Manufacturing method of all-solid rechargeable battery

Abstract

A method for manufacturing an all-solid rechargeable battery, according to an embodiment, comprises: a step of allowing a first prismatic case having a concave first outer surface and a second prismatic case to face each other; a step of positioning an all-solid state cell including a positive electrode, a solid electrode layer, a negative electrode, and an elastic member, between the first prismatic case and the second prismatic case; and a step of deforming the first outer surface of the first prismatic case to be flat by fastening the first prismatic case and the second prismatic case to each other.

Description

Method for manufacturing an all-solid-state secondary battery

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

[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] The above-described information disclosed in the background technology of this invention is only intended to enhance understanding of the background of the present invention, and therefore may include information that does not constitute prior art.

[0004] The embodiments are intended to provide a method for manufacturing an all-solid-state secondary battery capable of stably maintaining performance by preventing deformation of the shape of a square case due to internal pressure.

[0005] However, the technical problems to be solved by the present invention are not limited to the problems described above, and other problems not mentioned can be clearly understood by those skilled in the art from the description of the invention described below.

[0006] According to one embodiment of the present invention for solving the above technical problem, a method for manufacturing an all-solid-state secondary battery includes the steps of: opposing a first rectangular case and a second rectangular case having a concave first outer surface; positioning an all-solid-state cell including a positive electrode, a solid electrolyte layer, a negative electrode, and an elastic member between the first rectangular case and the second rectangular case; and deforming the first outer surface of the first rectangular case to be flat by fastening the first rectangular case and the second rectangular case.

[0007] In the step of facing the first square case and the second square case, the first inner side of the first square case may face the second inner side of the second square case and may be convex toward the second inner side.

[0008] The first rectangular case includes a first bottom case and a first side wall case extending vertically from both ends of the first bottom case, and the second rectangular case includes a second bottom case and a second side wall case extending vertically from both ends of the second bottom case, and the first inner side surface of the first bottom case can face the second inner side surface of the second bottom case.

[0009] In the step of positioning the all-solid-state cell between the first square case and the second square case, the first central region, which is the central region of the first inner surface, can be in contact with the upper surface of the all-solid-state cell.

[0010] In the step of positioning the all-solid-state cell between the first square case and the second square case, a first peripheral region surrounding the first central region among the first inner surfaces may not be in contact with the upper surface of the all-solid-state cell.

[0011] In the step of flattening the first outer surface of the first square case, the first side fastening portion of the first side wall case and the second side fastening portion of the second side wall case can be fastened to each other.

[0012] The uneven shape of the first side fastening portion and the uneven shape of the second side fastening portion can be fastened to each other.

[0013] The first side fastening portion and the second side fastening portion can be welded to each other.

[0014] In the step of flattening the first outer surface of the first square case, the first inner surface of the first square case can all come into contact with the upper surface of the all-solid-state cell.

[0015] In the step of opposing the first square case and the second square case, the second bottom case of the second square case may have a flat second outer surface.

[0016] In the step of opposing the first square case and the second square case, the second bottom case of the second square case may have a concave second outer surface.

[0017] In the step of facing the first square case and the second square case, the second inner side surface of the second bottom case may face the first inner side surface of the first bottom case and may be convex toward the first inner side surface.

[0018] In the step of positioning the all-solid-state cell between the first square case and the second square case, the second central region, which is the central region of the second inner surface, can be in contact with the lower surface of the all-solid-state cell.

[0019] In the step of positioning the all-solid-state cell between the first square case and the second square case, a second peripheral region surrounding the second central region among the second inner surfaces may not be in contact with the lower surface of the all-solid-state cell.

[0020] In the step of flattening the first outer surface of the first bottom case, the second outer surface of the second bottom case can be flattened.

[0021] In the step of flattening the second outer surface of the second bottom case, the second inner surface of the second bottom case can all come into contact with the lower surface of the all-solid-state cell.

[0022] According to embodiments, by inserting an all-solid-state cell into a square case having a concave outer surface and then flattening the outer surface of the square case, the shape of the square case can be prevented from being deformed by internal pressure inside the square case.

[0023] Therefore, since the pressure applied to the all-solid-state cell can be maintained at a constant level, the performance of the all-solid-state secondary battery can be stably maintained.

[0024] The following drawings attached to this specification illustrate preferred embodiments of the present invention, and together with the detailed description of the invention described below, serve to further understand the technical idea of ​​the present invention, and therefore, the present invention should not be interpreted as being limited to matters described in such drawings.

