Separator for secondary battery, manufacturing method therefor, and secondary battery comprising same

Abstract

A method for manufacturing a separator for a secondary battery, in which ions of a base metal are intercalated into and deintercalated from a positive electrode and a negative electrode during a charging / discharging process, according to the present invention, may comprise the steps of: preparing a first compound containing the base metal and fluorine and a second compound containing a transition metal oxide; physically mixing the first compound and the second compound to prepare a coating layer source; and providing the coating layer source onto a substrate to form a coating layer, wherein in the step of physically mixing the first compound and the second compound to prepare the coating layer source, the molar ratio of the first compound is controlled to be higher than the molar ratio of the second compound in the coating layer source.

Description

Separator for secondary battery, method for manufacturing same, and secondary battery including same

[0001] The present invention relates to a separator for a secondary battery, a method for manufacturing the same, and a secondary battery including the same, and more specifically, to a separator for a secondary battery provided with a coating layer including a first compound including a base metal and fluorine and a second compound including a transition metal oxide on a substrate, a method for manufacturing the same, and a secondary battery including the same.

[0002] With the development of portable mobile electronic devices such as smartphones, MP3 players, and tablet PCs, as well as electric vehicles, the demand for secondary batteries that can store electric energy is explosively increasing.

[0003] Compared to nickel-cadmium batteries or nickel-hydrogen batteries, which were previously used as secondary batteries, research and development is underway on secondary batteries with high energy density and long lifespan.

[0004] In secondary batteries, the separator prevents direct contact between the cathode and anode, preventing internal short-circuiting. It also provides a pathway for metal ions to move during charging and discharging. This separator is a key component of secondary batteries, directly impacting their safety and performance.

[0005] Previously, polyolefin-based separators such as polyethylene or polypropylene were used as separators for lithium secondary batteries. However, to solve the problems of low wettability to electrolyte and low safety due to thermal shrinkage, research and development are being conducted on separators coated with inorganic substances using polymer binders.

[0006] For example, Korean Patent Publication No. 10-2009-0056811 (Application No. 10-2008-0097364) discloses a technology for manufacturing a secondary battery separator using an organic solvent, the separator having a porous coating layer having inorganic particles coated on a porous substrate having porous pores to improve heat resistance, electrolyte insolubility, and impregnation properties. However, when manufacturing a secondary battery separator using an organic solvent, the use and recovery of the organic solvent incurs a lot of costs, which increases the manufacturing cost, and the use of toxic chemicals may result in various regulatory sanctions.

[0007] The technical problem to be solved by the present invention is to provide a method for manufacturing a secondary battery separator that improves the capacity of a secondary battery.

[0008] Another technical problem to be solved by the present invention is to provide a separator for a secondary battery with improved electrolyte and wettability.

[0009] Another technical problem that the present invention seeks to solve is to provide a separator for a secondary battery with improved ionic conductivity.

[0010] Another technical problem that the present invention seeks to solve is to provide a secondary battery that can overcome the irreversible capacity problem caused by the solid electrolyte interface of the negative electrode.

[0011] Another technical problem that the present invention seeks to solve is to provide a secondary battery with improved overall energy density.

[0012] Another technical problem that the present invention seeks to solve is to provide a method for manufacturing a separator for a secondary battery with reduced manufacturing process costs.

[0013] Another technical problem that the present invention seeks to solve is to provide a method for manufacturing a separator for a secondary battery with a shortened manufacturing time.

[0014] Another technical problem that the present invention seeks to solve is to provide a method for manufacturing a separator for a secondary battery that is easy to mass-produce.

[0015] The technical problems to be solved by the present invention are not limited to those described above.

[0016] To solve the above technical problem, the present invention provides a method for manufacturing a separator for a secondary battery.

[0017] According to one embodiment, a method for manufacturing a secondary battery separator in which ions of a base metal are intercalated and deintercalated into a positive electrode and a negative electrode during a charge / discharge process includes the steps of preparing a first compound including the base metal and fluorine, and a second compound including a transition metal oxide, physically mixing the first compound and the second compound to prepare a coating layer source, and providing and coating the coating layer source on a substrate to form a coating layer, wherein in the step of physically mixing the first compound and the second compound to prepare the coating layer source, the molar ratio of the first compound in the coating layer source may be controlled to be higher than the molar ratio of the second compound.

[0018] According to one embodiment, the molar ratio of the second compound and the first compound within the coating layer source may be controlled to be greater than 1:1 and less than 1:3.

[0019] According to one embodiment, the step of physically mixing the first compound and the second compound to prepare the coating layer source may include the steps of preparing the first compound, the second compound, a conductive agent, a binder, and an organic solvent, providing the first compound, the second compound, and the conductive agent to a ball milling device and mixing them to prepare a base source; and providing the base source and the binder to the organic solvent and stirring them to prepare the coating layer source.

[0020] According to one embodiment, the weight ratio of the first compound and the second compound provided in the organic solvent may be 70 wt%, the weight ratio of the conductive material may be 20 wt%, and the weight ratio of the binder may be 10 wt%.

[0021] According to one embodiment, the conductive material may include Super P, the binder may include PVDF (Polyvinylidene fluoride), and the organic solvent may include NMP (N-Methyl-2-pyrrolidone).

[0022] In one embodiment, the base metal may include sodium (Na), the first compound may include sodium fluoride (NaF), and the second compound may include manganese monoxide (MnO).

[0023] In one embodiment, the substrate may include any one of a polyethylene separator, a polypropylene separator, a ceramic coated separator, or a glass fiber separator.

[0024] In order to solve the above technical problem, the present invention provides a separator for a secondary battery manufactured by the above-described manufacturing method.

