Preparation method for lithium-sulfur battery

Abstract

The present invention relates to a preparation method for a lithium-sulfur battery, and particularly, to a method for activating a lithium-sulfur battery through initial discharge. The present invention is characterized by activating a lithium-sulfur battery through constant voltage (CV) discharge before the initial charging of the lithium-sulfur battery. A preparation method for a lithium-sulfur battery according to one embodiment of the present invention can exhibit the effect of significantly reducing initial discharge time during a battery activation process.

Description

Method for manufacturing lithium-sulfur batteries

[0001] The present invention relates to a method for manufacturing a lithium-sulfur battery, and more particularly, to a first discharge method in an activation process of a lithium-sulfur battery.

[0002] This application claims priority to Korean Patent Application No. 2023-0119903, filed with the Korean Intellectual Property Office on September 8, 2023, the entire disclosure of which is incorporated herein by reference.

[0003] Interest in energy storage technology has been growing steadily. As its applications expand to include energy for mobile phones, camcorders, laptops, and even electric vehicles, research and development efforts on electrochemical devices such as secondary batteries are becoming increasingly concrete. Electrochemical devices are receiving the most attention in this regard, and the development of rechargeable secondary batteries is a particular focus. Recent research and development efforts in these batteries are focused on novel electrode and battery designs to improve capacity density and specific energy.

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

[0005] In a lithium-sulfur battery, sulfur is the starting material for the reaction during discharge, and the ring-structured S8 is the starting material. As the discharge progresses, it goes through a linear structure of continuous reduction reactions, lithium polysulfide (LiPS: Li2Sx, 8≥x≥1), and moves from the anode to the cathode in a dissolved state in the electrolyte, and is sequentially reduced to the monomeric polysulfide with a lower energy level. The negatively charged polysulfide dissolves in a liquid organic solvent and moves to the cathode according to the chemical potential and the concentration gradient between the anode and cathode. Ultimately, the insoluble substance Li2S (S8 + 16Li → 8Li2S) in a reduced state is generated. When charging, the “shuttle” mechanism occurs as the oxidation reaction goes through the reverse order of the above to return to the original substance S8.

[0006] In lithium-sulfur batteries with these mechanism characteristics, the activation process before the life cycle is a key process that can suppress additional resistance variables during the life evaluation operation by sufficiently distributing LiPS in the electrolyte around the anode. During this process, lithium polysulfide (LiPS) shuttling affects the overall performance of the cell and can have a serious impact on the anode degradation in particular. During the discharge process, sulfur is reduced to lithium polysulfides, and this intermediate product dissolves in the electrolyte and diffuses, causing problems. Lithium polysulfides cause capacity reduction due to the shuttle effect on the surface of the lithium metal anode, and some of them are reduced to lithium sulfide (Li2S2, Li2S), which is an insulator, causing active material loss and hindering the movement of lithium ions, thereby lowering the rate characteristics.

[0007] These side reactions lead to a decrease in Coulombic efficiency and cathode instability, degrading overall battery performance. Therefore, it is necessary to establish a new activation process for lithium-sulfur batteries and apply it to battery manufacturing.

[0008] In particular, the activation process of conventional lithium-sulfur batteries has been problematic in that the process time is too long when discharging at a low rate (C-rate) to effectively convert S8+ 16Li → 8Li2S during the initial discharge. Therefore, for the mass production of lithium-sulfur batteries, it is necessary to establish a novel activation process that can drastically shorten the initial activation process time.

[0009] Accordingly, the problem to be solved by the present invention is to provide a method for manufacturing a lithium-sulfur battery to solve the above-described problem, and in particular, a method for manufacturing a lithium-sulfur battery including a novel battery activation process.

[0010] Through this, the present invention aims to provide a method for manufacturing a lithium-sulfur battery that dramatically shortens the process time while maintaining excellent battery performance.

[0011] To solve the above problem,

[0012] According to one aspect of the present invention, a method for manufacturing a lithium-sulfur battery according to the following embodiments is provided.

[0013] A method for manufacturing a lithium-sulfur battery according to the first embodiment is as follows:

[0014] (S10) A process for manufacturing a spare battery including an electrode assembly and an electrolyte; and

[0015] (S20) An activation process for activating the above-mentioned reserve battery;

[0016] The electrode assembly includes a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, wherein the positive electrode includes a positive electrode active material including sulfur (S),

[0017] The above (S20) process includes the following steps.

[0018] (S21) Constant voltage (CV) discharging step, and

[0019] (S22) Aging step in discharge state

[0020] According to the second embodiment, in the first embodiment,

[0021] The above step (S21) may be performed before the first charging of the reserve battery.

[0022] According to the third embodiment, in the first embodiment or the second embodiment,

[0023] The above (S21) constant voltage discharge may be performed at a voltage selected from 1.0 V to 2.0 V.

[0024] According to the fourth embodiment, in any one of the first to third embodiments,

[0025] The above (S21) constant voltage discharge may be performed at a voltage selected from 1.7 V to 1.9 V.

[0026] According to the fifth embodiment, in any one of the first to fourth embodiments,

[0027] The above (S21) constant voltage discharge may be terminated at a C-rate of 0.001C to 0.1C.

[0028] According to the sixth embodiment, in any one of the first to fifth embodiments,

[0029] The above (S21) constant voltage discharge may be terminated at 0.010C to 0.10C based on the C-rate.

[0030] According to the seventh embodiment, in any one of the first to sixth embodiments,

[0031] The above (S21) constant voltage discharge may be performed in the range of 0.1C to 0.5C based on the C-rate.

[0032] According to the eighth embodiment, in any one of the first to seventh embodiments,

[0033] The above (S22) aging step may be performed in an atmosphere of 20°C to 30°C.

[0034] According to the ninth embodiment, in any one of the first to eighth embodiments,

[0035] After the above (S22) aging step, a (S23) constant current (CC) charging step may be included.

[0036] According to the tenth embodiment, in any one of the first to ninth embodiments,

[0037] The above (S20) activation process may be performed in an environment where the reserve battery is pressurized.

[0038] According to the eleventh embodiment, in any one of the first to tenth embodiments,

[0039] The above pressurization may be applied at a pressure higher than normal pressure.

[0040]

[0041] According to another aspect of the present invention, lithium-sulfur batteries of the following embodiments are provided.

[0042] A lithium-sulfur battery according to the 12th embodiment,

[0043] A lithium-sulfur battery comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode comprises a positive electrode active material containing elemental sulfur (S).

