All-solid-state lithium secondary battery and method for manufacturing the same

Abstract

The present invention relates to an all-solid-state lithium secondary battery and a manufacturing method thereof. The all-solid-state lithium secondary battery includes a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer. The negative electrode active material layer includes a carbon structure and silver nanoparticles. The carbon structure includes a structure in which a plurality of graphene sheets are connected to each other. The plurality of graphene sheets includes two or more graphene sheets having different plane directions.

Description

[Technical Field]

[0001] The present invention relates to an all-solid-state lithium secondary battery and a method for manufacturing the same. [Background technology]

[0002] While secondary batteries have primarily been applied to small devices such as mobile devices and notebook computers, their application has recently expanded to medium and large-scale applications. For example, they are being used in fields requiring high energy and high output, such as energy storage systems (ESS) and electric vehicles (EVs).

[0003] On the other hand, there has recently been a growing interest in all-solid lithium secondary batteries. These all-solid lithium secondary batteries use a non-flammable inorganic solid electrolyte instead of a liquid electrolyte, and are attracting attention because they have higher thermal stability than lithium secondary batteries that use a liquid electrolyte, and the risk of explosion due to leakage during overcharging is very low, eliminating the need for additional equipment to prevent such explosions.

[0004] However, because all-solid-state lithium secondary batteries use a somewhat larger solid electrolyte, there are many attempts to improve the energy density of the battery. For this purpose, a metal layer that can form an alloy with lithium, such as lithium metal, is used as the negative electrode active material layer. However, when such a metal layer is used, as the lithium deposited on the metal layer ionizes and dissolves, a void is created between the solid electrolyte and the metal layer, which negatively affects the operation of the battery. In addition, during the discharge of an all-solid-state lithium secondary battery, lithium metal is deposited in a dendritic (dendrite) manner from the surface of the metal layer, which reduces the lifespan and stability of the all-solid-state lithium secondary battery.

[0005] To solve these problems, conventional methods have been used that involve placing end plates at the positive and negative electrodes to prevent void formation and applying high external pressure. However, when using end plates to apply external pressure, the volume of the all-solid-state lithium secondary battery increases excessively, leading to a decrease in the energy density of the all-solid-state lithium secondary battery.

[0006] Therefore, there is a need for new methods that can improve the lifespan and stability of all-solid-state lithium-ion batteries. [Overview of the project] [Problems that the invention aims to solve]

[0007] One problem that this invention aims to solve is to provide an all-solid-state lithium secondary battery in which lithium ions can be reduced during charging to effectively store lithium metal, thereby improving initial charge / discharge efficiency and improving lifespan characteristics.

[0008] Another problem that this invention aims to solve is to provide a price-competitive all-solid-state lithium secondary battery by reducing the content of silver nanoparticles used.

[0009] Another problem that the present invention aims to solve is to provide a method for manufacturing the all-solid-state lithium secondary battery described above. [Means for solving the problem]

[0010] According to one embodiment of the present invention, an all-solid-state lithium secondary battery is provided, comprising a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer, wherein the negative electrode active material layer comprises a carbon structure and silver nanoparticles, the carbon structure comprises a structure in which a plurality of graphene sheets are linked together, and the plurality of graphene sheets comprises two or more graphene sheets having different planar orientations from each other.

[0011] According to another embodiment of the present invention, a method for manufacturing an all-solid-state lithium secondary battery is provided, comprising: a first step of reducing silver ions in a mixture of silver ions and a carbon structure to form a dry mixed powder containing the carbon structure and silver nanoparticles disposed on the carbon structure; and a second step of forming a negative electrode active material layer on a negative electrode current collector via a negative electrode mixture containing the dry mixed powder. [Effects of the Invention]

[0012] The all-solid-state lithium secondary battery according to the present invention, having a negative electrode active material layer containing a carbon structure and silver nanoparticles as described herein, allows lithium ions to be effectively stored in the negative electrode during charging by the negative electrode active material layer through reduction and deposition. Furthermore, during discharge, the stored lithium can dissolve into lithium ions and move to the positive electrode. The carbon structure increases the mobility of the lithium ions, thereby improving the initial charge / discharge efficiency and lifespan characteristics of the battery. Additionally, by using the carbon structure, the above-mentioned lithium ion movement can be effectively achieved even with low-content silver nanoparticles, thereby increasing the price competitiveness of the manufactured all-solid-state lithium secondary battery. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic diagram illustrating an all-solid-state lithium secondary battery according to one embodiment of the present invention. [Figure 2] This is a schematic diagram illustrating an all-solid-state lithium secondary battery according to one embodiment of the present invention. [Figure 3] This is a schematic diagram illustrating the carbon structure mentioned in the present invention. [Figure 4] This is a TEM image of the carbon structure mentioned in the present invention. [Figure 5] This is an SEM image of the carbon structure mentioned in the present invention. [Figure 6] This is a TEM image of the carbon structure used in Manufacturing Example 1 of the present invention. [Figure 7]This is a TEM image of the carbon structure used in Manufacturing Example 2 of the present invention. [Figure 8] These are TEM images of the carbon structure used in Example 1 of the present invention and the silver nanoparticles placed on the carbon structure. [Figure 9] This is an SEM image of the acetylene black used in Comparative Example 1 of the present invention. [Modes for carrying out the invention]

[0014] The terms and words used herein and in the claims should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather in a manner consistent with the technical idea of ​​the present invention, in accordance with the principle that inventors may appropriately define the concepts of terms in order to best describe their invention.

[0015] The terms used herein are for illustrative purposes only and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0016] In this specification, terms such as “includes,” “equip,” or “have” specify the presence of an implemented feature, figure, step, component, or combination thereof, and should be understood not to preclude the existence or possibility of adding one or more other features, figures, steps, components, or combinations thereof.

[0017] In this specification, "specific surface area" is measured by the BET method, and specifically can be calculated from the amount of nitrogen gas adsorbed at liquid nitrogen temperature (77K) using the BELSORP-mini II manufactured by BEL Japan.

[0018] I of this specification D / I G(Ratio) can be measured from the wavelength-peak graph during Raman spectrum measurement. Specifically, after setting the baseline and adjusting the graph so that the D peak and the G peak can be distinguished, divide the D peak intensity by the G peak intensity to obtain I D / I G which can be confirmed (using built-in software, NRS-2000B, manufactured by Jasco). In the Raman spectrum, the G peak near 1590 cm -1 is caused by the E 2 vibration mode of the sp 2g bond of carbon, and the D peak near 1350 cm -1 appears when there are defects in the sp 2 bond of carbon.

[0019] In this specification, the average thickness of the graphene sheets in the carbon structure is the average value of the thicknesses of 100 graphene sheets when the manufactured carbon structure or the carbon structure of the negative electrode active material layer is observed by TEM at a magnification of ×1,000,000.

[0020] In this specification, the average longest length of the graphene sheets in the carbon structure corresponds to the average value of the longest lengths of 100 graphene sheets when the manufactured carbon structure or the carbon structure of the negative electrode active material layer containing silver nanoparticles is observed by TEM at a magnification of ×250,000. Here, the longest length refers to the longest length when assuming a line connecting one point to another point within one graphene sheet.

[0021] In this specification, the average particle size of the silver nanoparticles corresponds to the average value of the particle sizes of 100 silver nanoparticles when the manufactured carbon structure containing silver nanoparticles or the carbon structure of the negative electrode active material layer containing silver nanoparticles is observed by TEM at a magnification of ×1,000,000.

[0022] In this specification, the oxygen content of the carbon structure can be measured by the method of elemental analysis of C, H, O, and N.

[0023] The present invention will be described in detail below.