[0025] According to one embodiment, the secondary battery separator, in which ions of a base metal are intercalated and deintercalated into a positive electrode and a negative electrode during a charge / discharge process, includes a substrate, and a coating layer disposed on the substrate and including a first compound including the base metal and fluorine, a second compound including a transition metal oxide, and a conductive material, wherein the second compound in the coating layer acts as a catalyst for decomposing the first compound, and the ions of the base metal include a first metal ion and a second metal ion, and the first metal ion includes an ion provided as an electrolyte by decomposing the base metal of a positive electrode active material included in the positive electrode during a charging process, and the second metal ion includes an ion provided as an electrolyte by decomposing the first compound by the second compound during a charging process.

[0026] According to one embodiment, when the coating layer is analyzed by XRD before charging / discharging, peaks corresponding to the first compound are observed at 39° and 56°, and peaks corresponding to the second compound are observed at 35°, 40°, 59°, 70°, and 74°, and when the coating layer is analyzed by XRD after charging / discharging, the intensity of the peaks corresponding to the first compound at 39° and 56° may be reduced compared to before charging / discharging the coating layer.

[0027] In one embodiment, the base metal may include sodium (Na), the first compound may include sodium fluoride (NaF), and the second compound may include manganese monoxide (MnO).

[0028] In order to solve the above technical problem, the present invention provides a secondary battery to which the above-described secondary battery separator is applied.

[0029] According to one embodiment, the secondary battery separator described above, a positive electrode having a positive active material including a base metal and disposed on the secondary battery separator, a negative electrode disposed spaced apart from the positive electrode with the secondary battery separator in the middle, and an electrolyte provided between the positive electrode and the negative electrode, wherein the secondary battery separator includes a coating layer of the secondary battery separator disposed to face the positive electrode, and during a charging process, the problem of irreversible capacity generation due to a solid electrolyte interface (SEI) formed on the negative electrode by the second metal ion generated in the coating layer and provided to the electrolyte can be overcome.

[0030] According to one embodiment, the secondary battery separator may include a first side adjacent to the positive electrode and a second side adjacent to the negative electrode, and the coating layer may be provided on the first side of the secondary battery separator.

[0031] According to one embodiment, the capacity of the secondary battery may be increased by the second metal ion.

[0032] A method for manufacturing a separator for a secondary battery according to the present invention may include a step of preparing a first compound containing a base metal and fluorine, and a second compound containing a transition metal oxide, a step of physically mixing the first compound and the second compound to manufacture a coating layer source, and a step of providing and coating the coating layer source on a substrate to form a coating layer.

[0033] In the step of physically mixing the first compound and the second compound to prepare the coating layer source, the molar ratio of the second compound (e.g., MnO) and the first compound (e.g., NaF) can be controlled to be greater than 1:1 and less than 1:3. Accordingly, a secondary battery separator that improves the capacity of a secondary battery (e.g., a sodium ion battery) can be provided.

[0034] The secondary battery separator manufactured by the above-described manufacturing method may include the substrate, and the coating layer disposed on the substrate and including the base metal (e.g., Na) and the first compound (e.g., NaF) containing fluorine, the second compound (e.g., MnO) containing a transition metal oxide, and a conductive material.

[0035] Accordingly, the wettability between the secondary battery separator and the electrolyte can be improved by the coating layer. As a result, the ionic conductivity of the secondary battery separator can be improved.

[0036] And, during the charging process, the first compound (e.g., NaF) of the coating layer may be decomposed by the second compound (MnO), thereby generating ions of the base metal (e.g., Na). As a result, ions of the base metal may be provided to the electrolyte, thereby improving the capacity of the secondary battery.

[0037] Therefore, the above secondary battery separator can be applied to the secondary battery (e.g., sodium ion battery) in which ions of the base metal (e.g., Na) are intercalated and deintercalated into the positive and negative electrodes during the charge / discharge process.

[0038] Figure 1 is a flowchart for explaining a manufacturing process of a separator for a secondary battery according to an embodiment of the present invention.

[0039] FIG. 2 is a drawing for explaining a first compound and a second compound according to an embodiment of the present invention.

[0040] Figure 3 is a flowchart illustrating a method for manufacturing a coating layer source according to an embodiment of the present invention.

[0041] FIG. 4 and FIG. 5 are drawings for explaining a method for manufacturing a base source according to an embodiment of the present invention.

[0042] FIG. 6 is a drawing for explaining a method for manufacturing a coating layer source according to an embodiment of the present invention.

[0043] FIG. 7 is a drawing for explaining a method of forming a coating layer on a substrate according to an embodiment of the present invention.

[0044] FIG. 8 is a drawing for explaining a separator for a secondary battery according to an embodiment of the present invention.

[0045] FIG. 9 is a drawing for explaining a secondary battery to which a secondary battery separator according to an embodiment of the present invention is applied.

[0046] Figure 10 is a voltage profile of a Na metal half cell to which a secondary battery separator according to Experimental Example 4 of the present invention is applied.

[0047] Figure 11 is a voltage profile of a Na metal half cell to which a separator according to Experimental Examples 5 to 7 of the present invention is applied.

[0048] Figure 12 is a voltage profile of a Na metal half cell to which a secondary battery separator according to Experimental Examples 1 to 3 of the present invention is applied.

[0049] Figure 13 is an SEM photograph of a coating layer in a separator for a secondary battery according to Experimental Example 2 of the present invention.

[0050] Figure 14 is a graph analyzed by XRD for a base source and a separator for a secondary battery according to Experimental Example 2 of the present invention.

[0051] Figure 15 is a graph for comparing ionic conductivity of separators for secondary batteries according to comparative examples and experimental examples of the present invention.

[0052] Figure 16 is a graph for comparing the characteristics of charge / discharge cycles of a Na metal full cell to which a secondary battery separator according to Comparative Example 1 and Experimental Example 2 of the present invention is applied.

