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

Abstract

A method for manufacturing a separator according to the present invention may comprise the steps of: preparing a substrate; preparing a composite metal oxide including a base metal and a transition metal; mixing the composite metal oxide, a conductive material, and a binder to prepare a coating layer source; and applying the coating layer source onto one surface of the substrate to manufacture the separator.

Description

Separator for a secondary battery, method of manufacturing the same, and secondary battery including the same

[0001] The 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 having a coating layer comprising a substrate and a composite metal oxide provided on one surface of the substrate, a method for manufacturing the same, and a secondary battery including the same.

[0002] With the advancement of portable mobile electronic devices such as smartphones, MP3 players, and tablet PCs, as well as electric vehicles, the demand for secondary batteries capable of storing electrical energy is increasing explosively.

[0003] Research and development is underway on secondary batteries that have higher energy density and longer lifespan compared to the nickel-cadmium or nickel-hydrogen batteries conventionally used as secondary batteries.

[0004] In secondary batteries, the separator prevents internal short circuits by blocking direct contact between the negative and positive electrodes, while simultaneously providing a pathway for base metal ions to move during the charging and discharging process. This separator is a core component of secondary batteries that directly affects their safety and performance. Accordingly, various types of separators for secondary batteries are being actively researched and developed.

[0005] For example, Korean Patent Publication No. 10-2022-0018951 (Application No. 10-2021-0104167) discloses a separator for a secondary battery comprising a porous polymer substrate having a plurality of pores, a plurality of inorganic particles located on at least one surface of the porous polymer substrate, and a urethane-bonded crosslinked polymer, wherein the urethane-bonded crosslinked polymer is located on part or all of the surface of the inorganic particles to connect and fix the inorganic particles together, and the glass transition temperature of the urethane-bonded crosslinked polymer is -15℃ to 32℃.

[0006] The technical problem that the present invention aims to solve is that during the charging and discharging of a secondary battery, ions of the base metal (Li + It is to provide a separation membrane that supplies ).

[0007] Another technical problem that the present invention aims to solve is to provide a separator in which, during the initial charging process of a secondary battery, the composite metal oxide of the coating layer undergoes oxidative decomposition to generate a residue that adsorbs lithium polysulfide.

[0008] Another technical problem that the present invention aims to solve is to provide a secondary battery with increased initial capacity.

[0009] Another technical problem that the present invention aims to solve is to provide a secondary battery with improved long-term stability against charge / discharge cycles.

[0010] Another technical problem that the present invention aims to solve is to provide a method for manufacturing a separation membrane with reduced manufacturing time.

[0011] Another technical problem that the present invention aims to solve is to provide a method for manufacturing a separation membrane with reduced manufacturing process costs.

[0012] Another technical problem that the present invention aims to solve is to provide a method for manufacturing a separation membrane that is easy to mass-produce.

[0013] The technical problems that the present invention aims to solve are not limited to those described above.

[0014] To solve the above technical problem, the present invention provides a method for manufacturing a separation membrane.

[0015] According to one embodiment, in a method for manufacturing a separator for a secondary battery in which ions of a base metal are intercalated and deintercalated into a negative electrode and a positive electrode during a charging / discharging process, the method for manufacturing the separator may include the steps of: preparing a substrate; preparing a composite metal oxide comprising the base metal and a transition metal; mixing the composite metal oxide, a conductive material, and a binder to prepare a coating layer source; and coating the coating layer source on one surface of the substrate to manufacture the separator.

[0016] According to one embodiment, the initial capacity of a secondary battery including the separator may be controlled according to the weight ratio of the composite metal oxide in the coating layer source.

[0017] According to one embodiment, the weight ratio of the composite metal oxide in the coating layer source is controlled to be greater than 40 wt% and less than 60 wt%, which may include increasing the initial capacity of the secondary battery.

[0018] According to one embodiment, the weight ratio of the conductive material in the coating layer source is controlled to be greater than 20 wt% and only 40 wt%, and the weight ratio of the binder in the coating layer source is controlled to be 20 wt%.

[0019] According to one embodiment, the composite metal oxide comprises lithium cobalt oxide (Li6CoO4), the conductive material comprises any one of Super P, carbon black, and carbon nanotubes, and the binder may comprise PVDF (Polyvinylidene fluoride).

[0020] According to one embodiment, the above material may include polyethylene.

[0021] To solve the above technical problem, the present invention provides a separation membrane manufactured by the manufacturing method described above.

[0022] According to one embodiment, the separator comprises a substrate and a coating layer having a composite metal oxide comprising a base metal and a transition metal provided on one surface of the substrate, and may include intercalation and deintercalation of ions of the base metal within the coating layer of the separator to a negative electrode and a positive electrode that do not contain the base metal during the charging / discharging process of a secondary battery including the separator.

[0023] According to one embodiment, during the initial charging process of the secondary battery, a voltage is applied to the surface of the separator, the composite metal oxide of the coating layer is oxidized and decomposed to produce a residue, and the ions of the base metal of the composite metal oxide of the coating layer are inserted into the negative electrode.

[0024] According to one embodiment, the substrate comprises polyethylene, and the composite metal oxide of the coating layer may comprise lithium cobalt oxide (Li6CoO4).

[0025] To solve the above technical problem, the present invention provides a secondary battery to which the above-described separator is applied.

[0026] According to one embodiment, in a secondary battery in which ions of a base metal are intercalated and deintercalated into a negative electrode and a positive electrode during a charging / discharging process, the secondary battery comprises a positive electrode having a positive electrode layer having sulfur, a negative electrode having a negative electrode layer having graphite disposed spaced apart from the positive electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte provided between the positive electrode and the negative electrode, wherein the separator comprises a substrate and a coating layer having a composite metal oxide comprising the base metal and a transition metal provided on one surface of the substrate, and the one surface of the substrate is a surface spaced apart from and opposite to the upper surface of the positive electrode.

[0027] According to one embodiment, during the initial charging process of the secondary battery, a voltage is applied to the surface of the separator to oxidatively decompose the composite metal oxide of the coating layer to produce a residue, and ions of the base metal of the composite metal oxide of the coating layer are inserted into the negative electrode, and subsequently, during the charging / discharging process of the secondary battery, lithium polysulfide generated is adsorbed onto the residue, thereby suppressing the shuttle effect of the lithium polysulfide.

