Porous structure comprising pore structure of various sizes, method for producing same, and electrode for secondary battery using same

Abstract

A porous structure for a secondary battery electrode according to a preferred embodiment of the present invention comprises a sulfur-containing active material, a conductive material, and a binder, and is manufactured by a phase transition method to have a pore structure of various sizes and shapes according to the location in the structure. Therefore, electrolyte-soluble intermediate products that are generated during charge-discharge reactions can be stored in pores inside the electrode and the active material can be prevented from separating from the electrode to effectively suppress a degradation in battery performance caused by a decrease in the amount of the active material due to dissolution of the active material.

Description

Porous structure including pore structures of various sizes, method for manufacturing the same, and electrode for secondary battery using the same

[0001] The present invention relates to an electrode for a secondary battery, and more particularly, to a high-performance electrode that can be used in a sulfur-containing secondary battery.

[0002] The applications of secondary batteries are expanding, from small batteries used in mobile phones and laptops to large-scale batteries for electric vehicles and energy storage devices. However, currently commercialized lithium-ion secondary batteries fail to meet the price and energy density requirements required for this expanding application. There is a need to develop batteries that are cheaper than currently commercialized lithium-ion secondary batteries and have higher theoretical energy densities. Accordingly, active research is being conducted on lithium-sulfur batteries using sulfur as the active material.

[0003] A lithium-sulfur battery is a secondary battery that uses a sulfur-based compound having a sulfur-sulfur bond (disulfide bond), such as S8, as a positive electrode active material, and a carbon-based material in which metal ions such as alkali metals such as lithium or lithium ions can be inserted / deinserted, as an anode active material. Lithium-sulfur batteries store or release electrical energy by utilizing an oxidation reaction in which the oxidation number of sulfur (S) increases and the oxidation number of sulfur (S) decreases as the S-S bond is broken during a reduction reaction (during discharge), and the oxidation number of sulfur (S) increases and the S-S bond is re-formed during an oxidation reaction (during charge).

[0004] Lithium-sulfur batteries are among the most promising batteries currently under development in terms of energy density. Furthermore, the sulfur-based materials used as cathode active materials have the advantage of being inexpensive and environmentally friendly.

[0005] The reaction mechanism of a lithium-sulfur battery is as follows.

[0006] S + 2Li → Li2S

[0007] Through this reaction, sulfur exhibits a high theoretical capacity of 1,672 mAh / g and a high theoretical energy density of 2,600 Wh / kg. Therefore, it is a promising next-generation secondary battery for application to large-scale batteries requiring high energy density, such as electric vehicles or energy storage devices. Meanwhile, sulfur (S8) cathode material reacts with lithium during discharge to form liquid multi-order polysulfides (e.g., Li2S) as an intermediate. x , 4≤x≤8) and is then reduced to a low-order polysulfide (e.g., Li2S2, Li2S) in a solid state. At this time, the liquid multi-order polysulfide has the property of melting from the positive electrode surface and dissolving in the electrolyte, so there is a problem that as the cycle progresses, the active material dissolves into the electrolyte and reacts with lithium, resulting in a shuttle effect, which causes loss of the active material.

[0008] Furthermore, when using sulfur-containing electrodes, the low electrical conductivity of sulfur, a nonconductor, leads to high resistance, posing technical challenges in creating electrodes with high sulfur contents of more than 5 mg per unit area. Therefore, efforts are underway to develop electrodes with high energy densities.

[0009] The present invention was conceived to solve the above-described problem, and its purpose is to suppress the phenomenon in which the performance of a battery is deteriorated due to a decrease in the amount of active material caused by sulfur-containing active material being eluted as the charge / discharge reaction of the battery progresses.

[0010] In order to achieve the above technical task, a porous structure for a secondary battery electrode according to a preferred example of the present invention may include a sulfur-containing active material, a conductive material, and a binder.

[0011] The porous structure may include columnar macropores provided therein and having a diameter of more than 50% and less than 100% of the thickness of the structure; and surface micropores provided on at least one surface layer.

[0012] The above macropores can provide a space for storing electrolyte soluble intermediate products formed during a secondary battery electrode reaction process.

[0013] The above surface micropores can provide surface properties to suppress the elution of the electrolyte soluble intermediate product to the outside of the electrode.

[0014] The average diameter of the above macropores may be 1 ㎛ to 495 ㎛, and the average diameter of the above surface micropores may be 1 nm to 200 nm.

[0015] The porous structure may additionally include micropores having an average diameter of more than 200 nm and less than 1 ㎛ and internal micropores having an average diameter of 1 nm to 200 nm.

[0016] The thickness of the above porous structure may be 2 ㎛ to 500 ㎛.

[0017] The above porous structure may be in a freestanding form.

[0018] The above porous structure may be manufactured by a phase transition method.

[0019] The above porous structure may include a laminated porous structure in which several layers are laminated.

[0020] The above-mentioned layered porous structure may be one in which the several layers are all layered in the same direction with respect to the thickness direction.

[0021] The above-mentioned layered porous structure may have at least one layer selected from among several layers laminated in an opposite direction with respect to the thickness direction.

[0022]

[0023] In order to achieve the above technical task, a secondary battery according to a preferred example of the present invention is

[0024] A cathode comprising a porous structure including a sulfur-containing active material, a conductive material and a binder;

[0025] A cathode positioned opposite to the anode and comprising lithium, sodium, calcium, potassium, magnesium metal, an alloy containing these, or a carbon-based compound capable of reversible oxidation / reduction reaction of ions of these metals;

[0026] A separator positioned between the positive and negative electrodes; and

[0027] It may include an electrolyte impregnated in the positive electrode, negative electrode and separator and containing a lithium salt.

[0028] The porous structure may include columnar macropores provided therein and having a diameter of more than 50% and less than 100% of the thickness of the structure, and surface micropores provided on at least one surface layer.

[0029] The surface layer of the above porous structure and the above electrolyte can form a solid-liquid interface.

[0030] The above macropores can provide a space for storing electrolyte soluble intermediate products formed during a secondary battery electrode reaction process.

[0031] The above surface micropores can provide surface properties to suppress the elution of the electrolyte soluble intermediate product to the outside of the electrode.

[0032] The average diameter of the above macropores may be 1 ㎛ to 495 ㎛, and the average diameter of the above surface micropores may be 1 nm to 200 nm.

[0033] The porous structure may additionally include micropores having an average diameter of more than 200 nm and less than 1 ㎛ and internal micropores having an average diameter of 1 nm to 200 nm.

[0034] The thickness of the above porous structure may be 2 ㎛ to 500 ㎛.

[0035] The above porous structure may be in a freestanding form.

[0036] The above porous structure may be manufactured by a phase transition method.

[0037] The above porous structure may include a laminated porous structure in which several layers are laminated.

[0038] The above-mentioned layered porous structure may have several layers all laminated in the same direction with respect to the thickness direction.