[0025] Figure 1 is a cross-sectional view of an all-solid-state battery.

[0026] Figure 2 is a cross-sectional view of an all-solid-state battery including a precipitated negative electrode.

[0027] Figure 3 is a flowchart of a method for manufacturing an all-solid-state secondary battery according to one embodiment.

[0028] FIG. 4 is a perspective view of one step of a method for manufacturing an all-solid-state secondary battery according to one embodiment.

[0029] Figure 5 is a cross-sectional view taken along the line V-V' of Figure 4.

[0030] Figures 6 to 8 are cross-sectional views sequentially illustrating the next steps of Figure 5.

[0031] Figure 9 is a flowchart of a method for manufacturing an all-solid-state secondary battery according to another embodiment.

[0032] FIG. 10 is a perspective view of one step of a method for manufacturing an all-solid-state secondary battery according to another embodiment.

[0033] Fig. 11 is a cross-sectional view taken along line XI-XI' of Fig. 10.

[0034] Figures 12 to 14 are cross-sectional views sequentially illustrating the next steps of Figure 11.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] Cathode for all-solid-state secondary batteries

[0040] In one embodiment, a positive electrode for an all-solid-state secondary battery is provided, comprising a current collector and a positive electrode active material layer positioned on the current collector, wherein the positive electrode active material layer comprises at least one of a positive electrode active material, a sulfide-based solid electrolyte, a binder, and a conductive material. However, without limitation thereto, the positive electrode for an all-solid-state secondary battery may comprise more or less components than the components described above.

[0041] In one embodiment, the positive electrode for the 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 agent to a current collector, followed by drying and rolling.

[0042] positive electrode active material

[0043] The above-mentioned positive electrode active material can be applied without limitation as long as it is generally used in all-solid-state secondary batteries. For example, the above-mentioned positive electrode active material may be a compound capable of reversible intercalation and deintercalation of lithium, and may include a compound represented by any one of the following chemical formulas.

[0044] Li a A 1-b X b D2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5);

[0045] 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);

[0046] 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);

[0047] Li a E 2-b Xb O 4-c D c (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05);

[0048] 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);

[0049] 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);

[0050] 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);

[0051] 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);

[0052] 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);

[0053] Li a Ni 1-b-c Mr b X c O 2-αT2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α < 2);

[0054] The a Nor b E c G d O2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1);

[0055] The a Nor b Co c Mn d G e O2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤0.5, 0.001 ≤ e ≤ 0.1);

[0056] The a NiG b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0057] The a CoG b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0058] The a Mn 1-b G b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0059] The a Mn2G b O4(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0060] The a Mn 1-g G g PO4(0.90 ≤ a ≤ 1.8, 0 ≤ g ≤ 0.5);

[0061] QO2; QS2; LiQS2;

[0062] V2O5; LiV2O5;

[0063] LiZO2;

[0064] LiNiVO4;

[0065] Li (3-f) J2(PO4)3(0 ≤ f ≤ 2);

[0066] Li (3-f) Fe2(PO4)3(0 ≤ f ≤ 2);

[0067] Li a FePO4(0.90 ≤ a ≤ 1.8).

[0068] 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.

[0069] 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).

[0070] 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.

[0071] [Chemical Formula 1]

[0072] Li a1 Ni x1 M 1 y1 M 2 1-x1-y1 O2

[0073] In the above chemical formula 1, 0.9≤a1≤1.8, 0.3≤x1≤1, 0≤y1≤0.7, and M 1 and M 2 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.

[0074] [Chemical Formula 2]

[0075] Li a2 Co x2 M 3 1-x2 O2

[0076] 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.

[0077] [Chemical Formula 3]

[0078] Li a3 Fe x3 M 4 (1-x3) PO4

[0079] 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.

[0080] 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.

[0081] 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.

[0082] Sulfide-based solid electrolyte

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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 having 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 50 It may have been calculated.

[0090] 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.

[0091] 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.

[0092] bookbinder

[0093] 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.

[0094] Challenge

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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 Zr 1-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 yTiO3, 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.

[0099] All-solid-state secondary battery

[0100] 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.

[0101] Figure 1 is a cross-sectional view of an all-solid-state battery.

[0102] 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.

[0103] cathode

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] 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.

[0121] Figure 2 is a cross-sectional view of an all-solid-state battery including a precipitated negative electrode.

[0122] 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.

