Electrodes for lithium-sulfur batteries and high-energy-density lithium-sulfur batteries containing the same

Abstract

The present invention relates to an electrode for a lithium-sulfur battery for improving energy density, comprising a current collector and an electrode active material layer located on at least one side surface of the current collector, wherein the electrode active material layer comprises a sulfur-carbon composite and a binder, the sulfur-carbon composite comprises a porous carbon material and a sulfur-based material, and the current collector comprises aluminum (Al) and has a thickness of about 9 μm or less.

Description

[Technical Field]

[0001] The present invention relates to an electrode for a lithium-sulfur battery and a lithium-sulfur battery containing the same.

[0002] This application claims priority based on Korean Patent Application No. 10-2023-0167317, filed on 27 November 2023, and all contents disclosed in the specification and drawings of said application are incorporated herein by reference. [Background technology]

[0003] As the applications of lithium-ion batteries expand beyond portable electronic devices to include electric vehicles (EVs) and electric storage systems (ESS), the need for high-capacity, high-energy-density, and long-life lithium-ion batteries is increasing.

[0004] Among the many types of lithium-ion secondary batteries, lithium-sulfur batteries are a battery system that uses a sulfur-based material containing sulfur-sulfur bonds as the positive electrode active material, and a carbon-based material where lithium ion intercalation / deintercalation occurs, or silicon or tin that form an alloy with lithium, as the negative electrode active material.

[0005] In lithium-sulfur batteries, sulfur, the main material of the positive electrode active material, has advantages in that it has a low weight per atom, is very abundant in resources, is easy to supply and demand, is inexpensive, is non-toxic, and is also environmentally friendly. [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The present invention aims to provide electrodes for realizing high-energy-density lithium-sulfur batteries and lithium-sulfur batteries containing the same.

[0007] In one embodiment, the present invention aims to provide an electrode that reduces the weight of the electrode, increases the specific gravity of the active material relative to the total weight of the electrode, and lowers the weight ratio of the current collector.

[0008] In one embodiment, the present invention aims to provide an electrode that can increase the specific gravity of the active material relative to the total weight of the electrode, even if it is a low-loading electrode.

[0009] In one embodiment, the present invention aims to provide a lithium-sulfur battery that achieves high energy density because the specific gravity of the active material is high relative to the total weight of the electrodes. [Means for solving the problem]

[0010] According to one aspect of the present invention, electrodes in the following embodiments are provided.

[0011] The electrode according to the first embodiment is Current collector and, An electrode active material layer located on at least one side surface of the current collector, An electrode including, The electrode active material layer comprises a sulfur-carbon composite and a binder. The sulfur-carbon composite comprises a porous carbon material and a sulfur-based material. The current collector shall contain aluminum (Al) and have a thickness of approximately 9 μm or less.

[0012] According to the second aspect, in the first aspect, The electrode has a value of 90 cm² calculated using the following formula 1. 2 It can satisfy a minimum of / mAh. [Formula 1]

number

[0013] According to the third aspect, in the first or second aspect, The value calculated using formula 1 above is between 100 and 150 cm. 2 It can satisfy the / mAh requirement.

[0014] According to the fourth aspect, in any one of the first to third aspects, The thickness of the current collector may be between 5 μm and 9 μm.

[0015] According to the fifth aspect, in any one of the first to fourth aspects, The sulfur-based material content in the electrode active material layer may be 65% by weight or more.

[0016] According to the sixth aspect, in any one of the first to fifth aspects, Sulfur loading capacity: 5mAh / cm² 2 The following are possible:

[0017] According to the seventh aspect, in any one of the first to sixth aspects, Sulfur loading capacity is 3.5 mAh / cm². 2 The following are possible:

[0018] According to another aspect of the present invention, a lithium-sulfur battery in the following embodiments is provided.

[0019] A lithium-sulfur battery according to the eighth aspect is, It includes a positive electrode, a negative electrode, a separator sandwiched between the positive and negative electrodes, and an electrolyte. At least one of the positive electrode and the negative electrode may be an electrode according to any one of the first to seventh embodiments.

[0020] According to the ninth aspect, in the eighth aspect, The weight ratio (El / S) of the electrolyte and sulfur may be 3.5 g / g or less.

[0021] According to the tenth aspect, in the eighth or ninth aspect, The energy density of the lithium-sulfur battery may be 350 Wh / kg or more. [Effects of the Invention]

[0022] According to one aspect of the present invention, there is an advantage in that the weight ratio of the active material to the total weight of the electrode can be increased.

[0023] Furthermore, even in low-loading electrodes for active materials, this method has the advantage of increasing the weight ratio of the active material to the total weight of the electrode, thereby improving the energy density of the battery using it.

[0024] Furthermore, according to one aspect of the present invention, the weight ratio of the current collector to the total weight of the electrodes is low, which has the advantage of enabling the realization of a lithium-sulfur battery with high energy density. [Brief explanation of the drawing]

[0025] [Figure 1] This graph shows the weight ratio of the current collector (Al foil) in the pouch-type battery according to the thickness of the current collector (Al foil) in Comparative Examples 1 to 6 and Examples 1 to 4. [Figure 2] This graph shows the relative energy density values ​​of batteries according to the thickness of the current collector (Al foil) for Comparative Examples 1 to 6 and Examples 1 to 4. [Modes for carrying out the invention]

[0026] The present invention will be described below in conjunction with embodiments.

[0027] The terms and words used in this specification and the claims are not to be construed as limited to their ordinary or dictionary meanings. Instead, in accordance with the principle that the inventor can appropriately define the concept of the terms in order to explain the invention in the best way, they are construed in meanings and concepts corresponding to the technical idea of the present invention.

[0028] Throughout this specification, when a part describes a certain component as "including" or "having", this means, unless otherwise specified, that it does not exclude other components and may further include other components.

[0029] Also, throughout this specification, terms and expressions such as "about", "substantially", "essentially" are used to mean at or near that numerical value when manufacturing and material tolerances specific to the recited meaning are presented, and are used to prevent unscrupulous infringers from improperly using the disclosed content where exact or absolute numerical values are recited to assist in the understanding of the present invention.

[0030] Throughout this specification, the description "A and / or B" means "A or B or both of these".

[0031] In the present invention, the "specific surface area" is measured by the BET method, specifically, it can be calculated from the nitrogen gas adsorption amount at liquid nitrogen temperature (77K) using BELSORP-mini II of BEL Japan.

[0032] The term "(poly)sulfide" used in this specification means "(poly)sulfide ion (S x 2- , 1 ≦ x ≦ 8)" and "lithium (poly)sulfide (Li2S x or LiS x - , 1 ≦ x ≦ 8)", covering both concepts.

[0033] As used herein, the term "composite" refers to a substance in which two or more materials are combined to form physically and chemically distinct phases while simultaneously exhibiting effective functions.

[0034] In this specification, the term "porosity" refers to the ratio of the volume occupied by pores to the total volume of a structure, using vol% as its unit, and can be used interchangeably with terms such as void ratio and porosity.

[0035] In this specification, unless otherwise specified, the porosity may be a value obtained by measuring the apparent density of the substance in question and using the actual density calculated based on the actual density and composition of the constituent components of the substance in question, using the following relational formula.

