Manufacturing method of secondary batteries

Abstract

The method for manufacturing a battery according to the present invention can reduce the number of charge / discharge cycles during the activation process and shorten the time required for the battery manufacturing process by adding a CV section. Furthermore, the method for manufacturing a battery can improve the electrochemical performance of the battery, such as improving battery capacity, by converting the remaining LiPS that was not completely phase-changed due to overvoltage to its final form to the maximum extent possible, reducing overvoltage, and uniformly distributing the LiPS around the positive electrode.

Description

[Technical Field]

[0001] This invention relates to a method for manufacturing a secondary battery, and more specifically, to a method for the initial discharge in the battery activation process.

[0002] This application claims priority based on Korean Patent Application No. 10-2022-0155730, filed on 18 November 2022, and all content disclosed in the specification and drawings of said application is incorporated herein. [Background technology]

[0003] In recent years, interest in energy storage technologies has been growing. As applications expand to mobile phones, camcorders, notebook PCs, and even electric vehicles, research and development of electrochemical devices such as rechargeable batteries are progressing rapidly. Electrochemical devices are one of the most noteworthy fields in this regard, and among them, the development of rechargeable batteries is a focus of attention. Recently, research and development has been progressing on the design of new electrodes and batteries to improve capacity density and specific energy in the development of such batteries.

[0004] Among these types of secondary batteries, lithium-sulfur batteries, with their light lithium negative electrode and sulfur positive electrode having a high discharge capacity, are attracting attention as high-energy-density secondary batteries due to their high energy density.

[0005] In a lithium-sulfur battery, sulfur uses S8 with a cyclic structure as the starting material for the reaction during discharge. As the discharge progresses, it goes through stages of lithium polysulfide (LiPS: Li2S8, Li2S6, Li2S5, Li2S4), which has a linear structure of continuous reduction reactions, dissolves in the electrolyte, and moves from the positive electrode to the negative electrode, and is sequentially reduced to lower monomeric polysulfides. Such negatively charged polysulfides dissolve in a liquid organic solvent and move to the negative electrode due to the chemical potential and the concentration gradient between the positive and negative electrodes. Eventually, Li2S (S8 + 16Li → 8Li2S), an insoluble substance in the reduced state, is produced. During charging, a "shuttle" mechanism occurs by returning to the original substance S8 through an oxidation reaction in the reverse order of the above sequence. In a lithium-sulfur battery with such a mechanism characteristic, the activation process before the life cycle is a core process that can suppress further resistance variables during the driving of life evaluation by sufficiently and uniformly distributing LiPS in the electrolyte around the positive electrode. In the above process, the shuttling of lithium polysulfide (LiPS) affects the overall performance degradation of the cell, and in particular, can seriously affect the degradation of the negative electrode. During the discharge process, sulfur is reduced to lithium polysulfide (lithium-polysulfides, Li2Sn, where 4 < n < 8), and problems occur when this intermediate product dissolves and diffuses into the electrolyte. Lithium polysulfide causes a decrease in capacity due to the shuttle effect on the surface of the negative electrode, which is lithium metal, and part of it is reduced to lithium sulfide (Li2S2, Li2S), which is a non-conductor, interfering with the movement of active material loss and lithium ions and thus degrading the rate performance. Such side reactions lead to a decrease in Coulombic efficiency and destabilization of the negative electrode, reducing the overall performance of the battery. Therefore, it is necessary to establish a new activation process for lithium-sulfur batteries and apply it to battery manufacturing.

Summary of the Invention

Problems to be Solved by the Invention

[0006] The present invention aims to provide a method for manufacturing a lithium-sulfur battery, particularly a method for manufacturing a battery that includes a novel battery activation step, in order to solve the aforementioned problems.

[0007] Other objectives and advantages of the present invention can be realized by the means and methods described in the claims, or combinations thereof. [Means for solving the problem]

[0008] According to a first aspect of the present invention, the present invention relates to a method for manufacturing a lithium-sulfur battery, the method comprising the steps of (S10) manufacturing a spare battery including an electrode assembly and an electrolyte, (S20) Includes an activation step of activating the spare battery, The electrode assembly includes a positive electrode, a negative electrode, and a separation membrane interposed between the positive electrode and the negative electrode, and the positive electrode includes a positive electrode active material containing sulfur. In step S10, the electrode assembly is impregnated with the electrolyte. The S20 step includes a step of discharging the spare battery, and the discharge is performed in the order of constant current discharge followed by constant voltage discharge.

[0009] According to a second aspect of the present invention, in the first aspect, the constant current discharge in the S20 stage is performed until a preset discharge termination voltage is reached, and the discharge termination voltage is set in the range of 1.3V to 1.8V.

[0010] According to a third aspect of the present invention, in the second aspect, in the S20 stage, the constant current discharge is performed at a C rate set in the range of 0.05 to 2 until a preset discharge termination voltage is reached.

[0011] According to a fourth aspect of the present invention, in the second or third aspect, the constant voltage discharge is performed until the remaining current of the battery reaches 0 mAh at a preset discharge termination voltage.

[0012] According to the fifth aspect of the present invention, in any one of the first to fourth aspects, before the step S20 is performed, the backup battery is not charged or discharged, and discharging is first applied to the backup battery among charging and discharging in the step S20.

[0013] According to the sixth aspect of the present invention, in any one of the second to fifth aspects, before the step S20 is performed, the backup battery is not charged or discharged, and the step S20 consists only of the step of discharging the backup battery once.

[0014] According to the seventh aspect of the present invention, in any one of the first to sixth aspects, discharging is performed in the step S20 less than 6 times.

[0015] According to the eighth aspect of the present invention, in any one of the first to eighth aspects, in the step S20, the constant current discharge is performed at a C rate in the range of 0.05 to 2.00.

[0016] According to the ninth aspect of the present invention, in any one of the first to eighth aspects, in the step S20, discharging is performed in a constant current mode until a preset discharge cut-off voltage.

[0017] According to the tenth aspect of the present invention, in any one of the first to ninth aspects, in the step S20, discharging is performed at a C rate in the range of 0.50 to 1.00.

