All-solid rechargeable battery and manufacturing method thereof

Abstract

A method for manufacturing an all-solid-state rechargeable battery, according to an embodiment, comprises the steps of: forming a unit cell including a positive electrode, a solid electrolyte layer, and a negative electrode; forming a planarizing layer on the unit cell to planarize the surface of the unit cell and thereby form an all-solid-state cell; stacking a plurality of the all-solid-state cells to form a stack cell; and sealing and pressurizing the stack cell using a pouch member.

Description

All-solid-state secondary battery and manufacturing method thereof

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

[0002] Recent reports of explosion risks in batteries using liquid electrolytes have led to the development of all-solid-state secondary batteries. All-solid-state secondary batteries are composed entirely of solid materials and utilize solid electrolytes. These all-solid-state secondary batteries are safe, eliminating the risk of explosion due to electrolyte leakage. They also offer the advantages of being easy to manufacture in thin forms, offering high energy density and the ability to produce large capacities.

[0003] These all-solid-state secondary batteries must maintain point contact for ion transfer. To achieve this, the multiple unit cells forming the stacked cells of the all-solid-state secondary battery must be uniformly pressurized throughout.

[0004] The embodiments are intended to provide an all-solid-state secondary battery and a manufacturing method thereof in which unit cells forming a stack cell are uniformly pressurized and the thickness can be minimized.

[0005] According to one embodiment, an all-solid-state secondary battery includes a stack cell in which a plurality of all-solid-state cells are stacked; and a pouch member for sealing the stack cell, wherein the all-solid-state cell includes a unit cell including a positive electrode, a solid electrolyte layer, and a negative electrode, and a planarization layer for planarizing a surface of the unit cell, wherein the planarization layer includes one selected from polyacrylate (PA), polyurethane (PU), silicone, and polyethylene (PE).

[0006] The thickness of the above flattening layer may be 0 to 300 μm.

[0007] The unit cell has a structure in which the solid electrolyte layer and the cathode are sequentially laminated on both sides of the anode based on the anode, the solid electrolyte layer includes a first solid electrolyte layer and a second solid electrolyte layer respectively positioned on both sides of the anode, the cathode includes a first cathode in contact with the first solid electrolyte layer, and a second cathode in contact with the second solid electrolyte layer, and the planarization layer may include a first planarization layer that planarizes the first cathode, and a second planarization layer that planarizes the second cathode.

[0008] One surface of the first cathode and one surface of the second cathode have a surface roughness greater than 0, the first planarization layer can cover at least a portion of one surface of the first cathode, and the second planarization layer can cover at least a portion of one surface of the second cathode.

[0009] The first planarization layer may have a first opening exposing one surface of the first cathode, and the second planarization layer may have a second opening exposing one surface of the second cathode.

[0010] The plurality of all-solid-state cells include a first all-solid-state cell and a second all-solid-state cell adjacent to each other, and the first planarization layer of the first all-solid-state cell can be in contact with the second planarization layer of the second all-solid-state cell.

[0011] The above unit cell has a structure in which the solid electrolyte layer and the cathode are sequentially laminated on one side of the anode, and the planarization layer can planarize the cathode.

[0012] One surface of the cathode has a surface roughness greater than 0, and the planarization layer can cover at least a portion of the one surface of the cathode.

[0013] The above planarization layer may have an opening exposing one surface of the cathode.

[0014] The plurality of all-solid-state cells include a first all-solid-state cell and a second all-solid-state cell adjacent to each other, and the planarization layer of the first all-solid-state cell can be in contact with the anode of the second all-solid-state cell.

[0015] In addition, a method for manufacturing an all-solid-state secondary battery according to one embodiment may include: forming a unit cell including a positive electrode, a solid electrolyte layer, and a negative electrode; forming a planarization layer on the unit cell to planarize a surface of the unit cell to form an all-solid-state cell; stacking a plurality of the all-solid-state cells to form a stack cell; and sealing and pressurizing the stack cell with a pouch member.

[0016] The above planarization layer can be formed using a coating process of coating a planarization material on the surface of the cathode.

[0017] The above flattening material may include any one selected from polyacrylate (PA), polyurethane (PU), silicone, and polyethylene (PE).

[0018] The above coating process may include any one polymer foam manufacturing process selected from extrusion, compression molding, injection molding, reaction injection molding, and solid state method.

[0019] The thickness of the above flattening layer can be formed to be 0 to 300 ㎛.

[0020] One surface of the cathode has a surface roughness greater than 0, and the planarization layer can cover at least a portion of the one surface of the cathode.

[0021] According to embodiments, by forming a planarization layer that flattens the surface of the unit cell, the stacked cell can be uniformly pressurized. Accordingly, the failure rate of the all-solid-state secondary battery can be reduced and its performance can be improved.

[0022] In addition, since the planarization layer is formed using a coating process, the thickness of the stack cell can be minimized, thereby reducing the overall weight of the all-solid-state secondary battery and increasing the energy density of the all-solid-state secondary battery.

[0023] Figure 1 is a cross-sectional view of an all-solid-state battery.

[0024] Figure 2 is a cross-sectional view of an all-solid-state battery including a precipitated negative electrode.

[0025] Figure 3 is a cross-sectional view of an all-solid-state secondary battery according to one embodiment.

[0026] Figure 4 is an enlarged cross-sectional view of part A of Figure 3.

[0027] Figure 5 is a schematic flowchart of a method for manufacturing an all-solid-state secondary battery according to one embodiment.

[0028] Figures 6 to 8 are cross-sectional views sequentially illustrating a method for manufacturing an all-solid-state secondary battery according to one embodiment.

[0029] Figure 9 is a cross-sectional view of an all-solid-state secondary battery according to another embodiment.

[0030] Figure 10 is an enlarged cross-sectional view of part B of Figure 9.

[0031] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention. The present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0032] Additionally, throughout the specification, whenever a part is said to "include" a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0033] To clearly illustrate various layers and regions in the drawings, their thicknesses are enlarged, and similar parts are designated by the same drawing reference numerals throughout the specification. When an element such as a layer, film, region, or plate is said to be "over" or "on" another element, this includes not only the case where it is "directly over" the other element, but also the case where there are other elements in between. Conversely, when an element is said to be "directly over" another element, it means that there are no other elements in between.

[0034] Furthermore, the term "layer" here includes not only shapes formed on the entire surface when observed in a plan view, but also shapes formed on a portion of the surface. Here, "or" is not interpreted in an exclusive sense; for example, "A or B" is interpreted to include A, B, A+B, etc.

[0035] Cathode for all-solid-state secondary batteries

[0036] In one embodiment, a positive electrode for an all-solid-state secondary battery is provided, which includes a current collecting layer and a positive electrode active material layer positioned on the current collecting layer, wherein the positive electrode active material layer includes at least one of a positive electrode active material, a sulfide-based solid electrolyte, a binder, and a conductive material. However, the positive electrode for an all-solid-state secondary battery is not limited thereto, and may include more or less components than the components described above.

[0037] In one embodiment, a positive electrode for an all-solid-state secondary battery is manufactured by applying a positive electrode composition including at least one of a positive electrode active material, a sulfide-based solid electrolyte, a binder, and a conductive material to a current collecting layer, followed by drying and rolling.

