Negative electrode, all-solid-state battery and method for preparing all-solid-state battery

Abstract

The present invention relates to a negative electrode, an all-solid-state battery, and a method of preparing an all-solid-state battery, the negative electrode including a current collector having a tensile strength ranging from about 1,000 MPa to 2,000 MPa and an active material layer. The current collector may be an Fe-Ni alloy foil containing about 10 wt% to 60 wt% nickel (Ni) and having an average grain size of less than 10 nm. An all-solid-state battery including the negative electrode and a method of making the same are also described. The method involves stacking and isostatic pressing at specific pressure, temperature and time parameters.

Description

[0001] Cross-references to related applications

[0002] This application claims the benefit of Korean Patent Application No. 10-2024-0065970, filed with the Korean Intellectual Property Office on May 21, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to the field of battery technology, and more specifically to a negative electrode for an all-solid-state battery, including its composition and characteristics, and a method for preparing such a battery. Background Technology

[0004] Lithium-ion rechargeable batteries using liquid electrolytes have been primarily used as secondary batteries for lithium-ion batteries. These batteries consist of a negative electrode and a positive electrode separated from each other by a polymer-containing separator, and include a liquid electrolyte. However, because the electrolyte exists in a liquid phase, lithium-ion rechargeable batteries employing liquid electrolytes present various safety concerns.

[0005] Therefore, all-solid-state batteries that use solid electrolytes instead of liquid electrolytes have been studied. Since all-solid-state batteries include a negative electrode, a positive electrode, and a solid electrolyte, and all components of an all-solid-state battery can be solid, they can prevent safety issues caused by liquid electrolytes compared to lithium secondary batteries that use liquid electrolytes.

[0006] Regarding the use of such all-solid-state batteries, Patent Document 1 proposes a method in which multiple cells of an all-solid-state battery are stacked to improve the energy density of the all-solid-state battery.

[0007] Specifically, Patent Document 1 discloses a method for preparing all-solid-state batteries by isostatic pressing, in order to solve the problem that the battery characteristics cannot be fully exhibited when multiple cell units of an all-solid-state battery are simply stacked.

[0008] However, when isostatic pressing is applied to the fabrication of all-solid-state batteries, pressure and time must be applied until the permissible limits of the isostatic pressing equipment are reached to densify the internal particles of the electrode and the interface between the electrode layer and the electrolyte layer, thereby improving resistance. In this process, the positive or negative electrode tabs may crack, which drastically increases the failure rate of all-solid-state batteries during fabrication.

[0009] Because the cell has tabs protruding along the stacking direction, this problem arises during the isostatic pressing process described above, inevitably leading to a horizontal difference between the tabs. During the isostatic pressing process, anisotropic pressing inevitably occurs on the protruding tabs, causing them to bend along the plate direction, which is expected to lead to breakage.

[0010] To address this problem, Patent Document 2 discloses the application of a current collector protection member, which serves as an additional insulating layer, to the protruding tab. As described above, according to Patent Document 2, when the protruding tab is subjected to isostatic pressing by applying the current collector protection member, breakage of the protruding tab can be prevented.

[0011] However, according to Patent Document 2, after isostatic pressing is completed, an additional process is required to remove the current collector protection component separately in order to electrically connect the cell to the external wire.

[0012] Specifically, according to Patent Document 2, when preparing an all-solid-state battery by stacking multiple cell units, the multiple cell units need to be stacked after removing the current collector protection member. Therefore, each cell unit needs to be isostatically pressed. Furthermore, as mentioned above, when preparing an all-solid-state battery by stacking multiple cell units formed in the above manner, gaps are formed between the cell units when the current collector protection member is removed. Therefore, when laminating and packaging after stacking multiple cell units, the protruding tabs may partially crack or break.

[0013] Furthermore, according to Patent Document 2, a stacked structure of multiple cell units is formed before isostatic pressing. Then, when the stacked structure of multiple cell units is isostatically pressed, the current collector protection member is fixed while being assembled to the positive and negative electrode tabs due to the protruding tabs of the multiple cell units. Therefore, the current collector protection member may be difficult to remove. Summary of the Invention

[0014] This invention aims to solve the aforementioned problems in the prior art while fully maintaining the advantages achieved by the prior art.

[0015] One aspect of the present invention is that, when isostatic pressing is used to prepare all-solid-state batteries to improve the energy density of all-solid-state batteries, even when pressure and time are applied without additional protective components until the allowable limit of the isostatic pressing equipment is reached to densify the internal particles of the electrode and the interface between the electrode layer and the electrolyte layer, thereby improving the resistance, the protruding tabs can be prevented from breaking.

[0016] In other words, the present invention aims to provide a negative electrode with improved resistance and improved energy density, which, when fabricated by isostatic pressing of an all-solid-state battery, prevents protruding tabs from breaking even when pressure and time are applied up to the permissible limits of the isostatic pressing equipment to densify the internal particles of the electrode and the interface between the electrode layer and the electrolyte layer.

[0017] In addition, the present invention also provides an all-solid-state battery including the negative electrode.

[0018] Furthermore, the present invention also provides a method for preparing an all-solid-state battery.

[0019] The technical problems to be solved by the present invention are not limited to those described above. Those skilled in the art will clearly understand from the following description any other technical problems not mentioned herein.

[0020] According to the present invention, a negative electrode, an all-solid-state battery, and a method for preparing an all-solid-state battery are provided.

[0021] (1) The present invention provides a negative electrode comprising a negative electrode current collector and a negative electrode active material layer formed on at least one surface of the negative electrode current collector, wherein the tensile strength of the negative electrode current collector is in the range of 1,000 MPa to 2,000 MPa.

[0022] (2) The present invention provides a negative electrode comprising a negative electrode current collector as described in (1), wherein the negative electrode current collector is an Fe-Ni alloy foil.