[0053] Figures 17 and 18 are images for comparing the chemical composition of a secondary battery separator before and after charge / discharge according to Experimental Example 2 of the present invention.

[0054] Figure 19 is an image and table analyzing the negative electrode of a Na metal full cell to which a secondary battery separator according to Experimental Example 2 of the present invention is applied.

[0055] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. However, the technical concept of the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided to ensure that the disclosed content is thorough and complete and to sufficiently convey the spirit of the present invention to those skilled in the art.

[0056] In this specification, when a component is referred to as being on another component, it means that it can be formed directly on the other component, or a third component may be interposed between them. In addition, in the drawings, the thicknesses of films and regions are exaggerated for the purpose of effectively explaining the technical contents.

[0057] Also, although terms such as first, second, and third have been used to describe various components in various embodiments of this specification, these components should not be limited by these terms. These terms are only used to distinguish one component from another. Thus, what is referred to as a first component in one embodiment may be referred to as a second component in another embodiment. Each embodiment described and illustrated herein also includes its complementary embodiments. Also, the term "and / or" has been used herein to mean including at least one of the components listed before and after.

[0058] In the specification, singular expressions include plural expressions unless the context clearly dictates otherwise. In addition, terms such as "comprise" or "have" are intended to specify the presence of a feature, number, step, component, or combination thereof described in the specification, and should not be construed as excluding the presence or addition of one or more other features, numbers, steps, components, or combinations thereof. In addition, the term "connection" is used in the present specification to mean both indirectly connecting multiple components and directly connecting them.

[0059] In addition, when describing the present invention below, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description will be omitted.

[0060]

[0061] FIG. 1 is a flowchart for explaining a manufacturing process of a separator for a secondary battery according to an embodiment of the present invention, FIG. 2 is a diagram for explaining a first compound and a second compound according to an embodiment of the present invention, FIG. 3 is a flowchart for explaining a method for manufacturing a coating layer source according to an embodiment of the present invention, FIG. 4 and FIG. 5 are diagrams for explaining a method for manufacturing a base source according to an embodiment of the present invention, FIG. 6 is a diagram for explaining a method for manufacturing a coating layer source according to an embodiment of the present invention, FIG. 7 is a diagram for explaining a method for forming a coating layer on a substrate according to an embodiment of the present invention, FIG. 8 is a diagram for explaining a separator for a secondary battery according to an embodiment of the present invention, and FIG. 9 is a diagram for explaining a secondary battery to which a separator for a secondary battery according to an embodiment of the present invention is applied.

[0062] Referring to FIGS. 1 and 2, a first compound (120) containing a base metal and fluorine, and a second compound (130) containing a transition metal oxide are prepared (S110).

[0063] The base metal may include, for example, sodium (Na).

[0064] The first compound (120) may include the base metal and fluorine. For example, it may include sodium fluoride (NaF). Accordingly, the first compound (120) may be electrochemically stable. Therefore, the first compound (120) may not be decomposed during the charge / discharge process. Accordingly, in order to provide the ions of the base metal of the first compound (120) to the electrolyte, a catalyst for decomposing the first compound (120) may be required.

[0065] The second compound (130) may include a transition metal oxide. For example, the second compound (130) may include manganese monoxide (MnO). Accordingly, the second compound (130) may decompose the first compound (120) during the charging process. In addition, the second compound (130) may be suitable as a catalyst for decomposing the first compound (120) because it is not decomposed during the charging / discharging process and does not cause a side reaction.

[0066] Referring to FIGS. 1, 3, and 4 to 6, the first compound (120) and the second compound (130) are physically mixed to produce a coating layer source (110) (S120).

[0067] In the step of manufacturing the coating layer source (110) by physically mixing the first compound (120) and the second compound (130), the molar ratio of the first compound (120) can be controlled to be higher than the molar ratio of the second compound (130).

[0068] According to one embodiment, the molar ratio of the second compound (130) and the first compound (120) can be controlled to be greater than 1:1 and less than 1:3. Accordingly, the capacity of the secondary battery described below can be improved.

[0069] In contrast, when the molar ratio of the second compound (130) and the first compound (120) is controlled to be 1:1 or less and 1:3 or more, the capacity of the secondary battery described below may be reduced.

[0070] Therefore, according to the present application embodiment, in the step of manufacturing the coating layer source (110) by physically mixing the first compound (120) and the second compound (130), the molar ratio of the second compound (130) and the first compound (120) can be controlled to be greater than 1:1 and less than 1:3. Accordingly, the secondary battery described below with improved capacity can be provided. For example, when the molar ratio of the second compound (130) and the first compound (120) is controlled to 1:2, the capacity of the secondary battery described below can be maximized.

[0071] Specifically, the step of physically mixing the first compound (120) and the second compound (130) to prepare the coating layer source (110) may include a step (S121) of preparing the first compound (120), the second compound (130), the conductive agent (140), the binder (150), and the organic solvent (160), a step (S122) of providing the first compound (120), the second compound (130), and the conductive agent (140) to a ball milling device and mixing them to prepare a base source (170), and a step (S123) of providing the base source (170) and the binder (150) to the organic solvent (160) and stirring them to prepare the coating layer source (110).

[0072] In the step of providing the first compound (120), the second compound (130), and the conductive agent (140) to the ball milling equipment and mixing them to manufacture the base source (170), for example, the conductive agent (140) may include Super P. For example, the weight ratio of the first compound (120) and the second compound (130) may be 1.0:1.2. For example, the weight ratio of the conductive agent (140) may be 20 wt%. For example, the atmosphere within the ball milling equipment may be an argon gas atmosphere. For example, the rotation speed of the ball milling equipment may be 500 rpm. For example, the mixing time of the first compound (120), the second compound (130), and the conductive agent (140) may be 24 hours. Accordingly, the base source (170) may be easily manufactured.