[0028] According to one embodiment, during the charging / discharging process of the secondary battery, the secondary battery may be charged up to 4.0V and the secondary battery may be discharged up to 1.6V.

[0029] According to one embodiment, the coating layer comprises lithium cobalt oxide (Li6CoO4), and the residue may comprise lithium cobalt oxide (LiCoO2) and cobalt oxide (Co3O4).

[0030] According to one embodiment, the secondary battery may include a graphite (anode)-sulfur (cathode) battery.

[0031] A method for manufacturing a separator according to the present invention may include the steps of: preparing a substrate (e.g., PE); preparing a composite metal oxide (e.g., Li6CoO4) comprising a base metal (e.g., Li) and a transition metal (e.g., Co); preparing a coating layer source by mixing the composite metal oxide, a conductive material (e.g., carbon), and a binder (e.g., PVDF); and manufacturing the separator by coating the coating layer source on one surface of the substrate.

[0032] In the step of manufacturing the coating layer source, the weight ratio of the composite metal oxide within the coating layer source can be controlled to be greater than 40 wt% and less than 60 wt%. Accordingly, ions of the base metal (e.g., Li) supplied to the negative and positive electrodes of a secondary battery including the separator + The amount of ) can be optimized. As a result, the above secondary battery with increased initial capacity can be provided.

[0033] And, the above-described secondary battery (e.g., graphite-sulfur battery) may include the anode having a positive electrode layer having sulfur, the cathode having a negative electrode layer having graphite disposed spaced apart from the anode, the separator disposed between the anode and the cathode, and an electrolyte provided between the anode and the cathode.

[0034] The separator may comprise the substrate (e.g., PE) and a coating layer having the composite metal oxide (e.g., Li6CoO4) comprising the base metal (e.g., Li) and the transition metal (e.g., Co) disposed on the one surface of the substrate. Furthermore, the one surface of the substrate of the separator may be a surface facing and spaced apart from the upper surface of the anode layer of the anode.

[0035] Accordingly, the composite metal oxide (e.g., Li6CoO4) of the coating layer of the separator in the secondary battery is oxidatively decomposed during the charging / discharging process of the secondary battery, and the ions of the base metal (e.g., Li) are transferred to the negative electrode and the positive electrode. + It can function as a source providing ). In addition, during the initial charging process of the secondary battery, the residue generated by the oxidative decomposition of the composite metal oxide of the coating layer of the separator (e.g., LiCoO2, The shuttle effect caused by lithium polysulfide can be suppressed by Co3O4.

[0036] As a result, the initial capacity and stability of the above secondary battery over long-term charge / discharge cycles can be improved.

[0037] FIG. 1 is a flowchart illustrating a method for manufacturing a separation membrane according to an embodiment of the present invention.

[0038] FIG. 2 is a drawing for explaining the description according to an embodiment of the present invention.

[0039] FIG. 3 is a flowchart illustrating a method for manufacturing a composite metal oxide according to an embodiment of the present invention.

[0040] FIG. 4 is a drawing illustrating a method for manufacturing a composite metal oxide source according to an embodiment of the present invention.

[0041] FIG. 5 is a drawing illustrating a method for manufacturing a composite metal oxide 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 the structure of a secondary battery to which a separator is applied according to an embodiment of the present invention.

[0045] FIG. 9 is a diagram illustrating the initial charging process and discharge process of a secondary battery to which a separator according to an embodiment of the present invention is applied.

[0046] Figure 10 is a graph showing the charging capacity of a half cell according to Comparative Example 1 of the present invention.

[0047] Figure 11 is a graph showing the charge / discharge capacity of a full cell according to Experimental Example 1 of the present invention.

[0048] FIG. 12 is a graph showing the characteristics of the charge / discharge cycle of a full cell according to Example 1 of the present invention.

[0049] FIG. 13 is a graph for comparing the charging capacity of half cells according to experimental examples of the present invention.

[0050] FIG. 14 is a graph for comparing the charge / discharge capacity of a half cell according to Experimental Example 1 of the present invention and a half cell according to comparative examples.

[0051] Figure 15 is an SEM image and XRD result for comparing the state of the coating layer of the separator before and after the initial charging of a full cell according to Experimental Example 1 of the present invention.

[0052] Figure 16 is a UV-Vis result for comparing the adsorption levels of lithium polysulfide and the separator of a full cell according to Experimental Example 1 and Comparative Example 1 of the present invention.

[0053] Figure 17 is the test result of an H-type cell to compare the adsorption level of lithium polysulfide and the separator of a full cell according to Experimental Example 1 and Comparative Example 1 of the present invention.

[0054] Figure 18 is a graph showing the discharge capacity of a half cell according to Experimental Example 1 of the present invention.

[0055] Figure 19 shows the results of measuring the charge capacity and discharge capacity for the charge / discharge cycle of a full cell according to Experimental Example 1 of the present invention.

[0056] FIG. 20 is a graph showing the discharge capacity for a long-term charge / discharge cycle of a full cell according to Experimental Example 1 of the present invention.

[0057] 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 ensure that the concept of the present invention is sufficiently conveyed to those skilled in the art.

[0058] In this specification, when a component is described as being on another component, it means that it may be formed directly on the other component or that a third component may be interposed between them. Additionally, in the drawings, the thicknesses of the films and regions are exaggerated for the effective description of the technical content.

[0059] Additionally, although terms such as first, second, third, etc., have been used to describe various components in the various embodiments of this specification, these components should not be limited by such terms. These terms are used merely to distinguish one component from another. Accordingly, what is referred to as the first component in one embodiment may be referred to as the second component in another embodiment. Each embodiment described and illustrated herein also includes its complementary embodiment. Furthermore, in this specification, "and / or" is used to mean including at least one of the components listed before and after it.

[0060] In the specification, singular expressions include plural expressions unless the context clearly indicates otherwise. Furthermore, terms such as "include" or "have" are intended to specify the existence of the features, numbers, steps, components, or combinations thereof described in the specification, and should not be understood as excluding the existence or addition of one or more other features, numbers, steps, components, or combinations thereof. Additionally, in this specification, "connection" is used to include both indirectly connecting and directly connecting the components of the plural.

[0061] In addition, in describing the present invention below, if it is determined that a detailed description of related known functions or configurations could unnecessarily obscure the essence of the invention, such detailed description will be omitted.