[0038] positive electrode active material

[0039] The cathode active material can be applied without limitation as long as it is one commonly used in all-solid-state secondary batteries. For example, the cathode active material may be a compound capable of reversible lithium intercalation and deintercalation, and may include a compound represented by any of the following chemical formulas.

[0040] Li a A 1-b X b D2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5);

[0041] Li a A 1-b X b O 2-c D c (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05);

[0042] Li a E 1-b X b O 2-c D c (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05);

[0043] Li a E 2-b X b O 4-c D c (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05);

[0044] Li a Ni 1-b-c Co b X c D α (0.90 ≤ a ≤1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.5, 0 <α ≤ 2);

[0045] Li a Ni 1-b-c Co b X c O 2-α T α(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2);

[0046] Li a Ni 1-b-c Co b X c O 2-α T2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2);

[0047] Li a Ni 1-b-c Mr b X c D α (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2);

[0048] Li a Ni 1-b-c Mr b X c O 2-α T α (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2);

[0049] Li a Ni 1-b-c Mr b X c O 2-α T2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2);

[0050] Li a Ni b HAVE BEEN c G d O2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1);

[0051] Li a Ni b Co c Mr d G eO2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤0.5, 0.001 ≤ e ≤ 0.1);

[0052] Li a NiG b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0053] Li a CoG b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0054] Li a Mn 1-b G b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0055] Li a Mn2G b O4(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0056] Li a Mn 1-g G g PO4(0.90 ≤ a ≤ 1.8, 0 ≤ g ≤ 0.5);

[0057] QO2; QS2; LiQS2;

[0058] V2O5; LiV2O5;

[0059] LiZO2;

[0060] LiNiVO4;

[0061] Li (3-f) J2(PO4)3(0 ≤ f ≤ 2);

[0062] Li (3-f) Fe2(PO4)3(0 ≤ f ≤ 2);

[0063] Li a FePO4(0.90 ≤ a ≤ 1.8).

[0064] In the above chemical formulas, A is selected from the group consisting of Ni, Co, Mn, and combinations thereof; X is selected from the group consisting of Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, and combinations thereof; D is selected from the group consisting of O, F, S, P, and combinations thereof; E is selected from the group consisting of Co, Mn, and combinations thereof; T is selected from the group consisting of F, S, P, and combinations thereof; G is selected from the group consisting of Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, and combinations thereof; Q is selected from the group consisting of Ti, Mo, Mn, and combinations thereof; Z is selected from the group consisting of Cr, V, Fe, Sc, Y, and combinations thereof; J is selected from the group consisting of V, Cr, Mn, Co, Ni, Cu, and combinations thereof.

[0065] The cathode active material may be, for example, lithium cobalt oxide (LCO), lithium nickel oxide (LNO), lithium nickel cobalt oxide (NC), lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide (NCM), lithium nickel manganese oxide (NM), lithium manganese oxide (LMO), or lithium iron phosphate (LFP).

[0066] The positive electrode active material may include a lithium nickel-based oxide represented by the following chemical formula 1, a lithium cobalt-based oxide represented by the following chemical formula 2, a lithium iron phosphate-based compound represented by the following chemical formula 3, or a combination thereof.

[0067] [Chemical Formula 1]

[0068] Li a1 Ni x1 M 1 y1 M 2 1-x1-y1 O2

[0069] In the above chemical formula 1, 0.9≤a1≤1.8, 0.3≤x1≤1, 0≤y1≤0.7, and M 1 and M2 is one or more elements independently selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, F, Fe, Mg, Mn, Mo, Nb, P, S, Si, Sr, Ti, V, W, and Zr.

[0070] [Chemical Formula 2]

[0071] Li a2 Co x2 M 3 1-x2 O2

[0072] In the above chemical formula 2, 0.9≤a2≤1.8, 0.6≤x2≤1, and M 3 is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Cu, F, Fe, Mg, Mn, Mo, Nb, P, S, Si, Sr, Ti, V, W, and Zr.

[0073] [Chemical Formula 3]

[0074] Li a3 Fe x3 M 4 (1-x3) PO4

[0075] In the above chemical formula 3, 0.9≤a3≤1.8, 0.6≤x3≤1, and M 4 is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, F, Fe, Mg, Mn, Mo, Nb, P, S, Si, Sr, Ti, V, W, and Zr.

[0076] The average particle diameter (D) of the above positive electrode active material 50 ) may be 1 μm to 25 μm, for example, 3 μm to 25 μm, 5 μm to 25 μm, 5 μm to 20 μm, 8 μm to 20 μm, or 10 μm to 18 μm. A cathode active material having such a particle size range can be harmoniously mixed with other components within the cathode active material layer and can realize high capacity and high energy density.

[0077] The above-mentioned positive electrode active material may be in the form of a secondary particle formed by agglomeration of a plurality of primary particles, or may be in the form of a single particle. In addition, the above-mentioned positive electrode active material may be spherical or nearly spherical in shape, or may be polyhedral or irregular in shape.

[0078] Sulfide-based solid electrolyte

[0079] Sulfide-based solid electrolytes include, for example, Li2S-P2S5, Li2S-P2S5--LiX (where X is a halogen element, for example, I or Cl), Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z. m S n (m, n are integers, Z is Ge, Zn or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (p, q are integers, and M is P, Si, Ge, B, Al, Ga or In), or a combination thereof.

[0080] Such sulfide-based solid electrolytes can be obtained, for example, by mixing Li2S and P2S5 in a molar ratio of 50:50 to 90:10, or 50:50 to 80:20, and optionally heat-treating them. Within the above mixing ratio range, a sulfide-based solid electrolyte having excellent ionic conductivity can be produced. Here, the ionic conductivity can be further improved by further including other components such as SiS2, GeS2, and B2S3.

[0081] Methods for mixing sulfur-containing raw materials for producing sulfide-based solid electrolytes include mechanical milling or the solution method. Mechanical milling involves placing the starting raw materials in a reactor and vigorously stirring them with a ball mill or similar device to finely atomize and mix them. Using the solution method, the starting raw materials are mixed in a solvent to obtain a solid electrolyte as a precipitate. Furthermore, heat treatment after mixing can solidify the crystals of the solid electrolyte and improve ionic conductivity. For example, a sulfide-based solid electrolyte can be produced by mixing sulfur-containing raw materials and heat-treating them twice or more, resulting in a sulfide-based solid electrolyte with high ionic conductivity and robustness.

[0082] For example, the sulfide-based solid electrolyte particles may include argyrodite-type sulfides. The argyrodite-type sulfides may include, for example, Li a M b P c S d A e (wherein a, b, c, d and e are all 0 or more and 12 or less, M is a metal other than Li or a combination of multiple metals other than Li, and A is F, Cl, Br, or I) and a specific example is Li 7-x PS 6-x A x (x is 0.2 or more and 1.8 or less, and A is F, Cl, Br, or I) can be expressed by the chemical formula. The above argyrodite-type sulfide is specifically Li3PS4, Li7P3S 11 , Li7PS6, Li6PS5Cl, Li6PS5Br, Li 5.8 PS 4.8 Cl 1.2 , Li 6.2 PS 5.2 Br 0.8 It could be the back.