[0018] According to the eleventh aspect of the present invention, in any one of the first to tenth aspects, the step S20 is performed in an environment where the backup battery is pressurized.

[0019] According to the twelfth aspect of the present invention, in the eleventh aspect, the pressure applied is a pressure equal to or higher than the atmospheric pressure.

[0020] According to the thirteenth aspect of the present invention, in any one of the first to twelfth aspects, the step S20 is performed at a temperature of 15°C to 40°C.

[0021] According to a fourteenth aspect of the present invention, in any one of the first to thirteenth aspects, an aging step is further performed after step S10 and before step S20, in which the spare battery is maintained in an atmosphere of 15°C to 40°C.

[0022] According to a 15th aspect of the present invention, in any one aspect of the first to 14th aspects, a charging step is performed during the discharge step in the S20 step, and the charging is performed in the order of constant current charging followed by constant voltage charging. [Effects of the Invention]

[0023] The battery manufacturing method according to the present invention can shorten the time required for the battery manufacturing process by reducing the number of charge-discharge cycles during the battery activation process and by adding a CV (Cold Voltage) section. Furthermore, the battery manufacturing method can improve the electrochemical performance of the battery, such as improving battery capacity, by converting the remaining LiPS that has not undergone a complete phase change due to overvoltage to its final form to the greatest extent possible, thereby reducing the overvoltage and uniformly distributing the LiPS around the positive electrode.

[0024] The following drawings accompanying this specification illustrate preferred embodiments of the invention and, together with the detailed description of the invention, serve to further illustrate the technical idea of ​​the invention. Therefore, the invention should not be construed as being limited solely to what is shown in the drawings. The shapes, sizes, scales, or proportions of elements in the drawings accompanying this specification may be exaggerated to emphasize a clearer description. [Brief explanation of the drawing]

[0025] [Figure 1] This figure shows a comparison of the high-rate discharge characteristics of batteries in the examples and comparative examples. [Figure 2] This figure shows a comparison of the Coulomb efficiency characteristics of batteries in the examples and comparative examples. [Figure 3]This figure shows a comparison of the power density of batteries in different State of Charge (SOC) intervals for the examples and comparative examples. [Modes for carrying out the invention]

[0026] Preferred embodiments of the present invention will now be described in detail with reference to the attached drawings. Prior to this, terms and words used in this specification and in the claims should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather in a manner appropriate to the technical idea of ​​the present invention, in accordance with the principle that the inventor himself may appropriately define the concepts of terms in order to best describe the invention. Accordingly, it should be understood that the embodiments and configurations shown in the drawings described herein are merely the most preferred embodiments of the present invention and do not represent the entirety of the technical idea of ​​the present invention, and that there may be a variety of equivalents and modifications that can be substituted therein at the time of this application.

[0027] When a part of the specification is described as "including," "having," or "equipping" a certain component, unless otherwise specified, it means that it may include other components, rather than excluding them.

[0028] Terms used throughout this specification, such as “approximately” and “substantially,” are used to mean, when specific manufacturing and material tolerances are presented, the numerical values ​​or values ​​close to those values, and are used to prevent unscrupulous infringers from unfairly using disclosures that refer to precise or absolute numerical values ​​to aid in understanding this application.

[0029] Throughout this specification, the phrase "A and / or B" means "A or B, or both."

[0030] The specific terms used in the following detailed descriptions are for convenience only and are not restrictive. The words “right,” “left,” “top,” and “bottom” indicate directions in the referenced drawings. The words “inward” and “outward” indicate directions toward or away from the geometric center of the specified device, system, and its components, respectively. “Forward,” “backward,” “upward,” “downward,” and related words and phrases indicate location and orientation in the referenced drawings and are not restrictive. Such terms include the words exemplified above, their derivatives, and words with similar meanings.

[0031] <Manufacturing method for secondary batteries> This invention relates to a method for manufacturing a secondary battery, and more specifically, to a method for manufacturing a lithium-sulfur secondary battery.

[0032] Specifically, the method for manufacturing a lithium-sulfur secondary battery of the present invention includes the steps of manufacturing a spare battery containing an electrode assembly and an electrolyte, and activating the spare battery. The method for manufacturing the battery may include a degassing step to remove the gas generated in the activation step. The electrode assembly includes a positive electrode, a negative electrode, and a separation membrane interposed between the positive electrode and the negative electrode, the positive electrode contains a positive electrode active material containing sulfur, and before performing the activation step, the electrode assembly is prepared by impregnating it with the electrolyte. Furthermore, in the present invention, the activation step of the method for manufacturing the battery includes the step of discharging the spare battery, and the discharge is characterized in that it is performed in the order of constant current (CC) discharge followed by constant voltage (CV) discharge.

[0033] As described above, by performing a CC-CV discharge step during the activation process, the remaining LiPS that is not completely phase-changed due to overvoltage can be converted to its final form to the maximum extent possible. This increases capacity and ensures excellent lifespan compared to conventional lithium-sulfur batteries. In addition, the process time is shortened and stability is improved.

[0034] Next, the method for manufacturing a lithium-sulfur battery according to the present invention will be described in detail for each step.

[0035] <S10: Manufacturing of Reserve Battery> First, a reserve battery including an electrode assembly and an electrolyte is manufactured (S10).

[0036] In the present specification, the reserve battery means a battery in a state where the formation process has not been completed. In the present invention, the formation process may mean a battery shipment preparation process including an activation and degassing process after the electrolyte is injected.

[0037] The electrode assembly includes a negative electrode, a positive electrode, and a separator disposed between the negative electrode and the positive electrode. Details regarding the negative electrode, positive electrode, and separator will be described later.

[0038] The method for manufacturing a secondary battery of the present invention includes a step of impregnating the electrode assembly with an electrolyte. After the electrode assembly is impregnated with the electrolyte, it can be activated by discharge described later. The electrolyte may include an organic solvent and a lithium salt. Details regarding the organic solvent and the lithium salt will be described later.