[0036] Porosity (vol%) = {1 - (apparent density / actual density)} × 100

[0037] In this specification, "particle size (D 10 )" refers to the particle size at the 10% reference level of the cumulative particle size distribution of the particle volume, and "particle size (D 50 )" refers to the particle size at the 50% reference level of the volume cumulative particle size distribution of the particles, and "particle size (D 90 )" refers to the particle size at the 90% reference level of the volume-cumulative particle size distribution of the particles.

[0038] The particle size D 10 , D 50 and D 90 These can be measured using the laser diffraction method. For example, particles can be dispersed in a dispersion medium, then placed in a commercially available laser diffraction particle size analyzer (e.g., Microtrac MT 3000), irradiated with ultrasound at approximately 28 kHz at an output of 60 W, and after obtaining a volume-cumulative particle size distribution graph, the particle sizes corresponding to 10%, 50%, and 90% of the volume-cumulative amount can be determined.

[0039] The present invention relates to electrodes for electrochemical elements and electrochemical elements including said electrodes, such as secondary batteries. The secondary battery may be a lithium secondary battery. The electrode according to the present invention may be at least one of a positive electrode and a negative electrode, for example, a positive electrode containing sulfur as an active material. The electrode may also contain a sulfur-based material as an active material, and the lithium secondary battery containing such an electrode may be a lithium-sulfur secondary battery (or lithium-sulfur battery).

[0040] Lithium-sulfur batteries involve the conversion reaction between lithium ions and sulfur at the positive electrode (S8 + 16Li + +16e - The theoretical specific capacity (specific capacity) of 8Li2S reaches 1,675 mAh / g, and when lithium metal is used as the negative electrode, it exhibits a theoretical energy density of 2,600 Wh / kg. This is an extremely high value compared to the theoretical energy densities of other battery systems that are currently being actively researched (Ni-MH batteries: 450 Wh / kg, Li-FeS batteries: 480 Wh / kg, Li-MnO2 batteries: 1,000 Wh / kg, Na-S batteries: 800 Wh / kg) and lithium-ion batteries (250 Wh / kg). Therefore, among the secondary batteries developed to date, it is attracting attention as a high-capacity, environmentally friendly, and inexpensive lithium secondary battery.

[0041] However, due to problems such as the large amount of electrolyte required, decreased efficiency of the positive electrode, and degradation of the negative electrode, it has not been possible to fully realize the theoretical capacity, and as a result, energy density has not been sufficiently improved. Therefore, research efforts to realize lithium-sulfur batteries with high energy density continue unabated.

[0042] In lithium-sulfur batteries, because the density of the sulfur-carbon composite used in the positive electrode is low, coating the current collector with the sulfur-carbon composite results in a relatively higher density of the current collector, leading to a higher weight ratio of the current collector to the total electrode weight. Consequently, it is currently difficult to realize high-energy-density batteries (e.g., pouch-type batteries) due to the relatively high weight ratio of the current collector within the electrode. Furthermore, when reducing the loading amount to realize a low-loading electrode for various purposes, such as increasing the surface utilization rate of carbon in the positive electrode to increase the electrochemical reaction rate, the proportion of active material in the electrode decreases, making it difficult to realize a high-energy-density battery for the same reasons as described above.

[0043] According to one embodiment of the present invention, an electrode is provided that reduces the weight of the electrode, increases the specific gravity of the active material relative to the total weight of the electrode, and lowers the weight ratio of the current collector.

[0044] <Electrode> An electrode according to one aspect of the present invention is, An electrode comprising a current collector and an electrode active material layer located on at least one side surface of the current collector, wherein the electrode active material layer comprises a sulfur-carbon composite and a binder.

[0045] According to one aspect of the present invention, the sulfur-carbon composite comprises a porous carbon material and a sulfur-based material.

[0046] According to one aspect of the present invention, the thickness of the current collector is approximately 9 μm or less.

[0047] Sulfur-carbon composite According to one embodiment of the present invention, the electrode is provided with a current collector that is relatively thinner than that of conventional electrodes that use a sulfur-carbon composite, in which a sulfur-based material is supported on a porous carbon material as the active material, thereby realizing an electrode that can be used in electrochemical elements having a high energy density.

[0048] For example, in one embodiment of the present invention, the sulfur-carbon composite may contain an active material for the positive electrode and be bound together by the binder to form an electrode active material layer. The sulfur-carbon composite includes a porous carbon material and a sulfur-based material.

[0049] In one embodiment of the present invention, the sulfur-based material is included as an active material in an electrochemical element, such as a secondary battery or lithium secondary battery or lithium sulfur battery, and can be used as an active material in a lithium sulfur battery without limitation. For example, the sulfur-based material may be inorganic sulfur (S8), lithium (poly)sulfide (Li2S x or LiS x - The organic sulfur compound may be an organosulfur compound, a carbon-sulfur polymer, or a mixture of two or more of these. In one embodiment of the present invention, the organosulfur compound may be, for example, 2,5-dimercapto-1,3,4-thiadiazole, 1,3,5-trithiocyanuic acid, or a mixture thereof. In one embodiment of the present invention, the carbon-sulfur polymer may be of the chemical formula (C2S x ) n Examples include those having (x=2.5~50, n≧2), but the present invention is not limited thereto.

[0050] In one embodiment of the present invention, the porous carbon material can be any carbon material with electrical conductivity, as long as it has a porous structure for supporting the sulfur-based material, and the porous carbon material has electrical conductivity, in addition to using a sulfur-based material with no or extremely low electrical conductivity as the electrode active material layer, in order to increase the electrical conductivity of the electrode active material layer. For example, the porous carbon material may be carbon nanotubes, carbon black, graphite, activated carbon, graphene, or a mixture of two or more of these, but the present invention is not limited thereto.

[0051] For example, the sulfur-carbon composite may have a structure in which the sulfur-based material is supported on the outer surface and / or the inner surface of the pores of the porous carbon material, but is not limited to this.

[0052] In one embodiment of the present invention, the sulfur-carbon composite may contain the sulfur-based material through physical adsorption with the porous carbon material, covalent bonding between the sulfur element (S) and carbon in the porous carbon material, or chemical bonding such as van der Waals forces. In particular, the sulfur-based material may be chemically bonded to the surface of the porous carbon material to form a composite.

[0053] In one embodiment of the present invention, the sulfur-carbon composite may have a form in which the sulfur-based material and the carbon material are simply mixed and composited, or it may have a core-shell structure as a coating or support. The core-shell structure as a coating is a form in which either the sulfur-based material or the carbon material is coated with the other substance, for example, the surface of the carbon material may be encased in sulfur, or vice versa. The support form may be a form in which the sulfur-based material is filled inside the carbon material, particularly in the internal pores. The form of the sulfur-carbon composite can be any form as long as it satisfies the sulfur-to-carbon material content ratio presented above, and is not particularly limited in the present invention.

[0054] In one embodiment of the present invention, the sulfur-carbon composite may have a sulfur element (S) content of approximately 60 wt% or more, 70 wt% or more, 75 wt% or more, or 99 wt% or less, relative to 100 wt% of the sulfur-carbon composite. For example, the sulfur-carbon composite may have a sulfur element (S) content of approximately 60 wt% to 99 wt%, 70 wt% to 99 wt%, 60 wt% to 90 wt%, 75 wt% to 90 wt%, 70 wt% to 85 wt%, 70 wt% to 80 wt%, 75 wt% to 80 wt%, or 70 wt% to 75 wt%, relative to 100 wt% of the sulfur-carbon composite.

