Electrode for secondary battery, secondary battery comprising same, and fabrication method for electrode for secondary battery

Abstract

Provided according to exemplary embodiments are an electrode for a secondary battery and a fabrication method for the electrode for a secondary battery. The electrode for a secondary battery includes an electrode current collector, a first active material layer disposed on the electrode current collector, and a second active material layer disposed on the first active material layer, wherein each of the first active material layer and the second active material layer may include an electrode active material, a solid electrolyte, a binder, and a conductive material. The binder content (wt%) in the first active material layer on the basis of the total weight of the first active material layer is greater than that in the second active material layer on the basis of the total weight of the second active material layer while the conductive material content (wt%) in the second active material layer on the basis of the total weight of the second active material layer may be greater than that in the first active material layer on the basis of the total weight of the first active material layer.

Description

Electrode for secondary battery, secondary battery including the same, and method for manufacturing electrode for secondary battery

[0001] The present disclosure relates to an electrode for a secondary battery, a secondary battery including the electrode, and a method for manufacturing the secondary battery.

[0002] Secondary batteries, which can be repeatedly charged and discharged, are widely used as power sources for portable electronic communication devices such as camcorders, mobile phones, and laptop PCs, thanks to the advancements in the information and communication and display industries. Furthermore, battery packs containing secondary batteries are being developed and applied as power sources for eco-friendly vehicles such as hybrid vehicles.

[0003] Examples of secondary batteries include lithium secondary batteries, nickel-cadmium batteries, and nickel-hydrogen batteries. Among these, lithium secondary batteries have high operating voltage and energy density per unit weight, and can be advantageous in terms of charging speed and weight reduction.

[0004] Lithium secondary batteries may contain liquid electrolytes. Liquid electrolytes can pose safety risks, such as leakage, explosion, and ignition, in response to rapid environmental changes, such as temperature fluctuations and external shocks. Therefore, all-solid-state batteries containing solidified electrolytes are being developed to ensure stability.

[0005] An all-solid-state battery may include an electrode assembly comprising a positive electrode, a negative electrode, and an electrolyte layer. The positive electrode, negative electrode, and / or electrolyte layer of the all-solid-state battery may include a solid electrolyte. As the application scope of all-solid-state batteries expands, longer lifespan, higher capacity, and higher energy density are required.

[0006] One object of the present disclosure is to provide an electrode for a secondary battery having improved energy density and output characteristics.

[0007] An object of the present disclosure is to provide a secondary battery having improved capacity and output characteristics.

[0008] One object of the present disclosure is to provide a method for manufacturing an electrode for a secondary battery having improved energy density and output characteristics.

[0009] According to embodiments of the present disclosure, an electrode for a secondary battery may include an electrode current collector, a first active material layer disposed on the electrode current collector, and a second active material layer disposed on the first active material layer. The first active material layer and the second active material layer may each include an electrode active material, a solid electrolyte, a binder, and a conductive material.

[0010] According to exemplary embodiments, the weight % (B1) of the binder included in the first active material layer based on the total weight of the first active material layer may be greater than the weight % (B2) of the binder included in the second active material layer based on the total weight of the second active material layer.

[0011] According to exemplary embodiments, the weight % (C2) of the conductive material included in the second active material layer based on the total weight of the second active material layer may be greater than the weight % (C1) of the conductive material included in the first active material layer based on the total weight of the first active material layer.

[0012] In some embodiments, the weight % (E1) of the solid electrolyte included in the first active material layer based on the total weight of the first active material layer may be greater than or equal to the weight % (E2) of the solid electrolyte included in the second active material layer based on the total weight of the second active material layer.

[0013] In one embodiment, the first active material layer and the second active material layer may each independently include a fluorine-based binder, a rubber-based binder, a polyalkylene oxide-based binder, or a combination thereof.

[0014] In one embodiment, the first active material layer and the second active material layer may include the same binder.

[0015] In one embodiment, the ratio of the weight % (B2) of the binder included in the second active material layer based on the total weight of the second active material layer to the weight % (B1) of the binder included in the first active material layer based on the total weight of the first active material layer (B2 / B1) may be 0.5 or more and less than 1.0.

[0016] In one embodiment, the first active material layer and the second active material layer may each independently include a carbon-based conductive material.

[0017] In one embodiment, the first active material layer and the second active material layer may include the same conductive material.

[0018] In one embodiment, the ratio (C2 / C1) of the weight % of the conductive material included in the second active material layer based on the total weight of the second active material layer to the weight % (C1) of the conductive material included in the first active material layer based on the total weight of the first active material layer may be greater than 1 and less than or equal to 1.4.

[0019] In one embodiment, the solid electrolyte may include a sulfide-based electrolyte.

[0020] In one embodiment, both the first active material layer and the second active material layer may include a sulfide-based electrolyte having an argyrodite-type crystal structure.

[0021] In one embodiment, the content (E1) of the solid electrolyte included in the first active material layer may be 3 wt% to 30 wt% based on the total weight of the first active material layer, and the content (E2) of the solid electrolyte included in the second active material layer may be 1 wt% to 25 wt% based on the total weight of the second active material layer.

[0022] In one embodiment, the electrode for a secondary battery has a ratio (B2 / B1) of a weight % of a binder included in the second active material layer based on a total weight of the second active material layer to a weight % of a binder included in the first active material layer based on a total weight of the first active material layer, based on a total weight of the first active material layer; a ratio (C2 / C1) of a weight % of a conductive material included in the first active material layer based on a total weight of the second active material layer to a weight % of a conductive material included in the first active material layer based on a total weight of the first active material layer, based on a total weight of the second active material layer; and a ratio (E2 / E1) of a weight % of a solid electrolyte included in the second active material layer based on a total weight of the second active material layer to a weight % of a solid electrolyte included in the first active material layer based on a total weight of the first active material layer, based on a total weight of the first active material layer, based on a total weight of the second active material layer, based on a weight % of a solid electrolyte included in the first active material layer based on a total weight of the first active material layer, based on a weight % of a solid electrolyte included in the second active material layer based on a total weight of the second active material layer, based on a weight % of a solid electrolyte included in the first active material layer based on a total weight of the first active material layer, based on a weight % of a solid electrolyte included in the first active material layer based on a weight of a solid electrolyte included in the second active material layer based on a weight ... second active material layer At least two of them can be satisfied.

[0023] In some embodiments, the electrode for the secondary battery may further include at least one active material layer disposed on the second active material layer.

[0024] Among the plurality of active material layers, the weight % (B) of the binder included in the nth active material layer, based on the total weight of the nth active material layer arranged as the nth (n is an integer greater than or equal to 1) from the electrode current collector n ) is the weight % (B) of the binder included in the n+1th active material layer based on the total weight of the n+1th active material layer arranged n+1th from the electrode current collector. n+1 ) is greater than the weight % (C) of the conductive material included in the nth active material layer based on the total weight of the nth active material layer. n ) is the weight % (C) of the conductive material included in the n+1th active material layer based on the total weight of the n+1th active material layer. n+1 ) may be smaller.

[0025] In one embodiment, among the plurality of active material layers, the weight % (E) of the solid electrolyte included in the nth active material layer based on the total weight of the nth active material layer n ) is the weight % (E) of the solid electrolyte included in the n+1th active material layer based on the total weight of the n+1th active material layer. n+1 ) may be more than that.

[0026] A lithium secondary battery according to exemplary embodiments may include the secondary battery electrode described above, a counter electrode facing the secondary battery electrode, and a solid electrolyte layer interposed between the secondary battery electrode and the counter electrode.

[0027] In some embodiments, the electrode for the secondary battery may be provided as a positive electrode.

[0028] According to a method for manufacturing an electrode for a secondary battery according to exemplary embodiments, a plurality of active material layers can be sequentially formed on an electrode current collector.

[0029] Among the above multiple active material layers, the weight % (B) of the binder included in the n+1th active material layer based on the total weight of the n+1th active material layer (n is an integer greater than or equal to 1) from the electrode current collector n+1 ) is the weight % (B) of the binder included in the nth active material layer based on the total weight of the nth active material layer from the electrode current collector. n ) is smaller than the weight % (C) of the conductive material included in the n+1th active material layer based on the total weight of the n+1th active material layer. n+1 ) is the weight % (C) of the conductive material included in the nth active material layer based on the total weight of the nth active material layer. n ) can be larger than

[0030] In some embodiments, the plurality of active material layers may be formed by coating electrode slurry on the electrode current collector to form a first active material layer, and coating electrode slurry on the nth (n is an integer greater than or equal to 1) active material layer to form an n+1th active material layer.