[0062]

[0063] FIG. 1 is a flowchart for explaining a method for manufacturing a separator according to an embodiment of the present invention, FIG. 2 is a diagram for explaining a substrate according to an embodiment of the present invention, FIG. 3 is a flowchart for explaining a method for manufacturing a composite metal oxide according to an embodiment of the present invention, FIG. 4 is a diagram for explaining a method for manufacturing a composite metal oxide source according to an embodiment of the present invention, FIG. 5 is a diagram for explaining a method for manufacturing a composite metal oxide 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, and FIG. 7 is a diagram for explaining a method of forming a coating layer on a substrate according to an embodiment of the present invention.

[0064] Referring to FIGS. 1 and FIGS. 2, a substrate (10) is prepared (S100).

[0065] The above substrate (10) may have a porous structure. For example, the above substrate (10) may be any one of a polyethylene (PE) separator, a polypropylene (PP) separator, a ceramic-coated separator, or a glass fiber separator.

[0066] Referring to FIGS. 1, 3 to 5, a composite metal oxide (100) comprising a base metal and a transition metal is prepared (S200).

[0067] The step (S200) of preparing the composite metal oxide (100) may include the step (S210) of preparing a composite metal oxide source (130) by mixing a base metal oxide (110) containing the base metal and a transition metal oxide (120) containing the transition metal, and the step (S220) of manufacturing the composite metal oxide (100) by calcining, grinding, and sieving the composite metal oxide source (130). For example, the base metal may be lithium (Li). For example, the transition metal may be cobalt (Co). For example, the base metal oxide (110) may be lithium oxide (Li2O). For example, the transition metal oxide (120) may be cobalt oxide (CoO).

[0068] And, in the step of preparing the composite metal oxide source (130), the base metal oxide (110) and the transition metal oxide (120) may be mixed and ball-milled in an inert gas atmosphere. For example, the base metal oxide (110) and the transition metal oxide (120) may be mixed such that their molar ratio is 3:1. For example, the ball milling may be performed at 200 rpm for 12 hours. Accordingly, the composite metal oxide source (130) can be easily manufactured.

[0069] Subsequently, in the step of manufacturing the composite metal oxide (100), the composite metal oxide source (130) may be calcined in an inert atmosphere. For example, the calcination may be performed at 700°C for 12 hours. Accordingly, the composite metal oxide (100) can be easily manufactured. For example, the composite metal oxide (100) may be lithium cobalt oxide (Li6CoO4). For example, when lithium cobalt oxide is used as the composite metal oxide (100), the initial capacity of the secondary battery may be improved compared to when lithium nickel oxide (LNO) is used.

[0070] Referring to FIGS. 1 and 6, a coating layer source (210) is prepared by mixing the composite metal oxide (100), the conductive material (140), and the binder (150) (S300).

[0071] The initial capacity of a secondary battery including a separator described later can be controlled according to the weight ratio of the composite metal oxide (100) within the coating layer source (210). For example, the composite metal oxide (100) may be lithium cobalt oxide (Li6CoO4). For example, the conductive material (140) may be any one of Super P, carbon black, and carbon nanotubes. For example, the binder (150) may be PVDF (Polyvinylidene fluoride). For example, the weight ratio of the conductive material (140) within the coating layer source (210) may be controlled to be greater than 20 wt% and less than 40 wt%, and the weight ratio of the binder (150) within the coating layer source (210) may be controlled to be 20 wt%. For example, the positive and negative electrodes of the secondary battery may not include the base metal (lithium, Li).

[0072] According to one embodiment, the weight ratio of the composite metal oxide (100) in the coating layer source (210) can be controlled to be greater than 40 wt% and less than 60 wt%. Accordingly, the amount of ions of the base metal supplied to the negative electrode and the positive electrode of the secondary battery can be optimized. Accordingly, the initial capacity of the secondary battery can be increased.

[0073] In contrast, if the weight ratio of the composite metal oxide (100) in the coating layer source (210) is controlled to 40 wt% or less, or 60 wt% or more, the amount of ions of the base metal supplied to the negative electrode and the positive electrode of the secondary battery is reduced, and the initial capacity of the secondary battery may be reduced.

[0074] Accordingly, according to an embodiment of the present application, the weight ratio of the composite metal oxide (100) in the coating layer source (210) can be controlled to be greater than 40 wt% and less than 60 wt%. Accordingly, the amount of ions of the base metal supplied to the negative electrode and the positive electrode of the secondary battery can be optimized. As a result, the secondary battery with increased initial capacity can be provided.

[0075] Referring to FIG. 1 and FIG. 7, the above-described separation membrane (300) is manufactured by coating the coating layer source (210) on one side of the substrate (10) (S400).

[0076] After the coating layer source (210) is coated on the one surface of the above substrate (10), it can be vacuum dried. For example, the coating layer source (210) can be dried in a vacuum oven at 60°C for 8 hours or more.

[0077] Accordingly, a coating layer (200) having the composite metal oxide (100) comprising the base metal and the transition metal can be easily formed on the one surface of the above-mentioned substrate (10).

[0078] In conclusion, the method for manufacturing the separation membrane (300) according to an embodiment of the present application may include the steps of: preparing the substrate (10); preparing the composite metal oxide (100) comprising the base metal and the transition metal; mixing the composite metal oxide (100), the conductive material (140), and the binder (150) to produce the coating layer source (210); and coating the coating layer source (210) on one surface of the substrate (10) to produce the separation membrane (300).

[0079] In the step of manufacturing the coating layer source (210), the weight ratio of the composite metal oxide (100) within the coating layer source (210) can be controlled to be greater than 40 wt% and less than 60 wt%. Accordingly, the amount of ions of the base metal supplied to the negative electrode and the positive electrode of the secondary battery including the separator (300) can be optimized. As a result, the secondary battery with increased initial capacity can be provided.

[0080] With reference to FIG. 7, the separator (300) manufactured by the above-described manufacturing method is described.

[0081] The above separator (300) may include the substrate (10) and the coating layer (200) having the composite metal oxide (100) comprising the base metal and the transition metal provided on one surface of the substrate (10). For example, the substrate (10) may be a polyethylene separator. For example, the composite metal oxide (100) of the coating layer (200) may be lithium cobalt oxide (Li6CoO4).