[0039] The above-mentioned layered porous structure may have at least one layer selected from among several layers laminated in an opposite direction with respect to the thickness direction.

[0040]

[0041] In order to achieve the above technical task, a method for manufacturing a porous structure for a secondary battery electrode according to a preferred example of the present invention is provided.

[0042] A step of preparing a sulfur slurry comprising a sulfur-containing active material, a conductive agent, a binder, and a mixed solvent;

[0043] A step of performing a phase transfer step of immersing the above sulfur slurry in a coagulation tank containing a non-solvent immediately after applying the above sulfur slurry on the substrate; and

[0044] It may include a step of separating the sulfur-containing electrode from the substrate after the above-mentioned phase transfer step and performing primary and secondary drying.

[0045] The porous structure manufactured through the above-described phase transition step may include columnar macropores having a diameter of more than 50% and less than 100% of the thickness of the structure provided therein; and surface micropores provided in at least one surface layer.

[0046] The above macropores can provide a space for storing electrolyte soluble intermediate products formed during a secondary battery electrode reaction process.

[0047] The above surface micropores can provide surface properties to suppress the elution of the electrolyte soluble intermediate product to the outside of the electrode.

[0048] After the above drying step, a step of manufacturing a layered porous structure by layering several of the above porous structures in the thickness direction may be additionally included.

[0049] The average diameter of the above macropores may be 1 ㎛ to 495 ㎛, and the average diameter of the above surface micropores may be 1 nm to 200 nm.

[0050] After the above drying step, a step of manufacturing a layered porous structure by layering several of the above porous structures in the thickness direction may be additionally included.

[0051] The above-mentioned laminated porous structure may have several layers all laminated in the same direction in the thickness direction, or at least one layer selected from the several layers may be laminated in the opposite direction with respect to the thickness direction.

[0052] The mixing ratio of the above sulfur-containing active material, the above conductive material, and the above binder may be a weight ratio of 4:2:4 to 6:2:2.

[0053] The non-solvent may include water, alcohol or a mixture thereof.

[0054] The above mixed solvent may be an organic solvent that is soluble in the above non-solvent.

[0055] The above mixed solvent may be a mixture of at least two selected from among an aprotic polar solvent, such as an amine solvent such as N,N-dimethylaminopropylamine or diethyltriamine; an ether solvent such as ethylene oxide or tetrahydrofuran; a ketone solvent such as methyl ethyl ketone; an ester solvent such as methyl acetate; and an aprotic polar solvent such as acetone, dimethylacetamide or N-methyl-2-pyrrolidone.

[0056] According to the present invention as described above, a porous structure for a secondary battery electrode according to an example of the present invention includes a sulfur-containing active material, a conductive material, and a binder, and is manufactured by a phase transfer method so as to have a pore structure having various sizes and shapes depending on the location of the structure, thereby storing an electrolyte soluble intermediate product formed during a charge / discharge reaction of a battery in the pores inside the electrode and preventing the active material from being released from the electrode, thereby effectively suppressing a phenomenon in which the performance of the battery is lowered due to a decrease in the amount of the active material caused by the eluted active material.

[0057] The effects of the present invention are not limited to those mentioned above, and may also include other effects that are not explicitly mentioned, although they can be clearly understood by those skilled in the art from the description throughout the specification.

[0058] Figure 1 is a schematic diagram of a porous structure for a secondary battery electrode according to an example of the present invention.

[0059] FIG. 2 is a scanning electron microscope (SEM) photograph showing the microstructure of the (a, b) surface layer and (c) cross-section of a porous structure according to one embodiment of the present invention.

[0060] FIG. 3 is a photograph of a porous structure according to one embodiment of the present invention and a structure that does not use a phase transition method.

[0061] FIG. 4 is a graph showing the sulfur content according to electrode thickness for a porous structure according to one embodiment of the present invention.

[0062] FIG. 5 is a scanning electron microscope (SEM) photograph and energy dispersive X-ray analysis (EDS) result of the top surface of a porous structure according to one embodiment of the present invention.

[0063] FIG. 6 is a scanning electron microscope (SEM) photograph and energy dispersive X-ray analysis (EDS) result of a cross-section of a porous structure according to one embodiment of the present invention.

[0064] FIG. 7 shows the results of measuring the porosity and total pore volume for (a) the electrodes of Comparative Examples 1 to 3 and (b) the electrodes of Examples 1 to 3 in a porous structure according to an example of the present invention.

[0065] Figure 8 shows the results of evaluating hydrophilicity of the surface of a porous structure according to one embodiment of the present invention.

[0066] Figure 9 shows the charge / discharge curve and charge / discharge cycle results of a sulfur battery using a porous structure as an electrode according to one embodiment of the present invention.

[0067] Figures 10 and 11 show the results of a dissolution experiment of a soluble active material (multi-order sulfide) after a charge / discharge test for a sulfur battery using a porous structure as an electrode according to one embodiment of the present invention.

[0068] Figure 12 shows the results of measuring the rate characteristics of a sulfur battery using a porous structure as an electrode according to one embodiment of the present invention.

[0069] Figures 13 to 15 are schematic diagrams showing electrodes of a laminated structure using various lamination methods using a porous structure according to one embodiment of the present invention.

[0070] FIG. 16 shows the results of measuring charge-discharge characteristics for a sulfur battery including a layered porous structure as an electrode, in which porous structures are laminated according to one embodiment of the present invention.

[0071] Figure 17 shows the results of a characteristic evaluation of a lithium-sulfur battery in the form of a pouch cell using a porous structure as an electrode according to one embodiment of the present invention.

[0072] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. The advantages and features of the present invention, and methods for achieving them, will become clear with reference to the embodiments described in detail below together with the attached drawings. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various different forms. These embodiments are provided only to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

[0073] Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used in a sense commonly understood by those of ordinary skill in the art to which the present invention pertains. Furthermore, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless explicitly and specifically defined otherwise. The terminology used herein is for the purpose of describing embodiments and is not intended to limit the present invention. In this specification, singular forms also include plural forms, unless specifically stated otherwise.

[0074] The terms "comprises" and / or "comprising" as used in the specification do not exclude the presence or addition of one or more other components, steps, operations and / or elements.

[0075]

[0076] Porous structure for secondary battery electrode and method for manufacturing the same

[0077] Figure 1 is a schematic diagram of a porous structure for a secondary battery electrode according to an example of the present invention.

[0078] Referring to FIG. 1, a porous structure (100) for a secondary battery electrode includes a sulfur-containing active material, a conductive material, and a binder, and in particular, the porous structure (100) may include columnar macropores (10) having a diameter of more than 50% and less than 100% of the thickness of the structure therein, and surface micropores (40) provided on at least one surface layer.

