Separator for secondary battery and secondary battery comprising the same

Abstract

Disclosed is a separator for a secondary battery, comprising: a porous polymer substrate having a plurality of pores; and a porous coating layer provided on at least one surface of the porous polymer substrate and comprising a plurality of inorganic particles and a crosslinked polymer containing a urethane bond, wherein the crosslinked polymer containing a urethane bond is partially or entirely provided on the surface of the inorganic particles, such that the inorganic particles are fixedly connected to each other, and the glass transition temperature (Tg) of the crosslinked polymer containing a urethane bond is -15 to 32℃. Also disclosed is a secondary battery comprising the separator.

Description

Technical Field

[0001] This disclosure relates to separators for secondary batteries and secondary batteries including the separators. Specifically, this disclosure relates to separators for secondary batteries having improved heat resistance and improved adhesion to the counter electrode, and secondary batteries including the separators.

[0002] This application claims priority to Korean Patent Application No. 10-2020-0099520, filed in Korea on August 7, 2020, the disclosure of which is incorporated herein by reference. Background Technology

[0003] In recent years, energy storage technology has received increasing attention. As its applications have expanded to power mobile phones, cameras, laptops, and even electric vehicles, the research and development of electrochemical devices has become increasingly important. In this context, electrochemical devices have garnered the most attention. Among these electrochemical devices, the development of rechargeable secondary batteries has become a focal point. Recently, active research has been conducted on designing novel electrodes and batteries to improve the capacity density and specific energy of such batteries.

[0004] Among commercially available rechargeable batteries, lithium-ion batteries, developed in the early 1990s, have attracted attention because they offer higher operating voltages and significantly higher energy densities compared to conventional batteries using aqueous electrolytes (such as Ni-MH, Ni-Cd, and lead sulfate batteries). However, these lithium-ion batteries have caused safety-related problems, such as fires and explosions, due to the use of organic electrolytes, and are difficult to manufacture.

[0005] Recently, lithium-ion polymer batteries have improved upon these shortcomings of lithium-ion batteries and are expected to become one of the next-generation batteries. However, compared with lithium-ion batteries, these lithium-ion polymer batteries still offer relatively low capacity, especially exhibiting insufficient discharge capacity at low temperatures. Therefore, there is an urgent need to improve this shortcoming.

[0006] Although such electrochemical devices are manufactured by many companies, their safety characteristics exhibit varying degrees of variation. Evaluating and ensuring the safety of these devices is crucial. The most important consideration is that the electrochemical equipment should not cause harm to the user due to malfunction. Therefore, safety standards strictly control ignition and smoke emissions in electrochemical devices. Regarding the safety characteristics of electrochemical devices, there is a significant concern about potential explosions when overheating leads to thermal runaway or perforation of the separator. In particular, polyolefin-based porous substrates, traditionally used as separators in electrochemical devices, exhibit severe thermal shrinkage at temperatures above 100°C due to their material properties and manufacturing processes, including orientation, potentially leading to short circuits between the anode and cathode.

[0007] To address the safety issues of the aforementioned electrochemical devices, a separator with a porous organic-inorganic coating has been proposed. This coating is formed by applying a mixture of excess inorganic particles and a binder polymer to at least one surface of a porous polymer substrate with multiple pores.

[0008] However, when this porous organic-inorganic coating is introduced into the separator, the separator exhibits problems such as increased resistance and reduced adhesion to the electrodes. Therefore, these problems need to be addressed. Summary of the Invention

[0009] Technical issues

[0010] This disclosure aims to address the problems of the prior art, and therefore aims to provide a separator for secondary batteries that exhibits improved adhesion to the electrodes and excellent heat resistance.

[0011] This disclosure also relates to providing an electrochemical device including the aforementioned separator.

[0012] Technical solution

[0013] In one aspect of this disclosure, a separator for a secondary battery is provided according to any of the following embodiments.

[0014] According to a first embodiment, a separator for a secondary battery is provided, comprising:

[0015] Porous polymer substrates with multiple pores; and

[0016] A porous coating is disposed on at least one surface of a porous polymer substrate and comprises a plurality of inorganic particles and a cross-linked polymer containing urethane bonds, wherein the cross-linked polymer containing urethane bonds is partially or entirely disposed on the surface of the inorganic particles such that the inorganic particles can be interconnected and fixed, and the glass transition temperature (Tg) of the cross-linked polymer containing urethane bonds is -15 to 32°C.

[0017] According to the second embodiment, a separator for a secondary battery as defined in the first embodiment is provided, wherein the glass transition temperature (Tg) of the crosslinked polymer containing urethane bonds is -10 to 30°C.

[0018] According to the third embodiment, a separator for a secondary battery as defined in the first or second embodiment is provided, wherein the separator for the secondary battery has an adhesion to the electrode of 30gf / 25mm or more and a heat shrinkage rate of 35% or less.

[0019] According to the fourth embodiment, a separator for a secondary battery as defined in any one of the first to third embodiments is provided, wherein the crosslinked polymer containing urethane bonds is obtained by a crosslinking reaction of at least one crosslinkable polymer during the activation step of the secondary battery.

[0020] According to a fifth embodiment, a separator for a secondary battery as defined in any one of the first to fourth embodiments is provided, wherein the porous polymer substrate is a polyolefin-based porous polymer substrate.

[0021] According to the sixth embodiment, a separator for a secondary battery as defined in any one of the first to fifth embodiments is provided, wherein the inorganic particles are inorganic particles with a dielectric constant of 5 or higher, inorganic particles with lithium-ion transport capability, or a mixture thereof.

[0022] According to a seventh embodiment, a secondary battery is provided, including a cathode, an anode, and a separator disposed between the cathode and the anode, wherein the separator is the same as defined in any of the first to sixth embodiments.

[0023] According to an eighth embodiment, a method for manufacturing a secondary battery including a separator as defined in the first embodiment is provided, the method comprising the following steps:

[0024] Prepare a slurry containing multiple inorganic particles, a crosslinkable polymer, and a dispersion medium;

[0025] The slurry is applied to at least one surface of a porous polymer substrate and then dried to prepare a primary separator with a porous coating.

[0026] An electrode comprising a current collector and an electrode active material layer disposed on at least one surface of the current collector is stacked on the top surface of a porous coating of a primary separator, with the electrode active material layer facing the porous coating, to prepare a primary separator-electrode composite.

[0027] Preparation of a secondary battery comprising the primary separator-electrode composite; and

[0028] Activate the secondary battery,

[0029] The crosslinkable polymer of the porous coating is crosslinked during the activation step of the secondary battery to obtain a crosslinked polymer containing urethane bonds.

[0030] According to the ninth embodiment, a method for manufacturing a secondary battery as defined in the eighth embodiment is provided, wherein the crosslinkable polymer comprises hydroxyl (-OH), isocyanate (-NCO), or both.