[0031] In some embodiments, the step of forming the plurality of active material layers may include a transfer process of forming a first active material layer by coating an electrode slurry on the electrode current collector, and transferring the (n+1)th (n is an integer greater than or equal to 1) active material layer onto the nth active material layer.

[0032] In one embodiment, the transfer process may include forming the n+1th active material layer by coating an electrode slurry on a transfer substrate, attaching the nth active material layer and the n+1th active material layer to each other, and removing the transfer substrate from the n+1th active material layer.

[0033] An electrode for a secondary battery may include an electrode current collector and an electrode active material layer. The binder content (weight %) in the lower layer adjacent to the electrode current collector among the electrode active material layers may be higher than the binder content (weight %) in the upper layer. Binder migration may be suppressed, thereby preventing detachment of the electrode active material layer.

[0034] The content (weight %) of the conductive material in the upper layer of the electrode active material layer may be relatively higher than in other regions. This allows a sufficient electron-conductive network to be formed in the upper layer, thereby enhancing the electrode active material layer and ensuring uniform electron conductivity.

[0035] The content (weight %) of the solid electrolyte in the lower layer of the electrode active material layer may be greater than the content (weight %) of the solid electrolyte in the upper layer. During the electrochemical reaction process, the ion transfer path in the lower layer is added / supplemented by the solid electrolyte, so that the ion conductivity of the electrode active material layer can become more uniform.

[0036] FIG. 1 is a schematic cross-sectional view showing an electrode for a secondary battery according to exemplary embodiments.

[0037] Figure 2 is a schematic cross-sectional view showing an electrode for a secondary battery according to exemplary embodiments.

[0038] Figure 3 is a schematic process flow diagram for explaining a method for manufacturing an electrode for a secondary battery according to exemplary embodiments.

[0039] Figure 4 is a schematic process flow diagram for explaining a method for manufacturing an electrode for a secondary battery according to exemplary embodiments.

[0040] According to embodiments of the present disclosure, an electrode for a secondary battery and a secondary battery including a solid electrolyte are provided.

[0041] In addition, according to embodiments of the present disclosure, a method for manufacturing the electrode for the secondary battery described above is provided.

[0042] Lithium secondary batteries according to embodiments of the present disclosure can be widely applied in green technology fields such as electric vehicles, battery charging stations, and other battery-powered solar and wind power generation. Furthermore, lithium secondary batteries according to embodiments of the present disclosure can be used in eco-friendly electric vehicles, hybrid vehicles, and other vehicles that prevent climate change by suppressing air pollution and greenhouse gas emissions.

[0043] Hereinafter, embodiments of the present disclosure will be described in more detail with reference to the drawings. However, the following drawings attached to this specification illustrate some embodiments of the present disclosure and, together with the contents of the invention described above, serve to further understand the technical concept of the present disclosure. Therefore, the present disclosure should not be interpreted as being limited to the matters described in such drawings.

[0044] The terms “upper layer,” “lower layer,” “top surface,” “bottom surface,” “first,” “second,” etc. used in this disclosure indicate the relative positions of each component and do not imply an absolute superior-subordinate relationship.

[0045] Hereinafter, unless otherwise specifically defined in the present disclosure, when a part such as a layer, film, thin film, region, or plate is said to be “on” or “over” another part, this may include not only the case where it is “directly on” the other part, but also the case where there is another part in between.

[0046] FIG. 1 is a schematic cross-sectional view showing an electrode for a secondary battery according to exemplary embodiments.

[0047] Referring to FIG. 1, an electrode for a secondary battery may include an electrode current collector (100) and an electrode active material layer (110) formed on the electrode current collector (100). The electrode active material layer (110) may be formed on both surfaces (e.g., the upper surface and the lower surface) of the electrode current collector (100).

[0048] The electrode active material layer (110) may include an electrode active material, a conductive material, a binder, and a solid electrolyte.

[0049] According to exemplary embodiments, the electrode active material layer (110) may include a plurality of active material layers sequentially arranged from the electrode current collector (100).

[0050] In one embodiment, the electrode active material layer (110) may include a first active material layer (111) disposed on an electrode current collector (100) and a second active material layer (112) disposed on the first active material layer (111). Each of the first active material layer (111) and the second active material layer (112) may include an electrode active material, a conductive material, a binder, and a solid electrolyte.

[0051] The binder may be included in a relatively high content (weight %) in the region adjacent to the electrode current collector (100) among the electrode active material layers (110).

[0052] According to exemplary embodiments, the content of the binder in the first active material layer (111) may be greater than the content of the binder in the second active material layer (112). For example, the weight % (B1) of the binder included in the first active material layer (111) based on the total weight of the first active material layer (111) may be greater than the weight % (B2) of the binder included in the second active material layer (112) based on the total weight of the second active material layer (112).

[0053] Hereinafter, the term “content of b in A” used in the present disclosure means the weight % of b included in A based on the total weight of A. For example, the content of the binder in the first active material layer (111) means the content (weight %) of the binder included in the first active material layer (111) based on the total weight of the first active material layer (111), and the content of the binder in the second active material layer (112) means the content (weight %) of the binder included in the second active material layer (112) based on the total weight of the second active material layer (112).

[0054] As the binder is included in a relatively high content in the active material layer in contact with the electrode current collector (100), the adhesion of the electrode active material layer (110) to the electrode current collector (100) can increase. In addition, binder migration, in which the binder moves and concentrates on the upper part of the electrode active material layer (110), can be suppressed, thereby improving electrical and physical contact between the electrode active material layer (110) and the electrode current collector (100). Accordingly, peeling or detachment of the electrode active material layer (110) can be prevented, and the interfacial resistance of the electrode current collector (100) and the electrode active material layer (110) can be reduced.

[0055] For example, if the electrode active material layer has an overall low binder content across the entire area, the adhesion between the electrode active material layer and the electrode current collector and the structural stability of the electrode may deteriorate. If the electrode active material layer has an overall high binder content across the entire area, the electronic and / or ionic conductivity of the electrode active material layer may deteriorate, and the capacity and output characteristics of the secondary battery may deteriorate.

[0056] In some embodiments, the ratio (B2 / B1) of the binder content (B2) in the second active material layer (112) to the binder content (B1) in the first active material layer (111) may be 0.1 or more and less than 1.0. When the binder content ratio (B2 / B1) is 0.1 or more, the binder may enable the electrode active material layer (110) to have low resistance while further improving mechanical properties and stability.

[0057] In one embodiment, the content ratio (B2 / B1) of the binder may be 0.2 or more and less than 1.0, 0.2 to 0.9, 0.3 or more and less than 1.0, 0.3 to 0.9, 0.5 or more and less than 1.0, 0.5 to 0.9, or 0.5 to 0.8. Within the above range, the adhesion between the electrode active material layer (110) and the electrode current collector (100) may be improved, while the energy density of the electrode active material layer (110) and the capacity of the secondary battery may be improved.

[0058] In one embodiment, the content (B1) of the binder included in the first active material layer (111) may be greater than about 0.1 wt% and less than or equal to 20 wt% based on the total weight of the first active material layer (111). Within the above range, adhesion between the electrode current collector (100) and the electrode active material layer (110) may be further enhanced while preventing a decrease in energy density and capacity.

[0059] In one embodiment, the content of the binder (B1) in the first active material layer (111) may be about 0.5 wt% to 10 wt%, 0.5 wt% to 5.0 wt%, 1.0 wt% to 3.0 wt%, or 1.0 wt% to 2.0 wt%.

[0060] In one embodiment, the content (B2) of the binder included in the second active material layer (112) may be 0.1 wt% to 10 wt% based on the total weight of the second active material layer (112). Within this range, the capacity and output characteristics of the secondary battery may be improved.

[0061] In one embodiment, the content of the binder (B2) in the second active material layer (112) may be about 0.1 wt% to 5.0 wt%, 0.1 wt% to 3.0 wt%, 0.5 wt% to 2.0 wt%, 0.5 wt% to 1.0 wt%, or 0.5 wt% to 0.9 wt%.

[0062] In some embodiments, the binder may include a fluorine-based binder, a rubber-based binder, a polyalkylene oxide-based binder, or a combination thereof. For example, the binder may include a rubber-based binder containing fluorine, nitrile groups, hydroxyl groups, or a combination thereof.

[0063] In one embodiment, the binder may include vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polyvinyl alcohol, polymethylmethacrylate, butadiene rubber (BR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), hydrogenated nitrile butadiene rubber (HNBR), polyethylene oxide (PEO), or the like. These may be included alone or in combination of two or more. By including the above-described binder, it is possible to provide appropriate stretchability and strength to the active material layer while ensuring sufficient compatibility with the slurry solvent during the manufacture of the active material layer. The binder included in the first active material layer (111) and the binder included in the second active material layer (112) may be the same or different.