[0023] (3) The present invention provides a negative electrode comprising a negative electrode current collector as described in any one of (1) or (2), said negative electrode current collector being a Ni-containing Fe-Ni alloy foil, said nickel content ranging from 10% by weight to 60% by weight.

[0024] (4) The present invention provides a negative electrode comprising a negative electrode current collector as described in any one of (1) to (3), wherein the negative electrode current collector is a Fe-Ni alloy foil with an average grain size ranging from greater than 0 nm to 50 nm.

[0025] (5) The present invention provides a negative electrode comprising a negative electrode current collector as described in any one of (1) to (4), wherein the elongation of the negative electrode current collector is in the range of 0% to 10%.

[0026] (6) The present invention provides a negative electrode comprising a negative electrode current collector as described in any one of (1) to (5), wherein the thickness of the negative electrode current collector is in the range of 4 μm to 20 μm.

[0027] (7) The present invention provides a negative electrode comprising a negative electrode active material layer as described in any one of (1) to (6), wherein the negative electrode active material layer comprises at least one selected from carbon-based negative electrode active materials, silicon-based negative electrode active materials and lithium metal negative electrode active materials.

[0028] (8) The present invention provides an all-solid-state battery comprising any one of (1) to (7) a negative electrode.

[0029] (9) The present invention provides an all-solid-state battery comprising the sulfide-based solid electrolyte described in (8).

[0030] (10) The present invention provides a method for preparing an all-solid-state battery, comprising preparing a negative electrode by forming a negative electrode active material layer on at least one surface of a negative electrode current collector (S10); preparing a unit cell by stacking the negative electrode, a solid electrolyte layer and a positive electrode prepared in S10 (S20); and isostatically pressing the unit cell prepared in S20 in the stacking direction (S30), wherein the tensile strength of the negative electrode current collector is in the range of 1,000 MPa to 2,000 MPa.

[0031] (11) The present invention provides a method for preparing the all-solid-state battery described in (10), wherein the unit cell has a structure in which a negative electrode, a solid electrolyte layer, a positive electrode, a solid electrolyte layer and a negative electrode are stacked in sequence.

[0032] (12) The present invention provides a method for preparing an all-solid-state battery as described in (10) or (11), wherein S30 is performed by isostatic pressing after vacuum lamination packaging of the cell obtained in S20.

[0033] (13) The present invention provides a method for preparing an all-solid-state battery according to any one of (10) to (12), wherein the isostatic pressing is carried out at a pressure in the range of 100 MPa to 1,000 MPa.

[0034] (14) The present invention provides a method for preparing an all-solid-state battery according to any one of (10) to (13), wherein the isostatic pressing is carried out at a temperature in the range of 50°C to 150°C.

[0035] (15) The present invention provides a method for preparing an all-solid-state battery according to any one of (10) to (14), wherein the isostatic pressing is performed for a period of 5 minutes to 120 minutes.

[0036] In some embodiments, the negative electrode includes a negative electrode current collector and a layer of negative electrode active material formed on at least one surface of the negative electrode current collector. The tensile strength of the negative electrode current collector ranges from about 1,000 MPa to 2,000 MPa.

[0037] The negative electrode current collector can be an Fe-Ni alloy foil. It can contain nickel (Ni) in the range of about 10% to 60% by weight. Alternatively, the Fe-Ni alloy foil can contain nickel (Ni) in the range of about 30% to 60% by weight. The average grain size of the negative electrode current collector can range from greater than about 0 nm to 50 nm or less than 10 nm. Additionally, the negative electrode current collector can have an elongation of about 0% to 10% and a thickness of about 4 μm to 20 μm.

[0038] The negative electrode active material layer may include at least one selected from carbon-based negative electrode active materials, silicon-based negative electrode active materials, and lithium metal negative electrode active materials.

[0039] The all-solid-state battery may include the aforementioned negative electrode. The all-solid-state battery may include a sulfide-based solid electrolyte.

[0040] A method for fabricating an all-solid-state battery includes: fabricating a negative electrode by forming a negative electrode active material layer on at least one surface of a negative electrode current collector; fabricating a unit cell by stacking a negative electrode, a solid electrolyte layer, and a positive electrode; and isostatically pressing the unit cell in the stacking direction. The tensile strength of the negative electrode current collector can range from about 1,000 MPa to 2,000 MPa.

[0041] The cell may have a structure in which a negative electrode, a solid electrolyte layer, a positive electrode, another solid electrolyte layer, and a negative electrode are stacked in sequence. Isostatic pressing of the cell may be performed after vacuum lamination packaging. Isostatic pressing may be performed at a pressure of approximately 100 MPa to 1,000 MPa and a temperature of approximately 50°C to 150°C for approximately 5 to 120 minutes. The negative electrode current collector may be an Fe-Ni alloy foil containing a nickel (Ni) content ranging from approximately 10% to 60% by weight and an average grain size ranging from greater than approximately 0 nm to 50 nm.

[0042] In some embodiments, the negative electrode includes a negative electrode current collector and a layer of negative electrode active material formed on at least one surface of the negative electrode current collector. The negative electrode current collector is an Fe-Ni alloy foil with a tensile strength ranging from about 1,000 MPa to 2,000 MPa, containing a nickel (Ni) content ranging from about 30% to 60% by weight, and having an average grain size of less than 10 nm.

[0043] As discussed, the method and system appropriately include the use of a controller or processor.

[0044] Unless otherwise stated, tensile strength values ​​are determined using a tensile strength analyzer at 25°C, including commercially available tensile strength analyzers such as the Zwick / Roell Z020 general-purpose tensile tester (Ulm, Germany). Attached Figure Description

[0045] The above and other objects, features and advantages of the invention will become more apparent from the detailed description that follows in conjunction with the accompanying drawings, in which:

[0046] Figure 1 and Figure 2 This is a cross-sectional view of a cell according to an embodiment of the present invention. Detailed Implementation

[0047] In order to understand the invention, it will be described in more detail below.