[0055] In the sulfur-carbon composite according to the present invention, the sulfur-based material is located on at least one of the surfaces of the porous carbon material, either the outer surface or the inner surface of the pores, and can be present in a region of less than 100% of the total surface of the porous carbon material, for example, about 1% to 95% or about 60% to 90%. When the sulfur is present on the surface of the porous carbon material within this range, it is most effective in terms of electron transfer area and electrolyte wettability. For example, since the sulfur is uniformly impregnated in a thin layer on the surface of the porous carbon material within this range, the electron transfer contact area can be increased during the charging and discharging process. If the sulfur were located on 100% of the total surface of the porous carbon material, the porous carbon material would be completely covered by the sulfur, reducing the wettability of the electrolyte, resulting in poor contact with the conductive material contained in the electrode, preventing electron transfer, and thus preventing participation in the reaction.

[0056] Next, an example of a method for producing the sulfur-carbon composite will be described. In one embodiment, the sulfur-carbon composite according to the present invention can be produced by a compounding method comprising the steps of (S1) mixing a porous carbon material and a sulfur-based material, and (S2) compounding.

[0057] The mixing in step (S1) is performed to increase the degree of mixing between the sulfur-based material and the porous carbon material, and in one embodiment, this can be done using a stirring device. At this time, the mixing time and speed can also be selectively adjusted according to the content and conditions of the raw materials.

[0058] The compounding method in step (S2) is not particularly limited in the present invention, and for example, methods such as dry compounding or wet compounding such as spray coating can be used.

[0059] For example, a method is available in which the mixture of sulfur and carbon material obtained after mixing is ball-milled to pulverize it, and then left in an oven at approximately 120°C to 160°C for about 20 minutes to 1 hour so that the molten sulfur can uniformly coat the internal and external surfaces of the carbon material.

[0060] The sulfur-carbon composite produced using the aforementioned manufacturing method has a structure that, while having a high specific surface area, also has a high sulfur load capacity and improved 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, and consequently, the capacity and life characteristics of lithium-sulfur batteries can be improved.

[0061] In one embodiment of the present invention, the sulfur-carbon composite is approximately 1.5 g / cm³ 3 It may have a density greater than or equal to the above. For example, the sulfur-carbon composite may have a density of about 1.5 g / cm³. 3 ~3.0g / cm 3 It may have a density of approximately 1.8 g / cm³. Alternatively, the sulfur-carbon composite may have a density of approximately 1.8 g / cm³. 3 ~2.5g / cm 3 , about 1.8g / cm 3 ~2.1 g / cm³ 3 Or approximately 1.9 g / cm³ 3 ~2.1 g / cm³ 3 For example, approximately 2.0 g / cm³ 3 It may have a density of [value].

[0062] Electrode thickness and Equation 1 An electrode containing a sulfur-based material as an active substance may have an electrode active material layer constructed using a sulfur-based material, a conductive material, and a binder. That is, by including the sulfur-based material structurally independently from the conductive material, an electrode with a high density of the electrode active material layer may be realized. In the present invention, since the sulfur-based material is supported on a porous carbon material and used as the active substance as a sulfur-carbon composite, the density of the electrode active material layer may be even lower than that of an electrode in which the sulfur-based material is structurally independent from the conductive material.

[0063] Therefore, the present invention provides an electrode in which the weight ratio of the current collector is relatively reduced in order to improve the density of the electrode active material layer, for example, the density of the sulfur-carbon composite within the electrode, in an electrode in which the above-mentioned sulfur-carbon composite is bound together with a binder to form an electrode active material layer.

[0064] For this reason, the thickness of the current collector may be limited to approximately 9 μm or less, but the reason for limiting the thickness of the current collector in this way is not limited to this.

[0065] For example, in one embodiment of the present invention, the electrode active material layer may have a porosity of about 60 vol% to 85 vol%. For example, the porosity of the electrode active material layer may be about 60 vol% to 80 vol%, 65 vol% to 80 vol%, 70 vol% to 80 vol%, or 75 vol% to 80 vol%, for example, about 78 vol%.

[0066] In this specification, the term "porosity" refers to the ratio of the volume occupied by pores to the total volume in a given structure, using vol% as its unit, and is interchangeable with terms such as porosity and density. The porosity can be measured in accordance with the ISO 15901:2019 method, which is known in the industry. In the present invention, the method for measuring the density is not limited to any particular method, and in one embodiment of the present invention, the porosity of the electrode active material layer can be measured, for example, in accordance with the mercury osmosis method (Hg porosimeter), and can be measured, for example, using a mercury porosimeter (Micromeritics AUTOPOREV). Furthermore, the porosity of the positive electrode active material layer may also be measured using the Brunauer-Emmett-Teller (BET) method, which uses an adsorbed gas such as nitrogen. For example, it can be measured using an analyzer from the BELSORP series manufactured by BEL Japan, such as the mini II, but the present invention is not limited to this. The porosity measured by such a method may represent the total volume of pores formed in the positive electrode active material layer. In addition, the porosity may also be calculated from the true density of the material constituting the positive electrode active material layer, the apparent density of the manufactured positive electrode active material layer, and the thickness of the positive electrode. For example, the porosity can be calculated as the value of [(true density - apparent density) / true density] × 100 (%) of the positive electrode active material layer.

[0067] The electrode according to one embodiment of the present invention has a value of 90 cm² calculated by the following formula 1. 2 It may satisfy the requirement of / mAh or higher. [Formula 1]

number

[0068] In one embodiment of the present invention, since the current collector does not affect the capacitance of the electrode, the lower the weight ratio of the current collector to the total weight of the electrode, that is, the higher the weight ratio of the components excluding the current collector (for example, the electrode active material layer) to the total weight of the electrode, the more advantageous it is for achieving a high energy density.

[0069] In one embodiment of the present invention, "electrode loading amount" is the amount of active material per unit area of ​​the electrode, and is converted, for example, to the electrode capacity value per unit area of ​​the electrode in mAh / cm². 2 This can be expressed as the value of . In this case, the higher the loading amount of the electrode, the greater the content of the active material in the electrode, and as a result the overall weight of the electrode can increase. Therefore, in the above formula 1, the increase in weight due to loading can be corrected by dividing by the value of the loading amount of the electrode.

[0070] Therefore, the higher the value obtained from Equation 1 above, the more likely it is that the electrode is suitable for use in electrochemical elements with high energy density.

[0071] For example, according to one embodiment of the present invention, the value obtained by formula 1 above is approximately 90 cm 2 An electrode exhibiting a value of 1 / mAh or higher may be provided. For example, the value obtained by formula 1 above is approximately 90 cm³. 2 / mAh~200cm 2 / mAh, 90cm 2 / mAh~180cm 2 / mAh, 90cm 2 / mAh~160cm 2 / mAh or 90cm 2 / mAh~150cm 2 An electrode with a value of / mAh may be provided. In one embodiment, the value according to formula 1 above is 95 cm⁻¹. 2 / mAh~150cm 2 / mAh, 100cm 2 / mAh~145cm 2 / mAh or 105.5cm2 / mAh~142.5cm 2 An electrode having a value of / mAh may be provided. While the electrode having the value of formula 1 above is advantageous for realizing electrodes and electrochemical elements with high energy density, the present invention is not limited thereto.