[0024] All-solid-state lithium secondary battery An all-solid-state lithium secondary battery according to one embodiment of the present invention includes a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer, wherein the negative electrode active material layer includes a carbon structure and silver nanoparticles, the carbon structure includes a structure in which a plurality of graphene sheets are linked together, and the plurality of graphene sheets may include two or more graphene sheets having different planar directions from each other.

[0025] (1) Negative electrode active material layer The all-solid-state lithium secondary battery may include a negative electrode active material layer. Specifically, the all-solid-state lithium secondary battery may include a negative electrode, which may include a negative electrode current collector and a negative electrode active material layer.

[0026] The negative electrode current collector is not particularly limited, as long as it does not cause a chemical change in the battery and is conductive. For example, the negative electrode current collector can be made of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc. Specifically, transition metals that readily adsorb carbon, such as nickel and stainless steel, can be used as the negative electrode current collector.

[0027] Referring to Figure 1, the negative electrode active material layer 100 can be arranged on at least one surface of the negative electrode current collector 110. Specifically, the negative electrode active material layer 100 can be arranged on one surface of the negative electrode current collector 110, or alternatively, on both sides of the negative electrode current collector (not shown).

[0028] The negative electrode active material layer may include a carbon structure and silver nanoparticles. Specifically, the negative electrode active material layer may consist of a carbon structure and silver nanoparticles.

[0029] 1) Carbon structure The carbon structure can serve as a transport pathway that allows lithium ions transferred from the positive electrode active material layer to be easily deposited and stored on the negative electrode current collector.

[0030] The carbon structure may include a structure in which multiple graphene sheets are linked together. Specifically, at least the secondary particles may be formed by two or more graphene sheets being directly or indirectly linked to each other. More specifically, the secondary particles may have a form in which a portion of one graphene sheet is linked to a portion of another adjacent graphene sheet.

[0031] Within the carbon structure, the plurality of graphene sheets can be linked to each other to form linear secondary particles, and more specifically, these linear secondary particles may include regions where the plurality of graphene sheets are partially aggregated. Because the carbon structure has a unique linear direct linkage structure, a robust network can be formed that enables improved electrical and ionic conductivity. This significantly improves the intercalation and transport of lithium ions.

[0032] More specifically, ordinary planar graphene has a two-dimensional arrangement with a thin thickness relative to the width of the surface. As a result, the conductive network formed within the electrode is mostly based on this two-dimensional arrangement. On the other hand, referring to Figures 4 and 5, the graphene sheets included in the carbon structure include multiple graphene sheets having an irregular arrangement. Specifically, the multiple graphene sheets included in the carbon structure can include two or more graphene sheets having different planar directions (directions perpendicular to the surface of the graphene sheet). That is, the carbon structure can have a three-dimensional arrangement formed by connecting graphene sheets arranged in various directions, and more specifically, the graphene sheets can have the three-dimensional arrangement and be arranged in a linear pattern that is long enough to have a predetermined length. Therefore, the formation of electrical and ionic conductive networks in various directions can be effectively carried out within the negative electrode active material layer, and the mobility of lithium ions can be improved. The graphene sheet may include multiple graphene sheets arranged in the same direction, but even in such cases, the graphene sheet may also include multiple graphene sheets arranged in different directions.

[0033] The carbon structure may further include connecting portions linked to at least some of the graphene sheets among a plurality of graphene sheets. In the present invention, when the carbon structure is manufactured, preliminary particles such as carbon black burst due to continuous oxidation to form the graphene sheets, and there may be portions that have not yet completely burst and maintain their original form. Here, the portions that maintain their form may correspond to the connecting portions. Therefore, the connecting portions may be in a non-graphene form, and the non-graphene form may mean a lump-like shape having a greater thickness than the graphene sheets, unlike the graphene sheets described above, and more specifically, a lump-like shape that has not completely burst.

[0034] A portion of each of the multiple graphene sheets may be directly connected to one another. Alternatively, at least some of the multiple graphene sheets may be connected to one another via the connecting portion, specifically, at least a portion of each of the multiple graphene sheets may be connected to the connecting portion. The carbon structure may also include either of the two methods of connection.

[0035] The carbon structure can be formed by oxidizing carbon black, such as acetylene black, furnace black, thermal black, channel black, and lamp black, which have a near-spherical particle morphology. Referring to the schematic diagram in Figure 3, the microstructure of carbon black (CB) can be deformed by oxidation to form particles containing multiple graphene sheets (GSCB). If the carbon black is in a secondary particle morphology, secondary particles can be formed by the aggregation of the particles containing multiple graphene sheets.

[0036] The average thickness of the graphene sheet can be 10 nm or less, specifically 0.34 nm to 10 nm, and more specifically 0.34 nm to 5 nm. When this range is met, the flexibility characteristic of the graphene sheet can be exhibited, and surface contact by the graphene sheet can be improved. As a result, a strong network for electrical conductivity and ionic conductivity can be formed, and lithium ion intercalation and transfer can be greatly improved.

[0037] The average maximum length (lateral size) of the graphene sheet can be 10 nm to 500 nm, more specifically 10 nm to 300 nm or less, more specifically 10 nm to 200 nm, and preferably 10 nm to 50 nm. The average maximum length of the graphene sheet can be controlled according to the degree of heat treatment; for example, after an oxidation treatment step, further heat treatment in an inert atmosphere can be performed to control the maximum length of the graphene sheet. When the above range is met, a strong network for electrical conductivity and ionic conductivity in various directions is formed, and the intercalation and transfer of lithium ions can be greatly improved.

[0038] The oxygen content of the carbon structure can be 1% by weight or more relative to the total weight of the carbon structure, specifically 1% to 10% by weight, and more specifically 5% to 10% by weight. When this range is met, suitable surface oxygen functional groups can form anchoring sites on the carbon structure to which silver nanoparticles can effectively adhere, and the dispersion and arrangement of the silver nanoparticles can be effectively carried out. As a result, even with a low content of silver nanoparticles, it is possible to sufficiently improve the capacity and initial charge / discharge efficiency of the all-solid-state lithium secondary battery.

[0039] The oxygen content can be achieved during the oxidation treatment of carbon black. Specifically, the oxidation treatment can form oxygen-containing functional groups on the surface of the carbon structure. The oxygen-containing functional group can be at least one selected from the group consisting of carboxyl groups, hydroxyl groups, carbonyl groups, etc. After the oxidation treatment step, the oxygen content can be further controlled by heat-treating the carbon structure in an inert atmosphere.

[0040] The carbon structure can have a higher degree of graphitization compared to carbon black before oxidation treatment. Specifically, the high structural stress generated by the surface tension of the spherical carbon black can be partially relieved by the formation of a planar graphene sheet, minimizing structural defects caused by curvature and resulting in stable sp 2 A structure can be formed, and the degree of graphitization of the manufactured conductive material can be increased.

[0041] When measuring the Raman spectrum of the carbon structure, D / I G It can be less than or equal to 2.0, specifically between 0.9 and 2.0, and more specifically between 1.1 and 1.8, for example between 1.3 and 1.8. In the Raman spectrum, at 1590 cm⁻¹ -1 The G peak in the vicinity is due to carbon sp. 2 Bond E 2g This is caused by the vibration mode, 1350cm -1 The nearby D peak is due to carbon sp. 2 This appears when a defect exists in the bond. That is, the above I D / I G When the peak ratio is met, it means that a relatively high degree of graphitization can be achieved, and as a result, when the carbon structure is used, a strong network for bioelectrical conductivity and ionic conductivity is formed within the negative electrode active material layer, and lithium ion intercalation and transport can be greatly improved.

[0042] The carbon structure can have a value of 0.2 or less calculated by the following formula 1, specifically between 0 and 0.20, specifically between 0 and 0.15, and preferably between 0 and 0.1.