[0082] Accordingly, during the initial charging process of the secondary battery including the separator (300), a voltage is applied to the surface of the separator (300), so that the composite metal oxide (100) of the coating layer (300) is oxidized and decomposed to produce residue, and ions of the base metal of the composite metal oxide (100) of the coating layer (300) can be inserted into the negative electrode of the secondary battery. For example, the residue may include lithium cobalt oxide (LiCoO2) and cobalt oxide (Co3O4). For example, the secondary battery can be charged up to 4V.

[0083]

[0084] Hereinafter, with reference to FIGS. 8 and FIGS. 9, the structure of a secondary battery to which the above-described separator (300) is applied, and the initial charging / discharging process of the secondary battery are described.

[0085] FIG. 8 is a diagram illustrating the structure of a secondary battery with a separator applied according to an embodiment of the present invention, and FIG. 9 is a diagram illustrating the initial charging process and discharge process of a secondary battery with a separator applied according to an embodiment of the present invention.

[0086] As illustrated in FIG. 8, the secondary battery (700) may include a positive electrode (400) comprising a positive electrode layer (410) having sulfur disposed on a positive electrode current collector (20), a negative electrode (500) disposed spaced apart from the positive electrode (400) and comprising a negative electrode layer (510) having graphite disposed on a negative electrode current collector (30), a separator (300) disposed between the positive electrode (400) and the negative electrode (500), and an electrolyte (600) provided between the positive electrode (400) and the negative electrode (500). For example, the positive electrode (400) and the negative electrode (450) of the secondary battery (700) may not include the base metal (e.g., lithium). For example, the secondary battery (700) may be a graphite (anode)-sulfur (cathode) battery.

[0087] As described above with reference to FIGS. 6 and 7, the separator (300) may comprise a substrate (10) and a coating layer (200) having a composite metal oxide (100) comprising a base metal and a transition metal disposed on one surface of the substrate (10). Furthermore, the one surface of the substrate (10) of the separator (300) may be a surface facing and spaced apart from the upper surface of the anode layer (410) of the anode (400). For example, the substrate (10) may be a polyethylene separator. For example, the composite metal oxide (100) of the coating layer (200) may be lithium cobalt oxide (Li6CoO4).

[0088] Accordingly, as illustrated in FIG. 9, during the initial charge process of the secondary battery (700), voltage is applied to the surface of the separator (300) so that the composite metal oxide of the coating layer (200) is oxidized and decomposed, thereby generating residue, and the ions (1) of the base metal of the composite metal oxide of the coating layer (200) can be intercalated into the negative electrode (500). For example, the secondary battery (700) can be initially charged up to 4V. For example, the residue may include lithium cobalt oxide (LiCoO2) and cobalt oxide (Co3O4).

[0089] And, during the initial discharge process of the secondary battery (700), the ions (1) of the base metal inserted into the negative electrode (500) can be deintercalated and moved to the positive electrode (400). For example, the secondary battery (700) can be discharged up to 1.6V.

[0090] Subsequently, when performing a charge / discharge cycle of the secondary battery (700), lithium polysulfide, which is an intermediate substance between lithium and sulfur generated during the charge / discharge cycle of the secondary battery (700), can be adsorbed onto the residue. Accordingly, the shuttle effect caused by the lithium polysulfide can be suppressed. As a result, the stability of the secondary battery (700) for long-term charge / discharge cycles can be improved.

[0091] In addition, during the process of performing the charge / discharge cycle of the secondary battery (700), the discharge capacity of the secondary battery (700) and the stability for the long-term charge / discharge cycle can be controlled according to the discharge voltage (Cut-off voltage) of the secondary battery (700).

[0092] According to one embodiment, during the charge / discharge cycle of the secondary battery (700), the secondary battery (700) can be charged up to 4.0V and discharged down to 1.6V. Accordingly, even if the number of charge / discharge cycles increases, the decrease in the discharge capacity of the secondary battery (700) is minimized and can be maintained stably for a long period of time.

[0093] In contrast, when the secondary battery (700) is charged to 4.0V and discharged to 1.0V during a charge / discharge cycle, the discharge capacity of the secondary battery (700) may gradually decrease as the number of charge / discharge cycles increases.

[0094] Accordingly, according to an embodiment of the present application, during a charge / discharge cycle of the secondary battery (700), the secondary battery (700) can be charged up to 4.0V and discharged up to 1.6V. Accordingly, even if the number of charge / discharge cycles increases, the decrease in the discharge capacity of the secondary battery (700) is minimized and can be maintained stably for a long period of time.

[0095] In conclusion, the secondary battery may include the anode (400) having a positive electrode layer (410) having sulfur, the cathode (500) having a negative electrode layer (510) having graphite spaced apart from the anode (400), the separator (300) disposed between the anode (400) and the cathode (500), and the electrolyte (600) provided between the anode (400) and the cathode (500).

[0096] The above separator (300) may include the above substrate (10) and the coating layer (200) comprising the above composite metal oxide (100) comprising the base metal and the transition metal disposed on the above one surface of the above substrate (10). And, the above one surface of the above substrate (10) of the separator (300) may be a surface facing and spaced apart from the upper surface of the anode layer (410) of the anode (400).

[0097] Accordingly, the composite metal oxide (100) of the coating layer (200) of the separator (300) in the secondary battery (700) can be oxidized and decomposed during the charging / discharging process of the secondary battery (700), and can function as a source providing ions (1) of the base metal to the negative electrode (500) and the positive electrode (400).

[0098] In addition, during the initial charging process of the secondary battery (700), the composite metal oxide (100) of the coating layer (200) of the separator (300) is oxidized and decomposed, and the resulting residue can suppress the shuttle effect caused by the lithium polysulfide.

[0099] As a result, the initial capacity and stability of the long-term charge / discharge cycle of the secondary battery (700) can be improved.

[0100]

[0101] Hereinafter, specific experimental examples and characteristic evaluation results of the separation membrane according to the embodiments of the present invention are described.

[0102]

[0103] Separator according to Experimental Example 1

[0104] Lithium oxide (Li2O) was prepared as the base metal oxide, and cobalt oxide (CoO) was prepared as the transition metal oxide. Then, in an inert gas atmosphere, the base metal oxide and the transition metal oxide were mixed so that their molar ratio was 3:1, and then ball milled (200 RPM, 12 hours) to produce a composite metal oxide source. Subsequently, the composite metal oxide source was calcined (700°C, 12 hours) in an inert gas atmosphere, ground using a mortar and pestle, and sieved (25 μm) to produce a powdered composite metal oxide (Li6CoO4, LCO).