[0064] A conductive material may be included in a relatively small amount in a region adjacent to the electrode current collector (100) among the electrode active material layers (110).

[0065] According to exemplary embodiments, the content of the conductive material in the second active material layer (112) may be greater than the content of the conductive material in the first active material layer (111). For example, the weight % (C2) of the conductive material included in the second active material layer (112) based on the total weight of the second active material layer (112) may be greater than the weight % (C1) of the conductive material included in the first active material layer (111) based on the total weight of the first active material layer (111).

[0066] For example, the farther away from the electrode current collector, the lower the electronic conductivity. Furthermore, as the loading of the electrode active material layer increases, the longer the electron transport path in the upper layer of the electrode active material layer, making it difficult to form a dense electronic conductive network.

[0067] According to exemplary embodiments, since the second active material layer (112) includes a relatively large amount of a conductive material, the electronic conductivity of the second active material layer (112) can be supplemented by the conductive material even when the second active material layer (112) is away from the electrode current collector (100). Accordingly, a conductive network can be uniformly formed in the upper and lower layers of the electrode active material layer (110), and the electronic conductivity of the electrode active material layer (110) and the output characteristics of the lithium secondary battery can be improved.

[0068] In some embodiments, the ratio (C2 / C1) of the content of the conductive material in the second active material layer (112) to the content of the conductive material in the first active material layer (111) may be greater than 1 and less than or equal to 5. When the content ratio (C2 / C1) of the conductive material is less than or equal to 5, a conductive network may be formed more uniformly in the entire area of ​​the electrode active material layer (110), and the internal resistance of the electrode active material layer (110) may be further reduced.

[0069] For example, the content ratio (C2 / C1) of the conductive material may be greater than 1 and less than or equal to 3, greater than 1 and less than or equal to 2.5, greater than 1 and less than or equal to 2, greater than 1 and less than or equal to 1.5, greater than 1 and less than or equal to 1.4, 1.1 to 2.5, 1.1 to 2, 1.1 to 1.5, or 1.2 to 1.4. Within the above range, the electronic conductivity of the upper layer and the electronic conductivity of the lower layer can be uniform, and the capacity and output of the electrode active material layer (110) can be further improved.

[0070] In some embodiments, the content (C1) of the conductive material included in the first active material layer (111) may be about 0.1 wt% to 10 wt% based on the total weight of the first active material layer (111). Within this range, electron transfer between electrode active materials may be further promoted, and since the conductive material is not included in an excessive amount, the capacity of the secondary battery may be further increased.

[0071] In one embodiment, the content (C1) of the conductive material in the first active material layer (111) may be about 0.1 wt% to 5.0 wt%, 0.1 wt% to 3.0 wt%, 0.5 wt% to 2.0 wt%, or 1.0 wt% to 2.0 wt%.

[0072] In some embodiments, the content (C2) of the conductive material included in the second active material layer (112) may be greater than about 0.1 wt% and less than or equal to 20 wt% based on the total weight of the second active material layer (112). Within this range, a conductive network may be formed more densely in the upper portion of the electrode active material layer (110), and the diffusion resistance within the electrode active material layer (110) may be further reduced.

[0073] In one embodiment, the content of the conductive material (C2) in the second active material layer (112) may be about 0.1 wt% or more and 10 wt% or less, 0.1 wt% or more and 5 wt% or less, 0.5 wt% to 3 wt%, 1.0 wt% to 3.0 wt%, or 1.5 wt% to 2.5 wt%.

[0074] In some embodiments, the conductive material may include a carbon-based conductive material such as graphite, carbon black, graphene, carbon nanofibers, carbon nanotubes, and / or a metal-based conductive material including a perovskite material such as tin, tin oxide, titanium oxide, LaSrCoO3, and LaSrMnO3. These may be included alone or in combination of two or more. The conductive material included in the first active material layer (111) and the conductive material included in the second active material layer (112) may be the same or different from each other.

[0075] In one embodiment, the first active material layer (111) and the second active material layer (112) may each include a carbon-based conductive material as a conductive material. The interfacial resistance between the active material particles and the internal resistance of the electrode active material layer (110) may be further reduced.

[0076] In some embodiments, the content of the solid electrolyte in the first active material layer (111) may be greater than or equal to the content of the solid electrolyte in the second active material layer (112). For example, the weight % (E1) of the solid electrolyte included in the first active material layer (111) based on the total weight of the first active material layer (111) may be greater than or equal to the weight % (E2) of the solid electrolyte included in the second active material layer (112) based on the total weight of the second active material layer (112).

[0077] For example, if the loading amount of the electrode active material layer increases, the ion transfer path in the lower layer of the electrode active material layer may become longer, which may deteriorate the lithiation and delithiation performance of the electrode active material. Accordingly, the ion transfer characteristics in the lower layer may be relatively deteriorated compared to those in the upper layer.

[0078] According to exemplary embodiments, since the lower layer of the electrode active material layer (110) includes a solid electrolyte in a content equal to or relatively higher than that of the upper layer, ion conductivity can be supplemented in the lower layer, thereby forming a dense ion conductive network within the electrode. Accordingly, even if the loading amount of the electrode increases, the electrode active material layer (110) can have a uniform ion conductive network, and the capacity and output characteristics of the secondary battery can be improved.

[0079] In one embodiment, the content (E1) of the solid electrolyte in the first active material layer (111) may be greater than the content (E2) of the solid electrolyte in the second active material layer (112). For example, the ratio (E2 / E1) of the content (E2) of the solid electrolyte in the second active material layer (112) to the content (E1) of the solid electrolyte in the first active material layer (111) may be 0.1 or more and less than 1.0. As the content ratio (E2 / E1) of the solid electrolyte is less than 1.0, the rate characteristics and discharge capacity of the lithium secondary battery may be further improved.

[0080] In one embodiment, the content ratio (E2 / E1) of the solid electrolyte may be 0.5 or more and less than 1.0, 0.8 or more and less than 1.0, or 0.9 or more and less than 1.0. Accordingly, an ion conductive network can be formed more uniformly within the electrode.

[0081] In one embodiment, the solid electrolyte may have a constant content distribution within the electrode active material layer (110). The content of the solid electrolyte may be uniform throughout the entire region of the electrode active material layer (110), and for example, the solid electrolyte content (E1) in the first active material layer (111) and the solid electrolyte content (E2) in the second active material layer (112) may be substantially the same. When the content is said to be constant or uniform, it may include not only a case where the content in all regions is mathematically the same, but also a case where the deviation between the minimum content and the maximum content is within 5% and can thus be considered substantially constant.

[0082] In one embodiment, the content (E1) of the solid electrolyte included in the first active material layer (111) may be 3 wt% to 30 wt% based on the total weight of the first active material layer (111). For example, the content (E1) of the solid electrolyte in the first active material layer (111) may be 3 wt% to 25 wt%, 5 wt% to 20 wt%, or 10 wt% to 20 wt%.

[0083] In one embodiment, the content (E2) of the solid electrolyte included in the second active material layer (112) may be 1 wt% to 25 wt% based on the total weight of the second active material layer (112). For example, the content (E2) of the solid electrolyte in the second active material layer (112) may be 1 wt% to 20 wt%, 3 wt% to 20 wt%, or 10 wt% to 20 wt%.

[0084] Within the above range of solid electrolyte content, the ionic conductivity of the electrode can be further improved, and the capacity and output characteristics can be further improved.

[0085] The solid electrolyte included in the first active material layer (111) and the solid electrolyte included in the second active material layer (112) may be the same or different.

[0086] In some embodiments, the electrode active material may have a constant content distribution within the electrode active material layer (110). For example, the content (A1) of the electrode active material in the first active material layer (111) and the content (A2) of the electrode active material in the second active material layer (112) may be substantially the same.

[0087] In one embodiment, the content (A1) of the electrode active material included in the first active material layer (111) may be 60 wt% to 99 wt% based on the total weight of the first active material layer (111). For example, the content (A1) of the electrode active material in the first active material layer (111) may be 70 wt% to 99 wt%, or 80 wt% to 95 wt%.

[0088] In one embodiment, the content (A2) of the electrode active material included in the second active material layer (112) may be 60 wt% to 99 wt% based on the total weight of the second active material layer (112). For example, the content (A2) of the electrode active material in the second active material layer (112) may be 70 wt% to 99 wt%, or 80 wt% to 95 wt%.

[0089] The electrode active material included in the first active material layer (111) and the electrode active material included in the second active material layer (112) may be the same or different.

