All-solid rechargeable battery

Abstract

Provided is an all-solid rechargeable battery. The all-solid rechargeable battery according to an embodiment includes: a plurality of unit cells including a negative electrode, a solid electrolyte layer, and a positive electrode; a first elastic sheet disposed between and at an outermost side of the plurality of unit cells to form a stack cell and buffering a volume change of the unit cells during charging and discharging; a second elastic sheet disposed at an outer side of the stack cell; and an end plate disposed at an outer side of the second elastic sheet, wherein the second elastic sheet includes a first layer for providing an elastic force to the stack cell and a second layer interposed between the first layer and the end plate to provide stress relaxation.

Description

All-solid-state secondary battery

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

[0002] Recent industrial demands have led to the active development of batteries with high energy density and safety. For example, lithium-ion batteries are being used not only in information and communication devices, but also in the automotive sector. Safety is particularly important in the automotive sector, as it is directly related to life.

[0003] Lithium-ion batteries currently on the market use electrolytes containing flammable organic solvents, which poses a risk of overheating and fire in the event of a short circuit. To address this issue, all-solid-state secondary batteries using solid electrolytes are being proposed.

[0004] All-solid-state secondary batteries do not use flammable organic solvents, significantly reducing the risk of fire or explosion even if a short circuit occurs. Therefore, these all-solid-state batteries significantly improve safety compared to lithium-ion batteries that use electrolytes.

[0005] The above-described information disclosed in the background technology of this invention is only intended to improve understanding of the background of the present disclosure and may therefore include information that does not constitute prior art.

[0006] One embodiment provides an all-solid-state secondary battery that controls pressure changes through volume changes during charge / discharge under pressure. One embodiment provides an all-solid-state secondary battery that compensates for thickness variations that may lead to uneven pressure within the cell and absorbs shock.

[0007] According to one embodiment, an all-solid-state secondary battery includes a plurality of unit cells including a negative electrode, a solid electrolyte layer, and a positive electrode, a first elastic sheet disposed between and at the outermost end of the plurality of unit cells to form a stack cell and buffer a change in volume of the unit cells during charging and discharging, a second elastic sheet disposed on the outside of the stack cell, and an end plate disposed on the outside of the second elastic sheet, wherein the second elastic sheet includes a first layer providing elasticity to the stack cell, and a second layer interposed between the first layer and the end plate to provide stress relief.

[0008] An all-solid-state secondary battery according to one embodiment further includes a pouch containing the stack cell, and the second elastic sheet can be disposed between an outer surface of the pouch and an inner surface of the end plate.

[0009] The first layer is arranged on the outer surface of the pouch and applies uniform pressure to the stack cell during the discharge process in which the thickness is reduced, thereby buffering the volume change of the stack cell during charging and discharging.

[0010] The second layer can uniformly apply pressure to the uneven thickness and surface curvature of the stack cell.

[0011] An all-solid-state secondary battery according to one embodiment further includes a pouch containing the stack cell and the second elastic sheet, wherein the second elastic sheet can be disposed between the outer surface of the stack cell and the inner surface of the pouch.

[0012] The loss tangent (tanδ1 = E1" / E1') of the first layer may be 0.01 to 0.1.

[0013] The loss tangent (tanδ2 = E2" / E2') of the second layer may be 0.2 to 0.3.

[0014] The first loss modulus (E1") of the first layer may be smaller than the second loss modulus (E2") of the second layer (E1") <E2").

[0015] The first storage modulus (E1') of the first layer may be smaller than the second storage modulus (E2') of the second layer (E1' <E2').

[0016] The first loss tangent (tanδ1) of the first layer may be smaller than the second loss tangent (tanδ2) of the second layer (tanδ1 <tanδ2).

[0017] One embodiment comprises a second elastic sheet composed of first and second layers on the outer surface of a stacked cell having a first elastic sheet between unit cells and at the outermost surface, thereby buffering volume changes during charging and discharging under pressure and uniformly controlling pressure according to volume changes. Accordingly, one embodiment can compensate for thickness deviation in the stacked cell to absorb shock.