[0031] According to the tenth embodiment, a method for manufacturing a secondary battery as defined in the eighth or ninth embodiment is provided, wherein the crosslinkable polymer includes a polyvinylidene polymer containing hydroxyl (-OH), isocyanate (-NCO) groups or both; a polyacrylic acid polymer containing hydroxyl (-OH), isocyanate (-NCO) groups or both; or both or more thereof.

[0032] According to the eleventh embodiment, a method for manufacturing a secondary battery as defined in any one of the eighth to tenth embodiments is provided, wherein the crosslinkable polymer comprises: polyvinylidene fluoride-trifluorochloroethylene-grafted-(methyl methacrylate-2-isocyanoethyl acrylate), polyvinylidene fluoride-trifluorochloroethylene-grafted-(ethyl acrylate-4-hydroxybutyl acrylate), polyvinylidene fluoride-grafted-(methyl methacrylate-2-isocyanoethyl acrylate), polyvinylidene fluoride-trifluorochloroethylene-grafted-(2-isocyanoethyl acrylate), polyvinylidene fluoride-grafted-(methyl acrylate-2-isocyanoethyl acrylate), polyvinylidene fluoride-trifluorochloroethylene-grafted-(methyl acrylate-2-isocyanoethyl acrylate), or two or more thereof; and ethyl acrylate-acrylonitrile-dimethacrylamide-acrylic acid-4-hydroxybutyl acrylate copolymer, ethyl acrylate-acrylonitrile-2-isocyanoethyl acrylate copolymer, etc. Cyanoethyl acrylate copolymer, methyl acrylate-acrylonitrile-dimethacrylamide-acrylic acid-4-hydroxybutyl acrylate copolymer, ethyl acrylate-acrylonitrile-acrylic acid-4-hydroxybutyl acrylate copolymer, ethyl acrylate-acrylonitrile-dimethacrylamide-4-hydroxybutyl acrylate copolymer, ethyl acrylate-dimethacrylamide-acrylic acid-4-hydroxybutyl acrylate copolymer, ethyl acrylate-acrylic acid-4-hydroxybutyl acrylate copolymer, methyl acrylate-acrylic acid-4-hydroxybutyl acrylate copolymer, methyl acrylate-acrylonitrile-dimethacrylamide-4-hydroxybutyl acrylate copolymer, methyl acrylate-dimethacrylamide-acrylic acid-4-hydroxybutyl acrylate copolymer, methyl acrylate-acrylic acid-4-hydroxybutyl acrylate copolymer, methyl acrylate-4-hydroxybutyl acrylate copolymer, or two or more thereof.

[0033] According to the twelfth embodiment, a method for manufacturing a secondary battery as defined in any one of the eighth to eleventh embodiments is provided, wherein the crosslinkable polymer includes polyvinylidene fluoride-trifluorochloroethylene-grafted-(methyl methacrylate-2-isocyanoethyl acrylate) and ethyl acrylate-acrylonitrile-dimethacrylamide-acrylic acid-4-hydroxybutyl acrylate copolymer, or ethyl acrylate-acrylonitrile-2-isocyanoethyl acrylate copolymer with polyvinylidene fluoride-trifluorochloroethylene-grafted-(ethyl acrylate-2-isocyanoethyl acrylate).

[0034] According to the thirteenth embodiment, a method for manufacturing a secondary battery as defined in any one of the eighth to twelfth embodiments is provided, wherein the step of activating the secondary battery includes an initial charging step and a high-temperature aging step.

[0035] According to the fourteenth embodiment, a method for manufacturing a secondary battery as defined in the thirteenth embodiment is provided, wherein the high-temperature aging step is performed at a temperature of 50°C or higher.

[0036] According to the fifteenth embodiment, a method for manufacturing a secondary battery as defined in the thirteenth or fourteenth embodiment is provided, the method for manufacturing the secondary battery further comprising a room temperature aging step performed at a temperature of 20°C to 40°C between the initial charging step and the high temperature aging step.

[0037] Beneficial effects

[0038] According to embodiments of this disclosure, before crosslinking, the crosslinkable polymer (crosslinkable polymer) present in the porous coating of the separator readily adheres to the active material layer of the electrode, thus improving the adhesion between the electrode and the separator (adhesion to the electrode, electrode-separator adhesion). Conversely, when a crosslinked polymer is directly introduced during the formation of the porous coating of the separator according to the prior art, the crosslinked polymer is rigid and exhibits low adhesion, thus failing to achieve sufficient adhesion between the separator and the active material layer of the electrode.

[0039] Since the crosslinked polymer included in the porous coating of the separator according to this disclosure is obtained by crosslinking at least one crosslinkable polymer included in the porous coating during the activation step of the secondary battery, no additional process is required after coating the crosslinkable polymer. In other words, in most cases, the crosslinkable polymer-containing coating according to the prior art is crosslinked by applying a slurry containing the crosslinkable polymer to at least one surface of a porous polymer substrate and then performing additional treatments (heat treatment, UV treatment, etc.). However, according to embodiments of this disclosure, the crosslinkable polymer can be crosslinked during the activation step performed during battery manufacturing without such an additional crosslinking step.

[0040] Furthermore, crosslinkable polymers are used as starting materials to provide the crosslinked polymers, rather than monomers as conventionally used. Therefore, when crosslinking is performed in the electrolyte during the activation step, the dissolution of monomers in the porous coating can be prevented.

[0041] Furthermore, the separator according to embodiments of this disclosure uses a cross-linked polymer with a low glass transition temperature (Tg) in its porous coating, thus ensuring heat resistance and electrolyte adhesion solely through the cross-linked polymer, without using any adhesive polymers (non-cross-linked polymers) that act as binders. Detailed Implementation

[0042] In the following, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Before the description, it should be understood that the terminology used in the specification and appended claims should not be construed as limited to its general and dictionary meaning, but rather as interpreted based on its meaning and concept corresponding to the technical aspects of the present disclosure. This is based on the principle of allowing the inventors to appropriately define terminology to obtain the best interpretation.

[0043] In one aspect of this disclosure, a separator for a secondary battery is provided, comprising: a porous polymer substrate having a plurality of pores;

[0044] A porous coating is disposed on at least one surface of a porous polymer substrate and comprises a plurality of inorganic particles and a cross-linked polymer containing urethane bonds, wherein the cross-linked polymer containing urethane bonds is partially or entirely disposed on the surface of the inorganic particles, such that the inorganic particles can be interconnected and fixed, and the glass transition temperature (Tg) of the cross-linked polymer containing urethane bonds is -15 to 32°C.

[0045] According to relevant technologies, the heat resistance of separators is improved by coating them with inorganic materials to enhance the safety of secondary batteries. High-heat-resistant adhesives are used to further improve heat resistance through coating. However, when cross-linked polymers are used as the high-heat-resistant adhesive polymer, additional cross-linking steps are required, increasing processing costs, and the coating formed on the separator after cross-linking hardens. Therefore, reducing adhesion to the electrodes during subsequent processes used to form the electrode assembly presents difficulties.