[0043] [Formula 1]

number

[0044] In the above formula 1, a is the specific surface area (m²) of the carbon structure measured by the nitrogen adsorption BET method. 2 The formula is given by ( / g), where b is the amount of iodine adsorbed by the carbon structure (mg / g). If the carbon structure contains pores inside or between particles, many small nitrogen (N2) molecules can be adsorbed into the pores. On the other hand, iodine (I2), which is a relatively large molecule, is less likely to enter the pores than nitrogen, and the amount of iodine adsorbed is not large. In other words, the value given by formula 1 is large when a pore structure is present. To put it another way, if the value given by formula 1 in the carbon structure is 0.2 or less, it means that the carbon structure does not contain micropores or contains only a small amount of them. In other words, if the micropores are absent, the degree to which iodine is adsorbed and the degree to which nitrogen is adsorbed are similar, so the value given by formula 1 is small. This means that the surface of the carbon structure is smooth (free surface). Specifically, most carbon black is transformed into a hollow structure by oxidation treatment, and the structure is destroyed by continuous oxidation treatment to form a graphene sheet. Here, a void structure can be formed, and the graphene sheet can be formed in a shape that is open to the outside.

[0045] The specific surface area (m²) of the carbon structure measured by the nitrogen adsorption BET method 2 ( / g) is 200m 2 It can be 200m or more 2 / g~1100m 2 It can be / g, more specifically 300m 2 / g~1100m 2 It can be / g, preferably 500m 2 / g~900m 2 / g, for example, 800m 2 / g~900m 2 It can be / g. When the above specific surface area range is met, silver nanoparticles can be stably arranged on the surface of the carbon structure, and lithium ion intercalation and transfer can be greatly improved.

[0046] The carbon structure can be contained in the negative electrode active material layer at an amount of 50% to 98% by weight, specifically 60% to 95% by weight, and more specifically 70% to 90% by weight. When this range is met, the decrease in energy density of the all-solid-state lithium secondary battery can be minimized, and the mobility of lithium ions can be effectively improved, thereby improving the initial charge / discharge efficiency and life characteristics of the all-solid-state lithium secondary battery. Since the carbon structure is manufactured by oxidizing carbon black composed of multiple primary particles, it has a unique shape that includes multiple graphene sheets generated by the rupture of spherical primary particles. Therefore, the carbon structure possesses the properties of carbon black and graphene to some extent simultaneously, and the carbon structure can have abundant surface oxygen functional groups during the oxidation process. Therefore, the carbon structure, due to the properties of carbon black, can solve the problems of low exfoliation and poor dispersibility that ordinary graphene has, and can maintain the high electrical conductivity characteristics of a thin graphene sheet. Therefore, when the carbon structure is used, aggregation of the carbon structure within the negative electrode active material layer can be suppressed, a strong network for electrical conductivity and ionic conductivity can be formed, and lithium ion intercalation and transfer can be greatly improved.

[0047] 2) Silver nanoparticles Because the aforementioned silver nanoparticles possess lithium-affinity properties, they can easily form alloys with lithium ions. As a result, the silver nanoparticles can form alloys with lithium ions transmitted from the positive electrode active material layer, thereby promoting the intercalation and diffusion of lithium ions into the negative electrode active material layer.

[0048] The silver nanoparticles may contain silver (Ag). Furthermore, the silver nanoparticles may further contain at least one selected from the group consisting of gold, platinum, palladium, silicon, aluminum, vizmus, tin, indium, and zinc. In contrast, the silver nanoparticles may consist solely of silver. The silver nanoparticles may be a solid phase.

[0049] The silver nanoparticles can be arranged on the surface of the carbon structure. Specifically, the silver nanoparticles can be formed by the reduction of silver ions in an aqueous silver ion solution on the surface of the carbon structure, thereby allowing the silver nanoparticles to be arranged on the surface of the carbon structure. Alternatively, the silver nanoparticles can be mixed with the carbon structure in powder form, and the silver nanoparticles can then be arranged on the surface of the carbon structure.

[0050] The average particle size of the silver nanoparticles can be 1 nm to 100 nm, specifically 1 nm to 50 nm, more specifically 1 nm to 30 nm, for example, 1 nm to 5 nm. When this range is met, the silver nanoparticles can be effectively dispersed within the negative electrode active material layer, and lithium ion intercalation and diffusion can be facilitated even at low levels of silver nanoparticle content. Furthermore, the initial efficiency and lifespan characteristics of the battery can be improved.

[0051] In the negative electrode active material layer, the silver nanoparticles can be present in an amount of 1% to 40% by weight relative to the total weight of the carbon structure and the silver nanoparticles, specifically 3% to 30% by weight, more specifically 5% to 20% by weight, for example, 7% to 10% by weight. When this range is met, lithium ions transferred to the positive electrode active material layer can be effectively alloyed with the silver nanoparticles, improving the electrochemical properties of the all-solid-state lithium secondary battery. Furthermore, by using silver nanoparticles with a slightly lower content, the energy density and price competitiveness of the all-solid-state lithium secondary battery can be improved.

[0052] In particular, the fact that the silver nanoparticle content can be 10% by weight or less, specifically 7% to 10% by weight, is due to the negative electrode active material layer containing the carbon structure. Alloying with lithium-affinity silver nanoparticles promotes the intercalation and diffusion of lithium ions into the negative electrode. In particular, the carbon structure described in this invention has a strong three-dimensional network and oxygen functional groups on its surface, which allows for effective dispersion and arrangement of silver nanoparticles. As a result, even with a small amount of silver nanoparticles, it is possible to sufficiently improve the capacity and initial charge / discharge efficiency of the all-solid-state lithium secondary battery.

[0053] Within the negative electrode active material layer, the weight ratio of the carbon structure to the silver nanoparticles can be 99:1 to 60:40, more specifically 97:3 to 70:30, and more specifically 95:5 to 80:20. When this is satisfied, the capacity and initial charge / discharge efficiency of the all-solid-state lithium secondary battery can be more effectively improved.

[0054] The loading amount of the negative electrode active material layer is 0.1 mg / cm³. 2 ~2.0 mg / cm³ 2 It can be 0.3 mg / cm³ 2 ~1.8 mg / cm³ 2 More specifically, 0.5 mg / cm³ 2 ~1.6 mg / cm³ 2 This is possible. When the above range is satisfied, the energy density is not hindered by the increase in the thickness of the negative electrode, and the effect of improving the initial efficiency and lifespan of the battery can be maximized.

[0055] The thickness of the negative electrode active material layer can be 1 μm to 100 μm, more specifically 1 μm to 50 μm, and more specifically 1 μm to 20 μm. When this range is satisfied, the energy density is not hindered by the increase in the thickness of the negative electrode, and the effect of improving the initial efficiency and lifespan of the battery can be maximized.

[0056] 3) Negative electrode binder The negative electrode active material layer may further contain a negative electrode binder. The negative electrode binder may include at least one selected from the group consisting of polyvinylidene fluoride (PVdF), polyvinyl alcohol (PVA), carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, polyvinylpyrrolidone, polytetrafluoroethylene (PTFE), polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), styrene-butadiene rubber (SBR), and fluororubber.

[0057] The negative electrode binder can be contained in the negative electrode active material layer in an amount of 1% to 20% by weight, more specifically 1% to 15% by weight, and more specifically 1% to 10% by weight. When this range is met, the resistance of the negative electrode can be kept at a low level, the mechanical properties of the negative electrode can be improved, and lithium ion intercalation and diffusion can be further promoted.