[0018] Figure 1 is a cross-sectional view showing an all-solid-state secondary battery according to one embodiment.

[0019] FIG. 2 is a cross-sectional view showing the formation of a lithium metal layer of an all-solid-state secondary battery according to one embodiment.

[0020] Figure 3 is a longitudinal cross-sectional view showing an all-solid-state secondary battery according to a first embodiment of the present invention.

[0021] [Revised 26.06.2024 by Rule 91] Figure 4 is a cross-sectional view showing an all-solid-state secondary battery according to the second embodiment of the present invention. Figure 5 is a table attached with images showing strong and weak fastening pressures on the pressure-sensitive paper according to the application of the first and second layers to the first to third comparative examples and the examples. Figure 6 is a table attached with images showing strong and weak fastening pressures on the pressure-sensitive paper according to the application of the first and second layers to the fourth to sixth comparative examples.

[0022] 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.

[0023] 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.

[0024] 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 is another element in between. Conversely, when an element is said to be "directly over" another element, it means that there is no other element in between.

[0025] 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.

[0026] Cathode for all-solid-state secondary batteries

[0027] 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.

[0028] 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.

[0029] positive electrode active material

[0030] 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.

[0031] Li a A 1-b X b D2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5);

[0032] 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);

[0033] 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);

[0034] Li a E 2-b Xb O 4-c D c (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05);

[0035] 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);

[0036] 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);

[0037] 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);

[0038] 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);

[0039] 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);

[0040] 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);

[0041] 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);

[0042] 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);

[0043] The a NiG b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0044] The a CoG b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0045] The a Mn 1-b G b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0046] The a Mn2G b O4(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0047] The a Mn 1-g G g PO4(0.90 ≤ a ≤ 1.8, 0 ≤ g ≤ 0.5);

[0048] QO2; QS2; LiQS2;

[0049] V2O5; LiV2O5;

[0050] LiZO2;

[0051] LiNiVO4;

[0052] Li (3-f) J2(PO4)3(0 ≤ f ≤ 2);

[0053] Li (3-f) Fe2(PO4)3(0 ≤ f ≤ 2);

[0054] Li a FePO4(0.90 ≤ a ≤ 1.8).

[0055] 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.

[0056] The above-mentioned positive electrode 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).

[0057] The above 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.

[0058] [Chemical Formula 1]

[0059] Li a1 Ni x1 M 1 y1 M 2 1-x1-y1 O2

[0060] 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.

[0061] [Chemical Formula 2]

[0062] Li a2 Co x2 M 3 1-x2 O2

[0063] 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.

[0064] [Chemical Formula 3]

[0065] Li a3 Fe x3 M 4 (1-x3) PO4

[0066] 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.

[0067] The average particle diameter (D50) of the positive electrode active material 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 positive electrode active material having such a particle diameter range can be harmoniously mixed with other components within the positive electrode active material layer and can realize high capacity and high energy density.

[0068] 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.

[0069] Sulfide-based solid electrolyte

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] According to one embodiment, the average particle diameter (D50) of the sulfide-based solid electrolyte particles 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 be small particles having an average particle diameter (D50) of 0.1 ㎛ to 1.0 ㎛, or may be large particles having an average particle diameter (D50) of 1.5 ㎛ to 5.0 ㎛, depending on the location or purpose of use. The sulfide-based solid electrolyte particles having such a particle diameter range can effectively penetrate between solid particles in a battery, and have excellent contact with an 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, for example, by measuring the sizes of about 20 particles in a scanning electron microscope image to obtain a particle size distribution and calculating D50 from this.

[0077] 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.

[0078] 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 this content range is satisfied, the positive electrode for an all-solid-state secondary battery can implement high capacity and high ionic conductivity while maintaining high adhesiveness, and the viscosity of the positive electrode composition can be maintained at an appropriate level, thereby improving processability.