[0044] The above lithium-sulfur battery is manufactured through an activation process, and when charging and discharging are repeated 10 times between 1.7 V and 2.5 V, the content of lithium polysulfide eluted into the electrolyte after 10 discharges is comprised between 170 parts by weight and 500 parts by weight based on 100 parts by weight of the content of lithium polysulfide eluted into the electrolyte after 1 discharge.

[0045] According to the 13th embodiment, in the 12th embodiment,

[0046] Based on 100 parts by weight of lithium polysulfide dissolved into the electrolyte after the first discharge, the content of lithium polysulfide dissolved into the electrolyte after the 10th discharge may be comprised between 180 parts by weight and 400 parts by weight.

[0047] According to the 14th embodiment, in the 12th embodiment or the 13th embodiment,

[0048] The content of lithium polysulfide eluted into the electrolyte after the above 10 discharges may be 20 parts by weight or less based on 100 parts by weight of elemental sulfur (S) in the positive electrode active material before the above 1 discharge.

[0049] According to the 15th embodiment, in any one of the 12th to 14th embodiments,

[0050] The content of lithium polysulfide eluted into the electrolyte after the first discharge may be 10 parts by weight or less based on 100 parts by weight of elemental sulfur (S) in the positive electrode active material before the first discharge.

[0051] According to the 16th embodiment, in any one of the 12th to 15th embodiments,

[0052] The above lithium-sulfur battery may be manufactured according to any one of the first to eleventh embodiments.

[0053] A method for manufacturing a lithium-sulfur battery according to one embodiment of the present invention can exhibit the effect of drastically shortening the initial discharge time during the activation process of the battery.

[0054] Furthermore, it can exhibit the effect of maintaining excellent battery life characteristics by suppressing initial battery degradation while drastically shortening the time required for manufacturing the battery.

[0055] Figure 1 shows a comparison of the capacity retention characteristics according to repeated charge and discharge of batteries according to Comparative Examples 1 and 2 and Examples 1 and 2.

[0056] Figure 2 shows the energy density characteristics according to repeated charge and discharge of the batteries according to Comparative Examples 1 and 2 and Examples 1 and 2.

[0057] Figure 3 shows the Coulomb efficiency characteristics according to repeated charge and discharge of the batteries according to Comparative Examples 1 and 2 and Examples 1 and 2.

[0058] Hereinafter, the present invention will be described in detail.

[0059] The term "(poly)sulfide" as used herein means "(poly)sulfide ion (S x 2- , 1≤x - ≤8)" and "lithium (poly)sulfide (Li2S) x or Li2S x - It is a concept that includes all of "1≤x ≤8".

[0060] The term "polysulfide" as used herein means "polysulfide ion (S x 2- , 1 <x - ≤8)" and "lithium polysulfide (Li2S) x or Li2S x - 1 <x ≤8)"를 모두 포함하는 개념이다.

[0061]

[0062] Method for manufacturing lithium-sulfur batteries

[0063] According to one aspect of the present invention, a method for manufacturing a lithium-sulfur battery is provided.

[0064] The present invention relates to a method for manufacturing a secondary battery, and more specifically, to a method for manufacturing a lithium-sulfur battery.

[0065] A method for manufacturing a lithium-sulfur battery according to one aspect of the present invention comprises: (S10) a process for manufacturing a spare battery including an electrode assembly and an electrolyte; and (S20) a process for activating the spare battery.

[0066] In one embodiment of the present invention, the method for manufacturing the lithium-sulfur battery may further include a degassing process for removing gas generated in the activation process.

[0067] In the present invention, the electrode assembly includes a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, and the positive electrode includes a positive electrode active material including sulfur (S).

[0068] In one embodiment of the present invention, the electrode assembly is prepared by being impregnated with the electrolyte before performing the (S20) activation process.

[0069] In addition, since the 'lithium-sulfur battery' to be manufactured in the present invention is manufactured as a spare battery in a fully charged state through the above (S10) process, the (S20) activation process is characterized in that it includes a discharge step before the first charge in order to activate the battery.

[0070] According to one aspect of the present invention, the above (S20) activation process is characterized in that the first discharge is performed under constant voltage (CV) conditions.

[0071] The activation process of a typical lithium-sulfur battery involves repeated charging and discharging to initiate a chemical reaction between the active material, sulfur, and lithium, and in particular, the initial discharge is performed under constant current (CC) conditions. However, according to one aspect of the present invention, the activation process can exhibit the effect of drastically reducing the number of charge and discharge repetitions by performing constant voltage (CV) discharge. Accordingly, it can exhibit the advantage of drastically shortening the time required for activating a lithium-sulfur battery compared to the conventional activation process. This can exhibit the advantage of enabling the mass production of lithium-sulfur batteries.

[0072] Furthermore, it shows the advantage of maintaining sufficiently superior effects in capacity, columbic efficiency, and lifespan characteristics compared to conventional lithium-sulfur batteries activated through the first CC discharge.

[0073]

[0074] Next, the method for manufacturing a lithium-sulfur battery according to the present invention will be described in detail for each process.

[0075] <S10 예비 전지의 제조>

[0076] First, a spare battery including an electrode assembly and an electrolyte is manufactured (S10).

[0077] In this specification, the reserve battery refers to a battery whose formation process has not yet been completed. In the present invention, the formation process may refer to a battery shipment preparation process that includes an activation and degassing process after the electrolyte is injected.

[0078] The above electrode assembly includes a cathode, an anode, and a separator disposed between the cathode and the anode. Details of the cathode, the anode, and the separator will be described later.

[0079] In the above process (S10), after a spare battery including an electrode assembly and an electrolyte is manufactured, a step (S11) of impregnating the electrode assembly with an electrolyte (e.g., an electrolyte solution) is included before the above process (S20). By impregnating the electrode assembly with the electrolyte, the electrode assembly can be activated by a process described below. The electrolyte can include an organic solvent and a lithium salt. Details regarding the organic solvent and the lithium salt will be described below.

[0080] The 'impregnation' of the above (S11) step is to sufficiently wet the electrode assembly with the electrolyte (e.g., electrolyte solution) so that activation of the electrode assembly can be performed more smoothly according to charging and discharging. The impregnation of the electrolyte can be performed, for example, by housing the electrode assembly in a battery case, pouring the electrolyte into the battery case, and then maintaining it at a predetermined temperature for a predetermined period of time. For example, after pouring the electrolyte, the case can be maintained for 12 to 100 hours, more preferably 24 to 75 hours, so that the electrolyte can permeate the interior of the electrode assembly.