[0058] Depending on the circumstances, the negative electrode active material layer may further contain at least one of lithium ions, lithium, and an alloy of lithium and silver nanoparticles. Specifically, when the all-solid-state lithium secondary battery is in operation, lithium ions transmitted from the positive electrode active material layer may cause at least one of lithium ions, lithium, and an alloy of lithium and silver nanoparticles to be present in the negative electrode active material layer.

[0059] (2) Positive electrode active material layer The all-solid-state lithium secondary battery may include a positive electrode active material layer. Specifically, the all-solid-state lithium secondary battery may include a positive electrode, and the positive electrode may include a positive electrode active material layer or consist of the positive electrode active material layer.

[0060] The positive electrode may include a positive electrode current collector. The positive electrode current collector is not particularly limited as long as it does not cause a chemical change to the positive electrode or battery and has high conductivity, and may include, for example, at least one selected from the group consisting of stainless steel, copper, aluminum, nickel, titanium, and calcined carbon, and specifically may include aluminum. The positive electrode current collector may further include a carbon-based conductive material and a binder, and a primer layer coated on the surface of the positive electrode current collector. This can greatly improve the bonding force and electrical conductivity between the positive electrode active material layer and the current collector.

[0061] The positive electrode active material layer can be arranged on at least one surface of the positive electrode current collector. Specifically, the positive electrode active material layer can be arranged on one or both surfaces of the positive electrode current collector.

[0062] The positive electrode active material layer may contain a positive electrode active material.

[0063] The positive electrode active material is a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; chemical formula Li 1+x Mn 2-x Lithium manganese oxides including O4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, LiMn2O4, LiMnO2, etc.; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, Cu2V2O7, etc.; chemical formula LiNi 1-x M x Ni-site type lithium nickel oxide represented by O2 (where M = Co, Mn, Al, Cu, Fe, P, Mg, Ca, Zr, Ti, Ru, Nb, W, B, Si, Na, K, Mo, V, or Ga, and x = 0.01 to 0.3); chemical formula LiMn 1-x M xO2 (where M = Co, Ni, Fe, Cr, Zn or Ta, and x = 0.01 - 0.1) or lithium manganese composite oxide represented by Li2Mn3MO8 (where M = Fe, Co, Ni, Cu or Zn); LiNi x Mn 2-x spinel-structured lithium manganese composite oxide represented by O4; LiMn2O4 in which part of Li in the chemical formula is substituted with alkaline earth metal ions; disulfide compound; LiMn x Fe 1-x PO4 (0 ≦ x ≦ 0.9); It can contain Fe2(MoO4)3, etc. However, it is not limited to only these.

[0064] The positive electrode active material can contain Li 1+x M y O 2+z and M can be at least one element selected from the group consisting of Ni, Co, Mn, Fe, P, Al, Mg, Ca, Zr, Zn, Ti, Ru, Nb, W, B, Si, Na, K, Mo, and V, and 0 ≦ x ≦ 5, 0 < y ≦ 2, 0 ≦ z ≦ 2. Specifically, the Li 1+x M y O 2+z is LiCoO2, LiNiO2, LiMnO2, Li[Ni 0.5 C o0.3 Mn 0.2 O2, Li[Ni 0.6 Co 0.2 Mn 0.2 O2, Li[Ni 0.7 Co 0.1 Mn 0.2 O2, Li[Ni 0.8 Co 0.1 Mn 0.1 O2, Li[Ni 0.9 Co<00000,66>Mn 0.05 O2, LiMn2O4, LiFePO 4、0.5 Li2MnO3·0.5Li[Mn 0.4 Ni 0.3 Co 0.3 O2 and can contain at least one selected from the group consisting of. Preferably, the Li 1+x My O 2+z is one of the following: Li[Ni 0.6 Co 0.2 Mn 0.2 O2, Li[Ni 0.7 Co 0.1 Mn 0.2 O2, Li[Ni 0.8 Co 0.1 Mn 0.1 O2, Li[Ni 0.9 Co 0.05 Mn 0.05 O2. Since the positive electrode active material contains Li 1+x M y O 2+z lithium can be sufficiently supplied to the negative electrode, and Li 1+x M y O 2+z does not cause a decrease in the overall performance of the battery and shows electrochemical activity after the first cycle, so the loss of battery capacity due to the irreversible capacity of the negative electrode can be eliminated. The Li 1+x M y O 2+z can be in the form of secondary particles formed by binding or granulating primary particles, or, alternatively, can be in the form of single particles.

[0065] The positive electrode active material can be contained in the positive electrode active material layer at 50% to 95% by weight, specifically 60% to 90% by weight.

[0066] The positive electrode active material layer can further contain a solid electrolyte.

[0067] Specifically, the solid electrolyte can contain at least one selected from the group consisting of polymer solid electrolytes, oxide-based solid electrolytes, sulfide-based solid electrolytes, and halide-based solid electrolytes.

[0068] The polymer solid electrolyte can be a composite of a lithium salt and a polymer resin. Specifically, the polymer solid electrolyte can be formed by adding a polymer resin to a solvated lithium salt. Specifically, the ionic conductivity of the polymer solid electrolyte is about 1×10 -7 S / cm or more, preferably about 1×10 -3 S / cm or more.

[0069] Examples of the polymer resin include polyether-based polymers, polycarbonate-based polymers, acrylate-based polymers, polysiloxane-based polymers, phosphazene-based polymers, polyethylene derivatives, alkylene oxide derivatives such as polyethylene oxide, phosphate ester polymers, polyaditization lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, polymers containing ionic dissociation groups, etc., and one or more of these can be included. Further, as the polymer resin, the polymer solid electrolyte can include, for example, branched copolymers obtained by copolymerizing amorphous polymers such as PMMA, polycarbonate, polysiloxane (pdms) and / or phosphazene as comonomers on a PEO (polyethylene oxide) main chain, comb-like polymer resins, and crosslinked polymer resins, and one or more of these can be included.

[0070] The lithium salt is ionizable and can be represented by Li + X - Although not particularly limited, examples of the anion of such a lithium salt include F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF -(CF3)6P - CF3SO3 - CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - CF3CF2(CF3)2CO - (CF3SO2) 2CH - (SF5)3C - (CF3SO2)3C - CF3(CF2)7SO3 - CF3CO2 - CH3CO2 - SCN - , (CF3CF2SO2)2N - Examples include the following.

[0071] The oxide-based solid electrolyte contains oxygen (O) and may have the ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table. Non-limiting examples include LLTO compounds, Li6La2CaTa2O 12 Li6La2ANb2O 12 (A is Ca or Sr), Li2Nd3TeSbO 12 Li3BO 2.5 N 0.5 , Li9SiAlO8, LAGP compounds, LATP compounds, Li 1+x Ti 2-x Al x Si y (PO4) 3-y (Here, 0≦x≦1, 0≦y≦1), LiAl x Zr 2-x (PO4)3 (where 0≦x≦1, 0≦y≦1), LiTi x Zr 2-x (PO4)3 (where 0 ≤ x ≤ 1, 0 ≤ y ≤ 1), may include one or more compounds selected from LISICON compounds, LIPON compounds, perovskite compounds, NASICON compounds, and LLZO compounds. However, it is not limited to these.

[0072] The sulfide-based solid electrolyte contains sulfur (S) and has the ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, and may include Li-PS glass or Li-PS glass ceramic. Non-limiting examples of such sulfide-based solid electrolytes include Li6PS5Cl, Li6PS5Br, Li6PS5I, Li2S-P2S5, Li2S-LiI-P2S5, Li2S-LiI-Li2O-P2S5, Li2S-LiBr-P2S5, Li2S-Li2O-P2S5, Li2S-Li3PO4-P2S5, Li2S-P2S5-P2O5, Li2S-P2S5-SiS2, Li2S-P2S5-SnS, Li2S-P2S5-Al2S3, Li2S-GeS2, Li2S-GeS2-ZnS, and may include one or more of these. However, this is not the only example.