[0123] The cathode coating layer (45) may include a metal, carbon material, or a combination thereof that acts as a catalyst.

[0124] 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.

[0125] 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.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] 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 ㎛.

[0130] 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.

[0131] solid electrolyte layer

[0132] 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.

[0133] 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.

[0134] 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 (D) of the solid electrolyte included in the solid electrolyte layer (30) 50 ) may be 1.5 ㎛ to 5.0 ㎛, or 2.0 ㎛ to 4.0 ㎛, or 2.5 ㎛ to 3.5 ㎛. When this particle size 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.

[0135] 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.

[0136] 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.

[0137] The thickness of the solid electrolyte layer may be, for example, 10 μm to 150 μm.

[0138] The solid electrolyte layer may further include an alkali metal salt, and / or an ionic liquid, and / or a conductive polymer.

[0139] 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.

[0140] 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.

[0141] 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.

[0142] 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.

[0143] 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.

[0144] 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.

[0145] 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.

[0146] 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.

[0147] 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.

[0148] Hereinafter, a method for manufacturing an all-solid-state secondary battery according to one embodiment will be described with reference to FIGS. 3 to 8.

[0149] FIG. 3 is a flowchart of a method for manufacturing an all-solid-state secondary battery according to one embodiment, FIG. 4 is a perspective view of one step of a method for manufacturing an all-solid-state secondary battery according to one embodiment, FIG. 5 is a cross-sectional view taken along line V-V' of FIG. 4, and FIGS. 6 to 8 are cross-sectional views sequentially showing the next steps of FIG. 5.

[0150] First, as shown in FIGS. 3 to 5, the first square case (110) and the second square case (120) are placed face to face (S100).

[0151] A first rectangular case (110) and a second rectangular case (120) may be combined to form a rectangular case (100). The first rectangular case (110) may include a first bottom case (111) and a first side wall case (112) extending in the vertical direction (Z) from both ends of the first bottom case (111). Similarly, the second rectangular case (120) may include a second bottom case (121) and a second side wall case (122) extending in the vertical direction (Z) from both ends of the second bottom case (121).

[0152] The first bottom case (111) may have a first outer surface (111a) that is concave downward with respect to the vertical direction (Z) and a first inner surface (111b) that is convex downward with respect to the vertical direction (Z). The second bottom case (121) may have a flat second outer surface (121a) and a flat second inner surface (121b).

[0153] At this time, the first inner side (111b) of the first bottom case (111) of the first square case (110) may face the second inner side (121b) of the second bottom case (121) of the second square case (120) and may be convex toward the second inner side (121b).

[0154] And, the first side wall case (112) of the first square case (110) can be positioned to correspond to the second side wall case (122) of the second square case (120).

[0155] Next, as illustrated in FIGS. 3 and 6, the all-solid-state cell (200) is positioned between the first rectangular case (110) and the second rectangular case (120) (S200). At this time, since the second inner surface (121b) of the second rectangular case (120) is flat, the entire area of ​​the second inner surface (121b) of the second rectangular case (120) comes into contact with the lower surface of the all-solid-state cell (200). However, since the first inner surface (111b) of the first rectangular case (110) protrudes downward in a convex manner, only the first central area (CA1), which is the central area of ​​the first inner surface (111b) of the first rectangular case (110), comes into contact with the upper surface of the all-solid-state cell (200). Accordingly, the first peripheral area (PA1) surrounding the first central area (CA1) of the first inner surface (111b) of the first square case (110) does not come into contact with the upper surface of the all-solid-state cell (200).

[0156] The all-solid-state cell (200) may include a plurality of unit cells (210) and a plurality of elastic members (220). Here, the unit cell (210) may include a positive electrode (211), a solid electrolyte layer (212), and a negative electrode (213). In addition, the positive electrode (211) may include a cathode, and the negative electrode (213) may include an anode. The positive electrode (211) may include a positive electrode current collecting layer (211a), and a positive electrode active material layer (211b) positioned on one surface of the positive electrode current collecting layer (211a). The positive electrode current collecting layer (211a) may have a plate shape or a foil shape. The cathode current collecting layer (211a) 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). The cathode active material layer (211b) may include any one selected from lithium salts such as 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 negative electrode (213) may include a negative electrode current collecting layer (213a) and a negative electrode coating layer (213b) positioned on one surface of the negative electrode current collecting layer (213a). The negative electrode current collecting layer (213a) may have a plate shape or a foil shape. The negative electrode current collecting layer (213a) may include various known metals and compounds that do not react with lithium. The negative electrode current collecting layer (213a) may include any one selected from stainless steel (SUS), copper (Cu), titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni).