[0073] And, in the step of providing the base source (170) and the binder (150) to the organic solvent (160) and stirring to prepare the coating layer source (110), for example, the organic solvent (160) may include NMP (N-Methyl-2-pyrrolidone). For example, the binder (150) may include PVDF (Polyvinylidene fluoride). For example, the weight ratio of the first compound (120) and the second compound (130) provided to the organic solvent (160) may be 70 wt%. For example, the weight ratio of the conductive material (140) provided to the organic solvent (160) may be 20 wt%. For example, the weight ratio of the binder (150) provided to the organic solvent (160) may be 10 wt%. Accordingly, the coating layer source (110) can be easily manufactured.

[0074] Referring to FIG. 1 and FIG. 7, the coating layer source (110) is provided on the substrate (10) and coated to form a coating layer (100) (S130).

[0075] The above-mentioned substrate (10) may include, for example, any one of a polyethylene separator, a polypropylene separator, a ceramic-coated separator, or a glass fiber separator that is commercially available and sold.

[0076] Accordingly, the substrate (10) may have low wettability with respect to commonly used electrolytes. In particular, the substrate (10) may have significantly low wettability with respect to electrolytes having high polarity, making it unsuitable for use as a separator for secondary batteries. Accordingly, for the purpose of improving wettability with respect to electrolytes, the coating layer (100) may be provided on the substrate (10).

[0077] In the step of providing and coating the coating layer source (110) on the substrate (10) to form the coating layer (100), after the coating layer source (110) is coated on the substrate (1), the coating layer source (110) may be dried. For example, the drying temperature may be 60°C. For example, the drying time may be 12 hours. Accordingly, the coating layer (100) is uniformly formed on the substrate (10), so that the secondary battery separator (200) provided with the coating layer (100) on the substrate (10) can be easily manufactured.

[0078] In conclusion, the method for manufacturing the secondary battery separator (200) according to the embodiment of the present application may include a step of preparing the first compound (120) containing the base metal and fluorine, and the second compound (130) containing a transition metal oxide, a step of physically mixing the first compound (120) and the second compound (130) to manufacture the coating layer source (110), and a step of providing and coating the coating layer source (110) on the substrate (10) to form the coating layer (100).

[0079] In the step of physically mixing the first compound (120) and the second compound (130) to prepare the coating layer source (110), the molar ratio of the second compound (130, for example, MnO) and the first compound (120, for example, NaF) can be controlled to be greater than 1:1 and less than 1:3. Accordingly, the secondary battery separator (200) that improves the capacity of the secondary battery can be provided.

[0080] Referring to FIG. 8, the secondary battery separator (200) is described.

[0081] The secondary battery separator (200) may include the substrate (10), and the coating layer (100) disposed on the substrate (10) and including the first compound (120) containing the base metal and fluorine, the second compound (130) containing a transition metal oxide, and the conductive material (140). As illustrated in FIG. 8, the coating layer (100) may have a form in which the binder (150) surrounds the first compound (120), the second compound (130), and the conductive material (140) in particle form. For example, the base metal may include sodium. For example, the first compound (120) may include sodium fluoride (NaF). For example, the second compound (130) may include manganese monoxide (MnO). For example, the conductive material (140) may include Super P. For example, the binder (150) may include PVDF (Polyvinylidene fluoride). Accordingly, the wettability with the electrolyte may be improved by the coating layer (10) provided on the substrate (10). As a result, the ionic conductivity of the secondary battery separator (200) may be improved.

[0082] Accordingly, the secondary battery separator (200) can be applied to the aforementioned secondary battery in which ions of the base metal are intercalated and deintercalated into the positive and negative electrodes during the charge / discharge process. For example, the base metal can include sodium. For example, the secondary battery can include a sodium ion battery.

[0083] And, the ions of the base metal may include a first metal ion and a second metal ion. The first metal ion may be generated when the base metal of the positive electrode active material included in the positive electrode is desorbed from the positive electrode active material during the charging process. As a result, the generated first metal ion may be provided as an electrolyte. And, the second metal ion may be generated when the first compound (120) is decomposed by the second compound (130). As a result, the generated second metal ion may be provided as an electrolyte. Therefore, the capacity of the secondary battery may be improved by the second metal ion provided as the electrolyte.

[0084] In conclusion, the secondary battery separator (200) according to the present application example may include the substrate (10), and the coating layer (100) disposed on the substrate (10) and including the first compound (120) containing the base metal and fluorine, the second compound (130) containing a transition metal oxide, and the conductive material (140).

[0085] Accordingly, the wettability between the secondary battery separator (200) and the electrolyte can be improved by the coating layer (100). As a result, the ionic conductivity of the secondary battery separator (200) can be improved.

[0086] And, during the charging process, the first compound (120, for example, NaF) of the coating layer (100) may be decomposed by the second compound (130, MnO), thereby generating ions of the base metal (for example, Na). As a result, ions of the base metal may be provided to the electrolyte, thereby improving the capacity of the secondary battery.

[0087] Accordingly, the secondary battery separator (200) can be applied to the secondary battery in which ions of the base metal are intercalated and deintercalated into the positive electrode and the negative electrode during the charge / discharge process.

[0088] Referring to FIG. 9, the secondary battery (600) to which the secondary battery separator (200) is applied is described.

[0089] The secondary battery (500) may include the secondary battery separator (200), the positive electrode (300) disposed on the secondary battery separator (200) and having the positive electrode active material including the base metal, the negative electrode (400) disposed spaced apart from the positive electrode (300) with the secondary battery separator (200) in the middle, and the electrolyte (500) provided between the positive electrode (300) and the negative electrode (400). For example, the base metal may include sodium. For example, the secondary battery (600) may include a sodium ion battery.