[0039] The impregnation is to sufficiently wet (wetting) the electrode assembly with the electrolyte so that the activation by charging and discharging of the electrode assembly can be performed more smoothly. The impregnation of the electrolyte can be performed, for example, by housing the electrode assembly in a battery case, injecting the electrolyte into the battery case, and then maintaining it at a predetermined temperature for a predetermined time. For example, after the injection of the electrolyte, it can be maintained for 12 hours to 100 hours, more preferably 24 hours to 75 hours, so that the electrolyte penetrates into the inside of the electrode assembly (aging step).

[0040] The impregnation of the electrode assembly may be performed at 15°C to 30°C, more specifically 20°C to 27°C. When it is within the above range, the impregnability of the electrode assembly can be improved, and the formation of dendrites in the negative electrode due to an excessively high temperature and the resulting risk of low voltage generation can be prevented, which is desirable.

[0041] On the other hand, in the present invention, the electrode assembly can be manufactured by methods known in the art, and the form of the electrode assembly is not particularly limited. For example, it may be a rolled type, a laminated type, or a laminated / folded type.

[0042] The aforementioned winding-type electrode assembly is manufactured by coating a current collector with electrode active material, drying and cleaning it, cutting it into a band of desired width and length, and then winding it spirally with a separator film sandwiched between the negative and positive electrodes.

[0043] The aforementioned laminated electrode assembly has a structure in which multiple positive and negative electrode unit cells are sequentially stacked, and has the advantage of easily obtaining a rectangular shape. However, it has the disadvantages of a complicated manufacturing process and the fact that when an impact is applied, the electrodes can detach and induce a short circuit.

[0044] Therefore, the electrode assembly has an advanced structure that is a hybrid of the winding type and the laminated type, and is an electrode assembly in which full cells or bi cells of a certain unit size are folded using a long, continuous separation film. Such an electrode assembly is a composite structure of existing folded and laminated types, and is called a "laminated / folded electrode assembly".

[0045] The aforementioned "full cell" refers to a unit cell consisting of a positive electrode / separation membrane / negative electrode unit structure, where the positive electrode and negative electrode are located on opposite sides of the cell, respectively. Examples of such full cells include the most basic structure of a positive electrode / separation membrane / negative electrode cell, and cells with a positive electrode / separation membrane / negative electrode / separation membrane / positive electrode / separation membrane / negative electrode. To construct an electrochemical cell using such full cells, multiple full cells are stacked so that the positive electrode and negative electrode face each other with a separation film interposed between them.

[0046] The "bicell" is a unit cell in which the same electrodes are located on both sides of the cell, such as the unit structure of anode / separator / cathode / separator / anode and the unit structure of cathode / separator / anode / separator / cathode. In order to construct an electrochemical cell using such a bicell, a bicell with an anode / separator / cathode / separator / anode structure (anode bicell) and a bicell with a cathode / separator / anode / separator / cathode structure (cathode bicell) are stacked so that they face each other with a separation film interposed therebetween. In some cases, a larger number of stacked bicells may be used.

[0047] On the other hand, in one embodiment of the present invention, after the impregnation step of the electrolytic solution and before the activation step, a degassing step for removing gas generated inside the battery may be performed.

[0048] <S20: Activation of the preliminary battery> An activation step is performed on the obtained preliminary battery. On the other hand, in this specification, the term "activation" means a process of supplying a predetermined amount of electricity to an electrode assembly or a battery cell that does not have electrical characteristics to cause the anode and the cathode to have electrical characteristics. By the activation step, reactions such as the formation of the SEI film, partial charging of the battery capacity, and lithiation of the cathode when using a carbon-based anode active material may occur.

[0049] On the other hand, in the present invention, the preliminary battery is in a state where charging and discharging have not been performed after impregnation with the electrolytic solution and before the activation step. More preferably, in the present invention, in the activation step, discharging is first applied to the preliminary battery among charging and discharging.

[0050] In the present invention, the activation step may be performed only by discharging the preliminary battery prepared in the step S10 once.

[0051] Alternatively, the activation step may repeat charging and discharging after the discharging step is first applied. At this time, it is desirable that the activation step is performed with less than 6 discharges.

[0052] In a more preferred embodiment of the present invention, the discharge is performed in the order of constant current (CC) discharge followed by constant voltage (CV) discharge. If the discharge is performed two or more times in the activation step, at least one discharge is performed in the order of constant current discharge followed by constant voltage discharge. In this case, it is preferable that the first discharge is performed in the order of constant current discharge followed by constant voltage discharge. Furthermore, in other embodiments, all discharges performed in the activation step may be performed in the order of constant current discharge followed by constant voltage discharge.

[0053] If constant voltage discharge is performed first, in lithium-sulfur batteries, not only will a momentary overcurrent occur, damaging the cells, but a considerable amount of unreacted active material will remain. Therefore, in this invention, it is desirable to perform constant current discharge followed by constant voltage discharge.

[0054] The constant current discharge is carried out until a preset discharge termination voltage is reached, and the discharge termination voltage can be set within the range of 1.3V to 1.8V.

[0055] In the S20 stage, the constant current discharge may be performed at a C rate set within the range of 0.05C to 2.00C, or 0.50C to 1.00C, until a preset discharge termination voltage is reached.

[0056] The constant voltage discharge may be performed until the charge termination current is reached at a preset discharge termination voltage. In one specific embodiment, the discharge may be terminated when the charge termination current reaches a point where the remaining current of the battery is 0 mAh.

[0057] In another embodiment, the constant voltage mode may be performed for approximately 20 minutes or more, approximately 1 hour or more, approximately 2 hours or more, or approximately 4 hours or more at a discharge termination voltage of 1.3V to 1.8V. On the other hand, the constant voltage discharge time should preferably not exceed 6 hours, within a range that does not cause over-discharge.

[0058] In this way, the battery activation process is initiated by discharge, and when the discharge is performed using a CC-CV method, the battery capacity is increased by activating even the inactive LiPS that remains after the phase change is not completely completed by overvoltage. Furthermore, since the activation process is simplified by this discharge method, the process time can be shortened compared to the conventional activation process performed in the order of charge-discharge. In addition, a similar level of lifespan characteristics can be ensured compared to batteries manufactured using conventional activation processes.