[0046] To address this difficulty, according to this disclosure, instead of pre-incorporating the crosslinked polymer into the porous coating of the separator, a crosslinkable polymer is incorporated into the porous coating to obtain the separator. Then, the separator is used to form an electrode assembly, and the crosslinkable polymer is fully crosslinked in the activation step after assembling the secondary battery. Here, to fully implement crosslinking in the activation step, a crosslinkable polymer having functional groups capable of forming reactive urethane crosslinks (urethane reactive functional groups) at low temperatures can be used. Furthermore, using a crosslinkable polymer instead of a crosslinkable monomer ensures that the porous coating does not dissolve in the electrolyte before crosslinking.

[0047] Furthermore, the separator according to this disclosure comprises a cross-linked polymer having a low glass transition temperature (Tg) of -15 to 32°C. Therefore, heat resistance and adhesion to the electrolyte can be ensured solely by the cross-linked polymer, without using any adhesive polymers (non-cross-linked polymers) used as binders.

[0048] Specifically, the porous polymer substrate can be a porous polymer film substrate or a porous polymer nonwoven mesh substrate.

[0049] The porous polymer membrane substrate can be a porous polymer membrane comprising polyolefins, such as polyethylene, polypropylene, polybutene, or polypentene. This polyolefin porous polymer thin film substrate achieves a shut-off function at temperatures ranging from 80 to 130°C.

[0050] Here, the polyolefin porous polymer membrane may be formed from a polymer including a polyolefin polymer, such as polyethylene, including high-density polyethylene, linear low-density polyethylene, low-density polyethylene or ultra-high molecular weight polyethylene, polypropylene, polybutene or polypentene, used alone or in combination of two or more.

[0051] Furthermore, porous polymer membrane substrates can be obtained by molding various polymers, such as polyesters other than polyolefins, into membranes. Additionally, porous polymer membrane substrates can have a stacked structure of two or more membrane layers, wherein each membrane layer can be formed from a polymer comprising the aforementioned polymers, such as polyolefins or polyesters, alone or in combination of two or more thereof.

[0052] In addition to the aforementioned polyolefins, porous polymer membrane substrates and porous polymer nonwoven substrates can be formed from polyester, such as polyethylene terephthalate or polybutylene terephthalate, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene oxide, polyphenylene sulfide, etc., alone or in combination.

[0053] There are no particular limitations on the thickness of the porous polymer substrate, which ranges from 1 to 100 μm, particularly 5 to 50 μm. Although there are no particular limitations on the size and porosity of the pores present in the porous polymer substrate, the pore diameter and porosity can be 0.01-50 μm and 10-95%, respectively.

[0054] The glass transition temperature (Tg) of cross-linked polymers containing urethane bonds is -15 to 32°C. The glass transition temperature (Tg) of cross-linked polymers containing urethane bonds can be -10 to 30°C, 0 to 30°C, 10 to 30°C, -10 to 5°C, or 5 to 30°C. Additionally, the glass transition temperature (Tg) of cross-linked polymers containing urethane bonds can be above -10°C, above 0°C, above 5°C, above 10°C, below 30°C, below 10°C, or below 5°C.

[0055] When the glass transition temperature of cross-linked polymers containing urethane bonds is below -15°C, their heat resistance may deteriorate. When the glass transition temperature is above 32°C, their adhesion to the electrode may deteriorate undesirably.

[0056] Furthermore, when the glass transition temperature of the cross-linked polymer containing urethane bonds meets the aforementioned range, no adhesive polymer (non-cross-linked polymer) can be used as a binder during the formation of the porous coating. This is because the cross-linked polymer contained in the porous coating of the separator according to this disclosure has a low glass transition temperature (Tg) of -15 to 32°C, and therefore can function like a conventional adhesive polymer. In other words, the cross-linked polymer improves the mechanical properties of the final porous coating, such as flexibility and elasticity, enabling the inorganic particles to interconnect and stably fix them to prevent a decrease in the mechanical properties of the separator with the porous coating, acting as a binder for the active material layer of the counter electrode, and also acting as a binder between the porous polymer substrate and the inorganic particles. As a result, in the separator according to this disclosure, heat resistance and adhesion to the counter electrode can be ensured solely by the cross-linked polymer without the use of an adhesive polymer (non-cross-linked polymer).

[0057] Crosslinked polymers containing urethane bonds can be obtained by urethane crosslinking of a polymer containing at least one urethane reactive functional group, namely hydroxyl (-OH), isocyanate group (-NCO), or both.

[0058] According to embodiments of this disclosure, crosslinkable polymers may include polyvinylidene polymers containing hydroxyl (-OH), isocyanate (-NCO) groups, or both; polyacrylic acid polymers containing hydroxyl (-OH), isocyanate (-NCO) groups, or both; or both or more thereof. Furthermore, the polyvinylidene polymer may be polyvinylidene ether or polyvinylidene ether copolymers (e.g., PVDF-CTFE, PVDF-HFP, PVDF-TFE, etc.) that further include repeating units derived from monomers containing hydroxyl (-OH), isocyanate (-NCO) groups, or both. Here, the copolymer may be a copolymer with different repeating units attached to its main chain, or a graft copolymer with different repeating units attached to its side chains. Monomers containing hydroxyl (-OH), isocyanate (-NCO) groups, or both may include alkyl (methyl) acrylates, etc. In addition to repeating units containing monomers with hydroxyl (-OH), isocyanate groups (-NCO), or both, the grafted repeating units may also contain repeating units derived from monomers without hydroxyl (-OH), isocyanate groups (-NCO), or both.

[0059] Specific examples of polyvinylidene polymers that are crosslinkable include polyvinylidene fluoride-trifluorochloroethylene-grafted-(methyl methacrylate-2-isocyanoethyl acrylate), polyvinylidene fluoride-trifluorochloroethylene-grafted-(ethyl acrylate-4-hydroxybutyl acrylate), polyvinylidene fluoride-grafted-(methyl methacrylate-2-isocyanoethyl acrylate), polyvinylidene fluoride-trifluorochloroethylene-grafted-(2-isocyanoethyl acrylate), polyvinylidene fluoride-grafted-(methyl acrylate-2-isocyanoethyl acrylate), polyvinylidene fluoride-trifluorochloroethylene-grafted-(methyl acrylate-2-isocyanoethyl acrylate), etc.