[0090] The secondary battery separator (200) of the secondary battery (600) may include a coating layer (100) of the secondary battery separator (200) being arranged to face the positive electrode (300). Specifically, the secondary battery separator (200) may include a first surface adjacent to the positive electrode (300) and a second surface adjacent to the negative electrode (400). Accordingly, the coating layer (100) may be provided on the first surface of the secondary battery separator (200).

[0091] Accordingly, during the charging process of the secondary battery (600), the base metal of the positive electrode active material included in the positive electrode (300) may be desorbed from the positive electrode active material, thereby generating the first metal ion. As a result, the first metal ion may be provided to the electrolyte (500). In addition, the first compound (120) including the base metal of the coating layer (100) of the secondary battery separator (200) may be decomposed by the second compound (130), thereby generating the second metal ion. As a result, the second metal ion may be provided to the electrolyte (500). That is, during the charging process of the secondary battery (600), not only is the first metal ion provided from the positive electrode active material of the positive electrode (400) to the electrolyte (500) of the secondary battery (600), but the second metal ion may also be additionally provided from the first compound (120) of the coating layer (100) of the secondary battery separator (200). Accordingly, the capacity of the secondary battery (600) may be improved by the second metal ion additionally provided to the electrolyte (500).

[0092] In general, during the charging / discharging process of the secondary battery (600), due to the specific surface area of ​​the negative electrode active material (e.g., hard carbon) included in the negative electrode (400) of the secondary battery (600), a solid electrolyte interface (SEI) is formed on the negative electrode (400), which may cause an irreversible capacity generation problem.

[0093] Meanwhile, the secondary battery (600) including the secondary battery separator (200) according to the present application embodiment, as described above, during the charging process, not only is the first metal ion provided from the positive electrode active material of the positive electrode (400) to the electrolyte (500) of the secondary battery (600), but the second metal ion can also be additionally provided from the first compound (120) of the coating layer (100) of the secondary battery separator (200).

[0094] Accordingly, the capacity of the secondary battery (600) can be improved by the second metal ion additionally provided to the electrolyte (500). Accordingly, not only can the problem of irreversible capacity generation due to the solid electrolyte interface formed on the negative electrode (400) be overcome, but the overall energy density of the secondary battery (600) can also be improved.

[0095]

[0096] Hereinafter, specific experimental examples and characteristic evaluation results of a secondary battery separator according to an embodiment of the present invention are described.

[0097]

[0098] Separator for secondary batteries according to Experimental Example 1

[0099] A commercially available glass fiber separator was prepared as a substrate, sodium fluoride (NaF) powder was prepared as a first compound, manganese monoxide (MnO) powder was prepared as a second compound, Super P powder was prepared as a conductive agent, PVDF (Polyvinylidene fluoride) was prepared as a binder, and NMP (N-Methyl-2-pyrrolidone) was prepared as an organic solvent.

[0100] The first compound, the second compound, and the conductive agent were provided to a ball milling device and ball milled (Ar gas atmosphere, 500 rpm, 24 hours) to prepare a base source. At this time, the molar ratio of the second compound and the first compound was controlled to be 1:1.

[0101] Then, the base source and the binder were provided to the solvent and stirred to prepare a coating layer source. At this time, the weight ratio of the first compound and the second compound provided to the organic solvent was controlled to 70 wt%, the weight ratio of the conductive material was controlled to 20 wt%, and the weight ratio of the binder was controlled to 10 wt%.

[0102] Then, the coating layer source was coated on the separator and dried (vacuum atmosphere, 60°C, 12 hours) to form a coating layer, thereby manufacturing a separator for a secondary battery.

[0103]

[0104] Separator for secondary batteries according to Experimental Example 2

[0105] In the process of manufacturing the base source, a secondary battery separator was manufactured in the same manner as Experimental Example 1, except that the molar ratio of the second compound and the first compound was controlled to 1:2.

[0106]

[0107] Separator for secondary batteries according to Experimental Example 3

[0108] In the process of manufacturing the base source, a secondary battery separator was manufactured in the same manner as Experimental Example 1, except that the molar ratio of the second compound and the first compound was controlled to 1:3.

[0109]

[0110] Separator for secondary batteries according to Experimental Example 4

[0111] In the process of manufacturing the base source, a secondary battery separator was manufactured in the same manner as Experimental Example 1, except that the second compound was not provided.

[0112]

[0113] Separator for secondary batteries according to Experimental Example 5

[0114] A secondary battery separator was manufactured in the same manner as Experimental Example 1, except that cobalt oxide (CoO) was prepared as the second compound and the first compound was not provided during the manufacturing process of the base source.

[0115]

[0116] Separator for secondary batteries according to Experimental Example 6

[0117] In the process of manufacturing the base source, a secondary battery separator was manufactured in the same manner as Experimental Example 1, except that the first compound was not provided.

[0118]

[0119] Separator for secondary batteries according to Experimental Example 7

[0120] A secondary battery separator was manufactured in the same manner as Experimental Example 1, except that nickel oxide (NiO) was prepared as the second compound and the first compound was not provided during the manufacturing process of the base source.

[0121]

[0122] Separator for secondary batteries according to Experimental Example 8

[0123] A secondary battery separator was manufactured in the same manner as Experimental Example 1, except that nickel oxide (NiO) was prepared as the second compound.

[0124]

[0125] Separator for secondary batteries according to Experimental Example 9

[0126] A secondary battery separator was manufactured using the same method as Experimental Example 2, except that a commercially available ceramic coating separator was prepared.

