invention, in which a PIM-COOH polymer film is first manufactured by the solution casting method, and divalent cations (Cu) are added in the post-processing step. 2+ Ni 2+ Zn 2+ This is the result of ion crosslinking with an aqueous solution containing ). The samples shown in Figure 10 are as follows: (a) PIM-COOH, (b) PIM-COOH·Cu composite, (c) PIM-COOH·Ni composite, (d) PIM-COOH·Zn composite.

[0062] As can be seen from Figure 11, polymer crosslinked films after ion crosslinking are difficult to dissolve using solvents such as THF. This means that the conventional method of producing PIM-COOH-based ion crosslinked films by placing the film in an aluminum chloride (AlCl3) solution after film production to induce ion exchange is limited in the production of electrode protective films through the solution casting method performed after dissolving the polymer composition as presented in the present invention.

[0063] Figure 12 shows the XRD results for a PIM-COOH and PEO-based epoxy resin composition according to one embodiment of the present invention. Generally, in the case of pure PEO, two strong peaks for (120) and (112) are known to appear at 19.36 and 23.72°. However, as can be seen from Figure 12, no peaks due to PEO crystal formation are observed in the results for the PIM-COOH and PEO-based epoxy resin composition. This means that the PEO chains in the PIM-COOH and PEO-based epoxy resin composition are in an amorphous form favorable to lithium ion movement, rather than a crystalline form that inhibits lithium ion movement.

[0064] Figure 13 shows the DSC results for a PIM-COOH and PEO-based epoxy resin composition according to one embodiment of the present invention. As can be seen from Figure 13, in the case of pure PEO (PEO 200K), a dissolution peak is observed at 62.8°C due to the crystalline portion contained, whereas in the case of the PIM-COOH and PEO-based epoxy composition, no dissolution peak due to PEO is observed. This means that, as confirmed by the XRD results, PEO does not form crystals within the polymer composition in the PIM-COOH and PEO-based epoxy composition.

[0065] Figure 14 shows the results of confirming the reaction between methanol, used as the solvent for the crosslinking agent solution, and lithium metal, which corresponds to the anode of the battery, in the interpenetrating polymer network of the conventional PIM-1 polymer substrate.

[0066] In the case of the conventional PIM-1 polymer substrate interpenetrating polymer network, methanol is used to dissolve the epoxy resin. However, if such a conventional method is used to manufacture the protective layer for the lithium metal anode of a battery, a violent reaction occurs between methanol and lithium metal, corroding the lithium metal and forming an irreversible form of lithium methoxide. Therefore, the conventional film manufacturing method cannot be directly applied in the battery field.

Claims

1. Chemical formula 1 below: 【Chemistry 1】 An electrode protective layer formed by crosslinking a homopolymer or copolymer containing repeating units represented by, or a mixture containing one or more thereof, by reaction with a crosslinking agent, In chemical formula 1, X is one of the following selected from the group consisting of X1 to X17. An electrode protective layer in which the number of repeating units is in the range of 10 to 500. 【Chemistry 2】

2. The aforementioned crosslinking agent has the following chemical formula 2: 【Transformation 3】 It has the following chemical structure: The electrode protective layer according to claim 1, wherein in chemical formula 2, R is one of a linear or branched alkylene group, a linear or branched alkylene group containing an oxygen atom, or an arylene group.

3. In chemical formula 2, R is represented by the following chemical formula: -(CH ２ ) ｍ -、 -(CH) ２ ) ｍ -O-(CH ２ ) ｌ - -(CH) ２ ) ｍ -O-(CH ２ ) ｌ - -CH ２ -O-(CH ２ ) ４ -O-CH ２ - 【Chemistry 4】 It is one of the following: The electrode protective layer according to claim 2, wherein m and l are identical or distinct integers from 1 to 6, and n is an integer from 1 to 10000.

4. A-scatter, An electrode comprising an electrode protective layer according to any one of claims 1 to 3, coated on the anode.

5. The electrode according to claim 4, wherein the anode is capable of storing and releasing lithium ions.

6. The electrode according to claim 4, wherein the anode is one or more selected from the group including Li, Na, K, Mg, Ca, Zn, Al, Si, Ge, Sn, or alloys thereof.

7. The electrode according to claim 4 as an anode, Electrolytes, An electrochemical cell, including a cathode.

8. The electrochemical cell according to claim 7, further comprising a separation membrane between the anode and the cathode.

9. The stage of preparing the anode, Chemical formula 1 below: 【Transformation 5】 A polymer providing step of providing a homopolymer or copolymer containing repeating units represented by, or a mixture containing one or more thereof, A film-forming composition manufacturing step involves mixing the polymer, crosslinking agent, and solvent, A film formation step in which a film is formed on the anode using the film-forming composition, A step of manufacturing a crosslinked polymerized film that crosslinks the aforementioned film, Includes, In chemical formula 1, X is one of the following selected from the group consisting of X1 to X17. A method for forming an electrode protective layer, wherein the number of repeating units is in the range of 10 to 500: 【Transformation 6】 。

10. The aforementioned crosslinking agent has the following chemical formula 2: 【Transformation 7】 It has the following chemical structure: The method for forming an electrode protective layer according to claim 9, wherein in chemical formula 2, R is one of a linear or branched alkylene group, a linear or branched alkylene group containing an oxygen atom, or an arylene group.

11. In chemical formula 2, R is represented by the following chemical formula: -(CH ２ ) ｍ -、 -(CH) ２ ) ｍ -O-(CH ２ ) ｌ - -(CH) ２ ) ｍ -O-(CH ２ ) ｌ - -CH ２ -O-(CH ２ ) ４ -O-CH ２ - 【Transformation 8】 It is one of the following: The method for forming an electrode protective layer according to claim 10, wherein m and l are each the same or different integers from 1 to 6, and n is an integer from 1 to 10000.

12. The method for forming an electrode protective layer according to claim 9, wherein the solvent is one or more selected from the group consisting of tetrahydrofuran (THF), N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), dimethylformamide (DMF), and dimethylacetamide (DMAc).

13. The crosslinked polymer film manufacturing step for crosslinking the aforementioned film is performed using the following reaction formula 1: 【Chemistry 9】 This is done through the reaction of The method for forming an electrode protective layer according to claim 9, wherein in the reaction formula 1, n is a repeating unit and is an integer from 10 to 500, and R is one of a linear or branched alkylene group, a linear or branched alkylene group containing an oxygen atom, or an arylene group.

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