[0060] Polyacrylic polymers containing hydroxyl (-OH), isocyanate (-NCO) groups or both can be homopolymers of acrylic monomers containing hydroxyl (-OH), isocyanate (-NCO) groups or both, or copolymers comprising repeating units derived from acryloyl monomers containing hydroxyl (-OH), isocyanate (-NCO) groups or both and at least one repeating unit derived from another monomer without such substituents. Specific examples of polyacrylate-based polymers include ethyl acrylate-acrylonitrile-dimethacrylamide-acrylic acid-4-hydroxybutyl acrylate copolymer, ethyl acrylate-acrylonitrile-2-isocyanoethyl acrylate copolymer, methyl acrylate-acrylonitrile-dimethacrylamide-acrylic acid-4-hydroxybutyl acrylate copolymer, ethyl acrylate-acrylonitrile-acrylic acid-4-hydroxybutyl acrylate copolymer, ethyl acrylate-acrylonitrile-dimethacrylamide-4-hydroxybutyl acrylate copolymer, methyl acrylate-acrylic acid-4-hydroxybutyl acrylate copolymer, methyl acrylate-acrylonitrile-dimethacrylamide-4-hydroxybutyl acrylate copolymer, methyl acrylate-dimethacrylamide-acrylic acid-4-hydroxybutyl acrylate copolymer, methyl acrylate-4-hydroxybutyl acrylate copolymer, etc.

[0061] According to embodiments of this disclosure, the crosslinkable polymer may include polyvinylidene fluoride-trifluorochloroethylene-grafted-(methyl methacrylate-2-isocyanoethyl acrylate) and ethyl acrylate-acrylonitrile-dimethacrylamide-acrylic acid-4-hydroxybutyl acrylate copolymer, or ethyl acrylate-acrylonitrile-2-isocyanoethyl acrylate copolymer with polyvinylidene fluoride-trifluorochloroethylene-grafted-(ethyl acrylate-2-isocyanoethyl acrylate).

[0062] The weight-average molecular weight of the crosslinked polymer containing urethane bonds can be 100,000 or more, 200,000 or more, 300,000 or more, 400,000 or more, or 700,000 or more, less than 4,000,000, less than 700,000, less than 400,000, or less than 300,000.

[0063] When the weight-average molecular weight of the crosslinked polymer containing urethane bonds meets the above-mentioned range, problems such as the porous coating peeling off from the porous polymer substrate due to insufficient interconnection and fixation of inorganic particles caused by dissolution during the crosslinking process, or the thermal shrinkage and deterioration of the separator, can be prevented. In this case, the crosslinked polymer can also be easily synthesized and a high yield can be obtained.

[0064] The weight-average molecular weight of the crosslinked polymer containing urethane bonds can be determined by using gel permeation chromatography (GPC, Agilent Infinity 1200 system). For example, the weight-average molecular weight can be determined in tetrahydrofuran (THF) as a solvent at 35 °C and a rate of 1.0 mL / min.

[0065] The weight ratio of the inorganic particles to the crosslinked polymer can be 70:30 - 95:5. When the weight ratio of the inorganic particles to the crosslinked polymer satisfies the above-defined range, problems such as a decrease in the pore size and porosity of the resulting porous coating caused by an increase in the crosslinked polymer content can be prevented. Problems such as deterioration of the peel resistance and heat resistance of the resulting porous coating caused by a decrease in the content of the crosslinked polymer can also be solved.

[0066] In the separator according to an embodiment of the present disclosure, in addition to the above-mentioned inorganic particles, the porous coating may further include other additives as its components.

[0067] According to the present disclosure, non-limiting examples of the inorganic particles may include inorganic particles having a dielectric constant of 5 or greater, particularly 10 or greater, inorganic particles having lithium ion transport ability, and mixtures thereof.

[0068] Non-limiting examples of the inorganic particles having a dielectric constant of 5 or greater may include BaTiO3, Pb(Zr,Ti)O3 (PZT), Pb 1-x La x Zr 1-y Ti y O3 (PLZT), Pb(Mg 1 / 3 Nb 2 / 3 )O3PbTiO3 (PMN-PT), hafnium oxide (HfO2), SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiC, AlO(OH), Al2O3·H2O, or mixtures thereof.

[0069] As used herein, the term "inorganic particles having lithium ion transport ability" refers to inorganic particles that contain lithium element and do not store lithium but transport lithium ions. Non-limiting examples of the inorganic particles having lithium ion transport ability include lithium phosphate (Li3PO4), lithium titanium phosphate (Li x Ti y (PO4)3, 0 < x < 2, 0 < y < 3), lithium aluminum titanium phosphate (Li x Al y Ti z (PO4)3, 0 < x < 2, 0 < y < 1, 0 < z < 3), (LiAlTiP)x O y Base glasses (1 < x < 4, 0 < y < 13), such as 14Li2O - 9Al2O3 - 38TiO2 - 39P2O5, lithium lanthanum titanate (Li x La y TiO3, 0 < x < 2, 0 < y < 3), lithium thiogermanate phosphate (Li x Ge y P z S w , 0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5), such as Li 3.25 Ge 0.25 P 0.75 S4, lithium nitride (Li x N y , 0 < x < 4, 0 < y < 2), such as Li3N, SiS2 - based glasses (Li x Si y S z , 0 < x < 3, 0 < y < 2, 0 < z < 4), such as Li3PO4 - Li2S - SiS2, P2S5 - based glasses (Li x P y S z , 0 < x < 3, 0 < y < 3, 0 < z < 7), such as LiI - Li2S - P2S5, or a mixture thereof.

[0070] Although there is no particular limitation on the thickness of the porous coating, the thickness of the porous coating can be 1 - 10 μm, particularly 1.5 - 6 μm. In addition, there is no particular limitation on the porosity of the porous coating, but the porosity can preferably be 35 - 65%.

[0071] According to an embodiment of the present disclosure, the porous coating can be an organic coating using an organic slurry or an aqueous coating using an aqueous slurry. Particularly in the case of an aqueous coating, it is more advantageous to facilitate film coating and reduce the resistance of the separator.

[0072] According to an embodiment of the present disclosure, the cross - linked polymer of the porous coating attaches inorganic particles to each other (i.e., the cross - linked polymers connect and fix the inorganic particles) so that they can maintain their binding state. In addition, the inorganic particles and the porous polymer substrate can be kept in mutual binding through the cross - linked polymer. The inorganic particles of the porous coating can form an interstitial volume while they are substantially in contact with each other, where the interstitial volume refers to the space defined by the inorganic particles, which is substantially in contact with each other in a closely packed or densely packed structure of the inorganic particles. The interstitial volume formed between the inorganic particles may become vacant to form pores.

[0073] According to embodiments of this disclosure, the partition may have a heat shrinkage rate of less than 35%, 1-35%, 5-33%, or 5-19%.

[0074] Here, the thermal shrinkage rate of the pre-crosslinked separator and the thermal shrinkage rate of the activated separator (finished separator) can be calculated by preparing a separator sample with a size of 5cm×5cm, storing the sample at 150℃ for 30 minutes, and then calculating the thermal shrinkage rate according to the formula [(initial length - 150℃ / length after 30 minutes of thermal shrinkage) / (initial length)] x 100. The thermal shrinkage rate of the activated separator can be determined by preparing a crosslinked separator after storing the pre-crosslinked separator under the same battery activation conditions, without the need for an electrode assembly step, and calculating the thermal shrinkage rate of the resulting finished crosslinked separator under the same conditions as described above.