[0127]

[0128] Separator for secondary batteries according to comparative example 1

[0129] A commercially available glass fiber separator was used as a separator for secondary batteries.

[0130]

[0131] Separator for secondary batteries according to comparative example 2

[0132] A commercially available ceramic coating separator was used as a separator for secondary batteries.

[0133] Presence or absence of a branch material coating layer Molar ratio of the second compound and the first compound Experimental example 1 Glass fiber OMnO:NaF = 1:1 Experimental example 2 Glass fiber OMnO:NaF = 1:2 Experimental example 3 Glass fiber OMnO:NaF = 1:3 Experimental example 4 Glass fiber OMnO only providing the first compound (NaF) Experimental example 5 Glass fiber OMnO only providing the second compound (CoO) Experimental example 6 Glass fiber OMnO only providing the second compound (MnO) Experimental example 7 Glass fiber OMnO only providing the second compound (NiO) Experimental example 8 Glass fiber OMnO:NaF = 1:1 Experimental example 9 Ceramic coating OMnO:NaF = 1:2 Comparative example 1 Glass fiber X- Comparative example 2 Ceramic coating X-

[0134] Figure 10 is a voltage profile of a Na metal half cell to which a secondary battery separator according to Experimental Example 4 of the present invention is applied.

[0135] Referring to Fig. 10, the charge capacity of a Na metal half cell to which a secondary battery separator according to Experimental Example 4 was applied was measured.

[0136] As can be seen in Fig. 10, sodium fluoride (NaF) is not decomposed within the coating layer of the secondary battery separator according to Experimental Example 4. This is interpreted as being due to the electrochemical stability of sodium fluoride (NaF). Accordingly, it can be seen that a catalyst for decomposing sodium fluoride (NaF) is required.

[0137]

[0138] Figure 11 is a voltage profile of a Na metal half cell to which a separator according to Experimental Examples 5 to 7 of the present invention is applied.

[0139] Referring to (a) of Fig. 11, the charge capacity was measured for a Na metal half cell (CoO / Na metal) to which a secondary battery separator according to Experimental Example 5 was applied, and referring to (b) of Fig. 11, the charge capacity was measured for a Na metal half cell (MnO / Na metal) to which a secondary battery separator according to Experimental Example 6 was applied, and referring to (c) of Fig. 11, the charge capacity was measured for a Na metal half cell (NiO / Na metal) to which a secondary battery separator according to Experimental Example 7 was applied.

[0140] As can be seen from (a) to (c) of Fig. 11, it can be seen that capacity is developed in the Na metal half cell to which the secondary battery separator according to Experimental Examples 5 and 7 is applied.

[0141] In contrast, it can be seen that no capacity is developed in the Na metal half cell to which the secondary battery separator according to Experimental Example 6 is applied. In other words, it can be seen that no side reaction occurs. This factor is interpreted to be due to the second compound (MnO) within the coating layer of the secondary battery separator according to Experimental Example 6. Accordingly, it can be seen that the second compound (MnO) is suitable as a catalyst for decomposing sodium fluoride (NaF).

[0142]

[0143] Figure 12 is a voltage profile of a Na metal half cell to which a secondary battery separator according to Experimental Examples 1 to 3 of the present invention is applied.

[0144] Referring to Fig. 12, the charge capacity was measured for a Na metal half cell (MnO_NaF 1:1) to which a secondary battery separator according to Experimental Example 1 was applied, the charge capacity was measured for a Na metal half cell (MnO_NaF 1:2) to which a secondary battery separator according to Experimental Example 2 was applied, and the charge capacity was measured for a Na metal half cell (MnO_NaF 1:3) to which a secondary battery separator according to Experimental Example 3 was applied.

[0145] As can be seen in Fig. 12, it can be seen that the capacity is developed in the Na metal half cell to which the secondary battery separator according to Experimental Examples 1 to 3 is applied. In addition, it can be seen that the highest capacity is developed in the Na metal half cell to which the secondary battery separator according to Experimental Example 2 is applied.

[0146] Therefore, in the method for manufacturing a separator for a secondary battery according to an embodiment of the present application, it can be seen that the method of controlling the molar ratio of the second compound (MnO) and the first compound (NaF) to be greater than 1:1 and less than 1:3 is a method for increasing the capacity of the secondary battery.

[0147]

[0148] Figure 13 is an SEM photograph of a coating layer in a separator for a secondary battery according to Experimental Example 2 of the present invention.

[0149] Referring to Fig. 13, the surface of the coating layer in the secondary battery separator according to Experimental Example 2 was photographed using SEM.

[0150] As can be seen in Fig. 13, it can be seen that the coating layer including the first compound (NaF) and the second compound (MnO) is uniformly formed on the substrate.

[0151]

[0152] Figure 14 is a graph analyzed by XRD for a base source and a separator for a secondary battery according to Experimental Example 2 of the present invention.

[0153] Referring to (a) of Fig. 14, the base source (MnO-NaF powder) according to Experimental Example 2 was analyzed by XRD, and referring to (b) of Fig. 14, before charging / discharging the Na metal half cell to which the secondary battery separator according to Experimental Example 2 was applied, the secondary battery separator according to Experimental Example 2 was analyzed by XRD for the coating layer, and referring to (c) of Fig. 14, after charging / discharging the Na metal half cell to which the secondary battery separator according to Experimental Example 2 was applied, the coating layer of the secondary battery separator according to Experimental Example 2 was analyzed by XRD.

[0154] As can be seen from (a) to (c) of FIG. 14, before charging / discharging the Na metal half cell to which the secondary battery separator according to Experimental Example 2 is applied, it can be seen that peaks corresponding to the first compound (NaF) are observed at 39° and 56° within the coating layer of the secondary battery separator according to Experimental Example 2, and peaks corresponding to the second compound (MnO) are observed at 35°, 40°, 59°, 70°, and 74°.