[0048] In this context, the terms and words used in this specification and claims should not be construed as having their usual dictionary meanings, but rather as relating to the technical scope of the invention, based on the fact that the inventors can appropriately define the concepts of the terms to best interpret the invention.

[0049] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used herein, unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the / said” are intended to also include the plural forms. These terms are intended only to distinguish one component from another, and the terms do not limit the nature, order, or sequence of these constitutive components. It will be further understood that when the terms “comprising” and / or “including” are used in this specification, they indicate the presence of the stated features, values, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, values, steps, operations, elements, components, and / or combinations thereof. As used herein, the term “and / or” includes any and all combinations of one or more of the associated enumerations. Throughout the specification, unless expressly stated to the contrary, the words “comprising” and variations such as “including” or “having” are to be understood as meaning to include the stated elements, but not excluding any other elements. Furthermore, the terms “unit,” “component,” “device,” and “module” described in this specification mean a unit for performing at least one function and operation, and may be implemented by hardware components or software components and combinations thereof.

[0050] While exemplary embodiments are described as using multiple units to perform exemplary processes, it should be understood that exemplary processes can also be performed by one or more modules. Furthermore, it should be understood that the term controller / control unit refers to a hardware device including a memory and a processor, specifically programmed to perform the processes described herein. The memory is configured to store modules, and the processor is specifically configured to execute said modules to perform one or more processes further described below.

[0051] Furthermore, the control logic of the present invention can be implemented as a non-volatile computer-readable medium on a computer-readable medium, which contains executable program instructions that are executed by a processor, controller, etc. Examples of computer-readable media include (but are not limited to) ROM, RAM, optical disc (CD)-ROM, magnetic tape, floppy disk, flash drive, smart card, and optical data storage device. The computer-readable medium can also be distributed across a network-connected computer system, thereby enabling the computer-readable medium to be stored and executed in a distributed manner via, for example, a telematics server or a controller area network (CAN).

[0052] Unless otherwise stated or obvious from the context, the term “about” as used herein is understood to mean within the normal tolerance range in the field, such as within two standard deviations of the mean. “About” can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless the context clearly indicates otherwise, all numerical values ​​provided herein are modified by the term “about”.

[0053] This invention provides a negative electrode, an all-solid-state battery, and a method for preparing an all-solid-state battery.

[0054] According to an embodiment of the present invention, the negative electrode can be a negative electrode for an all-solid-state battery, and specifically, it can be a negative electrode for an all-solid-state battery that has undergone isostatic pressing.

[0055] As described in the background section above, when fabricating all-solid-state batteries and performing isostatic pressing, pressure and time are applied until the permissible limits of the isostatic pressing equipment are reached to densify the internal particles of the electrodes and the interface between the electrode layer and the electrolyte layer, thereby improving resistance. Furthermore, the cell targeted for isostatic pressing includes uncoated portions protruding from the current collector for mounting electrode tabs, and / or electrode tabs (T, T') that are simultaneously protruding from the uncoated portions of the current collector in various ways. When such cell cells are subjected to isostatic pressing, the uncoated portions and / or tabs T and T' undergo anisotropic pressing due to the horizontal difference between the protruding uncoated portions and / or tabs T as viewed from the stacking direction, and the horizontal difference between the protruding uncoated portions and / or tabs T'. Therefore, the uncoated portions and / or tabs T and T' may crack. When the uncoated portions and / or tabs T and T' may crack as described above, additional steps for electrical connection are required to use the relevant cell cells as all-solid-state batteries. Additionally, if the current collector is also affected by cracking, the associated cell may become unusable.

[0056] However, according to embodiments of the present invention, since the negative electrode current collector included in the negative electrode has adjusted tensile strength, for cell batteries including uncoated portions (which protrude from the current collector and serve as tabs for providing electrodes) and / or tabs T and T' (which are disposed in various ways on the uncoated portions of the current collector and protrude simultaneously), even if pressure and time are applied up to the permissible limit of the isostatic pressing device, the uncoated portions and / or tabs T and T' can be prevented from breaking.

[0057] According to an embodiment of the present invention, the negative electrode includes a negative electrode current collector and a negative electrode active material layer formed on at least one surface of the negative electrode current collector, and the tensile strength of the negative electrode current collector can be in the range of 1,000 MPa to 2,000 MPa. Specifically, the tensile strength of the negative electrode current collector is at least 1,000 MPa, at least 1,010 MPa, at least 1,020 MPa, at least 1,030 MPa, at least 1,040 MPa, at least 1,050 MPa, at least 1,060 MPa, at least 1,070 MPa, at least 1,080 MPa, at least 1,090 MPa, at least 1,100 MPa, at least 1,110 MPa, at least 1,120 MPa, at least 1,130 MPa, and at least 1,140 MPa. At least 1,150 MPa, at least 1,160 MPa, at least 1,170 MPa, at least 1,180 MPa, at least 1,190 MPa, at least 1,200 MPa, at least 1,210 MPa, 1,220 MPa, 1,230 MPa, 1,240 MPa, 1,250 MPa, at least 1,260 MPa, at least 1,270 MPa, at least 1,280 MPa, at least 1,290 MPa, at least 1,300 MPa, or at least 1,310 MPa. In addition, the tensile strength of the negative electrode current collector is up to 2,000 MPa, up to 1,950 MPa, up to 1,900 MPa, up to 1,850 MPa, up to 1,800 MPa, up to 1,750 MPa, up to 1,700 MPa, up to 1,650 MPa, up to 1,600 MPa, up to 1,590 MPa, up to 1,580 MPa, up to 1,570 MPa, up to 1,560 MPa, up to 1,550 MPa, up to 1,540 MPa, up to 1,530 MPa, up to 1,520 MPa, up to 1,510 MPa, up to 1,500 MPa, up to 1,490 MPa, up to 1,480 MPa, or up to 1,470 MPa. Typically, copper foil used for current collectors in lithium-ion batteries, particularly all-solid-state batteries, has a tensile strength ranging from about 300 MPa to about 400 MPa. Aluminum foil ranges from about 250 MPa to about 300 MPa, nickel foil from about 700 MPa, and SUS foil from about 450 MPa to about 800 MPa. However, when pressure and time are applied up to the permissible limits of the isostatic pressing apparatus, copper, aluminum, nickel, and SUS foils all break due to anisotropic pressing of the uncoated portions and / or tabs T and T'. Conversely, for the negative electrode, because the tensile strength of the negative electrode current collector is adjusted, when isostatic pressing is used to prepare all-solid-state batteries, even with anisotropic pressing of the uncoated portions and / or tabs T and T', breakage of the protruding uncoated portions and / or tabs T and T' can be prevented.