[0083] Sulfide-based solid electrolyte particles containing these argyrodite-type sulfides have an ionic conductivity of 10, which is the ionic conductivity of a typical liquid electrolyte at room temperature. -4 10 inland -2 It has a high ionic conductivity approaching the S / cm range, can form a close bond between a positive electrode active material and a solid electrolyte without causing a decrease in ionic conductivity, and can further form a close interface between an electrode layer and a solid electrolyte layer. An all-solid-state battery including this can have improved battery performance, such as rate characteristics, Coulombic efficiency, and cycle life characteristics.

[0084] An argyrodite-type sulfide-based solid electrolyte can be prepared, for example, by mixing lithium sulfide, phosphorus sulfide, and optionally, a lithium halide. After mixing, a heat treatment may be performed. The heat treatment may include, for example, two or more heat treatment steps.

[0085] Average particle diameter (D) of sulfide-based solid electrolyte particles according to an embodiment 50 ) may be 5.0 ㎛ or less, for example, 0.1 ㎛ to 5.0 ㎛, 0.1 ㎛ to 4.0 ㎛, 0.1 ㎛ to 3.0 ㎛, 0.5 ㎛ to 2.0 ㎛, or 0.1 ㎛ to 1.5 ㎛. Alternatively, the sulfide-based solid electrolyte particles may have an average particle diameter (D) of 0.1 ㎛ to 1.0 ㎛ depending on the location or purpose of use. 50 ) may be small particles, or may have an average particle diameter (D) of 1.5 ㎛ to 5.0 ㎛. 50 ) may be large particles. Sulfide-based solid electrolyte particles with this particle size range can effectively penetrate between solid particles in a battery, and have excellent contact with the electrode active material and connectivity between solid electrolyte particles. The average particle size of the sulfide-based solid electrolyte particles may be measured from a microscope image, and for example, the particle size distribution is obtained by measuring the sizes of about 20 particles in a scanning electron microscope image, where D 50It may have been calculated.

[0086] The content of the solid electrolyte in the positive electrode for the all-solid-state battery may be 0.5 wt% to 35 wt%, for example, 1 wt% to 35 wt%, 5 wt% to 30 wt%, 8 wt% to 25 wt%, or 10 wt% to 20 wt%. This is the content relative to the total weight of components in the positive electrode, and specifically, it can be said to be the content relative to the total weight of the positive electrode active material layer.

[0087] In one embodiment, the positive electrode active material layer may include 50 wt% to 99.35 wt% of the positive electrode active material, 0.5 wt% to 35 wt% of the sulfide-based solid electrolyte, 0.1 wt% to 10 wt% of the fluorine-based resin binder, and 0.05 wt% to 5 wt% of the vanadium oxide, based on 100 wt% of the positive electrode active material layer. When the above content ranges are satisfied, the positive electrode for an all-solid-state secondary battery can maintain high adhesiveness while implementing high capacity and high ionic conductivity, and the viscosity of the positive electrode composition can be maintained at an appropriate level, thereby improving processability.

[0088] bookbinder

[0089] The binder serves to adhere the positive electrode active material particles well to each other and also to adhere the positive electrode active material well to the current collector, and representative examples thereof include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc.

[0090] Challenge

[0091] The above-described positive electrode active material layer may further include a conductive material. The conductive material is used to impart conductivity to the electrode, and may include, for example, carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, and carbon nanotubes; metal-based materials containing copper, nickel, aluminum, silver, and the like in the form of metal powder or metal fibers; conductive polymers such as polyphenylene derivatives; or combinations thereof.

[0092] The conductive material may be included in an amount of 0.1 wt% to 5 wt%, or 0.1 wt% to 3 wt%, based on the total weight of each component of the positive electrode for the all-solid-state battery, or based on the total weight of the positive electrode active material layer. Within the above content range, the conductive material can improve electrical conductivity without degrading battery performance.

[0093] When the positive electrode active material layer further includes a conductive material, the positive electrode active material layer may include 45 wt% to 99.25 wt% of the positive electrode active material, 0.5 wt% to 35 wt% of the sulfide-based solid electrolyte, 0.1 wt% to 10 wt% of the fluorine-based resin binder, 0.05 wt% to 5 wt% of the vanadium oxide, and 0.1 wt% to 5 wt% of the conductive material, based on 100 wt% of the positive electrode active material layer.

[0094] Meanwhile, the positive electrode for the lithium secondary battery may further include an oxide-based inorganic solid electrolyte in addition to the above-described solid electrolyte. The oxide-based inorganic solid electrolyte may be, for example, Li 1+x Ti 2-x Al(PO4)3(LTAP)(0≤x≤4), Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (0 <x<2, 0≤y<3), BaTiO3, Pb(Zr,Ti)O3(PZT), Pb 1-x La x Zr1-y Ti y O3(PLZT)(0≤x<1, 0≤y<1), PB(Mg3Nb 2 / 3 )O3-PbTiO3(PMN-PT), HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, lithium phosphate (Li3PO4), lithium titanium phosphate (Li x Ti y (PO4)3, 0 <x<2, 0<y<3), Li 1+x+y (Al, Ga) x (Ti, Ge) 2-x Si y P 3-y O 12 (0≤x≤1, 0≤y≤1), lithium lanthanum titanate (Li x La y TiO3, 0 <x<2, 0<y<3), Li2O, LiAlO2, Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2계 세라믹스, 가넷(Garnet)계 세라믹스 Li 3+x La3M2O 12 (M= Te, Nb, or Zr; x is an integer from 1 to 10), or a combination thereof.

[0095] All-solid-state secondary battery

[0096] In one embodiment, an all-solid-state secondary battery is provided, which includes the aforementioned positive electrode, negative electrode, and a solid electrolyte layer positioned between the positive electrode and negative electrode. The all-solid-state secondary battery may also be referred to as an all-solid-state battery or an all-solid-state lithium secondary battery.

[0097] Figure 1 is a cross-sectional view of an all-solid-state battery.

[0098] Referring to FIG. 1, the all-solid-state battery (1000) may have a structure in which an electrode assembly in which a negative electrode (40) including a negative electrode current collecting layer (41) and a negative electrode active material layer (43), a solid electrolyte layer (30), and a positive electrode (20) including a positive electrode active material layer (23) and a positive electrode current collecting layer (21) are laminated is housed in a case such as a pouch. The all-solid-state battery (1000) may further include an elastic layer (50) on the outer side of at least one of the positive electrode (20) and the negative electrode (40). Although FIG. 1 illustrates one electrode assembly including a negative electrode (40), a solid electrolyte layer (30), and a positive electrode (20), an all-solid-state battery may be manufactured by laminating two or more electrode assemblies.

[0099] cathode

[0100] An anode for an all-solid-state battery may include, for example, a current collecting layer and a negative electrode active material layer positioned on the current collecting layer. The negative electrode active material layer includes a negative electrode active material and may further include a binder, a conductive material, and / or a solid electrolyte.

[0101] The negative active material may include a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

[0102] Materials capable of reversibly intercalating / deintercalating lithium ions include carbon-based negative electrode active materials, such as crystalline carbon, amorphous carbon, or a combination thereof. Examples of crystalline carbon include graphite, such as natural graphite or artificial graphite in an amorphous, plate-like, flake-like, spherical, or fibrous form, and examples of amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, and calcined coke.