[0079] bookbinder

[0080] 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.

[0081] Challenge

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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 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.

[0086] All-solid-state secondary battery

[0087] In one embodiment, an all-solid-state secondary battery is provided, which includes the aforementioned positive electrode and 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.

[0088] Fig. 1 is a cross-sectional view of an all-solid-state secondary battery according to one embodiment. Referring to Fig. 1, the all-solid-state secondary battery (100) may have a structure in which an electrode assembly in which a negative electrode (400) including a negative electrode collector (401) and a negative electrode active material layer (403), a solid electrolyte layer (300), and a positive electrode (200) including a positive electrode active material layer (203) and a positive electrode collector (201) are laminated is housed in a case such as a pouch. The all-solid-state secondary battery (100) may further include an elastic layer (500) on the outer side of at least one of the positive electrode (200) and the negative electrode (400). Although Fig. 1 illustrates one electrode assembly including a negative electrode (400), a solid electrolyte layer (300), and a positive electrode (200), an all-solid-state battery may be manufactured by laminating two or more electrode assemblies.

[0089] cathode

[0090] An anode for an all-solid-state battery may include, for example, a current collector and a layer of anode active material positioned on the current collector. The layer of anode active material includes a cathode active material and may further include a binder, a conductive material, and / or a solid electrolyte.

[0091] The above 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.

[0092] The material capable of reversibly intercalating / deintercalating the lithium ions may include a carbon-based negative electrode active material, for example, crystalline carbon, amorphous carbon, or a combination thereof. Examples of the 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 the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, and the like.

[0093] As the above lithium metal alloy, an alloy of lithium and 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.

[0094] As the material capable of doping and dedoping the lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material can be used, and the Si-based negative electrode active material may be silicon, a silicon-carbon composite, or SiO. x(0<x<2), Si-Q 합금(상기 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), 상기 Sn계 음극 활물질로는 Sn, SnO2, Sn-R 합금(상기 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. 상기 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.

[0095] 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.

[0096] The average particle diameter (D50) of the above silicon particles may be 10 nm to 20 μm, for example, 10 nm to 500 nm. The silicon particles may exist in an oxidized form, and at this time, 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, it can be greater than 0 and less than 2. Here, the average particle diameter (D50) is measured by a particle size analyzer using laser diffraction and means the diameter of particles having a cumulative volume of 50% by volume in the particle size distribution.

[0097] The above 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.

[0098] The content of the negative active material in the above negative active material layer may be 95 wt% to 99 wt% with respect to the total weight of the negative active material layer.

[0099] 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.

[0100] The above binder serves to adhere the negative active material particles well to each other and also to adhere the negative active material well to the current collector. The binder may include an insoluble binder, a water-soluble binder, or a combination thereof.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] The negative electrode current collector 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.

[0106] 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.

[0107] FIG. 2 is a schematic cross-sectional view of an all-solid-state secondary battery including a precipitation-type negative electrode according to one embodiment. Referring to FIG. 2, the precipitation-type negative electrode (400') may include a current collector (401) and a negative electrode coating layer (405) positioned on the current collector. An all-solid-state battery including such a precipitation-type negative electrode (400') starts initial charging in a state in which no negative electrode active material is present, and upon charging, high-density lithium metal or the like is precipitated between the current collector (401) and the negative electrode coating layer (405) to form a lithium metal layer (404), which may function as a negative electrode active material. Accordingly, in an all-solid-state battery that has been charged at least once, the precipitation-type negative electrode (400') may include a current collector (401), a lithium metal layer (404) positioned on the current collector, and a negative electrode coating layer (405) positioned on the metal layer. The above lithium metal layer (404) refers to a layer in which lithium metal, etc. 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.

[0108] The above cathode coating layer (405) may include a metal, a carbon material, or a combination thereof that acts as a catalyst.