[0079] The macropores (10) are columnar pores located inside the structure (100), and are large pores that occupy a significant portion of the volume of the structure (100), and can serve to provide sufficient space for storing electrolyte soluble intermediate products formed during the secondary battery electrode reaction process.

[0080] Meanwhile, the surface micropores (40) are pores of the sub-nanometer scale, and are located on the surface layer of the structure (100) and have a size so fine that electrolyte-soluble intermediate products cannot escape between the pores, so that they can provide surface characteristics to suppress the phenomenon of intermediate products being eluted to the outside of the electrode and reducing the battery capacity. Therefore, the porous structure (100) having the characteristic of having pores of various sizes and shapes depending on the location can maintain the amount of active material that can continuously participate in the charge / discharge reaction of the battery because electrolyte-soluble intermediate products are trapped inside the pores by the macropores (10) and the surface micropores (40) and do not eluted to the outside, and ultimately can exhibit an excellent effect of maintaining the life characteristics of the secondary battery for a long time.

[0081] The thickness of the above porous structure (100) may be 2 ㎛ to 500 ㎛, specifically 50 to 320 ㎛, based on a single layer, but is not limited thereto, and the thickness may be appropriately adjusted depending on the amount of active material added or decreased according to the required battery characteristics. In addition, the porous structure (100) of the single layer may be laminated in several layers through the laminated porous structure described below to provide an electrode for a secondary battery with increased capacity.

[0082] The size of the above-mentioned macropores (10) is particularly greater than 50% and less than 100% of the thickness of the porous structure (100), specifically, it may have a size in the range of 70% to 97% of the thickness of the porous structure (100), and more specifically, it may have a size in the range of 85% to 95% of the thickness of the porous structure (100). The macropores (10) having a size within the above range are particularly preferable because they are in a range that maintains appropriate structural stability even when the structure (100) is provided as a battery electrode, and at the same time, they can exhibit the effect of providing a wide space that can accommodate the maximum amount of electrolyte-soluble intermediate products inside the structure (100). In one specific example, the size of the above-mentioned macropores (10) may have a size of 90% of the thickness of the porous structure (100), but is not limited thereto. For example, the size of the above macropores (40) may range from 1 ㎛ to 495 ㎛ in average diameter, but is not limited thereto.

[0083] The size of the above surface micropores (40) is a sub-nanometer scale pore having an extremely fine diameter to the extent that the passage of electrolyte-soluble intermediate products, for example, multi-order polysulfide materials, is restricted. Specifically, the average diameter of the micropores (40) may be in the range of 1 nm to 200 nm, more specifically, 50 nm to 150 nm, but is not limited thereto.

[0084] In addition, the porous structure (100) may further include pores present throughout the entire interior of the structure, in addition to macropores (10) and surface micropores (40). These medium-sized pores may include micropores (20) having an average diameter of more than 200 nm and less than 1 ㎛ and internal micropores (30) having an average diameter of 1 nm to 200 nm. The micropores (20) may be mainly present at the upper and lower portions of the porous structure (100), and the internal micropores (30) may be evenly present throughout the interior of the structure. The micropores (20) and internal micropores (30) exist within the porous structure (100) and may help prevent electrolyte-soluble intermediates from being eluted to the outside while being trapped within the pores.

[0085]

[0086] A method for manufacturing a porous structure according to one embodiment of the present invention is characterized by forming pores of specific sizes both within and on the surface of the structure by performing a phase transition method. First, a step of preparing a sulfur slurry comprising a sulfur-containing active material, a conductive agent, a binder, and a mixed solvent may be performed.

[0087] The sulfur-containing active material may be sulfur powder. The sulfur powder may be purchased as is, synthesized using a conventionally known method, or used after pretreatment and processing.

[0088] The conductive material may be one or a mixture of at least two selected from the group consisting of carbon black, acetylene black, ketjen black, graphite, vapor grown carbon fiber (VGCF), single-walled carbon nanotubes (SWCNT), multi-walled carbon nanotubes (MWCNT), and derivatives thereof.

[0089] The binder may include at least one selected from, for example, fluororesins such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride copolymers, and hexafluoropropylene (HFP); polyolefin resins such as polyacrylonitrile (PAN), polyethylene (PE), and polypropylene (PP); and derivatives thereof. Specifically, the binder may include, but is not limited to, polyvinylidene fluoride (PVDF). The polyvinylidene fluoride (PVDF) has the advantages of strong oxidation resistance, dissolution in a mixed solvent described below, good dispersibility for active materials and conductive materials, and excellent binding strength.

[0090] The above mixed solvent may be an organic solvent that is soluble in a non-solvent described below, specifically, water, alcohols, or a mixture thereof, and more specifically, may be an aprotic polar solvent having a dielectric constant of greater than 15. The above mixed solvent may include, for example, an amide type such as N,N-dimethylformamide (DMF) or N,N-dimethylacetamide (DMAc); a sulfoxide type such as dimethyl sulfoxide (DMSO); a lactam type such as N-methylpyrrolidone (NMP); a lactone type such as γ-butyrolactone; a cyclic ether type such as tetrahydrofuran (THF), 1,3-dioxane, or 1,4-dioxane; a ketone type such as acetone or methyl ethyl ketone; a nitrile type such as acetonitrile; and a mixture thereof. More specifically, the mixed solvent may be a mixture of at least one selected from acetone, dimethyl sulfoxide (DMSO), dimethylacetamide (DMAc), dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), and tetrahydrofuran (THF).

[0091] In particular, the mixed solvent may be a mixed solvent in which at least one organic solvent having a fast vaporization rate is mixed with at least one other organic solvent having a slow vaporization rate, and for example, a mixed solvent of acetone and NMP may be used. Since acetone vaporizes relatively quickly compared to NMP, it can play a role in expanding the size of the pores inside the porous structure through the phase transition process described below. In addition, compared to the case where only NMP is generally used as the main solvent, it has the advantage of shortening the slurry preparation time because it can dissolve a binder polymer, such as PVDF, in a short period of time. Specifically, the mixed solvent is a solvent in which NMP and acetone are mixed, and the mixing ratio thereof may be a weight ratio of 5:5 to 9:1, and in one specific example, a weight ratio of 8:2 may be used, but is not limited thereto.

[0092] The step of mixing the components to prepare the above-described sulfur slurry may first proceed with the step of preparing a binder solution by mixing the binder and the mixed solvent for ease of operation, and then mixing the active material and conductive agent later. Specifically, the preparation of the sulfur slurry is performed by first dissolving PVDF in acetone (20 wt%), then adding NMP (80 wt%) to prepare a binder solution, and then adding the sulfur-containing active material and conductive agent to the binder solution and mixing them.