[0075] According to embodiments of this disclosure, the separator can exhibit adhesion to the counter electrode of 30 gf / mm or more, 30-90 gf / 25 mm, 35-90 gf / 25 mm, or 70-90 gf / 25 mm.

[0076] Here, the adhesion of the electrode can be determined as follows.

[0077] The separator was laminated to the electrode (cathode or anode), and the resulting structure was then inserted between 100 μm thick polyethylene terephthalate (PET) films and bonded using a flatbed press. Here, the flatbed press was heated to 90°C for 1 second at a pressure of 8 MPa. The bonded separator and electrode ends were then mounted onto a UTM instrument (LLOYD Instrument LFPlus), and forces were applied in both directions at a rate of 300 mm / min. The force required to separate the separator from the electrode was then determined.

[0078] In another aspect of this disclosure, a method for manufacturing a secondary battery including a separator according to an embodiment of this disclosure is provided, the method comprising the following steps:

[0079] Prepare a slurry containing multiple inorganic particles, a crosslinkable polymer, and a dispersion medium;

[0080] The slurry is applied to at least one surface of a porous polymer substrate and then dried to prepare a primary separator with a porous coating.

[0081] An electrode comprising a current collector and an electrode active material layer disposed on at least one surface of the current collector is stacked on the top surface of a porous coating of a primary separator, with the electrode active material layer facing the porous coating, to prepare a primary separator-electrode composite.

[0082] Preparation of a secondary battery comprising the primary separator-electrode composite; and

[0083] Activate the secondary battery,

[0084] The crosslinkable polymer of the porous coating is crosslinked during the activation step of the secondary battery to obtain a crosslinked polymer containing urethane bonds.

[0085] Each step will be explained in more detail below.

[0086] First, to form a porous coating, a slurry can be prepared by dissolving a crosslinkable polymer in a dispersion medium, adding inorganic particles thereto, and dispersing them. The inorganic particles can be pre-milled to a specified average particle size before being added. Alternatively, the inorganic particles can be added to a solution of the crosslinkable polymer, and then milled and dispersed while controlling their predetermined average particle size using methods such as ball milling.

[0087] While there are no particular limitations on the method of applying a slurry for forming a porous coating onto a porous polymer substrate, slot coating or dip coating is preferred. Slot coating involves applying a slurry supplied through a slot die onto the entire surface of the substrate, and the coating thickness can be controlled based on the flux supplied by a metering pump. Dip coating involves immersing the substrate in a tank containing slurry for coating, and the coating thickness can be controlled based on the slurry concentration and the rate at which the substrate is removed from the tank. Furthermore, for more precise control of the coating thickness, post-metering using a Meyer bar or similar method can be performed after immersion.

[0088] The porous polymer substrate coated with the slurry can then be dried in a dryer, such as an oven, to form a porous coating on at least one surface of the porous polymer substrate.

[0089] Non-limiting examples of dispersion media used herein may include any one, or a mixture of two or more, selected from acetone, tetrahydrofuran, dichloromethane, chloroform, dimethylformamide, N-methyl-2-pyrrolidone, methyl ethyl ketone, cyclohexane, methanol, ethanol, isopropanol, propanol, and water.

[0090] After the slurry is coated onto the porous polymer substrate, the coated porous polymer substrate can be dried at 90-180°C or 100-150°C to remove the dispersion medium.

[0091] In this manner, a primary separator comprising a porous polymer substrate and a porous coating containing crosslinkable polymer and inorganic particles disposed on at least one surface of the porous polymer substrate is prepared.

[0092] Crosslinkable polymers contain urethane reactive functional groups, such as hydroxyl (-OH), isocyanate (-NCO), or both, and are then converted into crosslinked polymers containing urethane bonds through urethane crosslinking.

[0093] The crosslinkable polymers used in this article will be described above.

[0094] Then, electrodes comprising a current collector and an electrode active material layer disposed on at least one surface of the current collector are stacked on the top surface of the porous coating of the primary separator, and the electrode active material layer is brought into contact with the porous coating to prepare a primary separator-electrode composite.

[0095] A primary separator-electrode composite is introduced into the battery casing, and an electrolyte is injected into it to prepare a secondary battery.

[0096] A non-aqueous electrolyte is injected into a battery casing containing a preliminary separator-electrode composite, followed by sealing. An initial charging activation step can then be performed on the sealed preliminary battery to activate the electrode active materials and form a solid electrolyte interface (SEI) film on the electrode surface. Furthermore, an aging step can be added to allow the electrolyte injected prior to the activation step to fully permeate into the electrodes and separator.

[0097] While activating the electrode active material and forming the SEI film as described above, gases may be generated in the battery due to electrolyte decomposition, etc. As mentioned above, according to the prior art, such gases generated during the initial charging step can be released to the outside of the battery by reopening the battery casing or by cutting a portion of the battery casing.

[0098] Here, in the activation step of the secondary battery, the crosslinkable polymer of the porous coating is crosslinked to obtain a crosslinked polymer containing urethane bonds.

[0099] The secondary battery activation step is an initial charging step used to activate the electrode active materials and form an SEI film on the electrode surface. Furthermore, an aging step can be added to allow the electrolyte injected prior to the activation step to fully permeate into the electrodes and separators.

[0100] According to embodiments of this disclosure, the step of activating a secondary battery may include an initial charging step and a high-temperature aging step, or an initial charging step, a room temperature aging step, and a high-temperature aging step.

[0101] Initial charging can be performed at a state of charge (SOC) of 10% or higher, 30% or higher, or 50% or higher. There is no specific upper limit to the SOC; it can be 100% or 90%. Furthermore, initial charging can be performed at a cutoff voltage of 3.5V or higher, 3.5-4.5V, or 3.65-4.5V.

[0102] Initial charging can be performed at a C-rate of 0.05-2C or 0.1-2C.

[0103] The high-temperature aging step provides a condition under which the crosslinkable polymer of the porous coating can crosslink. For example, the high-temperature aging step can be carried out at temperatures above 50°C, 50-100°C, 60-100°C, or 60-80°C. The high-temperature aging step can be carried out for 0.5-2 days or 0.5-1.5 days.

[0104] Furthermore, a room temperature aging step can be added between the initial charging step and the high temperature aging step, and can be carried out at temperatures of 20-40℃, 23-35℃, 23-30℃, 23-27℃, or 23-25℃. Additionally, the room temperature aging step can last 1-7 days or 1-5 days.

[0105] According to embodiments of this disclosure, the activation step of the secondary battery can be performed by charging the secondary battery at a constant current (CC) of 0.1C to 3.65V with a SOC of 30%, storing the secondary battery at room temperature (25°C) for 3 days, and aging the secondary battery by storing it at a high temperature of 60°C for 1 day.