[0073] The halide-based solid electrolyte may, but is not limited to, include at least one of Li3YCl6 and Li3YBr6.

[0074] The solid electrolyte can be contained in the positive electrode active material layer at an amount of 5% to 50% by weight, specifically 10% to 30% by weight.

[0075] The positive electrode active material layer may further contain a positive electrode conductive material.

[0076] The positive electrode conductive material is not particularly limited as long as it does not cause a chemical change in the positive electrode or battery and is conductive. For example, the positive electrode conductive material may include one or more mixtures of conductive materials selected from graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; graphene; conductive fibers such as carbon nanofibers and carbon nanotubes; carbon fluoride; metal powders such as aluminum and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0077] The positive electrode conductive material can be contained in the positive electrode active material layer in an amount of 1% to 30% by weight.

[0078] The positive electrode active material layer may further contain a positive electrode binder.

[0079] The positive electrode binder is not particularly limited as long as it contains components that are useful for bonding the positive electrode active material, conductive material, etc., and for bonding to the current collector. Specifically, it may include at least one selected from the group consisting of polyvinylidene fluoride (PVdF), polyvinyl alcohol (PVA), carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, polyvinylpyrrolidone, polytetrafluoroethylene (PTFE), polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), styrene-butadiene rubber (SBR), and fluororubber.

[0080] The positive electrode binder can be contained in the positive electrode active material layer in an amount of 1% to 30% by weight.

[0081] The positive electrode active material layer may contain one or more additives as needed, such as oxidation stabilizing additives, reduction stabilizing additives, flame retardants, heat stabilizers, and antifogging agents.

[0082] (3) Solid electrolyte layer The all-solid-state lithium secondary battery may include a solid electrolyte layer.

[0083] The solid electrolyte layer can perform both an insulating role and function as an ion-conducting channel in an all-solid-state lithium secondary battery.

[0084] Referring to Figure 2, the solid electrolyte layer 300 can be placed between the negative electrode active material layer 100 and the positive electrode active material layer 200.

[0085] The solid electrolyte layer 300 includes the solid electrolyte. Specifically, the solid electrolyte may include at least one selected from the group consisting of polymer solid electrolytes, oxide-based solid electrolytes, and sulfide-based solid electrolytes.

[0086] The polymer solid electrolyte can be a composite of a lithium salt and a polymer resin. Specifically, the polymer solid electrolyte can be formed by adding a polymer resin to a solventized lithium salt. Specifically, the ionic conductivity of the polymer solid electrolyte is about 1 × 10⁻⁶. -7 S / cm or more, preferably about 1 × 10 -3 It can be S / cm or higher.

[0087] The polymer resins include polyether polymers, polycarbonate polymers, acrylate polymers, polysiloxane polymers, phosphazene polymers, polyethylene derivatives, alkylene oxide derivatives such as polyethylene oxide, phosphate ester polymers, polyagitation lysine, polyester sulfides, polyvinyl alcohol, polyvinylidene fluoride, and polymers containing ionic dissociation groups, and one or more of these may be included. The polymer solid electrolytes may also include branched copolymers obtained by copolymerizing a PEO (polyethylene oxide) main chain with amorphous polymers such as PMMA, polycarbonate, polysiloxane (pdms), and / or phosphazene as copolymerizers, comb-like polymers, and crosslinked polymers, and one or more of these may be included.

[0088] The aforementioned lithium salt is ionizable, Li + X - It can be represented as follows. There are no particular limitations on the anion of such a lithium salt, but F - Cl - , Br - , I - NO3 - , N(CN)2 - BF4- ClO4 - PF6 - (CF3)2PF4 - (CF3)3PF3 - (CF3)4PF2 - (CF3)5PF - (CF3)6P - CF3SO3 - CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - CF3CF2(CF3)2CO - (CF3SO2) 2CH - (SF5)3C - (CF3SO2)3C - CF3(CF2)7SO3 - CF3CO2 - CH3CO2 - SCN - , (CF3CF2SO2)2N - Examples include the following.

[0089] The oxide-based solid electrolyte contains oxygen (O) and may have the ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table. Non-limiting examples include LLOP compounds, Li6La2CaTa2O 12 Li6La2ANb2O 12 (A is Ca or Sr), Li2Nd3TeSbO 12 Li3BO 2.5 N 0.5 , Li9SiAlO8, LAGP compounds, LATP compounds, Li 1+x Ti 2-x Al x Si y (PO4) 3-y (Here, 0≦x≦1, 0≦y≦1), LiAl x Zr 2-x (PO4)3 (where 0≦x≦1, 0≦y≦1), LiTi x Zr 2-x(PO4)3 (where 0 ≤ x ≤ 1, 0 ≤ y ≤ 1), may include one or more compounds selected from LISICON compounds, LIPON compounds, perovskite compounds, NASICON compounds, and LLZO compounds. However, it is not limited to these.

[0090] The sulfide-based solid electrolyte contains sulfur (S) and has the ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, and may include Li-PS glass or Li-PS glass ceramic. Non-limiting examples of such sulfide-based solid electrolytes include Li6PS5Cl, Li6PS5Br, Li6PS5I, Li2S-P2S5, Li2S-LiI-P2S5, Li2S-LiI-Li2O-P2S5, Li2S-LiBr-P2S5, Li2S-Li2O-P2S5, Li2S-Li3PO4-P2S5, Li2S-P2S5-P2O5, Li2S-P2S5-SiS2, Li2S-P2S5-SnS, Li2S-P2S5-Al2S3, Li2S-GeS2, Li2S-GeS2-ZnS, and may include one or more of these. However, this is not the only example.

[0091] The solid electrolyte layer may further include a binder for the solid electrolyte layer. The binder for the solid electrolyte layer may be introduced for bonding between solid electrolytes and for bonding the solid electrolyte layer to battery elements (e.g., positive electrode, negative electrode, etc.) laminated on both sides of the solid electrolyte layer.

[0092] The material for the binder for the solid electrolyte layer is not particularly limited and can be appropriately selected from the range of components used as binders for solid electrolytes in all-solid-state lithium secondary batteries. Specifically, the binder for the solid electrolyte layer may include at least one selected from the group consisting of polyvinylidene fluoride (PVdF), polyvinyl alcohol (PVA), carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), styrene-butadiene rubber (SBR), styrene-butadiene styrene block copolymer (SBS), nitrile butadiene rubber (NBR), fluororubber, and acrylic binders.

[0093] The thickness of the solid electrolyte layer can be 10 μm to 90 μm, specifically 20 μm to 80 μm, taking into consideration ionic conductivity, physical strength, and the energy density of the battery to which it is applied. Furthermore, the tensile strength of the solid electrolyte layer is 500 kgf / cm². 2 ~2,000 kgf / cm² 2 It can be such. Furthermore, the porosity of the solid electrolyte layer 300 can be 15% or less, or about 10% or less.

[0094] The all-solid-state lithium secondary battery may further include a metal layer. Referring to Figure 2, the all-solid-state lithium secondary battery 10 may further include a negative electrode current collector 110 and a metal layer 120 located between the negative electrode active material layer 100 and the negative electrode current collector 110 in the charged state. The metal layer 120 may contain lithium, and more specifically, may consist of lithium.

[0095] The aforementioned metal layer may refer to a layer formed when lithium ions transferred from the positive electrode active material layer are stored on the negative electrode active material layer and the negative electrode current collector during charging of the all-solid-state lithium secondary battery. Therefore, the aforementioned metal layer becomes clearly visible during charging.

[0096] The aforementioned metal layer is observed during the discharge process, but theoretically it may not be observed during a complete discharge.