[0103] As an alloy of lithium metal, an alloy of lithium with one or more metals selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn can be used.

[0104] As a material that can be doped and dedoped with lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material can be used, and as a Si-based negative electrode active material, silicon, silicon-carbon composite, SiO x (0 <x≤2), Si-Q 합금(Q는 알칼리 금속, 알칼리 토금속, 13족 원소, 14족 원소, 15족 원소, 16족 원소, 전이금속, 희토류 원소 및 이들의 조합으로 이루어진 군에서 선택되는 원소이며, Si은 아님), Sn계 음극 활물질로는 Sn, SnO2, Sn-R 합금(R은 알칼리 금속, 알칼리 토금속, 13족 원소, 14족 원소, 15족 원소, 16족 원소, 전이금속, 희토류 원소 및 이들의 조합으로 이루어진 군에서 선택되는 원소이며, Sn은 아님) 등을 들 수 있고, 또한 이들 중 적어도 하나와 SiO2를 혼합하여 사용할 수도 있다. 원소 Q 및 R로는 Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, 및 이들의 조합으로 이루어진 군에서 선택되는 것을 사용할 수 있다.

[0105] The silicon-carbon composite may be, for example, a silicon-carbon composite including a core comprising crystalline carbon and silicon particles and an amorphous carbon coating layer positioned on the surface of the core. The crystalline carbon may be artificial graphite, natural graphite, or a combination thereof. As the amorphous carbon precursor, coal pitch, mesophase pitch, petroleum pitch, coal oil, petroleum heavy oil, or a polymer resin such as a phenol resin, a furan resin, or a polyimide resin may be used. At this time, the content of silicon may be 10 wt% to 50 wt% with respect to the total weight of the silicon-carbon composite. In addition, the content of the crystalline carbon may be 10 wt% to 70 wt% with respect to the total weight of the silicon-carbon composite, and the content of the amorphous carbon may be 20 wt% to 40 wt% with respect to the total weight of the silicon-carbon composite. In addition, the thickness of the amorphous carbon coating layer may be 5 nm to 100 nm.

[0106] Average particle diameter of silicon particles (D 50 ) may be 10 nm to 20 μm, for example, 10 nm to 500 nm. The silicon particles may exist in an oxidized form, and in this case, the atomic content ratio of Si:O in the silicon particles, which indicates the degree of oxidation, may be 99:1 to 33:67. The silicon particles may be SiO x It can be a particle, in which case SiO x In the range of x, the range can be greater than 0 and less than or equal to 2. Here, the average particle diameter (D 50 ) is measured by a particle size analyzer using laser diffraction and means the diameter of particles with a cumulative volume of 50% in the particle size distribution.

[0107] The Si-based negative electrode active material or Sn-based negative electrode active material can be used in combination with a carbon-based negative electrode active material. The mixing ratio of the Si-based negative electrode active material or Sn-based negative electrode active material and the carbon-based negative electrode active material can be 1:99 to 90:10 by weight.

[0108] The content of the negative active material in the negative active material layer may be 95 wt% to 99 wt% with respect to the total weight of the negative active material layer.

[0109] In one embodiment, the negative electrode active material layer further includes a binder and may optionally further include a conductive material. The content of the binder in the negative electrode active material layer may be 1 wt% to 5 wt% based on the total weight of the negative electrode active material layer. In addition, when the negative electrode active material layer further includes a conductive material, the negative electrode active material layer may include 90 wt% to 98 wt% of the negative electrode active material, 1 wt% to 5 wt% of the binder, and 1 wt% to 5 wt% of the conductive material.

[0110] The above binder serves to adhere the negative electrode active material particles well to each other and also to adhere the negative electrode active material well to the current collecting layer. The binder may include an insoluble binder, a water-soluble binder, or a combination thereof.

[0111] The above-described non-aqueous binder may include, for example, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer comprising ethylene oxide, an ethylene propylene copolymer, polystyrene, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.

[0112] The water-soluble binder may be a rubber-based binder or a polymer resin binder. The rubber-based binder may be selected from styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluororubber, and combinations thereof. The polymer resin binder may be selected from polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0113] When a water-soluble binder is used as the negative electrode binder, a thickener capable of imparting viscosity may be used together, and the thickener may include, for example, a cellulose-based compound. The cellulose-based compound may include carboxymethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, an alkali metal salt thereof, or a combination thereof. Na, K, or Li may be used as the alkali metal. The amount of the thickener used may be 0.1 to 3 parts by weight based on 100 parts by weight of the negative electrode active material.

[0114] The conductive material is used to provide conductivity to the electrode, and may include, for example, carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, and carbon nanotubes; metal-based materials in the form of metal powder or metal fibers, including copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0115] The cathode current collecting layer may be selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and a combination thereof.

[0116] As another example, the negative electrode for the all-solid-state battery may be a precipitation-type negative electrode. The precipitation-type negative electrode refers to a negative electrode that does not include a negative electrode active material when the battery is assembled, but in which lithium metal or the like is precipitated when the battery is charged, and this acts as a negative electrode active material.

[0117] Figure 2 is a cross-sectional view of an all-solid-state battery including a precipitated negative electrode.

[0118] Referring to FIG. 2, the precipitation-type negative electrode (40') may include a current collecting layer (41) and a negative electrode coating layer (45) positioned on the current collecting layer (41). An all-solid-state battery having such a precipitation-type negative electrode (40') starts initial charging in a state in which no negative electrode active material exists, and during charging, high-density lithium metal or the like is precipitated between the current collecting layer (41) and the negative electrode coating layer (45) to form a lithium metal layer (44), which may function as the negative electrode active material. Accordingly, in an all-solid-state battery that has been charged more than once, the precipitation-type negative electrode (40') may include a current collecting layer (41), a lithium metal layer (44) positioned on the current collecting layer (41), and a negative electrode coating layer (45) positioned on the metal layer. The lithium metal layer (44) refers to a layer in which lithium metal or the like is precipitated during the charging process of the battery, and may be referred to as a metal layer or a negative electrode active material layer.

[0119] The cathode coating layer (45) may include a metal, carbon material, or a combination thereof that acts as a catalyst.

[0120] The metal may include, for example, gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, zinc, or a combination thereof, and may consist of one of these or of an alloy of several types. When the metal is in particle form, its average particle diameter (D 50 ) may be less than about 4 μm, for example, 10 nm to 4 μm.

[0121] The carbon material may be, for example, crystalline carbon, amorphous carbon, or a combination thereof. The crystalline carbon may be, for example, natural graphite, artificial graphite, mesophase carbon microbeads, or a combination thereof. The amorphous carbon may be, for example, carbon black, activated carbon, acetylene black, Denka black, Ketjen black, or a combination thereof.

[0122] When the cathode coating layer (45) includes both metal and carbon material, the mixing ratio of the metal and carbon material may be, for example, a weight ratio of 1:10 to 2:1. In this case, the precipitation of lithium metal can be effectively promoted and the characteristics of the all-solid-state battery can be improved. The cathode coating layer (45) may include, for example, a carbon material supported with a catalytic metal, or may include a mixture of metal particles and carbon material particles.