[0072] For the reasons stated above, the thinner the thickness of the current collector, the more advantageous it is for achieving high energy in the electrodes. According to one embodiment of the present invention, the thickness of the current collector can be, for example, about 9 μm or less, for example, about 1 μm to 9 μm, 2 μm to 9 μm, 3 μm to 8.5 μm, 4 μm to 8.5 μm, 5 μm to 8.5 μm, 5.5 μm to 8.5 μm, 6 μm to 8 μm, 5.5 μm to 7 μm, or 5.5 μm to 6.5 μm. When the thickness of the current collector is within the above range, the weight of the electrodes relative to the capacitance of the electrodes is not significantly increased, which is advantageous for achieving high energy density and is also advantageous in that it prevents problems such as the current collector being torn apart. However, the present invention is not limited thereto.

[0073] In one embodiment of the present invention, the "thickness" of the current collector may be a value measured using a known thickness value of the current collector used, or a value measured using a known thickness measuring device. For example, the thickness may be measured using a thickness measuring device manufactured by Mitutoyo Corporation. Alternatively, the thickness of the current collector may be measured using an electron microscope image of the cross-section of the electrode.

[0074] As described above, in one embodiment of the present invention, if the loading amount of the electrode is excessively high, even if the thickness of the current collector is within the range described above, there is a possibility that the battery's energy density will not be significantly improved. For this reason, in one embodiment of the present invention, when the electrode's loading amount is below a certain level, a current collector of the thickness described above may be used.

[0075] In one embodiment of the present invention, the loading amount of the electrode is, for example, about 10 mAh / cm². 2The following is possible: For example, the loading amount of the electrode is approximately 0.5 mAh / cm². 2 ~10mAh / cm 2 It is possible.

[0076] In another embodiment of the present invention, the loading amount of the electrode is, for example, about 9 mAh / cm². 2 Below, 8mAh / cm 2 Below, 7mAh / cm 2 Below, 6mAh / cm 2 Below or 5mAh / cm² 2 The following may be the case: Alternatively, the loading amount of the electrode may be, for example, about 4.5 mAh / cm². 2 Below, 4.0mAh / cm 2 The following or 3.5mAh / cm² 2 The following are possible:

[0077] In yet another embodiment of the present invention, the loading amount of the electrode is, for example, about 1 mAh / cm². 2 ~5mAh / cm 2 , 1.5mAh / cm 2 ~5mAh / cm 2 , 2mAh / cm 2 ~5mAh / cm 2 , 2.1mAh / cm 2 ~5mAh / cm 2 , 2.2mAh / cm² 2 ~5mAh / cm 2 , 2.3mAh / cm² 2 ~5mAh / cm 2 Or 2.3mAh / cm² 2 ~5.0mAh / cm 2 , 2.3mAh / cm² 2 ~4.5mAh / cm 2 , 2.3mAh / cm² 2 ~4.0mAh / cm 2 , 2.3mAh / cm² 2 ~3.5mAh / cm 2 It is possible.

[0078] In one embodiment of the present invention, the "electrode loading amount" indicates the loading amount of sulfur (S) in the electrode, and may be measured according to a known method for measuring the loading amount of sulfur in an electrode. For example, the electrode loading amount may be a value calculated from the total weight of sulfur (S) contained in the electrode as an electrode active material. In this case, the weight of sulfur in the electrode may be measured from the amount of electrode active material added during the manufacturing stage, or after manufacturing, it may be measured by performing thermogravimetric analysis (TGA) on the electrode. On the other hand, when obtaining an electrode by disassembling a manufactured lithium sulfur battery, the lithium sulfur battery in a charged state is disassembled in an inactive atmosphere to obtain the electrode, the electrode is then cleaned and dried using an appropriate cleaning solvent, and then the electrode active material layer is scraped off and thermogravimetric analysis (TGA) is performed on the resulting product to measure and calculate the sulfur (S) content derived from the active material, but the measurement method is not limited to this. In this case, the measured sulfur capacity (1,200 mAh / g) can be calculated from the weight of sulfur obtained above. s The amount of sulfur loading can be calculated using ).

[0079] electrode active material layer In one embodiment of the present invention, the electrode is intended to solve the problem that in an electrode containing a high content of active material, the increase in energy density is not proportional to the increase in electrode density, and the electrode may be an electrode containing a high content of active material.

[0080] For example, the electrode may have a sulfur-based material content of about 65% by weight or more in the electrode active material layer. For example, the sulfur-based material content in the electrode active material layer may be about 65% to 99% by weight, 65% to 95% by weight, 65% to 90% by weight, 65% to 85% by weight, 70% to 85% by weight, 70% to 80% by weight, 70% to 75% by weight, 72.5% to 75% by weight, or 70% to 72.5% by weight, but the present invention is not limited thereto. In the present invention, when the sulfur-based material content in the electrode active material layer is within the above range, it is advantageous in increasing the capacity of the active material in the electrode while maintaining the content of the conductive carbon material and the binder at a constant level, thereby achieving high electrical conductivity and / or excellent bonding strength between the active materials, but the present invention is not limited thereto.

[0081] In one embodiment of the present invention, the content of sulfur-based material in the electrode active material layer may be calculated from the weight of sulfur-based material added, based on the total weight of electrode material added during the manufacturing stage of the electrode active material layer. Alternatively, it may be calculated from the value obtained by analyzing the content of sulfur-based material in the total weight of the electrode active material layer, excluding the weight of the current collector from the manufactured electrode. In this case, please refer to the above-described section on the method for measuring the loading amount for the method of analyzing the content of sulfur-based material in the electrode active material layer.

[0082] Current collector According to one aspect of the present invention, the current collector contains aluminum (Al).

[0083] For example, in one embodiment of the present invention, the current collector may be a current collector usable as a positive electrode and may contain aluminum.

[0084] In another embodiment of the present invention, the current collector may consist solely of aluminum (Al).

[0085] In yet another embodiment of the present invention, the current collector may include aluminum and further include current collector components used in the positive electrode. For example, the current collector may include aluminum along with stainless steel, nickel, titanium, calcined carbon, silver, or two or more of these components.

[0086] In one embodiment of the present invention, if the current collector further contains components other than aluminum, for example, a current collector can be made by laminating stainless steel on the surface of aluminum, or by laminating aluminum on the surface of stainless steel, or by surface treating the surface of aluminum with nickel, titanium, carbon, silver, or two or more of these components.

[0087] In one embodiment of the present invention, a current collector having minute irregularities formed on its surface can be used to improve the bonding force with the electrode active material layer formed on its surface, but the present invention is not limited thereto.

[0088] In one embodiment of the present invention, the current collector can be used in a wide variety of forms, such as a film, sheet, foil, net, porous material, foam, or nonwoven fabric. For example, the current collector may be aluminum foil.

[0089] The following describes in detail other components of the electrode according to one aspect of the present invention.