[0109] The metal may include, for example, gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, zinc, or a combination thereof, and may be composed of one type of these or may be composed of an alloy of several types. When the metal is present in the form of particles, the average particle diameter (D50) thereof may be about 4 μm or less, for example, 10 nm to 4 μm.

[0110] 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.

[0111] When the above-described negative electrode coating layer (405) includes both the metal and the carbon material, the mixing ratio of the metal and the 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 above-described negative electrode coating layer (405) may include, for example, a carbon material supported with a catalytic metal, or may include a mixture of metal particles and carbon material particles.

[0112] The above cathode coating layer (405) may include, for example, the metal and amorphous carbon, in which case it can effectively promote the precipitation of lithium metal.

[0113] The above cathode coating layer (405) may further include a binder, and the binder may be a conductive binder. In addition, the above cathode coating layer (405) may further include general additives such as fillers, dispersants, and ionic conductive agents.

[0114] The thickness of the cathode coating layer (405) may be, for example, 100 nm to 20 ㎛, or 500 nm to 10 ㎛, or 1 ㎛ to 5 ㎛.

[0115] The above-described precipitated negative electrode (400') may further include, for example, a thin film on the surface of the current collector, i.e., between the current collector and the negative electrode coating layer. 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 precipitated form of the lithium metal layer (404) 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.

[0116] solid electrolyte layer

[0117] The solid electrolyte layer (300) 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.

[0118] In one example, the solid electrolyte included in the positive electrode (200) and the solid electrolyte included in the solid electrolyte layer (300) may include the same compound or different compounds. For example, when both the positive electrode (200) and the solid electrolyte layer (300) 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 (200) and the solid electrolyte layer (300) 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.

[0119] Meanwhile, the average particle diameter (D50) of the solid electrolyte included in the positive electrode (200) may be smaller than the average particle diameter (D50) of the solid electrolyte included in the solid electrolyte layer (300). In this case, the energy density of the all-solid-state battery can be maximized while increasing the mobility of lithium ions, thereby improving the overall performance. For example, the average particle diameter (D50) of the solid electrolyte included in the positive electrode (200) 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 (300) 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 lithium ion transport is facilitated, resistance is suppressed, and the overall performance of the all-solid-state secondary battery can be improved. Here, the average particle diameter (D50) of the solid electrolyte can be measured using a particle size analyzer using laser diffraction. Alternatively, the particle size can be measured by selecting 20 or so random particles from a microscope image such as a scanning electron microscope, obtaining a particle size distribution, and calculating the D50 value from this.

[0120] The above solid electrolyte layer may further include a binder in addition to the solid electrolyte. At this time, the binder may be styrene butadiene rubber, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, an acrylate polymer, or a combination thereof, but is not limited thereto, and any binder used in the relevant technical field may be used. The acrylate polymer may be, for example, butyl acrylate, polyacrylate, polymethacrylate, or a combination thereof.

[0121] The above solid electrolyte layer can be formed by adding a solid electrolyte to a binder solution, coating the same on a base film, and drying the same. The solvent of the binder solution may be isobutyryl isobutyrate, xylene, toluene, benzene, hexane, or a combination thereof. Since the solid electrolyte layer formation process is widely known in the art, a detailed description thereof will be omitted.

[0122] The thickness of the solid electrolyte layer may be, for example, 10 ㎛ to 150 ㎛.

[0123] The above solid electrolyte layer may further include an alkali metal salt, and / or an ionic liquid, and / or a conductive polymer.

[0124] The above 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 ion conductivity by enhancing the lithium ion mobility of the solid electrolyte layer.

[0125] The above 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.

[0126] In addition, the lithium salt may be an imide-based one, and for example, the imide-based 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 an ionic liquid.

[0127] The above ionic liquid has a melting point below room temperature and is a salt or room-temperature molten salt that is liquid at room temperature and consists only of ions.

[0128] The above ionic liquid may be a compound including a) one or more cations selected from ammonium-based, pyrrolidinium-based, pyridinium-based, pyrimidinium-based, imidazolium-based, piperidinium-based, pyrazolium-based, oxazolium-based, pyridazinium-based, phosphonium-based, sulfonium-based, triazolium-based, and mixtures thereof, and b) one or more anions selected from 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-.