[0123] The cathode coating layer (45) may include, for example, a metal and amorphous carbon, in which case the precipitation of lithium metal can be effectively promoted.

[0124] The cathode coating layer (45) may further include a binder, and the binder may be a conductive binder. In addition, the cathode coating layer (45) may further include general additives such as fillers, dispersants, and ionic conductive agents.

[0125] The thickness of the cathode coating layer (45) may be, for example, 100 nm to 20 ㎛, or 500 nm to 10 ㎛, or 1 ㎛ to 5 ㎛.

[0126] The precipitation-type negative electrode (40') may further include, for example, a thin film on the surface of the current collecting layer (41), that is, between the current collecting layer (41) and the negative electrode coating layer (45). The thin film may include an element capable of forming an alloy with lithium. The element capable of forming an alloy with lithium may be, for example, gold, silver, zinc, tin, indium, silicon, aluminum, bismuth, etc., and may be composed of one type thereof or may be composed of multiple types of alloys. The thin film may further flatten the precipitation form of the lithium metal layer (44) and further improve the characteristics of the all-solid-state battery. The thin film may be formed by, for example, a vacuum deposition method, a sputtering method, a plating method, etc. The thickness of the thin film may be, for example, 1 nm to 500 nm.

[0127] solid electrolyte layer

[0128] The solid electrolyte layer (30) may include a sulfide-based solid electrolyte, an oxide-based solid electrolyte, etc. The specific details of the sulfide-based solid electrolyte and the oxide-based solid electrolyte are as described above.

[0129] In one example, the solid electrolyte included in the positive electrode (20) and the solid electrolyte included in the solid electrolyte layer (30) may include the same compound or different compounds. For example, when both the positive electrode (20) and the solid electrolyte layer (30) include an argyrodite-type sulfide-based solid electrolyte, the overall performance of the all-solid-state secondary battery may be improved. In addition, for example, when both the positive electrode (20) and the solid electrolyte layer (30) include the above-described coated solid electrolyte, the all-solid-state secondary battery may implement high capacity and high energy density while implementing excellent initial efficiency and lifespan characteristics.

[0130] Meanwhile, the average particle diameter (D) of the solid electrolyte included in the positive electrode (20) 50 ) is the average particle diameter (D) of the solid electrolyte included in the solid electrolyte layer (30). 50) may be smaller than the average particle size of the solid electrolyte (20). In this case, the overall performance can be improved by increasing the mobility of lithium ions while maximizing the energy density of the all-solid-state battery. For example, the average particle size (D) of the solid electrolyte included in the positive electrode (20) 50 ) may be 0.1 ㎛ to 1.0 ㎛, or 0.1 ㎛ to 0.8 ㎛, and the average particle diameter (D50) of the solid electrolyte included in the solid electrolyte layer (30) may be 1.5 ㎛ to 5.0 ㎛, or 2.0 ㎛ to 4.0 ㎛, or 2.5 ㎛ to 3.5 ㎛. When such a particle diameter range is satisfied, the energy density of the all-solid-state secondary battery can be maximized while the transfer of lithium ions is facilitated, thereby suppressing the resistance and improving the overall performance of the all-solid-state secondary battery. Here, the average particle diameter (D) of the solid electrolyte 50 ) may be measured by a particle size analyzer using laser diffraction. Alternatively, the particle size is measured by selecting 20 random particles from a microscope image such as a scanning electron microscope and obtaining a particle size distribution, where D 50 You can also calculate the value.

[0131] The solid electrolyte layer may further include a binder in addition to the solid electrolyte. The binder may include, but is not limited to, styrene butadiene rubber, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, an acrylate polymer, or a combination thereof, and any binder used in the art may be used. The acrylate polymer may be, for example, butyl acrylate, polyacrylate, polymethacrylate, or a combination thereof.

[0132] A solid electrolyte layer can be formed by adding a solid electrolyte to a binder solution, coating the solution on a substrate film, and drying the solution. The solvent for the binder solution may be isobutyryl isobutyrate, xylene, toluene, benzene, hexane, or a combination thereof. The solid electrolyte layer formation process is widely known in the art, so a detailed description will be omitted.

[0133] The thickness of the solid electrolyte layer may be, for example, 10 μm to 150 μm.

[0134] The solid electrolyte layer may further include an alkali metal salt, and / or an ionic liquid, and / or a conductive polymer.

[0135] The alkali metal salt may be, for example, a lithium salt. The content of the lithium salt in the solid electrolyte layer may be 1 M or more, for example, 1 M to 4 M. In this case, the lithium salt may improve ionic conductivity by enhancing the mobility of lithium ions in the solid electrolyte layer.

[0136] Lithium salts include, for example, LiSCN, LiN(CN)2, Li(CF3SO2)3C, LiC4F9SO3, LiN(SO2CF2CF3)2, LiCl, LiF, LiBr, LiI, LiB(C2O4)2, LiBF4, LiBF3(C2F5), lithium bis(oxalato)borate (LiBOB), lithium oxalyldifluoroborate (LIODFB), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(trifluoro methanesulfonyl)imide (LiTFSI, LiN(SO2CF3)2), lithium bis(fluorosulfonyl)imide (LiFSI, It may include LiN(SO2F)2), LiCF3SO3, LiAsF6, LiSbF6, LiClO4 or mixtures thereof.

[0137] Additionally, the lithium salt may be an imide type, for example, the imide type lithium salt may include lithium bis(trifluoro methanesulfonyl)imide (LiTFSI, LiN(SO2CF3)2), lithium bis(fluorosulfonyl)imide (LiFSI, LiN(SO2F)2). The lithium salt may maintain or improve ionic conductivity by appropriately maintaining chemical reactivity with the ionic liquid.

[0138] Ionic liquids are salts or molten salts that are composed only of ions and are liquid at room temperature, with a melting point below room temperature.

[0139] The ionic liquid comprises a) one or more cations selected from ammonium, pyrrolidinium, pyridinium, pyrimidinium, imidazolium, piperidinium, pyrazolium, oxazolium, pyridazinium, phosphonium, sulfonium, triazolium, and mixtures thereof, and b) BF4. - , PF6 - , AsF6 - , SbF6 - , AlCl4 - , HSO4 - , ClO4 - , CH3SO3 - , CF3CO2 - , Cl - , Br - , I - , BF4 - , SO4 - , CF3SO3 - , (FSO2)2N - , (C2F5SO2)2N - , (C2F5SO2)(CF3SO2)N - , and (CF3SO2)2N - It may be a compound containing one or more anions selected from among:

[0140] The ionic liquid may be, for example, one or more selected from the group consisting of N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide, N-butyl-N-methylpyrrolidinium bis(3-trifluoromethylsulfonyl)imide, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide, and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide.

[0141] In the solid electrolyte layer, the weight ratio of the solid electrolyte and the ionic liquid may be 0.1:99.9 to 90:10, for example, 10:90 to 90:10, 20:80 to 90:10, 30:70 to 90:10, 40:60 to 90:10, or 50:50 to 90:10. A solid electrolyte layer satisfying the above range can maintain or improve ionic conductivity by improving the electrochemical contact area with the electrode. Accordingly, the energy density, discharge capacity, rate characteristics, etc. of the all-solid-state battery can be improved.