[0106] In another aspect of this disclosure, an electrochemical device is provided, including a cathode, an anode, and a separator disposed between the cathode and the anode, wherein the separator is the aforementioned separator according to an embodiment of this disclosure.

[0107] Electrochemical devices include any device that performs an electrochemical reaction, and specific examples include all types of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors, such as supercapacitors. In particular, lithium secondary batteries are preferred among secondary batteries, including lithium metal secondary batteries, lithium-ion secondary batteries, lithium polymer secondary batteries, or lithium-ion polymer batteries.

[0108] The two electrodes (cathode and anode) used in conjunction with the separator according to this disclosure are not particularly limited and can be obtained by incorporating electrode active materials onto the electrode current collector using methods known in the art. Non-limiting examples of electrode active materials include conventional anode active materials that can be used as anodes in conventional electrochemical devices. Lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, or lithium composite oxides comprising combinations thereof are particularly preferred. Non-limiting examples of cathode active materials include conventional cathode active materials that can be used as cathodes in conventional electrochemical devices. Lithium-intercalating materials, such as lithium metal or lithium alloys, carbon, petroleum coke, activated carbon, graphite, or other carbon-containing materials, are particularly preferred. Non-limiting examples of anode current collectors include foils made of aluminum, nickel, or combinations thereof. Non-limiting examples of cathode current collectors include foils made of copper, gold, nickel, copper alloys, or combinations thereof.

[0109] The electrolyte that can be used in the electrochemical device disclosed herein is an electrolyte having A + B - Salts of structure, in which A + Including alkali metal cations such as L i+ Na + K + or a combination thereof, B - Including anions such as PF6 - BF4 - Cl - ,Br - I - ClO4 - AsF6 - CH3CO2 - CF3SO3 - N(CF3SO2)2 - C(CF2SO2)3 - Salts, or combinations thereof, are soluble or dissociated in organic solvents, including propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethyl methyl carbonate (EMC), γ-butyrolactone, or combinations thereof. However, this disclosure is not limited thereto.

[0110] Depending on the manufacturing process of the final product and the required performance of the final product, the electrolyte can be injected at an appropriate step in the process of manufacturing the battery. In other words, the electrolyte can be injected before battery assembly or as a final step in battery assembly.

[0111] The embodiments will now be described more fully to facilitate a clear understanding of this disclosure. However, the following examples may be embodied in many different forms and should not be construed as limiting oneself to the exemplary embodiments set forth herein. Rather, these exemplary embodiments are provided to make this disclosure thorough and complete, and to fully convey the scope of this disclosure to those skilled in the art.

[0112] Example 1

[0113] First, 15 parts by weight of polyvinylidene fluoride-trifluorochloroethylene (PVDF-CTFE)-graft-(methyl methacrylate (MMA)-2-isocyanatoethyl acrylate (AOI))(PVDF-CTFE)-graft-(methyl methacrylate-r-2-isocyanatoethyl acrylate) (PVDF-CTFE:MMA:AOI molar ratio = 70:18:12) and 15 parts by weight of ethyl acrylate (EA)-acrylonitrile (AN)-dimethylacrylamide (DMMA)-acrylic acid (AA)-4-hydroxybutyl acrylate copolymer (HBA) (Ethyl acrylate-r-acrylonitrile-r-dimethylacrylamide-r-acrylic acid-r-4-hydroxybutyl acrylate) A copolymer (molar ratio EA:AN:DMAA:AA:HBA = 40:15:30:0.5:14.5) was added as a crosslinkable polymer to 93 parts by weight of acetone as a dispersion medium, and the mixture was stirred at 60°C for about 3 hours to prepare a crosslinkable polymer solution. Next, 500 nm alumina (Al₂O₃) particles with an average particle size of 70 parts by weight were added to 75 parts by weight of acetone and dispersed to obtain a dispersion. This dispersion was then stirred with the crosslinkable polymer solution to obtain a slurry for porous coatings.

[0114] The obtained slurry was coated onto both sides of a 9 μm thick porous polyethylene membrane (resistance 0.66 ohms, air permeability 142 sec / 100 cc) using a dip-coating method, and dried in an oven at 100 °C to obtain a primary separator with a porous coating on both surfaces. Here, the total thickness of the porous coating is 6 μm.

[0115] Then, 96.7 parts by weight of Li[Ni] was used as the cathode active material. 0.6 Mn 0.2 Co 0.2A cathode mixture was prepared by mixing O2, 1.3 parts by weight of graphite as a conductive material, and 2.0 parts by weight of polyvinylidene fluoride as a binder. The resulting cathode mixture was dispersed in 1-methyl-2-pyrrolidone as a solvent to obtain a cathode mixture slurry. The slurry was coated on both sides of an aluminum foil with a thickness of 20 μm, dried, and pressurized to obtain a cathode.

[0116] In addition, an anode mixture was prepared by mixing 97.6 parts by weight of artificial graphite and natural graphite (weight ratio 90:10) as the anode active material, and 1.2 parts by weight of styrene-butadiene rubber (SBR) and 1.2 parts by weight of carboxymethyl cellulose (CMC) as binders. The anode mixture was dispersed in ion-exchanged water as a solvent to prepare an anode mixture slurry. The slurry was coated on both sides of a copper foil with a thickness of 20 μm, dried, and pressurized to obtain the anode.

[0117] Subsequently, LiPF6 was dissolved in an organic solvent containing a mixture of ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) in a volume ratio of 3:3:4 to a concentration of 1.0 M, thereby providing a non-aqueous electrolyte.

[0118] A primary separator-electrode composite is provided by inserting a primary separator between the cathode and the anode in such a way that at least one of the cathode active material layer and the anode active material layer is coated with a porous coating that faces the primary separator. The primary separator-electrode composite is then contained in a bag and an electrolyte is injected therein to obtain a secondary battery.

[0119] Then, the secondary battery equipped with the primary separator is charged at a constant current (CC) of 0.1C to 3.65V at SOC 30%, and then activated by an aging step of storing at room temperature (25°C) for 3 days and at a high temperature of 60°C for 1 day.

[0120] In the activation step, the isocyanate groups and hydroxyl groups of the crosslinkable polymer contained in the porous coating of the primary separator react with each other through an addition reaction to achieve urethane crosslinking, thereby providing a crosslinked polymer containing urethane bonds.

[0121] As a result, a separator for a secondary battery containing a cross-linked polymer with urethane bonds in a porous coating and a secondary battery containing the separator were finally obtained.