[0105] Carbon was prepared as a conductive material, and PVDF (Polyvinylidene fluoride) was prepared as a binder by dissolving it in an organic solvent (NMP, N-Methyl-2-Pyrrolidone). Then, the composite metal oxide and the conductive material were mixed in a mortar (15 minutes), provided to a binder solution (PDVF+NMP), and stirred (2,000 RPM, 5 minutes) to prepare a coating layer source. Specifically, the weight ratios of the composite metal oxide (Li6CoO4), the carbon, and the binder (PVDF) in the coating layer source were controlled to 50 wt%, 30 wt%, and 20 wt%, respectively.

[0106] A porous polyethylene separator was prepared as a substrate, and the coating layer source was coated on one side of the substrate and vacuum dried (60°C, for 8 hours or more) to produce a separator (substrate + coating layer).

[0107]

[0108] Separator according to Experimental Example 1-1

[0109] A membrane according to Experimental Example 1-1 was prepared using the same method as the membrane according to Experimental Example 1, except that the weight ratios of the composite metal oxide (Li6CoO4), carbon, and binder (PVDF) in the coating layer source were controlled to 40 wt%, 40 wt%, and 20 wt%, respectively.

[0110]

[0111] Separator according to Experimental Example 1-2

[0112] A membrane according to Experimental Example 1-2 was prepared using the same method as the membrane according to Experimental Example 1, except that the weight ratios of the composite metal oxide (Li6CoO4), carbon, and binder (PVDF) in the coating layer source were controlled to 60 wt%, 20 wt%, and 20 wt%, respectively.

[0113]

[0114] Separator according to Comparative Example 1

[0115] A separator according to Comparative Example 1 was prepared using the same method as the separator according to Experimental Example 1, except that the conductive material in the coating layer source was omitted.

[0116]

[0117] Separator according to Comparative Example 1-1

[0118] A separator according to Comparative Example 1-1 was prepared using the same method as the separator according to Experimental Example 1, except that lithium nickel oxide fluoride (LiNiOF, LNOF) was used instead of lithium cobalt oxide (Li6CoO4) as the composite metal oxide in the process of preparing the coating layer source.

[0119]

[0120] Separator according to Comparative Example 1-2

[0121] A separator according to Comparative Example 1-2 was prepared using the same method as the separator according to Experimental Example 1, except that in the process of preparing the coating layer source, lithium nickel oxide (LiNiO2, LNO) was used instead of lithium cobalt oxide (Li6CoO4) as the composite metal oxide.

[0122]

[0123] Separator according to Comparative Example 1-3

[0124] The separator according to Comparative Examples 1-3 was prepared using the same method as the separator according to Experimental Example 1, except that in the process of preparing the coating layer source, lithium phosphate oxide (Li3PO4, LPO) was used instead of lithium cobalt oxide (Li6CoO4) as the composite metal oxide.

[0125]

[0126] Half cell according to Experimental Example 1

[0127] (anode)

[0128] A positive electrode active material was prepared by mixing sulfur powder and carbon powder in a weight ratio of 3.5:1 using a mortar and pestle, followed by calcination (155°C, 12 hours). Then, Super P was prepared as a conductive material, and PVDF (Polyvinylidene fluoride) was prepared as a binder by dissolving it in an organic solvent (NMP, N-Methyl-2-Pyrrolidone). Subsequently, the positive electrode active material and the conductive material were mixed in a mortar and pestle (15 minutes), provided to a binder solution (PDVF+NMP), and stirred (2,000 RPM, 15 minutes) to prepare a positive electrode layer source. Specifically, the weight ratios of the positive electrode active material (sulfur + carbon), the binder (PVDF), and the conductive material (Super P) in the positive electrode layer source were controlled to 85 wt%, 12 wt%, and 3 wt%, respectively. Then, the anode layer source was coated onto a current collector (Al foil) and vacuum dried (80°C, for 8 hours or more) to produce an anode (current collector + anode layer).

[0129] (cathode)

[0130] We prepared a Li foil that is commercially available and sold.

[0131] (Separator)

[0132] A separation membrane was prepared according to Experimental Example 1.

[0133] (Electrolytes)

[0134] A liquid electrolyte was prepared by dissolving a lithium salt (LiTFSi, 0.8M) in a base solution (LiFSI (0.2M) + mixed solvent (DME / TTE, 1:2 v / v).

[0135] A half cell was manufactured by sequentially arranging and assembling the anode, the separator, and the cathode, and providing the electrolyte between the anode and the cathode.

[0136]

[0137] Half cell according to Experimental Example 1-1

[0138] A half cell according to Experimental Example 1-1 was prepared using the same method as the half cell according to Experimental Example 1, except that the membrane according to Experimental Example 1-1 was used instead of the membrane according to Experimental Example 1.

[0139]

[0140] Half cell according to Experimental Example 1-2

[0141] A half cell according to Experimental Example 1-2 was prepared using the same method as the half cell according to Experimental Example 1, except that the membrane according to Experimental Example 1-2 was used instead of the membrane according to Experimental Example 1.

[0142]

[0143] Half cell according to Comparative Example 1

[0144] A half cell according to Comparative Example 1 was prepared using the same method as the half cell according to Experimental Example 1, except that the membrane according to Comparative Example 1 was used instead of the membrane according to Experimental Example 1.

[0145]

[0146] Half cell according to Comparative Example 1-1

[0147] A half cell according to Comparative Example 1-1 was prepared using the same method as the half cell according to Experimental Example 1, except that the membrane according to Comparative Example 1-1 was used instead of the membrane according to Experimental Example 1.

[0148]

[0149] Half cell according to Comparative Example 1-2

[0150] A half cell according to Comparative Example 1-2 was prepared using the same method as the half cell according to Experimental Example 1, except that the membrane according to Comparative Example 1-2 was used instead of the membrane according to Experimental Example 1.

[0151]

[0152] Half cell according to Comparative Examples 1-3

[0153] A half cell according to Comparative Example 1-2 was prepared using the same method as the half cell according to Experimental Example 1, except that the membrane according to Comparative Example 1-2 was used instead of the membrane according to Experimental Example 1.