[0081] In one embodiment of the present invention, the impregnation of the electrode assembly can be performed at 15°C to 30°C, more specifically, at 20°C to 27°C, which is preferable in that the impregnation property of the electrode assembly can be improved and a change in the components of the electrolyte composition can be prevented when the temperature is within the above range.

[0082] In one embodiment of the present invention, the electrode assembly can be manufactured by a conventional method known in the art, and the shape of the electrode assembly is not particularly limited, and may be, for example, a wound type, a stack type, or a stack / folding type.

[0083] In one embodiment of the present invention, the coiled electrode assembly can be manufactured by coating an electrode active material or the like on a current collector, drying and pressing, cutting it into a band shape of a desired width and length, using a separator to separate the negative electrode and the positive electrode, and then winding it into a spiral shape.

[0084] In one embodiment of the present invention, the stacked electrode assembly can be manufactured by sequentially stacking a plurality of positive and negative electrode unit cells. The stacked electrode assembly can exhibit the advantage of being easy to obtain a square shape.

[0085] In one embodiment of the present invention, the stack / folding type electrode assembly is an advanced structure electrode assembly that is a hybrid form of the winding type and the stack type, and is an electrode assembly having a structure in which a full cell or bi-cell of a certain unit size is folded using a long, continuous separation film. An electrode assembly having this structure is a hybrid structure of the existing folding type and the stack type and is called a so-called 'stack / folding type electrode assembly'.

[0086] In one embodiment of the present invention, the 'full cell' is a unit cell composed of a unit structure of an anode / separator / cathode, and is a cell in which an anode and a cathode are positioned on each side of the cell. Such full cells include the most basic structure of an anode / separator / cathode cell and an anode / separator / cathode / separator / anode / separator / cathode cell. In order to construct an electrochemical cell using such a full cell, a plurality of full cells must be stacked so that the anode and the cathode face each other with a separator film interposed therebetween.

[0087] In one embodiment of the present invention, the 'bicell' is a unit cell in which the same electrodes are positioned on both sides of the cell, such as a unit structure of anode / separator / cathode / separator / anode and a unit structure of cathode / separator / anode / separator / cathode. In order to construct an electrochemical cell using such a bicell, a plurality of bicells must be stacked so that a bicell having a cathode / separator / cathode / separator / anode structure (anode bicell) and a bicell having a cathode / separator / anode / separator / cathode structure (cathode bicell) face each other with a separation film interposed therebetween. In some cases, a greater number of bicells may be stacked.

[0088] In one embodiment of the present invention, a degassing process for removing gas generated inside the battery (S12) may be performed before performing the activation process (S20) after the electrolyte impregnation step (S11).

[0089]

[0090] <S20 예비 전지의 활성화>

[0091] An activation process is performed on the reserve battery obtained above.

[0092] Meanwhile, in the present specification, the term 'activation' refers to a process of supplying a predetermined amount of electricity to an electrode assembly or battery cell that does not have electrical properties so that the positive and negative electrodes have electrical properties.

[0093] In one embodiment of the present invention, reactions such as formation of a solid electrolyte interlayer (SEI), partial charging of battery capacity, and lithiation of the negative electrode when using a carbon-based negative electrode active material may occur through the activation process, but the purpose of the activation process is not limited thereto.

[0094] Meanwhile, in the present invention, the reserve battery is in a state where charging and discharging are not performed before the activation process after impregnation with the electrolyte. More preferably, in the present invention, the activation process (S20) is the first to apply discharge among charging and discharging to the reserve battery.

[0095] In the present invention, the activation process (S20) may be performed by discharging the spare battery prepared in the step (S10) only once. Alternatively, the activation process may be performed by repeating charging and discharging after the initial discharging process, and in this case, it may be preferable that the activation process be performed less than 6 times, for example, 5 times or less, 4 times or less, 3 times or less, 2 times or less, or once.

[0096] In the present invention, the above (S20) activation process includes the following steps.

[0097] (S21) Constant voltage (CV) discharging step, and

[0098] (S22) Aging step in discharge state.

[0099]

[0100] According to one aspect of the present invention, the (S20) activation process includes a step of aging in a discharge state (S22) after a constant voltage discharge (S21).

[0101] In one embodiment of the present invention, the (S20) activation process may include one or more discharging steps, wherein at least one of the steps is performed to include an aging step after constant voltage discharging.

[0102] In another embodiment of the present invention, when the above (S20) activation process includes two or more discharge steps, the discharge performed first is a constant voltage discharge, and an aging step is necessarily included in the discharge state after the first constant voltage discharge.

[0103] In one embodiment of the present invention, the (S20) activation process can exhibit the effect of shortening the time required for activating the battery through initial discharge through constant voltage discharge (S21).

[0104] In one embodiment of the present invention, the constant voltage discharge may be performed by discharging at a constant voltage until a preset discharge type current is reached. For example, the constant voltage discharge may be performed by discharging at a constant voltage so that the discharge is terminated when the residual current reaches 0 mAh.

[0105] In another embodiment of the present invention, the constant voltage discharge may be performed by discharging at a constant voltage until the C-rate reaches 0.001C to 0.1C. For example, the constant voltage discharge may be performed by discharging at a constant voltage until the C-rate reaches 0.010C to 0.10C, specifically 0.030C to 0.070C, 0.05C to 0.10C, or 0.040C to 0.060C, for example 0.050C. The current rate (C rate) generally refers to the charge / discharge current (A) for the rated capacity value (Ah) of the battery, that is, the amount of current that can be used in 1 hour. The unit of the rate is C, which is an abbreviation for capacity.

[0106] In one embodiment of the present invention, the (S21) constant voltage discharge step may be performed at a constant voltage selected from, for example, 1.0 V to 2.0 V. Specifically, the (S21) constant voltage discharge step may be performed at a constant voltage selected from 1.5 V to 2.0 V, 1.6 V to 1.9 V, 1.7 V to 1.9 V, 1.7 V to 1.8 V, and may be performed at a voltage of, for example, 1.8 V. If the constant voltage discharge is performed at a voltage lower than the above range, the lithium salt and / or additive in the electrolyte may be decomposed, which may cause a problem of accelerating the degradation of the battery, or if the constant voltage discharge is performed at a voltage higher than the above range, the capacity development of the battery may be insufficient due to insufficient discharge.