[0122] Example 2

[0123] A separator for a secondary battery and a secondary battery comprising the separator were obtained in the same manner as in Example 1, except that 15 parts by weight of ethyl acrylate (EA)-acrylonitrile (AN)-2-isocyanatoethyl acrylate copolymer (EA:AN:AOI molar ratio = 10:80:10) and 15 parts by weight of polyvinylidene fluoride-chlorotrifluoroethylene (PVDF-CTFE)-graft-(ethyl acrylate (EA)-4-hydroxybutyl acrylate (HBA)) (PVDF-CTFE)-graft-(ethyl acrylate-r-4-hydroxybutyl acrylate) (PVDF-CTFE:EA:HBA = 45:44:11) were used as crosslinkable polymers.

[0124] Example 3

[0125] A separator for a secondary battery and a secondary battery comprising the separator were obtained in the same manner as in Example 1, except that 15 parts by weight of ethyl acrylate (EA)-acrylonitrile (AN)-2-isocyanatoethyl acrylate copolymer (EA:AN:AOI molar ratio = 80:10:10) and 15 parts by weight of polyvinylidene fluoride-chlorotrifluoroethylene (PVDF-CTFE)-graft-(ethyl acrylate (EA)-hydroxybutyl acrylate (HBA))(PVDF-CTFE)-graft-( acrylate-r-4-hydroxybutyl acrylate (molar ratio of PVDF-CTFE:EA:HBA = 45:44:11) is used as a crosslinkable polymer.

[0126] Comparative Example 1

[0127] A separator for a secondary battery and a secondary battery comprising the separator were obtained in the same manner as in Example 1, except that 15 parts by weight of polyvinylidene fluoride-trifluorochloroethylene (PVDF-CTFE)-graft-(methyl methacrylate (MMA)-2-isocyanatoethyl acrylate (AOI))(PVDF-CTFE)-graft-(methyl methacrylate-r-2-isocyanatoethyl acrylate) (molar ratio PVDF-CTFE:MMA:AOI = 40:48:12) and 15 parts by weight of ethyl acrylate (EA)-acrylonitrile (AN)-dimethylacrylamide (DMAA)-acrylic acid (AA)-4-hydroxybutyl acrylate (HBA) copolymer (Ethyl acrylate-r-acrylonitrile-r-dimethylacrylamide-r-acrylic acid-r-4-hydroxybutyl acrylate) were used. The copolymer (EA:AN:DMAA:AA:HBA molar ratio = 40:15:30:0.5:14.5) is used as a crosslinkable polymer.

[0128] Comparative Example 2

[0129] A separator for a secondary battery and a secondary battery comprising the separator were obtained in the same manner as in Example 1, except that 15 parts by weight of polyvinylidene fluoride-trifluorochloroethylene (PVDF-CTFE)-graft-(methyl methacrylate (MMA)-2-isocyanatoethyl acrylate (AOI))(PVDF-CTFE)-graft-(methyl methacrylate-r-2-isocyanatoethyl acrylate) (molar ratio PVDF-CTFE:MMA:AOI = 60:28:12) and 15 parts by weight of ethyl acrylate (EA)-acrylonitrile (AN)-dimethylacrylamide (DMAA)-acrylic acid (AA)-4-hydroxybutyl acrylate (HBA) copolymer (Ethyl acrylate-r-acrylonitrile-r-dimethylacrylamide-r-acrylic acid-r-4-hydroxybutyl acrylate) were used. The copolymer (EA:AN:DMAA:AA:HBA molar ratio = 40:15:30:0.5:14.5) is used as a crosslinkable polymer.

[0130] Comparative Example 3

[0131] A separator for a secondary battery and a secondary battery comprising the separator were obtained in the same manner as in Example 1, except that 15 parts by weight of ethyl acrylate (EA)-acrylonitrile (AN)-2-isocyanatoethyl acrylate (AOI) copolymer (EA:AN:AOI molar ratio = 85:5:10) and 15 parts by weight of polyvinylidene fluoride-chlorotrifluoroethylene (PVDF-CTFE)-graft-(ethyl acrylate (EA)-hydroxybutyl acrylate (HBA))(PVDF-CTFE)-graft-( acrylate-r-4-hydroxybutyl acrylate (molar ratio of PVDF-CTFE:EA:HBA = 45:44:11) is used as a crosslinkable polymer.

[0132] Test Results

[0133] Regarding the T of cross-linked polymers g The content of cross-linked polymers in the porous coating, the weight-average molecular weight of the cross-linked polymers, the electrode-septum adhesion, and the thermal shrinkage rate were evaluated for each septum in Examples 1-3 and Comparative Examples 1-3. The results are shown in Table 1 below.

[0134] Specifically, the testing methods are as follows.

[0135] (1) T of cross-linked polymers g (°C)

[0136] The Tc of the crosslinked polymer contained in the porous coating of each septum according to Examples 1-3 and Comparative Examples 1-3 was determined by using a differential scanning calorimeter (TA Instrument). g .

[0137] (2) Content of cross-linked polymers in porous coatings

[0138] The content of cross-linked polymers in the porous coating is taken as the total content of cross-linkable polymers in the solid components of the porous coating slurry.

[0139] (3) Determination of the weight-average molecular weight of the cross-linked polymer

[0140] The weight-average molecular weight of the crosslinked polymers was determined by gas permeation chromatography (Agilent Infinity 1200 system) in tetrahydrofuran (THF) solvent at 35 °C and a rate of 1.0 mL / min.

[0141] (4) Evaluation of electrode-septum adhesion (gf / 25mm)

[0142] The active material (natural graphite and artificial graphite (weight ratio 5:5)), conductive material (Super P), and binder (polyvinylidene fluoride (PVDF)) were mixed in a weight ratio of 92:2:6. The resulting mixture was dispersed in water to form a slurry, which was then coated onto copper foil to obtain the anode. The anode was cut into 25mm x 70mm dimensions.

[0143] Each partition according to Examples 1-3 and Comparative Examples 1-3 was cut to a size of 25mm × 70mm.

[0144] The prepared separator was laminated with the anode, and then the resulting structure was inserted between 100 μm thick PET films and adhered using a flatbed press. Here, the flatbed press was heated at 90°C for 1 second under a pressure of 8 MPa.

[0145] The adhered separator and the end of the anode were mounted onto the UTM instrument (LLOYD Instrument LF Plus), and forces were applied in both directions at a rate of 300 mm / min. The force required to separate the separator from the anode was measured.

[0146] (5) Evaluation of heat shrinkage rate

[0147] The thermal shrinkage rate of the activated separator was determined as follows: the pre-crosslinked separator was stored under the same battery activation conditions and then the crosslinked separator was prepared without the need for electrode assembly. The thermal shrinkage rate of the resulting crosslinked separator was calculated under the same conditions as above. That is, each separator sample was prepared into a size of 5cm x 5cm, and each sample was allowed to stand at 150°C for 30 minutes. Then, the thermal shrinkage rate (%) was calculated according to the formula: thermal shrinkage rate (%) = [(initial length – length after thermal shrinkage at 150°C for 30 minutes) / (initial length)] x 100.