[0090] In one embodiment of the present invention, the binder plays a role in improving the adhesion between active material particles and the adhesion between the active material and the current collector. Examples of binders include polyvinylidene 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 can be used. The binder resin may be included in an amount of about 1 wt% to 30 wt%, for example, 1 wt% to 20 wt%, or 1 wt% to 10 wt%, relative to the total weight of the positive electrode active material layer.

[0091] In one embodiment of the present invention, the electrode active material layer may further include other additives such as conductive materials, in addition to the sulfur-carbon composite and binder.

[0092] The conductive material, for example, is used to provide conductivity to the negative electrode and can be used without particular limitations as long as it does not cause chemical changes in the battery and has electronic conductivity. 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, and one or more of these can be used. When the conductive material is used, it can usually be contained in an amount of about 1 wt% to 30 wt%, for example, 1 wt% to 20 wt% or 1 wt% to 10 wt%, relative to the total weight of the positive electrode active material layer.

[0093] In one embodiment of the present invention, the electrode active material layer may further contain other active materials in addition to the sulfur-carbon composite described above.

[0094] In this case, any other active materials that may be included can be used without particular restriction, for example, as long as they can be used as active materials in lithium secondary batteries. Such active materials may include, but are not limited to, lithium transition metal oxides; lithium metallic iron phosphorus oxides; lithium nickel-manganese-cobalt oxides; oxides in which part of the lithium nickel-manganese-cobalt oxide is substituted with other transition metals; or two or more of these. For example, the positive electrode active material may be, for example, layered compounds such as lithium cobalt oxide (LiCoO2) and lithium nickel oxide (LiNiO2), or compounds substituted with one or more transition metals; chemical formula Li 1+x Mn 2-x Lithium manganese oxides such as O4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, Cu2V2O7; chemical formula LiNi1-x M x O2 (where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x = 0.01 - 0.3) of Ni-site type lithium nickel oxide; chemical formula LiMn 2-x M x O2 (where M = Co, Ni, Fe, Cr, Zn or Ta, and x = 0.01 - 0.1) or Li2Mn3MO8 (where M = Fe, Co, Ni, Cu or Zn) of lithium manganese composite oxide; lithium metal phosphate LiMPO4 (where M = Fe, CO, Ni, or Mn); lithium nickel - manganese - cobalt oxide Li 1+x (Ni a Co b Mn c ) 1-x O2 (x = 0 - 0.03, a = 0.3 - 0.95, b = 0.01 - 0.35, c = 0.01 - 0.5, a + b + c = 1); an oxide in which a part of lithium nickel - manganese - cobalt oxide is substituted with aluminum Li a [Ni b Co c Mn d Al e ) 1-f M1 f O2 (M1 is one or more selected from the group consisting of Zr, B, W, Mg, Ce, Hf, Ta, La, Ti, Sr, Ba, F, P and S; 0.8 ≤ a ≤ 1.2, 0.5 ≤ b ≤ 0.99, 0 < c < 0.5, 0 < d < 0.5, 0.01 ≤ e ≤ 0.1, 0 ≤ f ≤ 0.1); an oxide in which a part of lithium nickel - manganese - cobalt oxide is substituted with other transition metals Li 1+x (Ni a Co b [[ID=3,7]]Mn c M d ) 1-x O2 (x = 0 - 0.03, a = 0.3 - 0.95, b = 0.01 - 0.35, c = 0.01 - 0.5, d = 0.001 - 0.03, a + b + c + d = 1, M is any one selected from the group consisting of Fe, V, Cr, Ti, W, Ta, Mg and Mo), disulfide compounds; such as Fe2(MoO4)3, but not limited thereto.

[0095] <Lithium sulfur battery> Lithium-sulfur batteries according to other aspects of the present invention are, The device includes a positive electrode, a negative electrode, a separator sandwiched between the positive and negative electrodes, and an electrolyte, wherein at least one of the positive and negative electrodes is the electrode described above.

[0096] In one embodiment of the present invention, the positive electrode of the lithium-sulfur battery may be the electrode described above. For example, the positive electrode is an electrode comprising a current collector and an electrode active material layer located on at least one side surface of the current collector, wherein the electrode active material layer comprises a sulfur-carbon composite and a binder, the sulfur-carbon composite comprises a porous carbon material and a sulfur-based material, and the current collector comprises aluminum (Al) and may have a thickness of about 9 μm or less.

[0097] In one embodiment of the present invention, the positive electrode / separator / negative electrode unit structure may be referred to as an electrode assembly, and the electrode assembly may be stacked with the separator sandwiched between the negative electrode and the positive electrode to form a stacked or stack / folding structure, or it may be wound up to form a jelly roll structure. In addition, when a jelly roll structure is formed, a separator may be further arranged on the outside to prevent the negative electrode and the positive electrode from coming into contact with each other.

[0098] In one embodiment of the present invention, when the positive electrode is the electrode described above, the negative electrode will be described in detail.

[0099] The negative electrode may have a structure in which a negative electrode active material layer is formed on one or both sides of a long, sheet-like negative electrode current collector, and the negative electrode active material layer may contain a negative electrode active material and a binder resin. Furthermore, the negative electrode active material layer may further contain a conductive material as needed.

[0100] For example, the negative electrode can be manufactured by applying a negative electrode slurry, which is prepared by dispersing a negative electrode active material, a conductive material, and a binder in a solvent such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, to one or both sides of a long, sheet-like negative electrode current collector, and then rolling the slurry after removing the solvent using a drying process. On the other hand, when applying the negative electrode slurry, a negative electrode including a plain area can be manufactured by not applying the negative electrode slurry to a part of the negative electrode current collector, for example, one end of the negative electrode current collector.

[0101] The negative electrode active material is lithium (Li + The materials may include substances that can reversibly intercalate / deintercalate lithium ions, substances that can reversibly form lithium-containing compounds by reacting with lithium ions, lithium metals, or lithium alloys. The materials that can reversibly intercalate or deintercalate lithium ions may be, for example, crystalline carbon, amorphous carbon, or mixtures thereof, and include, but are not limited to, artificial graphite, natural graphite, graphitized carbon fiber, amorphous carbon, soft carbon, hard carbon, etc.

[0102] A substance capable of reversibly forming a lithium-containing compound by reacting with the aforementioned lithium ions may be, for example, tin oxide, titanium nitrate, or silicon-based compound.

[0103] The lithium alloy can be, for example, an alloy of a metal selected from the group consisting of lithium (Li) and sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), aluminum (Al), and tin (Sn). For example, the negative electrode active material can be lithium metal, and can be in the form of, for example, a lithium metal thin film or lithium metal powder.

[0104] The silicon-based compound can be Si, Si-Me alloy (where Me is one or more selected from the group consisting of Al, Sn, Mg, Cu, Fe, Pb, Zn, Mn, Cr, Ti, and Ni), SiO y (where 0 < y < 2), a Si-C composite, or a combination thereof, and can be, for example, SiO y (where 0 < y < 2). Since the silicon-based compound has a high theoretical capacity, when the silicon-based compound is included as the negative electrode active material, the capacity characteristics can be improved.