[0158] The cathode coating layer (213b) may include, but is not limited to, silver (Ag) and carbon (C). For example, the cathode coating layer (213b) 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 deposited between the negative electrode current collecting layer (213a) and the negative electrode coating layer (213b), and a lithium metal layer is formed between the negative electrode current collecting layer (213a) and the negative electrode coating layer (213b). After discharging the all-solid-state secondary battery, the lithium deposited between the negative electrode current collecting layer (213a) and the negative electrode coating layer (213b) is removed, so that the negative electrode current collecting layer (213a) and the negative electrode coating layer (213b) can come into direct contact.

[0159] The solid electrolyte layer (212) may be positioned between the positive electrode (211) and the negative electrode (213). That is, the solid electrolyte layer (212) may be positioned between the positive electrode active material layer (211b) and the negative electrode coating layer (213b). The solid electrolyte layer (212) may include, but is not limited to, various known sulfide-based solid electrolyte materials. For example, the solid electrolyte layer (212) 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 (212) may include at least one of an amorphous and a crystalline layer.

[0160] The elastic member (220) may include an elastic material such as rubber, elastomer, or foam.

[0161] A plurality of unit cells (210) are stacked, and a plurality of elastic members (220) are positioned between adjacent unit cells (210) and can be positioned between the outermost unit cell (210) and the square case (100).

[0162] In the embodiment illustrated in FIG. 3, the elastic member (220) is positioned between the unit cells (210) and also between the outermost unit cell (210) and the square case (100), but this is not necessarily limited to the case, and the elastic member (220) may be positioned only between the outermost unit cell (210) and the square case (100).

[0163] In order to minimize the interfacial resistance of the unit cell (210) including the solid electrolyte layer (212), the unit cell (210) must be maintained in a pressurized state. To this end, an elastic member (220) installed between the unit cells (210) and between the outermost unit cell (210) and the square case (100) can provide elasticity to the unit cell (210) so that a constant pressure can be applied to the unit cell (210).

[0164] The thickness of a conventional all-solid-state secondary battery having a square structure is fixed to the thickness of the square case, but the shape of the square case may be deformed to a convex shape due to internal pressure, i.e., elastic repulsive force, caused by an elastic member inside the square case. However, in the present embodiment, a first square case (110) having a concave first outer surface (111a) is manufactured in advance, and an all-solid-state secondary battery is manufactured using the first square case (110), thereby preventing deformation of the shape of the square case due to internal pressure, thereby stably maintaining performance. This will be described in more detail below.

[0165] Next, as shown in FIG. 3, FIG. 7, and FIG. 8, the first square case (110) and the second square case (120) are fastened together to deform the first outer surface (111a) of the first square case (110) flat (S300).

[0166] When the first square case (110) and the second square case (120) are fastened, the first side fastening portion (112a) formed on the first side wall case (112) of the first square case (110) and the second side fastening portion (122a) formed on the second side wall case (122) of the second square case (120) can be fastened to each other. The uneven shape of the second side fastening portion (122a) is combined and welded to the uneven shape of the first side fastening portion (112a), so that the first side fastening portion (112a) and the second side fastening portion (122a) can be fastened to each other. However, it is not necessarily limited thereto, and the structures of the first side fastening portion (112a) and the second side fastening portion (122a) can have various structures as long as they are structures for fastening.

[0167] Specifically, as illustrated in FIG. 7, by fastening the first square case (110) and the second square case (120), the first peripheral area (PA1) of the first bottom case (111) is pulled by the tensile force of the first side fastening portion (112a) and the second side fastening portion (122a), so that most of the first peripheral area (PA1) of the first inner surface (111b) of the first bottom case (111) comes into contact with the upper surface of the all-solid-state cell (200).

[0168] And, as illustrated in Fig. 8, the upper surface of the all-solid-state cell (200) expands due to the repulsive force of the elastic member (220), so that all areas (CA1, PA1) of the first inner surface (111b) of the first bottom case (111) come into contact with the upper surface of the all-solid-state cell (200). Accordingly, the first outer surface (111a) and the first inner surface (111b) of the first bottom case (111) are deformed to be flat.