[0058] According to an embodiment of the present invention, the negative electrode current collector can be an Fe-Ni alloy foil. As described above, when an Fe-Ni alloy foil is used as the negative electrode current collector, the tensile strength condition is met. Therefore, when isostatic pressing is performed to prepare an all-solid-state battery, even if anisotropic pressing is performed on the uncoated portion and / or the tabs T and T', breakage of the protruding uncoated portion and / or the tabs T and T' can be prevented. Furthermore, the battery power and durability may be further improved. The aforementioned Fe-Ni foil can be prepared by electroforming. In this case, the electroforming method can be replicated in a known manner, as long as the electroforming method can prepare an Fe-Ni alloy foil suitable for the negative electrode current collector according to the present invention.

[0059] According to embodiments of the present invention, the negative electrode current collector may be an Fe-Ni alloy foil containing 10 wt% and 60 wt% nickel. For example, the negative electrode current collector may be an Fe-Ni alloy foil containing nickel, wherein the nickel content is at least 10 wt%, at least 11 wt%, at least 12 wt%, at least 13 wt%, at least 14 wt%, at least 15 wt%, at least 16 wt%, at least 17 wt%, at least 18 wt%, at least 19 wt%, at least 20 wt%, at least 21 wt%, at least 22 wt%, at least 23 wt%, at least 24 wt%, at least 25 wt%, at least 26 wt%, at least 27 wt%, at least 28 wt%, at least 29 wt%, at least 30 wt%, at least 31 wt%, at least 32 wt%, at least 33 wt%, at least 34 wt%, at least 35 wt%, at least 36 wt%, at least 37 wt%, at least 38 wt%, at least 39 wt%, or at least 40 wt%. Alternatively, the negative electrode current collector can be an Fe-Ni alloy foil containing nickel, wherein the nickel content is at most 60 wt%, at most 55 wt%, at most 50 wt%, at most 49 wt%, at most 48 wt%, at most 47 wt%, at most 46 wt%, at most 45 wt%, at most 44 wt%, at most 43 wt%, at most 42 wt%, at most 41 wt%, or at most 40 wt%. In this case, the Fe-Ni alloy may contain residual amounts of iron in addition to nickel, and may contain impurities unavoidable according to the preparation method and process. When the negative electrode current collector is an Fe-Ni alloy containing the aforementioned amounts of nickel and iron, durability can be further improved while preventing a reduction in battery power of the negative electrode current collector.

[0060] According to embodiments of the present invention, the negative electrode current collector can be an Fe-Ni alloy foil with an average grain size ranging from 0 nm to 50 nm. Specifically, the negative electrode current collector can be an Fe-Ni alloy foil with an average grain size greater than 0 nm, at least 1 nm, at least 2 nm, at least 3 nm, at least 4 nm, at least 5 nm, at least 6 nm, at least 7 nm, at least 8 nm, at least 9 nm, or at least 10 nm. Alternatively, the negative electrode current collector can be an Fe-Ni alloy foil with an average grain size of at most 50 nm, at most 45 nm, at most 40 nm, at most 35 nm, at most 30 nm, at most 25 nm, at most 20 nm, at most 19 nm, at most 18 nm, at most 17 nm, at most 16 nm, at most 15 nm, at most 14 nm, at most 13 nm, at most 12 nm, at most 11 nm, or at most 10 nm. When the average grain size of the Fe-Ni alloy is adjusted to the above range, the durability can be further improved while meeting the tensile strength requirements of the negative electrode current collector.

[0061] According to embodiments of the present invention, the elongation of the negative electrode current collector can range from 0% to 10%. For example, the elongation of the negative electrode current collector can be at least 0%, at least 0.5%, at least 1.0%, at least 1.5%, at least 2.0%, at least 2.5%, at least 3.0%, at least 3.5%, at least 4.0%, or at least 4.5%. Furthermore, the elongation of the negative electrode current collector can be at most 10.0%, at most 9.5%, at most 9.0%, at most 8.5%, at most 8.0%, at most 7.5%, at most 7.0%, at most 6.5%, or at most 6.0%. When the elongation of the negative electrode current collector is adjusted to the above range, the mechanical properties of the negative electrode current collector can be further improved. Additionally, during the isostatic pressing process used to manufacture all-solid-state batteries, in addition to tensile strength, even when anisotropic pressing is applied to the uncoated portion and / or the tab T, breakage of the protruding uncoated portion and / or the tab T can be prevented.