[0142] The all-solid-state battery may be a unit cell having a structure of anode / solid electrolyte layer / cathode, a bi-cell having a structure of cathode / solid electrolyte layer / anode / solid electrolyte layer / cathode, or a laminated battery in which the structure of the unit cell is repeated.

[0143] The shape of the all-solid-state battery is not particularly limited, and may be, for example, coin-shaped, button-shaped, sheet-shaped, stacked, cylindrical, or flat. Furthermore, all-solid-state batteries can be applied to large-scale batteries used in electric vehicles, for example. For example, all-solid-state batteries can be used in hybrid vehicles such as plug-in hybrid electric vehicles (PHEVs). Furthermore, they can be used in fields requiring large amounts of power storage, such as electric bicycles or power tools.

[0144] Hereinafter, an all-solid-state secondary battery according to one embodiment will be described with reference to FIGS. 3 and 4.

[0145] FIG. 3 is a cross-sectional view of an all-solid-state secondary battery according to one embodiment, and FIG. 4 is an enlarged cross-sectional view of part A of FIG. 3.

[0146] As illustrated in FIGS. 3 and 4, an all-solid-state secondary battery according to one embodiment is a secondary battery capable of being charged and discharged, and includes a stack cell (100) and a pouch member (200).

[0147] A stack cell (100) may include a plurality of stacked all-solid-state cells (UC).

[0148] Each all-solid-state cell (UC) may include a unit cell (110) and a planarization layer (120).

[0149] A unit cell (110) may include an anode (111), a solid electrolyte layer (112), and a cathode (113). Here, the anode (111) may include a cathode, and the cathode (113) may include an anode.

[0150] The flattening layer (120) can flatten the surface of the unit cell (110).

[0151] In the embodiment illustrated in FIG. 3, a structure in which four all-solid-state cells (UC) are stacked is illustrated, but it is not necessarily limited thereto, and a variety of all-solid-state cells (UC) may be stacked.

[0152] When multiple all-solid-state cells (UC) are stacked, the planarization layer (120) of the all-solid-state cell (UC) can be in contact with the planarization layer (120) of the adjacent all-solid-state cell (UC).

[0153] As illustrated in FIGS. 3 and 4, the unit cell (110) may have a bi-cell structure in which a solid electrolyte layer (112) and a cathode (113) are sequentially laminated on both sides of the anode (111) based on the anode (111). Here, the positional relationship above and below is set based on the Z direction.

[0154] The positive electrode (111) may include a positive electrode current collecting layer (111a), and a first positive electrode active material layer (1111b) and a second positive electrode active material layer (1112b) positioned on both sides of the positive electrode current collecting layer (111a), respectively.

[0155] The positive electrode current collecting layer (111a) may have a plate shape or a foil shape. The positive electrode current collecting layer (111a) may include any one selected from aluminum (Al), indium (In), copper (Cu), magnesium (Mg), stainless steel (SUS), titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), germanium (Ge), and lithium (Li).

[0156] The first positive electrode active material layer (1111b) and the second positive electrode active material layer (1112b) may be formed by coating on both sides of the positive electrode current collecting layer (111a), respectively. However, it is not necessarily limited thereto and may be formed using various methods such as transfer. The first positive electrode active material layer (1111b) and the second positive electrode active material layer (1112b) may include any one selected from lithium salts such as lithium nickel cobalt manganese oxide (NCM), lithium cobalt oxide (LCO), lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide (NCA), lithium manganate, and lithium iron phosphate, nickel sulfide, copper sulfide, lithium sulfur, iron oxide, or vanadium oxide.

[0157] The solid electrolyte layer (112) may include a first solid electrolyte layer (1121) and a second solid electrolyte layer (1122) located on each of both sides of the anode (111).

[0158] The solid electrolyte layer (112) may be positioned between the positive electrode (111) and the negative electrode (113). That is, the first solid electrolyte layer (1121) may be positioned between the first positive electrode active material layer (1111b) and the first negative electrode coating layer (1131b), and the second solid electrolyte layer (1122) may be positioned between the second positive electrode active material layer (1112b) and the second negative electrode coating layer (1132b).

[0159] The solid electrolyte layer (112) may include, but is not limited to, various known sulfide-based solid electrolyte materials. For example, the solid electrolyte layer (112) may be Li2S-P2S5, Li2S-P2S5-LiX (X is a halogen element, for example, I, Cl), Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-ZmSn (m, n are positive numbers, Z is one of Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-LipMOq (p, q are positive numbers, M is P, Si, Ge, It may include one of B, Al, Ga, and In. The solid electrolyte layer (112) may include at least one of an amorphous and a crystalline layer.

[0160] The cathode (113) may include a first cathode (1131) in contact with the first solid electrolyte layer (1121), and a second cathode (1132) in contact with the second solid electrolyte layer (1122).

[0161] The first cathode (1131) may include a first cathode current collecting layer (1131a) and a first cathode coating layer (1131b) positioned on one surface of the first cathode current collecting layer (1131a). The first cathode coating layer (1131b) may be positioned between the first cathode current collecting layer (1131a) and the first solid electrolyte layer (1121). The second cathode (1132) may include a second cathode current collecting layer (1132a) and a second cathode coating layer (1132b) positioned on one surface of the second cathode current collecting layer (1132a). The second cathode coating layer (1132b) may be positioned between the second cathode current collecting layer (1132a) and the second solid electrolyte layer (1122).

[0162] The first negative electrode current collecting layer (1131a) and the second negative electrode current collecting layer (1132a) may have a plate shape or a foil shape. The first negative electrode current collecting layer (1131a) and the second negative electrode current collecting layer (1132a) may include various known metals and compounds that do not react with lithium. The outer surface (OS) of the first negative electrode current collecting layer (1131a) and the second negative electrode current collecting layer (1132a) may actually have an uneven surface. At this time, by measuring the thickness of the first negative electrode current collecting layer (1131a) and the second negative electrode current collecting layer (1132a) using a device such as a laser scanning microscope, the degree of unevenness of the outer surface (OS) of the first negative electrode current collecting layer (1131a) and the second negative electrode current collecting layer (1132a), i.e., the surface roughness, can be calculated.

[0163] Surface roughness refers to the surface roughness or the degree of surface irregularity. This surface roughness can be calculated using the maximum height (Rmax), the ten-point average roughness (Rz), and the centerline average roughness (Ra). When a surface roughness of 0 is defined as a flat surface, the outer surfaces (OS) of the first negative electrode current collecting layer (1131a) and the second negative electrode current collecting layer (1132a) can have a surface roughness greater than 0. Accordingly, the outer surfaces (OS) of the first negative electrode (1131) and the second negative electrode (1132) can have a surface roughness greater than 0.

[0164] The first cathode current collecting layer (1131a) and the second cathode current collecting layer (1132a) may include any one selected from stainless steel (SUS), copper (Cu), titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni).