[0154]

[0155] Full cell according to Experimental Example 1

[0156] (anode)

[0157] A positive electrode active material was prepared by mixing sulfur powder and carbon powder in a weight ratio of 3.5:1 using a mortar and pestle, followed by calcination (155°C, 12 hours). Then, Super P was prepared as a conductive material, and PVDF (Polyvinylidene fluoride) was prepared as a binder by dissolving it in an organic solvent (NMP, N-Methyl-2-Pyrrolidone). Subsequently, the positive electrode active material and the conductive material were mixed in a mortar and pestle (15 minutes), provided to a binder solution (PDVF+NMP), and stirred (2,000 RPM, 15 minutes) to prepare a positive electrode layer source. Specifically, the weight ratios of the positive electrode active material (sulfur + carbon), the binder (PVDF), and the conductive material (Super P) in the positive electrode layer source were controlled to 85 wt%, 12 wt%, and 3 wt%, respectively. Then, the anode layer source was coated onto a current collector (Al foil) and vacuum dried (80°C, for 8 hours or more) to produce an anode (current collector + anode layer).

[0158] (cathode)

[0159] Graphite powder was stirred using a mortar and pestle for 15 minutes. Then, carboxymethyl cellulose (CMC) was prepared as a binder by dissolving it in ultrapure water (DI water). Subsequently, the graphite powder and styrene-butadiene rubber (SBR) were provided to the binder solution (CMC + DI water) and mixed to prepare a cathode layer source. Specifically, the weight ratios of the graphite, the binder (CMC), and the styrene-butadiene rubber (SBR) in the cathode layer source were controlled to 97.5 wt%, 1 wt%, and 1.5 wt%, respectively. Then, the cathode layer source was coated onto a current collector (Cu foil) and vacuum dried (100°C, for 8 hours or more) to prepare a cathode (current collector + cathode layer).

[0160] (Separator)

[0161] A separation membrane was prepared according to Experimental Example 1.

[0162] (Electrolytes)

[0163] A liquid electrolyte was prepared by dissolving lithium salts (0.8M LiTFSI and 0.2M LiFSI) in a base solution (mixed solvent (DME / TTE, 1:2 v / v).

[0164] Using a 2032 coin cell, the anode, the separator, and the cathode were sequentially arranged and assembled, and the electrolyte was provided between the anode and the cathode to manufacture a full cell.

[0165]

[0166] Full cell according to Comparison Example 1

[0167] A full cell according to Comparative Example 1 was prepared using the same method as the full cell according to Experimental Example 1, except that the membrane according to Comparative Example 1 was used instead of the membrane according to Experimental Example 1.

[0168]

[0169] Figure 10 is a graph showing the charging capacity of a half cell according to Comparative Example 1 of the present invention.

[0170] Referring to Fig. 10, the initial charging capacity was confirmed by charging the half cell according to Comparative Example 1 to 4.0V.

[0171] As can be seen in Fig. 10, the initial charging capacity of the half cell according to Comparative Example 1 is 889 mAh / g.

[0172] Therefore, it can be seen that the separator of the half cell according to Comparative Example 1 can be used as a separator for supplying lithium ions because the coating layer of the separator includes a composite metal oxide (Li6CoO4).

[0173]

[0174] Figure 11 is a graph showing the charge / discharge capacity of a full cell according to Experimental Example 1 of the present invention.

[0175] Referring to Fig. 11, the initial charging capacity was measured by charging the full cell according to Experimental Example 1 to 4V, and the initial discharging capacity was measured by discharging it to 1.6V.

[0176] As can be seen in Fig. 11, due to the coating layer of the separator of the full cell according to Experimental Example 1, the initial charge capacity of the full cell according to Experimental Example 1 is 674 mAh / g and the initial discharge capacity is 482 mAh / g.

[0177] Accordingly, the base metal ions (Li₆CoO₄) generated from the composite metal oxide (Li₆CoO₄) of the coating layer of the separator of the full cell according to Experimental Example 1 are + It can be seen that ) is sufficiently supplied to the cathode and anode.

[0178]

[0179] FIG. 12 is a graph showing the characteristics of the charge / discharge cycle of a full cell according to Example 1 of the present invention.

[0180] Referring to Fig. 12, after the full cell according to Experimental Example 1 was initially charged at 4.0V and 0.05C-rate, the discharge capacity was measured while performing 100 charge / discharge cycles at 1.0V to 3.0V and 0.2C-rate.

[0181] As can be seen in Fig. 12, the Coulomb efficiency of the full cell according to Experimental Example 1 is 99.2%.

[0182] This factor is interpreted to be due to the fact that, during the charging / discharging process of the full cell according to Experimental Example 1, lithium ions are sufficiently supplied to the negative and positive electrodes by the oxidative decomposition of the composite metal oxide (Li6CoO4) of the coating layer of the separator of the full cell according to Experimental Example 1, and a stable SEI layer is formed on the surface of the negative electrode.

[0183]

[0184] FIG. 13 is a graph for comparing the charging capacity of half cells according to experimental examples of the present invention.

[0185] Referring to Fig. 13(a), the initial charging capacity was verified by charging the half cell according to Experimental Example 1-1 to 4.0V. Referring to Fig. 13(b), the initial charging capacity was verified by charging the half cell according to Experimental Example 1 to 4.0V. Referring to Fig. 13(c), the initial charging capacity was verified by charging the half cell according to Experimental Example 1-2 to 4.0V.

[0186] As can be seen in FIG. 13 (a) and (b),

[0187] It can be seen that the initial charging capacity of the half cell according to Experimental Example 1-1 is 450 mAh / g, the initial charging capacity of the half cell according to Experimental Example 1 is 720 mAh / g, and the initial charging capacity of the half cell according to Experimental Example 1-2 is 550 mAh / g. Accordingly, it can be seen that the initial charging capacity of the half cell according to Experimental Example 1 is the highest.

[0188] Therefore, in the method for manufacturing a separator according to an embodiment of the present application, controlling the weight ratio of a composite metal oxide in the coating layer source to be greater than 40 wt% and less than 60 wt% is a method for increasing the initial capacity of a secondary battery.

[0189]

[0190] FIG. 14 is a graph for comparing the charge / discharge capacity of a half cell according to Experimental Example 1 of the present invention and a half cell according to comparative examples.