[0090] In one embodiment, the electrode for a secondary battery described above has a ratio (B2 / B1) of the weight % of the binder included in the second active material layer based on the total weight of the second active material layer to the weight % (B1) of the binder included in the first active material layer based on the total weight of the first active material layer, of 0.1 or more and less than 1.0; a ratio (C2 / C1) of the weight % of the conductive material included in the first active material layer based on the total weight of the first active material layer to the weight % (C1) of the conductive material included in the first active material layer based on the total weight of the first active material layer, of 1 or more and 5 or less; a ratio (E2 / E1) of the weight % of the solid electrolyte included in the second active material layer based on the total weight of the second active material layer to the weight % (E1) of the solid electrolyte included in the first active material layer based on the total weight of the first active material layer, of 0.1 or more and less than 1.0; At least two of them can be satisfied: B2 / B1, C2 / C1 and E2 / E1 may be specifically as described above.

[0091] Figure 2 is a schematic cross-sectional view showing an electrode for a secondary battery according to exemplary embodiments.

[0092] Referring to FIG. 2, the electrode active material layer (110) may further include at least one active material layer (11n, 11n+1, 11m) disposed on the second active material layer (112). For example, the electrode active material layer (110) may have a multilayer structure of three, four, five, or six layers or more.

[0093] When the electrode active material layer (110) includes a plurality of active material layers of three or more layers, the plurality of active material layers may have a content gradient of the binder, conductive material, and / or solid electrolyte described above.

[0094] In one embodiment, the binder content may increase toward the lower part of the electrode active material layer (110). For example, among the plurality of active material layers, the binder content included in the nth active material layer arranged nth (n is an integer greater than or equal to 1) from the electrode current collector (100) is the weight % (B) based on the total weight of the nth active material layer. n ) is the weight % (B) of the binder included in the n+1-th active material layer arranged n+1-th from the electrode current collector (100) based on the total weight of the n+1-th active material layer n+1 ) can be greater than that.

[0095] In one embodiment, the content of the conductive material may increase toward the upper part of the electrode active material layer (110). For example, among the plurality of active material layers, the weight % (C) of the conductive material included in the n+1th active material layer based on the total weight of the n+1th active material layer n+1 ) is the weight % (C) of the conductive material in the nth active material layer based on the total weight of the nth active material layer. n ) can be greater than.

[0096] In one embodiment, the content of the solid electrolyte may increase toward the lower part of the electrode active material layer (110). For example, among the plurality of active material layers, the weight % (E) of the solid electrolyte included in the nth active material layer based on the total weight of the nth active material layer n) is the weight % (E) of the solid electrolyte included in the n+1th active material layer based on the total weight of the n+1th active material layer. n+1 ) can be greater than.

[0097] In one embodiment, the solid electrolyte content in the electrode active material layer (110) may be constant. For example, the weight % (E) of the solid electrolyte included in the nth active material layer based on the total weight of the nth active material layer n ) is the weight % (E) of the solid electrolyte included in the n+1th active material layer based on the total weight of the n+1th active material layer. n+1 ) can be substantially identical.

[0098] In one embodiment, the electrode active material can be uniformly distributed throughout the entire area of ​​the electrode active material layer (110).

[0099] For example, the weight % (A) of the electrode active material included in the nth active material layer based on the total weight of the nth active material layer n ) is the weight % (A) of the electrode active material contained in the n+1th active material layer based on the total weight of the n+1th active material layer. n+1 ) can be substantially identical.

[0100] According to exemplary embodiments, the electrode active material layer (110) may include an inorganic solid electrolyte as a solid electrolyte. For example, the solid electrolyte may include a sulfide-based electrolyte.

[0101] In one embodiment, the sulfide-based electrolyte may include a compound represented by the following chemical formula 1.

[0102] [Chemical Formula 1]

[0103] Li e Y f P g S h Z i

[0104] In chemical formula 1, 0<e<12, 0≤f≤6, 0≤g≤6, 0<h≤12, 0≤i≤9, Y is at least one element selected from the group consisting of B, Al, Ga, In, Si, Ge, Sn, Pb, As, Sb, Bi, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Hf, Ta, and W, and Z may be at least one element selected from the group consisting of F, Cl, Br, and I.

[0105] For example, the sulfide-based electrolyte may be an LPS-based solid electrolyte containing Li, P, and S, an LGPS-based solid electrolyte containing Li, P, Ge, and S, or an LSiPSCl-based solid electrolyte containing Li, Si, P, S, and Cl.

[0106] For example, as the sulfide-based electrolyte, Li2S-P2S5, Li 10 GeP2S 12 , Li 10 SnP2S 12 , Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 , Li 10 (Si 0.5 Ge 0.5 )P2S 12 , Li 10 (Ge 0.5 Sn 0.5 )P2S 12 , Li 10 (Si 0.5 Sn 0.5 )P2S 12 , Li 10 GeP2S 11.7 O 0.3 , Li 9.6 P3S 12 , Li9P3S9O3, Li 10.35 Ge 1.35 P 1.65 S 12 , Li 10.35 Si 1.35 P 1.65S 12 , Li 9.81 Sn 0.81 P 2.19 S 12 , Li 9.42 Si 1.02 P 2.1 S 9.96 O 2.04 , Li6PS5Cl, etc. can be used.

[0107] For example, the sulfide-based solid electrolyte may be a sulfide-based electrolyte having an argyrodite-type crystal structure.

[0108] In one embodiment, both the first active material layer (111) and the second active material layer (112) may include a sulfide-based electrolyte having an argyrodite-type crystal structure.

[0109] In some embodiments, the electrode active material layer (110) may further include an oxide-based electrolyte.

[0110] The above oxide-based electrolyte may include an ion-conducting compound containing a metal oxide and / or oxygen.

[0111] Examples of the above metal oxides include Al2O3, ZnO2, Ce2O3, TiO2, ZrO2, HfO2, MnO2, MgO, WO 2, Examples include V2O5.

[0112] Examples of the above ion conductive compounds include garnet compounds such as LLZO compounds; perovskite compounds such as LLTO compounds; Li 1+x Al x Ge 2-x (PO4)3(0 <x<2), Li 1+x Al x Ti 2-x (PO4)3(0 <x<2), Li 1+x Ti 2-x-y Al x Si y (PO4) 3-y (0≤x≤1, 0 <y≤1), LAGP계 화합물, LATP계 화합물, LiAlx Zr 2-x (PO4)3(0≤x≤1, 0≤y≤1), LiTi x Zr 2-x NASICON compounds such as (PO4)3(0≤x≤1, 0≤y≤1); LIPON compounds; Li6La2CaTa2O 12 ; Li6La2ANb2O 12 (A is Ca or Sr); Li2Nd3TeSbO 12 , Li3BO 2.5 N 0.5 ; Li9SiAlO8, etc. can be mentioned.

[0113] Figure 3 is a schematic process flow diagram for explaining a method for manufacturing an electrode for a secondary battery according to exemplary embodiments.

[0114] Referring to FIG. 3, an electrode active material layer (110) can be formed by coating an electrode slurry on an electrode current collector (100).

[0115] The electrode slurry may include an electrode active material, a binder, a conductive material, and a solid electrolyte. The electrode slurry may include a solvent to ensure appropriate processability.

[0116] The solvent may be selected depending on the electrode active material or binder included in the electrode slurry. The solvent may include, for example, a non-polar solvent, a low-polarity solvent, or a combination thereof.

[0117] For example, the organic solvent may include a tertiary amine solvent such as triethylamine; an ester solvent such as butyl butyrate; an aromatic solvent such as benzene, toluene, xylene, methoxybenzene, and anisole; a chain-like aliphatic solvent such as hexane, heptane, octane, nonane, and decane; a cyclic aliphatic solvent such as cycloheptane, etc. These may be included alone or in combination of two or more.

[0118] The first electrode slurry can be coated on the electrode collector (100) (e.g., step S31).

[0119] The second active material layer (112) can be formed directly on the first active material layer (111). For example, the first electrode slurry can be coated on the electrode current collector (100) or the second electrode slurry can be coated on the first active material layer (111) (e.g., step S32). The second electrode slurry can be dried and rolled to form the second active material layer (112) (e.g., step S33).

[0120] In one embodiment, a first active material layer (111) may be formed first, and a second electrode slurry may be applied onto the formed first active material layer (111). For example, the first electrode slurry applied onto the electrode current collector (100) may be completely dried, and then the second electrode slurry may be applied using a wet-on-dry method. The applied second electrode slurry may be dried and rolled to form a second active material layer (112).