[0105] Examples of the negative electrode current collector include copper, stainless steel, aluminum, nickel, titanium, fired carbon, those obtained by surface treatment of the surface of copper or stainless steel with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. The negative electrode current collector usually can have a thickness of about 3 μm to 500 μm, and similar to the positive electrode current collector, minute irregularities may be formed on the surface of the current collector to strengthen the binding force of the negative electrode active material. For example, it can be used in various forms such as films, sheets, foils, nets, porous bodies, foams, non-woven fabric bodies, etc.

[0106] The binder plays a role in improving the adhesion between negative electrode active material particles and the adhesion between the negative electrode active material and the negative electrode current collector. Examples include polyvinylidene 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 can be used. The binder may be included in an amount of about 1 wt% to 30 wt%, for example, 1 wt% to 20 wt% or 1 wt% to 10 wt%, based on the total weight of the negative electrode active material layer.

[0107] The conductive material included as needed is used to impart conductivity to the negative electrode and can be used without particular limitations as long as it does not cause chemical changes in the constructed battery and has electronic conductivity. 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, and one of these alone or a mixture of two or more can be used. When the conductive material is used, it can usually be included in an amount of about 1 wt% to 30 wt%, for example, about 1 wt% to 20 wt% or 1 wt% to 10 wt%, relative to the total weight of the negative electrode active material layer.

[0108] The separator is positioned within the electrode assembly in a manner that it is sandwiched between the negative electrode and the positive electrode. The separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without any particular limitations.

[0109] For example, the separator can be a porous polymer film, such as 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. In addition, ordinary porous nonwoven fabrics, such as nonwoven fabrics made from high-melting-point glass fibers or polyethylene terephthalate fibers, may also be used. Furthermore, coated separators containing ceramic components or polymeric substances may be used to ensure heat resistance or mechanical strength.

[0110] In one embodiment of the present invention, the lithium-sulfur battery may be provided in a form in which an electrode assembly comprising the positive electrode, negative electrode, and separator as constituent units is housed together with the electrolyte in a battery case.

[0111] In one embodiment of the present invention, the battery case can be selected without any particular limitations, as long as it is one of the types commonly used in the art, such as a pouch type, a metal can type, a cylindrical shape, a stacked shape, or a coin shape.

[0112] In one embodiment of the present invention, the lithium-sulfur battery may be a pouch-type, coin-type, or cylindrical battery, and may, for example, be a pouch-type battery, but the present invention is not limited thereto.

[0113] In one embodiment of the present invention, the electrolyte can be, for example, an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-like polymer electrolyte, a solid inorganic electrolyte, a molten inorganic electrolyte, or the like, and the type is not particularly limited.

[0114] In one embodiment of the present invention, the electrolyte may include a lithium salt.

[0115] In other embodiments of the present invention, the electrolyte may comprise a lithium salt and a non-aqueous solvent.

[0116] In yet another embodiment of the present invention, the electrolyte may comprise a lithium salt, a non-aqueous solvent, and an additive.

[0117] The lithium salt can be any compound capable of providing lithium ions for use in a lithium secondary battery, without any particular limitations. For example, the lithium salt can be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. The concentration of the lithium salt is preferably within a range of about 0.1M to 5.0M, for example, about 0.1M to 3.0M. When the concentration of the lithium salt falls within this range, the electrolyte has appropriate conductivity and viscosity, exhibiting excellent electrolyte performance and allowing lithium ions to move effectively.

[0118] In one embodiment of the present invention, the lithium salt may include LiTFSI.

[0119] The aforementioned non-aqueous solvent can be used without any particular limitations, as long as it serves as a medium through which ions participating in the electrochemical reaction of the battery can move. For example, non-aqueous solvents include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; carbonate solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; and R-CN (where R is C2-C2). 20 Nitriles such as linear, branched, or cyclic hydrocarbon groups (which may contain double-bonded aromatic rings or ether bonds); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used.

[0120] On the other hand, in one embodiment of the present invention, the electrolyte may contain a heterocyclic compound containing an oxygen atom or a sulfur atom, from the perspective of suppressing the formation of lithium dendrites and forming a polymer protective film that can reduce the decomposition of the electrolyte on the surface of the lithium-based metal and side reactions. The heterocyclic compound may be a 3- to 15-membered heterocyclic compound, for example, a 3- to 7-membered or 5- to 6-membered heterocyclic compound. The heterocyclic compound may be a heterocyclic compound substituted or unsubstituted with one or more selected from the group consisting of C1-4 alkyl groups, C3-8 cyclic alkyl groups, C6-10 aryl groups, halogen groups, nitro groups (-NO2), amine groups (-NH2), and sulfonyl groups (-SO2); or it may be a polycyclic compound of a heterocyclic compound with one or more selected from the group consisting of C3-8 cyclic alkyl groups and C6-10 aryl groups. When the heterocyclic compound is a heterocyclic compound substituted with a C1-4 alkyl group, radicals are stabilized and side reactions between the additive and the electrolyte can be suppressed. Furthermore, if the heterocyclic compound is substituted with a halogen group or a nitro group, it can form a functional protective film on the surface of the lithium-based metal. The functional protective film is stable and in a compact form, allowing for uniform deposition of the lithium-based metal and suppressing side reactions between the polysulfide and the lithium-based metal.

[0121] The aforementioned heterocyclic compounds include, for example, furan, 2-methylfuran, 3-methylfuran, 2-ethylfuran, 2-propylfuran, 2-butylfuran, 2,3-dimethylfuran, 2,4-dimethylfuran, 2,5-dimethylfuran, pyran, 2-methylpyran, 3-methylpyran, 4-methylpyran, benzofuran, 2-(2-nitrovinyl)furan, It may contain one or more substances selected from the group consisting of thiophene, 2-methylthiophene, 2-ethylthiophene, 2-propylthiophene, 2-butylthiophene, 2,3-dimethylthiophene, 2,4-dimethylthiophene, and 2,5-dimethylthiophene, for example, it may contain one or more substances selected from the group consisting of 2-methylfuran and 2-methylthiophene.

[0122] On the other hand, in one embodiment of the present invention, the non-aqueous solvent of the electrolyte may include an ether-based solvent, from the perspective of improving the charge and discharge performance of the battery. Examples of such ether-based solvents include cyclic ethers (e.g., 1,3-dioxolane, tetrahydrofuran, tetrahydropyran, etc.), linear ether compounds (e.g., 1,2-dimethoxyethane, etc.), and low-viscosity fluoride ethers, such as (1H,1H,2'H,3H-Decafluorodipropyl ether, Difluoromethyl 2,2,2-trifluoroethyl ether, 1,2,2,2-Tetrafluoroethyl trifluoromethyl ether, and 1,1,2,3,3,3-Hexafluoropropyl difluoromethyl ether. Examples include ether, 1H,1H,2'H,3H-decafluorodipropyl ether, pentafluoroethyl 2,2,2-trifluoroethyl ether, and 1H,1H,2'H-perfluorodipropyl ether, and a mixture of one or more of these may be included as a non-aqueous solvent.

[0123] In one embodiment of the present invention, the non-aqueous solvent may include a mixture of 2-methylfuran and dimethoxyethane.

[0124] In one embodiment of the present invention, the non-aqueous solvent may include a mixture having a volume ratio of 2-methylfuran and dimethoxyethane of about 5:1 (v / v) to 1:5 (v / v), for example, about 1:1 (v / v) to 1:5 (v / v).