[0059] On the other hand, in one embodiment of the present invention, step S20 may be performed in an environment in which the spare battery is pressurized. It is desirable that the pressurization be performed at a pressure of atmospheric pressure or higher. The term "atmospheric pressure" means the pressure when no other pressurizing device or depressurizing equipment is applied. For example, it may mean about 1 atm, which is normal atmospheric pressure. The pressurization is applied in a manner that ensures safety, and specifically, it may be performed by fastening the impregnated electrode assembly between two pressurizing jigs or pressurizing plates and pressurizing the impregnated electrode assembly.

[0060] The aforementioned pressure range can be, for example, 1 atm to 15 atm, more specifically 4 atm to 10 atm, while applying pressure. Applying pressure within this range is desirable because it prevents volume expansion and deformation of the negative electrode, allowing lithium to be inserted into the negative electrode stably and uniformly. On the other hand, the activation process can be carried out at 15°C to 40°C, or 20°C to 30°C. In this range, lithium mobility is improved, preventing lithium from being locally inserted into the electrode and enabling uniform charging.

[0061] On the other hand, in the present invention, a charging process may be performed during the discharge process in S20. When the charging process is performed, the charging may be performed in the order of constant current charging followed by constant voltage charging.

[0062] The charging can be performed by charging the electrode assembly so that the remaining capacity SOC of the electrode assembly becomes 40% or more. Specifically, during charging, in terms of preventing excessive volume expansion of the negative electrode active material (for example, a silicon-based active material) and deformation of the negative electrode, and preventing the formation of overvoltage of the negative electrode due to overcharging and the phenomenon of lithium reduction and precipitation due to the potential drop of the negative electrode, the charging can be performed by charging the electrode assembly so that the remaining capacity of the electrode assembly becomes 60% - 90%, more preferably 70% - 85%.

[0063] <S30: Degassing> In one embodiment of the present invention, after performing the activation step, a degassing process for removing the gas remaining in the battery can be performed.

[0064] Gas can be generated as a by-product due to the formation of the SEI layer and the formation of irreversible capacity after the activation of the battery. Therefore, a step of removing the by-products is performed for the use of the activated secondary battery, and the secondary battery can be manufactured in a usable form by the gas removal step. As the step of removing the gas, the methods commonly used in the field of secondary batteries can be performed without limitation. For example, the step of removing the gas can be performed by opening a part of the case in which the electrode assembly is housed, removing the gas, and then sealing it.

[0065] <Electrode assembly> In one embodiment of the present invention, the electrode assembly may include a negative electrode, a positive electrode, and a separator interposed between the negative electrode and the positive electrode.

[0066] The electrode assembly is placed in a battery case together with an electrolyte, and the case is sealed. In one embodiment of the present invention, the battery case is made of a metal material and can be a rectangular case or a cylindrical case.

[0067] The electrode assembly may include a negative electrode, a positive electrode, and a separation membrane, and may have a laminated configuration with the separation membrane interposed between the negative electrode and the positive electrode. The method for manufacturing the electrode assembly is not particularly limited and can be carried out by known methods. Furthermore, the electrode assembly is not particularly limited as long as it includes a negative electrode, a positive electrode, and a separation membrane interposed between the negative electrode and the positive electrode, and may have, for example, a jelly roll type, a laminated type, or a laminated / folded type structure.

[0068] <Negative electrode> In one specific embodiment of the present invention, the negative electrode may include a current collector and a negative electrode active material layer formed on the surface of the current collector. According to one specific embodiment of the present invention, the negative electrode active material layer includes a negative electrode active material and may further include a binder and a conductive material as needed.

[0069] In one embodiment of the present invention, the negative electrode active material is lithium metal; Li x Fe2O3 (0 ≤ x ≤ 1), Li x WO2(0≦x≦1), Sn x Me 1-x Me' y O z(Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen; 0 < x ≤ 1; 1 ≤ y ≤ 3; 1 ≤ z ≤ 8), etc. metal composite oxides; lithium alloys in which lithium and a different metal are alloyed; silicon-based alloys; tin-based alloys; metal oxides such as SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4 and Bi2O5; conductive polymers such as polyacetylene; Li-Co-Ni-based materials; titanium oxides; lithium titanium oxides; it may contain one or a mixture of two or more selected from the group consisting of carbon-based materials. In the lithium alloy, the different metal may contain one or more selected from Al and Mg. In addition, the carbon-based material may be one or more selected from the group consisting of crystalline artificial graphite, crystalline natural graphite, amorphous hard carbon, low-crystalline soft carbon, carbon black, acetylene black, graphene and fibrous carbon. Desirably, in the present invention, the negative electrode active material may be lithium metal or a lithium alloy.

[0070] In one embodiment of the present invention, the negative electrode active material may be lithium metal or an alloy of lithium and a different metal. At this time, the negative electrode active material layer is prepared in the form of a thin film containing the metal and can be laminated with a current collector to form a negative electrode. The lamination may be performed by applying pressure, and the current collector and the thin film may be heated to a temperature of room temperature or higher during pressurization. Also, the lamination may be performed by applying a roll press method.

[0071] In one embodiment of the present invention, the negative electrode current collector may be a negative electrode current collector commonly used in the art. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used. The negative electrode current collector usually has a thickness of 3 to 500 μm, and, similar to the positive electrode current collector, it is possible to form fine irregularities on the surface of the current collector to strengthen the bonding force of the negative electrode active material. For example, it can be used in various forms such as films, sheets, foils, nets, porous materials, foams, and nonwoven fabrics. For example, when a metal thin film current collector is used, the thickness of the current collector may be 1 μm to 20 μm.

[0072] <Positive electrode> The lithium-ion secondary battery is a lithium-sulfur battery. The positive electrode according to the present invention includes a current collector and a positive electrode active material layer disposed on at least one side surface of the current collector.

[0073] The current collector can be any material used in the art, which is electrically conductive and used as a current collector. For example, the positive electrode current collector can be made of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc. The positive electrode current collector usually has a thickness of 3 μm to 500 μm, and it is also possible to create fine irregularities on the surface of the positive electrode current collector to increase the adhesion strength of the positive electrode active material. The positive electrode current collector can be used in a variety of forms, such as films, sheets, foils, nets, porous materials, foams, and nonwoven fabrics.