[0093] The mixing ratio of the sulfur-containing active material, conductive agent, and binder may be 4:2:4 to 6:2:2 by weight. The sulfur slurry manufactured to have the above content range has excellent workability because its mixing property, viscosity, etc. are applied to the electrode manufacturing process, and also can be manufactured into a physically excellent electrode even in a secondary battery electrode manufactured by drying the slurry. The electrode manufacturing process may be applied by non-limiting examples such as roll coating, screen coating, doctor's knife, roll pressing, and tape casting. If the sulfur-containing active material is further increased within the above content range, the brittleness of the manufactured electrode may increase, resulting in a physically weak electrode. If the sulfur-containing active material is further decreased, there is a problem that the increase in battery capacity is limited. Specifically, the mixing ratio may be more preferably a weight ratio of 5:2:3 to 5.5:2:2.5, but is not limited thereto.

[0094]

[0095] Next, a phase transition step may be performed in which the sulfur slurry is applied onto a substrate and immediately after application, the substrate is immersed in a coagulation bath containing a non-solvent. That is, a phase transition process may be performed by exchanging the solvent and non-solvent within the sulfur slurry during the process in which the non-solvent penetrates into the sulfur slurry.

[0096] The phase inversion (phase separation) method is a method for manufacturing a porous polymer membrane. When a coating film containing a polymer membrane is immersed in a coagulation bath containing a non-solvent, the solvent in the coating film dissolves into the non-solvent, while the polymer does not dissolve in the non-solvent and coagulates, so that pores are formed in the places where the solvent escapes, forming a porous polymer membrane. The "coagulation" can be understood as a solidification process in which a polymer forms a three-dimensional, large polymer structure through physical or chemical crosslinking. Coagulation is an important process in the phase inversion method that determines the shape of the surface of the polymer membrane, the pore structure, etc.

[0097] When the sulfur slurry coated on the substrate is immersed in a coagulation bath containing a non-solvent and begins to coagulate, the surface layer of the sulfur slurry first comes into contact with the non-solvent, and the solvent in the surface layer dissolves into the non-solvent, and a high-concentration polymer phase that changes into a gel state while the viscosity of the surface layer rapidly increases can be formed. This high-concentration phase is formed as a polymer film on the surface of the structure through the final drying process, and a relatively low-concentration phase can remain inside the structure to form pores. In particular, micropores having a sub-nano-scale micro-diameter of about 200 nm or less can be formed in the polymer film on the surface of the structure formed by the high-concentration phase.

[0098] In the phase transition process by the exchange of solvent and nonsolvent, a porous structure of various sizes is formed. The controlling factors that affect the pore structure include the type and concentration of the polymer, the type and amount of the solvent and nonsolvent, the inflow rate of the nonsolvent, the type and amount of an appropriate solvent and nonsolvent, the composition of the slurry, the type and amount of the contained particles, the process temperature, etc. By appropriately combining or controlling these factors, the overall structure of the porous structure and the structure and size of the pores can be appropriately controlled.

[0099] The non-solvent may include water, alcohol or a mixture thereof, and in one specific example, distilled water may be used, but is not limited thereto.

[0100]

[0101] The above substrate may be a glass substrate, and as a conductor used as a current collector of the electrode, a foil containing a metal material such as aluminum (Al), nickel (Ni), or stainless steel may also be used.

[0102] Applying the above sulfur slurry onto a substrate can be performed, without limitation, using, for example, roll coating, screen coating, a doctor's knife, roll pressing, tape casting, etc.

[0103] Next, a step of separating and drying the sulfur-containing electrode from the substrate after the above-described phase transfer step can be performed.

[0104] The above sulfur-containing electrode can be naturally separated from the substrate by maintaining the immersion for a long period of time, for example, about 24 hours, after the phase transfer step of immersing the substrate coated with sulfur slurry in distilled water. The sulfur-containing electrode thus separated can be an independent, free-standing electrode and can be made more easily workable than when manufactured using a conventional slurry-based secondary battery electrode manufacturing method.

[0105] The drying step of the collected sulfur-containing electrode can be performed in two stages: primary and secondary drying. Specifically, the drying step can first dry the edges of the electrode through a primary drying process in a vacuum oven (50°C) for 2 minutes, and then dry the interior of the electrode through a secondary drying process for 20 minutes under the same conditions. The purpose of performing two stages of drying is to fix the electrode and prevent deformation of the electrode that occurs during the drying process. Thus, a porous structure manufactured by a phase transfer method with suppressed electrode deformation can be manufactured.

[0106]

[0107] Secondary battery having a porous structure

[0108] The present invention can provide a secondary battery having a positive electrode, a negative electrode, an electrolyte, and a separator including the above-described porous structure.

[0109] The porous structure included in the above positive electrode can be used in the same manner as described above. In particular, when assembling a secondary battery, the surface layer of the porous structure having surface micropores may be arranged in a direction in which it contacts the electrolyte, i.e., so that the surface layer and the electrolyte form a solid-liquid interface. On the other hand, the surface of the other side of the porous structure, i.e., the lower side, may be arranged in contact with a conductive substrate, such as a current collector. Since the surface micropores provided in the surface layer have the effect of suppressing the elution of electrolyte-soluble intermediate products formed during the secondary battery electrode reaction process to the outside of the electrode, it may be important to set the direction of the porous structure when constructing the secondary battery electrode. Since the porous structure has a surface layer having surface micropores and a pore gradient of unique and various sizes within the structure, the electrochemical characteristics, etc. may vary depending on the direction and number of stacking of the structure, the assembly method of the battery, etc.

[0110] The above-described negative electrode is positioned opposite the above-described positive electrode, and may include lithium, sodium, calcium, potassium, magnesium metal, an alloy containing these, or a carbon-based compound capable of reversible oxidation / reduction of ions of these metals. The porous structure of the positive electrode described above may be used in the same manner depending on changes in experimental conditions and methods. Therefore, it can be appropriately applied to lithium-sulfur batteries, sodium-sulfur batteries, calcium-sulfur batteries, potassium-sulfur batteries, etc., depending on the negative electrode used.

[0111] The above electrolyte is an ion transfer medium that allows electrolyte metal ions to move, and is impregnated into the positive electrode, negative electrode, and separator, and may contain a metal salt, such as a lithium salt, and an organic solvent.

[0112] The lithium salt is a salt that can be dissolved in an organic solvent to generate lithium ions, and the anion of the lithium salt is selected from monovalent to divalent unimolecular, polymolecular, and polymeric anions. For example, LiCF3SO3, LiPF6, LiClO4, LiBF4, LiB(C2O4), LiTFSI (lithium bis(trifluoro-methanesulfonyl)imide), LiNO3 (lithium nitrate), and combinations thereof can be used, and a mixture of two or more thereof can also be used. Specifically, LiTFSI can be used as the lithium salt. In addition to the electrolyte, an ionic additive for forming a passivating film on the negative electrode surface can be included, and LiNO3 (lithium nitrate) can be used as the lithium additive, but is not limited thereto.