[0062] According to embodiments of the present invention, the thickness of the negative electrode current collector can be from 4 μm to 20 μm. Specifically, the thickness of the negative electrode current collector can be at least 4 μm. Furthermore, the thickness of the negative electrode current collector can be at most 20 μm, at most 19 μm, at most 18 μm, at most 17 μm, at most 16 μm, at most 15 μm, at most 14 μm, at most 13 μm, at most 12 μm, at most 11 μm, at most 10 μm, at most 9 μm, at most 8 μm, at most 7 μm, or at most 6 μm. When the thickness of the negative electrode current collector is adjusted to the above range, the mechanical properties of the negative electrode current collector can be prevented from deteriorating, all-solid-state batteries with thinner thicknesses can be fabricated, and the energy density can be further improved.

[0063] According to an embodiment of the present invention, a solid electrolyte, a binder, or a conductive material may also be optionally included together with the negative electrode active material.

[0064] According to an embodiment of the present invention, the negative electrode active material may include a compound that allows reversible insertion or extraction of lithium ions. For example, the negative electrode active material layer may include at least one negative electrode active material selected from a carbon-based negative electrode active material, a silicon-based negative electrode active material, and a lithium metal negative electrode active material. More specifically, the negative electrode active material may include a carbon-based negative electrode active material, such as artificial graphite, natural graphite, graphitized carbon fiber, or amorphous carbon; a silicon-based negative electrode active material, such as Si, Si alloy, or SiO x (0 < x < 2); a metal compound, such as Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy, for forming an alloy with lithium; a metal oxide, such as SnO2, vanadium oxide, lithium vanadium oxide, for doping or dedoping of lithium ions; or a composite compound containing a metal compound and a carbonaceous material, such as a Si-C composite or a Sn-C composite. Alternatively, the negative electrode active material may include any one of the above materials, or a mixture of two materials may be used. In addition, the negative electrode active material may include a lithium metal thin film as the lithium metal negative electrode active material. In addition, the carbon-based negative electrode active material may include both low-crystalline carbon and high-crystalline carbon. Low-crystalline carbon includes soft carbon and hard carbon, and high-crystalline carbon includes amorphous, plate-like, flaky, spherical, or fibrous natural graphite or artificial graphite, kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesocarbon microbeads, mesophase pitch, and coke derived from petroleum or coal tar pitch.

[0065] According to an embodiment of the present invention, when the negative electrode active material layer includes a solid electrolyte, the solid electrolyte may be the same as or different from the solid electrolyte included in the solid electrolyte layer of the all-solid-state battery. Specifically, the solid electrolyte included in the negative electrode active material layer may be an azide-type sulfide-based solid electrolyte.

[0066] According to an embodiment of the present invention, when the negative electrode active material layer includes a binder, the binder is a component that helps bind components (such as the negative electrode active material, the solid electrolyte, and the conductive material) in the negative electrode active material layer. The binder may include at least one selected from polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HEP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene propylene diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), and fluororubber.

[0067] According to embodiments of the present invention, when the negative electrode active material layer includes a conductive material, the conductive material can be conductive without causing chemical changes in the all-solid-state battery. Specifically, the conductive material may include at least one of the following: graphite, such as natural or artificial graphite; carbon black, such as acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermally cracked carbon black; conductive fibers, such as carbon fibers or metal fibers, or fluorinated carbon; metal powder, such as aluminum powder or nickel powder; conductive whiskers, such as zinc oxide or potassium titanate; conductive metal oxides, such as titanium oxide; and conductive materials, such as polyphenylene derivatives.

[0068] The present invention provides an all-solid-state battery 100 including the negative electrode.

[0069] According to embodiments of the present invention, an all-solid-state battery may include a negative electrode, a solid electrolyte layer, and a positive electrode. Specifically, an all-solid-state battery may include a cell. According to the present invention, an all-solid-state battery can refer to a cell, and can refer to a structure formed by stacking multiple cell units. A cell may be a structure in which a negative electrode, a solid electrolyte layer, and a positive electrode are stacked sequentially. Specifically, as... Figure 1 As shown, a cell can be formed by sequentially stacking a first negative electrode current collector 10, a first negative electrode active material layer 11, a first solid electrolyte layer 30, a positive electrode active material layer 21, a positive electrode current collector 20, a second positive electrode active material layer 21', a second solid electrolyte layer 30', a second negative electrode active material layer 11', and a second negative electrode current collector 10'. In this case, the first negative electrode current collector and the second negative electrode current collector can each independently correspond to the aforementioned negative electrode current collector, and the first negative electrode active material layer and the second negative electrode active material layer can each independently correspond to the aforementioned negative electrode active material layer. Furthermore, the first solid electrolyte layer and the second solid electrolyte layer can be the same as or different from each other, the first negative electrode active material layer and the second negative electrode active material layer can be the same as or different from each other, and the first negative electrode current collector and the second negative electrode current collector can be the same as or different from each other.

[0070] According to embodiments of the present invention, the positive electrode current collector 20 may include a metal with high conductivity. The positive electrode current collector 20 may include various metals that allow the positive electrode active material layer to adhere easily, provided that the various metals are not reactive within the voltage range of the battery. Specifically, the negative electrode current collector may be, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, or silver. Furthermore, the thickness of the positive electrode current collector can typically range from 3 μm to 500 μm and can be used in various forms, such as films, sheets, foils, meshes, porous bodies, foams, or nonwoven fabrics.

[0071] According to an embodiment of the present invention, the positive electrode active material layers 21 and 21' may optionally include a solid electrolyte, a binder and a conductive material, as well as the positive electrode active material.

[0072] According to embodiments of the present invention, the positive electrode active material can be a lithium metal oxide for lithium insertion and extraction. For example, the lithium metal oxide may include at least one metal selected from cobalt, manganese, nickel, and iron. More specifically, the lithium metal oxide may be at least one selected from LiCoO2, LiNiO2, LiMn2O4, LiCoPO4, LiFePO4, and LiNixMnyCozO2 (x+y+z=1), and each lithium metal oxide may be doped and / or coated as needed.