[0125] In one embodiment of the present invention, the additive can be any additive that is suitable for use in lithium-sulfur batteries for the purpose of improving battery life characteristics, suppressing the decrease in battery capacity, and improving the discharge capacity of the battery, without any particular limitations. The additive may be included in an amount of about 0.1 wt% to 10 wt%, for example, 0.1 wt% to 5 wt%, relative to the total weight of the electrolyte.

[0126] In one embodiment of the present invention, the additive may include, for example, a nitrogen compound, and may include, for example, LiNO3.

[0127] On the other hand, in one embodiment of the present invention, the lithium-sulfur battery of the present invention may have a ratio (El / S) of the total weight of the electrolyte to the total weight of the sulfur element (S) in the positive electrode that is, for example, 3.5 g / g or less, for example, 3.3 g / g or less, or 3.2 g / g or less. Furthermore, the lithium-sulfur battery may have a ratio (El / S) of approximately 2.0 g / g to 3.5 g / g, for example, 2.0 g / g to 3.0 g / g or 2.5 g / g to 3.0 g / g. When using the sulfur-carbon composite according to the present invention, a lithium-sulfur battery with an El / S ratio within the above range can also be realized, thereby achieving the effect of improving energy density. However, lithium-sulfur batteries using the sulfur-carbon composite may also have an El / S ratio higher than the above range, and the present invention is not limited thereto.

[0128] In one embodiment of the present invention, the El / S ratio can be calculated during the manufacturing stage of a lithium-sulfur battery by measuring the weight of sulfur from the sulfur-based material introduced into the positive electrode and measuring the weight of the electrolyte injected.

[0129] In one embodiment of the present invention, the El / S ratio can be determined by measuring the weight of sulfur in the positive electrode according to the method described above in the section on the method for measuring the amount of sulfur loaded in the positive electrode, using the lithium sulfur battery in the state of a manufactured and completed product (final product) as a reference, and then disassembling the battery in a charged state, for example, at SOC (State of Charge) 100%, extracting the electrolyte from the positive electrode, negative electrode, separator and case, measuring the weight of all remaining components, and then subtracting the weight of the components remaining after extraction from the weight of the finished lithium sulfur battery as the weight of the electrolyte.

[0130] In one embodiment of the present invention, the lithium-sulfur battery may be a battery having a high energy density, for example, a battery having an energy density of 350 Wh / kg or more.

[0131] For example, the energy density of the lithium-sulfur battery may be approximately 350 Wh / kg to 450 Wh / kg, but is not limited to this.

[0132] In one embodiment of the present invention, the energy density of the lithium sulfur battery can be calculated according to the following formula by discharging it at a rate of 0.5C to 1.8V in constant current (CC) mode under a temperature of 25°C, charging it to 2.5V at a constant current of 0.2C, measuring the discharge capacity.

[0133] Energy density = [(discharge capacity × driving voltage)] / (cell weight)

[0134] Furthermore, according to yet another aspect of the present invention, a battery module is provided which includes the lithium-sulfur battery as a unit battery.

[0135] The aforementioned battery module can be used as a power source for medium to large-sized devices that require high-temperature stability, long cycle characteristics, and high capacity characteristics.

[0136] Examples of the aforementioned medium- and large-sized devices include, but are not limited to, power tools powered by battery-powered motors; electric vehicles, including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs); electric two-wheeled vehicles, including electric bicycles (E-bikes) and electric scooters; electric golf carts; and power storage systems.

[0137] The present invention will be described in detail below with reference to examples, drawings, and the like.

[0138] [Manufacturing of lithium-sulfur batteries] Manufacturing of positive electrodes An aluminum thin film (Al foil) was prepared as a current collector. An electrode slurry, prepared by mixing 96% by weight of sulfur-carbon composite (S8:CNT=75:25) and 4% by weight of polyacrylic acid (PAA), was applied to one side of the prepared current collector, and then dried to produce a positive electrode.

[0139] Tables 1 and 2 below show the thickness of the current collector used during electrode manufacturing, the amount of sulfur (S8) loaded into the electrode, and the value calculated using formula 1 below. [Formula 1]

number

[0140] Manufacturing of lithium-sulfur batteries The electrode manufactured as described above was used as the positive electrode, and a 60 μm thick lithium metal was prepared as the negative electrode.

[0141] The positive electrode and negative electrode were positioned facing each other, and a polyethylene separator (PE12, manufactured by Celgard, Inc.) with a thickness of 12 μm was sandwiched between them to prepare an electrode assembly.

[0142] A lithium-sulfur battery was manufactured by placing the prepared electrode assembly in a pouch-type case and injecting an electrolyte solution, which consisted of 0.75M lithium salt (LiTFSI) and 3 wt% lithium nitrate (LiNO3) dissolved in an organic solvent mixture of 2-methylfuran (2-MeF) and dimethoxyethane (DME) in a volume ratio of 3:7, so that the El / S ratio was 2.5 g / g.

[0143] Tables 1 and 2, and Figure 1 below, show the weight ratio of the positive electrode current collector (Al foil) in the manufactured pouch-type batteries.

[0144] [Evaluation of lithium-sulfur battery performance] Energy density Each of the lithium-sulfur batteries manufactured as described above was discharged at a constant current (CC) rate of 0.5C at room temperature (25°C) until it reached 1.8V, and then charged to 2.5V at a constant current (CC) rate of 0.3C to measure the discharge capacity per unit weight of sulfur (mAh / g (weight of sulfur)).

[0145] On the other hand, the energy density was measured from the measured discharge capacity according to Equation 2 below, and the relative values ​​of the energy density, with Comparative Example 1 (Table 1) and Comparative Example 4 (Table 2), which used a current collector with a thickness of 20 μm, as the reference, are shown in Tables 1, 2 and Figure 2 below, respectively, according to the respective loading amounts.

[0146] [Formula 2] Energy density (Wh / kg) = {[(Discharge capacity (mAh / g) × Driving voltage (V)) / 1000] / (Cell weight (kg))}

[0147] [Table 1]

[0148] [Table 2]

[0149] In Table 1, the electrode loading amount was 5.0 mAh / cm² in Comparative Example 1, Comparative Example 2, Comparative Example 3, and Examples 1 and 2. 2 In the case of relatively high-loading electrodes, as shown in Table 2, the electrode loading amount in Comparative Examples 4, 5, 6, and Examples 3 and 4 was 2.3 mAh / cm². 2 This is the case for a relatively low-loading electrode. Referring to Figure 1, the case for a high-loading electrode (loading amount: 5.0 mAh / cm²) 2 (Comparative Example 1, Comparative Example 2, Comparative Example 3 and Example 1, Example 2), Low Loading Electrode (Loading: Amount 2.3 mAh / cm²) 2 It can be confirmed that the mass ratio of the aluminum thin film is relatively lower compared to Comparative Examples 4, 5, 6, and Examples 3 and 4. This indicates that the change in the weight ratio of the current collector becomes more drastic as the loading amount decreases. It can also be confirmed that the mass ratio of the aluminum thin film naturally decreases as the thickness of the aluminum thin film decreases.