[0129] The ionic liquid may be at least one selected from the group consisting of, for example, 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.

[0130] In the above 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.

[0131] The above-mentioned all-solid-state battery may be a unit battery having a structure of positive electrode / solid electrolyte layer / negative electrode, a bi-cell having a structure of positive electrode / solid electrolyte layer / negative electrode / solid electrolyte layer / positive electrode, or a laminated battery in which the structure of the unit battery is repeated.

[0132] The shape of the above-mentioned all-solid-state battery is not particularly limited, and may be, for example, coin-shaped, button-shaped, sheet-shaped, stacked, cylindrical, flat, etc. In addition, the above-mentioned all-solid-state battery can be applied to large-scale batteries used in electric vehicles, etc. For example, the above-mentioned all-solid-state battery can be used in hybrid vehicles such as plug-in hybrid electric vehicles (PHEVs). In addition, it can be used in fields requiring large amounts of power storage, and for example, it can be used in electric bicycles or power tools.

[0133] Fig. 3 is a cross-sectional view showing an all-solid-state secondary battery according to a first embodiment of the present invention. Referring to Fig. 3, the all-solid-state secondary battery (1) of the first embodiment includes a plurality of unit cells (UC), a first elastic sheet (S1), a second elastic sheet (S2), and an end plate (EP).

[0134] A unit cell (UC) includes a cathode (400), a solid electrolyte layer (300), and an anode (200), as illustrated in Fig. 1, and may be formed as a bi-cell. A stack cell (SC) includes a plurality of unit cells (UC), and is formed by arranging a first elastic sheet (S1) between the unit cells (UC), and arranging the first elastic sheet (S1) at the outermost end of the unit cells (UC).

[0135] The first elastic sheet (S1) is arranged between and at the outermost edge of a plurality of unit cells (UC) to form a stack cell (SC) and cushion changes in the volume of the unit cells (UC) during charging and discharging. The second elastic sheet (S2) is arranged on the outer side of the first elastic sheet (S1) arranged at the outermost edge of the plurality of unit cells (UC), and may be formed in a multi-layer configuration.

[0136] During the manufacturing of a stack cell (SC), the two surfaces of the stack cell (SC) may become uneven due to various components, foreign substances, and alignment errors. In addition, due to the surface unevenness, when pressurizing the stack cell (SC) from both ends, pressure may be applied unevenly to each area.

[0137] The first elastic sheet (S1) and the second elastic sheet (S2) can buffer the volume change due to charging and discharging so that uniform pressure can be applied to the stack cell (SC) even if the surface of the stack cell (SC) is uneven.

[0138] The second elastic sheet (S2) includes a first layer (L1) that provides elasticity to a stack cell (SC) formed by a combination of the first elastic sheet (S1) and unit cells (UC), and a second layer (L2) that is interposed between the first layer (L1) and the end plate (EP) to provide stress relief.

[0139] Since the first layer (L1) has elasticity, it can evenly apply pressure to the unit cell (UC) through the first elastic sheet (S1) even during the discharge process in which the thickness is reduced. Therefore, the first layer (L1) can buffer the volume change of the stack cell (SC) during charging and discharging together with the first elastic sheet (S1). In addition to buffering the volume change of the first layer (L1), the second layer (L2) can even out the pressure unevenness caused by the uneven thickness and surface curvature of the stack cell (SC) through stress relief.

[0140] Comparing the first layer (L1) and the second layer (L2) in the second elastic sheet (S2), the first layer (L1) has relatively low stress relaxation performance and excellent elasticity, so it can buffer the pressure change due to thickness change during charging and discharging. To this end, since elasticity is important for the first layer (L1), the storage elastic modulus (E1') is more important than the loss elastic modulus (E1"). Therefore, the loss tangent (tanδ1) of the first layer (L1) is relatively smaller than that of the second layer (L2).