[0097] The present invention is significant in all-solid-state lithium secondary batteries, but may be less significant in lithium secondary batteries using liquid electrolytes. For example, when using a liquid electrolyte, lithium stored in the negative electrode (e.g., in the form of a metal layer) may remain exposed to the liquid electrolyte, making it difficult to completely store lithium in the negative electrode.

[0098] Manufacturing method for all-solid-state lithium secondary batteries A method for manufacturing an all-solid-state lithium secondary battery according to another embodiment of the present invention may include a first step of reducing silver ions in a mixture of silver ions and a carbon structure to form a dry mixed powder containing the carbon structure and silver nanoparticles disposed on the carbon structure, and a second step of forming a negative electrode active material layer on a negative electrode current collector via a negative electrode slurry containing the dry mixed powder. Here, the all-solid-state lithium secondary battery may be the same as the all-solid-state lithium secondary battery of the above-described embodiment. Furthermore, the negative electrode active material layer may be the same as the negative electrode active material layer of the above-described embodiment.

[0099] (1) Step 1 In the first step, a dry mixed powder is formed containing the carbon structure and silver nanoparticles arranged on the carbon structure. The dry mixed powder can be produced by mixing powdered silver nanoparticles and powdered carbon structure. Alternatively, the dry mixed powder can also be produced by mixing the carbon structure with a silver ion solution and then reducing the silver nanoions. Various methods can be used to reduce the silver nanoparticles, such as chemical reduction, electrochemical reduction, photochemical reduction, laser reduction, ultrasonic reduction, and sputtering. Preferably, a chemical reduction method using a polyol process or a microwave-assisted polyol method using microwaves can be used.

[0100] In the polyol process described above, the silver ion solution may contain a solvent and a stabilizer along with the silver ions. The solvent may be ethylene glycol, and the stabilizer may be polyvinylpyrrolidone, but is not necessarily limited to these.

[0101] The molar concentration of silver ions in the silver ion solution can be 1 mM to 1,000 mM, more specifically 1 mM to 500 mM, and more specifically 1 mM to 300 mM. When this molar concentration range is met, the content and size of the formed silver nanoparticles can be adjusted to an appropriate level, and the capacity, initial charge / discharge efficiency, and life characteristics of the all-solid-state lithium secondary battery can be effectively controlled.

[0102] In the first step, the reduction of the silver ions may include reacting the mixed solution at 100°C to 500°C, and more specifically, at 100°C to 300°C. That is, the reaction can be carried out by heat treatment at the above temperatures. This allows for the proper reduction of the silver ions and the acquisition of silver nanoparticles of a suitable size. Furthermore, in the above process, the silver nanoparticles can be arranged on the surface of the carbon structure.

[0103] Reducing the silver ions may include adjusting the pH of the mixed solution. Specifically, the mixed solution can be adjusted to have an acidity of pH 8 to pH 14, more specifically pH 9 to pH 13. This allows the silver ions to be properly reduced and silver nanoparticles of a suitable size to be obtained.

[0104] Next, the solid components of the mixed solution can be washed and then dried to obtain the dried mixed powder.

[0105] In the dry mixed powder, the weight ratio of the carbon structure to the silver nanoparticles can be 99:1 to 60:40, more specifically 97:3 to 70:30, and more specifically 95:5 to 80:20. When this is satisfied, the capacity and initial charge / discharge efficiency of the all-solid-state lithium secondary battery can be more effectively improved.

[0106] (2) Step 2 In the second step, a negative electrode active material layer can be formed on the negative electrode current collector by a negative electrode slurry containing the dry mixed powder. The negative electrode slurry may contain the dry mixed powder and a solvent for the negative electrode slurry.

[0107] The solvent for the negative electrode slurry can be selected from the group consisting of water, N-methylpyrrolidone, and the like, but is not necessarily limited to these.

[0108] The negative electrode slurry may further include a negative electrode binder. The negative electrode binder may be the same as the negative electrode binder in the above-described embodiment.

[0109] In the second step, the negative electrode slurry can be applied to the negative electrode current collector and dried to form the negative electrode active material layer. Depending on the circumstances, a pressurizing step may be added along with the application and drying step.

[0110] On the other hand, the method for manufacturing the all-solid-state lithium secondary battery may further include a step of forming the carbon structure before the first step.

[0111] The step of forming the carbon structure includes the steps of preparing preliminary particles and oxidizing and deforming the preliminary particles, the step of oxidizing and deforming the preliminary particles may include at least one of a) first heat treatment of the preliminary particles in an oxygen atmosphere or air atmosphere at a temperature of 200°C to 800°C, and b) reacting the preliminary particles with acidic vapor at 120°C to 300°C.

[0112] In the step of preparing the preliminary particles, the preliminary particles may be carbon black. Specifically, the preliminary particles may be at least one selected from the group consisting of acetylene black, furnace black, thermal black, channel black, and lamp black. More specifically, the preliminary particles may be acetylene black, which is produced at the highest temperature and basically has excellent graphitization.

[0113] The step of preparing the preliminary particles may include thermal decomposition of acetylene gas, by which carbon black, specifically acetylene black, can be formed. The acetylene gas may be high-purity acetylene gas, specifically acetylene gas with a purity of 95% or higher, and more specifically acetylene gas with a purity of 98% or higher.

[0114] The aforementioned thermal decomposition can decompose the acetylene gas at a temperature of 1500°C or higher, specifically 1500°C to 2200°C, and more specifically 1500°C to 2000°C. When this range is met, the degree of graphitization of the produced preliminary particles can be high, and consequently, the degree of graphitization of the produced secondary particles can also be high. Therefore, the electrical conductivity of the conductive material can be improved.

[0115] The aforementioned preliminary particles can be carbon black, but acetylene black is preferred for the following reasons. The graphene sheet contained in the carbon structure can be formed by deforming the surface of the preliminary particles through oxidation treatment. The acetylene black formed by thermal decomposition has a high degree of graphitization on its surface. Therefore, compared to oxidizing other carbon blacks that always contain some oxygen functional groups on their surface, the structure of the graphene sheet can be formed more smoothly when oxidizing the acetylene black.

[0116] The aforementioned pyrolysis can be carried out instantaneously by adjusting the internal temperature of the reactor within the aforementioned temperature range, then introducing acetylene gas into the reactor. Furthermore, by introducing air, oxygen, H2O, etc., during this process, the density of the conductive material, oxygen functional groups, etc., can be controlled, and the linkage structure within the carbon structure can be controlled.

[0117] The step of oxidizing and deforming the preliminary particles may include at least one of the following: a) performing a first heat treatment on the preliminary particles in an oxygen or air atmosphere at a heat treatment temperature of 200°C to 800°C (step a); and b) reacting the preliminary particles with acidic vapor at 120°C to 300°C (step b).

[0118] In step a, the oxygen atmosphere or air atmosphere can be formed by introducing oxygen or air into the reactor containing the preliminary particles. Specifically, during the first heat treatment, a graphene sheet structure can be formed in the reactor by an oxidation process depending on the appropriate amount and rate of oxygen or air inflow, the reaction temperature, and the reaction time. Furthermore, the conditions of the oxidation process may vary depending on differences in the density of the preliminary particles, the content of oxygen functional groups, etc.

[0119] In step a, the first heat treatment can be carried out in a reactor containing the preliminary particles, by adjusting the temperature of the reactor. The first heat treatment can be carried out at a heat treatment temperature of 200°C to 800°C, specifically at a heat treatment temperature of 200°C to 450°C. When this temperature range is met, excessive and rapid oxidation of the preliminary particles can be prevented, and a graphene sheet of a preferred size can be formed. The first heat treatment can be carried out for 1 to 50 hours.