[0107] In one embodiment of the present invention, the (S21) constant voltage discharge step may be performed, for example, in a range of 0.1C to 1.0 C-rate. Specifically, the (S21) constant voltage discharge step may be performed at a rate of 0.1C to 0.5C, or 0.1C to 0.3C. For example, the (S21) constant voltage discharge step may be performed at a rate of 0.1C or 0.3C. If the constant voltage discharge is performed at a rate lower than the above-described rate, there may be a problem that the process time intended to be shortened through the constant voltage discharge is not efficiently shortened, and if it is performed at a rate higher than the rate, there may be a problem that the capacity of the battery is reduced or the degradation of the battery is accelerated due to unstable discharge.

[0108] Next, after the above (S21) constant voltage discharge is completed, a step (S22) is included in which the discharged reserve battery is placed in a discharge state. This is called aging.

[0109] In one embodiment of the present invention, the step of aging in the discharge state (S22) is to achieve stability of SEI generated by discharge, stabilization of generated lithium polysulfide, and stabilization of electrolyte.

[0110] In one embodiment of the present invention, the aging step (S22) may preferably be performed under a room temperature atmosphere under the voltage and current at which the constant voltage discharge (S21) is terminated.

[0111] In one embodiment of the present invention, the aging step (S22) may be performed under an atmosphere of, for example, 20°C to 30°C, and specifically, may be performed under a room temperature atmosphere of 23°C to 25°C, for example, 25°C.

[0112] In one embodiment of the present invention, the (S22) aging step may preferably be performed within a time period of, for example, 12 hours or more and 48 hours or less, specifically 20 hours or more and 36 hours or less, and more specifically 20 hours or more and 24 hours or less. When the (S22) aging step is performed within the above-described time range, it may exhibit advantageous effects in terms of stabilizing the battery and shortening the process time to be achieved through the aging step.

[0113] In this way, when the battery activation process is initiated by discharge and the discharge is performed using the CV-aging method, the battery activation process time can be shortened, and even the inactive LiPS that remains due to overvoltage and cannot fully undergo phase change can be activated, thereby increasing battery capacity. In addition, a similar level of life characteristics can be secured compared to batteries manufactured through an activation process that prioritizes constant current discharge.

[0114] In one embodiment of the present invention, the (S20) activation process can be performed in an environment where the reserve battery is pressurized.

[0115] In one embodiment of the present invention, the pressurization may preferably be applied at a pressure higher than atmospheric pressure. The term "atmospheric pressure" refers to pressure under conditions where no separate pressurization or depressurization equipment is applied. For example, it may refer to approximately 1 atm, which is a general atmospheric condition. The pressurization is applied in terms of performing a safety process, and specifically, may be performed by fastening the impregnated electrode assembly between two pressurization jigs or pressurization plates and pressurizing the impregnated electrode assembly, but the method is not limited thereto.

[0116] In one embodiment of the present invention, the pressure range may be, for example, 1 atm to 15 atm, more specifically, 4 atm to 10 atm, while pressurizing. When pressurizing in the above pressure range, it may be preferable to prevent volume expansion and deformation of the negative electrode, thereby allowing lithium to be stably and uniformly inserted into the negative electrode.

[0117] In one embodiment of the present invention, the (S21) constant voltage discharge and (S22) aging steps may each be performed at least once, and after the (S22) aging step, the (S23) constant current (CC) charging step may be further included.

[0118] In one embodiment of the present invention, the constant current charging may be performed by charging the electrode assembly so that the state of charge (SOC) of the battery becomes 40% or more. For example, in order to prevent degradation due to passivation of the negative electrode during charging and / or deformation of the negative electrode due to expansion of the negative electrode, and to prevent the phenomenon of reduction and precipitation of lithium due to formation of overvoltage of the negative electrode caused by excessive charging and the resulting decrease in potential of the negative electrode, the charging may be performed so that the electrode assembly has a state of charge of 60% to 90%, more preferably 70% to 85%. However, the charging is not limited to 100% of the state of charge of the electrode assembly.

[0119] In one embodiment of the present invention, the constant current charging can be performed until the voltage at the end point is reached through a constant current.

[0120] In one embodiment of the present invention, the constant current charging may be performed until a voltage of, for example, 2.4 V to 2.7 V, specifically, a voltage of 2.5 V to 2.6 V, and may be performed until, for example, 2.5 V is reached.

[0121] In one embodiment of the present invention, the constant current charging may be performed at a rate of, for example, 0.1 C to 0.5 C based on the C-rate, specifically, at a rate of 0.1 C to 0.3 C, or at a rate of 0.1 C to 0.2 C. More specifically, it may be performed at a rate of 0.1 C.

[0122]

[0123] <S30 탈기>

[0124] In one embodiment of the present invention, after performing the activation process (S20), a degassing process (S30) may be performed to remove gas remaining in the battery.

[0125] Gas may be generated as a byproduct due to the formation of an SEI layer after activation of the battery, the generation of irreversible capacity, etc. Accordingly, a process for removing the byproduct can be performed to use the activated secondary battery, and the secondary battery can be manufactured in a usable form through the gas removal process. The gas removal step can be performed without limitation by any method commonly used in the secondary battery field.

[0126] In one embodiment of the present invention, the step of removing the gas can be performed, for example, by partially opening the case in which the electrode assembly is housed, removing the gas, and sealing the case.

[0127]

[0128] Hereinafter, the configuration of the lithium-sulfur battery will be described in detail.

[0129] In one embodiment of the present invention, the lithium-sulfur battery may be manufactured by loading the electrode assembly together with an electrolyte into a battery case and sealing the case.

[0130] In one embodiment of the present invention, the case may be made of a metal material, and may vary depending on the shape of the battery, such as a cylindrical case, a stacked case, a coin-shaped case, or a square case, and is not particularly limited in the present invention.

[0131]

[0132] Electrode assembly

[0133] First, the electrode assembly includes a cathode, an anode, and a separator interposed between the cathode and the anode.

[0134]

[0135] Bipolar

[0136] The positive electrode according to the present invention is not particularly limited as long as it is a positive electrode usable in a lithium-sulfur battery. For example, the positive electrode may include a current collector and a positive electrode active material layer disposed on at least one surface of the current collector.

[0137] In one embodiment of the present invention, the positive electrode is used in a lithium-sulfur battery and includes a compound containing elemental sulfur (S) as an active material. In one embodiment of the present invention, the elemental sulfur may be derived from at least one selected from the group consisting of inorganic sulfur (S8), Li2Sn(n≥1), disulfide compounds such as 2,5-dimercapto-1,3,4-thiadiazole, 1,3,5-trithiocyanuic acid, organic sulfur compounds, and carbon-sulfur polymers ((C2Sx)n, x=2.5 to 50, n≥2). In one embodiment of the present invention, the positive electrode may include inorganic sulfur (S8) as a positive electrode active material.