[0141] The second layer (L2) has relatively high stress relaxation performance and low elasticity, so it can improve unevenness due to surface curvature. For this purpose, the loss modulus (E2") of the second layer (L2) is most important, and the loss tangent (tanδ2) is relatively large compared to the first layer (L1).

[0142] The all-solid-state secondary battery (1) of the first embodiment further includes a pouch (P) containing a stack cell (SC). A second elastic sheet (S2) is arranged between the outer surface of the pouch (P) and the inner surface of the end plate (EP). The second elastic sheet (S2) is installed on the outside of the stack cell (SC).

[0143] In this case, the first layer (L1) is arranged on the outer surface of the pouch (P) so as to apply uniform pressure to the stack cell (SC) during the discharge process in which the thickness of the stack cell (SC) decreases, thereby buffering the volume change of the stack cell (SC) during charging and discharging. The second layer (L2) is arranged on the outer surface of the first layer (L1), so as to apply uniform pressure to the uneven thickness and surface curvature of the stack cell (SC).

[0144] 1st layer 2nd layer thickness 300㎛ 500㎛ 25℃ E'(MPa) 2.410 3.8 E"(MPa) 0.22 1.5 tanδ 0.09 0.245℃ E'(MPa) 2.41 8.1 E"(MPa) 0.23.6 tanδ 0.10.2

[0145] Referring to Table 1, the loss tangent (tanδ1= E1" / E1') obtained by the loss modulus (E1") / storage modulus (E1') in the first layer (L1) is 0.01 to 0.1, and the loss tangent (tanδ1= E1" / E1') obtained from the experimental value is 0.09 to 0.1. The loss tangent (tanδ2= E2" / E2') obtained by the loss modulus (E2") / storage modulus (E2') in the second layer (L2) is 0.2 to 0.3, and the loss tangent (tanδ2= E2" / E2') obtained from the experimental value is 0.2.

[0146] The first loss modulus (E1") of the first layer (L1) is smaller than the second loss modulus (E2") of the second layer (L2). <E2"). 제1레이어(L1)의 제1저장탄성률(E1')은 제2레이어(L2)의 제2저장탄성률(E2')보다 작다(E1'<E2'). 제1레이어(L1)의 제1손실탄젠트(tanδ1)는 제2레이어(L2)의 제2손실탄젠트(tanδ2)보다 작다(tanδ1<tanδ2).

[0147] Using dynamic mechanical analysis (DMA) equipment, the loss modulus (E1", E2") and storage modulus (E1', E2') of the first and second layers (L1, L2) of the second elastic sheet (S2) were confirmed and compared through a modulus scan according to temperature.

[0148] That is, in the first and second layers (L1, L2), the first loss tangent (tanδ1) is smaller than the second loss tangent (tanδ2) (tanδ1 <tanδ2)는 것을 확인하였다. 따라서 상온에서도, 셀 구동이 가해지는 온도에서도 모두 제2레이어(L2)의 응력완화 특성이 좋은 것을 알 수 있다. 즉 제2탄성시트(S2)에는 제1레이어(L1)와 함께 제2레이어(L2)를 포함하는 것이 중요함을 알 수 있다.

[0149] Fig. 4 is a cross-sectional view showing an all-solid-state secondary battery according to a second embodiment of the present invention. Referring to Fig. 4, the all-solid-state secondary battery (2) of the second embodiment further includes a pouch (P) containing a stack cell (SC) and a second elastic sheet (S2). The second elastic sheet (S2) is disposed between the outer surface of the stack cell (SC) and the inner surface of the pouch (P).

[0150] Even in this case, the first layer (L1) can apply uniform pressure to the stack cell (SC) during the discharge process in which the thickness of the stack cell (SC) decreases, thereby buffering the volume change of the stack cell (SC) during charging and discharging. The second layer (L2) is arranged on the inner surface of the pouch (P), so as to uniformly apply pressure to the uneven thickness and surface curvature of the stack cell (SC).