[0074] In one embodiment of the present invention, the positive electrode active material layer comprises a positive electrode active material, a conductive material, and a binder material. The positive electrode active material layer may contain the positive electrode active material in a proportion of 80 wt% to 97 wt%, the conductive material in a proportion of 2 wt% to 10 wt%, and the binder in a proportion of 2 wt% to 10 wt%, based on the total weight of the positive electrode active material, conductive material, and binder material.

[0075] In the present invention, the positive electrode active material contains a sulfur-carbon composite. Desirably, the positive electrode active material contains 80 wt% or more, desirably 90 wt% or more, of the sulfur-carbon composite based on 100 wt% of the positive electrode active material, and more desirably, the positive electrode active material may consist only of the sulfur-carbon composite. Also, it is desirable that the content of sulfur is 70 wt% or more based on 100 wt% of the sulfur-carbon composite.

[0076] In one embodiment of the present invention, the sulfur-carbon composite may be formed by simply mixing the sulfur and the carbon material to form a composite, or may be in the form of a coating or supported in a core-shell structure. The coating form of the core-shell structure is one in which either sulfur or the carbon material is coated with another substance. For example, the surface of the carbon material may be surrounded by sulfur, or vice versa. The carbon material has a porous structure having pores inside and on the surface of the main body, and in particular, it may be in a form in which sulfur is filled in the internal pores. The form of the sulfur-carbon composite can be any form as long as it satisfies the content ratio of the sulfur-based compound and the carbon material described below, and is not limited to the present invention. On the other hand, in the present invention, it is desirable that the content of sulfur is 70 wt% or more based on the total weight of the positive electrode active material.

[0077] Since sulfur alone has no electrical conductivity, it is used in combination with a carbon material.

[0078] In one embodiment of the present invention, the sulfur is inorganic sulfur (S8), Li2S n (n ≧ 1), 2,5-dimercapto-1,3,4-thiadiazole, 1,3,5-trithiocyanuric acid and other disulfide compounds, organic compounds, and carbon-sulfur polymers ((C2S x ) n , x = 2.5 to 50, n ≧ 2), and may be one or more selected from the group consisting of. Desirably, it may contain inorganic sulfur (S8).

[0079] The carbon material has a porous structure containing multiple non-uniform pores on its surface and inside, and acts as a support that provides a uniform and stably immobilizable framework for sulfur, compensating for the low electrical conductivity of sulfur and facilitating electrochemical reactions. In particular, in a sulfur-carbon composite, the carbon material that acts as a sulfur support has a large BET specific surface area and an appropriate particle size D 50 When it has a certain size, it can carry a high amount of sulfur while having a low irreversible capacity, which can increase the energy density and thus the utilization rate of sulfur during electrochemical reactions.

[0080] In one embodiment of the present invention, the BET specific surface area of ​​the carbon material is a minimum of 100 m². 2 It is 1 / g or more, and the maximum is 3,000m 2 It may be / g. Together with or independently of this, the carbon material has a primary particle size D 50 This can range from 1 μm to 50 μm.

[0081] BET specific surface area and particle size D of the carbon material 50 By satisfying the aforementioned range, sulfur can be uniformly dispersed on the internal and external surfaces of the carbon material, while reducing irreversible capacity and increasing the electrochemical reactivity of sulfur. Furthermore, the use of carbon material improves the electrochemical reactivity, stability, and electrical conductivity of the sulfur-carbon composite, thereby improving the capacity and lifespan characteristics of the lithium-sulfur battery, as well as ensuring optimal charge-discharge performance even when sulfur loss or volume change occurs during charging and discharging.

[0082] Particle size D of the primary particles 50 When the particle size exceeds 50 μm, the movement of lithium ions into the particle becomes difficult due to limitations on mass transfer, making it difficult to efficiently utilize the sulfur located at the carbon center. Primary particle size D 50 When the particle size is less than 1 μm, it is difficult to increase the solid content because a large amount of solvent is required during the electrode slurry preparation process. This results in insufficient pores between particles, leading to a decrease in output.

[0083] In the sulfur-carbon composite of the present invention, the carbon material used as the sulfur support can typically be produced by carbonizing precursors of various carbon materials.

[0084] On the other hand, in one embodiment of the present invention, the pores of the carbon material may have a diameter in the range of 0.5 nm to 200 nm with respect to the longest diameter. The carbon material is not particularly limited, as it can be spherical, rod-shaped, needle-shaped, plate-shaped, tubular, or bulk-shaped, and is suitable for use in lithium-sulfur batteries.

[0085] The carbon material may be any porous and conductive carbon-based material commonly used in the industry. For example, it may include graphite; graphene; carbon blacks such as Denka Black, Acetylene Black, Ketjen Black, Channel Black, Furnace Black, Lamp Black, and Thermal Black; carbon nanotubes (CNTs) such as single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs); carbon fibers such as graphite nanofibers (GNFs), carbon nanofibers (CNFs), and activated carbon fibers (ACFs); graphite such as natural graphite, artificial graphite, and expanded graphite; carbon nanoribbons; carbon nanobelts, carbon nanorods, and activated carbon.

[0086] In the sulfur-carbon composite according to the present invention, the sulfur is located on at least one surface, either inside or outside the pores of the carbon material, and may be present in a region of less than 100%, preferably 1% to 95%, and more preferably 60% to 90%, of the entire surface of the carbon material, both inside and outside. When the sulfur is present on the surface of the carbon material within this range, it can achieve the greatest effect in terms of electron transfer area and electrolyte wettability. Specifically, because the sulfur is thinly and uniformly impregnated into the surface of the carbon material within this range, the electron transfer contact area can be increased during the charge and discharge process. If the sulfur is located in a region of 100% of the entire surface of the carbon material, the carbon material is completely covered with sulfur, the wettability of the electrolyte is reduced, the contact with the conductive material contained in the electrode decreases, electrons are less likely to be transferred, and the sulfur cannot participate in the reaction.

[0087] <Manufacturing of sulfur-carbon composites> In one embodiment of the present invention, the sulfur-carbon composite is obtained by the following manufacturing method.