[0165] The first cathode coating layer (1131b) and the second cathode coating layer (1132b) may include silver (Ag) and carbon (C), but are not limited thereto. For example, the first cathode coating layer (1131b) and the second cathode coating layer (1132b) may have a structure in which particles formed of a metal or semiconductor including at least one of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn) are contained in a carbon layer including at least one of carbon black (CB), furnace black (FB), acetylene black (AB), ketjen black (KB), and graphene. When charging an all-solid-state secondary battery, lithium is precipitated between the first negative electrode current collecting layer (1131a) and the first negative electrode coating layer (1131b) or between the second negative electrode current collecting layer (1132a) and the second negative electrode coating layer (1132b), and a lithium metal layer is formed between the first negative electrode current collecting layer (1131a) and the first negative electrode coating layer (1131b) or between the second negative electrode current collecting layer (1132a) and the second negative electrode coating layer (1132b), and after discharging of the all-solid-state secondary battery, the lithium precipitated between the first negative electrode current collecting layer (1131a) and the first negative electrode coating layer (1131b) or between the second negative electrode current collecting layer (1132a) and the second negative electrode coating layer (1132b) is removed, and the first negative electrode current collecting layer (1131a) and the first negative electrode The coating layer (1131b) may be in direct contact, or the second negative electrode current collecting layer (1132a) and the second negative electrode coating layer (1132b) may be in direct contact. In this way, the thickness of the negative electrode (113) may change during charging and discharging of the all-solid-state secondary battery, and this change in the thickness of the negative electrode (113) may change the pressure exerted on the solid electrolyte layer (112), thereby causing stress to be generated in the solid electrolyte layer (112).

[0166] The planarization layer (120) may include a first planarization layer (121) that planarizes the first cathode (1131) and a second planarization layer (122) that planarizes the second cathode (1132).

[0167] The planarization layer (120) may include any one selected from an elastic material such as rubber, elastomer, foam, polyacrylate (PA), polyurethane (PU), silicone, and polyethylene (PE). The foam may include a urethane foam having a closed cell structure. Since the planarization layer (120) is formed by coating on the outer surface (OS) of the first negative electrode current collecting layer (1131a) and the second negative electrode current collecting layer (1132a), it may come into contact with the outer surface (OS) of the first negative electrode current collecting layer (1131a) and the second negative electrode current collecting layer (1132a) having an uneven surface and planarize the surface of the unit cell (110). The outer surface (120a) of the planarization layer (120) is formed by being coated, so it has a uniform surface, and the inner surface (120b) of the planarization layer (120) is in contact with the outer surface (OS) of the first negative electrode current collecting layer (1131a) and the second negative electrode current collecting layer (1132a) which have uneven surfaces, so it may have an uneven surface. Accordingly, the thickness (t) of the planarization layer (120) may be uneven. The thickness (t) of the planarization layer (120) may be 0 to 300 ㎛. Here, the first planarization layer (121) may cover at least a part of one surface of the first negative electrode (1131), and the second planarization layer (122) may cover at least a part of one surface of the second negative electrode (1132). At this time, the first planarization layer (121) may have a first opening (OH1) exposing one surface of the first cathode (1131), and the second planarization layer (122) may have a second opening (OH2) exposing one surface of the second cathode (1132). In this case, the thickness (t) of the first planarization layer (121) and the second planarization layer (122) may be minimized.

[0168] The pouch member (200) can house a stack cell (100) including a plurality of all-solid-state cells (UC) therein. The pouch member (200) can seal the stack cell (100) by housing it therein and keeping it embedded, thereby blocking external air from entering the stack cell (100).

[0169] In this way, by forming a planarization layer (120) that flattens the surface of the unit cell (110), the stack cell (100) can be uniformly pressurized. Accordingly, the failure rate of the all-solid-state secondary battery can be reduced and its performance can be improved.

[0170] In addition, since the flattening layer (120) is formed using a coating process, the thickness of the stack cell (100) can be minimized, thereby reducing the overall weight of the all-solid-state secondary battery and increasing the energy density of the all-solid-state secondary battery.

[0171] Hereinafter, a method for manufacturing an all-solid-state secondary battery according to the above embodiment will be described in detail with reference to the drawings.

[0172] FIG. 5 is a schematic flowchart of a method for manufacturing an all-solid-state secondary battery according to one embodiment, and FIGS. 6 to 8 are cross-sectional views sequentially illustrating a method for manufacturing an all-solid-state secondary battery according to one embodiment.

[0173] First, as shown in FIGS. 5 and 6, a unit cell (110) including an anode (111), a solid electrolyte layer (112), and a cathode (113) is formed (S100).

[0174] Next, a planarization layer (120) is formed on the unit cell (110) to planarize the surface of the unit cell (110), thereby forming an all-solid-state cell (UC) (S200). The planarization layer (120) can be formed by coating a planarization material on the surface of the cathode (113). The planarization material can include any one selected from elastic materials such as rubber, elastomer, foam, polyacrylate (PA), polyurethane (PU), silicone, and polyethylene (PE). The thickness (t) of the planarization layer (120) can be 0 to 300 ㎛. At a point where the thickness of the planarization layer (120) is 0, the planarization layer (120) can have openings (OH1, OH2).

[0175] The flattening layer (120) can be formed using a coating process. This coating process may include a polymer foam manufacturing process.

[0176] Known polymer foam manufacturing processes may include extrusion, compression molding, injection molding, reaction injection molding, solid state methods, etc.

[0177] Since the flattening layer (120) is formed using a coating process, the thickness of the stack cell (100) can be minimized, thereby reducing the overall weight of the all-solid-state secondary battery and increasing the energy density of the all-solid-state secondary battery.

[0178] Next, as shown in FIGS. 5 and 7, a plurality of all-solid-state cells (UC) are stacked to form a stack cell (100) (S300).

[0179] Next, as illustrated in FIGS. 5 and 8, the stack cell (100) is sealed and pressurized with a pouch member (200) (S400). The pouch member (200) can accommodate the stack cell (100) by hermetically bonding the edges of a pair of pouch sheets, each of which has an insulating resin containing a thermosetting polymer applied to its inner surface.

[0180] In this way, by forming a planarization layer (120) containing an elastic material on the surface of the unit cell (110) to planarize the surface of the unit cell (110), the stack cell (100) can be uniformly pressed. Accordingly, the failure rate of the all-solid-state secondary battery can be reduced and its performance can be improved.

[0181] Meanwhile, in the above embodiment, the unit cell (110) is described as a unit cell having a bi-cell structure in which a positive electrode active material layer (111b), a solid electrolyte layer (112), and a negative electrode (113) are sequentially laminated on both sides of the positive electrode current collecting layer (111a), but it is not necessarily limited thereto, and a unit cell (110) having a mono-cell structure in which a positive electrode active material layer (111b), a solid electrolyte layer (112), and a negative electrode (113) are sequentially laminated on one side of the positive electrode current collecting layer (111a) is also possible.

[0182] Hereinafter, with reference to FIGS. 9 and 10, an all-solid-state secondary battery according to another embodiment of the present invention will be described in detail.

[0183] Fig. 9 is a cross-sectional view of an all-solid-state secondary battery according to another embodiment, and Fig. 10 is an enlarged cross-sectional view of part B of Fig. 9.

[0184] The other embodiments illustrated in FIGS. 9 and 10 are substantially the same as the one illustrated in FIGS. 3 and 4 except that they are unit cells of a mono-cell structure, and thus a repeated description thereof will be omitted.