[0151] To this end, a pressure-sensitive film, which is a pressure-measuring film, was placed between the end plate (EP) and the stack cell (SC) to pressurize the end plate (EP), thereby confirming the uniformity of pressure in the all-solid-state secondary battery (1, 2).

[0152] The uniformity of the fastening pressure in the all-solid-state secondary battery (1, 2) was confirmed depending on the presence or location of the first and second layers (L1, L2) in the second elastic sheet (S2). That is, the uniformity of the fastening pressure could be confirmed by the red distribution of intensity shown in red on the pressure sensitive paper.

[0153] [Correction pursuant to Rule 91, June 26, 2024]

[0154] [Revised 26.06.2024 under Rule 91] Referring to Fig. 5, the degree and uniformity of the fastening pressure in the all-solid-state secondary batteries (1, 2) of the first and second embodiments were not significantly affected by the position of the pouch (P). It can be seen that the position of the pouch (P) surrounding the stack cell (SC) on the inside or outside of the first elastic sheet (S2) does not affect the uniformity of the fastening pressure. In other words, there was no significant difference in the image appearing in red on the pressure-sensitive paper.

[0155] In the experimental example with the first and second layers (L1, L2), the bonding pressure is uniform. That is, there is no significant difference in the image displayed in red on the pressure-sensitive paper. Therefore, it can be seen that a second layer (L2) with good stress-relief characteristics is required to alleviate the unevenness of the bonding pressure, and a first layer (L1) with good elasticity characteristics is required for normal cell operation.

[0156] In the first and third comparative examples without a second layer (L2), the bonding pressure was uneven. Specifically, the red image on the pressure-sensitive paper showed a significant difference in strength. Therefore, to reduce the difference in strength, i.e., to alleviate the unevenness in the bonding pressure, a second layer (L2) with excellent stress-relieving properties is required.

[0157] In the first and second comparative examples without the first layer (L1), cell operation was not achieved. No red color appeared on the pressure sensitive paper. In other words, this case could not be confirmed through the operating characteristics data. Therefore, it can be seen that a first layer (L1) with good elastic properties is necessary for normal cell operation.

[0158] [Correction pursuant to Rule 91, June 26, 2024]

[0159] With regard to Table 1, a first layer (L1) with a loss tangent (tanδ1= E1" / E1') in the range of 0.01 to 0.1 and a second layer (L2) with a loss tangent (tanδ1= E1" / E1') in the range of 0.2 to 0.3 are required.

[0160] [Correction under Rule 91 26.06.2024] Figure 6 shows the distribution of the fastening pressure when the loss tangent (tanδ1 = E1" / E1') of at least one of the first and second layers is 0.6 to 0.7. In the fourth comparative example, it can be seen that the loss tangent of the first and second layers is 0.6 to 0.7, and the distribution of the fastening pressure is uneven. In other words, it can be seen that the fastening pressure is not uniformly controlled.

[0161] In the fifth comparative example, it can be seen that the loss tangent of the first layer is 0.6 to 0.7, the loss tangent of the second layer (tanδ1 = E1" / E1') is 0.2 to 0.3, and the distribution of the fastening pressure is uneven. In other words, it can be seen that the fastening pressure is not controlled uniformly.

[0162] In the sixth comparative example, it can be seen that the loss tangent of the second layer is 0.6 to 0.7, the loss tangent of the first layer (tanδ1 = E1" / E1') is 0.01 to 0.1, and the distribution of the fastening pressure is uneven. In other words, it can be seen that the fastening pressure is not controlled uniformly.

[0163] The uneven pressurization shape was the most severe in the fourth comparative example, which applied the first and second layers outside the scope of the embodiment. The fifth comparative example, in which the first layer (L1) was outside the scope of the embodiment, showed good uniformity, but did not achieve sufficient pressurization. The sixth comparative example, in which the second layer (L2) was outside the scope, showed sufficient pressurization, but the uniformity was significantly reduced.