[0088] The method for producing the sulfur-carbon composite according to the present invention is not particularly limited and is commonly known in the art, and can be produced by a composite method comprising the steps of (S1) mixing a carbon material and sulfur, followed by (S2) compounding.

[0089] The mixing in step S1 is intended to increase the degree of mixing between the sulfur and the carbon material, and can be performed using a stirring device commonly used in this industry. In this case, the mixing time and speed can also be selectively adjusted according to the content and conditions of the raw materials.

[0090] The compounding method in step S2 is not particularly limited in the present invention, and methods commonly used in the industry may be used. For example, methods commonly used in the industry, such as dry compounding or wet compounding such as spray coating, may be used. For example, a method may be used in which the mixture of sulfur and carbon material obtained after mixing is heat-treated so that the molten sulfur is uniformly coated on the inside and outside surface of the carbon material. On the other hand, in one embodiment of the present invention, the mixture of sulfur and carbon material is ground by a method such as ball milling before the heat treatment. In one embodiment of the present invention, the heat treatment is carried out at a temperature of 120°C to 160°C for about 20 minutes to 24 hours, and a heating device such as an oven may be used.

[0091] The sulfur-carbon composite produced by the aforementioned manufacturing method has a high specific surface area, a high sulfur load capacity, and a structure that improves sulfur utilization. As a result, not only is the electrochemical reactivity of sulfur improved, but the accessibility and contactability of the electrolyte are also improved, thereby improving the capacity and lifespan characteristics of lithium-sulfur batteries.

[0092] In one embodiment of the present invention, the positive electrode active material may consist solely of the sulfur-carbon composite. In addition to the sulfur-carbon composite, it may further contain one or more additives selected from transition metal elements, group IIIA elements, group IVA elements, sulfur compounds of these elements, and alloys of these elements with sulfur.

[0093] In one specific embodiment of the present invention, the positive electrode active material layer may contain a lithium transition metal composite oxide represented by the following chemical formula 1.

[0094] [Chemical formula 1] Li a Ni b Co c M 1 d M 2 e O2 In the above chemical formula 1, M 1This is Mn, Al, or a combination thereof, and preferably Mn or Mn and Al.

[0095] Said M 2 This is one or more selected from the group consisting of Zr, W, Y, Ba, Ca, Ti, Mg, Ta, and Nb, preferably one or more selected from the group consisting of Zr, Y, Mg, and Ti, and more preferably Zr, Y, or a combination thereof. 2 While elements are not essential, when present in appropriate amounts, they can play a role in promoting particle growth during firing or improving the stability of the crystal structure.

[0096] conductive material The conductive material is used to impart conductivity to the negative electrode and can be used without particular limitations as long as it is conductive in the battery without inducing chemical changes. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, and carbon nanotubes; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. One of these may be used alone or in mixtures of two or more. The conductive material is usually included in an amount of 1 wt% to 30 wt%, preferably 1 wt% to 20 wt%, and more preferably 1 wt% to 10 wt%, relative to the total weight of the negative electrode active material layer.

[0097] Binder material The binder material plays a role in improving the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the positive electrode current collector. Specific examples include polyvinyllidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one or more of these may be used individually or in mixtures of two or more.

[0098] separation membrane The separation membrane is positioned within the electrode assembly, interposed between the negative electrode and the positive electrode. The separation membrane can be used without particular limitations, as long as it is a type of separator commonly used in lithium secondary batteries, separating the negative electrode and the positive electrode and providing a passage for lithium ions to move. Specifically, the separation membrane can be a porous polymer film, for example, a porous polymer film made from polyolefin polymers such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof. Alternatively, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber or polyethylene terephthalate fiber, can be used. Furthermore, to ensure heat resistance or mechanical strength, a separation membrane coated with a coating layer containing ceramic components or polymeric substances can be used.

[0099] battery Another aspect of the present invention relates to a secondary battery including the electrode assembly. The secondary battery has the electrode assembly and electrolyte housed together in a battery case, and the battery case can be any suitable one that is commonly used in the art, such as a pouch type or a metal can type, without any particular limitations. The shape of the battery is not particularly limited and can be a variety of shapes such as cylindrical, stacked, or coin-shaped.

[0100] electrolyte In the present invention, the electrolyte may include an organic solvent and a lithium salt.

[0101] Organic solvents The organic solvent serves as a medium that allows ions involved in the electrochemical reaction of the battery to move. The organic solvent can be any organic solvent commonly used in lithium secondary battery electrolytes, without limitation. For example, ethers, esters, amides, linear carbonates, and cyclic carbonates can be used individually or in combination of two or more. Among these, ether compounds are typically used.

[0102] The aforementioned ether compounds may include acyclic ethers or cyclic ethers.

[0103] For example, the acyclic ether may be one or more selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether, ethyl propyl ether, dimethoxyethane, diethoxyethane, ethylene glycol ethyl methyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol methyl ethyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol methyl ethyl ether, polyethylene glycol dimethyl ether, polyethylene glycol diethyl ether, and polyethylene glycol methyl ethyl ether.

[0104] For example, the cyclic ethers include 1,3-dioxolane, 4,5-dimethyl-dioxolane, 4,5-diethyl-dioxolane, 4-methyl-1,3-dioxolane, 4-ethyl-1,3-dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, 2,5-dimethoxytetrahydrofuran, 2-ethoxytetrahydrofuran, 2-methyl-1,3-dioxolane, 2-vinyl-1,3-dioxolane, 2,2-dimethyl-1,3-dioxolane, 2-methoxy-1,3-dioxolane, 2-ethyl-2-methyl-1,3-dioxolane, tetrahydropyran, 1,4-dioxane, 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, 1,4-dimethoxybenzene, and isosorbide dimethyl ether. It may be one or more selected from the group consisting of ether), furan, 2-methylfuran, 3-methylfuran, 2-ethylfuran, 2-butylfuran, 2,3-dimethylfuran, 2,4-dimethylfuran, 2,5-dimethylfuran, pyran, 2-methylpyran, 3-methylpyran, 4-methylpyran, benzofuran, 2-(2-nitrovinyl)furan, thiophene, 2-methylthiophene, 2-ethylthiophene, 2-propylthiophene, 2-butylthiophene, 2,3-dimethylthiophene, 2,4-dimethylthiophene, and 2,5-dimethylthiophene, but is not limited to these.