[0073] According to an embodiment of the present invention, when the positive electrode active material layer includes a solid electrolyte, the solid electrolyte may be the same as or different from the solid electrolyte included in the solid electrolyte layer of an all-solid-state battery. Specifically, the solid electrolyte included in the positive electrode active material layer may be an azide-type sulfide-based solid electrolyte.

[0074] According to embodiments of the present invention, when the positive electrode active material layer includes an adhesive, the adhesive is a component that facilitates bonding between the components of the positive electrode active material layer (e.g., the positive electrode active material, the solid electrolyte, and the conductive material). The adhesive may include at least one selected from polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HEP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene propylene diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), and fluororubber.

[0075] According to embodiments of the present invention, when the positive electrode active material layer comprises a conductive material, the conductive material can be conductive without causing chemical changes in the all-solid-state battery. Specifically, the conductive material can be at least one material selected from the following: graphite, such as natural or artificial graphite; carbon black, such as acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermally cracked carbon black; conductive fibers, such as carbon fibers or metal fibers; fluorinated carbon; metal powder, such as aluminum powder or nickel powder; conductive whiskers, such as zinc oxide or potassium titanate; conductive metal oxides, such as titanium oxide; and conductive materials, such as polyphenylene derivatives.

[0076] According to an embodiment of the present invention, the solid electrolyte layers 30 and 30' may optionally include an adhesive and a solid electrolyte.

[0077] According to embodiments of the present invention, the solid electrolyte in the solid electrolyte layer may be the same as or different from the solid electrolyte contained in the negative electrode active material layer and / or the positive electrode active material layer. Specifically, the solid electrolyte contained in the solid electrolyte layer may be at least one selected from sulfide-based solid electrolytes, oxide-based solid electrolytes, chloride-based solid electrolytes, and polymer solid electrolytes. More specifically, the solid electrolyte may be an azide-type sulfide-based solid electrolyte.

[0078] According to an embodiment of the invention, when the solid electrolyte layer includes an adhesive, the adhesive is a component that facilitates bonding between the solid electrolytes and may be selected from at least one of the following: polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HEP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene propylene diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), and fluororubber.

[0079] This invention provides a method for preparing an all-solid-state battery, thereby preparing an all-solid-state battery.

[0080] According to an embodiment of the present invention, a method for fabricating an all-solid-state battery includes: fabricating a negative electrode by forming a negative electrode active material layer on at least one surface of a negative electrode current collector (S10); fabricating a cell by stacking the negative electrode, solid electrolyte layer, and positive electrode formed in S10 (S20); and isostatically pressing the cell formed in S20 in the stacking direction (S30). The tensile strength of the negative electrode current collector can range from 1,000 MPa to 2,000 MPa. In the method for fabricating an all-solid-state battery according to the present invention, since the descriptions of the negative electrode, solid electrolyte layer, positive electrode, and cell are the same as those of the related components described above, their details will be omitted in the method for fabricating the all-solid-state battery. Unless otherwise stated, the negative electrode, solid electrolyte layer, positive electrode, and cell are the same as those of the components described above.

[0081] According to an embodiment of the present invention, "S10," the step of preparing the negative electrode, can be performed by forming a negative electrode active material layer on at least one surface of the negative electrode current collector. When the negative electrode active material layer is formed on at least one surface of the negative electrode current collector, the negative electrode active material layer can be formed by coating a negative electrode slurry (which is formed by mixing a negative electrode active material and a solvent) together with a solid electrolyte, a binder, or a conductive material onto the negative electrode current collector and drying the result. The content of each component used to prepare the negative electrode slurry can be adjusted within a known range based on the energy density and process performance of the all-solid-state battery. Furthermore, coating can be performed within a known range. Specifically, coating can be performed by applying the slurry onto the negative electrode current collector using a doctor blade. Drying can be performed within a known range. Specifically, drying can be performed using a convection oven.

[0082] According to an embodiment of the present invention, "S20," namely the step of preparing a unit cell for isostatic pressing, can be performed by stacking a negative electrode, a solid electrolyte layer, and a positive electrode. Specifically, "S20" can be performed by sequentially stacking a first negative electrode current collector 10, a first negative electrode active material layer 11, a first solid electrolyte layer 30, a first positive electrode active material layer 21, a positive electrode current collector 20, a second positive electrode active material layer 21', a second solid electrolyte layer 30', a second negative electrode active material layer 11', and a second negative electrode current collector 10'.

[0083] According to an embodiment of the invention, "S30," namely the step of performing isostatic pressing to improve the energy density of the all-solid-state battery, involves performing isostatic pressing on the cell obtained in S20 in the stacking direction. According to the invention, when a negative electrode current collector is applied, during the isostatic pressing of the cell obtained in S20 in S30, even if pressure and time are applied until the permissible limit of the isostatic pressing equipment is reached to densify the internal particles of the electrode and the interface between the electrode layer and the electrolyte layer, thereby improving resistance, the protruding tabs T and T' can be prevented from breaking without additional protective components.

[0084] According to an embodiment of the invention, "S30" can be performed by isostatic pressing after forming a vacuum-laminated package of the cell obtained in S20. When the cell is isostatically pressed, the vacuum lamination prevents the pressing medium from affecting the components within the cell, as the pressing medium would permeate into the cell. The interior of the lamination is maintained in a vacuum state, thereby preventing the formation of spaces other than the cell within the lamination, thus guiding the pressure from the isostatic pressing to be uniformly transmitted to the cell. In the vacuum lamination, the negative electrode current collectors 10 and 10' located on at least one outermost surface of the cell can be positioned in contact with an additional plate, and the vacuum lamination can then be formed together with the plate.