[0138] In one embodiment of the present invention, since the sulfur alone does not have electrical conductivity, it can be used in a composite with a carbon material. Accordingly, the positive electrode may include a sulfur-carbon composite as the positive electrode active material. Specifically, the positive electrode active material may include 80 wt% or more, preferably 90 wt% or more, of the sulfur-carbon composite relative to 100 wt% of the positive electrode active material, and more preferably, the positive electrode active material may be composed solely of the sulfur-carbon composite. In addition, it may be preferable that the content of sulfur (S) is 70 wt% or more relative to 100 wt% of the sulfur-carbon composite, but the present invention is not limited thereto.

[0139] The term "composite" used in this specification refers to a material in which two or more materials are combined to form physically and chemically different phases and exhibit more effective functions.

[0140] In one embodiment of the present invention, the sulfur-carbon composite may be a composite in which the sulfur and the carbon material are simply mixed, or may have a core-shell structured coating form or a supported form. The core-shell structured coating form is one in which either sulfur or the carbon material is coated with another material, for example, the surface of the carbon material may be wrapped with sulfur, or vice versa. The carbon material may have a porous structure having pores on the inside and the surface of the body, and in particular, may be a form in which the internal pores are filled with sulfur. The form of the sulfur-carbon composite may be any form that satisfies the content ratio of the sulfur-based compound and the carbon material described below, and is not limited thereto in the present invention. Meanwhile, in the present invention, it is preferable that the sulfur content is contained at least 70 wt% with respect to the total weight of the positive electrode active material.

[0141] The above carbon material has a porous structure including a large number of irregular pores on the surface and inside, and acts as a carrier providing a framework in which sulfur can be uniformly and stably fixed, and complements the low electrical conductivity of sulfur to enable the electrochemical reaction to proceed smoothly. In particular, in the sulfur-carbon complex, the carbon material acting as a carrier for sulfur has a large BET specific surface area and an appropriate particle size (D 50 ) size, the sulfur loading is high, but the irreversible capacity is low, and the energy density is high, so the utilization rate of sulfur in the electrochemical reaction can be increased.

[0142] In the sulfur-carbon composite of the present invention, the carbon material used as a sulfur carrier can generally be manufactured by carbonizing a precursor of various carbon materials.

[0143] The above carbon material may be any porous and conductive carbonaceous material commonly used in the art. For example, the carbon material may include at least one selected from the group consisting of graphite; graphene; carbon black such as Denka black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer 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.

[0144] In the sulfur-carbon composite according to the present invention, the sulfur is located on at least one of the inner and outer surfaces of the pores of the carbon material, and at this time, it may be present in an area of ​​less than 100%, preferably 1 to 95%, and more preferably 60 to 90% of the entire inner and outer surfaces of the pores of the carbon material.

[0145] In one embodiment of the present invention, the positive electrode active material layer may further include a binder material in addition to the active material and the carbon material to bind them together and provide adhesion to the current collector.

[0146] In one embodiment of the present invention, the binder material serves to improve adhesion between positive electrode active material particles and adhesion between the positive electrode active material and the positive electrode current collector, and specific examples thereof include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene butadiene rubber (SBR), fluoroelastomer, polyacrylamide (PAA), or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof.

[0147]

[0148] <Cathode>

[0149] 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.

[0150] In one embodiment of the present invention, the negative active material is lithium metal; LixFe2O3(0≤x≤1), LixWO2(0≤x≤1), SnxMe1-xMe'yOz (Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, elements of group 1, group 2, and group 3 of the periodic table, halogen; 0 <x≤1; 1≤y≤3; 1≤z≤8) 등의 금속 복합 산화물; 리튬과 이종 금속이 합금화된 리튬 합금; 규소계 합금; 주석계 합금; SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, 및 Bi2O5등의 금속 산화물; 폴리아세틸렌 등의 도전성 고분자; Li-Co-Ni 계 재료; 티타늄 산화물; 리튬 티타늄 산화물; 탄소계 재료로 이루어진 군에서 선택된 1종 또는 이 중 2종 이상의 혼합물을 포함할 수 있다. 상기 리튬 합금에서 이종 금속은 Al, Si, Sn, Pb, Zn, Bi, In, Mg, Ga 및 Cd 중 선택된 1종 이상을 포함할 수 있다. 한편, 상기 탄소계 재료는 결정질 인조 흑연, 결정질 천연 흑연, 비정질 하드 카본, 저결정질 소프트카본, 카본 블랙, 아세틸렌 블랙, 그래핀 및 섬유상 탄소로 이루어진 군으로부터 선택되는 하나 이상일 수 있다. 바람직하게는 본 발명에 있어서, 상기 음극 활물질은 리튬 금속 또는 리튬 합금일 수 있다.

[0151] 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, and in this case, the negative electrode active material layer may be prepared in the form of a thin film including the metal and laminated with a current collector to form the negative electrode. The lamination may be performed by applying pressure, and the current collector and the thin film may be heated to a temperature higher than room temperature during the pressurization. In addition, the lamination may be performed by applying a roll press method.

[0152] The above conductive material is used to provide conductivity to the negative electrode, and in the battery to be formed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any special restrictions. 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, summer black, carbon fiber, and carbon nanotube; metal powder or metal fiber 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, and the like. One of these may be used alone or a mixture of two or more may be used.

[0153]

[0154] <Separator>

[0155] In one embodiment of the present invention, the separator may be positioned within the electrode assembly so as to be interposed between the positive and negative electrodes. The separator separates the negative and positive electrodes and provides a passage for lithium ions to move. Any separator typically used as a separator in lithium secondary batteries may be used without particular limitations.

[0156] In one embodiment of the present invention, the separator may be a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, or the like, may be used. In addition, a separator coated with a coating layer containing a ceramic component or a polymer material to secure heat resistance or mechanical strength may be used.

[0157] In one embodiment of the present invention, the separator may be a solid electrolyte membrane, but is not limited thereto.

[0158] In one embodiment of the present invention, the separator may be included in the form of a solid electrolyte membrane attached to the surface of at least one of the positive and negative electrodes, but the present invention is not limited thereto.

[0159]

[0160] Electrolyte

[0161] In one embodiment of the present invention, the electrolyte includes a lithium salt to supply lithium ions into the battery.

[0162] In one embodiment of the present invention, the electrolyte may further include a non-aqueous solvent together with a lithium salt, but the present invention is not limited thereto.