[0155] And, after charging / discharging the Na metal half cell to which the secondary battery separator according to Experimental Example 2 was applied, it can be seen that the peak corresponding to the first compound (NaF) within the coating layer of the secondary battery separator according to Experimental Example 2 was reduced compared to before charging / discharging the Na metal half cell to which the secondary battery separator according to Experimental Example 2 was applied.

[0156] Accordingly, it can be seen that the first compound (NaF) in the coating layer of the secondary battery separator according to Experimental Example 2 is decomposed by the second compound (MnO) during the charge / discharge process.

[0157]

[0158] Figure 15 is a graph for comparing ionic conductivity of separators for secondary batteries according to comparative examples and experimental examples of the present invention.

[0159] Referring to (a) of Fig. 15, ionic conductivity was measured for the secondary battery separator (Bare GF) according to Comparative Example 1, the secondary battery separator (MnO-NaF(1:1) coated GF) according to Experimental Example 1, the secondary battery separator (MnO-NaF(1:1) coated GF) according to Experimental Example 2, the secondary battery separator (MnO-NaF(1:3) coated GF) according to Experimental Example 3, and the secondary battery separator (NiO-NaF(1:1) coated GF) according to Experimental Example 8. Referring to (b) of Fig. 15, the red solid line area indicated in (a) of Fig. 15 was enlarged. Referring to (c) of Fig. 15, ionic conductivity was measured for the secondary battery separator (CSS) according to Comparative Example 2, and the secondary battery separator (coated CCS) according to Experimental Example 9.

[0160] As can be seen in (a) and (b) of FIG. 15, the ionic conductivity of the secondary battery separator according to Comparative Example 1 is 0.0941 S / cm, and the ionic conductivity of the secondary battery separator according to Experimental Example 2 is 0.0946 S / cm. Accordingly, it can be seen that when a coating layer including the first compound (NaF) and the second compound (MnO) is provided on a substrate (glass fiber separator), the ionic conductivity is improved. Accordingly, it can be seen that the ionic conductivity of the secondary battery separator is improved by the coating layer provided on the substrate. This factor is interpreted to be due to the fact that the wettability between the secondary battery separator and the electrolyte is improved by the coating layer.

[0161] As can be seen from (c) of Fig. 15, the ionic conductivity of the secondary battery separator according to Comparative Example 2 is 0.49 mS / cm, and the ionic conductivity of the secondary battery separator according to Experimental Example 9 is 1.43 mS / cm. Accordingly, it can be seen that when a coating layer including the first compound (NaF) and the second compound (MnO) is provided on a substrate (ceramic coated separator), the ionic conductivity is improved.

[0162]

[0163] Figure 16 is a graph for comparing the characteristics of charge / discharge cycles of a Na metal full cell to which a secondary battery separator according to Comparative Example 1 and Experimental Example 2 of the present invention is applied.

[0164] Referring to Fig. 16, the capacity change was measured while performing 180 charge / discharge cycles for a Na metal full cell to which a secondary battery separator (Bare) according to Comparative Example 1 and a secondary battery separator (MnO-NaF separator) according to Experimental Example 2 were applied.

[0165] As can be seen in Fig. 16, the Na metal full cell to which the secondary battery separator according to Experimental Example 2 was applied has a higher capacity than the Na metal full cell to which the secondary battery separator according to Comparative Example 1 was applied. This factor is interpreted to be due to the fact that, in the coating layer of the secondary battery separator according to Experimental Example 2, during the charging process, the base metal ion (sodium ion) generated by the decomposition of the first compound (NaF) by the second compound (MnO) is provided as an electrolyte.

[0166] And, it can be seen that the capacity retention rate of the Na metal full cell to which the secondary battery separator according to Experimental Example 2 and the secondary battery separator according to Comparative Example 1 are applied is at a similar level.

[0167]

[0168] Figures 17 and 18 are images for comparing the chemical composition of a secondary battery separator before and after charge / discharge according to Experimental Example 2 of the present invention.

[0169] Referring to Fig. 17, before charging / discharging the Na metal half cell to which the secondary battery separator according to Experimental Example 2 was applied, the coating layer of the secondary transfer separator according to Experimental Example 2 was photographed using SEM, and EDS mapping analysis was performed on the photographed photograph, and the results were summarized in below. Referring to Fig. 18, after charging / discharging the Na metal half cell to which the secondary battery separator according to Experimental Example 2 was applied, the coating layer of the secondary battery separator according to Experimental Example 2 was photographed using SEM, and EDS mapping analysis was performed on the photographed photograph, and the results were summarized in below.

[0170] As can be seen in FIG. 18, FIG. 18, , and , before charging / discharging, the weight ratio of the Na element in the coating layer of the secondary battery separator according to Experimental Example 2 is 17.57 wt%. And, after charging / discharging, the weight ratio of the Na element in the coating layer of the secondary battery separator according to Experimental Example 2 is 11.37 wt%. Therefore, it can be seen that the weight ratio of the Na element in the coating layer of the secondary battery separator according to Experimental Example 2 decreases after charging / discharging. This factor is interpreted to be due to the fact that the first compound (NaF) in the coating layer of the secondary battery separator according to Experimental Example 2 is decomposed by the second compound (MnO).

[0171] ElementWt%Atomic%C36.6354.41O4.444.95F22.0820.74Na17.5713.64Mn19.286.26Total:100100

[0172] ElementWt%Atomic %C24.0739.08O8.9410.90F29.0029.77Na11.379.65P4.172.63Mn22.457.97Total:100100

[0173] Figure 19 is an image and table analyzing the negative electrode of a Na metal full cell to which a secondary battery separator according to Experimental Example 2 of the present invention is applied.