[0191] Referring to Fig. 14 (a), the initial charge / discharge capacity of the half cell according to Experiment 1 was measured. Referring to Fig. 14 (b), the initial charge / discharge capacity of the half cell according to Comparative Example 1-2 was measured. Referring to Fig. 14 (c), the initial charge / discharge capacity of the half cell according to Comparative Example 1-3 was measured.

[0192] As can be seen in FIG. 14 (a) to (c), the initial charging capacity of the half cell according to Experimental Example 1 is 796.5 mAh / g, the initial charging capacity of the half cell according to Comparative Example 1-2 is 321.0 mAh / g, and the initial charging capacity of the half cell according to Comparative Example 1-3 cannot be measured. Accordingly, it can be seen that the initial charging capacity of the half cell according to Experimental Example 1 is the highest.

[0193] Accordingly, it can be seen that in the step of manufacturing a coating layer source according to an embodiment of the present application, among lithium cobalt oxide (LCO), lithium nickel oxide (LNO), and lithium phosphate oxide (LPO), the method of using lithium cobalt oxide (LCO) as a composite metal oxide is the method that most improves the initial capacity of the secondary battery.

[0194]

[0195] Figure 15 is an SEM image and XRD result for comparing the state of the coating layer of the separator before and after the initial charging of a full cell according to Experimental Example 1 of the present invention.

[0196] Referring to Fig. 15(a), the surface of the coating layer of the separator of the full cell according to Experimental Example 1 was photographed by SEM, and referring to Fig. 15(c), the coating layer of the separator of the full cell according to Experimental Example 1 was analyzed by XRD. Also, referring to Fig. 15(b), the surface of the coating layer of the separator was photographed by SEM after the full cell according to Experimental Example 1 was initially charged at 4.0V and 0.05C-rate, and referring to Fig. 15(d), the coating layer of the separator was analyzed by XRD after the full cell according to Experimental Example 1 was initially charged at 4.0V and 0.05C-rate.

[0197] As can be seen in FIG. 15 (a) to (d), when the full cell according to Experimental Example 1 is first charged, the lithium cobalt oxide (Li6CoO4) in the coating layer of the separator of the full cell according to Experimental Example 1 is oxidized and decomposed, and the residue lithium cobalt oxide (LiCoO2) and cobalt oxide (Co3O4) are produced.

[0198]

[0199] Figure 16 is a UV-Vis result for comparing the adsorption level of lithium polysulfide between the separator of a full cell according to Experimental Example 1 and Comparative Example 1 of the present invention, and Figure 17 is a test result of an H-type cell for comparing the adsorption level of lithium polysulfide between the separator of a full cell according to Experimental Example 1 and Comparative Example 1 of the present invention.

[0200] Referring to FIG. 16, UV-Vis was measured for a first solution (Li2S6, 1M Li2S6 in DOL (Dimethoxyethane) / DME (Dimethyl Ether)) containing lithium polysulfide, UV-Vis was measured for a second solution (RM (Residual Material), LiCoO2 and Co3O4) prepared by first charging (4.0V, 0.05C-rate) a full cell according to Experimental Example 1, recovering the separator, and providing it to a solution containing lithium polysulfide, and UV-Vis was measured for a third solution (CNOVEL) prepared by first charging (4.0V, 0.05C-rate) a full cell according to Comparative Example 1, recovering the separator, and providing it to a solution containing lithium polysulfide. In addition, actual specimens of the first solution (Li2S6), the second solution (RM), and the third solution (CNOVEL) were photographed, and the photographs were inserted to the right of the UV-Vis graph. Referring to FIG. 17(a), the first solution (1M Li2S6in DOL / DME) was provided to the left of the H-type cell and the mixed solution (DOL / DME) was provided to the right. A separator recovered after the initial charging (4.0V, 0.05C-rate) of the full cell according to Comparative Example 1 was placed between the first solution and the mixed solution, and the color change of the mixed solution provided to the right of the H-type cell was observed over time (0h, 6h, 12h). Referring to Fig. 17(b), the first solution (1M Li2S6in DOL / DME) was provided to the left of the H-type cell and the mixed solution (DOL / DME) was provided to the right. A separator recovered after the first full cell according to Experimental Example 1 was placed between the first solution and the mixed solution, and the color change of the mixed solution provided to the right of the H-type cell was observed over time (0h, 6h, 12h).

[0201] As can be seen in FIG. 16, among the first to third solutions, S6 generated at approximately 260 nm of the second solution 2- It can be seen that the intensity of the peak corresponding to is the weakest, and the color of the second solution is the most transparent. This factor is interpreted to be due to the fact that lithium polysulfide (Li2S6) is adsorbed onto the residue (LiCoO2, Co3O4) generated on one side of the separator in the second solution.

[0202] As can be seen in FIG. 17, when a separator is provided in the center of an H-type cell without residue (LiCoO2, Co3O4), it can be seen that as time passes, the color of the mixed solution provided on the right side of the H-type cell becomes darker due to the concentration gradient of lithium polysulfide in the first solution provided on the left side of the H-type cell. That is, it can be seen that lithium polysulfide in the first solution penetrates the separator and diffuses into the mixed solution.

[0203] In contrast, when a separator (LiCoO2, Co3O4) with residue present in the center of the H-type cell is provided, it can be seen that the transparent color of the mixed solution provided on the right side of the H-type cell is maintained even as time passes. That is, it can be seen that lithium polysulfide in the first solution is adsorbed onto the residue of the separator, thereby inhibiting its diffusion into the mixed solution.

[0204] In summary, it can be seen that during the initial charging process of the full cell according to Experimental Example 1, the level of adsorption with lithium polysulfide is enhanced by lithium cobalt oxide (LiCoO2) and cobalt oxide (Co3O4), which are residues generated by the oxidative decomposition of the composite metal oxide (Li6CoO4) of the coating layer of the separator. Accordingly, it can be seen that the shuttle effect caused by lithium polysulfide generated during the charging / discharging process of the full cell according to Experimental Example 1 is suppressed.

[0205]

[0206] FIG. 18 is a graph showing the discharge capacity of a half cell according to Experimental Example 1 of the present invention, FIG. 19 is the result of measuring the charge capacity and discharge capacity for a charge / discharge cycle of a full cell according to Experimental Example 1 of the present invention, and FIG. 20 is a graph showing the discharge capacity for a long-term charge / discharge cycle of a full cell according to Experimental Example 1 of the present invention.