[0185] As illustrated in FIGS. 9 and 10, an all-solid-state secondary battery according to another embodiment of the present invention includes a stack cell (100) and a pouch member (200). The stack cell (100) may include a plurality of all-solid-state cells (UC) that are stacked. Each all-solid-state cell (UC) may include a unit cell (110) and a planarization layer (120).

[0186] A unit cell (110) may include an anode (111), a solid electrolyte layer (112), and a cathode (113). The unit cell (110) may have a mono-cell structure in which a solid electrolyte layer (112) and a cathode (113) are sequentially laminated on one side of the anode based on the anode.

[0187] The positive electrode (111) may include a positive electrode current collecting layer (111a) and a positive electrode active material layer (111b) positioned on one surface of the positive electrode current collecting layer (111a).

[0188] The solid electrolyte layer (112) may be positioned between the positive electrode (111) and the negative electrode (113). That is, the solid electrolyte layer (112) may be positioned between the positive electrode active material layer (111b) and the negative electrode coating layer (113b).

[0189] The cathode (113) may include a cathode current collecting layer (113a) and a cathode coating layer (113b) positioned on one surface of the cathode current collecting layer (113a). The cathode coating layer (113b) may be positioned between the cathode current collecting layer (113a) and the solid electrolyte layer (112).

[0190] The flattening layer (120) can flatten the surface of the unit cell (110).

[0191] The planarization layer (120) is formed by coating on the outer surface (OS) of the negative electrode current collecting layer (113a), so that it can be in contact with the outer surface (OS) of the negative electrode current collecting layer (113a) having an uneven surface and planarize the surface of the unit cell (110). The outer surface (120a) of the planarization layer (120) is formed by coating, so that it has a uniform surface, and the inner surface (120b) of the planarization layer (120) is in contact with the outer surface (OS) of the negative electrode current collecting layer (113a) having an uneven surface, so that it can have an uneven surface. At this time, by measuring the thickness of the negative electrode current collecting layer (113a) using a device such as a laser scanning microscope, the degree of unevenness of the outer surface (OS) of the negative electrode current collecting layer (113a), i.e., surface roughness, can be calculated. When a surface roughness of 0 is defined as a flat surface, the outer surface (OS) of the negative electrode current collecting layer (113a) may have a surface roughness greater than 0. Accordingly, the outer surface (OS) of the negative electrode (113) may have a surface roughness greater than 0.

[0192] Here, the planarization layer (120) can cover at least a portion of one surface of the cathode (113). At this time, the planarization layer (120) can have an opening (OH) that exposes one surface of the cathode (113). In this case, the thickness (t) of the planarization layer (120) can be minimized.

[0193] When multiple all-solid-state cells (UC) are stacked, the planarization layer (120) of the all-solid-state cell (UC) can be in contact with the anode (111) of the adjacent all-solid-state cell (UC).

[0194] In this way, by forming a planarization layer (120) that planarizes the surface of the unit cell (110), the stack cell (100) can be uniformly pressurized. Therefore, the failure rate of the all-solid-state secondary battery can be reduced and its performance can be improved. In addition, since the planarization layer (120) is formed using a coating process, the thickness of the stack cell (100) can be minimized, thereby reducing the overall weight of the all-solid-state secondary battery and increasing the energy density of the all-solid-state secondary battery.

[0195] Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims also fall within the scope of the present invention.

Claims

1. A stack cell in which multiple all-solid-state cells are stacked; and A pouch member sealing the above stack cell Including, The above all-solid-state cell includes a unit cell including an anode, a solid electrolyte layer, and a cathode, and a planarization layer that planarizes the surface of the unit cell. An all-solid-state secondary battery, wherein the planarization layer comprises one selected from polyacrylate (PA), polyurethane (PU), silicone, and polyethylene (PE).

2. In paragraph 1, An all-solid-state secondary battery, wherein the thickness of the flattening layer is 0 to 300 ㎛.

3. In paragraph 2, The above unit cell has a structure in which the solid electrolyte layer and the cathode are sequentially laminated on both sides of the anode based on the anode, The solid electrolyte layer includes a first solid electrolyte layer and a second solid electrolyte layer located on each side of the anode, The cathode includes a first cathode in contact with the first solid electrolyte layer, and a second cathode in contact with the second solid electrolyte layer, An all-solid-state secondary battery, wherein the planarization layer includes a first planarization layer that planarizes the first negative electrode, and a second planarization layer that planarizes the second negative electrode.

4. In paragraph 3, One surface of the first cathode and one surface of the second cathode have a surface roughness greater than 0, The first planarization layer covers at least a portion of one surface of the first cathode, An all-solid-state secondary battery, wherein the second planarization layer covers at least a portion of one surface of the second negative electrode.

5. In paragraph 4, The first planarization layer has a first opening exposing one surface of the first cathode, An all-solid-state secondary battery, wherein the second planarization layer has a second opening exposing one surface of the second cathode.

6. In paragraph 3, The above plurality of all-solid-state cells include a first all-solid-state cell and a second all-solid-state cell adjacent to each other, An all-solid-state secondary battery, wherein the first planarization layer of the first all-solid-state cell is in contact with the second planarization layer of the second all-solid-state cell.

7. In paragraph 2, The above unit cell has a structure in which the solid electrolyte layer and the cathode are sequentially laminated on one side of the anode, An all-solid-state secondary battery, wherein the planarization layer planarizes the negative electrode.

8. In paragraph 7, One surface of the above cathode has a surface roughness greater than 0, An all-solid-state secondary battery, wherein the planarization layer covers at least a portion of one surface of the negative electrode.

9. In paragraph 8, An all-solid-state secondary battery, wherein the planarization layer has an opening exposing one surface of the cathode.

10. In paragraph 7, The above plurality of all-solid-state cells include a first all-solid-state cell and a second all-solid-state cell adjacent to each other, An all-solid-state secondary battery, wherein the planarization layer of the first all-solid-state cell is in contact with the positive electrode of the second all-solid-state cell.

11. A step of forming a unit cell including a positive electrode, a solid electrolyte layer, and a negative electrode; A step of forming a planarization layer to planarize the surface of the unit cell on the unit cell to form an all-solid cell; A step of forming a stack cell by stacking a plurality of the above all-solid-state cells; and A step of sealing and pressurizing the above stack cell with a pouch member. A method for manufacturing an all-solid-state secondary battery comprising:

12. In paragraph 11, A method for manufacturing an all-solid-state secondary battery, wherein the above-mentioned planarization layer is formed using a coating process of coating a planarization material on the surface of the above-mentioned negative electrode.

13. In paragraph 12, A method for manufacturing an all-solid-state secondary battery, wherein the flattening material comprises any one selected from polyacrylate (PA), polyurethane (PU), silicone, and polyethylene (PE).

14. In paragraph 12, A method for manufacturing an all-solid-state secondary battery, wherein the coating process comprises any one polymer foam manufacturing process selected from extrusion molding, compression molding, injection molding, reaction injection molding, and a solid state method.

15. In paragraph 11, A method for manufacturing an all-solid-state secondary battery, wherein the thickness of the above-mentioned flattening layer is formed to be 0 to 300 ㎛.

16. In paragraph 11, One surface of the above cathode has a surface roughness greater than 0, A method for manufacturing an all-solid-state secondary battery, wherein the planarization layer covers at least a portion of one surface of the negative electrode.

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