[0113] The above lithium salt can be dissolved in an organic solvent and used as a non-aqueous electrolyte. The organic solvent may be a mixed organic solvent of DME (Dimethyl ether) and DOL (1,3-dioxolane), but is not limited thereto.

[0114] The separator is a porous material positioned between the positive and negative electrodes and is used as a passage for ions to move. For example, the separator may be an insulator material in the form of a porous film, nonwoven fabric, or woven fabric made of a material such as a polyolefin resin such as polyethylene or polypropylene, glass fiber, fluororesin, or nitrogen-containing aromatic polymer. The thickness of the separator may be advantageous as long as mechanical strength is maintained, as the thickness is thinner, in that the volumetric energy density of the battery increases and the internal resistance decreases.

[0115]

[0116] Layered electrode using porous structure

[0117] Figures 13 to 15 are schematic diagrams showing electrodes of a laminated structure using various lamination methods using a porous structure according to one embodiment of the present invention.

[0118] Referring to FIGS. 13 to 15, a porous structure according to an example of the present invention can be prepared as a laminated electrode by stacking several layers. Depending on the number of layers and the direction of stacking, a laminated porous structure having various pore gradient structures can be prepared, specifically according to the following three stacking methods.

[0119] First, a two-layer laminated porous structure (200) in which several layers of a porous structure (100), for example, two layers, are all laminated in the same direction, may be provided. This may be a structure in which the lower part of one porous structure (100) is vertically laminated in the thickness direction so that the surface of the other is in contact with the lower part of the other porous structure. In addition, a three-layer laminated porous structure (300) in which three porous structures (100) are all laminated in the same direction may be provided. In the laminated porous structures (200 and 300) in the same direction, since the lower part and the surface layer having micropores are in contact with each other, there is a structural characteristic in which a relatively large space is provided in the depth of each layer of the structure, while the upper and lower parts of each layer are provided with small pores. This structural feature has the effect of confining electrolyte-soluble intermediate products into the macropores located deep in each layer of the structure, and suppresses the soluble intermediate products from being eluted to the outside of the electrode, so that the active material can continuously participate in the charge / discharge reaction of the battery, thereby maintaining the life characteristics of the secondary battery for a long time. In addition, since each porous structure electrode layer (100) independently has the structural characteristics described above, when a plurality of these are continuously laminated to form a laminated porous structure, the improved elution suppression characteristics can be exhibited multiple times, and furthermore, there is an advantage of increasing the capacity of the electrode. Having a laminated porous structure to which the above-described same-direction lamination method is applied can be particularly advantageous in laminating electrodes having a thin thickness of about tens to hundreds of micrometers.

[0120] In addition, the porous structure may be provided as a face-to-face stacked porous structure (400) in which at least one layer selected from among several layers is stacked in an opposite direction with respect to the thickness direction. Specifically, it may be provided as a two-layer face-to-face stacked porous structure (400) in which two porous structures (100) are stacked in a facing direction, that is, the lower portions of the positive porous structure (100) and the reverse porous structure (100') are in facing contact with each other, and the surface layers in which surface micropores are formed are stacked to form the uppermost and lowermost surfaces of the final stacked structure. In particular, in the case of the face-to-face direction (the direction in which the surface layers are provided at both ends), it has the advantage of being able to suppress the outflow of intermediate products formed in each electrode layer from both sides, and can be easily stacked for thick electrodes.

[0121]

[0122] Hereinafter, the present invention will be described in more detail using examples and comparative examples. However, the following examples and comparative examples are intended to illustrate the present invention and are not intended to limit the scope of the present invention.

[0123]

[0124] Examples 1 to 3: Preparation of porous structures using a phase transition method

[0125] First, 10 parts by weight of sulfur, 4 parts by weight of Super-P as a conductive agent, 6 parts by weight of PVDF (polyvinylidene fluoride) as a binder, and 30 ml of a mixed solvent (NMP (N-methyl-pyrrolidone): acetone = 80:20 v / v)) are mixed, and then ball milled three times for 20 minutes each at 350 rpm / 1 hour to prepare a sulfur slurry. Additionally, a bubble removal step within the sulfur slurry is performed for 2 minutes.

[0126] Next, tape casting was performed on the above sulfur slurry on a glass substrate, and the tape was wrapped around a glass rod to control the coating thickness and the sulfur content per area (loading amount) of the electrode (active material weight per unit area). Depending on the number of tape layers, the sulfur content per area (loading amount) of the electrode was controlled to 2 mg / cm. 2 (5 layers, Example 1), 4 mg / cm 2 (10 layers, Example 2) and 8 mg / cm 2 (15 layers, Example 3) The sulfur slurry was applied under the conditions.

[0127] Afterwards, immediately after preparing the applied sulfur slurry, it was immersed in distilled water at room temperature, and after 1 hour, the distilled water was replaced with new water, and kept for approximately 24 hours, and then the electrode was collected. The collected electrode was first dried (edge ​​dried) for 2 minutes in a vacuum oven (50°C), and then secondarily dried for 20 minutes under the same conditions to produce a free-standing porous structure electrode.

[0128]

[0129] Comparative Examples 1 to 3: Electrode fabrication without using a phase transfer method

[0130] An electrode was manufactured using the same method as in the examples, except that the sulfur slurry was applied on aluminum (Al) foil and dried in an oven at 60°C, without using a phase transfer method. At this time, as in examples 1 to 3, the applied sulfur slurry had a sulfur content per area (loading amount) of 2 mg / cm 2 (Comparative Example 1), 4 mg / cm 2 (Comparative Example 2) and 8 mg / cm 2 (Comparative Example 3) was adjusted to the conditions.

[0131]

[0132] Battery Examples 1 to 3: Sulfur battery comprising a porous structure manufactured using a phase transfer method

[0133] The porous structures obtained by the phase transfer method of Examples 1 to 3 were used as electrodes. Glass fibers were used as separators, and the electrodes, glass fibers, and electrodes were assembled in the order of electrodes, glass fibers, and electrodes into Swagelok cells or pouch cells. After cell assembly, an electrolyte solution containing 1 M LiTFSI (lithium bis(trifluoro-methanesulfonyl)imide) salt and LiNO3 (lithium nitrate) additives dissolved in a mixed organic solvent of DME (dimethyl ether) and DOL (1,3-dioxolane) was injected into the cell.

[0134]

[0135] Battery Example 4: A sulfur battery including an electrode comprising a layered porous structure in which two layers of porous structures manufactured using a phase transfer method are laminated in the same direction.

[0136] It was prepared in the same manner as the battery manufacturing method of battery examples 1 to 3, but the sulfur content per electrode area (loading amount) was 2.15 mg / cm 2 A porous structure having a laminated structure in which two porous structures controlled by the thickness direction are laminated was used as an electrode. Specifically, the two porous structures were laminated so that the lower part of one porous structure touches the surface layer of the other porous structure (laminated in the same direction so that there is no change in the direction of the structure). Therefore, a porous structure having a laminated structure in which two layers are laminated was manufactured by a simple lamination method and used as an electrode for a sulfur battery. The final sulfur content per area (loading amount) of the electrode used in Battery Example 4 was 4.3 mg / cm 2 am.