[0105] Examples of esters of the aforementioned organic solvent include, but are not limited to, any one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone, and mixtures of two or more of these.

[0106] Specific examples of the aforementioned chain-like carbonate compounds include, but are not limited to, any one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methyl propyl carbonate, and ethyl propyl carbonate, or mixtures of two or more of these.

[0107] Furthermore, specific examples of the cyclic carbonate compounds mentioned above may include ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, vinylene carbonate, vinylethylene carbonate, and halides thereof, or mixtures of two or more of these. Examples of such halides include, but are not limited to, fluoroethylene carbonate (FEC).

[0108] Lithium salt The lithium salts mentioned above are compounds capable of providing lithium ions in an electrolyte. Examples of such lithium salts include LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3CO2, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiCH3SO3, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiC4BO8, LiCl, LiBr, and LiB 10 Cl 10 LiI or LiB(C2O4)2 may be used. In the present invention, it is desirable that the lithium salt includes Li-TFSI in order to enhance the potential for sulfur utilization and to realize high-capacity and high-voltage batteries. More preferably, the lithium salt may include LiN(CF3SO2)2(Li-TFSI) in an amount of 80 wt% or more, 90 wt% or more, or 100% based on 100 wt% of the total lithium salt.

[0109] The concentration of the lithium salt is in the range of 0.1 M to 2.0 M, preferably 0.5 M to 1 M, and more preferably 0.5 to 0.75 M. When the lithium salt concentration falls within this range, the electrolyte has appropriate conductivity and viscosity, exhibiting excellent electrolyte performance and allowing lithium ions to move effectively. If the lithium salt concentration is below this range, it becomes difficult to ensure ionic conductivity suitable for battery operation, and if it exceeds this range, the viscosity of the electrolyte increases, reducing the mobility of lithium ions, or the decomposition reaction of the lithium salt itself increases, potentially degrading the battery performance.

[0110] In one specific embodiment of the present invention, in an electrolyte comprising a first solvent, a second solvent, and a lithium salt, the molar ratio of the lithium salt to the second solvent and the first solvent may be 1:0.5 to 3:4.1 to 15. Furthermore, in one embodiment of the present invention, the molar ratio of the lithium salt to the second solvent and the first solvent may be 1:2:4 to 13, or 1:3:3 to 10, or 1:4:5 to 10. Thus, the electrolyte contained in the lithium-sulfur battery of the present invention may contain a first solvent containing a fluorine-based ether compound in a higher content ratio than the second solvent containing a glyme-based compound.

[0111] Other additives The electrolyte may further contain additives in addition to the components of the electrolyte, for the purpose of improving battery life characteristics, suppressing battery capacity reduction, and improving battery discharge capacity. For example, the additives may be nitrate compounds, nitrite compounds, haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexamethyl phosphate triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, either alone or in combination. The additives may be present in an amount of 0.1 wt% to 10 wt%, preferably 0.1 wt% to 5 wt%, relative to the total weight of the electrolyte.

[0112] In one specific embodiment of the present invention, the electrolyte may include a nitrate compound and / or a nitrite compound as an additive. Such nitrate / nitrite compounds form a stable film on the lithium metal electrode which is the negative electrode, thereby improving the charge-discharge efficiency. Such nitrate or nitrite compounds may include, but are not limited to, one or more selected from the group consisting of lithium nitrate (LiNO3), potassium nitrate (KNO3), cesium nitrate (CsNO3), barium nitrate (Ba(NO3)2), ammonium nitrate (NH4NO3), lithium nitrite (LiNO2), potassium nitrite (KNO2), cesium nitrite (CsNO2), and ammonium nitrite (NH4NO2); organic nitrate or nitrite compounds such as methyl nitrate, dialkylimidazolium nitrate, guanidine nitrate, imidazolium nitrate, pyridinium nitrate, ethyl nitrate, propyl nitrate, butyl nitrate, pentyl nitrate, and octyl nitrate; and organic nitro compounds such as nitromethane, nitropropane, nitrobutane, nitrobenzene, dinitrobenzene, nitropyridine, dinitropyridine, nitrotoluene, and dinitrotoluene, as well as combinations thereof. In one preferred embodiment of the present invention, the additive may include lithium nitrate.

[0113] The present invention will be described in detail below with reference to examples. However, the examples of the present invention can be modified in a variety of other forms, and the scope of the present invention is not limited to the examples described below. The examples of the present invention are provided to give a more complete explanation of the present invention to a person of average knowledge in the art.

[0114] <Examples> (Manufacturing of spare batteries) A sulfur-carbon composite was produced by uniformly mixing carbon nanotubes and sulfur and placing the mixture in an oven at 155°C for 30 minutes. The sulfur content in 100 wt% of the sulfur-carbon composite was 75 wt%. A slurry for producing a positive electrode was prepared by mixing 90 wt% of the produced sulfur-carbon composite, 5 wt% of Denka Black, and 5 wt% of a binder (styrene-butadiene rubber / carboxymethylcellulose, 7:3 by weight ratio). The solid content concentration in the slurry was 25 wt%. The slurry was applied to both sides of a 20 μm thick aluminum current collector, dried at 50°C for 12 hours, and pressed together using a roll press to produce a positive electrode. The load amount of positive electrode active material (relative to electrode area) was 2.5~2.7 mAh / cm². 2 The porosity was 70-83 vol%.

[0115] A 60 μm thick lithium thin film was prepared as the negative electrode.

[0116] As the electrolyte, a mixture was used in which 1,3-dioxolane and dimethyl ether (DOL:DME = 1:1 (volume ratio)) were dissolved in an organic solvent containing 1,3-dioxolane and dimethyl ether, along with 1 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and 1 wt% lithium nitrate (LiNO3).