[0121] In one embodiment, the second electrode slurry may be applied onto the first electrode slurry before the first electrode slurry is completely dried. For example, the electrode active material layer (110) may be formed in a wet-on-wet manner. The second electrode slurry may be applied, and the first electrode slurry and the second electrode slurry may be dried simultaneously to form the first active material layer (111) and the second active material layer (112).

[0122] In one embodiment, during the process of applying and drying the second electrode slurry, a concentration gradient of the binder, conductive material, and / or solid electrolyte may be formed within each of the first active material layer (111) and the second active material layer (112).

[0123] In one embodiment, spray coating, dip coating, spin coating, gravure coating, slot die coating, doctor blade coating, roll coating, knife coating, inkjet printing, screen printing, micro contact printing, imprinting, reverse offset printing, bar coating, gravure offset printing, etc. may be used as a method for applying the electrode slurry.

[0124] The electrode slurry may be applied in an appropriate loading amount, taking into account the desired thickness of the active material layer. In one embodiment, the active material layer may be rolled to achieve miniaturization and high energy density. The rolling may be performed according to a known method, for example, using a rolling jig.

[0125] In one embodiment, drying of the electrode slurry may mean a process of removing a solvent included in the electrode slurry so that the solvent content of the active material layer becomes 1 wt% or less, 0.5 wt% or less, or 0.1 wt% or less of the total weight of the active material layer.

[0126] For example, the active material layer may refer to a state in which the solvent has been removed from the electrode slurry through a drying process. For example, the state in which the solvent has been removed may refer to a state in which the solvent is contained in an amount of 1 wt% or less, 0.5 wt% or less, or 0.1 wt% or less relative to the total weight of the active material layer, or a state in which the solvent is not contained.

[0127] Figure 4 is a schematic process flow diagram for explaining a method for manufacturing an electrode for a secondary battery according to exemplary embodiments.

[0128] Referring to FIG. 4, the second active material layer (112) can be formed through a transfer process. For example, a substrate on which the second active material layer (112) is formed can be transferred onto the first active material layer (111) to form an electrode active material layer (110).

[0129] A first active material layer (111) can be formed by coating a first electrode slurry on an electrode current collector (100) (e.g., step S41). The above-described coating method can be used as a coating method for the first electrode slurry.

[0130] A second active material layer (112) can be formed by coating a second electrode slurry on a separate transfer substrate (e.g., step S41). The above-described coating method can be used as a coating method for the second electrode slurry.

[0131] Examples of the transfer substrate include films or sheets of organic or inorganic compounds. For example, the transfer substrate may include organic sheets such as cellulose, polyethylene, polyester, polypropylene, polyethylene terephthalate, or inorganic sheets such as glass fiber or ceramic.

[0132] A transfer substrate having a second active material layer (112) formed thereon can be attached onto the first active material layer (111) so that the first active material layer (111) and the second active material layer (112) are in contact with each other (e.g., step S43). In one embodiment, after the second active material layer (112) is placed on the first active material layer (111), the first active material layer (111) and the second active material layer (112) can be pressed together.

[0133] The transfer substrate can be removed from the second active material layer (112) (e.g., step S44). Since the binder content of the first active material layer (111) is relatively high, transfer failure can be prevented. For example, since the adhesive force between the first active material layer (111) and the second active material layer (112) is greater than the adhesive force between the second active material layer (112) and the transfer substrate, the transfer substrate can be easily removed from the second active material layer (112) while preventing peeling between the first active material layer (111) and the second active material layer (112).

[0134] According to exemplary embodiments, the above-described manufacturing method can be applied even when the electrode active material layer (110) includes a plurality of active material layers of three or more layers.

[0135] In one embodiment, the first active material layer may be formed by coating the electrode slurry on the electrode current collector (100). Thereafter, the n+1-th active material layer may be formed by directly coating the electrode slurry on the n-th (n is an integer greater than or equal to 1) active material layer formed from the electrode current collector (100).

[0136] In one embodiment, a first active material layer may be formed by coating an electrode slurry on an electrode current collector (100), and an n+1th active material layer may be transferred onto an nth (n is an integer greater than or equal to 1) active material layer formed from the electrode current collector (100).

[0137] For example, the n+1th active material layer can be formed by coating an electrode slurry on a separate transfer substrate. Thereafter, an electrode current collector (100) and a transfer substrate can be attached so that the nth active material layer and the n+1th active material layer are in contact with each other. The transfer substrate can be removed from the n+1th active material layer to form a plurality of active material layers.

[0138] Through the transfer process, active material layers having different compositions can be formed, and the concentration distribution within the electrode active material layer (110) can be easily controlled. Accordingly, even if the solid content and density increase, a uniform ion or electron transfer network can be formed within the electrode active material layer (110).

[0139] Therefore, the electrode active material layer (110) has a conductivity of 3.0 mAh / cm without any decrease in ionic conductivity and electronic conductivity. 2 The above high loading amount can be achieved, and the capacity and output characteristics of the lithium secondary battery can be improved together.

[0140] A lithium secondary battery according to exemplary embodiments may include the secondary battery electrode described above and a counter electrode facing the secondary battery electrode.

[0141] For example, a lithium secondary battery may include a positive electrode and a negative electrode opposite to the positive electrode. At least one of the positive electrode and the negative electrode may be the electrode for the secondary battery described above.

[0142] The positive electrode may include a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector. The positive electrode active material layer may be formed on both surfaces (e.g., the upper surface and the lower surface) of the positive electrode current collector.

[0143] The negative electrode may include a negative current collector and a negative active material layer disposed on the negative current collector. The negative active material layer may be formed on both surfaces (e.g., the upper surface and the lower surface) of the negative current collector.

[0144] According to exemplary embodiments, the electrode for the secondary battery described above can be provided as a positive electrode of a lithium secondary battery.

[0145] For example, the electrode active material may include a cathode active material. Examples of the cathode active material include a lithium iron phosphate compound, a lithium cobalt oxide, a lithium manganese oxide, a lithium nickel oxide, or a lithium composite oxide.

[0146] For example, the positive electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or lithium manganese oxide such as LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); LiV3O8, LiFe3O4, V2O 5　 It may include vanadium oxides such as Cu2VO7, lithium iron phosphate oxides such as LiFePO4, etc.

[0147] In some embodiments, the positive electrode active material may include a compound represented by the following chemical formula 2.

[0148] [Chemical Formula 2]

[0149] Li a Ni b M 1-b O2

[0150] In chemical formula 2, 0.95≤a≤1.08, b≥0.5, and M may be at least one element among Na, Mg, Ca, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Co, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, Ba, and Sr.

[0151] In one embodiment, the positive electrode active material may further include at least one of cobalt (Co) or manganese (Mn). For example, a nickel-cobalt-manganese (NCM) lithium oxide may be used as the positive electrode active material.

[0152] Nickel (Ni) can be used as a metal associated with the capacity of lithium secondary batteries. While higher nickel content can improve the capacity and output of lithium secondary batteries, excessive nickel content can shorten the battery's lifespan and compromise mechanical and electrical stability.

[0153] The conductivity or resistance of a lithium secondary battery can be improved by cobalt (Co), and the mechanical and electrical stability of a lithium secondary battery can be improved by manganese (Mn).

[0154] The chemical structure represented by Chemical Formula 2 represents the bonding relationship contained within the lattice structure or crystal structure of the positive electrode active material and does not exclude other additional elements. For example, M may serve as the main active element of the positive electrode active material. Chemical Formula 2 is provided to express the bonding relationship of the main active element and should be understood as a formula encompassing the introduction and substitution of additional elements.

[0155] In one embodiment, auxiliary elements may be further included in addition to the main active element to enhance the chemical stability of the positive electrode active material or the crystal structure. The auxiliary elements may be incorporated into the crystal structure to form bonds, and in this case, it should be understood that they are also included within the chemical structure range represented by Chemical Formula 2.

[0156] The positive electrode current collector may include aluminum (Al), indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), germanium (Ge), lithium (Li), or an alloy thereof. The positive electrode current collector may be a plate structure, a foil structure, or a carbon-coated foil structure comprising the above-described metal or alloy.

[0157] In one embodiment, the positive electrode collector may comprise aluminum or stainless steel coated or surface-treated with carbon, nickel, titanium, or silver.

[0158] In one embodiment, the electrode for a secondary battery described above can be provided as a negative electrode of a lithium secondary battery.

[0159] For example, the electrode active material may include an anode active material. Any anode active material known in the art capable of absorbing and desorbing lithium ions may be used without particular limitation.