[0137]

[0138] Battery Example 5: A sulfur battery including an electrode comprising a layered porous structure in which three layers of porous structures manufactured using a phase transfer method are laminated in the same direction.

[0139] The sulfur content per electrode area (loading amount) is 3.2 mg / cm2 A porous structure of a laminated structure was manufactured using the same method as in battery example 4 using three porous structures adjusted to . The final sulfur content per area (loading amount) of the electrode used in battery example 5 was 9.6 mg / cm 2 am.

[0140]

[0141] Battery Example 6: A sulfur battery including a layered porous structure electrode in which two layers of porous structures manufactured using a phase transfer method are laminated face to face.

[0142] The sulfur content per electrode area (loading amount) is 4.1 mg / cm 2 Two porous structures were used and laminated face to face in the thickness direction, specifically, a porous structure having a laminated structure in which the lower part of one porous structure is in contact with the lower part of the other porous structure was manufactured and used as an electrode for a sulfur battery. The final sulfur content per area (loading amount) of the electrode used in battery example 6 was 8.2 mg / cm 2 am.

[0143]

[0144] Battery Comparative Examples 1 to 3: Sulfur batteries including electrodes that do not use a phase transfer method

[0145] A sulfur battery was manufactured using the same method as in Battery Examples 1 to 3, except that the electrodes of Comparative Examples 1 to 3 were used.

[0146]

[0147] FIG. 2 is a scanning electron microscope (SEM) photograph showing the microstructure of the (a, b) surface layer and (c) cross-section of a porous structure according to one embodiment of the present invention.

[0148] Referring to FIGS. 2(a) and (b), it can be seen that the surface layer of the porous structure according to a preferred example of the present invention is provided with micropores having a diameter of approximately several nm to 200 nm. In addition, referring to FIG. 2(c), a cross-sectional photograph of the porous structure can be used to confirm macropores having a diameter that accounts for approximately 90% of the thickness of the structure.

[0149]

[0150] FIG. 3 is a photograph of a porous structure according to one embodiment of the present invention and a structure that does not use a phase transition method.

[0151] Referring to FIG. 3, as the amount of sulfur per area (loading amount) of the electrode increases, the comparative example electrode has a problem of tearing after drying, whereas it can be confirmed that the porous structure according to the embodiment of the present invention does not have a film shape deformed or damaged even when the amount of sulfur per area (loading amount) of the electrode increases.

[0152]

[0153] FIG. 4 is a graph showing the sulfur content according to electrode thickness for a porous structure according to one embodiment of the present invention.

[0154] Referring to Figure 4, the porous structure has a maximum of 8.6 mg / cm at a thickness of 300 ㎛ in a single layer. 2 It includes the sulfur content (loading amount) per electrode area, whereas for the sulfur electrode of the comparative example that did not use the phase transfer method, it is up to 8.1 mg / cm at a thickness of about 170 ㎛. 2 It can be confirmed that the sulfur content (loading amount) per electrode area is included.

[0155]

[0156] FIG. 5 is a scanning electron microscope (SEM) photograph and energy dispersive X-ray analysis (EDS) result of the top surface of a porous structure according to one embodiment of the present invention.

[0157] Referring to Fig. 5(a), on the electrode surface of the comparative example that did not use the phase transfer method, particle shapes of the slurry are observed instead of the smooth surface of the polymer film, and when checking the types of elements included on the surface, it can be seen that the sulfur (S) element included in the slurry is distributed mostly, and carbon (C) and fluorine (F) elements are distributed to a lesser extent.

[0158] On the other hand, referring to FIGS. 5(b) to 5(d), the upper surface of the porous structure manufactured using the phase transfer method can be observed to have a smooth and soft texture derived from the PVDF polymer, and on the surface thereof, it can be confirmed that nano-sized internal micropores, specifically, surface micropores having a pore size of several nm to 200 nm, are evenly formed throughout the surface layer. In addition, the surface of the porous structure manufactured using the phase transfer method also contains a large amount of fluorine (F) element derived from the PVDF polymer, indicating that it is mostly composed of PVDF and contains some sulfur (S) element.

[0159]

[0160] FIG. 6 is a scanning electron microscope (SEM) photograph and energy dispersive X-ray analysis (EDS) result of a cross-section of a porous structure according to one embodiment of the present invention.

[0161] Referring to FIGS. 6(a) to 6(d), in the cross-section of the electrode of the comparative example that did not use the phase transition method, it can be confirmed that the surface layer on the upper part of the structure has an uneven and uneven shape, and it can also be confirmed that the sulfur (S) element is distributed mostly throughout the first half of the electrode, and it can be confirmed that the fluorine (F) element derived from the binder polymer is evenly mixed into the inside of the electrode. On the other hand, referring to FIGS. 6(b) to 6(c), the distribution of the sulfur (S) element is greater than that of the fluorine (F) element in the deep layer inside the electrode, while the distribution of the fluorine (F) element is greater than that of the sulfur (S) element in the upper and lower parts. Accordingly, it can be confirmed that the porous structure using the phase transfer method of Examples 1 to 3 of the present invention does not simply have a homogeneously mixed structure, but rather a heterogeneous mixed region is formed in which a large amount of PVDF polymer is included in the upper and lower portions thereof and a sulfur active material is mainly disposed in the deep layer. In particular, it can be determined that sulfur or sulfur-derived compounds exist at the locations of the macropores formed inside the structure, as it is seen that a large amount of sulfur (S) element is distributed in the region where macropores are formed in the deep layer.

[0162] In addition, in FIGS. 6(b) to 6(d), it can be confirmed that columnar macropores are formed in the thickness direction of the porous structure, and it can be seen that these macropores are pores having a size of about 50% to 90% of the thickness of a single layer of the structure.

[0163]

[0164] FIG. 7 shows the results of measuring the porosity and total pore volume for (a) the electrodes of Comparative Examples 1 to 3 and (b) the electrodes of Examples 1 to 3 in a porous structure according to an example of the present invention.

[0165] Referring to Fig. 7, the pore surface area and volume can be measured using BET analysis (Brunauer-Emmett-Teller Analysis). P is the pressure of the injected N2 gas, P0 is the saturation pressure of the N2 gas, and P / P0 is the relative pressure. The adsorption isotherm, which rapidly increases in the low relative pressure range of P / P0 < 0.15 and rises vertically, may indicate the presence of nanopores with very small pore sizes. Therefore, it can be seen that the surface layer of the porous structure in that range contains nanoscale micropores. In addition, the hysteresis curve appearing in the relative pressure range of 0.15 < P / P0 < 0.95 may indicate the presence of micropores within the porous structure. Therefore, it can be seen that microscale micropores are included within the porous structure in that range. Furthermore, the increase in the adsorption isotherm in the high relative pressure range of P / P0 > 0.95 may indicate the presence of large macropores. Therefore, it can be seen that macropores exist within the porous structure in this range.