[0085] According to embodiments of the present invention, isostatic pressing can be performed at pressures ranging from 100 MPa to 1,000 MPa. For example, isostatic pressing can be performed at pressures of at least 100 MPa, at least 150 MPa, at least 200 MPa, at least 250 MPa, at least 300 MPa, at least 350 MPa, at least 400 MPa, or at least 450 MPa. Furthermore, isostatic pressing can be performed at pressures of up to 1,000 MPa, up to 950 MPa, up to 900 MPa, up to 850 MPa, up to 800 MPa, up to 700 MPa, up to 650 MPa, up to 600 MPa, up to 550 MPa, or up to 500 MPa. When isostatic pressing is performed within the aforementioned pressure range, resistance can be improved by densifying the internal particles of the electrode and the interface between the electrode layer and the electrolyte layer.

[0086] According to embodiments of the present invention, isostatic pressing can be performed at temperatures ranging from 50°C to 150°C. Specifically, isostatic pressing can be performed at temperatures of at least 50°C, at least 55°C, at least 60°C, at least 65°C, at least 70°C, at least 75°C, at least 80°C, at least 85°C, or at least 90°C. Additionally, isostatic pressing can be performed at temperatures of up to 150°C, up to 145°C, up to 140°C, up to 135°C, up to 130°C, up to 125°C, up to 120°C, up to 115°C, up to 110°C, up to 105°C, or up to 100°C. When isostatic pressing is performed within this temperature range, deformation and degradation of the cell due to temperature can be prevented, and the internal particles and interlayer interfaces of the electrodes can be made more highly compact.

[0087] According to embodiments of the present invention, isostatic pressing can be performed for a period of 5 to 120 minutes. For example, isostatic pressing can be performed for at least 5 minutes, at least 10 minutes, at least 15 minutes, at least 20 minutes, at least 25 minutes, or at least 30 minutes, and for a maximum of 120 minutes, at most 110 minutes, at most 100 minutes, at most 90 minutes, at most 80 minutes, at most 70 minutes, at most 60 minutes, at most 50 minutes, at most 40 minutes, or at most 30 minutes. When isostatic pressing is performed within this time range, productivity reduction due to isostatic pressing can be prevented, and the internal particles and interlayer interfaces of the electrode can be more highly densified.

[0088] The embodiments of the present invention will now be described in detail so that those skilled in the art can readily reproduce the invention. However, the present invention can be implemented in various different forms and is not limited to the embodiments described herein.

[0089] Preparation Examples

[0090] Preparation Example 1

[0091] Fe-Ni alloy foil current collectors with an average grain size of 10 nm were prepared by electroplating.

[0092] Comparative Preparation Example 1

[0093] Fe-Ni alloy foil current collectors with an average grain size of 180 nm were prepared by electroplating.

[0094] Experimental Example 1

[0095] The average grain size and tensile strength of the Fe-Ni alloy foils prepared in Preparation Example 1 and Comparative Preparation Example 1 were measured using the following methods, and the results are shown in the table below. 1.

[0096] • Average grain size (nm): Measured by XRD and calculated according to the following formula 1 (Scherrer formula).

[0097] [Formula 1]

[0098] FWHM=Kλ / LCOsθ

[0099] In Formula 1, “L” represents the crystal size, “θ” is the value obtained by dividing the analysis result expressed in terms of 2θ by “2”, “K” is a constant value, and “λ” is the wavelength used for XRD measurement.

[0100] • Tensile strength (MPa): Measured using a tensile strength tester.

[0101] Table 1

[0102] category Average grain size (nm) Tensile strength (MPa) Preparation Example 1 10 1,300 Comparative Preparation Example 1 180 500

[0103] As shown in Table 1, even when Fe-Ni alloy foil current collectors are prepared by the same electroplating scheme, they exhibit different tensile strengths due to differences in average grain size.

[0104] Examples and Comparative Examples

[0105] Example

[0106] Prepare a negative electrode, a positive electrode, and a solid electrolyte layer. Then, as follows... Figure 1As shown, a unit cell is fabricated as follows: a solid electrolyte layer is stacked on each side of the positive electrode active material layer of the positive electrode, such that one surface of the solid electrolyte layer is in contact with the positive electrode active material layer; then, a negative electrode active material layer is stacked on the other surface of the solid electrolyte layer, such that it is in contact with the solid electrolyte layer. After the unit cells are stacked on a plate, a vacuum lamination package is formed in the unit cells including the plate. The vacuum-laminated unit cells are then introduced into an isostatic pressing apparatus and isostatically pressed at a pressure of 450 MPa to fabricate an all-solid-state battery.

[0107] Comparative Examples

[0108] According to the embodiments, all-solid-state batteries were prepared in the same manner as in Example 1, except that a nickel current collector with a thickness of 10 μm was used instead of the negative electrode current collector prepared in Example 1.

[0109] In this case, the nickel current collector exhibited a tensile strength of 500 MPa, measured in the same manner as in Experimental Example 1.

[0110] Experimental Example 2

[0111] For the all-solid-state batteries prepared in the examples and comparative examples, after removing the vacuum lamination packaging, it was determined whether the tabs T and T' regions of the negative electrode current collector were broken.

[0112] Therefore, it was found that the all-solid-state battery prepared according to the embodiments did not crack in the tab region of the negative electrode current collector after isostatic pressing. However, it was found that the all-solid-state battery prepared according to the comparative embodiments cracked in the tab region of the negative electrode current collector.

[0113] Experimental Example 3

[0114] The molding process was carried out by charging the all-solid-state battery prepared according to the examples and comparative examples to 4.25V at a constant current of 0.05C at a temperature of 25°C, and discharging the all-solid-state battery to 2.5V at a constant current of 0.05C.