[0160] For example, the negative electrode active material may include carbon-based materials such as crystalline carbon, amorphous carbon, carbon composites, carbon fibers; lithium alloys; silicon or tin; etc.

[0161] Examples of the amorphous carbon include hard carbon, coke, mesocarbon microbeads (MCMB) calcined at 1500°C or lower, and mesophase pitch-based carbon fibers (MPCF). Examples of the crystalline carbon include graphite-based carbons such as natural graphite, artificial graphite, graphitized coke, graphitized MCMB, and graphitized MPCF. Elements included in the lithium alloy include aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium, and indium.

[0162] The negative current collector may include copper (Cu), aluminum (Al), indium (In), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), germanium (Ge), lithium (Li), or an alloy thereof. The positive current collector may be a plate structure, a foil structure, or a carbon-coated foil structure comprising the above-described metal or alloy.

[0163] In one embodiment, the negative electrode current collector may comprise copper coated or surface-treated with carbon, nickel, titanium, or silver.

[0164] Electrode tabs (positive electrode tab and negative electrode tab) may protrude from the positive electrode current collector and the negative electrode current collector, respectively, and may extend to one side of the case of the secondary battery. The electrode tabs may be fused together with the one side of the case to form electrode leads (positive electrode lead and negative electrode lead) that extend or are exposed to the outside of the case.

[0165] According to exemplary embodiments, a solid electrolyte layer may be interposed between the positive electrode and the negative electrode.

[0166] In some embodiments, a solid electrolyte layer in the form of a film or sheet is interposed between the positive electrode and the negative electrode, and then the solid electrolyte layer is physically or thermally compressed to manufacture a lithium secondary battery.

[0167] In some embodiments, the solid electrolyte layer may be formed via a transfer method. For example, a transfer substrate having the solid electrolyte layer formed thereon may be transferred onto the aforementioned secondary battery electrode. Thereafter, the solid electrolyte layer and the counter electrode may be positioned so that they face each other and are in contact, and then pressed together to manufacture a lithium secondary battery.

[0168] In some embodiments, the solid electrolyte may be formed directly on the positive electrode or the negative electrode. For example, a solid electrolyte layer may be formed by applying an electrolyte composition or solid electrolyte powder onto the secondary battery electrode described above and performing a curing process or a heat treatment process.

[0169] In one embodiment, the solid electrolyte layer may include a sulfide-based solid electrolyte and / or an oxide-based solid electrolyte. The sulfide-based solid electrolyte or the oxide-based solid electrolyte may be the same as the solid electrolyte included in the secondary battery electrode.

[0170] In one embodiment, the solid electrolyte layer may further include a polymer electrolyte. For example, the polymer electrolyte may include an ion-conductive polymer such as polyethylene oxide (PEO), polypropylene oxide (PPO), polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), polysiloxane, or a gel polymer electrolyte in which an electrolyte is contained in a polymer matrix.

[0171] The polymer electrolyte may further comprise a lithium salt. The lithium salt may be LiPF6, LiClO4, LiBF4, LiFSI, LiTFSI, LiSO3CF3, LiBOB, LiFOB, LiDFOB, LiDFBP, LiTFOP, LiPO2F2, LiCl, LiBr, LiI, LiB10 Cl 10 , LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, LiSCN, LiC(CF3SO2)3 or a combination thereof.

[0172] In one embodiment, an electrode cell is defined by an anode, a cathode, and a solid electrolyte layer, and a plurality of the electrode cells can be stacked to form an electrode assembly.

[0173] In one embodiment, a separator may be interposed between the positive electrode and the negative electrode. The separator may include a porous polymer film made of a polyolefin polymer, such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer. The separator may also include a nonwoven fabric formed of high-melting-point glass fibers, polyethylene terephthalate fibers, or the like.

[0174] For example, an electrode cell is defined by an anode, a cathode, and a separator, and an electrode assembly can be formed by a plurality of the electrode cells. For example, the electrode assembly can be formed by winding, stacking, folding, etc. of the separator.

[0175] In one embodiment, the lithium secondary battery may further include a non-aqueous electrolyte impregnating the positive electrode and the negative electrode.

[0176] The non-aqueous electrolyte may include a lithium salt and an organic solvent. Examples of the organic solvent include propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), methylpropyl carbonate, dipropyl carbonate, dimethylsulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, vinylene carbonate, sulfolane, gamma-butyrolactone, propylene sulfite, and tetrahydrofuran. These may be used alone or in combination of two or more.

[0177] The above electrode assembly may be housed within a case to define a lithium secondary battery. The lithium secondary battery may be manufactured in a cylindrical, square, pouch, or coin shape using, for example, a can.

[0178] The embodiments of the present disclosure described above include the following aspects and can be implemented through at least one of the following aspects.

[0179] According to a first aspect of the present disclosure, an electrode for a secondary battery comprises: an electrode current collector; and a first active material layer disposed on the electrode current collector and a second active material layer disposed on the first active material layer, wherein the first active material layer and the second active material layer each include an electrode active material, a solid electrolyte, a binder, and a conductive material, wherein a weight % (B1) of the binder included in the first active material layer based on the total weight of the first active material layer is greater than a weight % (B2) of the binder included in the second active material layer based on the total weight of the second active material layer, and a weight % (C2) of the conductive material included in the second active material layer based on the total weight of the second active material layer is greater than a weight % (C1) of the conductive material included in the first active material layer based on the total weight of the first active material layer.

[0180] In the first aspect, the electrode for a secondary battery according to the second aspect has a weight % (E1) of the solid electrolyte included in the first active material layer based on the total weight of the first active material layer, which is equal to or greater than the weight % (E2) of the solid electrolyte included in the second active material layer based on the total weight of the second active material layer.

[0181] In the first aspect or the second aspect, according to the third aspect, the first active material layer and the second active material layer each independently include a fluorine-based binder, a rubber-based binder, a polyalkylene oxide-based binder, or a combination thereof.

[0182] In any one of the first to third aspects, according to the fourth aspect, the first active material layer and the second active material layer include the same binder.

[0183] In any one of the first to fourth aspects, according to the fifth aspect, the ratio of the weight % (B2) of the binder included in the second active material layer based on the total weight of the second active material layer to the weight % (B1) of the binder included in the first active material layer based on the total weight of the first active material layer (B2 / B1) is 0.5 or more and less than 1.0.

[0184] In any one of the first to fifth aspects, according to the sixth aspect, the first active material layer and the second active material layer each independently include a carbon-based conductive material.

[0185] In any one of the first to sixth aspects, according to the seventh aspect, the first active material layer and the second active material layer include the same conductive material.

[0186] In any one of the first to seventh aspects, according to the eighth aspect, the ratio of the weight % (C2) of the conductive material included in the second active material layer based on the total weight of the second active material layer to the weight % (C1) of the conductive material included in the first active material layer based on the total weight of the first active material layer (C2 / C1) is greater than 1 and less than or equal to 1.4.

[0187] In any one of the first to eighth aspects, according to the ninth aspect, the solid electrolyte includes a sulfide-based electrolyte.

[0188] In any one of the first to ninth aspects, according to the tenth aspect, both the first active material layer and the second active material layer include a sulfide-based electrolyte having an argyrodite-type crystal structure.

[0189] In any one of the first to tenth aspects, according to the eleventh aspect, the content (E1) of the solid electrolyte included in the first active material layer is 3 wt% to 30 wt% based on the total weight of the first active material layer, and the content (E2) of the solid electrolyte included in the second active material layer is 1 wt% to 25 wt% based on the total weight of the second active material layer.

[0190] In any one of the first aspect to the eleventh aspect, according to the twelfth aspect, the ratio of the weight % (B2) of the binder included in the second active material layer based on the total weight of the second active material layer to the weight % (B1) of the binder included in the first active material layer based on the total weight of the first active material layer (B2 / B1) is 0.1 or more and less than 1.0; the ratio of the weight % (C2) of the conductive material included in the second active material layer based on the total weight of the second active material layer to the weight % (C1) of the conductive material included in the first active material layer based on the total weight of the first active material layer (C2 / C1) is more than 1 and 5 or less; And the ratio (E2 / E1) of the weight % (E2) of the solid electrolyte included in the second active material layer based on the total weight of the second active material layer to the weight % (E1) of the solid electrolyte included in the first active material layer based on the total weight of the first active material layer satisfies at least two of 0.1 or more and less than 1.0.