[0166] Meanwhile, the electrodes of comparative examples 1 to 3 that did not use the phase transfer method had a maximum surface area of ​​4.16 m 2 / g and maximum pore volume 0.019 cm 3 / g level, but in the electrodes of Examples 1 to 3 as porous structures using the phase transition method, the surface area of ​​the electrode increases as the amount of sulfur per electrode area (loading amount) (active material weight per unit area) increases, and the minimum surface area is 16.01 m 2 / g to maximum 17.84 m 2 / g and maximum pore volume 0.058 cm 3 / g to a maximum of 0.060 cm 3It can be confirmed that / g has been secured. Therefore, it can be confirmed that the porous structure using the phase transfer method has pores of various sizes formed compared to the pore structure manufactured by the general method, so the surface area is larger and the total pore volume is also increased.

[0167]

[0168] Figure 8 shows the results of evaluating the absorption (permeability) of electrolyte on the surface of a porous structure according to one embodiment of the present invention.

[0169] Referring to FIG. 8, the absorption rate of the electrolyte through the electrode surface can be measured through photographs taken at time intervals (0 s, 0.01 s, 0.05 s, 0.5 s, 1 s, and 1.5 s) during the process of dropping the electrolyte solution (DME / DOL) onto the electrode surface of the comparative example and the embodiment of the present invention. It can be seen that absorption proceeds so quickly that the shape of the water droplet cannot be seen immediately after dropping the electrolyte onto the electrode surface of the comparative example that did not use the phase transition method of FIG. 8(a), and it can be confirmed that the absorption rate is so fast that the electrolyte on the electrode surface does not exist at all in just 1.5 seconds. On the other hand, when an electrolyte is dropped on the surface of a porous structure manufactured using the phase transition method of FIG. 8(b), it can be seen that the absorption progresses slowly enough that electrolyte droplets remain formed for up to 0.05 seconds, and since it has a porous structure, the electrolyte eventually enters the pores and is absorbed by the capillary force, but it can be seen that the time for absorption to be completely complete to the point where no round electrolyte droplets remain on the surface of the electrode is measured to be 3 seconds. Accordingly, it can be inferred that the porous structure of the present invention has a slower electrolyte absorption rate in the surface layer than a conventional electrode, and thus micropores are formed on the surface of the electrolyte.

[0170]

[0171] Figure 9 shows the charge / discharge curve and charge / discharge cycle results of a sulfur battery using a porous structure as an electrode according to one embodiment of the present invention.

[0172] Referring to FIG. 9(a) and FIG. 9(b), battery comparative examples 1 to 3 show a capacity of less than 600 mAh / g as a result of measuring the charge / discharge characteristics at a rate of 0.1 C, but according to FIG. 9(c) and FIG. 9(d), battery examples 1 to 3 using a porous structure using a phase transfer method as an electrode show a relatively high capacity of 1,000 to 1,200 mAh / g under the same conditions, and it can be confirmed that the charge / discharge cycle characteristics are also maintained for a long period of time.

[0173]

[0174] FIG. 10 and FIG. 11 show the results of a dissolution experiment of a soluble active material (multi-order sulfide) after a discharge test for a sulfur battery using a porous structure as an electrode according to one embodiment of the present invention.

[0175] Referring to FIGS. 10 and 11, battery Example 2 (4 mg / cm2) and battery Comparative Example 2 (4 mg / cm2) were used and discharge was performed under 0.1 C conditions. The discharge voltage was maintained for 30 minutes to dissolve an excess of multi-order polysulfides, and then the batteries were disassembled and the separator was visually observed to confirm the amount of sulfur elution on the separator depending on the type of electrode. As a result, in the case of using the battery Example using the porous structure using the phase transfer method of the present invention as an electrode, since the electrode has relatively large pores inside, multi-order polysulfides in a liquid state can be effectively stored, and since micro-pores are formed on the surface, surface properties for suppressing the elution of electrolyte-soluble intermediates to the outside of the electrode are provided, and thus it can be visually confirmed that the amount of multi-order polysulfides leaking out of the electrode is reduced.

[0176]

[0177] Figure 12 shows the results of measuring the rate characteristics of a sulfur battery using a porous structure as an electrode according to one embodiment of the present invention.

[0178] Referring to FIG. 12, the initial specific capacities of the batteries were measured to be 1,110 mAh / g, 1,025 mAh / g, and 955 mAh / g under a rate condition of 0.1 C for battery examples 1 to 3, and it can be confirmed that the cycle is stably maintained even under fast rate conditions.

[0179]

[0180] FIG. 16 shows the results of measuring charge-discharge characteristics for a sulfur battery including a layered porous structure as an electrode, in which porous structures are laminated according to one embodiment of the present invention.

[0181] Referring to Figures 16(a) to (c), the first charge / discharge result (1 st , black solid line) showed a high capacity of about 900 mAh / g to 1,200 mAh / g, and among them, it can be confirmed that the battery example 5, which increased the sulfur content by increasing the sulfur content per electrode area (loading amount) by stacking three layers in the same direction, showed the best capacity. In particular, when the electrode in which the two-layer porous structure of battery example 6 was stacked in the face-to-face direction was used, the 10th cycle (10 th , it can be confirmed that it exhibits high capacity along with stable charge / discharge cycles even up to the olive solid line. Therefore, it was confirmed that the capacity and stability of lithium-sulfur batteries can be improved through structural design inside the electrode by controlling the pore gradient in the face-to-face direction.

[0182]

[0183] Figure 17 shows the results of a characteristic evaluation of a lithium-sulfur battery in the form of a pouch cell using a porous structure as an electrode according to one embodiment of the present invention.

[0184] Referring to Figure 17, the sulfur content per electrode area (loading amount) is 5.2 mg / cm 2The lithium-sulfur pouch cell with a sulfur loading of 23.4 mg exhibited a high capacity of approximately 1,100 mAh / g in the first cycle at a rate of 0.1 C and showed stable charge-discharge behavior up to the 16th cycle.

[0185]

[0186] Although embodiments of the present invention have been described with reference to the attached drawings, those skilled in the art will appreciate that the present invention can be implemented in other specific forms without altering the technical concept or essential features thereof. Therefore, the embodiments described above should be understood to be illustrative in all respects and not restrictive.