[0148] [Table 1]

[0149]

[0150] Referring to Table 1, the porous coatings according to Examples 1-3 contain materials with a glass transition temperature (T0) ranging from -15 to 32°C. g Each separator of the urethane-containing crosslinked polymer exhibits excellent properties in terms of electrode-seal adhesion and thermal shrinkage. Conversely, the porous coatings according to Comparative Examples 1 and 2 contain materials with a glass transition temperature (T0) higher than 32°C. gEach separator of the urethane-containing crosslinked polymer showed significantly reduced electrode-seal adhesion, and the separators of the porous coating of Comparative Example 3 containing urethane-containing crosslinked polymers with a glass transition temperature (Tg) below -15°C showed significantly reduced thermal shrinkage properties.

[0151] This disclosure has been described in detail. However, it should be understood that while the detailed description and specific embodiments indicate preferred embodiments of this disclosure, they are given by way of illustration only, as various variations and modifications within the scope of this disclosure will become apparent to those skilled in the art based on this detailed description.

Claims

1. A separator for a secondary battery, comprising: Porous polymer substrate with multiple pores; and A porous coating is disposed on at least one surface of a porous polymer substrate and comprises a plurality of inorganic particles and a cross-linked polymer containing urethane bonds, wherein the cross-linked polymer containing urethane bonds is partially or entirely disposed on the surface of the inorganic particles, such that the inorganic particles are interconnected and fixed, and the glass transition temperature (Tg) of the cross-linked polymer containing urethane bonds is -15 to 32°C. The cross-linked polymer containing urethane bonds is obtained by cross-linking at least one cross-linkable polymer during the activation step of the secondary battery.

2. The separator for a secondary battery according to claim 1, wherein the glass transition temperature (Tg) of the crosslinked polymer containing urethane bonds is -10 to 30°C.

3. The separator for a secondary battery according to claim 1, wherein the separator for a secondary battery has an adhesion to the electrode of 30gf / 25mm or more and a heat shrinkage rate of 35% or less.

4. The separator for a secondary battery according to claim 1, wherein the porous polymer substrate is a polyolefin-based porous polymer substrate.

5. The separator for a secondary battery according to claim 1, wherein the inorganic particles are inorganic particles with a dielectric constant of 5 or higher, inorganic particles with lithium-ion transport capability, or a mixture thereof.

6. A secondary battery comprising a cathode, an anode, and a separator disposed between the cathode and the anode according to any one of claims 1 to 5.

7. A method for manufacturing a secondary battery comprising the separator according to claim 1, the method comprising the following steps: Prepare a slurry containing multiple inorganic particles, a crosslinkable polymer, and a dispersion medium; The slurry is applied to at least one surface of a porous polymer substrate and then dried to prepare a primary separator with a porous coating. An electrode comprising a current collector and an electrode active material layer disposed on at least one surface of the current collector is stacked on the top surface of a porous coating of a primary separator, with the electrode active material layer facing the porous coating, to prepare a primary separator-electrode composite. Prepare a secondary battery including the primary separator-electrode composite; and Activate the secondary battery, The crosslinkable polymer of the porous coating is crosslinked during the activation step of the secondary battery to obtain a crosslinked polymer containing urethane bonds.

8. The method for manufacturing a secondary battery according to claim 7, wherein the crosslinkable polymer comprises hydroxyl (-OH), isocyanate (-NCO), or both.

9. The method for manufacturing a secondary battery according to claim 7, wherein the crosslinkable polymer comprises a polyvinylidene polymer containing hydroxyl (-OH), isocyanate (-NCO) groups or both; a polyacrylic acid polymer containing hydroxyl (-OH), isocyanate (-NCO) groups or both; or both or more thereof.

10. The method for manufacturing a secondary battery according to claim 7, wherein the crosslinkable polymer comprises: Polyvinylidene fluoride-trifluorochloroethylene-grafted-(methyl methacrylate-2-isocyanoethyl acrylate), polyvinylidene fluoride-trifluorochloroethylene-grafted-(ethyl acrylate-4-hydroxybutyl acrylate), polyvinylidene fluoride-grafted-(methyl methacrylate-2-isocyanoethyl acrylate), polyvinylidene fluoride-trifluorochloroethylene-grafted-(2-isocyanoethyl acrylate), polyvinylidene fluoride-grafted-(methyl acrylate-2-isocyanoethyl acrylate), polyvinylidene fluoride-trifluorochloroethylene-grafted-(methyl acrylate-2-isocyanoethyl acrylate), or two or more thereof; and ethyl acrylate-acrylonitrile-dimethacrylamide-acrylic acid-4-hydroxybutyl acrylate copolymer, ethyl acrylate-acrylonitrile-2-isocyanoethyl acrylate copolymer, methyl acrylate-acrylonitrile-dimethacrylamide-4-hydroxybutyl acrylate copolymer, ethyl ...-4-hydroxy Acrylic acid-4-hydroxybutyl acrylate copolymer, ethyl acrylate-acrylonitrile-acrylic acid-4-hydroxybutyl acrylate copolymer, ethyl acrylate-acrylonitrile-dimethacrylamide-4-hydroxybutyl acrylate copolymer, ethyl acrylate-dimethacrylamide-acrylic acid-4-hydroxybutyl acrylate copolymer, ethyl acrylate-acrylic acid-4-hydroxybutyl acrylate copolymer, ethyl acrylate-4-hydroxybutyl acrylate copolymer, methyl acrylate-acrylic acid-4-hydroxybutyl acrylate copolymer, methyl acrylate-acrylonitrile-dimethacrylamide-4-hydroxybutyl acrylate copolymer, methyl acrylate-dimethacrylamide-acrylic acid-4-hydroxybutyl acrylate copolymer, methyl acrylate-acrylic acid-4-hydroxybutyl acrylate copolymer, methyl acrylate-4-hydroxybutyl acrylate copolymer, or two or more thereof.

11. The method for manufacturing a secondary battery according to claim 7, wherein the crosslinkable polymer comprises polyvinylidene fluoride-trifluorochloroethylene-grafted-(methyl methacrylate-2-isocyanoethyl acrylate) and ethyl acrylate-acrylonitrile-dimethacrylamide-acrylic acid-4-hydroxybutyl acrylate copolymer, or ethyl acrylate-acrylonitrile-2-isocyanoethyl acrylate copolymer with polyvinylidene fluoride-trifluorochloroethylene-grafted-(ethyl acrylate-2-isocyanoethyl acrylate).

12. The method for manufacturing a secondary battery according to claim 7, wherein the step of activating the secondary battery includes an initial charging step and a high-temperature aging step.

13. The method for manufacturing a secondary battery according to claim 12, wherein the high-temperature aging step is performed at a temperature above 50°C.

14. The method for manufacturing a secondary battery according to claim 12, the method further comprising a room temperature aging step performed at a temperature of 20°C to 40°C between the initial charging step and the high temperature aging step.

Images