[0163] In one embodiment of the present invention, the non-aqueous solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move. The non-aqueous solvent may be any solvent commonly used in lithium-sulfur batteries without limitation, and examples thereof include ethers, esters, amides, chain carbonates, and cyclic carbonates, either singly or in combination of two or more. Among these, ether compounds may be representative.

[0164] The above ether compound may include an acyclic ether and a cyclic ether. For example, the acyclic ether may be at least one 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. For example, the cyclic ethers are 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, It may be at least one selected from the group consisting of 1,3-dimethoxy benzene, 1,4-dimethoxy benzene and isosorbid dimethyl ether, furan, 2-methyl furan, 3-methyl furan, 2-ethyl furan, 2-butyl furan, 2,3-dimethylfuran, 2,4-dimethylfuran, 2,5-dimethyl furan, pyran, 2-methylpyran, 3-methylpyran, 4-methylpyran, benzoburan, 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 thereto.

[0165]

[0166] lithium salt

[0167] The above lithium salt is a compound that can provide lithium ions in the electrolyte. Such lithium salts include LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3CO2, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiCH3SO3, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiC4BO8, LiCl, LiBr, LiB 10 Cl 10 , LiI or LiB(C2O4)2 can be used.

[0168] In the present invention, in order to increase the usability of sulfur and to realize a high-capacity and high-voltage battery, it is preferable that the lithium salt include Li-TFSI. More preferably, the lithium salt may include LiN(CF3SO2)2(Li-TFSI) in an amount of 80 wt% or more, or 90 wt% or more, or 100% based on 100 wt% of the total lithium salt, but the present invention is not limited thereto.

[0169] In one embodiment of the present invention, the concentration of the lithium salt may be, for example, in the range of 0.1 to 2.0 M, preferably 0.5 to 1 M, and more preferably 0.5 to 0.75 M. When the concentration of the lithium salt is within the above range, the electrolyte may exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions may move effectively, but the present invention is not limited thereto.

[0170]

[0171] Other additives

[0172] In addition to the electrolyte components, the electrolyte may further include additives for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery. For example, the additives may include nitric acid compounds, nitrous acid compounds, haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ethers, ethylene diamine, n-glyme, hexamethylphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, which may be used alone or in combination.

[0173] In a specific embodiment of the present invention, the electrolyte may include a nitric acid compound and / or a nitrite compound as an additive. The nitric acid compound / nitrite compound as described above has the effect of forming a stable film on the lithium metal electrode, which is the negative electrode, and improving the charge / discharge efficiency. Examples of such nitric acid or nitrite compounds include inorganic nitric acid or nitrite compounds such as 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 nitric acid or nitrous acid compounds such as methyl nitrate, dialkyl imidazolium nitrate, guanidine nitrate, imidazolium nitrate, pyridinium nitrate, ethyl nitrite, propyl nitrite, butyl nitrite, pentyl nitrite, and octyl nitrite; organic nitro compounds such as nitromethane, nitropane, nitrobutane, nitrobenzene, dinitrobenzene, nitro pyridine, dinitropyridine, nitrotoluene, and dinitrotoluene; and combinations thereof, but are not limited thereto. In a preferred embodiment of the present invention, the additive may include lithium nitrate.

[0174]

[0175] lithium-sulfur battery

[0176] According to another aspect of the present invention, a lithium-sulfur battery manufactured according to the method for manufacturing the lithium-sulfur battery is provided.

[0177] In particular, a lithium-sulfur battery activated by the above-described activation process is provided.

[0178] According to one aspect of the present invention, a lithium-sulfur battery manufactured by the above method comprises a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode comprises a positive electrode active material containing elemental sulfur (S), and the lithium-sulfur battery is manufactured through an activation process.

[0179] The lithium-sulfur battery is configured such that, when charging and discharging are repeated 10 times between 1.7 V and 2.5 V, the content of lithium polysulfide dissolved into the electrolyte after 10 discharges is between 170 parts by weight and 500 parts by weight, based on 100 parts by weight of the content of lithium polysulfide dissolved into the electrolyte after 1 discharge.

[0180] In one embodiment of the present invention, the lithium-sulfur battery may be configured such that the content of lithium polysulfide eluted into the electrolyte after 10 discharges is between 180 parts by weight and 400 parts by weight, based on 100 parts by weight of the content of lithium polysulfide eluted into the electrolyte after 1 discharge.

[0181] In one embodiment of the present invention, the lithium-sulfur battery may have a content of lithium polysulfide eluted into the electrolyte after 10 discharges of 170 to 500 parts by weight, 180 to 400 parts by weight, 200 to 380 parts by weight, 250 to 380 parts by weight, 300 to 380 parts by weight, or 350 to 370 parts by weight, based on 100 parts by weight of the content of lithium polysulfide eluted into the electrolyte after 10 discharges. When the amount of lithium polysulfide eluted after 1 discharge is within the above-described range compared to the amount of lithium polysulfide eluted after 10 discharges, it may be preferable in terms of implementing long-life characteristics of the lithium-sulfur battery, but the present invention is not limited thereto.

[0182] In general, lithium-sulfur batteries experience capacity degradation with repeated charge and discharge cycles due to the loss of positive electrode active materials by the shuttle effect. For example, with repeated charge and discharge cycles, the positive electrode active materials of lithium-sulfur batteries degrade into inorganic sulfur (S8) and lithium polysulfide (Li2Sx, 1 <x≤8) 간에 변환되고, 이때 상기 리튬폴리설파이드가 전해질로 용출된다.

[0183] According to one aspect of the present invention, an activated lithium-sulfur battery can achieve an effect of improving the life of the battery by reducing the content of lithium polysulfide eluted from the positive electrode into the electrolyte.

[0184] In this specification, the content of lithium polysulfide eluted into the electrolyte can be measured by a method of extracting lithium polysulfide from the electrolyte and then measuring it.

[0185] In one embodiment of the present invention, a lithium-sulfur battery is disassembled, an extraction solvent is added, the electrolyte is extracted, the battery is removed from the extract, and a methyl group-containing compound is added to extract lithium polysulfide (Li2Sx, 1) contained in the extract. <x≤8) 성분들의 메틸 유도체화를 수행하고, 메틸 유도체화된 성분들((CH3)2Sx, 1<x≤8)을 액체크로마토그래피(LC) / 자외선 분광계(UV)로 분석하여 분취하고, 기 결정된 검량선 및 상대적 감응인자(response factor)에 적용하여 전해질로 용출된 리튬폴리설파이드의 성분별 함량을 산출하는 단계를 포함하는 방법에 의해 상기 전해질로 용출된 리튬폴리설파이드의 함량이 분석될 수 있다. 여기서, 상기 기 결정된 검량선 및 상대적 감응인자는, 리튬폴리설파이드 성분들의 메틸 유도체화된 성분들의 일부 또는 전체에 대한 농도별 표준품을 제조한 후 액체크로마토그래피(LC) / 자외선 분광계(UV)로 분석하여 분취하여 검량선을 작성한 후, 검량선의 기울기를 이용하여 성분 별 상대적 감응인자를 결정하는 방법으로 준비된 것일 수 있다.