[0120] In step b, the preliminary particles can react with acidic vapor to oxidize and form a graphene sheet. Specifically, the acidic vapor can be vapor derived from an acidic solution such as HCl or HNO3. The temperature of the acidic vapor reacting with the preliminary particles can be between 120°C and 300°C.

[0121] After the step of oxidizing and deforming the preliminary particles, a second heat treatment in an inert atmosphere may be performed to increase the size of the formed graphene sheet. Specifically, the method for producing the carbon structure may further include the step of oxidizing and deforming the preliminary particles, followed by a second heat treatment of the oxidized and deformed preliminary particles in an inert atmosphere at a temperature of 500°C or higher. Here, the inert atmosphere can be formed by any one gas selected from the group consisting of vacuum, helium, argon, and nitrogen. The second heat treatment temperature can be 500°C or higher, specifically 500°C to 2800°C, and more specifically 600°C to 1600°C.

[0122] The mechanism by which the carbon structure described in this invention is formed is as follows. During the production of the carbon structure, spherical or linear carbon black, specifically acetylene black, in which the average size of spherical primary particles is 50 nm or less and the primary particles share a common structure, is subjected to oxidation treatment under specific conditions. In this case, the penetration of an oxidizing agent such as oxygen or acidic vapor and the oxidation reaction occur from defect portions such as grain boundaries and dislocations present in the fine unit structure of the carbon black. When the oxidation treatment is performed for a predetermined time within the temperature range mentioned in the production method, the oxidizing agent penetrates to the microstructure inside the carbon black and oxidation occurs. Here, in order to relieve the structural stress of the microstructure inside the primary particles, which has a radius of curvature larger than the radius of curvature of the spherical primary particle surface, the oxidation reaction is carried out rapidly inside. As a result, the carbon inside is oxidized to gases such as CO, CO2, and CH4, and the primary particles change into a hollow type. The continuous oxidation treatment destroys the surface structure of the hollow primary particles and almost completely eliminates the structural stress remaining in the spherical primary particles, and in this process, the graphene sheet appears. Therefore, the smaller the average size of the carbon black primary particles, the lower the internal density of the particles, and the higher the oxygen functional group content inside the primary particles rather than on the surface, the more the deformation process can be accelerated. Furthermore, step a is more preferable to step b in that it can further accelerate the deformation process.

[0123] Furthermore, the present invention provides a battery module including the all-solid-state lithium secondary battery as a unit battery, a battery pack including the battery module, and a device including the battery pack as a power source. Specific examples of the device include, but are not limited to, power tools powered by a battery-powered motor; 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; urban air mobility (UAMs); and power storage systems.

[0124] The present invention will be further described below with reference to examples, but these examples are for illustrative purposes only and the scope of the present invention is not limited to these examples.

[0125] Examples and Comparative Examples Manufacturing Example 1: Formation of Carbon Structures (1) Formation of preliminary particles (acetylene black) Acetylene black was formed by instantaneously injecting 98% pure acetylene gas into a reactor with an internal temperature of 2000°C and causing thermal decomposition.

[0126] (2) Production of secondary particles Next, the internal temperature of the reactor containing the acetylene black was raised to 250°C, and then the oxidation treatment was carried out for 30 hours while oxygen was introduced. As a result, a carbon structure was obtained that contained a linear chain of numerous graphene sheets linked together, with an average longest length (lateral size) of 41 nm, and the graphene sheets were arranged in different directions from one another. (See Figures 5 and 6)

[0127] Manufacturing Example 2: Manufacturing of Carbon Structures The carbon structure used in Manufacturing Example 1 was subjected to an additional heat treatment at 900°C for 1 hour in an inert atmosphere to obtain a carbon structure containing multiple graphene sheets linked together in a linear structure, with an average longest length (lateral size) of 65 nm, and in which the graphene sheets are arranged in different directions from one another (see Figure 7).

[0128] Example 1: Manufacturing of an all-solid-state lithium secondary battery (1) Manufacturing of the negative electrode A carbon structure, AgNO3, and polyvinylpyrrolidone were mixed in ethylene glycol solvent, and the pH was adjusted to a range of 8-14 via a NaOH pellet. The mixture was then stirred for 24 hours to produce a mixed solution. The mixed solution was subjected to Ar bubbling using an ultrasonic device and then heated and cooled repeatedly in the Continuous Wave Mode (2.45 GHz, 500 W) of a microwave reactor (LG Electronics) for 10 seconds, 20 seconds, 30 seconds, 1 minute, 2 minutes, and 5 minutes. This reduced the silver ions and arranged silver nanoparticles on the carbon structure. Next, the mixture was filtered and washed with an acetone solution and dried in a vacuum oven at 100°C for 24 hours to obtain a dried mixed powder containing the carbon structure and the silver nanoparticles arranged on the carbon structure (see Figure 8). The amount of silver nanoparticles supported was 10% by weight, and the average particle size of the silver nanoparticles was 1 nm.

[0129] The dry mixed powder and polyvinylidene fluoride were added to N-methylpyrrolidone (NMP) as a solvent and stirred to form a negative electrode slurry. In the negative electrode slurry, the weight ratio of the dry mixed powder to the polyvinylidene fluoride was 93:7.

[0130] The negative electrode slurry was applied to a stainless steel current collector (thickness: 15 μm), dried in a vacuum oven at 100°C for 12 hours, and then rolled using a roll press to produce a negative electrode including a stainless steel current collector and a negative electrode active material layer located on the stainless steel current collector. The thickness of the negative electrode active material layer was 10 μm, and the loading amount of the negative electrode active material layer was 1 mg / cm². 2 That was the case.

[0131] (2) Manufacturing of the positive electrode Li[Ni 0.82 Co 0.14 Mn 0.04 O2, Li6PS6Cl as a solid electrolyte, carbon nanofiber (VGCF, manufactured by Showa Denko) as a conductive material, and polytetrafluoroethylene as a binder were sequentially added to a container in a weight ratio of 77:20:1:2. After each component was added, the mixture was mixed using a Lab Blender for 30 seconds at 10,000 RPM for 10 repetitions to produce the cathode mixture. The mixture was then subjected to high-shear mixing for 5 minutes at 100°C and 100 rpm using a Twin Screw Kneader (manufactured by LG Electronics) to produce the cathode mixture. The cathode mixture was then used to produce a 200 μm thick free-standing film using a Two Roll Mill (manufactured by Inoue) at 100°C. Next, the film was placed on one surface of an aluminum current collector (thickness: 20 μm) coated with a primer, and the film was bonded to the current collector using a lamination roll maintained at 120°C to produce a positive electrode.

[0132] (3) Manufacturing of all-solid-state lithium secondary batteries A solid electrolyte slurry was prepared by mixing Li6PS6Cl solid electrolyte and nitrile butadiene rubber (NBR) with xylene as a solvent, and then mixing it with zirconia balls at 2,000 RPM for 1 minute 10 times in a Thinky Mixer. This slurry was coated onto a PET film release paper and dried in a vacuum oven at 45°C for 6 hours to prepare a solid electrolyte layer. Here, the weight ratio of Li6PS6Cl solid electrolyte to nitrile butadiene rubber (NBR) was 95:5 wt%, and the thickness of the prepared solid electrolyte layer was 100 μm.

[0133] After manufacturing an assembly by placing the solid electrolyte layer between the negative electrode and the positive electrode, the assembly was placed in a pouch and sealed. Next, the pouch was fixed on an Al plate, and then subjected to pressurization treatment at 500 MPa for 30 minutes using a warm isostatic pressure device to manufacture the all-solid-state lithium secondary battery of Example 1.