[0187]

[0188] [Explanation of symbols]

[0189] 100: porous structure (single layer), 100': reverse porous structure, 200: stacked porous structure (two layers, stacked in the same direction), 300: stacked porous structure (three layers, stacked in the same direction), 400: stacked porous structure (two layers, stacked face to face)

[0190] 10: macropores, 20: micropores, 30: internal micropores, 40: surface micropores

Claims

1. A porous structure comprising a sulfur-containing active material, a conductive agent and a binder, The above porous structure is, Columnar macropores provided inside and having a diameter greater than 50% and less than 100% of the thickness of the structure; and A porous structure for a secondary battery electrode, comprising surface micropores provided in at least one surface layer.

2. In paragraph 1, The above macropores provide a space for storing electrolyte soluble intermediate products formed during the secondary battery electrode reaction process. A porous structure for a secondary battery electrode, wherein the surface micropores provide surface properties for suppressing the elution of the electrolyte soluble intermediate product to the outside of the electrode.

3. In paragraph 1, The average diameter of the above macropores is 1 ㎛ to 495 ㎛, A porous structure for a secondary battery electrode, wherein the average diameter of the surface micropores is 1 nm to 200 nm.

4. In paragraph 1, A porous structure for a secondary battery electrode, further comprising micropores having an average diameter of more than 200 nm and less than 1 ㎛ and internal micropores having an average diameter of 1 nm to 200 nm inside the porous structure.

5. In paragraph 1, A porous structure for a secondary battery electrode, wherein the thickness of the porous structure is 2 ㎛ to 500 ㎛.

6. In paragraph 1, The above porous structure is a free-standing porous structure for a secondary battery electrode.

7. In paragraph 1, A porous structure for a secondary battery electrode, wherein the porous structure is manufactured by a phase transfer method.

8. In paragraph 1, The above porous structure is a porous structure for a secondary battery electrode, which includes a laminated porous structure in which several layers are laminated.

9. In paragraph 8, The above-mentioned laminated porous structure is a porous structure for a secondary battery electrode, wherein several layers are laminated in the same direction with respect to the thickness direction.

10. In paragraph 8, The above-mentioned layered porous structure is a porous structure for a secondary battery electrode, wherein at least one layer selected from several layers is layered in an opposite direction with respect to the thickness direction.

11. A cathode comprising a porous structure including a sulfur-containing active material, a conductive agent and a binder; A cathode positioned opposite to the anode and comprising a lithium, sodium, calcium, potassium, magnesium metal, an alloy containing these, or a carbon-based compound capable of reversible oxidation / reduction reaction of ions of these metals; A separator positioned between the positive and negative electrodes; and An electrolyte impregnated into the positive electrode, negative electrode and separator and containing a lithium salt; A secondary battery, wherein the porous structure comprises columnar macropores provided therein and having a diameter of more than 50% and less than 100% of the thickness of the structure, and surface micropores provided in at least one surface layer.

12. In paragraph 11, A secondary battery, wherein the surface layer of the porous structure and the electrolyte form a solid-liquid interface.

13. In paragraph 11, The above macropores provide a space for storing electrolyte soluble intermediate products formed during the secondary battery electrode reaction process. A secondary battery, wherein the surface micropores provide surface properties for suppressing the elution of the electrolyte soluble intermediate product to the outside of the electrode.

14. In paragraph 11, The average diameter of the above macropores is 1 ㎛ to 495 ㎛, A secondary battery, wherein the average diameter of the surface micropores is 1 nm to 200 nm.

15. In paragraph 11, A secondary battery further comprising micropores having an average diameter of more than 200 nm and less than 1 ㎛ and internal micropores having an average diameter of 1 nm to 200 nm inside the porous structure.

16. In paragraph 11, A secondary battery, wherein the thickness of the porous structure is 2 ㎛ to 500 ㎛.

17. In paragraph 11, The above porous structure is a secondary battery in a free-standing form.

18. In paragraph 11, A secondary battery, wherein the above porous structure is manufactured by a phase transfer method.

19. In paragraph 11, A secondary battery, wherein the porous structure comprises a laminated porous structure in which several layers are laminated.

20. In paragraph 19, A secondary battery in which the above-mentioned laminated porous structure is formed by laminating several layers in the same direction with respect to the thickness direction.

21. In paragraph 19, A secondary battery, wherein the above-mentioned laminated porous structure comprises at least one layer selected from several layers laminated in an opposite direction with respect to the thickness direction.

22. A step of preparing a sulfur slurry including a sulfur-containing active material, a conductive agent, a binder, and a mixed solvent; A step of performing a phase transfer step of immersing the above sulfur slurry in a coagulation tank containing a non-solvent immediately after applying the above sulfur slurry on a substrate; and A method for manufacturing a porous structure for a secondary battery electrode, comprising: a step of separating a sulfur-containing electrode from a substrate after the above-mentioned phase transfer step and performing primary and secondary drying; 23. In paragraph 22, The porous structure manufactured through the above phase transition step is Columnar macropores having a diameter greater than 50% and less than 100% of the thickness of the structure provided therein; and A method for manufacturing a porous structure for a secondary battery electrode, comprising surface micropores provided in at least one surface layer.

24. In paragraph 23, The above macropores provide a space for storing electrolyte soluble intermediate products formed during the secondary battery electrode reaction process. A method for manufacturing a porous structure for a secondary battery electrode, wherein the surface micropores provide surface characteristics for suppressing the elution of the electrolyte soluble intermediate product to the outside of the electrode.

25. In paragraph 23, The average diameter of the above macropores is 1 ㎛ to 495 ㎛, A method for manufacturing a porous structure for a secondary battery electrode, wherein the average diameter of the surface micropores is 1 nm to 200 nm.

26. In paragraph 22, After the above drying step, A method for manufacturing a porous structure for a secondary battery electrode, further comprising a step of manufacturing a layered porous structure by laminating several of the above porous structures in the thickness direction.

27. In paragraph 26, The above-mentioned laminated porous structure has several layers that are laminated in the same direction in the thickness direction, or A method for manufacturing a porous structure for a secondary battery electrode, wherein at least one layer selected from several layers is laminated in an opposite direction with respect to the thickness direction.

28. In paragraph 22, A method for manufacturing a porous structure for a secondary battery electrode, wherein the mixing ratio of the sulfur-containing active material, the conductive material, and the binder is 4:2:4 to 6:2:2 by weight.

29. In paragraph 22, A method for producing a porous structure for a secondary battery electrode, wherein the non-solvent comprises water, alcohol or a mixture thereof.

30. In paragraph 22, A method for manufacturing a porous structure for a secondary battery electrode, wherein the mixed solvent is an organic solvent that can be dissolved in the non-solvent.

31. In paragraph 22, A method for producing a porous structure for a secondary battery electrode, wherein the mixed solvent is a mixture of at least two kinds selected from among aprotic polar solvents such as amines such as N,N-dimethylaminopropylamine and diethyltriamine; ethers such as ethylene oxide and tetrahydrofuran; ketones such as methyl ethyl ketone; esters such as methyl acetate; and aprotic polar solvents such as acetone, dimethylacetamide and N-methyl-2-pyrrolidone.

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