[0169] In the past, the square case (100) was expanded outward by the repulsive force of the elastic member (220) inside the square case, but in the present embodiment, the solid-state cell (200) is inserted into the square case (100) in a state where a concave deformation is applied to the square case (100) in advance, so that the square case (100) is deformed by the repulsive force of the elastic member (220) and has a flat shape.

[0170] In this way, by inserting an all-solid-state cell into a square case having a concave outer surface and then flattening the outer surface of the square case, the shape of the square case can be prevented from being deformed by internal pressure inside the square case.

[0171] Therefore, since the pressure applied to the all-solid-state cell can be maintained at a constant level, the performance of the all-solid-state secondary battery can be stably maintained.

[0172] Meanwhile, in the above embodiment, only the first rectangular case has a concave first outer surface, but another embodiment is also possible in which the second rectangular case also has a concave second outer surface.

[0173] Hereinafter, with reference to FIGS. 9 to 14, a method for manufacturing an all-solid-state secondary battery according to another embodiment will be described in detail.

[0174] FIG. 9 is a flowchart of a method for manufacturing an all-solid-state secondary battery according to another embodiment, FIG. 10 is a perspective view of one step of a method for manufacturing an all-solid-state secondary battery according to another embodiment, FIG. 11 is a cross-sectional view taken along line XI-XI' of FIG. 10, and FIGS. 12 to 14 are cross-sectional views sequentially showing the next steps of FIG. 11.

[0175] The other embodiments illustrated in FIGS. 9 to 14 are substantially the same as the one embodiment illustrated in FIGS. 3 to 8 except for the second rectangular case, and thus a repeated description thereof will be omitted.

[0176] First, as shown in FIGS. 9 to 11, a first square case (110) having a concave first outer surface (111a) and a second square case (120) having a concave second outer surface (121a) are placed face to face (S10).

[0177] The first bottom case (111) may have a first outer surface (111a) that is concave downward in the vertical direction (Z) and a first inner surface (111b) that is convex downward in the vertical direction (Z). Similarly, the second bottom case (121) may have a second outer surface (121a) that is concave upward in the vertical direction (Z) and a second inner surface (121b) that is convex upward in the vertical direction (Z).

[0178] At this time, the first inner side (111b) of the first bottom case (111) faces the second inner side (121b) of the second bottom case (121) and is convex toward the second inner side (121b), and the second inner side (121b) may be convex toward the first inner side (111b).

[0179] Next, as shown in FIGS. 9 and 12, an all-solid-state cell (200) is positioned between the first square case (110) and the second square case (120) (S20).

[0180] At this time, since the first inner surface (111b) of the first square case (110) protrudes convexly downward, only the first central area (CA1) of the first inner surface (111b) comes into contact with the upper surface of the all-solid-state cell (200). Accordingly, the first peripheral area (PA1) of the first inner surface (111b) of the first square case (110) does not come into contact with the upper surface of the all-solid-state cell (200).

[0181] In addition, since the second inner side surface (121b) of the second square case (120) also protrudes upwardly in a convex manner, only the second central area (CA2), which is the central area of ​​the second inner side surface (121b), comes into contact with the lower surface of the all-solid-state cell (200). Accordingly, the second peripheral area (PA2) surrounding the second central area (CA2) among the second inner side surfaces (121b) of the second square case (120) does not come into contact with the lower surface of the all-solid-state cell (200).

[0182] Next, as shown in FIG. 9, FIG. 13, and FIG. 14, the first square case (110) and the second square case (120) are fastened to deform the first outer surface (111a) of the first square case (110) and the second outer surface (121a) of the second square case (120) flat (S30).

[0183] Specifically, as illustrated in FIG. 13, by fastening the first square case (110) and the second square case (120), the first peripheral area (PA1) of the first bottom case (111) is pulled by the tensile force of the first side fastening portion (112a) and the second side fastening portion (122a), so that most of the first peripheral area (PA1) of the first inner surface (111b) of the first bottom case (111) comes into contact with the upper surface of the all-solid-state cell (200). In addition, the second peripheral area (PA2) of the second bottom case (121) is pulled, so that most of the second peripheral area (PA2) of the second inner surface (121b) of the second bottom case (121) comes into contact with the lower surface of the all-solid-state cell (200).

[0184] And, as illustrated in Fig. 14, the upper surface of the all-solid-state cell (200) expands due to the repulsive force of the elastic member (220), so that all areas (CA1, PA1) of the first inner surface (111b) of the first bottom case (111) come into contact with the upper surface of the all-solid-state cell (200). Accordingly, the first outer surface (111a) and the first inner surface (111b) of the first bottom case (111) are deformed flat.