[0207] Referring to Fig. 18, the discharge capacity was measured by charging the half cell according to Experimental Example 1 to 4.0V and then discharging it to 1.0V. Referring to Fig. 19, a total of 3 charge / discharge cycles were performed by charging the full cell according to Experimental Example 1 to 4.0V and then discharging it to 1.0V. Referring to Fig. 20 (a), a total of 100 charge / discharge cycles were performed by charging the full cell according to Experimental Example 1 to 4.0V and then discharging it to 1.6V. Referring to Fig. 20 (b), a total of 100 charge / discharge cycles were performed by charging the full cell according to Experimental Example 1 to 4.0V and then discharging it to 1.0V.

[0208] As can be seen in Fig. 18, the discharge capacity of the half cell according to Experimental Example 1 is 620 mAh / g.

[0209] As can be seen in FIG. 19, when the full cell according to Experimental Example 1 is discharged to 1.0V, among the residues (LiCoO2, Co3O4) generated by the decomposition of the coating layer (Li6CoO4) of the separator during the initial charging process of the full cell according to Experimental Example 1, Co3O4 is lithium ions (Li + It can be seen that sufficient lithiation does not occur in the positive electrode of the full cell according to Experimental Example 1 by reacting with ).

[0210] As can be seen in FIG. 20, during the charging / discharging process of the full cell according to Experimental Example 1, it can be seen that the discharge capacity of the full cell is maintained significantly higher and more stably when discharged to 1.6V compared to when discharged to 1.0V.

[0211] Accordingly, in the embodiment of the present application, the method of discharging the secondary battery to 1.6V during the charge / discharge cycle process of the secondary battery is a method that minimizes the decrease in the discharge capacity of the secondary battery as the number of charge / discharge cycles increases and stably maintains the discharge capacity of the secondary battery during the long-term charge / discharge cycle process.

[0212]

[0213] Although the present invention has been described in detail using preferred embodiments, the scope of the invention is not limited to specific embodiments and should be interpreted by the appended claims. Furthermore, those skilled in the art will understand that many modifications and variations are possible without departing from the scope of the invention.

[0214] The separator for a secondary battery according to an embodiment of the present invention can be used in various devices such as lithium secondary batteries, graphite-sulfur batteries, electric vehicle batteries, mobile batteries, IT device batteries, and energy storage systems (ESS).

Claims

1. A method for manufacturing a separator for a secondary battery in which ions of a base metal are intercalated and deintercalated into the negative and positive electrodes during a charging / discharging process, Step of preparing the equipment; A step of preparing a complex metal oxide comprising the above base metal and transition metal; A step of preparing a coating layer source by mixing the above-mentioned composite metal oxide, conductive material, and binder; and A method for manufacturing a separation membrane comprising the step of manufacturing the separation membrane by coating the coating layer source on one surface of the above-described material.

2. In Paragraph 1, A method for manufacturing a separator, wherein the initial capacity of a secondary battery including the separator is controlled according to the weight ratio of the composite metal oxide in the above coating layer source.

3. In Paragraph 2, A method for manufacturing a separator comprising controlling the weight ratio of the composite metal oxide in the above coating layer source to be greater than 40 wt% and less than 60 wt%, thereby increasing the initial capacity of the secondary battery.

4. In Paragraph 3, A method for manufacturing a separator, comprising controlling the weight ratio of the conductive material in the coating layer source to be greater than 20 wt% and only 40 wt%, and controlling the weight ratio of the binder in the coating layer source to be 20 wt%.

5. In Paragraph 4, The above composite metal oxide includes lithium cobalt oxide (Li6CoO4), and The above conductive material comprises any one of Super P, carbon black, and carbon nanotubes, and The above binder is a method for manufacturing a separation membrane containing PVDF (Polyvinylidene fluoride).

6. In Paragraph 1, The above description describes a method for manufacturing a separation membrane containing polyethylene.

7. A separator comprising a substrate and a coating layer having a composite metal oxide comprising a base metal and a transition metal provided on one surface of the substrate, A separator comprising the intercalation and deintercalation of ions of the base metal within the coating layer of the separator, into a negative electrode and a positive electrode not containing the base metal during the charging / discharging process of a secondary battery including the separator.

8. In Paragraph 7, A separator comprising, in the initial charging process of the secondary battery, applying voltage to the surface of the separator so that the composite metal oxide of the coating layer is oxidized and decomposed to produce a residue, and ions of the base metal of the composite metal oxide of the coating layer are inserted into the negative electrode.

9. In Paragraph 7, The above description includes polyethylene, and The composite metal oxide of the coating layer above is a separator containing lithium cobalt oxide (Li6CoO4).

10. In a secondary battery in which ions of a base metal are intercalated and deintercalated into the negative and positive electrodes during the charging / discharging process, An anode comprising an anode layer having sulfur; A cathode comprising a cathode layer having graphite, disposed spaced apart from the anode; A separator disposed between the anode and the cathode; and The electrolyte provided between the anode and the cathode, comprising: The above separator comprises a substrate and a coating layer having a composite metal oxide comprising the base metal and the transition metal provided on one surface of the substrate, and A secondary battery comprising a surface of the above-described material that is spaced apart from and opposite to the upper surface of the positive electrode.

11. In Paragraph 10, In the initial charging process of the secondary battery, voltage is applied to the surface of the separator, causing the composite metal oxide of the coating layer to undergo oxidative decomposition to produce a residue, and ions of the base metal of the composite metal oxide of the coating layer are inserted into the negative electrode. A secondary battery comprising, subsequently, lithium polysulfide generated during the charging / discharging process of the secondary battery being adsorbed onto the residue, thereby suppressing the shuttle effect of the lithium polysulfide.

12. In Paragraph 11, A secondary battery comprising, in the charging / discharging process of the secondary battery, charging up to 4.0V and discharging up to 1.6V.

13. In Paragraph 11, The above coating layer comprises lithium cobalt oxide (Li6CoO4) The above residue is a secondary battery comprising lithium cobalt oxide (LiCoO2) and cobalt oxide (Co3O4).

14. In Paragraph 10, The above secondary battery includes a graphite (anode)-sulfur (cathode) battery.

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