[0117] A spare battery was manufactured by positioning the manufactured positive and negative electrodes facing each other, interposing a 16 μm thick, 68 vol% porous polyethylene film as a separation membrane between them, placing the film in a pouch, injecting the manufactured electrolyte, and sealing it. The battery was constructed by laminating and folding a total of seven positive electrodes and eight negative electrodes with the separation membrane in between.

[0118] Examples The spare batteries prepared as described above were placed in the jig and a pressure of approximately 7 atm was applied. Next, they were discharged in CC-CV mode using a PNE-0506 charger / discharger (manufacturer: PNE Solution). Constant current discharge was performed at a C rate of 0.5C, and the constant voltage mode was maintained for approximately 4 hours after reaching the discharge termination voltage of 1.8V until the discharge termination current reached 0mAh.

[0119] Comparative Example The prepared spare batteries were placed in the jig and a pressure of approximately 7 atm was applied. Next, the batteries were discharged using a PNE-0506 charger / discharger (manufacturer: PNE Solution) at 0.5C to 1.7V using a constant current method, and then charged at 0.3C to 2.5V using a constant current method, repeating this process six times.

[0120] Lifespan characteristic evaluation In each example and comparative example, the life characteristics of the batteries manufactured after the activation process were evaluated using a PNE-0506 charger / discharger (manufacturer: PNE solution). Each battery was charged to 2.5V at 0.3C using a constant current method, and discharged to 1.7V at 1C using a constant current method. The charge-discharge cycle was repeated until the discharge capacity reached 80% of the initial discharge capacity of 100%.

[0121] Figure 1 shows a comparison of the specific capacities of each battery under 1C discharge, and Figure 2 shows the Coulomb efficiency characteristics. According to these figures, the specific capacities of the example and the comparative example were similar under similar charge-discharge cycles, but the Coulomb efficiency of the example was found to be even superior.

[0122] Figure 3 shows the power density for each State of Charge (SOC) interval. The power density for each SOC interval was measured while decreasing the SOC by 10% increments from 95% to 15%. When each specific SOC of 95%, 85%, 75%, 65%, 55%, 45%, 35%, 25%, and 15% was reached, a 5C pulse current was applied in the discharge direction for 10 seconds, and the power density (kW / kg) was calculated by converting this to a voltage value. This can serve as an indicator of the degree of overvoltage when a pulse current is applied to each battery. After a 1-minute pause, the battery was charged at 0.1C until SOC 100%, then a charging current of 0.3C was applied for 10 seconds, and the measurement was repeated thereafter when the next specific SOC from the initial discharge criterion was reached. For lithium-sulfur batteries, the 75% SOC interval is the interval in which the lowest voltage is observed and the overvoltage is also the highest, making it a key interval in which battery performance can be confirmed. As shown in Figure 3, the power density of the example and the comparative example are at the same level at the point where the SOC is 75%, and they are at almost the same level in other sections as well. From this, it can be seen that the battery manufacturing method of the present invention secures a power density at the same level as the conventional technology, while reducing the number of charge-discharge cycles during the activation process compared to the conventional technology, shortening the time required for the battery manufacturing process, and thus exhibiting excellent process efficiency.

Claims

1. (S10) A step of manufacturing a spare battery including an electrode assembly and an electrolyte, (S20) An activation step in which the spare battery is activated, Includes, The electrode assembly includes a positive electrode, a negative electrode, and a separation membrane interposed between the positive electrode and the negative electrode, wherein the positive electrode includes a positive electrode active material containing sulfur. In step S10, the electrode assembly is impregnated with the electrolyte. The method for manufacturing a lithium-sulfur battery, wherein step S20 includes a step of discharging the spare battery, and the discharge is performed in the order of constant current discharge followed by constant voltage discharge.

2. The method for manufacturing a lithium-sulfur battery according to claim 1, wherein in step S20, the constant current discharge is performed until a preset discharge termination voltage is reached, and the discharge termination voltage is set in the range of 1.3V to 1.8V.

3. The method for manufacturing a lithium-sulfur battery according to claim 2, wherein in step S20, the constant current discharge is performed at a C rate set in the range of 0.05 to 2 until a preset discharge termination voltage is reached.

4. The method for manufacturing a lithium-sulfur battery according to claim 2, wherein the constant voltage discharge is performed until the battery's remaining current reaches 0 mAh at a preset discharge termination voltage.

5. A method for manufacturing a lithium-sulfur battery according to any one of claims 1 to 4, wherein the spare battery is not charged or discharged before step S20 is performed, and in step S20, discharge is applied first to the spare battery among the charging and discharging.

6. The method for manufacturing a lithium-sulfur battery according to claim 2, wherein the spare battery is not charged or discharged before step S20 is performed, and step S20 consists only of a step of discharging the spare battery once.

7. The method for manufacturing a lithium-sulfur battery according to claim 1, wherein in step S20, the discharge is performed in fewer than six cycles.

8. The method for manufacturing a lithium-sulfur battery according to claim 1, wherein in step S20, the constant current discharge is performed at a C rate in the range of 0.05 to 2.

00.

9. The method for manufacturing a lithium-sulfur battery according to claim 1, wherein in step S20, the discharge is performed in a constant current manner until a preset discharge termination voltage is reached.

10. The method for manufacturing a lithium-sulfur battery according to claim 1, wherein in step S20, the discharge is performed at a C rate in the range of 0.50 to 1.

00.

11. The method for manufacturing a lithium-sulfur battery according to claim 1, wherein step S20 is performed in an environment in which the spare battery is pressurized.

12. The method for manufacturing a lithium-sulfur battery according to claim 11, wherein the pressurization is performed by applying a pressure equal to or greater than atmospheric pressure.

13. The method for manufacturing a lithium-sulfur battery according to claim 1, wherein step S20 is performed at a temperature of 15°C to 40°C.

14. A method for manufacturing a lithium-sulfur battery according to claim 1, wherein an aging step is further performed after step S10 and before step S20, in which the reserve battery is maintained in an atmosphere of 15°C to 40°C.

15. A method for manufacturing a lithium-sulfur battery according to claim 1, wherein a charging step is performed during the discharge step in step S20, and the charging step is performed in the order of constant current charging followed by constant voltage charging.

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