[0174] Referring to Fig. 19, before and after performing charge / discharge of the Na metal full cell to which the secondary battery separator according to Experimental Example 2 was applied, the surface of the negative electrode (Hard Carbon) of the Na metal full cell to which the secondary battery separator according to Experimental Example 2 was applied was photographed using SEM, and the surface SEM images of the negative electrode (Har Carbon) taken after performing charge / discharge were analyzed using EDS mapping, and the results were organized in a table.

[0175] As can be seen in Fig. 19, after performing charge / discharge, it can be seen that the Mn element is practically not detected within the solid electrolyte interface (SEI) formed on the surface of the negative electrode. Therefore, it can be seen that the second compound (MnO) is not decomposed within the coating layer of the secondary battery separator according to Experimental Example 2 during the charge / discharge process.

[0176]

[0177] While the present invention has been described in detail using preferred embodiments, the scope of the present invention is not limited to the specific embodiments described above, and should be interpreted in accordance with the appended claims. Furthermore, those skilled in the art will appreciate that numerous modifications and variations are possible without departing from the scope of the present invention.

[0178] A secondary battery separator according to an embodiment of the present application, a method for manufacturing the same, and a secondary battery including the same can be utilized in various industrial fields such as electric vehicles, mobile devices, and energy storage devices.

Claims

1. A method for manufacturing a secondary battery separator in which ions of a base metal are intercalated and deintercalated into the positive and negative electrodes during the charge / discharge process. A step of preparing a first compound including the base metal and fluorine, and a second compound including a transition metal oxide; A step of physically mixing the first compound and the second compound to prepare a coating layer source; and A step of providing the above coating layer source on a substrate and coating it to form a coating layer, comprising: A method for manufacturing a separator for a secondary battery, wherein, in the step of manufacturing a coating layer source by physically mixing the first compound and the second compound, the molar ratio of the first compound in the coating layer source is controlled to be higher than the molar ratio of the second compound.

2. In paragraph 1, A method for manufacturing a separator for a secondary battery, wherein the molar ratio of the second compound and the first compound within the coating layer source is controlled to be greater than 1:1 and less than 1:

3.

3. In paragraph 1, The step of physically mixing the first compound and the second compound to prepare the coating layer source is: A step of preparing the first compound, the second compound, a conductive agent, a binder, and an organic solvent; A step of providing the first compound, the second compound, and the conductive agent to a ball milling device and mixing them to prepare a base source; and A method for manufacturing a separator for a secondary battery, comprising the step of providing the base source and the binder to the organic solvent and stirring to manufacture the coating layer source.

4. In paragraph 3, A method for manufacturing a separator for a secondary battery, wherein the weight ratio of the first compound and the second compound provided in the organic solvent is 70 wt%, the weight ratio of the conductive material is 20 wt%, and the weight ratio of the binder is 10 wt%.

5. In paragraph 4, The above challenge material includes Super P, The above binder contains PVDF (Polyvinylidene fluoride), A method for manufacturing a separator for a secondary battery, wherein the organic solvent comprises NMP (N-Methyl-2-pyrrolidone).

6. In paragraph 1, The above base metal includes sodium (Na), The first compound comprises sodium fluoride (NaF), The above second compound is a method for producing a separator for a secondary battery including manganese monoxide (MnO).

7. In paragraph 1, The above description relates to a method for manufacturing a separator for a secondary battery, the separator including any one of a polyethylene separator, a polypropylene separator, a ceramic-coated separator, or a glass fiber separator.

8. In a secondary battery separator, in which ions of the base metal are intercalated and deintercalated into the positive and negative electrodes during the charge / discharge process, Description; and A coating layer disposed on the above substrate, comprising a first compound including the base metal and fluorine, a second compound including a transition metal oxide, and a conductive material, The second compound within the coating layer comprises a catalyst that decomposes the first compound, The ions of the above base metal include a first metal ion and a second metal ion, The above first metal ion includes the base metal of the cathode active material included in the cathode being desorbed from the cathode active material during the charging process and provided as an electrolyte, A secondary battery separator comprising the second metal ion, which is generated by decomposition of the first compound by the second compound during the charging process and provided as the electrolyte.

9. In paragraph 8, A secondary battery separator, wherein when the coating layer is analyzed by XRD before charging / discharging, peaks corresponding to the first compound are observed at 39° and 56°, and peaks corresponding to the second compound are observed at 35°, 40°, 59°, 70°, and 74°, and wherein when the coating layer is analyzed by XRD after charging / discharging, the intensity of the peaks corresponding to the first compound at 39° and 56° is decreased compared to before charging / discharging the coating layer.

10. In paragraph 8, The above base metal includes sodium (Na), The first compound comprises sodium fluoride (NaF), The second compound is a secondary battery separator containing manganese monoxide (MnO).

11. The secondary battery separator according to Article 8; A cathode having a positive electrode active material including a base metal and disposed on the above secondary battery separator; A cathode positioned spaced apart from the anode, with the above secondary battery separator in the middle; and Including an electrolyte provided between the positive electrode and the negative electrode, The above secondary battery separator includes a secondary battery separator in which the coating layer of the secondary battery separator is positioned so as to face the positive electrode, A secondary battery comprising: a battery wherein the problem of irreversible capacity generation due to a solid electrolyte interface (SEI) formed on the negative electrode is overcome by the second metal ion generated in the coating layer and provided to the electrolyte during the charging process.

12. In paragraph 11, The above secondary battery separator comprises a first surface adjacent to the positive electrode and a second surface adjacent to the negative electrode, A secondary battery including a coating layer provided on the first surface of the secondary battery separator.

13. In paragraph 11, A secondary battery, wherein the capacity of the secondary battery is increased by the second metal ion.

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