[0164] As a result, it can be seen that the first and second layers (L1, L2) need to take charge of their respective functions and each have a functionally necessary area. That is, it can be seen that the first layer (L1) is necessary for normal operation of the cell, and the second layer (L2) is necessary for alleviating unevenness in the fastening pressure, i.e., stress relief.

[0165] The first and second embodiments can buffer volume changes during charging and discharging through the first and second layers (L1, L2) in a pressurized stack cell (SC) and evenly control pressure according to the volume changes. Accordingly, the first and second embodiments can absorb shock by compensating for thickness deviations in the first and second layers (L1, L2) in the stack cell (SC).

[0166] The above description is only one embodiment for implementing the method for manufacturing an all-solid-state battery, the process plate, and the all-solid-state battery according to the present disclosure, and the present disclosure is not limited to the above-described embodiment, and as claimed in the following claims, it will be understood that the technical spirit of the present disclosure encompasses a range in which various modifications can be implemented without departing from the gist of the present disclosure by anyone having ordinary skill in the art to which the present invention pertains.

[0167] - Explanation of symbols -

[0168] 1, 2: All-solid-state secondary battery 100: All-solid-state secondary battery

[0169] 200: positive pole 400, 400': negative pole

[0170] 201: Cathode current collector 203: Cathode active material layer

[0171] 300: Solid electrolyte layer 401: Negative current collector

[0172] 403: Negative active material layer 404: Lithium metal layer

[0173] 405: Cathode coating layer EP: End plate

[0174] L1: First layer L2: Second layer

[0175] P: Pouch S1: First elastic sheet

[0176] S2: Second elastic sheet SC: Stack cell

[0177] UC: unit cell

Claims

1. A plurality of unit cells including a cathode, a solid electrolyte layer, and an anode; A first elastic sheet arranged between and at the outermost end of a plurality of the above unit cells to form a stack cell and cushion changes in the volume of the above unit cells during charging and discharging; A second elastic sheet arranged on the outside of the stack cell; and End plate arranged on the outer side of the second elastic sheet Including, The above second elastic sheet A first layer providing elasticity to the above stack cell, and An all-solid-state secondary battery comprising a second layer interposed between the first layer and the end plate to provide stress relief.

2. In paragraph 1, Further comprising a pouch containing the above stack cell, An all-solid-state secondary battery, wherein the second elastic sheet is disposed between the outer surface of the pouch and the inner surface of the end plate.

3. In paragraph 2, The above first layer is An all-solid-state secondary battery, which is arranged on the outer surface of the pouch and applies uniform pressure to the stack cell during a discharge process in which the thickness decreases, thereby buffering changes in the volume of the stack cell during charging and discharging.

4. In paragraph 3, The above second layer An all-solid-state secondary battery that uniformly applies pressure to the uneven thickness and surface curvature of the stack cell.

5. In paragraph 1, It further includes a pouch containing the stack cell and the second elastic sheet, An all-solid-state secondary battery, wherein the second elastic sheet is disposed between the outer surface of the stack cell and the inner surface of the pouch.

6. In paragraph 1, An all-solid-state secondary battery having a loss tangent (tanδ1 = E1" / E1') of the first layer of 0.01 to 0.

1.

7. In paragraph 2, An all-solid-state secondary battery having a loss tangent (tanδ2 = E2" / E2') of the second layer of 0.2 to 0.

3.

8. In paragraph 1, The first loss modulus (E1") of the first layer is smaller than the second loss modulus (E2") of the second layer (E1") <E2") 전고체 이차 전지.

9. In paragraph 1, The first storage modulus (E1') of the first layer is smaller than the second storage modulus (E2') of the second layer (E1' <E2') 전고체 이차 전지.

10. In paragraph 1, The first loss tangent (tanδ1) of the first layer is smaller than the second loss tangent (tanδ2) of the second layer (tanδ1 <tanδ2) 전고체 이차 전지.

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