[0134] Examples 2-6: Manufacturing of all-solid-state lithium secondary batteries An all-solid-state lithium secondary battery was manufactured using the same method as in Example 1, except that the content and average particle size of silver nanoparticles were adjusted as shown in Table 1 by controlling the weight ratio of carbon structure, AgNO3, and polyvinylidenepyrrolidone, the pH value, and the reaction conditions in the microwave reactor.

[0135] Comparative Examples 1-2: Manufacturing of All-Solid-State Lithium-ion Secondary Batteries (1) Manufacturing of the negative electrode An all-solid-state lithium secondary battery was manufactured in the same manner as in Example 1, except that carbon black (PRINTEX, Orion Engineered Carbons) (see Figure 9) was used instead of the carbon structure, and the content and average particle size of silver nanoparticles were adjusted as shown in Table 1 by controlling the weight ratio of carbon black, AgNO3, and polyvinylidenepyrrolidone, the pH value, and the reaction conditions in the microwave reactor.

[0136] Comparative Example 3: Manufacturing of Lithium-ion Rechargeable Batteries (1) Manufacturing of negative and positive electrodes The negative and positive electrodes were manufactured using the same method as in Example 1.

[0137] (3) Manufacturing of lithium secondary batteries Next, a monocell was manufactured by placing the manufactured negative electrode and positive electrode with a 15 μm thick polyethylene separator between them. Then, an electrolyte (ethylene carbonate (EC) / ethyl methyl carbonate (EMC) = 1 / 2 (volume ratio), lithium hexafluorophosphate (LiPF 61 mol)) was injected into the monocell to manufacture a lithium secondary battery.

[0138] Comparative Example 4: Manufacturing of Lithium-ion Rechargeable Batteries A lithium secondary battery was manufactured using the same method as in Comparative Example 3, except that the content and average particle size of silver nanoparticles were adjusted as shown in Table 1 by controlling the weight ratio of carbon structure, AgNO3, and polyvinylidenepyrrolidone, the pH value, and the reaction conditions in the microwave reactor.

[0139] [Table 1]

[0140] [Table 2]

[0141] The aforementioned "specific surface area" was measured by the BET method, specifically calculated from the amount of nitrogen gas adsorbed at liquid nitrogen temperature (77K) using a BELSORP-mini II manufactured by BEL Japan. D / I G The (ratio) was determined from the wavelength-peak graph during Raman spectral measurement. Specifically, after setting a baseline and fitting the graph so that the D peak and G peak could be distinguished, the D peak intensity was divided by the G peak intensity to obtain I. D / I G This was confirmed (using embedded software, NRS-2000B, manufactured by Jasco).

[0142] The average thickness of the graphene sheets within the carbon structure corresponds to the average thickness of 100 graphene sheets when the negative electrode active material layer is observed using a TEM at a magnification of ×1,000,000.

[0143] The average longest length of the graphene sheets within the carbon structure corresponds to the average of the longest lengths of 100 graphene sheets when the negative electrode active material layer is observed using a TEM at a magnification of ×250,000. Here, the longest length refers to the longest length when assuming a line connecting one point to another within a single graphene sheet.

[0144] The oxygen content of the carbon structure was measured by elemental analysis of C, H, O, and N.

[0145] The average particle size of the silver nanoparticles corresponds to the average particle size of 100 silver nanoparticles when the carbon structure containing the silver nanoparticles in the negative electrode active material layer is observed by TEM at a magnification of ×1,000,000.

[0146] The content of the silver nanoparticles refers to the content in the negative electrode active material layer based on the total weight of the carbon structure and the silver nanoparticles.

[0147] Experimental Example 1: Evaluation of Initial Charge / Discharge Efficiency Each of the example and comparative example batteries was mounted in a pressurizing jig, and the bolts / nuts located at the corners of the square were fastened with the same pressure of 1 N·m to prepare a monocell. The initial charge / discharge efficiency was evaluated by the ratio of the first discharge capacity to the first charge capacity when the batteries were charged and discharged once at 60°C under the following conditions (see Table 3).

[0148] Charging conditions: 0.1C CC charging up to 4.25V, then CV charging with a 0.05C cutoff at 4.25V. Discharge conditions: 0.1C CC discharge up to 3.0V

[0149] Experimental Example 2: Evaluation of Volume Retention Rate The batteries in the examples and comparative examples were charged and discharged at 60°C under the following conditions, and the capacity retention rate (%) after 50 cycles was evaluated. The discharge capacity during the first charge / discharge cycle was used as the baseline (100%).

[0150] Charging conditions: 0.5C CC charging up to 4.25V, 0.5C cut-off. Discharge conditions: 0.33C CC discharge up to 3.0V

[0151] [Table 3]

Claims

1. It includes a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer. The negative electrode active material layer comprises a carbon structure and silver nanoparticles. The carbon structure includes a structure in which a plurality of graphene sheets are connected to each other, and the plurality of graphene sheets include two or more graphene sheets having different planar directions from each other. The average particle size of the silver nanoparticles is 1 nm to 50 nm. The silver nanoparticles are arranged on the surface of the carbon structure in a reduced-deposited state. The carbon structure is contained in the negative electrode active material layer at an amount of 50% to 98% by weight in an all-solid-state lithium secondary battery.

2. In the carbon structure, The all-solid-state lithium secondary battery according to claim 1, wherein the average thickness of the graphene sheet is 0.34 nm to 10 nm.

3. In the carbon structure, The all-solid-state lithium secondary battery according to claim 1, wherein the average maximum length of the graphene sheet is 10 nm to 500 nm.

4. When performing Raman spectral measurements on the carbon structure, The carbon structure I Ｄ / I Ｇ The all-solid-state lithium secondary battery according to claim 1, wherein the coefficient is 0.9 to 2.

0.

5. The specific surface area of ​​the carbon structure is 200 m². ２ / g ~ 1,100m ２ The all-solid-state lithium secondary battery according to claim 1, wherein the value is / g.

6. The all-solid-state lithium secondary battery according to claim 1, wherein the oxygen content of the carbon structure is 1% to 10% by weight relative to the total weight of the carbon structure.

7. In the negative electrode active material layer, The all-solid-state lithium secondary battery according to claim 1, wherein the silver nanoparticles are present in an amount of 1% to 40% by weight relative to the total weight of the carbon structure and the silver nanoparticles.

8. The all-solid-state lithium secondary battery according to claim 1, wherein the weight ratio of the carbon structure to the silver nanoparticles is 99:1 to 60:

40.

9. The all-solid-state lithium secondary battery according to claim 1, wherein the negative electrode active material layer further comprises a negative electrode binder.

10. The all-solid-state lithium secondary battery according to claim 1, wherein the thickness of the negative electrode active material layer is 1 μm to 100 μm.

11. Further including a negative electrode current collector, In the charged state, the material further includes a metal layer located between the negative electrode active material layer and the negative electrode current collector, The all-solid-state lithium secondary battery according to claim 1, wherein the metal layer contains lithium.

12. A first step involves reducing the silver ions in a mixture of silver ions and a carbon structure to form a dry mixed powder containing the carbon structure and silver nanoparticles arranged on the carbon structure. A method for manufacturing an all-solid-state lithium secondary battery, comprising a second step of forming a negative electrode active material layer on a negative electrode current collector via a negative electrode mixture containing the aforementioned dried mixed powder, All-solid-state lithium secondary batteries, It includes a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer. The negative electrode active material layer comprises a carbon structure and silver nanoparticles. The carbon structure includes a structure in which a plurality of graphene sheets are connected to each other, and the plurality of graphene sheets include two or more graphene sheets having different planar directions from each other. The carbon structure is contained in the negative electrode active material layer in an amount of 50% to 98% by weight. A method for manufacturing all-solid-state lithium secondary batteries.

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