[0191] In any one of the first to twelfth aspects, according to the thirteenth aspect, the electrode for the secondary battery further includes at least one active material layer disposed on the second active material layer, and among the plurality of active material layers, the weight % (B) of the binder included in the nth active material layer, based on the total weight of the nth active material layer disposed as the nth (n is an integer greater than or equal to 1) from the electrode current collector, n ) is the weight % (B) of the binder included in the n+1th active material layer based on the total weight of the n+1th active material layer arranged n+1th from the electrode current collector. n+1 ) is greater than the weight % (C) of the conductive material included in the nth active material layer based on the total weight of the nth active material layer. n ) is the weight % (C) of the conductive material included in the n+1th active material layer based on the total weight of the n+1th active material layer. n+1 ) is smaller than.

[0192] In the 13th aspect, according to the 14th aspect, among the plurality of active material layers, the weight % (E) of the solid electrolyte included in the nth active material layer based on the total weight of the nth active material layer n ) is the weight % (E) of the solid electrolyte included in the n+1th active material layer based on the total weight of the n+1th active material layer. n+1 ) is above.

[0193] A lithium secondary battery according to a 15th aspect of the present disclosure comprises an electrode for a secondary battery according to any one of the first to fourteenth aspects; a counter electrode facing the electrode for a secondary battery; and a solid electrolyte layer interposed between the electrode for a secondary battery and the counter electrode.

[0194] In the above 15th aspect, according to the 16th aspect, the electrode for the secondary battery is provided as a positive electrode.

[0195] A method for manufacturing an electrode for a secondary battery according to the 17th aspect of the present disclosure includes a step of sequentially forming a plurality of active material layers on an electrode current collector, and among the plurality of active material layers, the weight % (B) of a binder included in the n+1-th active material layer based on the total weight of the n+1-th active material layer (n is an integer greater than or equal to 1) from the electrode current collector n+1 ) is the weight % (B) of the binder included in the nth active material layer based on the total weight of the nth active material layer from the electrode current collector. n ) is smaller than the weight % (C) of the conductive material included in the n+1th active material layer based on the total weight of the n+1th active material layer. n+1 ) is the weight % (C) of the conductive material included in the nth active material layer based on the total weight of the nth active material layer. n ) is larger than.

[0196] In the 17th aspect, according to the 18th aspect, the step of forming the plurality of active material layers is to form a first active material layer by coating electrode slurry on the electrode current collector, and to form an n+1th active material layer by coating electrode slurry on the nth (n is an integer greater than or equal to 1) active material layer.

[0197] In the 17th aspect, according to the 19th aspect, the step of forming the plurality of active material layers includes a transfer process of forming a first active material layer by coating electrode slurry on the electrode current collector, and transferring the n+1th (n is an integer greater than or equal to 1) active material layer onto the nth active material layer.

[0198] In the 19th aspect, according to the 20th aspect, the transfer process includes forming the n+1th active material layer by coating an electrode slurry on a transfer substrate, attaching the nth active material layer and the n+1th active material layer to each other, and removing the transfer substrate from the n+1th active material layer.

[0199] Hereinafter, preferred embodiments are presented to help understand the present disclosure, but these embodiments are only illustrative of the present disclosure and do not limit the scope of the appended claims. It will be apparent to those skilled in the art that various changes and modifications to the embodiments are possible within the scope and technical idea of ​​the present disclosure, and it is natural that such changes and modifications fall within the scope of the appended claims.

[0200] Example 1

[0201] (1) Manufacturing of electrodes for secondary batteries

[0202] LiNi, a nickel-cobalt-manganese (NCM) oxide, as an electrode active material 0.8 Co 0.1 Mn 0.1A first electrode slurry was prepared by mixing O2, Li6PS5Cl as a solid electrolyte, butadiene rubber as a binder, and carbon black as a conductive material in an ester organic solvent at a weight ratio of 80:17.5:1:1.5. The first electrode slurry was uniformly applied to an aluminum foil and vacuum-dried at 80°C to form a first active material layer.

[0203] LiNi, a nickel-cobalt-manganese (NCM) oxide, as an electrode active material 0.8 Co 0.1 Mn 0.1 A second electrode slurry was prepared by mixing O2, Li6PS5Cl as a solid electrolyte, butadiene rubber as a binder, and carbon black as a conductive material in an ester-based organic solvent at a weight ratio shown in Table 1 below. The second electrode slurry was applied onto a transfer substrate (PET film) and vacuum-dried at 80°C to form a second active material layer.

[0204] After overlapping the aluminum foil and the transfer substrate so that the second active material layer faces and contacts the first active material layer, the positive electrode active material layer was manufactured by pressing at 270 MPa. The loading amount of the positive electrode active material layer was 4 mAh / cm 2 was adjusted. After this, the transfer substrate was removed from the positive electrode active material layer to obtain a positive electrode.

[0205] (2) Manufacturing of lithium secondary batteries

[0206] An all-solid-state secondary battery using lithiated indium as a counter electrode was manufactured. An argyrodite-type sulfide-based solid electrolyte was used as the solid electrolyte layer of the all-solid-state secondary battery.

[0207] Specifically, a sulfide-based solid electrolyte was placed in a circular mold with a diameter of 10 mm, pressed at 150 MPa, and then the positive electrode was placed on one surface of the solid electrolyte layer and pressed at 370 MPa. Lithium-ion indium was placed on the other surface of the solid electrolyte layer to manufacture an all-solid-state lithium secondary battery.

[0208] Examples 2 to 4

[0209] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the active material, solid electrolyte, binder, and conductive material were mixed in the weight ratios shown in Table 1 below when manufacturing the first electrode slurry and the second electrode slurry.

[0210] In Tables 1 and 2 below, “A content ratio” represents the ratio of the content (weight %) of A in the second active material layer to the content (weight %) of A in the first active material layer. For example, the binder content ratio means the ratio (B2 / B1) of the weight % of binder in the second active material layer to the weight % of binder in the first active material layer (B1).

[0211] Comparative Example 1

[0212] LiNi, a nickel-cobalt-manganese (NCM) oxide, as an electrode active material 0.8 Co 0.1 Mn 0.1 O2, Li6PS5Cl as a solid electrolyte, butadiene rubber as a binder, and carbon black as a conductive material were mixed in an ester-based organic solvent at the weight ratios shown in Table 1 below to prepare a cathode slurry. The cathode slurry was uniformly applied to an aluminum foil and vacuum-dried at 80°C to form a cathode active material layer having a single layer structure. The loading amount of the cathode active material layer was 4 mAh / cm 2 was adjusted to .

[0213] After this, a lithium secondary battery was manufactured in the same manner as in Example 1.

[0214] Comparative Example 2

[0215] LiNi, a nickel-cobalt-manganese (NCM) oxide, as an electrode active material 0.8 Co 0.1 Mn 0.1O2, Li6PS5Cl as a solid electrolyte, butadiene rubber as a binder, and carbon black as a conductive material were mixed in an ester organic solvent at a weight ratio of 80:17.5:0.5:2 to prepare a cathode slurry. The cathode slurry was uniformly applied to an aluminum foil and vacuum-dried at 80°C to form a cathode active material layer having a single layer structure. The loading amount of the cathode active material layer was 4 mAh / cm 2 was adjusted to .

[0216] After this, a lithium secondary battery was manufactured in the same manner as in Example 1.

[0217] Comparative Examples 3 and 4

[0218] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the active material, solid electrolyte, binder, and conductive material were mixed in the weight ratios shown in Table 2 below when manufacturing the first electrode slurry and the second electrode slurry.

[0219] Example 1 Example 2 Example 3 Example 4 First active material layer (weight %) Electrode active material (A1) 80 80 80 80 Solid electrolyte (E1) 17.5 17.5 17.5 17.5 Binder (B1) 1111 Conductive material (C1) 1.5 1.5 1.5 1.5 Second active material layer (weight %) Electrode active material (A2) 80 80 80 80 Solid electrolyte (E2) 17.5 17.4 17.5 17.5 Binder (B2) 0.5 0.8 0.7 0.9 Conductive material (C2) 2.0 1.8 1.8 1.6 Content ratio of binder content (B2 / B1) 0.5 0.8 0.7 0.9 Conductive material content ratio (C2 / C1) 1.3 3 1.2 1.2 1.07 Solid electrolyte Content ratio (E2 / E1) 1.0 0.9 9 1.0 1.0 Loading amount (mAh / cm 2 )4.04.04.04.0

[0220] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 First active material layer (weight %) Electrode active material (A1) 80 80 80 Solid electrolyte (E1) 17.5 17.5 17.5 Binder (B1) 10.5 0.7 Conductive material (C1) 1.5 2.0 1.8 Second active material layer (weight %) Electrode active material (A2) 80 80 80 Solid electrolyte (E2) 17.5 17.5 17.5 Binder (B2) 0.5 11 Conductive material (C2) 2.0 1.5 1.5 Content ratio of binder content (B2 / B1)--21.43 Conductive material content ratio (C2 / C1)--0.75 0.83 Solid electrolyte content ratio (E2 / E1)--1.0 1.0 Loading amount (mAh / cm2) 4.0 4.0 4.0

[0221] Experimental Example: Evaluation of Discharge Capacity and Rate Characteristics

[0222] The all-solid-state secondary batteries manufactured in the above examples and comparative examples were charged (CC-CV, 3.65 V cut-off) and discharged (CC, 1.88 V cut-off) at approximately 30°C using a charger / discharger (Won-A Tech Co., Ltd., WBCS3000) to evaluate the discharge capacity and rate characteristics.