[0115] Subsequently, the all-solid-state battery was charged to 4.25V at a constant current of 0.2C at 25°C, and then discharged to 2.5V at a constant current of 0.2C for a second cycle. The discharge capacity and average voltage were then measured.

[0116] Then, the all-solid-state battery was charged to 4.25V at a constant current of 0.5C at 25°C, and then discharged to 2.5V at a constant current of 0.5C for the sixth cycle. The discharge capacity and average voltage were then measured.

[0117] Furthermore, charging to 4.25V at a constant current of 0.2C at 25°C and then discharging to 2.5V at a constant current of 0.2C is considered one cycle, and this charging and discharging is repeated for a total of 57 cycles. Then, after measuring the discharge capacity in the eighth and 57th cycles, the capacity retention rate is measured based on the discharge capacity in the 57th cycle compared to the eighth cycle.

[0118] The discharge capacity, average voltage, and capacity retention measured in each step are shown in Table 2 below.

[0119] [Table 2]

[0120]

[0121] As shown in Table 2, it was found that compared with the comparative embodiment using a nickel current collector as the negative electrode current collector, the battery power and durability were improved by using a current collector with higher tensile strength prepared according to Example 1 of the present invention as the negative electrode current collector.

[0122] As described above, according to the present invention, when preparing an all-solid-state battery, even if pressure and time are applied until the permissible limit of the isostatic pressing equipment is reached, and isostatic pressing is performed until the permissible limit of the isostatic pressing equipment is reached, thereby densifying the internal particles of the electrode and the interface between the electrode layer and the electrolyte layer, it is still possible to prevent the protruding tabs from breaking, so that the negative electrode has improved resistance and improved energy density.

[0123] Furthermore, according to the present invention, since an all-solid-state battery including the negative electrode can be fabricated, an all-solid-state battery with improved resistance, excellent energy density and higher production efficiency can be fabricated.

[0124] While the invention has been described above with reference to exemplary embodiments and accompanying drawings, it is not limited thereto. Various modifications and alterations can be made by those skilled in the art without departing from the spirit and scope of the invention as claimed in the following claims.

Claims

1. A negative electrode, comprising: Negative electrode current collector; and A layer of negative electrode active material formed on at least one surface of the negative electrode current collector. The tensile strength of the negative electrode current collector ranges from 1,000 MPa to 2,000 MPa.

2. The negative electrode according to claim 1, wherein, The negative electrode current collector is an Fe-Ni alloy foil.

3. The negative electrode according to claim 1, wherein, The negative electrode current collector is an Fe-Ni alloy foil containing nickel, wherein the nickel content ranges from 10% to 60% by weight.

4. The negative electrode according to claim 1, wherein, The negative electrode current collector is an Fe-Ni alloy foil containing nickel, wherein the nickel content ranges from 30% to 60% by weight.

5. The negative electrode according to claim 1, wherein, The negative electrode current collector is an Fe-Ni alloy foil with an average grain size ranging from 0 nm to 50 nm.

6. The negative electrode according to claim 1, wherein, The negative electrode current collector is a Fe-Ni alloy foil with an average grain size range of less than 10 nm.

7. The negative electrode according to claim 1, wherein, The elongation of the negative electrode current collector ranges from 0% to 10%.

8. The negative electrode according to claim 1, wherein, The thickness of the negative electrode current collector ranges from 4 μm to 20 μm.

9. The negative electrode according to claim 1, wherein, The negative electrode active material layer comprises at least one selected from carbon-based negative electrode active materials, silicon-based negative electrode active materials, and lithium metal negative electrode active materials.

10. An all-solid-state battery comprising the negative electrode according to claim 1.

11. The all-solid-state battery according to claim 10, wherein, The all-solid-state battery includes a sulfide-based solid electrolyte.

12. A method for preparing an all-solid-state battery, the method comprising: The negative electrode is prepared by forming a layer of negative electrode active material on at least one surface of the negative electrode current collector; Unit cells are fabricated by stacking negative electrodes, solid electrolyte layers, and positive electrodes. and The cell units are subjected to isostatic pressing in the stacking direction. The tensile strength of the negative electrode current collector ranges from 1,000 MPa to 2,000 MPa.

13. The method for preparing an all-solid-state battery according to claim 12, wherein, The unit cell has a structure in which a negative electrode, a solid electrolyte layer, a positive electrode, a solid electrolyte layer, and a negative electrode are stacked in sequence.

14. The method for preparing an all-solid-state battery according to claim 12, wherein, After vacuum lamination packaging of the cell unit, the cell unit is subjected to isostatic pressing.

15. The method for preparing an all-solid-state battery according to claim 12, wherein, The isostatic pressing is carried out under pressures ranging from 100 MPa to 1,000 MPa.

16. The method for preparing an all-solid-state battery according to claim 12, wherein, The isostatic pressing is carried out at a temperature ranging from 50°C to 150°C.

17. The method for preparing an all-solid-state battery according to claim 12, wherein, The isostatic pressing is performed for a period of 5 to 120 minutes.

18. The method for preparing an all-solid-state battery according to claim 12, wherein, The negative electrode current collector is an Fe-Ni alloy foil containing nickel, wherein the nickel content ranges from 10% to 60% by weight.

19. The method for preparing an all-solid-state battery according to claim 12, wherein, The negative electrode current collector is an Fe-Ni alloy foil with an average grain size ranging from 0 nm to 50 nm.

20. A negative electrode comprising: Negative electrode current collector; and A layer of negative electrode active material formed on at least one surface of the negative electrode current collector. The negative electrode current collector is an Fe-Ni alloy foil with a tensile strength ranging from 1,000 MPa to 2,000 MPa. The negative electrode current collector is a nickel-containing Fe-Ni alloy foil, wherein the nickel content ranges from 30% to 60% by weight. The average grain size of the Fe-Ni alloy foil of the negative electrode current collector is less than 10 nm.

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