[0186] In one embodiment of the present invention, the content of lithium polysulfide eluted into the electrolyte may be measured according to the method disclosed in Korean Patent Publication No. 2023-0099320 (published on July 4, 2023), but is not limited thereto.

[0187] In one embodiment of the present invention, the content of lithium polysulfide eluted into the electrolyte after the 10 discharges may be, for example, 20 parts by weight or less based on 100 parts by weight of elemental sulfur (S) in the positive electrode active material before the 1 discharge. Specifically, it may be 0.1 to 20 parts by weight, 0.1 to 15 parts by weight, 1 to 15 parts by weight, 5 to 15 parts by weight, 10 to 15 parts by weight, or 11 to 13 parts by weight.

[0188] In one embodiment of the present invention, the content of lithium polysulfide eluted into the electrolyte after the single discharge may be, for example, 10 parts by weight or less based on 100 parts by weight of elemental sulfur (S) in the positive electrode active material before the single discharge. Specifically, the content may be 5 parts by weight or less. Specifically, the content may be 0.1 to 10 parts by weight, 0.1 to 5 parts by weight, 1 to 5 parts by weight, 5 to 10 parts by weight, or 3 to 7 parts by weight.

[0189] In the present specification, the content of elemental sulfur (S) in the positive electrode active material before the first discharge can be measured by a method of disassembling a charged battery to separate the positive electrode, obtaining a sulfur-carbon complex from the positive electrode, and then analyzing the components of the sulfur-carbon complex to measure the weight of elemental sulfur (S). For example, the method can be performed by removing the binder by means such as applying high temperature heat to the positive electrode or using a binder extract, obtaining a sulfur-carbon complex, and then measuring the weight of elemental sulfur (S) using a thermogravimetric analyzer (TGA).

[0190] In one embodiment of the present invention, the content of elemental sulfur (S) in the positive electrode active material before the first discharge may be measured by disassembling a charged battery to separate the positive electrode, performing elemental analyzer (EA), ion chromatography (IC), and inductively coupled plasma optical emission spectrometer (ICP-OES) analyses on the positive electrode sample, respectively, and synthesizing the contents of each component measured by each analysis to confirm the overall composition of the positive electrode sample and the content of by-products. Specifically, components containing C, S, N, H, and O may be confirmed through the EA analysis, components containing F may be confirmed through the IC analysis, and components containing Li and S may be confirmed through the ICP-OES analysis. At this time, the S and C components identified by the EA may be derived from the sulfur (S8) and carbon-based material used in the positive electrode, respectively, the N, H, and O components identified by the EA may be derived from by-products generated from the electrolyte during the charge and discharge process, and the F component identified by the IC may be derived from by-products generated from the lithium salt in the electrolyte during the charge and discharge process. In addition, the Li component identified by the ICP-OES may be derived from by-products generated from the negative electrode active material inserted from the negative electrode during the charge and discharge process or the lithium salt in the electrolyte, and the S component identified by the ICP-OES may be derived from by-products of Li2S or Li2S2 formed through stepwise reduction of the sulfur (S8) used in the positive electrode during charge and discharge.

[0191] In one embodiment of the present invention, the content of elemental sulfur (S) in the positive electrode active material before the first discharge may be measured according to the method disclosed in Korean Patent Publication No. 2023-0085616 (published on June 14, 2023), but is not limited thereto.

[0192]

[0193] Hereinafter, the present invention will be described in detail by way of examples to specifically explain the present invention.

[0194]

[0195] <(S10) Manufacturing of spare batteries>

[0196] Carbon nanotubes and sulfur were evenly mixed and placed in an oven at 155°C for 30 minutes to prepare a sulfur-carbon composite. The sulfur (S8) content was 75 wt% in 100 wt% of the sulfur-carbon composite (S8 / CNT weight ratio 75:25). A slurry for positive electrode production was prepared by mixing 90 wt% of the above-mentioned sulfur-carbon composite, 5 wt% of Denka Black, and 5 wt% of a binder (styrene butadiene rubber / carboxymethyl cellulose, 7:3 weight ratio). The solid content concentration in the slurry was 25 wt%.

[0197] The above slurry was applied to both sides of a 20 μm thick aluminum current collector, dried at 50°C for 12 hours, and pressed using a roll press to manufacture a positive electrode. The loading amount of the positive electrode active material (relative to the electrode area) was 2.6 mAh / cm 2 And the porosity was 75 vol%.

[0198] A lithium thin film with a thickness of 60 μm was prepared as the cathode.

[0199] As an electrolyte, a mixture of 1 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and 1 wt% lithium nitrate (LiNO3) was used in an organic solvent consisting of 1,3-dioxolane and dimethyl ether (DOL:DME = 1:1 (volume ratio)).

[0200] The above-mentioned manufactured positive and negative electrodes were positioned so as to face each other, and a polyethylene porous film having a thickness of 16 ㎛ and a porosity of 68 vol% was interposed as a separator between them. Then, the pouch was loaded, the above-mentioned manufactured electrolyte was injected, and the pouch was sealed to manufacture a spare battery. In the above-mentioned battery, a total of 7 positive electrodes and a total of 8 negative electrodes were configured in a stacked and folded form with the above-mentioned separator interposed therebetween.

[0201]

[0202] <(S20) Activation of the reserve battery>

[0203] Example 1

[0204] The spare battery prepared above was discharged in CV mode at 1.8 V, 0.1 C with a termination condition of 0.05 C. After discharge, it was aged at 25°C for 12 to 48 hours and then charged once in constant current (CC) mode at 2.5 V, 0.1 C.

[0205]

[0206] Example 2

[0207] The battery was activated in the same manner as in Example 1, except that the prepared spare battery was discharged at 1.8 V, 0.3 C constant voltage (CV) mode.

[0208]

[0209] Comparative Example 1

[0210] The reserve battery prepared above was discharged in CV mode at 1.8 V, 0.1 C with a termination condition of 0.05 C. After discharge, it was charged once in constant current (CC) mode at 2.5 V, 0.1 C without aging.