[0185] In addition, the lower surface of the all-solid cell (200) expands due to the repulsive force of the elastic member (220), so that all areas (CA2, PA2) of the second inner surface (121b) of the second bottom case (121) come into contact with the lower surface of the all-solid cell (200). Accordingly, the second outer surface (121a) and the second inner surface (121b) of the second bottom case (121) are deformed flat.

[0186] In this way, not only the first rectangular case, but also the second rectangular case has a concave second outer surface, so that the shape of the rectangular case can be more effectively prevented from being deformed by internal pressure within the rectangular case.

[0187] 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 step of opposing a first rectangular case and a second rectangular case having a concave first outer surface; A step of positioning an all-solid-state cell including an anode, a solid electrolyte layer, a cathode, and an elastic member between the first square case and the second square case; and A step of flattening the first outer surface of the first square case by connecting the first square case and the second square case. A method for manufacturing an all-solid-state secondary battery comprising:

2. In paragraph 1, In the step of opposing the first square case and the second square case, A method for manufacturing an all-solid-state secondary battery, wherein the first inner side of the first square case faces the second inner side of the second square case and is convex toward the second inner side.

3. In paragraph 2, The first rectangular case includes a first bottom case and a first side wall case extending vertically from both ends of the first bottom case, The second rectangular case includes a second bottom case and a second side wall case extending vertically from both ends of the second bottom case, A method for manufacturing an all-solid-state secondary battery, wherein the first inner side of the first bottom case faces the second inner side of the second bottom case.

4. In paragraph 3, In the step of positioning the all-solid-state cell between the first square case and the second square case, A method for manufacturing an all-solid-state secondary battery, wherein the first central region, which is the central region of the first inner surface, is in contact with the upper surface of the all-solid-state cell.

5. In paragraph 4, In the step of positioning the all-solid-state cell between the first square case and the second square case, A method for manufacturing an all-solid-state secondary battery, wherein a first peripheral region surrounding the first central region among the first inner surfaces does not contact the upper surface of the all-solid-state cell.

6. In paragraph 3, In the step of flattening the first outer surface of the first rectangular case, A method for manufacturing an all-solid-state secondary battery, wherein the first side fastening portion of the first side wall case and the second side fastening portion of the second side wall case are fastened to each other.

7. In paragraph 6, A method for manufacturing an all-solid-state secondary battery, wherein the uneven shape of the first side fastening portion and the uneven shape of the second side fastening portion are fastened to each other.

8. In paragraph 7, A method for manufacturing an all-solid-state secondary battery, wherein the first side fastening portion and the second side fastening portion are welded to each other.

9. In paragraph 3, In the step of flattening the first outer surface of the first rectangular case, A method for manufacturing an all-solid-state secondary battery, wherein the first inner surface of the first square case is in full contact with the upper surface of the all-solid-state cell.

10. In paragraph 3, In the step of opposing the first square case and the second square case, A method for manufacturing an all-solid-state secondary battery, wherein the second bottom case of the second rectangular case has a flat second outer surface.

11. In paragraph 3, In the step of opposing the first square case and the second square case, A method for manufacturing an all-solid-state secondary battery, wherein the second bottom case of the second rectangular case has a concave second outer surface.

12. In paragraph 11, In the step of opposing the first square case and the second square case, A method for manufacturing an all-solid-state secondary battery, wherein the second inner side of the second bottom case faces the first inner side of the first bottom case and is convex toward the first inner side.

13. In paragraph 11, In the step of positioning the all-solid-state cell between the first square case and the second square case, A method for manufacturing an all-solid-state secondary battery, wherein the second central region, which is the central region of the second inner surface, is in contact with the lower surface of the all-solid-state cell.

14. In paragraph 13, In the step of positioning the all-solid-state cell between the first square case and the second square case, A method for manufacturing an all-solid-state secondary battery, wherein a second peripheral region surrounding the second central region among the second inner surfaces does not contact the lower surface of the all-solid-state cell.

15. In paragraph 11, In the step of flattening the first outer surface of the first floor case, A method for manufacturing an all-solid-state secondary battery, wherein the second outer surface of the second bottom case is deformed to be flat.

16. In paragraph 15, In the step of flattening the second outer surface of the second bottom case, A method for manufacturing an all-solid-state secondary battery, wherein the second inner surface of the second bottom case is in full contact with the lower surface of the all-solid-state cell.

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