[0223] Specifically, charge and discharge were sequentially performed at C-rates of 0.1C, 0.2C, 0.33C, 0.5C, 1.0C, and 2.0C for 3 cycles each, with charge and discharge as one cycle. Charge and discharge were performed at the same C-rate. The discharge capacity in each cycle was measured, and the rate characteristics were evaluated by measuring the discharge capacity ratio (%) in each cycle based on the discharge capacity of the third cycle at 0.1C. In Comparative Example 2, the binder content was low, so electrode detachment occurred and the discharge capacity could not be measured.

[0224] The measurement results are shown in Table 3 below.

[0225] 0.1C discharge capacity (mAh / g) (3 cycle) Rate characteristics (%) 12 cycle (0.5C) 15 cycle (1.0C) 18 cycle (2.0C) Example 1 199.09 1.88 2.46 2.1 Example 2 199.89 3.68 5.77 1.1 Example 3 198.79 1.68 3.46 5.8 Example 4 198.89 0.08 1.96 8.7 Comparative Example 1 198.48 9.78 1.86 0.8 Comparative Example 2 Desorption---Comparative Example 3 186.68 3.25 9.125.1 Comparative Example 4 193.38 5.47 8.34 9.2

[0226] Referring to Table 3, the lithium secondary batteries according to the examples have high discharge capacity at the same loading amount and improved rate characteristics.

[0227] The lithium secondary batteries according to the comparative examples had low discharge capacities and deteriorated rate characteristics. In the case of comparative example 2, the cathode active material layer was 4.0 mAh / cm 2 Electrode detachment occurred during manufacturing with a loading amount of .

Claims

1. Electrode current collector; and It includes a first active material layer disposed on the electrode current collector and a second active material layer disposed on the first active material layer, The first active material layer and the second active material layer each include an electrode active material, a solid electrolyte, a binder, and a conductive material, The weight % (B1) of the binder included in the first active material layer based on the total weight of the first active material layer is greater than the weight % (B2) of the binder included in the second active material layer based on the total weight of the second active material layer, An electrode for a secondary battery, wherein the weight % (C2) of the conductive material included in the second active material layer based on the total weight of the second active material layer is greater than the weight % (C1) of the conductive material included in the first active material layer based on the total weight of the first active material layer.

2. In claim 1, the weight % (E1) of the solid electrolyte included in the first active material layer based on the total weight of the first active material layer is equal to or greater than the weight % (E2) of the solid electrolyte included in the second active material layer based on the total weight of the second active material layer.

3. In claim 1, the first active material layer and the second active material layer each independently include a fluorine-based binder, a rubber-based binder, a polyalkylene oxide-based binder, or a combination thereof. An electrode for a secondary battery.

4. An electrode for a secondary battery according to claim 1, wherein the first active material layer and the second active material layer include the same binder.

5. In claim 1, the ratio of the weight % (B2) of the binder included in the second active material layer based on the total weight of the second active material layer to the weight % (B1) of the binder included in the first active material layer based on the total weight of the first active material layer (B2 / B1) is 0.5 or more and less than 1.

0.

6. An electrode for a secondary battery according to claim 1, wherein the first active material layer and the second active material layer each independently include a carbon-based conductive material.

7. An electrode for a secondary battery according to claim 1, wherein the first active material layer and the second active material layer include the same conductive material.

8. In claim 1, the ratio of the weight % (C2) of the conductive material included in the second active material layer based on the total weight of the second active material layer to the weight % (C1) of the conductive material included in the first active material layer based on the total weight of the first active material layer (C2 / C1) is greater than 1 and less than or equal to 1.

4.

9. An electrode for a secondary battery according to claim 1, wherein the solid electrolyte comprises a sulfide-based electrolyte.

10. An electrode for a secondary battery according to claim 1, wherein both the first active material layer and the second active material layer include a sulfide-based electrolyte having an argyrodite-type crystal structure.

11. In claim 1, the content (E1) of the solid electrolyte included in the first active material layer is 3 wt% to 30 wt% based on the total weight of the first active material layer, An electrode for a secondary battery, wherein the content (E2) of the solid electrolyte included in the second active material layer is 1 wt% to 25 wt% based on the total weight of the second active material layer.

12. In claim 1, The ratio of the weight % (B2) of the binder included in the second active material layer based on the total weight of the second active material layer to the weight % (B1) of the binder included in the first active material layer based on the total weight of the first active material layer (B2 / B1) is 0.1 or more and less than 1.0; The ratio (C2 / C1) of the weight % of the conductive material included in the second active material layer based on the total weight of the second active material layer to the weight % of the conductive material included in the first active material layer based on the total weight of the first active material layer is greater than 1 and less than or equal to 5; and An electrode for a secondary battery, wherein the ratio (E2 / E1) of the weight % (E2) of the solid electrolyte included in the second active material layer based on the total weight of the second active material layer to the weight % (E1) of the solid electrolyte included in the first active material layer based on the total weight of the first active material layer is 0.1 or more and less than 1.0; and at least two of the following are satisfied.

13. In claim 1, the electrode for the secondary battery further includes at least one active material layer disposed on the second active material layer, Among the plurality of active material layers, the weight % (B) of the binder included in the nth active material layer, based on the total weight of the nth active material layer arranged as the nth (n is an integer greater than or equal to 1) from the electrode current collector n ) is the weight % (B) of the binder included in the n+1th active material layer based on the total weight of the n+1th active material layer arranged n+1th from the electrode current collector. n+1 ) is larger than Weight % (C) of conductive material included in the nth active material layer based on the total weight of the nth active material layer n ) is the weight % (C) of the conductive material included in the n+1th active material layer based on the total weight of the n+1th active material layer. n+1 ) smaller than a secondary battery electrode.

14. In claim 13, among the plurality of active material layers, the weight % (E) of the solid electrolyte included in the nth active material layer based on the total weight of the nth active material layer n ) is the weight % (E) of the solid electrolyte included in the n+1th active material layer based on the total weight of the n+1th active material layer. n+1 ) Ideal, electrode for secondary batteries.

15. An electrode for a secondary battery according to any one of claims 1 to 14; A counter electrode opposite to the above secondary battery electrode; and A lithium secondary battery comprising a solid electrolyte layer interposed between the secondary battery electrode and the counter electrode.

16. A lithium secondary battery according to claim 15, wherein the electrode for the secondary battery is provided as a positive electrode.

17. A step of sequentially forming a plurality of active material layers on an electrode collector, Among the above multiple active material layers, the weight % (B) of the binder included in the n+1th active material layer based on the total weight of the n+1th active material layer (n is an integer greater than or equal to 1) from the electrode current collector n+1 ) is the weight % (B) of the binder included in the nth active material layer based on the total weight of the nth active material layer from the electrode current collector. n ) is smaller than Weight % (C) of conductive material included in the n+1th active material layer based on the total weight of the n+1th active material layer n+1 ) is the weight % (C) of the conductive material included in the nth active material layer based on the total weight of the nth active material layer. n ) A method for manufacturing a secondary battery electrode.

18. In claim 17, the step of forming the plurality of active material layers comprises: A method for manufacturing an electrode for a secondary battery, comprising: forming a first active material layer by coating electrode slurry on the electrode current collector, and forming an n+1-th active material layer by coating electrode slurry on the n-th (n is an integer greater than or equal to 1) active material layer.

19. In claim 17, the step of forming the plurality of active material layers comprises: A method for manufacturing an electrode for a secondary battery, comprising a transfer process of forming a first active material layer by coating an electrode slurry on the electrode current collector, and transferring the n+1th (n is an integer greater than or equal to 1) active material layer onto the nth active material layer.

20. In claim 19, the transfer process comprises: A method for manufacturing an electrode for a secondary battery, comprising: forming an n+1th active material layer by coating an electrode slurry on a transfer substrate, attaching the nth active material layer and the n+1th active material layer to each other, and removing the transfer substrate from the n+1th active material layer.

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