[0211]

[0212] Comparative Example 2

[0213] The spare battery prepared above was discharged to 1.8 V at 0.1 C using a constant current (CC) method, and then CC charging and discharging were performed three times at 0.1 C to 2.5 V.

[0214]

[0215] Life Characteristics Assessment

[0216] In each example and comparative example, the life characteristics of the manufactured batteries were evaluated after performing the activation process.

[0217] For each battery, constant current discharge was performed at 0.1C to 1.8 V, and charging and discharging were repeated until the capacity reached 80% of the 100% discharge capacity of the first cycle.

[0218] Figure 1 shows a comparison of the capacity retention rate according to the charge / discharge cycle of each battery, Figure 2 shows a comparison of the specific capacity according to the charge / discharge cycle of each battery, and Figure 3 shows the coulomb efficiency characteristics according to the charge / discharge cycle of each battery.

[0219] According to Figures 1 to 3, it was confirmed that when aging is performed after constant voltage (CV) discharge during the initial discharge in the activation process, it can exhibit superior effects in lifespan, energy density (specific capacity), and coulombic efficiency as compared to constant current (CC) discharge.

[0220] On the other hand, it was confirmed that the life characteristics deteriorated prematurely due to battery degradation when aging was not performed after the first CV discharge during the activation process.

[0221] Meanwhile, while 4800 min was required for initial discharge in the activation according to Comparative Example 2, 1900 min was required for initial discharge in the activation according to Example 1, and thus, it was confirmed that the activation process time of a lithium-sulfur battery can be drastically shortened according to the present invention, thereby effectively shortening the process time while maintaining excellent performance of the lithium-sulfur battery.

[0222]

[0223] Evaluation of lithium polysulfide release rate

[0224] For a battery manufactured after the activation process described above, the content of elemental sulfur (S) among the sulfur-carbon complexes introduced during the manufacturing process was 100 parts by weight, and when charge and discharge were performed 10 times between 1.7 V and 2.5 V, the content of lithium polysulfide eluted into the electrolyte after 1 discharge and after 10 discharges was measured, and the results are shown in Table 1 below.

[0225] Two identically manufactured batteries were prepared for each of the examples and comparative examples, and the content of lithium polysulfide dissolved into the electrolyte after each discharge was measured according to the method disclosed in Korean Patent Publication No. 2023-0099320 (published on July 4, 2023).

[0226] Content of lithium polysulfide eluted into the electrolyte after 1 discharge (A) Content of lithium polysulfide eluted into the electrolyte after 10 discharges (B) Calculated value of the ratio of B / A (B:A = X:100) Example 1 Content of elemental sulfur (S) in sulfur-carbon complex Based on 100 parts by weight 311X=366 Example 2713X=186 Comparative example 1711X=157 Comparative example 2411X=275

[0227] Through the above series of experiments, it was confirmed that performing an aging step when performing the first CV discharge of a lithium-sulfur battery is effective in suppressing the initial degradation of the battery.

Claims

1. (S10) A process for manufacturing a spare battery including an electrode assembly and an electrolyte; and (S20) An activation process for activating the above-mentioned reserve battery; The electrode assembly includes a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, wherein the positive electrode includes a positive electrode active material including sulfur (S), The above (S20) process is characterized by a method for manufacturing a lithium-sulfur battery including the following steps: (S21) Constant voltage (CV) discharging step, and (S22) Aging step in discharge state.

2. In claim 1, A method for manufacturing a lithium-sulfur battery, characterized in that the above step (S21) is performed before the first charging of the reserve battery.

3. In claim 1, A method for manufacturing a lithium-sulfur battery, characterized in that the above (S21) constant voltage discharge is performed at a voltage selected from 1.0 V to 2.0 V.

4. In claim 3, A method for manufacturing a lithium-sulfur battery, characterized in that the above (S21) constant voltage discharge is performed at a voltage selected from 1.7 V to 1.9 V.

5. In claim 1, A method for manufacturing a lithium-sulfur battery, characterized in that the above (S21) constant voltage discharge is terminated at 0.001C to 0.1C based on the C-rate.

6. In claim 5, A method for manufacturing a lithium-sulfur battery, characterized in that the above (S21) constant voltage discharge is terminated at 0.010C to 0.10C based on the C-rate.

7. In claim 1, A method for manufacturing a lithium-sulfur battery, characterized in that the above (S21) constant voltage discharge is performed in a range of 0.1C to 0.5C based on the C-rate.

8. In claim 1, A method for manufacturing a lithium-sulfur battery, characterized in that the above (S22) aging step is performed in an atmosphere of 20°C to 30°C.

9. In claim 1, After the above (S22) aging step, (S23) A method for manufacturing a lithium-sulfur battery, characterized by including a constant current (CC) charging step.

10. In claim 1, A method for manufacturing a lithium-sulfur battery, characterized in that the above (S20) activation process is performed in an environment where the reserve battery is pressurized.

11. In claim 10, A method for manufacturing a lithium-sulfur battery, characterized in that the above pressurization is applied at a pressure higher than atmospheric pressure.

12. Including a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, The above positive electrode is a lithium-sulfur battery including a positive electrode active material containing elemental sulfur (S), The above lithium-sulfur battery is manufactured through an activation process, A lithium-sulfur battery characterized in that, when charging and discharging are repeated 10 times between 1.7 V and 2.5 V, the content of lithium polysulfide dissolved into the electrolyte after 10 discharges is comprised between 170 parts by weight and 500 parts by weight based on 100 parts by weight of the content of lithium polysulfide dissolved into the electrolyte after 1 discharge.

13. In claim 12, A lithium-sulfur battery characterized in that the content of lithium polysulfide eluted into the electrolyte after 10 discharges is comprised between 180 parts by weight and 400 parts by weight, based on 100 parts by weight of the content of lithium polysulfide eluted into the electrolyte after the first discharge.

14. In claim 12, A lithium-sulfur battery, characterized in that the content of lithium polysulfide eluted into the electrolyte after the 10 discharges is 20 parts by weight or less based on 100 parts by weight of elemental sulfur (S) in the positive electrode active material before the 1 discharge.

15. In claim 12, A lithium-sulfur battery, characterized in that the content of lithium polysulfide eluted into the electrolyte after the first discharge is 10 parts by weight or less based on 100 parts by weight of elemental sulfur (S) in the positive electrode active material before the first discharge.

16. In claim 12, A lithium-sulfur battery characterized in that the lithium-sulfur battery is manufactured according to any one of claims 1 to 11.

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