[0150] Referring to Figure 2, when the loading amount is low (loading amount: 2.3 mAh / cm²), 2 (Comparative Examples 4, 5, 6, and 3 and 4) As the specific gravity of aluminum in the electrode becomes relatively larger, compared to high-loading electrodes (loading amount: 5.0 mAh / cm²) 2 (Comparative Examples 1, 2, 3, and 1 and 2) It can be confirmed that as the thickness of the aluminum thin film decreases, the energy density gradient becomes steeper and more sloping upwards.

[0151] [Evaluation Results] From the results in Tables 1 and 2, it was confirmed that using electrodes with aluminum thin-film current collectors with a thickness of 9 μm or less significantly improves the energy density of lithium-sulfur batteries compared to cases with a thickness greater than 9 μm. For example, as shown in Table 1, in the case of a loading electrode (loading amount: 5.0 mAh / cm²) 2 When comparing Comparative Example 1, in which the aluminum thin film current collector had a thickness of 20 μm, with Example 2, in which the aluminum thin film current collector had a thickness of 6 μm, it was confirmed that the energy density was approximately 10% (more precisely, approximately 9.1%) higher. On the other hand, the values ​​of Equation 1 in Example 1 and Example 2 were 105.5 cm², respectively. 2 / mAh and 140.7cm 2 / mAh, 90cm 2 It can be seen that it is greater than / mAh.

[0152] On the other hand, as shown in Table 2, in the case of electrodes with a low loading amount (loading amount: 2.3 mAh / cm²), 2 When comparing Comparative Example 4, in which the aluminum thin film current collector has a thickness of 20 μm, with Example 4, in which the aluminum thin film current collector has a thickness of 6 μm, the relative energy density increased by approximately 17.8%, confirming that the increase in energy density was approximately twice that of electrodes with a relatively high loading amount. On the other hand, the values ​​of Equation 1 in Example 3 and Example 4 were 106.9 cm², respectively. 2 / mAh and 142.5cm 2 / mAh, 90cm 2 It can be seen that it is greater than / mAh.

[0153] On the other hand, in the comparative examples and examples, when an aluminum thin film was used as the current collector, the parameter of approximately 9 μm or less was calculated based on its thickness. However, the present invention is not limited in any way, and the parameter may also be calculated based on, for example, the type of current collector metal used and the weight and density of these metals. For example, when Al, Ni, Cu, or stainless steel (SUS) is used as the current collector, the density (d) (g / cm³) of these metals may be used. 3) and weight value as a basis for the weight per unit area (mg / cm³) of the metal. 2 In some cases, conditions are selected such that the value of ) is less than or equal to a specific value. For example, in one embodiment, the weight per unit area of ​​the current collector (mg / cm²) 2 If the value of ) is 0.9xd or less, the energy density of the sulfur cell can be improved, as in the case where the thickness of the aluminum thin film current collector is 9 μm or less. In this case, the densities of Al, Ni, Cu, and stainless steel (SUS) are 2.7 g / cm³ each. 3 8.91 g / cm³ 3 8.96 g / cm³ 3 and 7.93 g / cm³ 3 Therefore, when applying the relationship "0.9xd", the weight per unit area of ​​the current collector in the case of an Al current collector is 2.43 mg / cm³. 2 In the case of a Ni current collector, the weight per unit area of ​​the current collector is 8.019 mg / cm² if the following conditions are met. 2 In the case of a copper current collector, the weight per unit area of ​​the current collector is 8.064 mg / cm² if the following conditions are met. 2 The following conditions apply, and in the case of stainless steel (SUS) current collectors, the weight per unit area of ​​the current collector is 7.137 mg / cm³. 2 The following conditions satisfy the requirement that the aluminum thin-film current collector described above is 9 μm or less.

[0154] Although the embodiments described above have been explained with reference to those embodiments of this disclosure, a person skilled in the art or a person with ordinary knowledge in the art will understand that various modifications and changes can be made to the present invention without departing from the spirit and technical scope of the invention as described in the appended claims. Therefore, the technical scope of the present invention should not be limited by the contents described in the detailed description section of the specification, but should be defined by the appended claims.

Claims

1. Current collector and, An electrode active material layer located on at least one side surface of the current collector, An electrode including, The electrode active material layer comprises a sulfur-carbon composite and a binder. The sulfur-carbon composite comprises a porous carbon material and a sulfur-based material. The current collector is an electrode containing aluminum (Al) and having a thickness of 9 μm or less.

2. The electrode has a value of 90 cm² calculated using the following formula 1. ２ The electrode according to claim 1, satisfying the requirement of / mAh or more: [Formula 1] [Math 1] In the above formula 1, The weight of the electrodes and the weight of the current collector are measured in grams (g). The electrode loading amount is the amount of sulfur loaded into the electrode, and its unit is mAh / cm². ２ That is the case.

3. The value calculated using formula 1 above is 100 cm. ２ / mAh~150cm ２ The electrode according to claim 2, which satisfies the requirement of / mAh.

4. The electrode according to claim 1, wherein the thickness of the current collector is 5 μm to 9 μm.

5. The electrode according to claim 1, wherein the sulfur-based material content in the electrode active material layer is 65% by weight or more.

6. Sulfur loading rate: 5 mAh / cm³ ２ The electrode according to claim 1, which is as follows:

7. Sulfur loading rate: 3.5 mAh / cm² ２ The electrode according to any one of claims 1 to 6, which is as follows:

8. The electrode according to claim 1, wherein the current collector is composed solely of aluminum (Al).

9. The electrode according to claim 1, wherein the current collector comprises aluminum, stainless steel, nickel, titanium, calcined carbon, silver, or two or more of these components.

10. The electrode according to claim 1, wherein the current collector is in the form of one of a film, sheet, foil, net, porous body, foam, or nonwoven fabric.

11. Current collector and, An electrode active material layer located on at least one side surface of the current collector, An electrode including, The electrode active material layer comprises a sulfur-carbon composite and a binder. The sulfur-carbon composite comprises a porous carbon material and a sulfur-based material. The current collector contains a specific metal, and the weight per unit of the specific metal is (mg / cm³). ２ An electrode whose value is less than or equal to the value of "0.9 × density (d)".

12. The electrode according to claim 11, wherein the specific metal is composed of one of aluminum (Al), nickel (Ni), copper (Cu), or stainless steel (SUS).

13. The electrode according to claim 11 or 12, wherein the current collector is in the form of one of a film, sheet, foil, net, porous body, foam, or nonwoven fabric.

14. It includes a positive electrode, a negative electrode, a separator sandwiched between the positive and negative electrodes, and an electrolyte. At least one of the positive electrode and the negative electrode includes a current collector and an electrode active material layer located on at least one side surface of the current collector, The electrode active material layer comprises a sulfur-carbon composite and a binder. The sulfur-carbon composite comprises a porous carbon material and a sulfur-based material. The current collector is a lithium sulfur battery containing aluminum (Al) and having a thickness of 9 μm or less.

15. The lithium sulfur battery according to claim 14, wherein the weight ratio (El / S) of the electrolyte and sulfur is 3.5 g / g or less.

16. The lithium-sulfur battery according to claim 14 or 15, wherein the energy density of the lithium-sulfur battery is 350 Wh / kg or more.

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